Formation Of Oxygen Species Research Articles

Ultraviolet-induced oxidative damage to skin

Ultraviolet photons can be absorbed by various photosensitizers(endogenous andexogenous)and chromophores in skin,thereafter stimulate the formation of reactive oxygen species(ROS)through electronic transfer,which are involved in many pathological processes in skin.AIthough ROS atepartly removed by nonenzymic and enzymic antioxidants.residual ROS can cause a pro-oxidant/antioxidantdisequilibrium defined as oxidative stress that subsequently lcads to a change in skin pigmentation,damageto such molecules as DNA.as well as an increment in the expression of matrix metalloproteinases.cyclooxygenases,nitric oxide synthase,heme oxygenase,and so on. Key words: Ultraviolet rays; Reactive oxygen species; Injuries

Minireview: C2- and C4-position 17β-estradiol metabolites and their relation to breast cancer

C2- and C4-position 17beta-estradiol metabolites play an important role in breast carcinogenesis. 2-Hydroxyestradiol and 4-hydroxyestradiol are implicated in tumorigenesis via two pathways. These pathways entail increased cell proliferation and the formation of reactive oxygen species that trigger an increase in the likelihood of deoxyribonucleic acid mutations. 2-Methoxyestradiol, a 17beta-estradiol metabolite, however, causes induction of apoptosis in transformed and tumor cells; thus exhibiting an antiproliferative effect on tumor growth. The 4-hydroxyestradiol:2-methoxyestradiol and 2-hydroxyestradiol:2-methoxyestradiol ratios therefore ought to be taken into account as possible indicators of carcinogenesis.

Podophyllin, but not the constituents quercetin or kaempferol, induced genotoxicity in vitro and in vivo through ROS production

The genotoxic potential of podophyllin (PD) was investigated in this study. PD increased bacterial revertants and abnormal chromosomal structures in a concentration-dependent manner, both with and without metabolic activating enzymes, and increased the incidence of micronuclei in imprinted control region mouse reticulocytes. Results from three studied constituents of PD, such as podophyllotoxin, kampferol, and quercetin, suggested that the mutagenic effect of PD was not due to the presence of podophyllotoxin, kampferol, and quercetin and might be related to other components and the formation of reactive oxygen species. The detailed mutagenic mechanisms need further investigation, and the medicinal use of PD needs to be cautioned against.

Involvement of Lipid Rafts and Caveolins in UVA Signaling

This review provides an overview over the burden solar radiation confers to human skin. Individual exposure doses vary not only due to different ambient UV doses depending on season, time of day, geographical position and weather conditions, but just as importantly to seasonal variation in behaviour. The general photobiological mechanisms underlying UVA, UVB and infrared A signaling are marked. Rafts are tightly packed, ordered and dynamic membrane microdomains rich in sphingolipids and cholesterol. They contribute to signaling events by trapping signaling molecules e.g. receptors or enzymes in order to render them active or inactive. A special subtype of rafts are caveolae also found in basal keratinocytes representing a flask-shaped invagination of the cytoplasmic membrane which are stabilized by caveolins serving as a scaffolding protein to organize lipids and signal transducing proteins. Within UVA signaling these membrane domains have been identified to be a target and a source for formation of reactive oxygen species in keratinocytes. UVA responsiveness with regards to gene expression depends on the ratio of cholesterol vs ceramide in rafts and on the presence of caveolin-1. Cholesterol, phytosterols or several triterpenoids can stabilize these raft structure leading to inhibition of UVA signaling, whereas increased levels of 7-dehydrocholesterol found in Smith-Lemli-Opitz patients suffering from enhanced photosensitivity mainly towards UVA destabilize rafts.

Interferon-α2b (IFN-α2b)-induced apoptosis is mediated by p38 MAPK in hepatocytes from rat preneoplastic liver via activation of NADPH oxidase

It is still unclear how Interferon-alfa (IFN-α) acts on preventing the appearance of hepatocarcinogenesis. We have demonstrated that IFN-α2b induces hepatocytic transforming growth factor-beta1 (TGF-β1) production and secretion by inducing reactive oxygen species (ROS) formation through the activation of NADPH oxidase. This TGF-β1, alters antioxidant defences and induces programmed cell death. Since it was demonstrated that IFN-α induces apoptosis through the activation of p38 mitogen-activated protein kinase (p38 MAPK), this study was aimed to assess the role of this kinase in the IFN-α2b-induced apoptosis in rat liver preneoplasia; and to further evaluate the participation of NADPH oxidase. p38 MAPK pathway was activated during the IFN-α2b-induced apoptosis in rat liver preneoplasia. This activation was accompanied with phosphorylation of different transcription factors, depending on the time of IFN-α2b stimulus. Our data suggest that NADPH oxidase is activated by IFN-α2b through p38 MAPK. p38 MAPK-induced activation of NADPH oxidase is accomplished by a two-step pathway: first, ROS-independent and second ROS- and TGF-β1-dependent.

Recent advances in structure and reactivity of dissolved organic matter in natural waters

The goal of our research is to better understand the structure and reactivity of natural dissolved organic matter (DOM) in aquatic environments. A more detailed knowledge of these DOM characteristics would lead to a better understanding of carbon cycling in natural waters and processes associated with water treatment using free radical chemistry. Our specific interest in DOM in natural waters is several-fold: 1) the photochemical formation of reactive oxygen species, 2) photobleaching of the DOM in coastal oceans, and 3) using chromophoric DOM (CDOM) as a tracer of water masses and in carbon cycling. Our interest in water treatment is that DOM is the major sink of hydroxyl radicals employed in advanced oxidation processes for the destruction of pollutants and thus adversely affects the efficiency of the process. We are using the techniques of radiation chemistry to explore the fundamental free radical and redox chemistry of DOM. We have initiated a study of the free radical reactions of DOM using isolated fractions of Suwannee River fulvic and humic acids and isolates from various anthropogenic sources. We are also investigating the use of model compounds in an attempt to understand the free radical transients formed from DOM either as a result of free radical reactions or photochemical reactions.

Analysis of the influence of rhodium addition to platinum on its activity towards methanol electrooxidation by EIS

Influence of rhodium addition to platinum on the activity of the alloy in methanol electrooxidation has been studied using Pt–Rh/Au limited volume electrodes with various surface compositions including the pure Pt and Rh metals. Electrochemical impedance spectroscopy (EIS) was used in the study. In the case of the Pt–Rh alloy, the impedance picture of methanol oxidation is qualitatively the same as for the pure Pt electrode. However, impedance spectra strongly depend on alloy composition. Equivalent circuits suitable for methanol oxidation on Pt were also used in the case of Pt–Rh and similar fitting results were obtained. A reaction mechanism suggested in the literature for Pt, which involves two strongly adsorbed intermediates competing for the same adsorption sites, is likely also for the Pt–Rh alloys. However, fittings with a corresponding impedance model were unsuccessful for both Pt and Pt–Rh because of mathematical caveats, such that quantitative comparisons were not possible. Nevertheless, EIS results suggest that Rh inhibits the kinetics of formation of reactive oxygen species at the surface of the alloy.

Abstract 214: S100A6 Promotes Myocyte Survival by Interacting with the Receptor for Advanced Glycation End Products and Activating Akt

The receptor for advanced ligation end-products (RAGE) recognizes ligands from diverse families including the S100 calcium binding proteins S100A6 and S100B. In a rat model of myocardial infarction, we have reported the induction of S100B, the upregulation of S100A6 and RAGE mRNA and protein in peri-infarct left ventricular (LV) myocardium, increases in S100B and S1006 serum levels and demonstrated a direct interaction between S100B and S100A6 with RAGE in peri-infarct LV myocardium. To determine the functional role of the interaction of S100A6 and S100B with RAGE, we stimulated rat neonatal cardiac myocyte cultures transfected with a RAGE gene or a dominant-negative cytoplasmic deletion mutant of RAGE with S100B and/or S100A6 for 48 hrs. In RAGE overexpressing myocytes, although both S100 proteins induced the formation of reactive oxygen species, S100B > 10 nM induced myocyte apoptosis, as evidenced by increased terminal deoxynucleotidyltransferase-mediated UTP end labeling (TUNEL), FITC annexin V flow cytometry, cytochrome C release, phosphorylation of ERK1/2 and p53, and increased activity of caspase-3, whereas S100A6 < 10 nM inhibited basal myocyte apoptosis, increased the phosphorylation of Akt and the expression of NF-κB and in combination with S100B inhibited S100B-induced myocyte apoptosis [6.3±0.9% (vehicle), 16.1±0.1.2% (S100B), 4.1±0.4% (S100A6), 6.4±1.5% (S100B+S100A6) (TUNEL positive nuclei)]. The upstream Akt blocker LY294002, inhibited the RAGE dependent anti-apoptotic effects of S100A6 on basal- and S100B-induced myocyte apoptosis. In myocytes expressing dominant-negative RAGE, the contrasting effects of S100B and S100A6 on myocyte apoptosis were absent regardless of Akt inhibition. In conclusion, in a RAGE-dependent manner, S100A6 inhibits myocyte apoptosis via Akt activation.

Abstract 227: Activity of Soluble Guanylyl Cyclase, the Nitric Oxide Receptor, is Modulated by Cysteines Redox

The enzyme soluble guanylyl cyclase (sGC) increases cellular level of the second messenger cGMP upon stimulation by nitric oxide (NO), whose role is exemplified in the cardiovascular system where it governs smooth muscle cell proliferation, vascular relaxation and platelet aggregation. Various pathologies like diabetes, hypertension and hypercholesterolemia are associated with enhanced oxidative stress with increased formation of reactive oxygen (ROS) and nitrogen species (RNS). We recently showed that cysteines beta1C243 and beta1C122 are S-nitrosylated in sGC leading to its desensitization. We have now identified by Mass Spectrometry, two additional cysteines (beta1C571 and alpha1C516) as potentially modified. Our hypothesis is that loss in vascular reactivity in oxidative pathologies is mediated, in part, by desensitization of sGC via thiols oxidation. We studied the effect of oxidative stress on sGC in primary vascular smooth muscle cells (VSMC) by directly exposing them to hydrogen peroxide (H2O2) in the absence or presence of a catalase inhibitor Amino-Triazole (AT). H2O2 induced inhibition of NO-stimulated sGC activity in VSMC and in COS 7 cells transiently transfected with sGC. Desensitization of sGC was further increased in VSMC treated with both H2O2 and AT. Next, we conducted mutational analysis of the 4 cysteines to assess their involvement in redox sensing. Replacement of C571 and C122 eliminated the oxidative-dependent desensitization observed in the wild-type. In addition, peroxynitrite, a strong oxidant, inhibited the NO-stimulated sGC activity in a purified system without oxidation of the heme. In conclusion, our results suggest that sGC activity is directly modulated by the redox state of the cells. Moreover, the identified 4 cysteines can be modified by both ROS and RNS suggesting a complex modulation. Ultimately, our goal is to determine whether loss of vascular reactivity in oxidative pathophysiologies is in part mediated by desensitization of sGC and what are the involved cysteines. This work was supported by NIH GM067640, HL089771.

Abstract 5702: Oxidative Stress in Patients with Lone Atrial Fibrillation

Background: Lone atrial fibrillation (LAF) is a common arrhythmia, but its mechanism and the aggravated factor of arrhythmia are poorly understood. Oxidative stress has been implicated in the pathogenesis of heart failure. We have previously demonstrated that the amount of 4-hydroxy-2-nonenal (HNE) modified protein, which is a major lipid peroxidation product and a cytotoxic aldehyde, causes intracellular Ca2+ overload via reactive oxygen species (ROS) formation in cardiomyocytes and leads to develop arrhythmia. Accordingly we examined the levels of HNE and major histocompatibility complex (MHC) with the disease severity in LAF patients. Method: Atrial and ventricular myocardial samples were obtained from twelve patients (11 men and 1 woman, mean 48±14 years old) by endomyocardial biopsy in 10, autopsy sample in 1 and surgical resection sample in 1. Histological assessments and immunohistochemical analysis for HNE modified protein, MHC class-I and -II antigens (grade 0 to 3) were performed and compared with LAF severity. Results: Histological assessment showed that increased number of interstitial cells (mainly activated T cells) was observed only in the atrium but not in the ventricle. Moderate to severe expression of MHC antigens (grade 2 or 3) was more observed in the atrium than the ventricle (MHC-I: seven in atrium and three in ventricle; MHC-II: ten in atrium and four in ventricle). Atrial myocarditis was detected in 6 out of 11 samples. HNE modified protein was also more observed in the atrium than that in the ventricle. In addition, more severe expression of HNE staining was observed in the samples from persistent/chronic LAF than that in paroxysmal LAF. Conclusion: These data indicates that oxidative stress plays an important role as an aggravating factor in LAF patients.

Reactive oxygen species facilitate the insulin-dependent inhibition of glucagon-induced glucose production in the isolated perfused rat liver

Recent studies indicate that intracellular insulin signalling involves the formation of reactive oxygen species (ROS) by NADPH oxidases (NOX). ROS inhibit intracellular protein tyrosin phosphatases whereby phosphoprotein signalling is enhanced and prolonged. We used the isolated perfused rat liver and detected ROS formation by measuring the surface fluorescence at wavelengths specific for the intracellular ROS sensor carboxydihydrodichlorofluorescein. Insulin (2, 5, 20 nM) induced low level ROS formation that was abolished by the NOX inhibitor diphenyleneiodonium chloride (4 microM). Studying insulin-dependent inhibition of glucagon-activated glucose production showed that melatonin (50 microM), used as ROS scavenger, inhibited ROS formation and blunted the effect of insulin on glucose production. The data support the general notion that hormone-dependent ROS formation modifies intracellular signal transduction.

Temperature programmed desorption of oxygen from Pd films interfaced with Y2O3-doped ZrO2

The origin of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion was investigated via temperature-programmed-desorption (TPD) of oxygen, from polycrystalline Pd films deposited on 8 mol%Y2O3–stabilized–ZrO2 (YSZ), an O2− conductor, under high-vacuum conditions and temperatures between 50 and 250 °C. Oxygen was adsorbed both via the gas phase and electrochemically, as O2−, via electrical current application between the Pd catalyst film and a Au counter electrode. Gaseous oxygen adsorption gives two adsorbed atomic oxygen species desorbing at about 300 °C (state β1) and 340–500 °C (state β2). The creation of the low temperature peak is favored at high exposure times (exposure >1 kL) and low adsorption temperatures (Tads < 200 °C). The decrease of the open circuit potential (or catalyst work function) during the adsorption at high exposure times, indicates the formation of subsurface oxygen species which desorbs at higher temperatures (above 450 °C). The desorption peak of this subsurface oxygen is not clear due to the wide peaks of the TPD spectra. The TPD spectra after electrochemical O2− pumping to the Pd catalyst film show two peaks (at 350 and 430 °C) corresponding to spillover Oads and \( O^{{\delta - }}_{{\rm ads}} \) according to the reaction: $$ O^{{2 - }}_{{\rm (YSZ)}} \to {\text{O}}^{{\delta - }}_{{{\text{ads}}}} \to {\text{O}}_{{{\text{ads}}}} $$

Cerebral spectroscopic and oxidative stress studies in patients with schizophrenia who have dangerously violently offended

The aim of this study was to bring together all the results of in vivo studies of ethane excretion and cerebral spectroscopy in patients with schizophrenia who have dangerously seriously violently offended in order to determine the extent to which they shed light on the degree to which the membrane phospholipid hypothesis and the actions of free radicals and other reactive species are associated with cerebral pathophysiological mechanisms in this group of patients. The patients investigated were inpatients from a medium secure unit with a DSM-IV-TR diagnosis of schizophrenia. There was no history of alcohol dependency or any other comorbid psychoactive substance misuse disorder. Expert psychiatric opinion, accepted in court, was that all these patients had violently offended directly as a result of schizophrenia prior to admission. These offences consisted of homicide, attempted murder or wounding with intent to cause grievous bodily harm. Excreted ethane was analyzed and quantified by gas chromatography and mass spectrometry (m/z = 30). 31-phosphorus magnetic resonance spectroscopy data were obtained at a magnetic field strength of 1.5 T using an image-selected in vivo spectroscopy sequence (TR = 10 s; 64 signal averages localized on a 70 × 70 × 70 mm3 voxel). Compared with age- and sex-matched controls, in the patient group the mean alveolar ethane level was higher (p < 0.0005), the mean cerebral beta-nucleotide triphosphate was lower (p < 0.04) and the mean gamma-nucleotide triphosphate was higher (p < 0.04). There was no significant difference between the two groups in respect of phosphomonoesters, phosphodiesters or broad resonances. Our results are not necessarily inconsistent with the membrane phospholipid hypothesis, given that the patients studied suffered predominantly from positive symptoms of schizophrenia. The results suggest that there is increased cerebral mitochondrial oxidative phosphorylation in patients with schizophrenia who have dangerously and seriously violently offended, with an associated increase in oxygen flux and subsequent electron 'leakage' from the electron transport chain leading to the formation of superoxide radicals and other reactive oxygen species. In turn, these reactive species might cause increased lipid peroxidation in neuroglial membranes, thereby accounting for the observation of increased ethane excretion.

Formation of Reactive Oxygen Species in Lung Alveolar Cells: Effect of Vitamin E Deficiency

Reactive oxygen species (ROS) play an important role in the pathogenesis of numerous pulmonary diseases. Various mainly membrane-bound ROS-generating processes exist in alveolar cells. Vitamin E (vit. E) is the most important lipophilic antioxidant. However, the significance of vit. E levels in alveolar cells for the regulation of ROS generation has not been investigated so far. We demonstrated here that feeding rats with vit. E-depleted nourishment for 5 weeks reduced the concentration of vit. E in alveolar type II cell preparations to one-fifth the amount of control animals. This reduction of vit. E levels was associated with an approximately threefold increase in ROS generation in type II pneumocytes, lymphocytes, and macrophages. The contribution of individual processes of ROS formation in control animals differed strongly among these three cell types. However, vit. E deficiency induced predominantly nonmitochondrial ROS formation in alveolar cells. Expression and NAD(P)H-oxidase activity in alveolar type II cell preparations was not affected by vit. E deficiency. Moreover, protein kinase C (PKC) also did not seem to be responsible for vit. E deficiency-induced ROS generation in alveolar cells. Alimentary vit. E supplementation for 2 days corrected the cellular vit. E concentration but failed to normalize ROS generation in alveolar cells. These data let us assume that alimentary vit. E deficiency caused a preferentially nonmitochondria-mediated increase of ROS formation in type II pneumocytes, macrophages, and lymphocytes. However, the short-term supplementation of vit. E does not reverse these effects.

Unconventional effects of UVA radiation on cell cycle progression in S. pombe

UVA radiation, the most abundant solar UV radiation reaching Earth’s surface, induces oxidative stress through formation of reactive oxygen species (ROS) that can damage different cell components. Because of the broad spectrum of the possible targets of ROS, the cellular response to this radiation is complex. While extensive studies have allowed dissecting the effects of UVB, UVC and gamma radiations on cell cycle progression, few studies have dealt with the effect of UVA so far. Here we use Schizosaccharomyces pombe as a model organism to study biological effects of UVA radiation in living organisms. Through analysis of cell cycle progression in different mutant backgrounds we demonstrate that UVA delays cell cycle progression in G2 cells in a dose dependent manner. However, despite Chk1 phosphorylation and in contrast to treatments with others genotoxic agents, this cell cycle delay is only partially dependent on DNA integrity checkpoint pathway. We also demonstrate that UVA irradiation of S phase cells slows down DNA replication in a checkpoint independent manner, activates Chk1 to prevent entry into abnormal mitosis and induces formation of Rad22 (homologue to human Rad52) foci. This indicates that DNA structure integrity is challenged. Furthermore, the cell cycle delay observed in checkpoint mutants exposed to UVA is not abolished when stress response pathway is inactivated or when down regulation of protein synthesis is prevented. In conclusion, fission yeast is a useful model to dissect the fundamental molecular mechanisms involved in UVA response that may contribute to skin cancer and aging.

The use of dexrazoxane for the prevention of anthracycline extravasation injury

Background: The use of the anthracycline anticancer drugs doxorubicin, daunorubicin, epirubicin and idarubicin sometimes results in accidental extravasation injury and can be a serious complication of their use. Objective: The object of this review was to evaluate the preclinical and clinical literature on the use of dexrazoxane in preventing anthracycline-induced extravasation injury. Methods: A review of the literature was carried out using PubMed. Results/conclusions: Dexrazoxane, which is clinically used to reduce doxorubicin-induced cardiotoxicity, has been shown in two clinical studies and in several case reports to be highly efficacious in preventing anthracycline-induced extravasation injury. Dexrazoxane is a prodrug analog of the metal chelator EDTA that likely acts by removing iron from the iron–anthracycline complex, thus preventing formation of damaging reactive oxygen species.

Changes in Phospholipid Composition Studied by HPLC and Electric Properties of Liver Cell Membrane of Ethanol-Poisoned Rats

ABSTRACTEthanol introduced into the organism undergoes rapid metabolism to acetaldehyde and then to acetic acid. The process is accompanied by formation of reactive oxygen species (ROS), which damage mainly lipids of membrane cells. The effects of ROS can be neutralized by administering preparations with antioxidant properties. The natural preparations of this kind are teas.This paper reports data on the effect of green and black tea on the surface charge density, content of phospholipids, and level of lipid peroxidation products of liver cell membrane of rats chronically intoxicated with ethanol. Surface charge density of liver cells was measured by the electrophoresis method, whereas qualitative phospholipid composition was determined by the HPLC method.Ethanol administration caused an increase in the amount of all phospholipids, in surface charge density as well as in lipid peroxidation products. Ingestion of green and black tea with ethanol partially prevented these ethanol-induced changes, and the action of green tea was stronger than that of black tea.

Concurrent expression of heme oxygenase-1 and p53 in human retinal pigment epithelial cell line

Heme oxygenase-1 (HO-1) is a stress-responsive protein that is known to regulate cellular functions such as cell proliferation, inflammation, and apoptosis. Here, we investigated the effects of HO activity on the expression of p53 in the human retinal pigment epithelium (RPE) cell line ARPE-19. Cobalt protoporphyrin (CoPP) induced the expression of both HO-1 and p53 without significant toxicity to the cells. In addition, the blockage of HO activity with the iron chelator DFO or with HO-1 siRNA inhibited the CoPP-induced expression of p53. Similarly, zinc protoporphyrin (ZnPP), an inhibitor of HO, suppressed p53 expression in ARPE-19 cells, although ZnPP increased the level of HO-1 protein while inhibiting HO activity. Also, CoPP-induced p53 expression was not affected by the formation of reactive oxygen species (ROS). Based on these results, we conclude that HO activity is involved in the regulation of p53 expression in a ROS-independent mechanism, and also suggest that the expression of p53 in ARPE-19 cells is associated with heme metabolites such as biliverdin/bilirubin, carbon monoxide, and iron produced by the activity of HO.

Abstract 726: Nox4 Expression in Human Monocyte-Derived Macrophages: Upregulation by Oxidized LDL via a MEK-ERK1/2-dependent Pathway

Nox4 is member of the family of NADPH oxidase expressed in endothelium and smooth muscle cells, but has not previously been reported in human monocytes or monocyte-derived macrophages. We now identified Nox4 as a new Nox member in human monocytes and monocyte-derived macrophages. Nox4 and the phagocytic NADPH oxidase gp91/Nox2 were differentially regulated during monocyte differentiation. In contrast to Nox2, Nox4 protein expression was upregulated in mature human macrophages, and confocal microscopy revealed that Nox4 colocalized primarily with mitochondria. Exposure of macrophages to OxLDL for 24 h further increased Nox4 expression in a concentration-dependent manner. OxLDL-induced Nox4 expression was blocked by inhibitors of MEK1/2, UO126 and PD98059, but not by SB203580 and SP600125, inhibitors of p38MAPK or JNK, respectively. Furthermore, MEK inhibitors, but not inhibitors of p38MAPK or JNK, protected macrophages from OxLDL-induced cell injury, identifying a MEK/ERK1/2-dependent signaling pathway upstream of OxLDL-induced Nox4 expression that is involved in macrophage death. Previously, we showed that OxLDL stimulates the intracellular formation of reactive oxygen species (ROS) in human macrophages, but the source of these ROS remained elusive. We also demonstrated that the peroxyl radical scavenger Trolox protects macrophages from OxLDL-induced cell injury. Interestingly, Trolox did not prevent Nox4 expression induced by OxLDL, suggesting that Trolox acts downstream of OxLDL-induced Nox4 expression. These results not only identify Nox4 as a new intracellular source of ROS in macrophages, but also implicate Nox4 in OxLDL-induced ROS formation and macrophage death, which may have important implications for the pathogenesis of atherosclerosis.

Early nifurtimox-induced biochemical and ultrastructural alterations in rat heart

Nifurtimox (Nfx) and Benznidazole (Bz) are being used for the treatment of the acute phase of Chagas' disease. Recently, they were also considered for use in the indeterminate phase. Both the nitroheterocyclic drugs have serious toxic side effects. The mechanism of Nfx toxicity is associated with the formation of reactive oxygen species (ROS) generated during nitroreduction. Potential effects on cardiac function have not been established yet, despite the well-known cardiopathy often produced by the disease itself. We describe experiments testing some acute effects of Nfx on the male Sprague Dawley rat heart. Nifurtimox was present in the heart at 1, 3 and 6 h after intragastric (i.g) treatment. In vitro studies on Nfx microsomal and cytosolic nitroreductase activities showed that only the microsomal fraction had the ability to nitroreduce it. Cytochrome P450 and cytochrome P450 reductase would be involved in the process as suggested by their response to specific inhibitors. Nifurtimox increased the cardiac protein carbonyl content at 1 and 3 h and decreased the protein sulfhydryl content at 3 h. In addition, 24 h after treatment ultrastructural alterations such as marked cytoplasmic vacuolization, separation and loss of myofibrils and mitochondrial swelling were observed. Results suggest that Nfx administration might aggravate pre-existing adverse cardiac conditions. Human & Experimental Toxicology (2007) 26, 781 -788.