Antiproliferative activity of the ellagic acid-derived gut microbiota isourolithin A and comparison with its urolithin A isomer: the role of cell metabolism

Relevant Developments in the Use of Three-Component Reactions for the Total Synthesis of Natural Products. The last 15 Years

Multicomponent reactions (MCRs) offer a highly useful and valuable strategy that can fulfill an important role in synthesizing complex polysubstituted compounds, by simplifying otherwise long sequences and increasing their efficiency. The total synthesis of selected natural products employing three-component reactions as their common strategic MCR approach, is reviewed on a case-by-case basis with selected targets conquered during the last 15 years. The revision includes detailed descriptions of the selected successful sequences; relevant information on the isolation, and bioactivity of the different natural targets is also briefly provided.

Urolithin A affects cellular migration and modulates matrix metalloproteinase expression in colorectal cancer cells

Colorectal cancer (CRC) is the world's second most common gastrointestinal malignancy. Preventing tumor cell proliferation and dissemination is critical for patient survival. Polyphenols have a variety of health advantages and can help prevent cancer. The current study examined different cellular activities of the gut-microbiota metabolite urolithin A (UA) on several colon cancer cell lines. The results revealed that UA suppressed cell growth in a dose- and time-dependent manner. In the current investigation, UA substantially affected cell migration in the wound-healing experiment and greatly decreased the number of colonies generated in each CRC cell culture. UA decreased cellular migration in CRC cells 48 h after treatment, which was significant (p < .001) compared to the migration rate in untreated cells. When compared to untreated cells, UA slowed the process of colony formation by reducing the number of colonies or altering their morphological shape. The western blot analysis investigation revealed that UA inhibits cellular metastasis by lowering the expression levels of matrix metalloproteinases 1 and 2 (MMP1 and MMP2) by more than 43% and 41% (p < .001) in HT29, 28% and 149% (p < .001) in SW480, and 90% and 74% (p < .001) in SW620, respectively, at a 100 µM dosage of UA compared to the control. Surprisingly, at a 100 µM dosage of UA, the expression levels of the tissue inhibitor of metalloproteinases 1 (TIMP1) were elevated in HT29, SW480, and SW620 cells treated with 100 µM of UA by more than 89%, 57%, and 29%, respectively. Our findings imply that UA has anticancer properties and might be used therapeutically to treat CRC. The findings provided the first indication of the influence of UA on cellular migration and metastasis in colon cancer cells. All of these data showed that UA might be used as an adjuvant therapy in the treatment of various forms of CRC.

Absorption and Metabolism of Urolithin A and Ellagic Acid in Mice and Their Cytotoxicity in Human Colorectal Cancer Cells

Background

Ellagic acid is a natural polyphenol compound found in pomegranates, walnuts, and many berries. It is not easily absorbed, but it could be metabolized to urolithins by the gut microbiota. Urolithin A, one of the ellagic acid metabolites, has been proved to prolong the lifespan of C. elegans and increases muscle function of mice. The purpose of this current study was to analyze the absorption and metabolites of urolithin A and ellagic acid in mice and the anticancer effects of urolithin A, urolithin B, and ellagic acid in colorectal cancer cells.

Methods

Urolithin A and urolithin B were synthesized and analyzed by HPLC and NMR. A pharmacokinetic study of urolithin A was performed in mice by analyzing urolithin A and its metabolites in urines. Absorption and biotransformation of ellagic acid were also studied in mice by analyzing the plasma, liver, and feces. The cytotoxicity of urolithin A, urolithin B, and ellagic acid was assayed in SW480, SW620, HCT 116, and HT-29 cells.

Results

Urolithin A and urolithin B were synthesized and purified to reach 98.1% and 99% purity, respectively, and the structures were identified by NMR. In urolithin A intake analysis, urolithin A was only detectable at 3 h, not at 6-24 h; it suggested that urolithin A was rapidly metabolized to some unknown metabolites. Using UPLC-MS/MS analysis, the metabolites might be urolithin A 3-O-glucuronide, urolithin A 3-sulfate, and urolithin A-sulfate glucuronide. After feeding mice with ellagic acid for consecutive 14 days, ellagic acid contents could be detected in the fecal samples, but not in plasma and liver, and urolithin A was not detected in all samples. It suggests that ellagic acid is not easily absorbed and that the biotransformation of ellagic acid to urolithin A by intestinal flora might be very low. From the cytotoxicity assay, it was found that there was anticancer effect in urolithin A and urolithin B but not in ellagic acid. In contrast, ellagic acid promoted the proliferation of SW480 and SW620 cells.

Inhibition of Cancer Development by Natural Plant Polyphenols: Molecular Mechanisms

Malignant tumors remain one of the main sources of morbidity and mortality around the world. A chemotherapeutic approach to cancer treatment poses a multitude of challenges, primarily due to the low selectivity and genotoxicity of the majority of chemotherapeutic drugs currently used in the clinical practice, often leading to treatment-induced tumors formation. Highly selective antitumor drugs can largely resolve this issue, but their high selectivity leads to significant drawbacks due to the intrinsic tumor heterogeneity. In contrast, plant polyphenols can simultaneously affect many processes that are involved in the acquiring and maintaining of hallmark properties of malignant cells, and their toxic dose is typically much higher than the therapeutic one. In the present work we describe the mechanisms of the action of polyphenols on cancer cells, including their effects on genetic and epigenetic instability, tumor-promoting inflammation, and altered microbiota.

Promising remedies for cardiovascular disease: Natural polyphenol ellagic acid and its metabolite urolithins

BACKGROUND

Cardiovascular disease (CVD) is a significant worldwide factor contributing to human fatality and morbidity. With the increase of incidence rates, it is of concern that there is a lack of current therapeutic alternatives because of multiple side effects. Ellagic acid (EA), the natural polyphenol (C₁₄H₆O₈), is abundant in pomegranates, berries, and nuts. EA and its intestinal microflora metabolite, urolithins, have recently attracted much attention as a potential novel "medicine" because of their wide pharmacological properties.

PURPOSE

This study aimed to critically analyze available literature to summarize the beneficial effects of EA and urolithins, and highlights their druggability and therapeutic potential in various CVDs.

METHODS

We systematically studied research and review articles between 1984 and 2022 available on various databases to obtain the data on EA and urolithins with no language restriction. Their cardiovascular protective activities, underlying mechanism, and druggability were highlighted and discussed comprehensively.

RESULTS

We found that EA and urolithins may exert preventive and curative effects on CVD with negligible side effects and possibly regulate lipid metabolism imbalance, pro-inflammatory factor production, vascular smooth muscle cell proliferation, cardiomyocyte apoptosis, endothelial cell dysfunction, and Ca²⁺ intake and release. Potentially, this may lead to the prevention and amelioration of atherosclerosis, hypertension, myocardial infarction, cardiac fibrosis, cardiomyopathy, cardiac arrhythmias, and cardiotoxicities in vivo. Several molecules and signaling pathways are associated with their therapeutic actions, including phosphatidylinositol 3-kinase/protein kinase B, mitogen-activated protein kinase, NF-κB, nuclear factor erythroid-2 related factor 2, sirtuin1, miRNA, and extracellular signal-regulated kinase 1/2.

CONCLUSION

In vitro and in vivo studies shows that EA and urolithins could be used as valid candidates for early prevention and effective therapeutic strategies for various CVDs.

Postbiotics against Obesity: Perception and Overview Based on Pre-Clinical and Clinical Studies

Overweight and obesity are significant global public health concerns that are increasing in prevalence at an alarming rate. Numerous studies have demonstrated the benefits of probiotics against obesity. Postbiotics are the next generation of probiotics that include bacteria-free extracts and nonviable microorganisms that may be advantageous to the host and are being increasingly preferred over regular probiotics. However, the impact of postbiotics on obesity has not been thoroughly investigated. Therefore, the goal of this review is to gather in-depth data on the ability of postbiotics to combat obesity. Postbiotics have been reported to have significant potential in alleviating obesity. This review comprehensively discusses the anti-obesity effects of postbiotics in cellular, animal, and clinical studies. Postbiotics exert anti-obesity effects via multiple mechanisms, with the major mechanisms including increased energy expenditure, reduced adipogenesis and adipocyte differentiation, suppression of food intake, inhibition of lipid absorption, regulation of lipid metabolism, and regulation of gut dysbiosis. Future research should include further in-depth studies on strain identification, scale-up of postbiotics, identification of underlying mechanisms, and well-defined clinical studies. Postbiotics could be a promising dietary intervention for the prevention and management of obesity.

In Silico and In Vitro Study of Antioxidant Potential of Urolithins

In this work, quantum chemical calculations based on density functional theory (DFT) were performed to predict the antioxidant potential of four bioactive gut microbiota metabolites of the natural polyphenols ellagitannins (ETs) and ellagic acid (EA), also known as urolithins (UROs). In order to evaluate their ability to counter the effect of oxidative stress caused by reactive oxygen species (ROS), such as the hydroperoxyl radical (•OOH), different reaction mechanisms were investigated, considering water and lipid-like environments. Through our in silico results, it emerged that at physiological pH, the scavenging activity of all urolithins, except urolithin B, are higher than that of trolox and other potent antioxidants existing in nature, such as EA, α-mangostin, allicin, caffeine and melatonin. These findings were confirmed by experimental assays.

Urolithin A analog inhibits castration-resistant prostate cancer by targeting the androgen receptor and its variant, androgen receptor-variant 7

We investigated the efficacy of a small molecule ASR-600, an analog of Urolithin A (Uro A), on blocking androgen receptor (AR) and its splice variant AR-variant 7 (AR-V7) signaling in castration-resistant prostate cancer (CRPC). ASR-600 effectively suppressed the growth of AR+ CRPC cells by inhibiting AR and AR-V7 expressions; no effect was seen in AR- CRPC and normal prostate epithelial cells. Biomolecular interaction assays revealed ASR-600 binds to the N-terminal domain of AR, which was further confirmed by immunoblot and subcellular localization studies. Molecular studies suggested that ASR-600 promotes the ubiquitination of AR and AR-V7 resulting in the inhibition of AR signaling. Microsomal and plasma stability studies suggest that ASR-600 is stable, and its oral administration inhibits tumor growth in CRPC xenografted castrated and non-castrated mice. In conclusion, our data suggest that ASR-600 enhances AR ubiquitination in both AR+ and AR-V7 CRPC cells and inhibits their growth in vitro and in vivo models.

Separation of Isomeric Forms of Urolithin Glucuronides Using Supercritical Fluid Chromatography

Urolithins are gut microbiota metabolites produced in humans after consuming foods containing ellagitannins and ellagic acid. Three urolithin metabotypes have been reported for different individuals depending on the final urolithins produced. After absorption, they are conjugated with glucuronic acid (phase II metabolism), and these are the main circulating metabolites in plasma and reach different tissues. Different regioisomeric isomers of urolithin glucuronides have been described. Still, their identification and quantification in humans have not been properly reported due to resolution limitations in their analysis by reversed-phase high-performance liquid chromatography. In the present study, we report a novel method for separating these isomers using supercritical fluid chromatography. With this method, urolithin A 3- and 8-glucuronide, isourolithin A 3- and 9- glucuronide, and urolithin B 3-glucuronide (8-hydroxy urolithin 3-glucuronide; 3-hydroxy urolithin 8-glucuronide; 3-hydroxyurolithin 9-glucuronide; 9-hydroxyurolithin 3-glucuronide; and urolithin 3-glucuronide) were separated in less than 15 min. The proposed method was applied to successfully analyze these metabolites in urine samples from different volunteers belonging to different metabotypes.

Phosphorus-nitrogen compounds. Part 58. Syntheses, structural characterizations and biological activities of 4-fluorobenzyl-spiro(N/O)cyclotriphosphazene derivatives

The starting compound, tetrachloro-4-fluorobenzyl-spiro(N/O)cyclotriphosphazene (2), was synthesized from the substitution reaction of hexachlorocyclotriphosphazatriene (N₃P₃Cl₆; trimer; HCCP) with sodium 3-(4-fluorobenzylamino)-1-propanoxide (1). Reactions of spiro (2) with excess 1-(2-aminoethyl)-piperidine, 4-(2-aminoethyl)-morpholine, 1-(2-hydroxyethyl)piperidine and 4-(2-aminoethyl)morpholine yielded the fully substituted cyclotriphosphazene derivatives (2a-2d), respectively. Elemental analysis, mass spectrometry (ESI-MS), FTIR, ¹H-, ¹³C- and ³¹P-NMR data confirmed the structure of the new cyclotriphosphazenes (2a-2d); and the crystal structure of 2 was also identified by X-ray crystallography. The quantum mechanical DFT calculations of 2 were performed to estimate the geometry optimization, total energy, orientation of frontier molecular orbitals (HOMOs and LUMOs), and chemical parameters. In addition, antibacterial and antifungal activities of the fully substituted 4-fluorobenzyl-spiro(N/O)cyclotriphosphazenes (2a-2d) were investigated against G(+) and G(-) bacteria and fungi. Using agarose gel electrophoresis, the DNA cleavage activities of these phosphazenes on double-stranded plasmid DNA were evaluated. To evaluate the abilities of compounds 2a-2d to inhibit cell proliferation in different concentrations, the antiproliferative and antimigrative activities against prostate adenocarcinoma (PC3), breast cancer (MCF7) and colon cancer (HT29) cell lines were studied in vitro; and the compound 2c was determined to be the most efficient against the three cancer cells.Communicated by Ramaswamy H. Sarma.

Main Determinants Affecting the Antiproliferative Activity of Stilbenes and Their Gut Microbiota Metabolites in Colon Cancer Cells: A Structure-Activity Relationship Study

trans-Resveratrol can be catabolized by the gut microbiota to dihydroresveratrol, 3,4'-dihydroxy-trans-stilbene, lunularin, and 4-hydroxydibenzyl. These metabolites can reach relevant concentrations in the colon. However, not all individuals metabolize RSV equally, as it depends on their RSV gut microbiota metabotype (i.e., lunularin producers vs. non-producers). However, how this microbial metabolism affects the cancer chemopreventive activity of stilbenes and their microbial metabolites is poorly known. We investigated the structure-antiproliferative activity relationship of dietary stilbenes, their gut microbial metabolites, and various analogs in human cancer (Caco-2 and HT-29) and non-tumorigenic (CCD18-Co) colon cells. The antiproliferative IC₅₀ values of pterostilbene, oxy-resveratrol, piceatannol, resveratrol, dihydroresveratrol, lunularin, 3,4'-dihydroxy-trans-stilbene, pinosylvin, dihydropinosylvin, 4-hydroxy-trans-stilbene, 4-hydroxydibenzyl, 3-hydroxydibenzyl, and 4-trans-stilbenemethanol were calculated. IC₅₀ values were correlated with 34 molecular characteristics by bi- and multivariate analysis. Little or no activity on CCD18-Co was observed, while Caco-2 was more sensitive than HT-29, which was explained by their different capacities to metabolize the compounds. Caco-2 IC₅₀ values ranged from 11.4 ± 10.1 μM (4-hydroxy-trans-stilbene) to 73.9 ± 13.8 μM (dihydropinosylvin). In HT-29, the values ranged from 24.4 ± 11.3 μM (4-hydroxy-trans-stilbene) to 96.7 ± 6.7 μM (4-hydroxydibenzyl). At their IC₅₀, most compounds induced apoptosis and arrested the cell cycle at the S phase, pterostilbene at G₂/M, while 4-hydroxy-trans-stilbene and 3,4'-dihydroxy-trans-stilbene arrested at both phases. Higher Connolly values (larger size) hindered the antiproliferative activity, while a lower pKa1 enhanced the activity in Caco-2, and higher LogP values (more hydrophobicity) increased the activity in HT-29. Reducing the styrene double bond in stilbenes was the most critical feature in decreasing the antiproliferative activity. These results (i) suggest that gut microbiota metabolism determines the antiproliferative effects of dietary stilbenes. Therefore, RSV consumption might exert different effects in individuals depending on their gut microbiota metabotypes associated with RSV metabolism, and (ii) could help design customized drugs with a stilbenoid and (or) dibenzyl core against colorectal cancer.

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.

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.

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.

Phosphorus-Nitrogen Compounds. Part 64. Comparative Reactions of Spiro and Ansa(N/O) Cyclotetraphosphazenes with Bulky (4-Fluorobenzyl) N/N and N/O Donor Type Bidentate Reagents: Structure, Stereogenic Properties and Cytotoxic activity Studies

The reaction of octachlorocyclotetraphosphazene, N4P4Cl8 (1) (OCCP, tetramer) with an equimolar amount of sodium 3-(N-ferrocenylmethylamino)-1-propanoxide (L1) resulted in the formations of ferrocenyl-spiro-(2) and ferrocenyl-2-cis-4-dichloro-ansa-(3) cyclotetraphosphazenes. Both of the starting compounds...

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.

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.

The ellagic acid metabolites urolithin A and B differentially affect growth, adhesion, motility, and invasion of endometriotic cells in vitro

STUDY QUESTION

What are the effects of plant-derived antioxidant compounds urolithin A (UA) and B (UB) on the growth and pathogenetic properties of an in vitro endometriosis model?

SUMMARY ANSWER

Both urolithins showed inhibitory effects on cell behavior related to the development of endometriosis by differentially affecting growth, adhesion, motility, and invasion of endometriotic cells in vitro.

WHAT IS KNOWN ALREADY

Endometriosis is one of the most common benign gynecological diseases in women of reproductive age and is defined by the presence of endometrial tissue outside the uterine cavity. As current pharmacological therapies are associated with side effects interfering with fertility, we aimed at finding alternative therapeutics using natural compounds that can be administered for prolonged periods with a favorable side effects profile.

STUDY DESIGN, SIZE, DURATION

In vitro cultures of primary endometriotic stromal cells from 6 patients subjected to laparoscopy for benign pathologies with histologically confirmed endometriosis; and immortalized endometrial stromal (St-T1b) and endometriotic epithelial cells (12Z) were utilized to assess the effects of UA and UB on endometriotic cell properties. Results were validated in three-dimensional (3D) in vitro co-culture spheroids of 12Z and primary endometriotic stroma cells of one patient, and organoids from 3 independent donors with endometriosis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The effects on cell growth were measured by non-radioactive colorimetric assay to measure cellular metabolic activity as an indicator of cell viability (MTT assay) and flow cytometric cell cycle assay on primary cultures, St-T1b, and 12Z. Apoptosis analyses, the impact on in vitro adhesion, migration, and invasion were evaluated in the cell lines. Moreover, Real-Time Quantitative Reverse Transcription polymerase chain reaction (RT-qPCR) assays were performed on primary cultures, St- T1b and 12Z to evaluate a plausible mechanistic contribution by factors related to proteolysis (matrix metalloproteinase 2, 3 and 9 -MMP2, MMP3, MMP9-, and tissue inhibitor of metalloproteinases -TIMP-1-), cytoskeletal regulators (Ras-related C3 botulinum toxin substrate 1 -RAC1-, Rho-associated coiled-coil containing protein kinase 2 -ROCK2-), and cell adhesion molecules (Syndecan 1 -SDC1-, Integrin alpha V-ITGAV-). Finally, the urolithins effects were evaluated on spheroids and organoids by formation, viability, and drug screen assays.

MAIN RESULTS AND THE ROLE OF CHANCE

40 µM UA and 20 µM UB produced a significant decrease in cell proliferation in the primary endometriotic cell cultures (P < 0.001 and P < 0.01, respectively) and in the St-T1b cell line (P < 0.001 and P < 0.05, respectively). In St-T1b, UA exhibited a mean half-maximum inhibitory concentration (IC50) of 39.88 µM, while UB exhibited a mean IC50 of 79.92 µM. Both 40 µM UA and 20 µM UB produced an increase in cells in the S phase of the cell cycle (P < 0.01 and P < 0.05, respectively). The same concentration of UA also increased the percentage of apoptotic ST-t1b cells (P < 0.05), while both urolithins decreased cell migration after 24 h (P < 0.001 both). Only the addition of 5 µM UB decreased the number of St-T1b adherent cells. TIMP-1 expression was upregulated in response to treating the cells with 40 µM UA (P < 0.05). Regarding the 12Z endometriotic cell line, only 40 µM UA decreased proliferation (P < 0.01); while both 40 µM UA and 20 µM UB produced an increase in cells in the G2/M phase (P < 0.05 and P < 0.01, respectively). In this cell line, UA exhibited a mean IC50 of 40.46 µM, while UB exhibited a mean IC50 of 54.79 µM. UB decreased cell migration (P < 0.05), and decreased the number of adherent cells (P < 0.05). Both 40 µM UA and 20 µM UB significantly decreased the cellular invasion of these cells; and several genes were altered when treating the cells with 40 µM UA and 10 µM UB. The expression of MMP2 was downregulated by UA (P < 0.001), and expression of MMP3 (UA P < 0.001 and UB P < 0.05) and MMP9 (P < 0.05, both) were downregulated by both urolithins. Moreover, UA significantly downregulated ROCK2 (P < 0.05), whereas UB treatment was associated with RAC1 downregulation (P < 0.05). Finally, the matrix adhesion receptors and signaling (co)receptors SDC1 and ITGAV were downregulated upon treatment with either UA or UB (P < 0.01 and P < 0.05, respectively in both cases). Regarding the effects of urolithins on 3D models, we have seen that they significantly decrease the viability of endometriosis spheroids (80 µM UA and UB: P < 0.05 both) as well as affecting their area (40 µM UA: P < 0.05, and 80 µM UA: P < 0.01) and integrity (40 µM UA and UB: P < 0.05, 80 µM UA and UB: P < 0.01). On the other hand, UA and UB significantly inhibited organoid development/outgrowth (40 and 80 µM UA: P < 0.0001 both; 40 µM UB: P < ns-0.05-0.001, and 80 µM UB: P < 0.01-0.001-0.001), and all organoid lines show urolithins sensitivity resulting in decreasing viability (UA exhibited a mean IC50 of 33.93 µM, while UB exhibited a mean IC50 of 52.60 µM).

LARGE-SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

This study was performed on in vitro endometriosis models.

WIDER IMPLICATIONS OF THE FINDINGS

These in vitro results provide new insights into the pathogenetic pathways affected by these compounds and mark their use as a potential new therapeutic strategy for the treatment of endometriosis.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded EU MSCA-RISE-2015 project MOMENDO (691058). The authors have no conflicts of interest to declare.

Disposition of Dietary Polyphenols in Breast Cancer Patients' Tumors, and Their Associated Anticancer Activity: The Particular Case of Curcumin

SCOPE

Some polyphenol-derived metabolites reach human breast cancer (BC) tissues at concentrations that induce cell senescence. However, this is unknown for isoflavones, curcuminoids, and lignans. Here, their metabolic profiling in normal (NT) and malignant (MT) mammary tissues of newly-diagnosed BC patients and the tissue-occurring metabolites' anticancer activity are evaluated.

METHODS AND RESULTS

Patients (n = 26) consumed 3 capsules/day (turmeric, red clover, and flaxseed extracts plus resveratrol; 296.4 mg phenolics/capsule) from biopsy-confirmed diagnosis to surgery (5 ± 2 days) or did not consume capsules (n = 13). NT and MT, blood, and urine are analyzed by UPLC-QTOF-MS using targeted metabolomics. Anticancer activity was tested in MCF-7 and MDA-MB-231 BC cells. Mainly phase-II metabolites were detected (108, 84, 49, and 47 in urine, plasma, NT, and MT, respectively). Total metabolite concentrations reached 10.7 ± 11.1 and 2.5 ± 2.4 µmol L^-1 in NT and MT, respectively. Free curcumin, but not its glucuronide, was detected in the tissues (1.1 ± 1.8 and 0.2 ± 0.2 µmol L^-1 in NT and MT, respectively). Breast tissue-occurring metabolites' antiproliferation was mainly exerted in p53-wild-type MCF-7 cells by curcuminoids through cell cycle arrest, senescence, and apoptosis induction via p53/p21 induction, while isoflavone-derived metabolites exerted estrogenic-like activity.

CONCLUSION

Curcuminoids could be coadjuvants that might help fight BC upon regular consumption.

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.

Roles of the Polyphenol-Gut Microbiota Interaction in Alleviating Colitis and Preventing Colitis-Associated Colorectal Cancer

Accumulating evidence indicates that the gut microbiota can promote or inhibit colonic inflammation and carcinogenesis. Promotion of beneficial gut bacteria is considered a promising strategy to alleviate colonic diseases including colitis and colorectal cancer. Interestingly, dietary polyphenols, which have been shown to attenuate colitis and inhibit colorectal cancer in animal models and some human studies, appear to reach relatively high concentrations in the large intestine and to interact with the gut microbial community. This review summarizes the modulatory effects of polyphenols on the gut microbiota in humans and animals under healthy and diseased conditions including colitis and colitis-associated colorectal cancer (CAC). Existing human and animal studies indicate that polyphenols and polyphenol-rich whole foods are capable of elevating butyrate producers and probiotics that alleviate colitis and inhibit CAC, such as Lactobacillus and Bifidobacterium. Studies in colitis and CAC models indicate that polyphenols decrease opportunistic pathogenic or proinflammatory microbes and counteract disease-induced dysbiosis. Consistently, polyphenols also change microbial functions, including increasing butyrate formation. Moreover, polyphenol metabolites produced by the gut microbiota appear to have anticancer and anti-inflammatory activities, protect gut barrier integrity, and mitigate inflammatory conditions in cells and animal models. Based on these results, we conclude that polyphenol-mediated alteration of microbial composition and functions, together with polyphenol metabolites produced by the gut microbiota, likely contribute to the protective effects of polyphenols on colitis and CAC. Future research is needed to validate the causal role of the polyphenol-gut microbiota interaction in polyphenols' anti-colitis and anti-CAC effects, and to further elucidate mechanisms underlying such interaction.

Biotransformation of dietary phytoestrogens by gut microbes: A review on bidirectional interaction between phytoestrogen metabolism and gut microbiota

Phytoestrogens are a class of plant produced polyphenolic compounds with diphenolic structure, which is similar to 17β-estradiol. These phytoestrogens preferentially bind to estrogen receptors, however, with weak affinity. Recently, many studies have found that these phytoestrogens can be transformed by gut microbiota through novel enzymatic reactions into metabolites with altered bioactivity. Recent studies have also implied that these metabolites could possibly modulate the host gut ecosystem, gene expression, metabolism and the immune system. Thus, isolating gut microbes capable of biotransforming phytoestrogens and characterizing the novel enzymatic reactions involved are principal to understand the mechanisms of beneficial effects brought by gut microbiota and their metabolism on phytoestrogens, and to provide the theoretical knowledge for the development of functional probiotics. In the present review, we summarized works on gut microbial biotransformation of phytoestrogens, including daidzin (isoflavone), phenylnaringenin (prenylflavonoid), lignans, resveratrol (stilbene) and ellagitannins. We mainly focus on gut bacterial isolation, metabolic pathway characterization, and the bidirectional interaction of phytoestrogens with gut microbes to illustrate the novel metabolic capability of gut microbiota and the methods used in these studies.

Gut Bacterial Metabolite Urolithin A Decreases Actin Polymerization and Migration in Cancer Cells

SCOPE

Urolithin A (UA) is a gut-derived bacterial metabolite from ellagic acid found in pomegranates, berries, and nuts can downregulate cell proliferation and migration. Cell proliferation and cell motility require actin reorganization, which is under control of ras-related C3 botulinum toxin substrate 1 (Rac1) and p21 protein-activated kinase 1 (PAK1). The present study explores whether UA can modify actin cytoskeleton in cancer cells.

METHODS

The effect of UA on globular over filamentous actin ratio is determined utilizing Western blotting, immunofluorescence, and flow cytometry. Rac1 and PAK1 levels are measured by quantitative RT-PCR and immunoblotting. As a result, a 24 h treatment with UA (20 µm) significantly decreased Rac1 and PAK1 transcript levels and activity, depolymerized actin and wound healing. The effect of UA on actin polymerization is mimicked by pharmacological inhibition of Rac1 and PAK1. The effect is also mirrored by knock down using siRNA.

CONCLUSION

UA leads to disruption of Rac1 and Pak1 activity with subsequent actin depolymerization and migration. Thus, use of dietary UA in cancer prevention or as adjuvant therapy is promising.

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

Polyphenols have shown promising bioactivity in experimental in vitro and in vivo models for cancer chemoprevention. However, consumed orally, they are often transformed by gut microbes into new active principles with so far incompletely deciphered molecular mechanisms. Here, enterolacton, S-equol and urolithin A as representatives of metabolites of lignans, isoflavones and ellagitannins, respectively, were examined for their impact on HCT116 colon cancer cell growth, cooperativity with oxaliplatin and p53 dependency in vitro. Whereas enterolacton and S-equol (≤60 µM) did not elicit growth inhibition or positive cooperativity with oxaliplatin, urolithin A showed an IC50 value of 19 µM (72 h) and synergism with oxaliplatin. Urolithin A induced p53 stabilization and p53 target gene expression, and absence of p53 significantly dampened the antiproliferative effect of urolithin A (IC50(p53-/-) = 38 µM). P53 was dispensable for the G2/M arrest in HCT116 cells but required for induction of a senescence-like phenotype upon long-term exposure and for the observed synergism with oxaliplatin. Moreover, extracellular flux analyses and knockdown approaches uncovered a reduced glycolytic potential via the p53/TIGAR axis which was linked to the higher susceptibility of wildtype cells to urolithin A. Overall, the p53 status turned out to be an important determinant for the potential benefit of dietary ellagitannins in cancer chemoprevention or use in adjuvant therapy.

Synergetic Impact of Combined 5-Fluorouracil and Rutin on Apoptosis in PC3 Cancer Cells through the Modulation of P53 Gene Expression

Purpose: Prostate cancer is as far the most prevalent male cancer. Rutin (a glycoside from quercetin flavonoid) displays antioxidant activity leading to cell apoptosis. Combined effects of rutin with the widely used anti-cancer drug, 5-fluorouracil (5-FU), on prostate cancer cell line (PC3) was investigated herein.

Methods: Different concentrations of combined 5-FU and rutin were applied to PC3 cells compared to separate treatment for 48 hours. Cell viability, as well p53 gene expression respectively were assessed by MTT assay and real-time quantitative polymerase chain reaction (qPCR). Changes of Bcl-2 signal protein and apoptosis were determined using western blot and flow cytometry procedures, respectively. Clonogenic assay was used to colony counts assessment.

Results: 50% inhibitory concentration (IC50) of separate cell treatment with either rutin and 5-FU respectively were 900 μM and 3Mm, while combination index (CI) of combined 5-FU /rutin application reached a level of synergistic effects (0.33). Combination of 5-FU/rutin enhanced apoptosis and p53 gene expression in PC3 cells. PC3 cell colony counts and Bcl-2 signaling protein were decreased by 5-FU/rutin combination.

Conclusion: Synergistic effects of 5-FU/rutin combination on PC3 cells line enhanced apoptosis, p53 gene expression, and down-regulation of Bcl-2 protein, compared to control separate application. 5-FU/rutin combination does seem an interesting therapeutic pathway to be further investigated.

Urolithin B suppresses tumor growth in hepatocellular carcinoma through inducing the inactivation of Wnt/β-catenin signaling

Consumption of dietary ellagitannins (ETs) has been proven to benefit multiple chronic health disorders including cancers and cardiovascular diseases. Urolithins, gut microbiota metabolites derived from ETs, are considered as the molecules responsible for these health effects. Previous studies have demonstrated that urolithins exhibit antiproliferative effects on prostate, breast, and colon cancers. However, as for hepatocellular carcinoma (HCC), it remains elusive. Herein, we aim to investigate the function of urolithin B (UB), a member of urolithins family, in HCC. The effects of UB on cell viability, cell cycle and apoptosis were evaluated in HCC cells, and we found UB could inhibit the proliferation of HCC cells, which resulted from cell cycle arrest and apoptosis. Furthermore, UB could increase phosphorylated β-catenin expression and block its translocation from nuclear to cytoplasm, thus inducing the inactivation of Wnt/β-catenin signaling. Using a xenograft mice model, UB was found to suppress tumor growth in vivo. In conclusion, our data demonstrated that UB could inhibit the proliferation of HCC cells in vitro and in vivo via inactivating Wnt/β-catenin signaling, suggesting UB could be a promising candidate in the development of anticancer drugs targeting HCC.

Bacterial metabolism as responsible of beneficial effects of phytoestrogens on human health

Phytoestrogens (PE) are compounds found in plants such as soy (isoflavones), flax seeds and cereals (lignans) and pomegranates (ellagitannins). PE have shown estrogenic/antiestrogenic, antioxidant, anti-inflammatory, antineoplastic and apoptotic activities. The human studies are showing promising although inconsistent results about the beneficial effects of PE on ameliorating the menopausal symptoms or reducing the risk of certain cancers, cardiovascular disease or diabetes. The effects of PE on the organism are mediated by the intestinal microbiota, which transforms them into bioactive PE such as genistein, equol, enterolignans and certain urolithins. In this work, we review the most recent findings about the bacteria able to metabolize PE, together with the latest studies on the effects of PE on health. In addition, we describe the possible factors hindering the demonstration of the beneficial effect of PE on health, evincing the importance of measuring the actual circulating PE in order to encompass the variability of PE metabolism due to the intestinal microbiota. With this in mind, we also explore an approach to ensure the access to bioactive PE.

Dietary phytochemicals in colorectal cancer prevention and treatment: A focus on the molecular mechanisms involved

Worldwide, colorectal cancer (CRC) remains a major cancer type and leading cause of death. Unfortunately, current medical treatments are not sufficient due to lack of effective therapy, adverse side effects, chemoresistance and disease recurrence. In recent decades, epidemiologic observations have highlighted the association between the ingestion of several phytochemical-enriched foods and nutrients and the lower risk of CRC. According to preclinical studies, dietary phytochemicals exert chemopreventive effects on CRC by regulating different markers and signaling pathways; additionally, the gut microbiota plays a role as vital effector in CRC onset and progression, therefore, any dietary alterations in it may affect CRC occurrence. A high number of studies have displayed a key role of growth factors and their signaling pathways in the pathogenesis of CRC. Indeed, the efficiency of dietary phytochemicals to modulate carcinogenic processes through the alteration of different molecular targets, such as Wnt/β-catenin, PI3K/Akt/mTOR, MAPK (p38, JNK and Erk1/2), EGFR/Kras/Braf, TGF-β/Smad2/3, STAT1-STAT3, NF-кB, Nrf2 and cyclin-CDK complexes, has been proven, whereby many of these targets also represent the backbone of modern drug discovery programs. Furthermore, epigenetic analysis showed modified or reversed aberrant epigenetic changes exerted by dietary phytochemicals that led to possible CRC prevention or treatment. Therefore, our aim is to discuss the effects of some common dietary phytochemicals that might be useful in CRC as preventive or therapeutic agents. This review will provide new guidance for research, in order to identify the most studied phytochemicals, their occurrence in foods and to evaluate the therapeutic potential of dietary phytochemicals for the prevention or treatment of CRC by targeting several genes and signaling pathways, as well as epigenetic modifications. In addition, the results obtained by recent investigations aimed at improving the production of these phytochemicals in genetically modified plants have been reported. Overall, clinical data on phytochemicals against CRC are still not sufficient and therefore the preventive impacts of dietary phytochemicals on CRC development deserve further research so as to provide additional insights for human prospective studies.

Physiological Relevance of the Antiproliferative and Estrogenic Effects of Dietary Polyphenol Aglycones versus Their Phase-II Metabolites on Breast Cancer Cells: A Call of Caution

While preclinical studies suggest the breast cancer (BC) chemopreventive effects of dietary polyphenols, the human evidence is still very weak. The huge existing in vitro-in vivo gap is mainly due to the plethora of potential effects reported by in vitro studies that usually assay polyphenols as occurring in the food (beverages, extracts, foods) and/or derived aglycone metabolites with doubtful physiological relevance. Since phase-II metabolites can reach systemic tissues such as malignant breast tumors, we aimed here to compare for the first time the antiproliferative and estrogenic/antiestrogenic effects of dietary polyphenols and microbiota-derived metabolites (i.e., resveratrol, dihydroresveratrol, urolithins (A, B, and Isourolithin A), and the flavanone hesperetin), with those effects exerted by their physiologically relevant glucuronides and sulfates on human BC cell lines (MDA-MB-231 and MCF-7). Results showed that aglycones exerted dose-dependent antiproliferative and estrogenic/antiestrogenic activities, but both their glucuronide and sulfate conjugates lacked these activities. In addition, aglycones underwent phase-II metabolism in BC cells, mainly via sulfation, which determined the cell-dependent differences in the effects observed. Therefore, phase-II metabolism limits the antiproliferative, estrogenic, and antiestrogenic activities of dietary polyphenols on BC cells. Likewise, as a call of caution, enthusiasm should be limited for publishing effects that are not physiologically relevant.

A natural molecule, urolithin A, downregulates androgen receptor activation and suppresses growth of prostate cancer

Androgen ablation therapy is the primary therapeutic option for locally advanced and metastatic castration-resistant prostate cancer (CRPC). We investigated therapeutic effect of a dietary metabolite Urolithin A (UroA) and dissected the molecular mechanism in CRPC cells. Treatment with UroA inhibited cell proliferation in both androgen receptor-positive (AR⁺ ) (C4-2B) and androgen receptor-negative (AR^- ) (PC-3) cells however, AR⁺ CaP cells were more sensitive to UroA treatment as compared with AR^- CaP cells. Inhibition of the AR signaling was responsible for the UroA effect on AR⁺ CaP cells. Ectopic expression of AR in PC-3 cells sensitized them to UroA treatment as compared to the vector-expresseing PC-3 cells, which suggests that AR could be a target of UroA. Similarly, in enzalutamide-resistant C4-2B cells, a downregulation of AR expression also suppressed cell proliferation which was observed with the UroA treatment. Oral administration of UroA significantly suppressed the growth of C4-2B xenografts (P = 0.05) compared with PC-3 xenografts (P = 0.069) without causing toxicity to animals. Immunohistochemistry analysis confirmed in vitro findings such as downregulation of AR/pAKT signaling in UroA-treated C4-2B tumors, which suggests that UroA may be a potent chemo-preventive and therapeutic agent for CRPC.

Isolation of Human Intestinal Bacteria Capable of Producing the Bioactive Metabolite Isourolithin A from Ellagic Acid

Urolithins are intestinal microbial metabolites produced from ellagitannin- and ellagic acid-containing foods such as walnuts, strawberries, and pomegranates. These metabolites, better absorbed than their precursors, can contribute significantly to the beneficial properties attributed to the polyphenols ellagitannins and ellagic acid (EA). However, both the ability of producing the final metabolites in this catabolism (urolithins A, B and isourolithin A) and the health benefits associated with ellagitannin consumption differ considerably among individuals depending on their gut microbiota composition. Three human urolithin metabotypes have been previously described, i.e., metabotype 0 (urolithin non-producers), metabotype A (production of urolithin A as unique final urolithin) and metabotype B (urolithin B and/or isourolithin A are produced besides urolithin A). Although production of some intermediary urolithins has been recently attributed to intestinal species from Eggerthellaceae family named Gordonibacter urolithinfaciens and Gordonibacter pamelaeae, the identification of the microorganisms responsible for the complete transformation of EA into the final urolithins, especially those related to metabotype B, are still unknown. In the present research we illustrate the isolation of urolithin-producing strains from human feces of a healthy adult and their ability to transform EA into different urolithin metabolites, including isourolithin A. The isolates belong to a new genus from Eggerthellaceae family. EA transformation and urolithin production arisen during the stationary phase of the growth of the bacteria under anaerobic conditions. The HPLC-DAD-MS analyses demonstrated the sequential appearance of 3,8,9,10-tetrahydroxy-urolithin (urolithin M6), 3,8,9-trihydroxy-urolithin (urolithin C) and 3,9-dihydroxy-urolithin (isourolithin A) while 3,8-dihydroxy-urolithin (urolithin A) and 3-hydroxy-urolithin (urolithin B) were not detected. For the first time isourolithin A production capacity of pure strains has been described. The biological activity attributed to urolithins A and B and isourolithin A (anti-inflammatory, anti-carcinogenic, cardioprotective, and neuroprotective properties) explains the relevance of identifying these urolithin-producing bacteria as potential novel probiotics with applications in the development of functional foods and nutraceuticals. Their human administration could improve the health benefits upon ellagitannin consumption, especially in metabotype 0 individuals. However, further research is necessary to probe well-established beneficial effects on the host and safety requirements before being considered among the next-generation probiotics.

Gastrointestinal Simulation Model TWIN-SHIME Shows Differences between Human Urolithin-Metabotypes in Gut Microbiota Composition, Pomegranate Polyphenol Metabolism, and Transport along the Intestinal Tract

A TWIN-SHIME system was used to compare the metabolism of pomegranate polyphenols by the gut microbiota from two individuals with different urolithin metabotypes. Gut microbiota, ellagitannin metabolism, short-chain fatty acids (SCFA), transport of metabolites, and phase II metabolism using Caco-2 cells were explored. The simulation reproduced the in vivo metabolic profiles for each metabotype. The study shows for the first time that microbial composition, metabolism of ellagitannins, and SCFA differ between metabotypes and along the large intestine. The assay also showed that pomegranate phenolics preserved intestinal cell integrity. Pomegranate polyphenols enhanced urolithin and propionate production, as well as Akkermansia and Gordonibacter prevalence with the highest effect in the descending colon. The system provides an insight into the mechanisms of pomegranate polyphenol gut microbiota metabolism and absorption through intestinal cells. The results obtained by the combined SHIME/Caco-2 cell system are consistent with previous human and animal studies and show that although urolithin metabolites are present along the gastrointestinal tract due to enterohepatic circulation, they are predominantly produced in the distal colon region.

Effect of urolithins on oxidative stress of colorectal adenocarcinomacells-Caco-2

Urolithins (UROs) are metabolites derived from ellagic acid (EA) and ellagitannins (ETs) by gut microbiota after consumption of different ETs. The health effects attributed to UROs are numerous and diverse, ranging from antimalarial properties to anticancer activities and regulation of gene expression. The aim of this work was at assessing the effect of URO-A; -B; -C; -D on the oxidative status of colon epithelium using as a model colorectal adenocarcinoma cell line (Caco-2). No significant cytotoxic effects of UROs was noted, with the applied treatments. Supplementation of cell growth medium with a mixture of UROs decreased the level of intracellular reactive oxygen species both after short- and long-term exposure. UROs also affected the activity of antioxidative enzymes within the cell, especially catalase.

CONCLUSIONS

At concentrations reached in the lumen of the gut, UROs can exert beneficial effects on the cells by decreasing oxidative stress thus preventing the damage caused by reactive oxygen species.

Neuroprotective Effects of Bioavailable Polyphenol-Derived Metabolites against Oxidative Stress-Induced Cytotoxicity in Human Neuroblastoma SH-SY5Y Cells

Oxidative stress is involved in cell death in neurodegenerative diseases. Dietary polyphenols can exert health benefits, but their direct effects on neuronal cells are debatable because most phenolics are metabolized and do not reach the brain as they occur in the dietary sources. Herein, we evaluate the effects of a panel of bioavailable polyphenols and derived metabolites at physiologically relevant conditions against H₂O₂-induced apoptosis in human neuroblastoma SH-SY5Y cells. Among the 19 metabolites tested, 3,4-dihydroxyphenylpropionic acid, 3,4-dihydroxyphenylacetic acid, gallic acid, ellagic acid, and urolithins prevented neuronal apoptosis via attenuation of ROS levels, increased REDOX activity, and decreased oxidative stress-induced apoptosis by preventing the caspase-3 activation via the mitochondrial apoptotic pathway in SH-SY5Y cells. This suggests that dietary sources containing the polyphenol precursors of these molecules such as cocoa, berries, walnuts, and tea could be potential functional foods to reduce oxidative stress associated with the onset and progress of neurodegenerative diseases.

Diet, microorganisms and their metabolites, and colon cancer

Colorectal cancer is one of the so-called westernized diseases and the second leading cause of cancer death worldwide. On the basis of global epidemiological and scientific studies, evidence suggests that the risk of colorectal cancer is increased by processed and unprocessed meat consumption but suppressed by fibre, and that food composition affects colonic health and cancer risk via its effects on colonic microbial metabolism. The gut microbiota can ferment complex dietary residues that are resistant to digestion by enteric enzymes. This process provides energy for the microbiota but culminates in the release of short-chain fatty acids including butyrate, which are utilized for the metabolic needs of the colon and the body. Butyrate has a remarkable array of colonic health-promoting and antineoplastic properties: it is the preferred energy source for colonocytes, it maintains mucosal integrity and it suppresses inflammation and carcinogenesis through effects on immunity, gene expression and epigenetic modulation. Protein residues and fat-stimulated bile acids are also metabolized by the microbiota to inflammatory and/or carcinogenic metabolites, which increase the risk of neoplastic progression. This Review will discuss the mechanisms behind these microbial metabolite effects, which could be modified by diet to achieve the objective of preventing colorectal cancer in Western societies.

Effects on Nitric Oxide Production of Urolithins, Gut-Derived Ellagitannin Metabolites, in Human Aortic Endothelial Cells

The consumption of foodstuffs yielding circulating compounds able to maintain endothelial function by improving nitric oxide (NO) bioavailability can be considered as an effective strategy for cardiovascular disease prevention. This work assessed the in vitro effects of urolithin A, urolithin B, and urolithin B-glucuronide, ellagitannin-derived metabolites of colonic origin, on NO release and endothelial NO synthase (eNOS) activation in primary human aortic endothelial cells (HAECs). Urolithins were tested both individually at 15 μM and as a mixture of 5 μM each, at different time points. The biotransformation of these molecules in cell media due to cell metabolism was also evaluated by UHPLC-MSⁿ. The mix of urolithins at 5 μM significantly increased nitrite/nitrate levels following 24 h of incubation, while single urolithins at 15 μM did not modify NO bioavailability. Both the mix of urolithins at 5 μM and urolithin B-glucuronide at 15 μM activated eNOS expression. All urolithins underwent metabolic reactions, but these were limited to conjugation with sulfate moieties. This study represents a step forward in the understanding of cardiovascular health benefits of ellagitannin-rich foodstuffs and backs the idea that peripheral cells may contribute to urolithin metabolism.

In vivo relevant mixed urolithins and ellagic acid inhibit phenotypic and molecular colon cancer stem cell features: A new potentiality for ellagitannin metabolites against cancer

Colon cancer stem cells (CSCs) offer a novel paradigm for colorectal cancer (CRC) treatment and dietary polyphenols may contribute to battle these cells. Specifically, polyphenol-derived colon metabolites have the potential to interact with and affect colon CSCs. We herein report the effects against colon CSCs of two mixtures of ellagitannin (ET) metabolites, ellagic acid (EA) and the gut microbiota-derived urolithins (Uro) at concentrations detected in the human colon tissues following the intake of ET-containing products (pomegranate, walnuts). These mixtures reduce phenotypic and molecular features in two models of colon CSCs: Caco-2 cells and primary tumour cells from a patient with CRC. The mixture containing mostly Uro-A (85% Uro-A, 10% Uro-C, 5% EA) was most effective at inhibiting the number and size of colonospheres and aldehyde dehydrogenase activity (ALDH, a marker of chemoresistance) whereas the mixture containing less Uro-A but IsoUro-A and Uro-B (30% Uro-A, 50% IsoUro-A, 10% Uro-B, 5% Uro-C, 5% EA) had some effects on the number and size of colonospheres but not on ALDH. These data support a role for polyphenols metabolites in the control of colon cancer chemoresistance and relapse and encourage the research on the effects of polyphenols against CSCs.