Molecules and mediators of inflammation in equine heaves: mechanisms and markers of disease.

This study explores the mechanisms underlying pulmonary inflammation in equines suffering from heaves, or chronic obstructive pulmonary disease, focusing on molecular signals directing the migration of neutrophils to the airways. It further investigates matrix metalloproteinases, particularly MMP-9, for its potential role in the disease and possible application as a diagnostic marker.

Understanding the Inflammatory Mechanisms in Equine Heaves

• The research throws light on the mechanics of pulmonary inflammation happening, particularly in equines suffering from chronic obstructive pulmonary disease, also known as heaves.
• Study of the cellular and molecular reasons leading to this inflammation forms the core of this research. The inflammation is particularly characterized by the recruitment of substantial numbers of neutrophils to the lower airways.
• The article primarily focuses on the molecular signals that might direct the migration of these neutrophils from the circulation to the air spaces, exploring chemokines like interleukin-8 and macrophage inflammatory protein-2, lipid mediators like platelet activating factor and leukotriene B4, adhesion molecules like the b2 integrin, CD18, and transcription factors such as the nuclear factor kB.

Matrix Metalloproteinases (MMPs) and their Role

• From a clinical point of view, mediators that cause pulmonary injury in the case of heaves could be the key to finding specific markers for the disease and potential therapeutic targets.
• The study suggests a significant role for matrix metalloproteinases (MMPs), particularly MMP-9 in heaves, and offers it as a potential diagnostic marker.
• MMP-9 has the capability to degrade many extracellular matrix and basement membrane proteins, including gelatins and various types of collagen. These degradation processes are thought to be pivotal in various physiological tissue remodelling processes such as embryonic development and wound repair.

Testing MMP-9 Proteolysis in Inflammatory Cascade

• The overexpression of MMPs can lead to pathological tissue destruction. Because MMP-9 has broad substrate specificity, it can potentially play a role in many stages of the inflammatory response, including neutrophil recruitment and lung injury in equine heaves.
• There is evidence suggesting that damage to the basement membrane, which can allow neutrophils to migrate across the endothelium, is partially attributable to proteolysis by MMP-9-derived neutrophils.
• However, recent modelling work refutes a significant role for MMP-9 in neutrophil transendothelial migration.

Diagnosing Heaves Using MMP-9

• Raulo et al. (2001) detected markedly increased levels of pro-MMP-9, active MMP-9 and MMP-9 complexes in bronchoalveolar and tracheal lavage fluids from horses with symptomatic heaves compared to healthy controls. This suggest that the capacity for local MMP inhibition has been overwhelmed, allowing uncontrolled MMP-9 proteolysis to contribute to lung injury.
• This opens up a route to identifying and utilizing biologically active MMP-9 as a potential diagnostic marker for heaves.