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Comparative cytotoxicity of cadmium and mercury in a human bronchial epithelial cell line (BEAS-2B) and its role in oxidative stress and induction of heat shock protein 70.

Authors
Han-SG; Castranova-V; Vallyathan-V
Source
J Toxicol Environ Health, A 2007 May; 70(9-10):852-860
NIOSHTIC No.
20032079
Abstract
A number of toxic heavy metals, such as cadmium (Cd) and mercury (Hg), are widely used in occupational settings, and exposure to these metals is associated with the development of pulmonary diseases. Cytotoxicity, apoptosis, and reactive oxygen species (ROS) generation were tested to compare the biological reactivity of these two heavy metals using a human bronchial epithelial cell line, BEAS-2B. Further, heat-shock protein 70 (Hsp70) expression was observed as a sensitive indicator of cellular stress. Exposure to metals (0-50 M) for 72 h showed more significant cytotoxicity in Cd-treated than Hg-treated cells. Apoptosis was significantly increased in the cells exposed to 50 M of Cd (3.5-fold) and Hg (3.6-fold). Cd and Hg produced an induction of Hsp70 protein as assayed by Western blotting and enzyme-linked immunosorbent assay (ELISA). Induction of Hsp70 protein by these metals was inhibited by addition of N-acetylcysteine. However, addition of catalase blocked the synthesis of Hsp70 only in Hg-treated cells. Hsp70B and Hsp70C mRNA expression was induced by both metals, while Hsp70A mRNA expression showed no change. Electron spin resonance (ESR) tests showed that hydroxyl radical generation was greater in the reaction of cells with Hg compared to Cd. Intracellular generation of ROS was detected in the cells exposed to both Cd and Hg. These results suggest that both cytotoxicity and apoptosis were significantly elevated with all metals tested; however, Cd was relatively more toxic. Hsp70 protein and mRNA were sensitive to exposure to these metals. Depletion of sulfhydryl groups of cellular proteins and generation of ROS may be involved in metal-induced lung cell damage.
Keywords
Metal-compounds; Metal-fumes; Metal-industry; Metal-poisoning; Metal-workers; Bronchial-asthma; Cytotoxins; Cell-biology; Cell-damage; Cellular-respiration; Pulmonary-system-disorders; Pulmonary-function; Pulmonary-disorders; Pulmonary-system; Sensitivity-testing; Lung-irritants; Lung-cells; Carcinogenesis
Contact
Val Vallyathan, PhD, NIOSH, 1095 Willowdale Road, Morgantown, WV 26505, USA
CODEN
JTEHD6
CAS No.
7440-43-9; 7439-97-6
Publication Date
20070501
Document Type
Journal Article
Email Address
vav1@cdc.gov
Fiscal Year
2007
NTIS Accession No.
NTIS Price
Issue of Publication
9-10
ISSN
1528-7394
NIOSH Division
HELD
Priority Area
Manufacturing
Source Name
Journal of Toxicology and Environmental Health, Part A: Current Issues
State
WV
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