Extracellular RNAs in periodontopathogenic outer membrane vesicles promote TNF-α production in human macrophages and cross the blood-brain barrier in mice

Alzheimer's Disease and Porphyromonas gingivalis: Exploring the Links

Recent research highlights compelling links between oral health, particularly periodontitis, and systemic diseases, including Alzheimer's disease (AD). Although the biological mechanisms underlying these associations remain unclear, the role of periodontal pathogens, particularly Porphyromonas gingivalis, has garnered significant attention. P. gingivalis, a major driver of periodontitis, is recognized for its potential systemic effects and its putative role in AD pathogenesis. This review examines evidence connecting P. gingivalis to hallmark AD features, such as amyloid β accumulation, tau hyperphosphorylation, neuroinflammation, and other neuropathological features consistent with AD. Virulence factors, such as gingipains and lipopolysaccharides, were shown to be implicated in blood-brain barrier disruption, neuroinflammation, and neuronal damage. P. gingivalis-derived outer membrane vesicles may serve to disseminate virulence factors to brain tissues. Indirect mechanisms, including systemic inflammation triggered by chronic periodontal infections, are also supposed to exacerbate neurodegenerative processes. While the exact pathways remain uncertain, studies detecting P. gingivalis virulence factors and its other components in AD-affected brains support their possible role in disease pathogenesis. This review underscores the need for further investigation into P. gingivalis-mediated mechanisms and their interplay with host responses. Understanding these interactions could provide critical insights into novel strategies for reducing AD risk through periodontal disease management.

Opportunities and challenges of bacterial extracellular vesicles in regenerative medicine

Extracellular vesicles (EVs) are membrane-bound vesicles that are shed or secreted from the cell membrane and enveloped by a lipid bilayer. They possess stability, low immunogenicity, and non-cytotoxicity, exhibiting extensive prospects in regenerative medicine (RM). However, natural EVs pose challenges, such as insufficient targeting capabilities, potential biosafety concerns, and limited acquisition pathways. Although engineered EVs demonstrate excellent therapeutic efficacy, challenges such as low production yield and the complexity of engineering modifications constrain their further clinical applications. Bacteria have advantages such as rapid proliferation, diverse gene editing methods, mature cultivation techniques, and relatively easy preparation of bacterial EVs (BEVs), which can be used to effectively address the challenges currently encountered in the field of EVs. This review provides a description of the biogenesis and pathophysiological functions of BEVs, and strategies for optimizing BEVs preparation to attain efficiency and safety are discussed. An analysis of natural characteristics of BEVs is also conducted to explore how to leverage their advantages or mitigate their limitations, thereby overcoming constraints on the application of BEVs in RM. In summary, engineered BEVs possess characteristics such as high production yield, excellent stability, and high drug-delivering capabilities, laying the foundation for their application in RM.

Pathogenic mechanisms and potential applications of extracellular vesicles from periodontal pathogens in periodontitis

Periodontitis is a multifactorial disease characterized by chronic destruction of the periodontal supporting tissues and is closely associated with the dysbiosis of the plaque biofilm. It is the leading cause of tooth loss in adults. Bacterial extracellular vesicles (BEVs) are released from bacteria, which range in size from 20 to 400 nm. These vesicles contain various components derived from their parent bacteria, including nucleic acids, proteins, lipids, and other molecules, which facilitate functions such as molecular transfer, metabolic regulation, bacterial interactions, biofilm formation, and immune modulation. BEVs participated in the pathophysiological process of periodontitis. Recently emerging evidence also showed that the contents of EVs in saliva and gingival crevicular fluid (miRNAs, mRNAs, and proteins) could be used as potential biomarkers for periodontitis. While most current research focuses on human-derived components, much less is known about BEVs. Therefore, this review introduces the formation mechanisms and components of BEVs related to periodontitis. Then, this review summarizes the current information about the mechanism, the diagnostic and theraputic value of periodontal pathogen-derived extracellular vesicles in the development of periodontitis. Furthermore, the future challenges of exploring the role of BEVs in periodontitis are also discussed.

Adipose Tissue as a Major Launch Spot for Circulating Extracellular Vesicle-Carried MicroRNAs Coordinating Tissue and Systemic Metabolism

Circulating microRNAs (miRNAs), especially transported by extracellular vesicles (EVs), have recently emerged as major new participants in interorgan communication, playing an important role in the metabolic coordination of our tissues. Among these, adipose tissue displays an extraordinary ability to secrete a vast list of EV-carried miRNAs into the circulation, representing new hormone-like factors. Despite the limitations of current methodologies for the unequivocal identification of the origin and destination of EV-carried miRNAs in vivo, recent investigations clearly support the important regulatory role of adipose-derived circulating miRNAs in shaping the metabolism and function of other tissues including the liver, muscle, endocrine pancreas, cardiovascular system, gastrointestinal tract, and brain. Here, we review the most recent findings regarding miRNAs transported by adipose-derived EVs (AdEVs) targeting other major metabolic organs and the implications of this dialog for physiology and pathology. We also review here the current and potential future diagnostic and therapeutic applications of AdEV-carried miRNAs.

Insights into the regulatory role of bacterial sncRNA and its extracellular delivery via OMVs

Small noncoding RNAs (sncRNAs) play important regulatory roles in bacterial physiological processes and host-pathogen interactions. Meanwhile, bacterial outer membrane vesicles (OMVs), as naturally secreted outer membrane structures, play a vital role in the interaction between bacteria and their living environment, including the host environment. However, most current studies focus on the biological functions of sncRNAs in bacteria or hosts, while neglecting the roles and regulatory mechanisms of the OMVs that encapsulate these sncRNAs. Therefore, this review aims to summarize the intracellular regulatory roles of bacterial sncRNAs in promoting pathogen survival by regulating virulence, modulating bacterial drug resistance, and regulating iron metabolism, and their extracellular regulatory function for influencing host immunity through host-pathogen interactions. Additionally, we introduce the key role played by OMVs, which serve as important cargoes in bacterial sncRNA-host interactions. We propose emerging pathways of sncRNA action to further discuss the mode of host-pathogen interactions, highlighting that the inhibition of sncRNA delivery by OMVs may prevent the occurrence of infection to some extent. Hence, this review lays the foundation for future prophylactic treatments against bacterial infections and strategies for addressing bacterial drug resistance. KEY POINTS: •sncRNAs have intracellular and extracellular regulatory functions in bacterial physiological processes and host-pathogen interactions. •OMVs are potential mediators between bacterial sncRNAs and host cells. •OMVs encapsulating sncRNAs have more potential biological functions.

Microbial- and host immune cell-derived extracellular vesicles in the pathogenesis and therapy of periodontitis: A narrative review

Periodontitis is a chronic inflammatory disease caused by dysbiotic biofilms and destructive host immune responses. Extracellular vesicles (EVs) are circulating nanoparticles released by microbes and host cells involved in cell-to-cell communication, found in body biofluids, such as saliva and gingival crevicular fluid (GCF). EVs are mainly involved in cell-to-cell communication, and may hold promise for diagnostic and therapeutic purposes. Periodontal research has examined the potential involvement of bacterial- and host-cell-derived EVs in disease pathogenesis, diagnosis, and therapy, but data remains scarce on immune cell- or microbial-derived EVs. In this narrative review, we first provide an overview of the role of microbial and host-derived EVs on disease pathogenesis. Recent studies reveal that Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans-derived outer membrane vesicles (OMVs) can activate inflammatory cytokine release in host cells, while M1 macrophage EVs may contribute to bone loss. Additionally, we summarised current in vitro and pre-clinical research on the utilisation of immune cell and microbial-derived EVs as potential therapeutic tools in the context of periodontal treatment. Studies indicate that EVs from M2 macrophages and dendritic cells promote bone regeneration in animal models. While bacterial EVs remain underexplored for periodontal therapy, preliminary research suggests that P. gingivalis OMVs hold promise as vaccine candidates. Finally, we acknowledge the current limitations present in the field of translating immune cell derived EVs and microbial derived EVs in periodontology. It is concluded that microbial and host immune cell-derived EVs have a role in periodontitis pathogenesis and hence may be useful for studying disease pathophysiology, and as diagnostic and treatment monitoring biomarkers.

Insight into the potential of algorithms using AI technology as in vitro diagnostics utilizing microbial extracellular vesicles

Recently, the microbiome has been gaining significant attention in the healthcare sector as a next-generation factor. However, there remains a substantial gap in our understanding of the fundamental mechanisms of microbes, particularly regarding the effector microbial products exchanged between the microbiota and the host. Consequently, research on microbial extracellular vesicles (MEVs) has increased. MEVs, which are nano-sized, can circulate throughout the body and penetrate the bloodstream, carrying diverse information. Consequently, they are increasingly being utilized in medical applications. Additionally, AI technologies are being utilized in medicine. The combination of MEVs and AI technology is being explored for the development of algorithm-based in vitro diagnostics (IVD). Therefore, this study aims to review the integration of MEVs and AI technology as diagnostic tools for personalized medicine. This paper reviewed the MEV-based algorithms developed by a variety of human samples and AI technology. Additionally, most of MEV-based diagnostic models showed higher clinical performance. Several important factors are crucial for accurate diagnosis. First, optimizing sample types according to specific diseases is essential. Second, AI technology with higher diagnostic power yields more accurate results. Finally, incorporating additional markers can enhance diagnostic power. However, applying this tool in situ faces several limitations, including method standardization, sample size, and analysis techniques. In the future, we anticipate that research on MEVs will advance our understanding of their role in disease and establish the foundation for precision medicine strategies.

Extracellular vesicle production by oral bacteria related to dental caries and periodontal disease: role in microbe-host and interspecies interactions

Extracellular vesicles (EVs) are cell membrane-derived structures between 20-400 nm in size. In bacteria, EVs play a crucial role in molecule secretion, cell wall biogenesis, cell-cell communication, biofilm development, and host-pathogen interactions. Despite these increasing reports of bacterial-derived vesicles, there remains a limited number of studies that summarize oral bacterial EVs, their cargo, and their main biological functions. Therefore, the aim of this review is to present the latest research on oral bacteria-derived EVs and how they can modulate various physiological and pathological processes in the oral cavity, including the pathogenesis of highly relevant diseases such as dental caries and periodontitis and their systemic complications. Overall, caries-associated bacteria (such as Streptococcus mutans) as well as periodontal pathogens (including the red complex pathogens Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola) have all been shown to produce EVs that carry an array of virulent factors and molecules involved in biofilm and immune modulation, bacterial adhesion, and extracellular matrix degradation. As bacterial EV production is strongly impacted by genotypic and environmental variations, the inhibition of EV genesis and secretion remains a key potential future approach against oral diseases.

Transcriptome Analysis of HNSCC by Aggregatibacter actinomycetemcomitans Extracellular Vesicles

OBJECTIVES

The role of extracellular vesicles (EVs), also known as outer membrane vesicles (OMVs), secreted by oral bacteria in the progression of head and neck squamous cell carcinomas (HNSCCs), is largely unexplored. This study aimed to investigate the influence of bacterial EVs, specifically those derived from Aggregatibacter actinomycetemcomitans (Aa), on the progression of HNSCC.

MATERIALS AND METHODS

FaDu and UMSCC1 cell lines were treated with Aa-derived EVs, and oncogenic activities were assessed. Comprehensive cellular and RNA-sequencing transcriptome analyses were conducted to assess the impact of these EVs on cell cycle progression and gene expression.

RESULTS

Our findings reveal that Aa-derived EVs accelerate cell cycle progression through the S and G2 phases and enhance invasion in HNSCC cell lines. RNA-sequencing analysis showed that Aa-derived EVs exert a more significant effect on general transcript expression than on microRNA profiles, except for miR-146a, which is recognized as a key factor in both carcinogenesis and immune modulation.

CONCLUSIONS

Bacterial EVs, particularly from periodontal pathogens like Aa, are significant modulators within the oral cancer environment, potentially affecting cellular behavior and gene expression profiles. This study highlights the complex relationship between periodontal health and oral carcinogenesis, emphasizing the significant role of bacterial EVs in HNSCC progression.

The Critical Role of Host and Bacterial Extracellular Vesicles in Endometriosis

Endometriosis is a chronic, inflammatory, oestrogen-dependent disorder that is defined by the presence of endometrium-like tissue in the extra-uterine environment. It is estimated to affect approximately 10% of women of reproductive age, and the cause is still largely unknown. The heterogenous nature and complex pathophysiology of the disease results in diagnostic and therapeutic challenges. This review examines the emerging role of host extracellular vesicles (EVs) in endometriosis development and progression, with a particular focus on bacterial extracellular vesicles (BEVs). EVs are nano-sized membrane-bound particles that can transport bioactive molecules such as nucleic acids, proteins, and lipids, and therefore play an essential role in intercellular communication. Due to their unique cargo composition, EVs can play a dual role, both in the disease pathogenesis and as biomarkers. Both host and bacterial EVs (HEVs and BEVs) have been implicated in endometriosis, by modulating inflammatory responses, angiogenesis, tissue remodelling, and cellular proliferation within the peritoneal microenvironment. Understanding the intricate mechanisms underlying EVs in endometriosis pathophysiology and modulation of the lesion microenvironment may lead to novel diagnostic tools and therapeutic targets. Future research should focus on uncovering the specific cargo, the inter-kingdom cell-to-cell interactions, and the anti-inflammatory and anti-microbial mechanisms of both HEVs and BEVs in endometriosis in the hope of discovering translational findings that could improve the diagnosis and treatment of the disease.

Alzheimer's Disease-Derived Outer Membrane Vesicles Exacerbate Cognitive Dysfunction, Modulate the Gut Microbiome, and Increase Neuroinflammation and Amyloid-β Production

Although our understanding of the molecular biology of Alzheimer's disease (AD) continues to improve, the etiology of the disease, particularly the involvement of gut microbiota disturbances, remains a challenge. Outer membrane vesicles (OMVs) play a key role in central nervous system diseases, but the impact of OMVs on AD progression remains unclear. In this study, we hypothesized that AD-derived OMVs (OMVsAD) were a risk factor in AD pathology. To test our hypothesis, young APP/PS1 mice (AD mice) were given OMVsAD by gavage. Young AD mice were euthanized 120 days after gavage to assess the intestinal barrier, gut microbiota diversity, mediators of neuroinflammation, glial markers, amyloid burden, and short-chain fatty acid (SCFA) levels. Our results showed that OMVsAD accelerated cognitive dysfunction after 120 days of intragastric administration. Morris water maze experiment and new object recognition test showed that OMVsAD caused significantly poorer spatial ability learning and memory of the AD mice. We observed the OMVsAD-treated APP/PS1 mice display OMVs disrupting the intestinal barrier compared with controls of normal human-derived OMVs. Compared with the OMVsHC group, claudin-5 and ZO-1 related to the intestinal barrier were significantly downregulated in the OMVsAD group. The OMVsAD activate microglia in the cerebral cortex and hippocampus of AD mice, and the levels of IL-1β, IL-6, TNF-α, and NF-Κb were upregulated. We also found that OMVsAD increased Aβ production. 16S rRNA sequencing showed that OMVsAD negatively regulated the α- and β-diversity index of intestinal flora and reduced the levels of SCFA. OMVsAD may change the intestinal flora of young AD, damage the intestinal mucosa and blood-brain barrier, and accelerate AD neuropathological damage.

Improved Isolation Optimizes Downstream Application of Extracellular Vesicles Derived from Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis, secretes extracellular vesicles (EVs), which may play an important role in mediating interactions between bacteria and host cells. Mtb EVs can be isolated by means of various techniques, which differ in terms of their effectiveness. In the present study, we found that an exosome isolation kit (EI) yielded higher numbers of EVs than either differential centrifugation (DC) or exosome detection via an ultrafast-isolation system (EXODUS). We also found that the EXODUS method revealed a greater abundance of H37Rv components within EVs, compared with the DC and EI methods. Analysis of the downstream application of H37Rv EVs revealed their internalization by RAW264.7 macrophages, peaking at 6 h, with subsequent activation of the TLR2 signaling pathway leading to the expression of inflammatory cytokines including IL-6 and TNF-α. It was also found that H37Rv EVs could cross the blood-brain barrier (BBB) and enter the brain, peaking at 12 h post-injection, eliciting an inflammatory response in the cerebral parenchyma, cerebellum, and hippocampus that persisted for up to 6 days. These findings offer novel insights into the pathogenesis of Mtb-induced diseases and may guide the development of therapeutic strategies.

The emerging role of bacterial extracellular vesicles in human cancers

Bacterial extracellular vesicles (BEVs) have emerged as pivotal mediators between bacteria and host. In addition to being crucial players in host homeostasis, they have recently been implicated in disease pathologies such as cancer. Hence, the study of BEVs represents an intriguing and rapidly evolving field with substantial translational potential. In this review, we briefly introduce the fundamentals of BEV characteristics, cargo and biogenesis. We emphatically summarize the current relationship between BEVs across various cancer types, illustrating their role in tumorigenesis, treatment responses and patient survival. We further discuss the inherent advantages of BEVs, such as stability, abundance and specific cargo profiles, that make them attractive candidates for non-invasive diagnostic and prognostic approaches. The review also explores the potential of BEVs as a strategy for cancer therapy, considering their ability to deliver therapeutic agents, modulate the tumour microenvironment (TME) and elicit immunomodulatory responses. Understanding the clinical significance of BEVs may lead to the development of better-targeted and personalized treatment strategies. This comprehensive review evaluates the current progress surrounding BEVs and poses questions to encourage further research in this emerging field to harness the benefits of BEVs for their full potential in clinical applications against cancer.

The aryl hydrocarbon receptor and FOS mediate cytotoxicity induced by Acinetobacter baumannii

Acinetobacter baumannii is a pathogenic and multidrug-resistant Gram-negative bacterium that causes severe nosocomial infections. To better understand the mechanism of pathogenesis, we compare the proteomes of uninfected and infected human cells, revealing that transcription factor FOS is the host protein most strongly induced by A. baumannii infection. Pharmacological inhibition of FOS reduces the cytotoxicity of A. baumannii in cell-based models, and similar results are also observed in a mouse infection model. A. baumannii outer membrane vesicles (OMVs) are shown to activate the aryl hydrocarbon receptor (AHR) of host cells by inducing the host enzyme tryptophan-2,3-dioxygenase (TDO), producing the ligand kynurenine, which binds AHR. Following ligand binding, AHR is a direct transcriptional activator of the FOS gene. We propose that A. baumannii infection impacts the host tryptophan metabolism and promotes AHR- and FOS-mediated cytotoxicity of infected cells.

Bacterial Membrane Vesicles: The Missing Link Between Bacterial Infection and Alzheimer Disease

Periodontitis is a common chronic inflammatory disease, affecting approximately 19% of the global adult population. A relationship between periodontal disease and Alzheimer disease has long been recognized, and recent evidence has been uncovered to link these 2 diseases mechanistically. Periodontitis is caused by dysbiosis in the subgingival plaque microbiome, with a pronounced shift in the oral microbiota from one consisting primarily of Gram-positive aerobic bacteria to one predominated by Gram-negative anaerobes, such as Porphyromonas gingivalis. A common phenomenon shared by all bacteria is the release of membrane vesicles to facilitate biomolecule delivery across long distances. In particular, the vesicles released by P gingivalis and other oral pathogens have been found to transport bacterial components across the blood-brain barrier, initiating the physiologic changes involved in Alzheimer disease. In this review, we summarize recent data that support the relationship between vesicles secreted by periodontal pathogens to Alzheimer disease pathology.

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.

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.

Extracellular vesicles-Potential link between periodontal disease and diabetic complications

It has long been suggested that a bidirectional impact exists between periodontitis and diabetes. Periodontitis may affect diabetes glycemic control, insulin resistance, and diabetic complications. Diabetes can worsen periodontitis by delaying wound healing and increasing the chance of infection. Extracellular vesicles (EVs) are heterogeneous particles of membrane-enclosed spherical structure secreted by eukaryotes and prokaryotes and play a key role in a variety of diseases. This review will introduce the biogenesis, release, and biological function of EVs from a microbial and host cell perspective, discuss the functional properties of EVs in the development of periodontitis and diabetes, and explore their role in the pathogenesis and clinical application of these two diseases. Their clinical implication and diagnostic value are also discussed.

How aging influences the gut-bone marrow axis and alters hematopoietic stem cell regulation

The gut microbiome has come to prominence across research disciplines, due to its influence on major biological systems within humans. Recently, a relationship between the gut microbiome and hematopoietic system has been identified and coined the gut-bone marrow axis. It is well established that the hematopoietic system and gut microbiome separately alter with age; however, the relationship between these changes and how these systems influence each other demands investigation. Since the hematopoietic system produces immune cells that help govern commensal bacteria, it is important to identify how the microbiome interacts with hematopoietic stem cells (HSCs). The gut microbiota has been shown to influence the development and outcomes of hematologic disorders, suggesting dysbiosis may influence the maintenance of HSCs with age. Short chain fatty acids (SCFAs), lactate, iron availability, tryptophan metabolites, bacterial extracellular vesicles, microbe associated molecular patterns (MAMPs), and toll-like receptor (TLR) signalling have been proposed as key mediators of communication across the gut-bone marrow axis and will be reviewed in this article within the context of aging.

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.

Influences of bacterial extracellular vesicles on macrophage immune functions

Bacterial extracellular vesicles (EVs) are crucial mediators of information transfer between bacteria and host cells. Macrophages, as key effector cells in the innate immune system, have garnered widespread attention for their interactions with bacterial EVs. Increasing evidence indicates that bacterial EVs can be internalized by macrophages through multiple pathways, thereby influencing their immune functions. These functions include inflammatory responses, antimicrobial activity, antigen presentation, and programmed cell death. Therefore, this review summarizes current research on the interactions between bacterial EVs and macrophages. This will aid in the deeper understanding of immune modulation mediated by pathogenic microorganisms and provide a basis for developing novel antibacterial therapeutic strategies.

Effect of outer membrane vesicles of Lactobacillus pentosus on Tau phosphorylation and CDK5-Calpain pathway in mice

Alzheimer's disease (AD) stands as a neurodegenerative disorder causing cognitive decline, posing a significant health concern for the elderly population in China. This study explored the effects of outer membrane vesicles (OMVs) from the gut microbiota of AD patients on learning and memory abilities and Tau protein phosphorylation in mice. In contrast to the OMVs from healthy controls and the PBS treatment group, mice treated with AD-OMVs exhibited notable declines in learning and memory capabilities, as evidenced by results from the Morris water maze, Y-maze, and novel object recognition tests. Immunohistochemistry and Western blot assessments unveiled elevated levels of hyperphosphorylated Tau in the cortex and hippocampus of mice treated with AD-OMVs. However, there were no alterations observed in the total Tau levels. In addition, AD-OMVs treated mice showed increased neuroinflammation indicated by elevated astrocytes and microglia. Molecular mechanism studies demonstrated that AD-OMVs could activate GSK3β, CDK5-Calpain and NF-κB pathways in mice hippocampus. These studies suggest AD patient gut microbiota derived OMVs can promote host Tau phosphorylation and improved neuroinflammation.

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.

Interactions of Gram-Positive Bacterial Membrane Vesicles and Hosts: Updates and Future Directions

Extracellular vesicles (EVs) are lipid bilayers derived from cell membranes, released by both eukaryotic cells and bacteria into the extracellular environment. During production, EVs carry proteins, nucleic acids, and various compounds, which are then released. While Gram-positive bacteria were traditionally thought incapable of producing EVs due to their thick peptidoglycan cell walls, recent studies on membrane vesicles (MVs) in Gram-positive bacteria have revealed their significant role in bacterial physiology and disease progression. This review explores the current understanding of MVs in Gram-positive bacteria, including the characterization of their content and functions, as well as their interactions with host and bacterial cells. It offers a fresh perspective to enhance our comprehension of Gram-positive bacterial EVs.

Pseudomonas aeruginosa outer membrane vesicle-packed sRNAs can enter host cells and regulate innate immune responses

Bacterial outer membrane vesicles (OMVs) can package and deliver virulence factors into host cells, which is an important mechanism mediating host-pathogen interactions. It has been reported that small RNAs (sRNAs) can be packed into OMVs with varying relative abundance, which might affect the function and/or stability of host mRNAs. In this study, we used OptiPrep density gradient ultra-high-speed centrifugation to purify OMVs from Pseudomonas aeruginosa. Next, the sequences and abundance of sRNAs were detected by using Small RNA-Seq. In particular, sRNA4518698, sRNA2316613 and sRNA809738 were the three most abundant sRNAs in OMVs, which are all fragments of P. aeruginosa non-coding RNAs. sRNAs were shielded within the interior of OMVs and remained resistant to external RNase cleavage. The miRanda and RNAhybrid analysis demonstrated that those sRNAs could target a large number of host mRNAs, which were enriched in host immune responses by the functions of GO and KEGG enrichment. Experimentally, we demonstrated that the transfection of synthetic sRNA4518698, sRNA2316613, or sRNA809738 could reduce the expression of innate immune response genes in RAW264.7 cells. Together, we demonstrated that P. aeruginosa OMVs sRNAs can regulate innate immune responses. This study uncovered a mechanism in which the OMVs regulate host responses by transferring bacterial sRNAs.

Use of Biomaterials in 3D Printing as a Solution to Microbial Infections in Arthroplasty and Osseous Reconstruction

The incidence of microbial infections in orthopedic prosthetic surgeries is a perennial problem that increases morbidity and mortality, representing one of the major complications of such medical interventions. The emergence of novel technologies, especially 3D printing, represents a promising avenue of development for reducing the risk of such eventualities. There are already a host of biomaterials, suitable for 3D printing, that are being tested for antimicrobial properties when they are coated with bioactive compounds, such as antibiotics, or combined with hydrogels with antimicrobial and antioxidant properties, such as chitosan and metal nanoparticles, among others. The materials discussed in the context of this paper comprise beta-tricalcium phosphate (β-TCP), biphasic calcium phosphate (BCP), hydroxyapatite, lithium disilicate glass, polyetheretherketone (PEEK), poly(propylene fumarate) (PPF), poly(trimethylene carbonate) (PTMC), and zirconia. While the recent research results are promising, further development is required to address the increasing antibiotic resistance exhibited by several common pathogens, the potential for fungal infections, and the potential toxicity of some metal nanoparticles. Other solutions, like the incorporation of phytochemicals, should also be explored. Incorporating artificial intelligence (AI) in the development of certain orthopedic implants and the potential use of AI against bacterial infections might represent viable solutions to these problems. Finally, there are some legal considerations associated with the use of biomaterials and the widespread use of 3D printing, which must be taken into account.

Porphyromonas gingivalis and the pathogenesis of Alzheimer's disease

The cause of Alzheimer's disease (AD), and the pathophysiological mechanisms involved, remain major unanswered questions in medical science. Oral bacteria, especially those species associated with chronic periodontitis and particularly Porphyromonas gingivalis, are being linked causally to AD pathophysiology in a subpopulation of susceptible individuals. P. gingivalis produces large amounts of proteolytic enzymes, haem and iron capture proteins, adhesins and internalins that are secreted and attached to the cell surface and concentrated onto outer membrane vesicles (OMVs). These enzymes and adhesive proteins have been shown to cause host tissue damage and stimulate inflammatory responses. The ecological and pathophysiological roles of P. gingivalis OMVs, their ability to disperse widely throughout the host and deliver functional proteins lead to the proposal that they may be the link between a P. gingivalis focal infection in the subgingivae during periodontitis and neurodegeneration in AD. P. gingivalis OMVs can cross the blood brain barrier and may accelerate AD-specific neuropathology by increasing neuroinflammation, plaque/tangle formation and dysregulation of iron homeostasis, thereby inducing ferroptosis leading to neuronal death and neurodegeneration.

CA, Harmon B, Espinola JA, Reck Cechinel L, Batabyal R, Freishtat RJ, Hahn A. Bacterial small RNAs may mediate immune response differences seen in respiratory syncytial virus versus rhinovirus bronchiolitis

Bronchiolitis, a viral lower respiratory infection, is the leading cause of infant hospitalization, which is associated with an increased risk for developing asthma later in life. Bronchiolitis can be caused by several respiratory viruses, such as respiratory syncytial virus (RSV), rhinovirus (RV), and others. It can also be caused by a solo infection (e.g., RSV- or RV-only bronchiolitis) or co-infection with two or more viruses. Studies have shown viral etiology-related differences between RSV- and RV-only bronchiolitis in the immune response, human microRNA (miRNA) profiles, and dominance of certain airway microbiome constituents. Here, we identified bacterial small RNAs (sRNAs), the prokaryotic equivalent to eukaryotic miRNAs, that differ between infants of the 35th Multicenter Airway Research Collaboration (MARC-35) cohort with RSV- versus RV-only bronchiolitis. We first derived reference sRNA datasets from cultures of four bacteria known to be associated with bronchiolitis (i.e., Haemophilus influenzae, Moraxella catarrhalis, Moraxella nonliquefaciens, and Streptococcus pneumoniae). Using these reference sRNA datasets, we found several sRNAs associated with RSV- and RV-only bronchiolitis in our human nasal RNA-Seq MARC-35 data. We also determined potential human transcript targets of the bacterial sRNAs and compared expression of the sRNAs between RSV- and RV-only cases. sRNAs are known to downregulate their mRNA target, we found that, compared to those associated with RV-only bronchiolitis, sRNAs associated with RSV-only bronchiolitis may relatively activate the IL-6 and IL-8 pathways and relatively inhibit the IL-17A pathway. These data support that bacteria may be contributing to inflammation differences seen in RSV- and RV-only bronchiolitis, and for the first time indicate that the potential mechanism in doing so may be through bacterial sRNAs.

Effect of gut microbiota-derived metabolites and extracellular vesicles on neurodegenerative disease in a gut-brain axis chip

A new perspective suggests that a dynamic bidirectional communication system, often referred to as the microbiome-gut-brain axis, exists among the gut, its microbiome, and the central nervous system (CNS). This system may influence brain health and various brain-related diseases, especially in the realms of neurodevelopmental and neurodegenerative conditions. However, the exact mechanism is not yet understood. Metabolites or extracellular vesicles derived from microbes in the gut have the capacity to traverse the intestinal epithelial barrier or blood-brain barrier, gaining access to the systemic circulation. This phenomenon can initiate the physiological responses that directly or indirectly impact the CNS and its function. However, reliable and controllable tools are required to demonstrate the causal effects of gut microbial-derived substances on neurogenesis and neurodegenerative diseases. The integration of microfluidics enhances scientific research by providing advanced in vitro engineering models. In this study, we investigated the impact of microbe-derived metabolites and exosomes on neurodevelopment and neurodegenerative disorders using human induced pluripotent stem cells (iPSCs)-derived neurons in a gut-brain axis chip. While strain-specific, our findings indicate that both microbial-derived metabolites and exosomes exert the significant effects on neural growth, maturation, and synaptic plasticity. Therefore, our results suggest that metabolites and exosomes derived from microbes hold promise as potential candidates and strategies for addressing neurodevelopmental and neurodegenerative disorders.

The oral-brain axis: can periodontal pathogens trigger the onset and progression of Alzheimer's disease?

Alzheimer's disease (AD) is the most prevalent form of dementia, characterized by a progressive cognitive decline. Sporadic AD, accounting for more than 95% of cases, may arise due to the influence of environmental factors. It was reported that periodontitis, a common oral ailment, shares several risk factors with AD, including advanced age, smoking, diabetes, and hypertension, among others. Periodontitis is an inflammatory disease triggered by dysbiosis of oral microorganisms, whereas Alzheimer's disease is characterized by neuroinflammation. Many studies have indicated that chronic inflammation can instigate brain AD-related pathologies, including amyloid-β plaques, Tau protein hyperphosphorylation, neuroinflammation, and neurodegeneration. The potential involvement of periodontal pathogens and/or their virulence factors in the onset and progression of AD by the oral-brain axis has garnered significant attention among researchers with ongoing investigations. This review has updated the periodontal pathogens potentially associated with AD, elucidating their impact on the central nervous system, immune response, and related pathological processes in the brain to provide valuable insights for future research on the oral-brain axis.

Tenacibaculum dicentrarchi produce outer membrane vesicles (OMV) that are associated with the cytotoxic effect in rainbow trout head kidney macrophages

Tenacibaculum dicentrarchi is the second most important pathogen in Chilean salmon farming. This microorganism causes severe skin lesions on the body surface of farmed fish. The bacterium can also adhere to surfaces and form biofilm, survive in fish skin mucus, and possess different systems for iron acquisition. However, the virulence mechanisms are still not fully elucidated. Outer membrane vesicles (OMV) are nanostructures released by pathogenic Gram-negative bacteria during growth, but none has been described yet for T. dicentrarchi. In this study, we provide the first reported evidence of the fish pathogen T. dicentrarchi producing and releasing OMV from 24 h after incubation, increasing thereafter until 120 h. Analyses were conducted with T. dicentrarchi TdCh05, QCR29, and the type strain CECT 7612T . The OMV sizes, determined via scanning electron microscopy, ranged from 82.25 nm to 396.88 nm as per the strain and incubation time point (i.e., 24 to 120 h). SDS-PAGE revealed that the number of protein bands evidenced a drastically downward trend among the T. dicentrarchi strains. In turn, the OMV shared five proteins (i.e., 22.2, 31.9, 47.7, 56.3, and 107.1 kDa), but no protein pattern was identical. A heterogeneous amount of protein, RNA, and DNA were obtained, depending on the time at which OMV were extracted. Purified OMV were biologically active and induced a cytotoxic effect in macrophage-enriched cell cultures from rainbow trout (Oncorhynchus mykiss) head kidneys. This is the first step towards understanding the role that OMV could play in the pathogenesis of T. dicentrarchi.

BACTERIAL EXTRACELLULAR VESICLES IN THE REGULATION OF INFLAMMATORY RESPONSE AND HOST-MICROBE INTERACTIONS

ABSTRACT

Extracellular vesicles (EVs) are a new revelation in cross-kingdom communication, with increasing evidence showing the diverse roles of bacterial EVs (BEVs) in mammalian cells and host-microbe interactions. Bacterial EVs include outer membrane vesicles released by gram-negative bacteria and membrane vesicles generated from gram-positive bacteria. Recently, BEVs have drawn attention for their potential as biomarkers and therapeutic tools because they are nano-sized and can deliver bacterial cargo into host cells. Importantly, exposure to BEVs significantly affects various physiological and pathological responses in mammalian cells. Herein, we provide a comprehensive overview of the various effects of BEVs on host cells (i.e., immune cells, endothelial cells, and epithelial cells) and inflammatory/infectious diseases. First, the biogenesis and purification methods of BEVs are summarized. Next, the mechanisms and pathways identified by BEVs that stimulate either proinflammatory or anti-inflammatory responses are highlighted. In addition, we discuss the mechanisms by which BEVs regulate host-microbe interactions and their effects on the immune system. Finally, this review focuses on the contribution of BEVs to the pathogenesis of sepsis/septic shock and their therapeutic potential for the treatment of sepsis.

Gram-negative bacterial sRNAs encapsulated in OMVs: an emerging class of therapeutic targets in diseases

Small regulatory RNAs (sRNAs) encapsulated in outer membrane vesicles (OMVs) are critical post-transcriptional regulators of gene expression in prokaryotic and eukaryotic organisms. OMVs are small spherical structures released by Gram-negative bacteria that serve as important vehicles for intercellular communication and can also play an important role in bacterial virulence and host-pathogen interactions. These molecules can interact with mRNAs or proteins and affect various cellular functions and physiological processes in the producing bacteria. This review aims to provide insight into the current understanding of sRNA localization to OMVs in Gram-negative bacteria and highlights the identification, characterization and functional implications of these encapsulated sRNAs. By examining the research gaps in this field, we aim to inspire further exploration and progress in investigating the potential therapeutic applications of OMV-encapsulated sRNAs in various diseases.

Variations in the oral microbiome and metabolome of methamphetamine users

Drug addiction can seriously damage human physical and mental health, while detoxification is a long and difficult process. Although studies have reported changes in the oral microbiome of methamphetamine (METH) users, the role that the microbiome plays in the process of drug addiction is still unknown. This study aims to explore the function of the microbiome based on analysis of the variations in the oral microbiome and metabolome of METH users. We performed the 16S rRNA sequencing analysis based on the oral saliva samples collected from 278 METH users and 105 healthy controls (CTL). In addition, the untargeted metabolomic profiling was conducted based on 220 samples. Compared to the CTL group, alpha diversity was reduced in the group of METH users and the relative abundances of Peptostreptococcus and Gemella were significantly increased, while the relative abundances of Campylobacter and Aggregatibacter were significantly decreased. Variations were also detected in oral metabolic pathways, including enhanced tryptophan metabolism, lysine biosynthesis, purine metabolism, and steroid biosynthesis. Conversely, the metabolic pathways of porphyrin metabolism, glutathione metabolism, and pentose phosphate were significantly reduced. It was speculated that four key microbial taxa, i.e., Peptostreptococcus, Gemella, Campylobacter, and Aggregatibacter, could be involved in the toxicity and addiction mechanisms of METH by affecting the above metabolic pathways. It was found that with the increase of drug use years, the content of tryptamine associated with neuropsychiatric disorders was gradually increased. Our study provides novel insights into exploring the toxic damage and addiction mechanisms underlying the METH addiction.IMPORTANCEIt was found that with the increase of drug use years, the content of tryptamine associated with neuropsychiatric disorders gradually increased. The prediction models based on oral microbiome and metabolome could effectively predict the methamphetamine (METH) smoking. Our study provides novel insights into the exploration of the molecular mechanisms regulating the toxic damage and addiction of METH as well as new ideas for early prevention and treatment strategies of METH addiction.

New Perspectives on Crosstalks Between Bacterial Regulatory RNAs from Outer Membrane Vesicles and Eukaryotic Cells

Regulatory small RNAs (sRNAs) help the bacteria to survive harsh environmental conditions by posttranscriptional regulation of genes involved in various biological pathways including stress responses, homeostasis, and virulence. These sRNAs can be found carried by different membrane-bound vesicles like extracellular vesicles (EVs), membrane vesicles (MVs), or outer membrane vesicles (OMVs). OMVs provide myriad functions in bacterial cells including carrying a cargo of proteins, lipids, and nucleic acids including sRNAs. A few interesting studies have shown that these sRNAs can be transported to the host cell by membrane vesicles and can regulate the host immune system. Although there is evidence that sRNAs can be exported to host cells and sometimes can even cross the blood-brain barrier, the exact mechanism is still unknown. In this review, we investigated the new techniques implemented in various studies, to elucidate the crosstalks between bacterial cells and human immune systems by membrane vesicles carrying bacterial regulatory sRNAs.

Multiple Particle Tracking: A Method for Probing Biologically Relevant Mobility of Bacterial Extracellular Vesicles

Bacterial extracellular vesicles (bEVs) are produced by both Gram-negative and Gram-positive bacteria. These biological nanoparticles transport small molecules, nucleic acids, and proteins, enabling communication with both bacterial and mammalian cells. bEVs can evade and disrupt biological barriers, and their lipid membranes protect their cargo from degradation, facilitating long-distance communication in vivo. Furthermore, bacteria are easily manipulated and easily cultured. These combined factors make bEVs an ideal candidate for drug delivery applications. Thus, the study of how bEVs interact with biological barriers is interesting from both a signaling and drug delivery perspective. Here we describe methods for tracking bEV motion in biological matrices ex vivo. We outline methods for growth, isolation, quantification, and labeling, as well as techniques for tracking bEV motion ex vivo and quantifying these data. The methods described here are relevant to bEV communication with host cells as well as drug delivery applications using bEVs.

Extracellular vesicles from periodontal pathogens regulate hepatic steatosis via Toll-like receptor 2 and plasminogen activator inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) is associated with nonalcoholic fatty liver disease (NAFLD) by lipid accumulation in the liver. In this study, we showed that extracellular vesicles (EVs) from the periodontal pathogens Filifactor alocis and Porphyromonas gingivalis induced steatosis by inducing PAI-1 in the liver and serum of mice fed a low-fat diet. PAI-1 induction was not observed in TLR2-/- mice. When tested using HEK-Blue hTLR2 cells, human TLR2 reporter cells, the TLR2-activating ability of serum from NAFLD patients (n = 100) was significantly higher than that of serum from healthy subjects (n = 100). Correlation analysis confirmed that PAI-1 levels were positively correlated with the TLR2-activating ability of serum from NAFLD patients and healthy subjects. Amphiphilic molecules in EVs were involved in PAI-1 induction. Our data demonstrate that the TLR2/PAI-1 axis is important for hepatic steatosis by EVs of periodontal pathogens.

Bacterial extracellular vesicles at the interface of gut microbiota and immunity

Bacterial extracellular vesicles (BEVs) are nano-sized lipid-shielded structures released by bacteria and that play an important role in intercellular communication. Their broad taxonomic origins and varying cargo compositions suggest their active participation in significant biological mechanisms. Specifically, they are involved in directly modulating microbial ecosystems, competing with other organisms, contributing to pathogenicity, and influencing the immunity of their hosts. This review examines the mechanisms that underlie the modulatory effects of BEVs on gut dynamics and immunity. Understanding how BEVs modulate microbiota composition and functional imbalances is crucial, as gut dysbiosis is implicated not only in the pathogenesis of various gastrointestinal, metabolic, and neurological diseases, but also in reducing resistance to colonization by enteric pathogens, which is particularly concerning given the current antimicrobial resistance crisis. This review summarizes recent advancements in the field of BEVs to encourage further research into these enigmatic entities. This will facilitate a better understanding of intra- and interkingdom communication phenomena and reveal promising therapeutic approaches.

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.

Outer Membrane Vesicles from Acinetobacter baumannii: Biogenesis, Functions, and Vaccine Application

This review focuses on Acinetobacter baumannii, a Gram-negative bacterium that causes various infections and whose multidrug resistance has become a significant challenge in clinical practices. There are multiple bacterial mechanisms in A. baumannii that participate in bacterial colonization and immune responses. It is believed that outer membrane vesicles (OMVs) budding from the bacteria play a significant role in mediating bacterial survival and the subsequent attack against the host. Most OMVs originate from the bacterial membranes and molecules are enveloped in them. Elements similar to the pathogen endow OMVs with robust virulence, which provides a new direction for exploring the pathogenicity of A. baumannii and its therapeutic pathways. Although extensive research has been carried out on the feasibility of OMV-based vaccines against pathogens, no study has yet summarized the bioactive elements, biological activity, and vaccine applicability of A. baumannii OMVs. This review summarizes the components, biogenesis, and function of OMVs that contribute to their potential as vaccine candidates and the preparation methods and future directions for their development.

Periodontitis & preeclampsia: were outer membrane vesicles a potential connection?

Introduction: Preeclampsia (PE) is gestation-specific hypertension coupled by systemic multiple organ damages, remaining the leading causes of maternal and infant death worldwide.Materials and methods: Though numerous pathogenetic mechanisms have been engaged in this disorder and several methods have been undertaken to treat PE, few clinical strategies are effective in PE management, suggesting more studies from novel perspective being in great need to decipher the underlying mechanisms of PE.Results: Growing evidence shows that women with periodontitis, an oral microflora-induced chronic inflammation of the periodontal tissues, are more inclined to suffer PE, which may be tightly associated with microflora-derived outer membrane vesicles (OMVs). Latest studies reveal that OMVs are spherical membrane-enclosed entities released by bacteria and can gain free access to the circulation of the host and therefore reach the remote tissue of the host, participating the interaction among oral bacterial with the host and contribute to some systemic disease with carried bioactive materials.Conclusions: OMVs may be the underlying mechanism linking oral flora-induced periodontitis with dysfunction trophoblast and finally contributes to the pathogenesis of in PE. Here we provide evidence to support the potential roles of OMVs linking periodontal disease between PE.

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.

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.

Porphyromonas gingivalis outer membrane vesicles in cerebral ventricles activate microglia in mice

OBJECTIVE

Porphyromonas gingivalis (Pg) is thought to be involved in the progression of Alzheimer's disease (AD). Whether Pg or its contents can reach the brain and directly affect neuropathology is, however, unknown. Here, we investigated whether outer membrane vesicles (OMVs) of Pg translocate to the brain and induce the pathogenic features of AD.

MATERIAL AND METHODS

Pg OMVs were injected into the abdominal cavity of mice for 12 weeks. Pg OMV translocation to the brain was detected by immunohistochemistry using an anti-gingipain antibody. Tau protein and microglial activation in the mouse brain were examined by western blotting and immunohistochemistry. The effect of gingipains on inflammation was assessed by real-time polymerase chain reaction using human microglial HMC3 cells.

RESULTS

Gingipains were detected in the region around cerebral ventricles, choroid plexus, and ventricular ependymal cells in Pg OMV-administered mice. Tau and phosphorylated Tau protein increased and microglia were activated. Pg OMVs also increased the gene expression of proinflammatory cytokines in HMC3 cells in a gingipain-dependent manner.

CONCLUSION

Pg OMVs, including gingipains, can reach the cerebral ventricle and induce neuroinflammation by activating microglia. Pg OMVs may provide a better understanding of the implications of periodontal diseases in neurodegenerative conditions such as AD.

Bacterial outer membrane vesicles bound to bacteriophages modulate neutrophil responses to bacterial infection

Pseudomonas aeruginosa is a major human pathogen, particularly effective at colonizing the airways of patients with cystic fibrosis. Bacteriophages are highly abundant at infection sites, but their impact on mammalian immunity remains unclear. We previously showed that Pf4, a temperate filamentous bacteriophage produced by P. aeruginosa, modifies the innate immune response to P. aeruginosa infections via TLR3 signaling, but the underlying mechanisms remained unclear. Notably, Pf4 is a single-stranded DNA and lysogenic phage, and its production does not typically result in lysis of its bacterial host. We identified previously that internalization of Pf4 by human or murine immune cells triggers maladaptive viral pattern recognition receptors and resulted in bacterial persistence based on the presence of phage RNA. We report now that Pf4 phage dampens inflammatory responses to bacterial endotoxin and that this is mediated in part via bacterial vesicles attached to phage particles. Outer membrane vesicles (OMVs) are produced by Gram-negative bacteria and play a key role in host pathogen interaction. Recently, evidence has emerged that OMVs differentially package small RNAs. In this study, we show that Pf4 are decorated with OMVs that remain affixed to Pf4 despite of purification steps. These phages are endocytosed by human cells and delivered to endosomal vesicles. We demonstrate that short RNAs within the OMVs form hairpin structures that trigger TLR3-dependent type I interferon production and antagonize production of antibacterial cytokines and chemokines. In particular, Pf4 phages inhibit CXCL5, preventing efficient neutrophil chemotaxis in response to endotoxin. Moreover, blocking IFNAR or TLR3 signaling abrogates the effect of Pf4 bound to OMVs on macrophage activation. In a murine acute pneumonia model, mice treated with Pf4 associated with OMVs show significantly less neutrophil infiltration in BAL fluid than mice treated with purified Pf4. These changes in macrophage phenotype are functionally relevant: conditioned media from cells exposed to Pf4 decorated with OMVs are significantly less effective at inducing neutrophil migration in vitro and in vivo. These results suggest that Pf4 phages alter innate immunity to bacterial endotoxin and OMVs, potentially dampening inflammation at sites of bacterial colonization or infection.

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.

An update on our understanding of Gram-positive bacterial membrane vesicles: discovery, functions, and applications

Extracellular vesicles (EVs) are nano-sized particles released from cells into the extracellular environment, and are separated from eukaryotic cells, bacteria, and other organisms with cellular structures. EVs alter cell communication by delivering their contents and performing various functions depending on their cargo and release into certain environments or other cells. The cell walls of Gram-positive bacteria have a thick peptidoglycan layer and were previously thought to be unable to produce EVs. However, recent studies have demonstrated that Gram-positive bacterial EVs are crucial for health and disease. In this review, we have summarized the formation, composition, and characteristics of the contents, resistance to external stress, participation in immune regulation, and other functions of Gram-positive bacterial EVs, as well as their application in clinical diagnosis and treatment, to provide a new perspective to further our understanding of Gram-positive bacterial EVs.