Investigation of the intracellular and extracellular mechanisms underlying the process of aging

National Institute On Aging

Investigators

Abstract

We have established the conditions for detecting and quantifying the overall yield of extracellular vesicles (EVs) and DNA cargo frommouse plasma and tissues derived from murine models with aging-associated pathologies. In collaboration with other NIA and NCIresearch laboratories, we found increased amounts of repetitive DNA cargo in EVs following numerous genome insults. We have alsodiscovered altered EV characteristics, such as an increase in concentration and a decrease in size, in the murine models with aging-associated pathologies and are evaluating the possibility of using EVs as a biomarker of aging and age-related diseases. Given thecentral function of EVs in mediating intercellular communication and inflammation, we are investigating whether genome damage andthe aging process affect the cargo content of EVs. Moreover, we are investigating the biological effects of EVs on NF-kB-inflammatorysignaling, transcriptome, and neurotoxicity in recipient cells. This study will improve our understanding of the molecular basis of howEV alteration affects health span, including the connection between EVs and the activation of inflammatory cytokine signaling in thetissue microenvironments during aging. It has been demonstrated that short telomeres trigger a DNA damage response (DDR) in human cultured cells, resulting in apoptosisand senescence. Unresolved is the relationship between telomere shortening and the function of telomeric proteins, and thus age-related phenotypes. RAP1, a telomere-associated protein that also regulates transcription in extratelomeric regions, is one candidate.We created a knockin mouse carrying a Rap1 mutation incapable of telomere binding. Rap1 knockout embryonic fibroblasts exhibited arelocalization away from telomeres and an increase in cytosolic distribution comparable to that observed in human fibroblasts havingtelomere erosion. Rap1 knockin mice were viable, but exhibited transcriptomic alterations, proinflammatory cytokine/chemokinesignaling, decreased life-and health-span, as well as increased body weight/fasting blood glucose levels, spontaneous tumor incidence,and behavioral deficits. Our findings demonstrate mechanisms distinct from telomere-induced DDR that underlie age-relatedphenotypes and imply that altered Rap1 cellular localization may serve as a novel biomarker of aging.