Excess filaggrin in keratinocytes is removed by extracellular vesicles to prevent premature death and this mechanism can be hijacked by Staphylococcus aureus in a TLR2-dependent fashion. Journal of extracellular vesicles Filaggrin (FLG) protein is indispensable for multiple aspects of the epidermal barrier function but its accumulation in a monomeric filaggrin form may initiate premature keratinocytes death; it is unclear how filaggrin levels are controlled before the formation of storing keratohyalin granules. Here we show that keratinocyte-secreted small extracellular vesicles (sEVs) may contain filaggrin-related cargo providing a route of eliminating excess filaggrin from keratinocytes; blocking of sEV release has cytotoxic effects on those cells. Filaggrin-containing sEVs are found in plasma in both healthy individuals and atopic dermatitis patients. Staphylococcus aureus (S. aureus) enhances packaging and secretion of filaggrin-relevant products within the sEVs for enhanced export via a TLR2-mediated mechanism which is also linked to the ubiquitination process. This filaggrin removal system, preventing premature keratinocyte death and epidermal barrier dysfunction, is exploited by S. aureus which promotes filaggrin elimination from the skin that could help safeguard bacterial growth. 10.1002/jev2.12335

Extracellular vesicles from methicillin resistant stimulate proinflammatory cytokine production and trigger IgE-mediated hypersensitivity. Asano Krisana,Hirose Shouhei,Narita Kouji,Subsomwong Phawinee,Kawai Noriaki,Sukchawalit Rojana,Nakane Akio Emerging microbes & infections Extracellular vesicles (EVs) released from bacteria are enclosed particles carrying biological active molecules. They have been shown to play a role in bacterial communications and delivery of virulence factors to the host cells. is an opportunistic pathogen causing a variety of infections ranging from impetigo to septicaemia. The EVs released from have a high potential to be used for vaccine development against infections. However, it is important to clearly understand the impact of SaEVs on the host's immune response. Our study demonstrated that purified EVs from a clinical isolated methicillin-resistant (SaEVs) significantly stimulated proinflammatory cytokine production in mouse immune cells and induced host cell death. An impairment of cytokine production in the Toll-like receptor (TLR)-silenced macrophages suggested that SaEVs stimulate proinflammatory response via TLRs 2, 4 and 9. In mouse infection model, the results demonstrated that SaEV immunization did not provide protective effect. In contrast, all SaEV-immunized mice died within Day 1 after methicillin-resistant (MRSA) infection. After MRSA infection for 3 h, the production of IL-6, TNF-α and IL-17 in the spleen of SaEV-immunized mice was significantly higher than that of control mice. On Day 5 after the second immunization, total IgE in the serum was significantly enhanced, and a high titre of Th2-related cytokines was remarkably induced after stimulation of the spleen cells with SaEVs. These results suggested that MRSA-derived EVs act as an immunostimulant that induces inflammatory response and IgE-mediated hypersensitivity after MRSA infection. 10.1080/22221751.2021.1991239

Staphylococcus aureus membrane vesicles: an evolving story. Trends in microbiology Staphylococcus aureus is an important bacterial pathogen that causes a wide variety of human diseases in community and hospital settings. S. aureus employs a diverse array of virulence factors, both surface-associated and secreted, to promote colonization, infection, and immune evasion. Over the past decade, a growing body of research has shown that S. aureus generates extracellular membrane vesicles (MVs) that package a variety of bacterial components, many of which are virulence factors. In this review, we summarize recent advances in our understanding of S. aureus MVs and highlight their biogenesis, cargo, and potential role in the pathogenesis of staphylococcal infections. Lastly, we present some emerging questions in the field. 10.1016/j.tim.2024.04.003

membrane vesicles contain immunostimulatory DNA, RNA and peptidoglycan that activate innate immune receptors and induce autophagy. Journal of extracellular vesicles Gram-positive bacteria ubiquitously produce membrane vesicles (MVs), and although they contribute to biological functions, our knowledge regarding their composition and immunogenicity remains limited. Here we examine the morphology, contents and immunostimulatory functions of MVs produced by three strains; a methicillin resistant clinical isolate, a methicillin sensitive clinical isolate and a laboratory-adapted strain. We observed differences in the number and morphology of MVs produced by each strain and showed that they contain microbe-associated molecular patterns (MAMPs) including protein, nucleic acids and peptidoglycan. Analysis of MV-derived RNA indicated the presence of small RNA (sRNA). Furthermore, we detected variability in the amount and composition of protein, nucleic acid and peptidoglycan cargo carried by MVs from each strain. MVs activated Toll-like receptor (TLR) 2, 7, 8, 9 and nucleotide-binding oligomerization domain containing protein 2 (NOD2) signalling and promoted cytokine and chemokine release by epithelial cells, thus identifying that MV-associated MAMPs including DNA, RNA and peptidoglycan are detected by pattern recognition receptors (PRRs). Moreover, MVs induced the formation of and colocalized with autophagosomes in epithelial cells, while inhibition of lysosomal acidification using bafilomycin A1 resulted in accumulation of autophagosomal puncta that colocalized with MVs, revealing the ability of the host to degrade MVs via autophagy. This study reveals the ability of DNA, RNA and peptidoglycan associated with MVs to activate PRRs in host epithelial cells, and their intracellular degradation via autophagy. These findings advance our understanding of the immunostimulatory roles of Gram-positive bacterial MVs in mediating pathogenesis, and their intracellular fate within the host. 10.1002/jev2.12080

Extracellular vesicles from Staphylococcus aureus promote the pathogenicity of Pseudomonas aeruginosa. Microbiological research Co-infections with Staphylococcus aureus and Pseudomonas aeruginosa are common in patients with chronic wounds, but little is known about their synergistic effect mediated by extracellular vesicles (EVs). In this study, we investigated the effect of EVs derived from S. aureus (SaEVs) on the pathogenicity of P. aeruginosa. By using lipophilic dye, we could confirm the fusion between SaEV and P. aeruginosa membranes. However, SaEVs did not alter the growth and antibiotic susceptible pattern of P. aeruginosa. Differential proteomic analysis between SaEV-treated and non-treated P. aeruginosa was performed, and the results revealed that lipopolysaccharide (LPS) biosynthesis protein in P. aeruginosa significantly increased after SaEV-treatment. Regarding this result, we also found that SaEVs promoted LPS production, biofilm formation, and expression of polysaccharide polymerization-related genes in P. aeruginosa. Furthermore, invasion of epithelial cells by SaEV-pretreated P. aeruginosa was enhanced. On the other hand, uptake of P. aeruginosa by RAW 264.7 macrophages was impaired after pretreatment P. aeruginosa with SaEVs. Proteomic analysis SaEVs revealed that SaEVs contain the proteins involving in host cell colonization, inhibition of host immune response, anti-phagocytosis of the macrophages, and protein translocation and iron uptake of S. aureus. In conclusion, SaEVs serve as a mediator that promote P. aeruginosa pathogenicity by enhancing LPS biosynthesis, biofilm formation, epithelial cell invasion, and macrophage uptake impairment. 10.1016/j.micres.2024.127612