TY - THES A1 - Leitz, Michael R. T1 - Vergleichende Pharmakologie der Subtypen von menschlichen Beta- adrenergen Rezeptoren - Charakterisierung von stabil in CHO-Zellen transfizierten Rezeptoren T1 - Comparative pharmacology of Beta-adrenergic receptor subtypes - Characterization of stably transfected receptors in CHO-cells N2 - Seit langem werden auf das β-adrenerge System wirkende Pharmaka, v.a. β1-Antagonisten und β2-Agonisten, therapeutisch eingesetzt, allerdings sind die pharmakologischen Eigenschaften dieser Stoffe an den drei bekannten β-adrenergen Subtypen teilweise nur unzureichend untersucht. Ein Ziel dieser Arbeit war es daher, vergleichbare pharmakologische Daten für Agonisten (Adrenalin, Noradrenalin, Isoprenalin, Fenoterol, Salbutamol, Salmeterol, Terbutalin, Formoterol, Broxaterol) und Neutrale und Inverse Antagonisten (Propranolol, Alprenolol, Atenolol, Metoprolol, Bisoprolol, Carvedilol, Pindolol, BRL 37344, CGP 20712, SR 59230A, CGP 12177, ICI 118551) an allen drei Subtypen von adrenergen Rezeptoren in einem zellbiologisch identischen Hintergrund zu gewinnen. Dazu stellten wir stabil transfizierte CHO-Zelllinien her, die die einzelnen humanen β-adrenergen Subtypen in vergleichbarer Menge exprimierten. Nach der pharmakologischen Charakterisierung der einzelnen Rezeptorsubtypen erfolgte die Affinitätsmessung von klinisch häufig eingesetzten wie auch experimentell verwendeten Substanzen mit dem unselektiven β-adrenergen Antagonisten 125I-CYP als Radioligand. Darüber hinaus untersuchten wir die β-adrenerg vermittelte Stimulation der Adenylylcyclase in isolierten Membranen dieser Zelllinien. Alle untersuchten Substanzen zeigten charakteristische Bindungs- und funktionale Eigenschaften. Wir konnten nachweisen, dass einige β2- bzw. β3-Agonisten an den anderen Subtypen inversen Agonismus zeigen. Zusätzlich konnten β1-Antagonisten mit agonistischer Aktivität an β2- und β3-AR gefunden werden. Die gewonnenen Daten können somit helfen, klinisch beobachtete Effekte, wie z.B. die unerwünschten Wirkungen der entsprechenden Medikamente, besser zu verstehen. Insbesondere die Ergebnisse am β3-AR sind als Referenz und Ausgangspunkt weiterer Studien an diesem noch relativ wenig untersuchten Rezeptor wertvoll. N2 - Although many β1-receptor antagonists and β2-receptor agonists have been used in pharmacotherapy for many years their pharmacological properties at all three known subtypes of β-adrenergic receptors are not always well characterized. The aim of this study was, therefore, to provide comparative binding characteristics of agonists (epinephrine, norepinephrine, isoproterenol, fenoterol, salbutamol, salmeterol, terbutalin, formoterol, broxaterol) and antagonists (propranolol, alprenolol, atenolol, metoprolol, bisoprolol, carvedilol, pindolol, BRL 37344, CGP 20712, SR 59230A, CGP 12177, ICI 118551) at all three subtypes of human β-adrenergic receptors in an identical cellular background. We generated Chinese hamster ovary (CHO) cells stably expressing the three β-adrenergic receptor subtypes at comparable levels. We characterized these receptor subtypes and analyzed the affinity of routinely used drugs as well as experimental compounds in competition binding studies, using the non-selective antagonist 125I-cyanopindolol as a radioligand. Furthermore, we analyzed the β-receptor-mediated adenylyl cyclase activity in isolated membranes from these cell lines. The results from our experiments show that all compounds exhibit distinct patterns of selectivity and activity at the three β-receptor subtypes. In particular, a number of β2- or β3-receptor agonists that are inverse agonists at the other subtypes were identified. In addition, β1-receptor antagonists with agonistic activity at β2- and β3-receptors were found. These specific mixtures of agonism, antagonism, and inverse agonism at different subtypes may have important implications for the therapeutic use of the respective compounds. KW - Beta-adrenerge Rezeptoren KW - CHO-Zellen KW - Beta-Rezeptor Subtypen KW - stabile Transfektion KW - Beta- adrenergic receptors KW - CHO-cells KW - Beta-Receptor subtypes KW - stable transfection Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-18655 ER - TY - THES A1 - Leyh, Annekathrin T1 - In vitro Untersuchungen zur Genotoxizität von Insulin T1 - In vitro studies on genotoxicity of insulin N2 - Insulin ist ein essentielles Hormon im menschlichen Körper, welches für die Senkung der Blutglukosekonzentration, die Bildung von Energiespeichern und das Zellwachstum verantwortlich ist. Eine mit der Fehlregulation der Insulinproduktion einhergehenden Krankheit ist der Diabetes mellitus. Für diese Arbeit spielt der Typ 2 dieser Erkrankung eine wichtige Rolle. Es entwickelt sich bei Patienten mit diesem Typ des Diabetes mellitus langsam eine Insulinresistenz, die zunächst durch eine kompensatorische Überproduktion von Insulin charakterisiert ist. Dieser Zustand der Hyperinsulinämie kann Jahre bis Jahrzehnte andauern, ehe es zu einem Versagen der ß-Zellen des Pankreas und somit zu einer Hypoinsulinämie kommt. In dieser Arbeit war es Ziel herauszufinden, ob diese lange Zeit herrschende Hyperinsulinämie einen Einfluss auf die menschliche DNA hat. Die Genotoxizität von hohen Insulinkonzentrationen wurde in Hep-G2 Zellen, HT29 Zellen, sowie primären humanen peripheren Lymphozyten mithilfe des Comet Assays und des Mikrokerntests nachgewiesen. Oxidativer Stress bzw. dessen Reduzierung durch Antioxidantien und Inhibitoren wurde in HT29 Zellen mithilfe der DHE-Färbung detektiert. Diese Arbeit belegt dass sich Insulin schädigend auf das menschliche Genom in vitro auswirken kann. Eine besondere Relevanz haben die durchgeführten Experimente mit primären menschlichen Lymphozyten. Denn bei ihnen handelt es sich um Zellen, die im Gegensatz zu der auch genutzten humanen Leberkarzinomzelllinie Hep-G2 und der humanen Kolonkarzinomzelllinie HT29 nicht transformiert sind. Eine weitere wesentliche Erkenntnis dieser Arbeit ist, dass schon pathophysiologisch vorliegende Insulinkonzentrationen in der Lage sind Genomschädigungen in vitro zu induzieren. HT29 Zellen zeigten bei Kurzzeitbehandlung mit nur 1nM Insulin eine signifikante Erhöhung der DNA-Schädigung. Bei Langzeitexposition von 6 Tagen konnten schon 0,5nM signifikante DNA-Schäden hervorrufen. Diese durch Insulin hervorgerufenen Schäden könnten, falls sie so auch in vivo entstehen, bei Versagen von Reparaturmechanismen zur Entstehung von Mutationen und sich daraus entwickelnden Karzinomen beitragen. Aus diesem Grund war ein weiteres Ziel dieser Arbeit herauszufinden, ob bestimmte Antioxidantien oder Inhibitoren in der Lage sind die Insulin-induzierten Genomschädigungen zu verringern. Hierfür wurde Tempol, Apocynin, Plumbagin, VAS2870, Rotenone, PPP, HNMPA-(AM)3 und Wortmannin genutzt. Tatsächlich sind diese Substanzen in der Lage die durch Insulin hervorgerufene Schädigung zu reduzieren. Die positiven Ergebnisse dieser Arbeit könnten einen ersten Hinweis auf eine mögliche pharmakologische Intervention bei Hyperinsulinämie mit dem Ziel der Senkung des erhöhten Krebsrisikos geben. Eine wichtige Erkenntnis aus den Ergebnissen meiner Arbeit ist, dass die Reduzierung des oxidativen Stresses eine Reduzierung der Genomschädigung bewirkt. Die genutzten Substanzen Apocynin, Tempol, VAS2870 und Rotenone bewirkten in HT29 Zellen eine signifikante Reduzierung des durch Insulin ausgelösten oxidativen Stresses. Um aber genauere Aussagen über Möglichkeiten der Therapie bei Hyperinsulinämie zu treffen, sollten Folgestudien auch in vivo folgen, welche die in dieser Arbeit beschriebenen Effekte bestätigen. N2 - Insulin is an essential hormone in the human body, which is responsible for the reduction of blood glucose concentration, the formation of energy holding compounds, and cell growth. A disease associated with the dysregulation of insulin production is diabetes mellitus. For this work, the type 2 of the disease plays an important role. Patients with this type of diabetes mellitus gradually develop an insulin resistance, which is initially characterized by a compensatory overproduction of insulin. This state of hyperinsulinemia may last years or even decades, before it comes to a break-down of the beta cells of the pancreas, and hence to a hypoinsulinemia. The target of this study was to evaluate, whether these long term lasting hyperinsulinemia has an impact on human DNA. The genotoxicity of high insulin concentrations was detected in HepG2 cells, HT29 cells as well as primary human peripheral lymphocytes, using the comet assay and the micronucleus test. Oxidative stress and it´s reduction by antioxidants and inhibitors was detected in HT29 cells using the DHE staining. This work shows that insulin may damage the human genome in vitro. A special relevance show experiments carried out with primary human lymphocytes. Because these are not transformed like the human liver carcinoma cell line HepG2, and the human colon carcinoma cell line HT29, also studied. Another significant finding of this study is, that even pathophysiologically present insulin concentrations are capable to damage the genome in vitro. HT29 cells showed a significant increase in DNA damage when short-term treated with only 1nM insulin. After long-term exposure of 6 days already 0.5nM were capable to significantly damage DNA. This induced insulin damage could, if also occurring in vivo, contribute to the development of mutations and carcinomas, if mechanisms of repairs are failing. A further aim of this study was therefore to check whether certain antioxidants or inhibitors would be capable of reducing insulin-induced genome damages. For this Tempol, Apocynin, Plumbagin, VAS2870, Rotenone, PPP, HNMPA-(AM)3 and Wortmannin were used. In fact, these substances are capable to reduce the damage caused by insulin. The positive results of this work could be a first indication of a possible pharmacological intervention against hyperinsulinemia with the aim of lowering stringent cancer risk. An important conclusion of the results of my work is that reduction of oxidative stress results in a reduction of genome damage. The substances used, Apocynin, Tempol, VAS2870 and Rotenone, caused a significant reduction of insulin-induced oxidative stress, in HT29 cells. In order to make more detailed statements about possibilities of hyperinsulinemia therapy, follow-up studies in vivo are required which would back-up the findings of this study. KW - Insulin KW - Genotoxizität KW - Hyperinsulinämie Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-131986 ER - TY - THES A1 - Link, Samuel T1 - Aldosteron-vermittelte oxidative Nierenschädigung – Einfluss der antioxidativen Abwehr T1 - Aldosterone-dependent oxidative kidney damage – influence of the antioxidative defense N2 - Patienten mit erhöhten Aldosteronspiegeln zeigen eine gesteigerte Inzidenz für Malignome, insbesondere von Nierenzellkarzinomen. Das Ziel dieser Arbeit war es, die Aldosteron-vermittelte oxidative Nierenschädigung näher zu analysieren sowie die auf Zellebene gezeigte Beeinflussung der antioxidativen Schutzmechanismen im lebenden Organismus nachzuweisen und mögliche therapeutische Ansatzpunkte zu identifizieren. Dazu wurde ein Interventions-versuch über 28 Tage durchgeführt. Neben einer Aldosterongabe wurden folgende Interventionen verwendet: Spironolacton zur Blockade des Mineralkortikoid-Rezeptors (MR), Apocynin als Hemmstoff der NADPH-Oxidasen (Nox), L-NAME zur Blockade der NO-Synthasen (NOS), PDTC, einen Hemmstoff des Transkriptionsfaktors NF-kB sowie Sulforaphan, ein natürlicher Nrf2-Induktor. Eine weitere Gruppe erhielt Sulforaphan ohne additive Aldosterongabe. Die Nierenschäden wurden mittels histopathologischer Schädigungsscores und der Anzahl an DNA-Doppelstrangbrüche analysiert. Die Beeinflussung der antioxidativen Abwehr wurde durch die Aktivierung des Transkriptionsfaktors Nrf2 und durch die Quantifizierung antioxidativer Enzyme bestimmt. Im Nierengewebe führte Aldosteron zu einer Zunahme von oxidativem Stress. Histologisch zeigte sich ein Anstieg von glomerulären Schäden. Auch kam es zu einer deutlichen Zunahme von Doppelstrangbrüchen der DNA. Des Weiteren konnten wir zeigen, dass Aldosteron auch in vivo zu einer Zunahme der Nrf2-Aktivität führte, wobei sich dies auf Proteinebene nicht in einer (dauerhaften) Synthesesteigerung von antioxidativen Enzymen wiederspiegelte und keinen ausreichenden Schutz des Nierengewebes bot. Für die Interventionsgruppen konnte keine signifikante Auswirkung auf das Vorliegen von oxidativem Stress gezeigt werden. Dies könnte an der Versuchsdauer bzw. an der gewählten Nachweismethode gelegen haben. Nichtsdestotrotz zeigte die Blockade der Nox durch Apocynin bzw. der NOS durch L-NAME eine effektive Reduktion der histologischen und genomischen Schäden. Die L-NAME-Gruppe wies dabei die höchsten Blutdruckwerte auf, diese waren auch zur Aldosterongruppe signifikant gesteigert. Die beobachteten Effekte waren folglich nicht durch den in der Aldosterongruppe erfolgten Blutdruckanstieg, sondern vielmehr durch den Anstieg von oxidativem Stress zu erklären. Ebenfalls blieb die Nrf2-Aktivität bei der Gabe von Apocynin und L-NAME weitgehend auf Kontrollniveau, was dafürspricht, dass der in der Aldosterongruppe messbare Nrf2-Anstieg am ehesten als Reaktion auf chronisch erhöhten oxidativen Stress erfolgte, welcher durch die Interventionen ausblieb. Die Blockade von NF-κB mittels PDTC führte zu vergleichbaren Effekten wie Apocynin und L-NAME. Das deutet darauf hin, dass Aldosteron über die Aktivierung von NF-κB die vermehrte Synthese von pro-oxidativen Enzymen wie Nox und NOS anregt. Die Gabe von Spironolacton hatte den stärksten protektiven Effekt, sowohl auf histologische Veränderungen als auch auf das Entstehen von DNA-Doppelstrangbrüchen, wobei die Nrf2-Aktivität in dieser Gruppe ebenfalls auf Kontrollniveau blieb. Die Aldosteroneffekte wurden folglich über den MR vermittelt. Eine additive Nrf2-Induktion mittels Sulforaphan konnte auch keinen (dauerhaften) Effekt auf die Synthese antioxidativer Enzyme zeigen. Dennoch zeigte diese Gruppe einen ähnlich effektiven Schutz vor den oxidativen Nierenschäden wie die Gabe von Spironolacton. Vieles spricht dafür, dass die Wirkung von Sulforaphan dabei über seine Wirkung als direktes Antioxidans bzw. Radikalfänger und nicht über den Nrf2-Weg zu erklären ist. Aldosteron führt in der Niere über oxidativen Stress zu glomerulärer Fibrose und DNA-Schäden. Das könnte eine Erklärung für die gesteigerte Inzidenz von Nierenzellkarzinomen in Patienten mit erhöhten Aldosteronspiegeln darstellen. Unsere Ergebnisse sprechen dafür, dass Aldosteron über eine Signalkaskade über den MR zu einer Aktivierung von Nox und NOS führt. Der Aktivierung des Transkriptionsfaktors NF-κB scheint dabei durch die Synthese pro-oxidativer Enzyme eine Art Verstärker-Effekt zuzukommen. Als Reaktion auf den durch Aldosteron gesteigerten oxidativen Stress kommt es zu einer Aktivierung des antioxidativen Transkriptionsfaktors Nrf2, jedoch ohne dass dies zu einem ausreichenden Schutz des Nierengewebes führt. Mögliche therapeutische Ansatzpunkte für einen Schutz vor den durch Aldosteron vermittelten oxidativen Nierenschäden scheinen eher innerhalb der Aldosteronsignalkaskade, insbesondere in der Blockade des MR, als in der antioxidativen Abwehr zu liegen. N2 - Patients with hyperaldosteronism show an increased risk for kidney cancer. It is known that aldosterone leads to oxidative stress and DNA damage through NADPH-Oxidase (Nox) and NO-Synthase (NOS) which could be a possible starting point for mutagenesis. We investigated aldosterone-dependent oxidative damage in rat kidney and the influence of the anti-oxidative pathway regulated by nuclear factor-erythroid-2-related factor 2 (Nrf2). In rats with hyperaldosteronism the following interventions were used: Inhibition of the mineralocorticoid receptor (MR) with spironolactone, blockade of Nox with apocynin, inhibition of NOS by L-NAME, blocking of the proinflammatory transcription factor NF-κB with PTDC and activating of the Nrf2 pathway with sulphoraphane. Mediated by the MR aldosterone led to glomerulosclerosis and vascular remodeling in the kidney. The changes in the glomeruli seemed only partially induced by oxidative stress and were prevented by sulforaphane. Spironolacton, apocynin, L-NAME and PTDC were able to prevent aldosterone-induced vascular remodeling, suggesting that oxidative stress mediated by the MR and influenced by NF-κB seems to play a major role in vascular remodeling. In kidney tissue aldosterone led to an increase in oxidative stress and a clear rise of Nrf2 activation. Protein levels of GCLC, TRX, HO-1 and SOD showed no persistent effects to the changes in Nrf2 activation. Despite the activation of Nrf2 aldosterone led to a clear rise of DNA double-strand breaks in cortex and medulla. The different interventions were all able to reduce the aldosterone-induced DNA damage significantly, with the spironolactone group showing the lowest counts of DNA double-strand breaks. Even though the L-NAME-group showed the highest blood pressure levels it also had reduced DNA damage, proving that the observed effects were independent of increased blood pressure. Sulforaphane led to the strongest Nrf2-activation but was not able to enhance the Nrf2 levels significantly higher than aldosterone. Nonetheless sulforaphane clearly prevented aldosterone-induced DNA-damage, suggesting that sulforaphane acted at least partially as a direct radical scavenger. KW - Aldosteron KW - Oxidativer Stress KW - Antioxidans KW - Spironolacton KW - Hypernephrom KW - Sulforaphane KW - Sulforaphan Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-186037 ER - TY - JOUR A1 - Lohse, Christian A1 - Bock, Andreas A1 - Maiellaro, Isabella A1 - Hannawacker, Annette A1 - Schad, Lothar R. A1 - Lohse, Martin J. A1 - Bauer, Wolfgang R. T1 - Experimental and mathematical analysis of cAMP nanodomains JF - PLoS ONE N2 - In their role as second messengers, cyclic nucleotides such as cAMP have a variety of intracellular effects. These complex tasks demand a highly organized orchestration of spatially and temporally confined cAMP action which should be best achieved by compartmentalization of the latter. A great body of evidence suggests that cAMP compartments may be established and maintained by cAMP degrading enzymes, e.g. phosphodiesterases (PDEs). However, the molecular and biophysical details of how PDEs can orchestrate cAMP gradients are entirely unclear. In this paper, using fusion proteins of cAMP FRET-sensors and PDEs in living cells, we provide direct experimental evidence that the cAMP concentration in the vicinity of an individual PDE molecule is below the detection limit of our FRET sensors (<100nM). This cAMP gradient persists in crude cytosol preparations. We developed mathematical models based on diffusion-reaction equations which describe the creation of nanocompartments around a single PDE molecule and more complex spatial PDE arrangements. The analytically solvable equations derived here explicitly determine how the capability of a single PDE, or PDE complexes, to create a nanocompartment depend on the cAMP degradation rate, the diffusive mobility of cAMP, and geometrical and topological parameters. We apply these generic models to our experimental data and determine the diffusive mobility and degradation rate of cAMP. The results obtained for these parameters differ by far from data in literature for free soluble cAMP interacting with PDE. Hence, restricted cAMP diffusion in the vincinity of PDE is necessary to create cAMP nanocompartments in cells. KW - fluorescence resonance energy transfer KW - yellow fluorescent protein KW - radii KW - adenylyl cyclase signaling cascade KW - cell fusion KW - cytosol KW - isoproterenol KW - absorption KW - cyclic nucleotides such as cyclic adenosine monophosphate Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170972 VL - 12 IS - 4 ER - TY - JOUR A1 - Lohse, M. J. A1 - Böser, S. A1 - Klotz, Karl-Norbert A1 - Schwabe, U. T1 - Affinities of barbiturates for the GABA-receptor complex and A\(_1\) adenosine receptors: A possible explanation of their excitatory effects N2 - The effects of barbiturates on the GABA·receptor complex and the A\(_1\) adenosine receptor were studied. At the GABA-receptor complex the barbiturates inhibited the binding of [\(^{35}\)S]t-butylbicyclophosphorothionate [\(^{35}\)S]TBPT) and enhanced the binding of [\(^3\)H]diazepam. Kinetic and saturation experiments showed that both effects were allosteric. Whereas all barbiturates caused complete inhibition of [\(^{35}\)S]TBPT binding, they showed varying degrees of maximal enhancement of [\(^3\)H]diazepam binding; (±)methohexital was idenafied as the most efficacious compound for this enhancement. At the A\(_1\) adenosine receptor all barbiturates inhibited the binding of [\(^3\)H]N\(^6\)-phenylisopropyladenosine (\(^3\)H]PIA) in a competitive manner. The comparison of the effects on [\(^3\)H]diazepam and [\(^3\)H]PIA binding showed that excitatory barbiturates interact preferentially with the A\(_1\) adenosine receptor, and sedative/anaesthetic barbiturates with the GABA-receptor complex. It is speculated that the interaction with these two receptors might be the basis of the excitatory versus sedative/ anaesthetic properties of barbiturates. KW - Toxikologie KW - GABA-receptor complex KW - Adenosine receptors KW - Barbiturates Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60250 ER - TY - JOUR A1 - Lohse, M. J. A1 - Elger, B. A1 - Lindenborn-Fotinos, J. A1 - Klotz, Karl-Norbert A1 - Schwabe, U. T1 - Separation of solubilized A\(_2\) adenosine receptors of human platelets from non-receptor [\(^3\)H]NECA binding sites by gel filtration N2 - Human platelet membranes were solubilized with the zwitterionic detergent CHAPS (3-[3-(cholamidopropyl)dimethylammonio]- 1-propanesulfonate) and the solubilized extract subjected to gel ftltration. Binding of the adenosine receptor agonist [\(^3\)H]NECA (5'-N-ethylcarboxamidoadenosine) was measured to the eluted fractions. Two [\(^3\)H]NECA binding peaks were eluted, the first of them with the void volume. This first peak represented between 10% and 25% of the [\(^3\)H]NECA binding activity eluted from the column. It bound [\(^3\)H]NECA in a reversible, saturable and GTPdependent manner with an affinity of 46 nmol/1 and a binding capacity of 510 fmol/mg protein. Various adenosine receptor ligands competed for the binding of [\(^3\)H]NECA to the frrst peak with a pharmacological proftle characteristic for the A\(_2\) adenosine receptor as determined from adenylate cyclase experiments. In contrast, most adenosine receptor ligands did not compete for [\(^3\)H]NECA binding to the second, major peak. These results suggest that a solubilized A\(_2\) receptor-Gs protein complex of human platelets can be separated from other [\(^3\)H]NECA binding sites by gel filtration. This allows reliable radioligand binding studies of the A2 adenosine receptor of human plate1ets. KW - Toxikologie KW - A2 Adenosine receptor KW - Human platelets KW - Radioligand binding KW - Adenylate cyclase Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60309 ER - TY - CHAP A1 - Lohse, M. J. A1 - Klotz, K.-N. A1 - Schwabe, U. A1 - Christalli, G. A1 - Vittori, S. A1 - Grifantini, M. T1 - Pharmacology and Biochemistry of Adenosine Receptors N2 - Adenosine modulates a variety of physiological functions via membrane-bound receptors. These receptors couple via G proteins to adenylate cyclase and K+channels. The A1 subtype mediates an inhibition of adenylate cyclase and an opening of K+-channels, and the A2 subtype a Stimulation of adenylate cyclase. Both subtypes have been characterized by radioligand binding. This has facilitated the development of agonists and antagonists with more than 1000-fold A1 selectivity. A1-selective photoaffinity labels have been used for the biochemical characterization of A1 receptors and the study of their coupling to adenylate cyclase. Such selective ligands allow the analysis of the involvement of adenosine receptors in physiological functions. Selective interference with adenosine receptors provides new pharmacological tools and eventually new therapeutic approaches to a number of pathophysiological states. KW - Adenosinrezeptor KW - Pharmakologie KW - Toxikologie Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86251 ER - TY - JOUR A1 - Lohse, M. J. A1 - Klotz, K.-N. A1 - Ukena, D. A1 - Schwabe, U. T1 - Characterization of \([^3H]\)Phenobarbital Binding to Rat Brain Membranes JF - Neuroscience Letters N2 - The binding of \([^3H]\)phenobarbital to rat brain membranes was studied in order to determine its characteristics and specificity. The binding reaction was rapid and occurred at sites of low affinity. \((K_d = 700 μM)\) and very high density \((B_{max} = 2.7 nmoll/mg protein)\). It was unaffected by temperature changes from O°C to 95°C and was maximal at pH 5. Detergents in low concentrations markedly decreased the binding, apparently without solubilizing the binding sites. It is concluded that the binding of \([^3H]\) phenobarbital is a rather non-specific interaction with the plasma membrane. KW - barbiturates KW - radioligand binding KW - rat brain membranes Y1 - 1984 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127894 VL - 52 ER - TY - JOUR A1 - Lohse, M. J. A1 - Klotz, Karl-Norbert A1 - Diekmann, E. A1 - Friedrich, K. A1 - Schwabe, U. T1 - 2',3'-Dideoxy-N\(^6\)-cyclohexyladenosine: an adenosine derivative with antagonist properties at adenosine receptors N2 - Tbe 2',3'-dideoxy analogue of the potent A\(_1\) receptor agonist, N\(^6\)-cyclohexyladenosine (CHA), was synthesized as a potential antagonist for the A\(_1\) adenosine receptor. In sturlies on adenylate cyclase 2',3'-dideoxy-N\(^6\)-cyclohexyladenosine (ddCHA) did not show agonist properties at A\(_1\) or at A\(_2\) receptors. However, it antagonized the inhibition by R-PIA of adenylate cyclase activity of fat cell membranes via A\(_1\) receptors with a K\(_i\) value of 13 \(\mu\)M. ddCHA competed for the binding of the selective A1 receptor antagonist, [\(^3\) HJ8-cyclopentyl-1,3-dipropylxantbine ([\(^3\)H]DPCPX), to rat brain membranes with a K\(_i\) value of 4.8 \(\mu\)M; GTP did not affect the competition curve. In contrast to the marked stereoselectivity of the A\(_1\) receptor for the cx- and the natural ß-anomer of adenosine, the cx-anomer of ddCHA showed a comparable affinity for the A\(_1\) receptor (K\(_i\) value 13.9 \8\mu\)M). These data indicate that the 2'- and 3'-hydroxy groups of adenosine and its derivatives are required foragonist activity at and high affinity binding to A\(_1\) adenosine receptors and for the distinction between the cx- and ß-forms. KW - Toxikologie KW - Adenosine receptors KW - Adenylate cyclase KW - Adenosine receptor antagonists Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60282 ER - TY - JOUR A1 - Lohse, M. J. A1 - Klotz, Karl-Norbert A1 - Jakobs, K. H. A1 - Schwabe, U. T1 - Barbiturates are selective antagonists at A\(_1\) adenosine receptors N2 - Barbiturates in pharmacologically relevant . concentrations inhibit binding of (R)-\(N^6\)-phenylisopropyl[\(^3\)H]adenosine ([\(^3\)H]PIA) to solubilized A\(_1\) adenosine receptors in a concentration-dependent, stereospecific, and competitive manner. K\(_i\) values are similar to those obtained for membrane-bound receptors and are 31 \(\mu\)M for ( ± )-5-(1 ,3-dimethyl)-5-ethylbarbituric acid [( ± )DMBB] and 89 \(\mu\)M for ( ± )-pentobarbital. Kinetic experiments demoostrate that barbiturates compete directly for the binding site of the receptor. The inhibition of rat striatal adenylate cyclase by unlabelled (R)-\(N^6\)-phenylisopropyladenosine [(R)-PIA] is antagonized by barbiturates in the same concentrations that inhibit radioligand binding. The Stimulation of adenylate cyclase via A\(_2\) adenosine receptors in membranes from NIE 115 neuroblastoma cells is antagonized only by 10-30 times higher concentrations of barbiturates. lt is concluded that barbiturates are selective antagonists at the A1 receptor subtype. In analogy to the excitatory effects of methylxanthines it is suggested that A\(_1\) adenosine receptor antagonism may convey excitatory properties to barbiturates. Key Words: Adenosine receptors-Barbiturates - Adenylate cyclase-Receptor solubilization-[3H]PIA binding-N1E 115 cells. Lohse M. J. et al. Barbiturates are selective antagonists at A1 adenosine receptors. KW - Toxikologie KW - adenosine receptors KW - barbiturates KW - adenylate cyclase KW - receptor solubilization KW - N1E 115 cells KW - [3H]PIA binding Y1 - 1985 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60187 ER - TY - JOUR A1 - Lohse, M. J. A1 - Klotz, Karl-Norbert A1 - Lindenborn Fotinos, J. A1 - Reddington, M. A1 - Schwabe, U. A1 - Olsson, R. A. T1 - 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX) - a selective high affinity antagonist radioligand for A\(_1\) adenosine receptors N2 - The properties of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX) as an antagonist ligand for A\(_1\) adenosirre receptors were examined and conipared with other radioligands for this receptor. DPCPX competitively antagonized both the inhibition of adenylate cyclase activity via A\(_1\) adenosirre receptors and the stimulationvia A\(_2\) adenosirre receptors. The K\(_i\)-values of this antagonism were 0.45 nM at the A\(_1\) receptor of rat fat cells, and 330 nM at the A\(_2\) receptor of human platelets, giving a more than 700-fold A\(_1\)-selectivity. A similar A\(_1\)-selectivity was determined in radioligand binding studies. Even at high concentrations, DPCPX did not significantly inhibit the soluble cAMPphosphodiesterase activity of human platelets. [\(^3\)H]DPCPX (105 Ci/mmol) bound in a saturable manner with high affinity to A\(_1\) receptors in membranes of bovine brain and heart, and rat brain and fat cells (K\(_D\) -values 50-190 pM). Its nonspecific binding was about 1% of total at K\(_D\) , except in bovine myocardial membranes (about 10%). Binding studies with bovine myocardial membranes allowed the analysis of both the high and low agonist affinity states of this receptor in a tissue with low receptor density. The binding properties of [\(^3\)H]DPCPX appear superior to those of other agonist and antagonist radioligands for the A\(_1\) receptor. KW - Toxikologie KW - Adenosine receptors KW - Adenylate cyclase KW - Phosphodiesterase KW - Xanthines KW - Radioligands Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60246 ER - TY - JOUR A1 - Lohse, M. J. A1 - Klotz, Karl-Norbert A1 - Schwabe, U. A1 - Cristalli, G. A1 - Vittori, S. A1 - Grifantini, M. T1 - 2-Chloro-N\(^6\)-cyclopentyladenosine: a highly selective agonist at A\(_1\) adenosine receptors N2 - 2-Chloro-N\(^6\)-cyclopentyladenosine (CCPA) was synthesized as a potential high affinity ligand for At adenosine receptors. Binding of [\(^3\)H]PIA to A1 receptors of rat brain membranes was inhibited by CCP A with a Ki-value of 0.4 nM, compared to a Ki-value of 0.8 nM for the parent compound N\(^6\)-cyclopentyladenosine (CPA). Binding of [\(^3\)H]NECA to A\(_2\) receptors of rat striatal membranes was inhibited with a Ki-value of 3900 nM, demonstrating an almost 10,000-fold A\(_1\)-selectivity of CCPA. CCP A inhibited the activity of rat fat cell membrane adenylate cyclase, a model for the A\(_1\) receptor, with an IC\(_{50}\)-value of 33 nM, and it stimulated the adenylate cyclase activity of human platelet membranes with an EC\(_{50}\)-value of 3500 nM. The more than 100-fold A\(_1\)-selectivity compares favourably with a 38-fold selectivity of CPA. Thus, CCPA is an agonist at A\(_1\) adenosine receptors with a 4-fold higher selectivity and 2-fold higher affinity than CPA, and a considerably higher selectivity than the standard At receptor agonist R-N\(^6\) -phenylisopropyladenosine (R-PIA). CCP A represents the agonist with the highest selectivity for A\(_1\) receptors reported so far. KW - Toxikologie KW - Adenosine receptors KW - Adenylate cyclase Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60279 ER - TY - JOUR A1 - Lohse, M. J. A1 - Maurer, K. A1 - Klotz, Karl-Norbert A1 - Schwabe, U. T1 - Synergistic effects of calcium-mobilizing agents and adenosine on histamine release from rat peritoneal mast cells N2 - 1 Adenosine and its metabolically stable analogue N.etbyl-carboxamidoadenosine (NECA) enhance histamine release from rat peritoneal mast cells when tbese are stimulated by calciummobilizing agents. NECA and adenosine shift the concentration-response curve of tbe calcium ionophore A23187 to lower concentrations. 2 The potencies of NECA or adenosinein enhancing A23187-induced histamine release are dependent on the Ievel of stimulated release in tbe absence of adenosine analogues. At high Ievels of release their potencies are up to 20 times higher than at low Ievels. Consequently, averaged concentration-response curves of adenosine and NECA for enhancing bistamine release are shallow. 3 The adenosine transport blocker S-(p-nitrobenzyl)-6-thioinosine (NBTI) has no effect by itself at low Ievels of stimulated histamine release, but abolishes the enhancing effect of adenosine. At high Ievels of release, however, NBTI alone enhances the release of histamine. 4 lt is concluded that adenosine and calcium reciprocally enhance the sensitivity of the secretory processes to the effects of the other agent. The Ievels of intracellular adenosine obtained by trapping adenosine inside stimulated mast cells are sufficient to enhance histamine release substantially, suggesting that this effect may play a physiological and pathophysiological role. KW - Toxikologie Y1 - 1989 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60346 ER - TY - CHAP A1 - Lohse, Martin J. A1 - Klotz, Karl-Norbert A1 - Maurer, K. A1 - Ott, I. A1 - Schwabe, Ulrich T1 - Effects of adenosine on mast cells N2 - No abstract available KW - Adenosin KW - Mastzelle Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86101 ER - TY - JOUR A1 - Lohse, Martin J. A1 - Klotz, Karl-Norbert A1 - Salzer, Manfred J. A1 - Schwabe, Ulrich T1 - Adenosine regulates the \(Ca^{2+} \) sensitivity of mast cell mediator release : (histamine secretion/inositol phosphates/calcium) JF - Proceedings of the National Academy of Sciences of the United States of America N2 - Mast cells release histamine and other mediators of allergy in response to stimulation of their IgE receptors. This release is generally thought to be mediated by an elevation of cytosolic \(Ca^{2+}\). Recent evidence suggests that there might be factors that modulate the coupling between \(Ca^{2+}\) levels and mediator release. The present report identifies adenosine as one such modulator. Adenosine and several of its metabolically stable analogues were shown to enhance histamine release from rat peritoneal mast cells in response to stimuli such as concanavalin A. Metabolizing endogenous adenosine with adenosine deaminase dampened the response to stimuli, whereas trapping endogenous adenosine inside mast cells with nucleoside-transport inhibitors markedly enhanced stimulated histamine release. The metabolically stable adenosine analogue 5' -(N-ethylcarboxamido)adenosine (NECA) did not affect the initial steps in the sequence from IgE-receptor activation to mediator release, which are generation of inositol trisphosphate and increase of cytosolic \(Ca^{2+}\). However, NECA did enhance the release induced in ATP-permeabilized cells by exogenous \(Ca^{2+}\), but it had no effect on the release induced by phorbol esters. These data suggest that adenosine sensitizes mediator release by a mechanism regulating stimulus-secretion coupling at a step distal to receptor activation and second-messenger generation. Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-127883 VL - 85 ER - TY - JOUR A1 - Lohse, Martin J. A1 - Klotz, Karl-Norbert A1 - Schwabe, Ulrich T1 - Mechanism of A2 adenosine receptor activation. I. Blockade of A2 adenosine receptors by photoaffinity labeling N2 - It has previously been shown that covalent incorporation of the photoreactive adenosine derivative (R)-2-azido-N6-p-hydroxyphenytisopropyladenosine [(R)-AHPIA] into the A, adenosine receptor of intact fat cells leads to a persistent activation of this receptor, resulting in a reduction of celular cAMP Ieveis [Mol. Pharmacol. 30:403-409 (1986)]. In contrast, covalent incorporation of (R)-AHPIA into human platelet membranes, which contain only stimulatory A2 adenosine receptors, reduces adenytate cyclase Stimulation via these receptors. This effect of (R)-AHPIA is specific for the A2 receptor and can be prevented by the adenosine receptor antagonist theophylline. Binding studies in-dicate that up to 90% of A2 receptors can be blocked by photoincorporation of (R)-AHPIA. However, the remaining 10-20% of A2 receptors are sufficient to mediate an adenylate cyclase Stimulation of up to SOOk of the control value. Similarly, the activation via these 10-20% of receptors occurs with a halflife that is only 2 times Ionger than that in control membranes. This indicates the presence of a receptor reserve, with respect to both the extent and the rate of adenytate cyclase Stimulation. These observations require a modification of the models of receptor-adenytate cyclase coupling, which is described in the accompanying paper [Mol. Pharmacol. 39:524-530 (1991)]. KW - Adenosinrezeptor Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86073 ER - TY - CHAP A1 - Lohse, Martin J. A1 - Klotz, Karl-Norbert A1 - Schwabe, Ulrich T1 - Effects of barbiturates on A1 adenosine receptors of rat brain N2 - Barbiturates inhibit binding of radioligands to A 1(Ri) adenosine receptors of rat brain membranes. This inhibition is dose-dependent and stereospecific and occurs in the range of pharmacologically active concentrations. The displacement of radiolabelled A1antagonists by barbiturates is not modified by GTP, indicating that barbiturates might act as antagonists at this receptor. This action of barbiturates does not seem to be related to the binding of barbiturates to plasma membranes, as the latter process has different characteristics. Barbiturates also inhibit the binding of radioligands to solubilized A1receptors, and saturation and kinetic experiments suggest that this is due to a competitive antagonism. These results indicate that barbiturates interact with the recognition site of the A1adenosine receptor. KW - Barbiturat KW - Adenosinrezeptor KW - Ratte Y1 - 1985 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-70100 ER - TY - CHAP A1 - Lohse, Martin J. A1 - Klotz, Karl-Norbert A1 - Schwabe, Ulrich T1 - Functional characterization of A1 adenoosine receptors by photoaffinity labelling N2 - The ligand-binding subunit ofthe A1 adenosine receptor has been identified in membranes with the photoaffinity Iabel R-2-azido-N6-p-hydroxyphenylisopropyladenosine (R-AHPIA). Covalent labelling ofthe A1 receptor can also be achieved in intact cells. The dissociation of the radioiodinated label (1251-AHPIA) from isolated rat fat cells was incomplete after UV irradiation, leaving about 20°/o of irreversible specific binding. Such covalent labelling of the receptor led to a concentration-dependent reduction of cellular cyclic AMP levels. This persistent effect of covalent labeHing occurred with an IC50 value of 9 nM, as compared to an IC50 value of 0.9 nM for the direct reduction of cyclic AMP Ievels by the ligand. The difference in the IC5o values can be explained by assuming spare receptors. This hypothesis was verified in binding studies using [ 3HJPIA as a radioligand. R-AHPIA inhibited binding of [3H)PIA to intact fat cells with a K1 value of about 20 nM, which is about 20 tim es high er than the corresponding IC50 value of cyclic AMP reduction. These data show that the A1 receptor is activated according to the occupancy theory. The high sensitivity of the activation in intact ceJis is due to a large number of spare receptors. KW - Adenosinrezeptor Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86097 ER - TY - JOUR A1 - Lohse, Martin J. A1 - Klotz, Karl-Norbert A1 - Schwabe, Ulrich T1 - Effectes of temperature and membrane phase transitions on ligand binding to a2-receptors of human platelets N2 - The binding of agonists and antagonists to a2-adrenergic receptors of human platelets was studied. The receptors showed homogeneaus affinities for antagonists but two affinity states for the agonist (-)-epinephrine, which were modulated by guanine nucleotides. Van't Hoffplots of antagonist binding had a break point at about 18° and considerable diversity between 18° and 0°. Agonist binding to both affinity states showed a similar break point; agonist binding to the high affinity state was characterized by a large entropy component compared to the low affinity state. This entropy component was reduced at higher concentrations of sodium, indicating that it may be due to Iiberation of sodium ions. Measurements of the fluorescence of 1-anilin-8-naphthalenesulfonate showed thermotropic phase transitions of theplatelet membranes at about 17°. The transition temperature was decreased to about 12° by addition of 1 0 mM octanoic acid. Octanoic acidalso shifted the break points of the van't Hoffplot of antagonist and low affinity agonist binding from 18° to 12°. High affinity agonist binding, however, remained unchanged. It is concluded that agonist-specific thennodynamic characteristics of ligand binding to a2-receptors of human platelets can only be investigated by regarding differences between high and low affinity agonist binding. These differences include an entropy increase upon Iigand binding, which is in part due to enhanced liberation of sodium ions, and a loss of sensitivity to fluidity changes in the outer layer of the plasma membrane. KW - Molekularpharmakologie Y1 - 1986 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86023 ER - TY - JOUR A1 - Lohse, Martin J. A1 - Klotz, Karl-Norbert A1 - Schwabe, Ulrich T1 - Agonist photoaffinity labeling of A1 adenosine receptors: Persistent activation reveals spare receptors N2 - No abstract available. KW - Pharmazie KW - Pharmakologie Y1 - 1986 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-87966 ER - TY - JOUR A1 - Lorenz, Kristina A1 - Rosner, Marsha Rich T1 - Harnessing RKIP to combat heart disease and cancer JF - Cancers N2 - Cancer and heart disease are leading causes of morbidity and mortality worldwide. These diseases have common risk factors, common molecular signaling pathways that are central to their pathogenesis, and even some disease phenotypes that are interdependent. Thus, a detailed understanding of common regulators is critical for the development of new and synergistic therapeutic strategies. The Raf kinase inhibitory protein (RKIP) is a regulator of the cellular kinome that functions to maintain cellular robustness and prevent the progression of diseases including heart disease and cancer. Two of the key signaling pathways controlled by RKIP are the β-adrenergic receptor (βAR) signaling to protein kinase A (PKA), particularly in the heart, and the MAP kinase cascade Raf/MEK/ERK1/2 that regulates multiple diseases. The goal of this review is to discuss how we can leverage RKIP to suppress cancer without incurring deleterious effects on the heart. Specifically, we discuss: (1) How RKIP functions to either suppress or activate βAR (PKA) and ERK1/2 signaling; (2) How we can prevent cancer-promoting kinase signaling while at the same time avoiding cardiotoxicity. KW - RKIP KW - ERK1/2 KW - PKA KW - βAR KW - heart failure KW - cancer Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-262185 SN - 2072-6694 VL - 14 IS - 4 ER - TY - THES A1 - Lotz, Arietta Lucia T1 - Eine in-vitro-Untersuchung des Einflusses von Angiotensin II und Sulforaphan auf die Modulation des oxidativen Stresses anhand der NFκB- und Nrf 2-Aktivität in LLC-PK1 Zellen T1 - The influence of angiotensin II and sulforaphane on the modulation of oxidative stress in vitro based on NFκB and Nrf 2 activity in LLC-PK 1 cells N2 - Ausgangspunkt der Arbeit ist die klinische Beobachtung, dass Patienten mit arteriellem Hypertonus vermehrt Nierenerkrankungen entwickeln. Dabei zeigten sich in der Subgruppenanalyse vor allem erhöhte Inzidenzen der Niereninsuffizienz und der Nierenzellkarzinome. Als möglicher Pathomechanismus steht das Renin-Angiotensin-Aldosteron-System (RAAS-System) im Vordergrund. Dabei wird postuliert, dass erhöhte Angiotensin II-Spiegel zu einem Missverhältnis zwischen den Oxidations- und Reduktionspartnern in der Zelle führen, wodurch sich das oxidative Potential der Zelle ändert, und es vermehrt zur Bildung von Radikalen (ROS) kommt, die meist ungepaarte Elektronen in der Valenzschale oder instabile Verbindungen enthalten, wodurch sie besonders reaktionsfreudig mit Proteinen, Lipiden, Kohlenhydraten und auch der DNA interagieren. In der Folge kommt es zu DNA-Veränderungen in Form von Doppel- oder Einzelstrangbrüchen, DNA-Protein-Crosslinks, Basenmodifikationen und Basenverlusten, wodurch sich ein hohes mutagenes Potential ergibt. Dieser Ansatz zur Pathophysiologie bestätigte sich auch an den hier verwendeten porkinen Nierenzellmodell. Dabei zeigte sich nicht nur eine Veränderung der genomischen Stabilität nach Exposition gegenüber erhöhten Angiotensin II-Spiegeln, sondern auch eine Veränderung der DNA in Abhängigkeit von der Expositionsdauer der Zellen. Als nächster Schritt konnte die Modulation der Transkriptionsfaktoren Nrf 2 und NF-κB durch die Behandlung mit Angiotensin II und Sulforaphan nachgewiesen werden. Bei der Behandlung mit Sulforaphan ließ sich eine Nrf 2-Induktion nachweisen mit vermehrter Expression von antioxidativen und detoxifizierender Enzyme. Weiterhin zeigte sich im Rahmen der Behandlung erniedrigte NF-κB-Level. Bei der Modulation durch Angiotensin II stellte sich zunächst ein signifikant erniedrigtes Level an Nrf 2 in den Zellen dar, das im Verlauf von 24 Stunden anstieg und konsekutiv ließ sich eine maximale Proteinexpression zwischen 24 und 48 Stunden messen. Weiterhin wiesen die Zellen, die mit Angiotensin II behandelt wurden, erhöhte NF-κB Mengen/Zelle auf. Zudem zeigte sich der Einfluss erhöhter Glucosekonzentrationen auf eine progrediente genomischen Instabilität, die Veränderung der Transkriptionsfaktoren mit erhöhter Nrf 2-Induktion und mit Deregulation des Transkriptionsfaktors NF-κB wurde durch die Behandlung mit Sulforaphan nachgewiesen. Aufgrund dieser Rolle in der Tumorgenese sind mittlerweile einige Bestandteile des NF-κB- und des Nrf 2-Signalweges und auch Nrf 2-Aktivatoren wie Sulforaphan wichtige Zielstrukturen für die Entwicklung neuer Medikamente und Therapieoptionen. Besonders zeigt sich hierbei die Wichtigkeit bei Diabetes induzierten kardiovaskulären Folgeschäden mit frühzeitiger medikamentöser Behandlung. N2 - The starting point of this work is the clinical observation that patients with arterial hypertension develop more renal diseases. The subgroup analysis showed an increased incidence of renal insufficiency and renal cell carcinoma. The renin-angiotensin-aldosterone system (RAAS system) has been implicated as a possible pathomechanism. It is postulated that increased angiotensin II levels lead to a mismatch between the oxidation and reduction partners in the cell, which alters the oxidative potential of the cell and results in increased formation of radicals (ROS), most of which contain unpaired electrons in the valence shell or unstable compounds, making them particularly reactive with proteins, lipids, carbohydrates, and DNA. As a result, DNA changes occur in the form of double or single strand breaks, DNA-protein crosslinks, base modifications, and base losses, resulting in a high mutagenic potential. This approach to pathophysiology was also confirmed in the porky kidney cell model. This showed not only a change in genomic stability after exposure to elevated angiotensin II levels, but also a change in DNA depending on the duration of exposure of the cells. Next, modulation of the Nrf 2 and NF-κB transcription factors by angiotensin II and sulforaphane treatment was demonstrated. Treatment with sulforaphane showed Nrf 2 induction with increased expression of antioxidant and detoxifying enzymes. Furthermore, treatment revealed decreased NF-κB levels. When modulated by angiotensin II, cells initially showed a significantly reduced level of Nrf 2, which increased over the course of 24 hours. In addition, cells treated with angiotensin II demonstrated increased NF-κB levels. Moreover, the influence of increased glucose concentrations on progressive genomic instability, the alteration of transcription factors with increased Nrf 2 induction and with deregulation of the transcription factor NF-κB was demonstrated by treatment with sulforaphane. Because of this role in tumorigenesis, some components of the NF-κB and Nrf 2 signaling pathways, as well as Nrf 2 activators such as sulforaphane, are now important targets for the development of new drugs and therapeutic options. The importance of this is particularly evident in diabetes-induced cardiovascular complications with early drug treatment. KW - Oxidativer Stress KW - Angiotensin II KW - Sulforaphan KW - Nrf 2 Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-310573 ER - TY - JOUR A1 - Lutz, Werner K. T1 - Dose-response relationship for chemical carcinogenesis by genotoxic agents N2 - No abstract available KW - Toxikologie Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60766 ER - TY - JOUR A1 - Lutz, Werner K. T1 - Dose-response relationship and low dose extrapolation in chemical carcinogenesis [commentary] N2 - Data supporting various dose-respome relationships in chemical carcinogenesis are summarized. General principles are derived to explain the relationships between exposure dose, JI>NA adduct Ievel, induction of genetic changes, and tumor incidence. Some mechanistic aspects of epigenetic carcinogens (stimulation of ceU division and maldlfl'erentlation) are analyzed in a similar way. In a bomogeneous pnpulation, non-linearities are frequent. They are due to pbenomena of induction or saturation of enzymatic activities and to the multi-step nature of carcinog~: if a carcinogen acce1erates more than one step, the SUperposition of the dose- response curves for the indJvidual steps can result in an exponential relationship. A fourth power of the dose was the maximum seen in animals (fonnaldehyde). At the lowest dose Ievels, a proportionality between dose and tumor induction is postulated independent of the mechanism of action if the carcinogen aceeierotes the endogenous proass responsible for spootaneous tumor formation. Low-dose thresholds are expected only for situations where the carcinogen acts in a way that has no endogenous counterpart. Epidemiologfcal studies in humans show linear dose- response curves in all but two investigations. The difference from the strongly nonlinear slopes ·seen in animal studies could be due to the heterogeneity of the human population: if the individual sensitivity to a carcinogen is governed by a large number of genetic and Iife-style factors, the non-linea.rities will tend to cancel each other out and the dose- response curve becomes 'quasi-linear'. KW - Toxikologie Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60789 ER - TY - JOUR A1 - Lutz, Werner K. T1 - Endogenous genotoxic agents and processes as a basis of spontaneous carcinogenesis N2 - A list ofendogenaus DNA·damaging agents and processes is given. Endogenaus e/ectrophiles are found with the cosubstrates of physiological transfer reactions (S-adenosylrnethionine for methylation, A TP for phosphorylation, NAD\(^+\) for ADP-ribosylation, acetyl CoA for acetylation). Aldehyde groups (glyceraldehyde- 3-phosphate, formaldehyde, open forms of reducing sugars, degradation products of peroxidation) or alkylating degradation products derived from endogenaus nitrose compounds represent additional possibilities. Radical-forming reactions include leakage of the superoxide anion radical from terminal cytochromes and redox cycles, hydroxyl radical formation by the Fenton reaction from endogenaus hydrogen peroxide, and the formation of lipid peroxides. Genetic instability by spontaneaus deaminations and depurinations as well as replicative instability by tautomer errors andin the presence of mutagenic metal ions represent a third important dass of endogenaus genotoxic processes. The postulated endogenaus genotoxicity could form the mechanistic basis for what is called 'spontaneous' tumor incidence and explain the possibility of an increased tumor incidence after treatment of animals with non-genotoxic compounds exhibiting tumor-promoting activity only. Individual differences are expected to be seen also with endogenaus DNA damage. The presence of endogenaus DNA darnage implies that exogenaus DNAcarcinogen adducts give rise to an incremental darnage which is expected to be proportional to the carcinogen dose at lowest Ievels. An increased tumor risk due to exposure to exogenaus genotoxic carcinogens could therefore be assessed in terms of the background DNA damage~ for instance in multiples of the mean Ievel or of the interindividual variability in a population. KW - Toxikologie KW - Endogenous genotoxicity KW - Electrophiles KW - Radicals KW - Genetic instability KW - DNA damage KW - Spontaneous tumours KW - Carcinogen risk Individual susceptibili Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60816 ER - TY - JOUR A1 - Lutz, Werner K. T1 - In vivo covalent binding of organic chemicals to DNA as a quantitative indicator in the process of chemical carcinogenesis N2 - The covalent binding of chemical carcinogens to DNA of mammalian organs is expressed per unit dose, and a 'Covalent-Binding Index', CBI, is defined. CBI for various carcinogens span over 6 orders of magnitude. A similar range is observed for the carcinogenic potency in long-term bioassays on carcinogenicity. For the assessment of a risk from exposure to a carcinogen, the total DN A darnage can be estimated if the actual dose is also accounted for. A detailed description is given for planning and performing a DNA-binding assay. A complete literature survey on DNA binding in vivo (83 compounds) is given with a calculation of CBI, where possible, 153 compounds are listed where a covalent binding to any biological macromolecule has been shown in vivo or in vitro. Recent, so far unpublished findings with aflatoxin Mh macromolecule- bound aflatoxin Bh ·diethylstilbestrol, and 1,2-epithiobutyronitrile are included. A comparison of CBI for rat-liver DNA with hepatocarcinogenic potency reveals a surprisingly good quantitative correlation. Refinements for a DN A-binding assay are proposed. Possibilities and Iimitations in the use of D NA binding in chemical carcinogenesis are discussed extensively. KW - Toxikologie Y1 - 1979 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61122 ER - TY - JOUR A1 - Lutz, Werner K. T1 - Investigation of the potential for binding of di(2-ethylhexyl)phthalate (DEHP) to rat liver DNA in vivo N2 - It was the aim of this investigation to determine whether or not covalent binding of di(2-ethylhexyl) phthalate (DEHP) to rat liver DNA could be a mechanism of action contributing to the observed induction of liver tumors after lifetime feeding of rodents with high doses of DEHP. DEHP radiolabeled in different positionswas administered orally to female F344 rats with or without pretreatment for 4 weeks with 1% unlabeled DEHP in the diet. Livu DNA was isolated after 16 hr and analyzed for radioattivity. Administration of [\(^{14}\)C]carboxylate unabeled DEHP resulted in no measurable DNA radioactivity. With DEHP [\(^{14}\)C]· and [\(^{3}\)H]. labeled in the alcohol moiety as well as with 2-ethyl[1-\(^{14}\)C]hexanol, radioactivity was clearly measurable in the DNA. HPLC analysis of enzyme-degraded DNA relvealed that the normal nucleosides had incorporated radiolabel whereas no radioactivity was detectable in those fractions where the carcinogen-modified nucleoside adducts are expected. A quantitative evaluation of the negative data in terms of a Iimit of detection for a covalent binding Index (CBJ) indicates that covalent interaction with DNA is highly unlikely to be the mode of tumorigenic action of DEHP in rodents. KW - Toxikologie Y1 - 1986 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60957 ER - TY - JOUR A1 - Lutz, Werner K. T1 - Quantitative evaluation of DNA binding data for risk estimation and for classification of direct and indirect carcinogens N2 - Investigation of covalent DNA binding in vivo provided evidence for whether a test substance can be activated to metabolites able to reach and react with DNA in an intact organism. Fora comparison of DNA binding potencies of various compounds tested under different conditions, a normalization of the DNA lesion with respect to the dose is useful. A covalent binding index, CBI = (\(\mu\)mol chemical bound per mol DNA nucleotide )/(mmol chemical administered per kg body weight) can be determined for each compound. Whether covalent DNA binding results in tumor formation is dependent upon additional factors specific to the cell type. Thus far, all compounds which bind covalently to liver DNA in vivo have also proven tobe carcinogenic in a long-term study, although the liver was not necessarily the target organ for tumor growth. With appropriate techniques, DNA binding can be determined in a dose range which may be many orders of magnitude below the dose Ievels required for significant tumor induction in a long-term bioassay. Rat liver DNA bindingwas proportional to the dose of aflatoxin B1 afteroral administration of a dose between 100 \(\mu\)g/kg and 1 ng/kg. The lowest dose was in the range of generat human daily exposures. Demonstration of a lack of liver DNA binding (CBI<0.1) in vivo for a carcinogenic, nonmutagenic compound is a strong indication for an indirect mechanism of carcinogenic action. Carcinogens of this class do not directly produce a change in gene structure or function but disturb a critical biochemical control mechanism, such as protection from oxygen radicals, control of cell division, etc. Ultimately, genetic changes are produced indirectly or accumulate from endogenaus genotoxic agents. The question of why compounds which act via indirect mechanisms are more likely to exhibitanonlinear rangein the dose-response curve as opposed to the directly genotoxic agents or processes is discussed. KW - Toxikologie KW - Chemical carcinogenesis KW - Mechanism of action KW - Quantitative risk assessment KW - Genotoxicity KW - Dose-response relationship KW - Aflatoxin B1 Y1 - 1986 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60967 ER - TY - JOUR A1 - Lutz, Werner K. T1 - Endogenous formaldehyde does not produce detectable DNA-protein crosslinks in rat liver N2 - Formaldehydeis an electrophilic molecule able to crosslink DNA and protein. It has been found to induce tumors in the nasal epithelium in rodents. The safety margin between the maximum tolerated FA concentration in the work place and the concentration found to be tumorigenic in animal studies is very small. Because FA is produced endogenously as a result of a variety of oxidative demethylations, the assessment of the tumor risk from exogenaus FA exposure has tobe related quantitatively to the level of DNA-protein crosslinks induced by endogenaus FA generation. It is reported here that the high level of endogenaus FA formed in the liver after a large dose of methanol or of aminopyrine did not lead to any observable increase in DNA-protein crosslinks. Using positive and negative control data from in vitro incubations of liver homogenate with FA or methanol it is estimated that the endogenous level of DNA damage in the liver must be more than three orders of magnitude below the damage observed at tumorigenic concentrations for the rat nose. The fact that FA is formed endogenously cannot, therefore, be used to claim that exogenous FA merely leads to a negligible increase in DNA damage. KW - Toxikologie Y1 - 1986 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60972 ER - TY - JOUR A1 - Lutz, Werner K. T1 - Dosis-Wirkungs-Beziehungen in der chemischen Kanzerogenese T1 - Dose-response relations in chemical carcinogenesis N2 - Ich habe versucht darzulegen, daß mechanistische Überlegungen zur Extrapolation der Dosis-WirkungsBeziehung herangezogen werden können. Ein nichtlinearer Verlauf ist nicht nur bei den epigenetischen Kanzerogenen wahrscheinlich, sondern auch bei den DNA-bindenden. Echte Schwellen sind aber nur in solchen Fällen zu erwarten, wo kein endogenes Korrelat besteht. Immerhin können auch steile Nichtlinearitäten zu einer drastischen Risikoreduktion führen, so daß die Anstrengungen dahin gehen sollten, die Steigung und den Bereich des überproportionalen Abfalls experimentell zu zeigen. In einer heterogenen Population kann die 0 0- sis-Wirkungs-Kurve zusätzliche "Wellen" bekommen und wird dadurch grundsätzlich flacher. Im Extremfall ergibt sich eine lineare Dosis-Wirkungs-Beziehung unabhängig vom Wirkmechanismus des Kanzerogens. Diese Proportionalität zwischen tiefster Dosis und Effekt wird bei genotoxischen Kanzerogenen aus mechanistischen Gründen schon für eine homogene Population postuliert, doch kann dies in einer heterogenen Population auch bei epigenetischen Kanzerogenen in Frage kommen. KW - Toxikologie Y1 - 1990 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-80046 ER - TY - CHAP A1 - Lutz, Werner K. T1 - Quantitative evaluation of DNA-binding data in vivo for low-dose extrapolations N2 - no abstract available KW - Toxikologie Y1 - 1987 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-80079 ER - TY - CHAP A1 - Lutz, Werner K. T1 - Structural characteristics of compounds that can be activated to chemically reactive metabolites: use for a prediction of a carcinogenic potential N2 - Many mutagens and carcinogens act via covalent interaction of metabolic intermediates with DNA in the target cell. This report groups those structural elements which are often found to form the basis for a metabolism to such chemically reactive metabolites. ~mpounds which are chemically reactive per se and which do not require metabolic activation form group 1. Group 2 compri~es of olefins and aromatic hydrocarbons where the oxidation via an epoxide can be responsible for the generation of reactive species. Aromatic amines, hydrazines, and nitrosamirres form group 3 requiring an oxidation of a nitrogen atom or of a carbon atom in alpha position to a nitrosated amine. Group 4 compounds are halogenated hydrocarbons which can either give rise to radicals or can form an ·olefin (group 2) upon dehydrohalogenation. Group 5 compounds depend upon some preceding enzymatic activity either not available in the target cell or acting on positions in the molecule which are not directly involved in the subsequent formation of electrophilic atoms. Examples for each group are taken from the "List of Chemieals and Irrdustrial Processes Associated with Cancer in Humans" as compiled by the International Agency for the Research on Cancer, and it is shown that 91% of the organic carcinogens would have been detected on the basis of structural elements characteristic for group 1-5. As opposed to this very high sensitivity, the specificity ( the true negative fraction) of using this approach as a short-term test for carcinogenicity is shown to be bad because detoxification pathways have so far not been taken into account. These competing processes are so complex, however, that either only very extensive knowledge about pharmacokinetics, stability, and reactivity will be required or that in vivo systems have to be used to predict, on a quantitative basis, the darnage expected on the DNA. DNA-binding experiments in vivo are presented with benzene and toluene to demonstrate one possible way for an experimental assessment and it is shown that the detoxification reaction at the methyl group available only in toluene gives rise to a reduction by at least a factor of forty for the binding to rat liver DNA. This quantitative approach available with DNA-binding tests in vivo, also allows evaluation as to whether reactive metabolites and their DNA binding are always the most important single activities contributing to the overall carcinogenicity of a chemical. With the example of the livertumor inducing hexachlorocyclohexane isomers it is shown that situations will be found where reactive metabolites are formed and DNA binding in vivo is measurable but where this activity cannot be the decisive mode of carcinogenic action. It is concluded that the lack of structural elements known to become potentially reactive does not guarantee the lack of a carcinogenic potential. KW - Toxikologie KW - Structureactivity relationship KW - Reactive intermediates KW - Metabolic activation KW - DNA Binding KW - Covalent binding index KW - Carcinogens KW - Benzene Y1 - 1984 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-80105 ER - TY - CHAP A1 - Lutz, Werner K. T1 - Dose-response relationships in chemical carcinogenesis: from DNA adducts to tumor incidence N2 - Mechanistic possibilitles responsible for nonlinear shapes of the dose-response relationship in chemical carcinogenesis are discussed. (i) Induction and saturation of enzymatic activation and detoxification processes and of DNA repair affect the relationship between dose and steady-state DNA adduct Ievel; (ii) The fixation of DNA adducts in the form of mutations is accelerated by stimulation of the cell division, for Jnstance due to regenerative hyperplasia at cytotoxic dose Ievels; (iii) The rate of tumor formation results from a superposition of the rates of the individual steps. It can become exponential with dose if more than one step is accelerated by the DNA damage exerted by the genotoxic carcinogen. The strongly sigmoidal shapes often observed for dose-tumor incidence relationships in animal bioassays supports this analysis. A power of four for the dose in the su~linear part of the curve is the maximum observed (formaldehyde). In contrast to animal experiments, epidemiological data ln humans rarely show a slgnificant deviation from linearity. The discrepancy might be explained by the fact that a I arge nu mber of genes contribute to the overall sensitivity of an individual and to the respective heterogeneity within the human population. Mechanistic nonlinearities are flattened out in the presence of genetic and life-style factors which affect the sensitivity for the development of cancer. For a risk assessment, linear extrapolation from the high-dose lncidence to the spontaneaus rate can therefore be approprlate in a heterogeneous population even if the mechanism of action would result in a nonlinear shape of the dose-response curve in a homogeneaus population. KW - aflatoxin B1 KW - 2-acetylaminofluorene KW - DNA KW - adduct KW - covalent KW - binding KW - carcinogen KW - dose KW - extrapolation KW - individual KW - susceptibility KW - heterogeneous population KW - risk KW - tumour Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-71625 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Brändle, E. A1 - Zbinden, G. T1 - Effect of gum Arabic on aminopyrine demethylation in rats N2 - Stimulation of aminopyrine demethylation induced in rats by oral or i.p. administration of phenobarbital was partially inhibited in animals receiving daily treatments of 2 x 200 mg/kg gum Arabic p.o. KW - Toxikologie Y1 - 1978 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61146 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Büsser, M. T. A1 - Sagelsdorff, P. T1 - Potency of carcinogens derived from covalent DNA binding and stimulation of DNA synthesis in rat liver N2 - ~n order to investigate the role of the stimu~ation of ceU division for the initiation (and possi:bly promotion) of live·r tumors by chemical carcinogens, the incorporation of radiolabeUed thymidine into liver DNA was dete:rmined in male rats. Single doses of various level!s of af.latoxin 81, benzidine and carbon tetrachloride (aU known to be genotoxic via DNA binding} did not affect cell division, whereas several hepatoca:rcinogens known not to bind to DNA (alphaHCH, dofibrate, and 2,3;7,8-t!etrachlorodiibenzo~p~dioxin) gave rise to a dosedependent stimulation of Ii ver DNA synthesis within 24 h. An equation combining the infl.uences of mitotic stimu:lation, expressed as dose required to double the contro~ Ievei of DNA synthesis, and DNA binding potency, exp:ressed as t.he Covalent Binding Index, correliated weil with the cardnogenk potency for both dasses of hepatocardnogens. KW - Toxikologie Y1 - 1984 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61026 ER - TY - CHAP A1 - Lutz, Werner K. A1 - Cantoreggi, S. A1 - Velic, I. T1 - DNA binding and stimulation of cell division in the carcinogenicity of styrene 7,8-oxide N2 - [7-3H)Styrene 7,8-oxide was administered by oral gavage to male CD rats at a dose of 1.3 mg/kg. After 4 h, the forestomach was excised, DNA was isolated, purified to constant specific radioactivity and degraded nzymatically to the 3 '-nucleotides. Highperformance liquid chromatography fractions with the normal nucleotides contained most of the radiolabel, but a minute level of adduct label was also detccted. Using the units of the covalent binding index (micromoles adduct per mole DNA nucleotide)/(millimole chemical administered per kilogram body weight), a DNA binding potency of 1.0 was derived. A comparison of the covalent binding indices and carcinogenic potencies of other genotoxic forestarnach carcinogens showed that the tumorigenic activity of styrene oxide is unlikely to be purely genotoxic. Therefore, styrene oxide was compared with 3-tbutylhydroxyanisole (BHA) with respect to stimulation of cell proliferation in the forestomach. Male Fischer 344 rats were treated for four weeks at three dose levels of styrene oxide (0, 137, 275 and 550 mg/kg, three times per week by oral gavage) and BHA (0, 0.5, 1 and 2% in the diet); the highest doses had been reported to result in 84% and 22% carcinomas in the forestomach, respectively. Cell proliferation was assessed by incorporation of bromodeoxyuridine into DNA and immunohistochemical analysis. An increase in the lablling indexwas found in a11 treated animals. In the prefundic region of the forestomach, the labeHing index increased significantly, from 42% (controls) to 54% with styrene oxide and from 41 to 55% with BHA. Rats treated with BHA also had severe hyperplastic lesions in the prefundic region, i.e., at the location of BHA-induced forestomach carcinomas. The number of cells per millimetre of section length was increased up to 19 fold. Hyperplastic lesions were not seen with styrene oxide, despite the higher tumour incidence reported with this compound. We conclude that the carcinogenicity of styrene oxide to the forestomach most probably involves a mechanism in which marginal genotoxicity is combined with promotion by increased cell proliferation. KW - Styrol KW - DNS-Bindung KW - Zellteilung KW - Carcinogenität Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-71597 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Deuber, R. A1 - Caviezel, M. A1 - Sagelsdorff, P. A1 - Friederich, U. A1 - Schlatter, C. T1 - Trenbolone growth promotant: covalent DNA binding in rat liver and in Salmonella typhimurium, and mutagenicity in the Ames test N2 - DNA binding in vivo: (6,7-\(^3\)H]ß-trenbolone (ß-TBOH) was administered p.o. and i.p. to rats. After 8 or 16 h, DNA was isolated from the livers and purified to constant specific radioactivity. Enzymatic digestion to deoxyribonucleotides and separation by HPLC revealed about 90% ofthe DNA radioactivity eluting in the form of possible TBOH-nucleotide adducts. The extent of this genotoxicity, expressed in units of the Covalent Binding Index, CBI = (~mol TBOH bound per mol nucleotide)/(mmol TBOH administered per kg body weight) spanned from 8 t~ 17, i. e. was in the range found with weak genotoxic carcmogens. Ames test: low doses of ß-TBOH increased the number of revertants in Salmonella strain TAl 00 reproducibly and m a dose-dependent manner. The mutagenic potency was 0.2 revertants per nmol after preincubation of the bacteria (20 min at 37° C) with doses between 30 and 60 \(\mu\)g per plate (47 and 94 \(\mu\)g/ml preincubation mixture). Above this dose, the number of revertants decreased to control values, accompanied by a reduction in survival. The addition of rat liver S9 inhibited the mutagenicity. DNA binding in vitro: calf thymus DNA was incubated with tritiated ß-TBOH with and without rat liver S9 Highest DNA radioactivities were determined in the absence of the "activation" system. Addition of inactive S9 (without cofactors) reduced the DNA binding by a factor of up to 20. Intermediate results were found with active S9. DNA binding in Salmonella: ß-TBOH was irreversibly bound to DNA isolated from S. typhimurium TA100 after incubation of bacteria with [\(^3\)H]ß-TBOH. Conclusions: Covalent DNA binding appears to be the mechanism of an activation-independent ("direct") mutagenicity of TBOH which is not easily detected because of the bactericidal activity. The genotoxicity risk arising from exposure of humans to trenbolone residues in meat was estimated using the in vivo data and compared to that from the exposure to unavoidable genotoxins aflatoxin B1 and dimethylnitrosamine. It ts concluded that trenbolone residues represent only a low genotoxic risk. KW - Toxikologie KW - Trenbolone KW - Anabolieagent KW - DNA binding KW - Genotoxicity KW - Ames test KW - Salmonella typhimurium Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60897 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Früh, P. U. A1 - Simon, W. T1 - Microcalorimetric determination of ΔH0, ΔG0 and ΔS0 for the interaction of the carrier antibiotics nigericin and monensin with sodium and potassium ions N2 - The thermodynainic parameters ΔH0, ΔG0 and ΔS0 - and thereby the equilibrium constants - for the complexation of the carrier antibiotics nigericin and monensin with sodium and potassium ions in methanol at 25°C have been determined by microcalorimetry. Tbc results are discussed in terms of the nature of the interaction between ligands and cations. KW - Toxikologie Y1 - 1971 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61218 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Jaggi, W. A1 - Lüthy, J. A1 - Sagelsdorff, P. A1 - Schlatter, C. T1 - In vivo covalent binding of aflatoxin B\(_1\) and aflatoxin M\(_1\) to liver DNA of rat, mouse and pig N2 - [\(^{14}\)C] Aflatoxin B\(_1\) (AFB\(_1\)) was isolated from cultures of Aspergillus parasiticus grown on [1-\(^{114}\)C] sodium acetate. Covalent binding of AFB1 to liver DNA of rat and mouse was determined 6-8 h afteroral administration. The effectiveness of covalent binding, expressedas DNA binding per dose in the units of a 'Covalent Binding Index' (CBI), (\(\mu\)mol aflatoxin/mol DNA nucleotides)/(mmol aflatoxin/kg animal), was found to be 10 400 for rats and 240 for mice. These CBI partly explain the different susceptibility of the two species for the incidence of hepatic tumors. The corresponding values for pig liver DN A, 24 and 48 h after oral administration, were found to be as high as 19 100 and 13 300. DNA-binding has not so far been reported for this species although it could represent an appropriate animal model for studies where a human-like gastrointestinal tract physiology is desirable. Aflatoxin M \(_1\) ( AFM\(_1\)) is a metabolite found in the milk of cows that have been fed AFB\(_1\)-contaminated diet. [\(^{14}\)C] AFM\(_1\) was also found to be produced by cultures of A. parasiticus giving a yield of about 0.3% of the total aflatoxins. A test for covalent binding to rat liver DN A revealed a CBI of 2100 shoWing that AFM\(_1\) must also be regarded as a strong hepatocarcinogen. It is concluded that AFB\(_1\) contaminations should be avoided in dairy feed. KW - Toxikologie Y1 - 1980 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61097 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Jaggi, W. A1 - Schlatter, C. T1 - Covalent binding of diethylstilbestrol to DNA in rat and hamster liver and kidney [Short Communication] N2 - No abstract available KW - Toxikologie KW - Carcinogenesis KW - Covalent binding index - Diethylstilbestrol KW - DNA binching KW - Estrogen KW - Hormone Y1 - 1982 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61066 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Maier, P. T1 - Genotoxic and epigenetic chemical carcinogenesis: one process, different mechanisms N2 - Chemieals that induce cancer in an intact organism are called carcinogens. This term does not differentiale between their various modes of action. In this review, Werner Lutz and Peter Maier make a mechanistic distinction between carcinogens that alter the genetic information and carcinogens that interfere with epigenetic processes. They considercardnogenesis tobe an ongoing, part1y unavoidable process which is based on a succession of mutations, most likely in stem cells, leading to autonomaus cellular growth regulation. Chemical carcinogens either induce such changes through mutations (genotoxic carcinogens) or they aceeierate the accumulation of critica1 spontaneaus mut11tions (epigenetic carcinogens). Examples are given for both classes of carcinogens, and for the processes that act at genoto:tic/nuclear 11nd epigenetic/mitotic Ievels. KW - Toxikologie Y1 - 1988 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60884 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Poetzsch, J. A1 - Schlatter, J. A1 - Schlatter, C. T1 - The real role of risk assessment in cancer risk management N2 - Rtgulatory aclio11s Iaken to reduu tht risk of harmfultffects of exposure to chemieals ofltn arenot commensurDtt with the toxicologicDf risk SJsstS&ment. A numbtr of factors relating to psychology, sociology, economics Dntl politics rather than science and medicine afftct tht final decision. Wemer Lutz and colleagues illustratt the situation using tht feuktmia-indudng chtmiCJJI benzene as an examplt. KW - Toxikologie Y1 - 1991 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60730 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Schlatter, C. T1 - Saccharin does not bind to DNA of liver or bladder in the rat [Short Communication] N2 - No abstract available KW - Toxikologie Y1 - 1977 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61194 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Schlatter, C. T1 - Mechanism of the carcinogenic action of benzene: irreversible binding to rat liver DNA N2 - No abstract available KW - Toxikologie Y1 - 1977 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61208 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Schlatter, C. T1 - A closed inhalation system for pharmacokinetic and metabolism studies of volatile compounds with small laboratory animals N2 - In the inhalation system described an animal can be kept in the same atmosphere of a 2-liter desiccator for up to 24 h. The expired carbon dioxide is adsorbed with soda lime and the resulting reduced pressure is balanced by a supply of oxygen also used for the inflow of the chemical to be investigated. Urine and faeces can be collected ~eparately and the system allows a periodical control of the concentration of the chemical by sampling the air with needle and syringe. KW - Toxikologie Y1 - 1978 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-80145 ER - TY - CHAP A1 - Lutz, Werner K. A1 - Schlatter, C. T1 - Extrapolation of carcinogenicity data to low doses with a dose-response study of the binding of benzo(a)pyrene to rat liver DNA N2 - The binding of tritiated benzo(a)pyrene (BP) to liver DNA of 25 adult male rats (SIV 50) has been determined 50 h after a single intraperitoneal injection of doses between 40 ug/kg and 4; mg/kg. The dose-response relations~ ip is linear up to i mg/kg, shows a sigmoid step towards 2 mg/kg and a shallow linear. slope above that value. TlJe 0 bserved bin ding ranges from 1.7 to 180 nmoles BP per mole DNA phosphate. The non-linearity between 1 and 2 mg/kg could be explained 0):1 the basis of an induction of metabolizing enzymes. A pure1y mathematical extrapolation of therumour incidence from a carcinogenic dose (1 x 40mg/kg for a 20% hepatoma incidence in newborn mice) to human exposure levels (aboilt 0.1 ug/kg per day) would never have followed a step like the on~ found in our experiments. Our dose-effect study therefore shows how carcinogenitity data could be extrapolated in a biologically founded way to low doses. KW - Toxikologie Y1 - 1978 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-80157 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Schlatter, C. T1 - In vivo covalent binding of chemicals to DNA as a short-term test for carcinogenicity N2 - The determination of a covalent binding of radioactive chemieals to DNA in intact mammalian organisms is proposedas a short-term test for carcinogenicity. The effectiveness of covalent binding to rat liver DNA correlates well with the hepatocarcinogenicity known from long-term bioassays. The binding indices range over more than five orders of rriagnitude between the strongest hepatocarcinogen aflatoxin B 1 and the limit of detection of a binding with 100 f-LCi 14C-labelled chemical. The order of magnitude of binding is therefore a surprisingly good quantitative measure for carcinogenicity. The pattern of DNA binding sites is important especially for small alkylating agents where the determination of total binding might indicate a higher carcinogenic potency than is actually observed. KW - DNA KW - DNA-Binding KW - Carcinogen KW - Short-term Carcinogenicity Test KW - Aflatoxin KW - Toluene KW - Tritiated Water Y1 - 1979 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-80127 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Schlatter, J. T1 - Chemical carcinogens and overnutrition in diet-related cancer [commentary] N2 - The intake of known dietary carclnogens was compiled and the cancer risk was estlmated on the basis of carcinogenic potencies in animals as derived from the Carcinogenic Potency Database by Gold and co-workers. The total cancer risk was compared with the number of cancer cases attributed by epidemiologists to dietary factors (one-third of all cancer cases, i.e. -80 000 per one million Jives). Except for alcohol, the known dietary carcinogens could not account for more than a few bundred cancer cases. Tbis was seen both with tbe DNA-reactive carcinogens (beterocyclic aromatic amines, polycyclic aromatic hydrocarbons, N-nitroso compounds, estragole, aflatoxin B., ethyl carbamate, to name the most important factors) as wen as with those carclnogens wbich have not been shown to react with DNA (e.g. caffelc acid and the carcinogeruc metals arsenic and cadmium). Residues and contaminants turned out to be negligible. Among the various pmsibilities to explain the discrepancy we investigated the roJe of ovemutritlon. Dietary restriction in animals is weil known for its strong reducing effect on spontaneous tumor formation. These data can be used to derive a carcinogenic potency for excess macronutrients: tbe tumor incidence seen with the restrlcted animals is taken as a control value and the increased tumor incidence in the animals fed ad libitum is attributed to the additional feed iotake. For excess standard diet in rats, a carcinogenic potency TD50 of 16 glkg/day was deduced from a recent study. Ovemutrition in Switzerland, estimated to be 5.5 kcallkg/day, was converted to excess food (1.9 g/kg/day) and tbe cancer incidence was calculated. The result, 60 000 cancer cases per one million Jives, is provocatively close to the number of cases not explained by the known dietary chemical carcinogens. Mechanistic studies will be required to test our hypothesis and investigate the role of different types of macronutrients in ovemutrition. KW - Toxikologie Y1 - 1992 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-60712 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Schlatter, Josef T1 - The relative importance of mutagens and carcinogens in the diet. N2 - Known mutagens and carcinogens in the dict were compiled and the risk of cancer was estimated on the basis of average exposure Ievels in Switzerland and carcinogenic potencies from rodent bioassays. The analysis showed that, except for a1cohol, the sum of all known dietary carcinogens could only explain a few percent of the cancer deaths attributed by epidemiologists to dietary factors. The discrepancy was explained by a "carcinogenicity" of excess macronutrients. This hypothesis was based on an evaluation of dietary restriction experiments in rats and mice, where a dramatic reducing effect on spontaneaus tumour formation was seen. From these experiments, a "carcinogenic potency" was deduced for food in excess (TD50 approximately 16 g/kg per day). Ovemutrition in Switzerland was converted into excess food intake and the cancer risk estimated on the basis ofthe TD50 value. The resulting risk of60,000 cases per one million lives wou1d aJlow to explain by overnutrition almost all "diet-related" cancer deaths in humans. KW - Medizin Y1 - 1993 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-86311 ER - TY - JOUR A1 - Lutz, Werner K. A1 - Viviant, A. A1 - Schlatter, C. T1 - Nonlinear dose-response relationship for the binding of the carcinogen benzo(a)pyrene to rat liver DNA in vivo N2 - Wlth radioactive compound of high specific activity, the binding of carcinogene to DNA can be measured wlth doses that are ineffective ln long-term studies. The binding of tritiated benzo(a )pyrene to liver DNA of adult male rats has been determined 50 hr after a singie l.p. injection of doses between 40 1'9/kg and 4 mg/kg. The doseresponse relationship is linear up to 1 mg/kg, shows a step towards 2 mg/kg, and gives a shallow linear slope above that value. The observed binding ranges from 1.7 to 180 nmoles benzo(a)pyrene per mole DNA phosphate. The nonlinearity could be due to an induction of metabolizing enzymes. The microsomal aryl hydrocarbon hydroxylase activity increases significantly 24 hr after a single dose of 4 mg/kg and 48 hr after doses of 2 and 4 mg/kg, but no induction Ia found with 1 mg/kg. The binding from an equimolar dose is 35 times lower than the one found on mouse skin DNA and 300 times lower than that of N,Ndlmethylnitrosamine in rat liver. A good correlatlon exiats to the respective tumor formation in long-term studles. KW - Toxikologie Y1 - 1978 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-61179 ER -