Autophagy induction by rapamycin ameliorates experimental colitis and improves intestinal epithelial barrier function in IL-10 knockout mice

Effects of dietary melatonin supplementation on growth performance and intestinal health of rice field eel (Monopterus albus)

The objective was to assess the impact of melatonin supplementation on the growth performance and intestinal health of rice field eel, Monopterus albus. Three hundred and sixty fish (28.46 ± 0.24 g) were fed five diets supplemented with melatonin of 0, 30, 60, 120, and 240 mg/kg for 70 days. The study found that the variables FBW, WGR, SGR, and FCR exhibited a statistically significant quadratic relationship (P < 0.05) with the dietary melatonin concentrations, and the highest FBW, WGR and SGR as well as lowest FCR were observed in the 120 mg/kg melatonin group, digestive enzymes activities (such as amylase, trypsin, and lipase) also had significant quadratic relationship (P < 0.05), and the highest intestinal villus height and goblet cells were found in the 120 mg/kg diet (P < 0.01), melatonin in diets significantly increased SOD and CAT activities in serum, up-regulated the expression of anti-inflammatory factors (IL-10) and tight junction protein (ZO-1), and down-regulated the expression of pro-inflammatory factors (IL-1β, IL-8, IL-15, and TNF-α) in the gut, dietary melatonin improved the intestinal microflora compositions, in the group that supplementation a dosage of 120 mg/kg, there was a noticeable rise in the abundance of Firmicutes and the ratio of Firmicutes/Bacteroidota, compared with control group (P < 0.1). Conclusively, dietary supplementation of melatonin promoted growth performance, enhanced intestinal immune capacity and serum antioxidant level, and improved intestinal morphology properties and intestinal flora composition in M. albus. In conclusion, based on quadratic broken-line regression analysis of WGR and FCR, the optimal concentration of melatonin to be supplied is predicted to be 146-148 mg/kg.

Emerging Roles of Gut Serotonin in Regulation of Immune Response, Microbiota Composition and Intestinal Inflammation

Although the exact etiology of inflammatory bowel diseases (IBD) is unknown, studies have shown that dysregulated immune responses, genetic factors, gut microbiota, and environmental factors contribute to their pathogenesis. Intriguingly, serotonin (5-hydroxytryptamine or 5-HT) seems to be a molecule with increasingly strong implications in the pathogenesis of intestinal inflammation, affecting host physiology, including autophagy and immune responses, as well as microbial composition and function. 5-HT may also play a role in mediating how environmental effects impact outcomes in IBD. In this review, we aim to explore the production and important functions of 5-HT, including its impact on the gut. In addition, we highlight the bidirectional impacts of 5-HT on the immune system, the gut microbiota, and the process of autophagy and how these effects contribute to the manifestation of intestinal inflammation. We also explore recent findings connecting 5-HT signalling and the influence of environmental factors, particularly diet, in the pathogenesis of IBD. Ultimately, we explore the pleiotropic effects of this ancient molecule on biology and health in the context of intestinal inflammation.

Upregulated Tβ4 expression in inflammatory bowel disease impairs the intestinal mucus barrier by inhibiting autophagy in mice

Disrupted intestinal barrier homeostasis is fundamental to inflammatory bowel disease. Thymosin β4 (Tβ4) improves inflammation and has beneficial effects in dry-eye diseases, but its effects on the intestinal mucus barrier remain unknown. Therefore, this study evaluated the underlying regulatory mechanisms and effects of Tβ4 by examining Tβ4 expression in a mouse model with dextran sodium sulfate (DSS)-induced colitis and colonic barrier damage. Additionally, we intraperitoneally injected C57BL/6 mice with Tβ4 to assess barrier function, microtubule-associated protein 1 light chain 3 (LC3II) protein expression, and autophagy. Finally, normal human colon tissue and colon carcinoma cells (Caco2) were cultured to verify Tβ4-induced barrier function and autophagy changes. Mucin2 levels decreased, microbial infiltration increased, and Tβ4 expression increased in the colitis mouse model versus the control mice, indicating mucus barrier damage. Moreover, Tβ4-treated C57BL/6 mice had damaged intestinal mucus barriers and decreased LC3II levels. Tβ4 also inhibited colonic mucin2 production, disrupted tight junctions, and downregulated autophagy; these results were confirmed in Caco2 cells and normal human colon tissue. In summary, Tβ4 may be implicated in colitis by compromising the integrity of the intestinal mucus barrier and inhibiting autophagy. Thus, Tβ4 could be a new diagnostic marker for intestinal barrier defects.

Rapamycin extenuates experimental colitis by modulating the gut microbiota

BACKGROUND AND AIM

Autophagy and gut microbiota correlates closely with the inflammatory bowel disease. Herein, we aimed to study the roles of rapamycin on the gut microbiota in inflammatory bowel disease.

METHODS

Acute colitis was induced with dextran sodium sulfate (DSS) and 2,4,6-trinitrobenzenesulfonic acid solution in mice. Mice were administered with rapamycin or hydroxychloroquine. Weight loss, disease activity index scores, histopathological score, serum inflammatory cytokines, intestinal permeability, and colonic autophagy-related proteins were detected. Cecal content was also preserved in liquid nitrogen and subsequently analyzed following the 16S DNA sequencing. The antibiotic cocktail-induced microbiome depletion was performed to further investigate the relationship between autophagy activation and gut microbiota.

RESULTS

Compared with the control group, the colonic autophagy-related proteins of P62, mTOR, and p-mTOR increased significantly, while the levels of LC3B and ATG16L1 decreased (all P < 0.05) in the model group. After rapamycin intervention, the colonic pathology of mice improved, while the disease activity index score decreased substantially; the colon length increased, and the expression of IL-6 and TNF-α decreased. Following hydroxychloroquine treatment, some indicators suggested aggravation of colitis. Principal coordinates analysis showed that the DSS group was located on a separate branch from the rapamycin group but was closer to the hydroxychloroquine group. Compared with the DSS group, the rapamycin group was associated with higher abundances of f_Lactobacillaceae (P = 0.0151), f_Deferribacteraceae (P = 0.0290), g_Lactobacillus (P = 0.0151), g_Mucispirillum (P = 0.0137), s_Lactobacillus_reuteri (P = 0.0028), and s_Clostridium_sp_Culture_Jar-13 (P = 0.0082) and a lower abundance of s_Bacteroides_sartorii (P = 0.0180). Linear discriminant analysis effect size showed that rapamycin increased the abundances of Lactobacillus-reuteri, Prevotellaceae, Paraprevotella, Christensenella and Streptococcus and decreased those of Peptostreptococcaceae and Romboutsia Bacteroides-sartorii. Besides, the improvement effect of autophagy activation on colitis disappears following gut microbiome depletion.

CONCLUSION

The therapeutic effects of rapamycin on extenuating experimental colitis may be related to the gut microbiota.

The emerging roles of autophagy in intestinal epithelial cells and its links to inflammatory bowel disease

Landmark genome-wide association studies (GWAS) identified that mutations in autophagy genes correlated with inflammatory bowel disease (IBD), a heterogenous disease characterised by prolonged inflammation of the gastrointestinal tract, that can reduce a person's quality of life. Autophagy, the delivery of intracellular components to the lysosome for degradation, is a critical cellular housekeeping process that removes damaged proteins and turns over organelles, recycling their amino acids and other constituents to supply cells with energy and necessary building blocks. This occurs under both basal and challenging conditions such as nutrient deprivation. An understanding of the relationship between autophagy, intestinal health and IBD aetiology has improved over time, with autophagy having a verified role in the intestinal epithelium and immune cells. Here, we discuss research that has led to an understanding that autophagy genes, including ATG16L, ATG5, ATG7, IRGM, and Class III PI3K complex members, contribute to innate immune defence in intestinal epithelial cells (IECs) via selective autophagy of bacteria (xenophagy), how autophagy contributes to the regulation of the intestinal barrier via cell junctional proteins, and the critical role of autophagy genes in intestinal epithelial secretory subpopulations, namely Paneth and goblet cells. We also discuss how intestinal stem cells can utilise autophagy. Importantly, mouse studies have provided evidence that autophagy deregulation has serious physiological consequences including IEC death and intestinal inflammation. Thus, autophagy is now established as a key regulator of intestinal homeostasis. Further research into how its cytoprotective mechanisms can prevent intestinal inflammation may provide insights into the effective management of IBD.

Regulation of the autophagy plays an important role in acute kidney injury induced acute lung injury

AIM

This study aimed to investigate the regulatory role of autophagy in acute kidney injury (AKI) induced acute lung injury (ALI).

METHODS

The male Sprague-Dawley rats were divided into four groups: normal saline-treated sham rats (sham group), normal saline-treated ischemia-reperfusion injury rats (IRI group), 3-methyladenine-treated IRI rats (3-MA group), and rapamycin-treated IRI rats (RA group). The rats in the IRI rat model received the nephrectomy of the right kidney and was subjected to 60 mins of left renal pedicle occlusion, followed by 12, 24, 48, and 72 h of reperfusion. The levels of Scr, BUN, wet-to-dry ratio of lung, inflammatory cytokines, and oxidative stress were determined. The damage to tissues was detected by histological examinations. The western blot and immunohistochemistry methods were conducted to determine the expression of indicated proteins.

RESULTS

Renal IRI could induce the pulmonary injury after AKI, which caused significant increases in the function index of pulmonary and renal, the levels of inflammatory cytokines, and biomarkers of oxidative stress. In comparison to the IRI group, the RA group showed significantly decreased P62 and Caspase-3 expression and increased LC-II/LC3-I, Beclin-1, Bcl-2, and unc-51-like autophagy activating kinase 1 expression. Meanwhile, by suppressing the inflammation and oxidative stress, as well as inhibiting the pathological lesions in kidney and lung tissues, the autophagy could effectively ameliorate IRI-induced AKI and ALI.

CONCLUSIONS

Autophagy plays an important role in AKI-induced ALI, which could be used as a new target for AKI therapy and reduce the mortality caused by the complication.

circSMAD4 promotes experimental colitis and impairs intestinal barrier functions by targeting JAK2 through sponging miR-135a-5p

BACKGROUND

Numerous studies have explored the association between circular RNAs (circRNAs) and Crohn's disease (CD). However, the pathological role, biological functions, and molecular mechanisms of circRNAs in CD have not been fully elucidated.

METHODS

The circRNA microarray analysis was performed to identify deregulated circRNAs in colon tissues. The identified circRNA were verified through quantitative real time-polymerase chain reaction (qRT-PCR). In vivo and in vitro functional studies were performed to verify the role of circSMAD4 in CD and investigate the mechanisms involved.

RESULTS

We found that circSMAD4 was the most significantly upregulated circRNA. The expression level of circSMAD4 was positively correlated with levels of inflammatory factors. Overexpression of circSMAD4 impaired tight junction (TJ) proteins and enhanced apoptosis of epithelial cells. These effects were reversed by treatment with miR-135a-5p mimic. Mechanistic studies showed that circSMAD4 exerts its effects on CD by "sponging" miR-135a-5p to regulate Janus kinase 2 (JAK2). Si-circSMAD4 delivery through microspheres ameliorated experimental colitis and protected the intestinal barrier function in IL-10 knock-out mice.

CONCLUSION

This study shows that circSMAD4 regulates the progression of experimental colitis via the miR-135a-5p/JAK2 signaling axis and it may be a potential therapeutic target.

Emerging Role of Dendritic Cell Intervention in the Treatment of Inflammatory Bowel Disease

Dendritic cells (DCs) are the most important antigen-presenting cells and are pivotal in initiating effective adaptive immune responses to induce immune tolerance and maintain immune homeostasis. Inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis, is chronic, intestinal inflammatory and autoimmune disorder. DCs participate in IBD pathogenesis. This review is aimed at briefly discussing the role of DCs in IBD and the relationship between them and highlighting the prominent role of these cells in the treatment of these disorders.

PLGA-microspheres-carried circGMCL1 protects against Crohn's colitis through alleviating NLRP3 inflammasome-induced pyroptosis by promoting autophagy

This study aimed to at explore exploring the biological functions of dysregulated circRNA in Crohn's disease (CD) pathogenesis, with the overarching goal of and providing potential novel therapeutic targets. CircRNA microarray and quantitative real time-polymerase chain reaction (qRT-PCR) analyses were performed to investigate and verify the candidate dysregulated circRNA. The Next, clinical, in vivo, and in vitro studies were performed to investigate explore the biological function and mechanisms of the candidate circRNA in CD. The therapeutic effect of poly (lactic-co-glycolic acid)-microspheres (PLGA MSs)-carried oe-circGMCL1 in experimental colitis models of IL-10 knock-out mice was assessed. CircGMCL1 was identified as the candidate circRNA by microarray and qRT-PCR analyses. Results showed that circGMCL1 expression was negatively correlated with CD-associated inflammatory indices, suggesting that it is a CD-associated circRNA. Microarray and bioinformatics analyses identified miR-124-3p and Annexin 7 (ANXA7) as its downstream mechanisms. The in vitro studies revealed that circGMCL1 mediates its effects on autophagy and NLRP3 inflammasome-mediated pyroptosis in epithelial cells through the ceRNA network. Moreover, the in vivo studies identified the therapeutic effect of PLGA MSs-carried oe-circGMCL1 in experimental colitis models. This study suggests that circGMCL1 protects intestinal barrier function against Crohn's colitis through alleviating NLRP3 inflammasome-mediated epithelial pyroptosis by promoting autophagy through regulating ANXA7 via sponging miR-124-3p. Therefore, circGMCL1 can serve as a potential biological therapeutic target for Crohn's colitis.

Huangkui lianchang decoction attenuates experimental colitis by inhibiting the NF-κB pathway and autophagy

Ulcerative colitis (UC) is a chronic inflammatory colorectal disease characterized by excessive mucosal immune response activation and dysfunction of autophagy in intestinal epithelial cells. Traditional herbal preparations, including the Huangkui lianchang decoction (HLD), are effective in UC clinical treatment in East Asia, but the underlying mechanism is unclear. This study evaluated the therapeutic effects and associated molecular mechanisms of HLD in UC in vivo and in vitro. A C57BL/6 UC mouse model was established using 2.5% dextran sulfate sodium. The effects of HLD on the colonic structure and inflammation in mice were evaluated using mesalazine as the control. The anti-inflammatory effects of HLD were assessed using disease activity index (DAI) scores, histological scores, enzyme-linked immunosorbent assay, immunohistochemistry, immunofluorescence, and western blotting. HLD displayed a protective effect in UC mice by reducing the DAI and colonic histological scores, as well as levels of inflammatory cytokines and NF-κB p65 in colonic tissues. NCM460 lipopolysaccharide-induced cells were administered drug serum-containing HLD (HLD-DS) to evaluate the protective effect against UC and the effect on autophagy. HLD-DS exhibited anti-inflammatory effects in NCM460 cells by reducing the levels of inflammatory cytokines and increasing interleukin 10 levels. HLD-DS reduced p-NF-κB p65, LC3II/I, and Beclin 1 expression, which suggested that HLD alleviated colitis by inhibiting the NF-κB pathway and autophagy. However, there was no crosstalk between the NF-κB pathway and autophagy. These findings confirmed that HLD was an effective herbal preparation for the treatment of UC.

Rapamycin Alleviates 2,4,6-Trinitrobenzene Sulfonic Acid-Induced Colitis through Autophagy Induction and NF-κB Pathway Inhibition in Mice

Background

Recent genetic studies indicated that variants of autophagy genes were associated with the predisposition of Crohn's disease (CD). The autophagy deficiency may affect the innate and adaptive immunity, which is related to persistent and excessive inflammation of the bowel. However, it remains unclear how autophagy modulates the expression of immune response regulator NF-κB and proinflammatory cytokine TNF-α in CD.

Aim

We aimed to investigate the role of rapamycin on the expression of NF-κB p65 and TNF-α in 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)-induced mouse colitis and lipopolysaccharide (LPS)-induced HT-29 cells.

Methods

TNBS-induced colitis mice were treated with saline or rapamycin, and the disease activity index (DAI) and histological scores of colonic mucosa were evaluated. The expressions of p65, ATG16L1 and LC3 were detected by western blot and immunohistochemistry staining. The monodansylcadaverine (MDC) staining and transmission electron microscopy were developed to study the autophagy in LPS-induced HT-29 cells. Expression of TNF-α from colon tissue and HT-29 cells were detected by ELISA. The expressions of p65, ATG16L1 and LC3 in active CD patients were also investigated.

Results

Significantly more autophagosomes were observed in rapamycin-treated cells than in controls. Rapamycin remarkably upregulated the expression of ATG16L1 and LC3II, inhibited p65 nucleus translocation and secretion of TNF-α both in vivo and in vitro. The expression of both ATG16L1 and LC3II increased in mild to moderate CD specimens, while no significant difference was noted between severe CD and normal controls. The expression of p65 increased notably in severe CD compared to those in mild to moderate patients.

Conclusions

In LPS-treated HT-29 cells and TNBS-induced colitis, p65 is overexpressed, which results in exaggerated secretion of TNF-α and induce or worsen the inflammation in the bowel. Rapamycin protects against colitis through induction of autophagy, thus inhibiting the activation of NF-κB pathway and secretion of TNF-α.

A Quassinoid Diterpenoid Eurycomanone from Eurycoma longifolia Jack Exerts Anti-Cancer Effect through Autophagy Inhibition

Eurycomanone (EN) is one of the representative quassinoid diterpenoids from roots of Eurycoma longifolia Jack, a natural medicine that is widely distributed in Southeast Asia. Previous studies showed that EN induces cancer cell apoptosis and exhibits anti-cancer activity, but the molecular mechanism of EN against cancer has still not been elucidated. In this study, we examined the regulatory effect of EN on autophagy to reveal the mechanism of EN-mediated colon cancer growth inhibition. First, we found that EN is able to inhibit colon cancer cell proliferation and colony formation. The angiogenesis level in cancer cells was inhibited as well. Next, the treatment of EN led to the suppression of autophagy, which was characterized by the downregulation of the LC3-II level and the formation of GFP-LC3 puncta under EN treatment in colon cancer. Moreover, we revealed that the mTOR signaling pathway was activated by EN in a time- and concentration-dependent manner. Finally, autophagy induction protected colon cancer cells from EN treatment, suggesting that autophagy improves cell survival. Taken together, our findings revealed the mechanism of EN against colon cancer through inhibiting autophagy and angiogenesis in colon cancer, supporting that the autophagy inhibitor EN could be developed to be a novel anti-cancer agent.

Intestinal Barrier and Permeability in Health, Obesity and NAFLD

The largest surface of the human body exposed to the external environment is the gut. At this level, the intestinal barrier includes luminal microbes, the mucin layer, gastrointestinal motility and secretion, enterocytes, immune cells, gut vascular barrier, and liver barrier. A healthy intestinal barrier is characterized by the selective permeability of nutrients, metabolites, water, and bacterial products, and processes are governed by cellular, neural, immune, and hormonal factors. Disrupted gut permeability (leaky gut syndrome) can represent a predisposing or aggravating condition in obesity and the metabolically associated liver steatosis (nonalcoholic fatty liver disease, NAFLD). In what follows, we describe the morphological-functional features of the intestinal barrier, the role of major modifiers of the intestinal barrier, and discuss the recent evidence pointing to the key role of intestinal permeability in obesity/NAFLD.

Leaky Gut: Effect of Dietary Fiber and Fats on Microbiome and Intestinal Barrier

Intestinal tract is the boundary that prevents harmful molecules from invading into the mucosal tissue, followed by systemic circulation. Intestinal permeability is an index for intestinal barrier integrity. Intestinal permeability has been shown to increase in various diseases-not only intestinal inflammatory diseases, but also systemic diseases, including diabetes, chronic kidney dysfunction, cancer, and cardiovascular diseases. Chronic increase of intestinal permeability is termed 'leaky gut' which is observed in the patients and animal models of these diseases. This state often correlates with the disease state. In addition, recent studies have revealed that gut microbiota affects intestinal and systemic heath conditions via their metabolite, especially short-chain fatty acids and lipopolysaccharides, which can trigger leaky gut. The etiology of leaky gut is still unknown; however, recent studies have uncovered exogenous factors that can modulate intestinal permeability. Nutrients are closely related to intestinal health and permeability that are actively investigated as a hot topic of scientific research. Here, we will review the effect of nutrients on intestinal permeability and microbiome for a better understanding of leaky gut and a possible mechanism of increase in intestinal permeability.

miR-130a-3p, a Preclinical Therapeutic Target for Crohn's Disease

BACKGROUND

Crohn's disease [CD] is a chronic, relapsing and incurable inflammatory disorder. Micro RNAs [miRNAs], which modulate gene expression by binding to mRNAs, may make significant contributions to understanding the complex pathobiology and aetiology of CD. This study aimed to investigate the therapeutic role and mechanism of miR-130a-3p in CD.

METHODS

Differentially expressed miRNAs in colon tissues of CD patients and normal controls [NCs] were screened using an miRNA microarray and then validated by quantitative reverse transcriptase-PCR [qRT-PCR]. The functional role of miR-130a-3p in the pathogenesis of CD was then demonstrated by in vitro and in vivo studies. The target genes of miR-130a-3p and the associated signalling pathways were identified using bioinformatics analysis and experimental verification of the interactions between the target predicted by the algorithms and dysregulated mRNAs. The therapeutic role of miR-130a-3p in trinitro-benzene-sulfonic acid [TNBS]-induced colitis models was further investigated.

RESULTS

Our data demonstrated that miR-130a-3p is the most significantly upregulated miRNA and that miR-130a knockout significantly protects mice against TNBS-induced colitis. Gain- and loss-of-function studies indicated that miR-130a-3p promotes CD development by targeting ATG16L1 via the NF-κB pathway. Furthermore, an miR-130a-3p inhibitor significantly suppressed NLRP3 inflammasome activity by inducing autophagy in a mouse macrophage cell line [RAW264.7]. Therapeutically, an miR-130a-3p inhibitor effectively ameliorated the severity of TNBS-induced colitis.

CONCLUSION

Our study reveals that miR-130a-3p promotes CD progression via the ATG16L1/NF-κB pathway and serves as a potential preclinical therapeutic target in CD.