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.

National Institute of Health (NIH)
National Institute on Aging (NIA)
Research Project (R01)
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Cellular Mechanisms in Aging and Development Study Section (CMAD)
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Finkelstein, David B
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University of Kentucky
Schools of Medicine
United States
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Dotson 2nd, P Patrick; Karakashian, Alexander A; Nikolova-Karakashian, Mariana N (2015) Neutral sphingomyelinase-2 is a redox sensitive enzyme: role of catalytic cysteine residues in regulation of enzymatic activity through changes in oligomeric state. Biochem J 465:371-82
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Empinado, Hyacinth M; Deevska, Gergana M; Nikolova-Karakashian, Mariana et al. (2014) Diaphragm dysfunction in heart failure is accompanied by increases in neutral sphingomyelinase activity and ceramide content. Eur J Heart Fail 16:519-25
Deevska, Gergana; Sunkara, Manjula; Karakashian, Claudia et al. (2014) Effect of procysteine on aging-associated changes in hepatic GSH and SMase: evidence for transcriptional regulation of smpd3. J Lipid Res 55:2041-52
Deevska, Gergana M; Sunkara, Manjula; Morris, Andrew J et al. (2012) Characterization of secretory sphingomyelinase activity, lipoprotein sphingolipid content and LDL aggregation in ldlr-/- mice fed on a high-fat diet. Biosci Rep 32:479-90
Dobierzewska, Aneta; Shi, Lihua; Karakashian, Alexander A et al. (2012) Interleukin 1β regulation of FoxO1 protein content and localization: evidence for a novel ceramide-dependent mechanism. J Biol Chem 287:44749-60
Nikolova-Karakashian, Mariana N; Reid, Michael B (2011) Sphingolipid metabolism, oxidant signaling, and contractile function of skeletal muscle. Antioxid Redox Signal 15:2501-17
Dobierzewska, Aneta; Giltiay, Natalia V; Sabapathi, Sathish et al. (2011) Protein phosphatase 2A and neutral sphingomyelinase 2 regulate IRAK-1 protein ubiquitination and degradation in response to interleukin-1beta. J Biol Chem 286:32064-73
Deevska, Gergana M; Nikolova-Karakashian, Mariana N (2011) The twists and turns of sphingolipid pathway in glucose regulation. Biochimie 93:32-8
Nikolova-Karakashian, Mariana N; Rozenova, Krassimira A (2010) Ceramide in stress response. Adv Exp Med Biol 688:86-108

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