Root of Polygonum cuspidatum extract reduces progression of diabetes-induced mesangial cell dysfunction via inhibition of platelet-derived growth factor-BB (PDGF-BB) and interaction with its receptor in streptozotocin-induced diabetic rats.
ABSTRACT: Platelet-derived growth factor-BB (PDGF-BB) is highly expressed in the renal tissues of patients with diabetic nephropathy, and it plays an important role in the initiation and progression of diabetic nephropathy. The aim of this study was to evaluate the protective effects of root of Polygonum cuspidatum extract (PCE) on early renal glomerular proliferation in streptozotocin (STZ)-induced diabetic rats.PCE (100, 350 mg/kg/day) was administered to diabetic rats for 16 weeks. Blood glucose and albuminuria were measured. Renal histology, ?-smooth muscle actin (?-SMA), and proliferating cell nuclear antigen (PCNA) expression levels were also examined.After 16 weeks of treatment with PCE, severe hyperglycemia and albuminuria were observed in the diabetic rats. The expressions levels of ?-SMA and PCNA proteins were significantly increased in the glomeruli of the diabetic rats. The expression levels of PDGF-BB and its receptor expressions were greatly increased in the glomeruli of the diabetic rats. However, PCE markedly reduced albuminuria in the diabetic rats. PCE inhibited ?-SMA and PCNA up-regulation and ameliorated PDGF-BB and PEGFR-ß protein expression in the diabetic rats. In addition, the binding of PDGF-BB/PDGFR-ß was inhibited by PCE as shown by an in vitro assay.These results suggest that PCE has an inhibitory effect on mesangial proliferation in diabetic renal tissues via the inhibition of the interaction of PDGF-BB with its receptor. PCE may have beneficial effects in preventing the progression of diabetic nephropathy.
Project description:Renal fibrosis is a common complication of diabetic nephropathy and is a major cause of end-stage renal disease. Despite the suggested link between renal fibrosis and microRNA (miRNA) dysregulation in diabetic nephropathy, the identification of the specific miRNAs involved is still incomplete. The aim of this study was to investigate miRNA profiles in the diabetic kidney and to identify potential downstream targets implicated in renal fibrosis.miRNA expression profiling was investigated in the kidneys of 8-month-old Zucker diabetic fatty (ZDF) rats during overt nephropathy. Localisation of the most upregulated miRNA was established by in situ hybridisation. The candidate miRNA target was identified by in silico analysis and its expression documented in the diabetic kidney associated with fibrotic markers. Cultured tubule cells served to assess which of the profibrogenic stimuli acted as a trigger for the overexpressed miRNA, and to investigate underlying epigenetic mechanisms.In ZDF rats, miR-184 showed the strongest differential upregulation compared with lean rats (18-fold). Tubular localisation of miR-184 was associated with reduced expression of lipid phosphate phosphatase 3 (LPP3) and collagen accumulation. Transfection of NRK-52E cells with miR-184 mimic reduced LPP3, promoting a profibrotic phenotype. Albumin was a major trigger of miR-184 expression. Anti-miR-184 counteracted albumin-induced LPP3 downregulation and overexpression of plasminogen activator inhibitor-1. In ZDF rats, ACE-inhibitor treatment limited albuminuria and reduced miR-184, with tubular LPP3 preservation and tubulointerstitial fibrosis amelioration. Albumin-induced miR-184 expression in tubule cells was epigenetically regulated through DNA demethylation and histone lysine acetylation and was accompanied by binding of NF-?B p65 subunit to miR-184 promoter.These results suggest that miR-184 may act as a downstream effector of albuminuria through LPP3 to promote tubulointerstitial fibrosis, and offer the rationale to investigate whether targeting miR-184 in association with albuminuria-lowering drugs may be a new strategy to achieve fully anti-fibrotic effects in diabetic nephropathy.
Project description:OVE26 mouse was chosen to study the progressive changes in renal gene expression because it displays the most advanced albuminuria mouse models that assembles advanced human diabetic nephropathy. OVE26 mice induce inflammatory gene expression changes consistent with advanced renal disease, associated with severe albuminuria and not reported in any other diabetic models. They provide the first opportunity in a model of diabetic nephropathy to assess the effect of induction of inflammatory proteins that have been implicated in renal injury. Microarray expression was performed on whole kidney from control and diabetic mice at 2, 4 and 8 months of age and validated by rtPCR, in situ hybridization or immunohistochemistry.
Project description:OVE26 mouse was chosen to study the progressive changes in renal gene expression because it displays the most advanced albuminuria mouse models that assembles advanced human diabetic nephropathy. OVE26 mice induce inflammatory gene expression changes consistent with advanced renal disease, associated with severe albuminuria and not reported in any other diabetic models. They provide the first opportunity in a model of diabetic nephropathy to assess the effect of induction of inflammatory proteins that have been implicated in renal injury. Overall design: Microarray expression was performed on whole kidney from control and diabetic mice at 2, 4 and 8 months of age and validated by rtPCR, in situ hybridization or immunohistochemistry.
Project description:Green tea (GT), through its antioxidant properties, may be useful to treat or prevent human diseases. Because several lines of evidence suggest that oxidative stress contributes to the pathogenesis of diabetic nephropathy, we tested the hypothesis that GT prevents diabetes and hypertension-related renal oxidative stress, attenuating renal injury. Spontaneously hypertensive rats (SHR) with streptozotocin-induced diabetes and nondiabetic SHR were treated daily with tap water or freshly prepared GT (13.3 g/L). After 12 wk, the systolic blood pressure did not differ between treated and untreated nondiabetic or diabetic rats. However, body weight was less (P < 0.05) and glycemia was greater in diabetic SHR rats than in nondiabetic rats. Renal oxidative stress variables such as 8-hydroxy-2'-deoxyguanosine (8-OHdG) and nitrotyrosine expression, NADPH oxidase-dependent superoxide generation, and the expression of renal cortex Nox4 were greater (P < 0.05) in diabetic rats that received water (DW) than in nondiabetic rats that received water (CW). The 8-OHdG and NADPH oxidase-dependent superoxide generation were significantly less in rats treated with GT. Nitrotyrosine and Nox4 expression were significantly less in diabetic rats that received GT (DGT) than in DW. Likewise, the indices of renal injury, albuminuria, and renal expression of collagen IV were significantly greater in DW than in CW. These differences were significantly less in DGT than in DW. GT reestablished the redox state and reduced the indicators of nephropathy without altering glycemia and blood pressure levels in diabetic SHR. These findings suggest that the consumption of GT may ameliorate nephropathy in diabetic hypertensive patients.
Project description:Albuminuria is significantly reduced following Roux-en-Y gastric bypass (RYGB) surgery, suggesting a renoprotective effect of the intervention. Herein, we assess the relative impact of RYGB and RYGB equivalent non-surgical weight loss and glycaemic improvement on glomerular injury and global renal transcriptomic responses in the Zucker diabetic fatty rat (ZDF) model of diabetic nephropathy. We coined the term "medical bypass" (MB) to describe the intensive diet and pharmacotherapy based non-surgical intervention Adult ZDF rats underwent sham surgery (n=15) or RYGB (n=9). Nine sham-operated rats were calorie restricted and received insulin, liraglutide, metformin, ramipril, rosuvastatin and fenofibrate for 2 months (MB). Zucker fa/+ rats acted as healthy controls throughout. Bodyweight, glycaemia, albuminuria and glomerular injury specifically podocyte number, density and ultrastructure were assessed at follow up. Renal transcriptomes were compared by RNA-seq. RYGB resulted in 20-30% weight loss, normalized glycaemia and albuminuria and reduced indices of glomerular injury, specifically podocyte injury (foot process effacement). RYGB equivalent outcomes were obtained on all parameters following MB. Overall design: RNA-seq was performed to identify the renal transcriptomic profile of kidney disease in the ZDF rat, and to investigate the relative effects of Medical bypass intervention on the renal transcriptome. N=9 replicates were profiled.
Project description:Diabetic nephropathy is a major cause of end-stage kidney disease, and overactivity of the endocannabinoid/cannabinoid 1 receptor (CB1R) system contributes to diabetes and its complications. Zucker diabetic fatty (ZDF) rats develop type 2 diabetic nephropathy with albuminuria, reduced glomerular filtration, activation of the renin-angiotensin system (RAS), oxidative/nitrative stress, podocyte loss, and increased CB1R expression in glomeruli. Peripheral CB1R blockade initiated in the prediabetic stage prevented these changes or reversed them when animals with fully developed diabetic nephropathy were treated. Treatment of diabetic ZDF rats with losartan, an angiotensin II receptor-1 (Agtr1) antagonist, attenuated the development of nephropathy and down-regulated renal cortical CB1R expression, without affecting the marked hyperglycemia. In cultured human podocytes, CB1R and desmin gene expression were increased and podocin and nephrin content were decreased by either the CB1R agonist arachydonoyl-2'-chloroethylamide, angiotensin II, or high glucose, and the effects of all three were antagonized by CB1R blockade or siRNA-mediated knockdown of CNR1 (the cannabinoid type 1 receptor gene). We conclude that increased CB1R signaling in podocytes contributes to the development of diabetic nephropathy and represents a common pathway through which both hyperglycemia and increased RAS activity exert their deleterious effects, highlighting the therapeutic potential of peripheral CB1R blockade.
Project description:RhoA/ROCK signaling plays an important role in diabetic nephropathy, and ROCK inhibitor fasudil exerts nephroprotection in experimental diabetic nephropathy. In this study we investigated the molecular mechanisms underlying the protective actions of fasudil in a rat model of diabetic nephropathy.Streptozotocin (STZ)-induced diabetic rats, to which fasudil or a positive control drug enalapril were orally administered for 8 months. Metabolic parameters and blood pressure were assessed during the treatments. After the rats were euthanized, kidney samples were collected for histological and molecular biological studies. VEGF, VEGFR1, VEGFR2 and fibronectin expression, and Src and caveolin-1 phosphorylation in the kidneys were assessed using RT-PCR, Western blot and immunohistochemistry assays. The association between VEGFR2 and caveolin-1 was analyzed with immunoprecipitation.Chronic administration of fasudil (30 and 100 mg·kg(-1)·d(-1)) or enalapril (10 mg/kg, bid) significantly attenuated the glomerular sclerosis and albuminuria in the diabetic rats. Furthermore, fasudil treatment prevented the upregulation of VEGF, VEGFR1, VEGFR2 and fibronectin, and the increased association between VEGFR2 and caveolin-1 in the renal cortices, and partially blocked Src activation and caveolin-1 phosphorylation on tyrosine 14 in the kidneys, whereas enalapril treatment had no effects on the VEGFR2/Src/caveolin-1 signaling pathway.Fasudil exerts protective actions in STZ-induced diabetic nephropathy by blocking the VEGFR2/Src/caveolin-1 signaling pathway and fibronectin upregulation. Thus, VEGFR2 may be a potential therapeutic target for the treatment of diabetic nephropathy.
Project description:Altered nucleoside levels may be linked to pathogenic signaling through adenosine receptors. We hypothesized that adenosine dysregulation contributes to fibrosis in diabetic kidney disease. Our findings indicate that high glucose levels and experimental diabetes decreased uptake activity through the equilibrative nucleoside transporter 1 (ENT1) in proximal tubule cells. In addition, a correlation between increased plasma content of adenosine and a marker of renal fibrosis in diabetic rats was evidenced. At the cellular level, exposure of HK2 cells to high glucose, TGF-? and the general adenosine receptor agonist NECA, induced the expression of profibrotic cell activation markers ?-SMA and fibronectin. These effects can be avoided by using a selective antagonist of the adenosine A3 receptor subtype in vitro. Furthermore, induction of fibrosis marker ?-SMA was prevented by the A3 receptor antagonist in diabetic rat kidneys. In conclusion, we evidenced the contribution of purinergic signaling to renal fibrosis in experimental diabetic nephropathy.
Project description:Podocyte injury in diabetic kidney disease contributes to the development of albuminuria and subsequent renal decline. Clinically, gastric bypass surgery is associated with reductions in albuminuria, and rodent studies demonstrate coherent improvements in renal histology. We aimed to investigate the mechanisms underpinning remission of albuminuria following gastric bypass focussing on podocyte injury. Firstly, we tracked the evolution of albuminuria and cognate evidence of histological and ultrastructural damage to the glomerulus in male Zucker Diabetic Fatty rats. Secondly, we examined the impact of gastric bypass in these rats, focussing on podocyte injury. Thirdly, we conducted a global transcriptomic study profiling the shift in the renal transcriptome in the Zucker Diabetic Fatty rats rat and its relevance to human disease. Lastly, we explored whether gastric bypass could reverse the changes seen in the disease associated transcriptome. Albuminuria in the Zucker Diabetic Fatty rat developed by 12 weeks of age. This was accompanied by glomerulomegaly, podocyte stress and ultrastructural evidence of podocyte dedifferentiation. When animals underwent gastric bypass at 12 weeks of age, marked reductions in albuminuria in association with normalisation of glomerular tuft size, attenuation of podocyte stress and improvements in podocyte foot process morphology were observed within 2 months of surgery. A characteristic disease associated gene expression signature was observed in the kidneys of Zucker Diabetic Fatty rats, with a core set of alterations conserved in global analysis of the human DKD transcriptome. Many of the shared gene expression alterations were reversed by gastric bypass. Reductions in podocyte injury represent a key mechanism underpinning the remission of albuminuria following gastric bypass. Overall design: RNA-seq was performed to identify the renal transcriptomic profile of kidney disease in the ZDF rat, and to investigate the relative effects of Roux-en-Y gastric bypass intervention on the renal transcriptome. N=6 replicates were profiled.
Project description:Elevated serum uric acid (UA) is a risk factor for the development of kidney disease. Inhibitors of xanthine oxidase (XOi), an enzyme involved in UA synthesis, have protective effects at early stages of experimental diabetic nephropathy (DN). However, long-term effects of XOi in models of DN remain to be determined.The development of albuminuria, renal structure and molecular markers of DN were studied in type 2 diabetic Zucker obese (ZO) rats treated for 18 weeks with the XOi febuxostat and compared with vehicle-treated ZO rats, ZO rats treated with enalapril or a combination of both agents, and lean Zucker rats without metabolic defects.Febuxostat normalized serum UA and attenuated the development of albuminuria, renal structural changes, with no significant effects on BP, metabolic control or systemic markers of oxidative stress (OS). Most of these actions were comparable with those of enalapril. Combination treatment induced marked decreases in BP and was more effective in ameliorating structural changes, expression of profibrotic genes and systemic OS than either monotherapy. Febuxostat attenuated renal protein expression of TGF-ß, CTGF, collagen 4, mesenchymal markers (FSP1 and vimentin) and a tissue marker of OS nitrotyrosine. Moreover, febuxostat attenuated TGF-ß- and S100B-induced increased expression of fibrogenic molecules in renal tubular cells in vitro in UA-free media in an Akt kinase-dependent manner.Febuxostat is protective and enhances the actions of enalapril in experimental DN. Multiple mechanisms might be involved, such as a reduction of UA, renal OS and inhibition of profibrotic signalling.