Influence of Mercury Exposure on Oxidative Stress Biomarkers in Longitudinal Muscle of Holothuria forskali

Mercury (Hg) pollution is featuring as one of the major threat for marine ecosystem, biota and human health. Thereby, the objective of the current study was to evaluate the effect of environmentally relevant concentrations of mercury on oxidative stress, enzymatic and non-enzymatic antioxidant defenses and metallothionein levels in the longitudinal muscle of sea cucumber Holothuria forskali. With this purpose, sea cucumber were exposed to graded concentrations of mercury chloride HgCl2 (40, 80 and 160 µg L-1) for 96 h under controlled conditions. Our findings revealed that Hg burden in the longitudinal muscle tended to increase with increasing HgCl2 concentrations. The Hg exposure promoted muscular oxidative stress as evidenced by the increased levels of malondialdehyde (MDA), advanced oxidation protein product (AOPP) and metallothionein (MT) of treated animals compared with controls. Additionally, significant increases in the activities of the enzymatic (glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT)) and non-enzymatic (non-protein thiol (NPSH) and glutathione (GSH)) antioxidants were also observed in all treated groups. Overall, this study proved that mercury is able to produce deleterious effects even at the lowest environmentally-realistic concentration in the Holothuria forskali longitudinal muscle which may be considered as a target tissue of mercury accumulation in holothurian.