DIGITOXIN TREATMENT REDUCES NASAL EPITHELIAL CYTOKINES IN CF SUBJECTS

Abstract

ObjectivesCystic fibrosis (CF) is characterized by progressive lung inflammation. Proinflammatory proteins such as IL‐8 are highly expressed in CF airways secretions, and cardiac glycosides, such as digitoxin, can suppress hypersecretion of IL‐8 from cultured CF lung epithelial cells. The specific mechanism of digitoxin action in vitro is to inhibit the TNF‐α/NF‐κb signaling pathway. We tested the hypothesis that digitoxin could suppress this pathway in vivo, using CF nasal epithelial cells obtained during a Phase II, randomized, double‐blind, placebo‐controlled trial of two dose levels of digitoxin and placebo in CF.MethodsTwenty four CF subjects were randomized to take digitoxin 50 μg (n=8), 100 μg (n=8) daily or placebo (n=8) 100 μg for 28 days. Nasal epithelial cells were collected from patients pre‐ and post‐treatment and placed in Trizol for RNA isolation. Quality control (QC) was performed before microarray analysis. Expression levels were analyzed by using Affymetrix 1.0 Human Exon ST arrays at the Johns Hopkins Microarray Core Laboratory. Statistical analysis was performed with the Partek Genomic Suite and visualization of the data was performed in Spotfire.ResultsThree dimensional principal component analysis (PCA) plots revealed that the patient groups receiving placebo and 50 μg/day digitoxin fall into similar patterns which are distinct from the patient group taking 100 μg/day digitoxin. We identified 43,613 genes and 173 genes are significantly up‐ or down‐regulated in the patient group taking 100 μg digitoxin/daily. Interestingly, mRNAs encoding chemokine/cytokine or cell surface receptors in immune cells were decreased in nasal epithelial cells, including CCL2, CXCL1, CXCL2, CXCL3, IL‐1R, MHC class II, integrin α4, CD48, and CD300a in the patient group taking 100 μg digitoxin/daily.ConclusionsDigitoxin treatment in cystic fibrosis patients was associated with reductions in nasal epithelial cytokines and cell surface molecules found on immune cells and higher dose cohort (100 μg/daily) shows more significant changes in gene expression. Longer term exposures and microarray studies of circulating immune cells as compared with airways epithelial cells would be useful.Support or Funding InformationR01 FD003456