Oxidative stress and antioxidant defenses in goldfish liver in response to short-term exposure to arsenite

Arsenic is an environmental pollutant capable of causing oxidative stress, disturbance of metabolism, and cancer development. The present study was undertaken to investigate the effects of exposure to sodium arsenite on the glutathione pool, lipid peroxidation, protein carbonyl levels, global DNA methylation, and activities of six antioxidant enzymes in goldfish liver. In a preliminary experiment, 7-day exposure to 200 mu M sodium arsenite, but not 10 or 100 mu M disturbed the glutathione status. A detailed investigation of oxidative stress development and antioxidant responses was further examined during different periods of exposure to 200 mu M sodium arsenite. This treatment increased lipid peroxide levels after 1 and 4 days of exposure but did not affect thiobarbituric acid reactive substances and protein carbonyls. Oxidized glutathione and the oxidative stress index rose after 4 days, but de novo glutathione synthesis decreased both parameters after 7 days. Activities of the main antioxidant enzymes - superoxide dismutase, catalase, and glutathione peroxidase, were elevated after longer periods of exposure, indicating an enhanced antioxidant response. Arsenite exposure led to DNA hypomethylation, which is an early marker of disturbed epigenetic regulations. The findings suggest that goldfish livers cope with arsenic-induced oxidative stress mainly through adaptive changes in the glutathione pool and antioxidant enzymes. Environ. Mol. Mutagen. 48:658-665, 2007. (C) 2007 Wiley-Liss, Inc.