Suppression of rat Frizzled-2 attenuates hypoxia/reoxygenation-induced Ca2+ accumulation in rat H9c2 cells.

Growing evidence suggests that Ca(2+) overload is one of the major contributors of myocardial ischemia/reperfusion-induced injury. Since Frizzled-2 receptor, a seven transmembrane protein, transduces downstream signaling by specialized binding of Wnt5a to increase intracellular Ca(2+) release, this work aimed to investigate the effect of Frizzled-2 on Ca(2+) accumulation in H9c2 cells, which were subjected to hypoxia/reoxygenation to mimic myocardial ischemia/reperfusion. After exposing H9c2 cells to hypoxia/reoxygenation, we observed higher expression of Frizzled-2 and Wnt5a as compared to control group cells. Hypoxia/reoxygenation-induced intracellular Ca(2+) accumulation approached that of cells transfected with frizzled-2 plasmid. In cells treated with RNAi specifically designed against frizzled-2, intracellular Ca(2+) in both hypoxia/reoxygenation-treated cells and plasmid-treated cells were decreased. Rats that underwent ischemia/reperfusion injury exhibited increased intracellular Ca(2+) with high expression levels of Frizzled-2 and Wnt5a as compared to the sham group. Our data indicates that upon binding to Wnt5a, increased Frizzled-2 expression after hypoxia/reoxygenation treatment activated intracellular calcium release in H9c2 cells. Our findings provide a new perspective in understanding calcium overload in myocardial ischemia/reperfusion.