Background: In myocardial cells, relaxation is governed primarily by the sarcoplasmic reticulum (SR) Ca(2+)-ATPase transporting enzyme, which regulates Ca2+ sequestration into the SR. Human and experimental cardiomyopathies are associated with reduced SR Ca(2+)-ATPase activity.
Methods and results: To modify intracellular calcium mobilization, we created a recombinant adenovirus designed to over-express the cardiac SR Ca(2+)-ATPase (SERCA2a) under the control of the Rous sarcoma virus (RSV). In neonatal rat myocytes, Ad.RSV.SERCA2a increased the expression of SERCA2a in a concentration-dependent and time-dependent fashion. Enhancement of SR Ca(2+)-ATPase activity was even greater than increases in SERCA2a protein content in cells infected with Ad.RSV.SERCA2a for 48 hours at a multiplicity of infection (MOI) from 0.1 to 10.0 pfu/cell. Intracellular calcium transients measured in the neonatal cells infected with Ad.RSV.SERCA2a were characterized by an abbreviation of the relaxation phase, an increase in peak [Ca2+]i release, and a decrease in resting [Ca2+]i levels. Ad.RSV.SERCA2a also enhanced the contraction of the myocardial cells as detected by shortening measurements.
Conclusions: We found that adenovirus-mediated gene transfer of SR Ca(2+)-ATPase can modify intracellular calcium handling and shortening in myocardial cells. Such vectors should be useful in examining the role of reduced SERCA2a activity in the pathophysiology of heart failure and in developing strategies for gene therapy.