Background/Purpose: Recently, evidence is emerging that abnormal regulation of Th17 differentiation plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). However, the molecular mechanisms are poorly understood. In our previous study, we found that transcription factor RFX1 expression was inhibited in SLE CD4+ T cells, which leads to overexpression of autoimmune-related genes CD11a and CD70. Here, we further investigate whether RFX1 regulates Th17 differentiation in SLE.

Methods: 40 SLE patients and 30 healthy controls were recruited. CD4+ T cells were isolated by magnetic beads. All patients fulfilled at least 4 of the SLE classification criteria of the American College of Rheumatology. RFX1 and cytokines expression levels were detected by real-time PCR, western blot and ELISA. CD4+ T cells were transfected with RFX1 expression plasmid (pSG-RFX1) or siRNA-RFX1 by nucleofector device in combination with the human T-cell nucleofector kit. Luciferase report gene assay and Chromatin Immunoprecipitation (ChIP) and Electrophoretic Mobility Shift Assay (EMSA) were used to confirm the target gene of RFX1. H3 acetylation levels and H3 lys9 (H3K9) tri-methylation levels in the promoter region of IL17A were measured by ChIP-qPCR.

Results: Compared with normal controls, RFX1 protein levels were decreased and IL17A mRNA levels were increased significantly in SLE CD4+ T cells. The IL-17A protein levels in serum of SLE patients were increased significantly. A negative correlation was observed between IL17A mRNA levels and RFX1 protein in SLE CD4+ T cells. Luciferase report gene assay, ChIP and EMSA showed that RFX1 can repress promoter activity of IL17A through binding the promoter of IL17A. Transfection of siRNA-RFX1 leads to up-regulated expression of IL17A through increasing H3 acetylation level and reducing H3K9 tri-methylation level in normal CD4+ T cells. In contrast, transfection of pSG-RFX1 inhibits expression of IL17A through reducing H3 acetylation level and increasing H3K9 tri-methylation level of IL17A promoter in SLE CD4+ T cells.

Conclusion: RFX1 is involved in repressing IL17A expression through regulating the epigenetic modifications in the promoter region of IL17A in CD4+T cells. Decreased RFX1 expression contributes to abnormal regulation of Th17 cells in SLE patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/transcription-factor-rfx1-regulates-th17-differentiation-and-its-role-in-the-pathogenesis-of-systemic-lupus-erythematosus/