Behavioral state-dependent microglia Ca2+ dynamics

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Principal Investigator: Martin  Paukert
Organization: UNIVERSITY OF TEXAS HLTH SCIENCE CENTER
Fiscal Year: 2024
Award: $193,750
Funding agency: National Institute of Mental Health

We propose to investigate a novel form of microglia Ca2+ signal that we have discovered in awake behaving
mice. It is the first microglia Ca2+ signal identified so far that represents a direct response to active, vigilant
behavior and neuronal activity within short latency (<10 seconds). Due to the complexity of experimental
procedures and the paucity of available data very little is known about microglia Ca2+ dynamics in awake
behaving mice. This is in striking contrast to the expected importance of Ca2+ signaling for microglia function.
From work on cultured microglia it is known that basic cellular processes such as cytoskeletal rearrangements,
which are a prerequisite for cell motility and phagocytosis, as well as most mechanisms underlying the secretion
of signaling molecules such as cytokines depend on intracellular fluctuations of Ca2+. Microglia express
numerous membrane proteins to potentially translate extracellular signals into intracellular Ca2+ elevations.
Among these are purinergic receptors, immune system-related receptors as well as ion channels. Specifically,
microglia express L-type Ca2+ channels (LTCCs). LTCCs have attracted special attention because antagonists
of this class of ion channels, traditionally applied to control blood pressure, have demonstrated therapeutic
potential for limiting neuroinflammation and cognitive impairments accompanying neurodegenerative diseases.
The contribution of microglia LTCCs to this therapeutic potential is not yet well established and it is not clear
when these ion channels become normally activated. For this proposal we will employ two-photon microscopy
on transgenic mice with microglia-specific expression of the genetically-encoded Ca2+ indicator GCaMP6f. The
mice will be head-fixed on a motorized linear treadmill for precise control over speed and duration of enforced
locomotion events in addition to the monitoring of voluntary locomotion events. Locomotion represents a reliable
means to induce moderate arousal, a behavioral state of heightened vigilance. To avoid a bias by the
experimental conditions the studies will include imaging of microglia through chronic cranial windows several
weeks following surgery as well as acute surgery experiments for topical pharmacology. Our preliminary
pharmacological experiments suggest that locomotion-induced microglia Ca2+ elevations depend on LTCCs. In
Aim 1 we will conduct a systematic characterization of the newly discovered locomotion-induced microglia Ca2+
elevations. We will investigate the kinetic constraints of the responses and test whether V1 microglia Ca2+
responses are affected by visual stimulation. In Aim 2 we will combine microglia-selective gene deletion and
pharmacological experiments to determine which LTCC subtype predominantly contributes to the responses.
Upon successful completion of the proposed experiments we will have established a rigorous foundation for
rational design of future studies aimed at unraveling the consequences of vigilance-dependent microglia Ca2+
responses for circuit activity and behavior. These findings may then open new avenues for microglia-centered
therapeutic interventions in neurodegenerative and neuropsychiatric diseases.

Terms: <2-photon microscopy><Acute><Affect><Anesthesia><Anesthesia procedures><Animals><Area><Arousal><Astrocytes><Astrocytus><Astroglia><Attention><BP control><BP management><Behavior><Behavioral><Brain><Brain Nervous System><Cell Body><Cell Communication and Signaling><Cell Function><Cell Locomotion><Cell Migration><Cell Movement><Cell Physiology><Cell Process><Cell Signaling><Cells><Cellular Function><Cellular Matrix><Cellular Migration><Cellular Motility><Cellular Physiology><Cellular Process><Cephalic><Chronic><Cognitive Disturbance><Cognitive Impairment><Cognitive decline><Cognitive function abnormal><Cranial><Cytoskeletal System><Cytoskeleton><Data><Degenerative Neurologic Disorders><Deterioration><Development><Disturbance in cognition><Encephalon><Endocytosis><Event><Foundations><Future><Gene Deletion><Head><Hortega cell><Image><Immune><Immune system><Immunes><Impaired cognition><Impairment><Individual><Inflammatory><Intracellular Communication and Signaling><Investigation><Ion Channel><Ion Channel Gating><Ion Channel Gatings><Ionic Channels><Ischemia><K element><Kinetics><Length><Link><Locomotion><Macrophage><Mechanics><Membrane><Membrane Channels><Membrane Protein Gene><Membrane Proteins><Membrane-Associated Proteins><Mice><Mice Mammals><Microglia><Molecular><Monitor><Motor><Murine><Mus><Mφ><Nerve Cells><Nerve Unit><Nervous System Degenerative Diseases><Nervous System Diseases><Nervous System Disorder><Neural Cell><Neural Degenerative Diseases><Neural degenerative Disorders><Neurocyte><Neurodegenerative Diseases><Neurodegenerative Disorders><Neurologic Degenerative Conditions><Neurologic Disorders><Neurological Disorders><Neurons><Operative Procedures><Operative Surgical Procedures><Pathologic><Phagocytes><Phagocytic Cell><Phagocytosis><Pharmacology><Photic Stimulation><Population><Potassium><Procedures><Process><Purine Receptors><Purinergic Receptors><Purinoceptor><Receptor Protein><Regulation><Reporting><Residual><Residual state><Signal Transduction><Signal Transduction Systems><Signaling><Signaling Molecule><Slice><Source><Speed><Subcellular Process><Surface Proteins><Surgical><Surgical Interventions><Surgical Procedure><Synapses><Synaptic><Testing><Therapeutic><Therapeutic Intervention><Transgenic Mice><Translating><Trauma><Trees><Visual><Visual Stimulation><Work><amebocyte><antagonism><antagonist><astrocytic glia><attenuation><awake><biological signal transduction><blood pressure control><blood pressure management><brain cell><cell motility><cognitive dysfunction><cognitive loss><cognitive performance><conditional knock-out><conditional knockout><cytokine><degenerative diseases of motor and sensory neurons><degenerative neurological diseases><density><developmental><experience><experiment><experimental research><experimental study><experiments><extracellular><gene deletion mutation><gene manipulation><genetic manipulation><genetically manipulate><genetically perturb><gitter cell><imaging><interest><intervention therapy><intracellular skeleton><mechanic><mechanical><membrane structure><mesoglia><microglial cell><microgliocyte><neural inflammation><neurodegenerative illness><neuroinflammation><neuroinflammatory><neurological disease><neuronal><neuropsychiatric disease><neuropsychiatric disorder><novel><perivascular glial cell><pharmacologic><rational design><receptor><response><selective expression><selectively expressed><sensory input><surgery><synapse><targeted drug therapy><targeted drug treatments><targeted therapeutic><targeted therapeutic agents><targeted therapy><targeted treatment><treadmill><two photon excitation microscopy><two photon microscopy><vigilance><visual process><visual processing><voltage>