Simvastatin reduces the association of NMDA receptors to lipid rafts: a cholesterol-mediated effect in neuroprotection.
OBJECTIVE
Excess brain extracellular glutamate induced by cerebral ischemia leads to neuronal death, mainly through overactivation of N-methyl-D-aspartate (NMDA) receptors. The cholesterol-lowering drugs statins have been reported to protect from NMDA-induced neuronal death but, so far, the mechanism underlying this protection remains unclear. Because NMDA receptors have been reported to be associated with the cholesterol-rich membrane domains known as lipid rafts, we have investigated the effect of treatments that deplete cholesterol levels on excitotoxicity and on association of NMDA receptors to lipid rafts.


METHODS
Primary neuronal cultures were pretreated with inhibitors of cholesterol synthesis and cholesterol, and NMDA-induced cell death was determined by measuring release of lactate dehydrogenase. Lipid raft fractions were isolated and Western blots were performed.


RESULTS
Treatment with the inhibitors of cholesterol synthesis simvastatin, which inhibits the first step of cholesterol synthesis, or AY9944, which inhibits the last step of cholesterol synthesis, protected neurons from NMDA-induced neuronal death by 70% and 54%, respectively. Treatment with these compounds reduced neuronal cholesterol levels by 35% and 13%, respectively. Simvastatin and AY9944 reduced the association of the subunit 1 of NMDA receptors (NMDAR1) to lipid rafts by 42% and 21%, respectively, and did not change total expression of NMDAR1. Addition of cholesterol reduced neuroprotection by statins and AY9944, and partially reverted the effect of simvastatin on the association of NMDAR1 to lipid rafts.


CONCLUSIONS
These data demonstrate that reduction of cholesterol levels protects from NMDA-induced neuronal damage probably by reducing the association of NMDA receptors to lipid rafts.
Ponce
Jovita
J
Neuroscience Basic Research Lab, Fundació Institut d'Investigació en Ciències de Salut Germans Trias i Pujol, Badalona, Spain.
de la Ossa
Natalia Pérez
NP
Hurtado
Olivia
O
Millan
Mónica
M
Arenillas
Juan F
JF
Dávalos
Antonio
A
Gasull
Teresa
T
D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D002784:Cholesterol / Q000096:biosynthesis / Q000378:metabolism; D005260:Female; D021962:Membrane Microdomains / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009498:Neurotoxins / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D019821:Simvastatin / Q000494:pharmacology*; D001371:trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride / Q000494:pharmacology
D000924:Anticholesteremic Agents; D018696:Neuroprotective Agents; D009498:Neurotoxins; D016194:Receptors, N-Methyl-D-Aspartate; D001371:trans-1,4-Bis(2-chlorobenzaminomethyl)cyclohexane Dihydrochloride; D002784:Cholesterol; D019821:Simvastatin