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

Objectives/Hypothesis: 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. Study Design: In vitro, prospective study. Methods: 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-1 beta or tumor necrosis factor (TNF)-a after pretreatment with or without various inhibitors of signal transduction pathways. Results: 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-1 beta or TNF-a. Immunostaining revealed that IL-33positive nuclei were markedly increased by the treatment with IL-1 beta or TNF-a. Enzyme-linked immunosorbent assay showed that fibroblast-released TSLP was significantly increased by treatment with IL-1 beta or TNF-a. The upregulation of both IL-33 and TSLP proteins by treatment with IL-1 beta was prevented by inhibitors of pan- protein kinase C (PKC), p38 mitogen-activated protein kinase, and nuclear factor (NF)-?B. In the cells treated with TNF-a, upregulation of IL-33 protein was prevented by inhibitors of phosphoinositide 3-kinase (PI3K), c-Jun N-terminal kinase (JNK), and NF-?B, whereas upregulation of TSLP protein was prevented by inhibitors of pan-PKC, PI3K, JNK, and NF-?B. Conclusions: Expression of IL-33 and TSLP in nasal fibroblasts was regulated via distinct signal transduction pathways including NF-?B.