Adenosine Agonists Research Articles

Potent inhibitory effect on human platelet aggregation of the aerial part of Canna edulis

Canna edulis Ker Gawl has been used in Vietnamese Traditional Medicine for the treatment of heart diseases with very limited scientific evidence. This study aimed to evaluate the inhibitory effect on human platelet aggregation of the aerial part of C. edulis. Aerial C. edulis was firstly macerated with methanol, and then fractionated with different solvents to obtain 3 fractions: n-hexane, ethyl acetate and aqueous extracts. The inhibitory effects on human platelet aggregation of extracts were evaluated via three parameters: percentage inhibition of platelet aggregation (%I), area under the aggregation curve (AUC) and aggregation slope, using two agonists adenosine diphosphate (ADP) and collagen. The results showed that all extracts significantly inhibited platelet aggregation in a dose-dependent manner for both agonists. Moreover, all extracts significantly decreased AUC and slope, indicating their antiaggregatory effects on both general aggregation and aggregation velocity. Among extracts, the ethyl acetate fraction exhibited the strongest effect regardless of agonists used (%I at 4 mg/mL, 99.2% for both ADP and collagen). The n-hexane fraction also had significant inhibitory effect but it was weaker than the others (p < 0.05). This is the first study to demonstrate the potent antiplatelet effect of the aerial part of C. edulis. This plant could be a potential natural source for searching novel antiplatelet agents and developing dietary supplements for management of cardiovascular diseases.

Translational Experimental Basis of Indirect Adenosine Receptor Agonist Stimulation for Bone Regeneration: A Review.

Bone regeneration remains a significant clinical challenge, often necessitating surgical approaches when healing bone defects and fracture nonunions. Within this context, the modulation of adenosine signaling pathways has emerged as a promising therapeutic option, encouraging osteoblast activation and tempering osteoclast differentiation. A literature review of the PubMed database with relevant keywords was conducted. The search criteria involved in vitro or in vivo models, with clear methodological descriptions. Only studies that included the use of indirect adenosine agonists, looking at the effects of bone regeneration, were considered relevant according to the eligibility criteria. A total of 29 articles were identified which met the inclusion and exclusion criteria, and they were reviewed to highlight the preclinical translation of adenosine agonists. While preclinical studies demonstrate the therapeutic potential of adenosine signaling in bone regeneration, its clinical application remains unrealized, underscoring the need for further clinical trials. To date, only large, preclinical animal models using indirect adenosine agonists have been successful in stimulating bone regeneration. The adenosine receptors (A1, A2A, A2B, and A3) stimulate various pathways, inducing different cellular responses. Specifically, indirect adenosine agonists act to increase the extracellular concentration of adenosine, subsequently agonizing the respective adenosine receptors. The agonism of each receptor is dependent on its expression on the cell surface, the extracellular concentration of adenosine, and its affinity for adenosine. This comprehensive review analyzed the multitude of indirect agonists currently being studied preclinically for bone regeneration, discussing the mechanisms of each agonist, their cellular responses in vitro, and their effects on bone formation in vivo.

ADENOSINE INFLUENCES FOXP3 EXPRESSION OF T REGS VIA THE A2AR/CREB PATHWAY IN A MOUSE MODEL OF SEPSIS.

The adenosine concentration and forkhead box protein (Foxp3) expression in T regulatory cells (T regs ) are increased during sepsis. However, the mechanism by which adenosine induces Foxp3 expression is incompletely understood. A cecal ligation and puncture (CLP) model was constructed using C57BL/J mice. The plasma adenosine concentration and Foxp3 expression in splenic T regs were increased consistently for 15 days after sepsis onset. Analysis of the mean fluorescence intensity of Foxp3 and adenosine concentration in the same mice revealed a linear correlation. In the CLP model, adenosine 2a receptor (A2aR) blockade inhibited Foxp3 expression in T regs . In vitro activation of A2aR promoted Foxp3 expression in T regs and facilitated secretion of extracellular vesicles. Transcriptome sequencing revealed that A2aR blockade led to changes in cyclic adenosine monophosphate response element-binding protein (CREB) transcription in T regs in our sepsis model. Use of adenosine or A2aR agonists promoted CREB expression, CREB phosphorylation at S133, T reg expression of Foxp3, and enhanced inhibition of proliferation of cluster of differentiation (CD)4+ lymphocytes. A2aR blockade or inhibition of CREB expression inhibited Foxp3 expression in T regs . In the CLP model, use of CREB inhibitors could inhibit Foxp3 expression and reduce the bacterial load. In summary, adenosine in sepsis promotes CREB phosphorylation via A2aR which, in turn, upregulates Foxp3 expression in T regs .

Abstract 18621: Platelet Aggregation is Heightened in Those With Metabolic Syndrome and Less Effectively Mediated by Aspirin Therapy

Background: Patients with metabolic syndrome (MetS) are at a higher risk of developing cardiovascular disease (CVD); however, interventions to mitigate this risk are not fully known. Platelets play a significant role in atherothrombosis, and aspirin is an important, yet controversial therapy used for the primary prevention of CVD. In this study, we examined platelet phenotype in MetS and degree of inhibition from ex vivo aspirin administration. Methods: In a study examining the mechanisms of atherothrombosis in pro-inflammatory conditions, patients without clinical CVD were enrolled and underwent phenotyping. Patients with MetS (n = 34, age 53.3 ± 13 years, 59% male) were compared to patients with no MetS (n = 63, age 41.1 ± 16 years, 52% male). Platelet aggregation of freshly isolated platelets was measured via light transmission aggregometry (LTA) in resting and stimulated conditions, in response to agonists adenosine diphosphate (ADP), high and low dose of arachidonic acid (AA), and after ex vivo aspirin (ASA) administration. Results: MetS patients were older and similar in sex and race (Figure 1A). As expected, patients with MetS had higher individual components of MetS, yet similar LDL-C (Figure 1A). Platelet aggregation to low dose ADP (p=0.09) and AA (p=0.04) was significantly increased in MetS (Figure 1B). Platelet aggregation in response to AA and coincubation with ASA was significantly lower in the no MetS cohort (Figure 1C). The efficacy of aspirin therapy was significantly lower in MetS (Figure 1D). In response to high dose AA after ASA treatment, platelet aggregation increased as number of MetS parameters also increased (Figure 1E). However, no individual metabolic syndrome parameter appeared to be driving these findings (Figure 1E). Conclusion: Among MetS patients, platelet aggregation is heightened and less inhibited by aspirin than those with no MetS. Additional research is warranted to explore possible anti-platelet strategies in patients with MetS.

Abstract 15758: Platelet Aggregation is Elevated in Psoriasis and Associated With Cardiovascular Risk

Introduction: Psoriasis is associated with increased CV risk the mechanisms and prevention of which are not fully known. We evaluated the platelet phenotype (implicated in atherothrombosis) and in vitro response to aspirin in patients with psoriasis and its association with vascular stiffness and coronary atherosclerosis. Methods: Patients with psoriasis (n = 64, age 47.9 ± 15 years, 65% male), percent body surface area (BSA) of psoriasis 3%, were compared to controls (n = 40, age 40.8 ± 16 years, 45% male). Percent platelet aggregation in response to agonists adenosine diphosphate (ADP), collagen (Col), and arachidonic acid (AA - with and without aspirin) was measured in freshly isolated platelet-rich plasma via light transmission aggregometry (LTA). Vascular stiffness (via pulse wave velocity [PWV]) and CT coronary angiography were each performed as readouts of CV risk. Results: Compared to controls, psoriasis patients were older, of Caucasian ethnicity (Figure 1A), and overweight, but otherwise similar. Platelet aggregation after treatment with Col (p=0.01), ADP (p < 0.01), and AA (p = 0.05) were all higher in psoriasis vs. control (Figure 1B-D). Platelet aggregation after activation with high dose AA was similar between groups (Figure 1E) however co-incubation with high dose AA plus aspirin displayed incomplete platelet inhibition of psoriasis platelets vs. controls (Figure 1F). Platelet aggregation to low dose AA and high dose AA plus aspirin co-incubation were each higher in those with enhanced vascular stiffness (figure 1G/1H) and the presence of coronary plaque (Figure 1I/1J). Conclusion: Platelet aggregation is consistently elevated in psoriasis across a variety of agonists, incompletely inhibited by aspirin, and associated with biomarkers of CV risk such as vascular stiffness and the presence of coronary plaque. These findings highlight the need to evaluate various anti-platelet strategies to reduce atherothrombotic risk in patients with psoriasis.

Ticagrelor inverse agonist activity at the P2Y12 receptor is non-reversible versus its endogenous agonist adenosine 5´-diphosphate.

Ticagrelor is labelled as a reversible, direct-acting platelet P2Y12 receptor (P2Y12 R) antagonist that is indicated clinically for the prevention of thrombotic events in patients with acute coronary syndrome (ACS). As with many antiplatelet drugs, ticagrelor therapy increases bleeding risk in patients, which may require platelet transfusion in emergency situations. The aim of this study was to further examine the reversibility of ticagrelor at the P2Y12 R. Studies were performed in human platelets, with P2Y12 R-stimulated GTPase activity and platelet aggregation assessed. Cell-based bioluminescence resonance energy transfer (BRET) assays were undertaken to assess G protein-subunit activation downstream of P2Y12 R activation. Initial studies revealed that a range of P2Y12 R ligands, including ticagrelor, displayed inverse agonist activity at P2Y12 R. Only ticagrelor was resistant to washout and, in human platelet and cell-based assays, washing failed to reverse ticagrelor-dependent inhibition of ADP-stimulated P2Y12 R function. The P2Y12 R agonist 2MeSADP, which was also resistant to washout, was able to effectively compete with ticagrelor. In silico docking revealed that ticagrelor and 2MeSADP penetrated more deeply into the orthosteric binding pocket of the P2Y12 R than other P2Y12 R ligands. Ticagrelor binding to P2Y12 R is prolonged and more akin to that of an irreversible antagonist, especially versus the endogenous P2Y12 R agonist ADP. This study highlights the potential clinical need for novel ticagrelor reversal strategies in patients with spontaneous major bleeding, and for bleeding associated with urgent invasive procedures.

POTENT AND SELECTIVE A2AR MONOCLONAL ANTIBODY ANTAGONIST FOR THE TREATMENT OF CANCER

Abstract Background and significance The presence of adenosine at abnormally high concentrations in tumor microenvironment leads to the activation of adenosine receptor 2A (A2aR) and represents one of the mechanisms for cancer patients to be resistance to immune checkpoint blockade therapies. CD39 and CD73 play an important role in converting ATP to adenosine. Currently antibodies or small molecule inhibitors (SMIs) targeting CD39 and CD73, as well as SMIs targeting adenosine receptors, are under preclinical investigation and early clinical development. However, effective biologics targeting adenosine receptors has not been reported. Here we demonstrated that humanized anti-A2aR antibodies represent promising novel therapeutic candidates for developing immunotherapy to restore anti-tumor responses in solid tumors that only partially respond or are completely resistance to ICB therapies. Methods Humanized anti-human A2aR monoclonal antibodies (mAbs) were generated from mouse hybridoma antibody via classic CDR grafting method. The A2aR binding and non-human primate cross-reactivity were measured by FACS using human A2aR-expressing HEK293 cells as well as human and cynomolgus monkey PBMCs. Internalizing properties were determined by FACS and immunofluorescent method. The cellular potency of these mAbs was assessed by their capability of inhibiting cAMP production induced by A2aR agonist adenosine and NECA in hA2aR-overexpressing HEK293 cells. The ability of lead candidates to reverse adenosine-mediated suppression of human effector cell function was determined using standard CD3/CD28 activation conditions in the presence of A2aR agonist NECA. Results and Conclusion We successfully humanized anti-A2aR antibody discovered via hybridoma technology. Humanized anti-A2aR antibodies maintain binding, cross-reactivity to human and cynomolgus monkey A2aR, as well as internalizing property and A2aR-antagonizing potency, in comparison with parental antibody. Humanized antibodies are 5~10 fold more potent than clinical stage small molecule inhibitors CPI-444 and AB928 in inhibiting cAMP production. Blockade of A2aR with humanized antibody can restore activation and cytokine production of human T and NK cells suppressed by A2aR agonist adenosine or NECA. Thus, antibody-mediated blockade of A2aR pathway represents a novel strategy to mitigate adenosine-mediated tumor resistance to immune checkpoint blockade therapies.

Potential for modulation of platelet function via adenosine receptors during inflammation.

Traditionally, platelets are known to play an important role in haemostasis and thrombosis; however, they serve also as important modulators of inflammation and immunity. Platelets secrete adhesion molecules and cytokines, interact with leukocytes and endothelium, and express toll-like receptors involved in a direct interaction with pathogens. Platelets express A2A and A2B subtypes of receptors for adenosine. The activation of these receptors leads to an increase in cAMP concentration in the cytoplasm, thereby resulting in inhibited secretion of pro-inflammatory mediators and reduced cell activation. Therefore, platelet adenosine receptors could be a potential target for inhibiting platelet activation and thus down-regulating inflammation or immunity. The biological effects of adenosine are short-lasting, because the compound is rapidly metabolized; hence, its lability has triggered efforts to synthesize new, longer-lasting adenosine analogues. In this article, we have reviewed the literature regarding the pharmacological potential of adenosine and other agonists of A2A and A2B receptors to affect platelet function during inflammation. LINKED ARTICLES: This article is part of a themed issue on Platelet purinergic receptor and non-thrombotic disease. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.4/issuetoc.

P2X7 receptor-mediated depression-like reactions arising in the mouse medial prefrontal cortex.

Major depressive disorder is a frequent and debilitating psychiatric disease. We have shown in some of the acute animal models of major depressive disorder (tail suspension test and forced swim test) that depression-like behavior can be aggravated in mice by the microinjection into the medial prefrontal cortex of the P2X7R agonistic adenosine 5'-triphosphate or its structural analog dibenzoyl-ATP, and these effects can be reversed by the P2X7R antagonistic JNJ-47965567. When measuring tail suspension test, the prolongation of immobility time by the P2YR agonist adenosine 5'-[β-thio]diphosphate and the reduction of the adenosine 5'-(γ-thio)triphosphate effect by P2Y1R (MRS 2179) or P2Y12R (PSB 0739) antagonists, but not by JNJ-47965567, all suggest the involvement of P2YRs. In order to elucidate the localization of the modulatory P2X7Rs in the brain, we recorded current responses to dibenzoyl-ATP in layer V astrocytes and pyramidal neurons of medial prefrontal cortex brain slices by the whole-cell patch-clamp procedure; the current amplitudes were not altered in preparations taken from tail suspension test or foot shock-treated mice. The release of adenosine 5'-triphosphate was decreased by foot shock, although not by tail suspension test both in the hippocampus and PFC. In conclusion, we suggest, that in the medial prefrontal cortex, acute stressful stimuli cause supersensitivity of P2X7Rs facilitating the learned helplessness reaction.

Cystic fibrosis transmembrane conductance regulator potentiators attenuate platelet activation and aggregation in blood of healthy donors and COVID-19 patients

Cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl - channel and ABC transporter; its mutations cause the clinical picture of cystic fibrosis (CF). Of late, CFTR has emerged as an important regulator of platelet function, as CFTR dysfunction causes agonist-induced platelet hyperactivation. These findings are reminiscent of platelets from SARS-CoV-2 infected patients since thromboembolic complications represent hallmarks of severe COVID-19 that may critically contribute to morbidity and mortality. CFTR modulators have recently been introduced as a treatment for patients with various CFTR mutations, but have also been reported by us and others to enhance channel function of wild type CFTR. We therefore postulated that CFTR modulators may exert anti-coagulant effects on platelets of healthy donors (HD) and COVID-19 patients.We recruited 36 COVID-19 patients with moderate, and 34 COVID-19 patients with severe disease course (all w/o anti-platelet drugs), and 38 HDs. In line with our hypothesis, we observed significant reductions in platelet agonists adenosine diphosphate (ADP)- or thrombin receptor activating protein-6 (TRAP6)-induced CD62p/CD63 expression, Ca 2+ -mobilization, aggregation, and adhesion of platelets from HDs by pre-treatment with ivacaftor. In blood from COVID-19 patients, platelet activation correlates with disease severity, as demonstrated by a 5-fold and 8-fold increase in the proportion of CD62p + platelets from patients with moderate and severe disease, respectively, relative to HDs. Similarly, the proportion of CD63 + platelets in patients with severe COVID-19 was 2-fold higher than in HDs. Retrospective analysis of clinical data from a total of 4,050 CF patients with COVID-19 receiving single or combination therapy of ivacaftor, lumacaftor, tezacaftor, or elexacaftor in comparison to an untreated cohort revealed that CF therapy reduced the relative risk to suffer thromboembolism-associated cardiovascular events such as heart attack or deep vein thrombosis by 50.0% or 61.1%, respectively, suggesting an anti-thrombotic effect of CFTR modulators in CF COVID-19 patients. In line with this observation, ex vivo pre-treatment of platelets from acute COVID-19 patients with ivacaftor reduced Ca 2+ mobilization, adhesion, and aggregation of platelets .Our results demonstrate an anticoagulant effect of CFTR potentiators on platelets from HDs and severe COVID-19 patients and thus, suggest CFTR potentiators as a promising strategy to reduce the risk of thrombotic events in the clinical management of COVID-19 and similar pro-thrombotic disease states. F. Behrens received funding from the Berlin Institute of Health (BIH). L. Michalick reports grants from the BIH and the German Centre for Cardiovascular Research (DZHK). A. Haghikia is participant in the BIH-Charité Advanced Clinician Scientist Pilotprogram funded by the Charité - Universitätsmedizin Berlin and the BIH and reports a research grant within the BIH & MDC Focus Area Translational Vascular Biomedicine. R. Preissner reports partial funding of this work by the German Research Foundation (KFO339, TRR295). M. Witzenrath reports grants from the German Research Foundation (SFB-TR84 C06 and C09, SFB 1449 B02), and from the German Ministry of Education and Research (BMBF) in the framework of CAPSyS (01ZX1604B, 01ZX1304B), SYMPATH (01ZX1906A), PROVID (01KI20160A), Phage4Cure (16GW0141), MAPVAP (16GW0247) and NUM-NAPKON. W. M. Kuebler reports grants from the German Research Foundation (SFB-TR84 A2 and C9, SFB 1449 B1, SFB 1470 A4, KU1218/9-1, KU1218/11-1, and KU1218/12-1), the BMBF in the framework of SYMPATH (01ZX1906A) and PROVID (01KI20160A), and the DZHK. S. Simmons reports grants from the DZHK and the German Foundation for Heart Research (F-09-19). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Intramuscular Polydeoxyribonucleotides in Fibrotic and Atrophic Localized Scleroderma: An Explorative Prospective Cohort Study

Effective options in the quiescent, scantily inflammatory phase of localized scleroderma (morphea) are lacking. A cohort study in patients with histologically confirmed fibroatrophic morphea explored the therapeutic value of the anti-dystrophic A2A adenosine agonist polydeoxyribonucleotide (PDRN, one daily 5.625 mg/3 mL ampoule for 90 days with a three-month follow-up). Primary efficacy endpoints: Localized Scleroderma Cutaneous Assessment Tool mLoSSI and mLoSDI subscores for disease activity and damage in eighteen areas; Physicians Global Assessment for Activity (PGA-A) and Damage (PGA-D) VAS scores; skin echography. Secondary efficacy endpoints: mLoSSI, mLoSDI, PGA-A, PGA-D, and morphea areas (photographs) over time; Dermatology Life Quality Index (DLQI); skin biopsy scores and induration over time. Twenty-five patients enrolled; 20 completed the follow-up period. Highly significant improvements at the end of the 3-month treatment period: mLoSSI–73.7%, mLoSDI–43.9%, PGA-A–60.4%, PGA-D–40.3%, with further improvements at follow-up visit for all disease activity and damage indexes. Overall, the outcomes suggest that a daily PDRN ampoule intramuscularly for 90 days reduces disease activity and damage rapidly and significantly in quiescent, modestly inflammatory morphea with few currently therapeutic options. The COVID-19 pandemic and lockdowns caused difficulties in enrollment, and some patients were lost to follow-up. Due to low final enrollment, the study outcomes may have only an exploratory value, yet they appear impressive. The anti-dystrophic potential of the PDRN A2A adenosine agonist deserves further in-depth exploration.

In vitro Investigation of Platelet Dysfunction Induced by Osmotic Pressure Variations

Background: Severe variations in osmotic pressure are significant contributors to critical patient morbidity and mortality and might also affect platelet volume. We aimed to investigate possible osmotic-induced changes in mean platelet volume (MPV) and their possible effects on platelet aggregation activity (PLAG). Methods: We induced experimental variations of serum osmolality in blood samples from healthy volunteers (heparinized whole blood [WB]) and isolated platelets (platelet-rich plasma [PRP]) by adding isotonic, hypertonic, and hypotonic solutions of saline/water (pH = 7.2–7.4). PLAG was tested in WB samples with impedance aggregometry (IA) and in PRP samples with light transmission aggregometry (LTA) using three agonists: adenosine diphosphate (ADP, 10 μ<sc>m</sc>), thrombin receptor activating peptide (TRAP-6, 10 μ<sc>m</sc>), and arachidonic acid (500 μ<sc>m</sc>). Osmolality was either calculated using a formula or measured directly. Results: We found almost identical osmolalities in WB and PRP preparations. Osmotic stress did not produce significant changes in MPV. In IA testing, the hypotonic challenge of WB preparations produced significant reductions at 50% (p = 0.056) (95% CI: 11.2–2.4, in Ohms) of ADP and at 31% (p = 0.017) (95% CI: 13.4–8.6, in Ohms) of TRAP-6-induced PLAG, respectively. In PRP, we did not observe any variations in PLAG with LTA. Conclusions: We conclude that in vitro hypotonic stress of WB samples has an inhibitory effect on the PAR-1 (TRAP-6-induced) pathway and on the P2Y₁₂ (ADP-induced) pathway and reflects a distinct in vivo effect of hypoosmotic stress on WB human platelet preparations.

Extracellular adenosine 5ʹ-diphosphate promotes MCP-1/CCL2 expression via the P2Y13 purinergic receptor/ERK signaling axis in temporomandibular joint-derived mouse fibroblast-like synoviocytes

BackgroundTemporomandibular joint osteoarthritis (TMJ-OA) causes cartilage degeneration, bone cavitation, and fibrosis of the TMJ. However, the mechanisms underlying the fibroblast-like synoviocyte (FLS)-mediated inflammatory activity in TMJ-OA remain unclear.Methods and resultsReverse transcription-quantitative polymerase chain reaction analysis revealed that the P2Y1, P2Y12, and P2Y13 purinergic receptor agonist adenosine 5ʹ-diphosphate (ADP) significantly induces monocyte chemotactic protein 1 (MCP-1)/ C–C motif chemokine ligand 2 (CCL2) expression in the FLS1 synovial cell line. In contrast, the uracil nucleotide UTP, which is a P2Y2 and P2Y4 agonist, has no significant effect on MCP-1/CCL2 production in FLS1 cells. In addition, the P2Y13 antagonist MRS 2211 considerably decreases the expression of ADP-induced MCP-1/CCL2, whereas ADP stimulation enhances extracellular signal-regulated kinase (ERK) phosphorylation. Moreover, it was found that the mitogen-activated protein kinase/ERK kinase (MEK) inhibitor U0126 reduces ADP-induced MCP-1/CCL2 expression.ConclusionADP enhances MCP-1/CCL2 expression in TMJ FLSs via P2Y13 receptors in an MEK/ERK-dependent manner, thus resulting in inflammatory cell infiltration in the TMJ. Collectively, the findings of this study contribute to a partial clarification of the signaling pathway underlying the development of inflammation in TMJ-OA and can help identify potential therapeutic targets for suppressing ADP-mediated purinergic signaling in this disease.

Selective reduction of neurotransmitter release by cAMP-dependent pathways in mouse detrusor.

Parasympathetic nerve-mediated contractions of detrusor smooth muscle are generated by ATP and acetylcholine (ACh) release from efferent nerve terminals. In humans, ACh is responsible for detrusor contractions in normal human bladders, whereas ATP has an additional role in overactive bladder pathologies. The ATP metabolite, adenosine, relaxes nerve-mediated contractions, with a potential action via presynaptic adenosine A1 receptor activation and subsequent suppression of neuronal ATP release. We investigated the effect of A1 receptor activation and downstream cAMP-dependent pathways on nerve-mediated ATP and ACh release, and detrusor contraction in mouse detrusor. Bladders from male C57BL/6 mice (12 wk) were used for in vitro experiments. Upon electrical field stimulation of intact preparations (detrusor and mucosal layers), ATP or ACh release was measured simultaneously with tension recordings. Activation of A1 receptors by adenosine or exogenous agonists reduced the lower frequency component of nerve-mediated contractions and neuronal ATP release. The A1 receptor antagonist abolished these effects. A1 receptor activation inhibits adenylyl cyclase (AC) activity and cAMP generation. The effect of A1 receptor activation was mimicked by a PKA antagonist but not by modulators of exchange proteins activated by cAMP, demonstrating that modulation of nerve-mediated ATP release is via PKA. Adenosine had no effect on ACh release or the higher frequency component of nerve-mediated contractions. Differential regulation of neurotransmitter release is possible at the detrusor nerve-muscle junction, as demonstrated by A1 receptor activation, and downstream inhibition of AC, cAMP generation, and PKA. The ability to specifically attenuate ATP release offers a potential to target purinergic motor pathways enhanced in overactive bladder pathologies.

Intracardiac echocardiography-guided endomyocardial biopsy for the early detection of giant cell myocarditis causing recurrent ventricular tachycardia

Adenosine is present in all cells and is implicated in the control of the function of every tissue and organ. The elevated adenosine levels seem to play a significant role in a protection against cellular damage in the regions with increased metabolic demand and prevent the subsequent dysfunction of the affected organs. Furthermore, adenosine has been shown to play an important role not only in the regulation of pathophysiological processes, but also in the modulation of normal physiological processes, for example, the regulation of sleep and arousal as well as by impact on pre- or postsynaptic receptors involved in releasing neurotransmitters (e.g. glutamate, acetylcholine, norepinephrine, 5-hydroxytryptamine, dopamine, GABA and others).Experimental studies provide evidence supporting the role of adenosine as an endogenous anticonvulsant agent. Numerous adenosine agonists acting through A1, A2 and A3 receptors were proven as potent anticonvulsant compounds in a wide variety of animal models of epilepsy. However, despite their efficacy in such models, adenosine receptor agonists do not appear to be good candidates for successful clinical applications. The therapeutic range of systemically administered adenosine receptor agonists is very narrow and they often produce profound adverse events. It seems, therefore, that adenosine receptor agonists could only be used clinically when co-administered with other antiepileptic drugs or when used in local therapies, where their side effect profile is much more tolerable. An alternative strategy would be to enhance the natural adenosinergic feedback mechanism triggered by seizures by using adenosine uptake inhibitors. This approach seems very attractive as it would allow limiting the action only in the active areas such as seizure foci and thus, preventing the systemic side effects.

Agonist-Dependent Coupling of the Promiscuous Adenosine A2B Receptor to Gα Protein Subunits.

The adenosine A2B receptor (A2BAR) belongs to the rhodopsin-like G protein-coupled receptor (GPCR) family. It is upregulated under hypoxic conditions, in inflammation and cancer. Previous studies indicated the coupling of the A2BAR to different G proteins, mainly Gs, but in some cases Gq/11 or Gi, depending on the cell type. We have now utilized novel technologies, (i) heterologous expression of individual members of the Gαq/11 protein family (Gαq, Gα11, Gα14, and Gα15) in Gαq/11 knockout cells, and (ii) the TRUPATH platform, allowing the direct observation of Gα protein activation for each of the Gα subunits by bioluminescence resonance energy transfer (BRET) measurements. Three structurally diverse A2BAR agonists were studied: the cognate agonist adenosine, its metabolically stable analog NECA, and the non-nucleosidic partial agonist BAY 60-6583. Adenosine and NECA activated most members of all four Gα protein families (Gαs, Gαq/11, Gαi, and Gα12/13). Significant differences in potencies and efficacies were observed; the highest efficacies were determined at the Gα15, Gαs, and Gα12 proteins, and for NECA additionally at the Gαi2 protein. In contrast, the partial agonist BAY 60-6583 only activated Gα15, Gαs, and Gα12 proteins. Adenosine deaminase, an allosteric modulator of ARs, selectively increased the potency and efficacy of NECA and BAY 60-6583 at the Gα15 protein, while it had no effect or decreased efficacy at the other Gα proteins. We conclude that the A2BAR is preferably coupled to the Gα15, Gαs, and Gα12 proteins. Upon upregulation of receptor or Gα protein expression, coupling to further Gα proteins likely occurs. Importantly, different agonists can display different activation profiles.

Characteristics of Zusanli Dorsal Root Ganglion Neurons in Rats and Their Receptor Mechanisms in Response to Adenosine

Neural systems play important roles in the functions of acupuncture. But the unclear structure and mechanism of acupoints hinder acupuncture standardization and cause the acupuncture effects to be varying or even paradoxical. It has been broadly assumed that the efficacy of acupuncture depends on the biological signals triggered at acupoints and passed up along neural systems. However, as the first station to transmit such signals, the characters of the dorsal root ganglia (DRG) neurons innervating acupoints are still not well elucidated. We adopted Zusanli (ST36) as a representative acupoint and found most DRG neurons innervating ST36 acupoint are middle-size neurons with a single spike firing pattern. This suggests that proprioceptive neurons take on greater possibility than small size nociceptive neurons do to mediate the acupuncture signals. Moreover, we found that adenosine injected into ST36 acupoints could dose- and acupoint-dependently mimic the analgesic effect of acupuncture. However, adenosine could not elicit action potentials in the acutely isolated ST36 DRG neurons, but it inhibited ID currents and increased the areas of overshoots. Further, we found that 4 types of adenosine receptors were all expressed by ST36 DRG neurons, and A1, A2b, and A3 receptors were the principal reactors to adenosine. PerspectiveThis study provides the major characteristics of ST36 DRG neurons, which will help to analyze the neural pathway of acupuncture signals. At the same time, these findings could provide a new possible therapy for pain relief, such as injecting adenosine or corresponding agonists into acupoints.

Prognosis of adenosine triphosphate infusion for anticonvulsants efficacy in patients with intensive cancer pain: a prospective observational study

INTRODUCTION: Pain is a common symptom in cancer patients even when analgesics were given. OBJECTIVE: To assess the prognostic value of intravenous infusion of non-selective purine receptors agonist adenosine triphosphate for effectiveness of anticonvulsant gabapentin in cancer patients with moderate and severe pain who received non-selective inhibitor of cyclooxygenase plus weak opioid tramadol. MATERIALS AND METHODS: Thirty-four cancer patients with intensive pain were scheduled for the study. The intravenous infusion of adenosine triphosphate 35–45 mg∙kg–1∙min–1 was performed within the period from 100 to 160 minutes. Then all patients were taken gabapentin (900 mg in three times daily). Pain was estimated 30 minutes before infusion, 30 minutes after infusion, and after taking 900 mg/day gabapentin for 4 days. Moreover, we studied prognostic significance of adenosine triphosphate infusion for the effectiveness of gabapentin administration. RESULTS: We revealed significant reduction of pain intensity after adenosine triphosphate infusion (Z = 4.0; р &lt; 0.0001 — Wilcoxon signed rank test). The same result was obtained after taking of gabapentin for 4 days (Z = 4.9; р &lt; 0.0001 — Wilcoxon signed rank test). Moreover, we found statistically moderate correlation link (t(N – 2) = 3.94; closeness correlation = 0.57; р &lt; 0.0004 — Spearman’s rank correlation coefficient) between pain intensity value after adenosine triphosphate infusion and taking of gabapentin. Regression analysis demonstrated satisfactory predictive ability of the resulting model (R2 = 0.55 (corrected R2 = 0.53); F = 38.74; р &lt; 0.0001). CONCLUSIONS: 1. Intravenous infusion of adenosine triphosphate may has significance for prognosis of taking anticonvulsant gabapentin effectiveness in cancer patients with moderate and severe pain who received non-selective cyclooxygenase inhibitor plus weak opioid tramadol. 2. Intravenous infusion of adenosine triphosphate or taking anticonvulsant gabapentin may significantly reduce pain intensity in cancer patients who had weak effect of administration of non-selective inhibitor of cyclooxygenase plus weak opioid tramadol.

Sorghum Protein Extract Protects RBC from Sodium Nitrite-Induced Oxidative Stress and Exhibits Anticoagulant and Antiplatelet Activity

Oxidative stress plays a critical role in the progression of diabetes, arthritis, cancer, eryptosis, cardiovascular disease, and thrombosis. Currently, antioxidants from natural sources are in high demand due to their beneficial role in the management of said diseases. The purpose of the study was to evaluate the protective effect of sorghum protein buffer extract (SBE) on sodium nitrite-induced oxidative stress and thrombosis. Protein characterization of SBE was done using SDS-PAGE. Oxidative stress in RBC was induced using sodium nitrite (NaNO2) and the key stress markers such as lipid peroxidation (LPO), protein carbonyl content (PCC), and the level of antioxidant enzymes (SOD and CAT) were measured. The anticoagulant effect of SBE was identified by employing in-vitro plasma recalcification time, activated partial thromboplastin time (APTT), prothrombin time (PT), and in-vivo mouse tail bleeding time. SBE antiplatelet activity was examined using agonist adenosine diphosphate (ADP) and epinephrine-induced platelet aggregation. Non-toxic property of SBE was identified using in-vitro direct haemolytic, haemorrhagic, and edema forming activities using experimental mice. SBE revealed similar protein banding pattern under both reduced and non-reduced conditions on SDS-PAGE. Interestingly, SBE normalized the level of LPO, PCC, SOD, and CAT in stress-inducedRBCs. Furthermore, SBE showed anticoagulant effect in platelet rich plasma by enhancing the clotting time from the control 250 s to 610 s and bleeding time from the control 200 s to more than 500 s (p<0.01) in a dose dependent manner. In addition, SBE prolonged the clot formation process of only APTT but not PT. SBE inhibited the agonists ADP and epinephrine induced platelet aggregation. SBE did not hydrolyze RBC cells, devoid of edema and haemorrhage properties. This study demonstrates for the first time the anticoagulant, antiplatelet, and antioxidant properties of SBE. Thus, the observed results validate consumption of sorghum as good for health and well-being.

Positive Allosteric Modulation of A2AR Alters Immune Cell Responses and Ameliorates Psoriasis-Like Dermatitis in Mice

Psoriasis is an immune cell‒mediated inflammatory disease of the skin with a mixed T helper type 1/T helper type17 cytokine environment combined with an innate immune response engaging toll-like receptors. Inflammatory diseases are characterized by dysregulated immune cell responses and elevated levels of adenosine at disease sites. Adenosine, acting through the A2AR, regulates inflammation, immune response, T-cell homeostasis, and tissue repair. We have identified a unique means to enhance A2AR function using a positive allosteric modulator. We show that oral administration of the A2AR-positive allosteric modulator AEA061 reduced ear swelling, skin thickness, erythema, scale formation, and inflammatory cytokine expression in A2Ar+/+ but not in A2Ar-/- mice with imiquimod-induced psoriasis-like dermatitis. Similar clinical and mRNA improvements were observed with topical administration. AEA061 also reduced clinical scores and cytokine expression in a mouse model of IL-23‒induced psoriasis-like dermatitis. In addition, AEA061 attenuated imiquimod-induced expression of IFN-α in plasmacytoid dendritic cells invivo and IL-23 and IL-36α in conventional dendritic cells. TCR-mediated IL-17 expression in γδT cells invivo and IL-17 production by CD4+ T cells enriched for γδT cells invitro were also inhibited. Thus, the enhancement of A2AR responsiveness to the endogenous agonist adenosine through positive allosteric modulation is sufficient to enhance intrinsic homeostatic mechanisms attenuating disease progression.