Browsing by Subject "Neurogenesis"
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Item AMP-Activated Protein Kinase (AMPK) signaling regulates the age-related decline of hippocampal neurogenesis(2018-05) Wang, Brian S.; Jin, Kunlin; Hodge, Lisa M.; Singh, Meharvan; Sumien, Nathalie; Yang, ShaohuaAging is the progressive decline of physiological function and increased vulnerability to disease and death. By the year 2050, 2 billion people will be over the age of 60. Accompanying this, the incidence of age-associated neurological diseases is expected to rise. Thus, there is an urgent need to find therapies to promote healthy brain aging. The finding that neurogenesis continues into adulthood allows us to target endogenous neurogenesis as a potential therapeutic. However, the number of stem cells can decrease by about 80% in the aged brain and is a main cause for the decrease in brain function. The reasons for the age-related decline in neurogenesis can be due to intrinsic factors such as cell metabolism, which have been studied but its role in neurogenesis remains largely unexplored. Interestingly, neural stem cells (NSCs) possess metabolically different characteristics from their differentiated progeny, suggesting the need for a shift in cellular metabolism to accommodate the requirements for neurogenesis. In the process of the metabolic shift, the AMP-activated protein kinase (AMPK) plays a pivotal role for controlling stem cell proliferation and differentiation as a cell's master metabolic regulator. Additionally, AMPK has been reported to control the functions of signaling pathways that regulate the aging process, which suggests its potential involvement in the age-related decline of neurogenesis. Therefore, we hypothesize that inhibition of AMPK signaling activation (phosphorylation) in the old brain will cause a concomitant increase in hippocampal neurogenesis. Our specific aim is to establish whether AMPK signaling plays a critical role in the age-related decline of hippocampal neurogenesis. Our objectives for this aim are to (i) determine the expression pattern of AMPK in the subgranular and subventricular zones of young-adult and old mice using immunohistochemistry and Western blotting; and (ii) examine the impact of loss or gain of AMPK activation on hippocampal neurogenesis in young-adult and old mice using pharmacological agents Compound C (AMPK inhibitor) and 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR, AMPK activator). Our results show that (i) AMPK subunit isoforms are differentially expressed in the neurogenic regions – most are localized to the cytoplasm in the subgranular zone (SGZ) with the exception of α2 and β1, while most isoforms are found in the nucleus in the subventricular zone (SVZ) except α1; (ii) AMPK signaling activation was significantly increased in the SGZ and SVZ; and (iii) short-term but not long-term pharmacological inhibition of AMPK signaling could partially rescue hippocampal neurogenesis in the old brain. Taken together, these results indicate that AMPK is a critical mediator in the regulation of downstream processes for the age-related decline in hippocampal neurogenesis.Item Novel pharmacotherapy: NNI-362, an allosteric p70S6 kinase stimulator, reverses cognitive and neural regenerative deficits in models of aging and disease(BioMed Central Ltd., 2021-01-13) Sumien, Nathalie; Wells, Matthew S.; Sidhu, Akram; Wong, Jessica M.; Forster, Michael J.; Zheng, Qiao-Xi; Kelleher-Andersson, Judith A.Aging is known to slow the neurogenic capacity of the hippocampus, one of only two mammalian adult neurogenic niches. The reduction of adult-born neurons with age may initiate cognitive decline progression which is exacerbated in chronic neurodegenerative disorders, e.g., Alzheimer's disease (AD). With physiologic neurogenesis diminished, but still viable in aging, non-invasive therapeutic modulation of this neuron regeneration process remains possible. The discovery of truly novel neuron regenerative therapies could be identified through phenotypic screening of small molecules that promote adult-born neurons from human neural progenitor cells (hNPCs). By identifying neuron-generating therapeutics and potentially novel mechanism of actions, therapeutic benefit could be confirmed through in vivo proof-of-concept studies. The key aging and longevity mTOR/p70S6 kinase axis, a commonly targeted pathway, is substrate for potential selective kinase modulators to promote new hippocampal neurons from NPCs. The highly regulated downstream substrate of mTOR, p70S6 kinase, directly controls pleiotropic cellular activities, including translation and cell growth. Stimulating this kinase, selectively in an adult neurogenic niche, should promote NPC proliferation, and cell growth and survival in the hippocampus. Studies of kinase profiling and immunocytochemistry of human progenitor neurogenesis suggest that the novel small molecule NNI-362 stimulates p70S6 kinase phosphorylation, which, in turn, promotes proliferation and differentiation of NPCs to neurons. NNI-362 promoted the associative reversal of age- and disease-related cognitive deficits in aged mice and Down syndrome-modeled mice. This oral, allosteric modulator may ultimately be beneficial for age-related neurodegenerative disorders involving hippocampal-dependent cognitive impairment, specifically AD, by promoting endogenous hippocampal regeneration.