Objective To investigate the effects of homocysteine (Hcy) on methylation status and mRNA expression of TNF superfamily member 4 (TNFSF4) gene in THP-1 macrophages. Method Cultured THP-1 monocytes were induced to macrophages by 0.1μmol/L PMA treatment for 72h

then the differentiated THP-1 macrophages were incubated with homocysteine (50-1 000 μmol/L) for 24

48 or 72h. The status of methylation of TNFSF4 gene in THP-1 macrophages was analyzed by methylation specific polymerase chain reaction (MS-PCR).The expression level of TNFSF4 mRNA was determined by RT-PCR. Results The MS-PCR results showed that the unmethylated bands gradually became stronger

and the methylated bands gradually became weaker along with the prolongation of treatment time and the increased Hcy concentrations. The 72-hour treatment with Hcy induced a complete demethylation in the promotor region of TNFSF4 gene

where left the only unmethylated bands. Meanwhile

the TNFSF4 mRNA expression was also increased in a dose-dependent manner. Conclusion Hcy may contribute to atherogenesis by inducing demethylation in the promotion region of the TNFSF4 gene and increasing TNFSF4 expression in THP-1 macrophages.