Intestinal epithelial dopamine receptor signaling drives sex-specific disease exacerbation in a mouse model of multiple sclerosis

Exploring the mediating role of cerebrospinal fluid metabolites in the pathway from circulating inflammatory proteins to multiple sclerosis: A Mendelian randomization study

BACKGROUND

Multiple sclerosis (MS) is an autoimmune disease in which inflammation plays a pivotal role in its pathogenesis. The inflammatory response is regulated by a complex network of cells and mediators, including circulating proteins such as cytokines and inflammatory mediators. Metabolomics is a powerful analytical approach that may provide diagnostic and therapeutic targets for MS. However, the causal effects of circulating inflammatory proteins and cerebrospinal fluid metabolites (CSFMs) on MS, as well as whether CSFMs act as mediators, remain unclear.

OBJECTIVE

In this study, we obtained data on circulating inflammatory proteins, CSFMs, and MS from the largest genome-wide association study (GWAS) dataset of the International Multiple Sclerosis Genetics Consortium (IMSGC).

METHODS

We utilized the Mendelian randomization (MR) mediation analysis method to investigate the causal relationships among circulating inflammatory proteins, CSFMs and MS. Inverse variance weighting (IVW) served as the primary statistical method. Additionally, we explored whether CSFMs act as mediators in the pathway from circulating inflammatory proteins to MS.

RESULTS

Our findings reveal that there are five inflammatory proteins associated with MS. MR analysis reveals a positive correlation between the genetic prediction of three inflammatory proteins and the occurrence of MS. Our study reveals a link between 10 CSFMs and MS. Further MR analysis reveals a positive correlation between the genetic prediction of 6 CSFMs and the development of MS. Notably, CSFMs do not exhibit a reverse effect on MS. Our study establishes a significant causal effect of circulating inflammatory proteins and CSFMs on the progression of MS. Furthermore, CSFMs do not serve as an intermediary factor in the pathway connecting inflammatory proteins with MS. Circulating inflammatory proteins and CSFMs are causally associated with MS, and CSFMs do not appear to be intermediate factors in the pathway from inflammatory proteins to MS.

Young fecal microbiota transplantation improves working memory in aged recipient rats by increasing interleukin-4 and interleukin-17 levels

While transplanting the fecal microbiota from young to aged rodents has been extensively studied (that is, young FMT [yFMT]), its mechanism of alleviating working memory decline has not been fully elucidated. In this report, we aimed to investigate the effect of yFMT on the working memory of aged recipient rats performing delayed match-to-position (DMTP) tasks and the associated cellular and molecular mechanisms. The results revealed that yFMT mitigated the decline in DMTP task performance of aged recipients. This improvement was associated with a reshaped gut microbiota and increased levels of brain-derived neurotrophic factor, N-methyl-D-aspartate receptor subunit 1, and synaptophysin, enhancing synaptic formation and transmission. The remodeling of the gut microbiome influenced peripheral circulation and the hippocampus and medial prefrontal cortex by regulating the Th17/Treg ratio and microglial polarization. Ultimately, interleukin-4 and interleukin-17 emerged as potential key molecules driving the beneficial effects of FMT. These observations provide new insights into the gutbrain axis, emphasizing the connection between the gut and brain through the circulation system, and suggest an immunological mechanism that may help reverse age-related declines in the gut microbiota.

Circulating cell-free DNA methylation profiles as noninvasive multiple sclerosis biomarkers: A proof-of-concept study

In multiple sclerosis (MS), there is a critical need for non-invasive biomarkers to concurrently classify disease subtypes, evaluate disability severity, and predict long-term progression. In this proof-of-concept study, we performed low-coverage whole-genome bisulfite sequencing (WGBS) on 75 plasma cell-free DNA (cfDNA) samples and assessed the clinical utility of cfDNA methylation as a single assay for distinguishing MS patients from non-MS controls, identifying MS subtypes, estimating disability severity, and predicting disease trajectories. We identified thousands of differentially methylated CpGs and hundreds of differentially methylated regions (DMRs) that significantly distinguished MS from controls, separated MS subtypes, and stratified disability severity levels. These DMRs were highly enriched in immunologically and neurologically relevant regulatory elements (e.g., active promoters and enhancers) and contained motifs associated with neuronal function and T-cell differentiation. To distinguish MS subtypes and severity groups, we achieved area-under-the-curve (AUC) values ranging from 0.67 to 0.81 using DMRs and 0.70 to 0.82 using inferred tissue-of-origin patterns from cfDNA methylation, significantly outperforming benchmark neurofilament light chain (NfL) and glial fibrillary acidic protein (GFAP) in the same cohort. Finally, a linear mixed-effects model identified "prognostic regions" where baseline cfDNA methylation levels were associated with disease progression and predicted future disability severity (AUC=0.81) within a 4-year evaluation window. As we plan to generate higher-depth WGBS data and validation in independent cohorts, the present findings suggest the potential clinical utility of circulating cfDNA methylation profiles as promising noninvasive biomarkers in MS diagnosis and prognosis.

Dysbiosis and extraintestinal cancers

The gut microbiota plays a crucial role in safeguarding host health and driving the progression of intestinal diseases. Despite recent advances in the remarkable correlation between dysbiosis and extraintestinal cancers, the underlying mechanisms are yet to be fully elucidated. Pathogenic microbiota, along with their metabolites, can undermine the integrity of the gut barrier through inflammatory or metabolic pathways, leading to increased permeability and the translocation of pathogens. The dissemination of pathogens through the circulation may contribute to the establishment of an immune-suppressive environment that promotes carcinogenesis in extraintestinal organs either directly or indirectly. The oncogenic cascade always engages in the disruption of hormonal regulation and inflammatory responses, the induction of genomic instability and mutations, and the dysregulation of adult stem cell proliferation. This review aims to comprehensively summarize the existing evidence that points to the potential role of dysbiosis in the malignant transformation of extraintestinal organs such as the liver, breast, lung, and pancreas. Additionally, we delve into the limitations inherent in current methodologies, particularly the challenges associated with differentiating low loads gut-derived microbiome within tumors from potential sample contamination or symbiotic microorganisms. Although still controversial, an understanding of the contribution of translocated intestinal microbiota and their metabolites to the pathological continuum from chronic inflammation to tumors could offer a novel foundation for the development of targeted therapeutics.

Microbial metabolite-receptor interactions in the gut microbiome

The gut microbiome impacts many physiological processes that greatly influence host health and disease. Metabolites produced by the gut microbiota have emerged as central players in regulating these biological pathways, often through the engagement of specific host receptors. Despite the importance of these microbial metabolites and receptors in human biology, the vast majority of these interactions remain uncharted due to the complex nature of the gut microbiome and the multitude of metabolites that these microbes produce. Here, we highlight recent developments in identifying such host-gut microbiota interactions, including characterization of bioactive metabolites and their mechanisms of action. Understanding these pathways will enable the development of prophylactics and therapeutics for treating many inflammatory diseases that are impacted by the gut microbiota.

Fecal microbiome transplantation alleviates manganese-induced neurotoxicity by altering the composition and function of the gut microbiota via the cGAS-STING/NLRP3 pathway

Manganese (Mn) is an environmental pollutant, and overexposure can cause neurodegenerative disorders similar to Alzheimer's disease and Parkinson's disease that are characterized by β-amyloid (Aβ) overexpression, Tau hyperphosphorylation and neuroinflammation. However, the mechanisms of Mn neurotoxicity are not clearly defined. In our study, a knockout mouse model of Mn exposure combined with gut flora-induced neurotoxicity was constructed to investigate the effect of gut flora on Mn neurotoxicity. The results showed that the levels of Tau, p-Tau and Aβ in the hippocampus of C57BL/6 mice were greater than those in the hippocampus of control mice after 5 weeks of continuous exposure to manganese chloride (Mn content of 200 mg/L). Transplanted normal and healthy fecal microbiota from mice significantly downregulated Tau, p-Tau and Aβ expression and ameliorated brain pathology. Moreover, Mn exposure activated the cGAS-STING pathway and altered the cecal microbiota profile, characterized by an increase in Clostridiales, Pseudoflavonifractor, Ligilactobacillus and Desulfovibrio, and a decrease in Anaerotruncus, Eubacterium_ruminantium_group, Fusimonas and Firmicutes, While fecal microbiome transplantation (FMT) treatment inhibited this pathway and restored the microbiota profile. FMT alleviated Mn exposure-induced neurotoxicity by inhibiting activation of the NLRP3 inflammasome triggered by overactivation of the cGAS-STING pathway. Deletion of the cGAS and STING genes and FMT altered the gut microbiota composition and its predictive function. Phenotypic prediction revealed that FMT markedly decreased the abundances of anaerobic and stress-tolerant bacteria and significantly increased the abundances of facultative anaerobic bacteria and biofilm-forming bacteria after blocking the cGAS-STING pathway compared to the Mn-exposed group. FMT from normal and healthy mice ameliorated the neurotoxicity of Mn exposure, possibly through alterations in the composition and function of the microbiome associated with the cGAS-STING/NLRP3 pathway. This study provides a prospective direction for future research on the mechanism of Mn neurotoxicity.

Zuogui Jiangtang Jieyu prescription improves diabetes-related depression by modulation of gut microbiota and neuroinflammation in hippocampus

Context

There is a significant challenge associated with the co-morbidity of mental and physical illnesses throughout the world. A classic example of mental/physical co-morbidity is diabetes-related depression (DD).

Objective

DD is treated with Zuogui Jiangtang Jieyu prescription (ZJJ). Diabetes and psychiatric disorders are associated with dysbiosis of the gut microbiota. In this study, the aim is to examine the effects of ZJJ on gut microbiota and neuroinflammation in DD.

Methods

A model of DD was established and treated with medium and high doses of ZJJ as well as Metformin & Fluoxetine. A detection of depressive-like behavior was then conducted on the rats. Proinflammatory cytokines were measured in cerebrospinal fluid, and HPA axis-related proteins, glucose metabolism, and lipopolysaccharide (LPS) were measured in serum. Fecal samples from each group were collected and analyzed by 16S rRNA sequencing; TLR4 and MyD88 levels were detected by Western blot and immunohistochemistry (IHC) in the hippocampus.

Results

High doses of ZJJ (ZJJ-H) were found to alleviate HPA axis hyperactivity and improve gut microbiota in rats with DD. Additionally, ZJJ treatment attenuated the inflammatory response in cerebrospinal fluid, e.g. a significant reduction in proinflammatory factors, a decrease in serum LPS levels, and an inhibition of TLR4/MyD88-related pathways in the hippocampus.

Discussion and conclusion

ZJJ improved DD glucose metabolism and alleviated depression-like behaviors by improving gut microbiota and inhibiting hippocampal TLR4/Myd88 signaling pathways.

The role of the gut microbiota in neurodegenerative diseases targeting metabolism

In recent years, the incidence of neurodegenerative diseases (NDs) has gradually increased over the past decades due to the rapid aging of the global population. Traditional research has had difficulty explaining the relationship between its etiology and unhealthy lifestyle and diets. Emerging evidence had proved that the pathogenesis of neurodegenerative diseases may be related to changes of the gut microbiota's composition. Metabolism of gut microbiota has insidious and far-reaching effects on neurodegenerative diseases and provides new directions for disease intervention. Here, we delineated the basic relationship between gut microbiota and neurodegenerative diseases, highlighting the metabolism of gut microbiota in neurodegenerative diseases and also focusing on treatments for NDs based on gut microbiota. Our review may provide novel insights for neurodegeneration and approach a broadly applicable basis for the clinical therapies for neurodegenerative diseases.

Emerging chemophysiological diversity of gut microbiota metabolites

Human physiology is profoundly influenced by the gut microbiota, which generates a wide array of metabolites. These microbiota-derived compounds serve as signaling molecules, interacting with various cellular targets in the gastrointestinal tract and distant organs, thereby impacting our immune, metabolic, and neurobehavioral systems. Recent advancements have unveiled unique physiological functions of diverse metabolites derived from tryptophan (Trp) and bile acids (BAs). This review highlights the emerging chemophysiological diversity of these metabolites and discusses the role of chemical and biological tools in analyzing and therapeutically manipulating microbial metabolism and host targets, with the aim of bridging the chemical diversity with physiological complexity in host-microbe molecular interactions.

Sex-biased gut dopamine signaling in multiple sclerosis

Multiple sclerosis shows a strong sex bias, with unclear mechanisms. In this issue of Immunity, Peng et al. elucidate a female-biased increase in intestinal dopamine signaling that diminishes protective Lactobacillus and exacerbates inflammation in a mouse model of multiple sclerosis.