Thromboxane A₂ analog U46619 promotes vascular smooth muscle cell apoptosis via Hippo pathway inhibition and its clinical relevance in aortic dissection

Abstract

Apoptosis of human vascular smooth muscle cells (HAVSMCs) plays a pivotal role in the pathogenesis of aortic dissection (AD). In this study, we first observed in clinical samples that, compared with age- and sex-matched controls, patients with acute Stanford type A AD exhibited significantly elevated serum levels of thromboxane A₂ (TXA₂) stable metabolite thromboxane B₂ (TXB₂), accompanied by markedly reduced phosphorylation of Yes-associated protein (YAP) in aortic tissues. Notably, these two parameters showed a significant inverse correlation. In vivo, administration of the TXA₂ analog U46619 significantly reduced YAP phosphorylation in murine aortic tissues. In vitro, U46619 markedly increased the expression of pro-apoptotic proteins Bax and cleaved caspase-3 while decreasing the expression of the anti-apoptotic protein Bcl-2, thereby promoting HAVSMC apoptosis. Mechanistically, U46619 suppressed phosphorylation of YAP at Ser127, facilitating its nuclear translocation. Co-immunoprecipitation (Co-IP) assays demonstrated that nuclear YAP interacts specifically with the transcription factor p73 following U46619 stimulation. Furthermore, chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays confirmed that U46619 enhances p73 binding to the Bax promoter, thereby upregulating Bax transcription and protein expression, ultimately triggering HAVSMC apoptosis. Bioinformatic analysis of the public GSE52093 dataset further validated the upregulation of the TXA₂ receptor coding gene TBXA2R in AD aortic tissues and its expression correlation with core Hippo and apoptosis pathway genes. Collectively, our findings demonstrate a significant association between elevated serum TXB₂ and reduced YAP phosphorylation in aortic tissues. Both gain- and loss-of-function experiments further establish that TXA₂ signaling promotes HAVSMC apoptosis by inhibiting the Hippo–YAP pathway, enhancing YAP nuclear translocation and formation of a YAP–p73 transcriptional complex, thereby activating Bax transcription. These results suggest that the TXA₂–TP axis may contribute to AD pathogenesis via regulation of the Hippo–YAP–p73 signaling cascade, providing novel mechanistic insight and a potential therapeutic target for this lethal disease.