摘要
Epigenetic factors, including altered microRNA （miRNA） expression, may contribute to aberrant immune cell function in systemic lupus erythematosus （SLE）. MiRNA-let-7a （let-7a） has been shown to directly alter cell cycle progression and proinflammatory cytokine production. Due to the crucial role of let-7a in cell division and inflammation, we investigated let-7a-mediated proliferation and NFKB translocation in J774A. 1 macrophages and MES 13 mesangial cells in vitro. In immune-stimulated cells transfected with let-7a, cell proliferation was significantly increased over time. There was a significant increase in the number of immune-stimulated cells in S and G2 phases. Immune-stimulated cells overexpressing let-7a had increased nuclear translocation of NFKB. Bioinformatical analysis revealed that the E2F family, critical regulators of the G1-S transition, has potential binding sites for let-7a in their mRNA transcripts. Let-7a overexpression significantly increased the expression of the cell cycle activator E2F2 and increased retinoblastoma protein （Rb） phosphorylation in immune-stimulated cells. The cell cycle inhibitor E2F5 was significantly decreased in let-7a-transfected cells that were immune-stimulated. Bioinformatical analysis revealed E2F2 and NFKB are transcription factors predicted to regulate the let-7a promoter. We analyzed transcriptional regulation of let-7a by real-time RT-PCR using chromatin immunoprecipitation with E2F2 and NFKB antibodies. There was an increase in E2F2 and NFKB binding in DNA enriched for the let-7a promoter in immune-stimulated cells. Silencing E2F2 or NFKB significantly decreased let-7a expression and IL-6 production in immune-stimulated cells. Taken together, our results suggest that overexpression of let-7a may contribute to hyperplasia and the proinflammatory response in SLE.
Epigenetic factors, including altered microRNA （miRNA） expression, may contribute to aberrant immune cell function in systemic lupus erythematosus （SLE）. MiRNA-let-7a （let-7a） has been shown to directly alter cell cycle progression and proinflammatory cytokine production. Due to the crucial role of let-7a in cell division and inflammation, we investigated let-7a-mediated proliferation and NFKB translocation in J774A. 1 macrophages and MES 13 mesangial cells in vitro. In immune-stimulated cells transfected with let-7a, cell proliferation was significantly increased over time. There was a significant increase in the number of immune-stimulated cells in S and G2 phases. Immune-stimulated cells overexpressing let-7a had increased nuclear translocation of NFKB. Bioinformatical analysis revealed that the E2F family, critical regulators of the G1-S transition, has potential binding sites for let-7a in their mRNA transcripts. Let-7a overexpression significantly increased the expression of the cell cycle activator E2F2 and increased retinoblastoma protein （Rb） phosphorylation in immune-stimulated cells. The cell cycle inhibitor E2F5 was significantly decreased in let-7a-transfected cells that were immune-stimulated. Bioinformatical analysis revealed E2F2 and NFKB are transcription factors predicted to regulate the let-7a promoter. We analyzed transcriptional regulation of let-7a by real-time RT-PCR using chromatin immunoprecipitation with E2F2 and NFKB antibodies. There was an increase in E2F2 and NFKB binding in DNA enriched for the let-7a promoter in immune-stimulated cells. Silencing E2F2 or NFKB significantly decreased let-7a expression and IL-6 production in immune-stimulated cells. Taken together, our results suggest that overexpression of let-7a may contribute to hyperplasia and the proinflammatory response in SLE.
