Clenbuterol affects the expression of messenger RNA for interleukin 10 in peripheral leukocytes from horses challenged intrabronchially with lipopolysaccharides

On four occasions, four horses with heaves and four horses with small airway inflammatory diseases inhaled 0.9% saline based aerosol mixtures with or without lipopolysaccharides (LPS). Prior to the first saline and LPS inhalation, horses were untreated, while three and a half days prior to the third and forth inhalation horses had received 0.8 mu g/kg clenbuterol intravenously twice daily. The messenger RNA (mRNA) expression of tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta, IL-4, IL-6, IL-8, IL-10 and interferon-gamma (IFN-gamma) was investigated by RT-PCR, all of which were expressed in the white blood cells of samples collected. Inhalation of LPS only changed the cytokine expression profile of IL-10, IL-4 and TNF-alpha mRNA which were higher after challenge with LPS. However in those horses that were treated with clenbuterol the LPSinduced IL-10 mRNA expression was shown to be suppressed. Further changes in IL-4 and TNF-alpha were not significant. Thus the results of this study indicated that clenbuterol can modulate the expression of IL-10 mRNA in peripheral white blood cells in those horses with small airway diseases that have been exposed to LPS.