Impaired Ca2+-handling in HIF-1 alpha(+/-) mice as a consequence of pressure overload

The hypoxia-inducible factor (HIF)-1 is critically involved in the cellular adaptation to a decrease in oxygen availability. The influence of HIF-1 alpha for the development of cardiac hypertrophy and cardiac function that occurs in response to sustained pressure overload has been mainly attributed to a challenged cardiac angiogenesis and cardiac hypertrophy up to now. Hif-1 alpha (+/+) and Hif-1 alpha (+/-) mice were studied regarding left ventricular hypertrophy and cardiac function after being subjected to transverse aortic constriction (TAC). After TAC, both Hif-1 alpha (+/+) and Hif-1 alpha (+/-) mice developed left ventricular hypertrophy with increased posterior wall thickness, septum thickness and increased left ventricular weight to a similar extent. No significant difference in cardiac vessel density was observed between Hif-1 alpha (+/+) and Hif-1 alpha (+/-) mice. However, only the Hif-1 alpha (+/-) mice developed severe heart failure as revealed by a significantly reduced fractional shortening mostly due to increased end-systolic left ventricular diameter. On the single cell level this correlated with reduced myocyte shortenings, decreased intracellular Ca2+-transients and SR-Ca2+ content in myocytes of Hif-1a (+/-) mice. Thus, HIF-1 alpha can be critically involved in the preservation of cardiac function after chronic pressure overload without affecting cardiac hypertrophy. This effect is mediated via HIF-dependent modulation of cardiac calcium handling and contractility.