Enterohemorrhagic Escherichia coli O157 outer membrane vesicles induce interleukin 8 production in human intestinal epithelial cells by signaling via Toll-like receptors TLR4 and TLR5 and activation of the nuclear factor NF-κB

Outer membrane vesicles of carbapenem-resistant clinical Acinetobacter baumannii isolates protect both the vesicle-producing bacteria and non-resistant bacteria against carbapenems

Infections caused by carbapenem-resistant Acinetobacter baumannii (A. baumannii; CRAb) are associated with high patient morbidity and mortality. The serious threat for human health imposed by CRAb was recently underscored by identification of close-to-untouchable carbapenem- and tetracycline-resistant isolates. Since outer membrane vesicles (OMVs) of Gram-negative bacteria may contribute to antimicrobial resistance, our present study was aimed at investigating OMVs produced by the first two carbapenem- and tetracycline-resistant A. baumannii isolates in Europe. These isolates, denoted CRAb1 and CRAb2, contain large, nearly identical plasmids that specify multiple resistances. Both isolates produce OMVs that were analyzed by differential light scattering, transmission electron microscopy and proteomics. By comparison with OMVs from the plasmid-free non-carbapenem-resistant A. baumannii isolate Ab1, which is an isogenic ancestor of the CRAb1 isolate, we show that plasmid carriage by the CRAb1 and CRAb2 isolates leads to an increased OMV size that is accompanied by increased diversity of the OMV proteome. Our analyses show that OMVs from CRAb1 and CRAb2 are major reservoirs of proteins involved in antimicrobial resistance, including the plasmid-encoded carbapenemases New Delhi metallo-β-lactamase-1 (NDM-1), and carbapenem-hydrolyzing oxacillinase OXA-97 (OXA-97). Here we report that these OMV-borne carbapenemases hydrolyze imipenem and protect otherwise carbapenem-sensitive A. baumannii and Escherichia coli (E. coli) isolates against this antibiotic. In conclusion, our findings demonstrate that OMVs from highly drug-resistant CRAb confer protection against last-resort antibiotics to non-resistant bacterial pathogens.

The mechanism of outer membrane vesicle-mediated resistance to carbapenem antibiotics

The escalating prevalence of carbapenem resistance in Gram-negative bacteria presents a critical therapeutic challenge, demanding urgent elucidation of novel resistance mechanisms. This review systematically examines the emerging role of outer membrane vesicles (OMVs) as multifunctional mediators of carbapenem resistance, synthesizing recent advances in understanding their biological properties and mechanistic contributions. Through comprehensive analysis of β-lactamase dissemination pathways, we demonstrate that OMVs are extracellular vectors facilitating antibiotic degradation through enzymatic cargo delivery while concurrently acting as genetic transmission vehicles for resistance determinants. Crucially, OMVs exhibit functional versatility in enhancing bacterial survival via dual mechanisms: structurally, by promoting biofilm matrix formation that establishes antibiotic-protected niches, and immunologically, through modulation of host-pathogen interactions that impair microbial clearance. The review further identifies OMV-mediated antibiotic sequestration and competitive binding as underappreciated resistance amplifiers. These insights refine our understanding of resistance evolution and reveal OMV biogenesis pathways as promising therapeutic targets. This synthesis establishes OMVs as central players in carbapenem resistance architecture, providing a strategic framework for developing countermeasures against multidrug-resistant infections.

Crude Polygalae Radix after boiling with licorice decoction alleviates intestinal mucosal barrier injury of rats by regulating TLR4/NF-κB signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Polygala tenuifolia Willd. (pharmacologically termed Polygalae Radix, PR), a nootropic botanical in traditional Chinese medicine, demonstrates anxiolytic and cognitive-enhancing properties with two millennia of documented therapeutic applications. Long-term or large-dose use of crude Polygalae Radix (CPR) causes intestinal injury, which could be reduced by use of Glycyrrhiza uralensis Fisch. (licorice) decoction-boiled Polygalae Radix. However, the effects of boiling CPR with licorice decoction on reducing intestinal mucosal barrier injury have not been studied.

AIM OF THE STUDY

Our research mainly focused on the alleviating effects and underlying mechanism of CPR after boiling with licorice decoction on intestinal mucosal barrier injury in rats.

METHODS AND MATERIALS

SD rats were orally administered CPR and licorice decoction-boiled PR (LPR) extracts respectively for 15 consecutive days. Subsequently, levels of pro-inflammatory cytokines and immunoglobulins were measured, and histopathological changes in intestinal tissues were examined. The mRNA expression levels of pro-inflammatory cytokines were evaluated by qRT-PCR. The expression difference of TLR4/NF-κB signaling pathway key protein and tight junction (TJ) protein were evaluated using Western blotting and immunohistochemistry.

RESULTS

Processing PR with licorice decoction significantly ameliorated the downregulation of intestinal TJ proteins (occludin, claudin-1, and ZO-1) and elevated serum lipopolysaccharide levels induced by CPR. It alleviated the suppression of intestinal immunoglobulin A, serum immunoglobulin A and immunoglobulin G levels caused by CPR while mitigating intestinal mucosal injury and inflammatory responses. Additionally, processing PR with licorice decoction inhibited CPR-triggered upregulation of TLR4, NF-κB p65, p-NF-κB p65, and p-κBα proteins expression, while preventing IκBα downregulation in intestinal tissues. Furthermore, it significantly suppressed the upregulation of interleukin (IL)-6, IL-8, and tumor necrosis factor-α (TNF-α) mRNA expression while concurrently inhibiting the secretion levels of these pro-inflammatory cytokines in small intestine.

CONCLUSION

Our experimental data suggest that licorice decoction boiling effectively prevents CPR-induced reductions in TJ proteins and immunoglobulins expression, alleviates intestinal mucosal barrier injuries, and mediates these effects through suppression of TLR4/NF-κB signaling pathway activation and subsequent production of IL-6, IL-8, and TNF-α.

Outer membrane vesicles in gram-negative bacteria and its correlation with pathogenesis

There is a widespread distribution of gram-negative bacteria worldwide, which are responsible for the deaths of numerous patients each year. The illnesses they cause can be localized and systemic, and these bacteria possess several key virulence factors that contribute to their pathogenicity. In recent years, several distinct mechanisms of pathogenesis have evolved that remain largely unknown to scientists and medical experts. Among these, outer membrane vesicles (OMVs) are undoubtedly one of the most significant factors influencing virulence. OMVs contain various bacterial compounds and can have diverse effects on host organisms and the immune system, potentially exacerbating disease and inflammation while evading immune responses. This review comprehensively examines the role of OMVs in bacterial pathogenesis, their interaction with host cells, and their potential biomedical applications. Understanding the molecular mechanisms governing OMV biogenesis and function could pave the way for novel antimicrobial strategies and therapeutic interventions.

Antigen 43 associated with Escherichia coli membrane vesicles contributes to bacterial cell association and biofilm formation

Bacterial membrane vesicles (MVs) are produced by all bacteria and contribute to numerous bacterial functions due to their ability to package and transfer bacterial cargo. In doing so, MVs have been shown to facilitate horizontal gene transfer, mediate antimicrobial activity, and promote biofilm formation. Uropathogenic Escherichia coli is a pathogenic Gram-negative organism that persists in the urinary tract of its host due to its ability to form persistent, antibiotic-resistant biofilms. The formation of these biofilms is dependent upon proteins such as Antigen 43 (Ag43), which belongs to the widespread Autotransporter group of bacterial surface proteins. In E. coli, the autotransporter Ag43 has been shown to contribute to bacterial cell aggregation and biofilm formation via self-association of Ag43 between neighboring Ag43-expressing bacteria. As MVs package bacterial proteins, we investigated whether MVs produced by E. coli contained Ag43, and the ability of Ag43-expressing MVs to facilitate cell aggregation and biofilm formation. We showed that Ag43 expressing E. coli produced MVs that contained Ag43 on their surface and had an enhanced ability to bind to E. coli bacteria. Furthermore, we demonstrated that the addition of Ag43-containing MVs to Ag43-expressing E. coli significantly enhanced biofilm formation. These findings reveal the contribution of MVs harboring autotransporters in promoting bacterial aggregation and enhancing biofilm formation, highlighting the impact of MVs and their specific composition to bacterial adaptation and pathogenesis.IMPORTANCEAutotransporter proteins are the largest family of outer membrane and secreted proteins in Gram-negative bacteria which contribute to pathogenesis by promoting aggregation, biofilm formation, persistence, and cytotoxicity. Although the roles of bacterial autotransporters are well known, the ability of bacterial membrane vesicles (MVs) naturally released from the surface of bacteria to contain autotransporters and their role in promoting virulence remains less investigated. Our findings reveal that MVs produced by E. coli contain the autotransporter protein Ag43. Furthermore, we show that Ag43-containing MVs function to enhance bacterial cell interactions and biofilm formation. By demonstrating the ability of MVs to carry functional autotransporter adhesins, this work highlights the importance of MVs in disseminating autotransporters beyond the bacterial cell membrane to ultimately promote cellular interactions and enhance biofilm development. Overall, these findings have significant implications in furthering our understanding of the numerous ways in which MVs can facilitate bacterial persistence and pathogenesis.

Evolution and expression of TLR5a and TLR5b in lamprey (Lampetra japonica)

The lamprey serves as a key model organism for studying the origin and evolution of species, embryonic development, and the immune system. The immune system primarily relies on pattern recognition receptors, including Toll-like receptors (TLRs), with Toll-like receptor 5 (TLR5) having a particularly complex evolutionary history. Currently, although TLR5 is being identified in an expanding array of taxonomic groups, a comprehensive study on its evolutionary aspects is yet to be conducted. In this study, we identified Lj-TLR5a and Lj-TLR5b in Lampetra japonica and examined their distribution across various tissues in this species. Furthermore, we conducted preliminary investigations into their immune functions and discovered that, as primitive genes, they are highly sensitive to various pathogens. Upon recognizing flagellar proteins, both Lj-TLR5a and Lj-TLR5b work together; however, these TLRs may function independently in response to other stimuli. Subsequently, we performed comprehensive structural and evolutionary analyses of the TLR5 family, incorporating TLR5 data from various species at different evolutionary stages. Our findings revealed that TLR5a and TLR5b in lamprey are in a relatively primitive evolutionary state. Meanwhile, TLR5L differentiated during the early stages of evolution and exhibits a pseudogenic trend throughout this evolutionary process; notably, this TLR is currently preserved only in certain amphibian and reptile species. In cartilaginous fish, only one type of TLR5 is usually retained, whereas bony fish typically possess both TLR5 and TLR5S. TLR5S has a relatively simple structure, likely arising from repetitive whole-genome events in bony fishes. Among bony fishes, flesh-finned fish were found to retain only one TLR5, which eventually evolved into the TLR5 found in quadrupeds. In summary, this study provides significant insights into the origin and evolution of the TLR5 family by analyzing the evolutionary status and immune functions of Lj-TLR5a and Lj-TLR5b in Japanese lampreys.

Review on bacterial outer membrane vesicles: structure, vesicle formation, separation and biotechnological applications

Outer membrane vesicles (OMVs), shed by Gram-negative bacteria, are spherical nanostructures that play a pivotal role in bacterial communication and host-pathogen interactions. Comprising an outer membrane envelope and encapsulating a variety of bioactive molecules from their progenitor bacteria, OMVs facilitate material and informational exchange. This review delves into the recent advancements in OMV research, providing a comprehensive overview of their structure, biogenesis, and mechanisms of vesicle formation. It also explores their role in pathogenicity and the techniques for their enrichment and isolation. Furthermore, the review highlights the burgeoning applications of OMVs in the field of biomedicine, emphasizing their potential as diagnostic tools, vaccine candidates, and drug delivery vectors.

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.

Microscopic messengers: microbiota-derived bacterial extracellular vesicles in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a persistent and complex condition accomplished by inflammation of the gastrointestinal system, encompassing Crohn's disease (CD) and ulcerative colitis (UC). This condition is caused by the combination of genetic predispositions, environmental triggers, and dysregulated immunological responses, which complicates diagnosis and treatment. The latest developments in gastroenterology have revealed the critical significance of the gut microbiota in the pathogenesis of IBD. Extracellular vesicles (EVs) are a type of microbial component that potentially regulate intestinal inflammation. The impact of microbiota-derived bacterial EVs (bEVs) on intestinal inflammation is mediated through several methods. They can intensify inflammation or stimulate defensive responses by delivering immunomodulatory cargo. Improved comprehension could enhance inventive diagnostic and treatment strategies for IBD. This study aimed to explore the relationship between microbiota-derived bEVs and the complex nature of IBD. We performed a thorough analysis of the formation, composition, mechanisms of action, diagnostic possibilities, therapeutic implications, and future prospects of these microbiota-derived bEVs.

Impact of probiotics-derived extracellular vesicles on livestock gut barrier function

Probiotic extracellular vesicles (pEVs) are biologically active nanoparticle structures that can regulate the intestinal tract through direct or indirect mechanisms. They enhance the intestinal barrier function in livestock and poultry and help alleviate intestinal diseases. The specific effects of pEVs depend on their internal functional components, including nucleic acids, proteins, lipids, and other substances. This paper presents a narrative review of the impact of pEVs on the intestinal barrier across various segments of the intestinal tract, exploring their mechanisms of action while highlighting the limitations of current research. Investigating the mechanisms through which probiotics operate via pEVs could deepen our understanding and provide a theoretical foundation for their application in livestock production.

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.

Engineering Versatile Bacteria-Derived Outer Membrane Vesicles: An Adaptable Platform for Advancing Cancer Immunotherapy

In recent years, cancer immunotherapy has undergone a transformative shift toward personalized and targeted therapeutic strategies. Bacteria-derived outer membrane vesicles (OMVs) have emerged as a promising and adaptable platform for cancer immunotherapy due to their unique properties, including natural immunogenicity and the ability to be engineered for specific therapeutic purposes. In this review, a comprehensive overview is provided of state-of-the-art techniques and methodologies employed in the engineering of versatile OMVs for cancer immunotherapy. Beginning by exploring the biogenesis and composition of OMVs, unveiling their intrinsic immunogenic properties for therapeutic appeal. Subsequently, innovative approaches employed to engineer OMVs are delved into, ranging from the genetic engineering of parent bacteria to the incorporation of functional molecules. The importance of rational design strategies is highlighted to enhance the immunogenicity and specificity of OMVs, allowing tailoring for diverse cancer types. Furthermore, insights into clinical studies and potential challenges utilizing OMVs as cancer vaccines or adjuvants are also provided, offering a comprehensive assessment of the current landscape and future prospects. Overall, this review provides valuable insights for researchers involved in the rapidly evolving field of cancer immunotherapy, offering a roadmap for harnessing the full potential of OMVs as a versatile and adaptable platform for cancer treatment.

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.

Outer Membrane Vesicles Derived from Adherent-Invasive Escherichia coli Induce Inflammatory Response and Alter the Gene Expression of Junction-Associated Proteins in Human Intestinal Epithelial Cells

Adherent-invasive Escherichia coli (AIEC) pathobionts, which are characterized by their ability to adhere to and invade intestinal epithelial cells, are associated with the etiopathogenesis of inflammatory bowel diseases (IBDs). Outer membrane vesicles (OMVs) released by AIEC strains can facilitate the interaction of these bacteria with host cells through delivering bacterial effectors. The aim of this study was to determine the ability of OMVs derived from AIEC strain LF82 to induce the host immune response, leading to production of proinflammatory cytokines and also altering the gene expression of junction-associated proteins in the human epithelial colorectal adenocarcinoma Caco-2 cell line. OMVs were extracted from AIEC strain LF82, and the cell viability of Caco-2 cells treated with these vesicles was assessed by MTT assay. The morphology and size distribution of vesicles were analyzed using transmission electron microscopy and dynamic light scattering, respectively. Gene expression of occludin, ZO-1, claudin-2, E-cadherin, TLR-2, and TLR-4 in response to OMVs was assessed in Caco-2 cells by RT-qPCR. Moreover, the secretion of IL-8 and TNF-α into the supernatant of Caco-2 cells upon treatment with OMVs was measured using ELISA. Our results demonstrated that OMVs upregulated the gene expression level of TLRs and also altered the gene expression level of junction-associated proteins. OMVs derived from AIEC may play a major role in the promotion of intestinal inflammation and epithelial barrier dysfunction. However, further investigations are needed to elucidate the putative role of OMVs in the pathogenesis of AIEC and IBD.

Klebsiella pneumoniae-OMVs activate death-signaling pathways in Human Bronchial Epithelial Host Cells (BEAS-2B)

The programmed cell death pathways of apoptosis are important in mammalian cellular protection from infections. The activation of these pathways depends on the presence of membrane receptors that bind bacterial components to activate the transduction mechanism. In addition to bacteria, these mechanisms can be activated by outer membrane vesicles (OMVs). OMVs are spherical vesicles of 20-250 nm diameter, constitutively released by Gram-negative bacteria. They contain several bacterial determinants including proteins, DNA/RNA and proteins, that activate different cellular processes in host cells. This study focused on Klebsiella pneumoniae-OMVs in activating death mechanisms in human bronchial epithelial cells (BEAS-2B). Characterization of purified OMVs was achieved by scanning electron microscopy, nanoparticle tracking analysis and protein profiling. Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay while apoptotic induction was measured by flow cytometry and confirmed by western blotting. The OMVs produced showed a spherical morphology, with a diameter of 137.2 ± 41 nm and a vesicular density of 7.8 × 109 particles/mL Exposure of cell monolayers to 50 μg of K. pneumoniae-OMV for 14 h resulted in approximately 25 % cytotoxicity and 41.15-41.14 % of cells undergoing early and late apoptosis. Fluorescence microscopy revealed reduced cellular density, the presence of apoptotic bodies, chromatin condensation, and nuclear membrane blebbing in residual cells. Activation of caspases -3 and -9 and dysregulation of BAX, BIM and Bcl-xL indicated the activation of mitochondria-dependent apoptosis. Furthermore, a decrease in the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase involved endoplasmic reticulum stress with the potential formation of reactive oxygen species. These findings provide evidence for the role of OMVs in apoptosis and involvement in the pathogenesis of K. pneumoniae infections.

The role of TRIF protein in regulating the proliferation and antigen presentation ability of myeloid dendritic cells through the ERK1/2 signaling pathway in chronic low-grade inflammation of intestinal mucosa mediated by flagellin-TLR5 complex signal

Objective

The objective is to explore whether the flagellin-TLR5 complex signal can enhance the antigen presentation ability of myeloid DCs through the TRIF-ERK1/2 pathway, and the correlation between this pathway and intestinal mucosal inflammation response.

Methods

Mouse bone marrow-derived DC line DC2.4 was divided into four groups: control group (BC) was DC2.4 cells cultured normally; flagellin single signal stimulation group (DC2.4+CBLB502) was DC2.4 cells stimulated with flagellin derivative CBLB502 during culture; TLR5-flagellin complex signal stimulation group (ov-TLR5-DC2.4+CBLB502) was flagellin derivative CBLB502 stimulated ov-TLR5-DC2.4 cells with TLR5 gene overexpression; TRIF signal interference group (ov-TLR5-DC2.4+CBLB502+Pepinh-TRIFTFA) was ov-TLR5-DC2.4 cells with TLR5 gene overexpression stimulated with flagellin derivative CBLB502 and intervened with TRIF-specific inhibitor Pepinh-TRIFTFA. WB was used to detect the expression of TRIF and p-ERK1/2 proteins in each group of cells; CCK8 was used to detect cell proliferation in each group; flow cytometry was used to detect the expression of surface molecules MHCI, MHCII, CD80, 86 in each group of cells; ELISA was used to detect the levels of IL-12 and IL-4 cytokines in each group.

Results

Compared with the BC group, DC2.4+CBLB502 group, and ov-TLR5-DC2.4+CBLB502+Pepinh-TRIFTFA group, the expression of TRIF protein and p-ERK1/2 protein in ov-TLR5-DC2.4+CBLB502 group was significantly upregulated (TRIF: p = 0.02,  = 0.007,  = 0.048) (ERK1: p < 0.001, =0.0003,  = 0.0004; ERK2:p = 0.0003,  = 0.0012,  = 0.0022). The cell proliferation activity in ov-TLR5-DC2.4+CBLB502 group was enhanced compared with the other groups (p = 0.0001, p < 0.0001, p = 0.0015); at the same time, the expression of surface molecules MHCI, MHCII, CD80, 86 on DCs was upregulated (p < 0.05); and the secretion of IL-12 and IL-4 cytokines was increased, with significant differences (IL-12: p < 0.0001, p < 0.0001, p = 0.0005; IL-4: p =  < 0.0001, p =  < 0.0001, p = 0.0001). However, the ov-TLR5-DC2.4+CBLB502+Pepinh-TRIFTFA group, which was treated with TRIF signal interference, showed a decrease in intracellular TRIF protein and p-ERK1/2 protein, as well as a decrease in cell proliferation ability and surface stimulation molecules, and a decrease in the secretion of IL-12 and IL-4 cytokines (p < 0.05).

Conclusion

After stimulation of flagellin protein-TLR5 complex signal, TRIF protein and p-ERK1/2 protein expression in myeloid dendritic cells were significantly up-regulated, accompanied by increased proliferation activity and maturity of DCs, enhanced antigen presentation function, increased secretion of pro-inflammatory cytokines IL-12 and IL-4. This process can be inhibited by the specific inhibitor of TRIF signal, suggesting that the TLR5-TRIF-ERK1/2 pathway may play an important role in abnormal immune response and mucosal chronic inflammation infiltration mediated by flagellin protein in DCs, which can provide a basis for our subsequent animal experiments.

CRIg+ macrophages deficiency enhanced inflammation damage in IBD due to gut extracellular vesicles containing microbial DNA

Gut microbiota-derived extracellular vesicles (mEVs) are reported to regulate inflammatory response by delivering bacterial products into host cells. The complement receptor of the immunoglobulin superfamily macrophages (CRIg+ Mφ) could clear invading bacteria and their derivatives. Here, we investigate the role of CRIg+ Mφ and the mechanism by which mEVs regulate intestinal inflammation. We found that it is exacerbated in IBD patients and colitis mice by mEVs' leakage from disturbed gut microbiota, enriching microbial DNA in the intestinal mucosa. CRIg+ Mφ significantly decrease in IBD patients, allowing the spread of mEVs into the mucosa. The microbial DNA within mEVs is the key trigger for inflammation and barrier function damage. The cGAS/STING pathway is crucial in mEVs-mediated inflammatory injury. Blocking cGAS/STING signaling effectively alleviates inflammation caused by mEVs leakage and CRIg+ Mφ deficiency. Microbial DNA-containing mEVs, along with CRIg+ Mφ deficiency, stimulate inflammation in IBD, with the cGAS/STING pathway playing a crucial role.

Bacterial membrane vesicles in the pathogenesis and treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic and debilitating condition of relapsing and remitting inflammation in the gastrointestinal tract. Conventional therapeutic approaches for IBD have shown limited efficacy and detrimental side effects, leading to the quest for novel and effective treatment options for the disease. Bacterial membrane vesicles (MVs) are nanosized lipid particles secreted by lysis or blebbing processes from both Gram-negative and Gram-positive bacteria. These vesicles, known to carry bioactive components, are facsimiles of the parent bacterium and have been implicated in the onset and progression, as well as in the amelioration of IBD. This review discusses the overview of MVs and their impact in the pathogenesis, diagnosis, and treatment of IBD. We further discuss the technical challenges facing this research area and possible research questions addressing these challenges. We summarize recent advances in the diverse relationship between IBD and MVs, and the application of this knowledge as a viable and potent therapeutic strategy for IBD.

The potential role of gut microbiota outer membrane vesicles in colorectal cancer

Colorectal cancer (CRC) is a common malignant digestive tract tumor in colorectal regions. Considerable evidence now shows that the gut microbiota have essential roles in CRC occurrence and development. Most Gram-negative bacteria release outer membrane vesicles (OMVs) via outer membrane blistering, which contain specific cargoes which interact with host cells via intercellular communications, host immune regulation, and gut microbiota homeostasis. Studies have also shown that OMVs selectively cluster near tumor cells, thus cancer treatment strategies based on OMVs have attracted considerable research attention. However, little is known about the possible impact of gut microbiota OMVs in CRC pathophysiology. Therefore, in this review, we summarize the research progress on molecular composition and function of OMV, and review the microbial dysbiosis in CRC. We then focus on the potential role of gut microbiota OMVs in CRC. Finally, we examine the clinical potential of OMVs in CRC treatment, and their main advantages and challenges in tumor therapy.

Extracellular vesicles of the probiotic bacteria E. coli O83 activate innate immunity and prevent allergy in mice

BACKGROUND

E. coli O83 (Colinfant Newborn) is a Gram-negative (G-) probiotic bacterium used in the clinic. When administered orally, it reduces allergic sensitisation but not allergic asthma. Intranasal administration offers a non-invasive and convenient delivery method. This route bypasses the gastrointestinal tract and provides direct access to the airways, which are the target of asthma prevention. G- bacteria such as E. coli O83 release outer membrane vesicles (OMVs) to communicate with the environment. Here we investigate whether intranasally administered E. coli O83 OMVs (EcO83-OMVs) can reduce allergic airway inflammation in mice.

METHODS

EcO83-OMVs were isolated by ultracentrifugation and characterised their number, morphology (shape and size), composition (proteins and lipopolysaccharide; LPS), recognition by innate receptors (using transfected HEK293 cells) and immunomodulatory potential (in naïve splenocytes and bone marrow-derived dendritic cells; BMDCs). Their allergy-preventive effect was investigated in a mouse model of ovalbumin-induced allergic airway inflammation.

RESULTS

EcO83-OMVs are spherical nanoparticles with a size of about 110 nm. They contain LPS and protein cargo. We identified a total of 1120 proteins, 136 of which were enriched in OMVs compared to parent bacteria. Proteins from the flagellum dominated. OMVs activated the pattern recognition receptors TLR2/4/5 as well as NOD1 and NOD2. EcO83-OMVs induced the production of pro- and anti-inflammatory cytokines in splenocytes and BMDCs. Intranasal administration of EcO83-OMVs inhibited airway hyperresponsiveness, and decreased airway eosinophilia, Th2 cytokine production and mucus secretion.

CONCLUSIONS

We demonstrate for the first time that intranasally administered OMVs from probiotic G- bacteria have an anti-allergic effect. Our study highlights the advantages of OMVs as a safe platform for the prophylactic treatment of allergy. Video Abstract.

Extracellular vesicles as a novel mediator of interkingdom communication

Extracellular vesicles (EVs) are nanosized lipid bilayer-delimited particles secreted from almost all types of cells including bacteria, mammals and plants, and are presumed to be mediators of intercellular communication. Bacterial extracellular vesicles (BEVs) are nanoparticles with diverse diameters, ranging from 20 to 400 nm. BEVs are composed of soluble microbial metabolites, including nucleic acid, proteins, lipoglycans, and short-chain fatty acids (SCFAs). In addition, EVs may contain quorum sensing peptides that are endowed with the ability to protect bacteria against bacteriophages, form and maintain bacterial communities, and modulate the host immune system. BEVs are potentially promising therapeutic modalities for use in vaccine development, cancer immunotherapy regimens, and drug delivery cargos. Plant-derived EVs (PEVs), such as EVs derived from herbal medicines, can be absorbed by the gut microbiota and influence the composition and homeostasis of gut microbiota. This review highlights the roles of BEVs and PEVs in bacterial and plant physiology and discusses crosstalk among gut bacteria, host metabolism and herbal medicine. In summary, EVs represent crucial communication messengers in the gut microbiota, with potential therapeutic value in the delivery of herbal medicines.

From trash to treasure: the role of bacterial extracellular vesicles in gut health and disease

Bacterial extracellular vesicles (BEVs) have emerged as critical factors involved in gut health regulation, transcending their traditional roles as byproducts of bacterial metabolism. These vesicles function as cargo carriers and contribute to various aspects of intestinal homeostasis, including microbial balance, antimicrobial peptide secretion, physical barrier integrity, and immune system activation. Therefore, any imbalance in BEV production can cause several gut-related issues including intestinal infection, inflammatory bowel disease, metabolic dysregulation, and even cancer. BEVs derived from beneficial or commensal bacteria can act as potent immune regulators and have been implicated in maintaining gut health. They also show promise for future clinical applications in vaccine development and tumor immunotherapy. This review examines the multifaceted role of BEVs in gut health and disease, and also delves into future research directions and potential applications.

Membrane vesicles derived from Listeria monocytogenes might be a potential antigen delivery vector

Membrane vesicles (MVs) derived from Listeria monocytogenes (LM) have a natural nanoscale size and contain a variety of bacterial components. We speculated that LM MVs may be a novel delivery vector, but it is necessary to evaluate the safety and immunogenicity of LM MVs in vivo. Here, we isolated LM MVs and tested their safety and immunogenicity both in vitro and in vivo. The results showed that LM MVs stimulated RAW264.7 cells and DC2.4 cells to secrete the inflammatory cytokines IL-1β, TNF-α, IL-6 and IL-10. Intraperitoneal injection of LM MVs at 80 μg per C57BL/6 mouse did not cause lethal effects or irreversible pathological changes in major organs, indicating that LM MVs were safe. Intraperitoneal immunization of C57BL/6 mice twice with LM MVs mainly induced a high level of LM MV-specific IgG antibodies. In addition, we subcutaneously injected C57BL/6 mice with a mixture of ovalbumin and LM MVs and found that LM MVs exhibited a humoral immune adjuvant effect equal to that of the same amount of alum. The results of this study indicated that LM MVs have good safety and effective immunogenicity and may act as humoral immune adjuvants. Therefore, LM MVs are a potential new choice for antigen and drug delivery vectors.

Extracellular vesicles produced by avian pathogenic Escherichia coli (APEC) activate macrophage proinflammatory response and neutrophil extracellular trap (NET) formation through TLR4 signaling

BACKGROUND

Avian pathogenic Escherichia coli (APEC) is the major pathogen causing important avian diseases in poultry. As an important subtype of extraintestinal pathogenic E. coli, APEC has zoonotic potential and is considered a foodborne pathogen. APEC extracellular vesicles (EVs) may play vital roles in the interaction of the pathogen with its host cells. However, the precise roles played by APEC EVs are still not completely clear, especially in immune cells.

RESULTS

In this study, we investigated the relationships between APEC EVs and immune cells. The production and characteristics of the EVs of APEC isolate CT265 were identified. Toll like receptor 4 (TLR4) triggered the cellular immune responses when it interacted with APEC EVs. APEC EVs induced a significant release of proinflammatory cytokines in THP-1 macrophages. APEC EVs induced the macrophage inflammatory response via the TLR4/MYD88/NF-κB signaling pathway, which participated in the activation of the APEC-EV-induced NLRP3 inflammasome. However, the loss of lipopolysaccharide (LPS) from APEC EVs reduced the activation of the NLRP3 inflammasome mediated by TLR4/MYD88/NF-κB signaling. Because APEC EVs activated the macrophage inflammatory response and cytokines release, we speculated that the interaction between APEC EVs and macrophages activated and promoted neutrophil migration during APEC extraintestinal infection. This study is the first to report that APEC EVs induce the formation of neutrophil extracellular traps (NETs) and chicken heterophil extracellular traps. Treatment with APEC EVs induced SAPK/JNK activation in neutrophils. The inhibition of TLR4 signaling suppressed APEC-EV-induced NET formation. However, although APEC EVs activated the immune response of macrophages and initiated NET formation, they also damaged macrophages, causing their apoptosis. The loss of LPS from APEC EVs did not prevent this process.

CONCLUSION

APEC-derived EVs induced inflammatory responses in macrophages and NETs in neutrophils, and that TLR4 was involved in the APEC-EV-activated inflammatory response. These findings provided a basis for the further study of APEC pathogenesis.

Bacterial outer membrane vesicles in cancer: Biogenesis, pathogenesis, and clinical application

Outer membrane vesicles (OMVs) are spherical, nano-sized particles of bilayer lipid structure secreted by Gram-negative bacteria. They contain a series of cargos from bacteria and are important messengers for communication between bacteria and their environment. OMVs play multiple roles in bacterial survival and adaptation and can affect host physiological functions and disease development by acting on host cell membranes and altering host cell signaling pathways. This paper summarizes the mechanisms of OMV genesis and the multiple roles of OMVs in the tumor microenvironment. Also, this paper discusses the prospects of OMVs for a wide range of applications in drug delivery, tumor diagnosis, and therapy.

Microbe-host interactions: structure and functions of Gram-negative bacterial membrane vesicles

Bacteria-host interaction is a common, relevant, and intriguing biological phenomena. The host reacts actively or passively to the bacteria themselves, their products, debris, and so on, through various defense systems containing the immune system, the bacteria communicate with the local or distal tissues of the host via their own surface antigens, secreted products, nucleic acids, etc., resulting in relationships of attack and defense, adaptation, symbiosis, and even collaboration. The significance of bacterial membrane vesicles (MVs) as a powerful vehicle for the crosstalk mechanism between the two is growing. In the recent decade, the emergence of MVs in microbial interactions and a variety of bacterial infections, with multiple adhesions to host tissues, cell invasion and evasion of host defense mechanisms, have brought MVs to the forefront of bacterial pathogenesis research. Whereas MVs are a complex combination of molecules not yet fully understood, research into its effects, targeting and pathogenic components will advance its understanding and utilization. This review will summarize structural, extraction and penetration information on several classes of MVs and emphasize the role of MVs in transport and immune response activation. Finally, the potential of MVs as a therapeutic method will be highlighted, as will future research prospects.

Characterization of the Inflammatory Response Evoked by Bacterial Membrane Vesicles in Intestinal Cells Reveals an RIPK2-Dependent Activation by Enterotoxigenic Escherichia coli Vesicles

Although the immunomodulatory potency of bacterial membrane vesicles (MVs) is widely acknowledged, their interactions with host cells and the underlying signaling pathways have not been well studied. Herein, we provide a comparative analysis of the proinflammatory cytokine profile secreted by human intestinal epithelial cells exposed to MVs derived from 32 gut bacteria. In general, outer membrane vesicles (OMVs) from Gram-negative bacteria induced a stronger proinflammatory response than MVs from Gram-positive bacteria. However, the quality and quantity of cytokine induction varied between MVs from different species, highlighting their unique immunomodulatory properties. OMVs from enterotoxigenic Escherichia coli (ETEC) were among those showing the strongest proinflammatory potency. In depth analyses revealed that the immunomodulatory activity of ETEC OMVs relies on a so far unprecedented two-step mechanism, including their internalization into host cells followed by intracellular recognition. First, OMVs are efficiently taken up by intestinal epithelial cells, which mainly depends on caveolin-mediated endocytosis as well as the presence of the outer membrane porins OmpA and OmpF on the MVs. Second, lipopolysaccharide (LPS) delivered by OMVs is intracellularly recognized by novel caspase- and RIPK2-dependent pathways. This recognition likely occurs via detection of the lipid A moiety as ETEC OMVs with underacylated LPS exhibited reduced proinflammatory potency but similar uptake dynamics compared to OMVs derived from wild-type (WT) ETEC. Intracellular recognition of ETEC OMVs in intestinal epithelial cells is pivotal for the proinflammatory response as inhibition of OMV uptake also abolished cytokine induction. The study signifies the importance of OMV internalization by host cells to exercise their immunomodulatory activities. IMPORTANCE The release of membrane vesicles from the bacterial cell surface is highly conserved among most bacterial species, including outer membrane vesicles (OMVs) from Gram-negative bacteria as well as vesicles liberated from the cytoplasmic membrane of Gram-positive bacteria. It is becoming increasingly evident that these multifactorial spheres, carrying membranous, periplasmic, and even cytosolic content, contribute to intra- and interspecies communication. In particular, gut microbiota and the host engage in a myriad of immunogenic and metabolic interactions. This study highlights the individual immunomodulatory activities of bacterial membrane vesicles from different enteric species and provides new mechanistic insights into the recognition of ETEC OMVs by human intestinal epithelial cells.

Bacterial outer-membrane vesicles promote Vγ9Vδ2 T cell oncolytic activity

Background

Increasing evidence suggests the immune activation elicited by bacterial outer-membrane vesicles (OMVs) can initiate a potent anti-tumor immunity, facilitating the recognition and destruction of malignant cells. At present the pathways underlying this response remain poorly understood, though a role for innate-like cells such as γδ T cells has been suggested.

Methods

Peripheral blood mononuclear cells (PBMCs) from healthy donors were co-cultured with E. coli MG1655 Δpal ΔlpxM OMVs and corresponding immune activation studied by cell marker expression and cytokine production. OMV-activated γδ T cells were co-cultured with cancer cell lines to determine cytotoxicity.

Results

The vesicles induced a broad inflammatory response with γδ T cells observed as the predominant cell type to proliferate post-OMV challenge. Notably, the majority of γδ T cells were of the Vγ9Vδ2 type, known to respond to both bacterial metabolites and stress markers present on tumor cells. We observed robust cytolytic activity of Vγ9Vδ2 T cells against both breast and leukaemia cell lines (SkBr3 and Nalm6 respectively) after OMV-mediated expansion.

Conclusions

Our findings identify for the first time, that OMV-challenge stimulates the expansion of Vγ9Vδ2 T cells which subsequently present anti-tumor capabilities. We propose that OMV-mediated immune activation leverages the anti-microbial/anti-tumor capacity of Vγ9Vδ2 T cells, an axis amenable for improved future therapeutics.

Composition and functions of bacterial membrane vesicles

Extracellular vesicles are produced by species across all domains of life, suggesting that vesiculation represents a fundamental principle of living matter. In Gram-negative bacteria, membrane vesicles (MVs) can originate either from blebs of the outer membrane or from endolysin-triggered explosive cell lysis, which is often induced by genotoxic stress. Although less is known about the mechanisms of vesiculation in Gram-positive and Gram-neutral bacteria, recent research has shown that both lysis and blebbing mechanisms also exist in these organisms. Evidence has accumulated over the past years that different biogenesis routes lead to distinct types of MV with varied structure and composition. In this Review, we discuss the different types of MV and their potential cargo packaging mechanisms. We summarize current knowledge regarding how MV composition determines their various functions including support of bacterial growth via the disposal of waste material, nutrient scavenging, export of bioactive molecules, DNA transfer, neutralization of phages, antibiotics and bactericidal functions, delivery of virulence factors and toxins to host cells and inflammatory and immunomodulatory effects. We also discuss the advantages of MV-mediated secretion compared with classic bacterial secretion systems and we introduce the concept of quantal secretion.

Role of TLRs in EGFR-mediated IL-8 secretion by enteroaggregative Escherichia coli-infected cultured human intestinal epithelial cells

Enteroaggregative Escherichia coli (EAEC) is an emerging enteric pathogen associated with persistent diarrhea in travelers, immunocompromised patients and children worldwide. However, the pathogenesis of this organism is yet to be established. In this study, the role of Toll-like receptors (TLRs) was evaluated in epidermal growth factor receptor (EGFR)-mediated IL-8 secretion by EAEC-infected human small intestinal and colonic epithelial cells (INT-407 and HCT-15, respectively). We observed that EAEC-induced upregulation of TLR2, TLR4 and TLR5 transcripts in both types of cells, and the maximum level of these transcripts was seen in cells infected with EAEC-T8 (an invasive clinical isolate). All these TLRs made a significant contribution to the EAEC-T8-mediated EGFR activation in these cells. Furthermore, these TLRs were found to be associated with activation of the downstream effectors (ERK-1/2, PI3 kinase and Akt) and transcription factors (NF-κB, c-Jun, c-Fos and STAT-3) of EGFR-mediated signal transduction pathways. Moreover, the involvement of these TLRs was also noted in IL-8 secretion by both EAEC-T8-infected cell types. Our findings suggest that EAEC-induced upregulation of TLR2, TLR4 and TLR5 is important for the IL-8 response via EGFR-mediated signal transduction pathways in these cells.

The role and mechanisms of gram-negative bacterial outer membrane vesicles in inflammatory diseases

Outer membrane vesicles (OMVs) are spherical, bilayered, and nanosized membrane vesicles that are secreted from gram-negative bacteria. OMVs play a pivotal role in delivering lipopolysaccharide, proteins and other virulence factors to target cells. Multiple studies have found that OMVs participate in various inflammatory diseases, including periodontal disease, gastrointestinal inflammation, pulmonary inflammation and sepsis, by triggering pattern recognition receptors, activating inflammasomes and inducing mitochondrial dysfunction. OMVs also affect inflammation in distant organs or tissues via long-distance cargo transport in various diseases, including atherosclerosis and Alzheimer's disease. In this review, we primarily summarize the role of OMVs in inflammatory diseases, describe the mechanism through which OMVs participate in inflammatory signal cascades, and discuss the effects of OMVs on pathogenic processes in distant organs or tissues with the aim of providing novel insights into the role and mechanism of OMVs in inflammatory diseases and the prevention and treatment of OMV-mediated inflammatory diseases.

Translocation of outer membrane vesicles from enterohemorrhagic Escherichia coli O157 across the intestinal epithelial barrier

Outer membrane vesicles (OMVs) carrying virulence factors of enterohemorrhagic Escherichia coli (EHEC) are assumed to play a role in the pathogenesis of life-threatening hemolytic uremic syndrome (HUS). However, it is unknown if and how OMVs, which are produced in the intestinal lumen, cross the intestinal epithelial barrier (IEB) to reach the renal glomerular endothelium, the major target in HUS. We investigated the ability of EHEC O157 OMVs to translocate across the IEB using a model of polarized Caco-2 cells grown on Transwell inserts and characterized important aspects of this process. Using unlabeled or fluorescently labeled OMVs, tests of the intestinal barrier integrity, inhibitors of endocytosis, cell viability assay, and microscopic techniques, we demonstrated that EHEC O157 OMVs translocated across the IEB. OMV translocation involved both paracellular and transcellular pathways and was significantly increased under simulated inflammatory conditions. In addition, translocation was not dependent on OMV-associated virulence factors and did not affect viability of intestinal epithelial cells. Importantly, translocation of EHEC O157 OMVs was confirmed in human colonoids thereby supporting physiological relevance of OMVs in the pathogenesis of HUS.

Interactions between extracellular vesicles and microbiome in human diseases: New therapeutic opportunities

In recent decades, accumulating research on the interactions between microbiome homeostasis and host health has broadened new frontiers in delineating the molecular mechanisms of disease pathogenesis and developing novel therapeutic strategies. By transporting proteins, nucleic acids, lipids, and metabolites in their versatile bioactive molecules, extracellular vesicles (EVs), natural bioactive cell-secreted nanoparticles, may be key mediators of microbiota-host communications. In addition to their positive and negative roles in diverse physiological and pathological processes, there is considerable evidence to implicate EVs secreted by bacteria (bacterial EVs [BEVs]) in the onset and progression of various diseases, including gastrointestinal, respiratory, dermatological, neurological, and musculoskeletal diseases, as well as in cancer. Moreover, an increasing number of studies have explored BEV-based platforms to design novel biomedical diagnostic and therapeutic strategies. Hence, in this review, we highlight the recent advances in BEV biogenesis, composition, biofunctions, and their potential involvement in disease pathologies. Furthermore, we introduce the current and emerging clinical applications of BEVs in diagnostic analytics, vaccine design, and novel therapeutic development.

Emerging role of microbiota derived outer membrane vesicles to preventive, therapeutic and diagnostic proposes

The role of gut microbiota and its products in human health and disease is profoundly investigated. The communication between gut microbiota and the host involves a complicated network of signaling pathways via biologically active molecules generated by intestinal microbiota. Some of these molecules could be assembled within nanoparticles known as outer membrane vesicles (OMVs). Recent studies propose that OMVs play a critical role in shaping immune responses, including homeostasis and acute inflammatory responses. Moreover, these OMVs have an immense capacity to be applied in medical research, such as OMV-based vaccines and drug delivery. This review presents a comprehensive overview of emerging knowledge about biogenesis, the role, and application of these bacterial-derived OMVs, including OMV-based vaccines, OMV adjuvants characteristics, OMV vehicles (in conjugated vaccines), cancer immunotherapy, and drug carriers and delivery systems. Moreover, we also highlight the significance of the potential role of these OMVs in diagnosis and therapy.

Extracellular vesicles derived from host and gut microbiota as promising nanocarriers for targeted therapy in osteoporosis and osteoarthritis

Osteoporosis (OP), a systemic bone disease that causes structural bone loss and bone mass loss, is often associated with fragility fractures. Extracellular vesicles (EVs) generated by mammalian and gut bacteria have recently been identified as important mediators in the intercellular signaling pathway that may play a crucial role in microbiota-host communication. EVs are tiny membrane-bound vesicles, which range in size from 20 to 400 nm. They carry a variety of biologically active substances across intra- and intercellular space. These EVs have developed as a promising research area for the treatment of OP because of their nanosized architecture, enhanced biocompatibility, reduced toxicity, drug loading capacity, ease of customization, and industrialization. This review describes the latest development of EVs derived from mammals and bacteria, including their internalization, isolation, biogenesis, classifications, topologies, and compositions. Additionally, breakthroughs in chemical sciences and the distinctive biological features of bacterial extracellular vesicles (BEVs) allow for the customization of modified BEVs for the therapy of OP. In conclusion, we give a thorough and in-depth summary of the main difficulties and potential future of EVs in the treatment of OP, as well as highlight innovative uses and choices for the treatment of osteoarthritis (OA).

Effects of Massa Medicata Fermentata on the intestinal pathogenic flagella bacteria and visceral hypersensitivity in rats with irritable bowel syndrome

Objective: To investigate the effect of Massa Medicata Fermentata (MMF) on the changes of pathogenic flagellar bacteria and visceral hypersensitivity in rats with diarrhea irritable bowel syndrome (IBS-D). Methods: Thirty adult SD rats were randomly divided into normal control group (n = 10), model control group (n = 10), and MMF group (n = 10). Acetic acid enema combined with restraint stress was used to build the IBS-D visceral hypersensitivity model; Abdominal withdrawal reflex (AWR) test was used to assess the visceral sensitivity of rats; 16SrRNA sequencing was used to analyze the changes of intestinal bacteria in each group, and the content of pathogenic flagellated bacteria were quantitatively counted; The content of flagellin in colonic mucosa was detected by ELISA; TLR5 protein in colonic mucosa of rats was detected by Western Blot. Results: After IBS-D modeling, the visceral sensitivity of rats was significantly higher in the model control group than that in the normal control group (p = 0.0061), while it was significantly decreased in MMF group compared with the model control group (p = 0.0217), but without significant difference compared with the normal control group (p = 0.6851). The number of fecal Bifidobacterium and Lactobacillus in the model group were significantly decreased compared with the normal control group (p < 0.0001); While they were significantly increased in the MMF group compared with the model control group and normal control group (p = 0.009; p < 0.0001). The amount of fecal pathogenic flagellated bacteria in the model group was significantly increased compared with the normal control group (p = 0.001); However it was significantly reduced in MMF group compared with the model group (p = 0.026), which has no statistically difference with the normal control group (p = 0.6486). The content of flagellin in colonic mucosa was significantly increased in the model group when compared with the normal control group (p < 0.0001), and it was decreased in MMF group compared with the normal control group (p < 0.0001), but there was no statistical difference with the normal control group (p = 0.6545). The expression level of TLR5 protein in colonic mucosa of rat was significantly increased in model control group compared with the normal control group (p = 0.0034), However, it was significantly decreased in MMF group compared with normal control group (p = 0.0019), but it was no statistical difference with the normal control group (p = 0.7519). Conclusion: MMF can reduce visceral hypersensitivity by decreasing the content of pathogenic flagellated bacteria and their flagellin and inhibiting its specific receptor TLR5 protein expression in colonic mucosa in IBS-D rats.

Bacterial extracellular vesicles as bioactive nanocarriers for drug delivery: Advances and perspectives

Nanosized extracellular vesicles derived from bacteria contain diverse cargo and transfer intercellular bioactive molecules to cells. Due to their favorable intercellular interactions, cell membrane-derived bacterial extracellular vesicles (BEVs) have great potential to become novel drug delivery platforms. In this review, we summarize the biogenesis mechanism and compositions of various BEVs. In addition, an overview of effective isolation and purification techniques of BEVs is provided. In particular, we focus on the application of BEVs as bioactive nanocarriers for drug delivery. Finally, we summarize the advances and challenges of BEVs after providing a comprehensive discussion in each section. We believe that a deeper understanding of BEVs will open new avenues for their exploitation in drug delivery applications.

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Bacterial extracellular vesicles (BEVs) are excellent nanomaterials as drug delivery systems.

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The unique nanosized structures and biofunctions of BEVs are attractive for their use as nanomedicine platforms.

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BEVs have been investigated as biotherapeutics due to their loading capacity, ease of modification and industrialization.

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This review provides new insights of BEVs in drug delivery applications, discussing potential opportunities and challenges.

Mulberry Leaf Flavonoids Inhibit Liver Inflammation in Type 2 Diabetes Rats by Regulating TLR4/MyD88/NF-κB Signaling Pathway

The incidence of liver-related complications in type 2 diabetes mellitus (T2DM) is rapidly increasing, which affects the physical and mental health of T2DM patients. Mulberry leaf flavonoids (MLF) were confirmed to have certain effects on lowering blood glucose and anti-inflammation. In this study, the high-fat diet (HFD) + STZ method was used to establish T2DM rat model and the MLF was administered by gavage for eight weeks. During the experiment, body weight and blood glucose level were measured at different time points. The pathological changes of rat liver were observed by H&E staining. The serum glucolipid metabolic indicators of serum, fasting insulin (FINS), and inflammatory factors levels were detected by ELISA. The expression levels of toll-like receptor 4 (TLR4), TNF receptor-associated factor 6 (TRAF6), myeloid differentiation factor 88 (MyD88), inhibitor of NF-κB alpha (IκΒα), p-IκΒα, and nuclear factor kappa-B (NF-κB)/p65 protein in liver tissue were measured by Western Blot. After 8 weeks' MLF treatment, the blood glucose of rats showed a downward trend; glycolipid metabolism level and insulin resistance were improved, which suggested that MLF could improve the disorder of glucose and lipid metabolism. The pathological damage and inflammation of the liver in T2DM rats were significantly improved, the levels of related serum inflammatory factors were reduced, and the expression of liver tissue-related proteins was downregulated. Our results indicated that MLF could reduce blood glucose and inhibit the development of liver inflammation. The mechanisms may be associated with the activation of TLR4/MyD88/NF-κB signal pathway to reduce the levels of inflammatory factors in serum.

A novel Lactobacillus bulgaricus isolate can maintain the intestinal health, improve the growth performance and reduce the colonization of E. coli O157:H7 in broilers

1. This study aimed at the effects of a novel Lactobacillus bulgaricus (L. bulgaricus) strain and Enterohemorrhagic Escherichia coli (E. coli) O157: H7 on intestinal flora and growth performance of broilers, and the protective effect of L. bulgaricus on broilers in challenged experiment by E. coli O157: H7.2. In vitro bacteriostatic test showed that the cell-free supernatant (CFS) of L. bulgaricus isolate had obvious inhibitory effect on E. coli O157: H7.3. Eighty 1-day-old male broilers were randomly assigned into 4 treatment groups with 4 replicate per treatment. All group received basic diet in addition to the specific treatments: NC group, gavage with normal saline; In LBP group, gavage with L. bulgaricus isolate (1×10⁹ CFU/mL) during the whole process, and challenged with E. coli O157: H7 (3×10⁹ CFU/mL); EC group, gavage with E. coli O157: H7 (3×10⁹ CFU/mL); LB Group, gavage with L. bulgaricus isolate. At the age of 21 days, broilers were weighed and feed conversion ratio (FCR) was calculated. Cecum and cecal contents, ileum and feces samples were taken after slaughter.4. The challenge of E. coli O157: H7 resulted in an increase in TLR-4, NF-κB and IL-8 mRNA in cecal tissue, a decrease in Villus: crypt ratio in ileum, a decrease in overall diversity of intestinal microflora and a poor FCR.5. The L. bulgaricus isolate decreased the mRNA expression of TLR-4, NF-κB and IL-8 induced by E. coli O157: H7, reduced the content of E. coli O157: H7 in the cecum of broilers, increased the Villus: crypt ratio, increased the abundance of beneficial bacteria and overall diversity of intestinal microflora, made good FCR.6. The L. bulgaricus isolate can maintain the intestinal health, improve the growth performance of broilers and reduce the colonization of E. coli O157:H7 in the cecum.

Citrobacter rodentium(ϕStx2dact), a murine infection model for enterohemorrhagic Escherichia coli

The formation of attaching and effacing (A/E) lesions on intestinal epithelium, combined with Shiga toxin production, are hallmarks of enterohemorrhagic Escherichia coli (EHEC) infection that can lead to lethal hemolytic uremic syndrome. Although an animal infection model that fully recapitulates human disease remains elusive, mice orally infected with Citrobacter rodentium(ϕStx2dact), a natural murine pathogen lysogenized with an EHEC-derived Shiga toxin 2-producing bacteriophage, develop intestinal A/E lesions and toxin-dependent systemic disease. This model has facilitated investigation of how: (A) phage gene expression and prophage induction contribute to disease and are potentially triggered by antibiotic treatment; (B) virulence gene expression is altered by microbiota and the colonic metabolomic milieu; and (C) innate immune signaling is affected by Stx. Thus, the model provides a unique tool for accessing diverse aspects of EHEC pathogenesis.

Bacterial outer membrane vesicles and their functionalization as vehicles for bioimaging, diagnosis and therapy

In this review, we summarize the bioactivities of bacterial outer membrane vesicles, including biogenesis, immunogenicity, and interactions, followed by a discussion on their functionalization as nanocarriers for bioimaging, diagnosis, and therapy.

Gut Microbiota Extracellular Vesicles as Signaling Molecules Mediating Host-Microbiota Communications

Over the past decade, gut microbiota dysbiosis has been linked to many health disorders; however, the detailed mechanism of this correlation remains unclear. Gut microbiota can communicate with the host through immunological or metabolic signalling. Recently, microbiota-released extracellular vesicles (MEVs) have emerged as significant mediators in the intercellular signalling mechanism that could be an integral part of microbiota-host communications. MEVs are small membrane-bound vesicles that encase a broad spectrum of biologically active compounds (i.e., proteins, mRNA, miRNA, DNA, carbohydrates, and lipids), thus mediating the horizontal transfer of their cargo across intra- and intercellular space. In this study, we provide a comprehensive and in-depth discussion of the biogenesis of microbial-derived EVs, their classification and routes of production, as well as their role in inter-bacterial and inter-kingdom signaling.

An Update on the Role of Extracellular Vesicles in the Pathogenesis of Necrotizing Enterocolitis and Inflammatory Bowel Diseases

Some of the most fundamental influences of microorganisms inhabiting the human intestinal tract are exerted during infant development and impact the maturation of intestinal mucosa and gut immune system. The impact of bacteria on the host gut immune system is partially mediated via released extracellular vesicles (EVs). The heterogeneity in EV content, size, and bacterial species origin can have an impact on intestinal cells, resulting in inflammation and an immune response, or facilitate pathogen entry into the gut wall. In mammals, maintaining the integrity of the gut barrier might also be an evolutionary function of maternal milk EVs. Recently, the usage of EVs has been explored as a novel therapeutic approach in several pathological conditions, including necrotizing enterocolitis (NEC) and inflammatory bowel disease (IBD). In this review, we attempt to summarize the current knowledge of EV biology, followed by a discussion of the role that EVs play in gut maturation and the pathogenesis of NEC and IBD.

miR-142-5p regulates lipopolysaccharide-induced bovine epithelial cell proliferation and apoptosis via targeting BAG5

Bovine mastitis is a threat to the health of the dairy cow. MicroRNAs (miRs) serve an important role in the progression of bovine mastitis, regulating immune and defense responses. The present study aimed to investigate the possible effects and mechanisms of bovine mastitis underlying miR-142-5p and Bcl-2 associated athanogene 5 (BAG5) in in vitro lipopolysaccharide (LPS)-induced models. Reverse transcription-quantitative PCR and western blotting were performed to determine mRNA and protein expression levels, respectively. ELISAs were conducted to assess the levels of cytokines and an immunofluorescence assay was performed to determine the expression of BAG5. Cell Counting Kit-8, clone formation and 5-ethynyl-2'-deoxyuridine assays were conducted to determine cell viability and proliferation of bovine mammary epithelial MAC-T cells, respectively. Flow cytometry was performed to measure MAC-T cell cycle distribution and apoptosis, and a luciferase assay was conducted to verify whether BAG5 was a target of miR-142-5p. The results indicated that miR-142-5p was upregulated in MAC-T cells treated with LPS compared with the control group. miR-142-5p mimics transfection significantly activated the cytokines TNF-α, IL-1β, IL-6 and IL-8, and significantly increased the expression levels of NF-κB signaling pathway-related proteins in LPS-treated cells. The luciferase activity of MAC-T cells treated with miR-142-5p mimics and BAG5 3'untranslated region wild type decreased, compared with mutant type. By contrast, BAG5 overexpression significantly downregulated the levels of cytokines, including TNF-α, IL-1β, IL-6 and IL-8, in LPS-treated cells. BAG5 overexpression significantly promoted cell proliferation and viability, decreased apoptosis, and regulated Caspase-3, Caspase-9, Bcl-2 and Bax expression in LPS-treated MAC-T cells, which was significantly reversed by transfection with miR-142-5p mimics. In conclusion, the results of the present study suggested that miR-142-5p may promote the progression of bovine mastitis via targeting BAG5. Therefore, the present study provided the foundations for future investigations.

Host immunity and cellular responses to bacterial outer membrane vesicles

All Gram-negative bacteria produce outer membrane vesicles (OMVs) which are minute spherical structures emanating from the bacterial outer membrane. OMVs are primarily enriched in lipopolysaccharide (LPS) and phospholipids, as well as outer membrane and periplasmic proteins. Recent research has provided convincing evidence for their role in multiple aspects of bacterial physiology and their interaction with vertebrate host cells. OMVs play vital roles in bacterial colonization, delivery of virulence factors, and disease pathogenesis. Here, we discuss the interactions of OMVs with mammalian host cells with a focus on how bacteria use OMVs to modulate host immune responses that eventually enable bacteria to evade host immunity.

Bacterial Outer Membrane Vesicles as a Versatile Tool in Vaccine Research and the Fight against Antimicrobial Resistance

Gram-negative bacteria include a number of pathogens that cause disease in humans and animals. Although antibiotics are still effective in treating a considerable range of infections caused by Gram-negative bacteria, the alarming increase of antimicrobial resistance (AMR) induced by excessive use of antibiotics has raised global concerns. Therefore, alternative strategies must be developed to prevent and treat bacterial infections and prevent the advent of a postantibiotic era. Vaccines, one of the greatest achievements in the history of medical science, hold extraordinary potential to prevent bacterial infections and thereby reduce the need for antibiotics. Novel bacterial vaccines are urgently needed, however, and outer membrane vesicles (OMVs), naturally produced by Gram-negative bacteria, represent a promising and versatile tool that can be employed as adjuvants, antigens, and delivery platforms in the development of vaccines against Gram-negative bacteria. Here, we provide an overview of the many roles OMVs can play in vaccine development and the mechanisms behind these applications. Methods to improve OMV yields and a comparison of different strategies for OMV isolation aiming at cost-effective production of OMV-based vaccines are also reviewed.

Bacterial Outer Membrane Vesicles: From Discovery to Applications

Secretion of cellular components across the plasma membrane is an essential process that enables organisms to interact with their environments. Production of extracellular vesicles in bacteria is a well-documented but poorly understood process. Outer membrane vesicles (OMVs) are produced in gram-negative bacteria by blebbing of the outer membrane. In addition to their roles in pathogenesis, cell-to-cell communication, and stress responses, OMVs play important roles in immunomodulation and the establishment and balance of the gut microbiota. In this review, we discuss the multiple roles of OMVs and the current knowledge of OMV biogenesis. We also discuss the growing and promising biotechnological applications of OMV. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Extracellular vesicles-mediated interaction within intestinal microenvironment in inflammatory bowel disease

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EVs derived from different sources play modulatory functions in the intestine, especially interaction associated with microbiota.

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An EV-mediated interaction system was established to describe the possible mechanism of IBD pathogenesis and its cure.

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EVs-based treatments show great potential of clinical applications in IBD diagnosis and therapy.

Background

The intestinal tract is a complicated ecosystem with dynamic homeostasis via interaction of intestine and microbiota. Inflammatory bowel disease (IBD) is chronic intestinal inflammation involving dysbiosis of intestinal microenvironment. Extracellular vesicles (EVs), as vital characteristics of cell–cell and cell-organism communication, contribute to homeostasis in intestine. Recently, EVs showed excellent potential for clinical applications in disease diagnoses and therapies.

Aim of Review

Our current review discusses the modulatory functions of EVs derived from different sources in intestine, especially their effects and applications in IBD clinical therapy. EV-mediated interaction systems between host intestine and microbiota were established to describe possible mechanisms of IBD pathogenesis and its cure.

Key Scientific Concepts of Review

EVs are excellent vehicles for delivering molecules containing genetic information to recipient cells. Multiple pieces of evidence have illustrated that EVs participate the interaction between host and microbiota in intestinal microenvironment. In inflammatory intestine with dysbiosis of microbiota, EVs as regulators target promoting immune response and microbial reconstruction. EVs-based immunotherapy could be a promising therapeutic approach for the treatment of IBD in the near future.