脑缺血再灌注小鼠诱导免疫抑制与肺部感染易感性的关系

目的探讨脑缺血再灌注小鼠诱导免疫抑制与肺部感染易感性的关系。方法取32只体重20~25 g的C57BL/6J雄性小鼠,按随机数字法分为对照组(CON组)、肺部感染模拟组(SP组)、脑缺血再灌注组(MCAO组)、脑缺血再灌注后肺部感染模拟组(SAP组),每组各8只。通过线栓法建立MCAO模型及向气管内定量注入致病菌模拟肺部感染的发生。24 h后收集各组外周血及肺泡灌洗液(BAL)并检测肿瘤坏死因子-α(TNF-α)、干扰素-γ(IFN-γ)、白细胞介素-10(IL-10)表达量,计算BAL、血标本、肺匀浆中的菌落计数(CFU);72 h后观察肺和脾组织的病理改变并统计肺组织病理评分、脾指数,计算MCAO组及SAP组脑梗死体积。组间比较采用t检验。结果SAP组外周血TNF-α、IFN-γ低于CON组(87.20±4.37)ng/L比(112.96±9.91)ng/L、(86.71±11.25)ng/L比(126.42±14.61)ng/L,t=5.320、4.815,P<0.05],差异有统计学意义,而IL-10水平高于CON组(192.36±20.23)ng/L比(148.85±22.35)ng/L,t=-3.227,P<0.05],差异有统计学意义;BAL中SAP组除TNF-α高于SP组(47.13±3.84)ng/L比(64.31±11.25)ng/L,t=-3.236,P<0.05]外,其余炎性因子水平与CON及SP组差异无统计学意义。SAP组外周血、BAL及肺匀浆中的荷菌量明显高于SP组(6.77±16.79)×10⁴CFU/ml比0 CFU/ml、(14.07±7.59)×10⁵CFU/ml比(7.69±14.74)×10⁴CFU/ml、(5.03±2.85)×10⁶CFU/ml比(9.76±9.24)×10⁴CFU/ml]。光镜下显示SAP组肺部炎症严重程度高于CON组,但低于SP组,与肺组织病理评分相一致(9.00±2.27比0.53±0.30、15.20±2.52比0.53±0.30,t=-8.264、3.203,P<0.05)。SAP组与MCAO组存在脾细胞凋亡现象,但两组的脑梗死体积比较差异无统计学意义(35.80±11.74)%比(32.43±11.43)%,t=-0.435,P>0.05]。结论卒中诱导的免疫抑制增加发生肺部感染的易感性。

Cerebral ischemia-reperfusion-induced immunodeficiency and susceptibility of pneumonia in mice

Objective To investigate the correlation between cerebral ischemia-reperfusion-induced immunodeficiency and susceptibility of pneumonia in mice.Methods Totally,32 C57BL/6J male mice weighing 20-25 gwere divided by random digit method into control group(CON),Streptococcus pneumonia(SP)model group(SP group),middle cerebral artery occlusion reperfusion(MCAO)group(MCAO group),stroke-associated pneumonia(SAP)model group(SAP group),and 8 per group.At 24h after the operation,the peripheral blood and bronchoalveolar lavage(BAL)in each group were collected to detect the tumor necrosis factor-α(TNF-α),interferon-γ(IFN-γ),interleukin-10(IL-10)by enzyme linked immunosorbent assay(ELISA);BAL,peripheral blood and lung homogenate were used for bacterial culture by blood plate;The volume of cerebral infarction in MCAO and SAP groups was calculated by 2,3,5,-triphenyltetrazolium chloride(TTC)staining after 72 h.The above indicators were statistically analyzed by SPSS 22.0 software.Results The levels of TNF-αand IFN-γin SAP group were lower than those in CON group(87.20±4.37)ng/L vs.(112.96±9.91)ng/L,(86.71±11.25)ng/L vs.(126.42±14.61)ng/L,t=5.320,4.815,P<0.05],and IL-10 level was higher in SAP group than that in CON group(192.36±20.23)ng/L vs.(148.85±22.35)ng/L,t=-3.227,P<0.05].There was no significant difference in the level of inflammatory factors among groups(P>0.05),except for the TNF-αbetween SAP and SP groups(47.13±3.84)ng/L vs.(64.31±11.25)ng/L,t=-3.236,P<0.05]in BAL sample.A comparative study of bacterial load in peripheral blood(6.77±16.79)×10⁴CFU/ml vs.0],BAL(14.07±7.59)×10⁵CFU/ml vs.(7.69±14.74)×10⁴CFU/ml]and lung homogenate(5.03±2.85)×10⁶CFU/ml vs.(9.76±9.24)×10⁴CFU/ml]revealed the mount of bacteria in SAP increased when compared with SP group.The degree of pulmonary inflammatory reaction in SAP group was stronger than that in CON group and lighter than that in SP group,which was consistent with the pathological score of lung tissue.The apoptosis of spleen cells in SAP and MCAO groups was observed.There was no significant difference in the volume of cerebral infarction between MCAO and SAP groups(35.80±11.74)%vs.(32.43±11.43)%,t=-0.435,P>0.05].Conclusion Stroke-induced immunodeficiency is a risk factor for pneumonia after stroke.