title: Isololiolide, a carotenoid metabolite isolated from the brown alga Cystoseira tamariscifolia, is cytotoxic and able to induce apoptosis in hepatocarcinoma cells through caspase-3 activation, decreased Bcl-2 levels, increased p53 expression and PARP cleavage.
abstract: BACKGROUND
  Brown macroalgae have attracted attention because they display a wide range of biological activities, including antitumoral properties. Inthis study we isolated isololiolide from Cystoseira tamariscifolia for the first time.
  
  
  OBJECTIVE
  To examine the therapeutical potential of isololiolide against tumor cell lines.
  
  
  METHODS
  The structure of the compound was established and confirmed by 1D and 2D NMR as well as HRMS spectral analysis. The in vitro cytotoxicity was analyzed by colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay in tumoral as well as in non-tumoral cell lines. Cell cycle arrest and induction of apoptosis were assessed by flow cytometry. Alteration of expression levels in proteins important in the apoptotic cascade was analyzed by western blotting.
  
  
  RESULTS
  Isololiolidewas isolated for the first time from the brown macroalga C.tamariscifolia. Isololiolide exhibited significant cytotoxic activity against three human tumoral cell lines, namely hepatocarcinoma HepG2 cells, whereas no cytotoxicity was found in non-malignant MRC-5 and HFF-1 human fibroblasts. Isololiolide completely disrupted the HepG2 normal cell cycle and induced significant apoptosis. Moreover, western blot analysis showed that isololiolide altered the expression of proteins that are important in the apoptotic cascade, increasing PARP cleavage and p53 expression while decreasing procaspase-3 and Bcl-2 levels.
  
  
  CONCLUSIONS
  Isololiolide isolated from C. tamariscifolia is able to exert a selective cytotoxic activity on hepatocarcinoma HepG2 cells as well as induce apoptosis through the modulation of apoptosis-related proteins.
authors.affiliation: Centre of Marine Sciences, University of Algarve, Faculty of Sciences and Technology, Ed. 7, Campus of Gambelas, Faro, Portugal.
authors.forename: Catarina
authors.initials: C
authors.lastname: Vizetto-Duarte
authors.affiliation: Centre of Marine Sciences, University of Algarve, Faculty of Sciences and Technology, Ed. 7, Campus of Gambelas, Faro, Portugal.
authors.forename: Luísa
authors.initials: L
authors.lastname: Custódio
authors.affiliation: Centre of Marine Sciences, University of Algarve, Faculty of Sciences and Technology, Ed. 7, Campus of Gambelas, Faro, Portugal.
authors.forename: Katkam N
authors.initials: KN
authors.lastname: Gangadhar
authors.affiliation: Institute of Environmental, Chemical and Pharmaceutical Sciences, Federal University of Sao Paulo, 09972-270, Sao Paulo, Brazil.
authors.forename: João Henrique G
authors.initials: JH
authors.lastname: Lago
authors.affiliation: Center of Chemistry and Biochemistry, Department of Chemistry and Biochemistry, Faculty of Sciences University of Lisbon, Campo Grande, Ed. C8, Piso 5, 1749-016 Lisbon, Portugal.
authors.forename: Catarina
authors.initials: C
authors.lastname: Dias
authors.affiliation: Center of Chemistry and Biochemistry, Department of Chemistry and Biochemistry, Faculty of Sciences University of Lisbon, Campo Grande, Ed. C8, Piso 5, 1749-016 Lisbon, Portugal.
authors.forename: Ana Marta
authors.initials: AM
authors.lastname: Matos
authors.affiliation: Center of Chemistry and Biochemistry, Department of Chemistry and Biochemistry, Faculty of Sciences University of Lisbon, Campo Grande, Ed. C8, Piso 5, 1749-016 Lisbon, Portugal.
authors.forename: Nuno
authors.initials: N
authors.lastname: Neng
authors.affiliation: Center of Chemistry and Biochemistry, Department of Chemistry and Biochemistry, Faculty of Sciences University of Lisbon, Campo Grande, Ed. C8, Piso 5, 1749-016 Lisbon, Portugal.
authors.forename: José Manuel Florêncio
authors.initials: JM
authors.lastname: Nogueira
authors.affiliation: Centre of Marine Sciences, University of Algarve, Faculty of Sciences and Technology, Ed. 7, Campus of Gambelas, Faro, Portugal.
authors.forename: Luísa
authors.initials: L
authors.lastname: Barreira
authors.affiliation: Institute for Research in Biomedicine, Barcelona Science Park, Baldiri Reixac 10, 08028, Barcelona, Spain; CIBER-BBN, Networking Centre on Bioengineering, Biomaterials and Nanomedicine, Barcelona Science Park, Baldiri Reixac 10, 08028 Barcelona, Spain; University of Barcelona, Department of Organic Chemistry, Martí i Franqués 1-11, 08028 Barcelona, Spain.
authors.forename: Fernando
authors.initials: F
authors.lastname: Albericio
authors.affiliation: Center of Chemistry and Biochemistry, Department of Chemistry and Biochemistry, Faculty of Sciences University of Lisbon, Campo Grande, Ed. C8, Piso 5, 1749-016 Lisbon, Portugal.
authors.forename: Amelia P
authors.initials: AP
authors.lastname: Rauter
authors.affiliation: Centre of Marine Sciences, University of Algarve, Faculty of Sciences and Technology, Ed. 7, Campus of Gambelas, Faro, Portugal. Electronic address: jvarela@ualg.pt.
authors.forename: João
authors.initials: J
authors.lastname: Varela
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D006528:Carcinoma, Hepatocellular / Q000473:pathology*; D002338:Carotenoids / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D056945:Hep G2 Cells / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology*; D015394:Molecular Structure; D000459:Phaeophyceae / Q000737:chemistry; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: C000595707:BCL2 protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; C000611655:isololiolide; D002338:Carotenoids; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3
keywords: Apoptosis; Carotenoid metabolite; Cell cycle; Cystoseira; Isololiolide; Marine natural product