BACKGROUND: Lead is well known environmental pollutant, which can cause toxic effects in multiple organ systems. However, the influence of lead oxide nanoparticles, frequently emitted to the environment by high temperature technological processes, is still concealed. Therefore, we investigate lead oxide nanoparticle distribution through the body upon their entry into lungs and determine the microscopic and ultramicroscopic changes caused by the nanoparticles in primary and secondary target organs. METHODS: Adult female mice (ICR strain) were continuously exposed to lead oxide nanoparticles (PbO-NPs) with an average concentration approximately 106 particles/cm3 for 6 weeks (24 h/day, 7 days/week). At the end of the exposure period, lung, brain, liver, kidney, spleen, and blood were collected for chemical, histological, immunohistochemical and electron microscopic analyses. RESULTS: Lead content was found to be the highest in the kidney and lungs, followed by the liver and spleen; the smallest content of lead was found in brain. Nanoparticles were located in all analysed tissues and their highest number was found in the lung and liver. Kidney, spleen and brain contained lower number of nanoparticles, being about the same in all three organs. Lungs of animals exposed to lead oxide nanoparticles exhibited hyperaemia, small areas of atelectasis, alveolar emphysema, focal acute catarrhal bronchiolitis and also haemostasis with presence of siderophages in some animals. Nanoparticles were located in phagosomes or formed clusters within cytoplasmic vesicles. In the liver, lead oxide nanoparticle exposure caused hepatic remodeling with enlargement and hydropic degeneration of hepatocytes, centrilobular hypertrophy of hepatocytes with karyomegaly, areas of hepatic necrosis, occasional periportal inflammation, and extensive accumulation of lipid droplets. Nanoparticles were accumulated within mitochondria and peroxisomes forming aggregates enveloped by an electron-dense mitochondrial matrix. Only in some kidney samples, we observed areas of inflammatory infiltrates around renal corpuscles, tubules or vessels in the cortex. Lead oxide nanoparticles were dispersed in the cytoplasm, but not within cell organelles. There were no significant morphological changes in the spleen as a secondary target organ. Thus, pathological changes correlated with the amount of nanoparticles found in cells rather than with the concentration of lead in a given organ. CONCLUSIONS: Sub-chronic exposure to lead oxide nanoparticles has profound negative effects at both cellular and tissue levels. Notably, the fate and arrangement of lead oxide nanoparticles were dependent on the type of organs.

Bordeaux University UF STE Allée G Saint Hilaire 33615 Pessac Cedex France UMR 5254 IPREM CNRS UPPA Technopole Hélioparc 2 av P Angot 64053 Pau Cedex9 France EA 4592 Georessources and Environnement Bordeaux Montaigne University IPNB ENSEGID Allée F Daguin 33615 Pessac Cedex France

Department of Histology and Embryology Faculty of Medicine Masaryk University 625 00 Brno Czech Republic

Department of Pathological Morphology and Parasitology Faculty of Veterinary Medicine University of Veterinary and Pharmaceutical Sciences 612 42 Brno Czech Republic

Institute of Analytical Chemistry of the Czech Academy of Sciences 602 00 Brno Czech Republic

Institute of Animal Physiology and Genetics of the Czech Academy of Sciences 602 00 Brno Czech Republic

Institute of Animal Physiology and Genetics of the Czech Academy of Sciences 602 00 Brno Czech Republic Department of Animal Physiology and Immunology Institute of Experimental Biology Faculty of Science Masaryk University 625 00 Brno Czech Republic

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