Inhibitory effects of seven organosulphur compounds on clinical isolates of Candida species in vitro

Thirty clinical isolates of Candida albicans and 10 other Candida species were tested for susceptibility to 6 substituted dithiocarbamates and one dimercaptosuccinate. Dimethyldithiocarbamate, sodium pyrrolidine dithiocarbamate, and sodium diethyldithiocarbamate showed dose-dependent antifungal activity which was partially reversed by the addition of zinc, copper, or iron sulfate with greatest reversal at 2:1 metal to dithiocarbamate molar ratio. Anaerobiosis also interfered with dithiocarbamate antifungal activity.

Effect of chelation with meso-dimercaptosuccinic acid (DMSA) before and after the appearance of lead-induced neurotoxicity in the rat

This paper examines whether a chelating agent (DMSA) can prevent and reverse the effects of lead (Pb) as evidenced by changes in brain glial fibrillary acidic protein (GFAP) concentration and in the habituation pattern of rearing behavior. Male F344 rats (42 days old) received Pb acetate at 150 or 2000 ppm as Pb in their drinking water for 21 days and returned to regular water for another 21 days to observe recovery. Blood Pb (BPb) concentration rose to 37 and 82 microg/dl for 150 and 2000 ppm, respectively. Rats exposed to 150 ppm Pb exhibited changes in GFAP concentration and behavioral hyperactivity, when placed in an unfamiliar cage. The 2000 ppm Pb exposure caused greater changes in GFAP, but behavioral hyperactivity appeared only postexposure, when BPb was declining. Chelation (DMSA, 50 mg/kg po, 3 times/week for 21 days) decreased the BPb concentration, and prevented and reversed the Pb-induced changes in GFAP and rearing, but not in body weight. Administration of DMSA by itself for 21 days caused no untoward effects in brain GFAP, behavior, or body weight. Concurrent administration of DMSA and Pb resulted in no evidence of additive toxicity. Results indicate that: (1) A brief behavioral test of habituation is a sensitive index of neurotoxicity and chelating therapy; (2) Pb-induced hyperactivity depends upon BPb concentration regardless of whether activity is measured during or after exposure; (3) repeated treatment with DMSA is effective in reducing Pb neurotoxicity; (4) there was no evidence that DMSA enhanced the absorption of Pb. The finding that DMSA administered late in exposure can hasten the recovery of toxic signs suggests that extracellular Pb continues to play a significant role even after toxic signs have appeared.

Comparative in vivo lead mobilization of meso- and rac-2,3-dimercaptosuccinic acids in albino Wistar rats

Comparison of the racemic and meso forms of 2,3-dimercaptosuccinic acid (DMSA) in lead mobilization from lead-loaded albino Wistar rats demonstrates that the racemic form is significantly more effective in reducing femur lead levels. After four oral doses at 0.5 mmol/kg, femur lead levels were reduced to 87% of control values by meso-DMSA and to 50% of control levels by rac-DMSA. Similarly, when the dose was increased to 1.0 mmol/kg, femur lead levels were reduced to 69% of control levels by meso-DMSA and to 45% of control levels by rac-DMSA. A similar pattern was found for renal lead levels. Brain lead concentrations were significantly lower in treated groups than in control groups, but no differences were found between rac- and meso-DMSA. Rac-DMSA is more soluble than meso-DMSA in acetonitrile, ethyl acetate, and ethyl ether. The partition coefficient of rac-DMSA in the n-octanol/water system was found to be about 2.8. These results indicate that rac-DMSA deserves further attention as a possible substitute for meso-DMSA.

The effect of 2,3 dimercaptosuccinic acid in the treatment of lead poisoning in adults

Four patients, aged 22-60, belonging to a single family that had been exposed to lead-contaminated food for an unknown period, and nine workers, aged 20-65, who had been exposed to air-borne lead for 6-8 years, were evaluated for lead poisoning in our centres. Blood lead levels were 3.57 +/- 0.39 micromol/L (mean +/- SD) in the family members and 3.46 +/- 0.43 micromol/L (mean +/- SD) in the group of workers. 2,3 dimercaptosuccinic acid (DMSA) therapy was instituted in the four family members while the nine workers were closely monitored after being removed from the contaminated environment without receiving any chelation therapy. DMSA therapy given for the duration of 19 days reduced the blood lead levels to 0.63 +/- 0.44 micromol/L (mean +/- SD), P<0.01, in the four family members. No significant change was observed in the untreated group. The exposure time in the untreated group was probably longer than that in the treated group. Following long-term exposure most of the lead in the body is found in the bones and therefore not easily removed by chelation therapy. No side-effects were reported in the treated group and no rebound elevation of blood lead levels was observed during the therapy period or during the 12-week follow-up period following cessation of therapy. We conclude that 19 days of chelation therapy with DMSA in adults with moderate to severe lead poisoning is effective and safe.

Utilization of renal slices to evaluate the efficacy of chelating agents for removing mercury from the kidney

Mercury is an environmental contaminant that preferentially accumulates in the kidney. It has been previously shown using proton-induced X-ray emission analysis that mercury (HgCl2) accumulated in precision-cut rabbit renal cortical slices. In this study, the efficacy of seven chelating agents for the removal of Hg from renal slices has been examined. Rabbits were injected with HgCl2 (10 mg/kg) and 3 h later kidneys were sliced, or renal slices were exposed in vitro to a mildly toxic concentration of HgCl2 (5 x 10(-5)M, 4 h). The slices were then treated in vitro with 10 mM concentrations of EDTA, lipoic acid (LA), penicillamine (PA), glutathione (GSH), 1,4-dithiothreitol (DTT), DMSA, or DMPS. DMPS proved to be the most effective in mobilizing Hg from in vivo or in vitro HgCl2-exposed renal tissue ( > 85% of control after 3 h incubation). Relative efficacies for the seven agents were DMPS > DMSA, PA > DTT, GSH > LA, EDTA. The use of renal slices appears to be a useful in vitro tool for assessing the efficacy of chelating agents on mobilizing accumulated Hg from renal tissue.

Racemic-2,3-dimercaptosuccinic acid for inorganic mercury mobilization in rats

The efficiency of racemic-2,3-dimercaptosuccinic acid (rac-DMSA) compared with meso-2,3-dimercaptosuccinic acid (meso-DMSA) in mobilizing inorganic mercury was evaluated in female rats. Chelators were administered orally at a dose of 0.5, 1.0 or 2.0 mmol kg-1 on four consecutive days, 5 days after a single intraperitoneal 203Hg injection (with 0.5 mg HgCl2 kg-1). Both chelators reduced 203Hg retention in whole body and kidney and at higher doses also in the liver. Racemic-DMSA was more efficient at lower dose levels and equal to meso-DMSA at the highest dose level. Kidney retention decreased after rac-DMSA to 27, 10 and 10% of controls and after meso-DMSA to 68, 39 and 10% of control values at the 0.5, 1.0 and 2.0 mmol kg-1 dose level, respectively. Since meso-DMSA is already approved for human use, its stereoisomeric form, rac-DMSA, deserves further attention for treatment of mercury poisoning.

Comparative inhibition of yeast glutathione reductase by arsenicals and arsenothiols

Tri(gamma-glutamylcysteinylglycinyl)trithioarsenite (AsIII(GS)3) is formed in cells and is a more potent mixed-type inhibitor of the reduction of glutathione disulfide (GSSG) by yeast glutathione (GSH) reductase than either arsenite (AsIII) or GSH. The present work examines the effects of valence and complexation of arsenicals with GSH or L-cysteine (Cys) upon potency as competitive inhibitors of the reduction of GSH disulfide (GSSG) by yeast GSH reductase. Trivalent arsenicals were more potent inhibitors than their pentavalent analogs, and methylated trivalent arsenicals were more potent inhibitors than was inorganic trivalent As. Complexation of either inorganic trivalent As or methylarsonous diiodide (CH3As(III)I2) with Cys or GSH produced inhibitors of GSH reductase that were severalfold more potent than the parent arsenicals. In contrast, dimethylarsinous iodide ((CH3)2As(III)I) was a more potent inhibitor than its complexes with either GSH or Cys. Complexes of CH3AsIII with GSH (CH3-AsIII(GS)2) or with Cys (CH3AsIII(Cys)2) were the most potent inhibitors, with Ki's of 0.009 and 0.018 mM, respectively. Inhibition of GSH reductase by arsenicals or arsenothiols was prevented by addition of meso-2,3-dimercaptosuccinic acid (DMSA) to a mixture of enzyme, GSSG, and inhibitor before addition of NADPH. DMSA added to the reaction mixture after NADPH reversed inhibition by (CH3)2As(III)I but had little effect on inhibition by CH3As(III)I2, Ch3AsIII(GS)2, CH3AsIII(Cys)2, or AsIII(GS)3. Partial redox inactivation of the enzyme with NADPH increased the inhibitory potency of CH3As(III)I2 and (CH3)2As(III)I and changed the mode of inhibition for CH3As(III)I2 from competitive to noncompetitive. The greater potency of methylated trivalent arsenicals and arsenothiols than of inorganic trivalent As suggests that biomethylation of As could yield species that inhibit reduction of GSSG and alter the redox status of cells.

Low lead levels stunt neuronal growth in a reversible manner

The developing brain is particularly susceptible to lead toxicity; however, the cellular effects of lead on neuronal development are not well understood. The effect of exposure to nanomolar concentrations of lead on several parameters of the developing retinotectal system of frog tadpoles was tested. Lead severely reduced the area and branchtip number of retinal ganglion cell axon arborizations within the optic tectum at submicromolar concentrations. These effects of lead on neuronal growth are more dramatic and occur at lower exposure levels than previously reported. Lead exposure did not interfere with the development of retinotectal topography. The deficient neuronal growth does not appear to be secondary to impaired synaptic transmission, because concentrations of lead that stunted neuronal growth were lower than those required to block synaptic transmission. Subsequent treatment of lead-exposed animals with the chelating agent 2,3-dimercaptosuccinic acid completely reversed the effect of lead on neuronal growth. These studies indicate that impaired neuronal growth may be responsible in part for lead-induced cognitive deficits and that chelator treatment counteracts this effect.

Chelation in metal intoxication. XXXVIII: Effect of structurally different chelating agents in treatment of nickel intoxication in rat

Some structurally different chelating agents viz. alpha-mercapto-beta-(2-furyl) acrylic acid (MFA), alpha-mercapto-beta-(2-thienyl) acrylic acid (MTA), meso 2,3-dimercaptosuccinic acid (DMSA), 2,3-dimercaptopropane-1-sulfonate (DMPS), diethyl dithiocarbamate (DE-DTC), and N-benzyl-D-glucamine dithiocarbamate (NBG-DTC) were evaluated for their efficacy to mobilized nickel and reverse some nickel-induced biochemical alterations in experimental nickel intoxication. MFA, DMSA, and NBG-DTC appear more effective than their corresponding homologs, MTA, DMPS and DE-DTC, respectively, in enhancing urinary and fecal excretion of nickel and lowering tissue burden of nickel in nickel preexposed rats. These, particularly NBG-DTC, appear promising in the treatment of nickel (II) poisoning. However, there seems no definite relationship between the structure of the chelating agents examined and their ability to counteract the effects of nickel.

Assessment of the role of the glutathione and pentose phosphate pathways in the protection of primary cerebrocortical cultures from oxidative stress

Reactive oxygen species have been implicated in neuronal injury associated with various neuropathological disorders. However, little is known regarding the relationship between antioxidant enzyme capacity and resultant toxicity. The antioxidant pathways of primary cerebrocortical cultures were directly examined using a novel technique that measures pentose phosphate pathway (PPP) activity, which is enzymatically coupled to glutathione peroxidase (GPx) detoxification of hydrogen peroxide (H2O2). PPP activity was quantified from data obtained by gas chromatography/mass spectrometry analysis of released labeled lactate following metabolic degradation of [1,6-(13)C2, 6,6-(2)H2] glucose by cerebrocortical cultures. The antioxidant capacity of these cultures was systematically evaluated using H2O2, and the resultant toxicity was quantified by lactate dehydrogenase release. Exposure of primary mixed and purified astrocytic cultures to H2O2 caused stimulation of PPP activity in a concentration-dependent fashion from 0.25 to 22.2% and from 6.9 to 66.7% of glucose metabolized to lactate through the PPP, respectively. In the mixed cultures, chelation of iron before H2O2 exposure was protective and resulted in a correlation between PPP saturation and toxicity. Conversely, addition of iron, inhibition of GPx, or depletion of glutathione decreased H2O2-induced PPP stimulation and increased toxicity. These results implicate the Fenton reaction, reflect the pivotal role of GPx in H2O2 detoxification, and contribute to our understanding of the etiological role of free radicals in neuropathological conditions.

Pharmacological prevention of acute lead poisoning in Paramecium

To understand how lead (Pb2+) and other metals and chelating agents effect living cells, behavioral experiments in the marine ciliate Paramecium calkinsi were carried out. The duration of Backward Swimming Behavior (BSB) of Paramecium was partially reduced when cells were exposed to 100 microM of Ni2+, CD2+ and Co2+. In contrast, Pb2+ increased Paramecium BSB in a dose-dependent manner. Thus, 1, 10, 20, 50 and 100 microM of Pb2+ increased the duration of BSB by 20.4, 83.9, 143.2, 163.2 and 185.2%, respectively. The naphthalenesulphonamide W-7, a calcium channel blocker in lower organisms, abolished the increase of Paramecium BSB initially produced by Pb2+. Paramecium, poisoned with 10 MicroM of Pb2+, were also treated with putative Pb2+ chelating agents, such as meso-2-3-dimercaptosuccinic acid (DMSA), Ca-Na2-EDTA and ascorbic acid. These compounds inhibited the increase of the duration of BSB initially produced by Pb2+ in a dose-dependent manner. The potency of these antidotes in blocking the effects of Pb2+ was as follows: DMSA >> Ca-Na2-EDTA > ascorbic acid. These results provide evidence for a membrane-based mechanism of lead poisoning and support the use of DMSA as a lead antidote.

Acute and longer term effects of meso-2,3 dimercaptosuccinic acid (DMSA) on the behavior of lead-exposed and control mice

We investigated the effect of chelating agent meso-2,3 dimercaptosuccinic acid (DMSA) on spatial learning and forced-swim immobility in Binghamton Heterogeneous Stock (HET) mice. Forced-swim immobility (characterized by increasingly frequent bouts of complete motionlessness in a forced-swim test, i.e., behavioral despair) is reduced by exposure to lead. In Experiment 1, male and female HETs (n = 81) were assigned to lead-exposed (0.5% lead acetate ad lib in drinking fluid), pair-fed (PF), or water control groups. Six weeks after the termination of lead exposure, half of each group was injected intraperitoneally (IP) with 50 mg/kg DMSA or vehicle once per day for 5 days. Following treatment, all animals were tested for acquisition and extinction in the Morris Water maze, followed by immobility testing in an inescapable forced-swim task. Neither Pb nor DMSA affected Morris maze performance. However, consistent with previously published work, Pb reduced immobility in the forced-water swim relative to both PF and water controls. Additionally, lead-exposed males, but not females, showed sustained improvement following DMSA treatment on immobility measures. Experiment 2 was designed to demonstrate the effect of the above DMSA protocol on blood-Pb, and also examined the immediate effects of DMSA on immobility during treatment. Thus, in Experiment 2, animals were exposed to an identical Pb and DMSA treatment protocol, but the effects of DMSA on immobility during the course of DMSA treatment were measured, and animals were sacrificed immediately after treatment so that blood-Pb measures could be taken. Under these circumstances, DMSA markedly reversed the lead-induced reduction in immobility immediately during the treatment phase. Although DMSA clearly reduced blood-lead in males, its influence on female blood levels was far less. Taken together, the data from these experiments suggest that DMSA ameliorates lead-induced immobility changes in mice, but that gender may modulate DMSA's effect on blood-lead and longer-term behavioral effects. However, further work is needed to clarify the role of gender in response to DMSA.

Comparative evaluation of chelating agents on the mobilization of cadmium: a mechanistic approach

A comparative evaluation of chelating agents, namely, diethyl dithiocarbamate (DDC), dimethyl dithiocarbamate (DMDC), 1,4,8,11-tetraazacyclotetradecane (CYCLAM), 1,4,8,12-tetraazacyclopentadecane (TACPD), 2,3-dimercaptosuccinic acid (DMSA), and 2,3-dimercapto-1-propane sulfonate (DMPS) was conducted to assess their efficacy against acute cadmium (Cd) toxicity. DMSA and DMPS appeared to be most effective in reducing mortality as well as Cd burden of liver, kidneys, and brain in cadmium intoxicated mice. DMDC reduced Cd levels only in liver and kidneys, while DDC significantly enhanced its level in brain. CYCLAM and TACPD significantly increased the Cd level in liver and kidneys and were ineffective in brain. The therapeutic index as well as therapeutic efficacy was highest for DMSA followed by DMPS and DMDC. A fair degree of correlation was found to exist between (1) stability constant of Cd chelates and percent survival (r = .438, (2) stability constant and percent transport (r = .479), and (3) percent survival and percent transport (r =.447). However, the lipophilicity did not show any appreciable correlation with percent survival and stability constant of Cd chelates.

Evaluation of dithiol chelating agents as potential adjuvants for anti-IL-2 receptor lead or bismuth alpha radioimmunotherapy

The dithiol chelating agents 2,3-dimercapto-1-propanesulfonic acid (DMPS) and meso-2,3-dimercaptosuccinic acid (DMSA) were evaluated for use as potential adjuvants to reduce or prevent radiotoxicity in anti-interleukin-2 receptor (IL-2R) Lead-212 or Bismuth-212 alpha-radioimmunotherapy. DMPS was less toxic than DMSA to tumor cell lines in culture. No adverse effects on the ability of an anti-IL-2R monoclonal antibody (MAb) to bind to its specific antigen were detected using DMPS or DMSA at concentrations up to 600 ug/mL in 10% or 100% mouse serum. After a 5-day oral administration of chelating agent, neither acute nor chronic toxicities on blood hematology, blood chemistry or organ weights were observed for treated mice. DMPS and DMSA were effective in accelerating whole body clearance of the gamma-emitting tracer Bismuth-206. Both chelates significantly reduced femur uptake of tracer when compared to nontreated control mice. However, only DMPS prevented early (2 h postinjection) renal accumulation. These studies support the use of DMPS as a potential adjuvant chelation therapy in Lead-212 or Bismuth-212 radioimmunotherapy protocols.

Hydrogen peroxide in relation to proliferation and apoptosis in BHK-21 hamster fibroblasts

Addition of H2O2 at 100 microM, or 1 mM, to the culture medium of BHK-21 fibroblasts results in increased intracellular levels of H2O2. Whilst exposure of BHK-21 cells to lower levels of H2O2 (1 microM) actually stimulates proliferation, these higher oxidant concentrations not only depress proliferation rates but also lead to an increase in the appearance of apoptotic-like cells in the cultures. Other agents such as inhibitors of glutathione peroxidase and catalase, or mimics of superoxide dismutase, which also bring about elevated cellular levels of H2O2 in BHK-21 cells, similarly lead to decreased proliferation and an apparent increase in cells with apoptopic features. Thus intracellular conditions which are considered more prooxidant than normal, appear to favour apoptosis over proliferation in BHK-21 fibroblasts. Additionally these abnormal cellular conditions also appear to favour excessive DNA replication, in remaining non-apoptotic cells.

In vivo studies of cadmium-induced apoptosis in testicular tissue of the rat and its modulation by a chelating agent

In vivo CdCl2-induced apoptotic DNA fragmentation in the testes of the male Wistar rat has been demonstrated on agarose gel. Characteristic DNA migration patterns (laddering) provide evidence of apoptosis (programmed cell death) in testicular tissue of rats administered CdCl2 at a level of 0.03 mmol/kg 48 h previously. Evidence that administration of an appropriate cadmium chelating agent within the first 24 h can suppress some or all of the apoptotic changes in testicular DNA has also been obtained for the first time. A greater reduction in apoptosis is observed as the interval between the administration of the cadmium and that of the chelating agent is shortened. Administration of monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) to male Wistar rats given CdCl2 is effective in the modulation of the typically apoptotic DNA fragmentation and associated histopathologic injury when the antagonist is given within approximately 1 h after the CdCl2 exposure. When the antagonist is given at later times there is a progressively more pronounced degradation of the DNA into oligonucleotides as seen in the typical electrophoretic DNA ladder pattern found with apoptosis. There is also a progressive increase in histopathological tissue changes as the antagonist is administered at progressively greater intervals after the cadmium.

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.

In vivo indices of oxidative stress in lead-exposed C57BL/6 mice are reduced by treatment with meso-2,3-dimercaptosuccinic acid or N-acetylcysteine

Knowledge of lead's capacity to disrupt the prooxidant/antioxidant balance within mammalian tissues suggests that definitive therapy for chronic lead poisoning should encompass both chelating and antioxidant actions. The dithiol meso-2,3-Dimercaptosuccinic Acid (DMSA) is the first orally administered metal chelating agent to receive U.S. Food and Drug Administration (FDA) approval for the treatment of childhood plumbism and possesses the potential to function as an antioxidant by removing lead from the site of deleterious oxidation reactions. Five weeks of lead exposure was found to deplete glutathione (GSH) levels, increase oxidized glutathione (GSSG), and promote malondialdehyde (MDA) production in both liver and brain samples taken from C57BL/6 mice. GSH levels increased and GSSG and MDA levels decreased in groups of lead-exposed mice that received 1 mmol/kg DMSA or 5.5 mmol/kg N-acetylcysteine (NAC) for 7 d prior to sacrifice. Treatment with DMSA caused a reduction in blood, liver, and brain lead levels consistent with its function as a chelating agent, while treatment with NAC did not reduce these lead levels. However, NAC did cause a reduction in indices of oxidative stress in both brain and liver samples, which implies that this synthetic thiol-containing antioxidant is capable of abrogating lead-induced oxidative stress in vivo. Overall, these results suggest that lead-induced oxidative stress in vivo can be mitigated by pharmacologic interventions, which encompass both chelating as well as thiol-mediated antioxidant functions.

Effects of chelating agents on testicular toxicity in mice caused by acute exposure to nickel

N-Benzyl-D-glucaminedithiocarbamate (BGD), diethyldithiocarbamate (DDTC), dihydroxyethyldithiocarbamate (DHED), trans-1,2-cyclohexanediamine N,N,N',N'-tetraacetic acid (CDTA), and meso-2,3-dimercaptosuccinic acid (DMSA) were studied for their protective effects against the testicular toxicity in mice induced by acute exposure to nickel (Ni). Mice were injected intraperitoneally with NiCl2 (5 mgNi/kg) and 30 min or 24 h later, they were injected intraperitoneally with chelating agents (400 mumol/kg). Ni injection increased lipid peroxidation and concentrations of Ca and Fe in the testes, liver, and kidney, and decreased the testicular weight and the fertility rate. At 30 min after Ni treatment, the chelating agents other than CDTA effectively depressed Ni concentration in the testes. At 24 h after Ni treatment, DMSA, BGD, and DDTC were effective in mobilizing Ni from the testes. DMSA, BGD, and CDTA significantly prevented the increase in the lipid peroxidation, the increase in the concentrations of Ca and Fe in the testes, liver, and kidney, and the decrease in the fertility rate caused by Ni injection. Treatment with DMSA or BGD was more effective than that with the others in decreasing the testicular Ni concentration, resulting in effective protection against Ni-induced testicular damage.

Prolonged oral treatment with two monoesters of meso-2,3-dimercaptosuccinic acid for depleting inorganic mercury retention in suckling rats

Two monoesters of meso-2,3-dimercaptosuccinic acid (DMSA), monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) and mono-n-hexyl meso-2,3-dimercaptosuccinate (Mn-HDMS) were compared to DMSA in their efficiency to mobilize 203Hg in mercury-laden suckling rats. Seven-day-old pups were given 203Hg (18.5 kBq) with a dose of 0.5 mg Hg/kg/day as HgCl2 for five days. Seven days after the beginning of Hg loading a ten-day oral treatment with DMSA, Mi-ADMS, or Mn-HDMS was administered at a dose of 0.25 mmol/kg/day. At the end of experiment, radioactivity was measured in the whole body, liver, both kidneys, and brain. Monoesters of DMSA were superior to DMSA in decreasing body and organ Hg retention. The highest reduction in comparison to controls in groups treated with DMSA, Mi-ADMS, or Mn-HDMS occurred in the kidneys (48%, 97%, and 96%), followed by reduction in the liver (24%, 84%, and 83%), and in the brain (8%, 23%, and 23%, respectively). For both, Mi-ADMS and Mn-HDMS, the reductions in the whole body and organs were significantly greater than in controls or DMSA-treated rats. No difference between the efficiency of the two DMSA-monoesters was found.

Reversal of oxophenylarsine-induced inhibition of glucose uptake in MDCK cells

It has been shown that oxophenylarsine (PhAsO) inhibits glucose uptake in MDCK cells. In addition to the known impairment of cellular energy metabolism, this inhibition may contribute to the acute toxicity of trivalent organic arsenicals. We have investigated the effect of BAL, DMPS, DMSA, and other sulfur compounds on cellular incorporation of [U-14C]PhAsO and their efficacy to revert PhAsO-induced inhibition of glucose uptake. In the presence of [U-14C]PhAsO (2 microM), the radiolabel was steadily accumulated by the cells over 150 min without any signs of severe cell damage (e.g., altered morphology, increased LDH release). A notable decrease of cellular ATP was only observed at 150 min, whereas within 30 min uptake of D-[6-(14)C]glucose was reduced to 40% of controls. When BAL, DMPS, or DMSA was added after 30 min, the inhibition of glucose uptake was reversed, accompanied by a decrease in cell-associated radiolabel from [U-14C]-PhAsO. Water-soluble DMPS and DMSA required longer times than BAL for comparable effects. 2,3-Bis(acetylthio)propanesulfonamide, a thioester derivative, and dithiothreitol, a 1,4-dithiol, were effective only with the highest concentration tested (200 microM). 2-Mercaptoethanol neither reversed inhibition of glucose uptake nor influenced [U-14C]PhAsO incorporation. Our results show that inhibition of glucose uptake is a very early event in PhAsO cytotoxicity which occurs before any decrease of cellular energy metabolism and/or full cellular loading with arsenic comes into effect. The more rapid onset of action of lipophilic BAL compared to PhAsO action.

Oral dimercaptosuccinic acid and ongoing exposure to lead: effects on heme synthesis and lead distribution in a rat model

Lead (Pb) exposure and subsequent toxicity continues to be a significant problem in the United States. Treatment with meso-2,3-dimercaptosuccinic acid (DMSA) has been reported to be effective in reducing the body's Pb burden, with fewer adverse side effects than other chelating agents. The oral availability and relative safety of DMSA presents the controversial option of treating patients with Pb poisoning on an outpatient basis. Despite recommendations that children be removed from the Pb contaminated environment, some children will inevitably be exposed to environmental Pb while receiving oral DMSA therapy. The study hypothesized that oral DMSA chelation therapy is beneficial even when faced with continued dietary Pb. Sprague-Dawley rats were exposed to Pb in water for 35 days and then placed in various treatment groups, including groups administered oral DMSA with and without concurrent Pb exposure. The concentration of Pb in blood and critical organs and Pb diuresis were measured. The effect of Pb on heme synthesis was determined by assaying the urinary delta-aminolevulinic acid (delta-ALA), and blood zinc protoporphyrin (ZPP). DMSA reversed the hematological effects of Pb, decreased the blood, brain, bone, kidney, and liver Pb concentration, and produced a marked Pb diuresis, even when challenged with ongoing Pb exposure. In conclusion, even though DMSA treatment without exposure to Pb is optimal, oral DMSA could be beneficial even when challenged with ongoing Pb exposure.

Effect of monoisoamyl meso-2,3-dimercaptosuccinate on the pathology of acute cadmium intoxication

The ability of monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) to offset the characteristic organ pathology of intraperitoneally administered cadmium chloride (CdCl2) and that of the cadmium-cysteine complex has been examined in male Wistar rats. The tissues examined for damage were the testes, kidney, liver, pancreas, and bone marrow. At a high dose of CdCl2 (0.03 mmol/kg, ip) testicular damage was completely prevented by Mi-ADMS (0.50 mmol/kg, ip) given immediately. A decrease in the protective ability of the antagonist was observed following delayed administration of Mi-ADMS given at 1, 2, 4, and 24 h post CdCl2. At a lower dose of CdCl2 (0.006 mmol/kg, ip), Mi-ADMS furnished essentially full protection from testicular damage when given (0.50 mmol/kg, sc) at 0 and 1 h after CdCl2. The administration of cadmium-cysteine complex (0.01 mmol/kg, ip) induced notable renal tubular damage, which was antagonized by the administration of Mi-ADMS (0.50 mmol/kg, ip) as late as 4 h after the complex. At a 24-h delay, extensive tubular necrosis was found on sacrifice after 4 d. The administration of cadmium-cysteine complex ip reduced, but did not eliminate, the characteristic damage of the seminiferous tubules found for cadmium alone. There is a progressive reduction of testicular weight as the interval between cadmium and antagonist administration increases. The average kidney weights of the animals given CdCl2-cysteine complex were increased in comparison to normal controls. The antagonistic effects of Mi-ADMS treatment on cadmium intoxication in the kidneys and the testes of rats is very similar to that found for effective dithiocarbamate antagonists. In order to obtain complete protection of the testes from the deteterious effects of cadmium, such antagonists must be administered no later than about 1 h after the cadmium.

Combined therapeutic potential of meso-2,3-dimercaptosuccinic acid and calcium disodium edetate on the mobilization and distribution of lead in experimental lead intoxication in rats

Asymptomatic lead poisoning remains a serious public health problem in developed and developing countries. Chelation therapy particularly with calcium disodium ethelenediamine tetracetic acid (CaNa2EDTA) is often used therapeutically to reduce the body burden of lead. This chelating drug has serious side effects and drawbacks primarily related to redistribution of lead, nephrotoxicity, and essential metal depletion. The present study was planned to determine the effectiveness of CaNa2EDTA and meso-2,3-dimercaptosuccinic acid (DMSA) used in combination. Both drugs, when administered individually, resulted in significant urinary excretion of lead and lowered the tissue lead burden. Combined treatment with CaNa2EDTA and DMSA elicits an additive response in promoting urinary lead elimination, depleting body lead burden, and restoring altered lead-sensitive biochemical variables. Further, no redistribution of lead to brain or any other soft organ following combined DMSA-CaNa2EDTA treatment was observed indicating a definite advantage of combined therapy over the conventional treatment with CaNa2EDTA or DMSA alone. However, an elevation of serum transaminase activity, creatinine level, and depletion of blood zinc level may limit the usefulness of this combined treatment.