A1 antagonism in asthma: better than coffee?

Adenosine is a ubiquitous biological mediator with the capacity to produce both pro- and anti-inflammatory effects in tissues. Proinflammatory and bronchoconstrictive actions of adenosine in the asthmatic lung are well recognized, with the latter being mediated, in part, through A(1) receptor activation on airway smooth muscle. In this issue of the JCI, Sun et al. report findings in adenosine deaminase-deficient mice that suggest the occurrence of anti-inflammatory actions of adenosine in the lung, mediated through A(1) adenosine receptors on macrophages. Here we discuss the history of the study of adenosine receptor ligands for asthma and how enhanced understanding of adenosine receptor biology may aid in the rational exploitation of these receptors as therapeutic targets.