Prenylated xanthones from mangosteen (Garcinia mangostana) activate the AhR and Nrf2 pathways and protect intestinal barrier integrity in HT-29 cells

Lactobacillus-derived indole derivatives ameliorate intestinal barrier damage in rat pups with complementary food administration

The consumption of complementary foods can bring about diarrhea and intestinal barrier dysfunction in infants. In this study, three different Lactobacillus strains combined with L-tryptophan (Trp) were administered to rat pups with complementary foods. Complementary food feeding caused inflammatory cell infiltration, crypt structure irregularity and goblet cell reduction in the colon tissues of the rat pups. However, the oral administration of Trp combined with Lactiplantibacillus plantarum DPUL-S164 or Limosilactobacillus reuteri DPUL-M94 significantly restored the pathological changes in the colon tissues and inhibited the expression of pro-inflammatory cytokines in the colon and ileum of the rat pups. M94 or S164 combined with Trp intervention could promote the expression of cell differentiation genes and tight junction proteins, and restore the intestinal barrier damage caused by complementary foods in rat pups by activating the aryl hydrocarbon receptors (AhR) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. In addition, the indole-3-lactic acid (ILA), indole-3-propionic acid (IPA), or indole-3-carbaldehyde (I3C) level in the cecal contents of the rat pups increased after intervention of Trp combined with S164 or M94, which may account for the amelioration of intestinal barrier damage in rat pups administered with complementary foods. Furthermore, S164 or M94 combined with Trp intervention up-regulated the relative abundance of f_Lactobacillaceae, f_Akkermansiaceae, g_Lactobacillus, and g_Akkermansia in the intestinal tract of the rat pups. In conclusion, S164 or M94 combined with Trp intervention can ameliorate complementary food-induced intestinal barrier damage and gut flora disorder in rat pups by producing ILA, IPA, or I3C, which are AhR ligands.

p-Hydroxy benzaldehyde, a phenolic compound from Nostoc commune, ameliorates DSS-induced colitis against oxidative stress via the Nrf2/HO-1/NQO-1/NF-κB/AP-1 pathway

BACKGROUND

Ulcerative colitis (UC), a chronic idiopathic inflammatory bowel disease (IBD), presents with limited current drug treatment options. Consequently, the search for safe and effective drug for UC prevention and treatment is imperative. Our prior studies have demonstrated that the phenolic compound p-Hydroxybenzaldehyde (HD) from Nostoc commune, effectively mitigates intestinal inflammation. However, the mechanisms underlying HD's anti-inflammatory effects remain unclear.

PURPOSE

This study delved into the pharmacodynamics of HD and its underlying anti-inflammation mechanisms.

METHODS

For in vivo experiments, dextran sodium sulfate (DSS)-induced colitis mouse model was established. In vitro inflammation model was established using lipopolysaccharide (LPS)-induced RAW264.7 and bone marrow-derived macrophages (BMDMs). The protective effect of HD against colitis was determined by monitoring clinical symptoms and histological morphology in mice. The levels of inflammatory factors and oxidative stress markers were subsequently analyzed with enzyme-linked immunosorbent assay (ELISA) and biochemical kits. Furthermore, western blotting (WB), immunofluorescence (IF), luciferase reporter gene, drug affinity reaction target stability (DARTS) assay, molecular docking, and molecular dynamics (MD) simulation were used to determine the potential target and molecular mechanism of HD.

RESULTS

Our findings indicate that HD significantly alleviated the clinical symptoms and histological morphology of colitis in mice, and curtailed the production of pro-inflammatory cytokines, including TNF-α, IL-6, IFN-γ, COX-2, and iNOS. Furthermore, HD stimulated the production of SOD, CAT, and GSH-px, enhanced total antioxidant capacity (T-AOC), and reduced MDA levels. Mechanically, HD augmented the expression of Nrf2, HO-1, and NQO-1, while concurrently downregulating the phosphorylation of p65, IκBα, c-Jun, and c-Fos. ML385 and siNrf2 largely attenuated the protective effect of HD in enteritis mice and RAW 264.7 cells, as well as the promotion of HO-1 expression levels. ZnPP-mediated HO-1 knockdown reversed HD-induced inhibition of colonic inflammation. Luciferase reporter assay and IF assay confirmed the transcriptional activation of Nrf2 by HD. DARTS analysis, molecular docking, and MD results showed high binding strength, interaction efficiency and remarkable stability between Nrf2 and HD.

CONCLUSION

These outcomes extend our previous research results that HD can combat oxidative stress through the Nrf2/HO-1/NQO-1/NF-κB/AP-1 pathways, effectively alleviating colitis, and propose new targets for HD to protect against intestinal barrier damage.

Quercetin ameliorates ulcerative colitis by activating aryl hydrocarbon receptor to improve intestinal barrier integrity

Ulcerative colitis (UC) pathogenesis is largely associated with intestinal epithelial barrier dysfunction. A therapeutic approach to UC involves the repair of damaged intestinal barrier. Our study aimed to investigate whether aryl hydrocarbon receptor (AhR) mediated the intestinal barrier repair effects of quercetin to ameliorate UC. 3% dextran sulfate sodium was used to induce colitic mice, and quercetin (25, 50, and 100 mg/kg) was administered orally for 10 days to assess the therapeutic effects. In vitro, Caco-2 cells were used to explore the effect of quercetin on tight junction protein expression and AhR activation. The results showed that quercetin alleviated colitic mice by restoring tight junctions (TJs) integrity via an AhR-dependent manner (p < 0.05). In vitro, quercetin dose-dependently elevated the expressions of TJs protein ZO-1 and Claudin1, and activated AhR by enhancing the expression of CYP1A1 and facilitating AhR nuclear translocation in Caco-2 cells (p < 0.05). While AhR antagonist CH223191 reversed the therapeutic effects of quercetin (p < 0.05) and blocked quercetin-induced AhR activation and enhancement of TJs protein (p < 0.05). In conclusion, quercetin repaired intestinal barrier dysfunction by activating AhR-mediated enhancement of TJs to alleviate UC. Our research offered new perspectives on how quercetin enhanced intestinal barrier function.

Indole-3-Lactic Acid, a Tryptophan Metabolite of Lactiplantibacillus plantarum DPUL-S164, Improved Intestinal Barrier Damage by Activating AhR and Nrf2 Signaling Pathways

A growing body of evidence suggests that microbial tryptophan metabolites play a crucial role in maintaining intestinal barrier stability and modulating host immunity. Our previous study showed that the Lactiplantibacillus plantarum (L. plantarum ) DPUL-S164 intervention in mice with a high tryptophan (Trp) diet promotes indole-3-lactic acid (ILA) production in the mice's intestinal tract and ameliorates dextran sodium sulfate(DSS)-induced intestinal barrier damage in mice. In this study, we used the HT-29 cell monolayer model to evaluate the effect of the L. plantarum DPUL-S164 Trp metabolites (DPUL-S164-TM) on the intestinal barrier. We found that L. plantarum DPUL-S164-TM alleviated lipopolysaccharide (LPS)-induced intestinal barrier damage and inflammation of the HT-29 cell monolayer by promoting the expression of tight junction proteins (ZO-1, occludin, claudin1), activating the AhR and Nrf2 signaling pathways, and inhibiting the NF-κB signaling pathway. We found that the promotion of tight junction protein expression and the activation of the Nrf2 signaling pathway by L. plantarum DPUL-S164-TM were dependent on the AhR expression of HT-29 cells. Additionally, L. plantarum DPUL-S164-TM showed a dramatic increase in the ILA content. Therefore, we inferred that ILA in L. plantarum DPUL-S164-TM plays a key role in improving the intestinal barrier function and alleviating inflammation.

Omentin-1 ameliorates experimental inflammatory bowel disease via Nrf2 activation and redox regulation

AIMS

Omentin-1 production is decreased in patients with IBD. However, the specific role of Omentin-1 in IBD has not been fully elucidated. This study aimed to investigate the expression and role of Omentin-1 in IBD and the potential mechanisms.

MAIN METHODS

We collected human serum and colon biopsy samples at the Wuhan Union Hospital. Omentin-1 recombinant protein was injected intraperitoneally in a DSS-induced experimental IBD mouse model. Omentin-1 levels were measured in IBD patients, colitis mice, and LPS-induced HT-29 cells. Omentin-1 and/or a Nrf2 specific inhibitor (ML385) were administered to DSS mice and LPS-induced HT-29 cells. The effects of Omentin-1 on inflammation, intestinal barrier function, Nrf2 pathway, oxidative stress, and NF-κB signaling were detected in vivo and in vitro.

KEY FINDINGS

Serum Omentin-1 levels were significantly reduced in UC and CD patients compared with controls (173.7 (IQR, 120.1-221.2) ng/ml, 80.8 (43.8-151.8) ng/ml, and 270.7 (220.7-306.5) ng/ml, respectively). The levels of Omentin-1 were also significantly lower in colitis mice and LPS-induced HT-29 cells. Omentin-1 treatment effectively ameliorated inflammation and impaired intestinal barrier, decreased ROS and MDA levels, and increased GSH and SOD production in the DSS-induced colitis mice and LPS-induced HT-29 cells. Mechanically, Omentin-1 repaired the intestinal barrier by activating Nrf2, then improving oxidative stress and inhibiting NF-κB signaling. Furthermore, the interaction between Omentin-1 and Nrf2 was identified.

SIGNIFICANCE

Omentin-1 activates the Nrf2 pathway to regulate redox balance, ultimately protecting intestinal barrier function and reducing intestinal inflammation. In general, Omentin-1 can be used as a promising therapeutic target for IBD.

Ferroptosis in the colon epithelial cells as a therapeutic target for ulcerative colitis

BACKGROUND

Ferroptosis, a type of programmed cell death triggered by oxidative stress, was suspected to play a role in ulcerative colitis. Indigo naturalis is highly effective against ulcerative colitis, but its mechanism is unclear. This study found that indigo naturalis treatment suppressed ferroptosis.

METHODS

We analyzed 770 mRNA expressions of patients with ulcerative colitis. Suppression of ferroptosis by indigo naturalis treatment was shown using a cell death assay. Malondialdehyde levels and reactive oxygen species were analyzed in CaCo-2 cells treated with indigo naturalis. Glutathione metabolism was shown by metabolomic analysis. Extraction of the ingredients indigo naturalis from the rectal mucosa was performed using liquid chromatograph-mass spectrometry.

RESULTS

Gene expression profiling showed that indigo naturalis treatment increased antioxidant genes in the mucosa of patients with ulcerative colitis. In vitro analysis showed that nuclear factor erythroid-2-related factor 2-related antioxidant gene expression was upregulated by indigo naturalis. Indigo naturalis treatment rendered cells resistant to ferroptosis. Metabolomic analysis suggested that an increase in reduced glutathione by indigo naturalis. The protein expression of CYP1A1 and GPX4 was increased in the rectum by treatment with indigo naturalis. The main ingredients of indigo naturalis, indirubin and indigo inhibited ferroptosis. Indirubin was detected in the rectal mucosa of patients with ulcerative colitis who were treated with indigo naturalis.

CONCLUSIONS

Suppression of ferroptosis by indigo naturalis in the intestinal epithelium could be therapeutic target for ulcerative colitis. The main active ingredient of indigo naturalis may be indirubin.

Alpha-tocopherylquinone differentially modulates claudins to enhance intestinal epithelial tight junction barrier via AhR and Nrf2 pathways

Defects in intestinal epithelial tight junctions (TJs) allow paracellular permeation of noxious luminal antigens and are important pathogenic factors in inflammatory bowel disease (IBD). We show that alpha-tocopherylquinone (TQ), a quinone-structured oxidation product of vitamin E, consistently enhances the intestinal TJ barrier by increasing barrier-forming claudin-3 (CLDN3) and reducing channel-forming CLDN2 in Caco-2 cell monolayers (in vitro), mouse models (in vivo), and surgically resected human colons (ex vivo). TQ reduces colonic permeability and ameliorates colitis symptoms in multiple colitis models. TQ, bifunctionally, activates both aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathways. Genetic deletion studies reveal that TQ-induced AhR activation transcriptionally increases CLDN3 via xenobiotic response element (XRE) in the CLDN3 promoter. Conversely, TQ suppresses CLDN2 expression via Nrf2-mediated STAT3 inhibition. TQ offers a naturally occurring, non-toxic intervention for enhancement of the intestinal TJ barrier and adjunct therapeutics to treat intestinal inflammation.

The aryl hydrocarbon receptor in immune regulation and autoimmune pathogenesis

As a ligand-activated transcription factor, the aryl hydrocarbon receptor (AhR) is activated by structurally diverse ligands derived from the environment, diet, microorganisms, and metabolic activity. Recent studies have demonstrated that AhR plays a key role in modulating both innate and adaptive immune responses. Moreover, AhR regulates innate immune and lymphoid cell differentiation and function, which is involved in autoimmune pathogenesis. In this review, we discuss recent advances in understanding the mechanism of activation of AhR and its mediated functional regulation in various innate immune and lymphoid cell populations, as well as the immune-regulatory effect of AhR in the development of autoimmune diseases. In addition, we highlight the identification of AhR agonists and antagonists that may serve as potential therapeutic targets for the treatment of autoimmune disorders.

Modulating AHR function offers exciting therapeutic potential in gut immunity and inflammation

Aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a classical exogenous synthetic ligand of AHR that has significant immunotoxic effects. Activation of AHR has beneficial effects on intestinal immune responses, but inactivation or overactivation of AHR can lead to intestinal immune dysregulation and even intestinal diseases. Sustained potent activation of AHR by TCDD results in impairment of the intestinal epithelial barrier. However, currently, AHR research has been more focused on elucidating physiologic AHR function than on dioxin toxicity. The appropriate level of AHR activation plays a role in maintaining gut health and protecting against intestinal inflammation. Therefore, AHR offers a crucial target to modulate intestinal immunity and inflammation. Herein, we summarize our current understanding of the relationship between AHR and intestinal immunity, the ways in which AHR affects intestinal immunity and inflammation, the effects of AHR activity on intestinal immunity and inflammation, and the effect of dietary habits on intestinal health through AHR. Finally, we discuss the therapeutic role of AHR in maintaining gut homeostasis and relieving inflammation.

Cardamonin targets KEAP1/NRF2 signaling for protection against atherosclerosis

Atherosclerosis (AS)-induced cardiovascular disease is a leading cause of death worldwide. To date, there is still a lack of effective approaches for AS intervention. Cardamonin (CAD) is a bioactive food component, but its effect on AS is unknown. In this work, CAD was investigated for its effect on AS using low-density lipoprotein receptor knockout mice and tumor necrosis factor-alpha (TNF-α)-stimulated endothelial cells (ECs). After a 12-week intervention, CAD was found to significantly prevent AS formation in the aortic root and aortic tree, reduce the necrotic core area, and inhibit aortic inflammation and oxidative stress. Moreover, CAD quenched TNF-α-provoked inflammation and oxidative stress in ECs. RNA-sequencing identified nuclear factor erythroid-2 related factor 2 (NFE2L2, NRF2)/heme oxidase 1 (HO1) signaling to be drastically activated by CAD. CAD is a known activator of the aryl hydrocarbon receptor (AHR) which is a transcription factor of the NFE2L2 gene. Surprisingly, AHR was not required for CAD's action on the activation of NRF2/HO1 signaling since AHR gene silencing did not reverse this effect. Furthermore, a molecular docking assay showed a strong binding potential of CAD to the Kelch domain of the Kelch-like ECH-associated protein 1 (KEAP1) which sequesters NRF2 in the cytoplasm. Both CAD and the Kelch domain inhibitor Ki696 promoted NRF2 nuclear translocation, whereas the combination of CAD and Ki696 did not yield a greater effect compared with either CAD or Ki696, confirming the interaction of CAD with the Kelch domain. This work provides an experimental basis for CAD as a novel and effective bioactive food component in future AS interventions.

Low dose of arsenic exacerbates toxicity to mice and IPEC-J2 cells exposed with deoxynivalenol: Aryl hydrocarbon receptor and autophagy might be novel therapeutic targets

Deoxynivalenol (DON) and arsenic (As) are widespread environmental contaminants, which are frequently found in human and animal food products. The intestine is a common target of As and DON when they are digested. Numerous studies mainly evaluate the individual effects whereas their combined toxicity has rarely been elucidated. Hence, this study was to assess the effect of low dose of NaAsO₂ on DON-induced intestinal damage and explore the underling mechanism in mice and IPEC-J2 cells. The results showed that low dose of NaAsO₂ exacerbated DON-induced intestinal impairment by increasing intestinal permeability and decreasing the abundance of tight junction proteins (ZO-1, Occludin, Claudin-1). Further, low dose of NaAsO₂ enhanced the AhR signaling pathway and autophagy-related mRNA/protein expressions induced by DON. Interestingly, FICZ, an AhR activator, instead of CH223191, an AhR inhibitor, could alleviate toxicity of the low dose of NaAsO₂ in the mice and IPEC-J2 cells. Compared to the WT IPEC-J2 cells, the intestinal barrier damage was more serious in LC3B^-/- IPEC-J2 cells induced by low dose of NaAsO₂ combination with DON. Collectively, our study demonstrated that low dose of NaAsO₂ exacerbated DON-induced intestinal barrier impairment in vivo and in vitro. The present study also demonstrated that activation of AhR-mediated autophagy might be a self-protection mechanism. Hence, AhR and autophagy might be novel therapeutic targets to prevent or alleviate NaAsO₂ combined with DON-induced intestinal barrier impairment.

Prenylated xanthones with α-glucosidase and α-amylase inhibitory effects from the pericarp of Garcinia mangostana

Two new prenylated xanthones, mangoxanthones A-B (1-2), together with four known compounds 3-6, were isolated from the ethanol extract of the pericarp of Garcinia mangostana. The structures of these compounds have been elucidated based on spectroscopic analysis. The analysis results of chiral HPLC revealed compounds 1 and 2 were scalemic mixtures respectively. All isolated compounds were biologically evaluated for their α-glucosidase and α-amylase inhibitory effects using in-vitro assays. Compound 1 showed moderate inhibitory activities against α-glucosidase and α-amylase with IC₅₀ of 29.06 ± 1.86 and 22.74 ± 2.07 μM, respectively. Molecular docking predicted the binding sites of compound 1 to α-glucosidase and α-amylase. A preliminary structure-activity relationship was discussed.

Ellagic Acid Alleviates Oxidative Stress by Mediating Nrf2 Signaling Pathways and Protects against Paraquat-Induced Intestinal Injury in Piglets

The gastrointestinal tract is a key source of superoxide so as to be one of the most vulnerable to oxidative stress damage. Ellagic acid (EA), a polyphenol displays widely biological activities owing to its strong antioxidant properties. Here, we investigated the protective benefits of EA on oxidative stress and intestinal barrier injury in paraquet (PQ)-challenged piglets. A total of 40 weaned piglets were randomly divided into five groups: Control, PQ, 0.005% EA-PQ, 0.01% EA-PQ, and 0.02% EA-PQ. Piglets were intraperitoneally injected with 4 mg/kg (BW) PQ or saline on d-18, and sacrificed on d-21 of experiment. EA treatments eliminated growth-check induced by PQ and increased serum superoxide dismutase (SOD) activity but decreased serum malondialdehyde (MDA) level as compared to PQ group. EA supplementation promoted Nrf2 nuclear translocation and enhanced heme oxygenase-1 (HO-1) and quinone oxidoreductase 1 (NQO1) protein abundances of small intestinal mucosa. Additionally, EA improved PQ-induced crypt deepening, goblet cells loss, and villi morphological damage. Consistently, EA increased tight junction protein expression as was evident from the decreased serum diamine oxidase (DAO) levels. EA could ameliorate the PQ-induced oxidative stress and intestinal damage through mediating Nrf2 signaling pathway. Intake of EA-rich food might prevent oxidative stress-mediated gut diseases.

Garcinia mangostana and α-Mangostin Revive Ulcerative Colitis-Modified Hepatic Cytochrome P450 Profiles in Mice

&lt;b&gt;Background and Objective:&lt;/b&gt; Ulcerative colitis (UC) is inflammation of the large intestine with ulceration but can also cause extraintestinal manifestations (EIM) by damaging surrounding organs such as the liver. &lt;i&gt;Garcinia mangostana&lt;/i&gt; (GM) pericarp and α-mangostin (MGS) have been reported to have anti-inflammatory activity. This study evaluated the effects of GM pericarp extract and MGS on the expression of hepatic cytochrome P450 (CYP) enzymes as an EIM of UC. &lt;b&gt;Materials and Methods:&lt;/b&gt; Male ICR mice were orally administered GM pericarp extract (40, 200 and 1000 mg/kg/day), MGS (30 mg/kg/day) or sulfasalazine (SUL) (100 mg/kg/day) daily for 7 days. On days 4-7, UC was induced by dextran sulfate sodium (DSS 40 kDa, 6 g/kg/day). Profiles of CYP mRNA expression were determined by RT/qPCR. Alkoxyresorufin &lt;i&gt;O&lt;/i&gt;-dealkylation (including ethoxy-, methoxy-, pentoxy- and benzyloxy-resorufin), aniline hydroxylation and erythromycin &lt;i&gt;N&lt;/i&gt;-demethylation CYP responsive activities were also examined. &lt;b&gt;Results:&lt;/b&gt; The DSS-induced UC mice showed suppressed expression&lt;i&gt; &lt;/i&gt;of &lt;i&gt;Cyp1a1&lt;/i&gt;, &lt;i&gt;Cyp1a2&lt;/i&gt;, &lt;i&gt;Cyp2b9/10&lt;/i&gt;, &lt;i&gt;Cyp2e1&lt;/i&gt;, &lt;i&gt;Cyp2c29&lt;/i&gt;, &lt;i&gt;Cyp2d9&lt;/i&gt;, &lt;i&gt;Cyp3a11&lt;/i&gt; and &lt;i&gt;Cyp3a13&lt;/i&gt; mRNAs. The GM pericarp extract and MGS restored expression of all investigated CYPs and their responsive enzyme activities in DSS-induced UC mice to levels comparable to the control and parallel to the effects of the anti-inflammatory control SUL. &lt;b&gt;Conclusion:&lt;/b&gt; The GM is a promising therapy to restore UC-modified hepatic CYP profiles.

Pharmacokinetic Analysis of Carnosic Acid and Carnosol in Standardized Rosemary Extract and the Effect on the Disease Activity Index of DSS-Induced Colitis

Rosemary extract (RE) is an approved food preservative in the European Union and contains dietary phytochemicals that are beneficial for gastrointestinal health. This study investigated the effects of RE on dextran sodium sulfate (DSS)-induced colitis and also determined the pharmacokinetics of dietary phytochemicals administered to mice via oral gavage. Individual components of rosemary extract were separated and identified by LC–MS/MS. The pharmacokinetics of two major diterpenes from RE, carnosic acid (CA) and carnosol (CL), administered to mice via oral gavage were determined. Then, the effect of RE pre-treatment on the disease activity index (DAI) of DSS-induced colitis in mice was investigated. The study determined that 100 mg/kg RE significantly improved DAI in DSS-induced colitis compared to negative control. Sestrin 2 protein expression, which increased with DSS exposure, was reduced with RE treatment. Intestinal barrier integrity was also shown to improve via fluorescein isothiocyanate (FITC)–dextran administration and Western blot of zonula occludens-1 (ZO-1), a tight junction protein. Rosemary extract was able to improve the DAI of DSS-induced colitis in mice at a daily dose of 100 mg/kg and showed improvement in the intestinal barrier integrity. This study suggests that RE can be an effective preventative agent against IBD.