Alleviation of gut inflammation by Cdx2/Pxr pathway in a mouse model of chemical colitis

A comprehensive review of small molecules, targets, and pathways in ulcerative colitis treatment

Ulcerative colitis (UC), a chronic inflammatory bowel disease (IBD), poses significant clinical challenges because of its complex pathophysiology, long-term nature, and the limited efficacy of existing treatments. Small-molecule compounds, particularly those that are able to modulate inflammation-related signaling pathways and, in many cases, occur in nature, offer a promising alternative or supplement to conventional therapies. Studies on molecules for UC therapeutics reported in 1394 publications over the past 30 years were collected from the Web of Science (WOS) database. Only studies that verified therapeutic efficacy through animal experiments were included. Through an analysis of the molecular classes, structures, common targets, and pathways using network pharmacology, we identified 14 classes of compounds, 5 direct-target modules, and 3 crucial downstream pathways. Alkaloids, phenylpropanoids, flavonoids, and terpenes (and their derivatives) appeared most frequently and mainly targeted lipid metabolism, oxidative stress, immune regulation, signaling transduction, and cancer-related pathways. Notably, there has been an increasing trend of applying naturally sourced compounds in both preclinical and clinical trials, especially flavonoids, over the last five years. Although progress in UC research has been made, the majority of studies have focused on the overall therapeutic effects and biomarker alterations, with limited emphasis on the direct targets and underlying mechanisms. These findings highlight the need to explore novel small-molecule therapeutic strategies for UC, focusing on clearly defined targets and precise modes of action.

Recent developments and new directions in the use of natural products for the treatment of inflammatory bowel disease

BACKGROUND

Inflammatory bowel disease (IBD) represents a significant global health challenge, and there is an urgent need to explore novel therapeutic interventions. Natural products have demonstrated highly promising effectiveness in the treatment of IBD.

PURPOSE

This study systematically reviews the latest research advancements in leveraging natural products for IBD treatment.

METHODS

This manuscript strictly adheres to the PRISMA guidelines. Relevant literature on the effects of natural products on IBD was retrieved from the PubMed, Web of Science and Cochrane Library databases using the search terms "natural product," "inflammatory bowel disease," "colitis," "metagenomics", "target identification", "drug delivery systems", "polyphenols," "alkaloids," "terpenoids," and so on. The retrieved data were then systematically summarized and reviewed.

RESULTS

This review assessed the different effects of various natural products, such as polyphenols, alkaloids, terpenoids, quinones, and others, in the treatment of IBD. While these natural products offer promising avenues for IBD management, they also face challenges in terms of clinical translation and drug discovery. The advent of metagenomics, single-cell sequencing, target identification techniques, drug delivery systems, and other cutting-edge technologies heralds a new era in overcoming these challenges.

CONCLUSION

This paper provides an overview of current research progress in utilizing natural products for the treatment of IBD, exploring how contemporary technological innovations can aid in discovering and harnessing bioactive natural products for the treatment of IBD.

Characterization of Eurotium cristatum Fermented Thinned Young Apple and Mechanisms Underlying Its Alleviating Impacts on Experimental Colitis

A hundred million tons of young apples are thinned and discarded in the orchard per year, aiming to increase the yield and quality of apples. We fermented thinned young apples using a potential probiotic fungus, Eurotium cristatum, which notably disrupted the microstructure of raw samples, as characterized by the scanning electron microscope. Fermentation substantially altered the metabolite profiles of samples, which are predicted to alleviate colitis via regulating inflammatory response and response to lipopolysaccharide by using network pharmacology analysis. In vivo, oral gavage of water extracts of E. cristatum fermented young apples (E.YAP) effectively alleviated DSS-induced colitis, restored the histopathology damage, reduced the levels of inflammatory cytokines, and promoted colonic expressions of tight junction proteins. Moreover, E.YAP ameliorated gut dysbacteriosis by increasing abundances of Lactobacillus,Blautia, Muribaculaceae, and Prevotellaceae_UCG-001 while inhibiting Turicibacter, Alistipes, and Desulfovibrio. Importantly, E.YAP increased colonic bile acids, such as CA, TCA, DCA, TUDCA, and LCA, thereby alleviating colitis via PXR/NF-κB signaling. Furthermore, a synbiotic combination with Limosilactobacillus reuteri WX-94, a probiotic strain isolated from feces of healthy individuals with anti-inflammatory properties, augmented anticolitis capacities of E.YAP. Our findings demonstrate that E.YAP could be a novel, potent, food-based anti-inflammatory prebiotic for relieving inflammatory injuries.

Microbial tryptophan catabolism as an actionable target via diet-microbiome interactions

In recent years, the role of microbial tryptophan (Trp) catabolism in host-microbiota crosstalk has become a major area of scientific interest. Microbiota-derived Trp catabolites positively contribute to intestinal and systemic homeostasis by acting as ligands of aryl hydrocarbon receptor and pregnane X receptor, and as signaling molecules in microbial communities. Accumulating evidence suggests that microbial Trp catabolism could be therapeutic targets in treating human diseases. A number of bacteria and metabolic pathways have been identified to be responsible for the conversion of Trp in the intestine. Interestingly, many Trp-degrading bacteria can benefit from the supplementation of specific dietary fibers and polyphenols, which in turn increase the microbial production of beneficial Trp catabolites. Thus, this review aims to highlight the emerging role of diets and food components, i.e., food matrix, fiber, and polyphenol, in modulating the microbial catabolism of Trp and discuss the opportunities for potential therapeutic interventions via specifically designed diets targeting the Trp-microbiome axis.

Delineating the role of nuclear receptors in colorectal cancer, a focused review

Colorectal cancer (CRC) stands as one of the most prevalent form of cancer globally, causing a significant number of deaths, surpassing 0.9 million in the year 2020. According to GLOBOCAN 2020, CRC ranks third in incidence and second in mortality in both males and females. Despite extensive studies over the years, there is still a need to establish novel therapeutic targets to enhance the patients' survival rate in CRC. Nuclear receptors (NRs) are ligand-activated transcription factors (TFs) that regulate numerous essential biological processes such as differentiation, development, physiology, reproduction, and cellular metabolism. Dysregulation and anomalous expression of different NRs has led to multiple alterations, such as impaired signaling cascades, mutations, and epigenetic changes, leading to various diseases, including cancer. It has been observed that differential expression of various NRs might lead to the initiation and progression of CRC, and are correlated with poor survival outcomes in CRC patients. Despite numerous studies on the mechanism and role of NRs in this cancer, it remains of significant scientific interest primarily due to the diverse functions that various NRs exhibit in regulating key hallmarks of this cancer. Thus, modulating the expression of NRs with their agonists and antagonists, based on their expression levels, holds an immense prospect in the diagnosis, prognosis, and therapeutical modalities of CRC. In this review, we primarily focus on the role and mechanism of NRs in the pathogenesis of CRC and emphasized the significance of targeting these NRs using a variety of agents, which may represent a novel and effective strategy for the prevention and treatment of this cancer.

Recent Advances in Biologically Active Ingredients from Natural Drugs for Sepsis Treatment

Sepsis refers to the dysregulated host response to infection; its incidence and mortality rates are high. It is a worldwide medical problem but there is no specific drug for it. In recent years, clinical and experimental studies have found that many monomer components of traditional Chinese medicine have certain effects on the treatment of sepsis. This paper reviews the advances in research on the active ingredients of traditional Chinese medicine involved in the treatment of sepsis in recent years according to their chemical structure; it could provide ideas and references for further research and development in Chinese materia medica for the treatment of sepsis.

Aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) play both distinct and common roles in the regulation of colon homeostasis and intestinal carcinogenesis

Both aryl hydrocarbon receptor (AhR) and pregnane X receptor (PXR) belong among key regulators of xenobiotic metabolism in the intestinal tissue. AhR in particular is activated by a wide range of environmental and dietary carcinogens. The data accumulated over the last two decades suggest that both of these transcriptional regulators play a much wider role in the maintenance of gut homeostasis, and that both transcription factors may affect processes linked with intestinal tumorigenesis. Intestinal epithelium is continuously exposed to a wide range of AhR, PXR and dual AhR/PXR ligands formed by intestinal microbiota or originating from diet. Current evidence suggests that specific ligands of both AhR and PXR can protect intestinal epithelium against inflammation and assist in the maintenance of epithelial barrier integrity. AhR, and to a lesser extent also PXR, have been shown to play a protective role against inflammation-induced colon cancer, or, in mouse models employing overactivation of Wnt/β-catenin signaling. In contrast, other evidence suggests that both receptors may contribute to modulation of transformed colon cell behavior, with a potential to promote cancer progression and/or chemoresistance. The review focuses on both overlapping and separate roles of the two receptors in these processes, and on possible implications of their activity within the context of intestinal tissue.

Mice lacking intestinal Nr1i2 have normal intestinal homeostasis under steady-state conditions and are not hypersensitive to inflammation under lipopolysaccharide treatment

Nr1i2, a nuclear receptor known for its key function in xenobiotic detoxification, has emerged as a potential regulator of intestinal homeostasis and inflammation. However, the role of Nr1i2 in different intestinal segments remains poorly known. Moreover, in vivo investigations on intestinal Nr1i2 have essentially been performed in whole-body Nr1i2 knockout (Nr1i2-/- ) mice where the deletion of Nr1i2 in all tissues may affect the intestinal phenotype. To better understand the role of Nr1i2 in the intestine, we generated intestinal epithelial-specific Nr1i2 knockout (iNr1i2-/- ) mice and studied the duodenum, jejunum, ileum, and colon of these animals during steady-state conditions and lipopolysaccharide (LPS)-induced inflammation. As compared to control (iNr1i2+/+ ) mice, iNr1i2-/- mice showed normal intestinal permeability as assessed by in vivo FITC-dextran test. The expression of genes involved in inflammation, tight- and adherens-junction, proliferation, glucose, and lipid metabolism was comparable in the duodenum, jejunum, ileum, and colon of iNr1i2-/- and iNr1i2+/+ mice. In line with these findings, histological analyses of the jejunum revealed no difference between iNr1i2-/- and iNr1i2+/+ mice. When treated with LPS, the intestine of iNr1i2-/- mice had no increased inflammatory response as compared to iNr1i2+/+ mice. Moreover, the health monitoring of LPS-treated iNr1i2-/- and iNr1i2+/+ mice was similar. Taken together, our results demonstrate that the specific deletion of Nr1i2 in the intestinal epithelium does not cause major intestinal damages in mice during both steady-state and inflammatory conditions.

Glycosides as Potential Medicinal Components for Ulcerative Colitis: A Review

Ulcerative colitis (UC) is a chronic, non-specific disease of unknown etiology. The disease develops mainly in the rectum or colon, and the main clinical symptoms include abdominal pain, diarrhea, and purulent bloody stools, with a wide variation in severity. The specific causative factors and pathogenesis of the disease are not yet clear, but most scholars believe that the disease is caused by the interaction of genetic, environmental, infectious, immune, and intestinal flora factors. As for the treatment of UC, medications are commonly used in clinical practice, mainly including aminosalicylates, glucocorticoids, and immunosuppressive drugs. However, due to the many complications associated with conventional drug therapy and the tendency for UC to recur, there is an urgent need to discover new, safer, and more effective drugs. Natural compounds with biodiversity and chemical structure diversity from medicinal plants are the most reliable source for the development of new drug precursors. Evidence suggests that glycosides may reduce the development and progression of UC by modulating anti-inflammatory responses, inhibiting oxidative stress, suppressing abnormal immune responses, and regulating signal transduction. In this manuscript, we provide a review of the epidemiology of UC and the available drugs for disease prevention and treatment. In addition, we demonstrate the protective or therapeutic role of glycosides in UC and describe the possible mechanisms of action to provide a theoretical basis for preclinical studies in drug development.

Microbial Metabolites as Ligands to Xenobiotic Receptors: Chemical Mimicry as Potential Drugs of the Future

Xenobiotic receptors, such as the pregnane X receptor, regulate multiple host physiologic pathways including xenobiotic metabolism, certain aspects of cellular metabolism, and innate immunity. These ligand-dependent nuclear factors regulate gene expression via genomic recognition of specific promoters and transcriptional activation of the gene. Natural or endogenous ligands are not commonly associated with this class of receptors; however, since these receptors are expressed in a cell-type specific manner in the liver and intestines, there has been significant recent effort to characterize microbially derived metabolites as ligands for these receptors. In general, these metabolites are thought to be weak micromolar affinity ligands. This journal anniversary minireview focuses on recent efforts to derive potentially nontoxic microbial metabolite chemical mimics that could one day be developed as drugs combating xenobiotic receptor-modifying pathophysiology. The review will include our perspective on the field and recommend certain directions for future research. SIGNIFICANCE STATEMENT: Xenobiotic receptors (XRs) regulate host drug metabolism, cellular metabolism, and immunity. Their presence in host intestines allows them to function not only as xenosensors but also as a response to the complex metabolic environment present in the intestines. Specifically, this review focuses on describing microbial metabolite-XR interactions and the translation of these findings toward discovery of novel chemical mimics as potential drugs of the future for diseases such as inflammatory bowel disease.

Therapeutic Potential of Bioactive Components from Scutellaria baicalensis Georgi in Inflammatory Bowel Disease and Colorectal Cancer: A Review

Scutellaria baicalensis Georgi (SBG), an herbal medicine with various biological activities, including anti-inflammatory, anticancer, antiviral, antibacterial, and antioxidant activities, is effective in treatment of colitis, hepatitis, pneumonia, respiratory infections, and allergic diseases. This herbal medicine consists of major active substances, such as baicalin, baicalein, wogonoside, and wogonin. Inflammatory bowel disease (IBD) comprises a group of inflammatory conditions of the colon and small intestine, with Crohn's disease and ulcerative colitis being the main types. IBD can lead to serious complications, such as increased risk of colorectal cancer (CRC), one of the most common cancers worldwide. Currently, there is no cure for IBD, and its incidence has been increasing over the past few decades. This review comprehensively summarizes the efficacy of SBG in IBD and CRC and may serve as a reference for future research and development of drugs for IBD and cancer treatment.

Scutellaria baicalensis and its constituents baicalin and baicalein as antidotes or protective agents against chemical toxicities: a comprehensive review

Scutellaria baicalensis (SB), also known as the Chinese skullcap, has a long history of being used in Chinese medicine to treat a variety of conditions ranging from microbial infections to metabolic syndrome and malignancies. Numerous studies have reported that treatment with total SB extract or two main flavonoids found in its root and leaves, baicalin (BA) and baicalein (BE), can prevent or alleviate the detrimental toxic effects of exposure to various chemical compounds. It has been shown that BA and BE are generally behind the protective effects of SB against toxicants. This paper aimed to review the protective and therapeutic effects of SB and its main components BA and BE against chemical compounds that can cause intoxication after acute or chronic exposure and seriously affect different vital organs including the brain, heart, liver, and kidneys. In this review paper, we had a look into a total of 221 in vitro and in vivo studies from 1995 to 2021 from the scientific databases PubMed, Scopus, and Web of Science which reported protective or therapeutic effects of BA, BE, or SB against drugs and chemicals that one might be exposed to on a professional or accidental basis and compounds that are primarily used to simulate disease models. In conclusion, the protective effects of SB and its flavonoids can be mainly attributed to increase in antioxidants enzymes, inhibition of lipid peroxidation, reduction of inflammatory cytokines, and suppression of apoptosis pathway.

Role of Vitamin K in Intestinal Health

Intestinal diseases, such as inflammatory bowel diseases (IBDs) and colorectal cancer (CRC) generally characterized by clinical symptoms, including malabsorption, intestinal dysfunction, injury, and microbiome imbalance, as well as certain secondary intestinal disease complications, continue to be serious public health problems worldwide. The role of vitamin K (VK) on intestinal health has drawn growing interest in recent years. In addition to its role in blood coagulation and bone health, several investigations continue to explore the role of VK as an emerging novel biological compound with the potential function of improving intestinal health. This study aims to present a thorough review on the bacterial sources, intestinal absorption, uptake of VK, and VK deficiency in patients with intestinal diseases, with emphasis on the effect of VK supplementation on immunity, anti-inflammation, intestinal microbes and its metabolites, antioxidation, and coagulation, and promoting epithelial development. Besides, VK-dependent proteins (VKDPs) are another crucial mechanism for VK to exert a gastroprotection role for their functions of anti-inflammation, immunomodulation, and anti-tumorigenesis. In summary, published studies preliminarily show that VK presents a beneficial effect on intestinal health and may be used as a therapeutic drug to prevent/treat intestinal diseases, but the specific mechanism of VK in intestinal health has yet to be elucidated.

Xenobiotic receptors and the regulation of intestinal homeostasis: harnessing the chemical output of the intestinal microbiota

The commensal bacteria that reside in the gastrointestinal tract exist in a symbiotic relationship with the host, driving the development of the immune system and maintaining metabolic and tissue homeostasis in the local environment. The intestinal microbiota has the capacity to generate a wide array of chemical metabolites to which the cells of the intestinal mucosa are exposed. Host cells express xenobiotic receptors, such as the aryl hydrocarbon receptor (AhR) and the pregnane X receptor (PXR), that can sense and respond to chemicals that are generated by nonhost pathways. In this review, we outline the physiological and immunological processes within the intestinal environment that are regulated by microbial metabolites through the activation of the AhR and the PXR, with a focus on ligands generated by the stepwise catabolism of tryptophan.

Therapeutic effect of baicalin on inflammatory bowel disease: A review

ETHNOPHARMACOLOGICAL RELEVANCE

Baicalin (BI) is an important biologically active flavonoid isolated from the root of Scutellaria radix (Huang Qin). Traditionally Scutellaria radix was the common drug of dysentery. As the main flavonoid compound, there is a distribution tendency of baicalin to the intestinal tract and it has a protective effect on the gastrointestinal tract.

AIM OF THE REVIEW

This review aims to compile up-to-date and comprehensive information on the efficacy of baicalin in vitro and in vivo, about treating inflammatory bowel disease. Relevant information on the therapeutic potential of baicalin against inflammatory bowel disease was collected from the Web of Science, Pubmed and so on. Additionally, a few books and magazines were also consulted to get the important information.

RESULTS

The mechanisms of baicalin against inflammatory bowel disease mainly include anti-inflammation, antioxidant, immune regulation, maintenance of intestinal barrier, maintenance of intestinal flora balance. Also, BI can relieve parts of extraintestinal manifestations (EIMs), and prevent colorectal cancer.

CONCLUSION

Baicalin determined the promising therapeutic prospects as potential supplementary medicines for the treatment of IBD.

The Interface between Cell Signaling Pathways and Pregnane X Receptor

Highly expressed in the enterohepatic system, pregnane X receptor (PXR, NR1I2) is a well-characterized nuclear receptor (NR) that regulates the expression of genes in the liver and intestines that encode key drug metabolizing enzymes and drug transporter proteins in mammals. The net effect of PXR activation is to increase metabolism and clear drugs and xenobiotics from the body, producing a protective effect and mediating clinically significant drug interaction in patients on combination therapy. The complete understanding of PXR biology is thus important for the development of safe and effective therapeutic strategies. Furthermore, PXR activation is now known to specifically transrepress the inflammatory- and nutrient-signaling pathways of gene expression, thereby providing a mechanism for linking these signaling pathways together with enzymatic drug biotransformation pathways in the liver and intestines. Recent research efforts highlight numerous post-translational modifications (PTMs) which significantly influence the biological function of PXR. However, this thrust of research is still in its infancy. In the context of gene-environment interactions, we present a review of the recent literature that implicates PXR PTMs in regulating its clinically relevant biology. We also provide a discussion of how these PTMs likely interface with each other to respond to extracellular cues to appropriately modify PXR activity.

Protective Effect of Baicalin against Clostridioides difficile Infection in Mice

This study investigated the prophylactic and therapeutic efficacies of baicalin (BC), a plant-derived flavone glycoside, in reducing the severity of Clostridioides difficile infection (CDI) in a mouse model. In the prophylactic trial, C57BL/6 mice were provided with BC (0, 11, and 22 mg/L in drinking water) from 12 days before C. difficile challenge through the end of the experiment, whereas BC administration started day 1 post challenge in the therapeutic trial. Both challenge and control groups were infected with 10⁶ CFU/mL of hypervirulent C. difficile BAA 1803 spores or sterile PBS, and the clinical and diarrheal scores were recorded for 10 days post challenge. On day 2 post challenge, fecal and tissue samples were collected from mice prophylactically administered with BC for microbiome and histopathologic analysis. Both prophylactic and therapeutic supplementation of BC significantly reduced the severity of colonic lesions and improved CDI clinical progression and outcome compared with control (p < 0.05). Microbiome analysis revealed a significant increase in Gammaproteobacteria and reduction in the abundance of protective microbiota (Firmicutes) in antibiotic-treated and C. difficile-infected mice compared with controls (p < 0.05). However, baicalin supplementation favorably altered the microbiome composition, as revealed by an increased abundance in beneficial bacteria, especially Lachnospiraceae and Akkermansia. Our results warrant follow-up investigations on the use of BC as an adjunct to antibiotic therapy to control gut dysbiosis and reduce C. difficile infection in humans.

Herbal pair Huangqin-Baishao: mechanisms underlying inflammatory bowel disease by combined system pharmacology and cell experiment approach

BACKGROUND

Inflammatory bowel disease (IBD) is a severe digestive system condition, characterized by chronic and relapsing inflammation of the gastrointestinal tract. Scutellaria baicalensis Georgi (Huangqin, HQ) and Paeonia lactiflora Pall (Baishao, BS) from a typical herbal synergic pair in traditional Chinese medicine (TCM) for IBD treatments. However, the mechanisms of action for the synergy are still unclear. Therefore, this paper aimed to predict the anti-IBD targets and the main active ingredients of the HQ-BS herbal pair.

METHODS

A systems pharmacology approach was used to identify the bioactive compounds and to delineate the molecular targets and potential pathways of HQ-BS herbal pair. Then, the characteristics of the candidates were analyzed according to their oral bioavailability and drug-likeness indices. Finally, gene enrichment analysis with DAVID Bioinformatics Resources was performed to identify the potential pathways associated with the candidate targets.

RESULTS

The results showed that, a total of 38 active compounds were obtained from HQ-BS herbal pair, and 54 targets associated with IBD were identified. Gene Ontology and pathway enrichment analysis yielded the top 20 significant results with 54 targets. Furthermore, the integrated IBD pathway revealed that the HQ-BS herbal pair probably acted in patients with IBD through multiple mechanisms of regulation of the nitric oxide biosynthetic process and anti-inflammatory effects. In addition, cell experiments were carried out to verify that the HQ-BS herbal pair and their Q-markers could attenuate the levels of nitric oxide (NO), prostaglandin E2 (PGE2), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-stimulated THP-1-derived macrophage inflammation. In particular, the crude materials exerted a much better anti-inflammatory effect than their Q-markers, which might be due to their synergistic effect.

CONCLUSION

This study provides novel insight into the molecular pathways involved in the mechanisms of the HQ-BS herbal pair acting on IBD.

The role of medicinal products in the treatment of inflammatory bowel diseases (IBD) through inhibition of TLR4/NF-kappaB pathway

Inflammatory bowel disease (IBD) is a lifelong and recurrent disease of the gastrointestinal tract that afflicts many people in the world. Growing evidence has currently indicated that dysfunction of immune system, particularly toll-like receptors 4 (TLR4) signaling pathway dysfunction plays a pivotal part in the pathogenesis of IBD. TLR4 signaling is involved both in the pathogenesis and in the efficacy of treatment of IBD. There are some medicinal products and herbal medicines, which their role in the treatment of IBD through modulation of TLR4 signaling has been implicated. The purpose of this review article is to summarize those medicinal products and herbal medicines.

Baicalin Is Curative Against Rotavirus Damp Heat Diarrhea by Tuning Colonic Mucosal Barrier and Lung Immune Function

BACKGROUND

Previous studies have indicated that rotavirus (RV) is a causative factor for diarrhea and gastroenteritis in pediatric and neonatal settings. Baicalin has many functions, including antibacterial, antiinflammatory, and antihypertensive activities. However, the immunological mechanism of RV-induced diarrhea with heat-dampness syndrome (RV-DH) remains unclear.

AIMS

The aim of this study is to explore the role of baicalin in RV-DH diarrhea and its underlying mechanism.

METHODS

A mouse model of pediatric RV-DH diarrhea was established and treated with baicalin. The concentrations of cytokines were detected by enzyme-linked immunosorbent assay. Messenger RNA (mRNA) expression levels were detected by quantitative real-time polymerase chain reaction (qRT-PCR), while protein expression levels were determined by Western blotting and immunohistochemistry. Flow cytometry was used to detect the frequency of lymphocytes.

RESULTS

The concentrations of interleukin-1β (IL-1β), IL-2, IL-6, IL-8, RVvb, and secretory immunoglobulin A (SIgA) in bronchoalveolar lavage fluid (BALF) and colonic mucosa were significantly increased in the RV-DH group. Decreased expression of occludin, claudin-1, and zonula occludens-1 (ZO-1) indicated loss of tight junction function and disturbances in intestinal mucosal permeability in the RV-DH group. Flow cytometry analysis showed a high rate of CD8⁺ lymphocytes and low amount of CD4⁺ lymphocytes in the RV-DH group. Treatment of RV-DH mice with baicalin significantly reduced the duration of diarrhea and ameliorated the symptoms and pathological and immunological changes. Furthermore, baicalin inhibited STAT1 and activated STAT3 signaling pathways.

CONCLUSIONS

These findings indicate the curative and immunoregulatory properties of baicalin and have direct practical and clinical relevance for the treatment of RV-DH enteritis in humans.

Activation of PXR by Alpinetin Contributes to Abrogate Chemically Induced Inflammatory Bowel Disease

Alpinetin is a naturally occurring flavonoid from the ginger plants. We previously reported the identification of alpinetin as a ligand of human pregnane X receptor (hPXR). The current study investigated the role of alpinetin as a putative PXR activator in ameliorating chemically induced inflammatory bowel disease (IBD). We found that oral administration of alpinetin significantly alleviated the severity of dextran sulfate sodium (DSS)-induced colitis in mice by decreasing the inflammatory infiltration, the levels of the pro-inflammatory mediators, and the PXR target genes in the colon. In vitro, alpinetin blocked the nuclear translocation of p-p65 in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Further, alpinetin significantly upregulated PXR target genes and inhibited TNF-α-induced NF-κB-luciferase activity in LS174T colorectal cells; however, this regulatory effects were lost when cellular PXR gene was knocked down. In PXR transactivation assays, alpinetin increased both mouse and human PXR transactivation in a dose-dependent manner. Ligand occluding mutants, S247W/C284W and S247W/C284W/S208W, in hPXR-reporter assays, abrogated alpinetin-induced hPXR transactivation. Finally, alpinetin bound to the hPXR-ligand-binding domain (LBD) was confirmed by competitive ligand binding assay. The current study significantly extends prior observations by validating a PXR/NF-κB regulatory mechanism governing alpinetin's anti-inflammatory effects in a murine model of IBD.

Obacunone Protects Against Ulcerative Colitis in Mice by Modulating Gut Microbiota, Attenuating TLR4/NF-κB Signaling Cascades, and Improving Disrupted Epithelial Barriers

Obacunone, a natural limonoid compound abundantly distributed in citrus fruits, possesses various biological properties, such as antitumor, antioxidant, and antiviral activities. Recent studies suggested an anti-inflammatory activity of obacunone in vitro, but its efficacy on intestinal inflammation remains unknown. This study was designed to evaluate the effects and mechanisms of obacunone in ameliorating intestinal inflammation in a mouse model of ulcerative colitis (UC). We found that obacunone efficiently alleviated the severity of dextran sulfate sodium (DSS)-induced mouse UC by modulating the abnormal composition of the gut microbiota and attenuating the excessive activation of toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) signaling. The intestinal epithelial barrier was disrupted in DSS colitis mice, which was associated with activation of inflammatory signaling cascades. However, obacunone promoted the expression of tight junction proteins (TJP1 and occludin) and repressed the activation of inflammatory signaling cascades. In summary, our findings demonstrated that obacunone attenuated the symptoms of experimental UC in mice through modulation of the gut microbiota, attenuation of TLR4/NF-κB signaling cascades, and restoration of intestinal epithelial barrier integrity.

Garcinoic Acid Is a Natural and Selective Agonist of Pregnane X Receptor

Pregnane X receptor (PXR) is a master xenobiotic-sensing transcription factor and a validated target for immune and inflammatory diseases. The identification of chemical probes to investigate the therapeutic relevance of the receptor is still highly desired. In fact, currently available PXR ligands are not highly selective and can exhibit toxicity and/or potential off-target effects. In this study, we have identified garcinoic acid as a selective and efficient PXR agonist. The properties of this natural molecule as a specific PXR agonist were demonstrated by the screening on a panel of nuclear receptors, the assessment of the physical and thermodynamic binding affinity, and the determination of the PXR-garcinoic acid complex crystal structure. Cytotoxicity, transcriptional, and functional properties were investigated in human liver cells, and compound activity and target engagement were confirmed in vivo in mouse liver and gut tissue. In conclusion, garcinoic acid is a selective natural agonist of PXR and a promising lead compound toward the development of new PXR-regulating modulators.

Patchouli alcohol activates PXR and suppresses the NF-κB-mediated intestinal inflammatory

ETHNOPHARMACOLOGICAL RELEVANCE

The pregnane-X-receptor (PXR) is involved in inflammatory bowel disease (IBD). Patchouli alcohol (PA) has anti-inflammatory effects; however, the effect of PA on IBD pathogenesis remains largely unknown.

AIM OF THE STUDY

The aim of the present study was to investigate the anti-inflammatory effect of PA, primarily focused on crosstalk between PA-mediated PXR activation and NF-κB inhibition.

MATERIALS AND METHODS

We evaluated the anti-inflammatory effect of PA with respect to PXR/NF-κB signalling using in vitro and in vivo models. In vitro, PA, identified as a PXR agonist, was evaluated by hPXR transactivation assays and through assessing for CYP3A4 expression and activity. NF-κB inhibition was analysed based on NF-κB luciferase assays, NF-κB-mediated pro-inflammatory gene expression, and NF-κB nuclear translocation after activation of PXR by PA. In vivo, colonic mPXR and NF-κB signalling were analysed to assess PA-mediated the protective effect against dextran sulphate sodium (DSS)-induced colitis. Furthermore, pharmacological inhibition of PXR was further evaluated by examining PA protection against DSS-induced colitis.

RESULTS

PA induced CYP3A4 expression and activity via an hPXR-dependent mechanism. PA-mediated PXR activation attenuated inflammation by inhibiting NF-κB activity and nuclear translocation. The anti-inflammatory effect of PA on NF-κB was abolished by PXR knockdown. PA prevented DSS-induced inflammation by regulating PXR/NF-κB signalling, whereas pharmacological PXR inhibition abated PA-mediated suppressive effects on NF-κB inflammation signalling.

CONCLUSIONS

PA activates PXR signalling and suppresses NF-κB signalling, consequently causing amelioration of inflammation. Our results highlight the importance of PXR-NF-κB crosstalk in colitis and suggest a novel therapeutic reagent.

Activation of PXR by alantolactone ameliorates DSS-induced experimental colitis via suppressing NF-κB signaling pathway

Alantolactone (ALA) is a sesquiterpene lactone with potent anti-inflammatory activity. However, the effect of ALA on intestinal inflammation remains largely unknown. The present study demonstrated that ALA significantly ameliorated the clinical symptoms of dextran sulfate sodium (DSS)-induced mice colitis as determined by body weight loss, diarrhea, colon shortening, inflammatory infiltration and histological injury. In mice exposed to DSS, ALA treatment significantly lowered pro-inflammatory mediators, including nuclear factor-kappa B (NF-κB) activation. In vitro, ALA inhibited NF-κB nuclear translocation and dose-dependently activated human/mouse pregnane X receptor (PXR), a key regulator gene in inflammatory bowel disease (IBD) pathogenesis. However, the pocket occluding mutants of the ligand-binding domain (LBD) of hPXR, abrogated ALA-mediated activation of the receptor. Overexpression of hPXR inhibited NF-κB-reporter activity and in this setting, ALA further enhanced the hPXR-mediated inhibition of NF-κB-reporter activity. Furthermore, silencing hPXR gene demonstrated the necessity for hPXR in downregulation of NF-κB activation by ALA. Finally, molecular docking studies confirmed the binding affinity between hPXR-LBD and ALA. Collectively, the current study indicates a beneficial effect of ALA on experimental IBD possibly via PXR-mediated suppression of the NF-κB inflammatory signaling.

Pregnane X Receptor Activation Triggers Rapid ATP Release in Primed Macrophages That Mediates NLRP3 Inflammasome Activation

The pregnane X receptor (PXR) is a ligand-activated nuclear receptor that acts as a xenobiotic sensor, responding to compounds of foreign origin, including pharmaceutical compounds, environmental contaminants, and natural products, to induce transcriptional events that regulate drug detoxification and efflux pathways. As such, the PXR is thought to play a key role in protecting the host from xenobiotic exposure. More recently, the PXR has been reported to regulate the expression of innate immune receptors in the intestine and modulate inflammasome activation in the vasculature. In the current study, we report that activation of the PXR in primed macrophages triggers caspase-1 activation and interleukin-1β release. Mechanistically, we show that this response is nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain-containing 3-dependent and is driven by the rapid efflux of ATP and P2X purinoceptor 7 activation following PXR stimulation, an event that involves pannexin-1 gating, and is sensitive to inhibition of Src-family kinases. Our findings identify a mechanism whereby the PXR drives innate immune signaling, providing a potential link between xenobiotic exposure and the induction of innate inflammatory responses.

Baicalein Inhibits Dextran Sulfate Sodium-induced Mouse Colitis

Background

Baicalein is a bioactive flavone that is originally extracted from the root of Scutellaria baicalensis Georgi. This plant has long served as Chinese herbal medicine in the management of multiple diseases including inflammatory bowel diseases. Although it has been revealed that baicalein inhibits experimental colitis in mice, the molecular mechanisms still remain largely unrecognized.

Methods

The experimental colitis was induced in mice by 3% dextran sulfate sodium (DSS) in drinking water. The mice were given baicalein (10 or 25 mg/kg) by gavage for 7 days before and after DSS administration. Expression of COX-2 and inducible nitric oxide synthase (iNOS) and molecules involved in NF-κB signaling, such as inhibitor of κBα (IκBα), pIκBα, p65, and phospho-p65 was examined by Western blot analysis in the tissue of the mouse colon. Activity of IκB kinase β (IKKβ) was assessed by measuring the relative amount of radioactive γ-phosphate of ATP transferred to the IκBα substrate protein. The expression and phosphorylation of STAT3 and its target gene cyclin D1 were also measured.

Results

Baicalein prominently mitigated the severity of DSS-induced colitis in mice. It inhibited the expression of COX-2 and iNOS. Moreover, baicalein attenuated activity and phosphorylation of IKKβ and subsequent degradation of IκBα. Baicalein suppressed the phosphorylation and nuclear translocation of p65, resulting in a reduced DNA binding activity of NF-κB. Baicalein also suppressed the phosphorylation of STAT3 and expression of cyclin D1. Baicalein exhibited the synergistic effect on inhibition of COX-2 induced by DSS with curcumin, an ingredient of turmeric.

Conclusions

Protective effects of baicalein on DSS-induced colitis are associated with suppression of NF-κB and STAT3 signaling pathways, which may contribute to its cancer preventive effects on colon carcinogenesis.

Clinical applications of small molecule inhibitors of Pregnane X receptor

The canonical effect of Pregnane X Receptor (PXR, NR1I2) agonism includes enhanced hepatic uptake and a concomitant increase in the first-pass metabolism and efflux of drugs in mammalian liver and intestine. In patients undergoing combination therapy, PXR-mediated gene regulation represents the molecular basis of numerous food-drug, herb-drug, and drug-drug interactions. Moreover, PXR activation promotes chemotherapeutic resistance in certain malignancies. Additional research efforts suggest that sustained PXR activation exacerbates the development of fatty liver disease. Additional metabolic effects of PXR activation in liver are the inhibition of fatty acid oxidation and gluconeogenesis. The identification of non-toxic and selective PXR antagonists is therefore of current research interest. Inhibition of PXR should decrease adverse effects, improve therapeutic effectiveness, and advance clinical outcomes in patients with cancer, fatty liver, and diabetes. This review identifies small molecule PXR antagonists described to date, discusses possible molecular mechanisms of inhibition, and seeks to describe the likely biomedical consequences of the inhibition of this nuclear receptor superfamily member.

GC/MS-Based Metabolomics Approach to Evaluate the Effect of Jackyakgamcho-Tang on Acute Colitis

The objective of this study was to examine the effects of Jackyakgamcho-tang (JGT) on acute colitis. GC/MS-based metabolomics and NGS-based metagenomics were applied to investigate the alteration of metabolites and microbiota in an acute colitis model. The severity of acute colitis symptoms was alleviated by JGT treatment. Induction of colitis and JGT treatment changed compositions of gut microbiota and inflammatory cytokine levels (TNF-α and IL-6). They also substantially change metabolites (i.e., lactic acid, linoleic acid, monostearin, and palmitoylglycerol). In addition, some clear correlations were observed among metabolites, cytokine, and microbiota. This study highlights the applicability of metabolomics and metagenomics study for evaluating anti-inflammatory effects of a new functional herbal medicine as a therapeutic agent for acute colitis.

Intestinal regulation of suppression of tumorigenicity 14 (ST14) and serine peptidase inhibitor, Kunitz type -1 (SPINT1) by transcription factor CDX2

The type II membrane-anchored serine protease, matriptase, encoded by suppression of tumorgenicity-14 (ST14) regulates the integrity of the intestinal epithelial barrier in concert with its inhibitor, HAI-1 encoded by serine peptidase inhibitor, Kunitz type -1 (SPINT1). The balance of the protease/inhibitor gene expression ratio is vital in preventing the oncogenic potential of matriptase. The intestinal cell lineage is regulated by a transcriptional regulatory network where the tumor suppressor, Caudal homeobox 2 (CDX2) is considered to be an intestinal master transcription factor. In this study, we show that CDX2 has a dual function in regulating both ST14 and SPINT1, gene expression in intestinal cells. We find that CDX2 is not required for the basal ST14 and SPINT1 gene expression; however changes in CDX2 expression affects the ST14/SPINT1 mRNA ratio. Exploring CDX2 ChIP-seq data from intestinal cell lines, we identified genomic CDX2-enriched enhancer elements for both ST14 and SPINT1, which regulate their corresponding gene promoter activity. We show that CDX2 displays both repressive and enhancing regulatory abilities in a cell specific manner. Together, these data reveal new insight into transcriptional mechanisms controlling the intestinal matriptase/inhibitor balance.

Baicalein ameliorates TNBS-induced colitis by suppressing TLR4/MyD88 signaling cascade and NLRP3 inflammasome activation in mice

Baicalein (5,6,7-trihydroxyflavone), a predominant bioactive component isolated from the root of Scutellaria baicalensis Georgi, has established potent anti-inflammatory activity via multi-targeted mechanisms. However, little is known about the effect of baicalein on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis, which shares pathology related to human Crohn’s disease (CD). The present study demonstrated that baicalein alleviated the severity of TNBS-induced colitis in mice by decreasing the activity of myeloperoxidase (MPO) and the expression of pro-inflammatory mediators. The decline in the activation of nuclear factor-kappa B (NF-κB) and p38 mitogen-activated protein kinase (MAPK) correlated with a decrease in the expression of mucosal toll-like receptor 4 (TLR4) and its adaptor myeloid differentiation factor 88 (MyD88). In vitro, baicalein down-regulated the TLR4/MyD88 signaling cascades (NF-κB and MAPKs) in lipopolysaccharide (LPS)-stimulated macrophages. At the upstream level, baicalein bound to the hydrophobic region of the myeloid differentiation protein-2 (MD-2) pocket and inhibited the formation of the LPS-induced MD-2/TLR4 complex. Furthermore, baicalein reduced NOD-like receptor 3 (NLRP3) inflammasome activation and downstream interleukin-1β expression in a dose-dependent manner. Our study provided evidence for the first time that baicalein attenuated TNBS-induced colitis, at least in part, via inhibition of TLR4/MyD88 signaling cascade as well as inactivation of NLRP3 inflammasome.

Role of pregnane X-receptor in regulating bacterial translocation in chronic liver diseases

Bacterial translocation (BT) has been impeccably implicated as a driving factor in the pathogenesis of a spectrum of chronic liver diseases (CLD). Scientific evidence accumulated over the last four decades has implied that the disease pathologies in CLD and BT are connected as a loop in the gut-liver axis and exacerbate each other. Pregnane X receptor (PXR) is a ligand-activated transcription factor and nuclear receptor that is expressed ubiquitously along the gut-liver-axis. PXR has been intricately associated with the regulation of various mechanisms attributed in causing BT. The importance of PXR as the mechanistic linker molecule in the gut-liver axis and its role in regulating bacterial interactions with the host in CLD has not been explored. PubMed was used to perform an extensive literature search using the keywords PXR and bacterial translocation, PXR and chronic liver disease including cirrhosis. In an adequate expression state, PXR acts as a sensor for bile acid dysregulation and bacterial derived metabolites, and in response shapes the immune profile beneficial to the host. Activation of PXR could be therapeutic in CLD as it counter-regulates endotoxin mediated inflammation and maintains the integrity of intestinal epithelium. This review mainly focuses PXR function and its regulation in BT in the context of chronic liver diseases.

HuangQin Decoction Attenuates CPT-11-Induced Gastrointestinal Toxicity by Regulating Bile Acids Metabolism Homeostasis

Irinotecan (CPT-11) is a potent chemotherapeutic agent, however, its clinical usage is often limited by the induction of severe gastrointestinal (GI) toxicity, especially late-onset diarrhea. HuangQin Decoction (HQD), commonly used for the treatment of GI ailments, has been proved could significantly ameliorate the intestinal toxicity of CPT-11. To reveal the mechanisms of CPT-11-induced toxicity and the modulation effects of HQD, a previous untargeted metabolomics study was performed and the results indicated that HQD may protect the GI tract by altering the metabolism of bile acids (BAs). Nevertheless, the untargeted assays are often less sensitive and/or efficient. In order to further confirm our previous findings, here in this paper, serum and tissues metabolic profiles of 17 BAs were analyzed using liquid chromatography-tandem mass spectrometry based targeted metabolomics. The results indicated that serum and tissues levels of most BAs were significantly decreased after CPT-11 administration, except some hydrophobic BAs. Co-treatment with HQD could markedly attenuate CPT-11-induced GI toxicity and reverse the alterations of hydrophobic BAs. Despite the fact that the BAs pool size remained unchanged, the balance of BAs had shifted leading to decreased toxicity after HQD treatment. The present study demonstrated for the first time that the precise interaction between HQD, CPT-11-induced intestinal toxicity and BAs’ homeostasis.

An untargeted metabolomics approach to determine component differences and variation in their in vivo distribution between Kuqin and Ziqin, two commercial specifications of Scutellaria Radix

Kuqin (KQ) and Ziqin (ZQ), derived from the roots of Scutellaria baicalensis Georgi, are two important commercial specifications of Scutellariae Radix (SR, termed Huang qin in Chinese).

Aryl hydrocarbon receptor signaling modifies Toll-like receptor-regulated responses in human dendritic cells

Currently, it is not well understood how ligands of the aryl hydrocarbon receptor (AhR) modify inflammatory responses triggered by Toll-like receptor (TLR) agonists in human dendritic cells (DCs). Here, we show that AhR ligands 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the tryptophan derivatives 6-formylindolo[3,2-b] carbazole (FICZ), kynurenine (kyn), and the natural dietary compound indole-3-carbinol (I3C) differentially modify cytokine expression in human monocyte-derived DCs (MoDCs). The results show that TLR-activated MoDCs express higher levels of AhR and are more sensitive toward the effects of AhR ligands. Depending on the cytokine, treatment with AhR ligands led to a synergistic or antagonistic effect of the TLR-triggered response in MoDCs. Thus, activation of AhR increased the expression of interleukin (IL)-1β, but decreased the expression of IL-12A in TLR-activated MoDCs. Furthermore, TCDD and FICZ may have opposite effects on the expression of cytochrome P4501A1 (CYP1A1) in TLR8-activated MoDCs indicating that the effect of the specific AhR ligand may depend on the presence of the specific TLR agonist. Gene silencing showed that synergistic effects of AhR ligands on TLR-induced expression of IL-1β require a functional AhR and the expression of NF-κB RelB. On the other hand, repression of IL-12A by TCDD and FICZ involved the induction of the caudal type homeobox 2 (CDX2) transcription factor. Additionally, the levels of DC surface markers were decreased in MoDCs by TCDD, FICZ and I3C, but not by kyn. Overall, these data demonstrate that AhR modulates TLR-induced expression of cytokines and DC-specific surface markers in MoDCs involving NFκB RelB and the immune regulatory factor CDX2.

Pregnane X Receptor Activation Attenuates Inflammation-Associated Intestinal Epithelial Barrier Dysfunction by Inhibiting Cytokine-Induced Myosin Light-Chain Kinase Expression and c-Jun N-Terminal Kinase 1/2 Activation

The inflammatory bowel diseases (IBDs) are chronic inflammatory disorders with a complex etiology. IBD is thought to arise in genetically susceptible individuals in the context of aberrant interactions with the intestinal microbiota and other environmental risk factors. Recently, the pregnane X receptor (PXR) was identified as a sensor for microbial metabolites, whose activation can regulate the intestinal epithelial barrier. Mutations in NR1I2, the gene that encodes the PXR, have been linked to IBD, and in animal models, PXR deletion leads to barrier dysfunction. In the current study, we sought to assess the mechanism(s) through which the PXR regulates barrier function during inflammation. In Caco-2 intestinal epithelial cell monolayers, tumor necrosis factor-α/interferon-γ exposure disrupted the barrier and triggered zonula occludens-1 relocalization, increased expression of myosin light-chain kinase (MLCK), and activation of c-Jun N-terminal kinase 1/2 (JNK1/2). Activation of the PXR [rifaximin and [[3,5-Bis(1,1-dimethylethyl)-4-hydroxyphenyl]ethenylidene]bis-phosphonic acid tetraethyl ester (SR12813); 10 μM] protected the barrier, an effect that was associated with attenuated MLCK expression and JNK1/2 activation. In vivo, activation of the PXR [pregnenolone 16α-carbonitrile (PCN)] attenuated barrier disruption induced by toll-like receptor 4 activation in wild-type, but not Pxr-/-, mice. Furthermore, PCN treatment protected the barrier in the dextran-sulfate sodium model of experimental colitis, an effect that was associated with reduced expression of mucosal MLCK and phosphorylated JNK1/2. Together, our data suggest that the PXR regulates the intestinal epithelial barrier during inflammation by modulating cytokine-induced MLCK expression and JNK1/2 activation. Thus, targeting the PXR may prove beneficial for the treatment of inflammation-associated barrier disruption in the context of IBD.

Inhibitory Effects of Multiple-Dose Treatment with Baicalein on the Pharmacokinetics of Ciprofloxacin in Rats

Ciprofloxacin is used as a treatment for urinary and respiratory tract infections in clinical practice. Baicalein, a major flavonoid present in Scutellaria baicalensis, is a well-known and potent antibacterial compound used in complementary and alternative medicine practices. The present study aimed to clarify the effects of multiple-dose treatment with baicalein on the pharmacokinetics of ciprofloxacin in rats. Following the oral administration of baicalein (20, 40, or 80 mg/kg) for five consecutive days, the rats received an oral administration of ciprofloxacin (20 mg/kg). Blood samples were collected at specific time points, and the plasma concentrations of ciprofloxacin were determined by using high-performance liquid chromatography. To evaluate the mechanisms underlying the interaction between baicalein and ciprofloxacin, a rhodamine 123 accumulation assay was performed in LS-180 cells. A pharmacokinetic study revealed that multiple-dose treatment with baicalein significantly decreased the peak serum concentration (C_max ), area under the curve (AUC_{0 → 480 min} ), and relative bioavailability (F_rel ) of ciprofloxacin (p < 0.05). The rhodamine 123 accumulation assay revealed that treatment with baicalein for 48 h markedly reduced the intracellular accumulation of rhodamine 123. Taken together, these findings suggest that baicalein may result in the therapeutic failure of ciprofloxacin or other quinolone-based antibiotics used for chemotherapy in clinical practice. Copyright © 2016 John Wiley & Sons, Ltd.

Achaete scute-like 2 suppresses CDX2 expression and inhibits intestinal neoplastic epithelial cell differentiation

The role of Achaete scute-like 2 (Ascl2) in colorectal cancer (CRC) cell differentiation is unknown. LS174T, HT-29 and Caco-2 cells have high Ascl2 expression, while Lovo and SW480 cells have low Ascl2 expression. LS174T and HT-29 cells with Ascl2 knockdown were transfected with caudal type homeobox 2 (CDX2) promoter constructs and used for luciferase assays and chromatin immunoprecipitation (ChIP) assays. Ascl2 knockdown promoted differentiation of CRC cells into a goblet cell phenotype, as determined by increased expression of MUC2, TFF3, and CDX2. Ascl2 knockdown activated CDX2 expression through a transcriptional mechanism via direct binding of Ascl2 to the proximal E-box of the CDX2 promoter. Ascl2 over-expression in Lovo and SW480 cells inhibited a goblet cell phenotype, as determined by reduced CDX2 and MUC2 expression. Inverse correlations between Ascl2 and CDX2, and Ascl2 and MUC2 mRNA levels, as well as Ascl2 and CDX2 protein levels were observed in CRC cancerous samples. This study demonstrates CDX2 repression by Ascl2 and highlights a role for Ascl2 in CRC cell differentiation. These findings suggest that the Ascl2/CDX2 axis may serve as a potential therapeutic target in colorectal cancer.

Rifaximin Improves Clostridium difficile Toxin A-Induced Toxicity in Caco-2 Cells by the PXR-Dependent TLR4/MyD88/NF-κB Pathway

BACKGROUND

Clostridium difficile infections (CDIs) caused by Clostridium difficile toxin A (TcdA) lead to severe ulceration, inflammation and bleeding of the colon, and are difficult to treat.

AIM

The study aimed to evaluate the effect of rifaximin on TcdA-induced apoptosis in intestinal epithelial cells and investigate the role of PXR in its mechanism of action.

METHODS

Caco-2 cells were incubated with TcdA and treated with rifaximin (0.1-10 μM) with or without ketoconazole (10 μM). The transepithelial electrical resistance (TEER) and viability of the treated cells was determined. Also, the expression of zona occludens-1 (ZO-1), toll-like receptor 4 (TLR4), Bcl-2-associated X protein (Bax), transforming growth factor-β-activated kinase-1 (TAK1), myeloid differentiation factor 88 (MyD88), and nuclear factor-kappaB (NF-κB) was determined.

RESULTS

Rifaximin treatment (0.1, 1.0, and 10 μM) caused a significant and concentration-dependent increase in the TEER of Caco-2 cells (360, 480, and 680% vs. TcdA treatment) 24 h after the treatment and improved their viability (61, 79, and 105%). Treatment also concentration-dependently decreased the expression of Bax protein (-29, -65, and -77%) and increased the expression of ZO-1 (25, 54, and 87%) and occludin (71, 114, and 262%) versus TcdA treatment. The expression of TLR4 (-33, -50, and -75%), MyD88 (-29, -60, and -81%) and TAK1 (-37, -63, and -79%) were also reduced with rifaximin versus TcdA treatment. Ketoconazole treatment inhibited these effects.

CONCLUSION

Rifaximin improved TcdA-induced toxicity in Caco-2 cells by the PXR-dependent TLR4/MyD88/NF-κB pathway mechanism, and may be useful in the treatment of CDIs.

Flavonoids in Inflammatory Bowel Disease: A Review

Inflammatory bowel disease (IBD) is characterized by chronic inflammation of the intestine that compromises the patients’ life quality and requires sustained pharmacological and surgical treatments. Since their etiology is not completely understood, non-fully-efficient drugs have been developed and those that have shown effectiveness are not devoid of quite important adverse effects that impair their long-term use. In this regard, a growing body of evidence confirms the health benefits of flavonoids. Flavonoids are compounds with low molecular weight that are widely distributed throughout the vegetable kingdom, including in edible plants. They may be of great utility in conditions of acute or chronic intestinal inflammation through different mechanisms including protection against oxidative stress, and preservation of epithelial barrier function and immunomodulatory properties in the gut. In this review we have revised the main flavonoid classes that have been assessed in different experimental models of colitis as well as the proposed mechanisms that support their beneficial effects.

Tanshinone IIA ameliorates dextran sulfate sodium-induced inflammatory bowel disease via the pregnane X receptor

Tanshinone IIA (Tan IIA) (C₁₉H₁₈O₃) is one of the major active lipophilic components in a conventional Chinese medicine called danshen, and it has long been used in the People’s Republic of China and other neighboring countries to treat patients suffering from inflammatory bowel disease (IBD). Previous experiments by many teams determined which mechanism of Tan IIA is relevant to the treatment of IBD associated with inflammation and the pregnane X receptor (PXR). The current study demonstrated that Tan IIA is an efficacious PXR agonist and its ability to induce CYP3A4 mRNA and protein expression was mediated by the transactivation of PXR, a known target of abrogating inflammation in IBD. Clinical symptoms in mice and histological assessment data suggested that administration of Tan IIA in mice demonstrated significant protection and showed that in DSS-induced IBD it acts in a concentration-dependent manner. PXR-silenced mice treated with Tan IIA demonstrated low protection against DSS-induced mouse IBD and exacerbated the severity of IBD compared with wild-type mice; PXR-silenced mice demonstrated the necessity for PXR in Tan IIA-mediated upregulation of xenobiotic metabolism genes. The IBD treatment effects of Tan IIA are partially due to PXR-mediated upregulation of xenobiotic metabolism and downregulation of inflammatory mediators. The novel findings reported here may contribute to the effective utilization of Tan IIA and its derivatives as a PXR ligand in the treatment of human IBD. This suggests that Tan IIA may have considerable clinical utility.

The anti-inflammatory effect and potential mechanism of cardamonin in DSS-induced colitis

Cardamonin is a naturally occurring chalcone with strong anti-inflammatory activity. However, the direct effect of cardamonin on intestinal inflammation remains elusive. In the present study, we found that cardamonin markedly ameliorated dextran sulfate sodium-induced mouse body weight loss, diarrhea, colon shortening, spleen swelling, and histological damage, which correlated with a decline in the activity of myeloperoxidase and the production of nitric oxide, tumor necrosis factor-α and interleukin-6 in the colon. The upregulation of toll-like receptor 4 after dextran sulfate sodium treatment was associated with an increase in the activation of myeloid differentiation factor 88, interleukin-1 receptor-associated kinase-1, nuclear factor-κB (NF-κB) p65, inhibitor κBα, and inhibitor κB kinase-α/β, as well as the mitogen-activated protein kinase molecules of extracellular signal-regulated kinase and c-Jun NH2-terminal kinase, and this upregulation was reversed by cardamonin administration. Moreover, cardamonin blocked the nuclear translocation of NF-κB p65, inhibited NF-κB-luciferase activity, and downregulated NF-κB target genes expression. The present study clearly demonstrates a beneficial effect of cardamonin on experimental inflammatory bowel disease via a mechanism associated with suppression of toll-like receptor 4 expression and inactivation of NF-κB and mitogen-activated protein kinase pathways. This study may give insight into the further evaluation of the therapeutic potential of cardamonin or its derivatives for human inflammatory bowel disease.

SUMOylation and Ubiquitylation Circuitry Controls Pregnane X Receptor Biology in Hepatocytes

Several nuclear receptor (NR) superfamily members are known to be the molecular target of either the small ubiquitin-related modifier (SUMO) or ubiquitin-signaling pathways. However, little is currently known regarding how these two post-translational modifications interact to control NR biology. We show that SUMO and ubiquitin circuitry coordinately modifies the pregnane X receptor (PXR, NR1I2) to play a key role in regulating PXR protein stability, transactivation capacity, and transcriptional repression. The SUMOylation and ubiquitylation of PXR is increased in a ligand- and tumor necrosis factor alpha -: dependent manner in hepatocytes. The SUMO-E3 ligase enzymes protein inhibitor of activated signal transducer and activator of transcription-1 (STAT1) STAT-1 (PIAS1) and protein inhibitor of activated STAT Y (PIASy) drive high levels of PXR SUMOylation. Expression of protein inhibitor of activated stat 1 selectively increases SUMO(3)ylation as well as PXR-mediated induction of cytochrome P450, family 3, subfamily A and the xenobiotic response. The PIASy-mediated SUMO(1)ylation imparts a transcriptionally repressive function by ameliorating interaction of PXR with coactivator protein peroxisome proliferator-activated receptor gamma coactivator-1-alpha. The SUMO modification of PXR is effectively antagonized by the SUMO protease sentrin protease (SENP) 2, whereas SENP3 and SENP6 proteases are highly active in the removal of SUMO2/3 chains. The PIASy-mediated SUMO(1)ylation of PXR inhibits ubiquitin-mediated degradation of this important liver-enriched NR by the 26S proteasome. Our data reveal a working model that delineates the interactive role that these two post-translational modifications play in reconciling PXR-mediated gene activation of the xenobiotic response versus transcriptional repression of the proinflammatory response in hepatocytes. Taken together, our data reveal that the SUMOylation and ubiquitylation of the PXR interface in a fundamental manner directs its biologic function in the liver in response to xenobiotic or inflammatory stress.

Ginsenosides Regulate PXR/NF-κB Signaling and Attenuate Dextran Sulfate Sodium-Induced Colitis

Pregnane X receptor (PXR) activation exhibits anti-inflammatory effects via repressing nuclear factor-κB (NF-κB); however, its overactivation may disrupt homeostasis of various enzymes and transporters. Here we found that ginsenosides restore PXR/NF-κB signaling in inflamed conditions without disrupting PXR function in normal conditions. The effects and mechanisms of ginsenosides in regulating PXR/NF-κB signals were determined both in vitro and in vivo. Ginsenosides significantly inhibited NF-κB activation and restored the expression of PXR target genes in tumor necrosis factor-α-stimulated LS174T cells. Despite not being PXR agonists, ginsenosides repressed NF-κB activation in a PXR-dependent manner. Ginsenosides significantly increased the physical association between PXR and the NF-κB p65 subunit and thereby decreased the nuclear translocation of p65. Ginsenoside Rb1 and compound K (CK) were major bioactive compounds in the regulating PXR/NF-κB signaling. Consistently, ginsenosides significantly attenuated dextran sulfate sodium-induced experimental colitis, which was associated with restored PXR/NF-κB signaling. This study indicates that ginsenosides may elicit anti-inflammatory effects via targeting PXR/NF-κB interaction without disrupting PXR function in healthy conditions. Ginsenoside Rb1 and CK may serve as leading compounds in the discovery of new drugs that target PXR/NF-κB interaction in therapy for inflammatory bowel disease.