Targeted Expression of Receptor-Associated Late Transducer Inhibits Maladaptive Hypertrophy via Blocking Epidermal Growth Factor Receptor Signaling

Receptor-associated late transducer (RALT) is a feedback inhibitor of epidermal growth factor receptor signaling. RALT has been shown previously to be induced in the ischemic heart and to promote cardiomyocyte apoptosis in vitro. However, the role of RALT in cardiac hypertrophy remains unclear. We hypothesized that forced expression of RALT in the murine heart would protect the heart against cardiac hypertrophy in vivo. We investigated the effect of cardiac overexpression of rat RALT on cardiac hypertrophy induced by angiotensin II and isoproterenol in RALT transgenic mice and wild-type littermates. The extent of cardiac hypertrophy was assessed by 2D and M-mode echocardiography as well as by molecular and pathological analyses of cardiac samples. Constitutive expression of rat RALT in cardiac myocytes of murine heart attenuated both hypertrophic and inflammatory responses and preserved cardiac function. These beneficial effects were associated with the attenuation of the epidermal growth factor receptor-dependent cascade that was triggered by angiotensin II and isoproterenol stimulation. Additional evidence demonstrated that RALT expression blocked fibrosis in vivo and collagen synthesis in vitro. Therefore, cardiac overexpression of RALT improves cardiac function and inhibits maladaptive hypertrophy, inflammation, and fibrosis through attenuating epidermal growth factor receptor-dependent signaling. (Hypertension. 2009;53:539-548.)