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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:30 |
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Conference: Bucharest University Faculty of Physics 2002 Meeting
Section: Electricity and Biophysics: Honorary Session Dedicated to Professors: Victor Gheorghe (Head of the Dept. 1972-1984) and Grigore Turcu
Title:
The Interaction Between Hyperici Herba Extract
and Artificial Lipid Bilayers
Authors:
Macri Beatrice Mihaela, Ioana Neagoe, Maria-Luiza Flonta
Affiliation:
Department of Animal Physiology and Biophysics,
Faculty of Biology
E-mail
Keywords:
Abstract:
Extracts of different species of Hypericaceae are used for clinical treatment of depressive disorders. They also present antiviral and apoptotic properties. The major constituents are Hyp and its derivates, which are thought to be the responsible agents of the curative effects. Although their anti-depressive mechanism is not known yet, their unspecific action could be related to a depolarization of the cell membrane, responsible for the apoptotic action [1].
We used planar lipid bilayers to determine the action of hypericins on membranes considering different Hyp concentrations, membrane composition and I-V characteristics [2,3].
A large range of Hyperici extract concentration [0,1-10 mg/ml] was used, for one side and both side application. No modification of the capacitance was observed for one or both side application. For both side application, the conductance increase is dependent on Hyp concentration and is higher than for one side application.
Pure and mixed bilayers were used to test Hyp insertion. In PC and PC:PS bilayers, the capacitance variation is insignificant for the entire range of concentrations. In mixed PC:PS:CHOL bilayers, the capacitance increases after Hyp addition, the effect being dependent of CHOL content. The conductance varies strongly in all types of bilayers. In PC:CHOL and PC:PS:CHOL bilayers, the conductance increases with increasing CHOL content, but the effect is smaller than for pure PC bilayers.
Hyp could insert in lipid bilayers depending on their CHOL content and it permeabilizes the membrane. Its effect is voltage-dependent as indicates the non-linear charactheristic I-V [3]. The persistence of the permeabilization effect even in PC bilayers where Hyp insertion doesn’t occur, suggests a surface effect of Hyp, resulting in a local disorder of the lipids chains.
Keywords: Hyperici Herba, Depolarization, Lipid bilayers, Membrane permeabilization.
Abreviations: PC - phosphatidylcoline; PS – phosphatidylserine; CHOL – cholesterol; Hyp – hypericin.
References:
1. Chaloupka R.; Petit P. X.; Israel N.; Sureau F. Over-expression of Bcl-2 does not protect cells from hypericin photo-induced mitochondrial membrane depolarization, but delays subsequent events in the apoptotic pathway. FEBS Lett Dec 3;462 (3), 295-301, 1999
2. Movileanu L., Neagoe I., Flonta M.L Interaction of the antioxidant flavonoid quercetin with planar lipid bilayers, Int. J. Pharmac., 205: 135-146, 2000
3. Tombola F., Carlesso C., Szabň I., de Bernard M., Reyrat J.M., Telford J.L., Rappuolli R., Montecucco C., Papini E., Zoratti M., Helicobacter pylori Vacuoling Toxin Forms Anion-Selective Channels in Planar Lipid Bilayers: Possible Implications for the Mechanism of Cellular Vacuolation, Biophys J., 76:1401-1409, 1999
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