NAD+ Precursors and Intestinal Inflammation: Therapeutic Insights Involving Gut Microbiota

The oxidized form of nicotinamide adenine dinucleotide (NAD+) is a critical metabolite for living cells. NAD+ may act either as a cofactor for many cellular reactions as well as a coenzyme for different NAD+-consuming enzymes involved in the physiological homeostasis of different organs and systems. In mammals, NAD+ is synthesized from either tryptophan or other vitamin B3 intermediates that act as NAD+ precursors. Recent research suggests that NAD+ precursors play a crucial role in maintaining the integrity of the gut barrier. Indeed, its deficiency has been associated with enhanced gut inflammation and leakage, and dysbiosis. Conversely, NAD+-increasing therapies may confer protection against intestinal inflammation in experimental conditions and human patients, with accumulating evidence indicating that such favorable effects could be, at least in part, mediated by concomitant changes in the composition of intestinal microbiota. However, the mechanisms by which NAD+-based treatments affect the microbiota are still poorly understood. In this context, we have focused specifically on the impact of NAD+ deficiency on intestinal inflammation and dysbiosis in animal and human models. We have further explored the relationship between NAD+ and improved host intestinal metabolism and immunity and the composition of microbiota in vivo. Overall, this comprehensive review aims to provide a new perspective on the effect of NAD+-increasing strategies on host intestinal physiology.

Inorganic Nanosheet-Shielded Probiotics: A Self-Adaptable Oral Delivery System for Intestinal Disease Treatment

The oral delivery of probiotics is commonly adopted for intestinal disease treatments in clinical settings; however, the probiotics suffer from a strong acidic attack in the gastric area and the low-efficiency intestinal colonization of naked probiotics. Coating living probiotics with synthetic materials has proven effective in enabling the adaption of bacteria to gastrointestinal environments, which, unfortunately, may shield the probiotics from initiating therapeutic responses. In this study, we report a copolymer-modified two-dimensional H-silicene nanomaterial (termed SiH@TPGS-PEI) that can facilitate probiotics to adapt to diverse gastrointestinal microenvironments on-demand. Briefly, SiH@TPGS-PEI electrostatically coated on the surface of probiotic bacteria helps to resist erosive destruction in the acidic stomach and spontaneously degrades by reacting with water to generate hydrogen, an anti-inflammatory gas in response to the neutral/weakly alkaline intestinal environment, thus exposing the probiotic bacteria for colitis amelioration. This strategy may shed new light on the development of intelligent self-adaptive materials.

Alterations in p53, Microsatellite Stability and Lack of MUC5AC Expression as Molecular Features of Colorectal Carcinoma Associated with Inflammatory Bowel Disease

Colitis-associated colorectal carcinoma (CAC) occurs in inflammatory bowel disease (IBD) because of the "chronic inflammation-dysplasia-cancer" carcinogenesis pathway characterized by p53 alterations in the early stages. Recently, gastric metaplasia (GM) has been described as the initial event of the serrated colorectal cancer (CRC) process, resulting from chronic stress on the colon mucosa. The aim of the study is to characterize CAC analyzing p53 alterations and microsatellite instability (MSI) to explore their relationship with GM using a series of CRC and the adjacent intestinal mucosa. Immunohistochemistry was performed to assess p53 alterations, MSI and MUC5AC expression as a surrogate for GM. The p53 mut-pattern was found in more than half of the CAC, most frequently stable (MSS) and MUC5AC negative. Only six tumors were unstable (MSI-H), being with p53 wt-pattern (p = 0.010) and MUC5AC positive (p = 0.005). MUC5AC staining was more frequently observed in intestinal mucosa, inflamed or with chronic changes, than in CAC, especially in those with p53 wt-pattern and MSS. Based on our results, we conclude that, as in the serrated pathway of CRC, in IBD GM occurs in inflamed mucosa, persists in those with chronic changes and disappears with the acquisition of p53 mutations.

The Ah Receptor from Toxicity to Therapeutics: Report from the 5th AHR Meeting at Penn State University, USA, June 2022

The aryl hydrocarbon receptor (AHR) is a sensor of low-molecular-weight molecule signals that originate from environmental exposures, the microbiome, and host metabolism. Building upon initial studies examining anthropogenic chemical exposures, the list of AHR ligands of microbial, diet, and host metabolism origin continues to grow and has provided important clues as to the function of this enigmatic receptor. The AHR has now been shown to be directly involved in numerous biochemical pathways that influence host homeostasis, chronic disease development, and responses to toxic insults. As this field of study has continued to grow, it has become apparent that the AHR is an important novel target for cancer, metabolic diseases, skin conditions, and autoimmune disease. This meeting attempted to cover the scope of basic and applied research being performed to address possible applications of our basic knowledge of this receptor on therapeutic outcomes.

Hepatitis E Virus Infection in Patients with Chronic Inflammatory Bowel Disease Treated with Immunosuppressive Therapy

BACKGROUND

Medical treatment of inflammatory bowel disease (IBD) has evolved significantly, and treatment with immunomodulators is recommended. These medications may alter the patient's immune response and increase the risk of opportunistic infections. Our aim was to evaluate the prevalence and the incidence of acute or chronic HEV infection in IBD patients under immunomodulatory treatment.

PATIENTS AND METHODS

We conducted a retrospective, multicenter, observational study between 2017 and 2018. IBD outpatients hospitalized for the infusion of immunomodulators were included in 16 French centers. During their daily hospitalization, blood samples were drawn for HEV serology (IgM and IgG) and HEV RNA detection.

RESULTS

A total of 488 patients were included, of which 327 (67%) patients had Crohn's disease and 161 (33%) ulcerative colitis. HEV IgM was detected in 3 patients, but HEV RNA was undetectable in all patients. The HEV IgG seroprevalence rate was 14.2%. IgG-positive patients were older at sampling (p = 0.01) and IBD diagnosis (p = 0.03), had higher seafood consumption (p = 0.01) and higher doses of azathioprine (p = 0.03). Ileal and upper digestive tract involvement was more frequent in IgG-positive patients (p = 0.009), and ileocolic involvement was more frequent in IgG-negative patients (p = 0.01). Under multivariate analysis, age > 50 years [OR: 2.21 (1.26, to 3.85), p = 0.004] was associated with previous HEV infection.

CONCLUSION

Systematic screening for HEV infection is not needed among IBD patients on immunomodulatory medications. However, in the event of abnormal liver test findings, HEV should be part of the classic diagnostic assessment.

HIF-Dependent NFATC1 Activation Upregulates ITGA5 and PLAUR in Intestinal Epithelium in Inflammatory Bowel Disease

Intestinal epithelial cells exist in physiological hypoxia, leading to hypoxia-inducible factor (HIF) activation and supporting barrier function and cell metabolism of the intestinal epithelium. In contrast, pathological hypoxia is a common feature of some chronic disorders, including inflammatory bowel disease (IBD). This work was aimed at studying HIF-associated changes in the intestinal epithelium in IBD. In the first step, a list of genes responding to chemical activation of hypoxia was obtained in an in vitro intestinal cell model with RNA sequencing. Cobalt (II) chloride and oxyquinoline treatment of both undifferentiated and differentiated Caco-2 cells activate the HIF-signaling pathway according to gene set enrichment analysis. The core gene set responding to chemical hypoxia stimulation in the intestinal model included 115 upregulated and 69 downregulated genes. Of this set, protein product was detected for 32 genes, and fold changes in proteome and RNA sequencing significantly correlate. Analysis of publicly available RNA sequencing set of the intestinal epithelial cells of patients with IBD confirmed HIF-1 signaling pathway activation in sigmoid colon of patients with ulcerative colitis and terminal ileum of patients with Crohn's disease. Of the core gene set from the gut hypoxia model, expression activation of ITGA5 and PLAUR genes encoding integrin α5 and urokinase-type plasminogen activator receptor (uPAR) was detected in IBD specimens. The interaction of these molecules can activate cell migration and regenerative processes in the epithelium. Transcription factor analysis with the previously developed miRGTF tool revealed the possible role of HIF1A and NFATC1 in the regulation of ITGA5 and PLAUR gene expression. Detected genes can serve as markers of IBD progression and intestinal hypoxia.

Chemical Characterization of Bioactive Components of Rosa canina Extract and Its Protective Effect on Dextran Sulfate Sodium-Induced Intestinal Bowel Disease in a Mouse Model

Rosa canina is a well-known medicinal plant used in folk remedy that alleviates various disorders, including inflammation, gastritis, and diarrhea. The objective of this investigation was to identify and quantify the phenolic components of R. canina methanolic extract (RCME) and to determine its protective action with dextran sulfate sodium (DSS)-generated mice colitis model. RCME chemical analysis was done using Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry, and experimental animals received RCME at different doses before colitis induction by oral DSS administration during 7 days. Another group received sulfasalazine as a positive control. Colitis damages and RCME benefits were assessed using histopathological and biochemical changes and improvements. Many phenolic compounds have been identified. In addition, the DSS intoxication induced an alteration of colonic epithelium associated with an oxidative stress state. DSS administration led to an increase or decrease of intracellular mediators such as free iron and ionizable calcium. RCME consumption effectively protected against colonic histological/biochemical alterations induced by DSS intoxication providing support for the traditional use of this plant.

Nanoparticle-Mediated Drug Delivery Systems For The Treatment Of IBD: Current Perspectives

Inflammatory bowel disease (IBD), which mainly consists of Crohn’s disease and ulcerative colitis, is a chronic and relapsing inflammatory condition of the gastrointestinal tract. The traditional treatment strategies relied on frequent administration of high dosages of medications, including antibiotics, non-steroidal anti-inflammatory drugs, biologics, and immunomodulators, with the goal of reducing inflammation. Some of these medications were effective in alleviating the early-stage inflammatory symptoms, but their long-term efficacies were compromised by the accumulation of toxicities. Recently, nanoparticle (NP)-based drugs have been widely studied for their potential to solve such problems. Various mechanisms/strategies, including size-, charge-, pH-, pressure-, degradation-, ligand-receptor-, and microbiome- dependent drug delivery systems, have been exploited in preclinical studies. A certain number of NP delivery systems have sought to target drugs to the inflamed intestine. Although several NP-based drugs have entered clinical trials for the treatment of IBD, most have failed due to premature drug release, weak targeting ability, and the high immune toxicity of some of the synthetic nanomaterials that have been used to fabricate the NPs. Therefore, there is still a need for rationally designed and stable NP drug delivery system that can specifically target drugs to the disease site, prolong the drug’s residence time, and minimize systemic side effects. This review will analyze the current state of the art in NP-mediated drug delivery for IBD treatment. We will focus on topics such as deliverable targets (at the tissue or cellular level) for treating inflammation; the target-homing NP materials that can interact with such targets; and the major administration routes for treating IBD. These discussions will integrate notable trends in the research and development of IBD medications, including multi-responsive NP-mediated delivery and naturally-derived targeting NPs. Finally, current challenges and future directions will be presented in the hopes of advancing the study of NP-mediated strategies for treating IBD.

Intestinal Epithelial Cell Endoplasmic Reticulum Stress and Inflammatory Bowel Disease Pathogenesis: An Update Review

The intestinal epithelial cells serve essential roles in maintaining intestinal homeostasis, which relies on appropriate endoplasmic reticulum (ER) function for proper protein folding, modification, and secretion. Exogenous or endogenous risk factors with an ability to disturb the ER function can impair the intestinal barrier function and activate inflammatory responses in the host. The last decade has witnessed considerable progress in the understanding of the functional role of ER stress and unfolded protein response (UPR) in the gut homeostasis and its significant contribution to the pathogenesis of inflammatory bowel disease (IBD). Herein, we review recent evidence supporting the viewpoint that deregulation of ER stress and UPR signaling in the intestinal epithelium, including the absorptive cells, Paneth cells, goblet cells, and enteroendocrine cells, mediates the action of genetic or environmental factors driving colitis in experimental animals and IBD patients. In addition, we highlight pharmacologic application of chaperones or small molecules that enhance protein folding and modification capacity or improve the function of the ER. These molecules represent potential therapeutic strategies in the prevention or treatment of IBD through restoring ER homeostasis in intestinal epithelial cells.

The endogenous nociceptin/orphanin FQ-NOP receptor system as a potential therapeutic target for intestinal disorders

In 1995, by reverse pharmacology approach, used here for the first time in the history of pharmacology, nociceptin/orphanin FQ (N/OFQ) has been discovered as the endogenous ligand of a preidentified receptor named opioid receptor like 1. Subsequent studies showed that N/OFQ and its receptor (N/OFQergic system) are widely distributed in central and peripheral nervous systems as well as in peripheral organs of human and animals, and represent a system that is involved in a very large range of biological functions such as pain perception, intestinal motility and secretion, immune modulation, stress. From the time of its discovery to now, a high number of NOP agonists and antagonists have been synthesized and tested in various pathologies. Nevertheless, none of the molecules targeting N/OFQergic system have currently succeeded in going through clinical trials concerning gut pathologies, indicating that further studies are required. The work from Dr. Fichna et al., published in the present issue of Neurogastroenterology and Motility, adds another brick in the wall of understanding the role of N/OFQergic system in IBS-D pathology by the pharmacological evaluation of a new NOP receptor agonist, SCH 221510, in animal models of intestinal alterations (diarrhea and visceral hyperalgesia). Interestingly, authors report clinical data confirming the involvement of N/OFQergic system in IBS-D patients and, consequently, suggest this system as a valuable therapeutic target for IBS-D pathology. This minireview aims to give a brief summary of experimental and clinical studies focusing on the N/OFQergic system as pharmacological target for the therapeutic treatment of intestinal pathologies such as IBS and IBD.

Lymphohaematopoietic abnormalities and systemic lymphoproliferative disorder in interleukin-2 receptor gamma chain-deficient mice

Interleukin-2 (IL-2) receptor gamma chain-deficient mice with a truncated mutation showed the absence or severe reduction of natural killer cells, decreased numbers of T- and B-cells, marked hypoplasia of the thymus and peripheral lymphoid tissues, defective formation of lymphoid follicles and germinal centre in the peripheral lymphoid tissues, and the absence of Peyer's patches in the intestinal mucosa. In addition, marked splenomegaly with extramedullary haematopoiesis, increased level of IgM and decreased levels of IgG and IgE in serum, severe reduction of conventional B cells (B-2) in the peripheral lymphoid tissues, the presence of IgM-producing CD5+ B cells (B-1) and their differentiation into plasma cells and Motto cells in the spleen, and increased production and differentiation of macrophages in various tissues were found in the mutant mice. However, the development of both marginal metallophilic macrophage populations in the spleen and of their related macrophages in the other tissues of the mutant mice was severely impaired. All these abnormalities seem to be induced by the loss-of-function of the IL-2 receptor gamma chain. From 8 weeks of age on, inflammatory changes occurred in the intestines, mesenteric lymph nodes, lungs, liver, and kidneys of the mutant mice. Besides the absence of Hassall's corpuscles, thymic cysts were frequently observed in the mutant mice. These pathological abnormalities suggest that the gamma chain is implicated not only in lymphoid and haematopoietic development but also in thymic epithelial cell ontogeny.