地塞米松对高氧肺损伤大鼠肺组织基质金属蛋白酶及其组织抑制剂表达的影响

Study on effect of dexamethasone on the expression of matrix metalloproteinase and its tissue inhibitors in hyperoxia - induced lung injury

目的 观察地塞米松对高氧暴露大鼠肺组织中基质金属蛋白酶(MMPs)及其组织抑制剂(TIMPs)表达的影响,探讨地塞米松治疗高氧肺损伤的作用机制。方法 2周龄Wistar大鼠32只,随机分为空气组和高氧组(各16只)。高氧暴露7 d后,取两组大鼠各8只检测支气管肺泡灌洗液(BALF)蛋白含量和肺湿/干重比(W/D),并观察肺组织病理学改变。余16只大鼠行肺组织培养,空气组8只作为空气对照组,高氧组8只各设高氧对照组,高氧+地塞米松1×10-8、1×10-6和1×10-4mol/L组,培养24 h后用逆转录-聚合酶链反应(RT-PCR)检测肺组织中MMP-2、MMP-9、TIMP-1、TIMP-2 mRNA的表达。结果①与空气组相比,高氧组肺组织出现水肿、出血、炎性细胞浸润;BALF中蛋白含量、W/D明显增高。②高氧对照组MMPs、TIMPs mRNA表达和MMP-2/TIMP-2、MMP-9/TIMP-1比值较空气对照组明显增高。③地塞米松能剂量依赖性下调MMP-2、MMP-9 mRNA表达;对TIMP-1、TIMP-2 mRNA表达有一定程度的抑制效应;随地塞米松浓度的增加,MMP-2/TIMP-2、MMP-9/TIMP-1比值亦逐渐降低。结论 地塞米松下调MMPs mRNA表达,调节MMPs/TIMPs之间的失衡,可能是其减轻高氧肺损伤的机制之一。

Objective To observe the effect of dexamethasone on the mRNA expression of matrix metalloproteinase(MMPs) and tissue inhibitor of metalloproteinase(TIMPs) in the lung tissue and to explore the protective mechanism of dexamethasone in hyeroxia - induced lung injury. Methods Thirty - two two - week old Wistar rats were randomly divided into atmospheric - air group (n = 16) and hyperoxia group (n = 16). After 7 days of continuous exposure to high concentration O2(≥95%), the lung wet/dry(W/D) ratio > the protein content in bronchoalveolar lavage fluid (BALF) and histopathological changes of the lung were measured in 16 rats(8 in each group). The lung tissue specimens of the other 16 rats were cultured, 8 among which served as stmospheric - air control group, the remainder in the hyperoxia group were divided into hyperoxia control group, hyperoxia + dexamethasone (1×10-8 mol/L ) group, hyperoxia + dexamethasone (1×10-6 mol/L) group, and hyperoxia + dexamethasone (1×10-4 mol/L) group. Eight samples were examined in each group. After cultured for 24 hours, the lung tissue were collected and its mRNA expression of MMP - 2, MMP - 9, TIMP - 1 and TIMP - 2 were determined by reverse transcription - polymerase chain reaction (RT - PCR). Results (1) Pulmonary edema, hemorrhage and extensive inflammatory cells infiltration were observed in hyperoxia group, but no such changes were found in the atmospheric- air group. The lung W/D and the protein content in BALF in hyperoxia group were significantly higher than those in atmospheric air groups. (2)The mRNA expressions of MMP - 2, MMP - 9, TIMP - 1, TIMP - 2 and the ratio of MMP - 2/TIMP - 2, MMP - 9/TIMP - 1 were significantly higher in the hyperoxic group than those in the atmospheric - air group. (3)Dexamethasone could down - regulate the mRNA expressions of MMP - 2 and MMP - 9 in a concentration dependant manner. The mRNA expressions of TIMP - 1, TIMP - 2 also could be reduced by dexamethasone. Decreasing ratios of MMP - 2/TIMP - 2 and MMP - 9/TIMP - 1 were found in correlation with increasing concentration of dexamethasone. Conclusion Dexamethasone can reduce the mRNA expressions of MMPs as well as regulate the balance of MMPs/TIMPs, which may be one of the mechanism of its protective effect on hyperoxia - induced lung injury.