Youming Peng

Rapamycin Ameliorates Kidney Fibrosis by Inhibiting the Activation of mTOR Signaling in Interstitial Macrophages and Myofibroblasts

Interstitial fibrosis is an inevitable outcome of all kinds of progressive chronic kidney disease (CKD). Emerging data indicate that rapamycin can ameliorate kidney fibrosis by reducing the interstitial infiltrates and accumulation of extra cellular matrix (ECM). However, the cellular mechanism that regulates those changes has not been well understood yet. In this study, we revealed the persistent activation of mammalian target of rapamycin (mTOR) signaling in the interstitial macrophages and myofibroblasts, but rarely in injured proximal epithelial cells, CD4+ T cells, neutrophils, or endothelial cells, during the development of kidney fibrosis. Administration of rapamycin to unilateral ureteral obstruction (UUO) mice significantly suppressed the immunoreactivity of mTOR signaling, which decreased the inflammatory responses and ECM accumulation in the obstructed kidneys. Isolated macrophages from rapamycin-treated obstructed kidneys presented less inflammatory activity than vehicle groups. In vitro study confirmed that rapamycin significantly inhibited the fibrogenic activation of cultured fibroblasts (NIH3T3 cells), which was induced by the stimulation of TGF-β1. Further experiment revealed that rapamycin did not directly inhibit the fibrogenesis of HK2 cells with aristolochic acid treatment. Our findings clarified that rapamycin can ameliorate kidney fibrosis by blocking the mTOR signaling in interstitial macrophages and myofibroblasts.

NEPHROTOXICITY OF HIGH- AND LOW-OSMOLAR CONTRAST MEDIA: The protective role of amlodipine in a rat model

Purpose: To evaluate the nephrotoxicity of high- and low-osmolar contrast media (HOCM, LOCM) on kidneys in Sprague-Dawley rats. The protective role of amlodipine was studied. Material and Methods: Forty rats of both sexes were randomly divided into 5 groups (n = 8/group) and glycerine for inducing renal failure was given to all rats except controls. Results: In diatrizoate-injected rats, blood urea nitrogen (BUN) and serum creatinine (SCr) were increased; levels of phospholipase A2 (PLA2), lipid peroxide (LPO) and calcium were also increased in renal tissues. There was no significant difference between LOCM (iohexol) animals and glycerol controls either in the renal levels of PLA2, LPO and calcium or in the levels of BUN and SCr. The histologic changes were milder in the LOCM animals than in the HOCM animals. In the group pretreated with amlodipine, no increase in the levels of BUN or SCr was discovered and the renal content of PLA2, LPO and calcium were significantly lower than in the HOCM group; the renal injuries induced by diatrizoate were alleviated. Conclusion: The HOCM, diatrizoate, was more toxic to rat kidneys than the LOCM iohexol; PLA2, LPO and calcium load played a role in producing renal function impairment induced by diatrizoate meglumine; amlodipine protected the renal tissue from nephrotoxicity induced by diatrizoate.

Mangiferin attenuate sepsis-induced acute kidney injury via antioxidant and anti-inflammatory effects.

Background: Acute kidney injury (AKI) is a frequent and serious complication of sepsis. A growing body of evidence now suggests that inflammatory reactions and tubular dysfunction induced by oxidative stress involved in the mechanisms of the disease. This study aimed to determine the role of anti-inflammatory and anti-oxidant activities of mangiferin (MA) in sepsis-induced AKI. Methods: We investigated the effects of MA on apoptosis of rat kidney proximal tubular cell (RPTC), together with renal function and morphological alterations of mice undergoing cecal-ligation and puncture (CLP). The levels of oxidative stress in kidney tissues were also determined. Moreover, we mainly focus on the effects of MA in regulating the production of NLRP3 and Nrf2 in the present study. Results: The exposure to LPS (5 Vg/ml) yielded a significant increase of apoptosis in RPTC cells, which was largely inhibited by MA pretreatment. MA attenuates renal dysfunction and ameliorates the morphological changes in the septic mice induced by CLP. MA inhibits oxidative stress, decreases serum levels of IL-1F and IL-18, and prevents tubular epithelial cells apoptosis in kidneys of CLP mice model. Data in this study also suggest that MA promotes Nrf2 expression and suppresses renal NLRP3 inflammasome activation. Conclusion: In summary, MA protects against sepsis-induced AKI through NLRP3 inflammasome inhibition and Nrf2 up-regulation. Thus, the mangiferin could thus be a promising candidate for development of a multi-potent drug. i 2014 S. Karger AG, Basel

Arkadia-Smad7-Mediated Positive Regulation of TGF-β Signaling in a Rat Model of Tubulointerstitial Fibrosis

Background/Aims: Upregulation of transforming growth factor beta (TGF-β)/Smad signaling has been implicated in the primary pathogenesis of renal fibrosis. The ubiquitin-proteasome pathway has an important influence on TGF-β signaling through regulating Smad degradation. As E3 ubiquitin ligases, both Arkadia and Smurf2 are involved in this prosess. In this study, we focused on Arkadia, Smurf2, Smad7, and TGF-β type I receptor (TβRI), principal molecules in the regulation of TGF-β signaling, to understand the regulatory mechanism of ubiquitin-proteasomal degradation of TGF-β signaling in the pathogenesis of renal fibrosis. Methods: A unilateral ureteral obstruction (UUO) model was employed, and sham-operated rats were used as controls. Renal lesions and the expression of Arkadia, Smurf2, Smad7, TβRI, TGF-β1, and type 1 collagen (COL-1) were detected by Western blot, immunoprecipitation, immunohistochemistry, and/or reverse transcription-polymerase chain reaction. Results: The results indicated progressive tubulointerstitial fibrosis, high expression levels of Arkadia, Smurf2, TβRI, TGF-β1 mRNA, type 1 collagen mRNA, and Smad7 mRNA, and low levels of Smad7 protein in the kidneys of rats with unilateral ureteral obstruction, in which Smurf2 interacted with both Smad7 and TβRI, and Arkadia only interacted with Samd7 but not with TβRI. Conclusion: Reduction of Smad7 resulting from ubiquitin-dependent degradation may be mainly attributed to Arkadia, and Arkadia-Smad7-mediated positive regulation of TGF-β signaling may play a promoting role in the progression of tubulointerstitial fibrosis.

AEG-1 participates in TGF-beta1-induced EMT through p38 MAPK activation

Epithelial–mesenchymal transition (EMT) is an important cellular event in organogenesis, cancer and renal tubulointerstitial fibrosis. Transforming growth factor‐beta1 (TGF‐beta1) is the key inducer of EMT and the p38 mitogen‐activated protein kinases (p38 MAPK), an major intracellular signal transduction pathway is involved in TGF‐beta1‐induced EMT. Astrocyte elevated gene‐1 (AEG‐1) represents an chief genetic determinant regulating multiple events in tumorigenesis. Our present study is to explore the role of AEG‐1 in TGF‐beta1‐induced p38 MAPK activation and EMT process in human renal tubular epithelial (HK‐2) cells. The protein expressions of AEG‐1, the markers of EMT and p38 phosphorylation were measured by Western blot. The protein expression of AEG‐1 was increased in HK‐2 cells treated with TGF‐beta1. Knockdown of AEG‐1 potently inhibited phosphorylation of p38 MAPK and reversed TGF‐beta1‐induced EMT. Over‐expression of AEG‐1 via AEG‐1 transfection elicited p38 MAPK phosphorylation and promoted EMT. The effects of AEG‐1 during EMT were blocked by a p38‐specific inhibitor. Our findings suggest that AEG‐1 plays an important role in TGF‐beta1‐induced EMT through activation of p38 MAPK in proximal tubular epithelial cells.

Norcantharidin Inhibits Renal Interstitial Fibrosis by Blocking the Tubular Epithelial-Mesenchymal Transition

Epithelial–mesenchymal transition (EMT) is thought to contribute to the progression of renal tubulointerstitial fibrosis. Norcantharidin (NCTD) is a promising agent for inhibiting renal interstitial fibrosis. However, the molecular mechanisms of NCTD are unclear. In this study, a unilateral ureteral obstruction (UUO) rat model was established and treated with intraperitoneal NCTD (0.1 mg/kg/day). The UUO rats treated with NCTD showed a reduction in obstruction-induced upregulation of α-SMA and downregulation of E-cadherin in the rat kidney (P<0.05). Human renal proximal tubule cell lines (HK-2) stimulated with TGF-β1 were treated with different concentrations of NCTD. HK-2 cells stimulated by TGF-β1 in vitro led to downregulation of E-cadherin and increased de novo expression of α-SMA; co-treatment with NCTD attenuated all of these changes (P<0.05). NCTD reduced TGF-β1-induced expression and phosphorylation of Smad2/3 and downregulated the expression of Snail1 (P<0.05). These results suggest that NCTD antagonizes tubular EMT by inhibiting the Smad pathway. NCTD may play a critical role in preserving the normal epithelial phenotype and modulating tubular EMT.

Renoprotective approaches and strategies in acute kidney injury.

Acute kidney injury (AKI) is a major renal disease associated with high mortality rate and increasing prevalence. Decades of research have suggested numerous chemical and biological agents with beneficial effects in AKI. In addition, cell therapy and molecular targeting have been explored for reducing kidney tissue damage and promoting kidney repair or recovery from AKI. Mechanistically, these approaches may mitigate oxidative stress, inflammation, cell death, and mitochondrial and other organellar damage, or activate cytoprotective mechanisms such as autophagy and pro-survival factors. However, none of these findings has been successfully translated into clinical treatment of AKI. In this review, we analyze these findings and propose experimental strategies for the identification of renoprotective agents or methods with clinical potential. Moreover, we propose the consideration of combination therapy by targeting multiple targets in AKI.

Protective effects of curcumin on acute gentamicin-induced nephrotoxicity in rats

BACKGROUND Gentamicin-induced nephrotoxicity is one of the most common causes of acute kidney injury (AKI). The phenotypic alterations that contribute to acute kidney injury include inflammatory response and oxidative stress. Curcumin has a wide range biological functions, especially as an antioxidant. This study was designed to evaluate the renoprotective effects of curcumin treatment in gentamicin-induced AKI. METHODS Gentamicin-induced AKI was established in female Sprague-Dawley rats. Rats were treated with curcumin (100 mg/kg body mass) by intragastric administration, once daily, followed with an intraperitoneal injection of gentamicin sulfate solution at a dose of 80 mg/kg body mass for 8 consecutive days. At days 3 and 8, the rats were sacrificed, and the kidneys and blood samples were collected for further analysis. RESULTS The animals treated with gentamicin showed marked deterioration of renal function, together with higher levels of neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule 1 (KIM-1) in the plasma as compared with the controls. Animals that underwent intermittent treatment with curcumin exhibited significant improvements in renal functional parameters. We also observed that treatment with curcumin significantly attenuated renal tubular damage, apoptosis, and oxidative stress. Curcumin treatment exerted anti-apoptosis and anti-oxidative effects by up-regulating Nrf2/HO-1 and Sirt1 expression. CONCLUSIONS Our data clearly demonstrate that curcumin protects kidney from gentamicin-induced AKI via the amelioration of oxidative stress and apoptosis of renal tubular cells, thus providing hope for the amelioration of gentamicin-induced nephrotoxicity.

Atherosclerosis is associated with plasminogen activator inhibitor type‐1 in chronic haemodialysis patients

Aim:  The aim of the present report was to investigate the probable association of circulating levels of PAI‐1 and expression of PAI‐1 in internal iliac artery walls with atherosclerotic disease in chronic haemodialysis (HD) patients.

A selective cyclooxygenase-2 inhibitor decreases transforming growth factor-β1 synthesis and matrix production in human peritoneal mesothelial cells

High glucose concentration, which provides the chief driving force in peritoneal dialysis, has been considered to be an important initial factor that contributes to peritoneal thickening and fibrosis. Human peritoneal mesothelial cells (HPMCs) and the expansion of extracellular matrix (ECM) play important roles in the pathological process of peritoneal fibrosis. Peritoneal matrix accumulation is a characteristic of peritoneal fibrosis (PF). Continuous ambulatory peritoneal dialysis (CAPD) patients with upregulation of transforming growth factor‐β1 (TGF‐β1) in their drained effluent show an increased risk of PF. Inhibition of TGF‐β1 expression in human peritoneal mesothelial cells (HPMCs) may provide a potential treatment for PF. sc58236, a highly selective cyclooxygenase‐2 (COX‐2) inhibitor, reduces proteinuria and mRNA expression of TGF‐β1 and collagen III and IV in the remnant kidney, but their effects on ECM turnover in HPMCs are unknown. The aims of this study were to investigate the effects of sc58236 on TGF‐β1 expression and matrix production in HPMCs. HPMCs were cultured from human omentum by an enzyme digestion method. To examine the effect of sc58236 on TGF‐β1 and ECM secretion, HPMC were incubated in medium F12 with high concentration of d‐glucose (4.25%) in the presence and absence of 20 μM sc58236. The mRNA expression of COX‐2, TGF‐β1 and collagen I (Col I) were determined by semi‐quantification reverse transcription PCR (RT—PCR). Prostaglandin E2 (PGE2) concentration in the culture medium was measured by enzyme‐linked immunosorbent assay (ELISA). The protein of TGF‐β1 was determined by ELISA and the activity of TGF‐β1 present in the conditioned media was measured using the mink lung epithelial cell (MLEC) growth inhibition assay. Proteins of COX‐2 and Col were determined by Western blot. The results showed that primary cultures of HPMCs do express the mRNA for COX‐2 and stimulation of these cells with 4.25% d‐glucose induced a marked increase in COX‐2 mRNA expression and protein. PGE2 expression was obviously up‐regulated with stimulation by 4.25% d‐glucose. Addition of 20 μM sc58236 significantly inhibited PGE2 release into the culture medium. mRNA expression and bioactive and total protein of TGF‐β1 and Col I were significantly increased in HPMCs stimulated with 4.25% d‐glucose compared to the control group with F12 media, which was reversed in the presence of sc58236 (20 μM). An obvious decrease in TGF‐β1 mRNA expression and bioactive and total protein were found in sc58236 treated groups compared to the group stimulated with 4.25% d‐glucose. Exposure of HPMCs to sc58236 reduced Col I secretion. Sc58236 reduces the expression of TGF‐β1 in HPMCs stimulated by 4.25% d‐glucose and reduces ECM production through PGE2 production. These studies suggest that sc58236, a highly selective cyclooxygenase‐2 (COX‐2) inhibitor, may have a specific role in ameliorating the course of progressive peritoneal fibrosis under long‐term peritoneal dialysis states.