Advertisement

Role of Oxidative Injury in the Pathogenesis of Methylmercury Neurotoxicity

  • M. Anthony Verity
  • Ted Sarafian
Part of the Rochester Series on Environmental Toxicity book series (RSET)

Abstract

We have previously demonstrated (J. Neuropath. Exp. Neurol. 48:1–10, 1989) that the pathogenesis of methylmercury (MeHg) induced cytotoxicity in suspensions of cerebellar granule neurons was not strictly coupled to the reduction of ATP or combined inhibition of ATP or macromolecule synthesis, but suggested a component of free-radical injury. The present studies reveal that MeHg initiates a dose- and time-dependent lipoperoxidation measured as malonaldehyde generation or induction of a 2′,7′-dichlorofluorescein (DCFA) signal representing oxygen radical species generation. A simultaneous decline in GSH occurred. Partial protection was given by EGTA (a Ca2+ chelator) or desferoxamine (Fe2+ chelation with inhibition of the Fenton reaction and OH radical production). However, no cytoprotection was found with alpha-tocopherol succinate although significant inhibition of lipoperoxidation was observed. Analogous experiments in cerebellar granule cell culture revealed a dose-dependent (0.5–μM) increase in the specific activity of GSH accompanied by increased lipoperoxidation and neuronal cell injury. Such paradoxical induction of GSH occurred in glial cells, whose endogenous content was higher than that of neuron culture. Inhibition of gamma-glutamyl cysteine synthetase by buthionine sulfoximine (BSO) lowered cellular GSH and strongly potentiated MeHg-induced lipoperoxidation and cell death in neuron culture but had minimal effect in glial culture.

It is likely that activated oxygen species and lipoperoxidation significantly contribute to the pathogenesis of alkylmercury induced injury but are not singly causal to the final cytotoxic event. Other processes, especially intracellular protein degradation of -SH sensitive proteins or permeases, modification of cytoskeletal proteins, activation of phospholipase A2 and activation of protein kinase C contribute to the final lethal event.

Keywords

Cerebellar Granule Cerebellar Granule Cell Cerebellar Granule Neuron Buthionine Sulfoximine Intracellular Protein Degradation 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Anderson, M. E. and Meister, A., 1987, Intracellular delivery of cysteine. Methods Enzymol. 143:313.PubMedCrossRefGoogle Scholar
  2. Braughler, J. M., Duncan, L. A. and Goodman, T., 1985, Calcium enhances in vitro free radical-induced damge to brain synaptosomes, mitochondria and cultured spinal cord neurons. J. Neurochem. 45:1288.PubMedCrossRefGoogle Scholar
  3. Chang, L. W., Gilbert, M. and Sprecher, J., 1978, Modificaiton of methyl mercury neurotoxicity by vitamin E. Environ. Res. 17:356.PubMedCrossRefGoogle Scholar
  4. Chang, L. W. and Suber, R., 1982, Protective effect of selenium on methyl mercury toxicity: A possible mechanism. Bull. Environ. Contam. Toxciol. 29:285.CrossRefGoogle Scholar
  5. Chavez, E. and Holguin, J. A., 1988, Mitochondrial calcium release as induced by mercuric ion. J. Biol. Chem. 263:3582.PubMedGoogle Scholar
  6. Davies, K. J. A. and Goldberg, A. L., 1987. Oxygen radicals stimulate intracellular proteolysis and lipid peroxidation by independent mechanism in erythrocytes. J. Biol. Chem. 262:8220.PubMedGoogle Scholar
  7. Davies, K. J. A. and Delsignore, M. E., 1987. Protein damage and degradation by oxygen radicals. III. Modification of secondary and tertiary structure. J. Biol. Chem. 262:9908.PubMedGoogle Scholar
  8. Dethmers, J. K. and Meister, A., 1981. Glutathione export by human lymphoid cells: Depletion of glutathione by inhibition of its synthesis decreases export and increases sensitivity to irradiation. Proc. Natl. Acad. Sci. U.S.A. 78:7492.PubMedCrossRefGoogle Scholar
  9. Duke, R. C., Chervenak, R. and Cohen, J. J., 1983. Endogenous endonuclease-induced DNA fragmentation: An early event in cell-mediated cytolysis. Proc. Natl. Acad. Sci. U.S.A. 80:6361.PubMedCrossRefGoogle Scholar
  10. Ganther, H. E., Goudie, C., Sunde, M. L., Kopecky, M. J., Wagner, R., Oh, S-H., and Hoekstra, W. G., 1972. Selenium: Relation to decreased toxicity of methyl mercury added to diets containing tuna. Science 75:1122.CrossRefGoogle Scholar
  11. Ganther, H. E., 1978. Methylmercury toxicity and metabolism by selenium and vitamin E: Possible mechanism. Environ. Health Perspect. 25:71.PubMedCrossRefGoogle Scholar
  12. Ganther, H. E., 1980. Interactions of vitamin E and selenium with mercury and silver. Ann. N. Y. Acad. Sci. 355:212.PubMedCrossRefGoogle Scholar
  13. Griffith, O. W. and Meister, A., 1979. Potent and specific inhibition of glutathione synthesis by buthionine sulfoximine (S-n-butyl homocysteine sulfoximine). J. Biol. chem. 254:7558.PubMedGoogle Scholar
  14. Hirota, Y., Yamguchi, S., Shimojoh, N. and Sano, K-I, 1980. Inhibitory effect of methylmercury on the activity of glutathione peroxidase. Toxicol. Appl. Phrmacol. 53:174.CrossRefGoogle Scholar
  15. Ichikawa, H., Ronowicz, K., Hicks, M. and Gebicki, J. M., 1987. Lipid peroxidation is not the cause of lysis of human erythrocytes exposed to inorganic or methylmercury. Arch. Biochem. Biophys. 259:45.CrossRefGoogle Scholar
  16. Iwata, H., Okamoto, H. and Ohsawa, Y., 1973. Effect of selenium on methyl mercury poisoning. Res. Commun. Pathol. Pharmacol. 5:673.Google Scholar
  17. Jones, D. P., Thor, H., Smith, M. T., Jewell, S. A. and Orrenius, S., 1983. Inhibition of ATP-dependent microsomal calcium ion sequestration during oxidative stress and its prevention by glutathione. J. Biol Chem. 258:6390.PubMedGoogle Scholar
  18. Kasuya, M., 1975. The effect of vitamin E on the toxicity of alkyl mercurials on nervous tissue in culture. Toxicol. Appl. Pharmacol. 32:347.PubMedCrossRefGoogle Scholar
  19. Kasuya, M., 1976. Effect of selenium on the toxicity of methylmercury on nervous tissue in culture. Toxicol. Appl. Pharmacol. 35:11.PubMedCrossRefGoogle Scholar
  20. Kauppinen, R. A., Komulainen, H. and Taipale, H., 1989. Cellular mechanisms underlying the increase in cytosolic free calcium concentration induced by methylmercury in cerebrocortical synaptosomes from guinea pig. J. Pharmacol. Exp. Ther. 248:1248.PubMedGoogle Scholar
  21. Meister, A., 1983. Selective modification of glutathione metabolism. Science 220:4761.CrossRefGoogle Scholar
  22. Messer, A., 1977. The maintenance and identification of mouse cerebellar granule cells in monolayer culture. Brain Res. 130:1.PubMedCrossRefGoogle Scholar
  23. Moore, W. R., Anderson, M. E., Meister, A., Murata, K., and Kimura, A., 1989. Increased capacity for glutathione synthesis enhances resistance to radiation in Escherichia coli: A possible model for mammalian cell protection. Proc. Natl. Acad. Sci. U.S.A. 86:1461.PubMedCrossRefGoogle Scholar
  24. Nishigaki, S., Kamura, Y, Maki, T., Yamada, H., Shimamura, Y, Ochiai, S. and Kimura, Y, 1974. Mercury-selenium correlations in connection with body weight in muscle of sea fish. Ann. Rep. Tokyo Mat. Res. Lab. Pub.Health 25:235.Google Scholar
  25. Ohi, G., Nishigaki, S., Seki, H., Kamura, Y., Maki, T., Konno, H., Ochiai, S., Yamada, H., Shimamura, Y., Mizoguchi, I. and Yagyu, H., 1976. Efficacy of selenium in tuna and selenite in modifying methylmercury intoxicaiton. Environ. Res. 12:49.PubMedCrossRefGoogle Scholar
  26. Orrenius, S., McConkey, D. J. and Nicotera, P., 1988. Mechanisms of oxidant-induced cell damage. In: Oxy-radicals in Molecular Biology and Pathology. Alan R. Liss, Inc., pp. 327-339.Google Scholar
  27. Pascoe, G. A. and Reed, D. J., 1989. Cell calcium, vitamin E and the thiol redox system in cytotoxicity. In: Free Radical Biology and Medicine 6:209.CrossRefGoogle Scholar
  28. Potter, S. D. and Matrone, G., 1977. A tissue culture model for mercury-selenium interactions. Toxicol. Appl. Pharmacol. 40:201.PubMedCrossRefGoogle Scholar
  29. Prasad, K. N. and Ramanujam, S., 1980. Vitamin E and vitamin C alter the effect of methylmercuric chloride on neuroblastoma and glioma cells in culture. Environ. Res 21:343.PubMedCrossRefGoogle Scholar
  30. Reglinski, J., Hoey, S., Smith, W. E. and Sturrock, R. D., 1988. Cellular reponse to oxidative stress at sulfydryl group receptor sites on the erythrocyte membrane. J. Biol. Chem. 263:12360.PubMedGoogle Scholar
  31. Sarafian, T. A., Cheung, M. K. and Verity, M. A., 1984. In vitro methyl mercury inhibition of protein synthesis in neonatal cerebellar perikarya. Neuropathol. Appl. Neurobiol. 10:85.PubMedCrossRefGoogle Scholar
  32. Sarafian, T. and Verity, M. A., 1985. Inhibition of RNA and protein synthesis in isolated cerebellar cells by in vitro and in vivo methyl mercury. Neurochem. Pathol. 3:27.PubMedCrossRefGoogle Scholar
  33. Sarafian, T. and Verity, M. A., 1986. Influence of thyroid hormones on rat cerebellar cell aggregation and survival in culture. Devel. Brain Res. 26:261.CrossRefGoogle Scholar
  34. Sarafian, T. and Verity, M. A., 1986. Mechanism of apparent transcription inhibition by methylmercury in cerebellar neurons. J. Neurochem. 47:625.PubMedCrossRefGoogle Scholar
  35. Sarafian, T., Hagler, J., Vartavarian, L. and Verity, M. A., 1989. Rapid cell death induced by methylmercury in suspension of cerebellar granule neurons. J. Neuropathol. Exp. Neurol. 48:1.PubMedCrossRefGoogle Scholar
  36. Shier, W. T. and DuBourdieu, D. J., 1983. Stimulation of phospholipid hydrolysis and cell death by mercuric chloride: Evidence for mercuric ion acting as a calcium-mimetic agent. Biochem. Biophys. Res. Commun. 110:758.PubMedCrossRefGoogle Scholar
  37. Stacey, N. H. and Klaassen, K., 1981. Inhibition of lipid peroxidation with prevention of cellular injury in isolated rat hepatocytes. Toxicol. Appl. Pharmacol. 58:8, 1981.PubMedCrossRefGoogle Scholar
  38. Stacey, N. H. and Kappus, H., 1982. Cellular toxicity and lipid peroxidation in response to mercury. Toxicol. Appl. Pharmacol. 63:29.PubMedCrossRefGoogle Scholar
  39. Tsan, M-F, Danis, E. H., DelVecchio, P. J. and Rosano, C. L., 1985, Enhancement of intracellular glutathione protects endothelial cells against oxidant damage. Biochem. Biophys. Res. Commun. 127:270.PubMedCrossRefGoogle Scholar
  40. Verity, M. A., Brown, W. J. and Cheung, M., 1975. Organic mercurial encephalopathy: In vivo and in vitro effects of methyl mercury on synaptosomal respiration. J. Neurochem. 25:759.PubMedCrossRefGoogle Scholar
  41. Weir, K., Sarafian, T., and Verity, M. A., 1990. Methylmercury induces paradoxical increase in reduced glutathione (GSH) in cerebellar granule cell culture. Toxicol. 10:25.Google Scholar
  42. Welsh, S. O. and Soares, J. H. Jr., 1976. The protective effect of vitamin E and selenium against methyl mercury toxicity in the Japanese quail. Nutrition Rep. Int. 13:43.Google Scholar
  43. Williamson, J. M. and Meister, A., 1981. Stimulation of hepatic glutathione formation by administration of L-2-oxothiazolidine-4-carboxylate, a 5-oxo-L-prolinase substrate. Proc. Natl. Acad. Sci. U.S.A. 78:936.PubMedCrossRefGoogle Scholar
  44. Yagi, K., 1976. A simple fluorometric assay for lipoperoxide in blood plasma. Biochem. Med. 15:212.PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1991

Authors and Affiliations

  • M. Anthony Verity
    • 1
  • Ted Sarafian
    • 1
  1. 1.Department of Pathology (Neuropathology) and Brain Research InstituteUCLA School of MedicineLos AngelesUSA

Personalised recommendations