title: Inducible IL-33 expression by mast cells is regulated by a calcium-dependent pathway.
abstract: IL-33 is an IL-1 family cytokine that displays dual functions: a cytokine via its receptor, T1/ST2, or a chromatin-binding factor within the nucleus. Functionally, it promotes Th2-associated immunity by enhancing the activation and survival of several cell types. However, the pathways regulating IL-33 expression are still unclear. Although several cells display constitutive expression of IL-33, we showed previously that mast cells expressed low levels of IL-33 constitutively but that IL-33 was induced upon IgE-mediated activation. This was mediated via a calcium-dependent mechanism. In this study, we define the pathway through which this inducible IL-33 is regulated. Importantly, this pathway does not alter expression in cells with high constitutive IL-33 expression, such as epithelial cells or fibroblasts. Our data show that, upstream of calcium, inhibition of PI3K and Sphk activity decreases inducible IL-33 expression to IgE/Ag activation. Additionally, expression of Sphk1 short hairpin RNA prevents upregulation of IL-33 expression. Downstream of calcium, NFAT activity is necessary and sufficient for inducible IL-33 expression. We also demonstrate calcium-dependent transcription from two regions of the IL-33 gene that contain putative NFAT-binding sites, one upstream of exon 1 and one upstream of the start site. Interestingly, we show that blocking other calcium pathways, including inositol triphosphate receptor, or NF-κB inhibits IgE-driven IL-1β, another IL-1 family cytokine, but it has no influence on inducible IL-33 expression. In summary, our data demonstrate cell-specific differences in the regulation of IL-33 expression and define a pathway critical for the expression of inducible IL-33 by mast cells upon their activation.
authors.affiliation: Division of Allergy-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Chia-Lin
authors.initials: CL
authors.lastname: Hsu
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Bryce
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000276:immunology; D001854:Bone Marrow Cells / Q000276:immunology / Q000378:metabolism; D002118:Calcium / Q000502:physiology*; D020013:Calcium Signaling / Q000276:immunology; D002460:Cell Line; D003432:Cross-Linking Reagents / Q000378:metabolism; D006801:Humans; D007073:Immunoglobulin E / Q000502:physiology; D000067596:Interleukin-33; D007378:Interleukins / Q000096:biosynthesis* / Q000235:genetics; D008407:Mast Cells / Q000276:immunology* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000502:physiology; D050778:NFATC Transcription Factors / Q000502:physiology; D041681:NIH 3T3 Cells; D012333:RNA, Messenger / Q000096:biosynthesis; D017455:Receptors, IgE / Q000378:metabolism / Q000502:physiology; D015533:Transcriptional Activation / Q000276:immunology
chemical_list: D003432:Cross-Linking Reagents; C506535:Il33 protein, mouse; D000067596:Interleukin-33; D007378:Interleukins; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D012333:RNA, Messenger; D017455:Receptors, IgE; D007073:Immunoglobulin E; D002118:Calcium