[Show abstract][Hide abstract] ABSTRACT: We investigated and compared the mechanisms by which two dust mite proteolytic allergens, Der p 1 and Der p 3, and a peptide
agonist of proteinase-activated receptor 2 (PAR2AP) trigger interleukin (IL)-8 release from human pulmonary epithelial cells (A549). Although all three stimuli tested induced
the up-regulation of IL-8 (mRNA and protein), the Der p 1-mediated signaling events did not exactly match those induced by
PAR2AP and Der p 3. First, Der p 1 was less effective in stimulating IL-8 gene transcriptional activity than PAR2AP and Der p 3. Second, Der p 1-mediated IL-8 expression was mainly dependent on NF-κB, whereas Der p 3 and PAR2AP regulated IL-8 expression through the activation of both NF-κB and AP-1. Third, although all three MAP kinases, ERK1/2,
p38, and JNK, were activated, Der p 1 induced IL-8 release exclusively via the ERK1/2 signaling pathway, whereas PAR2AP and Der p 3 also involved the other kinases. Fourth, in HeLa cells, Der p 1 was able to up-regulate IL-8 secretion independent
of PAR2 expression, and in contrast with PAR2AP and Der p 3, Der p 1 was unable to affect calcium signaling via PAR2 in PAR2-expressing KNRK cells. Finally, cleavage by Der p 1 of a synthetic peptide representing the N-terminal activation-cleavage
site of PAR2 did not release a high potency activator of PAR2 as does Der p 3. We conclude that Der p 1 (but not Der p 3)-induced IL-8 production in A549 epithelial cells is independent
of PAR2 activation.