Magnolol alleviates pulmonary fibrosis inchronic obstructive pulmonary disease by targeting transient receptor potential vanilloid 4-ankyrin repeat domain.

Transient receptor potential vanilloid 4 (TRPV4) plays a role in regulating pulmonary fibrosis (PF). While several TRPV4 antagonists including magnolol (MAG), have been discovered, the mechanism of action is not fully understood. This study aimed to investigate the effect of MAG on alleviating fibrosis in chronic obstructive pulmonary disease (COPD) based on TRPV4, and to further analyze its mechanism of action on TRPV4. COPD was induced using cigarette smoke and LPS. The therapeutic effect of MAG on COPD-induced fibrosis was evaluated. TRPV4 was identified as the main target protein of MAG using target protein capture with MAG probe and drug affinity response target stability assay. The binding sites of MAG at TRPV4 were analyzed using molecular docking and small molecule interaction with TRPV4-ankyrin repeat domain (ARD). The effects of MAG on TRPV4 membrane distribution and channel activity were analyzed by co-immunoprecipitation, fluorescence co-localization, and living cell assay of calcium levels. By targeting TRPV4-ARD, MAG disrupted the binding between phosphatidylinositol 3 kinase γ and TRPV4, leading to hampered membrane distribution on fibroblasts. Additionally, MAG competitively impaired ATP binding to TRPV4-ARD, inhibiting TRPV4 channel opening activity. MAG effectively blocked the fibrotic process caused by mechanical or inflammatory signals, thus alleviating PF in COPD. Targeting TRPV4-ARD presents a novel treatment strategy for PF in COPD.

Ligustilide attenuates airway remodeling in COPD mice by covalently binding to MH2 domain of Smad3 in pulmonary epithelium, disrupting the Smad3-SARA interaction.

Airway remodeling is one of the hallmarks of chronic obstructive pulmonary disease (COPD) and is closely related to the dysregulation of epithelial-mesenchymal transition (EMT). Smad3, an important transcriptional regulator responsible for transducing TGF-ß1 signals, is a promising target for EMT modulation. We found that ligustilide (Lig), a novel Smad3 covalent inhibitor, effectively inhibited airway remodeling in cigarette smoke (CS) combined with lipopolysaccharide (LPS)-induced COPD mice. Oral administration of an alkynyl-modified Lig probe was used to capture and trace target proteins in mouse lung tissue, revealing Smad3 in airway epithelium as a key target of Lig. Protein mass spectrometry and Smad3 mutation analysis via in-gel imaging indicated that the epoxidized metabolite of Lig covalently binds to the MH2 domain of Smad3 at Cys331/337. This irreversible bonding destroys the interaction of Smad3-SARA, prevents Smad3 phosphorylation activation, and subsequently suppresses the nuclear transfer of p-Smad3, the EMT process, and collagen deposition in TGF-ß1-stimulated BEAS-2B cells and COPD mice. These findings provide experimental support that Lig attenuates COPD by repressing airway remodeling which is attributed to its suppression on the activation of EMT process in the airway epithelium via targeting Smad3 and inhibiting the recruitment of the Smad3-SARA heterodimer in the TGF-ß1/Smad3 pathway.