Potential Roles of Exosomal lncRNAs in the Intestinal Mucosal Immune Barrier

Abstract

The intestinal mucosal immune barrier protects the host from the invasion of foreign pathogenic microorganisms. Immune cells and cytokines in the intestinal mucosa maintain local and systemic homeostasis by participating in natural and adaptive immunity. Deficiency of the intestinal mucosal immune barrier is associated with a variety of intestinal illnesses. Exosomes are phospholipid bilayer nanovesicles that allow cell-cell communication by secreting physiologically active substances including proteins, lipids, transcription factors, mRNAs, micro-RNAs (miRNAs), and long noncoding RNAs (lncRNAs). Exosomal lncRNAs are involved in immune cell differentiation and the modulation of the immune response. This review briefly introduces the potential role of exosomal lncRNAs in the intestinal mucosal immune barrier and discusses their relevance to intestinal illnesses.

Figure 1

Functions of exosomal lncRNAs on intestinal mucosal immune system. Exosomal lncRNAs promote Th17 cell differentiation and IFN-γ secretion of Th1 cells, regulate the polarization of Treg cells and macrophages, reprogram DCs into a tolerant phenotype, affect the cytokine secretion and inflammatory signaling pathways, and participate in immune response and immune evasion of cancer cells.

Figure 2

Formation of exosomes and mechanisms of exosomal lncRNA in the intestinal mucosal immune barrier. The formation of the exosome begins at endosomes formation and then maturates to multivesicular bodies (MVBs). MVBs either fuse with lysosomes and are degraded or fuse with the plasma membrane resulting in the release of free exosomes to the extracellular environment. Exosomes may contain various cargoes including proteins, mRNAs, lncRNAs, and miRNAs. Exosomal lncRNAs participate in the intestinal mucosal immune response by influencing the activity of transcription factors or acting as scaffolds for chromatin modification complex, miRNA sponges, translation inhibitors, or mRNA degradation signals. This leads to the regulation of various biological events including the integrity of IECs, polarization of macrophages, differentiation of CD4⁺ T cells, and some inflammatory signaling pathways.