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Intramural elastase injection increases responsiveness of isolated bronchial segments
1Department of Physiology, University of Western Australia, Perth, Australia.
Pulmonary Pharmacology
|August 1, 1996
Summary
Inflammatory proteases may degrade the airway wall
Area of Science:
- Pulmonary Physiology
- Biochemistry
Background:
- The airway wall's smooth muscle is connected to cartilage via a fibro-elastic matrix.
- This matrix normally allows the inner airway to decouple from the outer wall during muscle contraction.
Purpose of the Study:
- To investigate if proteases from inflammatory cells can degrade the fibro-elastic matrix.
- To determine if matrix degradation increases airway responsiveness.
Main Methods:
- Porcine bronchial segments were perfused and their responsiveness to acetylcholine (ACh) was measured.
- Airway lumen narrowing was directly imaged using fiber-optic endoscopy.
- Elastase was injected into the airway wall to simulate protease activity.
Main Results:
- Elastase injection doubled the sensitivity to ACh in perfused bronchial segments.
- Maximal airway narrowing increased significantly after elastase treatment.
- Elastase did not affect smooth muscle contraction force.
Conclusions:
- Proteases may increase airway responsiveness by degrading the fibro-elastic matrix.
- This degradation could lead to increased airway wall uncoupling and altered mechanics.
- Findings suggest a mechanism for protease-induced airway hyperresponsiveness.