The adenosine a2b receptor: its role in inflammation

Area of Science:

• Pharmacology
• Immunology
• Molecular Biology

Background:

• Adenosine A2b receptor research was limited by a lack of selective agonists/antagonists.
• Recent development of xanthine and pyrrolpyrimidine antagonists has enabled receptor localization and functional studies.
• Genetically modified animals (loss/over-expression) suggest an anti-inflammatory role for A2b receptors.

Purpose of the Study:

• To review the influence of the adenosine A2b receptor on inflammation across different tissues.
• To highlight the cell-type-dependent nature of A2b receptor's inflammatory actions.

Main Methods:

• Literature review of studies investigating adenosine A2b receptor function.
• Analysis of data from new antagonist compounds and genetically modified animal models.
• Examination of A2b receptor's role in specific tissues like the anterior pituitary, bronchial smooth muscle, and intestinal epithelium.

Main Results:

• A2b receptors in the anterior pituitary stimulate IL-6 and VEGF secretion and influence gap-junctional communication.
• The receptor mediates pro-inflammatory cytokine release from various cells, including mast cells and epithelial cells.
• A HIF-1alpha binding site in the A2b receptor gene promoter links it to hypoxia and angiogenesis.

Conclusions:

• The adenosine A2b receptor plays a significant role in inflammation, but its effect can be pro- or anti-inflammatory depending on the cell type.
• Targeting A2b receptors shows potential for treating autoimmune diseases like type I diabetes.
• Several A2b receptor antagonists are in preclinical or early clinical development (Phase I) for therapeutic applications, including asthma treatment (e.g., CVT-6883).