Lei Yu, Na Li, Jisheng Zhang, Yan Jiang

Epigenetic regulation has been shown to play an important role in the development of inflammatory diseases, including chronic rhinosinusitis and nasal polyps. The latter are characterized by epithelial mis-differentiation and infiltration of inflammatory cytokines. H3K4me3 has been shown to be involved in regulating lineage commitment. However, the underlying mechanisms, especially in human nasal epithelial cells (HNEpC), remain underexplored. The objective of this study was to investigate the role of H3K4me3 in HNEpC differentiation treated with the Th2 cytokine IL-13. The expression levels of mRNA and proteins were investigated using reverse transcription-polymerase chain reaction (RT-PCR) assays and Western blot in nasal polyp tissues and human nasal epithelial cells respectively. We measured these levels of H3K4me3, MLL1 and targeted genes compared with control subjects. We demonstrate that expression of H3K4me3 and its methyltransferase MLL1 was significantly upregulated in IL-13-treated HNEpC. This elevation was also observed in nasal polyps. Expression of cilia-related transcription factors FOXJ1 and DNAI2 decreased, while goblet cell-derived genes CLCA1 and MUC5a increased upon IL-13 treatment. Mechanistically, knockdown of MLL1 restored expression of these four genes induced by IL-13. These findings suggest that H3K4me3 is a critical regulator in control of nasal epithelial cell differentiation. MLL1 may be a potential therapeutic target for nasal inflammatory diseases.