Chemistry, Pharmacology, and Toxicology of Monoisoamyl Dimercaptosuccinic Acid: A Chelating Agent for Chronic Metal Poisoning.

Arsenic, a metalloid, is known to cause deleterious effects in various body organs, particularly the liver, urinary bladder, and brain, and these effects are primarily mediated through oxidative stress. Chelation therapy has been considered one of the promising medical treatments for arsenic poisoning. Meso 2,3- dimercaptosuccinic acid (DMSA) has been recognized as one of the most effective chelating drugs to treat arsenic poisoning. However, the drug is compromised with a number of shortcomings, including the inability to treat chronic arsenic poisoning due to its extracellular distribution. Monoisoamyl 2,3-dimercaptosuccinic acid, one of the analogues of meso 2,3-dimeraptosuccinic acid (DMSA), is a lipophilic chelator and has shown promise to be considered as a potential future chelating agent/antidote not only for arsenic but also for a few other heavy metals like lead, mercury, cadmium, and gallium arsenide. The results from numerous studies carried out in the recent past, mainly from our group, strongly support the clinical application of MiADMSA. This review paper summarizes most of the scientific details including the chemistry, pharmacology, and safety profile of MiADMSA. The efficacy of MiADMSA mainly against arsenic toxicity but also a few other heavy metals was also discussed. We also reviewed a few other strategies in order to achieve the optimum effects of MiADMSA, like combination therapy using two chelating agents or coadministration of a natural and synthetic antioxidant (including phytomedicine) along with MiADMSA for treatment of metal/metalloid poisoning. We also briefly discussed the use of nanotechnology (nano form of MiADMSA i.e. nano-MiADMSA) and compared it with bulk MiADMSA. All these strategies have been shown to be beneficial in getting more pronounced therapeutic efficacy of MiADMSA, as an adjuvant or as a complementary agent, by significantly increasing the chelating efficacy of MiADMSA.

Interaction study of monoisoamyl dimercaptosuccinic acid with bovine serum albumin using biophysical and molecular docking approaches.

Monoisoamyl 2,3-dimercaptosuccinic acid (MiADMSA), a lipophilic chelator has been evaluated for its potential use as an antidote in arsenic poisoning. The pharmacokinetics and pharmacodynamics properties of a drug could be understood via study its mechanism of interaction with bovine serum albumin protein (BSA). Therefore, the interaction between MiADMSA with BSA was investigated using various spectroscopic techniques and computational methods. Linear quenching of BSA intrinsic fluorescence intensity with the increasing concentration of MiADMSA was observed in the fluorescence study. Furthermore, synchronous results revealed that MiADMSA slightly changed the conformation of BSA. The binding constant value of the BSA-MiADMSA complex was found 1.60 × 104 M-1 at 298 K. The value of thermodynamic parameters ΔG, ΔH, and ΔS described that the process is spontaneous, endothermic, and hydrophobic forces are involved in the interaction of MiADMSA with BSA. Competitive site marker experiments showed that MiADMSA binds to site-II of BSA. Conformational changes of BSA with the interaction of MiADMSA were apparent by CD, UV-Visible, FT-IR, and 3D fluorescence spectroscopy. To strengthen the experimental findings we have also performed a theoretical study on the BSA-MiADMSA complex. Two sites were identified with docking score of - 6.642 kcal/mol at site IIa and - 3.80 kcal/mol for site IIb via molecular docking study. Molecular dynamics simulation study inferred the stability of the BSA-MiADMSA complex which was analyzed in a long simulation run. The experimental and computational studies have shown the effective binding of MiADMSA with BSA which is essential for the transportation and elimination of a drug from the body.

Comparative efficacy of Nano and Bulk Monoisoamyl DMSA against arsenic-induced neurotoxicity in rats.

Chelation therapy is considered as a safe and effective strategy to combat metal poisoning. Arsenic is known to cause neurological dysfunctions such as impaired memory, encephalopathy, and peripheral neuropathy as it easily crosses the blood-brain barrier. Oxidative stress is one of the mechanisms suggested for arsenic-induced neurotoxicity. We prepared Solid Lipid nanoparticles loaded with Monoisoamyl 2, 3-dimercaptosuccinic acid (Nano-MiADMSA), and compared their efficacy with bulk MiADMSA for treating arsenic-induced neurological and other biochemical effects. Solid lipid nanoparticles entrapping MiADMSA were synthesized and particle characterization was carried out by transmission electron microscopy (TEM) and dynamic light scattering (DLS). An in vivo study was planned to investigate the therapeutic efficacy of MiADMSA-encapsulated solid lipid nanoparticles (Nano-MiADMSA; 50 mg/kg orally for 5 days) and compared it with bulk MiADMSA against sodium meta-arsenite exposed rats (25 ppm in drinking water, for 12 weeks) in male rats. The results suggested the size of Nano-MiADMSA was between 100-120 nm ranges. We noted enhanced chelating properties of Nano-MiADMSA compared with bulk MiADMSA as evident by the reversal of oxidative stress variables like blood δ-aminolevulinic acid dehydratase (δ-ALAD), Reactive Oxygen Species (ROS), Catalase activity, Superoxide Dismutase (SOD), Thiobarbituric Acid Reactive Substances (TBARS), Reduced Glutathione (GSH) and Oxidized Glutathione (GSSG), Glutathione Peroxidase (GPx), Glutathione-S-transferase (GST) and efficient removal of arsenic from the blood and tissues. Recoveries in neurobehavioral parameters further confirmed nano-MiADMSA to be more effective than bulk MiADMSA. We conclude that treatment with Nano-MiADMSA is a better therapeutic strategy than bulk MiADMSA in reducing the effects of arsenic-induced oxidative stress and associated neurobehavioral changes.

Monoisoamyl DMSA reduced copper-induced neurotoxicity by lowering 8-OHdG level, amyloid beta and Tau protein expressions in Sprague-Dawley rats.

INTRODUCTION: copper dyshomeostasis has long been linked with several neurodegenerative disorders. The binding of Cu with amyloid beta and other neuronal proteins in the brain leads to the generation of oxidative stress, which eventually causes neurotoxicity. METHOD: the present study was aimed at elucidating the efficacy of monoisoamyl 2,3-dimercaptosuccinic acid (MiADMSA) and d-penicillamine (DPA) (0.3 mEq kg-1, oral administration for 2 weeks) against Cu(ii)-induced (20 mg kg-1, oral administration for 16 weeks) neurotoxicity in Sprague-Dawley (SD) rats. RESULTS: we observed that the MiADMSA treatment modulated the altered oxidative and nitrosative stress parameters, antioxidant enzymes, and acetylcholinesterase (AChE) activity. Significant improvements were noticed in the neurobehavioral parameters except for the memory parameter. We also observed moderate improvement of memory impairment in the rats treated with MiADMSA and DPA post Cu(ii) exposure, as assessed by a passive avoidance test. Disease progression involves multiple factors and results in the up-regulation of intra and extracellular proteins such as amyloid beta and tau proteins; the expressions of these proteins were significantly reduced by the treatment proposed in our study, and these results were confirmed by ELISA and qRT-PCR. The expression of caspase-3 was higher in Cu(ii)-exposed rats, whereas it was lower in the MiADMSA-treated group. The proposed treatment reduced the copper-induced histological changes in the cortex and hippocampus regions of the brain. CONCLUSION: it can be summarised from the present study that MiADMSA is effective in reducing Cu(ii)-induced oxido-nitrosative stress, antioxidant defense enzymes, neurobehavioral changes, neuronal markers, apoptotic markers, and their genetic expressions. We conclude that chelation therapy using MiADMSA might be a promising approach for the treatment of copper-induced neurotoxicity.

MiADMSA ameliorate arsenic induced urinary bladder carcinogenesis in vivo and in vitro.

BACKGROUND AND PURPOSE: Arsenicosis is a major threat to public health and is a major cause of the development of urinary bladder cancer. Oxidative/ nitrosative stress is one of the key factors for these effects but the involvement of other associated factors is less known. There is a lack of data for the efficacy of chelator against urinary bladder carcinogenesis. The present study demonstrates the early signs of arsenic exposed urinary bladder carcinogenesis and its attenuation by Monoisoamyl dimercaptosuccinic acid (MiADMSA). METHODS: Male rats were exposed to 50 ppm of sodium arsenite and dimethylarsinic acid (DMA) via drinking water for 18 weeks and treated with MiADMSA (50 mg/kg, orally once daily for 5 days) for 3 weeks with a gap one week between the two courses of treatments. We compared in vivo data with in vitro by co-exposing 100 nM of sodium arsenite and DMA to rat (NBT-II) as well as human transitional epithelial carcinoma (T-24) cells with 100 nM of MiADMSA. RESULTS: The data showed that sodium arsenite and DMA exposure significantly increased the tissue arsenic contents, ROS, TBARS levels, catalase, SOD activities and significantly decreased GSH level which might be responsible for an increased 8-OHdG level. These changes might have increased pro-oncogenic biomarkers like MMP-9 and survivin in serum, bladder tissues, NBT-II, and T-24 cells. High cell migration and clonogenic potential in NBT-II and T-24 cells exposed to arsenic suggest pronounced carcinogenic potential. Significant recovery in these biomarkers was noted on treatment with MiADMSA. CONCLUSION: Early signs of urinary bladder carcinogenesis were observed in arsenic and DMA exposed rats which were linked to metal accumulation, oxidative/ nitrosative stress, 8-OHdG, MMP-9 and survivin which were reduced by MiADMSA possibly via its efficient chelation abilities in vivo and in vitro.

Effects of combined arsenic and lead exposure on the brain monoaminergic system and behavioral functions in rats: Reversal effect of MiADMSA.

In this study, we evaluated the therapeutic efficacy of monoisoamyldimercaptosuccinic acid (MiADMSA) against individual and combined effects of arsenic (As) and lead (Pb) on the monoaminergic system and behavioral functions in rats. Pregnant rats were exposed to sodium metaarsenite (50 ppm) and lead acetate (0.2%) individually and in combination (As = 25 ppm + Pb = 0.1%) via drinking water from gestation day (GD) 6 to postnatal day (PND) 21. MiADMSA (50 mg/kg body weight) was given orally through gavage for 3 consecutive days to pups from PND 18 to PND 20. The results showed increases in synaptosomal epinephrine, dopamine, and norepinephrine levels with individual metal exposures and decreases with combined exposure to As and Pb in the cortex, cerebellum, and hippocampus in PND 21, PND 28, and 3 months age-group rats. We found decreased activity of mitochondrial monoamine oxidase in the selected brain regions following individual and combined exposures to Pb and As. In addition, rats treated with Pb and As alone or in combination showed significant deficits in open-field behavior, grip strength, locomotor activity, and exploratory behavior at PND 28 and 3 months of age. However, MiADMSA administration showed reversal effects against the As- and/or Pb-induced impairments in the monoaminergic system as well as in behavioral functions of rats. Our data demonstrated that the mixture of Pb and As induced synergistic toxicity to developing brain leading to impairments in neurobehavioral functions and also suggest therapeutic efficacy of MiADMSA against Pb- and/or As-induced developmental neurotoxicity.

Combinatorial drug delivery strategy employing nano-curcumin and nano-MiADMSA for the treatment of arsenic intoxication in mouse.

Chelation therapy is the mainstream treatment for heavy metal poisoning. Apart from this, therapy using antioxidant/herbal extracts are the other strategies now commonly being tried for the treatment. We have previously reported individual beneficial efficacy of nanoparticle mediated administration of an antioxidant like 'curcumin' and an arsenic chelator 'monoisoamyl 2,3-dimercaptosuccinic acid (MiADMSA)' for the treatment of arsenic toxicity compared to bulk drugs. The present paper investigates our hypothesis that a combination drug delivery therapy employing two nanosystems, a chelator and a strong antioxidant, may produce more pronounced therapeutic effects compared to individual effects in the treatment of arsenic toxicity. An in-vivo study was conducted wherein arsenic as sodium arsenite (100 ppm) was administered in drinking water for 5 months to Swiss albino mice. This was followed by a treatment protocol comprising of curcumin encapsulated chitosan nanoparticles (nano-curcumin, 15 mg/kg, orally for 1 month) either alone or in combination with MiADMSA encapsulated polymeric nanoparticles (nano-MiADMSA, 50 mg/kg for last 5 days) to evaluate the therapeutic potential of the combination treatment. Our results demonstrated that co-treatment with nano-curcumin and nano-MiADMSA provided beneficial effects in a synergistic way on the adverse changes in oxidative stress parameters and metal status induced by arsenic.

Chemoprotective effect of monoisoamyl 2, 3-dimercaptosuccinate (MiADMS) on cytokines expression in cadmium chloride treated human lung cells.

Cadmium is commercially profitable element, but it causes toxicity in humans and animals leading to diseases in various organs. The main route of cadmium exposure to humans is through inhalation. Lungs respond to insult through secretion of cytokines. In this study, the chemoprotective effect of monoisoamyl 2, 3-dimercaptosuccinate (MiADMS) was evaluated on viability and cytokines expression in CdCl2 treated human lung A549 cells by cytokine array. Cells were treated with 0, 50, 75, and 100 µM CdCl2 alone, 300 µM MiADMS alone, and co-treated with 300 µM MiADMS and 75 µM CdCl2 for 24 h. The viability was measured by crystal violet dye. The level of cytokines in the cells' lysate and cell culture medium was measured using Ray Biotech's Human Cytokine Array 6 in control cells, 75 µM CdCl2 alone and MiADMS co-treated cells. Array results were validated by ELISA kit. The CdCl2 caused a dose dependent decrease in cell viability, while MiADMS co-treatment resulted in a significant increase in viability of CdCl2 treated cells. Morphology of the cells treated with CdCl2 was destroyed, while MiADMS restored the lost shape in CdCl2 treated cells. In addition, the cells co-treated with MiADMS and CdCl2 showed modulation of cytokines expression in comparison to the CdCl2 alone treated cells. The ELISA results showed the similar pattern of cytokine expression as Human Cytokine Array and validated the array results. These results clearly show the chemoprotective effect of MiADMS and suggest that MiADMS can be used as antidote at moderate dose against CdCl2 toxicity.

Nanoencapsulation of DMSA monoester for better therapeutic efficacy of the chelating agent against arsenic toxicity.

AIMS: Exposure to toxic metals remains a widespread occupational and environmental problem in world. Chelation therapy is a mainstream treatment used to treat heavy metal poisoning. This paper describes the synthesis, characterization and therapeutic evaluation of monoisoamyl 2,3-dimercaptosuccinic acid (MiADMSA)-encapsulated polymeric nanoparticles as a detoxifying agent for arsenic poisoning. MATERIALS & METHODS: Polymeric nanoparticles entrapping the DMSA monoester, which can evade the reticulo-endothelial system and have a long circulation time in the blood, were prepared. Particle characterization was carried out by transmission electron microscopy and dynamic light scattering. An in vivo study was conducted to investigate the therapeutic efficacy of MiADMSA-encapsulated polymeric nanoparticles (nano- MiADMSA; 50 mg/kg orally for 5 days) and comparison drawn with bulk MiADMSA. Swiss albino mice exposed to sodium arsenite for 4 weeks were treated for 5 days to evaluate alterations in blood, brain, kidney and liver oxidative stress variables. The study also evaluated the histopathological changes in tissues and the chelating potential of the nanoformulation. RESULTS: Our results show that nano-MiADMSA have a narrow size distribution in the 50-nm range. We observed an enhanced chelating potential of nano-MiADMSA compared with bulk MiADMSA as evident in the reversal of biochemical changes indicative of oxidative stress and efficient removal of arsenic from the blood and tissues. Histopathological changes and urinary 8-OHdG levels also prove better therapeutic efficacy of the novel formulation for arsenic toxicity. CONCLUSION: The results from our study show better therapeutic efficacy of nano-MiADMSA in removing arsenic burden from the brain and liver.

Alterations in apoptotic caspases and antioxidant enzymes in arsenic exposed rat brain regions: reversal effect of essential metals and a chelating agent.

Arsenic (As) widely studied for its effects as a neurotoxicant. The present study was designed to evaluate the protective effect of calcium, zinc or monoisoamyl dimercaptosuccinic acid (MiADMSA), either individually or in combination on As induced oxidative stress and apoptosis in brain regions (cerebral cortex, hippocampus and cerebellum) of postnatal day (PND) 21, 28 and 3 months old rats. Arsenic exposure significantly decreased the activities of superoxide dismutase (SOD) isoforms, catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) with increase in glutathione s transferase (GST) while lipid peroxidation (LPx), arsenic levels, mRNA expression of caspase 3 and 9 were significantly increased in different brain regions. Arsenic induced alterations in these parameters were greater in PND 28 and more pronounced in cerebral cortex. From the results it is evident that combined supplementation of calcium and zinc along with MiADMSA would be most effective compared to individual administration in reducing arsenic induced neurotoxicity.

Reversal effect of monoisoamyl dimercaptosuccinic acid (MiADMSA) for arsenic and lead induced perturbations in apoptosis and antioxidant enzymes in developing rat brain.

Oxidative stress (OS) has been implicated in the pathophysiology of many neurodegenerative disorders. Several studies have shown that exposure to arsenic (As) and lead (Pb) produces oxidative stress, one of the most noted molecular mechanisms for the neurotoxicity of these metals. In the present study, we examined the effect of combined exposure to these metals (As and Pb) on the activity levels of antioxidant enzymes and apoptotic marker enzymes in brain regions (cerebral cortex, hippocampus and cerebellum) of rats at postnatal day (PND) 21, 28 and 3 months age and compared the toxicity levels with individual metals (As or Pb). Further, we also evaluated the therapeutic efficacy of a chelating agent, monoisoamyl dimercaptosuccinic acid (MiADMSA) against arsenic and lead induced developmental neurotoxicity. Pregnant rats were exposed to sodium meta-arsenite (50 ppm) and lead acetate (0.2%) individually, and in combination (As=25 ppm+Pb=0.1%) via drinking water throughout perinatal period (GD 6 to PND 21). MiADMSA (50 mg/kg, orally through gavage) was given for three consecutive days to the PND 18 pups (i.e., PND 18 to PND 20). Exposure to metal mixture resulted in a significant decrease in the activity levels of antioxidant enzymes such as manganese-superoxide dismutase (Mn-SOD), Cu/Zn superoxide dismutase (Cu/Zn-SOD), catalase (CAT) and glutathione peroxidase (GPx) while the malondialdehyde (MDA) levels and mRNA expression levels of caspase-3 and caspase-9 were significantly increased in all the three brain regions. The observed alterations were greater with exposure to metal mixture than individual metals (As or Pb) and the changes were more prominent at PND 28 and greater in cerebral cortex than hippocampus and cerebellum. Interestingly, chelation therapy with MiADMSA showed significant recovery in antioxidant enzymes, lipid peroxidation and gene expression levels of caspase-3 and caspase-9. From these findings, it can be concluded that combined exposure to As and Pb showed an additive effect on antioxidant enzymes than individual metal exposure and chelation therapy with MiADMSA significantly reversed the As and Pb induced apoptosis and oxidative stress, a major contributing factor to neurotoxicity.

MiADMSA protects arsenic-induced oxidative stress in human keratinocyte 'HaCaT' cells.

Arsenic toxicity may lead to skin manifestations and arsenic accumulation in keratinised tissue. Thus human keratinocytes has been extensively used to study dermal effects of arsenic exposure. The present study was aimed to investigate time and dose-dependent effects of arsenic using HaCaT cell line. Another major focus of the study was to evaluate if treatment with monoisoamyl dimercaptosuccinic acid (MiADMSA) offers protection against arsenic-induced oxidative stress and apoptotic cell death using HaCaT cells. HaCaT cell lines were incubated to three different concentrations of arsenic (10, 30 and 50 µM) for 24 h to identify the toxic dose by measuring oxidative stress variables. Later, MiADMSA pre-incubation for an hour preceded arsenic exposure (30 µM). We evaluated cell morphology, lactate dehydrogenase, glutathione linked enzyme and antioxidant enzyme activities to measure oxidative stress status, while MTT assay and caspase 9 and 3 levels were determined for cell viability and apoptotic status. The present study suggests arsenic-induced toxicity in a concentration-dependant manner. Arsenic also caused a significant increase in lactate dehydrogenase accompanied by an elevated antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase and caspase activity). Interestingly, pre-treatment of cell with MiADMSA elicited significant protection against arsenic-induced oxidative stress and apoptotic cell death. The present findings are of clinical relevance and suggest MiADMSA to be a promising candidate in protecting skin against arsenic-induced toxic effects, which need further exploration using in vivo experimental models.

Monoisoamyl 2,3-dimercaptosuccinic acid attenuates arsenic induced toxicity: behavioral and neurochemical approach.

Chronic exposure to arsenic in drinking water is associated with skin lesions, neurological effects, hypertension and high risk of cancer. The treatment in use at present employs administration of thiol chelators, such as meso-2,3-dimercaptosuccinic acid (DMSA) which are compromised with number of limitations due to their lipophobic nature. To address this problem, therapeutic efficacy of monoisoamyl meso-2,3-dimercaptosuccinic acid (MiADMSA), an analog of DMSA having lipophilic character, was examined against chronic arsenic poisoning in rats. Adult male Wistar rats were orally exposed to arsenic (2mg sodium arsenite/kg body weight) for 10 weeks followed by treatment with MiADMSA (50mg/kg, orally, once daily for 5 consecutive days). As-exposed rats showed significant differences in behavioral functions (open field behavior, total locomotor activity, grip strength and exploratory behavior) and water maze learning. Further, the biochemical studies performed on three brain regions (cerebellum, cortex and hippocampus) also showed significant elevation in malondialdehyde (MDA) levels with a concomitant decrease in the oxidative stress marker enzymes Mn-superoxide dismutase (Mn-SOD), Cu/Zn-superoxide dismutase (Cu/Zn-SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S-transferase (GST). The alterations were more pronounced in cortex compared to cerebellum and hippocampus. The results showed that MiADMSA significantly reversed the As-induced alterations in behavior and biochemical variables suggestive of oxidative injury.

Arsenic induced neuronal apoptosis in guinea pigs is Ca2+ dependent and abrogated by chelation therapy: role of voltage gated calcium channels.

Arsenic contaminated drinking water has affected more than 200 million people globally. Chronic arsenicism has also been associated with numerous neurological diseases. One of the prime mechanisms postulated for arsenic toxicity is reactive oxygen species (ROS) mediated oxidative stress. In this study, we explored the kinetic relationship of ROS with calcium and attempted to dissect the calcium ion channels responsible for calcium imbalance after arsenic exposure. We also explored if mono- or combinational chelation therapy prevents arsenic-induced (25ppm in drinking water for 4 months) neuronal apoptosis in a guinea pig animal model. Results indicate that chronic arsenic exposure caused a significant increase in ROS followed by NO and calcium influx. This calcium influx is mainly dependent on L-type voltage gated channels that disrupt mitochondrial membrane potential, increase bax/bcl2 levels and caspase 3 activity leading to apoptosis. Interestingly, blocking of ROS could completely reduce calcium influx whereas calcium blockage partially reduced ROS increase. While in general mono- and combinational chelation therapies were effective in reversing arsenic induced alteration, combinational therapy of DMSA and MiADMSA was most effective. Our results provide evidence for the role of L-type calcium channels in regulating arsenic-induced calcium influx and DMSA+MiADMSA combinational therapy may be a better protocol than monotherapy in mitigating chronic arsenicosis.

Monensin potentiates lead chelation efficacy of MiADMSA in rat brain post chronic lead exposure.

The present study evaluates combination therapy with a chelating agent, MiADMSA and a Na(+) ionophore, monensin against sub-chronic lead toxicity in rats. Animals were exposed to 0.1% lead in drinking water for 16 weeks and then treated with either MiADMSA at 50mg/kg body weight, or monensin at 10mg/kg, or both in combination for a period of 5 days was administered. Biomarkers indicative of oxidative stress like ROS, GSH, GSSG and TBARS demonstrated lead-induced toxic manifestations in blood, kidney and brain. Antioxidants like SOD, catalase and glutathione peroxidase along with specific lead biomarker, blood ALAD were also severely depleted in lead intoxicated animals. Serum parameters and histopathological findings supported the said results. MiADMSA treatment during both mono- and combination therapy with monensin, restored the antioxidant status and recovered biochemical and haematological variables due to lead. However, monensin alone was not found to be effective in the given scenario. Interestingly, combination therapy in its ability to revert lead-induced overall systemic toxicity was only found at par with the MiADMSA monotherapy except for its chelation potential. Monensin given in combination with MiADMSA potentiated its lead chelation ability especially from brain, along with maintaining the normal copper concentrations in the organ unlike MiADMSA monotherapy.

Therapeutic profile of T11TS vs. T11TS+MiADMSA: a hunt for a more effective therapeutic regimen for arsenic exposure.

Arsenic exposure is a serious health hazard worldwide. We have previously established that it may result in immune suppression by upregulating Th2 cytokines while downregulating Th1 cytokines and causing lymphocytic death. Treatment modalities for arsenic poisoning have mainly been restricted to the use of chelating agents in the past. Only recently have combination therapies using a chelating agent in conjunction with other compounds such as anti-oxidants, micronutrients and various plant products, been introduced. In the present study, we used T11TS, a novel immune potentiating glycopeptide alone and in combination with the sulfhydryl-containing chelator, mono-iso-amyl-dimarcaptosuccinic acid (MiADMSA) as a therapeutic regimen to combat arsenic toxicity in a mouse model. Results indicated that Th1 cytokines such as TNF-α, IFNγ, IL12 and the Th2 cytokines such as IL4, IL6, IL10 which were respectively downregulated and upregulated following arsenic induction were more efficiently restored to their near normal levels by T11TS alone in comparison with the combined regimen. Similar results were obtained with the apoptotic proteins studied, FasL, BAX, BCL2 and the caspases 3, 8 and 9, where again T11TS proved more potent than in combination with MiADMSA in preventing lymphocyte death. The results thus indicate that T11TS alone is more efficient in immune re-establishment after arsenic exposureas compared to combination therapy with T11TS+MiADMSA.

Monoisoamyl 2, 3-dimercaptosuccinic acid (MiADMSA) demonstrates higher efficacy by oral route in reversing arsenic toxicity: a pharmacokinetic approach.

Monoisoamyl DMSA (MiADMSA), a lipophilic chelating agent has emerged as a promising drug for the treatment of arsenic. The present study aimed at exploring the optimum dose and route of administration for achieving maximum arsenic elimination with minimal side effects. We also carried out a pharmacokinetic analysis of this drug to support arsenic chelation. Rats were exposed to arsenic (25 ppm) for 6 months and later received MiADMSA (50 or 100 mg/kg) orally and via i.p. route for 5 days. Oxidative stress parameters and arsenic levels in soft tissues, liver function test and histopathology of liver and kidney were performed. Plasma kinetic of MiADMSA (plasma-free drug and total drug) at 50 and 100 mg/kg p.o. was carried out. Arsenic exposure resulted in significant oxidative stress and hepatotoxicity. MiADMSA at 50 mg/kg dose administered orally provided about 45% and 75% protection against oxidative stress and in lowering body arsenic burden, respectively, against 25% and 40% via i.p. route. Pharmacokinetic analysis supported prolonged availability of the drug through oral administration. Collectively, these findings led us to conclude that oral administration of MiADMSA was more effective than intraperitoneal administration and that the minimum effective dose with least side effects was 50 mg/kg.

Mitigative action of monoisoamyl-2,3-dimercaptosuccinate (MiADMS) against cadmium-induced damage in cultured rat normal liver cells.

Cadmium is non-essential, carcinogenic and multitarget pollutant in the environment. Monoisoamyl-2,3-dimercaptosuccinate (MiADMS) is an ester of dimercaptosuccinic acid that acts as an antioxidant and chelator. Therefore, the mitigative action of MiADMS on viability, morphology, antioxidative enzymes and cell cycle were studied on rat liver cells treated with cadmium chloride (CdCl2). The cells were treated with 150 µM CdCl2 alone or cotreated with 300 µM MiADMS (concurrently, 2 h or 4 h post-CdCl2 treatment) for 24 h. The viability of cells treated with CdCl2 alone was decreased in comparison to the control cells. Cotreatment with MiADMS resulted in an increase in cell viability in comparison to the CdCl2 alone treated cells. The CdCl2 treatment altered the morphological shape of the cells, while cotreatment with MiADMS restored the shape. Antioxidative enzymes activities were decreased in the cells treated with CdCl2 alone, while MiADMS cotreatment resulted in an increase in enzyme activities. The CdCl2 arrested the cells in S phase of the cell cycle. Cotreatment with MiADMS alleviated cell cycle arrest by shifting to G1 phase. These results clearly show the mitigative action of MiADMS on CdCl2 toxicity and may suggest that MiADMS can be used as an antidote against cadmium.

MiADMSA reverses impaired mitochondrial energy metabolism and neuronal apoptotic cell death after arsenic exposure in rats.

Arsenicosis, due to contaminated drinking water, is a serious health hazard in terms of morbidity and mortality. Arsenic induced free radicals generated are known to cause cellular apoptosis through mitochondrial driven pathway. In the present study, we investigated the effect of arsenic interactions with various complexes of the electron transport chain and attempted to evaluate if there was any complex preference of arsenic that could trigger apoptosis. We also evaluated if chelation with monoisoamyl dimercaptosuccinic acid (MiADMSA) could reverse these detrimental effects. Our results indicate that arsenic exposure induced free radical generation in rat neuronal cells, which diminished mitochondrial potential and enzyme activities of all the complexes of the electron transport chain. Moreover, these complexes showed differential responses towards arsenic. These early events along with diminished ATP levels could be co-related with the later events of cytosolic migration of cytochrome c, altered bax/bcl(2) ratio, and increased caspase 3 activity. Although MiADMSA could reverse most of these arsenic-induced altered variables to various extents, DNA damage remained unaffected. Our study for the first time demonstrates the differential effect of arsenic on the complexes leading to deficits in bioenergetics leading to apoptosis in rat brain. However, more in depth studies are warranted for better understanding of arsenic interactions with the mitochondria.

Co-administration of meso 2,3-dimercaptosuccinic acid monoesters reduces arsenic concentration and oxidative stress in gallium arsenide exposed rats.

1. Gallium arsenide (GaAs), a semiconductor, exerts toxicity as a result of its constitutive moieties; that is, gallium and arsenic that becomes dissociated after exposure. The present study focuses on reducing arsenic concentration from the target organs using monoesters of meso 2,3-dimercaptosuccinic acid (DMSA) either individually or in combination. 2. Animals were exposed to GaAs (0.0014 mol/kg, orally for 8 weeks) and then treated with monoisoamyl DMSA (MiADMSA), monocyclohexyl DMSA (MchDMSA) or monomethyl DMSA (MmDMSA) either individually (0.3 mmol/kg, orally) or in combination (0.15 mmol/kg each, orally) for five consecutive days. 3. GaAs exposure significantly inhibited blood δ-aminolevulinic acid dehydrogenase (ALAD), suggesting alterations in the heme synthesis pathway. Whereas a significant increase in blood, liver and kidney reactive oxygen species accompanied by an increase in lipid peroxidation points to the involvement of oxidative stress in GaAs toxicity. 4. GaAs also significantly disturbed glutathione metabolism. Hepatic and renal catalase activity decreased significantly, whereas hepatic and renal superoxide dismutase activity, as well as serum transaminases activity, showed marginal increase. Treatment with MiADMSA in combination with MchDMSA showed better therapeutic efficacy compared with other treatments in the aforementioned variables. 5. Co-administration of MiADMSA with MchDMSA provided better therapeutic effects, including reduction of arsenic burden, compared with all other treatments.