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KMID : 0811720090130010027
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Korean Journal of Physiology & Pharmacology
2009 Volume.13 No. 1 p.27 ~ p.32
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Oxidized Low-density Lipoprotein- and Lysophosphatidylcholine-induced
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Kim Moon-Young
Suh Suk-Hyo
Choi Soo-Seung
Liang Guo-Hua
Kim Ji-Aee
Choi Shin-Ku
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Abstract
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The effects of oxidized low-density lipoprotein (OxLDL) and its major lipid constituent lysophosphatidylcholine (LPC) on Ca2＋ entry were investigated in cultured human umbilical endothelial cells (HUVECs) using fura-2 fluorescence and patch-clamp methods. OxLDL or LPC increased intracellular Ca2＋ concentration ([Ca2＋]i), and the increase of [Ca2＋]i by OxLDL or by LPC was inhibited by La3＋ or heparin. LPC failed to increase [Ca2＋]i in the presence of an antioxidant
tempol. In addition, store-operated Ca2＋ entry (SOC), which was evoked by intracellular Ca2＋ store depletion in Ca2＋-free solution using the sarcoplasmic reticulum Ca2＋ 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 [Ca2＋]i and simultaneously activated non-selective cation (NSC) currents. LPC-induced NSC currents were inhibited by 2-APB, La3＋ 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 Ca2＋ to 1 μM activated large-conductance Ca2＋-activated K＋ (BKCa) current spontaneously, and this activated BKCa current was further enhanced by OxLDL or by LPC. From these results, we concluded that OxLDL or its main component LPC activates Ca2＋-permeable Ca2＋-activated NSC current and BKCa current simultaneously, thereby increasing SOC.
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KEYWORD
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Oxidized LDL, Endothelial cell, Store-operated Ca2＋ entry, Large conductance Ca2＋-activated K＋ channel, Nonselective cation current
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