Aging potentiates Abeta-induced depletion of SNAP-25 in mouse hippocampus.
Previously we showed that in Tg2576 mouse hippocampus, synaptosomal-associated protein 25 (SNAP-25) immunoreactivity (IR) is greatly reduced and intracerebroventricular injection of anti-Abeta reverses this depletion. 3- and 24-month-old wild-type mice received juxta-amygdala injection of Abeta42 and hippocampal sections were analyzed for glial fibrillary acidic protein (GFAP)- and SNAP-25-IR at intervals after injections. In young mice, SNAP-IR declined >95% at 1 week in DG-Smi and remained low until 8 weeks, while decreasing in SR, SL and hilum by 8-27% at 1 week and returning to baseline by 2 weeks. There was no change in DG-SMm. In old mice, DG-Smi was specifically depleted in SNAP-IR by >95% even before injection. At 2 weeks, SNAP-IR had declined in all layers by 30-39% of baseline values and by 8 weeks had returned to control values, except the DG-SMm which showed only a 10% reduction at 2 weeks. Baseline GFAP-IR was 10-fold higher in old than in young mice in the fimbria/IC but not appreciably changed in hippocampus. In young mice, the injections of Abeta caused 20-fold increases in GFAP-IR in the fimbria/IC and 2-fold increases in the hippocampal neuropil at 1 week, all of which values returned to baseline by 8 weeks. In old mice, Abeta injections caused relatively much larger increases in GFAP-IR in the hippocampal neuropil than in the fimbria/IC and the GFAP-IR remained greatly increased at 8 weeks.


CONCLUSIONS
the Abeta effect on presynaptic SNAP-25 depletion is increased with age. DG-SMi shows the most severe changes and therefore may represent the most critical site in hippocampus for Abeta neurotoxicity.
Chauhan
Neelima B
NB
Neurology Service (127), Edward Hines Jr VA Hospital, Hines, IL 60141, USA.
Lichtor
Terry
T
Siegel
George J
GJ
D000375:Aging / Q000187:drug effects* / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000494:pharmacology*; D000818:Animals; D006624:Hippocampus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D050825:Synaptosomal-Associated Protein 25; D013997:Time Factors
D016229:Amyloid beta-Peptides; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C494209:Snap25 protein, mouse; D050825:Synaptosomal-Associated Protein 25