OBJECTIVETo study the effects of curcumin on the expressions of collagen type I protein and transforming growth factor-beta1 mRNA in lung tissues of rats with pulmonary fibrosis.

METHODS96 male SD rats were randomly divided into four groups with 24 rats in each group: the normal control group, the model group, the prednisone treated group, and the curcumin treated group. Pulmonary fibrosis was induced by intra-bronchial injection of bleomycin A5. From the 15(th) day after bleomycin administration, rats in the prednisone treated group and the curcumin treated group were given prednisone (5 mg/kg) or curcumin (300 mg/kg) respectively once daily by intragastric administration. In the same way, rats in the normal control group and the model group were given 1% Sodium Carboxymethyl Cellulose (10 ml/kg) once daily. The histological changes of lung tissue were evaluated by Haematoxylin-eosin (HE) and Masson's trichrome. The rats were randomly sacrificed on the 21(st), 28(th), 42(nd) and 56(th) day after bleomycin administration. The type I collagen expression was analyzed by immunohistochemistry. The transforming growth factor-beta(1) (TGF-beta(1)) mRNA expression of lung was detected by the semi-quantitative reverse transcription polymerase chain reaction (RT-PCR).

RESULTSPulmonary fibrosis in the curcumin treated group was significantly reduced as compared with the model group and the prednisone treated group on the 42(nd) and 56(th) day (P < 0.05). The expression of type I collagen protein in the curcumin treated group was significantly decreased than that in the model group and the prednisone treated group on the 28(th), 42(nd) and 56(th) day after bleomycin administration (P < 0.05). The TGF-beta(1) mRNA expression in the curcumin treated group was 0.61 +/- 0.09 and 0.48 +/- 0.16 respectively on the 21(st) and 28(th) day after bleomycin administration (P < 0.05). It was significantly decreased than that in the model group on the 21(st), 28(th) day after bleomycin administration and lower as compared with the prednisone treated group on the 21(st) day (P < 0.05).

CONCLUSIONCurcumin could suppress BLM-induced pulmonary fibrosis in rats at the fibrosing stage, with the possible mechanism of inhibiting the synthesis and deposition of type I collagen protein and depressing the overexpression of TGF-beta(1) mRNA. The therapeutic effect of curcumin on pulmonary fibrosis is better than prednisone.