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NogoA-expressing astrocytes limit peripheral macrophage infiltration after ischemic brain injury in primates

ABSTRACT: Reactive astrocytes play critical roles after brain injury, but their precise function is not well defined, particularly in humans and nonhuman primates (NHPs). Here, we utilized single nuclei transcriptomics to characterize astrocytes after ischemic stroke in the primary visual cortex (V1) of the marmoset monkey. We observed nearly complete segregation between stroke and control astrocyte clusters. Screening the top 30 differentially expressed genes to identify candidates that might limit stroke recovery, we discovered that RTN4A/ NogoA, a neurite-outgrowth inhibitory protein previously associated specifically with oligodendrocytes but not astrocytes, was expressed in a majority of reactive astrocytes. Robust NogoA upregulation on reactive astrocytes following stroke was confirmed in both the marmoset and human brain, whereas rodents exhibited only a marginal change in NogoA expression following stroke. Further, in vivo and in vitro studies determined that NogoA mediated an anti-inflammatory response which likely contributes to limiting deeper infiltration of peripheral macrophages into the surviving parenchyma during the subacute post-stroke period. These findings are directly relevant to the development of NogoA-targeting therapies designed for clinical use shortly after ischemic stroke. In addition, our data have uncovered the complexity of astrocyte responses in primates, which highlights the importance of preclinical model selection for discovery research designed to identify novel therapeutics for brain injury.

ORGANISM(S): Callithrix jacchus

PROVIDER: GSE179141 | GEO | 2021/10/18

REPOSITORIES: GEO

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Project description:MartínJiménez2017 - Genome-scale reconstruction of the human astrocyte metabolic network This model is described in the article: Genome-Scale Reconstruction of the Human Astrocyte Metabolic Network. Martín-Jiménez CA, Salazar-Barreto D, Barreto GE, González J. Front Aging Neurosci 2017; 9: 23 Abstract: Astrocytes are the most abundant cells of the central nervous system; they have a predominant role in maintaining brain metabolism. In this sense, abnormal metabolic states have been found in different neuropathological diseases. Determination of metabolic states of astrocytes is difficult to model using current experimental approaches given the high number of reactions and metabolites present. Thus, genome-scale metabolic networks derived from transcriptomic data can be used as a framework to elucidate how astrocytes modulate human brain metabolic states during normal conditions and in neurodegenerative diseases. We performed a Genome-Scale Reconstruction of the Human Astrocyte Metabolic Network with the purpose of elucidating a significant portion of the metabolic map of the astrocyte. This is the first global high-quality, manually curated metabolic reconstruction network of a human astrocyte. It includes 5,007 metabolites and 5,659 reactions distributed among 8 cell compartments, (extracellular, cytoplasm, mitochondria, endoplasmic reticle, Golgi apparatus, lysosome, peroxisome and nucleus). Using the reconstructed network, the metabolic capabilities of human astrocytes were calculated and compared both in normal and ischemic conditions. We identified reactions activated in these two states, which can be useful for understanding the astrocytic pathways that are affected during brain disease. Additionally, we also showed that the obtained flux distributions in the model, are in accordance with literature-based findings. Up to date, this is the most complete representation of the human astrocyte in terms of inclusion of genes, proteins, reactions and metabolic pathways, being a useful guide for in-silico analysis of several metabolic behaviors of the astrocyte during normal and pathologic states. This model is hosted on BioModels Database and identified by: MODEL1608180000. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:Glaucoma leads to vision loss due to retinal ganglion cell death. Astrocyte reactivity contributes to neurodegeneration. Our recent study found that lipoxin B4 (LXB4), produced by retinal astrocytes, has direct neuroprotective actions on retinal ganglion cells. In this study, we aimed to investigate how the autacoid LXB4 influences astrocyte reactivity in the retina under inflammatory cytokine-induced activation and ocular hypertension conditions. The protective activity of LXB4 was investigatedin vivousing the mouse silicone-oil model of chronic ocular hypertension (n=40). By employing a range of analytical techniques, including bulk RNA-seq, RNAscope in-situhybridization, qPCR, and lipidomic analyses, we discovered the formation of neuroprotective lipoxins in rodents (including the retina and optic nerve), primates (optic nerve), and human brain astrocytes, indicating their presence across various species. Our findings in the mouse retina demonstrated significant dysregulation of the lipoxin pathway in response to chronic ocular hypertension, leading to an increase in 5-lipoxygenase (5-LOX) activity and a decrease in 15-lipoxygenase activity. This dysregulation was coincident with a marked upregulation of astrocyte reactivity. Reactive human brain astrocytes also showed a significant increase in 5-LOX. Administration of LXB4 regulated the lipoxin pathway, restored and amplified LXA4 generation (another lipoxin with distinct bioactions), and mitigated astrocyte reactivity in mouse retinas and human brain astrocytes. In conclusion, the lipoxin pathway is functionally expressed in rodents, primates, and human astrocytes, and is a resident neuroprotective pathway that is downregulated in reactive astrocytes. Novel cellular targets for LXB4’s neuroprotective action are inhibition of astrocyte reactivity and restoration of lipoxin generation. Amplifying the lipoxin pathway is a potential target to disrupt or prevent astrocyte reactivity in neurodegenerative diseases.

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NogoA-expressing astrocytes limit peripheral macrophage infiltration after ischemic brain injury in primates

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