Soluble Epoxide Hydrolase Inhibitor Prevents Homocysteine‐induced Cardiac Hypertrophy via Epoxyeicosatrienoic Acid–mediated Inhibition of TRPC3 Channels

Abstract

ObjectivesActivation of soluble epoxide hydrolase (sEH), a key enzyme catalyzing the degradation of epoxyeicosatrienoic acids (EETs), has been implicated in cardiac remodeling. We previously demonstrated the involvement of sEH and transient receptor potential isoform 3 (TRPC3) channels in homocysteine‐induced hypertrophy of cardiac cells. This study investigated the anti‐hypertrophic effect of sEH inhibitor with the aim to reveal the link between sEH/EETs and TRPC3 channels in cardiac hypertrophy associated with hyperhomocysteinemia.Materials and methodsMale Wistar rats on 10‐week standard or 2% (WT/WT) high methionine diet were given drinking water supplemented with or without the specific sEH inhibitor 1‐trifluoromethoxyphenyl‐3‐(1‐propionylpiperidin‐4‐yl) urea (TPPU, 5mg/L). In vitro, H9c2 cells were treated with homocysteine (100 μmol/L) in the presence or absence of TPPU (10 μmol/L) or 11,12‐EET (1 μmol/L). Cardiac remodeling was evaluated by echocardiography and histological analysis. Plasma homocysteine level and EETs content were determined by ELISA. Hypertrophic markers were detected by western blot and qPCR. TRPC3 channel current was recorded by patch clamp in whole‐cell mode.ResultsTPPU lowered the heart to body weight ratio, inhibited expressions of the hypertrophic markers atrial natriuretic factor (ANP) and β‐myosin heavy chain (β‐MHC), and reduced the size of cardiomyocytes in hyperhomocysteinemic rats. TPPU treatment ameliorated ejection fraction (85.50±0.87% vs. 74.18±2.19%, p<0.05) and fraction shortening (50.30±1.32% vs. 42.27±0.68%, p<0.01) of the hyperhomocysteinemic rats. Rats with hyperhomocysteinemia showed reduced levels of EETs and increased expression of TRPC3 channels, which were reversed by TPPU treatment. In vitro, TPPU and 11,12‐EET inhibited H9c2 cell enlargement induced by homocysteine, along with a downregulation of hypertrophic markers and TRPC3 channels. Homocysteine significantly increased TRPC3 channel current (4.74±0.49 vs. 1.76±0.21 pA/pF in control, p<0.001) and the enhancement was inhibited by TPPU (2.44±0.29 pA/pF, p<0.01).ConclusionsInactivation of sEH alleviates homocysteine‐induced cardiac hypertrophy and improves cardiac function. EET‐mediated inhibition of TRPC3 channels contributes to the protective effect of the sEH inhibitor TPPU.