Adenosine A2A receptor agonist prevents cardiac remodeling and dysfunction in spontaneously hypertensive male rats after myocardial infarction

Antihypertensive Effect of New Agonist of Adenosine Receptor in Spontaneously Hypertensive Rats

BACKGROUND

Systemic arterial hypertension is a risk factor for cardiac, renal, and metabolic dysfunction. The search for new strategies to prevent and treat cardiovascular diseases led to the synthesis of new N-acylhydrazones to produce antihypertensive effect. Adenosine receptors are an alternative target to reduce blood pressure because of their vasodilatory action and antioxidant properties, which may reduce oxidative stress characteristic of systemic arterial hypertension.

OBJECTIVE

To evaluate the antihypertensive profile of novel selenium-containing compounds designed to improve their interaction with adenosine receptors.

METHODS

Vascular reactivity was evaluated by recording the isometric tension of pre-contracted thoracic aorta of male Wistar rats after exposure to increasing concentrations of each derivative (0.1 to 100 μM). To investigate the antihypertensive effect in spontaneously hypertensive rats, systolic, diastolic, and mean arterial pressure and heart rate were determined after intravenous administration of 10 and 30 μmol/kg of the selected compound LASSBio-2062.

RESULTS

Compounds named LASSBio-2062, LASSBio-2063, LASSBio-2075, LASSBio-2076, LASSBio-2084, LASSBio-430, LASSBio-2092, and LASSBio-2093 promoted vasodilation with mean effective concentrations of 15.5 ± 6.5; 14.6 ± 2.9; 18.7 ± 9.6; 6.7 ± 4.1; > 100; 6.0 ± 3.6; 37.8 ± 11.8; and 15.9 ± 5.7 μM, respectively. LASSBio-2062 (30 μmol/kg) reduced mean arterial pressure in spontaneously hypertensive rats from 124.6 ± 8.6 to 72.0 ± 12.3 mmHg (p < 0.05). Activation of adenosine receptor subtype A3 and potassium channels seem to be involved in the antihypertensive effect of LASSBio-2062.

CONCLUSIONS

The new agonist of adenosine receptor and activator of potassium channels is a potential therapeutic agent to treat systemic arterial hypertension.

Inhibition of visceral adipose tissue-derived pathogenic signals by activation of adenosine A2AR improves hepatic and cardiac dysfunction of NASH mice

A2AR-disrupted mice is characterized by severe systemic and visceral adipose tissue (VAT) inflammation. Increasing adenosine cyclase (AC), cAMP, and protein kinase A (PKA) formation through A2AR activation suppress systemic/VAT inflammation in obese mice. This study explores the effects of 4 wk A2AR agonist PSB0777 treatment on the VAT-driven pathogenic signals in hepatic and cardiac dysfunction of nonalcoholic steatohepatitis (NASH) obese mice. Among NASH mice with cardiac dysfunction, simultaneous decrease in the A2AR, AC, cAMP, and PKA levels were observed in VAT, liver, and heart. PSB0777 treatment significantly restores AC, cAMP, PKA, and hormone-sensitive lipase (HSL) levels, decreased SREBP-1/FASN, MCP-1, and CD68 levels, reduces infiltrated CD11b+ F4/80+ cells and adipogenesis in VAT of NASH + PSB0777 mice. The changes in VAT were accompanied by the suppression of hepatic and cardiac lipogenic/inflammatory/injury/apoptotic/fibrotic markers, the normalization of cardiac contractile [sarco/endoplasmic reticulum Ca2+ ATPase (SERCA2)] marker, and cardiac dysfunction. The in vitro approach revealed that conditioned media (CM) of VAT of NASH mice (CMnash) trigger palmitic acid (PA)-like lipotoxic (lipogenic/inflammatory/apoptotic/fibrotic) effects in AML-12 and H9c2 cell systems. Significantly, A2AR agonist pretreatment-related normalization of A2AR-AC-cAMP-PKA levels was associated with the attenuation of CMnash-related upregulation of lipotoxic markers and the normalization of lipolytic (AML-12 cells) or contractile (H9C2 cells) marker/contraction. The in vivo and in vitro experiments revealed that A2AR agonists are potential agent to inhibit the effects of VAT inflammation-driven pathogenic signals on the hepatic and cardiac lipogenesis, inflammation, injury, apoptosis, fibrosis, hypocontractility, and subsequently improve hepatic and cardiac dysfunction in NASH mice.NEW & NOTEWORTHY Protective role of adenosine A2AR receptor (A2AR) and AC-cAMP-PKA signaling against nonalcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH) possibly via its actions on adipocytes is well known in the past decade. Thus, this study evaluates pharmacological activities of A2AR agonist PSB0777, which has already demonstrated to treat NASH. In this study, the inhibition of visceral adipose tissue-derived pathogenic signals by activation of adenosine A2AR with A2AR agonist PSB0777 improves the hepatic and cardiac dysfunction of high-fat diet (HFD)-induced NASH mice.

N-Acylhydrazone Pharmacophore's Analgesic and Anti-inflammatory Profile: Recent Advancements during the Past Ten Years

Due to its important biological and pharmacological properties, in the field of medicinal chemistry and drug discovery, the N-acylhydrazone motif has shown to be extremely adaptable and promising. This scaffold has become a crucial component in the synthesis of numerous bioactive agents. N-Acylhydrazones are also interesting biological and synthetic tools due to their easy and straightforward synthesis. The current review provides a summary of the analgesic and anti-inflammatory activities of N-acylhydrazone derivatives over the past ten years. A brief discussion of structure-activity relationships is also provided which may guide researchers in medicinal chemistry to develop derivatives based on N-acylhydrazone scaffold as potent anti-inflammatory candidates.

Off-Target Effects of P2Y12 Receptor Inhibitors: Focus on Early Myocardial Fibrosis Modulation

Several studies have demonstrated that, beyond their antithrombotic effects, P2Y12 receptor inhibitors may provide additional off-target effects through different mechanisms. These effects range from the preservation of endothelial barrier function to the modulation of inflammation or stabilization of atherosclerotic plaques, with an impact on different cell types, including endothelial and immune cells. Many P2Y12 inhibitors have been developed, from ticlopidine, the first thienopyridine, to the more potent non-thienopyridine derivatives such as ticagrelor which may promote cardioprotective effects following myocardial infarction (MI) by inhibiting adenosine reuptake through sodium-independent equilibrative nucleoside transporter 1 (ENT1). Adenosine may affect different molecular pathways involved in cardiac fibrosis, such as the Wnt (wingless-type)/beta (β)-catenin signaling. An early pro-fibrotic response of the epicardium and activation of cardiac fibroblasts with the involvement of Wnt1 (wingless-type family member 1)/β-catenin, are critically required for preserving cardiac function after acute ischemic cardiac injury. This review discusses molecular signaling pathways involved in cardiac fibrosis post MI, focusing on the Wnt/β-catenin pathway, and the off-target effect of P2Y12 receptor inhibition. A potential role of ticagrelor was speculated in the early modulation of cardiac fibrosis, thanks to its off-target effect.

The effect of extracorporeal shock wave on joint capsule fibrosis based on A2AR-Nrf2/HO-1 pathway in a rat extending knee immobilization model

Joint capsule fibrosis, a common complication of joint immobilization, is mainly characterized by abnormal collagen deposition. The present study aimed to investigate the effect of extracorporeal shock wave therapy (ESWT) on reduced collagen deposition in the joint capsule during immobilization-induced joint capsule fibrosis. Additionally, the potential involvement of the adenosine A2A receptor (A2AR)-Neurotrophic factor e2-related factor 2 (Nrf2)/Haem oxygenase-1 (HO-1) pathway was explored. Thirty 3-month-old male Sprague-Dawley rats were randomly assigned to five groups: control (C), immobilization model (IM), natural recovery (NR), ESWT intervention (EI), and ESWT combined with A2AR antagonist SCH 58261 intervention (CI). After the left knee joints of rats in the IM, NR, EI and CI groups were immobilized using a full-extension fixation brace for 4 weeks, the EI and CI groups received ESWT twice a week for 4 weeks. The CI group was also treated with ESWT following intraperitoneal injection of SCH 58261 (0.01 mg/kg) for 4 weeks. The range of motion of the left knee joint was measured, and the protein levels of collagens I and III, A2AR, phosphorylated-protein kinase A/protein kinase A (p-PKA/PKA), p-Nrf2/Nrf2, and HO-1 were analysed by Western blotting. The IM and NR groups showed significantly greater arthrogenic contracture than the C group (P < 0.05). Compared to the NR group, the EI and CI groups exhibited significant improvement in arthrogenic contracture (P < 0.05). Conversely, the EI group showed lower contracture than the CI group (P < 0.05). Similar results were observed for collagen deposition and the protein levels of collagens I and III. The intervention groups (EI and CI groups) showed higher levels of p-Nrf2/Nrf2 and HO-1 than the NR group (P < 0.05). Moreover, the EI group exhibited higher levels of p-PKA/PKA, p-Nrf2/Nrf2, and HO-1 than the CI group (P < 0.05). However, no significant difference was found in the A2AR levels among the five groups (P > 0.05). ESWT may activate A2AR, leading to the phosphorylation of PKA. Subsequently, Nrf2 may be activated, resulting in the upregulation of HO-1, which then reduces collagen deposition and alleviates immobilization-induced joint capsule fibrosis.

Adenosine signaling as target in cardiovascular pharmacology

Increasing evidence demonstrated the relevance of adenosine system in the onset and development of cardiovascular diseases, such as hypertension, myocardial infarct, ischemia, hypertension, heart failure, and atherosclerosis. In this regard, intense research efforts are being focused on the characterization of the pathophysiological significance of adenosine, acting at its membrane receptors named A1, A2A, A2B, and A3 receptors, in cardiovascular diseases. The present review article provides an integrated and comprehensive overview about current clinical and pre-clinical evidence about the role of adenosine in the pathophysiology of cardiovascular diseases. Particular attention has been focused on current scientific evidence about the pharmacological ligands acting on adenosine pathway as useful tools to manage cardiovascular diseases.

Anticancer agents incorporating the N-acylhydrazone scaffold: Progress from 2017 to present

The N-acylhydrazone motif has been shown to be particularly adaptable and promising in the area of medicinal chemistry and drug development, due to its significant biological and pharmacological characteristics. Moreover, N-acylhydrazones are appealing synthetic and biological tools because of their simple and straightforward synthesis. This scaffold has emerged as a fundamental building block for the synthesis of bioactive compounds. Particularly, the N-acylhydrazone scaffold served as a base for the synthesis of a number of potent anticancer agents acting via different mechanisms. An updated summary of the anticancer activity of N-acylhydrazone derivatives described in the literature (from 2017 to 2022) is provided in the current review. It discusses the structure-activity relationship (SAR) of N-acylhydrazone derivatives exhibiting anticancer potential, which could be helpful in designing and developing new derivatives as effective antiproliferative candidates in the future.

The evolving view of thermogenic fat and its implications in cancer and metabolic diseases

The incidence of metabolism-related diseases like obesity and type 2 diabetes mellitus has reached pandemic levels worldwide and increased gradually. Most of them are listed on the table of high-risk factors for malignancy, and metabolic disorders systematically or locally contribute to cancer progression and poor prognosis of patients. Importantly, adipose tissue is fundamental to the occurrence and development of these metabolic disorders. White adipose tissue stores excessive energy, while thermogenic fat including brown and beige adipose tissue dissipates energy to generate heat. In addition to thermogenesis, beige and brown adipocytes also function as dynamic secretory cells and a metabolic sink of nutrients, like glucose, fatty acids, and amino acids. Accordingly, strategies that activate and expand thermogenic adipose tissue offer therapeutic promise to combat overweight, diabetes, and other metabolic disorders through increasing energy expenditure and enhancing glucose tolerance. With a better understanding of its origins and biological functions and the advances in imaging techniques detecting thermogenesis, the roles of thermogenic adipose tissue in tumors have been revealed gradually. On the one hand, enhanced browning of subcutaneous fatty tissue results in weight loss and cancer-associated cachexia. On the other hand, locally activated thermogenic adipocytes in the tumor microenvironment accelerate cancer progression by offering fuel sources and is likely to develop resistance to chemotherapy. Here, we enumerate current knowledge about the significant advances made in the origin and physiological functions of thermogenic fat. In addition, we discuss the multiple roles of thermogenic adipocytes in different tumors. Ultimately, we summarize imaging technologies for identifying thermogenic adipose tissue and pharmacologic agents via modulating thermogenesis in preclinical experiments and clinical trials.

Non-Invasive Assessment of Locally Overexpressed Human Adenosine 2A Receptors in the Heart of Transgenic Mice

A_2A adenosine receptors (A_2A-AR) have a cardio-protective function upon ischemia and reperfusion, but on the other hand, their stimulation could lead to arrhythmias. Our aim was to investigate the potential use of the PET radiotracer [¹⁸F]FLUDA to non-invasively determine the A_2A-AR availability for diagnosis of the A_2AR status. Therefore, we compared mice with cardiomyocyte-specific overexpression of the human A_2A-AR (A_2A-AR TG) with the respective wild type (WT). We determined: (1) the functional impact of the selective A_2AR ligand FLUDA on the contractile function of atrial mouse samples, (2) the binding parameters (B_{max and} K_D) of [¹⁸F]FLUDA on mouse and human atrial tissue samples by autoradiographic studies, and (3) investigated the in vivo uptake of the radiotracer by dynamic PET imaging in A_2A-AR TG and WT. After A_2A-AR stimulation by the A_2A-AR agonist CGS 21680 in isolated atrial preparations, antagonistic effects of FLUDA were found in A_2A-AR-TG animals but not in WT. Radiolabelled [¹⁸F]FLUDA exhibited a K_D of 5.9 ± 1.6 nM and a B_max of 455 ± 78 fmol/mg protein in cardiac samples of A_2A-AR TG, whereas in WT, as well as in human atrial preparations, only low specific binding was found. Dynamic PET studies revealed a significantly higher initial uptake of [¹⁸F]FLUDA into the myocardium of A_2A-AR TG compared to WT. The hA_2A-AR-specific binding of [¹⁸F]FLUDA in vivo was verified by pre-administration of the highly affine A_2AAR-specific antagonist istradefylline. Conclusion: [¹⁸F]FLUDA is a promising PET probe for the non-invasive assessment of the A_2A-AR as a marker for pathologies linked to an increased A_2A-AR density in the heart, as shown in patients with heart failure.

Shenfu Administration Improves Cardiac Fibrosis in Rats With Myocardial Ischemia-Reperfusion Through Adenosine A2a Receptor Activation

OBJECTIVE

Shenfu injection (SFI) is commonly used for cardiac dysfunction in China. Adenosine receptors have been reported to exert anti-fibrosis effects. The intent of this study was to evaluate that SFI attenuates cardiac fibrosis through activating of adenosine A_2a receptor (A_2aR) in rats with myocardial ischemia-reperfusion (MI/R).

METHODS

Sprague Dawley male rats were randomly divided into five groups, nine rats in each group. Injections in all rat groups were carried out prior to reperfusion, and in the sham and MI/R groups, only vehicle was injected. Injections in the remaining group were as follows: 5 mL/kg in the SFI group; 15 mg/kg nicorandil in the A₂R agonist group; and 5 mL/kg SFI plus 5 mg/kg MSX-3 in the SFI + A_2aR antagonist group. Changes in cyclic adenosine monophosphate (cAMP) and the development of myocardial infarction and cardiac fibrosis were documented among the groups. Additionally, the levels of A_2aR, collagen Ⅰ, collagen Ⅲ, fibronectin, and matrix metalloproteinase-9 (MMP-9) were measured.

RESULTS

Following injection with SFI or nicorandil, the cAMP concentration, infarct area, and cardiac fibrosis induced by MI/R injury were significantly decreased (p < 0.05). Additionally, the levels of collagen Ⅰ, collagen Ⅲ, fibronectin, and MMP-9 were clearly suppressed by SFI or nicorandil when compared with the MI/R group (p<0.01). However, the protective effects of SFI were counteracted by MSX-3. A negative correlation between A_2aR and collagen I and collagen III was found (p = 0.00).

CONCLUSION

SFI activated the A_2aR to reduce myocardial fibrosis caused by MI/R injury, which provided an underlying mechanism of action of SFI.

Effect of S-Se Bioisosteric Exchange on Affinity and Intrinsic Efficacy of Novel N-acylhydrazone Derivatives at the Adenosine A2A Receptor

In this work, we evaluated the conformational effect promoted by the isosteric exchange of sulfur by selenium in the heteroaromatic ring of new N-acylhydrazone (NAH) derivatives (3-8, 13, 14), analogues of the cardioactive compounds LASSBio-294 (1) and LASSBio-785 (2). NMR spectra analysis demonstrated a chemical shift variation of the iminic Csp2 of NAH S/Se-isosters, suggesting a stronger intramolecular chalcogen interaction for Se-derivatives. To investigate the pharmacological profile of these compounds at the adenosine A2A receptor (A2AR), we performed a previously validated functional binding assay. As expected for bioisosteres, the isosteric-S/Se replacement affected neither the affinity nor the intrinsic efficacy of our NAH derivatives (1-8). However, the N-methylated compounds (2, 6-8) presented a weak partial agonist profile at A2AR, contrary to the non-methylated counterparts (1, 3-5), which appeared as weak inverse agonists. Additionally, retroisosterism between aromatic rings of NAH on S/Se-isosters mimicked the effect of the N-methylation on intrinsic efficacy at A2AR, while meta-substitution in the phenyl ring of the acyl moiety did not. This study showed that the conformational effect of NAH-N-methylation and aromatic rings retroisosterism changed the intrinsic efficacy on A2AR, indicating the S/Se-chalcogen effect to drive the conformational behavior of this series of NAH.

The evolving view of thermogenic adipocytes - ontogeny, niche and function

The worldwide incidence of obesity and its sequelae, such as type 2 diabetes mellitus, have reached pandemic levels. Central to the development of these metabolic disorders is adipose tissue. White adipose tissue stores excess energy, whereas brown adipose tissue (BAT) and beige (also known as brite) adipose tissue dissipate energy to generate heat in a process known as thermogenesis. Strategies that activate and expand BAT and beige adipose tissue increase energy expenditure in animal models and offer therapeutic promise to treat obesity. A better understanding of the molecular mechanisms underlying the development of BAT and beige adipose tissue and the activation of thermogenic function is the key to creating practical therapeutic interventions for obesity and metabolic disorders. In this Review, we discuss the regulation of the tissue microenvironment (the adipose niche) and inter-organ communication between BAT and other tissues. We also cover the activation of BAT and beige adipose tissue in response to physiological cues (such as cold exposure, exercise and diet). We highlight advances in harnessing the therapeutic potential of BAT and beige adipose tissue by genetic, pharmacological and cell-based approaches in obesity and metabolic disorders.

Cardiorespiratory Effects of Three Infusion Doses of Adenosine in Conscious Goats: A Preliminary Study

Adenosine (AD) has been implicated in human healthcare as an endogenous signaling nucleotide in both physiologic and pathologic states. The effects of AD on cardiorespiratory parameters in ruminants has not yet been studied. The objective of this study was to evaluate the cardiac and respiratory changes that resulted from an intravenous AD infusion in goats. Six clinically healthy adult goats weighing 28 ± 2 kg were randomly assigned to one of four treatments in a crossover design with a seven day washout period. The goats received a 0.9 % saline solution (SAL treatment) and three AD treatments (AD 50, 100 and 200) intravenously at a dose rate of 50, 100 and 200 μg/kg/min. Cardiorespiratory and key cardiac parameters were measured before the treatment (baseline), during the infusion (dInf) and at 1, 3, 5 and 10 min after each infusion was discontinued. The AD 100 produced a significant increase in HR (p = 0.001) and the AD 200 resulted in significant rises in HR (p = 0.006) and RR (p = 0.001) compared with the baseline. This study concluded that the AD infusion could trigger an increase in HR and RR in a dose-dependent manner in healthy goats.

Novel curcumin analog (cis-trans curcumin) as ligand to adenosine receptors A2A and A2B: potential for therapeutics

All four of the adenosine receptor (AR) subtypes mediate pain and have been targeted by pharmacologists to generate new therapeutics for chronic pain. The vanilloid phytochemicals, which include curcumin, capsaicin, and gingerol, have been shown to alleviate pain. However, there is little to no literature on the interaction of vanilloid phytochemicals with ARs. In this study, photochemical methods were used to generate a novel isomer of curcumin (cis-trans curcumin or CTCUR), and the interactions of both curcumin and CTCUR with the two Gs-linked AR subtypes were studied. Competitive binding assays, docking analysis, and confocal fluorescence microscopy were performed to measure binding affinity; cell survival assays were used to measure toxicity; and cAMP assays were performed to measure receptor activation. Competitive binding results indicated that CTCUR binds to both AR A2A and AR A2B with Ki values of 5 μM and 7 μM, respectively, which is consistent with our docking results. Fluorescence microscopy data also shows binding for A2B and A2A. Cell survival results show that CTCUR and CUR are nontoxic at the tested concentrations in these cell lines. Overall, our results suggest that vanilloid phytochemicals may be slightly modified to increase interaction with Gs-ARs, and thereby can be further explored to provide a novel class of non-opioid antinociceptives.

Role of Adenosine and Purinergic Receptors in Myocardial Infarction: Focus on Different Signal Transduction Pathways

Myocardial infarction (MI) is a dramatic event often caused by atherosclerotic plaque erosion or rupture and subsequent thrombotic occlusion of a coronary vessel. The low supply of oxygen and nutrients in the infarcted area may result in cardiomyocytes necrosis, replacement of intact myocardium with non-contractile fibrous tissue and left ventricular (LV) function impairment if blood flow is not quickly restored. In this review, we summarized the possible correlation between adenosine system, purinergic system and Wnt/β-catenin pathway and their role in the pathogenesis of cardiac damage following MI. In this context, several pathways are involved and, in particular, the adenosine receptors system shows different interactions between its members and purinergic receptors: their modulation might be effective not only for a normal functional recovery but also for the treatment of heart diseases, thus avoiding fibrosis, reducing infarcted area and limiting scaring. Similarly, it has been shown that Wnt/β catenin pathway is activated following myocardial injury and its unbalanced activation might promote cardiac fibrosis and, consequently, LV systolic function impairment. In this regard, the therapeutic benefits of Wnt inhibitors use were highlighted, thus demonstrating that Wnt/β-catenin pathway might be considered as a therapeutic target to prevent adverse LV remodeling and heart failure following MI.

Role of Cardiac A2A Receptors Under Normal and Pathophysiological Conditions

This review presents an overview of cardiac A2A-adenosine receptors The localization of A2A-AR in the various cell types that encompass the heart and the role they play in force regulation in various mammalian species are depicted. The putative signal transduction systems of A2A-AR in cells in the living heart, as well as the known interactions of A2A-AR with membrane-bound receptors, will be addressed. The possible role that the receptors play in some relevant cardiac pathologies, such as persistent or transient ischemia, hypoxia, sepsis, hypertension, cardiac hypertrophy, and arrhythmias, will be reviewed. Moreover, the cardiac utility of A2A-AR as therapeutic targets for agonistic and antagonistic drugs will be discussed. Gaps in our knowledge about the cardiac function of A2A-AR and future research needs will be identified and formulated.

Synthesis and anticancer properties of novel hydrazone derivatives incorporating pyridine and isatin moieties

Nine novel hydrazone derivatives (4a-i) incorporating pyridine and isatin moieties were synthesized through one-pot, four-component heterocyclic condensation reactions. The structures of all new compounds (2a-e, 3a, 3c-e, and 4a-e) were identified by ¹ H nuclear magnetic resonance (NMR), ¹³ C NMR, and Fourier-transform infrared spectroscopic techniques and elemental analysis. Cell viability assays for the tested hydrazone derivatives were performed and the log IC₅₀ values of the compounds were calculated after a 24-h treatment. All hydrazide derivatives tested showed a promising antitumor activity against A-2780 cells as compared with the standard drug docetaxel with a log IC₅₀ value of 0.2200 μM (p < .05). Seven of the examined compounds (4b-e, 4g-i) showed high cytotoxic activity against A-2780 cells as compared with the standard drug docetaxel. Whereas the log IC₅₀ of docetaxel was 0.2200 μM for A-2780 cells at 24 h, the IC₅₀ values of these compounds were -0.4987, -0.4044, -0.8138, -0.3868, -0.6954, -0.4751, and 0.1809 μM, respectively. Three of the compounds, 4b, 4d, and 4i, showed high cytotoxic activity against MCF-7 cells as compared with docetaxel (p < .05). Whereas the log IC₅₀ of docetaxel was 0.2400 μM for MCF-7 cells at 24 h, the log IC₅₀ values of compounds 4b, 4d, and 4i were -0.1293, -0.1700, and 0.2459 μM, respectively.

Adenosine and Its Receptors: An Expected Tool for the Diagnosis and Treatment of Coronary Artery and Ischemic Heart Diseases

Adenosine is an endogenous nucleoside which strongly impacts the cardiovascular system. Adenosine is released mostly by endothelial cells and myocytes during ischemia or hypoxia and greatly regulates the cardiovascular system via four specific G-protein-coupled receptors named A₁R, A_2AR, A_2BR, and A₃R. Among them, A₂ subtypes are strongly expressed in coronary tissues, and their activation increases coronary blood flow via the production of cAMP in smooth muscle cells. A_2A receptor modulators are an opportunity for intense research by the pharmaceutical industry to develop new cardiovascular therapies. Most innovative therapies are mediated by the modulation of adenosine release and/or the activation of the A_2A receptor subtypes. This review aims to focus on the specific exploration of the adenosine plasma level and its relationship with the A_2A receptor, which seems a promising biomarker for a diagnostic and/or a therapeutic tool for the screening and management of coronary artery disease. Finally, a recent class of selective adenosine receptor ligands has emerged, and A_2A receptor agonists/antagonists are useful tools to improve the management of patients suffering from coronary artery disease.

Focusing on Adenosine Receptors as a Potential Targeted Therapy in Human Diseases

Adenosine is involved in a range of physiological and pathological effects through membrane-bound receptors linked to G proteins. There are four subtypes of adenosine receptors, described as A1AR, A2AAR, A2BAR, and A3AR, which are the center of cAMP signal pathway-based drug development. Several types of agonists, partial agonists or antagonists, and allosteric substances have been synthesized from these receptors as new therapeutic drug candidates. Research efforts surrounding A1AR and A2AAR are perhaps the most enticing because of their concentration and affinity; however, as a consequence of distressing conditions, both A2BAR and A3AR levels might accumulate. This review focuses on the biological features of each adenosine receptor as the basis of ligand production and describes clinical studies of adenosine receptor-associated pharmaceuticals in human diseases.

Adenosine A2A receptor activation prevents DOCA-salt induced hypertensive cardiac remodeling via iBAT

Hypertensive cardiac remodeling is a constellation of abnormalities that includes cardiomyocyte hypertrophy and death and tissue fibrosis. Adenosine is a long-known vasodilator, through interacting with its four cell surface receptor subtypes in cardiovascular system. However, it is unclear that whether adenosine A2A receptor (A2AR) activation is involved in the cardiac remodeling in hypertension. WT mice were utilized to induce DOCA-salt sensitive hypertension and received A2AR agonist CGS21680 or antagonist KW6002 treatment. Cardiac functional phenotyping measurement by echocardiography showed that CGS21680 improved cardiac dysfunction in DOCA-salt mice. Moreover, CGS21680 reduced cardiomyocyte hypertrophy, cardiac inflammation and fibrosis. However, iBAT depletion surgery induces dramatic cardiac remodeling in DOCA-salt mice, and the protective function of CGS21680 was blocked without intact iBAT. Mechanistically, A2AR agonist CGS21680 increased iBAT-derived fibroblast growth factor 21 (FGF21). Our data suggest that activation of A2AR could be a potential therapeutic strategy in preventing heart damage in hypertension.

Molecular hybrid design, synthesis, in vitro and in vivo anticancer evaluation, and mechanism of action of N-acylhydrazone linked, heterobivalent β-carbolines

A series of N-acylhydrazone-linked, heterobivalent β-carboline derivatives was designed and synthesized from l-tryptophan in a nine-step reaction sequence. The effort resulted in the heterobivalent β-carbolines 10a-t in good yields. The target compounds were characterized by ¹H NMR, ¹³C NMR and high-resolution mass spectrometry (HRMS). The in vitro cytotoxic activity of the synthesized compounds was evaluated against normal EA.HY926 cells and five cancer cell lines: LLC (Lewis lung carcinoma), BGC-823 (gastric carcinoma), CT-26 (murine colon carcinoma), Bel-7402 (liver carcinoma), and MCF-7 (breast carcinoma). Compound 10e, with an IC₅₀ value of 2.41 μM against EA.HY926 cells, was the most potent inhibitor. It showed cytotoxicity against all five cancer cell lines of different origin - murine and human, with IC₅₀ values ranging from 4.2 ± 0.7 to 18.5 ± 3.1 μM. A study of structure-activity relationships indicated that the influence on cytotoxic activities of the substituent in the R₉'-position followed the tendency, 2,3,4,5,6-perfluorophenylmethyl > 4-fluorobenzyl > 3-phenylpropyl group. The antitumor efficacies of the selected compounds were also evaluated in mice. Compound 10e exhibited potent antitumor activity, with tumor inhibition of more than 40% for Sarcoma 180 and 36.7% for Lewis lung cancer. Furthermore, the pharmacological mechanisms showed that compound 10e has a certain impairment in the motility of LLC cells, which suggests the anti-metastatic potential. And compound 10e inhibited angiogenesis in chicken chorioallantoic membrane assay, and the anti-angiogenetic potency was more potent than the reference drug combretastatin A4-phosphate (CA4P) at a concentration 50 μM.

Gastroprotective effects of N-acylarylhydrazone derivatives on ethanol-induced gastric lesions in mice are dependent on the NO/cGMP/KATP pathway

The gastroprotective effects of N-acylarylhydrazone derivatives on ethanol-induced gastric lesions in mice were investigated with respect to the NO/cGMP/K_ATP pathway. To investigate our hypothesis, the mice were intraperitoneally pretreated with glibenclamide, L-NAME, or ODQ 30 min before treatment with DMSO, LASSBio-294 (1, 2, and 4 mg/kg, p.o.), LASSBio-897 (0.5, 1, and 2 mg/kg, p.o.), or omeprazole. After 1 h, the mice received absolute ethanol (4 ml/kg) by gavage to induce gastric mucosal lesions, and the microscopic and macroscopic parameters were evaluated. GSH (non-protein sulfhydryl groups) and MDA (malondialdehyde) concentrations, hemoglobin levels, nitric oxide production, myeloperoxidase (MPO) activity, and TNF-α and IL-1β levels were also analyzed in the stomach after absolute ethanol administration. Pretreatment with LASSBio-294 or LASSBio-897 significantly reduced the microscopic and macroscopic lesion area. The compounds restored the GSH, MDA, and hemoglobin levels and reduced MPO activity. Moreover, the compounds significantly reduced nitrate and nitrite concentrations in the stomach samples after ethanol administration. Molecular docking studies revealed that LASSBio-294 and LASSBio-897 interact with active sites of the eNOS (endothelial nitric oxide synthase) enzymes through hydrogen bonds. LASSBio-294 and LASSBio-897 also reduced TNF-α and IL-1β levels. It was observed that a NO synthase inhibitor, an ATP-sensitive potassium channel blocker, and a guanylate cyclase inhibitor significantly reversed the gastroprotective effects of these compounds. Thus, the gastroprotective effect of LASSBio-294 and LASSBio-897 against gastric lesions is mediated through the NO/cGMP cascade, followed by blocking of the K_ATP channels.

Pharmacology of Adenosine Receptors: The State of the Art

Adenosine is a ubiquitous endogenous autacoid whose effects are triggered through the enrollment of four G protein-coupled receptors: A₁, A_2A, A_2B, and A₃. Due to the rapid generation of adenosine from cellular metabolism, and the widespread distribution of its receptor subtypes in almost all organs and tissues, this nucleoside induces a multitude of physiopathological effects, regulating central nervous, cardiovascular, peripheral, and immune systems. It is becoming clear that the expression patterns of adenosine receptors vary among cell types, lending weight to the idea that they may be both markers of pathologies and useful targets for novel drugs. This review offers an overview of current knowledge on adenosine receptors, including their characteristic structural features, molecular interactions and cellular functions, as well as their essential roles in pain, cancer, and neurodegenerative, inflammatory, and autoimmune diseases. Finally, we highlight the latest findings on molecules capable of targeting adenosine receptors and report which stage of drug development they have reached.

A2A Receptor Activation Attenuates Hypertensive Cardiac Remodeling via Promoting Brown Adipose Tissue-Derived FGF21

Adipocytes play important roles in regulating cardiovascular health and disease. However, the molecular mechanism underlying the endocrine role of brown adipose tissue (BAT) in pathological cardiac remodeling remains unknown. Herein we show that adenosine A_2A receptor (A_2AR) knockout (A_2ARKO) causes interscapular BAT (iBAT) dysfunction, leading to accelerated cardiac remodeling in hypertension compared with wild-type (WT) mice. Surgical iBAT depletion induces dramatic cardiac remodeling in WT but not in A_2ARKO hypertensive mice. AMPK/PGC1α signaling-induced fibroblast growth factor 21 (FGF21) in brown adipocytes is required for A_2AR-mediated inhibition of hypertensive cardiac remodeling. Recombinant FGF21 administration improves cardiac remodeling in iBAT-depleted hypertensive mice. More importantly, brown adipocyte-specific A_2ARKO inhibits FGF21 production and accelerates cardiac damage in hypertension. Consistently, brown adipocyte-specific FGF21 knockout abolishes the effects of A_2AR agonism in attenuating hypertensive cardiac remodeling. Our findings reveal a distinctive endocrine role of BAT in hypertensive cardiac remodeling via activating A_2AR/FGF21 pathway.

Adenosine Receptors As Drug Targets for Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a clinical condition characterized by pulmonary arterial remodeling and vasoconstriction, which promote chronic vessel obstruction and elevation of pulmonary vascular resistance. Long-term right ventricular (RV) overload leads to RV dysfunction and failure, which are the main determinants of life expectancy in PAH subjects. Therapeutic options for PAH remain limited, despite the introduction of prostacyclin analogs, endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and soluble guanylyl cyclase stimulators within the last 15 years. Through addressing the pulmonary endothelial and smooth muscle cell dysfunctions associated with PAH, these interventions delay disease progression but do not offer a cure. Emerging approaches to improve treatment efficacy have focused on beneficial actions to both the pulmonary vasculature and myocardium, and several new targets have been investigated and validated in experimental PAH models. Herein, we review the effects of adenosine and adenosine receptors (A₁, A_2A, A_2B, and A₃) on the cardiovascular system, focusing on the A_2A receptor as a pharmacological target. This receptor induces pulmonary vascular and heart protection in experimental models, specifically models of PAH. Targeting the A_2A receptor could potentially serve as a novel and efficient approach for treating PAH and concomitant RV failure. A_2A receptor activation induces pulmonary endothelial nitric oxide synthesis, smooth muscle cell hyperpolarization, and vasodilation, with important antiproliferative activities through the inhibition of collagen deposition and vessel wall remodeling in the pulmonary arterioles. The pleiotropic potential of A_2A receptor activation is highlighted by its additional expression in the heart tissue, where it participates in the regulation of intracellular calcium handling and maintenance of heart chamber structure and function. In this way, the activation of A_2A receptor could prevent the production of a hypertrophic and dysfunctional phenotype in animal models of cardiovascular diseases.