Mechanism of epigallocatechin-3-gallate in alleviating polychlorinated biphenyls-induced immunotoxicity in Scyllaparamamosain.

Polychlorinated biphenyls (PCBs) are pervasive environmental pollutants within marine ecosystems, posing substantial risks to aquatic organisms due to their enduring toxicological effects. This study examines the immunotoxic effects of PCBs exposure (1 ng/L) on the mud crab, Scylla paramamosain, and investigates the ameliorative potential of epigallocatechin-3-gallate (EGCG), a catechin compound. Mud crabs were exposed to an environmentally relevant concentration of 1 ng/L PCBs for 7 days, followed by intrahemocoelic injection of EGCG at a dose of 1 mg/kg body weight. Hemolymph was collected to measure total hemocyte count (THC), antioxidant enzyme activities and immune parameters. Apoptosis rate, phagocytic rate, ROS content and immune-related gene expression were also determined. The results indicate that EGCG effectively mitigates PCBs-induced apoptosis and enhances total hemocyte counts. Moreover, post-PCBs exposure treatment with EGCG significantly elevates the activity of key enzymes involved in antimicrobial and antioxidant defense mechanisms, including superoxide dismutase (SOD), catalase (CAT), acid phosphatase (ACP), and glutathione (GSH), highlighting its potential protective role against oxidative and microbial stress. Histological analysis of the hepatopancreas confirms that EGCG, a polyphenol derived from green tea, alleviates tissue damage induced by PCBs exposure. In addition to mitigating PCBs-induced immunotoxicity in S. paramamosain, this study also demonstrates that EGCG effectively reduces DNA damage in PCBs-exposed S. paramamosain. Furthermore, at the genetic level, exposure to PCBs led to the disruption of immune-related gene expression in hemocytes, while EGCG facilitated their recovery. This study enhances our understanding of the mechanisms by which EGCG alleviates the immunotoxic effects of aquatic environmental pollutants on aquatic organisms.