Objective—To analyze effects of hay dust exposure
on interleukin-8 (IL-8) concentration, percentage of
neutrophils, and neutrophil chemotactic activity in
bronchoalveolar lavage fluid (BALF) of horses with
chronic obstructive pulmonary disease (COPD).
Animals—16 healthy horses and 29 horses with
Procedure—IL-8 concentration, percentage of neutrophils,
and neutrophil chemotactic activity in BALF
were measured. Values were analyzed with respect
to hay dust exposure. These variables were also measured
in 5 asymptomatic horses with COPD after the
induction of clinical signs by changing feed from
silage to hay.
Results—IL-8 concentrations and chemotactic activity
in BALF were greater in horses with COPD, compared
with healthy horses, and greater in horses with
COPD exposed to hay dust, compared with nonexposed
affected horses. An increase in IL-8 concentration
accompanied by an increase in percentage of
neutrophils in BALF and development of clinical signs
of COPD were induced in asymptomatic horses with
COPD by changing feed from silage to hay.
Conclusions and Clinical Relevance—Exposure of
horses with COPD to hay dust components resulted
in an increase in IL-8 secretion at the bronchoalveolar
surface. This chemokine may play a role in the pathogenesis
of COPD, because it causes neutrophil accumulation
in the bronchoalveolar space. Our results
underscore the importance of eliminating dust
sources for the treatment and prevention of COPD in
horses. (Am J Vet Res 2000;61:1369–1374)
Objective—To evaluate time-dependent alterations in gene expression of chemokines in bronchial epithelium of recurrent airway obstruction (RAO)-affected horses and whether alterations resulted from increases in gene expression of interleukin (IL)-17 in cells isolated from bronchoalveolar lavage fluid (BALF).
Animals—8 RAO-susceptible horses and 9 control horses.
Procedure—In 2 experiments, both groups of horses were evaluated after being maintained on pasture and after being stabled and fed dusty hay for 1, 14, 35, and 49 days (experiment 1) or 14 and 28 days (experiment 2). In experiment 1, gene expression of IL-8, chemokine (C-X-C motif) ligand 1 (CXCL1), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), and Toll-like receptor 4 (TLR4) in epithelium and IL-8, IL-17, and TLR4 in BALF cells was measured. In experiment 2, bronchial biopsy specimens were evaluated for IL-8 immunoreactivity.
Results—In RAO-susceptible horses after 14 days of challenge exposure, there was a 3- and 10-fold increase in gene expression of IL-8 for epithelial and BALF cells and an increase in IL-8 immunoreactivity in epithelial cells. Challenge exposure failed to alter gene expression of CXCL1, GM-CSF, G-CSF, and TLR4 in epithelial cells of any horses at any time point. During challenge exposure, gene expression of BALF cell IL-17 was downregulated in control horses (day 1) and upregulated in RAO-affected horses (day 35).
Conclusions and Clinical Relevance—Epithelial-derived IL-8 may promote airway neutrophilia, but the inciting stimulus is unlikely to be IL-17 because upregulation of this gene is subsequent to that of IL-8 in epithelial cells.