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The common inhalation anesthetic isoflurane has been shown to induce apoptosis, which then leads to accumulation of β-amyloid protein, the hallmark feature of Alzheimer disease neuropathogenesis. The underlying molecular mechanism of the isoflurane-induced apoptosis is largely unknown. We, therefore, set out to assess whether isoflurane can induce apoptosis by regulating Bcl-2 family proteins, enhancing reactive oxygen species (ROS) accumulation, and activating the mitochondrial pathway of apoptosis. We performed these studies in cultured cells, primary neurons, and mice. Here we show for the first time that treatment with 2% isoflurane for 6 h can increase pro-apoptotic factor Bax levels, decrease anti-apoptotic factor Bcl-2 levels, increase ROS accumulation, facilitate cytochrome c release from the mitochondria to the cytosol, induce activation of caspase-9 and caspase-3, and finally cause apoptosis as compared with the control condition. We have further found that isoflurane can increase the mRNA levels of Bax and reduce the mRNA levels of Bcl-2. The isoflurane-induced ROS accumulation can be attenuated by the intracellular calcium chelator BAPTA. Finally, the anesthetic desfiurane does not induce activation of mitochondrial pathway of apoptosis. These results suggest that isoflurane may induce apoptosis through Bcl-2 family proteins- and ROS-associated mitochondrial pathway of apoptosis. These findings, which have identified at least partially the molecular mechanism by which isoflurane induces apoptosis, will promote more studies aimed at studying the potential neurotoxic effects of anesthetics. [ABSTRACT FROM AUTHOR]

Perioperative factors including hypoxia, hypocapnia, and certain anesthetics have been suggested to contribute to Alzheimer disease (AD) neuropathogenesis. Desflurane is one of the most commonly used inhalation anesthetics. However, the effects of desflurane on AD neuropathogenesis have not been previously determined. Here, we set out to assess the effects of desflurane and hypoxia on caspase activation, amyloid precursor protein (APP) processing, and amyloid β-protein (Aβ) generation in H4 human neuroglioma cells (H4 naïve cells) as well as those over-expressing APP (H4-APP cells). Neither 12% desflurane nor hypoxia (18% O2) alone affected caspase-3 activation, APP processing, and Aβ generation. However, treatment with a combination of 12% desflurane and hypoxia (18% O2) (desflurane/hypoxia) for 6 h induced caspase-3 activation, altered APP processing, and increased Aβ generation in H4-APP cells. Desflurane/hypoxia also increased levels of a-site APP-cleaving enzyme in H4-APP cells. In addition, desflurane/hypoxia-induced Aβ generation could be reduced by the broad caspase inhibitor benzyloxycarbonyl-VAD. Finally, the Aβ aggregation inhibitor clioquinol and γ-secretase inhibitor L-685,458 attenuated caspase-3 activation induced by desflurane/hypoxia. In summary, desflurane can induce Aβ production and caspase activation, but only in the presence of hypoxia. Pending in vivo confirmation, these data may have profound implications for anesthesia care in elderly patients, and especially those with AD. [ABSTRACT FROM AUTHOR]

The amyloid precursor protein (APP) and its pathogenic by-product amyloid-β protein (Aβ) play central roles in Alzheimer disease (AD) neuropathogenesis. APP can be cleaved by β-secretase (BACE) and α-secretase to produce APP-C99 and APP-C83. These C-terminal fragments can then be cleaved by γ-secretase to produce Aβ and p3, respectively. p3 has been reported to promote apoptosis, and Aβ is the key component of senile plaques in AD brain. APP adaptor proteins with phosphotyrosine-binding domains, including ShcA (SHC1), ShcC (SHC3), and Fe65 (APBB1), can bind to and interact with the conserved YENPTY motif in the APP-C terminus. Here we have described for the first time the effects of RNA interference (RNAi) silencing of ShcA, ShcC, and Fe65 expression on APP processing and Aβ production. RNAi silencing of ShcC led to reductions in the levels of APP-C-terminal fragments (APP- CTFs) and Aβ in H4 human neuroglioma cells stably overexpressing full-length APP (H4-FL-APP cells) but not in those expressing APP-C99 (H4-APP-C99 cells). RNAi silencing of ShcC also led to reductions in BACE levels in H4-FL-APP cells. In contrast, RNAi silencing of the homologue ShcA had no effect on APP processing or All levels. RNAi silencing of Fe65 increased APP-CTF levels, although also decreasing Aβ levels in H4-FL-APP cells. These findings suggest that pharmacologically blocking interaction of APP with ShcC and Fe65 may provide novel therapeutic strategies against AD. [ABSTRACT FROM AUTHOR]