BACKGROUND Nanotechnology is a rapidly advancing industry with many new products already available to the public. Therefore, it is essential to gain an understanding of the possible health risks associated with exposure to nanomaterials and to identify biomarkers of exposure. In this study, we investigated the fibrogenic potential of SWCNT synthesized by chemical vapor deposition using cobalt (Co) and molybdenum (Mo) as catalysts. Following a single oropharyngeal aspiration of SWCNT in rats, we evaluated lung histopathology, cell proliferation, and growth factor mRNAs at 1 and 21 days post-exposure. Comparisons were made to vehicle alone (saline containing a biocompatible nonionic surfactant), inert carbon black (CB) nanoparticles, or vanadium pentoxide (V2O5) as a known inducer of fibrosis. RESULTS SWCNT or CB caused no overt inflammatory response at 1 or 21 days post-exposure as determined by histopathology and evaluation of cells (>95% macrophages) in bronchoalveolar lavage (BAL) fluid. However, SWCNT induced the formation of small, focal interstitial fibrotic lesions within the alveolar region of the lung at 21 days. A small fraction of alveolar macrophages harvested by BAL from the lungs of SWCNT-exposed rats at 21 days were bridged by unique intercellular carbon structures that extended into the cytoplasm of each macrophage. These "carbon bridge" structures between macrophages were also observed in situ in the lungs of SWCNT-exposed rats. No carbon bridges were observed in CB-exposed rats. SWCNT caused cell proliferation only at sites of fibrotic lesion formation as measured by bromodeoxyuridine uptake into alveolar cells. SWCNT increased platelet-derived growth factor (PDGF)-A, PDGF-B, and PDGF-C mRNA levels significantly at 1 day as measured by Taqman quantitative real-time RT-PCR. At 21 days, SWCNT did not increase any mRNAs evaluated, while V2O5 significantly increased mRNAs encoding PDGF-A, -B, and -C chains, PDGF-R alpha, osteopontin (OPN), connective tissue growth factor (CTGF), and transforming growth factor (TGF)-beta1. CONCLUSION Our findings indicate that SWCNT do not cause lung inflammation and yet induce the formation of small, focal interstitial fibrotic lesions in the alveolar region of the lungs of rats. Of greatest interest was the discovery of unique intercellular carbon structures composed of SWCNT that bridged lung macrophages. These "carbon bridges" offer a novel and easily identifiable biomarker of exposure.

中文翻译：

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单壁碳纳米管（SWCNT）诱导的大鼠肺间质纤维化与PDGF mRNA水平升高和独特的细胞间碳结构的形成相关，这些结构在原位桥接肺泡巨噬细胞。

背景技术纳米技术是快速发展的产业，已经有许多新产品可供公众使用。因此，至关重要的是要了解与纳米材料暴露有关的潜在健康风险，并确定暴露的生物标志物。在这项研究中，我们研究了使用钴（Co）和钼（Mo）作为催化剂通过化学气相沉积法合成的SWCNT的纤维化潜力。在大鼠单口咽吸入SWCNT后，我们评估了暴露后1天和21天的肺组织病理学，细胞增殖和生长因子mRNA。对单独的媒介物（含有生物相容性非离子表面活性剂的盐水），惰性炭黑（CB）纳米粒子或作为纤维化的已知诱发剂的五氧化二钒（V2O5）进行了比较。结果根据组织病理学和支气管肺泡灌洗液（BAL）中细胞（> 95％巨噬细胞）的评估，SWCNT或CB在暴露后1或21天未引起明显的炎症反应。但是，SWCNT会在21天时在肺泡区域内诱导形成小的局灶性间质纤维化病变。在第21天，BAL从暴露于SWCNT的大鼠肺中收集的一小部分肺泡巨噬细胞被独特的胞间碳结构桥接，该结构延伸到每个巨噬细胞的细胞质中。在暴露于SWCNT的大鼠的肺中，也原位观察到巨噬细胞之间的这些“碳桥”结构。在暴露于CB的大鼠中未观察到碳桥。如通过溴脱氧尿苷摄取到肺泡细胞中所测量的，SWCNT仅在纤维化病变形成的部位引起细胞增殖。通过Taqman实时定量RT-PCR测定，SWCNT在1天时显着提高了血小板衍生生长因子（PDGF）-A，PDGF-B和PDGF-C mRNA的水平。在第21天，SWCNT没有增加任何评估的mRNA，而V2O5显着增加了编码PDGF-A，-B和-C链，PDGF-Rα，骨桥蛋白（OPN），结缔组织生长因子（CTGF）和转化的mRNA。生长因子（TGF）-beta1。结论我们的发现表明SWCNT不会引起肺部炎症，但会诱导大鼠肺泡区域形成小的局灶性间质纤维化病变。最令人感兴趣的是发现独特的细胞间碳结构，该结构由桥接肺巨噬细胞的SWCNT组成。这些“碳桥”提供了一种新颖且易于识别的暴露生物标记。