Aryl Hydrocarbon Receptor Activation Modulates Intestinal Epithelial Barrier Function by Maintaining Tight Junction Integrity

Lactobacillus paracasei Jlus66 relieves DSS-induced ulcerative colitis in a murine model by maintaining intestinal barrier integrity, inhibiting inflammation, and improving intestinal microbiota structure

PURPOSE

Ulcerative colitis (UC) is a serious health problem with increasing morbidity and prevalence worldwide. The pathogenesis of UC is complex, currently believed to be influenced by genetic factors, dysregulation of the host immune system, imbalance in the intestinal microbiota, and environmental factors. Currently, UC is typically managed using aminosalicylates, immunosuppressants, and biologics as adjunctive therapies, with the risk of relapse and development of drug resistance upon discontinuation. Therefore, further research into the pathogenesis of UC and exploration of potential treatment strategies are necessary to improve the quality of life for affected patients. According to previous studies, Lactobacillus paracasei Jlus66 (Jlus66) reduced inflammation and may help prevent or treat UC.

METHODS

We used dextran sulfate sodium (DSS) to induce a mouse model of UC to assess the effect of Jlus66 on the progression of colitis. During the experiment, we monitored mouse body weight, food and water consumption, as well as rectal bleeding. Hematoxylin-eosin staining was performed to assess intestinal pathological damage. Protein imprinting and immunohistochemical methods were used to evaluate the protein levels of nuclear factor-kappa B (NF-κB), mitogen-activated protein kinase (MAPK), and tight junction (TJ) proteins in intestinal tissues. Fecal microbiota was analyzed based on partial 16S rRNA gene sequencing.

RESULTS

Jlus66 supplementation reduced the degree of colon tissue damage, such as colon shortening, fecal occult blood, colon epithelial damage, and weight loss. Supplementation with Jlus66 reduced DSS-induced upregulation of cytokine levels such as TNF-α, IL-1β, and IL-6 (p < 0.05). The NF-κB pathway and MAPK pathway were inhibited, and the expression of TJ proteins (ZO-1, Occludin, and Claudin-3) was upregulated. 16S rRNA sequencing of mouse cecal contents showed that Jlus66 effectively regulated the structure of the intestinal biota.

CONCLUSION

In conclusion, these data indicate that Jlus66 can alter the intestinal biota and slow the progression of UC, providing new insights into potential therapeutic strategies for UC.

The aryl hydrocarbon receptor pathway: a linking bridge between the gut microbiome and neurodegenerative diseases

The Aryl hydrocarbon receptor (AHR) is a cytosolic receptor and ligand-activated transcription factor widely expressed across various cell types in the body. Its signaling is vital for host responses at barrier sites, regulating epithelial renewal, barrier integrity, and the activities of several types of immune cells. This makes AHR essential for various cellular responses during aging, especially those governing inflammation and immunity. In this review, we provided an overview of the mechanisms by which the AHR mediates inflammatory response at gut and brain level through signals from intestinal microbes. The age-related reduction of gut microbiota functions is perceived as a trigger of aberrant immune responses linking gut and brain inflammation to neurodegeneration. Thus, we explored gut microbiome impact on the nature and availability of AHR ligands and outcomes for several signaling pathways involved in neurodegenerative diseases and age-associated decline of brain functions, with an insight on Parkinson's and Alzheimer's diseases, the most common neurodegenerative diseases in the elderly. Specifically, we focused on microbial tryptophan catabolism responsible for the production of several AHR ligands. Perspectives for the development of microbiota-based interventions targeting AHR activity are presented for a healthy aging.

3,5-Dimethyl-8-methoxy-3,4-dihydro-1H-isochromen-6-ol Attenuates Ulcerative Colitis via Targeting NLRP3 in Mice

3,5-Dimethyl-8-methoxy-3,4-dihydro-1H-isochromen-6-ol (DMD) is a polyketide compound obtained from the endophytic fungus Penicillium sp. HJT-A-10 of Rhodiola tibetica. R. tibetica is a nourishing food and also used in traditional Chinese medicine and Xizang medicine. In dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) mice, DMD significantly alleviated the pathological symptom of UC. Network pharmacology studies have shown that nucleotide-binding domain-like receptor family pyrin domain containing (NLRP) 3 is the primary target protein of DMD associated with anti-UC. In molecular biology studies, DMD suppressed the activation of NLRP3 and decreased the expression of downstream inflammatory proteins and pro-inflammatory cytokines in UC. The finding was further verified in knockout mice. DMD lost the effect of attenuating DSS-induced UC in NLRP3-/- mice. In conclusion, this study demonstrates that DMD reduces inflammatory response and balances the barrier integrity to attenuate UC via targeting NLRP3, and DMD is a potential natural agent or dietary supplement for attenuating UC.

Protective effects of ginsenosides on ulcerative colitis: a meta-analysis and systematic review to reveal the mechanisms of action

BACKGROUND

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon. Ginsenoside may be an ideal agent for UC treatment. However, its efficacy and safety are unknown. We aim to conduct a systematic evaluation to assess the effects and potential mechanisms of ginsenosides in animal models of UC.

METHODS

Six electronic databases will be searched (PubMed, Embase, Web of Science, China Knowledge Network (CNKI), China Science and Technology Journal Database (CQVIP), and Wanfang Data Knowledge). SYRCLE list will be used to assess the quality of literature, and STATA 15.1 for data analysis. Time-dose effects analysis will be used to reveal the time-dosage response relations between ginsenosides and UC.

RESULTS

Ultimately, fifteen studies involving 300 animals were included. Preliminary evidence was shown that ginsenosides could reduce Disease Activity Index (DAI) scores, weight loss, histological colitis score (HCS), spleen weight, Malondialdehyde (MDA), Myeloperoxidase (MPO) activity, interleukin-1β (IL-1β), interleukin 6 (IL-6), tumor necrosis factor α (TNF-α) and increase colon length (CL), myeloperoxidase (GSH), interleukin 4 (IL-4), interleukin 10 (IL-10), Zonula Occludens-1 (ZO-1) and occludin. Results of time-dose interval analysis indicated that ginsenosides at a dosage of 5-200 mg/kg with an intervention time of 7-28 days were relatively effective.

CONCLUSIONS

Preclinical evidence suggests that ginsenoside is a novel treatment for UC. And the mechanisms of ginsenosides in treating UC may involve anti-inflammatory, antioxidant, barrier protection, intestinal flora regulation, and immune regulation. Although, due to the high heterogeneity, further large-scale and high-quality preclinical studies are needed to examine the protection of ginsenosides against UC.

Aryl hydrocarbon receptor confers protection against macrophage pyroptosis and intestinal inflammation through regulating polyamine biosynthesis

Rationale: The aryl hydrocarbon receptor (AhR) functions in the regulation of intestinal inflammation, but knowledge of the underlying mechanisms in innate immune cells is limited. Here, we investigated the role of AhR in modulating the functions of macrophages in inflammatory bowel disease pathogenesis. Methods: The cellular composition of intestinal lamina propria CD45+ leukocytes in a dextran sulfate sodium (DSS)-induced mouse colitis model was determined by single-cell RNA sequencing. Macrophage pyroptosis was quantified by analysis of lactate dehydrogenase release, propidium iodide staining, enzyme-linked immunosorbent assay, western blot, and flow cytometry. Differentially expressed genes were confirmed by RNA-seq, RT-qPCR, luciferase assay, chromatin immunoprecipitation, and immunofluorescence staining. Results: AhR deficiency mediated dynamic remodeling of the cellular composition of intestinal lamina propria (LP) CD45+ immune cells in a colitis model, with a significant increase in monocyte-macrophage lineage. Mice with AhR deficiency in myeloid cells developed more severe dextran sulfate sodium induced colitis, with concomitant increased macrophage pyroptosis. Dietary supplementation with an AhR pre-ligand, indole-3-carbinol, conferred protection against colitis while protection failed in mice lacking AhR in myeloid cells. Mechanistically, AhR signaling inhibited macrophage pyroptosis by promoting ornithine decarboxylase 1 (Odc1) transcription, to enhance polyamine biosynthesis. The increased polyamine, particularly spermine, inhibited NLRP3 inflammasome assembly and subsequent pyroptosis by suppressing K+ efflux. AHR expression was positively correlated with ODC1 in intestinal mucosal biopsies from patients with ulcerative colitis. Conclusions: These findings suggest a functional role for the AhR/ODC1/polyamine axis in maintaining intestinal homeostasis, providing potential targets for treatment of inflammatory bowel disease.

Metabolic characteristics of evodiamine were associated with its hepatotoxicity via PPAR/PI3K/AKT/NF-кB/tight junction pathway-mediated apoptosis in zebrafish

Evodiae Fructus (EF), an herbal medicine, possesses remarkable anti-inflammatory and analgesic properties. It exhibits insecticidal activity as a potent insecticide candidate. However, the toxic characteristics of EF and the underlying mechanisms have not been comprehensively elucidated comprehensively. Thus, we comprehensively explored the toxic components of EF and established the relationship between the therapeutic and toxic effects of EF, encouraging its therapeutic use. We found that evodiamine (EVO), one of the main ingredients of EF, can truly reflect its analgesic properties. In phenotype observation trials, low doses of EVO (< 35 ng/mL) exhibited distinct analgesic activity without any adverse effects in zebrafish. However, EVO dose-dependently led to gross morphological abnormalities in the liver, followed by pericardial edema, and increased myocardial concentrations. Furthermore, the toxic effects of EVO decreased after processing in liver microsomes but increased after administering CYP450 inhibitors in zebrafish, highlighting the prominent effect of CYP450s in EVO-mediated hepatotoxicity. EVO significantly changed the expression of genes enriched in multiple pathways and biological processes, including lipid metabolism, inflammatory response, tight junction damage, and cell apoptosis. Importantly, the PPAR/PI3K/AKT/NF-кB/tight junction-mediated apoptosis pathway was confirmed as a critical functional signaling pathway inducing EVO-mediated hepatotoxicity. This study provided a typical example of the overall systematic evaluation of traditional Chinese medicine (TCM) and its active ingredients with significant therapeutic effects and simultaneous toxicities, especially metabolic toxicities.

Ginsenoside CK Alleviates DSS-Induced IBD in Mice by Regulating Tryptophan Metabolism and Activating Aryl Hydrocarbon Receptor via Gut Microbiota Modulation

Dysbiosis of gut microbiota is believed to be associated with inflammatory bowel disease (IBD). Ginsenoside compound K (CK), the main metabolite of Panax ginseng ginsenoside, has proven effective as an anti-inflammatory agent in IBD. However, the mechanisms by which CK modulates gut microbiota to ameliorate IBD remain poorly understood. Herein, CK demonstrated the potential to suppress the release of proinflammatory cytokines by gut microbiota modulation. Notably, supplementation with CK promoted the restoration of a harmonious balance in gut microbiota, primarily by enhancing the populations of Lactobacillus and Akkermansia. Furthermore, CK considerably elevated the concentrations of tryptophan metabolites derived from Lactobacillus that could activate the aryl hydrocarbon receptor. Overall, the promising alleviative efficacy of CK primarily stemmed from the promotion of Lactobacillus growth and production of tryptophan metabolites, suggesting that CK should be regarded as a prospective prebiotic agent for IBD in the future.

Echinacea purpurea Polysaccharide Ameliorates Dextran Sulfate Sodium-Induced Colitis by Restoring the Intestinal Microbiota and Inhibiting the TLR4-NF-κB Axis

Ulcerative colitis (UC) is a chronic intestinal ailment which cannot be completely cured. The occurrence of UC has been on the rise in recent years, which is highly detrimental to patients. The effectiveness of conventional drug treatment is limited. The long-term usage of these agents can lead to substantial adverse effects. Therefore, the development of a safe and efficient dietary supplement is important for the prevention of UC. Echinacea purpurea polysaccharide (EPP) is one of the main bioactive substances in Echinacea purpurea. EPP has many favorable effects, such as antioxidative, anti-inflammatory, and antitumor effects. However, whether EPP can prevent or alleviate UC is still unclear. This study aims to analyze the effect and mechanism of EPP on UC in mice using a 3% dextran sulfate sodium (DSS)-induced UC model. The results showed that dietary supplementation with 200 mg/kg EPP significantly alleviated the shortening of colon length, weight loss, and histopathological damage in DSS-induced colitis mice. Mechanistically, EPP significantly inhibits the activation of the TLR4/NF-κB pathway and preserves the intestinal mechanical barrier integrity by enhancing the expression of claudin-1, ZO-1, and occludin and reducing the loss of goblet cells. Additionally, 16S rRNA sequencing revealed that EPP intervention reduced the abundance of Bacteroides, Escherichia-Shigella, and Klebsiella; the abundance of Lactobacillus increased. The results of nontargeted metabonomics showed that EPP reshaped metabolism. In this study, we clarified the effect of EPP on UC, revealed the potential function of EPP, and supported the use of polysaccharide dietary supplements for UC prevention.

Aryl Hydrocarbon Receptor Signalling in the Control of Gut Inflammation

Aryl hydrocarbon receptor (AHR), a transcription factor activated by many natural and synthetic ligands, represents an important mediator of the interplay between the environment and the host's immune responses. In a healthy gut, AHR activation promotes tolerogenic signals, which help maintain mucosal homeostasis. AHR expression is defective in the inflamed gut of patients with inflammatory bowel diseases (IBD), where decreased AHR signaling is supposed to contribute to amplifying the gut tissue's destructive immune-inflammatory responses. We here review the evidence supporting the role of AHR in controlling the "physiological" intestinal inflammation and summarize the data about the therapeutic effects of AHR activators, both in preclinical mouse models of colitis and in patients with IBD.

CPX-351 exploits the gut microbiota to promote mucosal barrier function, colonization resistance, and immune homeostasis

ABSTRACT

CPX-351, a liposomal combination of cytarabine plus daunorubicin, has been approved for the treatment of adults with newly diagnosed, therapy-related acute myeloid leukemia (AML) or AML with myelodysplasia-related changes, because it improves survival and outcome of patients who received hematopoietic stem cell transplant compared with the continuous infusion of cytarabine plus daunorubicin (referred to as "7 + 3" combination). Because gut dysbiosis occurring in patients with AML during induction chemotherapy heavily affects the subsequent phases of therapy, we have assessed whether the superior activity of CPX-351 vs "7 + 3" combination in the real-life setting implicates an action on and by the intestinal microbiota. To this purpose, we have evaluated the impact of CPX-351 and "7 + 3" combination on mucosal barrier function, gut microbial composition and function, and antifungal colonization resistance in preclinical models of intestinal damage in vitro and in vivo and fecal microbiota transplantation. We found that CPX-351, at variance with "7 + 3" combination, protected from gut dysbiosis, mucosal damage, and gut morbidity while increasing antifungal resistance. Mechanistically, the protective effect of CPX-351 occurred through pathways involving both the host and the intestinal microbiota, namely via the activation of the aryl hydrocarbon receptor-interleukin-22 (IL-22)-IL-10 host pathway and the production of immunomodulatory metabolites by anaerobes. This study reveals how the gut microbiota may contribute to the good safety profile, with a low infection-related mortality, of CPX-351 and highlights how a better understanding of the host-microbiota dialogue may contribute to pave the way for precision medicine in AML.

Role of aryl hydrocarbon receptors in infection and inflammation

The aryl hydrocarbon receptor (AhR) is a transcription factor that is activated by various ligands, including pollutants, microorganisms, and metabolic substances. It is expressed extensively in pulmonary and intestinal epithelial cells, where it contributes to barrier defense. The expression of AhR is pivotal in regulating the inflammatory response to microorganisms. However, dysregulated AhR expression can result in endocrine disorders, leading to immunotoxicity and potentially promoting the development of carcinoma. This review focuses on the crucial role of the AhR in facilitating and limiting the proliferation of pathogens, specifically in relation to the host cell type and the species of etiological agents involved in microbial pathogen infections. The activation of AhR is enhanced through the IDO1-AhR-IDO1 positive feedback loop, which is manipulated by viruses. AhR primarily promotes the infection of SARS-CoV-2 by inducing the expression of angiotensin-converting enzyme 2 (ACE2) and the secretion of pro-inflammatory cytokines. AhR also plays a significant role in regulating various types of T-cells, including CD4+ T cells and CD8+ T cells, in the context of pulmonary infections. The AhR pathway plays a crucial role in regulating immune responses within the respiratory and intestinal barriers when they are invaded by viruses, bacteria, parasites, and fungi. Additionally, we propose that targeting the agonist and antagonist of AhR signaling pathways could serve as a promising therapeutic approach for combating pathogen infections, especially in light of the growing prevalence of drug resistance to multiple antibiotics.

Lactiplantibacillus plantarum-Derived Indole-3-lactic Acid Ameliorates Intestinal Barrier Integrity through the AhR/Nrf2/NF-κB Axis

Our previous studies have shown that Lactiplantibacillus plantarum DPUL-S164-derived indole-3-lactic acid (ILA) ameliorates intestinal epithelial cell barrier injury by activating aryl hydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathways and promoting tight junction protein expression. This study further explored the crucial substances of L. plantarum DPUL-S164 in alleviating intestinal barrier damage in mice through a dextran sodium sulfate-induced ulcerative colitis mouse model. Compared to dead L. plantarum DPUL-S164 (D-S164), live L. plantarum DPUL-S164 (S164) and its tryptophan metabolite, ILA, showed an effective ameliorating effect on the intestinal barrier injury of mice treated by antibiotic cocktail and sodium dextran sulfate, suggesting that the crucial substances of L. plantarum DPUL-S164 ameliorating intestinal barrier injury are its extracellular metabolites. Furthermore, S164 and its tryptophan metabolite, ILA, ameliorate intestinal barrier injury and suppress intestinal inflammation by activating the AhR-Nrf2 pathway and inhibiting the nuclear factor kappa-B (NF-κB) pathway. These results suggest that L. plantarum DPUL-S164 ameliorates intestinal epithelial barrier damage in mice, primarily by producing ILA as a ligand to activate the AhR pathway.

Telmisartan loading thermosensitive hydrogel repairs gut epithelial barrier for alleviating inflammatory bowel disease

Inflammatory bowel disease (IBD) remains a global health concern with a complex and incompletely understood pathogenesis. In the course of IBD development, damage to intestinal epithelial cells and a reduction in the expression of tight junction (TJ) proteins compromise the integrity of the intestinal barrier, exacerbating inflammation. Notably, the renin-angiotensin system and angiotensin II receptor type 1 (AT1R) play a crucial role in regulating the pathological progression including vascular permeability, and immune microenvironment. Thus, Telmisartan (Tel), an AT1R inhibitor, loading thermosensitive hydrogel was constructed to investigate the potential of alleviating inflammatory bowel disease through rectal administration. The constructed hydrogel exhibits an advantageous property of rapid transformation from a solution to a gel state at 37°C, facilitating prolonged drug retention within the gut while mitigating irritation associated with rectal administration. Results indicate that Tel also exhibits a beneficial effect in ameliorating colon shortening, colon wall thickening, cup cell lacking, crypt disappearance, and inflammatory cell infiltration into the mucosa in colitis mice. Moreover, it significantly upregulates the expression of TJ proteins in colonic tissues thereby repairing the intestinal barrier damage and alleviating the ulcerative colitis (UC) disease process. In conclusion, Tel-loaded hydrogel demonstrates substantial promise as a potential treatment modality for IBD.

Progress in the study of intestinal microbiota involved in morphine tolerance

Morphine is a widely used opioid for treatment of pain. The attendant problems including morphine tolerance and morphine dependence pose a major public health challenge. In recent years, there has been increasing interest in the gastrointestinal microbiota in many physiological and pathophysiological processes. The connectivity network between the gut microbiota and the brain is involved in multiple biological systems, and bidirectional communication between them is critical in gastrointestinal tract homeostasis, the central nervous system, and the microbial system. Many research have previously shown that morphine has a variety of effects on the gastrointestinal tract, but none have determined the function of intestinal microbiota in morphine tolerance. This study reviewed the mechanisms of morphine tolerance from the perspective of dysregulation of microbiota-gut-brain axis homeostasis, by summarizing the possible mechanisms originating from the gut that may affect morphine tolerance and the improvement of morphine tolerance through the gut microbiota.

Protective effect of synbiotic combination of Lactobacillus plantarum SC-5 and olive oil extract tyrosol in a murine model of ulcerative colitis

BACKGROUND

Ulcerative colitisis (UC) classified as a form of inflammatory bowel diseases (IBD) characterized by chronic, nonspecific, and recurrent symptoms with a poor prognosis. Common clinical manifestations of UC include diarrhea, fecal bleeding, and abdominal pain. Even though anti-inflammatory drugs can help alleviate symptoms of IBD, their long-term use is limited due to potential side effects. Therefore, alternative approaches for the treatment and prevention of inflammation in UC are crucial.

METHODS

This study investigated the synergistic mechanism of Lactobacillus plantarum SC-5 (SC-5) and tyrosol (TY) combination (TS) in murine colitis, specifically exploring their regulatory activity on the dextran sulfate sodium (DSS)-induced inflammatory pathways (NF-κB and MAPK) and key molecular targets (tight junction protein). The effectiveness of 1 week of treatment with SC-5, TY, or TS was evaluated in a DSS-induced colitis mice model by assessing colitis morbidity and colonic mucosal injury (n = 9). To validate these findings, fecal microbiota transplantation (FMT) was performed by inoculating DSS-treated mice with the microbiota of TS-administered mice (n = 9).

RESULTS

The results demonstrated that all three treatments effectively reduced colitis morbidity and protected against DSS-induced UC. The combination treatment, TS, exhibited inhibitory effects on the DSS-induced activation of mitogen-activated protein kinase (MAPK) and negatively regulated NF-κB. Furthermore, TS maintained the integrity of the tight junction (TJ) structure by regulating the expression of zona-occludin-1 (ZO-1), Occludin, and Claudin-3 (p < 0.05). Analysis of the intestinal microbiota revealed significant differences, including a decrease in Proteus and an increase in Lactobacillus, Bifidobacterium, and Akkermansia, which supported the protective effect of TS (p < 0.05). An increase in the number of Aspergillus bacteria can cause inflammation in the intestines and lead to the formation of ulcers. Bifidobacterium and Lactobacillus can regulate the micro-ecological balance of the intestinal tract, replenish normal physiological bacteria and inhibit harmful intestinal bacteria, which can alleviate the symptoms of UC. The relative abundance of Akkermansia has been shown to be negatively associated with IBD. The FMT group exhibited alleviated colitis, excellent anti-inflammatory effects, improved colonic barrier integrity, and enrichment of bacteria such as Akkermansia (p < 0.05). These results further supported the gut microbiota-dependent mechanism of TS in ameliorating colonic inflammation.

CONCLUSION

In conclusion, the TS demonstrated a remission of colitis and amelioration of colonic inflammation in a gut microbiota-dependent manner. The findings suggest that TS could be a potential natural medicine for the protection of UC health. The above results suggest that TS can be used as a potential therapeutic agent for the clinical regulation of UC.

AhR Activation Ameliorates Intestinal Barrier Damage in Immunostressed Piglets by Regulating Intestinal Flora and Its Metabolism

The primary factor leading to elevated rates of diarrhea and decreased performance in piglets is immunological stress. The regulation of immune stress through the intestinal flora is a crucial mechanism to consider. In total, 30 weaned piglets were randomly allocated to five groups: the basal diet group (Control), basal diet + lipopolysaccharides group (LPS), basal diet + 250 μg/kg 6-Formylindolo [3,2-b] carbazole + LPS group (FICZ), basal diet + 3mg/kg Cardamonin + LPS group (LCDN), and basal diet + 6mg/kg Cardamonin + LPS group (HCDN/CDN). The results showed that compared with those of the LPS group, the expression of tight junction proteins (occludin; claudin-1) in the FICZ group was significantly increased, and the mRNA levels of IL-1β and TNF-α were significantly reduced (p < 0.05). HCDN treatment had a better effect on LPS-induced intestinal barrier damage in this group than it did in the LCDN group. HCDN treatment leads to a higher villus height (VH), a higher ratio of villi height to crypt depth (V/C), higher tight junction proteins (ZO-1; occludin), and higher short-chain fatty acids (SCFAs). In addition, correlation analyses showed that Succinivibrio was positively correlated with several SCFAs and negatively correlated with prostaglandin-related derivatives in the FICZ group and CDN group (p < 0.05). In summary, Cardamonin alleviates intestinal mucosal barrier damage and inflammatory responses by regulating the intestinal microbiota and its metabolism.

Ageratina adenophora causes intestinal integrity damage in goats via the activation of the MLCK/ROCK signaling pathway

As a global toxin invasive species, the whole herb of Ageratina adenophora (A. adenophora) contains various sesquiterpenes, which can cause various degrees of toxic reactions characterized by inflammatory damage when ingested by animals. Current studies on the toxicity of A. adenophora have focused on parenchymatous organs such as the liver and spleen, but few studies have been conducted on the intestine as the organ that is first exposed to A. adenophora and digests and absorbs its toxic components. In this study, after feeding goats with 40 % A. adenophora herb powder for 90 d, we found that the intestinal structure of goats showed pathological changes characterized, and the damage to the small intestinal segments was more severe than that of the large intestine. The MLCK/ROCK signaling pathway was activated, the cytoskeleton underwent centripetal contraction, the composition of tight junctions between intestinal epithelial cells was altered table, Occludin, Claudin-1 and Zonula occluden (ZO-1) amount was decreased, and the intestinal mechanical barrier was disrupted. The intestinal damage markers diamine oxidase (DAO) and D-lactate (D-LA) levels were elevated. In addition, we also found that intestinal bacteria translocate and enter the portal vein to colonize the liver and mesenteric lymph nodes. The expression of intestinal pro-inflammatory factors and anti-inflammatory factors was changed, the intestinal immune function was disrupted. The present study is the first to analyze the mechanism of poisoning of A. adenophora from the intestinal tract in compound-gastric animals.

Benvitimod Inhibits IL-4- and IL-13-Induced Tight Junction Impairment by Activating AHR/ARNT Pathway and Inhibiting STAT6 Phosphorylation in Human Keratinocytes

Tight junctions are involved in skin barrier functions. In this study, the expression of CLDN1, CLDN4, and OCLN was found to decrease in skin lesions of atopic dermatitis by bioinformatics analysis. Immunohistochemistry staining in skin specimens from 12 patients with atopic dermatitis and 12 healthy controls also showed decreased CLDN1, CLDN4, and OCLN expression in atopic dermatitis lesions. In vitro studies showed that IL-4 and IL-13 downregulated CLDN1, CLDN4, and OCLN expression in HaCaT cells as well as CLDN4 and OCLN expression in human primary keratinocytes. This effect, which was mediated through the Jak-signal transducer and activator of transcription 6 signaling pathway, increased paracellular flux of 4-kDa dextran. Benvitimod, a new drug for atopic dermatitis, upregulated CLDN4 and OCLN through the aryl hydrocarbon receptor/aryl hydrocarbon receptor nuclear translocator pathway. Benvitimod induced nuclear translocation of NRF2 and reduced production of ROS in keratinocytes, thus inhibiting IL-4-/IL-13-induced CLDN1 downregulation and signal transducer and activator of transcription 6 phosphorylation. These results indicate that T helper 2 cytokines are involved in tight junction impairment, and benvitimod can inhibit these effects.

6-formylindolo[3, 2-b]carbazole alters gut microbiota and prevents the progression of ankylosing spondylitis in mice

Ankylosing spondylitis (AS), is known as a chronic inflammatory autoimmune disease, there is evidence to suggest that gut microbiota disorders may be related to the occurrence and development of AS. Studies have shown that 6-formylindolo[3, 2-b]carbazole (FICZ) has the ability to modulate intestinal homeostasis and inhibit inflammatory responses. The purpose of this work is to evaluate the protective role of FICZ in treating AS and elucidate potential mechanisms. FICZ was administered to the proteoglycan (PG)-induced AS mice for 7 consecutive weeks. The effects of FICZ on AS mice were evaluated by the disease severity, intestinal histopathology, proinflammatory cytokine levels, and intestinal mucosal barrier function. The gut microbiota compositions were profiled through 16S rDNA high-throughput sequencing. We found that FICZ significantly reduced the severity of AS and resulted in the downregulating of TNF-α and IL-17A inflammatory cytokines. Moreover, FICZ ameliorated pathological changes in the ileal and improved intestinal mucosal barrier function. Furthermore, FICZ altered the composition of the gut microbiota by increasing the Bacteroidetes/Firmicutes phylum ratio and enriched the genes related to "glycan biosynthesis and metabolism", thus reversing the process of AS. In conclusion, FICZ suppressed the progression of AS and altered gut microbiota in AS mice, which provided new insight into AS therapy strategy.

A cross talk between microbial metabolites and host immunity: Its relevance for allergic diseases

BACKGROUND

Allergic diseases, including respiratory and food allergies, as well as allergic skin conditions have surged in prevalence in recent decades. In allergic diseases, the gut microbiome is dysbiotic, with reduced diversity of beneficial bacteria and increased abundance of potential pathogens. Research findings suggest that the microbiome, which is highly influenced by environmental and dietary factors, plays a central role in the development, progression, and severity of allergic diseases. The microbiome generates metabolites, which can regulate many of the host's cellular metabolic processes and host immune responses.

AIMS AND METHODS

Our goal is to provide a narrative and comprehensive literature review of the mechanisms through which microbial metabolites regulate host immune function and immune metabolism both in homeostasis and in the context of allergic diseases.

RESULTS AND DISCUSSION

We describe key microbial metabolites such as short-chain fatty acids, amino acids, bile acids and polyamines, elucidating their mechanisms of action, cellular targets and their roles in regulating metabolism within innate and adaptive immune cells. Furthermore, we characterize the role of bacterial metabolites in the pathogenesis of allergic diseases including allergic asthma, atopic dermatitis and food allergy.

CONCLUSION

Future research efforts should focus on investigating the physiological functions of microbiota-derived metabolites to help develop new diagnostic and therapeutic interventions for allergic diseases.

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.

Alpha-tocopherylquinone-mediated activation of the Aryl Hydrocarbon Receptor regulates the production of inflammation-inducing cytokines and ameliorates intestinal inflammation

This study investigated the role of Alpha-tocopherylquinone (TQ) in regulating the intestinal immune system and the underlying mechanisms. In the experimental dextran sodium sulfate and T cell-mediated colitis models, TQ significantly reduced the mRNA levels of interleukin (IL)-6, IL-1β, IL-17A, IL-23, and tumor necrosis factor (TNF)-α and the abundance of proinflammatory macrophages, T helper (Th)17 cells, and ILC3s in the colons of wild-type mice. TQ also prevented lipopolysaccharide (LPS)-induced activation of NFκB and signal transducer and activator of transcription (Stat)-3 pathways in the human macrophage U937 cells. Pharmacological inhibition or CRISPR-Cas-9-mediated knockout of Aryl hydrocarbon Receptor (AhR) prevented the anti-inflammatory effects of TQ in the LPS-treated U937 cells. Furthermore, TQ reduced the mRNA levels of the LPS-induced pro-inflammatory cytokines in the WT but not Ahr-/- mice splenocytes. TQ also reduced IL-6R protein levels and IL-6-induced Stat-3 activation in Jurkat cells and in vitro differentiation of Th17 cells from wild-type but not Ahr-/- mice naive T cells. Additionally, TQ prevented the pro-inflammatory effects of LPS on macrophages and stimulation of T cells in human PBMCs and significantly reduced the abundance of tumor necrosis factor-α, IL-1β, and IL-6hi inflammatory macrophages and Th17 cells in surgically resected Crohn's disease (CD) tissue. Our study shows that TQ is a naturally occurring, non-toxic, and effective immune modulator that activates AhR and suppresses the Stat-3-NFκB signaling.

Potential Dietary and Therapeutic Strategies Involving Indole-3-Carbinole in Preclinical Models of Intestinal Inflammation

Diet-microbiota interactions are emerging as important contributors in the pathogenesis of inflammatory bowel diseases (IBD), characterized by chronic inflammation of the GI tract. The aryl hydrocarbon receptor (AhR) transcription factor regulates xenobiotic metabolism and is activated by exogenous ligands, including indole-3-carbinole (I3C), which is found in cruciferous vegetables. However, studies investigating the impact of dietary I3C and AhR in preclinical models resembling human IBD are lacking. Mice (WT or AhR KO in IECs, 6-8 weeks) or SAMP/YitFC and AKR/J control (4 weeks, m/f) were fed an AhR ligand-depleted or I3C (200 ppm)-supplemented diet. There were increased levels of LPS and exacerbated inflammation, resulting in increased mortality in AhRΔIEC mice fed the AhR ligand-depleted diet in response to chronic DSS. The mechanisms underlying the protective effects of I3C supplementation during colonic colitis involved amelioration of intestinal inflammation and restoration of the altered gut microbiota, particularly the families of clostridicae and lachnospriaceae. Furthermore, the AhR-depleted diet led to the emergence of pathobiont Parvibacter caecicola in WT mice. SAMP/YitFc mice with spontaneous ileitis showed significant recovery in epithelial abnormalities when fed dietary I3C. These data demonstrate the critical role of AhR and the mechanisms of dietary I3C in maintaining epithelial homeostasis and ameliorating inflammation.

PE (0:0/14:0), an endogenous metabolite of the gut microbiota, exerts protective effects against sepsis-induced intestinal injury by modulating the AHR/CYP1A1 pathway

Sepsis is known to cause damage to the intestinal mucosa, leading to bacterial translocation, and exacerbation of both local and remote organ impairments. In the present study, fecal samples were collected from both septic and healthy individuals. Analysis through 16s rRNA sequencing of the fecal microbiota revealed that sepsis disrupts the balance of the gut microbial community. Recent research has highlighted the association of lipid metabolism with disease. By analyzing the fecal metabolome, four lipid metabolites that showed significant differences between the two groups were identified: PE (O-16:0/0:0), PE (17:0/0:0), PE (0:0/14:0), and PE (12:0/20:5 (5Z, 8Z, 11Z, 14Z, 17Z)). Notably, the serum levels of PE (0:0/14:0) were higher in the healthy group. Subsequent in vitro and in vivo experiments demonstrated the protective effects of this compound against sepsis-induced intestinal barrier damage. Label-free proteomic analysis showed significant differences in the expression levels of the aryl hydrocarbon receptor (AHR), a protein implicated in sepsis pathogenesis, between the LPS-Caco-2 and LPS-Caco-2 + PE (0:0/14:0) groups. Further analysis, with the help of Discovery Studio 3.5 software and co-immunoprecipitation assays, confirmed the direct interaction between AHR and PE (0:0/14:0). In the cecal ligation and puncture (CLP) model, treatment with PE (0:0 /14:0) was found to up-regulate the expression of tight junction proteins through the AHR/Cytochrome P450, family 1, subfamily A, and polypeptide 1 (CYP1A1) pathway. This highlights the potential therapeutic use of PE (0:0/14:0) in addressing sepsis-induced intestinal barrier damage.

Intraspecific difference of Latilactobacillus sakei in inflammatory bowel diseases: Insights into potential mechanisms through comparative genomics and metabolomics analyses

Inflammatory bowel diseases (IBDs) are chronic inflammatory diseases of the gastrointestinal tract that have become a global health burden. Studies have revealed that Latilactobacillus sakei can effectively alleviate various immune diseases, including colitis, rheumatoid arthritis, and metabolic disorders. Here, we obtained 72 strains of L. sakei from 120 fermentation and fecal samples across China. In total, 16 strains from different sources were initially screened in an in vitro Caco-2 model induced by dextran sulfate sodium. Subsequently, six strains (four exhibiting effectiveness and two exhibiting ineffectiveness) were selected for further validation in an in vivo colitis mouse model. The results demonstrated that L. sakei strains exhibited varying degrees of amelioration of the colitis disease process. Notably, L. sakei CCFM1267, the most effective strain, significantly restored colon length and tight-junction protein expression, and reduced the levels of cytokines and associated inflammatory enzymes. Moreover, L. sakei CCFM1267 upregulated the abundance of Enterorhabdus, Alloprevotella, and Roseburia, leading to increased levels of acetic acid and propionic acid. Conversely, the other four strains (L. sakei QJSSZ1L4, QJSSZ4L10, QGZZYRHMT1L6, and QGZZYRHMT2L6) only exhibited a partial remission effect, while L. sakei QJSNT1L10 displayed minimal impact. Therefore, L. sakei CCFM1267 and QJSNT1L10 were selected for further exploration of the mechanisms underlying their differential mitigating effects. Comparative genomics analysis revealed significant variations between the two strains, particularly in genes associated with carbohydrate-active enzymes, such as the glycoside hydrolase family, which potentially contribute to the diverse profiles of short-chain fatty acids in vivo. Additionally, metabolome analysis demonstrated that acetylcholine and indole-3-acetic acid were the main differentiating metabolites of the two strains. Therefore, the strains of L. sakei exhibited varying degrees of effectiveness in alleviating IBD-related symptoms, and the possible reasons for these variations were attributed to discrepancies in the carbohydrate-active enzymes and metabolites among the strains.

Activation of the aryl hydrocarbon receptor in inflammatory bowel disease: insights from gut microbiota

Inflammatory bowel disease (IBD) is a chronic inflammatory intestinal disease that affects more than 3.5 million people, with rising prevalence. It deeply affects patients' daily life, increasing the burden on patients, families, and society. Presently, the etiology of IBD remains incompletely clarified, while emerging evidence has demonstrated that altered gut microbiota and decreased aryl hydrocarbon receptor (AHR) activity are closely associated with IBD. Furthermore, microbial metabolites are capable of AHR activation as AHR ligands, while the AHR, in turn, affects the microbiota through various pathways. In light of the complex connection among gut microbiota, the AHR, and IBD, it is urgent to review the latest research progress in this field. In this review, we describe the role of gut microbiota and AHR activation in IBD and discussed the crosstalk between gut microbiota and the AHR in the context of IBD. Taken as a whole, we propose new therapeutic strategies targeting the AHR-microbiota axis for IBD, even for other related diseases caused by AHR-microbiota dysbiosis.

Gut Microbiota-Derived 5-Hydroxyindoleacetic Acid Alleviates Diarrhea in Piglets via the Aryl Hydrocarbon Receptor Pathway

With the improvement in sow prolificacy, formula feeding has been increasingly used in the pig industry. Diarrhea remains a serious health concern in formula-fed (FF) piglets. Fecal microbiota transplantation (FMT) is an efficacious strategy to reshape gut microbiota and the metabolic profile for treating diarrhea. This study aims to investigate whether FMT from breast-fed piglets could alleviate diarrhea in FF piglets. The piglets were randomly assigned to the control (CON) group, FF group, and FMT group. Our results showed that FF piglets exhibited a higher diarrhea incidence, damaged colonic morphology, and disrupted barrier function. In contrast, FMT treatment normalized the morphology and barrier function. FMT suppressed the JNK/MAPK pathway and production of proinflammatory cytokines. Additionally, FF piglets had a lower abundance of the beneficial bacterial genus Bifidobacterium compared to CON piglets. Following FMT administration, Bifidobacterium was restored. Meanwhile, 5-HIAA, a metabolite of tryptophan, and AHR-responsive CYP1A1 and CYP1B1 were upregulated. Importantly, integrated multiomics analysis revealed a strong positive correlation between Bifidobacterium and 5-HIAA. In vitro, 5-HIAA supplementation reversed the LPS-induced disruption of tight junctions and production of proinflammatory cytokines in IPEC-J2 cells. In conclusion, FMT reduced diarrhea incidence and improved growth performance. The alleviative effect of FMT on diarrhea was associated with Bifidobacterium and 5-HIAA.

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

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

Interactions between gut microbiota and polyphenols: A mechanistic and metabolomic review

BACKGROUND

Polyphenols are a class of naturally sourced compounds with widespread distribution and an extensive array of bioactivities. However, due to their complex constituents and weak absorption, a convincing explanation for their remarkable bioactivity remains elusive for a long time. In recent years, interaction with gut microbiota is hypothesized to be a reasonable explanation of the potential mechanisms for natural compounds especially polyphenols.

OBJECTIVES

This review aims to present a persuasive explanation for the contradiction between the limited bioavailability and the remarkable bioactivities of polyphenols by examining their interactions with gut microbiota.

METHODS

We assessed literatures published before April 10, 2023, from several databases, including Scopus, PubMed, Google Scholar, and Web of Science. The keywords used include "polyphenols", "gut microbiota", "short-chain fatty acids", "bile acids", "trimethylamine N-oxide", "lipopolysaccharides" "tryptophan", "dopamine", "intestinal barrier", "central nervous system", "lung", "anthocyanin", "proanthocyanidin", "baicalein", "caffeic acid", "curcumin", "epigallocatechin-3-gallate", "ferulic acid", "genistein", "kaempferol", "luteolin", "myricetin", "naringenin", "procyanidins", "protocatechuic acid", "pterostilbene", "quercetin", "resveratrol", etc. RESULTS: The review first demonstrates that polyphenols significantly alter gut microbiota diversity (α- and β-diversity) and the abundance of specific microorganisms. Polyphenols either promote or inhibit microorganisms, with various factors influencing their effects, such as dosage, treatment duration, and chemical structure of polyphenols. Furthermore, the review reveals that polyphenols regulate several gut microbiota metabolites, including short-chain fatty acids, dopamine, trimethylamine N-oxide, bile acids, and lipopolysaccharides. Polyphenols affect these metabolites by altering gut microbiota composition, modifying microbial enzyme activity, and other potential mechanisms. The changed microbial metabolites induced by polyphenols subsequently trigger host responses in various ways, such as acting as intestinal acid-base homeostasis regulators and activating on specific target receptors. Additionally, polyphenols are transformed into microbial derivatives by gut microbiota and these polyphenols' microbial derivatives have many potential advantages (e.g., increased bioactivity, improved absorption). Lastly, the review shows polyphenols maintain intestinal barrier, central nervous system, and lung function homeostasis by regulating gut microbiota.

CONCLUSION

The interaction between polyphenols and gut microbiota provides a credible explanation for the exceptional bioactivities of polyphenols. This review aids our understanding of the underlying mechanisms behind the bioactivity of polyphenols.

Intestinal barrier in inflammatory bowel disease: A bibliometric and knowledge-map analysis

BACKGROUND

Barrier surfaces composed of specialized epithelial cells separate the host body from the external environment, and are essential for maintaining proper intestinal physiologic and immune homeostasis.

AIM

To explore the development trends and research hotspots of intestinal barrier research in inflammatory bowel disease (IBD).

METHODS

The publications related to the intestinal barrier in IBD were obtained from the Web of Science Core Collection database. Bibliometric analysis and visualization were conducted using VOSviewer, CiteSpace and R software.

RESULTS

A total of 4482 articles published between 2002 and 2022 were identified. The United States is dominant in intestinal barrier research, whereas the University of Chicago is the most active institution. Jerrold from Harvard Medical School was the most productive authors with the most citations. The journals Inflammatory Bowel Disease and Gastroenterology have made significant contributions in this field. The keywords appearing at high frequency related to the intestinal barrier in IBD were detected, including nuclear factor kappa B, tumor necrosis factor-α, apoptosis, oxidative stress and probiotics. Among them, antioxidants, Akkermansia muciniphila, nanoparticles, short-chain fatty acids and extracellular vesicles have received growing interest in recent research.

CONCLUSION

The intestinal barrier field is developing rapidly with extensive cooperation. Targeting the gut microbiota and dietary metabolism to regulate the intestinal barrier has shown promising prospective applications and has generated broad interest. The importance of the intestinal barrier in IBD is gradually being fully recognized, providing a new therapeutic perspective for improving inflammation and prognosis.

Aryl hydrocarbon receptor utilises cellular zinc signals to maintain the gut epithelial barrier

Zinc and plant-derived ligands of the aryl hydrocarbon receptor (AHR) are dietary components affecting intestinal epithelial barrier function. Here, we explore whether zinc and the AHR pathway are linked. We show that dietary supplementation with an AHR pre-ligand offers protection against inflammatory bowel disease in a mouse model while protection fails in mice lacking AHR in the intestinal epithelium. AHR agonist treatment is also ineffective in mice fed zinc depleted diet. In human ileum organoids and Caco-2 cells, AHR activation increases total cellular zinc and cytosolic free Zn2+ concentrations through transcription of genes for zinc importers. Tight junction proteins are upregulated through zinc inhibition of nuclear factor kappa-light-chain-enhancer and calpain activity. Our data show that AHR activation by plant-derived dietary ligands improves gut barrier function at least partly via zinc-dependent cellular pathways, suggesting that combined dietary supplementation with AHR ligands and zinc might be effective in preventing inflammatory gut disorders.

Impact of Gut Bacterial Metabolites on Psoriasis and Psoriatic Arthritis: Current Status and Future Perspectives

There is growing evidence that supports a role of gut dysbiosis in the pathogenesis of psoriasis (Pso). Thus, probiotic supplementation and fecal microbiota transplantation may serve as promising preventive and therapeutic strategies for patients with Pso. One of the basic mechanisms through which the gut microbiota interacts with the host is through bacteria-derived metabolites, usually intermediate or end products produced by microbial metabolism. In this study, we provide an up-to-date review of the most recent literature on microbial-derived metabolites and highlight their roles in the immune system, with a special focus on Pso and one of its most common comorbidities, psoriatic arthritis.

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.

Triclocarban exposure aggravates dextran sulfate sodium-induced colitis by deteriorating the gut barrier function and microbial community in mice

Triclocarban (TCC) is an antibacterial component widely used in personal care products with potential toxicity possessing public health issues. Unfortunately, enterotoxicity mechanisms of TCC exposure remain largely unknown. Using a combination of 16S rRNA gene sequencing, metabolomics, histopathological and biological examinations, this study systematically explored the deteriorating effects of TCC exposure on a dextran sulfate sodium (DSS)-induced colitis mouse model. We found that TCC exposure at different doses significantly aggravated colitis phenotypes including shortened colon length and altered colonic histopathology. Mechanically, TCC exposure further disrupted intestinal barrier function, manifested by significant downregulation of the number of goblet cells, mucus layer thickness and expression of junction proteins (MUC-2, ZO-1, E-cadherin and Occludin). The gut microbiota composition and its metabolites such as short-chain fatty acids (SCFAs) and tryptophan metabolites were also markedly altered in DSS-induced colitis mice. Consequently, TCC exposure markedly exacerbated colonic inflammatory status of DSS-treated mice by activating NF-κB pathway. These findings provided new evidence that TCC could be an environmental hazards for development of IBD or even colon cancer.

Impairment of aryl hydrocarbon receptor signalling promotes hepatic disorders in cancer cachexia

BACKGROUND

The aryl hydrocarbon receptor (AHR) is expressed in the intestine and liver, where it has pleiotropic functions and target genes. This study aims to explore the potential implication of AHR in cancer cachexia, an inflammatory and metabolic syndrome contributing to cancer death. Specifically, we tested the hypothesis that targeting AHR can alleviate cachectic features, particularly through the gut-liver axis.

METHODS

AHR pathways were explored in multiple tissues from four experimental mouse models of cancer cachexia (C26, BaF3, MC38 and APCMin/+ ) and from non-cachectic mice (sham-injected mice and non-cachexia-inducing [NC26] tumour-bearing mice), as well as in liver biopsies from cancer patients. Cachectic mice were treated with an AHR agonist (6-formylindolo(3,2-b)carbazole [FICZ]) or an antibody neutralizing interleukin-6 (IL-6). Key mechanisms were validated in vitro on HepG2 cells.

RESULTS

AHR activation, reflected by the expression of Cyp1a1 and Cyp1a2, two major AHR target genes, was deeply reduced in all models (C26 and BaF3, P < 0.001; MC38 and APCMin/+ , P < 0.05) independently of anorexia. This reduction occurred early in the liver (P < 0.001; before the onset of cachexia), compared to the ileum and skeletal muscle (P < 0.01; pre-cachexia stage), and was intrinsically related to cachexia (C26 vs. NC26, P < 0.001). We demonstrate a differential modulation of AHR activation in the liver (through the IL-6/hypoxia-inducing factor 1α pathway) compared to the ileum (attributed to the decreased levels of indolic AHR ligands, P < 0.001), and the muscle. In cachectic mice, FICZ treatment reduced hepatic inflammation: expression of cytokines (Ccl2, P = 0.005; Cxcl2, P = 0.018; Il1b, P = 0.088) with similar trends at the protein levels, expression of genes involved in the acute-phase response (Apcs, P = 0.040; Saa1, P = 0.002; Saa2, P = 0.039; Alb, P = 0.003), macrophage activation (Cd68, P = 0.038) and extracellular matrix remodelling (Fga, P = 0.008; Pcolce, P = 0.025; Timp1, P = 0.003). We observed a decrease in blood glucose in cachectic mice (P < 0.0001), which was also improved by FICZ treatment (P = 0.026) through hepatic transcriptional promotion of a key marker of gluconeogenesis, namely, G6pc (C26 vs. C26 + FICZ, P = 0.029). Strikingly, these benefits on glycaemic disorders occurred independently of an amelioration of the gut barrier dysfunction. In cancer patients, the hepatic expression of G6pc was correlated to Cyp1a1 (Spearman's ρ = 0.52, P = 0.089) and Cyp1a2 (Spearman's ρ = 0.67, P = 0.020).

CONCLUSIONS

With this set of studies, we demonstrate that impairment of AHR signalling contributes to hepatic inflammatory and metabolic disorders characterizing cancer cachexia, paving the way for innovative therapeutic strategies in this context.

Arabinogalactan ameliorates benzo[a]pyrene-induced intestinal epithelial barrier dysfunction via AhR/MAPK signaling pathway

Benzo[a]pyrene (B[a]P), a kind of pollutant, can disrupt the gut microbiota, but its effects on the function of intestinal epithelial barrier (IEB) is still unclear. Arabinogalactan (AG), a natural polysaccharide, can protect intestinal tract. Thus, the purpose of this study was to evaluate the effect of B[a]P on IEB function and the mitigation effect of AG on the IEB dysfunction induced by B[a]P using a Caco-2 cell monolayer model. We found B[a]P could damage the IEB integrity by inducing cell cytotoxicity, increasing lactate dehydrogenase leakage, decreasing the transepithelial electrical resistance, and increasing fluorescein isothiocyanate-dextran flux. The mechanism of B[a]P-induced IEB damage may through induction of oxidative stress, including increasing reactive oxygen species levels, decreasing glutathione levels, reducing the activity of superoxide dismutase, and increasing malonaldehyde levels. Moreover, it can be due to increasing secretion of pro-inflammatory cytokines (interleukin [IL]-1β, IL-6, and tumor necrosis factor [TNF]-α), down-regulated expression of tight junction (TJ) proteins (claudin-1, zonula occludens [ZO]-1, and occludin), and induced activation of aryl hydrocarbon receptor (AhR)/mitogen activated protein kinase (MAPK) signaling pathway. Remarkably, AG ameliorated B[a]P-induced IEB dysfunction through inhibited oxidative stress and pro-inflammatory factor secretion. Our study demonstrated B[a]P could damage the IEB and AG could alleviate this damage.

Gut Microbial Metabolite Butyrate and Its Therapeutic Role in Inflammatory Bowel Disease: A Literature Review

Background and objective: Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a chronic inflammatory disorder characterized by aberrant immune responses and compromised barrier function in the gastrointestinal tract. IBD is associated with altered gut microbiota and their metabolites in the colon. Butyrate, a gut microbial metabolite, plays a crucial role in regulating immune function, epithelial barrier function, and intestinal homeostasis. In this review, we aim to present an overview of butyrate synthesis and metabolism and the mechanism of action of butyrate in maintaining intestinal homeostasis and to discuss the therapeutic implications of butyrate in IBD. Methods: We searched the literature up to March 2023 through PubMed, Web of Science, and other sources using search terms such as butyrate, inflammation, IBD, Crohn's disease, and ulcerative colitis. Clinical studies in patients and preclinical studies in rodent models of IBD were included in the summary of the therapeutic implications of butyrate. Results: Research in the last two decades has shown the beneficial effects of butyrate on gut immune function and epithelial barrier function. Most of the preclinical and clinical studies have shown the positive effect of butyrate oral supplements in reducing inflammation and maintaining remission in colitis animal models and IBD patients. However, butyrate enema showed mixed effects. Butyrogenic diets, including germinated barley foodstuff and oat bran, are found to increase fecal butyrate concentrations and reduce the disease activity index in both animal models and IBD patients. Conclusions: The current literature suggests that butyrate is a potential add-on therapy to reduce inflammation and maintain IBD remission. Further clinical studies are needed to determine if butyrate administration alone is an effective therapeutic treatment for IBD.

Engineered bacteria producing aryl-hydrocarbon receptor agonists protect against ethanol-induced liver disease in mice

BACKGROUND AND PURPOSE

Gut bacteria metabolize tryptophan into indoles. Intestinal levels of the tryptophan metabolite indole-3-acetic acid are reduced in patients with alcohol-associated hepatitis. Supplementation of indole-3-acetic acid protects against ethanol-induced liver disease in mice. The aim of this study was to evaluate the effect of engineered bacteria producing indoles as Aryl-hydrocarbon receptor (Ahr) agonists.

METHODS

C57BL/6 mice were subjected to chronic-plus-binge ethanol feeding and orally given PBS, control Escherichia coli Nissle 1917 (EcN) or engineered EcN-Ahr. The effects of EcN and EcN-Ahr were also examined in mice lacking Ahr in interleukin 22 (Il22)-producing cells.

RESULTS

Through the deletion of endogenous genes trpR and tnaA, coupled with overexpression of a feedback-resistant tryptophan biosynthesis operon, EcN-Ahr were engineered to overproduce tryptophan. Additional engineering allowed conversion of this tryptophan to indoles including indole-3-acetic acid and indole-3-lactic acid. EcN-Ahr ameliorated ethanol-induced liver disease in C57BL/6 mice. EcN-Ahr upregulated intestinal gene expression of Cyp1a1, Nrf2, Il22, Reg3b, and Reg3g, and increased Il22-expressing type 3 innate lymphoid cells. In addition, EcN-Ahr reduced translocation of bacteria to the liver. The beneficial effect of EcN-Ahr was abrogated in mice lacking Ahr expression in Il22-producing immune cells.

CONCLUSIONS

Our findings indicate that tryptophan metabolites locally produced by engineered gut bacteria mitigate liver disease via Ahr-mediated activation in intestinal immune cells.

Targeting the aryl hydrocarbon receptor by gut phenolic metabolites: A strategy towards gut inflammation

The Aryl Hydrocarbon Receptor (AHR) is a ligand-dependent transcription factor able to control complex transcriptional processes in several cell types, which has been correlated with various diseases, including inflammatory bowel diseases (IBD). Numerous studies have described different compounds as ligands of this receptor, like xenobiotics, natural compounds, and several host-derived metabolites. Dietary (poly)phenols have been studied regarding their pleiotropic activities (e.g., neuroprotective and anti-inflammatory), but their AHR modulatory capabilities have also been considered. However, dietary (poly)phenols are submitted to extensive metabolism in the gut (e.g., gut microbiota). Thus, the resulting gut phenolic metabolites could be key players modulating AHR since they are the ones that reach the cells and may exert effects on the AHR throughout the gut and other organs. This review aims at a comprehensive search for the most abundant gut phenolic metabolites detected and quantified in humans to understand how many have been described as AHR modulators and what could be their impact on inflammatory gut processes. Even though several phenolic compounds have been studied regarding their anti-inflammatory capacities, only 1 gut phenolic metabolite, described as AHR modulator, has been evaluated on intestinal inflammatory models. Searching for AHR ligands could be a novel strategy against IBD.

Spermidine protects intestinal mucosal barrier function in mice colitis via the AhR/Nrf2 and AhR/STAT3 signaling pathways

BACKGROUND

Aryl hydrocarbon receptor (AhR) activation promotes intestinal barrier repair and enhances the gut mucosal barrier function in inflammatory bowel diseases (IBD). Spermidine is beneficial in several murine models of IBD and may affect AhR activity. However, the precise effects of spermidine on the intestinal barrier and AhR remain unclear. This study was designed to investigate whether spermidine affects AhR and gut barrier function in IBD models as well as, its underlying mechanism.

METHODS

We used dextran sulfate sodium (DSS)- and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced mice, as well as, Caco2 cells incubated with TNF-α and IFN-γ to establish multiple IBD models, followed by spermidine intervention. Alcian blue/Periodic acid-Schiff (AB/PAS) staining, Fluorescein isothiocyanate (FITC)-dextran permeability assay, transepithelial electrical resistance (TER), tight junction protein (TJs) expression, and 16S rRNA scope in situ hybridization were performed to assess intestinal barrier function. AhR expression and the associated pathways were measured. AhR-targeted adeno-associated virus (AAV) and siRNA were used to explore the related molecular mechanisms.

RESULTS

Spermidine significantly attenuated the increased intestinal permeability, decreased TER, abnormal distribution of TJs in colitis, and bacterial translocation from the gut tract. Additionally, it significantly increased AhR and Nrf2 expression and inhibited STAT3 phosphorylation. However, the protective effects of spermidine and the related alterations in pathway proteins were largely abolished by the specific inhibition of AhR.

CONCLUSION

Our study demonstrated that spermidine rescues intestinal barrier defects in mice with colitis via the AhR-Nrf2 and AhR-STAT3 pathways, providing a potential therapeutic agent for IBD and other conditions associated with dysregulated gut barrier function.

Heat Stress-Induced Intestinal Barrier Impairment: Current Insights into the Aspects of Oxidative Stress and Endoplasmic Reticulum Stress

Heat stress (HS) occurs when the sensible temperature of animals exceeds their thermoregulatory capacity, a condition that exerts a detrimental impact on health and growth. The intestinal tract, as a highly sensitive organ, has been shown to respond to HS by exhibiting mucosal injury, intestinal leakage, and disturbances in the gut microbiota. Oxidative stress and endoplasmic reticulum stress (ERS) are both potential outcomes of long-term exposure to high temperatures and have been linked to apoptosis, autophagy, and ferroptosis. In addition, HS alters the composition of the gut microbiota accompanied by changed levels of bacterial components and metabolites, rendering the gut more vulnerable to stress-related injury. In this review, we present recent advances in mechanisms of oxidative stress-associated ERS in response to HS, which is destructive to intestinal barrier integrity. The involvement of autophagy and ferroptosis in ERS was highlighted. Further, we summarize the relevant findings regarding the engagement of gut microbiota-derived components and metabolites in modulation of intestinal mucosal injury induced by HS.

Gut microbe-derived milnacipran enhances tolerance to gut ischemia/reperfusion injury

There are significant differences in the susceptibility of populations to intestinal ischemia/reperfusion (I/R), but the underlying mechanisms remain elusive. Here, we show that mice exhibit significant differences in susceptibility to I/R-induced enterogenic sepsis. Notably, the milnacipran (MC) content in the enterogenic-sepsis-tolerant mice is significantly higher. We also reveal that the pre-operative fecal MC content in cardiopulmonary bypass patients, including those with intestinal I/R injury, is associated with susceptibility to post-operative gastrointestinal injury. We reveal that MC attenuates mouse I/R injury in wild-type mice but not in intestinal epithelial aryl hydrocarbon receptor (AHR) gene conditional knockout mice (AHR^flox/flox) or IL-22 gene deletion mice (IL-22^-/-). Collectively, our results suggest that gut microbiota affects susceptibility to I/R-induced enterogenic sepsis and that gut microbiota-derived MC plays a pivotal role in tolerance to intestinal I/R in an AHR/ILC3/IL-22 signaling-dependent manner, revealing the pathological mechanism, potential prevention and treatment drugs, and treatment strategies for intestinal I/R.

Beneficial Effects of Hordenine on a Model of Ulcerative Colitis

Hordenine, a phenethylamine alkaloid, is found in a variety of plants and exhibits a broad array of biological activities and pharmacological properties, including anti-inflammatory and anti-fibrotic effects. However, the efficacy and underlying mechanisms of hordenine in treating ulcerative colitis (UC) remain unclear. To address this, we examined the therapeutic effects of hordenine on dextran sodium sulphate (DSS)-induced UC by comparing disease activity index (DAI), colon length, secretion of inflammatory factors, and degree of colonic histological lesions across diseased mice that were and were not treated with hordenine. We found that hordenine significantly reduced DAI and levels of pro-inflammatory factors, including interleukin (IL)-6, IL-1β, and tumor necrosis factor alpha (TNF-α), and also alleviated colon tissue oedema, colonic lesions, inflammatory cells infiltration and decreased the number of goblet cells. Moreover, in vitro experiments showed that hordenine protected intestinal epithelial barrier function by increasing the expression of tight junction proteins including ZO-1 and occludin, while also promoting the healing of intestinal mucosa. Using immunohistochemistry and western blotting, we demonstrated that hordenine reduced the expression of sphingosine kinase 1 (SPHK1), sphingosine-1-phosphate receptor 1 (S1PR1), and ras-related C3 botulinum toxin substrate 1 (Rac1), and it inhibited the expression of phosphorylated signal transducer and activator of transcription 3 (p-STAT3) in colon tissues. Thus, hordenine appears to be effective in UC treatment owing to pharmacological mechanisms that favor mucosal healing and the inhibition of SPHK-1/S1PR1/STAT3 signaling.

ROS Scavenging and inflammation-directed polydopamine nanoparticles regulate gut immunity and flora therapy in inflammatory bowel disease

Dysfunction of the intestinal mucosal immune system and dysbiosis of the intestinal microflora can induce inflammatory bowel disease. However, drug-mediated clinical treatment remains a challenge due to its poor therapeutic efficacy and severe side effects. Herein, a ROS scavenging and inflammation-directed nanomedicine is designed and fabricated by coupling polydopamine nanoparticles with mCRAMP, an antimicrobial peptide, while wrapping macrophage membrane in the outer layer. The designed nanomedicine reduced the secretion of pro-inflammatory cytokines and elevate the expression of anti-inflammatory cytokine in vivo and in vitro inflammation models, demonstrating its significant ability of improving inflammatory responses. Importantly, the macrophage membrane encapsulated nanoparticles exhibit the obviously enhanced targeting performance in local inflamed tissues. Furthermore, the 16S rRNA sequencing of fecal microorganisms showed that probiotics increased and pathogenic bacteria were inhibited after oral delivery the nanomedicine, indicating that the designed nano platform played a significant role in optimizing intestinal microbiome. Taken together, the designed nanomedicine are not only easy to prepare and exhibit high biocompatibility, but also show the inflammatory targeting property, anti-inflammatory function and positive regulation of intestinal flora, thus providing a new idea for the intervention and treatment of colitis. STATEMENT OF SIGNIFICANCE: Inflammatory bowel disease (IBD), a chronic and intractable disease, may lead to colon cancer in severe cases without effective treatment. However, clinical drugs are largely ineffective owing to insufficient therapeutic efficacies and side effects. Herein, we constructed a biomimetic polydopamine nanoparticle for oral administration to treat the IBD by modulating mucosal immune homeostasis and optimizing intestinal microorganisms. In vitro and in vivo experiments showed that the designed nanomedicine not only exhibits the anti-inflammatory function and inflammatory targeting property but also positively regulate the gut microflora. Taken together, the designed nanomedicine combined immunoregulation and intestinal microecology modulation to significantly enhance the therapeutic effect on colitis in mice, thus providing a new approach for the clinical treatment of colitis.

Tyrosol inhibits NF-κB pathway in the treatment of enterotoxigenic Escherichia coli-induced diarrhea in mice

Tyrosol is one of the main polyphenol compounds in white wine and extra virgin olive oil (EVOO), which plays an antioxidant and anti-inflammatory role in vitro. In the present study, we investigated the possible anti-inflammatory mechanism of tyrosol in Escherichia coli (ETEC)-induced diarrhea in mice. ICR mice were randomly divided into control group, ETEC group, and ETEC + Tyrosol group with 10 mice in each group. In addition to the control group, a bacterial diarrhea model was induced in mice by continuous administration of 0.2 ml × 10⁹ CFU/ml ETEC. After 7 days, the ETEC + Tyrosol group was given tyrosol (20 mg/kg) once a day by gavage, during which the body weight of mice and the degree of diarrhea were measured daily. On the 15th day, all animals in this experiment were sacrificed, colon tissue was collected, and colon length was recorded. Our results indicate that tyrosol significantly attenuated the extent of ETEC-induced diarrhea, including inhibition of pro-inflammatory cytokine, repair of the intestinal epithelial mechanical barrier, and significant inhibition of NF-κB activation. This finding is helpful for the development and further application of tyrosol in the treatment of diarrhea.

Kynurenine pathway metabolites modulated the comorbidity of IBD and depressive symptoms through the immune response

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is defined as chronic inflammation in the gastrointestinal tract. Notably, more than 20% of people with IBD experience depressive symptoms. Understanding the immunological mechanism of chronic intestinal inflammation on cognitive behavior has become a key research focus. Previous studies have shown that a dysregulated immune response contributes to chronic inflammation and depressive symptoms. The tolerant phenotype exhibited by immune cells regulates the course of chronic inflammation in distinct ways. In addition, neuroglia, such as microglia and astrocytes specific to the brain, are also influenced by deregulated inflammation to mediate the development of depressive symptoms. The kynurenine pathway (KP), a significant tryptophan metabolic pathway, transforms tryptophan into a series of KP metabolites that modulate chronic inflammation and depressive symptoms. In particular, indoleamine 2,3-dioxygenase 1 (IDO1), a rate-limiting enzyme in the KP, is activated by chronic inflammation and leads to the production of kynurenine. In addition, disruption of the brain-gut axis induced by IBD allows kynurenine to cross the blood-brain barrier (BBB) and form a series of neuroactive kynurenine metabolites in glial cells. Among them, quinolinic acid continuously accumulates in the brain, indicating depression. Thus, KP metabolites are critical for driving the comorbidity of IBD and depressive symptoms. In this review, the pathological mechanism of KP metabolite-mediated chronic intestinal inflammation and depressive symptoms by regulating the immune response is summarized according to the latest reports.

Bifidobacterium bifidum Ameliorates DSS-Induced Colitis in Mice by Regulating AHR/NRF2/NLRP3 Inflammasome Pathways through Indole-3-lactic Acid Production

In this study, the effectors and mechanisms of Bifidobacterium bifidum FL-276.1 and B. bifidum FL-228.1 in alleviating dextran sulfate sodium (DSS)-induced colitis were investigated. Both FL-276.1 and FL-228.1 significantly alleviated DSS-induced colitis, whether they were supplemented from the beginning of the experiment (whole course intervention) or after the DSS induction started (partial intervention). Aryl hydrocarbon receptor (AHR) and the nuclear factor erythroid 2-related factor 2 (NRF2) pathways were activated in mice colons, while the NLR family pyrin domain containing 3 (NLRP3) was downregulated under the whole course intervention modes. Indole-3-lactic acid, an AHR ligand produced by FL-276.1 and FL-228.1, could regulate the AHR/NRF2/NLRP3 pathway in Caco-2 monolayers, thus upregulating the tight junction proteins and protecting the integrity of the epithelial barrier. These results are conducive to promoting clinical trials and product development of probiotics for alleviating colitis.

Indole-3-propionic acid alleviates chondrocytes inflammation and osteoarthritis via the AhR/NF-κB axis

BACKGROUND

Osteoarthritis (OA) is a common chronic disease characterized by chronic inflammation and extracellular matrix degradation. Indole-3-propionic acid (IPA) is a tryptophan metabolite secreted by intestinal flora, which can exert anti-inflammatory effects in a variety of diseases. In this study, we further investigated the potential therapeutic role of IPA in OA and the underlying mechanism.

METHODS

IL-1β was utilized to induce chondrocyte inflammation. Then, the cytotoxicity of IPA on rat chondrocytes was assessed. Meanwhile, RT-qPCR, Griess reaction, ELISA, Western blot and immunofluorescence were performed to evaluate the expression of inflammatory factors and stromal proteins, and the NF-κB pathway in chondrocytes treated with IL-1β alone, with IPA or with aryl hydrocarbon receptor (AhR) knockdown. An OA rat model was established by anterior cruciate ligament transection, and hematoxylin-eosin staining, Safranin-O/Fast Green staining and immunochemistry were applied to estimate OA severity.

RESULTS

IPA did not affect cellular viability at concentrations up to 80 µM. IPA significantly inhibited the IL-1β-induced expression of inflammatory factors (Nitric oxide, PGE2, TNF-α, IL-6, iNOS and COX-2) and matrix-degrading enzymes (MMP-3, MMP-13 and ADAMTS-5), upregulated the expression of anabolic markers (aggrecan and collagen-II) and inactivated the NF-κB pathway. However, AhR knockdown could abolish the above protection capabilities and the suppression of the NF-κB pathway induced by IPA. Furthermore, IPA significantly reduced serum inflammatory cytokines expression, cartilage destruction and synovitis in vivo, demonstrating its protective role in OA progression.

CONCLUSION

IPA improved IL-1β-induced chondrocyte inflammation and extracellular matrix degradation through the AhR/NF-κB axis, which provides an innovative therapeutic strategy for OA.