Clara cell secretory protein is reduced in equine recurrent airway obstruction.

This research article explores the reduction in Clara cell secretory protein (CCSP) in horses experiencing recurrent airway obstruction (RAO), a common inflammatory lung disease in the species.

Research Context and Hypothesis

• The study revolves around understanding and investigating the incidence of Recurrent Airway Obstruction (RAO) in horses. RAO in horses is an inflammatory lung disease, which is typically induced by repeated exposure to mold, dust, and bacterial components in the environment.
• RAO has a range of symptoms, including mucus hyperproduction, neutrophilic inflammation, bronchoconstriction, coughing, and other symptoms. In chronically affected animals, it can lead to lung remodeling, characterized by hyperplasia of smooth muscles, collagen deposition, lymphoid hyperplasia, and impaired aerobic performance. This study hypothesized that a reduction in Clara cell secretory protein (CCSP) — which typically counteracts inflammation in the lung — is a key aspect of RAO in horses.

Research Methodology

• To test the hypothesis, the researchers created recombinant equine CCSP and specific antiserum. Percutaneous lung biopsies were then conducted on six horses — three of whom were healthy and three of whom were affected by RAO — both before and after the induction of RAO.
• The CCSP gene expression in tissue plus the protein concentration in lung lavage fluid were determined. Moreover, both light and immunogold ultrastructural methods were employed to conduct immunocytochemical analyses. These analyses were meant to check for any reduction in CCSP staining in lung tissue of animals with RAO.

Research Findings

• From the findings, it was noted that the immunogold label in Clara cell granules was less in animals with chronic RAO as compared to normal animals and was completely absent in animals that had active disease.
• The median lung lavage CCSP concentration in healthy horses was found to be 132 and 129 ng/ml, while in RAO horses, it was 62 and 24 ng/ml before and after challenge, respectively.
• Immunocytochemical analyses demonstrated a reduction in CCSP staining in the lung tissue of RAO-affected animals.
• Gene expression of CCSP in the lungs was significantly higher in healthy animals than in animals with chronic RAO.

Conclusion

• In conclusion, the researchers found preliminary evidence that chronic environmentally induced lung inflammation in horses is characterized by reduced CCSP production and subcellular changes in Clara cells. However, these findings are preliminary and further research is needed to fully understand this relationship.