MLK3-MKK3/6-p38MAPK信号转导通路在大鼠内毒素性急性肺损伤中的作用

目的 探讨MLK3-MKK3/6-p38MAPK信号转导通路在大鼠内毒素性急性肺损伤中的作用.方法 健康成年雄性SD大鼠78只,体重200～250 g,随机分为4组:对照组(C组,n=6)、急性肺损伤组(ALI组,n=24)、MLK3抑制剂K252a组(MK组,n=24)和p38MAPK特异性抑制剂SB203580组(MS组,n=24).ALI组尾静脉注射内毒素5 mg/kg制备大鼠急性肺损伤模型,C组给予等容量生理盐水,MK组和MS组于注射内毒素前30 min经尾静脉分别注射K252a 75μg/kg、SB203580 10 mg/kg.ALI组、MK组和MS组于注射内毒素后1、3、6、12 h(1-4)时各组随机取6只大鼠,C组于给予生理盐水后即刻处死取肺,采用ELISA法测定支气管肺泡灌洗液中TNF-α浓度,称重后计算肺湿干重比,采用Western b1ot法测定p-MLK3、p-MKK3/6及p-p38MAPK的表达,观察肺组织病理学结果.结果 与C组比较,ALI组、MK组和MS组各时点支气管肺泡灌洗液中TNF-α浓度、肺湿干重比、p-MLK3、p-MKK3/6及p-p38MAPK的表达水平升高(P＜0.01);与ALI组比较,MK组上述指标降低,MS组支气管肺泡灌洗液中TNF-α浓度、肺湿干重比、p-p38MAPK表达水平降低(P＜0.05).病理学结果显示:MK组和MS组肺组织损伤较ALI组减轻.结论 MLK3-MKK3/6-p38MAPK信号转导通路在大鼠内毒素性急性肺损伤中起重要作用.

Role of MLK3-MKK3/6-p38MAPK signal transduction pathway in lipopolysaccharide-induced acute lung injury in rats

Objective To evaluate the role of MLK3-MKK3/6-p38MAPK signal transduction pathway in lipopolysaccharide (LPS)-induced acute lung injury (ALI) in rats. Methods Seventy-eight healthy adult male SD rats weighing 200-250 g were randomly divided into 4 groups: control group (group C, n = 6), ALI group ( n =24), MLK3 inhibitor K252a group (group MK, n = 24) and p38MAPK specific inhibitor SB203580 group (group MS, n = 24). ALI was induced by iv injection of LPS 5 mg/kg via tail vein, while the equal volume of normal saline was given instead in group C. K252a 75 μg/kg and SB203580 10 mg/kg were injected intravenously via tail vein 30 min before LPS administration in group MK and MS respectively. The rats were killed at 1, 3, 6 and 12 h (T1-4) after LPS administration in group ALI, MK and MS (6 rats at each time point) and immediately after normal saline administration in group C. The lungs were removed for microscopic examination. The left lung was lavaged.The broncho-alveolar lavage fluid (BALF) was collected. The concentration of TNF-α in the BALF was determined by ELISA. W/D lung weight ratio was calculated. The expression of p-MLK3, p-MKK3/6 and p-p38MAPK were determined by Western blot. Results The concentration of TNF-α in the BALF, W/D lung weight ratio, and expression of p-MLK3, p-MKK3/6 and p-p38MAPK were significantly higher in the other three groups than in group C (P ＜ 0.01). The parameters mentioned above were significantly lower in group MK, and the concentration of TNF-α in the BALF, W/D lung weight ratio, and p-p38MAPK expression were significantly lower in group MS than in group ALI (P ＜ 0.05). The microscopic examination showed that LPS-induced ALI was less severe in group MK and MS than in group ALI. Conclusion MLK3-MKK3/6-p38MAPK signal transduction pathway plays an important role in LPS-induced ALI in rats.