5-Aza-2’-dC Differentially Affects P.g.-LPS–stimulated Inflammatory-related Gene Expression in THP-1 Macrophage

Objectives: To investigate the possible DNA methylation change on specific inflammatory-related genes in macrophage stimulated by P.g.-LPS.
Methods: PMA-induced human monocyte THP-1 cells (1x10⁶/ml) were stimulated with P.g.-LPS (low dose: 100ng/ml; high dose: 1μg/ml) for 24hr in the presence or absence of DNA methylation inhibitor 5-aza-2’-deoxycytidine (5-aza-2’-dC) (10μM), and mRNA expression of specific genes was evaluated by reverse transcription-polymerase chain reaction (RT-PCR).
Results: Under the stimulation of P.g.-LPS, mRNA expression of TLR2 and TLR9 decreased at low dose but increased significantly at high dose. However, mRNA expression of TLR4 decreased slightly at both doses. As for the pro-inflammatory gene expression, up-regulation of TNF-α, IL-1α, and CXCL2 was detected within 24hrs at cells stimulated with both doses of P.g.-LPS. Upon co-treatment with 5-aza-2’-dC, down-regulation of TLR2, TLR4, TLR9, IL-1α, CXCL2 and up-regulation of TNF-α gene expression were observed. Moreover, 5-aza-2’-dC treatment prolonged P.g.-LPS (low dose)-induced mRNA expression of IL-1α and CXCL2.
Conclusions: DNA methylation inhibitor 5-aza-2’-dC differentially affected P.g.-LPS–stimulated inflammatory-related gene expression in THP-1 macrophage, implicating the involvement of DNA methylation in innate response to P.g. infection.