氢化可的松对内毒素致急性肺损伤大鼠多形核白细胞氧自由基释放的影响

目的　　观察氢化可的松 (6mg/kg)对内毒素致急性肺损伤 (ALI)大鼠多形核白细胞(PMN)释放氧自由基 (OFR)及肺部病理改变的影响 ,探讨激素在ALI中发挥作用的可能机制。方法复制大鼠ALI模型 ,随机分为空白组、内毒素组 (LPS组 )、氢化可的松组 (HC组 ) ,空白组于注药后 6h、LPS组和HC组分别于注药后 2、4、6h抽血检测OFR释放 ,同时比较各组间肺组织病理改变。结果　(1)LPS组大鼠肺病理符合ALI表现。 (2 )OFR释放 3组比较有差异显著意义 (P <0 0 1) ,LPS组较空白组明显增强 (P <0 0 5 ) ,并在观察时间内 (2～ 6h)不断升高。HC组在各时点较LPS组均明显降低(P <0 0 5 ) ,在 4h抑制作用最明显 ,达 98 2 %。 (3)肺病理半定量评分 ,3组间差异有显著意义 (P <0 0 1)。与空白组相比 ,LPS组与HC组评分均显著升高 (P <0 0 5 )。而与LPS组相比 ,HC组病理评分显著降低 (P <0 0 5 )。结论　在LPS诱导ALI大鼠模型中 ,OFR大量释放在ALI发病中起了重要作用 ,6mg/kgHC可使肺损伤改善 ,同时对OFR释放可产生明显、持续的抑制 ,提示HC对ALI起保护作用 ,机制可能是通过抑制PMN释放OFR而实现

Effects of hydrocortisone on oxygen free radicals released by polymorphonuclear neutrophils in lipopolysaccharide-induced acute lung injury in mice

BACKGROUND: Corticosteroid treatment of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) has been one of the most controversial clinical issues in critical care. Although the administration of high-dose corticosteroids does not benefit patients with early septic shock and ARDS, recent clinical trials have indicated that treatment with relatively low-dose corticosteroids (2 to 3 mg/kg/day of methylprednisolone or equivalent) may improve outcome when used for late ARDS or persistent septic shock. The underlying mechanism was not fully clarified. Whether the administration of corticosteroids can arrest neutrophil-driven organ injury once started remains to be elucidated. OBJECTIVE: To observe the effects of hydrocortisone (HC, 6 mg/kg) on oxygen free radicals (OFR) released by PMN and pulmonary pathological changes in rat ALI model induced by lipopolysaccharide (LPS), to investigate the possible mechanism through which corticosteroids exert protective effect on ALI. METHODS: A rat model of ALI was induced by peritoneal injection of 2 x 10(12) Escherichia coli/kg. Fifty-six rats were randomly divided into three groups: normal control group, LPS group and HC group (6 mg/kg). Samples were collected 2 h, 4 h and 6 h after giving LPS to LPS and HC group (6 h after giving normal saline in normal control group) to measure the level of OFR released by PMN using chemiluminescence method based on lumino, and to compae of pulmonary pathological changes among the three groups. RESULTS: Pathological examination with light microscope in LPS group showed thickened pulmonary interstitia, inflammatory cell infiltration, edema and hemorrhage, which were in accordance with the features of ALI. There were significant differences in the release of OFR by PMN among the three groups (P < 0.01). The level of OFR released by PMN in LPS group was significantly higher than that of the control group, and continued to increase during the observation period (2 - 6 h after LPS). The release of OFR by PMN in HC group was significantly suppressed as compared with LPS group, which was peaked at 4 h after LPS injection (to 98.2%); there were also significant differences in the grades of ALI pathologic changes among the three groups (P < 0.01). The grades of ALI pathologic changes in LPS group were significantly increased when compared with the normal control group (P < 0.05) while significantly decreased in HC group as compared with LPS group (P < 0.05). CONCLUSION: It was demonstrated in the LPS induced ALI model that OFR might play an important role in onset of ALI. Intervening with HC (6 mg/kg) treatment could ameliorate the lung injury and exert significant and sustained suppression on the release of OFR by PMN, showing that HC has a protective effect on LPS induced ALI and its theraputic effect occurs possibly through suppression on the release of OFR by PMN.