Role of TLR4/NF-κB signaling pathway in long-term cognitive impairment induced by multiple exposures to sevoflurane anesthesia in neonatal rats / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the role of Toll-like receptor 4 (TLR4)/nuclear transcription factor κB (NF-κB) signaling pathway in long-term cognitive impairment induced by multiple exposures to sevoflurane anesthesia in neonatal rats.Methods:Seventy-five SPF healthy newborn Sprague-Dawley rats of either sex, aged 6 days, weighing 12-20 g, were divided into 3 groups ( n=25 each) using a random number table method: control group (group C), multiple exposures to sevoflurane anesthesia group (group S) and TLR4 inhibitor plus multiple exposures to sevoflurane anesthesia group (group I+ S). The rats in group S and group I inhaled 3% sevoflurane for 2 h at 6, 7 and 8 days after birth. TLR4 inhibitor TAK-242 10 mg/kg was intraperitoneally injected before each exposure to sevoflurane in group I, and the equal volume of normal saline was given instead in the other two groups. The spontaneous activity was evaluated by open field test on day 29 after birth, and the cognitive function was assessed by Morris water maze test on days 30-34 after birth. After the behavioral test, the blood samples from the abdominal aorta were collected, and then the rats were sacrificed under deep anesthesia to isolate the hippocampal tissues for measurement of the levels of S100β and neuron-specific enolase (NSE) in serum and hippocampal interleukin-1β (IL-1β), IL-6 and tumor necrosis factor α (TNF-α) (by enzyme-linked immunosorbent assay), expression of TLR4, NF-κB p65 and phosphorylated NF-κB p65 (p-NF-κB p65) (by Western blot) and for microscopic examination of the pathological changes of hippocampal CA1 region after HE staining. Results:Compared with group C, the escape latency was significantly prolonged, the number of crossing the original platform was reduced, the TLR4 expression was up-regulated, the ratio of p-NF-κB p65/NF-κB p65 was increased, the levels of serum S100β protein and NSE and hippocampal IL-1β, IL-6 and TNF-α were increased ( P<0.05), and the pathological changes in the hippocampal CA1 region were aggravated in group S. Compared with group S, the escape latency was significantly shortened, the number of crossing the original platform was increased, TLR4 expression was down-regulated, the ratio of p-NF-κB p65/NF-κB p65 was decreased, the levels of S100β and NSE in serum and hippocampal IL-1β, IL-6 and TNF-α were decreased ( P<0.05), and the pathological changes in hippocampal CA1 area were significantly attenuated in group P. Conclusions:The mechanism by which multiple exposures to sevoflurane anesthesia induces long-term cognitive impairment is related to activation of TLR4/NF-κB signaling pathway and increase in hippocampal inflammatory responses in neonatal rats.