Regulation of interleukin‐33 and thymic stromal lymphopoietin in human nasal fibroblasts by proinflammatory cytokines

Abstract

Epithelial-derived interleukin (IL)-33 and thymic stromal lymphopoietin (TSLP) are critical regulators of innate and adaptive immune responses associated with Th2 cytokine-mediated inflammation, including allergic rhinitis. IL-33 and TSLP are expressed not only in epithelial cells but also fibroblasts, endothelial cells, and smooth muscle cells at nasal mucosal sites. However, the role and the regulation of IL-33 and TSLP in nasal fibroblasts remain unknown. We investigated the signal transduction regulation of IL-33 and TSLP induced by proinflammatory cytokines in nasal fibroblasts. In vitro, prospective study. Nasal fibroblasts were derived from human nasal mucosa without allergic rhinitis. Expression of IL-33 and TSLP was examined in nasal fibroblasts treated with proinflammatory cytokines IL-1β or tumor necrosis factor (TNF)-α after pretreatment with or without various inhibitors of signal transduction pathways. In nasal fibroblasts, both Western blotting and reverse transcriptase-polymerase chain reaction demonstrated that expression of mRNAs and proteins of IL-33 and TSLP was increased by treatment with IL-1β or TNF-α. Immunostaining revealed that IL-33-positive nuclei were markedly increased by the treatment with IL-1β or TNF-α. Enzyme-linked immunosorbent assay showed that fibroblast-released TSLP was significantly increased by treatment with IL-1β or TNF-α. The upregulation of both IL-33 and TSLP proteins by treatment with IL-1β was prevented by inhibitors of pan- protein kinase C (PKC), p38 mitogen-activated protein kinase, and nuclear factor (NF)-κB. In the cells treated with TNF-α, upregulation of IL-33 protein was prevented by inhibitors of phosphoinositide 3-kinase (PI3K), c-Jun N-terminal kinase (JNK), and NF-κB, whereas upregulation of TSLP protein was prevented by inhibitors of pan-PKC, PI3K, JNK, and NF-κB. Expression of IL-33 and TSLP in nasal fibroblasts was regulated via distinct signal transduction pathways including NF-κB.