title: Radicicol but not geldanamycin evokes oxidative stress response and efflux protein inhibition in ARPE-19 human retinal pigment epithelial cells.
abstract: Drug delivery to retinal cells has represented a major challenge for ophthalmologists for many decades. However, drug targeting to the retina is essential in therapies against retinal diseases such as age-related macular degeneration, the most common reason of blindness in the developed countries. Retinal cells are chronically exposed to oxidative stress that contributes to cellular senescence and may cause neovascularization in the most severe age-related macular degeneration cases. Various pre- and clinical studies have revealed that heat shock protein 90 (HSP90) inhibitors, such as geldanamycin and radicicol, are promising drugs in the treatment of different malignant processes. In this study, our goal was to compare the effects of 0.1 microM, 1 microM or 5 microM geldanamycin or radicicol on the oxidative stress response, cytotoxicity, and efflux protein activity (a protein pump which removes drugs from cells) in ARPE-19 (human retinal pigment epithelial, RPE) cells. Our findings indicate that geldanamycin and radicicol increased HSP70 and HSP27 expression analyzed by western blotting. Cellular levels of protein carbonyls were increased in response to 0.1 microM (P=0.048 for 24 h, P=0.018 for 48 h) or 5 microM (P=0.030 for 24 h, P=0.046 for 48 h) radicicol but not to geldanamycin analyzed by ELISA assay. In addition, HNE-protein adducts were accumulated in the RPE cells exposed to 0.1 microM or 5 microM radicicol but not to geldanamycin analyzed by western blotting. However, MTT assay revealed that 5 microM geldanamycin reduced cellular viability 20-30% (P<0.05 for 24 h, P<0.01 for 48 h), but this was not observed at any radicicol concentration in RPE cells. Interestingly, the increased oxidative stress response was associated with efflux protein inhibition (20-30%) when the cells were exposed to 1 microM or 5 microM (P<0.05) radicicol, but not in geldanamycin-treated RPE cells. These novel findings help in understanding the influence of HSP90 inhibition and regulatory mechanisms of drug delivery to retinal cells.
authors.affiliation: Department of Ophthalmology, University of Kuopio, Kuopio, Finland.
authors.forename: Tuomas
authors.initials: T
authors.lastname: Ryhänen
authors.forename: Eliisa
authors.initials: E
authors.lastname: Mannermaa
authors.forename: Niku
authors.initials: N
authors.lastname: Oksala
authors.forename: Johanna
authors.initials: J
authors.lastname: Viiri
authors.forename: Tuomas
authors.initials: T
authors.lastname: Paimela
authors.forename: Antero
authors.initials: A
authors.lastname: Salminen
authors.forename: Mustafa
authors.initials: M
authors.lastname: Atalay
authors.forename: Kai
authors.initials: K
authors.lastname: Kaarniranta
mesh_terms: D016227:Benzoquinones / Q000494:pharmacology*; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D055551:HSP27 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D047029:Lactams, Macrocyclic / Q000494:pharmacology*; D018942:Macrolides / Q000494:pharmacology*; D018832:Molecular Chaperones; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D010857:Pigment Epithelium of Eye / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D050050:Protein Carbonylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D016227:Benzoquinones; D055551:HSP27 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D018942:Macrolides; D018832:Molecular Chaperones; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D047428:Protein Kinase Inhibitors; C057725:HSPB1 protein, human; C035359:monorden; C001277:geldanamycin