A comparison of pro-inflammatory cytokine mRNA expression in equine bronchoalveolar lavage (BAL) and peripheral blood

An imbalance in various cytokine mRNA expression in bronchoalveolar lavage (BAL) and peripheral blood mononuclear cells (PBMC) in horses suffering from recurrent airway obstruction (RAO) has been demonstrated; however, the natural variation of cytokine expression in healthy horses has yet to be described. The objectives of this study were to: (1) identify age-related differences in the expression of pro-inflammatory cytokines in BAL and PBMC, (2) compare the expression of pro-inflammatory cytokines between BAL and PBMC, and (3) evaluate the relationship between BAL pro-inflammatory cytokine expression and BAL cytology. Cells from BAL and PBMC were collected from 66 horses and stimulated with LPS and PGN. The expression of IL-1β, IL-6, IL-8, TNF-α and TLR-4 were measured using qPCR. A significant age-related decrease for IL-1β and IL-8 in BAL, significant difference in cytokine mRNA expressions between BAL and PBMC and a significant relationship between TLR-4 and IL-8 in LPS stimulated BAL samples and the percentage of neutrophils in BAL cytology were found. In conclusion, the natural age-related decrease in pro-inflammatory cytokine expression in BAL is new knowledge; this in contrast to other age-related findings associated with PBMC, where pro-inflammatory cytokines are known to increase with age in both horses and humans, the phenomenon known as 'inflamm-aging'.