Dissertation > Excellent graduate degree dissertation topics show

The Role of INrf2in Diabetic Nephropathy Induced Apoptosis of Renal Glomerulus Cells

Author: HanChong
Tutor: LiuZhiMin
School: Second Military Medical University
Course: Internal Medicine
Keywords: diabetic nephropathy apoptosis INrf2 Nrf2 Bcl-2
CLC: R587.2
Type: Master's thesis
Year: 2013
Downloads: 24
Quote: 0
Read: Download Dissertation

Abstract

BackgroundDiabetes mellitus (DM) is a public health concern and projections for the future are alarming.According to WHO, diabetes affects over170million people worldwide, and this will rise tomore than300millions by2030. About one third of diabetic patients has progressivedeterioration of renal function and ultimately requires renal replacement therapy by dialysis or transplantation. Diabetic nephropathy (DN)is the most common complications ofdiabetes and also the main cause of the mortality fordiabetic patients. The first manifestation of diabeticnephropathy in humans is increased urinary albumin excretion,which usually progresses to nephrotic-rangeproteinuria. The morphological substrates for these functionalabnormalities of the glomerular filter apparatusinclude glomerular hypertrophy, thickening of glomerularbasement membrane, and expansion of mesangial extracellularmatrix. Advanced diabetic nephropathy is characterizedby glomerulosclerosis, demise of glomerularcapillaries, tubulointerstitial degeneration, and fibrosisassociated with precipitous decline of glomerular filtrationrate.The prevention of diabetic nephropathyhas become a global concern for thosewho are working in diabetic care and management.To date, several interventions have been shown toslow the progression of diabetic nephropathy, includingtight glucose, blood pressure control, lipid lowering and blockade ofthe renin-angiotensin system. However, none of thecurrently available modalities can cure or prevent diabeticnephropathy.Therefore,to understand the detail mechanism of diabetic nephropathy and develop an effective approach to prevent or delay the progression of diabetic nephropathyfor diabetic patients is urgently needed.Hyperglycemia as well as hyperlipidemia and inflammation werethree main metabolic abnormalities in diabetes, all which areable to stimulate generation of reactive oxygenspecies (ROS). The ROS seem to be the common denominator in various pathways and are central to the pathogenesis of hyperglycemic injury.Extra generation of ROSis known to be critically causative of the development ofdiabetic nephropathy. In addition to their ability to directly inflict macromolecular damage, ROS can function as signaling molecules. ROS mediate hyperglycemia-induced activation of signal transduction cascades and transcription factors leading to transcriptional activation of profibrotic genes in the kidney. The effect of antioxidant therapy is well documented in cell and animal studies, although convincing evidence for clinical efficacy is still lacking.The transcription factor NFE2-related factor2(Nrf2) is amaster regulator ofcellular redox status, andrecently, several studies have indicated preventive effectof Nrf2on high glucose(HG) induced oxidative damage inthe cultured cells and potentially on the diabetic complicationsin animal models.Upon exposure ofcells to oxidative stress or electrophilic compounds, Nrf2is activated and translocates into the nucleus tobind to antioxidant-responsive elements (AREs) in the genesencoding antioxidant enzymes such as NADPH quinoneoxidoreductase (NQO-1), glutathione S-transferase (GST), hemeoxygenase-1(HO-1), and γ-glutamylcysteine synthetase,increasing their expression to play a role of detoxification,antioxidation, and anti-inflammation.In the absence of cellularstress, Nrf2is tethered within the cytoplasm by an inhibitorypartner, inhibitor of Nrf2(INrf2), also known as’Kelch-likeerythroid cell-derived protein with CNC homology (ECH)-associated protein1’(Keap1),which interactswith the actin cytoskeleton. KEAP1could mediate a rapid ubiquitination and subsequent degradationof Nrf2by the proteasome.INrf2serves as a substrate linker protein for interactions with thecullin3(Cul3)-based E3ubiquitin ligase to regulate the stability ofNrf2. Covalent conjugation of proteins byubiquitin usually involves three enzymatic activities for activating(El), conjugating (E2) and ligating (E3) ubiquitin to a substrate. In this case, Nrf2serves as thesubstrate, whereas Cul3serves as a scaffold protein that forms theE3ligase complex with ring box protein1(Rbxl) that recruits acognate E2enzyme. INrf2,through its N-terminal BTB/POZ domain, binds to Cul3, through its C-terminal Kelch domain binds to thesubstrate Nrf2, leading to the ubiquitylation and proteasomaldegradation of Nrf2through the26S proteasome. Exposure to a number of stressors andinducing agents leads to dissociation of Nrf2from INrf2, therebyrescuing Nrf2from proteasomal degradation and permitting entry of Nrf2into the nucleus.Structural and functional analyses of INrf2identified an evolutionarily conserved Kelch (DGR) domain, which interacts with several proteins. Although Nrf2is a well known substrate for INrf2, the DGR domain of INrf2has been reported also to bind other proteins, including Nrfl, PGAM5, prothymosin-a, fetal Alz clone1, and IKKβ. It indicats that INrf2plays several different roles in cell signaling and cellular process through its interacting partners. Recently, INrf2is shown to target anti-apoptotic Bcl-2protein for degradation and control cellular apoptosis. INrf2can also, through its DGR domain, interact with PGAM5proteins and regulates Bcl-xL.The aim of this study is to investigate whether INrf2take part in diabetic nephropathy and how it functions. We firstly found that INrf2is up-regulated in rat models of diabetic nephropathy and in high glucose(HG) induced oxidative damage of cultured cells. Up-regultaion of INrf2led to increase of oxidative stress and promoted apoptosis of HRMC cells. We showed that INrf2promoted cell apoptosis inoxidative stress in diabetic nephropathy through down-regulation of Nrf2and Bcl-2.Objective:To investigate the expression level of INrf2in diabetic nephropathy; to identify the role of INrf2in renal cell apoptosis; to explore the molecular mechanism of INrf2in diabetic nephropathy.Methods:We examined INrf2expression in diabetic nephropathy rat model induced by STZ and in HRMC cell model induced by high glocuse. Through forced overexpression and siRNA induced down-regulation of INrf2, we investigated the effect of INrf2dysregualtion on HRMC cell apoptosis by evaluating DNA fragmentation and cleaved-caspase3. High glucose induced ROS was examined using CM-DCFH-DA assay. The Nrf2activation was examined by analyzing its expression, nuclear amount and transcriptional activity. Co-immunoprecipitation was used to determine INrf2-Nrf2, INrf2-Bcl-2and Bcl-2-Bax interaction changes.Results:STZ successfully induced renal cell apoptosis in diabetic nephropathy rat model, and INrf2was up-regulated in this rat model. High glucose successfully induced ROS generation and cell apoptosis in HRMC cells, and INrf2was up-regulated in this cell model. Forced overexpression of INrf2promoted high glucose induced apoptosis of HRMC, and knock-down of INrf2attenuated high glucose induced apoptosis of HRMC. Forced overexpression of INrf2resulted in suppression of Nrf2and Bcl-2. INrf2inhibited Nrf2activation and promote ROS generation; in the mean time, INrf2promotes Bcl-2degradation and caused increase of Bax levels.Conclusions:1. INrf2is up-regulated in diabetic nephropathy.2. INrf2promoted high glucose induced oxidative stress and led to increased apoptosis of HRMC cells.3. INrf2inhibited Nrf2activation and promoted ROS generation in diabetic nephropathy.4. INrf2promoted Bcl-2degradation and led to increased cell apoptosis in diabetic nephropathy.

Related Dissertations

CLC: > Medicine, health > Internal Medicine > Endocrine diseases and metabolic diseases > Islet disease > Diabetic coma and other complications
© 2012 www.DissertationTopic.Net Mobile