Actin dynamics at focal adhesions: a common endpoint and putative therapeutic target for proteinuric kidney diseases.

Proteinuria encompasses diverse causes including both genetic diseases and acquired forms such as diabetic and hypertensive nephropathy. The basis of proteinuria is a disturbance in size selectivity of the glomerular filtration barrier, which largely depends on the podocyte: a terminally differentiated epithelial cell type covering the outer surface of the glomerulus. Compromised podocyte structure is one of the earliest signs of glomerular injury. The phenotype of diverse animal models and podocyte cell culture firmly established the essential role of the actin cytoskeleton in maintaining functional podocyte structure. Podocyte foot processes, actin-based membrane extensions, contain 2 molecularly distinct "hubs" that control actin dynamics: a slit diaphragm and focal adhesions. Although loss of foot processes encompasses disassembly of slit diaphragm multiprotein complexes, as long as cells are attached to the glomerular basement membrane, focal adhesions will be the sites in which stress due to filtration flow is counteracted by forces generated by the actin network in foot processes. Numerous studies within last 20 years have identified actin binding and regulatory proteins as well as integrins as essential components of signaling and actin dynamics at focal adhesions in podocytes, suggesting that some of them may become novel, druggable targets for proteinuric kidney diseases. Here we review evidence supporting the idea that current treatments for chronic kidney diseases beneficially and directly target the podocyte actin cytoskeleton associated with focal adhesions and suggest that therapeutic reagents that target the focal adhesion-regulated actin cytoskeleton in foot processes have potential to modernize treatments for chronic kidney diseases.

Amelioration of Diabetic Nephropathy Using a Retinoic Acid Receptor ß2 Agonist.

Vitamin A (VA) and its derivatives, known as retinoids, play critical roles in renal development through retinoic acid receptor ß2 (RARß2). Disruptions in VA signaling pathways are associated with the onset of diabetic nephropathy (DN). Despite the known role of RARß2 in renal development, the effects of selective agonists for RARß2 in a high-fat diet (HFD) model of DN are unknown. Here we examined whether AC261066 (AC261), a highly selective agonist for RARß2, exhibited therapeutic effects in a HFD model of DN in C57BL/6 mice. Twelve weeks of AC261 administration to HFD-fed mice was well tolerated with no observable side effects. Compared with HFD-fed mice, HFD + AC261-treated mice had improved glycemic control and reductions in proteinuria and urine albumin-to-creatinine ratio. Several cellular hallmarks of DN were mitigated in HFD + AC261-treated mice, including reductions in tubule lipid droplets, podocyte (POD) effacement, endothelial cell collapse, mesangial expansion, and glomerular basement membrane thickening. Mesangial and tubule interstitial expression of the myofibroblast markers α-smooth muscle actin (α-SMA) and type IV collagen (Col-IV) was lower in HFD + AC261-treated mice compared with HFD alone. Ultrastructural and immunohistochemistry analyses showed that, compared with HFD-fed mice, HFD + AC261-treated mice showed preservation of POD foot process and slit-diaphragm morphology, an increase in the levels of slit-diagram protein podocin, and the transcription factor Wilms tumor-suppressor gene 1 in PODs. Given the need for novel DN therapies, our results warrant further studies of the therapeutic properties of AC261 in DN.

Targeted inhibition of Axl receptor tyrosine kinase ameliorates anti-GBM-induced lupus-like nephritis.

Glomerulonephritis (GN) is a typical lesion in autoantibody and immune complex disorders, including SLE. Because the Gas6/Axl pathway has been implicated in the pathogenesis of many types of GN, targeting this pathway might ameliorate GN. Consequently, we have studied the efficacy and mechanism of R428, a potent selective Axl inhibitor, in the prevention of experimental anti-GBM nephritis. Axl upregulation was investigated with Sp1/3 siRNA in the SV40-transformed mesangial cells. For Axl inhibition, a daily dose of R428 (125 mg/kg) or vehicle was administered orally. GN was induced with anti-GBM sera. Renal disease development was followed by serial blood urine nitrogen (BUN) determinations and by evaluation of kidney histology at the time of sacrifice. Axl-associated signaling proteins were analyzed by Western blotting and inflammatory cytokine secretion was analyzed by Proteome array. SiRNA data revealed the transcription factor Sp1 to be an important regulator of mesangial Axl expression. Anti-GBM serum induced severe nephritis with azotemia, protein casts and necrotic cell death. R428 treatment diminished renal Axl expression and improved kidney function, with significantly decreased BUN and glomerular proliferation. R428 treatment inhibited Axl and significantly decreased Akt phosphorylation and renal inflammatory cytokine and chemokine expression; similar effects were observed in anti-GBM antiserum-treated Axl-KO mice. These studies support a role for Axl inhibition in glomerulonephritis.

Tubular basement membrane immune complex deposition is associated with activity and progression of lupus nephritis: a large multicenter Chinese study.

Tubulointerstitial injury is found frequently in lupus nephritis. Immune complex deposits can occur in the tubular basement membranes (TBMs), although its significance in lupus nephritis patients remains unclear. This study assessed the clinical and prognostic features of lupus nephritis patients with TBM deposits in a large Chinese multicenter cohort. Complete data were collected from 195 patients with renal biopsy-proven lupus nephritis diagnosed in the Peking University First Hospital as the discovery cohort. A total of 102 lupus nephritis patients were enrolled from another four centers as the validation cohort. The status of TBM deposits was retrospectively assessed using electron microscopy, and the associations of the deposits with clinical data, pathological characteristics and renal outcomes were further analyzed. The percentage of positive TBM deposits was nearly 30% in the lupus nephritis patients. Using immuno-gold labeling, we found that 10/10 patients were positive for IgG, 7/10 were C3d positive, 6/10 were C1q positive, and 1/10 were C4d positive. Patients with TBM deposits presented with more active features, including a higher SLEDAI score (SLE Disease Activity Index) ( p < 0.001), higher serum creatinine level ( p = 0.001) and lower serum C3 level ( p < 0.001). These patients also presented with higher scores for most renal pathological indices, including the total activity indices score ( p < 0.001) and total chronicity indices score ( p = 0.001). TBM deposits affected renal outcomes in the univariate Cox hazards regression analysis (HR = 4.2, 95% CI = 1.3-14.3, p = 0.02). In conclusion, TBM deposits were common in lupus nephritis patients and correlated closely with the clinical disease activity and renal outcome.

Neuropilin1 regulates glomerular function and basement membrane composition through pericytes in the mouse kidney.

Neuropilin1 (Nrp1) is a co-receptor best known to regulate the development of endothelial cells and is a target of anticancer therapies. However, its role in other vascular cells including pericytes is emergent. The kidney is an organ with high pericyte density and cancer patients develop severe proteinuria following administration of NRP1B-neutralizing antibody combined with bevacizumab. Therefore, we investigated whether Nrp1 regulates glomerular capillary integrity after completion of renal development using two mouse models; tamoxifen-inducible NG2Cre to delete Nrp1 specifically in pericytes and administration of Nrp1-neutralizing antibodies. Specific Nrp1 deletion in pericytes did not affect pericyte number but mutant mice developed hematuria with glomerular basement membrane defects. Despite foot process effacement, albuminuria was absent and expression of podocyte proteins remained unchanged upon Nrp1 deletion. Additionally, these mice displayed dilation of the afferent arteriole and glomerular capillaries leading to glomerular hyperfiltration. Nidogen-1 mRNA was downregulated and collagen4α3 mRNA was upregulated with no significant effect on the expression of other basement membrane genes in the mutant mice. These features were phenocopied by treating wild-type mice with Nrp1-neutralizing antibodies. Thus, our results reveal a postdevelopmental role of Nrp1 in renal pericytes as an important regulator of glomerular basement membrane integrity. Furthermore, our study offers novel mechanistic insights into renal side effects of Nrp1 targeting cancer therapies.

Effect of mycophenolic acid in experimental, nontransplant glomerular diseases: new mechanisms beyond immune cells.

Mycophenolic acid (MPA) was introduced into clinical practice as immunosuppressive drug therapy to prevent allograft rejection. Since then, its clinical application has widened. Our goal was to review the lessons learned from experimental nontransplant glomerular disease models on the mechanisms of MPA therapy. T and B lymphocytes are preferentially dependent on de novo purine synthesis. By inhibiting the rate-limiting enzyme of de novo purine synthesis, MPA depletes the pool of deoxyguanosine triphosphate (dGTP) and inhibits proliferation of these immune cells. Furthermore, MPA can also induce apoptosis of immune cells and is known to inhibit synthesis of fucose- and mannose-containing membrane glycoproteins altering the surface expression and binding ability of adhesion molecules. However, MPA exerts a direct effect also on nonimmune cells. Mesangial cells are partially dependent on de novo purine biosynthesis and are thus susceptible to MPA treatment. Additionally, MPA can inhibit apoptosis in podocytes and seems to be beneficial in preserving the expression of nephrin and podocin, and by attenuation of urokinase receptor expression leads to decreased foot-process effacement. In summary, our manuscript sheds light on the molecular mechanisms underlying the antiproteinuric effect of MPA. Overall, MPA is an excellent treatment option in many immunologic glomerulopathies because it possesses immunosuppressive properties, has a remarkable effect on nonimmune cells and counteracts the proliferation of mesangial cells, expansion of mesangial matrix, and foot-process effacement of podocytes combined with a low systemic toxicity.

Erythropoietin protects the tubular basement membrane by promoting the bone marrow to release extracellular vesicles containing tPA-targeting miR-144.

Renal fibrosis is an inevitable outcome of chronic kidney disease (CKD). Erythropoietin (EPO) has been recently reported to be able to mitigate renal fibrosis. The mechanism underlying the protective effect of EPO, however, remains elusive. In the present study, employing a mouse model of renal tubulointerstitial fibrosis induced by unilateral ureteral obstruction (UUO), we demonstrated that EPO markedly reduced the disruption of the tubular basement membrane (TBM) through attenuating the activation of tissue plasminogen activator (tPA) and matrix metalloproteinase 9 (MMP9), the major matrix proteolytic network in the obstructed kidney. Instead of acting directly on tPA in the kidney, EPO strongly increased the level of circulating microRNA (miR)-144, which was delivered to the injured renal fibroblasts via extracellular vesicles (EVs) to target the tPA 3'-untranslated region and suppress tPA expression. The protective effect of EPO on mouse TBM was inhibited by miR-144 antagomir. Furthermore, in vitro results confirmed that EPO could stimulate bone marrow-derived Sca-1(+)CD44(+)CD11b(-)CD19(-) cells to secrete miR-144-containing EVs, which markedly suppressed tPA expression, as well as metalloproteinase 9 (MMP9) level and activity, in cultured renal fibroblasts. In conclusion, our study provides the first evidence that EPO protects mouse renal TBM through promoting bone marrow cells to generate and secrete miR-144, which, in turn, is efficiently delivered into the mouse kidney via EVs to inhibit the activation of the tPA/MMP9-mediated proteolytic network. This finding thus suggests that EPO, a hormone widely used to treat anemia in CKD, is a potential therapeutic strategy for renal fibrosis.

PF-1355, a mechanism-based myeloperoxidase inhibitor, prevents immune complex vasculitis and anti-glomerular basement membrane glomerulonephritis.

Small vessel vasculitis is a life-threatening condition and patients typically present with renal and pulmonary injury. Disease pathogenesis is associated with neutrophil accumulation, activation, and oxidative damage, the latter being driven in large part by myeloperoxidase (MPO), which generates hypochlorous acid among other oxidants. MPO has been associated with vasculitis, disseminated vascular inflammation typically involving pulmonary and renal microvasculature and often resulting in critical consequences. MPO contributes to vascular injury by 1) catabolizing nitric oxide, impairing vasomotor function; 2) causing oxidative damage to lipoproteins and endothelial cells, leading to atherosclerosis; and 3) stimulating formation of neutrophil extracellular traps, resulting in vessel occlusion and thrombosis. Here we report a selective 2-thiouracil mechanism-based MPO inhibitor (PF-1355 [2-(6-(2,5-dimethoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide) and demonstrate that MPO is a critical mediator of vasculitis in mouse disease models. A pharmacokinetic/pharmacodynamic response model of PF-1355 exposure in relation with MPO activity was derived from mouse peritonitis. The contribution of MPO activity to vasculitis was then examined in an immune complex model of pulmonary disease. Oral administration of PF-1355 reduced plasma MPO activity, vascular edema, neutrophil recruitment, and elevated circulating cytokines. In a model of anti-glomerular basement membrane disease, formerly known as Goodpasture disease, albuminuria and chronic renal dysfunction were completely suppressed by PF-1355 treatment. This study shows that MPO activity is critical in driving immune complex vasculitis and provides confidence in testing the hypothesis that MPO inhibition will provide benefit in treating human vasculitic diseases.

Notoginsenoside R1 ameliorates podocyte adhesion under diabetic condition through α3ß1 integrin upregulation in vitro and in vivo.

BACKGROUND: Decreased expression of α3ß1 integrin may contribute to reduction in podocyte adhesion to glomerular basement membrane (GBM), which represents a novel early mechanism leading to diabetic kidney disease (DKD). Here, we examined the protective effects of Notoginsenoside R1 (NR1) on podocyte adhesion and α3ß1 integrin expression under diabetic condition in vitro and in vivo. METHODS: Conditionally immortalized mouse podocytes were exposed to high glucose (HG) with 10 and 100µg /ml of NR1 for 24 h. Podocyte adhesion, albuminuria, oxidative markers, renal histopathology, podocyte number per glomerular volume, integrin-linked kinase (ILK) activity and α3ß1 integrin expression were measured in vitro and in vivo. RESULTS: HG decreased podocyte adhesive capacity and α3ß1 integrin expression, the main podocyte anchoring dimer to the GBM. However, NR1 ameliorated impaired podocyte adhesive capacity and partially restored α3ß1 integrin protein and mRNA expression. These in vitro observations were confirmed in vivo. In streptozotocin(STZ)-induced diabetic rats, treatment with NR1 (5 and 10 mg· kg(-1)· d(-1)) for 12 weeks partially restored the number of podocytes per glomerular volume and glomerular α3ß1 integrin expression, as well as ameliorated albuminuria, histopathology and oxidative stress. NR1 also inhibited glomerular ILK activity in diabetic rats. CONCLUSION: NR1, a novel antioxidant, ameliorated glucose-induced impaired podocyte adhesive capacity and subsequent podocyte depopulation partly through α3ß1 integrin upregulation. These findings might provide a potential new therapeutic option for the treatment of DKD.

Glomerular endothelial surface layer acts as a barrier against albumin filtration.

Glomerular endothelium is highly fenestrated, and its contribution to glomerular barrier function is the subject of debate. In recent years, a polysaccharide-rich endothelial surface layer (ESL) has been postulated to act as a filtration barrier for large molecules, such as albumin. To test this hypothesis, we disturbed the ESL in C57Bl/6 mice using long-term hyaluronidase infusion for 4 weeks and monitored albumin passage using immunolabeling and correlative light-electron microscopy that allows for complete and integral assessment of glomerular albumin passage. ESL ultrastructure was visualized by transmission electron microscopy using cupromeronic blue and by localization of ESL binding lectins using confocal microscopy. We demonstrate that glomerular fenestrae are filled with dense negatively charged polysaccharide structures that are largely removed in the presence of circulating hyaluronidase, leaving the polysaccharide surfaces of other glomerular cells intact. Both retention of native ferritin [corrected] in the glomerular basement membrane and systemic blood pressure were unaltered. Enzyme treatment, however, induced albumin passage across the endothelium in 90% of glomeruli, whereas this could not be observed in controls. Yet, there was no net albuminuria due to binding and uptake of filtered albumin by the podocytes and parietal epithelium. ESL structure and function completely recovered within 4 weeks on cessation of hyaluronidase infusion. Thus, the polyanionic ESL component, hyaluronan, is a key component of the glomerular endothelial protein permeability barrier.

Celecoxib modifies glomerular basement membrane, mesangium and podocytes in OVE26 mice, but ibuprofen is more detrimental.

The role of COXs/PGs (cyclo-oxygenases/prostaglandins) in diabetic kidneys remains unclear. NSAIDs (non-steroidal anti-inflammatory drugs) that inhibit COXs/PGs are known for their renal toxicity, and COX-2 inhibitors worsen cardiovascular outcomes in susceptible individuals. Given the renal controversies concerning COX-2 inhibitors, we compared the effect of chronic NSAIDs (non-selective, ibuprofen; COX-2-selective, celecoxib) on diabetic kidneys in OVE26 mice from 8 weeks of age. Systolic BPs (blood pressures) were increased by NSAIDs in diabetic mice at 20 weeks, but were unchanged at 32 weeks. Although NSAIDs further increased diabetic kidney/body weight ratios, they did not affect albuminuria. Mesangial matrix was increased 2-fold by celecoxib but not ibuprofen. Electron microscopy revealed that NSAIDs reduced GBM (glomerular basement membrane) thickness and slit pore diameters. Although diabetics had increased glomerular diameters and reduced foot process densities, these were unaltered by NSAIDs. Celecoxib does not exacerbate the diabetic state, but PG inhibition may contribute to disease progression by modifying the GBM, mesangial area and podocyte structure in OVE26 mice. Despite these findings, celecoxib remains safer than a similar dose of ibuprofen. The present study substantiates the need to more closely consider selective COX-2 inhibitors such as celecoxib as alternatives to non-selective NSAIDs for therapeutic management in a setting of chronic kidney disease.

Dipeptidyl peptidase IV inhibitor attenuates kidney injury in streptozotocin-induced diabetic rats.

Dipeptidyl peptidase (DPP) IV inhibitors are probably beneficial for preventing diabetic complication and modulating glucagon-like peptide-1 receptor (GLP-1R) expression. The aim of this study was to determine whether the DPP IV inhibitor LAF237 (vildagliptin) has renoprotective qualities in streptozotocin-induced diabetic rats. Diabetic and nondiabetic rats were treated with an oral dose of 4 or 8 mg/kg/day LAF237 or placebo for 24 weeks, and renal injury was observed by light and electron microscopy. We also assessed DPP IV activity, active GLP-1 level, cAMP and 8-hydroxy-deoxyguanosine excretion, and GLP-1R, cleaved caspase 3, and transforming growth factor-ß1 (TGF-ß1) expression. LAF237 significantly decreased proteinuria, albuminuria, and urinary albumin/creatinine ratio, improved creatinine clearance, and dose-dependently inhibited interstitial expansion, glomerulosclerosis, and the thickening of the glomerular basement membrane in diabetic rats. It is noteworthy that LAF237 markedly down-regulated DPP IV activity and increased active GLP-1 levels, which probably prevented oxidative DNA damage and renal cell apoptosis by activating the GLP-1R and modulating cAMP. Renoprotection was also associated with a reduction in TGF-ß1 overexpression. Our study suggests that DPP IV inhibitors may ameliorate diabetic nephropathy as well as reduce the overproduction of TGF-ß1. The observed renoprotection is probably attributable to inhibition of DPP IV activity, mimicking of incretin action, and activation of the GLP-1R.

Statin attenuates experimental anti-glomerular basement membrane glomerulonephritis together with the augmentation of alternatively activated macrophages.

Macrophages are heterogeneous and include classically activated M1 and alternatively activated M2 macrophages, characterized by pro- and anti-inflammatory functions, respectively. Macrophages that express heme oxygenase-1 also exhibit anti-inflammatory effects. We assessed the anti-inflammatory effects of statin in experimental anti-glomerular basement membrane glomerulonephritis and in vitro, focusing on the macrophage heterogeneity. Rats were induced anti-glomerular basement membrane glomerulonephritis and treated with atorvastatin (20 mg/kg/day) or vehicle (control). Control rats showed infiltration of macrophages in the glomeruli at day 3 and developed crescentic glomerulonephritis by day 7, together with increased mRNA levels of the M1 macrophage-associated cytokines, interferon-gamma, tumor necrosis factor-alpha, and interleukin-12. In contrast, statin reduced the level of proteinuria, reduced infiltration of macrophages in glomeruli with suppression of monocyte chemotactic protein-1 expression, and inhibited the formation of necrotizing and crescentic lesions. The number of glomerular ED3-positive macrophages decreased with down-regulation of M1 macrophage-associated cytokines. Furthermore, statin augmented ED2-positive M2 macrophages with up-regulation of the M2 macrophage-associated chemokines and cytokines, chemokine (C-C motif) Iigand-17 and interleukin-10. Statin also increased the glomerular interleukin-10-expressing heme oxygenase-1-positive macrophages. Statin inhibited macrophage development, and suppressed ED3-positive macrophages, but augmented ED2-positive macrophages in M2-associated cytokine environment in vitro. We conclude that the anti-inflammatory effects of statin in glomerulonephritis are mediated through inhibition of macrophage infiltration as well as augmentation of anti-inflammatory macrophages.

A different perspective on the filtration barrier after kidney stone formation: An immunohistochemical and biochemical study.

The aim of this study is to investigate whether the filtration barrier is affected by experimental kidney stone formation. Thirty-two rats divided into 4 equally groups (n = 8) at random. Group I control; Group II 1% ethylene glycol; Group III 1% Ethylene glycol + 0.25% Ammonium chloride; Group IV 1% Ethylene glycol + 0.5% Ammonium chloride group. Tissues applied hematoxylin-eosin, periodic-acid-Schiff, Pizzolato's staining. Immunohistochemically stained with integrin α3ß1, type IV collagen, laminin, nephrin, CD2-associated protein (CD2AP) and podocin to show the filtration barrier structure. The TUNEL method was used for apoptosis. The amount of calcium, magnesium, creatinine and uric acid in urine and blood samples, also urine microprotein determined. Stones were formed in all experimental groups. Urine calcium, creatinine, uric acid levels decreased, magnesium levels were not changed. No statistically significant change was observed in blood serum results and TUNEL analysis. Immunohistochemical results showed an increase in nephrin, podocin, CD2AP, laminin and a decrease in integrin α3ß1 and type IV collagen. Consequently, there is an increase in the expression densities of the proteins incorporated in the structure to prevent loss of functionality in the cellular part supporting the structure against a weakening of the basement membrane structure in the glomerular structure in which urine is filtered.

Ameliorative effect of white tea from 50-year-old tree of Camellia sinensis L. (Theaceae) on kidney damage in diabetic mice via SIRT1/AMPK pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Diabetic kidney damage (DKD) is one of the most common complications of diabetes, which is known as a chronic inflammatory kidney disease caused by persistent hyperglycemia. White tea was originally used as a folk medicine to treat measles in ancient China. What arouses our interest is that there is a traditional method to treat diabetes with white tea taken from over 30-year-old tree of Camellia sinensis L. However, there are few reports on the renal protection of white tea. AIM OF THE STUDY: This present study was designed to study the potential protective effects of white tea (WT) and old tree white tea (OTWT) on high-fat-diet (HFD) combined with streptozotocin (STZ)-induced type 2 diabetic mice to explore the possible mechanism of WT/OTWT against DKD. MATERIALS AND METHODS: C57BL/6 mice were randomly divided into four groups: NC, T2D, WT (400 mg/kg·b.w, p.o.), OTWT (400 mg/kg·b.w, p.o.). Diabetes was established in all groups except NC group, by six weeks of HFD feeding combined with STZ (50 mg/kg, i.p.) for 3 times, treatments were administered for six weeks and then all the animals were decapitated; kidney tissues and blood samples were collected for the further analysis, including: levels of insulin, lipid metabolism (TG, TC, HDL, LDL, FFA), antioxidative enzymes (catalase (CAT), super oxide dismutase (SOD), glutathione peroxidase (GPx)), blood urea nitrogen (BUN) and creatine, inflammatory cytokines (TNF-α, IL-1ß, COX-2, iNOS, MCP-1), advanced glycation end products (AGE), receptor of AGE (RAGE), Nrf2, AMPK, SIRT1, and PGC-1α. H&E, PAS and Masson staining were performed to examine the histopathological alterations of the kidneys. RESULTS: Our data showed that WT and OTWT reversed the abnormal serum lipids (TG, TC, HDL, LDL, FFA) in T2D mice, upregulated antioxidative enzymes levels (CAT, SOD, GPx) and inhibit the excessive production of proinflammatory mediators (including MCP-1, TNF-α, IL1ß, COX-2 and iNOS) by varying degrees, and OTWT was more effective. In histopathology, OTWT could significantly alleviate the accumulation of renal AGE in T2D mice, thereby improving the structural changes of the kidneys, such as glomerular hypertrophy, glomerular basement membrane thickening and kidney FIbrosis. CONCLUSIONS: Both WT and OTWT could alleviate the diabetic changes in T2D mice via hypoglycemic, hypolipidemic, anti-oxidative and anti-inflammatory effects, while OTWT was more evident. OTWT could prominently alleviate the accumulation of AGE in the kidneys of T2D mice, thereby ameliorating the renal oxidative stress and inflammatory damage, which was associated with the activation of SIRT1/AMPK pathway.

Preventive effect of taurine on experimental type II diabetic nephropathy.

BACKGROUND: It has been verified that taurine has some preventive effects on diabetes and its complications when used alone or together with other drugs, but there are few reports about taurine on the prevention of diabetic nephropathy, the mechanisms of which are still unknown. METHODS: Taurine was administered to type diabetic rats induced by high fat high sugar diet combined with STZ injection. The preventive effect of taurine on diabetic nephropathy was investigated by detecting blood glucose, lipid metabolism, kidney function and glomerular basement membrane metabolism. RESULTS: Taurine could lower blood glucose, TG, TC, BUN, Scr, NAG, U-PRO, the expression of laminin B1(LBN1) mRNA, and increase HDL-C of diabetic rats. CONCLUSIONS: The results indicated that taurine could prevent the occurrence and development of diabetic nephropathy by decreasing blood glucose, improving lipid metabolism, glomerular basement membrane metabolism, and kidney function.

[Pentosan polysulfate sodium prevents kidney morphological changes and albuminuria in rats with type 1 diabetes]. / El pentosán polisulfato de sodio previene las alteraciones morfológicas renales y la albuminuria en ratas con diabetes tipo 1.

Decreased levels of glycosaminoglycans (GAGs) have been observed in the kidney and other organs, in human and animal models of diabetes. Long-term administration of heparins and other glycosaminoglycans has demonstrated a beneficial effect on morphological and functional kidney abnormalities in diabetic rats. We assessed the effect of pentosan polysulfate sodium (PPS), a semi-synthetic glycosaminoglycan with low anticoagulant activity, on kidney involvement in streptozotocin diabetic rats. Diabetes was induced in male Sprague-Dawley rats by i.v. administration of streptozotocin (STZ). Animals were randomly allocated to three groups: C = control, STZ and STZ + PPS = pretreated with PPS (15 mg/kg, s.c.). After three months of follow-up, blood and 24 h-urine samples were obtained, the animals were sacrificed and the kidney microdissected for morphometric analysis. Urinary albumin excretion was markedly increased in untreated diabetic rats (C = 0.26 ± 0.03 vs STZ = 7.75 ± 1.8 mg/24 h) and PPS treatment partially prevented the albumin rise (3.7 ± 0.7 mg/24 h), without affecting the metabolic control HbA1c (C = 3.6 ± 1.7; STZ = 8.82 ± 0.47; STZ + PPS = 8.63 ± 0.54). Electron microscope observation revealed typical renal lesions described in experimental diabetes (STZ group). PPS administration prevents the tubular basement membrane thickening and the loss of cytoarchitecture induced by experimental diabetes. Our data demonstrate that long-term administration of PPS has a favourable effect on morphological and functional abnormalities in kidneys of diabetic rats and suggests a potential therapeutic use for this compound.

Long-term therapeutic effect of vitamin D analog doxercalciferol on diabetic nephropathy: strong synergism with AT1 receptor antagonist.

The intrarenal renin-angiotensin system (RAS) plays a key role in the development of diabetic nephropathy. Recently, we showed that combination therapy with an AT(1) receptor blocker (ARB) and an activated vitamin D analog produced excellent synergistic effects against diabetic nephropathy, as a result of blockade of the ARB-induced compensatory renin increase. Given the diversity of vitamin D analogs, here we used a pro-drug vitamin D analog, doxercalciferol (1alpha-hydroxyvitamin D(2)), to further test the efficacy of the combination strategy in long-term treatment. Streptozotocin-induced diabetic DBA/2J mice were treated with vehicle, losartan, doxercalciferol (0.4 and 0.6 microg/kg), or losartan and doxercalciferol combinations for 20 wk. Vehicle-treated diabetic mice developed progressive albuminuria and glomerulosclerosis. Losartan alone moderately ameliorated kidney injury, with renin being drastically upregulated. A similar therapeutic effect was seen with doxercalciferol alone, which markedly suppressed renin and angiotensinogen expression. The losartan and doxercalciferol combination most effectively prevented albuminuria, restored glomerular filtration barrier structure, and dramatically reduced glomerulosclerosis in a dose-dependent manner. These effects were accompanied by blockade of intrarenal renin upregulation and ANG II accumulation. These data demonstrate an excellent therapeutic potential for doxercalciferol in diabetic renal disease and confirm the concept that blockade of the compensatory renin increase enhances the efficacy of RAS inhibition and produces synergistic therapeutic effects in combination therapy.

Mechanical forces and TGFbeta1 reduce podocyte adhesion through alpha3beta1 integrin downregulation.

BACKGROUND: Podocyturia is a marker of diabetic nephr- opathy, a possible determinant of its progression and a powerful risk factor for cardiovascular disease. A reduction in podocyte adhesion to the glomerular basement membrane (GBM) via downregulation of alpha3beta1 integrin expression, the main podocyte anchoring dimer to the GBM, may represent one of the mechanisms of podocyturia in glomerular disease. This study investigated the role of mechanical forces and transforming growth factor beta1 (TGFbeta1) in podocyte adhesion and integrin expression. METHODS: Conditionally immortalized murine podocytes were exposed to mechanical stretch and/or TGFbeta1 for 48 h. Podocyte adhesion, apoptosis and alpha3beta1 integrin expression were assessed. RESULTS: Stretch and TGFbeta1 significantly reduced podocyte adhesion and alpha3beta1 integrin expression, events paralleled by increased apoptosis. Blockade of beta1 integrin, with a specific antibody, demonstrated a reduced podocyte adhesion indicating that beta1 integrin downregulation was required for the loss of podocyte adhesion. This was linked to an increase in podocyte apoptosis. The role of apoptosis in podocyte adhesion was further investigated using caspase-3 inhibitors. Podocyte apoptosis inhibition did not affect stretch- and TGFbeta1-mediated integrin downregulation and the loss of podocyte adhesion, suggesting that alpha3beta1 integrin downregulation is sufficient to alter cell adhesion. Although stretch significantly increased podocyte TGFbeta type I, II and III receptors but not podocyte TGFbeta1 secretion, the combination of stretch and TGFbeta1 did not show any additive or synergistic effects on podocyte adhesion and alpha3beta1 integrin expression. CONCLUSIONS: These results suggest that downregulation of alpha3beta1 integrin expression, by mechanical forces or TGFbeta1, is per se sufficient to reduce podocyte adhesion. Apoptosis may represent a parallel important determinant of the podocyte loss from the GBM.

Nephrotic syndrome induced by dibasic sodium phosphate injections for twenty-eight days in rats.

Sprague-Dawley rats received once daily tail-vein injections of 360 mM dibasic sodium phosphate solution at 8 mL/kg for fourteen or twenty-eight days. Clinical examination revealed persistent proteinuria from three days after the first dosing and thereafter severe proteinuria from eight days or later in the phosphate-treated groups. Proteinuria developed without remission even after fourteen-day withdrawal in the fourteen-day dosed group. Phosphate-treated animals developed lipemia, hypercholesterolemia, anemia, higher serum fibrinogen levels, and lower serum albumin/globulin ratios on day 29. Renal weight increased significantly compared with control animals, and the kidneys appeared pale and enlarged with a rough surface. Histopathologically, glomerular changes consisted of mineralization in whole glomeruli, glomerular capillary dilatation, partial adhesion of glomerular tufts to Bowman's capsule, and mesangiolysis. Ultrastructural lesions such as an increased number of microvilli, effacement of foot processes, and thickening of the glomerular basement membrane, and immunocytochemical changes in podocytes, mainly decreased podoplanin-positive cells and increased desmin expression, were also conspicuous in the phosphate-treated rats for twenty-eight days. Marked tubulointerstitial lesions were tubular regeneration and dilatation, protein casts, mineralization in the basement membrane, focal interstitial inflammation, and fibrosis in the cortex. These clinical and morphological changes were similar to features of human nephrotic syndrome.