The microRNAs miR-211-5p and miR-204-5p modulate ER stress in human beta cells.

Abstract

MicroRNAs (miRNAs) are a class of small non-coding RNAs that regulate gene expression. Type 1 diabetes is an autoimmune disease characterized by insulits (islets inflammation) and pancreatic beta cell destruction. The pro-inflammatory cytokines interleukin-1β (IL-1β) and interferon-γ (IFN-γ) are released during insulitis and trigger endoplasmic reticulum (ER) stress and expression of pro-apoptotic Bcl-2 proteins in beta cells, thus contributing to their death. The nature of miRNAs that regulate ER stress and beta cell apoptosis remains to be elucidated. We have performed a global miRNA expression profile on cytokine-treated human islets and observed a marked down-regulation of miR-211-5p. By real-time PCR and western blot analysis, we confirmed cytokine-induced changes in the expression of miR-211-5p and the closely related miR-204-5p and downstream ER-stress related genes in human beta cells. Blocking of endogenous miRNA-211-5p and miR-204-5p by the same inhibitor (it is not possible to block separately these two miRs) increased human beta cell apoptosis, as measured by Hoechst/Propidium Iodide staining and by determination of cleaved caspase-3 activation. Interestingly, miRs-211-5p and 204-5p regulate the expression of several ER stress markers downstream of PERK, particularly the pro-apoptotic transcription factor CHOP. Blocking CHOP expression by a specific siRNA partially prevented the increased apoptosis observed following miR-211-5p/miR-204-5p inhibition. These observations identify a novel crosstalk between miRNAs, ER stress and beta cell apoptosis in early type 1 diabetes.