[Importance of researches on chronic effects by manufactured nanomaterials].
ABSTRACT Manufactured nanomaterials are the most important substances for the nanotechnology. The nanomaterials possess different physico-chemical properties from bulk materials. The new properties may lead to biologically beneficial effects and/or adverse effects. However, there are no standardized evaluation methods at present. Some domestic research projects and international OECD programs are ongoing, in order to share the health impact information of nanomaterials or to standardize the evaluation methods. From 2005, our institutes have been conducting the research on the establishment of health risk assessment methodology of manufactured nanomaterials. In the course of the research project, we revealed that the nanomaterials were competent to cause chronic effects, by analyzing the intraperitoneal administration studies and carcinogenic promotion studies. These studies suggested that even aggregated nanomaterials were crumbled into nanosized particles inside the body during the long-term, and the particles were transferred to other organs. Also investigations of the toxicokinetic properties of nanomaterials after exposure are important to predict the chronically targeted tissues. The long lasting particles/fibers in the particular tissues may cause chronic adverse effects. Therefore, focusing on the toxicological characterization of chronic effects was considered to be most appropriate approach for establishing the risk assessment methods of nanomaterials.
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ABSTRACT: Single-walled carbon nanotubes (SWCNT) are new materials of emerging technological importance. As SWCNT are introduced into the life cycle of commercial products, their effects on human health and environment should be addressed. We demonstrated that pharyngeal aspiration of SWCNT elicited unusual pulmonary effects in C57BL/6 mice that combined a robust but acute inflammation with early onset yet progressive fibrosis and granulomas. A dose-dependent increase in the protein, LDH, and gamma-glutamyl transferase activities in bronchoalveolar lavage were found along with accumulation of 4-hydroxynonenal (oxidative biomarker) and depletion of glutathione in lungs. An early neutrophils accumulation (day 1), followed by lymphocyte (day 3) and macrophage (day 7) influx, was accompanied by early elevation of proinflammatory cytokines (TNF-alpha, IL-1beta; day 1) followed by fibrogenic transforming growth factor (TGF)-beta1 (peaked on day 7). A rapid progressive fibrosis found in mice exhibited two distinct morphologies: 1) SWCNT-induced granulomas mainly associated with hypertrophied epithelial cells surrounding SWCNT aggregates and 2) diffuse interstitial fibrosis and alveolar wall thickening likely associated with dispersed SWCNT. In vitro exposure of murine RAW 264.7 macrophages to SWCNT triggered TGF-beta1 production similarly to zymosan but generated less TNF-alpha and IL-1beta. SWCNT did not cause superoxide or NO.production, active SWCNT engulfment, or apoptosis in RAW 264.7 macrophages. Functional respiratory deficiencies and decreased bacterial clearance (Listeria monocytogenes) were found in mice treated with SWCNT. Equal doses of ultrafine carbon black particles or fine crystalline silica (SiO2) did not induce granulomas or alveolar wall thickening and caused a significantly weaker pulmonary inflammation and damage.AJP Lung Cellular and Molecular Physiology 12/2005; 289(5):L698-708. DOI:10.1152/ajplung.00084.2005 · 4.04 Impact Factor
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ABSTRACT: Inhaled ultrafine particles trigger peripheral thrombotic complications. We have analyzed the systemic prothrombotic risk following lung inflammation induced by pulmonary carbon nanotubes (CNTs). Intratracheal instillation in Swiss mice of 200 and 400 microg of multiwall ground CNTs triggered substantial lung neutrophil, but not macrophage influx, 24 h later. The detection of circulating platelet-leukocyte conjugates exclusively 6 h after CNT instillation pointed to early but transient activation of circulating platelets. At 24 h, elevated plasma procoagulant microvesicular tissue factor activity was found in CNT-exposed but not in saline-exposed mice. However, at 24 h, both the tail and jugular vein bleeding times were prolonged in CNT-exposed but not in saline-exposed mice, arguing against strong CNT-induced platelet activation at this point. Nevertheless, at 24 h, enhanced peripheral thrombogenicity was detected in CNT-exposed but not in saline-exposed mice, via quantitative photochemically induced carotid artery thrombosis measurements. P-selectin neutralization abrogated platelet-leukocyte conjugate formation and microvesicular tissue factor generation, and abolished the CNT-induced thrombogenicity amplification. In contrast, the weak vascular injury-triggered thrombus formation in saline-treated mice was not affected by P-selectin neutralization at 24 h. The mild CNT-induced lung inflammation translates via rapid but mild and transient activation of platelets into P-selectin-mediated systemic inflammation. Leukocyte activation leads to tissue factor release, in turn eliciting inflammation-induced procoagulant activity and an associated prothrombotic risk.Journal of Thrombosis and Haemostasis 06/2007; 5(6):1217-26. DOI:10.1111/j.1538-7836.2007.02557.x · 5.55 Impact Factor
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ABSTRACT: Engineered nanosized materials, such as single-wall carbon nanotubes (SWCNT), are emerging as technologically important in different industries. The unique physical characteristics and the pulmonary toxicity of SWCNTs raised concerns that respiratory exposure to these materials may be associated with cardiovascular adverse effects. In these studies we evaluated aortic mitochondrial alterations by oxidative stress assays, including quantitative polymerase chain reaction of mitochondrial (mt) DNA and plaque formation by morphometric analysis in mice exposed to SWCNTs. A single intrapharyngeal instillation of SWCNTs induced activation of heme oxygenase-1 (HO-1), a marker of oxidative insults, in lung, aorta, and heart tissue in HO-1 reporter transgenic mice. Furthermore, we found that C57BL/6 mice, exposed to SWCNT (10 and 40 mug/mouse), developed aortic mtDNA damage at 7, 28, and 60 days after exposure. mtDNA damage was accompanied by changes in aortic mitochondrial glutathione and protein carbonyl levels. Because these modifications have been related to cardiovascular diseases, we evaluated whether repeated exposure to SWCNTs (20 mug/mouse once every other week for 8 weeks) stimulates the progression of atherosclerosis in ApoE(-/-) transgenic mice. Although SWCNT exposure did not modify the lipid profiles of these mice, it resulted in accelerated plaque formation in ApoE(-/-) mice fed an atherogenic diet. Plaque areas in the aortas, measured by the en face method, and in the brachiocephalic arteries, measured histopathologically, were significantly increased in the SWCNT-treated mice. This response was accompanied by increased mtDNA damage but not inflammation. Taken together, the findings are of sufficient significance to warrant further studies to evaluate the systemic effects of SWCNT under workplace or environmental exposure paradigms.Environmental Health Perspectives 04/2007; 115(3):377-82. DOI:10.1289/ehp.9688 · 7.03 Impact Factor