The extracellular vesicle of gut microbial Paenalcaligenes hominis is a risk factor for vagus nerve-mediated cognitive impairment

Gut microbiota-astrocyte axis: new insights into age-related cognitive decline

With the rapidly aging human population, age-related cognitive decline and dementia are becoming increasingly prevalent worldwide. Aging is considered the main risk factor for cognitive decline and acts through alterations in the composition of the gut microbiota, microbial metabolites, and the functions of astrocytes. The microbiota-gut-brain axis has been the focus of multiple studies and is closely associated with cognitive function. This article provides a comprehensive review of the specific changes that occur in the composition of the gut microbiota and microbial metabolites in older individuals and discusses how the aging of astrocytes and reactive astrocytosis are closely related to age-related cognitive decline and neurodegenerative diseases. This article also summarizes the gut microbiota components that affect astrocyte function, mainly through the vagus nerve, immune responses, circadian rhythms, and microbial metabolites. Finally, this article summarizes the mechanism by which the gut microbiota-astrocyte axis plays a role in Alzheimer's and Parkinson's diseases. Our findings have revealed the critical role of the microbiota-astrocyte axis in age-related cognitive decline, aiding in a deeper understanding of potential gut microbiome-based adjuvant therapy strategies for this condition.

Gut-brain axis interplay via STAT3 pathway: Implications of Helicobacter pylori derived secretome on inflammation and Alzheimer's disease

Helicobacter pylori is a pathogenic bacterium that causes gastritis and gastric carcinoma. Besides gastric complications its potential link with gut-brain axis disruption and neurological disorders has also been reported. The current study investigated the plausible role and its associated molecular mechanism underlying H. pylori mediated gut-brain axis disruption and neuroinflammation leading to neurological modalities like Alzheimer's disease (AD). We have chosen the antimicrobial resistant and susceptible H. pylori strains on the basis of broth dilution method. We have observed the increased inflammatory response exerted by H. pylori strains in the gastric as well as in the neuronal compartment after treatment with Helicobacter pylori derived condition media (HPCM). Further, elevated expression of STAT1, STAT3, and AD-associated proteins- APP and APOE4 was monitored in HPCM-treated neuronal and neuron-astrocyte co-cultured cells. Excessive ROS generation has been found in these cells. The HPCM treatment to LN229 causes astrogliosis, evidenced by increased glial fibrillary acidic protein. Our results indicate the association of STAT3 as an important regulator in the H. pylori-mediated pathogenesis in neuronal cells. Notably, the inhibition of STAT3 by its specific inhibitor, BP-1-102, reduced the expression of pSTAT3 and AD markers in neuronal compartment induced by HPCM. Thus, our study demonstrates that H. pylori infection exacerbates inflammation in AGS cells and modulates the activity of STAT3 regulatory molecules. H. pylori secretome could affect neurological compartments by promoting STAT3 activation and inducing the expression of AD-associated signature markers. Further, pSTAT-3 inhibition mitigates the H. pylori associated neuroinflammation and amyloid pathology.

Desmodium styracifolium (Osb.) Merr. Extracts alleviate cholestatic liver disease by FXR pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Cholestatic liver disease (CLD) is a disease characterized by cholestasis. Farnesoid X receptor (FXR) is a nuclear receptor that maintains homeostasis in bile acid metabolism. Studies have shown that gut microbiota interfered with the FXR pathway. Modulation of FXR to inhibit cholestasis has become a key measure in the treatment of CLD. In traditional folk medicine, Desmodium styracifolium (Osb.) Merr. was used as a primary treatment for gallstones, gonorrhea, jaundice, cholecystitis and other diseases. Modern pharmacological studies had also found that the herb has anti-calculus, anti-inflammatory, antioxidant, diuretic and liver damage. Therefore, we speculated that Desmodium styracifolium (Osb.) Merr. extracts (DME) could alleviate CLD through the FXR pathway and might be associated with the gut microbiota. However, studies of DME alleviating CLD through the FXR pathway have not been reported.

AIM OF STUDY

To study the effect and mechanism of DME in relieving CLD through in vivo and in vitro experiments.

MATERIALS AND METHODS

First, mice were administrated with alpha-naphthyl isothiocyanate (ANIT) to establish a CLD model in vivo. Meanwhile, HepG2 cells were induced by lithocholic acid (LCA) to establish the CLD model in vitro. To evaluate the therapeutic effect of DME on CLD mice, hematoxylin-eosin (HE) staining, and biochemical indicators were performed. The prototype of the blood components in mice serum was detected by ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). 16S rDNA sequencing was used to analyze the gut microbiota. Finally, the protein and mRNA expression of the FXR pathway in mice liver tissues or HepG2 cells were detected by Western blot, qRT-PCR, or immunofluorescence.

RESULTS

Pathological testing and biochemical indexes showed that DME significantly reduced serum ALT, AST, ALP, TBIL, DBIL, TBA and liver TBA levels, and attenuated liver tissue injury, necrosis and jaundice in CLD mice. In addition, MetagenomeSeq analysis of gut microbiota showed that DME significantly up-regulated the abundance of Parvibacter, down-regulated the abundance of Paenalcaligenes, and regulated bile acid homeostasis. In terms of mRNA expression, DME significantly upregulated the mRNA levels of Nr1h4, Abcb11, Cyp7a1 and Slc10a1. Meanwhile, in terms of protein expression, DME significantly up-regulated the protein expression levels of FXR, BSEP, CYP7A1 and NTCP, which regulated bile acid homeostasis. Finally, the molecular docking results showed that the components of DME, such as Lumichrome, Daidzein and Folic acid, all had good binding ability with FXR, and the surface plasmon resonance (SPR) results also showed that both Lumichrome and Daidzein had a relatively high affinity with FXR.

CONCLUSION

DME alleviated CLD through the FXR pathway, and the mechanisms might be associated with the gut microbiota.

Tryptophan Metabolism in Alzheimer's Disease with the Involvement of Microglia and Astrocyte Crosstalk and Gut-Brain Axis

Alzheimer's disease (AD) is an age-dependent neurodegenerative disease characterized by extracellular Amyloid Aβ peptide (Aβ) deposition and intracellular Tau protein aggregation. Glia, especially microglia and astrocytes are core participants during the progression of AD and these cells are the mediators of Aβ clearance and degradation. The microbiota-gut-brain axis (MGBA) is a complex interactive network between the gut and brain involved in neurodegeneration. MGBA affects the function of glia in the central nervous system (CNS), and microbial metabolites regulate the communication between astrocytes and microglia; however, whether such communication is part of AD pathophysiology remains unknown. One of the potential links in bilateral gut-brain communication is tryptophan (Trp) metabolism. The microbiota-originated Trp and its metabolites enter the CNS to control microglial activation, and the activated microglia subsequently affect astrocyte functions. The present review highlights the role of MGBA in AD pathology, especially the roles of Trp per se and its metabolism as a part of the gut microbiota and brain communications. We (i) discuss the roles of Trp derivatives in microglia-astrocyte crosstalk from a bioinformatics perspective, (ii) describe the role of glia polarization in the microglia-astrocyte crosstalk and AD pathology, and (iii) summarize the potential of Trp metabolism as a therapeutic target. Finally, we review the role of Trp in AD from the perspective of the gut-brain axis and microglia, as well as astrocyte crosstalk, to inspire the discovery of novel AD therapeutics.

The extracellular vesicle of depressive patient-derived Escherichia fergusonii induces vagus nerve-mediated neuroinflammation in mice

BACKGROUND

Gut microbiota dysbiosis is closely associated with psychiatric disorders such as depression and anxiety (DA). In our preliminary study, fecal microbiota transplantation from volunteers with psychological stress and subclinical symptoms of depression (Vsd) induced DA-like behaviors in mice. Escherichia fergusonii (Esf) was found to be more abundant in the feces of Vsd compared to healthy volunteers. Therefore, we investigated the effect of Esf on DA-like behavior and neuroinflammation in mice with and without celiac vagotomy.

METHODS AND RESULTS

Orally gavaged Esf increased DA-like behaviors, tumor necrosis factor (TNF)-α, and toll-like receptor-4 (TLR4) expression, and NF-κB+Iba1+ and lipopolysaccharide (LPS)+Iba1+ cell populations, while decreasing serotonin, 5-HT1A receptor, and brain-derived neurotrophic factor (BDNF) expression in the hippocampus and prefrontal cortex. However, celiac vagotomy attenuated Esf-induced DA-like behavior and neuroinflammation. Orally gavaged extracellular vesicle (EV) from Vsd feces (vfEV) or Esf culture (esEV) induced DA-like behavior and inflammation in hippocampus, prefrontal cortex and colon. However, celiac vagotomy attenuated vfEV- or esEV-induced DA-like behaviors and inflammation in the brain alone, while vfEV- or esEV-induced blood LPS and TNF-α levels, colonic TNF-α expression and NF-κB-positive cell number, and fecal LPS level were not. Although orally gavaged fluorescence isothiocyanate-labeled esEV was translocated into the blood and hippocampus, celiac vagotomy decreased its translocation into the hippocampus alone.

CONCLUSIONS

esEVs may be translocated into the brain via the vagus nerve and bloodstream, subsequently inducing TNF-α expression and suppressing serotonin, its receptor, and BDNF expression through the activation of TLR4-mediated NF-κB signaling, thereby contributing to DA pathogenesis.

Outer membrane vesicles of Acinetobacter baumannii DS002 carry circular DNA similar to bovine meat and milk factors (BMMFs) and SPHINX 2.36 and probably play a role in interdomain lateral gene transfer

The discovery of Replication Competent Circular DNA molecules in mammalian cells and tissues is being linked to debilitating diseases, such as multiple sclerosis (MS), bovine spongiform encephalopathy (BSE), and colorectal cancer (CRC). These circular DNA molecules, otherwise known as bovine meat and milk factors (BMMFs) and Slow Progressive Hidden INfections of variable (X) latency (SPHINX), bear significant (80%) sequence similarity with the plasmids of Acinetobacter baumannii strains. Nanostructures, such as bacterial outer membrane vesicles (OMVs) serve as vehicles for transporting biomolecular cargo and have the potential to facilitate interkingdom lateral mobility of DNA. Strengthening the proposed hypothesis, this study demonstrates that OMVs derived from A. baumannii DS002 carrying four plasmids and genome (pTS236) of phage, AbDs1, successfully reached different parts of the body, including the central nervous system, following the injection of fluorescein isothiocyanate (FITC)-labeled OMVs into experimental mice. Out of the four OMV-associated plasmids, three (pTS4586, pTS9900, and pTS134338) were identified within the lumen, and the fourth one (pTS11291) was found on the surface of OMVs. In addition to the indigenous plasmids, the phage-encoded protein, Orf96, anchored on the surface of the OMVs by establishing a strong interaction with the OMV-associated porin, OmpA. Intriguingly, a subset of labeled OMVs, when incubated with Neuro2A cells, translocated across the membrane and reached to the cytoplasmic space of the cells. Collectively, the experimental evidence presented herein underscores the promising potential of OMVs as vehicles for delivering molecular cargo containing plasmids and phage genomes to diverse mammalian tissues and cells.

IMPORTANCE

Several independent studies have demonstrated the existence of replication competent circular DNA molecules of bacterial and viral origin in mammalian cells and tissues. However, studies about their origin and lateral mobility to mammalian cells are scarce. Our work describes the existence of circular DNA, similar to that of DNA molecules identified in mammalian cells, OMVs derived from soil isolate of A. baumannii DS002. Furthermore, the work also provides visual evidence that demonstrates the passage of labeled OMVs to different organs of experimental mice within hours after intravenously administering OMVs into experimental mice. Some of the labeled OMVs have even crossed the membrane of Neuro2A, suggesting the existence of interkingdom horizontal mobility between bacteria and mammals.

Heat-Processed Soybean Germ Extract and Lactobacillus gasseri NK109 Supplementation Reduce LPS-Induced Cognitive Impairment and Colitis in Mice

Soybean alleviates cognitive impairment. In our preparatory experiment, we found that dry-heat (90 °C for 30 min)-processed soybean embryo ethanol extract (hSE) most potently suppressed lipopolysaccharide (LPS)-induced tumor necrosis factor (TNF)-α expression in BV2 cells among dry-heat-, steaming-, and oil exclusion-processed soybean embryo ethanol extracts (SEs). Heat processing increased the absorbable soyasaponin Bb content of SE. Therefore, we investigated whether hSE and its supplement could mitigate LPS-impaired cognitive function in mice. Among dry-heat-, steaming-, and oil exclusion-processed SEs, hSE mitigated LPS-impaired cognitive function more than parental SE. hSE potently upregulated LPS-suppressed brain-derived neurotropic factor (BDNF) expression in the hippocampus, while LPS-induced TNF-α and IL-1β expression in the hippocampus and colon were downregulated. Lactobacillus gasseri NK109 additively increased the cognitive function-enhancing activity of hSE in mice with LPS-induced cognitive impairment as follows: the hSE and NK109 mix potently increased cognitive function and hippocampal BDNF expression and BDNF-positive neuron cell numbers and decreased TNF-α expression and NF-κB-positive cell numbers in the hippocampus and colon. These findings suggest that hSE and its supplement may decrease colitis and neuroinflammation by suppressing NF-κB activation and inducing BDNF expression, resulting in the attenuation of cognitive impairment.

Microbiota-Derived Extracellular Vesicle as Emerging Actors in Host Interactions

The human microbiota is an intricate micro-ecosystem comprising a diverse range of dynamic microbial populations mainly consisting of bacteria, whose interactions with hosts strongly affect several physiological and pathological processes. The gut microbiota is being increasingly recognized as a critical player in maintaining homeostasis, contributing to the main functions of the intestine and distal organs such as the brain. However, gut dysbiosis, characterized by composition and function alterations of microbiota with intestinal barrier dysfunction has been linked to the development and progression of several pathologies, including intestinal inflammatory diseases, systemic autoimmune diseases, such as rheumatic arthritis, and neurodegenerative diseases, such as Alzheimer's disease. Moreover, oral microbiota research has gained significant interest in recent years due to its potential impact on overall health. Emerging evidence on the role of microbiota-host interactions in health and disease has triggered a marked interest on the functional role of bacterial extracellular vesicles (BEVs) as mediators of inter-kingdom communication. Accumulating evidence reveals that BEVs mediate host interactions by transporting and delivering into host cells effector molecules that modulate host signaling pathways and cell processes, influencing health and disease. This review discusses the critical role of BEVs from the gut, lung, skin and oral cavity in the epithelium, immune system, and CNS interactions.

Effects of bacterial extracellular vesicles derived from oral and gastrointestinal pathogens on systemic diseases

Oral microbiota and gastrointestinal microbiota, the two largest microbiomes in the human body, are closely correlated and frequently interact through the oral-gut axis. Recent research has focused on the roles of these microbiomes in human health and diseases. Under normal conditions, probiotics and commensal bacteria can positively impact health. However, altered physiological states may induce dysbiosis, increasing the risk of pathogen colonization. Studies suggest that oral and gastrointestinal pathogens contribute not only to localized diseases at their respective colonized sites but also to the progression of systemic diseases. However, the mechanisms by which bacteria at these local sites are involved in systemic diseases remain elusive. In response to this gap, the focus has shifted to bacterial extracellular vesicles (BEVs), which act as mediators of communication between the microbiota and the host. Numerous studies have reported the targeted delivery of bacterial pathogenic substances from the oral cavity and the gastrointestinal tract to distant organs via BEVs. These pathogenic components subsequently elicit specific cellular responses in target organs, thereby mediating the progression of systemic diseases. This review aims to elucidate the extensive microbial communication via the oral-gut axis, summarize the types and biogenesis mechanisms of BEVs, and highlight the translocation pathways of oral and gastrointestinal BEVs in vivo, as well as the impacts of pathogens-derived BEVs on systemic diseases.

The potential role of gut microbiota-derived metabolites as regulators of metabolic syndrome-associated mitochondrial and endolysosomal dysfunction in Alzheimer's disease

Although the role of gut microbiota (GMB)-derived metabolites in mitochondrial and endolysosomal dysfunction in Alzheimer's disease (AD) under metabolic syndrome remains unclear, deciphering these host-metabolite interactions represents a major public health challenge. Dysfunction of mitochondria and endolysosomal networks (ELNs) plays a crucial role in metabolic syndrome and can exacerbate AD progression, highlighting the need to study their reciprocal regulation for a better understanding of how AD is linked to metabolic syndrome. Concurrently, metabolic disorders are associated with alterations in the composition of the GMB. Recent evidence suggests that changes in the composition of the GMB and its metabolites may be involved in AD pathology. This review highlights the mechanisms of metabolic syndrome-mediated AD development, focusing on the interconnected roles of mitochondrial dysfunction, ELN abnormalities, and changes in the GMB and its metabolites. We also discuss the pathophysiological role of GMB-derived metabolites, including amino acids, fatty acids, other metabolites, and extracellular vesicles, in mediating their effects on mitochondrial and ELN dysfunction. Finally, this review proposes therapeutic strategies for AD by directly modulating mitochondrial and ELN functions through targeting GMB metabolites under metabolic syndrome.

Biology of Exfoliation of Plasma Membrane-Derived Vesicles and the Radiation Response: Historical Background, Applications in Biodosimetry and Cell-Free Therapeutics, and Quantal Mechanisms for Their Release and Function with Implications for Space Travel

This historical review of extracellular vesicles in the setting of exposure to ionizing radiation (IR) traces our understanding of how vesicles were initially examined and reported in the literature in the late 1970s (for secreted exosomes) and early 1980s (for plasma membrane-derived, exfoliated vesicles) to where we are now and where we may be headed in the next decade. An emphasis is placed on biophysical properties of extracellular vesicles, energy consumption and the role of vesiculation as an essential component of membrane turnover. The impact of intercellular signal trafficking by vesicle surface and intra-vesicular lipids, proteins, nucleic acids and metabolites is reviewed in the context of biomarkers for estimating individual radiation dose after exposure to radiation, pathogenesis of disease and development of cell-free therapeutics. Since vesicles express both growth stimulatory and inhibitory molecules, a hypothesis is proposed to consider superposition in a shared space and entanglement of molecules by energy sources that are external to human cells. Implications of this approach for travel in deep space are briefly discussed in the context of clinical disorders that have been observed after space travel.

Exploring the gut microbiota's crucial role in acute pancreatitis and the novel therapeutic potential of derived extracellular vesicles

During acute pancreatitis, intestinal permeability increases due to intestinal motility dysfunction, microcirculatory disorders, and ischemia-reperfusion injury, and disturbances in the intestinal flora make bacterial translocation easier, which consequently leads to local or systemic complications such as pancreatic and peripancreatic necrotic infections, acute lung injury, systemic inflammatory response syndrome, and multiple organ dysfunction syndrome. Therefore, adjusting intestinal ecosystem balance may be a promising approach to control local and systemic complications of acute pancreatitis. In this paper, we reviewed the causes and manifestations of intestinal flora disorders during acute pancreatitis and their complications, focused on the reduction of acute pancreatitis and its complications by adjusting the intestinal microbial balance, and innovatively proposed the treatment of acute pancreatitis and its complications by gut microbiota-derived extracellular vesicles.

Gut proinflammatory bacteria is associated with abnormal functional connectivity of hippocampus in unmedicated patients with major depressive disorder

Accumulating evidence has revealed the gut bacteria dysbiosis and brain hippocampal functional and structural alterations in major depressive disorder (MDD). However, the potential relationship between the gut microbiota and hippocampal function alterations in patients with MDD is still very limited. Data of resting-state functional magnetic resonance imaging were acquired from 44 unmedicated MDD patients and 42 demographically matched healthy controls (HCs). Severn pairs of hippocampus subregions (the bilateral cornu ammonis [CA1-CA3], dentate gyrus (DG), entorhinal cortex, hippocampal-amygdaloid transition area, and subiculum) were selected as the seeds in the functional connectivity (FC) analysis. Additionally, fecal samples of participants were collected and 16S rDNA amplicon sequencing was used to identify the altered relative abundance of gut microbiota. Then, association analysis was conducted to investigate the potential relationships between the abnormal hippocampal subregions FC and microbiome features. Also, the altered hippocampal subregion FC values and gut microbiota levels were used as features separately or together in the support vector machine models distinguishing the MDD patients and HCs. Compared with HCs, patients with MDD exhibited increased FC between the left hippocampus (CA2, CA3 and DG) and right hippocampus (CA2 and CA3), and decreased FC between the right hippocampal CA3 and bilateral posterior cingulate cortex. In addition, we found that the level of proinflammatory bacteria (i.e., Enterobacteriaceae) was significantly increased, whereas the level of short-chain fatty acids producing-bacteria (i.e., Prevotellaceae, Agathobacter and Clostridium) were significantly decreased in MDD patients. Furthermore, FC values of the left hippocampal CA3- right hippocampus (CA2 and CA3) was positively correlated with the relative abundance of Enterobacteriaceae in patients with MDD. Moreover, altered hippocampal FC patterns and gut microbiota level were considered in combination, the best discrimination was obtained (AUC = 0.92). These findings may provide insights into the potential role of gut microbiota in the underlying neuropathology of MDD patients.

The Role of the Intestinal Flora and Its Derivatives in Neurocognitive Disorders: A Narrative Review from Surgical Perspective

Perioperative neurocognitive dysfunction is a significant concern for population health, impacting postoperative recovery and increasing the financial burden on patients. With an increasing number of surgical procedures being performed, the prevention and management of perioperative neurocognitive dysfunction have garnered significant attention. While factors such as age, lifestyle, genetics, and education are known to influence the development of cognitive dysfunction, recent research has highlighted the role of the gut microbiota in neurological health. An increased abundance of pro-inflammatory gut microbiota can trigger and worsen neuroinflammation, neuronal cell damage, and impaired cellular autophagy. Moreover, the inflammation-promoting gut microbiota can disrupt immune function, impair neuroautophagy, and affect the production and circulation of extracellular vesicles and neurotransmitters. These factors collectively play a role in the onset and advancement of cognitive impairment. This narrative review delves into the molecular mechanisms through which gut microbiota and their derivatives contribute to cognitive impairment, focusing on the impact of anesthesia surgery, changes in gut microbial populations, and perioperative cognitive impairment associations. The study suggests that alterations in the abundance of various bacterial species and their metabolites pre- and post-surgery may be linked to postoperative cognitive impairment. Furthermore, the potential of probiotics or prebiotics in addressing cognitive impairment is discussed, offering a promising avenue for investigating the treatment of perioperative neurocognitive disorders.

Lactobacillus plantarum-Derived Extracellular Vesicles Modulate Macrophage Polarization and Gut Homeostasis for Alleviating Ulcerative Colitis

Extracellular vesicles released by probiotics have been demonstrated to effectively alleviate intestinal inflammation, yet the precise underlying mechanisms remain unclear. In this research, for the first time, Lactobacillus plantarum UJS001 (LP-UJS) was isolated from fermented sauerkraut in Zhenjiang, China. Thereafter, the therapeutic effect of LP-UJS-derived extracellular vesicles (LP-UJS-EVs) on dextran sulfate sodium-induced ulcerative colitis (UC) in mice was analyzed to elucidate the immune mechanisms. According to our findings, LP-UJS-EVs played a pivotal role in restoring the intestinal barrier and alleviating intestinal inflammation. Notably, LP-UJS-EVs induced M2 polarization of macrophages, promoted the release of IL-10 and TGF-β, inhibited the release of histamine, IL-6, and TNF-α, and exerted regulatory effects on intestinal microflora, as evidenced by the reduced abundances of Coprococcus, Parabacteroides, Staphylococcus, and Allobaculum, alongside the enhanced abundance of Prevotella. Furthermore, both LP-UJS and LP-UJS-EVs affected the lysine degradation pathway and significantly increased the abundance of related metabolites, especially oxoadipic acid. In summary, our results underscore the substantial therapeutic potential of LP-UJS and its secreted EVs in the treatment of UC.

A probiotic NVP1704 alleviates stress-induced sleeplessness/depression-like symptoms in mice by upregulating serotonergic and GABAergic systems and downregulating NF-κB activation

Sleeplessness (insomnia) is a potential symptom of depression. A probiotic NVP1704 alleviates depression-like behavior and neuroinflammation in mice. Therefore, to understand whether NVP1704 could be effective against sleeplessness in vivo, we exposed immobilization stress (IS) in mice, then orally administered NVP1704 for 5 days, and assayed depression/anxiety-like behavior in the open field, elevated plus maze, and tail suspension tests, sleeping latency time, and sleep duration, euthanized then by exposure to CO2, and analyzed their related biomarkers. Oral administration of NVP1704 decreased IS-induced depression/anxiety-like behavior and sleeping latency time and increased IS-suppressed sleeping duration. NVP1704 increased IS-suppressed expression of γ-aminobutyric acid (GABA), GABAA receptor α1 (GABAARα1) and α2 subunits (GABAARα2), serotonin, 5-HT receptors (5-HT1AR and 5-HT1BR), and melatonin receptors (MT1R and MT2R) in the prefrontal cortex and thalamus. NVP1704 also increased the IS-suppressed GABAARα1-positive cell population in the prefrontal cortex and decreased IS-induced corticosterone, TNF-α, and IL-6 expression and the NF-κB+Iba1+ cell population in the brain and myeloperoxidase, TNF-α, and IL-6 expression and the NF-κB+CD11c+ cell population in the colon. Based on these findings, NVP1704 may alleviate depression/anxiety/sleeplessness-like behaviors through the upregulation of serotonergic and GABAergic systems and downregulation of NF-κB activation.

Extracellular Vesicles as Mediators of Neuroinflammation in Intercellular and Inter-Organ Crosstalk

Neuroinflammation, crucial in neurological disorders like Alzheimer's disease, multiple sclerosis, and hepatic encephalopathy, involves complex immune responses. Extracellular vesicles (EVs) play a pivotal role in intercellular and inter-organ communication, influencing disease progression. EVs serve as key mediators in the immune system, containing molecules capable of activating molecular pathways that exacerbate neuroinflammatory processes in neurological disorders. However, EVs from mesenchymal stem cells show promise in reducing neuroinflammation and cognitive deficits. EVs can cross CNS barriers, and peripheral immune signals can influence brain function via EV-mediated communication, impacting barrier function and neuroinflammatory responses. Understanding EV interactions within the brain and other organs could unveil novel therapeutic targets for neurological disorders.

The Emerging Role of Human Gut Bacteria Extracellular Vesicles in Mental Disorders and Developing New Pharmaceuticals

In recent years, further evidence has emerged regarding the involvement of extracellular vesicles in various human physiopathological conditions such as Alzheimer's disease, Parkinson's disease, irritable bowel syndrome, and mental disorders. The biogenesis and cargo of such vesicles may reveal their impact on human health nd disease and set the underpinnings for the development of novel chemical compounds and pharmaceuticals. In this review, we examine the link between bacteria-derived exosomes in the gastrointestinal tract and mental disorders, such as depression and anxiety disorders. Crucially, we focus on whether changes in the gut environment affect the human mental state or the other way around. Furthermore, the possibility of handling bacteria-derived exosomes as vectors of chemicals to treat such conditions is examined.

Lipopolysaccharide-producing Veillonella infantium and Escherichia fergusonii cause vagus nerve-mediated cognitive impairment in mice

Gut microbiota communicates bidirectionally with the brain through the nervous, immune, and endocrine systems of the gut. In our preliminary study, the fecal microbiota of volunteers with mild cognitive impairment (Fmci) exhibited a higher abundance of Escherichia fergusonii (NK2001), Veillonella infantium (NK2002), and Enterococcus faecium (NK2003) populations compared with those of healthy volunteers. Therefore, we examined the effects of Fmci, NK2001 (gram-negative), NK2002 (gram-negative-like), and NK2003 (gram-positive) on cognitive impairment-like behavior, neuroinflammation, and colitis in mice with or without antibiotics. Fmci transplantation increased cognitive impairment-like behavior, hippocampal tumor necrosis factor (TNF)-α expression, and the size of toll-like receptor (TLR)4+Iba1+, TLR2+Iba1+, and NF-κB+Iba1+ cell populations independent of antibiotic treatment. Oral gavage of NK2001, NK2002, or NK2003, which induced TNF-α expression in Caco-2 cells, significantly increased cognitive impairment-like behavior and hippocampal TNF-α expression and Iba1-positive cell populations and decreased brain-derived neurotrophic factor (BDNF) expression in mice. Celiac vagotomy significantly decreased NK2001- or NK2002-induced cognitive impairment-like behavior and hippocampal Iba1+ cell population and TNF-α expression and increased NK2001- or NK2002-suppressed hippocampal BDNF expression. However, NK2003-induced cognitive impairment-like behavior and hippocampal Iba1+ cell population and TNF-α expression were partially, but not significantly, attenuated by celiac vagotomy. Furthermore, celiac vagotomy did not affect NK2001-, NK2002-, or NK2003-induced lipopolysaccharide (LPS) levels in the blood and feces and TNF-α expression and NF-κB-positive cell population in the colon. In conclusion, LPS-producing NK2001 and NK2002 and LPS-nonproducing NK2003 may induce NF-κB-mediated neuroinflammation through the translocation of byproducts such as LPS and peptidoglycan into the brain through gut-blood/vagus nerve-brain and gut-blood-brain pathways, respectively, resulting in cognitive impairment.

Peripheral extracellular vesicles in neurodegeneration: pathogenic influencers and therapeutic vehicles

Neurodegenerative diseases (NDDs) such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis epitomize a class of insidious and relentless neurological conditions that are difficult to cure. Conventional therapeutic regimens often fail due to the late onset of symptoms, which occurs well after irreversible neurodegeneration has begun. The integrity of the blood-brain barrier (BBB) further impedes efficacious drug delivery to the central nervous system, presenting a formidable challenge in the pharmacological treatment of NDDs. Recent scientific inquiries have shifted focus toward the peripheral biological systems, investigating their influence on central neuropathology through the lens of extracellular vesicles (EVs). These vesicles, distinguished by their ability to breach the BBB, are emerging as dual operatives in the context of NDDs, both as conveyors of pathogenic entities and as prospective vectors for therapeutic agents. This review critically summarizes the burgeoning evidence on the role of extracerebral EVs, particularly those originating from bone, adipose tissue, and gut microbiota, in modulating brain pathophysiology. It underscores the duplicity potential of peripheral EVs as modulators of disease progression and suggests their potential as novel vehicles for targeted therapeutic delivery, positing a transformative impact on the future landscape of NDD treatment strategies. Search strategy A comprehensive literature search was conducted using PubMed, Web of Science, and Scopus from January 2000 to December 2023. The search combined the following terms using Boolean operators: "neurodegenerative disease" OR "Alzheimer's disease" OR "Parkinson's disease" OR "Amyotrophic lateral sclerosis" AND "extracellular vesicles" OR "exosomes" OR "outer membrane vesicles" AND "drug delivery systems" AND "blood-brain barrier". MeSH terms were employed when searching PubMed to refine the results. Studies were included if they were published in English, involved human subjects, and focused on the peripheral origins of EVs, specifically from bone, adipose tissue, and gut microbiota, and their association with related diseases such as osteoporosis, metabolic syndrome, and gut dysbiosis. Articles were excluded if they did not address the role of EVs in the context of NDDs or did not discuss therapeutic applications. The titles and abstracts of retrieved articles were screened using a dual-review process to ensure relevance and accuracy. The reference lists of selected articles were also examined to identify additional relevant studies.

The emerging roles of microbiota-derived extracellular vesicles in psychiatric disorders

Major depressive disorder, schizophrenia, and bipolar disorder are three major psychiatric disorders that significantly impact the well-being and overall health of patients. Some researches indicate that abnormalities in the gut microbiota can trigger certain psychiatric diseases. Microbiota-derived extracellular vesicles have the ability to transfer bioactive compounds into host cells, altering signaling and biological processes, ultimately influencing the mental health and illness of the host. This review aims to investigate the emerging roles of microbiota-derived extracellular vesicles in these three major psychiatric disorders and discusses their roles as diagnostic biomarkers and therapies for these psychiatric disorders.

Advances in molecular mechanisms and therapeutic strategies for central nervous system diseases based on gut microbiota imbalance

BACKGROUD

Central nervous system (CNS) diseases pose a serious threat to human health, but the regulatory mechanisms and therapeutic strategies of CNS diseases need to be further explored. It has been demonstrated that the gut microbiota (GM) is closely related to CNS disease. GM structure disorders, abnormal microbial metabolites, intestinal barrier destruction and elevated inflammation exist in patients with CNS diseases and promote the development of CNS diseases. More importantly, GM remodeling alleviates CNS pathology to some extent.

AIM OF REVIEW

Here, we have summarized the regulatory mechanism of the GM in CNS diseases and the potential treatment strategies for CNS repair based on GM regulation, aiming to provide safer and more effective strategies for CNS repair from the perspective of GM regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The abundance and composition of GM is closely associated with the CNS diseases. On the basis of in-depth analysis of GM changes in mice with CNS disease, as well as the changes in its metabolites, therapeutic strategies, such as probiotics, prebiotics, and FMT, may be used to regulate GM balance and affect its microbial metabolites, thereby promoting the recovery of CNS diseases.

Transient Receptor Potential Channels in the Healthy and Diseased Blood-Brain Barrier

The large family of transient receptor potential (TRP) channels are integral membrane proteins that function as environmental sensors and act as ion channels after activation by mechanical (touch), physical (heat, pain), and chemical stimuli (pungent compounds such as capsaicin). Most TRP channels are localized in the plasma membrane of cells but some of them are localized in membranes of organelles and function as intracellular Ca2+-ion channels. TRP channels are involved in neurological disorders but their precise role(s) and relevance in these disorders are not clear. Endothelial cells of the blood-brain barrier (BBB) express TRP channels such as TRP vanilloid 1-4 and are involved in thermal detection by regulating BBB permeability. In neurological disorders, TRP channels in the BBB are responsible for edema formation in the brain. Therefore, drug design to modulate locally activity of TRP channels in the BBB is a hot topic. Today, the application of TRP channel antagonists against neurological disorders is still limited.

Deciphering the intricate linkage between the gut microbiota and Alzheimer's disease: Elucidating mechanistic pathways promising therapeutic strategies

BACKGROUND

The gut microbiome is composed of various microorganisms such as bacteria, fungi, and protozoa, and constitutes an important part of the human gut. Its composition is closely related to human health and disease. Alzheimer's disease (AD) is a neurodegenerative disease whose underlying mechanism has not been fully elucidated. Recent research has shown that there are significant differences in the gut microbiota between AD patients and healthy individuals. Changes in the composition of gut microbiota may lead to the development of harmful factors associated with AD. In addition, the gut microbiota may play a role in the development and progression of AD through the gut-brain axis. However, the exact nature of this relationship has not been fully understood.

AIMS

This review will elucidate the types and functions of gut microbiota and their relationship with AD and explore in depth the potential mechanisms of gut microbiota in the occurrence of AD and the prospects for treatment strategies.

METHODS

Reviewed literature from PubMed and Web of Science using key terminologies related to AD and the gut microbiome.

RESULTS

Research indicates that the gut microbiota can directly or indirectly influence the occurrence and progression of AD through metabolites, endotoxins, and the vagus nerve.

DISCUSSION

This review discusses the future challenges and research directions regarding the gut microbiota in AD.

CONCLUSION

While many unresolved issues remain regarding the gut microbiota and AD, the feasibility and immense potential of treating AD by modulating the gut microbiota are evident.

Gut-Brain Interactions and Their Impact on Astrocytes in the Context of Multiple Sclerosis and Beyond

Multiple Sclerosis (MS) is a chronic autoimmune inflammatory disease of the central nervous system (CNS) that leads to physical and cognitive impairment in young adults. The increasing prevalence of MS underscores the critical need for innovative therapeutic approaches. Recent advances in neuroimmunology have highlighted the significant role of the gut microbiome in MS pathology, unveiling distinct alterations in patients' gut microbiota. Dysbiosis not only impacts gut-intrinsic processes but also influences the production of bacterial metabolites and hormones, which can regulate processes in remote tissues, such as the CNS. Central to this paradigm is the gut-brain axis, a bidirectional communication network linking the gastrointestinal tract to the brain and spinal cord. Via specific routes, bacterial metabolites and hormones can influence CNS-resident cells and processes both directly and indirectly. Exploiting this axis, novel therapeutic interventions, including pro- and prebiotic treatments, have emerged as promising avenues with the aim of mitigating the severity of MS. This review delves into the complex interplay between the gut microbiome and the brain in the context of MS, summarizing current knowledge on the key signals of cross-organ crosstalk, routes of communication, and potential therapeutic relevance of the gut microbiome. Moreover, this review places particular emphasis on elucidating the influence of these interactions on astrocyte functions within the CNS, offering insights into their role in MS pathophysiology and potential therapeutic interventions.

Extracellular Vesicles: The Invisible Heroes and Villains of COVID-19 Central Neuropathology

Acknowledging the neurological symptoms of COVID-19 and the long-lasting neurological damage even after the epidemic ends are common, necessitating ongoing vigilance. Initial investigations suggest that extracellular vesicles (EVs), which assist in the evasion of the host's immune response and achieve immune evasion in SARS-CoV-2 systemic spreading, contribute to the virus's attack on the central nervous system (CNS). The pro-inflammatory, pro-coagulant, and immunomodulatory properties of EVs contents may directly drive neuroinflammation and cerebral thrombosis in COVID-19. Additionally, EVs have attracted attention as potential candidates for targeted therapy in COVID-19 due to their innate homing properties, low immunogenicity, and ability to cross the blood-brain barrier (BBB) freely. Mesenchymal stromal/stem cell (MSCs) secreted EVs are widely applied and evaluated in patients with COVID-19 for their therapeutic effect, considering the limited antiviral treatment. This review summarizes the involvement of EVs in COVID-19 neuropathology as carriers of SARS-CoV-2 or other pathogenic contents, as predictors of COVID-19 neuropathology by transporting brain-derived substances, and as therapeutic agents by delivering biotherapeutic substances or drugs. Understanding the diverse roles of EVs in the neuropathological aspects of COVID-19 provides a comprehensive framework for developing, treating, and preventing central neuropathology and the severe consequences associated with the disease.

Comparison analysis of microbial agent and different compost material on microbial community and nitrogen transformation genes dynamic changes during pig manure compost

This study aimed to assess the impact of microbial agent and different compost material, on physicochemical parameters dynamic change, nitrogen-transfer gene/bacterial community interaction network during the pig manure composting. Incorporating a microbial agent into rice straw-mushroom compost reduced the NH3 and total ammonia emissions by 25.52 % and 14.41 %, respectively. Notably, rice straw-mushroom with a microbial agent reduced the total ammonia emissions by 37.67 %. NH4+-N and pH emerged as primary factors of phylum-level and genus-level microorganisms. Microbial agent increased the expression of narG, nirK, and nosZ genes. Rice straw-mushroom elevated the content of amoA, nirK, nirS, and nosZ genes. Alcanivorax, Luteimonas, Pusillimonas, Lactobacillus, Aequorivita, Clostridium, Moheibacter and Truepera were identified as eight core microbial genera during the nitrogen conversion process. This study provides a strategy for reducing ammonia emissions and analyzes the potential mechanisms underlying compost processes.

Therapeutics for neurodegenerative diseases by targeting the gut microbiome: from bench to bedside

The aetiologies and origins of neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and Huntington's disease (HD), are complex and multifaceted. A growing body of evidence suggests that the gut microbiome plays crucial roles in the development and progression of neurodegenerative diseases. Clinicians have come to realize that therapeutics targeting the gut microbiome have the potential to halt the progression of neurodegenerative diseases. This narrative review examines the alterations in the gut microbiome in AD, PD, ALS and HD, highlighting the close relationship between the gut microbiome and the brain in neurodegenerative diseases. Processes that mediate the gut microbiome-brain communication in neurodegenerative diseases, including the immunological, vagus nerve and circulatory pathways, are evaluated. Furthermore, we summarize potential therapeutics for neurodegenerative diseases that modify the gut microbiome and its metabolites, including diets, probiotics and prebiotics, microbial metabolites, antibacterials and faecal microbiome transplantation. Finally, current challenges and future directions are discussed.

Extracellular vesicles of Weizmannia coagulans lilac-01 reduced cell death of primary microglia and increased mitochondrial content in dermal fibroblasts in vitro

We investigated the properties of extracellular vesicles from the probiotic Weizmannia coagulans lilac-01 (Lilac-01EVs). The phospholipids in the Lilac-01EV membrane were phosphatidylglycerol and mitochondria-specific cardiolipin. We found that applying Lilac-01EVs to primary rat microglia in vitro resulted in a reduction in primary microglial cell death (P < .05). Lilac-01EVs, which contain cardiolipin and phosphatidylglycerol, may have the potential to inhibit cell death in primary microglia. The addition of Lilac-01EVs to senescent human dermal fibroblasts suggested that Lilac-01 EVs increase the mitochondrial content without affecting their membrane potential in these cells.

Rapid Biodistribution of Fluorescent Outer-Membrane Vesicles from the Intestine to Distant Organs via the Blood in Mice

A cell's ability to secrete extracellular vesicles (EVs) for communication is present in all three domains of life. Notably, Gram-negative bacteria produce a specific type of EVs called outer membrane vesicles (OMVs). We previously observed the presence of OMVs in human blood, which could represent a means of communication from the microbiota to the host. Here, in order to investigate the possible translocation of OMVs from the intestine to other organs, the mouse was used as an animal model after OMVs administration. To achieve this, we first optimized the signal of OMVs containing the fluorescent protein miRFP713 associated with the outer membrane anchoring peptide OmpA by adding biliverdin, a fluorescence cofactor, to the cultures. The miRFP713-expressing OMVs produced in E. coli REL606 strain were then characterized according to their diameter and protein composition. Native- and miRFP713-expressing OMVs were found to produce homogenous populations of vesicles. Finally, in vivo and ex vivo fluorescence imaging was used to monitor the distribution of miRFP713-OMVs in mice in various organs whether by intravenous injection or oral gavage. The relative stability of the fluorescence signals up to 3 days post-injection/gavage paves the way to future studies investigating the OMV-based communication established between the different microbiotas and their host.

Does gut brain axis has an impact on Parkinson's disease (PD)?

Parkinson's Disease (PD) is becoming a growing global concern by being the second most prevalent disease next to Alzheimer's Disease (AD). Henceforth new exploration is needed in search of new aspects towards the disease mechanism and origin. Evidence from recent studies has clearly stated the role of Gut Microbiota (GM) in the maintenance of the brain and as a root cause of various diseases and disorders including other neurological conditions. In the case of PD, with an unknown etiology, the GM is said to have a larger impact on the disease pathophysiology. Although GM and its metabolites are crucial for maintaining the normal physiology of the host, it is an undeniable fact that there is an influence of GM in the pathophysiology of PD. As such the Enteroendocrine Cells (EECs) in the epithelium of the intestine are one of the significant regulators of the gut-brain axis and act as a communication mediator between the gut and the brain. The communication is established via the molecules of neuroendocrine which are said to have a crucial part in neurological diseases such as AD, PD, and other psychiatry-related disorders. This review is focused on understanding the proper role of GM and EECs in PD. Here, we also focus on some of the metabolites and compounds that can interact with the PD genes causing various dysfunctions in the cell and facilitating the disease conditions using bioinformatical tools. Various mechanisms concerning EECs and PD, their identification, the latest studies, and available current therapies have also been discussed.

Microbial Extracellular Vesicles in Host-Microbiota Interactions

Extracellular vesicles have emerged as key players in cellular communication, influencing various physiological processes and pathophysiological progression, including digestion, immune response, and tissue repairs. Recently, a class of EVs derived from microbial communities has gained significant attention due to their pivotal role in intercellular communication and their potential as biomarkers and biotherapeutic agents. Microbial EVs are membrane-bound molecules encapsulating bioactive metabolites that modulate host physiological and pathological processes. This chapter discusses the evolving history of microbiota-produced EVs, including their discovery, characterization, current research status, and their diverse mechanisms of interaction with other microbes and hosts. This review also highlights the importance of EVs in health and disease and discusses recent research that shows promising results for the therapeutic potential of EVs.

Do Bacterial Outer Membrane Vesicles Contribute to Chronic Inflammation in Parkinson's Disease?

Parkinson's disease (PD) is an increasingly common neurodegenerative disease. It has been suggested that the etiology of idiopathic PD is complex and multifactorial involving environmental contributions, such as viral or bacterial infections and microbial dysbiosis, in genetically predisposed individuals. With advances in our understanding of the gut-brain axis, there is increasing evidence that the intestinal microbiota and the mammalian immune system functionally interact. Recent findings suggest that a shift in the gut microbiome to a pro-inflammatory phenotype may play a role in PD onset and progression. While there are links between gut bacteria, inflammation, and PD, the bacterial products involved and how they traverse the gut lumen and distribute systemically to trigger inflammation are ill-defined. Mechanisms emerging in other research fields point to a role for small, inherently stable vesicles released by Gram-negative bacteria, called outer membrane vesicles in disease pathogenesis. These vesicles facilitate communication between bacteria and the host and can shuttle bacterial toxins and virulence factors around the body to elicit an immune response in local and distant organs. In this perspective article, we hypothesize a role for bacterial outer membrane vesicles in PD pathogenesis. We present evidence suggesting that these outer membrane vesicles specifically from Gram-negative bacteria could potentially contribute to PD by traversing the gut lumen to trigger local, systemic, and neuroinflammation. This perspective aims to facilitate a discussion on outer membrane vesicles in PD and encourage research in the area, with the goal of developing strategies for the prevention and treatment of the disease.

Gut-bacteria derived membrane vesicles and host metabolic health: a narrative review

The intestinal microbiota, consisting of an estimated 10^10-10^11 organisms, regulate physiological processes involved in digestion, metabolism, and immunity. Surprisingly, these intestinal microorganisms have been found to influence tissues that are not directly in contact with the gut, such as adipose tissue, the liver, skeletal muscle, and the brain. This interaction takes place even when intestinal barrier function is uncompromised. An increasing body of evidence suggests that bacterial membrane vesicles (bMVs), in addition to bacterial metabolites such as short-chain fatty acids, are able to mediate effects of the microbiota on these host tissues. The ability of bMVs to dissipate from the intestinal lumen into systemic circulation hereby facilitates the transport and presentation of bacterial components and metabolites to host organs. Importantly, there are indications that the interaction between bMVs and tissues or immune cells may play a role in the etiology of (chronic metabolic) disease. For example, the gut-derived bMV-mediated induction of insulin resistance in skeletal muscle cells and pro-inflammatory signaling by adipocytes possibly underlies diseases such as type 2 diabetes and obesity. Here, we review the current knowledge on bMVs in the microbiota's effects on host energy/substrate metabolism with a focus on etiological roles in the onset and progression of metabolic disease. We furthermore illustrate that vesicle production by bacterial microbiota could potentially be modulated through lifestyle intervention to improve host metabolism.

Vagal interoception of microbial metabolites from the small intestinal lumen

The vagus nerve is proposed to enable communication between the gut microbiome and brain, but activity-based evidence is lacking. Herein, we assess the extent of gut microbial influences on afferent vagal activity and metabolite signaling mechanisms involved. We find that mice reared without microbiota (germ-free, GF) exhibit decreased vagal afferent tone relative to conventionally colonized mice (specific pathogen-free, SPF), which is reversed by colonization with SPF microbiota. Perfusing non-absorbable antibiotics (ABX) into the small intestine of SPF mice, but not GF mice, acutely decreases vagal activity, which is restored upon re-perfusion with bulk lumenal contents or sterile filtrates from the small intestine and cecum of SPF, but not GF, mice. Of several candidates identified by metabolomic profiling, microbiome-dependent short-chain fatty acids, bile acids, and 3-indoxyl sulfate stimulate vagal activity with varied response kinetics, which is blocked by co-perfusion of pharmacological antagonists of FFAR2, TGR5, and TRPA1, respectively, into the small intestine. At the single-unit level, serial perfusion of each metabolite class elicits more singly responsive neurons than dually responsive neurons, suggesting distinct neuronal detection of different microbiome- and macronutrient-dependent metabolites. Finally, microbial metabolite-induced increases in vagal activity correspond with activation of neurons in the nucleus of the solitary tract, which is also blocked by co-administration of their respective receptor antagonists. Results from this study reveal that the gut microbiome regulates select metabolites in the intestinal lumen that differentially activate chemosensory vagal afferent neurons, thereby enabling microbial modulation of interoceptive signals for gut-brain communication.

HIGHLIGHTS

Microbiota colonization status modulates afferent vagal nerve activityGut microbes differentially regulate metabolites in the small intestine and cecumSelect microbial metabolites stimulate vagal afferents with varied response kineticsSelect microbial metabolites activate vagal afferent neurons and brainstem neurons via receptor-dependent signaling.

The emerging role of exosomes in communication between the periphery and the central nervous system

Exosomes, membrane-enclosed vesicles, are secreted by all types of cells. Exosomes can transport various molecules, including proteins, lipids, functional mRNAs, and microRNAs, and can be circulated to various recipient cells, leading to the production of local paracrine or distal systemic effects. Numerous studies have proved that exosomes can pass through the blood-brain barrier, thus, enabling the transfer of peripheral substances into the central nervous system (CNS). Consequently, exosomes may be a vital factor in the exchange of information between the periphery and CNS. This review will discuss the structure, biogenesis, and functional characterization of exosomes and summarize the role of peripheral exosomes deriving from tissues like the lung, gut, skeletal muscle, and various stem cell types in communicating with the CNS and influencing the brain's function. Then, we further discuss the potential therapeutic effects of exosomes in brain diseases and the clinical opportunities and challenges. Gaining a clearer insight into the communication between the CNS and the external areas of the body will help us to ascertain the role of the peripheral elements in the maintenance of brain health and illness and will facilitate the design of minimally invasive techniques for diagnosing and treating brain diseases.

Extracellular vesicles derived from Porphyromonas gingivalis induce trigeminal nerve-mediated cognitive impairment

INTRODUCTION

Porphyromonas gingivalis (PG)-infected periodontitis is in close connection with the development of Alzheimer's disease (AD). PG-derived extracellular vesicles (pEVs) contain inflammation-inducing virulence factors, including gingipains (GPs) and lipopolysaccharide (LPS).

OBJECTIVES

To understand how PG could cause cognitive decline, we investigated the effects of PG and pEVs on the etiology of periodontitis and cognitive impairment in mice.

METHODS

Cognitive behaviors were measured in the Y-maze and novel object recognition tasks. Biomarkers were measured using ELISA, qPCR, immunofluorescence assay, and pyrosequencing.

RESULTS

pEVs contained neurotoxic GPs and inflammation-inducible fimbria protein and LPS. Gingivally exposed, but not orally gavaged, PG or pEVs caused periodontitis and induced memory impairment-like behaviors. Gingival exposure to PG or pEVs increased TNF-α expression in the periodontal and hippocampus tissues. They also increased hippocampal GP+Iba1+, LPS+Iba1+, and NF-κB+Iba1+ cell numbers. Gingivally exposed PG or pEVs decreased BDNF, claudin-5, and N-methyl-D-aspartate receptor expression and BDNF+NeuN+ cell number. Gingivally exposed fluorescein-5-isothiocyanate-labeled pEVs (F-pEVs) were detected in the trigeminal ganglia and hippocampus. However, right trigeminal neurectomy inhibited the translocation of gingivally injected F-EVs into the right trigeminal ganglia. Gingivally exposed PG or pEVs increased blood LPS and TNF-α levels. Furthermore, they caused colitis and gut dysbiosis.

CONCLUSION

Gingivally infected PG, particularly pEVs, may cause cognitive decline with periodontitis. PG products pEVs and LPS may be translocated into the brain through the trigeminal nerve and periodontal blood pathways, respectively, resulting in the cognitive decline, which may cause colitis and gut dysbiosis. Therefore, pEVs may be a remarkable risk factor for dementia.

Targeting the blood-brain barrier to delay aging-accompanied neurological diseases by modulating gut microbiota, circadian rhythms, and their interplays

The blood-brain barrier (BBB) impairment plays a crucial role in the pathological processes of aging-accompanied neurological diseases (AAND). Meanwhile, circadian rhythms disruption and gut microbiota dysbiosis are associated with increased morbidity of neurological diseases in the accelerated aging population. Importantly, circadian rhythms disruption and gut microbiota dysbiosis are also known to induce the generation of toxic metabolites and pro-inflammatory cytokines, resulting in disruption of BBB integrity. Collectively, this provides a new perspective for exploring the relationship among circadian rhythms, gut microbes, and the BBB in aging-accompanied neurological diseases. In this review, we focus on recent advances in the interplay between circadian rhythm disturbances and gut microbiota dysbiosis, and their potential roles in the BBB disruption that occurs in AAND. Based on existing literature, we discuss and propose potential mechanisms underlying BBB damage induced by dysregulated circadian rhythms and gut microbiota, which would serve as the basis for developing potential interventions to protect the BBB in the aging population through targeting the BBB by exploiting its links with gut microbiota and circadian rhythms for treating AAND.

Bacterial extracellular vesicles: an emerging avenue to tackle diseases

A growing body of research, especially in recent years, has shown that bacterial extracellular vesicles (bEVs) are one of the key underlying mechanisms behind the pathogenesis of various diseases like pulmonary fibrosis, sepsis, systemic bone loss, and Alzheimer's disease. Given these new insights, bEVs are proposed as an emerging vehicle that can be used as a diagnostic tool or to tackle diseases when used as a therapeutic target. To further boost the understanding of bEVs in health and disease we thoroughly discuss the contribution of bEVs in disease pathogenesis and the underlying mechanisms. In addition, we speculate on their potential as novel diagnostic biomarkers and how bEV-related mechanisms can be exploited as therapeutic targets.

Engineered bacterial extracellular vesicles for central nervous system diseases

The prevalence of central nervous system (CNS) diseases is on the rise as the population ages. The presence of various obstacles, particularly the blood-brain barrier (BBB), poses a challenge for drug delivery to the CNS. An expanding body of study suggests that gut microbiota (GM) plays an important role in CNS diseases. The communication between GM and CNS diseases has received increasing attention. Accumulating evidence indicates that the GM can modulate host signaling pathways to regulate distant organ functions by delivering bioactive substances to host cells via bacterial extracellular vesicles (BEVs). BEVs have emerged as a promising platform for the treatment of CNS diseases due to their nanostructure, ability to penetrate the BBB, as well as their low toxicity, high biocompatibility, ease of modification and large-scale culture. Here, we discuss the biogenesis, internalization mechanism and engineering modification methods of BEVs. We then focus on the use and potential role of BEVs in the treatment of CNS diseases. Finally, we outline the main challenges and future prospects for the application of BEVs in CNS diseases. We hope that the comprehensive understanding of the BEVs-based gut-brain axis will provide new insights into the treatment of CNS diseases.

Bifidobacterium bifidum and Lactobacillus paracasei alleviate sarcopenia and cognitive impairment in aged mice by regulating gut microbiota-mediated AKT, NF-κB, and FOXO3a signaling pathways

Sarcopenia is closely associated with gut dysbiosis. Probiotics alleviate gut dysbiosis. Therefore, we selected probiotics Lactobacillus paracasei P62 (Lp) and Bifidobacterium bifidum P61 (Bb), which suppressed muscle RING-finger protein-1 (MuRF1) expression and NF-κB activation in C2C12 cells, and examined their effects on muscle mass loss and dysfunction in aged mice. Oral administration of Lp, Bb, or their mix (LB) increased grip strength and treadmill running distance and time. They significantly increased muscle weight in aged mice. They also increased AKT activation, PGC1α, SIRT1, and myosin heavy chain (MyHC) expression, MyHC-positive cell population, and cell size in the gastrocnemius (GA) muscle, while FOXO3a and NF-κB activation, MuRF1, muscle atrophy F-box, and p16 expression, and NF-κB+CD11c+ cell population decreased. Furthermore, they reduced cognitive impairment-like behavior, IL-6 expression, FOXO3a activation, and NF-κB-positive cell population in the hippocampus, GA, and colon, while hippocampal brain-derived neurotropic factor expression increased. They shifted gut microbiota composition in aged mice: they increased Akkermansiaceae and Bacteroidaceae populations, which were positively correlated with total muscle weight and MyHC expression, and decreased Odoribacteraceae and Deferribacteriaceae populations, which were positively correlated with MuRF1 and IL-6 expression. LB alleviated sarcopenia- and cognitive impairment-like symptoms more potently than Lp or Bb alone. Based on these findings, probiotics, particularly Lp, Bb, and LB, can alleviate aging-dependent sarcopenia and cognitive impairment by regulating gut microbiota-mediated AKT, NF-κB, and/or FOXO3a signaling pathways.

Impact of Microbiome-Brain Communication on Neuroinflammation and Neurodegeneration

The gut microbiome plays a pivotal role in maintaining human health, with numerous studies demonstrating that alterations in microbial compositions can significantly affect the development and progression of various immune-mediated diseases affecting both the digestive tract and the central nervous system (CNS). This complex interplay between the microbiota, the gut, and the CNS is referred to as the gut-brain axis. The role of the gut microbiota in the pathogenesis of neurodegenerative diseases has gained increasing attention in recent years, and evidence suggests that gut dysbiosis may contribute to disease development and progression. Clinical studies have shown alterations in the composition of the gut microbiota in multiple sclerosis patients, with a decrease in beneficial bacteria and an increase in pro-inflammatory bacteria. Furthermore, changes within the microbial community have been linked to the pathogenesis of Parkinson's disease and Alzheimer's disease. Microbiota-gut-brain communication can impact neurodegenerative diseases through various mechanisms, including the regulation of immune function, the production of microbial metabolites, as well as modulation of host-derived soluble factors. This review describes the current literature on the gut-brain axis and highlights novel communication systems that allow cross-talk between the gut microbiota and the host that might influence the pathogenesis of neuroinflammation and neurodegeneration.

Unveiling the role of gut-brain axis in regulating neurodegenerative diseases: A comprehensive review

Emerging evidence have shown the importance of gut microbiota in regulating brain functions. The diverse molecular mechanisms involved in cross-talk between gut and brain provide insight into importance of this communication in maintenance of brain homeostasis. It has also been observed that disturbed gut microbiota contributes to neurological diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis and aging. Recently, gut microbiome-derived exosomes have also been reported to play an essential role in the development and progression of neurodegenerative diseases and could thereby act as a therapeutic target. Further, pharmacological interventions including antibiotics, prebiotics and probiotics can influence gut microbiome-mediated management of neurological diseases. However, extensive research is warranted to better comprehend this interconnection in maintenance of brain homeostasis and its implication in neurological diseases. Thus, the present review is aimed to provide a detailed understanding of gut-brain axis followed by possibilities to target the gut microbiome for improving neurological health.

Roles of bacterial extracellular vesicles in systemic diseases

Accumulating evidence suggests that in various systems, not all bidirectional microbiota-host interactions involve direct cell contact. Bacterial extracellular vesicles (BEVs) may be key participants in this interkingdom crosstalk. BEVs mediate microbiota functions by delivering effector molecules that modulate host signaling pathways, thereby facilitating host-microbe interactions. BEV production during infections by both pathogens and probiotics has been observed in various host tissues. Therefore, these vesicles released by microbiota may have the ability to drive or inhibit disease pathogenesis in different systems within the host. Here, we review the current knowledge of BEVs and particularly emphasize their interactions with the host and the pathogenesis of systemic diseases.

Decoding the role of gut microbiota in Alzheimer's pathogenesis and envisioning future therapeutic avenues

Alzheimer's disease (AD) emerges as a perturbing neurodegenerative malady, with a profound comprehension of its underlying pathogenic mechanisms continuing to evade our intellectual grasp. Within the intricate tapestry of human health and affliction, the enteric microbial consortium, ensconced within the milieu of the human gastrointestinal tract, assumes a role of cardinal significance. Recent epochs have borne witness to investigations that posit marked divergences in the composition of the gut microbiota between individuals grappling with AD and those favored by robust health. The composite vicissitudes in the configuration of the enteric microbial assembly are posited to choreograph a participatory role in the inception and progression of AD, facilitated by the intricate conduit acknowledged as the gut-brain axis. Notwithstanding, the precise nature of this interlaced relationship remains enshrouded within the recesses of obscurity, poised for an exhaustive revelation. This review embarks upon the endeavor to focalize meticulously upon the mechanistic sway exerted by the enteric microbiota upon AD, plunging profoundly into the execution of interventions that govern the milieu of enteric microorganisms. In doing so, it bestows relevance upon the therapeutic stratagems that form the bedrock of AD's management, all whilst casting a prospective gaze into the horizon of medical advancements.

Bacterial extracellular vesicles - brain invaders? A systematic review

Introduction

Knowledge on the human gut microbiota in health and disease continues to rapidly expand. In recent years, changes in the gut microbiota composition have been reported as a part of the pathology in numerous neurodegenerative diseases. Bacterial extracellular vesicles (EVs) have been suggested as a novel mechanism for the crosstalk between the brain and gut microbiota, physiologically connecting the observed changes in the brain to gut microbiota dysbiosis.

Methods

Publications reporting findings on bacterial EVs passage through the blood-brain barrier were identified in PubMed and Scopus databases.

Results

The literature search yielded 138 non-duplicate publications, from which 113 records were excluded in title and abstract screening step. From 25 publications subjected to full-text screening, 8 were excluded. The resulting 17 publications were considered for the review.

Discussion

Bacterial EVs have been described with capability to cross the blood-brain barrier, but the mechanisms behind the crossing remain largely unknown. Importantly, very little data exists in this context on EVs secreted by the human gut microbiota. This systematic review summarizes the present evidence of bacterial EVs crossing the blood-brain barrier and highlights the importance of future research on gut microbiota-derived EVs in the context of gut-brain communication across the blood-brain barrier.

Gut microbiota regulates blood-cerebrospinal fluid barrier function and Aβ pathology

Accumulating evidence indicates that gut microbiota dysbiosis is associated with increased blood-brain barrier (BBB) permeability and contributes to Alzheimer's disease (AD) pathogenesis. In contrast, the influence of gut microbiota on the blood-cerebrospinal fluid (CSF) barrier has not yet been studied. Here, we report that mice lacking gut microbiota display increased blood-CSF barrier permeability associated with disorganized tight junctions (TJs), which can be rescued by recolonization with gut microbiota or supplementation with short-chain fatty acids (SCFAs). Our data reveal that gut microbiota is important not only for the establishment but also for the maintenance of a tight barrier. Also, we report that the vagus nerve plays an important role in this process and that SCFAs can independently tighten the barrier. Administration of SCFAs in AppNL-G-F mice improved the subcellular localization of TJs at the blood-CSF barrier, reduced the β-amyloid (Aβ) burden, and affected microglial phenotype. Altogether, our results suggest that modulating the microbiota and administering SCFAs might have therapeutic potential in AD via blood-CSF barrier tightening and maintaining microglial activity and Aβ clearance.

Bacterial Membrane Vesicles: Physiological Roles, Infection Immunology, and Applications

Bacterial or fungal membrane vesicles, traditionally considered as microbial metabolic wastes, are secreted mainly from the outer membrane or cell membrane of microorganisms. However, recent studies have shown that these vesicles play essential roles in direct or indirect communications among microorganisms and between microorganisms and hosts. This review aims to provide an updated understanding of the physiological functions and emerging applications of bacterial membrane vesicles, with a focus on their biogenesis, mechanisms of adsorption and invasion into host cells, immune stimulatory effects, and roles in the much-concerned problem of bacterial resistance. Additionally, the potential applications of these vesicles as biomarkers, vaccine candidates, and drug delivery platforms are discussed.

Remodeling of Gut Microbiota by Probiotics Alleviated Heat Stroke-Induced Necroptosis in Male Germ Cells

SCOPE

Systemic heat stress (or heatstroke; HS) induces germ cell death and spermatogenesis disorders in men and male mammals. Also, it affects the immune environment of the circulatory system promoting gut inflammation and intestinal permeability, leading to pathogenic infection. In this study, the crosstalk between the gut and testis (gut-testis axis) under HS is explored, by examining the effects of intestinal immune status on the health of the male reproductive system in mice.

METHODS AND RESULTS

A mouse model of systemic heat stress is established to investigate the effect of probiotics on testis health. The results reveal that pro-inflammatory factor receptor activation pathway and pathogen infection response pathway are significantly upregulated in HS testes, leading to necroptosis, while pro-inflammatory factor and endotoxin are detected locally in the intestine and then entered the blood. The study then uses probiotics to intervene in gut microbiota, which results in milder gut microbial changes, lower inflammatory responses in the HS gut, and less necroptosis in the HS testes.

CONCLUSION

Probiotics-based remodeling of gut microbiota (GM) reduces the proliferation of abnormal bacteria and decreases the spread of gut-derived inflammatory mediators into the blood circulation under long-term systemic heat stress, which relieves inflammation on germ cells.

Emerging therapeutic role of gut microbial extracellular vesicles in neurological disorders

Extracellular vesicles (EVs) serve as cell-to-cell and inter-organ communicators by conveying proteins and nucleic acids with regulatory functions. Emerging evidence shows that gut microbial-released EVs play a pivotal role in the gut-brain axis, bidirectional communication, and crosstalk between the gut and the brain. Increasing pre-clinical and clinical evidence suggests that gut bacteria-released EVs are capable of eliciting distinct signaling to the brain with the ability to cross the blood-brain barrier, exerting regulatory function on brain cells such as neurons, astrocytes, and microglia, via their abundant and diversified protein and nucleic acid cargo. Conversely, EVs derived from certain species of bacteria, particularly from gut commensals with probiotic properties, have recently been shown to confer distinct therapeutic effects on various neurological disorders. Thus, gut bacterial EVs may be both a cause of and therapy for neuropathological complications. This review marshals the basic, clinical, and translational studies that significantly contributed to our up-to-date knowledge of the therapeutic potential of gut microbial-derived EVs in treating neurological disorders, including strokes, Alzheimer's and Parkinson's disease, and dementia. The review also discusses the newer insights in recent studies focused on developing superior therapeutic microbial EVs via genetic manipulation and/or dietary intervention.