Mitochondrial Effects on Sensitivity to Anesthetics

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Our laboratory exploits a very simple animal model, the nematode C. elegans, to investigate the molecular mechanism of volatile anesthetic action. We have established that genes and physiologic pathways that alter anesthetic sensitivity in the nematode also alter sensitivity in mammals. The importance of the fact that the same molecular pathways affect sensitivity across different species is hard to overstate. We have identified a group of genes that alter mitochondrial function and control the sensitivity of C. elegans to volatile anesthetics (VAs). A point mutation in gas-1, which encodes the 49 kDa subunit of complex I of the mitochondrial electron transport chain, causes the animal to be very hypersensitive to all VAs. In addition, we have found that a subset of patients, children with metabolic defects most clearly related to complex I function, are profoundly hypersensitive to sevoflurane. This finding provides a clinical correlate to the basic study of very simple animal model. The sum of our work clearly implicates mitochondrial function as a novel mechanism that contributes to the control of anesthetic response. In this proposal we will extend our studies in the nematode to test our hypothesis that alterations in complex I function change anesthetic sensitivity via direct effects on metabolism, and via indirect effects on specific downstream proteins. The specific aims to test these hypotheses are: 1. Determine which subunits of complex I alter anesthetic sensitivity in C. elegans. The function of this complex is key to mediating behavior in VAs in nematodes, and may have a parallel role in patients with mitochondrial disease. 2. Measure the effect of volatile anesthetics on ubiquinone binding to complex I. We hypothesize that this binding site may be a target of action for volatile anesthetics. 3. Determine genes and gene sets whose expression changes as a downstream effect of complex I dysfunction. We will carefully focus our analysis to expression profiles that alter anesthetic sensitivity by a subtraction strategy that focuses on changes specific to neurons. The microarray analysis will be validated by using RNAi to specifically reduce levels of expression of genes discovered in thisaim, and test the resultant effects on behavior in VAs This superb animal model allows putative molecular targets of VAs to be confirmed or refuted by assessing whole animal behavior. Such a tractable animal model is crucial to unraveling the mechanism of action of this very important class of anesthetic agents.