Role of IKK and ERK pathways in intrinsic inflammation of cystic fibrosis airways


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Abstract

In cystic fibrosis (CF) patients, pulmonary inflammation is a major cause of morbidity and mortality and may precede bacterial colonization. The aim of the present study was to investigate the molecular mechanisms underlying intrinsic inflammation in cystic fibrosis airways. Using different cystic fibrosis cell models, we first demonstrated that, beside a high constitutive nuclear factor of kappaB (NF-κB) activity, CF cells showed a higher activator protein-1 (AP-1) activity as compared to their respective control cells. Gene expression profiles, confirmed by RT-PCR and ELISA, showed over-expression of numerous NF-κB and AP-1-dependent pro-inflammatory genes in CF cells in comparison with control cells. Activation of NF-κB was correlated with higher inhibitor of κB kinase (IKK) activity. In addition, Bio-plex phosphoprotein assays revealed higher extracellular signal-regulated kinase (ERK) phosphorylation in CFT-2 cells. Inhibition of this kinase strongly decreased expression of pro-inflammatory genes coding for growth-regulated proteins (Gro-α, Gro-β and Gro-γ) and interleukins (IL-1β, IL-6 and IL-8). Moreover, inhibition of secreted interleukin-1β (IL-1β) and basic fibroblast growth factor (bFGF) with neutralizing antibodies reduced pro-inflammatory gene expression. Our data thus demonstrated for the first time that the absence of functional cystic fibrosis transmembrane conductance regulator (CFTR) at the plasma membrane leads to an intrinsic AP-1, in addition to NF-κB, activity and consequently to a pro-inflammatory state sustained through autocrine factors such as IL-1β and bFGF.

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