title: Demonstration of an olfactory bulb-brain translocation pathway for ZnO nanoparticles in rodent cells in vitro and in vivo.
abstract: ZnO nanoparticles (ZnO-NPs) are widely used in the engineering and cosmetic industries, and inhaled airborne particles pose a known hazard to human health; their translocation into humans is a recognized public health concern. The pulmonary-blood pathway for ZnO-NP toxicity is well documented, but whether translocation of these particles can also occur via an olfactory bulb-brain route remains unclear. The potential toxicity of ZnO-NPs for the human central nervous system (CNS) is predicated on the possibility of their translocation. Our study investigated translocation of ZnO-NPs both in vitro using the neuronal cell line PC12 and in vivo in a Sprague-Dawley rat model. Our findings indicate that the zinc-binding dye, Newport-Green DCF, binds ZnO stoichiometrically and that ZnO-NP concentration can therefore be measured by the fluorescence intensity of the bound dye in confocal fluorescence microscopy. Confocal data obtained using Newport-Green DCF-2 K(+)-conjugated ZnO-NPs along with the membrane probe FM1-43 demonstrated endocytosis of ZnO-NPs by PC12 cells. In addition, Fluozin-3 measurement showed elevation of cytosolic Zn(2+) concentration in these cells. Following in vivo nasal exposure of rats to airborne ZnO-NPs, olfactory bulbs and brains that were examined by Newport-Green fluorescence and TEM particle measurement clearly showed the presence of ZnO-NPs in brain. We conclude that an olfactory bulb-brain translocation pathway for airborne ZnO-NPs exists in rats, and that endocytosis is required for interneuron translocation of these particles.
authors.affiliation: Department of Microbiology, Soochow University, Shihlin, Shilin District, Taipei 111, Taiwan.
authors.forename: Yi-Yun
authors.initials: YY
authors.lastname: Kao
authors.forename: Tsun-Jen
authors.initials: TJ
authors.lastname: Cheng
authors.forename: De-Ming
authors.initials: DM
authors.lastname: Yang
authors.forename: Chin-Tien
authors.initials: CT
authors.lastname: Wang
authors.forename: Yin-Mei
authors.initials: YM
authors.lastname: Chiung
authors.forename: Pei-Shan
authors.initials: PS
authors.lastname: Liu
mesh_terms: D000818:Animals; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D053758:Nanoparticles / Q000008:administration & dosage / Q000633:toxicity*; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D009830:Olfactory Bulb / Q000166:cytology / Q000187:drug effects*; D018034:Olfactory Receptor Neurons / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D016716:PC12 Cells; D052638:Particulate Matter / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D015034:Zinc Oxide / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000633:toxicity*
chemical_list: D052638:Particulate Matter; D015034:Zinc Oxide