WTAP Promotes the Excessive Proliferation of Airway Smooth Muscle Cells in Asthma by Enhancing AXIN1 Levels Through the Recognition of YTHDF2.

Asthma is a common chronic respiratory disease in children, the incidence rate of which has increased in recent years. Wilms tumour 1-associated protein (WTAP) is an N6-methyladenosine (m6A) methyltransferase. The purpose of this study was to explore the specific mechanism of WTAP in asthma progression, and clarify the intricate interplay between m6A modifications, WTAP, AXIN1, and their collective impact on airway smooth muscle cells (ASMCs) proliferation in asthma. Platelet-derived growth factor-BB (PDGF-BB)-treated ASMCs were used to establish an asthma model in vitro. The cell phenotype was tested using CCK-8, transwell, and wound healing assays. The expression of the Wnt signalling pathway was detected by western blotting. In addition, the relationship between WTAP/YTDHF2 and AXIN1 was assessed by a double luciferase reporter assay. Actinomycin D treatment and RT‒qPCR assays were performed to determine the mRNA stability of AXIN1. We found that WTAP was significantly increased in PDGF-BB-treated ASMCs. Knockdown of WTAP inhibited the excessive cell viability and migration of ASMCs induced by PDGF-BB. Furthermore, WTAP knockdown increased AXIN1 levels and inhibited the Wnt signalling pathway. Furthermore, WTAP knockdown decreased the m6A levels and enhanced the mRNA stability of AXIN1. WTAP overexpression showed the opposite effect. In addition, YTHDF2 was demonstrated to be the reader that recognizes the WTAP-mediated m6A modification of AXIN1. YTHDF2 knockdown enhanced the mRNA stability of AXIN1 and reversed the effect of WTAP overexpression on PDGF-BB-treated ASMCs. WTAP knockdown inhibited the excessive cell viability and migration of ASMCs by enhancing the m6A levels of AXIN1, which was further recognized by YTHDF2. The upregulation of AXIN1 mediated by the WTAP/YTHDF2 axis further inhibited the Wnt signalling pathway. Our study provides a new method for the treatment of asthma. This work not only deepens our understanding of the molecular underpinnings of asthma but also identifies potential therapeutic targets for the development of novel treatments aimed at inhibiting ASMC proliferation and alleviating asthma symptoms.