Dynorphin A (1-17) induces apoptosis in striatal neurons in vitro through alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate/kainate receptor-mediated cytochrome c release and caspase-3 activation.
Dynorphin A (1-17), an endogenous opioid neuropeptide, can have pathophysiological consequences at high concentrations through actions involving glutamate receptors. Despite evidence of excitotoxicity, the basic mechanisms underlying dynorphin-induced cell death have not been explored. To address this question, we examined the role of caspase-dependent apoptotic events in mediating dynorphin A (1-17) toxicity in embryonic mouse striatal neuron cultures. In addition, the role of opioid and/or glutamate receptors were assessed pharmacologically using dizocilpine maleate (MK(+)801), a non-equilibrium N-methyl-D-aspartate (NMDA) antagonist; 6-cyano-7-nitroquinoxaline-2,3-dione, a competitive alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate antagonist; or (-)-naloxone, a general opioid antagonist. The results show that dynorphin A (1-17) (>or=10 nM) caused concentration-dependent increases in caspase-3 activity that were accompanied by mitochondrial release of cytochrome c and the subsequent death of cultured mouse striatal neurons. Moreover, dynorphin A-induced neurotoxicity and caspase-3 activation were significantly attenuated by the cell permeable caspase inhibitor, caspase-3 inhibitor-II (z-DEVD-FMK), further suggesting an apoptotic cascade involving caspase-3. AMPA/kainate receptor blockade significantly attenuated dynorphin A-induced cytochrome c release and/or caspase-3 activity, while NMDA or opioid receptor blockade typically failed to prevent the apoptotic response. Last, dynorphin-induced caspase-3 activation was mimicked by the ampakine CX546 [1-(1,4-benzodioxan-6-ylcarbonyl)piperidine], which suggests that the activation of AMPA receptor subunits may be sufficient to mediate toxicity in striatal neurons. These findings provide novel evidence that dynorphin-induced striatal neurotoxicity is mediated by a caspase-dependent apoptotic mechanism that largely involves AMPA/kainate receptors.
Singh
I N
IN
Department of Anatomy and Neurobiology, University of Kentucky College of Medicine, 800 Rose Street, Lexington, KY 40536-0298, USA.
Goody
R J
RJ
Goebel
S M
SM
Martin
K M
KM
Knapp
P E
PE
Marinova
Z
Z
Hirschberg
D
D
Yakovleva
T
T
Bergman
T
T
Bakalkin
G
G
Hauser
K F
KF
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology*; D005260:Female; D051379:Mice; D008813:Mice, Inbred ICR; D009474:Neurons / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D011247:Pregnancy; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000378:metabolism; D018092:Kainic Acid Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism
D053148:Caspase 3; D020169:Caspases; D045304:Cytochromes c; D004399:Dynorphins; D018691:Excitatory Amino Acid Antagonists; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; C505409:Casp3 protein, mouse