Essential role of sympathetic endothelin A receptors for adverse cardiac remodeling

In preclinical studies, endothelin receptor A (ET A ) antagonists (ET A i) attenuated the progression of heart failure (HF). However, clinical HF trials failed to demonstrate beneficial effects of ET A i. These conflicting data may be explained by the possibility that established HF drugs such as adrenergic receptor blockers interfered with the mechanism of ET A i action in clinical trials. Here we report that mice lacking ET A only in sympathetic neurons (SN-KO) showed less adverse structural remodeling and cardiac dysfunction in response to pathological pressure overload induced by transverse aortic constriction (TAC). In contrast, mice lacking ET A only in cardiomyocytes (CM-KO) were not protected. TAC led to a disturbed sympathetic nerve function as measured by cardiac norepinephrine (NE) tissue levels and [ 124 I]-metaiodobenzylguanidine-PET, which was prevented in SN-KO. In a rat model of HF, ET A i improved cardiac and sympathetic nerve function. In cocultures of cardiomyocytes (CMs) and sympathetic neurons (SNs), endothelin-1 (ET1) led to a massive NE release and exaggerated CM hypertrophy compared with CM monocultures. ET A -deficient CMs gained a hypertrophic response through wild-type SNs, but ET A -deficient SNs failed to mediate exaggerated CM hypertrophy. Furthermore, ET1 mediated its effects indirectly via NE in CM-SN cocultures through adrenergic receptors and histone deacetylases, resulting in activation of the prohypertrophic transcription factor myocyte enhancer factor 2. In conclusion, sympathetic ET A amplifies ET1 effects on CMs through adrenergic signaling pathways. Thus, antiadrenergic therapies may blunt potentially beneficial effects of ET A i. Taken together, this may indicate that patients with β blocker intolerance or disturbed sympathetic nerve function could be evaluated for a potential benefit from ET A i.