Lung exposure of titanium dioxide nanoparticles induces innate immune activation and long-lasting lymphocyte response in the Dark Agouti rat

Abstract

Nanomaterial of titanium dioxide (TiO2) is manufactured in large-scale production plants, resulting in risks for accidental high exposures of humans. Inhalation of metal oxide nanoparticles in high doses may lead to both acute and long-standing adverse effects. By using the Dark Agouti (DA) rat, a strain disposed to develop chronic inflammation following exposure to immunoactivating adjuvants, we investigated local and systemic inflammatory responses after lung exposure of nanosized TiO2 particles up to 90 days after intratracheal instillation. TiO2 induced a transient response of proinflammatory and T-cell-activating cytokines (interleukin [IL]-1α, IL-1β, IL-6, cytokine-induced neutrophil chemoattractant [CINC]-1, granulocyte-macrophage colony-stimulating factor [GM-CSF], and IL-2) in airways 1-2 days after exposure, accompanied byaninfluxofeosinophilsand neutrophils. Neutrophil numbers remained elevated for 30 days, whereas the eosinophils declined to baseline levels at Day 8, simultaneously with an increase of dendritic cells and natural killer (NK) cells. The innate immune activation was followed by a lymphocyte expansion that persisted throughout the 90-day study. Lymphocytes recruited to the lungs were predominantly CD4+ helper T-cells, but we also demonstrated presence of CD8+T-cells, B-cells, and CD25+T-cells. In serum, we detected both an early cytokine expression at Days 1-2 (IL-2, IL-4, IL-6, CINC-1, IL-10, and interferon-gamma [IFN-γ] and a second response at Day 16 of tumor necrosis factor-alpha (TNF-α), indicating systemic late-phase effects in addition to the local response in airways. In summary, these data demonstrate a dynamic response to TiO2 nanoparticles in the lungs of DA rats, beginning with an innate immune activation of eosinophils, neutrophils, dendritic cells, and NK cells, followed by a long-lasting activation of lymphocytes involved in adaptive immunity. The results have implications for the assessment of risks for adverse and persistent immune stimulation following nanoparticle exposures in sensitive populations.

Surface modifications of silica nanoparticles are crucial for their inert versus proinflammatory and immunomodulatory properties

“…We also demonstrated an increase of eosinophils in NS mice exposed to SiO 2 NPs, a phenomenon also observed in rats after titanium NP exposure. 10 The observation that, 24 hours after intratracheal instil lation, the percentage of FITC + cells in S mice was higher compared to NS mice, is in agreement with our earlier study. 28 NP uptake occurred mainly by pulmonary macrophages, as has been observed in healthy animals.…”

“…the circulatory and lymphatic systems, causing longlasting cell damage. 10,11 Several studies show that SiO 2 NPs induce dosedependent cytotoxicity in in vitro systems, including human lung epithelial cells 12 and bronchoalveolar carcino maderived cells 13 and human alveolar barrier, 14 as well as murine macrophages. 15 Shortterm instillations or inhalation exposure to amorphous SiO 2 NPs showed that these particles possess the potential to cause toxic effects in the lung.…”

Significance of Intratracheal Instillation Tests for the Screening of Pulmonary Toxicity of Nanomaterials

“…The changes in total cell counts in BALF may affect the influx of not only macrophages but also neutrophils, and that is not sufficient to reflect the neutrophil inflammation. There are reports that the proinflammatory cytokines interleukin-1 (IL-1), IL-6 and tumor necrosis factor (TNF) were upregulated in the acute period in animal models exposed to inhaled crystalline silica and TiO 2 [33][34][35]. These transient upregulations of proinflammaory cytokines may play a key role in sustained pulmonary inflammation, but changes in proinflammatory cytokines may not sufficiently reflect the pulmonary toxicity of nanomaterials due to the short response period, and may not be useful as predictive markers of the pulmonary toxicity of nanomaterials.…”

Differential cellular responses in healthy mice and in mice with established airway inflammation when exposed to hematite nanoparticles

“…The risk of being exposed to NPs is particularly high for those working with the production of engineered NPs (European Union, SWD (2012) 288 final). Recently, it has been shown that exposure to engineered NPs can induce airway inflammation in animals (Gustafsson et al, 2011;Rossi et al, 2010;Roursgaard et al, 2011), induce adverse health effects in sensitized mice during the development of eosinophilic airway inflammation (Jonasson et al, 2013), and also induce lung tissue fibrosis in mice (Ryman-Rasmussen et al, 2009).…”