ABSTRACT
BACKGROUND: The use of remifentanil in a context of potential prematurity led us to explore ex vivo the opioid effects on the immature mouse brain. Remifentanil enhances medullary glutamatergic N-methyl-D-aspartate (NMDA) receptor activity. Furthermore, in neonatal mouse cortex, NMDA was previously shown to exert either excitotoxic or antiapoptotic effects depending on the cortical layers. With the use of a model of acute cultured brain slices, we evaluated the potential necrotic and apoptotic effects of remifentanil, alone or associated with its glycine vehicle (commercial preparation of remifentanil, C.P. remifentanil), on the immature brain. METHODS: Cerebral slices from postnatal day 2 mice were treated up to 5 hours with the different compounds, incubated alone or in the presence of NMDA. The necrotic effect was studied by measuring lactate dehydrogenase activity and 7-Aminoactinomycin D labeling. Apoptotic death was evaluated by measurement of caspase-3 activity and cleaved caspase-3 protein levels, using Western blot and immunohistochemistry. Extrinsic and intrinsic apoptotic pathways were investigated by measuring caspase-8, caspase-9 activities, Bax protein levels, and mitochondrial integrity. RESULTS: C.P. remifentanil was ineffective on necrotic death, whereas it significantly reduced caspase-3 activity and cortical cleaved caspase-3 levels. C.P. remifentanil inhibited cortical Bax protein expression, caspase-9 activity, and preserved mitochondrial integrity, whereas it had no effect on caspase-8 activity. Its action targeted the neocortex superficial layers, and it was reversed by the opioid receptors antagonist naloxone and the NMDA antagonist MK801. Remifentanil and glycine acted synergistically to inhibit apoptotic death. In addition, C.P. remifentanil enhanced the antiapoptotic effect of NMDA, whereas it did not improve NMDA excitotoxicity in brain slices. CONCLUSION: The present data indicate that at a supraclinical concentration C.P. remifentanil had no pronecrotic effect but exerted ex vivo antiapoptotic action on the immature mouse brain, involving the opioid and NMDA receptors, and the mitochondrial-dependent apoptotic pathway. Assessment of the impact of the antiapoptotic effect of remifentanil in in vivo neonatal mouse models of brain injury will also be essential to measure its consequences on the developing brain.
Subject(s)
Analgesics, Opioid/pharmacology , Apoptosis/drug effects , Brain/cytology , Brain/drug effects , Piperidines/pharmacology , Analgesics, Opioid/pharmacokinetics , Animals , Animals, Newborn , Blotting, Western , Caspase 3/metabolism , Cell Death/drug effects , Cell Nucleus/drug effects , Cell Nucleus/ultrastructure , Drug Synergism , Glycine/pharmacology , Half-Life , Immunohistochemistry , In Vitro Techniques , L-Lactate Dehydrogenase/metabolism , Mice , Microscopy, Electron , Mitochondria/drug effects , Mitochondria/ultrastructure , Piperidines/pharmacokinetics , Receptors, N-Methyl-D-Aspartate/drug effects , Remifentanil , bcl-2-Associated X Protein/metabolismABSTRACT
OBJECTIVE: In humans, antenatal alcohol exposure elicits various developmental disorders, in particular in the brain. Numerous studies focus on the deleterious effects of alcohol on neural cells. Although recent studies suggest that alcohol can affect angiogenesis in adults, the impact of prenatal alcohol exposure on brain microvasculature remains poorly understood. METHODS: We used a mouse model to investigate effects of prenatal alcohol exposure on the cortical microvascular network in vivo and ex vivo and the action of alcohol, glutamate, and vascular endothelial growth factor A (VEGF) on activity, plasticity, and survival of microvessels. We used quantitative reverse transcriptase polymerase chain reaction, Western blot, immunohistochemistry, calcimetry, and videomicroscopy. We characterized the effect of prenatal alcohol exposure on the cortical microvascular network in human controls and fetal alcohol syndrome (FAS)/partial FAS (pFAS) patients at different developmental stages. RESULTS: In mice, prenatal alcohol exposure induced a reduction of cortical vascular density, loss of the radial orientation of microvessels, and altered expression of VEGF receptors. Time-lapse experiments performed on brain slices revealed that ethanol inhibited glutamate-induced calcium mobilization in endothelial cells, affected plasticity, and promoted death of microvessels. These effects were prevented by VEGF. In humans, we evidenced a stage-dependent alteration of the vascular network in the cortices of fetuses with pFAS/FAS. Whereas no modification was observed from gestational week 20 (WG20) to WG22, the radial organization of cortical microvessels was clearly altered in pFAS/FAS patients from WG30 to WG38. INTERPRETATION: Prenatal alcohol exposure affects cortical angiogenesis both in mice and in pFAS/FAS patients, suggesting that vascular defects contribute to alcohol-induced brain abnormalities.
