Biomedical subjects

U Muscatello

Publications and source records attributed to U Muscatello.

At least 19 recordsLinked to original sources

PubMed2000

Short-term hypothermia activates hepatic mitochondrial sn-glycerol-3-phosphate dehydrogenase and thermogenic systems.

The contribution of the sn-glycerol-3-phosphate (G-3-P) shuttle in the control of energy metabolism is well established. It is also known that its activity may be modulated by hormones involved in thermogenesis, such as thyroid hormones or dehydroepiandrosterone and its metabolites, that act by inducing de novo synthesis of mitochondrial G-3-P dehydrogenase (mGPDH). However, little is known as to the factors that may influence the activity without enzyme induction. In the present study we investigated the possible role of the G-3-P shuttle in the thermogenic response to different hypothermic stresses. It was found that a decrease of body temperature causes the liver rapidly to enhance mGPDH activity and G-3-P-dependent respiration. The enhancement, which does not result from de novo synthesis of enzymes, has the potential of increasing heat production both by decreased ATP synthesis during the oxidation of G-3-P and by activation of the glycolytic pathway.

Adenosine Triphosphate↗

PubMed2000

Lipid oxidation deletes the nanodomain organization of artificial membranes.

Nanoscopic domains with different crystal structures have been induced in closed artificial membranes and have been directly imaged by atomic force microscopy at a spatial resolution better than 0.3 nm. These observations provide experimental evidence to the hydrophobic mismatching theory of lateral phase separation phenomena. Under oxidant conditions, the lipid-lipid assembly reorganizes into a new steady-state structure with disappearance of specific nanodomains. This finding may contribute to understanding the mechanism of peroxidative damage to membrane properties. In fact, alterations of specific modes of molecular conformation and packing may lead to perturbation of specific properties.

Lipids↗

PubMed1999

Zidovudine-induced experimental myopathy: dual mechanism of mitochondrial damage.

Myopathy often complicates Zidovudine (AZT) treatment in patients with acquired immunodeficiency syndrome (AIDS). The pathogenesis of the myopathy is controversial, since clinical phenomena intrinsic to AIDS may interfere per se with the onset of the myopathy. In the present work we investigated the in vivo effect of AZT in an animal model species (rat) not susceptible to HIV infection. Histochemical and electron microscopic analyses demonstrated that, under the experimental conditions used, the in vivo treatment with AZT does not cause in skeletal muscle true dystrophic lesions, but rather mitochondrial alterations confined to the fast fibers. In the same animal models, the biochemical analysis confirmed that mitochondria are the target of AZT toxicity in muscles. The effects of AZT on mitochondria energy transducing mechanisms were investigated in isolated mitochondria both in vivo and in vitro. Membrane potential abnormalities, due to a partial impairment of the respiratory chain capability observed in muscle mitochondria from AZT-treated rats, closely resemble those of control mitochondria in the presence of externally added AZT. mtDNA deletion analysis by PCR amplification and Southern blot analysis did not show any relevant deletion, while mtDNA depletion analysis demonstrated a significant decrease in mtDNA in AZT-treated rats. The present findings show that AZT causes damage to mitochondria by two mechanisms: a short-term mechanism that affects directly the respiratory chain, and a long-term mechanism that alters the mitochondrial DNA thus impairing the mitochondrial protein synthesis. In addition, the ultrastructural observations indicate that the fiber types are differently affected upon AZT treatment, which poses a number of questions as to the pathogenesis of this myopathy.

Animals↗

PubMed1997

Effect of cardiolipin on functional properties of isolated rat liver mitochondria.

The specific involvement of cardiolipin in modulating and/or controlling the activity of a number of mitochondrial carriers, enzymes and receptors is well documented; however, comparatively less understood is its role for the integrated functions of intact mitochondria. The aim of the present research was to get a better insight into this problem by investigating the effect of in vitro addition of cardiolipin on the properties of isolated liver mitochondria. The results obtained show that cardiolipin induces extensive structural and functional perturbations at the level of the inner mitochondrial membrane. In fact, addition of cardiolipin to intact mitochondria causes a significant increase of proton leak associated with a parallel increase of respiratory rate in State 4. Concomitantly, a slight uncoupling of phosphorylation associated with a moderate increase in ATPase activity is observed. Furthermore, the pore-mediated membrane permeability to calcium is drastically modified, an effect that can be reversed by addition of cyclosporin.

Adenosine Triphosphatases↗

PubMed1996

Atomic force microscopy observations of acyl chains in phospholipids.

The potential use of atomic force microscopy (AFM) to image the mode of assembly and to measure the corresponding lattice parameters of model systems consisting of ordered aggregates of cardiolipin molecules has been investigated. An unprecedented resolution of about 0.2 nm has been achieved on suitably prepared specimens. This enables the orientational order and the positional correlations of the individual molecules in the lattice to be defined, and submolecular details, such as the acyl chains and the polar groups, to be imaged. The structural parameters derived from AFM have been compared with those obtained by transmission electron diffraction of the same specimen and found to be in excellent agreement. AFM turns out to be a powerful and probably a unique tool to reveal local phase variations in systems, such as biological membranes, that have non-homogeneous composition and organization.

Aluminum Silicates↗

PubMed1992

Interaction of carnitine with mitochondrial cardiolipin.

The physiological role of L-carnitine is to determine the transport of acyl-CoA through the mitochondrial membrane. However, some observations may also suggest a direct effect of the molecule per se on the physical properties of the membrane, most probably at the level of the binding site. This possibility has been investigated by studying the influence of adriamycin, a drug that binds to cardiolipin, on the effect of carnitine on isolated rat liver mitochondria. It has been found that adriamycin almost abolishes the activating effect of carnitine on state 2 respiration. The effect and its inhibition is seen by using either the L-form of carnitine or the D-form or both. Cardiolipin removes the effect of adriamycin and restores the activation by carnitine. It is proposed that some effects of carnitine on mitochondrial properties may be the result of interaction of carnitine with cardiolipin at the membrane level.

Animals↗

PubMed1992

Mitochondrial inner membrane permeability changes induced by octadecadienoic acid hydroperoxide. Role of mitochondrial GSH pool.

The effect of exogenous octadecadienoic acid hydroperoxide (HPODE) on the functional properties of inner membrane of isolated rat liver mitochondria, as evaluated by the measurement of the membrane potential (delta psi) has been studied. Very low concentrations of HPODE (1.5-4.5 nmol/mg prot.) do not modify the delta psi of control mitochondria appreciably while bringing about the drop of delta psi, in a concentration-dependent mode, in mitochondria with a GSH level diminished by approx. 60%. Mitochondrial GSH depletion was obtained by intraperitoneal administration of buthionine sulfoximine, a specific inhibitor of GSH synthesis, to rats. The presence in the incubation system of GSH-methyl ester which normalizes mitochondrial GSH, fully prevents any drop in levels of delta psi induced by HPODE. The same protective effect has been presented by EGTA, which chelates the available Ca2+. Neither an antioxidant nor a specific inhibitor of mitochondrial phospholipase A2 are able to prevent the HPODE effect. From the results obtained we can assume that HPODE itself, at the concentrations used here, induces permeability changes in the inner membrane, with the loss of coupled functions, when the GSH mitochondrial level is below a critical value.

Animals↗

PubMed1992

Changes in liver structure and function after short-term and long-term treatment of rats with dehydroepiandrosterone.

The effects on the liver of feeding a diet containing 0.2% dehydroepiandrosterone were studied after short (7 d) and long (100 d) periods of treatment in rats. The short-term treatment caused hypertrophy of the hepatocytes that, at the ultrastructural level, seemed to be due to proliferation of peroxisomes and (to a minor extent) of mitochondria. The mitochondria seemed to have undergone transition from expanded to condensed configuration; accordingly, after isolation, their rate of coupled respiration was greater than that of control mitochondria. After long-term treatment, the structure of the hepatocytes reverted toward normal. In fact, at the ultrastructural level, the number and the size of peroxisomes was not significantly different from those of the controls, but degenerative phenomena were observed in the mitochondria. Attempts are made to explain the above ultrastructural and biochemical findings in view of the effects of dehydroepiandrosterone on the energy metabolism of liver.

Administration, Oral↗

PubMed1991

The protecting effect of L-carnitine on Ca(2+)-loaded rat liver mitochondria.

It is shown that L-carnitine strongly increases the ability of rat liver mitochondria to respond to the train of Ca2+ additions by a transient stimulation of the State-4 respiration rate. Such an effect requires ATP and the L-carnitine efficiency strongly decreases when ATP is omitted. Oleate influences the mitochondria in a fashion opposite to that of L-carnitine. The oleate effect is strongly diminished by L-carnitine. Again, the L-carnitine effect requires ATP, and D-carnitine fails to substitute for L-carnitine. It is suggested that L-carnitine removes, in an ATP-dependent manner, endogenous or added fatty acids, which are involved in oxidative damage of Ca(2+)-loaded mitochondria.

Adenosine Triphosphate↗

PubMed1991

A 31P-NMR study on the energy state of rat liver in an experimental model of chronic dietary iron overload.

31P-NMR spectroscopy of rat liver perchloric acid extracts was utilized to assess the hepatic energy state in an experimental model of chronic dietary iron overload. Oral administration of iron for a period of 65 days that induces a steady ten-fold increase in hepatic iron concentration causes a significant decrease in the hepatic ATP level not associated with appreciable modifications of ADP and Pi levels. The phosphorylation ratio appears on the average decreased. The values of the energy state parameters revert to the normal if the concentration of iron in the liver is reversed below the critical level upon withdrawal of iron treatment after 45 days for a period of 20 days. The implication of these energy modifications for the pathogenesis of cell damage in the siderosis is discussed.

Adenosine Diphosphate↗

PubMed1991

[The role of malate in regulating the rate of mitochondrial respiration in vitro].

Depletion of endogenous malate by preincubation of mitochondria at 30 degrees C in substrate-free media sharply decreases the rate of citrate oxidation and inhibits mitochondrial respiration in the presence of pyruvate and alpha-ketoglutarate. Addition of catalytic amounts of endogenous malate and its production via succinate oxidation promote rapid oxidation of citrate and pyruvate in the mitochondria and abolishes the lag period with alpha-ketoglutarate Malate increases the rate of membrane potential generation after addition of citrate, pyruvate or alpha-ketoglutarate to mitochondrial suspensions. Studies with controlled malate concentrations revealed that the changes in malate concentrations observed in the mitochondria in the presence of gluconeogenesis-inducing hormones may be due to the influence of these hormones on mitochondrial oxidation.

Animals↗

PubMed1990

Early mitochondrial disfunction in bromobenzene treated mice: a possible factor of liver injury.

The membrane potential of liver mitochondria isolated from bromobenzene treated mice was studied. Specifically, the efficiency of the energy-transducing mitochondrial membrane was measured during the phase between the occurrence of a massive loss of hepatic GSH, after 2-3 hr of bromobenzene intoxication, and the appearance of lipid peroxidation and cell death (12-15 hr after treatment). Partial uncoupling of oxidative phosphorylation was observed in mitochondria during the early period of intoxication (3-9 hr). These anomalies in oxidative metabolism did not result in irreversible damage to the mitochondrial inner membrane. The possibility that phenolic metabolites of bromobenzene are responsible for the uncoupling effects was examined. Orto- and especially para-bromphenol reproduced the alterations of mitochondrial function when added to normal mitochondria at concentrations comparable to those found in the livers of the intoxicated animals. Since the concentration of the bromophenols (especially p-bromophenol) largely increases after the intoxication times as tested here, mitochondrial uncoupling may represent a mechanism of liver damage acting synergistically with or even independently of other factors such as oxidative stress and lipid peroxidation.

Alanine Transaminase↗

PubMed1989

Perturbation in liver mitochondrial Ca2+ homeostasis in experimental iron overload: a possible factor in cell injury.

The functional state of isolated mitochondria and specifically the integrity of the inner membrane, were investigated in the liver of rats made siderotic by dietary supplementation with carbonyl iron. The concentration of iron in the hepatic tissue increased progressively up to nearly 40 days and reached a steady-state level. When the iron content reached a threshold value (higher than 90 nmol/mg protein) the occurrence of in vivo lipid peroxidation in the mitochondrial membrane was detected. This process did not result in gross alterations in the mitochondrial membrane, as indicated by electron microscopy, phosphorylative capability and membrane potential measurements. On the contrary, the induction of lipoperoxidative reaction appeared to be associated with the activation of Ca2+ release from mitochondria. This was shown to occur as a consequence of rather subtle modifications in the inner membrane structure via a specific efflux route, which appeared to be linked to the oxidation level of mitochondrial pyridine nucleotides. The induction of this Ca2+ release from iron-treated mitochondria resulted in enhancement of Ca2+ cycling, a process which dissipates energy to reaccumulate into mitochondria the released Ca2+. The perturbation in mitochondrial Ca2+ homeostasis reported here may be a factor in the onset of cell damage in this experimental model of hepatic iron overload.

Animals↗

PubMed1989

Biochemical mechanism of GSH depletion induced by 1,2-dibromoethane in isolated rat liver mitochondria. Evidence of a GSH conjugation process.

HPLC measurements of GSH and GSSG levels in isolated rat liver mitochondria, on addition of 1,2-dibromoethane (DBE), revealed the presence of a glutathione (GSH)-conjugating pathway of DBE. This process required the structural integrity of the mitochondrial matrix and inner membrane complex and was inhibited by the uncouplers of oxidative phosphorylation, particularly 2,4-dinitrophenol. On the other hand it was not affected by the energetic state of the mitochondria, since other mitochondrial inhibitors like KCN and oligomycin did not have any effect on it. This process also did not require the involvement of mitochondrial inner membrane transport systems, based on the measurement of the mitochondrial transmembrane potential. The involvement of mitochondrial GSH-S-transferases, located either in the matrix or in the intermembrane space, is discussed.

Animals↗

PubMed1989

An Na-23 and P-31 NMR investigation of sonicated cardiolipin sodium salt in aqueous medium.

Na-23 and P-31 nuclear magnetic resonance was used to investigate the structure and dynamics of Na+ trapped in the enclosed aqueous spaces of unilamellar vesicles of Cardiolipin sodium salt. After sonicated Cardiolipin sodium salt forms a clear solution in aqueous medium and gives rise to a narrow, isotropic P-31 NMR line. This line was attributed to the presence of either vesicles or more complex liquid crystalline structures showing superposed-signals for inner and outer phosphate groups. The use of paramagnetic shift reagent Dy(PPPi)2 made it possible to observe only the line of the phosphate groups arranged within the structures. From an analysis of the spin-lattice relaxation parameters of Na-23 at 21.04 MHz and 52.6 MHz, the correlation time tau = 1.3 x 10(-9) sec was estimated. It was then possible to calculate the value of 1.9 MHz for the quadrupolar coupling parameter. These findings were interpreted in terms of the occurrence of specific bindings between Na+ and the phosphate moieties within the unilamellar structures of Cardiolipin.

Cardiolipins↗

PubMed1989

Changes in mitochondrial activity caused by ammonium salts and the protective effect of carnitine.

Ammonium salts added to isolated rat liver mitochondria deviate alpha-ketoglutarate to glutamate synthesis, thus decreasing its availability as respiratory substrate. As a consequence a decrease of respiratory rate is observed which is paralleled by progressive mitochondrial swelling. It was demonstrated that L-carnitine may abolish this swelling thus improving structural and metabolic state of mitochondria.

Acetates↗

PubMed1988

Effect of amrinone on myocardial mitochondria function.

The effect of amrinone on cardiac mitochondria of guinea pig was studied. It was found that amrinone does not change the respiratory function of cardiac mitochondria in the presence of alpha-ketoglutarate, whereas it inhibits glutamate oxidation. It was also found that amrinone strongly inhibits the activity of glutamic dehydrogenase of both crude extract from sonicated heart mitochondria and of purified preparation from bovine liver. This inhibition may explain the effect of amrinone on the oxidation of glutamate in mitochondria. These results are discussed in view of the contradictory effects of amrinone on cardiac and other tissues.

Amrinone↗

PubMed1988

The effect of iron overload on the mitochondrial porphyrin level in the hexachlorobenzene induced experimental porphyria.

Liver mitochondria isolated from rats treated with hexachlorobenzene plus iron, present a lower content of total porphyrin in respect to that of mitochondria from rats fed hexachlorobenzene alone. The in vitro mitochondrial porphyrin accumulation processes have been studied in mitochondria from iron loaded rats. It has been found that under these conditions the active porphyrin uptake process, which is driven by the K+ transmembrane gradient, is maximally inhibited in the presence of pentachlorophenol at a concentration similar to that found in vivo in the hexachlorobenzene experimental porphyria. By contrast the same degree of inhibition is presented by control mitochondria only in the presence of pentachlorophenol plus valinomycin, a condition which collapses the transmembrane K+ gradient. A strict correlation between porphyrin uptake and K+ concentration has been found in control as well as in iron treated mitochondria. A possible involvement of peroxidative reactions in the mitochondrial membranes has been proposed as a cause of the changes in the permeability properties of the mitochondrial membranes in the experimental chronic hepatic porphyria under conditions of iron overload.

Animals↗