A2B receptor antagonist 1

G Protein-Coupled Receptors in Asthma Therapy: Pharmacology and Drug Action

Asthma is a heterogeneous inflammatory disease of the airways that is associated with airway hyperresponsiveness and airflow limitation. Although asthma was once simply categorized as atopic or nonatopic, emerging analyses over the last few decades have revealed a variety of asthma endotypes that are attributed to numerous pathophysiological mechanisms. The classification of asthma by endotype is primarily routed in different profiles of airway inflammation that contribute to bronchoconstriction. Many asthma therapeutics target G protein-coupled receptors (GPCRs), which either enhance bronchodilation or prevent bronchoconstriction. Short-acting and long-acting β 2-agonists are widely used bronchodilators that signal through the activation of the β 2-adrenergic receptor. Short-acting and long-acting antagonists of muscarinic acetylcholine receptors are used to reduce bronchoconstriction by blocking the action of acetylcholine. Leukotriene antagonists that block the signaling of cysteinyl leukotriene receptor 1 are used as an add-on therapy to reduce bronchoconstriction and inflammation induced by cysteinyl leukotrienes. A number of GPCR-targeting asthma drug candidates are also in different stages of development. Among them, antagonists of prostaglandin D2 receptor 2 have advanced into phase III clinical trials. Others, including antagonists of the adenosine A2B receptor and the histamine H4 receptor, are in early stages of clinical investigation. In the past decade, significant research advancements in pharmacology, cell biology, structural biology, and molecular physiology have greatly deepened our understanding of the therapeutic roles of GPCRs in asthma and drug action on these GPCRs. This review summarizes our current understanding of GPCR signaling and pharmacology in the context of asthma treatment. SIGNIFICANCE STATEMENT: Although current treatment methods for asthma are effective for a majority of asthma patients, there are still a large number of patients with poorly controlled asthma who may experience asthma exacerbations. This review summarizes current asthma treatment methods and our understanding of signaling and pharmacology of G protein-coupled receptors (GPCRs) in asthma therapy, and discusses controversies regarding the use of GPCR drugs and new opportunities in developing GPCR-targeting therapeutics for the treatment of asthma.

Preliminary Evidence of the Potent and Selective Adenosine A2B Receptor Antagonist PSB-603 in Reducing Obesity and Some of Its Associated Metabolic Disorders in Mice

The adenosine A_2A and A_2B receptors are promising therapeutic targets in the treatment of obesity and diabetes since the agonists and antagonists of these receptors have the potential to positively affect metabolic disorders. The present study investigated the link between body weight reduction, glucose homeostasis, and anti-inflammatory activity induced by a highly potent and specific adenosine A_2B receptor antagonist, compound PSB-603. Mice were fed a high-fat diet for 14 weeks, and after 12 weeks, they were treated for 14 days intraperitoneally with the test compound. The A₁/A_2A/A_2B receptor antagonist theophylline was used as a reference. Following two weeks of treatment, different biochemical parameters were determined, including total cholesterol, triglycerides, glucose, TNF-α, and IL-6 blood levels, as well as glucose and insulin tolerance. To avoid false positive results, mouse locomotor and spontaneous activities were assessed. Both theophylline and PSB-603 significantly reduced body weight in obese mice. Both compounds had no effects on glucose levels in the obese state; however, PSB-603, contrary to theophylline, significantly reduced triglycerides and total cholesterol blood levels. Thus, our observations showed that selective A_2B adenosine receptor blockade has a more favourable effect on the lipid profile than nonselective inhibition.

1,8-disubstituted xanthine derivatives: synthesis of potent A2B-selective adenosine receptor antagonists

3-Unsubstituted xanthine derivatives bearing a cyclopentyl or a phenyl residue in the 8-position were synthesized and developed as A2B adenosine receptor antagonists. Compounds bearing polar substituents were prepared to obtain water-soluble derivatives. 1-Alkyl-8-phenylxanthine derivatives were found to exhibit high affinity for A2B adenosine receptors (ARs). 1,8-disubstituted xanthine derivatives were equipotent to or more potent than 1,3,8-trisubstituted xanthines at A2B ARs, but generally less potent at A1 and A2A, and much less potent at A3 ARs. Thus, the new compounds exhibited increased A2B selectivity versus all other AR subtypes. 9-Deazaxanthines (pyrrolo[2,3-d]pyrimidindiones) appeared to be less potent at A2B ARs than the corresponding xanthine derivatives. 1-Propyl-8-p-sulfophenylxanthine (17) was the most selective compound of the present series, exhibiting a K(i) value of 53 nM at human A2B ARs and showing greater than 180-fold selectivity versus human A1 ARs. Compound 17 was also highly selective versus rat A1 ARs (41-fold) and versus the other human AR subtypes (A2A > 400-fold and A3 > 180-fold). The compound is highly water-soluble due to its sulfonate function. 1-Butyl-8-p-carboxyphenylxanthine (10), another polar analogue bearing a carboxylate function, exhibited a K(i) value of 24 nM for A2B ARs, 49-fold selectivity versus human and 20-fold selectivity versus rat A1 ARs, and greater than 150-fold selectivity versus human A2A and A3 ARs. 8-[4-(2-Hydroxyethylamino)-2-oxoethoxy)phenyl]-1-propylxanthine (29) and 1-butyl-8-[4-(4-benzyl)piperazino-2-oxoethoxy)phenyl]xanthine (35) were among the most potent A2B antagonists showing K(i) values at A2B ARs of 1 nM, 57-fold (29) and 94-fold (35) selectivity versus human A1, ca. 30-fold selectivity versus rat A1, and greater than 400-fold selectivity versus human A2A and A3 ARs. The new potent, selective, water-soluble A2B antagonists may be useful research tools for investigating A2B receptor function.

Design, synthesis, and molecular docking studies of new [1,2,4]triazolo[4,3-a]quinoxaline derivatives as potential A2B receptor antagonists

Many shreds of evidence have recently correlated A2B receptor antagonism with anticancer activity. Hence, the search for an efficient A2B antagonist may help in the development of a new chemotherapeutic agent. In this article, 23 new derivatives of [1,2,4]triazolo[4,3-a]quinoxaline were designed and synthesized and its structures were confirmed by different spectral data and elemental analyses. The results of cytotoxic evaluation of these compounds showed six promising active derivatives with IC₅₀ values ranging from 1.9 to 6.4 μM on MDA-MB 231 cell line. Additionally, molecular docking for all synthesized compounds was performed to predict their binding affinity toward the homology model of A2B receptor as a proposed mode of their cytotoxic activity. Results of molecular docking were strongly correlated with those of the cytotoxic study. Finally, structure activity relationship analyses of the new compounds were explored.

Involvement of adenosine A2B receptor in radiation-induced translocation of epidermal growth factor receptor and DNA damage response leading to radioresistance in human lung cancer cells

Background: Adenosine receptors are involved in tumor growth, progression, and response to therapy. Among them, A2B receptor is highly expressed in various tumors. Furthermore, ionizing radiation induces translocation of epidermal growth factor receptor (EGFR), which promotes DNA repair and contributes to radioresistance. We hypothesized that A2B receptor might be involved in the translocation of EGFR.
Methods: We investigated whether A2B receptor is involved in EGFR translocation and DNA damage response (γH2AX/53BP1 focus formation) of lung cancer cells by means of immunofluorescence studies. Radiosensitivity was evaluated by colony formation assay after γ-irradiation.
Results: A2B receptor was expressed at higher levels in cancer cells than in normal cells. A2B receptor antagonist treatment or A2B receptor knockdown suppressed EGFR translocation, γH2AX/53BP1 focus formation, and colony formation of lung cancer cell lines A549, calu-6 and NCI-H446, compared with a normal cell line (beas-2b). γ-Irradiation-induced phosphorylation of src and EGFR was also attenuated by suppression of A2B receptor expression.
Conclusion: Activation of A2B receptor mediates γ-radiation-induced translocation of EGFR and phosphorylation of src and EGFR, thereby promoting recovery of irradiated lung cancer cells from DNA damage.
General significance: Our results indicate that A2B receptors contribute to radiation resistance in a cancer-cell-specific manner, and may be a promising target for radiosensitizers in cancer radiotherapy.