Effect of exogeneous adiponectin on hippocampal AGEs-ROS-ERS pathway in aged mice with postoperative cognitive dysfunction

Objective To evaluate the effect of exogeneous adiponectin on hippocampal advanced glycation end products(AGEs)-reactive oxygen species(ROS)-endoplasmic reticulum stress(ERS)pathway in aged mice with postoperative cognitive dysfunction(POCD). Methods Thirty-two healthy male C57BL/6 mice, aged 18 months, weighing 20-25 g, were randomly divided into 4 groups(n=8 each)using a random number table: control group(group C), POCD group, exogeneous adiponectin group(group APN), and vehicle group(group Veh). Splenectomy was performed to establish the POCD model in aged mice anesthetized with intraperitoneal pentobarbital sodium.In group APN, adiponectin 0.1 μg/g(in 2 μl of phosphate buffer solution)was injected into the lateral cerebral ventricle at 30 min before establishing the model.Phosphate buffer solution 2 μl was given at 30 min before establishing the model in group Veh.Cognitive function was assessed on day 7 after surgery.The mice were then sacrificed, and the hippocampus was harvested for determination of the area of AGE deposition(by immuno-histochemistry), levels of ROS(by flow cytometry), and levels of glucose-regulated protein 78(GRP78), C/EBP-homologous protein(CHOP), caspase-12 and ROS(using Western blot). Results Compared with group S, the freezing time in the contextual fear conditioning test was significantly shortened, the area of AGE deposition and levels of ROS, CHOP and caspase-12 were increased, and the level of GRP78 was decreased in POCD, APN and Veh groups.Compared with POCD and Veh groups, the freezing time in the contextual fear conditioning test was significantly prolonged, the area of AGE deposition and levels of ROS, CHOP and caspase-12 were decreased, and the level of GRP78 was increased in group APN. Conclusion Exogeneous adiponectin decreases the occurrence of POCD probably by blocking hippocampal AGEs-ROS-ERS pathway in aged mice. Key words: Adiponectin; Aged; Postoperative complications; Cognition disorders; Advanced glycosylation end products; Reactive oxygen species; Endoplasmic reticulum; Hippocampus