title: Perturbation of mitosis through inhibition of histone acetyltransferases: the key to ochratoxin a toxicity and carcinogenicity?
abstract: Ochratoxin A (OTA) is one of the most potent rodent renal carcinogens studied to date. Although controversial results regarding OTA genotoxicity have been published, it is now widely accepted that OTA is not a mutagenic, DNA-reactive carcinogen. Instead, increasing evidence from both in vivo and in vitro studies suggests that OTA may promote genomic instability and tumorigenesis through interference with cell division. The aim of the present study was to provide further support for disruption of mitosis as a key event in OTA toxicity and to understand how OTA mediates these effects. Immortalized human kidney epithelial cells (IHKE) were treated with OTA and monitored by differential interference contrast microscopy for 15 h. Image analysis confirmed that OTA at concentrations ≥ 5 μM, which correlate with plasma concentrations in rats under conditions of carcinogenesis, causes sustained mitotic arrest and exit from mitosis without nuclear or cellular division. Mitotic chromosomes were characterized by aberrant condensation and premature sister chromatid separation associated with altered phosphorylation and acetylation of core histones. To test if OTA directly interferes with histone acetyltransferases (HATs) which regulate lysine acetylation of histones and nonhistone proteins, a cell-free HAT activity assay was conducted using total nuclear extracts of IHKE cells. In this assay, OTA significantly blocked HAT activity in a concentration-dependent manner Overall, results from this study provide further support for a mechanism of OTA carcinogenicity involving interference with the mitotic machinery and suggest HATs as a primary cellular target of OTA.
authors.affiliation: Department of Toxicology, Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany.
authors.forename: Kristin
authors.initials: K
authors.lastname: Czakai
authors.forename: Katja
authors.initials: K
authors.lastname: Müller
authors.forename: Pasquale
authors.initials: P
authors.lastname: Mosesso
authors.forename: Gaetano
authors.initials: G
authors.lastname: Pepe
authors.forename: Markus
authors.initials: M
authors.lastname: Schulze
authors.forename: Antje
authors.initials: A
authors.lastname: Gohla
authors.forename: Debasis
authors.initials: D
authors.lastname: Patnaik
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Dekant
authors.forename: Jonathan M G
authors.initials: JM
authors.lastname: Higgins
authors.forename: Angela
authors.initials: A
authors.lastname: Mally
mesh_terms: D000107:Acetylation / Q000187:drug effects; D002273:Carcinogens / Q000633:toxicity*; D002455:Cell Division; D002460:Cell Line; D004249:DNA Damage; D004847:Epithelial Cells / Q000187:drug effects; D051548:Histone Acetyltransferases / Q000037:antagonists & inhibitors*; D006657:Histones / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000187:drug effects; D008938:Mitosis / Q000187:drug effects*; D009153:Mutagens / Q000633:toxicity; D009793:Ochratoxins / Q000633:toxicity*; D010766:Phosphorylation / Q000187:drug effects
chemical_list: D002273:Carcinogens; D006657:Histones; D009153:Mutagens; D009793:Ochratoxins; C025589:ochratoxin A; D051548:Histone Acetyltransferases