Preventive Effects of Quercetin against Benzo[a]pyrene-Induced DNA Damages and Pulmonary Precancerous Pathologic Changes in Mice

Diallyl Sulfide-Mediated Modulation of the Fatty Acid Synthase (FASN) Leads to Cancer Cell Death in BaP-Induced Lung Carcinogenesis in Swiss Mice

Purpose

Diallyl sulfide (DAS), one of the organo-sulfur secondary metabolites in garlic, has been shown to inhibit the proliferation of cancer cells. The present study aimed to evaluate the mechanism of DAS in the prevention of benzo[a]pyrene (BaP)-induced lung cancer in a murine model.

Materials and Methods

The mice were exposed to 50 mg/kg of BaP twice a week for 4 weeks in order to induce lung carcinoma. Pretreatment of mice with DAS (100 mg/kg) was started 2 weeks before BaP exposure and further continued for 21 weeks. The effect of DAS and BaP was evaluated by studying various parameters in the serum and tissues of the treated or untreated BaP-exposed mice.

Results

The histopathological findings demonstrated that DAS prevented the progression of malignant lung cancer and metastasis in the liver. A significant drop was observed in BaP-induced tumor marker enzymes (ADA, AHH, γ-GT, LDH) in the serum of the mice treated with DAS. Moreover, DAS treatment resulted in the recovery of antioxidant enzymes, SOD and CAT, in BaP-exposed mice. The induction of apoptosis and the destruction of cellular ROS were detected in cancer cells from the mice pre-treated with DAS. The immunohistochemical analysis revealed the up-regulation of fatty acid synthase (FASN) in the lungs and liver tissues of BaP-exposed mice and the treatment with DAS inhibited FASN expression.

Conclusion

The findings of the present study indicated that DAS-induced apoptosis is strongly associated with the downregulation of FASN in tumor tissues. To the best of our knowledge, this is the first study that describes the role of FASN in BaP-induced lung carcinogenesis.

Quercetin attenuated oxidative DNA damage through NRF2 signaling pathway in rats with DMH induced colon carcinogenesis

Accumulating recent studies have demonstrated the preventive and therapeutic effects of polyphonic compounds such as quercetin in colorectal cancer. Therefore, we aimed to evaluate the underlying mechanisms for positive effects of quercetin in rats with 1,2-dimethylhydrazine (DMH)- induced colorectal cancer. For this purpose, male Wistar rats were classified as 6 groups, including group 1 without any intervention, group 2 as quercetin received rats (50 mg/kg), groups 3 as DMH received rats (20 mg/kg) group 4-6 DMH and quercetin received rats. DNA damage, DNA repair, the expression levels and activities of enzymic antioxidants, non-enzymic antioxidants, and NRF2/Keap1 signaling were evaluated in colon tissues of all groups. Our results showed significant suppression of DNA damage and induction of DNA repair in DMH + Quercetin groups, particularly in entire-period in comparison to other groups (p < .05). The expression levels and activities of enzymic and non-enzymic antioxidants were increased in DMH + Quercetin groups (p < .05). Lipid and protein peroxidation were significantly suppressed in DMH + Quercetin groups (p < .05). In addition, quercetin also modulated NRF2/Keap1 signaling and its targets, detoxifying enzymes in DMH + Quercetin groups. Our finding demonstrated that quercetin supplementation effectively reversed DMH-mediated oxidative stress and DNA damage through targeting NRF2/Keap1 signaling pathway.

Antitumor activity of Cuphea ignea extract against benzo(a)pyrene-induced lung tumorigenesis in Swiss Albino mice

Lung cancer has one of the highest mortality rates among various types of cancer and is the most frequent cancer in the world. The incidence of lung cancer is increasing rapidly, in parallel with an increased incidence of smoking. Effective chemoprevention may be an alternative strategy to control the incidence of lung cancer. Thus, the objective of current work was to ascertain the possible preventive and therapeutic efficacies of Cuphea ignea extract in a mouse model of lung tumorigenesis and its cytotoxicity toward the A549 human lung cancer cell line. Lung tumorigenesis was induced by the oral administration of benzo(a)pyrene (50 mg/kg b.w.) twice per week to Swiss albino mice for 4 weeks. Benzo(a)pyrene-treated mice were orally administered C. ignea (300 mg/kg body weight, 5 days/week) for 2 weeks before or 9 weeks after the first benzo(a)pyrene dose, for a total of 21 weeks. At the end of the administration period, various parameters were measured in the serum and lung tissues. The results revealed that the oral administration of benzo(a)pyrene resulted in increases in relative lung weight, serum levels of tumor markers (ADA, AHH, and LDH), and the inflammatory marker NF-κB, and a decreased total antioxidant capacity compared with the control. In addition, decreased levels of enzymatic and non-enzymatic antioxidants, with a concomitant increase in lipid peroxidation, metalloproteinases (MMP-2 and MMP-12), and the angiogenic marker VEGF were detected in lung tissues. Moreover, benzo(a)pyrene administration induced the upregulation of PKCα, COX-2, and Bcl-2 expression, with the downregulation of BAX and caspase-3 expression. C. ignea treatment alleviated all alterations in these parameters, which was further confirmed by the histopathological analysis of lung tissues. The findings of the current work provide the first verification of the preventive and therapeutic potentials of C. ignea extract against benzo(a)pyrene-induced lung tumorigenesis in mice.

Acute benzo[a]pyrene treatment causes different antioxidant response and DNA damage in liver, lung, brain, stomach and kidney

Acute effects of oxidative damage induced by benzo[a]pyrene (B[a]P) on various organs are still not clear. In this study, we investigated oxidative stress and DNA damage in liver, lung, stomach, brain and kidney of ICR male mice induced by acute B[a]P treatment. B[a]P treatment led to a significant decrease at the different doses in body weight. For the variations of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione (GSH) and GSH/GSSG, significant increases were observed at 24 h, then decreased till 72 h after B[a]P injection. The increase percent indicated in a dose- dependent decrease manner. However, glutathione peroxidase (GPx), GSSG and MDA were significantly increased in a time- and dose-dependent increase manner. DNA damage showed the significant and top levels at 24 h, and increased in proportion to the doses of B[a]P treatment. The total induction could be indicated by the variation of MDA at 24 h after B[a]P injection and showed the following order of predominance: lung > liver > kidney = stomach > brain. This was further certificated by histopathological changes in the examined organs. Additionally, the levels of serum glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT), and blood urea nitrogen (UN), creatinine were also significantly increased at 24 h after B[a]P injection. These findings suggested the disturbance of antioxidant responses and aggravation of DNA damages, and the different responses on various organs induced by acute B[a]P treatment in organism.

Safety Aspects of the Use of Quercetin as a Dietary Supplement

The flavonoid quercetin is frequently found in low amounts as a secondary plant metabolite in fruits and vegetables. Isolated quercetin is also marketed as a dietary supplement, mostly as the free quercetin aglycone, and frequently in daily doses of up to 1000 mg d^-1 exceeding usual dietary intake levels. The present review is dedicated to safety aspects of isolated quercetin used as single compound in dietary supplements. Among the numerous published human intervention studies, adverse effects following supplemental quercetin intake have been rarely reported and any such effects were mild in nature. Published adequate scientific data for safety assessment in regard to the long-term use (>12 weeks) of high supplemental quercetin doses (≥1000 mg) are currently not available. Based on animal studies involving oral quercetin application some possible critical safety aspects could be identified such as the potential of quercetin to enhance nephrotoxic effects in the predamaged kidney or to promote tumor development especially in estrogen-dependent cancer. Furthermore, animal and human studies with single time or short-term supplemental quercetin application revealed interactions between quercetin and certain drugs leading to altered drug bioavailability. Based on these results, some potential risk groups are discussed in the present review.

Vehicular Traffic-Related Polycyclic Aromatic Hydrocarbon Exposure and Breast Cancer Incidence: The Long Island Breast Cancer Study Project (LIBCSP)

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants, known human lung carcinogens, and potent mammary carcinogens in laboratory animals. However, the association between PAHs and breast cancer in women is unclear. Vehicular traffic is a major ambient source of PAH exposure.

OBJECTIVES

Our study aim was to evaluate the association between residential exposure to vehicular traffic and breast cancer incidence.

METHODS

Residential histories of 1,508 participants with breast cancer (case participants) and 1,556 particpants with no breast cancer (control participants) were assessed in a population-based investigation conducted in 1996-1997. Traffic exposure estimates of benzo[a]pyrene (B[a]P), as a proxy for traffic-related PAHs, for the years 1960-1995 were reconstructed using a model previously shown to generate estimates consistent with measured soil PAHs, PAH-DNA adducts, and CO readings. Associations between vehicular traffic exposure estimates and breast cancer incidence were evaluated using unconditional logistic regression.

RESULTS

The odds ratio (95% CI) was modestly elevated by 1.44 (0.78, 2.68) for the association between breast cancer and long-term 1960-1990 vehicular traffic estimates in the top 5%, compared with below the median. The association with recent 1995 traffic exposure was elevated by 1.14 (0.80, 1.64) for the top 5%, compared with below the median, which was stronger among women with low fruit/vegetable intake [1.46 (0.89, 2.40)], but not among those with high fruit/vegetable intake [0.92 (0.53, 1.60)]. Among the subset of women with information regarding traffic exposure and tumor hormone receptor subtype, the traffic-breast cancer association was higher for those with estrogen/progesterone-negative tumors [1.67 (0.91, 3.05) relative to control participants], but lower among all other tumor subtypes [0.80 (0.50, 1.27) compared with control participants].

CONCLUSIONS

In our population-based study, we observed positive associations between vehicular traffic-related B[a]P exposure and breast cancer incidence among women with comparatively high long-term traffic B[a]P exposures, although effect estimates were imprecise.

CITATION

Mordukhovich I, Beyea J, Herring AH, Hatch M, Stellman SD, Teitelbaum SL, Richardson DB, Millikan RC, Engel LS, Shantakumar S, Steck SE, Neugut AI, Rossner P Jr., Santella RM, Gammon MD. 2016. Vehicular traffic-related polycyclic aromatic hydrocarbon exposure and breast cancer incidence: the Long Island Breast Cancer Study Project (LIBCSP). Environ Health Perspect 124:30-38; http://dx.doi.org/10.1289/ehp.1307736.

Quercetin inhibits multiple pathways involved in interleukin 6 secretion from human lung fibroblasts and activity in bronchial epithelial cell transformation induced by benzo[a]pyrene diol epoxide

The interaction between epithelial and stromal cells through soluble factors such as cytokines plays an important role in carcinogenesis. Breaking this cancer-promoting interaction poses an opportunity for cancer prevention. The tumor-promoting function of interleukin 6 (IL-6) has been documented; however, the underlying mechanisms of this function in lung carcinogenesis are not well elucidated. Here, we show that benzo[a]pyrene diol epoxide (BPDE, the active metabolite of cigarette smoke carcinogen benzo[a]pyrene)-induced human bronchial epithelial cell (HBEC) transformation was enhanced by IL-6 in vitro. The carcinogen/IL-6-transformed cells exhibited higher expression of STAT3 (signal transducer and activator of transcription 3) when compared with cells transformed by BPDE alone. Constitutive STAT3 activation drove cell proliferation and survival through anti-apoptosis gene expression. We further show that quercetin, a dietary compound having preventive properties for lung cancer, decreased BPDE-stimulated IL-6 secretion from human lung fibroblasts through inhibition of the NF-κB and ERK pathways. The inhibition was accomplished at clinically achievable concentrations of the compound. Finally, quercetin blocked IL-6-induced STAT3 activation in HBECs, and IL-6 enhancement of HBEC transformation by BPDE was abolished by quercetin treatment. Altogether, our data reveal novel mechanisms for IL-6 in lung carcinogenesis and for the preventive role of quercetin in the process. © 2015 Wiley Periodicals, Inc.

Benzo(a)pyrene induced lung cancer: Role of dietary phytochemicals in chemoprevention

Lung cancer is the major cause of overall cancer deaths, and chemoprevention is a promising strategy to control this disease. Benzo(a)pyrene [B(a)P], a polycyclic aromatic hydrocarbon, is one among the principal constituents of tobacco smoke that plays a key role in lung carcinogenesis. The B(a)P induced lung cancer in mice offers a relevant model to study the effect of natural products and has been widely used by many researchers and found considerable success in ameliorating the pathophysiological changes of lung cancer. Currently available synthetic drugs that constitute the pharmacological armamentarium are themselves effective in managing the condition but not without setbacks. These hunches have accelerated the requisite for natural products, which may be used as dietary supplement to prevent the progress of lung cancer. Besides, these agents also supplement the conventional treatment and offer better management of the condition with less side effects. In the context of soaring interest toward dietary phytochemicals as newer pharmacological interventions for lung cancer, in the present review, we are attempting to give a silhouette of mechanisms of B(a)P induced lung carcinogenesis and the role of dietary phytochemicals in chemoprevention.

Quercetin suppresses cytochrome P450 mediated ROS generation and NFκB activation to inhibit the development of 7,12-dimethylbenz[a]anthracene (DMBA) induced hamster buccal pouch carcinomas

Increased production of reactive oxygen species (ROS) has long been recognized to play a pivotal role in carcinogenesis. Quercetin, a naturally occurring dietary flavonoid is known for its ROS scavenging properties. The present study was designed to investigate the chemopreventive and chemotherapeutic effects of quercetin based on cytochrome P450 (CYP) mediated ROS generation, ROS-induced cellular damage and activation of the NFκB signalling circuit during 7,12-dimethylbenz[a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis. Administration of quercetin inhibited the development of DMBA-induced HBP carcinomas by impairing CYP-mediated ROS production via downregulation of the expression of CYP1A1 and CYP1B1, and upregulation of antioxidant defences. Attenuation of ROS generation by quercetin in turn abrogated NFκB signalling by preventing the phosphorylation and degradation of IκB, nuclear translocation of NFκB and transactivation of its target genes associated with cell proliferation and apoptosis evasion. Thus dietary flavonoids such as quercetin that can block ROS generation and inhibit the redox regulated transcription factor NFκB, by virtue of their antioxidant potential are promising candidates for future antioxidant-based anticancer regimens.

In vitro and in vivo evaluation of the anticarcinogenic and cancer chemopreventive potential of a flavonoid-rich fraction from a traditional Indian herb Selaginella bryopteris

Prevention of cancer through nutritional intervention has gained significant recognition in recent years. Evidence revealed from mechanistic investigations coupled with molecular epidemiology show an inverse association of dietary flavonoids intake with cancer risk. The chemopreventive and anticarcinogenic potential of Selaginella bryopteris, a traditional Indian herb referred to as ‘Sanjeevani’ in the Ayurvedic system of medicine, was examined in the present study. Comprehensive in vitro and in vivo studies were conducted on the flavonoid-rich benzene fraction of the aqueous extract that demonstrated a significant cytoprotective activity. Biomarkers of chemoprevention such as proliferative index and status of cell-cycle regulatory proteins, antioxidant property, anti-inflammatory effect, reversal of stress-induced senescence and genoprotective effect were investigated in human and murine cell cultures. Chemopreventive potential was assessed in benzopyrene-induced lung carcinogenesis and 7,12-dimethyl benz(a)anthracene-mediated skin papillomagenesis test models. Inhibition of DNA fragmentation, unperturbed cell-cycle regulation, maintenance of intracellular antioxidant defence, anti-inflammatory activity, prevention of stress-induced senescence and genoprotective effects against methyl isocyanate carcinogenicity was observed. Medium-term anticarcinogenicity and two-stage skin papillomagenesis tests strongly substantiated our in vitro observations. Results from the present study provide evidence of anticarcinogenic and chemopreventive activities of S. bryopteris hitherto unreported and reaffirm the nutritional significance of flavonoids in cancer prevention.

Antioxidant intervention of smoking-induced lung tumor in mice by vitamin E and quercetin

Background

Epidemiological and in vitro studies suggest that antioxidants such as quercetin and vitamin E (VE) can prevent lung tumor caused by smoking; however, there is limited evidence from animal studies.

Methods

In the present study, Swiss mouse was used to examine the potential of quercetin and VE for prevention lung tumor induced by smoking.

Results

Our results suggest that the incidence of lung tumor and tumor multiplicity were 43.5% and 1.00 ± 0.29 in smoking group; Quercetin has limited effects on lung tumor prevention in this in vivo model, as measured by assays for free radical scavenging, reduction of smoke-induced DNA damage and inhibition of apoptosis. On the other hand, vitamin E drastically decreased the incidence of lung tumor and tumor multiplicity which were 17.0% and 0.32 ± 0.16, respectively (p < 0.05); and demonstrated prominent antioxidant effects, reduction of DNA damage and decreased cell apoptosis (p < 0.05). Combined treatment with quercetin and VE in this animal model did not demonstrate any effect greater than that due to vitamin E alone. In addition, gender differences in the occurrence of smoke induced-lung tumor and antioxidant intervention were also observed.

Conclusion

We conclude that VE might prevent lung tumor induced by smoking in Swiss mice.

Health effects of quercetin: from antioxidant to nutraceutical

Quercetin, a member of the flavonoids family, is one of the most prominent dietary antioxidants. It is ubiquitously present in foods including vegetables, fruit, tea and wine as well as countless food supplements and is claimed to exert beneficial health effects. This includes protection against various diseases such as osteoporosis, certain forms of cancer, pulmonary and cardiovascular diseases but also against aging. Especially the ability of quercetin to scavenge highly reactive species such as peroxynitrite and the hydroxyl radical is suggested to be involved in these possible beneficial health effects. Consequently, numerous studies have been performed to gather scientific evidence for these beneficial health claims as well as data regarding the exact mechanism of action and possible toxicological aspects of this flavonoid. The purpose of this review is to evaluate these studies in order to elucidate the possible health-beneficial effects of the antioxidant quercetin. Firstly, the definitions as well as the most important aspects regarding free radicals, antioxidants and oxidative stress will be discussed as background information. Subsequently, the mechanism by which quercetin may operate as an antioxidant (tested in vitro) as well as the potential use of this antioxidant as a nutraceutical (tested both ex vivo and in vivo) will be discussed.

Impact of smoking status on the biological behavior of lung cancer

Cigarette smoking is the most established risk factor for lung carcinogenesis; however, its effects on the progression of lung cancer are still unclear. We reviewed the clinical investigations on this issue, which imply that smoking status is a treatment predictor and prognostic factor for several subtypes of lung cancer. Moreover, gene alterations and various protein expressions of tumor progression were recognized more frequently in the tumor tissues of smokers than in those of the never smokers. A cellular analysis revealed that tobacco-specific chemical compounds cause genetic or epigenetic alterations, modulate expressions of large numbers of genes that include molecules related to proliferation, invasion and metastasis, and deteriorate anti-tumor immunity. Our findings suggest that smoking promotes the progression of lung cancer, and that elucidating the molecular mechanisms may help to clarify the therapeutic targets.

A critical review of the data related to the safety of quercetin and lack of evidence of in vivo toxicity, including lack of genotoxic/carcinogenic properties

Quercetin is a naturally-occurring flavonol (a member of the flavonoid family of compounds) that has a long history of consumption as part of the normal human diet. Because a number of biological properties of quercetin may be beneficial to human health, interest in the addition of this flavonol to various traditional food products has been increasing. Prior to the use of quercetin in food applications that would increase intake beyond that from naturally-occurring levels of the flavonol in the typical Western diet, its safety needs to be established or confirmed. This review provides a critical examination of the scientific literature associated with the safety of quercetin. Results of numerous genotoxicity and mutagenicity, short- and long-term animal, and human studies are reviewed in the context of quercetin exposure in vivo. To reconcile results of in vitro studies, which consistently demonstrated quercetin-related mutagenicity to the absence of carcinogenicity in vivo, the mechanisms that lead to the apparent in vitro mutagenicity, and those that ensure absence of quercetin toxicity in vivo are discussed. The weight of the available evidence supports the safety of quercetin for addition to food.