Pine bark extract (Pycnogenol^®) suppresses cigarette smoke-induced fibrotic response via transforming growth factor-β1/Smad family member 2/3 signaling

Chronic obstructive pulmonary diseases (COPD) is an important disease featured as intense inflammation, protease imbalance, and air flow limitation and mainly induced by cigarette smoke (CS). In present study, we explored the effects of $Pycnogenol^{(R)}$ (PYC, pine bark extract) on pulmonary fibrosis caused by CS+lipopolysaccharide (LPS) exposure. Mice were treated with LPS intranasally on day 12 and 26, followed by CS exposure for 1 h/day (8 cigarettes per day) for 4 weeks. One hour before CS exposure, 10 and 20 mg/kg of PYC were administered by oral gavage for 4 weeks. PYC effectively reduced the number of inflammatory cells and proinflammatory mediators caused by CS+LPS exposure in bronchoalveolar lavage fluid. PYC inhibited the collagen deposition on lung tissue caused by CS+LPS exposure, as evidenced by Masson's trichrome stain. Furthermore, transforming growth $factor-{\beta}1$ ($TGF-{\beta}1$) expression and Smad family member 2/3 (Smad 2/3) phosphorylation were effectively suppressed by PYC treatment. PYC markedly reduced the collagen deposition caused by CS+LPS exposure, which was closely involved in $TGF-{\beta}1$/Smad 2/3 signaling, which is associated with pulmonary fibrotic change. These findings suggest that treatment with PYC could be a therapeutic strategy for controlling COPD progression.