We have shown that the commonly used inhalant anesthetic isoflurane induces caspase activation and increases generation of Ab, the key component of senile plaques in Alzheimer's disease (AD) patients. Currently, it is not clear whether isoflurane, as well as other commonly used inhalant anesthetics, sevoflurane and desflurane, can induce these effects in vivo. This is an important question since increased A2 generation and caspase activation by anesthesia could conceivably serve to trigger or exacerbate the development of AD. Based on preliminary data, our central hypothesis is that isoflurane and sevoflurane, but not desflurane, can initiate a cascade of events that begins with caspase activation and results in the generation of Ab. The overarching goal of this proposal is to assess the potential role of routine general anesthesia as a risk factor for AD. The primary objective of this application is to determine the in vivo relevance of our previously observed in vitro effects of isoflurane, sevoflurane and desflurane on apoptosis and Ab generation.
In aim 1, we will systematically assess the effects of isoflurane, sevoflurane and desflurane on caspase activation, apoptosis, APP processing, and Ab generation in naove mice and, if necessary, AD transgenic mice. The mice will be treated with either isoflurane, sevoflurane, or desflurane, and potential effects on caspase activation, apoptosis, levels of full-length-APP, APP-C-terminal fragments and Ab, and levels and activities of BACE and 3-secretase will be determined. We will also explore the extent to which any or all of these effects can be reduced by caspase inhibitors, e.g., Z-VAD. If we are unable to measure endogenous A2 in naive mice, we will repeat these studies in AD transgenic mice, B6.Cg-Tg(APPswe, PSEN1dE9)85Dbo/J mice. In the second aim of this study, we will attempt to confirm our findings in normal human brain tissues harvested during temporal lobe resection from patients who have received isoflurane or desflurane anesthesia for surgical treatment of epilepsy, as it is not feasible to collect such data from normal human subjects. We will examine the effects of isoflurane and desflurane (but not sevoflurane as it can trigger seizure in epilepsy patients) on caspase activation, apoptosis, levels of full- length APP, APP C-terminal fragments and Ab, and levels and activities of BACE and gamma-secretase in patients who have received these inhalant anesthetics versus patients who have received non-inhalant anesthetics. The proposed research aims to provide in vivo relevance to our previous in vitro studies, and to offer new insight regarding the effects of isoflurane, sevoflurane and desflurane on caspase activation, apoptosis, APP processing and Ab generation in vivo. The data generated in this project should also provide some firm answers regarding the extent to which general anesthesia using isoflurane, sevoflurane or desflurane may initiate or accelerate the development of AD. The results of this study will ultimately guide clinicians with regard to how to provide the safest anesthesia care for patients, especially the elderly and those with AD.
The proposed research will determine potential neurotoxic effects of inhalation anesthetics isoflurane, sevoflurane and desflurane in inducing cell death and increasing amyloid-b protein in mice and in humans. The results from the proposed studies will tell us whether or not isoflurane, sevoflurane and desflurane can increase the risk of Alzheimer's disease, and help us to develop safer anesthetics to provide better anesthesia care for patients, especially Alzheimer's disease patients and elderly patients.
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