Background Cockroaches are potent aeroallergens associated with asthma. Several reports suggest that a novel group of G proteinlinked receptors, protease-activated receptors (PARs), may be involved in the intracellular signaling pathway induced by aeroallergens of the epithelial cells. Objective To investigate the mechanisms of American cockroach allergens (CraA) on interleukin 8 (IL-8) in human pulmonary epithelial cells. Methods Protease activities of CraA were quantified by the Azocoll method. The gene and protein expressions of IL-8 from CraA-stimulated A549 cells were quantified by real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. The activity of different mitogen-activated protein kinases (MAPKs) was assessed by Western blot. Results CraA-induced A549 cell IL-8 secretion in a dose-dependent manner at both the messenger RNA and protein levels. CraA-induced IL-8 secretion can be blocked by serine protease inhibitors, phenylmethane sulfonyl fluoride, and aprotinin but not by other protease inhibitors. Blocking antibodies against the cleavage sites of PAR-2 and PAR-3, but not of PAR-1, inhibited CraA-induced IL-8 production. CraA induced significant PAR-2 and PAR-3 messenger RNA upregulation and extracellular-regulated kinase (ERK/1/2) and Jun N-terminal kinase (JNK) phosphorylation but not p38 MAPK. Furthermore, ERK1/2 (U0126) and JNK (SP600125) inhibitors inhibited CraA-induced IL-8 secretion by 100% and 45%, respectively. Conclusions Both PAR-2 and PAR-3 might play a role in CraA-induced IL-8 secretion from human airway epithelial cells. It signals mainly through the ERK1/2 and partly from the JNK pathways. The key receptors and signaling molecules mediate cytokine release from the respiratory epithelium and can be potential therapeutic targets in treating cockroach allergy.
All Science Journal Classification (ASJC) codes
- Immunology and Allergy
- Pulmonary and Respiratory Medicine