Biology subjects

Kolcheva, M.

Publications and source records attributed to Kolcheva, M..

3 recordsLinked to original sources

bioRxiv2024

Dizocilpine derivatives with neuroprotective effect lacking the psychomimetic side effects

We aimed to prepare novel dibenzosuberane derivatives that act on N-methyl-D-aspartate (NMDA) receptors with potential neuroprotective effects. Our approach involved modifying the tropane moiety of MK-801, a potent open-channel blocker known for its psychomimetic side effects, by introducing a seven-membered ring with substituted base moieties specifically to alleviate these undesirable effects. Our in silico analyses showed that these derivatives should have high gastrointestinal absorption and cross the blood-brain barrier (BBB). Our pharmacokinetic studies in rats supported this conclusion and confirmed the ability of leading compounds 3l and 6f to penetrate the BBB. Electrophysiological experiments showed that all compounds exhibited different inhibitory activity towards the two major NMDA receptor subtypes, GluN1/GluN2A and GluN1/GluN2B. Of the selected compounds intentionally differing in the inhibitory efficacy, 6f showed high relative inhibition ([~]90% for GluN1/GluN2A), while 3l showed moderate inhibition ([~]50%). An in vivo toxicity study determined that compounds 3l and 6f were safe at 10 mg/kg doses with no adverse effects. Behavioral studies demonstrated that these compounds did not induce hyperlocomotion or impair prepulse inhibition of startle response in rats. Neuroprotective assays using a model of NMDA-induced hippocampal neurodegeneration showed that compound 3l at a concentration of 30 M significantly reduced hippocampal damage in rats. These results suggest that these novel dibenzosuberane derivatives are promising candidates for developing NMDA receptor-targeted therapies with minimal psychotomimetic side effects.

neuroscience↗

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↗

bioRxiv2024

Independent regulation of early trafficking of NMDA receptors by ligand-binding domains of the GluN1 and GluN2A subunits

The essential role of N-methyl-D-aspartate receptors (NMDARs) in excitatory neurotransmission is underscored by numerous pathogenic variants in the GluN subunits, including those identified in their ligand-binding domains (LBDs). The prevailing hypothesis postulates that the endoplasmic reticulum (ER) quality control machinery verifies the agonist occupancy of NMDARs; however, whether it controls the structure of LBDs or the functionality of NMDARs is unknown. Using alanine substitutions combined with microscopy and electrophysiology, we found that surface expression of GluN1/GluN2A receptors, the primary NMDAR subtype in the adult forebrain, strongly correlates with EC50 values for glycine and L-glutamate. Interestingly, co-expression of both GluN1 and GluN2A subunits with alanine substitutions led to an additive reduction in the surface number of GluN1/GluN2A receptors, as did co-expression of both GluN1 and GluN2A subunits containing closed cleft conformation of LBDs. The synchronized ER release confirmed the altered regulation of early trafficking of GluN1/GluN2A receptors bearing alanine substitutions in the LBDs. Furthermore, the human versions of GluN1/GluN2A receptors containing pathogenic GluN1-S688Y, GluN1-S688P, GluN1-D732E, GluN2A-S511L, and GluN2A-T690M variants exhibited distinct surface expression compared to the corresponding alanine substitutions. Mutant cycles of GluN1-S688, GluN1-D732, GluN2A-S511, and GluN2A-T690 residues revealed, in most cases, a weak correlation between surface expression of the mutant GluN1/GluN2A receptors and their EC50 values for glycine or L-glutamate. Consistent with our experimental data, molecular modeling and dynamics showed that the ER quality control machinery likely perceives structural changes of the LBDs but not the functionality of GluN1/GluN2A receptors. Significant statementOur study showed that structural changes in LBDs independently regulate the early trafficking of GluN1/GluN2A receptors and that the surface numbers of mutant GluN1/GluN2A receptors do not necessarily correlate with their agonist sensitivity. In addition, we validated a novel system of synchronized release of GluN1/GluN2A receptors from the ER. Together, our experimental and in silico findings support the urgency of further detailed research on the regulation of early trafficking of NMDARs, as it may open the avenue to targeted therapeutic intervention of CNS disorders associated with pathogenic variants in GluN subunits.

neuroscience↗