title: Cellular and molecular mechanisms of the selective regulation of IL-12 production by 12/15-lipoxygenase.
abstract: IL-12 drives type I immune responses and can mediate chronic inflammation that leads to host defense as well as disease. Recently, we discovered a novel role for 12/15-lipoxygenase (12/15-LO) in mediating IL-12p40 expression in atherosclerotic plaque and in isolated macrophages. We now demonstrate that 12/15-LO regulates IL-12 family cytokine production in a cell-type and stimulus-restricted fashion. LPS-stimulated elicited peritoneal macrophages derived from 12/15-LO-deficient (Alox15) mice produced reduced IL-12 and IL-23 levels, but comparable amounts of several other inflammatory mediators tested. Furthermore, LPS stimulation triggered an increase in wild-type macrophage 12/15-LO activity, whereas pharmacological inhibition of 12/15-LO activity suppressed LPS-induced IL-12 production in wild-type macrophages. 12/15-LO-deficient macrophages also produced reduced levels of IL-12 in response to TLR2 stimulation, but not in response to CpG (TLR9) or CD40/CD40L-mediated activation. In contrast to our previous finding of reduced IL-12 production in the setting of atherosclerosis, we found that comparable IL-12 levels were produced in Alox15 and wild-type mice during an acute response to LPS in vivo. This paradox may be explained by normal production of IL-12 by 12/15-LO-deficient neutrophils and dendritic cells, which are major sources of IL-12 during acute inflammation. Finally, we detected selectively decreased association of the transcription factors IFN consensus sequence binding protein and NF-kappaB with the IL-12p40 promoter in 12/15-LO-deficient macrophages. Taken together, these findings reveal a highly selective pathway to IL-12 production that may prove a useful target in chronic inflammation while sparing the acute response to infection.
authors.affiliation: The Wistar Institute, Philadelphia, PA 19104, USA.
authors.forename: Melissa K
authors.initials: MK
authors.lastname: Middleton
authors.forename: Tanya
authors.initials: T
authors.lastname: Rubinstein
authors.forename: Ellen
authors.initials: E
authors.lastname: Puré
mesh_terms: D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000172:deficiency / Q000276:immunology / Q000378:metabolism*; D001093:Arachidonate 15-Lipoxygenase / Q000172:deficiency / Q000276:immunology / Q000378:metabolism*; D002478:Cells, Cultured; D016207:Cytokines / Q000032:analysis / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D050835:Interferon Regulatory Factors; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D018664:Interleukin-12 / Q000096:biosynthesis* / Q000276:immunology; D008262:Macrophage Activation / Q000276:immunology; D017737:Macrophages, Peritoneal / Q000276:immunology* / Q000378:metabolism; D008297:Male; D051379:Mice; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism; D021122:Protein Subunits / Q000096:biosynthesis / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000099185:Interferon Regulatory Factor-8
chemical_list: D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase; D016207:Cytokines; D050835:Interferon Regulatory Factors; D007371:Interferon-gamma; D018664:Interleukin-12; D016328:NF-kappa B; D021122:Protein Subunits; D000099185:Interferon Regulatory Factor-8; C475064:12-15-lipoxygenase