Molecular Dynamics Simulations of Adenosine Receptors: Advances, Applications and Trends

New insights into the pharmacological mechanisms of Jinqi Jiangtang Tablets in the treatment of type 2 diabetes mellitus: A multi-omics approach combined with experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Type 2 diabetes mellitus (T2DM) is a prevalent chronic metabolic disorder characterized by impaired glucose homeostasis and insulin dysfunction. Despite ongoing efforts, the management of T2DM remains challenging due to its complex pathogenesis and the limited effectiveness of current treatments. Jinqi Jiangtang Tablets (JQJTT), a well-established Traditional Chinese Medicine (TCM) formula, have shown promising clinical benefits in regulating blood glucose levels and improving metabolic health in T2DM patients. However, the specific pharmacological mechanisms behind its efficacy are still not fully understood, prompting the need for deeper exploration into its therapeutic actions.

AIM OF THE STUDY

This study aims to elucidate the pharmacologically active ingredients and mechanisms of JQJTT in T2DM using multi-omics methods combined with experimental verification.

MATERIALS AND METHODS

Liquid chromatography-mass spectrometry (LC-MS) identified the chemical profile of JQJTT, and targets were screened via SwissTargetPrediction database. T2DM-related targets were acquired from GeneCards and Gene Expression Omnibus (GEO) databases. Therapeutic targets were ascertained by intersecting JQJTT and T2DM targets, followed by Protein-Protein Interaction (PPI) network analysis. GO and KEGG pathway enrichment was performed, and the compound-target-pathway network was built using Cytoscape. Mendelian randomization, single-sample Gene Set Enrichment Analysis (ssGSEA), and CIBERSORT analyses were executed to explore immune cell involvement. Single-cell RNA sequencing (scRNA-seq) identified affected cell types, while molecular docking and molecular dynamics (MD) simulation assessed compound-target affinities. Metabolomics and 16S rDNA sequencing analyzed JQJTT's effects on metabolites and gut microbiota.

RESULTS

LC-MS identified 161 compounds in JQJTT. Through network pharmacology, 6 core targets (AKT1, MMP9, HSP90AA1, CASP3, IL-6, PTGS2) were screened, and PI3K/AKT, NFκB, and lipid metabolism were pinpointed as key regulatory pathways. Mendelian randomization linked 39 immune cell types to T2DM, while ssGSEA and CIBERSORT suggested JQJTT potentially modulated the proportion of immune cells. scRNA-seq indicated JQJTT may affect macrophage polarization. Tangeritin, isorhamnetin, and kaempferol were determined as the main active compounds with glucose-lowering effects confirmed in vitro. In vivo experiments validated the molecular mechanisms of JQJTT against T2DM. Metabolomics unearthed 56 differentially abundant metabolites, primarily in linoleic acid, arachidonic acid, and pyruvaldehyde metabolisms. JQJTT also improved gut microbiota diversity in T2DM.

CONCLUSION

JQJTT treated T2DM through a multi-target, multi-pathway approach, including attenuating inflammation, reshaping macrophage polarization, enhancing insulin signaling, regulating metabolites, and restoring intestinal flora balance.

Mechanisms of isorhamnetin inhibition of osteoclast differentiation: insights from molecular dynamics simulations and in vitro/in vivo experiments

Background

Osteoporosis (OP) represents a widespread bone remodeling disorder within the domain of orthopedics, markedly compromising the quality of life in the elderly population. The need to develop more efficient therapeutic approaches to attenuate bone resorption by suppressing the excessive activation of osteoclasts (OCs) remains urgent. The plant flavonoid Isorhamnetin (Iso), recognized for its potent antioxidant properties, has been the subject of extensive research regarding its potential in treating bone-related conditions.

Method

This study adopts a comprehensive methodology to evaluate Iso's impact on bone metabolism and its therapeutic possibilities for treating OP. By integrating network pharmacology, molecular dynamics simulations, and surface plasmon resonance (SPR), we performed in vitro phenotypic analyses to systematically evaluate the inhibitory effect of Iso on OC differentiation. The mechanisms behind Iso's inhibition of OC differentiation were further elucidated. In vivo testing was also performed to substantiate the therapeutic effects of Iso in an OP animal model.

Results

At low concentrations, Iso showed no cytotoxicity and did not interfere with cell proliferation in RAW 264.7 cells. Iso effectively inhibited RANKL-induced osteoclast differentiation in these cells, while downregulating related genes levels (Nfatc1, Ctsk, Trap, c-Fos). Molecular dynamics simulations and surface plasmon resonance confirmed Iso's dual binding to both RANKL and RANK. KEGG pathway enrichment analysis results indicated that Iso modulates the MAPK, NF-κB/PI3K-AKT, and calcium signaling pathways. Western blot analysis revealed that Iso treatment targeting the RANKL/RANK binding pathway significantly downregulated phosphorylation levels of JNK, P38, AKT, and p65. Concurrently, Iso stimulation markedly increased IκBα expression, thereby rescuing its degradation. Furthermore, Iso demonstrated a robust inhibitory effect on reactive oxygen species levels in vitro. Furthermore, in OVX mice, Iso treatment increased bone density, modulated serum bone metabolism markers, and downregulated transcriptional levels of OC marker genes.

Conclusion

Iso exhibits therapeutic potential for OP by selectively targeting and disrupting the RANKL-RANK interaction. This intervention modulates the expression of intracellular transcription factors and multiple signaling pathways, thereby inhibiting the maturation of OCs. Through mitigating OC-mediated bone loss, Iso holds significant promise as a potent therapeutic agent for OP.

Pivotal role of JNK protein in the therapeutic efficacy of parthenolide against breast cancer: Novel and comprehensive evidences from network pharmacology, single-cell RNA sequencing and metabolomics

This study aimed to evaluate the efficacy and therapeutic mechanism of parthenolide (PTL) in breast cancer (BC) through a comprehensive strategy integrating network pharmacology, single-cell RNA sequencing (scRNA-seq) and metabolomics. In network pharmacology, 70 therapeutic targets were identified, of which 16 core targets were filtered out through seven classical algorithms of Cytohubba plugin. Additionally, the hub module of PPI network was extracted using MCODE plugin. Molecular docking and molecular dynamics simulation showed a potent binding affinity between PTL and JNK, subsequently validated by MST and SPR assays. Further, Mendelian randomization analysis indicated that JNK was causally associated with BC. GO and KEGG enrichment analyses revealed that PTL counteracted BC via promoting ROS generation, inducing apoptosis and suppressing proliferation, which potentially involved the coordinated regulation of MAPK and FoxO1 pathways. Moreover, ssGSEA and scRNA-seq analysis suggested that PTL may act on T cell immune microenvironment of BC. Subsequently, these bioinformatics-based predictions were experimentally validated using in-vitro and in-vivo models. Finally, metabolome profiling unveiled that PTL remodeled the glycine, serine and threonine metabolism as well as biosynthesis of unsaturated fatty acids, and thereby contributed to BC inhibition. From molecular, immune and metabolic perspectives, this study not only provided a unique insight into the mechanistic details of PTL against BC, but also proposed a novel promising therapeutic strategy for BC.

Synthesis, characterization and larvicidal studies of ethyl 3-benzoyl-7-(piperidin-1-yl)indolizine-1-carboxylate analogues against Anopheles arabiensis and cheminformatics approaches

According to WHO, in 2021, there was an estimation of 247 million malaria cases from 84 malaria-endemic countries. Globally an estimated count of 2 billion malaria cases and 11.7 million deaths due to malaria were recorded in the past two decades. Further, the emergence of drug-resistant mosquitos threatens mankind. Therefore, the development of newer larvicidal agents is the need of the hour. This research identifies a new series of variably substituted indolizines for their effectiveness in controlling Anopheles arabiensis larvae through larvicidal activity. The series of Ethyl 3-benzoyl-7-(piperidin-1-yl)indolizine-1-carboxylate analogues (4a-j) were synthesized by reacting 4-(piperidin-1-yl)pyridine, phenacyl bromides with ethyl propiolate via 1, 3-dipolar cycloaddition and the green metrics of the process are reported. All the newly synthesized compounds were characterized by spectroscopic techniques such as 1H NMR,13C NMR, FT-IR, and HRMS. The larvicidal effectiveness of the newly synthesized compounds was assessed against Anopheles arabiensis. Among the compounds studied, namely 4c, 4d, 4e, and 4f, displayed the most notable larval mortality rates within the series, reaching 73%, 81%, 76%, and 71% respectively, in contrast with the negative control acetone. In comparison, the standard Temephos exhibited a mortality rate of 99% at the same concentration. Furthermore, computational approaches including molecular docking and molecular dynamics simulations identified the potential targets of the series compounds as the larval Acetylcholinesterase (AChE) enzyme and the Sterol Carrier Protein-2 (SCP-2) protein. However, it is essential for these computational predictions to undergo experimental validation.

RAGE: a potential target for Epimedium's anti-neuroinflammation role in vascular dementia-insights from network pharmacology and molecular simulation

Vascular dementia (VaD), a cognitive impairment resulting from cerebrovascular issues, could be mitigated by Epimedium. This study investigates Epimedium's efficacy in VaD management through a systematic review, network pharmacology, molecular docking, and molecular dynamic simulations (MDS). Comprehensive literature searches were conducted across various databases. Epimedium's pharmacological properties were analyzed using the TCMSP database. Integration with the Aging Atlas database enabled the identification of shared targets between Epimedium and VaD. A protein-protein interaction (PPI) network was constructed, and central targets' topological attributes were analyzed using Cytoscape 3.9.1. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were conducted using "ClusterProfiler" R package. The interactions between Epimedium and central targets were assessed by Molecular docking and MDS. Epimedium and its 23 bioactive components counteracted oxidative stress, neuroinflammation, and neuronal damage, thereby attenuating cognitive deterioration in VaD. A total of 78 common targets were identified, with 22 being significantly related to aging. Enrichment analysis identified 1769 GO terms and 139 KEGG pathways, highlighting the AGE-RAGE signaling pathway. Molecular docking revealed that 23 bioactive components, except Linoleyl acetate, effectively interacted with top central targets (JUN, MAPK14, IL6, FOS, TNF). MDS demonstrated that flavonoids Icariin, Kaempferol, Luteolin, and Quercetin formed stable complexes with RAGE. The study identifies RAGE as a novel therapeutic target for Epimedium in the mitigation of VaD via its anti-inflammatory properties.

The impact of cycleanine in cancer research: a computational study

Cancer is imposing a global health burden because of the steady increase in new cases. Moreover, current anticancer therapeutics are associated with many drawbacks, mainly the emergence of resistance and the severe adverse effects. Therefore, there is a continuous need for developing new anticancer agents with novel mechanisms of action and lower side effects. Natural products have been a rich source of anticancer medication. Cycleanine, a natural product, was reported to exert an antiproliferative effect on ovarian cancer cells by causing apoptosis through activation of caspases 3/7 and cleavage of poly (ADP-ribose) polymerase to form poly (ADP-ribose) polymerase-1 (PARP1). It is well-established that PARP1 is associated with carcinogenesis, and different PARP1 inhibitors are approved as anticancer drugs. In this study, the cytotoxic activity of cycleanine was computationally investigated to determine whether it is a PARP1 inhibitor or a caspase activator. Molecular docking and molecular dynamics (MD) simulations were utilized for this purpose. The results showed that cycleanine has a good binding affinity to PARP1; moreover, MD simulation showed that it forms a stable complex with the enzyme. Consequently, the results showed that cycleanine is a potential inhibitor of the PARP1 enzyme.

Exploring the mechanism of action of licorice in the treatment of COVID-19 through bioinformatics analysis and molecular dynamics simulation

Purpose: The rapid worldwide spread of Corona Virus Disease 2019 (COVID-19) has become not only a global challenge, but also a lack of effective clinical treatments. Studies have shown that licorice can significantly improve clinical symptoms such as fever, dry cough and shortness of breath in COVID-19 patients with no significant adverse effects. However, there is still a lack of in-depth analysis of the specific active ingredients of licorice in the treatment of COVID-19 and its mechanism of action. Therefore, we used molecular docking and molecular dynamics to explore the mechanism of action of licorice in the treatment of COVID-19.

Methods: We used bioinformatics to screen active pharmaceutical ingredients and potential targets, the disease-core gene target-drug network was established and molecular docking was used for verification. Molecular dynamics simulations were carried out to verify that active ingredients were stably combined with protein targets. The supercomputer platform was used to measure and analyze stability of protein targets at the residue level, solvent accessible surface area, number of hydrogen bonds, radius of gyration and binding free energy.

Results: Licorice had 255 gene targets, COVID-19 had 4,628 gene targets, the intersection gene targets were 101. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene ontology (GO) analysis showed that licorice played an important role mainly through the signaling pathways of inflammatory factors and oxidative stress. Molecular docking showed that Glycyrol, Phaseol and Glyasperin F in licorice may playe a role in treating COVID-19 by acting on STAT3, IL2RA, MMP1, and CXCL8. Molecular dynamics were used to demonstrate and analyze the binding stability of active ingredients to protein targets.

Conclusion: This study found that Phaseol in licorice may reduce inflammatory cell activation and inflammatory response by inhibiting the activation of CXCL8 and IL2RA; Glycyrol may regulate cell proliferation and survival by acting on STAT3. Glyasperin F may regulate cell growth by inhibiting the activation of MMP1, thus reducing tissue damage and cell death caused by excessive inflammatory response and promoting the growth of new tissues. Therefore, licorice is proposed as an effective candidate for the treatment of COVID-19 through STAT3, IL2RA, MMP1, and CXCL8.

Antitubercular, Cytotoxicity, and Computational Target Validation of Dihydroquinazolinone Derivatives

A series of 2,3-dihydroquinazolin-4(1H)-one derivatives (3a–3m) was screened for in vitro whole-cell antitubercular activity against the tubercular strain H37Rv and multidrug-resistant (MDR) Mycobacterium tuberculosis (MTB) strains. Compounds 3l and 3m with di-substituted aryl moiety (halogens) attached to the 2-position of the scaffold showed a minimum inhibitory concentration (MIC) of 2 µg/mL against the MTB strain H37Rv. Compound 3k with an imidazole ring at the 2-position of the dihydroquinazolin-4(1H)-one also showed significant inhibitory action against both the susceptible strain H37Rv and MDR strains with MIC values of 4 and 16 µg/mL, respectively. The computational results revealed the mycobacterial pyridoxal-5′-phosphate (PLP)-dependent aminotransferase (BioA) enzyme as the potential target for the tested compounds. In vitro, ADMET calculations and cytotoxicity studies against the normal human dermal fibroblast cells indicated the safety and tolerability of the test compounds 3k–3m. Thus, compounds 3k–3m warrant further optimization to develop novel BioA inhibitors for the treatment of drug-sensitive H37Rv and drug-resistant MTB.

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.

The design of TOPK inhibitors using structure-based pharmacophore modeling and molecular docking based on an MD-refined homology model

The TOPK enzyme (also known as PBK) is a serine-threonine protein kinase that is rarely detected in normal tissues yet is found to be overexpressed and activated in a variety of cancers such as lung, colorectal, breast, and esophageal cancer. Its prevalence in cancerous cells is associated with their poor prognosis and responsiveness to treatment. This enzyme plays a vital role in cell division, specifically in regulating cytokinesis. Unlike drugs targeting early phases in mitosis, inhibition of cytokinesis by targeting biomolecules that are unique to multiplying cells poses no threat to the normal function of non-multiplying cells. Studies have shown that inhibition of cytokinesis is promising in suppressing the growth of proliferating cancerous cells as exemplified by the complete tumor regression seen with the suppression of TOPK. Herein, we report the identification of potent TOPK inhibitors with anticancer potential using a structure-based drug design approach. The only available crystal structure of TOPK corresponds to a double mutant (T9E and T198E) dimer with a distorted N-lobe conformation, thus 3D homology modeling was implemented to rebuild the enzyme's native conformation. The resulting refined model was used to generate 3D pharmacophore models for the virtual screening of small molecules databases. Retrieved hits were filtered, docked into the ATP binding site of the enzyme, rescored, and the binding free energies for the top consensually scoring hits were calculated. Consequently, 45 compounds were selected and their in vitro inhibitory activity against TOPK was tested revealing four potential hits with the most active compound having an IC₅₀ of 3.85 µM. This compound will be chosen as a lead compound to synthesize analogs aiming to enhance potency and drug-like properties and to enrich the SAR data.

In vitro anti-TB properties, in silico target validation, molecular docking and dynamics studies of substituted 1,2,4-oxadiazole analogues against Mycobacterium tuberculosis

The alarming increase in multi- and extensively drug-resistant (MDR and XDR) strains of Mycobacterium tuberculosis (MTB) has triggered the scientific community to search for novel, effective, and safer therapeutics. To this end, a series of 3,5-disubstituted-1,2,4-oxadiazole derivatives (3a-3i) were tested against H37Rv, MDR and XDR strains of MTB. Of which, compound 3a with para-trifluorophenyl substituted oxadiazole showed excellent activity against the susceptible H37Rv and MDR-MTB strain with a MIC values of 8 and 16 µg/ml, respectively.To understand the mechanism of action of these compounds (3a-3i) and identify their putative drug target, molecular docking and dynamics studies were employed against a panel of 20 mycobacterial enzymes reported to be essential for mycobacterial growth and survival. These computational studies revealed polyketide synthase (Pks13) enzyme as the putative target. Moreover, in silico ADMET predictions showed satisfactory properties for these compounds, collectively, making them, particularly compound 3a, promising leads worthy of further optimisation.

Methodological approaches for the analysis of transmembrane domain interactions: A systematic review

The study of protein-protein interactions (PPI) has proven fundamental for the understanding of the most relevant cell processes. Any protein domain can participate in PPI, including transmembrane (TM) segments that can establish interactions with other TM domains (TMDs). However, the hydrophobic nature of TMDs and the environment they occupy complicates the study of intramembrane PPI, which demands the use of specific approaches and techniques. In this review, we will explore some of the strategies available to study intramembrane PPI in vitro, in vivo, and, in silico, focusing on those techniques that could be carried out in a standard molecular biology laboratory regarding its previous experience with membrane proteins.

Purinergic GPCR transmembrane residues involved in ligand recognition and dimerization

We compare the GPCR-ligand interactions and highlight important residues for recognition in purinergic receptors-from both X-ray crystallographic and cryo-EM structures. These include A1 and A2A adenosine receptors, and P2Y1 and P2Y12 receptors that respond to ADP and other nucleotides. These receptors are important drug discovery targets for immune, metabolic and nervous system disorders. In most cases, orthosteric ligands are represented, except for one allosteric P2Y1 antagonist. This review catalogs the residues and regions that engage in contacts with ligands or with other GPCR protomers in dimeric forms. Residues that are in proximity to bound ligands within purinergic GPCR families are correlated. There is extensive conservation of recognition motifs between adenosine receptors, but the P2Y1 and P2Y12 receptors are each structurally distinct in their ligand recognition. Identifying common interaction features for ligand recognition within a receptor class that has multiple structures available can aid in the drug discovery process.

CHK1 kinase inhibition: identification of allosteric hits using MD simulations, pharmacophore modeling, docking and MM-PBSA calculations

The CHK1 kinase plays a pivotal role in the DNA damage response pathway. Hence, inhibition of CHK1 appeared as a promising strategy to overcome the resistance problem of chemotherapeutic agents resulting from the overexpression of CHK1 that enables cancerous cells to repair their chemotherapy-induced DNA damage. In this study, different computational drug design techniques were employed to identify new CHK1 inhibitors targeting its allosteric pocket. A 1 μs MD simulation of the apo form of the enzyme was run to study its native dynamics. The resulting trajectory was analyzed to select a frame where the ATP binding pocket is most occluded while its allosteric counterpart is most exposed to be used in the design of potential allosteric inhibitors that could trap the enzyme in such nearly inactive state. Besides the selected frame, another three crystal structures of CHK1 complexed with allosteric inhibitors were utilized to generate structure-based pharmacophore models. Seven pharmacophores were generated and utilized in virtual screening of different databases. The retrieved hits were filtered and then docked into the allosteric pocket. Finally, the binding energies of the top-ranked docked hits were calculated. Twenty compounds were selected as candidates for biological evaluation against CHK1 enzyme. The biological screening results showed moderate activities where the percentage of CHK1 inhibition ranged from zero to 28.26%. Four of the tested compounds showed percentage of CHK1 inhibition greater than 20%, of which, two compounds were identified as allosteric hits that upon further optimization could be converted into lead-like compounds.

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.