Inhibition of 7,12-dimethylbenz[a]anthracene-induced mammary tumors and DNA adducts by garlic powder

Nano-immunomodulators: prospective applications to combat drug resistant bacterial infections and related complications

Antimicrobial resistance (AMR) is a growing problem in our healthcare sector, it can make infections more difficult and expensive to treat and lead to treatment failure and increased risk of death. Currently, at least 700,000 people worldwide die each year from AMR. Alternative methods for mitigating drug-resistant bacterial infections are desperately needed because of the unacceptably low rate of conventional antibiotic discovery. Therefore, the implementation of various therapeutic strategies is necessary to deal with drug-resistant bacteria and immunomodulation is one of them which is highly encouraged through various studies. Immunomodulators are different biological or synthetic substances that possess the capability of inducing, suppressing, or overall modulating the innate and adaptive immune system. Some phytochemicals, including flavonoids, glycosides, polysaccharides, terpenoids, essential oils, peptides, synthetic molecules, and synthetic biomaterials, can play a crucial role in the fight against bacterial infections directly or indirectly by enhancing the activity of existing antibiotics or by boosting immunity. Nanotechnology can be used to modulate immune responses through various fabrication methods and strategies of design and for drug formulation by encapsulating potential compounds/molecules in the form of nanoparticles and by surface modification or capping of nanomaterials. This approach can improve drug solubility, stability, and bioavailability, reduce toxicity, and help to increase the effectiveness of drugs against resistant microorganisms. This review aims to provide current developments in the field of immunomodulators of different origins that can be combined with nanotechnology and exploited as potential future drugs or adjuvants to fight drug-resistant bacterial pathogens.

Prognostic significance of natural products against multidrug tumor resistance

Cancer is a pervasive, constantly evolving, and significant public health concern. The number of new cancer cases has risen dramatically in the last decades, making it one of the top causes of poor health and mortality worldwide. Although various treatment strategies, including surgery, radiation, and pharmaceutical therapies, have evolved into more sophisticated, precise methods, there is not much improvement in the cancer-related death toll. Consequently, natural product-based therapeutic discoveries have recently been considered an alternative approach. According to an estimate, one-third of the top twenty medications in today's market have a natural plant-product-based origin. Accordingly, primary prevention is an essential component of worldwide cancer control. This review provides an overview of the mechanisms of action of bioactive ingredients in natural dietary products that may contribute to the prevention and management of multiple malignancies.

Garlic constituents for cancer prevention and therapy: From phytochemistry to novel formulations

Garlic (Allium sativum L.) is one of the oldest plants cultivated for its dietary and medicinal values. This incredible plant is endowed with various pharmacological attributes, such as antimicrobial, antiarthritic, antithrombotic, antitumor, hypoglycemic, and hypolipidemic activities. Among the various beneficial pharmacological effects of garlic, the anticancer activity is presumably the most studied. The consumption of garlic provides strong protection against cancer risk. Taking into account the multi-targeted actions and absence of considerable toxicity, a few active metabolites of garlic are probably to play crucial roles in the killing of cancerous cells. Garlic contains several bioactive molecules with anticancer actions and these include diallyl trisulfide, allicin, diallyl disulfide, diallyl sulfide, and allyl mercaptan. The effects of various garlic-derived products, their phytoconstituents and nanoformulations have been evaluated against skin, prostate, ovarian, breast, gastric, colorectal, oral, liver, and pancreatic cancers. Garlic extract, its phytocompounds and their nanoformulations have been shown to inhibit the different stages of cancer, including initiation, promotion, and progression. Besides, these bioactive metabolites alter the peroxidation of lipid, activity of nitric oxide synthetase, nuclear factor-κB, epidermal growth factor receptor, and protein kinase C, cell cycle, and survival signaling. The current comprehensive review portrays the functions of garlic, its bioactive constituents and nanoformulations against several types of cancers and explores the possibility of developing these agents as anticancer pharmaceuticals.

Chemical constituents and medicinal properties of Allium species

Allium species, belonging to Alliaceae family, are among the oldest cultivated vegetables used as food. Garlic, onions, leeks and chives, which belong to this family, have been reported to have medicinal properties. The Allium species constituents have been shown to have antibacterial and antioxidant activities, and, in addition, other biological properties. These activities are related to their rich organosulfur compounds. These organosulfur compounds are believed to prevent the development of cancer, cardiovascular, neurological, diabetes, liver diseases as well as allergy and arthritis. There have also been reports on toxicities of these compounds. The major active compounds of Allium species includes, diallyl disulfide, diallyl trisulfide, diallyl sulfide, dipropyl disulfide, dipropyl trisulfide, 1-propenylpropyl disulfide, allyl methyl disulfide and dimethyl disulfide. The aim of this review is to focus on a variety of experimental and clinical reports on the effectiveness, toxicities and possible mechanisms of actions of the active compounds of garlic, onions, leek and chives.

Purification and Characterization of the Principal Antimutagenic Bioactive as Ethoxy-Substituted Phylloquinone from Spinach (Spinacea oleracea L.) Based on Evaluation in Models Including Human Lymphoblast TK+/- Cells

During in vitro analysis, spinach (Spinacea oleracea L.) leaf extracts displayed varying antimutagenicity when analyzed in models including human lymphoblast (TK^+/-) cell line (thymidine kinase gene mutation assay) and Escherichia coli MG1655 (rifampicin resistance assay) against chemically (ethyl methanesulfonate and 5-azacytidine) induced mutagenicity. Highest antimutagenicity was displayed by the quinone extract. The principal bioactive compound exhibited fluorescence in TLC at 366 nm (termed C4) resolved at R_f 0.32 and t_R 15.2 min in TLC and HPLC, respectively. On the TLC plate, three spots (C1-C3), observed at 254 nm, displayed comparatively lesser antimutagenicity. Furthermore, biochemical and spectroscopic analyses using MALDI-TOF MS and NMR indicated the nature of the potent compound (C4) as an ethoxy-substituted phylloquinone derivative [2-ethoxy-3-((E)-3,7,11,15-tetramethylhexadec-2-enyl)naphthalene-1,4-dione]. The C4 compound did not display any cytotoxicity and hence possesses significant nutraceutical-based intervention possibility to combat the onset of mutation-associated disease(s).

Forkhead Box Q1 Is a Novel Target of Breast Cancer Stem Cell Inhibition by Diallyl Trisulfide

Diallyl trisulfide (DATS), a metabolic byproduct of garlic, is known to inhibit the growth of breast cancer cells in vitro and in vivo This study demonstrates that DATS targets breast cancer stem cells (bCSC). Exposure of MCF-7 and SUM159 human breast cancer cells to pharmacological concentrations of DATS (2.5 and 5 μm) resulted in dose-dependent inhibition of bCSC, as evidenced by a mammosphere assay and flow cytometric analysis of aldehyde dehydrogenase 1 (ALDH1) activity and the CD44(high)/CD24(low)/epithelial specific antigen-positive fraction. DATS-mediated inhibition of bCSC was associated with a decrease in the protein level of FoxQ1. Overexpression of FoxQ1 in MCF-7 and SUM159 cells increased ALDH1 activity and the CD49f(+)/CD24(-) fraction. Inhibition of ALDH1 activity and/or mammosphere formation upon DATS treatment was significantly attenuated by overexpression of FoxQ1. In agreement with these results, stable knockdown of FoxQ1 using small hairpin RNA augmented bCSC inhibition by DATS. Expression profiling for cancer stem cell-related genes suggested that FoxQ1 may negatively regulate the expression of Dachshund homolog 1 (DACH1), whose expression is lost in invasive breast cancer. Chromatin immunoprecipitation confirmed recruitment of FoxQ1 at the DACH1 promoter. Moreover, inducible expression of DACH1 augmented DATS-mediated inhibition of bCSC. Expression of FoxQ1 protein was significantly higher in triple-negative breast cancer cases compared with normal mammary tissues. Moreover, an inverse association was observed between FoxQ1 and DACH1 gene expression in breast cancer cell lines and tumors. DATS administration inhibited ALDH1 activity in vivo in SUM159 xenografts. These results indicate that FoxQ1 is a novel target of bCSC inhibition by DATS.

Topical (+)-catechin emulsified gel prevents DMBA/TPA-induced squamous cell carcinoma of the skin by modulating antioxidants and inflammatory biomarkers in BALB/c mice

An emulsified gel of (+)-catechin was developed and evaluated topically against DMBA/TPA-induced squamous cell carcinoma of the skin in BALB/c mice.

Anticlastogenic effect of diosgenin on 7,12-dimethylbenz(a)anthracene treated experimental animals

The present investigation explores the anticlastogenic effect of diosgenin on 7,12-dimethylbenz(a)anthracene (DMBA) treated clastogenesis. The frequency of bone marrow micronucleated polychromatic erythrocytes (MnPCEs), chromosomal aberrations (CA), deoxyribonucleic acid (DNA) damage as cytogenetic markers and the levels of lipid peroxidation by-products, activities of enzymatic antioxidant and the status of detoxification agents were performed to assess the anticlastogenic effects of diosgenin on DMBA treated hamsters. Intraperitoneal injection of DMBA (30 mg/kg bw) leads to clastogenesis in hamster. Elevated MnPCEs frequencies, CA, DNA damage, enhanced lipid peroxidation by products, declined antioxidant activities and detoxification cascade were observed in DMBA treated hamsters. Oral pretreatment with diosgenin (80 mg/kg bw) daily for a period of five days significantly reduced the frequency of MnPCEs, CA, DNA damage and normalized the levels of lipid peroxidation by products with increased activities of antioxidants and detoxification agents in DMBA alone treated hamsters. Outcome of the present study revealed that diosgenin has potent anticlastogenic effects on DMBA treated hamsters.

Radioprotective effect of alk(en)yl thiosulfates derived from allium vegetables against DNA damage caused by X-ray irradiation in cultured cells: antiradiation potential of onions and garlic

To evaluate a radioprotective effect of sodium n-propyl thiosulfate (NPTS) and sodium 2-propenyl thiosulfate (2PTS) derived from onions and garlic, respectively, rat hepatoma H4IIE cells and mouse lymphoma L5178Y cells were preincubated with each of these compounds for 48 hours at 37°C before receiving 10 Gy of X-ray irradiation. Cell damage caused by the irradiation was quantified as comet tail moment, which represents the degree of DNA damage. X-ray-induced DNA damage was significantly decreased in both H4IIE and L5178Y cells by micromolar concentrations of NPTS and 2PTS compared with the control without the compounds. The protective effect was more potent with 2PTS than NPTS. Onions and garlic have antiradiation potential.

In vitro assessment of oxidative stress and apoptotic mechanisms of garlic extract in the treatment of acute promyelocytic leukemia

INTRODUCTION

Garlic supplementation in diet has been shown to be beneficial to cancer patients. Recently, its pharmacological role in the prevention and treatment of cancer has received increasing attention. However, the mechanisms by which garlic extract (GE) induces cytotoxicity, oxidative stress, and apoptosis in cancer cells remain largely unknown.

OBJECTIVE

The present study was designed to use HL-60 cells as a test model to evaluate whether or not GE-induced cytotoxicty and apoptosis in human leukemia (HL-60) cells is mediated through oxidative stress.

METHODS

Human leukemia (HL-60) cells were treated with different concentrations of GE for 12 hr. Cell survival was determined by MTT assay. The extent of oxidative cell/tissue damage was determined by measuring malondialdehyde (lipid peroxidation biomarker) concentrations by spectrophotometry. Cell apoptosis was measured by flow cytometry assessment (Annexin-V and caspase-3 assays) and agarose gel electrophoresis (DNA laddering assay).

RESULTS

Data obtained from the MTT assay indicated that GE significantly (p < 0.05) reduced the viability of HL-60 cells in a concentration-dependent manner. We detected a significant (p < 0.05) increase in malondialdehyde (MDA) concentrations in GE-treated HL-60 cells compared to the control. Flow cytometry data showed a strong concentration-response relationship between GE exposure and Annexin-V positive HL-60 cells. Similarly, a statistically significant and concentration-dependent increase (p <0.05) were recorded with regard to caspase-3 activity in HL-60 cells undergoing late apoptosis. These results were confirmed by data of DNA laddering assay showing a clear evidence of nucleosomal DNA fragmentation in GE-treated cells.

CONCLUSION

Our finding indicates that GE-induced cytotoxicity and apoptosis in HL-60 cells involve phosphatidylserine externalization, caspase-3 activation, and nucleosomal DNA fragmentation associated with the formation of MDA, a by-product of lipid peroxidation and biomarker of oxidative stress. At therapeutic concentrations, GE-induced cytotoxic and apoptotic effects in HL-60 cells is mediated by oxidative stress.

Protective effects of garlic and silymarin on NDEA-induced rats hepatotoxicity

Background ­— The present study was conducted to investigate the chemopreventive effects of garlic extract and silymarin on N-nitrosodiethylamine (NDEA) and carbon tetrachloride (CCl₄)-induced hepatotoxicity in male albino rats. Methods and Results — Animals were pretreated with garlic, silymarin or both for one week prior to the injection of NDEA. Then animals received a single injection of NDEA followed by weekly subcutaneous injections of CCl₄ for 6 weeks. Oral administration was then continued along with the injection of CCl₄ for the duration of the experiment. Serum aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), hepatic lipid peroxidation (LPO), superoxide dismutase (SOD), reduced glutathione (GSH), glutathione-S-transferase (GST) and glutathione reductase (GSR) were measured. Injection of NDEA induced a significant elevation in serum AST, ALT and ALP. In the liver, NDEA increased oxidative stress through the increase in LPO and decrease in SOD, and GSH-dependent enzymes. Although administration of garlic or silymarin significantly reduced the liver toxicity, combined administration was more effective in preventing the development of hepatotoxicity. Conclusion — These novel findings suggest that silymarin and garlic have a synergistic effect, and could be used as hepatoprotective agents against hepatotoxicity.

Garlic: nature's protection against physiological threats

Currently reliance on natural products is gaining popularity to combat various physiological threats including oxidative stress, cardiovascular complexities, cancer insurgence, and immune dysfunction. The use of traditional remedies may encounter more frequently due to an array of scientific evidence in their favor. Garlic (Allium sativum) holds a unique position in history and was recognized for its therapeutic potential. Recent advancements in the field of immunonutrition, physiology, and pharmacology further explored its importance as a functional food against various pathologies. Extensive research work has been carried out on the health promoting properties of garlic, often referred to its sulfur containing metabolites i.e. allicin and its derivatives. Garlic in its preparations are effective against health risks and even used as dietary supplements such as age garlic extract (AGE) and garlic oil etc. Its components/formulations can scavenge free radicals and protect membranes from damage and maintains cell integrity. It also provides cardiovascular protection mediated by lowering of cholesterol, blood pressure, anti-platelet activities, and thromboxane formation thus providing protection against atherosclerosis and associated disorders. Besides this, it possesses antimutagenic and antiproliferative properties that are interesting in chemopreventive interventions. Several mechanisms have been reviewed in this context like activation of detoxification phase-I and II enzymes, reactive oxygen species (ROS) generation, and reducing DNA damage etc. Garlic could be useful in preventing the suppression of immune response associated with increased risk of malignancy as it stimulates the proliferation of lymphocytes, macrophage phagocytosis, stimulates the release of interleukin-2, tumor necrosis factor-alpha and interferon-gamma, and enhances natural killer cells. In this paper much emphasis has been placed on garlic's ability to ameliorate oxidative stress, core role in cardiovascular cure, chemopreventive strategies, and indeed its prospective as immune booster.

N-Nitrosodimethylamine changes the expression of glutathione S-transferase in the liver of male mice: The role of antioxidants

The present study investigated the protective effect of gossypol, selenium, zinc, or glutathione (GSH) against dimethylnitrosamine (DMN)-induced hepatotoxicity in the livers of male mice. The expression and the activity of glutathione S-transferase (GST), levels of GSH, and free radicals (malondialdehyde (MDA)), as well as the activity of glutathione reductase were determined after the treatment of mice for seven consecutive days with low or high doses of gossypol, selenium, zinc, or GSH. In experimental groups, DMN was administered as a single dose for 2 h after the repeated dose treatments of mice for seven consecutive days with each antioxidant. DMN reduced the expression and inhibited the activity of GST. However, repeated treatments of mice with low-dose gossypol or high dose of either selenium or GSH followed by a single dose of DMN induced the expression and the activity of GST. In contrast, low-dose treatments of mice with zinc, selenium, or GSH followed by a single dose of DMN reduced the expression and the activity of GST compared to either control or DMN-treated groups. In addition, high-dose treatment with either gossypol or selenium markedly induced the levels of GSH compared to either control or DMN-treated groups. Interestingly, pretreatment of mice with high dose of either gossypol or selenium for seven consecutive days followed by a single dose of DMN decreased the levels of MDA, whereas DMN induced such levels. It is concluded that high dose of either gossypol or selenium is a stronger protector than zinc and GSH in ameliorating the toxic effects of DMN.

Effect of garlic on lipid peroxidation and antioxidation enzymes in DMBA-induced skin carcinoma

OBJECTIVE

Naturally occurring phytochemicals display an active cancer preventive strategy to inhibit, delay, or reverse human carcinogenesis. Studies have indicated that certain daily-consumed dietary phytochemicals have cancer protective effects mediated by carcinogens. Lipid peroxide plays a detrimental role in all cancers including skin carcinogenesis. Garlic, a phytochemical, has acquired a special position in the folklore of many cultures as a formidable prophylactic and therapeutic medicinal agent. In this report, we pursue the chemopreventive effect of aqueous garlic on skin carcinogenesis.

METHODS

"Swiss albino mice" were divided into five groups depending on the combination of skin cancer-inducing 7,12-dimethylbenz[a]anthracene and garlic treatments. Histology of the affected skin and biochemical assays for lipid peroxide, catalase, superoxide dismutase, glutathione-S-transferase, and glutathione peroxidase were performed to demonstrate the effect of garlic in mice. Immunoblotting was performed with cyclo-oxygenase-2, p53, and caspase-3 to demonstrate expressions of the respective proteins in skin lysates.

RESULTS

Garlic extracts inhibited the oxidative modification of lipids, thus protecting cells from injury by the oxidized molecules. The best chemopreventive action of garlic was observed in mice in which garlic treatment was performed before and after the induction of skin carcinogenesis. Garlic ingestion delayed formation of skin papillomas in animals and simultaneously decreased the size and number of papillomas, which was also reflected in the skin histology of the mice treated.

CONCLUSION

The protective effects against skin cancer elicited by garlic in mice are believed to be due at least in part to the induction cellular defense systems.

S-Allylcysteine reduces breast tumor cell adhesion and invasion

Previous studies show that aqueous garlic extract and its derivatives (e.g. S-allylcysteine [SAC]) prevent carcinogen-induced breast tumorigenesis. However, investigations testing the effect of SAC on later stages of breast tumorigenesis and/or metastasis have produced mixed results. Here we show that SAC significantly reduced anchorage-dependent and -independent growth of MDA-MB-231 breast tumor cells in a dose- and time-dependent fashion, and sub-lethal SAC-treatment altered mammary tumor cell adhesion and invasion through components of the extracellular matrix. We provide evidence to suggest increased expression of E-cadherin and reduced MMP-2 expression and activity are partially responsible for inhibition of mammary tumor cell invasion by SAC. Because E-cadherin and MMP-2 are important in cancer metastasis, these results suggest a link between SAC induction of E-cadherin and reduction of MMP2 activity with the inhibition of cell motility and invasion; thus providing evidence that events leading to breast cancer metastasis are repressed by sub-lethal SAC-treatment.

Protective effects of garlic powder against potassium dichromate-induced oxidative stress and nephrotoxicity

Potassium dichromate (K(2)Cr(2)O(7))-induced nephrotoxicity is associated with oxidative stress. In the present work the effect of garlic powder, a recognized antioxidant, on K(2)Cr(2)O(7)-induced nephrotoxicity and oxidative stress was studied. Rats were fed a 2% garlic powder diet for 1 month. A single injection of K(2)Cr(2)O(7) (15 mg/kg) to rats induced tubule interstitial damage and an increase in the following markers of renal injury 2 days later: blood urea nitrogen (4.6-fold), serum creatinine (9.7-fold), proteinuria (35.9-fold), urinary excretion of N-acetyl-beta-d-glucosaminidase (12.9-fold) and glutathione-S-transferase (2.3-fold) and a decrease of 65% in serum glutathione peroxidase activity. In addition, K(2)Cr(2)O(7) injection increased the following nitrosative and oxidative stress markers in kidney: 3-nitrotyrosine (1.9-fold), 4-hydroxy-2-nonenal (2.1-fold), malondialdehyde (1.8-fold) and protein carbonyl content (1.7-fold). It was found that garlic powder feeding was able to prevent by 44-71% the alterations in the markers of renal injury studied, by 55% the histological damage, and by 47-100% the increase in markers of oxidative and nitrosative stress. It is concluded that the ability of garlic powder to ameliorate K(2)Cr(2)O(7)-induced renal injury is associated with its antioxidant properties. Our data support the use of garlic powder as a renoprotective agent.

The antioxidant properties of garlic compounds: allyl cysteine, alliin, allicin, and allyl disulfide

Garlic and garlic extracts, through their antioxidant activities, have been reported to provide protection against free radical damage in the body. This study investigated antioxidant properties of garlic compounds representing the four main chemical classes, alliin, allyl cysteine, allyl disulfide, and allicin, prepared by chemical synthesis or purification. Alliin scavenged superoxide, while allyl cysteine and allyl disulfide did not react with superoxide. Allicin suppressed the formation of superoxide by the xanthine/xanthine oxidase system, probably via a thiol exchange mechanism. Alliin, allyl cysteine, and allyl disulfide all scavenged hydroxyl radicals; the rate constants calculated based on deoxyribose competitive assay were 1.4-1.7 x 10(10), 2.1-2.2 x 10(9), and 0.7-1.5 x 10(10) M (1) second(1), respectively. Contrary to previous reports, allicin did not exhibit hydroxyl radical scavenging activity in this study. Alliin, allicin, and allyl cysteine did not prevent induced microsomal lipid peroxidation, but both alliin and allyl cysteine were hydroxyl scavengers, and allyl disulfide was a lipid peroxidation terminator. In summary, our findings indicated that allyl disulfide, alliin, allicin, and allyl cysteine exhibit different patterns of antioxidant activities as protective compounds against free radical damage.

Cancer chemoprevention with garlic and its constituents

Advance metastasized cancers are generally incurable; hence an effort to prolong the process of carcinogenesis through chemoprevention has emerged consistent with this notion. In recent years, a considerable attention has been placed to identify naturally occurring chemopreventive substances capable of inhibiting, retarding or reversing the process of carcinogenesis. A number of phenolic substances, particularly those present in dietary and medicinal plants, have been shown to possess substantial anticarcinogenic and antimutagenic activities. Epidemiological observations and laboratory studies, both in cell culture and animal models have indicated anticarcinogenic potential of garlic and its constituents, which has been traditionally used for varied human ailments around the world. Chemical analysis has indicated that protective effects of garlic appear to be related to the presence of organosulfur compounds mainly allyl derivatives. Several mechanisms have been presented to explain cancer chemopreventive effects of garlic-derived products. These include modulation in activity of several metabolizing enzymes that activate and detoxify carcinogens and inhibit DNA adduct formation, antioxidative and free radicals scavenging properties and regulation of cell proliferation, apoptosis and immune responses. Recent data show that garlic-derived products modulate cell-signaling pathways in a fashion that controls the unwanted proliferation of cells thereby imparting strong cancer chemopreventive as well as cancer therapeutic effects. This review discusses mechanistic basis of cancer chemopreventive effects of garlic-derived products, their implication in cancer management and ways and means to take these agents from bench to real life situations.

Aged garlic extract has potential suppressive effect on colorectal adenomas in humans

Epidemiological and animal studies suggest AGE and its organosulfur constituents, such as S-allylcysteine and S-allylmercaptocysteine have anticarcinogenic effects. To confirm these effects in humans, a preliminary double-blind, randomized clinical trial using high-dose AGE (AGE 2.4 mL/d) as an active treatment and low-dose AGE (AGE 0.16 mL/d) as a control was performed on patients with colorectal adenomas-precancerous lesions of the large bowel. The study enrolled 51 patients who were diagnosed as carrying colorectal adenomas. The patients were randomly assigned to the two groups after adenomas larger than 5 mm in diameter were removed by polypectomy. The number and size of adenomas right before intake (0 mo) and at 6 and 12 mo after intake were measured using colonoscopy. Thirty-seven patients (19 in the active group, 18 in the control group) completed the study and were evaluated for the efficacy of AGE. The number of adenomas increased linearly in the control group from the beginning (the baseline), but AGE significantly suppressed both the size and number of colon adenomas in patients after 12 mo of high-dose treatment (P=0.04). The results suggest AGE suppresses progression of colorectal adenomas in humans. It appears that AGE has multiple pathways to reduce cancer incidence and suppress its growth and proliferation.

The role of reactive oxygen species (ROS) production on diallyl disulfide (DADS) induced apoptosis and cell cycle arrest in human A549 lung carcinoma cells

Diallyl disulfide (DADS), an oil soluble constituent of garlic (Allium sativum), has been reported to cause antimutagentic and anticarcinogenic effects in vitro and in vivo by modulating phases I and II enzyme activities. In recent years, several studies suggested that the chemopreventive effects of DADS can also be attributed to induction of cell cycle arrest and apoptosis in cancer cells. In the present study, we reported that DADS-induced cell cycle arrest at G2/M and apoptosis in human A549 lung cancer cells in a time- and dose-dependent manner. Additionally, a significant increase of intracellular reactive oxygen species (ROS) was induced in A549 cells less than 0.5h after DADS treatment, indicating that ROS may be an early event in DADS-modulated apoptosis. Treatment of A549 cells with N-acetyl cysteine (NAC) completely abrogated DADS-induced cell cycle arrest and apoptosis. The result indicated that oxidative stress modulates cell proliferation and cell death induced by DADS.

Anticarcinogenic properties of garlic: a review

Garlic is a popular spice added to several edible preparations and is a remedy for a variety of ailments. Epidemeological as well as laboratory studies have shown that garlic consumption reduces certain cancer incidences in the stomach, colon, mammary, cervical, etc. This article focuses on the general chemistry, metabolism, anticarcinogenic properties, mechanism of action behind the anticarcinogenic effects, functional foods based on garlic; and future areas of research. Garlic has been shown to metabolized into N-aceryl-S-allyl cysteine, allyl mercaptan, diallyl disulfide, diallyl sulfide, diallyl sulfoxide, diallyl sulfone, and allyl methyl sulfide. Garlic has been thought to bring about its anticarcinogenic effect through a number of mechanisms, such as the scavenging of radicals, increasing gluathione levels, increasing the activities of enzymes such as glutathione S-transferase, catalase, inhibition of cytochrome p4502E1, DNA repair mechanisms, prevention of chromosomal damage etc. Future research should standardize the dosage of garlic and type, ie., whether it should be taken fresh, cooked, or aged. The formulation of odorless functional foods with the retention of anticarcinogenic activity should be further studied.

Dietary factors modifying breast cancer risk and relation to time of intake

Multiple factors contribute to the development of human breast cancer. However, environmental factors, especially dietary factors, appear to have the greatest effects. Evidence obtained in epidemiological studies has been corroborated by laboratory findings. Dietary components strongly associated with breast cancer include fat and phytochemicals. A diet high in n-3 polyunsaturated fatty acid (PUFA) or monounsaturated fatty acid (MUFA) and low in n-6 PUFA is protective against breast cancer. Some phytochemicals present in fruits and vegetables are also protective. Time of intake appears to be important: lifetime protection may be achieved if one is exposed to a dietary factor that lowers breast cancer risk early in life. Synergistic and antisynergistic interactions between dietary factors can modify breast cancer risk. The available evidence suggests that breast cancer risk can be reduced by early dietary intervention.

Organosulfur compounds from alliaceae in the prevention of human pathologies

A strong association between elevated plasma low-density-lipoprotein (LDL) and the development of cardiovascular diseases (CVD) has been established. Oxidation of LDL (Ox-LDL) promotes vascular dysfunction, enhances the production and release of inflammatory mediators such as reactive oxygen species and contribute to the initiation and progression of atherosclerosis. In addition, Ox-LDL enhances the production and release of tumor necrosis factor (TNF-alpha), interleukin (IL)-6, arachidonic acid metabolites and nitric oxide (NO) that are responsible for various human pathologies including cancer. Organosulfur compounds (OSC) from alliaceae modulate the glutathione (GSH) redox cycle and inhibits NFkappa-B activation in human T cells. Furthermore, OSC bioactivities include antioxidant, antibacterial, anticarcinogenic, antiatherogenic, immunostimulatory, and liver protection potential.

Kimchi and an Active Component, β-Sitosterol, Reduce Oncogenic H-Rasv12-Induced DNA Synthesis

The Korean fermented vegetable food, kimchi, has been demonstrated to have anticancer functional properties. This study examined the effect of kimchi samples, methanol extracts of commercially grown baechu cabbage kimchi (CK) and organically grown baechu cabbage kimchi (OK), as well as the dichloromethane fraction (DCM fr.) from CK, and the active compound (AC), which has been identified as largely beta-sitosterol, from DCM fr., on the Ras-dependent signaling pathway. CK, OK, and DCM fr. exhibited a greater inhibition against the proliferation of Rat2 fibroblasts transformed with Ras(v12) (HO6) than parental Rat2 fibroblasts. In addition, OK and DCM fr. showed a higher inhibitory effect than CK. Furthermore, we employed the single-cell microinjection technique, combined with 3-bromo-5'-deoxyuridine incorporation, to examine the effects of kimchi samples on DNA synthesis induced by microinjected oncogenic Ras(v12). When the DCM fr. and AC were used to treat Rat1 fibroblasts overexpressing human insulin receptors (HIRc-B) and microinjected with oncogenic H-Ras(v12), the DNA synthesis of injected cells was decreased, suggesting that kimchi might block the signaling pathway of oncogenic Ras(v12), thus preventing the proliferation of transformed cells. This study provides additional evidence that kimchi and its active components, including beta-sitosterol, have potential in both the prevention and treatment of cancer, and presents convincing evidence that the anticancer effects may be a result of an inhibition of Ras oncogene signaling.

Prevention of chemical carcinogen DNA binding and inhibition of nuclear RNA polymerase activity by organosulfur compounds as the possible mechanisms for their anticancer initiation and proliferation effects

This report examines the transcriptional roles and DNA binding properties of the three major organosulfur compounds (OSCs) from garlic, diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS). We found DADS and DATS, but not DAS, could be activated by the versatile epoxide-forming oxidant dimethyldioxirane (DMDO) and could strongly inhibit nuclear RNA synthesis in vitro. We also found that when incubated together with [3H]-labeled 17beta-estradiol (E(2)) for activation by DMDO, DADS and DATS, but not DAS, were able to prevent the binding of [3H]E(2) to DNA. This preventive effect of DADS and DATS was confirmed when liver microsomes were used, and further verified by 32P post-labeling analysis. Additionally, we discovered that the DMDO treated DADS and DATS, but not DAS, were able to directly inhibit the enzyme RNA polymerase per se. These novel findings provide new insights into the potential mechanisms of the preventive effects of OSCs on tumor initiation and promotion.

Apoptosis induction by S-allylcysteine, a garlic constituent, during 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis

The apoptosis-inducing capacity of S-allylcysteine (SAC), a water-soluble garlic constituent, during 7,12-dimethylbenz[a]anthracene-induced hamster buccal pouch (HBP) carcinogenesis was investigated in male Syrian hamsters using DNA fragmentation and the apoptosis-associated proteins, tissue transglutaminase (tTG) and Bcl-2. Hamsters were divided into four groups of six animals each. Animals in group 1 were painted with a 0.5% solution of DMBA in liquid paraffin on the right buccal pouches three times a week for 14 weeks. Group 2 animals painted with DMBA as in group 1, in addition received 200 mg kg(-1) body weight SAC orally on days alternate to DMBA application. Group 3 animals received SAC as in group 2. Group 4 animals received neither DMBA nor SAC and served as the control. The experiment was terminated at the end of 14 weeks. Administration of SAC (200 mg kg(-1) body weight) to animals painted with DMBA inhibited DMBA-induced HBP carcinogenesis as revealed by the absence of neoplasms, induction of tTG and inhibition of Bcl-2 expression. The results of the present study suggest that SAC may exert its chemopreventive effect by inducing apoptosis.

Mechanisms by which garlic and allyl sulfur compounds suppress carcinogen bioactivation. Garlic and carcinogenesis

Overall, a host of studies provides compelling evidence that garlic and its organic allyl sulfur components are effective inhibitors of the cancer process. These studies reveal that the benefits of garlic are not limited to a specific species, to a particular tissue, or to a specific carcinogen. Several mechanisms are likely to account for this protection. Notable among these is a depression in nitrosamine formation and a reduction in carcinogen bioactivation. The benefits provided by garlic must be viewed as part of the entire diet, since several dietary constituents can influence the degree of protection. More than one compound is responsible for the anticancer properties associated with garlic. Future research should focus on how genetic variability and daily environmental factors influence the anticancer benefits attributed to garlic and its allyl sulfur components.

Carbon tetrachloride-induced changes in the activity of phase II drug-metabolizing enzyme in the liver of male rats: role of antioxidants

Glutathione S-transferases and glutathione play an important role in the detoxification of most toxic agents. In the present study, the protective effects of some antioxidants (L-ascorbic acid (AA), vitamin E (VE) or garlic) on carbon tetrachloride-induced changes in the activity of alanine amino transferase (ALT), aspartate amino transferase (AST), glutathione S-transferase (GST), and the level of glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) were studied. The activities of ALT, and AST were assayed in plasma, whereas the activity of GST and the levels of GSH and TBARS were determined in the livers of rats. The current study included two experiments. In the first experiment, animals received single oral dose of CCl4 (400 mg/kg body weight) after administration of AA (100 mg/kg b.w.), VE (100 mg/kg b.w.) or garlic (800 mg/kg b.w.) as single oral doses. In the second experiment, rats received repeated oral doses of antioxidants for 12 consecutive days followed by a single oral dose of CCl4 on the 13th day and killed after that by 24 h. Treatment of male rats with CCl4 significantly increased the activity of ALT and AST in plasma, and the levels of both GSH and TBARS in the liver. On the other hand, CCl4 inhibited the activity of GST after single dose treatment. Single-dose treatments of rats with AA, VE or garlic prior to the administration of CCl4 could not restore the alterations in the activity of ALT and AST caused by CCl4 to the normal control level. However, repeated dose treatments with these agents restored such alterations to the normal level. We observed that VE is more effective than AA and garlic in restoring the inhibition of GST activity caused by CCl4 to the normal level after single dose treatments. On the other hand, AA and VE are more effective than garlic in restoring the induced TBARS level caused by CCl4 to the normal control level after repeated dose treatments. It has been observed that the tested antioxidants were able to antagonize the toxic effects of CCl4, and such counteracting effects were more pronounced when they were administered as repeated doses prior to administration of CCl4.

Organosulfur compounds from Allium and the chemoprevention of cancer

Allium vegetables and their associated organosulfur constituents are extensively studied for their chemopreventive potential against cancer. This article overviews their anticarcinogenic and antigenotoxic properties. Epidemiological studies (mostly case-control studies) provide strong evidence that Allium vegetable consumption reduces the incidence of gastric and colon cancer while the association between Allium vegetable consumption and other cancers is less convincing. Furthermore, many experimental studies have demonstrated that organosulfur compounds and Allium extracts have inhibitory effects on carcinogenesis in animals. These inhibitory effects are supported by many diverse mechanisms, including inhibition of carcinogen formation, modulation of carcinogen metabolism, inhibition of mutagenesis and genotoxicity, inhibition of cell proliferation and increase of apoptosis, inhibition of angiogenesis, and immune system enhancement. Before such constituents or extracts can be used in chemopreventive trials, it is important to verify their lack of toxicity and to investigate further their precise mechanisms of action throughout the whole process of carcinogenesis.

The influence of heating on the anticancer properties of garlic

Allyl sulfur compounds are the major active constituents found in crushed garlic. Research has revealed that garlic and its lipid- or water-soluble components have many pharmacologic properties; however, studies also demonstrate that heating has a negative influence on these beneficial effects. We recently conducted several studies to investigate the influence of microwave or oven heating on the anticarcinogenesis property of garlic. Our studies showed that as little as 60 s of microwave heating or 45 min of oven heating can block garlic's ability to inhibit in vivo binding of mammary carcinogen [7,12-dimethylbenzene(a)anthracene (DMBA)] metabolites to rat mammary epithelial cell DNA. Allowing crushed garlic to "stand" for 10 min before microwave heating for 60 s prevented the total loss of anticarcinogenic activity. Our studies demonstrated that this blocking of the ability of garlic was consistent with inactivation of alliinase. These studies suggest that heating destroyed garlic's active allyl sulfur compound formation, which may relate to its anticancer properties.

A historical perspective on garlic and cancer

Epidemiological and laboratory studies provide insight into the anticarcinogenic potential of garlic and its constituent compounds. Both water- and lipid-soluble allyl sulfur compounds are effective in blocking a myriad of chemically induced tumors. Part of the protection from these compounds probably relates to a block in nitrosamine formation and metabolism. However, blockage in the initiation and promotion phases of the carcinogenicity of various compounds, including polycyclic hydrocarbons, provide evidence that garlic and its constituents can alter several phase I and II enzymes. Their ability to block experimentally induced tumors in a variety of sites including skin, mammary and colon, suggests a general mechanism of action. Changes in DNA repair and in immunocompetence may also account for some of this protection. Some, but not all, allyl sulfur compounds can also effectively retard tumor proliferation and induce apoptosis. Changes in cellular thiol and phosphorylation stains may account for some of these antitumorigenic properties. The anticarcinogenic potential of garlic can be influenced by several dietary components including specific fatty acids, selenium, and vitamin A. Since garlic and its constituents can suppress carcinogen formation, carcinogen bioactivation, and tumor proliferation it is imperative that biomarkers be established to identify which individuals might benefit most and what intakes can occur with ill consequences.

Cholesterol-lowering effect of garlic extracts and organosulfur compounds: human and animal studies

The medicinal use of garlic dates back thousands of years, but there was little scientific support of its therapeutic and pharmacologic properties until recently. In the past decade, the cancer-protective effects of garlic have been well established by epidemiologic studies and animal experiments. However, the cardiovascular-protective properties of garlic are less well understood. In particular, despite the reported hypocholesterolemic effect of garlic, the mechanism of the effect is unclear. In a recent randomized, double-blind, placebo-controlled intervention study, we showed that aged garlic extract (AGE) supplementation was effective in lowering plasma concentration of total cholesterol by 7% and LDL cholesterol by 10% in hypercholesterolemic men compared with subjects consuming a placebo. Supplementation of AGE in animal diets similarly reduced plasma concentrations of total cholesterol and triacylglycerol by 15 and 30%, respectively. In subsequent experiments using cultured rat hepatocytes, we found 44--87% inhibition of cholesterol synthesis by the water-extractable fraction (WEF), methanol-extractable fraction (MEF) and petroleum ether-extractable fraction (PEF) of fresh garlic, and Kyolic (liquid form of AGE). These observations suggested that hydrophilic and hydrophobic compounds of garlic are inhibitory to cholesterol synthesis. Because S-allylcysteine (SAC) alone was less potent than Kyolic, which contains SAC and other sulfur compounds, a maximal inhibition appears to require a concerted action of multiple compounds of garlic. In a series of experiments, we further characterized the inhibitory potency of individual water-soluble and lipid-soluble compounds of garlic. Among water-soluble compounds, SAC, S-ethylcysteine (SEC), and S-propylcysteine (SPC) inhibited cholesterol synthesis by 40--60% compared with 20--35% by gamma-glutamyl-S-allylcysteine (GSAC), gamma-glutamyl-S-methylcysteine (GSMC) and gamma-glutamyl-S-propylcysteine (GSPC). Lipid-soluble sulfur compounds (i.e., diallyl sulfide, diallyl disulfide, diallyl trisulfide, dipropyl sulfide and dipropyl trisulfide) at low concentrations (0.05--0.5 mol/L) slightly (10--15%) inhibited cholesterol synthesis but became highly cytotoxic at high concentrations (1.0--4.0 mol/L). All water-soluble compounds, except S-allylmercaptocysteine, were not cytotoxic, judging from the release of cellular lactate dehydrogenase into the culture medium. Taken together, the results of our studies indicate that the cholesterol-lowering effects of garlic extract, such as AGE, stem in part from inhibition of hepatic cholesterol synthesis by water-soluble sulfur compounds, especially SAC.

S-allyl cysteine reduces oxidant load in cells involved in the atherogenic process

Oxidation of low-density lipoprotein (LDL) and activation of the pleiotropic transcription factor nuclear factor kappa B (NF-kappaB), are often the chemical and molecular alterations associated with the development of the atherosclerotic lesion. We have reported previously on the antioxidant properties of a garlic compound, S-allyl cysteine (SAC), and its ability to inhibit damage caused by oxidative stress in bovine endothelial cells. In this study, the antioxidant effects of SAC were further determined, using several in vitro assay systems. First, we determined the effect of SAC on Cu2+-induced oxidation of LDL. Varying concentrations of SAC were co-incubated with a standardized Cu2+/LDL solution, and LDL-oxidation was then ascertained by determining the formation of thiobarbituric acid reactive substances (TBARS). SAC inhibited LDL-oxidation at an optimum concentration of 1 mM. In another experiment, we determined the effects of SAC on oxidized-LDL (ox-LDL) activation of J774 murine macrophages and human umbilical vein endothelial cells (HUVEC). Cells were grown on 96-well plates, preincubated with SAC at 37 degrees C and 5% CO2 for 24 h, washed, and exposed to ox-LDL for 24 h. Levels of hydrogen peroxide (H2O2) were determined by a fluorometric assay. In both cell lines, SAC exhibited dose-dependent inhibition of H2O2 formation. We also studied the effects of SAC on NF-kappaB activation in HUVEC using tumor necrosis factor-a (TNF-alpha) or H2O2 as stimulators. Cells were grown in 75 cm2 flasks at 37 degrees C and 5% CO2 and were preincubated with SAC 24 h before stimulation with TNF-alpha or H2O2. Nuclear extracts were then prepared and NF-kappaB activation was determined using an electrophoretic mobility shift assay with a 32P-labeled probe. SAC exhibited dose-dependent inhibition of NF-kappaB activation. Our data suggest that SAC may act via antioxidant mechanisms to inhibit the atherogenic process.

Effects of garlic on 7,12-Dimethylbenz[a]anthracene-induced hamster buccal pouch carcinogenesis

The inhibitory effect of garlic (Allium sativum Linn) on 7, 12-dimethylbenz[a]anthracene (DMBA)-induced buccal pouch carcinogenesis was investigated in male Syrian hamsters. Measurement of lipid peroxidation, reduced glutathione (GSH), glutathione peroxidase (GPx), and glutathione S-transferase (GST) was used to monitor the chemopreventive potential of garlic. All hamsters painted on their buccal pouches with DMBA alone for 14 weeks developed well-differentiated squamous cell carcinomas. Diminished lipid peroxidation in the oral tumor tissue was accompanied by a significant increase in the levels of GSH, GPx, and GST. Administration of 250 mg/kg body weight aqueous garlic extract three times a week for 14 weeks effectively suppressed DMBA-induced oral carcinogenesis as revealed by the reduced incidence of neoplasms. The results of the present study suggest that garlic may exert its chemopreventive effects by modulating lipid peroxidation and enhancing the levels of GSH, GPx, and GST.

Effects of chemoprotective agents on the metabolic activation of the carcinogenic arylamines PhIP and 4-aminobiphenyl in human and rat liver microsomes

Carcinogenic aromatic amines, including the heterocyclic amines, may pose a significant health risk to humans. To determine the potential for chemoprotective intervention against the carcinogenicity of these arylamines and to better understand their mechanism of action, a range of agents, most of them natural dietary constituents, was examined in vitro for their ability to modulate the N-hydroxylation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 4-aminobiphenyl (ABP), an initial step in their bioactivation. Experiments were conducted with rat and human liver microsomes. The agents (diallyl sulfide, indole-3-carbinol, alpha-angelicalactone, cafestol/kahweol palmitates, cafestol, kahweol, benzylisothiocyanate, genistin, formononetin, daidzin, equol, biochanin A, Oltipraz, tannic acid, quercetin, ethoxyquin, green tea, and black tea) comprised a variety of chemical classes that included sulfur-containing compounds, antioxidants, flavonoids, phytoestrogens, diterpenes, and polyphenols. Several of these agents, quercetin, ethoxyquin, and black tea, were found to strongly inhibit PhIP N-hydroxylation in rat liver microsomes, resulting in a nearly 85-90% decrease in activity at 100 microM or 0.2%. Tannic acid and green tea, in addition to these agents, were also strong inhibitors of ABP N-hydroxylation. In human liver microsomes, each of these agents was strongly inhibitory (approx 85-95% at 100 microM or 0.02%) of PhIP and ABP N-hydroxylation. Theaflavins and polyphenols were judged to be the primary inhibiting components in the teas, the theaflavins showing the most potent effect. These results demonstrate that chemoprotective agents can inhibit the bioactivation of carcinogenic arylamines, and this is likely to be one of the mechanisms of protection.

Heating garlic inhibits its ability to suppress 7, 12-dimethylbenz(a)anthracene-induced DNA adduct formation in rat mammary tissue

The present studies compared the impact of heating, either by microwave or convection oven, on the ability of garlic to reduce the in vivo bioactivation of 7,12-dimethylbenz(a)anthracene (DMBA) in 55-d-old female Sprague-Dawley rats. In study 1, rats were fed a semipurified casein-based diet and treated by gastric gavage thrice weekly for 2-wk with crushed garlic (0.7 g in 2 mL corn oil) or the carrier prior to DMBA treatment (50 mg/kg body weight). Providing crushed garlic reduced by 64% (P < 0.05) the quantity DMBA-induced DNA adducts present in mammary epithelial cells compared to controls. In study 2, microwave treatment for 60 s, but not 30 s, decreased (P < 0.05) the protection provided by garlic against DMBA-induced adduct formation. In study 3, allowing crushed garlic to stand for 10 min prior to microwave heating for 60 s significantly (P < 0.05) restored its anticarcinogenic activity. Microwave heating of garlic for 30 s resulted in a 90% loss of alliinase activity. Heating in a convection oven (study 4) also completely blocked the ability of uncrushed garlic to retard DMBA bioactivation. Study 5 revealed that providing either 0.105 micromol diallyl disulfide or S-allyl cysteine by gastric gavage thrice weekly for 2 wk was effective in retarding DMBA bioactivation but isomolar alliin was not. These studies provide evidence that alliinase may be important for the formation of allyl sulfur compounds that contribute to a depression in DMBA metabolism and bioactivation.

Garlic, onion and cereal fibre as protective factors for breast cancer: a French case-control study

The role of diet on breast cancer risk was investigated in a case-control study of 345 patients diagnosed with primary breast carcinoma between 1986 and 1989 in the north-east of France (Lorraine). For each case, one control was matched for age (+/-3 years) and socio-economic status. The dietary history questionnaire consisted of a self-administered food frequency questionnaire, a 6-day food diary and an energy expenditure record. It also elicited personal characteristics and medical history. While taking into account total caloric intake and established risk factors, breast cancer risk was shown to decrease as consumption of fibre (p value for trend = 0.03), and garlic and onions (p value for trend <10(-6)) increased. This study also supports the epidemiologic evidence that saturated fat intake and breast cancer risk are associated in post-menopausal women (p value for trend = 0.03). Conversely, it suggests that unsaturated fat intake could lower the risk in the same subgroup (p value for trend = 0.03). Our findings on protective factors of breast cancer could induce effective preventive measures and warrant further experimental investigations to isolate specific subfractions.

Depressed p34cdc2 kinase activity and G2/M phase arrest induced by diallyl disulfide in HCT-15 cells

The present studies reveal the antiproliferative property of diallyl disulfide (DADS) in cultured human colon tumor cells (HCT-15) relative to its ability to decrease the proportion of cells in the G1 phase and increase the proportion of cells in the G2/M phase. The shift in the proportion of cells blocked in the G2/M phase increased as the concentration and duration of DADS exposure increased. Refeeding DADS-treated cells (50 microM) with complete medium without DADS resulted in a return to normal proliferation rates. Consistent with the G2/M phase arrest, DADS exposure inhibited p34cdc2 kinase activity within four hours of treatment. The maximum depression in p34cdc2 kinase activity (53%) occurred when 25 microM DADS was added to the medium. The present studies suggest that depressed p34cdc2 kinase activity is likely one of the early cellular events that may account for the antiproliferative property of DADS.

Chemopreventive properties of indole-3-carbinol (I3C): inhibition of DNA adduct formation of the dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine (PhIP), in female F344 rats

Indole-3-carbinol (I3C), a naturally occurring inhibitor of experimental carcinogenesis, was evaluated for its possible inhibitor effect on DNA-adduct formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a dietary mutagen, in female F344 rats. PhIP is a mammary carcinogen in female F344 rats and a colon carcinogen in male F344 rats. Four-week-old animals (4/group) were maintained on powdered AIN-76A diet with or without 13C (0.02% or 0.1%, w/w) for 58 days. PhIP (0.04%, w/w) was added to the diet from days 15 through 42. Animals were killed on days 43 and 58. DNA isolated from mammary epithelial cells (MECs), colon, liver, and white blood cells (WBCs) was analyzed for PhIP-DNA adducts by 32P-postlabeling assays. On day 43, adduct levels of the group receiving 0.1% dietary I3C decreased in MECs (91.9%), colon (67.2%), liver (69.2%), and WBCs (82.3%). On day 58, DNA adduct formation was inhibited in the colon (81.3-82.2%) at both dietary I3C concentrations, and in liver (46.8%) only in the animals fed 0.1% I3C. When incorporated in the diet after exposure to dietary PhIP (0.04% for 2 weeks), 13C (0.1%) had no effect on the rate of removal of PhIP-DNA adducts over the next 28 days. It is concluded that dietary I3C inhibits PhIP-DNA adduct formation in the female F344 rat but does not affect adduct removal. I3C may be a promising chemopreventive agent in PhIP-induced carcinogenesis in rats.

Allyl sulfides from garlic suppress the in vitro proliferation of human A549 lung tumor cells

The present studies compared the antiproliferative effects of diallyl trisulfide (DATS) and diallyl disulfide (DADS) on cultured human neoplastic (A549) and nonneoplastic (MRC-5) lung cells. Addition of 10 microM DATS reduced A549 growth by 47%, whereas 10 microM DADS decreased growth by only 20%. DATS treatment (10 microM) did not alter MRC-5 cell growth. DATS (10 microM) caused a marked and progressive increase in intracellular Ca2+ in A549 cells during the first four hours after treatment. Intracellular Ca2+ in A549 cells exposed to DATS returned to near control levels within one hour after refeeding complete medium without DATS. Exposure to 1 microM DATS for 24 hours significantly induced apoptosis, as indicated by increased DNA fragmentation. The ability of DATS and DADS to suppress neoplastic growth is consistent with increasing evidence that several garlic components have anticarcinogenic and antitumorigenic properties.

Modulation of phase I and phase II xenobiotic-metabolizing enzymes by selenium-enriched garlic in rats

Previous research showed that treatment with selenium-enriched garlic (Se-garlic) was able to inhibit the initiation phase of mammary carcinogenesis in the dimethyl-benz[a]anthracene (DMBA) model in rats. The present study was designed to investigate the following parameters: 1) DMBA-DNA adduct formation in liver and mammary gland, 2) urinary excretion of DMBA metabolites, 3) phase I and phase II xenobiotic-metabolizing enzymes, and 4) tissue selenium levels as a function of Se-garlic supplementation. Prior feeding with an Se-garlic-containing diet (at 3 ppm Se) for two weeks resulted in a consistent reduction of all DMBA adducts in liver and mammary gland. This was accompanied by a 40% increase in urinary excretion of DMBA metabolites over a two-day period. Several liver P-450 enzymes were examined in rats fed a diet supplemented with 1, 2, or 3 ppm Se. Compared with controls receiving 0.1 ppm Se, no significant alteration in activity was detected with respect to P-450 1A1 (responsible for DMBA activation), 1A2, 2B1, 2E1, and 3A4. In contrast, glutathione S-transferase and uridine 5'-diphosphate-glucuronyltransferase activities were elevated to a maximum of 2- to 2.5-fold in liver and kidney. As expected, there was a dose-dependent elevation of selenium concentrations in liver, kidney, mammary gland, and plasma as a function of the level of Se-garlic supplementation. Our data seem to suggest that an increased detoxification of carcinogen via the phase II conjugating enzymes might represent a mechanism of tumor suppression by Se-garlic.

Chemoprotection against the formation of colon DNA adducts from the food-borne carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in the rat

The mutagenic heterocyclic aromatic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), is a pyrolysis product in cooked foods that has been shown to be a rat colon carcinogen and has been implicated in the etiology of human colon cancer. In order to identify chemoprotection strategies that could be carried out in humans, a pilot study was conducted in which PhIP-DNA-adduct levels were quantified in the colons of male F344 rats that had been subjected to 16 different putative chemoprotection regimens, followed by a gavage of PhIP (50 mg/kg) and sacrifice 24 h later. The 16 treatments (Oltipraz, benzylisothiocyanate, diallyl sulfide, garlic powder, ethoxyquin, butylated hydroxyanisole, glutathione, indole-3-carbinol, alpha-angelicalactone, kahweol/cafestol palmitates, quercetin, green tea, black tea, tannic acid, amylase-resistant starch, and physical exercise) comprised sulfur-containing compounds, antioxidants, flavonoids, diterpenes, polyphenols, high dietary fiber, etc. The strongest inhibition of PhIP-DNA adduct formation in the colon was observed upon pretreatment with black tea, benzylisothiocyanate, and a mixture (1:1) of kahweol:cafestol palmitates, which resulted in 67, 66, and 54% decreases in colon PhIP-DNA adduct levels, as compared with controls. Preliminary studies on their mechanism of action indicated that only kahweol:cafestol caused a substantial induction of glutathione S-transferase isozymes (GSTs) that are thought to be important in the detoxification of PhIP. Notably, this induction occurred in the liver rather than in the colon.

DNA adducts of heterocyclic amines: formation, removal and inhibition by dietary components

The dietary mutagens 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) are carcinogenic in rodents. In F344 rats PhIP induces mammary tumors in females and colon tumors in males, while IQ induces tumors principally in the liver, Zymbal gland and intestines. In CDF1 mice, IQ induces liver, lung and forestomach tumors. We have evaluated the dynamics of formation, removal and inhibition of PhIP- and IQ-DNA adducts in these rodents. After bolus doses (50 mg/kg, by gavage) of IQ or PhIP, both IQ- and PhIP-DNA adducts were removed rapidly from both target and nontarget organs, while after 3-4 weeks of feeding IQ or PhIP (0.01-0.04%) adduct removal was much slower. Gavaging of male F344 rats with PhIP (0.1-1000 micrograms/kg/day) for 23 days resulted in accumulation of PhIP-DNA adducts in various organs, but adducts were detectable only at 100 or 1000 micrograms/kg/day. Urinary excretion of unchanged PhIP was a constant proportion (1.6-2.1%) of the daily dose over the entire dose range and was independent of duration of exposure. When weanling female F344 rats were exposed to dietary PhIP (0.01-0.04%) for 1-4 weeks, the presence of either conjugated linoleic acid (CLA; 0.1-1.0%) or indole-3-carbinol (13C; 0.1%) in the diet inhibited PhIP-DNA adduct formation (58-99%) in various organs, including the mammary gland and the colon. Similarly, the inclusion of 0.075% 4-ipomeanol (IPO) in the diet of male CDF1 mice exposed for 3 weeks to dietary IQ (0.01%) resulted in inhibition of IQ-DNA adduct formation (30-59%) in the target organs (liver, lungs, stomach) but not in a number of other organs. It is concluded that (1) the rate of PhIP- and IQ-DNA adduct removal depends on the dose and frequency of administration, (2) urinary PhIP may be a good biomarker of recent PhIP exposure and (3) CLA, I3C and IPO are potential chemopreventive agents against PhIP- or IQ-induced tumors in rodents.