Atherosclerosis is the main underlying cause of major cardiovascular diseases such as stroke and heart attack. Oxidized phospholipids such as oxidized 1-palmitoyl-2-arachidonoyl-sn-Glycero-3-phosphorylcholine (OxPAPC) accumulate in lesions of and promote atherosclerosis. OxPAPC activates endothelial cells, a critical early event of atherogenesis. Epoxyisoprostane E2 (El) is an oxidized fatty acid contained at the sn-2 position of 1-palmitoyl-2-epoxyisoprostane E2-sn-glycero-3-phosphorylcholine (PEIPC), the most active component of OxPAPC in regulating inflammation. OxPAPC and its components including PEIPC activate endothelial cells to express an array of genes in different categories including oxidative stress response genes such as tumor suppressor gene OKL38 and Heme oxygenase-1 (HO-1). El can be released by lipase from PEIPC. In this study, we examined the ability of El to stimulate oxidative stress response in endothelial cells. El released from OxPAPC and synthetic El stimulated the expression of oxidative stress response gene OKL38 and antioxidant gene HO-1. Treatment of endothelial cells with El increased the production of superoxide. NADPH oxidase inhibitor Apocynin and superoxide scavenger N-acetyl-cysteine (NAC) significantly attenuated El-stimulated expression of OKL38 and HO-1. We further demonstrated that El activated oxidative stress-sensitive transcription factor Nrf2. Silencing of Nrf2 with siRNA significantly reduced El stimulated expression of OKL38 and HO-1. Thus, we demonstrated that El induced oxidative stress in endothelial cells leading to increased expression of oxidative stress response gene OKL38 and HO-1 via Nrf2 signaling pathway relevant to atherosclerosis. (C) 2014 Elsevier Inc. All rights reserved.