Polyphenols as possible bioprotectors against cytotoxicity and DNA damage induced by ochratoxin A

Antioxidative and Anticancer Potential of Luteolin: A Comprehensive Approach Against Wide Range of Human Malignancies

Luteolin is widely distributed phytochemical, a flavonoid, in kingdom plantae. Luteolin with potential antioxidant activity prevent ROS-induced damages and reduce oxidative stress which is mainly responsible in pathogenesis of many diseases. Several chemo preventive activities and therapeutic benefits are associated with luteolin. Luteolin prevents cancer via modulation of numerous pathways, that is, by inactivating proteins; such as procaspase-9, CDC2 and cyclin B or upregulation of caspase-9 and caspase-3, cytochrome C, cyclin A, CDK2, and APAF-1, in turn inducing cell cycle arrest as well as apoptosis. It also enhances phosphorylation of p53 and expression level of p53-targeted downstream gene. By Increasing BAX protein expression; decreasing VEGF and Bcl-2 expression it can initiate cell cycle arrest and apoptosis. Luteolin can stimulate mitochondrial-modulated functions to cause cellular death. It can also reduce expression levels of p-Akt, p-EGFR, p-Erk1/2, and p-STAT3. Luteolin plays positive role against cardiovascular disorders by improving cardiac function, decreasing the release of inflammatory cytokines and cardiac enzymes, prevention of cardiac fibrosis and hypertrophy; enhances level of CTGF, TGFβ1, ANP, Nox2, Nox4 gene expressions. Meanwhile suppresses TGFβ1 expression and phosphorylation of JNK. Luteolin helps fight diabetes via inhibition of alpha-glucosidase and ChE activity. It can reduce activity levels of catalase, superoxide dismutase, and GS4. It can improve blood glucose, insulin, HOMA-IR, and HbA1c levels. This review is an attempt to elaborate molecular targets of luteolin and its role in modulating irregularities in cellular pathways to overcome severe outcomes during diseases including cancer, cardiovascular disorders, diabetes, obesity, inflammation, Alzheimer's disease, Parkinson's disease, hepatic disorders, renal disorders, brain injury, and asthma. As luteolin has enormous therapeutic benefits, it could be a potential candidate in future drug development strategies.

Involvement of multiple epigenetic mechanisms by altered DNA methylation from the early stage of renal carcinogenesis before proliferative lesion formation upon repeated administration of ochratoxin A

Ochratoxin A (OTA) is a rat renal carcinogen that induces karyomegaly and micronuclei in proximal tubular epithelial cells (PTECs). We previously performed comprehensive gene profiling of alterations in promoter-region methylation and gene expression in PTECs of rats treated with OTA for 13 weeks. The OTA-specific gene profile was obtained by excluding genes showing expression changes similar to those upon treatment with 3-chloro-1,2-propanediol, a renal carcinogen not inducing karyomegaly. In this study, we validated the candidate genes using methylated DNA enrichment PCR and real-time RT-PCR, and identified Gen1, Anxa3, Cdkn1a, and Osm as genes showing OTA-specific epigenetic changes. These genes and related molecules were subjected to gene expression and immunohistochemical analyses in the PTECs of rats treated with OTA, other renal carcinogens, or non-carcinogenic renal toxicants for 4 or 13 weeks. Cdkn1a upregulation and increase of p21WAF1/CIP1+ karyomegalic PTECs were observed with OTA, matching the findings associated with micronucleus-inducing carcinogens. This suggested that the increase of p21WAF1/CIP1+ karyomegalic PTECs is linked to micronucleus formation, which in turn accelerates chromosomal instability. The upregulation of Cdkn1a-related genes with OTA suggests the acquisition of a senescence-associated secretory phenotype, which promotes the establishment of a carcinogenic environment. Meanwhile, OTA specifically caused a decrease of GEN1+ PTECs reflecting Gen1 downregulation and an increase of ANXA3+ PTECs reflecting Anxa3 upregulation, as well as Osm upregulation. OTA may efficiently disrupt pathways for repairing the DNA double-strand breaks that it itself causes, via Gen1 downregulation, and enhance cell proliferation through the upregulation of Anxa3 and Osm. This may exacerbate the chromosomal instability from the early stage of OTA-induced renal carcinogenesis before proliferative lesions form. OTA may cause renal carcinogenesis involving multiple epigenetic mechanisms.

The Novel Role of the NLRP3 Inflammasome in Mycotoxin-Induced Toxicological Mechanisms

Mycotoxins are secondary metabolites produced by several fungi and moulds that exert toxicological effects on animals including immunotoxicity, genotoxicity, hepatotoxicity, teratogenicity, and neurotoxicity. However, the toxicological mechanisms of mycotoxins are complex and unclear. The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome is a multimeric cytosolic protein complex composed of the NLRP3 sensor, ASC adapter protein, and caspase-1 effector. Activation of the NLRP3 inflammasome plays a crucial role in innate immune defence and homeostatic maintenance. Recent studies have revealed that NLRP3 inflammasome activation is linked to tissue damage and inflammation induced by mycotoxin exposure. Thus, this review summarises the latest advancements in research on the roles of NLRP3 inflammasome activation in the pathogenesis of mycotoxin exposure. The effects of exposure to multiple mycotoxins, including deoxynivalenol, aflatoxin B1, zearalenone, T-2 toxin, ochratoxin A, and fumonisim B1, on pyroptosis-related factors and inflammation-related factors in vitro and in vivo and the pharmacological inhibition of specific and nonspecific NLRP3 inhibitors are summarized and examined. This comprehensive review contributes to a better understanding of the role of the NLRP3 inflammasome in toxicity induced by mycotoxin exposure and provides novel insights for pharmacologically targeting NLRP3 as a novel anti-inflammatory agent against mycotoxin exposure.

Revisiting luteolin: An updated review on its anticancer potential

Numerous natural products found in our diet, such as polyphenols and flavonoids, can prevent the progression of cancer. Luteolin, a natural flavone, present in significant amounts in various fruits and vegetables plays a key role as a chemopreventive agent in treating various types of cancer. By inducing apoptosis, initiating cell cycle arrest, and decreasing angiogenesis, metastasis, and cell proliferation, luteolin is used to treat cancer. Its anticancer properties are attributed to its capability to engage with multiple molecular targeted sites and modify various signaling pathways in tumor cells. Luteolin has been shown to slow the spread of cancer in breast, colorectal, lung, prostate, liver, skin, pancreatic, oral, and gastric cancer models. It exhibits antioxidant properties and can be given to patients receiving Doxorubicin (DOX) chemotherapy to prevent the development of unexpected adverse reactions in the lungs and hematopoietic system subjected to DOX. Furthermore, it could be an excellent candidate for synergistic studies to overcome drug resistance in cancer cells. Accordingly, this review covers the recent literature related to the use of luteolin against different types of cancer, along with the mechanisms of action. In addition, the review highlights luteolin as a complementary medicine for preventing and treating cancer.

In vitro and in vivo induction of ochratoxin A exposure-related micronucleus formation in rat proximal tubular epithelial cells and expression profiling of chromosomal instability-related genes

Ochratoxin A (OTA) is a renal carcinogen in rats, and repeated administration induces karyomegaly in proximal tubular epithelial cells (PTECs) of the outer stripe of the outer medulla (OSOM) before inducing proliferative lesions. To investigate whether OTA induces micronuclei (MN) in PTECs, we performed an in vitro MN assay using rat renal NRK-52E PTECs after treatment for ≤21 days, and an in vivo OSOM MN assay in rats treated with OTA, other renal carcinogens, or non-carcinogenic renal toxicants for 4 or 13 weeks. The in vitro assay revealed an increased frequency of micronucleated cells from the acceptable dose level for cell viability, even after 21 days of treatment. The in vivo assay also revealed a dose- and treatment period-dependent increase in PTECs with γ-H2AX+ MN. OTA-specific gene expression profiling by OSOM RNA sequencing after week 13 revealed the altered expression of genes related to microtubule-kinetochore binding, the kinesin superfamily, centriole assembly, DNA damage repair, and cell cycle regulation. MN formation was also observed with other renal carcinogens that induce karyomegaly similarly to OTA. These results imply that γ-H2AX+ MN formation by OTA treatment is related to the induction of chromosomal instability accompanying karyomegaly formation before proliferative lesions form, providing a new insight into the carcinogenic mechanism that may be relevant to humans.

Recent Updates on Source, Biosynthesis, and Therapeutic Potential of Natural Flavonoid Luteolin: A Review

Nature gives immense resources that are beneficial to humankind. The natural compounds present in plants provide primary nutritional values to our diet. Apart from food, plants also provide chemical compounds with therapeutic values. The importance of these plant secondary metabolites is increasing due to more studies revealing their beneficial properties in treating and managing various diseases and their symptoms. Among them, flavonoids are crucial secondary metabolite compounds present in most plants. Of the reported 8000 flavonoid compounds, luteolin is an essential dietary compound. This review discusses the source of the essential flavonoid luteolin in various plants and its biosynthesis. Furthermore, the potential health benefits of luteolins such as anti-cancer, anti-microbial, anti-inflammatory, antioxidant, and anti-diabetic effects and their mechanisms are discussed in detail. The activity of luteolin and its derivatives are diverse, as they help to prevent and control many diseases and their life-threatening effects. This review will enhance the knowledge and recent findings regarding luteolin and its therapeutic effects, which are certainly useful in potentially utilizing this natural metabolite.

A review of the protective effects of chlorogenic acid against different chemicals

Chlorogenic acid (CGA) is a naturally occurring non-flavonoid polyphenol found in green coffee beans, teas, certain fruits, and vegetables, that exerts antiviral, antitumor, antibacterial, and antioxidant effects. Several in vivo and in vitro studies have demonstrated that CGA can protect against toxicities induced by chemicals of different classes such as fungal/bacterial toxins, pharmaceuticals, metals, pesticides, etc., by preservation of cell survival via reducing overproduction of nitric oxide and reactive oxygen species and suppressed pro-apoptotic signaling. CGA antioxidant effects mediated through the Nrf2-heme oxygenase-1 signaling pathway were shown to enhance the levels of antioxidant enzymes such as superoxide dismutase, catalase, glutathione-S-transferases, glutathione peroxidase, and glutathione reductase as well as glutathione content. Also, CGA could suppress inflammation via inhibition of toll-like receptor 4 and MyD88, and the phosphorylation of inhibitor of kappa B and p65 subunit of NF-κB, resulting in diminished levels of downstream inflammatory factors including interleukin (IL)-1 β, IL-6, tumor necrosis factor-α, macrophage inflammatory protein 2, cyclooxygenase-2, and prostaglandin E2. Moreover, CGA inhibited apoptosis by reducing Bax, cytochrome C, and caspase 3 and 9 expression while increasing Bcl-2 levels. The present review discusses several mechanisms through which CGA may exert its protective role against such agents. Chemical and natural toxic agents affect human health. Phenolic antioxidant compounds can suppress free radical production and combat these toxins. Chlorogenic acid is a plant polyphenol present in the human diet and exerts strong antioxidant properties that can effectively help in the treatment of various toxicities.

Limonene from Agastache mexicana essential oil produces antinociceptive effects, gastrointestinal protection and improves experimental ulcerative colitis

ETHNOPHARMACOLOGY RELEVANCE

Agastache mexicana is a popular plant of great demand in folk medicine, essentially due to its calming properties and for alleviating arthritic, muscular and abdominal pain. Despite its spectrum for pain relief, pharmacological studies of its bioactive constituents have been barely investigated.

AIM OF THE STUDY

To evaluate protective properties of the A. mexicana and bioactive compounds improving pathological gastrointestinal conditions in rodents.

MATERIAL AND METHODS

Different doses of the essential oil of A. mexicana ssp. mexicana and ssp. xolocotziana (30-562.2 mg/kg, i.p.) and individual monoterpenes (3-300 mg/kg, i.p.) were evaluated in an abdominal pain model. The most active monoterpene limonene and sulfasalazine (reference drug, 100 mg/kg, p.o.) were also evaluated in the oxazolone-induced colitis model using an oral gavage, where some inflammatory cytokines were analyzed by enzyme-linked immunosorbent assays. Finally, colonic histological assessment and gastroprotection in the absolute ethanol-induced ulcer model were explored.

RESULTS

Our results demonstrated that the essential oil of both subspecies produced a significant reduction in the abdominal writhes, where monoterpenes limonene and pulegone were partially responsible bioactive metabolites. Limonene showed the major antinociceptive efficacy in the writhing test. It also significantly decreased hyperalgesia, pathological biomarkers, and colonic inflammatory cytokines in the oxazolone-induced colitis model, as well as prevention in gastric damage.

CONCLUSIONS

Present results provide scientific evidence to reinforce the use of A. mexicana in the traditional medicine for gastrointestinal conditions, mainly related to pain and inflammation, demonstrating the potential of monoterpenes as natural products in the therapeutics of gastrointestinal affections such as ulcer, colitis, and abdominal pain.

Preventive effects of the antioxidant and antigenotoxic Achyrocline satureioides extract against zearalenone-induced mammal cytogenotoxicity and histological damage

Zearalenone (ZEN), a Fusarium’s mycotoxin, is immunotoxic, genotoxic, hepatonephrotoxic and, affects the reproductive system. ZEN induces toxic and genotoxic effects on humans and other animals. Achyrocline satureioides has several medicinal properties. Moreover, the aqueous extract of A. satureioides is a safe agent that exerts low cytotoxicity and no genotoxicity. This extract is a promissory candidate to counteract ZEN effects. The present study aimed to investigate the capacity of cold aqueous extract from A. satureioides to protect against ZEN multi-target toxicity in different experimental mammal models. Anticytotoxicity was evaluated by neutral red uptake and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium reduction assays. Comet assay and micronuclei test, oxidative stress (TBARs), and histopathological damage were evaluated in Balb/C mice. Anticytotoxic studies indicated that cold aqueous extract (100 and 300 μg/ml) protected from damage induced by ZEN (50 μg/ml) on Vero cells. In vivo studies indicated that ZEN (40 mg/kg body weight) induced an increase of genotoxicity: micronuclei (34 MNPCE/1000 PCE) and increase of damage (tail moment) in blood cells. Also, it increased lipid peroxidation in liver and kidneys and generated several histopathological alterations in both organs. Cold aqueous extract (100 mg/kg body weight) protected from genotoxicity induced by ZEN in both tests. Cold aqueous extract, also, reduced the lipid peroxidation and histopathological damage in liver and kidneys. In conclusion, the cold aqueous extract of A. satureioides that contains bioactive flavonoids prevents the multi-target toxicity induced by ZEN improving all the parameters evaluated in vitro and in vivo, which is a valuable and original finding in order to develop future treatments for human and veterinary medicine.

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

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

Evaluation of the genotoxic and antigenotoxic potential of lignin-derivative BP-C2 in the comet assay in vivo

The genotoxic and antigenotoxic potential of BP-C2, a novel lignin-derived polyphenolic composition with ammonium molybdate, was investigated as a radioprotector/radiomitigator for civil applications and as a medical countermeasure for radiation emergencies. Using the alkaline comet assay and methyl methanesulfonate (MMS, 40 mg/kg) as the DNA-damaging agent, these effects of BP-C2 on liver, bone marrow cells and blood leukocytes in rats were studied. The DNA damage was estimated by the DNA content in the comet tail (TDNA, %) 1, 6 and 18 h post exposure to MMS. BP-C2 at doses of 20, 200 and 2000 mg/kg did not exert genotoxic activity in the tested tissues in rats. BP-C2 administered at doses of 20, 100 and 200 mg/kg 1 h before MMS significantly (p < 0.01) mitigated MMS-induced DNA damage, showing a strong genoprotective effect in the liver. In blood leukocytes and bone marrow samples of animals treated with BP-C2, the TDNA % was slightly higher than in the negative control (vehicle) but significantly lower than in the positive control (MMS). Thus, BP-C2 exerted a genoprotective effect against MMS-induced DNA damage to a greater extent towards liver cells, requiring further evaluation of this substance as a genoprotective agent.

Ochratoxin A-induced genotoxic and epigenetic mechanisms lead to Alzheimer disease: its modulation with strategies

Ochratoxin A (OTA) is a naturally occurring mycotoxin mostly found in food items including grains and coffee beans. It induces DNA single-strand breaks and has been considered to be carcinogenic. It is recognized as a serious threat to reproductive health both in males and females. OTA is highly nephrotoxic and carcinogenic, and its potency changes evidently between species and sexes. There is a close association between OTA, mutagenicity, carcinogenicity, and genotoxicity, but the underlying mechanisms are not clear. Reports regarding genotoxic effects in relation to OTA which leads to the induction of DNA adduct formation, protein synthesis inhibition, perturbation of cellular energy production, initiation of oxidative stress, induction of apoptosis, influences on mitosis, induction of cell cycle arrest, and interference with cytokine pathways. All these mechanisms are associated with nephrotoxicity, hepatotoxicity, teratotoxicity, immunological toxicity, and neurotoxicity. OTA administration activates various mechanisms such as p38 MAPK, JNKs, and ERKs dysfunctions, BDNF disruption, TH overexpression, caspase-3 and 9 activation, and ERK-1/2 phosphorylation which ultimately lead to Alzheimer disease (AD) progression. The current review will focus on OTA in terms of recent discoveries in the field of molecular biology. The main aim is to investigate the underlying mechanisms of OTA in regard to genotoxicity and epigenetic modulations that lead to AD. Also, we will highlight the strategies for the purpose of attenuating the hazards posed by OTA exposure.

Genotoxic effects of mycotoxins

Fungi produce mycotoxins in the presence of appropriate temperature, humidity, sufficient nutrients and if the density of the mushroom mass is favorable. Although all mycotoxins are of fungal origin, all toxic compounds produced by fungi are not called mycotoxins. The interest in mycotoxins first started in the 1960s, and today the interest in mycotoxin-induced diseases has increased. To date, 400 mycotoxins have been identified and the most important species producing mycotoxins belongs to Aspergillus, Penicillium, Alternaria and Fusarium genera. Mycotoxins are classified as hepatotoxins, nephrotoxins, neurotoxins, immunotoxins etc. In this review genotoxic and also other health effects of some major mycotoxin groups like Aflatoxins, Ochratoxins, Patulin, Fumonisins, Zearalenone, Trichothecenes and Ergot alkaloids were deeply analyzed.

Risk assessment of ochratoxin A in food

The European Commission asked EFSA to update their 2006 opinion on ochratoxin A (OTA) in food. OTA is produced by fungi of the genus Aspergillus and Penicillium and found as a contaminant in various foods. OTA causes kidney toxicity in different animal species and kidney tumours in rodents. OTA is genotoxic both in vitro and in vivo; however, the mechanisms of genotoxicity are unclear. Direct and indirect genotoxic and non-genotoxic modes of action might each contribute to tumour formation. Since recent studies have raised uncertainty regarding the mode of action for kidney carcinogenicity, it is inappropriate to establish a health-based guidance value (HBGV) and a margin of exposure (MOE) approach was applied. For the characterisation of non-neoplastic effects, a BMDL 10 of 4.73 μg/kg body weight (bw) per day was calculated from kidney lesions observed in pigs. For characterisation of neoplastic effects, a BMDL 10 of 14.5 μg/kg bw per day was calculated from kidney tumours seen in rats. The estimation of chronic dietary exposure resulted in mean and 95th percentile levels ranging from 0.6 to 17.8 and from 2.4 to 51.7 ng/kg bw per day, respectively. Median OTA exposures in breastfed infants ranged from 1.7 to 2.6 ng/kg bw per day, 95th percentile exposures from 5.6 to 8.5 ng/kg bw per day in average/high breast milk consuming infants, respectively. Comparison of exposures with the BMDL 10 based on the non-neoplastic endpoint resulted in MOEs of more than 200 in most consumer groups, indicating a low health concern with the exception of MOEs for high consumers in the younger age groups, indicating a possible health concern. When compared with the BMDL 10 based on the neoplastic endpoint, MOEs were lower than 10,000 for almost all exposure scenarios, including breastfed infants. This would indicate a possible health concern if genotoxicity is direct. Uncertainty in this assessment is high and risk may be overestimated.

Kaempferol derivatives isolated from Lens culinaris Medik. reduce DNA damage induced by etoposide in peripheral blood mononuclear cells

Bioactive compounds isolated from plants are considered to be attractive candidates for cancer therapy. In this study, we examined the effect of kaempferol, its derivatives, the polyphenol fraction (PF) and an extract (EX) isolated from the aerial parts of Lens culinaris Medik. on DNA damage induced by etoposide in human cells. We also studied the effect of these compounds and their combinations on cell viability. The studies were conducted on HL-60 cells and human peripheral blood mononuclear cells (PBMCs). We used the comet assay in the alkaline version to evaluate DNA damage. To examine cell viability we applied the trypan blue exclusion assay. We demonstrated that kaempferol glycoside derivatives isolated from the aerial parts of Lens culinaris Medik. reduce DNA damage induced by etoposide in PBMCs, but do not have an impact on DNA damage in HL-60 cells. We also showed that kaempferol induces DNA damage in HL-60 cells and leads to an increase of DNA damage provoked by etoposide. Our data suggest that kaempferol derivatives can be further explored as a potential agent protecting normal cells against DNA damage induced by etoposide. Moreover, kaempferol's ability to induce DNA damage in cancer cells and to increase DNA damage caused by etoposide may be useful in designing and improving anticancer therapies.

Baicalein Inhibits Stx1 and 2 of EHE: Effects of Baicalein on the Cytotoxicity, Production, and Secretion of Shiga Toxins of Enterohaemorrhagic Escherichia coli

Shiga toxin-producing enterohaemorrhagic Escherichia coli (EHEC) O157:H7 is an important foodborne pathogen. Baicalein (5,6,7-trihydroxylflavone), a flavone isolated from the roots of Scutellaria baicalensis, is considered as a potential antibacterial agent to control foodborne pathogens. Among seven compounds selected by in silico screening of the natural compound database, baicalein inhibited the cytotoxicity of both Shiga toxins 1 and 2 (Stx1 and Stx2) against Vero cells after pretreatment at 0.13 mmol/L. In addition, baicalein reduced the susceptibility of Vero cells to both Stx1 and Stx2. Real-time qPCR showed that baicalein increased transcription of stx1 but not of stx2. However, baicalein had no effects on production or secretion of Stx1 or Stx2. Docking models suggested that baicalein formed a stable structure with StxB pentamer with low intramolecular energy. The results demonstrate that inhibitory activity of baicalein against the cytotoxicity of both Stx1 and Stx2 might be due to of the formation of a binding structure inside the pocket of the Stx1B and Stx2B pentamers.

Protective effects of phenolic acids on mercury-induced DNA damage in precision-cut kidney slices

Objective(s):

Precision-cut tissue slices are considered an organotypic 3D model widely used in biomedical research. The comet assay is an important screening test for early genotoxicity risk assessment that is mainly applied on in vitro models. The aim of the present study was to provide a 3D organ system for determination of genotoxicity using a modified method of the comet assay since the stromal components from the original tissue make this technique complicated.

Materials and Methods:

A modified comet assay technique was validated using precision-cut hamster kidney slices to analyze the antigenotoxic effect of the phenolic compounds caffeic acid, chlorogenic acid, and rosmarinic acid in tissue slices incubated with 15 µM HgCl₂. Cytotoxicity of the phenolic compounds was studied in Vero cells, and by morphologic analysis in tissue slices co-incubated with HgCl₂ and phenolic compounds.

Results:

A modification of the comet assay allows obtaining better and clear comet profiles for analysis. Non-cytotoxic concentrations of phenolic acids protected kidney tissue slices against mercury-induced DNA damage, and at the same time, were not nephrotoxic. The highest protection was provided by 3 µg/ml caffeic acid, although 6 µg/ml rosmarinic and 9 µg/ml chlorogenic acids also exhibited protective effects.

Conclusion:

This is the first time that a modification of the comet assay technique is reported as a tool to visualize the comets from kidney tissue slices in a clear and simple way. The phenolic compounds tested in this study provided protection against mercury-induced genotoxic damage in precision-cut kidney slices.

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.

Ochratoxin A activates neutrophils and kills these cells through necrosis, an effect eliminated through its conversion into ochratoxin α

Ochratoxin A (OTA) is a mycotoxin produced by several species of fungi from the Aspergillus and Penicillium genera that frequently grow in improperly stored food products. OTA has carcinogenic, teratogenic and nephrotoxic potential and sustains a high half-life in human blood. Despite the recently efforts to decontaminate OTA through its conversion into its metabolite ochratoxin alpha (OTα), there are just a few reports in literature comparing the toxic effects of these toxins. Thus, herein we studied and compared the proinflammatory and toxicological effects of OTA and its metabolite OTα in human neutrophils in vitro. The effect of OTA and OTα on human neutrophils viability was evaluated by trypan blue, annexin-V and propidium iodide methods as well as by the analysis of cytomorphological alterations. The ATP levels were also evaluated using the luciferin-luciferase bioluminescence assay. The alteration on mitochondrial potential was assessed by a mitoscreen flow cytometry mitochondrial membrane potential detection kit and the intracellular calcium levels through the probe FLUO-4/AM. To study the human neutrophils' oxidative burst, the fluorescent probe dichlorodihydrofluorescein diacetate was used. OTA induced an increase on the intracellular calcium, human neutrophils' oxidative burst followed by depletion of ATP levels and alterations on mitochondrial potential leading to cell death by necrosis, while OTα did not induce significant toxic effects. Our results strongly suggest that the toxicity in human neutrophils induced by OTA started with the release of calcium from internal stores triggering several neutrophils' activities that culminate in cell death by necrosis.

Evaluation of renal in vitro models used in ochratoxin research

Ochratoxin A (OTA) induces renal carcinomas in rodents with a specific localisation in the S3 segment of proximal tubules and distinct early severe tissue alterations, which have been observed also in other species. Pronounced species- and sex-specific differences in toxicity occur and similar effects cannot be excluded in humans, however precise mechanism(s) remain elusive until today. In such cases, the use of in vitro models for mechanistic investigations can be very useful; in particular if a non-genotoxic mechanism of cancer formation is assumed which include cytotoxic effects. However, potential genotoxic mechanisms can also be investigated in vitro. A crucial issue of in vitro research is the choice of the appropriate cell model. Apparently, the cellular target of OTA is the renal proximal tubular cell; therefore cells from this tissue area are the most reasonable model. Furthermore, cells from affected species should be used and can be compared to cells of human origin. Another important parameter is whether to use primary cultures or to choose a cell line from the huge variety of cell lines available. In any case, important characteristics and quality controls need to be verified beforehand. Therefore, this review discusses the renal in vitro models that have been used for the investigation of renal ochratoxin toxicity. In particular, we discuss the choice of the models and the essential parameters making them suitable models for ochratoxin research together with exemplary results from this research. Furthermore, new promising models such as hTERT-immortalised cells and 3D-cultures are briefly discussed.

Ochratoxin A: Molecular Interactions, Mechanisms of Toxicity and Prevention at the Molecular Level

Ochratoxin A (OTA) is a widely-spread mycotoxin all over the world causing major health risks. The focus of the present review is on the molecular and cellular interactions of OTA. In order to get better insight into the mechanism of its toxicity and on the several attempts made for prevention or attenuation of its toxic action, a detailed description is given on chemistry and toxicokinetics of this mycotoxin. The mode of action of OTA is not clearly understood yet, and seems to be very complex. Inhibition of protein synthesis and energy production, induction of oxidative stress, DNA adduct formation, as well as apoptosis/necrosis and cell cycle arrest are possibly involved in its toxic action. Since OTA binds very strongly to human and animal albumin, a major emphasis is done regarding OTA-albumin interaction. Displacement of OTA from albumin by drugs and by natural flavonoids are discussed in detail, hypothesizing their potentially beneficial effect in order to prevent or attenuate the OTA-induced toxic consequences.

Phenolic acid protects of renal damage induced by ochratoxin A in a 28-days-oral treatment in rats

The present study aimed to characterize the chlorogenic acid (ChlA) capacity to reverse the toxic effects induced by ochratoxin A (OTA) in a subacute toxicity test in rats. Male Wistar rats were fed orally by gavage for 28 days with OTA (0.4mg/kg bw/day), ChlA (5mg/kg bw/day) or the combination OTA (0.4mg/kg bw/day)+ChlA (5mg/kg bw/day). No deaths, no decrease in feed intake or body weight in any experimental group were recorded. The negative control group and the animals treated with ChlA alone showed no changes in any parameters evaluated. In OTA-treated group significant changes such as decrease in urine volume, proteinuria, occult blood, increase in serum creatinine values; decrease in absolute and relative kidney weight and characteristics histopathological lesions that indicated kidney damage were observed. However, limited effect on oxidative stress parameters were detected in kidneys of OTA-treated group. Animals treated with the combination OTA+ChlA were showed as negative control group in the evaluation of several parameters of toxicity. In conclusion, ChlA, at given concentration, improved biochemical parameters altered in urine and serum and pathological damages in kidneys induced by OTA exposure, showing a good protective activity, but not by an apparent antioxidant mechanism.

Ochratoxin A at low concentrations inhibits in vitro growth of canine umbilical cord matrix mesenchymal stem cells through oxidative chromatin and DNA damage

Ochratoxin A (OTA) exposure during pregnancy in laboratory animals induces delayed/abnormal embryo development. Foetal adnexa-derived mesenchymal stem cells (MSCs) could help evaluate the developmental risk of exposure to chemicals in advanced gestational age. We tested the effects of OTA at concentrations ranging from 2.5×10(-4) to 25nM on growth parameters of canine umbilical cord matrix (UCM)-derived MSCs. The hypothesis that oxidative chromatin and DNA damage could underlie OTA-mediated cell toxicity was also investigated. After in vitro exposure, OTA significantly decreased cell density and increased doubling time in a passage- and concentration-dependent manner and no exposed cells survived beyond passage 5. Significantly higher rates of cells showed condensed and fragmented chromatin and oxidized DNA, as assessed by OxyDNA assay. These findings showed that in vitro exposure to OTA, at picomolar levels, perturbs UCM-MSC growth parameters through oxidative chromatin and DNA damage, suggesting possible consequences on canine foetal development.