New paradigms in cell death in human diabetic nephropathy
ABSTRACT Cell death is thought to contribute to progressive renal cell depletion in diabetic nephropathy. Unbiased gene expression profiling identified novel cell death molecules in human diabetic nephropathy. The expression of TNF-related apoptosis-inducing ligand (TRAIL), its decoy receptor osteoprotegerin, and receptors Fas (a Fas ligand receptor) and CD74 (a migration inhibitory factor (MIF) receptor) were induced in human diabetic nephropathy. Cell culture studies supported the functional relevance of this observation and the relationship to a high glucose environment. To define novel proapoptotic proteins upregulated in diabetic nephropathy, functional genomic screens for novel apoptosis mediators were integrated with genome-wide expression profiling and identified candidates for further functional analysis, including brain acid-soluble protein 1 (BASP1). Several lines of evidence point toward induction of endoplasmic reticulum stress response in human diabetic nephropathy. Functional studies defining an unequivocal contribution of endoplasmic reticulum stress to cell death in this setting are still needed. Further comparative studies will be required to define whether there is a specific aspect of apoptosis in progressive human diabetic nephropathy or whether the mechanisms are shared among all patients with chronic kidney disease. The next challenge will be to define the consequence of therapeutic interference of the apoptosis pathways in diabetic nephropathy and chronic kidney disease.
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ABSTRACT: Apoptosis is a driving force of diabetic end-organ damage, including diabetic nephropathy (DN). However, the mechanisms that modulate diabetes-induced cell death are not fully understood. Heat shock protein 27 (HSP27/HSPB1) is a cell stress protein that regulates apoptosis in extrarenal cells and is expressed by podocytes exposed to toxins causing nephrotic syndrome. We investigated the regulation of HSPB1 expression and its function in podocytes exposed to factors contributing to DN, such as high glucose and angiotensin (Ang) II. HSPB1 expression was assessed in renal biopsies from patients with DN, minimal change disease or focal segmental glomerulosclerosis (FSGS), in a rat model of diabetes induced by streptozotocin (STZ) and in Ang II-infused rats. The regulation of HSPB1 was studied in cultured human podocytes and the function of HSPB1 expressed in response to pathophysiologically relevant stimuli was explored by short interfering RNA knockdown. Total kidney HSPB1 mRNA and protein expression was increased in rats with STZ-induced diabetes and in rats infused with Ang II. Upregulation of HSPB1 protein was confirmed in isolated diabetic glomeruli. Immunohistochemistry showed increased glomerular expression of HSPB1 in both models and localized glomerular HSPB1 to podocytes. HSPB1 protein was increased in glomerular podocytes from patients with DN or FSGS. In cultured human podocytes HSPB1 mRNA and protein expression was upregulated by high glucose concentrations and Ang II. High glucose, but not Ang II, promoted podocyte apoptosis. HSPB1 short interfering RNA (siRNA) targeting increased apoptosis in a high-glucose milieu and sensitized to Ang II or TGFβ1-induced apoptosis by promoting caspase activation. In conclusion, both high glucose and Ang II contribute to HSPB1 upregulation. HSPB1 upregulation allows podocytes to better withstand an adverse high-glucose or Ang II-rich environment, such as can be found in DN.Laboratory Investigation 09/2011; 92(1):32-45. DOI:10.1038/labinvest.2011.138 · 3.83 Impact Factor
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ABSTRACT: MicroRNAs are a class of highly conserved, small, noncoding RNAs that tailor gene expression mainly at the posttranscriptional level. The aim of the present study was to investigate the renal expression profiles of microRNAs and their potential involvement in early diabetic nephropathy. Diabetic models were induced with streptozotocin in DBA/2 mice. MicroRNAs were detected by microarray and subjected to bioinformatics analyses. Real-time PCR and Western blots were performed. The relationships between pathological changes and microRNA expression were evaluated by linear regression analysis. Apoptosis and proliferation of cultured mesangial cells treated with microRNA inhibitor were determined by flow cytometry and MTT assay, respectively. Nine microRNAs, including miR-1187, miR-320, miR-214, miR-34a, miR-762, miR-466f, miR-720, miR-744 and miR-1937b, were increased significantly. Another 9 microRNAs, including miR-1907, miR-195, miR-568, miR-26b, miR-703, miR-1196, miR-194, miR-805 and miR-192, were decreased remarkably in diabetic mice. The levels of microRNA repressing BCL2 decreased. Accordingly, BCL2 levels were found elevated and caspase-3 and caspase-8 levels decreased in the diabetic group. MicroRNA-195 expression was negatively related to glomeruli diameter, mesangial score and extracellular matrix (ECM) accumulation. Moreover, the microRNA-195 inhibitor protected mesangial cells from apoptosis and promoted the cellular proliferation in vitro. These results demonstrated that the abated microRNA-195 expression protected mesangial cells from apoptosis, suggesting that the antiapoptosis in a microRNA-regulated manner may play an important role in the early stages of diabetic nephropathy.Journal of nephrology 10/2011; 25(4):566-76. DOI:10.5301/jn.5000034 · 2.00 Impact Factor
- Advances in the Study of Genetic Disorders, 11/2011; , ISBN: 978-953-307-305-7