Effects of meso-2,3-dimercaptosuccinic acid (DMSA) on methyl mercury-induced teratogenesis in mice

Effects of in utero meso-2,3-dimercaptosuccinic acid with calcium and ascorbic acid on lead-induced fetal development

To examine the effects of meso-2,3-dimercaptosuccinic acid (DMSA) on developmental toxicity resulting from exposure to lead in utero, female albino mice were exposed to lead by drinking water contaminated with lead acetate for 4 weeks. After the cessation of lead exposure, female mice were supplemented by gavage with saline solution, DMSA, or DMSA and calcium as well as ascorbic acid from the fourth day of gestation until parturition, respectively. Lead levels (blood, liver, and bone) were measured at birth. Pups were then tested about neural development including surface righting reflex, cliff avoidance and air righting reflex. The markers of physical maturation, such as body weight, pinna unfolding, incisor eruption, and eye opening were also recorded. DMSA treatment decreased blood lead levels of pregnant mice, however, increased lead levels in both liver and bone of fetus, and delayed the early physical and neural development of offspring. Calcium and ascorbic acid reduced the transfer of lead to fetus. In conclusion, DMSA treatment during pregnancy enhances lead-induced fetal developmental toxicity.

Developmental toxicity of metal chelating agents

Chelation therapy is the basis for the treatment of metal poisoning. A number of chelating agents have been widely used since the 1950s. Since these agents can be potentially given to a metal-intoxicated pregnant woman, their intrinsic developmental toxicities are a matter of concern. While the embryo/fetal toxic effects of some chelators have been reported to occur at doses higher than those currently given in the medical treatment of metal poisoning, according to experimental data the potential use of other metal antidotes is controversial. In those cases, the benefits and risks of usage should be carefully weighed. The developmental toxicity of known chelators of clinical interest is presented here. Chelating agents were divided according to the following structurally related categories: polyaminocarboxylic acids, chelators with vicinal -SH groups, beta-mercapto-alpha-aminoacids, hydroxamic acids, ortho-hydroxycarboxylic acids, and miscellaneous agents. Since it has been demonstrated that the teratogenic potential of most chelators is, at least in part, due to induced trace element deficiencies, the advisability of mineral supplements during chelation treatment is also discussed.

Assessment of the protective activity of monisoamyl meso-2,3-dimercaptosuccinate against methylmercury-induced maternal and embryo/fetal toxicity in mice

The protective activity of monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS), a new monoester of 2,3-dimercaptosuccinic acid (DMSA), on methylmercury-induced maternal and developmental toxicity was assessed in mice. A series of four Mi-ADMS injections was given s.c. at 0.25, 6, 24, and 48 h after oral administration of 25 mg/kg of methylmercury chloride (MMC) given on day 10 of gestation. Mi-ADMS effectiveness was tested at 0, 23.8, 47.6 and 95 mg/kg. Cesarean sections were performed on gestation day 18. All live fetuses were examined for external, internal, and skeletal abnormalities. Oral MMC administration resulted in an increase in the number of resorptions, and a decrease in fetal body weight, whereas the incidence of cleft palate, micrognathia, and skeletal variations was also increased in the fetuses of the MMC-treated groups. Although significant amelioration of MMC-induced embryolethality by Mi-ADMS was not noted at any dose, MMC-induced fetotoxicity was reduced by administration of this agent at 23.8, 47.6, and 95 mg/kg. However, the intrinsic toxicity of Mi-ADMS would be a restrictive factor for the possible therapeutic use of this chelator in pregnant women exposed to organic mercury.

Effects of maternal stress on methylmercury-induced developmental toxicity in mice

The developmental toxicity of combined exposure to maternal restraint stress and methylmercury chloride (MMC) was assessed in Swiss mice. On day 10 of gestation, four groups of plug-positive female mice were treated (p.o.) with a single dose of 12.5 or 25 mg MMC/kg. Immediately after MMC exposure, two of those groups were subjected to restraint for 14 hr. Control groups included restrained and unrestrained pregnant mice nonexposed to MMC. Combined exposure to 25 mg MMC/kg and restraint enhanced MMC-induced maternal toxicity, which included deaths and decreased body weight gain and food consumption. The number of nonviable implants was also increased significantly following concurrent exposure to MMC (25 mg/kg) and restraint, with the percentage of postimplantation loss increased from 64% (MMC alone) to 100% (MMC plus restraint). However, the types and incidence of internal and skeletal anomalies observed after administration of 12.5 mg MMC/kg were not increased by maternal restraint. These results suggest that maternal stress would enhance the MMC-induced maternal and embryo/fetal toxicity at doses of MMC that are highly toxic to the dams, whereas at doses that are less acutely toxic the role of maternal stress would not be significant.

Prevention by chelating agents of metal-induced developmental toxicity

Chelating agents such as calcium disodium ethylenediaminetetraacetate (EDTA), 2,3-dimercaptopropanol (BAL), or D-penicillamine (D-PA) have been widely used for the past 4 decades as antidotes for the treatment of acute and chronic metal poisoning. In recent years, meso-2,3-dimercaptosuccinic acid (DMSA), sodium 2,3-dimercapto-1-propanesulfonate (DMPS) and sodium 4,5-dihydroxybenzene-1,3-disulfonate (Tiron) have also shown to be effective to prevent against toxicity induced by a number of heavy metals. The purpose of the present article was to review the protective activity of various chelating agents against the embryotoxic and teratogenic effects of well-known developmental toxicants (arsenic, cadmium, lead, mercury, uranium, and vanadium). DMSA and DMPS were found to be effective in alleviating arsenate- and arsenite-induced teratogenesis, whereas BAL afforded only some protection against arsenic-induced embryo/fetal toxicity. Also, DMSA, DMPS, and Tiopronin were effective in ameliorating methyl mercury-induced developmental toxicity. Although the embryotoxic and teratogenic effects of vanadate were significantly reduced by Tiron, no significant amelioration of uranium-induced embryotoxicity was observed after treatment with this chelator.

Metal-induced developmental toxicity in mammals: a review

It is well established that certain metals are toxic to embryonic and fetal tissues and can induce teratogenicity in mammals. The main objective of this paper has been to summarize the toxic effects that excesses of certain metals may cause on mammalian development. The reviewed elements have been divided into four groups: (a) metals of greatest toxicological significance (arsenic, cadmium, lead, mercury, and uranium) that are wide-spread in the human environment, (b) essential trace metals (chromium, cobalt, manganese, selenium, and zinc), (c) other metals with evident biological interest (nickel and vanadium), and (d) metals of pharmacological interest (aluminum, gallium, and lithium). A summary of the therapeutic use of chelating agents in the prevention of metal-induced developmental toxicity has also been included. meso-2,3-Dimercaptosuccinic acid (DMSA) and sodium 2,3-dimercaptopropane-1-sulfonate (DMPS) have been reported to be effective in alleviating arsenic- and mercury-induced teratogenesis, whereas sodium 4,5-dihydroxybenzene-1,3-disulfonate (Tiron) would protect against vanadium- and uranium-induced developmental toxicity.

Evaluation of the protective activity of 2,3-dimercaptopropanol and sodium 2,3-dimercaptopropane-1-sulfonate on methylmercury-induced developmental toxicity in mice

The embryotoxic and teratogenic effects of methylmercury in experimental animals have been established by several investigators. The protective activity of 2,3-dimercaptopropanol (BAL) and sodium 2,3-dimercaptopropane-1-sulfonate (DMPS, a chelator used in the treatment of inorganic and organic mercury) on methylmercury chloride (MMC)-induced maternal and developmental toxicity in mice has been evaluated in the present study. BAL and DMPS were administered subcutaneously or by gavage to pregnant mice immediately after a single oral administration of 30 mg MMC/kg given on day 10 of gestation and at 24, 48, and 72 h thereafter. Amelioration by BAL and DMPS of MMC embryo/fetotoxicity was assessed at 15, 30, and 60 mg/kg/day and at 90, 180, and 350 mg/kg/day, respectively. Treatment with BAL did not ameliorate the maternal toxicity or the developmental toxicity of MMC observed in the mouse. In contrast, DMPS at 90, 180, and 360 mg/kg/day significantly reduced the maternal lethality of MMC, whereas treatment with 180 and 360 mg DMPS/kg/day showed significant protective activity against MMC-induced embryotoxicity and teratogenicity. Based on the present findings, DMPS might be a useful chelator against the maternal and developmental toxicity induced by methylmercury.