We recently reported that oxidized LDL (oxLDL) induces an oscillatory increase in intracellular calcium ([Ca2+](i)) levels in macrophages. Furthermore, we have shown that these [Ca2+](i) oscillations mediate oxLDL's ability to inhibit macrophage apoptosis in response to growth factor deprivation. However, the signal transduction pathways by which oxLDL induces [Ca2+](i) oscillations have not been elucidated. In this study, we show that these oscillations are mediated in part by intracellular mechanisms, as depleting extracellular Ca2+ did not completely abolish the effect. Inhibiting sarco-endoplasmic reticulum ATPase (SERCA) completely blocked [Ca2+](i) oscillations, suggesting a role for Ca2+ reuptake by the ER. The addition of oxLDL resulted in an almost immediate activation of sphingosine kinase (SK), which can increase sphingosine-1-phosphate (S1P) levels by phosphorylating sphingosine. Moreover, S1P was shown to be as effective as oxLDL in blocking macrophage apoptosis and producing [Ca2+](i) oscillations. This suggests that the mechanism in which oxLDL generates [Ca2+](i) oscillations may be 1) activation of SK, 2) SK-mediated increase in S1P levels, 3) S1P-mediated Ca2+ release from intracellular stores, and 4) SERCA-mediated Ca2+ reuptake back into the ER.-Chen, J. H., M. Riazy, S. W. Wang, J. M. Dai, V. Duronio, and U. P. Steinbrecher. Sphingosine kinase regulates oxidized low density lipoprotein-mediated calcium oscillations and macrophage survival. J. Lipid Res. 2010. 51: 991-998.