A3.22 Upregulated microRNA-182 Expression is Associated with Enhanced Conventional CD4<sup>+</sup>T Cell Proliferation in SLE
Authors: Tobias Alexander, Claudia Haftmann, Lars Templin, Jens Humrich, Gerd-Rüdiger Burmester, Andreas Radbruch, Falk Hiepe, Mir-Farzin Mashreghi
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> Recent reports have shown dysregulated microRNAs (miRNAs) in murine models of lupus, among them increased expression of miRNA-182, which has been demonstrated to target the transcription factor <i>FOXO1</i> in activated murine CD4<sup>+</sup> T cells. The loss of <i>FOXO1</i> activity in T cells is associated with spontaneous T cell activation, clonal expansion and autoantibody production, all of which are present in systemic lupus erythematosus (SLE). <h3>Methods</h3> Expression levels of microRNA-182 (miR-182) and <i>FOXO1</i> were analysed with RT-PCR in freshly isolated and magnetic purified peripheral blood CD4<sup>+</sup> T cells from 9 patients with SLE and age/sex-matched healthy controls (HC). Multicolor flow cytometry was performed to analyse CD4<sup>+</sup> T cell expression for CCR7, CD45RA, Ki-67, Foxp3, the interleukin-7 receptor-α (CD127) and phosphorylated STAT-5a (pSTAT5). Analysis of serum IL-7 levels was performed with ELISA in 27 SLE patients and HC (R&amp;D systems). The Wilcoxon signed-rank test was used for statistical analysis. <h3>Results</h3> MiRNA-182 was significantly upregulated in CD4<sup>+</sup> T cells from SLE patients compared to HC (median relative expression 8.89 × 10E-7 versus 3.96 × 10E-7, <i>p</i> = 0.008) while <i>FOXO1</i> mRNA levels were decreased, yet without reaching statistical significance. Analysis of Ki-67 expression revealed an increased percentage of proliferating CD4<sup>+</sup> T cells in SLE (5.23% versus 2.21%, <i>p</i> = 0.006), which was more prominent in Foxp3<sup>-</sup> conventional T cells (Tcons) than in Foxp3<sup>+</sup> regulatory T cells (Tregs). Overall, CD4<sup>+</sup> T cellular proliferation in SLE was associated with increased frequencies of CD45RA<sup>–</sup> CCR7<sup>–</sup> effector memory T cells and enhanced basal pSTAT5 levels (median MFI 503.5 versus 399.0, <i>p</i> = 0.010), suggesting a recent stimulation with common gamma chain(γc)-signalling cytokines. In this regard, Tcons from SLE samples displayed decreased expression levels for the <i>FOXO1</i> target gene CD127 (MFI 2021 versus 2553, p = 0.049) and serum IL-7 levels were significantly higher in SLE when compared to HC (17.0 pg/ml versus 10.2 pg/ml, <i>p</i> = 0.001). <h3>Conclusions</h3> MiR-182 expression has been shown to be directly dependent on STAT5 activation and to promote the clonal expansion of murine activated CD4<sup>+</sup> T cells. Our data suggest that enhanced IL7R/STAT5 signalling presumably mediates the induction of miR182 expression, which in turn promotes the proliferation of Tcons in SLE. The relative contribution of IL7R/miR-182/FOXO1 axis on the enhanced proliferative capacity of SLE Tcons remains elusive and merit further investigation. Collectively, our data provide new insights in the pathophysiology of T cell hyper- activity in SLE and identifies miR-182 as a candidate target for future therapeutic approaches.