短链脂肪酸对脂多糖诱导的大鼠急性呼吸窘迫综合征的影响及其作用机制

Effects and mechanism of short chain fatty acids on lipopolysaccharide induced acute respiratory distress syndrome in rats

目的探讨短链脂肪酸(SCFAs)对脂多糖(LPS)诱导的大鼠急性呼吸窘迫综合征(ARDS)的影响及作用机制。方法20只雄性SD大鼠按照随机数字表法分为对照组、模型组、低剂量SCFAs组与高剂量SCFAs组,每组5只,对照组及模型组予以生理盐水,低、高剂量SCFAs组分别予以低剂量SCFAs(乙酸钠300 mg/kg,丙酸钠100 mg/kg,丁酸钠100 mg/kg)和高剂量SCFAs(乙酸钠600 mg/kg,丙酸钠200 mg/kg,丁酸钠200 mg/kg),提前灌胃7 d。随后对照组大鼠气管内灌注生理盐水,其他三组通过气管内灌注LPS(5 mg/kg)构建大鼠ARDS模型。造模12 h后处死大鼠,检测动脉血氧分压(PaO_(2))、肺湿/干重比(W/D),HE染色观察肺组织病理变化,ELISA法检测血清及支气管肺泡灌洗液(BALF)中肿瘤坏死因子(TNF)-α、白细胞介素(IL)-6、IL-10的浓度,Western blotting检测肺组织中c-Jun氨基末端激酶(JNK)、p-JNK、细胞外调节蛋白激酶(ERK)、p-ERK、p38丝裂原活化蛋白激酶(MAPK)、p-p38 MAPK、核因子κB(NF-κB)p65、p-NF-κB p65蛋白的表达,免疫组化检测结肠组织中紧密连接蛋白ZO-1、Occludin的表达。结果与对照组比较,模型组PaO_(2)降低,肺W/D、肺损伤病理评分升高,血清及BALF中TNF-α、IL-6、IL-10浓度明显增高,肺组织中p-JNK/JNK、p-ERK/ERK、p-p38 MAPK/p38 MAPK和p-NF-κB p65/NF-κB p65比值明显升高,结肠组织中ZO-1、Occludin蛋白相对表达量明显降低(P<0.05)。与模型组比较,低、高剂量SCFAs组PaO_(2)升高,肺W/D、肺损伤病理评分降低,血清及BALF中TNF-α、IL-6浓度下降,IL-10浓度进一步升高,肺组织中p-JNK/JNK、p-ERK/ERK、p-p38 MAPK/p38 MAPK和p-NF-κB p65/NF-κB p65比值降低,结肠组织中ZO-1、Occludin蛋白相对表达量增高(P<0.05)。与低剂量SCFAs组比较,高剂量SCFAs组上述指标改善更明显(P<0.05)。结论SCFAs具有调节免疫与炎症的作用,能有效减轻LPS诱导的大鼠ARDS,其机制可能与通过增强肠道屏障功能、抑制MAPK和NF-κB信号通路活化,从而减少致炎因子释放、增加抗炎因子生成有关。

Objective To investigate the effects and mechanism of short chain fatty acids(SCFAs)on lipopolysaccharide(LPS)induced acute respiratory distress syndrome(ARDS)in rats.Methods Twenty male SD rats were randomly divided into control group,model group,low-dose SCFAs group and high-dose SCFAs group(5 each).Rats in control and model groups were given normal saline,in low-dose SCFAs group were given sodium acetate 300 mg/kg,sodium propionate 100 mg/kg and sodium butyrate 100 mg/kg,and in high-dose SCFAs were given sodium acetate 600 mg/kg,sodium propionate 200 mg/kg and sodium butyrate 200 mg/kg by gavage for 7 days in advance.And then the rats in control group were perfused with normal saline,and in the other 3 groups were perfused with LPS(5 mg/kg)into trachea to establish ARDS model.The rats were sacrificed 12 hours after modeling,and the arterial oxygen partial pressure(PaO_(2))and lung wet/dry weight ratio(W/D)were measured,and HE staining was performed to observe the pathological changes of lung tissues.The concentrations of tumour necrosis factor(TNF)-α,interleukin(IL)-6 and IL-10 in serum and bronchoalveolar lavage fluid(BALF)were detected by ELISA.Western blotting was used to detect c-Jun N-terminal kinase(JNK),p-JNK,extracellular regulated protein kinases(ERK),p-ERK,p38 mitogen-activated protein kinase(MAPK),p-p38 MAPK,nuclear factor kappa-B(NF-κB)p65 and p-NF-κB p65 protein expression in lung tissues.The expression of tight junction protein ZO-1 and Occludin in colonic tissue were detected by immunohistochemistry.Results Compared with control group,PaO_(2)decreased,lung W/D and lung pathological injury score increased,the concentration of TNF-αand IL-6 in serum and BALF significantly increased,and the concentration of IL-10 increased,the relative protein expressions of p-JNK/JNK,p-ERK/ERK,p-p38 MAPK/p38 MAPK and p-NF-κB p65/NF-κB p65 in lung tissues significantly increased,while the relative expression of ZO-1 and Occludin protein significantly decreased in colonic tissues in model group(P<0.05).Compared with model group,PaO_(2)increased,lung W/D and lung pathological injury score decreased,and TNF-α,IL-6 in serum and BALF decreased,the concentration of IL-10 increased further,while the relative expressions of p-JNK/JNK,p-ERK/ERK,p-p38 MAPK/p38 MAPK and p-NF-κB p65/NF-κB p65 protein in lung tissue decreased,and the relative expression of tight junction protein ZO-1 and Occludin in colon tissue increased in low and high dose SCFAs groups(P<0.05).Compared with low-dose SCFAs group,the indexes mentioned above in the high-dose SCFAs group improved more significantly(P<0.05).Conclusion SCFAs could regulate immunity and inflammation,and effectively improved LPS-induced ARDS in rats,the mechanism might be related to enhancement of intestinal barrier and inhibition of MAPK and NF-κB signaling pathway activation,thereby reducing the release of inflammatory factors and increasing the production of anti-inflammatory factors.