title: The selective cytotoxicity of the alkenyl glucosinolate hydrolysis products and their presence in Brassica vegetables.
abstract: Cruciferous vegetable consumption correlates with reduced risk of cancer. This chemopreventative activity may involve glucosinolates and their hydrolysis products. Glucosinolate-derived isothiocyanates have been studied for their toxicity and chemopreventative properties, but other hydrolysis products (epithionitriles and nitriles) have not been thoroughly examined. We report that these hydrolysis products differ in their cytotoxicity to human cells, with toxicity most strongly associated with isothiocyanates rather than epithionitriles and nitriles. We explored mechanisms of this differential cytotoxicity by examining the role of oxidative metabolism, oxidative stress, mitochondrial permeability, reduced glutathione levels, cell cycle arrest and apoptosis. 2-Propenylisothiocyanate and 3-butenylisothiocyanate both inhibited cytochome P450 1A (CYP1A) enzyme activity in CYP expressing MCL-5 cells at high cytotoxic doses. Incubation of MCL-5 cells with non-cytotoxic doses of 2-propenylisothiocyanate for 24h resulted in a dose-dependent inhibition of ethoxyresorufin O-deethylase, yet failed to affect CYP1A1 mRNA expression indicating interference with enzyme activity rather than inhibition of transcription. Increased reactive oxygen species (ROS) production was observed only for 2-propenylisothiocyanate treatment. 2-Propenylisothiocyanate treatment lowered reduced glutathione levels whereas no changes were noted with 3,4-epithiobutylnitrile. Cell cycle analysis showed that 2-propenylisothiocyanate induced a G2/M block whereas other hydrolysis products showed only marginal effects. We found that 2-propenylisothiocyanate and 3-butenylisothiocyanate induced cell death predominantly via necrosis whereas, 3,4-epithiobutylnitrile promoted both necrosis and apoptosis. Thus the activity of glucosinolate hydrolysis products includes cytotoxicity that is compound-class specific and may contribute to their putative chemoprotection properties.
authors.affiliation: Cell and Molecular Biology, Imperial College London, SW7 2AZ, UK; School of Food Sciences and Technology, Universiti Malaysia Terengganu, Malaysia.
authors.forename: Nurul H A
authors.initials: NH
authors.lastname: Kadir
authors.affiliation: Computational and Systems Medicine, Imperial College London, SW7 2AZ, UK.
authors.forename: Rhiannon
authors.initials: R
authors.lastname: David
authors.affiliation: Cell and Molecular Biology, Imperial College London, SW7 2AZ, UK.
authors.forename: John T
authors.initials: JT
authors.lastname: Rossiter
authors.affiliation: Computational and Systems Medicine, Imperial College London, SW7 2AZ, UK. Electronic address: n.gooderham@imperial.ac.uk.
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Gooderham
mesh_terms: D016588:Anticarcinogenic Agents / Q000378:metabolism / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001937:Brassica / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D019363:Cytochrome P-450 CYP1A1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D059565:G2 Phase Cell Cycle Checkpoints / Q000187:drug effects; D005961:Glucosinolates / Q000378:metabolism / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D017879:Isothiocyanates / Q000378:metabolism / Q000494:pharmacology*; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D009336:Necrosis; D009570:Nitriles / Q000378:metabolism / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects; D010539:Permeability; D013997:Time Factors; D014162:Transfection
chemical_list: D016588:Anticarcinogenic Agents; D065607:Cytochrome P-450 Enzyme Inhibitors; D005961:Glucosinolates; D017879:Isothiocyanates; D009570:Nitriles; C079114:butenylisothiocyanate; D019363:Cytochrome P-450 CYP1A1; D005978:Glutathione
keywords: Brassica; Chemoprevention; Cytotoxicity; Glucosinolate hydrolysis products