Hermanova, Z. | Search bioRxiv

bioRxiv2024

Potent and reversible open-channel blocker of NMDA receptor derived from dizocilpine with enhanced membrane-to-channel inhibition

N-methyl-D-aspartate receptors (NMDARs) play a significant role in developing several central nervous system (CNS) disorders. Currently, memantine, used for treating Alzheimers disease, and ketamine, known for its anesthetic and antidepressant properties, are two clinically used NMDAR open-channel blockers. However, despite extensive research into NMDAR modulators, many have shown either harmful side effects or inadequate effectiveness. For instance, dizocilpine (MK-801) is recognized for its powerful psychomimetic effects due to its high-affinity and nearly irreversible inhibition of the GluN1/GluN2 NMDAR subtypes. Unlike ketamine, memantine and MK-801 also act through a unique, low-affinity "membrane-to-channel inhibition" (MCI). We aimed to develop an open-channel blocker based on MK-801 with distinct inhibitory characteristics from memantine and MK-801. Our novel compound, K2060, demonstrated effective voltage-dependent inhibition in the micromolar range at key NMDAR subtypes, GluN1/GluN2A and GluN1/GluN2B, even in the presence of Mg2+. K2060 showed reversible inhibitory dynamics and a partially trapping open-channel blocking mechanism with a significantly stronger MCI than memantine. Using hippocampal slices, 30 {micro}M K2060 inhibited excitatory postsynaptic currents in CA1 hippocampal neurons by [~]51%, outperforming 30 {micro}M memantine ([~]21% inhibition). K2060 exhibited No Observed Adverse Effect Level (NOAEL) of 15 mg/kg upon intraperitoneal administration in mice. Administering K2060 at a 10 mg/kg dosage resulted in brain concentrations of approximately 2 {micro}M, with peak concentrations (Tmax) achieved within 15 minutes. Finally, applying K2060 with trimedoxime and atropine in mice exposed to tabun improved treatment outcomes. These results underscore K2060s potential as a therapeutic agent for CNS disorders linked to NMDAR dysfunction.

neuroscience↗

bioRxiv2023

Astrocyte-like subpopulation of NG2 glia in the adult mouse cortex exhibits characteristics of neural progenitor cells and is capable of forming neuron-like cells after ischemic injury

Glia cells expressing neuron-glial antigen 2 (NG2) play a critical role as oligodendrocyte precursor cells (OPCs) in the healthy brain; however, their differentiation potential after ischemic injury remains an unresolved question. Here, we aimed to elucidate the heterogeneity and role of NG2 glia in the ischemic brain. We used transgenic mice to label NG2-expressing cells and their progeny with red fluorescent protein tdTomato in the healthy brains and those after focal cerebral ischemia (FCI). Based on single-cell RNA sequencing, the labeled glial cells were divided into five distinct subpopulations. The identity of these subpopulations was determined based on gene expression patterns. In addition, membrane properties were further analyzed using the patch-clamp technique. Three of the observed subpopulations represented OPCs, whereas the fourth group exhibited characteristics of cells destined for oligodendrocyte fate. The fifth subpopulation of NG2 glia carried astrocytic markers. Importantly, we detected features of neural progenitors in these cells. This subpopulation was present in both healthy and post-ischemic tissue; however, its gene expression changed after ischemia, with genes related to neurogenesis being more abundant. Neurogenic gene expression was monitored over time and complemented by immunohistochemical staining, which showed increased numbers of Purkinje cell protein 4-positive NG2 cells at the edge of the ischemic lesion 12 days after FCI, and NeuN-positive NG2 cells 28 days after injury, indicating the existence of neuron-like cells that develop from NG2 glia in the ischemic tissue. Our results provide further insight into the differentiation plasticity and neurogenic potential of NG2 glia after stroke. Main PointsO_LIDifferent subpopulations of NG2 glia in the healthy and ischemic adult cortex were identified based on their gene expression and membrane properties. C_LIO_LIAstrocyte-like NG2 glia exhibit neurogenic gene expression and are more abundant in post-ischemic tissue. C_LIO_LIProgeny of NG2-positive cells carrying neuronal marker NeuN was observed at the edge of the ischemic lesion. C_LI

neuroscience↗