Triptolide attenuates cardiac remodeling by inhibiting pyroptosis and EndMT via modulating USP14/Keap1/Nrf2 pathway

Background: Cardiac remodeling is a common pathological feature in many cardiac diseases, characterized by cardiac hypertrophy and fibrosis. Triptolide (TP) is a natural compound derived from Tripterygium wilfordii Hook F. However, the related mechanism of it in cardiac remodeling has not been fully understood. Methods and results: Transverse aortic constriction (TAC)-induced cardiac hypertrophic mouse model and angiotensin II (Ang II) -induced cardiomyocytes hypertrophic model were performed. Firstly, the results indicate that TP can improve cardiac function, decreased cardiomyocyte surface area and fibrosis area, as well as lowered the protein expressions of brain natriuretic peptide (BNP), 8 -major histocompatibility complex (8-MHC), type I and III collagen (Col I and III). Secondly, TP suppressed cardiac pyroptosis, and decreased the levels of Interleukin-18 (IL -18), Interleukin-18 (IL -18) by Enzyme -linked immunosorbent assay (ELISA), and pyroptosisassociated proteins. Furthermore, TP enhanced the expressions of Nuclear factor erythroid 2related factor 2 (Nrf2) and Heme oxygenase 1 (HO -1). Interestingly, when Nrf2 was silenced by siRNA, TP lost its properties of reducing pyroptosis and cardiac hypertrophy. In addition, in the Transforming Growth Factor 81 (TGF-81)-induced primary human coronary artery endothelial cells (HCAEC) model, TP was found to inhibit the process of endothelial-to-mesenchymal transition (EndMT), characterized by the loss of endothelial -specific markers and the gain of mesenchymal markers. This was accompanied by a suppression of Slug, Snail, and Twist expression. Meanwhile, the inhibitory effect of TP on EndMT was weakened when Nrf2 was silenced by siRNA. Lastly, potential targets of TP were identified through network pharmacology analysis, and found that Ubiquitin-Specific Protease 14 (USP14) was one of them. Simultaneously, the data indicated that decrease the upregulation of USP14 and Kelch-like ECH-Associated Protein 1 (Keap1) caused by cardiac remodeling. However, Keap1 was decreased and Nrf2 was increased when USP14 was silenced. Furthermore, CoIP analysis showed that USP14 directly interacts with Keap1. Conclusion: TP can observably reduce pyroptosis and EndMT by targeting the USP14/Keap1/Nrf2 pathway, thereby significantly attenuating cardiac remodeling.