Metallothioneins attenuate methylmercury-induced neurotoxicity in cultured astrocytes and astrocytoma cells.
Metallothionein-I (MT-I) was expressed in neonatal rat primary astrocyte cultures and an astrocytoma cell line by pGFAP-MT-I plasmid transfection under the control of the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter. Following transient transfection of the pGFAP-MT-I plasmid, MT-I mRNA and MT-I protein levels were determined by Northern blot and immunoprecipitation analyses, respectively. The ability of cells overexpressing MT-I to withstand acute methylmercury (MeHg) treatment was measured by the release of preloaded Na2(51)CrO4, an indicator of membrane integrity. Transfection with the pGFAP-MT-I plasmid led to increased mRNA (2.5-fold in astrocytes and 7.4-fold in astrocytomas) and MT-I protein (2.4-fold in astrocytes and 4.0-fold in astrocytomas) levels compared with their respective controls. Increased expression of MT-I was associated with attenuated release of Na2(51)CrO4 upon MeHg (5 microM) treatment. These results demonstrate that MT-I can be highly expressed both in primary astrocyte cultures and astrocytomas by pGFAP-MT-I plasmid transfection, and lend credence to the hypothesis that increased expression of MT-I affords protection against the cytotoxic effects of MeHg. Taken together, the data suggest that MTs offer effective cellular adaptation of MeHg cytotoxicity.
Yao
C P
CP
Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157-1083, USA.
Allen
J W
JW
Aschner
M
M
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001254:Astrocytoma / Q000378:metabolism*; D002478:Cells, Cultured; D005904:Glial Fibrillary Acidic Protein / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008668:Metallothionein / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008767:Methylmercury Compounds / Q000494:pharmacology; D010957:Plasmids / Q000008:administration & dosage; D051381:Rats; D014162:Transfection / Q000235:genetics
D005904:Glial Fibrillary Acidic Protein; D008767:Methylmercury Compounds; D008668:Metallothionein