The Regulatory Effect of ERK1 Pathway in the DNA Hypomethylation of MRL/lpr Mice

Background: Defective ERK1 activity may regulate the DNA hypomethylation in T cells of lupus mice. Aims: To investigate the function of ERK1 in regulating DNA hypomethylation and explore the potential molecular mechanisms involved in lupus mice. Methods: CD4+T cells were isolated from MRL/lpr and BALB/c mice, activated in vitro in the presence or absence of 5-azacytidine (5-Aza) (a DNA methyltransferase inhibitor)/U0126 (a selective inhibitor of the ERK signaling pathway) respectively. The positive rate of CD4+T cell was measured by flow cytometry, and expression levels of CD70, ERK1, DNA transferase 1 (DNMT1) were estimated by RT-PCR and Western blot. The methylated DNA is detected using the Capture and Detection antibodies, then quantified colorimetrically. Results: The expression level of p-ERK1 in MRL/lpr mice was significantly lower than healthy control (P<0.05); Meanwhile, down regulation of DNMT1 and DNA hypomethylation were found in MRL/lpr mice T cells. In contrary, the expression levels of CD70 increased when compared with healthy control (P<0.05). The same changes were seen in healthy CD4+T cells treated with U0126. Conclusions: DNA hypomethylation regulating mechanisms in lupus T cells were associated with ERK1 signal pathway. U0126 could inhibit ERK1 signal transduction pathway in normal T cells, and induce DNA hypomethylation by regulating the expression of methylation sensitive gene CD70.