糖皮质激素受体对内毒素性急性肺损伤大鼠的保护作用及机制

The protection efffcts of glucocorticoid receptor on LPS-induced acute lung injury in rats

目的 探讨糖皮质激素受体（glucocorticoid receptor,GR）在内毒素急性肺损伤（acute lung injury,ALI）中的作用及机制.方法 SD雄性大鼠84只,随机数字表法分为5组：Control组,仅注射生理盐水;脂多糖（lipopoIysaccharide,LPS）组,经尾静脉注射LPS 5 mg/kg;地塞米松（dexamethasone,DEX）＋LPS组,注射LPS前30 min腹腔注射Dex 6 mg/kg;米非司酮（RU486）组,皮下注射GR拮抗剂RU486 20 mg/kg,90 min后经尾静脉注射生理盐水;RU486＋Dex＋LPS组,按照上述顺序分别注射RU486、Dex和LPS.Control组和RU486组6 h后,其余3组分别在1、3、6 h各时间点处死.检测各组大鼠支气管肺泡灌洗液（brobehoalveolar lavage fluid,BALF）中蛋白浓度,肺水系数（1ung index,LI）,肺组织的病理变化,凋亡指数（apoptosis index,AI）以及肺组织中p38MAPK的活化状态及表达.结果 与Control组BALF中蛋白浓度（49±5）g/L、LI（2.36±0.14）、AI（12.0±1.7）%相比,LPS组分别为（77±9）g/L、5.93±0.44、（43.9±3.1）%（P＜0.05）,HE染色显示肺组织炎症和损伤严重.与LPS组相比,Dex＋LPS组分别为（54±4）g/L、3.77±0.48、（32.7±2.7）%（P＜0.05）,且肺组织损伤程度减轻,应用GR抑制剂RU486后,Dex的肺保护作用消失.另外,LPS组肺组织中磷酸化p38MAPK（p-p38MAPK）的表达与Control组相比显著升高（P＜0.05）;与LPS相比,Dex＋LPS组p-p38MAPK表达下调（P＜0.05）,而RU486＋Dex＋LPS组的表达上调（P＞0.05）.结论 糖皮质激素受体在内毒素导致的急性肺损伤中发挥着重要的作用.激素活化的GR可能通过抑制p38MAPK的活化/磷酸化抑制肺组织细胞的凋亡,缓解肺损伤的程度.

Objective To examine the role of glucocorticoid receptor（GR） in regulation of lipopolysaccharide（LPS）-induced lung injury. Methods 84 mail Sprague-Dawley rats were randomly divided into five groups： Control group, received an injection of 0.9% sodium chloride; LPS group, received LPS injection（5 mg/kg, intravenously,i.v.）;Dex＋LPS group, received dexamethasone injection （6 mg/kg, intraperitoneally, i.p.）; RU486 group, received glucocorticoid receptor antagonist RU486 injection （20 mg/kg,subcutaneously, s.c.）; RU486＋Dex＋LPS group, received the injections of the three drugs seriatim as mentioned previously. All the animals were killed under anesthesia by intraperitoneal injection of pentobarbital at each time point. The concentration of albumin in bronchoalveolar lavage fluids（BALF）, lung index（LI）, apoptosis index（AI）, the histopathologic changes of lung tissues, activation of p38MAPK and expression in lung tissue were detected. Results BALF protein content（77±9） g/L, LI（5.93±0.44）, AI（43.9±3.1 ）%significantly increased at 6h after LPS administration than those in Control group （49±5） g/L, 2.36±0.14, （12.0±1.7）%（P＜0.05）. Pulmonary H-E stain showed serious pulmonary inflammation and conspicuous lung injury .Compared with the LPS group, the albumin leakage（54±4） g/L, LI（3.77±0.48）,AI（ 32.7±2.7）%in Dex＋LPS group was significantly attenuated with protection of tissue damage （P＜0.05）, while all the protective effects of Dex might be cancelled by GR antagonist （RU486）. Western blot analysis showed the expression of p-p38MAPK in lung tissues was significantly increased in LPS group than that in Control group （P＜0.05）.The expression of p-p38MAPK was down-regulated in Des＋LPS group than that in LPS group（P＜0.05）,but the expression in RU486＋Dex＋LPS group was similar to LPS group （P＞0.05）. Conclusion GR plays an essential role in regulation of LPS-induced ALI.Anti-apoptosis effects of hormone-activated GR may be mediated by inhibition of p38MAPK phosphorylation/activation.