Polyenylphosphatidylcholine opposes the increase of cytochrome P-4502E1 by ethanol and corrects its iron-induced decrease

Dietary iron overload damages membrane phospholipids and decreases microsomal cytochromes P-450. We wondered whether this might also pertain to cytochrome P-4502El (2E1) and whether polyenyiphosphatidylcholine (PPC), a 94-96% pure mixture of linoleate-rich polyunsaturated phosphatidylcholines that protects against alcohol-induced liver injury, also affects 2E1, either in the presence or absence of iron. Accordingly, rats were fed for 8 weeks our standard liquid diet containing ethanol (36% of energy) or isocaloric carbohydrates, with either PPC (3 g/1000 Cal) or equivalent amounts of linoleate (as safflower oil). 2E1 was assessed by Westem blots and by two of its characteristic enzyme activities: the microsomal ethanol oxidizing system (MEOS), evaluated by the conversion of ethanol to acetaldehyde (determined by head space GC), and p-nitrophenolhydroxylase (PNP) activity, measured by HPLC with W detection of 4nitrocatechol. With ethanol (36% of energy) replacing carbohydrates, 2E1 content increased 10-fold, with a corresponding increase in PNP and MEOS activities, but when carbonyl iron (5 g/1000 Cal) was added, the induction was significantly reduced. This iron-induced decrease was corrected by PPC. PPC is rich in linoleate, but when the latter was given as triglycerides (safflower oil), there was no effect, whereas hepatic nonheme iron content was the same in both these groups. It also was found that in the absence of iron, the ethanol-mediated induction of 2E1 and its corresponding enzyme activities were significantly less with PPC ( p < 0.001) than with safflower oil. In addition, in alcohol-fed animals, PPC decreased the oxidative stress (as determined by F₂-isoprostanes), which reflects yet another hepatoprotective effect of PPC.     

Influence of sex hormonal status on alcohol-induced oxidative injury in male and female rat liver

BACKGROUND: Oxidative stress contributes to the development of liver injury after chronic alcohol intake. Women exhibit greater sensitivity to alcohol-induced liver disease than do men. The aim of the study was to determine the relationship between the sex hormone status of male and female rats and the degree of alcohol-induced oxidative stress in the liver. METHODS: Male and female rats were pair-fed a liquid diet that contained 36% of their total daily calories as ethanol (EtOH group) or maltose (control group). Blood and liver samples were collected at the end of 8 weeks of diet. RESULTS: Male EtOH rats experienced a reduction in plasma testosterone (T) and an increase in estradiol (E2) levels, with an increase in their calculated E2/T ratio with respect to their controls. Malonaldehyde (MDA) levels, an index of lipid peroxidation, and protein carbonyl content, an index of protein oxidation, in the liver were greater among the EtOH groups in females than in males. In males, an inverse correlation was found between hepatic MDA and circulating T levels, and a direct correlation was disclosed between MDA and estradiol levels. In addition, the hepatic histopathological score correlated inversely with the plasma T levels and directly with the calculated E2/T ratio, an index of feminization. CONCLUSIONS: Alcohol-induced oxidative injury, which contributes to hepatic injury in both male and female rats, is enhanced in females compared with males. A role for plasma T levels in protecting male rat liver from ethanol-induced oxidative injury can be hypothesized.     

L-Buthionine (S,R) sulfoximine depletes hepatic glutathione but protects against ethanol-induced liver injury

BACKGROUND: L-Buthionine (S,R) sulfoximine (BSO) is an inhibitor of glutathione biosynthesis and has been used as an effective means of depleting glutathione from cells and tissues. Here we investigated whether treatment with BSO enhanced ethanol-induced liver injury in mice. METHODS: Female C57Bl/6 mice were pair fed with control and ethanol-containing liquid diets in which ethanol was 29.2% of total calories. During the final 7 days of pair feeding, groups of control-fed and ethanol-fed mice were given 0, 5 or 7.6 mM BSO in the liquid diets. RESULTS: Compared with controls, ethanol given alone decreased total liver glutathione. This effect was exacerbated in mice given ethanol with 7.6 mM BSO, causing a 72% decline in hepatic glutathione. While ethanol alone caused no decrease in mitochondrial glutathione, inclusion of 7.6 mM BSO caused a 2-fold decline compared with untreated controls. L-Buthionine (S,R) sulfoximine did not affect ethanol consumption, but serum ethanol levels in BSO-treated mice were nearly 6-fold lower than in mice given ethanol alone. The latter decline in serum ethanol was associated with a significant elevation in the specific activities of cytochrome P450 2E1 and alcohol dehydrogenase in livers of BSO-treated animals. Ethanol consumption caused a 3.5-fold elevation in serum alanine aminotransferase levels but the enzyme fell to control levels when BSO was included in the diet. L-Buthionine (S,R) sulfoximine administration also attenuated ethanol-induced steatosis, prevented the leakage of lysosomal cathepsins into the cytosol, and prevented the ethanol-elicited decline in proteasome activity. CONCLUSIONS: L-Buthionine (S,R) sulfoximine, administered with ethanol, significantly depleted hepatic glutathione, compared with controls. However, despite the decrease in hepatic antioxidant levels, liver injury by ethanol was alleviated, due, in part, to a BSO-elicited acceleration of ethanol metabolism.     

The role of oxidative stress in NASH and fatty liver model.

The aim of this study was to investigate whether oxidative stress is related to the development of liver injury and an iron chelator, deferoxamine (DFO) can prevent lipid peroxidation resulting in reduced liver injury as well as reduce preneoplastic lesions induced by a choline-deficient l-amino acid-defined (CDAA) diet. CDAA diet administration resulted in an increased serum ALT level after one week. Hepatocytes in rat liver fed a CDAA diet showed malondialdehyde (MDA) accumulation. But simultaneous DFO treatment for one week reduced this elevation of ALT as well as MDA accumulation in the liver. Feeding rats a CDAA diet for 14 weeks led to the development of severe liver fibrosis and preneoplastic lesions detected as enzyme-altered lesions. DFO treatment also prevented the expression of activated stellate cells, resulting in the reduction of liver fibrosis as well as reducing the development of preneoplastic lesions. These results indicate that iron chelation can reduce the development of preneoplastic lesions in a CDAA diet model.     

Glutamine is highly effective in preventing in vivo cobalt-induced oxidative stress in rat liver

AIM: To evaluate the in vivo effect of glutamine on cobalt-generated oxidative stress and (HO-1) induction in rat liver. METHODS: Fasted female Wistar rats received a single injection of cobalt chloride (375 μmol/kg body weight) and then were killed at different times. Lipid peroxidation and soluble and enzymatic antioxidant defense system (reduced glutathione (GSH), catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD)) were measured in liver homogenates. Ferritin and ferritin iron contents as well as heme oxygenase-1 (HO-1) activity and expression were also determined. The antioxidant properties of glutamine (GIn) were also evaluated. RESULTS: Cobalt chloride increased lipid peroxidation (50% over control values) 1 h after treatment. GSH reached a minimum at 3 h (40%) increasing thereafter. Twelve hours after CoCl2 injection, the antioxidant enzymes CAT, GSH-Px and SOD also diminished by about 30%. Heme oxygenase-1 induction was observed 6 h after treatment reaching a maximum value of 14-fold over the controls, 12 h after cobalt treatment. A 1.7-fold increase in ferritin and ferritin-bound iron 24 h after treatment were also obtained. Administration of glutamine (300 mg/kg body weight) by gavage 24 h before CoCl2 treatment entirely prevented the increase in thiobarbituric acid reactive substances (TBARS) content, the decrease in GSH levels, and partially reverted heme oxygenase-1 induction. CONCLUSION: These results suggested that a natural product such as glutamine prevents glutathione depletion and consequently heme oxygenase induction.     

Effects of alcohol and oxidative stress on liver pathology: the role of the mitochondrion

This article represents the proceedings of a symposium at the 2001 Research Society on Alcoholism meeting in Montreal, Canada. The chairs were Alan Cahill and Carol C. Cunningham. The presentations were (1) Mitochondrial regulation of ethanol-induced hepatocyte apoptosis: possible involvement of proapoptotic Bcl-2 family protein Bax, by Masayuki Adachi and Hiromasa Ishii; (2) Effects of ethanol on mitochondrial reactive oxygen species production and oxidative protein modification, by Shannon M. Bailey; (3) Acute ethanol binges elicit widespread oxidative mitochondrial DNA damage and depletion: protective effects of antioxidants and inhibitors of ethanol metabolism, by Bernard Fromenty; and (4) Effects of chronic ethanol consumption upon hepatic mtDNA oxidative modification and depletion, by Alan Cahill and Adrian Davies.     

脉络宁抑制氧化应激保护缺血性脑损伤

目的 探讨脉络宁对氧化应激和缺血性脑损伤的影响.方法 健康雄性昆明小鼠126只,分为假手术组(n=18)、生理盐水对照组(n=54)和脉络宁组(n=54).建立大脑中动脉闭塞(middle cerebral artery occlusion,MCAO)模型,脉络宁组和生理盐水对照组MCAO 2 h后分别经尾静脉给予脉络宁注射液和同体积生理盐水,然后每隔24 h重复1次.在MCAO 12、24和72 h分别进行神经功能评分、脑水含量、梗死体积、膜电位以及蛋白质氧化应激代谢产物3-硝基酪氨酸(3-nitrotyrosine,3-NT)、脂质氧化应激代谢产物4-羟基壬烯醛(4-hydroxy-2-nonenal,HNE)和核酸氧化应激代谢产物8-羟基脱氧鸟苷(8-hydroxy-2'-deoxyguanosine,8-OHdG)检测.结果 在脑缺血后不同时间点,脉络宁注射液均可显著改善脑缺血小鼠的神经功能、减轻脑水肿和缩小梗死体积,其中以72 h最为显著;脉络宁注射液可逆转脑皮质和内囊区的线粒体膜电位降低,显著下调缺血后皮质、内囊和血清3-NT、HEN 和8-OHdG的升高,其中以降低HNE效果最为显著.结论 脉络宁注射液能有效保护小鼠缺血性脑损伤,其机制与抑制氧化应激,尤其是抗脂质氧化有关.     

Increased oxidative DNA damage in patients with alcohol dependence and its correlation with alcohol withdrawal severity

Background: Chronic and excessive alcohol consumption enhances the formation of reactive oxygen species (ROS) and ethanol‐derived free radicals. 8‐Hydroxy‐2′‐deoxyguanosine (8‐OHdG) is a marker to estimate ROS‐induced DNA damage. The study objective was to compare serum 8‐OHdG levels between patients with alcohol dependence and healthy controls and to investigate the correlation between this marker and the severity of alcohol withdrawal syndrome (AWS). Methods: We recruited 79 patients with alcohol dependence and 63 healthy control subjects. The severity of AWS was evaluated using the Chinese version of the revised Clinical Institute Withdrawal Assessment for Alcohol Scale (CIWA‐Ar‐C) every 8 hours. Levels of 8‐OHdG, malondialdehyde (MDA), and other biologic indexes were assayed at baseline for patient and control groups, and after 1‐week detoxification for the patient group. Results: The 8‐OHdG and MDA levels in the alcoholic group were significantly higher than those in the control group (0.34 vs. 0.27 ng/ml and 13.5 vs. 10.1 μM, respectively). Both 8‐OHdG and MDA were significantly correlated with the highest CIWA‐Ar‐C (correlation coefficient = 0.39, p < 0.001 and 0.26, p = 0.02, respectively). In linear regression analysis, only 8‐OHdG level was significantly correlated with the highest CIWA‐Ar, but not MDA level (regression coefficient beta = 0.33, p = 0.003 and 0.17, p = 0.12, respectively). MDA, but not 8‐OHdG levels, significantly decreased after 1 week of detoxification. Conclusions: These results indicate that our alcohol‐dependent individuals are vulnerable to excessive production of free radicals. Notably, the oxidative DNA damage persisted after 1‐week detoxification. The AWS severity was correlated with the increase in oxidative stress, particularly the 8‐OHdG levels. The impact of sustained abstinence in alcoholic patients needs to be investigated in future studies.     

Silymarin protects against acute ethanol-induced hepatotoxicity in mice

BACKGROUND: Accumulated evidence has demonstrated that both oxidative stress and abnormal cytokine production, especially tumor necrosis factor-alpha (TNF), play important etiological roles in the pathogenesis of alcoholic liver disease (ALD). Agents that have both antioxidant and anti-inflammation properties, particularly anti-TNF production, represent promising therapeutic interventions for ALD. We investigated the effects and the possible mechanism(s) of silymarin on liver injury induced by acute ethanol (EtOH) administration. METHODS: Nine-week-old mice were divided into 4 groups, control, silymarin treatment, EtOH treatment, and silymarin/EtOH treatment, with 6 mice in each group. Because control and silymarin values were virtually identical, only control treatment is shown for ease of viewing. Ethanol-treated mice received EtOH [5 g/kg body weight (BW)] by gavage every 12 hours for a total of 3 doses. Control mice received an isocalorical maltose solution. In the silymarin/EtOH group, silymarin was dissolved in the EtOH and gavaged simultaneously with EtOH at a dose of 200 mg/kg BW. At 4 hours after the last dosing, the mice were anesthetized and subsequent serum alanine aminotransferase (ALT) level, hepatic lipid peroxidation, enzymatic activity of hepatic cytochrome P450 2E1, hepatic TNF-alpha, and glutathione (GSH) levels were measured. Histopathological change was assessed by hematoxylin and eosin staining. RESULTS: Acute EtOH administration caused prominent hepatic microvesicular steatosis with mild necrosis and an elevation of serum ALT activity, induced a significant decrease in hepatic GSH in conjunction with enhanced lipid peroxidation, and increased hepatic TNF production. Supplementation with a standardized silymarin attenuated these adverse changes induced by acute EtOH administration. CONCLUSIONS: Silymarin protects against the liver injury caused by acute EtOH administration. In view of its nontoxic nature, it may be developed as an effective therapeutic agent for alcohol-induced liver disease by its antioxidative stress and anti-inflammatory features.     

Ubiquitin-proteasome system and oxidative stress in liver transplantation

A major issue in organ transplantation is the development of a protocol that can preserve organs under optimal conditions. Damage to organs is commonly a consequence of flow deprivation and oxygen starvation following the restoration of blood flow and reoxygenation. This is known as ischemia-reperfusion injury(IRI): a complex multifactorial process that causes cell damage. While the oxygen deprivation due to ischemia depletes cell energy, subsequent tissue oxygenation due to reperfusion induces many cascades, from reactive oxygen species production to apoptosis initiation. Autophagy has also been identified in the pathogenesis of IRI, although such alterations and their subsequent functional significance are controversial. Moreover, proteasome activation may be a relevant pathophysiological mechanism. Different strategies have been adopted to limit IRI damage, including the supplementation of commercial preservation media with pharmacological agents or additives. In this review, we focus on novel strategies related to the ubiquitin proteasome system and oxidative stress inhibition, which have been used to minimize damage in liver transplantation.     

A voluntary oral ethanol-feeding rat model associated with necroinflammatory liver injury

Background: The intragastric (IG) ethanol infusion model results in fatty liver, necrosis, inflammation and fibrosis. This model was utilized to study the pathogenesis of alcoholic liver disease (ALD). Disadvantages of the IG model include maintenance of the animals and equipment expense. To develop a voluntary feeding model for ALD, we took advantage of two important observations in the IG model: (i) female rats demonstrate greater severity of alcohol‐induced liver injury than males and (ii) rats fed fish oil as a source of fatty acids develop more severe alcoholic liver injury than rats fed other fatty acids with ethanol. Methods: Female Wistar rats (205 to 220 g) were fed for 8 weeks a diet containing 8% ethanol, fish oil (30% of calories), protein, and dextrose. Pair‐fed controls (FD) received dextrose in amounts isocaloric to ethanol. The following measurements were made: liver pathology [fatty liver (0 to 4), necrosis, inflammation and fibrosis by Sirius Red], endotoxin and alanine aminotransferase (ALT) in plasma, urine ethanol, lipid peroxidation, nuclear factor kappa‐B (NF‐κB) and mRNA levels for tumor necrosis factor‐alpha (TNF‐α), cyclooxygenase‐2 (COX‐2), and inducible nitric oxide synthase (iNOS). Protein levels for iNOS and nitrotyrosine were evaluated by immunohistochemistry and Western Blot analysis. Liver proteasome and cytochrome P450 2E1 activity and protein levels of asialoglycoprotein receptor (ASGPR) were also evaluated. In addition, mRNA levels of fibrogenic markers were assessed. Results: All animals lost weight for the initial 2 to 3 weeks but then gained weight until killing at 8 weeks. There was, however, a significant difference (p < 0.05) in weight between the ethanol‐fed (Etoh) and (FD) groups at the end of the experiment. The mean urine ethanol levels ranged between 190 and 240 mg/dl. The severity of pathological changes was greater (p < 0.01) in Etoh vs. FD: fatty liver, 3.0 ± 1.2 vs. 1.2 ± 0.4; necrosis (foci/mm²), 3.9 ± 2.3 vs. 0.4 ± 0.3; inflammation (cells/mm²), 19.0 ± 6.3 vs. 1.8 ± 0.6. Centrilobular collagen deposition (% area), assessed by Sirius Red staining, was greater in Etoh vs. FD. Levels of endotoxin, ALT, CYP2E1 and lipid peroxidation markers were also higher (p < 0.01) in Etoh vs. FD. Levels of NF‐κB and mRNA of pro‐inflammatory mediators (TNF‐α, COX‐2, iNOS) and procollagen‐I were increased (p < 0.05) in ethanol‐fed rats. Immunohistochemical analysis showed more intense staining for both iNOS and nitrotyrosine in the centrilobular areas in the Etoh vs. FD groups. The greater area of positive staining for iNOS and nitrotyrosine in Etoh vs. FD was confirmed by Western Blot analysis. An increase in the expression of mRNA for profibrogenic genes (p < 0.05) was seen in ethanol‐fed rats. Conclusions: A voluntary feeding regimen consisting of fish oil and ethanol in female rats is technically less demanding yet produces pathological and biochemical changes similar to those observed with the IG model. Pathological changes include fatty liver, necrosis and inflammation. Increased NF‐κB and mRNA and protein levels of the pro‐inflammatory mediators TNF‐α, COX‐2 and iNOS, coincided with the presence of necroinflammatory changes. The voluntary feeding regimen is proposed as an alternative to the IG model in the study of alcoholic liver injury.     

Management of alcoholic liver disease: an update

Treatment of alcoholic liver disease is for the most part based on the stage of the disease and the pathogenic event that is being targeted. The primary treatment modalities that are considered in the treatment of alcoholic liver disease include abstinence, agents that suppress inflammation, anticytokine therapy, nutritional support, modifiers of alcohol metabolism, anti-oxidants, and inhibitors of hepatic fibrosis. Future therapeutic options include exploration of new pathways such as the patatin-like phospholipase domain containing 3 protein (PNPLA-3).     

Sub-lethal oxidative stress triggers the protective effects of ischemic preconditioning in the mouse liver

BACKGROUND/AIMS: While ischemic preconditioning confers significant protection against subsequent prolonged periods of ischemia, the mechanisms triggering protection remain speculative. We hypothesize that a sub-lethal oxidative stress during ischemic preconditioning induces defense mechanisms preventing subsequent lethal injury. METHODS: We used mouse models of partial and total hepatic ischemia for 75 min. Ischemic preconditioning consisted of 10-min ischemia and 15-min reperfusion prior to the prolonged ischemic insult. RESULTS: Tissue levels of peroxides increased about three times after 10 min of ischemia and normalized within 15 min of reperfusion. This limited oxidative stress during ischemic preconditioning prevented the negative effects of subsequent prolonged ischemia as assessed by AST-levels, TUNEL-staining of hepatocytes and animal survival. N-Acetylcysteine inhibited the mild oxidative burst of ischemic preconditioning, and fully reversed the protective effects of preconditioning. The protective role of a sub-lethal oxidative stress was supported by the benefit of delivery of an H2O2-analog through the portal vein prior to a long ischemic insult. This challenge conferred similar protection as ischemic preconditioning. CONCLUSIONS: We conclude that the mild burst of oxidative stress generated during ischemic preconditioning triggers protective mechanisms against subsequent, otherwise lethal, ischemic injury. The pathway possibly includes enhancement of natural anti-oxidative stress mechanisms.     

Role of the diet as a link between oxidative stress and liver diseases

Oxidative stress is caused by an imbalance between the production of reactive oxygen(free radicals) and the body’s ability(antioxidant capacity) to readily detoxify the reactive intermediates or easily repair the resulting damage. An adequate diet, characterized by daily intake of foods associated with improvementsin the total antioxidant capacity of individuals and reduced incidence of diseases related to oxidation, can modulate the degree of oxidative stress. In fact, dietderived micronutrients may be direct antioxidants, or are components of antioxidant enzymes, leading to improvement of some indicators of hepatic function. However, although their increased dietary intake might be beneficial, literature data are still controversial. This review summarizes what is known about the effects of diet nutrients on oxidative stress, inflammation and liver function. Moreover, we have analyzed:(1) the main nutritional components involved in the production and/or removal of free radicals; and(2) the role of free radicals in the pathogenesis of several hepatic diseases and related comorbidities.     

Rosuvastatin protects against oxidative stress and DNA damage in vitro via upregulation of glutathione synthesis

Statins, inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, exert various beneficial effects independent of serum cholesterol reduction; among others is antioxidative action. Human promyelocytic cells (HL-60) were used to examine the effect of the statin rosuvastatin on reactive oxygen species-induced DNA damage, formation of oxidative stress and expression of glutathione metabolising enzymes.Rosuvastatin from 10 nM significantly reduced DNA damage induced by phorbol 12-myristate 13-acetate (PMA) or by hydrogen peroxide, as assessed by the comet assay. PMA-provoked formation of reactive oxygen species, measured by flow cytometric measurement, was also prevented by rosuvastatin. Pre-incubation of cells with rosuvastatin revealed a protective effect of the statin even after its removal from the incubation medium. Total glutathione in cells treated with PMA, with and without co-incubation with rosuvastatin, was increased significantly in cells incubated with rosuvastatin alone. The quantification of the mRNA and activity of glutathione synthesizing enzymes by PCR showed a significant upregulation of γ-glutamylcysteine synthetase.In conclusion, rosuvastatin exerts antioxidative effects, which are also capable of preventing DNA damage. These effects seem to be independent of HMG-CoA reductase inhibition and involve the induction of the expression of antioxidant defense enzymes.     

Protective effect of alcohol consumption for fatty liver but not metabolic syndrome

AIM:To investigate the effect of alcohol on the metabolic syndrome (MS) and fatty liver in Japanese men and women.METHODS:A cross-sectional study was conducted in a medical health checkup program at a general hospital.This study involved 18 571 Japanese men and women,18-88 years of age,with a mean body mass index of 22.6 kg/m 2.A standardized questionnaire was administered.The total amount of alcohol consumed per week was calculated,and categorized into four grades.Fatty liver was examined by ultrasound modified criteria of the revised National Cholesterol Educa-tion Program Adult Treatment Panel Ⅲ and the new International Diabetes Federation.RESULTS:The prevalence of fatty liver decreased in men and women with light to moderate alcohol consumption,whereas the prevalence of MS was not so changed.The prevalence of fatty liver of any grade in men was lower than that in those with no or minimal alcohol consumption.In women with light to moderate alcohol consumption,prevalence of fatty liver was lower than that in women with no or minimal alcohol consumption.By logistic regression analysis,the odds ratio (OR) for MS in women with light alcohol consumption was decreased to 1.0,but this change was not clear in men.The OR for fatty liver was clearly 1.0 in men with any level of alcohol consumption and in women with light to moderate consumption.CONCLUSION:Light to moderate alcohol consumption has a favorable effect for fatty liver,but not for MS in Japanese men and women.