The expression of messenger RNA for tumor necrosis factor-α; interleukins 1β, 6, 8, and 10; tissue growth factor-β; and interferon-γ in bronchoalveolar lavage fluid cells from horses challenged with lipopolysaccharide and treated with clenbuterol

Abstract

The aim was to study the effects of a β-agonist (clenbuterol) on lipopolysaccharide (LPS)—induced cytokine expression of bronchoalveolar cells. Four horses with low-grade small airway diseases and four horses with recurrent airway obstruction were challenged on three occasions with aerosols containing Salmonella LPS or a 0.9% saline solution. Before the first LPS challenge, horses were not treated. Before the second and third challenges, horses received intravenous clenbuterol (Ventipulmin), 0.8 μg/kg twice daily, for 3.5 days. A 2-week washout period was allowed between the challenges. Bronchoalveolar lavage fluid (BALF) was obtained, and maximal intrapleural pressure (ΔP plmax) was measured 6 hours after each challenge. After cytologic examination was performed, the messenger RNA expression in the BALF cell pellet of the following cytokines was investigated by reverse-transcriptase polymerase chain reaction: tumor necrosis factor-α (TNF-α), interleukin (IL)-1α, IL-1β, IL-4, IL-6, IL-8 (CXCL8), IL-10, tissue growth factor-β (TGF-β), and interferon-γ (IFN-γ). Treatment with clenbuterol caused a decrease in maximal intrapleural pressure toward more normal values in the recurrent airway obstruction group. IL-4 mRNA expression could not be demonstrated. Only IFN-γ and IL-10 were statistically significantly different in the three trials, indicating modulation of the LPS-induced inflammatory response by clenbuterol treatment. The expected inhibition by clenbuterol on LPS-induced expression of TNF-α mRNA or stimulation of IL-10 mRNA could not be clearly shown. However, IL-1, IL-10, and IFN-γ mRNA tended to be downregulated by clenbuterol in all horses; whereas IL-6 mRNA appeared to be downregulated in horses with small airway diseases only. Despite its limitations, this study showed that clenbuterol appeared to modulate the communication between the different cell types in equine airways. A different clenbuterol dosing strategy, a different sample time, and a heavier challenge might have caused more significant changes.