Antisense-Inhibition of Plasma Membrane Ca2+ Pump Induces Apoptosis in Vascular Smooth Muscle Cells

The effect of antisense oligodeoxynucleotides (ODNs) of plasma membrane Ca²⁺-pumping ATPase (PMCA) on rat aortic vascular smooth muscle cells (VSMCs) in primary culture was examined. More than 80% of the PMCA expressed in cultured VSMCs was the PMCA-1B subtype. Exposed to antisense ODNs against PMCA-1, not only the expression of the PMCA protein but also mRNA of PMCA-1B was diminished in a concentration-dependent manner. Extracellular Na+-independent ⁴⁵Ca²⁺ efflux catalyzed via PMCA was inhibited with antisense ODNs. Both the resting and ionomycin- or ATP-stimulated levels of intracellular Ca²⁺ were increased by antisense ODNs. Furthermore, prolonged treatment with antisense ODNs caused apoptosis in VSMCs. The occurrence of apoptosis was inhibited by FK506, a potent immunosuppressant. These results demonstrate that the PMCA was specifically inhibited by antisense ODNs and suggest that PMCA plays an important role in regulation of intracellular Ca²⁺ concentrations, especially at the resting condition to prevent an occurrence of apoptosis that may be induced through the activation of calcineurin.