Gut microbiota, pathogenic proteins and neurodegenerative diseases

Cross-talk between adipose tissue and microbiota-gut-brain-axis in brain development and neurological disorder

The gut microbiota is an important factor responsible for the physiological processes as well as pathogenesis of host. The communication between central nervous system (CNS) and microbiota occurs by different pathways i.e., chemical, neural, immune, and endocrine. Alteration in gut microbiota i.e., gut dysbiosis causes alteration in the bidirectional communication between CNS and gut microbiota and linked to the pathogenesis of neurological and neurodevelopmental disorder. Therefore, now-a-days microbiota-gut-brain-axis (MGBA) has emerged as therapeutic target for the treatment of metabolic disorder. But, experimental data available on MGBA from basic research has limited application in clinical study. In present study we first summarized molecular mechanism of microbiota interaction with brain physiology and pathogenesis via collecting data from different sources i.e., PubMed, Scopus, Web of Science. Furthermore, evidence shows that adipose tissue (AT) is active during metabolic activities and may also interact with MGBA. Hence, in present study we have focused on the relationship among MGBA, brown adipose tissue, and white adipose tissue. Along with this, we have also studied functional specificity of AT, and understanding heterogeneity among MGBA and different types of AT. Therefore, molecular interaction among them may provide therapeutic target for the treatment of neurological disorder.

The Current Potential Pathogenesis of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease mainly characterized by the accumulation of ubiquitinated proteins in the affected motor neurons. At present, the accurate pathogenesis of ALS remains unclear and there are still no effective treatment measures for ALS. The potential pathogenesis of ALS mainly includes the misfolding of some pathogenic proteins, the genetic variation, mitochondrial dysfunction, autophagy disorders, neuroinflammation, the misregulation of RNA, the altered axonal transport, and gut microbial dysbiosis. Exploring the pathogenesis of ALS is a critical step in searching for the effective therapeutic approaches. The current studies suggested that the genetic variation, gut microbial dysbiosis, the activation of glial cells, and the transportation disorder of extracellular vesicles may play some important roles in the pathogenesis of ALS. This review conducts a systematic review of these current potential promising topics closely related to the pathogenesis of ALS; it aims to provide some new evidences and clues for searching the novel treatment measures of ALS.

The role of NF-κB signaling pathway in reactive astrocytes among neurodegeneration after methamphetamine exposure by integrated bioinformatics

BACKGROUND

Methamphetamine (METH) is a highly addictive stimulant that has become one of the top five risk substances cause deaths from substance abuse. METH exposure increases the risk of neurodegenerative disease (ND), such as Parkinson's disease (PD), leading to disability and death. Activation of reactive astrocytes is an essential factor in neurodegeneration, and their complex role in METH exposure remains unclear. This study explored the role of reactive astrocyte overactivation in neurodegeneration after METH exposure.

METHODS

METH bulk RNA sequencing data (GSE107015 and GSE98793) and single-cell RNA sequencing data (GSE119861) were obtained from the GEO database. We performed immune infiltration analysis on the bulk RNA data. After cell clustering using the single-cell RNA data, astrocytes were extracted for downstream analysis. Differentially expressed genes (DEGs) were identified from the bulk and single-cell RNA sequencing datasets, and GO, KEGG, and GSEA pathway analyses were performed. The PPI network and random forest methods were performed on the overlapping genes of the DEGs to screen hub genes. To explore the common ground between METH exposure and neurodegenerative diseases, we applied a random forest algorithm to PD chip data (GSE99039 and GSE72267) to establish a diagnostic model using the hub genes in METH. New object recognition and the Morris water maze were used to examine cognitive function in mice exposed to METH for 14 days in vivo. Astrocytes were cocultured with neurons for the detection of intercellular crosstalk.

RESULTS

DEGs in the METH group significantly enriched pathways related to NDs, inflammation, and the NF-κB signaling pathway. Immune infiltration analysis revealed significantly increased infiltration of monocytes, T cells, and NK cells and decreased infiltration of neutrophils in the METH group. An intersection of 44 hub genes was screened based on the PPI network and random forest algorithm. These genes suggest that there might be similar pathogenesis between METH exposure and PD. METH exposure resulted in learning memory impairment, hippocampal astrocyte activation, and upregulation of NF-κB expression in mice. Activation of reactive astrocytes cocultured with neurons causes neural damage.

CONCLUSIONS

This study explored the crosstalk between astrocytes and neurons in METH exposure, providing a potential pathogenesis to explore the altered immune microenvironment involving reactive astrocytes after METH exposure.

Gut-Brain Axis Deregulation and Its Possible Contribution to Neurodegenerative Disorders

The gut-brain axis is an essential communication pathway between the central nervous system (CNS) and the gastrointestinal tract. The human microbiota is composed of a diverse and abundant microbial community that compasses more than 100 trillion microorganisms that participate in relevant physiological functions such as host nutrient metabolism, structural integrity, maintenance of the gut mucosal barrier, and immunomodulation. Recent evidence in animal models has been instrumental in demonstrating the possible role of the microbiota in neurodevelopment, neuroinflammation, and behavior. Furthermore, clinical studies suggested that adverse changes in the microbiota can be considered a susceptibility factor for neurological disorders (NDs), such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). In this review, we will discuss evidence describing the role of gut microbes in health and disease as a relevant risk factor in the pathogenesis of neurodegenerative disorders, including AD, PD, HD, and ALS.

Microbiota Metabolites and Immune Regulation Affect Ischemic Stroke Occurrence, Development, and Prognosis

The gut microbiota are not only related to the development and occurrence of digestive system disease, but also have a bidirectional relationship with nervous system diseases via the microbiota-gut-brain axis. At present, correlations between the gut microbiota and neurological diseases, including stroke, are one of the focuses of investigation and attention in the medical community. Ischemic stroke (IS) is a cerebrovascular disease accompanied by focal neurological deficit or central nervous system injury or death. In this review, we summarize the contemporary latest research on correlations between the gut microbiota and IS. Additionally, we discuss the mechanisms of gut microbiota implicated in IS and related to metabolite production and immune regulation. Moreover, the factors of gut microbiota that affecting IS occurrence, and research implicating the gut microbiota as potential therapeutic targets for IS, are highlighted. Our review highlights the evidential relationships and connections between the gut microbiota and IS pathogenesis and prognosis.

Effect and mechanism of chlorogenic acid on cognitive dysfunction in mice by lipopolysaccharide-induced neuroinflammation

Background

Neuroinflammation is an important factor causing numerous neurodegenerative pathologies. Inflammation can lead to abnormal neuronal structure and function and even death, followed by cognitive dysfunction. There is growing evidence that chlorogenic acid has anti-inflammatory effects and immunomodulatory activity.

Purpose

The aim of this study was to elucidate the potential targets and molecular mechanisms of chlorogenic acid in the treatment of neuroinflammation.

Methods

We used the lipopolysaccharide-induced neuroinflammation mouse model and the lipopolysaccharide-stimulated BV-2 cells in vitro model. Behavioral scores and experiments were used to assess cognitive dysfunction in mice. HE staining and immunohistochemistry were used to assess neuronal damage in the mouse brain. Immunofluorescence detected microglia polarization in mouse brain. Western blot and flow cytometry detected the polarization of BV-2 cells. The migration of BV-2 cells was detected by wound healing assay and transwell assay. Potential targets for chlorogenic acid to exert protective effects were predicted by network pharmacology. These targets were then validated using molecular docking and experiments.

Results

The results of in vivo experiments showed that chlorogenic acid had an obvious ameliorating effect on neuroinflammation-induced cognitive dysfunction. We found that chlorogenic acid was able to inhibit BV-2 cells M1 polarization and promote BV-2 cells M2 polarization in vitro while also inhibiting the abnormal migration of BV-2 cells. Based on the network pharmacology results, we identified the TNF signaling pathway as a key signaling pathway in which chlorogenic acid exerts anti-neuroinflammatory effects. Among them, Akt1, TNF, MMP9, PTGS2, MAPK1, MAPK14, and RELA are the core targets for chlorogenic acid to function.

Conclusion

Chlorogenic acid can inhibit microglial polarization toward the M1 phenotype and improve neuroinflammation-induced cognitive dysfunction in mice by modulating these key targets in the TNF signaling pathway.

Connecting the Gut Microbiota and Neurodegenerative Diseases: the Role of Bile Acids

With the acceleration of global population aging, neurodegenerative diseases (NDs) will become the second leading cause of death in the world, which seriously threatens human life and health. Alzheimer's disease and Parkinson's disease are the most common and typical NDs. The exact mechanisms of the NDs occurrence and development remain unclear, which may be related to immune, oxidative stress, and abnormal aggregation of pathogenic proteins. Studies have suggested that gut microbiota (GM) influences brain function and plays an important role in regulating emotional and cognitive function. Recently, bile acids (BAs) have become the "star molecule" in the microbiota-gut-brain (MGB) axis research. BAs have been reported to exert anti-inflammatory, antioxidant, and neuroprotective activities in NDs. However, the role of BAs in the connection between GM and the central nervous system (CNS) is still unclear. In this review, we will review the possible mechanisms of BAs between GM and NDs and explore the function of BAs to provide ideas for the prevention and treatment of NDs in the future.