脂多糖可致敏高浓度氧对新生小鼠未成熟脑的损伤

Lipopolysaccharide sensitizes neonatal mice to hyperoxia-induced immature brain injury

目的探讨低浓度脂多糖(LPS)处理后高浓度氧对新生小鼠未成熟脑损伤的影响及其作用机制。方法 48只PND3C57新生小鼠随机分为空气组、LPS处理组、高氧组、高氧+LPS组,采用LPS腹腔注射0.3 mg/kg,30 min后95%高浓度氧暴露24 h,LPS处理组、高氧组给予相应单因素处理,PND5断头取脑:(1)Tomato lectin免疫组化染色观测脑室周围白质小胶质细胞形态变化;(2)检测脑组织内脂质氧化物MDA含量;(3)Real-time PCR检测TNF-αmRNA表达变化;(4)Western-blot检测capsase-3蛋白表达。结果 Tomato lectin染色显示LPS组、高氧组及LPS+高氧组均可见脑室周围白质内小胶质细胞由静息态转化为激活态,高氧组激活的小胶质细胞数、脑内MDA含量、TNF-αmRNA表达、caspase-3蛋白表达均高于空气组、LPS组(P<0.05),LPS处理后高氧暴露(LPS+高氧组)能显著增强高氧暴露后的小胶质细胞活化效应(P<0.05)。结论高浓度氧暴露诱导小胶质细胞活化致未成熟脑损伤,低浓度LPS处理后能致敏上述效应。

Objective To explore the effect of low-concentration lipopolysaccharide （LPS） pretreatment on hyperoxia-induced immature brain injury in neonatal mice and explore and the related mechanisms. Methods Forty-eight neonatal mice on postnatal day 3 （PND3） were randomized into normal control group, LPS （0.3 mg/kg） group, hyperoxia group （hyperoxia exposure for 24 h）, and hyperoxia＋LPS group （hyperoxia exposure for 24 h 30 min after 0.3 mg/kg LPS treatment）. At PND5, all the neonatal mice were sacrificed to examine the morphological changes of microglia in the periventricular white matter using Tomato lectin staining, measure malondialdehyde （MDA） content in the immature brain, detect mRNA expression of tumor necrosis factor-α （TNF-α） using real-time PCR, and determine caspase-3 protein expression with Western blotting. Results Compared with the control group, exposures to LPS, hyperoxia, and both all resulted in microglia activation in the periventricular white matter. The number of activated microglia, MDA content, TNF-α mRNA expression and caspase-3 protein expression in the immature brain were significantly higher in hyperoxia group than in the control group and LPS group （P＆lt;0.05）. LPS pretreatment significantly enhanced hyperoxia-induced microglia activation in the immature brain （P＆lt;0.05）. Conclusion Hyperoxia causes immature brain injury mediated by microglia activation, and LPS pretreatment can enhance such brain injury in neonatal mice.