In vivo nephrotoxic action of an isomeric mixture of S-(1-phenyl-2-hydroxyethyl)glutathione and S-(2-phenyl-2-hydroxyethyl)glutathione in Fischer-344 rats

Food flavor cinnamaldehyde-induced biochemical and histological changes in the kidney of male albino wistar rat

Rats were given food flavor cinnamaldehyde (CNMA) orally by gavage at the dose of 2.14, 6.96, 22.62 and 73.5mg/kg body weight/day for 10, 30 and 90 days. Only the group of rats treated with CNMA at the dose 73.5mg/kg body weight/day for 90 days showed histological changes in the kidney followed by increased activities of renal, serum and urinary enzymes. CNMA-induced glucosuria in these rats was accompanied by marked proteinuria and creatinuria. Increased serum blood urea nitrogen and serum creatinine and decreased serum protein and glucose levels were observed in these rats. Thus, CNMA at the dose of 73.5mg/kg body weight/day for 90 days exert its effect on kidney of male albino wistar rat and its effect is time and dose dependent.

Role of aldose reductase and oxidative damage in diabetes and the consequent potential for therapeutic options

Aldose reductase (AR) is widely expressed aldehyde-metabolizing enzyme. The reduction of glucose by the AR-catalyzed polyol pathway has been linked to the development of secondary diabetic complications. Although treatment with AR inhibitors has been shown to prevent tissue injury in animal models of diabetes, the clinical efficacy of these drugs remains to be established. Recent studies suggest that glucose may be an incidental substrate of AR, which appears to be more adept in catalyzing the reduction of a wide range of aldehydes generated from lipid peroxidation. Moreover, inhibition of the enzyme has been shown to increase inflammation-induced vascular oxidative stress and prevent myocardial protection associated with the late phase of ischemic preconditioning. On the basis of these studies, several investigators have ascribed an important antioxidant role to the enzyme. Additionally, ongoing work indicates that AR is a critical component of intracellular signaling, and inhibition of the enzyme prevents high glucose-, cytokine-, or growth factor-induced activation of protein kinase C and nuclear factor-kappa-binding protein. Thus, treatment with AR inhibitors prevents vascular smooth muscle cell growth and endothelial cell apoptosis in culture and inflammation and restenosis in vivo. Additional studies indicate that the antioxidant and signaling roles of AR are interlinked and that AR regulates protein kinase C and nuclear factor-kappaB via redox-sensitive mechanisms. These data underscore the need for reevaluating anti-AR interventions for the treatment of diabetic complications. Potentially, the development of newer drugs that selectively inhibit AR-mediated glucose metabolism and signaling, without affecting aldehyde detoxification, may be useful in preventing inflammation associated with the development of diabetic complications, particularly micro- and macrovascular diseases.

GSTM1 polymorphism and styrene metabolism: insights from an acute accidental exposure

Two workers were accidentally exposed to unusually high styrene concentrations (>1000 ppm) for about 30 min. In addition to the main styrene metabolites, mandelic acid (MA) and phenylglyoxylic acid (PGA), other minor metabolites, including specific mercapturic acids, (R,R)- and (S,R)-N-acetyl-S-(1-phenyl-2-hydroxyethyl)-L-cysteine [(R,R)-M1 and (S,R)-M1] and (R,R)- and (S,R)-N-acetyl-S-(2-phenyl-2-hydroxyethyl)-L-cysteine [(R,R)-M2 and (S,R)-M2], 4-vinylphenol-glucuronide and -sulfate, and phenylglycine, were determined by Liquid Chromatography Electrospray Tandem Mass Spectrometry (LC-ESI-MS/MS) in urine samples collected 12, 24, 36, 48, 75 and 99 h after the episode. The genotypes of microsomal epoxide hydrolase, glutathione-S-transferases M1-1 (GSTM1), T1-1 (GSTT1) and P1-1 (GSTP1) were characterized by PCR-based methods. The two subjects showed similar peak levels of MA and PGA, as well as 4-vinylphenol conjugates, whereas mercapturic acids were five times higher in the subject bearing the GSTM1pos than in the GSTM1null subject. Also, relative proportions of diasteroisomers of mercapturic acids were influenced by the GSTM1 polymorphism.

Exposure to hydrocarbons and renal disease: an experimental animal model

The association between hydrocarbon exposure and chronic glomerulonephritis is still a controversial scientific issue. Recent epidemiological evidence suggests a role of exposure to hydrocarbons in the progression of glomerulonephritis towards chronic renal failure. The present experimental study on rats has been designed to assess the possible role of styrene in the progression of adriamycin (ADR) nephrosis, a well known model of renal fibrosis following nephrotic syndrome induced by ADR. Female Sprague-Dawley rats were exposed to styrene, 300 ppm, 6 h/day, 5 days/week for 12 weeks (group 1); treated with ADR, 2 mg/Kg, i.v., twice on day 1 and day 15 of the study (group 2); Additional groups of animals received both the styrene and ADR treatments (group 3) or served as controls (group 4). The urinary excretion of total and single proteins (albumin, Retinol-Binding Protein (RBP), Clara Cell 16 Kd protein (CC16), fibronectin) was measured monthly, whereas histopathology and determinations requiring blood sampling were carried out at the end of the experiment. A progressive increase in total proteinuria, falling in the nephrotic range already by the 6th week was observed in ADR-treated groups. Styrene exposure caused up to a 3- to 5-fold increase as compared to controls. Co-exposure to ADR and styrene also resulted in a proteinuria much greater than that caused by ADR alone. The interactive effect of styrene and ADR was statistically significant for albuminuria and urinary fibronectin. A similar response was observed for glomerular filtration rate at the end of the experiment, styrene-exposed animals showing hyperfiltration as compared to their respective control group. At the end of the experiment, histopathological scoring for interstitial infiltration and fibrosis was also significantly higher in styrene-treated animals as compared to their respective control groups. In ADR-treated rats, low molecular weight proteinuria (l.m.w.p.) was only slightly affected, suggesting minimal tubular dysfunction associated with extensive tubular atrophy. However, styrene-exposed animals showed l.m.w.p. higher than their respective controls. In summary, in this animal model we were able to confirm both styrene-induced microproteinuria, mainly albuminuria and minor increases in l.m.w.p., observed among occupationally exposed workers and the role of hydrocarbon exposure as a factor accelerating the progression of renal disease suggested by epidemiological investigations in patients suffering from chronic renal disease. Whereas in rats exposed to styrene only, microproteinuria was stable over time and minor histopathological changes were noted at the end of the experiment, evidence of a role of solvent exposure in the progression of ADR nephropathy was obtained in terms of both renal dysfunction and interstitial fibrosis. The mechanistic basis of styrene-ADR interaction is unclear. However, experimental evidence is consistent with epidemiological findings suggesting the need to avoid solvent exposure in patients suffering from renal diseases.

Role of SAM-dependent thiol methylation in the renal toxicity of several solvents in mice

The role of S-adenosylmethionine (SAM)-dependent thiol methylation in the nephrotoxicity of seven industrial solvents was studied in mice. The seven following solvents were utilized: bromobenzene (BB), styrene (STY), tetrachloroethylene (TTCE), trichloroethylene (TCE), 1,1-dichloroethylene (DCE), 1,2-dichloroethane (DCA) and hexachlorobutadiene (HCB). The experimental model comprised mice pretreated with periodate oxidized adenosine (ADOX) (100 micromol kg(-1) i.p.) 30 min before injection of solvents. In the first 4 h after ADOX treatment, the SAM levels were about fourfold higher than controls for the liver and kidney. The S-adenosylhomocysteine (SAH) levels were increased by factors of 11 and 14 and the SAM/SAH ratios were decreased by factors of 3 and 10 for the liver and kidney, respectively. These results show that ADOX treatment probably induces an inhibition of methyltransferase SAM-dependent in the liver and kidney and thus decreases the methylation capabilities. A single oral administration of BB (500 or 800 mg kg(-1)), TTCE (3500 or 4000 mg kg(-1)), TCE (3000 or 3500 mg kg(-1)) or STY (400 or 600 mg kg(-1)) did not induce renal toxicity, evaluated by the percentage of damaged tubules compared to controls. On the other hand, the three solvents DCE, HCB and DCA were nephrotoxic and the percentage of damaged tubules observed for each solvent was significantly different from the value of <1.8% for controls: 19% and 40% for DCE (130 and 200 mg kg(-1)), 50% and 46% for HCB (80 and 100 mg kg(-1)) and 5.1% and 7.6% for DCA (1000 and 1500 mg kg(-1)). The ADOX treatment in the mice did not modify the renal toxicity of the seven solvents. Thus, their renal toxicity, when it existed, was probably independent of the SAM-dependent thiolmethyltransferase activity in the mice. The results of this study are discussed from two viewpoints. The first concerns the general considerations on inhibition of thiol methyltransferase activities in mice and the second is related to the different solvents that are evoked individually.

S-[(1 and 2)-phenyl-2-hydroxyethyl]cysteine-induced alterations in renal mitochondrial function in male Fischer-344 rats

Previous studies from our laboratory have shown that mitochondrial dysfunction may be an important early event in S-[(1 and 2)-phenyl-2-hydroxyethyl]cysteine (PHEC)-induced cytotoxicity in isolated rat renal proximal tubules. The present study has therefore examined in more detail PHEC-induced mitochondrial dysfunction, both in vivo and in vitro, using isolated renal cortical mitochondria. Renal cortical mitochondria isolated from PHEC-treated rats in vivo showed depressed effects on the mitochondrial respiration and oxidative phosphorylation in both a dose (0, 250, and 500 micromol/kg iv)- and time (0-24 h)-dependent manner in the presence of both succinate (Site 2) and malate plus alpha-ketoglutarate (Site 1) as respiratory substrates, with initial significant depression occurring as early as 4 h following treatment with 500 micromol PHEC/kg. Similar mitochondrial dysfunctions were observed in vitro in concentration- and time-dependent manners with both respiratory substrates. PHEC also caused a marked dose-dependent inhibition of mitochondrial succinate dehydrogenase and NADH cytochrome c reductase activities both in vivo and in vitro, with initial inhibition occurring as early as 4 h after in vivo administration and 45 min after exposure to PHEC in vitro, while the NADH dehydrogenase activity was not considerably inhibited. The mitochondrial ATPase activity was significantly decreased 4 and 24 h following treatment with PHEC (500 micromol/kg). These results suggest that PHEC exerts its inhibitory effect on the mitochondrial respiration and oxidative phosphorylation through the action on the mitochondrial electron transport chain. PHEC significantly reduced the activity of adenine nucleotide translocase as well as the net uptake of substrates by mitochondria without affecting their efflux within 2-4 h after its injection (500 micromol/kg). On the other hand, significant renal damage, as assessed by morphological study, appeared as early as 24 h following such treatment. The observation of similar effects after both in vivo and in vitro exposures may suggest that the effect on mitochondria may have a pathogenic role in PHEC-induced renal injury in rats. PHEC produces mitochondrial toxicity that results from an inactivation of mitochondrial anionic substrate transporters as well as from an inhibition of activities of adenine nucleotide translocase and dehydrogenases.

Occupational hydrocarbon exposure and chronic nephropathy

This review aims at discussing the questions raised by the hydrocarbon-related chronic nephropathy and its possible consequence, the hydrocarbon-related chronic renal failure. It has been attempted to adopt the point of view of the clinician. Therefore, the most important part of the review is devoted to a presentation and an analysis of the available data on humans. The main features of the available studies on human subjects are presented, their conclusions discussed in the light of the possible methodological flaws, and practical conclusions drawn. After a discussion of the main difficulties encountered for selecting the suitable exposure indicator, the studies are discussed in order of decreasing quality of the study design (cohort, case-control, cross-sectional studies, and the case reports). It is concluded that a great deal of controversies about chronic hydrocarbon-related nephropathy is explained by differences in the study design and that hydrocarbon-induced nephropathy is probably more than a mere hypothesis, although a causal relationship has not yet been proven. Finally, some practical consequences for dealing with a hydrocarbon-exposed patient diagnosed with a kidney disease and the need for further research are discussed.

Role of extracellular glutathione and gamma-glutamyltranspeptidase in the disposition and kidney toxicity of inorganic mercury in rats

The role of extracellular glutathione (GSH) and membrane-bound gamma-glutamyltranspeptidase (gamma-GT) as contributory factors in the disposition and toxicity of inorganic mercury (HgCl2, 1 mg kg-1, i.p.) was investigated in rats pretreated with acivicin (AT-125, 10 mg kg-1), a gamma-GT inhibitor. A high degree of gamma-GT inhibition (75%) and of protection (90%) against HgCl2-induced nephrotoxicity was obtained in gamma-GT-inhibited rats 24 h post-treatment. Pretreatment with acivicin affected the fractional distribution profile of 203 Hg, resulting in a twofold decrease in the renal incorporation of mercury 4 h post-treatment and a threefold increase in the 24-h urinary excretion of mercury. Plasma radioactivity remained constant over 24 h in rats dosed with 203Hg alone, whereas it decreased by 60% between 4 h and 24 h in gamma-GT-inhibited rats. In gamma-GT-inhibited rats treated with HgCl2 the renal and plasma reduced glutathione (GSH) content increased by 68% and 330% respectively, as compared to controls. The gamma-GT inhibition affected the distribution profile of mercury within urinary proteins, shifting the binding of mercury from the high-molecular-weight fraction (3% against 80%) to the low-molecular-weight fraction (72% against 10%). A significant but less impressive shift of mercury from the high- to the low-molecular-weight fraction also arose in the plasma. These results taken together support the pivotal role of extracellular GSH and membrane-bound gamma-GT in the renal incorporation, toxicity and excretion of inorganic mercury in rats.

Review of the metabolic fate of styrene

Styrene and styrene oxide have been implicated as reproductive toxicants, neurotoxicants, or carcinogens in vivo or in vitro. The use of these chemicals in the manufacture of plastics and polymers and in the boat-building industry has raised concerns related to the risk associated with human exposure. This review describes the literature to date on the metabolic fate of styrene and styrene oxide in laboratory animals and in humans. Many studies have been conducted to assess the metabolic fate of styrene in rats, and investigations on the metabolism of styrene in humans have been of considerable interest. Limited research has been done to assess metabolism in the mouse. The metabolism of styrene to styrene oxide and further conversion to styrene glycol (via epoxide hydrolase), mandelic acid, and phenylglyoxylic acid has been given considerable attention, and is considered to be the major pathway of activation and detoxication for humans. While the hydrolysis of styrene oxide to styrene glycol historically has been the favored pathway for the rat, studies in more recent years have indicated that glutathione conjugation also is a viable and significant pathway for both the rat and the mouse. This pathway has not been established in humans. Mandelic acid and phenylglyoxylic acid have been used as urinary markers of exposure in humans exposed to styrene. Extensive investigations have been conducted on the kinetics of styrene and styrene oxide in rodents. In people, the kinetics of styrene and styrene oxide in the blood of occupationally exposed workers and volunteers have been determined. Pharmacokinetic models developed in the last decade have become increasingly complex, with the most recent physiologically based model describing the kinetics of styrene and styrene oxide. This model shows pronounced species differences in sensitivity coefficients for styrene or styrene oxide between mice, rats, and humans, where mice are the more sensitive species to the Vmax for both epoxide hydrolase and monooxygenase. This result is particularly interesting in light of the recent findings of extensive mortality and hepatotoxicity for mice exposed to relatively low levels of styrene (250 to 500 ppm), while rats and humans exhibit only nasal and eye irritations at exposure concentrations well above 500 ppm.

Cytogenotoxicity of N-acetyl-S-(1/2-phenyl-2-hydroxyethyl)-cysteine (NAPEC) in cultured human blood lymphocytes

N-Acetyl-S-(1/2-phenyl-2-hydroxyethyl)-cysteine (NAPEC) is a cysteine conjugate derived from the glutathione conjugate of styrene oxide. The dose- and time-dependent effects of NAPEC on SCEs and cell kinetics were studied in cultured human blood lymphocyte in vitro. Different concentrations of NAPEC (0-1500 microM) were added into the lymphocyte cultures. After 36 h of exposure, both the induction of SCEs and cell-cycle delay were increased with increasing concentrations of NAPEC. When the lymphocyte cultures were exposed to 1000 microM NAPEC for 22, 36 and 72 h during a total of 72-h culture period, no significant differences in the induction of SCEs or cell-cycle delay were noticed due to 3 exposure times. These results suggest that NAPEC possesses the potential to induce SCEs and to inhibit cell-cycle progression and such potential seems to be independent of duration of exposure to NAPEC.

Effects of different styrene metabolites on cytotoxicity, sister-chromatid exchanges and cell-cycle kinetics in human whole blood lymphocytes in vitro

5 metabolites of styrene were tested in vitro for their cytotoxic effects, induction of SCEs and changes in cell-cycle progression in cultured human blood lymphocytes. Fresh heparinized peripheral blood (0.3 ml) from normal volunteers was cultured for a total of 72 h in 5 ml of RPMI 1640 medium containing 10% fetal calf serum, 0.1% garamycine, 1% glutamine and 1% phytohaemagglutinin. Styrene-7,8-oxide (SO), styrene glycol (SG), phenylglyoxylic acid (PGA), S-[1,2-phenyl-2-hydroxyethyl]-glutathione (PEG) (a glutathione conjugate of styrene oxide), N-acetyl-S-[1,2-phenyl-2-hydroxyethyl]-cysteine (NAPEC) in dimethyl sulfoxide (DMSO) were injected into the cultures 36 h after initial culture, so that the exposure time for these metabolites was 36 h. The final concentration of SO was 100 microM and those of the other metabolites were 500 microM. 24 h before harvest, BrdU (10 micrograms/ml) was added into the cultures for assessing cytogenetic endpoints. SO showed significant induction of SCEs and cell-cycle delay as well as a significant decline of cell survival. The same phenomena, but of less magnitude, were also observed with NAPEC, a cysteine derivative of SO. On the other hand, SG, PGA and PEG failed to produce any significant changes of these endpoints compared to the control. Thus, the present results have demonstrated that, in addition to SO, NAPEC possesses some cytogenotoxic potential and hence, these two metabolites together could contribute to the genotoxicity of styrene in human blood lymphocytes.

Dose-dependent genotoxic effects of styrene on human blood lymphocytes and the relationship to its oxidative and metabolic effects

Although the genotoxic potential of styrene is known, very limited information is available regarding its dose-dependent genotoxic response to human blood lymphocytes and how such response correlates with different metabolic events in whole blood lymphocytes. The present study was therefore carried out to study such a relationship using in vitro human blood lymphocytes from healthy volunteers. To study genotoxic response to styrene, sister chromatid exchanges (SCEs), cell cycle, and cell survival were analyzed. Lymphocytes were cultured for 72 hr in the presence of different concentrations of styrene (0-1,000 microM). Twenty-four hr before harvest, BrdU (5 micrograms/ml) was added to assess the increase in SCEs and cell cycle delay. Both the SCE frequency and the cell cycle length were increased linearly with increasing concentrations of styrene up to 200 microM, without addition of any exogenous metabolizing system. Above 200 microM, no further increase in genotoxic response occurred. The range of concentrations (10-200 microM) at which increase of cell cycle length due to styrene was observed did not impair the viability of the cells, suggesting that such cell cycle delay is a genotoxic-related event and not caused by cytotoxicity. In vitro metabolic transformation of styrene in whole-blood lymphocyte cultures without the presence of any exogenous metabolic activation system showed the formation of a reactive intermediate, styrene 7,8-oxide, to be capacity-limited, as verified from a nonlinear increase in the formation of styrene glycol. The value of such metabolic parameter reached a plateau above 200 microM styrene. The same phenomenon of saturation has also been observed with regard to other metabolic effects due to styrene in whole blood lymphocytes in culture, such as dose-dependent increase in lipid peroxidation and depletion of blood lymphocyte glutathione. Based on the relationship between the formation of different metabolic events and the genotoxicity of styrene, it may be possible that the genotoxic properties of styrene in human blood lymphocytes may be mediated initially not only by the formation of the presumably reactive styrene 7,8-oxide, but also by that of a reactive oxygen species as well. However, the present data are not sufficient enough to definitely identify the role of reactive oxygen species in such toxicity and therefore it warrants further study.

Species differences in the nephrotoxic response to S-(1,2-dichlorovinyl)glutathione

The present study was carried out to investigate the species differences in the nephrotoxic response to S-(1,2-dichlorovinyl)glutathione (DCVG) using rats, hamsters and guinea-pigs. DCVG was given intraperitoneally in physiological saline to groups of 5 animals at doses 0, 165 and 330 mumol/kg. Urine was collected for 24 h and the animals were then sacrificed. Significantly increased levels of urinary glucose, N-acetyl-beta-D-glucosaminidase, gamma-glutamyl transpeptidase, proteins and blood urea nitrogen were observed in rats at both dose levels of DCVG. An increase, but not of similar magnitude, of these biochemical parameters was noted in hamsters only at the higher dose of DCVG. Guinea-pigs showed significant increases in these biochemical parameters at the lower dose, but not at the higher dose. Light-microscopic studies showed increasing proximal tubular necrosis (PTN) in rats with increasing dose of DCVG, but PTN involving straight tubules only was observed at the higher dose in hamsters. PTN was again observed in guinea-pigs at the lower dose, but not at the higher dose of DCVG.

Effects of cysteine derivatives of styrene on the transport of p-aminohippurate ion in renal plasma membrane vesicles

The effects of cysteine conjugates of styrene, e.g. S-1/2-(phenyl-hydroxyethyl) cysteine (PEC) and its N-acetyl derivative (NAPEC) on the transport of p-amino-hippurate (PAH) ion in plasma membranes were studied in vitro using isolated rat renal brush-border membrane (BBM) and basolateral membrane (BLM) vesicles. The uptake of PAH was significantly inhibited by both PEC and NAPEC in both the membrane vesicles, as verified by decrease of the membrane/medium concentration ratio of PAH as the concentration of either PEC or NAPEC in the medium increased. These results show that both PEC and NAPEC are capable of interfering with the accumulation of PAH (a model organic anion for renal tubular transport system) by both energy-independent and energy-dependent carrier-mediated transport processes. The inhibition of PAH uptake in BBM vesicles due to 10 mM PEC or NAPEC was found to be nearly competitive, almost similar to probenecid, whereas in BLM vesicles such inhibition was found to be partially noncompetitive, as verified by the double reciprocal plots. Both PEC and NAPEC showed dose-dependent inhibition of the specific activity of the marker enzyme in each membrane, e.g. gamma-glutamyl transferase in BBM and Na(+)-K(+)-ATPase in BLM vesicles. However, no such inhibition was noticed with probenecid. The in vitro pretreatment with probenecid prevented the inhibition of gamma-glutamyl transferase activity in BBM due to PEC or NAPEC, but such was not the case for the Na(+)-K(+)-ATPase activity in BLM. In conclusion, the data suggest that the transport of cysteine or N-acetylcysteine conjugates of styrene by renal proximal tubular cells across both the membrane vesicles accompanied by the inhibition of the membrane-specific enzymes may lead to cellular dysfunction and consequently to the initial development of their nephrotoxicity.