Role of Barrier Integrity and Dysfunctions in Maintaining the Healthy Gut and Their Health Outcomes

DUOX2 activation drives bacterial translocation and subclinical inflammation in IBD-associated dysbiosis

BACKGROUND

Inflammatory bowel diseases (IBDs) are characterised by dysbiosis and a leaky gut. The NADPH oxidase dual oxidase 2 (DUOX2) is upregulated in patients with IBD, yet its role in driving the disease remains unclear.

OBJECTIVE

We interrogated the functional consequences of epithelial DUOX2 activity for the host and microbiome.

DESIGN

DUOX2 function was studied in mice with epithelial-specific DUOX2 overactivation (vTLR4), inactivation (vTLR4 DUOXA IEC-KO) and wild-type controls. We assessed the effect of dysbiosis on DUOX2 signalling and intestinal permeability (FITC-dextran, serum zonulin, bacterial translocation) with germ-free (GF) mice engrafted with IBD or healthy microbiota. RNA sequencing of colonic mucosa and microbiota and faecal metabolomics were used to characterise the host-microbe interface. Mechanistic studies were conducted in mouse colonoids, IBD biopsies and patient serum samples.

RESULTS

DUOX2 activity increased permeability and bacterial translocation and induced subclinical inflammation in vTLR4 mice. GF vTLR4 mice had increased DUOX2 activity and permeability but no subclinical inflammation. In patients with IBD, DUOX2 expression was positively associated with plasma zonulin levels and negatively associated with ZO-1 expression. Engraftment of GF mice with IBD stool increased DUOX2 activity and triggered low-grade inflammation and permeability defects in mice. DUOX2 activity functionally altered the microbiome, reduced butyrate metabolism and promoted proinflammatory and pro-oncogenic bacterial metabolites. Butyrate and histone deacetylase (HDAC) inhibitors blocked DUOX2 activation and reversed its effects.

CONCLUSIONS

Elevated DUOX2 signalling contributes to epithelial barrier dysfunction, microbiome alterations and subclinical inflammation. Butyrate and HDAC inhibitors reversed these effects, indicating that DUOX2 may be a therapeutic target in IBD.

Gastric Infusion of Short-Chain Fatty Acids Improves Health via Enhance Liver and Intestinal Immune Response and Antioxidant Capacity in Goats

In the present study, we comprehensively investigated the impacts of the infusion of three short-chain fatty acids (SCFAs), sodium acetate (SA), propionate (SP), and butyrate (SB), to examine their respective roles in the gastrointestinal tract (GIT) health and innate immunity of twenty adult Guanzhong milk goats of 1.5 years of age. Infusion of SCFAs resulted in upregulating the activity of certain antioxidant enzymes in comparison with the control group. The SA group significantly (p < 0.05) increased the activity of the catalase (CAT) in the liver, glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) in the colon, and maleic dialdehyde (MDA) in the jejunum. SP significantly (p < 0.05) upregulated the activity of the total antioxidant capacity (T-AOC) in the ileum, CAT and MDA in the jejunum, CAT in the colon, and SOD in the liver. SB was significantly (p < 0.05) upregulated the activity of the T-AOC in the ileum, CAT in the jejunum, and T-AOC, CAT, SOD, and GSH-Px in the colon. Infusion of SCFAs resulted in significant (p < 0.05) increases in pro-inflammatory and anti-inflammatory cytokines in the intestine compared to the control group. We found that the SA group significantly (p < 0.05) upregulated the level of interleukin-1 beta (IL-1β) in the ileum and jejunum, as well as the levels of IL-6 and TNF-α in the colon, while the SP group significantly (p < 0.05) increased the level of IL-1β in the jejunum and the level of interleukin-10 (IL-10) in the colon. Furthermore, the SB group significantly (p < 0.05) upregulated levels of IL-1β in the jejunum, interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α) in the colon, and IL-10 in the cecum. Furthermore, some intestinal tight-junction proteins were significantly increased by SCFA infusion. SA significantly (p < 0.05) increased the claudin level in the ileum and occludin in the colon, while the SP group significantly (p < 0.05) upregulated the level of occludin in the jejunum and the claudin level in the ileum. Moreover, SB significantly (p < 0.05) increased the occludin level in the jejunum, claudin level in the ileum, and zonula occludens-1 (ZO-1) level in the colon and cecum. There are many positive associations among antioxidant, inflammatory cytokine, and tight-junction protein indexes in the liver and intestine. In conclusion, our results suggest that the gastric infusion of SA, SP, and SB might improve goat intestinal health through the positive influence on the antioxidant capacity, pro-inflammatory and anti-inflammatory cytokines, and tight-junction proteins.

Link between gut damage and neurotoxicity with gender differences in zebrafish: Dibutyl phthalate-driven microbiota dysbiosis as a possible major cause

Among plasticizers, dibutyl phthalate (DBP) is widely used in in industry, posing significant health risks to aquatic organisms. In this study, adult male and female zebrafish were exposed to 0 and 30 μg/L DBP for 15 days. Behavioral monitoring, immunofluorescence, protein immunoblotting, and high-throughput sequencing were used to investigate the critical role of the gut microbiome in DBP-induced dysfunction of the zebrafish gut-brain axis. The results showed pronounced, sex-specific toxic effects of acute DBP exposure in adult zebrafish, with males experiencing more severe neurological damage, while females exhibited greater intestinal damage. DBP exposure caused marked anxiety behaviors in males and significant weight loss in females. Males showed reduced neuronal expression, while females exhibited increased intestinal permeability and lower levels of the tight junction protein (ZO-1). The Firmicutes/Bacteroidota (F/B) ratio decreased, indicating severe gut microbiota dysbiosis. Changes in the gut and fecal microbiota composition, along with PICRUSt2 functional predictions, suggest that female zebrafish experienced more severe metabolic disturbances than males. Analysis of key gene expression in the brain-derived neurotrophic factor (bdnf) pathway revealed that changes in the abundance of tryptophan-metabolizing bacteria in the gut may explain the sex-specific effects of DBP on neurotransmitter serotonin levels in the brain, which influence the gut-brain axis in zebrafish. This study contributes to the understanding of toxic effects of DBP on aquatic organisms and provides strong evidence for assessing its environmental risks.

Korean Mistletoe (Viscum album var. coloratum) Ethanol Extracts Enhance Intestinal Barrier Function and Alleviate Inflammation

Korean mistletoe (Viscum album var. coloratum, KML) offers remarkable therapeutic potential for a variety of diseases. This study aims to evaluate the effects and potential molecular mechanisms of KML ethanol extracts (KMLE), focusing on intestinal barrier function and tight junctions (TJs) in an interleukin (IL)-6-induced Caco-2 cell monolayer model and a dextran sodium sulfate (DSS)-induced ulcerative colitis (UC) mouse model. KMLE is non-cytotoxic in Caco-2 cells and demonstrated strong antioxidant activity. KMLE alleviated significant barrier dysfunction and protected tight junction proteins (TJPs) in vitro. Furthermore, KMLE alleviated clinical symptoms and histopathological damage, upregulated TJPs, and suppressed the inflammatory cytokines in vivo. Additionally, six bioactive compounds were identified in KMLE by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In conclusion, KMLE ameliorated intestinal barrier dysfunction in vitro and in vivo. These findings underscore the potential of KMLE as a therapeutic agent for UC, providing insights into the mechanisms through anti-inflammatory properties and its ability to restore TJ integrity.

Inflammatory bowel disease risk gene C1ORF106 regulates actin dynamics in intestinal epithelial cells

Background and aims

C1ORF106 has previously been associated with inflammatory bowel diseases (IBD) via large-scale genetic studies. Increased intestinal permeability is a hallmark of IBD and is observed in at-risk individuals prior to the appearance of clinical symptoms. C1ORF106 was previously shown to regulate intestinal barrier permeability through the regulation of adherens junction stability and through the formation of tight junctions, which impacted actin assembly. However, the downstream impact and molecular mechanisms involved in actin regulation by C1ORF106 haven't been explored. Our study aimed at identifying which pathways involved in intestinal epithelial barrier regulation and F-actin regulation are impacted by C1ORF106 and its IBD-associated variant.

Methods

We knocked down (KD) the expression of C1ORF106 in human colonic epithelial cells and characterized the function of the 333F variant in intestinal epithelial spheroid cultures obtained from patient-derived human induced pluripotent stem cell (hiPSC). We measured barrier permeability and characterized spheroid formation, actin regulation and cell migration though immunofluorescence, western blots and permeability assays.

Results

C1ORF106 KD leads to impaired cortical actin belt dynamics and regulation of stress fiber formation, resulting in increased cell constriction, impaired barrier permeability, cell polarity and cell migration. Moreover, we demonstrated that an inhibition of ROCK rescues the actin belt and cell polarity phenotypes in C1ORF106 KD cells, demonstrating that C1ORF106 regulates these phenotypes through a ROCK-dependent mechanism. We also observed an altered nmMYO2-P localization in C1ORF106 KD cells associated with the formation of Vacuolar Apical Compartments (VACs), which are important for 3D epithelial spheroid formation. We observed a similar impact on cell polarity in intestinal epithelial spheroids obtained from hiPSC carrying the 333F variant, providing additional support that this pathway is involved in disease development.

Conclusion

We provide insights into the molecular mechanisms by which C1ORF106 controls actin dynamics to regulate intestinal epithelial integrity.

An Evaluation of Soybean Protein Concentrate as a Replacement for Fish Meal with Methionine Supplementation in Diets for Hybrid Sturgeon (Acipenser baerii ♀ × A. schrenckii ♂)

Soy protein concentrate (SPC) is a cost-effective alternative to fish meal (FM) in aquaculture, but its deficiency in essential amino acids, particularly methionine, limits its application. This study evaluated the effects of methionine supplementation on growth, liver and intestinal health, and muscle quality in hybrid sturgeon (Acipenser baerii ♀ × A. schrenckii ♂) fed SPC-based diets. Four diets were formulated: an FM control diet, and SPC diets supplemented with 0% (M0), 0.25% (M2.5), and 0.50% (M5) methionine. Replacing FM with SPC without methionine (M0) significantly reduced weight gain and the protein efficiency ratio (PER) while increasing the feed conversion ratio (FCR) and hepatic lipid accumulation. Methionine supplementation (M5) restored growth performance, the PER, and muscle texture to levels comparable to the FM group. Intestinal enzyme activities (lipase and trypsin), villus height, and goblet cell counts significantly improved in the M5 group. Gene expression analysis showed that M5 upregulated tight junction genes (claudin1, occludin) and anti-inflammatory genes (tgfβ, lysozyme) while reducing pro-inflammatory cytokines (il1β, il8). In the liver, M5 reduced oxidative stress markers such as malondialdehyde (MDA) and improved antioxidant enzyme activities (SOD, CAT) while optimizing lipid metabolism, as evidenced by lower triglyceride (TG) and total cholesterol (TC) levels. Muscle quality analysis showed that M5 significantly increased muscle hardness, chewiness, and fiber density compared to M0. In conclusion, methionine supplementation at 0.50% effectively mitigates the negative effects of SPC, improving growth, liver and intestinal health, and muscle quality in hybrid sturgeon.

Caco2/HT-29 In Vitro Cell Co-Culture: Barrier Integrity, Permeability, and Tight Junctions' Composition During Progressive Passages of Parental Cells

Epithelial linings are crucial for the maintenance of physiological barriers. The intestinal epithelial barrier (IEB) consists of enterocytes through tight junctions and mucus-secreting cells and can undergo physiological modifications throughout life. To reproduce as closely as possible the IEB main features over time, in vitro co-cultures of Caco2/HT-29 70/30 formed by parental Caco2 and HT-29 cells sub-cultivated for more than 40 passages were set up. The measurements of the transepithelial electrical resistance (TEER) identified two populations: physiological TEER co-cultures (PC) with values > 50 Ωcm2 formed by parental cells with fewer than 40 passages, and leaky TEER co-cultures (LC) with values < 50 Ωcm2 formed by parental cells with more than 40 passages. In LC, paracellular permeability increased in parallel. By immunofluorescence and Western blot analysis, an increase in claudin 2 was observed in LC vs. PC, with no differences in occludin expression. MUC-2 immunoreactivity was stronger in PC than in LC. LC also showed an enhanced vulnerability to TNFα+IFN-γ. These results reproduce the main morpho-functional modifications reported in the human leaky/aged gut and support the usefulness of our in vitro cell model for studying the molecular processes underlying these modifications and testing drug/nutraceutical treatments to ameliorate leaky gut aging.

The relationship between amino acids and gastroesophageal reflux disease: evidence from a mendelian randomization analysis combined with a meta-analysis

Background

Gastroesophageal Reflux Disease (GERD), a prevalent gastrointestinal disorder globally, exhibits variable prevalence across regions, with higher frequencies observed in Western nations and lower in Asian countries. Key contributing factors encompass unhealthy eating patterns, tobacco use, consumption of alcohol, excess weight, and obesity, along with health conditions such as gestation and diabetes. Common manifestations include heartburn and a burning discomfort behind the breastbone, which, without appropriate management, can progress to more severe issues like esophagitis and Barrett's esophagus. Approaches to management and prevention primarily involve modifications in lifestyle, pharmacotherapy, and surgical interventions when deemed necessary. Utilizing Omics Mendelian Randomization (OMR) to investigate the causative links between genetic variants and diseases provides insights into the biological underpinnings of gastroesophageal reflux diseasec. It aids in pinpointing novel targets for therapy. The influence of amino acids in gastroesophageal reflux disease demonstrates the complexity, having the potential to both mitigate and intensify symptoms, underscoring the significance of personalized nutrition and therapeutic strategies.

Methods

This study is based on the omics mendelian randomization method, coupled with meta-analysis techniques, to enhance the precision of the research findings. Furthermore, a reverse validation procedure was implemented to validate the association between the positive findings and disease outcomes further. Throughout the study, multiple correction measures were employed to ensure the accuracy and reliability of the results.

Results

Based on our research methodology, we have ultimately discovered that glutamate exacerbates gastroesophageal reflux disease, increasing its risk. The data supporting this includes analysis of 20 amino acids and outcomes from the Finnish database, which showed that glutamate had an odds ratio (OR) for gastroesophageal reflux disease risk of 1.175(95% confidence interval (CI): 1.000 ~ 1.380, P = 0.05), and a beta value of 0.161. Analysis with outcomes from the UK database indicated that glutamate had an OR for gastroesophageal reflux disease risk of 1.399(95% CI: 1.060 ~ 1.847, P = 0.018) and a beta value of 0.336. After conducting a meta-analysis of the MR results and applying multiple corrections, the combined OR of glutamate for gastroesophageal reflux disease risk was 1.227 (95% CI: 1.068 ~ 1.411 P = 0.043); the beta values of the three primary MR outcomes were consistent in direction. Building on the positive results, reverse validation with outcome data from two different database sources for glutamate showed: in the Finngen database, with gastroesophageal reflux disease as the exposure, the Inverse Variance Weighted (IVW) method resulted in a P-value of 0.059; in the IEU database under the same condition, the IVW P-value was 1.433.

Conclusions

Glutamate may increase the risk and exacerbate the progression of gastroesophageal reflux disease through mechanisms such as impacting the nervous system and promoting inflammatory responses. Delving into the role of glutamate in gastroesophageal reflux disease enriches our understanding of the disease's biological mechanisms and may offer new strategies for clinical treatment and nutritional management. This insight can aid in developing healthier dietary plans, thereby benefiting patients.

Deciphering the tripartite interaction of urbanized environment, gut microbiome and cardio-metabolic disease

The world is experiencing a sudden surge in urban population, especially in developing Asian and African countries. Consequently, the global burden of cardio-metabolic disease (CMD) is also rising owing to gut microbiome dysbiosis due to urbanization factors such as mode of birth, breastfeeding, diet, environmental pollutants, and soil exposure. Dysbiotic gut microbiome indicated by altered Firmicutes to Bacteroides ratio and loss of beneficial short-chain fatty acids-producing bacteria such as Prevotella, and Ruminococcus may disrupt host-intestinal homeostasis by altering host immune response, gut barrier integrity, and microbial metabolism through altered T-regulatory cells/T-helper cells balance, activation of pattern recognition receptors and toll-like receptors, decreased mucus production, elevated level of trimethylamine-oxide and primary bile acids. This leads to a pro-inflammatory gut characterized by increased pro-inflammatory cytokines such as tumour necrosis factor-α, interleukin-2, Interferon-ϒ and elevated levels of metabolites or metabolic endotoxemia due to leaky gut formation. These pathophysiological characteristics are associated with an increased risk of cardio-metabolic disease. This review aims to comprehensively elucidate the effect of urbanization on gut microbiome-driven cardio-metabolic disease. Additionally, it discusses targeting the gut microbiome and its associated pathways via strategies such as diet and lifestyle modulation, probiotics, prebiotics intake, etc., for the prevention and treatment of disease which can potentially be integrated into clinical and professional healthcare settings.

Pathogenesis and treatment of colitis-associated colorectal cancer: Insights from Traditional Chinese Medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Inflammatory Bowel Disease (IBD) is an inflammatory intestinal disease, and with prolonged illness duration, the annual risk of IBD progressing to colitis-associated colorectal cancer (CAC) gradually increases. In recent years, there has been a noticeable trend towards the application of traditional Chinese medicine (TCM) in the treatment of CAC.

AIM OF THIS REVIEW

This comprehensive review summarizes the pathogenesis of CAC and details the therapeutic benefits of TCM in treating CAC, including various TCM prescriptions and ingredients, establishing the theoretical foundation for the application of TCM in CAC treatment.

METHODS

We assessed literature published before March 24, 2024, from several databases, including Web of Science, PubMed, Scopus and Google Scholar. The keywords used include "traditional Chinese medicine", "traditional Chinese medicine prescriptions", "traditional Chinese medicine ingredients", "herbal medicine", "colitis-associated colorectal cancer", "inflammatory bowel disease", "colorectal cancer" and "colitis-cancer transformation". We conducted a comprehensive collection and collation of pertinent scientific articles from various databases, focusing on the efficacy of TCM in the prevention and treatment of "colitis-cancer transformation".

RESULTS

This paper provides a concise summary and thorough analysis of twenty-eight prescriptions and ingredients of TCM for the prevention and treatment of CAC, based on existing experimental and clinical research. There are positive signs that TCM can effectively prevent and treat the "colitis-cancer transformation" through repairing the intestinal mucosal barrier, correcting intestinal flora imbalance, and regulating intestinal immune responses.

CONCLUSION

TCM possesses comprehensive regulatory advantages that are multifaceted, multilevel, and multitarget. It has a definite curative effect in the prevention and treatment of CAC. It is essential to enhance the clinical efficacy of TCM in the prevention and treatment of CAC based on syndrome differentiation and treatment, with the assistance of modern medicine.

Towards Improved Bioavailability of Cereal Inositol Phosphates, Myo-Inositol and Phenolic Acids

Cereals are among the foods rich in myo-inositol hexakisphosphate (phytic acid, IP6), lower myo-inositol phosphates (IPx), a wide range of phenolic compounds, as well as vitamins, minerals, oligosaccharides, phytosterols and para-aminobenzoic acid, and are attributed with multiple bioactivities, particularly associated with the prevention of metabolic syndrome and colon cancer. The bran fraction of wheat, maize, brown rice and other cereals contains high levels of phytate, free and total phenolics, and endogenous enzymes such as amylases, phytase, xylanase, β-glucanase and feruloyl esterase, whose activities can be increased by germination. The preliminary steps of digestion begin in the oral cavity where substrates for the action of endogenous cereal and salivary enzymes start to be released from the food matrix. IP6 released from phytate complexes with arabinoxylans, starch and protein bodies would eventually enhance the absorption of nutrients, including phenolics, by regulating tight junctions and, together with ferulic acid (FA), would maintain cell barrier integrity and epithelial antibacterial immunity. In addition, both IP6 and FA exert potent and complementary antioxidant effects, while FA together with IPx generated through advanced hydrolysis of IP6 by endogenous and microbial phytases may affect digestive enzyme activity and incretin secretion, resulting in modulated insulin and glucagon release and prevention of various diabetic complications. Contrary to widespread negative attitudes towards phytate, in this review, we present the strategy of selecting cereals with high phytate and phenolic content, as well as high endogenous phytase, feruloyl esterase and endoxylanase activities, to produce value-added health-promoting foods. The advanced hydrolysis of phytate and phenolic compounds by cereal and/or microbial enzymes would generate substantial amounts of "enzymatically generated inositol" (EGI), including IP6, IPx and myo-inositol, the compounds that, together with free FA, provide enhanced bioavailability of cereal nutrients through multiple synergistic effects not previously realised.

Sleep deprivation-induced shifts in gut microbiota: Implications for neurological disorders

Sleep deprivation is a prevalent issue in contemporary society, with significant ramifications for both physical and mental well-being. Emerging scientific evidence illuminates its intricate interplay with the gut-brain axis, a vital determinant of neurological function. Disruptions in sleep patterns disturb the delicate equilibrium of the gut microbiota, resulting in dysbiosis characterized by alterations in microbial composition and function. This dysbiosis contributes to the exacerbation of neurological disorders such as depression, anxiety, and cognitive decline through multifaceted mechanisms, including heightened neuroinflammation, disturbances in neurotransmitter signalling, and compromised integrity of the gut barrier. In response to these challenges, there is a burgeoning interest in therapeutic interventions aimed at restoring gut microbial balance and alleviating neurological symptoms precipitated by sleep deprivation. Probiotics, dietary modifications, and behavioural strategies represent promising avenues for modulating the gut microbiota and mitigating the adverse effects of sleep disturbances on neurological health. Moreover, the advent of personalized interventions guided by advanced omics technologies holds considerable potential for tailoring treatments to individualized needs and optimizing therapeutic outcomes. Interdisciplinary collaboration and concerted research efforts are imperative for elucidating the underlying mechanisms linking sleep, gut microbiota, and neurological function. Longitudinal studies, translational research endeavours, and advancements in technology are pivotal for unravelling the complex interplay between these intricate systems.

Effects of POPs-induced SIRT6 alteration on intestinal mucosal barrier function: A comprehensive review

Persistent organic pollutants (POPs) are pervasive organic chemicals with significant environmental and ecological ramifications, extending to adverse human health effects due to their toxicity and persistence. The intestinal mucosal barrier, a sophisticated defense mechanism comprising the epithelial layer, mucosal chemistry, and cellular immunity, shields the host from external threats and fosters a symbiotic relationship with intestinal bacteria. Sirtuin 6 (SIRT6), a sirtuin family member, is pivotal in genome and telomere stability, inflammation regulation, and metabolic processes. Result shows POPs have been implicated in the intestinal diseases, particularly in intestinal barrier dysfunction, through mechanisms such as cellular damage, epigenetic alterations, inflammation, microbiota changes, and metabolic disruptions. While the impact of SIRT6 expression changes on intestinal barrier functions has been reviewed, the mechanisms linking POPs to SIRT6 remain elusive. This review summarized the latest research results on the effects of POPs on intestinal barrier, discussed the role of SIRT6 from multiple mechanism perspectives, proposed new research directions on POPs, SIRT6 and intestinal health, and explored the therapeutic potential of SIRT6.

Impact of Epithelial Claudin-4 and Leukotriene B4 Receptor 2 in Normoganglionic Hirschsprung Disease Colon on Post Pull-through Enterocolitis

PURPOSE

To investigate whether Leukotriene B4 receptor 2 (BLT-2), an upstream regulator of tight junction protein (TJP) Claudin-4, and TJPs could be etiologic factors in Hirschsprung-associated enterocolitis (HAEC) after pull-through (PT) for Hirschsprung disease (HD).

METHODS

Normoganglionic colon (HD-N) and aganglionic rectum (HD-A) specimens from rectal/rectosigmoid (R/RS) or descending/transverse (D/T) HD were assessed using quantitative polymerase chain reaction (qPCR) for Occludin, TJP-1, TJP-2, Junctional adhesion molecule (JAM)-1, JAM-2, Claudin-1, Claudin-3, Claudin-4, and BLT-2 and immunoblotting for Claudin-4 using fresh specimens obtained intraoperatively (2021-2024; n = 17; R/RS = 15 and D/T = 2). Claudin-4 immunohistochemistry was also evaluated quantitatively using preserved (n = 29; R/RS = 20 and D/T = 9; 2009-2021) and fresh HD specimens for comparison with anorectal malformation patients having colostomy closure as controls (n = 42) and between HD-A versus HD-N, R/RS versus D/T, and HAEC (+) versus HAEC (-). Technically inadequate or transitional zone PT were excluded.

RESULTS

Subjects were 123 PT cases. Mean ages at PT/colostomy closure (years) were R/RS: 2.7 ± 2.9, D/T: 1.6 ± 2.2, and controls: 1.4 ± 0.7. Postoperative HAEC occurred 18 times in 14 PT cases (grade I = 5, grade II = 13). Post-PT HAEC was significantly more frequent in D/T (50.0% versus 6.4%; p < 0.001); Claudin-4 was significantly lower in HD-N from post-PT HAEC cases, especially D/T (p < 0.05) on immunohistochemistry. Claudin-4 was significantly lower in HD-N/HD-A compared with controls on immunoblotting (p < 0.05) and immunohistochemistry (p < 0.001). qPCR showed TJP-1, TJP-2, JAM-1, JAM-2, Claudin-4, and BLT-2 were significantly lower in HD-N/HD-A compared with controls.

CONCLUSIONS

Lower Claudin-4 and BLT2 in post-PT HAEC HD-N (especially D/T) suggests generalized epithelial barrier derangement with possible etiologic implications for HAEC.

LEVEL OF EVIDENCE

Ⅱ.

Faecal intestinal permeability and intestinal inflammatory markers in older adults with age-related disorders: A systematic review and meta-analysis

This systematic review and meta-analysis appraised previous findings to uncover potential faecal intestinal permeability and intestinal inflammatory markers in older adults. A comprehensive literature search led to the identification of ten eligible studies with findings of potential faecal intestinal permeability (zonulin and alpha-1-antitrypsin) and intestinal inflammatory markers [calprotectin, lactoferrin and neutrophil gelatinase-associated lipocalin (NGAL)]. Most of the cases (n > 2) [Parkinson's disease (PD) and Alzheimer's disease (AD)] exhibited higher faecal alpha-1-antitrypsin, zonulin and calprotectin levels. The present meta-analysis confirmed significantly higher faecal alpha-1-antitrypsin in older persons with PD compared to non-PD [MD = 22.92 mg/dL; 95 % CI = 14.02-31.81, p < 0.00001; I2 = 0 % (p = 0.73)]. There was, however, no significant difference in faecal zonulin between PD and non-PD individuals [MD = 26.88 ng/mL; 95 % CI = -29.26-83.01, p = 0.35; I2 = 94 % (p < 0.0001)]. Meanwhile, faecal calprotectin was higher in older adults with GI symptoms, multiple system atrophy (MSA) or PD than the healthy controls [MD = 9.51 μg/g; 95 % CI = 0.07-18.95, p = 0.05; I2 = 84 % (p < 0.00001)]. Altogether, faecal calprotectin appears to be a potential intestinal inflammatory marker whereas previous findings on faecal alpha-1-antitrypsin as an intestinal permeability marker remain limited and require further validation.

Gut microbiota biotransformation of drug glucuronides leading to gastrointestinal toxicity: Therapeutic potential of bacterial β-glucuronidase inhibition in mycophenolate-induced enteropathy

AIMS

Drug-induced enteropathy is often associated with the therapeutic use of certain glucuronidated drugs. One such drug is mycophenolic acid (MPA), a well-established immunosuppressant of which gastrointestinal adverse effects are a major concern. The role of bacterial β-glucuronidase (β-G) from the gut microbiota in MPA-induced enteropathy has recently been discovered. Bacterial β-G hydrolyzes MPAG, the glucuronide metabolite of MPA excreted in the bile, leading to the digestive accumulation of MPA that would favor in turn these adverse events. We therefore hypothesized that taming bacterial β-G activity might reduce MPA digestive exposure and prevent its toxicity.

MAIN METHODS

By using a multiscale approach, we evaluated the effect of increasing concentrations of MPA on intestinal epithelial cells (Caco-2 cell line) viability, proliferation, and migration. Then, we investigated the inhibitory properties of amoxapine, a previously described bacterial β-G inhibitor, by using molecular dynamics simulations, and evaluated its efficiency in blocking MPAG hydrolysis in an Escherichia coli-based β-G activity assay. The pharmacological effect of amoxapine was evaluated in a mouse model.

KEY FINDINGS

We observed that MPA impairs intestinal epithelial cell homeostasis. Amoxapine efficiently blocks the hydrolysis of MPAG to MPA and significantly reduces digestive exposure to MPA in mice. As a result, administration of amoxapine in MPA-treated mice significantly attenuated gastrointestinal lesions.

SIGNIFICANCE

Collectively, these results suggest that the digestive accumulation of MPA is involved in the pathophysiology of MPA-gastrointestinal adverse effects. This study provides a proof-of-concept of the therapeutic potential of bacterial β-G inhibitors in glucuronidated drug-induced enteropathy.

Role of Extracellular Vesicles in Crohn's Patients on Adalimumab Who Received COVID-19 Vaccination

Crohn's disease (CD) is a type of inflammatory bowel disease (IBD) affecting the gastrointestinal tract that can also cause extra-intestinal complications. Following exposure to the mRNA vaccine BNT162b2 (Pfizer-BioNTech) encoding the SARS-CoV-2 Spike (S) protein, some patients experienced a lack of response to the biological drug Adalimumab and a recrudescence of the disease. In CD patients in progression, resistant to considered biological therapy, an abnormal increase in intestinal permeability was observed, more often with a modulated expression of different proteins such as Aquaporin 8 (AQP8) and in tight junctions (e.g., ZO-1, Claudin1, Claudin2, Occludin), especially during disease flares. The aim of this study is to investigate how the SARS-CoV-2 vaccine could interfere with IBD therapy and contribute to disease exacerbation. We investigated the role of the SARS-CoV-2 Spike protein, transported by extracellular vesicles (EVs), and the impact of various EVs components, namely, exosomes (EXOs) and microvesicles (MVs), in modulating the expression of molecules involved in the exacerbation of CD, which remains unknown.

Clostridium butyricum regulates intestinal barrier function via trek1 to improve behavioral abnormalities in mice with autism spectrum disorder

BACKGROUND

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental disorder that has been found to be associated with dysregulation of gastrointestinal functions and gut microbial homeostasis (the so-called "gut-brain axis"). ASD is often accompanied by poor performances in social interaction and repetitive behaviors. Studies on the gut-brain axis provide novel insights and candidate targets for ASD therapeutics and diagnosis. Based on the ASD mice model, this work aims to reveal the mechanisms behind the interaction of intestinal barrier function and probiotics in ASD mouse models.

RESULTS

We found an altered intestinal barrier in both BTBR T+ Itpr3tf/J (BTBR) and valproic acid (VPA) mice, including increased intestinal permeability, decreased expression of intestinal tight junction proteins (claudin1, claudin3, and occludin), and increased levels of IL-6, TNF-α, and IFN-γ. Based on intestinal microbial alternation, C. butyricum can drive reduced expression of histone deacetylases 1 (HDAC1) and enhanced intestinal barrier function, significantly promoting behavioral abnormalities of ASD in BTBR mice. In parallel, we confirmed that C. butyricum was involved in the regulation of intestinal function by the Trek1 channel, indicating that it is a target of C. butyricum/butyric acid to improve intestinal barrier function in ASD mice.

CONCLUSIONS

Our finding provides solid evidence for the gut microbiota involved in ASD through the brain-gut axis. In addition, the probiotics C. butyricum hold promise to improve gut health and ameliorate behavioral abnormalities associated with ASD.

Hydroethanolic Extract of Lepidium apetalum Willdenow Alleviates Dextran Sulfate Sodium-Induced Colitis by Enhancing Intestinal Barrier Integrity and Inhibiting Oxidative Stress and Inflammasome Activation

The prevalence of ulcerative colitis (UC) has surged in Asian nations recently. The limitations of traditional drug treatments, including biologics, have spurred interest in herbal medicines for managing UC. This study aimed to elucidate the protective mechanisms of hydroethanolic extract from Lepidium apetalum Willdenow (LWE) on intestinal integrity and inflammation in a dextran sodium sulfate (DSS)-induced colitis model of inflammatory bowel disease (IBD). Using UPLC-MS/MS analysis, eleven phytochemicals were identified in LWE, including catechin, vicenin-2, and quercetin. LWE restored transepithelial electrical resistance (TEER) and reduced paracellular permeability in IL-6-stimulated Caco-2 cells, increasing the expression of the tight junction proteins ZO-1 and occludin. LWE treatment alleviated DSS-induced colitis symptoms in mice, reducing body weight loss, disease activity index values, and spleen size, while improving colon length and reducing serum FITC-dextran levels, indicating enhanced intestinal barrier function. LWE suppressed NLRP3 inflammasome activation, reducing protein levels of pro-caspase-1, cleaved-caspase-1, ASC, and NLRP3, as well as mRNA levels of IL-1β, IL-6, and TNF-α. LWE treatment upregulated activity and mRNA levels of the antioxidant enzymes SOD1 and NQO1. Additionally, LWE modulated the Nrf2/Keap1 pathway, increasing p-Nrf2 levels and decreasing Keap1 levels. LWE also restored goblet cell numbers and reduced fibrosis in DSS-induced chronic colitis mice, increasing gene and protein expressions of ZO-1 and occludin. In summary, LWE shows promise as a therapeutic intervention for reducing tissue damage and inflammation by enhancing intestinal barrier function and inhibiting colonic oxidative stress-induced inflammasome activation.

Exploring the therapeutic potential of porphyran extracted from Porphyra haitanensis in the attenuation of DSS-induced intestinal inflammation

Ulcerative colitis is a chronic, spontaneous inflammatory bowel disease that primarily affects the colon. This study aimed to explore how Porphyra haitanensis porphyran (PHP) modulates the immune response and the associated mechanisms that alleviate dextran sulphate sodium-induced colitis in mice. Histological assessments via H&E staining and AB-PAS staining revealed that PHP intervention partially restored the number of goblet cells and improved intestinal mucosal function. Immunohistochemical and Western blot analyses of claudin-1, occludin, and MUC-2 demonstrated that PHP could repair the intestinal barrier and reduce colon damage by upregulating the expression of these proteins. PHP intervention was associated with a decrease in pro-inflammatory cytokine expression and an increase in anti-inflammatory cytokine expression. Moreover, the expression of proteins involved in intestinal immune homing, such as CCR-9, CCL-25, MAdCAM-1, and α4β7, was significantly suppressed in response to PHP treatment. Conversely, PHP upregulates the expression of CD40 and TGF-β1, both of these can promote healing and reduce inflammation in the gut lining. This study demonstrates that PHP can ameliorate ulcerative colitis by enhancing the intestinal barrier and modulating immune responses. These findings offer valuable insights into the potential utility of P. haitanensis as a promising natural product for managing ulcerative colitis.

Gingipain-carrying outer membrane vesicles from Porphyromonas gingivalis cause barrier dysfunction of Caco-2 cells by releasing gingipain into the cytosol

Ingestion of Porphyromonas gingivalis, a periodontal pathogen, disrupts the intestinal barrier in mice. However, the involvement of outer membrane vesicles (OMVs) secreted from P. gingivalis in the destruction of the intestinal barrier remains unclear. In this study, we tested the hypothesis that OMVs carrying gingipains, the major cysteine proteases produced by P. gingivalis, affects the intestinal barrier function. OMVs increased the permeability of the Caco-2 cell monolayer, a human intestinal epithelial cell line, accompanied by degradation of the tight junction protein occludin. In contrast, OMVs prepared from mutant strains devoid of gingipains failed to induce intestinal barrier dysfunction or occludin degradation in Caco-2 cells. A close histological examination revealed the intracellular localization of gingipain-carrying OMVs. Gingipain activity was detected in the cytosolic fraction of Caco-2 cells after incubation with OMVs. These results suggest that gingipains were internalized into intestinal cells through OMVs and transported into the cytosol, where they then directly degraded occludin from the cytosolic side. Thus, P. gingivalis OMVs might destroy the intestinal barrier and induce systemic inflammation via OMV itself or intestinal substances leaked into blood vessels, causing various diseases.

Administration of Gracilariopsis lemaneiformis polysaccharide attenuates cisplatin-induced inflammation and intestinal mucosal damage in colon-26 carcinoma tumor-bearing mice

BACKGROUND

Our preliminary research revealed that the polysaccharide GP90 from Gracilariopsis lemaneiformis enhanced the antitumor effect of cisplatin, indicating that GP90 may increase the chemotherapeutic sensitivity. However, it is still necessary to fully understand whether GP90 can also improve the intestinal barrier dysfunction and systemic inflammation induced by cisplatin.

RESULTS

GP90 has been demonstrated to inhibit the excessive release of nitirc oxide, interleukin (IL)-6, IL-1β and tumor necrosis factor (TNF)-α induced by lipopolysaccharide in RAW264.7 cells. In vivo, GP90 effectively ameliorated the decrease in the serum CD4+ /CD8+ T-cell ratio induced by cisplatin and significantly reduced the increase in the inflammatory cytokines, CD4+ Foxp3+ , CD4+ granzyme B+ and CD4+ TNF-α induced by cisplatin. Furthermore, when combined with cisplatin, GP90 increases the protein expression levels of mucin-2 and zonula occludens-1 in the mouse small intestine. Additionally, GP90 combined with cisplatin has a modulatory effect on the intestinal microbiota by elevating the Firmicutes-to-Bacteroidetes ratio and the relative abundance of beneficial microorganisms (Lachnospiraceae bacterium), at the same time as reducing the abundance of cisplatin specific Bacteroides acidifaciens and elevating the content of butyric acid and isobutyric acid.

CONCLUSION

Collectively, these findings indicate that GP90 potentially mitigates inflammation and protects the intestinal barrier in tumor-bearing organisms undergoing chemotherapy. © 2024 Society of Chemical Industry.

Cell Surface Modification-Mediated Primary Intestinal Epithelial Cell Culture Platforms for Assessing Host-Microbiota Interactions

Background: Intestinal epithelial cells (IECs) play a crucial role in regulating the symbiotic relationship between the host and the gut microbiota, thereby allowing them to modulate barrier function, mucus production, and aberrant inflammation. Despite their importance, establishing an effective ex vivo culture method for supporting the prolonged survival and function of primary IECs remains challenging. Here, we aim to develop a novel strategy to support the long-term survival and function of primary IECs in response to gut microbiota by employing mild reduction of disulfides on the IEC surface proteins with tris(2-carboxyethyl)phosphine. Methods: Recognizing the crucial role of fibroblast-IEC crosstalk, we employed a cell surface modification strategy, establishing layer-to-layer contacts between fibroblasts and IECs. This involved combining negatively charged chondroitin sulfate on cell surfaces with a positively charged chitosan thin film between cells, enabling direct intercellular transfer. Validation included assessments of cell viability, efficiency of dye transfer, and IEC function upon lipopolysaccharide (LPS) treatment. Results: Our findings revealed that the layer-by-layer co-culture platform effectively facilitates the transfer of small molecules through gap junctions, providing vital support for the viability and function of primary IECs from both the small intestine and colon for up to 5 days, as evident by the expression of E-cadherin and Villin. Upon LPS treatment, these IECs exhibited a down-regulation of Villin and tight junction genes, such as E-cadherin and Zonula Occludens-1, when compared to their nontreated counterparts. Furthermore, the transcription level of Lysozyme exhibited an increase, while Mucin 2 showed a decrease in response to LPS, indicating responsiveness to bacterial molecules. Conclusions: Our study provides a layer-by-layer-based co-culture platform to support the prolonged survival of primary IECs and their features, which is important for understanding IEC function in response to the gut microbiota.

Jingfang granules ameliorate inflammation and immune disorders in mice exposed to low temperature and high humidity by restoring the dysregulation of gut microbiota and fecal metabolites

The dramatic changes in global climate on human health have been extremely severe. The immune disorder caused by low temperature and high humidity (LTHH) have become a severe public health issue. Clinically, Jingfang granule (JF) has the effect of dispelling cold and eliminating dampness, and is widely used in the treatment of cold caused by wind and cold, autoimmune diseases, and COVID-19 with cold-dampness stagnating in the lung pattern. Our study aims to elucidate the effect of JF on LTHH-induced immune disorders in mice as well as the underlying mechanisms. In this study, JF increased the spleen index, improved fecal character, repaired the intestinal barrier and alleviated intestinal inflammatory responses. Most importantly, JF ameliorated immune disorder in LTHH mice, which was manifested primarily by the significant increase in gdT, CD8+ Tcm, and CD8+ Tem cells, as well as the decrease in TH1, TH17, CD4+ Tem1, CD4+ Tem2, immature NK, mature NK cells, and M1-like macrophages. Interestingly, the JF treatment not only regulated the gut microbiota by decreasing the abundance of harmful bacteria, as well as up-regulating the abundance of beneficial bacteria, but also ameliorated the metabolic disorders by reversing the levels of fecal metabolites to normality. The results of the correlation analysis demonstrated a significant association among gut microbiota, fecal metabolites and immune cells. In addition, JF inhibited the TLR4/NF-κB/NLRP3 pathway in LTHH mice. In conclusion, our results suggested that JF alleviated inflammation and immune disorders in LTHH mice by restoring gut microbiota and fecal metabolism.

Biological Activities of p-Hydroxycinnamic Acids in Maintaining Gut Barrier Integrity and Function

It is well established that p-Hydroxycinnamic acids (HCAs), including ferulic, caffeic, sinapic, and p-coumaric acids, possess a characteristic phenylpropanoid C6-C3 backbone and account for about one-third of the phenolic compounds in our diet. HCAs are typically associated with various plant cell wall components, including mono-, di-, and polysaccharides, sterols, polyamines, glycoproteins, and lignins. Interestingly, enzymes produced by intestinal microbes liberate HCAs from these associations. HCAs are completely absorbed in their free form upon ingestion and undergo specific reactions upon absorption in the small intestine or liver. The gut epithelium, composed of intestinal epithelial cells (IECs), acts as a physical barrier against harmful bacteria and a site for regulated interactions between bacteria and the gut lumen. Thus, maintaining the integrity of the epithelial barrier is essential for establishing a physiochemical environment conducive to homeostasis. This review summarizes the protective effects of HCAs on the intestinal barrier, achieved through four mechanisms: preserving tight junction proteins (TJPs), modulating pro-inflammatory cytokines, exerting antioxidant activity, and regulating the intestinal microbiota.

Lactobacillus plantarum GX17 benefits growth performance and improves functions of intestinal barrier/intestinal flora among yellow-feathered broilers

Lactobacillus plantarum has recently been found to be a natural source feed additive bacteria with great advantages in food safety and animal welfare. Discovering novel strains with commercial application potentiation could benefit the local poultry industry, and in particular support Chinese farmers. In this study, we tested a recently isolated novel strain of Lactobacillus plantarum GX17 as a feed additive on the growth performance and intestinal barrier functions of 1-day-old Chinese yellow-feather chicks. As good as other commercial probiotics, feeding with Lactobacillus plantarum GX17 showed significant improvements in humoral immune responses and enhanced the immune effect after vaccination for either the Newcastle disease vaccine or the avian influenza vaccine. This study also found that feeding with Lactobacillus plantarum GX17 improved the feed-to-weight ratio and caused a significant increase of the villus length to crypt depth ratio. Furthermore, Lactobacillus plantarum GX17 significantly up-regulated the mRNA expression of CLDN, MUC2, and TLR2, all of which are jejunum-associated barrier genes, indicating an improvement of the intestinal barrier functions by enhancing the tight junction between epithelia cells. These results are comparable to the effects of feeding the commercial complex probiotics that improve the expression levels of CLDN, ocludin, MUC2, TLR2, and TLR4. In terms of maintaining intestinal health, commercial complex probiotics increased the relative abundance of Parabacteroides and Romboutsia, while Lactobacillus plantarum GX17 increased the relative abundance of Pseudoflavonifractor. Our data suggest that Lactobacillus plantarum GX17 could enhance the intestinal absorption of nutrients and therefore improve the growth performance of Chinese yellow-feather chicks. In conclusion, compared with the commercial complex probiotics, Lactobacillus plantarum GX17 has more positive effects on the growth performance and intestinal barrier function of yellow-feather chickens, and can be used as a feed additive.

Hydroethanolic Extract of Fritillariae thunbergii Bulbus Alleviates Dextran Sulfate Sodium-Induced Ulcerative Colitis by Enhancing Intestinal Barrier Integrity

The incidence of ulcerative colitis (UC), an inflammatory disorder of the gastrointestinal tract, has rapidly increased in Asian countries over several decades. To overcome the limitations of conventional drug therapies, including biologics for UC management, the development of herbal medicine-derived products has received continuous attention. In this study, we evaluated the beneficial effects of a hydroethanolic extract of Fritillariae thunbergii Bulbus (FTB) in a mouse model of DSS-induced UC. The DSS treatment successfully induced severe colonic inflammation and ulceration. However, the severity of colitis was reduced by the oral administration of FTB. Histopathological examination showed that FTB alleviated the infiltration of inflammatory cells (e.g., neutrophils and macrophages), damage to epithelial and goblet cells in the colonic mucosal layer, and fibrotic lesions. Additionally, FTB markedly reduced the gene expression of proinflammatory cytokines and extracellular matrix remodeling. Immunohistochemical analysis showed that FTB alleviated the decrease in occludin and zonula occludens-1 expression induced by DSS. In a Caco-2 monolayer system, FTB treatment improved intestinal barrier permeability in a dose-dependent manner and increased tight junction expression. Overall, FTB has potential as a therapeutic agent through the improvement of tissue damage and inflammation severity through the modulation of intestinal barrier integrity.

Expression of Cell-Adhesion Molecules in E. coli: A High Throughput Screening to Identify Paracellular Modulators

Cell-adhesion molecules (CAMs) are responsible for cell-cell, cell-extracellular matrix, and cell-pathogen interactions. Claudins (CLDNs), occludin (OCLN), and junctional adhesion molecules (JAMs) are CAMs' components of the tight junction (TJ), the single protein structure tasked with safeguarding the paracellular space. The TJ is responsible for controlling paracellular permeability according to size and charge. Currently, there are no therapeutic solutions to modulate the TJ. Here, we describe the expression of CLDN proteins in the outer membrane of E. coli and report its consequences. When the expression is induced, the unicellular behavior of E. coli is replaced with multicellular aggregations that can be quantified using Flow Cytometry (FC). Our method, called iCLASP (inspection of cell-adhesion molecules aggregation through FC protocols), allows high-throughput screening (HTS) of small-molecules for interactions with CAMs. Here, we focused on using iCLASP to identify paracellular modulators for CLDN2. Furthermore, we validated those compounds in the mammalian cell line A549 as a proof-of-concept for the iCLASP method.

Combined Supplementation of Clostridium butyricum and Bifidobacterium infantis Diminishes Chronic Unpredictable Mild Stress-Induced Intestinal Alterations via Activation of Nrf-2 Signaling Pathway in Rats

Exposure to long-term chronic unpredictable mild stress (CUMS) can cause redox imbalance and inflammation, which may affect the integrity of the gut barrier. The present study was conducted to investigate the effects of a probiotics bacterium mixture, including Clostridium butyricum (C. butyricum) and Bifidobacterium infantis (B. infantis), on the intestinal homeostasis in rats exposed to multiple low-intensity stressors for 28 days. The mechanism of CUMS-induced altered intestinal homeostasis was evaluated by focusing on the nuclear factor-E2-related factor-2 (Nrf-2) pathway. In contrast to the CUMS group, probiotic mixture supplementation significantly (p < 0.01) reversed the stress-induced elevated corticosterone level, protein and lipid oxidation, and increased enzymatic and non-enzymatic antioxidant levels, as well as upregulated Nrf-2/HO-1 pathway. Probiotics supplementation further significantly (p < 0.01) decreased the CUMS-induced inflammation, altered T-lymphocyte levels, and suppressed the protein expression of nuclear factor kappa B (NF-κB) in rat intestines. Improvement in histological changes and intestinal barrier integrity further validate the beneficial effects of probiotic mixtures on CUMS-induced altered intestinal morphology. In conclusion, our results suggest that the combination of C. butyricum and B. infantis significantly attenuated CUMS-induced oxidative stress, inflammation, and T-lymphocyte modulation by upregulating Nrf-2/HO-1 signaling and inhibiting NF-κB expression in rat intestine.

Gut microbiota composition is altered in a preclinical model of type 1 diabetes mellitus: Influence on gut steroids, permeability, and cognitive abilities

Sex steroid hormones are not only synthesized from the gonads but also by other tissues, such as the brain (i.e., neurosteroids) and colon (i.e., gut steroids). Gut microbiota can be shaped from sex steroid hormones synthesized from the gonads and locally interacts with gut steroids as in turn modulates neurosteroids. Type 1 diabetes mellitus (T1DM) is characterized by dysbiosis and also by diabetic encephalopathy. However, the interactions of players of gut-brain axis, such as gut steroids, gut permeability markers and microbiota, have been poorly explored in this pathology and, particularly in females. On this basis, we have explored, in streptozotocin (STZ)-induced adult female rats, whether one month of T1DM may alter (I) gut microbiome composition and diversity by 16S next-generation sequencing, (II) gut steroid levels by liquid chromatography-tandem mass spectrometry, (III) gut permeability markers by gene expression analysis, (IV) cognitive behavior by the novel object recognition (NOR) test and whether correlations among these aspects may occur. Results obtained reveal that T1DM alters gut β-, but not α-diversity. The pathology is also associated with a decrease and an increase in colonic pregnenolone and allopregnanolone levels, respectively. Additionally, diabetes alters gut permeability and worsens cognitive behavior. Finally, we reported a significant correlation of pregnenolone with Blautia, claudin-1 and the NOR index and of allopregnanolone with Parasutterella, Gammaproteobacteria and claudin-1. Altogether, these results suggest new putative roles of these two gut steroids related to cognitive deficit and dysbiosis in T1DM female experimental model. This article is part of the Special Issue on "Microbiome & the Brain: Mechanisms & Maladies".

The crosstalk between gut barrier impairment, mitochondrial dysfunction, and microbiota alterations in people living with HIV

Functional and structural damage of the intestinal mucosal barrier significantly contribute to translocation of gut microbial products into the bloodstream and are largely involved in HIV-1 associated chronic immune activation. This microbial translocation is largely due to a progressive exhaustion of intestinal macrophage phagocytic function, which leads to extracellular accumulation of microbial derived components and results in HIV-1 disease progression. This study aims to better understand whether the modulation of gut microbiota promotes an intestinal immune restoration in people living with HIV (PLWH). Long-term virologically suppressed PLWH underwent blood, colonic, and fecal sampling before (T0) and after 6 months (T6) of oral bacteriotherapy. Age- and gender-matched uninfected controls (UC) were also included. 16S rRNA gene sequencing was applied to all participants' fecal microbiota. Apoptosis machinery, mitochondria, and apical junctional complex (AJC) morphology and physiological functions were analyzed in gut biopsies. At T0, PLWH showed a different pattern of gut microbial flora composition, lower levels of occludin (p = 0.002) and zonulin (p = 0.01), higher claudin-2 levels (p = 0.002), a reduction of mitochondria number (p = 0.002), and diameter (p = 0.002), as well as increased levels of lipopolysaccharide (LPS) (p = 0.018) and cCK18 (p = 0.011), compared to UC. At T6, an increase in size (p = 0.005) and number (p = 0.008) of mitochondria, as well as amelioration in AJC structures (p < 0.0001) were observed. Restoration of bacterial richness (Simpson index) and biodiversity (Shannon index) was observed in all PLWH receiving oral bacteriotherapy (p < 0.05). Increased mitochondria size (p = 0.005) and number (p = 0.008) and amelioration of AJC structure (p < 0.0001) were found at T6 compared to T0. Moreover, increased occludin and zonulin concentration were observed in PLWH intestinal tracts and decreased levels of claudin-2, LPS, and cCK18 were found after oral bacteriotherapy (T0 vs. T6, p < 0.05 for all these measures). Oral bacteriotherapy supplementation might restore the balance of intestinal flora and support the structural and functional recovery of the gut mucosa in antiretroviral therapy treated PLWH.

Effects of short-chain fatty acids on intestinal function in an enteroid model of hypoxia

The healthy GI tract is physiologically hypoxic, but this may be perturbed by certain acute and chronic stressors that reduce oxygen availability systemically. Short-chain fatty acids have been shown to have beneficial effects on intestinal barrier function and inflammation. Therefore, our objective was to see whether short-chain fatty acids (SCFA) would improve GI barrier function, reduce production of pro-inflammatory cytokines, and increase the expression of genes regulating GI barrier function in enteroids exposed to hypoxia. Human duodenal enteroid monolayers were placed under hypoxia (1.0% O₂) for 72 h with either 24, or 48 h pre-treatment with a high acetate ratio of SCFA's or high butyrate ratio or placed under hypoxia concurrently. Transepithelial electrical resistance (TEER) increased with SCFA pre-treatment, especially 48 h of pre-treatment and this was maintained through the first 48 h of hypoxia while cells saw barrier function dramatically decrease by 72 h of hypoxia exposure. Inflammatory protein secretion largely decreased with exposure to hypoxia, regardless of SCFA pre-treatment. Gene expression of several genes related to barrier function were decreased with exposure to hypoxia, and with concurrent and 24 h SCFA pre-treatment. However, 48 h SCFA pre-treatment with a high butyrate ratio increased expression of several metabolic and differentiation related genes. Overall, pre-treatment or concurrent treatment with SCFA mixtures were not able to overcome the negative impacts of hypoxia on intestinal function and cells ultimately still cannot be sustained under hypoxia for 72 h. However, 48 h pre-treatment maintains TEER for up to 48 h of hypoxia while upregulating several metabolic genes.

Redox and Metabolic Regulation of Intestinal Barrier Function and Associated Disorders

The intestinal epithelium forms a physical barrier assembled by intercellular junctions, preventing luminal pathogens and toxins from crossing it. The integrity of tight junctions is critical for maintaining intestinal health as the breakdown of tight junction proteins leads to various disorders. Redox reactions are closely associated with energy metabolism. Understanding the regulation of tight junctions by cellular metabolism and redox status in cells may lead to the identification of potential targets for therapeutic interventions. In vitro and in vivo models have been utilized in investigating intestinal barrier dysfunction and in particular the free-living soil nematode, Caenorhabditis elegans, may be an important alternative to mammalian models because of its convenience of culture, transparent body for microscopy, short generation time, invariant cell lineage and tractable genetics.

Electrical cell-substrate impedance sensing (ECIS) as a tool to study microbial-cell interactions

ECIS is an impedance-based method to study the cellular responses to a stimulus. Manipulating the alternating current frequencies in ECIS helped reveal the adherent monolayer properties, including morphology, spreading, proliferation, changes in junctional proteins and barrier integrity. Our objective in the current study was to understand the progression of Pseudomonas infection in the airway epithelial cells using ECIS. The study also aimed at understanding the feasibility of using ECIS to study drug interactions on monolayer barrier functions. A significant reduction in impedance was noted in response to Pseudomonas infection, indicating loss of morphology and cell viability. At frequencies lower than 2000 Hz, a gradual decrease in impedance was observed during the early phase of infection, indicating a loss of junctional integrity. On the other hand, at frequencies above 16,000 Hz, a reduction in impedance was observed only during the later phases of infection. This suggested that Pseudomonas reduced the barrier integrity of cells during the early phase to gain access into the cells. Changes in cell morphology and subsequent loss of cell viability occur during the later phases of infection. Azithromycin is known to increase the barrier integrity of the monolayer (by increasing the expression of junctional proteins). We observed that pretreatment of A549 monolayers with azithromycin inhibited the progression of infection by Pseudomonas ATCC 27853 and delayed the infection of the epithelium by S373 clinical isolate. Our study is the report on the mechanism of bacterial infection progression using ECIS. It can be observed that an improvement in the barrier integrity reduces the susceptibility to bacterial infections. ECIS was demonstrated to be an effective tool for studying microbial-cell interactions and the role of drug molecules.

Therapeutic effects and mechanisms of plant-derived natural compounds against intestinal mucositis

Intestinal mucositis is a clinically related adverse reaction of antitumor treatment. Majority of patients receiving high-dose chemical therapy, radiotherapy, and bone-marrow transplant suffer from intestinal mucositis. Clinical manifestations of intestinal mucositis mainly include pain, body-weight reduction, inflammatory symptom, diarrhea, hemoproctia, and infection, which all affect regular nutritional input and enteric function. Intestinal mucositis often influences adherence to antitumor treatment because it frequently restricts the sufferer’s capacity to tolerate treatment, thus resulting in schedule delay, interruption, or premature suspension. In certain circumstances, partial and general secondary infections are found, increasing the expenditures on medical care and hospitalization. Current methods of treating intestinal mucositis are provided, which do not always counteract this disorder. Against this background, novel therapeutical measures are extremely required to prevent and treat intestinal mucositis. Plant-derived natural compounds have lately become potential candidates against enteric injury ascribed to the capacity to facilitate mucosal healing and anti-inflammatory effects. These roles are associated with the improvement of intestinal mucosal barrier, suppression of inflammatory response and oxidant stress, and modulation of gut microflora and immune system. The present article aims at systematically discussing the recent progress of plant-derived natural compounds as promising treatments for intestinal mucositis.

Unique and redundant functions of cytoplasmic actins and nonmuscle myosin II isoforms at epithelial junctions

The integrity and functions of epithelial barriers depend on the formation of adherens junctions (AJs) and tight junctions (TJs). A characteristic feature of AJs and TJs is their association with the cortical cytoskeleton composed of actin filaments and nonmuscle myosin II (NM-II) motors. Mechanical forces generated by the actomyosin cytoskeleton are essential for junctional assembly, stability, and remodeling. Epithelial cells express two different actin proteins and three NM-II isoforms, all known to be associated with AJs and TJs. Despite their structural similarity, different actin and NM-II isoforms have distinct biochemical properties, cellular distribution, and functions. The diversity of epithelial actins and myosin motors could be essential for the regulation of different steps of junctional formation, maturation, and disassembly. This review focuses on the roles of actin and NM-II isoforms in controlling the integrity and barrier properties of various epithelia. We discuss the effects of the depletion of individual actin isoforms and NM-II motors on the assembly and barrier function of AJs and TJs in model epithelial monolayers in vitro. We also describe the functional consequences of either total or tissue-specific gene knockout of different actins and NM-II motors, with a focus on the development and integrity of different epithelia in vivo.

Human milk oligosaccharides induce acute yet reversible compositional changes in the gut microbiota of conventional mice linked to a reduction of butyrate levels

Human Milk Oligosaccharides (HMOs) are glycans with prebiotic properties known to drive microbial selection in the infant gut, which in turn influences immune development and future health. Bifidobacteria are specialized in HMO degradation and frequently dominate the gut microbiota of breastfed infants. However, some species of Bacteroidaceae also degrade HMOs, which may prompt selection also of these species in the gut microbiota. To investigate to what extent specific HMOs affect the abundance of naturally occurring Bacteroidaceae species in a complex mammalian gut environment, we conducted a study in 40 female NMRI mice administered three structurally different HMOs, namely 6'sialyllactose (6'SL, n = 8), 3-fucosyllactose (3FL, n = 16), and Lacto-N-Tetraose (LNT, n = 8), through drinking water (5%). Compared to a control group receiving unsupplemented drinking water (n = 8), supplementation with each of the HMOs significantly increased both the absolute and relative abundance of Bacteroidaceae species in faecal samples and affected the overall microbial composition analyzed by 16s rRNA amplicon sequencing. The compositional differences were mainly attributed to an increase in the relative abundance of the genus Phocaeicola (formerly Bacteroides) and a concomitant decrease of the genus Lacrimispora (formerly Clostridium XIVa cluster). During a 1-week washout period performed specifically for the 3FL group, this effect was reversed. Short-chain fatty acid analysis of faecal water revealed a decrease in acetate, butyrate and isobutyrate levels in animals supplemented with 3FL, which may reflect the observed decrease in the Lacrimispora genus. This study highlights HMO-driven Bacteroidaceae selection in the gut environment, which may cause a reduction of butyrate-producing clostridia.

Skin barrier defects in atopic dermatitis: From old idea to new opportunity

Atopic dermatitis (AD) is the most common chronic skin inflammatory disease, with a profound impact on patients’ quality of life. AD varies considerably in clinical course, age of onset and degree to which it is accompanied by allergic and non-allergic comorbidities. Skin barrier impairment in both lesional and nonlesional skin is now recognized as a critical and often early feature of AD. This may be explained by a number of abnormalities identified within both the stratum corneum and stratum granulosum layers of the epidermis. The goal of this review is to provide an overview of key barrier defects in AD, starting with a historical perspective. We will also highlight some of the commonly used methods to characterize and quantify skin barrier function. There is ample opportunity for further investigative work which we call out throughout this review. These include: quantifying the relative impact of individual epidermal abnormalities and putting this in a more holistic view with physiological measures of barrier function, as well as determining whether these barrier-specific endotypes predict clinical phenotypes (e.g. age of onset, natural history, comorbidities, response to therapies, etc). Mechanistic studies with new (and in development) AD therapies that specifically target immune pathways, Staphylococcus aureus abundance and/or skin barrier will help us understand the dynamic crosstalk between these compartments and their relative importance in AD.