TGR5 agonist inhibits intestinal epithelial cell apoptosis via cAMP/PKA/c-FLIP/JNK signaling pathway and ameliorates dextran sulfate sodium-induced ulcerative colitis

Selenomethionine attenuates Klebsiella pneumoniae-induced jejunal injury in rabbits by inhibiting the TLR4/NF-κB pathway

Klebsiella pneumoniae (KP) infection often causes diarrhoea and intestinal barrier damage in young rabbits. The objective of this study was to explore whether selenomethionine (SeMet) can attenuate the jejunal injury caused by KP in rabbits. Therefore, we investigated the protective effect of SeMet by performing haematoxylin-eosin (HE), alcian blue periodic acid Schiff (AB-PAS), proliferating nuclear antigen (PCNA), TUNEL and immunofluorescence staining. In addition, the concentrations of Interleukin-1β (IL-1β), Interleukin-6 (IL-6), Tumor necrosisfactor-α (TNF-α) and Interleukin-10 (IL-10) in the jejunal tissue were detected by enzyme-linked immunosorbent assay (ELISA). The results showed that after KP infection, the productivity of rabbits decreased, and the mucosal barrier of the jejunum was damaged. Moreover, KP induced jejunal inflammation, activated the TLR4/NF-κB signalling pathway, and promoted the expression of the IL-1β, IL-6, and TNF-α. In addition, KP increased the apoptotic response of intestinal cells and upregulated the expression of caspase-3 and caspase-9. SeMet pretreatment significantly decreased the degree of intestinal epithelial cell apoptosis. Therefore, we showed that SeMet can reduce inflammation and enhance intestinal barrier function to improve the production performance of rabbits infected with KP.

Luteolin Modulate Endoplasmic Reticulum Stress by Targeting SIRT1 to Ameliorate DSS-Induced Ulcerative Colitis in Mice

Ulcerative colitis (UC) is a recurrent, chronic disease whose main symptoms include weight loss, diarrhea, and blood in the stool. In recent years, the incidence of UC has been increasing year by year, which seriously affects the daily life of patients. Luteolin (Lut), as a flavonoid, is widely found in a variety of vegetables and fruits and has been shown to have a variety of pharmacological activities. This work investigated the effects of Lut on dextrose sodium sulfate (DSS)-induced ulcerative colitis (UC) in mice, with a special focus on the role of endoplasmic reticulum (ER) stress in this. The outcomes demonstrated that colitis symptoms, including disease phenotype, elevated inflammatory factor levels, intestinal barrier damage, and gut microbiota disruption, were considerably alleviated in UC model mice treated with luteolin. Also, Lut alleviated ER stress and apoptosis in UC mice. We then explored the effects of Lut on ER stress and apoptosis induced by thapsigargin (TG) and tunicamycin (TM) in HT29 cells in vitro. It was found that Lut treatment inhibited TM/TG-induced ER stress and apoptosis. However, these inhibitory effects of Lut were attenuated by SIRT1 silencing in TM-treated HT29 cells. In conclusion, our results suggest that Lut supplementation in a mouse model of colitis improves the symptoms of colitis in mice, which provides a theoretical basis for further application of Lut in the prevention of inflammation-related diseases in humans.

TGR5 attenuates DOCA-salt hypertension through regulating histone H3K4 methylation of ENaC in the kidney

Epithelial sodium channel (ENaC), located in the collecting duct principal cells of the kidney, is responsible for the reabsorption of sodium and plays a critical role in the regulation of extracellular fluid volume and consequently blood pressure. The G protein-coupled bile acid receptor (TGR5) is a membrane receptor mediating effects of bile acid and is implicated in kidney diseases. The current study aims to investigate whether TGR5 activation in the kidney regulated ENaC expression and potential mechanism. Lithocholic acid (LCA), a TGR5 agonist, markedly decreased systolic blood pressure induced by DOCA-salt in mice, which was associated with decreased ENaC expression in the kidney. DOCA-salt treatment increased renal expression of histone H3 lysine 4 trimethylation (H3K4me3) and decreased expression of lysine-specific demethylase 5A (KDM5A), a lysine demethylase, which was markedly reversed by LCA. TGR5 knockout caused further increased systolic blood pressure and ENaC expression in mice with DOCA-salt in association with increased H3K4me3 and decreased KDM5A. In immortalized mouse cortical collecting duct (mpkCCD) cells LCA markedly inhibited aldosterone-induced ENaC-mediated current. LCA treatment or TGR5 overexpression markedly inhibited ENaC and H3K4me3 protein expression in association with decreased KDM5A in mpkCCD cells treated with either aldosterone or angiotensin II. Inhibition or knockdown of KDM5A in mpkCCD cells prevented LCA-induced downregulation of ENaC expression by promoting H3K4me3 on the ENaC transcription start site. LCA upregulated KDM5A expression was likely through JNK/c-Jun signal pathway. In conclusion, LCA decreased blood pressure and ENaC protein expression in the kidney of mice with DOCA-salt, likely through activating TGR5 and upregulating KDM5A-induced H3K4me3 demethylation in ENaC promoter region.

Gancao Xiexin decoction attenuated experimental colitis through suppressing ACSL4-mediated ferroptosis

ETHNOPHARMACOLOGICAL RELEVANCE

The Gancao Xiexin decoction (GCXXD), comprising Glycyrrhiza glabra L., Pinellia ternata (Thunb.) Makino, Scutellaria baicalensis Georgi, Zingiber officinale Roscoe, Panax ginseng C.A.Mey. , Coptis chinensis Franch. , Ziziphus jujuba Mill. , represents a traditional Chinese medicinal formulation utilized for the treatment of ulcerative colitis (UC). Nevertheless, the potential mechanism behind GCXXD treatment for UC is not yet fully elucidated.

AIM OF THE STUDY

Ulcerative colitis is a chronic inflammatory disorder of the gastrointestinal system distinguished by intestinal barrier destruction. Previous studies have indicated that excessive ferroptosis activation in intestinal epithelial cells (IECs) can worsen damage and focal permeability abnormalities in the colon. One of the main mechanisms of ferroptosis is lipid peroxides, which are dependent on long-chain acyl-CoA synthetase 4 (ACSL4) for the synthesis of membrane phospholipids. Recent research findings have provided evidence that GCXXD significantly reduces the symptoms of ulcerative colitis (UC) by preserving the intestinal mucosal barrier. So, we aim to demonstrate that the pharmacological mechanism of GCXXD is related to ferroptosis mediated by ACSL4 in this research.

MATERIALS AND METHODS

In this investigation, we evaluated the GSE134025 datasets and established an experimental colitis model caused by DSS and treated with a 20 mg/kg ACSL4 inhibitor (rosiglitazone). Colon pathological alterations and Alcian blue staining were used to confirm ACSL4 inhibition as a possible therapy for UC. We then examined illness symptoms, intestinal mucosa repair, and ferroptosis markers in UC mice after treated with GCXXD (9,12,15 g/kg). Transcriptome study of colon tissues revealed more about the underlying mechanism of GCXXD in the treatment of UC. Finally, we co-administered the ACSL4 upstream agonist with GCXXD in the treatment of UC to show that GCXXD reduced inflammation in UC by modifying ACSL4-induced ferroptosis.

RESULTS

Through GSE134025 dataset analysis, we discovered that ACSL4 was substantially expressed in UC patients and that its inhibitors successfully reduced the clinical signs and symptoms of UC colon. Furthermore, we found that GCXXD improved colon length and body weight while increasing the expression of mucin, occuldin, and Claudin-1. It also lowered colon inflammatory cell infiltration and levels of IL-1β and TNF-α. In the meantime, GCXXD efficiently decreased ferroptosis-related indicators in colitis mice, such as MDA, Fe2+, COX2, and ACSL4, while also upregulated GPX4 expression. Using KEGG analysis of the genes that were differently expressed between the 3% DSS and GCXXD treatment group, we were able to discover important connections between the hippo signaling pathway, Arachidonic acid metabolism with GCXXD treatment. Due to the fact that TEAD4 functions as an upstream transcription factor for ACSL4, we combined GCXXD and Py-60, a YAP agonist in the treatment of UC. It was worth noting that GCXXD's inhibitory effect of on intestinal mucosa damage and ferroptosis was lessened when the ACSL4 upstream pathway was activated.

CONCLUSION

Gancao Xiexin decoction attenuated ferroptosis in UC which might through TEAD4/ACSL4 pathway.

Phillygenin ameliorates tight junction proteins reduction, fibrosis, and apoptosis in mice with chronic colitis via TGR5-mediated PERK-eIF2α-Ca2+ pathway

Ulcerative colitis (UC) is an idiopathic, relapsing, and etiologically complicated chronic inflammatory bowel disease. Despite substantial progress in the management of UC, the outcomes of mucosal barrier repair are unsatisfactory. In this study, phillygenin (PHI) treatment alleviated the symptoms of chronic colitis in mice, including body weight loss, severe disease activity index scores, colon shortening, splenomegaly, oxidative stress, and inflammatory response. In particular, PHI treatment ameliorated the tight junction proteins (TJs) reduction, fibrosis, apoptosis, and intestinal stem cell activity, indicating that PHI exerted beneficial effects on the intestinal mucosal barrier in mice with chronic colitis. In the NCM460 cells damage model, dextran sulfate sodium triggered the sequential induction of TJs reduction, fibrosis, and apoptosis. Takeda G protein-coupled receptor-5 (TGR5) dysfunction mediated NCM460 cell injury. Moreover, PHI treatment enhanced TJs and suppressed fibrosis and apoptosis to maintain NCM460 cell function, depending on TGR5 activation. PHI promoted TGR5 activation and elevated intracellular cyclic adenosine monophosphate levels in HEK 293T cells transfected with TGR5 expression plasmids. Cellular thermal shift assay and molecular docking studies confirmed that PHI directly binds to TGR5, indicating that PHI is an agonist of TGR5. The process of PERK-eIF2α pathway-mediated endoplasmic reticulum Ca2+ release was involved in NCM460 cell injury as well, which was associated with TGR5 dysfunction. When NCM460 cells were pretreated with PHI, the PERK-eIF2α pathway and elevated Ca2+ levels were blocked. In conclusion, our study demonstrated a novel mechanism that PHI inhibited the PERK-eIF2α-Ca2+ pathway through TGR5 activation to against DSS-induced TJs reduction, fibrosis, and apoptosis.

Scutellarin alleviated ulcerative colitis through gut microbiota-mediated cAMP/PKA/NF-κB pathway

PURPOSE

Ulcerative colitis (UC) is a chronic, non-specific inflammatory condition of the colon, characterized by recurrent episodes and a notable lack of effective pharmacological treatments. Scutellarin, a natural component, exhibits appreciable pharmacological effects and therapeutic potential for various diseases. However, its effects on UC are not fully understood, and the precise mechanisms remain to be deciphered. This study aimed to assess the therapeutic efficacy of scutellarin and elucidate its underlying mechanisms in treating UC.

METHODS

This study utilized dextran sulfate sodium (DSS)-induced mice to evaluate the therapeutic potential of scutellarin against UC and to elucidate the mechanisms involving the gut microbiota. An antibiotics cocktail (ABX) and fecal microbiota transplantation (FMT) were also used to determine the mechanistic role of the gut microbiota. An integrative approach combining fecal metabolomics and network pharmacology analysis was used to explore the gut microbiota-directed molecular mechanism.

RESULTS

The results showed that scutellarin provided various therapeutic benefits in UC management, including alleviating weight loss, slowing disease progression, and reducing inflammatory damage in colon structures. The improved gut microbiota after scutellarin administration contributed to these effects. Fecal metabolome revealed that scutellarin selectively mitigated DSS-induced dysregulation of gut microbiota-derived metabolites, including glycolic acid, γ-aminobutyric acid, glutamate, tryptophan, xanthine, and β-hydroxypyruvate. Network pharmacology analysis, along with in vivo experimental verification, implicated the cAMP/PKA/NF-κB pathway in the action of these metabolites in treating UC, which may be the mechanism responsible for scutellarin's curative effects on UC.

CONCLUSION

This study demonstrates the potential of scutellarin in alleviating UC by activating the cAMP/PKA/NF-κB pathway through gut microbiota-derived metabolites, highlighting scutellarin as a promising therapeutic agent for UC.

Bile Acid Signaling in Metabolic and Inflammatory Diseases and Drug Development

Bile acids are the end products of cholesterol catabolism. Hepatic bile acid synthesis accounts for a major fraction of daily cholesterol turnover in humans. Biliary secretion of bile acids generates bile flow and facilitates biliary secretion of lipids, endogenous metabolites, and xenobiotics. In intestine, bile acids facilitate the digestion and absorption of dietary lipids and fat-soluble vitamins. Through activation of nuclear receptors and G protein-coupled receptors and interaction with gut microbiome, bile acids critically regulate host metabolism and innate and adaptive immunity and are involved in the pathogenesis of cholestasis, metabolic dysfunction-associated steatotic liver disease, alcohol-associated liver disease, type-2 diabetes, and inflammatory bowel diseases. Bile acids and their derivatives have been developed as potential therapeutic agents for treating chronic metabolic and inflammatory liver diseases and gastrointestinal disorders. SIGNIFICANCE STATEMENT: Bile acids facilitate biliary cholesterol solubilization and dietary lipid absorption, regulate host metabolism and immunity, and modulate gut microbiome. Targeting bile acid metabolism and signaling holds promise for treating metabolic and inflammatory diseases.

Cyclic adenosine 3', 5'-monophosphate (cAMP) signaling is a crucial therapeutic target for ulcerative colitis

The pathogenesis of ulcerative colitis (UC), a chronic intestine inflammatory disease primarily affecting adolescents, remains uncertain. Contemporary studies suggest that a confluence of elements, including genetic predispositions, environmental catalysts, dysregulated immune responses, and disturbances in the gut microbiome, are instrumental in the initiation and advancement of UC. Among them, inflammatory activation and mucosal barrier damage caused by abnormal immune regulation are essential links in the development of UC. The impairment of the mucosal barrier is intricately linked to the interplay of various cellular mechanisms, including oxidative stress, autophagy, and programmed cell death. An extensive corpus of research has elucidated that level of cyclic adenosine 3',5'-monophosphate (cAMP) undergo modifications in the midst of inflammation and participate in a diverse array of cellular operations that mitigate inflammation and the impairment of the mucosal barrier. Consequently, a plethora of pharmacological agents are currently under development, with some advancing through clinical trials, and are anticipated to garner approval as novel therapeutics. In summary, cAMP exerts a crucial influence on the onset and progression of UC, with fluctuations in its activity being intimately associated with the severity of the disease's manifestation. Significantly, this review unveils the paramount role of cAMP in the advancement of UC, offering a tactical approach for the clinical management of individuals afflicted with UC.

[Swertiamarin ameliorates 2, 4, 6-trinitrobenzenesulfonic acid-induced colitis in mice by inhibiting intestinal epithelial cell apoptosis]

OBJECTIVE

To investigate the mechanism by which swertiamarin (STM) ameliorates CD-like colitis in mice.

METHODS

A Caco-2 cell model of TNF-α-stimulated apoptosis was established and divided into three groups: Con, TNF-α and STM, and the effects of STM on apoptosis and barrier function were assessed by Tunel staining, western blotting, immunofluorescence, and transepithelial electric resistance (TEER). A mouse model of 2, 4, 6-trinitrobenzenesulfonic acid (TNBS) -induced CD-like colitis was established to assess the effects of STM on colitis, intestinal barrier function and epithelial cell apoptosis. The regulatory role of the PI3K/AKT pathway in STM-induced resistance to intestinal epithelial cell apoptosis was investigated in both the cell model and mouse models.

RESULTS

TUNEL staining showed that in Caco-2 cells with TNF-α stimulation, STM treatment significantly reduced the percentage of TUNEL-stained cells (P<0.05). STM obviously reduced TNF-α-induced enhancement of cleaved-caspase 3 and Bax expressions (P<0.05), increased Bcl-2 expression (P<0.05), protected intestinal barrier integrity and function by restoring transepithelial electrical resistance (TEER) of the cells, promoted normal localization and expressions of the tight junction proteins (ZO1 and claudin 1) (P<0.05), and inhibited the expression of pro-inflammatory factors (IL-6 and CCL3) (P<0.05) in TNF-α-stimulated Caco-2 cells. In the mouse models, STM significantly alleviated TNBS-induced CD-like colitis and intestinal barrier dysfunction (P<0.05) as shown by improved weight loss, lowered Disease Activity Index (DAI) score and inflammation score, reduction of IL-6 and CCL3 release, and restoration of intestinal barrier permeability, colonic TEER, bacterial translocation, and localization and expressions of the tight junction proteins. Mechanistically, STM inhibited the expressions of p-PI3K and p-AKT in both the cell model and mouse model(P<0.05), and treatment with 740Y-P (a PI3K/AKT pathway activator) significantly attenuated the inhibitory effect of STM on TNF-α-induced apoptosis in Caco-2 cells (P<0.05).

CONCLUSION

STM inhibits intestinal epithelial cell apoptosis at least in part by suppressing activation of the PI3K/AKT pathway to ameliorate intestinal barrier dysfunction and colitis in mice.

5-Methoxytryptophan Alleviates Dextran Sulfate Sodium-Induced Colitis by Inhibiting the Intestinal Epithelial Damage and Inflammatory Response

Background

Colitis is a refractory intestinal inflammatory disease significantly affecting the quality of a patient's life and increasing the risk of exacerbation. The primary factors leading to colitis encompass infections, insufficient blood flow, and the buildup of collagen as well as white blood cells. Among various available therapeutics, 5-methoxytryptophan (5-MTP) has emerged as one of the protectants by inhibiting inflammatory damage. Nonetheless, there is no report on the role of 5-MTP in the treatment of colitis.

Materials and Methods

To verify the anti-inflammatory effect of 5-MTP in vivo, we first constructed mouse model with dextran sulfate sodium-induced colitis. Furthermore, the macrophage infiltration and release of inflammatory factors through western blot (WB) and hematoxylin-eosin staining analyses were examined. Intestinal epithelial cell tight junction damage and apoptosis were investigated by WB analysis, immunofluorescence, and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Finally, we examined the generation of cellular inflammation and analyzed the influence of 5-MTP on M1 polarization at the cellular level.

Results

This study initially confirmed that 5-MTP possessed an excellent therapeutic effect on colitis. 5-MTP inhibits macrophage infiltration and the generation of inflammatory factors. In addition to its effects on immune cells, 5-MTP significantly inhibits intestinal epithelial cell tight junction damage and apoptosis in vivo. Moreover, it inhibits inflammation and M1 polarization response in vitro.

Conclusion

5-MTP counteracts excessive inflammation, thereby preventing intestinal epithelial tight junction damage. In addition, inhibition of apoptosis suggests that 5-MTP may be a potential therapeutic agent for colitis.

TGR5 deficiency in excitatory neurons ameliorates Alzheimer's pathology by regulating APP processing

Bile acids (BAs) metabolism has a significant impact on the pathogenesis of Alzheimer's disease (AD). We found that deoxycholic acid (DCA) increased in brains of AD mice at an early stage. The enhanced production of DCA induces the up-regulation of the bile acid receptor Takeda G protein-coupled receptor (TGR5), which is also specifically increased in neurons of AD mouse brains at an early stage. The accumulation of exogenous DCA impairs cognitive function in wild-type mice, but not in TGR5 knockout mice. This suggests that TGR5 is the primary receptor mediating these effects of DCA. Furthermore, excitatory neuron-specific knockout of TGR5 ameliorates Aβ pathology and cognition impairments in AD mice. The underlying mechanism linking TGR5 and AD pathology relies on the downstream effectors of TGR5 and the APP production, which is succinctly concluded as a "p-STAT3-APH1-γ-secretase" signaling pathway. Our studies identified the critical role of TGR5 in the pathological development of AD.

Baitouweng decoction alleviates ulcerative colitis by regulating tryptophan metabolism through DOPA decarboxylase promotion

Background

Baitouweng decoction (BTW) is a classic botanical drugs formula that has been widely used clinically for the treatment of gut-related disorders in China. However, its role in ameliorating ulcerative colitis (UC) remains to be explored.

Purpose

The study aimed to determine the therapeutic efficacy and potential mechanism of action of BTW on dextran sodium sulfate (DSS)-induced colitis mice.

Methods

In vivo: 3.5% DSS-induced experimental colitis mice were treated with BTW (Pulsatilla chinensis (Bunge) Regel, Phellodendron chinense C. K. Schneid, Coptis chinensis Franch and Fraxinus chinensis Roxb), kynurenine or DOPA decarboxylase (DDC) inhibitor (carbidopa). In vitro: Caco-2 cells were stimulated with TNF-α to activate inflammation and later treated with various concentrations of BTW and carbidopa. Model evaluation included body weight, disease activity index (DAI) score, colon length and histopathology. Cytokine levels were measured by flow cytometry. Protein levels were analyzed by proteomics and functionally annotated. The levels of tryptophan metabolites in mouse serum and colon were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Alcian Blue/Phosphate Acid Schiff (AB/PAS) staining, immunohistochemistry and western blot were used to assess the intestinal barrier function and detect the protein expression levels.

Results

BTW significantly reduced the DAI, ameliorated colonic injury and regulated inflammatory cytokines in DSS-induced colitis mice. The botanical drugs formula also promoted intestinal epithelial barrier repair by enhancing the expression of the tight junction (TJ) proteins. Tryptophan metabolic signaling pathway was significantly enriched in DSS-induced UC mice, and BTW decreased the level of kynurenine, increased indole metabolites. The therapeutic effect of BTW was evidently reduced when kynurenine was given to mice. Also, BTW promoted DDC protein expression and activated the aryl hydrocarbon receptor (AHR)/IL-22 signaling pathway.

Conclusion

BTW improves ulcerative colitis by promoting DDC expression, regulating the conversion of tryptophan metabolism from the kynurenine pathway to the indole metabolism pathway, thereby modulating tryptophan metabolism to increase indole metabolites, and activating AHR receptors to restore intestinal barrier function.

Activation of TGR5 Increases Urine Concentration by Inducing AQP2 and AQP3 Expression in Renal Medullary Collecting Ducts

Introduction

G protein-coupled bile acid receptor (TGR5), the first G protein-coupled receptor for bile acids identified, is capable of activating a variety of intracellular signaling pathways after interacting with bile acids. TGR5 plays an important role in multiple physiological processes and is considered to be a potential target for the treatment of various metabolic diseases, including type 2 diabetes. Evidence has emerged that genetic deletion of TGR5 results in an increase in basal urine output, suggesting that it may play a critical role in renal water and salt reabsorption. The present study aims to elucidate the effect and mechanism of TGR5 activation on urine concentration.

Methods

Mice were treated with TGR5 agonists (LCA and INT-777) for 3 days. The 24-h urine of mice was collected and analyzed for urine biochemical parameters. The mRNA expressions were detected by real-time PCR, and the protein expressions were detected by western blot. Immunohistochemistry and immunofluorescence were performed to examine the cellular location of proteins. The cultured primary medullary collecting duct cells were pretreated with H89 (a PKA inhibitor) for 1 h, followed by 12-h treatment of LCA and INT-777. Luciferase reporter assays were used to detect the effect of CREB on the gene transcription of AQPs. Gel electrophoretic mobility shift assays were used to analyze DNA-protein interactions.

Results

Treatment of mice with the TGR5 agonist LCA and INT-777 markedly reduced urine output and increased urine osmolality, accompanied by a marked increase in AQP2 and AQP3 protein expression and membrane translocation. In cultured primary medullary collecting duct cells, LCA and INT-777 dose-dependently upregulated AQP2 and AQP3 expression in a cAMP/PKA-dependent manner. Mechanistically, both AQP2 and AQP3 gene promoter contains a putative CREB-binding site, which can be bound and activated by CREB as assessed by both gene promoter-driven luciferase and gel shift assays.

Conclusion

Collectively, our findings demonstrate that activation of TGR5 can promote urine concentration by upregulation of AQP2 and AQP3 expression in renal collecting ducts. TGR5 may represent an attractive target for the treatment of patients with urine concentration defect.

Update on the development of TGR5 agonists for human diseases

The G protein-coupled bile acid receptor 1 (GPBAR1) or TGR5 is widely distributed across organs, including the small intestine, stomach, liver, spleen, and gallbladder. Many studies have established strong correlations between TGR5 and glucose homeostasis, energy metabolism, immune-inflammatory responses, and gastrointestinal functions. These results indicate that TGR5 has a significant impact on the progression of tumor development and metabolic disorders such as diabetes mellitus and obesity. Targeting TGR5 represents an encouraging therapeutic approach for treating associated human ailments. Notably, the GLP-1 receptor has shown exceptional efficacy in clinical settings for diabetes management and weight loss promotion. Currently, numerous TGR5 agonists have been identified through natural product-based approaches and virtual screening methods, with some successfully progressing to clinical trials. This review summarizes the intricate relationships between TGR5 and various diseases emphasizing recent advancements in research on TGR5 agonists, including their structural characteristics, design tactics, and biological activities. We anticipate that this meticulous review could facilitate the expedited discovery and optimization of novel TGR5 agonists.

Molecular insights into experimental models and therapeutics for cholestasis

Cholestatic liver disease (CLD) is a range of conditions caused by the accumulation of bile acids (BAs) or disruptions in bile flow, which can harm the liver and bile ducts. To investigate its pathogenesis and treatment, it is essential to establish and assess experimental models of cholestasis, which have significant clinical value. However, owing to the complex pathogenesis of cholestasis, a single modelling method can merely reflect one or a few pathological mechanisms, and each method has its adaptability and limitations. We summarize the existing experimental models of cholestasis, including animal models, gene-knockout models, cell models, and organoid models. We also describe the main types of cholestatic disease simulated clinically. This review provides an overview of targeted therapy used for treating cholestasis based on the current research status of cholestasis models. In addition, we discuss the respective advantages and disadvantages of different models of cholestasis to help establish experimental models that resemble clinical disease conditions. In sum, this review not only outlines the current research with cholestasis models but also projects prospects for clinical treatment, thereby bridging basic research and practical therapeutic applications.

Bile acid metabolism and signaling in health and disease: molecular mechanisms and therapeutic targets

Bile acids, once considered mere dietary surfactants, now emerge as critical modulators of macronutrient (lipid, carbohydrate, protein) metabolism and the systemic pro-inflammatory/anti-inflammatory balance. Bile acid metabolism and signaling pathways play a crucial role in protecting against, or if aberrant, inducing cardiometabolic, inflammatory, and neoplastic conditions, strongly influencing health and disease. No curative treatment exists for any bile acid influenced disease, while the most promising and well-developed bile acid therapeutic was recently rejected by the FDA. Here, we provide a bottom-up approach on bile acids, mechanistically explaining their biochemistry, physiology, and pharmacology at canonical and non-canonical receptors. Using this mechanistic model of bile acids, we explain how abnormal bile acid physiology drives disease pathogenesis, emphasizing how ceramide synthesis may serve as a unifying pathogenic feature for cardiometabolic diseases. We provide an in-depth summary on pre-existing bile acid receptor modulators, explain their shortcomings, and propose solutions for how they may be remedied. Lastly, we rationalize novel targets for further translational drug discovery and provide future perspectives. Rather than dismissing bile acid therapeutics due to recent setbacks, we believe that there is immense clinical potential and a high likelihood for the future success of bile acid therapeutics.

Metabolite-sensing GPCRs in rheumatoid arthritis

Persistent inflammation in damaged joints results in metabolic dysregulation of the synovial microenvironment, causing pathogenic alteration of cell activity in rheumatoid arthritis (RA). Recently, the role of metabolite and metabolite-sensing G protein-coupled receptors (GPCRs) in the RA-related inflammatory immune response (IIR) has become a focus of research attention. These GPCRs participate in the progression of RA by modulating immune cell activation, migration, and inflammatory responses. Here, we discuss recent evidence implicating metabolic dysregulation in RA pathogenesis, focusing on the connection between RA-related IIR and GPCR signals originating from the synovial joint and gut. Furthermore, we discuss future directions for targeting metabolite-sensing GPCRs for therapeutic benefit, emphasizing the importance of identifying endogenous ligands and investigating the various transduction mechanisms involved.

Mechanism of action of the bile acid receptor TGR5 in obesity

G protein-coupled receptors (GPCRs) are a large family of membrane protein receptors, and Takeda G protein-coupled receptor 5 (TGR5) is a member of this family. As a membrane receptor, TGR5 is widely distributed in different parts of the human body and plays a vital role in regulating metabolism, including the processes of energy consumption, weight loss and blood glucose homeostasis. Recent studies have shown that TGR5 plays an important role in glucose and lipid metabolism disorders such as fatty liver, obesity and diabetes. With the global obesity situation becoming more and more serious, a comprehensive explanation of the mechanism of TGR5 and filling the gaps in knowledge concerning clinical ligand drugs are urgently needed. In this review, we mainly explain the anti-obesity mechanism of TGR5 to promote the further study of this target, and show the electron microscope structure of TGR5 and review recent studies on TGR5 ligands to illustrate the specific binding between TGR5 receptor binding sites and ligands, which can effectively provide new ideas for ligand research and promote drug research.

cFLIPL alleviates myocardial ischemia-reperfusion injury by regulating pyroptosis

Alleviating myocardial ischemia-reperfusion injury (MIRI) plays a critical role in the prognosis and improvement of cardiac function following acute myocardial infarction. Pyroptosis is a newly identified form of cell death that has been implicated in the regulation of MIRI. In our study, H9c2 cells and SD rats were transfected using a recombinant adenovirus vector carrying cFLIPL , and the transfection was conducted for 3 days. Subsequently, H9c2 cells were subjected to 4 h of hypoxia followed by 12 h of reoxygenation to simulate an in vitro ischemia-reperfusion model. SD rats underwent 30 min of ischemia followed by 2 h of reperfusion to establish an MIRI model. Our findings revealed a notable decrease in cFLIPL expression in response to ischemia/reperfusion (I/R) and hypoxia/reoxygenation (H/R) injuries. Overexpression of cFLIPL can inhibit pyroptosis, reducing myocardial infarction area in vivo, and enhancing H9c2 cell viability in vitro. I/R and H/R injuries induced the upregulation of ASC, cleaved Caspase 1, NLRP3, GSDMD-N, IL-1β, and IL-18 proteins, promoting cell apoptosis. Our research indicates that cFLIPL may suppress pyroptosis by strategically binding with Caspase 1, inhibiting the release of inflammatory cytokines and preventing cell membrane rupture. Therefore, cFLIPL could potentially serve as a promising target for alleviating MIRI by suppressing the pyroptotic pathway.

PVA enema ameliorates DSS-induced acute colitis in mice

BACKGROUND

Ulcerative colitis (UC) represents a clinically challenging condition characterized by persistent damage to the colonic epithelial mucosa as the principal pathological feature. Polyvinyl alcohol (PVA) solution, primarily composed of glue, is a biodegradable polymer material that has found utility in the medical field. This research endeavors to investigate the therapeutic potential of PVA water solution in ameliorating UC in mice.

METHODS

UC was induced in 48 C57BL/6 mice by administering 2.5% DSS in their diet for 6 days. Mice were treated with different concentrations of PVA (0.1 mg/ml PVA, 0.3 mg/ml PVA, 1 mg/ml PVA, 3 mg/ml PVA, 10 mg/ml PVA) enemas (n = 6). Disease Activity Index (DAI) and histologic score were evaluated for inflammation degree. Furthermore, mouse colon organoids were cultured, which were used to assess the effects of PVA on expansion in vitro.

RESULTS

PVA aqueous solutions (1 mg/ml and 3 mg/ml) were able to alleviate the DAI in mice. By DAY 6, there was a significant 3/5-fold decrease in DAI within the 1 mg/ml PVA group (p = 0.02). Histopathology scores demonstrated improvements, while the levels of inflammatory factors in the intestinal mucosal tissue were reduced. Additionally, it was confirmed that PVA could promote the expansion of colonic organoids in vitro.

CONCLUSIONS

In summary, our investigation has yielded findings indicating that PVA holds the potential to ameliorate symptoms associated with colitis in murine subjects afflicted by DSS-induced colitis, primarily through its facilitation of intestinal stem cell expansion. This study might provide a new candidate for the clinical treatment of ulcerative colitis.