Cytochrome P-450 4F18 Is the Leukotriene B4 ω-1/ω-2 Hydroxylase in Mouse Polymorphonuclear Leukocytes

Abstract

, we have identified the enzyme that catalyzes the -1 and -2 oxidation of LTB 4 in mouse myeloid cells as CYP4F18. As determined by mass spectrometry, this enzyme catalyzes the conversion of LTB 4 to 19-OH LTB 4 and to a lesser extent 18-OH LTB 4 . Inhibition of CYP4F18 resulted in a marked increase in calcium flux and a 220% increase in the chemotactic response of mouse PMN to LTB 4 . CYP4F18 expression was induced in bone marrow-derived dendritic cells by bacterial lipopolysaccharide, a ligand for TLR4, and by poly(I⅐C), a ligand for TLR3. However, when bone marrow-derived myeloid dendritic cells trafficked to popliteal lymph nodes from paw pads, the expression of CYP4F18 was down-regulated. The results identify CYP4F18 as a critical protein in the regulation of LTB 4 metabolism and functional responses in mouse PMN and identify it as the functional orthologue of human PMN CYP4F3A.How polymorphonuclear leukocytes (PMN), 2 macrophages, and dendritic cells (DC) control the initiation and amplification of innate and adaptive immune responses is a critical question, and the 5-lipoxygenase product of arachidonic acid metabolism leukotriene B 4 (LTB 4 ) is central to the amplification process. LTB 4 is equal to the most potent chemoattractant known for myeloid cells (1-6) and is synthesized from arachidonic acid by the action and interactions of 5-lipoxygenase, the five-lipoxygenase-activating protein, and leukotriene A 4 hydrolase (7). LTB 4 mediates its activity in these cells via the high affinity G proteincoupled receptor BLT1 (8 -10).LTB 4 has been implicated in the pathogenesis of multiple inflammatory diseases including inflammatory bowel disease (11-14), glomerulonephritis (15, 16), allograft rejection in kidney transplant models (17, 18), and cardiac allograft rejection (19). Studies with knock-out mice for the five-lipoxygenase-activating protein combined with LTB 4 receptor antagonists have supported a role for LTB 4 in murine collagen arthritis (20), in the EAE model of multiple sclerosis (21), and in mediating a primate model of asthma (22). In atherosclerosis, 5-lipoxygenase has been identified as a risk gene in a mouse model, and 5-lipoxygenase-rich cells have been identified in atheroscleotic plaques of mice and humans (23, 24). Furthermore, a protein closely related to CYP4F3A, presumably a mouse member of the CYP4F family, was strongly induced in foam cells in mice (23). Blockade of BLT1 has been associated with decreased progression of atherosclerosis in APOE1Ϫ/Ϫ mice (25,26). Understanding the molecular basis of LTB 4 signal termination is critical to elucidating how animals control the amplitude of inflammation in LTB 4 -dependent settings.There are two general cellular mechanisms that have the potential to terminate the responsiveness to LTB 4 and to all other chemoattractant molecules for G protein-coupled receptors. The first is the enzymatic metabolism of ligands. The second is receptor desensitization, which is based on G protein-coupled receptor kinases and ␤-arrestin (27, 28). The desensi...

Maresin-like Lipid Mediators Are Produced by Leukocytes and Platelets and Rescue Reparative Function of Diabetes-Impaired Macrophages

“…It is very likely that the 22-hydroxylation of DHA or 14 S/R -HDHA for 14,22-diHDHA biosynthesis are catalyzed by P450 CYP4 family as these P450s are responsible for ϖ-hydroxylation of fatty acids and eicosanoids (Kikuta et al, 2002). Moreover, CYP4F is expressed in human leukocytes (Kikuta et al, 2004); mouse CYP4F18 is an orthologue of human PMN CYP4F3A (Christmas et al, 2006); CYP1A1, 2U1, 2J2, 4A11, 4F2, and 5A1were expressed as both proteins and mRNAs in PLT (Jarrar et al, 2013). Systematic studies are needed to define the specific P450s responsible for 14,22-diHDHA formation in leukocytes and PLT.…”

Leukotriene B4 Augments and Restores FcγRs-dependent Phagocytosis in Macrophages

“…Although there are no reports on LTB 4 production in response to Fc␥Rs signaling, it is reasonable to consider that phospholipase C␥-dependent calcium mobilization leads to LTB 4 production upon cross-linking of Fc␥Rs by immune complexes. Macrophages are known to express CYP4F18, an LTB 4 -oxidizing cytochrome P450 enzyme (34). Thus, LTB 4 produced during phagocytosis might be oxidized rapidly by this enzyme under our experimental conditions.…”

Role of Cytochrome P450s in Inflammation

“…It has lower activity for LTB 4 and higher activity for arachidonic acid, compared to CYP4F3A. The mouse homologue of CYP4F3A was identified as Cyp4f18 (Christmas et al, 2006), and knockout of Cyp4f18 abolishes LTB 4 hydroxylase activity in mouse neutrophils (Winslow et al, 2014). However, there are significant differences between mice and humans.…”