Adenovirus-mediated gene transfer reconstitutes depressed sarcoplasmic reticulum Ca²⁺-ATPase levels and shortens prolonged cardiac myocyte Ca²⁺ transients

Background: Decreased expression of the sarcoplasmic reticulum (SR) Ca²⁺-ATPase of the cardiac myocyte (SERCA2) and abnormal Ca²⁺ regulation have been independently linked to human heart failure. This study was designed to determine whether expression of a SERCA2 transgene could reconstitute depressed cardiac myocyte SERCA2 levels, augment SR Ca²⁺ uptake, and shorten prolonged excitation-contraction (EC)-associated Ca²⁺ transients in neonatal rat cardiac myocytes (NM). Methods and Results: Cultured NM were treated with phorbol-12-myristate-13-acetate (PMA), a compound that decreases endogenous SERCA2 expression and results in prolongation of EC-assocIated Ca²⁺ transients. PMA-treated NM had a 75% reduction in SERCA2 mRNA and a 40% reduction in SERCA2 protein levels. SERCA2 adenovirus infection increased SERCA2 mRNA expression to 2.5 times control and reconstituted SERCA2 protein levels in PMA-treated cells. This reconstitution was associated with a 32.4% reduction in the time for decline of the Indo-1 Ca²⁺ transient to half-maximum levels (t( 1/4 )) [Ca²⁺](i)) (P<.05). A 34.5% augmentation of oxalate-facilitated SR Ca²⁺ uptake was also documented in SERCA2 adenovirus-infected cells (P<.05). Conclusions: Adenovirus-mediated expression of a SERCA2 transgene can reconstitute depressed endogenous SERCA2 levels, shorten prolonged Ca²⁺ transients, and augment SR Ca²⁺ uptake. It is conceivable that such an approach might be used in vivo to normalize altered Ca²⁺ regulation in human heart failure.