β-Adrenergic agonists exert their 'anti-inflammatory' effects in monocytic cells through the IκB/NF-κB pathway

Abstract

In addition to their well-studied bronchodilatory and cardiotonic effects, β-adrenergic agonists carry anti-inflammatory properties by inhibiting cytokine production by human mononuclear cells. In a model of human promonocytic THP-1 cells stimulated with lipopolysaccharide (LPS), we showed that β-agonists inhibited tumor necrosis factor-α and interleukin-8 production predominantly via the β2-adrenergic receptor through the generation of cAMP and activation of protein kinase A. This effect was reproduced by other cAMP-elevating agents such as prostaglandins and cAMP analogs. Activation and nuclear translocation of the transcription factor nuclear factor-κB induced by LPS were inhibited with treatment with β-agonists, an effect that was prominent at late time points (> 1 h). Although the initial IκB-α degradation induced by LPS was minimally affected by β-agonists, the latter induced a marked rebound of the cytosolic IκB-α levels at later time points (> 1 h), accompanied by an increased IκB-α cytoplasmic half-life. This potentially accounts for the observed nuclear factor-κB sequestration in the cytoplasmic compartment. We postulate that the anti-inflammatory effects of β-agonists reside in their capacity to increase cytoplasmic concentrations of IκB-α, possibly by decreasing its degradation.