Effects of asbestos and beryllium on release of alveolar macrophage enzymes

Enzymatic Changes in Alveolar Macrophages of Rats Exposed to Lead and Nickel by Inhalation

In previous inhalation studies, rats exposed to aerosol concentrations of lead oxide (Pb2O3), 150 μg/m3; lead chloride (PbCl2), 100 μg/m3; nickel oxide (NiO), 120 μg/m3; and nickel chloride (NiCl2), 109 μg/m3; significant changes were observed in the lungs and alveolar macrophages. In this study the hydroiytic enzymes, acetylesterase, acid and alkaline phos-phatases, lysozyme, and beta-glucuronidase, in alveolar macrophages and lung washout fluid from rats subjected to the inhalation of the lead and nickel aerosols were examined. Washed alveolar macrophages from animals exposed to lead and nickel aerosols were found to contain reduced quantities of the various hydrolytic enzymes (except for acetylesterase) when compared with those from control rats. On the other hand, a significant increase in enzymatic activity was noted in lung washout fluid from exposed animals. The functional efficiency of macrophages, relative enzyme changes, and the mechanism of action of metals are discussed. It is important to note that the changes observed in these studies were from animals exposed to metallic concentrations near their Threshold Limit Values.

Bérylliose pulmonaire chronique (2e partie)

INTRODUCTION

Chronic beryllium disease (CBD) is an occupational lung disease caused by the inhalation of beryllium dust, fumes or metallic salts.

CURRENT DATA

Beryllium affects the lungs via particles deposited in the pulmonary alveoli. These are ingested by alveolar macrophages which act as antigen presenting cells to CD4+ T lymphocytes. T lymphocytes proliferate in response to beryllium antigens and combined with macrophages produce numerous epithelioid granulomas with the release of inflammatory cytokines (IFNgamma, IL-2, TNFalpha and IL6) and growth factors. Beryllium induces macrophage apoptosis which reduces its clearance from the lung which in turn contributes to the host's continual re-exposure and thus a chronic granulomatous disorder. Pulmonary granulomatous inflammation is the primary manifestation of CBD, but the disease occasionally involves other organs such as the liver, spleen, lymph nodes and bone marrow. The clinical, radiological, and histopathological features of CBD can be difficult to distinguish from sarcoidosis. The Beryllium lymphocyte proliferation test (BeLPT) demonstrates a beryllium specific immune response, confirms the diagnosis of CBD, and excludes sarcoidosis.

CONCLUSIONS AND PERSPECTIVES

CBD provides a human model of pulmonary granulomatous disease produced by an occupational exposure, occurring more frequently in those with a genetic pre-disposition. It can be differentiated from sarcoidosis by specific immunological testing.

Scintigraphy with J001X, a Klebsiella membrane glycolipid, for the early diagnosis of chronic berylliosis: results from an experimental model

A glycolipid (J001X) isolated from the membrane proteoglycans of a non-pathogenic strain of Klebsiella pneumoniae was developed to bind selectively to macrophages. A scintigraphic technique could thus be developed and applied to an experimental model of lung berylliosis. Six baboons were injected intratracheally with a beryllium metal suspension. Three to 24 months later, they were submitted to both an anatomical and a functional respiratory evaluation. Two baboons were explored at the early stage of alveolitis and four baboons at a more advanced stage characterised by a granulomatous disorder. Scintigraphy was performed using J001X labelled with 99mtechnetium administered as an aerosol. In the six baboons, conventional imaging techniques (chest x ray film, computed tomography scan, gallium scintigraphy), failed to show either any lung abnormality or mediastinal lymph nodes consistent with beryllium disease. In the two recently contaminated baboons, J001X scintigraphy showed a well defined parenchymal fixation facing the contaminated lobe. In the four baboons who were at a more advanced stage of berylliosis, J001X fixation was always focused paratracheally without any significant involvement of the lung parenchyma. The subcarinal and laterotracheal lymph nodes seen at necropsy corresponded to J001X scintigraphic fixations. In conclusion, when compared with conventional techniques such as chest x ray film, computed tomography scan, magnetic resonance imaging, and gallium scintigraphy, J001X scintigraphy has proved its ability to detect occult lesions in experimental berylliosis in baboons. By comparison with gallium scintigraphy, scintigraphy with J001X appears to have superior sensitivity and can be performed in four hours.

Asbestos fibres inhibit the in vitro activity of lymphokine-activated killer (LAK) cells from healthy individuals and patients with malignant mesothelioma

Asbestos exposure is associated with an increased incidence of several malignancies, including malignant mesothelioma (MM). This study evaluates the relationship between asbestos exposure and the in vitro generation and function of LAK cells, an immune effector cell population with powerful lytic activity against MM cells. Both serpentine (chrysotile) and amphibole (amosite and crocidolite) forms of asbestos fibres suppress LAK cell generation, viability (by 5-11%, P less than 0.02) and cell recovery (by 13-15%, P less than 0.02). However, the LAK cells generated in the presence of the amphiboles were as effective as unexposed cells in lysing both standard tumour cell targets (K562, 56.4% lysis versus 61.5%, respectively, P greater than 0.5; NS; Daudi, 60.5% lysis versus 64.5% P greater than 0.5; NS), and MM tumour cell targets (mean of three MM cell lines 48.3% versus 46.3%, P greater than 0.5; NS), whereas the function of LAK cells generated in the presence of chrysotile was significantly reduced against three out of the five tumour cell targets tested (P less than 0.03). In the presence of asbestos fibres, LAK cell function was reduced against all five tumour cell targets (P less than 0.01), irrespective of whether the cell donors were healthy individuals or patients with MM. NK cell activity was also suppressed (P less than 0.01). The serpentine form of asbestos, chrysotile, was significantly more suppressive of both effector cell functions than either of the amphiboles (P less than 0.01). These findings suggest that asbestos exposure may suppress the function and in some instances the generation of immune effector cell mechanisms, thereby increasing the risk of disease and malignancy.

The effect of beryllium compound solubility on in vitro canine alveolar macrophage cytotoxicity

Pulmonary alveolar macrophage cells (PAM), obtained by bronchopulmonary lavage of Beagle dogs, were exposed in vitro to beryllium oxide (BeO) particles calcined at either 500 or 1000 degrees C or to beryllium sulfate (BeSO4). Cell viability was determined by trypan blue dye exclusion after 20 h in culture. The most toxic material tested was BeSO4, followed by BeO calcined at 500 degrees C, then BeO calcined at 1000 degrees C. An in vitro dissolution technique was used to measure the relative solubility of the BeO particles. The BeO prepared at 500 degrees C exhibited greater solubility compared with BeO prepared at 1000 degrees C. This study extends previous work by examining the effects of beryllium compounds on canine PAM, and by relating PAM cytotoxicity with measured values of beryllium compound solubility.

The in vitro cytotoxicity of asbestos fibers: I. P388D1 cells

In this study, the cytotoxicity of 13 fibrous samples of known fiber number and dimensions has been established in P388D1 cells. The cells were exposed in vitro to dust concentrations of 10 or 50 micrograms/ml and, after incubation for 24 or 48 hours, any changes in cellular viability, lactate dehydrogenase, and glucosaminidase levels were determined. In general, there was a close association between the reduction in cellular viability and the loss of intracellular enzymes induced by each dust, the chrysotile asbestos samples proving more cytotoxic than the amphiboles. The cytotoxicity of the fibrous dusts was shown to be related to the number of fibers greater than 8 micron in length in the samples.

The effects of chrysotile and crocidolite asbestos on the lower respiratory tract: analysis of bronchoalveolar lavage constituents

This study was designed to evaluate the effects of amphibole and serpentine asbestos inhalation on the constituents of the lower respiratory tract. Bronchoalveolar lavage (BAL) analyses were performed on three groups of rats: one group was exposed to chrysotile (serpentine) asbestos, another group was exposed to crocidolite amphibole asbestos, while a third group was sham-exposed. Intermittent inhalational exposures lasted three months. The total BAL cell yields and the macrophage content of BAL cells were significantly lower after asbestos exposure, especially in the chrysotile-exposed group. These effects persisted for as long as 1 year after the cessation of exposure. Multinucleated macrophages were seen in BAL cells from both asbestos-exposed groups. Striking ultrastructural alterations of macrophage morphology were noted in BAL cells from both groups of asbestos-exposed rats. Chrysotile fibers were not seen in any BAL cells from chrysotile-exposed animals. However, 15 months after terminating the exposure regimen, a sizeable proportion of BAL macrophages from crocidolite-exposed rats contained phagocytosed asbestos fibers. Significantly higher beta-glucuronidase and lactate dehydrogenase activity was found in BAL fluids from both asbestos-exposed groups and was detected 17-18 months after exposure had ceased. These observations have served as useful correlates of asbestos-mediated injury to the lower respiratory tract. They have also provided evidence of continual pathological sequelae occurring long after withdrawal from asbestos exposure.

Asbestos-induced alterations of human lymphoid cell mitogenic responses

Using mitogenic assays, we have investigated the short term effects of two asbestos (amosite and chrysotile) fibers on lymphocyte functions in vitro. These oppositely charged fibers produced different alterations in mitogenesis. The blastogenic responses of concanavalin-A (Con-A) and pokeweed mitogen stimulated human peripheral blood mononuclear cells (PBMN) were significantly increased by the inclusion of 6 micrograms of chrysotile to the culture media. Amosite fibers proved to be inhibitory in all tests. When PBMN were depleted of monocytes, asbestos-related alterations of Con-A responsiveness were unchanged among the remaining cells. However, the addition of chrysotile to phytohemagglutinin (PHA) cultures resulted in a significant increase of the mitogenic response. When PBMN were enriched for T lymphocytes, and again cultured with the mitogens and fibers, the Con-A response still displayed impressive enhancement with chrysotile. In contrast to an intact PBMN population, PHA-induced blastogenesis among these T-enriched lymphocytes was significantly elevated. These experiments demonstrate that asbestos can induce significant changes in the functional integrity of PBMN following a relatively short exposure time in culture.