Ascorbic acid efficiently enhances neuronal synthesis of norepinephrine from dopamine
| Autor: | Zhi-chao Qu, Rafal R. Nazarewicz, Sergey Dikalov, James M. May |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
medicine.medical_specialty
Dopamine Ascorbic Acid Dopamine beta-Hydroxylase Article Antioxidants Norepinephrine (medication) Neuroblastoma Norepinephrine chemistry.chemical_compound Superoxides Cell Line Tumor Internal medicine Extracellular medicine Humans Neurons HEPES Analysis of Variance Dose-Response Relationship Drug Chemistry Superoxide General Neuroscience Extracellular Fluid Ascorbic acid Dehydroascorbic Acid Glutathione Endocrinology Dehydroascorbic acid Intracellular medicine.drug |
| Zdroj: | Brain Research Bulletin. 90:35-42 |
| ISSN: | 0361-9230 |
| Popis: | Ascorbic acid enhances synthesis of norepinephrine from dopamine in adrenal chromaffin cells by serving as a co-factor for chromaffin granule dopamine β-hydroxylase (DβH). However, there is controversy regarding in situ kinetics of the ascorbate effect in chromaffin cells, as well as whether they apply to neuronal cells. In this study we evaluated the stimulation of norepinephrine synthesis from dopamine in cultured SH-SY5Y neuroblastoma cells. These cells contained neither ascorbate nor norepinephrine in culture, but when provided with dopamine, they generated intracellular norepinephrine at rates that were stimulated several fold by intracellular ascorbate. Ascorbate-induced increases in norepinephrine synthesis in dopamine-treated cells were linear over 60 minutes, despite saturation of intracellular ascorbate. Norepinephrine accumulation after 60 minutes of incubation with 100 μM dopamine was half-maximal at intracellular ascorbate concentrations of 0.2 – 0.5 mM, which fits well with the literature Km for ascorbate of DβH using dopamine as a substrate. Moreover, these ascorbate concentrations were generated by initial extracellular ascorbate concentrations of less than 25 μM due to concentrative accumulation by the ascorbate transporter. Treatment with 100 μM dopamine acutely increased cellular superoxide generation, which was prevented by ascorbate loading, but associated with a decrease in intracellular ascorbate when the latter was present at concentrations under 1 mM. These results show that ascorbate promptly enhances norepinephrine synthesis from dopamine by neuronal cells, that it does so at physiologic intracellular concentrations in accord with the kinetics of DβH, and that it both protects cells from superoxide and by providing electrons to DβH. |
| Databáze: | OpenAIRE |
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