Faculty of Medicine
Faculty of Medicine
UNIverse - Public Research Portal

[FG] Walker Ulrich

Projects & Collaborations

13 found
Show per page
Project cover

NETosis and mitochondrial DNA in the pathogenesis, diagnosis and activity of systemic lupus erythematosus and ANCA-associated vasculitis.

Research Project  | 2 Project Members

Activated neutrophils have been implicated in the pathogenesis of Systemic Lupus Erythematosus (SLE) and the ANCA-associated vasculitides (AAV). Upon activation with various stimuli, neutrophils release DNA and chromatin material into the extracellular space, a process coined neutrophil extracellular trap (NET) formation. Toll-like receptor (TLR) 9 can recognize double stranded (ds)DNA and initiate the characteristic type I interferon (IFN) signature that has been implicated in the breakdown of peripheral tolerance and generation of autoreactive T- and B-cells. Recent data suggests that subjects with SLE are characterized by impaired NET degradation, disseminating the availability of extracellular DNA as a proinflammatory stimulus to the innate immune system. NETs may also contain mitochondrial DNA (mtDNA), a dsDNA molecule which is phylogenetically evolved from bacteria and rich in hypomethylated CpG sequences, thus especially suited to trigger TLR9 signaling and disease flares. Working Hypothesis: SLE and AAV patients have increased plasma concentrations of circulating extracellular mtDNA, possibly released by NET formation. Elevated mtDNA concentrations are associated with disease flares. NET formation on the one hand contributes to overt mtDNA release, and on the other hand is modulated by circulating mtDNA or nDNA, as well as by hormones and cytokines.Overall objectives and specific aims: We aim to analyse the extent and nature of circulating extracellular DNA species (mtDNA vs. nuclear DNA) in SLE and AAV and determine if mtDNA plasma concentrations can serve as a marker for diagnosis and disease activity. Furthermore, we aim to determine which factors promote, modulate and inhibit the NETotic release of mtDNA in comparison to nuclear DNA.Experimental methods and design: Using quantitative PCR, we will determine circulating DNA concentrations (mtDNA and nuclear DNA) in centrifuged plasma samples from patients with SLE and AAV and compare them with those of healthy controls and patients with rheumatoid arthritis (RA). Uni- and multivariate statistics will correlate circulating DNA plasma concentrations with disease activity, using known disease activity markers as covariates. In vitro work will examine the triggers and inhibitors of NETosis in AID derived neutrophils and plasma and analyse their presence in patients plasma in comparison with that from healthy controls. Expected value of the proposed project: Manifest mtDNA release is likely to contribute to the pathology of SLE and AAV by feeding back to neutrophil activation and thereby to disease activity and systemic inflammation. An increased understanding of how this aberrancy is brought about will facilitate new targeted therapeutic approaches. An immediate benefit of this study is that it will indicate whether or mtDNA quantification in patient plasma can serve as the basis for a novel test for disease screening and activity.

Project cover

Significance of mannose-binding lectin and the lectin pathway in acute and recurrent ischemia/repefusion injury

Research Project  | 4 Project Members

Mannose-binding lectin (MBL), a circulating pattern-recognition protein of the lectin pathway of complement is involved in the clearance of microorganisms and apoptotic cells. The concentration of functional MBL multimers is profoundly influenced by several polymorphisms in the MBL2 gene on chromosome 10, resulting in remarkable variations in serum MBL concentrations in apparently healthy individuals. Beyond infections, recent experimental studies have acknowledged additional important roles of MBL in atherosclerosis and ischemia/reperfusion (IR) injury. However, human data are scarce. This proposal aims to characterise in more depth the role of MBL and the lectin pathway in three human diseases, in which acute or repetitive I/R injury and/or atherosclerosis contribute to pathophysiology and outcome: systemic lupus erythematosus.primary (SLE), systemic sclerosis (SSc), and primary open angle glaucoma (POAG). In the SLE cohort sub-study, association of MBL deficiency with vascular events will be investigated in subjects from the well characterized Swiss SLE cohort. This is of importance, as SLE patients have an increased cardiovascular mortality and morbidity compared to the average individual. In the SSc cohort sub-study, activity of the lectin pathway including levels of MBL and the ficolins will be correlated with disease activity and organ involvement in individuals from a large European SSc cohort. Our preliminary data from a previous small Australian SSc cohort indicates that MBL deficiency might be associated with less organ damage. Hence, it might be worth to explore inhibition of the MBL or the lectin pathway in the future. In the POAG case-control sub-study, activity of the complement system in general and the lectin pathway in particular will be examined in POAG cases compared to healthy controls. This is of interest, as vascular dysfunction and repetitive I/R injury seem to be a hallmark in the pathogenesis of POAG, and current treatment options are limited. This project will lead to a more comprehensive understanding of the pathogenesis and the importance of MBL and the lectin pathway in I/R injury in SLE, SSc and POAG. Furthermore, it might facilitate future therapeutic interventions like inhibition of MBL or the lectin pathway to ameliorate I/R injury in these settings.

Project cover

Somatisch erworbene Mitochondrienläsionen bei idiopathischer und Sklerodermie-assoziierter Lungenfibrose

Research Project  | 3 Project Members

Scleroderma (also called systemic sclerosis, SSc) and idiopathic interstitial lung fibrosis are rare diseases with a very high mortality; in fact interstitial lung involvement is the most frequent cause of death in SSc. Progressive fibrosis of the lung is the hallmark of both diseases and results from an excess synthesis and deposition of collagen. The etiology of the fibrosis in these conditions is poorly understood. Despite some evidence for an involvement of the immune system, the pulmonary collagen deposits are rarely amenable to immunosuppressive therapy in clinical practice. There is now mounting evidence for an important role of reactive oxygen species (ROS) which may perpetuate the fibrotic process in response to an unidentified chronic injury. In this grant proposal we aim to investigate the role of somatically acquired lesions in mitochondria as perpetuators of the frequently relentless disease process. Mitochondria are on the one hand the main cellular producers of ROS and on the other hand themselves subject to oxidative injury of their genome (e.g. mitochondrial DNA, mtDNA), lipids and protein structures. We specifically propose to investigate the hypothesis that mitochondrial injury accumulates with time during the disease process and contributes to, or may even be the main driver of ROS production and subsequent fibrosis. Our hypothesis hinges on the fact that mtDNA damage leads to respiratory chain dysfunction, a fact which subsequently generates even more free radicals which then either attack the respiratory chain itself, or in turn damage mtDNA. ROS may therefore close vicious circles composed of interconnected mtDNA and respiratory chain insults. Such vicious circles may continue to operate even in the absence of the inciting event of lung fibrosis and therefore account for its relentless progression. We will investigate this hypothesis by quantifying mtDNA mutation loads in a host of well characterized human lung biopsies and in the bleomycin model of lung fibrosis. We will then relate mutation loads to markers of pulmonary ROS production, respiratory chain function, as well as disease characteristics (fibrosis type, severity, and duration). We finally aim to demonstrate the direct pathogenetic relevance of mitochondrial dysfunction by establishing fibroblasts devoid of a single molecule of mtDNA (termed ?rho0´ fibroblasts) and by investigating the fibrotic phenotype of rho0 fibroblasts in vitro in terms of TGF-â release and collagen synthesis. We will also differentiate mitochondrial from nuclear effects in healthy and diseased individuals by examining the fibrotic potential of rho0 fibroblasts in comparison with fibroblasts harbouring wild-type mtDNA. Our new insights into the pathogenesis of lung fibrosis will help in the understanding of lung fibrosis and the rational development of antifibrotic drugs.

Project cover

VEDOSS - Very early diagnosis of systemic sclerosis.

Research Project  | 1 Project Members

Frühe Statien der Systemsklerose sind klinisch gekennzeichnet durch das fast obligat initial vorhandene Raynaudphänomen, eine Sklerodaktylie sowie bestimmte Antikörper im Serum. Viele Patienten mit früher Sklerodermie präsentieren sich auch mit einem veränderten Kapillarmuster am Kapillarbett in der Nagelfalzmikroskopie. Jedes dieser frühen Krankheitsmerkmale ist jedoch für sich alleine nicht spezifisch für die Erkrankung. Es ist derzeit auch nicht bekannt, welcher Prozentsatz der Patienten mit einer Kombination mehrerer Merkmale eine Sklerodermie entwickelt. Das Primärziel der Studie ist es, eine Screeningmethode bzw. eine Kombination von Screeninguntersuchungen zu entwickeln, die es erlaubt, die spätere Entwicklung zur Systemsklerose bereits zu einem frühen Zeitpunkt mit höherer Spezifität und Sensitivität vorauszusagen.