FTO regulates the proliferation and apoptosis of pulmonary artery smooth muscle cells through m6A demethylation modification.

Background: To investigate whether FTO-mediated N6-methyladenosine (m6A) demethylation affects the proliferative/apoptotic phenotype of mouse pulmonary artery smooth muscle cells (PASMCs).

Methods: The hypoxia model of PASMCs was established to examine changes in FTO protein expression and m6A modification levels. Cell transfection, m6A expression profiling, mRNA stability testing, and protein-RNA binding assays were used to explore the effects of FTO and its downstream target, CACNA1d, on PASMC proliferation and apoptosis.

Results: Hypoxia downregulated FTO expression and upregulated m6A modification, leading to enhanced proliferation and reduced apoptosis in PASMCs. Overexpression of FTO reversed these effects, while FTO knockdown under normoxia mimicked the hypoxia-induced "pro-proliferative and anti-apoptotic" changes. Genome-wide m6A profiling identified CACNA1d as a potential downstream target of FTO, with YTHDC1 acting as the m6A reader. FTO binds CACNA1d mRNA and reduces its stability via m6A demethylation. CACNA1d knockdown partially mitigated the hypoxia-induced changes in PASMC proliferation and apoptosis. In addition, when the hypoxic culture was returned to normoxic culture, the level of apoptosis in PASMCs was restored to the pre-hypoxic level, and this was still observed after the overexpression of FTO or knockdown of CACNA1d expression.

Conclusion: FTO downregulation in hypoxic PASMCs increases m6A modification, promoting proliferation and inhibiting apoptosis by enhancing CACNA1d expression.