L-Arg对LPS诱导的急性肺损伤大鼠肺表面活性物质和肺泡巨噬细胞功能的影响

Effect of L-arginine on pulmonary surfactant and alveolar macrophages in rats with pulmonary injury induced by lipopolysaccharide

目的:探讨L-精氨酸(L-Arg)对脂多糖(LPS)诱导的急性肺损伤大鼠肺表面活性物质和肺泡巨噬细胞功能的影响。方法:舌下静脉注射脂多糖(LPS)复制肺损伤模型。健康雄性SD大鼠48只,随机分为对照组、模型组(LPS组)和L-Arg治疗组(L-Arg组)(n=16)。分别于给予LPS 3 h或6 h后给予生理盐水(对照组及LPS组,ip)和L-Arg(500 mg/kg ip)(L-Arg治疗组),治疗3 h。原位杂交法(ISH)检测肺组织中肺表面活性蛋白A(SP-A)mRNA的表达;测定肺泡灌洗液(BALF)中的总蛋白(TP)。体外分离培养大鼠肺泡巨噬细胞,以LPS(终浓度10 mg/L)处理巨噬细胞,观察L-Arg对肺泡巨噬细胞的影响。结果:与对照组比较,大鼠肺损伤后SP-A mRNA表达减弱,BALF中TP增多(P<0.01)。肺损伤3 h用L-Arg治疗3 h后,SP-A mRNA阳性细胞表达明显增强,BALF中TP较LPS组相同时间点明显降低(P<0.05,P<0.01),肺损伤减轻。体外实验中,与正常对照组相比,LPS组细胞培养上清中乳酸脱氢酶(LDH)、一氧化氮(NO)、肿瘤坏死因子-α(TNFα-)和白细胞介素-6(IL-6)浓度明显增高(P<0.01);L-Arg明显减少LPS所致的LDH的释放,降低TNFα-和IL-6浓度。结论:L-Arg可减轻内毒素性肺损伤,此机制可能与增强SP-AmRNA表达有关;LPS可刺激巨噬细胞分泌促炎因子和NO,L-Arg可抑制LPS对巨噬细胞的作用。

Objective： To investigate the effect of L-Arginine（L-Arg） on pulmonary surfactant （PS） expression and alveolar macrophage （AM） in rats with pulmonary injury induced by lipopolysaccharide （LPS）. Methods： Model of acute lung injury （ALI） was made by injection （iv） with LPS 5 mg/kg in rats. Fourty-eight male SD rats were randomly divided into 3 groups（n= 16）： control, model （LPS） and L-Arg groups. L-Arg （500 mg/kg ip,L-Arg group） or saline（control and LPS group） was administrated at 3 h or 6 h after LPS injection respectively for 3 h. The expression of surfactant protein A（SP-A） mRNA in the lung tissue was detected by ISH. The total protein（TP） in the bron- choalveolar lavage fluid （BALF） was detected. Rat AM were isolated from the bronchial alveolar lavage fluid of SD rats and harvested by selec- tive plating technique. LPS and L-Arg were added to the culture medium. The concentration of nitric oxide （NO）,the activity of lactate dehy- drogenase （LDH）, the contents of tumor necrosis factor-a（TNF-a） and interleukin-6（IL-6） in the culture supernatants were respectively mea- sured. Results： Compared with the control group, the expression of SP-A mRNA was significantly decreased, the TP concentration was singnif- icantly increased in LPS group. Compared with LPS group at the same time points, treatment with L-Arg at 3 h after LPS, the expression of SP- A mRNA in lung tissue was increased markedly, whereas TP concentration was decreased significantly. In cultured rat AM, LDH activity, NO, TNF-ct and IL-6 contents in culture medium were significantly increased in LPS group to compared with those of control group. LDH activ- ity, TNF-a and IL-6 contents were decreased in L-Arg group compared with those of LPS group. Conclusion： L-Arg can protect the lung a- gainst LPS-induced pulmonary injury by up-regulating the expression of PS and inhibiting inflammatory transmitters from AM.