The role of barrier function, autophagy, and cytokines in maintaining intestinal homeostasis

Intestinal homeostasis is maintained through the interplay of the intestinal mucosa, local and systemic immune factors, and the microbial content of the gut. The cellular processes of autophagy, endoplasmic reticulum stress, the unfolded protein response and regulation of reactive oxygen species production are required to maintain a balance between pro-inflammatory responses against potential pathogens and a tolerogenic response towards commensal bacteria. Intestinally active cytokines regulate innate immune pathways and cellular pathways within the gut mucosa. Disruption of these processes, or alterations in the cytokine milieu, can result in an improper response to the commensal gut microbial community leading to inappropriate inflammation characteristic of conditions such as inflammatory bowel disease

Staphylococcus aureus virulence factors identified by using a high-throughput Caenorhabditis elegans-killing model

Staphylococcus aureus is an important human pathogen that is also able to kill the model nematode Caenorhabditis elegans. We constructed a 2,950-member Tn917 transposon insertion library in S. aureus strain NCTC 8325. Twenty-one of these insertions exhibited attenuated C. elegans killing, and of these, 12 contained insertions in different genes or chromosomal locations. Ten of these 12 insertions showed attenuated killing phenotypes when transduced into two different S. aureus strains, and 5 of the 10 mutants correspond to genes that have not been previously identified in signature-tagged mutagenesis studies. These latter five mutants were tested in a murine renal abscess model, and one mutant harboring an insertion in nagD exhibited attenuated virulence. Interestingly, Tn917 was shown to have a very strong bias for insertions near the terminus of DNA replication

Staphylococcal Biofilm Exopolysaccharide Protects against Caenorhabditis elegans Immune Defenses

Staphylococcus epidermidis and Staphylococcus aureus are leading causes of hospital-acquired infections that have become increasingly difficult to treat due to the prevalence of antibiotic resistance in these organisms. The ability of staphylococci to produce biofilm is an important virulence mechanism that allows bacteria both to adhere to living and artificial surfaces and to resist host immune factors and antibiotics. Here, we show that the icaADBC locus, which synthesizes the biofilm-associated polysaccharide intercellular adhesin (PIA) in staphylococci, is required for the formation of a lethal S. epidermidis infection in the intestine of the model nematode Caenorhabditis elegans. Susceptibility to S. epidermidis infection is influenced by mutation of the C. elegans PMK-1 p38 mitogen-activated protein (MAP) kinase or DAF-2 insulin-signaling pathways. Loss of PIA production abrogates nematocidal activity and leads to reduced bacterial accumulation in the C. elegans intestine, while overexpression of the icaADBC locus in S. aureus augments virulence towards nematodes. PIA-producing S. epidermidis has a significant survival advantage over ica-deficient S. epidermidis within the intestinal tract of wild-type C. elegans, but not in immunocompromised nematodes harboring a loss-of-function mutation in the p38 MAP kinase pathway gene sek-1. Moreover, sek-1 and pmk-1 mutants are equally sensitive to wild-type and icaADBC-deficient S. epidermidis. These results suggest that biofilm exopolysaccharide enhances virulence by playing an immunoprotective role during colonization of the C. elegans intestine. These studies demonstrate that C. elegans can serve as a simple animal model for studying host–pathogen interactions involving staphylococcal biofilm exopolysaccharide and suggest that the protective activity of biofilm matrix represents an ancient conserved function for resisting predation

One-pot synthesis of pH-responsive Eudragit-mesoporous silica nanocomposites enable colonic delivery of glucocorticoids for the treatment of inflammatory bowel disease

Oral glucocorticoids are backbones for the acute management of inflammatory bowel disease (IBD). However, the clinical effectiveness of conventional oral dosage forms of glucocorticoids is hindered by their low delivery efficiency and systemic side effects. To overcome this problem, a smart drug delivery system with high loading capacity and colonic release by coating functionalized mesoporous silica nanoparticles (MSNs) with a pH‐responsive polymer Eudragit S100 is proposed. In vitro dissolution tests show that Eudragit‐coated MSNs can limit the burst release of loaded prednisolone and budesonide in the gastric environment with more than 60% of the drugs released only at colonic pH (i.e., pH ≥ 7). In vivo therapeutic efficacy of budesonide‐loaded nanoparticles is tested in a murine model of dextran sodium sulfate‐induced colitis. An oral budesonide dose of 0.2 mg kg−1 nanoparticles with Eudragit coating improves the disease activity index compared to other groups. Interestingly, both coated and uncoated nanoparticles show pathological improvements demonstrated by similar levels of histological colitis score. However, coated nanoparticles significantly decrease mRNA expression of the cytokines (Il‐1β, Il‐17, and Il‐10) particularly in proximal colon, indicating colonic delivery. Overall, this study demonstrates the effectiveness of a simple method to fabricate targeted nanomedicine for the treatment of IBD.Peer reviewe

The gut bacterium and pathobiont Bacteroides vulgatus activates NF-κB in a human gut epithelial cell line in a strain and growth phase dependent manner

The gut microbiota is increasingly implicated in the pathogenesis of Crohn's disease (CD) and ulcerative colitis (UC) although the identity of the bacteria that underpin these diseases has remained elusive. The pathobiont Bacteroides vulgatus has been associated with both diseases although relatively little is known about how its growth and functional activity might drive the host inflammatory response. We identified an ATP Binding Cassette (ABC) export system and lipoprotein in B. vulgatus ATCC 8482 and B. vulgatus PC510 that displayed significant sequence similarity to an NF-κB immunomodulatory regulon previously identified on a CD-derived metagenomic fosmid clone. Interestingly, the ABC export system was specifically enriched in CD subjects suggesting that it may be important for colonization and persistence in the CD gut environment. Both B. vulgatus ATCC 8482 and PC510 activated NF-κB in a strain and growth phase specific manner in a HT-29/kb-seap-25 enterocyte like cell line. B. vulgatus ATCC 8482 also activated NF-κB in a Caco-2-NF-κBluc enterocyte like and an LS174T-NF-κBluc goblet cell like cell lines, and induced NF-κB-p65 subunit nuclear translocation and IL-6, IL-8, CXCL-10 and MCP-1 gene expression. Despite this, NF-κB activation was not coincident with maximal expression of the ABC exporter or lipoprotein in B. vulgatus PC510 suggesting that the regulon may be necessary but not sufficient for the immunomodulatory effects

Defining Transabdominal Intestinal Ultrasound Treatment Response and Remission in Inflammatory Bowel Disease: Systematic Review and Expert Consensus Statement

Background and Aims No consensus exists on defining intestinal ultrasound response, transmural healing, or transmural remission in inflammatory bowel disease, nor clear guidance for optimal timing of assessment during treatment. This systematic review and expert consensus study aimed to define such recommendations, along with key parameters included in response reporting. Methods Electronic databases were searched from inception to July 26, 2021, using pre-defined terms. Studies were eligible if at least two intestinal ultrasound [IUS] assessments at different time points during treatment were reported, along with an appropriate reference standard. The QUADAS-2 tool was used to examine study-level risk of bias. An international panel of experts [n = 18] rated an initial 196 statements [RAND/UCLA process, scale 1–9]. Two videoconferences were conducted, resulting in additional ratings of 149 and 13 statements, respectively. Results Out of 5826 records, 31 full-text articles, 16 abstracts, and one research letter were included; 83% [40/48] of included studies showed a low concern of applicability, and 96% [46/48] had a high risk of bias. A consensus was reached on 41 statements, with clear definitions of IUS treatment response, transmural healing, transmural remission, timing of assessment, and general considerations when using intestinal ultrasound in inflammatory bowel disease. Conclusions Response criteria and time points of response assessment varied between studies, complicating direct comparison of parameter changes and their relation to treatment outcomes. To ensure a unified approach in routine care and clinical trials, we provide recommendations and definitions for key parameters for intestinal ultrasound response, to incorporate into future prospective studies.publishedVersio

The impact of clinical experience on decision-making regarding the treatment and management of mild-to-moderate ulcerative colitis.

peer reviewe

Modelling the benefits of an optimised treatment strategy for 5-ASA in mild-to-moderate ulcerative colitis.

peer reviewedOBJECTIVES: 5-aminosalicylate (mesalazine; 5-ASA) is an established first-line treatment for mild-to-moderate ulcerative colitis (UC). This study aimed to model the benefits of optimising 5-ASA therapy. METHODS: A decision tree model followed 10 000 newly diagnosed patients with mild-to-moderately active UC through induction and 1 year of maintenance treatment. Optimised treatment (maximising dose of 5-ASA and use of combined oral and rectal therapy before treatment escalation) was compared with standard treatment (standard doses of 5-ASA without optimisation). Modelled data were derived from published meta-analyses. The primary outcomes were patient numbers achieving and maintaining remission, with an analysis of treatment costs for each strategy conducted as a secondary outcome (using UK reference costs). RESULTS: During induction, there was a 39% increase in patients achieving remission through the optimised pathway without requiring systemic steroids and/or biologics (6565 vs 4725 for standard). Potential steroidal/biological adverse events avoided included: seven venous thromboembolisms and eight serious infections. Out of the 6565 patients entering maintenance following successful induction on 5-ASA, there was a 21% reduction in relapses when optimised (1830 vs 2311 for standard). This translated into 297 patients avoiding further systemic steroids and 214 biologics. Optimisation led to an average net saving of £272 per patient entering the model for the induction and maintenance of remission over 1 year. CONCLUSION: Modelling suggests that optimising 5-ASA therapy (both the inclusion of rectal 5-ASA into a combined oral and rectal regimen and maximisation of 5-ASA dose) has clinical and cost benefits that supports wider adoption in clinical practice