Oxidized Low-density Lipoprotein- and Lysophosphatidylcholine-induced Ca<SUP>2＋</SUP> Mobilization in Human Endothelial Cells

Oxidized Low-density Lipoprotein- and Lysophosphatidylcholine-induced Ca<SUP>2＋</SUP> Mobilization in Human Endothelial Cells

The effects of oxidized low-density lipoprotein (OxLDL) and its major lipid constituent lysophosphatidylcholine (LPC) on Ca^2＋ entry were investigated in cultured human umbilical endothelial cells (HUVECs) using fura-2 fluorescence and patch-clamp methods. OxLDL or LPC increased intracellular Ca^2＋concentration ([Ca^2＋]_i), and the increase of [Ca^2＋]_i by OxLDL or by LPC was inhibited by La^3＋ or heparin. LPC failed to increase [Ca^2＋]_i in the presence of an antioxidant tempol. In addition, store-operated Ca^2＋ entry (SOC), which was evoked by intracellular Ca^2＋ store depletion in Ca^2＋-free solution using the sarcoplasmic reticulum Ca^2＋ pump blocker, 2, 5-di-t-butyl-1, 4-benzohydroquinone (BHQ), was further enhanced by OxLDL or by LPC. Increased SOC by OxLDL or by LPC was inhibited by U73122. In voltage-clamped cells, OxLDL or LPC increased [Ca^2＋]_iand simultaneously activated non-selective cation (NSC) currents. LPC-induced NSC currents were inhibited by 2-APB, La^3＋ or U73122, and NSC currents were not activated by LPC in the presence of tempol. Furthermore, in voltage-clamped HUVECs, OxLDL enhanced SOC and evoked outward currents simultaneously. Clamping intracellular Ca^2＋ to 1 &#1356;M activated large-conductance Ca^2＋-activated K^＋ (BK_Ca) current spontaneously, and this activated BK_Ca current was further enhanced by OxLDL or by LPC. From these results, we concluded that OxLDL or its main component LPC activates Ca^2＋-permeable Ca^2＋-activated NSC current and BK_Ca current simultaneously, thereby increasing SOC.