BACKGROUND:Faecalibacterium prausnitzii plays a crucial role in ulcerative colitis (UC) remission, but its action mechanism is unknown. Here, we aimed to explore the potential mechanisms focusing on the interaction of F. prausnitzii with host immune response and its potential modulation on gut microbiome. METHODS:RNA-seq analysis together with 16S rRNA sequencing and metabolomics were performed in a dextran sodium sulfate (DSS)-induced colitis mouse model followed by F. prausnitzii gavage. To present evidence of sIgA involved in the anti-inflammatory effects of F. prausnitzii, we further applied immunoglobulin A (IgA) knockout mice and secretory IgA (sIgA) depletion mouse models using polymeric immunoglobulin receptor (pIgR) neutralizing antibody. Colonic immune cells were characterized by flow cytometry. The fecal relative abundance of F. prausnitzii, inecalcitol, and colonic IgA expression were assessed in UC patients. RESULTS:F. prausnitzii markedly ameliorated colitis by alleviating intestinal inflammation and barrier dysfunction, with significantly decreased abundance of pro-inflammatory taxa (Enterococcus, Desulfovibrio, Escherichia-Shigella, and Enterorhabdus) and increased abundance of Lachnospiraceae NK4A136_group. Functions related to intestinal immune network for IgA production pathway were up-regulated shown by transcriptomics and KEGG pathway analysis. Increased expression of IgA production associated genes including MHCII-related genes, Aicda, and Tnfrsfl3c were verified, accompanied by up-regulated colonic IgA and pIgR. The IgA knockout mice and sIgA depletion model weakened the anti-inflammation and microbiota-modulation effects of F. prausnitzii, which was further proved by fecal microbiota transplantation (FMT). The shift profile of fecal metabolites after F. prausnitzii supplement was characterized by increased production of inecalcitol, which may account for the enhanced IgA response. In a cohort of UC patients, the relative abundance of F. prausnitzii was decreased and positively correlated with colonic IgA expression and negatively correlated with disease severity. CONCLUSIONS:F. prausnitzii effectively alleviated colonic inflammation and modulated dysbiosis via enhancing colonic IgA response, thus showing promise as a UC treatment.

Fecal microbiota transplantation (FMT) is a promising therapy for inflammatory bowel disease (IBD) via rectifying gut microbiota. The aim of this study was to identify a mechanism of how specific bacteria-associated immune response contributes to alleviated colitis. Forty donors were divided into high (donor H) and low (donor L) groups according to the diversity and the abundance of Bacteroides and Faecalibacterium by 16S rRNA sequencing. FMT was performed on dextran sulfate sodium (DSS)-induced colitis in mice. Mice with colitis showed significant improvement in intestinal injury and immune imbalance after FMT with group donor H (P < 0.05). Bacteroides thetaiotaomicron and Faecalibacterium prausnitzii were identified as targeted strains in donor feces by real-time PCR and droplet digital PCR. Mice with colitis were treated with mono- or dual-bacterial gavage therapy. Dual-bacterial therapy significantly ameliorated intestinal injury compared with mono-bacterial therapy (P < 0.05). Dual-bacterial therapy increased the M2/M1 macrophage polarization and improved the Th17/Treg imbalance and elevated IL-10 production by Tregs compared with the DSS group (P < 0.05). Metabolomics showed increased abundance of lecithin in the glycerophospholipid metabolism pathway. In conclusion, B. thetaiotaomicron and F. prausnitzii, as the key bacteria in donor feces, alleviate colitis in mice. The mechanism may involve increasing lecithin and regulating IL-10 production of intestinal Tregs. NEW & NOTEWORTHY We demonstrate that donors with high abundance of Bacteroides and Faecalibacterium ameliorate dextran sulfate sodium (DSS)-induced colitis in mice by fecal microbiota transplantation (FMT). The combination therapy of Bacteroides thetaiotaomicron and Faecalibacterium prausnitzii is superior to mono-bacterial therapy in ameliorating colitis in mice, of which mechanism may involve promoting lecithin and inducing IL-10 production of intestinal Tregs.

Intestinal barrier dysfunction usually occurred in acute pancreatitis (AP) but the mechanism remains unclear. In this study, RNA sequencing of ileum in L-arginine-induced AP mice demonstrated that phosphoenolpyruvate kinase 1 (Pck1) was significantly up-regulated. Increased Pck1 expression in intestinal epithelial cells (IECs) was further validated in ileum of AP mice and duodenum of AP patients. In AP mice, level of Pck1 was positively correlated with pancreatic and ileal histopathological scores, serum amylase activity, and intestinal permeability (serum diamine oxidase (DAO), D-lactate, and endotoxin). In AP patients, level of Pck1 had a positive correlation with Ranson scores, white blood cell count and C-reactive protein. Inhibition of Pck1 by 3-Mercaptopicolinic acid hydrochloride (3-MPA) alleviated pancreatic and ileal injuries in AP mice. AP + 3-MPA mice showed improved intestinal permeability, including less epithelial apoptosis, increased tight junction proteins (TJPs) expression, decreased serum DAO, D-lactate, endotoxin, and FITC-Dextran levels, and reduced bacteria translocation. Lysozyme secreted by Paneth cells and mucin2 (MUC2) secretion in goblet cells were also partly restored in AP + 3-MPA mice. Meanwhile, inhibition of Pck1 improved intestinal immune response during AP, including elevation of M2/M1 macrophages ratio and secretory immunoglobulin A (sIgA) and reduction in neutrophils infiltration. In vitro, administration of 3-MPA dramatically ameliorated inflammation and injuries of epithelial cells in enteroids treated by LPS. In conclusion, inhibition of Pck1 in IECs might alleviate AP via modulating intestinal homeostasis.

Mucin-2 (MUC2) secreted by goblet cells participates in the intestinal barrier, but its mechanism in acute necrotizing pancreatitis (ANP) remains unclear. In acute pancreatitis (AP) patients, the functions of goblet cells (MUC2, FCGBP, CLCA1, and TFF3) decreased, and MUC2 was negatively correlated with AP severity. ANP rats treated with pilocarpine (PILO) (PILO+ANP rats) to deplete MUC2 showed more serious pancreatic and colonic injuries, goblet cell dysfunction, gut dysbiosis, and bacterial translocation than those of ANP rats. GC-MS analysis of feces showed that PILO+ANP rats had lower levels of butyric acid, isobutyric acid, isovaleric acid, and hexanoic acid than those of ANP rats. The expression of MUC2 was associated with colonic injury and gut dysbiosis. All these phenomena could be relieved, and goblet cell functions were also partially reversed by MUC2 supplementation in ANP rats. TNF-alpha-treated colonoids had exacerbated goblet cell dysfunction. MUC2 expression was negatively correlated with the levels of pro-inflammatory cytokines (IL-1 beta and IL-6) (p < .05) and positively related to the expression of tight junction proteins (Claudin 1, Occludin, and ZO1) (p < .05). Downregulating MUC2 by siRNA increased the levels of the pro-inflammatory cytokines in colonoids. MUC2 might maintain intestinal homeostasis to alleviate ANP.

Objective:To explore the effect of probiotics Lactiplantibacillus plantarum(LP) WCFS1 by gavage on acute necrotizing pancreatitis (ANP) and associated ileum injury in mice. Methods:Twenty-four healthy male mice were gavaged with broad-spectrum antibiotics for 3 weeks to establish microbiota-depleted mice, and then randomly divided into control group (CON), ANP model group (ANP), LP gavage group (LP) and LP gavage and ANP induced group (LP+ ANP) , with 6 mice in each group. Mice in LP and LP+ ANP group were treated by gavage of LP (1×10 9 CFU/ml, 0.2 ml/day per mouse) for 1 week, while CON and ANP were gavaged with sterile phosphate buffered saline for 1 week instead. The ANP model was induced by intraperitoneal injection with caerulein (100 μg/kg) for 10 times with 1-hour interval between two injections and the 10th injection with lipopolysaccharide(LPS) 5 mg/kg intraperitoneally, and the mice were sacrificed 2 h later. Levels of LP in stool and ileal mucosa were detected by real-time PCR; the pancreas and ileum were collected for pathological examination to observe the extent of tissue inflammation and to score the pathology. Serum amylase activities were determined by enzymatic kinetic chemistry; serum inflammators levels and intestinal permeability were detected by ELISA; levels of inflammators in pancreatic and ileal tissues were detected by real-time PCR; ileal tight-junction proteins (occludin, claudin-1 and ZO-1) were measured by immunofluorescence staining. Results:LP levels in the stool and ileal mucosa of mice were significantly increased after LP gavage, and the differences were statistically significant (913.30±39.12 vs 2.39±1.39, 23.11±0.50 vs 1.38±0.28, all P value <0.05). The pathological scores of pancreatic tissue of CON, LP, ANP and LP+ ANP group were (0.26±0.41), (0.17±0.26), (8.55±0.46) and (6.30±0.45); the serum amylase activities were (219.70±19.73), (217.60±11.30), (2896.24±98.32) and (1837.13±131.60)U/L, IL-1β were (0.87±0.28), (1.4±0.85), (67.41±6.45) and (36.33±5.65)pg/ml, IL-6 were (0.74±0.27), (0.16±0.16), (280586.12±39163.92) and (107912.75±31283.47)pg/ml, IL-10 were (35.52±5.27), (50.99±15.34), (2008.45±184.83) and (3070.35±403.71)pg/ml; the expression level of pancreatic IL-1β mRNA was 1.42±0.39, 0.95±25, 20.53±0.50 and 10.69±1.01, IL-6 mRNA was 1.31±0.44, 0.93±0.023, 21.97±1.71 and 11.54±1.75, IL-10 mRNA was 0.93±0.14, 0.75±0.15, 0.99±0.21 and 1.76±0.19; there was no significant difference between LP and CON group, and pancreatic pathological scores, serum amylase、IL-1β and IL-6 levels, and the expression level of pancreatic IL-1β and IL-6 mRNA were significantly decreased in LP+ ANP group compared with those in ANP group, while serum IL-10 levels and the expression level of pancreatic IL-10 mRNA were significantly increased compared with ANP group, and all the differences were statistically significant (all P values <0.05). The pathological scores of ileal tissue of CON, LP, ANP and LP+ ANP group were 0, 0, (3.17±0.41) and (1.67±0.52); the levels of serum DAO of CON, LP, ANP and LP+ ANP group were (0.03±0.03), (0.02±0.02), (0.50±0.05) and (0.49±0.06)ng/ml; LPS levels were (2.75±0.35), (3.74±0.28), (7.19±0.92) and (5.88±0.38)ng/ml; the expression level of ileal IL-1β mRNA was 1.21±0.20, 1.17±0.09, 1.81±0.25 and 1.63±0.21; IL-6 mRNA was 1.01±0.29, 2.83±0.42, 54.45±8.50 and 16.87±4.42; IL-10 mRNA was 1.12±0.41, 6.09±2.51, 11.65±1.47 and 29.86±2.93. There was no significant difference between LP and CON group, except that the ileal IL-10 mRNA expression was significantly higher than that of CON group. Ileal pathological scores, serum LPS levels and the expression level of ileal IL-6 mRNA were significantly lower in LP+ ANP group than those in ANP group, while the expression level of ileal IL-10 mRNA was significantly higher than that of ANP group; the expression of ileal tight junction proteins (ocludin, claudin-1, ZO-1) was significantly higher than those in ANP group, and all the differences were statistically significant (all P values <0.05). Conclusions:LP WCFS1 gavage could ameliorate the injury of pancreatic and ileal barrier in caerulein-induced ANP mice.

Toll-like receptor 4 (TLR4) has been identified as a potentially promising therapeutic target in acute pancreatitis (AP). However, the role of intestinal TLR4 in AP and AP-associated gut injury remains unclear. This study aimed to explore the relationship between intestinal TLR4 and gut microbiota during AP. A mouse AP model was establish by intraperitoneal injection of L-arginine. Pancreatic injury and intestinal barrier function were evaluated in wild-type and intestinal epithelial TLR4 knockout (TLR4ΔIEC) mice. Gut microbiota was analyzed by 16S rRNA sequencing. Quadruple antibiotics were applied to induce microbiota-depleted mice. Differentially expressed genes in gut were detected by RNA sequencing. L. reuteri treatment was carried out in vivo and vitro study. Compared with wild-type mice, AP and AP-associated gut injury were exacerbated in TLR4ΔIEC mice in a gut microbiota-dependent manner. The relative abundance of Lactobacillus and number of Paneth cells remarkably decreased in TLR4ΔIEC mice. The KEGG pathway analysis derived from RNA sequencing suggested that genes affected by intestinal TLR4 deletion were related to the activation of nod-like receptor pathway. Furthermore, L. reuteri treatment could significantly improve the pancreatic and intestinal injury in TLR4ΔIEC mice through promoting Paneth cells in a NOD2-dependent manner. Loss of intestinal epithelial TLR4 exacerbated pancreatic and intestinal damage during AP, which might be attributed to the gut microbiota dysbiosis especially the exhausted Lactobacillus. L. reuteri might maintain intestinal homeostasis and alleviate AP via Paneth cells modulation.Abbreviations: AP Acute pancreatitis, TLR4 Toll-like receptor 4, IL-1β Interleukin-1β, IL-6 Interleukin-6, TNF-α Tumor necrosis factor-α, SIRS Systematic inflammatory response syndrome, LPS Lipopolysaccharides, SPF Specific pathogen-free, ZO-1 Zonula occludens-1, CON Control, H&E Hematoxylin and eosin, FISH Fluorescence in situ hybridization, DAPI 4',6-diamidino-2-phenylindole, PCoA Principal co-ordinates analysis, SCFA Short chain fatty acid, LEfSe Linear discriminant analysis Effect Size, ANOVA Analysis of variance, F/B Firmicutes/Bacteroidetes, PCA Principal component analysis, NOD2 Nod-like receptor 2, ABX antibiotics, PCNA proliferating cell nuclear antigen.

We demonstrate that AP patients and experimental AP mice exhibited a dysfunction of Paneth cells. Our in vivo research showed that the severity of AP was exacerbated by the long-term dysfunction of Paneth cells, which was associated with gut microbiota disorder.

BACKGROUND:To retrospectively analyze the effects of routine treatment and blood purification combined with antibiotics on the extravascular lung water index (EVLWI), inflammatory factors, and treatment outcomes in patients with severe acute pancreatitis (SAP) complicated with acute respiratory distress syndrome (ARDS).METHODS:A total of 131 SAP patients admitted to the intensive care unit of Suzhou Ninth Hospital Affiliated to Soochow University from January 2019 to December 2020 were retrospectively enrolled in this study. Patients were divided into two groups according to the treatment methods. In addition to conventional treatment, 60 patients in group A received continuous blood purification (CBP) treatment and 71 patients in group B did not. The EVLWI, inflammatory factors, remission time of clinical symptoms, curative effect, and patient outcomes were recorded at admission and after 1, 3, 5, and 7 days of treatment.RESULTS:There was a statistically significant difference in the clinical symptom relief time and the clinical efficacy between the two groups of patients (P<0.05). The mortality rate of patients in group A was 3.33%, which was significantly lower than the 14% mortality rate observed in patients in group B (P<0.05). The EVLWI, as well as the C-reactive protein (CRP), interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α levels were significantly lower in group A patients compared to group B patients on day 1, 3, and 7 post-treatment (P<0.05). There was also a significant difference in APACHE II scores between the two groups (P<0.05). The incidence of adverse reactions in group A was 6.7%, which was significantly lower than the 22.5% incidence observed in group B (P<0.05).CONCLUSIONS:Continuous blood purification combined with antibacterial drugs is safe and has a significant effect on the treatment of SAP patient complicated with ARDS, including effectively relieving clinical symptoms and signs, reducing the level of inflammatory factors, and promoting early disease outcomes.