Biomedical subjects

H Ischiropoulos

Publications and source records attributed to H Ischiropoulos.

78 records · Page 5Linked to original sources

PubMed1990

Effect of aging on pulmonary superoxide dismutase.

Pulmonary Cu,Zn superoxide dismutase was examined in young (1-month-old), adult (4-5-month-old) and aged (24-months-old) rats to determine if partially inactive forms of the enzyme accumulate in the lung with age. Measurement of Cu,Zn superoxide dismutase activity in lung homogenates showed that total Cu,Zn superoxide dismutase activity/mg DNA was essentially the same in adult and aged rats. The average value of Cu,Zn superoxide dismutase/mg DNA for young rats was less than half that of adult and aged rats. Cu,Zn superoxide dismutase was purified from the lung homogenates and fractionated into isoelectric variants by either isoelectric focusing or chromatofocusing. Three main isoelectric variants of Cu,Zn superoxide dismutase were recovered with pI values of 5.15, 4.88 and 4.75. In all age groups studied, the pI 4.88 variant had a markedly higher specific activity than the other two variants, as well as the highest metal content and greatest resistance to inactivation of all three variants. The pI 4.88 variant declined from 88% of the total Cu,Zn superoxide dismutase activity in the young animals to only 70% in the aged animals. The results of this study indicate that the proportion of the relatively inactive forms of pulmonary Cu,Zn superoxide dismutase increased with age.

Aging↗

PubMed1989

Effect of interferon inducers on superoxide anion generation from rat liver microsomes detected by lucigenin chemiluminescence.

Microsomal superoxide anion (O2-) production was detected using the chemiluminigenic probe, bis-N-Methylacridinium nitrate (lucigenin). Superoxide dismutase (SOD) inhibited 55% of the light emission but in the presence of a detergent (Triton X100) SOD inhibited the light emission by 94%. Lucigenin chemiluminescence from rat liver microsomes supplemented with NADPH was found to be selective and sensitive in detecting the O2- production. Treatment of rats with poly IC and LPS resulted in a decrease of the hepatic microsomal cytochrome P450 content by 44% and 37% respectively. The decrease in the cytochrome P450 contents was accompanied by a decrease in LgCl from the hepatic microsomal fractions by 61% for the poly IC and by 51% for the LPS treated rats. This is the first report to demonstrate that decreased P450 in the presence of normal amounts of cytochrome P450(c) reductase produce correspondingly less O2- from the microsomes.

Acridines↗

PubMed1989

Serum copper concentration as an index of experimental lung injury.

Serum copper (Cu) concentration was evaluated as an index of lung injury in two rat models of pneumotoxicity: hemithoracic irradiation and monocrotaline ingestion. In both models there was a dose- and time-dependent increase in serum Cu concentration. This hypercupremia paralleled the development of pulmonary endothelial dysfunction (decreased lung plasminogen activator activity and increased prostacyclin production) and pulmonary fibrosis (hydroxyproline accumulation). In the radiation model, lung injury and hypercupremia persisted for at least 6 months, and were spared similarly when the total dose was delivered in multiple daily fractions as compared to single doses. In irradiated rats, the elevated serum Cu concentration was accompanied by increases in plasma ceruloplasmin, lung Cu concentration, and lung Cu/Zn superoxide dismutase (SOD) activity. In monocrotaline-treated rats, lung damage and hypercupremia also were accompanied by a reduction in liver Cu concentration, and by a direct correlation between the concentrations of Cu and SGOT in the serum. In both models, some but not all modifiers of lung damage (penicillamine, angiotensin converting enzyme inhibitors, pentoxifylline) also partially prevented the insult-induced hypercupremia. In contrast, serum iron concentration was largely independent of treatment in all experiments. These data suggest that elevated serum copper concentration is an accurate and minimally invasive index of lung injury in irradiated and monocrotaline-treated rats.

Alanine Transaminase↗

PubMed1989

Oxygen tolerance in neonatal rats: role of subcellular superoxide generation.

We compared the superoxide anion generating capacity of subcellular fractions from the lungs of neonatal and adult rats. Microsomal and mitochondrial fractions from adult rats produced approximately three times more superoxide (nanomoles per minute per milligram protein) than fractions from neonatal rats in the presence of 100% O2. Subcellular superoxide anion generating capacity was also examined in adult and neonatal rats exposed to greater than 95% fractional concentration of O2 in inspired gas. The O2- produced by mitochondrial and microsomal fractions of adult and neonatal rats increased above control levels for the first 24 h and declined below control values after 48 h of exposure in adults, whereas the elevated O2- production was sustained in microsomal fractions of neonates through 60 h. During the course of hyperoxic exposure, the largest difference in the superoxide generating capacity between adult and neonate was observed after 8-24 h of hyperoxia. The microsomal and mitochondrial fractions from adult rats produced three to seven times more O2- compared with neonatal rats. Cu,Zn superoxide dismutase (SOD) increased during the course of hyperoxia only in neonates at 8, 24, and 48 h of exposure. No change was observed in the activity of Mn SOD. The ratio of SOD activity (units per lung) to subcellular superoxide generating capacity (nanomoles per minute per lung) was calculated for the normal adults and neonates. The ratio for adult rats averaged 23 and 17 for mitochondrial and microsomal fractions, respectively, and 51 for neonatal rats for both subcellular fractions under normoxic conditions. These results suggest that O2- tolerance of neonates may be explained by the favorable balance between antioxidant defenses and subcellular superoxide generating capacity. The role of increased activity of Cu,Zn SOD as an accompanying or a causative phenomenon in O2 tolerance of neonates could not be determined from these experiments.

Aging↗

PubMedDate not supplied

Evaluation of the probe 2',7'-dichlorofluorescin as an indicator of reactive oxygen species formation and oxidative stress.

The use of dichlorofluorescin (DCFH) as a measure of reactive oxygen species was studied in aqueous media. Hydrogen peroxide oxidized DCFH to fluorescent dichlorofluorescein (DCF), and the oxidation was amplified by the addition of ferrous iron. Hydrogen peroxide-induced DCF formation in the presence of ferrous iron was completely inhibited by deferoxamine and partially inhibited by ethylenediaminetetraacetic acid, but was augmented by diethylenetriaminepentaacetic acid. Iron-peroxide-induced oxidation of DCFH was partially inhibited by catalase but not by horseradish peroxidase. Nonchelated iron-peroxide oxidation of DCFH was partially inhibited by several hydroxyl radical scavengers, but was independent of the scavenger concentration, and this suggests that free hydroxyl radical is not involved in the oxidation of DCFH in this system. Superoxide anion did not directly oxidize DCFH. Data suggest that H2O2-Fe(2+)-derived oxidant is mainly responsible for the nonenzymatic oxidation of DCFH. In addition, peroxidase alone and oxidants formed during the reduction of H2O2 by peroxidase oxidize DCFH. Since DCFH oxidation may be derived from several reactive intermediates, interpretation of specific reactive oxygen species involved in biological systems should be approached with caution. However, DCFH remains an attractive probe as an overall index of oxidative stress in toxicological phenomena.

Catalase↗

PubMedDate not supplied

Peroxynitrite, a cloaked oxidant formed by nitric oxide and superoxide.

Peroxynitrite [oxoperoxonitrate(1-), ONOO-] may be formed in vivo from superoxide and nitric oxide. The anion is stable, but the acid (pKa = 6.8) decays to nitrate with a rate of 1.3 s-1 at 25 degrees C. The experimental activation parameters of this process are delta H++ = +18 +/- 1 kcal/mol, delta S++ = +3 +/- 2 cal/(mol.K), and delta G++ = +17 +/- 1 kcal/mol. Peroxynitrite (or its protonated form) oxidizes some compounds such as thiols and thioethers in a biomolecular reaction. The reactions with glutathione and cysteine have activation enthalpies of 10.9 and 9.7 kcal/mol, respectively, which are lower than that of the isomerization reaction. Peroxynitrite reacts with other compounds such as dimethyl sulfoxide and deoxyribose in a unimolecular reaction for which the activation of peroxynitrite is rate-limiting. In theory, activation could involve (1) heterolysis to OH- and NO2+ (delta rxn Gzero' = 13 kcal/mol at pH 7) or (2) homolysis to .OH and .NO2 (delta rxn Gzero = 21 kcal/mol), and these processes also could be involved in the isomerization to nitrate. However, thermodynamic and kinetic considerations indicate that neither process is feasible, although binding to metal ions may reduce the large activation energy associated with heterolysis. An intermediate closely related to the transition state for isomerization of ONOOH to HONO2 may be the strongly oxidizing intermediate responsible for hydroxyl radical-like oxidations mediated by ONOOH. Thus, peroxynitrite reacts with different compounds by at least two distinct mechanisms, and the hydroxyl radical is not involved in either.

Cysteine↗