Protection by cholesterol-extracting cyclodextrins: a role for N-methyl-D-aspartate receptor redistribution.
Cyclodextrins (CDs) are cyclic oligosaccharides composed of a lipophilic central cavity and a hydrophilic outer surface. Some CDs are capable of extracting cholesterol from cell membranes and can affect function of receptors and proteins localized in cholesterol-rich membrane domains. In this report, we demonstrate the neuroprotective activity of some CD derivatives against oxygen-glucose deprivation (OGD), N-methyl-D-aspartic acid (NMDA) and glutamate in cortical neuronal cultures. Although all CDs complexed with NMDA or glutamate, only beta-, methylated beta- and sulfated beta-CDs displayed neuroprotective activity and lowered cellular cholesterol. Only CDs that lowered cholesterol levels redistributed the NMDA receptor NR2B subunit, PSD-95 (postsynaptic density protein 95 kDa) and neuronal nitric oxide synthase (nNOS) from Triton X-100 insoluble membrane domains to soluble fractions. Cholesterol repletion counteracted the ability of methylated beta-CD to protect against NMDA toxicity, and reversed NR2B, PSD-95 and nNOS localization to Triton X-100 insoluble membrane fraction. Surprisingly, neuroprotective CDs had minimal effect on NMDA receptor-mediated increases in intracellular Ca(2+) concentration ([Ca(2+)](i)), but did suppress OGD-induced increases in [Ca(2+)](i). beta-CD, but not Mbeta-CD, also caused a slight block of NMDA-induced currents, suggesting a minor contribution to neuroprotection by direct action on NMDA receptors. Taken together, data suggest that cholesterol extraction from detergent-resistant microdomains affects NMDA receptor subunit distribution and signal propagation, resulting in neuroprotection of cortical neuronal cultures against ischemic and excitotoxic insults. Since cholesterol-rich membrane domains exist in neuronal postsynaptic densities, these results imply that synaptic NMDA receptor subpopulations underlie excitotoxicity, which can be targeted by CDs without affecting overall neuronal Ca(2+) levels.
Abulrob
Abedelnasser
A
Cerebrovascular Research Group, Institute for Biological Sciences, National Research Council of Canada, 1200 Montreal Road, Ottawa, Ontario, K!A 0R6, Canada.
Tauskela
Joseph S
JS
Mealing
Geoff
G
Brunette
Eric
E
Faid
Karim
K
Stanimirovic
Danica
D
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D003505:Cyclodextrins / Q000494:pharmacology*; D019610:Cytoprotection / Q000187:drug effects* / Q000502:physiology; D000076122:Disks Large Homolog 4 Protein; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D020925:Hypoxia-Ischemia, Brain / Q000188:drug therapy / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D021962:Membrane Microdomains / Q000187:drug effects* / Q000378:metabolism; D008565:Membrane Proteins; D008745:Methylation; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors / Q000378:metabolism; D009410:Nerve Degeneration / Q000188:drug therapy / Q000378:metabolism / Q000517:prevention & control; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D009498:Neurotoxins / Q000037:antagonists & inhibitors / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D051381:Rats; D011940:Receptor Aggregation / Q000187:drug effects / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects* / Q000378:metabolism; D013457:Sulfur Compounds / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D003505:Cyclodextrins; D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D018691:Excitatory Amino Acid Antagonists; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C121001:NR2B NMDA receptor; D009419:Nerve Tissue Proteins; D018696:Neuroprotective Agents; D009498:Neurotoxins; D016194:Receptors, N-Methyl-D-Aspartate; D013457:Sulfur Compounds; C033652:postsynaptic density proteins; D018698:Glutamic Acid; D016202:N-Methylaspartate; D002784:Cholesterol; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D002118:Calcium