Phospholipase A 2 activity in ox-LDL-stimulated mesangial gated the changes in PGE 2 , cytosolic PLA 2 and intracelcells and modulation by ␣-tocopherol. lular calcium ion content ([Ca 2ϩ ] i) after treatment with Background. Oxidized LDL increases the production of oxidized LDL. The effects of ␣-Toc and probucol upon both prostaglandin E 2 (PGE 2) and thromboxane B 2 (TXB 2) these parameters were also studied in cultured rat mesin rat mesangial cells. These increases were suppressed by angial cells. antioxidants such as ␣-tocopherol (␣-Toc) or probucol. Methods. We investigated the mechanism by which oxidized LDL leads to an increase in PGE 2 production using rat mesan-METHODS gial cells in culture. We also examined how ␣-Toc supresses this augmentation, by measuring intracellular Ca 2ϩ and phos-Culture of mesangial cells with human LDL pholipase A 2 (PLA 2) activity. Results. In rat mesangial cells, oxidized LDL increased PLA 2 Rat mesangial cells (1 to 3 ϫ 10 6 or 3 to 5 ϫ 10 7 cells) activity by increasing the intracellular calcium ion content, were incubated for more than 24 hours in serum-free which resulted in the induction of PGE 2 production. On the RPMI-1640 medium with various concentrations (0, 50, other hand, pretreatment of cells with ␣-Toc, which resulted 100, to 200 g/ml) of native LDL or LDL oxidized in a large uptake of ␣-Toc in cell membranes, markedly supby Cu 2ϩ. pressed the augmentation of PGE 2 production and PLA 2 activity by oxidized LDL in a dose dependent manner. However, Determination of PGE 2 cytosolic PLA 2 partially purified from mesangial cells was not inhibited by ␣-Toc despite an increase of ␣-Toc.
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