Macrophage activation induces formation of the anti-inflammatory lipid cholesteryl-nitrolinoleate (original) (raw)
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Biochemistry
Nitroalkene derivatives of fatty acids act as adaptive, antiinflammatory 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 cholesteryllinoleate by activated murine J774.1 macrophages, yielding the mononitrated nitroalkene CLNO 2 (cholesteryl-nitrolinoleate). CLNO 2 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 (N G -nitro-L-arginine methyl ester). Macrophage (J774.1 and bone-marrowderived cells) inflammatory responses were suppressed when activated in the presence of CLNO 2 or LNO 2 (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.
The Journal of Trauma: Injury, Infection, and Critical Care, 2003
life-threatening syndrome that occurs in intensive care unit patients. Lipopolysaccharide (LPS) has been implicated as one of major causes of sepsis. Nitric oxide (NO) and cytokines are involved in sepsisinduced inflammatory responses. This study is aimed at evaluating the effects of NO on the modulation of pro-and antiinflammatory cytokines in LPS-activated macrophages and its possible mechanism.
Nitrosative Capacity of Macrophages Is Dependent on Nitric-oxide Synthase Induction Signals
Journal of Biological Chemistry, 2000
Nitrosative stress can occur when reactive nitric oxide (NO) species compromise the function of biomolecules via formation of NO adducts on critical amine and thiol residues. The capacity of inducible nitric-oxide synthase (iNOS) to generate nitrosative stress was investigated in the murine macrophage line ANA-1. Sequential activation with the cytokines IFN-␥ and either tumor necrosis factor-␣ or interleukin-1 resulted in the induction of iNOS and production of nitrite (20 nM/min) but failed to elicit nitrosation of extracellular 2,3-diaminonapthalene. Stimulation with IFN-␥ and bacterial lipopolysaccharide increased the relative level of iNOS protein and nitrite production of ANA-1 cells 2-fold; however, a substantial level of NO in the media was also observed, and nitrosation of 2,3-diaminonapthalene was increased greater than 30-fold. Selective scavenger compounds suggested that the salient nitrosating mechanism was the NO/O 2 reaction leading to N 2 O 3 formation. These data mimicked the pattern observed with a 5 M concentration of the synthetic NO donor (Z)-1-[N-ammoniopropyl)-N-(n-propyl)amino]diazen-1-ium-1,2-diolate (PAPA/NO). The NO profiles derived from iNOS can be distinct and depend on the inductive signal cascades. The diverse consequences of NO production in macrophages may reside in the cellular mechanisms that control the ability of iNOS to form N 2 O 3 and elicit nitrosative stress.
Endocrinology, 2008
Nitration products of unsaturated fatty acids are formed via NO-dependent oxidative reactions and appear to be a new class of endogenous antiinflammatory mediators. Nitroalkene derivatives of nitrated linoleic acid (LNO2) and nitrated oleic acid (OA-NO2) alleviate inflammatory responses in macrophages, but the underlying mechanisms remain to be fully defined. Herein we report that LNO2 and OA-NO2 suppress proinflammatory signal transducer and activator of transcription (STAT) signaling in macrophages. In RAW264.7 cells, a murine macrophage cell line, LNO2 and OA-NO2 inhibited the lipopolysaccharide (LPS)-induced STAT1 phosphorylation and the STAT1-dependent transcriptional activity, thereby suppressing expression of its target gene such as iNOS and MCP-1. The nitroalkene-mediated inhibition of STAT1 activity was not affected by 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (a NO scavenger), GW9662 (a peroxisome proliferator-activated receptor-γ-specific antagonis...
Circulation Research, 2002
Nitration of unsaturated fatty acids such as linoleate by NO-derived reactive species forms novel derivatives (including nitrolinoleate [LNO 2 ]) that can stimulate smooth muscle relaxation and block platelet activation by either NO/cGMP or cAMP-dependent mechanisms. Here, LNO 2 was observed to inhibit human neutrophil function. LNO 2 , but not linoleic acid or the nitrated amino acid 3-nitrotyrosine, dose-dependently (0.2 to 1 mol/L) inhibited superoxide (O 2 ·Ϫ ) generation, Ca 2ϩ influx, elastase release, and CD11b expression in response to either phorbol 12-myristate 13-acetate or N-formyl-Met-Leu-Phe. LNO 2 did not elevate cGMP, and inhibition of guanylate cyclase by 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one did not restore neutrophil responses, ruling out a role for NO. In contrast, LNO 2 caused elevations in intracellular cAMP in the presence and absence of phosphodiesterase inhibition, suggesting activation of adenylate cyclase. Compared with phorbol 12-myristate 13-acetate-activated neutrophils, N-formyl-Met-Leu-Phe-activated neutrophils were more susceptible to the inhibitory effects of LNO 2 , indicating that LNO 2 may inhibit signaling both upstream and downstream of protein kinase C. These data suggest novel signaling actions for LNO 2 in mediating its potent inhibitory actions. Thus, nitration of lipids by NO-derived reactive species yields products with antiinflammatory properties, revealing a novel mechanism by which NO-derived nitrated biomolecules can influence the progression of vascular disease. (Circ Res. 2002;91:375-381.)
The role of nitric oxide in inflammatory reactions
FEMS Immunology & …, 2007
Nitric oxide (NO) was initially described as a physiological mediator of endothelial cell relaxation, an important role in hypotension. NO is an intercellular messenger that has been recognized as one of the most versatile players in the immune system. Cells of the innate immune system – macrophages, neutrophils and natural killer cells – use pattern recognition receptors to recognize the molecular patterns associated with pathogens. Activated macrophages then inhibit pathogen replication by releasing a variety of effector molecules, including NO. In addition to macrophages, a large number of other immune-system cells produce and respond to NO. Thus, NO is important as a toxic defense molecule against infectious organisms. It also regulates the functional activity, growth and death of many immune and inflammatory cell types including macrophages, T lymphocytes, antigen-presenting cells, mast cells, neutrophils and natural killer cells. However, the role of NO in nonspecific and specific immunity in vivo and in immunologically mediated diseases and inflammation is poorly understood. This Minireview will discuss the role of NO in immune response and inflammation, and its mechanisms of action in these processes.
Nitrated Fatty Acids: Endogenous Anti-inflammatory Signaling Mediators
Journal of Biological Chemistry, 2006
Nitroalkene derivatives of linoleic acid (LNO 2 ) and oleic acid (OA-NO 2 ) are present; however, their biological functions remain to be fully defined. Herein, we report that LNO 2 and OA-NO 2 inhibit lipopolysaccharide-induced secretion of proinflammatory cytokines in macrophages independent of nitric oxide formation, peroxisome proliferator-activated receptor-γ activation, or induction of heme oxygenase-1 expression. The electrophilic nature of fatty acid nitroalkene derivatives resulted in alkylation of recombinant NF-κB p65 protein in vitro and a similar reaction with p65 in intact macrophages. The nitroalkylation of p65 by fatty acid nitroalkene derivatives inhibited DNA binding activity and repressed NF-κB-dependent target gene expression. Moreover, nitroalkenes inhibited endothelial tumor necrosis factor-α-induced vascular cell adhesion molecule 1 expression and monocyte rolling and adhesion. These observations indicate that nitroalkenes such as LNO 2 and OA-NO 2 , derived from reactions of unsaturated fatty acids and oxides of nitrogen, are a class of endogenous anti-inflammatory mediators.
Nitric oxide as a regulator of inflammatory processes
Nitric oxide (NO) plays an important role in mediating many aspects of inflammatory responses. NO is an effector molecule of cellular injury, and can act as an anti-oxidant. It can modulate the release of various inflammatory mediators from a wide range of cells participating in inflammatory responses (e.g., leukocytes, macrophages, mast cells, endothelial cells, and platelets). It can modulate blood flow, adhesion of leukocytes to the vascular endothelium and the activity of numerous enzymes, all of which can have an impact on inflammatory responses. In recent years, NO-releasing drugs have been developed, usually as derivatives of other drugs, which exhibit very powerful anti-inflammatory effects.
Nitration of arachidonic acid (AA) to nitroarachidonic acid (AANO 2 ) leads to anti-inflammatory intracellular activities during macrophage activation. However, less is known about the capacity of AANO 2 to regulate the production of reactive oxygen species under proinflammatory conditions. One of the immediate responses upon macrophage activation involves the production of superoxide radical (O 2 À ) due to the NADPH-dependent univalent reduction of oxygen to O 2 À by the phagocytic NADPH oxidase isoform (NOX2), the activity of NOX2 being the main source of O 2 À in monocytes/macrophages.
Modulation of Nitric Oxide Synthesis in Inflammation
Arzneimittelforschung, 2011
The role of nitric oxide (NO) derived from constitutive (cNOS) and inducible (iNOS) nitric oxide synthase and its relationship to oxygenderived free radicals and prostaglandins was investigated in two models of inflammation namely, carrageenan granuloma air pouch (acute model) and Freund's adjuvant-induced arthritis (chronic model) in rats. Inflammation was assessed by measurement of NO and prostaglandin E 2 (PGE 2 ) levels and the lysosomal leakage of the enzyme N-acetyl-Β-Dglucosaminidase (NAG) into the exudate of the granuloma pouch 4 h after carrageenan injection. Evaluation of paw volume and determination of serum NO, lipid peroxide (LP) and PGE 2 levels were used for assessment of adjuvant-arthritis either after 4 days (early phase) or 16 days (late phase) of adjuvant injection. Results of the study showed that administration of either N G -nitro-L-aginine methyl ester (L-NAME) (nonselective cNOS/iNOS inhibitor) or aminoguanidine (AG) (selective iNOS inhibitor), prior to carrageenan injection or during development of adjuvant arthritis, caused a significant reduction in NO and PGE 2 levels and in the NAG activity of the granuloma inflammatory exudate, whereas a decrease in paw volume and in serum NO level were noticed in the adjuvant model as related to untreated rats. Similar treatment with Larginine failed to elaborate a significant change in the parameters measured. Other observations included: no noticeable differences between results of early and late phases of adjuvant arthritis; no clear correlation between NO, LP and PGE 2 levels in the adjuvant arthritis inflammation; and inability of the NOS inhibitors to modify the levels of serum LP that is increased during adjuvant-induced arthritis. These data give further evidence that NO is implicated in the development of both acute and chronic inflammation and that NOS inhibitors have potential anti-inflammatory activity. Further studies are required to unravel the mechanisms by which NO interacts with other mediators of inflammation.