Biological response and morphological assessment of individually dispersed multi-wall carbon nanotubes in the lung after intratracheal instillation in rats

Abstract

Biological responses of multi-wall carbon nanotubes (MWCNTs) were assessed after a single intratracheal instillation in rats. The diameter and median length of the MWCNTs used in this study were approximately 60 nm and 1.5 μm, respectively. Groups of male Sprague-Dawley rats were intratracheally instilled with 0.04, 0.2, or 1 mg/kg of the individually dispersed MWCNT suspension. After instillation, the bronchoalveolar lavage fluid was assessed for inflammatory cells and markers, and the lung, liver, kidney, spleen, and cerebrum were histopathologically evaluated at 3-day, 1-week, 1-month, 3-month, and 6-month post-exposure. Transient pulmonary inflammatory responses were observed only in the lungs of the group of rats exposed to 1 mg/kg of MWCNTs. Morphology of the instilled MWCNTs in the lungs of rats was assessed using light microscopy and transmission electron microscopy (TEM). Light microscopy examination revealed that MWCNTs deposited in the lungs of the rats were typically phagocytosed by the alveolar macrophages and these macrophages were consequently accumulated in the alveoli until 6-month post-exposure. The 400 TEM images obtained showed that all MWCNTs were located in the alveolar macrophages or macrophages in the interstitial tissues, and MWCNTs were not located in the cells of the interstitial tissues. There was no evidence of chronic inflammation, such as angiogenesis or fibrosis, induced by MWCNT instillation. These results suggest that MWCNTs were being processed and cleared by alveolar macrophages.

Lung toxicity assessment using bronchoalveolar lavage fluid and pleural lavage fluid cytology by intratracheal treatment in rats

“…The BALF cytokine parameters such as IL-5, IL-6, MCP-1 and GRO/ KC had good correlation to lung inflammation, but not IL-1α, IL-1β, IL-2, IL-4, IL-10, GM-CSF, INF-γ, TNF-α, IL-12, IL-18. Several papers reported usefulness of the BALF analysis on pulmonary damage (Henderson et al, 1985;Henderson, 2005;Kobayashi et al, 2010). Our present study confirmed the usefulness of the BALF for pulmonary toxicity assessment.…”

In vivo Toxicity Studies of Pristine Carbon Nanotubes: A Review

“…Moreover, the authors did not find any evidence of chronic inflammation, such as angiogenesis or fibrosis, induced by MWNT instillation (Kobayashi et al, 2010). Light microscopic examination indicated that MWNT aggregates deposited in the lungs were phagocytized by alveolar macrophages and were accumulated in the lungs until 6-month post-exposure.…”

“…Light microscopic examination indicated that MWNT aggregates deposited in the lungs were phagocytized by alveolar macrophages and were accumulated in the lungs until 6-month post-exposure. These aggregates were located in the alveolar or interstitial macrophages, but individual MWNTs were not present in the cells of the interstitial tissue (Kobayashi et al, 2010). However, in the light micrograph panels, provided by the authors (Kobayashi et al, 2010) MWNTs seem to extend outside the macrophages in several directions, which is commonly referred to as incomplete or frustrated phagocytosis that is known to be a proinflammatory condition (Balkwill & Mantovani, 2001).…”

“…In a study where rats were instilled with 0.04, 0.2, or 1 mg/kg of individually dispersed MWNTs in Tween 80 (Kobayashi et al, 2010), it has been observed that pulmonary inflammatory responses occur only in the lungs of the group treated with the highest dose. Moreover, the authors did not find any evidence of chronic inflammation, such as angiogenesis or fibrosis, induced by MWNT instillation (Kobayashi et al, 2010).…”

Long‐term retention of pristine multi‐walled carbon nanotubes in rat lungs after intratracheal instillation

“…To prepare a stable suspension, MWCNTs, which were synthesized using a floating catalyst method (Nikkiso Co. Ltd., Japan), were sonicated (180W) for 30 min in an aqueous solution of 0.5 mg ml −1 polyoxyethylene octyl phenyl ether (Triton‐X, Wako Pure Chemical Industries Co. Ltd., Osaka, Japan) using an ultrasonic bath (5510‐MT; Branson Ultrasonics Co., Danbury, CT, USA) according to previously described methods (Kobayashi et al ., 2010; Chen et al ., 2011; Morimoto et al ., 2012). …”