Dylan Holly, M.Ed.

Skeletal muscle is a complex and dynamic tissue that can adapt to mechanical stress or lack thereof. Muscle is not only responsible for human movement in a three dimensional world but is also a major storehouse for amino acids and metabolic machinery. When subjected to an unloaded state typically seen in a bedrest, casted, or microgravity situation the muscle atrophies, or in other words wastes away. Along with this wasting comes a decrease in muscular strength and endurance. This presents a major problem for people that have been injured, sick, or hanging around the space station too long. When it comes time to re-load the limb(s) and start the rehabilitation process these people have to not only rehab the injured bone, joint, or connective tissue but also the muscle surrounding the area. It makes sense that if we can somehow prevent even some of this muscle atrophy that we should do so. Our lab has identified a role that the mu-splice variant of neuronal nitric oxide synthase (nNOSu) plays in the atrophy process. nNOSu normally resides at the cell membrane but when a muscle is subjected to unloading this nNOSu molecule begins to move into the cell where it sets off a cascade of intracellular events leading to muscle degradation. This translocation of nNOSu is due to elevated levels of chemical reaction byproducts known a reactive oxygen species (ROS). Most of these ROS are generated by a membrane bound enzyme known as NADPH oxidase2 (Nox2). Past studies have shown that if you inhibit Nox2 then nNOSu stays at the cell membrane and atrophy is mitigated. While Nox2 activity is directly related to nNOSu activity, the mechanisms underlying Nox2 activity are not well understood. The purpose of this study is to further disseminate the relationship between Nox2 and its upstream and downstream regulators and provide pilot data for further research. We have identified two "players" that may have a direct impact on Nox2 activity known as Acid Sphingomyelinase (ASMase) and Cyclophilin A (Cyc A). Our goal in this study is to induce upregulation of Nox2 activity by way of unloading the hindlimbs of rodents (disuse model) and inhibit Nox2 activity by utilizing an inhibitory compound known as gp91ds-tat. After the experimental intervention we will measure the amounts of ASMase and Cyc A and determine the correlation between these levels and Nox2 activity.