Circulating microRNAs in Inflammatory Bowel Diseases. In: Igaz P, editor. Circulating microRNAs in Disease Diagnostics and their Potential Biological Relevance. Basel: Springer; 2015. pp. 197-214. [DOI: 10.1007/978-3-0348-0955-9_9]

MicroRNA-31 Targets Thymic Stromal Lymphopoietin in Mucosal Infiltrated CD4+ T Cells: A Role in Achieving Mucosal Healing in Ulcerative Colitis?

BACKGROUND

Ulcerative colitis (UC) is characterized by disruption of the mucosal intestinal barrier. MicroRNAs, single-stranded noncoding RNAs of approximately 22nt, are dysregulated in UC. MicroRNAs targeting thymic stromal lymphopoietin (TSLP), a cytokine involved in T-cell maturation and polarization, may be involved in regulating UC inflammation and mucosal healing.

METHODS

Biopsy samples from non-UC (n = 38), inactive UC (n = 18), and active UC (n = 23) patients were analyzed for mRNA (real-time quantitative polymerase chain reaction) or TSLP protein expression (enzyme-linked immunosorbent assay). Flow cytometry was used to isolate CD4+ T cells from biopsies. The functional mechanism was shown using luciferase assays and antago-miR transfections. The TSLP/miR-31 association was analyzed on 196 subjects from a previous clinical trial that tested the anti-IL-13 drug tralokinumab, whereas mucosal healing effects were studied on a subset of patients (n = 13) from this trial.

RESULTS

We found that TSLP is reduced at both mRNA and protein levels in inflamed UC patients when compared with healthy subjects, in both whole biopsies and biopsy-isolated CD4+ CD25+ T cells. The expression of miR-31, predicted to target TSLP, inversely co-related to the levels of TSLP mRNA in T cells. Blocking miR-31 in vitro in T cells increased both TSLP mRNA expression and protein secretion. Luciferase assays showed that miR-31 directly targeted TSLP mRNA, suggesting a direct mechanistic link. We also found that TSLP is increased in patients who achieve mucosal healing, comparing biopsies before and after treatment from the tralokinumab trial.

CONCLUSIONS

Our data suggest a role for TSLP in promoting mucosal healing and regulating inflammation in UC, whereas miR-31 can directly block this effect.

Downregulation of miR-214-3p May Contribute to Pathogenesis of Ulcerative Colitis via Targeting STAT6

MicroRNAs (miRs) are small noncoding RNA molecules and recently have demonstrated that altered expression and functions are their tight association with ulcerative colitis (UC). Previous microarray study reported that miR-214 was downregulated in the sigmoid colon of patients with active UC, but the roles of miR-214 in the pathogenesis of UC remain to be elucidated. In this study, significant lower level of miR-214-3p and higher level of STAT6 in the intestinal mucosa of active UC patients compared with the health controls were confirmed by quantitative real-time PCR. Results of luciferase reporter assays and western blot demonstrated that miR-214-3p directly targets STAT6 and negatively regulates the expression of STAT6 at the posttranscriptional level. Furthermore, the expression of miR-214-3p was decreased in TNF-α treated HT29 cells and STAT6 protein level was increased in a time-dependent manner. Silenced STAT6 and upregulation of miR-214-3p could decrease the level of INF-γ in TNF-α treated HT29 cells. Additionally, the results of the present study indicate that miR-214-3p and STAT6 axis may be a novel therapeutic target for intestinal inflammation of patients with active UC.