An Epoxyisoprostane Is a Major Regulator of Endothelial Cell Function

Abstract

The goal of these studies was to determine the effect of 5,6-epoxyisoprostane, EI, on human aortic endothelial cells (HAEC). EI can form as a phospholipase product of 1-palmitoyl-2-(5,6-epoxyisoprostane E2)-sn-glycero-3-phosphocholine, PEIPC, a pro-inflammatory molecule that accumulates in sites of inflammation where phospholipases are also increased. To determine the effect of EI on HAEC, we synthesized several stereoisomers of EI using a convergent approach from the individual optically pure building blocks, the epoxyaldehydes 5 and 6 and the bromoenones 14 and 16. The desired stereoisomer of EI can be prepared from these materials in only six operations and thus large amounts of the product can be obtained. The trans/trans isomers had the most potent activity, suggesting specificity in the interaction of EI with the cell surface. EI has potent anti-inflammatory effects in HAEC. EI strongly inhibits the production of MCP-1, a major monocyte chemotactic factor, and either decreases or minimally increases the levels of ten pro-inflammatory molecules increased by PEIPC. EI also strongly downregulates the inflammatory effects of IL-1β, a major inflammatory cytokine. Thus EI, a hydrolytic product of PEIPC, has potent anti-inflammatory function.

HDL inhibits the effects of oxidized phospholipids on endothelial cell gene expression via multiple mechanisms

“…Transcriptional changes of multiple genes in dose-response experiments, using varying concentrations of OxPAPC and HDL, are inconsistent with nonspecifi c sequestration of OxPAPC by HDL. This is further supported by the fact by guest, on May 11, 2018 www.jlr.org effects of EI, which regulates many of the same genes as OxPAPC and PEIPC ( 28 ), are undiminished by cotreatment with HDL. Additional research may identify other bioactive constituents of OxPAPC, or products of OxPAPC degradation, which remain active toward HAECs in the presence of HDL.…”

“…The 5,6-epoxyisoprostane (EI) was synthesized as described previously, and a single analog, EI4, was used in this study ( 28 ). Cholesterol-cyclodextrin complex was purchased from Sigma-Aldrich.…”

“…We therefore addressed the question of whether HDL can protect against the effects of the epoxyisoprostane (EI) formed from the sn -2 hydrolysis of PEIPC. EI has recently been characterized and shown to recapitulate ‫ف‬ 50% of the effects of PEIPC, including the activation of oxidative stress response and ER stress response pathways ( 28 ). However, in contrast to OxPAPC and PEIPC, EI induces an anti-infl ammatory phenotype in HAECs.…”

Fatty acid epoxyisoprostane E2 stimulates an oxidative stress response in endothelial cells

“…In this study, we showed that fatty acid fraction of OxPAPC, specifically epoxyisoprostane E2, possess the same activity of OxPAPC/PEIPC in stimulating superoxide production and the expression of OKL38 and HO-1 in endothelial cells. We most recently showed that EI also modulated the expression of other genes regulated by OxPAPC[12]. The net effect of EI on atherosclerosis will be the interest of future study.…”

“…We have previous shown that the sn-2 position is required for the activity of OxPAPC in stimulating monocyte binding and gene expression in endothelial cells[9,10]. Our most recent studies demonstrate that EI, the PLA2 hydrolysis product of PEIPC, though poorly regulating inflammatory function, is able to regulate 40% of the genes regulated by PEIPC[12]. This study examines the ability of EI to regulate oxidative stress.…”