Bronchial vascular congestion and angiogenesis

Abstract

The bronchial vasculature is the systemic arterial blood supply to the lung. Although small relative to the pulmonary blood flow, the bronchial vasculature serves important functions and is modified in a variety of pulmonary and airway diseases.Congestion of the bronchial vasculature may narrow the airway lumen in inflammatory airway diseases, and formation of new bronchial vessels (angiogenesis) is implicated in the pathology of a variety of chronic inflammatory, infectious and ischaemic pulmonary diseases. The remarkable ability of the bronchial vasculature to remodel has implications for disease pathogenesis.The contributions of the bronchial vasculature to the pathogenesis of pulmonary disease are reviewed in this article. Eur Respir J 1997; 10: 1173-1180. The bronchial circulation is ideally situated to play an important role in lung defence and in the pathogenesis of a number of airway diseases. The bronchial microvasculature provides nutrient blood flow to the airway epithelium and is important for proper functioning of the mucociliary escalator. Bronchial blood flow is responsive to changes in neural and humoral stimuli and plays a role in conditioning of inspired air. The focus of this review is the potential involvement of the bronchial vasculature in contributing to the pathogenesis of a variety of airway diseases. In particular, we have focused on the possibility of airway narrowing as a consequence of bronchial vascular congestion, and the remarkable proliferative capacity of the bronchial vessels in response to a variety of pulmonary diseases. Bronchial vascular congestionHyperaemia of the bronchial vasculature is often included in descriptions of the pathology of asthma. An example of hyperaemia of the bronchial vasculature is shown in figure 1. This photomicrograph shows a crosssection of a human airway from a patient who died of asthma. The apparent increase in the size and number of vessels inside and outside the smooth muscle layer is clearly visible, suggesting that vascular dilation and proliferation (angiogenesis) could be important components of the airway wall remodelling in asthmatic patients. The airway vasculature is of considerable interest in asthma because it can contribute to the excessive airway narrowing, which is characteristic of this disease. A diagram of an airway ( fig. 2) illustrates the two bronchial vascular plexuses: the peribronchial plexus, located in the adventitial space between the muscle and the surrounding lung parenchyma; and the submucosal vascular plexus, located beneath the epithelial layer. Dilation, exudation or transudation from these vessels could contribute to the excessive airway narrowing observed in asthma. Relaxation of the bronchial vascular smooth muscle and/or an increase in the intravascular pressure will lead to congestion of these vessels. This bronchial vascular congestion could result in a reduction in the area of the airway lumen and/or an increase in the outer diameter of the airway. The latter effect could uncouple the airway smoo...

Pulmonary vascular changes in asthma and COPD

“…In the airways, the bronchial circulation is arranged as two plexus, a submucosal plexus running through the subepithelial layer between the ASM bundles and epithelium, and a peribronchial vascular plexus which supplies the adventitia behind the ASM layer [21]. It is thought that the ASM could play an important regulatory role in the vascular remodelling within the bronchial circulatory system [22][23][24][25] via the release of different cytokines, growth factors, and the expression of adhesion molecules and deposition of extracellular matrix (ECM) components [26][27][28][29] to influence endothelial cell behaviour. The adventitia is mostly composed of alveolar sacs, which have a small layer of endothelial cells and interstitial fibroblasts.…”

“…Ang-2 allows the migration of the immature vessel as a sprouting tip, through the localised tissue [22,23], while Ang-1 allows for the freshly formed vessel behind the sprouting tip to be stabilised with ECM deposition, formation of a new vascular BM and mural cell recruitment [24]. In fact, pericytes have the ability to sprout and form new tubes on their own, for endothelial cells to then penetrate and complete the angiogenic process [25].…”

Bronchial angiogenesis in severe glucocorticoid-dependent asthma

“…The pathophysiological implications of these changes as components of airway remodelling of living patients with chronic severe asthma are not fully understood. Plasma exudation and vascular congestion are induced by various mediators, such as histamine and sulfidopeptide leukotrienes, known to be released in asthma, and may contribute to the acute airway obstruction observed in asthmatic subjects following allergen exposition [1,4].…”

Vasoconstriction after inhalation of budesonide: A study in the isolated and perfused rat lung

“…ICS are known to exert their effect on airway vasculature through a delayed genomic [3] and a non-genomic phenomena, in common with topical steroids, thereby causing significant vasoconstriction in the larger airways and modifying, at least in part, some of the pathophysiological components of airway narrowing in bronchial asthma [4]. These clinically observed effects include suppression of proinflammatory responses such as hyperperfusion, microvasculature hyperpermeability, oedema formation, inflammatory cell recruitment and the formation of new blood vessels [5,6 ]. Inhaled fluticasone propionate (FP) has been shown to reduce blood flow in airway mucosa of asthmatics and healthy volunteers [1].…”