Persistent nuclear factor-kappa B activation in Ucp2-/- mice leads to enhanced nitric oxide and inflammatory cytokine production.

Bai Y, Onuma H, Bai X, Medvedev AV, Misukonis M, Weinberg JB, Cao W, Robidoux J, Floering LM, Daniel KW, Collins S
J Biol Chem. 2005 280 (19): 19062-9

PMID: 15757894 · PMCID: PMC1382174 · DOI:10.1074/jbc.M500566200

One of the phenotypes of mice with targeted disruption of the uncoupling protein-2 gene (Ucp2-/-) is greater macrophage phagocytic activity and free radical production, resulting in a striking resistance to infectious microorganisms. In this study, the molecular mechanisms of this enhanced immune response were investigated. We found that levels of nitric oxide measured in either plasma or isolated macrophages from Ucp2-/- mice are significantly elevated in response to bacterial lipopolysaccharide challenge compared with similarly treated Ucp2+/+ mice. Likewise, expression of inducible nitric-oxide synthase and inflammatory cytokines is higher in Ucp2-/- mice in vivo and in vitro. Key steps in the activation cascade of nuclear factor (NF)-kappa B, including I kappa B kinase and nuclear translocation of NF-kappa B subunits, are all remarkably enhanced in Ucp2-/- mice, most notably even under basal conditions. The elevated basal activity of I kappa B kinase in macrophages from Ucp2-/- mice can be blocked by cell-permeable inhibitors of superoxide and hydrogen peroxide generation, but not by a specific inhibitor for inducible nitric-oxide synthase. Isolated mitochondria from Ucp2-/- cells produced more superoxide/hydrogen peroxide. We conclude that mitochrondrially derived reactive oxygen from Ucp2-/- cells constitutively activates NF-kappa B, resulting in a "primed" state to both potentiate and amplify the inflammatory response upon subsequent stimulation.

MeSH Terms (41)

Algorithms Animals Blotting, Northern Blotting, Western Cyclooxygenase 2 Cytokines Cytosol Enzyme-Linked Immunosorbent Assay Enzyme Activation Free Radicals Genotype Hydrogen Peroxide I-kappa B Kinase Inflammation Ion Channels Lipopolysaccharides Macrophages Male Membrane Transport Proteins Mice Mice, Inbred C57BL Mice, Transgenic Mitochondria Mitochondrial Proteins Models, Biological NADPH Oxidases NF-kappa B Nitrates Nitric Oxide Nitric Oxide Synthase Nitrites Oligonucleotide Array Sequence Analysis Oxygen Phenotype Prostaglandin-Endoperoxide Synthases Protein-Serine-Threonine Kinases Spleen Subcellular Fractions Superoxides Time Factors Uncoupling Protein 2

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