Abstract
Ivy leaf dry extract EA 575(®) is used to improve complaints of chronic inflammatory bronchial diseases and acute inflammation of the respiratory tract accompanied by coughing. Its mechanism of action has so far been explained by influencing β(2)-adrenergic signal transduction. In the present study, we investigated a possible influence on adenosine receptor A(2B) (A(2B)AR) signalling, as it has been described to play a significant and detrimental role in chronic inflammatory airway diseases. The influence of EA 575(®) on A(2B)AR signalling was assessed with measurements of dynamic mass redistribution. Subsequently, the effects on A(2B)AR-mediated second messenger cAMP levels, β-arrestin 2 recruitment, and cAMP response element (CRE) activation were examined using luciferase-based HEK293 reporter cell lines. Lastly, the impact on A(2B)AR-mediated IL-6 release in Calu-3 epithelial lung cells was investigated via the Lumit™ Immunoassay. Additionally, the adenosine receptor subtype mediating these effects was specified, and A(2B)AR was found to be responsible. The present study demonstrates an inhibitory influence of EA 575(®) on A(2B)AR-mediated general cellular response, cAMP levels, β-arrestin 2 recruitment, CRE activation, and IL-6 release. Since these EA 575(®)-mediated effects occur within a time frame of several hours of incubation, its mode of action can be described as indirect. The present data are the first to describe an inhibitory effect of EA 575(®) on A(2B)AR signalling. This may offer an explanation for the beneficial clinical effects of the extract in adjuvant asthma therapy.