title: Nitric oxide mediates natural polyphenol-induced Bcl-2 down-regulation and activation of cell death in metastatic B16 melanoma.
abstract: Intravenous administration to mice of trans-pterostilbene (t-PTER; 3,5-dimethoxy-4'-hydroxystilbene) and quercetin (QUER; 3,3',4',5,6-pentahydroxyflavone), two structurally related and naturally occurring small polyphenols, inhibits metastatic growth of highly malignant B16 melanoma F10 (B16M-F10) cells. t-PTER and QUER inhibit bcl-2 expression in metastatic cells, which sensitizes them to vascular endothelium-induced cytotoxicity. However, the molecular mechanism(s) linking polyphenol signaling and bcl-2 expression are unknown. NO is a potential bioregulator of apoptosis with controversial effects on Bcl-2 regulation. Polyphenols may affect NO generation. Short-term exposure (60 min/day) to t-PTER (40 microM) and QUER (20 microM) (approximate mean values of the plasma concentrations measured within the first hour after intravenous administration of 20 mg of each polyphenol/kg) down-regulated inducible NO synthetase in B16M-F10 cells and up-regulated endothelial NO synthetase in the vascular endothelium and thereby facilitated endothelium-induced tumor cytotoxicity. Very low and high NO levels down-regulated bcl-2 expression in B16M-F10 cells. t-PTER and QUER induced a NO shortage-dependent decrease in cAMP-response element-binding protein phosphorylation, a positive regulator of bcl-2 expression, in B16M-F10 cells. On the other hand, during cancer and endothelial cell interaction, t-PTER- and QUER-induced NO release from the vascular endothelium up-regulated neutral sphingomyelinase activity and ceramide generation in B16M-F10 cells. Direct NO-induced cytotoxicity and ceramide-induced mitochondrial permeability transition and apoptosis activation can explain the increased endothelium-induced death of Bcl-2-depleted B16M-F10 cells.
authors.affiliation: Department of Physiology, University of Valencia, 46010 Valencia, Spain.
authors.forename: Paula
authors.initials: P
authors.lastname: Ferrer
authors.forename: Miguel
authors.initials: M
authors.lastname: Asensi
authors.forename: Sonia
authors.initials: S
authors.lastname: Priego
authors.forename: María
authors.initials: M
authors.lastname: Benlloch
authors.forename: Salvador
authors.initials: S
authors.lastname: Mena
authors.forename: Angel
authors.initials: A
authors.lastname: Ortega
authors.forename: Elena
authors.initials: E
authors.lastname: Obrador
authors.forename: Juan M
authors.initials: JM
authors.lastname: Esteve
authors.forename: José M
authors.initials: JM
authors.lastname: Estrela
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D016923:Cell Death / Q000187:drug effects*; D045744:Cell Line, Tumor; D015536:Down-Regulation; D004730:Endothelium, Vascular / Q000502:physiology / Q000503:physiopathology; D005419:Flavonoids / Q000494:pharmacology*; D019254:Genes, bcl-2; D006861:Hydrogen Peroxide / Q000378:metabolism; D008297:Male; D008545:Melanoma; D051379:Mice; D008810:Mice, Inbred C57BL; D051336:Mitochondrial Membranes / Q000502:physiology; D009362:Neoplasm Metastasis; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology*; D009573:Nitrites / Q000378:metabolism; D010636:Phenols / Q000494:pharmacology*; D059808:Polyphenols; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D005419:Flavonoids; D009566:Nitrates; D009573:Nitrites; D010636:Phenols; D059808:Polyphenols; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D009569:Nitric Oxide; D006861:Hydrogen Peroxide