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Methylmercury is an environmental pollutant that causes neurotoxicity. Recent studies have reported that the ubiquitin-proteasome system is involved in defense against methylmercury toxicity through the degradation of proteins synthesizing the pyruvate. Mitochondrial accumulation of pyruvate can enhance methylmercury toxicity. In addition, methylmercury exposure induces several immune-related chemokines, specifically in the brain, and may cause neurotoxicity. This summary highlights several molecular mechanisms of methylmercury-induced neurotoxicity. [ABSTRACT FROM AUTHOR]

Attenuation of the renal toxicity of cis-diamminedichloroplatinum (CDDP) is important in the use of this effective but cytotoxic anticancer agent. We have previously shown that the renal toxicity of CDDP can be efficiently reduced by the induction of metallothionein (MT) by preadministration of bismuth compounds in mice. Bismuth subnitrate (BSN) is used as an antigastric ulcer agent and as an antidiarrheic agent, and is suitable for inducing MT in the kidney in cancer patients. However, due to the low absorption rate of Bi from the gastrointestinal tract, the efficacy of BSN in inducing renal MT is low. In the present study, we examined the effects of citrate as a vehicle for oral administration of BSN on the tissue distribution of Bi and induction of MT in the kidneys and tumors in mice inoculated with Meth-A fibrosarcoma. Renal levels of MT and Bi were markedly increased in the mice given BSN dissolved in citrate solution compared with those given BSN suspended in saline. On the other hand, the use of citrate increased Bi accumulation in the tumor only slightly and did not increase tumor MT levels. Administration of BSN with citrate efficiently depressed the renal toxicity of CDDP, but did not affect its antitumor activity. Since both BSN and citrate are used clinically as pharmaceuticals, the combination regimen of BSN and citrate may be readily applicable as a countermeasure against the adverse side effects of CDDP without affecting its antitumor activity. [ABSTRACT FROM AUTHOR]

To determine whether low-dose oral administration of cadmium (Cd) induces renal toxicity, six groups of female Sprague-Dawley rats were fed a diet containing low amounts of CdCl2 or Cd-polluted rice at concentrations up to 40 ppm, and were killed after 12, 18, and 22 months (experiment 1). In addition to the determination of cortical Cd levels and histopathological assessment of kidneys, labeling indices (LIs) for proliferating cell nuclear antigen (PCNA) in the renal cortical tubular epithelium of Cd-treated rats were determined as a measure of regenerative activity. For comparison, the kidneys of rats given diets containing small to large amounts of CdCl2 up to 600 ppm for 4 months were similarly examined (experiment 2). Animals in experiment 1 demonstrated spontaneous chronic nephropathy and fluctuation in the tubular PCNA LI, but these findings were not correlated with renal Cd levels at 22 months. PCNA LI on the other hand, appeared to be linked to the severity of chronic nephropathy. In experiment 2, levels of CdCl2 of 200 ppm or more clearly induced degeneration and apoptosis of proximal tubules with high correlations between renal Cd levels, PCNA LI, and the severity of tubular degeneration. The results demonstrated that, in contrast to high-dose Cd administration, treatment with 40 ppm or less for 22 months did not influence tubular regeneration as a component of nonspecific chronic nephropathy, suggesting that long-term oral administration of low levels of Cd does not injure renal tubules in female rats. [ABSTRACT FROM AUTHOR]

To elucidate the protective role of metallothionein (MT) in the prevention of cisplatinum ( cis-DDP) toxicity, we investigated the lethal and renal toxicities caused by cis-DDP in MT-null transgenic mice in comparison with wild-type control mice, and examined the effect of pretreatment with bismuth nitrate or zinc sulfate on the cis-DDP nephrotoxicity. The MT-null mice were of mixed 129 Ola and C57BL/6 genetic background. Since no differences in cis-DDP nephrotoxicity were observed between these strains, C57BL/6J mice were used as the wild-type control. The basal MT levels in the kidneys were negligible in the MT-null mice and 2.93 ± 0.77 μg/g tissue in the C57BL/6J mice. In terms of both the lethal and renal toxicities of cis-DDP, MT-null mice were far more sensitive than C57BL/6J mice. Preinduction of renal MT synthesis by administration of bismuth nitrate or zinc sulfate protected C57BL/6J mice from cis-DDP nephrotoxicity. In the case of MT-null mice, however, renal MT could not be induced by pretreatment with these metal compounds, and renal toxicity of cis-DDP was not prevented by this pretreatment. These results suggest that MT is an important factor with the potential to suppress the development of cis-DDP toxicity. [ABSTRACT FROM AUTHOR]

The effect of selenite coadministration on the toxicity and antitumor activity of repeated treatment with high doses of cis-diamminedichloroplatinum (cis-DDP) was examined in mice. Sodium selenite was injected s.c. into separate abdominal sites of mice together with cis-DDP at a molar ratio of 1:3.5 (selenite to cis-DDP) on day 0. The same amount of selenite was given daily for 4 subsequent days (days 1-4). This fixed administration schedule was repeated weekly for a total of 7 weeks. Under the experimental conditions used, the lethal toxicity, renal toxicity [indicated by an increase in blood urea nitrogen (BUN) and plasma creatinine levels], hepatic toxicity (indicated by an increase in plasma GPT and GOT activity), and myelotoxicity (indicated by a decrease in the numbers of leukocytes and platelets) observed in mice given repeated doses of cis-DDP alone (15 or 25 mumol/kg, s.c.) were significantly depressed by the coadministration of sodium selenite. Treatment with cis-DDP alone (15, 20, or 25 mumol/kg, s.c.) resulted in some dose-dependent prolongation of the life span of mice transplanted either s.c. with colon adenocarcinoma 38 (colon 38) or i.p. with P388 leukemia (P388) but did not completely depress the tumor growth, and the animals died of either progressive disease or cis-DDP-induced toxicity. However, following the coadministration of 7.1 mumol/kg selenite with 25 mumol/kg cis-DDP, all of the mice transplanted either s.c. with colon 38 or i.p. with P388 survived for as long as 4 months after the end of the treatment and showed no evidence of malignancy. These results indicate that selenite coadministration enables the use of increasing doses of cis-DDP and, consequently, enhances the antitumor effect of cis-DDP by depressing its side effects. [ABSTRACT FROM AUTHOR]

The effects of bismuth nitrate pretreatment on the toxicity and antitumor activity of cis-diamminedichloroplatinum (cisplatin, CDDP) were examined in nude mice that had been inoculated with human bladder-tumor tissue. Pretreatment with bismuth nitrate depressed the renal toxicity of CDDP without compromising its activity against a transplantable human bladder tumor. Renal metallothionein (MT) and bismuth (Bi) levels in nude mice were markedly increased by Bi preadministration, but no significant MT induction was observed in inoculated human bladder-tumor tissue in which only a trace amount of Bi was incorporated. Furthermore, it was confirmed that tumor platinum (Pt) concentrations in CDDP-treated mice were not affected by Bi pretreatment. Thus, the administration of Bi compounds prior to chemotherapy with CDDP may provide an effective mode of treatment for advanced bladder tumors. [ABSTRACT FROM AUTHOR]

The effect of pretreatment with metallothionein (MT)-inducing metals (Zn, Cu, Bi, Co, Cd or Hg) on paraquat (PQ) toxicity was investigated in mice. PQ lethality was remarkably reduced by pretreatment with the above MT-inducing metals. The protective effect of pretreatment with these metals on PQ lethality was significantly correlated with MT levels in the lung, a target tissue of PQ toxicity, in mice administered MT-inducing metals, but not with MT in the liver or kidney. The increase in pulmonary lipid peroxidation in mice treated with PQ was significantly inhibited by Zn pretreatment. Zn was the most effective of the MT-inducing metals used in this experiment in protecting mice against PQ lethality. Of those monitored, the only pulmonary free radical scavenging factor increased by Zn pretreatment was MT. Other free radical scavenging factors (activities of Superoxide dismutase, glutathione peroxidase and catalase, and concentration of non-protein thiols level) were not influenced by Zn treatment. These results indicate that the induction of pulmonary MT protects against the lethality and lung toxicity of PQ. Pulmonary MT may scavenge free radicals produced by PQ, thereby protecting against lethal pulmonary toxicity. [ABSTRACT FROM AUTHOR]

The protective effects of metallothionein (MT) preinduction by bismuth subnitrate (BSN) against the renal toxicity of cis-diamminedichloroplatinum (cis-DDP), the cardiotoxicity of adriamycin (ADR), and the lethal and bone marrow toxicities of these drugs were observed in mice receiving cis-DDP and ADR simultaneously. Preinduction of MT biosynthesis by BSN, which is currently used as an antidiarrheal drug, did not affect the antitumor activities of the two drugs, suggesting that the beneficial effects of the preinduction of MT biosynthesis by BSN may be applicable for therapy involving cis-DDP and ADR, either alone or in combination. [ABSTRACT FROM AUTHOR]