Adenosine as a pro-inflammatory mediator in asthma.

Area of Science:

• Pulmonary Medicine
• Pharmacology

Background:

• Adenosine is a molecule produced by cells during energy or oxygen deficit.
• It can act as an autocoid, influencing local cellular functions.
• Adenosine's role in airway function, particularly in asthma, requires further elucidation.

Purpose of the Study:

• To investigate the effects of inhaled adenosine on airway function in asthmatic and normal subjects.
• To explore the potential mechanisms and modulators of adenosine-induced bronchoconstriction.
• To examine the development of tachyphylaxis with repeated adenosine exposure.

Main Methods:

• Inhalation challenges with adenosine in asthmatic and normal subjects.
• Assessment of bronchoconstriction.
• Evaluation of the effects of theophylline, sodium cromoglycate, nedocromil sodium, histamine, H1-antagonists, and cyclo-oxygenase inhibitors.
• Repeated exposure studies to assess tachyphylaxis.

Main Results:

• Inhalation of adenosine induced significant bronchoconstriction in asthmatic subjects, but not in normal subjects.
• The bronchoconstriction in asthmatics was reduced by theophylline, sodium cromoglycate, nedocromil sodium, histamine, H1-antagonists, and cyclo-oxygenase inhibitors.
• Repeated adenosine exposure led to tachyphylaxis and cross-tachyphylaxis with exercise-induced bronchoconstriction, but not allergen-induced bronchoconstriction.

Conclusions:

• Adenosine acts as a potent bronchoconstrictor in individuals with asthma.
• Theophylline and other agents can attenuate adenosine-induced bronchoconstriction, indicating purinergic receptor involvement.
• Adenosine-induced bronchoconstriction may involve indirect mechanisms, potentially up-regulating endogenous bronchoconstrictor factors in asthma.