Title: (empty line)
Author: Herr Dr. Amoneit
Last saved by: Saritas, Sevim
Company: ichp

Liposome Modification by Different Phases of Cigarette Smoke. 
Palmina Nadezhda, Chasovskaya Tatyana, Maltseva Elena, Menshov Valery, Trofimov Alexey 
Emanuel Institute Biochemical Physics RAS, Moscow, Russia; e-mail: npalm@sky.chph.ras.ru

Mechanisms by which cigarette smoke contributes to a number of lung and other diseases are often related to the development of oxidative stress. A large body of studies refers to the effects imposed on oxidation processes in living systems by the particulate matter (consisting to a large extent of the tar chemicals) and gaseous phase (GP) of the smoke, and their results are rather controversial. In the present work, we examined the effects of the GP and the tar of the smoke on the lipid peroxidation (LPO) and on the structure of different lipid regions in liposomes, which have been prepared from phosphatidylcholine (PC). The LPO development was analyzed in terms of the total unsaturation of lipids (double-bond content, DB) and the formation of dienic conjugates (DC), ketodienes (KD) and malonic dialdehyde (MDA). The average rates (V_av) and the effective rate constants (k) of the spontaneous and initiated LPO processes in liposomes were calculated. Expectedly, the exposure of liposomes to either the GP or the tar led first of all to a significant and very sharp decrease in the DB content. However, the formations of the oxidation products revealed different dynamics: The MDA generation was inhibited, while the DC and the KD formation increased during the first few hours of the LPO development followed by its inhibition. The smoke constituents exhibited the opposite effects on the structure of lipid bilayer of liposomes: GP markedly enhanced the microviscosity of liposomal membranes, whereas the tar caused drastic microviscosity lowering. The reported results disclose for the first time the intricacy of chemical and structural response of liposomal characteristics to the smoke constituents, which is of prime import for harnessing liposomes as experimental model to assess the oxidative impact of the smoke.