title: Aerosolized ZnO nanoparticles induce toxicity in alveolar type II epithelial cells at the air-liquid interface.
abstract: The majority of in vitro studies characterizing the impact of engineered nanoparticles (NPs) on cells that line the respiratory tract were conducted in cells exposed to NPs in suspension. This approach introduces processes that are unlikely to occur during inhaled NP exposures in vivo, such as the shedding of toxic doses of dissolved ions. ZnO NPs are used extensively and pose significant sources for human exposure. Exposures to airborne ZnO NPs can induce adverse effects, but the relevance of the dissolved Zn(2+) to the observed effects in vivo is still unclear. Our goal was to mimic in vivo exposures to airborne NPs and decipher the contribution of the intact NP from the contribution of the dissolved ions to airborne ZnO NP toxicity. We established the exposure of alveolar type II epithelial cells to aerosolized NPs at the air-liquid interface (ALI) and compared the impact of aerosolized ZnO NPs and NPs in suspension at the same cellular doses, measured as the number of particles per cell. By evaluating membrane integrity and cell viability 6 and 24 h post-exposure, we found that aerosolized NPs induced toxicity at the ALI at doses that were in the same order of magnitude as doses required to induce toxicity in submersed cultures. In addition, distinct patterns of oxidative stress were observed in the two exposure systems. These observations unravel the ability of airborne ZnO NPs to induce toxicity without the contribution of dissolved Zn(2+) and suggest distinct mechanisms at the ALI and in submersed cultures.
authors.affiliation: Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
authors.forename: Yumei
authors.initials: Y
authors.lastname: Xie
authors.forename: Nolann G
authors.initials: NG
authors.lastname: Williams
authors.forename: Ana
authors.initials: A
authors.lastname: Tolic
authors.forename: William B
authors.initials: WB
authors.lastname: Chrisler
authors.forename: Justin G
authors.initials: JG
authors.lastname: Teeguarden
authors.forename: Bettye L S
authors.initials: BL
authors.lastname: Maddux
authors.forename: Joel G
authors.initials: JG
authors.lastname: Pounds
authors.forename: Alexander
authors.initials: A
authors.lastname: Laskin
authors.forename: Galya
authors.initials: G
authors.lastname: Orr
mesh_terms: D000336:Aerosols; D056809:Alveolar Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D015824:Blood-Air Barrier / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018929:Cell Culture Techniques; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D051379:Mice; D053758:Nanoparticles; D018384:Oxidative Stress / Q000187:drug effects; D010316:Particle Size; D011650:Pulmonary Alveoli / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D015034:Zinc Oxide / Q000633:toxicity*
chemical_list: D000336:Aerosols; D015034:Zinc Oxide