肠道菌群通过戊酸调节脂多糖诱导的急性肺损伤

Intestinal flora regulates lipopolysaccharide-induced acute lung injury through valeric acid

目的 观察广谱抗生素诱导的肠道菌群改变对脂多糖(lipopolysaccharide,LPS)诱导的急性肺损伤(acute lung injury,ALI)的作用,探讨肠道菌群调节LPS诱导的ALI的机制。方法 6周龄SD大鼠(体重170 g±10 g)随机分为对照组(CK组)和美罗培南组(M组),每组10只。M组大鼠使用美罗培南实现肠道细菌清除。采集两组大鼠粪便标本,进行16S rDNA微生物群落分析和短链脂肪酸(short chain fatty acids,SCFAs)分析。LPS诱导大鼠ALI后抽血检测血SCFAs、血清炎症因子水平、肺组织病理切片、肺湿/干重比及大鼠肺微血管内皮细胞单层通透性等。结果 美罗培南给药后肠道菌群多样性和构成发生了变化;M组大鼠粪便中丙酸、丁酸、异丁酸、戊酸、异戊酸、己酸水平均较CK组下降,以戊酸下降最为显著(t=9.242,P<0.001);M组大鼠血浆中戊酸和己酸水平较CK组显著下降,以血液中的戊酸水平降低最显著(t=4.000,P<0.005);LPS诱导的ALI后M组大鼠血清炎症因子水平较CK组无显著升高;两组间病理切片提示炎症细胞浸润无显著差异;M组大鼠肺湿/干重比较CK组显著升高(P<0.050);戊酸作用后显著改善LPS诱导的大鼠肺微血管内皮细胞单层通透性增高(t=8.134,P<0.001)。结论 美罗培南应用可以造成大鼠肠道菌群失调与SCFAs水平的变化。肠道菌群可以通过血液中戊酸水平的改变实现对ALI的保护作用。

Objective To observe the effect of changes in intestinal flora induced by broad spectrum antibiotics on lipopolysaccharide(LPS)-induced acute lung injury(ALI),and explore the mechanism of the regulation of LPS-induced ALI by intestinal flora.Methods Sprague-Dawley rats(6-weeks-old,weighting 170 g±10 g) were randomly divided into control group(group CK,n=10) and meropenem group(group M,n=10).The M group was given meropenem to achieve intestinal bacterial clearance.Stool samples were collected from the two groups of rats for 16S rDNA microbial community analysis and short chain fatty acid(SCFAs) analysis.Blood SCFAs,blood inflammatory factor concentrations,pathological section of lung tissue,lung wet/dry weight ratio,and pulmonary microvascular endothelial monolayer permeability of the rats were detected after ALI was induced by LPS.Results The diversity and composition of intestinal flora changed after meropenem administration.The levels of propionic acid,butyric acid,isobutyric acid,valeric acid,isovaleric acid and caproic acid in feces of rats in group M were lower than those in group CK,and valeric acid decreased most significantly(t=9.242,P<0.001).The levels of valeric acid and caproic acid in plasma of rats in group M were significantly lower than those in group CK,and that of valeric acid in blood decreased most significantly(t=4.000,P<0.005).After induction of ALI,the level of inflammatory factors in group M was not significantly higher than that in group CK,and pathological sections showed no significant difference in inflammatory cell infiltration between the two groups.The wet/dry lung weight ratio of rats in the LPS-induced ALI in group M was significantly higher than that in the group CK(P<0.050).Valeric acid significantly improved the LPS-induced increase in monolayer permeability of pulmonary microvascular endothelial cells(t=8.134,P<0.001).Conclusion Meropenem administration can cause gut dysbiosis and changes in SCFAs levels.Intestinal flora can protect ALI by changing the level of valeric acid in blood.