Comparison of metals in cytotoxicity, free radical generation, and heat shock protein expression in a human bronchial epithelial cell line, BEAS-2B.
A number of toxic heavy metals such as arsenic (As), chromium (Cr), cadmium (Cd), mercury (Hg), nickel (Ni), vanadium (V), and manganese (Mn) are widely used in occupational settings, and exposure to these metals is associated with the development of pulmonary disease. Cytotoxicity, apoptosis, and reactive oxygen species (ROS) generation were tested to compare the biological reactivity of these heavy metals using a human bronchial epithelial cell line, BEAS-2B. Also, heat shock protein 70 (Hsp70) expression was observed as an early and sensitive biomarker of cellular stress. Exposure to metals (50 microM) for 24 hr caused significant cytotoxicity for all the metals tested. Among the metals tested, As (20%), Cr (10%), Cd (30%), and Mn (44%) showed less than 50% survival rate compared to control cells. Apoptosis was significantly increased in the cells exposed to 50 microM of As (2.2-fold), Cr (4.5-fold), and Cd (2.5-fold). Intracellular ROS generation has the capacity to induce DNA damage, alter signal transduction, and cause lipid peroxidation leading to either apoptosis or carcinogenesis. Electron spin resonance (ESR) was used to detect short-lived free radical intermediates generated in the reaction of metal with cells. Hydroxyl radical generation was greater in the presence of As, Cr, Cd, and Hg compared to the other metals. As, Cd, and Hg showed a high expression of Hsp70 protein in Western blotting and ELISA while Cr, Ni, V, and Mn did not show any significant increase of Hsp70 protein. These results suggest that both cytotoxicity and apoptosis were significant with all metals tested; however As, Cd, Cr, and Hg were relatively most toxic metals tested. Generation of ROS may be involved in metal induced lung cell damage. Metal-induced Hsp70 expression could be a sensitive indicator of lung cell injury by As, Cd, and Hg.
Metals; Cytotoxicity; Cytotoxins; Cytotoxic-effects; Free-radicals; Free-radical-generation; Heavy-metals; Toxic-effects; Occupational-exposure; Pulmonary-system-disorders; Exposure-levels; Exposure-assessment; Respiratory-system-disorders; DNA-damage; Lipid-peroxidation; Carcinogenesis; Lung-cells; Lung-disorders
The Toxicologist. Society of Toxicology 44th Annual Meeting and ToxExpo, March 6-10, 2005, New Orleans, Louisiana