The role of reactive oxygen species in arsenite and monomethylarsonous acid-induced signal transduction in human bladder cells: acute studies

Arsenicals are known to induce ROS, which can lead to DNA damage, oxidative stress, and carcinogenesis. A human urothelial cell line, UROtsa, was used to study the effects of arsenicals on the human bladder. Arsenite [As(III)] and monomethylarsonous acid [MMA(III)] induce oxidative stress in UROtsa cells after exposure to concentrations as low as 1 microM and 50 nM, respectively. Previous research has implicated ROS as signaling molecules in the MAPK signaling pathway. As(III) and MMA(III) have been shown to increase phosphorylation of key proteins in the MAPK signaling cascade downstream of ErbB2. Both Src phosphorylation (p-Src) and cyclooxygenase-2 (COX-2) are induced after exposure to 50 nM MMA(III) and 1 microM As(III). These data suggest that ROS production is a plausible mechanism for the signaling alterations seen in UROtsa cells after acute arsenical exposure. To determine importance of ROS in the MAPK cascade and its downstream induction of p-Src and COX-2, specific ROS antioxidants (both enzymatic and non-enzymatic) were used concomitantly with arsenicals. COX-2 protein and mRNA was shown to be much more influenced by altering the levels of ROS in cells, particularly after MMA(III) treatment. The antioxidant enzyme superoxide dismutase (SOD) effectively blocked both As(III)-and MMA(III)- associated COX-2 induction. The generation of ROS and subsequent altered signaling did lead to changes in protein levels of SOD, which were detected after treatment with either 1 microM As(III) or 50 nM MMA(III). These data suggest that the generation of ROS by arsenicals may be a mechanism leading to the altered cellular signaling seen after low-level arsenical exposure.     

Intracellular generation of reactive oxygen species by mitochondria

Mitochondria have bioenergetic properties that strongly suggest their involvement in the cellular formation of reactive oxygen species (ROS). Apparent confirmation of this process has come from work with isolated mitochondria, which have been shown to produce H(2)O(2) from dismutating superoxide radicals. Two different sites were reported to shuttle single electrons to oxygen out of the normal respiratory sequence. However, the mechanisms for ROS formation at these two sites are controversial. Arguments against mitochondrial ROS formation in the living cell are based on the fact that bioenergetic alterations may result from the mechanical removal of mitochondria from their natural environment. Furthermore, the invasive detection methods that are generally used may be inappropriate because of the possible interaction of the detection system with mitochondrial constituents. The use of non-invasive detection methods has proved that ROS formation does not occur unless changes in the physical state of the membrane are established. The aim of this commentary is to discuss critically the arguments in favor of mitochondria as the main intracellular source of ROS. The pros and cons of working with isolated mitochondria, as well as the detection methodology are carefully analyzed to judge whether or not the above assumption is correct. The conclusion that mitochondria are the main ROS generators in the cell contradicts the fact that ROS release was not observed. However, if electron flow from ubiquinol to the bc(1) complex is hindered due to changes in lipid fluidity, single electrons may transfer to dioxygen and produce H(2)O(2) via superoxide radicals.     

NADPH oxidase-mitochondria axis-derived ROS mediate arsenite-induced HIF-1α stabilization by inhibiting prolyl hydroxylases activity

Arsenic exposure has been shown to induce hypoxia inducible factor 1α (HIF-1α) accumulation, however the underlying mechanism remains unknown. In the present study, we tested the hypothesis that arsenic exposure triggered the interaction between NADPH oxidase and mitochondria to promote reactive oxygen species (ROS) production, which inactivate prolyl hydroxylases (PHDs) activity, leading to the stabilization of HIF-1α protein. Exposure of human immortalized liver cell line HL-7702 cells to arsenite induced HIF-1α accumulation in a dose-dependent manner, which was abolished by SOD mimetic MnTMPyP. Inhibition of NADPH oxidase with diphenyleneiodonium chloride (DPI) or inhibition of mitochondrial respiratory chain with rotenone significantly blocked arsenite-induced ROS production, and the mitochondria appeared to be the major source of ROS production. Arsenite treatment inhibited HIF-1α hydroxylation by prolyl hydroxylases (PHDs) and increased HIF-1α stabilization, but did not affect HIF-1α mRNA expression and Akt activation. Supplementation of ascorbate or Fe(II) completely abolished arsenite-induced PHDs inhibition and HIF-1α stabilization. In conclusion, these results define a unique mechanism of HIF-1α accumulation following arsenic exposure, that is, arsenic activates NADPH oxidase–mitochondria axis to produce ROS, which deplete intracellular ascorbate and Fe(II) to inactivate PHDs, leading to HIF-1α stabilization.     

Selective iNOS inhibition reduces renal damage induced by cisplatin

Cisplatin is a chemotherapeutic agent used in the treatment of several cancer tumors; however, nephrotoxicity has restricted its use. Reactive oxygen species and peroxynitrite, which is formed by the reaction between superoxide anion and nitric oxide (NO*), are implicated in cisplatin-induced nephrotoxicity. In contrast, both toxic and beneficial effects of NO* have been suggested in cisplatin-induced nephrotoxicity. Therefore, nowadays the role of NO* in this experimental model remains controversial. The aim of the present work was to elucidate the role of NO* in cisplatin-induced renal damage using N-[3-(aminomethyl)benzyl]acetamidine (1400W), a selective and irreversible inhibitor of iNOS. The mRNA levels of iNOS were increased in cisplatin-treated rats. The administration of 1400W reduced the cisplatin induced histological damage, renal dysfunction (increase in proteinuria and kidney injury molecule expression and decrease in creatinine clearance), tubulointerstitial infiltration, oxidative stress (increase in renal malondialdehyde and inmmunostaining for 4-hydroxy-2-nonenal) and nitrosative stress (immunostaining for 3-nitrotyrosine). In addition, the administration of 1400W was unable to modify systolic blood pressure in control rats. Our data demonstrate that selective iNOS inhibition reduces the cisplatin-induced nephrotoxicity and nitrosative stress which strongly suggest that in this experimental model (1) the NO* production is toxic and (2) iNOS is the main source of NO*.     

Vitamin E protects against the mitochondrial damage caused by cyclosporin A in LLC-PK1 cells

Cyclosporin A (CsA) has nephrotoxic effects known to involve reactive oxygen species (ROS), since antioxidants prevent the kidney damage induced by this drug. Given that mitochondria are among the main sources of intracellular ROS, the aims of our study were to examine the mitochondrial effects of CsA in the porcine renal endothelial cell line LLC-PK1 and the influence of the antioxidant Vitamin E (Vit E).Following the treatment of LLC-PK1 cells with CsA, we assessed the mitochondrial synthesis of superoxide anion, permeability transition pore opening, mitochondrial membrane potential, cardiolipin peroxidation, cytochrome c release and cellular apoptosis, using flow cytometry and confocal microscopy procedures. Similar experiments were done after Vit E preincubation of cells.CsA treatment increased superoxide anion in a dose-dependent way. CsA opened the permeability transition pores, caused Bax migration to mitochondria, and decreased mitochondrial membrane potential and cardiolipin content. Also CsA released cytochrome c into cytosol and provoked cellular apoptosis. Vit E pretreatment inhibited the effects that CsA induced on mitochondrial structure and function in LLC-PK1 cells and avoided apoptosis.CsA modifies mitochondrial LLC-PK1 cell physiology with loss of negative electrochemical gradient across the inner mitochondrial membrane and increased lipid peroxidation. These features are related to apoptosis and can explain the cellular damage that CsA induces. As Vit E inhibited these effects, our results suggest that they were mediated by an increase in ROS production by mitochondria.     

Antioxidant activities of the flaxseed lignan secoisolariciresinol diglucoside, its aglycone secoisolariciresinol and the mammalian lignans enterodiol and enterolactone in vitro.

The flaxseed lignan secoisolariciresinol diglucoside (SDG) and mammalian lignans enterodiol (ED) and enterolactone (EL) were previously shown to be effective antioxidants against DNA damage and lipid peroxidation. Others reported inhibition of activated cell chemiluminescence by supra-physiological concentrations of secoisolariciresinol (SECO), ED and EL. Thus, we evaluated the antioxidant efficacy of potential physiological concentrations of SDG, SECO, ED and EL against 1,1-diphenyl-2-picrylhydrazyl (DPPH()), and 2,2'-azo-bis(2-amidinopropane) dihydrochloride (AAPH)-initiated peroxyl radical plasmid DNA damage and phosphatidylcholine liposome lipid peroxidation. SDG and SECO were effective (p<0.01) antioxidants against DPPH() at 25-200muM; whereas, ED and EL were inactive. Efficacy of lignans and controls against AAPH peroxyl radical-induced DNA damage was: SDG>SECO=17alpha-estradiol>ED=EL>genistein>daidzein. Lignan efficacy against AAPH-induced liposome lipid peroxidation was: SDG>SECO=ED=EL. Plant lignan antioxidant activity was attributed to the 3-methoxy-4-hydroxyl substituents of SDG and SECO, versus the meta mono-phenol structures of ED and EL. Benzylic hydrogen abstraction and potential resonance stabilization of phenoxyl radicals in an aqueous environment likely contributed to the antioxidant activity of the mammalian lignans. These represent likely extra- and intracellular antioxidant activities of flax-derived lignans at concentrations potentially achievable in vivo.     

Rescuing hepatocytes from iron-catalyzed oxidative stress using vitamins B1 and B6

In the following rescue experiments, iron-mediated hepatocyte oxidative stress cytotoxicity was found to be prevented if vitamin B1 or B6 was added 1 h after treatment with iron. The role of iron in catalyzing Fenton-mediated oxidative damage has been implicated in iron overload genetic diseases, carcinogenesis (colon cancer), Alzheimer’s disease and complications associated with the metabolic syndrome through the generation of reactive oxygen species (ROS). The objectives of this study were to interpret the cytotoxic mechanisms and intracellular targets of oxidative stress using “accelerated cytotoxicity mechanism screening” techniques (ACMS) and to evaluate the rescue strategies of vitamins B1 and B6. Significant cytoprotection by antioxidants or ROS scavengers indicated that iron-mediated cytotoxicity could be attributed to reactive oxygen species. Of the B6 vitamers, pyridoxal was best at rescuing hepatocytes from iron-catalyzed lipid peroxidation (LPO), protein oxidation, and DNA damage, while pyridoxamine manifested greatest protection against ROS-mediated damage. Thiamin (B1) decreased LPO, mitochondrial and protein damage and DNA oxidation. Together, these results indicate that added B1 and B6 vitamins protect against the multiple targets of iron-catalyzed oxidative damage in hepatocytes. This study provides insight into the search for multi-targeted natural therapies to slow or retard the progression of diseases associated with Fenton-mediated oxidative damage.     

BCNU-induced gR2 DEFECT mediates S-glutathionylation of Complex I and respiratory uncoupling in myocardium

A deficiency of mitochondrial glutathione reductase (or GR2) is capable of adversely affecting the reduction of GSSG and increasing mitochondrial oxidative stress. BCNU [1,3-bis (2-chloroethyl)-1-nitrosourea] is an anticancer agent and known inhibitor of cytosolic GR ex vivo and in vivo. Here we tested the hypothesis that a BCNU-induced GR2 defect contributes to mitochondrial dysfunction and subsequent impairment of heart function. Intraperitoneal administration of BCNU (40 mg/kg) specifically inhibited GR2 activity by 79.8 ± 2.7% in the mitochondria of rat heart. However, BCNU treatment modestly enhanced the activities of mitochondrial Complex I and other ETC components. The cardiac function of BCNU-treated rats was analyzed by echocardiography, revealing a systolic dysfunction associated with decreased ejection fraction, decreased cardiac output, and an increase in left ventricular internal dimension and left ventricular volume in systole. The respiratory control index of isolated mitochondria from the myocardium was moderately decreased after BCNU treatment, whereas NADH-linked uncoupling of oxygen consumption was significantly enhanced. Extracellular flux analysis to measure the fatty acid oxidation of myocytes indicated a 20% enhancement after BCNU treatment. When the mitochondria were immunoblotted with antibodies against GSH and UCP3, both protein S-glutathionylation of Complex I and expression of UCP3 were significantly up-regulated. Overexpression of SOD2 in the myocardium significantly reversed BCNU-induced GR2 inhibition and mitochondrial impairment. In conclusion, BCNU-mediated cardiotoxicity is characterized by the GR2 deficiency that negatively regulates heart function by impairing mitochondrial integrity, increasing oxidative stress with Complex I S-glutathionylation, and enhancing uncoupling of mitochondrial respiration.     

Prooxidant action of knipholone anthrone: Copper dependent reactive oxygen species generation and DNA damage

Knipholone (KP) and knipholone anthrone (KA) are natural 4-phenylanthraquinone structural analogues with established differential biological activities including in vitro antioxidant and cytotoxic properties. By using DNA damage as an experimental model, the comparative Cu(II)-dependent prooxidant action of these two compounds were studied. In the presence of Cu(II) ions, the antioxidant KA (3.1–200 μM) but not KP (6–384 μM) caused a concentration-dependent pBR322 plasmid DNA strand scission. The DNA damage induced by KA could be abolished by reactive oxygen species scavengers, glutathione and catalase as well as EDTA and a specific Cu(I) chelator bathocuproine disulfonic acid. In addition to Cu(II) chelating activity, KA readily reduces Cu(II) to Cu(I). Copper-dependent generation of reactive oxygen species and the subsequent macromolecular damage may be involved in the antimicrobial and cytotoxic activity of KA.     

Cardioprotective effects of a proanthocyanidin-rich fraction from Croton celtidifolius Baill: Focus on atherosclerosis

Proanthocyanidins are the most abundant polyphenols in human diets. Epidemiological studies have pointed to proanthocyanidins as promising molecules that could prevent the development of several coronary syndromes by inhibiting the atherogenic process. The present study was designed to investigate the antiatherogenic effects of a proanthocyanidin-rich fraction (PRF) obtained from Croton celtidifolius Baill (Euphorbiaceae) barks. In isolated human LDL, PRF caused a concentration-dependent inhibition of Cu²⁺-induced oxidative modifications, evidenced by the increasing of the lag phase of lipid peroxidation and decreasing in the oxidation rate (V_max), moreover, the protein moieties from LDL were protected against Cu²⁺-induced oxidation. In human umbilical vein endothelial cells (HUVECs), PRF reduced the ROS production stimulated by oxidized LDL. Herein, we demonstrate that oral treatment with PRF improved endothelium-dependent vasorelaxation in hypercholesterolemic LDL receptor knockout mice (LDLr^−/−), however, the fraction did not modify plasma lipids and atherosclerotic lesion size in this experimental model. Finally, our results showed for the first time that PRF prevent isolated LDL oxidation, decrease oxidative stress in endothelial cells and improve endothelial function in mice.     

Antioxidative function and biodistribution of [Gd@C82(OH)22]n nanoparticles in tumor-bearing mice

Oxidative stress is considered to be one of the important mechanisms involved in carcinogenesis. In our previous study, gadolinium endohedral metallofullerenol ([Gd@C82(OH)22]n nanoparticles) have shown high inhibitory activity on hepatoma cell (H22) growth in mice. To explore the antioxidative functions of nanoparticles, we investigated the biodistribution of [Gd@C82(OH)22]n nanoparticles, the changes of blood coagulation profiles, the metabolism of reactive oxygen species (ROS) in the tumor-bearing mice as well as the possible relationships between nanoparticles treatment and ROS production in this paper. The activities of hepatic superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione S-transferase (GST) and catalase (CAT) as well as the levels of reduced glutathione (GSH), protein-bound thiols and malondialdehyde (MDA) were compared between the tumor-bearing mice and normal mice. Transplanted tumors were grown in mice by subcutaneous injection of murine hepatoma cells in the mice. The comparison of the above parameters between nanoparticles and cyclophosphamide (CTX) therapy were also investigated. [Gd@C82(OH)22]n administration can efficiently restore the damaged liver and kidney of the tumor-bearing mice. All the activities of enzymes and other parameters related to oxidative stress were reduced after [Gd@C82(OH)22]n treatment and tended closely to the normal levels. The results suggest that [Gd@C82(OH)22]n nanoparticle treatment could regulate ROS production in vivo.     

Protective effect of diphlorethohydroxycarmalol isolated from Ishige okamurae against high glucose-induced-oxidative stress in human umbilical vein endothelial cells

In the present study, the protective effect of diphlorethohydroxycarmalol (DPHC) isolated from Ishige okamurae, a brown algae, on high glucose-induced-oxidative stress was investigated using human umbilical vein endothelial cells (HUVECs). High concentration of glucose (30 mM) treatment induced cytotoxicity whereas DPHC prevented cells from high glucose-induced damage; restoring cell viability was significantly increased. In addition, the lipid peroxidation, intracellular reactive oxygen species (ROS), and nitric oxide (NO) levels induced by high glucose treatment were effectively inhibited by addition of DPHC in a dose-dependent manner. DPHC also suppressed the over-expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins as well as nuclear factor-kappa B (NF-κB) activation induced by high glucose in HUVECs. These finding indicate that DPHC might be used as potential pharmaceutical agent which will reduce the damage caused by high glucose-induced-oxidative stress associated with diabetes.     

Protective effect of fluvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on copper-induced hydroxyl radical generation in the rat heart

The present study was examined the effect of fluvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on Cu(II)-induced hydroxyl radical generation (OH) in the extracellular fluid of rat myocardium. Rats were anesthetized and sodium salicylate in Ringer's solution (0.5 nmol/microl/min) was infused through a microdialysis probe to detect the generation of OH as reflected by the non-enzymatic formation of 2,3-dihydroxybenzoic acid (DHBA) in the myocardium. When Cu(II) was infused through the microdialysis probe, Cu(II) increased in OH formation trapped as 2,3-DHBA in the dialysate. When fluvastatin (100 microM) was administered to Cu(II) (50 microM)-pretreated animals, the levels of 2,3-DHBA at 300 min after administration of fluvastatin significantly decreased. In cumulative dose dependent experiments, three concentrations of Cu(II), 10, 25 and 50 microM, were infused through the microdialysis probe in the rat myocardium. A positive linear correlation between Cu(II) and the formation of 2,3-DHBA (R(2)=0.980) was observed. However, when corresponding experiments were performed with fluvastatin (100 microM) pretreated animals, the level of 2,3-DHBA decreased. These results suggest that blocking LDL oxidation by fluvastatin may attenuate Cu(II)-induced OH formation in the rat heart.     

ROS signaling, oxidative stress and Nrf2 in pancreatic beta-cell function

This review focuses on the emerging evidence that reactive oxygen species (ROS) derived from glucose metabolism, such as H₂O₂, act as metabolic signaling molecules for glucose-stimulated insulin secretion (GSIS) in pancreatic beta-cells. Particular emphasis is placed on the potential inhibitory role of endogenous antioxidants, which rise in response to oxidative stress, in glucose-triggered ROS and GSIS. We propose that cellular adaptive response to oxidative stress challenge, such as nuclear factor E2-related factor 2 (Nrf2)-mediated antioxidant induction, plays paradoxical roles in pancreatic beta-cell function. On the one hand, induction of antioxidant enzymes protects beta-cells from oxidative damage and possible cell death, thus minimizing oxidative damage-related impairment of insulin secretion. On the other hand, the induction of antioxidant enzymes by Nrf2 activation blunts glucose-triggered ROS signaling, thus resulting in reduced GSIS. These two premises are potentially relevant to impairment of beta-cells occurring in the late and early stage of Type 2 diabetes, respectively. In addition, we summarized our recent findings that persistent oxidative stress due to absence of uncoupling protein 2 activates cellular adaptive response which is associated with impaired pancreatic beta-cell function.     

Exposure to ZnO nanoparticles induces oxidative stress and cytotoxicity in human colon carcinoma cells

Engineered nanoparticles offer great promise in many industrial and biomedical applications, however little information is available about gastrointestinal toxicity. The purpose of this study was to assess the cytotoxicity, oxidative stress, apoptosis and proinflammatory mediator release induced by ZnO nanoparticles on human colon carcinoma LoVo cells. The biological activity of these particles was related to their physico-chemical characteristics. The physico-chemical characteristics were evaluated by analytical electron microscopy. The cytotoxicity was determined by growth curves and water-soluble tetrazolium assay. The reactive oxygen species production, cellular glutathione content, changes of mitochondrial membrane potential and apoptosis cell death were quantified by flow cytometry. The inflammatory cytokines were evaluated by enzyme-linked immunoadsorbent assay. Treatment with ZnO (5 μg/cm² corresponding to 11.5 μg/ml) for 24 h induced on LoVo cells a significant decrease of cell viability, H₂O₂/OH increase, O2⁻ and GSH decrease, depolarization of inner mitochondrial membranes, apoptosis and IL-8 release. Higher doses induced about 98% of cytotoxicity already after 24 h of treatment. The experimental data show that oxidative stress may be a key route in inducing the cytotoxicity of ZnO nanoparticles in colon carcinoma cells. Moreover, the study of the relationship between toxicological effects and physico-chemical characteristics of particles suggests that surface area does not play a primary role in the cytotoxicity.     

Ascorbic acid protects against lipopolysaccharide-induced intra-uterine fetal death and intra-uterine growth retardation in mice

Lipopolysaccharide (LPS) has been associated with adverse developmental outcomes including embryonic resorption, intra-uterine fetal death (IUFD), intra-uterine growth retardation (IUGR) and preterm labor. Reactive oxygen species (ROS) mediate LPS-induced developmental toxicity. Ascorbic acid is an antioxidant. In the present study, we investigated the effect of ascorbic acid on LPS-induced IUFD and IUGR in mice. All ICR pregnant mice except controls received an intraperitoneal (75 microg/kg, i.p.) injection of LPS daily on gd 15-17. The experiment was carried out in three different modes. In mode A, the pregnant mice were pretreated with a single dose (500 mg/kg, i.p.) of ascorbic acid before LPS. In mode B, the pregnant mice were administered with a single dose (500 mg/kg, i.p.) of ascorbic acid at 3h after LPS. In mode C, the pregnant mice were administered with 500 mg/kg (i.p.) of ascorbic acid at 30 min before LPS, followed by additional dose (500 mg/kg, i.p.) of ascorbic acid at 3h after LPS. The number of live fetuses, dead fetuses and resorption sites was counted on gd 18. Live fetuses in each litter were weighed. Crown-rump and tail lengths were examined and skeletal development was evaluated. Results showed that maternally administered LPS significantly increased fetal mortality, decreased fetal weight and crown-rump and tail lengths of live fetuses, and retarded skeletal ossification in caudal vertebrae, anterior and posterior phalanges, and supraoccipital bone. LPS-induced IUFD and IUGR were associated with lipid peroxidation and GSH depletion in maternal liver, placenta and fetal liver. Pre-treatment with ascorbic acid significantly attenuated LPS-induced lipid peroxidation, decreased fetal mortality, and reversed LPS-induced fetal growth and skeletal development retardation. By contrast to pre-treatment, post-treatment with ascorbic acid had less effect on LPS-induced IUFD, although post-treatment significantly attenuated LPS-induced lipid peroxidation and reversed LPS-induced fetal growth and skeletal development retardation. Furthermore, post-treatment with ascorbic acid reduced the protective effects of pre-treatment on LPS-induced IUFD. All these results suggest that pre-treatment with ascorbic acid protected against LPS-induced fetal death and reversed LPS-induced growth and skeletal development retardation via counteracting LPS-induced oxidative stress, whereas post-treatment had less effect on LPS-induced IUFD.     

The iron-chelating drug triapine causes pronounced mitochondrial thiol redox stress

Triapine (Tp) is an iron chelator with activity against several types of cancer. Iron-Tp [Fe(III)(Tp)₂] can be redox-cycled to generate reactive oxygen species that may contribute to its cytotoxicity. However, evidence for this mechanism in cells is limited. The cytosolic and mitochondrial thioredoxins (Trx1 and Trx2, respectively) are essential for cell survival. They are normally maintained in the reduced state, and support the function of many intracellular proteins including the peroxiredoxins (Prxs). Their redox status can indicate oxidant stress in their respective subcellular compartments. Tp treatment of human lung A549 cells caused almost complete oxidation of Trx2 and its dependent peroxiredoxin (Prx3), but there was no effect on Trx1 redox status. Significant inhibition of total TrxR activity did not occur until Tp levels were 4-fold above those needed to cause Trx2 oxidation. While Tp caused a 36-45% decline in reduced glutathione (GSH) levels, GSH accounted for >99% of the total glutathione in the absence and presence of Tp. In vitro studies demonstrated that cysteine reduces Fe(III)(Tp)₂ to Fe(II)(Tp)₂, and cysteine was faster and more efficient than reduced glutathione (GSH) in this regard. Fe(III)(Tp)₂ also mediated the oxidation of purified Trx2 in vitro. Thus, Fe(III)(Tp)₂ itself, and/or various reactive species that may result from its redox cycling, could account for Trx2 and Prx3 oxidation in Tp-treated cells. The striking difference between the effects on Trx2 and Trx1 implies a pronounced thiol redox stress that is largely directed at the mitochondria. These previously unrecognized effects of Tp could contribute to its overall cytotoxicity.     

New advances in molecular mechanisms and the prevention of adriamycin toxicity by antioxidant nutrients

Anthracyclines (doxorubicin, daunorubicin, epirubicin, and idarubicin) are currently the most effective group of anti-neoplastic drugs used in clinical practice. Of these, doxorubicin (also called adriamycin) is a key chemotherapeutic agent in cancer treatment, although its use is limited as a consequence of the chronic and acute toxicity associated with this drug. The molecular mechanisms of doxorubicin account for both the anti-cancer and the toxic side effects. Many antioxidants have been assayed, with positive or negative results, to prevent the toxicity of doxorubicin. The present review has two main goals: (1) to report the latest findings regarding the molecular mechanisms of doxorubicin toxicity; (2) to update our understanding of the role of natural antioxidants in preventive therapy against doxorubicin-induced toxicity. This review provides new evidence for the chemoprevention of doxorubicin toxicity, making use of natural antioxidants – in particular vitamin E, vitamin C, coenzyme Q, carotenoids, vitamin A, flavonoids, polyphenol, resveratrol, antioxidant from virgin olive oil and selenium – and offers new insights into the molecular mechanisms of doxorubicin toxicity with respect to DNA damage, free radicals and other parameters.