)-HETE in rabbit lung, as a major product of AA from mast cells, and as a major product of stenosed canine coronary arteries

This article is available online at http://www.jlr.org Arachidonic acid (AA) metabolism is implicated in cellular and physiologic regulation, infl ammatory diseases, and cancer ( 1 ). In colon cancers, cyclooxygenase (COX)-2 expression is increased, and conversely, 15-prostaglandin dehydrogenase (PGDH) is downregulated ( 2 ). There is also evidence for COX-2/15-PGDH counterregulation in gastric, breast, and lung cancers ( 3–5 ). The magnitude of the upregulation/downregulation may even serve as an independent predictor of progression and survival ( 6, 7 ). This “proliferative switch” is hypothesized to increase tumorigenesis and angiogenesis via increased prostaglandin (PG) E 2 formation ( Fig. 1A ) and a feed-forward loop for COX-2 ( 8, 9 ). However, COX-2-mediated AA metabolism also generates other eicosanoids, including 11and 15-hydroperoxyeicosatetraenoic acids (HPETE) and, after reductive metabolism, the more stable 11and 15-hydroxyeicosatetraenoic acids (HETE) ( 10, 11 ) ( Fig. 1A, B ). 15-HPETE is also a major product of the lipoxygenase pathway, through various 15or 12/15-lipoxygenases (LOX; Fig. 1B ) ( 12 ). 15PGDH then oxidizes 11or 15-HETE to the , -unsaturated ketone-containing oxo-eicosatetraenoic acids (ETE) ( 13, 14 ). Confi rmation of the dehydrogenase pathway has been obtained using numerous experimental paradigms. 15-oxoETE was found as a major product of 15-PGDH-mediated oxidation of 15( S )-HETE in rabbit lung, as a major product of AA from mast cells, and as a major product of stenosed canine coronary arteries ( 15–17 ). In addition, either COX/15-PGDH-mediated or LOX/15-PGDH-mediated Abstract Cyclooxygenases (COX) metabolize arachidonic acid (AA) to hydroxyeicosatetraenoic acids (HETE), which can then be oxidized by dehydrogenases, such as 15-hydroxyprostaglandin dehydrogenase (15-PGDH), to oxo-eicosatetraenoic acids (ETE). We have previously established that 11-oxo-eicosatetraenoic acid (oxo-ETE) and 15-oxo-ETE are COX-2/15-PGDH-derived metabolites. Stable isotope dilution (SID) chiral liquid chromatography coupled with electron capture atmospheric pressure chemical ionization (ECAPCI) single reaction monitoring (SRM) MS has been used to quantify uptake of 11-oxo-ETE and 15-oxo-ETE in both LoVo cells and human umbilical vein endothelial cells (HUVEC). Intracellular 11-oxoand 15-oxo-ETE concentrations reached maximum levels within 1 h and declined rapidly, with signifi cant quantitative differences in uptake between the LoVo cells and the HUVECs. Maximal intracellular concentrations of 11-oxo-ETE were 0.02 ng/4 × 10 5