SEIZURE INHIBITION AND DELAYED EPILEPTOGENESIS BY [italic] IN VIVO[/italic] rAAV-MEDIATED NEUROPEPTIDE Y GENE TRANSFER
Abstract number :
D.01
Submission category :
Year :
2003
Submission ID :
3615
Source :
www.aesnet.org
Presentation date :
12/6/2003 12:00:00 AM
Published date :
Dec 1, 2003, 06:00 AM
Authors :
Cristina Richichi, Deborah E. Lin, Daniela Stefanin, Daniele Colella, Giuliano Grignaschi, Gunther Sperk, Matthew J. During, Annamaria Vezzani Neuroscience, Mario Negri Inst for Pharmacol Res, Milano, Italy; Molecular Medicine, University of Auckland, Auc
We investigated the effect of long-term neuropeptide Y (NPY) gene transduction in the rat hippocampus on epileptogenesis and limbic seizures using a recombinant adeno-associated viral vector (rAAV).
rAAV carrying the NPY gene under the control of neuronal enolase promoter (2 [mu]l rAAV-NSE-NPY, 4.2x108) was injected in both septal and temporal aspects of the rat hippocampus bilaterally. Controls were rats injected with equivalent volumes of empty-vector. Two different rAAV-NSE-NPY vectors were used with serotype 2 or serotype 1 and 2 capsid proteins respectively. Four to 8 weeks after gene delivery, rats were implanted with hippocampal and cortical electrodes for EEG analysis of seizures. One week after surgery, rAAV-NSE-NPY rats and their controls (n= 6-8 each exp group) were injected intrahippocampally (ih, 40 ng) or intracerebroventricularly (icv, 250 ng) with kainic acid or electrically stimulated in the ventral hippocampus according to a well established fast kindling protocol.
NPY gene transduction was assessed by [italic]in situ[/italic] hybridization analysis of mRNA and by peptide immunocytochemistry.
The expression of the transgene significantly increased 5-7 days after ih administration of the vector, gene transduction was maximal at 4 weeks and lasted for about 6 months. When using serotype 2 rAAV-NSE-NPY, the peptide was specifically increased in hilar interneurons and their axonal projections for about 1.5 mm from the injection site. In serotype 2 rAAV-NSE-NPY injected rats, the number of EEG seizures and their duration were reduced by 50% on average and the time to seizure onset was delayed by 2-fold after ih or icv kainate. When using serotype 1 and 2 rAAV-NSE-NPY, the peptide was increased also in the terminal field of mossy fibres for about 3 mm from injection site. These rats had a 75% reduction of EEG seizures and a 2-fold delay in their onset after ih or icv kainate. In serotype 1 and 2 rAAV-NSE-NPY injected rats, the threshold for afterdischarge induction was increased by 40% in the stimulated hippocampus and the number of stimuli to reach stages 3 and 4-5 of kindling was increased by 2-fold.
These data show that (i) rAAV mediates neuron specific long-term transduction of NPY gene in the rat hippocampus; (ii) NPY overexpression in hilar interneurons and in mossy fibres potently inhibits seizures and delays epileptogenesis. Thus, chronic increase of an inhibitory peptide in crucial brain sites may represent a novel strategy for antiepileptic treatment.
[Supported by: HFSP RG0045-2000 (AV,GS)
Fondazione Cariplo (AV)
New Zealand Health Res Council (MD)]