Objective: Against recent reports concerning cytokine or chemokine in mouse or rat inner ear cells, it is almost unknown whether human inner ear cells would produce cytokine or chemokine. We have for the first time established the human inner-ear-derived fibroblasts from endolymphatic sac.
Methods: The expression levels of Toll-like receptors (TLRs) in human endolymphatic sac fibroblasts, and the effect on cytokine or chemokine production of the TLR ligands have been examined. To demonstrate the intracellular pathways involved in the regulation of cytokine-production, we used specific inhibitors of c-Jun N-terminal kinase (JNK), extracellular signal-related kinase (ERK), p38 mitogen-activated protein kinase (p38 MAPK)-signaling and N-acetyl-l-cysteine (NAC).
Results: TLR 2, 3, 4 and 9 were highly expressed in human endolymphatic sac fibroblasts. The TLR 3 ligand, polyinosinic-polycytidylic acid (poly(I:C)) significantly enhanced the secretion of thymic stromal lymphopoietin (TSLP), B lymphocyte stimulator (BLyS), IFNγ-inducible protein 10 (IP-10), and macrophage inflammatory protein 1 alpha (MIP-1α) from the cells. The inhibitor of JNK strongly reduced the poly(I:C)-induced TSLP-production. The antioxidant drug, NAC also reduced the TSLP-production in fibroblasts stimulated with poly(I:C).
Conclusion: Our findings suggest human inner-ear-endolymphatic sac derived fibroblasts can produce the cytokine and chemokine in response to TLR ligands and play a certain role during the initiation of an immune response.
Keywords: Cytokine; Endolymphatic sac; Fibroblasts; Inner ear; Toll-like receptor ligands.
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