Heparin-induced release of extracellular superoxide dismutase to human blood plasma

Insights into the Molecular Mechanism of Endothelial Glycocalyx Dysfunction during Heart Surgery

The endothelial glycocalyx (EGC) is a layer of proteoglycans (associated with glycosaminoglycans) and glycoproteins, which adsorbs plasma proteins on the luminal surface of endothelial cells. Its main function is to participate in separating the circulating blood from the inner layers of the vessels and the surrounding tissues. Physiologically, the EGC stimulates mechanotransduction, the endothelial charge, thrombocyte adhesion, leukocyte tissue recruitment, and molecule extravasation. Hence, severe impairment of the EGC has been implicated in various pathological conditions, including sepsis, diabetes, chronic kidney disease, inflammatory disorders, hypernatremia, hypervolemia, atherosclerosis, and ischemia/reperfusion injury. Moreover, alterations in EGC have been associated with altered responses to therapeutic interventions in conditions such as cardiovascular diseases. Investigation into the function of the glycocalyx has expanded knowledge about vascular disorders and indicated the need to consider new approaches in the treatment of severe endothelial dysfunction. This review aims to present the current understanding of the molecular mechanisms underlying cardiovascular diseases and to elucidate the impact of heart surgery on EGC dysfunction.

Effect of acute heparin administration on glycocalyx thickness and endothelial function in healthy younger adults

The endothelial glycocalyx is a dynamic, gel-like layer that is critical to normal vascular endothelial function. Heparin impairs the endothelial glycocalyx and reduces vascular endothelial function in a murine model; however, this has yet to be tested in healthy humans. We hypothesized that a single bolus dose of heparin would increase circulating glycocalyx components and decrease endothelial glycocalyx thickness resulting in blunted brachial artery vasodilation in healthy younger adults. Healthy adults (n = 19, aged 18-39 yr, 53% female) underwent measurements of the endothelial glycocalyx and vascular endothelial function at baseline and after a single bolus 5,000 U dose of heparin. The glycocalyx components syndecan-1 and heparan sulfate were measured from plasma samples using enzyme-linked immunosorbent assays. Glycocalyx thickness was determined as perfused boundary region (PBR) in sublingual microvessels using the GlycoCheck. Endothelial function was measured via ultrasonography and quantified as brachial artery flow-mediated dilation (FMD). Following acute heparin administration, there was no increase in syndecan-1 or heparan sulfate (P = 0.90 and P = 0.49, respectively). In addition, there was no change in PBR 4-7 µm (P = 0.55), PBR 10-25 µm (P = 0.63), or 4-25 µm (P = 0.49) after heparin treatment. Furthermore, we did not observe a change in FMDmm (P = 0.23), FMD% (P = 0.35), or plasma nitrite concentrations (P = 0.10) in response to heparin. Finally, time to peak dilation and peak FMD normalized to shear stress were unchanged following heparin (P = 0.59 and P = 0.21, respectively). Our pilot study suggests that a single bolus intravenous dose of heparin does not result in endothelial glycocalyx degradation or vascular endothelial dysfunction in healthy younger adults.NEW & NOTEWORTHY The endothelial glycocalyx's role in modulating vascular endothelial dysfunction with aging and disease is becoming increasingly recognized. This study presents novel findings that acute heparin administration is not a feasible method to experimentally degrade the endothelial glycocalyx and measure concurrent changes in vascular endothelial function in healthy humans. Alternative approaches will be needed to translate findings from preclinical studies and test the effects of acute endothelial glycocalyx degradation on vascular endothelial function in humans.

Interleukin-1β triggers muscle-derived extracellular superoxide dismutase expression and protects muscles from doxorubicin-induced atrophy

Doxorubicin, a conventional chemotherapeutic agent prescribed for cancer, causes skeletal muscle atrophy and adversely affects mobility and strength. Given that doxorubicin-induced muscle atrophy is attributable primarily to oxidative stress, its effects could be mitigated by antioxidant-focused therapies; however, these protective therapeutic targets remain ambiguous. The aim of this study was to demonstrate that doxorubicin triggers severe muscle atrophy via upregulation of oxidative stress (4-hydroxynonenal and malondialdehyde) and atrogenes (atrogin-1/MAFbx and muscle RING finger-1) in association with decreased expression of the antioxidant enzyme extracellular superoxide dismutase (EcSOD), in cultured C2C12 myotubes and mouse skeletal muscle. Supplementation with EcSOD recombinant protein elevated EcSOD levels on the cellular membrane of cultured myotubes, consequently inhibiting doxorubicin-induced oxidative stress and myotube atrophy. Furthermore, doxorubicin treatment reduced interleukin-1β (IL-1β) mRNA expression in cultured myotubes and skeletal muscle, whereas transient IL-1β treatment increased EcSOD protein expression on the myotube membrane. Notably, transient IL-1β treatment of cultured myotubes and local administration in mouse skeletal muscle attenuated doxorubicin-induced muscle atrophy, which was associated with increased EcSOD expression. Collectively, these findings reveal that the regulation of skeletal muscle EcSOD via maintenance of IL-1β signalling is a potential therapeutic approach to counteract the muscle atrophy mediated by doxorubicin and oxidative stress. KEY POINTS: Doxorubicin, a commonly prescribed chemotherapeutic agent for patients with cancer, induces severe muscle atrophy owing to increased expression of oxidative stress; however, protective therapeutic targets are poorly understood. Doxorubicin induced muscle atrophy owing to increased expression of oxidative stress and atrogenes in association with decreased protein expression of extracellular superoxide dismutase (EcSOD) in cultured C2C12 myotubes and mouse skeletal muscle. Supplementation with EcSOD recombinant protein increased EcSOD levels on the cellular membrane of cultured myotubes, resulting in inhibition of doxorubicin-induced oxidative stress and myotube atrophy. Doxorubicin treatment decreased interleukin-1β (IL-1β) expression in cultured myotubes and skeletal muscle, whereas transient IL-1β treatment in vivo and in vitro increased EcSOD protein expression and attenuated doxorubicin-induced muscle atrophy. These findings reveal that regulation of skeletal muscle EcSOD via maintenance of IL-1β signalling is a possible therapeutic approach for muscle atrophy mediated by doxorubicin and oxidative stress.

Endothelial Dysfunction in Patients Undergoing Cardiac Surgery: A Narrative Review and Clinical Implications

Cardiac surgery is one of the highest-risk procedures, usually involving cardiopulmonary bypass and commonly inducing endothelial injury that contributes to the development of perioperative and postoperative organ dysfunction. Substantial scientific efforts are being made to unravel the complex interaction of biomolecules involved in endothelial dysfunction to find new therapeutic targets and biomarkers and to develop therapeutic strategies to protect and restore the endothelium. This review highlights the current state-of-the-art knowledge on the structure and function of the endothelial glycocalyx and mechanisms of endothelial glycocalyx shedding in cardiac surgery. Particular emphasis is placed on potential strategies to protect and restore the endothelial glycocalyx in cardiac surgery. In addition, we have summarized and elaborated the latest evidence on conventional and potential biomarkers of endothelial dysfunction to provide a comprehensive synthesis of crucial mechanisms of endothelial dysfunction in patients undergoing cardiac surgery, and to highlight their clinical implications.

Oxidative Stress in Plasma from Patients with Marfan Syndrome Is Modulated by Deodorized Garlic Preliminary Findings

Marfan syndrome (MFS) is a genetic disorder of connective tissue that affects the fibrillin-1 protein (FBN-1). It is associated with the formation of aneurysms, damage to the endothelium and oxidative stress (OS). Allium sativum (garlic) has antioxidant properties; therefore, the goal of this study was to show the antioxidant effect of deodorized garlic (DG) on antioxidant enzymes and OS markers in the plasma of patients with MFS. The activity of antioxidant enzymes such as extracellular superoxide dismutase (EcSOD), peroxidases, glutathione peroxidase (GPx), gluthatione-S-tranferase (GST), and thioredoxin reductase (TrxR) was quantified, and nonenzymatic antioxidant system markers including lipid peroxidation (LPO), carbonylation, nitrates/nitrites, GSH, and vitamin C in plasma were determined in patients with MFS before and after treatment with DG. The results show that DG increased the activity of the EcSOD, peroxidases, GPx, GST, TrxR (p ≤ 0.05) and decrease LPO, carbonylation, and nitrates/nitrites (p ≤ 0.01). However, glutathione was increased (p = 0.01) in plasma from patients with MFS. This suggests that treatment with garlic could lower the OS threshold by increasing the activity of antioxidant enzymes and could help in the prevention and mitigation of adverse OS in patients with MFS.

Heparan sulfate proteoglycan glypican-1 and PECAM-1 cooperate in shear-induced endothelial nitric oxide production

This study aimed to clarify the role of glypican-1 and PECAM-1 in shear-induced nitric oxide production in endothelial cells. Atomic force microscopy pulling was used to apply force to glypican-1 and PECAM-1 on the surface of human umbilical vein endothelial cells and nitric oxide was measured using a fluorescent reporter dye. Glypican-1 pulling for 30 min stimulated nitric oxide production while PECAM-1 pulling did not. However, PECAM-1 downstream activation was necessary for the glypican-1 force-induced response. Glypican-1 knockout mice exhibited impaired flow-induced phosphorylation of eNOS without changes to PECAM-1 expression. A cooperation mechanism for the mechanotransduction of fluid shear stress to nitric oxide production was elucidated in which glypican-1 senses flow and phosphorylates PECAM-1 leading to endothelial nitric oxide synthase phosphorylation and nitric oxide production.

The Rationale for Angiotensin Receptor Neprilysin Inhibitors in a Multi-Targeted Therapeutic Approach to COVID-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disease (COVID-19) determines the angiotensin converting enzyme 2 (ACE2) down-regulation and related decrease in angiotensin II degradation. Both these events trigger “cytokine storm” leading to acute lung and cardiovascular injury. A selective therapy for COVID-19 has not yet been identified. Clinical trials with remdesivir gave discordant results. Thus, healthcare systems have focused on “multi-targeted” therapeutic strategies aiming at relieving systemic inflammation and thrombotic complications. No randomized clinical trial has demonstrated the efficacy of renin angiotensin system antagonists in reducing inflammation related to COVID-19. Dexamethasone and tocilizumab showed encouraging data, but their use needs to be further validated. The still-controversial efficacy of these treatments highlighted the importance of organ injury prevention in COVID-19. Neprilysin (NEP) might be an interesting target for this purpose. NEP expression is increased by cytokines on lung fibroblasts surface. NEP activity is elevated in acute respiratory distress syndrome and it is conceivable that it is also high in COVID-19. NEP is implicated in the degradation of natriuretic peptides, bradykinin, substance P, adrenomedullin, and apelin that account for prevention of organ injury. Thus, NEP/angiotensin receptor type 1 (AT1R) inhibitor sacubitril/valsartan (SAC/VAL) may increase levels of these molecules and block AT1Rs required for ACE2 endocytosis in SARS-CoV-2 infection. Moreover, SAC/VAL has a positive impact on acute heart failure that is very frequently observed in deceased COVID-19 patients. The current review aims to summarize actual therapeutic strategies for COVID-19 and to examine the data supporting the potential benefits of SAC/VAL in COVID-19 treatment.

A non-circulating pool of factor XI associated with glycosaminoglycans in mice

BACKGROUND

The homologous plasma proteins prekallikrein and factor XI (FXI) circulate as complexes with high molecular weight kininogen. Although evidence supports an interaction between the prekallikrein-kininogen complexes and vascular endothelium, there is conflicting information regarding FXI binding to endothelium.

OBJECTIVE

To study the interaction between FXI and blood vessels in mice.

METHODS

C57Bl/6 wild-type or F11-/- mice in which variants of FXI were expressed by hydrodynamic tail vein injection, received intravenous infusions of saline, heparin, polyphosphates, protamine, or enzymes that digest glycosaminoglycans (GAGs). Blood was collected after infusion and plasma was analyzed by western blot for FXI.

RESULTS AND CONCLUSIONS

Plasma FXI increased 5- to 10-fold in wild-type mice after infusion of heparin, polyphosphates, protamine, or GAG-digesting enzymes, but not saline. Similar treatments resulted in a much smaller change in plasma FXI levels in rats, and infusions of large boluses of heparin did not change FXI levels appreciably in baboons or humans. The releasable FXI fraction was reconstituted in F11-/- mice by expressing murine FXI, but not human FXI. We identified a cluster of basic residues on the apple 4 domain of mouse FXI that is not present in other species. Replacing the basic residues with alanine prevented the interaction of mouse FXI with blood vessels, whereas introducing the basic residues into human FXI allowed it to bind to blood vessels. Most FXI in mice is noncovalently associated with GAGs on blood vessel endothelium and does not circulate in plasma.

Carcinogenesis and Reactive Oxygen Species Signaling: Interaction of the NADPH Oxidase NOX1-5 and Superoxide Dismutase 1-3 Signal Transduction Pathways

SIGNIFICANCE

Reduction/oxidation (redox) balance could be defined as an even distribution of reduction and oxidation complementary processes and their reaction end products. There is a consensus that aberrant levels of reactive oxygen species (ROS), commonly observed in cancer, stimulate primary cell immortalization and progression of carcinogenesis. However, the mechanism how different ROS regulate redox balance is not completely understood. Recent Advances: In the current review, we have summarized the main signaling cascades inducing NADPH oxidase NOX1-5 and superoxide dismutase (SOD) 1-3 expression and their connection to cell proliferation, immortalization, transformation, and CD34+ cell differentiation in thyroid, colon, lung, breast, and hematological cancers.

CRITICAL ISSUES

Interestingly, many of the signaling pathways activating redox enzymes or mediating the effect of ROS are common, such as pathways initiated from G protein-coupled receptors and tyrosine kinase receptors involving protein kinase A, phospholipase C, calcium, and small GTPase signaling molecules.

FUTURE DIRECTIONS

The clarification of interaction of signal transduction pathways could explain how cells regulate redox balance and may even provide means to inhibit the accumulation of harmful levels of ROS in human pathologies.

Ling-Yang-Gou-Teng-decoction prevents vascular dementia through inhibiting oxidative stress induced neurovascular coupling dysfunction

ETHNOPHARMACOLOGICAL RELEVANCE

Vascular dementia (VaD) is the common cognitive disorder derived mainly from lacunar stroke (LS). The oxidative stress induced neurovascular coupling (NVC) dysfunction involves in the pathogenesis of VaD. Currently, there is no specific drug for VaD. Ling-Yang-Gou-Teng -Decoction (LG), a well-known traditional Chinese formula, has been used for preventing VaD in clinic.

AIM OF THE STUDY

In this study, we aimed to investigate the underlying mechanism of LG on VaD in rats.

MATERIALS AND METHOD

VaD was replicated with autologous micro-thrombi against the background of hypercholesterolemia induced with high fatty diet. PTX (68.90 mg/kg/day), LG with three dosages (2.58, 8.14, 25.80 g/kg/day) was orally administrated to VaD rats, respectively. The NVC sensitivity was defined as the ratio of the microcirculative cerebral blood velocity (CBV) to the electroencephalograph (EEG) before and after penicillin stimulation. Behavioral performance, pathological changes of brain and oxidation related molecules were detected to assess the effects of LG on VaD.

RESULTS

LG exhibited beneficial effects on the VaD, which was demonstrated as improved exploratory, learning and memory abilities, relieved vascular or neural pathological changes in cerebral cortex or hippocampus. LG maintained NVC sensitivity, which was confirmed as significantly increased ΔCBV and the elevated ratio of ΔCBV/ΔqEEG. The underlying mechanisms of LG was associated with antioxidant effects, which was confirmed as significantly decreased nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) expression, and increased superoxide dismutase 3 (SOD3) expression. LG also reduced iNOS, increased nNOS and eNOS expression to restore NO bioavailability.

CONCLUSIONS

The results suggested that LG prevented VaD may associate with inhibiting oxidative stress, protecting NO bioavailability, and then maintaining NVC sensitivity.

Redox Regulation of the Superoxide Dismutases SOD3 and SOD2 in the Pulmonary Circulation

When evaluating the role of redox-regulating signaling in pulmonary vascular diseases, it is intriguing to consider the modulation of key antioxidant enzymes like superoxide dismutase (SOD) because SOD isoforms are regulated by redox reactions, and, in turn, modulate downstream redox sensitive processes. The emerging field of redox biology is built upon understanding the regulation and consequences of tightly controlled and specific reduction-oxidation reactions that are critical for diverse cellular processes including cell signaling. Of relevance, both the site of production of specific reactive oxygen and nitrogen species and the site of the antioxidant defenses are highly compartmentalized within the cell. For example, superoxide is generated during oxidative phosphorylation in the mitochondria as well as by a number of enzymatic sources within the cytosol and at the cell membrane. In the pulmonary circulation, these sources include the mitochondrial electron transport chain, NADPH oxidases (NOX1-4, Duox1,2), nitric oxide synthases, and xanthine oxidase; this important topic has been thoroughly reviewed recently [1]. In parallel with these different cellular sites of superoxide production, the three SOD isoforms are also specifically localized to the cytosol (SOD1), mitochondria (SOD2) or extracellular compartment (SOD3). This chapter focuses on the role of redox mechanisms regulating SOD2 and SOD3, with an emphasis on these processes in the setting of pulmonary hypertension.

Vascular Localization of the Heparin-binding Serpins Antithrombin, Heparin Cofactor II, and Protein C Inhibitor

Heparin is one of the most widely used drugs in the world, acting as an anticoagulant by stimulating the reaction between heparin-binding serpins and the serine proteases of the coagulation cascade. To determine whether the heparin-binding serpins antithrombin (AT), heparin cofactor II (HCII), and protein C inhibitor (PCI) were bound to glycosaminoglycans on the endothelial wall, a bolus of heparin (100 U/kg body weight) was in jected into human volunteers, and serpin concentrations and activities were measured in both pre- and postheparin plasma. No increase in circulating concentrations of AT, HCII, or PCI were observed in postheparin plasma. Sim ilarly, AT and HCII activities did not increase in posthe parin plasma. In contrast, the concentration of another heparin-binding protein, lactoferrin (LF), increased six- fold after heparin injection. Immunohistochemistry of hu man artery was performed using polyclonal antisera to AT, HCII, PCI, LF, and tissue factor pathway inhibitor (TFPI), another heparin-binding protein released by hep arin injection. AT, HCII, and PCI were present in the intima, whereas LF, TFPI, and traces of AT were found on the surface of the vessel wall. The distribution of the proteins in the vessel wall supports the results of the hep arin-injection studies and may give valuable clues to the role of each protein in vascular homeostasis.

Infusion of Hibiscus sabdariffa L. Modulates Oxidative Stress in Patients with Marfan Syndrome

Marfan syndrome (MFS) is associated with progressive aortic dilatation, endothelial dysfunction, and oxidative stress that contribute to the early acute dissection of the vessel and can end up in rupture of the aorta and sudden death. Many studies have described that the organic acids from Hibiscus sabdariffa Linne (HSL) calyces increase cellular antioxidant capacity and decrease oxidative stress. Here we evaluate if the antioxidant properties of HSL infusion improve oxidative stress in MFS patients. Activities of extra cellular super oxide dismutase (ECSOD), glutathione peroxidase (GPx), glutathione-S-transferase (GST), glutathione reductase (GSSG-R), glutathione (GSH), lipid peroxidation (LPO) index, total antioxidant capacity (TAC), and ascorbic acid were determined in plasma from MFS patients. Values before and after 3 months of the treatment with 2% HSL infusion were compared in control and MFS subjects. After treatment, there was a significant decrease in ECSOD (p = 0.03), EGPx (p = 0.04), GST (p = 0.03), GSH (p = 0.01), and TAC and ascorbic acid (p = 0.02) but GSSG-R activity (p = 0.04) and LPO (p = 0.02) were increased in MFS patients in comparison to patients receiving the HSL treatment and C subjects. Therefore, the infusion of HSL calyces has antioxidant properties that allow an increase in antioxidant capacity of both the enzymatic and nonenzymatic systems, in the plasma of the MSF patients.

The effects of hypochlorous acid and neutrophil proteases on the structure and function of extracellular superoxide dismutase

Extracellular superoxide dismutase (EC-SOD) is expressed by both macrophages and neutrophils and is known to influence the inflammatory response. Upon activation, neutrophils generate hypochlorous acid (HOCl) and secrete proteases to combat invading microorganisms. This produces a hostile environment in which enzymatic activity in general is challenged. In this study, we show that EC-SOD exposed to physiologically relevant concentrations of HOCl remains enzymatically active and retains the heparin-binding capacity, although HOCl exposure established oxidative modification of the N-terminal region (Met32) and the formation of an intermolecular cross-link in a fraction of the molecules. The cross-linking was also induced by activated neutrophils. Moreover, we show that the neutrophil-derived proteases human neutrophil elastase and cathepsin G cleaved the N-terminal region of EC-SOD irrespective of HOCl oxidation. Although the cleavage by elastase did not affect the quaternary structure, the cleavage by cathepsin G dissociated the molecule to produce EC-SOD monomers. The present data suggest that EC-SOD is stable and active at the site of inflammation and that neutrophils have the capacity to modulate the biodistribution of the protein by generating EC-SOD monomers that can diffuse into tissue.

Oxidative stress and redox regulation on hippocampal-dependent cognitive functions

Hippocampal-dependent cognitive functions rely on production of new neurons and maintenance of dendritic structures to provide the synaptic plasticity needed for learning and formation of new memories. Hippocampal formation is exquisitely sensitive to patho-physiological changes, and reduced antioxidant capacity and exposure to low dose irradiation can significantly impede hippocampal-dependent functions of learning and memory by reducing the production of new neurons and alter dendritic structures in the hippocampus. Although the mechanism leading to impaired cognitive functions is complex, persistent oxidative stress likely plays an important role in the SOD-deficient and radiation-exposed hippocampal environment. Aging is associated with increased production of pro-oxidants and accumulation of oxidative end products. Similar to the hippocampal defects observed in SOD-deficient mice and mice exposed to low dose irradiation, reduced capacity in learning and memory, diminishing hippocampal neurogenesis, and altered dendritic network are universal in the aging brains. Given the similarities in cellular and structural changes in the aged, SOD-deficient, and radiation-exposed hippocampal environment and the corresponding changes in cognitive decline, understanding the shared underlying mechanism will provide more flexible and efficient use of SOD deficiency or irradiation to model age-related changes in cognitive functions and identify potential therapeutic or intervention methods.

Bang-bang model for regulation of local blood flow

The classical model of metabolic regulation of blood flow in muscle tissue implies the maintenance of basal tone in arterioles of resting muscle and their dilation in response to exercise and/or tissue hypoxia via the evoked production of vasodilator metabolites by myocytes. A century-long effort to identify specific metabolites responsible for explaining active and reactive hyperemia has not been successful. Furthermore, the metabolic theory is not compatible with new knowledge on the role of physiological radicals (e.g., nitric oxide, NO, and superoxide anion, O2 (-) ) in the regulation of microvascular tone. We propose a model of regulation in which muscle contraction and active hyperemia are considered the physiologically normal state. We employ the "bang-bang" or "on/off" regulatory model which makes use of a threshold and hysteresis; a float valve to control the water level in a tank is a common example of this type of regulation. Active bang-bang regulation comes into effect when the supply of oxygen and glucose exceeds the demand, leading to activation of membrane NADPH oxidase, release of O2 (-) into the interstitial space and subsequent neutralization of the interstitial NO. Switching arterioles on/off when local blood flow crosses the threshold is realized by a local cell circuit with the properties of a bang-bang controller, determined by its threshold, hysteresis, and dead-band. This model provides a clear and unambiguous interpretation of the mechanism to balance tissue demand with a sufficient supply of nutrients and oxygen.

Muscle contraction increases interstitial nitric oxide as predicted by a new model of local blood flow regulation

The prevailing metabolic theory of local blood flow regulation suggests the dilatation of arterioles in response to tissue hypoxia via the emission of multiple metabolic vasodilators by parenchymal cells. We have proposed a mechanism of regulation, built from well-known components, which assumes that arterioles are normally dilated in metabolically active tissues, due to the emission of NO by the endothelium of microvessels. Regulation of local blood flow aims at preventing an excessive supply of oxygen (O2) and glucose to the tissue and thus provides an adequate supply, in contrast to the metabolic regulation theory which requires permanent hypoxia to generate the metabolic vasodilators. The mediator of the restrictive signal is superoxide anion (O2(-)) released by membrane NAD(P)H oxidases into the interstitial space, where it neutralizes NO at a diffusion-limited rate. This model predicts that the onset of muscle contraction will lead to the cessation of O2(-) production, which will cause an elevation of interstitial NO concentration and an increase in fluorescence of the NO probe DAF-FM after its conversion to DAF-T. The time course of DAF-T fluorescence in contracting muscle is predicted by also considering the washout from the muscle of the interstitially loaded NO indicator. Experiments using pulse fluorimetry confirmed an increase in the interstitial concentration of NO available for reaction with DAF-FM during bouts of muscle contraction. The sharp increase in interstitial [NO] is consistent with the hypothesis that the termination of the neutralizing superoxide flow into the interstitium is associated with the activation of mitochondria and a reduction of the interstitial oxygen tension. The advantage of the new model is its ability to explain the interaction of metabolic activity and local blood flow through the adequate delivery of glucose and oxygen.

Superoxide dismutase isoenzyme activities in plasma and tissues of Iraqi patients with breast cancer

Breast cancer is the first of the most common ten cancers in Iraq. Its etiology is mulifactorial, oxidative stress and lipid peroxidation being suggested to play important roles in carcinogenesis. The purpose of this study was to investigate the oxidant-antioxidant status in breast cancer patients, by measuring SOD isoenzyme activities (total SOD, CuZn-SOD, Mn-SOD and EC-SOD) in plasma and breast tumors, and by estimating thiobarbituric reactive substance (TBRS) in tissue homogenates. General increase in total SOD activity was observed in plasma and tissue samples of breast tumors, greater in the malignant when compared to benign group (p<0.05). Mn- SOD showed a significant decrease in tissue malignant samples (p<0.05), and insignificant decrease in plasma malignant samples compared with control and benign samples. Plasma EC-SOD activity in both patient benign and malignant breast tumors demonstrated 3.5% and 22.8% increase, respectively. However, there was a decrease in tissue EC-SOD activity in malignant breast tumors when compared with benign. A similar tendency was noted for TBRS.We suggested that elevated total SOD might reflect a response to oxidative stress, and then may predict a state of excess reactive oxygen species in the carcinogenesis process. If there is proteolytic removal of the heparin binding domain, EC-SOD will lose its affinity for the extracellular matrix and diffuse out of the tissue. This will result in a decreased EC-SOD activity, thus leading to an increase in the steady-state concentration of O2- in this domain, and increase in EC-SOD activity in extracellular fluid. This might explain the result recorded here concerning the decrease in tissue EC-SOD activity and increase in plasma of breast cancer patients.

Early oxidative change in low density lipoproteins during progressive chronic renal failure

Modified low density lipoproteins (LDL), including their oxidized forms, have been widely implicated in the etiology of atherosclerosis and concomitant cardiovascular disease (CVD) in chronic renal failure (CRF). The nature of events that lead to oxidative changes in LDL proteins are not clearly understood. Thus, patients suffering from CRF were grouped into mild, moderate and severe categories based on their blood urea and serum creatinine levels. Progression of CRF was accompanied not only with gradual increase in serum malondialdehyde (MDA) but also parallel increase in conjugated diene and MDA levels in LDL fractions separated from serum. Serum superoxide dismutase (SOD) activity was concurrently found to decrease, along with a decrease in high-density lipoprotein (HDL) cholesterol, during the progression of CRF. Gradual increase in the appearance of LDL oxidation products seems to accompany progressive manifestation of CRF. The results presented suggest that determination of serum MDA and SOD levels may enhance the diagnostic significance of the study of lipid profile in determining the risk for cardio vascular disease in CRF.

Evidence for the nitric oxide pathway as a potential mode of action in fenoldopam-induced vascular injury

Fenoldopam, a dopaminergic DA1 agonist, induces vasodilatation via nitric oxide (NO), and this may be associated with mesenteric arterial injury. NO is produced from the enzymatic action of nitric oxide synthase (NOS), which is regulated by the shear-stress mediating protein caveolin-1. Profound vasodilatation and accompanied decreased shear are early events that could initiate vascular injury. Therefore, it is of interest to determine the role of caveolin-1 and the NO pathway in fenoldopam-induced vascular injury. At sites of fenoldopam-induced mesenteric arterial injury, decreased caveolin-1 expression and apoptosis were prominent immunohistochemical findings. An additional finding at these sites of injury were loss and/or reduced expression of caveolin-1 regulated structural proteins, connexin-43, (gap junction) ZO-1, and claudin (tight junctions). Because functional loss of caveolin-1 is associated with increased NOS activity and vasodilatation via NO, studies were conducted to show a NO donor produced vascular lesions in the mesenteric arteries morphologically similar to those induced by fenoldopam. Moreover, the incidence and severity of fenoldopam-induced vascular injury were reduced when an NOS inhibitor or a scavenger of NO-generated free radicals were coadministered with fenoldopam. Collectively, these data suggest that caveolin-1 and its regulated NO pathway may play an important role in vasodilatory drug-induced vascular injury.

Oxidative stress and adult neurogenesis--effects of radiation and superoxide dismutase deficiency

Hippocampus plays an important role in learning and memory and in spatial navigation. Production of new neurons that are functionally integrated into the hippocampal neuronal network is important for the maintenance of functional plasticity. In adults, production of new neurons in the hippocampus takes place in the subgranular zone (SGZ) of dentate gyrus. Neural progenitor/stem cells go through processes of proliferation, differentiation, migration, and maturation. This process is exquisitely sensitive to oxidative stress, and perturbation in the redox balance in the neurogenic microenvironment can lead to reduced neurogenesis. Cranial irradiation is an effective treatment for primary and secondary brain tumors. However, even low doses of irradiation can lead to persistent elevation of oxidative stress and sustained suppression of hippocampal neurogenesis. Superoxide dismutases (SODs) are major antioxidant enzymes for the removal of superoxide radicals in different subcellular compartments. To identify the subcellular location where reactive oxygen species (ROS) are continuously generated after cranial irradiation, different SOD deficient mice have been used to determine the effects of irradiation on hippocampal neurogenesis. The study results suggest that, regardless of the subcellular location, SOD deficiency leads to a significant reduction in the production of new neurons in the SGZ of hippocampal dentate gyrus. In exchange, the generation of new glial cells was significantly increased. The SOD deficient condition, however, altered the tissue response to irradiation, and SOD deficient mice were able to maintain a similar level of neurogenesis after irradiation while wild type mice showed a significant reduction in the production of new neurons.

Smoking and COPD increase sputum levels of extracellular superoxide dismutase

Extracellular superoxide dismutase (ECSOD) is the major superoxide-scavenging enzyme in the lung. Certain ECSOD polymorphisms are protective against COPD. We postulated that smokers and COPD subjects would have altered levels of ECSOD in the lung, airway secretions, and/or plasma. Lung tissue ECSOD was evaluated from nonsmokers, smokers, and subjects with mild to very severe COPD by Western blot, immunohistochemistry, and ELISA. ECSOD levels in plasma, bronchoalveolar lavage fluid (BALF), and induced-sputum supernatants were analyzed by ELISA and correlated with smoking history and disease status. Immunohistochemistry identified ECSOD in extracellular matrix around bronchioles, arteries, and alveolar walls, with decreases seen in the interstitium and vessels of severe COPD subjects using digital image analysis. Plasma ECSOD did not differ between COPD subjects and controls nor based on smoking status. ECSOD levels in induced sputum supernatants were elevated in current smokers and especially in COPD subjects compared to nonsmokers, whereas corresponding changes could not be seen in the BALF. ECSOD expression was reduced around vessels and bronchioles in COPD lungs. Substantial increases in sputum ECSOD in smokers and COPD is interpreted as an adaptive response to increased oxidative stress and may be a useful biomarker of disease activity in COPD.

Carbon monoxide-releasing molecule CORM-3 suppresses vascular endothelial cell SOD-1/SOD-2 activity while up-regulating the cell surface levels of SOD-3 in a heparin-dependent manner

The role of CO in the modulation of antioxidant enzyme function has not been investigated, yet. In this study we assessed the effects and potential mechanisms of the ruthenium-based water-soluble CO-releasing molecule CORM-3 in the modulation of superoxide dismutase (SOD) activity/binding in vascular endothelial cells (HUVECs). To this end, HUVECs were treated with CORM-3 (100 μM) and assessed for total SOD activity in cell lysates (cell-associated SOD activity) and cell culture supernatants (soluble SOD). In parallel, release/binding of extracellular SOD (SOD-3) in the absence or presence of heparin (1-10 IU/ml), a key factor regulating SOD-3 cell-surface binding, was investigated. In addition, the effects of CORM-3 on the modulation of purified SOD-1 and SOD-2 activity in a cell-free system were also assessed. The results obtained indicate that CORM-3 effectively suppresses the activity of both purified SOD-1 and SOD-2. These findings were accompanied by CORM-3-dependent attenuation of total cell-associated SOD activity (without affecting SOD-1/SOD-2 protein expression) and a subsequent increase in ROS production (DHR123 oxidation) in HUVECs. In parallel, a concomitant increase in soluble-SOD activity (due to increased SOD-3 release from the cell surface) was observed in the cell culture supernatants. However, in the presence of heparin, total cell-associated SOD activity was significantly increased by CORM-3, because of increased binding of SOD-3 to HUVECs. Taken together these findings indicate for the first time that CORM-3 modulates both the activity of intracellular SOD (i.e., SOD-1 and SOD-2) and the binding of extracellular SOD (SOD-3) to the cell surface.

Extracellular superoxide dismutase polymorphism in mice: Allele-specific effects on phenotype

Extracellular superoxide dismutase (ecSOD) protects the extracellular matrix from oxidative stress. We previously reported a new allele for ecSOD, expressed in 129P3/J mice (129), which differs from the wild type (wt), expressed in C57BL/6J and other strains, by two amino acid substitutions and a 10-bp deletion in the 3' UTR of the mRNA (A. Pierce et al., 2003, Arterioscler. Thromb. Vasc. Biol.23:1820-1825). The newly discovered allele is associated with a phenotype of significantly increased circulating and heparin-releasable enzyme activities and levels. To examine the properties of the two forms of ecSOD in an identical environment we generated, by extensive backcrossing of ecSOD heterozygous progeny to C57BL/6J females, a congenic C57 strain with the 129 (or wt) allele of ecSOD. These mice are homozygous for nearly 5000 SNPs across all chromosomes, as determined by the Affymetrix Parallele Mouse 5K SNP panel. This study describes the generation of the congenic mice (genetically >99.8% identical) and their ecSOD phenotype. The congenic mouse plasma ecSOD activity before and after heparin administration recapitulates the differences reported in the founder mice. Tissue enzyme distribution is similar in both congenic groups, although the 129 allele is associated with higher levels of enzyme expression despite lower levels of enzyme mRNA. In these characteristics the phenotype is allele driven, with little impact from the rest of the genome. The congenic mice carrying the 129 allele have mRNA levels that are in between those in the founder 129P3/J and C57BL/6J strains. We conclude that the ecSOD phenotype in most aspects of enzyme expression is allele driven, with the exception of tissue mRNA levels, for which a significant contribution by the surrounding (host) genome is observed. These results also suggest potential allele-specific differences in the regulation of ecSOD synthesis and intracellular processing/secretion of ecSOD, independent of the genotype context. Most importantly, the congenic mice offer an excellent model to examine the regulatory mechanisms of ecSOD expression and the role of ecSOD in various diseases involving oxidative stress.

High levels of autoantibodies against catalase and superoxide dismutase in nasopharyngeal carcinoma

INTRODUCTION

Autoantibodies against the antioxidant enzymes have been described in Epstein-Barr virus-associated diseases. Here, we hypothesize that Epstein-Barr virus (EBV), which is associated with nasopharyngeal carcinoma (NPC), induces anticatalase and/or antisuperoxide dismutase autoantibodies that inhibit catalase and/or superoxide dismutase activities and thereby contribute to the oxidative stress status described in this pathology.

METHODS

Using a standard enzyme-linked immunosorbent assay (ELISA), the levels of immunoglobulin G (IgG), and M (IgM) directed against catalase and superoxide dismutase in the sera of 30 NPC patients and 30 healthy control individuals were evaluated. The antioxidative profile was tested among the same patients by measuring serum catalase and superoxide dismutase activities. To investigate the implication of EBV in the establishment of autoantibody production in NPC patients, a correlation study between serological testing for EBV viral capsid antigen immunoglobulin G (VCA IgG) and autoantibodies against both enzymes was undertaken.

FINDINGS

The levels of IgG against superoxide dismutase and catalase were found to be increased in sera patients compared to controls (P<0.001). NPC patients exhibited decreased catalase (P<0.001) and superoxide dismutase activities (P<0.001) in their sera. However, a positive correlation between superoxide dismutase IgM antibody and IgG antibody titers to VCA (P<0.05, r=0.483, n=21) was found. A positive correlation between catalase (IgM) antibodies and IgG antibody titers to VCA (P<0.05, r=0.546, n=30) was also found.

CONCLUSION

High levels of anticatalase and antisuperoxide dismutase antibodies in the sera of NPC patients were found.

The impact of different biocompatible coated cardiopulmonary bypass circuits on inflammatory response and oxidative stress

This study was to compare the impact of different biocompatible coated circuits on inflammatory response and oxidative stress induced during cardiopulmonary bypass (CPB). Seventy-eight patients undergoing elective coronary artery bypass grafting (CABG) with CPB were randomly assigned to five groups with different biocompatible coated circuits: Trillium, Bioline, Phosphorylcholine, Polymethoxyethyl acrylate (PMEA), and the uncoated control group. Blood was drawn at three different time points: before CPB, 6 and 72 hours post CPB. Unlike the Trillium group, serum levels of TNF-α in the Bioline and Phosphorylcholine groups significantly increased only at 72 hours post CPB (p < 0.05). Serum levels of IL-6 significantly increased at 6 and 72 hours post CPB in all groups (p < 0.01). The Trillium group showed a significant increase of IL-10 compared to the control group at 72 hours post CPB (p < 0.05). Serum levels of NOx in the Phosphorylcholine group significantly decreased at 6 hours post CPB compared to baseline (p < 0.05). Both the Bioline and Phosphorylcholine groups showed statistical decreases in serum NOx levels compared with other groups at 6 hours post CPB (p < 0.05). A significant difference in NOx levels between the Bioline and the control group was also observed at 72 hours post CPB. Myeloperoxidase levels were significantly elevated at 6 and 72 hours post CPB in all groups (p < 0.05). Inflammatory response and oxidative stress are elevated during CABG with CPB. Heparin-coated and the Phosphorylcholine-coated circuits induce less inflammatory responses and oxidative stress compared to other circuits.

SOD3 R231G polymorphism associated with coronary artery disease and myocardial infarction. The Ludwigshafen Risk and Cardiovascular Health (LURIC) study

This study examined the superoxide dismutase 3 (SOD3) R231G polymorphism in relation to the severity of coronary artery disease (CAD) and the risk of myocardial infarction (MI) in 3211 individuals; 94.4% of study participants were homozygous for SOD3 231RR and 5.5% were heterozygous for SOD3 231RG. The odds ratios of the RG and GG genotype (adjusted for age, gender and for conventional cardiovascular risk factors) were 2.02 (95% CI, 1.23-3.33, p=0.005) for the highest vs the lowest Friesinger coronary score and 1.40 (95% CI, 1.02-1.92, p=0.037) for MI, respectively. Further the SOD3 RG and GG genotype was associated with lower alpha-tocopherol levels than the wild type SOD3 RR genotype. It is concluded that the SOD3 231RG and GG genotype is associated with lower alpha-tocopherol levels and the severity of CAD and the risk of MI.

Overexpression of extracellular superoxide dismutase attenuates heparanase expression and inhibits breast carcinoma cell growth and invasion

Increased expression of heparanase stimulates the progression of various human cancers, including breast cancer. Therefore, a deeper understanding of the mechanisms involved in regulating heparanase is critical in developing effective treatments for heparanase-overexpressing cancers. In this study, we investigated the potential use of extracellular superoxide dismutase (EcSOD) to enhance the inhibitory effects of heparin/low molecular weight heparin (LMWH) in breast cancer cells. EcSOD binds to cell surfaces and the extracellular matrix through heparin-binding domain (HBD). Deleting this HBD rendered the protein a more potent inhibitor of breast cancer growth, survival, and invasion. Among the treatment combinations examined, EcSODDeltaHBD plus LMWH provided the best tumor suppressive effects in inhibiting breast cancer growth and invasion in vitro. We have further shown that overexpression of EcSOD decreased accumulation of vascular endothelial growth factor in the culture medium and increased the level of intact cell surface-associated heparan sulfate, thus implicating inhibition of heparanase expression as a potential mechanism. Overexpression of EcSOD inhibited steady-state heparanase mRNA levels by >50% as determined by quantitative reverse transcription-PCR. Moreover, heparanase promoter activation was suppressed by EcSOD as indicated by a luciferase reporter assay. These findings reveal a previously unrecognized molecular pathway showing that regulation of heparanase transcription can be mediated by oxidative stress. Our study implies that overexpression of EcSOD is a promising strategy to enhance the efficacy of heparin/LMWH by inhibiting heparanase as a novel treatment for breast cancer.

Oxidative Stress and Myocardial Damage during Elective Percutaneous Coronary Interventions and Coronary AngiographyA Comparison of Blood-borne Isoprostane and Troponin Release

The role of oxidative stress in clinical cardiology is still controversial. The aims of the present study were to examine if minor ischaemic episodes as may occur during elective percutaneous coronary intervention (PCI) induce oxidative stress and, eventually, if oxygen stress correlates with myocardial injury. Thirty eight and nine patients underwent PCI and diagnostic coronary angiography, respectively. Peripheral blood was sampled at different time points for plasma analyses of: 8-iso-PGF2alpha (free radical-mediated oxidative stress); 15-keto-dihydro-PGF2alpha (cyclooxygenase-mediated inflammation); troponin-T (myocardial injury); hsCRP, vitamin A and vitamin E; and, total antioxidants status (TAS). In both groups 8-iso-PGF2alpha increased transiently by approximately 80% (p < 0.001) during the procedure. There was a minor troponin-T release (p < 0.001) after PCI, but no correlation with 8-iso-PGF2alpha. Troponin-T did not increase after angiography. 15-keto-dihydro-PGF2alpha decreased by 50% after ended procedure, but increased by 100% after 24 h compared to baseline. hsCRP increased significantly (p < 0.001) from baseline to the next day in the PCI-group, but not in the angiography group. Vitamins and TAS decreased slightly after the procedures. It is concluded that a moderate oxidative stress was induced by both elective PCI and coronary angiography but that no correlation was found between oxidative stress and myocardial injury in this setting. This indicates that other mechanisms than ischaemia-reperfusion episodes caused an elevation in plasma isoprostane such like the injury at a vascular site mutual for both procedures. A secondary finding from the study was elevated markers of early inflammatory response, not only after PCI, but also after angiography.

Superoxide dismutase is regulated by LAMMER kinase in Drosophila and human cells

LAMMER kinases (also known as CDC-2-like or CLKs) are a family of dual specificity serine/threonine protein kinases that are found in all sequenced eukaryotic genomes. In the fission yeast, Schizosaccharomyces pombe, the LAMMER kinase gene, Lkh1, positively regulates the expression of the antioxidant defense genes, superoxide dismutase 1 (sod1+, CuZn-SOD) and catalase (ctt1+, CAT). We have shown that mutations in the Drosophila LAMMER kinase gene, Darkener of apricot (Doa), protect against the decrease in life span caused by the reactive oxygen species (ROS) generator paraquat, and at the same time show an increase in cytoplasmic (CuZn-Sod or SOD1) and mitochondrial superoxide dismutase (Mn-Sod or SOD2) protein levels and activity. The siRNA-mediated knock down of the human LAMMER kinase gene, CLK-1, in HeLa and MCF-7 human cell lines leads to an increase in both SOD1 activity and mRNA transcript levels. These data suggest that SOD1 is negatively regulated by LAMMER kinases in Drosophila and human cell lines and that this regulation may be conserved during evolution.

Redox control of endothelial function and dysfunction: molecular mechanisms and therapeutic opportunities

The endothelium is essential for the maintenance of vascular homeostasis. Central to this role is the production of endothelium-derived nitric oxide (EDNO), synthesized by the endothelial isoform of nitric oxide synthase (eNOS). Endothelial dysfunction, manifested as impaired EDNO bioactivity, is an important early event in the development of various vascular diseases, including hypertension, diabetes, and atherosclerosis. The degree of impairment of EDNO bioactivity is a determinant of future vascular complications. Accordingly, growing interest exists in defining the pathologic mechanisms involved. Considerable evidence supports a causal role for the enhanced production of reactive oxygen species (ROS) by vascular cells. ROS directly inactivate EDNO, act as cell-signaling molecules, and promote protein dysfunction, events that contribute to the initiation and progression of endothelial dysfunction. Increasing data indicate that strategies designed to limit vascular ROS production can restore endothelial function in humans with vascular complications. The purpose of this review is to outline the various ways in which ROS can influence endothelial function and dysfunction, describe the redox mechanisms involved, and discuss approaches for preventing endothelial dysfunction that may highlight future therapeutic opportunities in the treatment of cardiovascular disease.

Extracellular superoxide dismutase (ecSOD) in vascular biology: an update on exogenous gene transfer and endogenous regulators of ecSOD

Extracellular superoxide dismutase (ecSOD) is the major extracellular scavenger of superoxide (O(2)(.-)) and a main regulator of nitric oxide (NO) bioactivity in the blood vessel wall, heart, lungs, kidney, and placenta. Involvement of O(2)(.-) has been implicated in many pathological processes, and removal of extracellular O(2)(.-) by ecSOD gene transfer has emerged as a promising experimental technique to treat vascular disorders associated with increased oxidant stress. In addition, recent studies have clarified mechanisms that regulate ecSOD expression, tissue binding, and activity, and they have provided new insight into how ecSOD interacts with other factors that regulate vascular function. Finally, studies of a common gene variant in humans associated with disruption of ecSOD tissue binding suggest that displacement of the enzyme from the blood vessel wall may contribute to vascular diseases. The purpose of this review is to summarize recent research findings related to ecSOD function and gene transfer and to stimulate other investigations into the role of this unique antioxidant enzyme in vascular pathophysiology and therapeutics.

Chemically modified heparin inhibits mesangial cell proliferation induced by high glucose through interfering with the cell cycle

The aims of this study were to investigate whether chemically modified non-anticoagulation heparin derivate (Periodate-Oxidized/Borohydride-Reduced modified heparin (OR-heparin)) can inhibit high glucose-induced human mesangial cell proliferation and its influence on the cell cycle. OR-heparin with low anticoagulation activity inhibited high glucose-induced early proliferation in a dose-dependent manner. OR-heparin released high glucose-arrested mesangial cells at G(1) phase, and dose-dependently increased S phase. OR-heparin also inhibited high glucose-activated ERK1/2 phosphorylation, induced p27(Kip1) expression, and suppressed reactive oxygen species (ROS) accumulation in a dose-dependent manner. Our results suggest that OR-heparin releases high glucose-arrested cells on G(1) phase and inhibits high glucose-induced mesangial cell proliferation through blocking ERK1/2 phosphorylation and delaying S phase progression, which may be in correlation with OR-heparin suppressing ROS accumulation.

Oxidative stress during coronary artery bypass operations: importance of surgical trauma and drug treatment

OBJECTIVE

To investigate oxidative stress and myocardial injury at different stages of coronary artery bypass grafting (CABG).

DESIGN

Twenty patients underwent CABG with use of cardiopulmonary bypass (CPB) and with intermittent sampling of plasma and urine. Main markers were: 8-iso-PGF2alpha (oxidative stress); troponin T (myocardial injury); and 15-keto-dihydro-PGF2alpha and hsCRP (inflammation).

RESULTS

Plasma 8-iso-PGF2alpha increased after start of surgery, but there was no further rise during CPB or after aortic cross-clamp release and no significant myocardial arterio-venous differences. An increase in troponin T was seen early after the operation, but no relationship was established between 8-iso-PGF2alpha and troponin T. 8-iso-PGF2alpha levels were elevated by preoperative withdrawal of acetylsalicylic acid (ASA) but reduced by intraoperative use of heparin. 15-keto-dihydro-PGF2alpha was elevated during operation and hsCRP following operation.

CONCLUSIONS

In the present study oxidative stress was multifactorial in origin with main impacts from surgical trauma, less from CPB and little if any from myocardial ischemia-reperfusion events. In addition, cardiovascular drugs in common use like ASA and heparin seemed to influence the pro- and antioxidant balance, a finding that has to be confirmed in future studies.

Heparin impairs glycocalyx barrier properties and attenuates shear dependent vasodilation in mice

The endothelial glycocalyx is a hydrated mesh of polysaccharides and adsorbed plasma proteins that forms the true interface between the flowing blood and the endothelium. We hypothesized in the present study that competitive binding of heparin to glycocalyx-associated proteins would affect glycocalyx barrier properties and mechanotransduction of shear stress to the endothelium. In anesthetized mice, the clearance of 70-kDa dextrans from the circulation was increased (P<0.05 versus saline) 1 hour after heparin (1.25 U) and glycocalyx degradation with hyaluronidase (35 U; amount cleared in 30 minutes after saline: 11+/-5%; after heparin: 45+/-8%; after hyaluronidase: 30+/-3%). Clearance of 40-kDa dextrans increased (P<0.05 versus saline) to a lesser extent after both treatments (saline: 46+/-3%; heparin: 60+/-5%; hyaluronidase: 60+/-2%). The dilator response of second-order arterioles in cremaster muscle during reactive hyperemia was reduced for < or =90 minutes after heparin as reflected by a decrease (P=0.008) in t(50) of diameter recovery, and this effect was associated with a diminished NO bioavailability. Infusion of hyaluronidase resulted in reductions (P<0.05) in baseline and peak reactive hyperemic diameter, whereas, despite an increase in wall shear rate at the beginning of reactive hyperemia, t(50) of diameter recovery was not affected. In conclusion, our data in mice show that a heparin challenge is associated with increased vascular leakage of dextrans and impaired arteriolar vasodilation during reactive hyperemia. Our data suggest that protein-heparan sulfate interactions are important for a functional glycocalyx.

Purification, identification, characterization, and cDNA cloning of a high molecular weight extracellular superoxide dismutase of hamster that transiently increases in plasma during arousal from hibernation

We previously studied antioxidant profiles in the plasma of hibernating Syrian hamsters and found a transient increase of a superoxide radical-scavenging activity during the arousal phase. In this report, we purified and identified the high molecular weight superoxide dismutase (SOD)-like factor from the plasma of arousing hamsters. The cyanide-sensitive 240 kDa SOD-like factor showed a significant homology to mammalian extracellular SOD (EC-SOD) reported, although the molecular mass of EC-SOD was 135 kDa. The cDNA cloning revealed that the 240 kDa SOD-like factor was identical to the hamster ortholog of EC-SOD. It consisted of 245 amino acid residues including a signal sequence of 20 amino acid residues. Five cysteine residues that would participate in inner- and inter-subunit bonds were well conserved among species. Interestingly, there were four potential N-glycosylation sites in hamster EC-SOD, whereas there is only one site in other species. The amino acid sequence analysis indicated that three of the four sites were modified. These results suggest that the anomalistically high molecular weight of hamster EC-SOD is ascribed, at least in part, to the addition of extra sugar chains. Furthermore, results obtained here also propose the involvement of EC-SOD in the antioxidative defense of hibernating hamsters.

Cloning and characterization of two alleles of the murine extracellular superoxide dismutase gene

We have recently documented the existence of a second allele of ecSOD in mice. Thus far, this allele was only found in the 129P3/J strain. It is characterized by two point mutations leading to amino acid changes as well as a 10 bp deletion from the 3' UTR. We have also shown that the phenotype is profoundly affected by the genotype. In order to obtain a tool to investigate the differences in the properties as well as the posttranscriptional regulation of expression of the two alleles we now describe the creation and characterization of stably transfected CHO-K1 cell lines expressing either of these alleles. CHO-K1 cells were chosen because they do not express endogenous ecSOD and are easy to transfect. We demonstrate that the transfected cells secrete substantial amounts of glycosylated ecSOD, detected by Western blot analyses, ConA-Sepharose affinity chromatography and activity measurements.

Up-regulation of an extracellular superoxide dismutase-like activity in hibernating hamsters subjected to oxidative stress in mid- to late arousal from torpor

Torpor-arousal cycles, one of the inherent features in hibernators, are associated with a rapid increase in body temperature and respiration, and it would lead to elevation of reactive oxygen species (ROS) generation. However, hibernators apparently tolerate this oxidative stress. We have observed in Syrian hamsters (Mesocricetus auratus) a maximal temperature shift and respiratory rate in mid- to late arousal (16-33 degrees C rectal temperature) from torpor. To examine plasma antioxidant status during arousal, we studied total superoxide radical-scavenging activity in plasma by electron spin resonance. The superoxide radical-scavenging activity reached a maximum at 32 degrees C, coincident with a peak in plasma uric acid levels, a ROS generation indicator. The up-regulated activity at 32 degrees C was attributable to the peak of the activity eluted at 260-kDa on gel-filtration chromatography, but was not to small antioxidant molecules such as ascorbate and alpha-tocopherol. The activity eluted at 260-kDa increased 3-fold at 32 degrees C compared with that of the torpid state, and was not detected either at 6 h after the onset of arousal or in the euthermic state. Moreover, the activity exhibited extracellular SOD-like properties: its induction in plasma by heparin injection and its affinity for heparin. Our results suggest that the 260-kDa extracellular SOD-like activity plays a role in the tolerance for the oxidative stress during arousal from torpor.

Heparin-released extracellular superoxide dismutase is reduced in patients with coronary artery atherosclerosis

OBJECTIVES

We studied whether the amount of heparin-released extracellular superoxide dismutase (EC-SOD), which is an antioxidative enzyme, is associated with coronary artery disease (CAD).

METHODS AND RESULTS

EC-SOD was measured in plasma at basal and at post-heparin injection in 315 patients. Heparin-released EC-SOD was calculated as the difference between the two values. After exclusion of a mutant EC-SOD group (n = 27:8.6%), 288 patients were divided into three groups by angiographic findings; those with normal coronary (the normal group; n = 63), those with atherosclerosis without significant stenosis (the mild atherosclerosis group; n = 36), and those with significant stenosis (the atherosclerosis group; n = 189). Although the basal values were similar among the three groups, heparin-released EC-SOD levels were significantly lower in the atherosclerosis group (131.0 +/- 42.8 ng/ml, p = 0.0003) than in the normal group (156.9 +/- 66.2 ng/ml). Moreover, logistic analysis revealed that heparin-released EC-SOD independently contributed to CAD. The coronary score showed a significant correlation with heparin-released EC-SOD. As for factors affecting the level of heparin-released EC-SOD, the level of high-density lipoprotein cholesterol and age showed a positive correlation.

CONCLUSIONS

The results suggest that heparin-released EC-SOD is significantly reduced in CAD and that the tissue-bound location of this enzyme might be important for antioxidative function.

Experimental hyperhomocysteinemia impairs coronary flow velocity reserve

BACKGROUND

Hyperhomocysteinemia has been identified as an independent risk factor for coronary artery disease. One mechanism is considered to be deteriorated endothelial function that is recovered by vitamin C. However, its direct action on coronary circulation has yet to be examined. This study was designed to test the hypothesis that experimental acute hyperhomocysteinemia would impair coronary flow velocity reserve (CFR) by increasing oxidative stress.

METHODS

Eleven healthy male volunteers (aged 23.3+/-0.9 years) were enrolled. CFR induced by intravenous 5'-adenosine triphosphate infusion was measured by transthoracic-Doppler echocardiography. Measurements were taken before and 4 h after administration of a placebo, oral methionine (L-methionine 0.1 g/kg) or oral methionine plus vitamin C (2 g) on 3 separate days.

RESULTS

The baseline average diastolic peak velocity (APV) was similar in all 3 groups. In the methionine group, plasma homocysteine increased (12.9+/-7.0 to 32.1+/-9.4 nmol/ml, p<0.0001), while APV under hyperemic conditions (APV-hyp) and CFR significantly decreased (87.2+/-11.4 cm/sec and 4.02+/-0.70 to 73.2+/-10.2 cm/sec and 3.35+/-0.52, p=0.0022 and 0.0030, respectively). Moreover, there was a significant inverse correlation between the plasma homocysteine and CFR (r=-0.620, p=0.0021). However, upon simultaneous administration of vitamin C, APV-hyp and CVR did not decrease despite an elevation in plasma homocysteine.

CONCLUSIONS

Experimentally induced acute hyperhomocysteinemia significantly decreased CFR, and this decrease was significantly reversed by vitamin C administration. Oxidative stress is suggested to play a major role in the deleterious effects of homocysteine on the coronary microcirculation.

Decreased plasma extracellular superoxide dismutase level in patients with vasospastic angina

OBJECTIVE

Extracellular superoxide dismutase (EC-SOD) is the major extracellular scavenger of superoxides, and one of the main regulators of nitric oxide bioactivity in vessel walls. Here, we examined whether plasma EC-SOD level was associated with vasospastic angina (VSA), and if it was a risk factor for VSA.

METHODS AND RESULTS

We assigned 105 patients with normal or mildly stenotic coronary arteries into either a VSA (n=58) or chest pain syndrome (CPS) (n=47) groups. Plasma EC-SOD and other biochemical variables were measured, and major coronary risk factors were assessed. Results showed that apart from smoking status there were no significant differences in patient characteristics and biochemical variables between the two groups. In the VSA group, prevalence of smoking was significantly higher (53% versus 26%, p=0.0055), and plasma EC-SOD level was significantly lower (68.9+/-18.5 ng/ml versus 83.8+/-25.9 ng/ml; p=0.0009). Not only smoking (OR 2.742, 95% CI 1.032-7.287, p=0.0431) but also plasma EC-SOD (OR 0.971, 95% CI 0.949-0.993, p=0.0102) was an independent risk factor for VSA.

CONCLUSIONS

In patients with VSA, plasma EC-SOD level was substantially reduced. Furthermore, plasma EC-SOD level followed by cigarette smoking was the most predictive risk factor for coronary spasms.

Extracellular superoxide dismutase exists as an octamer

Human extracellular superoxide dismutase (EC-SOD) is involved in the defence against oxidative stress induced by the superoxide radical. The protein is a homotetramer stabilised by hydrophobic interactions within the N-terminal region. During the purification of EC-SOD from human aorta, we noticed that material with high affinity for heparin-Sepharose formed not only a tetramer but also an octamer. Analysis of the thermodynamic stability of the octamer suggested that the C-terminal region is involved in formation of the quaternary structure. In addition, we show that the octamer is composed of both aEC-SOD and iEC-SOD folding variants. The presence of the EC-SOD octamer with high affinity may represent a way to influence the local concentration of EC-SOD to protect tissues specifically sensitive to oxidative damage.

Disulfide between Cys392 and Cys438 of human serum albumin is redox-active, which is responsible for the thioredoxin-supported lipid peroxidase activity

Human serum albumin (HSA) is an abundant protein found in blood plasma and extracellular fluids. Previously, we found that HSA has a distinct thioredoxin (Trx)-dependent lipid peroxidase activity in the presence of palmitoyl-CoA. In this paper, we identified the redox-active disulfide, which can be specifically reduced by Trx, responsible for the Trx-dependent lipid peroxidase activity. The IIB-III fragment of HSA (Pro299-Leu585) sustained the Trx-dependent lipid peroxidase activity. Chemical modification of the Trx-reduced IIB-III with a thiol-specific modification agent resulted in a complete loss of the peroxidase activity. The analysis of tryptic-peptides derived from the inactivated HSA and IIB-III revealed that Cys392 and Cys438, which exist as an intramolecular disulfide bond in HSA, were preferentially modified in both HSA and IIB-III. Taken together, these results suggested that HSA has a capability to reduce lipid hydroperoxide with the use of Trx as an in vivo electron donor, and that the redox-active disulfide between Cys392 and Cys438 acts as a primary site of the catalysis for the Trx-linked lipid peroxidase activity.

Extracellular superoxide dismutase

The extracellular space is protected from oxidant stress by the antioxidant enzyme extracellular superoxide dismutase (EC-SOD), which is highly expressed in selected tissues including blood vessels, heart, lungs, kidney and placenta. EC-SOD contains a unique heparin-binding domain at its carboxy-terminus that establishes localization to the extracellular matrix where the enzyme scavenges superoxide anion. The EC-SOD heparin-binding domain can be removed by proteolytic cleavage, releasing active enzyme into the extracellular fluid. In addition to protecting against extracellular oxidative damage, EC-SOD, by scavenging superoxide, preserves nitric oxide bioactivity and facilitates hypoxia-induced gene expression. Loss of EC-SOD activity contributes to the pathogenesis of a number of diseases involving tissues with high levels of constitutive extracellular superoxide dismutase expression. A thorough understanding of the biological role of EC-SOD will be invaluable for developing novel therapies to prevent stress by extracellular oxidants.

Simvastatin Versus Ezetimibe

Background— Statins may exert important pleiotropic effects, ie, improve endothelial function, independently of their impact on LDL cholesterol. In humans, however, pleiotropic effects of statins have never been unequivocally demonstrated because prolonged statin treatment always results in reduced LDL cholesterol levels. We therefore tested the hypothesis that similar reductions in LDL cholesterol with simvastatin and ezetimibe, a novel cholesterol absorption inhibitor, result in different effects on endothelial function.

Methods and Results— Twenty patients with chronic heart failure were randomized to 4 weeks of simvastatin (10 mg/d) or ezetimibe (10 mg/d) treatment. Flow-dependent dilation (FDD) of the radial artery was determined by high-resolution ultrasound before and after intra-arterial vitamin C to determine the portion of FDD inhibited by radicals (ΔFDD-VC). Activity of extracellular superoxide dismutase, a major vascular antioxidant enzyme system, was determined after release from the endothelium by a heparin bolus injection. Endothelial progenitor cells were analyzed with an in vitro assay. Simvastatin and ezetimibe treatment reduced LDL cholesterol to a similar extent (15.6% versus 15.4%; P =NS), whereas changes in mevalonate, the product of HMG-CoA-reductase, differed between groups (Δmevalonate-simvastatin, −1.04±0.62 versus Δmevalonate-ezetimibe, 1.79±0.94 ng/mL; P <0.05 between groups). Importantly, FDD was markedly improved after simvastatin (10.5±0.6% versus 5.1±0.7%; P <0.01) but not after ezetimibe treatment (5.6±0.5% versus 5.8±0.6%; P =NS). ΔFDD-VC was substantially reduced after simvastatin but not after ezetimibe treatment. Extracellular superoxide dismutase activity was increased by >100% ( P <0.05) after simvastatin but not ezetimibe treatment. Simvastatin treatment increased the number of functionally active endothelial progenitor cells, whereas ezetimibe had no effect.

Conclusions— Four weeks of simvastatin treatment improves endothelial function independently of LDL cholesterol lowering, at least in part by reducing oxidant stress. Simvastatin may thereby exert important pleiotropic effects in humans.