Biomimetic superabsorbent hydrogel acts as a gut protective dynamic exoskeleton improving metabolic parameters and expanding A. muciniphila.

The rising prevalence of obesity and metabolic disorders worldwide highlights the urgent need to find new long-term and clinically meaningful weight-loss therapies. Here, we evaluate the therapeutic potential and the mechanism of action of a biomimetic cellulose-based oral superabsorbent hydrogel (OSH). Treatment with OSH exerts effects on intestinal tissue and gut microbiota composition, functioning like a protective dynamic exoskeleton. It protects from gut barrier permeability disruption and induces rapid and consistent changes in the gut microbiota composition, specifically fostering Akkermansia muciniphila expansion. The mechanobiological, physical, and chemical structures of the gel are required for A. muciniphila growth. OSH treatment induces weight loss and reduces fat accumulation, in both preventative and therapeutic settings. OSH usage also prevents liver steatosis, immune infiltration, and fibrosis, limiting the progression of non-alcoholic fatty liver disease. Our work shows the potential of using OSH as a non-systemic mechanobiological approach to treat metabolic syndrome and its comorbidities.

Mucosal Overexpression of Thymic Stromal Lymphopoietin and Proinflammatory Cytokines in Patients With Autoimmune Atrophic Gastritis.

INTRODUCTION: The immune mechanisms underlying human autoimmune atrophic gastritis (AAG) are poorly understood. We sought to assess immune mucosal alterations in patients with AAG. METHODS: In 2017-2021, we collected gastric corpus biopsies from 24 patients with AAG (median age 62 years, interquartile range 56-67, 14 women), 26 age-matched and sex-matched healthy controls (HCs), and 14 patients with Helicobacter pylori infection (HP). We investigated the lamina propria mononuclear cell (LPMC) populations and the mucosal expression of thymic stromal lymphopoietin (TSLP) and nicotinamide phosphoribosyltransferase (NAMPT). Ex vivo cytokine production by organ culture biopsies, under different stimuli (short TSLP and zinc-l-carnosine), and the gastric vascular barrier through plasmalemma vesicle-associated protein-1 (PV1) were also assessed. RESULTS: In the subset of CD19+ LPMC, CD38+ cells (plasma cells) were significantly higher in AAG compared with HC. Ex vivo production of tumor necrosis factor (TNF)-α, interleukin (IL)-15, and transforming growth factor ß1 was significantly higher in AAG compared with HC. At immunofluorescence, both IL-7R and TSLP were more expressed in AAG compared with HC and HP, and short TSLP transcripts were significantly increased in AAG compared with HC. In the supernatants of AAG corpus mucosa, short TSLP significantly reduced TNF-α, while zinc-l-carnosine significantly reduced interferon-γ, TNF-α, IL-21, IL-6, and IL-15. NAMPT transcripts were significantly increased in AAG compared with HC. PV1 was almost absent in AAG, mildly expressed in HC, and overexpressed in HP. DISCUSSION: Plasma cells, proinflammatory cytokines, and altered gastric vascular barrier may play a major role in AAG. TSLP and NAMPT may represent potential therapeutic targets, while zinc-l-carnosine may dampen mucosal inflammation.

BNT162b2 vaccine induces antibody release in saliva: a possible role for mucosal viral protection?

Vaccination against an airborne pathogen is very effective if it induces also the development of mucosal antibodies that can protect against infection. The mRNA-based vaccine-encoding SARS-CoV-2 full-length spike protein (BNT162b2, Pfizer/BioNTech) protects also against infection despite being administered systemically. Here, we show that upon vaccination, cognate IgG molecules are also found in the saliva and are more abundant in SARS-CoV-2 previously exposed subjects, paralleling the development of plasma IgG. The antibodies titer declines at 3 months from vaccination. We identified a concentration of specific IgG in the plasma above which the relevant IgG can be detected in the saliva. Regarding IgA antibodies, we found only protease-susceptible IgA1 antibodies in plasma while they were present at very low levels in the saliva over the course of vaccination of SARS-CoV-2-naïve subjects. Thus, in response to BNT162b2 vaccine, plasma IgG can permeate into mucosal sites and participate in viral protection. It is not clear why IgA1 are detected in low amount, they may be proteolytically cleaved.

A 'Multiomic' Approach of Saliva Metabolomics, Microbiota, and Serum Biomarkers to Assess the Need of Hospitalization in Coronavirus Disease 2019.

BACKGROUND AND AIMS: The SARS-CoV-2 pandemic has overwhelmed the treatment capacity of the health care systems during the highest viral diffusion rate. Patients reaching the emergency department had to be either hospitalized (inpatients) or discharged (outpatients). Still, the decision was taken based on the individual assessment of the actual clinical condition, without specific biomarkers to predict future improvement or deterioration, and discharged patients often returned to the hospital for aggravation of their condition. Here, we have developed a new combined approach of omics to identify factors that could distinguish coronavirus disease 19 (COVID-19) inpatients from outpatients. METHODS: Saliva and blood samples were collected over the course of two observational cohort studies. By using machine learning approaches, we compared salivary metabolome of 50 COVID-19 patients with that of 270 healthy individuals having previously been exposed or not to SARS-CoV-2. We then correlated the salivary metabolites that allowed separating COVID-19 inpatients from outpatients with serum biomarkers and salivary microbiota taxa differentially represented in the two groups of patients. RESULTS: We identified nine salivary metabolites that allowed assessing the need of hospitalization. When combined with serum biomarkers, just two salivary metabolites (myo-inositol and 2-pyrrolidineacetic acid) and one serum protein, chitinase 3-like-1 (CHI3L1), were sufficient to separate inpatients from outpatients completely and correlated with modulated microbiota taxa. In particular, we found Corynebacterium 1 to be overrepresented in inpatients, whereas Actinomycetaceae F0332, Candidatus Saccharimonas, and Haemophilus were all underrepresented in the hospitalized population. CONCLUSION: This is a proof of concept that a combined omic analysis can be used to stratify patients independently from COVID-19.

Gut vascular barrier impairment leads to intestinal bacteria dissemination and colorectal cancer metastasis to liver.

Metastasis is facilitated by the formation of a "premetastatic niche," which is fostered by primary tumor-derived factors. Colorectal cancer (CRC) metastasizes mainly to the liver. We show that the premetastatic niche in the liver is induced by bacteria dissemination from primary CRC. We report that tumor-resident bacteria Escherichia coli disrupt the gut vascular barrier (GVB), an anatomical structure controlling bacterial dissemination along the gut-liver axis, depending on the virulence regulator VirF. Upon GVB impairment, bacteria disseminate to the liver, boost the formation of a premetastatic niche, and favor the recruitment of metastatic cells. In training and validation cohorts of CRC patients, we find that the increased levels of PV-1, a marker of impaired GVB, is associated with liver bacteria dissemination and metachronous distant metastases. Thus, PV-1 is a prognostic marker for CRC distant recurrence and vascular impairment, leading to liver metastases.

The role of gut vascular barrier in experimental alcoholic liver disease and A. muciniphila supplementation.

The translocation of bacterial components from the intestinal lumen into the portal circulation is crucial in the pathogenesis of alcoholic liver disease (ALD). Recently the important role of the gut vascular barrier (GVB) was elucidated in alcoholic liver disease. Here we report about the influence of A. muciniphila supplementation in experimental ALD on the GVB. Ethanol feeding was associated with increased Pv-1, indicating altered endothelial barrier function, whereas A. muciniphila administration tended to restore GVB. To further investigate GVB in experimental ALD, ß-catenin gain-of-function mice, which display an enhanced GVB, were ethanol-fed. ß-catenin gain-of-function mice were not protected from ethanol-induced liver injury, suggest an alternative mechanism of ethanol-induced GVB disruption. The description of the GVB in ALD could pave the way for new therapeutic options in the future.

Endogenous murine microbiota member Faecalibaculum rodentium and its human homologue protect from intestinal tumour growth.

The microbiota has been shown to promote intestinal tumourigenesis, but a possible anti-tumourigenic effect has also been postulated. Here, we demonstrate that changes in the microbiota and mucus composition are concomitant with tumourigenesis. We identified two anti-tumourigenic strains of the microbiota-Faecalibaculum rodentium and its human homologue, Holdemanella biformis-that are strongly under-represented during tumourigenesis. Reconstitution of ApcMin/+ or azoxymethane- and dextran sulfate sodium-treated mice with an isolate of F. rodentium (F. PB1) or its metabolic products reduced tumour growth. Both F. PB1 and H. biformis produced short-chain fatty acids that contributed to control protein acetylation and tumour cell proliferation by inhibiting calcineurin and NFATc3 activation in mouse and human settings. We have thus identified endogenous anti-tumourigenic bacterial strains with strong diagnostic, therapeutic and translational potential.

Microbiota-driven gut vascular barrier disruption is a prerequisite for non-alcoholic steatohepatitis development.

BACKGROUND & AIMS: Fatty liver disease, including non-alcoholic fatty liver (NAFLD) and steatohepatitis (NASH), has been associated with increased intestinal barrier permeability and translocation of bacteria or bacterial products into the blood circulation. In this study, we aimed to unravel the role of both intestinal barrier integrity and microbiota in NAFLD/NASH development. METHODS: C57BL/6J mice were fed with high-fat diet (HFD) or methionine-choline-deficient diet for 1 week or longer to recapitulate aspects of NASH (steatosis, inflammation, insulin resistance). Genetic and pharmacological strategies were then used to modulate intestinal barrier integrity. RESULTS: We show that disruption of the intestinal epithelial barrier and gut vascular barrier (GVB) are early events in NASH pathogenesis. Mice fed HFD for only 1 week undergo a diet-induced dysbiosis that drives GVB damage and bacterial translocation into the liver. Fecal microbiota transplantation from HFD-fed mice into specific pathogen-free recipients induces GVB damage and epididymal adipose tissue enlargement. GVB disruption depends on interference with the WNT/ß-catenin signaling pathway, as shown by genetic intervention driving ß-catenin activation only in endothelial cells, preventing GVB disruption and NASH development. The bile acid analogue and farnesoid X receptor agonist obeticholic acid (OCA) drives ß-catenin activation in endothelial cells. Accordingly, pharmacologic intervention with OCA protects against GVB disruption, both as a preventive and therapeutic agent. Importantly, we found upregulation of the GVB leakage marker in the colon of patients with NASH. CONCLUSIONS: We have identified a new player in NASH development, the GVB, whose damage leads to bacteria or bacterial product translocation into the blood circulation. Treatment aimed at restoring ß-catenin activation in endothelial cells, such as administration of OCA, protects against GVB damage and NASH development. LAY SUMMARY: The incidence of fatty liver disease is reaching epidemic levels in the USA, with more than 30% of adults having NAFLD (non-alcoholic fatty liver disease), which can progress to more severe non-alcoholic steatohepatitis (NASH). Herein, we show that disruption of the intestinal epithelial barrier and gut vascular barrier are early events in the development of NASH. We show that the drug obeticholic acid protects against barrier disruption and thereby prevents the development of NASH, providing further evidence for its use in the prevention or treatment of NASH.

FXR modulates the gut-vascular barrier by regulating the entry sites for bacterial translocation in experimental cirrhosis.

BACKGROUND & AIMS: Pathological bacterial translocation (PBT) in cirrhosis is the hallmark of spontaneous bacterial infections, increasing mortality several-fold. Increased intestinal permeability is known to contribute to PBT in cirrhosis, although the role of the mucus layer has not been addressed in detail. A clear route of translocation for luminal intestinal bacteria is yet to be defined, but we hypothesize that the recently described gut-vascular barrier (GVB) is impaired in experimental portal hypertension, leading to increased accessibility of the vascular compartment for translocating bacteria. MATERIALS: Cirrhosis was induced in mouse models using bile-duct ligation (BDL) and CCl4. Pre-hepatic portal-hypertension was induced by partial portal vein ligation (PPVL). Intestinal permeability was compared in these mice after GFP-Escherichia coli or different sized FITC-dextrans were injected into the intestine. RESULTS: Healthy and pre-hepatic portal-hypertensive (PPVL) mice lack translocation of FITC-dextran and GFP-E. coli from the small intestine to the liver, whereas BDL and CCl4-induced cirrhotic mice demonstrate pathological translocation, which is not altered by prior thoracic-duct ligation. The mucus layer is reduced in thickness, with loss of goblet cells and Muc2-staining and expression in cirrhotic but not PPVL mice. These changes are associated with bacterial overgrowth in the inner mucus layer and pathological translocation of GFP-E. coli through the ileal epithelium. GVB is profoundly altered in BDL and CCl4-mice with Ileal extravasation of large-sized 150 kDa-FITC-dextran, but only slightly altered in PPVL mice. This pathological endothelial permeability and accessibility in cirrhotic mice is associated with augmented expression of PV1 in intestinal vessels. OCA but not fexaramine stabilizes the GVB, whereas both FXR-agonists ameliorate gut to liver translocation of GFP-E. coli. CONCLUSIONS: Cirrhosis, but not portal hypertension per se, grossly impairs the endothelial and muco-epithelial barriers, promoting PBT to the portal-venous circulation. Both barriers appear to be FXR-modulated, with FXR-agonists reducing PBT via the portal-venous route. LAY SUMMARY: For intestinal bacteria to enter the systemic circulation, they must cross the mucus and epithelial layer, as well as the gut-vascular barrier. Cirrhosis disrupts all 3 of these barriers, giving bacteria access to the portal-venous circulation and thus, the gut-liver axis. Diminished luminal bile acid availability, cirrhosis and the associated reduction in farnesoid x receptor (FXR) signaling seem, at least partly, to mediate these changes, as FXR-agonists reduce bacterial translocation via the portal-venous route to the liver in cirrhosis.

Organ-specific protection mediated by cooperation between vascular and epithelial barriers.

Immune privilege is a complex process that protects organs from immune-mediated attack and damage. It is accomplished by a series of cellular barriers that both control immune cell entry and promote the development of tolerogenic immune cells. In this Review, we describe the vascular endothelial and epithelial barriers in organs that are commonly considered to be immune privileged, such as the brain and the eye. We compare these classical barriers with barriers in the intestine, which share features with barriers of immune-privileged organs, such as the capacity to induce tolerance and to protect from external insults. We suggest that when intestinal barriers break down, disruption of other barriers at distant sites can ensue, and this may underlie the development of various neurological, metabolic and intestinal disorders.

Gene expression profile of endothelial cells during perturbation of the gut vascular barrier.

It has been widely demonstrated that tolerance against gut microbiota is compartmentalized to mucosal sites where microbes mostly reside. How the commensal bacteria are excluded from the entrance into the blood stream via intestinal capillaries that are located beneath the gut epithelium was not clear. We recently described the existence of a new anatomical structure, the 'gut vascular barrier' (GVB), both in murine and human intestines that plays a fundamental role in avoiding indiscriminate trafficking of bacteria from the gut into the blood circulation. The vascular barrier integrity could be altered by Salmonella typhimurium, a pathogen capable of systemic dissemination, through the modulation of the Wnt/ß-catenin signaling pathway. Here we have analyzed the differences in gut endothelial gene expression profiles during Salmonella infection and have identified some interesting characteristics of endothelial to mesenchymal transition. These findings add new insights in the gut-liver axis.

The EGFR-specific antibody cetuximab combined with chemotherapy triggers immunogenic cell death.

Cetuximab is a monoclonal antibody that is effective in the treatment of metastatic colorectal cancer (mCRC). Cetuximab blocks epidermal growth factor receptor (EGFR)-ligand interaction and inhibits downstream RAS-ERK activation. However, only some activating mutations in RAS affect cetuximab efficacy, and it is not clear what else mediates treatment success. Here we hypothesized that cetuximab induces immunogenic cell death (ICD) that activates a potent antitumor response. We found that cetuximab, in combination with chemotherapy, fostered ICD in CRC cells, which we measured via the endoplasmic reticulum (ER) stress response and an increase in phagocytosis by dendritic cells. ICD induction depended on the mutational status of the EGFR signaling pathway and on the inhibition of the splicing of X-box binding protein 1 (XBP1), an unfolded protein response (UPR) mediator. We confirmed the enhanced immunogenicity elicited by cetuximab in a mouse model of human EGFR-expressing CRC. Overall, we demonstrate a new, immune-related mechanism of action of cetuximab that may help to tailor personalized medicine.

A gut-vascular barrier controls the systemic dissemination of bacteria.

In healthy individuals, the intestinal microbiota cannot access the liver, spleen, or other peripheral tissues. Some pathogenic bacteria can reach these sites, however, and can induce a systemic immune response. How such compartmentalization is achieved is unknown. We identify a gut-vascular barrier (GVB) in mice and humans that controls the translocation of antigens into the blood stream and prohibits entry of the microbiota. Salmonella typhimurium can penetrate the GVB in a manner dependent on its pathogenicity island (Spi) 2-encoded type III secretion system and on decreased ß-catenin-dependent signaling in gut endothelial cells. The GVB is modified in celiac disease patients with elevated serum transaminases, which indicates that GVB dismantling may be responsible for liver damage in these patients. Understanding the GVB may provide new insights into the regulation of the gut-liver axis.