Cystic fibrosis (CF) lung disease is characterized by chronic and exaggerated inflammation in the airways. Despite recent developments to therapeutically overcome the underlying functional defect in the cystic fibrosis transmembrane conductance regulator, there is still an unmet need to also normalize the inflammatory response. The prolonged and heightened inflammatory response in CF is, in part, mediated by a lack of intrinsic down-regulation of the proinflammatory NF-κB pathway. We have previously identified reduced expression of the NF-κB down-regulator A20 in CF as a key target to normalize the inflammatory response. Here, we have used publicly available gene array expression data together with a statistically significant connections' map (sscMap) to successfully predict drugs already licensed for the use in humans to induce A20 mRNA and protein expression and thereby reduce inflammation. The effect of the predicted drugs on A20 and NF-κB(p65) expression (mRNA) as well as proinflammatory cytokine release (IL-8) in the presence and absence of bacterial LPS was shown in bronchial epithelial cells lines (16HBE14o−, CFBE41o−) and in primary nasal epithelial cells from patients with CF (Phe508del homozygous) and non-CF controls. Additionally, the specificity of the drug action on A20 was confirmed using cell lines with tnfαip3 (A20) knockdown (siRNA). We also show that the A20-inducing effect of ikarugamycin and quercetin is lower in CF-derived airway epithelial cells than in non-CF cells.A20 | NF-κB | connectivity mapping | drug repositioning | CF airway inflammation

Background and Purpose NF‐κB‐driven inflammation is negatively regulated by the zinc finger protein A20. Gibberellic acid (GA3) is a plant‐derived diterpenoid with documented anti‐inflammatory activity, which is reported to induce A20‐like zinc finger proteins in plants. Here, we sought to investigate the anti‐inflammatory effect of GA3 in airway epithelial cells and determine if the anti‐inflammatory action relates to A20 induction. Experimental Approach Primary nasal epithelial cells and a human bronchial epithelial cell line (16HBE14o‐) were used. Cells were pre‐incubated with GA3, stimulated with Pseudomonas aeruginosa LPS; IL‐6 and IL‐8 release, A20, NF‐κB and IκBα expression were then evaluated. To determine if any observed anti‐inflammatory effect occurred via an A20‐dependent mechanism, A20 was silenced using siRNA. Key Results Cells pre‐incubated with GA3 had significantly increased levels of A20 mRNA (4 h) and protein (24 h), resulting in a significant reduction in IL‐6 and IL‐8 release. This effect was mediated via reduced IκBα degradation and reduced NF‐κB (p65) expression. Furthermore, the anti‐inflammatory action of GA3 was abolished in A20‐silenced cells. Conclusions and Implications We showed that A20 induction by GA3 attenuates inflammation in airway epithelial cells, at least in part through its effect on NF‐κB and IκBα. GA3 or gibberellin‐derived derivatives could potentially be developed into anti‐inflammatory drugs for the treatment of chronic inflammatory diseases associated with A20 dysfunction. Linked Articles This article is part of a themed section on Inflammation: maladies, models, mechanisms and molecules. To view the other articles in this section visit 10.1111/bph.2016.173.issue-4

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