Purpose: Cell proliferation is a common histological feature of lupus nephritis (LN) in the autoimmune disease systemic lupus erythematosus (SLE). MicroRNAs (miRNAs) are small, non-coding RNAs that post-transcriptionally regulate gene expression. In this study, we used in vitro approaches to investigate cell proliferation through E2F-mediated activation of miRNA-let-7a. Methods: A mouse macrophage and a mouse mesangial cell line were transfected with let-7a mimics or a non-targeting control and treated with control or stimulating media. Cell cycle distribution was measured by flow cytometry. Proliferation was measured by MTT assay. Cells were transfected with E2F2 siRNA or a non-targeting control. Let-7a and E2F2 expression were measured by real-time RT-PCR. NFκB activation and IL-6 protein levels were measured by ELISA. Results: Let-7a decreased the number of stimulated cells in G0-G1 phase, resulting in an increase in S and G2-M phase. Cell proliferation was increased in stimulated cells transfected with let-7a. Let-7a significantly increased NFκB activation and E2F2 mRNA expression in stimulated cells. Silencing E2F2 significantly decreased let-7a expression and IL-6 production in stimulated cells. Conclusion: Let-7a induces macrophage and mesangial cell growth and proliferation, in part by activating the transcription factors NFκB and E2F2. This positive feedback loop may explain one mechanism of hyperplasia in lupus.
- Copyright © 2013 by The American Association of Immunologists, Inc.