title: The ω-3 epoxide of eicosapentaenoic acid inhibits endothelial cell proliferation by p38 MAP kinase activation and cyclin D1/CDK4 down-regulation.
abstract: OBJECTIVE
  Dietary intake of ω-3 polyunsaturated fatty acids (ω-3 PUFAs) like eicosapentaenoic acid (EPA) decreases cancer risk, while arachidonic acid and other ω-6 PUFAs increase risk, but the underlying mechanisms are unclear. Cytochrome P450 (CYP)-derived epoxides contribute to enhanced tumourigenesis due to ω-6 PUFA intake. Thus, ω-6 arachidonic acid epoxides (EETs) inhibit apoptosis and stimulate proliferation by up-regulating cyclin D1 expression in cells. The present study evaluated the corresponding ω-3 PUFA epoxides and assessed their role in the regulation of cell proliferation.
  
  
  METHODS
  Four chemically stable EPA epoxides (formed at the 8,9-, 11,12-, 14,15- and 17,18-olefinic bonds) were synthesized and tested against growth-related signalling pathways in brain microvascular endothelial bEND.3 cells. Cell cycle distribution was determined by flow cytometry and cyclin gene expression by immunoblotting and real-time PCR. The role of the p38 mitogen-activated protein (MAP) kinase in cyclin D1 dysregulation was assessed using specific inhibitors and dominant-negative expression plasmids.
  
  
  RESULTS
  The ω-3 17,18-epoxide of EPA decreased cell proliferation, interrupted the cell cycle in S-phase and down-regulated the cyclin D1/cyclin-dependent kinase (CDK)-4 complex, whereas the 8,9-, 11,12- and 14,15-epoxides were either inactive or enhanced proliferation. Cyclin D1 down-regulation by 17,18-epoxy-EPA was mediated by activation of the growth-suppressing p38 MAP kinase, but the alternate EPA-epoxides were inactive.
  
  
  CONCLUSIONS
  The present findings suggest that the epoxide formed by CYP enzymes at the ω-3 olefinic bond may contribute to the beneficial effects of ω-3 PUFA by down-regulating cyclin D1 and suppressing cell proliferation.
authors.affiliation: Pharmacogenomics and Drug Development Group, Faculty of Pharmacy, University of Sydney, New South Wales, Australia.
authors.forename: Pei H
authors.initials: PH
authors.lastname: Cui
authors.forename: Nenad
authors.initials: N
authors.lastname: Petrovic
authors.forename: Michael
authors.initials: M
authors.lastname: Murray
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D019938:Cyclin D1 / Q000235:genetics / Q000378:metabolism*; D051358:Cyclin-Dependent Kinase 4 / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D015118:Eicosapentaenoic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004852:Epoxy Compounds / Q000737:chemistry / Q000494:pharmacology; D051379:Mice; D009369:Neoplasms / Q000209:etiology / Q000517:prevention & control; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: C530105:Ccnd1 protein, mouse; D004852:Epoxy Compounds; D012333:RNA, Messenger; D019938:Cyclin D1; D015118:Eicosapentaenoic Acid; C495902:Cdk4 protein, mouse; D051358:Cyclin-Dependent Kinase 4; D048051:p38 Mitogen-Activated Protein Kinases