Proteasome inhibition induces cytokeratin accumulation in vivo

Chronic ethanol ingestion leads to inhibition of proteasomal activity. As a consequence, proteins accumulate in liver cells. Cytokeratin accumulation as seen in alcoholic hepatitis could lead to the formation of Mallory bodies. In order to study the phenomenon of cytokeratin accumulation in liver cells, rats were fed ethanol or dextrose for 1 month and some were given the proteasome inhibitor, PS-341, to augment the inhibitory effect of ethanol feeding. This was done to study the involvement of proteasome inhibition in the process of cytokeratin accumulation. There was a marked increase in the accumulation of polyubiquitinated proteins, and heat shock proteins (hsp) 25 and 70 in the liver of rats treated with PS-341. Similarly, cytokeratin-8 (CK-8) levels were markedly increased in the liver homogenates of rats fed ethanol when given PS-341. When normal mouse cultured hepatocytes were transfected with cytokeratin-18 (CK-18) tagged with red fluorescent protein (RFP), CK-18 aggresomes formed because proteasome was overloaded. These data provide new evidence that proteasome inhibition is involved in cytokeratin accumulation, when aggresomes are formed in tissue culture. Accumulation of cytokeratin in this way may ultimately lead to Mallory body formation as seen in alcoholic hepatitis.     

Methionine-supplemented diet augments hepatotoxicity and prooxidant status in chronically ethanol-treated rats

The purpose of this study was to investigate whether high methionine (HM) diet may influence the development of ethanol-induced hepatotoxicity and prooxidant–antioxidant balance in the liver. Rats received drinking water containing ethanol (20% v/v) and/or methionine supplemented diet (2% w/w) for 75 days. Although prooxidant–antioxidant balance did not change in the liver of rats in HM group, ethanol treatment was observed to increase plasma transaminase activities, and malondialdehyde (MDA) and protein carbonyl (PC) levels, but not glutathione (GSH), vitamin E and vitamin C levels, and superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione transferase (GST) activities in the liver of rats as compared to controls. However, ethanol plus HM diet caused further increases in plasma transaminase activities and hepatic MDA and PC levels. In addition, SOD, GSH-Px and GST activities were observed to decrease, but GSH, vitamin E and vitamin C levels remained unchanged in the liver as compared to ethanol, HM and control groups. Our results show that HM diet may augment hepatotoxicity and oxidative stress in the liver of chronically ethanol-treated rats.     

Hepatic glutathione mediated antioxidant system in ethanol treated rats: Decline with age.

Alcoholism is a pervasive problem. The aim of the present study was to clarify the effect of ethanol on the hepatic glutathione antioxidant system in young and elderly rats. Male albino Wistar rats of two age groups (3 months and 18 months old) were divided into two experimental groups. The first group of untreated rats served as controls (C; young n=6 and old n=6) and second group received ethanol (Et; young n=6 and old n=6) 2g of ethanol/kg b.w. for 2 months. After the completion of last treatment glutathione (GSH) and antioxidant enzymes glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione-S-transferase (GST) were determined. All these parameters including GST were remarkably decreased in the liver with advancing of age. The ethanol treatment decreased GSH, GSH-Px and GR, whereas, GST was increased in both age groups. The decrease of hepatic antioxidant status with ethanol and aging may be due to over production of free radicals. The changes of parameters studied were greater in the older than in the young rats. In conclusion, ethanol stress exhibited age dependent response on glutathione mediated antioxidant system in the liver.     

Antioxidant and methyl donor effects of betaine versus ethanol-induced oxidative stress in the rat liver

Oxidative stress is one hypothesis for the association of ethanol consumption with cardiovascular, cerebrovascular, and liver diseases. Thus, we examined whether oral betaine can act as a preventive agent in ethanol-induced oxidative stress on the rat liver. A total of 32 male Sprague–Dawley rats were divided into four equal groups. The control group received normal saline. The ethanol group was administered ethanol (4 g/kg). The betaine group received betaine [1.5 % (w/w) of the total diet], and the betaine plus ethanol group (Bet. & Eth.) were administered with betaine; after 120 min, the rats received ethanol. All of the treatments were applied for 2 months via gavage. Elevation of glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were observed in the betaine-treated groups. Thiobarbituric acid reactive substances (TBARS, an indicator of lipid peroxidation) concentration also decreased in the betaine-treated rats as compared to the ethanol group. There was also a significant reduction in plasma total homocysteine (tHcy) concentration in the betaine and Bet. & Eth. groups as compared to the ethanol-treated rats. In contrast, ethanol treatment in rats resulted in significant lower antioxidant enzyme activities (GPx and SOD), and indicated lipid peroxidation to the liver, as monitored by the elevation in TBARS level. Administration of ethanol to rats also induced toxicity in their liver, as shown by the histopathological findings, whereas betaine could suppress liver damages in the Bet. & Eth. group. Overall, oral pretreatment with betaine significantly prevented ethanol-induced oxidative stress and hyperhomocysteinemia via increasing antioxidant enzyme activities and decreasing tHcy concentration. Thus, betaine may be recommended as a therapeutic agent for patients with liver damages induced by oxidative stress in various diseases.     

The effect of betaine treatment on triglyceride levels and oxidative stress in the liver of ethanol-treated guinea pigs

We investigated the effect of betaine supplementation on ethanol induced steatosis and alterations in prooxidant and antioxidant status in the liver of guinea pigs. Animals were fed with normal chow or betaine containing chow (2% w/w) for 30 days. Ethanol (3 g/kg, i.p.) was given for the last 10 days. We found that ethanol treatment caused significant increases in plasma transaminase activities, hepatic triglyceride and lipid peroxide levels. Significant decreases in glutathione (GSH), -tocopherol and total ascorbic acid (AA) levels were also observed, but hepatic superoxide dismutase, glutathione peroxidase and glutathione transferase activities remained unchanged as compared with those in controls. Betaine treatment together with ethanol in guinea pigs is found to decrease hepatic triglyceride, lipid peroxide levels and serum transaminase activities and to increase GSH levels. No changes in a-tocopherol and total AA levels and antioxidant enzyme activities were observed with betaine treatment in alcohol treated guinea pigs. In addition, histopathological assessment of guinea pigs showed that betaine reduced the alcoholic fat accumulation in the liver. Based on these data, betaine treatment has a restoring effect on the alterations in triglyceride, lipid peroxide and GSH levels following ethanol ingestion.     

基于Nrf2/ARE信号通路探讨白藜芦醇治疗非酒精性脂肪性肝炎大鼠的作用机制

目的　基于Nrf2/ARE信号通路探讨白藜芦醇治疗非酒精性脂肪性肝炎大鼠的作用机制。 方法　利用高脂饮食法进行非酒精性脂肪性肝炎大鼠造模。大鼠分为对照组（CD组）、高脂饮食组（HCD组）、白藜芦醇组（HCD + RSV组）及（白藜芦醇+ OAD85）组（HCD + RSV + OAD85组）,每组8只。CD组始终喂养普通饲料,其他组自由高脂饮食。（HCD + RSV）组及（HCD + RSV + OAD85）组在喂养第4周开始灌胃给予10 mg/kg RSV或（10 mg/kg RSV + 100 μg/kg OAD85）,连续灌胃给药28 d（OAD85为Nrf2/ARE抑制剂齐墩果酸衍生物）。HE染色观察肝组织病理学改变,肝组织冰冻切片油红O染色观察脂肪量变化,试剂盒检测ALT、AST、TC、TG、HDL、LDL和FFA,Western-blot和qRT-PCR检测Keap1、Nrf2、ARE、NQO1、HO-1蛋白和mRNA表达。 结果　与CD组相比,HCD组肝脂肪变性、小叶炎症、门静脉炎症、肿胀程度NASH评分、脂肪含量及血清中ALT、AST升高（P<0.05）,与HCD组相比,（HCD + RSV）组上述指标均降低（P<0.05）,HCD组与（HCD + RSV + OAD85）组差异无统计学意义（P>0.05）。与CD组相比,HCD组NQO1、HO-1、Nrf2、ARE蛋白及mRNA表达均明显升高（P<0.001）,Keap1蛋白表达降低（P<0.001）,与HCD组对比,（HCD + RSV）组NQO1、HO-1、Nrf2、ARE蛋白及mRNA表达亦明显增加（P<0.001）,Keap1蛋白及mRNA表达明显降低（P<0.001）,HCD组与（HCD + RSV + OAD85）组差异无统计学意义（P>0.05）。 结论　白藜芦醇治疗非酒精性脂肪性肝炎大鼠可能是基于Nrf2/ARE信号通路激活机制,从而改善氧化应激水平,可减轻肝病理损伤。     

Gadolinium chloride suppresses styrene-induced cytochrome P450s expression in rat liver

To assess the effect of gadolinium (Gd) on the expression of several forms of cytochrome P450 (P450s) and antioxidant enzymes, we treated rats with gadolinium chloride (25 mg as Gd/kg body weight) 4 h after styrene (a multiple P450 inducer) treatment (600 mg/kg). Gd treatment significantly suppressed styrene-inducible cytochrome P4502B1 (CYP2B1), CYP2B2, CYP2E1, and CYP3A2 mRNA expressions to 48.6%, 69.8%, 61.1%, and 38.5%, accompanying with the reduction of proteins expression to 1.42%, 31.2%, 21.1% and 21.1%, respectively, compared with styrene alone treatment. Gd suppressed styrene-inducible CYP1A2 expression, but only at the protein level. On the other hand, styrene treatment caused a decrease in reduced form of glutathione (GSH), as well as increases in lipid peroxide and serum ALT and AST activities, suggesting the occurrence of hepatic damage probably due to styrene-induced oxidative stress in rat liver. Post-treatment of Gd attenuated this styrene-caused hepatic damage. Moreover, mRNA expressions of cellular antioxidant enzymes such as catalase, CuZn-superoxide dismutase (CuZnSOD) and glutathione peroxidase (GPX) were hardly changed by styrene and/or Gd treatment. In summary, Gd suppressed styrene-inducible expression of not only CYP2B1 but also several forms of P450 at both the mRNA and protein levels, along with attenuation of styrene-caused liver damage. These findings suggested that Gd is a chemo-preventive agent against hepatic damage caused by xenobiotics requiring biotransformation.     

Protective Role of Artemisia Afra Aqueous Extract on Tissue Antioxidant Defense Systems in Streptozotocin-Induced Diabetic Rats

Changes in antioxidant capacity in the body as a result of oxidative stress play an important role in the development of diabetic complications. The aim of this study was to evaluate the effect of aqueous extract of Artemisia afra Jacq. ex Willd. on antioxidant defense systems in the liver and kidney of streptozotocin-induced diabetic rats. Administration of the extract to diabetic rats for 21 days significantly reduced blood glucose levels and increased body weight. The diabetic animals exhibited decreased levels of glutathione reductase (GR), glutathione peroxidase (GPx), superoxide dismutase (SOD) and reduced glutathione (GSH) in the liver and kidney, which were restored to near normal levels following treatment with the herb. The increased levels of lipid peroxidation observed in the tissues of diabetic rats were also reverted back to near normalcy after administering the extract. These findings revealed the protective role of A. afra on tissues by reducing oxidative stress which could be attributed to its flavonoids content. The efficacy of the plant compared favourably well with glibenclamide, a standard hypoglycemic drug.     

Sasa quelpaertensis leaves ameliorate alcohol-induced liver injury by attenuating oxidative stress in HepG2 cells and mice

Oxidative stress plays a crucial role in the progression of alcoholic liver diseases and substances of antioxidant property are of special interest for therapeutic purposes. We investigated the hepatoprotective effect of leaf extracts of Sasa quelpaertensis, an edible bamboo mainly cultivated in Jeju Island, South Korea. We examined the cytotoxicity of different extracts (distilled water, 20–80% EtOH) of S. quelpaertensis on HepG2 cells and their hepatoprotective effect on HepG2 cells stimulated by ethanol (800?mM, 24?h). Furthermore, we measured reactive oxygen species (ROS) production, ethanol toxicity induced cell death, and the activity of antioxidant enzymes. In in vivo experiments, liver damage was induced by oral administration of 5?g/kg ethanol with or without potent ethanol extract of S. quelpaertensis (10 or 100?mg/kg) 12?h interval for a total of 3 doses. Only 80% ethanol extract of S. quelpaertensis (SQEE80) exhibited cytoprotective effect on HepG2 cells against alcohol-induced toxicity. SQEE80 treatment (250, 500?μg/mL) in ethanol exposed HepG2 cells showed significant attenuation of ROS production and ethanol toxicity induced cell death. Furthermore, SQEE80 markedly increased the activity of antioxidant enzyme glutathione peroxidase 1 in ethanol exposed HepG2 cells compared to ethanol stimulated cells. In in vivo experiments, SQEE80 treatment evidently suppressed the alcohol-induced histopathological changes in liver, serum ethanol content, and expression of cytochrome P450 2E1. Furthermore, SQEE80 significantly reversed the reduction of glutathione level in the ethanol challenged liver. Taken together, we suggest the possibility of developing SQEE80 as a natural hepatoprotective substance in attenuating alcohol-induced oxidative stress.     

Protective effect of black tea on integral membrane proteins in rat liver

Ethanol intoxication is accompanied by oxidative stress formation. Consequently, it leads to disturbances in cellular metabolism that can alter the structure and function of cell membrane components. Black tea displays antioxidant properties, protects membrane phospholipids and may protect integral membrane proteins. In the present study, we examined whether black tea induces changes in the liver integral membrane proteins of 12-months old rats chronically intoxicated with ethanol. To estimate qualitatively and quantitatively the levels of the liver integral membrane proteins, the proteins were selectively hydrolyzed by trypsin, the obtained peptides were resolved by HPLC and the levels of specific amino acids within the individual peptides were determined. All of the obtained peptides contained phenylalanine (Phe), cysteine (Cys) and lysine (Lys). Compared to the control group, rats in the ethanol intoxication group showed decreased liver levels of integral membrane proteins as well as fewer trypsin-hydrolyzed peptides and amino acids in the hydrolyzed peptides. Administration of black tea to ethanol-intoxicated rats partially protected proteins against the structural changes caused by ethanol. Black tea prevented decreases in the levels of cysteine (in about 90% of cases), lysine (in about 60% of cases), phenylalanine (in about 70% of cases) and examined peptides (in about 60% of cases). The liver protein level was higher (by about 18%) in rats who received black tea and ethanol than in those who received ethanol alone. In conclusion, black tea partially protects the composition and level of rat liver cell integral membrane proteins against changes caused by ethanol intoxication.     

Effect of acute ethanol treatment on biochemical and histopathological factors in rat liver in an experimental sepsis model

The aim of this study was to investigate the contribution of acute alcohol in sepsis-related liver damages using a Cecal Ligation and Puncture (CLP) model. Rats were divided into 7 groups (5 rats/group): control (saline-injected), sham-operated, CLP, ethanol (1.0 and 2.0 g/kg b.w) and CLP+ethanol. The CLP+ethanol group received a single dose of ethanol following sepsis induction. Sepsis induction caused early changes in lipid peroxidation products in liver, whereas ethanol alone (2.0 g/kg b.w) resulted in a significant increase (~21%) in lipid peroxidation, which was further increased (~57%) in CLP rats treated with alcohol. CLP operation and alcohol treatment exhibited additive effects on plasma catalase, liver glutathione and glutathione S-transferase (GST), which were primarily suppressed due to ethanol. Hepatic cytochrome P4501A1, which was elevated in CLP rats, was reversed in the CLP+ethanol group. Plasma tumor necrosis factor-α was markedly elevated (~85%) in septic rats, but was unaffected in septic rats having received ethanol. Histopathological observations revealed that inflammatory reactions in liver in response to CLP operation are not intensified by ethanol administration. On the basis of biochemical and histopathological results, it can be concluded that acute ethanol treatment is responsible for early changes in oxidative stress, which may lead to polymicrobial sepsis-related organ damage.     

The effect of 1,25-dihydroxyvitamin D3 on liver damage,oxidative stress,and advanced glycation end products in experimental nonalcoholic- and alcoholic- fatty liver disease

Background/aim Oxidative stress and advanced glycation end products (AGEs) formation are proposed as effective mechanisms in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and alcoholic liver disease (ALD). 1,25(OH)2D3 was proposed to have antioxidant, antiinflammatory and antiglycation properties. In this study, the effect of 1,25(OH)2D3 treatment on oxidative stress parameters and AGEs levels together with hepatic histopathology was investigated in high fructose (HFr) or ethanol (EtOH)-treated rats. Materials and methods Rats were treated with fructose (30%) or ethanol (5-20%) in drinking water with and without 1,25(OH)2D3 treatment (5 µg/kg two times a week) for 8 weeks. Insulin resistance (IR), oxidative stress parameters, AGEs, triglyceride (TG), and hydroxyproline (Hyp) levels together with histopathology were investigated in the liver. Results1,25(OH)2D3 decreased hepatic reactive oxygen species, lipid and protein oxidation products together with histopathological improvements in HFr- and EtOH-treated rats. 1,25(OH)2D3 treatment was observed to decrease significantly serum and hepatic AGEs in HFr group, and hepatic AGEs in EtOH group.Conclusion Our results clearly show that 1,25(OH)2 D3 treatment may be useful in the alleviation of hepatic lesions by decreasing glycooxidant stress in both NAFLD and ALD models created by HFr- and EtOH-treated rats, respectively.