重症中暑早期肠黏膜屏障功能损害与全身炎症反应的相关性研究

The correlation analysis of intestinal mucosal barrier function damage with systemic inflammation reaction during severe heatstroke

目的观察重症中暑对肠黏膜屏障功能的影响，并探讨其与全身炎症反应的相关性。方法SPF级雄性BALB／c小鼠按随机数字表法分为正常对照组、40℃热打击组、42℃热打击组，每组6只。正常对照组小鼠始终置于（25．0±0．5）℃常温下；热打击组小鼠置于温度（35．5±0．5）℃、湿度（60±5）％环境直至体温达40℃或42℃后，于常温下复温12h。各组小鼠内眦取血，采用酶联免疫吸附试验（ELISA）检测血浆脂多糖（LPS）、肿瘤坏死因子-α（TNF-α）、白细胞介素-6（IL-6）水平及二胺氧化酶（DAO）活性，紫外分光光度计检测血浆D-乳酸水平。处死小鼠，取肠系膜淋巴结（MLN）、肝、脾、肺、肾组织及门、腔静脉血进行细菌菌落计数，观察肠道细菌移位情况；取回肠组织，镜下观察小肠黏膜组织形态学和超微结构改变。采用Pearson分析判断肠黏膜屏障功能损害与全身炎症反应的相关性。结果与正常对照组比较，热打击后小鼠血浆LPS、炎症指标TNF—α和IL-6水平、肠屏障功能指标DAO和D-乳酸水平以及细菌移位率均明显升高，以42℃热打击组损伤更为明显[LPS（EU／L）：740±50比340±40，TNF-α（ng／L）：148．06±36．61比12．89±1．67，IL-6（ng／L）：110．91±9．97比18．02±2．20，DAO（U／L）：1760±400比670±50，D-乳酸（mg／L）：9．60±1．48比5．08±0．28，细菌移位率：78．6％（33／42）比9．5％（4／42），均P〈0．01]。相关性分析结果显示：42℃热打击小鼠血浆LPS、TNF-α、IL-6与DAO活性（r值分别为0．834、0．808、0．836）和D-乳酸（r值分别为0．811、0．811、0．800）均呈显著正相关（均P=0．000）。镜下观察显示，热打击后小鼠肠黏膜组织及超微结构均出现明显病理学改变，以42℃热打击造成的损伤更加明显，出现肠黏膜明显萎缩、绒毛脱落、淋巴细胞及中性粒细胞浸润、表面微绒毛稀疏及排列紊乱、上皮细胞间紧密连接增宽、线粒体明显肿胀、内质网明显扩张。结论重症中暑早期即可导致小鼠肠黏膜损害，且肠黏膜屏障功能障碍与全身炎症反应密切相关。

Objective To observe the effect of severe heatstroke on intestinal mucosal barrier function, and explore its correlation with systemic inflammatory reaction. Methods The SPF male BALB/e mice were randomly divided into normal control group, 40℃ heat stress group and 42℃ heat stress group, with 6 mice in each group. The mice in normal control group were observed at normal temperature with （25.0± 0.5） ℃ , and the mice in heat stress groups were challenged with a temperature of （35.5± 0.5）℃ and a humidity of （60±5）% until body temperature increase up to 40℃ or 42℃ followed by recovering the surroundings temperature to normal temperature for 12 hours. The blood of medial angle of eye of mice in each group was collected for determination of plasma lipopolysaccharide （LPS）, tumor necrosis factor-ct （TNF-or）, interleukin-6 （IL-6） levels, and diamine oxidase （DAO） activity with enzyme linked immunosorbent assay （ELISA）. The level of D-lactic acid was determined with ultraviolet speetrophotometer. Then the mice in each group were sacrificed, and mesenteric lymph node （MLN）, liver, spleen, lung, kidney tissues, and the blood from portal vein and caval vein were collected for colony count to observe the intestinal bacterial translocation. The ileum tissue was collected for observation of changes in histomorphology and ultrastructure of small intestine mucous membrane with microscope. Pearson linear regression analysis was used to explore the correlation between intestinal mucosal barrier dysfunction and systemic inflammatory response. Results Compared with normal control group, plasma LPS, inflammatory parameters such as TNF-α and IL-6, and gut barrier function parameters such as DAO and D-lactic acid levels as well as the rate of bacterial translocation after heat stress were significantly increased, and the differences were more obvious in 42 ℃ heat stress group [LPS （EU/L）： 740±50 vs. 340±40, TNF-α （ng/L）： 148.06±36.61 vs. 12.89 ± 1.67, IL-6 （ng/L）： 110.91 ± 9.97 vs. 18.02 ±2.20, DAO （U/L）： 1 760±400 vs. 670 ±50, D-lactic acid （rag/L）： 9.60 ±1.48 vs. 5.08 ± 0.28, rate of bacterial translocation： 78.6% （33/42） vs. 9.5% （4/42）, all P 〈 0.01]. It was shown by Pearson linear regression analysis that plasma LPS, TNF- α, IL-6 were positively correlated with DAO activity （r values were 0.834, 0.808, 0.836, respectively） and D-lactic acid （r values were 0.811, 0.811, 0.800, respectively） in 42℃ heat stress group （all P = 0.000）. It was showed by microscope that the changes in histomorphology and ultrastructure changes in intestinal mucosa were found after heat stress, and was obvious in 42 ℃ heat stress group as following： villus atrophy and falling off, infiltration of neutrophils and lymphocytes, the microvillus on the surface of mucosa ceils were short and small, arranged in disorder, the tight junction between epithelial cells became widen, the mitochondrion and endoplasmic reticulum swelled obviously. Conclusion During the early stage of severe heatstroke, the damage of intestinal mucosal was obvious, and it has close correlation with systemic inflammatory response.