Biology subjects

Shuttleworth, C. W.

Publications and source records attributed to Shuttleworth, C. W..

4 recordsLinked to original sources

bioRxiv2025

Initiation site of experimentally-evoked spreading depolarizations influence tissue outcomes in a murine stroke model

Spreading depolarization waves (SDs) are implicated in secondary expansion of brain injuries and are the target for initial clinical intervention trials. However, the assumption that SD directly causes neuronal injury has been challenged by recent findings with experimentally-induced SD in stroke models. The current study addressed this controversy by examining whether stroke consequences are confounded by the precise location of experimental SD initiation. Focal ischemic lesions were generated by transient distal middle cerebral artery occlusion in male mice. Clusters of SDs (6 at 10-min intervals) were induced by either focal KCl application or optogenetic stimulation during occlusion. SDs were initiated either in regions close to the infarct core (penumbral-SD; <50% perfusion) or in less compromised tissue in the same hemisphere (remote-SD; >70% perfusion). Despite the fact that all SDs fully invaded stroke expansion areas, the location of experimental SD induction had significant effects on stroke outcomes measured 48 hours after reperfusion. Penumbral-SDs resulted in larger infarct expansion than seen in control stroke mice lacking experimentally-imposed SD. Conversely, remote-SDs led to significantly smaller infarcts than stroke alone. Laser speckle contrast imaging of blood flow in injury expansion areas showed enhanced hypoperfusion responses after penumbral-SDs and larger hyperemic responses after remote-SDs, suggesting that differential vascular responses could contribute to stroke outcomes. Overall, this study helps to reconcile different prior reports by showing that experimentally-induced SDs can either exacerbate or reduce stroke-induced injury depending on the SD initiation site and further strengthens evidence for injurious roles of SDs initiating in vulnerable brain tissue.

neuroscience↗

bioRxiv2023

Synaptic Zn2+ contributes to deleterious consequences of spreading depolarizations

Spreading depolarizations (SDs) are profound waves of neuroglial depolarization that can propagate repetitively through injured brain. Recent clinical work has established SD as an important contributor to expansion of acute brain injuries and have begun to extend SD studies into other neurological disorders. A critical challenge is to determine how to selectively prevent deleterious consequences of SD. In the present study, we determined whether a wave of profound Zn2+ release is a key contributor to deleterious consequences of SD, and whether this can be targeted pharmacologically. Focal KCl microinjection was used to initiate SD in the CA1 region of the hippocampus in murine brain slices. An extracellular Zn2+ chelator with rapid kinetics (ZX-1) increased SD propagation rates and improved recovery of extracellular DC potential shifts. Under conditions of metabolic compromise, tissues showed sustained impairment of functional and structural recovery following a single SD. ZX-1 effectively improved recovery of synaptic potentials and intrinsic optical signals in these vulnerable conditions. Fluorescence imaging and genetic deletion of a presynaptic Zn2+ transporter confirmed synaptic release as the primary contributor to extracellular accumulation and deleterious consequences of Zn2+ during SD. These results demonstrate a role for synaptic Zn2+ release in deleterious consequences of SD and show that targeted extracellular chelation could be useful for disorders where repetitive SD enlarges infarcts in injured tissues.

neuroscience↗

bioRxiv2023

Repetitive Spreading Depolarization induces the activation of cell differentiation, synaptic plasticity and neuroprotective pathways.

Spreading depolarization (SD) is a slowly propagating wave of profound depolarization that sweeps through cortical tissue. While much emphasis has been placed on the damaging consequences of SD, there is uncertainty surrounding the potential activation of beneficial pathways such as cell survival and plasticity. The present study used unbiased assessments of gene expression to evaluate that compensatory and repair mechanisms could be recruited following SD, regardless of the induction method, which prior to this work had not been assessed. We also tested assumptions of appropriate controls and the spatial extent of expression changes that are important for in vivo SD models. SD clusters were induced with either KCl focal application or optogenetic stimulation in healthy mice. Cortical RNA was extracted and sequenced to identify differentially expressed genes (DEGs). SDs using both induction methods significantly upregulated 16 genes (versus sham animals) that included the cell proliferation-related genes FOS, JUN, and DUSP6, the plasticity-related genes ARC and HOMER1, and the inflammation-related genes PTGS2, EGR2, and NR4A1. The contralateral hemisphere is commonly used as control tissue for DEG studies, but its activity could be modified by near-global disruption of activity in the adjacent brain. We found 21 upregulated genes when comparing SD-involved cortex versus tissue from the contralateral hemisphere of the same animals. Interestingly, there was almost complete overlap (21/16) with the DEGs identified using sham controls. Neuronal activity also differs in SD initiation zones, where sustained global depolarization is required to initiate propagating events. We found that gene expression varied as a function of the distance from the SD initiation site, with greater expression differences observed in regions further away. Functional and pathway enrichment analyses identified axonogenesis, branching, neuritogenesis, and dendritic growth as significantly enriched in overlapping DEGs. Increased expression of SD-induced genes was also associated with predicted inhibition of pathways associated with cell death, and apoptosis. These results identify novel biological pathways that could be involved in plasticity and/or circuit modification in brain tissue impacted by SD. These results also identify novel functional targets that could be tested to determine potential roles in recovery and survival of peri-infarct tissues. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=46 SRC="FIGDIR/small/530317v2_ufig1.gif" ALT="Figure 1"> View larger version (9K): org.highwire.dtl.DTLVardef@1193589org.highwire.dtl.DTLVardef@9f68forg.highwire.dtl.DTLVardef@1a4f56org.highwire.dtl.DTLVardef@14eb6f4_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

Non-canonical glutamate signaling in a genetic model of migraine with aura

Migraine with aura is an extremely common but poorly understood sensory circuit disorder. Monogenic models allow an opportunity to understand its mechanisms, in particular because the migraine aura is associated with spreading depolarizations that can be measured physiologically. Using fluorescent glutamate imaging in awake mice carrying a familial hemiplegic migraine type 2 mutation, we recorded previously undescribed spontaneous plumes of glutamate signaling that anatomically overlapped with reduced density of GLT-1a positive astrocyte processes. These events could be mimicked in wild-type animals by inhibition of glutamate clearance, which we show to be slower during sensory processing in FHM2 carriers. Plumes depended on calcium mediated vesicular release from neurons, but not action potentials. Importantly, a rise in both basal glutamate and plume frequency predicted the onset of spreading depolarization in WT and FHM2 animals, providing a novel mechanism in migraine with aura and by extension the many other neurological disorders where spreading depolarizations occur.

neuroscience↗