title: Sulforaphane induces oxidative stress and death by p53-independent mechanism: implication of impaired glutathione recycling.
abstract: Sulforaphane (SFN) is a naturally-occurring isothiocyanate best known for its role as an indirect antioxidant. Notwithstanding, in different cancer cell lines, SFN may promote the accumulation of reactive oxygen species (ROS) and cause cell death e.g. by apoptosis. Osteosarcoma often becomes chemoresistant, and new molecular targets to prevent drug resistance are needed. Here, we aimed to determine the effect of SFN on ROS levels and to identify key biomarkers leading to ROS unbalance and apoptosis in the p53-null MG-63 osteosarcoma cell line. MG-63 cells were exposed to SFN for up to 48 h. At 10 μM concentration or higher, SFN decreased cell viability, increased the%early apoptotic cells and increased caspase 3 activity. At these higher doses, SFN increased ROS levels, which correlated with apoptotic endpoints and cell viability decline. In exposed cells, gene expression analysis revealed only partial induction of phase-2 detoxification genes. More importantly, SFN inhibited ROS-scavenging enzymes and impaired glutathione recycling, as evidenced by inhibition of glutathione reductase (GR) activity and combined inhibition of glutathione peroxidase (GPx) gene expression and enzyme activity. In conclusion, SFN induced oxidative stress and apoptosis via a p53-independent mechanism. GPx expression and activity were found associated with ROS accumulation in MG-63 cells and are potential biomarkers for the efficacy of ROS-inducing agents e.g. as co-adjuvant drugs in osteosarcoma.
authors.affiliation: CESAM & Laboratory of Biotechnology and Cytomics, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.
authors.forename: José Miguel P
authors.initials: JM
authors.lastname: Ferreira de Oliveira
authors.affiliation: CESAM & Laboratory of Biotechnology and Cytomics, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.
authors.forename: Maria
authors.initials: M
authors.lastname: Costa
authors.affiliation: CESAM & Laboratory of Biotechnology and Cytomics, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.
authors.forename: Tiago
authors.initials: T
authors.lastname: Pedrosa
authors.affiliation: CESAM & Laboratory of Biotechnology and Cytomics, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Pinto
authors.affiliation: CESAM & Laboratory of Biotechnology and Cytomics, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.
authors.forename: Catarina
authors.initials: C
authors.lastname: Remédios
authors.affiliation: CESAM & Laboratory of Biotechnology and Cytomics, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.
authors.forename: Helena
authors.initials: H
authors.lastname: Oliveira
authors.affiliation: Lenitudes, Lisboa, Portugal; Faculty of Health Sciences, University Fernando Pessoa, R. Carlos da Maia 296, Porto, Portugal; Center for Health Studies & Research, University of Coimbra, Avenida Dias da Silva, Coimbra, Portugal; Faculdade de Ciências da Saúde - Universidade da Beira Interior, Avenida Infante D. Henrique, Covilhã, Portugal.
authors.forename: Francisco
authors.initials: F
authors.lastname: Pimentel
authors.affiliation: Luzitin SA, R. Bayer 16, Coimbra, Portugal; Blueclinical Phase I, R. Sarmento de Beires 153, Porto, Portugal.
authors.forename: Luís
authors.initials: L
authors.lastname: Almeida
authors.affiliation: CESAM & Laboratory of Biotechnology and Cytomics, Department of Biology, University of Aveiro, Campus Universitário de Santiago, Aveiro, Portugal.
authors.forename: Conceição
authors.initials: C
authors.lastname: Santos
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D017879:Isothiocyanates / Q000494:pharmacology*; D012516:Osteosarcoma / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects*; D013454:Sulfoxides; D013997:Time Factors
chemical_list: D000975:Antioxidants; D014408:Biomarkers, Tumor; D004791:Enzyme Inhibitors; D017879:Isothiocyanates; D013454:Sulfoxides; C016766:sulforaphane; D005978:Glutathione