Cyclooxygenase-derived proangiogenic metabolites of epoxyeicosatrienoic acids

Abstract

Arachidonic acid (ARA) is metabolized by cyclooxygenase (COX) and cytochrome P450 to produce proangiogenic metabolites. Specifically, epoxyeicosatrienoic acids (EETs) produced from the P450 pathway are angiogenic, inducing cancer tumor growth. A previous study showed that inhibiting soluble epoxide hydrolase (sEH) increased EET concentration and mildly promoted tumor growth. However, inhibiting both sEH and COX led to a dramatic decrease in tumor growth, suggesting that the contribution of EETs to angiogenesis and subsequent tumor growth may be attributed to downstream metabolites formed by COX. This study explores the fate of EETs with COX, the angiogenic activity of the primary metabolites formed, and their subsequent hydrolysis by sEH and microsomal EH. Three EET regioisomers were found to be substrates for COX, based on oxygen consumption and product formation. EET substrate preference for both COX-1 and COX-2 were estimated as 8,9-EET > 5,6-EET > 11,12-EET, whereas 14,15-EET was inactive. The structure of two major products formed from 8,9-EET in this COX pathway were confirmed by chemical synthesis: ct-8,9-epoxy-11-hydroxy-eicosatrienoic acid (ct-8,9-E-11-HET) and ct-8,9-epoxy-15-hydroxy-eicosatrienoic acid (ct-8,9-E-15-HET). ct-8,9-E-11-HET and ct-8,9-E-15-HET are further metabolized by sEH, with ct-8,9-E-11-HET being hydrolyzed much more slowly. Using an s.c. Matrigel assay, we showed that ct-8,9-E-11-HET is proangiogenic, whereas ct-8,9-E-15-HET is not active. This study identifies a functional link between EETs and COX and identifies ct-8,9-E-11-HET as an angiogenic lipid, suggesting a physiological role for COX metabolites of EETs.omega-6 fatty acids | epoxyeicosatrienoic acids | metabolism | cyclooxygenase | angiogenesis A rachidonic acid (ARA) is an omega-6 fatty acid that is metabolized by three major classes of enzymes, cyclooxygenases (COXs), lipoxygenases, and cytochrome P450s (CYPs), to produce an array of biologically active metabolites (1-3). The CYP pathway transforms ARA into four epoxyeicosatrienoic acids (EETs) in addition to hydroxylated metabolites (1). EETs have several biological actions, and are considered antihypertensive, antiinflammatory, neuroprotective, cardioprotective, and analgesic (4). EETs also play a role in angiogenesis (5-10), the formation of new blood vessels from preexisting vessels that is important for many physiological and pathological processes, including cancer (11).EETs can enhance tumor growth and metastasis through their angiogenic activity (12); however, this activity is transient due to their metabolic instability. EETs are further metabolized by epoxide hydrolases (EHs), primarily soluble epoxide hydrolase (sEH), to their corresponding diols (4, 13), which are generally not biologically active (14) (Fig. 1A). Inhibition of sEH prolongs EET biological activity, potentiating their angiogenic activity, leading to increased tumor growth and metastasis in some systems (12, 15) (Fig. 1B).ARA can also be metabolized by COX to form proangiogenic and proinflammator...

Soluble epoxide hydrolase as a therapeutic target for pain, inflammatory and neurodegenerative diseases

“…Zhang, et al, 2013). A partial hypothesis to explain this is that an angiogenic metabolite of 8,9-EET can be formed by COX enzymes but the metabolite does not form in the presence of COX inhibitors or competing omega-3 lipids (Rand, et al, 2017). The EDPs which cannot form an analogous angiogenic metabolite are inherently antiangiogenic and the EETs, in the presence of celecoxib, are as well.…”

Immune disorder in endometrial cancer: Immunosuppressive microenvironment, mechanisms of immune evasion and immunotherapy (Review)

“…COX is the rate-limiting enzyme in the synthesis of prostaglandins. COX exists both as a constitutively expressed isoform (COX-1) and a regulated isoform (COX-2) ( 74 ). COX-2 enables tumor cells to escape immunological surveillance ( 75 , 76 ).…”

Differential Effects of sEH Inhibitors on the Proliferation and Migration of Vascular Smooth Muscle Cells

“…Even though COX-2 was induced by EETs in PDGF-treated VSMCs, EET did not enhance PDGF-stimulated VSMC migration, unlike AUDA ( Figure 4 A,B). Recent studies have shown that 5,6-EET, 8,9-EET, and 11,12-EET, but not 14,15-EET, can be metabolized by COX-2 to produce mitogenic and angiogenic metabolites (e.g., ct-8,9-epoxy-11-hydroxy-eicosatrienoic acid), which are then subjected to sEH metabolism [ 45 , 46 ]. Although their roles in the migration of VSMCs are yet to be elucidated, it seems possible that sEH inhibition by AUDA stabilizes these metabolites, as well as EET, thereby facilitating VSMC migration.…”