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This study was designed to evaluate the effect of ethanol on the peroxidation of human low-density lipoprotein (LDL) initiated by oxygen free radicals (O(2)(.-) and (.)OH in the absence of ethanol; O(2)(.-) and ethanol-derived peroxyl radicals, RO(2)(.), in the presence of ethanol) generated by gamma radiolysis. Initial radiolytic yields as determined by several markers of lipid peroxidation [i.e. decrease in endogenous antioxidants alpha-tocopherol and beta-carotene, formation of conjugated dienes and of thiobarbituric acid-reactive substances (TBARS)] were determined in 3 g liter(-1) LDLs (expressed as total LDL concentration) in the absence of ethanol or its presence at six different concentrations (0.42-17 x 10(-2) mol liter(-1)). Ethanol acted as an antioxidant by decreasing the rate of consumption of LDL endogenous antioxidants and the yields of formation of lipid peroxidation products, and by delaying the onset of the propagation phase for conjugated dienes and TBARS. With regard to the different markers studied, except for alpha-tocopherol and beta-carotene consumption, the effect of ethanol did not appear to be dependent on its concentration. Indeed, (.)OH were scavenged by ethanol at the lowest ethanol concentration (0.42 x 10(-2) mol liter(-1)), leading to RO(2)(.). These RO(2)(.) resulted in lower radiation-induced yields related to endogenous antioxidant consumption or to formation of lipid peroxidation products (for example, approximately 10% of RO(2)(.) oxidized LDLs from TBARS). Thus, under our in vitro conditions, ethanol behaved as an antioxidant when added to the LDL solutions. This should be taken into account in the reported antioxidant activity of wine. This is also of interest when lipophilic compounds have to be added as ethanolic solutions to LDLs to evaluate in vitro their antioxidant activity toward LDL peroxidation.

This study was designed to evaluate the antioxidant effect of aminoguanidine toward human low-density lipoproteins (LDLs) initiated by oxygenated free radicals (*OH/O(2)*-) generated by gamma radiolysis. Initial radiolytic yields related to the markers of lipid peroxidation [i.e. decrease in endogenous alpha-tocopherol and beta-carotene, formation of thiobarbituric acid-reactive substances (TBARS) and conjugated dienes] were determined in 3 g liter(-1) LDLs (expressed as total LDL concentration) in the absence and presence of 10 different concentrations of aminoguanidine (from 0.04 to 5 mmol liter(-1)). Fluorescence and relative electrophoretic mobility of oxidized LDLs were also studied as markers that indirectly reflect the attack of the protein moiety of LDLs (namely apolipoprotein B). Our data clearly showed the inhibitory effect of aminoguanidine on lipid peroxidation induced in LDLs by *OH/O(2)*- in a concentration-dependent manner. This effect probably resulted from a scavenging activity of aminoguanidine toward *OH. In contrast, aminoguanidine did not appear to react significantly with O(2)*-, which resulted in a poor residual lipid peroxidation. Our data led us to determine an optimum [aminoguanidine]/[LDL] ratio ranging from 250 to 500 to obtain the best in vitro protection of LDLs under our experimental conditions. It is also of great interest that aminoguanidine was able to protect endogenous alpha-tocopherol and beta-carotene of LDLs upon *OH/O(2)*(-)-induced oxidation.

Susceptibility of lipoproteins to oxidation is partly determined by their content in endogenous antioxidants, but also by the polyunsaturated fatty acids (PUFA)/monounsaturated fatty acids (MUFA) ratio. The aim of our study was to enrich human high-density lipoproteins (HDLs) with dioleoylphosphatidylcholine (DOPC) in order to modify the PUFA/MUFA ratio while maintainig the alpha-tocopherol/PUFA ratio constant and to appreciate the consequences of this enrichment before and after copper-induced oxidation. The enrichment of HDLs with DOPC was obtained by incubation of these lipoproteins with DOPC liposomes and further reisolation of HDLs. The consequent 40% HDL enrichment in MUFA was concomitant with a 35% loss in PUFA (MUFA/PUFA ratio = 1.43). The enrichment of HDLs with DOPC led to a 40% decrease in alpha-tocopherol content, which kept a constant alpha-tocopherol/PUFA ratio. The DOPC-HDLs exhibited a lower oxidizability by copper than the nonenriched HDLs (NE-HDLs), as shown by their twofold longer lag phase and the threefold lower propagation rate. Moreover, DOPC-HDLs led to a six- to sevenfold lower production of hydroperoxide molecular species from phosphatidylcholine and cholesteryl esters than NE-HDLs after 24 h copper oxidation. With regard to the cholesterol effluxing capacity, copper oxidation of HDLs led to a decrease of this property. However, our results clearly showed that DOPC enrichment of HDLs allowed us to keep a better effluxing capacity than in NE-HDLs after 24 h oxidation (22.3% vs 17.4%, respectively). Since apo A-I was degraded as well in DOPC-HDLs as in NE-HDLs, the better effluxing capacity of DOPC-HDLs could not come from a preserved integrity of apo A-I. It could be partly related to the improved fluidity of oxidized DOPC-HDLs compared to oxidized NE-HDLs, as shown by electron spin resonance data (correlation-relaxation time at 24 degreesC = 2.20 ns vs 3.00 ns after 24 h oxidation, in DOPC-HDLs and in NE-HDLs, respectively). Besides, it could also be hypothesized that the sevenfold lower content of phosphatidylcholine hydroperoxides in DOPC-HDLs than in NE-HDLs after 24 h copper oxidation could be involved in the better ability of oxidized DOPC-HDLs to mobilize cellular cholesterol.

This study was performed to elucidate the mechanism by which adenosine triphosphate (ATP) encapsulated into liposomes was able to protect against experimental brain ischemia in the rat. After intracarotidal administration of liposomally entrapped ATP, the ATP blood level increased dramatically whereas no change was observed after administration of free ATP. This suggested that liposomes may protect ATP from its degradation by endothelial ectonucleotidases. On the other hand, it was observed that after administration of liposomally entrapped carboxyfluorescein (CF) to ischemic rats, the distribution of the brain fluorescence under the form of numerous punctiform structures was completely different from the diffuse fluorescence obtained with free CF injections. These data suggest that under certain hypoxic conditions the blood-brain barrier is open allowing the liposomes to reach the cerebral parenchyma. The mechanism of brain uptake is, however, still unclear: endothelial tight junctions opening or endothelial transcytosis.

The aim of our study was to evaluate the carbonylation and the carbonylated fragmentation of apolipoprotein B upon low-density lipoprotein (LDL) oxidation induced in vitro by copper and OH / O 2 − free radicals generated by γ-radiolysis. Therefore, we developed a very sensitive Western blot immunoassay using 2,4-dinitrophenylhydrazine which allows the revelation of the apolipoprotein B carbonylation and its carbonylated fragmentation. The main results of this study show that (i) apolipoprotein B carboylation is present during the lag phase of LDL oxidation in the two oxidative processes and (ii) apolipoprotein B carbonylated fragmentation was not detected during the lag phase of copper-oxidized LDL but was detected during the propagation phase. By contrast, apolipoprotein B carbonylated fragmentation was detected in the lag phase of OH / O 2 − oxidized LDL.

Adenosine triphosphate (ATP) was proposed in various medical applications, as a possible bioenergetic substrate. Unfortunately, ATP is very difficult to use at a therapeutic level because of its high sensitivity to enzymatic hydrolysis making this molecule unstable in biological fluids. ATP is also a highly hydrophilic molecule that is unable to cross biological membranes. To try to develop a system able to protect ATP against degradation and to efficiently deliver this bioenergetic substrate, its liposomal encapsulation in multilamellar vesicles was carried out. One of the studies described in this paper deals with the efficiency of liposomal ATP in the treatment of cerebral ischemia. Our results show that encapsulation was able to protect ATP from its degradation by ectonucleotidases and that liposomal ATP was active against experimental brain ischemia. The other study deals with the effect of ATP on the motility and the acrosomal reaction of human spermatozoa. The results show that co-incubating ATP-loaded liposomes with sperm cells was able to induce the process of capacitation in vitro and might therefore be a useful tool in the procedure of in vitro fertilization.

The fate of a drug after administration in vivo is determined by a combination of several processes: distribution and elimination when given intravenously and absorption, distribution and elimination when an extravascular route is used. Regardless of the mechanisms involved, each of these processes depends mainly on the physico-chemical properties of the drug and therefore, for the most part, on its chemical structure.

This study was designed to evaluate the antioxidant effect of probucol on peroxidation of low-density lipoproteins (LDLs) initiated by oxygenated free radicals ( O2· -) and ethanol-derived peroxyl radicals ( ${\rm RO}_{2}{}^{\cdot}$ ) generated by ? radiolysis. Initial radiolytic yields related to the markers of lipid peroxidation [i.e. decrease in endogenous ?-tocopherol, formation of thiobarbituric acid-reactive substances (TBARS) and conjugated dienes] were determined as a function of LDL concentration (1.5 and $3\ {\rm g}\ {\rm l}^{-1}$ , expressed as total LDL) and in the absence or the presence of probucol at different concentrations (2.3× 10-6, $3.5\times 10^{-6}$ , 9× 10-6 and $20.5\times 10^{-6}\ {\rm mol}\ {\rm l}^{-1}$ ). Our results showed that probucol was able to decrease not only the yields of TBARS and conjugated dienes but also the levels of these peroxidation products obtained at high doses (2500 Gy) compared ...

The aim of this work was to specify the mechanisms involved in the radical oxidation of human high-density lipoprotein (HDL) and to compare these mechanisms with those described previously for the oxidation of low-density lipoprotein (LDL) under the same experimental conditions (Bonnefont-Rousselot et al., Radiat, Res. 134, 271-282, 1993). The oxidation of HDL, initiated by .OH or .OH/O(.-)2 free radicals from gamma radiolysis of water, was evaluated as a function of increasing radiation dose by analyzing quantitatively the decrease of endogenous alpha-tocopherol and the formation of oxidation products (thiobarbituric acid-reactive substances and conjugated dienes). All qualitative conclusions were supported by quantitative data (radiation yields and concentrations of the oxidation markers at high radiation doses) and by the mechanisms of the kinetics, .OH free radicals in the absence of oxygen were less efficient in initiating HDL oxidation than in the presence of oxygen (action of .OH/O(.-)2 free radicals), which was in agreement with the enhancement of the action of .OH free radicals by oxygen. The remaining significant level of vitamin E in HDLs at high radiation doses in the absence of oxygen could be explained by a regeneration of vitamin E by an oxidation product that was able to reduce the alpha-tocopheroxyl radical. The yields related to the decrease in the vitamin E content of HDLs after exposure to radiation with .OH or .OH/O(.-)2 free radicals were slightly higher than those obtained previously in LDLs under similar experimental conditions. Moreover, in the presence of oxygen, .OH free radicals led to a lower formation of thiobarbituric acid-reactive substances in HDLs than in LDLs. Such discrepancies in the behavior of these two lipoprotein fractions could be related to the differences in the chemical composition of HDLs and LDLs.

The aim of this study was to analyze quantitatively the oxidative modification of low-density lipoproteins (LDLs) induced by OH· free radicals produced by gamma radiolysis, in the absence or in the presence of oxygen (action of OH· free radicals, or simultaneous action of OH· and ${\rm O}_{2}^{\overline{\cdot}}$ free radicals, respectively). The effects of increasing radiation doses on aqueous LDL solutions have been monitored by several parameters: a decrease in endogenous vitamin E, the formation of thiobarbituric acidreactive substances (TBARS) and conjugated dienes, the appearance of a differential fluorescence (excitation wavelength = 360 nm), and an increase in the relative electrophoretic mobility. Initial radiation yields (decrease in vitamin E, formation of TBARS) have been determined at pH 7 as a function of LDL concentration (from 0.75 to 9 g liter-1). From the comparison of these yields with those of OH· and ${\rm O}_{2}^{\overline{\cdot}}$ free radicals produced by water radiolysis, we have d...

This study aimed to analyze quantitatively the initiation and the consequences of low-density lipoprotein (LDL) peroxidation by O2·−/HO2· free radicals produced by gamma radiolysis. The action of i...

The water-soluble immunomodulator muramyldipeptide has been encapsulated in oligolamellar liposomes (mean diameter 200 nm) of various lipid compositions. These liposomes were sterilized by Millipore filtration without loss of entrapped solute and are therefore suitable for i.v. administration. The amount of encapsulated MDP increased when the volume of aqueous phase (containing a given MDP concentration) used for hydrating the phospholipid film increased and this did not vary for at least 15 days when the liposomes were kept at 4°C. The presence of cholesterol did not modify the encapsulation results but prevented the leakage of encapsulated water-soluble solute in serum-containing media. The internalization of various types of liposomes by murine peritoneal macrophages has been studied in order to define the best conditions for activating macrophages. For a given lipid composition, sterile oligolamellar vesicles (suitable for i.v. injection) were more efficient than multilamellar vesicles in rendering macrophages capable of inhibiting the growth of a syngeneic tumor, particularly when these vesicles contained muramyldipeptide in their aqueous space and cholesterol in their lipidic phase.