轻型链球菌缓解铜绿假单胞菌感染小鼠模型的 炎症反应及机制的初步探讨

A preliminary study for the mechanism of Streptococcus mitis in mouse model of Pseudomonas aeruginosa infection

摘要:

目的：探讨轻型链球菌（Streptococcus mitis，S.mitis）在铜绿假单胞菌（Pseudomonas aeruginosa，PAO1）感染小鼠模型中缓解炎症作用及可能机制。方法：将野生型和TLR2基因缺陷型小鼠随机分为4组，每组20只，通过气管内注入铜绿假单胞菌（PAO1组）、轻型链球菌（S.mitis组）、铜绿假单胞菌+轻型链球菌混合菌液（PAO1+S.mitis组）和生理盐水（PBS组）建立模型，HE染色观察肺组织病理学改变，ELISA检测肺泡灌洗液中炎症因子白细胞介素-6（interleukin-6，IL-6）和肿瘤坏死因子-α（tumor necrosis factor-α，TNF-α）的表达，计数肺泡灌洗液细胞总数及细胞分类。结果：野生型小鼠中肺组织病理学显示：PAO1组肺泡间隙增宽明显，有大量炎症细胞浸润，PAO1+S.mitis组炎症较PAO1组稍轻；S.mitis组和PBS组肺组织结构正常，基本未见炎症细胞浸润；肺泡灌洗液中PAO1组IL-6和TNF-α的含量高于PAO1+S.mitis组（P=0.032，P=0.007），S.mitis组和PBS组仅有少量表达；PAO1组BALF细胞总数及中性粒细胞计数均较PAO1+S.mitis组、S.mitis组和PBS组增加（均P＜0.05）。TLR2基因缺陷型小鼠中肺组织病理学显示：PAO1组和PAO1+S.mitis组均有肺泡间隙增宽，炎症细胞浸润，肺泡灌洗液中PAO1组和PAO1+S.mitis组IL-6和TNF-α的表达没有统计学差异（P=1.000，P=1.000），S.mitis组和PBS组仅有少量表达；PAO1组和PAO1+S.mi－tis组支气管肺泡灌洗液细胞总数及中性粒细胞计数没有统计学差异（P=1.000，P=1.000）。结论：轻型链球菌可缓解铜绿假单胞菌炎症反应与TLR2有关。

Abstract:

Objective：To investigate the alleviation of inflammatory effects and mechanisms of Streptococcus mitis in infection with Pseudomonas aeruginosa. Methods：Wild-type C57BL/6 and TLR2-/- mice were randomly assigned into 4 groups（20 in each group）. They were treated with an intratracheal instilla－tion of Pseudomonas aeruginosa（PAO1 group），Streptococcus mitis（S.mitis group），Pseudomonas aeruginosa and Streptococcus mitis（PAO1+S.mitis group），and phosphate-buffered saline（PBS group），respectively. The mice were sacrificed at 48 h after instillation；the pathological changes in lung tissues were ex－amined with hematoxylin-eosin（HE）；the levels of IL-6 and TNF-α in broncho-alveolar lavage fluid（BALF） were evaluated by ELISA；the total cell counts and neutrophil counts in the BALF were quantified. Results：In wild-type C57BL/6 mice，the bronchi and blood vessels in PAO1 group was infiltrated by a large number of inflammatory cells and was complicated with alveolar septum thickening. The pathological changes were milder in PAO1+S.mitis group than in PAO1 group，while there was no significant pathological changes in lung tissue in PBS group and S.mitis group. The levels of IL-6，TNF-α were significantly higher in PAO1 group than that in PAO1+S.mitis group（P=0.032，P=0.007）. The total number of BALF cells and neutrophils in PAO1 group was the highest among the four groups（P＜0.05）. In TLR2-/- mice，alveolar septum thickening and the infiltration of inflammatory cells was ob－served in PAO1 group and PAO1+S.mitis group. No statistically significant difference in the expression of IL-6，TNF-α，total number of BALF cells and neutrophils in PAO1 group and PAO1+S.mitis group（all P=1.000） was observed. Conclusion：Streptococcus mitis can alleviate the inflammatory response of Pseudomonas aeruginosa and is related to TLR2.