Formation Of Asbestos Bodies Research Articles

The role of single nucleotide polymorphisms related to iron homeostasis in mesothelioma susceptibility after asbestos exposure: a genetic study on autoptic samples.

Asbestos-related diseases still represent a major public health problem all over the world. Among them, malignant mesothelioma (MM) is a poor-prognosis cancer, arising from the serosal lining of the pleura, pericardium and peritoneum, triggered by asbestos exposure. Literature data suggest the key role of iron metabolism in the coating process leading to the formation of asbestos bodies, considered to be both protective and harmful. Two sample sets of individuals were taken into consideration, both residing in Broni or neighboring cities (Northwestern Italy) where an asbestos cement factory was active between 1932 and 1993. The present study aims to compare the frequency of six SNPs involved in iron trafficking, previously found to be related to protection/predisposition to MM after asbestos exposure, between 48 male subjects with documented asbestos exposure who died of MM and 48 male subjects who were exposed to asbestos but did not develop MM or other neoplastic respiratory diseases (Non-Mesothelioma Asbestos Exposed - NMAE). The same analysis was performed on 76 healthy male controls. The allelic and genotypic frequencies of a sub-group of 107 healthy Italian individuals contained in the 1000 genomes database were considered for comparison. PCR-multiplex amplification followed by SNaPshot mini-sequencing reaction was used. The findings presented in this study show that the allelic and genotypic frequencies for six SNP markers involved in iron metabolism/homeostasis and the modulation of tumor microenvironment are not significantly different between the two sample sets of MM and NMAE. Therefore, the SNPs here considered do not seem to be useful markers for individual susceptibility to mesothelioma. This finding is not in agreement with previous literature.

Asbestos and Iron.

Theories of disease pathogenesis following asbestos exposure have focused on the participation of iron. After exposure, an open network of negatively charged functional groups on the fiber surface complexes host metals with a preference for iron. Competition for iron between the host and the asbestos results in a functional metal deficiency. The homeostasis of iron in the host is modified by the cell response, including increased import to correct the loss of the metal to the fiber surface. The biological effects of asbestos develop in response to and are associated with the disruption of iron homeostasis. Cell iron deficiency in the host following fiber exposure activates kinases and transcription factors, which are associated with the release of mediators coordinating both inflammatory and fibrotic responses. Relative to serpentine chrysotile, the clearance of amphiboles is incomplete, resulting in translocation to the mesothelial surface of the pleura. Since the biological effect of asbestos is dependent on retention of the fiber, the sequestration of iron by the surface, and functional iron deficiency in the cell, the greater clearance (i.e., decreased persistence) of chrysotile results in its diminished impact. An inability to clear asbestos from the lower respiratory tract initiates a host process of iron biomineralization (i.e., asbestos body formation). Host cells attempt to mobilize the metal sequestered by the fiber surface by producing superoxide at the phagosome membrane. The subsequent ferrous cation is oxidized and undergoes hydrolysis, creating poorly crystalline iron oxyhydroxide (i.e., ferrihydrite) included in the coat of the asbestos body.

Nanoscale transformations of amphiboles within human alveolar epithelial cells

Amphibole asbestos is related to lung fibrosis and several types of lung tumors. The disease-triggering mechanisms still challenge our diagnostic capabilities and are still far from being fully understood. The literature focuses primarily on the role and formation of asbestos bodies in lung tissues, but there is a distinct lack of studies on amphibole particles that have been internalized by alveolar epithelial cells (AECs). These internalized particles may directly interact with the cell nucleus and the organelles, exerting a synergistic action with asbestos bodies (AB) from a different location. Here we document the near-atomic- to nano-scale transformations induced by, and taking place within, AECs of three distinct amphiboles (anthophyllite, grunerite, “amosite”) with different Fe-content and morphologic features. We show that: (i) an Fe-rich layer is formed on the internalized particles, (ii) particle grain boundaries are transformed abiotically by the internal chemical environment of AECs and/or by a biologically induced mineralization mechanism, (iii) the Fe-rich material produced on the particle surface does not contain large amounts of P, in stark contrast to extracellular ABs, and (iv) the iron in the Fe-rich layer is derived from the particle itself. Internalized particles and ABs follow two distinct formation mechanisms reaching different physicochemical end-states.

Assessment of asbestos body formation by high resolution FEG–SEM after exposure of Sprague–Dawley rats to chrysotile, crocidolite, or erionite

This work presents a comparative FEG–SEM study of the morphological and chemical characteristics of both asbestos bodies and fibres found in the tissues of Sprague–Dawley rats subjected to intraperitoneal or intrapleural injection of UICC chrysotile, UICC crocidolite and erionite from Jersey, Nevada (USA), with monitoring up to 3 years after exposure.Due to unequal dosing based on number of fibres per mass for chrysotile with respect to crocidolite and erionite, excessive fibre burden and fibre aggregation during injection that especially for chrysotile would likely not represent what humans would be exposed to, caution must be taken in extrapolating our results based on instillation in experimental animals to human inhalation. Notwithstanding, the results of this study may help to better understand the mechanism of formation of asbestos bodies.For chrysotile and crocidolite, asbestos bodies are systematically formed on long asbestos fibres. The number of coated fibres is only 3.3% in chrysotile inoculated tissues. In UICC crocidolite, Mg, Si, and Fe are associated with the fibres whereas Fe, P and Ca are associated with the coating. Even for crocidolite, most of the observed fibres are uncoated as coated fibres are about 5.7%. Asbestos bodies do not form on erionite fibres. The crystal habit, crystallinity and chemistry of all fibre species do not change with contact time, with the exception of chrysotile which shows signs of leaching of Mg.A model for the formation of asbestos bodies from mineral fibres is postulated. Because the three fibre species show limited signs of dissolution in the tissue, they cannot act as source of elements (primarily Fe, P and Ca) promoting nucleation and growth of asbestos bodies. Hence, the limited number of coated fibres should be due to the lack of nutrients or organic nature.

An assessment of asbestos body formation in extrapulmonary sites: liver and spleen.

Asbestos bodies (ABs) form as asbestos fibers become coated by a cellular iron- and protein-rich matrix. ABs have been reported in lymph nodes and a few extrapulmonary sites, but no data exist as to their formation outside of the lung. It is not clear whether the AB found in these extrapulmonary areas have been transported as mature structures from the lung or formed at the extrapulmonary site. This study was designed to determine if ABs are produced in extrapulmonary sites. The guinea pig efficiently forms ferruginous bodies in the lung and so it was chosen as a model to test the coating efficiency of amosite asbestos fibers in lung, liver and spleen. Sized amosite asbestos (5 mg) was administered either endotracheally into lung (n = 2) or directly into liver (n = 4) and spleen (n = 4) of healthy 10-week-old male guinea pigs. The lung, liver and splenic tissues were removed at 40 and 180 days post inoculation and were examined histologically for the presence of AB via light microscopy. Uncoated fibers isolated from the tissues were characterized by electron microscopy. The coating efficiency was calculated as a ratio of uncoated/coated fibers per organ. The coating efficiency ratios of fibers that were collected at 40 days post-injection from the individual sites were: lung - 350:1, liver - 4200:1, and spleen - 220,000:1. At 6 months post-injection the ratios for the individual sites consisted of: lung - 176:1, liver - 11,000:1, and spleen - 1000:1. This study indicates that AB can be formed in extrapulmonary sites and that the coating efficiency in the lung is much greater than that within the liver or spleen.

FERRITIN ADSORPTION ON AMOSITE FIBERS: POSSIBLE IMPLICATIONS IN THE FORMATION AND TOXICITY OF ASBESTOS BODIES

Abstract In order to investigate how endogenous iron can be deposited in vivo on inhaled mineral fibers during early stages of formation of asbestos bodies, in vitro experiments were per formed on the adsorption of ferritin onto amosite asbestos. The mineral dust was found to adsorb the protein from an aqueous solution containing 0.3 mg/ml horse spleen ferritin. In order to simulate physiological conditions the aqueous solution was adjusted with 150 mM saline. Polyacrylamide-SDS gel electrophoresis of the desorbed protein showed sub-units of approximately 13 and 15 kD, aside from the 20-kD subunit present in the native protein. This suggests that as a result of interactions between ferritin molecules and the solid surface of the mineral fibers, the protein iron core may be released or partially exposed. Data indicate these interactions may have implications in the observed mineral fiber toxicities.

FERRITIN ADSORPTION ON AMOSITE FIBERS: POSSIBLE IMPLICATIONS IN THE FORMATION AND TOXICITY OF ASBESTOS BODIES

In order to investigate how endogenous iron can be deposited in vivo on inhaled mineral fibers during early stages of formation of asbestos bodies, in vitro experiments were per formed on the adsorption of ferritin onto amosite asbestos. The mineral dust was found to adsorb the protein from an aqueous solution containing 0.3 mg/ml horse spleen ferritin. In order to simulate physiological conditions the aqueous solution was adjusted with 150 mM saline. Polyacrylamide-SDS gel electrophoresis of the desorbed protein showed sub-units of approximately 13 and 15 kD, aside from the 20-kD subunit present in the native protein. This suggests that as a result of interactions between ferritin molecules and the solid surface of the mineral fibers, the protein iron core may be released or partially exposed. Data indicate these interactions may have implications in the observed mineral fiber toxicities.

IN VIVO ACCUMULATION OF IRON ON CROCIDOLITE IS ASSOCIATED WITH DECREMENTS IN OXIDANT GENERATION BY THE FIBER

In vivo exposures to fibrous silicates are characterized by the formation of asbestos bodies. These structures consist of the original fiber with a coating of inexact composition, but it will include iron and protein. We tested the hypothesis that this iron, accumulated on asbestos bodies, participates in electron transport and oxidant generation. Thirty-day-old, male guinea pigs were intratracheally instilled with 1.0 mg crocidolite. Six months later, the animals were anesthetized, euthanized, and the fibers were isolated from the lungs. Energy-dispersive x-ray analysis and x-ray photoelectron spectroscopy confirmed an accumulation of metal onto the fiber after in vivo exposure. Stains for iron demonstrated a heterogeneous distribution of the metal on the silicate, while the uptake of a commercially available polyclonal antibody to ferritin localized to beaded enlargements along the coated 3+ fibers. Chelatable [Fe ] associated with the fiber increased after in vivo exposure. However, oxidant generation by asbestos bodies was decreased relative to uncoated fibers despite the elevation in the concentration of metal associated with the crocidolite. We conclude that iron is accumulated onto fibers in the lungs of guinea pigs. Some portion of this accumulation of iron is in the form of ferritin, and this metal is not chemically reactive in oxidant production. Asbestos bodies may represent a successful attempt by the host to sequester the metal adsorbed to the surface of a fiber and diminish the oxidative challenge introduced by a fibrous silicate. Subsequently, the generation of free radicals by the fibrous silicate is diminished.

Asbestos body formation in the human lung: distinctions, by type and size.

The fraction of fibers coated in a total of 3,800 asbestos fibers from 38 patients with disease related to asbestos (100 fibers per patient) was determined, according to asbestos fiber type and size parameters. Among the 3,800 fibers, 638 (16.8%) were coated and 3,162 were uncoated. All fibers were analyzed at 2,000 x magnification (lower limit of detection: 2 microns for length and 0.06 microns for diameter). The diameter of the totally coated fibers (28.4% of total bodies; 181/638) was not measured. The percentage of coated fibers varied with the asbestos type; it was 27.1% (335/1235) for amosite fibers, 16.0% (228/1423) for crocidolite, 6.6% (60/908) for tremolite or actinolite, 6.5% (14/214) for anthophyllite, and 5% (1/20) for chrysotile fibers. Most coated fibers were longer than 10 microns and had an aspect ratio (length/diameter) of more than 20. Approximately 60% of coated fibers had an aspect ratio of more than 100. The longer the fiber, the greater the percentage of coated fibers, regardless of diameter. The increase in the percentage associated with length was more marked in fibers with a smaller diameter; the percentage of coated fibers was, therefore, greater in fibers 30 microns or less in diameter. However, in fibers longer than 30 microns, the relationship to percentage of coated fibers was not as clear, and the diameter was less important. Accordingly, the fibers with high aspect ratios, particularly long fibers, tended to show asbestos body formation. The percentage of long fibers was highest in amosite, and the percentage of fibers with an aspect ratio of more than 100 was highest in amosite and crocidolite.(ABSTRACT TRUNCATED AT 250 WORDS)

Ultrastructural pulmonary changes in mice exposed to aerosolized Periodontal Pack Powder

An electron microscopic study was undertaken to investigate pulmonary ultrastructural changes in mice following exposure to an aerosolized Periodontal Pack Powder (PPP), and to determine if the asbestos fiber, which contains 7% PPP, is respirable. One hundred and sixty-five animals were used in this study. Seventy-two of the animals were exposed to the powder twice weekly for a minimum of two weeks and a maximum of four weeks. Fifty animals were exposed to the PPP (without asbestos), with the same exposure sequence used. Forty-three animals served as non-exposed controls. Randomly selected groups of exposed and control mice were killed at designated intervals between two and 12 weeks. Microscopic examination of the lungs revealed early interstitial pneumonia. These changes were seen in both treatment groups. Late changes included a generalized resolution of the pneumonia (seen in both treatment groups) with residual diffuse interstitial fibrosis, persistence of asbestos fibers within the tissue, and early asbestos body formation (seen only in animals exposed to asbestos-containing PPP). This study documents that the asbestos in Periodontal Pack Powder is both respirable and potentially pathogenic. Dentists who have used this product could conceivably be a population at risk for pulmonary fibrosis and/or obstructive airways disease.

Mouse peritoneal macrophages are capable of asbestos body formation in vitro

Mouse peritoneal macrophages are capable of asbestos body formation in vitro

Clearance of anthophyllite fibers from the rat lung and the formation of asbestos bodies

The length distributions of both uncoated and coated fibers in the rat lung were measured at various times up to 2 years following exposure to anthophyllite asbestos by inhalation. Fibers were measured by optical microscopy using a membrane filter technique which enables fibers with diameters down to about 0.2 μm to be detected. The frequency of uncoated fibers less than 5 μm in length decreased from 52% at 100 days after exposure to 19% after 2 years. These findings confirm and extend earlier investigations which showed that fibers in this length range are cleared more efficiently from the lung than longer fibers. The length distributions of uncoated and coated fibers were dissimilar. No coated fiber <10 μm in length was detected at any time and the greatest frequency invariably occurred in the 40- to 80-μm range. All fibers longer than 80 μm appeared to be coated. Although the appearance of coated fibers in the rat lung differs from those in human lung, there are similarities in the length distributions of uncoated and coated fibers.

Formation of Asbestos Bodies under the Influence of Parenteral Iron Overload

The effect of parenteral administration of iron (dextran) on the number of asbestos fibers in the lungs, formation of asbestos bodies and the development of interstitial fibrosis was studied in guinea pigs exposed intratracheally to anthophyllite dust. The treatment did not accelerate, either qualitatively or quantitatively, the formation of asbestos bodies or retard the development of interstitial fibrosis. The number of naked asbestos fibers was also similar in anthophyllite-inoculated animals to those similarly inoculated, but having had, additionally, a previous saturation with iron.

Biochemical Changes and Pulmonary Response of Guinea Pigs to Asbestos Dust

Abstract The biochemical and histopathological changes in lungs of guinea pigs were studied 120 days after intratracheal injection of three varieties of asbestos dusts, viz. chrysotile, amosite and anthophyllite. The salient histopathological features observed were the development of dust cell lesions in the lungs of animals exposed to the different varieties of asbestos. Maximum fibrosis and minimal asbestos body formation was observed in animals exposed to chrysotile and anthophyllite, respectively. With amosite and anthophyllite the development of diffuse interstitial fibrosis ensued, accompanied by well developed asbestos body formation in the amosite exposed animals. Biochemical studies revealed significant alterations in various phosphorylated compounds, an accumulation of orthophosphate and depletion of esters and nucleotides being very marked. RNA content increased significantly in the amosite treated group while the nucleic acid content remained unaltered in the chrysotile group.

Fibrogenic response in murine lungs to asbestos

Pulmonary fibrogenic response was investigated in mice following intratracheal inoculation of amosite, anthophylite and tremolite varieties of Indian asbestos and studies were made over a period of 150 days. At early periods all the varieties produced acute inflammatory reaction in the lungs. Thick reticulum fibers were encountered at later periods with amosite, while only thin reticulum fibers developed with anthophyllite or tremolite variety. The formation of asbestos bodies did not take place with any of the asbestos varieties even at 150 days. The deviation in the pulmonary fibrogenic response in mice has been attributed to species difference.

Small animals in the study of pathological effects of asbestos

The main pathological effects attributed to asbestos are carcinogenesis and fibrogenesis. Statistical studies have shown that asbestos workers may expect a higher morbidity not only from cancer of the lung and mesothelioma but also from cancer at other sites. Carcinomas have been reported in animals following the injection of asbestos, but the production of carcinomas by inhaled asbestos is less easy to demonstrate; most examples of experimental carcinogenesis with asbestos have been produced in rats. Rats and man react differently to asbestos in that rats do not produce asbestos bodies. The fibrosis that follows inhalation of asbestos has been frequently described, but studies with specific pathogen free animals have shown that, like the fibrosis that may follow the inhalation of silica dust, gross fibrosis involving the production of abnormal amount of collagen probably requires the intervention of infection as well as asbestos. Because of the difficulties encountered in the direct investigation of carcinogenesis and fibrogenesis resulting from the inhalation of asbestos, attention has been directed to the mechanisms by which the lung is able to protect itself against these fibrous dusts. While non-fibrous dusts and short fibers can be ingested by macrophages and removed via the bronchus, the long fibers that may also reach the alveolar regions may not be removed by this mechanism. The probability that a fiber may reach the alveoli depends largely on the fiber diameter and only to a small extent on the fiber length, so that, for example, fibers 100 mum long may reach the alveoli of a guinea pig. These long fibers may become coated with a ferroprotein derived from hemoglobin to form an asbestos body and, after morphological changes, the asbestos body may be broken up, the fragments ingested by macrophages and dissolved. The lung is thus cleared of asbestos. In the guinea pig lung, consolidated areas from which the asbestos has disappeared shows signs of return to normal. THIS CLEARANCE MECHANISM IS INHIBITED BY OTHER FACTORS: quartz dust may almost completely inhibit asbestos body formation; tobacco smoke has a considerable effect, and even very heavy loads of carbon may act similarly. The normal lung appears able to efficiently eliminate small loads of both nonfibrous and fibrous dust, including the carcinogenic asbestos fibers. The capacity is not unlimited, however, and when the load is heavy there is a much greater probability that fibers will not be detoxicated. In addition, other factors such as silica dust and tobacco smoke may remove the protective mechanism in the lungs.

Asbestos bodies, their formation, composition and character

Asbestos bodies extracted from human lungs have been examined under the electron microscope to determine their morphology and diffraction characteristics. The asbestos bodies were extracted from the lungs of persons exposed to the four types of commercial asbestos fiber, namely cocidolite, amosite, anthophyllite and chrysotile. Asbestos bodies were rarely formed on fibers less than 10 μm in length and practically always on straight fibers. They were found to occur on all the four commercial varieties of asbestos but less frequently on chrysotile fibers. The characteristics of the individual fibers were found to play a large part in determining the range and frequency of body shapes observed. There appears to be no evidence to suggest stepwise formation of asbestos bodies. Asbestos bodies were found to have a major crystalline component which is structurally similar to extracts of ferritin produced from animal and human organs. The material forming the asbestos body is definitely biological in origin and corresponded closely to the material defined in the medical literature as hemosiderin.

Chemical characterization of uncoated asbestos fibers from the lungs of asbestos workers by electron microprobe analysis.

Lung tissues have been obtained from workmen with defined asbestos fiber exposure. These tissues have been prepared by the carbon extraction technique and examined with the electron microprobe analyzer. The uncoated fibers present in these specimens have been chemically characterized and compared with standard reference asbestos samples. The bulk chemistry of the fibers observed in lung tissues is similar to that of the reference fibers so that identification may be made. However, a statistical analysis of the measured emission characteristics from anthophyllite and amosite indicates that some magnesium loss has taken place. This loss appears to correlate with the magnesium content of the fibers. A slight iron increase was also noted in the same fibers, probably related to an incipient asbestos body formation.

Formation of the Asbestos Body. A Comparative Study with Three Types of Asbestos

Abstract Asbestos bodies were produced experimentally in the lungs of hamsters by intratracheal instillation of three types of asbestos: soft chrysotile, harsh chrysotile, and amosite. Though some differences were noted, harsh chrysotile and amosite fibers were converted into asbestos bodies by the same successive steps that were previously described for soft chrysotile: (1) phagocytosis of asbestos by alveolar macrophages and other phagocytic cells and incorporation into phagolysosomes; (2) accumulation of iron micelles around the fibers, possibly by fusion of asbestos-containing phagosomes with hemosiderin granules; and (3) compaction of the micelles and clearing of the peripheral zone, to form a mature asbestos body. Formation of asbestos bodies seems to be a continuous process with old bodies growing in thickness and uncoated fibers being converted into bodies months or years after instillation of asbestos. Possible origins of hemosiderin granules are discussed. Striking hyperplasia of cell organelles was found, presumably indicative of their participation in the development of the asbestos bodies.

Further observations on the ultrastructure and chemistry of the formation of asbestos bodies

The examination of pleural granulomas during the first 14 days after the injection of chrysotile asbestos dust in experimental animals produced new evidence on the formation of asbestos bodies. In those species which produced bodies readily, the longer dust fibers were seldom phagocytosed by a single macrophage, but were surrounded by macrophages which eventually fused to form giant cells. It is while dust fibers were surrounded by partially fused macrophages that the earliest signs of body coating were seen. It is therefore suggested that only those fibers that are retained in a site of partial fusion for some time ever become coated. The coating process probably ceases when fusion is complete and the body is completely enclosed in a fully formed giant cell. The first coating material of the asbestos bodies seems to be some form of acid mucopolysaccharide, but this coating soon becomes impregnated with ferritin or hemosiderin to form the well-known Perls-positive bodies.