The Role Of MiR-155 In MG And The Effect Of Dexamethasone On MiR-155

Objective:This study is aimed to investigate the role of miR-155 in the pathogenesis of myasthenia gravis (MG) by detecting the expression of miR-155 in PBMCs and peripheral blood B lymphocyte of myasthenia gravis (MG) patients and normal individuals, and comparing the expression of miR-155, the proliferation and activation of B cells, the supernatant concentration of anti-AchR-IgG and it's isotype anti-AchR-IgG1,2,3 between dexamethasone and PBS influenced B cells of MG patients, analyzing the relationship between these results, so as to offer a theoretical basis of the targeted therapy with miR-155.Methods:Collected 38 MG patients (including 23 generalized type patients and 15 ocular type patients) and 23 healthy controls, then extracted the PBMCs from the peripheral blood, and the B cell was extracted by immunomagnetic microbeads. The expressions of miR-155 on PBMCs and on B cells were detected by real time PCR. Then, use dexamethasone and PBS intervention 7 cases of B cells of generalized type patients in vitro, detected the expression of miR-155, the proliferation and activation of B cells. Meanwhile the supernatant fluid concentration of anti-AchR-IgG and it's isotype anti-AchR-IgG1,2,3 with ELISA.Results:(1) The expression of miR-155 in PBMCs of generalized MG subgroup was higher than that of control group (4.24±1.24 VS 1.21±0.41), and the difference were significant (p<0.05). However, there was no significant difference between ocular MG subgroup and control group(4.24±1.24,1.12±0.32, p>0.05; 1.12±0.32 VS 1.21±0.41, p>0.05)。(2) The expression of miR-155 in B cells of generalized MG subgroup was much higher than that of control group(18.04±3.88 VS 5.42±2.25), and the difference has obvious statistical significance(p<0.01). (3)Under the intervention of Dexamethasone, the expression of miR-155 in B cells of generalized MG subgroup were lower than that of the PBS intervention(6.87±2.28 VS 13.96±2.98), and the difference was significance (p<0.05); (4) However, under the same cell culture conditions, the proliferation of B cells has no significant difference with that of the PBS intervention (p>0.05). (5) And the same conditions, the activation of B cells has no significant difference, too(p>0.05). (6) The concentration of anti-AchR-IgGl have obviously statistically significant difference (0.051±0.007 VS 0.064±0.010, p= 0.01), but the concentration of anti-AchR-IgG and its subtype anti-AchR-IgG2, anti-AchR-IgG3 in supernatant fluid was little lower than that of with PBS intervention (0.306±0.060 VS 0.343±0.053; 0.036±0.008 VS 0.040±0.079; 0.011±0.004 VS 0.014±0.005), and the differences were no significance (p>0.05)Conclusion: (1)The high expression of miR-155 may causes the MG occur.(2) Dexamethasone may reduce the antibody class switch of B cell by suppression the expression of miR-155 to improve the symptom of MG patients.