Abstract:

Objective To investigate the effects of 5-azacytidine and estradiol on the methylation of CpG motifs and expression of DNA methyltransferase1（DNMT1） mRNA in patients with systemic lupus erythematosus （SLE） and normal controls. Methods Peripheral blood lymphocytes isolated from 12 patients with SLE and 11 normal human controls were stimulated with phytohaemagglutinin for one day followed by additional 3-day culture with or without the presence of 5-azacytidine of 1 μmol/L or estradiol of 30 μg/L respectively. Then, the methylation of CpG motifs was detected by flow cytometry using anti-5-methylcytosine antibody, and DNMT1 mRNA expression by real time reverse transcription-PCR. Results After treatment with 5-azacytidine, a decrease was observed in the methylation of CpG motifs, but not in the expression of DNMT1 mRNA in peripheral lymphocytes from patients with SLE （t = 18.60, P < 0.01; t = 1.56， P > 0.05） and in those from the normal controls （t = 5.63, P < 0.01; t=2.17, P > 0.05） compared with untreated lymphocytes. Nevertheless, there were no significant changes in the methylation of CpG motifs or expression of DNMT1 mRNA in lymphocytes from patients with SLE （t = 1.53，0.93, respectively, both P > 0.05） and normal controls （t = 1.93，0.11，respectively, both P > 0.05） after the treatment with estradiol. Conclusions The methylation of CpG motifs is suppressed efficiently by 5-azacytidine, and the suppression is unlikely to be associated with the decrease of DNMT1 mRNA. Estradiol has no significant impact on the methylation of CpG motifs and expression of DNMT1 mRNA in lymphocytes.

Key words: systemic lupus erythematosus, CpG motifs methylation, DNA Methyltransferase, 5-azacytidine, estradiol