Adenosine-receptor subtypes: their relevance to adenosine-mediated responses in asthma and chronic obstructive pulmonary disease.

Adenosine administration by inhalation elicits concentration-related bronchoconstriction in subjects with asthma and chronic obstructive pulmonary disease (COPD). The mechanisms of adenosine-induced bronchoconstriction appear to involve a selective interaction with activated mast cells with subsequent release of preformed and newly-formed mediators. Further evidence linking adenosine signalling to asthma and COPD comes from the finding that many cell types that play important roles in the exacerbation of these conditions express adenosine receptors and demonstrate relevant effects through stimulation of these receptors. Therefore, blockade of these receptors may be a valuable approach to the treatment of asthma and chronic obstructive pulmonary disease. Promising adenosine-receptor targets for novel therapeutics of asthma and chronic obstructive pulmonary disease have recently been identified in a number of inflammatory cell types, including mast cells, eosinophils, lymphocytes, neutrophils, and macrophages. The recent characterisation of the A2B receptors indicates the human lung mast cell as one of the most strategic cellular targets.