The harmful effect of prolonged high-dose methylprednisolone in acute lung injury.

Although many literatures have shown that prolonged high-dose administration of corticosteroids is hazardous and not indicated to therapy acute lung injury (ALI), there is little information on the harmful effect of prolonged high-dose corticosteroids in acute lung injury. In this study, we aimed to investigate the effect of prolonged high-dose methylprednisolone (MPL) on ALI and improve knowledge regarding the appropriate use of corticosteroids in ALI. The different doses of MPL (3, 30, 180mg·kg(-1)) were given via tail vein injection 1h after the first time LPS administration and were daily administrated for 14days. Lung tissues and lavage samples were isolated for biochemical determinations and histological measurements at 12h, 7days and 14days after LPS administration. Single administration of 180mg·kg(-1) MPL decreased the lung injury score, wet-to-dry ratio, the total cell numbers and level of procollagen type III in BALF at 12h after LPS challenge. However, prolonged therapy with 180mg·kg (-1) MPL for 7days and 14days decreased the number of AMs in BALF and increased the above-mentioned indexes. These results suggested that the prolonged high-dose MPL has harmful effects to treat LPS-induced ALI in rats.