FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 1999
It has been reported in several cell lines that exposure to low levels of reactive oxygen species... more It has been reported in several cell lines that exposure to low levels of reactive oxygen species can exert a stimulatory effect on their proliferation. We have previously shown that mild oxidative conditions can also counteract apoptotic stimuli. A constitutive cellular production of low levels of superoxide and hydrogen peroxide originates from various sources; among these, gamma-glutamyl transpeptidase (GGT), the plasma membrane-bound activity in charge of metabolizing extracellular reduced glutathione, has recently been included. Since the inhibition of GGT is a sufficient stimulus for the induction of apoptosis in selected cell lines, we investigated whether this effect might result from the suppression of the mentioned GGT-dependent prooxidant reactions, on the theory that the latter may represent a basal antiapoptotic and proliferative signal for the cell. Experiments showed that: 1) GGT activity in U937 monoblastoid cells is associated with the production of low levels of hy...
Oxidative events ‐ the oxidation of low-density lipoproteins (LDL) in the first place ‐ have been... more Oxidative events ‐ the oxidation of low-density lipoproteins (LDL) in the first place ‐ have been shown to participate in the progression of atherosclerosis and precipitation of cardiovascular events. This occurs through modulation of important components of lesions of the vessel wall (smooth muscle cell proliferation, protease/antiprotease balance, endothelial functions). Our recent studies have provided evidence that the enzyme gamma-glutamyltransferase (GGT), normally found in serum, is often accumulated within the plaque environment in substantial amounts, and that this activity is a potential source of a variety of prooxidant species. Concurrently, epidemiological research has conclusively documented that the serum levels of GGT are an independent factor in prognosis of myocardial infarction and stroke in atherosclerotic patients. Several signs suggest that the GGT appearing in plaque tissue may originate from the serum enzyme, which in facts associates with the circulating lip...
Gamma-glutamyltransferase (GGT) is a well-established independent risk factor for cardiovascular ... more Gamma-glutamyltransferase (GGT) is a well-established independent risk factor for cardiovascular mortality related to atherosclerotic disease. Four GGT fractions have been identified in plasma, but only b-GGT fraction accumulates in atherosclerotic plaques, and correlates with other histological markers of vulnerability. The present study was aimed to evaluate whether macrophagic lineage cells may provide a source of b-GGT within the atherosclerotic plaque. GGT expression and release were studied in human monocytes isolated from peripheral blood of healthy donors. The growth factors GM-CSF and M-CSF were used to induce differentiation into M1-like and M2-like macrophages, respectively. Plaque GGT was investigated in tissue samples obtained from patients undergoing carotid endoarterectomy. We found that M1-like macrophages express higher levels of GGT as compared to M2-like, and that both monocytes and M1-like macrophages-but not M2-like-are able to release the b-GGT fraction upon ac...
GGT showed an independent prognostic value after adjustment for possible confounders, including a... more GGT showed an independent prognostic value after adjustment for possible confounders, including alcohol consumption, and beyond established risk factors, such as extent of coronary atherosclerotic disease, left ventricular ejection fraction, age, serum glucose, cholesterol subfractions, ...
The metabolism of glutathione by membrane-bound &ggr;-glutamyl transpeptidase (GGT) has b... more The metabolism of glutathione by membrane-bound &ggr;-glutamyl transpeptidase (GGT) has been recently recognized as a basal source of hydrogen peroxide in the extracellular space. Significant levels of GGT activity are expressed by malignant tumours, and in melanoma cell lines they were found to correlate with the malignant behaviour. As hydrogen peroxide and other oxidants can affect signal transduction pathways at several levels, the present study was aimed to verify: (i) the occurrence of GGT-dependent production of hydrogen peroxide in melanoma cells; (ii) the effects of GGT-dependent prooxidant reactions on known redox-sensitive cellular targets, i.e. protein thiols, the nuclear transcription factor NF-kappa B and p53. Two melanoma Me665/2 cell clones, exhibiting traces of (clone 2/21) or high (clone 2/60) GGT activity, were studied. The occurrence of GGT-dependent production of hydrogen peroxide was apparent in 2/60 cells, in which it was accompanied by lower levels of cell surface protein thiols. In 2/60 cells, GGT expression was also associated with higher levels of NF-kappa B activation, as compared to GGT-poor 2/21 cell clone. Indeed, stimulation or inhibition of GGT activity in 2/60 cells resulted in progressive activation or inactivation of NF-kappa B, respectively. An analysis of the p53 gene product indicated lack of protein expression in 2/60 cells, whereas a mutant protein was highly expressed in 2/21 cells. Taken together, these results indicate that the expression of GGT activity can provide melanoma cells with an additional source of hydrogen peroxide, and that such prooxidant reactions are capable to modify protein thiols at the cell surface level. In addition, GGT expression results in an up-regulation of the transcription factor NF-kappa B, which could explain the higher metastatic behaviour reported for GGT-rich melanoma cells as compared to their GGT-poor counterparts.
Many studies have implicated the role of oxidant stress in a wide range of human diseases and hav... more Many studies have implicated the role of oxidant stress in a wide range of human diseases and have led to the rapid expansion of research in this area. With many experimental approaches a direct detection of the production of reactive oxygen species (ROS) and free radicals is not possible. Free radicals are very reactive, short-lived and react in a non-specific way, so that ongoing oxidative damage is generally analyzed by measurement of secondary products e.g. H2O2, "oxidized" proteins, peroxidized lipids and their break-down products, "oxidized" DNA or by fluorographic analysis in combination with fluorescent dyes e.g. dichlorofluorescin (DCFH). The histochemical visualization of selected molecular markers for oxidative phenomena can often provide valuable information concerning the distribution of oxidative processes in vivo. A number of biochemical methods are available for the monitoring of almost all oxidant stress-related processes, although their applicab...
The activity of glucose-6-phosphate dehydrogenase (G6PD) was studied in five brain areas of rats ... more The activity of glucose-6-phosphate dehydrogenase (G6PD) was studied in five brain areas of rats aged 5 to 90 days. The areas studied were: the olfactory bulb (OB), cortex, hippocampus, striatum and septum. The G6PD activity increased more than 2-fold from 5 to 90 days in the OB, while it was almost constant in the other areas. At every stage of development, the G6PD activity was significantly higher in the OB than in the other areas. The G6PD pattern was compared with 6-phosphogluconate dehydrogenase (6PGD), glutathione reductase (GR); glutathione peroxidase (GPX), catalase (CAT) and superoxide dismutase (SOD) in order to find synergistic interactions among activities of these enzymes during development. Over the considered period, the activity of 6PGD increased significantly in the OB, while no significant difference in activity was detected in the other areas. GR increased significantly and progressively at each developmental stage in all areas. GPX showed a progressive increase ...
International journal for vitamin and nutrition research. Internationale Zeitschrift für Vitamin- und Ernährungsforschung. Journal international de vitaminologie et de nutrition, 1997
Oxidant stress--i.e. the prevalence within the cell of oxidizing species over the cellular antiox... more Oxidant stress--i.e. the prevalence within the cell of oxidizing species over the cellular antioxidant potential--is recognized as a primary factor in the pathogenesis of a series of important human pathologies. The possibility of a preventive or therapeutic intervention by means of antioxidant factors, including those naturally contained in diet, increases the importance of a correct understanding of the molecular mechanisms involved in such pathologies. A number of sophisticated biochemical methods are available, for the monitoring of nearly all oxidant stress-related processes; their applicability to in vivo conditions is however limited. In these conditions, the histochemical visualization in tissue sections and isolated cells of selected molecular markers for oxidative phenomena can often provide valuable information about the distribution of processes in vivo. This paper includes an overview of the basic biochemical reactions occurring during oxidant stress and lipid peroxidat...
Confocal laser scanning fluorescence microscopy plus image videoanalysis was used to visualize th... more Confocal laser scanning fluorescence microscopy plus image videoanalysis was used to visualize the tissue areas and the subcellular sites first involved by oxidative stress and lipid peroxidation, in the well-established experimental model of lipid peroxidation induced by haloalkane intoxication in the liver cell. The fluorescent reagent 3-hydroxy-2-naphthoic acid hydrazide was employed to derivativize the carbonyl functions originating from the lipoperoxidative process in situ, in liver cryostat sections from in vivo intoxicated rats, as well as in isolated hepatocytes exposed in vitro to the pro-oxidant action of haloalkanes. The results obtained indicate that: 1) the detection of fluorescent derivatives of carbonyls indeed offers a gain in sensitivity, 2) haloalkane-induced lipid peroxidation in hepatocytes primarily involves the perinuclear endoplasmic reticulum, whereas the plasma membrane and the nuclear compartment are unaffected, and 3) lipid peroxidation also induces an inc...
Bollettino della Società italiana di biologia sperimentale, Jan 30, 1984
Intoxication of NMRI Albino mice with bromobenzene is often followed by the appearance of neurolo... more Intoxication of NMRI Albino mice with bromobenzene is often followed by the appearance of neurological symptoms. The possibility was investigated that the intoxication results in glutathione (GSH) depletion in central nervous systems as seen in other tissues, and that such a depletion is followed by the development of lipid peroxidation. 18-20 hours after bromobenzene administration (15 mmoles/Kg, p.o.) GSH content of prosencephalic and metencephalic regions was depleted by 39 and 55%, respectively. Lipid peroxidation (measured by the tissue content of malonildialdehyde) was observed only when GSH content reached a threshold value, which was different for prosencephalon as compared to metencephalon (2-1.5 mumoles GSH/g and 1.2-0.7 mumoles GSH/g, respectively). Possible mechanisms underlying the phenomenon are discussed.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 1999
It has been reported in several cell lines that exposure to low levels of reactive oxygen species... more It has been reported in several cell lines that exposure to low levels of reactive oxygen species can exert a stimulatory effect on their proliferation. We have previously shown that mild oxidative conditions can also counteract apoptotic stimuli. A constitutive cellular production of low levels of superoxide and hydrogen peroxide originates from various sources; among these, gamma-glutamyl transpeptidase (GGT), the plasma membrane-bound activity in charge of metabolizing extracellular reduced glutathione, has recently been included. Since the inhibition of GGT is a sufficient stimulus for the induction of apoptosis in selected cell lines, we investigated whether this effect might result from the suppression of the mentioned GGT-dependent prooxidant reactions, on the theory that the latter may represent a basal antiapoptotic and proliferative signal for the cell. Experiments showed that: 1) GGT activity in U937 monoblastoid cells is associated with the production of low levels of hy...
Oxidative events ‐ the oxidation of low-density lipoproteins (LDL) in the first place ‐ have been... more Oxidative events ‐ the oxidation of low-density lipoproteins (LDL) in the first place ‐ have been shown to participate in the progression of atherosclerosis and precipitation of cardiovascular events. This occurs through modulation of important components of lesions of the vessel wall (smooth muscle cell proliferation, protease/antiprotease balance, endothelial functions). Our recent studies have provided evidence that the enzyme gamma-glutamyltransferase (GGT), normally found in serum, is often accumulated within the plaque environment in substantial amounts, and that this activity is a potential source of a variety of prooxidant species. Concurrently, epidemiological research has conclusively documented that the serum levels of GGT are an independent factor in prognosis of myocardial infarction and stroke in atherosclerotic patients. Several signs suggest that the GGT appearing in plaque tissue may originate from the serum enzyme, which in facts associates with the circulating lip...
Gamma-glutamyltransferase (GGT) is a well-established independent risk factor for cardiovascular ... more Gamma-glutamyltransferase (GGT) is a well-established independent risk factor for cardiovascular mortality related to atherosclerotic disease. Four GGT fractions have been identified in plasma, but only b-GGT fraction accumulates in atherosclerotic plaques, and correlates with other histological markers of vulnerability. The present study was aimed to evaluate whether macrophagic lineage cells may provide a source of b-GGT within the atherosclerotic plaque. GGT expression and release were studied in human monocytes isolated from peripheral blood of healthy donors. The growth factors GM-CSF and M-CSF were used to induce differentiation into M1-like and M2-like macrophages, respectively. Plaque GGT was investigated in tissue samples obtained from patients undergoing carotid endoarterectomy. We found that M1-like macrophages express higher levels of GGT as compared to M2-like, and that both monocytes and M1-like macrophages-but not M2-like-are able to release the b-GGT fraction upon ac...
GGT showed an independent prognostic value after adjustment for possible confounders, including a... more GGT showed an independent prognostic value after adjustment for possible confounders, including alcohol consumption, and beyond established risk factors, such as extent of coronary atherosclerotic disease, left ventricular ejection fraction, age, serum glucose, cholesterol subfractions, ...
The metabolism of glutathione by membrane-bound &ggr;-glutamyl transpeptidase (GGT) has b... more The metabolism of glutathione by membrane-bound &ggr;-glutamyl transpeptidase (GGT) has been recently recognized as a basal source of hydrogen peroxide in the extracellular space. Significant levels of GGT activity are expressed by malignant tumours, and in melanoma cell lines they were found to correlate with the malignant behaviour. As hydrogen peroxide and other oxidants can affect signal transduction pathways at several levels, the present study was aimed to verify: (i) the occurrence of GGT-dependent production of hydrogen peroxide in melanoma cells; (ii) the effects of GGT-dependent prooxidant reactions on known redox-sensitive cellular targets, i.e. protein thiols, the nuclear transcription factor NF-kappa B and p53. Two melanoma Me665/2 cell clones, exhibiting traces of (clone 2/21) or high (clone 2/60) GGT activity, were studied. The occurrence of GGT-dependent production of hydrogen peroxide was apparent in 2/60 cells, in which it was accompanied by lower levels of cell surface protein thiols. In 2/60 cells, GGT expression was also associated with higher levels of NF-kappa B activation, as compared to GGT-poor 2/21 cell clone. Indeed, stimulation or inhibition of GGT activity in 2/60 cells resulted in progressive activation or inactivation of NF-kappa B, respectively. An analysis of the p53 gene product indicated lack of protein expression in 2/60 cells, whereas a mutant protein was highly expressed in 2/21 cells. Taken together, these results indicate that the expression of GGT activity can provide melanoma cells with an additional source of hydrogen peroxide, and that such prooxidant reactions are capable to modify protein thiols at the cell surface level. In addition, GGT expression results in an up-regulation of the transcription factor NF-kappa B, which could explain the higher metastatic behaviour reported for GGT-rich melanoma cells as compared to their GGT-poor counterparts.
Many studies have implicated the role of oxidant stress in a wide range of human diseases and hav... more Many studies have implicated the role of oxidant stress in a wide range of human diseases and have led to the rapid expansion of research in this area. With many experimental approaches a direct detection of the production of reactive oxygen species (ROS) and free radicals is not possible. Free radicals are very reactive, short-lived and react in a non-specific way, so that ongoing oxidative damage is generally analyzed by measurement of secondary products e.g. H2O2, "oxidized" proteins, peroxidized lipids and their break-down products, "oxidized" DNA or by fluorographic analysis in combination with fluorescent dyes e.g. dichlorofluorescin (DCFH). The histochemical visualization of selected molecular markers for oxidative phenomena can often provide valuable information concerning the distribution of oxidative processes in vivo. A number of biochemical methods are available for the monitoring of almost all oxidant stress-related processes, although their applicab...
The activity of glucose-6-phosphate dehydrogenase (G6PD) was studied in five brain areas of rats ... more The activity of glucose-6-phosphate dehydrogenase (G6PD) was studied in five brain areas of rats aged 5 to 90 days. The areas studied were: the olfactory bulb (OB), cortex, hippocampus, striatum and septum. The G6PD activity increased more than 2-fold from 5 to 90 days in the OB, while it was almost constant in the other areas. At every stage of development, the G6PD activity was significantly higher in the OB than in the other areas. The G6PD pattern was compared with 6-phosphogluconate dehydrogenase (6PGD), glutathione reductase (GR); glutathione peroxidase (GPX), catalase (CAT) and superoxide dismutase (SOD) in order to find synergistic interactions among activities of these enzymes during development. Over the considered period, the activity of 6PGD increased significantly in the OB, while no significant difference in activity was detected in the other areas. GR increased significantly and progressively at each developmental stage in all areas. GPX showed a progressive increase ...
International journal for vitamin and nutrition research. Internationale Zeitschrift für Vitamin- und Ernährungsforschung. Journal international de vitaminologie et de nutrition, 1997
Oxidant stress--i.e. the prevalence within the cell of oxidizing species over the cellular antiox... more Oxidant stress--i.e. the prevalence within the cell of oxidizing species over the cellular antioxidant potential--is recognized as a primary factor in the pathogenesis of a series of important human pathologies. The possibility of a preventive or therapeutic intervention by means of antioxidant factors, including those naturally contained in diet, increases the importance of a correct understanding of the molecular mechanisms involved in such pathologies. A number of sophisticated biochemical methods are available, for the monitoring of nearly all oxidant stress-related processes; their applicability to in vivo conditions is however limited. In these conditions, the histochemical visualization in tissue sections and isolated cells of selected molecular markers for oxidative phenomena can often provide valuable information about the distribution of processes in vivo. This paper includes an overview of the basic biochemical reactions occurring during oxidant stress and lipid peroxidat...
Confocal laser scanning fluorescence microscopy plus image videoanalysis was used to visualize th... more Confocal laser scanning fluorescence microscopy plus image videoanalysis was used to visualize the tissue areas and the subcellular sites first involved by oxidative stress and lipid peroxidation, in the well-established experimental model of lipid peroxidation induced by haloalkane intoxication in the liver cell. The fluorescent reagent 3-hydroxy-2-naphthoic acid hydrazide was employed to derivativize the carbonyl functions originating from the lipoperoxidative process in situ, in liver cryostat sections from in vivo intoxicated rats, as well as in isolated hepatocytes exposed in vitro to the pro-oxidant action of haloalkanes. The results obtained indicate that: 1) the detection of fluorescent derivatives of carbonyls indeed offers a gain in sensitivity, 2) haloalkane-induced lipid peroxidation in hepatocytes primarily involves the perinuclear endoplasmic reticulum, whereas the plasma membrane and the nuclear compartment are unaffected, and 3) lipid peroxidation also induces an inc...
Bollettino della Società italiana di biologia sperimentale, Jan 30, 1984
Intoxication of NMRI Albino mice with bromobenzene is often followed by the appearance of neurolo... more Intoxication of NMRI Albino mice with bromobenzene is often followed by the appearance of neurological symptoms. The possibility was investigated that the intoxication results in glutathione (GSH) depletion in central nervous systems as seen in other tissues, and that such a depletion is followed by the development of lipid peroxidation. 18-20 hours after bromobenzene administration (15 mmoles/Kg, p.o.) GSH content of prosencephalic and metencephalic regions was depleted by 39 and 55%, respectively. Lipid peroxidation (measured by the tissue content of malonildialdehyde) was observed only when GSH content reached a threshold value, which was different for prosencephalon as compared to metencephalon (2-1.5 mumoles GSH/g and 1.2-0.7 mumoles GSH/g, respectively). Possible mechanisms underlying the phenomenon are discussed.
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