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.

中文翻译：

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红沼泽小龙虾原酚氧化酶和MAPK/Nrf2通路对镉胁迫的响应

摘要 免疫反应是甲壳类动物体内由各种分子、细胞和信号通路组成的复杂网络。镉诱导的免疫抑制已被广泛研究，但其对小龙虾 proPO 的潜在机制仍有待阐明。在这项研究中，红沼泽小龙虾 Procambarus clarkii 接受亚致死 Cd2+ 浓度（即 1.5 和 10 mg/L）96 小时后，评估了血淋巴中 proPO 活性与肝胰腺中 p38MAPK 和 Nrf2 活化之间的关系. 结果表明，血淋巴 THC 和 proPO 水平显着降低，伴随肝胰腺 ROS 含量的增加（P < 0.01），呈剂量和时间依赖性。通过IHC检测，与对照组相比，Cd2+处理组p38MAPK和Nrf2的表达和活化显着增加，且p-p38/p38和Nrf2的水平均与proPO活性密切相关（P < 0.01）。肝胰腺可能通过 ROS 介导的 MAPK/Nrf2 途径参与全身 proPO 活性。