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.     

Nephrotoxic potential of N-(3,5-dichloro-4-fluorophenyl)succinimide in Fischer 344 rats: comparison with N-(3,4,5-trichlorophenyl)succinimide.

Numerous structure-nephrotoxicity relationship studies from our laboratory have demonstrated that N-(3,5-dichlorophenyl)succinimide (NDPS) is one of the most potent nephrotoxicants among the N-arylsuccinimides. The purpose of this study was to extend our previous structure-nephrotoxicity relationship studies by examining the effect of addition of a fluoro verses a chloro group at the 4-phenyl position in NDPS. Male Fischer 344 rats (four rats/group) received a single intraperitoneal (i.p.) injection of N-(3,5-dichloro-4-fluorophenyl)succinimide (NDCFPS) or N-(3,4,5-trichlorophenyl)succinimide (NTCPS)(0.4 or 0.8 mmol/kg) or vehicle, and renal function monitored at 24 and 48 h. NDCFPS did not induce significant nephrotoxicity at either dose tested. In contrast, NTCPS (0.4 or 0.8 mmol/kg) induced marked nephrotoxicity characterized by diuresis, increased proteinuria, glucosuria, elevated kidney weight and increased blood urea nitrogen (BUN) concentration. NTCPS also induced marked proximal tubular necrosis at both doses tested. Neither NDCFPS nor NTCPS induced hepatotoxicity at either dose tested. The results of these experiments indicate that addition of a fluoro group at the 4-position on the phenyl ring of NDPS produces a nonnephrotoxicant NDPS derivative (NDCFPS), while addition of a chloro group at this site produces an NDPS derivative with similar nephrotoxic potential to NDPS. The mechanism for this differential effect between 4-halophenyl substitution is unclear, but may result from increased hydrolysis of the succinimide ring and/or increased clearance of N-arylsuccinimide metabolites when a fluoro group is added to the 4-position of the phenyl ring.     

Effect of succinimide ring modification on N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity in Sprague-Dawley and Fischer 344 rats

N-(3,5-Dichlorophenyl)succinimide (NDPS) has proven to be an effective experimental agricultural fungicide. However, NDPS produces marked nephrotoxicity in Sprague-Dawley and Fischer 344 rats. The purpose of this study was to determine the importance of an intact, unsubstituted succinimide ring for acute NDPS-induced nephrotoxicity. Structural modifications included ring opening, reduction of one or both carbonyl groups, breaking the ethylene carbon-carbon bond and mono- or dialkyl substitution on the succinimide ring. Sprague-Dawley or Fischer 344 rats were administered NDPS or an NDPS analog (0.1, 0.2, 0.4, 0.8 or 1.0 mmol/kg) or sesame oil (2.5 ml/kg, i.p.) and renal function was monitored at 24 h and 48 h. All structural modifications produced compounds with markedly reduced nephrotoxic potential in both Sprague-Dawley and Fischer 344 rats when compared to NDPS. However, N,N-diacetyl-3,5-dichloroaniline and N-(3,5-dichlorophenyl)pyrrolidine-2-one were more lethal than NDPS. The reduced renal effects of the NDPS analogs did not correlate with lipophilic character. These results indicate that an intact, unsubstituted succinimide ring is optimal for acute NDPS-induced nephrotoxicity.     

Nephrotoxic and hepatotoxic potential of imidazolidinedione-, oxazolidinedione- and thiazolidinedione-containing analogues of N-(3,5-dichlorophenyl)succinimide (NDPS) in Fischer 344 rats

Nephrotoxicity of the agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) in rats is believed to involve metabolism on the succinimide ring. To further investigate this hypothesis, we synthesized and tested the following NDPS analogues, which contain other cyclic imide rings and may therefore be metabolized differently than NDPS: 3-(3,5-dichlorophenyl)-2,4-oxazolidinedione (DCPO), 3-(3,5-dichlorophenyl)-2,4-imidazolidinedione (DCPI), 3-(3,5-dichlorophenyl)-1-methyl-2,4-imidazolidinedione (DCPM) and 3-(3,5-dichlorophenyl)-2,4-thiazolidinedione (DCPT). Male Fischer 344 rats were administered DCPO, DCPI, DCPM, DCPT (0.6 or 1.0 mmol/kg, i.p. in corn oil), NDPS (0.6 mmol/kg, i.p. in corn oil) or corn oil (4 ml/kg). As evidenced by diuresis, proteinuria, elevated blood urea nitrogen levels, increased kidney weights and proximal tubular damage, NDPS produced severe nephrotoxicity in the rats. In contrast, DCPO, DCPI, DCPM and DCPT were mild nephrotoxicants. None of the compounds elevated serum alanine transferase activity or liver weights in the rats, however DCPT produced centrilobular necrosis. These experiments confirm that NDPS-induced nephrotoxicity is critically dependent on the presence of the succinimide ring. Furthermore, replacement of the succinimide ring with a thiazolidinedione ring produced a more pronounced effect on the liver than on the kidney. Liver damage has been reported in type II diabetic patients taking troglitazone, rosiglitazone and pioglitazone. Since these compounds also contain a thiazolidinedione ring, DCPT may be useful for investigating the role of this structural feature in hepatotoxicity.     

Renal and hepatic toxicity of N-arylsuccinimides in Fischer 344 rats

The role of aromaticity in the nephrotoxic potential of N-arylsuccinimides was studied in male Fischer 344 rats. Rats were administered a single intraperitoneal (i.p.) injection of an N-arylsuccinimide derivative (0.4 or 1.0 mmol/kg) or sesame oil (2.5 ml/kg), and the renal function monitored at 24 and 48 h. The parent compound in this series, N-phenylsuccinimide (NPS), had previously been shown to induce only minimal renal effects, having no effect on urine volume, blood urea nitrogen concentration, kidney weight, p-aminohippurate accumulation or renal morphology. Only an increase in tetraethylammonium uptake has been observed following NPS administration to rats. These effects were not enhanced by reducing aromaticity (N-cyclohexylsuccinimide (NCS]. Compounds with increased aromaticity N-(1-naphthyl)succinimide (NNS), N-(1-anthracenyl)succinimide (1-NAS) and N-(9-anthracenyl)succinimide (9-NAS)--also only weakly affected renal function. However, NNS (1.0 mmol/kg) and, to a lesser degree, 9-NAS (1.0 mmol/kg) proved to be hepatotoxins. Liver damage was most pronounced near central vein regions of the lobule and least evident around periportal sites. Damaged liver tissue exhibited unusually large deposits of connective tissue and hypertrophied hepatocytes with numerous vacuoles in their cytoplasm. Therefore, derivatives of NPS with increased or decreased aromaticity relative to the parent compound do not exhibit the ability to induce moderate or marked nephrotoxicity. However, increasing aromaticity did produce the derivatives NNS and 9-NAS, which are hepatotoxins. These compounds represent the first members in this series of compounds to induce acute hepatotoxicity.     

Structure-nephrotoxicity relationships for para-substituted N-phenylsuccinimides in Sprague-Dawley and Fischer 344 rats

N-(3,5-Dichlorophenyl)succinimide (NDPS) has proven to be one of the most nephrotoxic compounds of a series of N-(halophenyl)succinimides. Previous studies in our laboratory have demonstrated that chlorine content and position on the phenyl ring are important determinants for NDPS-induced nephrotoxicity. The purpose of this study was to investigate the relationship between the electron donating or withdrawing nature of phenyl group substituents and the nephrotoxic potential of the corresponding fungicides. Rats were administered a para-substituted N-phenylsuccinimide (0.4 or 1.0 mmol/kg, i.p.) or sesame oil (2.5 ml/kg, i.p.), and renal function was monitored at 24 h and 48 h. In Sprague-Dawley rats, a clear nephrotoxicity was produced by NDPS. Weak nephrotoxicity was produced by N-(4-tert-butylphenyl)succinimide (NBPS). NDPS also was the most nephrotoxic compound in Fischer 344 rats, while weak nephrotoxicity was produced by NBPS. Lipophilic character (e.g. partition coefficient) did not correlate with acute nephrotoxicity in either rat strain. These results also indicate that there is a no correlation between the electronic nature of the phenyl substituents and resulting nephrotoxicity.     

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.     

Renal effects of N-(3,5-disubstitutedphenyl)-succinimides in the Fischer 344 rat.

Previous studies have demonstrated the importance of substitution at the 3- and 5-positions of the phenyl ring in N-phenylsuccinimides for the production of nephrotoxicants in this series of compounds. The purpose of this study was to determine if the electronic nature of the 3,5-substituents is an important determinant for nephrotoxic potential. Male Fischer 344 rats (four rats per group) were administered a single intraperitoneal injection of a succinimide (0.4 or 1.0 mmol kg-1) or vehicle, and the renal function was monitored for 48 h. Only N-(3,5-dichlorophenyl)succinimide (0.4 or 1.0 mmol kg-1) induced marked changes in renal function. Urine volume, BUN concentration and proteinuria were increased following N-(3,5-dinitrophenyl)succinimide (1.0 mmol kg-1) treatment but other renal parameters and renal morphology were unchanged in this treatment group. These results indicate that the presence of halogen atoms at the 3- and 5-positions of the phenyl ring in N-phenylsuccinimides is more important for nephrotoxic potential than the presence of non-halogen substituents. The reason why halogen substitution is an important determinant for N-phenylsuccinimide nephrotoxicity is unknown.     

Nephrotoxicity of N-(3,5-dihalophenyl)succinimides in Fischer 344 rats

Previous studies have demonstrated that N-(3,5-dichlorophenyl)succinimide (NDCPS) is the most nephrotoxic compound among the N-(mono- or dichlorophenyl)succinimides. The purpose of this study was to examine the nephrotoxic potential of the different N-(3,5-dihalophenyl)succinimides (NDHPS) to determine the importance of the halogen species for NDHPS-induced nephrotoxicity. Male Fischer 344 rats were administered a single intraperitoneal injection of an NDHPS (0.4, 0.8, or 1.0 mmol/kg) or vehicle (2.5 ml/kg), and renal function was monitored at 24 and 48 h. NDCPS or N-(3,5-diiodophenyl)succinimide administration produced the greatest nephrotoxic response. Nephrotoxicity was characterized by diuresis, increased proteinuria, glucosuria, increased kidney weight and blood urea nitrogen (BUN) concentration, decreased accumulation of p-aminohippurate (PAH) and tetraethylammonium (TEA) by renal cortical slices and proximal tubular necrosis. N-(3,5-Dibromophenyl)succinimide injection produced mild nephrotoxicity, while N-(3,5,-difluorophenyl)succinimide administration did not result in nephrotoxicity. These results indicate that the halogen species can influence the nephrotoxicity produced by the NDHPS. In addition, nephrotoxic potential did not correlate with fungicidal efficacy, which suggests that the nephrotoxic and fungicidal mechanisms of these compounds might be different.     

Sodium sulfate potentiates N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA) nephrotoxicity in the Fischer 344 rat

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity as its major toxicity in rats. Previous studies have shown that NDPS induces nephrotoxicity following oxidation of the succinimide ring to form N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and the hydrolysis product of NDHS, N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA). Our recent work found that sodium sulfate potentiated NDPS nephrotoxicity, suggesting that sulfate conjugation of NDPS metabolites might be a bioactivation step mediating NDPS nephrotoxicity. The purpose of this study was to determine if sodium sulfate also potentiated the nephrotoxicity of the two nephrotoxic metabolites of NDPS and further to see if sodium sulfate potentiated NDHS and 2-NDHSA nephrotoxicity to the same degree. Male Fischer 344 rats (4-16 rats/group) received an intraperitoneal (ip) injection of sodium sulfate (10 mg/kg) 20 min before a non-nephrotoxic dose (0.05 mmol/kg, ip) of NDHS or 2-NDHSA, or vehicle (12.5% dimethyl sulfoxide in sesame oil). Renal function was then monitored over 48 h. Sodium sulfate pretreatment potentiated the renal effects of a non-nephrotoxic dose of NDHS and 2-NDHSA to induce nephrotoxicity. Nephrotoxicity was characterized by diuresis, increased proteinuria, elevated blood urea nitrogen (BUN) concentration, increased kidney weight and proximal tubular necrosis. Differences in the potentiation of NDHS and 2-NDHSA nephrotoxicity by sodium sulfate were also observed as NDHS nephrotoxicity was potentiated to a lesser degree than 2-NDHSA-induced nephrotoxicity. These results support the likelihood that one or more sulfate conjugate(s) of NDPS metabolites contribute to NDPS nephrotoxicity.     

Structure-nephrotoxicity relationships for meta-substituted N-phenylsuccinimides

The N-phenylsuccinimides are being evaluated as experimental agricultural fungicides. The purpose of this study was to examine the relationship between the electron withdrawing or electron donating properties of phenyl ring substituents on meta-substituted N-phenylsuccinimide (NPS) derivatives and the nephrotoxic potential of the corresponding fungicides. Male Fischer 344 rats were administered a single intraperitoneal injection of a succinimide (0.4 or 1.0 mmol/kg) or vehicle (sesame oil, 2.5 ml/kg), and renal function monitored at 24 and 48 hr. Non-halogen-substituted NPS derivatives produced little evidence of nephrotoxicity at the doses used in this study. Among the meta-halogen derivatives of NPS, N-(3-chlorophenyl)succinimide (NCPS) was the most nephrotoxic. NCPS-induced nephrotoxicity was characterized by diuresis, proteinuria, hematuria, elevated blood urea nitrogen (BUN) concentration, decreased organic ion accumulation and proximal tubular necrosis. However, all renal effects produced by NCPS were mild to moderate. These results suggest that the electron withdrawing or donating property of a functional group is not a good predictor of the nephrotoxic potential for the corresponding fungicide. In addition, lipophilicity did not correlate with nephrotoxic potential for the meta-substituted NPS derivatives evaluated in this study.     

Nephrotoxicity of N-(3,5-dichlorophenyl)succinimide metabolites in vivo and in vitro

The experimental fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) has been shown to produce selective nephrotoxicity at least in part through the actions of one or more metabolites. The purpose of this study was to (1) determine the nephrotoxic potential of three known NDPS metabolites; N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS), N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (NDHSA), and N-(3,5-dichlorophenyl)malonamic acid (DMA) and (2) examine the role of renal biotransformation in NDPS-induced nephrotoxicity. In one set of experiments, male Fischer 344 rats were administered a single intraperitoneal (ip) injection of NDPS or a NDPS metabolite (0.2, 0.4, or 1.0 mmol/kg) or vehicle (sesame oil, 2.5 ml/kg) and renal function was monitored at 24 and 48 hr. Both NDHS and NDHSA administration (0.2 or 0.4 mmol/kg) resulted in nephrotoxicity similar to that produced by NDPS (0.4 or 1.0 mmol/kg). DMA administration resulted in only minor renal effects. Addition of NDPS to renal cortical slices prepared from naive Fischer 344 rats resulted in decreases in p-aminohippurate (PAH) and tetraethylammonium (TEA) accumulation at NDPS media concentrations of 10(-4) and 10(-5) M or greater, respectively. Pretreatment of rats with microsomal enzyme activity modifiers (phenobarbital, 3-methylcholanthrene, cobalt chloride, or piperonyl butoxide) had little effect on in vitro effects of NDPS on PAH or TEA accumulation. A pattern of PAH or TEA uptake similar to that observed for NDPS was observed in vitro with NDPS-d4, a nonnephrotoxic analog of NDPS labeled on the succinimide ring with deuterium. Of the NDPS metabolites tested in vitro for nephrotoxicity, only NDHS produced decreases in PAH and TEA accumulation similar to those produced by NDPS. These results suggest that the NDPS metabolites NDHS and NDHSA are nephrotoxic compounds. However, the role of these metabolites in NDPS-induced nephrotoxicity remains to be determined. In addition, it appears that NDPS has direct effects on renal function, but these effects do not appear to be of major toxicological significance in vivo. Direct renal bioactivation of NDPS or its known metabolites to nephrotoxic species does not appear to occur 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.     

Acute nephrotoxicity induced by N-(3,5-dichlorophenyl)-3-hydroxysuccinamic acid in Fischer 344 rats

N-(3,5-Dichlorophenyl)succinimide (NDPS) induces nephrotoxicity via one or more metabolites which arise from oxidation of the succinimide ring. The purpose of this study was to examine the nephrotoxic potential of N-(3,5-dichlorophenyl)-3-hydroxysuccinamic acid (3-NDHSA), a potential metabolite of NDPS and a positional isomer of N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (2-NDHSA), a known nephrotoxic metabolite of NDPS. Male Fischer 344 rats were administered a single intraperitoneal injection of 3-NDHSA (0.2 or 0.4 mmol/kg) or sesame oil (2.5 mmol/kg), and renal function was monitored at 24 and 48 h. Both doses of 3-NDHSA induced diuresis, increased proteinuria, glucosuria and hematuria, elevated blood urea nitrogen (BUN) concentrations and kidney weights, decreased organic ion accumulation by renal cortical slices, and induced proximal tubular necrosis. The characteristics of 3-NDHSA-induced nephrotoxicity were identical to NDPS-induced nephropathy, but were evident at lower doses with 3-NDHSA. These results demonstrate that 3-NDHSA is a nephrotoxicant which might contribute to NDPS-induced nephropathy.     

Nephrotoxicity of N-(3-bromophenyl)-2-hydroxysuccinimide: role of halogen groups in the nephrotoxic potential of N-(halophenyl)succinimides

Among N-(halophenyl)succinimides, N-(3,5-dichlorophenyl)succinimide (NDPS) is a potent nephrotoxicant as well as an agricultural fungicide. Although two chloride groups on the phenyl ring are essential to induce optimal nephrotoxicity, the role of halogen groups in NDPS nephrotoxicity is not clear. In this study, N-(3-bromophenyl)-2-hydroxysuccinimide (NBPHS) was prepared as a monohalophenyl derivative of N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS), an oxidative and nephrotoxicant metabolite of NDPS. The nephrotoxic potential of NBPHS was evaluated in vivo and in vitro to determine the role of halogen groups in N-(halophenyl)succinimide nephrotoxicity. Male Fischer 344 rats (four/group) were administered a single intraperitoneal (i.p.) injection of NBPHS (0.1, 0.4 or 0.8 mmol/kg) or vehicle (25% dimethyl sulfoxide in sesame oil) and renal function monitored for 48 h. Administration of NBPHS (0.8 mmol/kg) induced nephrotoxicity, while very mild changes or no changes in renal function were observed following administration of 0.4 mmol/kg or 0.1 mmol/kg of NBPHS, respectively. Nephrotoxicity induced by NBPHS (0.8 mmol/kg) was characterized by diuresis, transiently increased proteinuria, glucosuria and hematuria, elevated kidney weight, and reduced tetraethylammonium (TEA) uptake by renal cortical slices, and was not as marked as nephrotoxicity induced by NDHS (0.1 mmol/kg) or NDPS (0.4 mmol/kg). In the in vitro studies, the effects of NBPHS on organic ion accumulation, pyruvate-stimulated gluconeogenesis, and lactatc dehydrogenase (LDH) release were measured using renal cortical slices. NBPHS decreased p-aminohippurate (PAH) and TEA accumulation at NBPHS bath concentrations of 0.05 mM and 0.5 mM or greater, respectively. Renal gluconeogenesis was inhibited by NBPHS at 1 mM bath concentration, while LDH leakage was not increased at NBPHS bath concentrations up to 1 mM. The results demonstrate that NBPHS is a mild nephrotoxicant in vivo and in vitro, but does not have cytotoxic effects to renal tissues at the concentrations tested. From these results, it appears that halogen groups are essential to the nephrotoxic potential of N-(halophenyl)-2-hydroxysuccinimides or N-(halophenyl)succinimides and play an important role in the mechanism of NDPS nephrotoxicity following NDHS formation.     

Effect of dimethyl sulfoxide on N-(3,5-dichlorophenyl)succinimide (NDPS) and NDPS metabolite nephrotoxicity

Dimethyl sulfoxide (DMSO) is frequently used as a solvent to assist in dissolving compounds which are not readily soluble in other injection vehicles. The purpose of this study was to determine the suitability of DMSO as a vehicle for administering the nephrotoxicant, N-(3,5-dichlorophenyl)succinimide, (NDPS) and two nephrotoxicant NDPS metabolites, N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid (NDHSA). Male Fischer 344 rats (4/group) were administered a single intraperitoneal injection of NDPS (0.4 or 0.8 mmol/kg), NDHS (0.1 or 0.2 mmol/kg), or NDHSA (0.1 or 0.2 mmol/kg) dissolved in 25% DMSO in sesame oil or 100% sesame oil (2.5 ml/kg), while control rats received vehicle only. Renal function was then monitored at 24 and 48 h. Including DMSO in the vehicle markedly attenuated NDPS 0.4 mmol/kg-induced nephrotoxicity and reduced NDPS 0.8 mmol/kg-induced renal effects. Thus, the magnitude of the attenuating effect of DMSO depended in part on the nephrotoxicant dose of NDPS. In addition, NDHS nephrotoxicity was not altered by DMSO and only slight effects on NDHSA nephrotoxicity were observed. These results suggest that DMSO is capable of attenuating NDPS nephrotoxicity, and that the primary mechanism of this interaction might be due to an inhibition of the biotransformation of NDPS to NDHS.     

Acute nephrotoxicity of N-phenyl and N-(monochlorophenyl) succinimides in Fischer 344 and Sprague-Dawley rats

The experimental fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) has been shown to be nephrotoxic in Sprague-Dawley and Fischer 344 rats. The purpose of this study was to evaluate the role of the chlorine atoms in NDPS-induced nephropathy. Male Sprague-Dawley or Fischer 344 rats received a single intraperitoneal injection of a phenylsuccinimide (0.4 or 1.0 mmol/kg) or sesame oil (2.5 ml/kg), and renal function was monitored at 24 h and 48 h. In Sprague-Dawley rats urine volume was increased by NDPS and N-(3-chlorophenyl)succinimide (3-NCPS) (0.4 and 1.0 mmol/kg) at 24 h but only by NDPS at 48 h. Accumulation of both p-aminohippurate (PAH) and tetraethylammonium (TEA) was decreased only by NDPS (1.0 mmol/kg) administration. N-(2-chlorophenyl)succinimide (2-NCPS) or N-(4-chlorophenyl) succinimide (4-NCPS) (1.0 mmol/kg) administration reduced only basal and lactate-stimulated PAH accumulation. Only NDPS increased blood urea nitrogen (BUN) concentration and kidney weight. In Fischer 344 rats results were similar to those obtained in Sprague-Dawley rats, except that 3-NCPS was the only monochlorophenylsuccinimide which produced a decrease in PAH accumulation by renal cortical slices. N-Phenylsuccinimide had little effect on any renal parameter studied in either rat strain. The order of increasing nephrotoxicity generally paralleled the increasing partition. coefficients of the compounds. These results indicate that reducing the chlorine substitution of NDPS produces compounds with reduced nephrotoxic potential. In addition, lipophilic character might be a predictor for the nephrotoxic potential of N-(halophenyl)succinimides in Sprague-Dawley and Fischer 344 rats.     

Effect of sulfation substrates/inhibitors on N-(3,5-dichlorophenyl)succinimide nephrotoxocity in Fischer 344 rats.

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) is an acute nephrotoxicant in rats. Our previous studies suggested that sulfate conjugation of NDPS metabolites might be a bioactivation step mediating NDPS nephrotoxicity. In this study, effects of substrates and/or inhibitors of sulfation on NDPS nephrotoxicity were examined to explore further the role of sulfation in NDPS nephrotoxicity. Male Fischer rats (4-8/group) were administered one of the following intraperitoneal (ip) pretreatment (dose, pretreatment time) prior to NDPS (0.6 mmol/kg) or NDPS vehicle (sesame oil, 2.5 ml/kg): (1) no pretreatment, (2) dehydroepiandrosterone (DHEA) (0.5 mmol/kg, 1 h), or (3) 2,6-dichloro-4-nitrophenol (DCNP) (0.04 mmol/kg, 1 h). Following NDPS or NDPS vehicle administration, renal function was monitored at 24 and 48 h. Pretreatment with DHEA, a typical substrate for and an inhibitor of hydroxysteroid (alcohol) sulfotransferase, resulted in marked protection against NDPS nephrotoxicity. A selective inhibitor of phenol sulfotransferase, DCNP, afforded little attenuation in NDPS nephrotoxicity. These results suggest that alcohol sulfate conjugates of NDPS metabolites, rather than phenolic sulfate conjugates, may be a penultimate or ultimate nephrotoxicant species mediating NDPS nephrotoxicity. The marked, but not complete, protection by DHEA also suggests that there are other metabolites or mechanisms responsible for NDPS nephrotoxicity.     

Effect of calcium antagonism by nifedipine and chlorpromazine on acute N-(3,5-dichlorophenyl)succinimide-induced nephrotoxicity in Fischer 344 rats

The nephrotoxicity induced by a wide variety of chemical compounds can be attenuated by agents which modify calcium ion (Ca2+) movement across membranes or calcium-dependent processes. The purpose of this study was to examine the ability of nifedipine, a calcium channel blocking drug, and chlorpromazine (CPZ), an antagonist of many calcium-dependent processes, to attenuate the nephrotoxicity induced by the agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) or its metabolite N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS). Male Fischer 344 rats (4 rats per group) were pretreated intraperitoneally (i.p.) with nifedipine (0.25 or 0.50 mg/kg), CPZ (1.0 or 5.0 mg/kg) or vehicle 1 h before NDPS (0.4 mmol/kg), NDHS (0.1 mmol/kg) or vehicle (sesame oil, 2.5 ml/kg). In separate experiments, rats were pretreated with nifedipine (0.25 or 0.50 mg/kg/day, i.p.) starting 2 days before NDPS or NDPS vehicle and continuing throughout the experiment. Renal function was monitored at 24 and 48 h. Nifedipine (single or multiple treatments) and CPZ (1.0 mg/kg) were ineffective in substantially altering NDPS (0.4 mmol/kg)-induced nephrotoxicity. However, CPZ (5.0 mg/kg) markedly attenuated all aspects of NDPS-induced nephropathy. Also, CPZ (5.0 mg/kg) partially protected against NDHS (0.1 mmol/kg)-induced renal effects. These results demonstrate the inability of the calcium channel blocker nifedipine to attenuate NDPS nephrotoxicity. Attenuation of NDPS nephrotoxicity by CPZ could suggest that CPZ is antagonizing calcium influx into renal tissue and/or renal intracellular calcium-dependent processes to modify the renal response to NDPS. However, the inability of CPZ to markedly attenuate NDHS nephrotoxicity could indicate that CPZ protected against NDPS nephrotoxicity by inhibiting biotransformation of the parent compound to its toxic chemical species.     

Effect of three n-acetylamino acids on N-(3,5-dichlorophenyl)succinimide (NDPS) and ndps metabolite nephrotoxicity in Fischer 344 rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) induces nephrotoxicity in mammals characterized as polyuric renal failure and proximal tubular necrosis. Recent studies have suggested that NDPS-induced nephrotoxicity may be mediated by metabolites arising from the nephrotoxic NDPS metabolites N-(3,5-dichlorophenyl)-2-hydroxysuccinimide (NDHS) and/or N-(3,5-dichlorophenyl)-2-succinamic acid (2-NDHSA). The purpose of this study was to examine the effects of N-acetylcysteine (NAC), a nucleophilic agent, and two nonnucleophilic N-acetylamino acids, N-acetylserine (NAS) and N-acetylalanine (NAA), on NDPS and NDPS metabolite-induced nephrotoxicity. Male Fischer 344 rats (4-8/group) were administered intraperitoneally (ip) an N-acetylamino acid (1 mmol/kg) 2 h before an ip injection of NDPS (0.4 mmol/kg), NDHS (0.1 mmol/kg), 2-NDHSA (0.1 mmol/kg), or vehicle. Renal function was then monitored at 24 and 48 h. NAC pretreatment markedly attenuated NDPS-, NDHS-, and 2-NDHSA-mediated nephrotoxicity. The nonnucleophilic N-acetylamino acids (NAS, NAA) only partly reduced NDPS and NDHS nephrotoxicity, and they had little effect on 2-NDHSA nephrotoxicity. These results suggest that reactive NDPS metabolites may be formed from NDHS and 2-NDHSA and that nucleophilic substrates (e.g., NAC) may offer protection from NDPS-induced nephrotoxicity. However, mechanisms other than chemical neutralization of reactive NDPS metabolites may also be contributing to the attenuation of NDPS nephrotoxicity, since nonnucleophilic N-acetylamino acids (e.g., NAA) also provided some protection against NDPS and NDHS nephrotoxicity.