Heparin inhibits hyperventilation-induced late-phase hyperreactivity in dogs.

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Pharmacology

Background:

• Hyperventilation can trigger bronchoconstriction, leading to airway inflammation and hyperreactivity.
• The late-phase response involves increased peripheral airway resistance, mediator production, and cellular infiltration.
• Airway hyperreactivity (AHR) is a key characteristic of asthma and other obstructive lung diseases.

Purpose of the Study:

• To investigate the inhibitory effects of inhaled heparin on the late-phase airway response to hyperventilation.
• To determine if heparin can mitigate airway obstruction, inflammation, and hyperreactivity post-dry air challenge (DAC).

Main Methods:

• Utilized fiberoptic bronchoscopy to measure peripheral airway resistance (RP) and airway reactivity (DeltaRP) to histamine.
• Administered aerosolized heparin or vehicle before DAC in a human and canine model.
• Analyzed bronchoalveolar lavage fluid (BALF) for cellular content and eicosanoid mediators (leukotrienes, prostaglandins).

Main Results:

• Dry air challenge induced significant late-phase airway obstruction, inflammation, and AHR in vehicle-treated subjects.
• Inhaled heparin pretreatment attenuated airway obstruction by approximately 50%.
• Heparin inhibited eosinophil infiltration, reduced leukotriene and prostaglandin levels in BALF, and abolished AHR.

Conclusions:

• Inhaled heparin effectively inhibits the late-phase airway response to hyperventilation.
• Heparin's mechanism involves reducing eosinophil migration and the release of eicosanoid mediators.
• These findings suggest a potential therapeutic role for inhaled heparin in managing hyperventilation-induced airway dysfunction.