Angiotensin II and TNF{alpha} as mediators of ATP-dependent potassium channel remodeling in post-infarction heart failure.

Cardiovasc Res. 2009 May 21; Tavares NI, Philip-Couderc P, Baertschi AJ, Lerch R, Montessuit CAIMS: Angiotensin II (Ang II) and tumor necrosis factor alpha (TNFalpha) are involved in the progression from compensated hypertrophy to heart failure. Here we test their role in the remodeling of ATP-dependent potassium channel (K(ATP)) in heart failure, conferring increased metabolic and diazoxide sensitivity. Methods and Results We observed increased expression of both angiotensinogen and TNFalpha in the failing rat myocardium, with a regional gradient matching that of the K(ATP) subunit Kir6.1 expression. Both angiotensinogen and TNFalpha expression correlated positively with Kir6.1 and negatively with Kir6.2 expression across the post-infarction myocardium. To further identify a causal relationship, cardiomyocytes isolated from normal rat hearts were exposed in vitro to Ang II or TNFalpha. We observed increased Kir6.1 and SUR subunit and reduced Kir6.2 subunit mRNA expression in cardiomyocytes cultured with Ang II or TNFalpha, similar to what was observed in failing hearts. In patch-clamp experiments, cardiomyocytes cultured with Ang II or TNFalpha exhibited responsiveness to diazoxide, in terms of both K(ATP) current and action potential shortening. This was not observed in untreated cardiomyocytes, and resembles the diazoxide sensitivity of failing cardiomyocytes that also overexpress Kir6.1. Ang II exerted its effect through induction of TNFalpha expression, because TNFalpha-neutralizing antibody abolished the effect of Ang II, and in failing hearts regional expression of angiotensinogen matched TNFalpha expression. Finally, Ang II and TNFalpha regulated K(ATP) subunit expression, possibly through differential expression of Forkhead box transcription factors. CONCLUSIONS: This study identifies Ang II and TNFalpha as mediators of the remodeling of K(ATP) channels in heart failure.