Bioavailability of beryllium oxide particles: an in vitro study in the murine J774A.1 macrophage cell line model

Innate and Adaptive Immunity in Noninfectious Granulomatous Lung Disease

Sarcoidosis and chronic beryllium disease are noninfectious lung diseases that are characterized by the presence of noncaseating granulomatous inflammation. Chronic beryllium disease is caused by occupational exposure to beryllium containing particles, whereas the etiology of sarcoidosis is not known. Genetic susceptibility for both diseases is associated with particular MHC class II alleles, and CD4+ T cells are implicated in their pathogenesis. The innate immune system plays a critical role in the initiation of pathogenic CD4+ T cell responses as well as the transition to active lung disease and disease progression. In this review, we highlight recent insights into Ag recognition in chronic beryllium disease and sarcoidosis. In addition, we discuss the current understanding of the dynamic interactions between the innate and adaptive immune systems and their impact on disease pathogenesis.

A role for TNF-α in alveolar macrophage damage-associated molecular pattern release

Chronic beryllium disease (CBD) is a metal hypersensitivity/autoimmune disease in which damage-associated molecular patterns (DAMPs) promote a break in T cell tolerance and expansion of Be2+/self-peptide-reactive CD4+ T cells. In this study, we investigated the mechanism of cell death induced by beryllium particles in alveolar macrophages (AMs) and its impact on DAMP release. We found that phagocytosis of Be led to AM cell death independent of caspase, receptor-interacting protein kinases 1 and 3, or ROS activity. Before cell death, Be-exposed AMs secreted TNF-α that boosted intracellular stores of IL-1α followed by caspase-8-dependent fragmentation of DNA. IL-1α and nucleosomal DNA were subsequently released from AMs upon loss of plasma membrane integrity. In contrast, necrotic AMs released only unfragmented DNA and necroptotic AMs released only IL-1α. In mice exposed to Be, TNF-α promoted release of DAMPs and was required for the mobilization of immunogenic DCs, the expansion of Be-reactive CD4+ T cells, and pulmonary inflammation in a mouse model of CBD. Thus, early autocrine effects of particle-induced TNF-α on AMs led to a break in peripheral tolerance. This potentially novel mechanism may underlie the known relationship between fine particle inhalation, TNF-α, and loss of peripheral tolerance in T cell-mediated autoimmune disease and hypersensitivities.

Reduction of Nanoparticle Load in Cells by Mitosis but Not Exocytosis

The long-term fate of biomedically relevant nanoparticles (NPs) at the single cell level after uptake is not fully understood yet. We report that lysosomal exocytosis of NPs is not a mechanism to reduce the particle load. Biopersistent NPs such as nonporous silica and gold remain in cells for a prolonged time. The only reduction of the intracellular NP number is observed via cell division, e.g., mitosis. Additionally, NP distribution after cell division is observed to be asymmetrical, likely due to the inhomogeneous location and distribution of the NP-loaded intracellular vesicles in the mother cells. These findings are important for biomedical and hazard studies as the NP load per cell can vary significantly. Furthermore, we highlight the possibility of biopersistent NP accumulation over time within the mononuclear phagocyte system.

Dissolution and biodurability: Important parameters needed for risk assessment of nanomaterials

Biopersistence and biodurability have the potential to influence the long-term toxicity and hence pathogenicity of particles that deposit in the body. Therefore, biopersistence and biodurability are considered to be important parameters needed for the risk assessment of particles and fibres. Dissolution, as a measure of biodurability, is dependent on the chemical and physical properties (size, surface area, etc.) of particles and fibres and also of the suspension medium including its ionic strength, pH, and temperature. In vitro dissolution tests can provide useful insights as to how particles and fibres may react in biological environments; particles and fibres that release ions at a higher rate when suspended in vitro in a specific simulated biological fluid will be expected to do so when they exist in a similar biological environment in vivo. Dissolution of particles and fibres can follow different reaction kinetics. For example, the majority of micro-sized particles and fibres follow zero-order reaction kinetics. In this case, although it is possible to calculate the half-time of a particle or fibre, such calculation will be dependent on the initial concentration of the investigated particle or fibre. Such dependence was eliminated in the shrinking sphere and fibre models where it was possible to estimate the lifetimes of particles and fibres as a measure of their biodurability. The latter models can be adapted for the dissolution studies of nanomaterials. However, the models may apply only to nanomaterials where their dissolution follows zero-order kinetics. The dissolution of most nanomaterials follows first-order kinetics where dependence on their initial concentration of the investigated nanomaterials is not required and therefore it is possible to estimate their half-times as a measure of their biodurability. In dissolution kinetics for micro-sized and nano-sized particles and fibres, knowledge of dissolution rate constants is necessary to understand biodurability. Unfortunately, many studies on dissolution of nanoparticles and nanofibres do not determine the dissolution rates and dissolution rate constants. The recommendation is that these parameters should be considered as part of the important descriptors of particle and fibre physicochemical properties, which in turn, will enable the determination of their biodurability.

An official American Thoracic Society statement: diagnosis and management of beryllium sensitivity and chronic beryllium disease

RATIONALE

Beryllium continues to have a wide range of industrial applications. Exposure to beryllium can lead to sensitization (BeS) and chronic beryllium disease (CBD).

OBJECTIVES

The purpose of this statement is to increase awareness and knowledge about beryllium exposure, BeS, and CBD.

METHODS

Evidence was identified by a search of MEDLINE. The committee then summarized the evidence, drew conclusions, and described their approach to diagnosis and management.

MAIN RESULTS

The beryllium lymphocyte proliferation test is the cornerstone of both medical surveillance and the diagnosis of BeS and CBD. A confirmed abnormal beryllium lymphocyte proliferation test without evidence of lung disease is diagnostic of BeS. BeS with evidence of a granulomatous inflammatory response in the lung is diagnostic of CBD. The determinants of progression from BeS to CBD are uncertain, but higher exposures and the presence of a genetic variant in the HLA-DP β chain appear to increase the risk. Periodic evaluation of affected individuals can detect disease progression (from BeS to CBD, or from mild CBD to more severe CBD). Corticosteroid therapy is typically administered when a patient with CBD exhibits evidence of significant lung function abnormality or decline.

CONCLUSIONS

Medical surveillance in workplaces that use beryllium-containing materials can identify individuals with BeS and at-risk groups of workers, which can help prioritize efforts to reduce inhalational and dermal exposures.

Biological exposure metrics of beryllium-exposed dental technicians

Beryllium is commonly used in the dental industry. This study investigates the association between particle size and shape in induced sputum (IS) with beryllium exposure and oxidative stress in 83 dental technicians. Particle size and shape were defined by laser and video, whereas beryllium exposure data came from self-reports and beryllium lymphocyte proliferation test (BeLPT) results. Heme oxygenase-1 (HO1) gene expression in IS was evaluated by quantitative polymerase chain reaction. A high content of particles (92%) in IS >5 μ in size is correlated to a positive BeLPT risk (odds ratio [OR] = 3.4, 95% confidence interval [CI]: 0.9-13). Use of masks, hoods, and type of exposure yielded differences in the transparency of IS particles (gray level) and modulate HO1 levels. These results indicate that parameters of size and shape of particles in IS are sensitive to workplace hygiene, affect the level of oxidative stress, and may be potential markers for monitoring hazardous dust exposures.

Immunotoxicity of 3 chemical forms of beryllium following inhalation exposure

The toxicity of 3 chemical forms of beryllium (Be) was compared in this study. A total of 160 mice equally divided into 4 groups were exposed by inhalation (nose only) for 3 consecutive weeks, 5 d/week, 6 h/d. One group was used as control, while the 3 others were exposed to fine particles of Be metal, Be oxide (BeO), or Be aluminum (BeAl). Except for the controls, the target level of exposure was 250 μg/m(3). In all, 35 mice/group were sacrificed 1 week postexposure and another 5 mice 3 weeks postexposure. The BeO group showed the highest lung Be concentration with higher interleukin 12 (IL-12) and interferon-γ (IFN-γ) levels, while the Be group produced the most severe lung inflammation and higher tumor necrosis factor-α (TNF-α) and CD4+ T cells levels. Data suggested that Be and BeO apparently produced more pulmonary toxicity than BeAl. However, this conclusion is not definitive, because of different confounding factors such as particle sizes, specific surface area, and solubility.

Release of beryllium into artificial airway epithelial lining fluid

Inhaled beryllium particles that deposit in the lung airway lining fluid may dissolve and interact with immune-competent cells resulting in sensitization. As such, solubilization of 17 beryllium-containing materials (ore, hydroxide, metal, oxide, alloys, and process intermediates) was investigated using artificial human airway epithelial lining fluid. The maximum beryllium release in 7 days was 11.78% (from a beryl ore melter dust), although release from most materials was < 1%. Calculated dissolution half-times ranged from 30 days (reduction furnace material) to 74,000 days (hydroxide). Despite rapid mechanical clearance, billions of beryllium ions may be released in the respiratory tract via dissolution in airway lining fluid. Beryllium-containing particles that deposit in the respiratory tract dissolve in artificial lung epithelial lining fluid, thereby providing ions for absorption in the lung and interaction with immune-competent cells in the respiratory tract.

Dissolution of beryllium in artificial lung alveolar macrophage phagolysosomal fluid

Dissolution of a lung burden of poorly soluble beryllium particles is hypothesized to be necessary for development of chronic beryllium lung disease (CBD) in humans. As such, particle dissolution rate must be sufficient to activate the lung immune response and dissolution lifetime sufficient to maintain chronic inflammation for months to years to support development of disease. The purpose of this research was to investigate the hypothesis that poorly soluble beryllium compounds release ions via dissolution in lung fluid. Dissolution kinetics of 17 poorly soluble particulate beryllium materials that span extraction through ceramics machining (ores, hydroxide, metal, copper-beryllium [CuBe] fume, oxides) and three CuBe alloy reference materials (chips, solid block) were measured over 31 d using artificial lung alveolar macrophage phagolysosomal fluid (pH 4.5). Differences in beryllium-containing particle physicochemical properties translated into differences in dissolution rates and lifetimes in artificial phagolysosomal fluid. Among all materials, dissolution rate constant values ranged from 10(-5) to 10(-10)gcm(-2)d(-1) and half-times ranged from tens to thousands of days. The presence of magnesium trisilicate in some beryllium oxide materials may have slowed dissolution rates. Materials associated with elevated prevalence of CBD had faster beryllium dissolution rates [10(-7)-10(-8)gcm(-2)d(-1)] than materials not associated with elevated prevalence (p<0.05).

Chronic beryllium disease: an updated model interaction between innate and acquired immunity

During the last decade, there have been concerted efforts to reduce beryllium (Be) exposure in the workplace and thereby reduce potential cases of this occupational lung disorder. Despite these efforts, it is estimated that there are at least one million Be-exposed individuals in the U.S. who are potentially at risk for developing chronic beryllium disease (CBD). Previously, we reviewed the current CBD literature and proposed that CBD represents a model interaction between innate and acquired immunity (Sawyer et al., Int Immunopharmacol 2:249-261, 2002). We closed this review with a section on "future directions" that identified key gaps in our understanding of the pathogenesis of CBD. In the intervening period, progress has been made to fill in some of these gaps, and the current review will provide an update on that progress. Based on recent findings, we provide a new hypothesis to explain how Be drives sustained chronic inflammation and granuloma formation in CBD leading to progressive compromised lung function in CBD patients. This paradigm has direct implications for our understanding of the development of an immune response to Be, but is also likely applicable to other immune-mediated lung diseases of known and unknown etiology.

Release of beryllium from beryllium-containing materials in artificial skin surface film liquids

PURPOSE

Skin exposure to soluble beryllium compounds causes systemic sensitization in humans. Penetration of poorly soluble particles through intact skin has been proposed as a mechanism for beryllium sensitization; however, this mechanism is controversial. The purpose of this study was to investigate the hypothesis that particulate beryllium compounds in contact with skin surface release ions via dissolution in sweat.

METHODS

Dissolution of 11 particulate beryllium materials (hydroxide, metal, oxides and copper-beryllium fume), 3 copper-beryllium alloy reference materials (chips and solid block), and 4 copper-beryllium alloy tools was measured over 7 days in artificial sweat buffered to pH 5.3 and pH 6.5.

RESULTS

All test materials released beryllium ions in artificial sweat. Particulate from a reduction furnace that contained both crystalline and amorphous beryllium was the most soluble compound-40% dissolved in 8 h. Rates of beryllium release from all other particulate and reference materials were faster at pH 5.3 than at pH 6.5 (P < 0.05). At pH 5.3, values of the chemical dissolution rate constant, k [g (cm² day)⁻¹] differed significantly for hydroxide, metal, and oxide -1.7 ± 0.0 × 10⁻⁷, 1.7 ± 0.6 × 10⁻⁸, and 1.0 ± 0.5 × 10⁻⁹, respectively (P < 0.05). Up to 30 μg of beryllium was released from the alloy tools within 1 h. Dissolution rates in artificial sweat were equal to or faster than values previously determined for these materials in lung models.

CONCLUSIONS

Poorly soluble beryllium materials undergo dissolution in artificial sweat, suggesting that skin exposure is a biologically plausible pathway for development of sensitization. Skin surface acidity, which is regulated by sweat chemistry and bacterial hydrolysis of sebum lipids varies by anatomical region and may be an exposure-modifying factor for beryllium particle dissolution.

A reconsideration of acute Beryllium disease

CONTEXT

Although chronic beryllium disease (CBD) is clearly an immune-mediated granulomatous reaction to beryllium, acute beryllium disease (ABD) is commonly considered an irritative chemical phenomenon related to high exposures. Given reported new cases of ABD and projected increased demand for beryllium, we aimed to reevaluate the patho physiologic associations between ABD and CBD using two cases identified from a survey of beryllium production facility workers.

CASE PRESENTATION

Within weeks after exposure to beryllium fluoride began, two workers had systemic illness characterized by dermal and respiratory symptoms and precipitous declines in pulmonary function. Symptoms and pulmonary function abnormalities improved with cessation of exposure and, in one worker, recurred with repeat exposure. Bronchoalveolar lavage fluid analyses and blood beryllium lymphocyte proliferation tests revealed lymphocytic alveolitis and cellular immune recognition of beryllium. None of the measured air samples exceeded 100 microg/m(3), and most were < 10 microg/m(3), lower than usually described. In both cases, lung biopsy about 18 months after acute illness revealed noncaseating granulomas. Years after first exposure, the workers left employment because of CBD.

DISCUSSION

Contrary to common understanding, these cases suggest that ABD and CBD represent a continuum of disease, and both involve hypersensitivity reactions to beryllium. Differences in disease presentation and progression are likely influenced by the solubility of the beryllium compound involved.

RELEVANCE TO PRACTICE

ABD may occur after exposures lower than the high concentrations commonly described. Prudence dictates limitation of further beryllium exposure in both ABD and CBD.

Immunological responses in C3H/HeJ mice following nose-only inhalation exposure to different sizes of beryllium metal particles

Beryllium is used in a wide variety of industries. Chronic beryllium disease is the most common occupational disease among workers following exposure to Be. The objective of this study was to determine the immunologic effects of two different particle sizes of Be metal, <2.5 microm (fine Be or Be-F) and <10 microm (inhalable Be or Be-I) on C3H/HeJ mice following 3 weeks of nose-only inhalation exposure at a target concentration of 250 microg m(-3). Mice were sacrificed either on day 28 or day 42 (Be-F group only) after exposure. The mass median aerodynamic diameter obtained in the inhalation chamber was 1.5 +/- 0.1 microm for Be-F and 4.1 +/- 0.6 microm for Be-I. Results showed peri-bronchial inflammation with early granulomatous changes in exposed mice. The extent of the inflammation appeared more severe for mice sacrificed at day 42. Splenocyte proliferation was higher for mice exposed to fine particles compared with Be-I and control animals. Flow-cytometric analysis indicated a significantly greater expression of CD4(+), CD8(+) and intracellular IFN-gamma expression for both Be particle sizes, particularly for fine particles. Cytokine assays of bronchoalveolar lavage revealed significantly greater levels of IL-12, TNF-alpha and IFN-gamma for mice exposed to fine particles. Our findings suggest that exposure to fine particles may induce more pronounced immunological effects than inhalable particles.

Beryllium: A Modern Industrial Hazard

Beryllium exposure can cause a granulomatous lung disease in workers who develop a lymphocyte-mediated sensitization to the metal. Workers in diverse industries are at risk because beryllium's properties are critical to nuclear, aerospace, telecommunications, electronic, metal alloy, biomedical, and semiconductor industries. The occupational air concentration standard's failure to protect beryllium workers is driving many scientific and occupational health advances. These developments include study of bioavailability of different physicochemical forms of beryllium, medical surveillance to show effectiveness of skin protection in preventing sensitization in high-risk processes, gene-environment interaction, transgenic mice for use in experimental research, and risk-based management of industrial exposures in the absence of effective exposure-response information. Beryllium sensitization and disease prevention are paradigms for much broader public health action in both occupational and general population settings.

Secondary ion mass spectroscopy demonstrates retention of beryllium in chronic beryllium disease granulomas

OBJECTIVE

We hypothesized that beryllium (Be) might persist in lung granulomas in patients with chronic beryllium disease (CBD).

METHODS

A total of 33 Be-exposed ceramics workers underwent transbronchial biopsy. They were classified based on histopathology and Be-lymphocyte proliferation test as CBD or other categories. Lung tissue sections were analyzed using secondary ion mass spectroscopy.

RESULTS

Be was detected in the lungs of all Be-exposed groups. Be levels were increased within the granulomas of patients with CBD compared with the Be levels outside granulomas. Notably, Be was detectable in the lungs of CBD patients who had ceased exposure to Be an average of 9 years previously.

CONCLUSIONS

Be was detected in the lungs of all Be-exposed subjects, with the highest levels of persistent Be inside CBD lung granulomas. Be antigen persistence may help explain the chronicity of this granulomatous disorder.

Beryllium exposure: dermal and immunological considerations

OBJECTIVE

People exposed to beryllium compounds are at increased risk of developing beryllium sensitization and chronic beryllium disease (CBD). The purpose of this short communication is to present information regarding the potential importance of skin exposure to beryllium, an exposure and alternate immune response pathway to the respiratory tract, which has been largely overlooked in epidemiologic and exposure assessment studies.

METHODS

We reviewed the published literature, including epidemiologic, immunologic, genetic, and laboratory-based studies of in vivo and in vitro models, to assess the state of knowledge concerning skin exposure to beryllium.

RESULTS

Reduction in inhalation exposure to beryllium has not resulted in a concomitant reduction in the occurrence of beryllium sensitization or CBD, suggesting that continued prevalence may be due, in part, to unchecked skin exposure to beryllium-containing particles.

CONCLUSIONS

Recent developments in our understanding of the multiple exposure pathways that may lead to beryllium sensitization and CBD suggest that a prudent approach to worker protection is to assess and minimize both skin and inhalation exposures to beryllium.

Differences in dissolution behavior in a phagolysosomal simulant fluid for single-constituent and multi-constituent materials associated with beryllium sensitization and chronic beryllium disease

Particle dissolution within macrophage phagolysosomes is hypothesized to be an important source of dissolved beryllium for input to the cell-mediated immune reaction associated with development of beryllium sensitization and chronic beryllium disease (CBD). To better understand the dissolution of beryllium materials associated with elevated prevalence of sensitization and CBD, single-constituent (beryllium oxide (BeO) particles sampled from a screener operation, finished product BeO powder, finish product beryllium metal powder) and multi-constituent (particles sampled from an arc furnace during processing of copper-beryllium alloy) aerosol materials were studied. Dissolution rates were measured using phagolysosomal simulant fluid (PSF) in a static dissolution technique and then normalized to measured values of specific surface area to calculate a chemical dissolution rate constant (k) for each material. Values of k, in g/(cm2 day), for screener BeO particles (1.3 +/- 1.9 x 10(-8)) and for BeO powder (1.1 +/- 0.5 x 10(-8)) were similar (p = 0.45). The value of k observed for beryllium metal powder (1.1 +/- 1.4 x 10(-7)) was significantly greater than observed for the BeO materials (p < 0.0003). For arc furnace particles, k (1.6 +/- 0.6 x 10(-7)) was significantly greater than observed for the BeO materials (p < 0.00001), despite the fact that the chemical form of beryllium in the aerosol was BeO. These results suggest that dissolution of beryllium differs among physicochemical forms of beryllium and direct measurement of dissolution is needed for multi-constituent aerosol. Additional studies of the dissolution behavior of beryllium materials in a variety of mixture configurations will aid in developing exposure-response models to improve understanding of the risk of beryllium sensitization and CBD.