Expression of toll-like receptor 2 mRNA in bronchial epithelial cells is not induced in RAO-affected horses.

The research article investigates the role of innate immune mechanisms in recurrent airway obstruction (RAO) in horses, focusing on toll-like receptor 2 (TLR2), interleukin (IL)-8, and a zinc finger protein A20. The study found that while stabling increases IL-8, it doesn’t affect TLR2 or A20. The results suggest other molecules in the TLR2 cascade might contribute to fungal-induced airway inflammation and that A20 may help modulate airway inflammation.

Research Objectives and Methodology

• The main objective of the study was to determine the expression of TLR2, IL-8, and A20 mRNA in the lungs of horses suffering from RAO when they were stabled and pastured. The researchers hypothesized that TLR2 and IL-8 mRNA levels were higher in RAO during stabling compared to control samples and that A20 mRNA showed a negative association with the numbers of airway inflammatory cells.
• To determine these results, the researchers examined airway obstruction and inflammatory cell counts in bronchoalveolar lavage. They also quantified the expression of TLR2, IL-8, and A20 mRNA using quantitative reverse transcription PCR (qRT-PCR) in 6 RAO-affected and 6 control horses, during and after exposure to hay and straw.

Key Findings

• The research found an increase in airway obstruction and neutrophils in RAO-affected horses during stabling. While stabling increased IL-8, the mRNA of TLR2 and A20 was unaffected. TLR2 and A20 were significantly correlated with a correlation coefficient of 0.83.
• The mRNA of A20 demonstrated a negative association with inflammatory cells. That means as the A20 mRNA expression increased, the amount of inflammatory cells decreased.

Conclusions and Implications

• The study concluded that stabling does not lead to an increase in TLR2 expression. This suggests that other molecules or processes in the TLR2 cascade might be significant in causing fungal-induced airway inflammation in horses.
• The findings also point to a possible role for A20 in regulating airway inflammation. The zinc finger protein appears to modulate inflammation as its mRNA expression levels are inversely related to the number of inflammatory cells. Further research into A20’s role could lead to new strategies for managing RAO in horses.