Recent Advances in the In-silico Structure-based and Ligand-based Approaches for the Design and Discovery of Agonists and Antagonists of A2A Adenosine Receptor

Detergent induced structural perturbations in peanut agglutinin: insights from spectroscopic and molecular dynamic simulation studies

The three dimensional structure of a protein is very important for its structure. Studies relating to protein structure have been numerous and the effect of denaturants on proteins can help understand the process of protein folding and misfolding. Detergents are important denaturants and play important roles in various fields. Here we explored the effect of sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide (CTAB) on the structure of peanut agglutinin (PNA). The protein was purified from its natural source and impact of SDS and CTAB was studied by circular dichroism, intrinsic fluorescence, 8-anilino-1-napthalenesulfonic acid, molecular docking and molecular dynamics simulation. Pure peanut agglutinin showed a trough at 220 nm and positive ellipticity peak at 195 nm, specific for lectins. Results from the experimental and simulation studies suggest how oppositely charged detergents can interact differently and lead to varied structural perturbations in PNA. Both the surfactants induce all α protein-like circular dichroism in the protein, above its critical micelle concentrations, with significant change in accessible surface area that became more hydrophobic upon the treatment. Major interactions between the surfactants and protein, resulting in PNA conformational rearrangement, are electrostatic and van der Waals interactions. However, CTAB, a cationic surfactant, has similar effects as anionic surfactant (SDS) but at significantly very low concentration. Though the effects followed same pattern in both the surfactant treatment, i.e. above respective CMC, the surfactants were inducing all α protein-like conformation in PNA.

Discovery of novel A2AR antagonist via 3D-QSAR pharmacophore modeling: neuroprotective effects in 6-OHDA-induced SH-SY5Y cells and haloperidol-induced Parkinsonism in C57 bl/6 mice

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder which is caused by abrupt degeneration of dopaminergic neuronal cells in the substantia nigra pars compacta (SNPc) area of the midbrain. Adenosine A2A receptors have become promising therapeutic targets for PD; however, many A2A receptor antagonists face challenges, such as limited accessibility or failure in clinical trials due to poor selectivity and bioavailability. To identify novel A2A receptor antagonists, a 3D-QSAR-pharmacophore modeling approach was employed, involving virtual screening of ZINC, NCI, and MayBridge databases. The virtual hits were filtered via ADMET criteria to select compounds with favorable bioavailability and solubility profiles. From the MayBridge database, a potent monocyclic A2A receptor antagonist, AW00032 (N-(furan-2-ylmethyl)-5-methylthiazole-4-yl) thiophene-2-sulfonamide, was identified. AW00032 possessed key pharmacophoric features: two lipophilic hydrogen bond acceptors, one hydrophobic aliphatic/aromatic group, and one aromatic ring. Docking analysis revealed AW00032 had a strong binding affinity for A2A receptors (1.23 nM, ∆G - 10.49 kcal/mol), and its ADMET profile indicated good bioavailability. In 6-OHDA induced SH-SY5Y cells, AW00032 increased dopamine levels and tyrosine hydroxylase (TH) expression, demonstrating its potential as an A2A receptor antagonist. AW00032, discovered through 3D-QSAR pharmacophore modeling, also reduced reactive oxygen species (ROS) levels and showed depletion in mitochondrial dysfunction in 6-OHDA-induced SH-SY5Y cells. It exhibited A2A receptor antagonist activity comparable to the standard antagonist ZM241385, partially restoring dopamine and TH levels. Furthermore, AW00032 improved behavioral symptoms in haloperidol-induced C-57 bl/6 mice.

Modulation of glucose metabolism-related genes in diabetic rats treated with herbal synthetic anti-diabetic compound (α-HSA): insights from transcriptomic profiling

OBJECTIVES

Eugenia jambolana is a medicinal plant traditionally used for treating diabetes. The bioactive compound FIIc, which is derived from the fruit pulp of E. jambolana, has been identified and purified as α-HSA. Previous studies have demonstrated that administration of α-HSA for 6 weeks improved glycemic index and dyslipidemia in rats with T2D. This study investigated the molecular mechanism underlying the potential therapeutic effects of α-HSA in experimentally induced diabetic rats.

METHODS

Male Wistar rats were divided into four groups: diabetic control, diabetic treated with FIIc, diabetic treated with α-HSA, and diabetic treated with glibenclamide. Over a 6-week experimental period, transcriptomic analysis was conducted on liver, skeletal, and pancreatic tissue samples collected from the rats.

RESULTS

The study findings revealed significant upregulation of genes associated with glucose metabolism and insulin signaling in the groups treated with FIIc and α-HSA, compared to the diabetic control group. Moreover, pro-inflammatory genes were downregulated in these treatment groups. These results indicate that α-HSA has the potential to modulate key metabolic pathways, improve glucose homeostasis, enhance insulin sensitivity, and alleviate inflammation.

CONCLUSIONS

This study provides compelling scientific evidence supporting the potential of α-HSA as a therapeutic agent for diabetes treatment. The observed upregulation of genes related to glucose metabolism and insulin signaling, along with the downregulation of pro-inflammatory genes, aligns with the pharmacological activity of α-HSA in controlling glucose homeostasis and improving insulin sensitivity. These findings suggest that α-HSA holds promise as a novel therapeutic approach for managing diabetes and its associated complications.

Structure-activity features of purines and their receptors: implications in cell physiopathology

The purine molecular structure consists of fused pyrimidine and imidazole rings. Purines are main pieces that conform the structure of nucleic acids which rule the inheritance processes. Purines also work as metabolic intermediates in different cell functions and as messengers in the signaling pathways throughout cellular communication. Purines, mainly ATP and adenosine (ADO), perform their functional and pharmacological properties because of their structural/chemical characteristics that make them either targets of mutagenesis, mother frameworks for designing molecules with controlled effects (e.g. anti-cancer), or chemical donors (e.g., of methyl groups, which represent a potential chemoprotective action against cancer). Purines functions also come from their effect on specific receptors, channel-linked and G-protein coupled for ATP, and exclusively G-coupled receptors for ADO (also known as ADORAs), which are involved in cell signaling pathways, there, purines work as chemical messengers with autocrine, paracrine, and endocrine actions that regulate cell metabolism and immune response in tumor progression which depends on the receptor types involved in these signals. Purines also have antioxidant and anti-inflammatory properties and participate in the cell energy homeostasis. Therefore, purine physiology is important for a variety of functions relevant to cellular health; thus, when these molecules present a homeostatic imbalance, the stability and survival of the cellular systems become compromised.

Role and Function of Adenosine and its Receptors in Inflammation, Neuroinflammation, IBS, Autoimmune Inflammatory Disorders, Rheumatoid Arthritis and Psoriasis

The physiological effects of endogenous adenosine on various organ systems are very complex and numerous which are elicited upon activation of any of the four G-protein-coupled receptors (GPCRs) denoted as A1, A2A, A2B and A3 adenosine receptors (ARs). Several fused heterocyclic and non-xanthine derivatives are reported as a possible target for these receptors due to physiological problems and lack of selectivity of xanthine derivatives. In the present review, we have discussed the development of various new chemical entities as a target for these receptors. In addition, compounds acting on adenosine receptors can be utilized in treating diseases like inflammation, neuroinflammation, autoimmune and related diseases.

Adenosine Receptors in Modulation of Central Nervous System Disorders

The ubiquitous signaling nucleoside molecule, adenosine is found in different cells of the human body to provide its numerous pharmacological role. The associated actions of endogenous adenosine are largely dependent on conformational change of the widely expressed heterodimeric G-protein-coupled A1, A2A, A2B, and A3 adenosine receptors (ARs). These receptors are well conserved on the surface of specific cells, where potent neuromodulatory properties of this bioactive molecule reflected by its easy passage through the rigid blood-brainbarrier, to simultaneously act on the central nervous system (CNS). The minimal concentration of adenosine in body fluids (30-300 nM) is adequate to exert its neuromodulatory action in the CNS, whereas the modulatory effect of adenosine on ARs is the consequence of several neurodegenerative diseases. Modulatory action concerning the activation of such receptors in the CNS could be facilitated towards neuroprotective action against such CNS disorders. Our aim herein is to discuss briefly pathophysiological roles of adenosine on ARs in the modulation of different CNS disorders, which could be focused towards the identification of potential drug targets in recovering accompanying CNS disorders. Researches with active components with AR modulatory action have been extended and already reached to the bedside of the patients through clinical research in the improvement of CNS disorders. Therefore, this review consist of recent findings in literatures concerning the impact of ARs on diverse CNS disease pathways with the possible relevance to neurodegeneration.

P1 Receptor Agonists/Antagonists in Clinical Trials - Potential Drug Candidates of the Future

BACKGROUND

Adenosine mediates various physiological and pathological conditions by acting on its four P1 receptors (A1, A2A, A2B and A3 receptors). Omnipresence of P1 receptors and their activation, exert a wide range of biological activities. Thus, its modulation is implicated in various disorders like Parkinson's disease, asthma, cardiovascular disorders, cancer etc. Hence these receptors have become an interesting target for the researchers to develop potential therapeutic agents. Number of molecules were designed and developed in the past few years and evaluated for their efficacy in various disease conditions.

OBJECTIVE

The main objective is to provide an overview of new chemical entities which have crossed preclinical studies and reached clinical trials stage following their current status and future prospective.

METHODS

In this review we discuss current status of the drug candidates which have undergone clinical trials and their prospects.

RESULTS

Many chemical entities targeting various subtypes of P1 receptors are patented; twenty of them have crossed preclinical studies and reached clinical trials stage. Two of them viz adenosine and regadenoson are approved by the Food and Drug Administration.

CONCLUSION

This review is an attempt to highlight the current status, progress and probable future of P1 receptor ligands which are under clinical trials as promising novel therapeutic agents and the direction in which research should proceed with a view to come out with novel therapeutic agents.

Medicinal Chemistry and Therapeutic Potential of Agonists, Antagonists and Allosteric Modulators of A1 Adenosine Receptor: Current Status and Perspectives

Adenosine is a purine nucleoside, responsible for the regulation of a wide range of physiological and pathophysiological conditions by binding with four G-protein-coupled receptors (GPCRs), namely A1, A2A, A2B and A3 adenosine receptors (ARs). In particular, A1 AR is ubiquitously present, mediating a variety of physiological processes throughout the body, thus represents a promising drug target for the management of various pathological conditions. Agonists of A1 AR are found to be useful for the treatment of atrial arrhythmia, angina, type-2 diabetes, glaucoma, neuropathic pain, epilepsy, depression and Huntington's disease, whereas antagonists are being investigated for the treatment of diuresis, congestive heart failure, asthma, COPD, anxiety and dementia. However, treatment with full A1 AR agonists has been associated with numerous challenges like cardiovascular side effects, off-target activation as well as desensitization of A1 AR leading to tachyphylaxis. In this regard, partial agonists of A1 AR have been found to be beneficial in enhancing insulin sensitivity and subsequently reducing blood glucose level, while avoiding severe CVS side effects and tachyphylaxis. Allosteric enhancer of A1 AR is found to be potent for the treatment of neuropathic pain, culminating the side effects related to off-target tissue activation of A1 AR. This review provides an overview of the medicinal chemistry and therapeutic potential of various agonists/partial agonists, antagonists and allosteric modulators of A1 AR, with a particular emphasis on their current status and future perspectives in clinical settings.

Therapeutic Potentials of A2B Adenosine Receptor Ligands: Current Status and Perspectives

BACKGROUND

Adenosine receptors (ARs) are classified as A1, A2A, A2B, and A3 subtypes belong to the superfamily of G-protein coupled receptors (GPCRs). More than 40% of modern medicines act through either activation or inhibition of signaling processes associated with GPCRs. In particular, A2B AR signaling pathways are implicated in asthma, inflammation, cancer, ischemic hyperfusion, diabetes mellitus, cardiovascular diseases, gastrointestinal disorders, and kidney disease.

METHODS

This article reviews different disease segments wherein A2B AR is implicated and discusses the potential role of subtype-selective A2B AR ligands in the management of such diseases or disorders. All the relevant publications on this topic are reviewed and presented scientifically.

RESULTS

This review provides an up-to-date highlight of the recent advances in the development of novel and selective A2B AR ligands and their therapeutic role in treating various disease conditions. A special focus has been given to the therapeutic potentials of selective A2B AR ligands in the management of airway inflammatory conditions and cancer.

CONCLUSIONS

This systematic review demonstrates the current status and perspectives of A2B AR ligands as therapeutically useful agents that would assist medicinal chemists and pharmacologists in discovering novel and subtype-selective A2B AR ligands as potential drug candidates.