Caspase involvement in autophagy

Caspases are a family of cysteine proteases widely known as the principal mediators of the apoptotic cell death response, but considerably less so as the contributors to the regulation of pathways outside cellular demise. In regards to autophagy, the modulatory roles of caspases have only recently begun to be adequately described. In contrast to apoptosis, autophagy promotes cell survival by providing energy and nutrients through the lysosomal degradation of cytoplasmic constituents. Under basal conditions autophagy and apoptosis cross-regulate each other through an elaborate network of interconnections which also includes the interplay between autophagyrelated proteins (ATGs) and caspases. In this review we focus on the effects of this crosstalk at the cellular level, as we aim to concentrate the main observations from research conducted so far on the fine-tuning of autophagy by caspases. Several members of this protease-family have been found to directly interact with key ATGs involved in different tiers across the autophagic cascade. Therefore, we firstly outline the core mechanism of macroautophagy in brief. In an effort to emphasize the importance of the intricate cross-regulation of ATGs and caspases, we also present examples drawn from Drosophila and plant models regarding the contribution of autophagy to apoptotic cell death during normal development

Mycophenolic acid ameliorates anti-dsDNA antibody binding to proximal tubular epithelial cells and the subsequent induction of inflammatory and fibrotic processes

Poster Presentations - PO1M Pathogenesis: PO1.M.3OBJECTIVES: Severe active proliferative lupus nephritis is associated with inflammation in the renal parenchyma and elevated levels of anti-dsDNA antibodies. Up to 70% of patients with lupus nephritis show immune deposits along the tubular basement membrane, and the severity of tubulo-interstitial inflammation and injury correlate with long-term renal prognosis. We investigated the interaction between polyclonal anti-dsDNA antibodies isolated from patients with lupus nephritis and cultured proximal tubular epithelial cells (PTEC), and the effect of mycophenolic acid (MPA). METHODS: Human polyclonal anti-dsDNA antibodies were isolated from patients with lupus nephritis using affinity chromatography. Their interaction with PTEC in the presence or absence of MPA (5μg/ml) was assessed by flow cytometry, cellular ELISA and immunohistochemistry. Induction of IL-6, IL-8, MCP-1 and fibronectin was assessed by commercial ELISAs, and MAPK activation by Western blot analysis. RESULTS: Anti-dsDNA antibodies bound directly to PTEC surface without the need for bridging chromatin material, and were then internalized, in a time- and temperature-dependent manner, into the cytoplasmic and nuclear compartments. Binding of anti-dsDNA antibodies to PTEC induced cell proliferation, IL-6 secretion through JNK activation, and MCP-1 through p38 MAPK activation. Activation of ERK, p38 MAPK and JNK contributed to the induction of IL-8 and fibronectin secretion by anti-dsDNA antibodies (p<0.05 for all compared to control IgG). MPA inhibited anti-dsDNA antibody binding to PTEC, its induction of cell proliferation, activation of ERK, p38 MAPK and JNK, and IL-6, IL-8, MCP-1 and fibronectin secretion. CONCLUSIONS: Our data demonstrate the significance of anti-dsDNA antibody interaction with PTEC in the pathogenesis of tubulo-interstitial inflammation and fibrosis in lupus nephritis, and the therapeutic effect of MPA in this regard.link_to_OA_fulltextThe 9th International Congress on Systemic Lupus Erythematosus (SLE), Vancouver, Canada, 24-27 June 2010. In Lupus, 2010, v. 19 n. 1 suppl., p. 115, abstract no. PO1.M.

Mycophenolic acid reduces anti-DNA antibody binding and cytokine secretion in renal proximal tubular epithelial cells - implications in lupus nephritis

PURPOSE: Lupus nephritis is a severe organ manifestation of systemic lupus erythematosus. Cardinal features of lupus nephritis include elevated levels of circulating anti-DNA antibodies, their deposition in the mesangium and tubular basement membrane, mesangial proliferation and inflammation. Subsets of anti-DNA antibodies have been shown to be internalized by various cells and transferred to the nucleus where they elicit alterations in cellular functions. Proximal tubular epithelial cells (PTEC) constitute the predominant cell type within the tubulo-interstitium, and there is compelling evidence to suggest that they play a pivotal role in the immunopathogenesis of various renal parenchymal diseases including lupus nephritis. Mycophenolate mofetil (MMF) is a new immunosuppressant used for the treatment of lupus nephritis. Although its action on lymphocyte proliferation is well documented, its effect on non-immune cells has not been fully elucidated. This study aims to investigate the modulatory role of mycophenolic acid (MPA), the active metabolite of MMF, on anti-DNA antibody binding and internalization in PTEC and their subsequent effect on cytokine secretion. METHODS: Polyclonal double-stranded anti-DNA antibodies were isolated from serum samples of 10 patients with lupus nephritis using DNA-cellulose and protein A-Sepharose affinity chromatography. HK-2 cells were used in this study, which are normal PTEC immortalized by the transduction with the human papilloma virus 16 E6/E7 genes. Growth-arrested HK-2 cells were stimulated with normal IgG or anti-DNA antibodies (final concentration 10 g/ml) in the presence or absence of MPA (5 g/ml) for periods up to 48 h, after which time the supernatant was collected to measure IL-6 and IL-8 secretion. Binding and internalization of anti-DNA antibodies to HK-2 cells under control and experimental conditions was determined by cellular ELISA and immunohistochemistry, respectively. RESULTS: Anti-DNA antibody binding to HK-2 cells correlated with SLE disease activity. Anti-DNA antibodies bound to the cell surface of HK-2 cells and were localized to the nucleus within 30 min of administration. This was accompanied by a significant induction of IL-6 and IL-8 secretion when compared to normal IgG (P 0.05 for both). Such effects were more prominent in cells stimulated with anti-DNA antibodies derived from active patients. Co-incubation of anti-DNA antibodies with MPA significantly reduced anti-DNA antibody binding and cytokine secretion (P 0.05). CONCLUSION: Our data demonstrated that MPA reduced anti-DNA antibody binding to HK-2 cells and subsequent induction of cytokine secretion, suggestive that MPA may reduce inflammatory responses in the tubulo-interstitium during pathogenesis of lupus nephritis

Downregulation of endothelial microRNA-200b supports cutaneous wound angiogenesis by desilencing GATA binding protein 2 and vascular endothelial growth factor receptor 2

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