Environmental Health Perspectives 105, Supplement 5, September 1997

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Efflux of Reduced Glutathione after Exposure of Human Lung Epithelial Cells to Crocidolite Asbestos

Scott A. Golladay,* Sun-Hee Park, and Ann E. Aust

Department of Chemistry and Biochemistry, Utah State University, Logan, Utah

Abstract
This study investigated glutathione (GSH) homeostasis in human lung epithelial cells (A549) exposed to crocidolite. Exposure of A549 cells to 3 µg/cm 2 crocidolite resulted in a decrease in intracellular reduced glutathione by 36% without a corresponding increase in GSH disulfide. After a 24-hr exposure to crocidolite, 75% of the intracellular GSH lost was recovered in the extracellular medium, of which 50% was in reduced form. Since the half-life of reduced GSH in culture medium was less than 1 hr, this suggests that reduced GSH was released continuously from the cells after treatment. The release of GSH did not appear to result from nonspecific membrane damage, as there was no concomitant release of lactate dehydrogenase or 14 C-adenine from loaded cells after crocidolite treatment for 24 hr. Crocidolite exposure resulted in the formation of S -nitrosothiols but no increase in the level of GSH-protein mixed disulfides or GSH conjugates. Exposure of A549 cells to crocidolite for 24 hr decreased gamma glutamylcysteine synthetase ( gamma -GCS) activity by 47% without changes in the activities of GSH reductase, GSH peroxidase, GSH S -transferase, or glucose-6-phosphate dehydrogenase. Treatment of cells with crocidolite pretreated with the iron chelator desferrioxamine B resulted in the same level of intracellular GSH depletion and efflux and the same decrease in gamma -GCS activity as treatment with unmodified crocidolite, which suggests that iron-catalyzed reactions were not responsible for the GSH depletion. -- Environ Health Perspect 105(Suppl 5):1273-1277 (1997)

Key words : asbestos, glutathione, glutathione disulfide, reduced glutathione efflux, iron, crocidolite, A549 cells, human lung epithelial cells

This paper is based on a presentation at The Sixth International Meeting on the Toxicology of Natural and Man-Made Fibrous and Non-Fibrous Particles held 15-18 September 1996 in Lake Placid, New York. Manuscript received at EHP 26 March 1997; accepted 10 July 1997.

We are grateful to C.-C. Chao for many helpful comments. This work was supported by a grant from the National Institute of Environmental Health Sciences (ESO5814).

Address correspondence to Dr. A.E. Aust, Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300. Telephone: (801) 797-1629. Fax: (801) 797-3390. E-mail: aaust@cc.usu.edu

*Present address: Research and Development Division, Anesta Corporation, 4745 Wiley Post Way, Plaza 6, Suite 650, Salt Lake City, UT 84116.

Abbreviations used: A549, human lung epithelial cells; CPM, counts per min; DF, desferrioxamine B; G6PDH, glucose-6-phosphate dehydrogenase; gamma -GCS, gamma glutamylcysteine synthetase; GPx, glutathione peroxidase; iNOS, inducible form of nitric oxide synthase; GR, glutathione reductase; GSH, reduced glutathione; GSSG, glutathione disulfide (oxidized glutathione); GST, glutathione- S -transferase; HPLC-EC, high-performance liquid chromatography with dual electrochemical detection; LDH, lactate dehydrogenase; NO, nitric oxide.

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Last Update: November 26, 1997