Nephrotoxicity induced by C- and N-arylsuccinimides

Degradation of dimethachlon by a newly isolated bacterium Paenarthrobacter sp. strain JH-1 relieves its toxicity against Chlorella ellipsoidea

Dimethachlon, a broad-spectrum dicarboximide fungicide, poses a hazard to the safety of human and ecosystem due to its residue in the environment. A high-efficient dimethachlon degrading bacteria JH-1 belonging to Paenarthrobacter sp. was isolated and characterized. Strain JH-1 can utilize high concentration of dimethachlon as sole carbon source for growth and degrade 98.53% of 300 mg·L^-1 dimethachlon within 72 h. Crude enzyme of strain JH-1 could degrade 99.76% of 100 mg·L^-1 dimethachlon within 2 h. The optimum degradation condition of dimethachlon by strain JH-1 was at 35 °C and pH 7.0. Dimethachlon was degraded in Paenarthrobacter sp. JH-1 as following: it was firstly converted to 4-(3,5-dichloroanilino)-4-oxobutanoic acid and then subjected to the hydrolysis to 3,5-dichloroaniline and succinic acid, the latter was further degraded. Dimethachlon inhibited the growth of Chlorella ellipsoidea, while Paenarthrobacter sp. JH-1 could degrade dimethachlon to relieve its toxicity. This work facilitates our knowledge of the degradation mechanism of dimethachlon and offers potential resource of microbial strains for the bioremediation of dimethachlon-contaminated environments in the future.

Removal of dimethachlon from soils using immobilized cells and enzymes of a novel potential degrader Providencia stuartii JD

The first potential degrader capable of detoxifying dimethachlon (NDPS) was isolated and identified as Providencia stuartii JD, whose free cells and freely crude enzymes degraded more than 80% and 90% of 50 mg L^-1 NDPS in liquid culture within 7 d and 2 h, respectively. Strain JD metabolized NDPS through the typical pathway, in which NDPS was firstly transformed into succinic acid and 3, 5-dichloroanilin, and the latter was then converted to phenol, which was subsequently degraded to muconic acid further subjected to the mineralization. The immobilization obviously improved the stability and adaptability of cells and enzymes. In laboratory non-sterile soils treated by free or immobilized cells and enzymes, 50 mg kg^-1 NDPS decreased to 15.66 and 13.32 mg kg^-1, or 8.32 and 2.18 mg kg^-1 within 7 d, respectively. In field, immobilized cells and enzymes exhibited significantly higher efficiencies in removing 20.250 kg a.i. ha^-1 NDPS wettable powder from soils after 9 d (96.02% and 98.56%) than free cells and enzymes (79.35% and 66.45%). This study highlights that strain JD promises the great potential to remove hazardous NDPS residues and its immobilized cells and enzymes possess the more promising advantages in the bioremediation of NDPS-contaminated soils in situ.

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.

Effect of structural modifications on 3-(3,5-dichlorophenyl)-2,4-thiazolidinedione-induced hepatotoxicity in Fischer 344 rats

Glitazones, used for type II diabetes, have been associated with liver damage in humans. A structural feature known as a 2,4-thiazolidinedione (TZD) ring may contribute to this toxicity. TZD rings are of interest since continued human exposure via the glitazones and various prototype drugs is possible. Previously, we found that 3-(3,5-dichlorophenyl)-2,4-thiazolidinedione (DCPT) was hepatotoxic in rats. To evaluate the importance of structure on DCPT toxicity, we therefore studied two series of analogs. The TZD ring was replaced with: a mercaptoacetic acid group {[[[(3,5-dichlorophenyl)amino]carbonyl]thio]acetic acid, DCTA}; a methylated TZD ring [3-(3,5-dichlorophenyl)-5-methyl-2,4-thiazolidinedione, DPMT]; and isomeric thiazolidinone rings [3-(3,5-dichlorophenyl)-2- and 3-(3,5-dichlorophenyl)-4-thiazolidinone, 2-DCTD and 4-DCTD, respectively]. The following phenyl ring-modified analogs were also tested: 3-phenyl-, 3-(4-chlorophenyl)-, 3-(3,5-dimethylphenyl)- and 3-[3,5-bis(trifluoromethyl)phenyl]-2,4-thiazolidinedione (PTZD, CPTD, DMPT and DFMPT, respectively). Toxicity was assessed in male Fischer 344 rats 24 h after administration of the compounds. In the TZD series only DPMT produced liver damage, as evidenced by elevated serum alanine aminotransferase (ALT) activities at 0.6 and 1.0 mmol kg(-1) (298.6 ± 176.1 and 327.3 ± 102.9 Sigma-Frankel units ml(-1) , respectively) vs corn oil controls (36.0 ± 11.3) and morphological changes in liver sections. Among the phenyl analogs, hepatotoxicity was observed in rats administered PTZD, CPTD and DMPT; with ALT values of 1196.2 ± 133.6, 1622.5 ± 218.5 and 2071.9 ± 217.8, respectively (1.0 mmol kg(-1) doses). Morphological examination revealed severe hepatic necrosis in these animals. Our results suggest that hepatotoxicity of these compounds is critically dependent on the presence of a TZD ring and also the phenyl substituents.

Health effects from long-range transported contaminants in Arctic top predators: An integrated review based on studies of polar bears and relevant model species

The aim of this review is to provide a thorough overview of the health effects from the complexed biomagnified mixture of long-range transported industrial organochlorines (OCs), polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFCs) and mercury (Hg) on polar bear (Ursus maritimus) health. Multiple scientific studies of polar bears indicate negative relationships between exposure to these contaminants and health parameters; however, these are all of a correlative nature and do not represent true cause-and-effects. Therefore, information from controlled studies of farmed Norwegian Arctic foxes (Vulpes lagopus) and housed East and West Greenland sledge dogs (Canis familiaris) were included as supportive weight of evidence in the clarification of contaminant exposure and health effects in polar bears. The review showed that hormone and vitamin concentrations, liver, kidney and thyroid gland morphology as well as reproductive and immune systems of polar bears are likely to be influenced by contaminant exposure. Furthermore, exclusively based on polar bear contaminant studies, bone density reduction and neurochemical disruption and DNA hypomethylation of the brain stem seemed to occur. The range of tissue concentration, at which these alterations were observed in polar bears, were ca. 1-70,000 ng/g lw for OCs (blood plasma concentrations of some PCB metabolites even higher), ca. 1-1000 ng/g lw for PBDEs and for PFCs and Hg 114-3052 ng/g ww and 0.1-50 microg/g ww, respectively. Similar concentrations were found in farmed foxes and housed sledge dogs while the lack of dose response designs did not allow an estimation of threshold levels for oral exposure and accumulated tissue concentrations. Nor was it possible to pinpoint a specific group of contaminants being more important than others nor analyze their interactions. For East Greenland polar bears the corresponding daily SigmaOC and SigmaPBDE oral exposure was estimated to be 35 and 0.34 microg/kg body weight, respectively. Furthermore, PFC concentrations, at which population effect levels could occur, are likely to be reached around year 2012 for the East Greenland polar bear subpopulation if current increasing temporal trends continue. Such proposed reproductive population effects were supported by physiological based pharmacokinetic (PBPK) modelling of critical body residues (CBR) with risk quotients >or=1 for SigmaPCB, dieldrin, SigmaPFC and SigmaOHC (organohalogen contaminant). The estimated daily TEQ for East Greenland polar bears and East Greenland sledge dogs were 32-281-folds above WHO SigmaTEQ guidelines for humans. Compared to human tolerable daily intake (TDI), these were exceeded for PCBs, dieldrin, chlordanes and SigmaHCH in East Greenland polar bears. Comparisons like these should be done with caution, but together with the CBR modelling and T-score estimations, these were the only available tools for polar bear risk evaluation. In conclusion, polar bears seem to be susceptible to contaminant induced stress that may have an overall sub-clinical impact on their health and population status via impacts on their immune and reproductive systems.

Effect of gender, dose, and time on 3-(3,5-dichlorophenyl)-2,4-thiazolidinedione (DCPT)-induced hepatotoxicity in Fischer 344 rats

1. The thiazolidinedione ring present in drugs available for type II diabetes can contribute to hepatic injury. Another thiazolidinedione ring-containing compound, 3-(3,5-dichlorophenyl)-2,4-thiazoli-dinedione (DCPT), produces liver damage in rats. Accordingly, the effects of gender, dose, and time on DCPT hepatotoxicity were therefore evaluated. 2. Male rats were more sensitive to DCPT (0.4-1.0 mmol kg(-1) by intraperitoneal administration) as shown by increased serum alanine aminotransferase levels and altered hepatic morphology 24 h post-dosing. Effects in both genders were dose dependent. In males, DCPT (0.6 mmol kg(-1)) produced elevations in alanine aminotransferases and changes in liver sections 3 h after dosing that progressively worsened up to 12 h. DCPT-induced renal effects were mild. 3. It is concluded that male rats are more susceptible to DCPT hepatotoxicity and that damage occurs rapidly. DCPT primarily affects the liver and can be a useful compound to investigate the role of the thiazolidinedione ring in hepatic injury. However, the gender dependency and rapid onset of DCPT hepatotoxicity require further investigation.

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.

Transamination in the metabolism of the nephrotoxicant N-(3,5-dichlorophenyl)succinimide in rats

The agricultural fungicide N-(3,5-dichlorophenyl)succinimide (NDPS) is nephrotoxic in rats. Due to the involvement of NDPS metabolism in its mechanism of toxicity, the detailed biotransformation of 14C-NDPS in rats was previously evaluated using high-performance liquid chromatography-electrospray ionization-mass spectrometry. In the present report, we describe the identification of two novel amino metabolites of NDPS, which were present in significant amounts in rat kidney tissues. Using liquid chromatography-tandem mass spectrometry and synthetic standards, the two metabolites were identified as N-(3,5-dichlorophenyl)-2-aminosuccinamic acid (2-NDASA) and its N-acetylated derivative (N-acetyl-2-NDASA). The mechanism of formation of 2-NDASA was studied in vitro. Incubations were carried out in rat liver and kidney cytosols using the major oxidative metabolite of NDPS, N-(3,5-dichlorophenyl)-2-hydroxysuccinamic acid, as the substrate. Formation of 2-NDASA in vitro was confirmed using mass spectrometry. Inhibitors of alcohol dehydrogenase (4-methylpyrazole) and aldehyde dehydrogenase (disulfiram) reduced 2-NDASA formation by 40 to 50%. Menadione (an inhibitor of aldehyde oxidase) and quercetin (an inhibitor of carbonyl reductase) did not show any effects. (Aminooxy)acetic acid, an inhibitor of pyridoxal 5'-phosphate-containing enzymes such as aminotransferases, almost completely abolished the formation of 2-NDASA. Using liquid chromatography-mass spectrometry, the transamination mechanism was further supported by the incorporation of a 15N-amino group in 2-NDASA when 15N-glutamic acid was included in the incubation mixture. Results from these studies show that transamination is a metabolic pathway in the clearance of NDPS in rats, and that cytosolic dehydrogenases and aminotransferases may be involved in this process.

Mechanism of Cytotoxicity of Copper(I) Complexes of 1,2-Bis(diphenylphosphino)ethane

The cytotoxic properties of arylphosphines are regulated by metals. We have synthesized a series of copper(I) complexes of 1,2-bis(diphenylphosphino)ethane (DPPE) and tested their in vitro cytotoxicity in a human lung carcinoma cell line H460. One of the complexes [Cu(2)(DPPE)(3)(CH(3)CN)(2)](ClO(4))(2) (C1), showed maximum cytotoxicity comparable to that of adriamycin. Treatment of cells with C1 caused DNA damage in vitro and activated the p53 pathway. Flow cytometry revealed that growth inhibition by C1 was due to a combination of cell cycle arrest and apoptosis. Simultaneous addition of C1 and adriamycin increased the cytotoxicity of either compound, suggesting the potential use of adriamycin in combination with C1. DNA binding and simulation studies suggest that adriamycin binds to DNA synergistically in the presence of C1. Thus, we have identified C1, a copper(I) complex of DPPE, as a potential chemotherapeutic drug for further testing, which could be used either alone or in combination with other chemotherapeutic drugs.