Partial divergence of cytokine mRNA expression in bronchial tissues compared to bronchoalveolar lavage cells in horses with recurrent airway obstruction.

This research article examines a study conducted on horses with Recurrent Airway Obstruction (RAO) to explore the role of various cytokines in bronchial and bronchoalveolar tissues during both acute crisis and remission periods. The study found that the expression levels of IL-8 mRNA significantly increased in both tissues during a crisis but the expression of other cytokines didn’t necessarily mirror in bronchial epithelium and bronchoalveolar lavage cells.

Study Purpose and Methodology

• This study aimed to examine the mRNA expression levels of specific cytokines in bronchial epithelium tissues of horses suffering from Recurrent Airway Obstruction (RAO) during acute crisis and remission periods. The cytokines in question were IL-5, IL-6, IL-8, IL-10, IL-17 and transforming growth factor beta1 (TGF-beta1).
• The research also looked to compare cytokine mRNA levels in endobronchial biopsies and bronchoalveolar lavage (BAL) cells.
• Seven horses diagnosed with RAO were examined during a respiratory crisis and again after two months in remission spent on pasture. During this remission period, six healthy horses also on pasture were subjected to the same examination.
• Quantitative real-time PCR (RT-PCR) was employed to evaluate mRNA expression for these cytokines.

Key Findings

• During a respiratory crisis, the expression of IL-8 mRNA was noted to increase significantly in both endobronchial biopsies and BAL cells. Similar trends were observed for IL-10 mRNA in BAL cells, but the upregulation was not statistically significant (p=0.059).
• The expression of IL-8 mRNA in BAL cells during crisis was positively correlated with relative IL-6 mRNA expression. Additionally, bronchial epithelial expression levels of IL-10 and TGF-beta1 mRNA showed a positive correlation.
• Examining the relationship of mRNA expression in BAL to biopsy in individual RAO horses, there was a positive correlation with IL-6 to IL-8 mRNA expression in BAL during respiratory crisis, which also corresponded positively with IL-8 expression in biopsies during pasture time.

Conclusions and Implications

• The study found no significant variation in the level of cytokine mRNA in endobronchial biopsies or in BAL cells when comparing RAO horses at pasture to the control group.
• The study supports previous findings that IL-8 mRNA is upregulated in both BAL cells and bronchial epithelium during a crisis in RAO horses. However, it also suggests that apart from IL-8, the expression of other cytokines does not necessarily mirror between the bronchial epithelium and BAL cells in horses with RAO.
• The researchers suggest that endobronchial tissue samples, which can be repeatedly taken over time, offer valuable information for understanding time-dependent changes in inflammatory processes in an animal model of asthma. This is due to their complementary – but not identical – markers of inflammation when compared with BAL cells.