The role of glutathione in p-aminophenol-induced nephrotoxicity in the mouse.

p-Aminophenol (PAP) produces nephrotoxicity in rats through a mechanism presumably involving oxidation and conjugation with glutathione (GSH). Recently it was found that PAP also causes nephrotoxicity in mice as evidenced by elevated blood urea nitrogen (BUN) and serum creatinine levels. The objective of this study was to further investigate the mechanism and elucidate the role of GSH in PAP-induced nephrotoxicity in the mouse. Male C57BL/6 mice injected i.p. with various doses of PAP were sacrificed at 12 hr for measurement of BUN and serum creatinine levels and determination of the extent of renal cortical nonprotein sulfhydryl (NPSH) and GSH depletion. PAP depleted renal cortical NPSH content in a dose- and time-dependent manner. Depletion of NPSH in mouse kidney did not occur at PAP doses below 600 mg/kg. Buthionine sulfoximine, an inhibitor of GSH synthesis, decreased nephrotoxicity. Ascorbate, a reducing agent, prevented PAP-induced nephrotoxicity and attenuated renal cortical NPSH depletion. However, acivicin and aminooxyacetic acid, inhibitors of gamma-glutamyltranspeptidase and beta-lyase, respectively, did not prevent toxicity in the mouse. Piperonyl butoxide, an inhibitor of cytochrome P-450 enzymes, enhanced nephrotoxicity and renal cysteine depletion but not GSH depletion. The results suggest that PAP-induced nephrotoxicity in the mouse may involve oxidation and formation of a GSH conjugate.     

Coincubation of Rat Renal Proximal Tubules with Hepatic Subcellular Fractions Potentiates the Effects of para-Aminophenol

Treatment of rats with para-aminophenol (PAP) (300 mg/kg ip)produced decreases in renal nonprotein sulfhydryl (NPSH) content,oxygen consumption, and adenine nucleotide concentrations 2–4hr following administration. In contrast, incubation of ratrenal tubules with up to 1 mM PAP for 4 hr produced inconsistentchanges in renal tubules. This discrepancy suggested that extrarenalmetabolism of PAP may be involved in PAP bioactivation and nephrotoxicity.We designed the present studies to test the hypothesis thathepatic metabolism of PAP potentiates the effects of PAP onrenal tubules. Incubation of renal tubules with 0.5 mM PAP and10 mg protein from hepatic postmitochondrial supernatant (S9fraction) in the absence of glutathione (GSH) for 4 hr did notalter renal oxygen consumption or adenine nucleotide metaboliteconcentrations. We observed no changes when we incubated tubuleswith 0.5 mM PAP and 1 mM GSH in the absence of hepatic S9 fraction.However, incubation of renal tubules with 0.5 mM PAP, 1 mM GSH,and 10 mg hepatic S9 protein for 4 hr significantly decreasedrenal oxygen consumption and adenosine triphosphate and totalnucleotide concentrations. These data suggest that the effectsof PAP in renal tubules may be potentiated by enzymatic metabolismof PAP, possibly involving oxidation and GSH conjugation. Fromexperiments using hepatic microsomes or cytosol instead of S9fraction, we found that changes were produced when we incubatedtubules with PAP in the presence of hepatic microsomes, butnot cytosol. These data suggest that hepatic microsomal metabolismof PAP may contribute to the production of changes in renaltubules in vitro. PAP-induced changes in renal proximal tubuleswere prevented when we included a ß- nicotinamideadenine dinucleotide phosphate (NADPH) generating system inthe incubation medium. The protective effect of NADPH persistedwhen microsomes were inactivated by incubation with 1-aminobenzotriazole,a cytochrome P450 inhibitor. These data suggest that cytochromeP450-dependent oxidation is not involved in the production orprevention of PAP-induced changes in renal tubules. The enzyme(s)responsible for PAP bioactivation and the mechanism(s) by whichNADPH protects renal tubules from PAP-induced decrements inoxygen consumption and adenine nucleotide concentrations arecurrently unclear.     

The contribution of oxidation and deacetylation to acetaminophen nephrotoxicity in female Sprague-Dawley rats

Young adult female rats are more susceptible to acetaminophen (APAP) induced nephrotoxicity than are male rats. The purpose of the present study was to assess the contribution of oxidation and deacetylation to the expression of APAP nephrotoxicity. Male and female rats received APAP (1100 mg kg⁻¹ i.p.) alone or following pretreatment with 1-aminobenzotriazole (ABT), a suicide inhibitor of cytochromes P450, or tri-o-tolylphosphate (TOTP), an irreversible carboxyesterase inhibitor. Rats were sacrificed 6 or 24 h following administration of 1100 mg APAP kg⁻¹ containing [ring-¹⁴C]APAP. Blood urea nitrogen (BUN) concentration was used as an index of nephrotoxicity. Renal and hepatic non-protein sulfhydryl (NPSH) contents and covalent binding of radiolabel derived from APAP were determined 6 h following APAP administration. Pretreating female rats with ABT, TOTP, or both compounds prevented the APAP-induced elevation in BUN concentration at 24 h. Pretreatment with ABT or ABT plus TOTP prevented APAP-induced depletion of both hepatic and renal NPSH content at 6 h in female rats. In male rats, APAP treatment did not significantly affect hepatic NPSH content. However, renal NPSH content in males was significantly decreased following APAP treatment and the decrease was prevented when rats were pretreated with ABT or ABT plus TOTP. Covalent binding of radiolabel derived from APAP was significantly greater in female kidney as compared to male kidney. Further, covalent binding in female kidney was significantly decreased when rats were pretreated with ABT, TOTP or both. These data suggest that both oxidative metabolism and deacetylation may contribute to APAP-induced nephrotoxicity in rats.     

Acetaminophen nephrotoxicity in the rat. II. Strain differences in nephrotoxicity and metabolism of p-aminophenol, a metabolite of acetaminophen

Acetaminophen (APAP) produces renal necrosis restricted to the straight segment of the proximal tubule in Fischer 344 (F344) rats. On the other hand, Sprague-Dawley (SD) rats are extremely resistant to the nephrotoxic effects of APAP. Such strain differences may be due to different susceptibilities to the nephrotoxic metabolite, p-aminophenol (PAP). PAP administration in both strains of rats resulted in a renal lesion indistinguishable from the APAP-induced renal lesion in F344 rats. The PAP-induced renal lesions in F344 rats, however, were generally more severe than those in SD rats. PAP-induced renal functional changes (elevation in blood urea nitrogen and reduction in the accumulation of p-aminohippurate by renal cortical slices) correlated with strain-dependent histopathological changes. Analysis of urinary metabolites over a 24-hr period following PAP administration (200 and 400 mg/kg) indicated that more PAP was excreted as APAP in SD than in F344 rats. Covalent binding of PAP to renal microsomes in vitro was much greater in F344 rats than in SD rats at substrate concentrations less than 5 mM. These results suggest that strain differences in PAP-induced nephrotoxicity may be related to differences in the intrarenal activation of PAP. Furthermore, strain differences in APAP-induced nephrotoxicity may be related to strain differences in the activation of the nephrotoxic metabolite, PAP.     

Lack of Correlation between para-Aminophenol Toxicity in Vivo and in Vitro in Female Sprague--Dawley Rats

The present study was designed to test the hypothesis that para-aminophenol(PAP) nephrotoxicity is due to autooxidation. We compared renalfunctional responses following PAP administration to femaleSprague-Dawley rats and following incubation of renal proximaltubules with PAP. The concentrations of PAP selected for invitro incubations produced cytotoxicity (for example, a decreasein oxygen consumption or adenine nucleotide concentration) inrat renal epithelial cells or rabbit proximal tubule suspensions.In rats, PAP (300 mg/kg ip) caused proximal tubular necrosiswithin 24 hr. Changes in renal function 24 hr following PAPadministration included increased kidney weight and blood ureanitrogen concentration and decreased renal glutathione (GSH)content and adenine nucleotide concentrations. PAP did not causehepatic damage. Within 2–4 hr following PAP administration,renal GSH content and adenine nucleotide concentrations weresignificantly decreased. In renal cortical slices prepared fromPAP-treated rats, oxygen consumption and accumulation of organicions (para-aminohippurate and tetraethylammonium) were significantlydecreased compared with renal cortical slices prepared fromcontrol rats. In liver, GSH content was significantly decreasedfrom 1 to 4 hr following PAP administration. In contrast tothe effects of PAP in vivo, renal proximal tubules showed littleevidence of injury when incubated with 0.1 or 0.5 mM PAP forup to 4 hr in the presence or absence of amino acids in theincubation medium. When tubules were incubated with 1 mM PAPfor 4 hr in the presence of amino acids, GSH content, AMP concentration,and TEA uptake were significantly decreased. When amino acidswere removed from the incubation medium, 1 mM PAP caused decreasesin oxygen consumption and ATP concentration after 4 hr of incubation.Functional changes observed during incubation with PAP in vitrowere not consistent with functional changes observed in vivo.The discrepancy between PAP toxicity in vivo and in vitro suggeststhat autooxidation is unlikely to be responsible for PAP nephrotoxicityand that nephrotoxicity in vivo is primarily mediated by extrarenalbioactivation. Further, depletion of hepatic GSH content priorto changes in renal function suggests that PAP or a PAP metabolitemay conjugate with hepatic GSH. These observations suggest thatPAP nephrotoxicity may be mediated by PAP-GSH conjugates ratherthan autooxidation of PAP in the kidney.     

Renal toxicity caused by cisplatinum in glutathione-depleted metallothionein-null mice

To elucidate the protective role of metallothionein (MT) and glutathione (GSH) in renal toxicity caused by cisplatinum (cis-DDP), we examined the sensitivity of GSH-depleted MT-null mice to the renal toxicity of cis-DDP. Blood urea nitrogen and creatinine values in the serum, and histopathological change in the kidney were utilized as indicators of nephrotoxicity caused by cis-DDP. Although cis-DDP exerted renal toxicity in MT-null mice and wild-type mice, the toxicity was more conspicuous in the MT-null mice than in the wild-type mice. Moreover, renal toxicity caused by cis-DDP was enhanced significantly by a decrease in the renal GSH level by buthionine sulfoximine (BSO) pretreatment in both kinds of mice. The cis-DDP-caused nephrotoxicity that was enhanced by BSO-mediated GSH depletion was much more severe in the MT-null mice than in the wild-type mice. However, preadministration of zinc sulfate cancelled the BSO-enhanced, cis-DDP-dependent renal toxicity in the wild-type mice, but not in the MT-null mice. In the present study, we found that MT and GSH play an important, cooperative role in detoxification of severe kidney damage caused by cis-DDP. Moreover, the renal MT preinduced by zinc could protect mice from cis-DDP nephrotoxicity enhanced by GSH depletion.     

Protective effects of apigenin and myricetin against cisplatin-induced nephrotoxicity in mice

Context: Currently, the outcomes of the use of cisplatin in cancer therapy is limited by nephrotoxicity.

Objective: This study aims to investigate the nephroprotective role of apigenin and myricetin against cisplatin-induced nephrotoxicity in mice.

Materials and methods: Adult female Wistar Albino mice were divided into eight groups (n?=?8). Group I served as normal control. Groups II, III and IV received apigenin (3?mg/kg, i.p.), myricetin (3?mg/kg, i.p.) or their combination respectively, for seven days. Group V served as positive control group, received vehicles for seven days and cisplatin (7.5?mg/kg, i.p.) for three days starting at day five. Groups VI, VII and VIII received apigenin, myricetin or their combination, respectively for seven days as well as cisplatin injection for three days starting at day five. by the end of the experimental period, a biochemical study involving, nephrotoxicity markers [serum creatinine (Cr) and blood urea nitrogen (BUN)], apoptotic marker [caspase 3], inflammatory mediators [tumour necrosis factor alpha (TNF-α), interleukin 6 (IL-6), cyclooxygenase I and II (COXI, COXII)] and oxidative stress biomarkers [malondialdehyde (MDA), reduced glutathione (GSH) and catalase] was conducted. In addition, renal histopathological alterations were evaluated.

Results: Apigenin, myricetin and their combination significantly reduced blood BUN, serum Cr, caspase-3TNF-α, IL-6, COXI and COXII, MDA levels and significantly increased GSH level and catalase activity parallel to, histopathological improvement in kidney tissues.

Discussion and conclusion: Apigenin and myricetin exhibited a protective and promising preventive strategy against cisplatin-induced nephrotoxicity due to their antioxidant and anti-inflammatory effects.     

Effect of antioxidants on para-aminophenol-induced toxicity in LLC-PK1 cells

The present studies were designed to investigate the susceptibility of LLC-PK1 cells to cytotoxicity induced by para-aminophenol (PAP) and the ability of antioxidants to prevent PAP-induced cytotoxicity. LLC-PK1 cells were incubated for 4 h with varying concentrations of PAP (0-0.2 mM). Incubation was continued for 20 h and viability was monitored at 24 h after initial exposure to PAP. For coincubation experiments, cells were incubated for 4 h with various antioxidants [including ascorbate, glutathione (GSH), butylated hydroxytoluene (BHT), beta-nicotinamide adenine dinucleotide (NADH), or beta-nicotinamide adenine dinucleotide phosphate (NADPH)] in the absence or presence of 0.1 mM PAP. For preincubation experiments, cells were incubated for 1 h with ascorbate, GSH or NADPH. Antioxidants were removed and cells were exposed to 0 or 0.1 mM PAP for 4 h. Viability was determined 24 h following PAP exposure. LLC-PK1 cells displayed a steep concentration-response relationship for PAP; 0.1 mM PAP caused approximately 50% loss of viability. Coincubation with ascorbate, GSH and NADPH was without effect on cell viability in the absence of PAP and attenuated PAP-induced losses in viability. In contrast, NADH was ineffective in preventing PAP-induced cytotoxicity. BHT alone produced a significant loss of cell viability and was ineffective in preventing PAP cytotoxicity. Inability of NADH to prevent PAP-induced cytotoxicity was related to rapid degradation of NADH in aqueous solution. Preincubation of cells with ascorbate or GSH but not NADPH was associated with attenuation of PAP-induced cytotoxicity. These data suggest that (1) PAP is cytotoxic to LLC-PK1 cells, (2) a portion of PAP cytotoxicity is due to nonenzymatic oxidation that occurs in the incubation medium, and (3) a portion of PAP cytotoxicity is due to enzymatic or nonenzymatic oxidation that occurs within cells.     

Peroxidative damage and nephrotoxicity of dichlorovinylcysteine in mice

Male NMRI mice were treated i.p. with dichlorovinylcysteine (DCVC) in a dosage of 2.5-500 mg/kg-1 and renal cortical slices from naive mice were incubated with 0-125 micrograms/ml-1 DCVC. The effects of DCVC on blood urea nitrogen (BUN), reduced glutathione (GSH) content, malondialdehyde (MDA) production, p-aminohippuric acid (PAH)- and tetraethylammonium (TEA)-accumulation and glucose synthesis (gluconeogenesis) were measured. DCVC depleted GSH in a time- and dose-dependent manner. Depletion of renal cortical GSH by DCVC was more pronounced in the kidney cortex than in the liver. DCVC caused a dose-dependent increase of ethane exhalation and of MDA production in the renal cortex. When animals were kept in a closed system, decrease in oxygen concentration increased the peroxidative damage. No increase of MDA concentration was observed in the liver. Treatment of mice with DCVC induced a dose-dependent increase in BUN and decreased the accumulation of PAH and TEA in renal cortical slices. Pretreatment of mice with aminooxyacetic acid (AOAA) and (+) cyanidanol-3 (CY) caused a significant reduction in DCVC-induced lipid peroxidation and nephrotoxicity. In vitro incubation of renal cortical slices of naive mice with DCVC resulted in a concentration-dependent increase in MDA and a concentration-dependent decrease in the accumulations of PAH, TEA and of gluconeogenesis. In conclusion, the interaction of DCVC and/or its metabolites with membrane lipids may be responsible for lipid peroxidation and nephrotoxicity. The formation of lipid peroxidation products was greater under hypoxic conditions and appeared to be related to the DCVC-induced nephrotoxicity. This data suggests lipid peroxidation as a possible mechanism of DCVC-induced nephrotoxicity.     

Gender-Related Differences in Susceptibility to Acetaminophen-Induced Protein Arylation and Nephrotoxicity in the CD-1 Mouse

Acetaminophen (APAP) is a commonly used analgesic and antipyretic agent which, in high doses, causes liver and kidney necrosis in man and animals. Damage in both target organs is greatly dependent upon biotransformation. However, in the CD-1 mouse only males exhibit cytochrome P450-dependent nephrotoxicity and selective protein covalent binding. The lack of renal toxicity in female mice may reflect the androgen dependence of renal CYP2E1. To study this, female mice were pretreated with testosterone propionate and then challenged 6 days later with APAP. Groups of control males and females were similarly challenged with APAP for comparison. All groups exhibited hepatotoxicity after APAP with similar glutathione (GSH) depletion, covalent binding, centrilobular necrosis, and elevation of plasma sorbitol dehydrogenase activity. By contrast, APAP-induced nephrotoxicity occurred only in males and in the females pretreated with testosterone. No nephrotoxicity was evident in APAP-challenged control females. The selective pattern of hepatic and renal protein arylation previously reported for male mice was similarly observed in testosterone-pretreated female mice. Western blot analysis of microsomes showed that testosterone increased renal CYP2E1 levels without altering hepatic CYP2E1. Testosterone pretreatment, in vivo, also resulted in increased activation of APAP in vitro in kidney microsomes with no effect on the in vitro activation of APAP in liver microsomes. These data suggest that APAP-mediated GSH depletion, covalent binding, and toxicity in the kidneys of testosterone-pretreated females results from increased APAP activation by the testosterone-induced renal CYP2E1. This further suggests that renal, rather than hepatic, biotransformation of APAP to a toxic electrophile is central to APAP-induced nephrotoxicity in the mouse.     

Disruption of multidrug and toxin extrusion MATE1 potentiates cisplatin-induced nephrotoxicity

Multidrug and toxin extrusion 1 (MATE1/SLC47A1) is expressed in the brush-border membrane of renal proximal tubules and mediates the efflux of cationic drugs. In the present study, the role of MATE1 in the nephrotoxicity of cisplatin was investigated in vivo and in vitro. Cisplatin (15 mg/kg) was administered intraperitoneally to wild-type (Mate1(+/+)) and Mate1 knockout (Mate1(−/−)) mice. Lifespan was significantly shorter in Mate1(−/−) mice than Mate1(+/+) mice. Three days after the administration of cisplatin, plasma creatinine and blood urea nitrogen (BUN) levels were increased in both Mate1(+/+) and Mate1(−/−) mice compared with vehicle-treated controls, and creatinine clearance was decreased. Moreover, a significant rise in creatinine and BUN levels was observed in cisplatin-treated Mate1(−/−) mice in comparison to Mate1(+/+) mice. A pharmacokinetic analysis revealed the plasma concentration and renal accumulation of cisplatin to be higher in Mate1(−/−) mice than Mate1(+/+) mice 1 h after a single intravenous administration of cisplatin (0.5 mg/kg). Furthermore, the combination of a selective MATE inhibitor, pyrimethamine, with cisplatin also elevated creatinine and BUN levels compared to cisplatin alone. In experiments in vitro, the cellular uptake of cisplatin was stimulated by the expression of mouse MATE1 as well as organic cation transporters OCT1 and OCT2. In conclusion, MATE1 mediates the efflux of cisplatin and is involved in cisplatin-induced nephrotoxicity.     

Ameliorative effects of gallic acid on gentamicin-induced nephrotoxicity in rats

Abstract

The major side effect of gentamicin (GEN) is nephrotoxicity which in turn restricts the clinical use of this drug. In this study, the effect of gallic acid (GA) on gentamicin-induced nephrotoxicity was studied. A total number of 28 male Wistar rats were randomly divided into four experimental groups: control, GEN (100 mg/kg/day), GEN + GA (30 mg/kg/day), GA (30 mg/kg/day). All drug administrations were done intraperitoneally (i.p) for eight consecutive days. Twenty-four hours after the last administration, blood samples were collected to determine serum creatinine (Cr), blood urea nitrogen (BUN). The right kidney was used for histological examination. Malondialdehyde (MDA), glutathione (GSH), nitric oxide (NO) levels and catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activity were assayed in left renal tissue. Results showed a significant increase in the levels of MDA, NO, Cr, and BUN and decrease of GSH, CAT, GPx, and SOD by GEN administration. Co-administration with GA showed reduction in the levels of MDA, NO, Cr, and BUN and increase in GSH, CAT, GPx, and SOD. Also, the nephroprotective effect of GA was confirmed by the histological examination of the kidneys. The results of our study showed that GA exerts a significant nephroprotective effect against GEN-induced nephrotoxicity.     

Mechanism of chloroform nephrotoxicity : I. Time course of chloroform toxicity in male and female mice

Chloroform (CHCl3) nephrotoxicity in male mice could be detected as early as 2 hr after CHCl3 administration (250 microliter/kg, sc) as decreased ability of renal cortical slices to accumulate p-aminohippurate (PAH) and tetraethylammonium (TEA). The decrease was preceded and paralleled by a reduction of renal cortical nonprotein sulfhydryl (NPSH) concentration, an index of tissue reduced glutathione concentration. Histologic alterations were not observed until NPSH concentrations and PAH and TEA accumulation had reached the nadir, 5 hr after CHCl3 administration. Female mice exhibited no evidence of nephrotoxicity to CHCl3 even when the dose was increased to 1000 microliter/kg or when pretreated with diethyl maleate to reduce renal cortical NPSH concentrations prior to CHCl3 injection. The extent of hepatotoxicity was similar in male and female mice and decreases of hepatic NPSH concentrations also were detected by 1.5 hr after CHCl3 administration. The rapid response of the kidney to CHCl3 toxicity in male mice and the similarity of liver toxicity in both sexes suggests that nephrotoxicity occurs independently of hepatotoxicity. Furthermore, the ability to detect these early changes in vivo following CHCl3 administration may permit the development of an in vitro model to evaluate the mechanism of CHCl3 nephrotoxicity.     

Nephrotoxicity of bromobenzene in mice

I.p. administration of bromobenzene to male mice at doses ranging from 0 to 9.4 mmol/kg resulted in a dose-dependent increase in blood urea nitrogen (BUN) and serum glutamic-pyruvic transaminase (SGPT) activity and a decrease in renal cortical accumulation of para-aminohippurate (PAH) and tetraethylammonium (TEA). Induction of renal and hepatic mixed-function oxidases by beta-naphthoflavone (BNF) did not result in any alterations in the hepatotoxic or nephrotoxic response to bromobenzene. Renal and hepatic non-protein sulfhydryl (NPSH) concentrations were decreased significantly 1 h after administration of bromobenzene (7.5 mmol/kg) and were maximally depleted in both organs to 18% of control after 7 h. Depletion of renal NPSH by bromobenzene was dose-dependent up to 9.4 mmol/kg. Treatment of mice with diethyl maleate (DEM) (0.6 ml/kg) 60 min prior to bromobenzene administration resulted in greater hepatotoxicity, evidenced by increased SGPT, while renal toxicity was unchanged. These data demonstrate that large doses of bromobenzene produce functional alterations in the kidney.     

Contribution of acetaminophen-cysteine to acetaminophen nephrotoxicity II. Possible involvement of the gamma-glutamyl cycle

Acetaminophen (APAP) nephrotoxicity has been observed both in humans and research animals. Our recent investigations have focused on the possible involvement of glutathione-derived APAP metabolites in APAP nephrotoxicity and have demonstrated that administration of acetaminophen-cysteine (APAP-CYS) potentiated APAP-induced renal injury with no effects on APAP-induced liver injury. Additionally, APAP-CYS treatment alone resulted in a dose-responsive renal GSH depletion. This APAP-CYS-induced renal GSH depletion could interfere with intrarenal detoxification of APAP or its toxic metabolite N-acetyl-p-benzoquinoneimine (NAPQI) and may be the mechanism responsible for the potentiation of APAP nephrotoxicity. Renal-specific GSH depletion has been demonstrated in mice and rats following administration of amino acid gamma-glutamyl acceptor substrates for gamma-glutamyl transpeptidase (gamma-GT). The present study sought to determine if APAP-CYS-induced renal glutathione depletion is the result of disruption of the gamma-glutamyl cycle through interaction with gamma-GT. The results confirmed that APAP-CYS-induced renal GSH depletion was antagonized by the gamma-glutamyl transpeptidase (gamma-GT) inhibitor acivicin. In vitro analysis demonstrated that APAP-CYS is a gamma-glutamyl acceptor for both murine and bovine renal gamma-GT. Analysis of urine from mice pretreated with acivicin and then treated with APAP, APAP-CYS, or acetaminophen-glutathione identified a gamma-glutamyl-cysteinyl-acetaminophen metabolite. These findings are consistent with the hypothesis that APAP-CYS contributes to APAP nephrotoxicity by depletion of renal GSH stores through interaction with the gamma-glutamyl cycle.     

Contribution of acetaminophen-cysteine to acetaminophen nephrotoxicity in CD-1 mice: I. Enhancement of acetaminophen nephrotoxicity by acetaminophen-cysteine

Acetaminophen (APAP) nephrotoxicity has been observed both in humans and research animals. Recent studies suggest a contributory role for glutathione (GSH)-derived conjugates of APAP in the development of nephrotoxicity. Inhibitors of either gamma-glutamyl transpeptidase (gamma-GT) or the probenecid-sensitive organic anion transporter ameliorate APAP-induced nephrotoxicity but not hepatotoxicity in mice and inhibition of gamma-GT similarly protected rats from APAP nephrotoxicity. Protection against APAP nephrotoxicity by disruption of these GSH conjugate transport and metabolism pathways suggests that GSH conjugates are involved. APAP-induced renal injury may involve the acetaminophen-glutathione (APAP-GSH) conjugate or a metabolite derived from APAP-GSH. Acetaminophen-cysteine (APAP-CYS) is a likely candidate for involvement in APAP nephrotoxicity because it is both a product of the gamma-GT pathway and a probable substrate for the organic anion transporter. The present experiments demonstrated that APAP-CYS treatment alone depleted renal but not hepatic glutathione (GSH) in a dose-responsive manner. This depletion of renal GSH may predispose the kidney to APAP nephrotoxicity by diminishing GSH-mediated detoxification mechanisms. Indeed, pretreatment of male CD-1 mice with APAP-CYS before challenge with a threshold toxic dose of APAP resulted in significant enhancement of APAP-induced nephrotoxicity. This was evidenced by histopathology and plasma blood urea nitrogen (BUN) levels at 24 h after APAP challenge. APAP alone was minimally nephrotoxic and APAP-CYS alone produced no detectable injury. By contrast, APAP-CYS pretreatment did not alter the liver injury induced by APAP challenge. These data are consistent with there being a selective, contributory role for APAP-GSH-derived metabolites in APAP-induced renal injury that may involve renal-selective GSH depletion.     

Studies on the effects ofl(αS,5S)-α-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT-125) on 4-aminophenol-induced nephrotoxicity in the Fischer 344 rat

4-Aminophenol (para-aminophenol; PAP) causes selective necrosis to the S₃ segment of the proximal tubule in experimental animals. The mechanism of PAP nephrotoxicity has not been fully elucidated, although it has been suggested to involve glutathione (GSH)-dependentS-conjugation followed by processing by the enzyme -glutamyl transpeptidase (GT) to the corresponding cysteineS-conjugate. This proposed toxicity mechanism was probed further by administering L-(S,5S)--amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid (AT-125), a potent GT inhibitor, to Fischer 344 (F344) rats before treatment with PAP (100 mg/kg). AT-125 pretreatment did not appear to protect against PAP-induced nephrotoxicity as assessed by renal histopathology, clinical chemistry and proton nuclear magnetic resonance (¹H NMR) spectroscopy of urine. These data suggest that renal GT activity is not a prerequisite for PAP nephrotoxicity and that the generation of a cysteineS-conjugate is not a unique requirement for the induction of PAP nephrotoxicity.     

Cisplatin nephrotoxicity is mediated by gamma glutamyltranspeptidase, not via a C-S lyase governed biotransformation pathway

Cisplatin exhibits dose-limiting nephrotoxicity in rodents and man. This study investigates the mechanism of cisplatin nephrotoxicity in vivo and in an in vitro model system. Nephrotoxicity was induced in rats (6 mg/kg cisplatin i.p.) and mice (10 mg/kg cisplatin i.p.). Cisplatin administration significantly elevated blood urea nitrogen (BUN) and serum creatinine in male Sprague Dawley rats day 5 post-treatment (BUN Delta+28+/-5 micromol/ml; serum creatinine Delta+108+/-4 nmol/ml, P<0.05) and in male C57BL6 mice day 4 post-treatment (BUN Delta+21+/-4 micromol/ml; serum creatinine Delta+81+/-5 nmol/ml, P<0.05). Nephrotoxicity was confirmed by histological analysis that revealed significant damage to the proximal tubules of cisplatin- versus saline vehicle-treated animals. Inhibition of gamma glutamyltranspeptidase prevented cisplatin nephrotoxicity in Sprague Dawley rats (day 5 BUN Delta+1+/-2 micromol/ml; serum creatinine Delta+8+/-4 nmol/ml) and C57BL6 mice (day 4 BUN Delta+1+/-0.8 micromol/ml; serum creatinine Delta-1+/-2 nmol/ml), but not cellular toxicity in rat proximal tubular (RPT) or human proximal tubular (HPT) cultures. Inhibition of aminopeptidase N (AP-N) or renal dipeptidase (RDP) in male Sprague Dawley rats, or in RPT and HPT cell cultures, did not reduce cisplatin toxicity. In contrast to published findings inhibition of C-S lyase did not prevent the nephrotoxicity of cisplatin in vivo or cellular toxicity in vitro. These data demonstrate that the biotransformation enzymes AP-N, RDP and C-S lyase are not implicated in the metabolism of cisplatin to a nephrotoxic metabolite as has been previously hypothesised. Instead, our data demonstrate that gamma glutamyltranspeptidase is a key enzyme involved in mediating cisplatin nephrotoxicity, which potentially acts to cleave cisplatin-GSH conjugates to a toxic metabolite.     

Nephrotoxicity of p-aminophenol,a metabolite of acetaminophen,in the Fischer 344 rat

Acetaminophen (APAP) produces proximal tubular necrosis in the Fischer 344 rat. APAP is deacetylated to p-aminophenol (PAP) in the hamster, and PAP has been reported to be a potent specific cortical nephrotoxicant in the rat. However, the role of PAP in APAP nephrotoxicity has not been defined. Therefore, it was of interest to quantify PAP formation after APAP administration and to correlate PAP formation with renal injury produced by APAP in the Fischer 344 rat. Urinary PAP excretion, measured as an index of PAP formation, increased with increasing doses of APAP. In addition, APAP was metabolized to PAP in isolated perfused kidneys. PAP at doses as low as 100 mg/kg produced significant renal toxicity (elevation in blood urea nitrogen and reduction in accumulation of p-aminohippurate by thin renal cortical slices). Ortho- and meta-aminophenol were not nephrotoxic. Pretreatment with polybrominated biphenyls or β-naphthoflavone, inducers of mixed function oxidases, protected against nephrotoxicity of PAP, possibly as a result of enhanced hepatic biotransformation of the parent compound. These studies indicate that PAP is a potent, selective nephrotoxicant that can be generated from APAP by the kidney and may be responsible for the renal necrosis subsequent to APAP administration.     

Antioxidant and anti-inflammatory effects of Nasturtium officinale involved in attenuation of gentamicin-induced nephrotoxicity

Background and purpose: Gentamicin (GM) is used against bacterial infections. The aim of our investigation was to evaluate the role of inflammation and also oxidative damage in nephrotoxic potential of GM and protective effects of Nasturtium officinale (watercress) against GM-induced nephrotoxicity in Wistar rats.

Material and methods: The animals were divided into eight groups: control, solvent, GM (80?mg/kg IP), GM with three doses (50, 100 and 200?mg/kg/d) of hydroalcoholic extract of watercress and one group only received high dose of extract and a group which received GM plus vitamin E for 10 consecutive days. Then, the animals were killed and kidney tissues were separated. Finally reactive oxygen species (ROS), glutathione (GSH) content, lipid peroxidation (LPO), protein carbonyl (PCO), nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α) were evaluated. Also, pathological examination and measuring of blood urea nitrogen (BUN) and creatinine (Cr) were done.

Results: The administration of GM for 10 d resulted in an increase in kidney markers (BUN and Cr) and pathological changes in kidney tissue. Also, oxidative stress was evident in GM group by increased ROS, LPO and PCO level and GSH oxidation. Increased in inflammation process was shown by increase in NO and TNF-α. Administration of watercress extract was able to protect against deterioration in nephrotoxic markers and suppressed the increase in oxidative stress and inflammation markers.

Conclusions: Our study showed the critical role of oxidative damage and inflammation in GM-induced nephrotoxicity that markedly inhibited by administration of watercress. Therefore, watercress can be suggested for prevention of GM-induced nephrotoxicity.