Phytochemicals in the Management of Arsenic Toxicity.

Arsenic toxicity is a major concern due to its deleterious consequences for human health. Rapid industrialization also has weakened the quality of the environment by introducing pollutants that may disrupt balanced ecosystems, adversely and irreversibly impacting humans, plants, and animals. Arsenic, an important toxicant among all environmental hazards, can lead to several detrimental effects on cells and organs, impacting the overall quality of life. Nevertheless, arsenic also has a rich history as a chemotherapeutic agent used in ancient days for the treatment of diseases such as malaria, cancer, plague, and syphilis when other chemotherapeutic agents were yet to be discovered. Arsenicosis-mediated disorders remain a serious problem due to the lack of effective therapeutic options. Initially, chelation therapy was used to metabolically eliminate arsenic by forming a complex, but adverse effects limited their pharmacological use. More recently, plant-based products have been found to provide significant relief from the toxic effects of arsenic poisoning. They act by different mechanisms affecting various cellular processes. Phytoconstituents such as curcumin, quercetin, diallyl trisulfide, thymoquinone, and others act via various molecular pathways, primarily by attenuating oxidative damage, membrane damage, DNA damage, and proteinopathies. Nonetheless, most of the phytochemicals reviewed here protect against the adverse effects of metal or metalloid exposure, supporting their consideration as alternatives to chelation therapy. These agents, if used prophylactically and in conjunction with other chemotherapeutic agents, may provide an effective approach for management of arsenic toxicity. In a few instances, such strategies like coadministration of phytochemicals with a known chelating agent have led to more pronounced elimination of arsenic from the body with lesser off-site adverse effects. This is possible because combination treatment ensures the use of a reduced dose of chelating agent with a phytochemical without compromising treatment. Thus, these therapies are more practical than conventional therapeutic agents in ameliorating arsenic-mediated toxicity. This review summarizes the potential of phytochemicals in alleviating arsenic toxicity on the basis of available experimental and clinical evidence.

Recent Advances in Therapeutic Applications of Bisbenzimidazoles.

Nitrogen-containing heterocycles are one of the most common structural motifs in approximately 80% of the marketed drugs. Of these, benzimidazoles analogues are known to elicit a wide spectrum of pharmaceutical activities such as anticancer, antibacterial, antiparasitic, antiviral, antifungal as well as chemosensor effect. Based on the benzimidazole core fused heterocyclic compounds, crescent-shaped bisbenzimidazoles were developed which provided an early breakthrough in the sequence-specific DNA recognition. Over the years, a number of functional variations in the bisbenzimidazole core have led to the emergence of their unique properties and established them as versatile ligands against several classes of pathogens. The present review provides an overview of diverse pharmacological activities of the bisbenzimidazole analogues in the past decade with a brief account of its development through the years.

Countering effects of a combination of podophyllotoxin, podophyllotoxin ß-D-glucoside and rutin hydrate in minimizing radiation induced chromosomal damage, ROS and apoptosis in human blood lymphocytes.

The present study was conceptualized with the aim of developing a safe radioprotector for human application against radiation induced toxicity. For this study, a formulation (G-002M) prepared by combining three active principles isolated from rhizomes of Podophyllum hexandrum, was evaluated for its potential to protect genomic DNA of human blood cells exposed to different doses of radiation (5,7&10Gy). Blood samples were pretreated (-1hr to exposure) with G-002M. Parameters of Premature Chromosome Condensation (PCC) assay like PCC-index, PCC-rings and PCC-fragments were used to estimate radiation induced chromosomal aberrations. Radiation (7Gy) induce ROS generation and its modulation by G-002M was determined by flow-cytometry and fluorescent microscopy while apoptosis (0,2,24&48 hr) was analyzed using TUNEL assay. Effect on spindle organization in G2/M arrested cells by all the three compounds individually was studied using immunofluorescence microscopy. Irradiation caused dose dependent linear increase in PCC-rings and fragments, while decline in PCC index. G-002M pretreatment significantly decreased these chromosomal aberrations at all the radiation doses and assisted cell survival as indicated by increased PCC index compared with radiation only group. Significant decrease in radiation induced intracellular ROS (45 ± 3%) and apoptosis (49.9%) was also exhibited by the formulation. On podophyllotoxin treatment, most of the cells have shown blocked spindles however, depicted normal arrangement. G-002M also demonstrated a highly significant Dose Modifying Factor or DMF (PCC-rings: 2.27 and PCC-fragments: 1.60). Present study based on many parameters along with DMF study, strongly suggests that G-002M is an effective formulation with a potential to minimize chromosomal damage even at very high radiation doses.

Sodium tungstate induced neurological alterations in rat brain regions and their response to antioxidants.

Tungsten, recognized recently as an environmental contaminant, is being used in arms and ammunitions as substitute to depleted uranium. We studied the effects of sodium tungstate on oxidative stress, few selected neurological variables like acetylcholinesterase, biogenic amines in rat brain regions (cerebral cortex, hippocampus and cerebellum) and their prevention following co-administration of N-acetylcysteine (NAC), naringenin and quercetin. Animals were sub-chronically exposed to sodium tungstate (100 ppm in drinking water) and orally co-supplemented with different antioxidants (0.30 mM) for three months. Sodium tungstate significantly decreased the activity of acetylcholinesterase, dopamine, nor-epinephrine and 5-hydroxytryptamine levels while it increased monoamine oxidase activity in different brain regions. Tungstate exposure produced a significant increase in biochemical variables indicative of oxidative stress while, neurological alterations were more pronounced in the cerebral cortex compared to other regions. Co-administration of NAC and flavonoids with sodium tungstate significantly restored glutathione, prevented changes in the brain biogenic amines, reactive oxygen species (ROS) and TBARS levels in the different brain regions. The protection was more prominent in the animals co-administered with NAC. We can thus conclude that sodium tungstate induced brain oxidative stress and the alterations in some neurological variables can effectively be reduced by co-supplementation of NAC.

Arsenic and nicotine co-exposure lead to some synergistic effects on oxidative stress and apoptotic markers in young rat blood, liver, kidneys and brain.

Arsenic and nicotine exposure has been a major health concern globally. Individually both these toxicants increase the risk to various diseases including cancers. However, limited information exists on the co-exposure. In this study, we evaluate the effects of their individual and combined exposure and if co-exposure to these toxicants might have a synergism or antagonism. Male rats were exposed to a very low dose of arsenic (25 ppm in drinking water) or nicotine (0.25 mg/kg, sub-cutaneously) for a period of 5 months and post exposure various biochemical variables indicative of oxidative stress and apoptosis evaluated. Almost all glutathione linked enzymes showed marked alteration in individual as well as co-exposure treated groups. While serum creatinine and apoptosis indicator, lactate dehydrogenase (LDH) were significantly increased in both treatments, an additive effect was noted in co-exposure group. A similar trend was also seen in brain and liver but not in kidneys. Gene expression studies showed marked reduction in catalase, Cu-Zn SOD, GST, there was a significant up regulation in Bax, caspase 3 in various tissues along with urinary 8-OHdG levels, indicative of DNA damage and apoptosis. Interestingly, a decrease in liver arsenic concentration was noted in co-exposed group compared to arsenic alone exposed group. In conclusion, the present study suggests that arsenic and nicotine exhibited significant toxicity during individual exposure whereas co-exposure to these toxins showed variable conditions (indicative of both synergism and antagonism) in male rats.

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.

Curcumin encapsulated in chitosan nanoparticles: a novel strategy for the treatment of arsenic toxicity.

Water-soluble nanoparticles of curcumin were synthesized, characterized and applied as a stable detoxifying agent for arsenic poisoning. Chitosan nanoparticles of less than 50 nm in diameter containing curcumin were prepared. The particles were characterized by TEM, DLS and FT-IR. The therapeutic efficacy of the encapsulated curcumin nanoparticles (ECNPs) against arsenic-induced toxicity in rats was investigated. Sodium arsenite (2mg/kg) and ECNPs (1.5 or 15 mg/kg) were orally administered to male Wistar rats for 4 weeks to evaluate the therapeutic potential of ECNPs in blood and soft tissues. Arsenic significantly decreased blood δ-aminolevulinic acid dehydratase (δ-ALAD) activity, reduced glutathione (GSH) and increased blood reactive oxygen species (ROS). These changes were accompanied by increases in hepatic total ROS, oxidized glutathione, and thiobarbituric acid-reactive substance levels. By contrast, hepatic GSH, superoxide dismutase and catalase activities significantly decreased on arsenic exposure, indicative of oxidative stress. Brain biogenic amines (dopamine, norepinephrine and 5-hydroxytryptamine) levels also showed significant changes on arsenic exposure. Co-administration of ECNPs provided pronounced beneficial effects on the adverse changes in oxidative stress parameters induced by arsenic. The results indicate that ECNPs have better antioxidant and chelating potential (even at the lower dose of 1.5 mg/kg) compared to free curcumin at 15 mg/kg. The significant neurochemical and immunohistochemical protection afforded by ECNPs indicates their neuroprotective efficacy. The formulation provides a novel therapeutic regime for preventing arsenic toxicity.

A possible mechanism for combined arsenic and fluoride induced cellular and DNA damage in mice.

Arsenic and fluoride are major contaminants of drinking water. Mechanisms of toxicity following individual exposure to arsenic or fluoride are well known. However, it is not explicit how combined exposure to arsenic and fluoride leads to cellular and/or DNA damage. The present study was planned to assess (i) oxidative stress during combined chronic exposure to arsenic and fluoride in drinking water, (ii) correlation of oxidative stress with cellular and DNA damage and (iii) mechanism of cellular damage using IR spectroscopy. Mice were exposed to arsenic and fluoride (50 ppm) either individually or in combination for 28 weeks. Arsenic or fluoride exposure individually led to a significant increase in reactive oxygen species (ROS) generation and associated oxidative stress in blood, liver and brain. Individual exposure to the two toxicants showed significant depletion of blood glutathione (GSH) and glucose 6-phosphate dehydrogenase (G6PD) activity, and single-stranded DNA damage using a comet assay in lymphocytes. We also observed an increase in the activity of ATPase, thiobarbituric acid reactive substance (TBARS) and a decreased, reduced and oxidized glutathione (GSH : GSSG) ratio in the liver and brain. Antioxidant enzymes like superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) were decreased and increased in liver and brain respectively. The changes were more pronounced in liver compared to brain suggesting liver to be more susceptible to the toxic effects of arsenic and fluoride. Interestingly, combined exposure to arsenic and fluoride resulted in less pronounced toxic effects compared to their individual effects based on biochemical variables, IR spectra, DNA damage (TUNEL and comet assays) and histopathological observations. IR spectra suggested that arsenic or fluoride perturbs the strength of protein and amide groups; however, the shifts in peaks were not pronounced during combined exposure. These results thus highlight the role of arsenic- or fluoride-induced oxidative stress, DNA damage and protein interaction as the major determinants of toxicity, along with the differential toxic effects during arsenic-fluoride interaction during co-exposure. The study further corroborates our earlier observations that at the higher concentration co-exposures to these toxicants do not elicit synergistic toxicity.

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.

Arsenic-induced oxidative stress and its reversibility.

This review summarizes the literature describing the molecular mechanisms of arsenic-induced oxidative stress, its relevant biomarkers, and its relation to various diseases, including preventive and therapeutic strategies. Arsenic alters multiple cellular pathways including expression of growth factors, suppression of cell cycle checkpoint proteins, promotion of and resistance to apoptosis, inhibition of DNA repair, alterations in DNA methylation, decreased immunosurveillance, and increased oxidative stress, by disturbing the pro/antioxidant balance. These alterations play prominent roles in disease manifestation, such as carcinogenicity, genotoxicity, diabetes, cardiovascular and nervous systems disorders. The exact molecular and cellular mechanisms involved in arsenic toxicity are rather unrevealed. Arsenic alters cellular glutathione levels either by utilizing this electron donor for the conversion of pentavalent to trivalent arsenicals or directly binding with it or by oxidizing glutathione via arsenic-induced free radical generation. Arsenic forms oxygen-based radicals (OH(•), O(2)(•-)) under physiological conditions by directly binding with critical thiols. As a carcinogen, it acts through epigenetic mechanisms rather than as a classical mutagen. The carcinogenic potential of arsenic may be attributed to activation of redox-sensitive transcription factors and other signaling pathways involving nuclear factor κB, activator protein-1, and p53. Modulation of cellular thiols for protection against reactive oxygen species has been used as a therapeutic strategy against arsenic. N-acetylcysteine, α-lipoic acid, vitamin E, quercetin, and a few herbal extracts show prophylactic activity against the majority of arsenic-mediated injuries in both in vitro and in vivo models. This review also updates the reader on recent advances in chelation therapy and newer therapeutic strategies suggested to treat arsenic-induced oxidative damage.

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.

Concomitant exposure to arsenic and organophosphates on tissue oxidative stress in rats.

Increased use of organophosphates (OPs) and ever increasing arsenic levels in drinking water and their co-existence in the environment could be potentially hazardous. The present study examines the effects of dichlorvos (DDVP) or monocrotophos (MCP) and sodium meta arsenite, individually or in combination for 16 weeks on variables indicative of hematological and tissue oxidative injury in rats. Co-exposure to DDVP, MCP or arsenic produced significant inhibition of brain and serum AChE levels suggesting synergism. Significant increase in hepatic reactive oxygen species and brain thiobarbituric acid reactive substances was observed in arsenic and OPs exposed animals. Co-exposure to arsenic and OPs exhibited synergism in case of ROS while antagonism was noted in case of TBARS. Serum transaminases increased significantly on exposure to OPs and arsenic suggesting liver injury which was less pronounced in case of co-exposure to DDVP and arsenic. WBC counts too showed less pronounced increase on co-exposure to arsenic with OPs compared to all other exposure. Blood arsenic level decreased on co-exposure to arsenic with OPs. The present study points to some interesting observations regarding interaction between arsenic and organophosphates. While, exposure to arsenic, DDVP and MCP lead to significant oxidative stress, their co-exposure not necessarily produce synergistic effects.

Modulation of ionizing radiation induced oxidative imbalance by semi-fractionated extract of Piper betle: an in vitro and in vivo assessment.

The study was planned to evaluate modulatory effect of aqueous extract of Piper betle leaf (PBL) on ionizing radiation mediated oxidative stress leading to normal tissues damage during radiotherapy and other radiation exposures. The total polyphenols and flavonoids known as free radical scavenger (chelators) were measured in the extract. To ascertain antioxidant potential of PBL extract we studied free radical scavenging, metal chelation, reducing power, lipid peroxidation inhibition and ferric reducing antioxidant properties (FRAP) using in vitro assays. Mice were exposed to varied radiation doses administered with the same extract prior to irradiation to confirm its oxidative stress minimizing efficacy by evaluating ferric reducing ability of plasma, reduced glutathione, lipid peroxidation and micro-nuclei frequency. PBL extract was effective in scavenging DPPH (up to 92% at 100 microg/ml) and superoxide radicals (up to 95% at 80 microg/ml), chelated metal ions (up to 83% at 50 microg/ml) and inhibited lipid peroxidation (up to 55.65% at 500 microg/ml) in a dose dependant manner using in vitro model. Oral administration of PBL extract (225 mg/kg body weight) 1 hr before irradiation in mice significantly enhanced (p < 0.01) radiation abated antioxidant potential of plasma and GSH level in all the observed organs. The treatment with extract effectively lowered the radiation induced lipid peroxidation at 24 hrs in all the selected organs with maximum inhibition in thymus (p < 0.01). After 48 hrs, lipid peroxidation was maximally inhibited in the group treated with the extract. Frequency of radiation induced micronucleated cells declined significantly (34.78%, p < 0.01) at 24 hrs post-irradiation interval by PBL extract administration. The results suggest that PBL extract has high antioxidant potential and relatively non-toxic and thus could be assertively used to mitigate radiotherapy inflicted normal tissues damage and also injuries caused by moderate doses of radiation during unplanned exposures.

Protective effects of selenium, calcium, and magnesium against arsenic-induced oxidative stress in male rats.

Inorganic arsenic is a potent carcinogen and environmental pollutant. More than one hundred million people are reported to be exposed to elevated concentrations of arsenic mainly via drinking water. Essential trace elements can affect toxicity of metals by interacting with metals at the primary site of action and can also modify the body's response to toxic metals by altering their metabolism and transport. This study investigates the effects of concomitant administration of selenium, magnesium, and calcium with arsenic on blood biochemistry and oxidative stress. Selenium was the most effective in reducing arsenic-induced inhibition of blood delta-aminolevulinic acid dehydratase (ALAD) activity and liver oxidative stress. Calcium and magnesium also showed favourable effects on haematological and other biochemical parameters. Because selenium was the most effective, it should be added to chelation therapy to achieve the best protective effects against arsenic poisoning in humans.

Reversal of arsenic-induced hepatic apoptosis with combined administration of DMSA and its analogues in guinea pigs: role of glutathione and linked enzymes.

Arsenicosis, due to contaminated drinking water in the Indo-Bangladesh region, is a serious health hazard in terms of morbidity and mortality. Reactive oxygen species (ROS) generated due to arsenic toxicity have been attributed as one of the initial signals that impart cellular toxicity, which is controlled by the internal antioxidant glutathione (GSH). In the present study, we investigated (i) the role of GSH and its linked enzymes, glutathione peroxidase and glutathione reductase, in reversing chronic arsenic toxicity using a thiol chelating agent, meso-2,3-dimercaptosuccinic acid (DMSA), or one of its analogues individually or in combination; (ii) if alterations in the carbon side chain of DMSA increased efficacy; and (iii) whether the combination therapy enhance arsenic removal from hepatic tissue and prevent hepatic apoptosis. Results indicated that chronic arsenic exposure led to a ROS-mediated, mitochondrial-driven, caspase-dependent apoptosis in hepatic cells with a significant increase in glutathione disulfide (GSSG) levels and decreased glutathione reductase levels. Monotherapy with DMSA and its analogues did show minimal recovery postchelation. However, the combination of DMSA with long carbon chain analogues like monoisoamyl DMSA (MiADMSA) or monocyclohexyl DMSA (MchDMSA) showed a better efficacy in terms of reducing the arsenic burden as well as reversing altered biochemical variables indicative of oxidative stress and apoptosis. We also observed that GSH and its linked enzymes, especially glutathione reductase, play a vital role in scavenging ROS, maintaining GSH pools, and providing clinical recoveries. On the basis of the above observations, we recommend that combinational therapy of DMSA and its long carbon chain analogues MiADMSA or MchDMSA would be more effective in arsenic toxicity.

Combined administration of taurine and monoisoamyl DMSA protects arsenic induced oxidative injury in rats.

Arsenic is a naturally occurring element that is ubiquitously present in the environment. High concentration of naturally occurring arsenic in drinking water is a major health problem in different parts of the world. Despite arsenic being a health hazard and a well documented carcinogen, no safe, effective and specific preventive or therapeutic measures are available. Among various recent strategies adopted, administration of an antioxidant has been reported to be the most effective. The present study was designed to evaluate the therapeutic efficacy of monoisoamyl dimercaptosuccinic acid (MiADMSA), administered either individually or in combination with taurine post chronic arsenic exposure in rats. Arsenic exposed male rats (25 ppm, sodium arsenite in drinking water for 24 weeks) were treated with taurine (100 mg/kg, i.p., once daily), monoisoamyl dimercaptosuccinic acid (MiADMSA) (50 mg/kg, oral, once daily) either individually or in combination for 5 consecutive days. Biochemical variables indicative of oxidative stress along-with arsenic concentration in blood, liver and kidney were measured. Arsenic exposure significantly reduced blood delta-aminolevulinic acid dehydratase (ALAD) activity, a key enzyme involved in the heme biosynthesis and enhanced zinc protoporphyrin (ZPP) level. Clinical hematological variables like white blood cells (WBC), mean cell hemoglobin (MCH), and mean cell hemoglobin concentration (MCHC) showed significant decrease with a significant elevation in platelet (PLT) count. These changes were accompanied by significant decrease in superoxide dismutase (SOD) activity and increased catalase activity. Arsenic exposure caused a significant decrease in hepatic and renal glutathione (GSH) level and an increase in oxidized glutathione (GSSG). These biochemical changes were correlated with an increased uptake of arsenic in blood, liver and kidney. Administration of taurine significantly reduced hepatic oxidative stress however co-administration of a higher dose of taurine (100 mg/kg) and MiADMSA provided more pronounced effects in improving the antioxidant status of liver and kidney and reducing body arsenic burden compared to the individual treatment of MiADMSA or taurine. The results suggest that in order to achieve better effects of chelation therapy, co-administration of taurine with MiADMSA might be preferred.

Co-administration of zinc and n-acetylcysteine prevents arsenic-induced tissue oxidative stress in male rats.

Arsenic is a widespread environmental toxicant that may cause neuropathy, skin lesions, vascular lesions and cancer upon prolonged exposure. Improving nourishment like supplementation of micronutrients, antioxidants, vitamins and amino acids could be able to halve the risk in those who were previously the poor nourished. The present study was planned to investigate the preventive effects of zinc and n-acetylcysteine (NAC) supplementation either alone or in combination with arsenic on selected biochemical variables indicative of oxidative stress and liver injury in male rats. For 3 weeks 25 male wistar rats were exposed to arsenic as sodium arsenite (2 mg/kg, orally through gastric intubation) either alone or in combination with NAC (10 mg/kg, intraperitoneally), zinc (5 mg/kg, orally) or zinc plus NAC. Animals were sacrificed 24h after the last dosing for various biochemical parameters. Concomitant administration of zinc with arsenic showed remarkable protection against blood delta-aminolevulinic acid dehydratase (ALAD) activity as well as providing protection to hepatic biochemical variables indicative of oxidative stress (like thiobarbituric acid reactive substances (TBARS) level, catalase) and tissue injury. NAC supplementation on the other hand, was moderately effective in protecting animals from the toxic effects of arsenic. Interestingly, concomitant administration of zinc and NAC was most effective compared to zinc or NAC in eliciting above-mentioned protective effects. The above results suggest significant protective value of combined zinc and NAC administration in acute arsenic exposure.

Combined administration of N-acetylcysteine and monoisoamyl DMSA on tissue oxidative stress during arsenic chelation therapy.

The present study deals with the therapeutic potential of combined administration of N-acetylcysteine (NAC) along with monoisoamyl DMSA (MiADMSA) against chronic arsenic poisoning in guinea pigs. Animal were exposed to 50 ppm arsenic in drinking water for 8 mo and subsequently treated for 5 consecutive days with 100 mg/kg NAC (orally) and MiADMSA (intraperitoneally), individually or in combination (50 mg/kg each). Arsenic exposure produced a significant depletion of blood delta- aminolevulinic acid dehydrate (ALAD) activity, increased the blood zinc protoporphyrin (ZPP) level, and reduced blood and liver glutathione (GSH) levels in guinea pigs. Hepatic oxidized glutathione (GSSG) and thiobarbituric acid reactive substance (TBARS) levels showed a marked increase, whereas hepatic alkaline phosphatase (ALP) activity decreased and acid phosphatase (ACP) activity increased on arsenic exposure. Significant depletion of liver transaminase activities on arsenic exposure suggests organ injury. Administration of MiADMSA, alone and in combination with NAC after arsenic exposure, was able to significantly enhance hepatic GSH and to reduce GSSG and TBARS levels compared to the arsenic control. Biochemical variables indicative of liver injury generally remained insensitive to any of these treatments. The recoveries in parameters indicative of oxidative stress were more marked in guinea pigs treated with combined administration of NAC and MiADMSA than monotherapy. Interestingly, there was a more pronounced depletion of arsenic from blood and tissues after combined treatment with NAC plus MiADMSA than MiADMSA. Blood and tissues copper, zinc, iron, and calcium concentrations showed a significant increase after arsenic exposure, which showed improvement, particularly after combined administration of MiADMSA and NAC. Based on these data, a proposal can be made that greater effectiveness in chelation treatment against chronic arsenic poisoning (i.e., turnover in the oxidative stress and removed of arsenic from the system) could be achieved by combined administration of an antioxidant (preferably having a thiol moiety) with MiADMSA.

Arsenic induced blood and brain oxidative stress and its response to some thiol chelators in rats.

Chronic arsenic toxicity is a widespread problem, not only in India and Bangladesh but also in various other regions of the world. Exposure to arsenic may occur from natural or industrial sources. The treatment that is in use at present employs administration of thiol chelators, such as meso 2,3-dimercaptosuccinic acid (DMSA) and sodium 2,3-dimercaptopropane 1-sulfonate (DMPS), which facilitate its excretion from the body. However, these chelating agents are compromised with number of limitations due to their lipophobic nature, particularly for their use in cases of chronic poisoning. During chronic exposure, arsenic gains access into the cell and it becomes mandatory for a drug to cross cell membrane to chelate intracellular arsenic. To address this problem, analogs of DMSA having lipophilic character, were examined against chronic arsenic poisoning in experimental animals. In the present study, therapeutic efficacy of meso 2,3-dimercaptosuccinic acid (DMSA), sodium 2,3-dimercaptopropane 1-sulfonate (DMPS), monoisoamyl DMSA (MiADMSA) were compared in terms of reducing arsenic burden, as well as recovery in the altered biochemical variables particularly suggestive of oxidative stress. Adult male Wistar rats were given 100-ppm arsenic for 10 weeks followed by chelation therapy with the above chelating agents at a dose of 50 mg/Kg (orally) once daily for 5 consecutive days. Arsenic exposure resulted in marked elevation in reactive oxygen species (ROS) in blood, inhibition of ALAD activity and depletion of GSH. These changes were accompanied by significant decline in blood hemoglobin level. MiADMSA was the most effective chelator in reducing ROS in red blood cells, and in restoring blood ALAD compared to two other chelators. Brain superoxide dismutase (SOD) and glutathione peroxidase (GPx) decreased, while ROS and TBARS increased significantly following arsenic exposure. There was a significant increase in the activity of glutathione-S-transferase (GST) with a corresponding decline in its substrate i.e. glutathione. Among all the three chelators, MiADMSA showed maximum reduction in the level of ROS in brain. Additionally, administration of MiADMSA was most effective in counteracting arsenic induced inhibition in brain ALAD, SOD and GPx activity. Based on these results and in particular higher metal decorporation from blood and brain, we suggest MiADMSA to be a potential drug of choice for the treatment of chronic arsenic poisoning. However, further studies are required for the choice of appropriate dose, duration of treatment and possible effects on other major organs.

Beneficial effect of combined administration of some naturally occurring antioxidants (vitamins) and thiol chelators in the treatment of chronic lead intoxication.

Ameliorative effects of few naturally occurring antioxidants like ascorbic acid (vitamin C), alpha-tocopherol (vitamin E) either alone or in combination with meso-2,3-dimercaptosuccinic acid (DMSA) or monoisoamyl DMSA (MiADMSA), on parameters indicative of oxidative stress in the liver, kidney, brain and blood of lead-exposed rats were studied. Male Wistar rats were exposed to 0.1% lead acetate in drinking water for 3 months and treated thereafter with DMSA or its analogue MiADMSA (50 mg/kg, intraperitoneally), either individually or in combination with vitamin E (5 mg/kg, intramuscularly) or vitamin C (25 mg/kg, orally) once daily for 5 days. The effects of these treatments in influencing the lead-induced alterations in haem synthesis pathway, hepatic, renal and brain oxidative stress and lead concentration from the soft tissues were investigated. Exposure to lead produced a significant inhibition of delta-aminolevulinic acid dehydratase (ALAD) activity from 8.44+/-0.26 in control animals to 1.76+/-0.32 in lead control, reduction in glutathione (GSH) from 3.56+/-0.14 to 2.57+/-0.25 and an increase in zinc protoporphyrin level from 62.0+/-3.9 to 170+/-10.7 in blood, suggesting altered haem synthesis pathway. Both the thiol chelators and the two vitamins were able to increase blood ALAD activity towards normal, however, GSH level responded favorably only to the two thiol chelators. The most prominent effect on blood ALAD activity was, however, observed when MiADMSA was co-administered with vitamin C (7.51+/-0.17). Lead exposure produced a significant depletion of hepatic GSH from 4.59+/-0.78 in control animals to 2.27+/-0.47 in lead controls and catalase activity from 100+/-3.4 to 22.1+/-0.25, while oxidized glutathione (GSSG; 0.34+/-0.05 to 2.05+/-0.25), thiobarbituric acid reactive substance (TBARS; 1.70+/-0.45 to 5.22+/-0.50) and glutathione peroxidase (GPx) levels (3.41+/-0.09 to 6.17+/-0.65) increased significantly, pointing to hepatic oxidative stress. Altered, reduced and oxidized GSH levels showed significant recovery after MiADMSA and DMSA administration while, vitamins E and C were effective in reducing GSSG and TBARS levels and increasing catalase activity. Administration of MiADMSA alone and the combined administration of vitamin C along with DMSA and MiADMSA were most effective in increasing hepatic GSH levels to 4.88+/-0.14, 4.09+/-0.12 and 4.30+/-0.06, respectively. Hepatic catalase also reached near normal level in animals co-administered vitamin C with DMSA or MiADMSA (82.5+/-4.5 and 84.2+/-3.5, respectively). Combined treatments with vitamins and the thiol chelators were also able to effectively reduce lead-induced decrease in renal catalase activity and increase in TBARS and GPx level. Combination therapy, however, was unable to provide an effective reversal in the altered parameters indicative of oxidative stress in different brain regions, except in catalase activity. The result also suggests a beneficial role of vitamin E when administered along with the thiol chelators (particularly with MiADMSA) in reducing body lead burden. Blood lead concentration was reduced from 13.3+/-0.11 in lead control to 0.3+/-0.01 in MiADMSA plus vitamin E-treated rats. Liver and kidney lead concentration also showed a most prominent decrease in MiADMSA plus vitamin E co-administered rats (5.29+/-0.16 to 0.63+/-0.02 and 14.1+/-0.21 to 1.51+/-0.13 in liver and kidney, respectively). These results thus suggest that vitamin C administration during chelation with DMSA/MiADMSA was significantly beneficial in reducing oxidative stress however, it had little or no additive effect on the depletion of lead compared with the effect of chelators alone. Thus, the co-administration of vitamin E during chelation treatment with DMSA or MiADMSA could be recommended for achieving optimum effects of chelation therapy.