Early, transient increase in complexin I and complexin II in the cerebral cortex following traumatic brain injury is attenuated by N-acetylcysteine.
Alteration of excitatory neurotransmission is a key feature of traumatic brain injury (TBI) in which extracellular glutamate levels rise. Although increased synaptic release of glutamate occurs at the injury site, the precise mechanism is unclear. Complexin I and complexin II constitute a family of cytosolic proteins involved in the regulation of neurotransmitter release, competing with the chaperone protein alpha-SNAP (soluble N-ethylmaleimide-sensitive factor-attachment protein) for binding to the synaptic vesicle protein synaptobrevin as well as the synaptic membrane proteins SNAP-25 and syntaxin, which together form the SNAP receptor (SNARE) complex. Complexin I is predominantly a marker of axosomatic (inhibitory) synapses, whereas complexin II mainly labels axodendritic and axospinous synapses, the majority of which are excitatory. In order to examine the role of these proteins in TBI, we have studied levels of both complexins in the injured hemisphere by immunoblotting over a time period ranging from 6 h to 7 days following lateral fluid-percussion brain injury in the rat. Transient increases in the levels of complexin I and complexin II proteins were detected in the injured cerebral cortex 6 h following TBI. This increase was followed by a decrease of complexin I in the injured cortex and hippocampus, and a decrease in both complexins in the injured thalamus region at day 3 and day 7 post-injury. The early, transient increase in the injured cortex was completely blocked by N-acetylcysteine (NAC) administered 5 min following trauma, suggesting an involvement of oxidative stress. Neuronal loss was also reduced in the injured hemisphere with post-TBI NAC treatment. Our findings suggest a dysregulation of both inhibitory and excitatory neurotransmission following traumatic injury that is responsive to antioxidant treatment. These alterations in complexin levels may also play an important role in neuronal cell loss following TBI, and thus contribute to the pathophysiology of cerebral damage following brain injury.
Yi
Jae-Hyuk
JH
Department of Medicine, Hôpital Saint-Luc, University of Montreal, Montreal, Quebec, Canada.
Hoover
Rachel
R
McIntosh
Tracy K
TK
Hazell
Alan S
AS
D000111:Acetylcysteine / Q000494:pharmacology* / Q000627:therapeutic use; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D001930:Brain Injuries / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D002540:Cerebral Cortex / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D004195:Disease Models, Animal; D016166:Free Radical Scavengers / Q000494:pharmacology / Q000627:therapeutic use; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D009410:Nerve Degeneration / Q000378:metabolism / Q000503:physiopathology; D009419:Nerve Tissue Proteins / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D050600:SNARE Proteins / Q000187:drug effects / Q000378:metabolism; D013570:Synaptic Membranes / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D033942:Adaptor Proteins, Vesicular Transport; D016166:Free Radical Scavengers; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D050600:SNARE Proteins; C095992:complexin I; C095993:complexin II; D018698:Glutamic Acid; D000111:Acetylcysteine