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Rap1 ameliorates renal tubular injury in diabetic nephropathy.

ABSTRACT: Rap1b ameliorates high glucose (HG)-induced mitochondrial dysfunction in tubular cells. However, its role and precise mechanism in diabetic nephropathy (DN) in vivo remain unclear. We hypothesize that Rap1 plays a protective role in tubular damage of DN by modulating primarily the mitochondria-derived oxidative stress. The role and precise mechanisms of Rap1b on mitochondrial dysfunction and of tubular cells in DN were examined in rats with streptozotocin (STZ)-induced diabetes that have Rap1b gene transfer using an ultrasound microbubble-mediated technique as well as in renal proximal epithelial tubular cell line (HK-2) exposed to HG ambiance. The results showed that Rap1b expression decreased significantly in tubules of renal biopsies from patients with DN. Overexpression of a constitutively active Rap1b G12V notably ameliorated renal tubular mitochondrial dysfunction, oxidative stress, and apoptosis in the kidneys of STZ-induced rats, which was accompanied with increased expression of transcription factor C/EBP-? and PGC-1?. Furthermore, Rap1b G12V also decreased phosphorylation of Drp-1, a key mitochondrial fission protein, while boosting the expression of genes related to mitochondrial biogenesis and antioxidants in HK-2 cells induced by HG. These effects were imitated by transfection with C/EBP-? or PGC-1? short interfering RNA. In addition, Rap1b could modulate C/EBP-? binding to the endogenous PGC-1? promoter and the interaction between PGC-1? and catalase or mitochondrial superoxide dismutase, indicating that Rap1b ameliorates tubular injury and slows the progression of DN by modulation of mitochondrial dysfunction via C/EBP-?-PGC-1? signaling.

SUBMITTER: Xiao L

PROVIDER: S-EPMC3964498 | biostudies-literature | 2014 Apr

REPOSITORIES: biostudies-literature

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Rap1 ameliorates renal tubular injury in diabetic nephropathy.

Xiao Li L Zhu Xuejing X Yang Shikun S Liu Fuyou F Zhou Zhiguang Z Zhan Ming M Xie Ping P Zhang Dongshan D Li Jun J Song Panai P Kanwar Yashpal S YS Sun Lin L

Diabetes 20131218 4

Rap1b ameliorates high glucose (HG)-induced mitochondrial dysfunction in tubular cells. However, its role and precise mechanism in diabetic nephropathy (DN) in vivo remain unclear. We hypothesize that Rap1 plays a protective role in tubular damage of DN by modulating primarily the mitochondria-derived oxidative stress. The role and precise mechanisms of Rap1b on mitochondrial dysfunction and of tubular cells in DN were examined in rats with streptozotocin (STZ)-induced diabetes that have Rap1b g ...[more]

PMID: 24353183

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Project description:Background: Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease worldwide with limited treatment options. The intricate pathogenesis of dysregulated lipid metabolism leading to the development of DKD remains obscure. Lipophagy, which refers to the autophagic degradation of intracellular lipid droplets, has been found to be impaired in DKD, resulting in renal tubule dysfunction and ectopic lipid deposition (ELD). The lipotoxity in renal tubules is closely related to the pathogenesis of DKD. Therefore, it is crucial to develop effective and safe agents that can restore autophagic flux and lipophagy in renal tubules for potential preventive interventions. Purpose: This study seeks to investigate the preventive effect of sodium butyrate (NaB) on ELD in the progression of DKD and elucidate the underlying mechanisms involved.Methods: The beneficial effects of NaB were investigated in glucolipotoxicity (GLT)-stimulated HK-2 cells and the streptozotocin (STZ) injection combined with a high-fat diet induced DKD model mice. Additionally, we managed to silence transcription factor EB (TFEB) in HK-2 cells and establish the renal specific silence model by retrograde ureteral infusion of AAV9-shTFEB in mice. We investigated the expression profile of RNAs in HK-2 cells through. The mechanism of NaB is demonstrated by RNA sequencing (RNA-seq), pulldown MS assay, SPR experiments etc.Results: Our findings revealed that serum butyrate level is reduced in DKD patients and is statistically correlated with urinary protein excretion and eGFR. Sodium butyrate (NaB) dose-dependently improved lipid deposition in HK-2 cells and renal tubular epithelial cells of DKD model mice. This effect may be attributed to the promotion of TFEB dephosphorylation, as NaB can directly interact with PPP2R1A to activate PP2A phosphorylation activity. Therefore, NaB may play a role in improving renal lipid deposition in DKD through the PP2A-TFEB pathway. Conclusion: NaB acts as a PP2A-TFEB axis activator that restores lipophagy to ameliorate ELD and renal dysfunction in DKD.

Project description:BackgroundDiabetic nephropathy (DN) is a severe complication of diabetes mellitus (DM). Pancreas or islet transplantation has been reported to prevent the development of DN lesions and ameliorate or reverse existing glomerular lesions in animal models. Shortage of pancreas donor is a severe problem. Islets derived from stem cells may offer a potential solution to this problem.ObjectiveTo evaluate the effect of stem cell-derived islet transplantation on DN in a rat model of streptozotocin-induced DM.MethodsPancreatic progenitor cells were isolated from aborted fetuses of 8 weeks of gestation. And islets were prepared by suspension culture after a differentiation of progenitor cells in medium containing glucagon-like peptide-1 (Glp-1) and nicotinamide. Then islets were transplanted into the liver of diabetic rats via portal vein. Blood glucose, urinary volume, 24 h urinary protein and urinary albumin were measured once biweekly for 16 weeks. Graft survival was evaluated by monitoring human C-peptide level in rat sera and by immunohistochemical staining for human mitochondrial antigen and human C-peptide in liver tissue. The effect of progenitor-derived islets on filtration membrane was examined by electron microscopy and real-time polymerase chain reaction (PCR). Immunohistochemical staining, real-time PCR and western blot were employed for detecting fibronectin, protein kinase C beta (PKCβ), protein kinase A (PKA), inducible nitric oxide synthase (iNOS) and superoxide dismutase (SOD).ResultsIslet-like clusters derived from 8th gestational-week human fetal pancreatic progenitors survived in rat liver. And elevated serum level of human C-peptide was detected. Blood glucose, 24 h urinary protein and urinary albumin were lower in progenitor cell group than those in DN or insulin treatment group. Glomerular basement membrane thickness and fibronectin accumulation decreased significantly while podocytes improved morphologically in progenitor cell group. Furthermore, receptor of advanced glycation end products and PKCβ became down-regulated whereas PKA up-regulated by progenitor cell-derived islets. And iNOS rose while SOD declined.ConclusionsDN may be reversed by transplantation of human fetal pancreatic progenitor cell-derived islets. And fetal pancreatic progenitor cells offer potential resources for cell replacement therapy.

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Rap1 ameliorates renal tubular injury in diabetic nephropathy.

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Rap1 ameliorates renal tubular injury in diabetic nephropathy.

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