Regulation of phagosomal iron release from murine macrophages by nitric oxide.
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ABSTRACT:
SUBMITTER: Mulero V
PROVIDER: S-EPMC1222663 | biostudies-other | 2002 Jul
REPOSITORIES: biostudies-other
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Project description:Excess nitric oxide (NO) production occurs in several pathological states, including neurodegeneration, ischemia, and inflammation, and is generally accompanied by increased oxidative/nitrosative stress. Carnosine [?-alanine-histidine (?-Ala-His)] has been reported to decrease oxidative/nitrosative stress-associated cell damage by reducing the amount of NO produced. In this study, we evaluated the effect of carnosine on NO production by murine RAW 264.7 macrophages stimulated with lipopolysaccharides?+?interferon-?. Intracellular NO and intracellular and extracellular nitrite were measured by microchip electrophoresis with laser-induced fluorescence and by the Griess assay, respectively. Results showed that carnosine causes an apparent suppression of total NO production by stimulated macrophages accompanied by an unexpected simultaneous drastic increase in its intracellular low toxicity endproduct, nitrite, with no inhibition of inducible nitric oxide synthase (iNOS). ESI-MS and NMR spectroscopy in a cell-free system showed the formation of multiple adducts (at different ratios) of carnosine-NO and carnosine-nitrite, involving both constituent amino acids (?-Ala and His) of carnosine, thus providing a possible mechanism for the changes in free NO and nitrite in the presence of carnosine. In stimulated macrophages, the addition of carnosine was also characterized by changes in the expression of macrophage activation markers and a decrease in the release of IL-6, suggesting that carnosine might alter M1/M2 macrophage ratio. These results provide evidence for previously unknown properties of carnosine that modulate the NO/nitrite ratio of stimulated macrophages. This modulation is also accompanied by changes in the release of pro-inflammatory molecules, and does not involve the inhibition of iNOS activity.
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Project description:Classical stimulation of macrophages (MLPS/IFNγ) elicits the expression of inducible nitric oxide synthase (iNOS), generating large amounts of nitric oxide (NO) and inhibiting respiration. Consequent upregulation of glycolysis and a disrupted tricarboxylic acid (TCA) cycle underpin this switch to a pro-inflammatory phenotype. Here we show that the NOS cofactor tetrahydrobiopterin (BH4) modulates key aspects of metabolic remodelling in activated bone-marrow-derived macrophages (BMDMs) via NO production. Using two complementary mouse models that each lack the capacity for inducible NO generation, through different mechanisms, we reveal that NO regulates macrophage respiratory function via changes in the abundance of critical N-module subunits in Complex I, by HIF1α-mediated glycolytic remodelling, and by modulating levels of the critical TCA cycle metabolites, and inflammatory mediators, citrate, succinate, and itaconate. Taken together, our findings reveal new critical roles for iNOS-derived NO that are required for metabolic remodelling and cytokine production in macrophage inflammatory responses.
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