Nephrotoxicity of hexachloro-1,3-butadiene in the mouse: the effect of age, sex, strain, monooxygenase modifiers, and the role of glutathione

Sex-related differences in renal toxicodynamics in rodents

INTRODUCTION

An issue yet to be addressed, in the investigation of the xenobiotic toxicity, is a detailed characterization of the sex differences in toxicological responses. The 'sex issue' is particularly significant in nephrotoxicology as the kidney is a relevant target organ for xenobiotics and few studies have approached this subject in the past. There is a strong need to improve our understanding regarding the influence of sex in toxicology, given their increased requirement to establish the limits of exposure to chemicals in the environment and at work.

AREAS COVERED

In this review, the authors provide the reader with the current knowledge of sex differences in kidney toxicity for rats and mice. To make the review easier to consult, these studies have been organized according to the class of xenobiotic.

EXPERT OPINION

From the analysis of the present knowledge emerges a dramatic need for information on sex differences in xenobiotics toxicity. Although animals are reasonably good predictors of adverse renal effects in patients, there is need to identify alternative methods (e.g. in vitro/ex vivo) to better study sex differences in organ toxicity.

Segmentary effects on the renal proximal tubule due to hexachloro-1,3-butadiene in rats: biomarkers related to gender

Renal tissue biomarkers (glutamine synthetase and p-aminohippuric acid uptake) were studied in male and female rats after treatment with hexachloro-1,3-butadiene. Reduced glutathione content also was also determined in liver and kidney. Histopathological examination (light microscopy) was then performed. The aim was to define sex differences in nephrotoxic effects caused by the solvent injected i.p. at 50, 100 and 200 mg kg(-1) dose. The rats were sacrificed 24 and 48 h after treatment; after 24 h a significant (P < 0.05) dose-dependent depletion of liver reduced glutathione was observed in male rats only; after 48 h male and female rats showed a significant (P < 0.05) increase at 50 and 100 mg kg(-1) doses. Reduced glutathione in the kidney was increased in male but not in female rats 24 and 48 h after treatment. Glutamine synthetase activity in renal tissue showed a significant (P < 0.05) dose-dependent decrease 24 and 48 h after treatment in both sexes, but is was significantly (P < 0.05) greater in female rats after 48 h. p-Aminohippuric acid uptake in renal cortical slices appeared significantly (P < 0.05) decreased in both sexes at the higher dose 24 h after treatment but this was significantly (P < 0.05) greater in female rats. A further significant (P < 0.05) impairment was observed after 48 h in males treated with a 200 mg kg(-1) dose. In addition, a slight but significant (P < 0.05) loss of p-aminohippuric acid uptake was observed 48 h after treatment with a 100 mg kg(-1) dose in both sexes. Light microscopy showed that the pars recta of the proximal tubule was mainly affected and tubular damage increased according to dose and time, involving the inner medulla and cortex. In conclusion, female rats show a significantly earlier and higher susceptibility of the kidney to toxic effects of hexachloro-1,3-butadiene.

Development of resistance against hexachlorobutadiene in the proximal tubules of young male rat

Hexachlorobutadiene (HCBD) is a potent nephrotoxin in rodents that can cause degeneration, necrosis and regeneration in renal tubular epithelial cells. Its toxicity is due to its conjugation by glutathione (GSH) to form glutathione S-conjugate, by the enzyme glutathione S-transferase and finally to the related cysteine-conjugate. This metabolite is then actively taken up by kidney and cleared in the renal tubular epithelial cells, rich in beta-lyase, to a reactive thiol derivative that covalently binds to the macromolecules. In this study, different groups of 28-day male Wistar albino (W/A) rats were dosed daily with 25 mg/kg HCBD for 2, 3, 4 and 7 days; control group dosed with corn oil. Data showed that in the 2- and 3-day treated groups there was substantial necrosis to the straight portion of the proximal tubules (pars recta or S3 segment), rich in glutamine transaminase K (GTK/beta-lyase). In the 4-day treated group, the renal proximal tubules had regenerated and showed a basophilic appearance. In animals treated for 7 days, it was observed that the kidney appeared to have returned to normal and had become resistant to further doses of HCBD. To define the time for the kidney to regain susceptibility to HCBD, 18- and 25-day studies with both low (25 mg/kg) and high (100 mg/kg) doses of HCBD (following two initial doses of 25 mg/kg) were performed. In the 18-day study, histopathological examination of the kidneys in animals of this group and also animals in the 25-day study, which received two further doses of HCBD, showed that the severity of kidney damage is much less than in the 2-day treated animals, a clear indication that the tubular cells were still resistant to the low dose of HCBD. Concentration of blood urea nitrogen, as a marker of kidney damage, in these two groups also confirmed the results. In animals re-exposed to the high dose of HCBD, data showed that the susceptibility to HCBD was starting to return.

Mechanism of sex-related differences in nephrotoxicity of 1.2-dichloropropane in rats

The contribution of testosterone to the nephrotoxic effects of 1,2-dichloropropane (DCP) was assessed by a series of castration and sex hormone replacement experiments on Wistar rats. The nephrotoxic action of DCP was evaluated by measuring the accumulation of organic anion and release of aspartate aminotransferase into the incubation medium using a renal cortical slice model. Our data show that sex, castration, and testosterone pretreatment are factors that influence the effect of DCP on renal cortical slices of rats Males appear to be more sensitive to nephrotoxic effects of DCP than females, male castration prevents the nephrotoxic effects of DCP, and pretreatment of females and castrated males with testosterone increases the susceptibility to DCP. In this study an attempt was made to evaluate the role of sex differences in the expression of enzymes participating in Phase I and Phase II detoxication reactions in order to explain the differences in sensitivity of the two genders to the nephrotoxic action of DCP. Our results implicate gender-specific expression of cytochrome P-450 in the kidneys as a predominant factor that determines the different susceptibilities of male and female rats to the nephrotoxic effect of DCP. We propose that the oxidation of DCP by CYP IIE1 is the first saturable and limiting step in the metabolic activation of DCP to nephrotoxic metabolites. It appears that, despite the fact that the nephrotoxic effect of DCP is determined mainly by its cysteine-conjugated metabolites, gluthathione (GSH) content and glutathione S-transferase (GST) activity in kidney are not directly related to increased androgen-related susceptibility to DCP.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhanced hexachloro-1:3-butadiene nephrotoxicity in rats with a preexisting adriamycin-induced nephrotic syndrome

Renal damage was assessed by histopathology and urinalysis in male Wistar rats treated with either hexachloro-1:3-butadiene (HCBD; a single 170-mg/kg ip dose that caused proximal tubule necrosis), adriamycin (ADR; a single 5-mg/kg ip dose that caused minimal glomerular changes up to 35 days), or HCBD given 2 wk after ADR and compared with age-matched control rats for 21 days. Urinalysis values in ADR-treated rats showed minimal renal changes. HCBD significantly elevated urine volume (10-fold), protein (5-fold), glucose (175-fold), and brush border enzymes (10-600-fold), indicating severe proximal tubular damage, but most parameters returned to pretreatment levels 6 days after treatment. In ADR-pretreated rats subsequently given HCBD, both the urinary alkaline phosphatase and the ratio of kidney: body weight were significantly higher for longer periods. Histopathology demonstrated that the HCBD-induced proximal tubular lesion was confined to the outer stripe of the outer medulla. Advanced regeneration and repair was evident 21 days after HCBD treatment. In the ADR-pretreated rats the HCBD-induced lesion was more severe and affected the entire cortex and was characterized by marked tubular epithelial calcification, with little evidence of repair and tubular restitution 21 days after treatment. Enzyme histochemistry showed gamma-glutamyltranspeptidase localized to the proximal tubules. After HCBD treatment the enzyme staining was lost and subsequently returned in parallel with histological recovery up to 21 days. The distribution and intensity of gamma-glutamyltranspeptidase was unchanged in ADR-treated rats. The distribution and intensity of gamma-glutamyltranspeptidase in kidneys of ADR-pretreated rats given HCBD had not returned to normal by day 21. The results of this study indicate that pretreatment with ADR increases HCBD-induced nephrotoxic damage and decreases renal cortical repair capacity.

Spontaneous renal lesions in CD-1 and B6C3F1 mice

Incidence and pathology of naturally occurring renal lesions in CD-1 and B6C3F1 mice are evaluated, tabulated, and discussed. In CD-1 mice, most frequent non-neoplastic renal lesion was interstitial nephritis (72.6%) followed by amyloidosis (40.6%), mononuclear cell infiltration (23.6%), tubular mineralization (12.8%), cortical cysts (8.2%), hydronephrosis (6.7%), tubular dilatation (5.9%), and tubular degeneration/regeneration (4.7%). Cortical epithelial origin renal cell carcinomas were observed in one male (0.13%) and one female mice (0.13%). In B6C3F1 mice, most commonly occurring non-neoplastic renal lesion was mononuclear cell infiltration (29.8%) followed by tubular mineralization (11.3%), interstitial nephritis (6.8%), tubular vacuolization (4.5%), tubular degeneration/regeneration (2.5%), and cortical cysts (1.3%). Cortical cell adenoma was the only primary renal neoplasm which was observed in one female mice (0.16%). In both strains, other renal lesions were less frequent.

Sex- and age-related nephrotoxicity due to 1,2-dichloropropane in vitro

Sex- and age-related nephrotoxicity due to 1,2-dichloropropane was studied in vitro by means of renal cortical slices obtained from Wistar rats. Reduced glutathione content, organic anion accumulation (p-aminohippurate), and release of malondialdehyde (to measure the extent of lipid peroxidation), aspartate aminotransferase, gamma-glutamyltransferase and lactate dehydrogenase into the incubation medium were determined. Sex differences in naive rats parameters were slight, but male were more susceptible to toxic effects of 1,2-dichloropropane than female rats; glutathione depletion, lipid peroxidation, and loss of organic anion accumulation were higher in male than in female slices. During senescence, naive male rats showed a progressive decrease of glutathione content (statistically significant from 7-9 months of age), increase of spontaneous lipid peroxidation from the same age, and increase of signs of cytotoxicity (release of aspartate aminotransferase and lactate dehydrogenase into the incubation medium) from 3-4 months of age. A loss of organic anion accumulation started from 7-9 months of age. Slices from rats of 3-4 months old showed the apparently highest susceptibility to 1,2-dichloropropane but depletion of glutathione content and loss of organic anion accumulation were at the same level in the oldest rats. The age decrease of control values caused the differences in the percentage ratio and then, apparently, a lower DCP effect. On the contrary, the increase of aspartate aminotransferase released in the incubation medium by DCP-treated slices corresponded to the age-related increase in cytotoxicity.

Age- and sex-dependent dichlorovinyl cysteine (DCVC) accumulation and toxicity in the mouse kidney: relation to development of organic anion transport and beta-lyase activity

The age- and sex-dependent changes in mouse kidney accumulation and toxicity of S-1,2-dichlorovinyl cysteine (DCVC) was investigated. The results were compared to developmental changes in the basal activities of organic anion transport in vitro (PAH uptake) and of cysteine conjugate beta-lyase (substrate: benzothiazolyl cysteine). Following 14C-DCVC (5 mg/kg body wt. orally), the renal 14C-accumulation increased with age, whereas the degree of tubular DCVC lesions was about the same at all time points. Regarding the sex differentiation in adult mice, both the kidney 14C-accumulation levels and the kidney lesion (5 mg/kg DCVC) were most accentuated in the female mouse. However, at a higher dose (25 mg/kg), the male kidney was most affected. Changes in the anion transport and beta-lyase activities did not directly mirror the age-dependent increase in kidney radioactivity. Sex differences in anion transport and beta-lyase activities were also seen, the former activity being highest in the male mouse and the latter in the female. The conflicting results of 14C-accumulation and histopathology in developing mice, may be explained by the ongoing development of the kidney; increase in the number of functionally active nephrons may result in an increased 14C-accumulation (in d.p.m./mg wet wt.) but still the same degree of lesion, when estimated per nephron. In the adult mice, the higher susceptibility of the female may be correlated to the higher beta-lyase activity in the same sex. Regarding the inversed results at a higher dose, rate limitations of transport and bioactivation systems may play a role.

Bioactivation of hexachlorobutadiene by glutathione conjugation

Glutathione (GSH) conjugation reactions in the metabolism of hexachlorobutadiene (HCBD), in rats and mice, initiate a series of metabolic events resulting in the formation of reactive intermediates in the proximal tubular cells of the kidney. The GSH S-conjugate 1-(glutathion-S-yl)-1,2,3,4,4-pentachlorobutadiene (GPCB), which is formed by conjugation of HCBD with GSH in the liver, is not reactive and is eliminated from the liver in the bile or plasma, or both. GPCB may be translocated intact to the kidney and processed there by gamma-glutamyl transpeptidase and dipeptidases to the corresponding cysteine S-conjugate. Alternatively, gamma-glutamyl transpeptidase and dipeptidases present in epithelial cells of the bile duct and small intestine may catalyse the conversion of GPCB to cysteine S-conjugates. The kidney concentrates both GSH and cysteine S-conjugates and processes GSH conjugates to cysteine S-conjugates. A substantial fraction of HCBD cysteine S-conjugate thus concentrated in the kidney is metabolized by renal cysteine conjugate beta-lyase to reactive intermediates. The selective formation of reactive intermediates in the kidney most likely accounts for the organ-specific effects of HCBD. Alternatively, cysteine S-conjugates may be acetylated to yield excretable mercapturic acids.

Role of gamma-glutamyltranspeptidase and beta-lyase in the nephrotoxicity of hexachloro-1,3-butadiene and methyl mercury in mice

Male Swiss OF1 mice received a single oral dose of either 80 mg/kg hexachloro-1,3-butadiene (HCBD) or 80 mg/kg methyl mercury (MeHg). Examination of cryostat kidney sections stained for alkaline phosphatase (APP) revealed damage to about 50% of the proximal tubules after 8 h. Pretreatment with the gamma-glutamyltranspeptidase (gamma-GT) inactivator AT-125 (Acivin, 50 mg/kg i.p., plus 50 mg/kg p.o., reduced the number of damaged tubules by 59 and 58% in mice treated with HCBD and MeHg, respectively. Pretreatment with the two beta-lyase inhibitors, amino-oxyacetic acid (AOAA, 3 x 100 mg/kg p.o.) and DL-propargylglycine (PPG, 300 mg/kg i.p. plus 300 mg/kg p.o.), reduced HCBD nephrotoxicity by 46 and 59%, respectively, but did not protect against MeHg nephrotoxicity. The results support a role for gamma-GT and beta-lyase in the mouse renal toxicity of HCBD and implicate gamma-GT but not beta-lyase in MeHg-induced nephrotoxicity in mice.

Deacetylation and further metabolism of the mercapturic acid of hexachloro-1,3-butadiene by rat kidney cytosol in vitro

Hexachloro-1,3-butadiene (HCBD) is more nephrotoxic to female than male rats. Metabolism of HCBD involves conjugation with glutathione followed by formation of the cysteine conjugate S-(pentachloro-1,3-butadienyl) cysteine (PCBD-CYS) and then the mercapturic acid N-acetyl-S-pentachloro-1,3-butadienyl-cysteine (PCBD-NAC). PCBD-NAC is also more nephrotoxic to female rats than male rats. The deacetylation of [14C]-PCBD-NAC to PCBD-CYS and the binding of radiolabelled metabolites to protein has been studied using renal cytosol preparations from male and female rats in vitro, since a sex-related difference in these reactions could explain the difference in nephrotoxicity found in vivo. PCBD-NAC was rapidly metabolised by renal cytosol. The rate of metabolism was similar with either male or female renal cytosol, and the major metabolite identified was PCBD-CYS. N-Acetylation of PCBD-CYS to PCBD-NAC was not detected in the presence of either male or female renal cytosol. Covalent binding of radioactivity from [14C]-PCBD-NAC to cytosolic protein could be detected after 5 min incubation, and although the extent of binding was similar for both male and female cytosol at early time periods, after 60 min incubation more binding was found in the presence of male cytosol. Covalent binding was largely prevented by aminooxyacetic acid, an inhibitor of cysteine conjugate beta-lyase, suggesting a role for this enzyme in the activation of HCBD. These results indicate that the sex differences in the nephrotoxicity of HCBD and PCBD-NAC in the rat are not attributable to differences in the rate of deacetylation of PCBD-NAC to give the proximate nephrotoxin PCBD-CYS.

Metabolism of hexachloro-1,3-butadiene in mice: in vivo and in vitro evidence for activation by glutathione conjugation

1. The metabolism of 14C-hexachloro-1,3-butadiene (HCBD) was studied in mice and in subcellular fractions from mouse liver and kidney. 2. In the presence of glutathione (GSH), liver microsomes and cytosol transformed HCBD to S-(pentachlorobutadienyl)glutathione (PCBG). PCBG formation in subcellular fractions from mouse kidney was very limited. Oxidative metabolism of HCBD by cytochrome P-450 could not be demonstrated. 3. Cysteine conjugate beta-lyase was present in mitochondria and cytosol from mouse liver and kidney. 4. After an oral dose of 30 mg/kg 14C-HCBD, mice eliminated 67.5-76.7% of dose in faeces; urinary elimination accounted for 6.6-7.6%. 5. Metabolites of HCBD identified are: S-(pentachlorobutadienyl)glutathione in faeces; S-(pentachlorobutadienyl)-L-cysteine, N-acetyl-S-(pentachlorobutadienyl)-L-cysteine and 1,1,2,3-tetrachlorobutenoic acid in urine. 6. The results suggest that conjugation of HCBD with GSH in liver, followed by renal processing of the glutathione S-conjugates and beta-lyase-catalysed formation of reactive intermediates, accounts for the organ specific toxicity of HCBD in mice.

Probenecid-induced protection against acute hexachloro-1,3-butadiene and methyl mercury toxicity to the mouse kidney

Male Swiss OF1 mice received a single oral dose of either 80 mg/kg hexachloro-1,3-butadiene (HCBD) or 40 mg/kg methyl mercury (MeHg). Examination of cryostat kidney sections stained for alkaline phosphatase (APP) revealed damage to about 50% of the proximal tubules after 8 h. Treatment with the organic anion transport inhibitor probenecid (i.p., 3 x 0.75 mmol/kg) did not have any renal effect in normal mice but reduced the number of damaged tubules by 80 and 90% in mice treated with HCBD and MeHg respectively. The results support the conclusion that the toxicity of HCBD and MeHg to the mouse kidney is related to a probenecid-sensitive transport process. It cannot be stated from the present investigation whether the inhibition nephrotoxicity data are related to classic organic anion secretion by the kidney.

Studies on the mechanism of nephrotoxicity and nephrocarcinogenicity of halogenated alkenes

There is now a considerable weight of evidence from studies in a number of different laboratories with different haloalkenes to suggest that these compounds undergo conjugation with glutathione followed by degradation of the S-conjugate (Figure 1) to produce cytotoxic, and in some cases mutagenic, metabolites. These effects are dependent upon the sequential metabolism by gamma-glutamyl transferase and dipeptidases to produce the cysteine conjugates, and the presence of renal transport systems which concentrate the chemical in renal cells. These conjugates then appear to undergo further metabolism to a reactive thiol by the renal enzyme cysteine-conjugate beta-lyase, a process which can be blocked by inhibiting the enzyme with AOAA. Renal beta-lyase is present in both the cytosol and mitochondrial fractions, but toxicity studies in isolated cells and mitochondria indicate that the primary mode of action of these compounds is the inhibition of mitochondrial respiration, suggesting that the mitochondrial beta-lyase may be more important than the cytosolic enzyme in cysteine S-conjugate bioactivation. In addition to the renal cell injury caused by the presumed reactive thiol metabolite, reaction with DNA also occurs as the chlorinated, but not fluorinated, analogs are mutagenic, and in the case of HCBD, carcinogenic. Thus the target organ, cellular and subcellular specificity of haloalkene-S-conjugates, is due to the presence of bioactivating enzymes and the susceptibility of certain biochemical processes. The precise relationship between (1) the mitochondrial effects and cytotoxicity and (2) the interaction of the chemical with DNA and its mutagenicity require more precise understanding in order to elucidate the mechanism of S-conjugate-induced cell death and carcinogenicity. The routes and rates of metabolism of some of these compounds, with respect to glutathione conjugation vs. oxidative metabolism, in both experimental animals and man are required to help assess the risk associated with this class of chemicals.

Transport of N-acetyl-S-pentachloro-1,3-butadienylcysteine by rat renal cortex

N-acetyl-S-pentachloro-1,3-butadienyl-L-cysteine (PCBD-NAC) is a postulated metabolite derived from glutathione conjugation of hexachloro-1,3-butadiene and is nephrotoxic in the rat. Because PCBD-NAC causes selective necrosis to the pars recta of the proximal tubule, and is an organic anion it might be expected to be transported by the renal organic anion transport system. Rat renal cortical slices were used to characterise the transport. 14C-PCBD-NAC uptake was temperature dependent and reduced by the metabolic inhibitors cyanide and iodoacetate. Probenecid and sulphinpyrazone, specific competitive inhibitors of the anion transport system, and dinitrophenol, a metabolic inhibitor as well as a competitive inhibitor of anion transport, reduced PCBD-NAC transport. Organic cations or uric acid transport inhibitors did not alter PCBD-NAC accumulation by the slices. These data are consistent with the transport of PCBD-NAC by the renal organic anion secretory system.

Role of renal metabolism and excretion in 5-nitrofuran-induced uroepithelial cancer in the rat

5-Nitrofurans have been used in the study of chemical carcinogenesis. There is substantial evidence that N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide (FANFT) is deformylated to 2-amino-4-(5-nitro-2-furyl)thiazole (ANFT) in the process of FANFT-induced bladder cancer. Paradoxically, ANFT is less potent as a uroepithelial carcinogen than FANFT when fed to rats. Feeding aspirin with FANFT to rats decreases the incidence of bladder cancer. Isolated kidneys were perfused with 5-nitrofurans to determine renal clearances and whether aspirin acts to decrease urinary excretion of the carcinogen. In FANFT-perfused kidneys, FANFT was deformylated to ANFT and excreted (1.06 +/- 0.22 nmol/min) at a rate eightfold higher than excretion of FANFT. In kidneys perfused with equimolar ANFT, excretion of ANFT was 0.25 +/- 0.05 nmol/min, which suggests a coupling of renal deformylation of FANFT to excretion of ANFT in FANFT-perfused kidneys. Neither aspirin nor probenecid altered the urinary excretion or half-life of FANFT or ANFT. In rats fed 0.2% FANFT as part of their diet, coadministration of aspirin (0.5%) increased urinary excretion of ANFT during a 12-wk feeding study, which suggests decreased tissue binding or metabolism of ANFT. Kidney perfusion with acetylated ANFT (NFTA), a much less potent uroepithelial carcinogen, resulted in no ANFT excretion or accumulation, which indicates the specificity of renal deformylase. Renal deformylase activity was found in broken cell preparations of rat and human kidney. These data describe a unique renal metabolic/excretory coupling for these compounds that appears to explain the differential carcinogenic potential of the 5-nitrofurans tested. These results are consistent with the hypothesis that aspirin decreases activation of ANFT by inhibiting prostaglandin H synthase.

Hexachloro-1,3-butadiene-induced hydropic change in mouse liver

Hexachloro-1,3-butadiene (HCBD) produced a time- and dose-related increase in hepatic water content following i.p. administration to male Alderley Park (Alpk/AP) mice. The increase in liver water was maximal 1-2 days after a single dose of 50 mg kg-1 and had returned to normal by day 5. Associated with the increased water, there was a parallel increase in Na+ and K+ ions, with no overall change in intracellular cation concentration. Liver non-protein sulphydryl content showed no consistent time-related decrease after 50 mg kg-1 HCBD. Histopathological examination of the liver showed fine cytoplasmic vacuolation of periportal hepatocytes which was more marked following 100 or 200 mg kg-1 than 50 mg kg-1 HCBD. In one animal, following 200 mg kg-1 HCBD, the liver showed ballooning and degeneration of periportal hepatocytes. Ultrastructural changes were evident 4 h after 50 mg kg-1 and consisted of mitochondrial swelling in periportal hepatocytes, whilst pericentral hepatocytes appeared normal. By 16 h, marked mitochondrial swelling and some proliferation of smooth endoplasmic reticulum were evident in periportal hepatocytes. Male mice of the C57BL/10J and C3H strains appeared to be more sensitive to HCBD-induced hepatic hydropic change than did the male and female Alpk/AP strain and male Balbc and DBA/2J strains. It appears that HCBD or a metabolite causes disruption of mitochondria in periportal hepatocytes which results in an influx of water and ions into the cell without compromising the Na+ pump.