B lymphocyte stimulator (BLyS), B cell activating factor (BAFF), a member of the tumor necrosis factor ligand superfamily has potent co-stimulatory activity on B cells, and BLyS-production in the airway mucosa is of potential importance as it triggers innate and adaptive immune responses. To investigate whether airway fibroblast could express BLyS, we examined BLyS-expression in human nasal airway fibroblasts and compared to its expression in tonsillar and skin fibroblasts as well as the effect of the Toll-like receptor (TLR) ligands on that in human nasal airway fibroblasts. The expression of BLyS by nasal fibroblasts in the presence of polyinocinic-polycytidykic acid (poly(I:C)) was markedly induced, to a level of more than 100 times higher than that observed in the absence of poly(I:C). In order to demonstrate the intracellular pathways involved in poly(I:C)-induced BLyS-expression, we used specific inhibitors of phosphatidylinositol 3-kinase (PI3-kinase), spleen tyrosine kinase (Syk), p38 mitogen-activated protein kinase (p38 MAPK), c-Jun N-terminal kinase (JNK), and extracellular-signal related kinase (ERK)-signaling in these events. Pre-incubation with the PI3-kinase inhibitor LY294002 or Wortmanin reversed the poly(I:C)-induced production and expression of BLyS. Syk kinase inhibitor Piceatannol partially reduced its production and expression. Thus, we were able to show that PI3-kinase signaling is directly involved in poly(I:C)-induced BLyS-expression in nasal airway fibroblasts. These results indicate that human nasal airway fibroblasts strongly induce BLyS-expression and production by poly(I:C) through PI3-K signaling during airway immune responses.
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