产前使用地塞米松对坏死性小肠结肠炎新生鼠Toll样受体4表达的影响

目的观察产前使用地塞米松(dexamethasone,DEX)对新生大鼠坏死性小肠结肠炎(necrotizing enterocoli-tis,NEC)发生率及肠道Toll样受体4(toll like receptor 4,TLR4)表达的影响,探讨其对NEC的保护作用及可能的机制。方法实验分为正常对照组、产前地塞米松干预组(DEX组)、产前生理盐水干预组(normal saline,NS组)3组,于孕16、17、18 d时DEX组孕鼠肌肉注射DEX 0.5 mg/(kg.d),NS组每天注射NS 0.3 ml。DEX组及NS组所生新生鼠建立NEC动物模型。正常对照组不予处理。于第5天处死新生鼠,观察近回盲部肠组织病理变化并做评分;免疫组化法检测TLR4蛋白的表达;其余小肠部分Q-PCR法检测TLR4 mRNA的表达。结果与NS组相比,DEX组新生鼠NEC发生率明显降低(P<0.01)。正常对照组未出现NEC症状,NS组新生鼠出现典型的NEC症状,DEX组NEC症状比NS组出现得更晚、更轻;与正常对照组相比,DEX组和NS组肠组织病理学评分及TLR4表达显著增高(P<0.05);与NS组相比,DEX组肠组织病理学评分及TLR4表达显著降低(P<0.05)。结论产前使用DEX对NEC大鼠具有保护作用,其机制可能是通过降低TLR4的表达从而发挥抗炎效应。

Antenatal dexamethasone downregulates toll-like receptor 4 in neonatal rats with necrotizing enterocolitis

Objective To observe the effect of antenatal dexamethasone(DEX) treatment on expression of toll-like receptor 4(TLR4) in neonatal rats with necrotizing enterocolitis(NEC),and to explore its protective effect and potential mechanisms.Methods Twelve pregnant Sprague-Dawley(SD) rats were randomly divided into three groups with 4 rats in each group,including a normal control group(NC group),a DEX group and a normal saline group(NS group).On the gestational days 16,17 and 18,rats of the DEX group and the NS group were intramuscularly injected with DEX [0.5 mg/(kg·d)] and normal saline(0.3 ml/d),respectively.All rats of the three groups were delivered spontaneously(term=22 d).Neonatal rats of the DEX group and NS group(except NC group) were selected to establish NEC models by artificial feeding,cold exposure after hypoxic-reoxygenation and LPS intragastric administration.General conditions of neonatal rats were observed in each group.All the neonatal rats were sacrificed on the 5th day after birth and proximal intestine tissues of rat ileocecal junction were obtained.Pathological changes of the tissues were examined by pathological sectioning and hematoxylin and eosin(HE) staining,and protein expression of TLR4 was detected by immunohistochemical method.Total RNA was extracted from the rest of intestinal tissues,and mRNA expression of TLR4 was detected by Quantitative Real-time PCR(Q-PCR).Results Incidence of NEC in the DEX group was lower than that in the NS group.Typical NEC symptoms were observed in rats of the NS group but not the NC group,while the symptoms were later and milder in rats of the DEX group.Histopathologic scores and TLR4 expressions of the DEX and NS groups were significantly higher than those of the NC group(P<0.05),and the two indicators of the DEX group were significantly lower than those of the NS group(P<0.05).Conclusion Antenatal DEX has a protective effect on rat model of NEC probably by downregulating TLR4 expression to exert an anti-inflammatory effect.