The Expression Of DNA Methylation Related Genes From Patients With Systemic Lupus Erythematosus

Objectives: Systemic lupus erythematosus (SLE) is a progressive and recurrent autoimmune disease involving poly-organs of human body. Evidence indicates that the DNA methylation aberration maybe responsible for the emergence of immune disorder in SLE patients. In theory, DNA methylation-related genes including DNA methyltransferase(DNMTs), DNA demethylase(mbd2), methyl-CpG binding protein (MeCP2) may play an important role in activating some autoimmunity associated genes which can further give rise to SLE. The aim of this paper is to explore the expression level of DNMTs, DNA demethylase and MeCP2 and their correlation with SLE Disease Activity Index (SLEDAI). Meanwhile, we take the expression level of lymphocyte function-associated antigen 1 (LFA-1; CD11a/CD18) as a mirror of DNA methylation pattern and analyze the effect of the expression level of DNA methylation-related genes on the DNA methylation.Materials and Methods: 34 Patients with SLE who met the 1997 American Rheumatism Association (ARA) lupus criteria for SLE were recruited from the inpatient department of the Tongji Hospital and Ruijin Hospital. Patients were divided into active disease and inactive disease according to SLE disease activity index (SLEDAI). 17 control subjects were recruited from healthy volunteers. Peripheral blood mononuclear cells (PBMCs) were isolated by density gradient centrifugation and total RNA was isolated. The transcription levels of DNMTs, mbd2, MeCP2 and CD11a were detected by using RT-PCR. Statistical analyses for comparison of two groups were conducted by student t test and relationships were conducted by correlation analysis using SAS6.12 software. Significance was defined at p<0.05 and very significance at p<0.01.Results: The results demonstrate that DNMT1 mRNA levels in SLE-inactive patients are very significantly lower than those in normal controls (t=5.90, P=0.0001) .DNMT1 mRNA levels in SLE-active patients are very significantly lower than those in normal controls (t=6.93, P=0.0001) ,but not significantly different from those in SLE-inactive patients (t=1.75, P=0.0895). DNMT3A mRNA levels do not display significant differences among SLE-active patients, SLE-inactive patients and healthy control. The transcription levels of DNMT3B mRNA are so low that few DNMT3B bands can be detected by densitometry. mbd2 mRNA levels in SLE-inactive patients are very significantly higher than those in healthy control (t=12.8, P=0.0001) .mbd2 mRNA levels in SLE-active patients are very significantly higher than those in healthy control (t=20.0, P=0.0001) .mbd2 mRNA levels in SLE-active patients are also very significantly higher than those in SLE-inactive patients (t=8.89, P=0.0001) .MeCP2 mRNA levels do not show significant differences among SLE-active patients, SLE-inactive patients and healthy control. CD11a mRNA levels in SLE-inactive patients are very significantly higher than those in healthy control (t=5.35, P=0.0001) . CD11a mRNA levels in SLE-active patients are very significantly higher than those in healthy control (t=6.57, P=0.0001) .CD11a mRNA levels in SLE-active patients are very significantly higher than those in SLE-inactive patients (t=2.99, P=0.0061). MeCP2 and mbd2 mRNA levels in healthy control display significant positive correlation (r=0.550, P=0.0222) .mbd2 and CD11a mRNA levels in SLE patients display significant positive correlation (r=0.392, P=0.0218) . CD11a mRNA levels in SLE patients display significant positive correlation with SLEDAI (r=0.539, P=0.001) .Also mbd2 mRNA levels in SLE patients display significant positive correlation with SLADAI (r=0.737, P=0.0001).Conclusions: (1) Imbalance of methylation and demethylation, low expression of DNMT1 and high expression of mbd2, may induce hypomethylation and over expression of SLE related genes such as LFA-1 which aggravates the clinical manifestation of SLE and contributes to the high SLEDAI score. (2) DNMT3A and DNMT3B may play no roles in the development of SLE. (3) MeCP2 and mbd2 may inter-restrict in healthy control and this relationship may be destroyed in SLE patients.