Luteolin ameliorates experimental colitis in mice through ERK-mediated suppression of inflammation, apoptosis and autophagy

Autophagy: A potential target for natural products in the treatment of ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease primarily affecting the mucosa of the colon and rectum. UC is characterized by recurrent episodes, often necessitating lifelong medication use, imposing a significant burden on patients. Current conventional and advanced treatments for UC have the disadvantages of insufficient efficiency, susceptibility to drug resistance, and notable adverse effects. Therefore, developing effective and safe drugs has become an urgent need. Autophagy is an intracellular degradation process that plays an important role in intestinal homeostasis. Emerging evidence suggests that aberrant autophagy is involved in the development of UC, and modulating autophagy can effectively alleviate experimental colitis. A growing number of studies have established that autophagy can interplay with endoplasmic reticulum stress, gut microbiota, apoptosis, and the NLRP3 inflammasome, all of which contribute to the pathogenesis of UC. In addition, a variety of intestinal epithelial cells, including absorptive cells, goblet cells, and Paneth cells, as well as other cell types like neutrophils, antigen-presenting cells, and stem cells in the gut, mediate the development of UC through autophagy. To date, many studies have found that natural products hold the potential to exert therapeutic effects on UC by regulating autophagy. This review focuses on the possible effects and pharmacological mechanisms of natural products to alleviate UC with autophagy as a potential target in recent years, aiming to provide a basis for new drug development.

Potential effects and mechanism of flavonoids extract of Callicarpa nudiflora Hook on DSS-induced colitis in mice

Callicarpa nudiflora Hook (C. nudiflora) is an anti-inflammatory, antimicrobial, antioxidant, and hemostatic ethnomedicine. To date, little has been reported regarding the activity of C. nudiflora against ulcerative colitis (UC). In this study, we investigated the effect of a flavonoid extract of C. nudiflora on Dextran Sulfate Sodium (DSS)-induced ulcerative colitis in mice. Mice in the treatment group (CNLF+DSS group) and drug-only (CNLF group) groups were administered 400 mg/kg of flavonoid extract of C. nudiflora leaf (CNLF), and drinking water containing 2.5 % DSS was given to the model and treatment groups. The symptoms of colitis were detected, relevant indicators were verified, intestinal barrier function was assessed, and the contents of the cecum were analyzed for intestinal microorganisms. The results showed that CNLF significantly alleviated the clinical symptoms and histological morphology of colitis in mice, inhibited the increase in pro-inflammatory factors (TNF-α, IL-6, IL-1β, and IFN-γ), and increased the level of IL-10. The expression of NF-κB and MAPK inflammatory signal pathway-related proteins (p-p65, p-p38, p-ERK, p-JNK) was regulated. The expression of tight junction proteins (ZO-1, OCLDN, and CLDN1) was increased, while the content of D-LA, DAO, and LPS was decreased. In addition, 16S rRNA sequencing showed that CNLF restored the gut microbial composition, and increased the relative abundance of Prevotellaceae, Intestinimonas butyriciproducens, and Barnesiella_intestinihominis. In conclusion, CNLF alleviated colitis by suppressing inflammation levels, improving intestinal barrier integrity, and modulating the intestinal microbiota, and therefore has promising future applications in the treatment of UC.

Effect of the Pseudopleuronectes americanus-derived Pleurocidin on DSS-induced Ulcerative colitis in mice and its preliminary molecular mechanisms

Pleurocidin is an antimicrobial peptide derived from the mucous membranes of the skin or intestinal secretions of Pseudopleuronectes americanus that has antimicrobial and immunomodulatory activities. Ulcerative colitis is recognized as a widespread human disease that may be influenced by environmental and genetic factors. Evidence emphasizes the critical role of the gut microbiota in UC. Synthetic Pleurocidin was analyzed by a combination of liquid chromatography and mass spectrometry. Pleurocidin pharmacological effects were evaluated by DAI score, colon histological score, cytokine levels, and tight junction protein expression in mice. The preliminary molecular mechanism was explored by the levels of key proteins in the NF-κB and MAPK inflammatory signaling pathways in colon tissues. The main analytical methods such as immunohistochemistry, immunofluorescence, enzyme-linked immunosorbent assay (ELISA), and Western blot were used. We then used 16S rRNA gene sequences to characterize the gut microbiota. Firstly, our study demonstrated that rectal injection of Pleurocidin at 5 mg/kg body weight alleviated clinical symptoms and colonic histopathological changes in UC mice caused by DSS. Secondly, Pleurocidin altered the abnormal levels of inflammatory and immune-related cytokines in serum, modulated the significant down-regulation of tight junction proteins, and inhibited the expression of NF-κB and MAPK inflammatory signaling pathway-related proteins. Finally, Pleurocidin can regulate gut microbiota, increase the relative abundance of beneficial bacteria and reduce the relative abundance of harmful bacteria. In conclusion, Pleurocidin alleviates UC symptoms in mice, and its effects on the gut microbiome may be potential pathways. It is providing a promising therapeutic option for UC.

Targeting autophagy drug discovery: Targets, indications and development trends

Autophagy plays a vital role in sustaining cellular homeostasis and its alterations have been implicated in the etiology of many diseases. Drugs development targeting autophagy began decades ago and hundreds of agents were developed, some of which are licensed for the clinical usage. However, no existing intervention specifically aimed at modulating autophagy is available. The obstacles that prevent drug developments come from the complexity of the actual impact of autophagy regulators in disease scenarios. With the development and application of new technologies, several promising categories of compounds for autophagy-based therapy have emerged in recent years. In this paper, the autophagy-targeted drugs based on their targets at various hierarchical sites of the autophagic signaling network, e.g., the upstream and downstream of the autophagosome and the autophagic components with enzyme activities are reviewed and analyzed respectively, with special attention paid to those at preclinical or clinical trials. The drugs tailored to specific autophagy alone and combination with drugs/adjuvant therapies widely used in clinical for various diseases treatments are also emphasized. The emerging drug design and development targeting selective autophagy receptors (SARs) and their related proteins, which would be expected to arrest or reverse the progression of disease in various cancers, inflammation, neurodegeneration, and metabolic disorders, are critically reviewed. And the challenges and perspective in clinically developing autophagy-targeted drugs and possible combinations with other medicine are considered in the review.

Indole-3-acetic acid ameliorates dextran sulfate sodium-induced colitis via the ERK signaling pathway

Microbiota-derived catabolism of nutrients is closely related to ulcerative colitis (UC). The level of indole-3-acetic acid (IAA), a microbiota-dependent metabolite of tryptophan, was decreased significantly in the feces of UC patients. Thus supplementation with IAA could be a potential therapeutic method for ameliorating colitis. In this work, the protective effect of supplementation with IAA on dextran sulfate sodium (DSS)-induced colitis was evaluated, and the underlying mechanism was elucidated. The results indicated that the administration of IAA significantly relieved DSS-induced weight loss, reduced the disease activity index (DAI), restored colon length, alleviated intestinal injury, and improved the intestinal tight junction barrier. Furthermore, IAA inhibited intestinal inflammation by reducing the expression of proinflammatory cytokines and promoting the production of IL-10 and TGF-β1. In addition, the ERK signaling pathway is an important mediator of various physiological processes including inflammatory responses and is closely associated with the expression of IL-10. Notably, IAA treatment induced the activation of extracellular signal-regulated kinase (ERK), which is involved in the progression of colitis, while the ERK inhibitor U0126 attenuated the beneficial effects of IAA. In summary, IAA could attenuate the clinical symptoms of colitis, and the ERK signaling pathway was involved in the underlying mechanism. Supplementation with IAA could be a potential option for preventing or ameliorating UC.

Natural compounds target programmed cell death (PCD) signaling mechanism to treat ulcerative colitis: a review

Ulcerative colitis (UC) is a nonspecific inflammatory bowel disease characterized by abdominal pain, bloody diarrhea, weight loss, and colon shortening. However, UC is difficult to cure due to its high drug resistance rate and easy recurrence. Moreover, long-term inflammation and increased disease severity can lead to the development of colon cancer in some patients. Programmed cell death (PCD) is a gene-regulated cell death process that includes apoptosis, autophagy, necroptosis, ferroptosis, and pyroptosis. PCD plays a crucial role in maintaining body homeostasis and the development of organs and tissues. Abnormal PCD signaling is observed in the pathological process of UC, such as activating the apoptosis signaling pathway to promote the progression of UC. Targeting PCD may be a therapeutic strategy, and natural compounds have shown great potential in modulating key targets of PCD to treat UC. For instance, baicalin can regulate cell apoptosis to alleviate inflammatory infiltration and pathological damage. This review focuses on the specific expression of PCD and its interaction with multiple signaling pathways, such as NF-κB, Nrf2, MAPK, JAK/STAT, PI3K/AKT, NLRP3, GPX4, Bcl-2, etc., to elucidate the role of natural compounds in targeting PCD for the treatment of UC. This review used (ulcerative colitis) (programmed cell death) and (natural products) as keywords to search the related studies in PubMed and the Web of Science, and CNKI database of the past 10 years. This work retrieved 72 studies (65 from the past 5 years and 7 from the past 10 years), which aims to provide new treatment strategies for UC patients and serves as a foundation for the development of new drugs.

Integrating network pharmacology and experimental validation to explore the mechanisms of luteolin in alleviating fumonisin B1-induced intestinal inflammatory injury

Contamination with fumonisin B1 (FB1) represents a global health problem. FB1 exposure may also trigger intestinal injury by activating inflammatory responses, leading to a reduction in production performance and economic benefits. However, the mechanism of FB1-induced intestinal inflammatory injury is still unclear. At the same time, it is urgent to develop antibiotic alternatives and therapeutic targets to alleviate antibiotic resistance and to ensure effective treatment of intestinal inflammatory injury. We combined network pharmacology and in vitro experiments to explore the core therapeutic targets and potential mechanism of luteolin in FB1-induced intestinal inflammatory injury. Network pharmacology and molecular docking revealed that nuclear factor kappa B (NF-κB) p65, extracellular signal-regulated kinase (ERK), interleukin 6 (IL-6) and IL-1β are the important targets, and the NF-κB and ERK signalling pathways are critical in FB1-induced intestinal inflammatory injury. Besides, in vitro experiments further demonstrated that luteolin can inhibit FB1-induced intestinal inflammatory injury by inhibiting activation of the NF-κB and ERK signalling pathways and reducing the expression of IL-6 and IL-1β in IPEC-J2 cells. We have comprehensively illustrated the potential targets and molecular mechanism by which luteolin can alleviate FB1-induced intestinal inflammatory injury. Luteolin may be an effective antibiotic alternative to prevent intestinal inflammatory injury.

Luteolin alleviates ulcerative colitis in rats via regulating immune response, oxidative stress, and metabolic profiling

Ulcerative colitis (UC) is an inflammatory bowel disease and associated with metabolic imbalance. Luteolin (LUT) reportedly exhibits anti-inflammatory activity. However, its regulatory effects on metabolites remain indistinct. Here, the effects of LUT on immune response and oxidative stress in UC were determined. Serum metabolomics profiles of UC rats treated with LUT were obtained utilizing liquid chromatography-mass spectrometry. The results revealed that LUT treatment alleviated colon tissue injury, colon shortening, weight loss, and inflammatory response in UC rats. Additionally, the levels of superoxide dismutase and total antioxidant capacity were elevated, but malondialdehyde content was reduced in serum of UC rats, while these changes were abrogated by LUT. Metabolomics analysis unveiled that l-malic acid, creatinine, l-glutamine, and l-lactic acid levels were remarkably decreased, while dimethyl sulfone, 5-methylcytosine, cysteine-S-sulfate, and jasmonic acid levels were notably increased after LUT treatment. Furthermore, differential metabolites primarily participated in d-glutamine and d-glutamate metabolism, glutathione metabolism, and citrate cycle pathways. In summary, these results demonstrated that LUT improved immune response, alleviated oxidative stress, and altered metabolites in UC rats. This study lays the root for further exploring the mechanism of LUT in the treatment of UC.

Cod (Gadus) skin collagen peptide powder reduces inflammation, restores mucosal barrier function, and inhibits fibrosis in dextran sodium sulfate-induced colitis in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Ulcerative colitis (UC) is a chronic inflammatory bowel disease of unknown etiology. Cod (Gadus), a kind of herb from the Chinese herb. Traditionally, it has used to treat trauma, reduce swelling and relieve pain in order to exert its anti-inflammatory activity. Recent reports based on its hydrolyzed or enzymatic extracts have shown its anti-inflammatory, mucosal barrier protecting properties. However, its mechanism of improvement in ulcerative colitis is not clear.

AIM OF THE STUDY

This study aimed to explore the preventive and protective effect of cod skin collagen peptide powder (CP) on mice with UC and to explore the underlying mechanism.

MATERIALS AND METHODS

Mice with dextran sodium sulfate (DSS)-induced UC were treated with CP by gavage, and the anti-inflammatory effects of CP were assessed using general physical, pro-inflammatory cytokine, histopathological, immunohistochemical, macrophage flow cytometry, and inflammatory signaling pathway assays.

RESULTS

CP ameliorates inflammation by upregulating mitogen-activated protein kinase phosphatase-1 (MKP-1) and thereby decreasing the phosphorylation levels of P38 and JNK. It also polarizes macrophages in the colon towards the M2 phenotype, which helps to reduce tissue damage and promotes colon repair. At the same time, CP also inhibits the development of fibrosis, one of the complications of UC, by upregulating ZO-1, Occludin, and downregulating α-SMA, Vimentin, Snail, and Slug.

CONCLUSION

In this study, we found CP reduced inflammation in mice with UC by inducing MKP-1 expression, which caused dephosphorylation of mitogen-activated protein kinase (MAPK). CP also restored mucosal barrier function and inhibited the development of fibrosis complicating UC in these mice. Taken together, these results suggested that CP improved the pathological manifestations of UC in mice, suggesting that it can play a biological role as a nutritional supplement for preventing and treating UC.

Cadmium affects autophagy in the human intestinal cells Caco-2 through ROS-mediated ERK activation

Cadmium is a toxic metal that enters the food chain. Following oral ingestion, the intestinal epithelium has the capacity to accumulate high levels of this metal. We have previously shown that Cd induces ERK1/2 activation in differentiated but not proliferative human enterocytic-like Caco-2 cells. As autophagy is a dynamic process that plays a critical role in intestinal mucosa, we aimed the present study 1) to investigate the role of p-ERK1/2 in constitutive autophagy in proliferative Caco-2 cells and 2) to investigate whether Cd-induced activation of ERK1/2 modifies autophagic activity in postconfluent Caco-2 cell monolayers. Western blot analyses of ERK1/2 and autophagic markers (LC3, SQSTM1), and cellular staining with acridine orange showed that ERK1/2 and autophagic activities both decreased with time in culture. GFP-LC3 fluorescence was also associated with proliferative cells and the presence of a constitutive ERK1/2-dependent autophagic flux was demonstrated in proliferative but not in postconfluent cells. In the latter condition, serum and glucose deprivation triggered autophagy via a transient phosphorylation of ERK1/2, whereas Cd-modified autophagy via a ROS-dependent sustained activation of ERK1/2. Basal autophagy flux in proliferative cells and Cd-induced increases in autophagic markers in postconfluent cells both involved p-ERK1/2. Whether Cd blocks autophagic flux in older cell cultures remains to be clarified but our data suggest dual effects. Our results prompt further studies investigating the consequences that Cd-induced ERK1/2 activation and the related effect on autophagy may have on the intestinal cells, which may accumulate and trap high levels of Cd under some nutritional conditions.

Natural flavones from edible and medicinal plants exhibit enormous potential to treat ulcerative colitis

Ulcerative colitis (UC) is a chronic aspecific gut inflammatory disorder that primarily involves the recta and colons. It mostly presents as a long course of repeated attacks. This disease, characterized by intermittent diarrhoea, fecal blood, stomachache, and tenesmus, severely decreases the living quality of sick persons. UC is difficult to heal, has a high recurrence rate, and is tightly related to the incidence of colon cancer. Although there are a number of drugs available for the suppression of colitis, the conventional therapy possesses certain limitations and severe adverse reactions. Thus, it is extremely required for safe and effective medicines for colitis, and naturally derived flavones exhibited huge prospects. This study focused on the advancement of naturally derived flavones from edible and pharmaceutical plants for treating colitis. The underlying mechanisms of natural-derived flavones in treating UC were closely linked to the regulation of enteric barrier function, immune-inflammatory responses, oxidative stress, gut microflora, and SCFAs production. The prominent effects and safety of natural-derived flavones make them promising candidate drugs for colitis treatment.

Comparison of the molecular mechanisms of Fuzi Lizhong Pill and Huangqin decoction in the treatment of the cold and heat syndromes of ulcerative colitis based on network pharmacology

OBJECTIVE

The aim of this study was to illuminate the similarities and differences of two prescriptions as "cold" and "heat" drugs for treating ulcerative colitis (UC) with the simultaneous occurrence of heat and cold syndrome via network pharmacology.

METHODS

(1) Active compounds of Fuzi-Lizhong Pill (FLP) and Huangqin Decoction (HQT) were retrieved from the TCMSP database, and their common active compounds were compared using the Venn diagram. (2) Potential proteins targeted to three sets of compounds either (i) shared by FLP and HQT, (ii) unique to FLP or (iii) unique to HQT were screened from the STP, STITCH and TCMSP databases, and three corresponding core compound sets were identified in Herb-Compound-Target (H-C-T) networks. (3) Targets related to UC were identified from the DisGeNET and GeneCards databases and compared with the FLP-HQT common targets to identify potential targets of FLP-HQT compounds related to UC. (4) Three potential target sets were imported into the STRING database for protein‒protein interaction (PPI) analysis, and three core target sets were defined. (5) The binding capabilities and interacting modes between core compounds and key targets were verified by molecular docking via Discovery Studio 2019 and molecular dynamics (MD) simulations via Amber 2018. (6) The target sets were enriched for KEGG pathways using the DAVID database.

RESULTS

(1) FLP and HQT included 95 and 113 active compounds, respectively, with 46 common compounds, 49 FLP-specific compounds and 67 HQT-specific compounds. (2) 174 targets of FLP-HQT common compounds, 168 targets of FLP-specific compounds, and 369 targets of HQT-specific compounds were predicted from the STP, STITCH and TCMSP databases; six core compounds specific to FLP and HQT were screened in the FLP-specific and HQT-specific H-C-T networks, respectively. (3) 103 targets overlapped from the 174 predicted targets and the 4749 UC-related targets; two core compounds for FLP-HQT were identified from the FLP-HQT H-C-T network. (4) 103 FLP-HQT-UC common targets, 168 of FLP-specific targets and 369 of HQT-specific targets had shared core targets (AKT1, MAPK3, TNF, JUN and CASP3) based on the PPI network analysis. (5) Molecular docking demonstrated that naringenin, formononetin, luteolin, glycitein, quercetin, kaempferol and baicalein of FLP and HQT play a critical role in treating UC; meanwhile, MD simulations revealed the stability of protein‒ligand interactions. (6) The enriched pathways indicated that most targets were related to anti-inflammatory, immunomodulatory and other pathways. Compared with the pathways identified using traditional methods, FLP-specific pathways included the PPAR signaling pathway and the bile secretion pathway, and HQT-specific pathways included the vascular smooth muscle contraction pathway and the natural killer cell-mediated cytotoxicity pathway etc. CONCLUSION: In this study, we clarified the common mechanisms of FLP and HQT in treating UC and their specific mechanisms in treating cold and heat syndrome in UC through compound, target and pathway distinction and a literature comparison based on network pharmacology; these results provide a new perspective on the detailed mechanism of "multidrugs and single-disease" thought in traditional Chinese medicine.

Metabolomics integrated network pharmacology reveals the mechanism of Ma-Mu-Ran Antidiarrheal Capsules on acute enteritis mice

Acute enteritis (AE) is a type of digestive disease caused by biochemical factors that irritate the intestinal tract or pathogenic bacteria that infect it. In China, Ma-Mu-Ran Antidiarrheal Capsules (MMRAC) have been applied against diarrhea caused by AE and bacillary dysentery for many years, but the underlying mechanisms of their beneficial effects are not known. In the present study, network pharmacology and metabolomics were performed to clarify the active ingredients of MMRAC and explore the specific mechanism of MMRAC on AE mice. A total of 43 active components of MMRAC with 87 anti-AE target genes were identified, and these target genes were enriched in IL-17 and HIF-1 signaling pathways. Integration analysis revealed that purine metabolism was the critical metabolic pathway by which MMRAC exerted its therapeutic effect against AE. Specifically, MAPK14, MMP9, PTGS2, HIF1A, EGLN1, NOS2 were the pivotal targets of MMRAC for the treatment of AE, and Western blot analysis revealed MMRAC to decrease protein levels of these pro-inflammatory signaling molecules. According to molecular docking, these key targets have a strong affinity with the MMRAC compounds. Collectively, MMRAC relieved the colon inflammation of AE mice via regulating inflammatory signaling pathways to reduce hypoxia and improved energy metabolism.

Application Potential of Luteolin in the Treatment of Viral Pneumonia

Aim of the Review. This study aims to summarize the therapeutic effect of luteolin on the pathogenesis of viral pneumonia, explore its absorption and metabolism in the human body, evaluate the possibility of luteolin as a drug to treat viral pneumonia, and provide a reference for future research. Materials and Methods. We searched MEDLINE/PubMed, Web of Science, China National Knowledge Infrastructure, and Google Scholar and collected research on luteolin in the treatment of viral pneumonia and related diseases since 2003. Then, we summarized the efficacy and potential of luteolin in directly inhibiting viral activity, limiting inflammatory storms, reducing pulmonary inflammation, and treating pneumonia complications. Results and Conclusion. Luteolin has the potential to treat viral pneumonia in multiple ways. Luteolin has a direct inhibitory effect on coronavirus, influenza virus, and respiratory syncytial virus. Luteolin can alleviate the inflammatory factor storm induced by multiple factors by inhibiting the function of macrophages or mast cells. Luteolin can reduce pulmonary inflammation, pulmonary edema, or pulmonary fibrosis induced by multiple factors. In addition, viral pneumonia may cause multisystem complications, while luteolin has extensive protective effects on the gastrointestinal system, cardiovascular system, and nervous system. However, due to the first-pass metabolism mediated by phase II enzymes, the bioavailability of oral luteolin is low. The bioavailability of luteolin can be improved, and its potential value can be further developed by changing the dosage form or route of administration.

Jianpi-Qingchang decoction alleviates ulcerative colitis by modulating endoplasmic reticulum stress-related autophagy in intestinal epithelial cells

Endoplasmic reticulum stress (ERS)-related autophagy is involved in the occurrence and development of ulcerative colitis (UC). Therefore, regulating ERS-related autophagy is a potential therapeutic target for the treatment of UC. Jianpi-Qingchang (JPQC) decoction, consisting of nine Chinese herbal medicines, is used to treat patients with UC. However, its mechanism of action has not been completely elucidated. Here, we aimed to reveal the therapeutic effects and mechanisms of JPQC in UC. We established a colitis model using dextran sulfate sodium (DSS) and an ERS model using thapsigargin (Tg) and administered JPQC. We systematically examined ERS-related autophagy associated protein expression, inflammatory cytokines, apoptotic cells, and autophagic flux. Moreover, the cellular ultrastructure was observed via transmission electron microscopy (TEM). We found that JPQC reduced disease activity index (DAI) scores, counteracted colonic tissue damage, decreased the number of autophagosomes, inhibited proinflammatory cytokines, enhanced anti-inflammatory cytokines, and dampened ERS-related autophagy associated protein gene expression.

Enhancement of oral bioavailability and anti-colitis effect of luteolin-loaded polymer micelles with RA (rosmarinic acid)-SS-mPEG as carrier

OBJECTIVE

Polymer micelles were prepared (L-RSPMs) with luteolin and synthetic RA-SS-mPEG polymeric material before evaluation of their anti-inflammatory effect on 2, 4, 6-trinitro-benzene-sulfonic acid (TNBS)-induced ulcerative colitis (UC) model in rats.

METHODS

The synthetic RA-SS-mPEG was characterized with NMR spectroscopy, before preparation of luteolin-coated RA-SS-mPEG polymer micelles. The in vitro characterization and evaluation of the formulation were accomplished, couple with its pharmacokinetic parameters. The levels of PEG2, MDA, CRP and GSH, as well as concentrations of TNF-α, IL1-β, IL-6 and IL-10 in serum and colon tissue were detected via ELISA kit. The degree of colon injury and inflammation was evaluated via histopathologic examination.

RESULTS

L-RSPMs displayed small average droplet size (133.40 ± 4.52 nm), uniformly dispersed (PDI: 0.163 ± 0.011), good stability, slow release and enhanced solubility. We observed 353.28% increase in the relative bioavailability of L-RSPMs compared to free luteolin, while the half-life of the micelle was extended by 6.16h. Compared to model (M) group, luteolin (low and high doses) and L-RSPMs (low and high doses) significantly reduced levels of MDA, PEG2, CRP, TNF-α, IL-6 and IL-1β in colon tissue and serum of colitic rats but dose dependently increased IL-10 and SOD levels (p < 0.01). Histopathologic examination of colon showed that luteolin (low and high doses) and L-RSPMs (low and high doses) improved colonic inflammation in colitic rats to varying degrees compared to M group.

CONCLUSION

L-RSPMs could improve TNBS-induced colon inflammation by enhancing bioavailability, promoting antioxidant effects and regulating cytokine release, which may become a potential agent for UC treatment in clinical settings.

Luteolin alleviates ulcerative colitis by restoring the balance of NCR-ILC3/NCR+ILC3 to repairing impaired intestinal barrier

Ulcerative colitis (UC) is a multifactorial, refractory chronic inflammatory disease. The primary factor leading to prolonged ulcerative colitis is the imbalance of the group 3 innate lymphoid cells (ILC3) subgroup resulting in the delayed reconstruction of damaged intestinal barrier. Previous studies show that luteolin had efficacy on UC, however, the potency of luteolin on restoring the balance of NCR^-ILC3/NCR⁺ILC3 to repairing impaired intestinal barrier remains unclear. In this study, to investigate the potential mechanism of luteolin on ILC3 subgroup, we first evidenced that luteolin could promote transformation NCR^-MNK3 to NCR⁺MNK3 in vitro. Then, a UC model was established in C57BL/6J mice to assess the efficacy of luteolin in restoring ILC3 subgroup balance and repairing intestinal barrier in chronic UC. Finally, the experiments in vitro validated the potential mechanism of luteolin in regulating ILC3 plasticity. The results showed that luteolin significantly alleviated the symptoms of DSS-induced UC in mice, including preventing body weight loss and decreasing the disease activity index (DAI) and intestinal damages. Additionally, luteolin increased NCR⁺ILC3 levels, promoted the production of IL-22 and decreased the levels of IL-17a and INF-γ in the intestine, and encourage intestinal barrier function recovery in UC mice by promoting the expression of ZO-1 and Occludin. Experiments in vitro revealed that luteolin facilitated the transformation of NCR^-MNK3 to NCR⁺MNK3 and promoted the secretion of IL-22, which was linked to the Notch pathway. All results revealed that luteolin restored the balance of NCR^-ILC3/NCR⁺ILC3 and contributed to repair of injured intestinal epithelium to alleviate ulcerative colitis.

Unraveling the Molecular Mechanism of Xuebijing Injection in the Treatment of Chronic Obstructive Pulmonary Disease by Combining Network Pharmacology and Affymetrix Array

Xuebijing injection (XBJ), one of the classical prescriptions for treating inflammation-related diseases, has been used to chronic obstructive pulmonary disease (COPD) in clinical practice. However, its molecular mechanism is still unclear. Network pharmacology combined with Affymetrix arrays and molecular docking techniques were applied to explore the molecular mechanism of XBJ for COPD. Predictive analysis of 728 active compounds in XBJ and 6 sets of Affymetrix arrays expression data resulted in 106 potential therapeutic targets. Next, based on the active compound-co-target network topology analysis, most of these targets were found to be modulated by quercetin, myricetin, and ellagic acid. Furthermore, protein–protein interaction (PPI) analysis revealed that the key targets may be EGFR, STAT3, AKT1, CCND1, MMP9, AR, ESR1, and PTGS2. Then, by constructing a component-target-pathway network, we found that XBJ was a multi-pathway, multi-target, multi-compound synergistic therapy for COPD, and four key targets were involved in the FoxO signaling pathway. Luteolin and salvianolic acid b had the optimal binding ability to several key proteins. Therefore, we hypothesize that quercetin, myricetin, ellagic acid, luteolin, and salvianolic acid b mainly contribute to the therapeutic effect of XBJ on COPD by modulating the FoxO signaling pathway by regulating EGFR, STAT3, AKT1, and CCND1. XBJ exerts anti-inflammatory and antioxidative stress effects through the PI3K/Akt/FoxO axis combined with MMP9, AR, ESR1, and PTGS2 to regulate other signaling pathways.

Ultrasound Improved the Non-Covalent Interaction of β-Lactoglobulin with Luteolin: Regulating Human Intestinal Microbiota and Conformational Epitopes Reduced Allergy Risks

The present study aims to investigate the effects of ultrasound on the non-covalent interaction of β-lactoglobulin (β-LG) and luteolin (LUT) and to investigate the relationship between allergenicity and human intestinal microbiota. After treatment, the conformational structures of β-LG were changed, which reflected by the decrease in α-helix content, intrinsic fluorescence intensity and surface hydrophobicity, whereas the β-sheet content increased. Molecular docking studies revealed the non-covalent interaction of β-LG and LUT by hydrogen bond, van der Walls bond and hydrophobic bond. β-LG-LUT complex treated by ultrasound has a lower IgG/IgE binding ability and inhibits the allergic reaction of KU812 cells, depending on the changes in the conformational epitopes of β-LG. Meanwhile, the β-LG-LUT complex affected the composition of human intestinal microbiota, such as the relative abundance of Bifidobacterium and Prevotella. Therefore, ultrasound improved the non-covalent interaction of β-LG with LUT, and the reduction in allergenicity of β-LG depends on conformational epitopes and human intestinal microbiota changes.

Network Pharmacology and Molecular Docking Analysis on Molecular Mechanism of Qingzi Zhitong Decoction in the Treatment of Ulcerative Colitis

Ulcerative colitis (UC) is a disease with complex pathological mechanisms. We explored the potential molecular mechanisms behind the therapeutic functions of Qingzi Zhitong decoction (QZZTD) in the treatment of UC by network pharmacology and molecular docking. QZZTD is a formula of Chinese traditional medicine consisting of 10 herbs. The potential active ingredients of QZZTD and their target genes were obtained from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform database, and UC-related target genes were obtained from GeneCards and OMIM databases. A total of 138 co-identified target genes were obtained by plotting the intersection target Venn diagram, and then the STRING database and Cytoscape software were used to establish protein-protein interaction networks and herb-ingredient-target networks. Four key active compounds and nine key proteins were identified. Then, Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses showed that the biological functions of potential target genes were associated with DNA transcription, signaling receptor and ligand activity, cytokine activity, cellular autophagy, and antioxidant pathways, with related pathways involving the phosphatidylinositol 3-kinase (PI3K)-Akt signaling pathway, advanced glycosylation end product (AGE)-RAGE signaling pathway, tumor necrosis factor (TNF) signaling pathway, and IL-17 signaling pathway. Moreover, the binding activities of key target genes and essential active compounds of Chinese herbal medicines in QZZTD were further validated by molecular docking. This demonstrated that quercetin, luteolin, hyndarin, and beta-sitosterol had good binding to eight key proteins, and Akt1 was the target protein with the best binding activity, suggesting that Akt1 could be the essential mediator responsible for signaling transduction after QZZTD administration. The rat experiment verified that QZZTD inhibited PI3K-Akt pathway activation and reduced inflammation in UC. In conclusion, our study suggested four potential key active components, including quercetin, were identified in QZZTD, which could interact with Akt1 and modulate the activation of the PI3K-Akt pathway. The other three pathways may also be involved in the signaling transduction induced by QZZTD in the treatment of UC.

Natural Products Modulate Cell Apoptosis: A Promising Way for the Treatment of Ulcerative Colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease impacting patients’ quality of life and imposing heavy societal and economic burdens. Apoptosis of intestinal epithelial cells (IECs) has been considered an early event during the onset of UC and plays a crucial role in disease development. Thus, effectively inhibiting apoptosis of IECs is of critical significance for the clinical management of UC, presenting a potential direction for the research and development of pharmacotherapeutic agents. In recent years, research on the ameliorative effects of natural products on UC through inhibiting IECs apoptosis has attracted increasing attention and made remarkable achievements in ameliorating UC. In this review, we summarized the currently available research about the anti-apoptotic effects of natural products on UC and its mechanisms involving the death-receptor mediated pathway, mitochondrial-dependent pathway, ERS-mediated pathway, MAPK-mediated pathway, NF-κB mediated pathway, P13k/Akt pathway, JAK/STAT3 pathway, and NLRP3/ASC/Caspase-1 pathway. Hopefully, this review may yield useful information about the anti-apoptotic effects of natural products on UC and their potential molecular mechanisms and provide helpful insights for further investigations.

Protective Effect of Ganoderma atrum Polysaccharide on Acrolein-Induced Apoptosis and Autophagic Flux in IEC-6 Cells

This study was designed to explore the beneficial effect and mechanism of Ganoderma atrum (G. atrum) polysaccharide (PSG-1) on acrolein-induced IEC-6 cells. Our results indicated that PSG-1 significantly reduced the impairment of acrolein on cell viability, decreased oxidative stress, and enabled normal expression of tight junction (TJ) proteins that were inhibited by acrolein in IEC-6 cells. Furthermore, PSG-1 attenuated the elevation of microtubule-associated proteins light chain 3 (LC3) and Beclin 1-like protein 1 (Beclin 1) and increased the protein levels of phospho-mTOR (p-mTOR) and phospho-akt (p-akt), indicating that PSG-1 activated the mammalian target of rapamycin (mTOR) signaling pathway and alleviated acrolein-induced autophagy in IEC-6 cells. Moreover, PSG-1 markedly attenuated the acrolein-induced apoptosis, as evidenced by the increase in mitochondrial membrane potential (MMP) and B-cell lymphoma 2 (Bcl-2) expression, and the decrease in cysteine aspartate lyase (caspase)-3 and caspase-9. In addition, autophagy the inhibitor inhibited acrolein-induced TJ and apoptosis of IEC-6 cells, while the apoptosis inhibitor also inhibited acrolein-induced TJ and autophagy, suggesting that autophagy and apoptosis were mutually regulated. Taken together, the present study proved that PSG-1 could protect IEC-6 cells from acrolein-induced oxidative stress and could repair TJ by inhibiting apoptosis and autophagic flux, where autophagy and apoptosis were mutually regulated.

Structural characterization of polysaccharide from yellow sweet potato and ameliorates DSS-induced mice colitis by active GPR41/MEK/ERK 1/2 signaling pathway

A polysaccharide isolated from yellow sweet potato (Ipomoea batatas (L.) Lam.) consisted of Rha, Ara, Gal, Glc, GalA, GlcA with the ratio of 1.00, 2.00, 3.63, 1.21, 1.17, 1.14, respectively. The molecular weight (Mw) of RSPP-A was determinted to be 2.51×10⁶ kDa. Methylation, Nuclear Magnetic Resonance (NMR) (1D & 2D) and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that RSPP-A possessed six glycosidic bonds including α-L-Araf-(1→, →5)-α-L-Araf-(1→, →6)-β-D-Galp-(1→, β-D-Glcp-(1→, →3)-α-L-Araf-(1→, →3)-α-L-Rhap-(1→. In dextran sulfate sodium (DSS) induced mouse-acute-colitis model, the results indicated that RSPP-A could down- regulate the secretion of IL-6 and IL-1β, and promote the secretion of IL-10 in serum and colon, which also suggested that RSPP-A could enhance the contents of short chain fatty acids(SCFAs) and up-regulate the expression of G protein-coupled receptor (GPR41) in colon. Moreover, the expression of Mitogen-activated protein kinase kinase (MEK), extracellular signal-regulated kinase 1/2 (ERK1/2) were up-regulated in colon after intervention with RSPP-A, result from above suggested that the anti-inflammatory activity might be related to the production of SCFA, activating GPR41/MEK/ERK1/2 signaling pathway.

Mechanism of Jianpi Qingchang Huashi Recipe in treating ulcerative colitis: A study based on network pharmacology and molecular docking

BACKGROUND

Ulcerative colitis (UC) is a refractory intestinal disease with alternating onset and remission and a long disease course, which seriously affects the health and quality of life of patients. The goal of treatment is to control clinical symptoms, induce and maintain remission, promote mucosal healing, and reduce recurrence. Clinical trials have shown unsatisfactory clinical response rates. As a supplementary alternative medicine, traditional Chinese medicine has a rich history and has shown good results in the treatment of UC. Because of the quality of herbal medicine and other factors, the curative effect of traditional Chinese medicine is not stable enough. The mechanism underlying the effect of Jianpi Qingchang Huashi Recipe (JPQCHSR) on inducing UC mucosal healing is not clear.

AIM

To investigate the potential mechanism of JPQCHSR for the treatment of UC based on network pharmacology and molecular docking.

METHODS

Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform was used to extract the active components and action targets of JPQCHSR, and the target names were standardized and corrected through UniProt database. The related targets of UC were obtained through GeneCards database, and the intersection targets of drugs and diseases were screened by jvenn online analysis tool. The visual regulatory network of "Traditional Chinese medicine-active components-target-disease" was constructed using Cytoscape software, the protein interaction network was constructed using STRING database, and enrichment analysis of gene ontology and Kyoto Encyclopedia of Genes and Genomes pathways was conducted through R software. At last, the active components were docked with the core target through SYBYL-X 2.1.1 software.

RESULTS

Through database analysis, a total of 181 active components, 302 targets and 205 therapeutic targets were obtained for JPQCHSR. The key compounds include quercetin, luteolin, kaempferol, etc. The core targets involved STAT3, AKT1, TP53, MAPK1, MAPK3, JUN, TNF, etc. A total of 2861 items were obtained by GO enrichment analysis, and 171 items were obtained by KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment analysis. The results of molecular docking showed that the key active components in JPQCHSR had certain affinity with the core target.

CONCLUSION

The treatment of UC with JPQCHSR is a complex process of multi-component, multi-target and multi-pathway regulation. The mechanism of this Recipe in the treatment of UC can be predicted through network pharmacology and molecular docking, so as to provide theoretical reference for it to better play its therapeutic role.

Luteolin alleviates inorganic mercury-induced kidney injury via activation of the AMPK/mTOR autophagy pathway

Inorganic mercury is a ubiquitous toxic pollutant in the environment. Exposure to inorganic mercury can cause various poisonous effects, including kidney injury. However, no safe and effective treatment for kidney injury caused by inorganic mercury has been found and used. Luteolin (Lut) possesses various beneficial bioactivities. Here, our research aims to investigate the protective effect of Lut on renal injury induced by mercury chloride (HgCl₂) and identify the underlying autophagy regulation mechanism. Twenty-eight 6-8 weeks old Wistar rats were randomly assigned to four groups: control, HgCl₂, HgCl₂ + Lut, and Lut. We performed the determination of oxidative stress and renal function indicators, histopathological analysis, the terminal deoxynucleotidyl transferase-mediated deoxyuracil nucleoside triphosphate nick-end labeling assay to detect apoptosis, western blot detection of autophagy-related protein levels, and atomic absorption method to detect mercury content. Our results showed that Lut ameliorated oxidative stress, apoptosis and restored the autophagy and renal function caused by HgCl₂ in rats. Concretely, the level of nuclear factor E2-related factor, renal adenosine monophosphate-activated protein kinase (AMPK) expression, and autophagy regulation-related proteins levels were down-regulated, and the mammalian target of rapamycin (mTOR) expression was up-regulated by HgCl₂ treatment. However, Lut treatment reversed the above changes. Notably, Lut reduced the accumulation of HgCl₂ in the kidneys and promoted the excretion of HgCl₂ through urine. Collectively, our results demonstrate that Lut can attenuate inorganic mercury-induced renal injury via activating the AMPK/mTOR autophagy pathway. Therefore, Lut may be a potential biological medicine to protect against renal damage induced by HgCl₂.

Anti-Inflammation Activity of Flavones and Their Structure-Activity Relationship

Flavones are an important class of bioactive constituents in foods, and their structural diversity enables them to interact with different targets. In particular, flavones are known for their anti-inflammatory activity. Herein, we summarized commonly applied in vitro, in vivo, and clinical models in testing anti-inflammatory activity of flavones. The anti-inflammatory structure-activity relationship of flavones was systematically mapped and supported with cross comparisons of that with flavanones, flavanols, and isoflavones. Hydroxyl groups (-OH) are indispensable for the anti-inflammatory function of flavones, and -OH at the C-5 and C-4' positions enhance while -OH at the C-6, C-7, C-8, and C-3' positions attenuate their activity. Moreover, the C2-C3 single bond, -OH at the C-3 and B-ring positions undermine flavone aglycones' activity. Most of the flavone aglycones function through NF-κB, MAPK, and JNK-STAT pathways, and their possible cell binding targets are kinase, aryl hydrocarbon receptor (AhR), G-protein coupled receptors, and estrogen receptors. However, the structure and anti-inflammatory activity relationship of flavones were unclear, and further research shall be conducted to close the gap in order to guide development of evidence-based functional foods.

Effects of Qing Chang Suppository Powder and its Ingredients on IL-17 Signal Pathway in HT-29 Cells and DSS-induced Mice

BACKGROUND

Qingchang Suppository, a formula used for more than 30 years in Longhua Hospital, has shown satisfactory clinical effects on Ulcerative Colitis (UC). However, its therapeutic mechanism has not been fully elucidated.

PURPOSE

The study aims to investigate the effects of Qingchang Suppository powder (QCSP) and its ingredients by regulating the IL-17A signaling pathway which plays an important role in the development of UC.

METHODS

HPLC was used to analyze the main ingredients (Gallic acid, Indigo, Indirubin) in QCSP. HT-29 cells were induced by rhIL-17A and TNF-α, and IL-17A related protein expressions were determined by western blot. BALB/C mice were induced by 4% Dextran Sodium sulfate (DSS). The effects of QCSP and its ingredients were evaluated by measuring weight loss, disease activity index (DAI), colon length, histological analysis. Western blot was used for analysis of IL-17A and MAPK related proteins p-ERK, p-JNK, p-P38. Quantitative reverse transcription polymerase chain reaction (q-PCR) was used to detect the expression of IL-17A, HSP90 and ACT1 in colon tissue. Cytokines such as IL-17A, IL-1β, IFN-γ and TNF-α were determinated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

QCSP had good therapeutic effect on DSS-induced colitis in mice. QCSP significantly relieved weight loss, restored colon length, repaired colon lesions, reduced histological scores and DAI, decreased TNF-α, IL-1β, IL-17 and IFN-γ contents, significantly suppressed the gene expressions of IL-17A, ACT1 and HSP90, and up-regulated the expressions of tight junction proteins like ZO-1 and Occludin. IL-17A pathway related proteins such as IL-17A, IL-17RA, HSP90, MAPKs, P-iκbα and iNOS were significantly increased in vitro and in vivo.

CONCLUSIONS

This paper reveals that QCSP inhibited the IL-17A signaling pathway in HT-29 cells and DSS induced mice, presenting a new mechanism of QCS on treating UC.

Bovine β-Lactoglobulin Covalent Modification by Flavonoids: Effect on the Allergenicity and Human Intestinal Microbiota

The present study aims to investigate the structure of covalent conjugates of bovine β-lactoglobulin (BLG) and flavonoids (luteolin, myricetin, and hyperoside), and their effect on the allergenicity and human intestinal microbiota. Covalent modification of amino acids in BLG by flavonoids was confirmed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and o-phthaldialdehyde assay. The secondary and conformational structures of BLG were changed by the covalent modification, which were determined by the circular dichroism, Fourier transform infrared spectroscopy, fluorescence spectroscopy, and UV spectroscopy. The enzyme-linked immunosorbent assay (ELISA) and cell experiments indicated that BLG covalent conjugates could reduce IgE/IgG binding capacities and suppress the allergy reactivity of RBL-2H3 cells, suggesting that the covalent modification modulated the balance of T cells. Meanwhile, covalent modification of BLG with these flavonoids can alter the diversity of human intestinal microbiota and the community abundance at phylum, family, and genus levels. The results revealed that covalent modification of BLG with flavonoids alters human intestinal microbiota, might result in the reduction of allergenicity, which could provide information for confirming the relationship between food allergy and the intestinal microbial ecosystem.

Tong Xie Yao Fang: A Classic Chinese Medicine Prescription with Potential for the Treatment of Ulcerative Colitis

The prescription of Tong Xie Yao Fang (TXYF) was derived from the Yuan dynasty “Dan Brook Heart Law,” which was a representative formula for treating liver-spleen disharmony, diarrhea, and abdominal pain. The prescription is composed of four herbs for soothing the liver and strengthening the spleen. TXYF is reportedly capable of eliminating discomfort in ulcerative colitis (UC). This classic formula has been widely used for regulating gastrointestinal motor dysfunction and repairing colon mucosa. This review aims to provide current information on the pharmacology and clinical research of TXYF in the treatment of UC, and to critically appraise that information, in order to guide the future clinical use and experimental study of TXYF in the treatment of UC. We searched online databases including PubMed, CNKI, and Google Scholar for research published between 2010 and 2020 on TXYF and its efficacy in the treatment of UC. The findings indicated that TXYF has anti-inflammatory and immunomodulatory effects, regulates cell signal transduction, brain-gut axis, and intestinal flora in UC, and may promote targeting of bone mesenchymal stem cells (BMSCs) to the colonic mucosa and accelerate healing of the colonic mucosal barrier. In addition, the results of clinical studies showed that TXYF has good efficacy and few adverse reactions in the treatment of UC. Although it has achieved some success, the research is limited by deficiencies; there is a lack of unified standards for the construction of UC animal models and for administration regimen. In addition, the dosage of TXYF is not consistent and lacks pharmacological verification, and clinical trial data are not detailed or sufficiently rigorous. Therefore, a more rigorous, comprehensive, and in-depth study of TXYF in the treatment of UC is needed.

Luteolin alleviates ulcerative colitis through SHP-1/STAT3 pathway

BACKGROUND

Previous studies have demonstrated that Luteolin has a positive effect on epithelial barrier integrity by promoting the function of tight protein, however, little is known about the underline mechanism of Luteolin. In this study, we constructed Caco-2 cell monolayer to explore the effects and the regulation mechanism of Luteolin in intestinal epithelial barrier integrity.

METHODS

Caco-2 cells were co-treated with TNF-α, Interferon-γ (IFN-γ) and Luteolin for 24 h. Overexpression or knockdown of SHP-1 was applied to study the effects of protein phosphoserine phosphatase-1 (SHP-1) on epithelial barrier integrity. Cell viability was tested by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Barrier function was detected by trans-epithelial electrical resistance (TEER) and FITC-dextran assay. The expression levels of SHP-1, phosphorylation signal transducer and activator of transcription 3 (p-STAT3), STAT3 and tight junction proteins were measured by qRT-PCR or western blot. In vivo model of ulcerative colitis was established to detect the function of Luteolin in ulcerative colitis.

RESULTS

We clarified that Luteolin protected intestinal epithelial barrier function of Caco-2 monolayers by increasing the resistance values and tight junction (TJ) protein expression. The expression of OCLN, CLDN1, and ZO1 was increased by Luteolin, while the expression of CLDN2 was decreased. Furthermore, Luteolin significantly alleviated the symptom of ulcerative colitis in DSS-induced mice. The in vitro cell model proved that overexpression of SHP-1 promotes the epithelial barrier function and knockdown of SHP-1 or STAT3 activation destroyed the protective effects of Luteolin on the expression of TJ proteins.

CONCLUSION

We found that the treatment of Luteolin promoted epithelial barrier function and Luteolin might preserve intestinal epithelial barrier function through suppression of STAT3 signaling pathway by SHP-1.

Luteolin suppresses 5-hydroxytryptamine elevation in stimulated RBL-2H3 cells and experimental colitis mice

Increased 5-hydroxytryptamine may be associated with the development and progression of inflammatory bowel disease. In this study, we examined the suppressive effect of flavonoids on the increased intra- and extracellular 5-hydroxytryptamine levels in rat mast RBL-2H3 cells, known to produce 5-hydroxytryptamine by the phorbol 12-myristate 13-acetate stimulation. Among the flavonoids examined, luteolin and quercetin significantly reduced the cellular 5-hydroxytryptamine concentration. Gene and protein expression analyses revealed that luteolin significantly suppressed cellular tryptophan hydroxylase 1 expression induced by phorbol 12-myristate 13-acetate stimulation. Mitogen-activated protein kinase/extracellular signal-regulated kinase signaling was also suppressed by luteolin, suggesting that this pathway is one of targets of 5-hydroxytryptamine modulation by luteolin. An in vivo experimental colitis model was prepared by administering 2.5% dextran sodium sulfate in drinking water to C57BL/6 mice for seven days. The ingestion of 0.1% dietary luteolin suppressed the increasing 5-hydroxytryptamine in the colorectal mucosa. In conclusion, luteolin possesses a suppressive effect on extensive 5-hydroxytryptamine formation in both experimental RBL-2H3 cells and colitis models.

Luteolin alleviates inflammation and modulates gut microbiota in ulcerative colitis rats

Ulcerative colitis (UC) is a chronic inflammatory bowel disease related to intestinal dysbiosis. Luteolin has been reported to reduce inflammation. However, it remains unclear whether luteolin ameliorates UC and regulates gut microbiota. In this study, we investigated the effects of luteolin on colonic structure and inflammation of dextran sulfate sodium (DSS)-induced rats using hematoxylin-eosin staining, immunohistochemistry and enzyme-linked immunosorbent assay and evaluated the effects of luteolin on gut microbiota using 16S rDNA sequencing. We found that luteolin treatment significantly reduced colonic damage, and inhibited colonic inflammation in UC rats, evidenced by the decreased levels of NF-κB, IL-17 and IL-23 in UC rats and the increased level of PPAR-γ. In addition, the 16S rDNA sequencing analysis revealed that luteolin treatment could alter diversity and composition of gut microbiota in UC rats. Lactobacillus, Bacteroides, Roseburia and Butyricicoccus were dominant genera in the luteolin group. Luteolin treatment reduced DSS-induced increased ratios of Lactobacillus and Prevotella_9. Furthermore, KEGG analysis revealed that gut microbiota was mainly related to DNA repair and recombination proteins, ribosome, purine metabolism, peptidases, and pyrimidine metabolism. In conclusion, our results revealed that luteolin could alleviate DSS-induced colitis in rats, and gut microbiota had the potential to serve as promising biomarkers for uncovering the mechanism by which luteolin improved UC.

The genotoxicity potential of luteolin is enhanced by CYP1A1 and CYP1A2 in human lymphoblastoid TK6 cells

Luteolin (5,7,3',4'-tetrahydroxyflavone) belongs to the flavone subclass of flavonoids. Luteolin and its glycosides are present in many botanical families, including edible plants, fruits, and vegetables. While the beneficial properties of luteolin have been widely studied, fewer studies have investigated its toxicity. In the present study, using human lymphoblastoid TK6 cells and our newly developed TK6-derived cell lines that each stably express a single human cytochrome P450 (CYP1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C18, 2C9, 2C19, 2D6, 2E1, 3A4, 3A5, and 3A7), we systematically evaluated luteolin-induced cytotoxicity and genotoxicity, and the role of specific CYPs in the bioactivation of luteolin. Treatments with luteolin for 4-24 h induced cytotoxicity, apoptosis, DNA damage, and chromosome damage in a concentration-dependent manner. Subsequently, we observed that luteolin-induced cytotoxicity and genotoxicity, measured by the high-throughput micronucleus assay, were significantly increased in TK6 cells transduced with CYP1A1 and 1A2. In addition, key apoptosis and DNA damage biomarkers, including cleaved PARP-1, cleaved caspase-3, and phosphorylated histone 2AX (γH2A.X), were all significantly increased in the CYP1A1- and 1A2-expressing cells compared with the empty vector controls. Analysis by LC-MS/MS revealed that TK6 cells biotransformed the majority of luteolin into diosmetin, a less toxic O-methylated flavone, after 24 h; the presence of CYP1A1 and 1A2 partially reversed this process. Altogether, these results indicate that metabolism by CYP1A1 and 1A2 enhanced the toxicity of luteolin in vitro. Our results further support the utility of our TK6 cell system for identification of the specific CYPs responsible for chemical bioactivation and toxicity potential.

Protection against Alzheimer's disease by luteolin: Role of brain glucose regulation, anti-inflammatory activity, and the gut microbiota-liver-brain axis

Luteolin is a widely distributed flavone herbs and vegetables. It has anti-oxidant and anti-inflammatory activities and improves glucose metabolism by potentiating insulin sensitivity and improving β-cell function and mass. Alzheimer's disease (AD) is induced by the deposition of amyloid-beta (Aβ) in the hippocampus and the formation of neurotoxic Aβ plaques. The Aβ deposition is associated with increased formation of Aβ from amyloid precursor protein by up-regulation of β-secretase and β-site amyloid precursor protein-cleaving enzyme 1 (BACE1). Furthermore, Aβ accumulation is increased by brain insulin resistance. The impairment of insulin/IGF-1 signaling mainly in the hippocampus and brain insulin resistance is connected to signals originating in the liver and gut microbiota, known as the gut microbiota-liver-brain axis. This indicates that the changes in the production of short-chain fatty acids by the gut microbiota and pro-inflammatory cytokines can alter insulin resistance in the liver and brain. Luteolin is detected in the brain tissues after passing through the blood-brain barrier, where it can directly influence neuroinflammation and brain insulin resistance and modulate Aβ deposition. Luteolin (10-70 mg/kg bw for rodents) can modulate the systemic and brain insulin resistance, and it suppresses AD development directly, and it influences Aβ deposition by activation of the gut microbiota-liver-brain axis. In this review, we evaluate the potential of luteolin to mitigate two potential causes of AD, neuroinflammatory processes, and disruption of glucose metabolism in the brain. This review suggests that luteolin intake can enhance brain insulin resistance and neuroinflammation, directly and indirectly, to protect against the development of Alzheimer's-like disease, and the gut microbiota-liver-brain axis is mainly involved in the indirect pathway. However, most studies have been conducted in animal studies, and human clinical trials are needed.