Interleukin-4 Induces CpG Site-Specific Demethylation of the Pendrin Promoter in Primary Human Bronchial Epithelial Cells.

Pendrin is upregulated in bronchial epithelial cells following IL-4 stimulation via binding of STAT6 to an N4 GAS motif. Basal CpG methylation of the pendrin promoter is cell-specific. We studied if a correlation exists between IL-4 sensitivity and the CpG methylation status of the pendrin promoter in human bronchial epithelial cell models.

METHODS: Real-time PCR and pyrosequencing were used to respectively quantify pendrin mRNA levels and methylation of pendrin promoter, with and without IL-4 stimulation, in healthy and diseased primary HBE cells, as well as NCI-H292 cells.

RESULTS: Increases in pendrin mRNA after IL-4 stimulation was more robust in NCI-H292 cells than in primary cells. The amount of gDNA methylated varied greatly between the cell types. In particular, CpG site 90 located near the N4 GAS motif was highly methylated in the primary cells. An additional CpG site (90bis), created by a SNP, was found only in the primary cells. IL-4 stimulation resulted in dramatic demethylation of CpG sites 90 and 90bis in the primary cells.

CONCLUSIONS: IL-4 induces demethylation of specific CpG sites within the pendrin promoter. These epigenetic alterations are cell type specific, and may in part dictate pendrin mRNA transcription.