Cardiac volume overload rapidly induces oxidative stress-mediated myocyte apoptosis and hypertrophy.

Oxidative stress stimulates both growth and apoptosis in cardiac myocytes in vitro. We investigated the role of oxidative stress in the initial phases of cardiac remodeling induced in an animal model by volume overload. As plausible candidates for a connection between oxidative stress and cardiomyocyte apoptosis or hypertrophy, we explored the behaviour of two MAPKs, specifically JNK and ERK. At 48 h of overload, the greatest increase in oxidative stress coincided with a peak of cardiomyocyte apoptosis. This was possibly induced through the mitochondrial metabolism, as evidenced by the release of cytochrome c and a significant increase in the active forms of caspase-9 and -3, but not caspase-8. Oxidative stress markers significantly decreased at 96 h of overload, combined with a marked attenuation of apoptosis and the appearance of hypertrophy. The highest levels of JNK and the lowest levels of ERK phosphorylation were observed at 48 h of overload. Conversely, a sharp increase in ERK phosphorylation was detected at 96 h of overload coinciding with the hypertrophic response. Together these results show that oxidative stress is an early and transient event in myocardial volume overload. They suggest that oxidative stress mediates amplitude dependent apoptotic and hypertrophic responses in cardiomyocytes through the selective activation of, respectively, JNK and ERK.

Acylphosphatase induced modifications in the functional properties of erythrocyte membrane sodium pump.

Human red cell acylphosphatase actively hydrolyzes the Na+/K(+)-ATPase phosphoenzyme from erythrocyte membrane. This effect occurred with amounts of acylphosphatase (up to 10 units/mg membrane protein) within the physiological range, and the low value of the apparent Km (0.147 +/- 0.050 microM) indicates that the enzyme has a high affinity for this substrate. When added at the above concentration to inside out vesicles from human erythrocytes, acylphosphatase significantly enhanced the rate of strophantidine-sensitive ATP hydrolysis. The same amounts of acylphosphatase stimulated, although to a lower extent, the rate of ATP-dependent 22Na+ influx (normal efflux). Thus, the calculated stoichiometry for Na+/ATP was 2.68 in the absence of acylphosphatase and 1.06 in the presence of 10 units/mg vesicle protein of the enzyme. Conversely, acylphosphatase addition strongly decreased the rate of ATP-dependent 86Rb+(K+) efflux (normal influx) which, with 10 units/mg vesicle protein, was almost suppressed. As a consequence, the Na+/Rb+ ratio, calculated as 1.52 in the absence of acylphosphatase rose to 72.5 in the presence of 10 units/mg vesicle protein of this enzyme. These results suggest that, because of its hydrolytic activity on the phosphoenzyme intermediate, acylphosphatase 'uncouples' erythrocyte membrane Na+,K+ pump. Possible mechanisms for this effect are discussed.

Possible role of acylphosphatase, Bcl-2 and Fas/Fas-L system in the early changes of cardiac remodeling induced by volume overload.

To identify early adaptive processes of cardiac remodeling (CR) in response to volume overload, we investigated the molecular events that may link intracellular Ca(2+) homeostasis alterations and cardiomyocyte apoptosis. In swine heart subjected to aorto-cava shunt for 6, 12, 24, 48 and 96 h sarcoplasmic reticulum (SR) Ca(2+) pump activity was reduced until 48 h (-30%), but a recovery of control values was found at 96 h. The decrease in SR Ca(2+)-ATPase (SERCA2a) expression at 48 h, was more marked (-60%) and not relieved by a subsequent recovery, while phospholamban (PLB) concentration and phosphorylation were unchanged at all the considered times. Conversely, acylphosphatase activity and expression significantly increased from 48 to 96 h (+40%). Bcl-2 expression increased significantly from 6 to 24 h, but at 48 h, returned to control values. At 48 h, microscopic observations showed that overloaded myocardium underwent substantial damage and apoptotic cell death in concomitance with an enhanced Fas/Fas-L expression. At 96 h, apoptosis appeared attenuated, while Fas/Fas-L expression was still higher than control values and cardiomyocyte hypertrophy became to develop. These data suggest that in our experimental model, acylphosphatase could be involved in the recovery of SERCA2a activity, while cardiomyocyte apoptosis might be triggered by a decline in Bcl-2 expression and a concomitant activation of Fas.

Modifications induced by acylphosphatase in the functional properties of heart sarcolemma Na+,K+ pump.

Acylphosphatase purified from cardiac muscle actively hydrolyzes the phosphoenzyme intermediate of heart sarcolemma Na+,K(+)-ATPase. This effect occurred with acylphosphatase amounts (up to 800 units/mg membrane protein) that fall within the physiological range and the low value of the apparent Km (0.69 x 10(-7) M) indicates a considerable affinity of the enzyme towards this specific substrate. Acylphosphatase addition to purified sarcolemmal vesicles significantly increased the rate of Na+,K(+)-dependent ATP hydrolysis. Maximal stimulation, observed with 800 units/mg protein, resulted in an ATPase activity which was about 2-fold over basal value. The same acylphosphatase amounts significantly stimulated, in a similar and to an even greater extent, the rate of ATP driven Na+ transport into sarcolemmal vesicles. These findings lead to suppose that an accelerated hydrolysis of the phosphoenzyme may result in an enhanced activity of heart sarcolemmal Na+,K+ pump, therefore suggesting a potential role of acylphosphatase in the control of this active transport system.

A novel interaction mechanism accounting for different acylphosphatase effects on cardiac and fast twitch skeletal muscle sarcoplasmic reticulum calcium pumps.

In cardiac and skeletal muscle Ca2+ translocation from cytoplasm into sarcoplasmic reticulum (SR) is accomplished by different Ca2+-ATPases whose functioning involves the formation and decomposition of an acylphosphorylated phosphoenzyme intermediate (EP). In this study we found that acylphosphatase, an enzyme well represented in muscular tissues and which actively hydrolyzes EP, had different effects on heart (SERCA2a) and fast twitch skeletal muscle SR Ca2+-ATPase (SERCA1). With physiological acylphosphatase concentrations SERCA2a exhibited a parallel increase in the rates of both ATP hydrolysis and Ca2+ transport; in contrast, SERCA1 appeared to be uncoupled since the stimulation of ATP hydrolysis matched an inhibition of Ca2+ pump. These different effects probably depend on phospholamban, which is associated with SERCA2a but not SERCA1. Consistent with this view, the present study suggests that acylphosphatase-induced stimulation of SERCA2a, in addition to an enhanced EP hydrolysis, may be due to a displacement of phospholamban, thus to a removal of its inhibitory effect.

Effect of 1,25-dihydroxyvitamin D3 on proliferation in senescent IMR-90 human fibroblasts.

The response of IMR-90 human fetal lung fibroblasts at high population doubling level (PDL > 42) to 1,25-dihydroxyvitamin D3[1,25(OH)2D3] was investigated to clarify whether some metabolic and molecular parameters of senescent cells are affected by the hormone treatment. Pyruvate kinase, lactate dehydrogenase and glucose-6-phosphate dehydrogenase activity significantly increased after treatment of confluent-phase cells with 10 nM 1,25(OH)2D3 for 24 h. Steroid specificity was established by the failure of 10 nM levels of 25-hydroxyvitamin D3 to affect the enzyme activities, while estradiol-17 beta and progesterone produced a slight increase in glucose-6-phosphate dehydrogenase and lactate dehydrogenase levels, respectively. 1,25(OH)2D3 also affected fibroblast proliferation, protein content/cell and DNA synthesis. The cell number significantly decreased after a 48 h incubation with 1,25(OH)2D3 at various concentrations (0.01-1 nM) when compared with control fibroblasts, while an increase in the protein content/cell was demonstrated. The same experiment, carried out by protracting the incubation with the hormone for 72 h, showed a similar trend, but 10 nM 1,25(OH)2D3 was also able to inhibit cell proliferation and to stimulate protein synthesis. The incorporation of [3H]thymidine into DNA increased after the treatment of high PDL fibroblasts with 0.01-1 nM of hormone for 48 h in comparison with controls.

Acylphosphatase levels of human erythrocytes during cell ageing.

Human erythrocytes contain an acylphosphatase isoenzyme, whose concentration during cell ageing was determined by an enzyme immunoassay. Erythrocytes were age-fractionated by isopycnic centrifugation in "Percoll" density gradients. Acylphosphatase concentration was found to rise with the increase of cell density. Maximum values were attained in the mature erythrocytes and there was only a slight decrease in the older cells. Acylphosphatase activity in human erythrocytes of different ages followed a similar pattern, a finding which was confirmed for rabbit red cells with different levels of reticulocytes. The most probable mechanism for the increase of acylphosphatase content and activity during red cell maturation appears to be a de novo synthesis of this enzyme during the reticulocyte stage and its storage, virtually unaffected, in the mature erythrocytes. The possible consequences of increased acylphosphatase levels on the metabolic modifications associated with erythrocyte ageing are discussed.

1,25-dihydroxyvitamin D3 inhibits proliferation of IMR-90 human fibroblasts and stimulates pyruvate kinase activity in confluent-phase cells.

This study tested the hypothesis that 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) plays a role in regulating some aspects of metabolism in IMR-90 normal human fetal lung fibroblasts. Among the enzymes studied, only pyruvate kinase showed a significant increase after treatment of confluent-phase cells with 1,25(OH)2D3 at various concentrations (0.1-100 nM range) for 24 h. A parallel increase in lactate output was observed. Steroid specificity was established by the failure of 10 nM levels of 25-hydroxyvitamin D3, estradiol-17 beta and progesterone to affect pyruvate kinase activity. The determination of the time course of [3H]-2-deoxy-D-glucose transport indicated that the hormone did not influence the transmembrane transport system of D-glucose. The addition of the inhibitors cycloheximide and actinomycin D to the culture medium abolished, at least in part, the 1,25(OH)2D3 stimulation of pyruvate kinase activity, suggesting the probable dependence of the hormone effect on cellular RNA and protein synthesis. 1,25(OH)2D3 also affected fibroblast growth and DNA synthesis. Cell number significantly decreased after 2-5 days treatment with 10 nM hormone in comparison with control fibroblasts, and also the incorporation of [3H]thymidine into DNA decreased after treatment of the cells with 1 and 10 nM hormone for 48 h. In conclusion, these data demonstrate that 1,25(OH)2D3 stimulates pyruvate kinase activity in confluent-phase IMR-90 human fibroblasts by a mechanism probably dependent on de novo protein synthesis, and also affects cell growth and DNA synthesis in sub-confluent-phase cells.

Post-mortem modifications of the specific activity of some brain enzymes.

The post-mortem stability of some brain enzymes was studied. Over the time period under examination, the cytoplasmic enzymes investigated underwent a decisive decay, hexokinase being the most labile and acylphosphatase the most stable. On the other hand, structured activities such as Na+, K+-ATPase and Ca2+, Mg2+-ATPase showed an apparent transitory increase. The differences in post-mortem stability of soluble enzymes could be ascribed, at least in part, to their different susceptibility toward proteolytic activities, as suggested by the electrophoretic results.

Cerebral soluble ubiquitin is increased in patients with Alzheimer's disease.

A study concerning the amount of soluble ubiquitin in different cortical and subcortical regions of brains from patients with Alzheimer's disease compared to the amount in normal brains is presented. Several samples from 9 brain regions were processed and analyzed by liquid chromatography. In almost all the investigated cerebral regions the soluble ubiquitin content was significantly higher in pathologic tissue than in normal tissue. The primary structure of ubiquitin isolated from brain tissue affected by Alzheimer's degenerative processes was determined and resulted to be identical to normal human ubiquitin. These findings, together with the detection of polyubiquitinated proteins in paired helical filaments of neurofibrillary tangles described by several authors, suggest that an impairment of the process of intracellular, ubiquitin-dependent proteolysis might play an important role in the pathogenesis of this neurodegenerative disease. On the other hand, the expression of the correct polypeptide sequence in brain with Alzheimer's disease seems to exclude a mutation of the polyubiquitin gene as a cause of these alterations.

Changes in Na+,K(+)-ATPase, Ca2(+)-ATPase and some soluble enzymes related to energy metabolism in brains of patients with Alzheimer's disease.

Hexokinase, lactate dehydrogenase, acylphosphatase, (Na+,K+)-ATPase and Ca2(+)-ATPase of selected areas from postmortem Alzheimer's disease brains were studied. Hexokinase and lactate dehydrogenase were significantly changed in all the examined subcortical nuclei. (Na+,K+)-ATPase activity was altered in several areas of Alzheimer's disease brains. No changes in Ca2(+)-ATPase and acylphosphatase were observed. The main alterations of the assayed enzymes were observed in subcortical areas but not in cortical areas of Alzheimer's disease brains.

Analysis of the optical properties of bile.

Invasive bile determination is very useful in the diagnosis of many gastric pathologies. At the moment, this measurement is performed with Bilitec 2000, an optical fiber sensor, that is based on absorption by bilirubin. Nevertheless, erroneous evaluations are possible, due to the different configurations which the bilirubin molecule can adopt. The optical behavior of human samples of pure bile and bile+gastric juice has been examined using an optical fiber spectrophotometer and two suitably modified Bilitec 2000 units. A protocol has been established for the treatment of biological fluids, in order to make it possible to study the behavior of their optical properties as a function of pH and concentration without causing any alteration in the samples. The analysis of pH dependence evidenced the presence of different calibration curves at different pH values: the self-aggregation of the bilirubin molecules observed in pure bile samples was almost totally absent in the gastric samples. Measurements carried out on Bilitec 2000 showed that the most appropriate wavelength for bilirubin detection in the stomach should be 470 nm.

Sarcoplasmic reticulum Ca2+-ATPase and acylphosphatase activities in muscle biopsies from patients with Duchenne muscular dystrophy.

Sarcoplasmic reticulum Ca2+-ATPase, acylphosphatase and other soluble enzymes (creatine kinase, lactate dehydrogenase, aldolase and pyruvate kinase) were assayed in muscle biopsies from patients affected by Duchenne muscular dystrophy (DMD) and from normal controls. Specific activities of all the soluble enzymes were decreased in dystrophic muscle, acylphosphatase exhibiting the most marked and significant decrease comparable to that of creatine kinase, in spite of a moderate increase in serum levels. Also, Ca2+-ATPase, particularly the calcium-dependent activity, was decreased in dystrophic muscle. A positive correlation, higher than with the other soluble enzymes, was obtained between acylphosphatase specific activity and the percentage of Ca2+-activation of Ca2+-ATPase. These findings: suggest an impairment of microsomal calcium uptake which could be, at least in part, responsible for sarcoplasmic calcium accumulation observed in DMD; do not disagree with an hypothesized role of acylphosphatase in intracellular calcium homeostasis, consistent with the enzyme's demonstrated hydrolytic activity on the phosphorylated intermediate of Ca2+-ATPase.

Increased acylphosphatase levels in erythrocytes from hyperthyroid patients.

Acylphosphatase activity and content were measured in erythrocytes from hyperthyroid patients and healthy controls. In addition, the soluble enzymes glucose-6-phosphate dehydrogenase, hexokinase, and the membrane bound (Na+ + K+)-ATPase and Ca2+-ATPase were assayed. Our results confirmed previous studies indicating a decrease of (Na+ + K+)-ATPase and an increase of Ca2+-ATPase activity in hyperthyroid erythrocytes. While glucose-6-phosphate dehydrogenase was not significantly changed, hexokinase and acylphosphatase activities were significantly higher in the hyperthyroid group. Both activities and content of acylphosphatase returned to normal levels in erythrocytes from treated patients, when they were euthyroid. These findings suggest that an excess of thyroid hormones may stimulate acylphosphatase biosynthesis in erythroid cells and indicate a potential clinical usefulness of this enzyme in hyperthyroidism.

Horse muscle acylphosphatase: a more rapid purification procedure and crystallization.

A crystalline acyl phosphatase has been obtained from horse muscle. The enzyme purified by a modified procedure which allowed to obtain a larger yield with respect to a method previously developped in this laboratory, was homogeneous by disc electrophoresis on polyacrylamide gel. Crystals of this enzymatic protein have been obtained by the addition of ammonium sulphate to around 52% saturation.

Changes in enzyme levels in human skeletal muscle during obstructive arteriopathy of the lower limbs.

Some enzymatic activities have been assayed in the gastrocnemius muscle of patients with obstructive arteriopathy of the lower limbs. The specific activities of all the examined glycolytic enzymes, of malate dehydrogenase and of glycerol-3-phosphate dehydrogenase are significantly decreased while the specific activities of two lysosomal enzymes, beta-glucuronidase and cathepsin A, are significantly higher than in the controls. Therefore it may be inferred that the metabolic capacity of glycolysis and of Krebs cycle are lowered. On the other hand the increased specific activity of lysosomal enzymes suggests the hypothesis that the above mentioned modifications and the morphologic alterations of the muscle and of the small blood vessels might be ascribed, at least partly, to a release of lysosomal hydrolases in active form.

[Reactive metabolites of oxygen, lipid peroxidation, total antioxidant capacity and vitamin E in essential arterial hypertension]. / Metaboliti reattivi dell'ossigeno, perossidazione lipidica, capacità antiossidante totale e vitamina E nell'ipertensione arteriosa essenziale.

Free radical oxidative stress has been implicated in the pathogenesis of a variety of human diseases. The purpose of this study was to explore the degree of oxidative stress in essential arterial hypertension (EAH). The study groups consisted of fifteen untreated EAH patients (WHO stages 1 and 2), aged 40 to 70 years, and fifteen, age and sex matched, normal controls. The levels of typical peroxidation products such as malondialdehyde and 4-hydroxyalkenals (with the LPO-586 test, Bioxytech), free radicals and other reactive oxygen metabolites (ROMs) (with the d-ROMs test, Diacron), vitamin E (with HPLC method) and total antioxidant capacity (with the TAS test, Randox) were determined in the plasma af all subjects. Compared to the control group EAH patients exhibited significantly higher ROMs levels (334.7 +/- 21.6 vs 249.2 +/- 23.3 Units, means values +/- S.E.M.), and of lipid peroxidation products (10.7 +/- 0.7 vs 8.09 +/- 0.9 nmol/ml). It must be noted that such increases were not observed in all EAH patients, but above all in those less young or with more severe hypertension. On the other hand no significant difference was found between EAH patients and normal controls as regards vitamin E concentration and total antioxidant capacity. These results suggest that EAH patients, in spite of their normal antioxidant defences, are more prone than normotensive subjects to oxidative stress because of an increased ROMs production. This could result in an inactivation of prostacyclin and NO, hence an enhancement of peripheral vascular resistance and an increase of hypertension. Another consequence might be an increased lipid peroxidation of low density lipoproteins, a condition which is known to be associated with accelerated atherosclerosis. The study of oxidant and antioxidant factors seems therefore useful in EAH patients in order to evaluate oxidative stress and to correct, if possible, the observed abnormalities with dietetic or pharmacologic therapy.

Reactive oxygen species and antioxidant status in essential arterial hypertension during therapy with dihydropyridine calcium channel antagonists.

PURPOSE: To evaluate reactive oxygen species and antioxidant status in essential arterial hypertension during therapy with dihydropiridine calcium channel antagonists. PATIENTS AND METHODS: Fifteen patients, affected by essential arterial hypertension, were examined. They received once a day oral dihydropyridine calcium antagonists for 10 weeks: five patients received felodipine (5 mg), five amlodipine (10 mg) and five lercanidipine (10 mg). The levels of end products of lipid peroxidation, free radicals and hydroperoxides and total antioxidant capacity were determined in the plasma of all subjects before and during treatment. Values are expressed as mean +/- S.E. Systolic blood pressure decreased from 171 +/- 4 to 135 +/- 6 mmHg (p < 0.01) and diastolic blood pressure decreased from 99 +/- 5 to 82 +/- 3 mmHg (p < 0.01). Hydroperoxides and free radicals decreased from 321.3 +/- 8.96 to 247.9 +/- 8.69 units (p < 0.01) and the end products of lipid peroxidation decreased from 11.0 +/- 1.93 to 6.74 +/- 1.41 nmol/ml (p < 0.01). Total antioxidant capacity increased from 0.74 +/- 0.03 to 1.05 +/- 0.05 mmol/l (p < 0.01). RESULTS: Imbalance in the pro-oxidant-antioxidant equilibrium shifts in favour of antioxydant namely oxidative stress decreases. The calcium channel antagonists decrease peripheral arterial resistances and therefore decrease or abolish relative ischaemia, moreover decrease arterial pressure and therefore normalize parietal stress on endothelial cells. As a conseguence they act on two hypothesized mechanisms of oxidative stress in hypertension. CONCLUSIONS: Dihydropyridine calcium antagonists used in this trial seem useful in hypertension because they decrease oxidative stress, and normalize of pressure values.

Altered redox status in the blood of psoriatic patients: involvement of NADPH oxidase and role of anti-TNF-α therapy.

BACKGROUND: Psoriasis is a chronic hyperproliferative inflammatory skin disease, characterized by a generalized redox imbalance. Anti-tumor necrosis factor (TNF)-α therapy is widely used for the treatment of this disease, but its effect on blood redox status hasn't been explored. OBJECTIVE: To investigate the effects of anti-TNF-α therapy on blood redox status in psoriatic patients. METHODS: Twenty-nine psoriatic patients (PSO) were divided into two groups: one remained untreated (NRT) and to another the anti-TNF-α therapy was prescribed (TR). The levels of main oxidative stress markers and total antioxidant capacity (TAC) in plasma, levels of total reactive oxygen species (ROS) production, lipoperoxidation, TAC, glutathione content, and activity of NADPH oxidase in white blood cells (WBC) were evaluated in PSO, in NTR and TR after 6 months of the study. RESULTS: Plasma levels of malondialdehyde (MDA) and protein carbonyl content (PCO), ROS production, lipoperoxidation, and glutathione content in WBC were increased, while TAC in both plasma and WBC was decreased in PSO with respect to controls. In the plasma of TR, levels of MDA and PCO were significantly lower with respect to PSO and NTR. The activity of NADPH oxidase was significantly increased in WBC of PSO and NTR but not in TR versus controls. DISCUSSION: Our results represent novel data about the redox status of WBC in psoriatic patients. A significant redox-balancing effect of anti-TNF-α therapy, probably associated with the normalization of NADPH oxidase activity in WBC, was demonstrated.