DNA demethylation-dependent enhancement of toll-like receptor-2 gene expression in cystic fibrosis epithelial cells involves SP1-activated transcription

摘要

Background The clinical course of cystic fibrosis(CF)is characterized by recurrent pulmonary infections and chronic inflammation.We have recently shown that decreased methylation of the toll-like receptor-2(TLR2)promoter leads to an apparent CF- related up-regulation of TLR2.This up-regulation could be responsible,in part,for the CF-associated enhanced proinflammatory responses to various bacterial products in epithelial cells.However,the molecular mechanisms underlying DNA hypomethylation-dependent enhancement of TLR2 expression in CF cells remain unknown. Results The present study indicates that there is a specific CpG region(CpG#18-20),adjacent to the SP1 binding site that is significantly hypomethylated in several CF epithelial cell lines.These CpGs encompass a minimal promoter region required for basal TLR2 expression,and suggests that CpG#18-20 methylation regulates TLR2 expression in epithelial cells.Furthermore,reporter gene analysis indicated that the SP1 binding site is involved in the methylation-dependent regulation of the TLR2 promoter.Inhibition of SP1 with mithramycin A decreased TLR2 expression in both CF and 5-azacytidine- treated non-CF epithelial cells.Moreover,even though SP1 binding was not affected by CpG methylation,SP1-dependent transcription was abolished by CpG methylation. Conclusions This report implicates SP1 as a critical component of DNA demethylation-dependent up-regulation of TLR2 expression in CF epithelial cells.