Electrophilic cyclopentenone neuroprostanes are anti-inflammatory mediators formed from the peroxidation of the ω-3 polyunsaturated fatty acid docosahexaenoic acid

The ω-3 polyunsaturated fatty acid docosahexaenoic acid (DHA) possesses potent anti-inflammatory properties and has shown therapeutic benefit in numerous inflammatory diseases. However, the molecular mechanisms of these anti-inflammatory properties are poorly understood. DHA is highly susceptible to peroxidation, which yields an array of potentially bioactive lipid species. One class of compounds are cyclopentenone neuroprostanes (A₄/J ₄-NPs), which are highly reactive and similar in structure to anti-inflammatory cyclopentenone prostaglandins. Here we show that a synthetic A₄/J₄-NP, 14-A₄-NP (A₄-NP), potently suppresses lipopolysaccharide-induced expression of inducible nitric-oxide synthase and cyclooxygenase-2 in macrophages. Furthermore, A₄-NP blocks lipopolysaccharide-induced NF-κB activation via inhibition of Iκ kinase-mediated phosphorylation of IκBα. Mutation on Iκ kinase β cysteine 179 markedly diminishes the effect of A ₄-NP, suggesting that A₄-NP acts via thiol modification at this residue. Accordingly, the effects of A₄-NP are independent of peroxisome proliferator-activated receptor-γ and are dependent on an intact reactive cyclopentenone ring. Interestingly, free radical-mediated oxidation of DHA greatly enhances its anti-inflammatory potency, an effect that closely parallels the formation of A₄/J₄-NPs. Furthermore, chemical reduction or conjugation to glutathione, both of which eliminate the bioactivity of A₄-NP, also abrogate the anti-inflammatory effects of oxidized DHA. Thus, we have demonstrated that A₄/J₄-NPs, formed via the oxidation of DHA, are potent inhibitors of NF-κB signaling and may contribute to the antiinflammatory actions of DHA. These findings have implications for understanding the anti-inflammatory properties of ω-3 fatty acids, and elucidate novel interactions between lipid peroxidation products and inflammation.