Chronic ethanol ingestion modifies liver microsomal phosphatidylserine inducing resistance to hydrolysis by exogenous phospholipase A2

Chronic and acute ethanol treatment modifies fluidity and composition in plasma membranes of a human hepatic cell line (WRL-68)

The aim of this study was to compare the effects of chronic (0.1 mol/L ethanol exposure during 30 days) and acute (0.5 mol/L ethanol exposure during 24 h) ethanol treatment on the physical properties and the lipid composition of plasma membranes of the WRL-68 cells (fetal human hepatic cell line). Using fluorescence polarization we found that ethanol treatment reduced membrane anisotropy due to disorganization of acyl chains in plasma membranes and consequently increased fluidity, as measured with the diphenylhexatriene probe. Addition of ethanol in vitro reduced anisotropy in control plasma membranes, whereas chronically ethanol-treated plasma membranes were relatively tolerant to the in vitro addition of ethanol. Acutely ethanol-treated plasma membranes exhibited a smaller anisotropy parameter value than control plasma membranes. We found a decrease in total phospholipid content in acute ethanol WRL-68 plasma membranes. Cholesterol content was increased in both ethanol treatments, and we also found a significant decrease in phosphatidylinositol and phosphatidylcholine and an increase in phosphatidylethanolamine content in ethanol-treated plasma membranes. Our data showed that ethanol treatment decreased the anisotropy parameter consistently with increased fluidity, while increasing the cholesterol/phospholipid ratio of plasma membranes of WRL-68 cells, but only chronically ethanol-treated plasma membranes exhibited tolerance to the in vitro addition of ethanol. It is important to note that some changes that were interpreted as a result of chronic ethanol treatment were also present in short-period ethanol treatments.

Changes in cytochromes P-450, 2E1, 2B1, and 4A, and phospholipases A and C in the intragastric feeding rat model for alcoholic liver disease: relationship to dietary fats and pathologic liver injury

The influence of dietary fat and alcohol on hepatic microsomal levels of cytochromes P-450 2E1, 2B, and 4A; phospholipases A and C; and UDP-glucuronosyltransferase was studied in the intragastric feeding rat model for alcoholic liver injury. Eight groups of animals were evaluated. Control and ethanol fed rats received either saturated fat or corn oil and were killed after 2 weeks and 1 month of feeding. All animals were pair-fed by continuous infusion of liquid diet through permanently implanted gastric cannulas. Alcoholic liver injury developed only in the corn oil-ethanol-fed groups and was manifest by 1 month. Livers were subjected to the following analyses: pathologic evaluation of liver injury; levels of cytochromes P-450 2E1, 2B, and 4A protein and mRNA; aniline hydroxylase activity; and phospholipase A and C and UDP-glucuronosyltransferase activities. Ethanol-induced increases in cytochromes P-450 2E1 and 2B protein determined by Western blotting were greatest in the corn oil-ethanol-fed group, which developed pathologic changes in the liver. Cytochromes P-450 2E1 and 2B1 mRNA levels were unaffected, suggesting that posttranscriptional mechanisms are responsible for the increase in the corresponding P-450 proteins. In contrast, cytochrome P-450 4A levels were higher in the saturated fat-ethanol groups compared with the corn oil-ethanol groups. Phospholipase A and phospholipase C levels were higher in the corn oil-ethanol groups compared with pair-fed dextrose controls and the saturated fat-ethanol groups. UDP-glucuronosyltransferase levels declined with time in the ethanol-fed groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Liver microsomal fatty acid composition in ethanol-fed rats: effect of different dietary fats and relationship to liver injury

The rat intragastric feeding model for alcoholic liver disease was used to study the effect of different diets on the fatty acid composition of liver microsomes. Rats were fed corn oil and ethanol (CE), saturated fat and ethanol (SF+E) or corn oil and dextrose (CD) for either 2 or 4 weeks. Rats were also fed saturated and dextrose (SF+D) for 4 weeks. In comparison with the CD diet, lower levels of arachidonic acid were detected in rats fed the CE, SF+E, and SF+D diets. However, the diet-induced changes in levels of arachidonic acid varied as a function of length of feeding. In rats fed the CE diet, we detected a significant decrease in the level of arachidonic acid compared with CD animals. Conversely, in rats fed the SF+E diet, the level of arachidonic acid increased compared with the SF+D group. In addition, a significant correlation was noted between levels of oleic acid and arachidonic acid in both corn oil (r = -0.85, p < 0.01) and saturated fat (r = -0.76, p < 0.05) groups. However, the changes in levels of arachidonic acid and oleic acid were in opposite directions in the two groups. Levels of docosahexaenoic acid decreased between the 2 and 4 weeks in animals maintained on the CE diet. Levels of stearic acid increased between 2 and 4 weeks in rats fed the SF+E diet. The lowest level of linoleic acid was detected in the SF+D and SF+E groups, but levels of linoleic acid remained constant in all groups throughout the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic ethanol intoxication induces adaptive changes at the membrane protein/lipid interface

Modifications were found to occur at the membrane protein/lipid interface of liver microsomes in animals that had been subjected to chronic ethanol ingestion. The effects were revealed by probing this region with 1,6-diphenyl-1,3,5-hexatriene (DPH), trimethylammonium-DPH (TMA-DPH) and DPH attached to the sn-2 chain of phosphatidylcholine (1-palmitoyl-2-[[2-[4-(6-phenyl-trans-1,3,5-hexatrienyl) phenyl]ethyl]carbonyl]-3-sn-phosphatidylcholine, DPH-PC). In intact membranes, it was found that the decay of the excited state was heterogeneous, this being modeled by fitting the data to a fluorescence lifetime distribution. The full-width of the distribution at half-maximum, which relates to the degree of excited state environmental heterogeneity, increased for each fluorophore, as a result of chronic ethanol treatment. For TMA-DPH and DPH the excited state heterogeneity could have arisen from, (i) the protein/lipid interface and (ii) varied degrees of water penetration into the lipid, due to the ability of these fluorophores to sample along the bilayer normal. By contrast, the DPH in DPH-PC, due to its tethering, was only able to sample the heterogeneity at the protein/lipid interface, as confirmed by a homogeneous decay in vesicles of microsomal lipid extracts. The increased degree of DPH-PC fluorescence decay heterogeneity in microsomes from chronic ethanol-treated animals as compared to controls, was found to persist in vesicles of extracted lipids, when apocytochrome C was included in the vesicle preparations as a model protein. This effectively eliminated a protein modification from being responsible and indicated that a chronic-ethanol induced alteration in the lipids was being expressed in the form of a physico-chemical modification at the protein/lipid interface. The degree of DPH-PC environmental heterogeneity was also directly increased by ethanol, however, membranes from chronic ethanol-treated animals were resistant to this effect, showing that the phenomenon of 'membrane tolerance' extends to the membrane protein/lipid interface.