OBJECTIVETo explore the effect of curcumin on TGF-β2 regulated peroxisome proliferater activated receptor y (PPAR-γ)/platelet derived growth factor β (PDGF-β) signaling pathway in lung fibroblasts of mice.

METHODSC57BL/6 mouse lung fibroblasts were in vitro cultured with TGF-β2, curcumin, or TGF-β2 plus curcumin. The cell proliferation was detected by cell growth counting in the blank control group, low, middle, and high dose curcumin groups (5, 25, 50 μmol/L), the TGF-β2 (10 ng/mL) group, TGF-β2 (10 ng/mL) plus curcumin (5, 25, 50 μmol/L) groups. mRNA expressions of PPAR-γ, platelet-derived growth factor receptor β (PDGFR-β), fibroblast growth factor R1 (FGFR1) were detected using reverse transcription PCR. Protein levels of PPAR-γ and collagen-1 were detected using Western blot and ELISA in the blank control group, the TGF-β2 group, the TGF-β2 (10 ng/mL) plus curcumin 50 μmol/L group.

RESULTSCompared with the blank control group, curcumin 50 μmol/L showed the most significant inhibition on cell proliferation at 48 h and 72 h. Compared with the TGF-β2 group, TGF-β2 (10 ng/mL) plus curcumin 50 mol/L also showed the most significant inhibition on cell proliferation at 48 h and 72 h. Compared with the blank control group, mRNA expressions of PPAR-γ and PDGF-β, as well as protein expression of PPAR-γ increased, the collagen-1 expression also increased in the TGF-β2 group (P < 0.05). Compared with the TGF-β2 group, mRNA expressions of PPAR-γ obviously increased in the TGF-β2 (10 ng/mL) plus curcumin 25 μmol/L group and the TGF-β2 (10 ng/mL) plus curcumin 50 μmol/L group, higher than that in the TGF-β2 (10 ng/mL) plus curcumin 5 [μmol/L group (P < 0.05). mRNA expressions of PPAR-γ was higher in the TGF-β2 (10 ng/mL) plus curcumin 50 μmol/L group than in the TGF-β2 (10 ng/mL) plus curcumin 25 μmol/L group (P < 0.05). mRNA expressions of PDGF-β was lower in TGF-β2 (10 ng/mL) plus curcumin groups than in the TGF-β2 group (P < 0.05). Besides, PDGF-β mRNA expressions were lower in the TGF-β2 (10 ng/mL) plus curcumin 50 μmol/L group than in the TGF-β2 (10 ng/mL) plus curcumin 5 μmol/L group and the TGF-β2 (10 ng/mL) plus curcumin 25 μmol/L group (P < 0.05). There was no statistical difference in FGFR1 mRNA expressions between the TGF-β2 group and 3 TGF-β2 plus curcumin groups (P > 0.05). Compared with the TGF-β2 group, PPAR-γ protein expressions increased and collagen-1 protein expressions decreased in the TGF-β2 (10 ng/mL) plus curcumin 50 μLmol/L group (P < 0.05, P < 0.01).

CONCLUSIONSCurcumin not only could inhibit TGF-β2 induced proliferation of lung fibroblasts, but also could inhibit the synthesis of collagens. These might be associated with up-regulating PPAR-γ expressions and down-regulating PDGF-β expressions. Therefore, curcumin might inhibit the occurrence and developing of lung fibrosis through blocking PPAR-γ/PDGF-β signaling pathway.