EZH2 negatively regulates IL-8 expression in human nasal epithelial cells through its histone methyltransferase activity

Abstract

Background: Chronic rhinosinusitis (CRS), characterized by persistent inflammation of the nasal and sinus mucosa, exhibits an escalating global prevalence and incidence. Interleukin-8 (IL-8), a key chemokine driving neutrophil recruitment, is implicated in CRS pathogenesis. While non-epigenetic mechanisms of IL8 regulation have been reported, the epigenetic landscape governing IL8 expression in CRS remains unexplored.

Objective: This study aimed to investigate the epigenetic regulation of IL-8 expression in human nasal epithelial cells (HNEpCs) with a focus on histone modification-mediated mechanisms.

Methods: Tumor necrosis factor-alpha (TNF-α) was selected as a prototypical pro-inflammatory stimulus through systematic screening. An in vitro model of IL-8 induction was established and validated in TNF-α-treated HNEpCs. Regulatory mechanisms were probed using bioinformatics tools (UCSC Genome Browser, Cistrome DB) and pharmacological inhibitors targeting histone-modifying enzymes. siRNA-mediated enhancer of zeste homolog 2 (EZH2) knockdown to assess its regulatory role in IL-8 expression; Chromatin Immunoprecipitation followed by quantitative PCR (ChIP-qPCR) to determine whether H3K27me3 is directly enriched at the IL8 promoter region under TNF-α stimulation.

Results: TNF-α stimulation induced time and concentration-dependent upregulation of IL-8 mRNA (p < 0.001) and protein secretion (p < 0.001) in HNEpCs. TNF-α-mediated IL-8 upregulation was abrogated by the addition of methyl-transferase inhibitors EPZ005687, EPZ6438, and BIX01294. SiRNA-mediated EZH2 depletion significantly enhanced both IL-8 mRNA (p < 0.001) and protein levels (p < 0.01). ChIP-qPCR confirmed TNF-α-dependent enrichment of H3K27me3 at the IL8 promoter, supporting EZH2-mediated transcriptional repression.

Conclusion: EZH2-dependent H3K27 trimethylation is a key epigenetic mechanism controlling IL-8 gene expression in HNEpCs.

Keywords

chronic rhinosinusitis / enhancer of zeste homolog 2 / epigenetics / histone methylation / interleukin-8

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