Inhibition of spontaneous mutagenesis by vanillin and cinnamaldehyde in Escherichia coli: Dependence on recombinational repair

Vanillin serves as a potential substitute for chemical chelator desferal in iron-overloaded mice

PURPOSE

Iron toxicity occurs under iron-overloaded settings, such as a high iron diet and blood transfusion, and damages important organs. Vanillin has been proven to have potential iron chelation capability. Given the negative effects of commonly used iron chelators like deferoxamine (DFO), we sought to examine the iron chelation potency of vanillin and evaluate its potential effect in the treatment of iron overload-related disorders.

METHODS

42 male NMRI mice were prepared for this purpose, and except for the negative control group, iron overload conditions were generated in them by injecting iron. Then normal saline (as a control), vanillin, and DFO (n = 7) were subsequently given to iron-overloaded mice. In the following, the activity of antioxidant enzymes catalase and superoxide dismutase were measured in the blood serum, brain, kidney, spleen, lung, and liver tissues of mice. Furthermore, the level of lipid peroxidation was determined by measuring the amount of malondialdehyde. Also, Perl's and H&E staining were used to examine the physiopathology changes of tissues.

FINDINGS

Vanillin, a natural antioxidant compound, outperformed deferoxamine, a chemical iron chelator. Along with a decrease in iron content, the activity of catalase and superoxide dismutase enhanced in the iron-overloaded groups that were treated with vanillin. The level of lipid peroxidation was also declined in the iron-overloaded mice receiving vanillin.

CONCLUSION

Vanillin can be used as a suitable substitute for chemical chelators with fewer side effects and equivalent efficiency. We encourage the use of this compound as a natural iron chelator following performing additional safety and efficacy studies.

Vanillin modulates activities linked to dysmetabolism in psoas muscle of diabetic rats

Skeletal muscles are important in glucose metabolism and are affected in type 2 diabetes (T2D) and its complications. This study investigated the effect of vanillin on redox imbalance, cholinergic and purinergic dysfunction, and glucose-lipid dysmetabolism in muscles of rats with T2D. Male albino rats (Sprague-Dawley strain) were fed 10% fructose ad libitum for 2 weeks before intraperitoneally injecting them with 40 mg/kg streptozotocin to induce T2D. Low (150 mg/kg bodyweight (BW)) and high (300 mg/kg BW) doses of vanillin were orally administered to diabetic rats. Untreated diabetic rats and normal rats made up the diabetic control (DC) and normal control (NC) groups, respectively. The standard antidiabetic drug was metformin. The rats were humanely put to sleep after 5 weeks of treatment and their psoas muscles were harvested. There was suppression in the levels of glutathione, activities of SOD, catalase, ENTPDase, 5'Nucleotidase and glycogen levels on T2D induction. This was accompanied by concomitantly elevated levels of malondialdehyde, serum creatine kinase-MB, nitric oxide, acetylcholinesterase, ATPase, amylase, lipase, glucose-6-phosphatase (G6Pase), fructose-1,6-biphophastase (FBPase) and glycogen phosphorylase activities. T2D induction further resulted in the inactivation of fatty acid biosynthesis, glycerolipid metabolism, fatty acid elongation in mitochondria and fatty acid metabolism pathways. There were close to normal and significant reversals in these activities and levels, with concomitant reactivation of the deactivated pathways following treatment with vanillin, which compared favorably with the standard drug (metformin). Vanillin also significantly increased muscle glucose uptake ex vivo. The results suggest the therapeutic effect of vanillin against muscle dysmetabolism in T2D as portrayed by its ability to mitigate redox imbalance, inflammation, cholinergic and purinergic dysfunctions, while modulating glucose-lipid metabolic switch and maintaining muscle histology.

Vanillin exerts therapeutic effects against hyperglycemia-altered glucose metabolism and purinergic activities in testicular tissues of diabetic rats

Testicular dysfunctions leading to male infertility has been reported in type 2 diabetes (T2D), with glucose dysmetabolism, cholinergic and purinergic dysfunction being major contributors. In the present study, the effect of vanillin on glucose metabolism, purinergic and cholinergic dysfunctions were investigated in testicular tissues of T2D rats. Male Sprague-Dawley rats were divided into 6 groups containing 5 rats each. T2D was induced in rats by administering 10 % fructose ad libitum for 14 days followed by a single intraperitoneal injection (40 mg/kg body weight) of streptozotocin. T2D rats were orally administered with vanillin at 150 and 300 mg/kg body weight (bw). Diabetic control (DC) consisted of untreated diabetic rats, while normal control (NC) consisted of normal rats and they were administered with distilled water only. Metformin was used as the standard antidiabetic drug. After 5 weeks treatment, the rats were sacrificed, and the testes were harvested. Induction of T2D led to significantly depleted testicular levels of glutathione, glycogen content, superoxide dismutase and catalase enzyme activities, with concomitantly elevated levels of nitric oxide, malondialdehyde, acetylcholinesterase, glucose-6-phosphatase, fructose-1,6-biphophastase, glycogen phosphorylase, amylase and lipase activities. These activities and levels were significantly reversed to near normal in rats treated with both doses of vanillin as compared with metformin. These results, when taken together, suggest the therapeutic effect of vanillin against hyperglycemia-mediated metabolic dysfunctions in testes of T2D rats. This is depicted by the ability of the phenolic to attenuate oxidative imbalance, purinergic and cholinergic dysfunctions, while suppressing glucose dysmetabolism.

Synergistic antioxidant capacities of vanillin and chitosan nanoparticles against reactive oxygen species, hepatotoxicity, and genotoxicity induced by aging in male Wistar rats

This study aimed to evaluate the synergistic effects of both vanillin (V) and chitosan nanoparticles (CNPs) in alleviating hepatotoxicity, oxidative injury, and genotoxicity induced by d-galactose (DG) and resulted from aging in male albino rats. Male Wistar rats were divided into seven groups (10 rats/group) as follows: control group, (DG) group (100 mg/kg), (V) group (100 mg/kg), CNPs either (low dose (LD) or CNPs (high dose (HD) (140 mg/kg) and (280 mg/kg), and CNPs (LD and HD) dose with V- and DG plus V-treated groups. The CNPs were characterized by transmission electron microscopy (TEM), zeta potential, and size distribution of nanoparticles. After 60 consecutive days of exposure, some biochemical parameters were measured as hepatic aminotransferases enzymes, lipid profile, tumor necrosis factor alpha, interleukin-6 (IL-6), markers of inflammation, tissue damage lactate dehydrogenase, C-reactive protein (CRP), mitochondrial potential activities, myeloperoxidase, xanthine oxidase, CRP, succinate dehydrogenase, mitochondria membrane potential, malondialdehyde levels and antioxidant enzymes (superoxide dismutase, catalase, glutathione reductase, and glutathione S-transferase), and adenosine triphosphate content with histological, alkaline comet assay, and TEM examination of the hepatic tissues. CNPs showed that size distribution (polydispersity index) 0.350 nm and the zeta potential measurement of CNPs were found to be -14.9 mV which revealed the high stability of CNPs. DG induced biochemical and cellular alterations in the hepatic tissues. CNPs and V synergistically afforded protection against hepatic injury and oxidative stress resulting from aging that was induced by DG. Consequently, CNPs were an effective agent in the drug delivery in the hepatic diseases medications and act as a carrier for V and thus make synergistic effect between CNPs and V that achieved the high antioxidant capacities. CNPs and V improved the hepatic enzymes, which act as anti-inflammatory and antigenotoxicity, and improved the antioxidant capacities in the hepatic tissues.

Vanillin Suppresses Cell Motility by Inhibiting STAT3-Mediated HIF-1α mRNA Expression in Malignant Melanoma Cells

Recent studies have shown that vanillin has anti-cancer, anti-mutagenic, and anti-metastatic activity; however, the precise molecular mechanism whereby vanillin inhibits metastasis and cancer progression is not fully elucidated. In this study, we examined whether vanillin has anti-cancer and anti-metastatic activities via inhibition of hypoxia-inducible factor-1α (HIF-1α) in A2058 and A375 human malignant melanoma cells. Immunoblotting and quantitative real time (RT)-PCR analysis revealed that vanillin down-regulates HIF-1α protein accumulation and the transcripts of HIF-1α target genes related to cancer metastasis including fibronectin 1 (FN1), lysyl oxidase-like 2 (LOXL2), and urokinase plasminogen activator receptor (uPAR). It was also found that vanillin significantly suppresses HIF-1α mRNA expression and de novo HIF-1α protein synthesis. To understand the suppressive mechanism of vanillin on HIF-1α expression, chromatin immunoprecipitation was performed. Consequently, it was found that vanillin causes inhibition of promoter occupancy by signal transducer and activator of transcription 3 (STAT3), but not nuclear factor-κB (NF-κB), on HIF1A. Furthermore, an in vitro migration assay revealed that the motility of melanoma cells stimulated by hypoxia was attenuated by vanillin treatment. In conclusion, we demonstrate that vanillin might be a potential anti-metastatic agent that suppresses metastatic gene expression and migration activity under hypoxia via the STAT3-HIF-1α signaling pathway.

Overview of the Role of Vanillin on Redox Status and Cancer Development

Bioactive natural products play critical roles in modern drug development, especially anticancer agents. It has been widely reported that various pharmacological activities of such compounds are related to their antioxidant properties. Vanillin is a natural substance widely found in many plant species and often used in beverages, foods, cosmetics, and pharmaceutical products. Antioxidant and anticancer potential have been described for this compound. Considering the importance of vanillin in the area of human health and food and pharmaceuticals sectors, in this review, we discuss the role of vanillin on redox status and its potential contribution to the prevention and the treatment of cancer.

Altered hepatic mRNA expression of immune response-associated DNA damage in mice liver induced by potassium bromate: Protective role of vanillin

Chronic exposure to potassium bromate (KBrO₃ ), a toxic halogen existing widely in the environment, environment through contaminated drinking water, has become a global problem of public health. The present study investigates the protective role of vanillin against KBrO₃ induced oxidative stress, distruption in inflammatory cytokines expression, DNA damage, and histopathological changes. Adult mice were exposed orally to KBrO₃ (2g/L of drinking water) for 2 weeks The co-administration of vanillin to the KBrO₃ -treated mice significantly prevented the plasma transaminases increase in. Furthermore, it inhibited hepatic lipid peroxidation (malondialdehyde), advanced oxidation protein product (AOPP) and protein carbonyl (PCO) formation and attenuated the KBrO₃ -mediated depletion of enzymatic and non enzymatic antioxidants catalase, superoxide dismutase, and glutathione peroxidase activities and glutathione level in the liver. In addition, vanillin markedly attenuated the expression levels of proinflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, interleukin-6, and COX2 and prevented KBrO₃ -induced hepatic cell alteration and necrosis, as indicated by histopathological data. DNA damage, as assessed by the alkaline comet assay, was also found to be low in the co-treated group. Thus, these findings show that vanillin acts as potent chemopreventive agent against KBrO₃ -mediated liver oxidative stress and genotoxicity through its antioxidant properties. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1796-1807, 2016.

The molecular basis for the pharmacokinetics and pharmacodynamics of curcumin and its metabolites in relation to cancer

This review addresses the oncopharmacological properties of curcumin at the molecular level. First, the interactions between curcumin and its molecular targets are addressed on the basis of curcumin's distinct chemical properties, which include H-bond donating and accepting capacity of the β-dicarbonyl moiety and the phenylic hydroxyl groups, H-bond accepting capacity of the methoxy ethers, multivalent metal and nonmetal cation binding properties, high partition coefficient, rotamerization around multiple C-C bonds, and the ability to act as a Michael acceptor. Next, the in vitro chemical stability of curcumin is elaborated in the context of its susceptibility to photochemical and chemical modification and degradation (e.g., alkaline hydrolysis). Specific modification and degradatory pathways are provided, which mainly entail radical-based intermediates, and the in vitro catabolites are identified. The implications of curcumin's (photo)chemical instability are addressed in light of pharmaceutical curcumin preparations, the use of curcumin analogues, and implementation of nanoparticulate drug delivery systems. Furthermore, the pharmacokinetics of curcumin and its most important degradation products are detailed in light of curcumin's poor bioavailability. Particular emphasis is placed on xenobiotic phase I and II metabolism as well as excretion of curcumin in the intestines (first pass), the liver (second pass), and other organs in addition to the pharmacokinetics of curcumin metabolites and their systemic clearance. Lastly, a summary is provided of the clinical pharmacodynamics of curcumin followed by a detailed account of curcumin's direct molecular targets, whereby the phenotypical/biological changes induced in cancer cells upon completion of the curcumin-triggered signaling cascade(s) are addressed in the framework of the hallmarks of cancer. The direct molecular targets include the ErbB family of receptors, protein kinase C, enzymes involved in prostaglandin synthesis, vitamin D receptor, and DNA.

Extract of Lillium candidum L. can modulate the genotoxicity of the antibiotic zeocin

Lilium candidum L. extract (LE) is well known in folk medicine for the treatment of burns, ulcers, inflammations and for healing wounds. This work aims to clarify whether the genotoxic potential of the radiomimetic antibiotic zeocin (Zeo) could be modulated by LE. Our results indicate that LE exerts no cytotoxic, DNA-damaging and clastogenic activity in in Chlamydomonas reinhardtii, Pisum sativum L. and Hordeum vulgare L. test systems over a broad concentration range. Weak but statistically significant clastogenic effects due to the induction of micronuclei and chromosome aberrations have been observed in H. vulgare L. after treatment with 200 and 300 μg/mL LE. To discriminate protective from adverse action of LE different experimental designs have been used. Our results demonstrate that the treatment with mixtures of LE and Zeo causes an increase in the level of DNA damage, micronuclei and "metaphases with chromatid aberrations" (MwA). Clear evidence has been also obtained indicating that pretreatment with LE given 4 h before the treatment with Zeo accelerates the rejoining kinetics of Zeo-induced DNA damage in P. sativum L. and C. reinhardtii, and can decrease clastogenic effect of Zeo measured as frequencies of micronuclei and MwA in H. vulgare L. Here, we show for the first time that LE can modulate the genotoxic effects of zeocin. The molecular mode of action strongly depends on the experimental design and varies from synergistic to protective effect (adaptive response-AR). Our results also revealed that LE-induced AR to zeocin involves up-regulation of DSB rejoining in C. reinhardtii and P. sativum L. cells.

Erythrocyte oxidative damage in rat treated with CCl4

Owing to the presence of hemoglobin and polyunsaturated fatty acids, erythrocytes are a convenient model to understand membrane oxidative damage induced by various xenobiotic pro-oxidants. This study investigated the antioxidant activity of vanillin, a naturally occurring food-flavoring agent, against carbon tetrachloride (CCl4)-induced erythrocyte damages in Wistar albino rats. A single injection of CCl4 (1 ml/kg, intraperitoneally [i.p.]) caused a significant induction of oxidative damage as evidenced by increased thiobarbituric acid reactive substances, protein carbonyl levels and osmotic fragility accompanied with a significant decrease in Na+/K+-ATPase and Ca2+-ATPase activities. Furthermore, catalase and superoxide dismutase activities were significantly elevated, while glutathione levels, glutathione- S-transferase and glutathione peroxidase activities were markedly reduced in the erythrocytes of CCl4-treated rats. Pretreatment of rats with vanillin (150 mg/kg/day, i.p.) for 3 consecutive days before CCl4 injection protected erythrocytes against the increase of lipid peroxidation and degradation of membrane proteins compared to CCl4-treated rats and exhibited marked prevention against CCl4-induced oxidative stress, alterations of membrane-bound enzymes as well as erythrocyte osmotic fragility. Our results suggest that vanillin plays a protective and curative role against the harmful effects of CCl4 on erythrocytes, thus ensuring membrane cell integrity.

Antimutagenic constituents of adlay (Coix lachryma-jobi L. var. ma-yuen Stapf) with potential cancer chemopreventive activity

Adlay has long been used in traditional Chinese medicine and as a nourishing food. The acetone extract of adlay hull had previously been demonstrated to possess potent antimutagenic activity. The aims of this study were to identify the antimutagenic constituents from adlay hull by using Ames antimutagenic activity-guide isolation procedures and to investigate their chemopreventive efficacies in cultured cells. The results demonstrated that six compounds showing great antimutagenic activity were identified by spectroscopic methods and by comparison with authentic samples to be p-hydroxybenzaldehyde, vanillin, syringaldehyde, trans-coniferylaldehyde, sinapaldehyde, and coixol. Two of them, trans-coniferylaldehyde and sinapaldehyde, exhibit relatively potent scavenging of DPPH radicals, inhibit TPA stimulated superoxide anion generation in neutrophil-like leukocytes, and induce Nrf2/ARE-driven luciferase activity in HSC-3 cells. Moreover, trans-coniferylaldehyde possesses cytoprotective efficacy against tert-butyl hydroperoxide-induced DNA double-strand breaks in cultured cells, and the chemopreventive potency induced by trans-coniferylaldehyde may be through the activation of kinase signals, including p38, ERK1/2, JNK, MEK1/2, and MSK1/2. In summary, we first identified six antimutagenic constituents from adlay hull. Among them, trans-coniferylaldehyde would be a highly promising agent for cancer chemoprevention and merits further investigation.

A comprehensive evaluation of the toxicology of cigarette ingredients: aromatic carbonyl compounds

CONTEXT

Aromatic carbonyls are typically used in the processing or flavoring of tobacco used in the manufacture of cigarettes.

OBJECTIVE

A battery of tests was used to compare the toxicity of mainstream smoke from experimental cigarettes containing different added levels of aromatic carbonyl compounds.

MATERIALS AND METHODS

Ten aromatic carbonyl compounds, nine of which have been reported in tobacco or in tobacco smoke, were added individually to experimental cigarettes at three different levels. The tenth compound, not found naturally in tobacco, was 2-phenoxyethyl isobutyrate. The lowest target inclusion level was 100 ppm and the highest was 10,000 ppm. Smoke from each of the 10 experimental cigarette types was evaluated using analytical chemistry, in vitro cytotoxicity, and mutagenicity testing. For one of the compounds, ethyl vanillin, a 90-day smoke inhalation study using rats was also performed.

RESULTS

Smoke chemistry was effectively unchanged by the addition of any of the compounds. Cytotoxicity, assessed by the neutral red uptake assay and using both gas-vapor and particulate phases of smoke, was unaffected by the addition of any of the test compounds. Mutagenicity, assessed by five strains of Salmonella typhimurium treated with smoke condensate, also was unaffected by any of the test compounds. In the rat inhalation study, there were effectively no differences between cigarettes without added ethyl vanillin and cigarettes containing ~8000 ppm of ethyl vanillin.

CONCLUSION

Even at the exaggerated inclusion levels in cigarette tobacco used in these tests, no adverse toxicological responses occurred for any of aromatic carbonyl compounds tested.

Apoptosis and cell cycle arrest of human colorectal cancer cell line HT-29 induced by vanillin

BACKGROUND

Vanillin is responsible for the flavor and smell of vanilla, a widely used flavoring agent. Previous studies showed that vanillin could enhance the repair of mutations and thus function as an anti-mutagen. However, its role in cancer, a disease that is closely related to mutation has not yet been fully elucidated.

METHODS

Hence, this study investigated the cytolytic and cytostatic properties of vanillin against HT-29, a human colorectal cancer cell line. Methods used including cell viability assay, acridine orange (AO)-ethidium bromide (EB) double staining cell morphological analysis, Cell cycle analysis, annexin V-propidium iodide apoptosis test and 5-bromo-2-deoxyuridine (BrdU)-labeling cell proliferation assay.

RESULTS

Results showed that apoptosis was induced by vanillin and the IC(50) for HT-29 and NIH/3T3 normal cell lines were 400 microg/ml and 1000 microg/ml, respectively. Different concentrations of vanillin arrest cell cycle at different checkpoints. 5-Bromo-2-deoxyuridine-labeling cell proliferation assay showed that G0/G1 arrest was achieved at lower concentration of vanillin (200 microg/ml) while cell cycle analysis by flow cytometer showed that G2/M arrest occurs at higher concentration of vanillin (1000 microg/ml).

CONCLUSION

Cytolytic and cytostatic effects shown by vanillin showed that it could be a useful colorectal cancer preventive agent. Further in vivo study should be carried out to confirm that similar effects could happen in animals.

DNA protective properties of vanillin against γ-radiation under different conditions: Possible mechanisms

Ionizing radiation is an important genotoxic agent. Protecting against this form of toxicant, especially by a dietary component, has several potential applications. In the present study, we have examined the ability of vanillin (4-hydroxy-3-methoxybenzaldehyde), a naturally occurring food flavouring agent, to inhibit radiation-induced DNA damage measured as strand breaks under in vitro, ex vivo and in vivo conditions besides the possible mechanisms behind the observed protection. Our study showed that there was a concentration-dependent inhibition of the disappearance of super-coiled (ccc) form of plasmid pBR322 (in vitro) upon exposure to 50 Gy of gamma-radiation. Presence of 0.5 mM vanillin has a dose-modifying factor (DMF) of 6.75 for 50% inactivation of ccc form. Exposure of human peripheral blood leucocytes (ex vivo) to gamma-radiation causes strand breaks in the cellular DNA, as assessed by comet assay. When leucocytes were exposed to 2 Gy of gamma-radiation there was an increase in parameters of comet assay such as %DNA in tail, tail length, 'tail moment' and 'Olive tail moment'. The presence of 0.5 mM vanillin during irradiation significantly reduced these parameters. Damage to DNA in mouse peripheral blood leucocytes after whole-body exposure of mice (in vivo) to gamma-radiation was studied at 1 and 2 h post-irradiation. There was recovery of DNA damage in terms of the above-mentioned parameters at 2 h post-irradiation. This was more than that observed at 1 h. The recovery was more in vanillin treated mice. Hence our studies showed that vanillin offers protection to DNA against radiation-induced damage possibly imparting a role other than modulation of DNA repair. To examine the possible mechanisms of radioprotection, in terms of radiation-derived radicals, we carried out the reaction of vanillin with ABTS*(+) radical spectrophotometrically besides with DNA peroxyl and carbonyl radicals by using pulse radiolysis. Our present investigations show that vanillin has ability to protect against DNA damage in plasmid pBR322, human and mouse peripheral blood leucocytes and splenic lymphocytes besides enhancing survival in splenic lymphocytes against gamma-radiation, and that the possible mechanism may involve scavenging of radicals generated during radiation, apart from modulation of DNA repair observed earlier.

Radioprotection of 4-hydroxy-3,5-dimethoxybenzaldehyde (VND3207) in culture cells is associated with minimizing DNA damage and activating Akt

Vanillin is a naturally occurring compound and food-flavoring agent with antioxidant and antimutagenic activities. In present study, we explored the radioprotective effect of a novel vanillin derivative VND3207 (4-hydroxy-3,5-dimethoxybenzaldehyde). VND3207 has a much higher potential in scavenging hydroxyl radical and superoxide radical than vanillin as indicated in the ESR spin-trapping measurement, and it can effectively protect plasmid DNA against 10-50 Gy gamma-ray induced breaks in vitro at the concentrations as low as 10-20 microM. Using human lymphoblastoid AHH-1 cells and human fibroblastoid HFS cells, we demonstrated that VND3207 at 5-40 microM concentrations significantly attenuated the inhibition of proliferation and occurrence of apoptosis produced by 1-8 Gy gamma-irradiation. In the cultured cells, VND3207 significantly decreased the initial production and residual level of DNA double-strand breaks (DSBs) induced by 2 or 8 Gy irradiation. Treatment of VND3207 enhanced the level of DNA-PKcs protein, a critical component of DNA DSB repair pathway in the cells with or without gamma-irradiation. Consistently, the phosphorylation of Akt protein, a mediator of survival signal, as well as its substrate GSK3beta was concurrently increased by VND3207. Our results suggest that VND3207 has radioprotection effect through its capabilities as a powerful antioxidant, in minimizing DNA damage, and activating survival signal Akt pathway, and it may be of value in the development of radioprotective compounds.

Directed molecular screening for RecA ATPase inhibitors

The roles of bacterial RecA in the evolution and transmission of antibiotic resistance genes make it an attractive target for inhibition by small molecules. We report two complementary fluorescence-based ATPase assays that were used to screen for inhibitors of RecA. We elected to employ the ADP-linked variation of the assay, with a Z' factor of 0.83 in 96-well microplates, to assess whether 18 select compounds could inhibit ATP hydrolysis by RecA. The compounds represented five sets of related inhibitor scaffolds, each of which had the potential to cross-inhibit RecA. Although nucleotide analogs, known inhibitors of GHL ATPases, and known protein kinase inhibitors were not active against RecA, we found that three suramin-like agents substantially inhibited RecA's ATPase activity.

Antimutagenicity of cinnamaldehyde and vanillin in human cells: Global gene expression and possible role of DNA damage and repair

Vanillin (VAN) and cinnamaldehyde (CIN) are dietary flavorings that exhibit antimutagenic activity against mutagen-induced and spontaneous mutations in bacteria. Although these compounds were antimutagenic against chromosomal mutations in mammalian cells, they have not been studied for antimutagenesis against spontaneous gene mutations in mammalian cells. Thus, we initiated studies with VAN and CIN in human mismatch repair-deficient (hMLH1(-)) HCT116 colon cancer cells, which exhibit high spontaneous mutation rates (mutations/cell/generation) at the HPRT locus, permitting analysis of antimutagenic effects of agents against spontaneous mutation. Long-term (1-3 weeks) treatment of HCT116 cells with VAN at minimally toxic concentrations (0.5-2.5mM) reduced the spontaneous HPRT mutant fraction (MF, mutants/10(6) survivors) in a concentration-related manner by 19-73%. A similar treatment with CIN at 2.5-7.5microM yielded a 13-56% reduction of the spontaneous MF. Short-term (4-h) treatments also reduced the spontaneous MF by 64% (VAN) and 31% (CIN). To investigate the mechanisms of antimutagenesis, we evaluated the ability of VAN and CIN to induce DNA damage (comet assay) and to alter global gene expression (Affymetrix GeneChip) after 4-h treatments. Both VAN and CIN induced DNA damage in both mismatch repair-proficient (HCT116+chr3) and deficient (HCT116) cells at concentrations that were antimutagenic in HCT116 cells. There were 64 genes whose expression was changed similarly by both VAN and CIN; these included genes related to DNA damage, stress responses, oxidative damage, apoptosis, and cell growth. RT-PCR results paralleled the Affymetrix results for four selected genes (HMOX1, DDIT4, GCLM, and CLK4). Our results show for the first time that VAN and CIN are antimutagenic against spontaneous mutations in mammalian (human) cells. These and other data lead us to propose that VAN and CIN may induce DNA damage that elicits recombinational DNA repair, which reduces spontaneous mutations.