The responses of prophenoloxidase and MAPK/Nrf2 pathway to cadmium stress in red swamp crayfish Procambarus clarkii

ABSTRACT The immune response is a complex network composed of various molecules, cells and signaling pathways in crustacean. Cadmium-induced immunosuppression has been widely researched, but its underlying mechanism on crayfish proPO remains to be elucidated. In this study, the relationship between proPO activity in haemolymph and the activation of p38MAPK and Nrf2 in hepatopancreas was evaluated after red swamp crayfish Procambarus clarkii were subjected to sub-lethal Cd2+ concentrations (i.e. 1,5 and 10 mg/L) for 96 h. Results indicated that there was a significant decrease in haemolymph THC and proPO levels accompanied by the increasing contents of hepatopancreas ROS (P < 0.01) in a dose- and time-dependent manner. By IHC detection, the expression and activation of p38MAPK and Nrf2 were remarkably increased in Cd2+ treatment groups compared with the control group, and the level of both p-p38/p38 and Nrf2 was closely related to proPO activity (P < 0.01). Hepatopancreas might be implicated in systemic proPO activity via ROS-mediated MAPK/Nrf2 pathway.