The AMPA receptor biophysical gating properties and binding site: Focus on novel curcumin-based diazepines as non-competitive antagonists.

INTRODUCTION: Investigating the binding site of six novel curcumin-based diazepine compounds as a non-competitive antagonist on ionotropic, AMPA-type glutamate receptors, including homomeric and heteromeric subunits. These receptors play a pivotal role in neurodegenerative diseases such as Alzheimer's and epilepsy due to excitotoxicity. Furthermore, it appears that AMPAR signaling plays a significant role in disease development outside the nervous system, as a potential relationship between AMPAR activation and cancer development may exist. OBJECTIVES: Study the biophysical gating effects of the curcumin-based diazepine on AMPAR variants and identify CBD binding sites on AMPARs with the hopes of discovering more potent drug candidates with less undesirable side effects. METHODS: Our current study uses patch-clamp electrophysiology technology to estimate whole-cell amplitudes changes when exposing HEK293T cells expressing AMPAR subunits to different curcumin-based diazepines. RESULTS: The non-competitive antagonist curcumin-based compounds successfully reduced AMPAR activation currents and increased the rate of desensitization and deactivation. CBD-4 and CBD-5 show the most significant impact on AMPARs, reducing the current by 7-fold. The results contrast with those obtained by the halogenated benzodiazepine-fused curcumins reported previously and lake pyrimidine and pyrazine moieties. This indicates that the N's presence in the effused rings plays a significant role in binding to receptors. CBD-4 showed the highest effect on GluA2 subunits in receptors, while CBD-5 most dramatically impacting GluA1 homomeric receptors, demonstrating that the compounds are more selective towards AMPA-type glutamate receptors. The compounds also showed significant cytotoxic activities against breast cancer cell line (MCF-7), with CBD-4 having the most significant impact. CONCLUSION: Curcumin-based compounds (i.e., CBD-4 and CBD-5) yield significant neurodegenerative drug potential, and it creates a novel structure with significant activities in reducing AMPAR excitation compared to traditional benzodiazepine analogs, yet their binding mechanisms are still not fully understood. Moreover, AMPARs appear to have a potential influence on cancer development, and the curcumin-based compounds might provide insight into the nature of this relationship.

Inhibition and assessment of the biophysical gating properties of GluA2 and GluA2/A3 AMPA receptors using curcumin derivatives.

The development of efficacious and safe drugs for the treatment of neurological diseases related to glutamate toxicity has been a focus in neuropharmacological research. Specifically, discovering antagonists to modulate the activity and kinetics of AMPA receptors, which are the fastest ligand-gated ion channels involved in excitatory neurotransmission in response to glutamate. Thus, the current study investigated novel curcumin derivatives on the biophysical properties of AMPA receptors, specifically on the homomeric GluA2 and the heteromeric GluA2/A3 subunits and assessed for inhibitory actions. The biophysical parameter (i.e., desensitization, deactivation, and peak currents) were measured by using whole-cell patch clamp electrophysiology with and without the administration of the derivatives onto HEK293 cells. CR-NN, CR-NNPh, CR-MeNH, and CR-NO of the tested derivatives showed inhibition on all AMPA receptors up to 6 folds. Moreover, the inhibitory derivatives also increased desensitization and deactivation, which further intensifies the compounds' neuroprotective effects. However, CR-PhCl, CR-PhF, and CR-PhBr did not show any significant changes on the peak current, deactivation or desensitization rates. By comparison to other discovered and widely used antagonist, the prepared curcumin derivatives are not selective to a specific AMPA subunit, instead implement its effect in the same way between all types of AMPA receptors. Additionally, the obtained results provide derivatives that not only noncompetitively inhibit AMPARs but also decrease its biophysical kinetics, specifically desensitization and deactivation rates. Hence, to potentially serve as a new AMPAR inhibitor with therapeutic potential, the current study provides compounds that are non-selective and non-competitive antagonist, which also effect the desensitization and deactivation rates of the receptor.

The inhibitory role of curcumin derivatives on AMPA receptor subunits and their effect on the gating biophysical properties.

Curcumin is a natural polyphenol that has a broad spectrum of therapeutic characters, including neuroprotective actions against various neurological diseases. However, the molecular mechanism behind its neuroprotective properties remains obscure. The current study investigated the neuroprotective properties of 7 different curcumin derivatives on the gating biophysical properties of AMPA receptors, specifically on the calcium-permeable homomeric GluA1 and calcium impermeable heteromeric GluA1/A2 subunits. Due to the association between excessive activation of AMPARs and neurotoxicity linked to numerous pathologies, we aim to target and manipulate the kinetics of AMPARs through these derivatives. The current study used patch-clamp electrophysiology to measure the whole-cell currents in the presence and absence of the curcumin derivatives onto HEK293 cells expressing AMPA subunits. Our results showed that some of the curcumin derivatives showed an inhibitory effect and altered the gating biophysical properties, namely, deactivation and desensitization. In the presence of those derivatives, the peak current measured was significantly reduced, and the desensitization and deactivation rates decreased as well, achieving slower kinetics of the receptor and depressing its activity. These results suggest that the two most promising derivatives have inhibitory actions and act as allosteric modulators. Many neurological diseases like epilepsy, ALS, and strokes are associated with overactivation of AMPA receptors. We can potentially synthesize a more potent neuroprotective drug to treat those neurological diseases, by understanding the most stable chemical interaction between the derivative and the receptor underlying the reported neuronal depressive properties.