地塞米松通过降低S100A8表达改善小鼠七氟醚麻醉手术后的认知功能障碍

目的 观察地塞米松对七氟醚麻醉手术后认知功能的改善及其作用机制. 方法 100只成年雄性C57BL/6小鼠,采用随机数字表法分为5组(每组20只):对照组(C组)、麻醉手术组(S组)、高剂量地塞米松治疗组(H组)、中剂量地塞米松治疗组(M组)和低剂量地塞米松治疗组(L组).C组不做处理,其余各组在麻醉后行腹腔探查术.H组、M组和L组分别给予20、2.0、0.2 mg/kg地塞米松,于术前1h经腹腔注射给药.术后24 h每组随机取10只小鼠海马组织,免疫组化检测海马小胶质细胞Iba1表达,RT-PCR检测S100A8、Toll样受体4(toll-like receptor 4,TLR4)、IL-6、IL-1β、TNF~ mRNA含量,Western blot检测S100A8蛋白.剩余小鼠进行5d水迷宫训练后,测定逃避潜伏期、穿越平台次数、目标象限游泳时间. 结果 与C组比较,S组小鼠术后逃避潜伏期[5d,(26.5±3.8)s]延长,穿越平台次数[(1.24±0.21)次]减少,目标象限游泳时间[(9.1±1.7)s]缩短(P＜0.05),小胶质细胞Iba1表达增加,S100A8(3.10±0.18)、TLR4(2.903±0.021)、IL-6(2.63±0.13)、IL-1β(3.733±0.160)、TNF-α(1.924±0.038) mRNA含量增加(P＜0.05).与S组比较,M组小鼠给药后逃避潜伏期缩短[5d,(17.8±2.3)s],穿越平台次数增加[(2.38±0.33)次],目标象限游泳时间延长[(14.5±2.0)s](P＜0.05);H组、M组小鼠小胶质细胞Iba1表达减少,S100A8(1.11±0.12、1.35±0.08)、TLR4(0.872±0.112、1.149±0.060)、IL-6(1.13±0.06、1.32±0.08)、IL-1β(0.755±0.059、0.941±0.133)、TNF-α(1.081 ±0.052、1.041±0.021)mRNA含量减少(P＜0.05). 结论 腹腔注射地塞米松(2.0 mg/kg),可改善小鼠七氟醚麻醉手术后认知功能,其机制可能与减少S100A8蛋白,抑制小胶质细胞活化,减少炎症因子表达有关.

Dexamethasone can improve cognitive dysfunction by down-regulating the expression level of S100A8 after sevoflurane anaesthesia in mice

Objective To investigate the effect of dexamethasone on cognitive function after sevoflurane anaesthesia and its potential mechanism.Methods One hundred adult male C57BL/6 mice were randomly divided into 5 groups(n=20) using a random number table:control group(group C),sevoflurane group (group S),high dosage(20 mg/kg) of dexamethasone group(group H),middle dosage(2.0 mg/kg) of dexamethasone group (group M) and low dosage(0.2 mg/kg) of dexamethasone group(group L).Group C accepted no special treatment,while other groups were exposed in sevoflurane and had laparotomy surgery.Group H,group M and group L mice were given dexamethasone one hour before inhalation via intraperitoneal injection.After 24 h of the operation,10 mice in each group were sacrificed randomly and tested for Iba1 expression using immunohistochemical staining in the mice's hippocampi.RT-PCR was used to detect the mRNA level of S100A8,Toll-like receptor 4(TLR4),IL-6,IL-1β and TNF-α.Expression of S100A8 protein was measured with Western blot.Other mice were subjected to a 5-day Morris water maze training and their escape latency,the frequency of crossing the platform and duration of swimming spent at the target quadrant were recorded.Results The escape latency period of group S mice was prolonged [5 d,(26.5±3.8) s] than the control group and the frequency of crossing platform was decreased (1.24±0.21) and the duration of swimming in the target quadrant was shortened [(9.1 ± 1.7) s].Expressions of Iba1 on microglia cells were increased,and the mRNA level of S100A8(3.10±0.18),TLR4(2.903±0.021),IL-6(2.63±0.13),IL-1β(3.733±0.160) and TNF-α (1.924±0.038) were increased as well (P＜0.05).The frequency of crossing the original platform (2.38±0.33) and duration of swimming spent at the target quadrant [(14.5±2.0) s] were increased in group M compared to group S and the escape latency [5 d,(17.8±2.3) s] was shortened (P＜0.05).The expression of Iba1 on microglia cells were decreased,and the S100A8 (1.11±0.12,1.35±0.08),TLR4 (0.872±0.112,1.149±0.060),IL-6 (1.13±0.06,1.32±0.08),IL-1β (0.755±0.059,0.941±0.133) and TNF-α (1.081±0.052,1.041±-0.021) mRNA level were decreased as well in both high dosage group and middle dosage group (P＜0.05).Conclusions Intraperitoneal injection of dexamethasone (2.0 mg/kg) can improve the cognitive function after sevoflurane anaesthesia.The potential mechanism could be reducing the expression of S100A8,inhibiting the activity of microglia cells and reducing the expression of inflammatory cytokines.