Effect of organosulfur compounds from garlic and cruciferous vegetables on drug metabolism enzymes

Mechanisms of colorectal and lung cancer prevention by vegetables: a genomic approach

Colorectal cancer (CRC) and lung cancer (LC) occur at high incidence, and both can be effectively prevented by dietary vegetable consumption. This makes these two types of cancer highly suitable for elucidating the underlying molecular mechanisms of cancer chemoprevention. Numerous studies have shown that vegetables exert their beneficial effects through various different mechanisms, but effects on the genome level remain mostly unclear. This review evaluates current knowledge on the mechanisms of CRC and LC prevention by vegetables, thereby focusing on the modulation of gene and protein expressions. The majority of the effects found in the colon are changes in the expression of genes and proteins involved in apoptosis, cell cycle, cell proliferation and intracellular defense, in favor of reduced CRC risk. Furthermore, vegetables and vegetable components changed the expression of many more genes and proteins involved in other pathways for which biologic meaning is less clear. The number of studies investigating gene and protein expression changes in the lungs is limited to only a few in vitro and animal studies. Data from these studies show that mostly genes involved in biotransformation, apoptosis and cell cycle regulation are affected. In both colon and lungs, genomewide analyses of gene and protein expression changes by new genomics and proteomics technologies, as well as the investigation of whole vegetables, are few in number. Further studies applying these 'omics' approaches are needed to provide more insights on affected genetic/biologic pathways and, thus, in molecular mechanisms by which different chemopreventive compounds can protect against carcinogenesis. Particularly studies with combinations of phytochemicals and whole vegetables are needed to establish gene expression changes in the colon, but especially in the lungs.

Potential of diallyl sulfide bearing pH-sensitive liposomes in chemoprevention against DMBA-induced skin papilloma

Diallyl sulfide (DAS), an active component of garlic, possesses strong anti-neoplastic properties against various forms of cancer. In the present study, we have evaluated chemo-preventive effects of liposomized DAS (conventional egg PC and pH-sensitive liposomes) against DMBA-induced skin papilloma. Various liposome-based novel formulations of DAS (250 microg/mouse) were applied topically, after one hour of exposure to DMBA (52 microg/mouse/dose), to the animals. The animals were treated thrice weekly for the total period of 12 weeks. The efficacy of the various liposomal formulations of DAS was evaluated on the basis of parameters such as incidence of tumorogenesis and total numbers and sizes of induced tumor nodules. The liposomized DAS formulations also were assessed for their effect on the expression of p53wt, p53mut, and p21/Waf1. The results of the present study showed that liposomized DAS could effectively delay the onset of tumorogenesis and reduce the cumulative numbers and sizes of tumor papillomas in treated mice. Treatment of DMBA-exposed animals with the liposomal formulation of DAS ensued in upregulation of p53wt and p21/Waf1, while levels of p53mut expression reduced down. The promising chemo-preventive nature of liposomal DAS may form the basis for establishing effective means of controlling various forms of cancer, including skin papilloma.

Potential of diallyl sulfide bearing pH-sensitive liposomes in chemoprevention against DMBA-induced skin papilloma

Diallyl sulfide (DAS), an active component of garlic, possesses strong anti-neoplastic properties against various forms of cancer. In the present study, we have evaluated chemo-preventive effects of liposomized DAS (conventional egg PC and pH-sensitive liposomes) against DMBA-induced skin papilloma. Various liposome-based novel formulations of DAS (250 microg/mouse) were applied topically, after one hour of exposure to DMBA (52 microg/mouse/dose), to the animals. The animals were treated thrice weekly for the total period of 12 weeks. The efficacy of the various liposomal formulations of DAS was evaluated on the basis of parameters such as incidence of tumorogenesis and total numbers and sizes of induced tumor nodules. The liposomized DAS formulations also were assessed for their effect on the expression of p53wt, p53mut, and p21/Waf1. The results of the present study showed that liposomized DAS could effectively delay the onset of tumorogenesis and reduce the cumulative numbers and sizes of tumor papillomas in treated mice. Treatment of DMBA-exposed animals with the liposomal formulation of DAS ensued in upregulation of p53wt and p21/Waf1, while levels of p53mut expression reduced down. The promising chemo-preventive nature of liposomal DAS may form the basis for establishing effective means of controlling various forms of cancer, including skin papilloma.

Consumption of brown onions (Alliumcepavar.cavalierand var.destiny) moderately modulates blood lipids, haematological and haemostatic variables in healthy pigs

Although garlic and onions have long been associated with putative cardiovascular health benefits, the effects of different commercially available onions and level of intake have not been studied. Therefore, the aim of the present study was to evaluate the potential health benefits of raw onions using the pig as a biomedical model. Twenty-five female (Large White×Landrace) pigs were used in a (2×2)+1 factorial experiment. Pigs were fed a standard grower diet supplemented with 100 g tallow/kg with the addition ofAllium cepavar.cavalieror var.destinyat 0, 10 or 25 g/MJ digestible energy for 6 weeks. Overall, the consumption of onions resulted in significant reductions in plasma triacylglycerol; however, the reductions were most pronounced in pigs feddestinyonions (−26 %,P=0·042). Total plasma cholesterol and LDL:HDL ratios were not significantly different. Onion supplementation, regardless of the variety, resulted in dose-dependent reductions in erythrocyte counts and Hb levels, while the white blood cell concentrations, particularly lymphocytes, were increased in pigs that consumed onions. Furthermore, indices of blood clotting were largely unaffected by onion consumption. In conclusion, dietary supplementation with raw brown onions has moderate lipid-modulating and immunostimulatory properties. However, daily onion intake >25 g/MJ digestible energy could be detrimental to erythrocyte numbers.

Quantitative evaluation of isothiocyanates as substrates and inhibitors of P-glycoprotein

The ATP-binding cassette transporter P-glycoprotein (P-gp) exerts a critical role in the systemic disposition of, and exposure to, lipophilic and amphipathic drugs, carcinogens, toxins and other xenobiotics. The ability of P-gp to transfer a wide variety of structurally unrelated compounds from the cell interior across the membrane bilayer remains intriguing. Since dietary chemicals in cruciferous and several other foods appear to exert anticarcinogenic effects by inducing phase II enzymes and inhibiting some phase I enzymes, the isothiocyanate constituents are frequently studied for interactions with various biomacromolecules as well as cytotoxins or isolated cells. Several prominent dietary isothiocyanates were characterized for their interaction with P-gp and their specific effects on the P-gp export activity of several marker substrates. Some of these compounds inhibit the active P-gp-mediated efflux of the fluorescent markers LDS-751 and daunorubicin with low potency, with the most potent among them, phenethyl isothiocyanate, inhibiting transport of the LDS-751 substrate with an IC(50) of approximately 240 microM. Overall, these isothiocyanates are unlikely to impede the xenobiotic defence function of P-gp even in the intestine where the concentrations are potentially high.

Potential protein markers for nutritional health effects on colorectal cancer in the mouse as revealed by proteomics analysis

It is suggested that colorectal cancer might be prevented by changes in diet, and vegetable consumption has been demonstrated to have a protective effect. Until now, little is known about the effects of vegetable consumption at the proteome level. Therefore, the effect of increased vegetable intake on the protein expression in the colonic mucosa of healthy mice was studied. Aim was to identify the proteins that are differentially expressed by increased vegetable consumption and to discriminate their possible role in the protection against colorectal cancer. Mice were fed four different vegetable diets, which was followed by analysis of total cellular protein from colonic mucosal cells by a combination of 2-DE and MS. We found 30 proteins that were differentially expressed in one or more diets as compared to the control diet. Six could be identified by MALDI-TOF MS: myosin regulatory light chain 2, carbonic anhydrase I, high-mobility group protein 1, pancreatitis-associated protein 3, glyceraldehyde-3-phosphate dehydrogenase and ATP synthase oligomycin sensitivity conferral protein. Alterations in the levels of these proteins agree with a role in the protection against colon cancer. We conclude that these proteins are suitable markers for the health effect of food on cancer. The observed altered protein levels therefore provide support for the protective effects of vegetables against colorectal cancer.

Modulation of p53 in 7,12-dimethylbenz[a]anthracene–induced skin tumors by diallyl sulfide in Swiss albino mice

Allium vegetables have been shown to have beneficial health effects against several chronic diseases including cancer. Diallyl sulfide (DAS), an organosulfur compound present in garlic, is well known for its chemopreventive properties in several tumor models. The pharmacologic role of DAS in prevention and treatment of cancer is well documented in the literature, but its molecular mechanism of action is not yet well defined. In the present study, modulation in p53 expression by topical application of DAS was recorded in 7,12-dimethylbenz[a]anthracene (DMBA)–induced skin tumors in Swiss albino mice. Western blot analysis and immunohistochemical protein detection, combined with multivariable flow cytometry, show that DAS application induces the expression of the wild-type (wt) p53 and down-regulates the expression of mutant (mut) p53. Immunoblotting analysis of tumors showed significant increase in levels of wtp53 by DAS application, whereas for mutp53 the DMBA-induced levels of protein were found to reduce to near normal levels with DAS application. The quantitative analysis of immunostained skin/tumor sections using image analysis and quantitative stereology showed 66.6% and 54.2% increases in wtp53 levels and 53.4% and 44.3% decreases in mutp53 levels in animals where DAS was applied 1 hour prior to or 1 hour after DMBA application, respectively. Flow cytometric analysis further confirmed modulation of wtp53 and mutp53 protein in DAS-supplemented tumors. The increase in the expression of wt tumor suppressor gene protein p53 was accompanied by elevation of the levels of cyclin-dependent kinase inhibitor p21/waf1. The percentage increase in the levels of p21/waf1 was found to be 72.9% and 61.3%, respectively, in DAS-supplemented groups before and after administration. These results thus show that DAS is a potential chemopreventive agent capable of modulating and regulating the tumor suppressor p53 along with its downstream effective molecule, p21/waf1. Thus, DAS can be a potential chemopreventive agent against skin tumor development.

Modulation of altered hepatic foci induction by diallyl sulphide in Wistar rats

Diallyl sulphide (DAS) is a sulphur-containing volatile compound present in garlic (Allium sativum). It has been shown to inhibit a number of chemically induced forms of cancer in experimental animals. The present study demonstrates the inhibitory effect of DAS on the development of diethylnitrosamine (DEN) initiated and 2-acetyl-aminofluorene (2-AAF) promoted preneoplastic altered hepatic foci (AHF) in Wistar rats. AHF were scored and analysed by quantitative stereology using the Image Analysis system from frozen liver sections stained for biological markers, namely glutathione S-transferase, placental form (GST-P), gamma-glutamyl transpeptidase (GGT), adenosine triphosphatase (ATPase), glucose-6-phosphatase (G6 Pase) and alkaline phosphatase (AlkPase). DAS-supplemented rats were found to restore the near-normal levels of enzymes GST-P and GGT when exposed to DEN and 2-AAF. DAS administration following DEN and 2-AAF exposure led to the restoration of enzymic activity of ATPase, G6 Pase and AlkPase, as evident by number and area of the foci. These findings suggest the protective role of DAS in rat hepatocarcinogenesis, by suppressing DEN- and 2-AAF-induced AHF development.

Effects of Cruciferous Vegetable Consumption on Urinary Metabolites of the Tobacco-Specific Lung Carcinogen 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanone in Singapore Chinese

Vegetable consumption, including cruciferous vegetables, is protective against lung cancer, but the mechanisms are poorly understood. The purpose of this study was to investigate the effects of cruciferous vegetable consumption on the metabolism of the tobacco-specific lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in smokers. The study was carried out in Singapore Chinese, whose mean daily intake of cruciferous vegetables is three times greater than that of people in the United States. Eighty-four smokers provided urine samples and were interviewed about dietary habits using a structured questionnaire, which included questions on consumption of nine commonly consumed cruciferous vegetables. Samples of these vegetables obtained in Singapore markets at three different times of year were analyzed for glucosinolates. Urine was analyzed for metabolites of NNK: 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) and its glucuronides (NNAL-Glucs). Glucobrassicins, which release indole-3-carbinols on chewing, were the major glucosinolates in seven of the nine cruciferous vegetables, accounting for 70.0% to 93.2% of all glucosinolates in these vegetables. There was a significant correlation (P = 0.01) between increased consumption of glucobrassicins and decreased levels of NNAL in urine after adjustment for number of cigarettes smoked per day; similar trends were observed for NNAL-Glucs (P = 0.08) and NNAL plus NNAL-Glucs (P = 0.03). These results are consistent with those of previous studies, which demonstrate that indole-3-carbinol decreases levels of urinary NNAL probably by inducing hepatic metabolism of NNK. The results are discussed with respect to the known chemopreventive activity of indole-3-carbinol against lung tumorigenesis by NNK in mice and the effects of isothiocyanates, which are also formed on consumption of cruciferous vegetables, on NNK metabolism. The results of this study demonstrate the complexities in assessing effects of cruciferous vegetables on carcinogen metabolism.

Diallyl disulfide increases rat h-ferritin, L-ferritin and transferrin receptor genes in vitro in hepatic cells and in vivo in liver

Of the oil-soluble organosulfur compounds derived from garlic, diallyl disulfide (DADS) is one of the most abundant. We examined the effect of DADS on gene expression in rat liver. By suppressive subtractive hybridization, we identified the heavy (H)-ferritin gene as a DADS-stimulated gene in the rat liver epithelial (REL) cells. DADS stimulation of H- and L (light)-ferritin mRNA was analyzed in REL cells and in rat liver. Incubation of the REL cells in 10 micro mol/L DADS for 4 h increased H-ferritin 1.9 +/- 0.2-fold, n = 3) and light(L)-ferritin mRNA 1.5 +/- 0.2-fold, n = 3). Stimulation did not occur in the presence of an inhibitor of transcription, actinomycin D. Stimulation of ferritin at the RNA and protein levels was also found in rats administered a DADS-enriched oil solution intragastrically. There was a 3 +/- 1.1-fold increase in H- and 3 +/- 0.14-fold increase for L-ferritin mRNA 24 h after the end of the infusion in the presence of DADS, (n = 3). The expression of the transferrin receptor, an iron transporter, was also enhanced by DADS in rat liver. In conclusion, our data suggest that DADS could modify iron homeostasis through the modulation of ferritin and transferrin receptor gene expression.