Inflammatory bowel disease - glycomics perspective

The interplay between gut microbiota and the unfolded protein response: Implications for intestinal homeostasis preservation and dysbiosis-related diseases

The unfolded protein response (UPR) is a complex intracellular signal transduction system that orchestrates the cellular response during Endoplasmic Reticulum (ER) stress conditions to reestablish cellular proteostasis. If, on one side, prolonged ER stress conditions can lead to programmed cell death and autophagy as a cytoprotective mechanism, on the other, unresolved ER stress and improper UPR activation represent a perilous condition able to trigger or exacerbate inflammatory responses. Notably, intestinal and immune cells experience ER stress physiologically due to their high protein secretory rate. Indeed, there is evidence of UPR's involvement in both physiological and pathological intestinal conditions, while less is known about its bidirectional interaction with gut microbiota. However, gut microbes and their metabolites can influence ER stress and UPR pathways, and, in turn, ER stress conditions can shape gut microbiota composition, with important implications for overall intestinal health. Thus, targeting UPR components is an intriguing strategy for treating ER stress-linked dysbiosis and diseases, particularly intestinal inflammation.

Diagnostic Procedures for Inflammatory Bowel Disease: Laboratory, Endoscopy, Pathology, Imaging, and Beyond

Diagnosing inflammatory bowel disease (IBD) can often be challenging, and differentiating between Crohn's disease and ulcerative colitis can be particularly difficult. Diagnostic procedures for IBD include laboratory tests, endoscopy, pathological tests, and imaging tests. Serological and stool tests can be easily performed in an outpatient setting and provide critical diagnostic clues. Although endoscopy is an invasive procedure, it offers essential diagnostic information and allows for tissue biopsy and therapeutic procedures. Video capsule endoscopy and device-assisted enteroscopy are endoscopic procedures used to evaluate the small bowel. In addition to endoscopy, magnetic resonance imaging, computed tomography, and ultrasound (US) are valuable tools for small bowel assessment. Among these, US is noninvasive and easily utilized, making its use highly practical in daily clinical practice. Endoscopic biopsy aids in the diagnosis of IBD and is crucial for assessing the histological activity of the disease, facilitating a thorough evaluation of disease remission, and aiding in the development of treatment strategies. Recent advances in artificial intelligence hold promise for enhancing various aspects of IBD management, including diagnosis, monitoring, and precision medicine. This review compiles current procedures and promising future tools for the diagnosis of IBD, providing comprehensive insights.

Anti-TNF Biologicals Enhance the Anti-Inflammatory Properties of IgG N-Glycome in Crohn's Disease

Crohn's disease (CD) is a chronic inflammation of the digestive tract that significantly impairs patients' quality of life and well-being. Anti-TNF biologicals revolutionised the treatment of CD, yet many patients do not adequately respond to such therapy. Previous studies have demonstrated a pro-inflammatory pattern in the composition of CD patients' immunoglobulin G (IgG) N-glycome compared to healthy individuals. Here, we utilised the high-throughput UHPLC method for N-glycan analysis to explore the longitudinal effect of the anti-TNF drugs infliximab and adalimumab on N-glycome composition of total serum IgG in 198 patients, as well as the predictive potential of IgG N-glycans at baseline to detect primary non-responders to anti-TNF therapy in 1315 patients. We discovered a significant decrease in IgG agalactosylation and an increase in monogalactosylation, digalactosylation and sialylation during the 14 weeks of anti-TNF treatment, regardless of therapy response, all of which suggested a diminished inflammatory environment in CD patients treated with anti-TNF therapy. Furthermore, we observed that IgG N-glycome might contain certain information regarding the anti-TNF therapy outcome before initiating the treatment. However, it is impossible to predict future primary non-responders to anti-TNF therapy based solely on IgG N-glycome composition at baseline.

Distinct Longitudinal Changes in Immunoglobulin G N-Glycosylation Associate with Therapy Response in Chronic Inflammatory Diseases

Immunosuppressants and biologicals are widely used therapeutics for various chronic inflammatory diseases (CID). To gain more detailed insight into their downstream effects, we examined their impact on serum immunoglobulin G (IgG) glycosylation. We analyzed IgG subclass-specific fragment crystallizable (Fc) N-glycosylation in patients suffering from various CID using the LC-MS approach. Firstly, we compared IgG Fc N-glycosylation between 128 CID patients and 204 healthy controls. Our results replicated previously observed CID-related decrease in IgG Fc galactosylation (adjusted p-value range 1.70 × 10⁻²–5.95 × 10⁻²²) and sialylation (adjusted p-value range 1.85 × 10⁻²–1.71 × 10⁻¹⁸). Secondly, to assess changes in IgG Fc N-glycosylation associated with therapy and remission status, we compared 139 CID patients receiving either azathioprine, infliximab, or vedolizumab therapy. We observed an increase in IgG Fc galactosylation (adjusted p-value range 1.98 × 10⁻²–1.30 × 10⁻¹⁵) and sialylation (adjusted p-value range 3.28 × 10⁻⁶–4.34 × 10⁻¹⁸) during the treatment. Furthermore, patients who reached remission displayed increased Fc galactosylation levels (p-value range 2.25 × 10⁻²–5.44 × 10⁻³) in comparison to patients with active disease. In conclusion, the alterations in IgG Fc glycosylation and the fact these changes are even more pronounced in patients who achieved remission, suggest modulation of IgG inflammatory potential associated with CID therapy.

Emerging role of protein modification in inflammatory bowel disease

The onset of inflammatory bowel disease (IBD) involves many factors, including environmental parameters, microorganisms, and the immune system. Although research on IBD continues to expand, the specific pathogenesis mechanism is still unclear. Protein modification refers to chemical modification after protein biosynthesis, also known as post-translational modification (PTM), which causes changes in the properties and functions of proteins. Since proteins can be modified in different ways, such as acetylation, methylation, and phosphorylation, the functions of proteins in different modified states will also be different. Transitions between different states of protein or changes in modification sites can regulate protein properties and functions. Such modifications like neddylation, sumoylation, glycosylation, and acetylation can activate or inhibit various signaling pathways (e.g., nuclear factor-‍κB (NF-‍κB), extracellular signal-regulated kinase (ERK), and protein kinase B (AKT)) by changing the intestinal flora, regulating immune cells, modulating the release of cytokines such as interleukin-1β (IL-‍‍1β), tumor necrosis factor-α (TNF‍-‍α), and interferon-‍γ (IFN-‍γ), and ultimately leading to the maintenance of the stability of the intestinal epithelial barrier. In this review, we focus on the current understanding of PTM and describe its regulatory role in the pathogenesis of IBD.

Lactobacillus casei ATCC 393 and it's metabolites alleviate dextran sulphate sodium-induced ulcerative colitis in mice through the NLRP3-(Caspase-1)/IL-1β pathway

Inflammatory bowel disease (IBD) represents a broad group of intestinal disorders, including ulcerative colitis (UC) and Crohn's disease (CD). Probiotics are increasingly being recognized as a means of treatment for people suffering from IBD. Our previous studies demonstrated that Lactobacillus casei ATCC 393 (L. casei ATCC 393) effectively alleviated enterotoxigenic Escherichia coli K88-induced intestinal barrier dysfunction. This study was conducted to investigate the protective effects of L. casei ATCC 393 and its metabolites on dextran sulfate sodium (DSS)-induced UC in C57BL/6 mice and the potential mechanism of these effects. The results showed that oral administration of L. casei ATCC 393 and its metabolites both effectively reversed the DSS-induced weight loss, and the reduction in the disease activity index (DAI), colon length, and villus height of colon tissue in mice. Compared to the DSS-induced model group, L. casei ATCC 393 and its metabolites significantly inhibited the infiltration of immune cells into the intestinal mucosa, decreased the production of pro-inflammatory factors, and increased the expression of anti-inflammatory factors in the serum and colon tissue, increased the expression levels of occludin, ZO-1, and claudin-1, and reduced the expression of nucleotide binding oligomeric domain-like receptor protein 3 (NLRP3), cysteine proteinase-1 (Caspase-1), IL-1β, and IL-18. In addition, L. casei ATCC 393 and its metabolites effectively improved DSS-induced gut microbiota dysbiosis. These results suggested that L. casei ATCC 393 and its metabolites alleviated the DSS-induced ulcerative inflammatory response in C57BL/6 mice through the NLRP3-(Caspase-1)/IL-1β signaling pathway.

Long Non-coding RNA MEG3 Alleviated Ulcerative Colitis Through Upregulating miR-98-5p-Sponged IL-10

Ulcerative colitis (UC) is a refractory chronic colitis disease with the particularly complex cause. Recently, long noncoding RNAs (lncRNAs) have been reported to be related to the development of UC. LncRNA MEG3 has been proved to play an anti-inflammatory role in a variety of inflammatory diseases, which share similar pathogenesis with UC, indicating the potential involvement of lncRNA MEG3 in UC. This study aims to investigate the functional role and underlying mechanism of lncRNA MEG3 in UC. Gradient concentration of H2O2 (0, 20, 50, 100, and 200 μM) was used to induce Caco-2 damage models in vitro. Cell viability was detected by cell counting kit-8 (CCK-8) assay. LncRNA MEG3, miR-98-5p, and IL-10 levels in H2O2-treated Caco-2 cells were assessed by performing real-time quantitative polymerase chain reaction (RT-qPCR). Moreover, the binding relationship between lncRNA MEG3 and miR-98-5p, as well as the binding relationship between miR-98-5p and IL-10, was validated using dual-luciferase reporter assay. 2, 4, 6-Trinitrobenzenesulfonic acid solution (TNBS) was applied to induce ulcerative colitis in young rats. The body weight, disease activity index (DAI), length and weight of the colons, pathological scores of UC rats, reactive oxygen species (ROS), and inflammatory cytokines were determined to evaluate the effects of lncRNA MEG3 on the progression of UC. Besides, hematoxylin-eosin (HE) staining was exploited to observe histological changes of UC rat colons. In addition, western blotting analysis was also performed to evaluate the apoptosis and pyroptosis-related protein levels. Moreover, lncRNA MEG3, miR-98-5p, and IL-10 levels in UC rat colons were further assessed by RT-qPCR. Meanwhile, IL-10 expression was determined using immunohistochemistry. LncRNA MEG3 and IL-10 levels were distinctly decreased while miR-98-5p was increased in Caco-2 damage models and UC rats. Bioinformatics analysis predicted the binding sites of lncRNA MEG3 to miR-98-5p and miR-98-5p to IL-10. Besides, dual-luciferase reporter assay validated the negative correlation between lncRNA MEG3 and miR-98-5p, miR-98-5p, and IL-10. Overexpressed lncRNA MEG3 reduced. DAI scores and colon weight/length ratio improved UC ulceration. In addition, upregulation of lncRNA MEG3 relieved oxidative stress, inflammatory response, apoptosis, and pyroptosis of UC rat colons. LncRNA MEG3 overexpression alleviates the serve ulceration of UC rat colons by upregulating IL-10 expression via sponging miR-98-5p. To sum up, this study reveals the protective role of lncRNA MEG3 in the development of UC and may provide potential therapeutic targets for UC.

Control of intestinal inflammation by glycosylation-dependent lectin-driven immunoregulatory circuits

Diverse immunoregulatory circuits operate to preserve intestinal homeostasis and prevent inflammation. Galectin-1 (Gal1), a β-galactoside-binding protein, promotes homeostasis by reprogramming innate and adaptive immunity. Here, we identify a glycosylation-dependent "on-off" circuit driven by Gal1 and its glycosylated ligands that controls intestinal immunopathology by targeting activated CD8⁺ T cells and shaping the cytokine profile. In patients with inflammatory bowel disease (IBD), augmented Gal1 was associated with dysregulated expression of core 2 β6-N-acetylglucosaminyltransferase 1 (C2GNT1) and α(2,6)-sialyltransferase 1 (ST6GAL1), glycosyltransferases responsible for creating or masking Gal1 ligands. Mice lacking Gal1 exhibited exacerbated colitis and augmented mucosal CD8⁺ T cell activation in response to 2,4,6-trinitrobenzenesulfonic acid; this phenotype was partially ameliorated by treatment with recombinant Gal1. While C2gnt1^-/- mice exhibited aggravated colitis, St6gal1^-/- mice showed attenuated inflammation. These effects were associated with intrinsic T cell glycosylation. Thus, Gal1 and its glycosylated ligands act to preserve intestinal homeostasis by recalibrating T cell immunity.

The Role of Glycosylation in Inflammatory Diseases

The diversity of glycan presentation in a cell, tissue and organism is enormous, which reflects the huge amount of important biological information encoded by the glycome which has not been fully understood. A compelling body of evidence has been highlighting the fundamental role of glycans in immunity, such as in development, and in major inflammatory processes such as inflammatory bowel disease, systemic lupus erythematosus and other autoimmune disorders. Glycans play an instrumental role in the immune response, integrating the canonical circuits that regulate innate and adaptive immune responses. The relevance of glycosylation in immunity is demonstrated by the role of glycans as important danger-associated molecular patterns and pathogen-associated molecular patterns associated with the discrimination between self and non-self; also as important regulators of the threshold of T cell activation, modulating receptors signalling and the activity of both T and other immune cells. In addition, glycans are important determinants that regulate the dynamic crosstalk between the microbiome and immune response. In this chapter, the essential role of glycans in the immunopathogenesis of inflammatory disorders will be presented and its potential clinical applications (diagnosis, prognosis and therapeutics) will be highlighted.

Adherent-Invasive E. coli: Update on the Lifestyle of a Troublemaker in Crohn's Disease

Besides genetic polymorphisms and environmental factors, the intestinal microbiota is an important factor in the etiology of Crohn's disease (CD). Among microbiota alterations, a particular pathotype of Escherichia coli involved in the pathogenesis of CD abnormally colonizes the intestinal mucosa of patients: the adherent-invasive Escherichia coli (AIEC) pathobiont bacteria, which have the abilities to adhere to and to invade intestinal epithelial cells (IECs), as well as to survive and replicate within macrophages. AIEC have been the subject of many studies in recent years to unveil some genes linked to AIEC virulence and to understand the impact of AIEC infection on the gut and consequently their involvement in CD. In this review, we describe the lifestyle of AIEC bacteria within the intestine, from the interaction with intestinal epithelial and immune cells with an emphasis on environmental and genetic factors favoring their implantation, to their lifestyle in the intestinal lumen. Finally, we discuss AIEC-targeting strategies such as the use of FimH antagonists, bacteriophages, or antibiotics, which could constitute therapeutic options to prevent and limit AIEC colonization in CD patients.

Biochemical and histopathological evidence for the beneficial effects of modafinil on the rat model of inflammatory bowel disease: involvement of nitric oxide pathway

BACKGROUND

Inflammatory bowel disease is an intestinal disorder presented by recurrent inflammation in the gastrointestinal tract. It has been reported that modafinil, also known as an awakening drug, has anti-inflammatory characteristics. The objective of this experiment is to investigate the protective effects of modafinil on colitis induced by acetic acid in rat and the involvement of nitric oxide pathway.

METHODS

Colitis was induced by intra-rectal instillation of 1 ml acetic acid (4%). After one h of colitis induction (first day), intraperitoneal injection of dexamethasone (1 mg/kg), modafinil (50, 100, and 150 mg/kg), nitric oxide synthase inhibitors (NOS)-N (G)-nitro-L-arginine methyl ester (L-NAME) 10 mg/kg, 7-nitroindazole 40 mg/kg, and aminoguanidine 50 mg/kg-was performed and continued for 2 consecutive days. Ultimately, macroscopic, microscopic, and biochemical assessments were performed.

RESULTS

While induction of colitis caused severe macroscopic lesions, administration of dexamethasone and modafinil (100 and 150 mg/kg) significantly improved macroscopic ulcers. Interestingly, the combination of modafinil with NOS inhibitors reversed the beneficial effects of modafinil on macroscopic destructions. In addition, the elevated level of interleukin-1beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) was decreased by modafinil. However, treatment with NOS inhibitors before modafinil neutralized the anti-inflammatory influence of modafinil. Additionally, histological disorders emerged by acetic acid in colon tissue remarkably were disappeared after treatment with modafinil.

CONCLUSIONS

In conclusion, modafinil has a protective effect on injuries induced by acetic acid in the colon of rat, which is presumably via the inhibition of inflammatory cascade and mediation of NO pathway.

Pyruvate kinase M2: A simple molecule with complex functions

Pyruvate kinase M2 is a critical enzyme that regulates cell metabolism and growth under different physiological conditions. In its metabolic role, pyruvate kinase M2 catalyzes the last glycolytic step which converts phosphoenolpyruvate to pyruvate with the generation of ATP. Beyond this metabolic role in glycolysis, PKM2 regulates gene expression in the nucleus, phosphorylates several essential proteins that regulate major cell signaling pathways, and contribute to the redox homeostasis of cancer cells. The expression of PKM2 has been demonstrated to be significantly elevated in several types of cancer, and the overall inflammatory response. The unusual pattern of PKM2 expression inspired scientists to investigate the unrevealed functions of PKM2 and the therapeutic potential of targeting PKM2 in cancer and other disorders. Therefore, the purpose of this review is to discuss the mechanistic and therapeutic potential of targeting PKM2 with the focus on cancer metabolism, redox homeostasis, inflammation, and metabolic disorders. This review highlights and provides insight into the metabolic and non-metabolic functions of PKM2 and its relevant association with health and disease.