MicroRNA-29b contributes to DNA hypomethylation of CD4+ T cells in systemic lupus erythematosus by indirectly targeting DNA methyltransferase 1

摘要

Background: The mechanism of DNA hypomethylation in systemic lupus erythematosus (SLE) has not been fully elucidated. Recent studies showed that miR-29b could regulate DNA methylation by targeting the DNA methylation machinery. However, the role of miR-29b in T cell aberrant DNA hypomethylation of SLE still remains unclear. Objective: In this study, we asked whether miR-29b regulate DNA methylation in lupus CD4+ T cells. Methods: The miR-29b expression was analyzed by quantitative polymerase chain reaction (qPCR). Sp1, DNMT1, CD11a and CD70 mRNA and protein levels were determined by qPCR, Western-blotting and flow cytometry, respectively. The global DNA methylation levels were evaluated by the Methyflash? DNA Methylation Quantification Kit. CD11a and CD70 promoter methyaltion levels were detected by bisulfate modification and methylation-sensitive high resolution melting analysis. Results: In SLE patients, the miR-29b levels were up-regulated as compared to healthy donors and its degree of overexpression was negatively correlated with sp1 and DNMT1 protein levels, respectively. Overexpression of miR-29b resulted in significant reduction of sp1 and DNMT1 expression. Further analysis demonstrated that overexpression of miR-29b in CD4+ T cells from healthy donors led to the DNA hypomethylation and up-regulation of genes encoding CD11a and CD70, and inhibition of miR-29b expression in CD4+ T cells from patients with lupus caused reverse effects. Conclusion: Our study suggests that miR-29b negatively regulates DNMT1 expression by targeting sp1 in T cells. The overexpression of miR-29b contributes to the reduction of DNMT1 levels and thereby DNA hypomethylation in SLE. This finding provides potential novel strategies for therapeutic interventions.