Assessment of the protective effects of selected dietary anticarcinogens against DNA damage and cytogenetic effects induced by benzo[a]pyrene in C57BL/6J mice

The role of the enzyme-modified comet assay in in vivo studies

The in vivo comet assay is an established genotoxicity test, with an OECD test guideline, but in its standard form it measures only DNA strand breaks. Including in the assay an additional step, in which the DNA is incubated with a lesion-specific enzyme, can provide important information about the nature of the DNA damage. Formamidopyrimidine DNA glycosylase, 8-oxoguanine DNA glycosylase or endonuclease III are commonly used in the in vitro genotoxicity test and in human biomonitoring to detect oxidised bases, but in vivo applications are rarer. A systematic literature search has identified a total of 60 papers that report such in vivo experiments, testing a variety of agents. In many cases, strand breaks were not seen, but significant levels of enzyme-sensitive sites were induced - indicating a mechanism of action involving oxidative stress. Compounds such as methyl methanesulfonate (MMS) or ethyl methanesulfonate (EMS) could be used as positive controls in both the standard and the enzyme-modified in vivo comet assays.

Nano-encapsulated chlorophyllin significantly delays progression of lung cancer both in in vitro and in vivo models through activation of mitochondrial signaling cascades and drug-DNA interaction

Chlorophyllin (CHL), a sodium-copper-salt derived from chlorophyll, has been widely used as a food-dye, also reportedly having some anti-cancer effect. We tested if PLGA-loaded CHL (NCHL) could have additional protective abilities through its faster and targeted drug delivery in cancer cells. Physico-chemical characterization of NCHL was done through atomic-force microscopy and UV-spectroscopy. NCHL demonstrated greater ability of drug uptake and strong anti-cancer potentials in non-small cell lung cancer cells, A549, as revealed from data of% cell viability, generation of reactive-oxygen-species and expression of bax, bcl2, caspase3, p53 and cytochrome c proteins. Circular dichroic spectral data indicated strong binding of NCHL with calf-thymus-DNA, causing a conformational/structural change in DNA. Further, NCHL could cross the blood-brain-barrier in mice and showed greater efficacy in recovery process of tissue damage, reduction in chromosomal aberrations and% of micronuclei in co-mutagens (Sodiumarsenite+Benzo[a]Pyrene)-treated mice at a much reduced dose, indicating its use in therapeutic oncology.

Chemopreventive potential of chlorophyllin: a review of the mechanisms of action and molecular targets

Chlorophyllin (CHL), a water soluble semisynthetic derivative of the ubiquitous plant pigment chlorophyll used as a food additive, is recognized to confer a wide range of health benefits. CHL has been shown to exhibit potent antigenotoxic, anti-oxidant, and anticancer effects. Numerous experimental and epidemiological studies have demonstrated that dietary supple-mentation of CHL lowers the risk of cancer. CHL inhibits cancer initiation and progression by targeting multiple molecules and pathways involved in the metabolism of carcinogens, cell cycle progression, apoptosis evasion, invasion, and angiogenesis. The modulatory effects of CHL on the hallmark capabilities of cancer appear to be mediated via abrogation of key oncogenic signal transduction pathways such as nuclear factor kappa B, Wnt/β-catenin, and phosphatidylinositol-3-kinase/Akt signaling. This review provides insights into the molecular mechanisms of the anticancer effects of dietary CHL.

Normalization of nano-sized TiO2-induced clastogenicity, genotoxicity and mutagenicity by chlorophyllin administration in mice brain, liver, and bone marrow cells

The intensive uses of titanium dioxide (TiO2) nanoparticles in sunscreens, toothpaste, sweats, medications, etc. making humans exposed to it daily by not little amounts and also increased its risks including genotoxicity. Thus, the present study was designed as one way to reduce nano-titanium-induced clastogenicity, genotoxicity, and mutagenicity in mice by co-administration of the free radical scavenger chlorophyllin (CHL). In addition, markers of oxidative stress were detected to shed more light on mechanism(s) underlying nano-sized TiO2 genotoxicity. Male mice were exposed to multiple injection into the abdominal cavity for five consecutive days with either CHL (40 mg/kg bw/day), or each of three dose levels of nano-sized TiO2 (500, 1000, or 2000 mg/kg bw/day) alone, or both simultaneously and sacrificed by cervical dislocation 24 h after the last treatment. After CHL co-administration, the observed dose-dependent genotoxicity of TiO2 nanoparticles indicated by the significant elevations in frequencies of both micronuclei and DNA damage induction was significantly decreased and returned to the negative control level. The observed induced mutations in p53 exons 5, 7, & 8 and 5 & 8 in the liver and brain, respectively, were declined in most cases. Moreover, CHL significantly decreased hepatic malondialdehyde level and significantly increased glutathione level and superoxide dismutase, catalase, and glutathione peroxidase activities that were significantly disrupted in animal groups treated with nano-TiO2 alone. In conclusion, the evidenced in vivo genotoxicity of nano-TiO2 in the present study was normalized after CHL co-administration which supports the previously suggested oxidative stress as the possible mechanism for titanium toxicity.

In vivo exposure to benzo(a)pyrene induces significant DNA damage in mouse oocytes and cumulus cells

STUDY QUESTION

Does in vivo exposure to benzo(a)pyrene (BaP) induce DNA damage in oocytes and cumulus cells (CCs) in mice?

SUMMARY ANSWER

Significant increases in DNA strand breaks in oocytes and CCs and in BaP-induced DNA adducts in CCs were detected in exposed mice compared with controls.

WHAT IS KNOWN ALREADY

BaP has well-known mutagenic and carcinogenic effects on somatic cells, and is also registered as potential reproductive toxicant by several environmental protection agencies. It has been shown to cause a significant increase in DNA adducts in ovarian tissues; however, to our knowledge, the genotoxic effects of BaP on oocytes and CCs have not been studied to date.

STUDY DESIGN, SIZE, DURATION

Female CD1 mice were exposed to BaP via the oral administration of a single dose of 13 mg/kg body weight (bw); matched controls were exposed to the vehicle only (soya oil). A total of 15 groups of 6 mice (exposed or controls) were sacrificed 2, 4, 6, 15 or 22 days after BaP exposure, and after collection of oviducts, the oocyte-CC complexes (COC) were released.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The alkaline comet assay was used to quantify the DNA breaks in oocytes and CCs; DNA damage was expressed as the Olive Tail Moment (OTM). Immunofluorescent staining was used to quantify BaP-induced DNA adducts in CCs. Fluorescence was expressed as the average grey value (AGVA; arbitrary units). The differences between the exposed and control groups were assessed using analysis of variance (ANOVA) and the non-parametric Mann-Whitney test.

MAIN RESULTS AND THE ROLE OF CHANCE

Higher levels of DNA damage were observed in the oocytes and CCs of BaP-exposed mice than in those of vehicle controls. Significant increases in OTM (mean ± SE) were detected in (i) oocytes from females exposed for 4 (10.5 ± 0.9 versus 3.1 ± 0.4, P < 0.0001) or 6 days before collection (15.6 ± 2.0 versus 3.6 ± 0.9, P < 0.0001) and (ii) CCs from females exposed 2 (6.4 ± 0.6 versus 2.1 ± 0.2, P < 0.0001), 4 (7.8 ± 0.4 versus 2.4 ± 0.1, P < 0.0001) or 6 days before collection (7.3 ± 0.3 versus 3.2 ± 0.5, P < 0.0001) compared with controls. A significant increase in benzo(a)pyrene-7,8-9,10 diol epoxide (BPDE)-DNA adducts and higher AGVA (mean ± SE) scores were observed in CCs from females exposed 2 (6.1 ± 0.3 versus 3.6 ± 0.5, P < 0.0001), 4 (7.5 ± 0.1 versus 3.4 ± 0.1, P < 0.0001) or 6 days before collection (11.6 ± 0.4 versus 3.7 ± 0.1, P < 0.0001) compared with control mice.

LIMITATIONS, REASONS FOR CAUTION

Mice were given one treatment via the oral route because this dose and mode of administration have been shown to induce detectable BPDE-DNA adduct levels in mouse organs and sperm cells. Additional data are needed to assess DNA damage in oocytes and CCs after chronic exposure to BaP in vivo.

WIDER IMPLICATIONS OF THE FINDINGS

To our knowledge, this is the first study examining the in vivo genotoxicity of BaP in oocytes and CCs. We observed significant DNA damage in the oocytes and CCs of mice after acute BaP exposure. BPDE-DNA adducts result directly from BaP metabolism while DNA breaks could result mainly from BPDE-DNA adduct excision and repair and/or through direct genotoxicity from increased reactive oxygen species. These results add new and important insights regarding the recently suggested toxicity of chronic BaP exposure in the ovary.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by a grant (93-CPQ 2012-05) from the DIRRECTE, Provence Alpes Côte d'Azur, France. None of the authors have any conflict of interest to declare.

Antigenotoxic properties of chlorophyll b against cisplatin-induced DNA damage and its relationship with distribution of platinum and magnesium in vivo

The chemotherapeutic agent cisplatin (cDDP) is widely used to treat a variety of solid and hematological tumors. However, cDDP exerts severe side effects, such as nephrotoxicity, neurotoxicity, and bone-marrow suppression. The use of some dietary compounds to protect organs that are not targets in association with chemotherapy has been encouraged. This study evaluated the protective effects of chlorophyll b (CLb) on DNA damage induced by cDDP by use of single-cell gel electrophoresis (SCGE) assays. Further, this investigation also determined platinum (Pt) and magnesium (Mg) bioaccumulation in mice tissues after treatment with CLb alone and/or in association of cDDP (simultaneous treatment) by inductively coupled plasma-mass spectroscopy (ICP-MS). All parameters were studied in peripheral blood cells (PBC), kidneys, and liver of mice after administration of CLb (0.2 or 0.5 mg/kg of body weight [b.w.]), cDDP (6 mg/kg b.w.), and the combination CLb 0.2 plus cDDP or CLb 0.5 plus cDDP. Pt accumulation in liver and kidneys was higher than that found in PBC, while DNA damage was higher in kidneys and liver than in PBC. Further, treatment with CLb alone did not induce DNA damage. Evidence indicates that genotoxic effects produced by cDDP may not be related to Pt accumulation and distribution. In combined treatments, CLb decreased DNA damage in tissues, but the PT contents did not change and these treatments also showed that CLb may be an important source of Mg. Thus, our results indicate that consumption of CLb-rich foods may diminish the adverse health effects induced by cDDP exposure.

Benzo[a]pyrene (BP) DNA adduct formation in DNA repair-deficient p53 haploinsufficient [Xpa(-/-)p53(+/-)] and wild-type mice fed BP and BP plus chlorophyllin for 28 days

We have evaluated DNA damage (DNA adduct formation) after feeding benzo[a]pyrene (BP) to wild-type (WT) and cancer-susceptible Xpa(-/-)p53(+/-) mice deficient in nucleotide excision repair and haploinsufficient for the tumor suppressor p53. DNA damage was evaluated by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ES-MS/MS), which measures r7,t8,t9-trihydroxy-c-10-(N (2)-deoxyguanosyl)-7,8,9,10-tetrahydrobenzo[a]pyrene (BPdG), and a chemiluminescence immunoassay (CIA), using anti-r7,t8-dihydroxy-t-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE)-DNA antiserum, which measures both BPdG and the other stable BP-DNA adducts. When mice were fed 100 ppm BP for 28 days, BP-induced DNA damage measured in esophagus, liver and lung was typically higher in Xpa(-/-)p53(+/-) mice, compared with WT mice. This result is consistent with the previously observed tumor susceptibility of Xpa(-/-)p53(+/-) mice. BPdG, the major DNA adduct associated with tumorigenicity, was the primary DNA adduct formed in esophagus (a target tissue in the mouse), whereas total BP-DNA adducts predominated in higher levels in the liver (a non-target tissue in the mouse). In an attempt to lower BP-induced DNA damage, we fed the WT and Xpa(-/-)p53(+/-) mice 0.3% chlorophyllin (CHL) in the BP-containing diet for 28 days. The addition of CHL resulted in an increase of BP-DNA adducts in esophagus, liver and lung of WT mice, a lowering of BPdG in esophagi of WT mice and livers of Xpa(-/-)p53(+/-) mice and an increase of BPdG in livers of WT mice. Therefore, the addition of CHL to a BP-containing diet showed a lack of consistent chemoprotective effect, indicating that oral CHL administration may not reduce PAH-DNA adduct levels consistently in human organs.

Gene expression signature of DMBA-induced hamster buccal pouch carcinomas: modulation by chlorophyllin and ellagic acid

Chlorophyllin (CHL), a water-soluble, semi-synthetic derivative of chlorophyll and ellagic acid (EA), a naturally occurring polyphenolic compound in berries, grapes, and nuts have been reported to exert anticancer effects in various human cancer cell lines and in animal tumour models. The present study was undertaken to examine the mechanism underlying chemoprevention and changes in gene expression pattern induced by dietary supplementation of chlorophyllin and ellagic acid in the 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis model by whole genome profiling using pangenomic microarrays. In hamsters painted with DMBA, the expression of 1,700 genes was found to be altered significantly relative to control. Dietary supplementation of chlorophyllin and ellagic acid modulated the expression profiles of 104 and 37 genes respectively. Microarray analysis also revealed changes in the expression of TGFβ receptors, NF-κB, cyclin D1, and matrix metalloproteinases (MMPs) that may play a crucial role in the transformation of the normal buccal pouch to a malignant phenotype. This gene expression signature was altered on treatment with chlorophyllin and ellagic acid. Our study has also revealed patterns of gene expression signature specific for chlorophyllin and ellagic acid exposure. Thus dietary chlorophyllin and ellagic acid that can reverse gene expression signature associated with carcinogenesis are novel candidates for cancer prevention and therapy.

Protective effect of ellagic acid (EA) on micronucleus formation induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in mammalian cells, in in vitro assays and in vivo

The beneficial effects of fruits and vegetables with respect to age-related diseases such as diabetes, atherosclerosis and several types of cancer are widely recognized and confirmed by several epidemiological studies. A possible approach for evaluating the protective potential of promising diet constituents is to evaluate their beneficial effect with respect to a set of biomarkers that are indicative of a potential risk for developing degenerative diseases. Among the numerous biomarkers of the effect of food-related carcinogens and for the assessment of the degree of risk for disease, chromosomal damage detection is very predictive. The aim of this study was to test antigenotoxic effect of ellagic acid (EA) both in in vitro and in vivo studies, in combination with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a methylating agent. EA, a naturally occurring and widely distributed plant phenol, has been intensively studied but with conflicting results, depending on the endpoints considered and the experimental material employed. In vitro and in vivo studies differ in their experimental schedule: in the in vitro study pre- and post-treatments and simultaneous treatments with EA were performed, while in the in vivo study only pre-treatment was carried out. The results of this study clearly demonstrate a protective action of EA with respect to MNNG-induced micronuclei and cell proliferation both in vitro and in vivo. The lack of effect in the post-treatment in in vitro experiments excludes a possible effect of EA on DNA-repair systems. On the other hand, consumption of EA can have a protective action against primary DNA damage induced by oxidative stress.

Dietary chlorophyllin inhibits the canonical NF-κB signaling pathway and induces intrinsic apoptosis in a hamster model of oral oncogenesis

Chlorophyllin, a water-soluble, semi-synthetic derivative of the ubiquitous green pigment chlorophyll is shown to exert potent anticarcinogenic effects. In the present study, we investigated the chemopreventive effects of chlorophyllin on 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis by analyzing the expression of NF-κB family members and markers of intrinsic apoptosis. Dietary administration of chlorophyllin (4 mg/kg bw) suppressed the development of HBP carcinomas by inhibiting the canonical NF-κB signaling pathway by downregulating IKKβ, preventing the phosphorylation of IκB-α, and reducing the expression of nuclear NF-κB. Inactivation of NF-κB signaling by chlorophyllin was associated with the induction of intrinsic apoptosis as evidenced by modulation of Bcl-2 family proteins, enforced nuclear localization of survivin, upregulation of apoptogenic molecules, activation of caspases, and cleavage of PARP. The results of the present study demonstrate that chlorophyllin inhibits the development of DMBA-induced HBP carcinogenesis by targeting NF-κB and the intrinsic apoptotic pathway. Thus, dietary agents such as chlorophyllin that simultaneously target divergent pathways of cell survival and cell death are novel candidates for cancer chemoprevention.