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Background: Nitroalkene fatty acids are electrophilic cell metabolites that mediate anti-inflammatory signaling actions. Results: Conjugated linoleic acid is the preferential unsaturated fatty acid substrate for nitration reactions during oxidative inflammatory conditions and digestion. Conclusion: Nitro-fatty acid formation in vivo occurs during metabolic and inflammatory reactions and modulates cell signaling. Significance: Nitro-conjugated linoleic acid transduces signaling actions of nitric oxide, nitrite, and conjugated linoleic acid.

DW. Hydrogen sulfide mediates vasoactivity in an O 2-dependent manner. Am J Physiol Heart Circ Physiol 292: H1953-H1960, 2007. First published January 19, 2007 doi:10.1152 doi:10. /ajpheart.01193.2006 has recently been shown to have a signaling role in vascular cells. Similar to nitric oxide (NO), H 2S is enzymatically produced by amino acid metabolism and can cause posttranslational modification of proteins, particularly at thiol residues. Molecular targets for H 2S include ATP-sensitive K ϩ channels, and H2S may interact with NO and heme proteins such as cyclooxygenase. It is well known that the reactions of NO in the vasculature are O 2 dependent, but this has not been addressed in most studies designed to elucidate the role of H 2S in vascular function. This is important, since H2S reactions can be dramatically altered by the high concentrations of O 2 used in cell culture and organ bath experiments. To test the hypothesis that the effects of H 2S on the vasculature are O2 dependent, we have measured real-time levels of H 2S and O2 in respirometry and vessel tension experiments, as well as the associated vascular responses. A novel polarographic H2S sensor developed in our laboratory was used to measure H2S levels. Here we report that, in rat aorta, H2S concentrations that mediate rapid contraction at high O2 levels cause rapid relaxation at lower physiological O2 levels. At high O2, the vasoconstrictive effect of H2S suggests that it may not be H2S per se but, rather, a putative vasoactive oxidation product that mediates constriction. These data are interpreted in terms of the potential for H2S to modulate vascular tone in vivo.

Extracellular superoxide dismutase (EC-SOD) is expressed at high levels in lungs. EC-SOD has a polycationic matrix-binding domain that binds to polyanionic constituents in the matrix. Previous studies indicate that EC-SOD protects the lung in both bleomycin-and asbestos-induced models of pulmonary fibrosis. Although the mechanism of EC-SOD protection is not fully understood, these studies indicate that EC-SOD plays an important role in regulating inflammatory responses to pulmonary injury. Hyaluronan is a polyanionic high molecular mass polysaccharide found in the extracellular matrix that is sensitive to oxidant-mediated fragmentation. Recent studies found that elevated levels of low molecular mass hyaluronan are associated with inflammatory conditions. We hypothesize that EC-SOD may inhibit pulmonary inflammation in part by preventing superoxide-mediated fragmentation of hyaluronan to low molecular mass fragments. We found that EC-SOD directly binds to hyaluronan and significantly inhibits oxidant-induced degradation of this glycosaminoglycan. In vitro human polymorphic neutrophil chemotaxis studies indicate that oxidative fragmentation of hyaluronan results in polymorphic neutrophil chemotaxis and that EC-SOD can completely prevent this response. Intratracheal injection of crocidolite asbestos in mice leads to pulmonary inflammation and injury that is enhanced in EC-SOD knock-out mice. Notably, hyaluronan levels are increased in the bronchoalveolar lavage fluid after asbestos-induced pulmonary injury, and this response is markedly enhanced in EC-SOD knock-out mice. These data indicate that inhibition of oxidative hyaluronan fragmentation probably represents one mechanism by which EC-SOD inhibits inflammation in response to lung injury.

This article is available online at http://www.jlr.org biomolecule nitration ( 1 ). Nitroalkene substituents are electrophilic and promote Michael addition of fatty acids with biological nucleophiles such as cysteine and histidine. The extent, rate, and reversibility of these reactions will be dictated both by the concentration and reactivity of individual nucleophiles. In this regard, protein structure and compartmentalization affect the reactivity of individual nucleophilic centers and will defi ne the molecular targets of electrophilic fatty acids.While enzymatically-oxygenated unsaturated fatty acids typically transduce anti-infl ammatory actions via specifi c g protein-coupled receptor ligand activity ( 2, 3 ), transcriptional responses to electrophilic fatty acids reveal that a broader array of signaling events are instigated ( 4, 5 ). The basis for this pleiotropy resides in the facile Michael addition of electrophilic fatty acid derivatives with nucleophilic centers of proteins that regulate structure and function ( 6 ). Functionally-signifi cant protein targets of electrophilic fatty acids include the transcriptional regulatory protein complex nuclear factor kappa B (NFkB), the