Project description:The rostral ventrolateral medulla (RVLM), a part of the medullary reticular formation, plays a major role in several physiological responses, including cardiovascular and sympathetic nervous system functions. Although aging causes disturbances in the responses of these physiological systems, RVLM involvement in these age-related changes is not clear. Previous work using high-throughput gene expression analysis of the RVLM in aged animals suggested that chemical neurotransmission-related genes might be downregulated with advancing age. Since the RVLM function involves a balance of inhibitory and excitatory inputs, which is largely mediated by gamma-aminobutyric acid (GABA) and excitatory amino acid (EAA) neurotransmission, we hypothesized that aging is associated with altered excitatory and/or inhibitory neurotransmission-related gene expression in the RVLM. To test this hypothesis, we micropunched an RVLM-containing area from young (3–5 months), middle-aged (12–14 months), and aged (22–26 months) Fischer 344 male rats. RNA purified from these micropunches was analyzed using GABA and Glutamate RT2 Profiler PCR arrays (n= 8–10). In addition, the expression of selected genes was validated at the RNA level using TaqMan® based- qPCR and at the protein level using western blotting. All the genes that displayed significant differential expression (1.5-fold, p < .05, FDR < .05) were identified to be downregulated in the RVLM of aged and middle-aged rats compared to young rats. Among the downregulated genes, the percentage of glutamate neurotransmission-related genes was higher than GABA neurotransmission-related genes. Solute carrier family 1 member 6 (Slc1a6) gene showed the highest fold downregulation at the RNA level in the RVLM of aged compared to young rats, and its protein product, Excitatory amino acid transporter 4 (EAAT4), showed a downregulatory trend in the RVLM of aged and middle-aged rats. These results suggest that molecular constituents of both GABA and glutamate neurotransmission might be altered in the RVLM of aged and middle-aged rats, and the changes in glutamate neurotransmission might be more prominent. Investigating age-associated anatomical and functional changes in RVLM GABA and glutamate neurotransmission might provide a foundation for understanding the effects of aging on physiological function.
Project description:Dietary methionine restriction (MR) has been shown to increase lifespan and decrease adiposity in rodents. This study was designed to examine the transcriptional effects of MR in metabolically relevant tissues. This experiment contains data from the liver. We analyzed MR-induced changes in gene expression using pooled RNA from liver of rats fed either a control purified amino acid diet (DL-methionine content of 0.86%) (CON) or a methionine-restricted diet (DL-methionine content of 0.172%)(MR). Rats were fed Purina rodent diet 5001 until 32 days of age and were then randomly assigned to be fed CON diet or MR diet for 20 months.
Project description:With advancing age, senescent cells accumulate as they are not efficiently cleared by the immune system anymore. Via a senescence-associated secretory phenotype, chronic senescent cells alter the microenvironment, creating an unfavorable milieu for neurogenesis and neurorepair. Using an innovative and rapid aging model, the African turquoise killifish, we have previously demonstrated a dramatic decline in neurogenic potential of non-glial progenitors with age. Even after traumatic brain injury, progenitor proliferation and neuron production was very low in aged killifish in comparison to young adult killifish, and overall neurorepair was incomplete. In the present study, we validated if the senolytic cocktail dasatinib and quercetin (D+Q) could reboot the neurogenic output by clearing chronic senescent cells from the aged killifish brain to re-create the necessary supportive environment. Our results confirm that the aged killifish telencephalon holds a very high senescent cell burden, which we could diminish by short-term systemic D+Q treatment. As a consequence of D+Q administration, proliferation of non-glial progenitors increased and more new neurons were generated and migrated into the parenchyma after injury. Injury-induced inflammation and glial scarring, a phenomenon only seen in aged killifish, remained unaltered. Senolytic treatment with D+Q might thus hold promise for improving brain function in aged populations, and is especially interesting for reviving the neurogenic potential of an already aged central nervous system.
Project description:Cellular senescence is a stress-induced, stable cell cycle arrest phenotype which generates a pro-inflammatory microenvironment, leading to chronic inflammation and age-associated diseases. Determining the fundamental molecular pathways driving senescence instead of apoptosis could enable the identification of senolytic agents to restore tissue homeostasis. Here, we identify thrombomodulin signaling as a key molecular determinant of the senescent cell fate. Although normally restricted to endothelial cells, thrombomodulin is rapidly upregulated and maintained throughout all phases of the senescent program in aged mammalian tissues and in senescent cell models. Mechanistically, thrombomodulin activates a proteolytic feed-forward signaling pathway by stabilizing a multi-protein complex in early endosomes, thus forming a molecular basis for the irreversibility of the senescent program and ensuring senescent cell viability. Therapeutically, thrombomodulin signaling depletion or inhibition using vorapaxar, an FDA-approved drug, effectively ablates senescent cells and restores tissue homeostasis in liver fibrosis models. Collectively, these results uncover proteolytic thrombomodulin signaling as a conserved pro-survival pathway essential for senescent cell viability, thus providing a pharmacologically exploitable senolytic target for senescence-associated diseases.
Project description:Senescent cells accumulate in organisms over time as a result of tissue damage and impaired immune surveillance and are thought to contribute to age-related tissue decline1,2. In agreement, genetic ablation studies reveal that elimination of senescent cells from aged tissues can ameliorate various age-related pathologies, including metabolic dysfunction and decreased physical fitness3-7. While small-molecule drugs capable of eliminating senescent cells (known as ‘senolytics’) partially replicate these phenotypes, many have uncertain mechanisms of action and all require continuous administration to be effective. As an alternative approach, we previously developed a cell-based senolytic therapy based on chimeric antigen receptor (CAR) T cells targeting uPAR, a cell-surface protein upregulated on senescent cells, and showed these can safely and efficiently eliminate senescent cells in young animals and reverse liver fibrosis8. We now show that uPAR-positive senescent cells accumulate during physiological aging and that they can be safely targeted with senolytic CAR T cells in aged animals. Treatment with anti uPAR CAR T cells ameliorates metabolic dysfunction by improving glucose tolerance and exercise capacity in physiological aging as well as in a model of metabolic syndrome. Importantly, the beneficial effects of senolytic CAR T cells are long lasting; single administration of a low dose is sufficient to achieve long-term therapeutic and preventive effects.
Project description:Cellular senescence is characterized by an irreversible cell cycle arrest and a pro-inflammatory senescence-associated secretory phenotype (SASP), which is a major contributor to aging and age-related diseases. Clearance of senescent cells has been shown to improve brain function in mouse models of neurodegenerative diseases. However, it is still unknown whether senescent cell clearance alleviates cognitive dysfunction during the aging process. To investigate this, we first conducted single-nuclei and single-cell RNA-seq in the hippocampus from young and aged mice. We observed an age-dependent increase in p16Ink4a senescent cells, which was more pronounced in microglia and oligodendrocyte progenitor cells and characterized by a SASP. We then aged INK-ATTAC mice, in which p16Ink4a-positive senescent cells can be genetically eliminated upon treatment with the drug AP20187 and treated them either with AP20187 or with the senolytic cocktail Dasatinib and Quercetin. We observed that both strategies resulted in a decrease in p16Ink4a exclusively in the microglial population, resulting in reduced microglial activation and reduced expression of SASP factors. Importantly, both approaches significantly improved cognitive function in aged mice. Our data provide proof-of-concept for senolytic interventions’ being a potential therapeutic avenue for alleviating age-associated cognitive impairment.
Project description:Dietary methionine restriction (MR) has been shown to increase lifespan and decrease adiposity in rodents. This study was designed to examine the transcriptional effects of MR in metabolically relevant tissues. This experiment contains data from the liver.