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Evaluation of cytokine production by equine alveolar macrophages exposed to lipopolysaccharide, Aspergillus fumigatus, and a suspension of hay dust

Tamarinde T. J. M. Laan DVM, PhD1, Sarah Bull PhD2,3, R. Scott Pirie BVM&S, PhD4, and Johanna Fink-Gremmels DVM, PhD5
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  • 1 Department of Equine Science, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 12-16, 3508 TD, Utrecht, The Netherlands.
  • | 2 Departments of Veterinary Pharmacy, Pharmacology, & Toxicology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 12-16, 3508 TD, Utrecht, The Netherlands.
  • | 3 Section of Clinical Pharmacology, Toxicology Unit, Department of Health, Imperial College, Ducane Rd, London, UK.
  • | 4 Easter Bush Veterinary Centre, Roslin, Midlothian EH259RG, UK.
  • | 5 Departments of Veterinary Pharmacy, Pharmacology, & Toxicology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 12-16, 3508 TD, Utrecht, The Netherlands.

Abstract

Objective—To evaluate cytokine production by equine alveolar macrophages after exposure to lipopolysaccharide (LPS), Aspergillus fumigatus, and hay dust, and determine the effect of clenbuterol on the cytokine response.

Animals—6 horses.

Procedures—Alveolar macrophages were exposed to PBS solution (negative control), LPS, hyphae and conidia of Aspergillus fumigatus (AF), or a suspension of hay dust (HDS) and incubated for 24 hours at 37°C. Concentrations of tumor necrosis factor (TNF)-α and interleukin (IL)-1β were measured in the supernatant. The procedure was repeated with cells that were concurrently incubated with 0.5µM clenbuterol.

Results—Exposure to HDS and AF significantly increased production of TNF-α by equine alveolar macrophages. The increase in TNF-α produced in response to HDS and AF was 5 and 7 times as great, respectively, as the increase measured in response to LPS. The concentration of IL-1β in the supernatant was significantly increased after exposure of cells to AF. Clenbuterol was effective at inhibiting TNF-α production by cells exposed to LPS, HDS, or AF.

Conclusions and Clinical Relevance—Increased production of TNF-α and IL-1 indicated that the proinflammatory cytokines produced by alveolar macrophages in response to allergens may play a role in recurrent airway obstruction (RAO) in horses. Equine alveolar macrophages are not only a primary pulmonary defense mechanism but may also influence the pathogenesis of equine RAO. The β2-adrenoceptor agonist clenbuterol, a drug that is commonly used for treatment of equine RAO, promotes immediate bronchodilation and may also contribute to downward modulation of the inflammatory response. (Am J Vet Res 2005;66:1584–1589)

Abstract

Objective—To evaluate cytokine production by equine alveolar macrophages after exposure to lipopolysaccharide (LPS), Aspergillus fumigatus, and hay dust, and determine the effect of clenbuterol on the cytokine response.

Animals—6 horses.

Procedures—Alveolar macrophages were exposed to PBS solution (negative control), LPS, hyphae and conidia of Aspergillus fumigatus (AF), or a suspension of hay dust (HDS) and incubated for 24 hours at 37°C. Concentrations of tumor necrosis factor (TNF)-α and interleukin (IL)-1β were measured in the supernatant. The procedure was repeated with cells that were concurrently incubated with 0.5µM clenbuterol.

Results—Exposure to HDS and AF significantly increased production of TNF-α by equine alveolar macrophages. The increase in TNF-α produced in response to HDS and AF was 5 and 7 times as great, respectively, as the increase measured in response to LPS. The concentration of IL-1β in the supernatant was significantly increased after exposure of cells to AF. Clenbuterol was effective at inhibiting TNF-α production by cells exposed to LPS, HDS, or AF.

Conclusions and Clinical Relevance—Increased production of TNF-α and IL-1 indicated that the proinflammatory cytokines produced by alveolar macrophages in response to allergens may play a role in recurrent airway obstruction (RAO) in horses. Equine alveolar macrophages are not only a primary pulmonary defense mechanism but may also influence the pathogenesis of equine RAO. The β2-adrenoceptor agonist clenbuterol, a drug that is commonly used for treatment of equine RAO, promotes immediate bronchodilation and may also contribute to downward modulation of the inflammatory response. (Am J Vet Res 2005;66:1584–1589)