Department of Anesthesiology, University of Virginia, Charlottesville, Virginia, USA.
Department of Anesthesiology, Guangxi Medical University Cancer Hospital, Nanning, China.
J Neurochem. 2021 Jul;158(2):328-341. doi: 10.1111/jnc.15368. Epub 2021 May 5.
Post-operative cognitive dysfunction (POCD) is common and is associated with poor clinical outcome. Toll-like receptor (TLR) 3 and 4 have been implied in the development of POCD. The role of TLR2, a major brain TLR, in POCD is not clear. High mobility group box-1 (HMGB1) is a delayed inflammatory mediator and may play a role in POCD. The interaction between HMGB1 and TLRs in the perioperative period is not known. We hypothesize that TLR2 contributes to the development of POCD and that HMGB1 regulates TLR2 for this effect. To test these hypotheses, 6- to 8-week old male mice were subjected to right carotid artery exposure under isoflurane anesthesia. CU-CPT22, a TLR1/TLR2 inhibitor, at 3 mg/kg was injected intraperitoneally 30 min before surgery and 1 day after surgery. Glycyrrhizin, a HMGB1 antagonist, at 200 mg/kg was injected intraperitoneally 30 min before surgery. Mice were subjected to Barnes maze and fear conditioning tests from 1 week after surgery. Hippocampus and cerebral cortex were harvested 6 hr or 12 hr after the surgery for Western blotting, ELISA, immunofluorescent staining, and chromatin immunoprecipitation. There were neuroinflammation and impairment of learning and memory in mice with surgery. Surgery increased the expression of TLR2 and TLR4 but not TLR9 in the brain of CD-1 male mice. CU-CPT22 attenuated surgery-induced neuroinflammation and cognitive impairment. Similarly, surgery induced neuroinflammation and cognitive dysfunction in C57BL/6J mice but not in TLR2 mice. TLR2 staining appeared in neurons and microglia. Surgery increased HMGB1 in the cell nuclei of the cerebral cortex and hippocampus. Glycyrrhizin ameliorated this increase and the increase of TLR2 in the hippocampus after surgery. Surgery also increased the amount of tlr2 DNA precipitated by an anti-HMGB1 antibody in the hippocampus. Our results suggest that TLR2 contributes to surgery-induced neuroinflammation and cognitive impairment. HMGB1 up-regulates TLR2 expression in the hippocampus after surgery to facilitate this contribution. Thus, TLR2 and HMGB1 are potential targets for reducing POCD.
术后认知功能障碍（POCD）很常见，并且与不良的临床结果相关。 Toll 样受体（TLR）3 和 4 已被暗示参与 POCD 的发展。主要的脑 TLR TLR2 在 POCD 中的作用尚不清楚。高迁移率族蛋白 B1（HMGB1）是一种延迟的炎症介质，可能在 POCD 中发挥作用。围手术期 HMGB1 与 TLRs 的相互作用尚不清楚。我们假设 TLR2 有助于 POCD 的发展，HMGB1 调节 TLR2 以产生这种作用。为了验证这些假设，将 6-8 周龄雄性小鼠在异氟烷麻醉下暴露右侧颈总动脉。CU-CPT22（TLR1/TLR2 抑制剂）在手术前 30 分钟和手术后 1 天以 3mg/kg 经腹腔注射。甘草酸在手术前 30 分钟以 200mg/kg 经腹腔注射。手术后 1 周，小鼠接受 Barnes 迷宫和恐惧条件反射测试。手术后 6 小时或 12 小时收获海马体和大脑皮层进行 Western blot、ELISA、免疫荧光染色和染色质免疫沉淀。手术引起了小鼠的神经炎症和学习记忆损伤。手术增加了 CD-1 雄性小鼠大脑中 TLR2 和 TLR4 的表达，但不增加 TLR9 的表达。CU-CPT22 减轻了手术引起的神经炎症和认知障碍。同样，手术在 C57BL/6J 小鼠中引起了神经炎症和认知功能障碍，但在 TLR2 小鼠中没有引起。TLR2 染色出现在神经元和小胶质细胞中。手术增加了大脑皮层和海马体细胞核中 HMGB1 的含量。甘草酸可改善术后 HMGB1 的增加和海马体 TLR2 的增加。手术还增加了用抗 HMGB1 抗体沉淀的 tlr2 DNA 在海马体中的量。我们的结果表明，TLR2 有助于手术引起的神经炎症和认知障碍。HMGB1 上调术后海马体 TLR2 的表达以促进这种作用。因此，TLR2 和 HMGB1 是减少 POCD 的潜在靶点。
