ENHANCING SELENOPROTEINS BY SELENIUM SUPPLEMENTATION AMONG PATIENTS SUFFERING FROM ARSENIC TOXICITY DUE TO INGESTION OF ARSENIC FROM GROUNDWATER IN BANGLADESH

Selenium supplements were given to patients in our clinical trial to combat arsenic poisoning in Bangladesh. The objective of our current study was to investigate the enhancement of a number of selenoproteins such as glutathione peroxidase (GPx) activity, selenoprotein P and thioredoxin reductase (TrxR) in serum samples in a group of arsenic patients after 0, 24 and 48 weeks of Se supplementation. The glutathione peroxidase (GPx) is a selenoprotein and it has been described as the body’s frontline defense against reactive oxidation species. More importantly, GPx is believed to be at least partly responsible for the reported anti-cancer properties of selenium. We have determined glutathione (GSH), and GPx activity, thioredoxin reductase (TrxR) activity and selenoprotein P in serum collected from arsenic patients before and after Se supplementation. Glutathione peroxidase (GPx) modifies the rate of the chemical reaction by reduced glutathione that includes the reduction of hydrogen peroxide and protects the cell from oxidative harm. Glutathione is used as the crucial electron donor to stimulate the reduced form of the selenocysteine. Thioredoxin reductase, a selenium-containing enzyme also offers protection against oxidative stress and plays important role in cell growth and transformation. Our assay of TrxR activity involves the reduction of 5,5’-dithio-bis(2-dintrobenzoic acid) by NADPH to 5-thio-2-nitrobenzoic acid (TNB) and measuring absorbance of this compound at 405-414 nm. The GPx activity, TrxR activity and selenoprotein P has significantly increased in arsenicosis patients after selenium supplementation over 48 week. There are also evidences that selenium in mammals promotes in vivo formation of seleno-bis-(S-gluthionylarsinium) ion and biliary excretion of this ion. Selenium appears to be an effective antidote for combating arsenic poisoning from drinking groundwater in Bangladesh.

Acknowledgements: The work has been supported by a grant from the National Institutes of Health, USA and partially by a grant from Wagner College.