Galangin 3-methyl ether alleviates mouse hypertrophic cardiomyopathy via targeting HDAC2 and subsequently inactivating the PI3K-AKT signaling pathway

Pathological cardiac hypertrophy is associated with intricate changes that can eventually lead to heart failure. Galangin is a natural flavonoid derived from the rhizome of the galangal plant that has shown protective effects against a variety of cardiomyopathies. Galangin undergoes methylation at the third hydroxyl position to form Galangin 3-methyl ether (G3-ME), thus increasing its lipophilicity, thereby facilitating its cellular entry and regulatory effects. In this study, we investigated the effects of G3-ME on hypertrophic cardiomyopathy (HCM) and the underlying mechanisms. Two established transgenic mouse models of HCM, i.e., Myh6^R404Q and Tnnt2^R109Q mice, were used for in vivo studies. For in vitro experiments, H9c2, a rat cardiomyocyte cell line, along with human embryonic stem cell-derived cardiomyocytes (hESC-CMs), were exposed to angiotensin II (Ang II, 1 μM). We showed that G3-ME (2.5-20 μM) dose-dependently inhibited the expression of pathological cardiac hypertrophy marker genes Nppa and Nppb in Ang II-treated H9c2 cells. G3-ME (5 μM) effectively mitigated the Ang II-induced expansion of H9c2 cells and hESC-CMs. In the two HCM mouse models, administration of G3-ME (20 or 50 mg·kg^-1·d^-1, i.g.) for 4 weeks significantly improved the cardiac hypertrophy phenotype. By conducting RNA sequencing combined with network pharmacology, we identified histone deacetylase 2 (HDAC2) as the direct target of G3-ME in H9c2 cells. We demonstrated that G3-ME inhibited both the phosphorylation of HDAC2 and the PI3K-AKT signaling pathway during the cardiac hypertrophy process in vivo and in vitro. Knockdown of HDAC2 resulted in inhibition of cardiac hypertrophy, whereas its overexpression facilitated cardiac hypertrophy through the PI3K-AKT signaling pathway. In conclusion, G3-ME attenuates pathological cardiac hypertrophy in vivo and in vitro by targeting HDAC2, leading to the inactivation of the PI3K-AKT signaling pathway. G3-ME may serve as a promising option for addressing hypertrophic cardiomyopathy.