Biology subjects

Gagolewicz, P. J.

Publications and source records attributed to Gagolewicz, P. J..

2 recordsLinked to original sources

bioRxiv2026

Towards Identifying a Molecular Activator of Spreading Depolarization Generated by the Ischemic Brain

Spreading depolarizations (SDs) are waves of mass depolarization that propagate through gray matter following Na+/K+-ATPase (NKA) failure because of stroke, traumatic brain injury or sudden cardiac arrest. SDs expand the initial site of neuronal injury and worsen clinical outcomes. The molecular events underlying SD initiation and propagation are not well understood. In this rodent study, we hypothesized that gray matter stressed by oxygen/glucose deprivation (OGD) releases a compound(s) that promotes SD, which we term a spreading depolarization activator (SDa). We used rat brain slices incubated in artificial cerebrospinal fluid (aCSF) and subjected to OGD to release a putative SDa. The aCSF was collected either prior to ("Pre-SD aCSF") or 10 min after initiation of OGD conditions ("Post-SDOGD aCSF"). These solutions were then separately superfused over a healthy, naive (non-stressed) brain slice. Post-SDOGD aCSF (with re-normalized O2 and glucose) evoked SD in 82.35% of the naive brain slices (n = 17) whereas Pre-SD aCSF evoked no SD in 10 naive slices. Then to investigate the NKA as a potential target of the SDa, we used a hemolysis assay, comparing the effects of Pre- or Post-SDOGD aCSF on red blood cell (RBC) lysis and compared it to the known hemolytic effect of the NKA-specific inhibitor, palytoxin. Post-SDOGD aCSF evoked neither swelling nor lysis of RBCs on its own. However, when a sub-threshold concentration (0.01-0.02 nM) of the specific NKA inhibitor palytoxin (PLTX) was added, a striking "priming" effect was observed, whereby Post-SDOGD aCSF evoked a highly significant increase in both RBC swelling and then hemolysis, compared to Pre-SD aCSF. High pressure liquid chromatography (HPLC) experiments show a several-fold increase in released molecules post-SD vs pre-SD. Overall, this study provides support for SDa release capable of inducing SD-associated swelling in brain slices and, when combined with a trace amount of PLTX, swelling/hemolysis of RBCs caused by NKA inhibition. A greater understanding of the molecular events underlying SD should identify novel targets to reduce recurrent SD-evoked neuronal injury under ischemic conditions.

neuroscience↗

bioRxiv2024

Simulated ischemia in live cerebral slices is mimicked by opening the Na+/K+ pump: clues to the generation of spreading depolarization.

The gray matter of the higher brain undergoes spreading depolarization (SD) in response to the increased metabolic demand of ischemia, promoting acute neuronal injury and death. The mechanism linking ischemic failure of the Na+/K+ ATPase (NKA) to the subsequent onset of a large inward current driving SD in neurons has remained a mystery because blockade of conventional channels does not prevent SD nor ischemic death. The marine poison palytoxin (PLTX) specifically binds the NKA transporter at extremely low concentrations, converting it to an open cationic channel, causing sudden neuronal Na+ influx and K+ efflux. Pump failure and induction of a strong inward current should induce dramatic SD-like activity. Indeed,1-10 nM PLTX applied to live coronal brain slices induces a propagating depolarization remarkably like SD induced by oxygen/glucose deprivation (OGD) as revealed by imaging. This PLTX depolarization (PD) mimicked other effects of OGD. In neocortex, as the elevated LT front passed by an extracellular pipette, a distinct negative DC shift was recorded, indicating cell depolarization, whether induced by OGD or by bath PLTX. Either treatment induced strong SD-like responses in the same higher and lower brain regions. Further, we imaged identical real-time OGD-SD or PD effects upon live pyramidal neurons using 2-photon microscopy. Taken together, these findings support our proposal that, like most biological poisons, PLTX mimics (and takes advantage of) a biological process,ie is brain ischemia. An endogenous PLTX-like molecule may open the NKA to evoke Na+ influx/K+ efflux that drive SD and the ensuing neuronal damage in its wake. New and NoteworthyWith stroke, traumatic brain injury, or sudden cardiac arrest, there is no therapeutic drug to aid brain protection and recovery. Within 2 minutes of severe ischemia, a wave of spreading depolarization (SD) propagates through gray matter. More SDs arise over hours, expanding injury. This period represents a therapeutic window to inhibit recurring SD and reduce damage but we do not understand the molecular sequence. Here we argue for a novel molecule to target.

neuroscience↗