Influence of Age on Arsenic-Induced Oxidative Stress in Rat

Influence of age on arsenic-induced (0.05, 0.1, and 0.2 lethal dose to 50?% population (LD₅₀) given intraperitoneally) oxidative stress was investigated in young, adult, and old rats at days?7 and 14 post-exposure. A significant dose-dependent effect of arsenic on biochemical variables suggestive of oxidative stress was noted at day?7 following exposure in old rats. The parameters which were significantly altered include an increased reactive oxygen species, thiobarbituric acid reactive substances (TBARS), catalase activity accompanied by a decreased glutathione level. At day?14 following arsenic exposure (0.05 and 0.1 LD₅₀ dose), we observed a significant oxidative injury as evident from significant depletion of superoxide dismutase (SOD) and catalase activities in blood and tissues in addition to more pronounced accumulation of arsenic in blood and tissues. Interestingly, the toxicity was pronounced in young and old rats compared with adult rats. Accumulation of arsenic found to be more prominent in old rats compared with young and adult, which might be due to impaired metabolism with ageing. We conclude that young and old animals are more vulnerable to the arsenic-induced oxidative injury which is comparable with arsenic accumulation in blood and tissues and duration of exposure.     

Influence of Arsenate on Lipid Peroxidation Levels and Antioxidant Enzyme Activities in Bacillus cereus Strain XZM002 Isolated from High Arsenic Aquifer Sediments

Bacillus cereus strain XZM002 isolated from high arsenic aquifer sediments of Datong Basin was applied to examine the effects of arsenate stress on antioxidant enzyme activities, lipid peroxidation levels and cell growth inhibition rate. After 2 d exposure, the cell growth inhibition rate enhanced with an increase of As(V) concentrations (0, 800, 1600 μg/l). Reactive oxygen species and glutathione contents, lipid peroxidation levels, and antioxidant enzymes (glutathione peroxidase, and other three) activities of the treated cells were significantly higher than those of the controls during 3 d exposure (p < 0.05). Besides, the levels of nine parameters reached maximum after 2 d exposure and increased significantly with increasing arsenate stress (p < 0.05). However, they returned to levels similar to those of the control on the fourth day of exposure. The results suggested that the antioxidant defense system in B. cereus strain XZM002 could protect the cells from oxidative damage induced by arsenate.     

Quercetin Administration During Chelation Therapy Protects Arsenic-Induced Oxidative Stress in Mice

We studied the efficacy of quercetin and a thiol chelating agent, monoisoamyl 2, 3-dimercaptosuccinic acid (MiADMSA) either individually or in combination against arsenic-induced oxidative stress and mobilization of metal in mouse. Animals were chronically exposed to 25 ppm arsenite as sodium arsenite in drinking water for 12 months followed by treatment with MiADMSA (0.2 mmol/kg, orally), quercetin (0.2 mmol, orally) either alone or in combination, once daily for 5 consecutive days. Arsenic exposure led to a significant depletion of blood δ-aminolevulinic acid dehydratase (ALAD) activity, glutathione, white (WBC) and red blood cell (RBC) counts, and an increase in platelet levels while significantly increasing the level of reactive oxygen species (in RBCs). Hepatic reduced catalase (CAT) and glutathione peroxidase activities showed a depletion, whereas thiobarbituric acid reactive substances (TBARS) levels increased on arsenic exposure indicating arsenite-induced oxidative stress in blood and liver. Kidney CAT activity showed a depletion, whereas TBARS levels increased on arsenic exposure. These biochemical changes were accompanied by an increase in blood, liver, and kidney arsenic concentration. Treatment with MiADMSA was effective in increasing ALAD activity, whereas quercetin was ineffective when given alone. Quercetin when co-administered with MiADMSA also provided no additional beneficial effect on blood ALAD activity but significantly brought altered platelet counts nearer to the normal value. In contrast, administration of quercetin alone provided significant beneficial effects on hepatic oxidative stress and kidney TBARS levels. Renal biochemical variables remained insensitive to arsenic and any of the treatments. Interestingly, combined administration of quercetin with MiADMSA had a remarkable effect in depleting total arsenic concentration from blood and soft tissues. These results lead us to conclude that quercetin administration during chelation treatment had some beneficial effects particularly on the protection of inhibited blood ALAD activity and depletion of arsenic level from target organs. The study supports our earlier conclusion that a co-administration of an antioxidant particularly flavonoids more beneficial than monotherapy with the chelating agents to achieve optimal effects of chelation in arsenite toxicity.     

Effects of individual and combined exposure to sodium arsenite and sodium fluoride on tissue oxidative stress, arsenic and fluoride levels in male mice

Arsenic and fluoride are potent toxicants, widely distributed through drinking water and food and often result in adverse health effects. The present study examined the effects of sodium meta-arsenite (100 mg/l in drinking water) and sodium fluoride (5 mg/kg, oral, once daily), administered either alone or in combination for 8 weeks, on various biochemical variables indicative of tissue oxidative stress and cell injury in Swiss albino male mice. A separate group was first exposed to arsenic for 4 weeks followed by 4 weeks of fluoride exposure. Exposure to arsenic or fluoride led to a significant depletion of blood delta-aminolevulinic acid dehydratase (ALAD) activity and glutathione (GSH) level. These changes were accompanied by increased level of blood and tissues reactive oxygen species (ROS) level. An increase in the level of liver and kidney thiobarbituric acid reactive substance (TBARS) along with a concomitant decrease in the activities of superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx) and reduced GSH content were observed in both arsenic and fluoride administered mice. The changes were significantly more pronounced in arsenic exposed animals than in fluoride. It was interesting to observe that during combined exposure the toxic effects were less pronounced compared to the effects of arsenic or fluoride alone. In some cases antagonistic effects were noted following co-exposure to arsenic and fluoride. Arsenic and fluoride concentration increased significantly on exposure. Interestingly, their concentration decreased significantly on concomitant exposure for 8 weeks. However, the group which was administered arsenic for 4 weeks followed by 4 weeks of fluoride administration showed no such protection suggesting that the antagonistic effect of fluoride on arsenic or vice versa is possible only during interaction at the gastro intestinal sites. These results are new and interesting and require further exploration.     

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.     

Oxidative Damage Induced by Arsenic in Mice or Rats: A Systematic Review and Meta-Analysis

In this meta-analysis, studies reporting arsenic-induced oxidative damage in mouse models were systematically evaluated to provide a scientific understanding of oxidative stress mechanisms associated with arsenic poisoning. Fifty-eight relevant peer-reviewed publications were identified through exhaustive database searching. Oxidative stress indexes assessed included superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GPx), glutathione-s-transferase (GST), glutathione reductase (GR), oxidized glutathione (GSSG), malondialdehyde (MDA), and reactive oxygen species (ROS). Our meta-analysis showed that arsenic exposure generally suppressed measured levels of the antioxidants, SOD, CAT, GSH, GPx, GST, and GR, but increased levels of the oxidants, GSSG, MDA, and ROS. Arsenic valence was important and GR and MDA levels increased to a significantly (P < 0.05) greater extent upon exposure to As³⁺ than to As⁵⁺. Other factors that contributed to a greater overall oxidative effect from arsenic exposure included intervention time, intervention method, dosage, age of animals, and the sample source from which the indexes were estimated. Our meta-analysis effectively summarized a wide range of studies and detected a positive relationship between arsenic exposure and oxidative damage. These data provide a scientific basis for the prevention and treatment of arsenic poisoning.     

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.     

Effect of Onosma echioides on DMBA/croton oil mediated carcinogenic response, hyperproliferation and oxidative damage in murine skin

The current study unveils the effect of O. echioides extract on two-stage skin carcinogenesis and on tumor promoter induced markers and oxidative stress in Swiss mice. Treatment of dorsal shaven cutaneous portions of the mice with single topical application of benzoyl peroxide (BPO) followed by exposure to ultraviolet B (UVB) radiation induced significant oxidative stress and elevated the marker parameters of tumor promotion. Similar effects were observed with 12-O-tetradecanoyl phorbol-13-acetate (TPA) treatment. Pretreatment of O. echioides extract (5 mg & 10 mg/Kg b.wt) in both the studies with BPO+UVB and TPA restored the levels of reduced glutathione (GSH) and cellular protective enzymes (p < 0.05). Concomitantly, malondialdehyde (MDA) formation and hydrogen peroxide (H2O2) content were also reduced significantly (p < 0.05) at both the doses. The promotion parameters tested (ornithine decarboxylase activity and DNA synthesis) were also significantly suppressed (p < 0.05). Thereafter, we proceeded with studies on mouse skin carcinogenesis. After ten days of 7,12-dimethylbenz(a)anthracene (DMBA) treatment, twice-weekly applications of croton oil for 20 weeks resulted in 100% incidence of tumors in the animals. However, O. echioides showed reduction in the number of tumors/ mouse and percentage of tumor bearing mice at the end of the study. The study was further histologically confirmed. The protective activity of the plant might be due to the two major constituents (alkannins and shikonins) present in the plant. O. echioides is thus, proposed to be helpful in prevention of experimental skin carcinogenesis.     

Combined administration of iron and monoisoamyl-DMSA in the treatment of chronic arsenic intoxication in mice

Co-administration of iron in combination with monoisoamyl dimercaptosuccinic acid (MiADMSA) against chronic arsenic poisoning in mice was studied. Mice preexposed to arsenic (25 ppm in drinking water for 6 months) mice were treated with MiADMSA (50 mg/kg, intraperitoneally) either alone or in combination with iron (75 or 150 mg/kg, orally) once daily for 5 days. Arsenic exposure led to a significant depletion of blood δ-aminolevulinic acid dehydratase (ALAD) activity, hematocrit, and white blood cell (WBC) counts accompanied by small decline in blood hemoglobin level. Hepatic reduced glutathione (GSH) level, catalase and superoxide dismutase (SOD) activities showed a significant decrease while, oxidized glutathione (GSSG) and thiobarbituric acid-reactive substances (TBARS) levels increased on arsenic exposure, indicating arsenic-induced hepatic oxidative stress. Liver aspartate and alanine transaminases (AST and ALT) activities also decreased significantly on arsenic exposure. Kidney GSH, GSSG, catalase level and SOD activities remained unchanged, while, TBARS level increased significantly following arsenic exposure. Brain GSH, glutathione peroxidase (GPx), and SOD activities decreased, accompanied by a significant elevation of TBARS level after chronic arsenic exposure. Treatment with MiADMSA was marginally effective in reducing ALAD activity, while administration of iron was ineffective when given alone. Iron when co-administered with MiADMSA restored blood ALAD activity. Administration of iron alone had no beneficial effects on hepatic oxidative stress, while in combination with MiADMSA it produced significant decline in hepatic TBARS level compared to the individual effect of MiADMSA. Renal biochemical variables were insensitive to any of the treatments. Combined administration of iron with MiADMSA also had no additional beneficial effect over the individual protective effect of MiADMSA on brain oxidative stress. Interestingly, combined administration of iron with MiADMSA provided more pronounced depletion of blood arsenic, while no additional beneficial effects on tissue arsenic level over the individual effect of MiADMSA were noted. The results lead us to conclude that iron supplementation during chelation has some beneficial effects particularly on heme synthesis pathway and blood arsenic concentration.     

Thioredoxin induction of peripheral blood mononuclear cells in mice in response to a single bout of swimming exercise

Thioredoxin (TRX) is a stress-inducible protein with diverse intracellular functions, which is expressed under conditions of oxidative stress. Exercise is known to cause oxidative stress by the generation of oxygen radicals from various biological pathways. The purpose of this study was to determine the level of TRX induction of cellular extracts prepared from peripheral blood mononuclear cells after a 30-min swimming exercise in mice. Plasma corticosterone concentration, considered to be a marker for exercise-induced various stress, rose significantly (p < 0.05) 0.5 h after exercise and rapidly dropped down following recovery. The carbonyl proteins as a marker of oxidative stress were significantly (p < 0.05) higher after 6 and 12 h of recovery in cytosolic extracts. The cytoplasm and nucleus TRX expressions were slightly higher to resting values after 12 and 24 h of recovery. The nucleus TRX expression was significantly (p < 0.05) higher after 24 h of recovery. These findings demonstrate that exercise-induced oxidative stress may be associated with increased intracellular TRX expression after 12 and/or 24 h after exercise in peripheral blood mononuclear cells. It is implied that this delayed and prolonged over-expression of TRX may play some roles in response to exercise-induced oxidative stress.     

Effects of arsenic exposure among semiconductor workers: a cautionary note on urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine

Arsenic is a notorious environmental toxicant and was found to cause oxidative stress in cultured cells and animals. However, little work has been done in human studies, especially for the population occupationally exposed to arsenic. In order to investigate the effect of occupational exposure to arsenic in oxidative stress, we measured urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) from 90 semiconductor workers including 50 exposed and 40 nonexposed subjects. A highly sensitive and specific isotope dilution LC-MS/MS method was used for quantification of 8-oxodGuo. The levels of inorganic arsenic (iAs3+, iAs5+), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in urine were determined by high-performance liquid chromatography-flow injection atomic absorption spectrometry (HPLC-FIAAS). Results showed that the mean urinary concentrations of total arsenic and 8-oxodGuo were significantly higher for exposed workers compared with the nonexposed workers. In addition, elevated urinary 8-oxodGuo concentrations of exposed workers were correlated with urinary levels of MMA (r = 0.44, P < 0.005) and the extent of primary methylation (the ratio of MMA to inorganic arsenic) (r = 0.40, P < 0.005). These findings suggested that occupational exposure to arsenic could result in the induction of oxidative stress. The presence and/or formation of MMA could play an important role in arsenic-involved injuries.     

Response of arsenic-induced oxidative stress,DNA damage,and metal imbalance to combined administration of DMSA and monoisoamyl-DMSA during chronic arsenic poisoning in rats

Arsenic and its compounds cause adverse health effects in humans. Current treatment 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 by number of limitations due to their lipophobic nature, particularly in case of chronic poisoning. Combination therapy is a new approach to ensure enhanced removal of metal from the body, reduced doses of potentially toxic chelators, and no redistribution of metal from one organ to another, following chronic metal exposure. The present study attempts to investigate dose-related effects of two thiol chelators, DMSA and one of its new analogues, monoisoamyl dimercaptosuccinic acid (MiADMSA), when administered in combination with the aim of achieving normalization of altered biochemical parameters suggestive of oxidative stress and depletion of inorganic arsenic following chronic arsenic exposure. Twenty-five adult male Wistar rats were given 25 ppm arsenic for 10 weeks followed by chelation therapy with the above chelating agents at a dose of 0.3 mmol/kg (orally) when administered individually or 0.15 mmol/kg and 0.3 mmol/kg (once daily for 5 consecutive days), respectively, when administered in combination. Arsenic exposure led to the inhibition of blood δ-aminolevulinic acid dehydratase (ALAD) activity and depletion of glutathione (GSH) level. These changes were accompanied by significant depletion of hemoglobin, RBC and Hct as well as blood superoxide dismutase (SOD) acitivity. There was an increase in hepatic and renal levels of thiobarbituric acid-reactive substances, while GSH:GSSG ratio decreased significantly, accompanied by a significant increase in metallothionein (MT) in hepatocytes. DNA damage based on denaturing polyacrylamide gel electrophoresis revealed significant loss in the integrity of DNA extracted from the liver of arsenic-exposed rats compared to that of normal animals. These changes were accompanied by a significant elevation in blood and soft-tissue arsenic concentration. Co-administration of DMSA and MiADMSA at lower dose (0.15 mmol/kg) was most effective not only in reducing arsenic-induced oxidative stress but also in depleting arsenic from blood and soft tissues compared to other treatments. This combination was also able to repair DNA damage caused following arsenic exposure. We thus recommend combined administration of DMSA and MiADMSA for achieving optimum effects of chelation therapy.     

Alleviation of Arsenic-Induced Pulmonary Oxidative Damage by GSPE as Shown during In vivo and In vitro Experiments

A long-term exposure to arsenic may lead to lung damage due to oxidative stress. In this context, GSPE can play a major role as a strong antioxidant. Our study attempted to reveal the connection between arsenic-induced lung injury and the antagonistic effect of GSPE. For this purpose, BEAS-2B cells and Kunming mice were exposed to different dosages of As₂O₃ and GSPE. Oxidative stress indicators were detected both in vivo and in vitro. Cell survival rate and morphological changes in the lung tissue (H&E staining) were evaluated as well. It was exhibited that As₂O₃ increased oxidative stress both in vivo and in vitro and decreased cells viability. In contrast, higher cell survival rate was revealed in the group treated with arsenic plus GSPE after 24 h as compared to that in the arsenic group. GSPE effectively reduced oxidative stress levels, along with increasing antioxidant capacity. In vivo experiments in arsenic-exposed group showed alveolar septum to be significantly thickened with considerable capillary congestion and invasion by inflammatory cells. After the intervention with GSPE, there seemed to be a dramatic reversal of morphology with thinning of the alveolar septum, decrease in capillary congestion, and number of inflammatory cells. This had shown that GSPE can effectively reduce the levels of oxidative stress, induced by arsenic in mice lung tissue. Conversely, antioxidant enzymes or products were increased. The experiment proved that GSPE can protect the lungs from oxidative damage induced by arsenic, and it may also be used as an antagonist against arsenic injuries.     

Oxidative stress in the pathogenesis of nonalcoholic fatty liver disease,in rats fed with a choline-deficient diet

Background/Aim : The pathogenesis of Nonalcoholic Fatty Liver Disease remains largely unknown, but oxidative stress seems to be involved. The aim of this study was to evaluate the role of oxidative stress in experimental hepatic steatosis induced by a choline-deficient diet. Methods : Fatty liver disease was induced in Wistar rats by a choline-deficient diet. The animals were randomized into three groups: I (G1) and II (G2), n=6 each - fed with a choline-deficient diet for four and twelve weeks respectively; Group III (control-G3; n=6) - fed with a standard diet for twelve weeks. Samples of plasma and liver were submitted to biochemical, histological and oxidative stress analysis. Variables measured included serum levels of aminotransferases (AST, ALT), cholesterol and triglycerides. Oxidative stress was measured by lucigenin-enhanced luminescence and the concentration of hydroperoxides (CE-OOH-cholesteryl ester) in the liver tissue. Results: We observed moderate macro- and microvesicular fatty change in periportal zones G1 and G2 as compared to controls (G3). In G2, fatty change was more severe. The inflammatory infiltrate was scanty and no fibrosis was seen in any group. There was a significant increase of AST and triglycerides in G1 and G2 as compared to control group G3. The lucigenin-amplified luminescence (cpm/mg/min × 10³) was significantly increased in G1 (1393±790) and G2 (7191±500) as compared to controls (513±170), p <0.05. The concentrations of CE-OOH were higher in G1 (5.7±0.9 nmol/mg protein) as compared to control (2.6±0.7 nmol/mg protein), p <0.05. Conclusion: 1) Oxidative stress was found to be increased in experimental liver steatosis; 2) The production of reactive oxygen species was accentuated when liver steatosis was more severe; 3) The alterations produced by oxidative stress could be an important step in the pathogenesis of nonalcoholic fatty liver disease.     

An Investigation Into the Effects of Long-Term 50-Hz Power-Frequency Electromagnetic Field Exposure on Hematogram,Blood Chemistry,Fibrosis, and Oxidant Stress Status in the Liver and the Kidney From Sprague–Dawley Rats

Power-frequency electromagnetic fields (PF-EMFs) at 50 Hz are potential health risk factors. This study aimed to explore the effects of long-term exposure to 50-Hz PF-EMFs on general physiological conditions in Sprague–Dawley (SD) rats. During a 24-week exposure period, the body mass and water and food intake of the animals were recorded regularly. The hematologic parameters were detected every 12 weeks, and blood chemistry analyses were performed every 4 weeks. After sacrifice, morphology was identified by hematoxylin–eosin, Masson, and immunohistochemical staining. Fibrosis-related gene expression and oxidative stress status were also detected. Compared with the control group, exposure to 30, 100, or 500 μT PF-EMF did not exert any effect on body mass, food intake, or water intake. Similarly, no significant differences were found in hematologic parameters or blood chemistry analyses among these groups. Furthermore, morphological assays showed that exposure to PF-EMFs had no influence on the structure of the liver or kidney. Finally, fibrosis-related gene expression and oxidative stress status were unaltered by PF-EMF exposure. The present study indicates that 24 weeks of exposure to PF-EMFs at intensities of 30, 100, or 500 μT might not affect hemograms, blood chemistry, fibrosis, or oxidative stress in the liver or kidney in SD rats. © 2020 Bioelectromagnetics Society     

Neuroglobin Involvement in the Course of Arsenic Toxicity in Rat Cerebellar Granule Neurons

Exposure to arsenic in drinking water results in a widespread environmental problem in the world, and the brain is a major target. Neuroglobin is a vertebrate heme protein regarded as playing neuroprotective role in hypoxia or oxidative stress. In this study, we investigated the toxic effects of sodium arsenite (NaAsO₂) on primary cultured rat cerebellar granule neurons (CGNs) and detected neuroglobin (Ngb) expression in rat CGNs exposed to NaAsO₂. Our results show that apoptosis was obviously induced by NaAsO₂ treatment in rat CGNs by annexin V-fluorescein isothiocyanate assay. Intracellular reactive oxygen species generation increased significantly in the cells exposed to NaAsO₂, and the apoptotic effects could be partially reversed by antioxidant N-acetyl-l-cysteine. Ngb protein and mRNA expression were significantly downregulated in rat CGNs shortly after NaAsO₂ exposure and then upregulated after a longer time of exposure. Furthermore, mRNA expression changed more than protein expression and the toxic effect of NaAsO₂ on Ngb expression is dose dependent. Higher Ngb expression was also detected in rat cerebellum, but not in other parts (cerebrum, hippocampus, and midbrain) of the brain exposed to NaAsO₂ for 16 weeks. Taken together, cytotoxic effects of NaAsO₂ on rat CGNs is induced at least partly by oxidative stress and Ngb may influence the course of arsenic toxicity in rat CGNs and rat cerebellum.     

Chronic unpredictable stress exacerbates 7,12-dimethylbenz (a) anthracene induced hepatotoxicity and nephrotoxicity in Swiss albino mice

Oxidative stress, a pervasive condition induced by stress has been implicated and recognized to be a prominent feature of various pathological states including cancer and their progression. The present study sought to validate the effectiveness of chronic unpredictable stress (CUS) on hepatic and renal toxicity in terms of alterations of various in vivo biochemical parameters, oxidative stress markers and the extent of DNA damage in Swiss albino mice. Animals were randomized into different groups based on their exposure to CUS alone, 7,12-dimethylbenz (a) anthracene (DMBA) alone (topical), DMBA-12-O-tetradecanoylphorbol-13-acetate (TPA) (topical), and exposure to CUS prior to DMBA or DMBA-TPA treatment, and sacrificed after 16 weeks of treatment. Prior exposure to CUS increased the pro-oxidant effect of carcinogen as depicted by significantly compromised levels of antioxidants; superoxide dismutase, catalase, glutathione-S-transferase, glutathione reductase, reduced glutathione in hepatic and renal tissues accompanied by a significant elevation of thiobarbituric acid reactive species (TBARS) as compared to DMBA alone or DMBA-TPA treatments. Loss of structural integrity at the cellular level due to stress-induced oxidative damage was demonstrated by significant increases in the hepatic levels of intracellular marker enzymes such as glutamate oxaloacetate transaminase, glutamate pyruvate transaminase and alkaline phosphatase, and significantly reduced levels of uric acid in kidney tissues. The results of DNA damage studies further positively correlated with all the above biochemical measurements. Thus, exposure to physical or psychological stress may significantly enhance the hepatotoxic and nephrotoxic potential of carcinogens through enhanced oxidative stress even if the treatment is topical.     

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.     

Possible GABAergic Modulation in the Protective Effect of Zolpidem in Acute Hypoxic Stress-induced Behavior Alterations and Oxidative Damage

Hypoxia is an environmental stressor that is known to elicit alterations in both the autonomic nervous system and endocrine functions. The free radical or oxidative stress theory holds that oxidative reactions are mainly underlying neurodegenerative disorders. In fact among complex metabolic reactions occurring during hypoxia, many could be related to the formation of oxygen derived free radicals, causing a wide spectrum of cell damage. In present study, we investigated possible involvement of GABAergic mechanism in the protective effect of zolpidem against acute hypoxia-induced behavioral modification and biochemical alterations in mice. Mice were subjected to acute hypoxic stress for a period of 2 h. Acute hypoxic stress for 2 h caused significant impairment in locomotor activity, anxiety-like behavior, and antinocioceptive effect in mice. Biochemical analysis revealed a significant increased malondialdehyde, nitrite concentrations and depleted reduced glutathione and catalase levels. Pretreatment with zolpidem (5 and 10 mg/kg, i.p.) significantly improved locomotor activity, anti-anxiety effect, reduced tail flick latency and attenuated oxidative damage (reduced malondialdehyde, nitrite concentration, and restoration of reduced glutathione and catalase levels) as compared to stressed control (hypoxia) (P < 0.05). Besides, protective effect of zolpidem (5 mg/kg) was blocked significantly by picrotoxin (1.0 mg/kg) or flumazenil (2 mg/kg) and potentiated by muscimol (0.05 mg/kg) in hypoxic animals (P < 0.05). These effects were significant as compared to zolpidem (5 mg/kg) per se (P < 0.05). Present study suggest that the possible involvement of GABAergic modulation in the protective effect of zolpidem against hypoxic stress.