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

Transethosomal system for enhanced transdermal delivery and therapeutic effect of caryophyllene oxide

AIM

This study focuses on the design and investigation a transethosomal formulation for enhanced topical delivery and improved analgesic activity of caryophyllene oxide. In addition, this work explores new potential mechanisms of analgesic activity of the active compound including alpha-amino-3-hydroxy-5-methyl-4-isooxazole-propionic acid (AMPA) and Cyclooxygenase 2 (COX-2).

METHODS

The transethosomal system containing various caryophyllene concentrations was prepared. The optimum formulation was characterized for the presence of nanovesicles by atomic force microscopy (AFM) and dynamic light scattering (DLS). FTIR was conducted to examine the interaction between the nanovesicle components. The ability of the representative system to enhance the delivery of caryophyllene oxide into and through the skin compared with a coarse emulsion, was examined using porcine ear skin, Franz diffusion cells, and HPLC analysis. The in vivo analgesic efficacy of caryophyllene oxide administrated from the nanovesicular carrier was assessed using the acetic acid-induced pain mouse model compared to a conventional topical formulation. In the second part of the study, the mechanism of analgesic activity of caryophyllene oxide was investigated using AMPA and COX-2 receptors activity in vitro assays.

RESULTS

Characterization studies revealed the presence of spherical nanovesicles with an average size of 450.7 ± 55.03 nm. The transethosomal system demonstrated superior skin penetration compared to a conventional emulsion, as demonstrated by the in vitro skin penetration study, with a caryophyllene oxide permeated amount of 40.3 ± 0.881 µg/cm2 via the transethosomal system compared to the emulsion which delivered only 29.5 ± 10.5 µg/cm2. Moreover, a significantly greater amount of caryophyllene oxide was extracted from the skin following the application of the transethosomal formulation (251.8 ± 76.03 µg/cm2) compared to that extracted from the skin following the ointment application (13.5 ± 0.6 µg/cm2). The in vivo experiment demonstrated that the transethosomal formulation significantly reduced writhing episodes, achieving an 80.5 % Maximum Possible Effect (%MPE) compared to 24.7 % for the conventional topical formulation. In vitro mechanistic studies indicated that caryophyllene oxide exhibited a potent COX-2 selectivity and significantly modulated AMPA receptor subunit activity, highlighting a potential mechanism for pain therapy via the two investigated mechanisms.

CONCLUSIONS

These findings underscore the effectiveness of the caryophyllene oxide transethosomal system in enhancing topical drug delivery and achieving adequate therapeutic efficacy, making it a promising candidate for further clinical development. The study's outcomes shed light on the possible mechanism of analgesia of caryophyllene oxide via COX and AMPAR modulation.

Deciphering the Biophysical Properties of Ion Channel Gating Pores by Coumarin-Benzodiazepine Hybrid Derivatives: Selective AMPA Receptor Antagonists

In the 1980s, the identification of specific pharmacological antagonists played a crucial role in enhancing our comprehension of the physiological mechanisms associated with α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors (AMPARs). The primary objective of this investigation was to identify specific AMPA receptor antagonists, namely 2,3-benzodiazepines, that function as negative allosteric modulators (NAMs) at distinct locations apart from the glutamate recognition site. These compounds have exhibited a diverse array of anticonvulsant properties. In order to conduct a more comprehensive investigation, the study utilized whole-cell patch-clamp electrophysiology to analyze the inhibitory effect and selectivity of benzodiazepine derivatives that incorporate coumarin rings in relation to AMPA receptors. The study's main objective was to acquire knowledge about the relationship between the structure and activity of the compound and comprehend the potential effects of altering the side chains on negative allosteric modulation. The investigation provided crucial insights into the interaction between eight CD compounds and AMPA receptor subunits. Although all compounds demonstrated effective blockade, CD8 demonstrated the greatest potency and selectivity towards AMPA receptor subunits. The deactivation and desensitization rates were significantly influenced by CD8, CD6, and CD5, distinguishing them from the remaining five chemicals. The differences in binding and inhibition of AMPA receptor subunits can be attributed to structural discrepancies among the compounds. The carboxyl group of CD8, situated at the para position of the phenyl ring, substantially influenced the augmentation of AMPA receptor affinity. The findings of this study highlight the potential of pharmaceutical compounds that specifically target AMPA receptors to facilitate negative allosteric modulation.

Multi-biological activity assessment and phytochemical characterization of an aqueous extract of the Cymbopogon citratus grown in Palestine

BACKGROUND

Plants have historically been a rich source of medicinal compounds, with many modern pharmaceuticals derived from botanical origins. In contemporary healthcare, there is a resurgence in utilizing botanical substances as recognized medicinal agents. This study delved into understanding the phytochemical makeup and the multifaceted biological activities of an aqueous extract from Cymbopogon citratus (C. citratus). The investigated activities were its effect on AMPA receptors, antioxidant capacity, anti-lipase, anti-α-amylase actions, cytotoxicity, and antimicrobial properties.

METHODS

The extract of C. citratus received a comprehensive investigation, which included the study of its phytochemical composition, assessment of its antioxidant and anti-lipase properties, evaluation of its capacity to inhibit α-amylase, analysis of its impact on cell viability, and assessment of its antimicrobial activity. The approaches are used to clarify the complex physiological and biochemical characteristics.

RESULTS

The results were compelling; receptor kinetics had a marked impact, notably on the GluA2 subunit. Regarding its medicinal potential, the extract demonstrated potent antioxidant and anti-diabetic activities with IC50 values of 15.13 and 101.14 µg/mL, respectively. Additionally, it displayed significant inhibitory effects on the lipase enzyme and showed cytotoxicity against the Hep3B cancer cell line, with IC50 values of 144.35 and 148.37 µg/mL. In contrast, its effects on the normal LX-2 cell line were minimal, indicating selectivity.

CONCLUSION

The aqueous extract of C. citratus shows promising therapeutic properties. The findings advocate for further research into its compounds for potential isolation, purification, and in-depth pharmacological studies, especially in areas like nervous system disorders, diabetes, obesity, and combating oxidative stress.

The effect of Lavandula Coronopifolia essential oil on the biophysical properties of desensitization and deactivation gating currents in ionotropic receptors

The rising incidence of cancer and the lack of effective therapeutic interventions for many neurological illnesses like Alzheimer's and epilepsy has prompted us to investigate the composition and effects of the Lavandula coronopifolia oil from Palestine on cancer cells and AMPA receptor subunits in the brain due to the vast range of beneficial properties of Lavandula coronopifolia essential oil (EO). GC/MS was used to analyze L. coronopifolia's EO chemistry. EO's cytotoxicity and biophysical effects on AMPA receptors were investigated using MTS and electrophysiological techniques. The GC-MS results revealed that L. coronopifolia EO has a high content of eucalyptol (77.23%), β-pinene (6.93%), and α-pinene (4.95%). The EO showed more significant antiproliferative selectivity activities against HepG2 cancer cell lines than HEK293T cell lines with IC₅₀ values of 58.51 and 133.22 µg/mL, respectively. The EO of L. coronopifolia affected AMPA receptor kinetics (desensitization and deactivation) and preferred homomeric GluA1 and heteromeric GluA1/A2 receptors. These findings indicate the potential therapeutic use of L. coronopifolia EO in the selective treatment of HepG2 cancer cell lines and neurodegenerative diseases.

Diversity of AMPA Receptor Ligands: Chemotypes, Binding Modes, Mechanisms of Action, and Therapeutic Effects

L-Glutamic acid is the main excitatory neurotransmitter in the central nervous system (CNS). Its associated receptors localized on neuronal and non-neuronal cells mediate rapid excitatory synaptic transmission in the CNS and regulate a wide range of processes in the brain, spinal cord, retina, and peripheral nervous system. In particular, the glutamate receptors selective to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) also play an important role in numerous neurological disorders and attract close attention as targets for the creation of new classes of drugs for the treatment or substantial correction of a number of serious neurodegenerative and neuropsychiatric diseases. For this reason, the search for various types of AMPA receptor ligands and studies of their properties are attracting considerable attention both in academic institutions and in pharmaceutical companies around the world. This review focuses mainly on the advances in this area published since 2017. Particular attention is paid to the structural diversity of new chemotypes of agonists, competitive AMPA receptor antagonists, positive and negative allosteric modulators, transmembrane AMPA regulatory protein (TARP) dependent allosteric modulators, ion channel blockers as well as their binding sites. This review also presents the studies of the mechanisms of action of AMPA receptor ligands that mediate their therapeutic effects.

α-Lipoic Acid Derivatives as Allosteric Modulators for Targeting AMPA-Type Glutamate Receptors' Gating Modules

The ionotropic glutamate receptor subtype α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) is responsible for most excitatory transmission in the brain. AMPA receptor function is altered in numerous neurological illnesses, making AMPA receptors appealing therapeutic targets for clinical intervention. Alpha-Lipoic acid (α-LA) is a naturally occurring compound, which functions as a co-factor in metabolism and energy production. α-LA is an antioxidant with various benefits in treating diabetes, including managing symptomatic diabetic neuropathy. This study will test a novel and innovative strategy to synthesize a new isomer of lipoic acid (R-LA) derivatives (bifunctional NO-donor/antioxidant) in one chemical on homomeric and heteromeric AMPA receptor subunits. We used patch-clamp electrophysiology to examine LA derivatives expressed in human embryonic kidney 293 cells (HEK293) for inhibition and changes in desensitization or deactivation rates. LA derivatives were shown to be potent antagonists of AMPA receptors, with an 8-11-fold reduction in AMPA receptor currents seen following the delivery of the compounds. Furthermore, the LA derivatives influenced the rates of desensitization and deactivation of AMPA receptors. Based on our results, especially given that α-LA is closely connected to the nervous system, we may better understand using AMPA receptors and innovative drugs to treat neurological diseases associated with excessive activation of AMPA receptors.

Targeting the kinetics mechanism of AMPA receptor inhibition by 2-oxo-3H-benzoxazole derivatives

Ionotropic glutamate receptors are ligand-gated ion channels found in most excitatory synapses in the brain that allow for rapid information transfer. Due to their quick excitatory processes, α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid-type glutamate (AMPA) receptors have been linked to various neurodegenerative disorders, including epilepsy and Parkinson's disease. It has been critical to develop new neuroprotective compounds that inhibit AMPA-sensitive glutamate-controlled channels allosterically, and many classes of AMPA receptor-inhibiting compounds have been synthesized and evaluated. The current study focuses on thirteen 2-oxo-3H-benzoxazole derivatives (COBs) as potential AMPA receptor modulators. The whole-cell patch-clamp technique was used to assess the effects of COBs on AMPA receptor subunits (i.e., GluA1, GluA2, GluA1/2, and GluA2/3) amplitudes in the human embryonic kidney (HEK293) cells and the rates of desensitization and deactivation before and after COBs delivery. According to our findings, the COBs bind AMPA receptors allosterically and alter AMPAR characteristics in various ways. COB-1, COB-2, and COB-13 were the most effective in decreasing AMPAR currents by around 10-12 folds compared to the other COBs. Furthermore, the COBs significantly impacted AMPA receptor deactivation and desensitization rates. Of the examined homomeric and heteromeric AMPAR subunits, GluA2 was the most impacted. COB compounds appear to be a viable candidate for future study and development in regulating neurological diseases involving AMPA receptors.

Curcumin, Resveratrol and Cannabidiol as Natural Key Prototypes in Drug Design for Neuroprotective Agents

Nowadays, neurodegenerative diseases (NDs), such as Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS), represent a great challenge in different scientific fields, such as neuropharmacology, medicinal chemistry, molecular biology and medicine, as all these pathologies remain incurable, with high socioeconomic impacts and high costs for governmental health services. Due to their severity and multifactorial pathophysiological complexity, the available approved drugs for clinic have not yet shown adequate effectiveness and exhibited very restricted options in the therapeutic arsenal; this highlights the need for continued drug discovery efforts in the academia and industry. In this context, natural products, such as curcumin (1), resveratrol (2) and cannabidiol (CBD, 3) have been recognized as important sources, with promising chemical entities, prototype models and starting materials for medicinal organic chemistry, as their molecular architecture, multifunctional properties and single chemical diversity could facilitate the discovery, optimization and development of innovative drug candidates with improved pharmacodynamics and pharmacokinetics compared to the known drugs and, perhaps, provide a chance for discovering novel effective drugs to combat NDs. In this review, we report the most recent efforts of medicinal chemists worldwide devoted to the exploration of curcumin (1), resveratrol (2) and cannabidiol (CBD, 3) as starting materials or privileged scaffolds in the design of multi-target directed ligands (MTDLs) with potential therapeutic properties against NDs, which have been published in the scientific literature during the last 10 years of research and are available in PubMed, SCOPUS and Web of Science databases.

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.

[Ligands of the AMPA-subtype glutamate receptors: mechanisms of action and novel chemotypes]

Ionotropic glutamate receptors of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) subtype play a key role in synaptic plasticity representing one of the mechanisms for learning and memory formation. They can also serve as targets for the development of novel classes of pharmaceuticals for the treatment or substantive correction of many serious neurodegenerative and psychoneurological disorders. The search and studies of various types of AMPA receptor ligands attract considerable attention from academic organizations and pharmaceutical companies all over the world. This review mainly focuses on recent advances in this field. The architecture and operational mechanism of the receptor as well as its major binding sites and ligand types are considered. Special attention is paid to the studies of mechanisms of action and novel chemotypes of AMPA receptor agonists and competitive antagonists, positive and negative allosteric modulators, auxiliary protein-dependent allosteric modulators, and ion channel blockers.

The impact of filtered water-pipe smoke on healthy versus cancer cells and their neurodegenerative role on AMPA receptor

Water pipe smoking is highly prevalent in developing countries, especially in Eastern Mediterranean regions. Research finds that more than 100 million people smoke a water pipe. Furthermore, tobacco smoking is one of the leading behavioral factors related to an increased risk of cancer, a leading cause of death globally. We aim to introduce a novel filtration system for water-pipe smoking and evaluate cytotoxic effects of common water pipe condensed smoke in comparison with our novel filtration system on normal (HEK293t) and cancer cell lines (Hep3B and MCF7) by MTS assay, alpha-fetoprotein (aFP), and apoptosis/necrosis effects. More so, the smoke substituents' neurotoxicity effect was evaluated by analyzing the depressive property on AMPA receptors (AMPARs). Our results showed that the silica filtration system was more effective than the water filtration system. The number of toxic compounds was reduced from 145 mg in distilled water extract (DWE) to 57.5 mg in silica solution extract (SSE). The SSE method also showed lower toxicity impacts on normal and cancerous cell lines (HEK293t, Hep3B, and MCF7) with CC₅₀ values 149.9, 10.14, and 8.9 µg/ml, relative to the DWE method (CC₅₀ values 77.1, 3.1, and 5.24 µg/ml, respectively). SSE extraction also reduced the α-FP (tumor marker test) to 2273.3 ng/ml which was closer in value to untreated cells (4066.7 ng/ml) in comparison with DWE which reduced it greatly to 1658.7 ng/ml, and the biophysical properties of AMPAR subunits demonstrate a reduced effect on desensitization rates of GluA2 homomer and GluA1/2 heteromer, using SSE relative to DWE. In conclusion, the condensed smoke of ordinary water pipe (DWE) has cytotoxic and neurotoxic impacts on various cell lines, while our newly developed system (SSE) was less toxic.

Patch Clamp Technology in the Twenty-First Century

In the almost four decades since its inception, the patch clamp technique has transitioned from a specialist skill to a method commonly used among many others in a lab. Development of patch clamp instrumentation has not been steady: A boost of product releases in rapid succession by multiple manufacturers in the 1990s had slowed to a trickle by the mid-2000s. In 2016, Sutter Instrument's entry into the market of turnkey patch clamp amplifier systems, defined as an amplifier with matching data acquisition hardware and software, caused a fresh breeze in a field in danger of going stale. Sutter has meanwhile completed the product line, culminating in the flagship dPatch^® Ultra-fast, Low-noise Digital Amplifier. The dPatch System constitutes a contemporary, digital design that features many firsts, including digital signal compensation, an extremely high bandwidth and fully integrated dynamic clamp capability, paired with the increasingly popular SutterPatch^® Software.This chapter compares feature sets of the new Sutter instrumentation with the established platforms by the other two providers of turnkey systems, Axon Instruments by Molecular Devices and HEKA Elektronik by Harvard Bioscience. A variety of products from other manufacturers, who rely on combination with components from other sources rather than offering turnkey systems, are listed, but for their conceptual diversity not compared at a great level of detail. The chapter further covers architectural considerations for patch clamp systems, headstage design, data acquisition strategies and efficient structuring of the recorded data, controlling and monitoring periphery, advanced technologies, such as software lock-in amplifier capability and dynamic clamp features, and application modules for efficient analysis of action potentials and postsynaptic events.

Glechoma curviflora Volatile Oil from Palestine: Chemical Composition and Neuroprotective, Antimicrobial, and Cyclooxygenase Inhibitory Activities

The rise of the emergence of microbial resistance of antibiotics, the dangerous side effects of nonsteroidal anti-inflammatory drugs, and noncompetent medications of Alzheimer's, Parkinson's, and other neurodegenerative diseases prompt scientists to search for phytochemicals that could be utilized in the remedy of lethal diseases. Glechoma curviflora (Boiss.) Kuntze (Nepeta curviflora) is a medicinal herb growing in the eastern parts of the Mediterranean Sea Basin and is widely consumed as a tea. The leaves of this plant have been traditionally used for the treatment of various infectious diseases. The current research was designed to identify the chemical composition of Glechoma curviflora (Boiss.) essential oil (EO) and to assess its antibacterial, antifungal, and cyclooxygenase inhibitory activities and the biophysical gating effect on AMPA receptors. Twenty phytochemicals were identified from G. curviflora leaves and flowers EO amounting to almost 100% of the total constituents using GC-MS technique, of which 1,6-dimethylspiro[4.5]decane (27.51%) 1, caryophyllene oxide (20.08%) 2, and β-caryophyllene (18.28%) 3 were the main constituents. The biophysical properties' effect from the plant extract on various AMPA-type receptors expressed in Human Embryonic Kidney (HEK293) cells was assessed by exploiting the whole-cell patch-clamp technique. Microdilution assay was adopted for assessing the antimicrobial property against eight virulent microbial strains whilst the cyclooxygenase inhibition effect was accomplished utilizing COX inhibitory screening colorimetric assay G. curviflora EO displayed potent activity against P. aeruginosa (MIC = 1.25 μg/mL), S. sonnei (MIC = 3.12 μg/mL), and E. coli (MIC = 1.25 μg/mL), compared with ciprofloxacin (positive control) and potent antibacterial activity against S. aureus, MRSA, S. sonnei, E. coli, and P. aeruginosa compared to Ampicillin (2nd positive control). It also showed anti-Candida (MIC = 6.25 μg/mL) and antimold (MIC = 3.125 μg/mL) activities compared with fluconazole (antifungal positive control). Likewise, our results showed an inhibition and biophysical impact of G. curviflora on all AMPARs subunits.

Ortho versus Meta Chlorophenyl-2,3-Benzodiazepine Analogues: Synthesis, Molecular Modeling, and Biological Activity as AMPAR Antagonists

2,3-Benzodiazepine compounds are an important family of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) antagonists that act in a noncompetitive manner. Due to the critical role of AMPARs in the synapse and various neurological diseases, significant scientific interest in elucidating the molecular basis of the function of the receptors has spiked. The analogues were synthesized to assess the functional consequence of removing the amine group of the phenyl ring, the potency and efficacy of inhibition by substituting a halogen group at the meta vs ortho position of the phenyl ring, and layout the prediction of potential drug candidates for AMPAR hyperactivation. Using the whole-cell patch-clamp technique, we assessed the effect of the derivative on the amplitude of various AMPA-type glutamate receptors and calculated the desensitization and deactivation rates before and after treatment of HEK293 cells. We noticed that the amino group is not necessary for inhibition as long as an electron-withdrawing group is placed on the meta position of the phenyl ring of BDZ. Furthermore, compound 4a significantly inhibited and affected the desensitization rate of the tested AMPARs but showed no effect on the deactivation rate. The current study paves the way to a better understanding of AMPARs and provides possible drug candidates of 2,3-BDZ different from the conventional derivatives.