Copper oxide nanoparticles induce oxidative stress mediated apoptosis in carp (Cyprinus carpio) larva

Abstract

Negative effects of metal oxide nanoparticles on the aquatic organisms and ecosystems have recently much considered. Copper oxide nanoparticles are widely used in various industrial, and this problem cause concerns for aquatic organisms. This study aimed to determine the acute toxicity and the effects of copper oxide nanoparticles (CuO NPs) on tissue histology, bioaccumulation, antioxidant enzymes activity and the expression of apoptosis genes of the carp (Cyprinus carpio) larvae. For this purpose, four days old carp larvae after determination of the lethal concentration (LC50-96h), were exposed to 0.1, 0.2, 0.5 and 1 mg/l of CuO nanoparticles and control in three replicates. After seven days, histological studies showed no specific tissue damage at the studied concentrations, but the activities of superoxide dismutase (SOD), glutathione S-transferases (GST) and catalase (CAT) enzymes in all of the treatments, showed a significant increase compared to control (P < .05). Furthermore, gene expression analysis indicated that exposure to all the sublethal concentrations of CuO NPs significantly increased expression of Bax gene and decreased expression of Bcl-2 gene in comparison with the control group (p < .05). The highest level of enzymes activity was observed in 0.5 mg/l of CuO NPs, but the highest cell apoptosis (Bax/Bcl-2 ratio) and bioaccumulation of NPs was in larvae treated with 1 mg/l of CuO NPs. It can be concluded that the absorption and high bioaccumulation of CuO NPs in the carp larvae could be the cause and initiator of apoptosis in this fish as a result of oxidative stress.