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. 2014 Feb;8(1):17-27.
doi: 10.3109/17435390.2012.744110. Epub 2012 Nov 14.

IL-1R signalling is critical for regulation of multi-walled carbon nanotubes-induced acute lung inflammation in C57Bl/6 mice

Affiliations

IL-1R signalling is critical for regulation of multi-walled carbon nanotubes-induced acute lung inflammation in C57Bl/6 mice

Teri Alyn Girtsman et al. Nanotoxicology. 2014 Feb.

Abstract

Exposure to certain engineered nanomaterials has been associated with pathological changes in animal models raising concerns about potential human health effects. MWCNT have been reported to activate the NLRP3 inflammasome in vitro, correlating with lung inflammation and pathology, in vivo. In this study, we investigated the role of IL-1 signalling in pulmonary inflammatory responses in WT and IL-1R-/- mice after exposure to MWCNT. The results suggest that MWCNT were effective in inducing acute pulmonary inflammation. Additionally, WT mice demonstrated significant increased airway resistance 24 h post exposure to MWCNT, which was also blocked in the IL-1R-/- mice. In contrast, by 28 days post exposure to MWCNT, the inflammatory response that was initially absent in IL-1R-/- mice was elevated in comparison to the WT mice. These data suggest that IL-1R signalling plays a crucial role in the regulation of MWCNT-induced pulmonary inflammation.

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Conflict of interest statement

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Figures

Figure 1
Figure 1
Characterisation of multi-walled carbon nanotubes was determined using electron microscopy. The images recorded using the scanning electron microscope show LN- and HN-MWCNT. Dry nanoparticle samples were placed on a conductive stick carbon tab on a 12 mm aluminium SEM stub. The stubs were place, uncoated, in a Hitachi S-4700 Field Emission Scanning Electron Microscope and imaged at 10 kv.
Figure 2
Figure 2
Total and differential Cell Counts are augmented in mice exposed to MWCNT. WT and IL-1R−/− mice were exposed to LN-MWCNT (2.5% Ni) and HN-MWCNT (5.54% Ni) (50 µg/30 µl) through oropharyngeal aspiration. After 24 h, the lungs were lavaged and total cell counts were determined using the Coulter Z2 particle counter (A). Cells from WLLF (4–10 × 104) were concentrated in PBS by Cytospin (Shandon, Thermo Scientific West Palm Beach, FL) centrifuged for 5 min at 1500 rpm. The slides were processed with Protocol Hema-3 Stain (Fisher Scientific, Houston, TX) (Eosin and Methylene Blue). Differential counts were determined using light microscopy (B and C). Blue and red arrows denote neutrophils and eosinophils, respectively (C). Results are means ± SE (n = 4 in each group). *p < 0.05, **p < 0.01, ***p < 0.001, #p < 0.05 (vs. WT group).
Figure 3
Figure 3
MWCNT induces chemotactic factors MCP-1 through the IL-1R−/− signalling pathway. WLLF was collected from WT and IL-1R−/− mice 24 h post exposure to LN and HN-MWCNT. The cells were isolated through centrifugation and the supernatants were assayed for IL-1β, IL-6*, TNF-α and MCP-1 by ELISA. *p < 0.05, ***p < 0.001 versus DM group, #p < 0.05 versus WT group. (*Due to shortage of sample, IL-6 assay included only HN-MWCNT WLLF).
Figure 4
Figure 4
Collagen deposition is augmented in the lungs of MWCNT-treated mice. Histopathology of lungs of IL-1R−/− mice exposed to MWCNT displays granuloma-like lesions and fibrotic tissue at 7 and 28 days post exposure. The WT or IL-1R−/− mice were euthanised at days 7 and 28 post exposure. After perfusion, the lung tissue from mice instilled with DM only or 50 mg LN- or HN-MWCNT was fixed in paraformaldehyde and imbedded in paraffin. Tissue sections that were stained with Gomori’s Trichrome demonstrate collagen-rich granulomas and surrounding fibrotic tissue in lungs of both WT and IL-1R−/− mice exposed with HN-MWCNT, but not DM (vehicle) control or LN-MWCNT-exposed mice (A). Collagen deposition in the lungs of WT or IL- 1R−/− mice following instillation with LN-, HN-MWCNT was assessed by hydroxyproline assay (n = 3–5 mice/group). The data were normalised by subtracting the mean background from the vehicle-treated mice, from the hydroxyproline levels of the particle-treated animals. Values are means ± SEM; * p < 0.05 compared to vehicle controls (B)
Figure 5
Figure 5
Pulmonary function at 24 h and 28 days post exposure to HN-MWCNT. Pulmonary function was assessed as a function of increasing methacholine dose in live mice at 24 h or 28 days after exposure to HN-MWCNT (A and B). Transpulmonary resistance (Medzhitov R) was assessed after anaesthetisation and tracheostomy (n = 6 for HN-MWCNT, n = 5 for vehicle (PBS) control). Two-factor ANOVA and Tukey post-hoc statistical analysis were performed to test for statistical significance of the effects of exposure to HN-MWCNT between WT and IL-1R−/− and between each of the vehicle controls. *p < 0.05 (C and D).
Figure 6
Figure 6
Acute and chronic influx of eosinophils in to the lungs of mice exposed to HN-MWCNT. WLL was performed on WT and IL-1R−/− mice 24 h or 28 days post exposure to HN-MWCT. The total cell and differential counts were performed. After 24 h of exposure, a significant influx of eosinophils was detected in the WLLF of WT mice in comparison to the vehicle control (*p > 0.05). After 28 days of exposure IL-1R−/− mice have demonstrate a prolonged eosinophilia compared to the vehicle-treated mice and the HN-MWCNT WT mice (*p > 0.05 vs. vehicle; #p > 0.05 vs. WT mouse) (A). EPO levels were assayed to verify the presence of eosinophils in the lavage fluid collected from the lungs of the mice exposed to HN-MWCNT (B).

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