The Beta-2-Adrenoreceptor Agonists, Formoterol and Indacaterol, but Not Salbutamol, Effectively Suppress the Reactivity of Human NeutrophilsIn Vitro

Abstract

The clinical relevance of the anti-inflammatory properties of beta-2 agonists remains contentious possibly due to differences in their molecular structures and agonist activities. The current study has compared the effects of 3 different categories of β2-agonists, namely, salbutamol (short-acting), formoterol (long-acting) and indacaterol (ultra-long-acting), at concentrations of 1–1000 nM, with human blood neutrophils in vitro. Neutrophils were activated with either N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP, 1 µM) or platelet-activating factor (PAF, 200 nM) in the absence and presence of the β2-agonists followed by measurement of the generation of reactive oxygen species and leukotriene B4, release of elastase, and expression of the β2-integrin, CR3, using a combination of chemiluminescence, ELISA, colorimetric, and flow cytometric procedures respectively. These were correlated with alterations in the concentrations of intracellular cyclic-AMP and cytosolic Ca2+. At the concentrations tested, formoterol and indacaterol caused equivalent, significant (P < 0.05 at 1–10 nM) dose-related inhibition of all of the pro-inflammatory activities tested, while salbutamol was much less effective (P < 0.05 at 100 nM and higher). Suppression of neutrophil reactivity was accompanied by elevations in intracellular cAMP and accelerated clearance of Ca2+ from the cytosol of activated neutrophils. These findings demonstrate that β2-agonists vary with respect to their suppressive effects on activated neutrophils.

Neutrophilic superoxide production can assess pharmacological and pharmacogenetic β‐adrenoreceptor effects

“…We observed effective inhibition of ROS production in all our 60 healthy donors with clinically relevant β 2 AR agonist concentrations . In concordance with previous studies, FORM was the most potent and SAL the least potent inhibitor of ROS production . The highly significant correlation of standardized pIC 50 values for all agonists demonstrated similar pharmacological responses toward treatment with different β 2 AR agonists in each individual proband.…”

“…An alternative approach to explore effects of β 2 AR agonists is to test patient cells ex vivo for cellular adrenoresponses. Primary neutrophils represent a rather monomorphic, highly abundant, and easily accessible cell population for ex vivo testing of the β 2 AR effects . Neutrophils contribute to a plethora of inflammatory processes including asthma, and one of the most important defense mechanisms in neutrophils is the production of reactive oxygen species (ROS) .…”

Effect of beta2-adrenergic agonists on eosinophil adhesion, superoxide anion generation, and degranulation

“…10 Furthermore, Anderson et al reported that formoterol suppressed the expression of adhesion molecules (CR3; CD11b/CD18) of neutrophils. 27 Taken together, we think that formoterol suppressed the eosinophil adhesion to ICAM-1 by suppressing the CD11b/CD18 expression on the eosinophil surface.…”

“…50 They also reported that cAMP accumulation is inversely correlated with eosinophil degranulation, and that the time course of cAMP accumulation closely paralleled that of inhibition of eosinophil degranulation. 50 As for neutrophils, formoterol increased cAMP more than salbutamol, 27,28 and suppressed neutrophil functions, including O 2 À generation, LTB 4 generation, and elastase release. 27,28 Furthermore, increased cAMP levels in neutrophils inhibited their adhesion.…”

“…50 As for neutrophils, formoterol increased cAMP more than salbutamol, 27,28 and suppressed neutrophil functions, including O 2 À generation, LTB 4 generation, and elastase release. 27,28 Furthermore, increased cAMP levels in neutrophils inhibited their adhesion. 51 Formoterol also increased cAMP levels to a greater degree than salbutamol in cultured rat cardiomyocytes.…”