Berberine inhibits Smad and non-Smad signaling cascades and enhances autophagy against pulmonary fibrosis.

UNLABELLED: Idiopathic pulmonary fibrosis (IPF) is a fibroproliferative lung disorder of unknown aetiology. Transforming growth factor-β1 (TGF-β1)-mediated Smad and non-Smad signaling cascades are considered as central players in accelerating pulmonary fibrosis. We earlier reported berberine's amelioration against TGF-β1-mediated pro-fibrotic effects in bleomycin-induced pulmonary fibrosis. The present study aimed to determine the regulatory role of berberine on abrogated Smad 2/3 and FAK-dependent PI3K/Akt-mTOR signaling cascades in bleomycin-induced pulmonary fibrosis. Male Wistar rats were subjected to single intratracheal instillation of bleomycin (2.5 U/kg) on day 0, and berberine treatments were provided in either preventive or therapeutic modes, respectively. Berberine mitigated the elevated expression of fibrotic markers, α-smooth muscle actin (α-SMA), fibronectin, collagens I and III and reversed bleomycin-induced ultrastructural alterations in the lungs. Berberine inhibited the bleomycin-induced raise in p-Smad 2/3 and enhanced Smad 7 expression. Berberine blocked the activation of FAK and PI3K/Akt against bleomycin-induced dysregulation, with subsequent raise in PTEN expression. In addition, by inhibiting p-mTOR, berberine stimulated autophagy as evidenced by increase in Beclin-1, LC3-II levels with enhanced autophagosome formation. Cumulatively, through targeted inhibition of dysregulated Smad and FAK-dependent PI3K/Akt-mTOR signaling axis, berberine attenuated the fibrotic insults of bleomycin. KEY MESSAGE: Berberine inhibits Smad 2/3 activation and enhances Smad 7 in bleomycin-induced rat lungs. Bleomycin-induced activation of FAK is inhibited by berberine. Berberine inhibits bleomycin-induced activation of PI3K/Akt cascade. Berberine inhibits mTOR activation to enhance autophagy and suppresses fibrotic markers.