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G Muzio

Publications and source records attributed to G Muzio.

At least 37 records · Page 2Linked to original sources
PubMed1997

Comparative evaluation of cytotoxicity and metabolism of four aldehydes in two hepatoma cell lines.

The metabolism of acetaldehyde (ACA), benzaldehyde (BA), propionaldehyde (PA) and valeraldehyde (VA) has been studied in two hepatoma cell lines, the rat HTC and mouse Hepa 1c1c7 cells. The cytotoxicity of the four aldehydes to these two cell lines has been compared. The end-points for evaluating cytotoxicity were 1) total macromolecular content (TMC) of confluent cultures, and 2) colony forming ability of dividing cells. These two assay systems had different sensitivities for the toxicity of aldehydes, probably due to different numbers of target cells. The activities of aldehyde dehydrogenases (NAD- and NADP-dependent, ALDH), alcohol dehydrogenase and aldehyde reductase were markedly greater in the HTC cell line compared to the Hepa 1c1c7 cell line, especially with BA as substrate. The cytotoxicities of aldehydes were generally stronger in the HTC cell line than in the Hepa 1c1c7 cell line; with the CF test. Particularly, BA was highly toxic to the HTC cells, which possessed the highest ALDH levels. Moreover, the treatment with (diethylamino)benzaldehyde, an ALDH inhibitor, completely abolished the toxicity of BA. Taken together, all these findings suggest that several cell lines expressing different aldehyde metabolizing activities could be used especially in the pre-screening phase to distinguish the metabolism-dependent cytotoxic effects from the metabolism independent effects.

Acetaldehyde↗
PubMed1996

Enzymatic pattern of aldehyde metabolism during HL-60 cell differentiation.

A number of metabolic changes, including modification of different enzyme activities, are linked to the acquisition of differentiated phenotype in HL-60 cells. Enzymes metabolizing aldehydes contribute to maintaining the intracellular steady-state concentration of aldehydes derived from lipid peroxidation. 4-Hydroxynonenal is one of the most important aldehydes produced by this process, and it is able to inhibit proliferation and induce differentiation of HL-60 human leukemic cells. We have now demonstrated that, after induction of HL-60 cell differentiation by 4-hydroxynonenal or DMSO, glutathione transferase activity increases in parallel to the degree of differentiation induction. Moreover, in 4-hydroxynonenal- or DMSO-treated cells, the concentration of reduced glutathione decreases five days after treatment. The rise of glutathione transferase activity, as well as the decrease of reduced glutathione, are possibly linked to the increase of detoxification capability of differentiated cells.

Alcohol Dehydrogenase↗
PubMed1995

Hepatocellular metabolism of 4-hydroxy-2,3-nonenal is impaired in conditions of chronic cholestasis.

4-Hydroxy-2,3-nonenal is a major aldehydic end-product of lipid peroxidation known to exert several biological and cytotoxic effects and to be produced during conditions of chronic cholestasis. Here we report that viable hepatocytes isolated from cholestatic livers of bile duct-ligated rats (BDL hepatocytes) show a significantly lower rate of HNE metabolism than control cells. This feature is likely to be the consequence of a significant inhibition in the activity of HNE-metabolizing cytosolic glutathione-S-transferase and alcohol dehydrogenase in BDL hepatocytes. Particulate NADP-dependent aldehyde dehydrogenase was also inhibited. No significant change was found for aldehyde reductase activity. A decreased hepatocellular metabolism of HNE can expose liver parenchymal and non-parenchymal cells to cytotoxic as well as pro-inflammatory and pro-fibrogenic effects of HNE, contributing to the development of chronic cholestatic liver damage.

Alcohol Dehydrogenase↗
PubMed1995

Changes of adenylate cyclase activity in AH-130 ascites hepatoma of Yoshida induced by enrichment with fatty acids.

Enrichment of hepatoma cells with arachidonic acid increases fluidity of plasma membranes, unstimulated lipid peroxidation and basal adenylate cyclase activity, whereas enrichment with stearic acid decreases fluidity and does not cause any variation in lipid peroxidation or adenylate cyclase. The increase in adenylate cyclase activity may be due to the increase not only in fluidity, but also in lipid peroxidation products. Indeed, adenylate cyclase is stimulated by 4-hydroxynonenal, one important product of lipid peroxidation, when added to plasma membranes. 4-hydroxynonenal increases adenylate cyclase two-fold in unenriched plasma membranes and three-fold in plasma membranes enriched with arachidonic acid in comparison with basal activity.

Adenylyl Cyclases↗
PubMed1995

Enrichment with arachidonic acid increases the sensitivity of hepatoma cells to the cytotoxic effects of oxidative stress.

Hepatoma cells are, at most, moderately sensitive to oxidative stress. An important cause of this lack of sensitivity is the decreased content of polyunsaturated fatty acids in comparison with normal cells. These fatty acids are one cellular target of oxygen radicals, by which they are broken down into several toxic carbonyl compounds. If the membrane phospholipids of tumor cells are enriched with polyunsaturated fatty acids, such as arachidonic acid, they become able to undergo lipid peroxidation in the presence of prooxidants. This effect is studied in the highly deviated Yoshida AH-130 ascites hepatoma and in two rat hepatoma cell lines. In parallel to their increased lipid peroxidation, cells enriched with arachidonic acid and exposed to ascorbic acid/FeSO4 showed lower viability and growth than unenriched ones.

Aldehydes↗
PubMed1994

Role of aldehyde metabolizing enzymes in mediating effects of aldehyde products of lipid peroxidation in liver cells.

It is well established that many types of tumor cells have reduced lipid peroxidation capacity compared to their normal counterparts. Changes in the activity of enzymes metabolizing aldehydes produced by lipid peroxidation have also been reported in a variety of tumor cells. We have investigated the relationship between changes in lipid peroxidation and changes in aldehyde-metabolizing enzymes in normal hepatocytes and two representative rat hepatoma cell lines, McA-RH-7777 and JM2. Compared to hepatocytes, both 7777 and JM2 cells have significantly lower basal and prooxidant-induced levels of lipid peroxidation than normal hepatocytes. Using 4-hydroxynonenal (4-HNE) as substrate, both cell lines also have significantly reduced activities of alcohol dehydrogenase (ADH) and glutathione S-transferase (GST) compared to hepatocytes. JM2 cells have significantly increased aldehyde dehydrogenase (ALDH) and aldehyde reductase (ALRD) activities with 4-HNE. In 7777 cells the ALDH and ALRD activities are not different from hepatocytes. The changes in enzyme activity are inversely correlated with the sensitivity of cells to 4-HNE. JM2 cells, with increased ALDH and ALRD and decreased ADH and GST, are much more resistant to the toxic effects of 4-HNE than 7777 cells. Normal hepatocytes and JM2 cells are approximately equally resistant to 4-HNE even though hepatocytes rely primarily on GST-mediated aldehyde conjugation to metabolize 4-HNE. Coupled with previous results from our laboratories, the overall increased sensitivity of certain hepatoma cells to lipid aldehydes appears due to decreased ability of these hepatoma cells to remove toxic products of lipid peroxidation. Moreover, hepatoma cells with increased levels of aldehyde dehydrogenase and aldehyde reductase appear most like hepatocytes in their ability to metabolize lipid aldehydes.

Aldehyde Dehydrogenase↗
PubMed1994

Oxygen free radicals are not the main factor in experimental gentamicin nephrotoxicity.

As a role for oxygen free radicals has been suggested in gentamicin (G) nephrotoxicity, we tested the hypothesis that exogenously administered glutathione (GSH), able to restore intracellular antioxidant potential, could be useful in reducing damage. Adult Sprague-Dawley rats were injected with saline (n = 30), subcutaneous (s.c.) G 100 (n = 23) and 150 mg/kg/day (n = 14), or s.c. G at the same dosages plus intraperitoneal (i.p.) GSH 1200 mg/kg/day (n = 24 and 14, respectively) for 7 days. In the G-100-day protocol, GSH-treated rats showed significantly lower renal G content (2.79 +/- 0.8 vs. 3.61 +/- 1.4 micrograms/mg prot) coupled with lower plasma urea (153 +/- 79 vs. 188 +/- 61 mg/dL) and creatinine levels (1.63 +/- 1 vs. 2.45 +/- 1 mg/dL). As to renal oxidant/antioxidant balance, local GSH was increased (0.32 +/- 0.01 vs. 0.19 +/- 0.01 microgram/mg prot) while lipid peroxidation, determined by production of thiobarbituric acid reactive substances (TBARS), was decreased (0.35 +/- 0.02 vs. 0.52 +/- 0.02 nmol/mg prot). In the G-150-mg protocol, GSH-treated rats showed no differences in renal gentamicin content or in blood urea and creatinine levels, in spite of a significantly lower renal TBARS production and a significantly higher GSH content. Urine enzyme excretion did not significantly change in GSH-treated vs. not-GSH-treated rats in both protocols. We conclude that: (a) GSH interferes with G nephrotoxicity mainly via a reduction in G uptake; (b) the oxidative renal stress is not crucial in inducing renal damage. In fact, when increased G dosages blunt the ability of GSH in reducing G uptake, no substantial protection is demonstrated.

Animals↗
PubMed1993

Ability of different hepatoma cells to metabolize 4-hydroxynonenal.

4-Hydroxynonenal (4-HNE), produced during the oxidative lipid breakdown of biological membranes, modulates various biochemical processes in normal liver and in hepatoma cells. It is very probable that the effects of 4-HNE are related to the quantity formed in the cells and to the cells' ability to metabolize it. Aldehyde catabolism takes place within the cells through oxidative and reductive enzymes, and through conjugation with intracellular glutathione. In this paper, the various enzymatic pathways involved in the metabolism of 4-HNE were studied in normal hepatocytes and in hepatoma cells. The hepatocyte pathway undergoes a complex variety of change during neoplastic transformation. In hepatoma cells, generally, 4-HNE metabolism was due mainly to aldehyde dehydrogenases, whereas in normal hepatocytes 4-HNE metabolism was mainly due to alcohol dehydrogenase and glutathione-S-transferase. The increase in oxidative enzymes compared to normal tissue was not the same in all types of hepatoma: in HTC hepatoma cells, the enzyme levels were considerably higher; in AH-130 hepatoma cells of Yoshida, they were lower in subcellular particles and similar in the cytosol. Indeed, consumption of externally-added 4-HNE in hepatoma cells was proportional to their content of 4-HNE metabolizing enzymes.

Alcohol Dehydrogenase↗
PubMed1993

Glutathione-S-transferase, alcohol dehydrogenase and aldehyde reductase activities during diethylnitrosamine-carcinogenesis in rat liver.

Several enzymes metabolize the toxic aldehydes produced during lipid peroxidation, such as 4-hydroxynonenal. During carcinogenesis induced by diethylnitrosamine in rat liver, an increase in aldehyde dehydrogenase, in comparison with normal liver, has already been shown. This paper demonstrates that, although to a lesser extent than aldehyde dehydrogenase, aldehyde reductase and glutathione-S-transferase also increase during carcinogenesis. Of the latter two enzymes, aldehyde reductase increases more markedly in a progressive fashion during the months of development of nodules and hepatoma. The increase of enzymes able to metabolize 4-hydroxynonenal, as well as other aldehydes, is certainly important in protecting tumour cells against cytotoxic effect of aldehydes.

Alcohol Dehydrogenase↗
PubMed1993

Tissue protein turnover during liver carcinogenesis.

Overall rates of tissue protein degradation in vivo during chemical hepatocarcinogenesis were estimated by a double-isotope method as well as from the accumulation of peptide intermediates in protein degradation induced by bestatin. Several parameters estimating rates of cell proliferation and cell loss have been measured in parallel. The two procedures adopted consistently indicated that protein turnover was significantly slowed down through the whole observation period (12 months after the initiating administration of DENA) in both 'preneoplastic' nodules and hepatomas as compared with control livers or perinodular tissue. Such a difference may confer a selective growth advantage to 'preneoplastic' and tumoral cells. Since protein degradation rates did not appreciably differ between nodules and hepatomas, either such advantage originated from some early step in the carcinogenetic process or it merely reflected the proliferative events in the two cell populations. Yet neither liver nodules nor hepatomas were characterized by very high rates of cell proliferation, however much increased with respect to control liver.

Animals↗
PubMed1991

Lipid peroxidation in rat AH-130 hepatoma cells enriched in vitro with arachidonic acid.

Tumor cells generally display low lipid peroxidation. A low content of polyunsaturated fatty acids in membrane phospholipids is a possible cause of their decreased susceptibility to lipid peroxidation. To investigate the importance of substrate availability in eliciting lipid peroxidation and to study cell viability in conditions of stimulated lipid peroxidation, AH-130 hepatoma cells were enriched with arachidonic acid. The enriched hepatoma cells showed increased mortality correlated with the increased incorporation of arachidonic acid in membrane phospholipids. When 0.5 mM arachidonic acid was added to hepatoma cells, this fatty acid reached a percentage content similar to that found in hepatocytes. Hepatoma cells enriched with this concentration were further incubated to determine their susceptibility to lipid peroxidation; mortality increased in parallel with increased thiobarbituric acid-reactive substance production. The highest mortality was in hepatoma cells treated with ascorbate/FeSO4. Mortality in normal cells was low, although they had a high production of thiobarbituric acid-reactive substances. The high capability of normal cells to metabolize the products of lipid peroxidation might explain the different viabilities of normal cells and hepatoma cells. It may therefore be possible to modify the composition of fatty acids of hepatoma cells in order to sensitize them to the toxic effect of prooxidant agents.

Animals↗
PubMed1991

Comparative subcellular distribution of benzaldehyde and acetaldehyde dehydrogenase activities in two hepatoma cell lines and in normal hepatocytes.

The NAD- and NADP-dependent aldehyde dehydrogenase (ALDH) activities were evaluated in two rat hepatoma cell lines, namely the well-differentiated MH1C1 line and the less differentiated HTC line. Each activity was determined in parallel in isolated rat hepatocytes, for comparison. The aliphatic aldehyde acetaldehyde (ACA) and the aromatic aldehyde benzaldehyde (BA) were used as substrates. With the first substrate the ALDH activities found in the crude cytoplasmic extracts were lower in hepatoma cells than in normal hepatocytes, especially when measured with NADP as coenzyme (ACA/NADP). Otherwise, with benzaldehyde as substrate the NAD-dependent enzyme activity (BA/NAD) was increased about 9-fold in HTC cells over hepatocytes and decreased in MH1C1 cells, while the NADP-dependent (BA/NADP) activity was increased 38- and 2.5-fold in HTC and MH1C1 cell lines, respectively. Studies on the subcellular distribution of these enzyme activities showed that the activity measured with acetaldehyde and NAD (ACA/NAD) was almost equally distributed between the cytosol and the subcellular particles in the three cell populations, but the ACA/NADP activity was shifted towards the cytosolic compartment in hepatomas, especially in HTC cells. The BA/NAD and BA/NADP ALDH activities found in the organelles of hepatoma cells were markedly reduced in comparison with hepatocytes, in favour of the cytosol. The most striking difference between the normal and the transformed cells was the 94-fold increase over hepatocytes of the BA/NADP activity, found in the cytosolic fractions of HTC cells. MH1C1 cells showed a less pronounced (7.5-fold) enhancement of this tumour-associated specific activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaldehyde↗
PubMed1991

Lipid peroxidation in fatty liver induced by caffeine in rats.

An increase in lipid peroxidation has been found in liver after poisoning with hepatotoxic substances and following dietary changes, i.e. choline-devoid diet and orotic acid-rich diet. In this study we analysed in the rat a model of fatty liver induced by administration of caffeine. The results seem to indicate an increased peroxidability in the liver of caffeine-treated animals, due to an increase in triglyceride content. A decrease of vitamin E which also occurs might contribute to the lipid peroxidation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1989

Oxidative metabolism of 4-hydroxy-2,3-nonenal during diethyl-nitrosamine-induced carcinogenesis in rat liver.

In some chemically-induced hepatomas and in cultured transformed cells the aldehyde dehydrogenase activity was found increased in the presence of aromatic aldehyde as substrate. We studied this enzyme during diethyl-nitrosamine carcinogenesis in rat liver by using an aliphatic aldehyde, 4-hydroxynonenal, as substrate. 4-Hydroxynonenal is an important product of lipid peroxidation. The NAD- and NADP-dependent aldehyde dehydrogenase of the cytosolic fraction and the NADP-dependent aldehyde dehydrogenase of the microsomes show higher values in nodules and hepatoma than in normal liver. These results suggest that increased aldehyde dehydrogenase, when 4-hydroxynonenal is used, can be considered a marker of the neoplastic process, in the same way as the level of aldehyde dehydrogenase increased in presence of aromatic aldehyde.

Aldehyde Dehydrogenase↗
PubMed1989

Fatty acid composition of phospholipids in mitochondria and microsomes during diethylnitrosamine carcinogenesis in rat liver.

Changes in lipid composition and function of subcellular organelles have been described in transplanted and primary tumours. We examine here the fatty acid composition of individual phospholipids (PL) in hyperplastic nodules and primary hepatoma induced by diethylnitrosamine (DEN), compared to that of normal liver and of transplantable Yoshida AH-130 hepatoma. Phosphatidylcholine and phosphatidylethanolamine fatty acid composition in mitochondria and microsomes from primary hepatoma were markedly different from normal liver; C18:0/C18:1 ratio was lower and the ratio between monosaturated and polyunsaturated fatty acids was higher. Linoleic acid content of mitochondrial cardiolipin, usually very high in normal rat liver, was notably lower in primary hepatoma. Cholesterol/phospholipid ratio in both microsomes and mitochondria from DEN-induced hepatoma was higher than in normal liver. Hyperplastic nodules showed no changes in cholesterol content whereas modifications in fatty acid composition were already observable. These modifications of membrane structure may be related to the functional changes found in nodular cells. Changes in fatty acid composition of membrane phospholipids, occurring in both primary hepatoma and preneoplastic nodules, might be one of the causes for decreased rate of lipid peroxidation peculiar to these tissues.

Animals↗
PubMed1986

Resistance to oxidative stress by hyperplastic and neoplastic rat liver tissue monitored in terms of production of unpolar and medium polar carbonyls.

The susceptibility of rat liver tissue to oxidative stress during its neoplastic transformation was analyzed by both qualitative and quantitative measurements of the carbonyl products of lipid peroxidation. Diethylnitrosamine was used as initiating agent of hepatocarcinogenesis and lipid peroxidation levels were monitored in the homogenates from normal liver, hyperplastic nodules and tumour, incubated in the presence or in the absence of ascorbate or adenosine diphosphate-iron complex. While the basal levels of lipid peroxidation in the three experimental conditions were found to be quite similar, in the presence of the pro-oxidant stimulus a remarkable reduction in aldehyde production was shown not only by the hepatoma tissue but also by the preneoplastic nodules.

Aldehydes↗