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Oxidative Stress Causes IL8 Promoter Hyperacetylation in Cystic Fibrosis Airway Cell Models

¹ Departments of Genetics and Pediatrics, Case Western Reserve University and ² Rainbow Babies and Children's Hospital, Cleveland, Ohio

Correspondence and requests for reprints should be addressed to Mitchell L. Drumm, Ph.D., Departments of Genetics and Pediatrics, Case Western Reserve University and Rainbow Babies and Children's Hospital, 10900 Euclid Ave., Cleveland, OH 44106-4948. E-mail: mitchell.drumm{at}case.edu

Dysregulated inflammation has been implicated in cystic fibrosis (CF) airway pathophysiology. The expression of inflammatory genes, like interleukin 8 (IL8), involves chromatin remodeling through histone acetylation. Inflammatory gene hyperacetylation could explain inflammatory mediator dysregulation seen in CF airways. CF airways are exposed to high levels of oxidative stress, and oxidative stress increases histone acetylation and inflammatory gene transcription. Loss of cystic fibrosis transmembrane conductance regulator (CFTR) may even reduce protection against oxidative stress. Consequently, increasing oxidative stress would likely lead to an imbalance of histone acetyl-transferase (HAT) and deacetylase (HDAC) stoichiometry and contribute to the heightened inflammatory response seen in the CF airway. We hypothesize that oxidative stress in CF airways causes increased acetylation of inflammatory gene promoters, contributing to transcriptional activity of these loci. Messenger RNA levels of IL8, IL6, CXCL1, CXCL2, CXCL3, and IL1 are significantly elevated in CF epithelial cell models. Histone H4 acetylation is lower at the IL8 promoter of the non-CF cell lines than the CF models. The reducing agent N-acetyl-cysteine decreases IL8 message and promoter H4 acetylation to non-CF levels, suggesting that oxidative stress contributes to IL8 expression in these models. H₂O₂ treatment causes increased IL-8 acetylation and mRNA in all cells, but less in the CF-model cells. Together these data suggest a model in which cells without functional CFTR are under increased oxidative stress. Our data suggest intrinsic alterations in the HAT/HDAC balance in CFTR-deficient cells, and that oxidative stress contributes to this alteration.

Key Words: chromatin • oxidative stress • histone acetylation

CLINICAL RELEVANCE Hyperacetylation is an emerging theme in inflammatory airway diseases. As there are potential pharmacologic modulators of acetylation and deacetylation, these processes are promising therapeutic targets for cystic fibrosis, chronic obstructive pulmonary disease, and asthma.

 

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