Differential effect of dopamine catabolism and uptake inhibition on dopamine-induced calcium dysregulation and viability loss.
The present study was aimed at evaluating of the effects of dopamine (DA) toxicity on PC12 cells' calcium homeostasis, cellular viability, and free radical levels. Moreover, the effect of receptor inhibition, and DA metabolism and reuptake antagonism on all parameters was also evaluated. Acute treatment with DA impaired the ability of PC12 cells to buffer excess calcium after K+-depolarization, decreased cellular viability by approximately 35%, and increased free radical levels by about 10% in a dose dependent manner. Pretreatment with both active and inactive pargyl monoamine oxidase inhibitors (MAOi) protected PC12 cells from DA toxicity on cellular viability and free radical levels, regardless of the presence or absence of their target enzymes in PC12 cells. These results suggest a lack of specific involvement of DA metabolism by MAO in dopamine's effects on cellular viability and production of free radicals. However, DA-induced dysregulation of calcium homeostasis seems to be more specifically mediated by DA metabolism by MAO. Results indicate that, in order for toxicity to occur the DA must be taken up into the cells. DA receptors do not mediate dopamine cytoxicity, and the D2 receptor plays a modest role in DA-induced calcium dysregulation and generation of free radicals. Moreover, DA-induced cell viability loss is not mediated by calcium, nor by caspase-3 enzyme, but is prevented by inhibition of mitochondrial permeability transition pores.
Cantuti-Castelvetri
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Laboratory of Neuroscience, United States Department of Agriculture, Jean Mayer Human Nutrition Research Center on Aging at Tufts University, Boston, MA 02111, USA. castelvet_ne@hnrc.tufts.edu
Joseph
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JA
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes; D005609:Free Radicals; D006706:Homeostasis / Q000187:drug effects*; D007700:Kinetics; D008995:Monoamine Oxidase / Q000378:metabolism; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D009627:Nomifensine / Q000494:pharmacology; D016716:PC12 Cells; D010293:Pargyline / Q000494:pharmacology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D017448:Receptors, Dopamine D2 / Q000502:physiology; D013134:Spiperone / Q000494:pharmacology
D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D018765:Dopamine Uptake Inhibitors; D005456:Fluorescent Dyes; D005609:Free Radicals; D008996:Monoamine Oxidase Inhibitors; D017382:Reactive Oxygen Species; D017448:Receptors, Dopamine D2; D009627:Nomifensine; D013134:Spiperone; D010293:Pargyline; D008995:Monoamine Oxidase; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D002118:Calcium; D004298:Dopamine