Daunorubicin-stimulated reactive oxygen metabolism in cardiac sarcosomes

High Sensitivity Determination of TNF-α for Early Diagnosis of Neonatal Infections with a Novel and Reusable Electrochemical Sensor

Early diagnosis is vital for the reduction of mortality caused by neonatal infections. Since TNF-α can be used as a marker for the early diagnosis, the detection of TNF-α with high sensitivity and specificity has great clinical significance. Herein, a highly sensitive and reusable electrochemical sensor was fabricated. Due to the high specificity of aptamers, TNF-α could be accurately detected from five similar cytokines, even from serum samples. In addition, Au nanoparticles (AuNPs) with a high surface area were able to combine a large number of doxorubicin hydrochloride (DOXh), which made the sensor have a high sensitivity. The sensor had a good linear relationship with TNF-α concentration in the range from 1 to 1 × 10⁴ pg/mL and the lowest detection limit is 0.7 pg/mL. More important was that the sensor could be reused 6 times by a crafty use of chain replacement reaction. Meanwhile, the detection time and cost were greatly reduced. Thus, we believe that these advantages of higher specificity and sensitivity, lower cost, and shorter detection time will provide a stronger potential for early diagnosis of neonatal infections in clinical applications.

The Influence of Anthracycline Therapy on Cardiac Function During Anesthesia

Cardiotoxicity is a well recognized complication of anthracycline (AC) therapy. Subtle abnormalities in myocardial function that become apparent only after exercise may exist in survivors of childhood cancer who have previously received AC, yet have normal resting cardiac function. To evaluate if anesthesia-induced changes in cardiac function differ in pediatric patients with previous AC therapy from healthy children and adolescents, we evaluated in a prospective study 43 patients, of whom 42 were analyzed. Twenty-one patients (AC-group), mean age 9.6 yr (range, 3-16 yr), who had received 193 (30-490) mg/m(2) of AC as a mean cumulative dose with normal resting cardiac function (shortening fraction [SF] 0.34, normal value > 0.30) underwent removal of a Hickman catheter under general anesthesia. Twenty-one patients, mean age 10.9 yr (range, 4-17 yr), who underwent placement of a Hickman catheter before chemotherapy served as the control. All children were premedicated with midazolam 0.5 mg/kg orally. Anesthesia was induced by sodium thiopental (5 mg/kg), fentanyl (3 micro g/kg), and rocuronium (0.6 mg/kg) and maintained with isoflurane (1 MAC) in N(2)O/O(2) (70/30). Before induction (baseline), 5 and 20 min after intubation (T1 and T2), and 20 min after extubation (control), cardiac function was assessed by transthoracic (baseline, control) and transesophageal (T1, T2) echocardiography. Compared with baseline (SF: 34.9 +/- 3.7 [AC], 34.1 +/- 3.7 [C] [not significant]; stroke volume index [SVI] 36 +/- 6 mL/m(2)[AC], 35 +/- 4 mL/m(2)[C] [not significant]; cardiac index [CI] 3.6 +/- 0.6 L/min/m(2)[AC], 3.2 +/- 0.5 L/min/m(2)[C] [not significant]), we found a significant decrease in SF and SVI in both groups at T1 (SF: 26.2 +/- 3.6 [AC] versus 28.6 +/- 3.6 [C] [P < 0.05]; SVI: 26 +/- 4 mL/m(2) [AC] versus 30 +/- 46 mL/m(2) [C] [P < 0.05]) and T2 (SF: 24.1 +/- 3.2 [AC] versus 28.2 +/- 2.5 [C] [P < 0.01], SVI: 26 +/- 6 mL/m(2) [AC] versus 31 +/- 5 mL/m(2) [C] [P < 0.01]), which was significantly greater in the AC group. There were no significant changes of variables of diastolic function (E/A ratio, isovolumetric relaxation time) between both groups. Previous treatment with AC may enhance the myocardial depressive effect of anesthetics even in patients with normal resting cardiac function.

IMPLICATIONS

Previous treatment with anthracylines, a group of chemotherapeutic drugs in use for childhood cancer, may enhance the myocardial depressive effect of anesthetics even in children and adolescents with normal resting cardiac function.

Nonenzymatic oxygen activation and stimulation of lipid peroxidation by doxorubicin-copper

Addition of cupric sulfate to neutral solutions of doxorubicin resulted in spectrophotometric, fluorometric, and chromatographic changes indicative of a direct chemical interaction. Associated with these changes was a copper-dependent consumption of dissolved oxygen and a superoxide dismutase-sensitive reduction of ferricytochrome c, suggesting the liberation of superoxide free radicals. Addition of equimolar ethylenediaminetetraacetic acid (EDTA) completely inhibited, but did not reverse, the effect of copper on the spectrophotometric, fluorometric, and chromatographic properties of the drug. EDTA also abolished the copper-stimulated consumption of oxygen and reduction of ferricytochrome regardless of the time of addition. Oxygen-free radical formation by the drug-copper complex was further implicated by the stimulation of lipid peroxidation, which was completely inhibited by adding EDTA. Inhibition by superoxide dismutase, catalase, and dimethyl urea implicates the involvement of assorted oxygen-free radicals in doxorubicin-copper stimulated lipid peroxidation. The data demonstrate that despite the implication of hydrogen peroxide and hydroxyl radicals in doxorubicin-copper stimulated lipid peroxidation, the immediate product of dioxygen reduction by the complex is superoxide-free radicals. The suggested occurrence of doxorubicin-copper complexes in vivo infers that nonenzymatic generation of oxygen-free radicals by the chelate may contribute to the mechanism of toxicity of doxorubicin and related anthraquinone anticancer agents observed clinically.

Toxicity of aromatic disulphides. I. Generation of superoxide radical and hydrogen peroxide by aromatic disulphides in vitro

The aromatic thiol, thiophenol, is readily autoxidized at neutral pH in a reaction which generates superoxide radical and hydrogen peroxide. The oxidation product, diphenyl disulphide, may be reduced back to thiophenol by glutathione and in the presence of an excess of the latter thiol a reduction/autoxidation cycle for generation of 'active oxygen' species is established. The autoxidation reaction is strongly catalysed by haematin; haemoglobin is also an effective mediator of 'active oxygen' generation from the diphenyl disulphide/glutathione couple, being oxidized to methaemoglobin in the process. Certain derivatives of diphenyl disulphide also generate superoxide radical and hydrogen peroxide in the presence of glutathione, although the rate of the reaction is strongly influenced by the nature of the substituent groups. Among the ring-substituted derivatives of diphenyl disulphide investigated, the rate of 'active oxygen' production decreased in the order 4-amino greater than 2-amino greater than 4-methyl greater than unsubstituted greater than 4-nitro greater than 2-carboxyl; little reaction was detected with the homologous compound, dibenzyl disulphide.

Carcinogenicity of some anticancer drugs--a survey

A list of 37 anticancer drugs with reported carcinogenicity or co-carcinogenicity has been compiled. These drugs include 16 alkylating agents, eight antimetabolites, four antibiotics, four hormones, one alkaloid, and four miscellaneous drugs. The reported carcinogenicity of these drugs in model systems and their possible mechanisms of action are reviewed together with structure-carcinogenicity relationships. These drugs have been reported to cause cancers in different sites in various test animals. Most of these drugs react with DNA, and the ultimate reactive forms of the drugs are electrophiles.

Involvement of superoxide radicals on adrenochrome formation stimulated by arachidonic acid in bovine heart sarcolemmal vesicles

Highly purified sarcolemmal membranes prepared from bovine heart muscle produced superoxide radicals, especially when incubated with NADPH or NADH, as revealed by the oxidation of adrenaline to adrenochrome. The reaction was inhibited by superoxide dismutase or by heat denaturation of the sarcolemmal vesicles. Less evident was the inhibitory effect shown by catalase, while mannitol, deferoxamine or dicumarol were uneffective. The formation of adrenochrome was an oxygen-dependent reaction with a Km for adrenaline of 8-10 microM. Moreover, the reaction was inhibited by preincubating the sarcolemmal membranes with propranolol, while the alpha-antagonist phentolamine was without effect. Adrenaline oxidation was unaffected by the presence of exogenous linolenic acid or methylarachidonic acid, while arachidonic acid, with a Km for this reaction of 175 microM, showed a marked stimulatory effect. This activation was suppressed by superoxide dismutase, catalase and NaCN, while mannitol was without effect. Moreover, the reaction was blocked by the cyclooxygenase inhibitor indomethacin, differently from the lipooxygenase inhibitor nordihydroguaiaretic acid. Also, the incubation of the sarcolemmal vesicles with phospholipase A2 and calcium produced a stimulation of adrenochrome formation which was partially suppressed by albumin. In the experiments using arachidonic acid or phospholipase A2, the addition of indomethacin blocked the adrenaline oxidation. These results indicate that arachidonic acid accentuated the heart sarcolemmal adrenochrome formation presumably by participating in the cyclooxygenase reaction.

Inhibition of bleomycin lung toxicity by N-acetyl cysteine in the rat

N-acetyl cysteine (NAC) has recently been shown to have antioxidant properties, and since bleomycin produces pulmonary damage via free oxygen radical toxicity, the possible protective effect of NAC on bleomycin lung toxicity was investigated. Rats received saline (n = 7), NAC (n = 6), bleomycin (n = 7) or bleomycin and NAC (n = 6) by direct intratracheal injection. Seven days later the animals were killed and the lungs processed for histology or morphometry. All rats treated with bleomycin only had typical changes of bleomycin lung toxicity whereas the animals treated with bleomycin and NAC had minimal pathology. The control animals had normal lungs. These results were confirmed by morphometry which demonstrated significantly higher volume densities (p less than .01) of alveolar wall and free alveolar cells in the bleomycin group compared to the other 3 groups. It is concluded that NAC inhibits bleomycin lung toxicity when administered by direct intratracheal injection.

Menadione-induced cytotoxicity is associated with protein thiol oxidation and alteration in intracellular Ca2+ homeostasis

The toxicological implications of alterations in intracellular thiol homeostasis during menadione metabolism have been investigated using freshly isolated rat hepatocytes. A strict correlation between depletion of protein sulfhydryl groups and loss of cell viability was observed. Loss of protein thiols preceded cell death, and occurred more rapidly in cells with decreased levels of reduced glutathione. Depletion of protein thiols was also associated with inhibition of Ca2+ efflux from the cells and perturbation of intracellular Ca2+ homeostasis. It is proposed that the oxidative stress induced by menadione metabolism in isolated hepatocytes results in the depletion of both soluble and protein thiols, and that the latter effect is critically associated with a perturbation of Ca2+ homeostasis and loss of cell viability.

Comparative cardiac oxygen radical metabolism by anthracycline antibiotics, mitoxantrone, bisantrene, 4'-(9-acridinylamino)-methanesulfon-m-anisidide, and neocarzinostatin

This study examined the effects of various anthracycline antibiotics and mitoxantrone, bisantrene, 4'-(9-acridinylamino)-methanesulfon-m-anisidide (m-AMSA), and neocarzinostatin on oxygen radical formation by cardiac sarcoplasmic reticulum and submitochondrial particles. Doxorubicin, daunorubicin, rubidazone, and aclacinomycin A stimulated superoxide production by both heart fractions in a dose-dependent fashion that appeared to follow saturation kinetics. The anthracycline drugs also significantly increased hydrogen peroxide production by heart sarcosomes and submitochondrial particles. On the other hand, mitoxantrone, bisantrene, m-AMSA, and neocarzinostatin did not significantly enhance cardiac reactive oxygen metabolism. Thus, it is unlikely that the mechanism of the cardiac toxicity produced by mitoxantrone and m-AMSA in patients previously treated with anthracycline drugs can be directly related to oxidation-reduction cycling catalyzed by cardiac flavin dehydrogenases.

Bis(alkylamino)anthracenedione antineoplastic agent metabolic activation by NADPH-cytochrome P-450 reductase and NADH dehydrogenase: diminished activity relative to anthracyclines

Stimulation of the rates of NAD(P)H oxidation, superoxide generation, and hydrogen peroxide formation by three anthracenedione antineoplastic agents in the presence of NADPH-cytochrome P-450 reductase, NADH dehydrogenase, or rabbit hepatic microsomes was studied and the results compared with those obtained for the anthracyclines Adriamycin and daunorubicin. In all cases the anthracenediones, including mitoxantrone and ametantrone, were significantly (5- to 20-fold) less effective than the anthracyclines in stimulating NAD(P)H oxidation, superoxide formation, or hydrogen peroxide production. Of the three anthracenediones studied, the ring-monohydroxylated compound showed the greatest activity followed by the ring-dihydroxylated derivative (mitoxantrone). In contrast, the non-ring-hydroxylated anthracenedione (ametantrone) was a relatively ineffective electron acceptor and inhibited the reduction of more effective acceptors such as Adriamycin. Michaelis-Menten kinetic constants were determined by analysis of the rates of NADPH oxidation. NADP+ and 2'-AMP inhibited the reduction of the ring-hydroxylated anthracenediones and anthracyclines, demonstrating the enzymatic nature of the reaction. The non-ring-hydroxylated anthracenedione inhibited the reduction of Adriamycin by both P-450 reductase and NADH dehydrogenase with 50% inhibition achieved at approximately 300 microM. Thus, there appears to exist a structural relationship between anthracenedione ring hydroxylation and metabolic activation. These results also suggest that the relative inability of the anthracenediones to function as artificial electron acceptors in comparison to the anthracyclines may be correlated with diminished anthracenedione cardiotoxicity.

1,4-Bis(2-[(2-hydroxyethyl)amino]ethylamino)-9,10-anthracenedione, an anthraquinone antitumour agent that does not cause lipid peroxidation in vivo; comparison with daunorubicin

Daunorubicin administration to mice produces a marked stimulation of lipid peroxidation in both liver and heart 48 hours following administration. In direct contrast 1,4-Bis((2-[(2-hydroxyethyl)amino]ethylamino))-9,10-anthracenedione (HAQ) does not induce lipid peroxidation in the liver and actually inhibits this event in the heart. In addition, neither daunorubicin nor HAQ deplete reduced glutathione in liver or heart 48 hours after drug administration. Daunorubicin induced glutathione (GSH) depletion was observed 2.5 hours following administration. These results correlate with daunorubicin increased microsomal oxygen consumption whilst HAQ produced no measurable effect on the rate of microsomal oxygen utilisation. It would appear that redox cycling to produce free radical oxygen involved in lipid peroxidation and GSH depletion, an established action of daunorubicin, does not occur with HAQ. This apparent lack of HAQ reactivity may help explain the relatively low cardiotoxicity of this novel antitumour agent.

Generation of hydroxyl radical by anticancer quinone drugs, carbazilquinone, mitomycin C, aclacinomycin A and adriamycin, in the presence of NADPH-cytochrome P-450 reductase

The generation of hydroxyl free radicals in the system consisting of purified NADPH-cytochrome P-450 reductase and anticancer quinone drugs, such as carbazilquinone, mitomycin C, aclacinomycin A and adriamycin, has been confirmed by two methods. In the spin trapping study, using N-tert-butyl-alpha-phenylnitrone as the spin trapping agent, four drugs generated hydroxyl radical-trapped signals, and the formation of the spin adduct was dependent on time and the enzyme concentration. Among the four drugs, the generation time of signal was in the order of carbazilquinone, aclacinomycin A, adriamycin and mitomycin C, but the magnitude of signal intensity was different. In both aclacinomycin A and adriamycin, the signal disappeared in a few minutes. Catalase completely inhibited the formation of the spin adduct, while superoxide dismutase did not significantly inhibit, but effected in some manner. The generation of hydroxyl radical was also confirmed by the ethylene production from methional. Among the four drugs, the order of the magnitude of ethylene production was different from that of signal intensity by ESR study. Catalase potently inhibited the ethylene production, while superoxide dismutase effected in some manner. From these results, the interactions of anticancer quinone drugs with NADPH-cytochrome P-450 reductase and oxygen, and the possible relations of the enzymes to the radical related actions of these drugs are discussed.

Studies on the mechanism of toxicity of the mycotoxin, sporidesmin. I. Generation of superoxide radical by sporidesmin

Sporidesmin (SDMS2), the mycotoxin responsible for 'facial eczema' in ruminants, contains a disulphide group which appears to be intimately involved in its toxic action. The reduced (dithiol) form of sporidesmin has been shown readily to undergo autoxidation in vitro in a reaction which generates superoxide radical (O2-). The autoxidation reaction, which takes place over a wide pH range, is strongly catalysed by trace amounts of copper, although the reaction was inhibited at high concentrations of this metal. Inhibition of the autooxidation of reduced sporidesmin (SDM(SH)2) was also observed in the presence of nickel, cobalt and manganese. Superoxide radical is also generated from SDMS2 itself in a cyclic reduction/autoxidation reaction with glutathione and other thiols; in view of the known toxicity of superoxide and its derivatives, it is suggested that oxygen-free-radicals may be involved in the initiation of the deleterious effects of the mycotoxin.

On the mechanism of reductive activation in the mode of action of some anticancer drugs

Bioactivation of a number of DNA-specific antitumor drugs depends on oxidoreduction. Bleomycin, neocarzinostatin and anthracycline glycosides are the best known among such drugs in terms of reductive activation processes. Their reduction results in short-lived radical or electrophilic intermediates attacking DNA stereospecifically. The physico-chemical properties of these drugs and the nature of DNA damage are reviewed. Models for DNA-intercalation, electron-donor systems involved in drug metabolisation, and the role of oxygen in radical reactions, are discussed in the light of recent reports.