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E Chiarpotto

Publications and source records attributed to E Chiarpotto.

At least 37 records · Page 2Linked to original sources
PubMed1995

Oxidative damage in human liver transplantation.

The aim of this study was to evaluate oxygen-dependent hepatic reperfusion injury in humans following orthotopic liver transplantation. To this end, a number of blood indices of impaired tissue redox balance were monitored in 19 adult patients for 3 weeks after liver transplantation. Both red cell malonaldehyde and plasma lipid peroxides increased significantly soon after organ reperfusion. This finding was consistently accompanied by decreased plasma vitamin E and red cell total glutathione. A peak of oxidative stress, as measured by the parameters monitored, was evident within 24 h after reperfusion, together with a maximum expression of cytolysis, as measured by plasma alanine aminotransferase. The occurrence of redox imbalance after hepatic reperfusion was shown to be linearly related to irreversible cell damage. As regards the low plasma levels of the two antioxidants after reperfusion, only that of vitamin E appeared statistically related to oxidative stress. With the background of an increasing body of proof, mainly from animal models, the involvement of toxic oxygen metabolites in hepatic cytolysis following orthotopic liver transplantation appears likely. The statistical correlation among the markers of redox imbalance monitored indicates their combined use in further investigation.

Adolescent↗
PubMed1995

Ethanol-induced potentiation of rat hepatocyte damage due to 1,2-dibromoethane.

Low amounts of 1,2-dibromoethane (DBE), not able per se to exert pro-oxidant and cytotoxic activity on rat hepatocyte suspensions, become effective when administered with carbon tetrachloride (CCl4), due to impairment of the glutathione transferase detoxication pathway by CCl4. Treatment of rats with a single dose of ethanol (2.5 g/kg body wt) 2 h before liver cell isolation potentiates the effect of DBE alone on both malonaldehyde formation and lactate dehydrogenase release by the hepatocyte. The potentiation of the DBE effects by ethanol may be through a series of mechanisms, such as a strong inactivation of hepatocyte glutathione transferase similar to that caused by CCl4, an increased basal level of lipid peroxidation and a significant loss of total glutathione.

Animals↗
PubMed1995

Acetaldehyde involvement in ethanol-induced potentiation of rat hepatocyte damage due to the carcinogen 1,2-dibromoethane.

Previous experiments with hepatocytes isolated from ethanol-treated rats showed that alcohol potentiates the toxic action of 1,2-dibromoethane (DBE) by inhibiting its metabolism via glutathione-S-transferase. The aim of this study was to investigate whether acetaldehyde, the main product of ethanol metabolism, may be responsible for such inactivation. By pretreatment with 4-methylpyrazole, an inhibitor of acetaldehyde formation, the ethanol inactivation of glutathione transferase was actually prevented. As a consequence of this protective action, 4-methylpyrazole also prevented the high basal lipid peroxidation and the potentiated DBE toxicity observed in hepatocytes from ethanol-dosed animals. Finally, the inactivation of glutathione-S-transferase by concentrations of acetaldehyde likely to occur in the ethanol-intoxicated animal was confirmed in an in vitro model by direct aldehyde addition to hepatocyte suspensions.

Acetaldehyde↗
PubMed1994

Oxidative stress in the development of human ischemic hepatitis during circulatory shock.

An increasing number of studies support the involvement of free radical-mediated oxidative reactions in the pathogenesis of tissue injury following ischemia reperfusion. In particular, a condition of oxidative stress is evident in patients with circulatory shock, a disease process often complicated by progressive organ failure sustained by inflammatory reactions. In all shock patients without signs of organ failure, a consistent increase of intermediate and final products of lipid peroxidation (lipid peroxides and aldehydes respectively) was observed. Impairment of the redox equilibrium in the tissues of these patients was confirmed by a significant reduction of glutathione and vitamin E hematic concentrations. Moreover, a selective increase of plasma aldehyde-protein adducts, actual proof of oxidative damage of macromolecules, is only present in the shock patients who, in addition, show hepatic cytolysis (ischemic hepatitis) as estimated by plasma levels of LDH5 isoenzyme. Aldehyde adducts well mark the progression of the disease towards multiple organ failure. Finally, the good statistical correlation between aldehyde-modified proteins and LDH5, as well as their distinct behaviour in control and ischemic hepatitis, support the involvement of oxidative damage in the expression and worsening of circulatory shock.

Alanine Transaminase↗
PubMed1993

Dehydroepiandrosterone pretreatment protects rats against the pro-oxidant and necrogenic effects of carbon tetrachloride.

A single intraperitoneal injection of dehydroepiandrosterone (3 beta-hydroxy-5-androsten-17-one, DHEA) 17 hr before carbon tetrachloride (CCl4) poisoning protects rats against liver injury induced by the haloalkane. In liver homogenates, both the increase in malondialdehyde production and the formation of fluorescent lipid peroxidation products are significantly reduced. Also, liver microsomes obtained from DHEA-pretreated rats incubated in vitro with CCl4 are less susceptible to lipid peroxidation than microsomes from normal animals. The release of liver enzymes into the blood is much reduced in DHEA-pretreated rats, confirming a cause-effect relationship between lipid peroxidation and hepatocyte death. Treatment with DHEA inhibits neither glucose-6-phosphate dehydrogenase activity in the cytosol, nor the microsomal mixed function oxidase system (cytochrome P450 content, aminopyrine demethylase and ethoxycoumarin de-ethylase activities). In animals treated with DHEA, the liver content of total glutathione and vitamin E is not modified. These results support the hypothesis that DHEA protects against CCl4-induced liver injury through its own antioxidant activity, rather than by interfering with the metabolism of the toxin or with the tissue level of primary antioxidants.

Animals↗
PubMed1993

Change of liver metabolism of 1,2-dibromoethane during simultaneous treatment with carbon tetrachloride.

The combination of carbon tetrachloride (CCl4) and 1,2-dibromoethane (DBE) in isolated rat hepatocytes led to a significant potentiation of both lipid peroxidation and of plasma membrane damage observed after a single treatment with CCl4. Such a synergistic effect appeared to be related to the CCl4-induced shift of DBE metabolism from the cytosolic conjugation with glutathione towards the microsomal transformation into toxic intermediates. In fact, CCl4 significantly inactivated hepatocyte total GSH-transferase, i.e. the DBE detoxification pathway. Furthermore, while the microsomal metabolism of CCl4 was not affected by the simultaneous presence of DBE, the amount of DBE reactive metabolites covalently bound to hepatocyte protein was significantly enhanced in the presence of CCl4.

Animals↗
PubMed1993

Rat hepatocytes in single cell suspension: a still suitable system for lipid peroxidation studies.

The investigation of toxic compounds which need a previous metabolic activation often gets advantage by the employment of cell suspensions, in most of the cases rat hepatocytes. In particular, this model system allows the characterization of lipid peroxidation kinetics, the evaluation of its pathogenetic role in the induction of cell death and the analysis of the interaction among different prooxidant compounds in bringing about both oxidative damage and cytolysis.

Aldehydes↗
PubMed1991

Lipid peroxidation and irreversible cell damage: synergism between carbon tetrachloride and 1,2-dibromoethane in isolated rat hepatocytes.

The combination of 1,2-dibromoethane (DBE) with carbon tetrachloride (CCl4) in the isolated rat hepatocyte model produces a significant potentiation of both lipid peroxidation and plasma membrane damage induced by the latter compound. The increase in malondialdehyde production precedes the hepatocyte damage, evaluated in terms both of lactate dehydrogenase leakage and trypan blue exclusion. When hepatocytes are isolated from vitamin E pretreated rats, both the prooxidant and the cytotoxic effects of CCl4 are prevented. Also the synergism between CCl4 and DBE on lipid peroxidation disappears completely while that on cell damage is strongly reduced. The increased lipid peroxidation appears to be one of the mechanisms of the observed synergism between CCl4 and DBE on hepatocyte damage. Regarding the antioxidant status of the hepatocyte challenged with CCl4 and DBE, an early and significant consumption of vitamin E is observed only in the presence of the mixture of these xenobiotics. Total nonprotein thiol content is not significantly modified by CCl4 poisoning while DBE, alone and in association with CCl4, markedly decreases it. Vitamin E supplementation does not prevent but moderately delays total nonprotein thiol depletion due to DBE or to the mixture. Finally, glutathione transferase activity is significantly reduced by CCl4 treatment and not by DBE, and vitamin E supplementation totally prevents such inhibition. The increased prooxidant effect of CCl4 plus DBE compared to CCl4 alone seems related to the shift in DBE metabolism consequent to the CCl4-dependent inactivation of glutathione transferase.

Animals↗
PubMed1991

In vivo and in vitro evidence concerning the role of lipid peroxidation in the mechanism of hepatocyte death due to carbon tetrachloride.

Isolated rat hepatocytes exposed to CCl4 showed a stimulated formation of malonaldehyde after only 30-60 min incubation. Conversely, the onset of hepatocyte death was a relatively late event, being significant only after 2-3 h of treatment. A cause-effect relationship between the two phenomena has been demonstrated by using hepatocytes isolated from rats pretreated with alpha-tocopherol. Comparable results were obtained in vivo where supplementation with alpha-tocopherol 15 h before CCl4 dosing induced a partial or complete protection against the drug's necrogenic effect, depending on the concentration of the haloalkane used. Moreover, the vitamin supplementation prevented the CCl4-induced increase of liver total calcium content, probably by blocking alterations in the liver cell plasma membranes due to lipid peroxidation.

Animals↗
PubMed1990

Inactivation of hepatocyte protein kinase C by carbon tetrachloride: involvement of drug's metabolic activation and prooxidant effect.

The involvement of CCl4 biotransformation mechanism in decreasing the Protein Kinase C activity has been analyzed in hepatocytes isolated from phenobarbital-pretreated rats. A significant inhibition (55%) and an almost total disappearance (87%) of the enzyme activity were observed at 15 min and at 30 min incubation with CCl4, respectively. Cell preincubation with Trolox or desferrioxamine allowed a marked whilst not complete protection of both cytosolic and particulate Protein Kinase C activity. These results show that the CCl4 reactive metabolites play a primary role in hepatocyte Protein Kinase C impairment and suggest that besides lipid peroxidation other mechanisms -possibly a derangement of Ca2+ homeostasis- may be involved in this process.

Animals↗
PubMed1990

Lipid peroxidation and covalent binding in the early functional impairment of liver Golgi apparatus by carbon tetrachloride.

The onset of the lipoprotein secretory block provoked by CCl4 in the whole animal was monitored after purification of liver Golgi membranes. Both lipid transit through the apparatus and hexosylation of the lipoprotein are markedly inhibited 5-15 min after poisoning. Pre-treating the animal with alpha-tocopherol, shown to prevent lipid peroxidation without modifying the covalent binding due to CCl4 metabolites, affords little protection against lipid accumulation in the Golgi, but total preservation of galactosyl transferase activity. While haloalkylation therefore appears to be the major mechanism of damage in the early phases of CCl4-induced derangement of lipid secretion, lipid peroxidation is probably more involved later; this is indicated by the marked, though never complete, protection against fatty liver afforded at 24 h after CCl4 poisoning by supplementation of the membrane with alpha-tocopherol.

Animals↗
PubMed1990

CCl4-induced increase of hepatocyte free arachidonate level: pathogenesis and contribution to cell death.

A significant increase of the intracellular level of free arachidonic acid was observed in intact rat hepatocytes after poisoning with very low concentrations of CCl4 (0.129-0.172 mM), shown not to exert direct solvent effect. It seems likely that activation of phospholipase A2 (PLA2) is the mechanism mainly responsible for the rise of cytosolic arachidonate, since the latter is prevented by the PLA2 inhibitors indomethacin and mepacrine. The CCl4-induced delay of arachidonic acid incorporation within the cell membrane phospholipids partly contributes to its intracellular accumulation in the early phases of the poisoning. The lack of any significant protection by metabolic inhibitors (SKF 525A, metyrapone), antioxidant compounds (promethazine, diphenylphenylenediamine DPPD) or antioxidant procedures (rat pretreatment with vitamin E) leads to exclude an involvement of CCl4 biotransformation in the increase of intracellular free arachidonate. Finally, the PLA2 inhibitors employed in this study did not afford protection against the enzymic leakage of CCl4-treated hepatocytes.

Animals↗
PubMed1989

Promethazine inhibits the formation of aldehydic products of lipid peroxidation but not covalent binding resulting from the exposure of rat liver fractions to CCl4.

Promethazine is known to have protective activity in relation to CCl4-induced liver necrosis. This hepatoprotective property has been investigated with regard to the free radical scavenging and antioxidant properties of promethazine using isolated hepatocytes and microsomal suspensions. CCl4 is activated in both systems to free radical metabolites that bind covalently to lipid and protein, and initiate lipid peroxidation. A large number of carbonyl products is produced during CCl4-induced lipid peroxidation; promethazine strongly inhibits the production of all classes of carbonyl compounds in both microsomal suspensions and isolated hepatocytes. In contrast, promethazine is a very weak inhibitor of the covalent binding of metabolites of CCl4. We conclude that promethazine acts by scavenging the trichloromethylperoxyl radical and lipid peroxyl radicals, and is a weak scavenger of the trichloromethyl radical. These data, when considered together with the hepatoprotective effects of promethazine, suggest that lipid peroxidation is of relatively more importance than covalent binding in the pathogenesis of CCl4-induced liver necrosis.

Aldehydes↗
PubMed1987

Electron spin resonance studies on isolated hepatocytes treated with ferrous or ferric iron.

Isolated rat hepatocytes incubated with iron salts in the presence of the spin trapping agent alpha-4-pyridyl-l-oxide N-tert-butyl nitrone (4-POBN) generate a clear electron spin resonance signal; this signal is not detectable in the absence of exogenous iron. The hyperfine splitting constants are identical whether ferrous or ferric iron is used. The free radical trapped does not appear to be an active oxygen species but rather a carbon-centred radical, which we here ascribe to a lipodienyl radical on the basis of its hyperfine splitting features. Support to this interpretation is lent by the fact that no such radical could be generated in hepatocytes fully protected against lipid peroxidation by pretreating the donor rats with alpha-tocopherol.

Animals↗
PubMed1987

Pro-hemolytic effect of aldehydic products of lipid peroxidation.

In order to evaluate the pro-hemolytic action exerted by different classes of biogenic aldehydes, normal red cells obtained from human beings of both sexes were incubated at 37 degrees C under iso or hypo-osmotic conditions in the presence of hydroxyalkenals or alkanals, in a concentration compatible with those actually recovered during red cell lipid peroxidation. None of the tested aldehydes showed a direct hemolytic effect, i.e. red cell lysis in iso-osmotic conditions. Conversely, almost all assayed alkanals and hydroxyalkenals exhibited a pre-lytic damage of human erythrocytes, as detected in the red cells suspended in hypo-osmotic medium. The highest pro-hemolytic effect was displayed by hexanal, nonanal, 2-nonenal and 4-hydroxynonenal.

Aldehydes↗