N-乙酰半胱氨酸对高氧肺损伤保护机制与p38丝裂素活化蛋白激酶途径的相关性研究

目的 观察p38丝裂素活化蛋白激酶(p38MAPK)信号途径在高氧肺损伤中的表达,探讨N-乙酰半胱氨酸(NAC)在高氧肺损伤中的保护作用及机制.方法 将30只幼年Wistar大鼠按随机数字表法分为空气对照组(A组)、高氧暴露组(B组)、高氧+NAC干预组(C组)、高氧+p38MAPK特异性抑制剂(SB203580)干预组(D组)、高氧+NAC+SB203580联合干预组(E组),每组6只.实验7 d后,光镜下观察肺组织病理改变,并行肺损伤评分;测定肺湿/干重(W/D)比值、支气管肺泡灌洗液(BALF)中总蛋白(TP)含量、肺通透系数;采用免疫组化法检测磷酸化p38MAPK(p-p38MAPK)在肺组织中的分布;用蛋白质免疫印迹法检测p-p38MAPK蛋白含量.结果 与A组比较,高氧各组均有不同程度的肺损伤,但药物干预各组(C、D、E组)肺损伤均较B组有所减轻.免疫组化显示,高氧各组p-p38MAPK阳性表达较A组明显增强,尤高表达在炎性浸润细胞;药物干预后(C、D、E组)p-p38MAPK阳性细胞较B组明显减少.蛋白质免疫印迹法显示,B组p-p38MAPK蛋白含量明显高于A组(0.20±0.03比0.11±0.01,P<0.05);干预后C、D、E组p-p38MAPK蛋白含量低于B组(0.16±0.02、0.15±0.01、0.14±0.02比0.20±0.03,均P<0.05),但仍高于A组(均P<0.05),而C、D、E组间则无明显差异.各组肺W/D比值、BALF中TP含量、肺通透系数改变与p-p38MAPK蛋白含量变化趋势一致.结论 高氧应激可激活损伤肺组织p38MAPK活性;NAC抗氧化肺保护作用机制可能是通过下调高氧诱导p38MAPK的激活而对肺损伤起保护作用.

Protective effect of N-acetylcysteine on hyperoxic lung injury and its relation with p38 mitogen-activated protein kinase signaling pathway

Objective To investigate the expression of p38 mitogen-activated protein kinase (MAPK) in hyperoxic lung injury (HLI), and explore the protective effect of N-acetylcysteine (NAC) on HLI and its mechanism. Methods Thirty Wistar rats aged 3 weeks old were divided into five groups with 6 rats in each group according to random digits table: room-air group (A), hyperoxia injury group (B), hyperoxia+NAC group (C), hyperoxia+p38MAPK inhibitor (SB203580) group (D), hyperoxia+NAC+SB203580 group (E). Rats in NAC groups were injected with NAC (200 mg/kg) intraperitoneally, and they received an intravenous injection of SB203580 (0.5 mg/kg) in SB203580 groups. The animals were sacrificed after 7 days of experiment. Lung pathology and grade of lung tissue injury were examined with light microscopy, lung wet/dry (W/D) ratio, total protein (TP) level in bronchoalveolar lavage fluid (BALF) and permeability coefficient were evaluated. The location and quantity of phosphorylation p38MAPK (p-p38MAPK) protein were detected by immunohistochemistry and Western blotting analysis respectively. Results The pathological changes in the lung in B group included severe alveolar oedema with inflammatory cells aggregation and red blood cell leakage, while the lung pathological pictures in C, D, E groups were improved significantly compared with B group. p-p38MAPK positive cells increased in B group compared with those in A group, involving many types of pulmonary cells, especially in infiltrating inflammatory cells. In C, D, E groups, the positive cells remarkably decreased compared with B group. p-p38MAPK content was higher in B group than that in A group (0.20±0.03 vs. 0.11±0.01, P<0.05), and p-p38MAPK expressions in C, D, E groups decreased significantly compared with B group (0.16±0.02, 0.15±0.01, 0.14±0.02 vs. 0.20±0.03, all P<0.05), but were higher than those in A group (all P<0.05). There was no significant difference in p-p38MAPK quantity among three groups. Changes in W/D ratio, TP and permeability coefficient among groups were comparable with those of p-p38MAPK protein quantity. Conclusion Reactive oxygen species (ROS) activated p38MAPK signaling pathway. NAC may exert a protective effect on HLI through attenuation of hyperoxia-induced p38MAPK activation.