Adenosine Receptor Antagonist Research Articles

2-Aryladenine Derivatives as a Potent Scaffold for Adenosine Receptor Antagonists: The 6-Morpholino Derivatives

A set of 2-aryl-9-H or methyl-6-morpholinopurine derivatives were synthesized and assayed through radioligand binding tests at human A1, A2A, A2B, and A3 adenosine receptor subtypes. Eleven purines showed potent antagonism at A1, A3, dual A1/A2A, A1/A2B, or A1/A3 adenosine receptors. Additionally, three compounds showed high affinity without selectivity for any specific adenosine receptor. The structure-activity relationships were made for this group of new compounds. The 9-methylpurine derivatives were generally less potent but more selective, and the 9H-purine derivatives were more potent but less selective. These compounds can be an important source of new biochemical tools and/or pharmacological drugs.

Development of Putative Bivalent Dicovalent Ligands for the Adenosine A1 Receptor.

Accumulating evidence suggests that G protein-coupled receptors (GPCRs) can exist and function in homodimer and heterodimer forms. The adenosine A1 receptor (A1R) has been shown to form both homodimers and heterodimers, but there is a lack of chemical tools to study these dimeric receptor populations. This work describes the synthesis and pharmacological evaluation of a novel class of bivalent GPCR chemical tools, where each ligand moiety of the bivalent compound contains a sulfonyl fluoride covalent warhead designed to be capable of simultaneously reacting with each A1R of an A1R homodimer. The novel compounds were characterised using radioligand binding assays, including washout assays, and functionally in cAMP assays. The bivalent dicovalent compounds were competitive A1R antagonists and showed evidence of covalent binding and simultaneous binding across an A1R homodimer. Greater selectivity for A1R over the adenosine A3 receptor was observed for bivalent dicovalent over the equivalent monovalent compounds, indicating subtype selectivity can be achieved with dual occupation by a bivalent dicovalent ligand.

Network pharmacology integrated with experimental validation to elucidate the mechanisms of action of the Guizhi-Gancao Decoction in the treatment of phenylephrine-induced cardiac hypertrophy

Context The mechanisms of Traditional Chinese Medicine (TCM) Guizhi-Gancao Decoction (GGD) remain unknown. Objective This study explores the mechanisms of GGD against cardiac hypertrophy. Materials and methods Network pharmacology analysis was carried out to identify the potential targets of GGD. In vivo experiments, C57BL/6J mice were divided into Con, phenylephrine (PE, 10 mg/kg/d), 2-chloroadenosine (CADO, the stable analogue of adenosine, 2 mg/kg/d), GGD (5.4 g/kg/d) and GGD (5.4 g/kg/d) + CGS15943 (a nonselective adenosine receptor antagonist, 4 mg/kg/d). In vitro experiments, primary neonatal rat cardiomyocytes (NRCM) were divided into Con, PE (100 µM), CADO (5 µM), GGD (10−5 g/mL) and GGD (10−5 g/mL) + CGS15943 (5 µM). Ultrasound, H&E and Masson staining, hypertrophic genes expression and cell surface area were conducted to verify the GGD efficacy. Adenosine receptors (ADORs) expression were tested via real-time polymerase chain reaction (PCR), western blotting and immunofluorescence analysis. Results Network pharmacology identified ADORs among those of the core targets of GGD. In vitro experiments demonstrated that GGD attenuated PE-induced increased surface area (with an EC50 of 5.484 × 10−6 g/mL). In vivo data shown that GGD attenuated PE-induced ventricular wall thickening. In vitro and in vivo data indicated that GGD alleviated PE-induced hypertrophic gene expression (e.g., ANP, BNP and MYH7/MYH6), A1AR over-expression and A2aAR down-expression. Moreover, CADO exerts effects similar to GGD, whereas CGS15943 eliminated most effects of GGD. Discussion and conclusions Our findings suggest the mechanism by which GGD inhibits cardiac hypertrophy, highlighting regulation of ADORs as a potential therapeutic strategy for HF.

Exogenous Ketone Supplement Administration Abrogated Isoflurane-Anesthesia-Induced Increase in Blood Glucose Level in Female WAG/Rij Rats.

It has been demonstrated that isoflurane-induced anesthesia can increase the blood glucose level, leading to hyperglycemia and several adverse effects. The administration of a mix of ketone diester (KE) and medium-chain triglyceride (MCT) oil, named KEMCT, abolished the isoflurane-anesthesia-induced increase in blood glucose level and prolonged the recovery time from isoflurane anesthesia in a male preclinical rodent model, Wistar Albino Glaxo/Rijswijk (WAG/Rij) rats. While most preclinical studies use exclusively male animals, our previous study on blood glucose changes in response to KEMCT administration showed that the results can be sex-dependent. Thus, in this study, we investigated female WAG/Rij rats, whether KEMCT gavage (3 g/kg/day for 7 days) can change the isoflurane (3%)-anesthesia-induced increase in blood glucose level and the recovery time from isoflurane-evoked anesthesia using the righting reflex. Moreover, KEMCT-induced ketosis may enhance both the extracellular level of adenosine and the activity of adenosine A1 receptors (A1Rs). To obtain information on the putative A1R mechanism of action, the effects of an A1R antagonist, DPCPX (1,3-dipropyl-8-cyclopentylxanthine; intraperitoneal/i.p. 0.2 mg/kg), on KEMCT-generated influences were also investigated. Our results show that KEMCT supplementation abolished the isoflurane-anesthesia-induced increase in blood glucose level, and this was abrogated by the co-administration of DPCPX. Nevertheless, KEMCT gavage did not change the recovery time from isoflurane-induced anesthesia. We can conclude that intragastric gavage of exogenous ketone supplements (EKSs), such as KEMCT, can abolish the isoflurane-anesthesia-induced increase in blood glucose level in both sexes likely through A1Rs in WAG/Rij rats, while recovery time was not affected in females, unlike in males. These results suggest that the administration of EKSs as an adjuvant therapy may be effective in mitigating metabolic side effects of isoflurane, such as hyperglycemia, in both sexes.

Targeting the adenosinergic system in restless legs syndrome: A pilot, "proof-of-concept" placebo-controlled TMS-based protocol.

Restless Legs Syndrome (RLS) is a common sleep disorder characterized by an urge to move the legs that is responsive to movement (particularly during rest), periodic leg movements during sleep, and hyperarousal. Recent evidence suggests that the involvement of the adenosine system may establish a connection between dopamine and glutamate dysfunction in RLS. Transcranial magnetic stimulation (TMS) is a non-invasive electrophysiological technique widely applied to explore brain electrophysiology and neurochemistry under different experimental conditions. In this pilot study protocol, we aim to investigate the effects of dipyridamole (a well-known enhancer of adenosinergic transmission) and caffeine (an adenosine receptor antagonist) on measures of cortical excitation and inhibition in response to TMS in patients with primary RLS. Initially, we will assess cortical excitability using both single- and paired-pulse TMS in patients with RLS. Then, based on the measures obtained, we will explore the effects of dipyridamole and caffeine, in comparison to placebo, on various TMS parameters related to cortical excitation and inhibition. Finally, we will evaluate the psycho-cognitive performance of RLS patients to screen them for cognitive impairment and/or mood-behavioral dysfunction, thus aiming to correlate psycho-cognitive findings with TMS data. Overall, this study protocol will be the first to shed lights on the neurophysiological mechanisms of RLS involving the modulation of the adenosine system, thus potentially providing a foundation for innovative "pharmaco-TMS"-based treatments. The distinctive TMS profile observed in RLS holds indeed the potential utility for both diagnosis and treatment, as well as for patient monitoring. As such, it can be considered a target for both novel pharmacological (i.e., drug) and non-pharmacological (e.g., neuromodulatory), "TMS-guided", interventions.

Effects of Intracerebral Aminophylline Dosing on Catalepsy and Gait in an Animal Model of Parkinson's Disease.

Parkinson's disease (PD) is a progressive disorder characterized by the apoptosis of dopaminergic neurons in the basal ganglia. This study explored the potential effects of aminophylline, a non-selective adenosine A1 and A2A receptor antagonist, on catalepsy and gait in a haloperidol-induced PD model. Sixty adult male Swiss mice were surgically implanted with guide cannulas that targeted the basal ganglia. After seven days, the mice received intraperitoneal injections of either haloperidol (experimental group, PD-induced model) or saline solution (control group, non-PD-induced model), followed by intracerebral infusions of aminophylline. The assessments included catalepsy testing on the bar and gait analysis using the Open Field Maze. A two-way repeated-measures analysis of variance (ANOVA), followed by Tukey's post hoc tests, was employed to evaluate the impact of groups (experimental × control), aminophylline (60 nM × 120 nM × saline/placebo), and interactions. Significance was set at 5%. The results revealed that the systemic administration of haloperidol in the experimental group increased catalepsy and dysfunction of gait that paralleled the observations in PD. Co-treatment with aminophylline at 60 nM and 120 nM reversed catalepsy in the experimental group but did not restore the normal gait pattern of the animals. In the non-PD induced group, which did not present any signs of catalepsy or motor dysfunctions, the intracerebral dose of aminophylline did not exert any interference on reaction time for catalepsy but increased walking distance in the Open Field Maze. Considering the results, this study highlights important adenosine interactions in the basal ganglia of animals with and without signs comparable to those of PD. These findings offer valuable insights into the neurobiology of PD and emphasize the importance of exploring novel therapeutic strategies to improve patient's catalepsy and gait.

Verification of In Vitro Anticancer Activity and Bioactive Compounds in Cordyceps Militaris-Infused Sweet Potato Shochu Spirits.

Many liqueurs, including spirits infused with botanicals, are crafted not only for their taste and flavor but also for potential medicinal benefits. However, the scientific evidence supporting their medicinal effects remains limited. This study aims to verify in vitro anticancer activity and bioactive compounds in shochu spirits infused with Cordyceps militaris, a Chinese medicine. The results revealed that a bioactive fraction was eluted from the spirit extract with 40% ethanol. The infusion time impacted the inhibitory effect of the spirit extract on the proliferation of colon cancer-derived cell line HCT-116 cells, and a 21-day infusion showed the strongest inhibitory effect. Furthermore, the spirit extract was separated into four fractions, A-D, by high-performance liquid chromatography (HPLC), and Fractions B, C, and D, but not A, exerted the effects of proliferation inhibition and apoptotic induction of HCT-116 cells and HL-60 cells. Furthermore, Fractions B, C, and D were, respectively, identified as adenosine, cordycepin, and N6-(2-hydroxyethyl)-adenosine (HEA) by comprehensive chemical analyses, including proton nuclear magnetic resonance (1H-NMR), Fourier transform infrared spectroscopy (FT-IR), and electrospray ionization mass spectrometry (ESI-MS). To better understand the bioactivity mechanisms of cordycepin and HEA, the agonist and antagonist tests of the A3 adenosine receptor (A3AR) were performed. Cell viability was suppressed by cordycepin, and HEA was restored by the A3AR antagonist MR1523, suggesting that cordycepin and HEA possibly acted as agonists to activate A3ARs to inhibit cell proliferation. Molecular docking simulations revealed that both adenosine and cordycepin bound to the same pocket site of A3ARs, while HEA exhibited a different binding pattern, supporting a possible explanation for the difference in their bioactivity. Taken together, the present study demonstrated that cordycepin and HEA were major bioactive ingredients in Cordyceps militaries-infused sweet potato shochu spirits, which contributed to the in vitro anticancer activity.

Inhibition of TNFalpha Release by Purine Nucleosides in a Human Monocyte-derived Microglial Model Exhibits Apparent Insensitivity to Adenosine, P2X, and P2Y Receptor Antagonism (P5-14.020)

Inhibition of TNFalpha Release by Purine Nucleosides in a Human Monocyte-derived Microglial Model Exhibits Apparent Insensitivity to Adenosine, P2X, and P2Y Receptor Antagonism (P5-14.020)

Abstract LB166: Discovery of CT3021, a novel potent adenosine A2a/A2b/A1 receptor triple antagonist

Abstract In a CD73-positive tumor microenvironment (TME), ATP released from apoptotic tumor cells converts to adenosine, generating an adenosine-rich immunosuppressive environment. Adenosine activates G-protein coupled receptors expressed on immune cells to achieve immune suppression, with a mechanism of action involving 1) dampening antitumor effector cells (T eff and NK cells) via adenosine engagement on A2a receptor, (2) reducing dendritic cell antigen presentation and promoting MDSC differentiation by activating A2b and A2a receptors, and (3) inducing chemotactic migration of immature plasmacytoid dendritic cells to infiltrate tumor tissue via A1 receptor. Furthermore, A1 receptor expression in certain tumors mediates an adenosine-driven tumor cell proliferation, likely through A1 receptor Gi coupling to the Hippo-YAP signal transduction pathway. Thus, pharmacologic inhibition of A2a, A2b, and A1 receptors by a triple antagonist in the context of adenosine-rich TME may represent an attractive strategy to achieve a better outcome in treating solid tumors. We discovered and characterized a novel adenosine receptor antagonist CT3021. CT3021 exhibits high binding affinity to A2a, A2b, and A1, with a Ki value of 0.37 nM, 1.76 nM, and 1.26 nM, respectively, and is selective against the A3 receptor and other 84 pharmacologically and/or toxicologically relevant targets. Schild analysis demonstrated that CT3021 is a competitive antagonist with a calculated KB value of 0.18 nM on A2a receptor in a whole cell cAMP assay in transfected HEK293 cells. In functional antagonist assays, CT3021 maintains its high potency full antagonism under an adenosine-rich TME-like condition (10-100 µM adenosine) both in transfected HEK293 cells and in isolated human T lymphocytes. CT3021 has a high oral bioavailability, a limited CNS exposure, and a favorable ADME profile. CT3021 is well tolerated in rats after repeat dosing. Further toxicology and efficacy studies are underway to explore the potential of CT3021 as a best-in-class adenosine receptor antagonist immunotherapy for the treatment of CD73 positive and A1 receptor positive solid tumors. Citation Format: Sandong Han, Nam Hee Kim, Hongmei He, Zhi Liang Chu. Discovery of CT3021, a novel potent adenosine A2a/A2b/A1 receptor triple antagonist [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB166.

Non-invasive caffeinated-nanovesicles as adipocytes-targeted therapy for cellulite and localized fats

Caffeine (CAF) is a non-selective adenosine A1 receptor antagonist which predominates in fat cells. When CAF binds to adenosine receptors, it increases cyclic adenosine monophosphate; inhibiting adipogenesis and inducing fat lipolysis. Resveratrol (RSV) is an antioxidant polyphenol possessing different anti-obesity mechanisms. Topical application of both hydrophilic CAF and lipophilic RSV is limited.This study aimed to develop novel caffeinated-resveratrol bilosomes (CRB) and caffeine-bilosomes (CB) that could non-invasively target and deposit in fat cells. RSV bilosomes (RB) were prepared as a non-targeted system for comparison. CRB showed nanosize (364.1 nm ±6.5 nm) and high entrapment for both active compounds. Rats treated topically with CRB revealed a significant decrease (P = 0.039) in body weight. Histological analysis of the excised skin demonstrated a reduction in the subcutaneous fatty layer thickness and a decrease in the size of connective tissue-imbedded fat cells. Kidney histological examination of RB-treated rats showed subcapsular tubular epithelial cells with cytoplasmic vacuolation. This reflects a systemic effect of RSV from the non-targeted RB compared to CRB, which had a targeting effect on the adipose tissue. In conclusion, CAF in CRB significantly enhanced RSV deposition in adipose tissue and assisted its local-acting effect for managing obesity and cellulite.

Antimanic-like effect of dipyridamole in the methylphenidate-induced hyperlocomotion.

Adenosinergic system has been implicated in the pathophysiology of bipolar disorder and drugs that affect adenosine neurotransmission have shown some efficacy as add-on therapy in manic patients. Thus, the aim of the present study was to screen adenosinergic drugs for antimanic-like effect in methylphenidate (MPH)-induced hyperlocomotion in mice. Male and female Swiss mice received a single allopurinol (50 and 200 mg/kg, ip), dipyridamole (20 mg/kg, ip), or inosine (50 mg/kg, ip) administration before an acute MPH challenge (5mg/kg, sc). In experiments with repeated treatment, male mice received a daily administration of allopurinol (25 and 50 mg/kg, ip), dipyridamole (20 mg/kg, ip), or inosine (50 mg/kg, ip) for 14 days. Finally, pretreatment with aminophylline (2mg/kg, sc), an unspecific adenosine receptor antagonist, was used to evaluate a putative adenosinergic mediation. Locomotor activity was measured in the automated activity chamber for 20 min. Acute and repeated dipyridamole reduced the increase in locomotor activity induced by MPH, while allopurinol and inosine had no effect. Aminophylline blocked the effect of dipyridamole in MPH-induced hyperlocomotion. The present results suggest that dipyridamole may have an antimanic-like effect through adenosine receptors and reinforce the proposal that the adenosine system may be an interesting target for new antimanic drugs.

Exploring Biginelli-based scaffolds as A2B adenosine receptor antagonists: Unveiling novel structure-activity relationship trends, lead compounds, and potent colorectal anticancer agents

Antagonists of the A2B adenosine receptor have recently emerged as targeted anticancer agents and immune checkpoint inhibitors within the realm of cancer immunotherapy. This study presents a comprehensive evaluation of novel Biginelli-assembled pyrimidine chemotypes, including mono-, bi-, and tricyclic derivatives, as A2BAR antagonists. We conducted a comprehensive examination of the adenosinergic profile (both binding and functional) of a large compound library consisting of 168 compounds. This approach unveiled original lead compounds and enabled the identification of novel structure-activity relationship (SAR) trends, which were supported by extensive computational studies, including quantum mechanical calculations and free energy perturbation (FEP) analysis. In total, 25 molecules showed attractive affinity (Ki < 100 nM) and outstanding selectivity for A2BAR. From these, five molecules corresponding to the new benzothiazole scaffold were below the Ki < 10 nM threshold, in addition to a novel dual A2A/A2B antagonist. The most potent compounds, and the dual antagonist, showed enantiospecific recognition in the A2BAR. Two A2BAR selective antagonists and the dual A2AAR/A2BAR antagonist reported in this study were assessed for their impact on colorectal cancer cell lines. The results revealed a significant and dose-dependent reduction in cell proliferation. Notably, the A2BAR antagonists exhibited remarkable specificity, as they did not impede the proliferation of non-tumoral cell lines. These findings support the efficacy and potential that A2BAR antagonists as valuable candidates for cancer therapy, but also that they can effectively complement strategies involving A2AAR antagonism in the context of immune checkpoint inhibition.

Diverse Pharmacological Potential of Pyridazine Analogs against Various Diseases.

Pyridazinone analogs possess diverse types of pharmacological activities, such as anticancer, antimicrobial, anticonvulsant, analgesic, anti-inflammatory, antioxidant, antihypertensive, antisecretory, antiulcer, and other useful pharmacological activities. They also possess cyclooxygenase (COX) inhibitors, dipeptidyl peptidase inhibitors, phosphodiesterase inhibitors, glutamate transporter activators, adenosine receptor antagonists, serotonin receptors antagonists, lipooxygenase, cholinesterase, vasodilator, and anesthetics. Pyridazine rings are the essential structure for some marketed drugs, such as pimobendan, levosimendan as a cardiotonic drug, and emorfozan as an analgesic and anti-inflammatory (Non-steroidal anti-inflammatory drug) agent. So, researchers all over the world have paid attention to synthesizing various pyridazinone compounds mainly due to the ease of design and synthesis of different analogs and variables in the pharmacological responses. This review article focuses on the pharmacological activities of different pyridazine analogs.

Therapeutic potency of A1 adenosine receptor antagonists in the treatment of cardiovascular diseases, current status and perspectives.

Cardiomyocytes form, transport, and metabolize the omnipresent metabolite adenosine. Depending upon the adenosine concentrations and the pharmacological properties of receptor subtypes, adenosine exerts (patho)physiological responses in the cardiovascular system. The objective of this review is to present different protective mechanisms of A1-adenosine receptor inhibitors in cardiovascular diseases. Literature references were collected and sorted using relevant keywords and key phrases as search terms in scientific databases such as Web of Science, PubMed and Google Scholar. A1 adenosine receptor regulates free fatty acid metabolism, lipolysis, heart rate, blood pressure, and cardiovascular toxicity. The evidence clearly supporting the therapeutic potency of pharmacological A1 adenosine receptors agonists and antagonists in modulating cardiovascular risk factor parameters and treatment of cardiovascular diseases. This review summarizes the protective role of pharmacological A1-adenosine receptor regulators in the pathogenesis of cardiovascular diseases for a better management of cardiovascular diseases.

Enhancing spinal cord stimulation-induced pain inhibition by augmenting endogenous adenosine signalling after nerve injury in rats

BackgroundThe mechanisms for spinal cord stimulation (SCS) to alleviate chronic pain are only partially known. We aimed to elucidate the roles of adenosine A1 and A3 receptors (A1R, A3R) in the inhibition of spinal nociceptive transmission by SCS, and further explored whether 2′-deoxycoformycin (dCF), an inhibitor of adenosine deaminase, can potentiate SCS-induced analgesia. MethodsWe used RNAscope and immunoblotting to examine the distributions of adora1 and adora3 expression, and levels of A1R and A3R proteins in the spinal cord of rats after tibial-spared nerve injury (SNI-t). Electrophysiology recording was conducted to examine how adenosine receptor antagonists, virus-mediated adora3 knockdown, and dCF affect SCS-induced inhibition of C-fibre-evoked spinal local field potential (C-LFP). ResultsAdora1 was predominantly expressed in neurones, whereas adora3 is highly expressed in microglial cells in the rat spinal cord. Spinal application of antagonists (100 μl) of A1R (8-cyclopentyl-1,3-dipropylxanthine [DPCPX], 50 μM) and A3R (MRS1523, 200 nM) augmented C-LFP in SNI-t rats (DPCPX: 1.39 [0.18] vs vehicle: 0.98 [0.05], P=0.046; MRS1523: 1.21 [0.07] vs vehicle: 0.91 [0.03], P=0.002). Both drugs also blocked inhibition of C-LFP by SCS. Conversely, dCF (0.1 mM) enhanced SCS-induced C-LFP inhibition (dCF: 0.60 [0.04] vs vehicle: 0.85 [0.02], P<0.001). In the behaviour study, dCF (100 nmol 15 μl−1, intrathecal) also enhanced inhibition of mechanical hypersensitivity by SCS in SNI-t rats. ConclusionsSpinal A1R and A3R signalling can exert tonic suppression and also contribute to SCS-induced inhibition of spinal nociceptive transmission after nerve injury. Inhibition of adenosine deaminase may represent a novel adjuvant pharmacotherapy to enhance SCS-induced analgesia.

Adenosine kinase gene modified mesenchymal stem cell transplantation retards seizure severity and associated cognitive impairment in a temporal lobe epilepsy rat model

PurposeTemporal lobe epilepsy (TLE) has a high risk of developing drug resistant and cognitive comorbidities. Adenosine has potential anticonvulsant effects as an inhibitory neurotransmitter, but drugs targeting its receptors and metabolic enzyme has inevitable side effects. Therefore, we investigated adenosine augmentation therapy for seizure control and cognitive comorbidities in TLE animals. MethodsUsing lentiviral vectors coexpressing miRNA inhibiting the expression of adenosine kinase (ADK), we produced ADK--rMSC (ADK knockdown rat mesenchymal stem cell). ADK--rMSC and LV-con-rMSC (rMSC transduced by randomized scrambled control sequence) were transplanted into the hippocampus of TLE rat respectively. ADK-+DPCPX group was transplanted with ADK--rMSC and intraperitoneally injected with DPCPX (adenosine A1 receptor antagonist). Seizure behavior, EEG, CA1 pyramidal neuron apoptosis, and behavior in Morris water maze and novel object recognition test were studied ResultsAdenosine concentration in the supernatants of 105 ADK--rMSCs was 13.8 ng/ml but not detectable in LV-con-rMSCs. ADK--rMSC (n = 11) transplantation decreased spontaneous recurrent seizure (SRS) duration compared to LV-con-rMSC (n = 11, P < 0.05). CA1 neuron apoptosis was decreased in ADK--rMSC (n = 3, P < 0.05). ADK--rMSC (n = 11) improved the Morris water maze performance of TLE rats compared to LV-con-rMSC (n = 11, escape latency, P < 0.01; entries in target quadrant, P < 0.05). The effect of ADK--rMSC on neuron apoptosis and spatial memory were counteracted by DPCPX. However, ADK--rMSC didn’t improve the performance in novel object recognition test. ConclusionAdenosine augmentation-based ADK--rMSC transplantation is a promising therapeutic candidate for TLE and related cognitive comorbidities.

Abstract PR15: Adenosine inhibits STING driven anti-tumor immunity in pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) is characterized by an immunosuppressed tumor immune microenvironment (TIME) where combinations of chemotherapy and immune checkpoint blockade (ICB) have shown limited efficacy. Standard of care FOLFIRINOX chemotherapy promotes replication stress associated cell death leading to an increase in extracellular ATP in the TIME and subsequent inflammation that favors anti-tumor immunity. Concomitantly, replication stress from chemotherapy also generates aberrant cytosolic DNA, which stimulates the production of 2’-3’ cGAMP, an immunotransmitter that activates STING in cells in the TIME. STING activation leads to the induction of Type 1 Interferon and a host of anti-tumor immune responses. Moreover, ATP augments leukocyte uptake of cGAMP, further increasing STING activation and promoting tumor immunity. However, acute ATP-dependent inflammation is self-limiting when ATP is inevitably converted to immunosuppressive adenosine (Ado) by extracellular ectonucleotidases (notably, CD39 and CD73) which are highly expressed in PDAC. As evidence of the tumor-promoting role of Ado in PDAC, we show in a Phase I neoadjuvant clinical trial for borderline resectable tumors (n=20) that resistance to neoadjuvant FOLFIRINOX and PD-1 inhibition is associated with an increase in adenosine-related gene expression. We deciphered a novel mechanism of adenosine-mediated immunosuppression whereby signaling through Ado receptors interrupts STING activation by cGAMP. Specifically, we show that NECA, a potent adenosine receptor agonist, inhibits phosphorylation of IRF3 downstream of STING activation and consequently blocks transcription of STING-driven IFNB1 in RAW264.7 macrophages, murine bone marrow-derived macrophages, and CD14+ human PBMCs. Under these same conditions, NECA increases IL-6 and IL-1B, highlighting a complex cytokine milieu controlled by ATP metabolism and STING signaling. These effects are reversed with the addition of AB928, an adenosine receptor antagonist. We considered that boosting cGAMP in the PDAC TIME might be sufficient to offset the effects of Ado signaling. In support of this approach, we show that blocking hydrolysis of cGAMP by inhibiting ENPP1 augments the efficacy of FOLFIRINOX against syngeneic murine PDAC tumors, despite the likely presence of adenosine. These findings support the conclusion that adenosine signaling interrupts anti-tumor STING signaling and demonstrate that ENPP-1 inhibition may provide therapeutic benefits by boosting STING and reducing adenosine during chemotherapy treatment in PDAC patients. Citation Format: Alykhan Premji, Jason Link, Takanobu Yamao, Khalid Rashid, Evan Abt, Amanda Labora, Charlotte Chan, Thuc Le, Zev Wainberg, Caius Radu, Timothy Donahue. Adenosine inhibits STING driven anti-tumor immunity in pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr PR15.

Extracellular Guanosine and Guanine Nucleotides Decrease Viability of Human Breast Cancer SKBR-3 Cells.

Though the physiological effects of adenosine and adenine nucleotides on purinergic receptors in cancer cells have been well studied, the influence of extracellular guanosine and guanine nucleotides on breast cancer cells remains unclear. Here, we show that extracellular guanosine and guanine nucleotides decrease the viability and proliferation of human breast cancer SKBR-3 cells. Treatment with guanosine or guanine nucleotides increased mitochondrial production of reactive oxygen species (ROS), and modified the cell cycle. Guanosine-induced cell death was suppressed by treatment with adenosine or the equilibrium nucleoside transporter (ENT) 1/2 inhibitor dipyridamole, but was not affected by adenosine receptor agonists or antagonists. These results suggest that guanosine inhibits adenosine uptake through ENT1/2, but does not antagonize adenosine receptors. In contrast, guanosine triphosphate (GTP)-induced cell death was suppressed not only by adenosine and dipyridamole, but also by the A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA), suggesting that GTP-induced cell death is mediated in part by an antagonistic effect on adenosine A1 receptor. Thus, both guanosine and GTP induce apoptosis of breast cancer cells, but via at least partially different mechanisms.

A COMPREHENSIVE REVIEW ON PHARMACOLOGICAL POTENTIALS OF CAFFEINE

Caffeine is a naturally occurring methylxanthine compound found in various plants, such as coffee beans, tea leaves, and cocoa beans. It is widely consumed worldwide in the form of beverages, dietary supplements, and medications. Caffeine exerts its pharmacological effects primarily through its interaction with adenosine receptors, resulting in widespread physiological and neurological changes. In the field of medicinal chemistry, caffeine has been extensively studied due to its diverse pharmacological actions and potential therapeutic applications. This abstract highlights the key pharmacological actions of caffeine and its relevance in medicinal chemistry research. Caffeine acts as a non-selective antagonist of adenosine receptors, particularly the A1 and A2A subtypes. By inhibiting adenosine binding, caffeine prevents the activation of these receptors, leading to increased neural activity and the release of neurotransmitters such as dopamine and glutamate. This mechanism of action underlies caffeine’s stimulant effects, including increased alertness, reduced fatigue, and improved cognitive function. Caffeine exhibits broncho dilatory effects by acting as a phosphodiesterase inhibitor, primarily targeting phosphodiesterase type 4 (PDE4). Inhibition of PDE4 prevents the breakdown of cyclic adenosine monophosphate (cAMP), leading to smooth muscle relaxation and bronchodilation. This property of caffeine has been utilized in the treatment of asthma and chronic obstructive pulmonary disease (COPD). Furthermore, caffeine possesses diuretic properties by inhibiting the reabsorption of sodium in the renal tubules. This leads to increased water excretion and urine production. The diuretic effects of caffeine have found applications in the management of fluid overload conditions, such as edema and heart failure. Additionally, caffeine has been investigated for its potential anticancer properties. Several studies have shown that caffeine can enhance the cytotoxic effects of certain chemotherapeutic agents, inhibit DNA repair mechanisms, and induce apoptosis in cancer cells. These findings have sparked interest in caffeine as an adjuvant therapy for cancer treatment, although further research is needed to establish its clinical efficacy and safety. In conclusion, caffeine exhibits a wide range of pharmacological actions, making it a versatile compound in medicinal chemistry research. Its interactions with adenosine receptors, phosphodiesterase, and renal tubules contribute to its stimulant, broncho dilatory, diuretic, and potentially anticancer effects. The understanding of caffeine’s pharmacological actions provides valuable insights for the development of novel drugs and therapeutic approaches in various fields of medicine.

Extrapolating the Coffee and Caffeine (1,3,7-Trimethylxanthine) Effects on Exercise and Metabolism-A Concise Review.

The consumption of coffee and caffeine (1,3,7-trimethylxanthine) is part of many cultures worldwide. Their properties include serving as a neurostimulant aid, enhancing energy substrate levels, and improving general exercise performance. Both present therapeutic effects that can also be used to control chronic and metabolic diseases due to four mechanisms: adenosine receptor antagonism, increased catecholamine concentrations, a phosphodiesterase inhibitor, and a stimulator of calcium-release channels. Despite the individual genetic variabilities, distinct mechanisms have been demonstrated to improve physical performance, thermogenesis, lipolysis, insulin sensitivity, and hormonal modulation. Thus, coffee consumption and caffeine supplementation may enhance physical and mental performance and may improve metabolic variables, reducing oxidative stress, inflammation, and insulin resistance. Current data reveal vital aspects of coffee and caffeine consumption in specific populations, although further studies are needed to define clinical interventions with caffeine in obesity and chronic conditions.