Taraxerone exerts antipulmonary fibrosis effect through Smad signaling pathway and antioxidant stress response in a Sirtuin1-dependent manner.

ABSTRACT

Idiopathic pulmonary fibrosis treatments are limited, often with severe side effects, highlighting the need for novel options. Taraxerone has diverse biomedical properties, but its mechanism remains unclear. This study investigates taraxerone's impact and the mechanisms involved in bleomycin-induced pulmonary fibrosis in mice. After establishing a pulmonary fibrosis mouse model, taraxerone was intraperitoneally injected continuously for 14-28 days. The in vivo antifibrotic and antioxidative stress effects of taraxerone were assessed. In vitro, the influence of taraxerone on transforming growth factor-ß1-induced myofibroblast transformation and oxidative stress was investigated. Subsequently, quantitative polymerase chain reaction screened the histone deacetylase and Sirtuin family, and taraxerone's effects on SIRT1 were assessed. After SIRT1 siRNA treatment, changes in myofibroblast transformation and antioxidant capacity in response to taraxerone were observed. Acetylation and phosphorylation levels of Smad3 were evaluated. We also examined the binding levels of SIRT1 with Pho-Smad3 and Smad3, as well as the nuclear localization of Smad2/3. EX527 confirmed SIRT1's in vivo action in response to taraxerone. In vitro experiments suggested that taraxerone inhibited myofibroblast differentiation by activating SIRT1 and reducing oxidative stress. We also observed a new interaction between SIRT1 and the Smad complex. Taraxerone activates SIRT1, enabling it to bind directly to Smad3. This leads to reduced Smad complex phosphorylation and limited nuclear translocation. As a result, the transcription of fibrotic factors is reduced. In vivo validation confirms taraxerone's SIRT1-mediated antifibrotic effectiveness. This suggests that targeting SIRT1-mediated inhibition of myofibroblast differentiation could be a key strategy in taraxerone-based therapy for pulmonary fibrosis.