Protective effects of flavonoids and two metabolites against oxidative stress in neuronal PC12 cells.
OBJECTIVE
Recent interest has focused on plant antioxidants as potentially useful neuroprotective agents. In most studies only the genuine forms of flavonoids were used, although they are rapidly metabolized. Therefore, we have compared protective activities of two flavonoids (luteolin, quercetin) and two of their bioavailable metabolites (3,4-DHPAA and 3,4-DHT) against oxidative stress, induced by peroxides (t-BHP, H(2)O(2)) and iron (FeSO(4)), in neuronal PC12 cells.


METHODS
We have measured their effect on the prevention of cell death (MTT assay), glutathione depletion (GSH assay), lipid peroxidation (MDA assay) and production of ROS (DCF assay). Differentiated PC12 cells were used as a model system of neuronal cells. The compounds (concentration range 6-25 micromol/L) were tested in preincubation and coincubation experiments.


RESULTS
In MTT and DCF assays all tested compounds showed excellent protection. When cells were exposed to peroxides, both metabolites increased GSH levels less efficiently than their parent flavonoids in both types of incubations. Following exposure to iron, only coincubation significantly prevented GSH depletion and the metabolites surprisingly mimicked the suppressive effect of flavonoids. MDA levels induced by all stressors were reduced more potently during coincubation than during preincubation with polyphenols. While the lipophilic metabolite 3,4-DHT exerted excellent antilipoperoxidant activity, the hydrophilic metabolite 3,4-DHPAA was less effective.


CONCLUSIONS
These results demonstrate that most of the protective effects of flavonoids against oxidative stress in PC12 cells are continued despite biodegradation of the parent flavonoids. In general, the lipophilic metabolite 3,4-DHT was more active than the hydrophilic 3,4-DHPAA.
Pavlica
Sanja
S
Institute of Biochemistry, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany.
Gebhardt
Rolf
R
D000818:Animals; D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D016877:Oxidants / Q000737:chemistry / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects*; D016716:PC12 Cells; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
D000975:Antioxidants; D005419:Flavonoids; D016877:Oxidants; D017382:Reactive Oxygen Species; D005978:Glutathione