title: Differing caspase-1 activation states in monocyte versus macrophage models of IL-1beta processing and release.
abstract: The release of IL-1beta as an active, mature cytokine requires proteolytic processing by caspase-1, which is recruited to signaling complexes that facilitate its autocatalytic proteolysis and activation. Caspase-1 processing has been characterized in human monocyte and murine macrophage model systems, and comparative analyses indicate significant mechanistic differences in caspase-1 activation by these cell types. In this study, we used an in vitro processing assay to compare caspase-1 activation in THP-1 human monocytes vs. Bac1.2F5 murine macrophages. These in vitro caspase-1 and IL-1beta processing reactions indicated a higher rate of constitutive caspase-1 activation in lysates from THP-1 vs. Bac1 cells. Transfer of small amounts of THP-1 lysate to Bac1 lysate rapidly increased in vitro procaspase-1 and proIL-1beta processing in the latter preparation. The transferable activation factor(s) was heat-labile, > or =10 kDa, and unaffected by immunodepletion of procaspase-1 from the THP-1 lysate. This transactivating effect of THP-1 lysate on processing in Bac1 lysates could be mimicked by addition of purified recombinant human caspase-1. The constitutive caspase-1 and IL-1beta processing reactions in THP-1 lysates were insensitive to pharmacological blockade by the tyrphostin, AG126, and the phospholipase A2 inhibitor bromoenol lactone (BEL); contrarily, the same processing reactions were inhibited in lysates from Bac1 cells pretreated with either AG126 or BEL. These observations indicate significant biochemical differences in the assembly and regulation of caspase-1 signaling complexes within human monocyte and murine macrophage models of inflammatory activation. These differences need to be considered when comparing or pharmacologically manipulating IL-1beta processing and release in various model systems.
authors.affiliation: Department of Pathology, Case School of Medicine, 2109 Adelbert Road, Cleveland, OH, 44106, USA.
authors.forename: J Michelle
authors.initials: JM
authors.lastname: Kahlenberg
authors.forename: George R
authors.initials: GR
authors.lastname: Dubyak
mesh_terms: D000818:Animals; D020170:Caspase 1 / Q000276:immunology* / Q000378:metabolism; D002460:Cell Line; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000276:immunology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D006801:Humans; D007113:Immunity, Innate / Q000187:drug effects / Q000276:immunology; D007375:Interleukin-1 / Q000276:immunology* / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D009000:Monocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D009281:Naphthalenes / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism; D054467:Phospholipases A2; D011753:Pyrones / Q000494:pharmacology; D020032:Tyrphostins / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology
chemical_list: D017077:Culture Media, Conditioned; D007375:Interleukin-1; D008070:Lipopolysaccharides; D009281:Naphthalenes; D011753:Pyrones; D020032:Tyrphostins; C069028:AG 127; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D010741:Phospholipases A; D054467:Phospholipases A2; D020170:Caspase 1