Project description:Aging is the predominant risk factor for neurodegenerative diseases. One key phenotype as brain ages is the aberrant innate immune response characterized by proinflammation. However, the molecular mechanisms underlying aging-associated proinflammation are poorly defined. Whether chronic inflammation plays a causal role in cognitive decline in aging and neurodegeneration has not been established. Here we established a mechanistic link between chronic inflammation and aging microglia, and demonstrated a causal role of aging microglia in neurodegenerative cognitive deficits. Expression of microglial SIRT1 reduces with the aging of microglia. Genetic reduction of microglial SIRT1 elevates IL-1β selectively, and exacerbates cognitive deficits in aging and in transgenic mouse models of frontotemporal dementia (FTD). Interestingly, the selective activation of IL-1β transcription by SIRT1 deficiency is likely mediated through hypomethylating the proximal promoter of IL-1β. Consistent with our findings in mice, selective hypomethylation of IL-1β at two CpG sites are found in normal aging humans and demented patients with tauopathy. Our findings reveal a novel epigenetic mechanism in aging microglia that contributes to cognitive deficits in neurodegenerative diseases. Study of changes related to alterations of SIRT1 levels in microglia of young and aged animals and in models of neurodegenerative dementia
Project description:Aging is the predominant risk factor for neurodegenerative diseases. One key phenotype as brain ages is the aberrant innate immune response characterized by proinflammation. However, the molecular mechanisms underlying aging-associated proinflammation are poorly defined. Whether chronic inflammation plays a causal role in cognitive decline in aging and neurodegeneration has not been established. Here we established a mechanistic link between chronic inflammation and aging microglia, and demonstrated a causal role of aging microglia in neurodegenerative cognitive deficits. Expression of microglial SIRT1 reduces with the aging of microglia. Genetic reduction of microglial SIRT1 elevates IL-1β selectively, and exacerbates cognitive deficits in aging and in transgenic mouse models of frontotemporal dementia (FTD). Interestingly, the selective activation of IL-1β transcription by SIRT1 deficiency is likely mediated through hypomethylating the proximal promoter of IL-1β. Consistent with our findings in mice, selective hypomethylation of IL-1β at two CpG sites are found in normal aging humans and demented patients with tauopathy. Our findings reveal a novel epigenetic mechanism in aging microglia that contributes to cognitive deficits in neurodegenerative diseases.
Project description:Aging induces cognitive decline and Th2 cytokines have been found to promote neurogenesis and cognitive functions. ILC2 are potent producers of IL-5 and IL-13. The role of ILC2 in cognitive function in the context of aging has not been investigated. We report tissue resident ILC2 accumulate in the choroid plexus of the brain in aged mice. They are long-lived and can switch between cellular dormancy and proliferation in response to replication stress. ILC2 play a direct role in promoting the cognitive functions in aged mice, through producing IL-5. IL-5 has neuroprotective functions including neurogenesis and reducing pro-inflammatory functions of microglia in aged mice.
Project description:Microglia repair injury and maintain homeostasis in the brain, but whether aberrant microglial activation can contribute to neurodegeneration remains unclear. Here, we use transcriptome profiling to demonstrate that deficiency in frontotemporal dementia (FTD) gene progranulin (Grn) leads to an age-dependent, progressive up-regulation of lysosomal and innate immunity genes, increased complement production, and synaptic pruning activity in microglia. During aging, Grn-/- mice show profound accumulation of microglia and preferential elimination of inhibitory synapses in the ventral thalamus, which contribute to hyperexcitability in the thalamocortical circuits and obsessive-compulsive disorder (OCD)-like grooming behaviors. Remarkably, blocking complement activation by deleting C1qa gene significantly reduces synaptic pruning by Grn-/- microglia, and mitigates neurodegeneration, behavioral phenotypes and premature mortality in Grn-/- mice. These results uncover a previously unrecognized role of progranulin in suppressing microglia activation during aging, and support the idea that blocking complement activation is a promising therapeutic target for neurodegeneration caused by progranulin deficiency. Gene expression study in multiple brain regions from a mouse model of progranulin deficiency Please note that 9 outlier samples were excluded from data analysis. Therefore, there are 326 raw data columns (i.e. 163 samples) in the non_normalized data matrix while 154 samples are represented here.
Project description:Alzheimer’s disease (AD) is an age-related neurodegenerative disorder characterized by progressive decline of cognitive ability. An important component of AD, and other chronic neurodegenerative diseases, is generation of an innate inflammatory response within the CNS, characterized by activation of microglia, the resident immune cells of the brain. Transcription factor PU.1 has been known to play an important role in myeloid and lymphoid cell development, however its function in microglia and how it contributes to disease pathology is not well understood. Using transcriptional and chromatin state profiles during AD-like pathology in the CK-p25 mouse model of neurodegeneration, we showed that PU.1 specifically targets noncoding regions which regulate expression changes of immune response genes during AD, suggesting it may act as master regulator of microglia activation. Here, we examine the role of PU.1 in neurodegeneration by using a conditional knockout (cKO) cassette (Cx3cr1CreER+/-) to inducibly deplete PU.1 from microglia in the CK-p25 mouse model of neurodegeneration. We found that knocking out PU.1 rescues multiple neurodegenerative phenotypes. Specifically, PU.1 inhibition reduces neurodegeneration-specific increase in microglia cell number, improves neuronal survival and reverses functional synaptic plasticity deficits in the hippocampus of the CK-p25 mouse.
Project description:Microglia repair injury and maintain homeostasis in the brain, but whether aberrant microglial activation can contribute to neurodegeneration remains unclear. Here, we use transcriptome profiling to demonstrate that deficiency in frontotemporal dementia (FTD) gene progranulin (Grn) leads to an age-dependent, progressive up-regulation of lysosomal and innate immunity genes, increased complement production, and synaptic pruning activity in microglia. During aging, Grn-/- mice show profound accumulation of microglia and preferential elimination of inhibitory synapses in the ventral thalamus, which contribute to hyperexcitability in the thalamocortical circuits and obsessive-compulsive disorder (OCD)-like grooming behaviors. Remarkably, blocking complement activation by deleting C1qa gene significantly reduces synaptic pruning by Grn-/- microglia, and mitigates neurodegeneration, behavioral phenotypes and premature mortality in Grn-/- mice. These results uncover a previously unrecognized role of progranulin in suppressing microglia activation during aging, and support the idea that blocking complement activation is a promising therapeutic target for neurodegeneration caused by progranulin deficiency.
Project description:Aging leads to a progressive deterioration in brain function, which will eventually result in cognitive decline and can develop into a dementia. The mechanisms underlying pathological cognitive decline in aging are still poorly understood. The peripheral immune system, as well as the meningeal lymphatic vasculature and the immune cells residing in the brain and meninges, are all affected by aging. Moreover, recent studies have linked the dysfunction of the meningeal lymphatic system and peripheral immunity to accelerated brain aging. We hypothesized that an age-related reduction in CCR7-dependent immune cell egress through the lymphatic vasculature mediates some aspects of aging-associated brain dysfunction, leading to cognitive decline and potentially exacerbating neurodegenerative diseases. Here, we report a reduction in CCR7 expression by meningeal T cells in aged mice and its associated increase in meningeal T-regulatory cells. Hematopoietic CCR7 deficiency mimicked the aging-associated changes in meningeal T cells and led to cognitive impairment. Interestingly, CCR7-deficient mice also presented impaired brain glymphatic function and showed increased amyloid beta (A) deposition when crossed with the 5xFAD transgenic mouse model of Alzheimer’s disease (AD). These results show that the aging-associated decrease in CCR7 expression impacts meningeal immunity, affects different aspects of brain function and exacerbates brain A pathology, highlighting its potential as a pathogenic mechanism for cognitive decline in aging and AD.
Project description:Aging is the primary risk factor for most neurodegenerative diseases, including Alzheimer's disease. Major hallmarks of brain aging include neuroinflammation/immune activation and reduced neuronal health/function. These processes contribute to cognitive dysfunction (a key risk factor for Alzheimer's disease), but their upstream causes are incompletely understood. Age-related increases in transposable element (TE) transcripts might contribute to reduced cognitive function with brain aging, as the reverse transcriptase inhibitor 3TC reduces inflammation in peripheral tissues and TE transcripts have been linked with tau pathology in Alzheimer's disease. However, the effects of 3TC on cognitive function with aging have not been investigated. Here, in support of a role for TE transcripts in brain aging/cognitive decline, we show that 3TC: (a) improves cognitive function and reduces neuroinflammation in old wild-type mice; (b) preserves neuronal health with aging in mice and Caenorhabditis elegans; and (c) enhances cognitive function in a mouse model of tauopathy. We also provide insight on potential underlying mechanisms, as well as evidence of translational relevance for these observations by showing that TE transcripts accumulate with brain aging in humans, and that these age-related increases intersect with those observed in Alzheimer's disease. Collectively, our results suggest that TE transcript accumulation during aging may contribute to cognitive decline and neurodegeneration, and that targeting these events with reverse transcriptase inhibitors like 3TC could be a viable therapeutic strategy.
Project description:Microglia are important immune cells in the brain. Microglia undergo a series of alterations during aging and increase the susceptibility to brain dysfunctions. However, the characteristics of microglia during the aging process are not fully understood. In this study, we mapped transcriptional and epigenetic profiles of microglia from 3- to 24-month-old mice. We observed unexpected gender divergences and identified age-dependent microglia (ADEM) genes in the aging process. We then compared characteristics between microglial aging and activation. To dissect the function of aged microglia excluding the influence from other aged brain cells, we established an accelerated microglial turnover model without directly affecting other brain cells. By this model, we achieved aged microglia in non-aged brains and confirmed that aged microglia per se contribute to cognitive decline. Collectively, we provide a comprehensive resource to decode the aging process of microglia, shedding light on how microglia maintain brain functions.
Project description:Microglia are important immune cells in the brain. Microglia undergo a series of alterations during aging and increase the susceptibility to brain dysfunctions. However, the characteristics of microglia during the aging process are not fully understood. In this study, we mapped transcriptional and epigenetic profiles of microglia from 3- to 24-month-old mice. We observed unexpected gender divergences and identified age-dependent microglia (ADEM) genes in the aging process. We then compared characteristics between microglial aging and activation. To dissect the function of aged microglia excluding the influence from other aged brain cells, we established an accelerated microglial turnover model without directly affecting other brain cells. By this model, we achieved aged microglia in non-aged brains and confirmed that aged microglia per se contribute to cognitive decline. Collectively, we provide a comprehensive resource to decode the aging process of microglia, shedding light on how microglia maintain brain functions.