Biology subjects

Quillinan, N.

Publications and source records attributed to Quillinan, N..

9 recordsLinked to original sources

bioRxiv2026

Novel neonatal hypoxic-ischemic model demonstrates neuroinflammation-associated memory deficits without neuronal loss

BackgroundNeonatal global hypoxic-ischemic cerebral injury is a leading cause of infant mortality and lifelong disability. Current rodent models do not replicate neonatal global cerebral ischemia (nGCI) and reperfusion injury. Here, we developed and characterized a rodent model of cardiac arrest and cardiopulmonary reperfusion (CA/CPR) to induce nGCI, producing acute systemic ischemia, mild neuronal injury, white matter alterations, and motor and memory deficits. MethodsRat pups underwent CA/CPR or sham procedure on postnatal day 9-11. CA/CPR in rat pups was performed under anesthesia while intubated. Asystole was induced with intravenous (IV) KCl and maintained for 10-14 minutes. Resuscitation included oxygen ventilation, chest compressions, and IV epinephrine. ResultsTwelve minutes of asystole provided an optimal balance between survival and systemic injury. Behavioral testing on postoperative day (POD) 7 revealed memory impairments. Despite the absence of overt neuronal death in the hippocampus or cerebellum, we observed evidence of glial activation and white matter alterations. ConclusionThis novel rodent model of nGCI addresses limitations in existing models while offering clinically relevant features to support future mechanistic and translational research. ImpactO_LIThis study validates cardiac arrest and cardiopulmonary resuscitation (CA/CPR) as a novel model for neonatal global cerebral ischemia (nGCI), complementing existing rodent models of unilateral and permanent injury by enabling investigation of both global ischemia and reperfusion injury. C_LIO_LInGCI results in memory impairment in the absence of overt neuronal cell death. Functional deficits are associated with neuroinflammatory responses in the hippocampus, white matter, and cerebellum. C_LIO_LINeonatal CA/CPR induces global cerebral ischemia which uniquely allows investigation of hindbrain structures, such as cerebellum, which are typically spared in existing rodent models of neonatal hypoxia-ischemia. C_LI

neuroscience↗

bioRxiv2025

Oxygen/glucose-deprivation causes long-term impairment of synaptic CaMKII movement

Learning and memory are thought to require hippocampal long-term potentiation (LTP), a form of synaptic plasticity that is persistently impaired after cerebral ischemia and that requires movement of the Ca2+/calmodulin-dependent protein kinase II (CaMKII) to excitatory synapses. We show here that oxygen/glucose-deprivation (OGD) in cultures hippocampal neurons causes a long-lasting impairment of CaMKII movement. Notably, CaMKII inhibition at 30 min after onset of OGD prevented the impairment in CaMKII movement. Thus, CaMKII mediates both, LTP mechanisms and their ischemia-induced impairment. These findings provide a mechanism by which ischemic conditions can impair LTP and explain how CaMKII inhibition after cerebral ischemia can prevent these LTP impairments.

neuroscience↗

bioRxiv2025

Enhanced Calcium Signaling in BLA Pyramidal Neurons Underlies a Sex and Circuit Specific Amygdala Dysfunction After Global Cerebral Ischemia

While advances in resuscitation science have improved cardiac arrest survival, we lack therapies to improve cognitive-affective outcomes in this patient population. Our lab has previously identified cognitive dysfunction in a mouse model of global cerebral ischemia (GCI) which has been attributed to hippocampal neurodegeneration and impaired hippocampal plasticity. However, no study has attempted to identify amygdala dysfunction after GCI, despite clinical evidence of emotional dysfunction, such as anxiety and Post-Traumatic Stress Disorder (PTSD). Therefore, it is important to identify the effect that GCI has on the amygdala, the emotional center of the brain. Our lab has a well-developed, translatable mouse model of GCI, the cardiac arrest/cardiopulmonary resuscitation model (CA/CPR), that has been instrumental in assessing amygdala function after GCI. We have utilized the amygdala-dependent delay-fear conditioning (DFC) paradigm to assess associative learning and memory and have performed field excitatory post-synaptic potential (fEPSP) recordings in two circuits within the amygdala, as measures of amygdala function. We have found a sex- and circuit-specific deficit in LTP of the cortical input to the basolateral amygdala (BLA), after GCI, that corresponds with a male specific associative learning and memory deficit. We found no evidence that these deficits of amygdala function can be attributed to GCI-induced neurodegeneration within the amygdala or altered locomotor function. We did, however, find that neuronal dendritic spine calcium signaling dynamics are enhanced in male survivors of GCI and are likely contributing to the observed LTP deficit and ultimately the deficit in associative learning and memory processes. Significance StatementWhile cognitive dysfunction has been well characterized in CA/CPR survivors, the development of emotional dysfunction that may arise in survivors is understudied. Poor follow up of CA/CPR survivors has left a gap in our knowledge about the effect that GCI has on the amygdala, the emotional center of the brain. Thus, this study utilized a pre-clinical mouse model of CA/CPR to characterize amygdala dysfunction that arises from GCI. We found a male-specific deficit in associative learning and memory that corresponds with a circuit specific LTP deficit, which arises from elevated calcium signaling in dendritic spines. Thus, this study provides valuable information and rationale for extended follow up of CA/CPR survivors to identify and treat the development of GCI-induced affective disorders.

neuroscience↗

bioRxiv2024

Harnessing micrometer-scale tPA beads for high plasmin flux and accelerated fibrinolysis

Rapid restoration of blood flow is critical in treating acute ischemic stroke. Current fibrinolytic therapies using tissue plasminogen activator (tPA) are limited by low recanalization rates and risks of off-target bleeding. Here, we present a strategy using tPA immobilized on micrometer-scale beads to enhance local plasmin generation. We synthesized tPA-functionalized beads of varying sizes (0.1 m and 1.0 m) and evaluated their efficacy. In vitro assays demonstrated that 1.0 m tPA-beads generated higher plasmin generation compared to free tPA and 0.1 m beads, overcoming antiplasmin inhibition and promoting a self-propagating wave of fibrinolysis. In a murine model of acute ischemic stroke, intravenous administration of 1.0 m tPA-beads at doses nearly two orders of magnitude lower than the standard free tPA dose led to rapid and near-complete thrombus removal within minutes. This approach addresses kinetic and transport limitations of current therapies and may reduce the risk of hemorrhagic complications. TeaserMicrometer-scale tPA beads improve stroke treatment by enhancing local clot-dissolving action.

bioengineering↗

bioRxiv2023

TRPM2-CaMKII signaling drives excessive GABAergic synaptic inhibition following ischemia

Following an ischemic insult to the brain, there is an acute loss of GABAergic inhibitory synapses and an increase in excitatory/ inhibitory (E/I) imbalance that drives neuronal hyperexcitability. It is unknown whether this E/I imbalance persists at delayed timepoints and contributes to chronic impairments in memory and long-term potentiation (LTP) in the hippocampus following ischemic brain injury. Here, we reveal a shift to reduced E/I ratio in hippocampal CA1 neurons via a persistent increase in postsynaptic GABAA receptor mediated inhibitory responses and clustering days after a global ischemic insult. This enhancement of postsynaptic inhibitory function and clustering required activation of the Ca2+-permeable TRPM2 ion channel and the Ca2+-dependent kinase, CaMKII. Thus, we propose a mechanism in which acute downregulation of GABAA receptors is followed by a strengthening of inhibitory synapses at delayed periods after ischemia. Targeting this mechanism has therapeutic potential to recover hippocampal plasticity and cognitive function post-ischemia. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=123 SRC="FIGDIR/small/556550v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@16ef5f2org.highwire.dtl.DTLVardef@1d51f19org.highwire.dtl.DTLVardef@ecc726org.highwire.dtl.DTLVardef@106cdd0_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2023

Distinct excitability of thalamocortical neurons correlates with the presence of cerebellar afferents

Thalamocortical (TC) neurons within the ventrolateral thalamus (VL) receive projections from the cerebellum and the basal ganglia (BG) to facilitate motor and non-motor functions. Tonic and rebound firing patterns in response to excitatory cerebellar and inhibitory BG inputs, respectively, are a canonical feature of TC neurons and plays a key role in signal processing. The intrinsic excitability of TC neurons has a strong influence on how they respond to synaptic inputs, however, it is unknown whether their afferents influence their firing properties. Understanding the input-specific firing patterns could shed light into movement disorders with cerebellar or BG involvement. Here, we used whole-cell electrophysiology in brain slices from C57BL/6 mice to investigate the firing of TC neurons with optogenetic confirmation of cerebellar or BG afferents. TC neurons with cerebellar afferents exhibited higher tonic and rebound firing rates than those with BG afferents. This increased firing was associated with faster action potential depolarization kinetics and a smaller afterhyperpolarization potential. We also found differences in the passive membrane properties and sag currents during hyperpolarization. Despite higher rebound firing in TC neurons with cerebellar afferents, there were no differences in T-type calcium channel function compared to those with BG inputs. These data suggest input-specific differences in sodium and SK, but not T-type calcium channels, impact firing properties in TC populations. Altogether, we showed that the pronounced divergence observed in TC neuron firing properties correlate with its heterogeneous anatomical connectivity, which could signify a distinct signal integration and processing by these neurons.

neuroscience↗

bioRxiv2023

Short-term CaMKII inhibition with tatCN19o does not erase pre-formed memory and is neuroprotective in non-rodents

The Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a central regulator of learning and memory, which poses a problem for targeting it therapeutically. Indeed, our study supports prior conclusions that long-term interference with CaMKII signaling can erase pre-formed memories. By contrast, short-term pharmacological CaMKII inhibition with tatCN19o interfered with learning in mice only mildly and transiently (for less than 1 h) and did not at all reverse pre-formed memories. This was at [≥]500fold of the dose that protected hippocampal neurons from cell death after a highly clinically relevant pig model of transient global cerebral ischemia: ventricular fibrillation followed by advanced life support and electrical defibrillation to induce return of spontaneous circulation. Of additional importance for therapeutic development, cardiovascular safety studies in mice and pig did not indicate any concerns with acute tatCN19o injection. Taken together, even though prolonged interference with CaMKII signaling can erase memory, acute short-term CaMKII inhibition with tatCN19o did not cause such retrograde amnesia that would pose a contraindication for therapy.

neuroscience↗

bioRxiv2023

Chronic Changes In Oligodendrocyte Sub-Populations After Middle Cerebral Artery Occlusion in Neonatal Mice.

BackgroundNeonatal stroke is common and causes life-long motor and cognitive sequelae. Because neonates with stroke are not diagnosed until days-months after the injury, chronic targets for repair are needed. We evaluated oligodendrocyte maturity and myelination and assessed oligodendrocyte gene expression changes using single cell RNA sequencing (scRNA seq) at chronic timepoints in a mouse model of neonatal arterial ischemic stroke. MethodsMice underwent sixty minutes of transient right middle cerebral artery occlusion (MCAO) on postnatal day 10 (p10) and received 5-ethynyl-2-deoxyuridine (EdU) on post-MCAO days 3-7 to label dividing cells. Animals were sacrificed 14 and 28-30 days post-MCAO for immunohistochemistry and electron microscopy. Oligodendrocytes were isolated from striatum 14 days post-MCAO for scRNA seq and differential gene expression analysis. ResultsThe density of Olig2+EdU+ cells was significantly increased in ipsilateral striatum 14 days post-MCAO and the majority of oligodendrocytes were immature. Density of Olig2+EdU+ cells declined significantly between 14 and 28 days post-MCAO without a concurrent increase in mature Olig2+EdU+ cells. By 28 days post-MCAO there were significantly fewer myelinated axons in ipsilateral striatum. scRNA seq identified a cluster of "disease associated oligodendrocytes (DOLs)" specific to the ischemic striatum, with increased expression of MHC class I genes. Gene ontology analysis suggested decreased enrichment of pathways involved in myelin production in the reactive cluster. ConclusionsOligodendrocytes proliferate 3-7 days post-MCAO and persist at 14 days, but fail to mature by 28 days. MCAO induces a subset of oligodendrocytes with reactive phenotype, which may be a therapeutic target to promote white matter repair.

neuroscience↗

bioRxiv2021

Extracellular vesicles Transfer Polarized Mitochondria and Increase Cellular Energetics in Ischemic Endothelial Cells

We have demonstrated, for the first time that microvesicles, a sub-type of extracellular vesicles (EVs) derived from hCMEC/D3: a human brain endothelial cell (BEC) line transfer polarized mitochondria to recipient BECs in culture and to neurons in mice acute brain cortical and hippocampal slices. This mitochondrial transfer increased ATP levels by 100 to 200-fold (relative to untreated cells) in the recipient BECs exposed to oxygen-glucose deprivation, an in vitro model of cerebral ischemia. We have also demonstrated that transfer of microvesicles, the larger EV fraction, but not exosomes resulted in increased mitochondrial function in hypoxic endothelial cultures. Gene ontology and pathway enrichment analysis of EVs revealed a very high association to glycolysis-related processes. In comparison to heterotypic macrophage- derived EVs, BEC-derived EVs demonstrated a greater selectivity to transfer mitochondria and increase endothelial cell survival under ischemic conditions. HighlightsO_LIMicrovesicles transfer mitochondria to endothelial cells and brain slice neurons C_LIO_LIMitochondrial transfer increased ATP in ischemic brain endothelial cells (BECs) C_LIO_LITransfer of microvesicles increased mitochondrial function in hypoxic BECs C_LIO_LITransfer of exosomes did not affect mitochondrial function in hypoxic BECs C_LIO_LIHomotypic BEC-derived EVs result in greater ATP levels in the recipient BECs C_LI

bioengineering↗