重度烧伤大鼠肠道组织HMGB1和TLR4表达增强且肠道免疫功能紊乱

Increased expression of HMGB1 and TLR4 in intestinal tissues and intestinal immune dysfunction in severely burned rats

目的探讨重度烧伤大鼠肠道高迁移率族蛋白B1(HMGB1)、Toll样受体4(TLR4)的表达及其与肠道免疫功能的关系。方法取40只雄性SD大鼠,随机分为对照组10只、重度烧伤组30只。对照组仅麻醉,重度烧伤组大鼠背部及腹侧造成全身60%烫伤。烧伤组大鼠在伤后6、12、18 h,各取10只颈椎脱臼处死,对照组大鼠10只麻醉后即刻处死。采用Western blot法检测肠组织中HMGB1和TLR4蛋白水平,流式细胞术测量CD3+T细胞的纯度和Th1细胞和Th2细胞亚群比率,ELISA检测肠组织匀浆γ干扰素(IFN-γ)、白细胞介素4(IL-4)和IL-10含量。结果与对照组相比,重度烧伤组伤后6、12、18 h,大鼠肠道组织中HMGB1和TLR4蛋白水平均显著高于对照组,且随着烧伤后时间的增加,蛋白水平均逐渐增加,重度烧伤组HMGB1及TLR4蛋白表达呈正相关。烧伤组伤后6、12、18 h,Th1细胞亚群比例显著增加,而Th2细胞亚群比例降低,Th1细胞/Th2细胞比值显著增加,Th1细胞比例与HMGB1及TLR4呈正相关,而Th2细胞比例与HMGB1及TLR4呈负相关。与对照组相比,重度烧伤组伤后6、12、18 h,大鼠肠道IFN-γ及IL-4水平均显著增加,而IL-10水平显著降低。且随着烧伤后时间的增加,IFN-γ及IL-4水平均逐渐增加,而IL-10水平逐渐降低。结论大鼠重度烧伤后,肠道组织内募集HMGB1激活TLR4信号通路,进一步激活下游信号转录因子,并释放一系列炎性细胞因子引起炎症反应,从而参与大鼠Th1细胞和Th2细胞介导的免疫功能障碍。

Objective To investigate the expressions of high mobility group box 1（ HMGB1） and Toll-like receptor 4（ TLR4） in the intestinal tract of severely burned rats and their relationship with intestinal immune function. Methods Forty male SD rats were randomly divided into control group（ n = 10） and severe burn group（ n = 30）. 60% of the rats＇ body（ the back and ventral side） was burned in the severe burn group,and only anesthesia was performed in normal control group.Rats were sacrificed at 6,12 and 18 hours after injury in the burn group,while sacrificed immediately after anesthesia in control group. The protein levels of HMGB1 and TLR4 in the intestinal tissue were detected by Western blotting. The purity of total T cells（ CD3＋T）,as well as the ratio of Th1 to Th2 cell subsets,was measured by flow cytometry. ELISA was performed to detect the concentrations of IFN-γ,IL-4 and IL-10. Results Compared with the control group,the protein expressions of HMGB1 and TLR4 in the severe burn group were significantly higher than that in the control group at 6,12 and18 hours after injury,in a time-dependent manner. A positive correlation between HMGB1 and TLR4 protein expressions in the severe burn group was observed. The ratio of Th1 to total T cells was significantly raised at 6,12 and 18 hours after burn injury,and the ratio of Th2 to total T cells decreased,and the ratio of Th1/Th2 significantly increased. Th1 cell percentage was positively correlated with HMGB1 and TLR4,while Th2 cell percentage was negatively correlated with HMGB1 and TLR4.Compared with the control group,the levels of IFN-γ and IL-4 in the intestinal tract were significantly elevated at 6,12 and 18 hours after severe burn injury,while the level of IL-10 was significantly reduced. With the increase of postburn time,the levels of IFN-γ and IL-4 gradually increased,while the level of IL-10 gradually decreased. Conclusion HMGB1 was recruited in the intestinal tissues to activate TLR4 signaling pathway after severe burn,further activates the downstream signal transcripts and releases a series of inflammatory cytokines to induce inflammatory response,which is involved in Th1 and Th2 cell mediated immune function obstacle of rats.