Ivy leaves dry extract EA 575® mediates biased ß2-adrenergic receptor signaling.

ABSTRACT

BACKGROUND: ß2-adrenergic receptor (ß2-AR) stimulation activates the G protein/cAMP pathway, which is opposed by the GRK2/ß-arrestin 2 pathway. The latter is undesirable in the treatment of respiratory diseases. HYPOTHESIS/PURPOSE: EA 575® is capable of mediating a biased ß2-adrenergic signaling pathway. METHODS: The impact of the ivy leaves dry extract EA 575® on ß2-adrenergic signaling was tested in a dynamic mass redistribution assay in HEK wild-type and in HEK ß-arrestin knock-out cells. cAMP formation and recruitment of ß-arrestin 2 were investigated using GloSensor™ and PathHunter® assays, respectively. NFκB transcriptional activity was determined in both HEK wild-type as well as HEK ß-arrestin knock-out cells. RESULTS: EA 575® inhibits the recruitment of ß-arrestin 2 and thereby enhances G protein/cAMP signaling under ß2-stimulating conditions, as evidenced by a corresponding increase in cAMP formation. While ß2-AR-mediated inhibition of NFκB transcriptional activity is ß-arrestin-dependent, EA 575® leads to significant inhibition of NFκB transcriptional activity in ß-arrestin knock-out cells and thus via a ß-arrestin-independent signaling pathway. CONCLUSION: EA 575® is the first active phytopharmaceutical ingredient for which biased ß2-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 ß-arrestin-mediated adverse effects in new combinatorial therapeutic approaches.