The role of the gut microbiota in acute kidney injury: a new therapeutic candidate?

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial and No Derivatives License (http:// creativecommons.org/licenses/by-nc-nd/4.0/) which permits unrestricted non-commercial use, distribution of the material without any modifications, and reproduction in any medium, provided the original works properly cited. The intestinal microbiota, a community of 100 trillion microorganisms (more than 1,000 species that consist of mostly bacteria but also viruses, fungi, and protozoa), plays an important role in maintaining homeostasis (especially in regard to mucosal immunity and nutrient metabolism) in the human gastrointestinal tract [1]. The intestinal epithelial barrier can be divided into three components; a biological barrier, a physical barrier, and an immune barrier [2]. The biological barrier is composed of bacterial and fungal symbionts that are closely attached to the intestinal mucosal surface and compete with pathogenic bacteria. The physical barrier refers to intestinal epithelial cells with apical tight junctions (TJs). Changes in TJs can lead to increased permeability, allowing bacteria, endotoxins, and macromolecules to enter the circulatory system. The immune barrier is the third system for maintaining microbial homeostasis. Dendritic cells in the lamina propria activate T cells to evoke an adaptive immune response. Innate lymphoid cells located in the gut epithelium have key defensive functions to produce or activate the release