title: Nonredundant roles for leukotriene B4 receptors BLT1 and BLT2 in inflammatory arthritis.
abstract: Lipid mediators derived from arachidonic acid through the cyclooxygenase and lipoxygenase pathways are known to be important mediators of inflammation. Studies in mouse models demonstrated an important role for the high-affinity leukotriene B(4) receptor BLT1 in arthritis, atherosclerosis, and asthma. BLT2, a low-affinity leukotriene B(4) receptor, was also shown to be a high-affinity receptor for cyclooxygenase-1 derived 12(S)-hydroxyheptadeca-5Z, 8E, 10E-trienoic acid. However, its biochemical activities and physiological roles remain unknown. In this study, we developed mice deficient in BLT2 by targeted disruption. The BLT2(-/-) mice developed normally, and analysis of immune cells showed that disruption of BLT2 did not alter BLT1 expression or function. Mast cells from the C57BL/6 mice but not from the BLT2(-/-) mice showed intracellular calcium mobilization in response to 12(S)-hydroxyheptadeca-5Z, 8E, 10E-trienoic acid. In an autoantibody-induced inflammatory arthritis model, the BLT2(-/-) mice showed reduced incidence and severity of disease, including protection from bone and cartilage loss. Reciprocal bone marrow transplant experiments identified that loss of BLT2 expression on a bone marrow-derived cell lineage offers protection against severe disease. Thus, BLT2, a unique receptor for 5-lipoxygenase- and cyclooxygenase-1-derived lipid mediators, represents a novel target for therapies directed at treating inflammation associated with arthritis.
authors.affiliation: James Graham Brown Cancer Center, Louisville, KY 40202, USA.
authors.forename: Steven P
authors.initials: SP
authors.lastname: Mathis
authors.forename: Venkatakrishna R
authors.initials: VR
authors.lastname: Jala
authors.forename: David M
authors.initials: DM
authors.lastname: Lee
authors.forename: Bodduluri
authors.initials: B
authors.lastname: Haribabu
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D001172:Arthritis, Rheumatoid / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D001854:Bone Marrow Cells / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D002634:Chemotaxis, Leukocyte / Q000235:genetics / Q000276:immunology; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism / Q000502:physiology*; D007719:Knee Joint / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D007975:Leukotriene B4 / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D018102:Receptors, Leukotriene B4 / Q000096:biosynthesis / Q000172:deficiency / Q000502:physiology*
chemical_list: D018836:Inflammation Mediators; C503704:Ltb4r1 protein, mouse; C412867:Ltb4r2 protein, mouse; D018102:Receptors, Leukotriene B4; D007975:Leukotriene B4