Cockroach proteases increase IL-8 expression in human bronchial epithelial cells via activation of protease-activated receptor (PAR)-2 and extracellular-signal-regulated kinase.
BACKGROUND
We have shown that serine proteases in German cockroach extract increase TNF-alpha-induced expression of IL-8 in human bronchial epithelial cells. The mechanism by which cockroach proteases regulate cytokine expression is unknown; however, protease-activated receptors (PARs) might play a role.


OBJECTIVE
We sought to determine the role of PARs and extracellular-signal-regulated kinase (ERK) in cockroach-induced regulation of IL-8 expression.


METHODS
16HBE14o- human bronchial epithelial cells were treated with the specific PAR-1 and PAR-2 agonists, TFRIFD and SLIGKV, respectively. IL-8 transcription was assessed by transiently transfecting cells with a luciferase-tagged IL-8 promoter construct, and in some cases, dominant-negative expression vectors. To block PAR cleavage, antibodies against the cleavage region of PAR-1 and PAR-2 were used. ERK phosphorylation was determined by Western blot.


RESULTS
Although both PAR-1 and PAR-2 were endogenously expressed in 16HBE14o- cells, selective activation of PAR-2 but not PAR-1 mimicked the effect of cockroach extract on IL-8 expression. Using a blocking antibody against cleavage of PAR-2 but not PAR-1 attenuated cockroach-extract-induced responses, suggesting that cockroach proteases cleave PAR-2. Treatment of cells with cockroach extract and SLIGKV each increased phosphorylation of ERK. Chemical or genetic inhibition of Ras and mitogen-activated protein kinase/ERK (MEK), upstream activators of ERK, each attenuated cockroach- and PAR-2-induced IL-8 transcription.


CONCLUSIONS
Cockroach proteases and PAR-2 activation synergistically increase TNF-alpha-induced IL-8 transcription via activation of ERK. These data suggest an important role for PAR-2 and ERK activation in the regulation of cytokine expression in airway epithelium in response to cockroach proteases.
Page
Kristen
K
Department of Pediatrics, Cincinnati Children's Hospital, Cincinnati, OH 45229, USA.
Strunk
Valerie S
VS
Hershenson
Marc B
MB
D000485:Allergens / Q000276:immunology; D000818:Animals; D001980:Bronchi / Q000166:cytology / Q000276:immunology*; D002460:Cell Line; D003058:Cockroaches / Q000201:enzymology / Q000276:immunology*; D010450:Endopeptidases / Q000276:immunology / Q000494:pharmacology*; D004847:Epithelial Cells / Q000276:immunology*; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D044464:Receptor, PAR-2 / Q000378:metabolism*; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
D000485:Allergens; D016209:Interleukin-8; D044464:Receptor, PAR-2; D014409:Tumor Necrosis Factor-alpha; D020928:Mitogen-Activated Protein Kinases; D010450:Endopeptidases; D018631:ras Proteins