The role of glucuronidation in N-(3,5-dichlorophenyl)succinimide (NDPS) nephrotoxicity: nephrotoxic potential of NDPS and NDPS metabolites in Gunn, Wistar, and Fischer 344 rats

Role of leukotrienes in N-(3,5-dichlorophenyl)succinimide (NDPS) and NDPS metabolite nephrotoxicity in male Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) can induce marked nephrotoxicity in rats following a single intraperitoneal (ip) administration of 0.4mmol/kg or greater. Although NDPS induces direct renal proximal tubular toxicity, a role for renal vascular effects may also be present. The purpose of this study was to examine the possible role of vasoconstrictor leukotrienes in NDPS and NDPS metabolite nephrotoxicity. Male Fischer 344 rats (4 rats/group) were administered diethylcarbamazine (DEC; 250 or 500mg/kg, ip), an inhibitor of LTA(4) synthesis, 1h before NDPS (0.4mmol/kg, ip), N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS, 0.1, 0.2, or 0.4mmol/kg, ip), or N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA, 0.1mmol/kg, ip) or vehicle. In a separate set of experiments, the LTD(4) receptor antagonist LY171883 (100mg/kg, po) was administered 0.5h before and again 6h after NDHS (0.1mmol/kg, ip) or 2-NDHSA (0.1mmol/kg, ip) or vehicle. Renal function was monitored for 48h post-NDPS or NDPS metabolite. DEC markedly reduced the nephrotoxicity induced by NDPS and its metabolites, while LY171883 treatments provided only partial attenuation of NDHS and 2-NDHSA nephrotoxicity. These results suggest that leukotrienes contribute to the mechanisms of NDPS nephrotoxicity.

Hyperbilirubinemia's protective effect against cisplatin nephrotoxicity in the Gunn rat

Gunn rats, deficient in the enzyme uridine diphosphate glucuronyl transferase, were used to investigate the effects of unconjugated hyperbilirubinemia in cisplatin nephrotoxicity. The effect of bilirubin on the antineoplastic activity of cisplatin in osteosarcoma cell lines was also determined. The in vivo model involved three groups of rats (n=6 rats/group): homozygous Gunn rats (j/j), heterozygous Gunn rats (j/+), and congenic Wistar rats. On day 0, all rats were given 4 mg/kg cisplatin intraperitoneally. Blood was sampled on days 0, 3, and 5 for bilirubin, BUN, and creatinine and kidneys were taken on day 5. Cell culture was performed in four canine osteosarcoma cell lines using the average concentrations of bilirubin for homozygous Gunn rats at day 0 and 3. Bilirubin was added to cell lines alone and with cisplatin. Cell viability was assessed using the CellTiter Blue assay. Serum bilirubin levels were highly elevated in Gunn j/j, moderately elevated in Gunn j/+, and undetectable in Wistar rats at day 0. Bilirubin provided a nephroprotective effect, with significantly lower BUN and creatinine in Gunn j/j when compared with Wistar rats at day 5. Histological grading demonstrated preservation of the S3 segment in Gunn j/j when compared with Wistar rats (P<0.05). Bilirubin had no significant effect on the antineoplastic effect of cisplatin at either concentration in the four cell lines (P<0.001). Hyperbilirubinemia in the Gunn rat provided marked preservation of renal function and histology in a cisplatin nephrotoxicity model. Exogenous bilirubin did not interfere with the antineoplastic activity of cisplatin in vitro.

Nephrotoxicity induced by the R- and S-enantiomers of N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and their sulfate conjugates in male Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity characterized as polyuric renal failure and mediated via metabolites arising from oxidation of the succinimide ring. Recent findings have suggested that the stereochemical nature of NDPS metabolites may be an important factor in NDPS metabolite-induced nephrotoxicity. The purpose of the present study was to determine the role of stereochemistry in the in vivo nephrotoxicity induced by R-(+)- and S-(-)-N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (R- and S-NDHS) and the in vitro nephrotoxicity induced by their enantiomeric sulfate conjugates, R-(-)- and S-(+)-N-(3,5-dichlorophenyl)-2-hydroxysuccinimide-O-sulfate (R- and S-NSC). Male Fischer 344 rats (four rats/group) were administered intraperitoneally (i.p.) an enantiomer of NDHS (0.05, 0.1 or 0.2 mmol/kg) or vehicle, and renal function monitored for 48 h. R-NDHS (0.1 or 0.2 mmol/kg) had little effect on renal function. In contrast, S-NDHS (0.1 mmol/kg) induced marked nephrotoxicity. The nephrotoxic potential of R- and S-NSC (0.5, 0.75 or 1.0mM) was determined using freshly isolated rat renal cortical cells (IRCC, 3-4 x 10(6)cells/ml). Cytotoxicity was determined by measuring the release of lactate dehydrogenase (LDH) at the end of a 1h incubation period. The LDH release observed in these studies was similar between R- and S-NSC. These results indicate that stereochemistry is an important factor for NDPS metabolite nephrotoxicity and that the role of stereochemistry, at least for NSC, occurs at extra-renal sites.

Metabolism of the nephrotoxicant N-(3,5-dichlorophenyl)succinimide in rats: evidence for bioactivation through alcohol-O-glucuronidation and O-sulfation

The agricultural fungicide, N-(3,5-dichlorophenyl)succinimide (NDPS), was shown to be nephrotoxic in rats. Previous studies have indicated that the metabolism of NDPS contributes to its mechanism of toxicity and both phase I and phase II pathways may be involved. In the current report, we investigated the detailed biotransformation of [(14)C]NDPS in rats using HPLC-ESI-MS. The chemical reactivity of the phase II NDPS metabolites was also evaluated. In vivo studies were conducted by administering [(14)C]NDPS to male Fischer 344 rats. Urine, tissue (liver and kidney), and plasma samples were analyzed. The mechanism of formation and chemical reactivity of the glucuronide and sulfate metabolites of NDPS were investigated in vitro using liver subcellular preparations. Major in vivo metabolites of NDPS were identified as the oxidative [N-(3,5-dichlorophenyl)-2- and 3-hydroxysuccinamic acid, 2-/3-NDHSA] and hydrolytic products [N-(3,5-dichlorophenyl)succinamic acid]. N-Acetylcysteine and cysteine (with intramolecular aminolysis) conjugates were also detected in rat urine and fecal extracts, respectively, suggesting the formation of reactive intermediate(s) in the metabolism of NDPS. Small amounts of the alcohol-O-glucuronide and O-sulfate of 2-/3-NDHSA were detected in rat urine, plasma, and tissue homogenates. The formation of these phase II metabolites was found to be mediated through the initial conjugation of N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) followed by hydrolysis. As compared to NDHS, NDHS-O-sulfate is approximately 500-fold more reactive toward GSH conjugation. In rat liver S9, fortifying phase II cofactors (UDPGA or PAPS) in incubation mixtures with NDHS also significantly increased the amount of GSH adducts produced. Results of this research demonstrate that phase II metabolites of NDPS were produced in rats. The formation of the alkyl alcohol-O-glucuronide and O-sulfate conjugates represents bioactivation pathways in the metabolism of NDPS that could potentially contribute to its mechanism of nephrotoxicity.

Nephrotoxicity induced by C- and N-arylsuccinimides

The succinimide ring is incorporated into hundreds of compounds that are widely used as agricultural, industrial, and pharmaceutical agents. Some succinimide derivatives that contain an aryl group on the ethylene bridge of the succinimide ring (C-arylsuccinimides) or on the nitrogen atom (N-arylsuccinimides) induce nephrotoxicity in humans and/or laboratory animals. Acute toxicity induced by this general class of compounds is typically characterized as polyuric renal failure, while chronic nephrotoxicity is seen as chronic interstitial nephritis. In this review, the structure-nephrotoxicity relationships, biotransformation, and mechanisms of nephrotoxicity for the C- and N-arylsuccinimides are examined.

Renal damage, metabolism and covalent binding following administration of the nephrotoxicant N-(3,5-dichlorophenyl)succinimide (NDPS) to male Fischer 344 rats

In vivo metabolism, nephrotoxicity and covalent binding to proteins were evaluated in male Fischer 344 rats that received [2,3-14C]-N-(3,5-dichlorophenyl)succinimide (14C-NDPS). Some animals were pretreated with the enzyme inducer phenobarbital (PB, 80 mg/kg per day, for 3 days, i.p. in saline) prior to receiving a non-nephrotoxic dose of 14C-NDPS (0.2 mmol/kg, i.p. in corn oil). Other rats were pretreated with the cytochrome P450 inhibitor 1-aminobenzotriazole (ABT, 100 mg/kg, 1 h prior to NDPS, i.p. in saline) before administration of a non-toxic or a toxic dose (0.2 or 0.6 mmol/kg, respectively, i.p. in corn oil) of 14C-NDPS. Non-pretreated animals received either dose of 14C-NDPS, but did not receive PB or ABT. All rats were sacrificed 6 h after administration of 14C-NDPS. Nephrotoxicity was monitored by measuring urine volume, urine protein concentrations, blood urea nitrogen levels, and kidney weights. The NDPS metabolic profile in tissue, blood, and urine was analyzed by HPLC. Covalent binding of 14C-NDPS-derived radioactivity to tissue proteins was also measured. Compared with non-pretreated rats, PB-pretreatment potentiated the toxicity of the non-toxic dose of 14C-NDPS. In contrast, ABT-pretreatment protected the rats against NDPS nephrotoxicity. The amount of N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA), an oxidative, nephrotoxic metabolite of NDPS, was elevated in kidney homogenates and urine by PB-pretreatment (0.2 mmol/mg NDPS). ABT pretreatment inhibited NDPS metabolism at both doses. Covalent binding of 14C-NDPS (0.2 mmol/kg)-derived radioactivity to renal and plasma proteins was higher in the PB-pretreated rats than in the non-pretreated animals. In contrast, ABT-pretreatment partially inhibited covalent binding at both doses of 14C-NDPS. Our results suggest that there is a relationship between oxidative metabolism of NDPS, covalent binding of an NDPS metabolite to renal proteins, and NDPS-induced nephrotoxicity in rats.

Role of stereochemistry in N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA) nephrotoxicity

The nephrotoxicity induced by the agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) is mediated through oxidative metabolites of NDPS. Oxidation of the succinimide ring in NDPS yields the nephrotoxic metabolites N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and its hydrolysis product N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA). The oxidation of NDPS on the succinimide ring also introduces an asymmetric carbon atom into these NDPS metabolites, so that R- and S- enantiomers of NDHS and 2-NDHSA are possible. The purpose of this study was to begin to explore the importance of the stereochemical orientation at the asymmetric carbon atom for the nephrotoxicity induced by NDPS metabolites. Male Fischer 344 rats were administered a single intraperitoneal (ip) injection of R-(+)- or S-(-)-2-NDHSA (0.05, 0.1 or 2.0 mmol/kg) or vehicle, and renal function was monitored for 48 h. R-2-NDHSA (0.1 mmol/kg) administration had little effect on renal function. R-2-NDHSA (0.2 mmol/kg) treatment induced mild diuresis on day 1, increased proteinuria, and a small increase in blood urea nitrogen (BUN) concentration, but no change in kidney weight or glucosuria. S-2-NDHSA (0.1 mmol/kg) induced marked nephrotoxicity as evidenced by diuresis on both post-treatment days, increased proteinuria, glucosuria, and increased kidney weight and BUN concentration. No evidence of hepatotoxicity was obtained in any treated group. Thus, the S-isomer of 2-NDHSA is a more potent nephrotoxicant than the R-isomer, and stereochemistry may play a role in NDPS metabolite-induced nephrotoxicity.

Gender differences in the potentiation of N-(3,5-dichlorophenyl)succinimide metabolite nephrotoxicity by phenobarbital

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces acute nephrotoxicity characterized as polyuric renal failure with proximal tubular necrosis. Phenobarbital pretreatment potentiates NDPS and N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS, a nephrotoxic metabolite of NDPS) nephrotoxicity in male rats. The purpose of this study was to determine the ability of phenobarbital pretreatment to potentiate (1) NDHS nephrotoxicity in female rats and (2) N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA, a nephrotoxic metabolite of NDHS) nephrotoxicity in male and female rats. Age-matched male and female Fischer 344 rats (4/group) were pretreated intraperitoneally (ip) with phenobarbital (75 mg/d, 3 d). At 24 h after the last injection of phenobarbital, an ip injection of NDHS (0.025 mmol/kg), 2-NDHSA (0.025 mmol/kg, females; 0.05 mmol/kg, males), or vehicle was given and renal function was monitored at 24 and 48 h post NDPS metabolite or vehicle. Additional groups received the NDPS metabolite or vehicle only and were also monitored for 48 h. In a separate experiment, male Fischer 344 rats were pretreated with piperonyl butoxide (PIBX, 1360 mg/kg) or the PIBX vehicle. 2-NDHSA (0.1 mmol/kg) or vehicle was administered (ip) 30 min after PIBX, and renal function was monitored for 24 h. Phenobarbital markedly potentiated 2-NDHSA nephrotoxicity in male rats as evidenced by increased kidney weight, increased blood urea nitrogen (BUN) concentration, and decreased tetraethylammonium (TEA) accumulation by renal cortical slices. PIBX had no effect on 2-NDHSA nephrotoxicity. Phenobarbital pretreatment did not markedly enhance the nephrotoxic potential of NDHS or 2-NDHSA in female rats. These results indicate that phenobarbital exhibits differential potentiation of NDPS metabolite nephrotoxicity in male and female rats and that the potentiation of 2-NDHSA nephrotoxicity observed in males is not due to cytochrome P-450-mediated oxidative biotransformation.

In vitro nephrotoxicity induced by N-(3,5-dichlorophenyl)succinimide (NDPS) metabolites in isolated renal cortical cells from male and female Fischer 344 rats: evidence for a nephrotoxic sulfate conjugate metabolite

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity in vivo that is characterized as acute polyuric renal failure and proximal tubular necrosis. However, earlier in vitro studies have failed to reproduce the in vivo nephrotoxicity seen with NDPS or its nephrotoxic metabolites N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA). The purpose of this study was to examine the nephrotoxic potential of NDPS, its known non-conjugated metabolites, the O-sulfate conjugate of NDHS (NSC), and the putative metabolite N-(3,5-dichlorophenyl)maleimide (NDPM) and its hydrolysis product N-(3,5-dichlorophenyl)maleamic acid (NDPMA) using freshly isolated renal cortical cells (IRCC). IRCC were obtained from untreated male or female Fischer 344 rats following collagenase perfusion of the kidneys. Cells (approximately 4 million per ml) (N=4) were incubated with up to 1.0 mM NDPS or an NDPS metabolite or vehicle for up to 120 min. Cytotoxicity was determined by measuring lactate dehydrogenase (LDH) release into the medium. Only NSC (>0.5 mM) and NDPM (> or =0.5 mM) exposure increased LDH release from IRCC. NSC 1.0 mM or NDPM 0.5 mM increased LDH release from IRCC within 15--30 min of exposure. NDPS or the remaining NDPS metabolites did not increase LDH release at bath concentrations of 1.0 mM for exposures of 120 min. IRCC from male and female rats responded similarly to the toxic effects of NDPS and its metabolites. These results demonstrate that sulfate conjugates of NDPS metabolites can be fast acting nephrotoxicants and could contribute to NDPS nephrotoxicity in vivo. These results also suggest that the kidney probably accumulates toxic sulfate conjugates of NDPS metabolites rather than forming the conjugates. In addition, mechanisms responsible for gender differences in nephrotoxicity seen with NDPS and NDPS metabolites in vivo either occur prior to renal accumulation of sulfate conjugates and/or represent biochemical/physiological differences between the genders.