Modulation of early [Ca2+]i rise in metabolically inhibited endothelial cells by xestospongin C.

Abstract

When energy metabolism is disrupted, endothelial cells lose Ca(2+) from endoplasmic reticulum (ER) and the cytosolic Ca(2+) concentration ([Ca(2+)](i)) increases. The importance of glycolytic energy production and the mechanism of Ca(2+) loss from the ER were analyzed. Endothelial cells from porcine aorta in culture and in situ were used as models. 2-Deoxy-D-glucose (2-DG, 10 mM), an inhibitor of glycolysis, caused an increase in [Ca(2+)](i) (measured with fura 2) within 1 min when total cellular ATP contents were not yet affected. Stimulation of oxidative energy production with pyruvate (5 mM) did not attenuate this 2-DG-induced rise of [Ca(2+)](i), while this maneuver preserved cellular ATP contents. The inhibitor of ER-Ca(2+)-ATPase, thapsigargin (10 nM), augmented the 2-DG-induced rise of [Ca(2+)](i). Xestospongin C (3 microM), an inhibitor of D-myo-inositol 3-phosphate [Ins(3)P]-sensitive ER-Ca(2+) release, abolished the rise. The results demonstrate that the ER of endothelial cells is very sensitive to glycolytic metabolic inhibition. When this occurs, the ER Ca(2+) store is discharged by opening of the Ins(3)P-sensitive release channel. Xestospongin C can effectively suppress the early [Ca(2+)](i) rise in metabolically inhibited endothelial cells.