Grape Seed Extract Eliminates Visceral Allodynia and Colonic Hyperpermeability Induced by Repeated Water Avoidance Stress in Rats

The impact of acute and chronic stress on gastrointestinal physiology and function: a microbiota-gut-brain axis perspective

The physiological consequences of stress often manifest in the gastrointestinal tract. Traumatic or chronic stress is associated with widespread maladaptive changes throughout the gut, although comparatively little is known about the effects of acute stress. Furthermore, these stress-induced changes in the gut may increase susceptibility to gastrointestinal disorders and infection, and impact critical features of the neural and behavioural consequences of the stress response by impairing gut-brain axis communication. Understanding the mechanisms behind changes in enteric nervous system circuitry, visceral sensitivity, gut barrier function, permeability, and the gut microbiota following stress is an important research objective with pathophysiological implications in both neurogastroenterology and psychiatry. Moreover, the gut microbiota has emerged as a key aspect of physiology sensitive to the effects of stress. In this review, we focus on different aspects of the gastrointestinal tract including gut barrier function as well as the immune, humoral and neuronal elements involved in gut-brain communication. Furthermore, we discuss the evidence for a role of stress in gastrointestinal disorders. Existing gaps in the current literature are highlighted, and possible avenues for future research with an integrated physiological perspective have been suggested. A more complete understanding of the spatial and temporal dynamics of the integrated host and microbial response to different kinds of stressors in the gastrointestinal tract will enable full exploitation of the diagnostic and therapeutic potential in the fast-evolving field of host-microbiome interactions.

The effects of Saccharomyces boulardii on rat colonic hypermotility induced by repeated water avoidance stress and the potential mechanism

Background

Saccharomyces boulardii (Sb) has been reported to have the potential to regulate gut motility. The aim of this experiment was to explore the possible function of Sb in gut hypermotility elicited by repeated water avoidance stress (WAS).

Methods

Adult male Wistar rats (N = 24) were divided into one of the following three groups: control (C), NS (normal saline) + WAS group (N), and Sb + WAS group (S). A diarrhea-predominant irritable bowel syndrome (IBS-D) model in rats was induced using the WAS method. Gut motility was evaluated by stool pellet expulsion per hour. The contractile activity of the colonic muscle strips was measured using an RM6240 multichannel physiological signal instrument. qRT-PCR and immunohistochemistry were used to assess Toll-like receptor 4 (TLR4) expression in colon tissue. ELISA was used to measure the level of cytokines in the serum and colonic tissue. Also, the microbiota composition was determined using high-throughput 16S rRNA sequencing.

Result

The results showed that oral Sb decreased the WAS-induced increased defecation and colonic hypermotility in vivo. Furthermore, Sb also decreased the contractile amplitude of colonic circular muscle (CM) and longitudinal muscle (LM) strips in a dose-dependent manner in vitro. Repeated WAS increased TLR4 expression, but Sb reversed it. Sb also reduced interleukin-6 (IL-6), IL-1β, and interferon-γ (IFN-γ) levels in serum and colonic tissue, while increasing IL-10 levels in colonic tissue. Meanwhile, the rats from the NS + WAS group had decreased microbiota diversity and had lower relative abundances of Patescibacteria, Epsilonbacteraeota, Cyanobacteria, and Turicibacter compared with controls. The rats in the Sb + WAS group showed a tendency to increase the relative abundance of Blautia when compared to control rats and had lower relative abundances of Acidobacteria and Anaerostipes compared with the NS + WAS group.

Conclusion

Our findings demonstrated that Sb improved colonic hypermotility in rats, reversed the high-expression of TLR4 in the colon caused by repeated WAS, modulated cytokines in the colon and serum, and altered the gut microbiota, indicating that Sb may be useful for IBS-D.

Bioactive compounds modulating Toll-like 4 receptor (TLR4)-mediated inflammation: pathways involved and future perspectives

Chronic inflammation is associated with the development and progression of several noncommunicable diseases, such as diabetes, cardiovascular disease, chronic kidney disease, cancer, and nonalcoholic fatty liver disease. Evidence suggests that pattern recognition receptors that identify pathogen-associated molecular patterns and danger-associated molecular patterns are crucial in chronic inflammation. Among the pattern recognition receptors, Toll-like receptor 4 (TLR4) stimulates several inflammatory pathway agonists, such as nuclear factor-κB, interferon regulator factor 3, and nod-like receptor pyrin domain containing 3 pathways, which consequently trigger the expression of pro-inflammatory biomarkers, increasing the risk of noncommunicable disease development and progression. Studies have focused on the antagonistic potential of bioactive compounds, following the concept of food as a medicine, in which nutritional strategies may mitigate inflammation via TLR4 modulation. Thus, this review discusses preclinical evidence concerning bioactive compounds from fruit, vegetable, spice, and herb extracts (curcumin, resveratrol, catechin, cinnamaldehyde, emodin, ginsenosides, quercetin, allicin, and caffeine) that may regulate the TLR4 pathway and reduce the inflammatory response. Bioactive compounds can inhibit TLR4-mediated inflammation through gut microbiota modulation, improvement of intestinal permeability, inhibition of lipopolysaccharide-TLR4 binding, and decreasing TLR4 expression by modulation of microRNAs and antioxidant pathways. The responses directly mitigated inflammation, especially nuclear factor-κB activation and inflammatory cytokines release. These findings should be considered for further clinical studies on inflammation-mediated diseases.

Nutraceuticals for the Treatment of IBD: Current Progress and Future Directions

Inflammatory bowel disease (IBD) is a chronic relapsing-remitting inflammatory disease of the gastrointestinal tract. Patients are usually diagnosed in adolescence and early adulthood and need lifelong treatment. In recent years, it has been found that diet plays an important role in the pathogenesis of IBD. Diet can change intestinal barrier function, affect the structure and function of intestinal flora, and promote immune disorder, thus promoting inflammation. Many patients believe that diet plays a role in the onset and treatment of the disease and changes their diet spontaneously. This review provides some insights into how nutraceuticals regulate intestinal immune homeostasis and improve intestinal barrier function. We reviewed the research results of dietary fiber, polyphenols, bioactive peptides, and other nutraceuticals in the prevention and treatment of IBD and sought better alternative or supplementary treatment methods for IBD patients.

Chronic psychological stress alters gene expression in rat colon epithelial cells promoting chromatin remodeling, barrier dysfunction and inflammation

Chronic stress is commonly associated with enhanced abdominal pain (visceral hypersensitivity), but the cellular mechanisms underlying how chronic stress induces visceral hypersensitivity are poorly understood. In this study, we examined changes in gene expression in colon epithelial cells from a rat model using RNA-sequencing to examine stress-induced changes to the transcriptome. Following chronic stress, the most significantly up-regulated genes included Atg16l1, Coq10b, Dcaf13, Nat2, Ptbp2, Rras2, Spink4 and down-regulated genes including Abat, Cited2, Cnnm2, Dab2ip, Plekhm1, Scd2, and Tab2. The primary altered biological processes revealed by network enrichment analysis were inflammation/immune response, tissue morphogenesis and development, and nucleosome/chromatin assembly. The most significantly down-regulated process was the digestive system development/function, whereas the most significantly up-regulated processes were inflammatory response, organismal injury, and chromatin remodeling mediated by H3K9 methylation. Furthermore, a subpopulation of stressed rats demonstrated very significantly altered gene expression and transcript isoforms, enriched for the differential expression of genes involved in the inflammatory response, including upregulation of cytokine and chemokine receptor gene expression coupled with downregulation of epithelial adherens and tight junction mRNAs. In summary, these findings support that chronic stress is associated with increased levels of cytokines and chemokines, their downstream signaling pathways coupled to dysregulation of intestinal cell development and function. Epigenetic regulation of chromatin remodeling likely plays a prominent role in this process. Results also suggest that super enhancers play a primary role in chronic stress-associated intestinal barrier dysfunction.

Ameliorative Effects of Humulus japonicus Extract and Polysaccharide-Rich Extract of Phragmites rhizoma in Rats with Gastrointestinal Dysfunctions Induced by Water Avoidance Stress

Chronic stress can cause the gastrointestinal disorders characterized by an altered bowel movement and abdominal pain. Studies have shown that Humulus japonicus extract (HJE) has anti-inflammatory and antidiarrheal effects, and Phragmites rhizoma extract (PEP) has antioxidative and antistress effects. The present study aimed to investigate the possible effects of HJE and PEP in rat models with stress-induced gastrointestinal dysfunctions. The rats were exposed to water avoidance stress (WAS, 1 h/day) for 10 days to induce gastrointestinal disorders. We found that WAS significantly increased fecal pellet output during 1 h stress, gastric emptying, colonic contractility, and permeability compared to the normal rats. Pretreatment with HJE and PEP (0.25 and 0.5 mL/kg, both administered separately) improved the increased gastric emptying and colonic contractility induced by electrical field stimulation, acetylcholine, and serotonin and also alleviated the increased colonic permeability. HJE and PEP also increased the claudin-1 and occludin expressions, reduced by WAS. WAS increased the concentration of TNF-α and TBARS and reduced FRAP. HJE and PEP recovered these effects. HJE and PEP improved the gastrointestinal disorders induced by WAS by upregulating the tight junction protein, possibly acting on cholinergic and serotonergic receptors to abolish the colonic hypercontractility and hyperpermeability and degradation of inflammatory cytokines via an antioxidant effect.

Saccharina japonica Ethanol Extract Ameliorates Depression/Anxiety-Like Behavior by Inhibiting Inflammation, Oxidative Stress, and Apoptosis in Dextran Sodium Sulfate Induced Ulcerative Colitis Mice

Saccharina japonica is a common marine vegetable in East Asian markets and has a variety of health benefits. This study was focused on the anti-depressant/anxiety effects of Saccharina japonica ethanol extract (SJE) on dextran sodium sulfate (DSS)-induced mice and its potential mechanism in their brain. Male C57BL/6 mice were treated with mesalazine and various doses of SJE (1, 2, and 4 g/kg body weight) for 2 weeks, followed by DSS treatment at the second week. The DSS-induced mice showed depression/anxiety-like behavior, which included shorter path length in the open field test and longer immobility time in the tail suspension test. L-SJE alleviated the depression-like behaviors. In the DSS-induced mice, reduced synaptic plasticity activated microglia, increased proinflammatory cytokines, decreased anti-inflammatory cytokine, and increased expression levels of Toll-like receptors-4, nuclear factor kappa-B, NOD-like receptors 3, apoptosis-associated speck-like protein, and Caspase-1 were observed, most of which were alleviated by SJE treatment. Furthermore, all the SJE groups could significantly enhance superoxide dismutase activity, while the L-SJE treatment decreased the contents of malondialdehyde, and the H-SJE treatment inhibited apoptosis. All these results showed that the SJE might serve as a nutritional agent for protecting the brain in ulcerative colitis mice.

Synergic interactions between polyphenols and gut microbiota in mitigating inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are a group of chronic and recurring inflammatory conditions in the colon and intestine. Their etiology is not fully understood but involves the combination of gut dysbiosis, genetics, immune functions, and environmental factors including diet. Polyphenols from plant-based food synergistically interact with gut microbiota to suppress inflammation and alleviate symptoms of IBD. Polyphenols increase the diversity of gut microbiota, improve the relative abundance of beneficial bacteria, and inhibit the pathogenic species. Polyphenols not absorbed in the small intestine are catabolized in the colon by microbiota into microbial metabolites, many of which have higher anti-inflammatory activity and bioavailability than their precursors. The polyphenols and their microbial metabolites alleviate IBD through reduction of oxidative stress, inhibition of inflammatory cytokines secretion (TNF-α, IL-6, IL-8, and IL-1β), suppression of NF-κB, upregulation of Nrf2, gut barrier protection, and modulation of immune function. Future studies are needed to discover unknown microbial metabolites of polyphenols and correlate specific gut microbes with microbial metabolites and IBD mitigating activity. A better knowledge of the synergistic interactions between polyphenols and gut microbiota will help to devise more effective prevention strategies for IBD. This review focuses on the role of polyphenols, gut microbiota and their synergistic interactions on the alleviation of IBD as well as current trends and future directions of IBD management.

Grape seed proanthocyanidin extract ameliorates dextran sulfate sodium-induced colitis through intestinal barrier improvement, oxidative stress reduction, and inflammatory cytokines and gut microbiota modulation

It is widely believed that grape seed proanthocyanidin extract (GSPE) exerts antioxidant and anti-inflammatory effects. Dietary supplementation with GSPE has been reported to alleviate colitis signs in mice, but the mechanisms involved require further exploration. The present study investigated how the oral administration of GSPE ameliorates colitis signs and reduces colitis-associated inflammation. C57BL/6 mice were treated with GSPE for 21 days. During the final 7 days of treatment, the mice were administered dextran sulfate sodium (DSS) dissolved in drinking water to induce experimental colitis. We found that GSPE treatment improved DSS-induced colitis, which was evidenced by decreases in disease activity index (DAI) scores, pathological scores, and oxidative stress and increases in zonula occludens-1 (ZO-1), occludin, and claudin-1 mRNA levels of colon tissue. Notably, the proinflammatory cytokines TNF-α and IL-1β were significantly downregulated as a result of GSPE treatment in colon tissues. GSPE treatment also reduced NLR family pyrin domain-containing 3 (NLRP3) inflammasome mRNA levels of colon tissue. Furthermore, an analysis of 16S rRNA sequences showed that GSPE rebalanced the DSS-damaged gut microbiota, including reducing Bacteroidetes, Dubosiella, and Veillonella, increasing Verrucomicrobia and Akkermansia, and elevating the Firmicutes to Bacteroidetes ratio. In conclusion, GSPE supplementation alleviates DSS-induced colitis by modulating inflammatory cytokines and oxidation stress, maintaining the intestinal barrier, and improving the microbial community. These results indicate that GSPE might be a new dietary strategy for the treatment of ulcerative colitis.

Puerarin from Pueraria lobata alleviates the symptoms of irritable bowel syndrome-diarrhea

As a functional bowel disorder, irritable bowel syndrome (IBS), especially IBS-diarrhea (IBS-D), affects approximately 9-20% of the population worldwide. Classical treatments for IBS usually result in some side effects and intestinal microbial disorders, which inhibit the clinical effects. Natural edible medicines with beneficial effects and few side effects have received more attention in recent years. Puerarin is the main active ingredient in pueraria and has been used in China to treat splenasthenic diarrhea and as a natural food in folk medicine for hundreds of years. However, there have been no reports of using puerarin in the treatment of IBS-D, and the underlying mechanism is also still unclear. In this study, a comprehensive model that could reflect the symptoms of IBS-D was established by combining neonatal maternal separation (NMS) and adult colonic acetic acid stimulation (ACAAS) in rats. The results showed that puerarin could reverse the abdominal pain and diarrhea in IBS-D rats. The therapeutic effect was realized by regulating the richness of the gut microbiota to maintain the stabilization of the intestinal micro-ecology. Furthermore, the possible mechanism might be related to the activity of the hypothalamic-pituitary-adrenal (HPA) axis by the suppressed expression of corticotropin-releasing hormone receptor (CRF) 1. At the same time, intestinal function was improved by enhancing the proliferation of colonic epithelial cells by upregulating the expression of p-ERK/ERK and by repairing the colonic mucus barrier by upregulating occludin expression. All these results suggest that puerarin could exert excellent therapeutic effects on IBS-D.

Histone H3K9 methylation regulates chronic stress and IL-6-induced colon epithelial permeability and visceral pain

BACKGROUND

Chronic stress is associated with activation of the HPA axis, elevation in pro-inflammatory cytokines, decrease in intestinal epithelial cell tight junction (TJ) proteins, and enhanced visceral pain. It is unknown whether epigenetic regulatory pathways play a role in chronic stress-induced intestinal barrier dysfunction and visceral hyperalgesia.

METHODS

Young adult male rats were subjected to water avoidance stress ± H3K9 methylation inhibitors or siRNAs. Visceral pain response was assessed. Differentiated Caco-2/BBE cells and human colonoids were treated with cortisol or IL-6 ± antagonists. Expression of TJ, IL-6, and H3K9 methylation status at gene promoters was measured. Transepithelial electrical resistance and FITC-dextran permeability were evaluated.

KEY RESULTS

Chronic stress induced IL-6 up-regulation prior to a decrease in TJ proteins in the rat colon. The IL-6 level inversely correlated with occludin expression. Treatment with IL-6 decreased occludin and induced visceral hyperalgesia. Chronic stress and IL-6 increased H3K9 methylation and decreased transcriptional GR binding to the occludin gene promoter, leading to down-regulation of protein expression and increase in paracellular permeability. Intrarectal administration of a H3K9 methylation antagonist prevented chronic stress-induced visceral hyperalgesia in the rat. In a human colonoid model, cortisol decreased occludin expression, which was prevented by the GR antagonist RU486, and IL-6 increased H3K9 methylation and decreased TJ protein levels, which were prevented by inhibitors of H3K9 methylation.

CONCLUSIONS & INFERENCES

Our findings support a novel role for methylation of the repressive histone H3K9 to regulate chronic stress, pro-inflammatory cytokine-mediated reduction in colon TJ protein levels, and increase in paracellular permeability and visceral hyperalgesia.

Polyphenol-Rich Foods for Human Health and Disease

Polyphenols are a class of well-known bioactive compounds widely distributed in the plant kingdom and abundant in plant foods and derived food products [...].