The Inefficiency of Low-concentration Curcumin Intervention in Ameliorating Chronic-stage Pulmonary Fibrosis

Curcumin, a polyphenol compound, is reported to exhibit ameliorative effects in acute lung injury and different organ fibrosis models. We have previously demonstrated that curcumin, at a dose of 75 mg/kg, could modulate inflammatory mediators and fibrinolytic system proteins in the inflammatory stage as well as fibroproliferative stage in a mouse model of bleomycin (BLM) induced pulmonary fibrosis. In this study, we investigated the efficacy of the same dose of curcumin in resolving the established fibrotic stage in a mouse model of BLM-induced pulmonary fibrosis. We prepared the fibrosis model by intranasal administration of BLM (2 mg/kg). Curcumin intervention was performed by intraperitoneal injection on 16th to 20th days post BLM exposure. The control group was administered with normal saline. The mice were sacrificed on the 21st day post BLM exposure. Histological analysis of the lung tissue samples indicated that curcumin (75 mg/kg) could not reverse the fibrotic features induced by BLM. We also performed RT-PCR and western blot to examine the molecular changes induced by BLM and curcumin. It was observed that curcumin could neither reduce the expressions of fibrotic markers nor restore the normal expressions of proteins in the fibrinolytic system. Our data suggest that a low dose of curcumin is not effective in ameliorating the fibrotic stage of BLM-induced pulmonary fibrosis. An increased dose or a formulation that increases the bioavailability of curcumin could probably exhibit promising effects against pulmonary fibrosis in the future.