Although type 2 diabetes is an important predictor of perioperative neurocognitive disorder (PND), little is currently known about its mechanism of action. Adult male db/db and db/m mice were subjected to four different treatments, including either sham or tibial fracture surgery as well as intraperitoneal injection of vehicle or TAK-242 (the selective inhibitor of TLR4) at 1, 24, and 48 h after surgery. The fear conditioning test was performed to detect cognitive impairment on post-operative day (POD) 3. The hippocampus was collected on POD 1 for western-blots and on POD 3 for western-blots, transmission electron microscopy, and electrophysiological experiments. Toll-like receptor 4 (TLR4) inhibition reversed more profound decline in the freezing behavior of db/db mice on POD 3. The surgery reduced the slope of hippocampal field excitatory postsynaptic potentials, and induced blood-brain barrier (BBB) damage in db/db mice on POD 3. The surgery also increased protein levels of TLR4, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, albumin, matrix metalloproteinase (MMP)-2, and MMP-9, and decreased protein levels of claudin-5, occludin, tissue inhibitor of matrix metalloproteinase (TIMP)-1, and TIMP-2 in the hippocampus of db/db and db/m mice. These changes were all reversed by TAK-242 treatment. At last, compared with those in post-operative db/m mice, the surgery increased protein levels of TLR4, TNF-α, and IL-1β, decreased protein levels of claudin-5 and occludin, and sustained the MMP/TIMP imbalance in the hippocampus of db/db mice on POD 3. Our results suggest that TLR4-mediated aggravated hippocampal MMP/TIMP imbalance, BBB disruption, sustained inflammatory cytokine release, and impairment of long-term potentiation play a key role in tibial fracture surgery-induced persistent PND in db/db mice.

尽管 2 型糖尿病是围手术期神经认知障碍 (PND) 的重要预测因素，但目前对其作用机制知之甚少。成年雄性 db/db 和 db/m 小鼠接受四种不同的治疗，包括假手术或胫骨骨折手术以及在 1、24 和 48 小时腹腔注射载体或 TAK-242（TLR4 的选择性抑制剂）手术后。进行恐惧条件反射测试以检测术后第 3 天 (POD) 的认知障碍。在 POD 1 上收集海马用于蛋白质印迹，在 POD 3 上收集海马用于蛋白质印迹、透射电子显微镜和电生理实验。Toll 样受体 4 (TLR4) 抑制逆转了 db/db 小鼠在 POD 3 上的冷冻行为更严重的下降。手术降低了海马场兴奋性突触后电位的斜率，并在 POD 3 时诱导了 db/db 小鼠的血脑屏障 (BBB) 损伤。手术还增加了 TLR4、肿瘤坏死因子 (TNF)-α、白细胞介素的蛋白质水平(IL)-1β、白蛋白、基质金属蛋白酶 (MMP)-2 和 MMP-9，降低海马中 claudin-5、occludin、基质金属蛋白酶组织抑制剂 (TIMP)-1 和 TIMP-2 的蛋白质水平db/db 和 db/m 小鼠。这些变化都被 TAK-242 治疗逆转了。最后，与术后 db/m 小鼠相比，手术增加了 TLR4、TNF-α 和 IL-1β 的蛋白水平，降低了 claudin-5 和 occludin 的蛋白水平，并维持了 MMP/TIMP 失衡。 POD 3 上 db/db 小鼠的海马体。