Search

International audience; IntroductionGut inflammation constitutes a growing health concern in developed countries. It may consist in spontaneous ailments of the gut, involving both the host immune system and microbiota, such as IBD, including ulcerative colitis and Crohn’s disease. It may be caused by a medical treatment, such as mucositis induced by cancer chemotherapy and/or radiotherapy. It coincides with a dysbiosis including a lack of anti-inflammatory bacteria. As an example, propionibacteria are lacking in the microbiota of newborns that develop necrotizing enterocolitis.Methods Dairy propionibacteria strains were tested in vitro on human PBMCs with respect to their ability to induce immunomodulatory cytokines. Selected strains were then tested in vitro with respect to their ability to protect mice from TNBS-induced colitis, from DSS-induced colitis, and from 5FU-induced mucositis.ResultsWe thus focused on the immunomodulatory properties of GRAS propionibacteria. Selected strains of Propionibacterium freudenreichii induced the regulatory IL-10 cytokine in human immune cells (Foligné et al., 2010, 2013), depending on surface proteins (Le Marechal et al., 2015). Mutation of the slpB gene suppressed this immunomodulatory effect and the resulting slpB mutant induced a rather proinflammatory response (Deutsch et al., 2017). Consumption of wild-type P. freudenreichii protected from colitis induced by both TNBS and by DSS. It alleviated severity of symptoms, modulated local and systemic inflammation, as well as colonic oxidative stress and epithelial cell damages (Plé et al., 2015, 2016; Rabah et al., 2020). Accordingly, consumption of Lactococcus lactis NCDO 2118 harboring pXIES-SEC:slpB and expressing the propionibacterial SlpB reduced severity of colitis, lowered weight loss, disease activity index, shortening of the colon length, and histopathological score, compared with mice treated with L. lactis NCDO 2118 wild-type strain (Belo et al., 2021).In the context of mucositis induced by the chemotherapy 5-FU, P. freudenreichii prevented weight loss, reduced inflammation and consequently intestinal damages. It regulated key markers, including Claudin-1 and IL-17a genes, as well as IL-12 and IL-1β cytokines levels (Cordeiro et al., 2018). Mutant strain slpB displayed opposite regulatory effect on cld1 expression and on IL-12 levels, and failed to afford protection towards 5-FU-mucositis (do Carmo et al., 2019).P. freudenreichii was further shown to produce extracellular vesicles (EVs), which mimic the immunomodulatory features of propionibacteria in vitro by modulating NF-κB transcription factor activity and IL-8 release in cultured human intestinal epithelial cells (Rodovalho et al., 2020). Proteomic analysis revealed presence of SlpB in these EVs.DiscussionThis work emphasizes the importance of SlpB in P. freudenreichii ability to reduce both mucositis and colitis inflammation. It opens perspectives for the development of probiotic products aimed at decreasing side effects of chemotherapy and at helping treatment of colitis, thanks to GRAS bacteria.

Propionibacterium freudenreichii is a probiotic Gram-positive bacterium with promising immunomodulatory properties. It modulates regulatory cytokines, mitigates the inflammatory response in vitro and in vivo These properties were initially attributed to specific bacterial surface proteins. Recently, we showed that extracellular vesicles (EVs) produced by P. freudenreichii CIRM-BIA129 mimic the immunomodulatory features of parent cells in vitro (i.e. modulating NF-κB transcription factor activity and IL-8 release) which underlies the role of EVs as mediators of the probiotic effects of the bacterium. The modulation of EV properties, and particularly of those with potential therapeutic applications such as the EVs produced by the probiotic P. freudenreichii, is one of the challenges in the field to achieve efficient yields with the desired optimal functionality. Here we evaluated whether the culture medium in which the bacteria are grown could be used as a lever to modulate the protein content and hence the properties of P. freudenreichii CIRM-BIA129 EVs. The physical, biochemical and functional properties of EVs produced from cells cultivated on laboratory Yeast Extract Lactate (YEL) medium and cow milk ultrafiltrate (UF) medium were compared. UF-derived EVs were more abundant, smaller in diameter and displayed more intense anti-inflammatory activity than YEL-derived EVs. Furthermore, the growth media modulated EV content in terms of both the identities and abundances of their protein cargos, suggesting different patterns of interaction with the host. Proteins involved in amino acid metabolism and central carbon metabolism were modulated, as were the key surface proteins mediating host-propionibacteria interactions.Importance Extracellular vesicles (EVs) are cellular membrane-derived nanosized particles that are produced by most cells in all three kingdoms of life. They play a pivotal role in cell-cell communication through their ability to transport bioactive molecules from donor to recipient cells. Bacterial EVs are important factors in host-microbe interactions. Recently we have shown that EVs produced by the probiotic P. freudenreichii exhibited immunomodulatory properties. We evaluate here the impact of environmental conditions, notably culture media, on P. freudenreichii EV production and function. We show that EVs display considerable differences in protein cargo and immunomodulation depending on the culture medium used. This work offers new perspectives for the development of probiotic EV-based molecular delivery systems, and reinforces the optimization of growth conditions as a tool to modulate the potential therapeutic applications of EVs.

The role of Propionibacterium freudenreichii in mitigating inflammation has been a subject of study for many years. Lately, it has been shown that immunomodulation properties are strain- specific and that the major responsible for inflammatory modulation ofimmunomodulation by strain CIRM-BIA129 is the presence of the surface layer protein B (SlpB), which has presented immunomodulation even when expressed in other bacteria. Extracellular vesicles (EVs) are nanosized spherical structures, produced by organisms of all kingdoms, including bacteria. They have been associated with inter-organism communication, pathogenesis, competition, and immunomodulation. Recent studies were aiming to address the role of EVs, in the probiotic effects of bacteria. The properties of P. freudenreichii CIRM-BIA129- derived EVs have been investigated. EVs produced by CIRM-BIA129 cultured in milk ultrafiltrate medium (UF) have been characterized by regarding size and morphology. UF-derived EVs displayed a monodisperse pattern with a modal size of 84.80 ± 2.34 nm. They are composed of a wide variety of proteins, mainly involved in metabolic processes, cellular processes and signaling, and storage and processing of information. A, among these proteins, SlpB was found in high abundance. P. freudenreichii EVs were able to inhibit, in a dose dependent manner, the increase of IL-8 production in HT-29 cells induced with LPS, due to NF-KB pathway inhibition, without causing cell cytotoxicity. EVs produced by a CIRM-BIA129 mutant strain with a knockout for SlpB showed a less efficient reduction in IL-8 production. Results have shown that the environmental conditions are able to modify EVs content and, consequently, their immunomodulatory effects. A change in the growth medium, from UF to YEL (yeast extract-lactate) showed a lower production of EVs, with a slightly larger size. EVs produced in YEL did not perform as well in the inhibition of the NF-KB pathway and had no effect on IL-8 production. Recent results have shown that P. freudenreichii EVs were able to protect Caco-2 cells from inflammation-induced excessive increasing permeability. These Altogether, these results show that Evs produced by beneficial propionibacteria are able to generate immunomodulationtrigger immunomodulation, similar to the parental strain. As for the SlpB role in EVs immunomodulation

International audience; Propionibacterium freudenreichii is a probiotic Gram-positive bacterium with promising immunomodulatory properties. It modulates regulatory cytokines and mitigates the inflammatory response in vitro and in vivo. These properties were initially attributed to specific bacterial surface proteins. Recently, we showed that extracellular vesicles (EVs) produced by P. freudenreichii CIRM-BIA129 mimic the immunomodulatory features of parent cells in vitro (i.e., modulating NF-κB transcription factor activity and interleukin-8 release), which underlies the role of EVs as mediators of the probiotic effects of the bacterium. The modulation of EV properties, and particularly of those with potential therapeutic applications, such as the EVs produced by the probiotic P. freudenreichii, is one of the challenges in the field to achieve efficient yields with the desired optimal functionality. Here, we evaluated whether the culture medium in which the bacteria are grown could be used as a lever to modulate the protein content and, hence, the properties of P. freudenreichii CIRM-BIA129 EVs. The physical, biochemical, and functional properties of EVs produced from cells cultivated on laboratory yeast extract lactate (YEL) medium and cow milk ultrafiltrate (UF) medium were compared. UF-derived EVs were more abundant and smaller in diameter, and they displayed more intense anti-inflammatory activity than YEL-derived EVs. Furthermore, the growth media modulated EV content in terms of both the identities and abundances of their protein cargos, suggesting different patterns of interaction with the host. Proteins involved in amino acid metabolism and central carbon metabolism were modulated, as were the key surface proteins mediating host-propionibacterium interactions. IMPORTANCE Extracellular vesicles (EVs) are cellular membrane-derived nanosized particles that are produced by most cells in all three kingdoms of life. They play a pivotal role in cell-cell communication through their ability to transport bioactive molecules from donor to recipient cells. Bacterial EVs are important factors in hostmicrobe interactions. Recently, we have shown that EVs produced by the probiotic P. freudenreichii exhibited immunomodulatory properties. We evaluate here the impact of environmental conditions, notably culture media, on P. freudenreichii EV production and function. We show that EVs display considerable differences in protein cargo and immunomodulation depending on the culture medium used. This work offers new perspectives for the development of probiotic EV-based molecular delivery systems and reinforces the optimization of growth conditions as a tool to modulate the potential therapeutic applications of EVs.

BactInflam IJL focuses on the bacterial components involved in some inflammatory diseases. In particular, in two of them: chronic inflammatory bowel disease (IBD) and mastitis, affecting human health and animal health, respectively.; International audience; Introduction: Bacterial extracellular vesicles (EVs) carry various macromolecules able to affect host-pathogen interactions, such as RNAs. Staphylococcus aureus, an important human and animal pathogen, releases EVs whose RNA content is still unkown. Here, we adress what classes of RNAs compose S. aureus EVs. Methods: S. aureus strain HG003 was cultured in Brain Heart Infusion medium under different in vitro conditions: early- and late-stationary phases, in the presence or absence of a sublethal concentration of vancomycin (0.5 μg/mL). EVswere purified from cell-free culture supernatants using density gradient ultracentrifugation. Bacterial and EV samples were submitted to phenolchloroform RNA extraction, DNAse treatment, and library preparation (Ovation Prokaryotic RNA-Seq, Nugen, rRNA depletion). Sequencing was performed using Illumina, NextSeq500, 75 cycles, single reading, High Output. Results: Particle yields were similar between conditions, however, EVs from late-stationary phases were ∼55% ,larger. On average, 78.0% of HG003 annotated genes were identified in EVs, while only ∼5% presented - 90% read coverage. Highly covered EV RNAs included mRNAs coding for virulence-factors (hld, agrBCD, psmB1, sbi, spa, isaB), ribosomal proteins, transcriptional regulators, and metabolic enzymes. sRNAs were also detected, including the bona fide rsaC. Interestingly, several of these RNAs were shown to belong to the same transcriptional units in S. aureus. Both nature and abundance of the RNAs in EVs were dramatically affected by growth conditions, whereas much less in the parent cells. Finally, the RNA abundance pattern differed between EVs and parent cells. Summary/Conclusion: To our knowledge, this is the first work characterizing the RNA cargo of S. aureus EVs. Our findings show that EV RNAs are shaped by the environment, and suggest the selective packaging of RNAs into EVs. Finally, this study also shedds light to the possible roles of potentially functional RNAs in S. aureus EVs, notably in host-pathogen interactions.