title: Synergistic neuroprotection by epicatechin and quercetin: Activation of convergent mitochondrial signaling pathways.
abstract: In view of evidence that increased consumption of epicatechin (E) and quercetin (Q) may reduce the risk of stroke, we have measured the effects of combining E and Q on mitochondrial function and neuronal survival following oxygen-glucose deprivation (OGD). Relative to mouse cortical neuron cultures pretreated (24h) with either E or Q (0.1-10μM), E+Q synergistically attenuated OGD-induced neuronal cell death. E, Q and E+Q (0.3μM) increased spare respiratory capacity but only E+Q (0.3μM) preserved this crucial parameter of neuronal mitochondrial function after OGD. These improvements were accompanied by corresponding increases in cyclic AMP response element binding protein (CREB) phosphorylation and the expression of CREB-target genes that promote neuronal survival (Bcl-2) and mitochondrial biogenesis (PGC-1α). Consistent with these findings, E+Q (0.1 and 1.0μM) elevated mitochondrial gene expression (MT-ND2 and MT-ATP6) to a greater extent than E or Q after OGD. Q (0.3-3.0μM), but not E (3.0μM), elevated cytosolic calcium (Ca(2+)) spikes and the mitochondrial membrane potential. Conversely, E and E+Q (0.1 and 0.3μM), but not Q (0.1 and 0.3μM), activated protein kinase B (Akt). Nitric oxide synthase (NOS) inhibition with L-N(G)-nitroarginine methyl ester (1.0μM) blocked neuroprotection by E (0.3μM) or Q (1.0μM). Oral administration of E+Q (75mg/kg; once daily for 5days) reduced hypoxic-ischemic brain injury. These findings suggest E and Q activate Akt- and Ca(2+)-mediated signaling pathways that converge on NOS and CREB resulting in synergistic improvements in neuronal mitochondrial performance which confer profound protection against ischemic injury.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Brain Repair Centre, Faculty of Medicine, Dalhousie University, Life Sciences Research Institute, 1348 Summer Street, P.O. Box 15000, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada. Electronic address: Matthew.Nichols@dal.ca.
authors.forename: M
authors.initials: M
authors.lastname: Nichols
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Brain Repair Centre, Faculty of Medicine, Dalhousie University, Life Sciences Research Institute, 1348 Summer Street, P.O. Box 15000, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada. Electronic address: Jin.Zhang@dal.ca.
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Anesthesiology, Center for Shock Trauma and Anesthesiology Research, University of Maryland School of Medicine, Baltimore, MD 21201, USA. Electronic address: bpolster@anes.umm.edu.
authors.forename: B M
authors.initials: BM
authors.lastname: Polster
authors.affiliation: Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada. Electronic address: pia.elustondo@dal.ca.
authors.forename: P A
authors.initials: PA
authors.lastname: Elustondo
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Brain Repair Centre, Faculty of Medicine, Dalhousie University, Life Sciences Research Institute, 1348 Summer Street, P.O. Box 15000, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada. Electronic address: Aruloli.Thirumaran@dal.ca.
authors.forename: A
authors.initials: A
authors.lastname: Thirumaran
authors.affiliation: Department of Basic Sciences, College of Dentistry, New York University, 345 East 24th Street, New York, NY 10010, USA. Electronic address: ep37@nyu.edu.
authors.forename: E V
authors.initials: EV
authors.lastname: Pavlov
authors.affiliation: Department of Pharmacology, Faculty of Medicine, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada; Department of Psychiatry, 5909 Veterans' Memorial Lane, 8th Floor Abbie J. Lane Memorial Building, QEII Health Sciences Centre, Halifax, Nova Scotia B3H 2E2, Canada. Electronic address: robertgs@dal.ca.
authors.forename: G S
authors.initials: GS
authors.lastname: Robertson
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D002118:Calcium / Q000378:metabolism; D002392:Catechin / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D015687:Cell Hypoxia / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D004357:Drug Synergism; D005947:Glucose / Q000172:deficiency; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000473:pathology / Q000502:physiology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology; D011794:Quercetin / Q000494:pharmacology*
chemical_list: D018696:Neuroprotective Agents; D002392:Catechin; D011794:Quercetin; D005947:Glucose; D002118:Calcium
keywords: cAMP response element-binding protein; flavonoid; mitochondria; neuroprotection; nitric oxide synthase; protein kinase B