Rhinovirus-Induced MMP-9 Expression Is Dependent on Fra-1, Which Is Modulated by Formoterol and Dexamethasone

Abstract

Matrix metalloproteinase-9 is implicated in airway inflammation and airway remodeling in asthma. We have previously confirmed that human rhinovirus-16 (HRV-16) infection increases MMP-9 expression both in vivo and in vitro. However, the role of the AP-1 sites within the MMP-9 promoter and the effect of commonly used asthma pharmacotherapies in modulating human rhinovirus (HRV)-induced MMP-9 production have not yet been elucidated. Experiments were performed in vitro in the human bronchial epithelial (HBE) cell line BEAS-2B and in primary HBE cells obtained from non-transplanted lungs. Using site-directed mutagenesis approaches, AP-1 sites were found to be necessary for HRV-induced MMP-9 promoter drive. EMSAs and supershift assays identified complexes consisting of Fos-related Ag-1 (Fra-1) in addition to other AP-1 subunits. Small interfering RNA approaches indicated that Fra-1 was induced upon HRV-16 infection in BEAS-2B cells and was necessary for MMP-9 expression in both BEAS-2B and primary HBE cells. Inhibition of MEK1/2 activity using PD98059 and U0126 reduced Fra-1 expression, DNA binding, MMP-9 promoter drive, and MMP-9 protein production. The long-acting β2-agonist formoterol and the glucocorticoid dexamethasone significantly reduced HRV-induced ERK phosphorylation, Fra-1, and MMP-9 expression in BEAS-2B cells. These data indicate that HRV-induced activation of the MEK/ERK MAPK pathway and Fra-1 expression are necessary for the upregulation of MMP-9 and can be modulated by two distinct but commonly used asthma pharmacotherapies. Together, these results offer insights into the mechanisms by which long-acting β2-agonists and glucocorticoids might reduce HRV-related asthma exacerbations.

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