House Dust Mite Allergen Der f 2-induced Phospholipase D1 Activation Is Critical for the Production of Interleukin-13 through Activating Transcription Factor-2 Activation in Human Bronchial Epithelial Cells

The purpose of this study was to identify the role of phospholipase D1 (PLD1) in Der f 2-induced interleukin (IL)-13 production. The major house dust mite allergen, Der f 2, increased PLD activity in human bronchial epithelial cells (BEAS-2B), and dominant negative PLD1 or PLD1 siRNA decreased Der f 2-induced IL-13 expression and production. Treatment of Der f 2 activated the phospholipase C gamma (PLC gamma)/protein kinase C alpha (PKC alpha)/p38 MAPK pathway. Der f 2-induced PLD activation was attenuated by PLC gamma inhibitors (U73122 and PAO), PKC alpha inhibitors (RO320432 and GO6976), and p38 MAPK inhibitors (SB203580 and SB202190). These results indicate that PLC gamma, PKC alpha, and p38 MAPK act as upstream activators of PLD in Der f 2-treated BEAS-2B cells. Furthermore, expression and production of IL-13 increased by Der f 2 were also blocked by inhibition of PLC gamma, PKC alpha, or p38 MAPK, indicating that IL-13 expression and production are related to a PLC gamma/PKC alpha/p38 MAPK pathway. We found that activating transcription factor-2 (ATF-2) was activated by Der f 2 in BEAS-2B cells and activation of ATF-2 was controlled by PLD1. When ATF-2 activity was blocked with ATF-2 siRNA, Der f 2-induced IL-13 expression and production were decreased. Thus, ATF-2 might be one of the transcriptional factors for the expression of IL-13 inDer f 2-treated BEAS-2B cells. Taken together, PLD1 acts as an important regulator in Der f 2-induced expression and production of IL-13 through activation of ATF-2 in BEAS-2B cells.This work was supported by Grant E00273 (2007) from the Korea Research Foundation and by Grant RB-2008-026-01000-0 from the Korea Science and Engineering Foundation funded by the Ministry of Education, Science, and Technology (MEST)