Biology subjects

Swanson, R. A.

Publications and source records attributed to Swanson, R. A..

9 recordsLinked to original sources

bioRxiv2026

Subspace communication in the hippocampal-retrosplenial axis

The capacity and flexibility of hippocampal circuits for transforming inputs into downstream outputs is fundamental for navigation and memory, yet the circuit-level mechanisms that allow this operation to adapt across experiences remain unknown. We approach this problem by performing large-scale (up to 1024-channel) recordings across the hippocampal-retrosplenial cortex (RSC) circuit in behaving mice, enabling simultaneous access to spiking activity in dentate gyrus (DG), CA3, CA2, CA1, RSC. Based on a linear dimensionality reduction technique known as partial canonical correlation analysis, we identify low-dimensional communication subspaces1 between two regions while accounting for measured third-area influences. These subspaces captured distinct input-output transformations in CA1, linking upstream (DG, CA3, and CA2) hippocampal activity to downstream cortical targets (RSC). Iintrinsic firing properties and anatomical location constrained subspace memberships--members were mapped to deep sublayers of the CA3-CA1-RSC axis during both spatial and non-spatial tasks. These subspaces could recombine overlapping neuronal pools to support distinct interareal interactions across changing experiences and brain states. Reactivation patterns of CA1-CA3 subspaces, but not those of CA1-RSC, during post-experience sleep correlated with replay, reflecting a plasticity-stability balance of the input-output transformation in the hippocampal-retrosplenial axis. Our data suggest a model in which hippocampal-neocortical communication reconfigures predetermined circuit motifs to flexibly encode experiences.

neuroscience↗

bioRxiv2025

Transcriptional and neuroprotective effects of hexokinase-2 inhibitors administered afterstroke

The inflammatory response induced by stroke can exacerbate injury to peri-infarct tissue. Microglia and other immune cells that mediate this response require increased glycolytic flux during pro-inflammatory activation. These cells, unlike neurons and most other cell types, utilize hexokinase-2 (HK2) rather than hexokinase-1 for glycolysis, such that HK2 inhibitors may selectively target them to suppress post-ischemic inflammation. Here we compared the effects of the non-selective hexokinase inhibitor 2-deoxyglucose to the HK2-selective inhibitors lonidamine and 3-bromopyruvate on secondary injury after stroke. A spatial transcriptomic assessment was performed in parallel to compare effects of the inhibitors on microglial gene expression and microglia - neuron interactions and to screen for off-target effects. Each of the inhibitors suppressed pro-inflammatory gene upregulation in peri-infarct microglia and attenuated the upregulation of cell stress functional pathways in the neighboring neurons, but had minimal effect on neuronal gene expression in uninjured cortex. The HK2-selective inhibitors were more effective than 2-deoxyglucose in suppressing morphological microglial changes, neuronal oxidative stress, and neurite loss. 3-bromopyruvate administered after stroke produced long-term improvements in functional outcome. Selective HK2 inhibitors may thus provide a clinically applicable means to suppress microglial activation and thereby improve outcomes after stroke without endangering neuronal energy metabolism.

neuroscience↗

bioRxiv2024

Topography of putative bidirectional interaction between hippocampal sharp wave ripples and neocortical slow oscillations

Systems consolidation relies on coordination between hippocampal sharp-wave ripples (SWRs) and neocortical UP/DOWN states during sleep. However, whether this coupling exists across neocortex and the mechanisms enabling it remain unknown. By combining electrophysiology in mouse hippocampus (HPC) and retrosplenial cortex (RSC) with widefield imaging of dorsal neocortex, we found spatially and temporally precise bidirectional hippocampo-neocortical interaction. HPC multi-unit activity and SWR probability was correlated with UP/DOWN states in mouse default mode network, with highest modulation by RSC in deep sleep. Further, some SWRs were preceded by the high rebound excitation accompanying DMN DOWN[->]UP transitions, while large-amplitude SWRs were often followed by DOWN states originating in RSC. We explain these electrophysiological results with a model in which HPC and RSC are weakly coupled excitable systems capable of bi-directional perturbation and suggest RSC may act as a gateway through which SWRs can perturb downstream cortical regions via cortico-cortical propagation of DOWN states.

neuroscience↗

bioRxiv2024

PATJ regulates cell stress responses and vascular remodeling post-stroke

PALS1-associated tight junction (PATJ) protein is linked to metabolic disease and stroke in human genetic studies. Despite the recognized role of PATJ in cell polarization, its specific functions in metabolic disease and ischemic stroke recovery remain largely unexplored. Using a mouse model of stroke, we found post-ischemic stroke duration-dependent increase of PATJ abundance in endothelial cells. PATJ knock-out (KO) HEK293 cells generated by CRISPR-Cas9 suggest roles for PATJ in cell proliferation, migration, mitochondrial stress response, and interactions with the Yes-associated protein (YAP)-1 signaling pathway. Notably, PATJ deletion altered YAP1 nuclear translocation. PATJ KO cells demonstrated extensive transcriptional reprograming based on RNA sequencing analysis. Crucially, we identified dysregulation in genes central to vascular development, stress response, and metabolism, including RUNX1, HEY1, NUPR1, and HK2. These insights offer a new understanding of PATJs complex regulatory functions within cellular and vascular physiology and help lay the groundwork for therapeutic strategies targeting endothelial PATJ-mediated pathways for stroke rehabilitation and neurovascular repair.

neuroscience↗

bioRxiv2024

Stress hyperglycemia exacerbates inflammatory brain injury after stroke

Post-stroke hyperglycemia occurs in 30% - 60% of ischemic stroke patients as part of the systemic stress response, but neither clinical evidence nor pre-clinical studies indicate whether post-stroke hyperglycemia affects stroke outcome. Here we investigated this issue using a mouse model of permanent ischemia. Mice were maintained either normoglycemic or hyperglycemic during the interval of 17 - 48 hours after ischemia onset. Post-stroke hyperglycemia was found to increase infarct volume, blood-brain barrier disruption, and hemorrhage formation, and to impair motor recovery. Post-stroke hyperglycemia also increased superoxide formation by peri-infarct microglia/macrophages. In contrast, post-stroke hyperglycemia did not increase superoxide formation or exacerbate motor impairment in p47phox-/- mice, which cannot form an active superoxide-producing NADPH oxidase-2 complex. These results suggest that hyperglycemia occurring hours-to-days after ischemia can increase oxidative stress in peri-infarct tissues by fueling NADPH oxidase activity in reactive microglia/macrophages, and by this mechanism contribute to worsened functional outcome.

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bioRxiv2024

Superoxide enters neurons via LRRC8A-containing volume-regulated anion channels

Superoxide (O2-) is both an intercellular signaling molecule and a cause of neuronal oxidative stress. Superoxide entry into neurons is thought to be indirect, requiring its dismutation to nonpolar hydrogen peroxide. Here we show instead that superoxide enters neurons directly, via LRRC8A-containing volume-sensitive organic anion channels. In primary cultures, neuronal oxidative stress induced either by NMDA receptor stimulation or exposure to authentic superoxide was blocked by the anion channel blockers DIDS and DCPIB and by LRRC8A gene disruption. In mouse cortex, neuronal oxidative stress induced by either NMDA injection or transient ischemia was likewise blocked by both DCPIB and LRRC8A gene disruption. These findings identify a role for LRRC8A-containing volume-sensitive organic anion channels in neuronal oxidative signaling, stress, and glutamate excitotoxicity.

neuroscience↗

bioRxiv2021

Cofilin pathology is a new player on α-synuclein-induced spine impairment in models of hippocampal synucleinopathy

Cognitive dysfunction and dementia are presently recognized as major complications in -synucleinopathies, namely in Dementia with Lewy Bodies (DLB) and Parkinsons disease with dementia (PDD). In these disorders, -Synuclein (Syn) accumulation affects severely the hippocampus by inducing synaptic dysfunction which culminates in cognitive impairment. To characterize the mechanisms underlying Syn-induced neuronal dysfunction we analysed the effect of overexpression or extracellular administration of Syn on hippocampal neurons. We observed that Syn induces the dysregulation of the actin-binding protein cofilin and its assembly into rod structures in a mechanism mediated by the cellular prion protein (PrPC). Moreover, we unraveled cofilin pathology as mediator of Syn-induced dendritic spine impairment in hippocampal neurons. Importantly, in a synucleinopathy mouse model with cognitive impairment we validated cofilin dysregulation and synaptic dysfunction at the same age when cognitive deficits were observed. Our data supports cofilin as a novel player on hippocampal synaptic dysfunction triggered by Syn on Lewy Body dementias.

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bioRxiv2019

α-synuclein aggregates induce c-Abl activation and neurodegeneration by a redox stress mechanism

ObjectiveRedox stress, c-Abl activation, and -synuclein aggregates each independently contribute to neurodegeneration in Parkinsons disease. Interactions between these factors may underlie convergent and feed-forward mechanisms of disease progression. Methods-synuclein aggregate formation was induced in neuronal cultures and mouse substantia nigra by exposure to pre-formed human -synuclein fibrils or by AAV-mediated over-expression of -synuclein. Aggregate formation, c-Abl activation, redox stress, and neurodegeneration were evaluated by immunohistochemistry and Western blots, and mouse motor function was evaluated using the rota-rod and pole tests. To suppress redox stress, cultures and mice were treated with N-acetyl cysteine, a thiol repletion agent that supports neuronal glutathione metabolism. ResultsIn primary neuron cultures, the formation of -synuclein aggregates led to redox stress and c-Abl activation. Redox stress alone, in the absence of -synuclein aggregates, was also sufficient to induced c-Abl activation. N-acetyl cysteine suppressed redox stress, and likewise suppressed both c-Abl activation and -synuclein aggregation. A similar pattern was observed in the two mouse models of Parkinsons disease. In both models, -synuclein aggregates in the substantia nigra were accompanied by redox stress, c-Abl activation, dopaminergic neurodegeneration and motor impairment, all of which were attenuated in mice treated with oral N-acetyl cysteine. InterpretationThese results indicate that -synuclein aggregates induce c-Abl activation by a redox stress mechanism. c-Abl in turn promotes -synuclein aggregation, and this potentially feed-forward process can be blocked by N-acetyl cysteine. The findings thus add mechanistic support for N-acetyl cysteine as a therapeutic for Parkinsons disease.

neuroscience↗

bioRxiv2018

Cofilin-actin rod formation in neuronal processes after brain ischemia

Functional impairment after brain ischemia results in part from loss of neuronal spines and dendrites, independent of neuronal death. Cofilin-actin rods are covalently linked aggregates of colfilin-1 and actin that form in neuronal processes (neurites) under conditions of ATP depletion and oxidative stress, and which cause neurite degeneration if not disassembled. ATP depletion and oxidative stress occur with differing severity, duration, and time course in different ischemic conditions. Here we evaluated four mouse models of brain ischemia to define the conditions that drive formation of cofilin-actin rods. Three of the models provide early reperfusion: transient middle cerebral artery occlusion (MCAo), transient bilateral common carotid occlusion (CCAo), and cardiac arrest / cardiopulmonary resuscitation (CA/CPR). Early reperfusion restores ATP generating capacity, but also induces oxidative stress. The fourth model, photothrombotic cortical infarction, does not provide reperfusion. Cofilin-actin rods were formed in each of these models, but with differing patterns. Where acute reperfusion occurred, rod formation was maximal within 4 hours after reperfusion. Where infarction occurred, rods continued to form for at least 24 hours after ischemic onset, and extended into the adjacent non-ischemic tissue. Interventions that limit cofilin-actin rod formation may help to preserve integrity of neuronal processes in permanent ischemia.

neuroscience↗