Role of Neutral Sphingomyelinase-2 in aging

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DESCRIPTION (provided by applicant): Aging is characterized by an altered immune function and stress response. It becomes increasingly clear that, at least in part, this is due to alterations in ability of the cells to respond to different stress inducers. The hypothesis to be tested in this proposal is that aging-induced up-regulation of neutral sphingomyelianse-2 (NSMase-2) activity underlies the exaggerated response of hepatocytes IL-1beta during aging. We further hypothesized that aging-associated increases in NSMase-2 activity are consequence of the decreases in the cellular glutathione level. Therefore, the long-term objective of our study is to understand the relation between aging, the altered cellular response to inflammation, and the state of oxidative stress. The following specific aims are proposed: Specific aim 1. To test the role of NSMase-2 as a mediator of aging-induced hyperresponsiveness to IL-1b. Studies in this specific aim will decipher the contribution of NSMase-2 to the IL-1b hyperresponsiveness of aged animals. Gene silencing approach will be used in vitro, in hepatocytes isolated from old rats, and in vivo, in aged animals. Specific aim 2. To study the IL-1b hyperresponsiveness in calorie-restricted aged rats. Calorie-restriction (CR) is known to increase the life span of experimental animals and to attenuate the onset of oxidative stress, including preventing aging-induced GSH/GSSH decline. Thus we hypothesized that CR attenuates IL-1B hyperresponsiveness of liver. This will be tested in vivo and in vitro. If NSMase-2 mediates IL-1b hyperresponsiveness by acting down-stream of GSH/GSSH changes, then NSMase-2 overexpression in aged CR should restore the aging-associated IL-1b hyperresponsiveness. This will be tested by adenoviral-mediated expression of NSMase-2 in isolated hepatocytes and intact liver from aged CR rats. Specific aim 3: To study the role of GSH in aging-associated NSMase-2 activation and IL-1b hyperresponsiveness. These studies will ask whether GSH depletion in aging and NSMase-2 activation are causatively linked and will establish a link between the onset of oxidative stress and the IL-1b hyperesponsivness in aged animals. The proposed studies will provide novel understanding on the cellular mechanisms involved in the onset of aging and may have practical application in the development of new anti-inflammatory drugs for the elderly.