Trimetazidine Protects from Mercury-Induced Kidney Injury.

INTRODUCTION: The presence of mercury in the environment is a worldwide concern. Inorganic mercury is present in industrial materials, is employed in medical devices, is widely used in batteries, is a component of fluorescent light bulbs, and it has been associated with human poisoning in gold mining areas. The nephrotoxicity induced by inorganic mercury is a relevant health problem mainly in developing countries. The primary mechanism of mercury toxicity is oxidative stress. Trimetazidine (TMZ) is an anti-ischemic drug, which inhibits cellular oxidative stress, eliminates oxygen-free radicals, and improves lipid metabolism. The aim of this study was to evaluate whether the administration of TMZ protects against mercuric chloride (HgCl2) kidney damage. METHODS: Adult male Wistar rats received only HgCl2 (4 mg/kg bw, sc) (Hg group, n = 5) or TMZ (3 mg/kg bw, ip) 30 min before HgCl2 administration (4 mg/kg bw, sc) (TMZHg group, n = 7). Simultaneously, a control group of rats (n = 4) was studied. After 4 days of HgCl2 injection, urinary flow, urea and creatinine (Cr) plasma levels, Cr clearance, urinary glucose, and sodium-dicarboxylate cotransporter 1 (NaDC1) in urine were determined. Lipid peroxidation (MDA) and glutathione (GSH) levels were measured in kidney homogenates. RESULTS: Rats only treated with HgCl2 showed an increase in urea and Cr plasma levels, urinary flow, fractional excretion of water, glucosuria, and NaDC1 urinary excretion as compared with the control group and a decrease in Cr clearance. TMZHg group showed a decrease in urea and Cr plasma levels, urinary flow, fractional excretion of water, glucosuria, NaDC1 urinary excretion, and an increase in Cr clearance when compared to the Hg group. Moreover, MDA and GSH levels observed in Hg groups were decreased and increased, respectively, by TMZ pretreatment. CONCLUSION: TMZ exerted a renoprotective action against HgCl2-induced renal injury, which might be mediated by the reduction of oxidative stress. Considering the absence of toxicity of TMZ, its clinical application against oxidative damage due to HgCl2-induced renal injury should be considered. The fact that TMZ is commercially available should simplify and accelerate the translation of the present data "from bench to bedside." In this context, TMZ become an interesting new example of drug repurposing.

Erythropoietin alters the pharmacokinetics of organic anions mainly eliminated by the kidney in rats.

Erythropoietin (EPO) is a cytokine originally used for its effects on the hematopoietic system, and is widely prescribed around the world. In the present study, the effects of EPO administration on p-aminohippurate (PAH, a prototype organic anion) pharmacokinetics and on the renal expression of PAH transporters were evaluated. Male Wistar rats were treated with EPO or saline (control group). After 42 h, PAH was administered, and plasma samples were obtained at different time points to determine PAH levels. PAH levels in renal tissue and urine were also assessed. The renal expression of PAH transporters was evaluated by Western blotting. EPO-treated rats showed an increase in PAH systemic clearance, in its elimination rate constant, and in urinary PAH levels, while PAH in renal tissue was decreased. Moreover, EPO administration increased the expression of the transporters of the organic anions evaluated. The EPO-induced increase in PAH clearance is accounted for by the increase in its renal secretion mediated by the organic anion transporters. The goal of this study is to add important information to the wide knowledge gap that exists regarding drug-drug interactions. Owing to the global use of EPO, these results are useful in terms of translation into clinical practice.

Novel finding of caveolin-2 in apical membranes of proximal tubule and first detection of caveolin-2 in urine: A promising biomarker of renal disease.

Caveolin-2 (Cav-2) is expressed in a variety of cell tissue, and it has also been found in renal tissue. The expression of Cav-2 in proximal tubules is still unclear. The aim of this study was to carry out a complete evaluation of the expression pattern of Cav-2 in rat renal cortex to clarify and deepen the knowledge about the localization of Cav-2 in the proximal tubules and also to evaluate its presence in urine. Male Wistar rats were used to assess Cav-2 expression by Western blot analysis in homogenates, apical, and basolateral membranes from kidney cortex, in lysates and total plasma membranes from renal cortical cell suspensions, in urine, and in urinary exosomes. Cav-2 was clearly expressed in renal cortex homogenates and in both apical and basolateral membranes isolated from kidney cortex, with a greater expression on the former membranes. It was also observed in lysates and in plasma membranes from cortical cell suspensions. Moreover, Cav-2 was found in urine and in its exosomal fraction. These results confirmed the presence of Cav-2 in proximal tubule cells in the kidney of healthy rats, and showed for the first time its expression at the apical membrane of these cells and in urine. Besides, urinary exosomal pathway could be involved in Cav-2 urinary excretion under normal conditions. We observed an increase in the urinary abundance of Cav-2 in two models of acute kidney injury, and thus we proposed the urinary excretion of Cav-2 as a potential biomarker of kidney injury.

Impact of the induced organic anion transporter 1 (Oat1) renal expression by furosemide on the pharmacokinetics of organic anions.

AIM: Furosemide is a loop diuretic. Different authors demonstrated that continuous administration of furosemide modulates the expression of organic anion transporters. This study was undertaken to simultaneously evaluate the effects of furosemide pretreatment on organic anion transporter 1 (Oat1) and multidrug resistance protein 2 (Mrp2) renal expressions, on p-aminohippurate (PAH) pharmacokinetics and on renal and urinary PAH levels in rats. METHODS: Male Wistar rats were treated with furosemide (6 mg/100 g body weight per day, subcutaneously, 4 days) (treated group) or saline (control group). On the fifth day, PAH was administered as a bolus infusion in the femoral vein, and plasma samples were obtained from femoral artery at different time points. PAH levels in renal tissue and urine were also assessed. Renal Oat1 and Mrp2 expressions were evaluated by western blotting. RESULTS: Furosemide pretreatment increased both the expression of Oat1 and Mrp2. PAH plasma concentrations decreased following a biexponential function. The furosemide-treated group showed higher PAH plasma levels, a lower systemic clearance and elimination rate constant from the peripheral compartment, indicating that PAH renal elimination was decreased. PAH levels in renal tissue were significantly elevated and in urine appeared to be significantly lower as compared with control animals. CONCLUSIONS: Furosemide pretreatment caused a significant decrease of PAH renal elimination, despite Oat1 and Mrp2 augmented renal expression. The goal of the present study is the addition of important information in the wide gap of knowledge that exists about drug-drug interactions. Because of furosemide worldwide use, the data obtained are interesting and useful in terms of translation to clinical practice.

Organic Anion Transporter 5 (Oat5) Urinary Excretion Is a Specific Biomarker of Kidney Injury: Evaluation of Urinary Excretion of Exosomal Oat5 after N-Acetylcysteine Prevention of Cisplatin Induced Nephrotoxicity.

Cisplatin is a commonly used chemotherapeutic agent. Its main side-effect is nephrotoxicity. It was reported that the organic anion transporter 5 (Oat5) urinary excretion is elevated, implying renal perturbation, when no modifications of traditional markers of renal damage are still observed in cisplatin-induced acute kidney injury (AKI). It was also demonstrated that Oat5 is excreted in urine by the exosomal pathway. This study was designated to demonstrate the specific response of the urinary excretion of exosomal Oat5 to kidney injury independently of other cisplatin toxic effects, in order to strengthen Oat5 urinary levels as a specific biomarker of AKI. To accomplish that aim, we evaluated if urinary excretion of exosomal Oat5 returns to its basal levels when cisplatin renal damage is prevented by the coadministration of the renoprotective compound N-acetylcysteine. Four days after cisplatin administration, AKI was induced in cisplatin-treated male Wistar rats (Cis group), as it was corroborated by increased urea and creatinine plasma levels. Tubular damage was also observed. In cotreated animals (Cis + NAC group), plasma urea and creatinine concentrations tended to return to their basal values, and tubular damage was improved. Urinary excretion of exosomal Oat5 was notably increased in the Cis group, but when renal injury was ameliorated by N-acetylcysteine coadministration, that increase was undetected. So, in this work we observed that urinary excretion of exosomal Oat5 was only increased if renal insult is produced, demonstrating its specificity as a renal injury biomarker.

Time course of organic anion transporter 5 (Oat5) urinary excretion in rats treated with cisplatin: a novel urinary biomarker for early detection of drug-induced nephrotoxicity.

Cisplatin is a widely used citostatic drug employed in the treatment of many solid tumors. Its principal side-effect is nephrotoxicity. The organic anion transporter 5 (Oat5) is exclusively expressed in the kidneys. The aim of this study was to evaluate the time course of Oat5 urinary excretion and changes in conventional biomarkers, such as creatinine and urea plasma levels (Urp and Crp), and protein and glucose urinary levels (Pu and Gluu), between others, and compared them to the onset and progression of histological changes after cisplatin treatment. Male Wistar rats were treated with cisplatin with 5 mg/kg b.w., i.p., and experiments were carried out after 2, 4, 7 and 14 days of treatment. Two days after cisplatin administration, only Oat5 urinary excretion was found markedly modified. On day 4, Urp, Crp, PU and GluU were increased. By the seventh day, a severe impairment in tubular architecture was observed, and from this point and thereon, Oat5 urinary excretion and PU showed a tendency to return to their basal values. Meanwhile, Urp, Crp and GluU tended to return to their basal values by the day 14 of treatment, when kidney morphology showed an important recovery. So Oat5 urinary abundance was elevated 2 days after cisplatin treatment, when no modifications of traditional markers of renal injury were still observed. Therefore, the results showed in this work, in addition to previous data obtained by our group, propose that Oat5 urinary excretion might potentially serve as a noninvasive early biomarker of cisplatin-induced nephrotoxicity.

Organic anion transporter 5 renal expression and urinary excretion in rats with vascular calcification.

It has been described renal damage in rats with vascular calcification. The organic anion transporter 5 (Oat5) is only expressed in kidney, and its urinary excretion was proposed as potential early biomarker of renal injury. The aim of this study was to evaluate the Oat5 renal expression and its urinary excretion in an experimental model of vascular calcification in comparison with traditional markers of renal injury. Vascular calcification was obtained by the administration of an overdose of vitamin D3 (300,000 IU/kg, b.w., i.m.) to male Wistar rats. Oat5 urinary abundance was evaluated by Western blotting. Traditional markers of renal injury, such as creatinine and urea plasma levels, urinary protein levels, and urinary alkaline phosphatase (AP) activity, were determined using commercial kits. Histology was assessed by hematoxylin/eosin staining. Oat5 renal expression was evaluated by Western blotting and by immunohistochemistry. An increased expression of Oat5 in renal homogenates, in apical membranes, and in its urinary excretion was observed in rats with vascular calcification. The traditional parameters used to evaluate renal function were not modified, with the exception of histology. It is possible to postulate the urinary excretion of Oat5 as a potential noninvasive biomarker of renal injury associated with vascular calcification.

Organic anion transporter 5 (Oat5) renal expression and urinary excretion in rats treated with cisplatin: a potential biomarker of cisplatin-induced nephrotoxicity.

Cisplatin is one of the most potent chemotherapeutic antitumor drugs used in the treatment of a wide range of solid tumors. Its primary dose-limiting side effect is nephrotoxicity. The organic anion transporter 5 (Oat5) is exclusively localized in the kidney. Oat5 urinary excretion was recently proposed as a potential early biomarker of acute kidney injury (AKI). The aim of this study was to evaluate Oat5 renal expression and its urinary excretion in rats exposed to different doses of cisplatin, in comparison with traditional markers of renal injury, like renal histology, creatinine and urea plasma levels, creatinine clearance, protein and glucose urinary levels and urinary alkaline phosphatase (AP) activity. Male Wistar rats were treated with a single injection of cisplatin at different doses of 1, 2, 5 and 10 mg/kg b.w., i.p. (Cis1, Cis2, Cis5 and Cis10, n = 4, respectively) and experiments were carried out 48 h after cisplatin administration. The renal expression of Oat5 was evaluated by immunohistochemistry and Western blotting. Oat5 abundance, AP activity, creatinine, glucose and proteins were assayed in urine. Creatinine clearance and creatinine and urea plasma levels were also evaluated. In this experimental model, plasma urea and creatinine levels, creatinine clearance, AP urinary activity and protein and glucose urinary levels were significantly modified only at the highest cisplatin dose of 10 mg/kg b.w., i.p., as compared to control rats. In contrast, Oat5 urinary abundance was increased in a dose-related manner after the administration of cisplatin. Oat5 urinary abundance was elevated at a dose as low as 1 mg/kg b.w., i.p., implying renal perturbation, when no modifications of traditional markers of renal injury are yet observed. Oat5 renal expression was decreased in a dose-related manner, both in homogenates and apical membranes from cisplatin-treated kidneys. The increase in urinary Oat5 excretion might explain the decrease in the amount of Oat5 molecules in the renal tubule cells. Hence, the preclinical animal results showed in this work propose that Oat5 urinary excretion might potentially serve as a non-invasive early biomarker of cisplatin-induced AKI.

Expression and function of renal and hepatic organic anion transporters in extrahepatic cholestasis.

Obstructive jaundice occurs in patients suffering from cholelithiasis and from neoplasms affecting the pancreas and the common bile duct. The absorption, distribution and elimination of drugs are impaired during this pathology. Prolonged cholestasis may alter both liver and kidney function. Lactam antibiotics, diuretics, non-steroidal anti-inflammatory drugs, several antiviral drugs as well as endogenous compounds are classified as organic anions. The hepatic and renal organic anion transport pathways play a key role in the pharmacokinetics of these compounds. It has been demonstrated that acute extrahepatic cholestasis is associated with increased renal elimination of organic anions. The present work describes the molecular mechanisms involved in the regulation of the expression and function of the renal and hepatic organic anion transporters in extrahepatic cholestasis, such as multidrug resistance-associated protein 2, organic anion transporting polypeptide 1, organic anion transporter 3, bilitranslocase, bromosulfophthalein/bilirubin binding protein, organic anion transporter 1 and sodium dependent bile salt transporter. The modulation in the expression of renal organic anion transporters constitutes a compensatory mechanism to overcome the hepatic dysfunction in the elimination of organic anions.