[Proteases and protease inhibitors of possible clinical relevance in COPD of horses].

This research paper examines the significance of proteases and protease inhibitors in the development of lung emphysema and chronic bronchitis in horses. The researchers found that while some processes found in human pathologies were not applicable to horses, there were other unique mechanisms at play, including the susceptibility to exogenous elastases from certain bacteria and the absence of certain protease inhibitors in equine respiratory tract.

Proteases and emphysema in horses

• The authors describe the important role that proteases, particularly elastases – enzymes that break down elastin, a key protein in lung tissue – play in the pathogenesis of pulmonary emphysema in horses.
• Contrary to human cases, where elastases originating from certain immune cells (neutrophil granulocytes and macrophages) contribute to the development of emphysema, these enzymes do not seem to be significant in the equine versions of the disease.
• However, researchers note that horses may be susceptible to exogenous elastases from bacteria belonging to the Streptomyces family. These external enzymes could trigger emphysema in horses.

Role of protease inhibitors in equine respiratory diseases

• Protease inhibitors, proteins that can block the activity of proteases, play a crucial role in controlling these enzymes. In the context of horses, these inhibitors seem to not effectively block exogenous elastases, especially considering the alpha 1-protease inhibitors.
• The paper also denies the presence of a disorder in horses equivalent to the human genetic deficiency in alpha 1-protease inhibitors, which can cause serious lung diseases.
• Like proteases, protease inhibitors are also considered important in the pathogenesis of chronic bronchitis.

Proteases, inflammation, and COPD in horses

• Neutral proteases from neutrophil granulocytes, a type of white blood cell, may contribute to the initiation or amplification of inflammation, a process linked to chronic bronchitis both in humans and horses.
• In humans, under normal conditions, these proteases are controlled by the secretory protease inhibitor HUSI-1. However, the researchers found that horses lack a comparable protease inhibitor in their respiratory ducts.
• The presence of protease activity in inflamed equine tracheobronchial secretions, which correlates with the severity of chronic obstructive pulmonary disease (COPD), could serve as a valuable diagnostic marker for this condition in horses.