Refine
Has Fulltext
- yes (14)
Is part of the Bibliography
- yes (14)
Year of publication
Document Type
- Journal article (12)
- Doctoral Thesis (2)
Keywords
- consortium (4)
- sphingolipids (4)
- genetic modifiers (3)
- investigators (3)
- common variants (2)
- ovarian cancer (2)
- single-nucleotide polymorphisms (2)
- CD4+ T cells (1)
- CD8+ T cells (1)
- Chemische Synthese (1)
Institute
- Institut für Organische Chemie (8)
- Theodor-Boveri-Institut für Biowissenschaften (5)
- Institut für Humangenetik (4)
- Institut für Virologie und Immunbiologie (4)
- Deutsches Zentrum für Herzinsuffizienz (DZHI) (1)
- Graduate School of Life Sciences (1)
- Institut für Geographie und Geologie (1)
- Institut für Hygiene und Mikrobiologie (1)
- Klinik und Poliklinik für Psychiatrie, Psychosomatik und Psychotherapie (1)
- Lehrstuhl für Tissue Engineering und Regenerative Medizin (1)
- Medizinische Fakultät (1)
- Neurologische Klinik und Poliklinik (1)
EU-Project number / Contract (GA) number
- 223175 (3)
Introduction:
Individuals carrying pathogenic mutations in the BRCA1 and BRCA2 genes have a high lifetime risk of breast cancer. BRCA1 and BRCA2 are involved in DNA double-strand break repair, DNA alterations that can be caused by exposure to reactive oxygen species, a main source of which are mitochondria. Mitochondrial genome variations affect electron transport chain efficiency and reactive oxygen species production. Individuals with different mitochondrial haplogroups differ in their metabolism and sensitivity to oxidative stress. Variability in mitochondrial genetic background can alter reactive oxygen species production, leading to cancer risk. In the present study, we tested the hypothesis that mitochondrial haplogroups modify breast cancer risk in BRCA1/2 mutation carriers.
Methods:
We genotyped 22,214 (11,421 affected, 10,793 unaffected) mutation carriers belonging to the Consortium of Investigators of Modifiers of BRCA1/2 for 129 mitochondrial polymorphisms using the iCOGS array. Haplogroup inference and association detection were performed using a phylogenetic approach. ALTree was applied to explore the reference mitochondrial evolutionary tree and detect subclades enriched in affected or unaffected individuals.
Results:
We discovered that subclade T1a1 was depleted in affected BRCA2 mutation carriers compared with the rest of clade T (hazard ratio (HR) = 0.55; 95% confidence interval (CI), 0.34 to 0.88; P = 0.01). Compared with the most frequent haplogroup in the general population (that is, H and T clades), the T1a1 haplogroup has a HR of 0.62 (95% CI, 0.40 to 0.95; P = 0.03). We also identified three potential susceptibility loci, including G13708A/rs28359178, which has demonstrated an inverse association with familial breast cancer risk.
Conclusions:
This study illustrates how original approaches such as the phylogeny-based method we used can empower classical molecular epidemiological studies aimed at identifying association or risk modification effects.
West African summer monsoon precipitation is characterized by distinct decadal variability. Due to its welldocumented link to oceanic boundary conditions in various ocean basins it represents a paradigm for decadal predictability. In this study, we reappraise this hypothesis for several sub-regions of sub-Saharan West Africa using the new German contribution to the coupled model intercomparison project phase 5 (CMIP5) near-term prediction system.
In addition, we assume that dynamical downscaling of the global decadal predictions leads to an enhanced predictive skill because enhanced resolution improves the atmospheric response to oceanic forcing and landsurface feedbacks. Based on three regional climate models, a heterogeneous picture is drawn: none of the regional climate models outperforms the global decadal predictions or all other regional climate models in every region nor decade. However, for every test case at least one regional climate model was identified which outperforms the global predictions. The highest predictive skill is found in the western and central Sahel Zone with correlation coefficients and mean-square skill scores exceeding 0.9 and 0.8, respectively.
BRCA1-associated breast and ovarian cancer risks can be modified by common genetic variants. To identify further cancer risk-modifying loci, we performed a multi-stage GWAS of 11,705 BRCA1 carriers (of whom 5,920 were diagnosed with breast and 1,839 were diagnosed with ovarian cancer), with a further replication in an additional sample of 2,646 BRCA1 carriers. We identified a novel breast cancer risk modifier locus at 1q32 for BRCA1 carriers (rs2290854, P = 2.7 x 10(-8), HR = 1.14, 95% CI: 1.09-1.20). In addition, we identified two novel ovarian cancer risk modifier loci: 17q21.31 (rs17631303, P = 1.4 x 10(-8), HR = 1.27, 95% CI: 1.17-1.38) and 4q32.3 (rs4691139, P = 3.4 x 10(-8), HR = 1.20, 95% CI: 1.17-1.38). The 4q32.3 locus was not associated with ovarian cancer risk in the general population or BRCA2 carriers, suggesting a BRCA1-specific association. The 17q21.31 locus was also associated with ovarian cancer risk in 8,211 BRCA2 carriers (P = 2 x 10(-4)). These loci may lead to an improved understanding of the etiology of breast and ovarian tumors in BRCA1 carriers. Based on the joint distribution of the known BRCA1 breast cancer risk-modifying loci, we estimated that the breast cancer lifetime risks for the 5% of BRCA1 carriers at lowest risk are 28%-50% compared to 81%-100% for the 5% at highest risk. Similarly, based on the known ovarian cancer risk-modifying loci, the 5% of BRCA1 carriers at lowest risk have an estimated lifetime risk of developing ovarian cancer of 28% or lower, whereas the 5% at highest risk will have a risk of 63% or higher. Such differences in risk may have important implications for risk prediction and clinical management for BRCA1 carriers.
Introduction: Several common alleles have been shown to be associated with breast and/or ovarian cancer risk for BRCA1 and BRCA2 mutation carriers. Recent genome-wide association studies of breast cancer have identified eight additional breast cancer susceptibility loci: rs1011970 (9p21, CDKN2A/B), rs10995190 (ZNF365), rs704010 (ZMIZ1), rs2380205 (10p15), rs614367 (11q13), rs1292011 (12q24), rs10771399 (12p11 near PTHLH) and rs865686 (9q31.2).
Methods: To evaluate whether these single nucleotide polymorphisms (SNPs) are associated with breast cancer risk for BRCA1 and BRCA2 carriers, we genotyped these SNPs in 12,599 BRCA1 and 7,132 BRCA2 mutation carriers and analysed the associations with breast cancer risk within a retrospective likelihood framework.
Results: Only SNP rs10771399 near PTHLH was associated with breast cancer risk for BRCA1 mutation carriers (per-allele hazard ratio (HR) = 0.87, 95% CI: 0.81 to 0.94, P-trend = 3 x 10\(^{-4}\)). The association was restricted to mutations proven or predicted to lead to absence of protein expression (HR = 0.82, 95% CI: 0.74 to 0.90, P-trend = 3.1 x 10\(^{-5}\), P-difference = 0.03). Four SNPs were associated with the risk of breast cancer for BRCA2 mutation carriers: rs10995190, P-trend = 0.015; rs1011970, P-trend = 0.048; rs865686, 2df P = 0.007; rs1292011 2df P = 0.03. rs10771399 (PTHLH) was predominantly associated with estrogen receptor (ER)-negative breast cancer for BRCA1 mutation carriers (HR = 0.81, 95% CI: 0.74 to 0.90, P-trend = 4 x 10\(^{-5}\)) and there was marginal evidence of association with ER- negative breast cancer for BRCA2 mutation carriers (HR = 0.78, 95% CI: 0.62 to 1.00, P-trend = 0.049).
Conclusions: The present findings, in combination with previously identified modifiers of risk, will ultimately lead to more accurate risk prediction and an improved understanding of the disease etiology in BRCA1 and BRCA2 mutation carriers.
Single Nucleotide Polymorphisms (SNPs) in genes involved in the DNA Base Excision Repair (BER) pathway could be associated with cancer risk in carriers of mutations in the high-penetrance susceptibility genes BRCA1 and BRCA2, given the relation of synthetic lethality that exists between one of the components of the BER pathway, PARP1 (poly ADP ribose polymerase), and both BRCA1 and BRCA2. In the present study, we have performed a comprehensive analysis of 18 genes involved in BER using a tagging SNP approach in a large series of BRCA1 and BRCA2 mutation carriers. 144 SNPs were analyzed in a two stage study involving 23,463 carriers from the CIMBA consortium (the Consortium of Investigators of Modifiers of BRCA1 and BRCA2). Eleven SNPs showed evidence of association with breast and/or ovarian cancer at p<0.05 in the combined analysis. Four of the five genes for which strongest evidence of association was observed were DNA glycosylases. The strongest evidence was for rs1466785 in the NEIL2 (endonuclease VIII-like 2) gene (HR: 1.09, 95% CI (1.03-1.16), p = 2.7x10(-3)) for association with breast cancer risk in BRCA2 mutation carriers, and rs2304277 in the OGG1 (8-guanine DNA glycosylase) gene, with ovarian cancer risk in BRCA1 mutation carriers (HR: 1.12 95% CI: 1.03-1.21, p = 4.8x10(-3)). DNA glycosylases involved in the first steps of the BER pathway may be associated with cancer risk in BRCA1/2 mutation carriers and should be more comprehensively studied.
Die Zelle stellt die kleinste Einheit des Lebens dar und zeichnet sich durch die hoch koordinierte Anordnung von mehreren Millionen (Bio-)Molekülen zu einem mikrometergroßen Objekt aus. Als struktureller Bestandteil der Lipiddoppelschicht eukaryotischer Zellen spielt neben Sterolen und Glycerolipiden die Verbindungsklasse der Sphingolipide eine zentrale Rolle bei der Aufrechterhaltung der Membranintegrität.[472] Darüber hinaus sind bioaktive Sphingolipide bei vielen grundlegenden zellulären Prozessen wie Apoptose, Wachstum, Differenzierung, Migration und Adhäsion entscheidend beteiligt.[87,120] Ein gestörtes Gleichgewicht des Sphingolipidmetabolismus und Defekte der entsprechenden Stoffwechselwege stehen im Zusammenhang mit vielen Krankheiten wie Krebs, Diabetes, Adipositas, Arteriosklerose, chronischen Entzündungen und Autoimmunerkrankungen sowie viraler und bakterieller Pathogenese.[22,143,473,474]
Die Entwicklung und Anwendung von Sphingolipidanaloga als potenzielle Wirkstoffe rückten in den letzten Jahren immer weiter in den Fokus der interdisziplinären Forschung von Biologen, Chemikern und Medizinern. Als bekanntestes Beispiel ist Fingolimod (FTY720) zu nennen, das als Sphingosin-1-phosphat-Mimetikum heute unter dem Markennamen Gilenya® erfolgreich als Arzneistoff zur Behandlung von Multipler Sklerose eingesetzt wird.[475] Es besteht jedoch die Gefahr, dass Fingolimod zur Schädigung anderer Zellfunktionen und zu gravierenden Nebeneffekten wie Bradykardie führen kann.[476] Da Sphingolipide ebenfalls in der Kontrolle von bakteriellen und viralen Infektionen essentiell beteiligt sind, spielen Sphingolipide und deren synthetisch dargestellte Derivate vermehrt eine Rolle in der Wirkstoffentwicklung im Kampf gegen pathogene Krankheitserreger.[175,477-479] Die Wirkweise von antimikrobiellen Sphingolipiden ist bisher nicht vollständig aufgeklärt. Für eine Weiterentwicklung von bekannten Medikamenten gegen verschiedene Krankheiten oder für die Entwicklung neuartiger Wirkstoffe gegen Erreger ist eine umfassende Untersuchung der zugrundeliegenden zellulären Mechanismen auf molekularer Ebene entscheidend.
Hierfür finden aufgrund der relativ einfachen Detektion mittels Fluoreszenzmikroskopie häufig fluoreszenzmarkierte Sphingolipidderivate breite Anwendung.[480] Die kovalent gebundene Farbstoffeinheit bringt jedoch wesentliche Nachteile mit sich, da sich die Biomoleküle durch die veränderte Struktur und Polarität in ihren biologischen Eigenschaften von den natürlichen Substraten unterscheiden können. Die Verwendung von bioorthogonal funktionalisierten Biomolekülen umgeht dieses Problem, da die strukturellen Änderungen minimal gehalten werden.
Nach dem zellulären Einbau dieser Derivate ist eine schnelle und spezifische Konjugation mit einem komplementären Fluorophor zu einem gewünschten Zeitpunkt durch sogenannte Click-Reaktionen wie CuAAC oder SPAAC möglich.[12,46] Das Prinzip der Click-Chemie wurde bereits auf eine Vielzahl an Biomolekülen wie Sphingolipide, Fettsäuren, Aminosäuren, Proteine, Kohlenhydrate, Nukleoside oder Nukleinsäuren (DNA und RNA) übertragen.[47,280] Jedoch bedarf es weiterer spezifisch modifizierter Verbindungen, die vielfältige bioorthogonale Reaktionen für die Untersuchung von Zellprozessen zulassen ‒ sowohl in vitro als auch in vivo.
Um neue Therapieansätze gegen verschiedene Krankheiten zu entwickeln und schwerwiegende Nebenwirkungen zu vermeiden, ist die detaillierte Erforschung hochkomplexer Zellvorgänge auf molekularer Ebene von entscheidender Bedeutung. Das Ziel dieser Arbeit war daher die Synthese und Charakterisierung von molekularen Werkzeugen, die in Kombination mit verschiedenen aktuellen Mikroskopie- und Massenspektrometriemethoden die Visualisierung und Untersuchung des Sphingolipidmetabolismus und weiterer biologischer Prozesse ermöglichen.
Zusammenfassend wurde in dieser Arbeit eine Vielzahl an Sphingolipiden und deren bioorthogonal funktionalisierte Analoga ausgehend von der Aminosäure L-Serin erfolgreich synthetisiert. Die vorgestellten Verbindungen eignen sich in Kombination mit Massenspektrometrie und Fluoreszenz- oder Elektronenmikroskopie als molekulare Werkzeuge zur Untersuchung des komplexen Sphingolipidmetabolismus sowie des Einbaus und der Dynamik von Sphingolipiden in Modell- und Zellmembranen. Sowohl in humanen und tierischen Zellen als auch in Bakterien wurden die azidmodifizierten Sphingolipide durch Click-Reaktionen visualisiert, um ein verbessertes Verständnis von bakteriellen und viralen Infektionsprozessen zu erhalten. Der modulare Ansatz der Click-Chemie ermöglicht die Verwendung verschiedener komplementär funktionalisierter Farbstoffe, die unterschiedliche Eigenschaften bezüglich der Membrandurchgängigkeit oder Absorptions- und Emissionswellenlängen besitzen und somit je nach biologischer Fragestellung gezielt eingesetzt werden können.
Alles in allem tragen die in dieser Arbeit synthetisierten Verbindungen dazu bei, die Rolle von Sphingolipiden bei Infektionsprozessen und Krankheitsverläufen auf subzellulärer Ebene aufzuklären. Dadurch wird ein entscheidender Beitrag für die Entwicklung neuartiger Wirkstoffe gegen bakterielle oder virale Erreger sowie innovativer Therapien gegen verschiedene humane Krankheiten geliefert.
A fine balance of regulatory (T\(_{reg}\)) and conventional CD4\(^+\) T cells (T\(_{conv}\)) is required to prevent harmful immune responses, while at the same time ensuring the development of protective immunity against pathogens. As for many cellular processes, sphingolipid metabolism also crucially modulates the T\(_{reg}\)/T\(_{conv}\) balance. However, our understanding of how sphingolipid metabolism is involved in T cell biology is still evolving and a better characterization of the tools at hand is required to advance the field. Therefore, we established a reductionist liposomal membrane model system to imitate the plasma membrane of mouse T\(_{reg}\) and T\(_{conv}\) with regards to their ceramide content. We found that the capacity of membranes to incorporate externally added azide-functionalized ceramide positively correlated with the ceramide content of the liposomes. Moreover, we studied the impact of the different liposomal preparations on primary mouse splenocytes in vitro. The addition of liposomes to resting, but not activated, splenocytes maintained viability with liposomes containing high amounts of C\(_{16}\)-ceramide being most efficient. Our data thus suggest that differences in ceramide post-incorporation into T\(_{reg}\) and T\(_{conv}\) reflect differences in the ceramide content of cellular membranes.
Recently, we have shown that C6-ceramides efficiently suppress viral replication by trapping the virus in lysosomes. Here, we use antiviral assays to evaluate a synthetic ceramide derivative α-NH2-ω-N3-C6-ceramide (AKS461) and to confirm the biological activity of C6-ceramides inhibiting SARS-CoV-2. Click-labeling with a fluorophore demonstrated that AKS461 accumulates in lysosomes. Previously, it has been shown that suppression of SARS-CoV-2 replication can be cell-type specific. Thus, AKS461 inhibited SARS-CoV-2 replication in Huh-7, Vero, and Calu-3 cells up to 2.5 orders of magnitude. The results were confirmed by CoronaFISH, indicating that AKS461 acts comparable to the unmodified C6-ceramide. Thus, AKS461 serves as a tool to study ceramide-associated cellular and viral pathways, such as SARS-CoV-2 infections, and it helped to identify lysosomes as the central organelle of C6-ceramides to inhibit viral replication.
In T cells, as in all other cells of the body, sphingolipids form important structural components of membranes. Due to metabolic modifications, sphingolipids additionally play an active part in the signaling of cell surface receptors of T cells like the T cell receptor or the co-stimulatory molecule CD28. Moreover, the sphingolipid composition of their membranes crucially affects the integrity and function of subcellular compartments such as the lysosome. Previously, studying sphingolipid metabolism has been severely hampered by the limited number of analytical methods/model systems available. Besides well-established high resolution mass spectrometry new tools are now available like novel minimally modified sphingolipid subspecies for click chemistry as well as recently generated mouse mutants with deficiencies/overexpression of sphingolipid-modifying enzymes. Making use of these tools we and others discovered that the sphingolipid sphingomyelin is metabolized to ceramide to different degrees in distinct T cell subpopulations of mice and humans. This knowledge has already been translated into novel immunomodulatory approaches in mice and will in the future hopefully also be applicable to humans. In this paper we are, thus, summarizing the most recent findings on the impact of sphingolipid metabolism on T cell activation, differentiation, and effector functions. Moreover, we are discussing the therapeutic concepts arising from these insights and drugs or drug candidates which are already in clinical use or could be developed for clinical use in patients with diseases as distant as major depression and chronic viral infection.
Genetic deficiency for acid sphingomyelinase or its pharmacological inhibition has been shown to increase Foxp3\(^+\) regulatory T-cell frequencies among CD4\(^+\) T cells in mice. We now investigated whether pharmacological targeting of the acid sphingomyelinase, which catalyzes the cleavage of sphingomyelin to ceramide and phosphorylcholine, also allows to manipulate relative CD4\(^+\) Foxp3\(^+\) regulatory T-cell frequencies in humans. Pharmacological acid sphingomyelinase inhibition with antidepressants like sertraline, but not those without an inhibitory effect on acid sphingomyelinase activity like citalopram, increased the frequency of Foxp3\(^+\) regulatory T cell among human CD4\(^+\) T cells in vitro. In an observational prospective clinical study with patients suffering from major depression, we observed that acid sphingomyelinase-inhibiting antidepressants induced a stronger relative increase in the frequency of CD4\(^+\) Foxp3\(^+\) regulatory T cells in peripheral blood than acid sphingomyelinase-non- or weakly inhibiting antidepressants. This was particularly true for CD45RA\(^-\) CD25\(^{high}\) effector CD4\(^+\) Foxp3\(^+\) regulatory T cells. Mechanistically, our data indicate that the positive effect of acid sphingomyelinase inhibition on CD4\(^+\) Foxp3\(^+\) regulatory T cells required CD28 co-stimulation, suggesting that enhanced CD28 co-stimulation was the driver of the observed increase in the frequency of Foxp3+ regulatory T cells among human CD4\(^+\) T cells. In summary, the widely induced pharmacological inhibition of acid sphingomyelinase activity in patients leads to an increase in Foxp3+ regulatory T-cell frequencies among CD4\(^+\) T cells in humans both in vivo and in vitro.