Mineral fibre toxicity: expression of retinoblastoma (Rb) and phospho-retinoblastoma (pRb) protein in alveolar epithelial and mesothelial cell lines exposed to fluoro-edenite fibres

The extracellular matrix protein fibulin-3/EFEMP1 promotes pleural mesothelioma growth by activation of PI3K/Akt signaling

Malignant pleural mesothelioma (MPM) is an aggressive tumor with poor prognosis and limited therapeutic options. The extracellular matrix protein fibulin-3/EFEMP1 accumulates in the pleural effusions of MPM patients and has been proposed as a prognostic biomarker of these tumors. However, it is entirely unknown whether fibulin-3 plays a functional role on MPM growth and progression. Here, we demonstrate that fibulin-3 is upregulated in MPM tissue, promotes the malignant behavior of MPM cells, and can be targeted to reduce tumor progression. Overexpression of fibulin-3 increased the viability, clonogenic capacity and invasion of mesothelial cells, whereas fibulin-3 knockdown decreased these phenotypic traits as well as chemoresistance in MPM cells. At the molecular level, fibulin-3 activated PI3K/Akt signaling and increased the expression of a PI3K-dependent gene signature associated with cell adhesion, motility, and invasion. These pro-tumoral effects of fibulin-3 on MPM cells were disrupted by PI3K inhibition as well as by a novel, function-blocking, anti-fibulin-3 chimeric antibody. Anti-fibulin-3 antibody therapy tested in two orthotopic models of MPM inhibited fibulin-3 signaling, resulting in decreased tumor cell proliferation, reduced tumor growth, and extended animal survival. Taken together, these results demonstrate for the first time that fibulin-3 is not only a prognostic factor of MPM but also a relevant molecular target in these tumors. Further development of anti-fibulin-3 approaches are proposed to increase early detection and therapeutic impact against MPM.

In vitro toxicity of fibrous glaucophane

The health hazard represented by the exposure to asbestos may also concern other minerals with asbestos-like crystal habit. One of these potentially hazardous minerals is fibrous glaucophane. Fibrous glaucophane is a major component of blueschist rocks of California (USA) currently mined for construction purposes. Dust generated by the excavation activities might potentially expose workers and the general public. The aim of this study was to determine whether fibrous glaucophane induces in vitro toxicity effects on lung cells by assessing the biological responses of cultured human pleural mesothelial cells (Met-5A) and THP-1 derived macrophages exposed for 24 h and 48 h to glaucophane fibres. Crocidolite asbestos was tested for comparison. The experimental configuration of the in vitro tests included a cell culture without fibres (i.e., control), cell cultures treated with 50 μg/mL (i.e., 15.6 μg/cm²) of crocidolite fibres and 25-50-100 μg/mL (i.e., 7.8-15.6-31.2 μg/cm²) of glaucophane fibres. Results showed that fibrous glaucophane may induce a decrease in cell viability and an increase in extra-cellular lactate dehydrogenase release in the tested cell cultures in a concentration dependent mode. Moreover, it was found that fibrous glaucophane has a potency to cause oxidative stress. The biological reactivity of fibrous glaucophane confirms that it is a toxic agent and, although it apparently induces lower toxic effects compared to crocidolite, exposure to this fibre may be responsible for the development of lung diseases in exposed unprotected workers and population.

Update of in vitro, in vivo and ex vivo fluoro-edenite effects on malignant mesothelioma: A systematic review (Review)

Fluoro-edenite (FE), asbestiform fiber found in Biancavilla (Sicily, Italy), presents various characteristics similar to the asbestos group, in particular two fibrous phases tremolite and actinolite. Indeed, epidemiological studies have shown that FE fibers have similar effects to those of asbestos fibers. Such studies have reported a high incidence of malignant mesothelioma (MM), an aggressive neoplasm of the serosal membranes lining the pleural cavity, in individuals residing there due to FE exposure in Biancavilla related to environmental contamination. Evidence has led to the classification of FE as a Group 1 human carcinogen by the International Agency for Research on Cancer (IARC). The aim of this systematic review is to compare the results achieved in in vitro, in vivo and ex vivo experimental studies involving FE in order to update the current knowledge on the pathogenesis and molecular mechanisms responsible for FE-mediated MM development as well as the availability of effective biomarkers for MM prevention and diagnosis. This review is focused on the pathophysiological mechanisms mediated by inflammation induced by FE fiber exposure and which are responsible for MM development. This review also discusses the discovery of new diagnostic and prognostic biomarkers for the management of this pathology. It is known that the risk of cancer development increases with chronic inflammation, arising from enhanced reactive oxygen species (ROS) and NO^• production stimulated by the body to remove exogenous agents, causing DNA damage and enhanced signal transduction that may lead to activation of oncogenes. Studies concerning MM biomarker discovery indicate that several biomarkers have been proposed for MM, but mesothelin is the only Food and Drug Administration (FDA)-approved biomarker for MM, with limitations. In recent studies, in silico analysis to identify selected miRNAs highly deregulated in cancer samples when compared with normal control have been developed. This in silico approach could represent an effort in the field of biomarker discovery for MM.

Modulation of microRNA expression levels after naturally occurring asbestiform fibers exposure as a diagnostic biomarker of mesothelial neoplastic transformation

Fluoro-edenite (FE) is a silicate mineral identified in the lava products of Monte Calvario from stone quarries located in the southeast of Biancavilla, a small city of the Etnean volcanic complex (Sicily, Italy). Inhalation of FE fibers has been associated with a higher incidence of Malignant Mesothelioma (MM), a highly aggressive neoplasm of the serosal membranes lining the pleural cavity. Only 5% of MM patients are diagnosed at an early stage and the median survival is approximate 6-12 months. Many diagnostic biomarkers have been proposed for MM. Several studies demonstrated that microRNAs (miRNAs) may be used as good non-invasive diagnostics, as well as prognostic biomarkers for various human diseases, including cancer. On these bases, the aim of the present study was to identify a set of miRNAs involved in the development and progression of MM and potentially used as diagnostic biomarkers. For these purposes, in silico analyses were performed on healthy/exposed to asbestos fibers subjects vs. patients with MM. These analyses revealed a set of miRNAs strictly involved in MM by merging the lists of miRNAs found differentially expressed in the three miRNA expression datasets analyzed. The result of these computational evaluations allowed the execution of functional in vitro experiments performed on normal pleural mesothelial cell line (MeT-5A) and MM cell line (JU77) in order to test the carcinogenetic effects and epigenetic modulation induced by FE exposure. The in vitro results showed that the expression levels of hsa-miR-323a-3p vary significantly in both supernatant- and cell-derived miRNAs derived from treated and untreated cells. Secreted and cellular hsa-miR-101-3p in MeT-5A treated with FE fibers and JU77 cells showed different trends of expression. As regard hsa-miR-20b-5p, there was no differential expression between secreted and cellular hsa-miR-20b-5p. This miRNA has been shown a significant up-regulation in JU77 cells vs. control and treated MeT-5A. As a future plan, translational analyses will be performed on a subset of patients chronically exposed to FE fibers to further verify the clinical role of such miRNAs in high-risk individuals and their possible use as biomarkers of FE exposure or MM early onset.

Attenuation of oxidative stress and chromosomal aberrations in cultured macrophages and pulmonary cells following self-sustained high temperature synthesis of asbestos

Inhalation of asbestos fibres can cause lung and pleural diseases in humans and constitutes a severe public health threat worldwide. The aim of the present study was to assess the biological effects induced in both pulmonary cells (A549) and monocyte/macrophage (RAW 264.7) cell lines by combustion slags obtained from asbestos through a self-sustained high-temperature synthesis (SHS) reaction. The SHS reaction involves rapid thermal treatment and displays great ability to neutralise asbestos. Cytotoxicity, redox status imbalance, lipid peroxide production, DNA strand breaks (comet assay) and chromosomal aberrations (cytokinesis block micronucleus test) were evaluated in cells exposed either to untreated asbestos fibres or to grinded SHS-generated slags of different granulometry, tested in cultured cells at varying doses and for varying exposure times. Our results show that asbestos fibres cause redox status imbalance, especially in monocyte/macrophage cell lines. Moreover, they promote lipid peroxidation and trigger genomic alterations. When the cells were exposed to slag powders, which are the products of SHS asbestos treatment, generation of lipid peroxides and induction of DNA strand breaks still persisted, due to the high content in iron and other metals detected in these samples. However, there was an attenuation of redox status imbalance and an absence of chromosomal aberrations, which probably reflects the loss of the asbestos fibrous structure following SHS reaction, as demonstrated by electron microscopy analyses. In conclusions, SHS-treated asbestos wastes can potentially have deleterious health effects due to the oxidative stress induced by inhaled powders but they loose the asbestos ability to induce chromosomal alterations.

Defense and protection mechanisms in lung exposed to asbestiform fiber: the role of macrophage migration inhibitory factor and heme oxygenase-1

Fluoro-edenite (FE), an asbestiform fiber, is responsible for many respiratory pathologies: chronic obstructive diseases, pleural plaques, fibrosis, and malignant mesothelioma. Macrophage migration inhibitory factor (MIF) is one of the first cytokines produced in response to lung tissue damage. Heme oxygenase-1 (HO-1) is a protein with protective effects against oxidative stress. It is up regulated by several stimuli including pro-inflammatory cytokines and factors that promote oxidative stress. In this research, the in vivo model of sheep lungs naturally exposed to FE was studied in order to shed light on the pathophysiological events sustaining exposure to fibers, by determining immunohistochemical lung expression of MIF and HO-1. Protein levels expression of HO-1 and MIF were also evaluated in human primary lung fibroblasts after exposure to FE fibers in vitro. In exposed sheep lungs, MIF and HO-1 immunoexpression were spread involving the intraparenchymal stroma around bronchioles, interstitium between alveoli, alveolar epithelium and macrophages. High MIF immunoexpression prevails in macrophages. Similar results were obtained in vitro, but significantly higher values were only detected for HO-1 at concentrations of 50 and 100 μg/mL of FE fibers. MIF and HO-1 expressions seem to play a role in lung self-protection against uncontrolled chronic inflammation, thus counteracting the strong link with cancer development, induced by exposure to FE. Further studies will be conducted in order to add more information about the role of MIF and HO-1 in the toxicity FE-induced.

Fibulin-3 as biomarker of malignant mesothelioma

Many malignant diseases are associated with past asbestos exposure; the most lethal and strictly related to previous fiber exposure being malignant mesothelioma (MM). Effective preventive protocols may include sensitive and specific biomarkers. The role of Fb-3 has been recently investigated for MM early detection, but its role is still under debate. After an independent search for scientific literature, nine studies were included for a systematic review. Human Fb-3 levels seem to be able to separate healthy people with previous exposure to asbestiform fibers from MM patients. Fb-3 blood levels can distinguish MM effusions from other malignant and benign effusions. Furthers investigations on more significant groups of patients are desirable to validate and assess the validity of combining Fb-3 with other biomarkers.

Indoor release of asbestiform fibers from naturally contaminated water and related health risk

This study investigates the occurrence of airborne asbestiform fibers released in indoor ambient due to the use of asbestos naturally contaminated water. Some experiments employed a laboratory physical model using an ultrasonic humidifier charged with contaminated groundwater. Other experiments were carried out at full scale to assess the release of asbestiform fibers during showering. Obtained results show that the concentration of the airborne asbestiform fibers released in the bathroom during showering is higher than the limit value set by the European and Italian Regulations, while the concentration of fibers released by the humidifier is much lower. However, it is noteworthy that the use of the humidifier at high exposure time results in similar health risk. Strong correlations were found between the concentration of the airborne asbestiform fibers and a novel surrogate parameter (i.e. the exposure-specific-water-consumption). These correlations can be used to monitor the asbestiform fibers concentration at varying operating conditions and therefore, to control the resulting health risk.

Analysis of fibulin-3 after exposure to asbestos-like fibers

A significantly increased incidence of malignant mesothelioma in Biancavilla (Sicily, Italy) has been ascribed to exposure to fluoro-edenite, a fibrous amphibole extracted from a local stone quarry. Fibulin-3 is a highly conserved glycoprotein proposed as a biomarker for malignant mesothelioma that belongs to the family of extracellular matrix proteins. Previous studies demonstrated high Fibulin-3 plasma levels in workers with pleural plaques exposed to fluoro-edenite. Therefore, in order to gain insight into the biomolecular mechanisms of fluoro-edenite toxicity, we performed the analysis of Fibulin-3 expression by immunohistochemistry in the lung samples derived from sheep belonging to the area of Biancavilla. Furthermore, an in vitro model of exposed fluoro-edenite fibroblasts was used to perform functional experiments to better understand the modulation of Fibulin-3 expression. The percentage of immunostained area by Fibulin-3 was very much higher in exposed lungs compared with non-exposed ones. The Fibulin-3 protein level was significantly expressed in primary human lung fibroblasts exposed to 50 and 100µg/ml of fluoro-edenite fibers for 72h, compared to the unexposed controls. The results from the present study further demonstrate the implication of Fibulin-3 during fluoro-edenite exposure. This would endorse our previous results regarding the use of Fibulin-3 as a possible screening biomarker for fluoro-edenite exposed individuals, thereby contributing to the monitoring of the population at risk. The present study also suggested that the Fibulin-3 overexpression may reflect a defensive response of the tissues after exogenous stimuli and may be implicated in cancer development, especially in the context of fluoro-edenite contamination. However, further studies are necessary in order to make Fibulin-3 a customized screening tool.

Fluoro-edenite induces fibulin-3 overexpression in non-malignant human mesothelial cells

Exposure to asbestos is associated with the development of mesothelioma. In addition to asbestos, other fibers have been identified as risk factors for malignant and non-malignant diseases of the lungs. Among these, fluoro-edenite (FE) was found in patients from Biancavilla (Sicily, Italy) with pleural and lung disease, suggesting its role for tumor expansion. In this context, the identification of early biomarkers useful for the diagnosis of cancer is mandatory. Fibulin-3 represents an important marker for the diagnosis of mesothelioma. However, it remains to be determined whether it is directly associated with exposure to asbestos-like fibers. In the present study, peripheral blood levels of fibulin-3 from 40 asbestos-exposed workers were compared with those detected in 27 street cleaners from Biancavilla. Intriguingly, the results showed that fibulin-3 levels were higher in the group of street cleaners compared with those of the asbestos-exposed workers, suggesting that these workers used the personal protective equipment according to the current regulations. These data suggest that subjects exposed to FE should be monitored for the risk of mesothelioma. FE and volcanic particulates are probably contained within dust inhaled by street cleaners from Biancavilla during their work activities. Based on these criteria, in this study, such fibers were used to treat mesothelial cells (MeT5A) in order to verify whether fibulin-3 levels are affected by these treatments. The results showed that only treatment with FE was associated with fibulin-3 overexpression at both the transcript and protein levels. It was previously demonstrated that mesothelial cells exhibited low levels of p27 following treatment with FE. Notably, p27 downregulation is associated with stathmin upregulation in cancer, conferring an aggressive phenotype of tumor cells. This observation prompted us to perform a computational evaluation demonstrating the activation of stathmin in lung cancer in patients exposed to asbestos. Overall, it can be speculated that both fibulin-3 and stathmin overexpression may be associated with the malignant transformation of mesothelial cells following exposure to asbestos-like fibers.

Occupational exposure to pesticides as a possible risk factor for the development of chronic diseases in humans (Review)

It is well known that pesticides are widely used compounds. In fact, their use in agriculture, forestry, fishery and the food industry has granted a huge improvement in terms of productive efficiency. However, a great number of epidemiological surveys have demonstrated that these toxic compounds can interact and exert negative effects not only with their targets (pests, herbs and fungi), but also with the rest of the environment, including humans. This is particularly relevant in the case of workers involved in the production, transportation, preparation and application of these toxicants. Accordingly, a growing body of evidence has demonstrated the correlation between occupational exposure to pesticides and the development of a wide spectrum of pathologies, ranging from eczema to neurological diseases and cancer. Pesticide exposure is often quite difficult to establish, as many currently used modules do not take into account all of the many variables that can occur in a diverse environment, such as the agricultural sector, and the assessment of the real risk for every single worker is problematic. Indeed, the use of personal protection equipment is necessary while handling these toxic compounds, but education of workers can be even more important: personal contamination with pesticides may occur even in apparently harmless situations. This review summarises the most recent findings describing the association between pesticide occupational exposure and the development of chronic diseases.

Occupational exposure to carcinogens: Benzene, pesticides and fibers (Review)

It is well known that the occupational exposure to contaminants and carcinogens leads to the development of cancer in exposed workers. In the 18th century, Percivall Pott was the first to hypothesize that chronic exposure to dust in the London chimney sweeps was associated with an increased risk of developing cancer. Subsequently a growing body of evidence indicated that other physical factors were also responsible for oncogenic mutations. Over the past decades, many carcinogens have been found in the occupational environment and their presence is often associated with an increased incidence of cancer. Occupational exposure involves several factors and the association between carcinogens, occupational exposure and cancer is still unclear. Only a fraction of factors is recognized as occupational carcinogens and for each factor, there is an increased risk of cancer development associated with a specific work activity. According to the International Agency for Research on Cancer (IARC), the majority of carcinogens are classified as 'probable' and 'possible' human carcinogens, while, direct evidence of carcinogenicity is provided in epidemiological and experimental studies. In the present review, exposures to benzene, pesticides and mineral fibers are discussed as the most important cancer risk factors during work activities.

Occupational and environmental exposure to pesticides and cytokine pathways in chronic diseases (Review)

Pesticides can exert numerous effects on human health as a consequence of both environmental and occupational exposures. The available knowledge base suggests that exposure to pesticides may result in detrimental reproductive changes, neurological dysfunction and several chronic disorders, which are defined by slow evolution and long-term duration. Moreover, an ever increasing amount of data have identified an association between exposure to pesticides and the harmful effects on the immune system. The real impact of alterations in humoral cytokine levels on human health, in particular in the case of chronic diseases, is still unclear. To date, studies have suggested that although exposure to pesticides can affect the immune system functionally, the development of immune disorders depends on the dose and duration of exposure to pesticides. However, many of the respective studies exhibit limitations, such as a lack of information on exposure levels, differences in the pesticide administration procedures, difficulty in characterizing a prognostic significance to the weak modifications often observed and the interpretation of obtained results. The main challenge is not just to understand the role of individual pesticides and their combinations, but also to determine the manner and the duration of exposure, as the toxic effects on the immune system cannot be separated from these considerations. There is a clear need for more well-designed and standardized epidemiological and experimental studies to recognize the exact association between exposure levels and toxic effects and to identify useful biomarkers of exposure. This review focuses on and critically discusses the immunotoxicity of pesticides and the impact of cytokine levels on health, focusing on the development of several chronic diseases.

Angiogenesis correlates with macrophage and mast cell infiltration in lung tissue of animals exposed to fluoro-edenite fibers

Angiogenesis plays a crucial role in progression of pleural malignant mesothelioma. A significantly increased incidence of pleural mesothelioma has been attributed to exposure to fluoro-edenite, a fibrous amphibole extracted from a local stone quarry. In this study, we have investigated the expression of CD68-positive macrophages, tryptase-positive mast cells and CD31 positive areas, as expression of microvascular density, in lung tissue of sheeps exposed to fluoro-edenite fibers vs controls, by immunohistochemical, morphometric and Western blot analysis. The result have evidenced a significant increase in the expression of CD68-positive macrophages, tryptase-positive mast cells as well as a significant increase in microvascular density evaluated as CD31 positive areas in lung tissue of of sheeps exposed to fluoro-edenite fibers vs controls. These data confirmed the important role played by tumor microenvironment components, including macrophages and mast cells, in favour of angiogenesis in pleural mesothelioma induced by fluoro-edenite exposure.

Sheep lymph-nodes as a biological indicator of environmental exposure to fluoro-edenite

A significantly increased incidence of pleural mesothelioma in Biancavilla (Sicily, Italy) has been attributed to exposure to fluoro-edenite (FE), a fibrous amphibole extracted from a local stone quarry. The lymph-nodes draining the pulmonary lobes of sheep grazing around the town were examined, to gain insights into fibre diffusion. The pasture areas of six sheep flocks lying about 3km from Biancavilla were located using the global positioning system. The cranial tracheobronchial and one middle mediastinal lymph-node as well as four lung tissue samples were collected from 10 animals from each flock and from 10 control sheep for light and scanning electron microscopy (SEM) examination. The lymph-nodes from exposed sheep were enlarged and exhibited signs of anthracosis. Histologically, especially at the paracortical level, they showed lymph-follicle hyperplasia with large reactive cores and several macrophages (coniophages) containing grey-brownish particulate interspersed with elements with a fibril structure, forming aggregates of varying dimensions (coniophage nodules). Similar findings were detected in some peribronchiolar areas of the lung parenchyma. SEM examination showed that FE fibres measured 8-41µm in length and 0.4-1.39µm in diameter in both lymph-nodes and lung tissue. Monitoring of FE fibres in sheep lymph-nodes using appropriate techniques can help set up environmental pollution surveillance.

Fluoro-edenite and carbon nanotubes: The health impact of 'asbestos-like' fibres

Several decades have passed since Wagner et al demonstrated a causal link between asbestos fibre inhalation and the development of pleural mesothelioma in 1960. It was later suggested that pleural plaques are a benign consequence of exposure to these fibres. Most recently, a significant association between exposure to asbestos and cancer diagnosed at various sites, such as the peritoneum, stomach, pharynx, colon and ovaries has been demonstrated. The great concerns about public health that arose from the scientific evidence presented above have led to the banning of asbestos in several countries. Over the years, the suspicion that particles with a high aspect ratio may have asbestos-like pathogenicity has been supported by increasing evidence. Natural occurring minerals, as well as man-made fibres, have proven capable of inducing either chronic inflammation of serous membranes, or, in some cases, the development of peritoneal and pleural mesothelioma. The pathogenic role of both fluoro-edenite and carbon nanotubes, two ‘asbestos-like’ fibres is summarized and discussed in this review. The data presented herein support the notion that occupational exposure to these two types of fibre contributes to the development of different types of cancer.

Cytotoxicity induced by exposure to natural and synthetic tremolite asbestos: an in vitro pilot study

Mineral fibers are potential carcinogens to humans. In order to help clarify the etiology of the pathological effects of asbestos, cellular reactions to natural and synthetic asbestos fibers were compared using a lung alveolar cancer cell line (A549 epithelial cells), considered the first target of inhaled micro-environmental contaminants. Natural asbestos tremolite (NAT) fibers were collected from rocks in NW Italy. Synthetic asbestos tremolite (SAT) was iron-free and therefore considered as standard tremolite. Both fibers, subjected to mineralogical characterization by X-ray powder diffractometry, electron microscopy and energy dispersive spectrometry, fell within the definition of respirable and potentially carcinogenic fibers. Several signs of functional and structural cell damage were found after treatment with both fibers, documented by viability, motility, and morphological perturbations. Phalloidin labeling showed irregular distribution of cytoskeletal F-actin, whereas immunohistochemical investigations showed abnormal expression of VEGF, Cdc42, β-catenin, assessed as risks indicators for cancer development. Both fibers caused significant loss of viability, even compared to UICC crocidolite, but, while SAT fibers exerted a more direct cytotoxic effect, survival of damaged cells expressing high VEGF levels was detected after NAT contact. This in vitro pilot study outlines potential health risks of NAT fibers in vivo related to their iron content, which could trigger signaling networks connected with cell proliferation and neoplastic transformation.