The flavonoid, eriodictyol, induces long-term protection in ARPE-19 cells through its effects on Nrf2 activation and phase 2 gene expression.
OBJECTIVE
Eriodictyol, a flavonoid found in citrus fruits, is among the most potent compounds reported to protect human RPE cells from oxidative stress-induced cell death. The present study sought to determine whether eriodictyol-induced phase 2 protein expression further enhances the resistance of human ARPE-19 cells to oxidative stress.


METHODS
The ability of eriodictyol to activate Nrf2 and to induce the phase 2 proteins heme-oxygenase (HO)-1 and NAD(P)H:quinone oxidoreductase (NQO)-1, and the cellular antioxidant glutathione (GSH) were analyzed. Cytoprotection assays in ARPE-19 cells that were overexpressing HO-1 or NQO-1 were performed, cell survival after short-term and long-term eriodictyol treatment was compared, and the mechanism of protection using a dominant negative Nrf2 and shRNA specific for HO-1 was tested.


RESULTS
Eriodictyol induced the nuclear translocation of Nrf2, enhanced the expression of HO-1 and NQO-1, and increased the levels of intracellular glutathione. ARPE-19 cells that overexpress HO-1 or NQO-1 were more resistant to oxidative stress-induced cell death than control cells. Eriodictyol induced long-term protection significantly greater than its short-term protection. This effect was correlated temporally with the activation of Nrf2 and the induction of phase 2 enzymes and could be blocked with the use of a dominant negative Nrf2 and shRNA specific to HO-1.


CONCLUSIONS
These findings indicate that the greatest benefit from eriodictyol may be its ability to regulate gene expression and enhance multiple cellular defenses to oxidative injury.
Johnson
Jennifer
J
Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA.
Maher
Pamela
P
Hanneken
Anne
A
D000975:Antioxidants / Q000494:pharmacology*; D018929:Cell Culture Techniques; D002470:Cell Survival; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D044950:Flavanones / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000502:physiology*; D005978:Glutathione / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000235:genetics* / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D010957:Plasmids; D012333:RNA, Messenger / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D020122:tert-Butylhydroperoxide / Q000633:toxicity
D000975:Antioxidants; D044950:Flavanones; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D012333:RNA, Messenger; D020122:tert-Butylhydroperoxide; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D016660:NAD(P)H Dehydrogenase (Quinone); C447479:NQO1 protein, human; D005978:Glutathione; C007619:eriodictyol