061 - Glucocorticoids resistance in Cystic Fibrosis - 05/12/08

Introduction: Cystic Fibrosis (CF) is the most common lethal autosomal recessive disease in Caucasian population. The gene mutated in CF encodes a chloride channel named CFTR (Cystic Fibrosis Transmembrane conductance Regulator). Lung dysfunction is the main cause of mortality in CF patients. Infection combined with inflammation lead to progressive destruction of the respiratory epithelium. Glucocorticoids (GC) are anti-inflammatory molecules commonly used to treat inflammation but with controversial efficiency among patients. The lack of efficiency could be due to resistance to GC already observed in others respiratory diseases. To test this hypothesis, we study the key steps in GC activation pathway in the lung to identify the molecular basis of such dysregulation. Our present studies focus on the regulation of the expression of the GR isoforms.

Methods: CF bronchial epithelial cell lines (IB3-1) and CF corrected (S9) were incubated with IL-1β (10ng/ml) with or without dexamethasone (dex, 1µM). Rates of secreted IL-8 were dosed by ELISA NF-κB activation was measured using NF-κB promotor coupled to luciferase. Expression of GR isoforms was measured by quantitative RT-PCR.

Results: In presence of IL-1β, dex can restore basal secretion of IL-8 at 16h in S9, whereas IB3-1 barely respond. Moreover, no effect of dex on NF-κB activation is observed in CF cells. There is a differential regulation of the GR isoforms expression at 16h in the two cell lines. The study of the GR activation window of activation in inflammatory conditions is currently in progress.

Conclusions: In this study we have shown a different regulation of inflammation by GC Our preliminary study on GR expression also suggests differences between CF and non-CF cell lines.

The present results require to be assessed in other cellular models and from CF lung biopsies. We will subsequently investigate the possible dysregulation of other key steps in GC activation pathway such as GR phosphorylation and nuclear translocation.