AUTHOR=Wang Hesong , Sun Ye , Xin Jinge , Zhang Tao , Sun Ning , Ni Xueqin , Zeng Dong , Bai Yang 

TITLE=Lactobacillus johnsonii BS15 Prevents Psychological Stress–Induced Memory Dysfunction in Mice by Modulating the Gut–Brain Axis

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.01941

DOI=10.3389/fmicb.2020.01941

ISSN=1664-302X

ABSTRACT=<p>Researchers are attempting to harness the advantages of the gut–brain axis to prevent neurocognitive disorders by enhancing intestinal health. In this study, four groups of ICR mice were orally gavaged with either phosphate-buffered saline (control and CW groups) or the probiotic strain <italic>Lactobacillus johnsonii</italic> BS15 (P and PW group; daily amounts of 2 × 10<sup>8</sup> colony-forming units) for 28 days. From days 22 to 28, the mice in the CW and PW groups were subjected to water-avoidance stress (WAS). The issue of whether psychological stress–induced memory dysfunction can be prevented via <italic>L. johnsonii</italic> BS15 pretreatment to modulate the gut–brain axis was investigated. Results show that <italic>L. johnsonii</italic> BS15 enhanced gut development by increasing villus height in the jejunum and ileum as well as villus height:crypt depth ratio in the ileum. <italic>L. johnsonii</italic> BS15 increased the activities of digestive enzymes, including trypsin and lipase in the jejunum and ileum. The intestinal goblet cell number was also increased by <italic>L. johnsonii</italic> BS15 pretreatment. Moreover, <italic>L. johnsonii</italic> BS15 balanced the gut microbiota by increasing the log<sub>10</sub> DNA gene copies of <italic>Lactobacillus</italic> spp. and <italic>L. johnsonii</italic> and decreasing that of Enterobacteriaceae in the cecum. <italic>L. johnsonii</italic> BS15 also exerted preventive effects on intestinal permeability WAS by modulating diamine oxidase and <sub>D</sub>-lactate levels in the serum and mRNA expression levels of the tight junction proteins claudin-1, occludin, and ZO-1 in the jejunum and ileum. <italic>L. johnsonii</italic> BS15 pretreatment modulated inflammatory factors, specifically tumor necrosis factor-alpha, interferon-gamma, and interleukin-10. <italic>L. johnsonii</italic> BS15 pretreatment improved their performance in two behavioral tests, namely the novel object and T-maze tests. This result indicates that psychological stress–induced memory dysfunction possibly could be prevented through the gut–brain axis. In addition, <italic>L. johnsonii</italic> BS15 exerted beneficial effects on the hippocampus by modulating memory-related functional proteins, especially those related to synaptic plasticity, such as brain-derived neurotrophic factor and stem cell factor. Moreover, <italic>L. johnsonii</italic> BS15 recovered antioxidant capacity and exerted protective effects on mitochondrion-mediated apoptosis in the hippocampus. Collectively, the modulation of the gut–brain axis by <italic>L. johnsonii</italic> BS15 could be considered a promising non-invasive treatment modality for psychological stress–induced memory dysfunction.</p>