Inhibitory effects of the β₂-adrenergic receptor agonist zilpaterol on the LPS-induced production of TNF-α in vitro and in vivo

In this study the anti-inflammatory properties of zilpaterol, a β₂-adrenergic receptor (AR) agonist specifically developed as a growth promoter in cattle were investigated. Although zilpaterol has a different structure compared with the β₂-AR agonists known to date, it was noted that it was able to bind to both the β₂-AR (K _i = 1.1 × 10^-6) and the β₁-AR (K_i = 1.0 × 10^-5). Using lipopolysaccharide (LPS)-exposed U937 macrophages, the production of cyclic adenosine-3′, 5′-cyclic monophosphate (cAMP) and tumor necrosis factor alpha (TNF-α) were investigated. Zilpaterol inhibited TNF-α release and induced intracellular cAMP levels in a dose-dependent manner. The inhibition of TNF-α release and induction of cAMP production was mainly mediated via the β₂-AR, as indicated by addition of β₁- and β₂-specific antagonists. The effects of zilpaterol were investigated in LPS-treated male Wistar rats after pretreatment with zilpaterol. Zilpaterol dosed at 500 μg/kg body weight reduced the TNF-α plasma levels. In conclusion, zilpaterol is a β₂-adrenergic agonist and an inhibitor of TNF-α production induced by LPS both in vivo and in vitro.