Objective: To observe the effects of curcumin on pulmonary fibrosis and functions on paraquat (PQ)-challenged rats, and investigate the possible mechanism.
Methods: 108 SPF Wistar rats were divided into three groups according to random number sheet: normal saline (NS) control group, PQ model group and curcumin-treatment group. The rats in each group were subdivided into three subgroups according to different time points (3, 7, 14 days), with 12 rats in each subgroup. PQ-challenged models were reproduced by intragastrical administration of PQ solution 50 mg/kg, and those in NS control group were given the equal volume of NS. After 30 minutes, the rats in curcumin-treatment group were given 200 mg/kg of curcumin by intraperitoneal injection, and those in NS control group and PQ model group were given the equal volume of NS. At 3, 7, 14 days, the tidal volume (VT) was examined, and the blood was drawn from femoral artery for blood gas analysis. Then the rats were sacrificed and the lung tissues were harvested, the hydroxyproline (Hyp) content was measured by alkaline hydrolysis; the expression of transforming growth factor-β1 (TGF-β1) was determined by immuno-histochemistry; the distribution and the change of the pulmonary collagen fiber were observed after Masson staining.
Results: After exposure to PQ, the VT and arterial partial pressure of oxygen (PaO2) were decreased gradually, and the levels of Hyp and TGF-β1 were increased gradually, reaching the trough or the peak at 14 days, which were significantly lower or higher than those in NS control group [14-day VT (mL): 1.52±0.33 vs. 2.81±0.47, 14-day PaO2 (kPa): 5.87±0.95 vs. 14.15±1.02, 14-day Hyp (μg/mg): 3.12±0.06 vs. 1.14±0.05, 14-day TGF-β1 (integral A value): 29.72±4.27 vs. 4.15±0.52, all P < 0.01]. After intervene of curcumin, the parameters were significantly improved as compared with those of PQ model group [14-day VT (mL): 2.34±0.19 vs. 1.52±0.33, 14-day PaO2 (kPa): 10.23±1.01 vs. 5.87±0.95, 14-day Hyp (μg/mg): 2.31±0.04 vs. 3.12±0.06, 14-day TGF-β1 (integral A value): 15.46±2.89 vs. 29.72±4.27, all P < 0.01]. It was shown by Masson staining that in PQ model group, with the PQ-poisoned time prolonging, diffused pulmonary fibrosis and a large number of collagen deposition were observed gradually, and the most serious collagen deposition was observed at 14 days; after intervene of curcumin, pulmonary fibrosis was alleviated significantly at different time points as compared with the PQ model group.
Conclusions: Curcumin can enhance the pulmonary function by reducing the deposition of collagen fiber and inhabiting pulmonary fibrosis of PQ-poisoned rats.