In heavey horses, IL-8 gene and protein expression in bronchial biopsies are up-regulated (Ainsworth et al, 2006) but the inciting stimuli are unknown. The objective of this study was to determine if, in response to hay dust exposure, chemokine and cell surface receptor (CSR) expression increases in primary bronchial cell cultures (BEC) from heavey horses.

BEC were established from 6 diseased and 6 control horses stabled and fed hay for 2 weeks. Cultures were incubated for 6 or 24 hours with solutions of PBS, hay dust, LPS and β-glucan. IL-8, CXCL2, IL-1β, TLR2, TLR4 and IL-1R1 gene expressions were measured by kinetic PCR. Group differences were detected using a Wilcoxon rank sum test with a Bonferroni correction.

Following PBS treatment, there were no differences between the 2 groups in chemokine or CSR expression. For each group, HDS and LPS but not β-glucan treatment up-regulated IL-8, CXCL2 and IL-1β expression. No treatment up-regulated TLR2, TLR-4 or IL-1R1 expression relative to PBS. The single group difference was an early CXCL2 up-regulation in hay dust-treated BEC from heavey horses. These data suggest that epithelial IL-8 or IL-1β but not CXCL2 expression requires signals from luminal or interstitial lung cells not present in BEC. (Funded USDA 2004-01235)