RESUMO
Fatty acids such as eicosapentaenoic acid (EPA) have been shown to be beneficial for neurological function and human health. It is widely thought that oxidation products of EPA are responsible for biological activity, although the specific EPA peroxidation product(s) which exert these responses have not yet been identified. In this work we provide the first evidence that the synthesized representative cyclopentenone IsoP, 15-A(3t)-IsoP, serves as a potent inhibitor of lipopolysaccharide-stimulated macrophage activation. The anti-inflammatory activities of 15-A(3t)-IsoP were observed in response not only to lipopolysaccharide, but also to tumor necrosis factor alpha and IL-1b stimulation. Subsequently, this response blocked the ability of these compounds to stimulate nuclear factor kappa b (NFκB) activation and production of proinflammatory cytokines. The bioactivity of 15-A(3t)-IsoP was shown to be dependent upon an unsaturated carbonyl residue which transiently adducts to free thiols. Site directed mutagenesis of the redox sensitive C179 site of the Ikappa kinase beta subunit, blocked the biological activity of 15-A(3t)-IsoP and NFκB activation. The vasoprotective potential of 15-A(3t)-IsoP was underscored by the ability of this compound to block oxidized lipid accumulation, a critical step in foam cell transformation and atherosclerotic plaque formation. Taken together, these are the first data identifying the biological activity of a specific product of EPA peroxidation, which is formed in abundance in vivo. The clear mechanism linking 15-A(3t)-IsoP to redox control of NFκB transcription, and the compound's ability to block foam cell transformation suggest that 15-A(3t)-IsoP provides a unique and potent tool to provide vaso- and cytoprotection under conditions of oxidative stress.
Assuntos
Ácidos Graxos/metabolismo , Isoprostanos/química , Isoprostanos/farmacologia , Ativação de Macrófagos/fisiologia , Macrófagos/metabolismo , NF-kappa B/antagonistas & inibidores , NF-kappa B/metabolismo , Transcrição Gênica/fisiologia , Animais , Linhagem Celular , Ácidos Graxos/fisiologia , Isoprostanos/fisiologia , Ativação de Macrófagos/efeitos dos fármacos , Macrófagos/efeitos dos fármacos , Camundongos , NF-kappa B/genética , Oxirredução , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/fisiologia , Transcrição Gênica/efeitos dos fármacosRESUMO
15-deoxy-Delta12,14-prostaglandin J2 (15-d-PGJ2) is a dehydration product of PGD2. This compound possesses a highly reactive polyunsaturated carbonyl moiety that is a substrate for Michael addition with thiol-containing biomolecules such as glutathione and cysteine residues on proteins. By reacting with glutathione and proteins, 15-d-PGJ2 is believed to exert potent biological activity. Despite the large number of publications that have ascribed bioactivity to this molecule, it is not known to what extent 15-d-PGJ2 is formed in vivo. Levels of free 15-d-PGJ2 measured in human biological fluids such as urine are low, and the biological importance of this compound has thus been questioned. Because of its reactivity, we hypothesized that 15-d-PGJ2 is present in vivo primarily as a Michael conjugate. Therefore, we undertook a detailed study of the metabolism of this compound in HepG2 cells that are known to metabolize other cyclopentenone eicosanoids. We report that HepG2 cells primarily convert 15-d-PGJ2 to a glutathione conjugate in which the carbonyl at C-11 is reduced to a hydroxyl. Subsequently, the glutathione portion of the molecule is hydrolyzed with loss of glutamic acid and glycine resulting in a cysteine conjugate. These findings confirm a general route for the metabolism of cyclopentenone eicosanoids in HepG2 cells and may pave the way for new insights regarding the formation of 15-d-PGJ2 in vivo.