Macrophage activation induces formation of the anti-inflammatory lipid cholesteryl-nitrolinoleate

Abstract

Nitroalkene derivatives of fatty acids act as adaptive, anti-inflammatory signalling mediators, based on their high-affinity PPARγ (peroxisome-proliferator-activated receptor γ ) ligand activity and electrophilic reactivity with proteins, including transcription factors. Although free or esterified lipid nitroalkene derivatives have been detected in human plasma and urine, their generation by inflammatory stimuli has not been reported. In the present study, we show increased nitration of cholesteryl-linoleate by activated murine J774.1 macrophages, yielding the mononitrated nitroalkene CLNO2 (cholesteryl-nitrolinoleate). CLNO2 levels were found to increase ~20-fold 24 h after macrophage activation with Escherichia coli lipopolysaccharide plus interferon-γ ; this response was concurrent with an increase in the expression of NOS2 (inducible nitric oxide synthase) and was inhibited by the •NO (nitric oxide) inhibitor L-NAME (NG-nitro-L-arginine methyl ester). Macrophage (J774.1 and bone-marrow-derived cells) inflammatory responses were suppressed when activated in the presence of CLNO2 or LNO2 (nitrolinoleate). This included: (i) inhibition of NOS2 expression and cytokine secretion through PPARγ and •NO-independent mechanisms; (ii) induction of haem oxygenase-1 expression; and (iii) inhibition of NF-κB (nuclear factor κB) activation. Overall, these results suggest that lipid nitration occurs as part of the response of macrophages to inflammatory stimuli involving NOS2 induction and that these by-products of nitro-oxidative reactions may act as novel adaptive down-regulators of inflammatory responses.

Conjugated Linoleic Acid Is a Preferential Substrate for Fatty Acid Nitration

“…In activated macrophages and rodent hearts subjected to ischemiareoxygenation, inhibition of nitric-oxide synthase (NOS) activity suppresses fatty acid nitration by ϳ50% (Fig. 3d) (19,47 Ϫ protonation (pK a 3.4) to HNO 2 . This includes phagolysosomes, actively respiring mitochondria, and tissues subjected to ischemic episodes or inflammation.…”

“…The mechanisms underlying biological fatty acid nitration and the structural characteristics of products require additional characterization (17)(18)(19). Importantly, NO 2 Ϫ -supplemented diets are associated with a variety of beneficial anti-inflammatory and metabolic actions, including the regulation of mitochondrial function, adipogenesis, oxygen delivery to tissues, and blood pressure (20).…”

Nrf2-dependent and -independent Responses to Nitro-fatty Acids in Human Endothelial Cells

“…In summary, the exemplary nitroalkene fatty acid derivative OA-NO 2 is a potent inducer of the HSR, adding a new dimension to the pleiotropic anti-inflammatory signaling mechanisms manifested by these products of oxidative inflammatory reactions (2,40,62). The small molecule activation of the HSR is an emerging therapeutic modality for a number of human diseases affecting protein folding and conformation, as well as inflammatory conditions such as ischemia-reperfusion injury (23).…”

Nitro-Oleic Acid Inhibits Firing and Activates TRPV1- and TRPA1-Mediated Inward Currents in Dorsal Root Ganglion Neurons from Adult Male Rats

“…Nitrated fatty acids, including nitro-oleic acid (OA-NO 2 ), nitro-linoleic acid and nitro-arachidonic acid, are present in tissues at low levels under normal conditions, and their levels are increased postprandially and during inflammation (Ferreira et al, 2009;Rudolph et al, 2010). These agents elicit a variety of cellular effects, including activation of peroxisome proliferator-activated receptor ␥, signal transducer and activator of transcription 1, nuclear factor erythroid 2-related factor 2, and mitogen-activated protein phosphatase 1 signaling pathways, as well as induction of heme oxygenase 1 expression and inhibition of nuclear factor-Bdependent gene expression (Ichikawa et al, 2008;Li et al, 2008;Kansanen et al, 2009;Wright et al, 2009).…”