MicroRNA (miRNA) have received increasing attention as posttranscriptional regulators that fine-tune the homeostasis of the inflammatory response. This study aimed to clarify whether miR-125a, which was identified in a pilot expression profiling step, is involved in the inflammatory chemokine pathway in systemic lupus erythematosus (SLE).
Independent verification of miR-125a expression in amplified samples from SLE patients and normal controls was performed by TaqMan quantitative polymerase chain reaction (PCR) analysis. A combination of 3 bioinformatic prediction techniques and reporter gene assays was used to identify miR-125a targets. In vitro systems of overexpression by transfection and inducible expression by stimulation were performed to investigate the function of miR-125a, which was followed by real-time quantitative PCR and enzyme-linked immunosorbent assay.
In SLE patients, the expression of miR-125a was reduced and the expression of its predicted target gene, KLF13, was increased. Bioinformatics predicted that miR-125a base-paired with sequences in the 3′-untranslated region of KLF13. Overexpression of miR-125a led to a significant reduction in the expression of RANTES and KLF13. MicroRNA-125a inhibited endogenous KLF13 expression in a dose-dependent manner, as determined using gain- and loss-of-function methods. A luciferase reporter system confirmed the miR-125a binding sites. Notably, miR-125a expression was induced in T cells in a dose- and time-dependent manner. Finally, the introduction of miR-125a into T cells from SLE patients alleviated the elevated RANTES expression.
MicroRNA-125a negatively regulates RANTES expression by targeting KLF13 in activated T cells. The underexpression of miR-125a contributes to the elevated expression of RANTES in SLE. Our findings extend the role of miRNA in the pathogenesis of lupus and provide potential strategies for therapeutic intervention.