Brain Advance Access originally published online on October 8, 2006
Brain 2006 129(12):3209-3223; doi:10.1093/brain/awl239
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Thiorphan, a neutral endopeptidase inhibitor used for diarrhoea, is neuroprotective in newborn mice
1 Inserm, U676 Service de Neurologie Pédiatrique, Paris 2 Université Paris 7, Faculté de Médecine Denis Diderot Service de Neurologie Pédiatrique, Paris 3 Institut Pasteur Service de Neurologie Pédiatrique, Paris 4 AP HP, Hôpital Robert Debré Service de Neurologie Pédiatrique, Paris 5 Laboratoire MERCI UPRESA 2122, Faculté de Médecine et de Pharmacie Rouen, France 6 Department of Psychiatry, Division of Neurochemistry Innsbruck, Austria
Correspondence to: Dr Pierre Gressens, Inserm U 676, Hôpital Robert Debré, 48 Boulevard Sérurier, 75019 Paris, France E-mail: gressens{at}rdebre.inserm.fr
Excitotoxic damage appears to be a critical factor in the formation of perinatal brain lesions associated with cerebral palsy (CP). When injected into newborn mice, the glutamatergic analogue, ibotenate, produces cortical lesions and white matter cysts that mimic human perinatal brain lesions. Neuropeptides are neuronal activity modulators and could therefore modulate glutamate-induced lesions. However, neuropeptides are rapidly degraded by peptidases. Racecadotril, which is rapidly metabolized to its active metabolite thiorphan, is a neutral endopeptidase (NEP) inhibitor used in clinical practice for diarrhoea with a remarkable safety profile. This study aimed to test the original hypothesis that thiorphan could be neuroprotective against ibotenate-induced lesions in newborn mice. Intraperitoneal administration of thiorphan reduced ibotenate-induced cortical lesions by up to 57% and cortical caspase-3 cleavage by up to 59%. This neuroprotective effect was long-lasting and was still observed when thiorphan was administered 12 h after the insult, showing a remarkable window for therapeutic intervention. Further supporting the neuroprotective effect of pharmacological blockade of NEP, mouse pups with a genetic deletion of NEP displayed a significantly reduced size of the ibotenate-induced cortical grey matter lesion when compared with wild-type animals. Thiorphan effects were mimicked by substance P (SP) and, in a less potent manner, by neurokinin A. Thiorphan effects were inhibited by blockers of NK1 and NK2 receptors. Real-time reverse transcription–polymerase chain reaction, autoradiography and immunohistochemistry confirmed the expression of NK1 and NK2 receptors in the neonatal murine neocortex. These data demonstrate that thiorphan prevents neonatal excitotoxic cortical damage, an effect largely mediated by SP. Thiorphan could represent a promising drug for the prevention of CP, which remains a challenging disease. In a broader context, these results also raise potential implications for the prevention of neurodegenerative diseases involving glutamate-mediated excitotoxic neuronal death.
Key Words: cerebral palsy; glutamate receptor; neuroprotection; neprilysin; NMDA
Abbreviations: CP, cerebral palsy; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; 125I-BH-SP, 125I-Bolton-Hunter substance P; MAPK, mitogen-associated protein kinase; NEP, neutral endopeptidase; NKA, neurokinin A; NKB, neurokinin B; NMDA, N-methyl-D-aspartate; PBS, phosphate-buffered saline; PCR, polymerase chain reaction; PK, protein kinase; SP, substance P
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Received April 7, 2006. Revised June 27, 2006. Accepted August 8, 2006.
*These authors have contributed equally to this work.
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  V. Degos, G. Loron, J. Mantz, and P. Gressens Neuroprotective Strategies for the Neonatal Brain Anesth. Analg., June 1, 2008; 106(6): 1670 - 1680. [Abstract] [Full Text] [PDF]
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