The Endogenous Alterations of the Gut Microbiota and Feces Metabolites Alleviate Oxidative Damage in the Brain of LanCL1 Knockout Mice.

Fangxing Zhang,Mengying Bao,Yang Chen,Luyun Wei,Yonghua Jiang,Zengnan Mo,Shengzhu Huang,Jinling Liao,Yanyu Zeng,Dehao Cao,Nana Qi,Qianqian Luo

doi:10.3389/fmicb.2020.557342

Abstract

Altered composition of the gut microbiota has been observed in many neurodegenerative diseases. LanCL1 has been proven to protect neurons and reduce oxidative stress. The present study was designed to investigate alterations of the gut microbiota in LanCL1 knockout mice and to study the interactions between gut bacteria and the brain. Wild-type and LanCL1 knockout mice on a normal chow diet were evaluated at 4 and 8–9 weeks of age. 16s rRNA sequence and untargeted metabolomics analyses were performed to investigate changes in the gut microbiota and feces metabolites. Real-time polymerase chain reaction analysis, AB-PAS staining, and a TUNEL assay were performed to detect alterations in the gut and brain of knockout mice. The serum cytokines of 9-week-old knockout mice, which were detected by a multiplex cytokine assay, were significantly increased. In the central nervous system, there was no increase of antioxidant defense genes even though there was only low activity of glutathione S-transferase in the brain of 8-week-old knockout mice. Interestingly, the gut tight junctions, zonula occludens-1 and occludin, also displayed a downregulated expression level in 8-week-old knockout mice. On the contrary, the production of mucus increased in 8-week-old knockout mice. Moreover, the compositions of the gut microbiota and feces metabolites markedly changed in 8-week-old knockout mice but not in 4-week-old mice. Linear discriminant analysis and t-tests identified Akkermansia as a specific abundant bacteria in knockout mice. Quite a few feces metabolites that have protective effects on the brain were reduced in 8-week-old knockout mice. However, N-acetylsphingosine was the most significant downregulated feces metabolite, which may cause the postponement of neuronal apoptosis. To further investigate the effect of the gut microbiota, antibiotics treatment was given to both types of mice from 5 to 11 weeks of age. After treatment, a significant increase of oxidative damage in the brain of knockout mice was observed, which may have been alleviated by the gut microbiota before. In conclusion, alterations of the gut microbiota and feces metabolites alleviated oxidative damage to the brain of LanCL1 knockout mice, revealing that an endogenous feedback loop mechanism of the microbiota-gut-brain axis maintains systemic homeostasis.

Highlights

MATERIALS AND METHODSThe gut microbiota, which contains 500–1000 species of commensal bacteria, is a huge system in the body and plays an important role in the maintenance of host systemic homeostasis, immune function, nutrient absorbance, and many other activities (Hooper and Gordon, 2001)
LanCL1 is regarded as being similar to glutathione S-transferase (GSTs) and plays a role in GSH-mediated antioxidant defense (Huang et al, 2014)
As we found in 8–9-week-old KO mice, loss of LanCL1 in the entire body causes dysfunction in the synthesis of Antimicrobial peptides (AMPs), which may lead to alterations of the gut microbial structure

Summary

Introduction

The gut microbiota, which contains 500–1000 species of commensal bacteria, is a huge system in the body and plays an important role in the maintenance of host systemic homeostasis, immune function, nutrient absorbance, and many other activities (Hooper and Gordon, 2001). Fecal metabolites have been found to play a crucial role in regulating the host’s health and systemic homeostasis (Koh et al, 2016), with significant effect on the nervous system. LanCL1, as a peripheral membrane protein that is notably expressed in the brain and testis, was first isolated from human erythrocyte membranes, and is regarded as a member of the eukaryotic LanC-like protein family (Mayer et al, 1998, 2001). The expression of LanCL1 is developmentally regulated and is induced by neuronal activity. Genetic deletion of LanCL1 causes enhanced oxidative stress and apoptotic neurodegeneration in the brain of mice (Huang et al, 2014)

Results

Discussion

Conclusion