Cockroach Allergen per a 7 Down-Regulates Expression of Toll-Like Receptor 9 and IL-12 Release from P815 Cells Through PI3K and MAPK Signaling Pathways

Background: As a major source of indoor allergens, cockroach causes perennial rhinitis and asthma. Recently, cockroach feces were reported to contain TLR2 agonist, which could directly activate neutrophils to release cytokines. CpG oligodeoxynucleotide (ODN), a Toll-like receptor (TLR)9 activator was also found to induce proinflammatory cytokine release from mast cells. However, influence of specific cockroach allergen on Th1 cytokine release and expression of TLR9 in mast cells remains uninvestigated. Methods: To investigate effects of Per a 7 on TLR expression and cytokine release from mast cells and their cell signaling mechanisms, P815 cells were challenged by recombinant Per a 7 (rPer a 7), and expression of TLR9 mRNA and protein was assessed mainly by real time PCR and flow cytometry analysis. Detection of phosphorylation of cell signaling components was performed with Western blotting technique. Results: The results showed that rPer a 7 induced up to 72 and 46% down-regulation of expression of TLR9 mRNA and protein, respectively following 16 h incubation period. It induced also approximately 41.1% reduction of IL-12 release. When PD98059, U0126 and LY294002 were pre-incubated with the cells for 30 min they diminished rPer a 7 induced reduction of TLR9 expression and IL-12 release, indicating these events are via activation of ERK and PI3K/Akt signaling pathways. Conclusion: Reduction of IL-12 production and expression of TLR9 in P815 mastocytoma cells by Per a 7 suggests that this major cockroach allergen might contribute to the development of cockroach allergy. Copyright (C) 2012 S. Karger AG, Basel