The effect of dietary flavonoids on DNA damage (strand breaks and oxidised pyrimdines) and growth in human cells

Enzyme-Directed and Organelle-Specific Sphere-to-Fiber Nanotransformation Enhances Photodynamic Therapy in Cancer Cells

Employing responsive nanoplatforms as carriers for photosensitizers represents an effective strategy to overcome the challenges associated with photodynamic therapy (PDT), including poor solubility, low bioavailability, and high systemic toxicity. Drawing inspiration from the morphology transitions in biological systems, a general approach to enhance PDT that utilizes enzyme-responsive nanoplatforms is developed. The transformation of phosphopeptide/photosensitizer co-assembled nanoparticles is first demonstrated into nanofibers when exposed to cytoplasmic enzyme alkaline phosphatase. This transition is primarily driven by alkaline phosphatase-induced changes of the nanoparticles in the hydrophilic and hydrophobic balance, and intermolecular electrostatic interactions within the nanoparticles. The resulting nanofibers exhibit improved ability of generating reactive oxygen species (ROS), intracellular accumulation, and retention in cancer cells. Furthermore, the enzyme-responsive nanoplatform is expanded to selectively target mitochondria by mitochondria-specific enzyme sirtuin 5 (SIRT5). Under the catalysis of SIRT5, the succinylated peptide/photosensitizer co-assembled nanoparticles can be transformed into nanofibers specifically within the mitochondria. The resulting nanofibers exhibit excellent capability of modulating mitochondrial activity, enhanced ROS formation, and significant anticancer efficacy via PDT. Consequently, the enzyme-instructed in situ fibrillar transformation of peptide/photosensitizers co-assembled nanoparticles provides an efficient pathway to address the challenges associated with photosensitizers. It is envisaged that this approach will further expand the toolbox for enzyme-responsive biomaterials for cancer therapy.

Quercetin induces its chemoprotective effects via hormesis

Quercetin is a polyphenol present in numerous fruits and vegetables and therefore widely consumed by humans with average daily dietary intakes of 10-20 mg/day. It is also a popular dietary supplement of 250-1000 mg/day. However, despite the widespread consumer interest in quercetin, due to its possible chemopreventive properties, the extensively studied quercetin presents a highly diverse and complex array of biological effects. Consequently, the present paper provides the first assessment of quercetin-induced hormetic concentration/dose responses, their quantitative features and mechanistic foundations, and their biological, biomedical, clinical, and public health implications. The findings indicate that quercetin-induced hormetic dose responses are widespread, being independent of biological model, cell type, and endpoint. These findings have the potential to enlighten future experimental studies with quercetin especially with respect to study design parameters and may also affect the appraisal of possible public health benefits and risks associated with highly diverse consumer consumption practices.

Role of bio-flavonols and their derivatives in improving mitochondrial dysfunctions associated with pancreatic tumorigenesis

Mitochondria, a cellular metabolic center, efficiently fulfill cellular energy needs and regulate crucial metabolic processes, including cellular proliferation, differentiation, apoptosis, and generation of reactive oxygen species. Alteration in the mitochondrial functions leads to metabolic imbalances and altered extracellular matrix dynamics in the host, utilized by solid tumors like pancreatic cancer (PC) to get energy benefits for fast-growing cancer cells. PC is highly heterogeneous and remains unidentified for a longer time because of its complex pathophysiology, retroperitoneal position, and lack of efficient diagnostic approaches, which is the foremost reason for accounting for the seventh leading cause of cancer-related deaths worldwide. PC cells often respond poorly to current therapeutics because of dense stromal barriers in the pancreatic tumor microenvironment, which limit the drug delivery and distribution of antitumor immune cell populations. As an alternative approach, various natural compounds like flavonoids are reported to possess potent antioxidant and anticancerous properties and are less toxic than current chemotherapeutic drugs. Therefore, we aim to summarize the current state of knowledge regarding the pharmacological properties of flavonols in PC in this review from the perspective of mitigating mitochondrial dysfunctions associated with cancer cells. Our literature survey indicates that flavonols efficiently regulate cellular metabolism by scavenging reactive oxygen species, mitigating inflammation, and arresting the cell cycle to promote apoptosis in tumor cells via intrinsic mitochondrial pathways. In particular, flavonols proficiently inhibit the cancer-associated proliferation and inflammatory pathways such as EGFR/MAPK, PI3K/Akt, and nuclear factor κB in PC. Overall, this review provides in-depth evidence about the therapeutic potential of flavonols for future anticancer strategies against PC; still, more multidisciplinary human interventional studies are required to dissect their pharmacological effect accurately.

Exploring the Multi-Faceted Potential of Carob (Ceratonia siliqua var. Rahma) Leaves from Morocco: A Comprehensive Analysis of Polyphenols Profile, Antimicrobial Activity, Cytotoxicity against Breast Cancer Cell Lines, and Genotoxicity

The botanical species Ceratonia siliqua L., commonly referred to as the Carob tree, and locally as "L'Kharrûb", holds significance as an agro-sylvo-pastoral species, and is traditionally utilized in Morocco for treating a variety of ailments. This current investigation aims to ascertain the antioxidant, antimicrobial, and cytotoxic properties of the ethanolic extract of C. siliqua leaves (CSEE). Initially, we analyzed the chemical composition of CSEE through high-performance liquid chromatography with Diode-Array Detection (HPLC-DAD). Subsequently, we conducted various assessments, including DPPH scavenging capacity, β-carotene bleaching assay, ABTS scavenging, and total antioxidant capacity assays to evaluate the antioxidant activity of the extract. In this study, we investigated the antimicrobial properties of CSEE against five bacterial strains (two gram-positive, Staphylococcus aureus, and Enterococcus faecalis; and three gram-negative bacteria, Escherichia coli, Escherichia vekanda, and Pseudomonas aeruginosa) and two fungi (Candida albicans, and Geotrichum candidum). Additionally, we evaluated the cytotoxicity of CSEE on three human breast cancer cell lines (MCF-7, MDA-MB-231, and MDA-MB-436) and assessed the potential genotoxicity of the extract using the comet assay. Through HPLC-DAD analysis, we determined that phenolic acids and flavonoids were the primary constituents of the CSEE extract. The results of the DPPH test indicated a potent scavenging capacity of the extract with an IC₅₀ of 302.78 ± 7.55 µg/mL, which was comparable to that of ascorbic acid with an IC₅₀ of 260.24 ± 6.45 µg/mL. Similarly, the β-carotene test demonstrated an IC₅₀ of 352.06 ± 12.16 µg/mL, signifying the extract's potential to inhibit oxidative damage. The ABTS assay revealed IC₅₀ values of 48.13 ± 3.66 TE µmol/mL, indicating a strong ability of CSEE to scavenge ABTS radicals, and the TAC assay demonstrated an IC₅₀ value of 165 ± 7.66 µg AAE/mg. The results suggest that the CSEE extract had potent antioxidant activity. Regarding its antimicrobial activity, the CSEE extract was effective against all five tested bacterial strains, indicating its broad-spectrum antibacterial properties. However, it only showed moderate activity against the two tested fungal strains, suggesting it may not be as effective against fungi. The CSEE exhibited a noteworthy dose-dependent inhibitory activity against all the tested tumor cell lines in vitro. The extract did not induce DNA damage at the concentrations of 6.25, 12.5, 25, and 50 µg/mL, as assessed by the comet assay. However, the 100 µg/mL concentration of CSEE resulted in a significant genotoxic effect compared to the negative control. A computational analysis was conducted to determine the physicochemical and pharmacokinetic characteristics of the constituent molecules present in the extract. The Prediction of Activity Spectra of Substances (PASS) test was employed to forecast the potential biological activities of these molecules. Additionally, the toxicity of the molecules was evaluated using the Protox II webserver.

Possible Side Effects of Polyphenols and Their Interactions with Medicines

Polyphenols are an important component of plant-derived food with a wide spectrum of beneficial effects on human health. For many years, they have aroused great interest, especially due to their antioxidant properties, which are used in the prevention and treatment of many diseases. Unfortunately, as with any chemical substance, depending on the conditions, dose, and interactions with the environment, it is possible for polyphenols to also exert harmful effects. This review presents a comprehensive current state of the knowledge on the negative impact of polyphenols on human health, describing the possible side effects of polyphenol intake, especially in the form of supplements. The review begins with a brief overview of the physiological role of polyphenols and their potential use in disease prevention, followed by the harmful effects of polyphenols which are exerted in particular situations. The individual chapters discuss the consequences of polyphenols’ ability to block iron uptake, which in some subpopulations can be harmful, as well as the possible inhibition of digestive enzymes, inhibition of intestinal microbiota, interactions of polyphenolic compounds with drugs, and impact on hormonal balance. Finally, the prooxidative activity of polyphenols as well as their mutagenic, carcinogenic, and genotoxic effects are presented. According to the authors, there is a need to raise public awareness about the possible side effects of polyphenols supplementation, especially in the case of vulnerable subpopulations.

Bioflavonoid-Induced Apoptosis and DNA Damage in Amastigotes and Promastigotes of Leishmania donovani: Deciphering the Mode of Action

Natural products from plants contain many interesting biomolecules. Among them, quercetin (Q), gallic acid (GA), and rutin (R) all have well-reported antileishmanial activity; however, their exact mechanisms of action are still not known. The current study is a step forward towards unveil the possible modes of action of these compounds against Leishmania donovani (the causative agent of visceral leishmaniasis). The selected compounds were checked for their mechanisms of action against L. donovani using different biological assays including apoptosis and necrosis evaluation, effects on genetic material (DNA), quantitative testing of nitric oxide production, ultrastructural modification via transmission electron microscopy, and real-time PCR analysis. The results confirmed that these compounds are active against L. donovani, with IC₅₀ values of 84.65 µg/mL, 86 µg/mL, and 98 µg/mL for Q, GA, and R, respectively. These compounds increased nitric oxide production and caused apoptosis and DNA damage, which led to changes in the treated cells’ ultrastructural behavior and finally to the death of L. donovani. These compounds also suppressed essential enzymes like trypanothione reductase and trypanothione synthetase, which are critical for leishmanial survival. The selected compounds have high antileishmanial potentials, and thus in-vivo testing and further screening are highly recommended.

Chromolaena odorata (Siam weed): A natural reservoir of bioactive compounds with potent anti-fibrillogenic, antioxidative, and cytocompatible properties

Protein fibrillation and oxidative damage are closely associated with the development of many chronic diseases such as Alzheimer's disease, Parkinson's disease and transthyretin amyloidoses. This work aimed at evaluating the fibrillogenic, antioxidant, anti-oxidative, hemolytic and cytotoxic activities of phenolic-rich extract from Chromolaena odorata (L) R.M. King & H. Rob aerial parts (COPE). As revealed by Thioflavin-T fluorescence, transmission electron microscopy, NBT redox cycling and ANS fluorescence analyses, COPE suppressed the fibril formation of hen egg-white lysozyme by directly binding to the protein and preventing surface exposure its of hydrophobic clusters. In addition, COPE demonstrated potent radical scavenging activities against DPPH˙ and ABTS˙⁺, chelated ferrous ions, and inhibited metal-catalyzed oxidation of bovine serum albumin. The observed effects could be explained by the high content of flavonoids (22.82 QE/g) and phenolics (190 mg GAE/g) present in COPE. UHPLC-ESI-QTOF-MS/MS analysis of COPE in negative ionization mode revealed that the predominant compounds were phenolics and terpenoids. Furthermore, COPE was found to exert very minimal cytotoxic effects against human red blood cells (≤ 5% hemolysis) and human embryonic kidney (HEK-293) cells (≥ 80% viability). These findings suggested that with further investigations, phenolic-rich extract from C odorata could be effectively valorized for pharmacological applications against protein fibrillogenic and oxidative damage related conditions.

Chemopreventive effect of troxerutin against hydrogen peroxide-induced oxidative stress in human leukocytes through modulation of glutathione-dependent enzymes

Troxerutin is a natural flavonoid present abundantly in tea, coffee, olives, wheat, and a variety of fruits and vegetables. Due to its diverse pharmacological properties, this flavonoid has aroused interest for treatment of various diseases, and consequently prompted investigation into its toxicological characteristics. The aim of this study was to evaluate the genotoxic and mutagenic effects and chemoprotective activity attributed to troxerutin using human peripheral blood leukocytes (PBLs) through several well-established experimental protocols based upon different parameters. Data demonstrated that troxerutin (100 to 1000 µM) induced no marked cytotoxic effect on PBLs after 24 hr, and did not produce strand breaks and mutagenicity. Regarding chemoprevention, this flavonoid attenuated cytotoxicity, genotoxicity, and mutagenicity initiated by hydrogen peroxide (H₂O₂) in human PBLs. Further, troxerutin demonstrated no marked cytotoxic effect on PBLs and exerted a protective effect against oxidative stress induced by H₂O₂ through modulation of GSH-dependent enzymes.

Genotoxic and cytotoxic properties of two medical plants (Teucrium arduini L.and Teucrium flavum L.) in relation to their polyphenolic contents

A large number of species belonging to the genus Teucrium are used in pharmacy and traditional medicine for the treatment of different diseases. This study aimed to evaluate the polyphenolic composition as well as genotoxic and cytotoxic effects of methanolic extracts from T. arduini and T. flavum, two native species found in Montenegro. We determined the total phenolic and flavonoid contents of these plants using spectrophotometric methods; the qualitative content of polyphenolic compounds was investigated by high-performance liquid chromatography (HPLC). Genotoxicity in cultured human lymphocytes was measured in the cytokinesis-block micronucleus assay (CBMN) and comet assay in the range between 125 and 1000 μg/mL. Cytotoxicity was assessed by the MTT viability assay in normal human MRC-5 fibroblasts and MDA-MB-231 breast carcinoma cells. The content of total phenolics and flavonoids in T. arduini extract was higher than in T. flavum (200.35 mg GA/g vs. 171.08 mg GA/g; 96.32 mg RU/g vs. 78.14 mg RU/g). The polyphenolic composition of both extracts was qualitatively similar and eight phenol compounds were identified. The most commonly present phenol was caffeic acid and among four flavonoids, the most common was quercetin. Both plant extracts were genotoxic in both the CBMN and comet assays at concentrations of 250, 500 and 1000 μg/mL. After 72 h of exposure, the extracts of T. arduini and T. flavum were found to induce cytotoxicity in MRC-5 fibroblasts but not in MDA-MB-231 breast cancer cells. The results suggest that the constituents of both plant species are genotoxic and cytotoxic, therefore these extracts warrant additional evaluation to be safely applied in humans.

Genotoxic Assessment of the Dry Decoction of Myracrodruon urundeuva Allemão (Anacardiaceae) Leaves in Somatic Cells of Drosophila melanogaster by the Comet and SMART Assays

Medicinal plants are worldwide used as an efficient treatment of many diseases. Myracrodruon urundeuva Allemão (Anacardiaceae) is widely used Brazilian folk medicine to treat inflammations and infections of the female genital tract, conditions of the stomach and throat, and to heal wounds on the skin and mucous membranes. Several pharmacological properties of extracts and compounds isolated from M. urundeuva are found in the literature, corroborating its uses as antiulcer and gastroprotective, anti-inflammatory and analgesic, as well as antimicrobial. Despite these many uses in traditional herbal medicine, there are few reports of its toxic-genetic effect. This work aimed to investigate the genotoxic and mutagenic potential in vivo of the dry decoction of M. urundeuva leaves on somatic cells of Drosophila melanogaster, through the Comet assay and somatic mutation and recombination test (SMART). Six concentrations (0.5, 1.0, 2.0, 4.0, 8.0, and 16.0 mg/mL) were studied after feeding individuals for 24 hr in culture medium hydrated with extracts of M. urundeuva. In the Comet assay, all concentrations showed a genotoxic effect significantly higher than the negative control group, treated with distilled water. The two highest concentrations were also superior to the positive control group, treated with cyclophosphamide (1 mg/mL). In the SMART, there was a mutagenic effect at all concentrations tested, with a clear dose-dependent relationship. Both recombination and mutation account for these mutagenic effects. The set of results indicate that the dry decoction of M. urundeuva leaves is genotoxic and mutagenic for D. melanogaster under the experimental conditions of this study. Environ. Mol. Mutagen. 61:329-337, 2020. © 2019 Wiley Periodicals, Inc.

Intracellular catalase activity instead of glutathione level dominates the resistance of cells to reactive oxygen species

Artesunate (ARS) induced significant reactive oxygen species (ROS) generation in HepG2, HeLa, and A549 lines. However, ARS induced ROS-dependent apoptosis in HeLa and A549 cell lines but ROS-independent apoptosis in HepG2 cells. A total of 200 μM hydrogen peroxide (H2O2) significantly induced cytotoxicity in HeLa cells, while H2O2 up to 300 μM did not induce cytotoxicity in HepG2 cells, further demonstrating the strong resistance of HepG2 cells to ROS. HeLa cells had much higher basic total glutathione (T-GSH) level than HepG2 cells, while the ratio of basic reduced glutathione (GSH)/oxidized glutathione (GSSG) in HepG2 cells was nearly twice than that in HeLa and A549 cells. Inhibition of glutathione markedly enhanced H2O2- or ARS-induced cytotoxicity in HeLa and A549 cell lines but modestly enhanced the cytotoxicity of H2O2 and even did not affect the cytotoxicity of ARS in HepG2 cells. Moreover, addition of GSH remarkably prevented H2O2- or ARS-induced cytotoxicity in HeLa and A549 cell lines, further indicating the involvement of GSH in scavenging ROS in the two cell lines. HepG2 cells exhibited higher catalase activity than HeLa cells, and inhibiting catalase activity by using 3-aminotriazole (3-AT, a specific inhibition of catalase) or catalase siRNA remarkably reduced the resistance of HepG2 cells to ROS, demonstrating the key roles of catalase for the strong resistance of HepG2 cells to ROS. Collectively, catalase activity instead of glutathione level dominates the resistance of cells to ROS.

Chemopreventive Potential of Ethanolic Extracts of Luobuma Leaves (Apocynum venetum L.) in Androgen Insensitive Prostate Cancer

Luobuma (Apocynum venetum L. (AVL)) is a popular beverage in Asia and has been reportedly to be associated with the bioactivities such as cardiotonic, diuretic, antioxidative, and antihypertensive. However, its biofunction as chemoprevention activity is seldom addressed. Herein, we aimed to characterize the anti-androgen-insensitive-prostate-cancer (anti-AIPC) bioactive compounds of Luobuma, and to investigate the associated molecular mechanisms. Activity-guided-fractionation (antioxidative activity and cell survivability) of Luobuma ethanolic extracts was performed to isolate and characterize the major bioactive compounds using Ultra Performance Liquid Chromatography (UPLC), Liquid Chromatography-Mass Spectrometry (LC-MS), and Nuclear Magnetic Resonance (NMR). Plant sterols (lupeol, stigamasterol and β-sitosterol) and polyphenolics (isorhamnetin, kaempferol, and quercetin) were identified. Lupeol, a triterpene found in the fraction (F8) eluted by 10% ethyl acetate/90% hexane and accounted for 19.3% (w/w) of F8, inhibited the proliferation of PC3 cells. Both lupeol and F8 induced G2/M arrest, inhibition of β-catenin signaling, regulation of apoptotic signal molecules (cytochrome c, Bcl-2, P53, and caspase 3 and 8), and suppression DNA repair enzyme expression (Uracil-DNA glycosylase (UNG)). To our knowledge, our study is the first report that lupeol inhibited the expression of UNG to elicit the cytotoxicity against androgen-insensitive-prostate-cancer cells. Collectively, Luobuma, which contains several antitumor bioactive compounds, holds the potential to be a dietary chemopreventive agent for prostate cancer.

Review of Ginkgo biloba-induced toxicity, from experimental studies to human case reports

Ginkgo biloba seeds and leaves have been used as a traditional herbal remedy for thousands of years, and its leaf extract has been consumed as a botanical dietary supplement for decades. Ginkgo biloba extract is a complex mixture with numerous components, including flavonol glycosides and terpene lactones, and is one of the most widely sold botanical dietary supplements worldwide. Concerns about potential health risks for the general population have been raised because of the widespread human exposure to Ginkgo biloba and its potential toxic and carcinogenic activities in rodents. The National Toxicology Program conducted 2-year gavage studies on one Ginkgo biloba leaf extract and concluded that there was clear evidence of carcinogenic activity of this extract in mice based on an increased incidence of hepatocellular carcinoma and hepatoblastoma. Recently, Ginkgo biloba leaf extract has been classified as a possible human carcinogen (Group 2B) by the International Agency for Research on Cancer. This review presents updated information on the toxicological effects from experimental studies both in vitro and in vivo to human case reports (caused by ginkgo seeds or leaves), and also summarizes the negative results from relatively large clinical trials.

Polyphenols and DNA Damage: A Mixed Blessing

Polyphenols are a very broad group of chemicals, widely distributed in plant foods, and endowed with antioxidant activity by virtue of their numerous phenol groups. They are widely studied as putative cancer-protective agents, potentially contributing to the cancer preventive properties of fruits and vegetables. We review recent publications relating to human trials, animal experiments and cell culture, grouping them according to whether polyphenols are investigated in whole foods and drinks, in plant extracts, or as individual compounds. A variety of assays are in use to study genetic damage endpoints. Human trials, of which there are rather few, tend to show decreases in endogenous DNA damage and protection against DNA damage induced ex vivo in blood cells. Most animal experiments have investigated the effects of polyphenols (often at high doses) in combination with known DNA-damaging agents, and generally they show protection. High concentrations can themselves induce DNA damage, as demonstrated in numerous cell culture experiments; low concentrations, on the other hand, tend to decrease DNA damage.

Tapirira guianensis Aubl. Extracts Inhibit Proliferation and Migration of Oral Cancer Cells Lines

Cancer of the head and neck is a group of upper aerodigestive tract neoplasms in which aggressive treatments may cause harmful side effects to the patient. In the last decade, investigations on natural compounds have been particularly successful in the field of anticancer drug research. Our aim is to evaluate the antitumor effect of Tapirira guianensis Aubl. extracts on a panel of head and neck squamous cell carcinoma (HNSCC) cell lines. Analysis of secondary metabolites classes in fractions of T. guianensis was performed using Nuclear Magnetic Resonance (NMR). Mutagenicity effect was evaluated by Ames mutagenicity assay. The cytotoxic effect, and migration and invasion inhibition were measured. Additionally, the expression level of apoptosis-related molecules (PARP, Caspases 3, and Fas) and MMP-2 was detected using Western blot. Heterogeneous cytotoxicity response was observed for all fractions, which showed migration inhibition, reduced matrix degradation, and decreased cell invasion ability. Expression levels of MMP-2 decreased in all fractions, and particularly in the hexane fraction. Furthermore, overexpression of FAS and caspase-3, and increase of cleaved PARP indicates possible apoptosis extrinsic pathway activation. Antiproliferative activity of T. guianensis extract in HNSCC cells lines suggests the possibility of developing an anticancer agent or an additive with synergic activities associated with conventional anticancer therapy.

Food Antioxidants and Their Anti-Inflammatory Properties: A Potential Role in Cardiovascular Diseases and Cancer Prevention

Mediterranean-style diets caused a significant decline in cardiovascular diseases (CVDs) in early landmark studies. The effect of a traditional Mediterranean diet on lipoprotein oxidation showed that there was a significant reduction in oxidative stress in the intervention group (Mediterranean diet + Virgin Olive Oil) compared to the low-fat diet group. Conversely, the increase in oxidative stress causing inflammation is a unifying hypothesis for predisposing people to atherosclerosis, carcinogenesis, and osteoporosis. The impact of antioxidants and anti-inflammatory agents on cancer and cardiovascular disease, and the interventive mechanisms for the inhibition of proliferation, inflammation, invasion, metastasis, and activation of apoptosis were explored. Following the Great Oxygen Event some 2.3 billion years ago, organisms have needed antioxidants to survive. Natural products in food preservatives are preferable to synthetic compounds due to their lower volatility and stability and generally higher antioxidant potential. Free radicals, reactive oxygen species, antioxidants, pro-oxidants and inflammation are described with examples of free radical damage based on the hydroxyl, nitric oxide and superoxide radicals. Flavonoid antioxidants with 2- or 3-phenylchroman structures such as quercetin, kaempferol, myricetin, apigenin, and luteolin, constituents of fruits, vegetables, tea, and wine, which may reduce coronary disease and cancer, are described. The protective effect of flavonoids on the DNA damage caused by hydroxyl radicals through chelation is an important mechanism, though the converse may be possible, e.g., quercetin. The antioxidant properties of carotenoids, which are dietary natural pigments, have been studied in relation to breast cancer risk and an inverse association was found with plasma concentrations: higher levels mean lower risk. The manipulation of primary and secondary human metabolomes derived especially from existing or transformed gut microbiota was explored as a possible alternative to single-agent dietary interventions for cancer and cardiovascular disease. Sustained oxidative stress leading to inflammation and thence to possibly to cancer and cardiovascular disease is described for spices and herbs, using curcumin as an example of an intervention, based on activation of transcription factors which suggest that oxidative stress, chronic inflammation, and cancer are closely linked.

Phytogenic pigments in animal nutrition: potentials and risks

Phytogenic pigments are secondary plant compounds responsible for coloring effects in plant tissues. In particular, phenolic flavonoids and terpenoid carotenoids, but also rare compounds like curcumin and betalain, form this group of biochemical agents used in animal nutrition. From the perspective of ecological mutuality between plants and animals, these compounds are of crucial importance because they serve as visual attraction for herbivores but also signal nutritional and/or health-promoting values. This review focuses on the properties of phytogenic pigments which are likely to impact feed intake and preferences of livestock. Also natural prophylactic and/or therapeutic properties and, in particular, the potential of pigments to enhance quality and health value of animal products for human consumption are important issues. Nevertheless, reasonable limits of use due to possible adverse indications have been suggested recently. Pathways of digestion, metabolism and excretion in animals play a crucial role not only in the evaluation of effectiveness but also in the prediction of potential risks for human consumption. The popularity of natural feed additives is growing; therefore, more research work is needed to better understand metabolic pathways in the animal's body and to better estimate the potentials and risks of pigmenting plant compounds used in animal nutrition.

Genotoxicity evaluation of the flavonoid, myricitrin, and its aglycone, myricetin

Myricitrin, a flavonoid extracted from the fruit, leaves, and bark of Chinese bayberry (Myrica rubra SIEBOLD), is currently used as a flavor modifier in snack foods, dairy products, and beverages in Japan. Myricitrin is converted to myricetin by intestinal microflora; myricetin also occurs ubiquitously in plants and is consumed in fruits, vegetables, and beverages. The genotoxic potential of myricitrin and myricetin was evaluated in anticipation of worldwide marketing of food products containing myricitrin. In a bacterial reverse mutation assay, myricetin tested positive for frameshift mutations under metabolic activation conditions whereas myricitrin tested negative for mutagenic potential. Both myricitrin and myricetin induced micronuclei formation in human TK6 lymphoblastoid cells under conditions lacking metabolic activation; however, the negative response observed in the presence of metabolic activation suggests that rat liver S9 homogenate may detoxify reactive metabolites of these chemicals in mammalian cells. In 3-day combined micronucleus/Comet assays using male and female B6C3F1 mice, no induction of micronuclei was observed in peripheral blood, or conclusive evidence of damage detected in the liver, glandular stomach, or duodenum following exposure to myricitrin or myricetin. Our studies did not reveal evidence of genotoxic potential of myricitrin in vivo, supporting its safe use in food and beverages.

Free radicals, natural antioxidants, and their reaction mechanisms

The normal biochemical reactions in our body, increased exposure to the environment, and higher levels of dietary xenobiotic's result in the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS).

Mechanistic evaluation of Ginkgo biloba leaf extract-induced genotoxicity in L5178Y cells

Ginkgo biloba has been used for many thousand years as a traditional herbal remedy and its extract has been consumed for many decades as a dietary supplement. Ginkgo biloba leaf extract is a complex mixture with many constituents, including flavonol glycosides and terpene lactones. The National Toxicology Program 2-year cancer bioassay found that G. biloba leaf extract targets the liver, thyroid gland, and nose of rodents; however, the mechanism of G. biloba leaf extract-associated carcinogenicity remains unclear. In the current study, the in vitro genotoxicity of G. biloba leaf extract and its eight constituents was evaluated using the mouse lymphoma assay (MLA) and Comet assay. The underlying mechanisms of G. biloba leaf extract-associated genotoxicity were explored. Ginkgo biloba leaf extract, quercetin, and kaempferol resulted in a dose-dependent increase in the mutant frequency and DNA double-strand breaks (DSBs). Western blot analysis confirmed that G. biloba leaf extract, quercetin, and kaempferol activated the DNA damage signaling pathway with increased expression of γ-H2AX and phosphorylated Chk2 and Chk1. In addition, G. biloba leaf extract produced reactive oxygen species and decreased glutathione levels in L5178Y cells. Loss of heterozygosity analysis of mutants indicated that G. biloba leaf extract, quercetin, and kaempferol treatments resulted in extensive chromosomal damage. These results indicate that G. biloba leaf extract and its two constituents, quercetin and kaempferol, are mutagenic to the mouse L5178Y cells and induce DSBs. Quercetin and kaempferol likely are major contributors to G. biloba leaf extract-induced genotoxicity.

Site-specific anticancer effects of dietary flavonoid quercetin

Food-derived flavonoid quercetin, widely distributed in onions, apples, and tea, is able to inhibit growth of various cancer cells indicating that this compound can be considered as a good candidate for anticancer therapy. Although the exact mechanism of this action is not thoroughly understood, behaving as antioxidant and/or prooxidant as well as modulating different intracellular signalling cascades may all play a certain role. Such inhibitory activity of quercetin has been shown to depend first of all on cell lines and cancer types; however, no comprehensive site-specific analysis of this effect has been published. In this review article, cytotoxicity constants of quercetin measured in various human malignant cell lines of different origin were compiled from literature and a clear cancer selective action was demonstrated. The most sensitive malignant sites for quercetin revealed to be cancers of blood, brain, lung, uterine, and salivary gland as well as melanoma whereas cytotoxic activity was higher in more aggressive cells compared to the slowly growing cells showing that the most harmful cells for the organism are probably targeted. More research is needed to overcome the issues of poor water solubility and relatively low bioavailability of quercetin as the major obstacles limiting its clinical use.

Review of genotoxicity studies of glyphosate and glyphosate-based formulations

An earlier review of the toxicity of glyphosate and the original Roundup™-branded formulation concluded that neither glyphosate nor the formulation poses a risk for the production of heritable/somatic mutations in humans. The present review of subsequent genotoxicity publications and regulatory studies of glyphosate and glyphosate-based formulations (GBFs) incorporates all of the findings into a weight of evidence for genotoxicity. An overwhelming preponderance of negative results in well-conducted bacterial reversion and in vivo mammalian micronucleus and chromosomal aberration assays indicates that glyphosate and typical GBFs are not genotoxic in these core assays. Negative results for in vitro gene mutation and a majority of negative results for chromosomal effect assays in mammalian cells add to the weight of evidence that glyphosate is not typically genotoxic for these endpoints in mammalian systems. Mixed results were observed for micronucleus assays of GBFs in non-mammalian systems. Reports of positive results for DNA damage endpoints indicate that glyphosate and GBFs tend to elicit DNA damage effects at high or toxic dose levels, but the data suggest that this is due to cytotoxicity rather than DNA interaction with GBF activity perhaps associated with the surfactants present in many GBFs. Glyphosate and typical GBFs do not appear to present significant genotoxic risk under normal conditions of human or environmental exposures.

Protective effects of extracts and flavonoids isolated from Scutia buxifolia Reissek against chromosome damage in human lymphocytes exposed to hydrogen peroxide

Flavonoids are claimed to protect against cardiovascular disease, certain forms of cancer and ageing, possibly by preventing initial DNA damage. Therefore, we investigated the protective effects of crude extract, ethyl acetate fraction and flavonoids (quercetin, quercitrin, isoquercitrin and rutin) isolated from the leaves from Scutia buxifolia against chromosome damage induced by H₂O₂ in human lymphocytes by analyzing cellular growth rate, cell viability, mitotic index and chromosomal instability. We found a differential response among the compounds tested, with the ethyl acetate fraction being more effective than the crude extract, a difference perhaps related to the presence of the antioxidants identified and quantified by HPLC/DAD. In general, quercetin, isoquercitrin and rutin recovered the mitotic index and chromosomal instability more than quercitrin after treatment with hydrogen peroxide.

The protective effect of the flavonoids on food-mutagen-induced DNA damage in peripheral blood lymphocytes from colon cancer patients

The food mutagens IQ (2-amino-3-methylimidazo[4,5-f]quinoline) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) are heterocyclic amines (HCA), generated when heating proteinaceous food. This study investigates the protective potential of the flavonoids quercetin (Q) and rutin (R) against oxidative stress induced in vitro by IQ and PhIP in lymphocytes from healthy individuals and untreated, newly diagnosed colon cancer patients using the Comet assay. In the presence of up to 500μM Q and R, the DNA damage resulting from a high dose of PhIP (75μM) or IQ (150μM) was significantly reduced (P<0.001) to levels comparable to six times lower IQ or 7.5 times lower PhIP doses. Lymphocytes from colon cancer patients had greater baseline DNA damage than those from healthy individuals (P<0.01) and this higher level of damage was also observed throughout in vitro treatment. Except for the >50years of age group and male gender, confounding factors such as smoking, drinking and/or dietary habits were not found to be significant. In conclusion, flavonoids reduced oxidative stress caused by food mutagens in vitro in lymphocytes of healthy individuals and colon cancer patients. Thus, dietary supplementation with flavonoid-rich vegetables and fruits may prove very effective in protecting against oxidative stress.

Myricetin induces pancreatic cancer cell death via the induction of apoptosis and inhibition of the phosphatidylinositol 3-kinase (PI3K) signaling pathway

Pancreatic cancer is the fourth leading cause of cancer related deaths and is a disease with poor prognosis. It is refractory to standard chemotherapeutic drugs or to novel treatment modalities, making it imperative to find new treatments. In this study, using both primary and metastatic pancreatic cancer cell lines, we have demonstrated that the flavonoid myricetin induced pancreatic cancer cell death in vitro via apoptosis, and caused a decrease in PI3 kinase activity. In vivo, treatment of orthotopic pancreatic tumors with myricetin resulted in tumor regression and decreased metastatic spread. Importantly, myricetin was non-toxic, both in vitro and in vivo, underscoring its use as a therapeutic agent against pancreatic cancer.

5-Methoxyflavanone induces cell cycle arrest at the G2/M phase, apoptosis and autophagy in HCT116 human colon cancer cells

Natural flavonoids have diverse pharmacological activities, including anti-oxidative, anti-inflammatory, and anti-cancer activities. In this study, we investigated the molecular mechanism underlying the action of 5-methoxyflavanone (5-MF) which has a strong bioavailability and metabolic stability. Our results show that 5-MF inhibited the growth and clonogenicity of HCT116 human colon cancer cells, and that it activated DNA damage responses, as revealed by the accumulation of p53 and the phosphorylation of DNA damage-sensitive proteins, including ataxia-telangiectasia mutated (ATM) at Ser1981, checkpoint kinase 2 (Chk2) at Thr68, and histone H2AX at Ser139. 5-MF-induced DNA damage was confirmed in a comet tail assay. We also found that 5-MF increased the cleavage of caspase-2 and -7, leading to the induction of apoptosis. Pretreatment with the ATM inhibitor KU55933 enhanced 5-MF-induced γ-H2AX formation and caspase-7 cleavage. HCT116 cells lacking p53 (p53(-/-)) or p21 (p21(-/-)) exhibited increased sensitivity to 5-MF compared to wild-type cells. 5-MF further induced autophagy via an ERK signaling pathway. Blockage of autophagy with the MEK inhibitor U0126 potentiated 5-MF-induced γ-H2AX formation and caspase-2 activation. These results suggest that a caspase-2 cascade mediates 5-MF-induced anti-tumor activity, while an ATM/Chk2/p53/p21 checkpoint pathway and ERK-mediated autophagy act as a survival program to block caspase-2-mediated apoptosis induced by 5-MF.

Antigenotoxic potential of Gymnema montanum leaves on DNA damage in human peripheral blood lymphocytes and HL-60 cell line

In this study we have evaluated the genoprotective effect of the ethanol extract of Gymnema montanum (GLEt) leaves in human peripheral blood lymphocytes and HL-60 cell line in vitro using the comet assay. DNA damage was induced by treating the cells with H(2)O(2) and methyl methane sulphonate (MMS). GLEt treatment effectively protected the lymphocytes and HL-60 cell line from H(2)O(2)-induced oxidative DNA damage in a dose-dependent manner whereas it was not effective against alkylative DNA damage caused by MMS. The global percent repair efficiency also showed that both pre- and post- GLEt treatment provided effective protection against H(2)O(2) induced DNA damage but not as effective against MMS. At 200 microg ml(-1) level, its repair capacity against H(2)O(2) induced DNA damage was comparable to that of vitamin-C (100 microM). Furthermore, exposure to GLEt reduced the formation of apoptotic cells caused by H(2)O(2), which was demonstrated by the decreased sub-G1-DNA content in cell cycle analysis and apoptotic frequencies of lymphocytes in an annexin-V binding assay. In addition, GLEt was found to have effective peroxide scavenging ability in dose-dependent manner. The protective efficiency of the extract was found to be directly proportional to its total phenolic content. The present study indicates that G. montanum leaves are a significant source of phytochemicals with antigenotoxic and antioxidant activity, and thus has potential therapeutic use.

Plant polyphenols in cancer and heart disease: implications as nutritional antioxidants

Certain dietary antioxidants such as vitamin E and vitamin C are important for maintaining optimum health. There is now much interest in polyphenolic products of the plant phenylpropanoid pathway as they have considerable antioxidant activity in vitro and are ubiquitous in our diet. Rich sources include tea, wine, fruits and vegetables although levels are affected by species, light, degree of ripeness, processing and storage. This confounds the formulation of databases for the estimation of dietary intakes. Most attention to date has focused on the flavonoids, a generic term which includes chalcones, flavones, flavanones, flavanols and anthocyanins. There is little convincing epidemiological evidence that intakes of polyphenols are inversely related to the incidence of cancer whereas a number of studies suggest that high intakes of flavonoids may be protective against CHD. In contrast, numerous cell culture and animal models indicate potent anticarcinogenic activity by certain polyphenols mediated through a range of mechanisms including antioxidant activity, enzyme modulation, gene expression, apoptosis, upregulation of gap junction communication and P-glycoprotein activation. Possible protective effects against heart disease may be due to the ability of some polyphenols to prevent the oxidation of LDL to an atherogenic form although anti-platelet aggregation activity and vasodilatory properties are also reported. However, some polyphenols are toxic in mammalian cells. Thus, until more is known about their bioavailability, metabolism and intracellular location, increasing intakes of polyphenols by supplements or food fortification may be unwise.

Bioassays for evaluating the water-extractable genotoxic and toxic potential of soils polluted by metal smelters

Physicochemical analyses of polluted soils are limited in their ability to determine all hazardous compounds, their bioavailability, and their combined effects on living organisms. Bioassays, on the other hand, can evaluate environmental quality more accurately. This study assesses the genotoxic potential of water extracts from soil polluted with metals (Pb, Cd, and Zn) by the former lead smelter in zerjav, Slovenia using comet assay with Tetrahymena thermophila and human hepatoma cells (HepG2). In addition, the toxicity of soil samples and their extracts was evaluated using Vibrio fischeri and delayed fluorescence of Lemna minor. Chemical analyses of metals using atomic absorption spectrophotometry (AAS) was performed for comparison. Measurements of the total metal concentrations showed that four of five plots near the former lead smelter were highly contaminated with Pb, Cd, and Zn, but the amount of metals in water/soil extracts was low at all the sampling plots. Genotoxicity was demonstrated using T. thermophila for the majority of the extracts, and HepG2 cells for only some of the extracts. Whereas V. fischeri indicated a gradual decrease in soil toxicity with greater distance from the smelter, the toxicity of extracts did not correlate with proximity. Low concentrations of metals in water extracts stimulated L. minor growth. The results indicate that comet assay with T. thermophila and HepG2 cells and the BSPT with V. fischeri are suitable protocols for screening the genotoxic and toxic potential of water/soil extracts by comet assay, whereas chemical analyses of total metal concentrations in soil do not solely suffice for evaluating metal pollution in the environment. Biological assays are thus crucial for risk assessment.

Dietary flavonoid intake and colorectal cancer: a case-control study

Diets rich in flavonoids may reduce the risk of developing colorectal cancer. Flavonoids are widely distributed in foods of plant origin, though in the UK tea is the main dietary source. Our objective was to evaluate any independent associations of total dietary and non-tea intake of four flavonoid subclasses and the risk of developing colorectal cancer in a tea-drinking population with a high colorectal cancer incidence. A population-based case-control study (264 cases with histologically confirmed incident colorectal cancer and 408 controls) was carried out. Dietary data gathered by FFQ were used to calculate flavonoid intake. Adjusted OR and 95 % CI were estimated by logistic regression. No linear association between risk of developing colorectal cancer and total dietary flavonol, procyanidin, flavon-3-ol or flavanone intakes was found, but non-tea flavonol intake was inversely associated with colorectal cancer risk (OR 0.6; 95 % CI 0.4, 1.0). Stratification by site of cancer and assessment of individual flavonols showed a reduced risk of developing colon but not rectal cancer with increasing non-tea quercetin intake (OR 0.5; 95 % CI 0.3, 0.8; P(trend) < 0.01). We concluded that flavonols, specifically quercetin, obtained from non-tea components of the diet may be linked with reduced risk of developing colon cancer.

Quercetin inhibits hydrogen peroxide-induced DNA damage and enhances DNA repair in Caco-2 cells

Flavonoids are known to have antioxidant activity that may limit DNA damage and help prevent degenerative diseases, including cancer. However, our knowledge of flavonoids' role in DNA protection/repair mechanism(s) is limited. This study investigated the effects of quercetin on DNA oxidation and DNA repair in Caco-2 cells with or without oxidant (H2O2) challenge. Quercetin (1, 100 microM) significantly reduced oxidative DNA damage, as measured by the number of single-strand breaks identified by single cell gel electrophoresis. Quercetin treatment also caused a measurable increase in the mRNA expression of human 8-oxoguanine DNA glycosylase (hOGG1) at 0 and 4h after H2O2 treatment (measured using RT-PCR). In addition, the highest level of quercetin tested (100 microM) maintained hOGG1 expression at basal levels or higher for up to 12h after H2O2 treatment, while oxidant treatment alone resulted in significant reduction of hOGG1 at 8h. Our study indicates that quercetin could protect DNA both by reducing oxidative DNA damage and by enhancing DNA repair through modulation of DNA repair enzyme expression.

Myricetin, quercetin, (+)-catechin and (-)-epicatechin protect against N-nitrosamines-induced DNA damage in human hepatoma cells

The aim of this study was to investigate the protective effect of myricetin, quercetin, (+)-catechin and (-)-epicatechin, against N-nitrosodibutylamine (NDBA) and N-nitrosopiperidine (NPIP)-induced DNA damage in human hepatoma cells (HepG2). DNA damage (strand breaks and oxidized purines/pyrimidines) was evaluated by the alkaline single-cell gel electrophoresis or Comet assay. (+)-Catechin at the lowest concentration (10 microM) showed the maximum reduction of DNA strand breaks (23%), the formation of endonuclease III (Endo III, 19-21%) and formamidopyrimidine-DNA glycosylase (Fpg, 28-40%) sensitive sites induced by NDBA or NPIP. (-)-Epicatechin also decreased DNA strand breaks (10 microM, 20%) and the oxidized pyrimidines/purines (33-39%) induced by NDBA or NPIP, respectively. DNA strand breaks induced by NDBA or NPIP were weakly reduced by myricetin at the lowest concentration (0.1 microM, 10-19%, respectively). Myricetin also reduced the oxidized purines (0.1 microM, 17%) and pyrimidines (0.1 microM, 15%) induced by NDBA, but not the oxidized pyrimidines induced by NPIP. Quercetin did not protect against NDBA-induced DNA damage, but it reduced the formation of Endo III and Fpg sensitive sites induced by NPIP (0.1 microM, 17-20%, respectively). In conclusion, our results indicate that (+)-catechin and (-)-epicatechin at the concentrations tested protect human derived cells against oxidative DNA damage effects of NDBA and NPIP. However, myricetin at the concentrations tested only protects human cells against oxidative DNA damage induced by NDBA and quercetin against oxidative DNA damage induced by NPIP.

Cytological and biochemical effects of St. John's Wort supplement (a complex mixture of St. John's Wort, Rosemary and Spirulina) on somatic and germ cells of Swiss Albino mice

Commercially available St. John’s wort supplement (SJWS) composed of an herbal mixture of St. John’s Wort (SJW), Rosemary (RM) and Spirulina (SP) is used as a dietary supplement for the treatment of psychiatric disorders. Although the minor ingredients, (RM and SP) are proven antioxidants, their quantity is quite insignificant as compared to the SJW, which is the major ingredient. Most of the toxic effects of SJWS are attributed to the main constituents of SJW which differ due to the influence of light (hypericin) and variations in temperature above freezing point (hyperforin). However, there are no reports on toxicity of SJWS maintained at room temperature in pharmacies and supermarkets. In view of the folkloric importance, immense (prescribed or unprescribed) use and a paucity of literature on SJWS, it was found worthwhile to (1) determine the genotoxic effects of SJWS in somatic and germ cells of mice and (2) investigate the role of biochemical changes, as a possible mechanism. The protocol included the oral treatment of mice with different doses (380, 760 and 1520 mg/kg/day) of SJWS for 7 days. The following experiments were conducted: (i) cytological studies on micronucleus test, (ii) cytogenetic analysis for meiotic chromosomes, (iii) cytological analysis of spermatozoa abnormalities, (iv) quantification of proteins and nucleic acids in hepatic and testicular cells and (v) estimation of malondialdehyde (MDA) and nonprotein sulfhydryl (NP-SH) in hepatic and testicular cells. The treatment increased the frequency of micronuclei in polychromatic erythrocytes (PCE) in the femora. It caused aberrations in chromosomes of testes and induced spermatozoa abnormalities. These changes might be attributed to the epigenetic mechanisms as revealed by an increase in concentrations of MDA and depletion of nucleic acids and NP-SH levels in both hepatic and testicular cells observed in the present study. Since, the samples of SJWS used were not drawn from extremities of light and temperature; the observed effect might not be related to the main constituents of SJW. However, these changes might be ascribed to the combined effect of terpenes, tannins, quercetin and flavonoids present in SJW.

Does physical exercise modify antioxidant requirements?

Physical training is known to induce a biochemical adaptive response which might require an increase in the ingestion and/or the absorption of micronutrients. A question that is still being raised is whether acute or chronic exercise modifies antioxidant requirements. First, the present review brings to light the most crucial studies on the topic. Second, it interprets the established relationships between antioxidant micronutrient intakes and the adaptive response of antioxidant systems. Finally, it exposes the major questions connected with antioxidant micronutrient requirements for athletes. To this effect, the training-load interaction with nutrition is taken into account. As oxidative stress cannot be avoided, the imbalance between oxidants and antioxidants can be alleviated to minimise oxidative damage and outcomes. There is growing evidence that one specific antioxidant cannot by itself prevent oxidative stress-induced damage, as direct adverse effects of supplementation are attributed to undesirable synergic effects. Other effects can be supposed that limit the endogenous adaptive effect of training. High doses of antioxidant supplements can minimise the effects of radical oxygen species themselves or generate pro-oxidant effects. Effects are only exhibited when nutritional status is deficient. There are no convincing effects of supplementation in well-trained athletes. Risk/benefit analysis emerges on evidence for an unknown risk of supranutritional intakes, a supposed impairment of adaptive effects and a still unknown long-term risk. Appropriate status can be achieved by a diversified and balanced diet, adapted to specific needs, by awareness of high-density food intakes (avoiding products containing a low density of micronutrients).

Phytochemicals as potential chemopreventive and chemotherapeutic agents in hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is the fifth commonest malignancy worldwide and the incidence is rising. Surgery, including transplantation resection, is currently the most effective treatment for HCC; however, recurrence rates are high and long-term survival is poor. Identifying novel chemopreventive and chemotherapeutic agents and targeting them to patients at high risk of developing HCC or following curative treatment may go some way towards improving prognosis. This review examines current knowledge regarding the chemopreventive and chemotherapeutic potential of phytochemicals in heptocarcinogenesis. Both in-vitro and animal studies demonstrate that several phytochemicals, including curcumin, resveratrol, green tea catechins, oltipraz and silibinin, possess promising chemopreventive and chemotherapeutic properties. Despite this, very few clinical trials have been performed. Problems regarding validation of biomarkers, agent delivery, side effects and patient selection are barriers that need to be overcome to determine the potential of such agents in clinical practice.

Human mast cells stimulate activated T cells: implications for multiple sclerosis

Multiple sclerosis is an autoimmune demyelinating disease of the central nervous system mainly mediated by Th1 and/or Th17 cells, which cross the blood-brain barrier. Recent evidence indicates that Th2 cells and mast cells, typically associated with allergic reactions, are also involved. Brain mast cells are critically located perivascularly and secrete numerous proinflammatory and vasoactive molecules that can disrupt the blood-brain barrier, a finding that precedes clinical or pathologic signs of multiple sclerosis. Brain mast cells in multiple sclerosis are activated by neural factors, including substance P, myelin basic protein, and corticotropin-releasing hormone, caused by acute stress, which induce release of several inflammatory mediators. Mast cells can stimulate activated T cells coming in contact with them at the blood-brain barrier, as well as after stimulation with myelin basic protein or substance P. Pretreatment with the flavone luteolin blocks mast cell stimulation and T cell activation, as well as experimental autoimmune encephalitis. Interactions between mast cells and T cells could constitute a new and unique therapeutic target for multiple sclerosis.

Genotoxicity evaluation of water soil leachates by Ames test, comet assay, and preliminary Tradescantia micronucleus assay

Combining genotoxicity/mutagenicity tests and physico-chemical methodologies can be useful for determining the potential genotoxic contaminants in soil samples. The aim of our study was to evaluate the genotoxicity of soil by applying an integrated physico-chemical-biological approach. Soil samples were collected at six sampling points in a Slovenian industrial and agricultural region where contamination by heavy metals and sulphur dioxide (SO(2)) are primarily caused by a nearby power plant. The in vitro alkaline version of the comet assay on water soil leachates was performed with Caco-2 and HepG2 cells. A parallel genotoxicity evaluation of the samples was performed by Ames test using Salmonella typhimurium and the Tradescantia micronucleus test. Pedological analyses, heavy metal content determination, and different physico-chemical analyses, were also performed utilizing standard methodology. Water leachates of soil samples were prepared according to standard methods. Since only a battery of biotests with prokaryotic and eukaryotic organisms or cells can accurately estimate the effects of (geno)toxicants in soil samples and water soil leachates, a combination of three bioassays, with cells or organisms belonging to different trophic levels, was used. Genotoxicity of all six water soil leachates was proven by the comet assay on both human cell lines, however no positive results were detected by bacterial assay, Ames test. The Tradescantia micronucleus assay showed increase in micronuclei formation for three samples. According to these results we can assume that the comet assay was the most sensitive assay, followed by the micronucleus test. The Ames test does not appear to be sensitive enough for water soil leachates genotoxicity evaluations where heavy metal contamination is anticipated.

Antigenotoxic effects of quercetin, rutin and ursolic acid on HepG2 cells: evaluation by the comet assay

In the present study, the chemoprotective effects of quercetin, rutin and ursolic acid on tert-butyl hydroperoxide (t-BHP)-induced DNA damage in a human hepatoma cell line (HepG2) were investigated by the comet assay. To determine whether protection was due to direct chemical interactions alone or to cellular-mediated responses three different types of treatments were used: simultaneous incubation of cells with individual test compounds and the toxicant; pre-treatment with test compound before addition of the toxicant followed or not by a recovery period. The expression of Hsp70 was quantified by Western blotting to test the involvement of heat shock proteins in the cellular responses to the test compounds. In addition, effects on proliferation were evaluated by the MTT assay. The results show that quercetin and ursolic acid prevented DNA damage and had antiproliferative properties in HepG2 cells suggesting an anticarcinogenic potential for these compounds. The protective effects of quercetin against t-BHP-induced DNA damage seem to be due to both direct effects on t-BHP toxicity and to cellularly mediated indirect effects which reflect the potentiation of the cellular antioxidant defenses. Ursolic acid seems to exert effects only through cellularly mediated mechanisms since it was not protective in simultaneous incubation. Quercetin and ursolic acid also showed to increase the rate of DNA repair. Rutin did not have effects at any level. These results, obtained with liver cells, emphasize and confirm the chemopreventive potential of quercetin and ursolic acid, which may help explain the lower cancer incidence in human population with high dietary intakes of fruits and vegetables. These results also demonstrate that Hsp70 is not involved in the observed effects in HepG2.