Stereoselectivity at the B2-adrenoceptor on macrophages is a major determinant of the anti-inflammatory effects of B2-agonists

Previous research has shown that β-adrenoceptor (β-AR) agonists have potent anti-inflammatory capabilities, e.g. represented by suppression of release of the proinflammatory cytokines. Aim of this research was to determine whether the effects of β-agonists on LPS-induced TNFα and IL-10 release are influenced by their different stereochemistry. In addition, the role of the β-AR subtypes was studied. The effect of two stereoisomers of the selective β2-AR agonist TA2005 [(R,R)- and (S,S)-] on the LPS-induced TNFα and IL-10 release by U937 macrophages was compared. The (R,R)-stereoisomer was 277 times more potent in inhibiting the TNFα release than the (S,S)-form. The (R,R)-stereoisomer also appeared to be more potent in increasing the IL-10 release. In radioligand binding studies the affinity of (R,R)-TA2005 for the β-adrenoceptor was 755 times higher than the (S,S)-TA2005 stereoisomer. In addition, the elevation of intracellular cAMP in U937 cells appeared to be stereoselective: (R,R)-TA2005 was more potent in elevating intracellular cAMP. The effect of both stereoisomers on the LPS-induced TNFα release could almost completely be antagonized by preincubation with the selective β2-AR-antagonist ICI-118551. Further evidence that the effect of the β-agonists is mediated via the β2-adrenoceptor subtype exclusively was acquired by incubation of U937 cells with selective β1- and β3-agonists. None of these receptor subtype agonists showed significant suppressive effect on TNFα release. This study provides additional proof that the anti-inflammatory effects of β2-agonists are mediated via the β2-adrenoceptor and indicates that these effects are highly dependent on the stereoselectivity of the ligand

Endotoxin-induced liver damage in rats is minimized by beta 2-adrenoceptor stimulation.

Contains fulltext : 58554.pdf (publisher's version ) (Closed access)OBJECTIVE AND DESIGN: To investigate the effects of beta(2)-adrenoceptor (beta(2)-AR) stimulation on endotoxin-induced liver damage and systemic cytokine levels in rats. SUBJECTS: Standard male Wistar rats. TREATMENT: A disease-model of lipopolysaccharide (LPS)-induced acute systemic inflammation was used. The beta(2)-selective AR agonist clenbuterol was administered before, during, and after LPS-challenge to investigate its effects on the acute inflammatory response and associated liver-failure. METHODS: The following parameters have been measured in plasma: TNF alpha, IL-1 beta, IL-6, IL-10, AST, ALT, and Bilirubin. Liver histological examination was performed to look for changes in tissue morphology. RESULTS: Administration of clenbuterol (p.o.) one hour before, or intravenous at the same time as LPS-challenge resulted in a marked reduction of plasma levels of TNF alpha, IL-1 beta, and IL-6. A change both in plasma-level and in time-concentration profile of the anti-inflammatory cytokine IL-10 was found. Clenbuterol minimized LPS-induced liver damage, as represented by significantly lowered concentrations of several parameters for liver-failure (AST, ALT, Bilirubin), and improved hepatic tissue morphology. Clenbuterol administration after LPS challenge failed to inhibit TNF alpha-release but reduced liver-damage. Simultaneous use of the beta(2)-AR antagonist propranolol augmented LPS-induced liver failure, suggesting a role of endogenous adrenoceptor-agonists in prevention of organ-failure during systemic inflammation. CONCLUSIONS: The results indicate that a selective beta(2)-AR agonist might be used as an additional therapeutic agent in the clinic for the treatment of (acute) systemic inflammatory disorders in order to reduce or prevent subsequent liver failure

Inhibitory effects of the beta-adrenergic receptor agonist zilpaterol on the LPS-induced production of TNF-alpha in vitro and in vivo.

Contains fulltext : 32642.pdf (publisher's version ) (Closed access)In this study the anti-inflammatory properties of zilpaterol, a beta2-adrenergic receptor (AR) agonist specifically developed as a growth promoter in cattle were investigated. Although zilpaterol has a different structure compared with the beta2-AR agonists known to date, it was noted that it was able to bind to both the beta2-AR (Ki = 1.1 x 10(-6)) and the beta1-AR (Ki = 1.0 x 10(-5)). Using lipopolysaccharide (LPS)-exposed U937 macrophages, the production of cyclic adenosine-3',5'-cyclic monophosphate (cAMP) and tumor necrosis factor alpha (TNF-alpha) were investigated. Zilpaterol inhibited TNF-alpha release and induced intracellular cAMP levels in a dose-dependent manner. The inhibition of TNF-alpha release and induction of cAMP production was mainly mediated via the beta2-AR, as indicated by addition of beta1- and beta2-specific antagonists. The effects of zilpaterol were investigated in LPS-treated male Wistar rats after pretreatment with zilpaterol. Zilpaterol dosed at 500 microg/kg body weight reduced the TNF-alpha plasma levels. In conclusion, zilpaterol is a beta2-adrenergic agonist and an inhibitor of TNF-alpha production induced by LPS both in vivo and in vitro