2020 — 2021 |
Eyo, Ukpong Bassey |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Mechanisms of Capillary-Associated Microglial Interactions
Project Summary The brain requires a significant amount of energy compared to other organs. This high energy demand is met by a dense network of blood vessel that deliver oxygen and nutrients and facilitates the removal of waste products. Therefore, the interactions between the neurovasculature and brain cells are important. While extensive work has been done to elucidate contributions by astrocytes and pericytes to vascular integrity, less work has been done to understand microglial interactions with the vasculature. Multiple lines of evidence suggest that microglia facilitate the development of the vasculature early in life and following injury or in disease. However, the extent of microglial interactions with the vasculature in homeostasis has not been adequately clarified. As resident immune cells, microglia are the brain?s first line of defense and it is possible that they could help detect pathogens or abnormalities in the circulation, but this would perhaps require stable physical interactions with the vasculature. In our preliminary studies for this project, we used in vivo two photon and electron microscopy approaches to document robust physical interactions between a subpopulation of microglial somata and the microvasculature (capillaries) across brain regions and brain age. Remarkably, even with pharmacological elimination and subsequent repopulation of microglia, the density of these capillary-associated microglia (CAM) was maintained suggesting that capillary association is a critical feature of microglial residence in the brain. In our proposed studies, we will: (1) attempt to differentiate CAMs from parenchymal microglia by using morphological, functional and transcriptional approaches; and (2) test the hypothesis that CAM interactions are facilitated by purine release from endothelial pannexins that recruit microglia through P2Y12 receptor sensing. This project is a first to thoroughly characterize capillary associated microglia and elucidate salient molecular mechanisms governing these interactions to understand microglia-vascular interactions in homeostasis.
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0.943 |
2021 |
Eyo, Ukpong Bassey |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Microglial-Neurovascular Dynamics and Regulation of Neurovascular Structure and Function
Project Summary The brain makes up 2% of the body?s weight but uses 20% of the body?s energy that is observed from the delivery of blood through the dense network of the neurovasculature. Neurovascular function is critical for optimal brain function and altered neurovascular function contributes or brain pathology. Microglia ate brain- resident immune cells that respond to brain injuries and disease but their interactions with the vasculature has been poorly explored. In my preliminary data, I extensively characterized microglial interactions with the neurovasculature in the healthy brain. Specifically, I have found that about a third of the microglia population physically interact with the neurovasculature through their cell bodies which are more stationary than their processes. Interestingly, a deficiency of Trem2, a microglial-specific risk gene for AD, results in a significant increase in microglial-vascular interactions. Finally, pharmacological elimination of CSF1R-expressing cells such as microglia resulted in increased vascular size and cerebral blood flow suggesting modulatory roles for microglia on the vasculature. In this project, I will further investigate this by (i) determining specific roles for microglia in regulating vascular structure and function; (ii) determining the requirement for astrocytic endfeet calcium signaling in mediating microglial-dependent vascular structure and functional regulation, and (iii) determine TREM2 roles in microglial-vascular interactions including vascular amyloid deposition in AD. These studies will provide insights into the cellular, molecular and mechanistic basis of microglial regulation of neurovascular structure and function.
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0.943 |
2021 |
Eyo, Ukpong Bassey |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Targeting Microglia in Febrile Status Epilepticus
PROJECT SUMMARY Febrile seizures are the most common form of childhood seizures. They affect 2-5% of children between the ages of 6 and 60 months. They occur with a rise in body temperature that is often associated with a fever, though the underlying mechanisms are not fully understood. In a subset of children with febrile seizure, seizures and convulsions are prolonged and are referred to as febrile status epilepticus (fSE). Some children that experience fSE go on to develop epilepsy in childhood or adulthood making childhood fSE a risk factor for subsequently developing epilepsy. Although the underlying mechanisms governing status epilepticus and epilepsy are known to emanate from neuronal dysfunction, compelling research in recent years suggest contributions from inflammation, broadly characterized, in fSE. This is evidenced by increased inflammatory mediators in fSE and reduced SE with broad-acting anti-inflammatory drugs. However, inflammation, can be generated by resident cells of the brain such as microglia and astrocytes as well as peripheral immune cells that can release inflammatory mediators outside the brain to alter neuronal function. Current research has thus far failed to delineate cell-specific contributions to inflammation in the context of fSE. In this project, we have begun to determine distinct contributions from microglia, the primary resident immune cell of the brain, in fSE. Given broadly detrimental roles for inflammation in fSE, it has been assumed that microglia, as inflammation-competent cells, promote fSE. Contrary to this assumption, our preliminary experimental results in both chemical- and hyperthermia- induced SE, indicate that microglia actually play beneficial roles in reducing SE severity in mouse models. Moreover, we have identified the microglial-specific P2Y12R as a candidate regulator of microglial beneficial contributions during experimental SE. Therefore, using well-established microglial elimination approaches, we will now: (1) test for general microglial roles in hyperthermia-induced SE and determine whether microglial regulate the neuroinflammatory environment in SE (Aim 1); (2) test for specific microglial P2Y12R roles in regulating microglial beneficial contributions to controlling hyperthermia-induced SE (Aim 2); and (3) determine microglial P2Y12R roles in the progression to temporal lobe epilepsy (TLE) using a novel mouse model follow early life exposure to hyperthermia-induced SE (Aim 3). This project is a first to adequately clarify microglial contributions in a mouse model of fSE as a pre-clinical model. This work will provide a framework for targeting microglia as a novel approach to ameliorate SE in general and fSE in particular.
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0.943 |