FTO/m6A Regulate Prenatal Nicotine-Induced eNOS Uncoupling and BP Susceptibility

BACKGROUND: Prenatal nicotine exposure from maternal smoking or e-cigarette use increases cardiovascular risk in offspring, but the underlying mechanisms remain unclear. We tested whether FTO (fat mass and obesity-associated protein)-mediated N6-methyladenosine RNA demethylation drives eNOS (endothelial nitric oxide [NO] synthase) uncoupling and programmed hypertensive susceptibility following prenatal nicotine exposure. METHODS: Using a clinically relevant rat model of chronic intermittent nicotine aerosol exposure or saline aerosol control during gestational days 4 to 21, experiments were performed in adult offspring and human umbilical vein endothelial cells. RESULTS: Prenatal chronic intermittent nicotine aerosol programmed a male-specific increase in hypertensive susceptibility without altering baseline blood pressure. Adult male offspring exhibited enhanced pressor responses to vasoconstrictor stimuli, impaired endothelium-dependent vasodilation, paradoxical eNOS overexpression, reduced NO bioavailability, increased superoxide and hydrogen peroxide production, impaired eNOS dimerization, and decreased tetrahydrobiopterin levels associated with reduced GTPCH1 (GTP cyclohydrolase-1) expression, consistent with eNOS uncoupling. Mechanistically, prenatal chronic intermittent nicotine aerosol increased vascular FTO expression and induced site-specific N6-methyladenosine hypomethylation of eNOS mRNA. Pharmacological inhibition of FTO with FB23-2 restored eNOS and GTPCH1 expression, improved eNOS dimerization, and normalized NO production in mesenteric arteries. In human umbilical vein endothelial cells, nicotine exposure recapitulated FTO-dependent eNOS uncoupling, which was reversed by FB23-2 or siRNA-mediated FTO knockdown. CONCLUSIONS: Prenatal nicotine exposure disrupts endothelial redox homeostasis through FTO-dependent N6-methyladenosine RNA demethylation, leading to tetrahydrobiopterin deficiency, eNOS uncoupling, and vascular dysfunction in male offspring. The FTO-tetrahydrobiopterin-eNOS pathway represents a novel epitranscriptomic mechanism underlying programmed hypertensive susceptibility and a potential therapeutic target for offspring exposed to nicotine during development.