DUST-MITE PROTEOLYTIC ALLERGENS INDUCE CYTOKINE RELEASE FROM CULTUREDAIRWAY EPITHELIUM

Endogenous proteolytic enzymes have been shown tp be potential sources of airway inflammation inducing proinflammatory cytokine release from respiratory epithelial cells; however, whether any of the exogenous p roteases from important allergen sources such as the house dust mite p resent in our environment behave in a similar fashion is unclear, To t his end, we have investigated whether the mite cysteine and serine pro teolytic allergens, Der p 1 and Der p 9, respectively, induced cytokin e production from primary human bronchial epithelial cells and from th e epithelial cell line BEAS-2B. Cells were exposed to mite proteases, and cells or supernatants were assayed for cytokine release, cytokine mRNA expression, and modulation of intracellular calcium ion concentra tion, Both proteases induced concentration- and time-dependent increas es in the release of granulocyte-macrophage (GM)-CSF, IL-6, and IL-8 a s well as an increase in the expression of IL-6 mRNA, Cytokine release and mRNA expression were first observed at 8 h and 2 h after protease exposure, respectively. The minimum concentration of each protease th at was required to stimulate GM-CSF, IL-6, and IL-8 release was simila r to 10 ng/ml, Cytokine release was initiated by I to 2 h of protease exposure, although maximum concentrations were detected only after a 2 4-h incubation. IL-6, but not IL-8 and GM-CSF, was shown to be degrade d by both proteases at concentrations of >2 mu g/ml. The proteases als o stimulated changes in the intracellular calcium ion concentration. A ll mite protease-induced phenomena were inhibited using appropriate pr otease inhibitors. These results suggest that the proteolytic activity of an allergen may stimulate the release of proinflammatory cytokines from human bronchial epithelium.