Modeling the Developmental Neurotoxicity of Chlorpyrifosin Vitro:Macromolecule Synthesis in PC12 Cells

Adverse Neurodevelopmental Effects of Dexamethasone Modeled in PC12 Cells: Identifying the Critical Stages and Concentration Thresholds for the Targeting of Cell Acquisition, Differentiation and Viability

“…Previous studies indicate that cell replication continues, albeit at a reduced rate, for at least 10 days after the addition of NGF (Song et al, 1998), and in keeping with that finding, DNA content continued to rise through 264 h in culture ( Figure 3a); indeed, the total number of cells approximately doubled between 168 h and 264 h. When DEX was administered from the outset of differentiation (ie simultaneously with the addition of NGF), it still elicited significant reductions in cell number, albeit to a lesser extent than had been seen in undifferentiated cells. The lowest concentration produced about 10% inhibition whereas deficits were about 30% at higher DEX concentrations.…”

“…As described previously (Song et al, 1998) PC12 cells (American Type Culture Collection, 1721-CRL) were grown in RPMI-1640 medium (Invitrogen, Carlsbad, CA) supplemented with 10% inactivated horse serum (Sigma Chemical Co., St Louis, MO), 5% fetal bovine serum (Sigma), and 50 mg/ml penicillin-streptomycin (Invitrogen); the added sera thus expose the cells to endogenous glucocorticoids. Cells were incubated with 7.5% CO 2 at 371C and the medium was changed every 2-3 days.…”

“…In the current study, we utilized rat pheochromocytoma PC12 cells, a model for evaluating neuronal cell replication and differentiation (Teng and Greene, 1994). In the presence of nerve growth factor (NGF), the cells gradually exit the mitotic cycle and begin to differentiate, developing axonal projections, electrical excitability, and the characteristics of two distinct phenotypes, cholinergic, and catecholaminergic neurons (Fujita et al, 1989;Song et al, 1998;Teng and Greene, 1994). These specific phenotypes are highly targeted by DEX treatment in vivo (Ebert et al, 1997;Hu et al, 1996;Kreider et al, 2005aKreider et al, , b, 2006Reznikov et al, 2004;Slotkin et al, 1991;Zahalka et al, 1993).…”

“…Accordingly, the PC12 model is particularly appropriate to evaluate the mechanisms underlying the effects of DEX on neural cell replication and differentiation into defined phenotypes. Indeed, the medium required to maintain PC12 cell replication, differentiation, and growth entails the use of sera containing endogenous glucocorticoids (Qiao et al, 2005;Song et al, 1998;Teng and Greene, 1994), so that, as with the situation in vivo, effects of DEX are exerted over and above the requisite normal concentration required to maintain neural cell development. At the same time, as with all in vitro models, the cell cultures lack many features common to the developing brain, including the ability to evaluate neuronalglial interactions or more architectural aspects of regional development.…”

“…Each neural cell contains only a single nucleus (Winick and Noble, 1965), so that the DNA content reflects the total number of cells (Song et al, 1998); since DEX arrests mitosis in the G 0 /G 1 phase (Greenberg et al, 2002), this relationship holds true even where DEX treatment affects cell acquisition. Indices of growth were provided by measurements of protein subfractions related to cell size and membrane surface area (Thai et al, 1996).…”