Biomedical subjects

G Rotilio

Publications and source records attributed to G Rotilio.

At least 55 records · Page 3Linked to original sources

PubMed1998

Decrease of cytochrome c oxidase protein in heart mitochondria of copper-deficient rats.

Copper deficiency has been reported to be associated with decreased cytochrome c oxidase activity, which in turn may be responsible for the observed mitochondrial impairment and cardiac failure. We isolated mitochondria from hearts of copper-deficient rats: cytochrome c oxidase activity was found to be lower than in copper-adequate mitochondria. The residual activity paralleled copper content of mitochondria and also corresponded with the heme amount associated with cytochrome aa3. In fact, lower absorption in the alpha-band region of cytochrome aa3 was found for copper-deficient rat heart mitochondria. Gel electrophoresis of protein extracted from mitochondrial membranes allowed measurements of protein content of the complexes of oxidative phosphorylation, revealing a lower content of complex IV protein in copper-deficient rat heart mitochondria. The alterations caused by copper deficiency appear to be specific for cytochrome c oxidase. Changes were not observed for F0F1ATP synthase activity, for heme contents of cytochrome c and b, and for protein contents of complexes I, III and V. The present study demonstrates that the alteration of cytochrome c oxidase activity observed in copper deficiency is due to a diminished content of assembled protein and that shortness of copper impairs heme insertion into cytochrome c oxidase.

Animals↗

PubMed1998

Rescue of cells from apoptosis by inhibition of active GSH extrusion.

Cells induced to apoptosis extrude glutathione in the reduced form concomitantly with (U937 cells) or before (HepG2 cells) the development of apoptosis, much earlier than plasma membrane leakage. Two specific inhibitors of carrier-mediated GSH extrusion, methionine or cystathionine, are able to decrease apoptotic GSH efflux across the intact plasma membrane, demonstrating that in these cell systems GSH extrusion occurs via a specific mechanism. While decreasing GSH efflux, cystathionine or methionine also decrease the extent of apoptosis. They fail to exert anti-apoptotic activity in cells previously deprived of GSH, indicating that the target of the protection is indeed GSH efflux. The cells rescued by methionine or cystathionine remained viable after removal of the apoptogenic inducers and were even able to replicate. This shows that a real rescue to perfect viability and not just a delay of apoptosis is achieved by forcing GSH to stay within the cells during apoptogenic treatment. All this evidence indicates that extrusion of reduced glutathione precedes and is responsible for the irreversible morphofunctional changes of apoptosis, probably by altering the intracellular redox state without intervention of reactive oxygen species, thus giving a rationale for the development of redox-dependent apoptosis under anaerobic conditions.

Apoptosis↗

PubMed1998

Hypoglycemia, hypoxia, and ischemia in a corticostriatal slice preparation: electrophysiologic changes and ascorbyl radical formation.

Experimental and clinical data suggest that oxygen and/or glucose deprivation alters electrical transmission in the brain and generates free radicals, which may mediate neuronal death. We have analyzed the effects of oxygen and/or glucose deprivation on both excitatory transmission, by measuring field potential amplitude, and free radical production, by using electron spin resonance (ESR) spectroscopy, in a corticostriatal slice preparation. Combined oxygen and/or glucose deprivation (ischemia) lasting 10 to 20 minutes induced a long-term depression of field potential amplitude. The ascorbyl radical could only be detected in brain slices during the reperfusion-phase after 30 minutes of ischemia. It appeared in the early minutes after the washout of ischemic medium and remained stable throughout the reperfusion phase. This radical was never detected in the external medium. Ischemia induced only a slight, but progressive, release of lactate dehydrogenase (LDH) into the external medium during the reperfusion phase. In contrast, exposure of slices to hypoxia or hypoglycemia alone resulted in transient depression of field potential amplitude, and no generation of ascorbyl radicals was observed on reperfusion. We propose that the long-lasting loss of electrical signals is the early sign of neuronal damage during ischemia. On the other hand, ascorbyl radical formation may be considered an indicator of neuronal injury after prolonged energy deprivation.

Animals↗

PubMed1997

Unique structural features of the monomeric Cu,Zn superoxide dismutase from Escherichia coli, revealed by X-ray crystallography.

The first three-dimensional structure of a functional monomeric Cu, Zn superoxide dismutase (from Escherichia coli, E_SOD) is reported at 2.0 A resolution (R-factor=16.8%). Compared to the homologous eukaryotic enzymes, E_SOD displays a perturbed antiparallel beta-barrel structure. The most striking structural features observed include extended amino acid insertions in the surface 1, 2-loop and S-S subloop, modification of the disulfide bridge connection, and loss of functional electrostatic residues, suggesting a modified control of substrate steering toward the catalytic center. The active site Cu2+ displays a distorted coordination sphere due to an unusually long bond to the metal-bridging residue His61. Inspection of the crystal packing does not show regions of extended contact indicative of a dimeric assembly. The molecular surface region involved in subunit dimerization in eukaryotic superoxide dismutases is structurally altered in E_SOD and displays a net polar nature.

Amino Acid Sequence↗

PubMed1997

Expression of a Cu,Zn superoxide dismutase typical of familial amyotrophic lateral sclerosis induces mitochondrial alteration and increase of cytosolic Ca2+ concentration in transfected neuroblastoma SH-SY5Y cells.

We have set up a model system for familial amyotrophic lateral sclerosis (FALS) by transfecting human neuroblastoma cell line SH-SY5Y with plasmids directing constitutive expression of either wild-type human Cu,Zn superoxide dismutase (Cu,ZnSOD) or a mutant of this enzyme (G93A) associated with FALS. We have tested mitochondrial function and determined cytosolic Ca2+ concentration in control cells (untransfected) and in cells expressing either wild-type Cu,ZnSOD or G93A. We report that G93A induces a significant loss of mitochondrial membrane potential, an increased sensitivity toward valinomycin and a parallel increase in cytosolic Ca2+ concentration. The above phenomena are not related to total Cu,ZnSOD content and activity in the cell.

Amyotrophic Lateral Sclerosis↗

PubMed1997

Effect of Val 73 --> Trp mutation on the reaction of "cambialistic" superoxide dismutase from Propionibacterium shermanii with hydrogen peroxide.

The H2O2 inactivation of the "cambialistic" superoxide dismutases from Propionibacterium shermanii, which is active with either iron or manganese at the active site, has been studied in the native and Val 73 --> Trp mutant enzymes. The wild-type iron-containing form of this enzyme is much more resistant to treatment with H2O2 with respect to the other metal-specific Fe superoxide dismutase isoenzymes. After incubation with high amounts of H2O2 the enzyme maintains more than 40% of the initial activity. The activity of the Val 73 --> Trp mutant drastically decreases to less than 5% of the initial activity after incubation with hydrogen peroxide. Amino acid analysis of the H2O2-treated mutant enzyme evidenced the loss of the Trp 73 residue which is shown to play a critical role in the stabilization of the monomer fold of the enzyme. On the other hand, the manganese-containing wild-type and mutant enzymes were completely resistant toward H2O2 demonstrating the specific role of iron in the inactivation process.

Binding Sites↗

PubMed1997

Comparative stability studies on the iron and manganese forms of the cambialistic superoxide dismutase from Propionibacterium shermanii.

The superoxide dismutase of Propionibacterium shermanii shows similar activity with iron and manganese bound at the active site of the protein. On the other hand, the iron form, in comparison to the manganese form, exhibits higher stability towards thermal- and pH-dependent inactivation. Upon inactivation the metal ions are released from the active site. Thus, in comparison to the manganese form, a higher stability of the iron-protein complex might be the triggering reason for this behavior.

Ammonium Sulfate↗

PubMed1997

Antiretroviral effect of combined zidovudine and reduced glutathione therapy in murine AIDS.

A combination of antiretroviral drugs acting at different points in the virus replication cycle was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS). Intramuscular administration of high doses of reduced glutathione (GSH, 100 mg/mouse/day) and AZT (0.25 mg/ml in drinking water) was found to reduce lymphoadenopathy (92%), splenomegaly (80%), and hypergammaglobulinemia (90%) significantly more than AZT alone. Combined treatment resulted in a reduction in proviral DNA content of 69, 66, and 60%, respectively, in lymph nodes, spleen, and bone marrow. Furthermore, the stimulation index of B cells was also significantly higher in animals receiving GSH and AZT whereas additional responses were not observed in the T cell stimulation index and blood lymphocyte phenotype analyses. In conclusion, the administration of high doses of GSH and AZT, a new combination of antiviral drugs, seems to provide additional advantages compared to single-agent therapy.

Animals↗

PubMed1997

Decrease of immunoreactive catalase protein in specific areas of ageing rat brain.

The activity of catalase, the main enzyme responsible for detoxification against hydrogen peroxide, decreases in specific brain areas of aged rats. The reduction of enzyme activity appears to be the consequence of a decreased protein expression rather than an impaired function of the native enzyme. In fact, diminution of the immunoreactive protein parallels enzyme activity decrease. Since the extent of decrease of both activity and protein content was observed to be area dependent, we hypothesise that this phenomenon may underlie, at least in part, the increased susceptibility of specific brain regions to oxidative insults observed in pathological situations related to ageing.

Aging↗

PubMed1997

Inhibition of copper amine oxidase by haloamines: a killer product mechanism.

The observation that the alkylamines 2-Br-ethylamine and 2-C1-ethylamine and 1,2-diaminoethane, the shortest diamine, are irreversible inhibitors of several copper amine oxidases led to the investigation of the mechanism by which these compounds react with the highly active amine oxidase from lentil seedlings. 1,2-Diaminoethane, 2-Br-ethylamine, and 2-C1-ethylamine were found to be both poor substrates and irreversible inhibitors of lentil amine oxidase; inactivation took place in both the presence and absence of oxygen. All three compounds strongly affected the spectrum of the enzyme, leading to the formation of a stable band at 336 nm both in anaerobiosis and in aerobiosis, consistent with an interaction with the enzyme cofactor 6-hydroxydopa. On the contrary, the corresponding propylamine compounds 1,3-diaminopropane, 3-Br-propylamine, and 3-C1-propylamine were reversible inhibitors of lentil amine oxidase. Inhibition was shown to be due to the aldehyde oxidation products rather than the short chain amines themselves; a reaction mechanism is presented which involves attack of the aldehyde on the 6-hydroxydopa-derived free radical catalytic intermediate. With 1,2-diaminoethane, 2-Br-ethylamine, and 2-C1-ethylamine, the complex produced will form a stable 6-membered ring, causing irreversible inhibition of the enzyme.

Amine Oxidase (Copper-Containing)↗

PubMed1997

Loss of GSH, oxidative stress, and decrease of intracellular pH as sequential steps in viral infection.

Madin-Darby canine kidney cells infected with Sendai virus rapidly lose GSH without increase in the oxidized products. The reduced tripeptide was quantitatively recovered in the culture medium of the cells. Since the GSH loss in infected cells was not blocked by methionine, a known inhibitor of hepatocyte GSH transport, a nonspecific leakage through the plasma membrane is proposed. UV-irradiated Sendai virus gave the same results, confirming that the major loss of GSH was due to membrane perturbation upon virus fusion. Consequent to the loss of the tripeptide, an intracellular pH decrease occurred, which was due to a reversible impairment of the Na+/H+ antiporter, the main system responsible for maintaining unaltered pHi in those cells. At the end of the infection period, a rise in both pHi value and GSH content was observed, with a complete recovery in the activity of the antiporter. However, a secondary set up of oxidative stress was observed after 24 h from infection, which is the time necessary for virus budding from cells. In this case, the GSH decrease was partly due to preferential incorporation of the cysteine residue in the viral proteins and partly engaged in mixed disulfides with intracellular proteins. In conclusion, under our conditions of viral infection, oxidative stress is imposed by GSH depletion, occurring in two steps and following direct virus challenge of the cell membrane without the intervention of reactive oxygen species. These results provide a rationale for the reported, and often contradictory, mutual effects of GSH and viral infection.

Adsorption↗

PubMed1997

Intracellular GSH content and HIV replication in human macrophages.

In vitro HIV-1 infection induced a significant decrease in intracellular reduced glutathione (GSH) in human macrophages. Such a decrease was observed at the time of infection corresponding to maximum release of virus from infected cells and was not related to cell cytotoxicity. GSH los was not related to its oxidation or leakage through the cell membrane. Inhibition of intracellular GSH synthesis by buthionine sulfoximine (BSO) did not further decrease GSH levels with respect to the decrease caused by HIV alone. However, treatment of macrophages with BSO significantly increased the HIV yield in the supernatant. Exogenous GSH strongly suppressed the production of p24 gag protein as well as the virus infectivity. Previous observations with other RNA and DNA viruses consistently showed that GSH antiviral effect occurred at late stages of virus replication and was related to the selective decrease of specific glycoproteins, such as gp120, which are particularly rich in disulfide bonds.

Buthionine Sulfoximine↗

PubMed1997

Purification of a fully metal-depleted Cu, Zn superoxide dismutase from copper-deficient rat liver.

A copper-deprived form of the enzyme Cu, Zn superoxide dismutase was identified in the liver of rats made copper-deficient by dietary restriction. In homogenates of such livers Cu, Zn superoxide dismutase presents a dis-homogeneous electrophoretic profile with respect to the native enzyme. When rat liver extracts were treated with exogenous copper an electrophoretic pattern resembling the native one was observed. Enzyme purified by chromatography on DE-52 resin shows two major components, one corresponding to genuine, native enzyme and another one, eluting at higher ionic strength. The latter protein (Fraction II) consists of several isoforms which show the same characteristics of the native superoxide dismutase as far as immunoreactivity and molecular weight are concerned, but with decreased contents of copper and zinc. Its catalytic constant, referring to copper content, was 15 times lower than that obtained for the native enzyme. Moreover, the catalytic power of purified Fraction II was not regained upon incubation with copper. The occurrence of a superoxide dismutase void of metals confirms the hypothesis that this protein plays a dual physiological role: in metal metabolism and in superoxide anion dismutation.

Animals↗

PubMed1997

Effect of Lys175 mutation on structure function properties of Propionibacterium shermanii superoxide dismutase.

The role of electrostatic factors in the enzyme-substrate encounter process of manganese and iron containing superoxide dismutases has been studied in the enzyme from Propionibacterium shermanii by chemical neutralization of lysine residues and site-directed mutagenesis of the highly conserved residue Lys175. Lysine residues have been neutralized by carbamoylation and Lys175 has been selectively replaced by isoleucine and arginine. Catalytic measurements show a dramatic decrease of the activity in the chemically modified enzyme. Electrostatic potential calculations evidence in the modified enzyme a large contraction of the positive potential areas which surround the active sites in the native enzyme, indicating that electrostatic factors are critical in the enzyme-substrate encounter process of Mn- and Fe-superoxide dismutases. The activity drastically decreases also in Lys175-->Ile but not in the Lys175-->Arg mutant. Brownian dynamics simulations indicate that the decrease of activity in the Lys175-->Ile mutant cannot be due only to a decrease of the enzyme-substrate association rate, suggesting that Lys175 plays a relevant role also in the structural stabilization of the active site.

Binding Sites↗

PubMed1996

The Cu,Zn superoxide dismutase from Escherichia coli retains monomeric structure at high protein concentration. Evidence for altered subunit interaction in all the bacteriocupreins.

Gel-filtration chromatography experiments performed at high protein concentrations demonstrate that the Cu,Zn superoxide dismutase from Escherichia coli is monomeric irrespective of the buffer and of ionic strength. The catalytic activity of the recombinant enzyme is comparable with that of eukaryotic isoenzymes, indicating that the dimeric structure commonly found in Cu,Zn superoxide dismutases is not necessary to ensure efficient catalysis. The analysis of the amino acid sequences suggests that an altered interaction between subunits occurs in all bacterial Cu,Zn superoxide dismutases. The substitution of hydrophobic residues with charged ones at positions located at the dimer interface of all known Cu,Zn superoxide dismutases could be specifically responsible for the monomeric structure of the E. coli enzyme.

Amino Acid Sequence↗

PubMed1996

Cocaine increases Sendai virus replication in cultured epithelial cells: critical role of the intracellular redox status.

Cocaine was found to increase parainfluenza-1 Sendai virus (SV) replication in Madin Darby canine kidney (MDCK) cells. Its effect was maximal when it was added before SV infection, while practically no effect was observed when cocaine was added at the time of or after infection. Enhanced SV replication was associated with increased viral protein expression. Cocaine also greatly reduced the intracellular level of glutathione (GSH), namely the most abundant cell thiol with antioxidant functions, recently proposed as an important factor influencing viral infection. Support for this view was provided in the present study by the reversal of cocaine-induced enhancement of SV replication when the intracellular content of GSH was restored by addition of exogenous GSH.

Animals↗

PubMed1996

Inhibition of murine AIDS by reduced glutathione.

The imbalance of the redox state in cells and body fluids in HIV-1-infected patients may result in progression of the disease as well as in immunologic disfuctions. In this report, we have evaluated whether the direct administration of high doses of reduced glutathione (GSH) exerts any antiviral activity and/or improves immune functions in a murine immunodeficiency animal model. Intramuscular administration of 50 or 100 mg GSH/mouse for five consecutive days weekly to LP-BM5-infected mice did not show local or systemic signs of acute toxicity. During the first 3 weeks from infection, a period in which clinical signs of disease were not yet detectable, GSH significantly reduced the viral load in lymph nodes and spleen as evaluated by a PCR semiquantitative assay of the proviral DNA content. At 10 weeks a GSH concentration-dependent reduction of splenomegaly, lymphadenopathy and hypergammaglobulinemia was evident in all treated mice. Evaluation of proviral DNA content showed that GSH was effective in inhibiting LP-BM5 infectivity in lymph nodes, spleen, and bone marrow at 100 mg/day, while it was less effective when administered at 50 mg/day. At 10 weeks some animals receiving the highest GSH dose died, thus only the mice receiving 50 mg GSH were followed up to 15 weeks without signs of toxicity. In this case, almost not significant differences among infected untreated or treated animals were observed. Thus, GSH is effective in reducing the proviral DNA load in the first period of infection. These data and the failure of sulfhydril supplementation to further counteract the progression of disease after 10 weeks of infection suggest that combinations of GSH and other antiviral agents may be useful for improving current antiviral therapies.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Age-related changes in the binding and uptake of Cu, Zn superoxide dismutase in rat liver cells.

The present paper reports the effect of aging on receptor mediated endocytosis of Cu, Zn superoxide dismutase in rat liver cells. The fate of bovine Cu, Zn superoxide dismutase conjugated to colloidal gold was followed by electron microscopy in young (2 months) and old (24 months) rats in situ, in vivo and in vitro experiments. The use of different models for the study of the binding and internalization of the enzyme allowed to discriminate the contribution of each different liver cell type. The data obtained demonstrate that aging of the liver affects binding and uptake of this enzyme. In particular both the number of binding sites and the rate of internalization were depressed in old rats. Therefore, the hypothesis of therapeutic application of superoxide dismutase for age-related diseases needs to be revalued in view of the fact that receptor-mediated endocytosis of this protein is a mechanism affected by senescence.

Age Factors↗