The combination of dapagliflozin and statins ameliorates renal injury through attenuating the activation of inflammasome-mediated autophagy in insulin-resistant rats.

Long-term use of a high-fat diet with high-fructose (HFF) intake could promote insulin resistance and induce lipid accumulation leading to kidney injury possibly via impairment of the autophagy process and enhancement of the inflammasome pathway. We investigated whether dapagliflozin as a monotherapy or combined with atorvastatin could restore kidney autophagy impairment and reduce inflammasome activation associated with kidney injury induced by HFF consumption. Male Wistar rats were given an HFF for 16 weeks and then treated with dapagliflozin with or without atorvastatin for 4 weeks. Impaired glucose tolerance, dyslipidemia, renal lipid accumulation along with impaired renal autophagy and activated inflammasome pathway promoted renal injury were exhibited in HFF rats. Dapagliflozin with or without atorvastatin treatment could partially restore disrupted metabolic parameters and reduce kidney injury. In particular, the combination treatment group showed significant amelioration of inflammasome activation and autophagy impairment. In conclusion, the combination therapy of dapagliflozin and atorvastatin has a positive effect on renal injury associated with autophagy and inflammasome activation induced by HFF in insulin-resistant rats. This study is the first report demonstrating the underlying mechanism associated with a combination treatment of dapagliflozin and atorvastatin on autophagy and inflammasome pathways in an insulin-resistant condition. Therefore, dapagliflozin in combination with atorvastatin may be a further preventive or therapeutic strategy for chronic kidney disease in an insulin-resistant or diabetic condition.

Potential Application of Gambogic Acid for Retarding Renal Cyst Progression in Polycystic Kidney Disease.

Abnormal cell proliferation and accumulation of fluid-filled cysts along the nephrons in polycystic kidney disease (PKD) could lead to a decline in renal function and eventual end-stage renal disease (ESRD). Gambogic acid (GA), a xanthone compound extracted from the brownish resin of the Garcinia hanburyi tree, exhibits various pharmacological properties, including anti-inflammation, antioxidant, anti-proliferation, and anti-cancer activity. However, its effect on inhibiting cell proliferation in PKD is still unknown. This study aimed to determine the pharmacological effects and detailed mechanisms of GA in slowing an in vitro cyst growth model of PKD. The results showed that GA (0.25-2.5 µM) significantly retarded MDCK cyst growth and cyst formation in a dose-dependent manner, without cytotoxicity. Using the BrdU cell proliferation assay, it was found that GA (0.5-2.5 µM) suppressed MDCK and Pkd1 mutant cell proliferation. In addition, GA (0.5-2.5 µM) strongly inhibited phosphorylation of ERK1/2 and S6K expression and upregulated the activation of phosphorylation of AMPK, both in MDCK cells and Pkd1 mutant cells. Taken together, these findings suggested that GA could retard MDCK cyst enlargement, at least in part by inhibiting the cell proliferation pathway. GA could be a natural plant-based drug candidate for ADPKD intervention.

A chalcone derivative retards renal cyst enlargement by inhibiting fluid secretion and cell proliferation in an in vitro model of polycystic kidney disease.

BACKGROUND: Renal bilateral fluid filled-cyst in polycystic kidney disease (PKD) is associated with abnormal epithelial cell proliferation and transepithelial fluid secretion which leads to end-stage renal disease (ESRD). A chalcone derivative, isoliquiritigenin (ISLQ), has been shown to have various pharmacological properties. Since several studies have shown that ISLQ could inhibit CFTR channel activity, it is interesting to see whether it can inhibit renal cyst enlargement. The present study was aimed to determine an inhibitory effect and the mechanism of chalcone derivatives on MDCK cyst progression and Pkd1 mutant cells. METHODS: MDCK cyst growth and cyst formation experiments, MTT assay, Ussing chamber experiment, BrdU cell proliferation assay and western blot analysis were performed in this study. RESULTS: Among four compounds of chalcone derivatives tested, CHAL-005 (100 µM) was found to inhibit MDCK cyst growth in a dose-dependent manner without cytotoxicity. It inhibited short-circuit current of chloride secretion as well as CFTR protein expression in MDCK cells. CHAL-005 significantly suppressed cell proliferation. In addition, CHAL-005 strongly reduced phosphorylation ERK1/2 and phosphorylation S6 kinase in MDCK and Pkd1 mutant cells. Interestingly, CHAL-005 activated phosphorylation of AMP kinase protein expression in MDCK and Pkd1 mutant cells. CONCLUSION: CHAL-005 slowed MDCK cyst progression by inhibiting CFTR expression and reducing ERK1/2 and mTOR/S6K signaling pathways as well as activating AMPK expression. Therefore, a chalcone derivative could represent as a promising drug candidate for polycystic kidney disease intervention.

Effects of dapagliflozin and statins attenuate renal injury and liver steatosis in high-fat/high-fructose diet-induced insulin resistant rats.

High-fat high-fructose diet (HFF) in obesity can induce dyslipidemia and lipid accumulation both in kidney and liver which related to insulin resistance and lipotoxicity-induced cellular damage. We investigated whether dapagliflozin with or without atorvastatin could improve lipid accumulation-induced kidney and liver injury in HFF-induced insulin resistant rats. Male Wistar rats were fed with HFF for 16 weeks and then received drug treatments for 4 weeks; vehicle, dapagliflozin, atorvastatin and dapagliflozin plus atorvastatin treatment groups. HFF rats demonstrated insulin resistance, dyslipidemia, liver injury and renal dysfunction associated with impaired renal lipid metabolism and lipid accumulation. Dapagliflozin and combination treatment could improve HFF-induced insulin resistance, lipogenesis and lipotoxicity-related renal oxidative stress, inflammation, fibrosis and apoptosis leading to kidney dysfunction recovery. Liver injury-associated inflammation was also improved by these two regimens. Notably, the reduced lipid accumulation in liver and kidney that linked to an improvement of lipid oxidation was prominent in the combination treatment. Therefore, dapagliflozin combined with atorvastatin treatment exert the beneficial effects on lipid metabolism and lipotoxicity in liver and kidney injury via the attenuation of oxidative stress, fibrosis and apoptosis in insulin resistant model.

Farnesoid X Receptor Activation Stimulates Organic Cations Transport in Human Renal Proximal Tubular Cells.

Farnesoid X receptor (FXR) is a ligand-activated transcription factor highly expressed in the liver and kidneys. Activation of FXR decreases organic cation transporter (OCT) 1-mediated clearance of organic cation compounds in hepatocytes. The present study investigated FXR regulation of renal clearance of organic cations by OCT2 modulation and multidrug and toxin extrusion proteins (MATEs). The role of FXR in OCT2 and MATEs functions was investigated by monitoring the flux of 3H-MPP+, a substrate of OCT2 and MATEs. FXR agonists chenodeoxycholic acid (CDCA) and GW4064 stimulated OCT2-mediated 3H-MPP+ uptake in human renal proximal tubular cells (RPTEC/TERT1 cells) and OCT2-CHO-K1 cells. The stimulatory effect of CDCA (20 µM) was abolished by an FXR antagonist, Z-guggulsterone, indicating an FXR-dependent mechanism. CDCA increased OCT2 transport activity via an increased maximal transport rate of MPP+. Additionally, 24 h CDCA treatment increased MATEs-mediated 3H-MPP+ uptake. Moreover, CDCA treatment increased the expression of OCT2, MATE1, and MATE2-K mRNA compared with that of the control. OCT2 protein expression was also increased following CDCA treatment. FXR activation stimulates renal OCT2- and MATE1/2-K-mediated cation transports in proximal tubules, demonstrating that FXR plays a role in the regulation of OCT2 and MATEs in renal proximal tubular cells.

Molecular signaling mechanisms of renal gluconeogenesis in nondiabetic and diabetic conditions.

The kidneys are as involved as the liver in gluconeogenesis which can significantly contribute to hyperglycemia in the diabetic condition. Substantial evidence has demonstrated the overexpression of rate-limiting gluconeogenic enzymes, especially phosphoenolpyruvate carboxykinase and glucose 6 phosphatase, and the accelerated glucose release both in the isolated proximal tubular cells and in the kidneys of diabetic animal models and diabetic patients. The aim of this review is to provide an insight into the mechanisms that accelerate renal gluconeogenesis in the diabetic conditions and the therapeutic approaches that could affect this process in the kidney. Increase in gluconeogenic substrates, reduced insulin concentration or insulin resistance, downregulation of insulin receptors and insulin signaling, oxidative stress, and inappropriate activation of the renin-angiotensin system are likely to participate in enhancing renal gluconeogenesis in the diabetic milieu. Several studies have suggested that controlling glucose metabolism at the renal level favors effective overall glycemic control in both type 1 and type 2 diabetes. Therefore, renal gluconeogenesis may be a promising target for effective glycemic control as a therapeutic strategy in diabetes.

Dapagliflozin not only improves hepatic injury and pancreatic endoplasmic reticulum stress, but also induces hepatic gluconeogenic enzymes expression in obese rats.

BACKGROUND: With an increasing prevalence of obesity and metabolic syndrome, exploring the effects and delineating the mechanisms of possible therapeutic agents are of critical importance. We examined the effects of SGLT2 inhibitor-dapagliflozin on insulin resistance, hepatic gluconeogenesis, hepatic injury and pancreatic ER stress in high-fat diet-induced obese rats. MATERIALS AND METHODS: Male Wistar rats were fed with normal diet (ND) or high-fat diet for 16 weeks. Then high-fat rats were given vehicle (HF) or dapagliflozin (1 mg/kg/day; HFDapa) or metformin (30 mg/kg/day; HFMet) for another 4 weeks. RESULTS: We found that dapagliflozin ameliorated high-fat diet-induced insulin resistance. The fasting plasma glucose level was comparable among groups, although dapagliflozin treatment led to substantial glycosuria. Hepatic gluconeogenic enzymes, PEPCK, G6Pase and FBPase, expression was not different in HF rats compared with ND rats. Meanwhile, dapagliflozin-treated group exhibited the elevation of these enzymes in parallel with the rise of transcription factor CREB, co-factor PGC1α and upstream regulator SIRT1. Hepatic oxidative stress, inflammation and NAFLD activity score as well as hepatic and pancreatic ER stress and apoptosis in obese rats were attenuated by dapagliflozin. CONCLUSION: We conclude that dapagliflozin improved obesity-related insulin resistance, hepatic and pancreatic injury independent of fasting plasma glucose level. Of note, dapagliflozin-induced glycosuria apparently triggered the up-regulation of hepatic gluconeogenic enzymes to prevent hypoglycemia.

Renal outcomes with sodium glucose cotransporter 2 (SGLT2) inhibitor, dapagliflozin, in obese insulin-resistant model.

A growing body of evidence indicates that obesity and insulin resistance contribute to the progression of renal disease. This study was performed to determine the effects of dapagliflozin, a novel sodium glucose cotransporter 2 (SGLT2) inhibitor, on renal and renal organic anion transporter 3 (Oat3) functions in high-fat diet fed rats, a model of obese insulin-resistance. Twenty-four male Wistar rats were divided into two groups, and received either a normal diet (ND) (n = 6) or a high-fat diet (HFD) (n = 18) for 16 weeks. At week 17, the HFD-fed rats were subdivided into three subgroups (n = 6/subgroup) and received either a vehicle (HFD), dapagliflozin (HFDAP; 1.0 mg/kg/day) or metformin (HFMET; 30 mg/kg/day), by oral gavage for four weeks. Metabolic parameters, renal function, renal Oat3 function, renal oxidative stress, and renal morphology were determined. The results showed that obese insulin-resistant rats induced by HFD feeding had impaired renal function and renal Oat3 function together with increased renal oxidative injury. Dapagliflozin or metformin treatment decreased insulin resistance, hypercholesterolemia, creatinine clearance and renal oxidative stress leading to improved renal function. However, dapagliflozin treatment decreased blood pressure, serum creatinine, urinary microalbumin and increased glucose excretions, and showed a greater ability to ameliorate impaired renal insulin signaling and glomerular barrier damage than metformin. These data suggest that dapagliflozin had greater efficacy than metformin for attenuating renal dysfunction and improving renal Oat3 function, at least in part by reducing renal oxidative stress and modulating renal insulin signaling pathways, and hence ameliorating renal injury.

Probiotic Lactobacillus paracasei HII01 protects rats against obese-insulin resistance-induced kidney injury and impaired renal organic anion transporter 3 function.

The relationship between gut dysbiosis and obesity is currently acknowledged to be a health topic which causes low-grade systemic inflammation and insulin resistance and may damage the kidney. Organic anion transporter 3 (Oat3) has been shown as a transporter responsible for renal handling of gut microbiota products which are involved in the progression of metabolic disorder. The present study investigated the effect of probiotic supplementation on kidney function, renal Oat3 function, inflammation, endoplasmic reticulum (ER) stress, and apoptosis in obese, insulin-resistant rats. After 12 weeks of being provided with either a normal or a high-fat diet (HF), rats were divided into normal diet (ND); ND treated with probiotics (NDL); HF; and HF treated with probiotic (HFL). Lactobacillus paracasei HII01 1 × 108 colony forming unit (CFU)/ml was administered to the rats daily by oral gavage for 12 weeks. Obese rats showed significant increases in serum lipopolysaccharide (LPS), plasma lipid profiles, and insulin resistance. Renal Oat 3 function was decreased along with kidney dysfunction in HF-fed rats. Obese rats also demonstrated the increases in inflammation, ER stress, apoptosis, and gluconeogenesis in the kidneys. These alterations were improved by Lactobacillus paracasei HII01 treatment. In conclusion, probiotic supplementation alleviated kidney inflammation, ER stress, and apoptosis, leading to improved kidney function and renal Oat3 function in obese rats. These benefits involve the attenuation of hyperlipidemia, systemic inflammation, and insulin resistance. The present study also suggested the idea of remote sensing and signaling system between gut and kidney by which probiotic might facilitate renal handling of gut microbiota products through the improvement of Oat3 function.

Dapagliflozin, a sodium-glucose co-transporter-2 inhibitor, slows the progression of renal complications through the suppression of renal inflammation, endoplasmic reticulum stress and apoptosis in prediabetic rats.

AIM: To evaluate the renoprotective roles of dapagliflozin in prediabetic rats in order to elucidate the effects of this sodium-glucose co-transporter-2 (SGLT2) inhibitor on the renal complications associated with metabolic dysfunction in diet-induced obesity. METHODS: Obesity was induced by feeding a high-fat diet (HFD) to male Wistar rats for 16 weeks. HFD-fed rats were treated with dapagliflozin (1 mg/kg/d) or metformin (30 mg/kg/d) by oral gavage for 4 weeks after insulin resistance had been established. The metabolic characteristics and renal function associated with lipid accumulation, inflammation, fibrosis, endoplasmic reticulum (ER) stress and apoptosis in the renal tissue were examined. RESULTS: The results showed that HFD-fed rats developed both obesity and impaired renal function, along with increased renal triglyceride accumulation. Importantly, dapagliflozin had greater efficacy in improving renal function and reducing both body weight and visceral fat accumulation than metformin treatment. Dapagliflozin and metformin were found to have similar effects regarding the suppression of renal triglycerides, superoxide dismutase (SOD) expression and malondialdehyde (MDA) levels, subsequently leading to a decrease in renal inflammation and fibrosis. Renal ER stress and apoptosis were increased in HFD-fed rats and were effectively reduced after administration of dapagliflozin. The expression of renal SGLT2 was not affected by administration of dapagliflozin or metformin. CONCLUSION: Collectively, these findings indicate that dapagliflozin exerts renoprotective effects by alleviating obesity-induced renal inflammation, fibrosis, ER stress, apoptosis and lipid accumulation in the prediabetic condition.

Activation of liver X receptor inhibits OCT2-mediated organic cation transport in renal proximal tubular cells.

Liver X receptor (LXR) is transcriptional factor that plays an important role in the regulation of energy metabolism such as cholesterol, lipid, and glucose metabolism as well as membrane transporters and channels. Using both in vitro and in vivo models, LXR regulation of the expression and function of renal organic cation transporter 2 (OCT2) was observed. Synthetic LXR agonist (GW3965) and endogenous LXR agonist (22R-hydroxycholesterol) significantly reduced the uptake of 3H-MPP+, a prototypic substrate of OCT2, in both OCT2- Chinese hamster ovary K1 and human renal proximal tubular cells (RPTEC/TERT1). GW3965 decreased transport activity of OCT2 via a reduction of the maximal transport rate of MPP+ without affecting transporter affinity. The inhibitory effect of GW3965 was attenuated by co-treatment with LXR antagonist (fenofibrate) indicating the inhibition was LXR-dependent mechanism. In addition, co-treatment with a retinoic X receptor (RXR) ligand, 9-cis retinoic acid enhanced the inhibitory effect of GW3965, indicating negative regulation of OCT2 transport activity by the LXR/RXR complex. Treatment RPTEC/TERT1 cells with GW3965 significantly reduced OCT2 protein expression without changing mRNA expression. In parallel, the effect of LXR activation on OCT2 function was investigated in intact mouse kidney. Treating mice with 50 mg/kg BW T0901317 for 14 days significantly decreased 3H-MPP+ uptake into renal cortical slices, correlating with decreased OCT2 protein expression in renal cortex without changes in mRNA expression levels. Taken together, LXR/RXR activation downregulates the protein expression and function of OCT2 in renal proximal tubule, suggesting LXR might affect the total profile of renal excretion of cationic compounds.

Cellular mechanisms underlying the inhibitory effect of flufenamic acid on chloride secretion in human intestinal epithelial cells.

Intestinal Cl- secretion is involved in the pathogenesis of secretory diarrheas including cholera. We recently demonstrated that flufenamic acid (FFA) suppressed Vibrio cholerae El Tor variant-induced intestinal fluid secretion via mechanisms involving AMPK activation and NF-κB-suppression. The present study aimed to investigate the effect of FFA on transepithelial Cl- secretion in human intestinal epithelial (T84) cells. FFA inhibited cAMP-dependent Cl- secretion in T84 cell monolayers with IC50 of ∼8 µM. Other fenamate drugs including tolfenamic acid, meclofenamic acid and mefenamic acid exhibited the same effect albeit with lower potency. FFA also inhibited activities of CFTR, a cAMP-activated apical Cl- channel, and KCNQ1/KCNE3, a cAMP-activated basolateral K+ channel. Mechanisms of CFTR inhibition by FFA did not involve activation of its negative regulators. Interestingly, FFA inhibited Ca2+-dependent Cl- secretion with IC50 of ∼10 µM. FFA inhibited activities of Ca2+-activated Cl- channels and KCa3.1, a Ca2+-activated basolateral K+ channels, but had no effect on activities of Na+-K+-Cl- cotransporters and Na+-K+ ATPases. These results indicate that FFA inhibits both cAMP and Ca2+-dependent Cl- secretion by suppressing activities of both apical Cl- channels and basolateral K+ channels. FFA and other fenamate drugs may be useful in the treatment of secretory diarrheas.

Atorvastatin improves renal organic anion transporter 3 and renal function in gentamicin-induced nephrotoxicity in rats.

What is the central question of this study? This study was designed to determine the renoprotective effects of atorvastatin treatment in an experimental model of gentamicin-induced nephrotoxicity through modulating the Nrf2 pathway by decreasing the oxidative stress. What is the main finding and its importance? Atorvastatin exerts a nephroprotective effect by attenuating oxidative stress, protecting renal function and renal organic anion transporter 3 function from the effects of gentamicin. Atorvastatin might protect the tissues via its antioxidant property and by modulating the antioxidant enzymes through the Nrf2 signalling pathway, which may be the underlying mechanisms of these protective effects. Recent evidence demonstrates that statins, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, exert not only lipid-lowering effects but also antioxidant, anti-inflammatory and anti-apoptotic effects. Nephrotoxicity, a serious side-effect of gentamicin, is related to an increase in reactive oxygen species in the kidney. This study was designed to determine the renoprotective effects of atorvastatin treatment in an experimental model of gentamicin-induced nephrotoxicity. Male Sprague-Dawley rats were used. Nephrotocixity was induced by i.p. injection of gentamicin, 100 mg kg(-1)  day(-1) , for 15 days. Atorvastatin, 10 mg kg(-1)  day(-1) , was administered by gavage 30 min before gentamicin injection (pretreatment) for 15 days or only on days 10-15 (post-treatment). Renal function and renal organic anion transporter 3 (Oat3) function and expression were examined. Gentamicin-treated rats demonstrated impaired renal function by attenuation of creatinine clearance and increased oxidative stress. Gentamicin treatment also decreased renal Oat3 function and expression as shown by decreased [(3) H]estrone sulfate uptake into renal cortical slices and decreased expression. The protein expressions of protein kinase C, Nrf2, NAD(P)H:quinone oxidoreductase 1, haeme oxygenase 1 and glutamate-cysteine ligase were markedly increased in gentamicin-treated rats, indicating the increase in oxidative stress. Administration of atorvastatin improved renal function and alleviated oxidative stress, and atorvastatin pretreatment had a greater ability to decrease oxidative stress than atorvastatin post-treatment. These effects helped to preserve renal function and Oat3 function and expression. These results indicate that atorvastatin has a renoprotective effect against gentamicin-induced nephrotoxicity by decreasing overoxidation in the kidney, and might be used in conjunction with gentamicin to protect against renal damage.

Adenosine monophosphate-activated protein kinase activation and suppression of inflammatory response by cell stretching in rabbit synovial fibroblasts.

Joint mobilization is known to be beneficial in osteoarthritis (OA) patients. This study aimed to investigate the effect of stretching on adenosine monophosphate-activated protein kinase (AMPK) activity and its role in modulating inflammation in rabbit synovial fibroblasts. Uniaxial stretching of isolated rabbit synovial fibroblasts for ten min was performed. Stretching-induced AMPK activation, its underlying mechanism, and its anti-inflammatory effect were investigated using Western blot. Static stretching at 20 % of initial length resulted in AMPK activation characterized by expression of phosphorylated AMPK and phosphorylated acetyl-Co A carboxylase. AMP-activated protein kinase phosphorylation peaked 1 h after stretching and declined toward resting activity. Using cell viability assays, static stretching did not appear to cause cellular damage. Activation of AMPK involves Ca2+ influx via a mechanosensitive L-type Ca2+ channel, which subsequently raises intracellular Ca2+ and activates AMPK via Ca2+/calmodulin-dependent protein kinase kinase ß (CaMKKß). Interestingly, stretching suppressed TNFα-induced expression of COX-2, iNOS, and phosphorylated NF-κB. These effects were prevented by pretreatment with compound C, an AMPK inhibitor. These results suggest that mechanical stretching suppressed inflammatory responses in synovial fibroblasts via a L-type Ca2+-channel-CaMKKß-AMPK-dependent pathway which may underlie joint mobilization's ability to alleviate OA symptoms.

Chitosan oligosaccharide suppresses synovial inflammation via AMPK activation: An in vitro and in vivo study.

Synovial inflammation plays an important role in the early pathogenesis of osteoarthritis (OA). Chitosan oligosaccharide (COS) has been shown to activate AMPK and suppress inflammatory responses in intestinal epithelial cells. This study aimed to investigate the effect of COS on AMPK activation and synovial inflammation using both primary cultures of synoviocytes and a rabbit model of anterior cruciate ligament (ACL) transection-induced OA. COS induced AMPK activation in both rabbit and human synoviocytes. The mechanism of COS-induced AMPK activation involves an increase in the ADP/ATP ratio but not calcium/calmodulin-dependent protein kinase kinase beta (CaMKKß). Interestingly, COS suppressed the TNFα-induced iNOS and COX-2 expression via an AMPK-dependent mechanism in both rabbit and human synoviocytes. Importantly, oral administration of COS (10mg/kg/day) induced AMPK activation and alleviated signs of inflammation including COX-2 expression in the synovium of a rabbit ACL transection model. Taken together, our results indicate that COS suppresses synovial inflammation in vitro and in vivo via AMPK activation. COS may be useful in the prevention of OA.

Pinocembrin attenuates gentamicin-induced nephrotoxicity in rats.

Oxidative stress mediated apoptosis of renal tubular cells is a major pathology of gentamicin-induced nephrotoxicity, which is one of the prevailing causes of acute renal failure. Pinocembrin is a major flavonoid found in rhizomes of fingerroot (Boesenbergia pandurata). It has pharmacological and biological activities including antimicrobial, anti-inflammatory, and antioxidant effects. Preclinical studies have suggested that pinocembrin protects rat brain and heart against oxidation and apoptosis induced by ischemia-reperfusion. The aim of the current study was to investigate the mechanisms of renoprotection elicited by pinocembrin in gentamicin-induced nephrotoxicity. Nephrotoxicity was induced in rats by intraperitoneal injection (i.p.) of gentamicin, and pinocembrin was administered via i.p. 30 min before gentamicin treatment for 10 days. Gentamicin-induced nephrotoxicity was indicated by the reduced renal function and renal Oat3 function and expression. Gentamicin treatment also stimulated Nrf2, HO-1, and NQO1, as well as the pro-apoptotic proteins Bax and caspase-3, concomitant with the attenuation of Bcl-XL expression in the renal cortical tissues. Pinocembrin pretreatment improved renal function and renal Oat3 function and reduced oxidative stress and apoptotic conditions. These findings indicate that pinocembrin has a protective effect against gentamicin-induced nephrotoxicity, which may be due in part to its antioxidant and anti-apoptotic effects, subsequently leading to improved renal function.

Nutraceutical for Autosomal Dominant Polycystic Kidney Disease Therapy.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited renal disorder caused by mutations of either PKD1 or PKD2 gene. Cyst formation initiates from a combination of abnormal cell proliferation along with enhanced fluid secretion. ADPKD is characterized by the progressive enlargement of cysts which destroy the renal parenchymal cells, resulting in renal failure. Currently, there is no effective treatment for this disease. Interestingly, several relevant therapeutic effects of herbal medicine relevant to pathogenic process of ADPKD have urged the researchers to search for potential candidate herb as nutraceutical for ADPKD therapy. Up to now, several natural compounds, such as triptolide, curcumin, ginkolide B, and steviol (stevia extract) have been shown to be able to retard cyst progression in ADPKD. The detailed mechanism of these compounds showed that triptolide enhanced calcium restoration, curcumin inhibited ERK & p-STAT3 pathways, ginkolide B inhibited Ras/MAPK pathway, and steviol activated AMPK, which inhibited CFTR channel and mTOR pathway in cell and mouse models of PKD. In addition, they are currently inpreclinical and clinical studies, respectively. This review focuses on the pathophysiology of ADPKD and the recent therapeutic approaches, especially a potential use of nutraceutical for the treatment of autosomal dominant polycystic kidney disease.

Inhibition of intestinal chloride secretion by piperine as a cellular basis for the anti-secretory effect of black peppers.

Piperine is the principal alkaloid in black peppers (Piper nigrum L.), which is a commonly included spice in anti-diarrheal formulations. Piperine has antispasmodic activities, but its anti-secretory effect is not known. Therefore, this study investigated the anti-secretory effect of piperine and its underlying mechanism. Piperine inhibited cAMP-mediated Cl- secretion in human intestinal epithelial (T84) cells, similar to black pepper extract. Intraluminal administration of piperine (2 µg/loop) suppressed cholera toxin-induced intestinal fluid accumulation by ∼85% in mice. The anti-secretory mechanism of piperine was investigated by evaluating its effects on the activity of transport proteins involved in cAMP-mediated Cl- secretion. Notably, piperine inhibited CFTR Cl- channel activity (IC50#8'6#10 µM) without affecting intracellular cAMP levels. The mechanisms of piperine-induced CFTR inhibition did not involve MRP4-mediated cAMP efflux, AMPK or TRPV1. Piperine also inhibited cAMP-activated basolateral K+ channels, but it had no effect on Na+-K+-Cl- cotransporters or Na+-K+ ATPases. Piperine suppressed Ca2+-activated Cl- channels (CaCC) without affecting intracellular Ca2+ concentrations or Ca2+-activated basolateral K+ channels. Collectively, this study indicates that the anti-secretory effect of piperine involves the inhibition of CFTR, CaCC and cAMP-activated basolateral K+ channels. Piperine represents a novel class of drug candidates for the treatment of diarrheal diseases caused by the intestinal hypersecretion of Cl-.

Losartan and Sodium Nitroprusside Effectively Protect against Renal Impairments after Ischemia and Reperfusion in Rats.

Ischemia and subsequent reperfusion are known to impair renal function. We examined several agents that might prevent renal impairment or enhance the recovery of renal function after ischemia/reperfusion injury in rats. Different degrees of preventive effects were observed in rats treated with captopril, BQ-123 (endothelin type A receptor antagonist), sodium nitroprusside (SNP, a nitric oxide donor), and losartan (angiotensin II type 1 receptor antagonist). Only minimal changes in renal morphology were observed after treatment with losartan, SNP, captopril, and BQ-123 compared with control animals. On the other hand, lesions were prominent in the N(G)-nitro-L-arginine-methyl ester (L-NAME)- and L-arginine-treated rats. The Na(+)-K(+) ATPase activity of ischemic kidneys was, however, preserved in all treatment groups, except in those treated with L-arginine and L-NAME, which showed a marked reduction in Na(+)-K(+) ATPase activity. Our post-treatment data suggest that losartan and SNP have the greatest potential for therapeutic use to mitigate post-ischemic renal damage and functional impairment.

Activation of liver X receptors reduces CFTR-mediated Cl(-) transport in kidney collecting duct cells.

Liver X receptors (LXRs) are transcription factors belonging to the nuclear receptor super family, which act as regulators of lipid and glucose metabolism. However, LXRs have been shown to regulate the function of transporters in the kidney, including the Na-Pi cotransporter, organic anion transporter, and epithelial Na(+) channel. In this report, we demonstrated the ability of LXR ligands, both endogenous [22 (R)-hydroxycholesterol] and synthetic (T0901317 and GW3965), to reduce CFTR-mediated Cl(-) secretion in a type I Madin-Darby canine kidney (MDCK) cell line and in murine primary inner medullary collecting duct (IMCD) cells, based on measurements of [Arg(8)]-vasopressin-induced Cl(-) current. However, treatment of MDCK cell monolayers with 5 µM T0901317 for 24 h did not alter ouabain-senstive current or Na(+)-K(+)-ATPase-α protein content. Furthermore, basolateral membranes permeabilization of MDCK cell monolayers still resulted in a decrease in apical Cl(-) current stimulated by both [Arg(8)]-vasopressin and 8-cholorophenyl-thio-cAMP, indicating that the factor(s) encoded by the target gene(s) of agonist-activated LXRs might be located at the apical membrane. Western blot analysis revealed that inhibition of Cl(-) secretion occurred via a decrease in CFTR protein, which was not due to downregulation of its mRNA expression. In addition, both synthetic LXR agonists significantly retarded the growth of forskolin-induced cysts formed in MDCK cells cultured in collagen gel. This is the first evidence showing that ligand-activated LXRs are capable of downregulating CFTR-mediated Cl(-) secretion of kidney cells and of retarding cyst growth in a MDCK cell model.