RESUMO
Depletion of calcium from the neuronal endoplasmic reticulum (ER) induces apoptosis. Isoflurane depletes calcium from sarcoplasmic reticulum (SR) of muscle, an analogue of ER in neurons, while sevoflurane maintains or increases SR calcium. We hypothesized that isoflurane, but not sevoflurane, induces apoptosis by depleting the ER calcium. Rat PC12 pheochromocytoma cells and primary cortical neurons were treated with equipotent doses of isoflurane and sevoflurane. Isoflurane, but not sevoflurane, at equipotent doses induced cell damage determined by both LDH release and MTT reduction assays, dose and time dependently, in both types of cells. Isoflurane at 2.4% for 24 h induced cytotoxicity in both cell types, which was characterized by nuclear condensation and fragmentation and activation of caspases 3 and 9. Isoflurane cytotoxicity was suppressed by dantrolene, a ryanodine receptor antagonist that inhibits abnormal calcium release from the ER. Isoflurane decreased the Bcl-2/Bax ratio by as much as 36% (P < 0.05). However, sevoflurane did not cause neuronal damage by apoptosis nor did it decrease the Bcl-2/Bax ratio. These results suggest that isoflurane and sevoflurane differentially affect the Bcl-2/Bax ratio and cell survival. At equipotent concentrations, isoflurane, but not sevoflurane, induces cytotoxicity in both PC12 cells and primary cortical neurons and decreases the Bcl-2/Bax ratio.
Assuntos
Anestésicos Inalatórios/farmacologia , Isoflurano/farmacologia , Éteres Metílicos/farmacologia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Laranja de Acridina , Animais , Apoptose/efeitos dos fármacos , Western Blotting , Cálcio/metabolismo , Caspase 3 , Caspase 9 , Caspases/metabolismo , Núcleo Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Células Cultivadas , Córtex Cerebral/citologia , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/metabolismo , Dantroleno/farmacologia , Retículo Endoplasmático/efeitos dos fármacos , Retículo Endoplasmático/metabolismo , Imuno-Histoquímica , Isoflurano/antagonistas & inibidores , Células PC12 , Ratos , Sevoflurano , Proteína X Associada a bcl-2RESUMO
BACKGROUND: The majority of surgical patients receive inhaled anesthetics, principally small haloalkanes and haloethers. Long-term cognitive problems occur in the elderly subsequent to anesthesia and surgery, and previous surgery might also be a risk factor for neurodegenerative disorders like Alzheimer and Parkinson disease. The authors hypothesize that inhaled anesthetics contribute to these effects through a durable enhancement of peptide oligomerization. METHODS: Light scattering, filtration assays, electron microscopy, fluorescence spectroscopy and size-exclusion chromatography was used to characterize the concentration-dependent effects of halothane, isoflurane, propofol, and ethanol on amyloid beta peptide oligomerization. Pheochromocytoma cells were used to characterize cytotoxicity of amyloid oligomers with and without the above anesthetics. RESULTS: Halothane and isoflurane enhanced amyloid beta oligomerization rates and pheochromocytoma cytotoxicity in vitro through a preference for binding small oligomeric species. Ethanol and propofol inhibited oligomerization at low concentration but enhanced modestly at very high concentration. Neither ethanol nor propofol enhanced amyloid beta toxicity in pheochromocytoma cells. CONCLUSIONS: Inhaled anesthetics enhance oligomerization and cytotoxicity of Alzheimer disease-associated peptides. In addition to the possibility of a general mechanism for anesthetic neurotoxicity, these results call for further evaluation of the interaction between neurodegenerative disorders, dementia, and inhalational anesthesia.
