Ivy leaves dry extract EA 575® mediates biased β2-adrenergic receptor signaling

Abstract

Backgroundβ2-adrenergic receptor (β2-AR) stimulation activates the G protein/cAMP pathway, which is opposed by the GRK2/β-arrestin 2 pathway. The latter is undesirable in the treatment of respiratory diseases. Hypothesis/PurposeEA 575® is capable of mediating a biased β2-adrenergic signaling pathway. MethodsThe impact of the ivy leaves dry extract EA 575® on β2-adrenergic signaling was tested in a dynamic mass redistribution assay in HEK wild-type and in HEK β-arrestin knock-out cells. cAMP formation and recruitment of β-arrestin 2 were investigated using GloSensor™ and PathHunter® assays, respectively. NFκB transcriptional activity was determined in both HEK wild-type as well as HEK β-arrestin knock-out cells. ResultsEA 575® inhibits the recruitment of β-arrestin 2 and thereby enhances G protein/cAMP signaling under β2-stimulating conditions, as evidenced by a corresponding increase in cAMP formation. While β2-AR-mediated inhibition of NFκB transcriptional activity is β-arrestin-dependent, EA 575® leads to significant inhibition of NFκB transcriptional activity in β-arrestin knock-out cells and thus via a β-arrestin-independent signaling pathway. ConclusionEA 575® is the first active phytopharmaceutical ingredient for which biased β2-adrenergic activation has been described. This shift towards G protein/cAMP signaling provides the molecular basis for the clinically proven efficacy of EA 575® in the treatment of lower respiratory tract diseases. In this light, EA 575® could potentially reduce β-arrestin-mediated adverse effects in new combinatorial therapeutic approaches.