The activity and expression of chitinase in the equine lung and its activity in normal horses and animals with recurrent airway obstruction.

The research studied the activity of chitinase, an enzyme, in the lungs of horses, particularly those with recurrent airway obstruction (RAO). The researchers did not observe significant difference in activity between horses with and without RAO, although further investigation is required to confirm the role of chitinase in RAO.

Recurrent Airway Obstruction and Chitinase

• The study focused on recurrent airway obstruction (RAO) – a chronic inflammatory condition in horses that may be comparable to human asthma. Both conditions involve dysfunctional Th2 immune responses.
• Chitinase and chitinase-like proteins were a particular focus. These proteins, produced among mammals, contain two active enzymes – chitotriosidase and acidic mammalian chitinase (AMCase). These enzymes can increase in response to various inflammatory conditions, such as asthma.

Methodology and Results

• The researchers extracted and analyzed bronchoalveolar lavage fluid – a solution obtained from the bronchi, part of the lung passageways – from horses with and without RAO. The aim was to assess the activity of chitinase following challenges with organic dust.
• No significant changes in chitinase activity were detected, although in one part of the study, horses with RAO showed increased chitinase activity that was just shy of being statistically significant.
• Determining the pH optimum and pH lability, or stability, of the activity indicated the presence of chitotriosidase among the chitinases.
• Further investigation involved RT-PCR amplification of the mRNA encoding chitotriosidase and AMCase in normal horse lung tissue. It revealed that chitotriosidase, but not AMCase, is expressed in the trachea, bronchi, and peripheral lung tissue of horses.
• The researchers also identified the gene for chitotriosidase in the horse genome from a particular database and analyzed its similarities with the corresponding genes in other species.

Conclusion

• The findings suggest that the role of chitotriosidase in equine RAO is unclear. Despite detecting the enzyme in various sections of the horse lung and observing increased activity in RAO horses in one investigation, no statistically significant changes in chitinase activity were overall established. Hence, further research is needed to ascertain the potential involvement of chitinase, particularly chitotriosidase, in equine RAO.