Arsenic (As) is a toxic metalloid element that is present in air, water and soil. Inorganic arsenic tends to be more toxic than organic arsenic. Examples of methylated organic arsenicals include monomethylarsonic acid [MMA(V)] and dimethylarsinic acid [DMA(V)]. Reactive oxygen species (ROS)-mediated oxidative damage is a common denominator in arsenic pathogenesis. In addition, arsenic induces morphological changes in the integrity of mitochondria. Cascade mechanisms of free radical formation derived from the superoxide radical, combined with glutathione-depleting agents, increase the sensitivity of cells to arsenic toxicity. When both humans and animals are exposed to arsenic, they experience an increased formation of ROS/RNS, including peroxyl radicals (ROO•), the superoxide radical, singlet oxygen, hydroxyl radical (OH•) via the Fenton reaction, hydrogen peroxide, the dimethylarsenic radical, the dimethylarsenic peroxyl radical and/or oxidant-induced DNA damage. Arsenic induces the formation of oxidized lipids which in turn generate several bioactive molecules (ROS, peroxides and isoprostanes), of which aldehydes [malondialdehyde (MDA) and 4-hydroxy-nonenal (HNE)] are the major end products. This review discusses aspects of chronic and acute exposures of arsenic in the etiology of cancer, cardiovascular disease (hypertension and atherosclerosis), neurological disorders, gastrointestinal disturbances, liver disease and renal disease, reproductive health effects, dermal changes and other health disorders. The role of antioxidant defence systems against arsenic toxicity is also discussed. Consideration is given to the role of vitamin C (ascorbic acid), vitamin E (α-tocopherol), curcumin, glutathione and antioxidant enzymes such as superoxide dismutase, catalase and glutathione peroxidase in their protective roles against arsenic-induced oxidative stress.

/pdf/arsenic-toxicity-oxidative-stress-and-human-disease-2lp5eu82d7.pdf

Arsenic: toxicity, oxidative stress and human disease.

Spermatogenesis is an extremely active replicative process capable of generating approxi mately 1,000 sperm a second. The high rates of cell division inherent in this process imply correspondingly high rates of mitochondrial oxygen consumption by the germinal epithelium. However, the poor vascularization of the testes means that oxygen tensions in this tissue are low1 and that competition for this vital element within the testes is extremely intense. Since both spermatogenesis2 and Leydig cell steroidogenesis3,4 are vulnerable to oxidative stress, the low oxygen tension that characterizes this tissue may be an important component of the mechanisms by which the testes protects itself from free radical-mediated damage. In addition, the testes contain an elaborate array of antioxidant enzymes and free radical scavengers to ensure that the twin spermatogenic and steroidogenic functions of this organ are not impacted by oxidative stress. These antioxidant defence systems are of major importance because peroxidative damage is currently regarded as the single most important cause of impaired testicular function underpinning the pathological consequences of a wide range of conditions from testicular torsion to diabetes and xenobiotic exposure. This chapter sets out the specific nature of these antioxidant defence systems and also reviews the factors that have been found to impair their activity, precipitating a state of oxidative stress in the testes and impairing the latter’s ability to produce viable spermatozoa capable of initiating and supporting embryonic development.

/pdf/antioxidant-systems-and-oxidative-stress-in-the-testes-54n1pge1q7.pdf

Antioxidant systems and oxidative stress in the testes.

Gender differences in the disposition and toxicity of metals

Exposure to toxic metals remains a widespread occupational and environmental problem in world. There have been a number of reports in the recent past suggesting an incidence of childhood lead poisoning and chronic arsenic poisoning due to contaminated drinking water in many areas of West Bengal in India and Bangladesh has become a national calamity. Low level metal exposure in humans is caused by air, food and water intake. Lead and arsenic generally interferes with a number of body functions such as the central nervous system (CNS), the haematopoietic system, liver and kidneys. Over the past few decades there has been growing awareness and concern that the toxic biochemical and functional effects are occurring at a lower level of metal exposure than those that produce overt clinical and pathological signs and symptoms. Despite many years of research, we are still far from an effective treatment of chronic plumbism and arsenicosis. Medical treatment of acute and chronic lead and arsenic toxicity is furnished by chelating agents. Chelating agents are organic compounds capable of linking together metal ions to form complex ring-like structures called chelates. They have been used clinically as antidotes for acute and chronic poisoning. 2, 3-dimercaprol (BAL) has long been the mainstay of chelation therapy for lead or arsenic poisoning. Meso 2, 3, -dimercaptosuccinic acid (DMSA) has been tried successfully in animals as well as in a few cases of human lead and arsenic poisoning. DMSA could be a safe and effective method for treating lead or arsenic poisoning, but one of the major disadvantages of chelation with DMSA has been its inability to remove lead from the intracellular sites because of its lipophobic nature. Further, it does not provide protection in terms of clinical/ biochemical recovery. A new trend in chelation therapy is to use combined treatment. This includes the use of structurally different chelators or a combination of an adjuvant and a chelator to provide better clinical/biochemical recovery in addition to lead mobilization. The present review article attempts to provide update information about the current strategies being adopted for a safe, effective and specific treatment for two major toxic metals or metalloid.

http://joh.sanei.or.jp/pdf/E47/E47_1_01.pdf

Strategies for safe and effective therapeutic measures for chronic arsenic and lead poisoning.

Background
Inorganic arsenic is a major water pollutant and a known human carcinogen that has a suppressive influence on spermatogenesis and androgenesis in male reproductive system. However, the actual molecular events resulting in male reproductive dysfunctions from exposure to arsenic remain unclear. In this context, we evaluated the mode of action of chronic oral exposure of sodium arsenite on hypothalamo-pituitary- testicular activities in mature male albino rats.

/pdf/effects-of-chronic-exposure-to-sodium-arsenite-on-qdjd3cfc0w.pdf

Effects of chronic exposure to sodium arsenite on hypothalamo-pituitary-testicular activities in adult rats: possible an estrogenic mode of action.

The present work examined the changes in testicular activities in relation to testicular oxidative stress in cyclophosphamide as well as human chorionic gonadotrophin (hCG) co-treated cyclophosphamide treated Wistar strain rats. Testicular activities were evaluated by the quantification of spermatogenesis and by the measurement of steroidogenic key enzyme activities along with plasma levels of testosterone. Testicular oxidative stress in relation to cyclophosphamide treatment was monitored by the study of products of free radicals like conjugated dienes and malondialdehyde (MDA) as well as the activity of testicular antioxidant enzymes like peroxidase and catalase. Cyclophosphamide treatment at the dose of 5 mg/kg body weight/day for 28 days resulted a significant diminution in the activities of testicular Δ5, 3β-hydroxysteroid dehydrogenase (Δ5, 3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD) activities, plasma level of testosterone along with significant reduction in the number of germ cells...

Testicular gametogenic and steroidogenic activities in cyclophosphamide treated rat: a correlative study with testicular oxidative stress.

Arsenic, a major water pollutant in India, produces toxic effects on female reproductive system in rodent models at the dose available in drinking water in arsenic-intoxicated zones. This study examines the coadministration of L-ascorbate (vitamin C) on ovarian steroidogenesis, plasma levels of gonadotrophins, brain monoamines, and ovarian as well as uterine peroxidase activities in sodium arsenite–treated rats. After sodium arsenite treatment, relative ovarian and uterine weights, ovarian Δ5-3β-HSD and 17β-HSD activities, plasma levels of gonadotrophins, norepinephrine levels in midbrain and diencephalon, and the activities of peroxidase in ovary and uterus were decreased significantly. On the other hand, serotonin levels in midbrain and diencephalon were increased significantly 28 days after sodium arsenite treatment at the dose of 0.4 ppm/100 g body weight/rat/day. All these parameters were protected significantly and in most cases were unchanged from control level when L-ascorbate at 25 mg/100 g body weight/rat/day was coadministered orally with sodium arsenite. This cotreatment of L-ascorbate with sodium arsenite also restored the estrous cycle in a regular manner. We concluded that L-ascorbate plays a pivotal role in maintaining normal ovarian activities and brain monoamines in arsenic-treated rats.

Protection of sodium arsenite-induced ovarian toxicity by coadministration of L-ascorbate (vitamin C) in mature wistar strain rat

Effect of arsenic on ovarian steroidogenesis at the dose available in drinking water at wide areas of West Bengal is reported here. Weights of ovary, uterus and vagina along with biochemical activities of ovarian delta 5-3 beta-hydroxysteroid dehydrogenase (delta 5-3 beta-HSD) and 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) and plasma levels of LH, FSH and estrogen were measured in mature rats of the Wistar strain at diestrous phase following subchronic treatment with sodium arsenite at a dose of 0.4 ppm/rat/day for 16 days (4 estrous cycles) and 28 days (7 estrous cycles). A significant reduction in plasma levels of LH, FSH and estrogen along with significant diminution in the activities of ovarian delta 5-3 beta-HSD and 17 beta-HSD were observed following sodium arsenite treatment for 28 days. This duration of treatment also resulted in a marked degree in diminution in the weights of ovary, uterus and vagina, but 16 days of treatment did not exhibit any significant effect on these above parameters. Arsenic-treated rats exhibited a prolonged diestrous phase in the estrous cycle in contrast to control rats having 4 days of a regular estrous cycle. Deposition of arsenic in ovary, uterus, vagina and plasma was also monitored in arsenic-treated rats. The results of our experiment suggest that duration of arsenic treatment is the critical factor for its adverse effect on ovarian activities at the dose within the range noted in drinking water at several areas of West Bengal in India.

Effect of sodium arsenite on plasma levels of gonadotrophins and ovarian steroidogenesis in mature albino rats : duration-dependent response

Effects of ascorbic acid supplementation on the activity of acid phosphatase (ACP), alkaline phosphatase (ALP), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) on liver, kidney and serum in cyclophosphamide-treated female virgin rats were investigated. Oral administration of cyclophosphamide at the dose of 5 mg/kg body weight/day for 12 days resulted in a significant elevation in ACP and ALP activities in liver, kidney and serum. Ascorbic acid supplementation at the dose of 25 mg/kg body weight/day showed a significant protection in the activity of ACP in liver, kidney and serum, but only in ALP activity in kidney. ALP activities in liver and serum were not restored to control level by ascorbic acid supplementation. Activities of GOT and GPT were elevated significantly in liver, kidney and serum after cyclophosphamide treatment, and were protected and restored to control level by ascorbic acid supplementation.

Effect of ascorbic acid supplementation on liver and kidney toxicity in cyclophosphamide-treated female albino rats

Effect of human chorionic gonadotrophin coadministration on ovarian steroidogenic and folliculogenic activities in cyclophosphamide treated albino rats.

Sampa Ghosh

Papers

Testicular gametogenic and steroidogenic activities in cyclophosphamide treated rat: a correlative study with testicular oxidative stress.

Protection of sodium arsenite-induced ovarian toxicity by coadministration of L-ascorbate (vitamin C) in mature wistar strain rat

Effect of sodium arsenite on plasma levels of gonadotrophins and ovarian steroidogenesis in mature albino rats : duration-dependent response

Effect of ascorbic acid supplementation on liver and kidney toxicity in cyclophosphamide-treated female albino rats

Effect of human chorionic gonadotrophin coadministration on ovarian steroidogenic and folliculogenic activities in cyclophosphamide treated albino rats.