Urolithin A gains in antiproliferative capacity by reducing the glycolytic potential via the p53/TIGAR axis in colon cancer cells

The cGAS-STING signaling pathway is modulated by urolithin A

During aging, general cellular processes, including autophagic clearance and immunological responses become compromised; therefore, identifying compounds that target these cellular processes is an important approach to improve our health span. The innate immune cGAS-STING pathway has emerged as an important signaling system in the organismal defense against viral and bacterial infections, inflammatory responses to cellular damage, regulation of autophagy, and tumor immunosurveillance. These key functions of the cGAS-STING pathway make it an attractive target for pharmacological intervention in disease treatments and in controlling inflammation and immunity. Here, we show that urolithin A (UA), an ellagic acid metabolite, exerts a profound effect on the expression of STING and enhances cGAS-STING activation and cytosolic DNA clearance in human cell lines. Animal laboratory models and limited human trials have reported no obvious adverse effects of UA administration. Thus, the use of UA alone or in combination with other pharmacological compounds may present a potential therapeutic approach in the treatment of human diseases that involves aberrant activation of the cGAS-STING pathway or accumulation of cytosolic DNA and this warrants further investigation in relevant transgenic animal models.

Greasing the Wheels of Pharmacotherapy for Colorectal Cancer: the Role of Natural Polyphenols

PURPOSE OF REVIEW

The main purpose of this review, mainly based on preclinical studies, is to summarize the pharmacological and biochemical evidence regarding natural polyphenols against colorectal cancer and highlight areas that require future research.

RECENT FINDINGS

Typically, colorectal cancer is a potentially preventable and curable cancer arising from benign precancerous polyps found in the colon's inner lining. Colorectal cancer is the third most common cancer, with a lifetime risk of approximately 4 to 5%. Genetic background and environmental factors play major roles in the pathogenesis of colorectal cancer. Theoretically, a multistep process of colorectal carcinogenesis provides enough time for anti-tumor pharmacotherapy of colorectal cancer. Chronic colonic inflammation, oxidative stress, and gut microbiota imbalance have been found to increase the risk for colorectal cancer development by creating genotoxic stress within the intestinal environment to generate genetic mutations and epigenetic modifications. Currently, numerous natural polyphenols have shown anti-tumor properties against colorectal cancer in preclinical research, especially in colorectal cancer cell lines. In this review, the current literature regarding the etiology and epidemiology of colorectal cancer is briefly outlined. We highlight the findings of natural polyphenols in colorectal cancer from in vitro and in vivo studies. The scarcity of human trials data undermines the clinical use of natural polyphenols as anti-colorectal cancer agents, which should be undertaken in the future.

Inhibitory Effects of Urolithins, Bioactive Gut Metabolites from Natural Polyphenols, against Glioblastoma Progression

We previously reported that proinflammatory cytokines, particularly tumor necrosis factor (TNF)-α, promoted tumor migration, invasion, and proliferation, thus worsening the prognosis of glioblastoma (GBM). Urolithins, the potent metabolites produced by the gut from pomegranate polyphenols, have anticancer properties. To develop an effective therapy for GBM, this study aimed to study the effects of urolithins against GBM. Urolithin A and B significantly reduced GBM migration, reduced epithelial-mesenchymal transition, and inhibited tumor growth. Moreover, urolithin A and B inhibited TNF-α-induced vascular cell adhesion molecule (VCAM)-1 and programmed death ligand 1 (PD-L1) expression, thereby reducing human monocyte (HM) binding to GBM cells. Aryl hydrocarbon receptor (AhR) level had higher expression in patients with glioma than in healthy individuals. Urolithins are considered pharmacological antagonists of AhR. We demonstrated that the inhibition of AhR reduced TNF-α-stimulated VCAM-1 and PD-L1 expression. Furthermore, human macrophage condition medium enhanced expression of PD-L1 in human GBM cells. Administration of the AhR antagonist attenuated the enhancement of PD-L1, indicating the AhR modulation in GBM progression. The modulatory effects of urolithins in GBM involve inhibiting the Akt and epidermal growth factor receptor pathways. The present study suggests that urolithins can inhibit GBM progression and provide valuable information for anti-GBM strategy.

Ellagic Acid and Cancer Hallmarks: Insights from Experimental Evidence

Cancer is a complex and multifaceted disease with a high global incidence and mortality rate. Although cancer therapy has evolved significantly over the years, numerous challenges persist on the path to effectively combating this multifaceted disease. Natural compounds derived from plants, fungi, or marine organisms have garnered considerable attention as potential therapeutic agents in the field of cancer research. Ellagic acid (EA), a natural polyphenolic compound found in various fruits and nuts, has emerged as a potential cancer prevention and treatment agent. This review summarizes the experimental evidence supporting the role of EA in targeting key hallmarks of cancer, including proliferation, angiogenesis, apoptosis evasion, immune evasion, inflammation, genomic instability, and more. We discuss the molecular mechanisms by which EA modulates signaling pathways and molecular targets involved in these cancer hallmarks, based on in vitro and in vivo studies. The multifaceted actions of EA make it a promising candidate for cancer prevention and therapy. Understanding its impact on cancer biology can pave the way for developing novel strategies to combat this complex disease.

Urolithin A in Health and Diseases: Prospects for Parkinson's Disease Management

Parkinson's disease (PD) is a chronic and progressive neurodegenerative disorder characterized by a complex pathophysiology and a range of symptoms. The prevalence increases with age, putting the ageing population at risk. Disease management includes the improvement of symptoms, the comfort of the patient's life, and palliative care. As there is currently no cure, growing evidence points towards the beneficial role of polyphenols on neurodegeneration. Numerous studies indicate the health benefits of the family of urolithins, especially urolithin A (UA). UA is a bacterial metabolite produced by dietary ellagitannins and ellagic acid. An expanding body of literature explores the involvement of the compound in mitochondrial health, and its anti-inflammatory, anti-oxidant, and anti-apoptotic properties. The review organizes the existing knowledge on the role of UA in health and diseases, emphasizing neurodegenerative diseases, especially PD. We gathered data on the potential neuroprotective effect in in vivo and in vitro models. We discussed the possible mechanisms of action of the compound and related health benefits to give a broader perspective of potential applications of UA in neuroprotective strategies. Moreover, we projected the future directions of applying UA in PD management.

Ellagitannins-Derived Intestinal Microbial Metabolite Urolithin A Ameliorates Fructose-Driven Hepatosteatosis by Suppressing Hepatic Lipid Metabolic Reprogramming and Inducing Lipophagy

Excessive fructose consumption exacerbates the progression of nonalcoholic fatty liver disease (NAFLD) by disrupting hepatic lipid homeostasis. This study sought to evaluate the efficacy of urolithin A (UroA) in a fructose-induced NAFLD mouse model. UroA was administered in the high-fructose-fed mice to investigate the antisteatotic effects in vivo. Fructose-stimulated HepG2 cells and primary hepatocytes were established for in vitro mechanistic assessment. The results suggested that UroA ameliorated fructose-induced hepatic steatosis in mice. Mechanistically, UroA impaired lipogenesis and enhanced β-oxidation in the livers of fructose-fed mice. Notably, UroA facilitated hepatic lipophagy through the AMPK/ULK1 pathway both in vivo and in vitro, degrading lipid droplets for fueling β-oxidation. This study indicates that UroA alleviates excessive lipid accumulation and restores lipid homeostasis in the livers of fructose-fed mice by suppressing lipid metabolic reprogramming and triggering lipophagy. Therefore, dietary supplementation of UroA or ellagitannins-rich foods may be beneficial for NAFLD individuals with high fructose intake.

The Impact of Ellagitannins and Their Metabolites through Gut Microbiome on the Gut Health and Brain Wellness within the Gut-Brain Axis

Ellagitannins (ETs) are a large group of bioactive compounds found in plant-source foods, such as pomegranates, berries, and nuts. The consumption of ETs has often been associated with positive effects on many pathologies, including cardiovascular diseases, neurodegenerative syndromes, and cancer. Although multiple biological activities (antioxidant, anti-inflammatory, chemopreventive) have been discussed for ETs, their limited bioavailability prevents reaching significant concentrations in systemic circulation. Instead, urolithins, ET gut microbiota-derived metabolites, are better absorbed and could be the bioactive molecules responsible for the antioxidant and anti-inflammatory activities or anti-tumor cell progression. In this review, we examined the dietary sources, metabolism, and bioavailability of ETs, and analyzed the last recent findings on ETs, ellagic acid, and urolithins, their intestinal and brain activities, the potential mechanisms of action, and the connection between the ET microbiota metabolism and the consequences detected on the gut-brain axis. The current in vitro, in vivo, and clinical studies indicate that ET-rich foods, individual gut microbiomes, or urolithin types could modulate signaling pathways and promote beneficial health effects. A better understanding of the role of these metabolites in disease pathogenesis may assist in the prevention or treatment of pathologies targeting the gut-brain axis.

The Synthesis of Urolithins and their Derivatives and the Modes of Antitumor Action

Urolithins are microbial metabolites derived from berries and pomegranate fruits, which display anti-inflammatory, anti-oxidative, and anti-aging activities. There are eight natural urolithins (urolithin A-E, M5, M6 and M7), which have been isolated by now. Structurally, urolithins are phenolic compounds and belong to 6H-dibenzo [b,d] pyran-6-one. They have drawn considerable attention because of their vast range of biological activities and health benefits. Recent studies also suggest that they possess anti-SARS-CoV-2 and anticancer effects. In this article, the recent advances in the synthesis of urolithins and their derivatives from 2015 to 2021 are reviewed. To improve or overcome the solubility and metabolism stability issues, the modifications of urolithins are mainly centered on the hydroxy group and lactone group, and some compounds have been found to display promising results and the potential for further study. The possible modes of antitumor action of urolithin are also discussed. Several signaling pathways, including PI3K-Akt, Wnt/β-catenin pathways, and multiple receptors (aryl hydrocarbon receptor, estrogen and androgen receptors) and enzymes (tyrosinase and lactate dehydrogenase) are involved in the antitumor activity of urolithins.

Urolithin A suppresses tumor progression and induces autophagy in gastric cancer via the PI3K/Akt/mTOR pathway

Urolithin A (UA) is a microbial metabolite of natural polyphenols ellagitannins and ellagic acid with well-established antitumor properties against various malignancies. However, the exact role of UA in gastric cancer (GC) progression remains largely unclear. In the present study, we investigated the effects and potential mechanisms of UA in GC in vitro and in vivo. Our results revealed that UA could suppress GC cell proliferation, inhibit migration and invasion, promote apoptosis, and induce autophagy via the phosphatidylinositol-3-kinase/protein kinase B/mammalian target of rapamycin pathway in vitro. The autophagy inhibitors 3-methyladenine and chloroquine augmented the inhibitory effect of UA on proliferation and promoted apoptosis, implying that UA mediated the cytoprotective role of autophagy. Meanwhile, the in vivo experiments showed that UA effectively suppressed tumor growth, enhanced the therapeutic effects, and alleviated chemotherapy toxicity in xenograft models. Overall, these findings offer novel insights into the role of UA in tumor therapy and suggest that UA may possess potential therapeutic applications for GC.

Urolithins: a Comprehensive Update on their Metabolism, Bioactivity, and Associated Gut Microbiota

Urolithins, metabolites produced by the gut microbiota from the polyphenols ellagitannins and ellagic acid, are discovered by the research group in humans almost 20 years ago. Pioneering research suggests urolithins as pleiotropic bioactive contributors to explain the health benefits after consuming ellagitannin-rich sources (pomegranates, walnuts, strawberries, etc.). Here, this study comprehensively updates the knowledge on urolithins, emphasizing the review of the literature published during the last 5 years. To date, 13 urolithins and their corresponding conjugated metabolites (glucuronides, sulfates, etc.) have been described and, depending on the urolithin, detected in different human fluids and tissues (urine, blood, feces, breastmilk, prostate, colon, and breast tissues). There has been a substantial advance in the research on microorganisms involved in urolithin production, along with the compositional and functional characterization of the gut microbiota associated with urolithins metabolism that gives rise to the so-called urolithin metabotypes (UM-A, UM-B, and UM-0), relevant in human health. The design of in vitro studies using physiologically relevant assay conditions (molecular forms and concentrations) is still a pending subject, making some reported urolithin activities questionable. In contrast, remarkable progress has been made in the research on the safety, bioactivity, and associated mechanisms of urolithin A, including the first human interventions.

Urolithin A targets the AKT/WNK1 axis to induce autophagy and exert anti-tumor effects in cholangiocarcinoma

Urolithin A (UA; 3,8-dihydroxybenzo[c]chromen-6-one), a metabolite generated by intestinal bacteria during the biotransformation of ellagitannins, has gained considerable attention in treating several cancers. Cholangiocarcinoma (CCA) remains one of the most lethal cancers; it grows in a special environment constantly exposed to both blood and bile. Since UA is known to undergo enterohepatic recirculation, we hypothesized that UA might have significant antitumor effects in CCA. Here, we investigated the therapeutic potential of UA in CCA and aimed to elucidate its mechanisms, including autophagy. UA treatment inhibited cell proliferation and induced G2/M phase cell cycle arrest in CCA cells. UA also suppressed cell migration and invasion, but did not cause apoptosis. Furthermore, Western blotting and immunocytochemistry demonstrated increased LC3-II accumulation, while electron microscopy demonstrated induced autophagosomes after UA treatment, suggesting that UA upregulated autophagy in CCA cells. In xenograft mice treated with UA, tumor growth was inhibited with increased LC3-II levels. On the other hand, phospho-kinase array demonstrated downregulation of the AKT/WNK1 pathway. LC3-II expression was elevated in WNK1 knocked down cells, indicating that WNK1 is the key signal for regulating autophagy. Thus, UA exerted antitumor effects by suppressing the AKT/WNK1 signaling pathway and inducing autophagy. In conclusion, UA, a natural, well-tolerated compound, may be a promising therapeutic candidate for advanced CCA.

Health functions and related molecular mechanisms of ellagitannin-derived urolithins

Ellagitannins are vital bioactive polyphenols that are widely distributed in a variety of plant-based foods. The main metabolites of ellagitannins are urolithins, and current research suggests that urolithins provide a variety of health benefits. This review focused on the role of the gut bacteria in the conversion of ellagitannins to urolithins. Based on the results of in vitro and in vivo studies, the health benefits of urolithins, including antioxidant, anti-inflammatory, anti-cancer, anti-obesity, anti-diabetic, anti-aging, cardiovascular protective, neuroprotective, kidney protective, and muscle mass protective effects, were thoroughly outlined, with a focus on their associated molecular mechanisms. Finally, we briefly commented on urolithins' safety. Overall, urolithins' diverse health benefits indicate the potential utilization of ellagitannins and urolithins in the creation of functional foods and nutraceuticals to treat and prevent some chronic diseases.

Microbial metabolite restricts 5-fluorouracil-resistant colonic tumor progression by sensitizing drug transporters via regulation of FOXO3-FOXM1 axis

The survival rate of colorectal cancer patients is adversely affected by the selection of tumors resistant to conventional anti-cancer drugs such as 5-fluorouracil (5FU). Although there is mounting evidence that commensal gut microbiota is essential for effective colon cancer treatment, the detailed molecular mechanisms and the role of gut microbial metabolites remain elusive. The goal of this study is to decipher the impact and mechanisms of gut microbial metabolite, urolithin A (UroA) and its structural analogue, UAS03 on reversal of 5FU-resistant (5FUR) colon cancers. Methods: We have utilized the SW480 and HCT-116 parental (5FU-sensitive) and 5FUR colon cancer cells to examine the chemosensitization effects of UroA or UAS03 by using both in vitro and in vivo models. The effects of mono (UroA/UAS03/5FU) and combinatorial therapy (UroA/UAS03 + 5FU) on cell proliferation, apoptosis, cell migration and invasion, regulation of epithelial mesenchymal transition (EMT) mediators, expression and activities of drug transporters, and their regulatory transcription factors were examined using molecular, cellular, immunological and flowcytometric methods. Further, the anti-tumor effects of mono/combination therapy (UroA or UAS03 or 5FU or UroA/UAS03 + 5FU) were examined using pre-clinical models of 5FUR-tumor xenografts in NRGS mice and azoxymethane (AOM)-dextran sodium sulfate (DSS)-induced colon tumors. Results: Our data showed that UroA or UAS03 in combination with 5FU significantly inhibited cell viability, proliferation, invasiveness as well as induced apoptosis of the 5FUR colon cancer cells compared to mono treatments. Mechanistically, UroA or UAS03 chemosensitized the 5FUR cancer cells by downregulating the expression and activities of drug transporters (MDR1, BCRP, MRP2 and MRP7) leading to a decrease in the efflux of 5FU. Further, our data suggested the UroA or UAS03 chemosensitized 5FUR cancer cells to 5FU treatment through regulating FOXO3-FOXM1 axis. Oral treatment with UroA or UAS03 in combination with low dose i.p. 5FU significantly reduced the growth of 5FUR-tumor xenografts in NRGS mice. Further, combination therapy significantly abrogated colonic tumors in AOM-DSS-induced colon tumors in mice. Conclusions: In summary, gut microbial metabolite UroA and its structural analogue UAS03 chemosensitized the 5FUR colon cancers for effective 5FU chemotherapy. This study provided the novel characteristics of gut microbial metabolites to have significant translational implications in drug-resistant cancer therapeutics.

Urolithins and intestinal health

There are trillions of microorganisms in the human intestine. They can react to the intestinal microenvironment by metabolizing food or producing small molecular compounds to affect the host's digestive ability and resist the risk of infection and autoimmune diseases. Many studies have revealed that intestinal flora and its metabolites play an important role in human physiology and the development of diseases. Urolithins are kind of intestinal microbiota metabolites of ellagitannins (ETs) and ellagic acid (EA) with potent biological activity in vivo. However, different individuals have different intestinal flora. According to the different metabolites from ETs and EA, it is divided into three metabo-types including UM-A, UM-B and UM-0. This paper reviews the origin of urolithins, the urolithin producing microorganisms and the effects of urolithins on regulating intestinal diseases. This review will provide a theoretical basis for the regulation of urolithins in the homeostasis of intestinal flora and a reference for the scientific utilization of urolithins and foods rich in ETs and EA.

The therapeutic potential of urolithin A for cancer treatment and prevention

BACKGROUND

Urolithin A is the metabolite of natural polyphenol ellagic acid and ellagitannins, generated by gut microbiota. Urolithin A is better absorbed in the gastrointestinal tract than its parent substances. Thus, the variable effects of ellagitannin-reach food (like pomegranate fruit, walnuts, tea, and others) on people's health might be linked with the differences in individual microbiota content. Urolithin A possesses various anti-inflammatory and anticancer effects, shown by in vivo and in vitro studies.

OBJECTIVE

In the current review, we consider anti-inflammatory and direct anticancer urolithin A effects as well as their molecular mechanisms, which might be the basement of clinical trials, estimating urolithin A anticancer effects.

CONCLUSION

Urolithin A attenuated the pro-inflammatory factors production (IL-6, IL-1β, NOS2 and others) in vitro studies. Oral urolithin A treatment caused prominent anticancer and anti-inflammatory action in various in vivo studies, including colitis rat model, carrageenan-induced paw edema mice model, models of pancreatic cancer, and models of obesity. The main molecular mechanisms of these effects might be the modulation of aryl hydrocarbon receptors, which antagonism may lead to decreasing of chronic inflammation. Other primary targets of urolithin A might be the processes of protein phosphorylation (for instance, it decreases the phosphorylation of protein kinase B) and p53 stabilization. Anti-inflammatory effects of urolithin A can be reached in physiologically relevant concentrations. This might be of vital importance for preventing immune suppression, associated with chronic inflammation in cancer. Considering the favorable urolithin A safety profile, it is the promising compound for cancer treatment and prevention.

Synergistic effects of natural compounds and conventional chemotherapeutic agents: recent insights for the development of cancer treatment strategies

Cancer is one of the leading causes of death in the world. Chemotherapy is presented as an option for treatment of this disease, however, low specificity, high resistance rates, toxicity and hypersensitivity reactions, make it necessary to search for therapeutic alternatives that increase the selectivity of treatment, reduce the side effects and enhance its antitumor potential. Natural products are accessible, inexpensive and less toxic sources; in addition, they have multiple mechanisms of action that can potentiate the outcome of chemotherapeutics. In this review, we present evidence on the beneficial effect of the interaction of dietary phytochemicals with chemotherapeutical agents for cancer treatment. This effect is generated by different mechanisms of action such as, increased tumoricidal effect via sensitization of cancer cells, reversing chemoresistance through inhibition of several targets involved in the development of drug resistance and, decreasing chemotherapy-induced toxicity in non-tumoral cells by the promotion of repair mechanisms. Studies discussed in this review will provide a solid basis for the exploration of the potential use of natural products in combination with chemotherapeutical agents, to overcome some of the difficulties that arise in the management of cancer patients.

The role of key gut microbial metabolites in the development and treatment of cancer

In recent years, the role of gut microbial metabolites on the inhibition and progression of cancer has gained significant interest in anticancer research. It has been established that the gut microbiome plays a pivotal role in the development, treatment and prognosis of different cancer types which is often mediated through the gut microbial metabolites. For instance, gut microbial metabolites including bacteriocins, short-chain fatty acids and phenylpropanoid-derived metabolites have displayed direct and indirect anticancer activities through different molecular mechanisms. Despite the reported anticancer activity, some gut microbial metabolites including secondary bile acids have exhibited pro-carcinogenic properties. This review draws a critical summary and assessment of the current studies demonstrating the carcinogenic and anticancer activity of gut microbial metabolites and emphasises the need to further investigate the interactions of these metabolites with the immune system as well as the tumour microenvironment in molecular mechanistic and clinical studies.

Insights from the p53 induced TIGAR protein 2 in the glycolytic pathway model

TIGAR is a p53 inducible gene that triggers changes in glycolytic metabolic pathway states. It is known that TIGAR expression lowers the fructose - 2, 6-bisphosphate levels resulting in an inhibition of glycolysis and decrease in intracellular ROS levels. Therefore, it is interesting to document data on p53 induced TIGAR protein 2 in the glycolytic pathway. We describe a two-oscillator model consisting of the p53-Mdm2 network and glycolytic pathway with the TIGAR protein. The numerical simulation of the model shows the suppression of glycolytic oscillation as the level of TIGAR protein increases in agreement with the experimental results reported. Thus, stochastic simulation data helps to understand the realistic behaviour in the pathway.

Effects of urolithin A on osteoclast differentiation induced by receptor activator of nuclear factor-κB ligand via bone morphogenic protein 2

Urolithin A (UA) is an intestinal microbial metabolite derived from ellagitannins and a promising agent for treating osteoarthritis. However, its effects on osteoporosis are unclear. This study explored the effects of urolithin A (UA) on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclasts and its underlying molecular mechanisms. RANKL treatment significantly increased tartrate-resistant acid phosphatase (TRACP) or osteoclast marker levels (P < 0.05), while adding UA decreased the RANKL-induced levels (P < 0.05) in RAW264.7 cells. Total RNA isolated from RANKL- or RANKL + UA-treated cells was sequenced, and the obtained transcriptome dataset revealed 2,399 differentially expressed genes. They were enriched in multiple pathways involved in rheumatoid arthritis, ERK1 and ERK2 cascade, regulation of inflammatory response, ECM-receptor interactions, and TNF signaling. Scanning electron microscopy showed that RANKL promoted bone resorption pits in bone biopsy specimens, whereas UA inhibited their formation. When bone morphogenic protein 2 (BMP2) was shRNA-silenced, the bone resorption pits were restored. Moreover, while RANKL significantly enhanced the levels of p-ERK2/ERK2, p-p38/p38, p-Akt1/Akt1, p-ERK1/ERK1, and osteoclast-related proteins (P < 0.05), UA reduced them. BMP2 silencing also reversed the UA inhibitory effect. Thus, UA represses the RANKL-induced osteoclast differentiation of RAW264.7 cells by regulating Akt1, p38, and ERK1/2 signaling, and BMP2 likely reverses the UA inhibitory effect via these pathways. We propose BMP2 as a potential drug target for treating bone metabolic diseases, such as osteoporosis.

Ellagic acid and intestinal microflora metabolite urolithin A: A review on its sources, metabolic distribution, health benefits, and biotransformation

Foods rich in ellagic tannins are first hydrolyzed into ellagic acid in the stomach and small intestine, and then converted into urolithins with high bioavailability by the intestinal flora. Urolithin has beneficially biological effects, it can induce adipocyte browning, improve cholesterol metabolism, inhibit graft tumor growth, relieve inflammation, and downregulate neuronal amyloid protein formation via the β3-AR/PKA/p38MAPK, ERK/AMPKα/SREBP1, PI3K/AKT/mTOR signaling pathways, and TLR4, AHR receptors. But differences have been reported in urolithin production capacity among different individuals. Thus, it is of great significance to explore the biological functions of urolithin, screen the strains responsible for biotransformation of urolithin, and explore the corresponding functional genes. Tannin acyl hydrolase can hydrolyze tannins into ellagic acid, and the genera Gordonibacter and Ellagibacter can metabolize ellagic acid into urolithins. Therefore, application of "single bacterium", "single bacterium + enzyme", and "microflora" can achieve biotransformation of urolithin A. In this review, the source and metabolic pathway of ellagic tannins, and the mechanisms of the biological function of a metabolite, urolithin A, are discussed. The current strategies of biotransformation to obtain urolithin A are expounded to provide ideas for further studies on the relationship between urolithin and human health.

Effects of red raspberry polyphenols and metabolites on biomarkers of inflammation and insulin resistance in type 2 diabetes: A pilot study

Berry fruits are rich in polyphenolic compounds (PCs) and may promote health benefits. Anthocyanin (ACNs) concentrations of red raspberry (RR)(Rubus idaeus) extracts were 887.6 ± 262.8 μg/g consisting mainly of...

Effect of Urolithin A on Bone Repair in Mice with Bone Defects

BACKGROUND

Bone defect difficult to manage clinically and it is a big challenge to repair it. Secondary metabolites source from herb has shown potential for the treatment of bone defect.

METHODS

Mesenchymal stem cells (MSCs) were isolated from mice and incubated with urolithin A (UA) (10, 25, and 50 µg/mL). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was performed to estimate apoptosis and mineralisation was evaluated by alkaline phosphatase assay and alizarin red S staining. A middle femoral defect was induced in mice and bone tissue was prepared for endochondral ossification by treating with UA. The effect of UA was estimated by determining markers of osteoblast proliferation in serum and micro-computed tomography to analyse bone defects.

RESULTS

UA enhanced mineralisation of MSCs and osteogenic gene markers in MSCs in vitro. Also, the bone defect score and bone mineral density were improved by UA. Moreover, UA ameliorated the altered Wnt3a protein and histopathological changes in bone defect mice.

CONCLUSION

Presented report conclude that UA enhances osteoblast proliferation in bone-defect mice by activating the Wnt pathway.

A mechanistic insight into the biological activities of urolithins as gut microbial metabolites of ellagitannins

Urolithins are the gut metabolites produced from ellagitannin-rich foods such as pomegranates, tea, walnuts, as well as strawberries, raspberries, blackberries, and cloudberries. Urolithins are of growing interest due to their various biological activities including cardiovascular protection, anti-inflammatory activity, anticancer properties, antidiabetic activity, and antiaging properties. Several studies mostly based on in vitro and in vivo experiments have investigated the potential mechanisms of urolithins which support the beneficial effects of urolithins in the treatment of several diseases such as Alzheimer's disease, type 2 diabetes mellitus, liver disease, cardiovascular disease, and various cancers. It is now obvious that urolithins can involve several cellular mechanisms including inhibition of MDM2-p53 interaction, modulation of mitogen-activated protein kinase pathway, and suppressing nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activity. Antiaging activity is the most appealing and probably the most important property of urolithin A that has been investigated in depth in recent studies, owing to its unique effects on activation of mitophagy and mitochondrial biogenesis. A recent clinical trial showed that urolithin A is safe up to 2,500 mg/day and can improve mitochondrial biomarkers in elderly patients. Regarding the importance of mitochondria in the pathophysiology of many diseases, urolithins merit further research especially in clinical trials to unravel more aspects of their clinical significance. Besides the nutritional value of urolithins, recent studies proved that urolithins can be used as pharmacological agents to prevent or cure several diseases. Here, we comprehensively review the potential role of urolithins as new therapeutic agents with a special focus on the molecular pathways that have been involved in their biological effects. The pharmacokinetics of urolithins is also included.

Punicalagin in Cancer Prevention-Via Signaling Pathways Targeting

The extract of pomegranate (Punica granatum) has been applied in medicine since ancient times due to its broad-spectrum health-beneficial properties. It is a rich source of hydrolyzable tannins and anthocyanins, exhibiting strong antioxidative, anti-inflammatory, and antineoplastic properties. Anticancer activities of pomegranate with reference to modulated signaling pathways in various cancer diseases have been recently reviewed. However, less is known about punicalagin (Pug), a prevailing compound in pomegranate, seemingly responsible for its most beneficial properties. In this review, the newest data derived from recent scientific reports addressing Pug impact on neoplastic cells are summarized and discussed. Its attenuating effect on signaling circuits promoting cancer growth and invasion is depicted. The Pug-induced redirection of signal-transduction pathways from survival and proliferation into cell-cycle arrest, apoptosis, senescence, and autophagy (thus compromising neoplastic progression) is delineated. Considerations presented in this review are based mainly on data obtained from in vitro cell line models and concern the influence of Pug on human cervical, ovarian, breast, lung, thyroid, colorectal, central nervous system, bone, as well as other cancer types.

Urolithins: The Gut Based Polyphenol Metabolites of Ellagitannins in Cancer Prevention, a Review

Cancer as a disease continues to ravage the world population without regard to sex, age, and race. Due to the growing number of cases worldwide, cancer exerts a significant negative impact on global health and the economy. Interestingly, chemotherapy has been used over the years as a therapeutic intervention against cancer. However, high cost, resistance, and toxic by-effects to treatment have overshadowed some of its benefits. In recent times, efforts have been ongoing in searching for anticancer therapeutics of plant origin, focusing on polyphenols. Urolithins are secondary polyphenol metabolites derived from the gut microbial action on ellagitannins and ellagic acid-rich foods such as pomegranate, berries, and nuts. Urolithins are emerging as a new class of anticancer compounds that can mediate their cancer-preventive activities through cell cycle arrest, aromatase inhibition, induction of apoptosis, tumor suppression, promotion of autophagy, and senescence, transcriptional regulation of oncogenes, and growth factor receptors. In this review, we discussed the growing shreds of evidence supporting these secondary phenolic metabolites' anticancer properties. Furthermore, we have pointed out some of the future directions needed to establish urolithins as anticancer agents.

Urolithin A induces cell cycle arrest and apoptosis by inhibiting Bcl-2, increasing p53-p21 proteins and reactive oxygen species production in colorectal cancer cells

Colorectal cancer (CRC) is the second most common gastrointestinal cancer globally. Prevention of tumor cell proliferation and metastasis is vital for prolonging patient survival. Polyphenols provide a wide range of health benefits and prevention from cancer. In the gut, urolithins are the major metabolites of polyphenols. The objective of our study was to elucidate the molecular mechanism of the anticancer effect of urolithin A (UA) on colorectal cancer cells. UA was found to inhibit the cell proliferation of CRC cell lines in a dose-dependent and time-dependent manner in HT29, SW480, and SW620 cells. Exposure to UA resulted in cell cycle arrest in a dose-dependent manner along with alteration in the expression of cell cycle-related protein. Treatment of CRC cell lines with UA resulted in the induction of apoptosis. Treatment of HT29, SW480, and SW620 with UA resulted in increased expression of the pro-apoptotic proteins, p53 and p21. Similarly, UA treatment inhibited the anti-apoptotic protein expression of Bcl-2. Moreover, exposure of UA induced cytochrome c release and caspase activation. Furthermore, UA was found to generate reactive oxygen species (ROS) production in CRC cells. These findings indicate that UA possesses anticancer potential and may be used therapeutically for the treatment of CRC.

Protective effects of resveratrol against the cardiac developmental toxicity of trichloroethylene in zebrafish embryos

Trichloroethylene (TCE), a prevalent environmental contaminant, has been shown to induce cardiac malformations. Resveratrol (RSV) is a natural polyphenolic compound exhibiting protective effects on heart development. To investigate if RSV could protect against TCE-induced heart defects, we exposed zebrafish embryos to TCE (10 ppb) in the presence or absence of RSV (1 μg/mL). Our results showed that RSV significantly attenuated TCE-induced heart defects in zebrafish embryos. The TCE-induced ROS (reactive oxygen species) generation, 8-OHdG (8-hydroxy-2`-deoxyguanosine) formation and cell proliferation were significantly counteracted by RSV. Moreover, RSV attenuated the TCE-induced changes in mRNA expression or activity of genes involved in AHR and Nrf2 signal pathways. We further showed that RSV might inhibit TCE-enhanced cell proliferation by rescuing the downregulation of the p53/p21 axis. In conclusion, our data demonstrates that RSV protects against the cardiac developmental toxicity of TCE by inhibiting AHR activity, oxidative stress and cell proliferation.

Therapeutic applications and biological activities of bacterial bioactive extracts

Bacteria are rich in a wide variety of secondary metabolites, such as pigments, alkaloids, antibiotics, and others. These bioactive microbial products serve a great application in human and animal health. Their molecular diversity allows these natural products to possess several therapeutic attributes and biological functions. That's why the current natural drug industry focuses on uncovering all the possible ailments and diseases that could be combated by bacterial extracts and their secondary metabolites. In this paper, we review the major utilizations of bacterial natural products for the treatment of cancer, inflammatory diseases, allergies, autoimmune diseases, infections and other diseases that threaten public health. We also elaborate on the identified biological activities of bacterial secondary metabolites including antibacterial, antifungal, antiviral and antioxidant activities all of which are essential nowadays with the emergence of drug-resistant microbial pathogens. Throughout this review, we discuss the possible mechanisms of actions in which bacterial-derived biologically active molecular entities could possess healing properties to inspire the development of new therapeutic agents in academia and industry.

Urolithin A Inhibits Epithelial-Mesenchymal Transition in Lung Cancer Cells via P53-Mdm2-Snail Pathway

PURPOSE

The epithelial-to-mesenchymal transition (EMT) is a fundamental process in tumor progression that endows cancer cells with migratory and invasive potential. Snail, a zinc finger transcriptional repressor, plays an important role in the induction of EMT by directly repressing the key epithelial marker E-cadherin. Here, we assessed the effect of urolithin A, a major metabolite from pomegranate ellagitannins, on Snail expression and EMT process.

METHODS

The role of Snail in urolithin A-induced EMT inhibition in lung cancer cells was explored by wound healing assay and cell invasion assay. The qRT-PCR and CHX assay were performed to investigate how urolithin A regulates Snail expression. Immunoprecipitation assays were established to determine the effects of urolithin A in mdm2-Snail interaction. In addition, the expression of p53 was manipulated to explore its effect on the expression of mdm2 and Snail.

RESULTS

The urolithin A dose-dependently upregulated epithelial marker and decreased mesenchymal markers in lung cancer cells. In addition, exposure to urolithin A decreased cell migratory and invasive capacity. We have further demonstrated that urolithin A inhibits lung cancer cell EMT by decreasing Snail protein expression and activity. Mechanistically, urolithin A disrupts the interaction of p53 and mdm2 which leads Snail ubiquitination and degradation.

CONCLUSION

We conclude that urolithin A could inhibit EMT process by controlling mainly Snail expression. These results highlighted the role of pomegranate in regulation of EMT program in lung cancer.

Ellagic Acid-Derived Urolithins as Modulators of Oxidative Stress

Oxidative stress is a state of excess of prooxidative species relative to the antioxidant defenses (enzymatic and nonenzymatic) in a living organism. The consequence of this imbalance is damage of the major cellular macromolecules (carbohydrates, lipids, proteins, and DNA), which further leads to a gradual loss of tissue and organ function. It has been shown that oxidative stress plays an important role in the pathogenesis of many chronic diseases (cardiovascular, metabolic, and neurodegenerative diseases and cancer) and in the process of aging. Thus, many strategies to combat oxidative stress have been proposed and tested. In this context, food rich in antioxidants has received great attention. Pomegranate, berries, and walnuts have been recognized as “superfood” particularly for their cardioprotective effects. The common characteristic of these foods is the high content of ellagitannins. Since tannins are not bioavailable, they have been neglected in nutrition science and even considered antinutrients for a long time. However, this view has changed dramatically once it was recognized that ellagic acid, released from ellagitannins in the gastrointestinal system, is further metabolized by colonic microbiota to bioavailable compounds—known as urolithins. Thus, urolithins (3,4-benzocoumarin derivatives) have emerged as novel natural bioactive compounds and are now the focus of extensive investigations. So far, urolithins were shown to be powerful modulators of oxidative stress and agents with potential anti-inflammatory, antiproliferative, and antiaging properties. Furthermore, a few synthetic derivatives of urolithins were recognized as lead compounds for new drug development. Available data on urolithin synthesis, physicochemical and pharmacokinetic characteristics, biological activity, and safety will be presented in this review.

Potential of the ellagic acid-derived gut microbiota metabolite - Urolithin A in gastrointestinal protection

Urolithin A (UA) is a metabolic compound generated during the biotransformation of ellagitannins by the intestinal bacteria. The physiologically relevant micromolar concentrations of UA, achieved in the plasma and gastrointestinal tract (GI) after consumption of its dietary precursors, have been revealed to offer GI protection. The health benefit has been demonstrated to be principally related to anticancer and anti-inflammatory effects. UA has been shown to possess the capability to regulate multiple tumor and inflammatory signaling pathways and to modulate enzyme activity, including those involved in carcinogen biotransformation and antioxidant defense. The purpose of this review is to gather evidence from both in vitro and in vivo studies showing the potential of UA in GI protection alongside suggested mechanisms by which UA can protect against cancer and inflammatory diseases of the digestive tract. The data presented herein, covering both studies on the pure compound and in vivo generated UA form its natural precursor, support the potential of this metabolite in treatment interventions against GI ailments.

Urolithin a attenuates IL-1β-induced inflammatory responses and cartilage degradation via inhibiting the MAPK/NF-κB signaling pathways in rat articular chondrocytes

Background

Osteoarthritis (OA) is characterized by inflammation and extracellular matrix (ECM) degradation and is one of the most common chronic degenerative joint diseases that causes pain and disability in adults. Urolithin A (UA) has been widely reported for its anti-inflammatory properties in several chronic diseases. However, the effects of UA on OA remain unclear. The aim of the current study was to investigate the anti-inflammatory effects and mechanism of UA in interleukin-1β (IL-1β)-induced chondrocytes.

Results

No marked UA cytotoxicity was noted, and UA protected cartilage from damage following IL-1β stimulation in micromasses. Moreover, UA promoted the expression of anabolic factors including Sox-9, Collagen II, and Aggrecan while inhibiting the expression of catabolic factors such as matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) in rat chondrocytes. Protective effects of UA were also observed in ex vivo organ culture of articular cartilage. Mechanistically, IL-1β significantly activated and upregulated the expression of p-ERK 1/2, p-JNK, p-P38, and p-P65, while UA protected chondrocytes against IL-1β-induced injury by activating the mitogen-activated kinase (MAPK)/nuclear factor-κB (NF-κB) signaling pathways.

Conclusion

Our results provide the evidence that UA could attenuate IL-1β-induced cell injury in chondrocytes via its anti-inflammatory action. UA may be a promising therapeutic agent in the treatment of OA.