Objective To investigate the effects of NG-nitro-L-arginine (L-NA) on pulmonary surfactant (PS) and pulmonary cells apoptosis in lipopolysaccharide (LPS) induced acute lung injury (ALI). Methods Twenty-four male Sprague-Dawley (SD) rats were randomly divided into three groups: control group, model group, L-NA group. Model of ALI was reproduced by injection of LPS 5 mg/kg via sublingual vein in model group and L-NA group. L-NA (20 mg/kg) was administered in L-NA group, while normal saline was administered in control group and model group 3 hours after LPS injection. The rats were sacrificed at 6 hours after LPS injection, and the lung tissue was obtained for measuring the expressions of pulmonary surfactant protein A (SP-A) mRNA by in situ hybridization (ISH) method; meanwhile, apoptosis rate was evaluated by flow cytometry; the expression of caspase-3 was evaluated by Western blotting analysis; Bcl-2 and Bax were evaluated respectively by immunohistochemisty (IHC). Results Compared with that of the control group, SP-A mRNA [absorbance (A) value] in the lung tissue was significantly decreased by LPS (0.071±0.017 vs. 0.113±0.021) in model group, apoptosis rate of pulmonary cells [(25.04±4.57)% vs. (11.37±3.08)%], caspase-3 protein expression (A value: 298.64±37.11 vs. 110.24±14.35) and Bax protein expression (A value: 0.145±0.011 vs. 0.076±0.010) were significantly increased, Bcl-2 protein expression (A value: 0.064±0.011 vs. 0.073±0.009) and Bcl-2/Bax (0.447±0.086 vs. 0.976±0.157) were decreased in model group (all P<0.01). L-NA was given at 3 hours after LPS administration, the expressions of SP-A mRNA (A value: 0.085±0.015) and Bcl-2 protein (A value: 0.070±0.087) increased markedly, compared with model group (P<0.01 and P<0.05), but there were no significant changes in the pulmonary cells apoptosis rate [(20.67±1.35)%], caspase-3 protein expression (A value: 268.75±42.56), Bax protein expression (A value: 0.142±0.012) and Bcl-2/Bax (0.498±0.069) between L-NA group and model group (all P>0.05). Conclusion L-NA had no effect on LPS-induced pulmonary cell apoptosis and had no effect on the expressions of caspase-3 and Bax, but L-NA can protect the lung from LPS-induced injury by up-regulating the expression of PS.%目的 探讨NG-硝基-L-精氨酸(L-NA)对内毒素性肺损伤大鼠肺表面活性物质(PS)和细胞凋亡的影响.方法 雄性SD大鼠24只,按随机数字表法均分为对照组、模型组、L-NA治疗组.模型组、L-NA治疗组舌下静脉注射脂多糖(LPS)复制内毒素性肺损伤模型;对照组给予等量生理盐水.L-NA治疗组于注射LPS 3 h后给予L-NA 20 mg/kg;对照组和模型组给予等量生理盐水.6 h后处死动物,取肺组织,用原位杂交法测定肺组织表面活性物质相关蛋白A(SP-A)mRNA表达;用流式细胞术检测肺组织细胞凋亡率;用蛋白质免疫印迹法(Western blotting)检测天冬氨酸特异性半胱氨酸蛋白酶3(caspase-3)蛋白表达;用免疫组化法测定Bcl-2和Bax蛋白表达.结果 与对照组比较,模型组SP-A mRNA表达[吸光度(A)值]明显下降(0.071±0.017比0.113±0.021),细胞凋亡率[(25.04±4.57)%比(11.37±3.08)%]、caspase-3蛋白表达(A值:298.64±37.11比110.24±14.35)、Bax蛋白表达(A值:0.145±0.011比0.076±0.010)明显升高,Bcl-2蛋白表达(A值:0.064±0.011比0.073±0.009)和Bcl-2/Bax比值(0.447±0.086比0.976±0.157)明显下降(均P<0.01).与模型组比较,L-NA治疗组SP-A mRNA表达(A值:0.085±0.015)和Bcl-2蛋白表达(A值:0.070±0.087)明显增强(P<0.01和P<0.05),但细胞凋亡率[(20.67±1.35)%]、caspase-3蛋白表达(A值:268.75±42.56)、Bax蛋白表达(A值:0.142±0.012)和Bcl-2/Bax比值(0.498±0.069)均无明显变化(均P>0.05).结论 L-NA不通过抑制肺细胞凋亡来减轻内毒素性肺损伤的程度,对调节凋亡相关基因caspase-3和Bax也无明显影响;而是可通过增强PS表达减轻内毒素性肺损伤.
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