LPS性肺损伤大鼠一氧化氮合酶表达和肺细胞凋亡变化

目的: 观察内毒素性肺损伤过程中肺细胞凋亡和一氧化氮合酶（NOS）mRNA表达的时程性变化及关系,探讨LPS性肺损伤（ALI）的发病机制。方法: 健康雄性SD大鼠48只,随机分成2组:①对照组：静注等量生理盐水；②模型组(LPS组)：静注LPS复制ALI模型,分别于给药1、3、6、9及12h后采集样品；逆转录聚合酶链反应（RT-PCR）法测定肺组织中NOSmRNA表达变化；电镜、流式细胞术检测肺细胞凋亡率；免疫组化法测定Bcl-2和Bax；光镜、电镜观察肺组织病理变化。结果: 与对照组比较，LPS组iNOSmRNA表达随时间延长而增强，给予LPS 3 h后有显著差异(P<0.05)，eNOSmRNA随时间延长而降低，给LPS 3 h时有显著差异(P<0.05)，nNOSmRNA在观察时间内没有变化；光镜和电镜下可见在观察时间内1 h起肺损伤随时间延长加重；流式细胞术显示LPS组凋亡细胞随时间延长增多，9 h达高峰，12 h有所降低；免疫组化结果显示，LPS组随时间延长Bcl-2减少，主要表现在肺上皮细胞，Bax增多；对照组无明显变化。结论: 不同一氧化氮合酶在ALI中表达强度不同；抗凋亡蛋白Bcl-2和促凋亡蛋白Bax是ALI时调节细胞凋亡的途径之一；一氧化氮合酶可能通过调节Bcl-2和Bax平衡而影响凋亡。

Changes of pulmonary apoptosis and NOS mRNA in the lipopolysaccharide-induced acute lung injury

AIM: To observe the chronological changes of pulmonary apoptosis and the expression of iNOS mRNA,nNOS mRNA and eNOS mRNA in lipopolysaccharide(LPS)-induced acute lung injury(ALI) and to investigate the mechanisms of ALI.METHODS: Rats were randomly divided into 2 groups: control group and LPS treated group.The rats were injected with either saline or LPS and killed at 1,3,6,9 and 12 h after LPS injection.The expressions of iNOS mRNA,nNOS mRNA and eNOS mRNA in the lung tissue were respectively measured with RT-PCR methods.Apoptosis and expressions of Bcl-2 and Bax were respectively determined by flow cytometry(FCM) and immunohistochemistry(IHC).The pathological changes of lung tissue were observed under light and electron microscope.RESULTS: Compared with that in control group,the expression of iNOS mRNA was significantly increased at 3,6,9 and 12 h after administration of LPS(P<0.05).The eNOS mRNA was significantly decreased at 3,6,9 and 12 h after administration of LPS(P<0.05).The nNOS mRNA had no significant change during the 12 h in LPS group.Degree of ALI was gradually worsened after administration of LPS.Apoptosis of pulmonary cells was significantly increased,and reached the top level at 9 h after administration of LPS(P<0.01).The expression of Bcl-2 was markedly decreased and the expression of Bax was significantly enhanced in alveolar and airway epithelial cells in LPS treated group.CONCLUSION: The expressions of iNOS mRNA,eNOS mRNA and nNOS mRNA are not identical in LPS-induced acute lung injury.NOS regulates the apoptosis of pulmonary cells through affecting the balance of Bcl-2 and Bax.