title: Neuroprotective effects of naturally occurring polyphenols on quinolinic acid-induced excitotoxicity in human neurons.
abstract: Quinolinic acid (QUIN) excitotoxicity is mediated by elevated intracellular Ca(2+) levels, and nitric oxide-mediated oxidative stress, resulting in DNA damage, poly(ADP-ribose) polymerase (PARP) activation, NAD(+) depletion and cell death. We evaluated the effect of a series of polyphenolic compounds [i.e. epigallocatechin gallate (EPCG), catechin hydrate, curcumin, apigenin, naringenin and gallotannin] with antioxidant properties on QUIN-induced excitotoxicity on primary cultures of human neurons. We showed that the polyphenols, EPCG, catechin hydrate and curcumin can attenuate QUIN-induced excitotoxicity to a greater extent than apigenin, naringenin and gallotannin. Both EPCG and curcumin were able to attenuate QUIN-induced Ca(2+) influx and neuronal nitric oxide synthase (nNOS) activity to a greater extent compared with apigenin, naringenin and gallotannin. Although Ca(2+) influx was not attenuated by catechin hydrate, nNOS activity was reduced, probably through direct inhibition of the enzyme. All polyphenols reduced the oxidative effects of increased nitric oxide production, thereby reducing the formation of 3-nitrotyrosine and poly (ADP-ribose) polymerase activity and, hence, preventing NAD(+) depletion and cell death. In addition to the well-known antioxidant properties of these natural phytochemicals, the inhibitory effect of some of these compounds on specific excitotoxic processes, such as Ca(2+) influx, provides additional evidence for the beneficial health effects of polyphenols in excitable tissue, particularly within the central nervous system.
authors.affiliation: University of New South Wales, Faculty of Medicine, Sydney, Australia.
authors.forename: Nady
authors.initials: N
authors.lastname: Braidy
authors.forename: Ross
authors.initials: R
authors.lastname: Grant
authors.forename: Seray
authors.initials: S
authors.lastname: Adams
authors.forename: Gilles J
authors.initials: GJ
authors.lastname: Guillemin
mesh_terms: D047310:Apigenin / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D002478:Cells, Cultured; D003474:Curcumin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D044950:Flavanones / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D047348:Hydrolyzable Tannins / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D010636:Phenols / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D059808:Polyphenols; D017378:Quinolinic Acid / Q000037:antagonists & inhibitors* / Q000633:toxicity*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000096:biosynthesis
chemical_list: D044950:Flavanones; D005419:Flavonoids; D047348:Hydrolyzable Tannins; D018696:Neuroprotective Agents; D010636:Phenols; D059808:Polyphenols; D009243:NAD; C002744:3-nitrotyrosine; D014443:Tyrosine; D047310:Apigenin; D002392:Catechin; C045651:epigallocatechin gallate; D007770:L-Lactate Dehydrogenase; C496320:NOS1 protein, human; D052248:Nitric Oxide Synthase Type I; D011065:Poly(ADP-ribose) Polymerases; D017378:Quinolinic Acid; C005273:naringenin; D003474:Curcumin