Curcumin attenuates high glucose-induced podocyte apoptosis by regulating functional connections between caveolin-1 phosphorylation and ROS.

AIM: Caveolin-1 (cav-1) is a major multifunctional scaffolding protein of caveolae. Cav-1 is primarily expressed in mesangial cells, renal proximal tubule cells and podocytes in kidneys. Recent evidence shows that the functional connections between cav-1 and ROS play a key role in many diseases. In this study we investigated whether regulating the functional connections between cav-1 and ROS in kidneys contributed to the beneficial effects of curcumin in treating diabetic nephropathy in vitro and in vivo. METHODS: Cultured mouse podocytes (mpc5) were incubated in a high glucose (HG, 30 mmol/L) medium for 24, 48 or 72 h. Male rats were injected with STZ (60 mg/kg, ip) to induce diabetes. ROS generation, SOD activity, MDA content and caspase-3 activity in the cultured cells and kidney cortex homogenate were determined. Apoptotic proteins and cav-1 phosphorylation were analyzed using Western blot analyses. RESULTS: Incubation in HG-containing medium time-dependently increased ROS production, oxidative stress, apoptosis, and cav-1 phosphorylation in podocytes. Pretreatment with curcumin (1, 5, and 10 µmol/L) dose-dependently attenuated these abnormalities in HG-treated podocytes. Furthermore, in HG-containing medium, the podocytes transfected with a recombinant plasmid GFP-cav-1 Y14F (mutation at a cav-1 phosphorylation site) exhibited significantly decreased ROS production and apoptosis compared with the cells transfected with empty vector. In diabetic rats, administration of curcumin (100 or 200 mg/kg body weight per day, ig, for 8 weeks) not only significantly improved the renal function, but also suppressed ROS levels, oxidative stress, apoptosis and cav-1 phosphorylation in the kidneys. CONCLUSION: Curcumin attenuates high glucose-induced podocyte apoptosis in vitro and diabetic nephropathy in vivo partly through regulating the functional connections between cav-1 phosphorylation and ROS.

Relationship Between Serum DNA Replication, Clinicopathological Characteristics and Prognosis of Hepatitis B Virus-associated Glomerulonephritis with Severe Proteinuria by Lamivudine Plus Adefovir Dipivoxil Combination Therapy.

OBJECTIVE: To explore the relationship between HBV DNA and the clinical manifestations, pathological types, injury severity, and prognosis with HBV-GN. METHODS: 102 patients with HBV-GN were divided into 3 groups, according to the serum titer of the HBV DNA. 24-h urine protein excretion, and other parameters were measured. Renal biopsy were performed. The association between HBV DNA and the pathological stage of membranous nephropathy was analyzed in 78 patients with HBV-MN. 24-h urine protein excretion was used for the evaluation of the prognosis, and the relationship between HBV DNA and prognosis were analyzed. RESULTS: Several findings were demonstrated with the increase of serum HBV DNA: 24-h urine protein excretion, plasma cholesterol, and triglycerides increased significantly (P%lt;0.05), while the plasma level of albumin decreased significantly (P%lt;0.05); The changes of serum creatinine, C3 and C4 were found but no statistical significance. Glomerular deposition of HBVAg increased, and the pathological injury was more severe. The clinical remission rate was lower in the high replication group after treatment as compared with the low replication group (P%lt;0.01). CONCLUSION: With the increase of serum HBV DNA, the urine protein excretion and the kidney injury were more severe, and the clinical remission rate was decreased.

Efficacy and safety of Abelmoschus manihot for primary glomerular disease: a prospective, multicenter randomized controlled clinical trial.

BACKGROUND: Abelmoschus manihot, a single medicament of traditional Chinese medicine, has been widely used to treat kidney disease. This is the first randomized controlled clinical trial to assess its efficacy and safety in patients with primary glomerular disease. STUDY DESIGN: Prospective, open-label, multicenter, randomized, controlled, clinical trial. SETTING & PARTICIPANTS: From May 2010 to October 2011, a total of 417 patients with biopsy-proven primary glomerular disease from 26 hospitals participated in the study. INTERVENTIONS: A manihot in the form of a huangkui capsule, 2.5 g, 3 times per day; losartan potassium, 50mg/d; or combined treatment, a huangkui capsule at 2.5 g 3 times per day, was combined with losartan potassium, 50mg/d. The duration of intervention was 24 weeks. OUTCOMES & MEASUREMENTS: The primary outcome was change in 24-hour proteinuria from baseline after treatment. Change in estimated glomerular filtration rate (eGFR) from baseline after treatment was a secondary outcome. The 24-hour proteinuria was measured every 4 weeks and eGFR was measured at 0, 4, 12, and 24 weeks. RESULTS: Mean baseline urine protein excretion was 1,045, 1,084, and 1,073 mg/d in the A manihot, losartan, and combined groups, respectively, and mean eGFR was 108, 106, and 106 mL/min/1.73 m2, respectively. After 24 weeks of treatment, mean changes in proteinuria were protein excretion of -508, -376, and -545 mg/d, respectively (P=0.003 for A manihot vs losartan and P<0.001 for the combined treatment vs losartan). Mean eGFR did not change significantly. The incidence of adverse reactions was not different among the 3 groups (P>0.05), and there were no severe adverse events in any group. LIMITATIONS: Results cannot be generalized to those with nephrotic syndrome or reduced eGFR. CONCLUSIONS: A manihot is a promising therapy for patients with primary kidney disease (chronic kidney disease stages 1-2) with moderate proteinuria.

[Clinical significance of toll-like receptor 4 expression on the surface of peripheral blood mononuclear cells in uremic patients].

OBJECTIVE: To explore the clinical significance of toll-like receptor 4 expression on the surface of peripheral blood mononuclear cells (PBMC) in uremic patients and observe the effect of ultrapure dialysate on the PBMC expression of TLR4 in these patients. METHODS: Eighty patients on maintenance dialysis were randomly divided into two groups: conventional dialysate group (CD, n=40), ultrapure dialysate group (UPD, n=40) and 40 uremic patients without dialysis in NHD group. The blood cells from all patients and 40 healthy controls were stained with FITC labeling anti-TLR4 monoclonal antibodies. Samples were collected and analyzed by flow cytometry. RESULTS: The expression of TLR4 was significantly lower in CD group (18.1±3.7) than in NHD group (24.5±4.6, P<0.05) and healthy control group (31.6±5.8, P<0.01). And marked difference existed between CD group (18.1±3.7) and UPD group (23.1±3.2, P<0.05) at Month 6 post-dialysis. In CD group the expression of TLR4 became significantly smaller as the duration of dialysis increased (P<0.05) while in UPD group although the expression of TLR4 became smaller as the duration of dialysis became longer. But the difference was not statistically significant (P>0.05). CONCLUSION: The PBMC expression of TLR4 becomes down-regulated in uremic patients with or without dialysis and its expression is smaller in conventional dialysate group than in ultrapure dialysate group. The conventional dialysate may suppress the expression of TLR4 while the phenomenon is absent in ultrapure dialysate group.

Effect of activin A on tubulointerstitial fibrosis in diabetic nephropathy.

AIM: The effect of activin A on tubulointerstitial fibrosis in diabetic nephropathy (DN) using streptozotocin (STZ)-induced diabetic rats and high glucose-cultured HK-2 cells was investigated. METHODS: Male Wistar rats were randomized into a normal control group (NC) and diabetes mellitus group (DM). Diabetes was induced by i.p. injection of STZ. Six rats were respectively killed 4, 8, 12 and 16 weeks after model establishment in each group. The changes of kidney weight/bodyweight (KW/BW), urine albumin excretion rate (AER) and creatinine clearance rate (Ccr) were determined. The morphology of tubulointerstitium was observed by light microscopy. Further biochemical analysis was provided using immunohistochemistry and real-time polymerase chain reaction. The different parameters in high glucose-cultured HK-2 cells were monitored by western blotting or enzyme-linked immunosorbent assay (ELISA) and the intervention of rh-follistatin on them was investigated. RESULTS: Compared with the NC group, there was marked enlargement in the levels of KW/BW, AER, Ccr and interstitial fibrosis index, and the production of P-Smad2/3 and fibronectin in the DM group from 8 to 16 weeks. Activin betaA, mainly located in tubular epithelial cells, was significantly higher in the DM group than that in the NC group throughout the study periods. Follistatin was abundant in the NC group, but was diminished gradually in the DM group. High glucose may facilitate the synthesis of activin betaA, transforming growth factor (TGF)-beta, P-Smad2/3 and fibronectin in HK-2 cells while rh-follistatin inhibited them except TGF-beta. CONCLUSION: Activin A is involved in tubulointerstitial fibrosis in DN by inducing the production of fibronectin through Smad signal pathway.

[Effects of valsartan, mycophenolate mofetil and their combined application on TRAIL and nuclear factor-kappaB expression in the kidneys of diabetic rats].

OBJECTIVE: To evaluate the expression of TNF-related apoptosis inducing ligand (TRAIL) and nuclear factor (NF)-kappaB in the kidney tissues of diabetic rats and the effects of valsartan, mycophenolate mofetil (MMF), and their combined application on the renal TRAIL and NF-kappaB expression. METHODS: Eighty uninephrectomized male Wistar rats were randomly divided into 2 groups: normal control (NC) group (n = 28), undergoing intraperitoneal injection of citric acid buffer, and diabetes mellitus (DM) group, undergoing intraperitoneal injection of streptozotocin (STZ) to establish DM models. The 52 DM rats were randomly divided into 7 equal subgroups: DM without treatment for 4 weeks (DM4), DM without treatment for 8 weeks (DM8) DM without treatment for 12 weeks (DM12) , and DM without treatment for 16 weeks (DM16), valsartan treatment (DM + V), MMF treatment (DM + M), and combined treatment (DM + V + M). The treatment subgroups were treated for 8 weeks immediately after the diabetic models ere established. Twenty-four hour urine was collected to measure the amount of protein 4, 8, 12, and 16 weeks after the induction of DM respectively. The rats were sacrificed. Blood samples were collected from the abdominal aorta to detect the blood urea nitrogen (BUN), serum creatinine (sCr), albumin, and glucose. The kidneys were taken out. Hypertrophy index (left kidney weight/body weight) was determined. Quantitative real time RT-PCR was performed to detect the expression of TRAIL and NF-kappaB mRNA. Immunohistochemistry was used to detect the protein expression of TRAIL and NF-kappaB. RESULTS: 1) The 24 h urine protein levels and hypertrophy indexes of all DM subgroups were significantly higher than those of the NC groups (all P <0.05). 24 h urine protein and hypertrophy index increased gradually and peaked in the l2th week; blood albumin gradually decreased since the 8th week(P <0.01), and BUN and sCr began to decrease only since the 16th week (both P <0.01). Compared with the DM 8 subgroup, the hypertrophy index and 24 h urine protein of the different treatment subgroups, especially the DM + V + M subgroup, were significantly lower (all P <0.05). 2) Quantitative real time RT-PCR showed that compared with the NC group, the TRAIL expression levels of the DM subgroups were significantly lower before the 12th week after induction of DM model (all P < 0.01), and then significantly higher in the 16th week (all P < 0.01). The TRAIL expression of the treatment groups, especially that of the DM + M subgroup, were significantly higher than that of the DM8 group (all P <0.05). Compared with the NC group, the NF-kappaB expression levels of the DM subgroups were significantly higher time-dependently (all P <0.01). Compared with the DM8 group, the NF-kappaB expression levels of the treatment subgroups, especially that of the DM + V + M subgroup were significantly lower (all P <0.05). 3) The expression of TRAIL was mainly located in the convoluted tubule of kidney, and no TRAIL protein expression was detected in the glomeruli or renal vasculature. The levels of NF-kappaB protein expression, shown in glomeruli and convoluted tubules, of all DM subgroups were all higher than that of the NC group. The NF-kappaB protein expression level of the DM + V + M subgroup was significantly lower. The number of NF-kappaB positive cells was significantly related to the mononuclear macrophage infiltration , kidney function, and structural lesion. CONCLUSION: An important monitoring factor in the autoimmune system, TRAIL closely participates in the pathogenesis of diabetic nephropathy, possibly controlled by NF-kappaB. In the early stage combination of valsartan and MMF may upregulate the expression of TRAIL, thus protecting the kidney function.

Effects of mycophenolate mofetil, valsartan and their combined therapy on preventing podocyte loss in early stage of diabetic nephropathy in rats.

BACKGROUND: Podocyte has inflammatory role in the development of diabetic nephropathy (DN). Mycophenolate mofetil (MMF), an anti-inflammatory agent, can suppress macrophage infiltration and reduce renal injury in streptozotocin-induced diabetic rats. Angiotensin II receptor blocker (ARB), another renal protecting agent, can decrease podocyte loss in DN. In this study, we detected the expression levels of monocyte chemoattractant protein-1 (MCP-1) and nephrin to evaluate podocyte's role in inflammatory reaction in DN, observe and compare the effect of MMF alone and in combination with valsartan, on preventing podocyte loss in streptozotocin (STZ) induced diabetic rats. METHODS: Diabetic model was constructed in uninephrectomized male Wistar rats by single peritoneal injection of STZ (65 mg/kg). The successfully induced diabetic rats were randomly divided into four groups: diabetes without treatment group (DM), valsartan treated group (DMV), MMF treated group (DMM), and combined therapy group (DMVM). Normal rats of the same sibling were chosen as control (NC). At the end of the 8th week, serum biochemistry, 24-hour urinary protein (UP) and the ratio of kidney weight/body weight (RWK/B) were measured. The rats were sacrificed for the observation of renal histomorphology through light and electron microscope. Nephrin, desmin and MCP-1 levels were detected by semi-quantitative immunohistochemical assays. Real-time quantitative PCR was used to detect the mRNA levels of nephrin and MCP-1. RESULTS: Compared with group NC, serum glucose level, 24-hour UP and RWK/B in group DM were significantly higher (P < 0.01), and the nephrin mRNA level in DM group was significantly lower (P < 0.05). The nephrin mRNA expression levels in group DMV, DMM and DMVM were all higher than that of DM group (P < 0.05) and no significant differences were found among the three treatment groups (P > 0.05). Treatment with MMF, valsartan or their combination could significantly decrease the 24-hour UP and RWK/B, and suppress glomerulosclerosis and interstitial fibrotic lesions in diabetic rats. In diabetic rats, the high expressions of desmin and MCP-1 in kidney were suppressed by valsartan, MMF or their combination. CONCLUSIONS: Podocytes are involved in the inflammatory reaction of diabetic rats. MMF could suppress MCP-1 and desmin expression, enhance nephrin expression, and attenuate proteinuria in diabetic rats. The combined therapy of valsartan and MMF did not show any superiority over monotherapies on renal protection. MMF may have renoprotective effect in early stages of diabetic nephropathy through preventing podocytes loss and anti-inflammatory activity.

Identification and isolation of kidney-derived stem cells from transgenic rats with diphtheria toxin-induced kidney damage.

Adult stem cells have been well characterized in numerous organs, with the exception of the kidneys. Therefore, the present study aimed to identify and isolate kidney-derived stem cells. A total of 12 Fischer 344 transgenic rats expressing the human diphtheria toxin receptor in podocyte cells of the kidney, were used in the present study. The rats were administered 5-bromo-2'-deoxyuridine (BrdU) in order to detect cellular proliferation. After 60 days, the rats were treated with the diphtheria toxin (DT), in order to induce kidney injury. Immunohistochemical analysis indicated that the number of BrdU-positive cells were increased following DT treatment. In addition, the expression of octamer-binding transcription factor 4 (Oct-4), a stem cell marker, was detected and suggested that kidney-specific stem cells were present in the DT-treated tissue samples. Furthermore, tissue samples exhibited repair of the DT-induced injury. Further cellular culturing was conducted in order to isolate the kidney-specific stem cells. After 5 weeks of culture, the majority of the cells were non-viable, with the exception of certain specialized, unique cell types, which were monomorphic and spindle-shaped in appearance. The unique cells were isolated and subjected to immunostaining and reverse transcription-polymerase chain reaction analyses in order to reconfirm the expression of Oct-4 and to detect the expression of Paired box 2 (Pax-2), which is necessary for the formation of kidney structures. The unique cells were positive for Oct-4 and Pax-2; thus suggesting that the identified cells were kidney-derived stem cells. The results of the present study suggested that the unique cell type identified in the kidneys of the DT-treated rats were kidney-specific stem cells that may have been involved in the repair of DT-induced tissue injury. In addition, these cells may provide a useful cell line for studying the fundamental characteristics of kidney stem cells, as well as identifying kidney-specific stem cell markers.

SIRT1 activator ameliorates the renal tubular injury induced by hyperglycemia in vivo and in vitro via inhibiting apoptosis.

We aimed to explore the role of SIRT1 in apoptosis in human kidney proximal tubule epithelial (HK-2) cells, and to determine whether resveratrol (RSV, a SIRT1 activator) could ameliorate apoptosis in rats with streptozotocin-induced diabetes mellitus (DM) and/or in high glucose (HG, 30mM) - stimulated HK-2 cells. Rats were distributed randomly into three groups: 1) control group, 2) DM group, and 3) DM with RSV group (DM+RSV; rats treated with 30mg/kg/d of RSV for 16 weeks). The physical, biochemical, and morphological parameters were then examined. Additionally, the deacetylase activity of SIRT1, and the expression levels of SIRT1 and of representative apoptosis markers, such as p53, acetylated p53, cleaved caspase-3, caspase-9, and cleaved PARP, were measured. HK-2 cells were stimulated by HG for different lengths of time to study the effect of HG on apoptosis. HK-2 cells were treated with or without RSV (25µM) to investigate if RSV has a protective effect on HG-induced apoptosis. A gene-specific small interfering RNA against SIRT1 was used to study the role of SIRT1 in apoptosis. More apoptosis was found in the DM rats than in the control rats. Similarly, the expression levels of cleaved caspase-3, cleaved PARP, and acetylated p53 were significantly higher, and the level of SIRT1 was significantly lower, in the HK-2 cells that were cultured under HG conditions than those in the HK-2 cells that were cultured under low glucose (5.5mM) conditions. Notably, treatment with RSV lessened the HG-induced changes in the levels of apoptosis indicators, and this inhibition of HG-induced apoptosis in HK-2 cells by RSV treatment was abolished by SIRT1 silencing. Our study showed that hyperglycemia contributes to apoptosis in rat kidney and HK-2 cells. SIRT1 activation by RSV can reduce urinary albumin excretion and proximal tubule epithelial apoptosis both in vitro and in vivo. Based on our study, SIRT1/p53 axis played an important role in the hyperglycemia induced apoptosis. These findings indicated that the increased expression of SIRT1, mediated by RSV, is a possible mechanism by which RSV prevents renal tubular injury in diabetic nephropathy (DN). So RSV has great clinical significance and could provide the basis for the new way to effective treatment to contain the morbidity and mortality associated with DN.

Downregulation of alpha-fetoprotein siRNA inhibits proliferation of SMMC-7721 cells.

AIM: To study the function of alpha-fetoprotein (AFP) in SMMC-7721 hepatoma cells. METHODS: A hairpin siRNA expressing plasmid pSilencer3.0-H1-afp was constructed and transfected into SMMC-7721 cells with Lipofectamine 2000. The expression of AFP was monitored by real-time RT-PCR and immunoassays, its effect on SMMC-7721 cell proliferation and cell death was detected by MTT and fluorescence activated cell sorter (FACS). RESULTS: The AFP-siRNA expressing plasmid downregulated the expression of AFP obviously (about 34%), and inhibited SMMC-7721 cell proliferation, but did not induce apoptosis. CONCLUSION: Downregulation of AFP siRNA inhibits proliferation of SMMC-7721 cells, but cannot cause apoptosis.

[Protective effects of Salvia miltiorrhiza on rats with streptozotocin diabetes and its mechanism].

OBJECTIVE: To explore the effects of Salvia miltiorrhiza on renal morphology and renal function of rats with streptozotocin diabetes. METHODS: Thirty male Wistar rats were randomly divided into three groups, which were normal control group, untreated group and Salvia miltiorrhiza-treated group. Diabetic nephropathy was induced in rats of the last two groups by intraperitoneal injection of streptozotocin after unilateral nephrectomy. Then the rats in the normal control and untreated groups were fed with normal saline while those in the Salvia miltiorrhiza-treated group were fed Salvia miltiorrhiza preparation for 8 weeks. The glomerular volume (VG), kidney-to-body weight ratio (KW/BW), urinary albumin excretion rate (UAER) and creatinine clearance (Ccr) were observed. The expression levels of transforming growth factor-beta1 (TGF-beta1), connective tissue growth factor (CTGF), fibronectin (FN) and plasminogen activator inhibitor-1 (PAI-1) were detected by real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) at the end of the experiment. RESULTS: UAER, Ccr, VG and KW/BW ratio were significantly higher in the untreated group than those in the normal control group (P<0.05). The expression levels of TGF-beta1, CTGF, PAI-1 and FN in the untreated group were also significantly higher as compared with those in the normal control group (P<0.05). UAER, Ccr, VG, KW/BW ratio and the levels of TGF-beta1, CTGF, PAI-1 and FN in the Salvia miltiorrhiza-treated group were obviously lower than those in the untreated group (P<0.05). CONCLUSION: Salvia miltiorrhiza can protect rats with streptozotocin diabetes from diabetic nephropathy by suppressing the over-expressions of TGF-beta1, CTGF, PAI-1 and FN in renal cortex.

Berberine improves kidney function in diabetic mice via AMPK activation.

Diabetic nephropathy is a major cause of morbidity and mortality in diabetic patients. Effective therapies to prevent the development of this disease are required. Berberine (BBR) has several preventive effects on diabetes and its complications. However, the molecular mechanism of BBR on kidney function in diabetes is not well defined. Here, we reported that activation of AMP-activated protein kinase (AMPK) is required for BBR-induced improvement of kidney function in vivo. AMPK phosphorylation and activity, productions of reactive oxygen species (ROS), kidney function including serum blood urea nitrogen (BUN), creatinine clearance (Ccr), and urinary protein excretion, morphology of glomerulus were determined in vitro or in vivo. Exposure of cultured human glomerulus mesangial cells (HGMCs) to BBR time- or dose-dependently activates AMPK by increasing the thr172 phosphorylation and its activities. Inhibition of LKB1 by siRNA or mutant abolished BBR-induced AMPK activation. Incubation of cells with high glucose (HG, 30 mM) markedly induced the oxidative stress of HGMCs, which were abolished by 5-aminoimidazole-4-carboxamide ribonucleoside, AMPK gene overexpression or BBR. Importantly, the effects induced by BBR were bypassed by AMPK siRNA transfection in HG-treated HGMCs. In animal studies, streptozotocin-induced hyperglycemia dramatically promoted glomerulosclerosis and impaired kidney function by increasing serum BUN, urinary protein excretion, and decreasing Ccr, as well as increased oxidative stress. Administration of BBR remarkably improved kidney function in wildtype mice but not in AMPKα2-deficient mice. We conclude that AMPK activation is required for BBR to improve kidney function in diabetic mice.

Cyclosporine A combined with medium/low dose prednisone in progressive IgA nephropathy.

The aim of the present study was to evaluate the efficacy of cyclosporine A (CsA) combined with medium/low dose prednisone in the treatment of progressive immunoglobulin A nephropathy (IgAN). Ninety-six patients who satisfied the inclusion criteria were enrolled in a prospective controlled clinical study. They were assigned into two groups and initially given either 0.6-0.8 mg/kg/day prednisone (maximum 40 mg/day) plus 3 mg/kg/day CsA (CsA group), or 1 mg/kg/day prednisone (maximum 60 mg/day) alone (steroid group). During therapy, the dose of prednisone was reduced in both groups and the dose of CsA was gradually tailed off over the first 3 months and maintained at 2 mg/kg/day in the CsA group. Urinary protein excretion, serum biochemical indexes, clinical efficacy and side effects of CsA were assayed. A significant decline in mean 24-hour urinary protein excretion (p < 0.05) was observed 1 month after treatment in patients in the CsA group, which was observed 2 months after treatment in the steroid group. The decline in mean 24-hour urinary protein excretion in the CsA group was more significant than in the steroid group. Serum albumin level increased significantly in the CsA group 2 months after therapy (p < 0.05). Moreover, at the end of the course, a higher remission rate was observed in patients with Lee's Grade III IgAN after combined treatment with prednisone and CsA (p < 0.05). No significant difference in clinical efficacy was observed in patients with Lee's Grade IV and Grade V IgAN between the two groups (p > 0.05). CsA at a dose of 2-3 mg/kg/day in combination with medium/low dose prednisone was effective in inducing remission of IgAN, especially for patients with Lee's Grade III IgAN, and is a safe and effective choice for short-term treatment of patients with progressive IgAN.

Curcumin prevents diabetic nephropathy against inflammatory response via reversing caveolin-1 Tyr14 phosphorylation influenced TLR4 activation.

Inflammation is involved in the development and/or progression of diabetic nephropathy (DN). Curcumin has been reported for its anti-inflammation activity in DN. However, the mechanisms involved in the renoprotective effects of curcumin have not been clearly demonstrated. In this study, we hypothesized that curcumin affected high glucose (HG)-induced inflammation profiles in vivo and in vitro and then prevented renal injury in diabetic rats via reversing cav-1 Tyr(14) phosphorylation that influenced TLR4 activation. Streptozotocin (STZ)-induced diabetic rats received vehicle or curcumin for twelve weeks and podocytes were treated with HG in the presence or absence of curcumin in vitro. To further evaluate the effect of cav-1 phosphorylation at Tyr(14) on HG-induced podocyte inflammation response and TLR4 activation, a recombinant plasmid GFP-Cav-1 Y14F with a mutated phosphorylation site of cav-1, was transfected into cultured podocytes. In vivo, curcumin improved histological abnormalities and fibrosis of a diabetic kidney, inhibited renal inflammatory gene expression and reduced cav-1 phosphorylation at Tyr(14) and the expression of TLR4. Pretreatment of podocytes with curcumin reduced HG-stimulated production of proinflammatory cytokines, TLR4 and the phosphorylation of cav-1. But immunohistochemistry in rat kidney showed that the elevation of TLR4 expression is more evident in the renal interstitum than in the glomerulus where podocytes are located, and the possibility that the anti-inflammatory effects of curcumin on other cells in the kidney may be mediated through the same molecular pathways as in podocytes. Our study suggests that curcumin treatment ameliorates DN via inhibition of inflammatory gene expression by reversing caveolin-1 Tyr(14) phosphorylation that influenced TLR4 activation.

Curcumin ameliorates epithelial-to-mesenchymal transition of podocytes in vivo and in vitro via regulating caveolin-1.

AIMS: Epithelial-mesenchymal transition (EMT) is recognized to play a key role in diabetic nephropathy (DN). Curcumin, the main active component of turmeric extracted from the roots of the Curcuma longa plant, has been reported for its anti-fibrotic effects in kidney fibrosis. The purpose of our study was to investigate the effects of curcumin in reversing epithelial-to-mesenchymal transition (EMT) of podocytes in vivo and in vitro. MATERIALS/METHODS: In vivo streptozotocin (STZ)-induced diabetic rats received vehicle or curcumin, and podocytes were treated with high glucose (HG) in the presence or absence of curcumin in vitro. And we investigated the effect of curcumin on HG-induced phosphorylation of cav-1 on the stability cav-1 and ß-catenin using immunoprecipitation and fluorescence microscopy analysis. RESULTS: Curcumin treatment dramatically ameliorated metabolic parameters, renal function, morphological parameters in diabetic rats. We found that HG treatment led to significant down-regulation of p-cadherin and synaptopodin, as well as remarkable up-regulation of α-SMA and FSP-1 in vivo and in vitro. Furthermore, curcumin inhibited HG-induced caveolin-1 (cav-1) Tyr(14) phosphorylation associating with the suppression of stabilization of cav-1 and ß-catenin. CONCLUSIONS: In summary, these findings suggest that curcumin prevents EMT of podocytes, proteinuria, and kidney injury in DN by suppressing the phosphorylation of cav-1, and increasing stabilization of cav-1 and ß-catenin.

Mesenchymal stem cells transplantation ameliorates glomerular injury in streptozotocin-induced diabetic nephropathy in rats via inhibiting macrophage infiltration.

Mesenchymal stem cells (MSCs) treatment has been shown to be effective in diabetic nephropathy (DN). However, the mechanisms involved in the renoprotective effects of MSCs have not been clearly demonstrated. Especially, there was no study on the relationship of MSCs and macrophages in diabetic kidney. To explore the effect of MSCs on macrophages in DN, streptozotocin-induced diabetes animals received no treatment or treatment with MSCs (2×10(6), via tail vein) for two continuous weeks. Eight weeks after treatment, physical, biochemical and morphological parameters were measured. Immunohistochemistry for fibronectin (FN), CollagenI, ED-1, monocyte chemoattractant protein-1 (MCP-1) was performed. Expressions of pro-inflammatory cytokines and hepatocyte growth factor (HGF) at gene level and protein level were determined by real-time reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Blood glucose, urinary albumin excretion, creatinine clearance were significantly reduced after MSCs treatment. The glomerulosclerosis as revealed by periodic acid Schiff stain and expression of FN and CollagenI was also dramatically attenuated. Most importantly, the expression of MCP-1 and the number of infiltrated macrophages in kidney were effectively suppressed by MSCs treatment. The expression of HGF in MSCs group was up-regulated. Meanwhile, the expressions of IL-1ß, IL-6 and TNFα were significantly down-regulated by MSCs treatment. Our study suggest that MSCs treatment ameliorates DN via inhibition of MCP-1 expression by secreting HGF, thus reducing macrophages infiltration, down-regulating IL-1ß, IL-6, TNFα expression in renal tissue in diabetic rats.

Dipeptidyl peptidase-IV is a potential molecular biomarker in diabetic kidney disease.

The present study was designed to identify the changes in microvesicle-dipeptidyl peptidase-IV (DPP IV) levels in human urine and serum, and to determine whether there were correlations with the severity of diabetic kidney disease (DKD). A total of 127 patients with type 2 diabetes mellitus (T2DM) were divided into three groups according to the urinary albumin/ creatinine ratio (UACR): microalbuminuria group (n = 50); macroalbuminuria group (n = 34) and normoalbuminuria group (n = 43), and 34 age- and sex-matched non-diabetic healthy subjects were selected as controls. Microvesicle-bound DPP IV and free urinary DPP IV were separated by a filtra-centrifugation method. The total microvesicles were captured by a specific monoclonal antibody, AD-1. DPP IV activity was determined by measuring the cleavage of chromogenic free 4-nitroaniline from Gly-Pro-p-nitroanilide at 405 nm with an ELISA plate reader. DPP IV protein levels were determined by ELISA and Western blot. Our results showed that the microvesicle-bound type was the major form of DPP IV in urine; the urinary microvesicle-DPP IV excretion of each T2DM group was significantly higher compared with controls. The urinary microvesicle-DPP IV level was positively correlated with UACR in patients with T2DM. These findings suggest that the urinary level of microvesicle-bound DPP IV is associated with the severity of DKD.