There are 39.6 million individuals aged 65 years or older in the US, a number expected to increase to approximately 72 million by 2030. Reduced immune function in the elderly is a major cause of morbidity, lower quality of life and death. Intriguingly, aging of thymus precedes aging of other organs and is a central feature and precursor of weak immune vigilance that appears in later life. Diminished ability of the thymus to produce naive T cells with progressive aging remains a puzzling phenomenon in Aging Research and to date, an intractable clinical condition that contributes to immune dysfunction in the elderly. This project will allow us to assess specific hypotheses and predictions about the relationship between age-related thymic demise and the role of 'thymic inflammaging' - in particular, the mechanism of inflammosome activation that causes thymic damage - with implications for understanding clinically relevant basic pathways to strengthen the immune system in the elderly. The current proposal is based on our discovery that aging of thymus can be substantially delayed by lowering the intrathymic caspase-1 activation via an Nlrp3 inflammasome dependent mechanism 7. The Nlrp3 (for nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3) inflammasome is formed via protein-protein interactions between Nlrp3, Asc and pro-caspase-1 proteins. The Nlrp3 inflammasome senses microbial byproducts as well as damage-associated molecular patterns (DAMPs) and upon assembly, causes caspase-1 activation, which in turn controls the secretion of pro-inflammatory cytokines IL-1b and IL-18. We identified that ceramides (lipids with sphingosine linked to a fatty acid) which increase in aging thymus, trigger the activation of Nlrp3 inflammasome. Ablation of Nlrp3 inflammasome in mice protects from thymic demise suggesting delayed immunological aging. Based on our novel findings, the central hypothesis of this proposal is that age-related thymic lipotoxicity via a canonical Nlrp3 Inflammasome dependent mechanism induces 'thymic inflammaging' and compromises thymic lymphopoiesis by impacting the integrity of thymic epithelial cells. The overall goal of this project is to identify basic mechanism of thymic demise that are amenable for future clinical intervention to delay or even reverse thymic involution in middle-aged or elderly people.

Public Health Relevance

Thymus produces specialized immune cells called T-lymphocytes. With progressive aging, thymus becomes dysfunctional thereby losing its ability to produce T-lymphocytes. The loss of thymic function eventually leads to lower immune surveillance in elderly. This research project is designed to understand the mechanism of loss of thymic function in aging with emphasis on a novel inflammation regulating pathway called the 'inflammasome'. The long-term goal of this project is to develop novel therapeutic strategies to strengthen immune function and enhance the health span of elderly.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG043608-04
Application #
8852033
Study Section
Aging Systems and Geriatrics Study Section (ASG)
Program Officer
Fuldner, Rebecca A
Project Start
2013-06-15
Project End
2018-05-31
Budget Start
2015-06-01
Budget End
2016-05-31
Support Year
4
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Yale University
Department
Veterinary Sciences
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
Ravussin, Anthony; Youm, Yun-Hee; Sander, Jil et al. (2018) Loss of Nucleobindin-2 Causes Insulin Resistance in Obesity without Impacting Satiety or Adiposity. Cell Rep 24:1085-1092.e6
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Spadaro, Olga; Camell, Christina D; Bosurgi, Lidia et al. (2017) IGF1 Shapes Macrophage Activation in Response to Immunometabolic Challenge. Cell Rep 19:225-234
Spadaro, Olga; Goldberg, Emily L; Camell, Christina D et al. (2016) Growth Hormone Receptor Deficiency Protects against Age-Related NLRP3 Inflammasome Activation and Immune Senescence. Cell Rep 14:1571-1580
Youm, Yun-Hee; Horvath, Tamas L; Mangelsdorf, David J et al. (2016) Prolongevity hormone FGF21 protects against immune senescence by delaying age-related thymic involution. Proc Natl Acad Sci U S A 113:1026-31
Camell, Christina D; Nguyen, Kim Y; Jurczak, Michael J et al. (2015) Macrophage-specific de Novo Synthesis of Ceramide Is Dispensable for Inflammasome-driven Inflammation and Insulin Resistance in Obesity. J Biol Chem 290:29402-13
Youm, Yun-Hee; Nguyen, Kim Y; Grant, Ryan W et al. (2015) The ketone metabolite ?-hydroxybutyrate blocks NLRP3 inflammasome-mediated inflammatory disease. Nat Med 21:263-9

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