@phdthesis{Hoffmann2010,
  author    = {Hoffmann, Dana},
  title     = {Neue Biomarker zum Nachweis von Nierentoxizit{\"a}t},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-48562},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {Der Prozess von der Entdeckung und Entwicklung eines potentiellen Arzneistoffs bis zu dessen Zulassung ist extrem kosten\&\#8208; und zeitintensiv und eine Vielzahl dieser Stoffe kann aufgrund toxischer Nebenwirkungen in pr{\"a}klinischen Studien nicht weiterentwickelt werden. Dabei ist die Niere eines der Hauptziele von Xenobiotika\&\#8208;induzierter Organtoxizit{\"a}t, jedoch ist eine fr{\"u}he Detektion von Nierensch{\"a}den schwierig. Den derzeitig verwendeten klinischen Parameter, wie Blutharnstoff (BUN) und Serumkreatinin fehlt es an Sensitivit{\"a}t und Spezifit{\"a}t, da sie Fremdstoff\&\#8208;induzierte Toxizit{\"a}t meist erst aufzeigen, wenn schon ein erheblicher Teil der Nierenfunktion beeintr{\"a}chtigt ist. Daher ist es notwendig, empfindlichere und zuverl{\"a}ssigere Biomarker zu identifizieren und zu validieren, welche kleinste Nierensch{\"a}digungen fr{\"u}her als traditionelle Parameter erkennen. In den letzten Jahren wurden in der Literatur aber auch von verschiedenen Projekten eine Reihe neuer gen\&\#8208;basierender und Urinbiomarker (Kim\&\#8208;1, Clusterin, Lipocalin\&\#8208;2, Timp\&\#8208;1) identifiziert. Ziel dieser Dissertation war es die Aussagekraft dieser Marker im Vergleich zu traditionellen Endpunkten, einschließlich klinische Chemie und Histopathologie an Gewebe\&\#8208;, Urin\&\#8208; und Serumproben von m{\"a}nnlichen Ratten, welche mit Modellsubstanzen f{\"u}r Nephrotoxizit{\"a}t (Aristolochias{\"a}ure und Gentamicin) oder nephrotoxischen Arzneistoffkandidaten (PredTox Projekt) behandelt wurden, mittels qRT\&\#8208;PCR, Immunhistochemie und ELISA zu untersuchen. Zusammenfassend kann man sagen, dass die Effekte auf Ebene der Gen\&\#8208; und Proteinexpression generell sehr gut mit den histopathologischen Ver{\"a}nderungen korrelieren. Sie konnten meist fr{\"u}her oder in niedrigeren Dosierungen als die traditionellen Nierenmarker BUN und Serumkreatinin detektiert werden. Eine erh{\"o}hte Expression und Exkretion von Kim\&\#8208;1 zeigte sich in allen Studien als eine der fr{\"u}hesten Antworten auf Sch{\"a}digung der proximalen Tubuli und stellt somit den empfindlichsten Biomarker dar. Die erh{\"o}hte Ausscheidung von Clusterin konnte teilweise vor einer ver{\"a}nderten Gen\&\#8208; und Proteinexpression im Gewebe detektiert werden und unterst{\"u}tzen die Verwendung von Clusterin als nicht\&\#8208;invasiven Biomarker. Obwohl eine gesteigerte Exkretion von Lipocalin\&\#8208;2 sehr fr{\"u}h nach Sch{\"a}digung des proximalen Tubulus detektiert werden konnte, ist diese nicht spezifisch f{\"u}r einen Nierenschaden. Dennoch k{\"o}nnte die vermehrte Expression/Ausscheidung von Lipocalin\&\#8208;2 als fr{\"u}he Antwort auf eine Entz{\"u}ndung oder einen Gewebeschaden eine sinnvolle Erg{\"a}nzung der routinem{\"a}ßigen Testung auf Toxizit{\"a}t darstellen. Ebenfalls konnte ein dosis\&\#8208; und zeitabh{\"a}ngiger Konzentrationsanstieg von einem Großteil der potentiellen Biomarker des „WideScreen™ Rat Kidney Toxicity Panels 1 and 2" im Urin beobachtet werden. Da jedoch die potentiellen Biomarker unterschiedliche Empfindlichkeiten besitzen und unter Umst{\"a}nden auch vom Mechanismus der Toxizit{\"a}t von Verbindungen abh{\"a}ngen, erscheint eine Kombination von verschiedenen Biomarkern zur fr{\"u}hzeitigen Erkennung von proximalen Nierensch{\"a}den sowie zur Verlaufskontrolle von Nierenerkrankungen sinnvoll. Durch die einfache Probenahme und leichte Bestimmung ist die Messung der neuen potentiellen Nierenbiomarker im Urin neben der Bestimmung der traditionellen Parameter der klinischen Chemie sowie der Histopathologie sinnvoll f{\"u}r die Identifizierung von Nierensch{\"a}digungen in pr{\"a}klinischen Studien.},
  subject      = {Biomarker},
  language  = {de}
}
@phdthesis{Mueller2012,
  author    = {M{\"u}ller, Stephanie},
  title     = {Identification of early molecular changes associated with Fumonisin B1-induced carcinogenesis in vivo and in vitro},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-71336},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Fumonisin B1 (FB1) is a mycotoxin produced by various Fusarium species and constitutes a major contaminant of maize worldwide. A 2-year carcinogenicity study of the National Toxicology Program (NTP) in Fischer N344 rats showed that male rats were most susceptible to FB1-induced tumor formation in the kidney. Histopathologically, a rare and highly malignant tumor type originating from the proximal tubules of rat kidney with increased potential for invasion and metastasis was identified. However, mechanisms underlying the FB1-induced carcinogenesis in kidneys of male rats are still not clear. Previous studies have shown that FB1-mediated disruption of sphingolipid metabolism via inhibition of ceramide synthase is a primary key event in FB1 toxicity. The disruption of sphingolipid metabolism may cause time- and dose-related changes in the relative balance of various bioactive intermediates. Furthermore, the ability of FB1 to induce renal cell death and subsequent compensatory cell proliferation is well known, but it does not completely explain the invasive growth characteristics and exceptionally high metastatic potential of FB1-induced tumors. Considering the complexity of sphingolipid metabolism and the fact that various sphingolipids (e.g. ceramide, sphingoid bases and their respective 1-phosphates) act on opposing signaling pathways, it is hypothesized that the balance between individual sphingolipids and thus the overall cellular response to FB1 may shift with time and by continuing FB1 exposure, resulting in the disruption of specific cell signaling pathways, which may promote tumor formation in kidney. To identify early FB1-induced gene expression patterns in the kidney, which may be associated with sphingolipid-mediated signaling pathways in cancer, a short-term i.p. study on FB1 in male Sprague Dawley rats was performed and changes in gene expression were analyzed using a qRT-PCR array that comprises 84 relevant genes of 6 pathways pivotally involved in the formation of cancer. Furthermore, apoptosis and cell proliferation as well as changes in specific sphingolipids were investigated in FB1-treated kidneys. As shown by classical histopathology (H\&E) and (immuno)-histochemical staining (TUNEL and BrdU), FB1 caused a time- and dose-dependent increase in tubular apoptosis in the cortex and OSOM of the kidney, which was compensated by the induction of proliferation in the affected areas. HPLC-MS/MS analysis of bioactive sphingolipids demonstrated that FB1 induced a marked elevation of the pro-apoptotic sphingoid bases sphinganine and sphingosine, which paralleled the time- and dose-dependent increase in renal tubular apoptosis. With prolonged exposure to FB1, increased metabolic conversion of the accumulated sphinganine to the sphinganine-1-phosphate, a second messenger with anti-apoptotic and proliferative properties, was observed in kidney. This finding was compliant with the increased regenerative cell proliferation in the cortex and OSOM. In addition to effects on sphingoid bases and their 1-phosphate metabolites, this study, for the first time, demonstrated reduced levels of specific ceramides in rat kidney after FB1 exposure. In particular, C16-ceramide, which is a widespread constituent of membrane-bound complex sphingolipids involved in cell adhesion, was time- and dose-dependently decreased after treatment with FB1. Besides its role as component of the cell membrane, C16-ceramide functions as a signaling molecule for the initiation of apoptosis in response to various stress stimuli. Under conditions of chronic FB1 exposure, a significant reduction in pro-apoptotic C16-ceramide together with markedly increased levels of anti-apoptotic and proliferation-promoting sphingoid base 1-phosphates may thus favor resistance to stress-induced apoptosis and facilitate the survival of abnormal cells with potential to initiate tumor formation. Our study also revealed that early exposure to FB1 resulted in increased expression of a plethora of genes involved in tumor initiation as well as tumor progression. While single FB1 exposure was demonstrated to predominately induce gene expression of proto-oncogenic transcription factors (e.g. Fos, Jun, Myc) and apoptotis-related genes (e.g. members of the tumor-necrosis factor family), repeated exposure resulted in marked upregulation of genes mediating cell survival and cell proliferation (e.g. Bcl-XL, Bcl-2, Nfκb1 and Egfr). Moreover, continued exposure to FB1 initiated increased expression of genes critically involved in tumor migration, adhesion, invasion and metastasis. A close correlation was established between gene expression changes in response to FB1 and known signaling pathways mediated by extracellular or intracellular action of sphingoid base 1-phosphates - bioactive lipids that were markedly increased after FB1 treatment. In particular, genes encoding components of the plasminogen activator system were abundantly upregulated. These mediate invasion and metastasis in response to So1P, and may hence particularly promote the formation of highly aggressive and invasive tumors in kidney as observed after chronic exposure to FB1. Thus, it is conceivable that upregulation of a majority of genes in response to FB1 may be a direct or indirect consequence of increased So1P signaling. Another aim of this study was to identify differences in the organ-specific susceptibility for tumor formation by comparing FB1-mediated effects on apoptosis, cell proliferation, sphingolipids, and selected cancer-related genes in kidney and liver. Collectively, the present results revealed that kidney and liver showed marked differences in several endpoints of FB1 toxicity, which seemed to be primarily associated with their different susceptibility to FB1-mediated alterations in sphingolipid metabolism. The strong correlation between histopathological lesions and alterations in sphingolipid metabolism as well as sphingoid base 1-phosphate accumulation and concomitant S1P receptor expression suggested that tumor formation and progression to highly malignant carcinomas seems to be rather favored in kidney compared to liver. However, genes mostly deregulated by FB1 treatment in kidney (PAI-1, Thbs1 and Itga2) were also found to be induced in liver. To verify FB1-induced gene expression in kidney, normal rat tubular epithelial (NRK-52E) cells were analyzed for FB1-induced expression changes of the same cancer-related genes as in vivo. The results of qRT-PCR analysis revealed that gene expression changes in NRK-52E cells after FB1 treatment strongly correlated with those found in rat kidney and paralleled the marked alterations in sphingolipid metabolism. Furthermore, a good correlation between FB1-induced expression changes of cancer-related genes obtained in vivo and in vitro and those known to be mediated by bioactive sphingoid base 1-phosphates in cancer was established. Moreover, experiments modeling the invasive behavior of NRK-52E cells showed that FB1 may enhance cell invasion, which also correlated with both the increase in invasion- and metastasis-associated genes and bioactive sphingoid base 1-phophates. Importantly, NRK-52E cells basally expressed the S1P receptors S1P2 and S1P3, which are known to be involved in tumor migration and invasion. Since these receptors were also identified as most abundant S1PRs in kidneys of male Sprague Dawley rats, they may present important mediators of gene expression and invasion in response to FB1 in vivo. In summary, FB1-mediated disruption of sphingolipid metabolism and subsequent time- and dose-related increase in intermediates, such as bioactive sphingoid base 1-phosphates, correlate with early changes in genes and signaling pathways that may mediate loss of growth control, replication, evasion of apoptosis, cell motility and invasion, and thus favor renal tumor formation in response to FB1. However, to clarify whether the obtained gene expression changes in cancer-related genes in kidney are specific to the biological action of sphingoid base 1-phosphates and their respective receptors, further mechanistic studies are necessary.},
  subject      = {Nephrotoxizit{\"a}t},
  language  = {en}
}
@phdthesis{Reiser2023,
  author    = {Reiser, Pia},
  title     = {Das Adverse Outcome Pathway (AOP) - Konzept als Grundlage f{\"u}r die Entwicklung mechanistischer tierversuchsfreier Ans{\"a}tze: Eine Fallstudie {\"u}ber Nephrotoxizit{\"a}t initiiert durch rezeptorvermittelte Endozytose und lysosomalen Overload},
  doi       = {10.25972/OPUS-31804},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-318046},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Zur Verbesserung der Pr{\"u}fung und Risikobewertung der zunehmenden Menge von Chemikalien und Arzneimitteln, gilt es neue Alternativen in Form von in vitro Pr{\"u}fmethoden mit mechanistisch relevanten Endpunkten zu finden. Einen solchen Rahmen bietet das konzeptionelle Konstrukt des Adverse Outcome Pathway (AOP)- Konzepts. Es erzeugt auf der Basis bestehenden Wissens einen mechanistischen und kausalen Zusammenhang mit Hilfe von mehreren Schl{\"u}sselereignissen (Key Event [KE]) zwischen einem initierenden molekularen Ereignis (Molecular Initiating Event [MIE]) und einem adversen Effekt (Adverse Outcome [AO]) auf biologischer Ebene. Im Rahmen dieser Arbeit wurde der AOP „Rezeptorvermittelte Endozytose und lysosomaler Overload f{\"u}hren zu Nephrotoxizit{\"a}t" am Zellkulturmodell proximaler Nierentubuluszellen weiterentwickelt. Es wurden in vitro Assays f{\"u}r die Zelllinien RPTEC/TERT1 (Mensch) und NRK-52 E (Ratte) f{\"u}r jedes KE etabliert. In dem AOP wird die Initiierung der Sch{\"a}digung des Nierengewebes durch rezeptorvermittelte Endozytose der Substanzen (MIE) mit folgendem lysosomalem Overload (KE 1) und der lysosomalen Membranruptur (KE 2) beschrieben. Es kommt zur Zellsch{\"a}digung (KE 3) und endet mit einem Schaden auf Organebene (AO). F{\"u}r KE 1 erfolgte die Visualisierung des lysosomal-assoziierten Membranproteins (lysosomal-associated Membranprotein [LAMP]) und in KE 2 die Darstellung der Protease Cathepsin D (CTSD) mittels Immunfluoreszenz. F{\"u}r KE 3 wurden spezifische Toxizit{\"a}tsdaten der Testsubstanzen mit dem CellTiter-Glo® Lumineszenz-Zellviabilit{\"a}tstest generiert. Gew{\"a}hlte Stressoren f{\"u}r den AOP war die Gruppe der Polymyxin-Antibiotika (Polymyxin B, Colistin, Polymyxin B Nonapeptid), das Aminoglykosid Gentamicin, das Glykopeptid Vancomycin sowie Cadmiumchlorid. In Zusammenschau der Ergebnisse der drei KEs war die Rangfolge der Auswirkungen der drei Polymyxin-Derivate {\"u}ber alle KEs konsistent. Polymyxin B erwies sich als aktivste Substanz, w{\"a}hrend Polymyxin B Nonapeptid die geringsten Auswirkungen zeigte. Als Ausblick in weiterf{\"u}hrenden Analysen der Arbeitsgruppe konnten bei Cadmiumchlorid trotz einer signifikanten Zytotoxizit{\"a}t (KE 3) nur geringe Auswirkungen in der LAMPExpression (KE 1) aufgezeigt werden. Des Weiteren erfolgte die Erstellung von Response-Response-Analysen, um mittels vorgeschalteter Schl{\"u}sselereignisse nachfolgende Effekte vorhersagen zu k{\"o}nnen. Projektpartner der Universit{\"a}t Utrecht entwickelten dar{\"u}ber hinaus eine quantitative in vitro in vivo Extrapolation (QIVIVE) mittels eines physiologisch basierten pharmakokinetischen (PBPK) Modells.},
  subject      = {Nephrotoxizit{\"a}t},
  language  = {de}
}