Chemoprevention of benzo(a)pyrene-induced colon polyps in ApcMin mice by resveratrol

Resveratrol as sensitizer in colorectal cancer plasticity

Despite tremendous medical treatment successes, colorectal cancer (CRC) remains a leading cause of cancer deaths worldwide. Chemotherapy as monotherapy can lead to significant side effects and chemoresistance that can be linked to several resistance-activating biological processes, including an increase in inflammation, cellular plasticity, multidrug resistance (MDR), inhibition of the sentinel gene p53, and apoptosis. As a consequence, tumor cells can escape the effectiveness of chemotherapeutic agents. This underscores the need for cross-target therapeutic approaches that are not only pharmacologically safe but also modulate multiple potent signaling pathways and sensitize cancer cells to overcome resistance to standard drugs. In recent years, scientists have been searching for natural compounds that can be used as chemosensitizers in addition to conventional medications for the synergistic treatment of CRC. Resveratrol, a natural polyphenolic phytoalexin found in various fruits and vegetables such as peanuts, berries, and red grapes, is one of the most effective natural chemopreventive agents. Abundant in vitro and in vivo studies have shown that resveratrol, in interaction with standard drugs, is an effective chemosensitizer for CRC cells to chemotherapeutic agents and thus prevents drug resistance by modulating multiple pathways, including transcription factors, epithelial-to-mesenchymal transition-plasticity, proliferation, metastasis, angiogenesis, cell cycle, and apoptosis. The ability of resveratrol to modify multiple subcellular pathways that may suppress cancer cell plasticity and reversal of chemoresistance are critical parameters for understanding its anti-cancer effects. In this review, we focus on the chemosensitizing properties of resveratrol in CRC and, thus, its potential importance as an additive to ongoing treatments.

Integrating Microbiome Analysis, Metabolomics, Bioinformatics, and Histopathology to Elucidate the Protective Effects of Pomegranate Juice against Benzo-alpha-pyrene-Induced Colon Pathologies

Polycyclic aromatic hydrocarbons, e.g., benzo[a]pyrene (BaP), are common dietary pollutants with potential carcinogenic activity, while polyphenols are potential chemopreventive antioxidants. Although several health benefits are attributed to polyphenol-rich pomegranate, little is known about its interaction with BaP. This study integrates histochemical, microbiomic, and metabolomic approaches to investigate the protective effects of pomegranate juice from BaP-induced pathologies. To this end, 48 Sprague-Dawley rats received, for four weeks, either pomegranate, BaP, both, or neither (n = 12 rats per group). Whereas histochemical examination of the colon indicated tissue damage marked by mucin depletion in BaP-fed animals, which was partially restored by administration of pomegranate juice, the fecal microbiome and metabolome retained their resilience, except for key changes related to pomegranate and BaP biotransformation. Meanwhile, dramatic microbiome restructuring and metabolome shift were observed as a consequence of the elapsed time (age factor). Additionally, the analysis allowed a thorough examination of fecal microbiome-metabolome associations, which delineated six microbiome clusters (marked by a differential abundance of Lactobacillaceae and Prevotellaceae, Rumincococcaceae, and Erysipelotrichaceae) and two major metabolome clusters (a sugar- and amino-acids-dominated metabotype vs. a cluster of fatty acids and hydrocarbons), with sugar alcohols maintaining a unique signature. In conclusion, using paired comparisons to minimize inter-individual animal variations allowed the dissection of temporal vs. treatment-derived variations. Microbiome-metabolome association clusters may be further exploited for metabotype prediction and gut-health biomarker discovery.

Resveratrol Loaded Liposomes Disrupt Cancer Associated Fibroblast Communications within the Tumor Microenvironment to Inhibit Colorectal Cancer Aggressiveness

Colorectal cancer (CRC) is a cancer-associated fibroblast, CAF-rich tumor. CAF promotes cancer cell proliferation, metastasis, drug resistance via secretes soluble factors, and extracellular matrices which leads to dense stroma, a major barrier for drug delivery. Resveratrol (RES) is a polyphenolic compound, has several pharmacologic functions including anti-inflammation and anticancer effects. Considering tumor microenvironment of CRC, resveratrol-loaded liposome (L-RES) was synthesized and employed to inhibit CAF functions. The L-RES was synthesized by thin-film hydration method. The cytotoxicity of L-RES was evaluated using MTT assay. Effect of L-RES treated CAF on tumor spheroid growth was performed. Cell invasion was determined using spheroid invasion assay. The effect of L-RES on 5-fluorouracil (5-FU) sensitivity of CRC cells was determined in co-cultured tumor spheroids. Subtoxic dose of L-RES was selected to study possible inhibiting CAF functions. Decreased CAF markers, α-SMA and IL-6 levels, were observed in L-RES treated activated fibroblast. Interestingly, the activated fibroblast promoted invasive ability and drug resistance of CRC cells in co-culture condition of both 2D and 3D cultures and was attenuated by L-RES treatment in the activated fibroblast. Therefore, L-RES provides a promising drug delivery strategy for CRC treatment by disrupting the crosstalk between CRC cells and CAF.

Delivery of Natural Agents by Means of Mesoporous Silica Nanospheres as a Promising Anticancer Strategy

Natural prodrugs derived from different natural origins (e.g., medicinal plants, microbes, animals) have a long history in traditional medicine. They exhibit a broad range of pharmacological activities, including anticancer effects in vitro and in vivo. They have potential as safe, cost-effective treatments with few side effects, but are lacking in solubility, bioavailability, specific targeting and have short half-lives. These are barriers to clinical application. Nanomedicine has the potential to offer solutions to circumvent these limitations and allow the use of natural pro-drugs in cancer therapy. Mesoporous silica nanoparticles (MSNs) of various morphology have attracted considerable attention in the search for targeted drug delivery systems. MSNs are characterized by chemical stability, easy synthesis and functionalization, large surface area, tunable pore sizes and volumes, good biocompatibility, controlled drug release under different conditions, and high drug-loading capacity, enabling multifunctional purposes. In vivo pre-clinical evaluations, a significant majority of results indicate the safety profile of MSNs if they are synthesized in an optimized way. Here, we present an overview of synthesis methods, possible surface functionalization, cellular uptake, biodistribution, toxicity, loading strategies, delivery designs with controlled release, and cancer targeting and discuss the future of anticancer nanotechnology-based natural prodrug delivery systems.

Increased mitochondrial content and function by resveratrol and select flavonoids protects against benzo[a]pyrene-induced bioenergetic dysfunction and ROS generation in a cell model of neoplastic transformation

Dietary polyphenols act in cancer prevention and may inhibit carcinogenesis. A possible mitochondrial mechanism for carcinogen-induced neoplastic transformation and chemoprevention by polyphenols, however, is largely unexplored. Using the Bhas 42 cell model of carcinogen-induced neoplastic transformation, we investigated benzo[a]pyrene (B[a]P) along with different polyphenols for their effects on mitochondrial content and function, and on mitochondrial and intracellular ROS generation. Bhas 42 cells were either co-treated with 5 μM polyphenol starting 2 h before exposure to 4 μM B[a]P for 24 or 72 h, or pre-treated with polyphenol for 24 h and removed prior to B[a]P exposure. Exposure to B[a]P decreased mitochondrial content (by 46% after 24 h and 30% after 72 h), decreased mitochondrial membrane potential and cellular ATP, and increased generation of mitochondrial superoxide and intracellular ROS. Polyphenol co-treatments protected against the decreased mitochondrial content, with resveratrol being the most effective (increasing the mitochondrial content after 72 h by 75%). Measurements after 24 h of mRNA for mitochondria-related proteins and of SIRT1 enzyme activity suggested an involvement of increased mitochondrial biogenesis in the polyphenol effects. The polyphenol co-treatments also ameliorated B[a]P-induced deficits in mitochondrial function (most strongly resveratrol), and increases in generation of mitochondrial superoxide and intracellular ROS. Notably, 24 h pre-treatments with polyphenols strongly suppressed subsequent B[a]P-induced increases, after 24 and 72 h, in mitochondrial superoxide and intracellular ROS generation, with resveratrol being the most effective. In conclusion, the results support a mechanism for B[a]P carcinogenesis involving impaired mitochondrial function and increased mitochondria-derived ROS, that can be ameliorated by dietary polyphenols. The evidence supports an increase in mitochondrial biogenesis behind the strong chemoprevention by resveratrol, and a mitochondrial antioxidant effect in chemoprevention by quercetin.

Mouse models of colorectal cancer: Past, present and future perspectives

Colorectal cancer (CRC) is the third most common diagnosed malignancy among both sexes in the United States as well as in the European Union. While the incidence and mortality rates in western, high developed countries are declining, reflecting the success of screening programs and improved treatment regimen, a rise of the overall global CRC burden can be observed due to lifestyle changes paralleling an increasing human development index. Despite a growing insight into the biology of CRC and many therapeutic improvements in the recent decades, preclinical in vivo models are still indispensable for the development of new treatment approaches. Since the development of carcinogen-induced rodent models for CRC more than 80 years ago, a plethora of animal models has been established to study colon cancer biology. Despite tenuous invasiveness and metastatic behavior, these models are useful for chemoprevention studies and to evaluate colitis-related carcinogenesis. Genetically engineered mouse models (GEMM) mirror the pathogenesis of sporadic as well as inherited CRC depending on the specific molecular pathways activated or inhibited. Although the vast majority of CRC GEMM lack invasiveness, metastasis and tumor heterogeneity, they still have proven useful for examination of the tumor microenvironment as well as systemic immune responses; thus, supporting development of new therapeutic avenues. Induction of metastatic disease by orthotopic injection of CRC cell lines is possible, but the so generated models lack genetic diversity and the number of suited cell lines is very limited. Patient-derived xenografts, in contrast, maintain the pathological and molecular characteristics of the individual patient’s CRC after subcutaneous implantation into immunodeficient mice and are therefore most reliable for preclinical drug development – even in comparison to GEMM or cell line-based analyses. However, subcutaneous patient-derived xenograft models are less suitable for studying most aspects of the tumor microenvironment and anti-tumoral immune responses. The authors review the distinct mouse models of CRC with an emphasis on their clinical relevance and shed light on the latest developments in the field of preclinical CRC models.

Gut Microbiota, Its Role in Induction of Alzheimer's Disease Pathology, and Possible Therapeutic Interventions: Special Focus on Anthocyanins

The human gut is a safe environment for several microbes that are symbiotic and important for the wellbeing of human health. However, studies on gut microbiota in different animals have suggested that changes in the composition and structure of these microbes may promote gut inflammation by releasing inflammatory cytokines and lipopolysaccharides, gut-wall leakage, and may affect systemic inflammatory and immune mechanisms that are important for the normal functioning of the body. There are many factors that aid in the gut’s dysbiosis and neuroinflammation, including high stress levels, lack of sleep, fatty and processed foods, and the prolonged use of antibiotics. These neurotoxic mechanisms of dysbiosis may increase susceptibility to Alzheimer’s disease (AD) and other neurodegenerative conditions. Therefore, studies have recently been conducted to tackle AD-like conditions by specifically targeting gut microbes that need further elucidation. It was suggested that gut dyshomeostasis may be regulated by using available options, including the use of flavonoids such as anthocyanins, and restriction of the use of high-fatty-acid-containing food. In this review, we summarize the gut microbiota, factors promoting it, and possible therapeutic interventions especially focused on the therapeutic potential of natural dietary polyflavonoid anthocyanins. Our study strongly suggests that gut dysbiosis and systemic inflammation are critically involved in the development of neurodegenerative disorders, and the natural intake of these flavonoids may provide new therapeutic opportunities for preclinical or clinical studies.

Consumption of an Oil Palm Fruit Extract Promotes Large Bowel Health in Rats

Oil palm fruit is widely used for edible oils, but the health benefits of other components are relatively unknown. We examined if consuming a polyphenol-rich extract of the fruit, from a vegetation by-product of oil processing, which also contains fibre, has gastro-intestinal benefits in rats on a Western-type diet (WD). The oil palm preparation (OPP) was added to food (OPP-F) or drinking water (OPP-D) to provide 50 mg of gallic acid equivalents (GAE)/d and compared to effects of high amylose maize starch (HAMS; 30%) in the diet or green tea extract (GT; 50 mg GAE/d) in drinking water over 4 wk. OPP treatments induced some significant effects (P < 0.05) compared to WD. OPP-D increased caecal digesta mass, caecal digesta concentrations of total SCFA, acetate and propionate (OPP-F increased caecal butyrate concentration), the numbers of mucus-producing goblet cells per colonic crypt, and caecal digesta abundance of some bacteria which may provide benefit to the host (Faecalibacterium prausnitzii, Akkermansia muciniphila and Ruminococcus gnavus). HAMS induced similar effects but with greater potency and had a broader impact on microbe populations, whereas GT had minimal impacts. These results suggest dietary OPP may benefit the large bowel.

Effects of single and combined toxic exposures on the gut microbiome: Current knowledge and future directions

Human populations are chronically exposed to mixtures of toxic chemicals. Predicting the health effects of these mixtures require a large amount of information on the mode of action of their components. Xenobiotic metabolism by bacteria inhabiting the gastrointestinal tract has a major influence on human health. Our review aims to explore the literature for studies looking to characterize the different modes of action and outcomes of major chemical pollutants, and some components of cosmetics and food additives, on gut microbial communities in order to facilitate an estimation of their potential mixture effects. We identified good evidence that exposure to heavy metals, pesticides, nanoparticles, polycyclic aromatic hydrocarbons, dioxins, furans, polychlorinated biphenyls, and non-caloric artificial sweeteners affect the gut microbiome and which is associated with the development of metabolic, malignant, inflammatory, or immune diseases. Answering the question 'Who is there?' is not sufficient to define the mode of action of a toxicant in predictive modeling of mixture effects. Therefore, we recommend that new studies focus to simulate real-life exposure to diverse chemicals (toxicants, cosmetic/food additives), including as mixtures, and which combine metagenomics, metatranscriptomics and metabolomic analytical methods achieving in that way a comprehensive evaluation of effects on human health.

The application of ApcMin/+ mouse model in colorectal tumor researches

PURPOSE

Apc^Min/+ mouse is an excellent animal model bearing multiple intestinal neoplasia, used to simulate human familial adenomatous polyposis and colorectal tumors. The key point of this model is the mutation of Apc gene, which is a significant tumor-suppressor gene in the Wnt signaling pathway. There are also some other possible mechanisms responsible for the development of colorectal tumors in the Apc^Min/+ mouse model, such as tumor-associated signaling pathways activation, the changes of tumor-related genes, and the involvement of some related proteins or molecules.

METHODS

The relevant literatures about Apc^Min/+ mouse model from PUBMED databases are reviewed in this study.

RESULTS

In recent years, increasing studies have focused on the application of Apc^Min/+ mouse model in colorectal tumor, trying to find effective therapeutic targets for further use.

CONCLUSION

This article will give a brief review on the related molecular mechanisms of the Apc^Min/+ mouse model and its application in colorectal tumor researches.

Effects of Psychological, Environmental and Physical Stressors on the Gut Microbiota

Stress, a ubiquitous part of daily human life, has varied biological effects which are increasingly recognized as including modulation of commensal microorganisms residing in the gastrointestinal tract, the gut microbiota. In turn, the gut microbiota influences the host stress response and associated sequelae, thereby implicating the gut microbiota as an important mediator of host health. This narrative review aims to summarize evidence concerning the impact of psychological, environmental, and physical stressors on gut microbiota composition and function. The stressors reviewed include psychological stress, circadian disruption, sleep deprivation, environmental extremes (high altitude, heat, and cold), environmental pathogens, toxicants, pollutants, and noise, physical activity, and diet (nutrient composition and food restriction). Stressors were selected for their direct relevance to military personnel, a population that is commonly exposed to these stressors, often at extremes, and in combination. However, the selected stressors are also common, alone or in combination, in some civilian populations. Evidence from preclinical studies collectively indicates that the reviewed stressors alter the composition, function and metabolic activity of the gut microbiota, but that effects vary across stressors, and can include effects that may be beneficial or detrimental to host health. Translation of these findings to humans is largely lacking at present. This gap precludes concluding with certainty that transient or cumulative exposures to psychological, environmental, and physical stressors have any consistent, meaningful impact on the human gut microbiota. However, provocative preclinical evidence highlights a need for translational research aiming to elucidate the impact of stressors on the human gut microbiota, and how the gut microbiota can be manipulated, for example by using nutrition, to mitigate adverse stress responses.

Alteration of benzo(a)pyrene biotransformation by resveratrol in ApcMin/+ mouse model of colon carcinogenesis

Epidemiological surveys have revealed that environmental and dietary factors contribute to most of the human cancers. Our earlier studies have shown that resveratrol (RVT), a phytochemical reduced the tumor number, size and incidence of dysplasias induced by benzo(a)pyrene (BaP), an environmental toxicant in the Apc^Min/+ mouse model of colon cancer. In this study we investigated to ascertain whether the preventive effects of RVT on BaP-induced colon carcinogenesis is a result of altered BaP biotransformation by RVT. For the first group of mice, 100 μg BaP/kg bw was administered in peanut oil via oral gavage over a 60 day period. For the second group, 45 μg RVT/kg bw was co-administered with BaP. For the third group, RVT was administered for 1 week prior to BaP exposure. Blood, colon and liver were collected from control and BaP/RVT-treated mice at 60 days post-BaP & RVT exposure. We have assayed activities and expression (protein & mRNA) of drug metabolizing enzymes such as cytochrome P4501A1 (CYP1A1), CYP1B1, and glutathione-S-transferase (GST) in colon and liver samples from the treatment groups mentioned above. An increased expression of CYP1A1 in liver and colon and of CYP1B1 in liver of BaP-treated mice was seen, while RVT inhibited the extent of biotransformation mediated by these enzymes in the respective tissue samples. In the case of GST, an increased expression in colon of BaP alone-treated mice was noted when RVT was administered prior to BaP or simultaneously with BaP. However, there is no change in liver GST expression between BaP and RVT treatment groups. The concentrations of BaP aqueous (phase II) metabolites were found to be greater than the organic (phase I) metabolites, suggesting that RVT slows down the phase I metabolism (metabolic activation) of BaP, while enhancing phase II metabolism (detoxification). Additionally, the BaP-DNA adduct concentrations measured in colon and liver of BaP + RVT-treated mice were low relative to their BaP counterparts. Taken together, our findings strongly suggest that RVT alleviates BaP-induced colon carcinogenesis by impairing biotransformation pathways and DNA adduct formation, and therefore holds promise as a chemopreventive agent.

Chemoprevention of intestinal tumorigenesis by the natural dietary flavonoid myricetin in APCMin/+ mice

Myricetin is a natural dietary flavonoid compound. We evaluated the efficacy of myricetin against intestinal tumorigenesis in adenomatous polyposis coli multiple intestinal neoplasia (APCMin/+) mice. Myricetin was given orally once a day for 12 consecutive weeks. APCMin/+ mice fed with myricetin developed fewer and smaller polyps without any adverse effects. Histopathological analysis showed a decreased number of dysplastic cells and degree of dysplasia in each polyp. Immunohistochemical and western blot analysis revealed that myricetin selectively inhibits cell proliferation and induces apoptosis in adenomatous polyps. The effects of myricetin were associated with a modulation the GSK-3β and Wnt/β-catenin pathways. ELISA analysis showed a reduced concentration of pro-inflammatory cytokines IL-6 and PGE2 in blood, which were elevated in APCMin/+ mice. The effect of myricetin treatment was more prominent in the adenomatous polyps originating in the colon. Further studies showed that myricetin downregulates the phosphorylated p38 MAPK/Akt/mTOR signaling pathways, which may be the mechanisms for the inhibition of adenomatous polyps by myricetin. Taken together, our data show that myricetin inhibits intestinal tumorigenesis through a collection of biological activities. Given these results, we suggest that myricetin could be used preventatively to reduce the risk of developing colon cancers.

The Role of Resveratrol in Cancer Therapy

Natural product compounds have recently attracted significant attention from the scientific community for their potent effects against inflammation-driven diseases, including cancer. A significant amount of research, including preclinical, clinical, and epidemiological studies, has indicated that dietary consumption of polyphenols, found at high levels in cereals, pulses, vegetables, and fruits, may prevent the evolution of an array of diseases, including cancer. Cancer development is a carefully orchestrated progression where normal cells acquires mutations in their genetic makeup, which cause the cells to continuously grow, colonize, and metastasize to other organs such as the liver, lungs, colon, and brain. Compounds that modulate these oncogenic processes can be considered as potential anti-cancer agents that may ultimately make it to clinical application. Resveratrol, a natural stilbene and a non-flavonoid polyphenol, is a phytoestrogen that possesses anti-oxidant, anti-inflammatory, cardioprotective, and anti-cancer properties. It has been reported that resveratrol can reverse multidrug resistance in cancer cells, and, when used in combination with clinically used drugs, it can sensitize cancer cells to standard chemotherapeutic agents. Several novel analogs of resveratrol have been developed with improved anti-cancer activity, bioavailability, and pharmacokinetic profile. The current focus of this review is resveratrol’s in vivo and in vitro effects in a variety of cancers, and intracellular molecular targets modulated by this polyphenol. This is also accompanied by a comprehensive update of the various clinical trials that have demonstrated it to be a promising therapeutic and chemopreventive agent.

Environmental Pollutant Benzo[a]Pyrene Impacts the Volatile Metabolome and Transcriptome of the Human Gut Microbiota

Benzo[a]pyrene (B[a]P) is a ubiquitous, persistent, and carcinogenic pollutant that belongs to the large family of polycyclic aromatic hydrocarbons. Population exposure primarily occurs via contaminated food products, which introduces the pollutant to the digestive tract. Although the metabolism of B[a]P by host cells is well known, its impacts on the human gut microbiota, which plays a key role in health and disease, remain unexplored. We performed an in vitro assay using 16S barcoding, metatranscriptomics and volatile metabolomics to study the impact of B[a]P on two distinct human fecal microbiota. B[a]P exposure did not induce a significant change in the microbial structure; however, it altered the microbial volatolome in a dose-dependent manner. The transcript levels related to several metabolic pathways, such as vitamin and cofactor metabolism, cell wall compound metabolism, DNA repair and replication systems, and aromatic compound metabolism, were upregulated, whereas the transcript levels related to the glycolysis-gluconeogenesis pathway and bacterial chemotaxis toward simple carbohydrates were downregulated. These primary findings show that food pollutants, such as B[a]P, alter human gut microbiota activity. The observed shift in the volatolome demonstrates that B[a]P induces a specific deviation in the microbial metabolism.

Olive oil prevents benzo(a)pyrene [B(a)P]-induced colon carcinogenesis through altered B(a)P metabolism and decreased oxidative damage in Apc(Min) mouse model

Colon cancer ranks third in cancer-related mortalities in the United States. Many studies have investigated factors that contribute to colon cancer in which dietary and environmental factors have been shown to play an integral role in the etiology of this disease. Specifically, human dietary intake of environmental carcinogens such as polycyclic aromatic hydrocarbons has generated interest in looking at how it exerts its effects in gastrointestinal carcinogenesis. Therefore, the objective of this study was to investigate the preventative effects of olive oil on benzo(a)pyrene [B(a)P]-induced colon carcinogenesis in adult Apc(Min) mice. Mice were assigned to a control (n=8) or treatment group (n=8) consisting of 25, 50 and 100-μg B(a)P/kg body weight (bw) dissolved in tricaprylin [B(a)P-only group] or olive oil daily via oral gavage for 60 days. Our studies showed that Apc(Min) mice exposed to B(a)P developed a significantly higher number (P<0.05) of larger dysplastic adenomas compared to those exposed to B(a)P + olive oil. Treatment of mice with B(a)P and olive oil significantly altered (P<0.05) the expression of drug-metabolizing enzymes in both the colon and liver tissues. However, only GST activity was significantly higher (P<0.05) in the liver of mice treated with 50- and 100-μg B(a)P/kg bw + olive oil. Lastly, olive oil promoted rapid detoxification of B(a)P by decreasing its organic metabolite concentrations and also decreasing the extent of DNA damage to colon and liver tissues (P<0.05). These results suggest that olive oil has a protective effect against B(a)P-induced colon tumors.

Inhibition of β-catenin signalling promotes DNA damage elicited by benzo[a]pyrene in a model of human colon cancer cells via CYP1 deregulation

Deregulation of Wnt/β-catenin signalling plays an important role in the pathogenesis of colorectal cancer. Interestingly, this pathway has been recently implicated in transcriptional control of cytochrome P450 (CYP) family 1 enzymes, which are responsible for bioactivation of a number of dietary carcinogens. In the present study, we investigated the impact of inhibition of Wnt/β-catenin pathway on metabolism and genotoxicity of benzo[a]pyrene (BaP), a highly mutagenic polycyclic aromatic hydrocarbon and an efficient ligand of the aryl hydrocarbon receptor, which is known as a primary regulator of CYP1 expression, in cellular models derived from colorectal tumours. We observed that a synthetic inhibitor of β-catenin, JW74, significantly increased formation of BaP-induced DNA adducts in both colorectal adenoma and carcinoma-derived cell lines. Using the short interfering RNA (siRNA) targeting β-catenin, we then found that β-catenin knockdown in HCT116 colon carcinoma cells significantly enhanced formation of covalent DNA adducts by BaP and histone H2AX phosphorylation, as detected by (32)P-postlabelling technique and immunocytochemistry, respectively, and it also induced expression of DNA damage response genes, such as CDKN1A or DDB2. The increased formation of DNA adducts formed by BaP upon β-catenin knockdown corresponded with enhanced production of major BaP metabolites, as well as with an increased expression/activity of CYP1 enzymes. Finally, using siRNA-mediated knockdown of CYP1A1, we confirmed that this enzyme plays a major role in formation of BaP-induced DNA adducts in HCT116 cells. Taken together, the present results indicated that the siRNA-mediated inhibition of β-catenin signalling, which is aberrantly activated in a majority of colorectal cancers, modulated genotoxicity of dietary carcinogen BaP in colon cell model in vitro, via a mechanism involving up-regulation of CYP1 expression and activity.

The pharmacology of resveratrol in animals and humans

In addition to thousands of research papers related to resveratrol (RSV), approximately 300 review articles have been published. Earlier research tended to focus on pharmacological activities of RSV related to cardiovascular systems, inflammation, and carcinogenesis/cancer development. More recently, the horizon has been broadened by exploring the potential effect of RSV on the aging process, diabetes, neurological dysfunction, etc. Herein, we primarily focus on the in vivo pharmacological effects of RSV reported over the past 5 years (2009-2014). In addition, recent clinical intervention studies performed with resveratrol are summarized. Some discrepancies exist between in vivo studies with animals and clinical studies, or between clinical studies, which are likely due to disparate doses of RSV, experimental settings, and subject variation. Nevertheless, many positive indications have been reported with mammals, so it is reasonable to advocate for the conduct of more definitive clinical studies. Since the safety profile is pristine, an added advantage is the use of RSV as a dietary supplement. This article is part of a Special Issue entitled: Resveratrol: Challenges in translating pre-clinical findings to improved patient outcomes.

Physiological levels of resveratrol metabolites are ineffective as anti-leukemia agents against Jurkat leukemia cells

Dietary resveratrol is metabolically transformed in vivo by the intestine and liver to produce resveratrol glucuronides and sulfates in humans. Little is known about the anticancer activities of these metabolic products. The majority of in vitro studies have investigated effects of resveratrol aglycone at supraphysiological levels. Physiological levels of resveratrol-3-O-glucuronide, resveratrol-4'-O-glucuronide, and resveratrol-3-O-sulfate, the major in vivo metabolites of dietary resveratrol, were evaluated as anticancer agents against Jurkat T leukemia cells. Propidium iodide was use to measure cell death and changes in cell cycle, and the mitochondrial membrane dye JC-1 was used to measure changes in mitochondrial membrane potential by flow cytometry. PKH67 was used to evaluate changes in proliferation of the cells by flow cytometry. Jurkat cells were exposed to 0, 2.5, 5, 10, 15, and 20 μM of each resveratrol metabolite, which are concentrations achievable in vivo. None of the resveratrol metabolites were able to kill Jurkat T leukemia cells or alter cell cycle or proliferation at these concentrations. Only resveratrol-3-O-sulfate induced depolarization of mitochondrial membranes but without induction of cell death. These results suggest that the in vivo transformation of resveratrol to these glucuronide and sulfate metabolites renders these agents ineffective against T leukemia cells.

Resveratrol: a supplementation for men or for mice?

Resveratrol is a polyphenolic compound found in several plants. In the last decades, the interest in this compound has enormously increased after benefits on metabolism and increased lifespan of various organisms have been reported with its supplementation. Several in-vitro and animal studies have observed that resveratrol can act on multiple molecular targets, including sirtuins, a class of NAD + -dependent deacetylases. Despite the enthusiastic results reported in many animal- and in-vitro studies, few trials have been performed in humans with contrasting results. These conflicting data may be due at least in part to differences in the characteristics of the patients enrolled, the dosages and the duration of supplementation. Furthermore, many questions remain still unsolved, such as the dose or the duration of treatment to maximize its effects, the bioavailability of resveratrol and the role of food matrix to improve its bioactivity.

In conclusion, at present the use of resveratrol as a supplement is not yet justified by the existing evidence.

Role of microRNAs in resveratrol-mediated mitigation of colitis-associated tumorigenesis in Apc(Min/+) mice

The pleiotropic effects of resveratrol include anti-inflammatory, antioxidant, and anticancer activities, and thus unique possibilities exist to explore mechanistic pathways of chemoprevention. The aim of this study was to investigate the role of microRNA (miRNA) alterations induced by resveratrol in the context of chemopreventive mechanisms against dextran sodium sulfate (DSS)-induced colitis-associated tumorigenesis in the Apc(Min/+) mouse. To that end, Apc(Min/+) mice were exposed to 2% DSS to enhance intestinal inflammation and polyp development. Concurrently, mice received either vehicle or resveratrol treatment via oral gavage for 5 weeks. Interestingly, treatment of DSS-exposed mice with resveratrol resulted in decreased number and size of polyps, fewer histologic signs of cell damage, and decreased proliferating epithelial cells in intestinal mucosa compared with vehicle. Resveratrol treatment dramatically reversed the effects of DSS on the numbers of specific inflammatory CD4(+) T cells, CD8(+) T cells, B cells, natural killer T cells, and myeloid-derived suppressor cells in mesenteric lymph nodes. Resveratrol treatment also decreased interleukin-6 (IL-6) and tumor necrosis factor-α protein levels and reduced IL-6 and cyclooxygenase-2 mRNA expression. Microarray analysis revealed 104 miRNAs exhibiting >1.5-fold differences in expression in the intestinal tissue of resveratrol-treated mice. Among them, two miRNAs with anti-inflammatory properties, miRNA-101b and miRNA-455, were validated to be upregulated with resveratrol treatment by reverse-transcription polymerase chain reaction. Pathway analysis revealed that numerous differentially regulated miRNAs targeted mRNAs associated with inflammatory processes with known roles in intestinal tumorigenesis. These results suggest that resveratrol mediates anti-inflammatory properties and suppresses intestinal tumorigenesis through miRNA modulation.

Resveratrol and clinical trials: the crossroad from in vitro studies to human evidence

Resveratrol (3,5,4’-trihydroxy-trans-stilbene) is a non-flavonoid polyphenol that may be present in a limited number of food-stuffs such as grapes and red wine. Resveratrol has been reported to exert a plethora of health benefits through many different mechanisms of action. This versatility and presence in the human diet have drawn the worldwide attention of many research groups over the past twenty years, which has resulted in a huge output of in vitro and animal (preclinical) studies. In line with this expectation, many resveratrol-based nutraceuticals are consumed all over the world with questionable clinical/scientific support. In fact, the confirmation of these benefits in humans through randomized clinical trials is still very limited. The vast majority of preclinical studies have been performed using assay conditions with a questionable extrapolation to humans, i.e. too high concentrations with potential safety concerns (adverse effects and drug interactions), short-term exposures, in vitro tests carried out with non-physiological metabolites and/or concentrations, etc. Unfortunately, all these hypothesis-generating studies have contributed to increased the number of ‘potential’ benefits and mechanisms of resveratrol but confirmation in humans is very limited. Therefore, there are many issues that should be addressed to avoid an apparent endless loop in resveratrol research. The so-called ‘Resveratrol Paradox’, i.e., low bioavailability but high bioactivity, is a conundrum not yet solved in which the final responsible actor (if any) for the exerted effects has not yet been unequivocally identified. It is becoming evident that resveratrol exerts cardioprotective benefits through the improvement of inflammatory markers, atherogenic profile, glucose metabolism and endothelial function. However, safety concerns remain unsolved regarding chronic consumption of high RES doses, specially in medicated people. This review will focus on the currently available evidence regarding resveratrol’s effects on humans obtained from randomized clinical trials. In addition, we will provide a critical outlook for further research on this molecule that is evolving from a minor dietary compound to a possible multi-target therapeutic drug.

The chemopreventive activity of the histone deacetylase inhibitor tributyrin in colon carcinogenesis involves the induction of apoptosis and reduction of DNA damage

The chemopreventive activity of the histone deacetylase inhibitor (HDACi) tributyrin (TB), a prodrug of butyric acid (BA), was evaluated in a rat model of colon carcinogenesis. The animals were treated with TB (TB group: 200mg/100g of body weight, b.w.) or maltodextrin (MD isocaloric control group: 300 mg/100g b.w.) daily for 9 consecutive weeks. In the 3rd and 4th weeks of treatment, the rats in the TB and MD groups were given DMH (40 mg/kg b.w.) twice a week. After 9 weeks, the animals were euthanized, and the distal colon was examined. Compared with the control group (MD group), TB treatment reduced the total number of aberrant crypt foci (ACF; p<0.05) as well as the ACF with ≥4 crypts (p<0.05), which are considered more aggressive, but not inhibited the formation of DMH-induced O6-methyldeoxyguanosine DNA adducts. The TB group also showed a higher apoptotic index (p<0.05) and reduced DNA damage (p<0.05) compared with MD group. TB acted as a HDACi, as rats treated with the prodrug of BA had higher levels of histone H3K9 acetylation compared with the MD group (p<0.05). TB administration resulted in increased colonic tissue concentrations of BA (p<0.05) compared with the control animals. These results suggest that TB can be considered a promising chemopreventive agent for colon carcinogenesis because it reduced the number of ACF, including those that were more aggressive. Induction of apoptosis and reduction of DNA damage are cellular mechanisms that appear to be involved in the chemopreventive activity of TB.

Bioaccessibility of polycyclic aromatic hydrocarbons: relevance to toxicity and carcinogenesis

INTRODUCTION

Bioaccessibility is a growing area of research in the field of risk assessment. As polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants, they are the toxicants of focus to establish cancer risks in humans. Orally ingested PAHs also cause toxicity and even affect the pharmacokinetic behavior of some therapeutic agents. Toward this end, bioaccessibility is being used as a tool to assess the risk of PAHs via dietary exposures.

AREAS COVERED

This review covers some in vitro bioaccessibility models for PAHs that have been used for the past one-and-a-half decade. This review also considers the factors that influence bioaccessibility and debates the merits and limitations of using a bioaccessibility concept for estimating risk from ingestion of PAH-contaminated soil and food. Finally, the authors discuss the implications of bioaccessibility for PAH-induced toxicity and cancers in the context of risk assessment.

EXPERT OPINION

So far, much of the focus on PAH bioaccessibility is centered on soil as a preferential matrix. However, ingestion of PAHs through diet far exceeds the amount accidentally ingested through soil. Therefore, bioaccessibility could be exploited as a tool to assess the relative risk of various dietary ingredients tainted with PAHs. While bioaccessibility is a promising approach for assessing PAH risk arising from various types of contaminated soils, none of the models proposed appears to be valid. Bioaccessibility values, derived from in vitro studies, still require validation from in vivo studies.

Resveratrol-based combinatorial strategies for cancer management

In recent years combination chemoprevention has been increasingly appreciated and investigated as a viable and effective strategy for cancer management. A plethora of evidence suggests that a combination of agents may afford synergistic (or additive) advantage for cancer management by multiple means, such as by (1) enhancing the bio-availability of chemopreventive agents, (2) modifying different molecular targets, and (3) lowering the effective dose of agent/drug to be used for cancer management. Resveratrol has been shown to afford chemopreventive and therapeutic effects against certain cancers. Recent studies are suggesting that resveratrol may be very useful when given in combination with other agents. The two major advantages of using resveratrol in combination with other agents are synergistically or additively enhancing the efficacy against cancer and limiting the toxicity and side effects of existing therapies. However, concerted and multidisciplinary efforts are needed to identify the most optimal combinatorial strategies.