Cytokines and glucocorticoids modulate human bronchial epithelial cell peptidases

Abstract

Peptidases play an important role in the regulation of peptide-mediated effects. Modulation of peptidase activity may therefore be a major mechanism to control peptide actions. Our aim was to analyse the effects of cytokines and glucocorticoids on peptidases expressed by human bronchial epithelial cells, which have been shown to be an important site for peptidase activity. The effects of cytokines [interleukin 1β (IL-1β), tumour necrosis factor α (TNF-α), IL-4, interferon γ (IFN-γ), and epidermal growth factor (EGF)] and/or dexamethasone (DEX) on both expression and activity of neutral endopeptidase (NEP) and aminopeptidase N (APN) by BEAS 2B cells were determined using flow cytometry and activity assays, respectively. IL-1β, and to a lesser extent, TNF-α and IL-4 increased NEP activity and expression, whereas IFN-γ decreased NEP. The effect of IL-1β was mediated, at least in part, via a cAMP-dependent pathway which did not involve prostaglandin E2 synthesis. APN was increased after 24-h stimulation with IFN-γ, whereas other stimuli had no effect. DEX strongly increased NEP and APN expression and activity, both in the absence and in the presence of cytokines. We conclude that cytokines and glucocorticoids are able to modulate the activity of NEP and APN on BEAS 2B cells. Our results suggest a role for the human bronchial epithelium in the control of inflammation and indicate that one beneficial effect of glucocorticoids on asthma may be upregulation of peptidases expressed by bronchial epithelial cells.