Journal of Neuroinflammation Research Report: Neuroprotective Effects of Prevotella copri Transplantation in a Traumatic Brain Injury Mouse Model

Background

Traumatic brain injury (TBI) affects over 50 million people globally each year and is considered a significant public health challenge. Secondary injuries associated with TBI are largely related to neuroinflammation and excessive reactive oxygen species (ROS) production, leading to neurodegenerative changes and chronic inflammation. Despite recent progress in understanding the pathological mechanisms and treatment strategies for TBI, effective clinical treatments remain relatively lacking. Moreover, some studies have shown that central nervous system diseases, including acute ischemic stroke, Alzheimer’s disease, and Parkinson’s disease, can be treated by modulating the gut microbiome.

Previous studies have found that TBI can lead to gut dysbiosis, specifically significant changes in the abundance and diversity of bacteria such as Pseudomonas, Burkholderia, Alloiococcus, and Moraxella. In a previous study, Gu et al. found that TBI significantly decreased the abundance of Prevotella copri (P. copri), and reference [15] also reported similar findings. P. copri is a gram-negative anaerobic bacterium capable of producing antioxidant short-chain fatty acids (SCFAs). However, there is a lack of in-depth research on the treatment of TBI by modulating specific gut strains. Therefore, this study explored the effects of P. copri transplantation on TBI and its relationship with the Guanosine (Guo)-PI3K/AKT signaling pathway.

Research Source

This research was authored by Nina Gu et al., from Chongqing Medical University, and published in the Journal of Neuroinflammation in 2024. The corresponding authors are Chongjie Cheng, Xiaochuan Sun, and Zhijian Huang, with email addresses 358187887@qq.com, sunxiaochuan@cqmu.edu.cn, and zhijian@cqmu.edu.cn, respectively.

Research Procedure

Experimental Model

Adult male C57BL/6J mice were used, and the TBI model was established using a standard CCI device (TBI-0310). The experiment consisted of eight main steps:

1. P. copri Abundance Time Course: The abundance of P. copri at different time points (1 day, 3 days, 7 days, 14 days, 21 days, 28 days) before and after injury was evaluated using quantitative PCR (qPCR).

2. Neurological Function Assessment: Mice were randomly divided into four groups: Sham, TBI, TBI+Vehicle, and TBI+P. copri. Short-term neurological function was assessed using the Neurological Severity Score (NSS) and wire-hanging test. Learning, memory, and anxiety behaviors were evaluated using the Morris water maze and open field test.

3. Gut Function Assessment: The effects of P. copri transplantation on body weight, food intake, gut permeability, and gut function were evaluated. Gut function was assessed using FITC-dextran permeability and barium meal X-ray imaging.

4. Gut Microbiome Analysis: The gut bacterial community composition was analyzed using 16S rDNA (V3+V4 region) sequencing.

5. Serum Metabolite Analysis: Serum metabolites were analyzed using UPLC-QQQ-MS/MS. Metabolites were analyzed using OPLS-DA and multivariate statistical models.

6. Guo Level Detection: Guo levels in the ipsilateral brain, serum, and feces were detected using ELISA.

7. Oxidative Stress and Blood-Brain Barrier (BBB) Analysis: Indicators such as CAT, SOD, ROS, etc., were analyzed. BBB permeability and neuronal apoptosis were evaluated using Western blot, immunofluorescence, and transmission electron microscopy.

8. PI3K/AKT Signaling Pathway: The expression levels of p-PI3K and p-AKT were analyzed by Western blot to evaluate the mediating role of the Guo-PI3K/AKT pathway in the neuroprotective effects of P. copri in TBI.

Main Research Findings

P. copri Abundance and Neurological Function

• P. copri Abundance: The abundance of P. copri significantly decreased after TBI, reaching its lowest point at 7 days, and gradually recovered but did not reach pre-injury levels.
• Neurological Function Assessment: P. copri treatment significantly improved the NSS scores, wire-hanging test results, and anxiety-related behaviors in the open field test in TBI mice.

Gut Function

• Body Weight and Food Intake: Body weight and food intake significantly decreased after TBI, but gradually recovered with P. copri treatment.
• Gut Permeability and Motility: FITC concentration and gut transit time were significantly increased in the TBI group, indicating increased gut permeability and impaired motility. P. copri treatment significantly improved these alterations, restoring gut barrier integrity and motility function.

Gut Microbiome and Metabolites

• 16S rDNA Sequencing Analysis: P. copri treatment increased the relative abundance of Akkermansia, Lactobacillus, Lachnospiraceae, and others in the gut microbiome, indicating that P. copri reshaped the gut microbiome.
• Serum Metabolite Analysis: Compared to the Sham and TBI groups, the TBI+P. copri group showed significantly increased levels of Guo in the serum.

Oxidative Stress and Neuroprotection

• Guo Levels: ELISA results showed that P. copri treatment significantly increased Guo levels in feces, serum, and brain.
• Oxidative Stress: Both P. copri and Guo treatment significantly increased CAT and SOD activities, reduced ROS and GSSG levels, and increased the GSH/GSSG ratio, indicating that P. copri effectively alleviated TBI-induced oxidative stress injury.
• BBB Permeability: P. copri and Guo treatment significantly increased the expression of Occludin and ZO-1, ameliorating TBI-induced BBB disruption.

Neuronal Apoptosis and PI3K/AKT Pathway

• Neuronal Apoptosis: TUNEL-positive neurons significantly increased in TBI mice, and P. copri treatment reduced these positive cells. Additionally, Western blot results showed that P. copri significantly increased Bcl-2 expression and decreased Bax expression.
• PI3K/AKT Signaling Pathway: P. copri and Guo treatment significantly increased the expression of p-PI3K and p-AKT, and the inhibitor LY294002 abrogated this increase and the neuroprotective effects.

Conclusion

This study is the first to demonstrate that P. copri transplantation can improve gastrointestinal function, reshape the gut microbiome, alleviate blood-brain barrier injury and neuronal apoptosis in TBI mice. These improvements may be mediated through the Guo-dependent PI3K/AKT signaling pathway. The results support the importance of P. copri as a potential therapeutic strategy for TBI and highlight the crucial role of the gut-brain axis in neurological recovery.