Effects of lead on viability and intracellular metal content of c6 rat glioma cells

Abstract

Cultured C6 rat glioma cells were exposed to lead (Pb) acetate (0, 1, 10, or 100 microM) for 3-4 d. Cells were analyzed for changes in viability and intracellular lead, iron, and copper concentrations after Pb treatment was discontinued. The results were compared with previous findings on astroglia and oligodendroglia in culture in order to evaluate C6 cultures as a model for Pb toxicity in glia. Viability was measured by three methods on the day Pb was removed from the cells (designated d 0), and 2 and 9 d after Pb treatment was discontinued (designated d 2 and 9). The methods used were trypan blue dye exclusion, total cell counts, and incorporation of [3H]-L-leucine into proteins. Small, dose-dependent reductions were observed on d 2 in the percentages of cells excluding dye. Decreased cell numbers were seen at all three Pb doses only on d 0. With respect to these two viability measurements, C6 cells responded like astroglia in culture to Pb, but not like oligodendroglia, which are more Pb-sensitive. We expected decreased amino acid incorporation to accompany the decreased viability of the cultures. Instead, increased amino acid incorporation, which indicates increased protein synthesis, was seen on d 0 and 2 at all three Pb doses, though total cellular protein did not increase. A similar response has been reported previously in oligodendroglial cultures. C6 cells treated for 3 with 1 or 100 microM Pb acetate were analyzed for intracellular metal content by atomic absorption aspectroscopy on d 4 and 11 after exposure to Pb was discontinued. The cells were found to take up large amounts of Pb intracellularly and store it for at least 11 d. Cells treated with FeCl2 instead of Pb took up Fe, but required a higher extracellular Fe concentration to achieve an intracellular Fe level comparable to that of Pb in Pb-treated cells. Pb uptake did not affect intracellular Fe or Cu concentrations. With respect to Pb and Fe uptake, C6 cells closely resembled immature astroglia in culture. Unlike C6 cells, however, astroglia showed elevations of intracellular Fe and Cu after Pb treatment. Thus, Pb effects on C6 cells resembled those on cultured oligodendroglia and astroglia in some respects but not in others. C6 cells appear to be an adequate model for selected events in glial toxicosis, such as Pb-stimulated protein synthesis in oligodendroglia and Pb uptake in astroglia, but not Pb-induced alterations of intracellular Cu and Fe in astroglia. Their use as a model for glial progenitor cells in Pb toxicity studies remains to be determined.

Induction of 78 kD glucose-regulated protein (GRP78) expression and redox-regulated transcription factor activity by lead and mercury in C6 rat glioma cells

“…Based on these examples, :induction of GRP78 by heavy metals in glia may have a role in neuroprotection. In the case of Pb, which has been studied in a temporal context in astroglia, C6 cells, and neuroblastoma cells, we propose the following model for cells chronically exposed to low levels of Pb (i.e., ---1 ~M in serum-containing medium, corresponding to blood Pb levels <-20 ~g/dl): (1) Pb crosses the plasma membrane of the cell and is accumulated intracellularly, as in astroglia (Holtzman et al, 1984;Tiffany-Castiglioni et aL, 1987) or C6 rat glioma cells (Tiffany-Castiglioni et al, 1988;Qian et al, 1999). Alternatively, Pb is excluded from the cell, as in the case of mature neurons (Holtzman et aL, 1984) or differentiated neuroblastoma cells (Lindahl et al, 1999); (2) Intracellular Pb binds strongly to GRP78 (Qian et al, 2000); (3) Functions of the endoplasmic reticulum are disrupted, including protein folding and protein trafficking to the trans-Golgi network; (4) ER stress signals induce grp78 gene expression; (5) GRP78 synthesis increases, which restores ER functions and/or facilitates Pb transport to other sites for sequestration or externalization.…”

Protective Effect of Ajuga multiflora BUNGE Extract on Lead Toxicity of Environmental Pollutant

“…Lead is a bluish-white tint heavy metal with atomic number 82, and exists as an oxide, such as lead monoxide (PbO), or as a salt form, such as lead sulfate (PbSO 4 ), in the natural world. Lead is widely used as a material in various fields, for instance, for storage batteries in industrial processes, paint, ceramics, toys as well as printing business (Tiffany et al, 1988). In particular, lead turns to dust or fumes at a high temperature in processes, and thus can be absorbed through skin or respiratory system, and the absorbed LA.…”

Potencial evocado auditivo cortical, análise bioquímica e morfológica em cérebro de ratos submetidos a tratamento subcrônico com chumbo: efeito protetor da suplementação com ferro

“…Foram utilizados os PEAC, sendo estes registrados com o uso de eletrodos de superfície e medida a latência absoluta dos componentes P1, N1 e P2, as quais foram passíveis de registros em todos os animais avaliados, corroborando com os estudos da literatura que utilizaram eletrodos de superfície, e ou implantáveis (SHAW, 1995;SHINBA, 1997;EHLERS et al, 1998;SHINBA, 1999;SHINBA, 2002;LAZAR;METHERATE, 2003;SAKATA;ONODA, 2006 -CASTIGLIONI et al, 1987-CASTIGLIONI et al, , 1988WANG et al, 2007aWANG et al, , 2007b…”