MicroRNA-155-induced T lymphocyte subgroup drifting in IgA nephropathy

MicroRNA-155 (miR-155) is an important immune regulator of T lymphocyte subgroup balance and function. This study was performed to explore the relationships between miR-155 expression in peripheral blood mononuclear cells (PBMCs), T lymphocyte subgroups, T lymphocyte regulators, and the clinical manifestations of IgA nephropathy (IgAN) patients.

Sixty biopsy-proven IgAN patients and 25 healthy controls were included in this study. The expression of miRNAs in PBMCs was determined using a microRNA microarray and real-time RT-PCR. T lymphocyte subgroups (Th1, Th2, Treg, and Th17), differentiation regulators (c-Maf, STATA-6, GATA-3, SOCS-1, and Fxop3), cytokines (IFN-γ, IL-5, IL-10, and IL-17), serum IgA1 glycosylation level, and Cosmc expression were examined using flow cytometry, qPCR, and ELISA.

Microarray analysis and qPCR suggested that the miR-155 level in PBMCs from IgAN patients was significantly lower than that in healthy controls (decreased 61%, 0.197 ± 0.068 vs 0.796 ± 0.13, p < 0.01). The expression of GATA-3 (0.08 ± 0.02 vs 0.04 ± 0.01, p = 0.035), SATA-6 (0.12 ± 0.02 vs 0.06 ± 0.01, p = 0.036), and SOCS-1 (0.04 ± 0.01 vs 0.03 ± 0.01, p = 0.01) was significantly higher in IgAN PBMCs compared to healthy controls, while that of Foxp3 (0.013 ± 0.003 vs 0.040 ± 0.01, p = 0.026) and Cosmc (0.08 ± 0.02 vs 0.19 ± 0.04, p = 0.024) was remarkably lower. Flow cytometric analysis revealed that the percentages of peripheral blood Th1 (17.35 ± 1.22 vs 20.89 ± 1.22, p = 0.042) and Treg cells (1.86 ± 0.15 vs 2.48 vs 0.26, p = 0.031) were significantly lower in IgAN patients than in normal controls; however, the percentages of Th2 (1.73 ± 0.29 vs 1.04 ± 0.18, p = 0.046) and Th17 (4.09 ± 0.45 vs 2.06 ± 0.21, p < 0.001) were remarkably higher. ELISA results indicated that serum Th1 cytokine INF-γ (40.77 ± 8.39 vs 83.02 ± 17.4 pg/mL, p = 0.035) and Treg cytokine IL-10 (0.77 ± 0.28 vs 4.18 ± 1.34 pg/mL, p = 0.02) levels were lower, while Th2 cytokine IL-5 (1.02 ± 0.17 vs 0.65 ± 0.07 pg/mL, p = 0.04) and Th17 cytokine IL-17 (53.78 ± 12.20 vs 28.87 ± 4.59 pg/mL, p = 0.05) were significantly higher in IgAN patients than in normal controls. Significant correlations were found between miR-155 levels and Foxp3, Cosmc level, 24-h urine protein amount, urine RBC count, serum IgA concentration, and IgA1 dys-glycosylation level.

A remarkably lower expression of peripheral lymphocyte miR-155 was observed in IgAN patients, leading to T lymphocyte subgroup drifting (increases in Th2 and Th17 along with decreases in Th1 and Treg), which inhibits Cosmc gene expression and worsens the aberrant glycosylation of IgA1 in IgAN patients. These results suggest that miR-155 may play an important role in the pathogenesis of IgAN and could serve as a potential disease biomarker.