Abstract
CYP4Fs were first identified as enzymes that catalyze hydroxylation of leukotriene B4 (LTB4). CYP4F18 has an unusual expression in neutrophils and was predicted to play a role in regulating LTB4-dependent inflammation. We compared chemotaxis of wild-type and Cyp4f18 knockout neutrophils using an in vitro assay. There was no significant difference in the chemotactic response to LTB4, but the response to complement component C5a increased 1.9-2.25-fold in knockout cells compared to wild-type (P < 0.01). This increase was still observed when neutrophils were treated with inhibitors of eicosanoid synthesis. There were no changes in expression of other CYP4 enzymes in knockout neutrophils that might compensate for loss of CYP4F18 or lead to differences in activity. A mouse model of dextran sodium sulfate colitis was used to investigate the consequences of increased C5a-dependent chemotaxis in vivo, but there was no significant difference in weight loss, disease activity, or colonic tissue myeloperoxidase between wild-type and Cyp4f18 knockout mice. This study demonstrates the limitations of inferring CYP4F function based on an ability to use LTB4 as a substrate, points to expanding roles for CYP4F enzymes in immune regulation, and underscores the in vivo challenges of CYP knockout studies.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Bone Marrow Cells / drug effects
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Bone Marrow Cells / immunology
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Bone Marrow Cells / pathology
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Chemokine CXCL1 / pharmacology
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Chemotaxis, Leukocyte / drug effects*
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Colitis / chemically induced
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Colitis / genetics
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Colitis / immunology*
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Colitis / pathology
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Complement C5a / pharmacology*
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Cytochrome P-450 Enzyme System / deficiency
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Cytochrome P-450 Enzyme System / genetics
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Cytochrome P-450 Enzyme System / immunology*
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Cytochrome P450 Family 4
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Dextran Sulfate
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Female
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Gene Expression Profiling
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Gene Expression Regulation
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Humans
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Isoenzymes / genetics
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Isoenzymes / immunology
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Leukotriene B4 / pharmacology
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Neutrophils / drug effects
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Neutrophils / immunology*
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Neutrophils / pathology
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Peptides / pharmacology
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Peroxidase / genetics
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Peroxidase / immunology
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Primary Cell Culture
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Receptors, Formyl Peptide / antagonists & inhibitors
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Receptors, Formyl Peptide / genetics
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Receptors, Formyl Peptide / immunology
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Weight Loss / drug effects
Substances
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CYP4F18 protein, mouse
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Chemokine CXCL1
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Cxcl1 protein, mouse
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Isoenzymes
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Peptides
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Receptors, Formyl Peptide
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Leukotriene B4
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Complement C5a
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Cytochrome P-450 Enzyme System
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Dextran Sulfate
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Peroxidase
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Cytochrome P450 Family 4