title: Cytotoxicity and genotoxicity of nano - and microparticulate copper oxide: role of solubility and intracellular bioavailability.
abstract: BACKGROUND
  Nano- or microscale copper oxide particles (CuO NP, CuO MP) are increasingly applied as catalysts or antimicrobial additives. This increases the risk of adverse health effects, since copper ions are cytotoxic under overload conditions.
  
  
  METHODS
  The extra- and intracellular bioavailability of CuO NP and CuO MP were explored. In addition, different endpoints related to cytotoxicity as well as direct and indirect genotoxicity of the copper oxides and copper chloride (CuCl2) were compared.
  
  
  RESULTS
  Comprehensively characterized CuO NP and CuO MP were analysed regarding their copper ion release in model fluids. In all media investigated, CuO NP released far more copper ions than CuO MP, with most pronounced dissolution in artificial lysosomal fluid. CuO NP and CuCl2 caused a pronounced and dose dependent decrease of colony forming ability (CFA) in A549 and HeLa S3 cells, whereas CuO MP exerted no cytotoxicity at concentrations up to 50 μg/mL. Cell death induced by CuO NP was at least in part due to apoptosis, as determined by subdiploid DNA as well as via translocation of the apoptosis inducing factor (AIF) into the cell nucleus. Similarly, only CuO NP induced significant amounts of DNA strand breaks in HeLa S3 cells, whereas all three compounds elevated the level of H2O2-induced DNA strand breaks. Finally, all copper compounds diminished the H2O2-induced poly(ADP-ribosyl)ation, catalysed predominantly by poly(ADP-ribose)polymerase-1 (PARP-1); here, again, CuO NP exerted the strongest effect. Copper derived from CuO NP, CuO MP and CuCl2 accumulated in the soluble cytoplasmic and nuclear fractions of A549 cells, yielding similar concentrations in the cytoplasm but highest concentrations in the nucleus in case of CuO NP.
  
  
  CONCLUSIONS
  The results support the high cytotoxicity of CuO NP and CuCl2 and the missing cytotoxicity of CuO MP under the conditions applied. For these differences in cytotoxicity, extracellular copper ion levels due to dissolution of particles as well as differences in physicochemical properties of the particles like surface area may be of major relevance. Regarding direct and indirect genotoxicity, especially the high copper content in the cell nucleus derived after cell treatment with CuO NP appears to be decisive.
authors: Annetta
authors: A
authors: Semisch
authors: Julia
authors: J
authors: Ohle
authors: Barbara
authors: B
authors: Witt
authors: Department of Food Chemistry and Toxicology, Karlsruhe Institute of Technology (KIT), Institute for Applied Biosciences, Adenauerring 20a, Karlsruhe 76131, Germany. andrea.hartwig@kit.edu.
authors: Andrea
authors: A
authors: Hartwig
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001682:Biological Availability; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects*; D003300:Copper / Q000737:chemistry / Q000493:pharmacokinetics / Q000633:toxicity*; D004249:DNA Damage; D004731:Endotoxins / Q000032:analysis; D006367:HeLa Cells; D006801:Humans; D007202:Indicators and Reagents; D053768:Metal Nanoparticles / Q000633:toxicity*; D015162:Micronucleus Tests; D008855:Microscopy, Electron, Scanning; D009153:Mutagens; D010316:Particle Size; D011064:Poly Adenosine Diphosphate Ribose / Q000378:metabolism; D012995:Solubility; D014178:Translocation, Genetic; D014783:Viscosity
chemical_list: D004731:Endotoxins; D007202:Indicators and Reagents; D009153:Mutagens; D011064:Poly Adenosine Diphosphate Ribose; D003300:Copper; D053148:Caspase 3; D053179:Caspase 7; C029892:cupric chloride; C000520:cuprous oxide; C030973:cupric oxide