褪黑素抑制大鼠急性肺损伤时磷酸化p38丝裂素活化蛋白激酶的表达

目的 探讨褪黑素(MT)对大鼠急性肺损伤(ALI)时肺脏的保护作用及可能机制.方法 将72只SD大鼠按随机数字表法均分为对照组、脂多糖(LPS)组和LPS+MT处理组.LPS组、LPS+MT组动物经气道内滴注LPS 1 ml/kg(200 μg/200 μl)染毒.LPS+MT组给药前后30 min分别经腹腔注射10 mg/kg MT;对照组、LPS组给予1 ml/kg乙醇-生理盐水溶剂.给药后3、6和10 h处死动物取肺组织,检测一氧化氮(NO)、丙二醛(MDA)含量及超氧化物歧化酶(SOD)活性;用免疫组化法检测磷酸化p38丝裂素活化蛋白激酶(p-p38MAPK)在肺组织的表达.结果 LPS组SOD活性(U/mg)较对照组明显降低(3 h:73.78±3.62比112.69±3.26,6 h:66.07±2.31比117.85±1.96,10 h:55.13±5.26比118.27±2.16,均P<0.01),而NO(μmol/mg)与MDA(nmol/mg)含量以及p-p38MAPK表达量(A值)显著升高(NO 3 h:8.19±0.48比2.32±0.20,6 h:11.71±0.27比2.08±0.15,10 h:16.53±0.60比2.76±0.21;MDA 3 h:11.43±0.68比2.86±0.21,6 h:19.63±1.29比2.85±0.19,10 h:26.63±2.00比2.84±0.28;p-p38MAPK 3 h:0.340±0.020比0.238±0.019,6 h:0.410±0.016比0.218±0.024,10 h:0.578±0.066比0.238±0.036,均P<0.01);应用MT能显著缓解上述变化3、6、10 h SOD(U/mg)为86.02±2.81、80.87±3.40、94.46±5.03,NO(μmol/mg)为3.80±0.28、5.32±0.22、7.24±0.52,MDA(nmol/mg)为8.18±0.84、7.84±0.78、6.43±1.06,p-p38MAPK(A值)为0.311±0.018、0.312±0.019、0.314±0.021,P<0.05或P<0.01].结论 MT对ALI时肺脏的保护作用可能与MT的抗氧化作用及抑制p-p38MAPK的过度表达有关.

Inhibitory effects of melatonin on the expression of phosphorylation p38 mitogen-activated protein kinase during acute lung injury in rats

Objective To investigate the protective effect of melatonin (MT) on lung tissues during acute lung injury (ALI) in rats and its possible mechanism. Methods Seventy-two Sprague-Dawley (SD) rats were randomly divided into three groups: control group, lipopolysaccharide (LPS) group and MT treatment group. In LPS group and MT treatment group, 1 ml/kg of LPS (200 μg/200 μl) was administered through the airway. In MT group, 10 mg/kg of MT was injected intraperitoneally before and after administration of LPS, and 1 ml/kg of ethanol-normal saline was given in control rats. The rats were sacrificed at 3, 6, 10 hours after administration of LPS, and the lung tissue was obtained for determination of the contents of nitrogen monoxide (NO) and malondialdehyde (MDA), and activity of superoxide dismutase (SOD). In addition, the expression of phosphorylation p38 mitogen-activated protein kinase (p-p38MAPK) in lung tissue was assayed with immunohistochemistry staining. Results Compared with control group, SOD activity (U/mg) decreased significantly in LPS group (3 hours: 73.78±3.62 vs. 112.69±3.26, 6 hours: 66.07±2.31 vs. 117.85±1.96, 10 hours: 55.13±5.26 vs. 118.27±2.16, all P<0.01), but NO (μmol/mg), MDA (nmol/mg) content and the expression of p-p38MAPK absorbance (A) value] increased obviously (NO: 8.19±0.48 vs. 2.32±0.20 at 3 hours, 11.71±0.27 vs. 2.08±0.15 at 6 hours, 16.53±0.60 vs. 2.76±0.21 at 10 hours; MDA: 11.43±0.68 vs. 2.86±0.21 at 3 hours, 19.63±1.29 vs. 2.85±0.19 at 6 hours, 26.63±2.00 vs. 2.84±0.28 at 10 hours; p-p38MAPK: 0.340±0.020 vs. 0.238±0.019 at 3 hours, 0.410±0.016 vs. 0.218±0.024 at 6 hours, 0.578±0.066 vs. 0.238±0.036 at 10 hours, all P<0.01). The administration of MT mitigated above contents significantly SOD (U/mg) was 86.02±2.81, 80.87±3.40, 94.46±5.03, NO (μmol/mg) was 3.80±0.28, 5.32±0.22, 7.24±0.52, MDA (nmol/mg) was 8.18±0.84, 7.84±0.78, 6.43±1.06, and p-p38MAPK (A value) was 0.311±0.018, 0.312±0.019, 0.314±0.021 at 3, 6, 10 hours, respectively, P<0.05 or P<0.01]. Conclusion MT possessed protective effect on lung tissues during ALI by its antioxidation effect and inhibition of over-expression of p-p38MAPK.