Autophagy inhibition attenuates TGF-β2-induced epithelial-mesenchymal transition in lens epithelial cells

Aims: Autophagy has been reported to play an essential role in fibrotic disorders. Known as fibrotic cataract, posterior capsular opacification (PCO) result from pathological epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs). This study aims to identify the role and potential mechanism of autophagy in TGF-beta 2-induced EMT in LECs. Main methods: Primary rabbit LECs were treated with TGF-beta 2 to induce EMT as a model of fibrotic cataract in vitro. 3-methyladenine, chloroquine, bafilomycin Al, and gene silencing of autophagy-related protein 7 (ATG7) were treated in LECs for autophagy inhibition, while rapamycin was utilized for autophagy activation. The expression levels of EMT/autophagy-associated markers were analyzed by qRT-PCR, western blotting, immunofluorescence and transmission electron microscopy. We additionally examined cell migration ability with transwell migration assay and wound healing assay. Key findings: TGF-beta 2 promoted autophagy flux during EMT progression of LECs in a time-dependent manner. Autophagy activation by rapamycin enhanced TGF-beta 2-triggered fibrogenic responses and cell migration in LECs, whereas pharmacological inhibition of autophagy alleviated TGF-beta 2-induced increases of EMT markers and cell migration of LECs. In addition, the phosphorylation of Smad2/3 induced by TGF-beta 2 was suppressed through autophagy inhibition, while it was promoted upon autophagy activation, indicating that TGF-beta 2/Smad signaling was involved in the modulation of autophagy on EMT in LECs. Furthermore, ATG7-silenced LECs exerted antifibrosis effect induced by TGF-beta 2 through downregulation of autophagy. Significance: Intervention/inhibition of autophagy could attenuate TGF-beta 2-induced EMT in LECs, which provides autophagy-related insights on preventing and treating the fibrotic cataract or other fibrotic diseases.