A systematic study on the influence of the main ingredients of an ivy leaves dry extract on the β2-adrenergic responsiveness of human airway smooth muscle cells. (April 2015)

• Record Type: Journal Article
• Authors: Greunke, Christian; Hage-Hülsmann, Anne; Sorkalla, Thomas; Keksel, Nelli; Häberlein, Felix; Häberlein, Hanns
• Is Part Of: Pulmonary pharmacology & therapeutics. Volume 31(2015:Apr.)
• Page Start: 92
• Page End: 98
• Publication Date: 2015-04
• Subjects: Ivy leaves dry extract -- Saponins -- Flavonoids -- Phenolic acids -- β2-adrenergic receptor; Respiratory organs -- Diseases -- Chemotherapy -- Periodicals; 615.7205
• DOI: 10.1016/j.pupt.2014.09.002
• Languages: English
• ISSNs: 1094-5539

Abstract

Abstract: The bronchospasmolytic and secretolytic effects of ivy leaves dry extracts can be explained by an increased β2 -adrenergic responsiveness of the bronchi. Recently, it was shown that α-hederin inhibits the internalization of β2 -adrenergic receptors (ß2 AR) under stimulating conditions. α-Hederin pretreated alveolar type II cells and human airway smooth muscle cells revealed an increased ß2 AR binding and an elevated intracellular cAMP level, respectively. In order to identify whether additional compounds also mediate an increased β2 -adrenergic responsiveness, we examined the ingredients of an ivy leaves dry extract (EA 575) protocatechuic acid, neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, rutin, kaempferol-3-O-rutinoside, 3, 4-, 3, 5- and 4, 5-dicaffeoylquinic acid, hederacoside B, and β-hederin. Within all the tested substances, only β-hederin inhibited the internalization of GFP-tagged ß2 AR in stably transfected HEK293 cells. Using fluorescence correlation spectroscopy β-hederin (1 μM, 24 h) pretreated HASM cells showed a statistically significant increase in the ß2 AR binding from 33.0 ± 8.9% to 44.1 ± 11.5% which was distributed with 36.0 ± 9.5% for τ bound1 and 8.1 ± 2.6% for τ bound2, respectively ( n = 8, p < 0.05). The increased binding was selectively found for the receptor–ligand complex with unrestricted lateral mobility ( τ bound1 of 0.9 ± 0.1 ms, D 1 = 9.1 ± 0.2 μm 2 /s, n = 8), whereas the binding of ß2 AR with hindered lateral mobility ( τ bound2 of 64.2 ± 47.6 ms, D 2 = 0.15 ± 0.02 μm 2 /s, n = 8) was not affected. Compared to control cells, a statistically significant increase of 17.5 ± 6.4% ( n = 4, p < 0.05) and 24.2 ± 5.8% ( n = 4, p < 0.001) in the cAMP formation was found for β-hederin pretreated HASM cells after stimulation with 10 μM of terbutaline and simultaneous stimulation with 10 μM terbutaline and 10 μM forskolin, respectively. Within this systematic study focusing on the influence of the ingredients of an ivy leaves dry extract on HASM cells it was possible to identify β-hederin as further component presumably responsible for the β2 -mimetic effects.