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Biomedical subjects

G Balla

Publications and source records attributed to G Balla.

At least 37 records · Page 2Linked to original sources
PubMed1993

Endothelial-cell heme uptake from heme proteins: induction of sensitization and desensitization to oxidant damage.

Iron-derived reactive oxygen species are implicated in the pathogenesis of various vascular disorders including atherosclerosis, vasculitis, and reperfusion injury. The present studies examine whether heme, when liganded to physiologically relevant proteins as in hemoglobin, can provide potentially damaging iron to intact endothelium. We demonstrate that reduced ferrohemoglobin, while relatively innocuous to cultured endothelial cells, when oxidized to ferrihemoglobin (methemoglobin), greatly amplifies oxidant (H2O2)-mediated endothelial-cell injury. Drawing upon our previous observation that free heme similarly primes endothelium for oxidant damage, we posited that methemoglobin, but not ferrohemoglobin, releases its hemes that can then be incorporated into endothelial cells. In support, cultured endothelial cells exposed to methemoglobin--in contrast to exposure to ferrohemoglobin, cytochrome c, or metmyoglobin--rapidly increased their heme oxygenase mRNA and enzyme activity, thereby supporting heme uptake; ferritin production was also markedly increased after such exposure, thus attesting to eventual incorporation of Fe. These cellular methemoglobin effects were inhibited by the heme-scavenging protein hemopexin and by haptoglobin or cyanide, agents that strengthen the liganding between heme and globin. If the endothelium is exposed to methemoglobin for a more prolonged period (16 hr), it accumulates large amounts of ferritin; concomitantly, and presumably associated with iron sequestration by this protein, the endothelium converts from hypersusceptible to hyperresistant to oxidative damage. We conclude that when oxidation of hemoglobin facilitates release of its heme groups, catalytically active iron is provided to neighboring tissue environments. The effect of this relinquished heme on the vasculature is determined both by extracellular factors--i.e., plasma proteins, such as haptoglobin and hemopexin--as well as intracellular factors, including heme oxygenase and ferritin. Acutely, if both extra- and intracellular defenses are overwhelmed, cellular toxicity arises; chronically, when ferritin is induced, resistance to oxidative injury may supervene.

Cells, Cultured↗
PubMed1993

[Effect of paracetamol on the acid hemolysis of erythrocytes, with special reference to the intracellular glutathione level].

The authors give account of their study concerning the effect of paracetamol on the acid haemolysis, and glutathione content of human erythrocytes. In vitro, paracetamol decreased intracellular glutathione content in a dose dependent manner. This may lead to an increased sensitivity of erythrocytes to the haemolytic effect of hydrochloric acid, what may explain the dose dependent decrease of time of haemolysis, presented in form of dynamic haemolysis curve. In vivo four hours following the oral intake of 500 mg paracetamol, although the intracellular glutathione content did not decrease significantly, shortening of the time of acid haemolysis could be demonstrated in more than half of the persons studied. No haemolysis was caused by the given dose of the drug.

Acetaminophen↗
PubMed1993

The role of reactive oxygen intermediates in the pathogenesis of chronic apical periodontitis.

The level of malondialdehyde, a stable end product of lipid peroxidation induced by reactive oxygen intermediates and the activity of two potent antioxidant enzymes, superoxide dismutase and glutathione peroxidase, was investigated in tissue homogenates of 22 surgical periapical granuloma specimens. Malondialdehyde levels were significantly higher and glutathione peroxidase activity was significantly lower in periapical granuloma samples than in healthy gingival tissue homogenates, which were used as controls. The activity of superoxide dismutase was similar in periapical granuloma and in control samples. Our results indicate an altered balance between the production and the elimination of toxic oxygen metabolites in chronic apical periodontitis. We hypothesize that reactive oxygen intermediates, which are being produced by activated phagocytic cells abundantly present in periapical granulomas, can contribute to periapical tissue injury and bone loss in this disease.

Adult↗
PubMed1993

Vitamin E, LDL, and endothelium. Brief oral vitamin supplementation prevents oxidized LDL-mediated vascular injury in vitro.

In previously reported in vitro studies, we found that heme, a physiologically widespread hydrophobic iron compound, can rapidly generate oxidized low-density lipoprotein (LDL), which then becomes cytotoxic to cultured vascular endothelial cells; both LDL oxidation and endothelial cytotoxicity were inhibited by incubation with exogenous alpha-tocopherol (vitamin E) or ascorbic acid (vitamin C). Seeking relevance to in vivo conditions, we performed a study in which 10 human volunteers were given daily antioxidant supplements of 800 IU of DL-alpha-tocopherol acetate alone or in combination with 1000 mg of ascorbic acid for 2 weeks. LDL resistance to heme oxidation ex vivo, as measured by the lag time for conjugated-diene formation, increased by as much as threefold from a mean +/- SD of 58 +/- 11 to 104 +/- 18 minutes (P < .001); LDL alpha-tocopherol increased from 11 +/- 2 to 26 +/- 6 molecules per LDL particle (P < .001); and most impressively, cytotoxicity to porcine aortic endothelial cells incubated with LDL conditioned with heme plus H2O2 or with copper was completely prevented (cytotoxicity before supplementation was 42 +/- 12%, decreasing after supplementation to 3 +/- 2%, P < .001). These measurements reverted to their presupplement levels within 2 weeks after participants stopped taking antioxidant supplements and were reproduced in 4 subjects taking 800 IU of DL-alpha-tocopherol acetate supplements alone but not in the same subjects taking 1000 mg ascorbic acid supplements alone. In conclusion, oral vitamin E supplementation increases LDL alpha-tocopherol content, increases LDL resistance to oxidation, and decreases the cytotoxicity of oxidized LDL to cultured vascular endothelial cells.

Adult↗
PubMed1993

Oxidized low-density lipoproteins and endothelium: oral vitamin E supplementation prevents oxidized low-density lipoprotein-mediated vascular injury.

Vitamin E supplements may decrease the incidence of myocardial infarction by inhibiting LDL oxidation to atherogenic moieties. We previously reported that hemin is a potent and relevant lipophilic source of iron that can rapidly intercalate into LDL, catalyzing its oxidation and promoting its cytolysis of endothelium. The effects of oral vitamin E on heme-catalyzed LDL oxidation and resulting endothelial damage were studied in 10 volunteers who received daily 800 I.U. of vitamin E with or without vitamin C (1000 mg) for 2 weeks. Prior, during, and 2 weeks after supplementation, plasma LDL was isolated and its number of alpha-tocopherol molecules, resistance to heme-catalyzed oxidation, and ability to damage porcine aortic endothelial cells were assayed. Vitamin E supplementation doubled the lag phase of LDL peroxidation as compared to control (104 +/- 18 vs. 58 +/- 11 min; p < 0.001) accompanied by an increase in alpha-tocopherol content of LDL particles (26 +/- 6 vs. 11 +/- 2 mol/mol; p < 0.001). Most intriguingly, LDL-mediated endothelial cell cytotoxicity was prevented (3 +/- 2% vs. 42 +/- 12%; p < 0.001). After a 2-week washout period, LDL alpha-tocopherol content, the lag time of LDL oxidation, and oxidized LDL-mediated cytolysis all returned to baseline levels. To determine whether supplements of vitamin E and vitamin C beneficially synergize in these effects, we monitored several volunteers on daily vitamin E alone or vitamin C alone. Vitamin E alone (at doses as low as 400 I.U./day) affected all measurements in a manner identical to that when it was taken with vitamin C. Vitamin C alone had no significant effect on these measurements. We conclude: dietary vitamin E supplementation provides cytoprotection against LDL oxidation-mediated endothelial cell injury, but this salutary effect is rapidly lost after supplementation is stopped.

Administration, Oral↗
PubMed1992

Ferritin: a cytoprotective antioxidant strategem of endothelium.

Phagocyte-mediated oxidant damage to vascular endothelium is likely involved in various vasculopathies including atherosclerosis and pulmonary leak syndromes such as adult respiratory distress syndrome. We have shown that heme, a hydrophobic iron chelate, is rapidly incorporated into endothelial cells where, after as little as 1 h, it markedly aggravates cytotoxicity engendered by polymorphonuclear leukocyte oxidants or hydrogen peroxide (H2O2). In contrast, however, if cultured endothelial cells are briefly pulsed with heme and then allowed to incubate for a prolonged period (16 h), the cells become highly resistant to oxidant-mediated injury and to the accumulation of endothelial lipid peroxidation products. This protection is associated with the induction within 4 h of mRNAs for both heme oxygenase and ferritin. After 16 h heme oxygenase and ferritin have increased approximately 50-fold and 10-fold, respectively. Differential induction of these proteins determined that ferritin is probably the ultimate cytoprotectant. Ferritin inhibits oxidant-mediated cytolysis in direct relation to its intracellular concentration. Apoferritin, when added to cultured endothelial cells, is taken up in a dose-responsive manner and appears as cytoplasmic granules by immunofluorescence; in a similar dose-responsive manner, added apoferritin protects endothelial cells from oxidant-mediated cytolysis. Conversely, a site-directed mutant of ferritin (heavy chain Glu62----Lys; His65----Gly) which lacks ferroxidase activity and is deficient in iron sequestering capacity, is completely ineffectual as a cytoprotectant. We conclude that endothelium and perhaps other cell types may be protected from oxidant damage through the iron sequestrant, ferritin.

Animals↗
PubMed1992

Induction of heme oxygenase is a rapid, protective response in rhabdomyolysis in the rat.

Heme proteins such as myoglobin or hemoglobin, when released into the extracellular space, can instigate tissue toxicity. Myoglobin is directly implicated in the pathogenesis of renal failure in rhabdomyolysis. In the glycerol model of this syndrome, we demonstrate that the kidney responds to such inordinate amounts of heme proteins by inducing the heme-degradative enzyme, heme oxygenase, as well as increasing the synthesis of ferritin, the major cellular repository for iron. Prior recruitment of this response with a single preinfusion of hemoglobin prevents kidney failure and drastically reduces mortality (from 100% to 14%). Conversely, ablating this response with a competitive inhibitor of heme oxygenase exacerbates kidney dysfunction. We provide the first in vivo evidence that induction of heme oxygenase coupled to ferritin synthesis is a rapid, protective antioxidant response. Our findings suggest a therapeutic strategy for populations at a high risk for rhabdomyolysis.

Animals↗
PubMed1992

Endothelial cell heme oxygenase and ferritin induction by heme proteins: a possible mechanism limiting shock damage.

Acutely, hemin sensitizes endothelial cells to oxidants but chronically protects the endothelium through the induction of ferritin. By releasing its heme, methemoglobin can sensitize endothelial cells in a fashion similar to free hemin. Furthermore, prolonged incubation with the endothelium allows methemoglobin to induce heme oxygenase and ferritin and concomitantly to modulate oxidant-mediated cytotoxicity. Methemoglobin but not hemoglobin, metmyoglobin or cytochrome c induces heme oxygenase and ferritin. Heme needs to be released from methemoglobin, since sodium cyanide, haptoglobin, and hemopexin inhibit the induction of these proteins. Neutrophils can oxidize hemoglobin to methemoglobin, which can subsequently induce both heme oxygenase and ferritin. We speculate that in shock with disseminated intravascular coagulation, marginated PMNs oxidize hemoglobin to heme-releasing methemoglobin. If critical defenses such as haptoglobin and hemopexin are overwhelmed, heme enters the endothelin cells, sensitizing them to oxidant damage. Endothelial cell adaptation via heme-induced heme oxygenase and ferritin production might limit ultimate progression to pulmonary and other vascular leak syndromes.

Animals↗
PubMed1992

The effect of silibinin (Legalon) on the the free radical scavenger mechanisms of human erythrocytes in vitro.

The effect of Legalon was investigated parallel with that of Adriblastina (doxorubicin) and paracetamol on some parameters characterizing the free radical scavenger mechanisms of human erythrocytes in vitro and on the time of acid hemolysis performed in aggregometer. Observations suggest that Adriblastina enhances the lipid peroxidation of the membrane of red blood cells, while paracetamol causes significant depletion of intracellular glutathione level, thus decreasing the free radical eliminating capacity of the glutathione peroxidase system. Legalon on the other hand, is able to increase the activity of both superoxide dismutase and glutathione peroxidase, which may explain the protective effect of the drug against free radicals and also the stabilizing effect on the red blood cell membrane, shown by the increase of the time of full haemolysis.

Acetaminophen↗
PubMed1991

[Urinary N-acetyl-beta-D-glucosaminidase activity in healthy, polycythemic and hypoxic newborn infants].

Urinary N-acetyl-beta-D-glucosaminidase (NAG) activity was assayed in 20 polycythemic newborns and prematures, together with 50 prematures suffering from hypoxia on the 1st, 2nd, 4th, 14th, and 28th day after birth. The enzyme was also assayed in 101 healthy newborns which provided normal reference values. NAG activity was factored by the creatinine concentration to given an index. There were significant difference in the NAG indices either between full-term and preterm babies or between appropriate for gestational age (AGA) and small for gestational age (SGA) neonates of the normal group. However, NAG excretion on the first day of life was significantly raised in the case of polycythemic newborns. Following partial plasma exchange, on the 14th day the NAG activity returned to the normal range. NAG activities of premature babies suffering from idiopathic respiratory distress syndrome (IRDS) were significantly elevated on the 1st, 2nd, 4th day but fell sharply to the 14th day. NAG activity fell to normal values by the 28th day. These results suggest that the urinary NAG index is a sensitive indicator of the renal tubular damage during the newborn period.

Acetylglucosaminidase↗
PubMed1991

Urinary N-acetyl-beta-D-glucosaminidase activity in healthy, polycythemic and hypoxic neonates.

The authors investigated the urinary N-acetyl-beta-D-glucosaminidase (NAG) activity in the case of 101 normal healthy and 20 polycythemic newborns and prematures, and 50 prematures suffering from hypoxia on the 1st, 2nd, 4th, 14th, and 28th day after birth. The obtained activities were referred to the creatinine concentrations of the urine samples and given as NAG index. There were no significant differences in the NAG indices either between fullterm and preterm babies or between appropriate for gestational age (AGA) and small for gestational age (SGA) neonates of the normal group. The NAG indices on the first day of life were significantly higher in the case of polycythemic newborn in comparison with the normal group (p less than 0.01). On the 14th day, after the partial plasma exchange, the NAG indices returned to the normal range. The premature babies suffering from IRDS received an average 10.1 days oxygen supplementation. Their NAG indices were significantly (p less than 0.01) higher on the 1st, 2nd, 4th days than those of the healthy prematures of the normal group and decreased considerably up to the 14th day. Finally the NAG indices reached the normal value on the 28th day. These results support the assumption that the urinary NAG index is a suitable indicator of the renal tubular damage during the newborn period.

Acetylglucosaminidase↗
PubMed1991

Exposure of endothelial cells to free heme potentiates damage mediated by granulocytes and toxic oxygen species.

Endothelial damage may follow exposure to toxic oxygen species generated by closely apposed ("marginated") granulocytes. Because iron markedly catalyzes oxidant damage in diverse systems, we wondered whether intercalculated heme, and/or its constituent iron, might potentiate oxidant damage of endothelium. Cultured monolayers of porcine aortic endothelial cells were exposed for brief periods to purified hemin. Uptake of heme was rapid, dose dependent, and not reversible by buffer or serum washes. Despite high levels of cell-associated heme, no direct heme-mediated cytotoxicity occurred, but heme-loaded endothelium became highly sensitive to oxidant challenge by (a) reagent H2O2, (b) enzymatically generated oxidants (xanthine/xanthine oxidase), or (c) phorbol-activated polymorphonuclear leukocytes. An increase in endothelial cell lipid peroxidation accompanied heme-augmented oxidant cytolysis, and both parameters were reduced in parallel by micromolar amounts of the hydrophobic oxygen radical scavenger/iron chelator U74500A. Endothelial uptake of heme was inhibited by a specific heme-binding protein, hemopexin. Concomitantly, hemopexin completely blocked augmented H2O2- and polymorphonuclear leukocyte-mediated cytotoxicity but only if added simultaneously and stoichiometrically with hemin. Significant loss of protection occurred if hemopexin addition was delayed 15 minutes, and protection was completely lost after a 60-minute interval. The iron moiety of heme was critical to oxidant sensitization because neither iron-free protoporphyrin IX nor tin-protoporphyrin was able to sensitize endothelial cells to H2O2 or activated polymorphonuclear leukocytes. These results may provide mechanistic insights into atherogenesis, reperfusion injury, and the organ injury accompanying hemoglobinemia or myoglobinemia.

Animals↗
PubMed1990

The effect of polycythemia and hypoxia on urinary N-acetyl-beta-D-glucosaminidase activity in newborns.

Urinary N-acetyl-beta-D-glucosaminidase activity was assayed in fullterm and preterm polycythemic neonates, in preterm infants with hypoxia, and in healthy newborns. There were no significant differences between fullterm and preterm babies or between appropriate for gestational age and small for gestational age neonates in the normal group. N-acetyl-beta-D-glucosaminidase excretion on the first day of life was significantly raised in polycythemic newborns (P less than 0.01). Fourteen days after partial plasma exchange the enzyme activity returned to normal. N-acetyl-beta-D-glucosaminidase activities in preterm babies with respiratory distress syndrome were significantly (P less than 0.01) raised on the 1st, 2nd, 4th days and fell sharply to the 14th day. N-acetyl-beta-D-glucosaminidase isoenzyme studies revealed that urine samples taken from preterm babies with respiratory distress syndrome in the first week after birth contained increased amounts of intermediate and B isoenzyme forms while there was a concomitant reduction in the amount of the A form present.

Acetylglucosaminidase↗
PubMed1990

Iron loading of endothelial cells augments oxidant damage.

Transition metals, particularly iron, will potentiate oxidant damage to isolated cell organelles, plasma membranes, and DNA when added to in vitro incubation systems. However, similar studies of intact cells have been hampered by the relative impermeability of whole cells to iron. We have iron loaded cultured endothelial cells by using the iron-chelating fungistat 8-hydroxyquinoline (8HQ). 8HQ forms lipophilic chelates with iron and rapidly transfers the metal across the intact plasma membrane of endothelial cells. After brief exposure to 8HQ and subsequent thorough washing of endothelial cells, the cell-associated iron cannot be removed by the powerful chelator deferoxamine, clearly indicating the intracellular location of 8HQ-transported iron. Iron-loaded cells (but not cells exposed to high concentrations of 8HQ or iron separately) are extremely sensitive to oxidants (1) produced externally by phorbol-stimulated granulocytes, (2) generated intracellularly by menadione, or (3) added as H2O2. In the latter instance, as little as 7 mumol/L H2O2 provokes destruction of approximately 50% of iron-loaded endothelial cells, whereas untreated endothelium readily survives exposure to H2O2 concentrations as high as 2 mmol/L. Cytotoxicity is accompanied by membrane lipid peroxidation (formation of thiobarbituric acid-reactive substances). Both cytotoxicity and lipid peroxidation are inhibited by the lipophilic 21-aminosteroid U74500A ("lazaroid") (50% inhibitory concentration = approximately 0.5 mumol/L), whereas deferoxamine (250 mumol/L) is ineffective (suggesting iron intercalation into hydrophobic domains of the cell). We conclude that this pharmacologic model for iron loading of intact cells may yield valuable insights into the pathogenic importance of intracellular iron in iron overload states, inflammation, and cellular injury.

Animals↗
PubMed1990

Heme uptake by endothelium synergizes polymorphonuclear granulocyte-mediated damage.

Transitional metals, particularly iron, markedly potentiate oxidant damage to isolated cell organelles. However, determining the probable importance of iron in damage to intact cells is difficult because of our inability experimentally to increase the cell content of this transition metal. We now report that heme is a uniquely effective iron delivery vehicle, capable of loading large amounts of potentially reactive iron into intact cells. We find that endothelial cells in vitro rapidly incorporate free heme and this heme-loading sensitizes endothelium to oxidant-mediated cytotoxicity caused by hydrogen peroxide, the hypoxanthine/xanthine oxidase system, or phorbol-stimulated PMN. Although the precise mechanism of the heme-aggravated cytotoxicity is not yet known, it closely parallels amplified lipid peroxidation in endothelial cell membranes suggesting the importance of lipid injury. Hemopexin, by complexing heme, protects endothelial cells from activated PMN, but only if added simultaneously. The hydrophobic iron chelator and antioxidant, U74500A, abrogates heme-augmented hydrogen peroxide and PMN-mediated endothelial damage. Such compounds, therefore, may have therapeutic potential in one or more of the listed clinical syndromes. We speculate that exposure of endothelium to free heme may potentiate vascular damage in various clinical syndromes, including acute renal failure after massive intravascular hemolysis, crush injuries, reperfusion after myocardial infarction (perhaps secondary to cardiac myoglobin release), retrolental fibroplasia associated with neonatal hemopexin deficiency, and, perhaps, atherosclerosis involving sites of turbulence that may trigger minor red blood cell lysis.

Animals↗
PubMed1990

An in vitro study of the hydroxyl scavenger effect of Cavinton.

The hydroxyl radical scavenging capability of vinpocetine was studied in vitro by aromatic hydroxylation and deoxyribose degradation methods. Hydroxyl radicals were generated by the Fenton reaction. The effect of vinpocetine was compared to other antioxidants, to mannitol, vitamin E and dimethyl sulfoxide. The antioxidant capacity of vinpocetine is near to vitamin E, and higher than that of mannitol.

Antioxidants↗
PubMed1990

Serum antioxidant activity in premature babies.

Autooxidation of bovine-brain homogenate proved to be a good model to determine the antioxidant capacity of sera. It was measured in parallel with the level of ceruloplasmin and apotransferrin in sera of 35 healthy children and 20 premature babies (gestational age 28-33 weeks). Antioxidant capacity was very low in premature babies with a nadir on the 4th postnatal day. Lipid-peroxidation of bovine-brain homogenate could be inhibited in vitro by the addition of exogen antioxidant. In this assay MTDQ-DS, Cavinton, DPA-HC1, vitamin E, A, C showed different antioxidant activity.

Adolescent↗