Allyl sulfides modify cell growth

Sn(OTf)2-Catalyzed Allylic Substitution of Thiols to Allyl Alcohols: Access to Allyl Sulfides

A novel method for the mild and efficient synthesis of allyl sulfides has been developed with allyl alcohols and thiols as substrates. The desired allyl sulfide was obtained using a catalytic amount of Sn(OTf)2 in dichloromethane at room temperature after a reaction time of 12 hours. A diverse range of allyl sulfides have been obtained with good to excellent yields, including both linear and cyclic derivatives (27 products). Additionally, gram-scale reactions can be easily carried out with only 1 mol% catalyst, giving over 90% yields, which further proves the efficiency of our approach in synthesis. This methodology has both deep research significance and application value, providing a new pathway to access sulfide compounds. We strongly believe our method would be attractive to synthetic chemists and would be widely used in synthetic chemistry.

Natural Hydrogen Sulfide Donors from Allium sp. as a Nutraceutical Approach in Type 2 Diabetes Prevention and Therapy

Type 2 diabetes mellitus (DM) is a socially relevant chronic disease with high prevalence worldwide. DM may lead to several vascular, macrovascular, and microvascular complications (cerebrovascular, coronary artery, and peripheral arterial diseases, retinopathy, neuropathy, and nephropathy), often accelerating the progression of atherosclerosis. Dietary therapy is generally considered to be the first step in the treatment of diabetic patients. Among the current therapeutic options, such as insulin therapy and hypoglycemic drugs, in recent years, attention has been shifting to the effects and properties-that are still not completely known-of medicinal plants as valid and inexpensive therapeutic supports with limited side effects. In this review, we report the relevant effects of medicinal plants and nutraceuticals in diabetes. In particular, we paid attention to the organosulfur compounds (OSCs) present in plant extracts that due to their antioxidant, hypoglycemic, anti-inflammatory, and immunomodulatory effects, can contribute as cardioprotective agents in type 2 DM. OSCs derived from garlic (Allium sp.), due to their properties, can represent a valuable support to the diet in type 2 DM, as outlined in this manuscript based on both in vitro and in vivo studies. Moreover, a relevant characteristic of garlic OSCs is their ability to produce the gasotransmitter H₂S, and many of their effects can be explained by this property. Indeed, in recent years, several studies have demonstrated the relevant effects of endogenous and exogenous H₂S in human DM, including by in vitro and in vivo experiments and clinical trials; therefore, here, we summarize the effects and the underlying molecular mechanisms of H₂S and natural H₂S donors.

H2S-releasing nanoemulsions: a new formulation to inhibit tumor cells proliferation and improve tissue repair

The improvement of solubility and/or dissolution rate of poorly soluble natural compounds is an ideal strategy to make them optimal candidates as new potential drugs. Accordingly, the allyl sulfur compounds and omega-3 fatty acids are natural hydrophobic compounds that exhibit two important combined properties: cardiovascular protection and antitumor activity. Here, we have synthesized and characterized a novel formulation of diallyl disulfide (DADS) and α-linolenic acid (ALA) as protein-nanoemulsions (BAD-NEs), using ultrasounds. BAD-NEs are stable over time at room temperature and show antioxidant and radical scavenging property. These NEs are also optimal H2S slow-release donors and show a significant anti-proliferative effect on different human cancer cell lines: MCF-7 breast cancer and HuT 78 T-cell lymphoma cells. BAD-NEs are able to regulate the ERK1/2 pathway, inducing apoptosis and cell cycle arrest at the G0/G1 phase. We have also investigated their effect on cell proliferation of human adult stem/progenitor cells. Interestingly, BAD-NEs are able to improve the Lin- Sca1+ human cardiac progenitor cells (hCPC) proliferation. This stem cell growth stimulation is combined with the expression and activation of proteins involved in tissue-repair, such as P-AKT, α-sma and connexin 43. Altogether, our results suggest that these antioxidant nanoemulsions might have potential application in selective cancer therapy and for promoting the muscle tissue repair.

Membrane Interactions of Phytochemicals as Their Molecular Mechanism Applicable to the Discovery of Drug Leads from Plants

In addition to interacting with functional proteins such as receptors, ion channels, and enzymes, a variety of drugs mechanistically act on membrane lipids to change the physicochemical properties of biomembranes as reported for anesthetic, adrenergic, cholinergic, non-steroidal anti-inflammatory, analgesic, antitumor, antiplatelet, antimicrobial, and antioxidant drugs. As well as these membrane-acting drugs, bioactive plant components, phytochemicals, with amphiphilic or hydrophobic structures, are presumed to interact with biological membranes and biomimetic membranes prepared with phospholipids and cholesterol, resulting in the modification of membrane fluidity, microviscosity, order, elasticity, and permeability with the potencies being consistent with their pharmacological effects. A novel mechanistic point of view of phytochemicals would lead to a better understanding of their bioactivities, an insight into their medicinal benefits, and a strategic implication for discovering drug leads from plants. This article reviews the membrane interactions of different classes of phytochemicals by highlighting their induced changes in membrane property. The phytochemicals to be reviewed include membrane-interactive flavonoids, terpenoids, stilbenoids, capsaicinoids, phloroglucinols, naphthodianthrones, organosulfur compounds, alkaloids, anthraquinonoids, ginsenosides, pentacyclic triterpene acids, and curcuminoids. The membrane interaction’s applicability to the discovery of phytochemical drug leads is also discussed while referring to previous screening and isolating studies.

Molecular mechanisms of garlic-derived allyl sulfides in the inhibition of skin cancer progression

Skin cancer is a serious concern whose incidence is increasing at an alarming rate. Allyl sulfides—i.e., sulfur metabolites in garlic oil—have been demonstrated to have anticancer activity against several cancer types, although the mechanisms underlying these effects remain enigmatic. Our previous study showed that diallyl trisulfide (DATS) is more potent than mono- and disulfides against skin cancer. DATS inhibits cell growth of human melanoma A375 cells and basal cell carcinoma (BCC) cells by increasing the levels of intracellular reactive oxygen species (ROS) and DNA damage and by inducing G2/M arrest, endoplasmic reticulum (ER) stress, and mitochondria-mediated apoptosis, including the caspase-dependent and -independent pathways. This short review focuses on the molecular mechanisms of garlic-derived allyl sulfides on skin cancer prevention.

Control of vascular smooth muscle cell growth by connexin 43

Connexin 43 (Cx43), the principal gap junction protein in vascular smooth muscle cells (VSMCs), regulates movement of ions and other signaling molecules through gap junction intercellular communication (GJIC) and plays important roles in maintaining normal vessel function; however, many of the signaling mechanisms controlling Cx43 in VSMCs are not clearly described. The goal of this study was to investigate mechanisms of Cx43 regulation with respect to VSMC proliferation. Treatment of rat primary VSMCs with the cAMP analog 8Br-cAMP, the soluble guanylate cyclase (sGC) stimulator BAY 41-2272 (BAY), or the Cx inducer diallyl disulfide (DADS) significantly reduced proliferation after 72 h compared with vehicle controls. Bromodeoxyuridine uptake revealed reduction (p < 0.05) in DNA synthesis after 6 h and flow cytometry showed reduced (40%) S-phase cell numbers after 16 h in DADS-treated cells compared with vehicle controls. Cx43 expression significantly increased after 270 min treatment with 8Br-cAMP, 8Br-cGMP, BAY or DADS. Inhibition of PKA, PKG or PKC reversed 8Br-cAMP-stimulated increases in Cx43 expression, whereas only PKG or PKC inhibition reversed 8Br-cGMP- and BAY-stimulated increases in total Cx43. Interestingly, stimulation of Cx43 expression by DADS was not dependent on PKA, PKG or PKC. Using fluorescence recovery after photobleaching, only 8Br-cAMP or DADS increased GJIC with 8Br-cAMP mediated by PKC and DADS mediated by PKG. Further, DADS significantly increased phosphorylation at MAPK-sensitive Serine (Ser)255 and Ser279, the cell cycle regulatory kinase-sensitive Ser262 and PKC-sensitive Ser368 after 30 min while 8Br-cAMP significantly increased phosphorylation only at Ser279 compared with controls. This study demonstrates that 8Br-cAMP- and DADS-enhanced GJIC rather than Cx43 expression and/or phosphorylation plays important roles in the regulation of VSMC proliferation and provides new insights into the growth-regulatory capacities of Cx43 in VSM.

Diallyl disulfide induces MUC5B expression via ERK2 in human airway epithelial cells

Garlic has been shown to have antimicrobial, hypolipidemic, antithrombotic, antitumor and immunostimulatory properties. The medicinal effects of garlic are derived from the flavonoid and organosulfur components. Diallyl disulfide (DADS), an organosulfur, is the main component responsible for the diverse biological effects of garlic. However, the effects of DADS on mucin gene expression in airway epithelial cells have not been reported to date. Therefore, this study was performed to investigate the effects and brief signaling pathway of DADS associated with MUC5B expression in NCI-H292 epithelial cells using RT-PCR, ELISA, western blot, immunocytochemistry and cell transfection with siRNA. DADS induced MUC5B expression and activated the phosphorylation of ERK1/2 MAPK. In addition, U0126 inhibited DADS-induced MUC5B expression and DADS-activated phosphorylation of ERK1/2 MAPK. Moreover, the immunopositive cells for MUC5B protein did not appear after treatment of DADS with U0126, and the knockdown of ERK2 MAPK by ERK2 MAPK siRNA significantly blocked DADS-induced MUC5B mRNA expression. However, DADS did not activate the phosphorylation of p38 MAPK, and SB203580 did not inhibit DADS-induced MUC5B expression. This is the first study to show that DADS-induced MUC5B expression appears to be regulated by activation of the ERK2 MAPK signaling pathway in human NCI-H292 airway epithelial cells.

Allicin purified from fresh garlic cloves induces apoptosis in colon cancer cells via Nrf2

Allicin (diallyl thiosulfinate) is the best-known biologically active component in freshly crushed garlic extract. We developed a novel, simple method to isolate active allicin, which yielded a stable compound in aqueous solution amenable for use in in vitro and in vivo studies. We focused on the in vitro effects of allicin on cell proliferation of colon cancer cell lines HCT-116, LS174T, HT-29, and Caco-2 and assessed the underlying mechanisms. This allicin preparation exerted a time- and dose-dependent cytostatic effect on these cells at concentrations ranging from 6.2 to 310 μM. Treatment with allicin resulted in HCT-116 apoptotic cell death as demonstrated by enhanced hypodiploid DNA content, decreased levels of B-cell non-Hodgkin lymphoma-2 (Bcl-2), increased levels of bax and increased capability of releasing cytochrome c from mitochondria to the cytosol. Allicin also induced translocation of NF-E2-related factor-2 (Nrf2) to the nuclei of HCT-116 cells. Luciferase reporter gene assay showed that allicin induces Nrf2-mediated luciferase transactivation activity. SiRNA knock down of Nrf2 significantly affected the capacity of allicin to inhibit HCT-116 proliferation. These results suggest that Nrf2 mediates the allicin-induced apoptotic death of colon cancer cells.

Consumption of S-allylcysteine inhibits the growth of human non-small-cell lung carcinoma in a mouse xenograft model

Lung cancer is one of the leading causes of cancer death in the world. Human non-small-cell lung carcinoma (NSCLC) accounts for almost 80% of lung cancer cases. Aberrant phosphoinositide 3-kinase (PI3K)/Akt/mTOR signaling pathways play important roles and have been widely observed in the development of NSCLC. Previous studies indicated that garlic extracts such as diallyl disulfide (DADS) and diallyl trisulfide (DATS) could inhibit the proliferation of several types of cancer in vitro. However, the inhibitory effects of S-allylcysteine (SAC) on the growth of NSCLC have not been demonstrated yet. Therefore, this study investigated whether consumption of SAC could prevent the growth of NSCLC in both in vitro and in vivo models. It was found that SAC significantly inhibited the proliferation of human NSCLC A-549 cells in vitro. Treatment of the NF-κB inhibitor, Bay-11-7082, could significantly inhibit the proliferation of NSCLC A-549 cells. The results demonstrated that SAC significantly suppressed the activation of mTOR, NF-κB, and cyclin D1 molecules in vitro. Furthermore, the results demonstrated that consumption of SAC significantly inhibited the growth of highly metastatic human NSCLC cells in tumor-bearing mice. Bioluminescence imaging and pathological and immunohistochemical (IHC) staining results also indicated that SAC could effectively suppress the growth and malignant progression of human NSCLC in vivo. The chemopreventive effects of SAC were associated with suppression of mTOR and NF-κB molecules in vivo. These results suggested that SAC could act as an effective agent against the malignant progression of human NSCLC in both in vitro and in vivo models.

Biological properties of garlic and garlic-derived organosulfur compounds

Medicinal properties of garlic (Allium sativum) have been widely known and used since ancient times till the present. Garlic enhances immune functions and has antibacterial, antifungal and antivirus activities. It is known to prevent platelet aggregation, and to have hypotensive and cholesterol- and triglyceride-lowering properties, although the latter features have been questioned. This review is focused on anticancer efficacy of Allium sativum, and attempts to explain the mechanisms of this action. Medicinal properties of garlic rely upon organosulfur compounds mostly derived from alliin. Organosulfur compounds originating from garlic inhibit carcinogen activation, boost phase 2 detoxifying processes, cause cell cycle arrest mostly in G2/M phase, stimulate the mitochondrial apoptotic pathway, increase acetylation of histones. Garlic-derived sulfur compounds influence also gap-junctional intercellular communication and participate in the development of multidrug resistance. This review presents also other little known aspects of molecular action of garlic-derived compounds, like modulation of cellular redox state, involvement in signal transduction and post-translational modification of proteins by sulfane sulfur or by formation of mixed disulfides (S-thiolation reactions).

Garlic allyl derivatives interact with membrane lipids to modify the membrane fluidity

As a novel approach to the mode of medicinal action of garlic, its constituents were comparatively studied with respect to their interactions with membrane lipids to modify the membrane fluidity. Allyl derivatives rigidified tumor cell and platelet model membranes consisting of unsaturated phospholipids and cholesterol at 20-500 muM with the potency being diallyl trisulfide (DATS) > diallyl disulfide (DADS) by preferentially acting on the hydrocarbon cores of lipid bilayers. They were also effective in rigidifying candida cell model membranes prepared with ergosterol and phospholipids at 100-500 microM with the potency being DADS > DATS > diallyl sulfide (DAS), but not bacteria cell model membranes without ergosterol. Alliin, a precursor of these DASs, was not active on any membranes at 500 microM. Both relative intensity and selectivity in membrane effects correlated with those in antiproliferative, antiplatelet and antimicrobial effects. In cell culture experiments, membrane-active DASs inhibited the growth of tumor cells cultured for 24 and 48 h at 20-500 muM to show the potency being DATS > DADS, together with rigidifying cell membranes by acting on their deeper regions more intensively. However, membrane-inactive allyl derivatives were not growth-inhibitory on tumor cells. The membrane lipid interactions of DASs appear to be one of possible mechanisms underlying different effects of garlic.

Membrane Activity-Guided Isolation of Antiproliferative and Antiplatelet Constituent from Evodiopanax Innovans

Bark of Evodiopanax innovans (Araliaceae) was subjected to membrane activity-guided extraction and chromatographic fractionation. The potency to interact with lipid membranes and change their fluidity was determined by measuring fluorescence polarization of liposomal and cell membranes. Plant preparations, including the MeOH extract and the specified fraction, reduced the fluidity of model biomembranes prepared with different phospholipids and cholesterol. Further purification led to the isolation of maltol 3- O-β-glucopyranoside, which inhibited tumor cell growth and platelet aggregation, together with rigidifying the cell membranes as well as the membrane-active antitumor compound (-)-epigallocatechin gallate and doxorubicin. The isolate at 100 μM and 1.0 mM showed growth inhibition of 13–49% against tumor cells cultured for 24 and 48 h. At 1.8–3.6 mM, it also produced 50% inhibition of platelet aggregation induced by collagen, adenosine 5′-diphosphate and thrombin. E. innovans is considered as a medicinal plant containing a potent bioactive constituent that exerts antiproliferative and antiplatelet effects through interaction with cell membranes to modify their fluidity.

Strategies for cancer prevention: the role of diet

Linkages between diet habits and cancer risk have surfaced from a multitude of epidemiological and preclinical studies. Collectively these studies provide rather compelling evidence that dietary components modify the incidence and biological behavior of tumors. While the risk of breast, prostate, colon, lung and liver cancers are frequently associated with dietary patterns, inconsistencies are not uncommon. These inconsistencies likely reflect the multi-factorial and complex nature of cancer and the specificity that individual dietary constituents have in modifying cancer related genetic pathways. The complexity of defining the role of diet is underscored by the numerous and diverse essential and non-essential components that may alter one or more phases of the cancer process. The explosive increase in the recognition of genes and pathways for regulating cell growth and development, and evaluating the response to hormones and other chemicals synthesized by the body, offers exciting opportunities for unraveling the molecular targets by which dietary components influence cancer prevention. It is recognized that all cells have unique ‘signatures’ that are characterized by active and inactive genes and cellular products. It is certainly plausible that bridging knowledge about these unique cellular characteristics with the molecular targets for nutrients can be used to assist in optimizing nutrition and minimizing cancer risk.

In vivo treatment by diallyl disulfide increases histone acetylation in rat colonocytes

Diallyl disulfide (DADS) is an organosulfur compound from garlic which exhibits various anticarcinogenic properties including inhibition of tumor cell proliferation. DADS antiproliferative effects were previously associated with an increase in histone acetylation in two human tumor colon cell lines, suggesting that DADS-induced histone hyperacetylation could be one of the mechanisms involved in its protective properties on colon carcinogenesis. The effects of DADS on histone H4 and H3 acetylation levels were investigated in vivo in colonocytes isolated from non-tumoral rat. Administrated by intracaecal perfusion or gavage, DADS increases histone H4 and H3 acetylation in colonocytes. Moreover, data generated using cDNA expression arrays suggest that DADS could modulate the expression of a subset of genes. These results suggest the involvement of histone acetylation in modulation of gene expression by DADS in normal rat colonocytes, which might play a role in its biological effects as well as in its anticarcinogenic properties in vivo.

Diallyl disulfide increases CDKN1A promoter-associated histone acetylation in human colon tumor cell lines

Diallyl disulfide (DADS) is an organosulfur compound from garlic, which inhibits colon tumor cell proliferation. In a previous study, we have shown that in Caco-2 and HT-29 cells DADS (200 microM) increases global histone acetylation, CDKN1A mRNA, and p21(waf1) protein levels and induces G2/M cell cycle arrest. These results suggested that DADS could inhibit cell proliferation through at least in part a transcriptional activation of CDKN1A expression involving histone acetylation. In this study, using chromatin immunoprecipitation assays, we demonstrate that in Caco-2 and HT-29 cells histone H4 and/or H3 acetylation is increased within CDKN1A promoter after 3 and 6 h treatments with DADS. These results strongly suggest that histone acetylation, a molecular mechanism implicated in the regulation of gene expression, could account for the induction of CDKN1A expression and the antiproliferating effects of DADS in colon tumor cells.

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.

Garlic Compound, Diallyl Disulfide Induces Cell Cycle Arrest in Prostate Cancer Cell Line PC-3

Prostate cancer is the most predominant cancer in men and related death rate increases every year. Till date, there is no effective therapy for androgen independent prostate cancer. Previous studies reported that aged garlic extract suppresses cancer growth. In the present study, diallyl disulfide [DADS], oil soluble organosulfur compound of garlic, was studied for its antiproliferative and induction of cell cycle arrest on prostate cancer cells in vitro. The suppression of cell growth was assessed by MTT assay. Induction of cell cycle arrest was assessed and confirmed by propidium iodide staining in flowcytometric analysis and western blotting analysis of major cell cycle regulator proteins. The results showed that DADS inhibited the growth of prostate cancer cells in a dose dependent manner, compared to the control. At 25 microM and 40 microM concentrations, DADS induced cell cycle arrest at G2/M transition in PC-3 cells. Western blotting analysis of cyclin A, B(1) and cyclin dependent kinase 1 [CDK1] revealed that DADS inhibited the cell cycle by downregulating CDK1 expression. It is concluded that DADS, inhibits proliferation of prostate cancer cells through cell cycle arrest. Dose dependent effect of DADS on PC-3 cell line was observed in the present study.

Linking tumor cell cytotoxicity to mechanism of drug action: an integrated analysis of gene expression, small-molecule screening and structural databases

An integrated, bioinformatic analysis of three databases comprising tumor-cell-based small molecule screening data, gene expression measurements, and PDB (Protein Data Bank) ligand-target structures has been developed for probing mechanism of drug action (MOA). Clustering analysis of GI50 profiles for the NCI's database of compounds screened across a panel of tumor cells (NCI60) was used to select a subset of unique cytotoxic responses for about 4000 small molecules. Drug-gene-PDB relationships for this test set were examined by correlative analysis of cytotoxic response and differential gene expression profiles within the NCI60 and structural comparisons with known ligand-target crystallographic complexes. A survey of molecular features within these compounds finds thirteen conserved Compound Classes, each class exhibiting chemical features important for interactions with a variety of biological targets. Protein targets for an additional twelve Compound Classes could be directly assigned using drug-protein interactions observed in the crystallographic database. Results from the analysis of constitutive gene expressions established a clear connection between chemo-resistance and overexpression of gene families associated with the extracellular matrix, cytoskeletal organization, and xenobiotic metabolism. Conversely, chemo-sensitivity implicated overexpression of gene families involved in homeostatic functions of nucleic acid repair, aryl hydrocarbon metabolism, heat shock response, proteasome degradation and apoptosis. Correlations between chemo-responsiveness and differential gene expressions identified chemotypes with nonselective (i.e., many) molecular targets from those likely to have selective (i.e., few) molecular targets. Applications of data mining strategies that jointly utilize tumor cell screening, genomic, and structural data are presented for hypotheses generation and identifying novel anticancer candidates.

Z-ajoene induces apoptosis of HL-60 cells: involvement of Bcl-2 cleavage

Garlic organosulfur components exhibit antitumor activity, but the molecular mechanisms underlying these effects have not been well characterized. We showed that Z-ajoene, a sulfur-rich compound purified from garlic, induced time- and dose-dependent apoptosis in HL-60 cells. This process implied the activation of caspase-3 and the cleavage of the antiapoptotic protein Bcl-2. The caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-[OMe]-fluoromethylketone inhibited Bcl-2 cleavage and apoptosis induced by Z-ajoene. This effect was partially prevented by treatment of HL-60 cells with the antioxidant N-acetylcysteine. Hence, the transmission of apoptotic signal induced by Z-ajoene involved a reactive oxygen species-dependent pathway leading to caspase-dependent Bcl-2 cleavage.

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.

Functional foods and health: a US perspective

Linkages between diet habits and the quality of life continue to surface on numerous fronts. Collectively these epidemiological, pre-clinical and clinical studies provide rather compelling evidence that numerous essential and non-essential dietary components are capable of influencing growth, development and performance and disease prevention. Scientific discoveries and widespread interest in the potential medicinal benefits of foods and food components have fostered a variety of content, health and structure-function claims. Unfortunately, defining the ideal diet is complicated by the numerous and diverse components that may influence biological processes. Inconsistencies in the literature may reflect the multi-factorial nature of these processes and the specificity that individual dietary constituents have in modifying genetic and epigenetic events. New and emerging genomic and proteonomic approaches and technologies offer exciting opportunities for identifying molecular targets for dietary components and thus determining mechanisms by which they influence the quality of life. All cells have unique 'signatures' that are characterized by active and inactive genes and cellular products. It is plausible that bridging knowledge about unique cellular characteristics with molecular targets for nutrients can be used to develop strategies to optimize nutrition and minimize disease risk.

Mechanisms of protection against aflatoxin B(1) genotoxicity in rats treated by organosulfur compounds from garlic

Diallyl sulfide (DAS) and diallyl disulfide (DADS), two garlic constituents, were found previously to inhibit aflatoxin B(1) (AFB(1))-initiated carcinogenesis in rat liver, DADS being the most effective. In order to study the mechanisms involved in this protection, we have examined the ability of liver microsomes and cytosols from DAS- and DADS-treated rats to modulate the mutagenicity and the metabolism of AFB(1). We also examined the effects of these compounds on the expression of cytochromes P450 (CYP) and phase II enzymes known to be involved in AFB(1) metabolism. Administration of DAS (1 mmol/kg for 4 days) to rats resulted in significant inhibition of microsome-mediated mutagenicity of AFB(1), whereas DADS treatment did not alter AFB(1) mutagenicity. DAS treatment increased the metabolism of AFB(1) mainly towards the formation of AFQ(1) and AFM(1), which might account for the reduction of AFB(1) microsomal-mediated mutagenicity. DADS treatment slightly affected the oxidative metabolism of AFB(1). DAS and DADS induced CYP3A2, CYP2B1 and CYP2B2, DAS being more potent. Cytosols from DAS- and DADS-treated rats produced a significant inhibition of AFB(1)-8,9-epoxide (AFBO)-induced mutagenicity and significantly increased the cytosolic formation of AFB(1)-glutathione conjugates, DADS treatment being more effective. Western blot analysis showed that DADS is a potent inducer of glutathione S-transferase A5 (rGSTA5) and AFB(1) aldehyde reductase 1 (rAFAR1), while DAS is a weak inducer of these enzymes. Finally, we demonstrated that antibodies raised against rGSTA5 strongly reduced the antimutagenic activity of cytosols from DAS- and DADS-treated rats against AFBO. All together, these results demonstrate that DAS prevents AFB(1) mutagenicity through a dual mechanism, i.e. by modulating both the phase I and II metabolism of AFB(1), whereas DADS acts mainly by increasing the phase II metabolism of AFB(1). The induction of rGSTA5 and rAFAR1 is probably the main mechanism by which allyl sulfides give protection against AFB(1)-induced carcinogenesis.

Identification of Molecular Targets and Biomarkers for Disease Resistance

Discoveries about molecular targets for nutrients will unquestionably provide important clues into how best to optimize nutrition for an individual. The "Credentialing" of nutrients in terms of their influence on genetic and epigenetic events that bring about a desired phenotypic change is surely within the future of nutrition science.

Diallyl disulfide (DADS) induces the antitumorigenic NSAID-activated gene (NAG-1) by a p53-dependent mechanism in human colorectal HCT 116 cells

Garlic is appealing as an anti-carcinogenic agent due to its ability to induce apoptosis in vitro and inhibit the formation and growth of tumors in animals in vivo. Diallyl disulfide (DADS) is a constituent of garlic that suppresses neoplastic cell growth and induces apoptosis. We examined the effects of DADS on various cancer cell lines to better understand its effect on apoptosis and apoptosis-related genes. The nonsteroidal anti-inflammatory drug (NSAID)-activated gene (NAG-1) has proapoptotic and antitumorigenic activities and is upregulated by anticancer agents such as NSAIDs. In this study, human colorectal HCT-116 (wild-type p53), HCT-15 (p53 mutant) and human prostate PC-3 (p53 mutant) cells were exposed to DADS. DADS inhibited cell proliferation in all cell lines albeit to a lesser extent in HCT-15 and PC-3 cells at 11.5 and 23 micromol/L. In HCT-116 cells, DADS induced p53 and NAG-1 in a dose-dependent manner and the induction of p53 preceded that of NAG-1. In HCT-116 cells, NAG-1 protein expression was increased 2.4-fold +/- 0.6 at 4.6 micromol/L and 6.1-fold +/- 1.7 at 23 micromol/L DADS, whereas p53 was induced 1.5-fold +/- 0.1 and 2.3-fold +/- 0.4. DADS did not induce NAG-1 or p53 in p53 mutant cell lines; however, NAG-1 expression was induced by sulindac sulfide. HCT-116 cells treated with 4.6 and 23 micromol/L DADS resulted in a 1.9- and 2.9-fold increase in apoptosis, respectively. In contrast, 23 micromol/L DADS induced apoptosis only 1.8-fold in HCT-15 cells and not at all in PC-3 cells. Thus, DADS-induced apoptosis and NAG-1 protein expression appear to occur via p53.