Molecular Evidence of the Inhibitory Potential of Melatonin against NaAsO2-Induced Aging in Male Rats.

Arsenic (As) poisoning is widespread due to exposure to pollution. The toxic level of (As) causes oxidative stress-induced aging and tissue damage. Since melatonin (MLT) has anti-oxidant and anti-aging properties, we aimed to evaluate the protective effect of MLT against the toxicity of sodium arsenite (NaAsO2). Healthy male NMRI mice were divided into eight different groups. The control group received a standard regular diet. Other groups were treated with varying diets, including MLT alone, NaAsO2, and NaAsO2 plus MLT. After one month of treatment, biochemical and pathological tests were performed on blood, heart, and lung tissue samples. NaAsO2 increased the levels of TNF-α, 8-hydroxy-2-deoxy guanosine (8OHdG), malondialdehyde (MDA), reactive oxygen species (ROS), and high mobility group box 1 (HMGB1), increased the expression of TNF receptor type 1-associated death domain (TRADD) mRNA and telomerase reverse transcriptase, and decreased the expression of Klotho (KL) mRNA in both plasma and tissues. In contrast, MLT reduced MDA, ROS, HMGB1, lactate, and TNF-α enhanced the mRNA expression of KL, and suppressed the mRNA expression of the TERT and TRADD genes. Thus, MLT confers potent protection against NaAsO2- induced tissue injury and oxidative stress.

Ferulic acid attenuates arsenic-induced cardiotoxicity in rats.

Arsenic (As), a potent environmental toxin, causes cardiac functional impairments. Ferulic acid (FA), a ubiquitous dietary hydroxycinnamate, exerts beneficial effects on human health. Hence, the present study investigated the effect of FA on myocardial oxidative stress parameters, ATP level, the status of cardiac cytoskeleton intermediate filaments-desmin and vimentin, and AMPK signaling proteins in As-intoxicated rats. Wistar rats were administered orally with FA-40 mg/kg and As-5 mg/kg alone and in combination for 30 days. Myocardial As content, serum cardiac marker enzyme activities including creatine kinase-isoenzyme, lactate dehydrogenase, and aspartate aminotransferase were increased in As-exposed rats. An accumulation of myocardial oxidants such as reactive oxygen species, lipid peroxidation, nitric oxide, protein carbonyl content, and histological aberrations was observed. A significant decrease of myocardial antioxidants comprises superoxide dismutase, catalase, glutathione peroxidase, reduced glutathione, and ascorbic acid and declined expression of desmin and vimentin was noted. Impaired energy signaling molecules AMPKα (Thr172), AMPKß1/2 (Ser108), ACC (Ser79), and intracellular myocardial ATP depletion were observed in As-intoxicated animals. FA attenuates As-induced cardiac dysfunction by restoring the expression of intermediate filaments and AMPK proteins. Based on the above findings, FA treatment could be used as a novel therapeutic against As-induced cardiac dysfunction.

Protective Effect of Azadirachta indica and Vitamin E Against Arsenic Acid-Induced Genotoxicity and Apoptosis in Rats.

Sodium arsenite (NaAsO2) is one of the major environmental toxicants with severe toxicological consequences in some developing and developed countries. Rats in Group A received normal saline. Genotoxicity and apoptosis were induced by single intraperitoneal injection of 10 mg/kg sodium arsenite to rats in Groups B-F. Rats in Groups C and D had earlier been pretreated with Azadirachta indica (100 and 200 mg/kg) or E and F with vitamin E (50 and 100 mg/kg), respectively. Markers of oxidative stress, inflammation, hepatic damage, genotoxicity, and apoptosis were assessed. Pretreatment of rats with either Azadirachta indica or vitamin E led to a significant (p <.05) increase in the activities of glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), and reduced glutathione (GSH) in the liver compared to the group that received NaAsO2 alone. Markers of oxidative stress and inflammation, malondialdehyde (MDA), hydrogen peroxide (H2O2) generation, nitric oxide (NO), and myeloperoxidase (MPO), were significantly (p <.05) lowered in rats pretreated with Azadirachta indica or vitamin E. The frequency of micronucleated polychromatic erythrocytes (MNPCEs) and expression of caspase-3 were significantly (p <.05) reduced in rats pretreated with either Azadirachta indica or vitamin E compared to rats intoxicated with arsenite. Histopathology of the liver showed areas of infiltration of inflammatory cells with deaths of numerous hepatocytes in NaAsO2-intoxicated rats, and these were reversed by Azadirachta indica. Together, we report for the first time the genoprotective and antiapoptotic effect of Azadirachta indica by a significant reduction in the frequency of micronuclei-induced apoptosis and oxidative stress by arsenic intoxication.

Linking arsenite- and cadmium-generated oxidative stress to microsatellite instability in vitro and in vivo.

Mismatch repair (MMR) corrects replicative errors and minimizes DNA damage that occurs frequently in microsatellites. MMR deficiency is manifested as microsatellite instability (MSI), which contributes to hypermutability and cancer pathogenesis. Genomic instability, including MSI and chromosomal instability, appears to be responsible for the carcinogenesis of arsenic and cadmium, common contaminants in our environment. However, few studies have addressed arsenic- or cadmium-induced MSI, especially its potential link with arsenic- or cadmium-generated oxidative stress, due to the lack of quantifiable MSI assays and cost-effective animal models. Here, using a dual-fluorescent reporter, we demonstrate that sub-lethal doses of cadmium or arsenite, but not arsenate, increased the MSI frequency in human colorectal cancer cells. Arsenite- and cadmium-induced MSI occurred concomitantly with increased levels of reactive species and oxidative DNA damage, and with decreased levels of MMR proteins. However, N-acetyl-l-cysteine (NAC) suppressed arsenite- and cadmium-induced MSI and oxidative stress while restoring the levels of MMR proteins in the cells. Similarly, MSI was induced separately by arsenite and cadmium, and suppressed by NAC, in zebrafish in a fluorescinated PCR-based assay with newly-developed microsatellite markers and inter-segmental comparisons. Of five selected antioxidants examined, differential effects were exerted on the MSI induction and cytotoxicity of both arsenite and cadmium. Compared to MMR-proficient cells, MMR-deficient cells were more resistant to arsenic-mediated and cadmium-mediated cytotoxicity. Our findings demonstrate a novel linkage between arsenite-generated and cadmium-generated oxidative stress and MSI induction. Our findings also caution that antioxidants must be individually validated before being used for preventing arsenite- and cadmium-induced MSI that is associated with cancer development.

Candesartan ameliorates arsenic-induced hypertensive vascular remodeling by regularizing angiotensin II and TGF-beta signaling in rats.

Arsenic exposure can cause several cardiovascular diseases, including hypertension, atherosclerosis and microvascular disease. Earlier, we reported that arsenic-mediated enhancement of angiotensin II (AngII) signaling can impair vascular physiology. Here, we investigated whether the AT1 receptor (AT1R) blocker candesartan can ameliorate the arsenic-induced hypertensive vascular remodeling in rats and whether the amelioration could relate to attenuation in vascular AngII and TGF-ß signaling. Rats were exposed to sodium arsenite (50ppm) through drinking water for 90 consecutive days. Candesartan (1mg/kg bw, orally) was administered once daily during the last 30days of arsenic exposure. Non-invasive blood pressure was recorded weekly in conscious rats, while AngII-induced change in mean arterial pressure in anaesthetized rats was measured by invasive method on the 91st day. On this day, blood was collected from other animals for measuring AngII level. Western blot of AT1, AT2 and TßRII receptors; ELISA of PTK, RasGAP, ERK-1/2, TGF-ß and CTGF; immunohistochemistry of phosphorylated Smad3, Smad4 and collagen III, hydroxyproline/total collagen estimation, collagen deposition by Masson's trichrome staining and histomorphometry were carried out in thoracic aorta. Arsenic increased non-invasive systolic, diastolic and mean arterial pressure. Further, AngII caused concentration-dependent incremental change in mean arterial pressure in the arsenic-exposed rats. Arsenic upregulated AT1 and TßRII receptor proteins; elevated the levels of PTK, ERK-1/2, TGF-ß and CTGF, decreased RasGAP level and augmented the immunoreactivities of Smad3, Smad4 and collagen III. Arsenic also increased hydroxyproline/total collagen level, proliferation of collagen fibres and thickness of aortic wall and collagenous adventitia. Candesartan normalized blood pressure, regularized receptor expressions, MAP kinase and TGF-ß signaling, restored collagen deposition and regressed aortic thickness. Our results demonstrate that candesartan can ameliorate the arsenic-mediated systemic hypertension and vascular remodeling in rats by regularizing the signaling pathways of AngII and TGF-ß.

U937 cell apoptosis induced by arsenite is prevented by low concentrations of mitochondrial ascorbic acid with hardly any effect mediated by the cytosolic fraction of the vitamin.

Arsenite directly triggers cytochrome c and Smac/DIABLO release in mitochondria isolated from U937 cells. These effects were not observed in mitochondria pre-exposed for 15 min to 10 µM L-ascorbic acid (AA). In other experiments, intact cells treated for 24-72 h with arsenite were found to die by apoptosis through a mechanism involving mitochondrial permeability transition. Pre-exposure (15 min) to low micromolar concentrations of AA and dehydroascorbic acid (DHA), resulting in identical cytosolic levels of the vitamin, had a diverse impact on cell survival, as cytoprotection was only observed after treatment with AA. Also the mitochondrial accumulation of the vitamin was restricted to AA exposure. An additional indication linking cytoprotection to the mitochondrial fraction of the vitamin was obtained in experiments measuring susceptibility to arsenite in parallel with loss of mitochondrial and cytosolic AA at different times after vitamin exposure. Finally, we took advantage of our recent findings that DHA potently inhibits AA transport to demonstrate that DHA abolishes all the protective effects of AA, under the same conditions in which the mitochondrial accumulation of the vitamin is prevented without affecting the overall cellular accumulation of the vitamin.

Alleviative effect of quercetin on rat testis against arsenic: a histological and biochemical study.

The preventive effect of quercetin on arsenic stimulated reproductive ailments in male Sprague Dawely (SD) rats was investigated. Twenty rats were divided into four groups. The first group served as a control and was provided tap water. The second group of rats was treated with sodium arsenite at the dose of 50 ppm in drinking water. The third group served as a positive control and received an oral dose of quercetin (50 mg/kg). In the fourth group, quercetin (50 mg/kg) was co-administered orally with arsenic (50 ppm in drinking water). All the treatments were carried out for 49 days. Arsenic treatment resulted in adverse morphological and histopathological changes in testis of rats including reduced epithelial height and tubular diameter, and increased luminal diameter. In contrast, these adverse effects of arsenic were eliminated by co-administration of quercetin. Additionally arsenic treatment significantly increased testicular thiobarbituric acid reactive substance (TBARS) levels while catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and glutathione reductase (GSR) activities, and plasma and intra-testicular testosterone concentrations, were decreased significantly. Lipid peroxidation (LPO) was significantly suppressed and depleted antioxidant defense mechanism was restored by the quercetin co-treatment. Also quercetin treatment resulted in a marked increase in plasma and testicular testosterone concentrations. On the basis of these findings, it was concluded that quercetin may be used as a potential therapeutic drug against arsenic induced reproductive toxicity.

Arsenic inhibits hedgehog signaling during P19 cell differentiation.

Arsenic is a toxicant found in ground water around the world, and human exposure mainly comes from drinking water or from crops grown in areas containing arsenic in soils or water. Epidemiological studies have shown that arsenic exposure during development decreased intellectual function, reduced birth weight, and altered locomotor activity, while in vitro studies have shown that arsenite decreased muscle and neuronal cell differentiation. The sonic hedgehog (Shh) signaling pathway plays an important role during the differentiation of both neurons and skeletal muscle. The purpose of this study was to investigate whether arsenic can disrupt Shh signaling in P19 mouse embryonic stem cells, leading to changes muscle and neuronal cell differentiation. P19 embryonic stem cells were exposed to 0, 0.25, or 0.5 µM of sodium arsenite for up to 9 days during cell differentiation. We found that arsenite exposure significantly reduced transcript levels of genes in the Shh pathway in both a time and dose-dependent manner. This included the Shh ligand, which was decreased 2- to 3-fold, the Gli2 transcription factor, which was decreased 2- to 3-fold, and its downstream target gene Ascl1, which was decreased 5-fold. GLI2 protein levels and transcriptional activity were also reduced. However, arsenic did not alter GLI2 primary cilium accumulation or nuclear translocation. Moreover, additional extracellular SHH rescued the inhibitory effects of arsenic on cellular differentiation due to an increase in GLI binding activity. Taken together, we conclude that arsenic exposure affected Shh signaling, ultimately decreasing the expression of the Gli2 transcription factor. These results suggest a mechanism by which arsenic disrupts cell differentiation.

Histological and histometrical study of the protective role of α-tocopherol against sodium arsenite toxicity in rat ovaries.

This study examines histometrical changes induced by sodium arsenite (SA), as an environmental pollutant, and investigates the protective effect of α-tocopherol on ovaries of SA-treated rats during the prenatal stage until sexual maturity. Rats were classified into groups: control, SA (8 ppm/day), α-tocopherol (100 ppm/day), and SA+α-tocopherol. Treatment was performed from pregnancy until maturation when the rats and ovaries were weighed. The Cavalieri method was used to estimate volume of the ovaries, cortex, medulla, and corpus luteum. The mean diameter of oocytes, granulosa cells, and nuclei were measured and volume was estimated using the Nucleator method. The number of oocytes and thickness of the zona pellucida (ZP) were determined using an optical dissector and orthogonal intercept method, respectively. SA reduced the body and ovary weight, the number of secondary, antral and Graafian oocytes, volume of the ovaries, cortex, medulla and corpus luteum, mean diameter and volume of oocytes in primordial and primary follicles, mean diameter and volume of oocyte nuclei in all types of follicles, and mean thickness of the ZP in secondary and antral follicles. Also, the mean diameter and volume of granulosa cells and their nuclei in antral and Graafian follicles decreased significantly. Vacuolization and vascular congestion in the corpus luteum and an increase in the number of atretic oocytes were seen in the SA group. Most of these parameters were unchanged from the control level in the SA+α-tocopherol group. It was concluded that α-tocopherol supplementation reduced the toxic effects of SA exposure on ovarian tissue in rats.

Biogenic synthesis of selenium nanoparticles and their effect on As(III)-induced toxicity on human lymphocytes.

A bioreductive capacity of a plant, Terminalia arjuna leaf extract, was utilized for preparation of selenium nanoparticles. The leaf extract worked as good capping as well as stabilizing agent and facilitated the formation of stable colloidal nanoparticles. Resulting nanoparticles were characterized using UV-Vis spectrophotometer, transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction analysis (XRD), respectively. The colloidal solution showed the absorption maximum at 390 nm while TEM and selected area electron diffraction (SAED) indicated the formation of polydispersed, crystalline selenium nanoparticles of size raging from 10 to 80 nm. FT-IR analysis suggested the involvement of O-H, N-H, C=O, and C-O functional group of the leaf extract in particle formation while EDAX analysis indicated the presence of selenium in synthesized nanoparticles. The effect of nanoparticles on human lymphocytes treated with arsenite, As(III), has been studied. Studies on cell viability using MTT assay and DNA damage using comet assay revealed that synthesized selenium nanoparticles showed protective effect against As(III)-induced cell death and DNA damage. Chronic ingestion of arsenic infested groundwater, and prevalence of arsenicosis is a serious public health issue. The synthesized benign nanoselenium can be a promising agent to check the chronic toxicity caused due to arsenic exposure.

Dual role of resveratrol in modulation of genotoxicity induced by sodium arsenite via oxidative stress and apoptosis.

The potential benefits of resveratrol as an anticancer (proapoptosis) and antioxidant (pro-survival) compound have been studied extensively. However, the role of resveratrol in modulation of the toxicity induced by sodium arsenite (NaAsO2) is still unclear. In the present study, we examined the effects of resveratrol on NaAsO2-induced cytotoxicity, DNA and chromosomal damage, cell cycle progression, apoptosis and oxidative stress in human lung adenocarcinoma epithelial (A549) cell line at concentrations from 1 to 20 µM after 24h exposure. Our results revealed that at 1 and 5 µM, resveratrol was found to exert benefit effects, promoting cell viability and proliferation over 24h NaAsO2 exposure, whereas, resveratrol was showed to inhibit cell survival under the same condition at 20 µM. Corresponding to the opposing effect of resveratrol at low vs. high concentrations, DNA and chromosomal damage, cell apoptotic rate and level of oxidative stress were also alleviated by lower concentrations (1, 5 µM) of resveratrol, but exacerbated by higher concentration (20 µM) resveratrol. Our study implicates that resveratrol is the most beneficial to cells at 1 and 5 µM and caution should be taken in applying resveratrol as an anticancer therapeutic agent or nutraceutical supplement due to its concentration dependent effect.

Effect of glucosamine and chitooligomer on the toxicity of arsenite against Escherichia coli.

Escherichia coli was selected as the sample to study the toxicity of arsenite in the presence of saccharides. The effect of glucosamine, N-acetylglucosamine, glucose, lactose, sucrose, glucosamine and cyclodextrin on the toxicity of arsenite against E. coli was investigated by microcalorimetry. The glucosamine and the tested chitooligomer decreased the toxicity of arsenite on cells of E. coli, and the effect of glucosamine was stronger than that of the chitooligomer. These results suggest that the glucosamine and chitooligomer may be employed as the assistant antidote for arsenite.

Efflux of glutathione and glutathione complexes from human erythrocytes in response to inorganic arsenic exposure.

The objective of the present study was to investigate if arsenic exposure results in glutathione efflux from human erythrocytes. Arsenite significantly depleted intracellular nonprotein thiol level in a time- and concentration-dependent manner. The intracellular nonprotein thiol level was decreased to 0.767 ± 0.0017 µmol/ml erythrocyte following exposure to 10 mM of arsenite for 4 h. Extracellular nonprotein thiol level was increased concomitantly with the intracellular decrease and reached to 0.481 ± 0.0005 µmol/ml erythrocyte in 4 h. In parallel with the change in extracellular nonprotein thiol levels, significant increases in extracellular glutathione levels were detected. Extracellular glutathione levels reached to 0.122 ± 0.0013, 0.226 ± 0.003, and 0.274 ± 0.004 µmol/ml erythrocyte with 1, 5, and 10 mM of arsenite, respectively. Dimercaptosuccinic acid treatment of supernatants significantly increased the glutathione levels measured in the extracellular media. Utilization of MK571 and verapamil, multidrug resistance-associated protein 1 and Pgp inhibitors, decreased the rate of glutathione efflux from erythrocytes suggesting a role for these membrane transporters in the process. The results of the present study indicate that human erythrocytes efflux glutathione in reduced free form and in conjugated form or forms that can be recovered with dimercaptosuccinic acid when exposed to arsenite.

Glutathione serves an extracellular defence function to decrease arsenite accumulation and toxicity in yeast.

Arsenic is an environmental toxin and a worldwide health hazard. Since this metalloid is ubiquitous in nature, virtually all living organisms require systems for detoxification and tolerance acquisition. Here, we show that during chronic exposure to arsenite [As(III)], Saccharomyces cerevisiae (budding yeast) exports and accumulates the low-molecular-weight thiol molecule glutathione (GSH) outside of cells. Extracellular accumulation of the arsenite triglutathione complex As(GS)3 was also detected and direct transport assays demonstrate that As(GS)3 does not readily enter cells. Yeast cells with increased extracellular GSH levels accumulate less arsenic and display improved growth when challenged with As(III). Conversely, cells defective in export and extracellular accumulation of GSH are As(III) sensitive. Taken together, our data are consistent with a novel detoxification mechanism in which GSH is exported to protect yeast cells from arsenite toxicity by preventing its uptake.

[6]-Gingerol isolated from ginger attenuates sodium arsenite induced oxidative stress and plays a corrective role in improving insulin signaling in mice.

Arsenic toxicity induces type 2 diabetes via stress mediated pathway. In this study, we attempt to reveal how sodium arsenite (iAs) could induce stress mediated impaired insulin signaling in mice and if an isolated active fraction of ginger, [6]-gingerol could attenuate the iAs intoxicated hyperglycemic condition of mice and bring about improvement in their impaired insulin signaling. [6]-Gingerol treatment reduced elevated blood glucose level and oxidative stress by enhancing activity of super oxide dismutase (SOD), catalase, glutathione peroxidase (GPx) and GSH. [6]-Gingerol also helped in increasing plasma insulin level, brought down after iAs exposure. iAs treatment to primary cell culture of ß-cells and hepatocytes in vitro produced cyto-degenerative effect and accumulated reactive oxygen species (ROS) in pancreatic ß-cells and hepatocytes of mice. [6]-Gingerol appeared to inhibit/intervene iAs induced cyto-degeneration of pancreatic ß-cells and hepatocytes, helped in scavenging the free radicals. The over-expression of TNFα and IL6 in iAs intoxicated mice was down-regulated by [6]-gingerol treatment. iAs intoxication reduced expression levels of GLUT4, IRS-1, IRS-2, PI3K, AKT, PPARγ signaling molecules; [6]-gingerol mediated its action through enhancing the expressions of these signaling molecules, both at protein and mRNA levels. Thus, our results suggest that [6]-gingerol possesses an anti-hyperglycemic property and can improve impaired insulin signaling in arsenic intoxicated mice.

All-trans retinoic acid protects against arsenic-induced uterine toxicity in female Sprague-Dawley rats.

BACKGROUND AND PURPOSE: Arsenic exposure frequently leads to reproductive failures by disrupting the rat uterine histology, hormonal integrity and estrogen signaling components of the rat uterus, possibly by generating reactive oxygen species. All-trans retinoic acid (ATRA) was assessed as a prospective therapeutic agent for reversing reproductive disorders. EXPERIMENTAL APPROACH: Rats exposed to arsenic for 28 days were allowed to either recover naturally or were treated simultaneously with ATRA for 28 days or treatment continued up to 56 days. Hematoxylin-eosin double staining was used to evaluate changes in the uterine histology. Serum gonadotropins and estradiol were assayed by ELISA. Expression of the estrogen receptor (ERα), an estrogen responsive gene vascular endothelial growth factor (VEGF), and cell cycle regulatory proteins, cyclin D1 and CDK4, was assessed by RT-PCR, immunohistochemistry and western blot analysis. KEY RESULTS: ATRA ameliorated sodium arsenite-induced decrease in circulating estradiol and gonadotropin levels in a dose- and time-dependent manner, along with recovery of luminal epithelial cells and endometrial glands. Concomitant up regulation of ERα, VEGF, cyclin D1, CDK4 and Ki-67 was also observed to be more prominent for ATRA-treated rats as compared to the rats that were allowed to recover naturally for 56 days. CONCLUSIONS AND IMPLICATIONS: Collectively, the results reveal that ATRA reverses arsenic-induced disruption of the circulating levels of gonadotropins and estradiol, and degeneration of luminal epithelial cells and endometrial glands of the rat uterus, indicating resumption of their functional status. Since structural and functional maintenance of the pubertal uterus is under the influence of estradiol, ATRA consequently up regulated the estrogen receptor and resumed cellular proliferation, possibly by an antioxidant therapeutic approach against arsenic toxicity.

Sodium arsenite-induced alteration in hepatocyte function of rat with special emphasis on superoxide dismutase expression pathway and its prevention by mushroom lectin.

This study was accomplished to exemplify the possible protective role of ascorbic acid and mushroom lectin against arsenic-induced cytotoxicity and impairment of superoxide dismutase (SOD) production pathway in hepatocytes of rat. Hepatocytes were isolated from rat and treated with sodium arsenite (AS), arsenic plus ascorbic acid (AS + AA) and arsenic plus mushroom lectin (AS + ML). A placebo control was also included. Arsenic treatment resulted in the depletion of cell proliferation, phagocytic activity (nitro blue tetrazolium index) and superoxide dismutase (SOD) activity, relative mRNA expression of superoxide dismutase 2 (SOD(2)) and enhanced production of nitric oxide (NO). Ascorbic acid, a standard antioxidant, could normalize cellular perturbation and SOD production pathway relating to gene expression, whereas partially purified Pleurotus florida lectin (PFL), an edible mushroom containing protein complex, maintained cellular activity and prevented stress by normalizing phagocytic (NBT index) and SOD activities vis-à-vis relative gene expression. It could further defend NO production of hepatocytes. Mushroom lectin strongly prevented sodium arsenite-induced damage of SOD production pathway in hepatocytes, and its effect was also comparable to a standard antioxidant, i.e. ascorbic acid.

The novel role of fenofibrate in preventing nicotine- and sodium arsenite-induced vascular endothelial dysfunction in the rat.

The present study investigated the effect of fenofibrate, an agonist of PPAR-alpha, in nicotine- and sodium arsenite-induced vascular endothelial dysfunction (VED) in rats. Nicotine (2 mg/kg/day, i.p., 4 weeks) and sodium arsenite (1.5 mg/kg/day, i.p., 2 weeks) were administered to produce VED in rats. The scanning electron microscopy study in thoracic aorta revealed that administration of nicotine or sodium arsenite impaired the integrity of vascular endothelium. Further, administration of nicotine or sodium arsenite significantly decreased serum and aortic concentrations of nitrite/nitrate and subsequently reduced acetylcholine-induced endothelium-dependent relaxation. Moreover, nicotine or sodium arsenite produced oxidative stress by increasing serum thiobarbituric acid reactive substances (TBARS) and aortic superoxide generation. However, treatment with fenofibrate (30 mg/kg/day, p.o.) or atorvastatin (30 mg/kg/day p.o., a standard agent) significantly prevented nicotine- and sodium arsenite-induced VED and oxidative stress by improving the integrity of vascular endothelium, increasing the concentrations of serum and aortic nitrite/nitrate, enhancing the acetylcholine-induced endothelium-dependent relaxation and decreasing serum TBARS and aortic superoxide anion generation. Conversely, co-administration of L-NAME (25 mg/kg/day, i.p.), an inhibitor of nitric oxide synthase, markedly attenuated these vascular protective effects of fenofibrate. The administration of nicotine or sodium arsenite altered the lipid profile by increasing serum cholesterol and triglycerides and consequently decreasing high-density lipoprotein levels, which were significantly prevented by treatment with fenofibrate or atorvastatin. It may be concluded that fenofibrate improves the integrity and function of vascular endothelium, and the vascular protecting potential of fenofibrate in preventing the development of nicotine- and sodium arsenite-induced VED may be attributed to its additional properties (other than lipid lowering effect) such as activation of eNOS and generation of NO and consequent reduction in oxidative stress.

Arsenic induces apoptosis of human umbilical vein endothelial cells through mitochondrial pathways.

To clarify the molecular mechanisms through which arsenic causes injuries to blood vessels, we analyzed the effects of sodium arsenite (NaAsO(2)) on the apoptosis of human umbilical vein endothelial cells (HUVECs), mitochondrial membrane potential (Delta Psi m), intracellular reactive oxygen species (ROS), and the expression of the related genes. HUVECs apoptosis increased and Delta Psi m decreased in a dose-dependent manner following arsenic treatment. Intracellular ROS showed 2 phase alterations: a slight decrease with low levels of arsenic (5 and 10 microM) treatment; but a sharp increase at higher concentrations (>or=20 microM). The arsenic-induced cell apoptosis and intracellular ROS were blocked by the addition of the antioxidant N-acetyl-L-cysteine (NAC). The mRNAs of superoxide dismutase 2 (SOD2) and NAD(P)H:quinone oxidoreductase 1 (NQO1) increased strikingly when cells were treated with a low concentration of NaAsO(2) (5 microM) and the level of induction was decreased with higher concentrations of arsenic treatment. Based on the results, we suggest that the decrease of Delta Psi m caused by arsenic and the resulting cell apoptosis may contribute to the injuries of blood vessel in arsenism. The decrease in intracellular ROS and the increase in SOD2 and NQO1 expressions observed when HUVECs were treated with low concentration of NaAsO(2), suggest the role of the two enzymes in protecting HUVECs from injuries of arsenic exposure.

Protective effect of Corchorus olitorius leaves on sodium arsenite-induced toxicity in experimental rats.

The present study was undertaken to evaluate the protective effect of aqueous extract of Corchorus olitorius leaves (AECO) against sodium arsenite-induced toxicity in experimental rats. The animals exposed to sodium arsenite at a dose of 10mg/kg body weight p.o. for 10days exhibited a significant inhibition (p<0.01) of hepatic and renal antioxidant enzymes namely superoxide dismutase, catalase, glutathione-S-transferase, glutathione peroxidase and glutathione reductase. In addition, arsenic intoxication significantly decreased (p<0.01) the level of reduced glutathione and increased (p<0.01) the levels of oxidized glutathione and thiobarbituric acid reactive substances in selected tissues. Treatment with AECO at doses of 50 and 100mg/kg body weight p.o. for 15days prior to arsenic intoxication significantly improved hepatic and renal antioxidant markers in a dose dependant manner. AECO treatment also significantly reduced the arsenic-induced DNA fragmentation of hepatic and renal tissues. Histological studies on the ultrastructural changes of liver and kidney supported the protective activity of the AECO. The results concluded that the treatment with AECO prior to arsenic intoxication has significant role in protecting animals from arsenic-induced hepatic and renal toxicity.