Antiproliferative effect of the garlic compound S-allyl cysteine on human neuroblastoma cells in vitro

S-allylcysteine ameliorates isoproterenol-induced cardiac toxicity in rats by stabilizing cardiac mitochondrial and lysosomal enzymes

This study was aimed to evaluate the preventive role of S-allylcysteine (SAC) on mitochondrial and lysosomal enzymes in isoproterenol (ISO)-induced rats. Male albino Wistar rats were pretreated with SAC (50, 100 and 150 mg/kg) daily for a period of 45 days. After the treatment period, ISO (150 mg/kg) was subcutaneously injected to rats at an interval of 24 h for two days. The activities of heart mitochondrial enzymes (isocitrate dehydrogenase, succinate dehydrogenase, malate dehydrogenase and alpha-ketoglutarate dehydrogenase) and respiratory chain enzymes (NADH dehydrogenase and cytochrome C oxidase) were decreased significantly (p<0.05) in ISO-induced rats. The activities of lysosomal enzymes (beta-glucuronidase, beta-N-acetyl glucosaminidase, beta-galactosidase, cathepsin-D and acid phosphatase) were increased significantly (p<0.05) in serum and heart of ISO-induced rats. Pretreatment with SAC (100 mg/kg and 150 mg/kg) for a period of 45 days increased significantly (p<0.05) the activities of mitochondrial and respiratory chain enzymes and decreased the activities of lysosomal enzymes significantly (p<0.05) in ISO-induced rats. Oral administration of SAC (50, 100 and 150 mg/kg) for a period of 45 days to normal rats did not show any significant (p<0.05) effect in all the parameters studied. The altered electrocardiogram (ECG) of ISO-treated rats was also restored to near normal by treatment with SAC (100 and 150 mg/kg). These results confirm the efficacy of SAC in alleviating ISO-induced cardiac damage.

International comparisons of prostate cancer mortality rates with dietary practices and sunlight levels

Prostate cancer mortality rates vary widely across the world. The purpose of this study is to identify environmental factors associated with prostate cancer mortality risk. Prostate cancer mortality rates in 71 countries were compared to per capita food intake rates using age-adjusted cancer rates (year 2000) from the International Agency for Research on Cancer, and food consumption data (1990-1992) provided by the Food and Agricultural Organization of the United Nations. Simple regression models were applied to prostate cancer mortality rates and consumption rates for 38 foods (or food categories), and sunlight levels (latitude from the equator and ultraviolet indexes). The analysis found a correlation between increased prostate cancer mortality rates and the consumption of total animal calories, total animal fat calories, meat, animal fat, milk, sugar, alcoholic beverages, and stimulants. The consumption of cereal grains and rice, in particular, correlated strongly with decreasing prostate cancer mortality. The analysis found that increased sunlight levels and consumption of oilseeds, soybeans, and onions also correlate with decreased prostate cancer mortality risk. Stepwise multiple regression analysis was used to build a regression model with minimum colinearity between the variables. Cereals, total animal fat calories, sugar, and onions are the foods that resulted in a model with the best fit. Cereals, ultraviolet index, sugar, and onions were the variables found to provide the best fit in a model when ambient sunlight exposure was included as a factor.

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.

Preventive effect of S-allylcysteine on lipid peroxides and antioxidants in normal and isoproterenol-induced cardiotoxicity in rats: a histopathological study

The consumption of diets rich in plant foods are associated with a reduced risk of cardiovascular diseases. This study was aimed to evaluate the role of S-allylcysteine (SAC) in isoproterenol (ISO)-induced myocardial infarction (MI) in rats. Subcutaneous injection of ISO (150 mg/kg) to Wistar rats showed a significant decrease in the activities of marker enzymes such as creatine kinase, lactate dehydrogenase, aspartate and alanine transaminases in heart and a significant increase in the levels of thiobarbituric acid reactive substances and lipid hydroperoxides in plasma and heart. ISO-induced rats also showed a significant decrease in the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione S-transferase in heart and the levels of glutathione and ascorbic acid in plasma and heart. Oral administration of SAC (100 and 150 mg/kg) to ISO-treated rats daily for a period of 45 days caused a significant increase in the activities of marker enzymes and improved the antioxidant status by decreasing lipid peroxidative products and increasing the activities of antioxidant enzymes and the levels of nonenzyomic antioxidants. Administration of SAC to normal rats did not show any significant effect. Histopathological findings of the myocardial tissue showed a protective role of SAC in ISO-treated rats. The effect at a dose of 150 mg/kg of SAC was more pronounced than that of the dose 100mg/kg and brought back all the parameters to near normal. The effect exerted by 100 mg/kg of SAC was similar to that of alpha-tocopherol (60 mg/kg). The results of our study show that SAC possesses antioxidant activity in ISO-induced experimental MI.

Redox-sensitive proteins are potential targets of garlic-derived mercaptocysteine derivatives

Molecular investigations support existing clinical and epidemiological data that garlic-derived allylsulfides reduce cancer risk. Various allylsulfides can diminish progression of cancer cells at either the G1/S or G2/M phase. Allylsulfide derivatives modify redox-sensitive signal pathways and cause growth inhibition, mitotic arrest, and apoptosis induction. Whether allylsulfides modify intracellular redox potentials by affecting the ratio of glutathione:glutathione disulfide and/or by interacting directly with sulfhydryl domains on regulatory or catalytic-signal proteins requires further investigation. To understand the possible biochemical mechanisms contributing to the protective effects of allylsulfides, we investigated the ability of these compounds to undergo enzyme-catalyzed transformations. In addition to catalyzing gamma-elimination reactions, gamma-cystathionase can perform beta-elimination reactions with cysteinyl S-conjugates derived from garlic extracts when the S-alkyl group (R) is larger than ethyl. The reaction products are pyruvate, ammonium, and a sulfur-containing fragment (RSH). beta-Lyase substrates of gamma-cystathionase thus far identified from garlic include: S-allyl-L-cysteine (R=CH2=CHCH2-), S-allylmercapto-L-cysteine (R=CH2=CHCH2S-), and S-propylmercapto-L-cysteine (R=CH3CH2CH2S-). Mercapto derivatives yield persulfide products (RSSH) that are potential sources of sulfane sulfur, which may modify protein function by reacting at important cysteinyl domains. Thus, beta-elimination reactions with cysteine S-conjugates in garlic may modify cancer-cell growth by targeting redox-sensitive signal proteins at sulfhydryl sites, thereby regulating cell proliferation and/or apoptotic responses. These interactions may be useful in identifying efficacy of garlic-derived compounds and/or developing other novel organosulfur compounds that may modify intracellular redox potentials or interact with thiols associated within cysteine domains in regulatory, catalytic, signal, or structural proteins.

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.

S-allyl cysteine attenuated CCl4-induced oxidative stress and pulmonary fibrosis in rats

This study examined effects of S-allyl cysteine (SAC) on carbon tetrachloride (CCl4)-induced interstitial pulmonary fibrosis in Wistar rats. CCl4 (0.5 ml/kg) was intraperitoneally injected into rats twice a week for 8 weeks, and SAC (50, 100, or 200 mg/kg), N-acetyl cysteine (NAC, 200 or 600 mg/kg), or L-cysteine (CYS, 600 mg/kg) were orally administrated to rats everyday for 8 weeks. SAC significantly reduced the increases of transforming growth factor beta, lipid peroxides, AST, and ALT in plasma, induced by CCl4. Although CCl4 is mainly metabolized by hepatic cytochrome P450, CCl4 induced systemic inflammation and some organ fibrosis. SAC dose-dependently and significantly attenuated CCl4-induced systemic inflammation and fibrosis of lung. SAC also inhibited the decrease of thiol levels, the increase of inducible nitric oxide synthase expression, the infiltration of leukocytes, and the generation of reactive oxygen species in lungs. Although NAC and CYS attenuated CCl4-induced pulmonary inflammation and fibrosis, the order of preventive potency was SAC > NAC > CYS according to their applied doses. These results indicate that SAC is more effective than other cysteine compounds in reducing CCl4-induced lung injury, and might be useful in prevention of interstitial pulmonary fibrosis.

Synthesis, characterization, and biological activity of a new palladium(II) complex with deoxyalliin

Synthesis, characterization, and biological activity of a new water-soluble Pd(II)–deoxyalliin (S-allyl-L-cysteine) complex are described in this article. Elemental and thermal analysis for the complex are consistent with the formula [Pd(C6H10NO2S)2].13C NMR,1H NMR, and IR spectroscopy show coordination of the ligand to Pd(II) through S and N atoms in a square planar geometry. Final residue of the thermal treatment was identified as a mixture of PdO and metallic Pd. Antiproliferative assays using aqueous solutions of the complex against HeLa and TM5 tumor cells showed a pronounced activity of the complex even at low concentrations. After incubation for 24 h, the complex induced cytotoxic effect over HeLa cells when used at concentrations higher than 0.40 mmol/L. At lower concentrations, the complex was nontoxic, indicating its action is probably due to cell cycle arrest, rather than cell death. In agreement with these results, the flow cytometric analysis indicated that after incubation for 24 h at low concentrations of the complex cells are arrested in G0/G1.Key words: palladium(II), deoxyalliin, S-allyl-L-cysteine, tumor cells, cancer.

Allicin (from garlic) induces caspase-mediated apoptosis in cancer cells

Garlic (Allium sativum) has been used for centuries for treating various ailments, and its consumption is said to reduce cancer risk and its extracts and components effectively block experimentally induced tumors. Allicin, the major component present in freshly crushed garlic, is one of the most biologically active compounds of garlic. We found that allicin inhibited the growth of cancer cells of murine and human origin. Allicin induced the formation of apoptotic bodies, nuclear condensation and a typical DNA ladder in cancer cells. Furthermore, activation of caspases-3, -8 and -9 and cleavage of poly(ADP-ribose) polymerase were induced by allicin. The present results demonstrating allicin-induced apoptosis of cancer cells are novel since allicin has not been shown to induce apoptosis previously. Our results also provide a mechanistic basis for the antiproliferative effects of allicin and partly account for the chemopreventive action of garlic extracts reported by earlier workers.

Induction of histone acetylation and inhibition of growth of mouse erythroleukemia cells by S-allylmercaptocysteine

Growth-inhibitory effects on DS19 mouse erythroleukemia cells were seen in the micromolar concentration range with allicin and S-allylmercaptocysteine and in the millimolar range with allyl butyrate, allyl phenyl sulfone, and S-allyl cysteine. Increased acetylation of histones was induced by incubation of cells with the allyl compounds at concentrations similar to those that resulted in the inhibition of cell proliferation. The induction of histone acetylation by S-allylmercaptocysteine was also observed in Caco-2 human colon cancer cells and T47D human breast cancer cells. In contrast to the effect on histone acetylation, there was a decrease in the incorporation of phosphate into histones when DS19 cells were incubated with 25 microM S-allylmercaptocysteine. Histone deacetylase activity was inhibited by allyl butyrate, but there was little or no effect with the allyl sulfur compounds examined in this study. A similar degree of downregulation of histone deacetylase and histone acetyltransferase was observed when DS19 cells were incubated with S-allylmercaptocysteine or allyl isothiocyanate. The induction of histone acetylation by S-allylmercaptocysteine was not blocked by a proteasome inhibitor. The mechanism by which S-allylmercaptocysteine induces histone acetylation remains to be characterized. It may be related in part to metabolism to allyl mercaptan, which is a more effective inhibitor of histone deacetylase.

Sulfoxides as urinary metabolites of S-allyl-L-cysteine in rats: evidence for the involvement of flavin-containing monooxygenases

S-Allyl-L-cysteine (SAC), a component of garlic and a metabolite of allyl halides, is a known substrate for multiple flavin-containing monooxygenases (FMOs). In the current study, we characterize the in vivo SAC metabolism by investigating the presence of SAC, N-acetyl-S-allyl-L-cysteine (NASAC), and their corresponding sulfoxides in the urine of rats given SAC (200 or 400 mg/kg i.p.). In some experiments, rats were given aminooxyacetic acid (AOAA), an inhibitor of cysteine conjugate beta-lyase, or methimazole, an alternative FMO substrate, 30 min prior to treatment with 200 mg/kg SAC. Nearly 40 to 50% of the dose was recovered in the 24-h collection period. In all treatment groups, the majority of the metabolites were excreted within 8 h. The major metabolites detected were NASAC and NASAC sulfoxide (NASACS; nearly 30-40% and 5-10% of the dose, respectively). Only small amounts of the dose (approximately 1.5%) were recovered as SAC and SAC sulfoxide (SACS). Methimazole pretreatment significantly reduced amounts of both SACS and NASACS detected in the urine when compared with rats given SAC only, whereas AOAA pretreatment had no effect. In vitro assays using rat liver microsomes were also carried out to compare the sulfoxidation rates of SAC and NASAC. The results showed that SAC was much more readily oxidized than NASAC. Collectively, the results provide evidence for the involvement of FMOs in the in vivo metabolism of SAC and that SAC is a much better substrate for FMOs than its corresponding mercapturic acid.

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.

Dual role of organosulfur compounds in foods: a review

Organosulfur compounds present in natural food are generally considered as beneficial for health because of their antioxidant and anticarcinogenic properties. This has led to their excessive and long-term consumption. However, there is also evidence that these compounds demonstrate toxicity and adverse health effects suggesting their potential dual biological roles. Thus, they can act as double-edged biological swords.

Physical, chemical, and biological properties of s-allylcysteine, an amino acid derived from garlic

Physical, chemical, and biological properties of S-allylcysteine (SAC) were investigated. SAC showed stable properties under tested conditions, and its acute/subacute toxicity was very minor in mice and rats (LD(50) value >54.7 mM/kg po; >20 mM/kg ip). The pharmacokinetics of SAC was investigated after oral administration of garlic supplement containing SAC to human volunteers. SAC from garlic consumption was rapidly absorbed from the gastrointestinal tract, however, the half-life and excretion time were more than 10 h and 30 h, respectively.

Effect of purified allicin, the major ingredient of freshly crushed garlic, on cancer cell proliferation

The diverse health benefit effects of garlic include its anticancer activity. However, very little is known about such activity of isolated garlic compounds, among which allicin (the major ingredient of crushed garlic) has been the least studied. The aim of this work was to determine whether pure allicin exhibits the antiproliferative effect reported for garlic in in vitro models. Allicin, but not its precursor alliin, inhibited proliferation of human mammary (MCF-7), endometrial (Ishikawa), and colon (HT-29) cancer cells (50% inhibitory concentration = 10-25 microM). Two of three tested primary lines of human fibroblasts displayed a similar response to allicin (50% inhibitory concentration = 16-40 microM), whereas the third line was almost unaffected by this compound. The pure allicin and water extract of garlic powder with equivalent allicin concentrations displayed a similar potency, suggesting that allicin is responsible for the antiproliferative effect of the extract. The growth inhibition was accompanied by accumulation of cells in the G0/G1 and G2/M phases of the cell cycle (MCF-7 cells) and not by a significant increase in cell death. Allicin caused a transient drop in the intracellular glutathione (GSH) level, the magnitude and kinetics of which significantly varied depending on cell type. The extent of the decrease in GSH levels correlated well (r = 0.75) with the growth inhibitory activity of allicin. On the basis of these findings, we suggest that allicin plays a major role in the antiproliferative effect of water-soluble garlic preparations and that this effect may be attributed to the ability of allicin to transiently deplete the intracellular GSH level.

Allyl sulfides modify cell growth

Extensive evidence points to the ability of allyl sulfides from garlic to suppress tumor proliferation both in vitro and in vivo. This antineoplastic effect is generally greater for lipid-soluble than water-soluble allyl sulfides. Both concentration and duration of exposure can increase the antiproliferative effects of lipid- and water-soluble allyl sulfides. Part of their antiproliferative effects may relate to an increase in membrane fluidity and a suppression of integrin glycoprotein IIb-IIIa mediated adhesion. Alterations in cholesterol, arachidonic acid, phospholipids and/or thiols may account for these changes in membrane function. Allyl sulfides are also recognized for their ability to suppress cellular proliferation by blocking cells in the G2/M phase and by the induction of apoptosis. This increase in the G2/M and apoptotic cell populations correlates with depressed p34cdc2 kinase activity, increased histone acetylation, increased intracellular calcium and elevated cellular peroxide production. While impressive pre-clinical data exist about the antineoplastic effects of allyl sulfur compounds, considerably more attention needs to be given to their effects in humans. The composition of the entire diet and a host of genetic/epigenetic factors will likely determine the true benefits that might arise from allyl sulfur compounds from garlic and other Allium foods.

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.

Garlic compounds minimize intracellular oxidative stress and inhibit nuclear factor-kappa b activation

Oxidative modification of LDL has been recognized as playing an important role in the initiation and progression of atherosclerosis. In this study, we determined the effects of aged garlic extract (AGE) and its major compound, S-allylcysteine (SAC), on oxidized LDL (Ox-LDL)-induced injury in endothelial cells (EC). Lactate dehydrogenase (LDH) release as an index of membrane damage, methylthiazol tetrazoium (MTT) assay for cell viability and thiobarbituric acid reactive substances (TBARS) indicating lipid peroxidation were measured. Ox-LDL caused an increase of LDH release, loss of cell viability and TBARS formation. Both AGE and SAC prevented all of these changes. To elucidate the mechanism, effects of AGE or SAC on intracellular glutathione (GSH) level in EC, and release of peroxide from EC and macrophages (M Phi) were determined. Ox-LDL depleted intracellular GSH and increased release of peroxides. Both AGE and SAC inhibited these changes. Effects of SAC on hydrogen peroxide (H(2)O(2)) or tumor necrosis factor (TNF)-alpha-induced nuclear factor (NF)-kappa B activation were determined. Pretreatment of EC with SAC inhibited NF-kappa B activation. We demonstrated that both AGE and SAC can protect EC from Ox-LDL-induced injury by preventing intracellular GSH depletion in EC and by minimizing release of peroxides from EC and M Phi. SAC also inhibited H(2)O(2)- or TNF-alpha-induced NF-kappa B activation. Our data suggest that AGE and its main compound, SAC, may be useful for prevention of atherosclerosis.

Possible mechanism by which allyl sulfides suppress neoplastic cell proliferation

Both oil- and water-soluble allyl sulfur compounds from garlic have been found to possess antitumorigenic properties. These antitumorigenic properties increase as exposure increases both in vitro and in vivo. Generally, oil-soluble allyl sulfur compounds are more effective antiproliferative agents than their water-soluble counterparts. The ability of these compounds to suppress proliferation is associated with a depression in cell cycle progression and the induction of apoptosis. This depression in cell division coincides with an increase in the percentage of cells blocked in the G(2)/M phase of the cell cycle. A depression in p34(cdc2) kinase may account for this blockage in cell division.

Alterations of prostate biomarker expression and testosterone utilization in human LNCaP prostatic carcinoma cells by garlic-derived S-allylmercaptocysteine

BACKGROUND

This study determined the effects of S-allylmercaptocysteine (SAMC), a phytoconstituent from garlic, on the expression of androgen-responsive biomarkers, prostate specific antigen (PSA), and prostate specific membrane antigen (PSMA), in human prostatic carcinoma cells (LNCaP).

METHODS

Secretion of PSA was determined as well as the activity of PSMA measured as a function of its ability to hydrolyze poly-gamma-glutamated folate and N-acetylaspartylglutamate (NAAG). Folate hydrolase capacity was also determined in SAMC-treated cells grown in charcoal stripped fetal calf serum (CS-FCS). In addition, testosterone disappearance was measured from culture media of SAMC-treated LNCaP and PC-3 cells as well as from cell free lysates.

RESULTS

PSA secretions were significantly decreased compared to control values at 1 day (8.4 +/- 2.6 vs. 18.9 +/- 1.7, P < 0.01), 4 days (18.9 +/- 5.3 vs. 73.8 +/- 4. 4, P < 0.001), and 6 days (35.6 +/- 2.1 vs. 96.5 +/- 17.9 ng/10(5) cells, P < 0.01; mean +/- SD). By contrast, PSMA activity measured as either folate hydrolase or NAAG dipeptidase (NAALADase) activity increased in cells treated with SAMC. PSMA-folate hydrolase activity in SAMC-treated cells grown in CS-FCS increased beyond that observed in cells grown in CS-FCS alone. Pre-exposure of LNCaP cells to SAMC resulted in enhanced rate of testosterone disappearance from culture media at 6 hr (P < 0.01) and at 48 hr (P < 0.001) compared to media from cells not previously exposed to SAMC. Results similar to these were also observed in androgen-independent PC-3 cells treated with SAMC. In lysates of SAMC-treated LNCaP cells, the rate of testosterone catabolism was twice that from phosphate buffered saline (PBS)-treated cells. SAMC-treated LNCaP cells grown in media supplemented with testosterone temporarily exhibited enhanced growth over a 2 day period but cell numbers declined later to levels similar to those of SAMC treatment.

CONCLUSIONS

These results show that SAMC exhibits differential effects on recognized biomarkers for LNCaP cells similar to those produced by androgen deprivation and strongly suggests that this effect may be mediated, in part, by diminishing the trophic effects of testosterone, likely by converting it to metabolites less reactive toward androgen receptors.

Formation of 14,15-Hepoxilins of the A3 and B3 Series through a 15-Lipoxygenase and Hydroperoxide Isomerase Present in Garlic Roots

We report herein for the first time the formation by freshly grown garlic roots and the structural characterization of 14,15-epoxide positional analogs of the hepoxilins formed via the 15-lipoxygenase-induced oxygenation of arachidonic acid. These compounds are formed through the combined actions of a 15(S)-lipoxygenase and a hydroperoxyeicosatetraenoic acid (HPETE) isomerase. The compounds were formed when either arachidonic acid or 15-HPETE were used as substrates. Both the "A"-type and the "B"-type products are formed although the B-type compounds are formed in greater relative quantities. Chiral phase high performance liquid chromatography analysis confirmed the formation of hepoxilins from 15(S)- but not 15(R)-HPETE, indicating high stereoselectivity of the isomerase. Additionally, the lipoxygenase was of the 15(S)-type as only 15(S)-hydroxyeicosatetraenoic acid was formed when arachidonic acid was used as substrate. The structures of the products were confirmed by gas chromatography-mass spectrometry of the methyl ester trimethylsilyl ether derivatives as well as after characteristic epoxide ring opening catalytically with hydrogen leading to dihydroxy products. That 15(S)-lipoxygenase activity is of functional importance in garlic was shown by the inhibition of root growth by BW 755C, a dual cyclooxygenase/lipoxygenase inhibitor and nordihydroguaiaretic acid, a lipoxygenase inhibitor. Additional biological studies were carried out with the purified intact 14(S), 15(S)-hepoxilins, which were investigated for hepoxilin-like actions in causing the release of intracellular calcium in human neutrophils. The 14,15-hepoxilins dose-dependently caused a rise in cytosolic calcium, but their actions were 5-10-fold less active than 11(S), 12(S)-hepoxilins derived from 12(S)-HPETE. These studies provide evidence that 15(S)-lipoxygenase is functionally important to normal root growth and that HPETE isomerization into the hepoxilin-like structure may be ubiquitous; the hepoxilin-evoked release of calcium in human neutrophils, which is receptor-mediated, is sensitive to the location within the molecule of the hydroxyepoxide functionality.

Effects of garlic compounds diallyl sulfide and diallyl disulfide on arylamine N-acetyltransferase activity in strains of Helicobacter pylori from peptic ulcer patients

Arylamine N-acctyltransferase (NAT) activities with p-aminobenzoic acid (PABA) and 2-aminofluorene (2-AF) were determined in the bacterium Helicobacter pylori collected from peptic ulcer patients. Two assay systems were performed, one with cellular cytosols, the other with intact cell suspensions. Cytosols or suspensions of H. pylori with or without specific concentrations of diallyl sulfide (DAS) or diallyl disulfide (DADS) co-treatment showed different percentages of 2-AF and PABA acetylation. The data indicated that there was decreased NAT activity associated with increased levels of DAS or DADS in H. pylori cytosols and suspensions. Viability studies on H. pylori demonstrated that DAS or DADS elicited dose-dependent bactericide affects on H. pylori cultures. The data also indicated that DAS and DADS decreased the apparent values of K(m) and Vmax of NAT enzyme from H. pylori in both systems examined. This report is the first demonstration that garlic components can affect H. pylori growth and NAT activity.

Reducing effects of garlic constituents on DNA adduct formation in human lymphocytes in vitro

A water extract of raw garlic (RGE) and two organosulfur compounds, diallyl sulfide and S-allylcysteine (SAC), were evaluated for their relative effectiveness in reducing benzo[a]pyrene (BaP)-DNA adduct formation in stimulated human peripheral blood lymphocytes in vitro. In replicate experiments, RGE significantly inhibited BaP-DNA adduct formation at concentrations of 0.001, 0.01, and 0.1 mg/ml. SAC also significantly decreased BaP-DNA adduct formation at concentrations of 0.01 and 0.1 mg/ml. For diallyl sulfide, no significant reduction in BaP-DNA adduct formation was found. BaP-DNA adduct formation was not associated with cell viability or proliferation of peripheral blood lymphocytes after the various treatments. No clear scavenging activity was detected for the garlic constituents. Aryl hydrocarbon hydroxylase activity was not decreased, nor was formation of sulfate and glucuronide conjugates of 3-hydroxy-BaP increased in the presence of RGE and SAC, indicating that increased glutathione S-transferase activity or a more efficient repair of BaP-DNA adducts may explain the observed effects. In addition, reactive oxygen species-induced 8-oxodeoxyguanosine in DNA was reduced in the presence of SAC. It is concluded that raw garlic and SAC may be useful in the prevention of BaP-associated tumorigenesis and that further evaluation of their preventive potential in humans at risk appears feasible.

S-allyl cysteine inhibits activation of nuclear factor kappa B in human T cells

Reactive oxygen species are involved in signal transduction pathways leading to nuclear factor kappa B (NF-kappa B) activation which has been implicated in the regulation of gene transcription. We recently reported that a garlic compound, S-allyl cysteine (SAC), protects bovine pulmonary artery endothelial cells from oxidant injury induced by hydrogen peroxide (H2O2). In this study we determined the effects of SAC on NF-kappa B activation in human T lymphocytes (Jurkat cells) induced by tumor necrosis factor alpha (TNF- alpha) and H2O2. Activated NF-kappa B in nuclear extracts was measured by an electrophoretic mobility shift assay using 32P-labeled probe. SAC consistently exhibited a dose-dependent inhibition of NF-kappa B activation induced by both TNF-alpha and H2O2. Supershift with specific antibodies to NF-kappa B subunits confirmed that the inducible retarded bands observed in the EMSA and p65-p50 heterodimer of the NF-kappa B/Rel protein. Our data suggest that SAC may act via antioxidant mechanisms to block NF-kappa B activation in Jurkat cells.

Diallyl disulfide inhibits the proliferation of human tumor cells in culture

Diallyl disulfide (DADS), an oil-soluble organosulfur compound in processed garlic, was more effective in inhibiting the in vitro growth of human tumor cell lines: HCT-15 (colon), A549 (lung), and SK MEL-2 (skin) than isomolar quantities of the water-soluble compound S-allyl cysteine (SAC). Addition of DADS (100 microM) was cytostatic to all three cell lines. The importance of the allyl and the disulfide groups were revealed by the lack of a comparable depression in the growth of HCT-15 cells exposed to its saturated analogue, dipropyl disulfide (DPDS). Treatment with DADS also resulted in a dose-dependent increase in intracellular free calcium in cells. A dose-dependent decrease in the activity of calcium-dependent ATPase enzyme occurred in HCT-15 cells exposed to increasing quantities of DADS. A correlation (r = -0.975) was found between the intracellular free calcium levels and the Ca-ATPase activity in DADS-treated cells. These studies document that DADS, a constituent of garlic oil, is an effective inhibitor of the growth of human neoplastic cells. Alterations in calcium hemostasis are likely involved in the growth inhibition/cytotoxicity caused by DADS.

Organosulfur compounds and cancer

There is evidence that organosulfur compounds can inhibit the induction and growth of cancer. Several organosulfur compounds are dietary constituents and Allium species are a rich source of such molecules. Some but not all epidemiological studies have suggested that consumption of garlic can decrease cancer incidence. There is substantial evidence that constituents of garlic including diallyl sulfides can inhibit the induction of cancer in experimental animals. Effects on both tumor initiation and promotion have been documented. Some effects may be mediated by modulation of carcinogen metabolism involving altered ratios of phase I and phase II drug metabolizing enzymes. 59,60 Inhibitory actions on the growth of tumor cells have been documented and, for some tumor cells, differentiating effects of diallyl sulfides can occur. A definitive mechanism of action has not been established and evidence exists for effects at several sites in carcinogen metabolism and regulation of tumor growth. It is not always clear that laboratory studies can be extrapolated to reasonable levels of consumption by humans of garlic or other Allium species.