title: Pyrin levels in human monocytes and monocyte-derived macrophages regulate IL-1beta processing and release.
abstract: Macrophages and their precursors, monocytes, are key cells involved in the innate immune response. Although both monocytes and macrophages produce caspase-1, the key enzyme responsible for pro-IL-1beta processing; macrophages are limited in their ability to activate the enzyme and release functional IL-1beta. In this context, because mutations in the pyrin gene (MEFV) cause the inflammatory disorder familial Mediterranean fever, pyrin is believed to regulate IL-1beta processing. To determine whether variations in pyrin expression explain the difference between monocytes and macrophages in IL-1beta processing and release, pyrin was studied in human monocytes and monocyte-derived macrophages. Although monocytes express pyrin mRNA and protein, which is readily inducible by endotoxin, monocyte-derived macrophages express significantly less pyrin mRNA and protein. Pyrin levels directly correlated with IL-1beta processing in monocytes and macrophages; therefore, we asked whether pyrin might promote IL-1beta processing and release. HEK293 cells were transfected with pyrin, caspase-1, apoptotic speck protein with a caspase recruitment domain, and IL-1beta. Pyrin induced IL-1beta processing and release in a dose-dependent manner. Conversely, pyrin small interference RNA suppressed pro-IL-1beta processing in both THP-1 cells and fresh human monocytes. In summary, both pyrin expression and IL-1beta processing and release are diminished upon the maturation of monocytes to macrophages. When pyrin is ectopically expressed or silenced, IL-1beta processing and release parallels the level of pyrin. In conclusion, in the context of endotoxin-induced activation of mononuclear phagocytes, pyrin augments IL-1beta processing and release.
authors.affiliation: Davis Heart and Lung Research Institute, Ohio State University, Columbus, OH 43210, USA.
authors.forename: Sudarshan
authors.initials: S
authors.lastname: Seshadri
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Duncan
authors.forename: Judith M
authors.initials: JM
authors.lastname: Hart
authors.forename: Mikhail A
authors.initials: MA
authors.lastname: Gavrilin
authors.forename: Mark D
authors.initials: MD
authors.lastname: Wewers
mesh_terms: D015153:Blotting, Western; D020170:Caspase 1 / Q000276:immunology / Q000378:metabolism; D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000276:immunology / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D053583:Interleukin-1beta / Q000276:immunology / Q000378:metabolism*; D008264:Macrophages / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D009000:Monocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D000071198:Pyrin; D012333:RNA, Messenger / Q000032:analysis; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: D003598:Cytoskeletal Proteins; D053583:Interleukin-1beta; C000604192:MEFV protein, human; D000071198:Pyrin; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D020170:Caspase 1