Downregulation of β1‐adrenergic receptors in rat C6 glioblastoma cells by hyperforin and hyperoside from St John's wort. (18th March 2013)

• Record Type: Journal Article
• Authors: Jakobs, Daniel; Hage‐Hülsmann, Anne; Prenner, Lars; Kolb, Christiane; Weiser, Dieter; Häberlein, Hanns
• Is Part Of: Journal of pharmacy and pharmacology. Volume 65:Number 6(2013:Jun.)
• Page Start: 907
• Page End: 915
• Publication Date: 2013-03-18
• Subjects: Pharmacy -- Periodicals; Pharmacology -- Periodicals; 615.1
• DOI: 10.1111/jphp.12050
• Languages: English
• ISSNs: 0022-3573

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <sec id="jphp12050-sec-0001" sec-type="section"> <title>Objectives</title> <p>While the use of St John's wort extracts as treatment for mild to moderate depression is well established the mode of action is still under investiation. Individual constituents of St John's wort extract were tested for possible effects on the β<sub>1</sub>AR density and a subsequent change in downstream signalling in rat C6 glioblastoma cells.</p> </sec> <sec id="jphp12050-sec-0002" sec-type="section"> <title>Methods</title> <p>The effect of compounds from St John's wort extract on the downregulation of β<sub>1</sub>‐adrenergic receptor‐GFP fusion proteins (β<sub>1</sub>AR‐green fluorescent protein (GFP)) of transfected rat C6 gliobastoma cells (C6‐β<sub>1</sub>AR‐GFP) was investigated by means of confocal laser scanning microscopy (LSM). The influence on the lateral mobility of β<sub>1</sub>AR‐GFP in C6‐β<sub>1</sub>AR‐GFP was investigated by fluorescence correlation spectroscopy. The formation of second messenger was determined by c‐AMP‐assay.</p> </sec> <sec id="jphp12050-sec-0003" sec-type="section"> <title>Key findings</title> <p>Confocal LSM revealed that pretreatment of cells with 1 μ<sc>m</sc> of hyperforin and hyperoside for 6 days, respectively, led to an internalization of β<sub>1</sub>AR‐GFP under non‐stimulating conditions. Observation by fluorescence correlation spectroscopy showed two diffusion time constants for control cells, with τ<sub>diff1</sub> = 0.78 ± 0.18 ms and τ<sub>diff2</sub> = 122.53 ± 69.41 ms, similarly distributed. Pretreatment with 1 μ<sc>m</sc> hyperforin or 1 μ<sc>m</sc> hyperoside for 3 days did not alter the τ<sub>diff</sub> values but decreased the fraction of τ<sub>diff1</sub> whereas the fraction of τ<sub>diff2</sub> increased significantly. An elevated level of β<sub>1</sub>AR‐GFP with hindered lateral mobility was in line with β<sub>1</sub>AR‐GFP internalization induced by hyperforin and hyperoside, respectively. A reduced β<sub>1</sub>‐adrenergic responsiveness was assumed for C6 gliobastoma cells after pretreatment for 6 days with 1 μ<sc>m</sc> of both hyperforin and hyperoside, which was confirmed by decreased cAMP formation of about 10% and 5% under non‐stimulating conditions. Decrease in cAMP formation by 23% for hyperforin and 15% for hyperoside was more pronounced after stimulation with 10 μ<sc>m</sc> dobutamine for 30 min.</p> </sec> <sec id="jphp12050-sec-0004" sec-type="section"> <title>Conclusions</title> <p>The treatment of C6 gliobastoma cells with hyperforin and hyperoside results in a reduced β<sub>1</sub>AR density in the plasma membrane and a subsequent reduced downstream signalling.</p> </sec> </abstract>