Effect of chronic ethanol treatment on lipid peroxidation in rat liver homogenate and subcellular fractions

Effect of Lycosome-Formulated Phosphatidylcholine on Parameters of Biological Oxidation after Single Intake of Moderate Amount of Alcohol

Ingestion of a single dose of alcohol, ranging from the intake of a moderate amount alcohol to binge drinking, is the most frequent form of alcohol consumption with poorly understood medical consequences and obscure prophylactics. The study was aimed to determine whether lycosome formulated phosphatidylcholine (PC-Lyc) containing two highly bioavailable antioxidants (PC and lycopene) ingested shortly before the alcohol-containing beverage may alleviate the biochemical markers of liver damage and parameters of biological oxidation associated with the intake of a moderate amount of alcohol. Healthy middle-aged volunteers were requested to consume a moderate amount of alcohol – 0.5 ml/kg or 1.0 ml/kg shortly after ingestion of a capsule containing 450 mg of regular phosphatidylcholine (PC, n=10), PC-Lyc (n=10), or placebo pill (PP, n=10). Serum levels of ethanol (EtOH), acetaldehyde (AA), liver-specific enzymes, total antioxidant capacity of serum (TAC), oxidized LDL (LDL-Px), and malonic dialdehyde (MDA) were measured at 1, 2.5, and 5 hours after dosing with alcohol. Ingestion of PC regardless of the formulation used had no effect on serum EtOH concentration dynamics. However, volunteers supplemented with PC-Lyc showed a better clearance of AA in serum as compared to other groups. There was a reduction in serum TAC values by 18.5% and 16.1% in both placebo groups ingesting 0.5 and 1.0 ml/kg of alcohol, respectively, at the end of observational period. This decline was preventable by supplementation of volunteers with PC and especially with PC-Lyc. Moreover, PC-Lyc promoted a reduction of serum MDA and reversed an increase in serum LDL-Px. In addition, ingestion of alcohol at 1.0 ml/kg dose caused a transient increase in serum alanine-aminotransferase activity which was abolished by both formulations of PC. Therefore, combinatory lycosomal formulation of PC and lycopene may prevent some metabolic abnormalities associated with single intake of moderate amount of alcohol. This trial is registered with ACTRN12617001335381.

Some basic properties of ascorbate-dependent antioxidative-defence factors from rat liver cytosol

Properties of the ascorbate-dependent antioxidative-defence factors from rat liver cytosol (Antonenkov and Sies, 1992, Biol. Chem. Hoppe-Seyler 373, 1111-1116) were investigated. The factors are assayed by their capacity to inhibit Fe/ADP-ascorbate (nonenzymatic) lipid peroxidation. Ammonium sulfate fractionation and gel-filtration of the dialysed cytosol on Sephadex G-200 or Sephacryl S-400 led to the separation of factors A and B, with approximate molecular masses of > 400 kDa and 60 kDa, respectively. After fractionation of cytosol, factors A and B required the presence of the thiol- reducing agent, dithioerythritol, for their activity; factor B more so than factor A. Inhibiting activity of factor B is displayed at higher ascorbate concentrations than that of factor A. Increasing the ionic strength strongly stimulated the inhibitory capacity of factor A, but only slightly that of factor B. Differences were observed in pH-dependence, though both factors were more active in neutral media (pH 6.2-6.8). Factors A and B had different time-courses of inhibition of TBARS formation and suppression of chemiluminescence intensity. Factor B was more stable in the course of thermal treatment. Repeated freezing and thawing did not affect the activity of both factors. However, factor A could be inactivated by ultrasonic treatment, whereas factor B was unaffected. A function of these factors could be to create more favourable conditions for the interaction of ascorbate as a very hydrophilic molecule with membrane-bound hydrophobic radicals.

Increase in cellular pool of low-molecular-weight iron during ethanol metabolism in rat hepatocyte cultures. Relationship with lipid peroxidation

Ethanol-induced lipid peroxidation was studied in primary rat hepatocyte cultures supplemented with ethanol at the concentration of 50 mM. Lipid peroxidation was assessed by two indices: (1) conjugated dienes by second-derivative UV spectroscopy in lipid extract of hepatocytes (intracellular content), and (2) free malondialdehyde (MDA) by HPLC-UV detection and quantitation for the incubation medium (extracellular content). In cultures supplemented with ethanol, free MDA increased significantly in culture media, whereas no elevation of conjugated diene level was observed in the corresponding hepatocytes. The cellular pool of low-mol-wt (LMW) iron was also evaluated in the hepatocytes using an electron spin resonance procedure. An early increase of intracellular LMW iron (< or = 1 hr) was observed in ethanol-supplemented cultures; it was inhibited by 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, whereas alpha-tocopherol, which prevented lipid peroxidation, did not inhibit the increase of LMW iron. Therefore, the LMW iron elevation was the result of ethanol metabolism and was not secondarily induced by lipid hydroperoxides. Thus, ethanol caused lipid peroxidation in rat hepatocytes as shown by the increase of free MDA, although no conjugated diene elevation was detected. During ethanol metabolism, an increase in cellular LMW iron was observed that could enhance conjugated diene degradation.

The effect of heparegen on antioxidant enzyme activities in ethanol-induced liver injury in rats

SOD, CAT, GSH-Px, and sulfhydryl compounds MDA contents in liver of rats treated with heparegen for 7, 14, and 21 days after alcoholic liver injury have been investigated. After use of this drug, we found beneficial effects on GSH-Px activity, sulfhydryl compounds (total and nonprotein), and MDA content and a partially beneficial effect on SOD and CAT activities. These enzyme activities after 21 days of drug administration were restored. Furthermore, heparegen shortens the time necessary for the return of AIAT and GGTP to normal value. This enzymatic data are supported by histological studies in light microscopy.

On the role of rat liver cytosol in suppression of low-level chemiluminescence during nonenzymatic lipid peroxidation

1. The effect of normal rat liver cytosol on the level of Fe/ADP-ascorbate-induced lipid peroxidation in the total particulate fraction (mitochondria plus microsomes) has been studied. The intensity of lipid peroxidation was measured using chemiluminescence technique and malondialdehyde (MDA) formation. 2. Dialysed cytosol significantly decreased the level of chemiluminescence, and to a much lesser extent, the rate of MDA production. 3. Gel filtration on a Sephadex G-200 column led to appearance of at least three cytosolic fractions which suppressed the low-level chemiluminescence. 4. The discovered components differed from each other by their molecular masses, kinetics of chemiluminescence inhibition and effects on intensity of MDA formation. 5. The putative functional role of antioxidative defence factors from rat liver cytosol is discussed.

Effect of chronic ethanol treatment on the t-butyl hydroperoxide-dependent lipid peroxidation in rat liver

1. The effect of chronic ethanol consumption on the level of the t-butyl hydroperoxide (Bu'OOH)-induced lipid peroxidation in rat liver homogenate and subcellular fractions was measured using chemiluminescence technique and malondialdehyde formation. 2. It was shown that under the action of ethanol the rate of lipid peroxidation was decreased in the whole and "postnuclear" liver homogenates. 3. Ethanol significantly decreased the intensity of lipid peroxidation in microsomes, but did not affect the Bu'OOH-dependent process in mitochondria. 4. The level of lipid peroxidation was reduced after incubation of the total particulate fraction (mitochondria plus microsomes) with the undialysed cytosol from ethanol-treated rat liver. Dialysis of the cytosol prevented depressive effect of ethanol treatment on lipid peroxidation. 5. Reduced glutathione (0.1-1.0 mM) was shown to decrease the rate of lipid peroxidation in rat liver microsomes, but did not affect its level in mitochondria. 6. Pyrazole injections to rats reduced and phenobarbital treatment increased the level of the Bu'OOH-dependent lipid peroxidation in liver microsomes. 7. The data obtained indicate that the Bu'OOH-dependent lipid peroxidation is not an appropriate marker of the ethanol-induced oxidative stress in rat liver cells.