Epoxyeicosatrienoic acid prevents maladaptive remodeling in pressure overload by targeting calcineurin/NFAT and Smad-7

Background: Emerging evidence demonstrates that epoxyeicosatrienoic acids (EETs) as important active eicosanoids that regulate cardiovascular homeostasis, but the mechanisms underlying its favorable anti-hypertrophic benefits in overpressure model remain obscure. Methods and results: Four weeks after transverse aortic constriction (TAC), TAC mice developed maladaptive cardiac hypertrophy and consequent cardiac failure. Conversely, a cardiotropic adeno-associated viral vector (AAV9) encoding CYP2J2 prevented transverse aortic constriction–induced cardiac hypertrophy with preserved ejection fraction. EET also conferred protection against phenylephrine-induced hypertrophy in H9c2 cardiomyoblasts. Further investigations indicate CYP2J2/EET exerts protection against cardiac hypertrophy through opposing the increase of intracellular Ca2+ level and Ca2+-mediated calcineurin/NFATc3 signaling. Meanwhile, extended myocardial fibrosis in TAC mice was also effectively abolished with the administration of AAV9-2J2. Intriguingly, TAC mice display activated TGF-β/Samd-3 signaling with decreased Smad-7 expression, whereas AAV9-2J2 attenuated the phosphorylation of Smad-3 without altering TGF-β expression, whilst preservation of Smad-7. Subsequently, the differentiation of cardiac fibroblasts into myofibroblasts in the presence of TGF-β1 stimulation was significantly disrupted with EET treatment, accompanied by declined Smad-3 activation and collagen production, whereas inhibition of Smad-7 with SiRNA Smad-7 substantially abrogated these effects of EET on cardiac fibroblasts. Conclusions: EET has synergistic actions on cardiomyocytes and cardiac fibroblasts, preventing cardiac hypertrophy through inhibition of Ca2+-mediated calcineurin/NFATc3 signaling cascades, and ameliorating myocardial fibrosis dependent on Smad-7. This work further extends the potential mechanisms of EET, providing a novel therapeutic approach for the treatment of pathological remodeling and heart failure.