asbestos--crocidolite and Granuloma

The most common causes of granulomatous inflammation are persistent pathogens and poorly-degradable irritating materials. A characteristic pathological reaction to intratracheal instillation, pharyngeal aspiration, or inhalation of carbon nanotubes is formation of epithelioid granulomas accompanied by interstitial fibrosis in the lungs. In the mesothelium, a similar response is induced by high aspect ratio nanomaterials, including asbestos fibers, following intraperitoneal injection. This asbestos-like behaviour of some engineered nanomaterials is a concern for their potential adverse health effects in the lungs and mesothelium. We hypothesize that high aspect ratio nanomaterials will induce epithelioid granulomas in nonadherent macrophages in 3D cultures.. Carbon black particles (Printex 90) and crocidolite asbestos fibers were used as well-characterized reference materials and compared with three commercial samples of multiwalled carbon nanotubes (MWCNTs). Doses were identified in 2D and 3D cultures in order to minimize acute toxicity and to reflect realistic occupational exposures in humans and in previous inhalation studies in rodents. Under serum-free conditions, exposure of nonadherent primary murine bone marrow-derived macrophages to 0.5 μg/ml (0.38 μg/cm2) of crocidolite asbestos fibers or MWCNTs, but not carbon black, induced macrophage differentiation into epithelioid cells and formation of stable aggregates with the characteristic morphology of granulomas. Formation of multinucleated giant cells was also induced by asbestos fibers or MWCNTs in this 3D in vitro model. After 7-14 days, macrophages exposed to high aspect ratio nanomaterials co-expressed proinflammatory (M1) as well as profibrotic (M2) phenotypic markers.. Induction of epithelioid granulomas appears to correlate with high aspect ratio and complex 3D structure of carbon nanotubes, not with their iron content or surface area. This model offers a time- and cost-effective platform to evaluate the potential of engineered high aspect ratio nanomaterials, including carbon nanotubes, nanofibers, nanorods and metallic nanowires, to induce granulomas following inhalation.

Topics: Animals; Arginase; Asbestos, Crocidolite; Cell Culture Techniques; Cells, Cultured; Culture Media, Serum-Free; Dose-Response Relationship, Drug; Epithelioid Cells; Granuloma; Humans; Imaging, Three-Dimensional; Lectins, C-Type; Macrophages; Male; Mannose Receptor; Mannose-Binding Lectins; Materials Testing; Mice; Mice, Inbred C57BL; Models, Biological; Nanostructures; Nanotubes, Carbon; Nitric Oxide Synthase Type II; Phagocytosis; Receptors, Cell Surface; Soot; Tumor Necrosis Factor-alpha

The present study assessed a carcinogenic hazard of multi-wall carbon nanotube (MWCNT) in intact (not genetically modified) rodents. MWCNT (1 mg/kg body weight, 7 animals), crocidolite (2 mg/kg body weight, 10 animals) or vehicle (2% carboxymethyl cellulose, 5 animals) was administered to male Fischer 344 rats (12 weeks old) by a single intrascrotal injection. Rats were autopsied immediately after death, when becoming moribund or at the end of the maximal observation period scheduled to be 52 weeks. After 37-40 weeks, however, 6 MWCNT-treated animals died or became moribund due to intraperitoneally disseminated mesothelioma (6/7, 85.7%) with bloody ascites. Peritoneal mesothelium was generally hypertrophic, and numerous nodular or papillary lesions of mesothelioma and mesothelial hyperplasia were developed. While mesothelioid cells were predominant in relatively early stage tumors, advanced stage mesotheliomas were constituted by 2 portions occupied by mesothelioid cells on the surface and spindle-shaped sarcomatous cells in the depth. In the latter, the histological transition was apparently observed between these 2 portions. Mesotheliomas were invasive to adjacent organs and tissues, and frequently metastasized into the pleura. Only 1 rat survived for 52 weeks in the MWCNT-treated group, and similar findings except mesothelioma were observed. All 10 crocidolite-treated and 5 vehicle-treated rats survived for 52 weeks without any particular changes except deposition of asbestos in the former case. It is thus indicated that MWCNT possesses carcinogenicity causing mesothelioma at a high rate in intact male rats under the present experimental conditions. The present data identifies a carcinogenic hazard of MWCNT and will serve as one of the indispensable evidences to be used for the risk assessment crucial for not only protection and improvement of human health and welfare, but also safe and acceptable development and prevalence of this and similar upcoming materials.

Topics: Anemia; Animals; Asbestos, Crocidolite; Ascites; Autopsy; Carboxymethylcellulose Sodium; Carcinogens; Dose-Response Relationship, Drug; Epithelium; Granuloma; Injections; Liver; Male; Mesothelioma; Nanotubes, Carbon; Particle Size; Peritoneum; Pharmaceutical Vehicles; Rats; Rats, Inbred F344; Scrotum; Suspensions; Time Factors; Tissue Adhesions

This report describes the cell biology of the development of asbestos bodies after a single intraperitoneal injection of a suspension of crocidolite asbestos fibers into the mouse peritoneal cavity. The majority of the infected fibers were found in aggregates of peritoneal macrophages, exudate cells, and fibrous tissue. These aggregates developed into granulomas containing not only numerous asbestos fibers, but also cells of various types, including macrophages, multinucleated giant cells, fibroblasts, plasma cells, granulocytes, and mast cells. Cytoplasmic ferritin was abundantly present in macrophages and giant cells. In addition, iron-rich inclusion bodies were detected. The results of this study show that asbestos body formation can occur outside the pleural cavity. Asbestos body formation occurred in the granulomas after periods of 1 month and longer. On the basis of morphologic criteria, various types of asbestos body were distinguished. X-ray microanalysis showed that variations in the density of the coat could attributed to the presence of chemical elements in various concentrations. Evidence is presented that asbestos body formation is an extracellular phenomenon.

Topics: Animals; Asbestos; Asbestos, Crocidolite; Cell Aggregation; Electron Probe Microanalysis; Granuloma; Inclusion Bodies; Injections, Intraperitoneal; Iron; Male; Mice; Mice, Inbred Strains; Microscopy, Electron; Peritoneal Cavity; Peritoneal Diseases

Fibrogenous effects of wollastonite, chrysotile and crocidolite have been investigated in experiments on animals. (Wollastonite is a calcium silicate of fibrous structure, occasionally applied as asbestos substitute). The experimental animals were intratracheally administered single doses of 50 mg of the test material suspended in 0.6 ml of physiological NaCl solution. The animals were decapitated 3, 6 and 9 months after the experiment. Fibrogenic properties were evaluated basing on the weight of wet lungs, content of lipids and hydroxyproline in lungs, as well as histopathological tests of lungs, mediastinal lymph nodes and spleen. Histopathological preparations were evaluated using an optical, microscope or transmission electron microscope. The findings of biochemical, pathomorphological, and ultrastructural studies demonstrated slight fibrogenic effects of wollastonite, as compared to chrysotile and crocidolite.

Topics: Animals; Asbestos; Asbestos, Crocidolite; Asbestos, Serpentine; Calcium Compounds; Granuloma; Lung; Lung Diseases; Lymph Nodes; Male; Rats; Rats, Inbred Strains; Silicates; Silicic Acid; Silicon Dioxide

Standard (UICC) crocidolite was subjected to ball milling to reduce the length of the fibre. These milled materials and the original standard sample were injected into the pleural cavity of rats to determine their ability to induce mesothelioma. Previous in vitro work on the same materials had suggested that biological activity was related to fibres greater than 6.5 microns in length and that the material milled for 4 and 8 h did not contain fibres in this range and was biologically inactive. The results of the animal work, however, did not follow this pattern; mesotheliomas occurred in rats in all treatment groups including the 4 and 8 h milled samples. Examination of the tissues and the dust recovered from them showed the presence of fibres greater than the suggested threshold. Attention is drawn to the problems associated with drawing conclusions from size distributions and in vitro studies without considering in vivo mechanisms.

Topics: Animals; Asbestos; Asbestos, Crocidolite; Female; Granuloma; Male; Mesothelioma; Microscopy, Electron; Particle Size; Pleural Diseases; Pleural Neoplasms; Rats; Rats, Inbred F344; Time Factors