Characterization of Large Unilamellar Vesicles as Models for Studies of Lipid Peroxidation Initiated by Azocompounds

Abstract

The aim of this work was to characterize large unilamellar vesicles (LUVETs) prepared by a hand-driven extrusion device in order to use them for studies of lipid peroxidation and antioxidant activity. Vesicle structure and size were examined by electron microscopy. Lipid and antioxidant content was determined before and after the extrusion procedure. Then LUVETs were subjected to autoxidation initiated by both the lipid-soluble 2,2'-azobis(2,4-dimethylvaleronitrile) and the water-soluble 2,2'-azobis(2-amidinopropane hydrochloride) azocompounds. The results demonstrated that: i) LUVETs prepared with lipid concentrations ranging between 25 and 150 mM were essentially unilamellar and reasonably homogeneous, with an average diameter of 90 nm; ii) the phospholipid, cholesterol and antioxidant amounts retained by filters were about 10-15%; iii) LUVETs were suitable for autoxidation studies initiated by the water-soluble azocompound both in the absence and presence of antioxidants. The lipid-soluble azocompound could be used only at low concentrations and its vesicle content had to be determined since part of the initiator was not incorporated into the lipid bilayer. These data suggest that LUVETs seem to be recommended for studies of lipid peroxidation and antioxidant activity.

The role of DT-diaphorase in the maintenance of the reduced antioxidant form of coenzyme Q in membrane systems.

“…The suspension was Vortex-stirred for 12 min. To prepare LUVETs, MLVs void of NADH and DT-diaphorase were prepared using an extruder as described (30 (Fig. 1).…”

Dietary Phenolic Acids Act as Effective Antioxidants in Membrane Models and in Cultured Cells, Exhibiting Proapoptotic Effects in Leukaemia Cells

“…After thermal equilibration of LUVET at 37°C, the appropriate amount of AAPH was added to the suspension in order to obtain a final AAPH concentration of 17 mM, suitable for LUVET peroxidation initiated by water soluble azo compounds [41]. The reaction cell was always protected from room light to avoid initiator photodecomposition.…”

Relationship between lipid peroxidation and rigidity in L-α-phosphatidylcholine-DPPC vesicles

“…Peroxidation kinetics in liposome can be more complex than that observed in homogeneous solution [7][8][9]. This complex kinetics can be related to both the compartmentalization of the substrates [10] and the dependence of the aggregate properties on subtle changes in its composition and/or experimental variables, such as temperature [11].…”