Role of hippocampal CD200R1 in perioperative neurocognitive disorders in mice

Objective To evaluate the role of hippocampal CD200 receptor 1 (CD200R1) in perioperative neurocognitive disorders (PND) in mice. Methods Sixty clean-grade male C57BL/6 mice, aged 9-10 months, weighing 32-38 g, were used in the study.The experiment was performed in two parts.Experiment Ⅰ Thirty-six mice were divided into 2 groups (n=18 each) using a random number table method: control group (group C) and PND group.Group C only received isoflurane anesthesia.Partial left lobectomy of the liver was performed under isoflurane anesthesia in group PND.Contextual fear conditioning test was performed at 1, 3 and 7 days after surgery, and the freezing time was recorded.The mice were then sacrificed, and the hippocampus was isolated for determination of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) contents (by enzyme-linked immunosorbent assay) and CD200 and CD200R1 expression (by Western blot). Experiment Ⅱ Twenty-four mice were divided into 2 groups (n=12 each) using a random number table method: CD200-Fc group and IgG1-Fc group.Recombinant proteins CD200-Fc and human IgG1-Fc were injected into the lateral cerebral ventricle in CD200-Fc group and IgG1-Fc group, respectively.Partial left lobectomy of the liver was performed after the end of injection.Contextual fear conditioning test was performed at 1 and 3 days after surgery, and the freezing time was recorded. Results Experiment Ⅰ Compared with group C, the freezing time in the contextual fear conditioning test was significantly shortened, and the contents of IL-1β were increased at 1 and 3 days after surgery, the contents of TNF-α were increased at 3 and 7 days after surgery, and the expression of CD200 and CD200R1 was up-regulated at 1 day after surgery in group PND (P<0.05). Experiment Ⅱ Compared with IgG1-Fc group, the freezing time in the contextual fear conditioning test was significantly prolonged at 1 day after surgery in CD200-Fc group (P<0.05). Conclusion Up-regulated expression of hippocampal CD200R1 is the endogenous protective mechanism of PND in mice. Key words: Neurocognitive disorders; CD200R1