FBXW7 ameliorates pulmonary arterial hypertension via reducing SPI1-mediated transcriptional activation of MFAP4

Abstract Background This study aimed to investigate the role of the FBXW7/SPI1/MFAP4 axis in pulmonary arterial hypertension (PAH). Methods An in vivo PAH model was constructed using a hypoxia chamber. The expression levels of FBXW7, SPI1 and MFAP4 were detected by immunofluorescence and Western blotting. Cardiopulmonary function was assessed; pathological changes in lung tissue were examined by HE staining, and inflammatory factors levels were measured using ELISA. For in vitro studies, a PAH model was simulated using hypoxia-induced pulmonary arterial smooth muscle cells (PASMCs). MFAP4-stable knockdown cells were constructed. Cell proliferation was evaluated with CCK8 and EdU assays, and cell migration was assessed using scratch wound and transwell assays. The targeting relationship between SPI1 and MFAP4 was verified by dual-luciferase reporter and ChIP-qPCR assays. Further, co-immunoprecipitation (Co-IP) and protein stability experiments were performed to confirm FBXW7-mediated ubiquitination of SPI1. Results In vivo, MFAP4 knockdown led to decreases in right ventricular systolic pressure (RVSP), mean pulmonary arterial pressure (mPAP), right ventricular (RV) contraction index, and pulmonary arterial (PA) wall thickness. In vitro, MFAP4 knockdown suppressed PASMC proliferation and migration. SPI1 was identified as an upstream transcription factor of MFAP4. FBXW7 was shown to promote SPI1 ubiquitination and its degradation in vitro. Overexpression of FBXW7 suppressed PAH progression both in vitro and in vivo, while simultaneous overexpression of either SPI1 or MFAP4 counteracted the protective effects of FBXW7 overexpression. Conclusion Decreased FBXW7 expression in PAH inhibits SPI1 ubiquitination and protein degradation, leading to increased MFAP4 levels, which ultimately promotes PAH progression.