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Mechanisms of increased airway microvascular permeability: role in airway inflammation and obstruction
1Department of Pharmacology, University of Western Australia, Nedlands.
Abstract:
1. Airway inflammation is a signal feature of human asthma, as is bronchial obstruction and the resultant airflow limitation. An obligatory accompaniment to airway inflammation is increased airway microvascular permeability, which in turn is causally related to bronchial oedema. In this review, we have attempted to describe the mechanisms of increased airway microvascular permeability and its relationship to oedema, bronchial obstruction and the hyperreactivity to spasmogenic stimuli which are such common features of asthma. 2. It is now clear that bronchial obstruction in chronic asthma can involve bronchial wall oedema and swelling in addition to reversible, elevated airway smooth muscle tone, mucus hypersecretion and airway plugging and potentially permanent structural changes in airway architecture. Inflammatory mediators released in the airway wall in asthma including histamine, platelet-activating factor, leukotrienes and bradykinin are potent inducers of increased bronchial microvascular permeability and are thus promoters of bronchial oedema, airway wall swelling and reduction in luminal calibre. 3. The primary mechanism believed to underlie acute increases in microvascular permeability is contraction of post-capillary venular endothelial cells, resulting in the formation of gaps between otherwise tightly associated cells. Extravasated plasma distributes to the interstitial spaces in the airway wall, resulting in oedema and swelling, but may also traverse the epithelium and collect in the airway lumen. 4. Luminal plasma may compromise epithelial integrity and cilial function and thus reduce mucus clearance. Plasma proteins may also promote the production of viscous mucus and the formation of luminal mucus plugs. Together, these effects can result in or contribute to airway obstruction and hyper-responsiveness. 5. An understanding of such mechanisms can provide insight concerning novel and effective anti-asthma therapies.
Insights
Airway inflammation in asthma increases microvascular permeability, causing bronchial edema and obstruction. Understanding these mechanisms offers insights into novel asthma therapies.
Area of Science:
- Pulmonary Medicine
- Immunology
- Pathophysiology
Background:
- Airway inflammation, bronchial obstruction, and airflow limitation are key features of asthma.
- Increased airway microvascular permeability is linked to bronchial edema and asthma symptoms.
- Inflammatory mediators in asthma exacerbate microvascular permeability, edema, and airway narrowing.
Purpose of the Study:
- To review the mechanisms of increased airway microvascular permeability in asthma.
- To explore the relationship between microvascular permeability, edema, obstruction, and hyperreactivity.
- To provide insights for developing new anti-asthma therapies.
Main Methods:
- Review of existing literature on asthma pathophysiology.
- Analysis of mechanisms driving airway microvascular permeability.
- Examination of the role of inflammatory mediators and endothelial cell contraction.
Main Results:
- Post-capillary venular endothelial cell contraction leads to gaps, increasing permeability.
- Extravasated plasma causes airway wall edema, swelling, and luminal narrowing.
- Luminal plasma impairs epithelial integrity, reduces mucus clearance, and promotes mucus plugs.
Conclusions:
- Increased airway microvascular permeability is a critical factor in asthma pathophysiology.
- Understanding these mechanisms is crucial for developing effective asthma treatments.
- Targeting microvascular permeability may offer novel therapeutic strategies for asthma.