Triptolide attenuates pulmonary fibrosis by inhibiting fibrotic extracellular matrix remodeling mediated by MMPs/LOX/integrin

Abstract

Background: Fibrotic extracellular matrix (ECM) remodeling characterized different types of pulmonary fibrosis, and its regulation could be a potential shared treatment strategy for pulmonary fibrosis. Purpose: We aimed to investigate the effect of triptolide on pulmonary fibrosis through the inhibition of several important aspects of fibrotic ECM remodeling. Methods: Bleomycin-induced pulmonary fibrosis mice and TGF-β1-induced primary lung fibroblasts were used. The effect of triptolide on pulmonary fibrosis was detected using histopathology, immunostaining, RT-qPCR, western blotting, ELISA, and protein activity assay. Results: Triptolide significantly alleviated bleomycin-induced pulmonary fibrosis in mice. It inhibited the expression of fibrotic genes α-SMA, collagen I, fibronectin, and vimentin and blocked the TGF-β-SMAD signaling pathway both in vivo and in vitro. In addition, triptolide regulated the expression and activity of MMPs during fibrosis. Interestingly, it suppressed the expression of lysyl oxidase, which was responsible for matrix cross-linking and elevated ECM stiffness. Furthermore, triptolide blocked the biomechanical stress transduction pathway integrin-β1-FAK-YAP signaling and attenuated the pro-fibrotic feedback of fibrotic ECM on fibroblasts via integrin inhibition. Conclusion: These findings show that triptolide prevents the key linkages of fibrotic ECM remodeling, including deposition, degradation, cross-linking, and pro-fibrotic feedback and, therefore, has potential therapeutic value for pulmonary fibrosis.

Keywords

• Pulmonary fibrosis
• Fibrotic extracellular matrix remodeling
• Triptolide
• MMPs
• LOX
• Integrin