[Therapeutic effects of different doses of methylprednisolone on smoke inhalation-induced acute lung injury in rats].

OBJECTIVE: To investigate the therapeutic effect of different doses of methylprednisolone (MP) in smoke inhalation-induced acute lung injury (SI-ALI). METHODS: Adult male Sprague-Dawley (SD) rats were divided into control group (group A, n = 6), smoke inhalation group (group B, smoke inhalation 30 minutes, n = 30) and smoke + MP 40, 4, 0.4 mg/kg intervention group (groups C, D, E; intraperitoneal injection of MP at 1 hour before smoke inhalation, n = 30) according to random number table method. The survival status of rats in each group was observed at 24 hours, and murine smoke inhalation induced trauma score (MSITS) according to the symptoms and signs of rats at 3 hours after smoke inhalation were scored. The blood of abdominal aorta of rats was collected. Then the rats were sacrificed to harvest bronchoalveolar lavage fluid (BALF) and lung tissue. The levels of interleukin (IL-6, IL-17a) in plasma and BALF were detected by enzyme linked immunosorbent assay (ELISA); the total number of white blood cells and the proportion of leukocytes or macrophages in BALF were calculated; the histopathological changes of lung were observed and the lung injury score was given; the expression of myeloperoxidase (MPO) and high mobility group protein B1 (HMGB1) in lung tissue were detected by Western Blot. RESULTS: /L): 5.40±1.67, 2.81±1.20 vs. 9.02±2.06; neutrophil ratio: 0.315±0.081, 0.273±0.080 vs. 0.590±0.096; IL-17a (ng/L): 22.63±8.62, 18.92±8.43 vs. 43.31±19.17; IL-6 (ng/L): 156.49±46.94, 123.66±64.91 vs. 253.43±80.03; all P < 0.01]; in addition, the expression of MPO and HMGB1 protein in lung tissues of MP groups with different doses were significantly decreased, the expression of MPO in group D was significantly lower than that in group E [MPO/β-actin (fold increase from group A): 2.14±0.97 vs. 4.35±0.87, P < 0.01], the expression of HMGB1 in groups C and D were significantly lower than that in group E [HMGB1/β-actin (fold increase from group A): 1.77±0.73, 1.23±0.67 vs. 3.65±1.08, both P < 0.05]. CONCLUSIONS: MP can significantly improve the survival rate of SI-ALI rats and reduce the acute pulmonary and systemic inflammatory response. The MP effect of 4 mg/kg was better than 40 mg/kg and 0.4 mg/kg.