title: Potentiation of hypericin-mediated photodynamic therapy cytotoxicity by MK-886: focus on ABC transporters, GDF-15 and redox status.
abstract: BACKGROUND
  Pretreatment with 5-LOX pathway inhibitor MK-886 potentiates cytotoxic effects of photodynamic therapy mediated by natural photosensitizer, hypericin. In this study, we focused on elucidating mechanisms beyond the increased efficacy of combined treatment.
  
  
  METHODS
  Metabolic activity/viability, caspase-3 activation/mitochondrial membrane potential dissipation, intracellular hypericin level, glutathione level and redox status (NAD(P)H/oxidized flavins ratio) analyses, as well as drug efflux assays, were performed by flow cytometry. Changes in protein expression of ATP-binding cassette transporters, GDF-15 and other selected proteins were evaluated by Western blotting. Silencing of gdf-15 was carried out to verify its role in response to treatment.
  
  
  RESULTS
  MK-886 pretreatment led to a concentration-dependent increase in intracellular hypericin content, accompanied by changes in ATP-binding cassette transporters levels and efflux efficiency. Intracellular accumulation of cytokine GDF-15 correlated with increased cell death markers; however, the impact of gdf-15 silencing on the evaluated markers was negligible. A marked decrease in the glutathione level of a majority of cells was observed after more toxic combination treatment.
  
  
  CONCLUSIONS
  The significant increase in cell death markers after combination treatment confirms the potentiating effect of MK-886 on hypericin-mediated photodynamic therapy in HT-29 and MCF-7 cells. Although BCRP downregulation was not confirmed as leading mechanism responsible for elevated levels of hypericin content, changes in expression and efflux activity of ABC transporters caused by MK-886 suggest its potential in combination treatment with drugs that are substrates of these transporters, predominantly MRP1. However, complex cellular response to MK-886 pretreatment needs to be considered and further elucidated.
authors.affiliation: Institute of Biology and Ecology, Faculty of Science, P.J. Šafárik University in Košice, Moyzesova 11, 040 01 Košice, Slovak Republic.
authors.forename: Barbora
authors.initials: B
authors.lastname: Kuchárová
authors.affiliation: Institute of Biology and Ecology, Faculty of Science, P.J. Šafárik University in Košice, Moyzesova 11, 040 01 Košice, Slovak Republic.
authors.forename: Jaromír
authors.initials: J
authors.lastname: Mikeš
authors.affiliation: Institute of Biology and Ecology, Faculty of Science, P.J. Šafárik University in Košice, Moyzesova 11, 040 01 Košice, Slovak Republic.
authors.forename: Rastislav
authors.initials: R
authors.lastname: Jendželovský
authors.affiliation: Institute of Biology and Ecology, Faculty of Science, P.J. Šafárik University in Košice, Moyzesova 11, 040 01 Košice, Slovak Republic.
authors.forename: Jana
authors.initials: J
authors.lastname: Vargová
authors.affiliation: Institute of Biology and Ecology, Faculty of Science, P.J. Šafárik University in Košice, Moyzesova 11, 040 01 Košice, Slovak Republic.
authors.forename: Lucia
authors.initials: L
authors.lastname: Mikešová
authors.affiliation: Institute of Biology and Ecology, Faculty of Science, P.J. Šafárik University in Košice, Moyzesova 11, 040 01 Košice, Slovak Republic.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Jendželovská
authors.affiliation: Institute of Biology and Ecology, Faculty of Science, P.J. Šafárik University in Košice, Moyzesova 11, 040 01 Košice, Slovak Republic.
authors.forename: Ján
authors.initials: J
authors.lastname: Kovaľ
authors.affiliation: Institute of Biology and Ecology, Faculty of Science, P.J. Šafárik University in Košice, Moyzesova 11, 040 01 Košice, Slovak Republic. Electronic address: peter.fedorocko@upjs.sk.
authors.forename: Peter
authors.initials: P
authors.lastname: Fedoročko
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis; D000873:Anthracenes; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D004357:Drug Synergism; D005978:Glutathione / Q000096:biosynthesis; D055436:Growth Differentiation Factor 15 / Q000037:antagonists & inhibitors; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D009369:Neoplasms / Q000188:drug therapy*; D010084:Oxidation-Reduction; D010569:Perylene / Q000031:analogs & derivatives* / Q000494:pharmacology; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D034741:RNA, Small Interfering / Q000378:metabolism; D002722:Chlorobenzenes
chemical_list: D018528:ATP-Binding Cassette Transporters; D000873:Anthracenes; D053148:Caspase 3; D005978:Glutathione; D055436:Growth Differentiation Factor 15; D007211:Indoles; D010569:Perylene; D017319:Photosensitizing Agents; D034741:RNA, Small Interfering; C526140:GDF15 protein, human; C060893:MK-886; D002722:Chlorobenzenes; C004965:hypericin
keywords: ABC transporters; GDF-15/NAG-1; Hypericin; MK-886; Photodynamic therapy; Redox status