Title: Intracellular accumulation dynamics and fate of zinc ions in alveolar epithelial cells exposed to airborne ZnO nanoparticles at the air–liquid interface

Abstract

Airborne nanoparticles (NPs) that enter the respiratory tract are likely to reach the alveolar region. Accumulating observations support a role for zinc oxide (ZnO) NP dissolution in toxicity, but the majority of in vitro studies were conducted in cells exposed to NPs in growth media, where large doses of dissolved ions are shed into the exposure solution. To determine the precise intracellular accumulation dynamics and fate of zinc ions (Zn²⁺) shed by airborne NPs in the cellular environment, we exposed alveolar epithelial cells to aerosolized NPs at the air-liquid interface (ALI). Using a fluorescent indicator for Zn²⁺, together with organelle-specific fluorescent proteins, we quantified Zn²⁺ in single cells and organelles over time. We found that at the ALI, intracellular Zn²⁺ values peaked 3 h post exposure and decayed to normal values by 12 h, while in submersed cultures, intracellular Zn²⁺ values continued to increase over time. The lowest toxic NP dose at the ALI generated peak intracellular Zn²⁺ values that were nearly 3 folds lower than the peak values generated by the lowest toxic dose of NPs in submersed cultures, and 8 folds lower than the peak values generated by the lowest toxic dose of ZnSO4 or Zn²⁺. At themore » ALI, the majority of intracellular Zn²⁺ was found in endosomes and lysosomes as early as 1 h post exposure. In contrast, the majority of intracellular Zn²⁺ following exposures to ZnSO₄ was found in other larger vesicles, with less than 10% in endosomes and lysosomes. In conclusion, together, our observations indicate that low but critical levels of intracellular Zn²⁺ have to be reached, concentrated specifically in endosomes and lysosomes, for toxicity to occur, and point to the focal dissolution of the NPs in the cellular environment and the accumulation of the ions specifically in endosomes and lysosomes as the processes underlying the potent toxicity of airborne ZnO NPs.« less

Authors:

Mihai, Cosmin ^[1]; Chrisler, William B. ^[2]; Xie, Yumei ^[1]; Hu, Dehong ^[1]; Szymanski, Craig J. ^[1]; Tolic, Ana ^[1]; Klein, Jessica A. ^[2]; Smith, Jordan N. ^[2]; Tarasevich, Barbara J. ^[3]; Orr, Galya ^[1]

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+ Show Author Affiliations

1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab.
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Fundamental & Computational Sciences Directorate
3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Energy & Environment Directorate

Publication Date:

Mon Dec 02 00:00:00 EST 2013

Research Org.:

Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Sciences Laboratory (EMSL)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1177706

Report Number(s):

PNNL-SA-99125
Journal ID: ISSN 1743-5390; 44627; 600306000

Grant/Contract Number:  

AC05-76RL01830; 1RC2ES018786-01

Resource Type:

Accepted Manuscript

Journal Name:

Nanotoxicology

Additional Journal Information:

Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 1743-5390

Publisher:

Informa Healthcare

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; 59 BASIC BIOLOGICAL SCIENCES; Intracellular; alveolar; epithelial; cells; nanoparticles; Environmental Molecular Sciences Laboratory; Airborne nanoparticles; air–liquid interface; endosomes; FluoZin-3; intracellular Zn2+; lysosomes