Intralysosomal iron chelation protects against oxidative stress-induced cellular damage

Oxidant-induced cell damage may be initiated by peroxidative injury to lysosomal membranes, catalyzed by intralysosomal low mass iron that appears to comprise a major part of cellular redox-active iron. Resulting relocation of lytic enzymes and low mass iron would result in secondary harm to various cellular constituents. In an effort to further clarify this still controversial issue, we tested the protective effects of two potent iron chelators--the hydrophilic desferrioxamine (dfo) and the lipophilic salicylaldehyde isonicotinoyl hydrazone (sih), using cultured lysosome-rich macrophage-like J774 cells as targets. dfo slowly enters cells via endocytosis, while the lipophilic sih rapidly distributes throughout the cell. Following dfo treatment, long-term survival of cells cannot be investigated because dfo by itself, by remaining inside the lysosomal compartment, induces apoptosis that probably is due to iron starvation, while sih has no lasting toxic effects if the exposure time is limited. Following preincubation with 1 mM dfo for 3 h or 10 microM sih for a few minutes, both agents provided strong protection against an ensuing approximately LD50 oxidant challenge by preventing lysosomal rupture, ensuing loss of mitochondrial membrane potential, and apoptotic/necrotic cell death. It appears that once significant lysosomal rupture has occurred, the cell is irreversibly committed to death. The results lend strength to the concept that lysosomal membranes, normally exposed to redox-active iron in high concentrations, are initial targets of oxidant damage and support the idea that chelators selectively targeted to the lysosomal compartment may have therapeutic utility in diminishing oxidant-mediated cell injury.     

Sulfide increases labile iron pool in RD4 cells

A linkage between sulfur and iron metabolism has been suggested since sulfide has the ability to release iron from ferritin in the presence of iron acceptors in vitro. Nevertheless, this linkage is still lacking evidence in vivo as well as in cellular models. In this study we have treated human RD4 skeletal muscle cells with sodium sulfide and measured the level of the labile iron pool (LIP) as well as the intracellular sulfide concentration. We have also detected the amounts of L-ferritin protein as well as the iron regulatory protein 2 (IRP2). The sulfide treatment resulted in a 100% increase in the amount of LIP after 1 and 2 h. We also found that the raise of the LIP levels was coupled to an elevation of the amounts of intracellular sulfide that increased by 60%. The bioavailability of the released iron was confirmed by a 100% increase in L-ferritin protein as well as a 60% decrease of the IRP2 protein levels. These results suggest that there is a linkage between sulfur metabolism and intracellular iron regulation in mammalian cells.     

Arabidopsis nitric oxide synthase1 is targeted to mitochondria and protects against oxidative damage and dark-induced senescence

The Arabidopsis thaliana protein nitric oxide synthase1 (NOS1) is needed for nitric oxide (NO) synthesis and signaling during defense responses, hormonal signaling, and flowering. The cellular localization of NOS1 was examined because it is predicted to be a mitochondrial protein. NOS1-green fluorescent protein fusions were localized by confocal microscopy to mitochondria in roots. Isolated mitochondria from leaves of wild-type plants supported Arg-stimulated NO synthesis that could be inhibited by NOS inhibitors and quenched by a NO scavenger; this NOS activity is absent in mitochondria isolated from nos1 mutant plants. Because mitochondria are a source of reactive oxygen species (ROS), which participate in senescence and programmed cell death, these parameters were examined in the nos1 mutant. Dark-induced senescence of detached leaves and intact plants progressed more rapidly in the mutant compared with the wild type. Hydrogen peroxide, superoxide anion, oxidized lipid, and oxidized protein levels were all higher in the mutant. These results demonstrate that NOS1 is a mitochondrial NOS that reduces ROS levels, mitigates oxidative damage, and acts as an antisenescence agent.     

Fiber type-specific nitric oxide protects oxidative myofibers against cachectic stimuli

Oxidative skeletal muscles are more resistant than glycolytic muscles to cachexia caused by chronic heart failure and other chronic diseases. The molecular mechanism for the protection associated with oxidative phenotype remains elusive. We hypothesized that differences in reactive oxygen species (ROS) and nitric oxide (NO) determine the fiber type susceptibility. Here, we show that intraperitoneal injection of endotoxin (lipopolysaccharide, LPS) in mice resulted in higher level of ROS and greater expression of muscle-specific E3 ubiqitin ligases, muscle atrophy F-box (MAFbx)/atrogin-1 and muscle RING finger-1 (MuRF1), in glycolytic white vastus lateralis muscle than in oxidative soleus muscle. By contrast, NO production, inducible NO synthase (iNos) and antioxidant gene expression were greatly enhanced in oxidative, but not in glycolytic muscles, suggesting that NO mediates protection against muscle wasting. NO donors enhanced iNos and antioxidant gene expression and blocked cytokine/endotoxin-induced MAFbx/atrogin-1 expression in cultured myoblasts and in skeletal muscle in vivo. Our studies reveal a novel protective mechanism in oxidative myofibers mediated by enhanced iNos and antioxidant gene expression and suggest a significant value of enhanced NO signaling as a new therapeutic strategy for cachexia.     

Nitric oxide synthase like activity-dependent nitric oxide production protects against chilling-induced oxidative damage in Chorispora bungeana suspension cultured cells

In the present study, we used suspension cultured cells from Chorispora bungeana Fisch. and C.A. Mey to investigate whether nitric oxide (NO) is involved in the signaling pathway of chilling adaptive responses. Low temperatures at 4 °C or 0 °C induced ion leakage, lipid peroxidation and cell viability suppression, which were dramatically alleviated by exogenous application of NO donor sodium nitroprusside (SNP). The levels of reactive oxygen species (ROS) were obviously reduced, and the activities of antioxidant enzymes such as ascorbate peroxidase (APX, EC 1.11.1.11), catalase (CAT, EC 1.11.1.6), glutathione reductase (GR, EC 1.6.4.2), peroxidase (POD, EC 1.11.1.7) and superoxide dismutase (SOD, EC 1.15.1.1) and the contents of ascorbic acid (AsA) and reduced glutathione (GSH) increased evidently in the presence of SNP under chilling stress. In addition, under low temperature conditions, treatment with NO scavenger PTIO or mammalian NO synthase (NOS) inhibitor l-NAME remarkably aggravated oxidative damage in the suspension cultures compared with that of chilling treatment alone. Moreover, measurements of NOS activity and NO production showed that both NOS activity and endogenous NO content increased markedly under chilling stress. The accumulation of NO was inhibited by l-NAME in chilling-treated cultures, indicating that most NO production under chilling may be generated from NOS-like activity. Collectively, these results suggest that chilling-induced NO accumulation can effectively protect against oxidative injury and that NOS like activity-dependent NO production might act as an antioxidant directly scavengering ROS or operate as a signal activating antioxidant defense under chilling stress, thus conferring an increased tolerance to chilling in C. bungeana suspension cultures.     

Pomegranate juice protects nitric oxide against oxidative destruction and enhances the biological actions of nitric oxide.

Pomegranate juice (PJ), which is a rich source of potent flavonoid antioxidants, was tested for its capacity to protect nitric oxide (NO) against oxidative destruction and enhance the biological actions of NO. Employing chemiluminescence headspace analysis, PJ was found to be a potent inhibitor of superoxide anion-mediated disappearance of NO. PJ was much more potent than Concord grape juice, blueberry juice, red wine, ascorbic acid, and DL-alpha-tocopherol. As little as 3 microl of a 6-fold dilution of PJ, in a reaction volume of 5000 microl, produced a marked antioxidant effect, whereas 300 microl of undiluted blueberry juice or nearly 1000 microl of undiluted Concord grape juice were required to produce similar effects. PJ and other antioxidant-containing products were found to augment the anti-proliferative action of NO (DETA/NO) on vascular smooth muscle cell (rat aorta) proliferation. PJ was much more effective than the other products tested and elicited no effects when tested alone in the absence of added NO. Similarly, neither PJ nor the other products enhanced the anti-proliferative action of alpha-difluoromethylornithine, a stable substance that inhibits cell growth by NO-independent mechanisms. In order to determine whether PJ is capable of increasing the production of NO by vascular endothelial cells, PJ was tested for its capacity to upregulate and/or activate endothelial NO synthase (eNOS) in bovine pulmonary artery endothelial cells. PJ elicited no effects on eNOS protein expression or catalytic activity. Moreover, PJ did not enhance promoter activity in the eNOS gene (COS-7 cells transfected with eNOS). These observations indicate that PJ possesses potent antioxidant activity that results in marked protection of NO against oxidative destruction, thereby resulting in augmentation of the biological actions of NO.     

Garlic provides protection to mice heart against isoproterenol-induced oxidative damage: role of nitric oxide

Garlic has been widely recognized as a cardioprotective agent. However, the molecular mechanism of its cardioprotective effects is not well established. Here we hypothesized that aqueous garlic homogenate may mediate cardioprotection via nitric oxide (NO). Mice were fed with saline and aqueous garlic homogenate (250 and 500 mgkg(-1)day(-1) orally) for 30 days. In another set of experiment, mice were pre-treated with saline, aqueous garlic homogenate (AGH) (250 mgkg(-1)day(-1) for 30 days), and AGH (30 days) along with L-NAME (20 mgkg(-1)day(-1) i.p. for last 7 days) before inducing acute myocardial infarction by isoproterenol (s.c. injection of isoproterenol 150 mgkg(-1)day(-1) for 2 days) and sacrificed after 48 h. Dose dependent increase in serum NO level was observed after garlic 250 and 500 mgkg(-1) dose feeding. While no change in serum SGPT and SGOT level, a significant decrease in serum LDH level was observed after garlic feeding. Garlic-induced NO formation was further confirmed in human aortic endothelial cells (HAEC). Administration of isoproterenol caused a significant decrease in endogenous antioxidants i.e., myocardial catalase, GSH and GPx activity, and mitochondrial enzyme activities like citrate synthase and β hydroxyacyl CoA dehydrogenase. All those deleterious cardiac changes induced by isoproterenol were significantly attenuated by garlic homogenate. However this beneficial effect of garlic was blunted when garlic was administered with L-NAME, a nonspecific inhibitor of nitric oxide synthase (NOS). Further, a significant increase in myocardial TBARS and decrease in total antioxidant activity was observed in L-NAME treated group compared to isoproterenol treated group. Administration of L-NAME in mice from control group lowered serum and cardiac NO levels without any change of oxidative stress parameters. In conclusion, our study provides novel evidence that garlic homogenate is protective in myocardial infarction via NO-signaling pathway in mice.     

Nitric oxide protects against polyethylene glycol-induced oxidative damage in two ecotypes of reed suspension cultures

Dune reed (DR) is the more tolerant ecotype of reed to environmental stresses than swamp reed (SR). Under osmotic stress mediated by polyethylene glycol (PEG-6000), the suspension culture of SR showed higher ion leakage, and more oxidative damage to the membrane lipids and proteins was observed compared with the relatively tolerant DR suspension culture. Treatment with sodium nitroprusside (SNP) can significantly alleviated PEG-induced ion leakage, thiobarbituric acid reactive substances (TBARS) and carbonyl contents increase in SR suspension culture. The levels of H(2)O(2) and O(2)(-) were reduced, and the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) were increased in both suspension cultures in the presence of SNP under osmotic stress, but lipoxygenase (LOX) activity was inhibited. 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO), a specific Nitric oxide (NO) scavenger, blocked the SNP-mediated protection. Depletion of endogenous NO with PTIO strongly enhanced oxidative damage in DR compared with that of PEG treatment alone, whereas had no effect on SR. Moreover, NO production increased significantly in DR while kept stable in SR under osmotic stress. Taken together, these results suggest that PEG induced NO release in DR but not SR can effectively protect against oxidative damage and confer an increased tolerance to osmotic stress in DR suspension culture.     

Resveratrol ameliorates oxidative DNA damage and protects against acrylamide-induced oxidative stress in rats

Acrylamide (ACR), used in many fields from industrial manufacturing to laboratory personnel work is also formed during the heating process through interactions of amino acids. Therefore ACR poses a significant risk to human health. This study aimed to elucidate whether resveratrol (RVT) treatment could modulate ACR-induced oxidative DNA damage and oxidative changes in rat brain, lung, liver, kidney and testes tissues. Rats were divided into four groups as control (C); RVT (30 mg/kg i.p. dissolved in 0.9% NaCl), ACR (40 mg/kg i.p.) and RVT + ACR groups. After 10 days rats were decapitated and tissues were excised. 8-hydroxydeoxyguanosine (8-OHdG) is a biomarker of oxidative DNA damage. 8-OHdG content in the extracted DNA solution was determined by enzyme-linked immunosorbent assay method. Malondialdehyde (MDA), glutathione (GSH) levels and myeloperoxidase activity (MPO) were determined in tissues, while oxidant-induced tissue fibrosis was determined by collagen contents. Serum enzyme activities, cytokine levels, leukocyte apoptosis were assayed in plasma. As an indicator of oxidative DNA damage, 8-OHdG levels significantly increased in ACR group and this was reversed significantly by RVT treatment. In ACR group, GSH levels decreased significantly while the MDA levels, MPO activity and collagen content increased in the tissues suggesting oxidative organ damage. In RVT-treated ACR group, oxidant responses reversed significantly. Serum enzyme activities, cytokine levels and leukocyte late apoptosis which increased following ACR administration, decreased with RVT treatment. Therefore supplementing with RVT can be useful in individuals at risk of ACR toxicity.     

Mitochondrial Hsp60, resistance to oxidative stress,and the labile iron pool are closely connected in Saccharomyces cerevisiae

In the present study, we have analyzed the role of the molecular chaperone Hsp60 in protection of Saccharomyces cerevisiae against oxidative damage. We constructed mutant strains in which the levels of Hsp60 protein, compared with wild-type cells, were four times greater, and the addition of doxycycline gradually reduces them to 20% of wild-type. Under oxidative-stress conditions, the progressive decrease in Hsp60 levels in these mutants resulted in reduced cell viability and an increase in both cell peroxide species and protein carbonyl content. Protection of Fe/S-containing enzymes from oxidative inactivation was found to be dose-dependent with respect to Hsp60 levels. As these enzymes release their iron ions under oxidative-stress conditions, the intracellular labile iron pool, monitored with calcein, was higher in cells with reduced Hsp60 levels. Consistently, the iron chelator deferoxamine protected low Hsp60-expressing cells from both oxidant-induced death and protein oxidation. These results indicate that the role of Hsp60 in oxidative-stress defense is explained by protection of several Fe/S proteins, which prevent the release of iron ions and thereby avert further damage.     

Exogenous nitric oxide improves seed germination in wheat against mitochondrial oxidative damage induced by high salinity

Effects of exogenous nitric oxide (NO) on starch degradation, oxidation in mitochondria and K⁺/Na⁺ accumulation during seed germination of wheat were investigated under a high salinity level. Seeds of winter wheat (Triticum aestivum L., cv. Huaimai 17) were pre-soaked with 0 mM or 0.1 mM of sodium nitroprusside (SNP, as nitric oxide donor) for 20 h just before germination under 300 mM NaCl. At 300 mM NaCl, exogenous NO increased germination rate and weights of coleoptile and radicle, but decreased seed weight. Exogenous NO also enhanced seed respiration rate and ATP synthesis. In addition, seed starch content decreased while soluble sugar content increased by exogenous NO pre-treatment, which was in accordance with the improved amylase activities in the germinating seeds. Exogenous NO increased the activities of superoxide dismutase (SOD, EC 1.15.1.1) and catalase (CAT, EC 1.11.1.6); whereas decreased the contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), and superoxide anions (O₂^??) release rate in the mitochondria. Exogenous NO also decreased Na⁺ concentration while increased K⁺ concentration in the seeds thereby maintained a balance between K⁺ and Na⁺ during germination under salt stress. It is concluded that exogenous NO treatment on wheat seeds may be a good option to improve seed germination and crop establishment under saline conditions.     

Metabolism of carcinogenic urethane to nitric oxide is involved in oxidative DNA damage

Carcinogenic urethane (ethyl carbamate) forms DNA adduct via epoxide, whereas carcinogenic methyl carbamate can not. To clarify a mechanism independent of DNA adduct formation, we examined DNA damage induced by N-hydroxyurethane, a urethane metabolite, using 32P-5'-end-labeled DNA fragments. N-hydroxyurethane induced Cu(II)-mediated DNA damage especially at thymine and cytosine residues. DNA damage was inhibited by both catalase and bathocuproine, suggesting a role for H(2)O(2) and Cu(I) in DNA damage. Free (*) OH scavengers did not inhibit the DNA damage, although methional did inhibit it. These results suggest that reactive species, such as the Cu(I)-hydroperoxo complex, cause DNA damage. Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) was increased by N-hydroxyurethane in the presence of Cu(II). When treated with esterase, N-hydroxyurethane induced 8-oxodG formation to a similar extent as that induced by hydroxylamine. Enhancement of DNA cleavages by endonuclease IV suggests that hydroxylamine induced depurination. Furthermore, hydroxylamine induced a significant increase in 8-oxodG formation in HL-60 cells but not in its H(2)O(2)-resistant clone HP 100 cells. o-Phenanthroline significantly inhibited the 8-oxodG formation in HL-60 cells, confirming the involvement of metal ions in the 8-oxodG formation by hydroxylamine. Electron spin resonance spectroscopy, utilizing Fe[N-(dithiocarboxy)sarcosine](3), demonstrated that nitric oxide (NO) was generated from hydroxylamine and esterase-treated N-hydroxyurethane. It is concluded that urethane may induce carcinogenesis through oxidation and, to a lesser extent, depurination of DNA by its metabolites.     

Green tea metabolite EGCG protects membranes against oxidative damage in vitro

Green tea polyphenols like epigallocatechin gallate (EGCG) have been proposed as a cancer chemopreventative. Several studies have shown that EGCG can act as an antioxidant by trapping proxyl radicals and inhibiting lipid peroxidation. The main propose of this study is to investigate the antioxidant capacity of EGCG using erythrocyte membrane-bound ATPases as a model. The effects of EGCG on t-butylhydroperoxide-induced lipid peroxidation and the activity of membrane-bound ATPases in human erythrocyte membranes were studied. The extent of oxidative damage in membranes was assessed by measuring lipid peroxidation, (TBARS, thiobarbituric acid reactive substances formation) and the activity of ATPases (Na(+)/K(+), Ca(2+), and CaM-activated Ca(2+) pump ATPases). EGCG blocked t-BHP induced lipid peroxidation in erythrocyte membranes, significantly (0.45 +/- 0.02 vs 0.20 +/- 0.01; t-BHP vs t-BHP + EGCG respectively, microm/L TBARS) (p < 0.05). EGCG also protected ATPases against t-BHP induced damage; for Na/K ATPase (2.4 +/- 0.2 vs 1.6 +/- 0.1 vs 2.44 +/- 0.2, nmol Pi/min/mg protein, control vs t-BHP vs t-BHP and EGCG respectively), for Ca ATPase (5.8 +/- 0.4 vs 3.9 +/- 0.3 vs 5.6 +/- 0.34, nmol Pi/min/mg protein, control vs t-BHP vs t-BHP and EGCG respectively) and for CaM-Ca ATPase (14.7 +/- 0.7 vs 7.3 +/- 0.4 vs 11.6 +/- 0.55, nmol Pi/min/mg protein, control vs t-BHP vs t-BHP and EGCG respectively) (p < 0.05). In conclusion our results indicate that EGCG is a powerful antioxidant that is capable protecting erythrocyte membrane-bound ATPases against oxidative stress.     

A putative Leishmania DNA polymerase theta protects the parasite against oxidative damage

Leishmania infantum is a protozoan parasite that is phagocytized by human macrophages. The host macrophages kill the parasite by generating oxidative compounds that induce DNA damage. We have identified, purified and biochemically characterized a DNA polymerase θ from L. infantum (LiPolθ), demonstrating that it is a DNA-dependent DNA polymerase involved in translesion synthesis of 8oxoG, abasic sites and thymine glycol lesions. Stably transfected L. infantum parasites expressing LiPolθ were significantly more resistant to oxidative and interstrand cross-linking agents, e.g. hydrogen peroxide, cisplatin and mitomycin C. Moreover, LiPolθ-overexpressing parasites showed an increased infectivity toward its natural macrophage host. Therefore, we propose that LiPolθ is a translesion synthesis polymerase involved in parasite DNA damage tolerance, to confer resistance against macrophage aggression.     

Human endothelial nitric oxide synthase gene delivery protects against cardiac remodeling and reduces oxidative stress after myocardial infarction

Nitric oxide (NO) has been shown to play a key role in the regulation of cardiac hypertrophy and fibrosis in response to myocardial ischemia in part by antagonizing the action of angiotensin II (Ang II). In this study, we investigated the potential protective role of human endothelial nitric oxide synthase (eNOS) in left ventricular (LV) remodeling after myocardial infarction (MI) by a somatic gene transfer approach. Male Wistar rats underwent coronary artery ligation to induce MI. One week after surgery, adenovirus encoding the human eNOS or luciferase gene under the control of the CMV promoter/enhancer was injected into rats via the tail vein, and animals were sacrificed at 1 and 5 weeks after gene transfer. Successful gene transfer was evaluated based on increased levels of NO and cGMP in the heart, measured at one week after eNOS gene delivery. Six weeks after MI, the LV end-diastolic pressure, heart weight, LV axis length and cardiomyocyte size were markedly increased compared to the Sham group, while eNOS gene delivery significantly reduced these parameters. Rats receiving control virus developed considerably more fibrotic lesions identified by Sirius Red staining and collagen I immunostaining compared to Sham rats, and eNOS gene delivery significantly reduced collagen accumulation. eNOS gene transfer also reduced TUNEL-positive apoptotic cells. The cardioprotective effect of NO was accompanied by reduced NADH and NADPH oxidase activities and superoxide formation, TGF-beta1 and p27 levels, JNK activation, NF-kappa B nuclear translocation, and caspase-3 activity. This study shows that NO may play an important role in attenuating cardiac remodeling and apoptosis after myocardial infarction via suppression of oxidative stress-mediated signaling pathways.     

Glutathione depletion in immortalized midbrain-derived dopaminergic neurons results in increases in the labile iron pool: Implications for Parkinson's disease

Glutathione depletion is one of the earliest detectable events in the Parkinsonian substantia nigra (SN), but whether it is causative for ensuing molecular events associated with the disease is unknown. Here we report that reduction in levels of glutathione in immortalized midbrain-derived dopaminergic neurons results in increases in the cellular labile iron pool (LIP). This increase is independent of either iron regulatory protein/iron regulatory element (IRP/IRE) or hypoxia inducible factor (HIF) induction but is both H₂0₂ and protein synthesis-dependent. Our findings suggest a novel mechanistic link between dopaminergic glutathione depletion and increased iron levels based on translational activation of TfR1. This may have important implications for neurodegeneration associated with Parkinson's disease in which both glutathione reduction and iron elevation have been implicated.     

Deficiency of inducible nitric oxide synthase protects against MPTP toxicity in vivo

MPTP produces clinical, biochemical, and neuropathologic changes reminiscent of those that occur in idiopathic Parkinson's disease (PD). In the present study we show that MPTP treatment led to activation of microglia in the substantia nigra pars compacta (SNpc), which was associated and colocalized with an increase in inducible nitric oxide synthase (iNOS) expression. In iNOS-deficient mice the increase of iNOS expression but not the activation of microglia was blocked. Dopaminergic SNpc neurons of iNOS-deficient mice were almost completely protected from MPTP toxicity in a chronic paradigm of MPTP toxicity. Because the MPTP-induced decrease in striatal concentrations of dopamine and its metabolites did not differ between iNOS-deficient mice and their wild-type littermates, this protection was not associated with a preservation of nigrostriatal terminals. Our results suggest that iNOS-derived nitric oxide produced in microglia plays an important role in the death of dopaminergic neurons but that other mechanisms contribute to the loss of dopaminergic terminals in MPTP neurotoxicity. We conclude that inhibition of iNOS may be a promising target for the treatment of PD.     

Pretreatment with methylprednisolone protects the isolated rat heart against ischaemic and oxidative damage

Methylprednisolone (MP), a synthetic glucocorticoid, is widely used clinically and experimentally as acute antiinflammatory treatment. The molecular actions of MP indicate that pretreatment with this drug may be cardioprotective. We investigated if giving rats MP prior to excising their hearts for Langendorff-perfusion protected cardiac function against oxidative stress, and if this was mediated by increasing antioxidant defence or influencing myocardial nitric oxide synthase (NOS). Rats (n=6-11 in each group) were injected with MP (40 mg/kg i.m.) or vehicle 24 and 12 h before Langendorff-perfusion with 30 min global ischaemia and 60 min reperfusion, or 10 min perfusion with 180 μmol/L hydrogen peroxide. Other hearts were exposed to 30 min global ischaemia 5 days after MP-injection. Additional hearts were sampled before, during, and after ischaemia for analyzing tissue activity of antioxidant enzymes. Tissue endothelial and inducible NOS (eNOS and iNOS) were investigated by immunoblotting and semiquantitative RT-PCR in a time-course after MP injection. Pretreatment with MP improved left ventricular function and increased coronary flow during postischaemic reperfusion, and this effect was sustained 5 days afterwards. When exposing hearts to hydrogen peroxide, MP improved coronary flow. Catalase, glutathione peroxidase, and oxidized glutathione were increased during reperfusion of MP-treated hearts compared to vehicle only. MP did not influence eNOS at protein or mRNA level. iNOS could not be detected by immunoblotting, indicating low cardiac enzyme content. Its mRNA initially increased the first hour after injection, thereafter decreased. In conclusions, pretreating rats with MP protects the heart against ischaemia-reperfusion dysfunction. This effect could be due to increase of tissue antioxidant activity during reperfusion. MP did not influence cardiac eNOS. mRNA for iNOS was influenced by MP, but the corresponding protein could not be detected.     

d-Propranolol protects against oxidative stress and progressive cardiac dysfunction in iron overloaded rats

d-Propranolol (d-Pro: 2-8?mg·(kg body mass)(-1)·day(-1)) protected against cardiac dysfunction and oxidative stress during 3-5?weeks of iron overload (2?mg Fe-dextran·(g body mass)(-1)·week(-1)) in Sprague-Dawley rats. At 3?weeks, hearts were perfused in working mode to obtain baseline function; red blood cell glutathione, plasma 8-isoprostane, neutrophil basal superoxide production, lysosomal-derived plasma N-acetyl-β-galactosaminidase (NAGA) activity, ventricular iron content, and cardiac iron deposition were assessed. Hearts from the Fe-treated group of rats exhibited lower cardiac work (26%) and output (CO, 24%); end-diastolic pressure rose 1.8-fold. Further, glutathione levels increased 2-fold, isoprostane levels increased 2.5-fold, neutrophil superoxide increased 3-fold, NAGA increased 4-fold, ventricular Fe increased 4.9-fold; and substantial atrial and ventricular Fe-deposition occurred. d-Pro (8?mg) restored heart function to the control levels, protected against oxidative stress, and decreased cardiac Fe levels. After 5?weeks of Fe treatment, echocardiography revealed that the following were depressed: percent fractional shortening (%FS, 31% lower); left ventricular (LV) ejection fraction (LVEF, 17%), CO (25%); and aortic pressure maximum (P(max), 24%). Mitral valve E/A declined by 18%, indicating diastolic dysfunction. Cardiac CD11b+ infiltrates were elevated. Low d-Pro (2?mg) provided modest protection, whereas 4-8?mg greatly improved LVEF (54%-75%), %FS (51%-81%), CO (43%-78%), P(max) (56%-100%), and E/A?>100%; 8?mg decreased cardiac inflammation. Since d-Pro is an antioxidant and reduces cardiac Fe uptake as well as inflammation, these properties may preserve cardiac function during Fe overload.