Nitrous Oxide Plus Isoflurane Induces Apoptosis and Increases β-Amyloid Protein Levels

Background: Some anesthetics have been suggested to induce neurotoxicity, including promotion of Alzheimer's disease neuro-pathogenesis. Nitrous oxide and isoflurane are common anesthetics. The authors set out to assess the effects of nitrous oxide and/or isoflurane on apoptosis and beta-amyloid (A beta) levels in H4 human neuroglioma cells and primary neurons from naive mice. Methods: The cells or neurons were exposed to 70% nitrous oxide and/or 1% isoflurane for 6 h. The cells or neurons and Methods: The cells or neurons were exposed to 70% nitrous oxide and/or 1% isoflurane for 6 h. The cells or neurons and conditioned media were harvested at the end of the treatment. Caspase-3 activation, apoptosis, processing of amyloid precursor protein, and A beta levels were determined. Results: Treatment with a combination of 70% nitrous oxide and 1% isoflurane for 6 h induced caspase-3 activation and apoptosis In H4 naive cells and primary neurons from naive mice. The 70% nitrous oxide plus 1% isoflurane, but neither alone, for 6 h Induced caspase-3 activation and apoptosis, and increased levels of beta-site amyloid precursor protein-cleaving enzyme and A beta in H4-amyloid precursor protein cells. In addition, the nitrous oxide plus isoflurane-induced A beta generation was reduced by a broad caspase inhibitor, Z-VAD. Finally, the nitrous oxide plus isoflurane-induced caspase-3 activation was attenuated by gamma-secretase inhibitor L-685,458, but potentiated by exogenously added A beta. Conclusion: These results suggest that the common anesthetics nitrous oxide plus isoflurane may promote neurotoxicity by inducing apoptosis and increasing A beta levels. The generated A beta may further potentiate apoptosis to form another round of apoptosis and A beta generation. More studies, especially the in vivo confirmation of these in vitro findings, are needed.