ToxSci Advance Access originally published online on September 21, 2009
Toxicological Sciences 2009 112(2):416-426; doi:10.1093/toxsci/kfp219
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Probucol Increases Glutathione Peroxidase-1 Activity and Displays Long-Lasting Protection against Methylmercury Toxicity in Cerebellar Granule Cells
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* Department of Neurochemistry and Neuropharmacology, Institut d'Investigacions Biomèdiques de Barcelona, CSIC-IDIBAPS, Barcelona 08036, Spain
Departamento de Bioquímica, CCB, Universidade Federal de Santa Catarina, Florianópolis, 88040900 Florianópolis, Santa Catarina, Brazil
CIBER Epidemiología y Salud Pública (CIBERESP), Barcelona 08036, Spain
Department of Cell Death and Proliferation, Institut d'Investigacions Biomèdiques de Barcelona, CSIC-IDIBAPS, Barcelona 08036, Spain
1 To whom correspondence should be addressed. Marcelo Farina: Fax: +55 (48) 3721-9672. E-mail: farina{at}ccb.ufsc.br and Cristina Suñol: Fax: +34 (93) 3638301. E-mail: csenqi{at}iibb.csic.es.
Received July 22, 2009; accepted August 29, 2009
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Abstract |
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Methylmercury (MeHg) is an environmental neurotoxicant whose molecular mechanisms underlying toxicity remain elusive. Here, we investigated molecular events involved in MeHg-induced neurotoxicity in cultured cerebellar granule cells (CGCs) as well as potential protective strategies for such toxicity. Glutathione peroxidase, isozyme 1 (GPx-1) activity was significantly (p = 0.0017) decreased at 24 h before MeHg-induced neuronal death (day in vitro 4). This event was related to enhanced susceptibilities to hydrogen peroxide or tert-butyl peroxide and increased lipid peroxidation. However, intracellular calcium levels, glutamate uptake, and glutathione levels, as well as glutathione reductase and catalase activities, were not changed by MeHg exposure at this time point. Probucol (PB), a lipid-lowering drug, displayed a long-lasting protective effect against MeHg-induced neurotoxicity. The beneficial effects of PB were correlated with increased GPx-1 activity and decreased lipid peroxidation. The protection afforded by PB was significantly higher when compared to the antioxidants, ascorbic acid and trolox. In vitro studies with the purified GPx-1 proved that MeHg inhibits and PB activates the enzyme activity. Overexpression of GPx-1 prevented MeHg-induced neuronal death. These data indicate that (1) GPx-1 is an important molecular target involved in MeHg-induced neurotoxicity and (2) PB, which increases GPx-1 activity in CGCs, induces enduring protection against such toxicity. The results bring out new insights on the potential therapeutic strategies for poisonings to MeHg and other pathological conditions related to increased production and/or decreased detoxification of peroxides.
Key Words: methylmercury; glutathione peroxidase-1; probucol; cerebellar granule cells; neurotoxicity.