The search for new approaches to treatment and prevention of
heart failure is a major challenge in medicine. The
adenosine triphosphate-sensitive
potassium (
KATP) channel has been long associated with the ability to preserve myocardial function and viability under stress. High surface expression of membrane
KATP channels ensures a rapid energy-sparing reduction in action potential duration (APD) in response to metabolic challenges, while cellular signaling that reduces surface
KATP channel expression blunts APD shortening, thus sacrificing energetic efficiency in exchange for greater cellular
calcium entry and increased contractile force. In healthy hearts,
calcium/calmodulin-dependent protein kinase II (
CaMKII) phosphorylates the Kir6.2
KATP channel subunit initiating a cascade responsible for
KATP channel endocytosis. Here, activation of
CaMKII in a transaortic banding (TAB) model of
heart failure is coupled with a 35-40% reduction in surface expression of
KATP channels compared to hearts from
sham-operated mice. Linkage between
KATP channel expression and
CaMKII is verified in isolated cardiomyocytes in which activation of
CaMKII results in downregulation of
KATP channel current. Accordingly, shortening of monophasic APD is slowed in response to
hypoxia or heart rate acceleration in failing compared to non-failing hearts, a phenomenon previously shown to result in significant increases in oxygen consumption. Even in the absence of
coronary artery disease, failing myocardium can be further injured by
ischemia due to a mismatch between metabolic supply and demand.
Ischemia-reperfusion injury, following ischemic preconditioning, is diminished in hearts with
CaMKII inhibition compared to wild-type hearts and this advantage is largely eliminated when myocardial
KATP channel expression is absent, supporting that the myocardial protective benefit of
CaMKII inhibition in
heart failure may be substantially mediated by
KATP channels. Recognition of
CaMKII-dependent downregulation of
KATP channel expression as a mechanism for vulnerability to injury in failing hearts points to strategies targeting this interaction for potential preventives or treatments.