Increase in lipoperoxides and prolyl hydroxylase activity in rat liver following chronic ethanol feeding

Insulin-Like Growth Factor-1 Deficiency and Cirrhosis Establishment

Cirrhosis represents the final stage of chronic liver damage, which can be due to different factors such as alcohol, metabolic syndrome with liver steatosis, autoimmune diseases, drugs, toxins, and viral infection, among others. Nowadays, cirrhosis is an important health problem and it is an increasing cause of morbidity and mortality, being the 14th most common cause of death worldwide. The physiopathological pathways that lead to fibrosis and finally cirrhosis partly depend on the etiology. Nevertheless, some common features are shared in this complex mechanism. Recently, it has been demonstrated that cirrhosis is a dynamic process that can be altered in order to delay or revert fibrosis. In addition, when cirrhosis has been established, insulin-like growth factor-1 (IGF-1) deficiency or reduced availability is a common condition, independently of the etiology of chronic liver damage that leads to cirrhosis. IGF-1 deprivation seriously contributes to the progressive malnutrition of cirrhotic patient, increasing the vulnerability of the liver to establish an inflammatory and oxidative microenvironment with mitochondrial dysfunction. In this context, IGF-1 deficiency in cirrhotic patients can justify some of the common characteristics of these individuals. Several studies in animals and humans have been done in order to test the replacement of IGF-1 as a possible therapeutic option, with promising results.

Binge alcohol promotes hypoxic liver injury through a CYP2E1-HIF-1α-dependent apoptosis pathway in mice and humans

Binge drinking, a common pattern of alcohol ingestion, is known to potentiate liver injury caused by chronic alcohol abuse. This study was aimed at investigating the effects of acute binge alcohol on hypoxia-inducible factor-1α (HIF-1α)-mediated liver injury and the roles of alcohol-metabolizing enzymes in alcohol-induced hypoxia and hepatotoxicity. Mice and human specimens assigned to binge or nonbinge groups were analyzed for blood alcohol concentration (BAC), alcohol-metabolizing enzymes, HIF-1α-related protein nitration, and apoptosis. Binge alcohol promoted acute liver injury in mice with elevated levels of ethanol-inducible cytochrome P450 2E1 (CYP2E1) and hypoxia, both of which were colocalized in the centrilobular areas. We observed positive correlations among elevated BAC, CYP2E1, and HIF-1α in mice and humans exposed to binge alcohol. The CYP2E1 protein levels (r = 0.629, p = 0.001) and activity (r = 0.641, p = 0.001) showed a significantly positive correlation with BAC in human livers. HIF-1α levels were also positively correlated with BAC (r = 0.745, p < 0.001) or CYP2E1 activity (r = 0.792, p < 0.001) in humans. Binge alcohol promoted protein nitration and apoptosis with significant correlations observed between inducible nitric oxide synthase and BAC, CYP2E1, or HIF-1α in human specimens. Binge-alcohol-induced HIF-1α activation and subsequent protein nitration or apoptosis seen in wild type were significantly alleviated in the corresponding Cyp2e1-null mice, whereas pretreatment with an HIF-1α inhibitor, PX-478, prevented HIF-1α elevation with a trend of decreased levels of 3-nitrotyrosine and apoptosis, supporting the roles of CYP2E1 and HIF-1α in binge-alcohol-mediated protein nitration and hepatotoxicity. Thus binge alcohol promotes acute liver injury in mice and humans at least partly through a CYP2E1-HIF-1α-dependent apoptosis pathway.

Supplementation of Pueraria radix water extract on changes of antioxidant enzymes and lipid profile in ethanol-treated rats

BACKGROUND

Water extract of Pueraria radix (PRWE), traditional oriental medicinal plant, may have an effect on the activity of hepatic antioxidant enzymes and lipid profile in ethanol-treated rats.

METHODS

Male Sprague-Dawley rats were divided into control, ethanol, PRWE and ethanol-PRWE supplemented groups. Twenty-five percent (v/v) ethanol (5 g/kg body weight) was orally administered once a day for 5 weeks. The PRWE was supplemented in a diet based on 1500 mg of raw PRWE/kg body weight/day.

RESULTS

Ethanol feeding resulted in a higher alcohol dehydrogenase (ADH) activity and lower aldehyde dehydrogenase (ALDH) activity. After PRWE supplementation, both activities were increased. The PRWE supplementation resulted in a significant decrease in the plasma and liver total cholesterol concentrations in the ethanol-treated rats. Ethanol administration significantly lowered the activities of hepatic superoxide dismutase (SOD) and catalase (CAT), whereas it increased the plasma and hepatic thiobarbituric acid reactive substances (TBARS) and the hepatic glutathione peroxidase (GSH-Px) activities. However, PRWE supplementation resulted in a significant increase in the SOD and CAT activities and a significant decrease in the TBARS and the GSH-Px activities in the ethanol-treated rats.

CONCLUSION

PRWE can contribute to alleviating the adverse effect of ethanol ingestion by enhancing the lipid metabolism as well as the hepatic antioxidant defense system.

Ethanol administration generates oxidative stress in the pancreas and liver, but fails to induce heat-shock proteins in rats

BACKGROUND

Heat-shock proteins (HSP) play an essential role in the sequestration and reparation of denatured cellular proteins. Because ethanol treatment can result in oxidative stress-induced protein damage, it is possible that expression of HSP is altered after ethanol consumption. Dose-response and time-course studies were performed to investigate whether acute and chronic intragastric ethanol administration can induce tissue damage, oxidative stress and expression of the heat-shock proteins HSP60 and HSP72 in the pancreas and liver of male Wistar rats.

METHODS

Laboratory and morphological analysis of pancreatic and liver damage were investigated. The degree of oxidative stress was assessed by measurement of the reduced glutathione content, lipid peroxidation and protein oxidation. The levels of HSP were examined by western blot analysis.

RESULTS

Ethanol administration dose- and time-dependently elevated the serum ethanol concentration and hepatic enzyme activities. Chronic ethanol treatment also resulted in morphological damage of the liver. We observed that acute and chronic ethanol consumption had markedly different effects on the oxidative parameters in the pancreas and liver. Acute ethanol administration caused oxidative stress in the liver, whereas there was no such effect in the pancreas. In contrast, chronic ethanol feeding resulted in oxidative stress in both the pancreas and the liver. Furthermore, neither acute nor chronic ethanol intake induced the synthesis of HSP, a major defense system against cellular damage in the examined organs.

CONCLUSION

Ethanol administration generates oxidative stress in the pancreas and liver, but fails to induce HSP in rats.

Effects of Puerariae Flos and Puerariae Radix extracts on antioxidant enzymes in ethanol-treated rats

This study was performed to investigate the effect of Puerariae Flos (PF) and Puerariae Radix (PR) water extracts on the activities and mRNA expression of three hepatic antioxidant enzymes in ethanol-treated rats. Male Sprague-Dawley rats were divided into four groups, a control, ethanol-treated, ethanol plus PF-treated, and ethanol plus PR-treated group with seven rats per group. Ethanol (25 % v/v, 5 g/kg body weight) was orally administered once a day for 5 weeks. The PF and PR water extracts were supplemented in a diet based on 1.2 g of raw PF or PR/kg body weight/day. Ethanol administration without the PF or PR supplement significantly lowered the activities of hepatic Cu/Zn SOD and catalase (CAT), whereas it increased the hepatic GSH-Px activity. However, the PF and PR supplementation resulted in a significant increase in the Cu/Zn SOD and/or CAT activities and a significant decrease in the GSH-Px activity in the ethanol-treated rats. The mRNA levels of these antioxidant enzymes in the ethanol-treated rats were normalized to the control level by the PF or PR supplement. The hepatic glutathione content, which was significantly lower in the ethanol-treated group than in the control group, was also normalized to the control level by supplementing with either PF or PR. The PF or PR supplement resulted in lowering the hepatic malondialdehyde to the control level in the ethanol-treated rats.

Antifibrogenic effect in vivo of low doses of insulin-like growth factor-I in cirrhotic rats

Insulin-like growth factor-I (IGF-I) is produced mainly in the liver and it induces beneficial effects on the nutritional status, the liver function and oxidative hepatic damage in cirrhotic rats. The aim of this work was to analyze the effect of IGF-I on mechanisms of fibrogenesis in cirrhotic rats. Liver cirrhosis was induced by CCl(4) inhalation and phenobarbital in Wistar rats. Ten days after stopping CCl(4) administration (day 0), rats received either IGF-I (2 microg/100 g bw/day) (CI+IGF) or saline (CI) subcutaneously during 14 days. Animals were sacrificed on day 15. As control groups were used: healthy rats (CO) and healthy rats treated with IGF-I (CO+IGF). Liver histopathology, hydroxyproline content, prolyl hydroxylase activity, collagen I and III mRNA expression and the evolution of transformed Ito cells into myofibroblasts were assessed. Among the two control groups (CO+IGF), no differences were found in hydroxyproline content and these levels were lower than those found in the two cirrhotic groups. Compared with untreated cirrhotic rats, the CI+IGF-I animals showed a significant reduction in hydroxyproline content, prolyl hydroxylase activity and collagen alpha 1(I) and alpha1(III) mRNA expression. A higher number of transformed Ito cells (alpha-actin +) was observed in untreated cirrhotic animals as compared to CO and CI+IGF groups. In summary, treatment with IGF-I reduced all of the studied parameters of fibrogenesis. In conclusion, low doses of IGF-I induce in vivo an antifibrogenic effect in cirrhotic rats.

The effect of chronic and acute ethanol treatment on morphology, lipid peroxidation, enzyme activities and Na+ transport systems on WRL-68 cells

In this study we measured some parameters that are associated with ethanol damage to the liver. The method allowed us to determine the injury that chronic and acute ethanol treatments produce at the cellular level without interference from homeostatic or compensatory mechanisms. The system used is a hepatic fetal human cell line, WRL-68, which retains, in culture, many of the liver-specific functions. WRL-68 cells do not metabolise ethanol, and consequently we could evaluate the effect of ethanol alone. We explored two different conditions: 30 days with 0.1 M ethanol (chronic treatment) and 24 h in the presence of 0.5 M ethanol (acute treatment). 1. The transmission electron microscopy studies revealed, in both treatments, the presence of granules not usually present in the cytoplasm of control cells and morphological mitochondrial alterations in chronically treated cells. 2. Lipid peroxidation, measured as the rate of malondialdehyde production, increased three and a half times in acutely treated cells and about twofold in chronically treated cells. 3. The percentage of total activity (activity in the medium/(activity in the medium + activity of the cells). 100) and the enzymatic activity in the culture medium of gamma glutamyl transpeptidase (GGT), alanine amino transferase (ALAT), aspartate amino transferase (ASAT) and alkaline phosphatase (AI-P), increased. 4. We measured some parameters related to the transport of sodium across the membrane. Cells chronically treated with ethanol had higher rate constants and effluxes than control cells. There was no difference between the total and passive efflux. Ethanol treated cells apparently lacked the ouabain sensitive pathway. In acutely treated cells, the total sodium efflux and the rate constant were enhanced. Sodium pools in the acutely treated cells were diminished and active sodium pumping was seven times higher than in control cells. 5. We determined the number of high affinity ouabain binding sites per cell. Ethanol did not alter the number of pumps, rather it seems to induce a functional alteration. Our results indicate that ethanol per se induces lipid peroxidation, alters enzymatic activities, sodium transport systems, sodium pools and cellular morphology, and that all these changes may be partly responsible for ethanol-induced hepatotoxicity. The data compare favourably with those reported in the literature for many different systems. Therefore our model for studying the mechanism of alcohol effects appears to be valid, with the advantage of being able to compare experiments that can be done in the same system and under the same conditions.

Blood and liver lipid peroxide status after chronic ethanol administration in rats

During the last decades a vast number of reports have aimed at elucidating the mechanisms behind alcohol-related organ injury, but the manner in which ethanol induces, e.g., liver damage is still an enigma. Increased oxidative stress has been put forward as one possible mechanism behind alcohol-related tissue damage. This paper focuses on the effect of chronic ethanol consumption on antioxidant status and lipid peroxide levels in blood and liver of rats. Alcohol was given twice daily in a total dose of 5 g ethanol/kg body wt. per day divided into two 2.5 g ethanol/kg body wt. doses as a 50% water solution, by gavage over 4 weeks. Chronic ethanol ingestion led neither to a significant change in lipid peroxide formation nor to a significant change in enzymatic antioxidant activities. Only concentrations of oxidized glutathione and of other non-enzymatic antioxidant such as vitamin E showed a tendency to decrease after alcohol application. The data presented could serve to emphasize no involvement of free radical-induced lipoperoxidation in the pathogenesis of ethanolic liver diseases.

Preventive effect of gomisin A, a lignan component of shizandra fruits, on acetaminophen-induced hepatotoxicity in rats

The preventive effect of gomisin A, a lignan component of shizandra fruits, on acetaminophen-induced hepatotoxicity in rats was examined by histological and biochemical analysis. Acetaminophen at a dose of 750 mg/kg was administered to male Wistar rats with or without pretreatment with 50 mg/kg of gomisin A. Gomisin A inhibited not only the elevation of serum aminotransferase activity and hepatic lipoperoxides content, characteristic of acetaminophen administration, but also the appearance of histological changes such as degeneration and necrosis of hepatocytes. However, gomisin A did not affect the decrease in liver glutathione content. These results suggest that gomisin A protects the liver from injury after administration of acetaminophen through the suppression of lipid peroxidation.

Clinical significance of serum 7S collagen in various liver diseases

Serum type IV collagen fragment (7S collagen domain) was measured in 30 controls and 152 liver disease patients with a radioimmunoassay using a polyclonal antibody to human placenta 7S collagen. The serum concentrations of 7S collagen (mean +/- SD) were 4.2 +/- 0.9 ng/mL in controls, 5.1 +/- 2.0 ng/mL in acute hepatitis, 6.5 +/- 2.5 ng/mL in chronic inactive hepatitis, 9.5 +/- 3.8 ng/mL in chronic active hepatitis, 14.4 +/- 7.5 ng/mL in liver cirrhosis, and 14.4 +/- 6.9 ng/mL in hepatocellular carcinoma. In acute hepatitis, 7S collagen was slightly increased, whereas type III procollagen N-peptide and prolyl hydroxylase were markedly increased. In chronic liver disease, 7S collagen concentrations increased with the severity of the disease, and also reflected the degree of fibrosis. The serum 7S collagen concentrations were significantly correlated with those of type III procollagen N-peptide and prolyl hydroxylase in all subjects. These results suggest that serum 7S collagen concentration is a useful diagnostic aid for determining hepatic collagen metabolism in liver diseases.

Influence of dietary zinc on hepatic collagen and prolyl hydroxylase activity in alcoholic rats

The effects of dietary zinc on hepatic collagen and prolyl hydroxylase activity in normal and alcoholic rats has been investigated in four groups of pair-fed male Wistar rats given either liquid ethanol or a control diet for 12 wk. Each group of pair-fed animals received a diet with a different zinc concentration (standard diet, 7.6 mg/L; low-zinc diet, 3.4 mg/L; zinc-supplemented diet, 76 mg/L; and zinc-extrasupplemented, 300 mg/L. There were no significant differences in hepatic collagen concentration and prolyl hydroxylase activity between alcoholic and normal rats receiving a standard diet (collagen, 77 +/- 5 and 73 +/- 6 micrograms/mg protein; and prolyl hydroxylase; 37 +/- 26 and 36 +/- 22 cpm/mg protein). Alcoholic rats fed a low-zinc diet showed increased prolyl hydroxylase activity (75 +/- 10 cpm/mg protein, p less than 0.05), although no changes in hepatic collagen (77 +/- 10 micrograms/mg protein) were observed in comparison with rats fed a standard alcoholic diet. By contrast, hepatic collagen was significantly lower in alcoholic rats fed a zinc-supplemented diet (66 +/- 4 and 63 +/- 3 micrograms/mg protein, p less than 0.05 and p less than 0.01, respectively), and hepatic prolyl hydroxylase activity was particularly lower in rats receiving zinc 300 mg/L (18 +/- 20 cpm/mg protein). Similar effects were observed in normal rats. We conclude that dietary zinc influences hepatic prolyl hydroxylase activity and collagen deposition in alcoholic rats, and in consequence, the control of dietary zinc is necessary to assess the effects of alcohol on collagen metabolism in rats.

The decrease of superoxide dismutase activity and depletion of sulfhydryl compounds in ethanol-induced liver injury

There appears to be increasing evidence that ethanol toxicity may be associated with an increased production of reactive oxygen intermediates. In rats we studied the effect of 4 weeks of ethanol ingestion on the liver cytosolic defense system against active oxygen species. Compared with the control rats, the ethanol-fed animals had a significantly higher liver malondialdehyde content and significantly lower reduced glutathione level. Moreover, ethanol feeding resulted in a decrease of superoxide dismutase and catalase activities while glutathione peroxidase activity was only slightly diminished. Thus, prolonged ethanol administration profoundly modified the hepatic status of the enzymatic defense system leading to lipid peroxidation that may disrupt vital functions of liver cells.