Beryllium-stimulated reactive oxygen species and macrophage apoptosis.
ABSTRACT Beryllium (Be), the etiologic agent of chronic beryllium disease, is a toxic metal that induces apoptosis in human alveolar macrophages. We tested the hypothesis that Be stimulates the formation of reactive oxygen species (ROS) which plays a role in Be-induced macrophage apoptosis. Mouse macrophages were exposed to 100 microM BeSO4 in the absence and presence of the catalytic antioxidant MnTBAP (100 microM). Apoptosis was measured as the percentage of TUNEL+ and caspase-8+ cells. ROS production was measured by flow cytometry using the fluorescence probes, dihydroethidine (DHE) and dichlorofluorescein diacetate (DCFH-DA). Be-exposed macrophages had increased TUNEL+ cells (15+/-1% versus controls 1+/-0.2%, P<0.05) and increased caspase-8+ cells (18.7+/-2% versus controls 1.8+/-0.4%, P<0.05). Be-induced caspase-8 activation, and a 4-fold increase in ROS formation, was ameliorated by exposure to MnTBAP. Hydrogen peroxide (30 microM) exposure potentiated Be-induced caspase-8 activation, and was also attenuated by MnTBAP. Our data are the first to demonstrate that Be stimulates macrophage ROS formation which plays an important role in Be-induced macrophage apoptosis.
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- "Be is believed to stimulate the formation of ROS, leading to Beinduced macrophage apoptosis . While the molecular mechanisms of Be-induced toxicity have yet to be elucidated, macrophage apoptosis is thought to contribute to the metalinduced CBD  . Be is also suspected to induce oxidative stress through the depletion of endogenous thiol antioxidants and the subsequent increase in ROS generation . "
ABSTRACT: Occupational and environmental exposures to metals are closely associated with an increased risk of various cancers. Although carcinogenesis caused by metals has been intensively investigated, the exact mechanisms of action are still unclear. Accumulating evidence indicates that reactive oxygen species (ROS) generated by metals play important roles in the etiology of degenerative and chronic diseases. This review covers recent advances in (1) metal-induced generation of ROS and the related mechanisms; (2) the relationship between metal-mediated ROS generation and carcinogenesis; and (3) the signaling proteins involved in metal-induced carcinogenesis, especially intracellular reduction-oxidation-sensitive molecules.Free Radical Biology and Medicine 06/2012; 53(4):742-57. DOI:10.1016/j.freeradbiomed.2012.06.002 · 5.71 Impact Factor
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- "Furthermore, Be-ferritin and Be salt up-regulate the expression of CD95 (Fas) on the surface of CBD BAL macrophages and induced the intracellular activation of caspase 3, caspase 8 and caspase 9, while CD95 surface expression and caspase activation were not observed in stimulated CBD BAL lymphocytes. Intracellular caspase activation in Be-stimulated macrophage cell lines was inhibited by the catalytic anti-oxidant MnTBAP showing that Bestimulated ROS likely played a role in caspase activation and apoptosis (Sawyer et al. 2005b). Be-specific CBD BAL CD4 + T cells may undergo cell death by other mechanisms unrelated to the Be-stimulated ROS and caspase activation, but mechanisms that eventually result in apoptosis. "
ABSTRACT: 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.Biology of Metals 10/2010; 24(1):1-17. DOI:10.1007/s10534-010-9376-3 · 2.69 Impact Factor
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- "The concentration chosen was well within the range of concentrations reported in the literature for use with cultured cells (see cited articles below), and this concentration did not induce any cytotoxicity in the sensitive NCM-460 cells. CuDIPS: 100 μM ; Bafilomycin A 1 : 1 nM  ; Catalase: 1000 U/mg; E-64d: 10 μg/mL ; 3-MA: 4 mM; HBED: 100 μM  ; HCS: 10 μM ; MnTBAP: 100 μM ; Pepstatin A: 10 μg/mL ; Rapa: 100 μM. "
ABSTRACT: We report that deoxycholate (DOC), a hydrophobic bile acid associated with a high-fat diet, activates the autophagic pathway in non-cancer colon epithelial cells (NCM-460), and that this activation contributes to cell survival. The DOC-induced increase in autophagy was documented by an increase in autophagic vacuoles (detected using transmission electron microscopy, increased levels of LC3-I and LC3-II (western blotting), an increase in acidic vesicles (fluorescence spectroscopy of monodansycadaverine and lysotracker red probes), and increased expression of the autophagic protein, beclin-1 (immunohistochemistry/western blotting). The DOC-induced increase in beclin-1 expression was ROS-dependent. Rapamycin (activator of autophagy) pre-treatment of NCM-460 cells significantly (P < .05) decreased, and 3-MA (inhibitor of autophagy) significantly (P < .05) increased the cell loss caused by DOC treatment, alone. Rapamycin pre-treatment of the apoptosis-resistant colon cancer cell line, HCT-116RC (developed in our laboratory), resulted in a significant decrease in DOC-induced cell death. Bafilomycin A(1) and hydroxychloroquine (inhibitors of the autophagic process) increased the DOC-induced percentage of apoptotic cells in HCT-116RC cells. It was concluded that the activation of autophagy by DOC has important implications for colon carcinogenesis and for the treatment of colon cancer in conjunction with commonly used chemotherapeutic agents.Journal of Toxicology 05/2009; 2009(1687-8191):785907. DOI:10.1155/2009/785907