Bioactivity of a peptide derived from acetylcholinesterase in hippocampal organotypic cultures.
While the molecular basis underlying the non-classical actions of acetylcholinesterase (AChE) is presently unknown, a candidate peptide sequence located at the C-terminus of AChE (AChE-peptide) has recently been identified. This study explored the bioactivity of synthetic AChE-peptide using in vitro organotypic cultures of rat hippocampus. Neurotrophic effects, detected as increased neurite outgrowth from MAP-immunopositive neurones, were apparent using 1 h exposure to 1-10 nM AChE-peptide. As exposure time increased, cell death occurred as indicated by TdT-mediated dUTP biotin nick-end labelling (TUNEL). This process was accelerated at higher AChE-peptide concentrations, with lactate dehydrogenase (LDH) efflux observed following prolonged exposure to 1-10 microM AChE-peptide. Apoptotic cells were detected by Hoechst 33342 staining following 24 h application of 10 nM AChE-peptide. However, propidium iodide reactivity revealed a simultaneous loss of membrane integrity indicative of necrosis, suggesting that AChE-peptide induces cell death via a continuum of apoptotic and necrotic processes. Prolonged exposure to AChE-peptide also resulted in a concentration-dependent reduction in neurite outgrowth from MAP2-positive neurons, although immunohistochemical studies provided some evidence of differential responsiveness in GABAergic, cholinergic and somatostatin neurones. In addition, bioactivity was sequence specific since a scrambled AChE-peptide analogue, as well as the corresponding BuChE-peptide, was ineffective. In conclusion, the bioactivity associated with the AChE-peptide sequence may account for the non-cholinergic actions of AChE, whilst its neurotrophic-apoptotic-necrotic spectrum of action may be involved in the aetiology of neurodegenerative disorders such as Alzheimer's disease.
Day
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University of Oxford, Department of Pharmacology, Mansfield Road, Oxford, OX1 3QT, UK.
Greenfield
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SA
D000110:Acetylcholinesterase / Q000378:metabolism*; D000544:Alzheimer Disease / Q000201:enzymology / Q000503:physiopathology; D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001483:Base Sequence / Q000502:physiology; D002450:Cell Communication / Q000502:physiology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009336:Necrosis; D009414:Nerve Growth Factors / Q000378:metabolism / Q000494:pharmacology; D016501:Neurites / Q000187:drug effects / Q000473:pathology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D009479:Neuropeptides / Q000378:metabolism* / Q000494:pharmacology; D009498:Neurotoxins / Q000378:metabolism* / Q000494:pharmacology; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology
D004791:Enzyme Inhibitors; D008869:Microtubule-Associated Proteins; D009414:Nerve Growth Factors; D009479:Neuropeptides; D009498:Neurotoxins; D007770:L-Lactate Dehydrogenase; D000110:Acetylcholinesterase