Curcumin protects against NMDA-induced toxicity: a possible role for NR2A subunit.
OBJECTIVE
Curcumin, a phenolic compound extracted from the rhizome of Curcuma longa, was found to attenuate NMDA-induced excitotoxicity in primary retinal cultures. This study was conducted to further characterize curcumin neuroprotective ability and analyze its effects on NMDA receptor (NMDAr).


METHODS
NMDAr modifications were analyzed in primary retinal cell cultures using immunocytochemistry, whole-cell patch-clamp recording and western blot analysis. Cell death was evaluated with the TUNEL assay in primary retinal and hippocampal cultures. Optical fluorometric recordings with Fura 2-AM were used to monitor [Ca(2+)](i).


RESULTS
Curcumin dose- and time-dependently protected both retinal and hippocampal neurons against NMDA-induced cell death, confirming its anti-excitotoxic property. In primary retinal cultures, in line with the observed reduction of NMDA-induced [Ca(2+)](i) rise, whole-cell patch-clamp experiments showed that a higher percentage of retinal neurons responded to NMDA with low amplitude current after curcumin treatment. In parallel, curcumin induced an increase in NMDAr subunit type 2A (NR2A) level, with kinetics closely correlated to time-course of neuroprotection and decrease in [Ca(2+)](i). The relation between neuroprotection and NR2A level increase was also in line with the observation that curcumin neuroprotection required protein synthesis. Electrophysiology confirmed an increased activity of NR2A-containing NMDAr at the plasma membrane level.


CONCLUSIONS
These results confirm the neuroprotective activity of curcumin against NMDA toxicity, possibly related to an increased level of NR2A, and encourage further studies for a possible therapeutic use of curcumin based on neuromodulation of NMDArs.
Matteucci
Andrea
A
Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Rome. andrea.matteucci@iss.it
Cammarota
Roberta
R
Paradisi
Silvia
S
Varano
Monica
M
Balduzzi
Maria
M
Leo
Lanfranco
L
Bellenchi
Gian C
GC
De Nuccio
Chiara
C
Carnovale-Scalzo
Giovanna
G
Scorcia
Giovanni
G
Frank
Claudio
C
Mallozzi
Cinzia
C
Di Stasi
Annamaria M
AM
Visentin
Sergio
S
Malchiodi-Albedi
Fiorella
F
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003474:Curcumin / Q000494:pharmacology*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D006624:Hippocampus / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D007608:Kainic Acid / Q000633:toxicity; D016202:N-Methylaspartate / Q000633:toxicity*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D012160:Retina / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000633:toxicity
D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; C120997:NR2A NMDA receptor; D018696:Neuroprotective Agents; D016194:Receptors, N-Methyl-D-Aspartate; D016202:N-Methylaspartate; D016291:Dizocilpine Maleate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D003474:Curcumin; D007608:Kainic Acid; D002118:Calcium