Biomarkers of oxidative stress in the land snail, Theba pisana for assessing ecotoxicological effects of urban metal pollution

This study investigates the biomarkers of oxidative stress and heavy metal accumulation for assessing ecotoxicological effects of urban metal pollution in Alexandria city, Egypt. This investigation was performed in the digestive gland of roadside Theba pisana snails obtained from six different sites in the city. Relationships between heavy metal (Zn, Cu, Pb and Cd) concentrations and oxidative stress indicators were also examined. The results showed that mean concentrations of the measured elements (μg g−1 dry weight) were higher in polluted sites when compared to the background levels of the reference site. The pattern of metals accumulation at all sites was Zn > Cu > Pb > Cd. In the metal polluted sites, snails displayed higher mean of catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) activities, lower reduced glutathione (GSH) content and higher levels of lipid peroxidation (LPO) compared to snails from the reference site. All oxidative stress parameters were positively correlated to heavy metal concentrations except GSH content which exhibits negative correlation with the concentrations of these metals. Our results suggest that the tested antioxidant defenses are sensitive parameters that could be useful as oxidative stress biomarkers in snails exposed to the actual metals in the environment. These biomarkers when complemented with metal accumulation in the digestive gland of snails may provide a powerful biomonitor for the assessment of environmental metal pollution.