11-Oxo-ETE, even though it is acyclic, has the same 11-oxo-moiety as the potent inhibitor of human umbilical vein endothelial cell (HUVEC) proliferation, 15d-PGJ2. This might account for the finding that 11-oxo-ETE was six times more potent than 15-oxo-ETE and equipotent with 15d-PGJ2 at inhibition of HUVEC proliferation. A HUVEC lysate treated with 11(R)-HETE did not produce any 11-oxo-ETE. Inhibitors,research,lifescience,medical In keeping with this observation, COX-2 was not detectable by Western blot in the HUVEC lysate. The targeted chiral lipidomics approach has made it possible to unequivocally demonstrate that 11(R)-HETE is a substrate for 15-PGDH and that it is converted to 11-oxo-ETE. This finding has provided

another role to 15-PGDH beside inactivation of PGs [110] in which Inhibitors,research,lifescience,medical the 11(R)-HETE-derived 11-oxo-ETE could exhibit a paracrine anti-proliferative effect on endothelial cells. It is noteworthy that 11-oxo-ETE was detected

as an endogenously derived lipid in human atherosclerotic plaques over ten years ago, but the biosynthesis and biological activity were not evaluated at that time [121]. Inhibitors,research,lifescience,medical 4. LOX Mediated Metabolism 4.1. 5-Lipoxygenases-Mediated Metabolism of Arachidonic Acid in Human Lymphoblastic Cell Line 5-LOX metabolism is thought to be involved in the etiology of inflammatory diseases [25,122,123]. There are also a number of reports relating inflammation to oxidative stress and cancer. In order to further explore the relationship between oxidative stress and cancer, the Inhibitors,research,lifescience,medical CESS cell line, a human lymphoblastoid line, which was established from peripheral blood cells of a patient with myelomonocytic leukemia, was used as model system [40]. Importantly CESS cell express both 5-LOX as well as FLAP. 5-LOX in the presence of FLAP is known to metabolize arachidonic acid

to 5(S)-HPETE, which is then further reduced to the corresponding 5(S)-HETE, Inhibitors,research,lifescience,medical or serves as precursor for the formation of LTs (Figure 5). Using our targeted chiral lipidomics approach with stable isotope dilution LC-ECAPCI/SRM/MS methodology, the eicosanoid concentrations in this cell line were determined after stimulation with the calcium ionophore A-23187 [40]. Figure 5 5-LOX-mediated formation of arachidonic acid metabolites and dGuo-adducts. HPNE, 4-hydroperoxy-2(E)-nonenal; DOOE, dioxo-6-octenoic acid. Reprinted ADP ribosylation factor with permission from Ref. [108]. A targeted lipidomics analysis of the native no GSK2656157 mw treatment (NT) CESS line was conducted after stimulation with the calcium ionophore A-23187. Analyses were also performed after ionophore treatment coupled with inhibition of LOX and COX pathways. 5(S)-HETE was used as indirect measurement of 5(S)-HPETE formation. Aclear increase in 5(S)-HETE formation was observed after treatment with ionophore A-23187 (Figure 6A). When the FLAP inhibitor, MK886 was used together with the calcium ionophore, 5(S)-HETE secretion was reduced to levels comparable with the levels observed with the un-stimulated cells.