Abstract
To examine the mechanism of steroid resistance in lung fibrosis, cytokines expressed in the lung tissue of mice with bleomycin-iduced lung fibrosis were studied.
1. Glucocorticoid administration (1mg/kg/day) did not affect the grade of lung fibrosis induced by intratracheal injection of bleomycin (3.76μg/g).
2. Cytokines expressed in the lung tissue were studied with the reverse-transcriptase polymerase chain reaction. Levels of promotor cytokines, such as TNFα, TGFβ, INFγ, and IL-2, were significantly higher in lung tissue from the bleomycin group. The expression of these cytokines in the glucocorticoid group was low, especially the peak value. Expression of IL-4 was high in the bleomycin group, and was not inhibited in the glucocorticoid group. Expression of the down-regulator cytokine IL-10 was also high in the bleomycin group and very low in the glucocorticoid group.
3. The non-selectivity of glucocorticoids with respect to promotor and suppressive cytokines may account in part for steroid resistance in bleomycin-induced pulmonary fibrosis.
