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1 Case Western Reserve University
* To whom correspondence should be addressed. E-mail: mitchell.drumm{at}case.edu.
Inflammatory cytokines, particularly the neutrophil chemoattractant interleukin-8 (IL-8), are elevated in the cystic fibrosis (CF) airway, even in the absence of detectable infection. The transcriptional regulation of many inflammatory genes, including IL8 (CXCL8), involves chromatin remodeling through histone acetylation. Nuclear factor
B (NF-
B) is known to facilitate histone acetylation of IL8 and other pro-inflammatory gene promoters, but we find that increased NF-
B activation cannot explain the elevated IL8 expression and promoter acetylation seen in CFTR- deficient cells. Recognized components of the NF-
B-co-activator complex, acetyl-transferase CBP, and P300, and the histone deacetylase HDAC1, are unchanged by CFTR activity. However, we find that the histone acetyl-transferase (HAT)/ HDAC balance is sensitive to CFTR function, as cells with reduced or absent CFTR function have decreased HDAC2 protein, resulting in hyperacetylation of the IL8 promoter and increased IL8 transcription. Reduced HDAC2 and HDAC2 activity, but not HDAC2 mRNA, is observed in cells deficient in CFTR. Suppressing HDAC2 expression by RNAi results in increased IL8 expression and promoter acetylation comparable to CFTR-deficient cells. Treating CFTR-deficient cells with N-acetyl-cysteine (NAC) increases HDAC2 expression to near control levels. Our data suggest that there is an intrinsic alteration in the HAT/HDAC balance in cells lacking CFTR function in vitro and in native tissue, and that oxidative stress is likely contributing to this alteration. This mechanism, found in other inflammatory airway diseases, provides an explanation for the apparent dysregulation of inflammatory mediators seen in the CF airway, as reduced histone deacetylation would potentially influence many genes.
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