A₃ Adenosine Receptors: Protective vs. Damaging Effects Identified Using Novel Agonists and Antagonists

Area of Science:

• Pharmacology
• Neuroscience
• Molecular Biology

Background:

• The A3 adenosine receptor (A3AR) plays a crucial role in various physiological processes.
• Selective agonists and antagonists are essential tools for investigating A3AR function.

Purpose of the Study:

• To explore the physiologic role of the A3 adenosine receptor.
• To characterize novel selective agonists and antagonists for A3AR research.

Main Methods:

• Development and utilization of selective A3AR agonists (e.g., IB-MECA, Cl-IB-MECA).
• Design and identification of selective A3AR antagonists using molecular modeling, including nonpurine heterocycles.
• Pharmacological characterization of novel compounds like MRS 1191, MRS 1220, and MRS 1523 for A3AR selectivity and affinity.

Main Results:

• Selective A3AR agonists IB-MECA and Cl-IB-MECA are available.
• Novel selective A3AR antagonists were identified across various heterocyclic classes.
• Specific compounds demonstrated high selectivity for A3AR over other adenosine receptor subtypes in human and rat tissues.
• A3AR agonists exhibit paradoxical dose-dependent effects: low nanomolar concentrations protect against apoptosis and ischemic damage, while acute high concentrations (>10 mM) induce cell death.

Conclusions:

• Selective A3AR modulators are valuable tools for studying receptor physiology.
• The dual role of A3AR agonists suggests potential therapeutic applications in inflammatory and ischemic conditions.
• A3AR agonists and/or antagonists may offer novel treatment strategies for inflammatory diseases.