OxLDL enhances L-type Ca2+ currents via lysophosphatidylcholine-induced mitochondrial reactive oxygen species (ROS) production

Objective: To examine the mechanisms underlying oxidised LDL-(oxLDL)-induced alterations in Ca2+ currents, an effect which underlies altered vascular contractility and cardiac myocyte function. Methods: Ca2+ currents (I-ca) were recorded by whole-cell patch-clamp in HEK293 cells expressing L-type Ca2+ channel alpha(1C) subunits or isolated rat ventricular myocytes. oxLDL (but not native LDL) significantly enhanced recombinant I-Ca, an effect mimicked by 1 mu M lysophosphatidylcholine (LPC). LPC failed to enhance ICa either in mitochondrial electron transport chain-depleted rho(0) cells, or in the presence of rotenone (1 mu M), or MPP+ (10 mu M). The LPC response was similarly ablated by ascorbate (200 mu M) or TROLOX (500 mu M) and by the mitochondria-targeted antioxidant, MitoQ (250 nM). In myocytes, enhancement of I-Ca, due to LPC was similarly abrogated with rotenone and MitoQ. These data suggest that LPC enhanced recombinant Ca2+ currents due to increased mitochondrial ROS production. In support with this, LPC enhanced fluorescence in HEK293 cells and cardiac myocytes loaded with a ROS-sensitive mitochondrial dye, reduced mitotracker red. Conclusion-LPC up-regulates L-type Ca2+ currents due to altered mitochondrial ROS production, an effect which mediates the response of the native ICa in cardiac myocytes to oxLDL. (c) 2005 European Society of Cardiology. Published by Elsevier B.V All rights reserved.