Role of IL-6 trans-signaling pathway in perioperative neurocognitive disorder in mice / 中华麻醉学杂志

ABSTRACT

Objective:To investigate the role of IL-6 trans-signaling pathway in perioperative neurocognitive disorder in mice.Methods:Eighty-four SPF healthy male C57BL/6 wild-type mice and 84 SPF healthy male IL-6R -/- mice, aged 12-14 weeks, weighing 25-35 g, were used.The 84 wild-type mice were divided into 4 groups ( n=21 each) using a random number table method: sham group (SH group), surgery group (S group), sgp130Fc (specific IL-6 trans-signaling pathway blocker) group (F group), and sgp130Fc+ surgery group (FS group). In S group and FS group, internal fixation was performed under general anesthesia with sevoflurane after tibial fracture.Mice only received anaesthesia with sevoflurane in SH group and F group.In FS group and F group, sgp130Fc 10 mg/kg was intraperitoneally injected before anesthesia.Blood samples were collected from the celiac vein at 24 h after surgery for determination of the concentrations of interleukin 6 (IL-6), IL-1β and tumor necrosis factor (TNF)-α in plasma by enzyme-linked immunosorbent assay (ELISA). Then the mice were sacrificed, brains were removed, and hippocampal tissues were obtained for measurement of the contents of IL-6, IL-1β and TNF-α (by ELISA) and for observation of activation of microglias in the hippocampal DG region (by immunofluorescence staining, n=6). Cognitive function was evaluated by contextual fear conditioning test ( n=15) on 3 days after surgery.Eighty-four IL-6R -/- mice were randomly divided into 4 groups ( n=21 each) sham group (KO-SH group), surgery group (KO-S group), saline group (KO-C group), and hyper IL-6 (specific IL-6 trans-signaling pathway activator) group (KO-H group). The treatment in KO-SH group and KO-S group was the same as those previously described in SH group and S group, respectively.0.9% NaCl solution 100 μl was intraperitoneally injected in KO-C group, 100 μl hyper IL-6 40 μg/kg was intraperitoneally injected in KO-H group, and 24 h later blood was collected from the celiac vein for measurement of the concentrations of IL-6, IL-1β and TNF-α in plasma by ELISA.Then the mice were sacrificed, brains were removed, and hippocampal tissues were obtained for determination of the contents of IL-6, IL-1β and TNF-α (by ELISA) and for observation of activation of microglias in the hippocampal DG region (by immunofluorescence staining, n=6). Cognitive function was evaluated by contextual fear conditioning test ( n=15) on 3 days after surgery. Results:Compared with SH group, the percentage of freezing time in the contextual fear conditioning test was significantly decreased, and the activation of microglias in the hippocampal DG region and levels of IL-6, IL-1β and TNF-α in plasma and hippocampi were increased in S group ( P<0.05). Compared with S group, the percentage of freezing time in the contextual fear conditioning test was significantly increased, and the activation of microglias in the hippocampal DG region and levels of IL-6, IL-1β and TNF-α in plasma and hippocampus were decreased in FS group ( P<0.05). There were no significant differences in the percentage of freezing time, activation of microglias in the hippocampal DG region, and levels of IL-6, IL-1β and TNF-α in plasma and hippocampi between KO-S group and KO-SH group ( P>0.05). Compared with KO-C group, the percentage of freezing time in the contextual fear conditioning test was significantly decreased, and the activiation of microglias in the hippocampal DG region and levels of IL-6, IL-1β and TNF-α in plasma and hippocampus were increased in KO-H group ( P<0.05). Conclusions:IL-6 trans-signaling pathway is involved in the process of perioperative neurocognitive disorder in mice.