Glutathione peroxidase mimics prevent TNFalpha- and neutrophil-induced endothelial alterations

Reactive Oxygen Species and Strategies for Antioxidant Intervention in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a life-threatening pulmonary condition characterized by the sudden onset of respiratory failure, pulmonary edema, dysfunction of endothelial and epithelial barriers, and the activation of inflammatory cascades. Despite the increasing number of deaths attributed to ARDS, a comprehensive therapeutic approach for managing patients with ARDS remains elusive. To elucidate the pathological mechanisms underlying ARDS, numerous studies have employed various preclinical models, often utilizing lipopolysaccharide as the ARDS inducer. Accumulating evidence emphasizes the pivotal role of reactive oxygen species (ROS) in the pathophysiology of ARDS. Both preclinical and clinical investigations have asserted the potential of antioxidants in ameliorating ARDS. This review focuses on various sources of ROS, including NADPH oxidase, uncoupled endothelial nitric oxide synthase, cytochrome P450, and xanthine oxidase, and provides a comprehensive overview of their roles in ARDS. Additionally, we discuss the potential of using antioxidants as a strategy for treating ARDS.

Antimicrobial and anti-viral effects of selenium nanoparticles and selenoprotein based strategies: COVID-19 and beyond

Deficiency of selenium (Se) has been described in a significant number of COVID-19 patients having a higher incidence of mortality, which makes it a pertinent issue to be addressed clinically for effective management of the COVID-19 pandemic. Se nanoparticles (SeNPs) provide a unique option for managing the havoc caused by the COVID-19 pandemic. SeNPs possess promising anti-inflammatory and anti-fibrotic effects by virtue of their nuclear factor kappa-light-chain-stimulator of activated B cells (NFκB), mitogen-activated protein kinase (MAPKs), and transforming growth factor-beta (TGF-β) modulatory activity. In addition, SeNPs possess remarkable immunomodulatory effects, making them a suitable option for supplementation with a much lower risk of toxicity compared to their elemental counterpart. Further, SeNPs have been shown to curtail viral and microbial infections, thus, making it a novel means to halt viral growth. In addition, it can be administered in the form of aerosol spray, direct injection, or infused thin-film transdermal patches to reduce the spread of this highly contagious viral infection. Moreover, a considerable decrease in the expression of selenoprotein along with enhanced expression of IL-6 in COVID-19 suggests a potential association among selenoprotein expression and COVID-19. In this review, we highlight the unique antimicrobial and antiviral properties of SeNPs and the immunomodulatory potential of selenoproteins. We provide the rationale behind their potentially interesting properties and further exploration in the context of microbial and viral infections. Further, the importance of selenoproteins and their role in maintaining a successful immune response along with their association to Se status is summarized.

Biological and Catalytic Properties of Selenoproteins

Selenocysteine is a catalytic residue at the active site of all selenoenzymes in bacteria and mammals, and it is incorporated into the polypeptide backbone by a co-translational process that relies on the recoding of a UGA termination codon into a serine/selenocysteine codon. The best-characterized selenoproteins from mammalian species and bacteria are discussed with emphasis on their biological function and catalytic mechanisms. A total of 25 genes coding for selenoproteins have been identified in the genome of mammals. Unlike the selenoenzymes of anaerobic bacteria, most mammalian selenoenzymes work as antioxidants and as redox regulators of cell metabolism and functions. Selenoprotein P contains several selenocysteine residues and serves as a selenocysteine reservoir for other selenoproteins in mammals. Although extensively studied, glutathione peroxidases are incompletely understood in terms of local and time-dependent distribution, and regulatory functions. Selenoenzymes take advantage of the nucleophilic reactivity of the selenolate form of selenocysteine. It is used with peroxides and their by-products such as disulfides and sulfoxides, but also with iodine in iodinated phenolic substrates. This results in the formation of Se-X bonds (X = O, S, N, or I) from which a selenenylsulfide intermediate is invariably produced. The initial selenolate group is then recycled by thiol addition. In bacterial glycine reductase and D-proline reductase, an unusual catalytic rupture of selenium-carbon bonds is observed. The exchange of selenium for sulfur in selenoproteins, and information obtained from model reactions, suggest that a generic advantage of selenium compared with sulfur relies on faster kinetics and better reversibility of its oxidation reactions.

Chemistry Related to the Catalytic Cycle of the Antioxidant Ebselen

The antioxidant drug ebselen has been widely studied in both laboratories and in clinical trials. The catalytic mechanism by which it destroys hydrogen peroxide via reduction with glutathione or other thiols is complex and has been the subject of considerable debate. During reinvestigations of several key steps, we found that the seleninamide that comprises the first oxidation product of ebselen underwent facile reversible methanolysis to an unstable seleninate ester and two dimeric products. In its reaction with benzyl alcohol, the seleninamide produced a benzyl ester that reacted readily by selenoxide elimination, with formation of benzaldehyde. Oxidation of ebselen seleninic acid did not afford a selenonium seleninate salt as previously observed with benzene seleninic acid, but instead generated a mixture of the seleninic and selenonic acids. Thiolysis of ebselen with benzyl thiol was faster than oxidation by ca. an order of magnitude and produced a stable selenenyl sulfide. When glutathione was employed, the product rapidly disproportionated to glutathione disulfide and ebselen diselenide. Oxidation of the S-benzyl selenenyl sulfide, or thiolysis of the seleninamide with benzyl thiol, afforded a transient thiolseleninate that also readily underwent selenoxide elimination. The S-benzyl derivative disproportionated readily when catalyzed by the simultaneous presence of both the thiol and triethylamine. The phenylthio analogue disproportionated when exposed to ambient or UV (360 nm) light by a proposed radical mechanism. These observations provide additional insight into several reactions and intermediates related to ebselen.

A Study of Selenium in Leprosy

INTRODUCTION

Leprosy is a chronic infection caused by Mycobacterium leprae. Selenium, on the other hand, is a substance, which is needed for its protective role against microorganism infection.

AIM

This study aims to know the association between selenium serum levels with bacteriological index.

METHODS

This is an analytical cross-sectional study model. Sampling was done with consecutive sampling method in Pirngadi General Hospital, Lau Simomo Leprosy Hospital and H. Adam Malik General Hospital. Samples were taken from patients' venous blood serum then selenium levels were measured.

RESULTS

This study found 30 leprosy patients consisted of 19 patients with paucibacillary (PB) leprosy and 11 patients with multibacillary (MB) leprosy. Selenium serum levels of patients with PB leprosy (mean = 97.16 µg/dL) were found to be significantly higher than MB leprosy (mean = 77.27 µg/dL) with p = 0.008 using t-test. The negative correlation between selenium serum levels with bacterial index in patients with leprosy was also found in this study using Spearman's rho test (r = - 0.499, p = 0.005).

CONCLUSIONS

Selenium serum levels of patients with PB leprosy are higher than patients with MB leprosy, and high bacteriological index in patients with leprosy were correlated with low selenium serum levels.

Selenium in the prevention of atherosclerosis and its underlying mechanisms

Atherosclerosis and related cardiovascular diseases (CVDs) represent the greatest threats to human health worldwide. Selenium, an essential trace element, is incorporated into selenoproteins that play a crucial role in human health and disease. Although findings from a limited number of randomized trials have been inconsistent and cannot support a protective role of Se supplementation in CVDs, prospective observational studies have generally shown a significant inverse association between selenium or selenoprotein status and CVD risk. Furthermore, a benefit of selenium supplementation in the prevention of CVDs has been seen in population with low baseline selenium status. Evidence from animal studies shows consistent results that selenium and selenoproteins might prevent experimental atherosclerosis, which can be explained by the molecular and cellular effects of selenium observed both in animal models and cell cultures. Selenoproteins of particular relevance to atherosclerosis are glutathione peroxidases, thioredoxin reductase 1, selenoprotein P, selenoprotein S. The present review is focusing on the existing evidence that supports the concept that optimal selenium intake can prevent atherosclerosis. Its underlying mechanisms include inhibiting oxidative stress, modulating inflammation, suppressing endothelial dysfunction, and protecting vascular cells against apoptosis and calcification. However, the benefit of selenium supplementation in the prevention of atherosclerosis remains insufficiently documented so far. Future studies with regard to the effects of selenium supplementation on atherosclerosis should consider many factors, especially the baseline selenium status, the dose and forms of selenium supplementation, and the selenoprotein genotype. Additionally, much more studies are needed to confirm the roles of selenoproteins in atherosclerosis prevention and clarify the underlying mechanisms.

ROS Signaling in the Pathogenesis of Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS)

The generation of reactive oxygen species (ROS) plays an important role for the maintenance of cellular processes and functions in the body. However, the excessive generation of oxygen radicals under pathological conditions such as acute lung injury (ALI) and its most severe form acute respiratory distress syndrome (ARDS) leads to increased endothelial permeability. Within this hallmark of ALI and ARDS, vascular microvessels lose their junctional integrity and show increased myosin contractions that promote the migration of polymorphonuclear leukocytes (PMNs) and the transition of solutes and fluids in the alveolar lumen. These processes all have a redox component, and this chapter focuses on the role played by ROS during the development of ALI/ARDS. We discuss the origins of ROS within the cell, cellular defense mechanisms against oxidative damage, the role of ROS in the development of endothelial permeability, and potential therapies targeted at oxidative stress.

The role of methoxy substituents in regulating the activity of selenides that serve as spirodioxyselenurane precursors and glutathione peroxidase mimetics

A series of o-(hydroxymethyl)phenyl selenides containing single or multiple methoxy substituents was synthesized, and the rate at which each compound catalyzed the oxidation of benzyl thiol to its disulfide with excess hydrogen peroxide was measured. This assay provided the means for comparing the relative abilities of the selenides to mimic the antioxidant selenoenzyme glutathione peroxidase. The mechanism for catalytic activity involves oxidation of the selenides to their corresponding selenoxides with hydrogen peroxide, cyclization to spirodioxyselenuranes, followed by reduction with two equivalents of thiol to regenerate the original selenide with concomitant disulfide formation. A single p-methoxy group on each aryl moiety afforded the highest catalytic activity, while methoxy groups in the meta position had little effect compared to the unsubstituted selenide, and o-methoxy groups suppressed activity. The installation of multiple methoxy groups on each aryl moiety provided no improvement. These results can be rationalized on the basis of dominating mesomeric and steric effects of the p- and o-substituents, respectively.

Ultrasound assisted multicomponent reactions: a green method for the synthesis of highly functionalized selenopyridines using reusable polyethylene glycol as reaction medium

A simple and benign one-pot protocol for the synthesis of 2-amino selenopyrindine derivatives 4 has been developed using ultrasound assisted multicomponent reactions of aldehydes, malononitrile and benzeneselenol in PEG-400.

Synthesis of Some Monoselenolipoic Acid Derivatives and Their Biological Evaluation as Anticancer Agents

6-Selenolipoic acid was synthesised from ethyl 6, 8-dichlorooctanoate in a one pot reaction with water as solvent, and was further converted in three steps to 14 N-substituted benzylidene-5-(1, 2-thiaselenolan-3-yl) pentanehydr-azides. The compounds exhibited moderate to high anticancer activities, some of them showing activity comparable to that of cisplatin.

Target- and mechanism-based therapeutics for neurodegenerative diseases: strength in numbers

The development of new therapeutics for the treatment of neurodegenerative pathophysiologies currently stands at a crossroads. This presents an opportunity to transition future drug discovery efforts to target disease modification, an area in which much still remains unknown. In this Perspective we examine recent progress in the areas of neurodegenerative drug discovery, focusing on some of the most common targets and mechanisms: N-methyl-d-aspartic acid (NMDA) receptors, voltage gated calcium channels (VGCCs), neuronal nitric oxide synthase (nNOS), oxidative stress from reactive oxygen species, and protein aggregation. These represent the key players identified in neurodegeneration and are part of a complex, intertwined signaling cascade. The synergistic delivery of two or more compounds directed against these targets, along with the design of small molecules with multiple modes of action, should be explored in pursuit of more effective clinical treatments for neurodegenerative diseases.

Pharmacological antioxidant strategies as therapeutic interventions for COPD

Cigarette/tobacco smoke/biomass fuel-induced oxidative and aldehyde/carbonyl stress are intimately associated with the progression and exacerbation of chronic obstructive pulmonary disease (COPD). Therefore, targeting systemic and local oxidative stress with antioxidants/redox modulating agents, or boosting the endogenous levels of antioxidants are likely to have beneficial effects in the treatment/management of COPD. Various antioxidant agents, such as thiol molecules (glutathione and mucolytic drugs, such as N-acetyl-L-cysteine and N-acystelyn, erdosteine, fudosteine, ergothioneine, and carbocysteine), have been reported to modulate various cellular and biochemical aspects of COPD. These antioxidants have been found to scavenge and detoxify free radicals and oxidants, regulate of glutathione biosynthesis, control nuclear factor-kappaB (NF-kappaB) activation, and hence inhibiting inflammatory gene expression. Synthetic molecules, such as specific spin traps like α-phenyl-N-tert-butyl nitrone, a catalytic antioxidant (ECSOD mimetic), porphyrins (AEOL 10150 and AEOL 10113), and a superoxide dismutase mimetic M40419, iNOS and myeloperoxidase inhibitors, lipid peroxidation inhibitors/blockers edaravone, and lazaroids/tirilazad have also been shown to have beneficial effects by inhibiting cigarette smoke-induced inflammatory responses and other carbonyl/oxidative stress-induced cellular alterations. A variety of oxidants, free radicals, and carbonyls/aldehydes are implicated in the pathogenesis of COPD, it is therefore, possible that therapeutic administration or supplementation of multiple antioxidants and/or boosting the endogenous levels of antioxidants will be beneficial in the treatment of COPD. This review discusses various novel pharmacological approaches adopted to enhance lung antioxidant levels, and various emerging beneficial and/or prophylactic effects of antioxidant therapeutics in halting or intervening the progression of COPD. This article is part of a Special Issue entitled: Antioxidants and Antioxidant Treatment in Disease.

Emerging role for antioxidant therapy in protection against diabetic cardiac complications: experimental and clinical evidence for utilization of classic and new antioxidants

Diabetes mellitus (DM) markedly potentiates the risk of cardiovascular morbidity and mortality among individuals with diabetes as compared to the non-diabetic population. After myocardial infarction (MI), DM patients have a higher incidence of death than do non-diabetics. The excess mortality and poor prognosis of these patients results primarily from the development of recurrent MI and heart failure (HF). Although several lines of evidence support a role for increased oxidative stress in a range of cardiovascular diseases, clinical trials examining the therapeutic efficacy of antioxidants have yielded conflicting results. The reasons for these incongruous results is multifactorial. An underlying theme has been lack of patient inclusion based on elevated indices of oxidative stress which could have diluted the population susceptible to benefit in the clinical trials. Laboratory evidence has accumulated indicating that oxidative stress is dramatically accentuated in cardiac abnormalities inherent in DM. In this review, we provide the emergence of experimental and clinical evidence supporting antioxidant supplementation as a cardioprotective intervention in the setting of DM. Specifically, focus will be directed on preclinical animal studies and human clinical trials that have tested the effect of antioxidant supplements on MI and HF events in the presence of DM.

Inhibition of oral midazolam clearance by boosting doses of ritonavir, and by 4,4-dimethyl-benziso-(2H)-selenazine (ALT-2074), an experimental catalytic mimic of glutathione oxidase

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

* The viral protease inhibitor ritonavir is known to inhibit clearance of intravenous midazolam. * ALT-2074, a catalytic mimic of glutathione oxidase, inhibits human cytochrome P450 3A (CYP3A) isoforms in vitro.

WHAT THIS STUDY ADDS

* Short-term administration of low-dose ritonavir increases area under the plasma concentration curve following oral midazolam by a factor of 28. * Therefore ritonavir is an appropriate positive control inhibitor for clinical drug interaction studies involving CYP3A substrates. * Midazolam clearance is weakly inhibited by ALT-2074, consistent with its in vitro profile.

AIMS

We evaluated whether 'boosting' doses of ritonavir can serve as a positive control inhibitor for pharmacokinetic drug-drug interaction studies involving cytochrome P450 3A (CYP3A). The study also determined whether 4,4-dimethyl-benziso-(2H)-selenazine (ALT-2074), an investigational organoselenium compound that acts as a catalytic mimic of glutathione oxidase, inhibits CYP3A metabolism in vivo.

METHODS

Thirteen healthy volunteers received single 3-mg oral doses of midazolam on three occasions: in the control condition, during co-treatment with low-dose ritonavir (three oral doses of 100 mg over 24 h), and during co-treatment with ALT-2074 (three oral doses of 80 mg over 24 h).

RESULTS

Ritonavir increased mean (+/-SE) total area under the curve (AUC) for midazolam by a factor of 28.4 +/- 4.2 (P < 0.001), and reduced oral clearance to 4.2 +/- 0.5% of control (P < 0.001). In contrast, ALT-2074 increased midazolam AUC by 1.25 +/- 0.11 (P < 0.05), and reduced oral clearance to 88 +/- 8% of control.

CONCLUSIONS

Low-dose ritonavir produces extensive CYP3A inhibition exceeding that of ketoconazole (typically 10- to 15-fold midazolam AUC enhancement), and is a suitable positive control index inhibitor for drug-drug interaction studies. ALT-2074 inhibits CYP3A metabolism to a small degree that is of uncertain clinical importance.

Micronutrients and HIV infection

The immune system requires several essential micronutrients to maintain an effective immune response. HIV infection destroys the immune system and promotes nutritional deficiencies, which further impair immunity. This article reviews the role of several micronutrients (vitamins A, C, E and D, the B vitamins, and minerals, selenium, iron and zinc) that are relevant for maintaining immune function. In addition, the deficiencies of these micronutrients have been associated with faster progression of HIV-1 disease. This review examines the evidence from observational studies of an association between micronutrient status and HIV disease, as well as the effectiveness of micronutrient supplementation on HIV-disease progression, pregnancy outcomes and nutritional status, among others, utilizing randomized clinical trials. Each micronutrient is introduced with a summary of its functions in human physiology, followed by the presentation of studies conducted in HIV-infected patients in relation to this specific micronutrient. Overall findings and recommendations are then summarized.

Vasospasm after subarachnoid hemorrhage in haptoglobin 2-2 mice can be prevented with a glutathione peroxidase mimetic

Vasospasm after subarachnoid hemorrhage (SAH) is attributable to inflammation and oxidative stress associated with extracellular hemoglobin (Hb). Haptoglobin (Hp) binds free Hb and the Hp-Hb complex is cleared by macrophages, and the Hp-2 isoform of Hp is associated with more oxidative stress and more severe vasospasm. We hypothesized that treatment with an anti-oxidant, the glutathione peroxidase mimetic SYI-2074, would reduce vasospasm after SAH in Hp-2 mice. We found that SAH induced significant vasospasm in Hp-2 mice (lumen patency reduced to 65.9%), but no vasospasm was seen in mice that received SYI-2074 after SAH (lumen patency of 98.7%). We conclude that vasospasm after SAH in Hp-2 mice can be prevented with SYI-2074, suggesting that oxidative stress contributes significantly to vasospasm.

The Role of Nrf2 in Cellular Innate Immune Response to Inflammatory Injury

Nuclear factor erythroid derived 2-related factor-2 (Nrf2) is a master transcription regulator of antioxidant and cytoprotective proteins that mediate cellular defense against oxidative and inflammatory stresses. Disruption of cellular stress response by Nrf2 deficiency causes enhanced susceptibility to infection and related inflammatory diseases as a consequence of exacerbated immuneediated hypersensitivity and autoimmunity. The cellular defense capacity potentiated by Nrf2 activation appears to balance the population of CD4⁺ and CD8⁺ of lymph node cells for proper innate immune responses. Nrf2 can negatively regulate the activation of pro-inflammatory signaling molecules such as p38 MAPK, NF-KB, and AP-1. Nrf2 subsequently functions to inhibit the production of pro-inflammatory mediators including cytokines, chemokines, cell adhesion molecules, matrix metalloprotein-ases, COX-2 and iNOS. Although not clearly elucidated, the antioxidative function of genes targeted by Nrf2 may cooperatively regulate the innate immune response and also repress the expression of proinflammatory mediators.

Design and synthesis of some biologically interesting natural and unnatural products based on organosulfur and selenium chemistry

Organosulfur and selenium chemistry has provided fertile ground for the discovery of novel synthetic methodology and for the design of bioactive molecules with potential therapeutic applications. Thus, acetylenic sulfones have been employed in novel strategies for the synthesis of nitrogen heterocycles, including several biologically active alkaloids. The conjugate addition of nitrogen nucleophiles containing ester or chloroalkyl substituents to acetylenic sulfones was followed by base-mediated intramolecular alkylation or acylation to afford variously substituted piperidines, pyrrolizidines, indolizidines, quinolizidines, decahydroquinolines, and 4-quinolones. The products include the dendrobatid alkaloids (–)-pumiliotoxin C, indolizidines (–)-167B, 207A, 209B, and 209D, as well as (–)-(ent)-julifloridine, (–)-lasubine II, myrtine, and two recently discovered alkaloids from the medicinal plant Ruta chalepensis , which had not been previously synthesized. Acetylenic sulfones were also incorporated on solid supports and employed in the types of cyclizations mentioned above, as well as for Diels–Alder reactions and a large variety of 1,3-dipolar cycloadditions. Conjugate additions of tertiary cyclic α-vinyl amines to acetylenic sulfones generated zwitterions that underwent exceptionally facile formal aza-Cope rearrangements to afford ring-expanded macrocyclic amines. An iterative version was developed and used in the synthesis of motuporamine A and B. With respect to organoselenium chemistry, two classes of compounds are described that function as novel mimetics of the selenoenzyme glutathione peroxidase (GPx), which protects cells from oxidative stress caused by the formation of peroxides during aerobic metabolism. They include cyclic seleninates and spirodioxyselenuranes, both of which efficiently catalyze the reduction of peroxides with thiols and are of potential value in the mitigation of oxidative stress. Their aromatic derivatives are generally less effective catalysts, but substituent effects can be used to modulate their activities. The mechanism of their catalytic cycles has been elucidated and Hammett plots indicate that the oxidation of Se(II) to Se(IV) is the rate-determining step for both classes. A methoxy-substituted aromatic spirodioxyselenurane provided the fastest rate for a small-molecule selenium compound that we have observed to date for the reduction of hydrogen peroxide with benzyl thiol.

A hyperlipidemic rabbit model provides new insights into pulmonary zinc exposure effects on cardiovascular health

This study ascertains the effects of zinc, a major component of particulate matter, on pulmonary and systemic endpoints using hyperlipidemic rabbits to model diet-induced human atherosclerosis. New Zealand White rabbits were fed a normal or cholesterol-enriched diet and then were intratracheally instilled 1x/week for 4 weeks with saline or 16 microg/kg of zinc, equal parts sulfate and oxide. Physiologic responses, blood after each exposure, and terminal bronchoalveolar lavage (BAL) were assessed. Rabbits fed a cholesterol-rich diet developed hyperlipidemia and had consistently higher circulating leukocyte counts than rabbits fed normal chow. Within minutes after zinc instillation, saturation of peripheral oxygen was decreased in hyperlipidemic rabbits and heart rate was increased in hyperlipidemic rabbits with total serum cholesterol levels greater than 200 mg/dl. Total circulating leukocytes levels were increased 24 h after the first zinc instillation, but upon repeated exposures this effect was attenuated. After repeated zinc exposures, BAL fluid (BALF) N-acetylglucosaminidase activity was increased regardless of hyperlipidemic state. Hyperlipidemic rabbits had an increase in BALF-oxidized glutathione and a decrease in serum nitrite. The study elucidates mechanisms by which the zinc metal component of PM drives cardiovascular health effects, as well as the possible susceptibility induced by hyperlipidemia. Furthermore, the study exemplifies the benefits of monitoring circulatory physiology during exposure as well as after exposure.

Catalase and glutathione peroxidase mimics

Overproduction of the reactive oxygen species (ROS) superoxide (O(2)(-)) and hydrogen peroxide (H(2)O(2)) are increasingly implicated in human disease and aging. ROS are also being explored as important modulating agents in a number of cell signaling pathways. Earlier work has focused on development of small catalytic scavengers of O(2)(-), commonly referred to as superoxide dismutase (SOD) mimetics. Many of these compounds also have substantial abilities to catalytically scavenge H(2)O(2) and peroxynitrite (ONOO(-)). Peroxides have been increasingly shown to disrupt cell signaling cascades associated with excessive inflammation associated with a wide variety of human diseases. Early studies with enzymatic scavengers like SOD frequently reported little or no beneficial effect in biologic models unless SOD was combined with catalase or a peroxidase. Increasing attention has been devoted to developing catalase or peroxidase mimetics as a way to treat overt inflammation associated with the pathophysiology of many human disorders. This review will focus on recent development of catalytic scavengers of peroxides and their potential use as therapeutic agents for pulmonary, cardiovascular, neurodegenerative and inflammatory disorders.

Decreased selenoprotein expression alters the immune response during influenza virus infection in mice

Previous work from our laboratory demonstrated that host selenium (Se) deficiency results in greater lung pathology and altered immune function in mice infected with influenza virus. Because selenoproteins play a key role in determining the oxidant status of the host, we utilized a transgenic mouse line carrying a mutant selenocysteine (Sec) tRNA ([Ser]Sec) transgene (t-trspi(6)A(-)). The levels of selenoproteins are decreased in these mice in a protein- and tissue-specific manner. Male t-trspi(6)A(-) and wild-type (WT) mice were infected with influenza and killed at various time points postinfection (p.i.). Lung mRNA levels for innate and pro-inflammatory cytokines increased with infection but did not differ between groups. However, at d 2 p.i., chemokine levels were greater in the t-trspi(6)A(-) mice compared with WT mice. Additionally, IFN-gamma was higher at d 7 p.i. in the t-trspi(6)A(-) mice and viral clearance slower. Despite these immune system changes, lung pathology was similar in t-trspi(6)A(-) and WT mice. (75)Se labeling experiments demonstrated that glutathione peroxidase (GPX)-1 and thioredoxin reductase, although greatly diminished in the lungs of t-trspi(6)A(-) mice, were not altered as a result of infection. GPX-1 activity in the lungs of the t-trspi(6)A(-) mice was approximately 82% of the WT mice. In addition, the GPX-1 activity in the lungs of Se-deficient mice was 125% less than in the t-trspi(6)A(-) mice. These results suggest that although selenoproteins are important for immune function, there is a threshold of GPX-1 activity that can prevent an increase in lung pathology during influenza infection.

Haptoglobin Genotype Determines Myocardial Infarct Size in Diabetic Mice

OBJECTIVES

We sought to understand the importance of oxidative stress in explaining why the haptoglobin (Hp) genotype determines myocardial infarction (MI) size in diabetes mellitus (DM).

BACKGROUND

Two common alleles (1 and 2) exist at the Hp locus in humans. The Hp 2 allele is associated with increased MI size in individuals with DM. In vitro, the Hp 2 protein is associated with increased generation of oxidatively active iron, whereas the Hp 1 protein is associated with increased production of the antioxidant cytokine interleukin (IL)-10.

METHODS

Myocardial infarction was produced by myocardial ischemia-reperfusion (IR) in DM C57BL/6 mice carrying the Hp 1 or Hp 2 allele. Myocardial oxidative stress after IR was assessed using electrospray ionization mass spectrometry. Redox active iron and IL-10 were measured in the serum after IR.

RESULTS

Myocardial infarction size was significantly larger in Hp 2 mice as compared with Hp 1 mice (44.3 +/- 9.3% vs. 21.0 +/- 4.0%, p = 0.03), and these larger infarctions were associated with a significant increase in a panel of hydroxyl-eicosatetraenoic acids. Redox active iron was greater in Hp 2 mice (0.45 +/- 0.11 micromol/l vs. 0.14 +/- 0.05 micromol/l, p = 0.02), whereas IL-10 was greater in Hp 1 mice (85.8 +/- 12.9 pg/microl vs. 46.7 +/- 10.8 pg/microl, p = 0.04) after IR. Administration of an antioxidant (BXT-51072) to Hp 2 mice reduced myocardial injury after IR by more than 80% (p = 0.003), but no myocardial protection was provided by the antioxidant to Hp 1 mice.

CONCLUSIONS

The increased MI size in DM Hp 2 mice occurring after IR may be due to increased oxidative stress.

Increased antioxidant capacity in healthy volunteers taking a mixture of oral antioxidants versus vitamin C or E supplementation

The objectives of this study were (1) to evaluate the capacity of human plasma that had been obtained from healthy adult volunteers before and after they ingested vitamin E or C to inhibit induced lipoperoxidation in vitro (antioxidant capacity of plasma [ACP]), and (2) to compare the efficiency of these vitamins with that of a commercial mixture of antioxidant vitamins, cofactors, and minerals (MAOx). Seventy-nine healthy individuals between 19 and 23 y of age were randomly assigned to 1 of 4 groups. Each received a daily dose of antioxidants for 7 d: vitamin C (n=18; 500 mg), vitamin E (n=21; 400 IU), vitamins C and E (n=19), or MAOx (n=21; 1.2 g). ACP and plasma malondialdehyde were measured at 4 and 24 h and 7 d. ACP increased significantly (P<.05) in all 4 groups within 4 h of antioxidant intake, and this effect was sustained throughout supplementation. Plasma ACP increased significantly over basal values in the group taking MAOx; relative increases were 42%, 44%, and 55% at 4 h, 24 h, and 7 d, respectively (P<.001). Smaller increases in plasma ACP were observed in the vitamin C group (25%, 32%, and 36%) and, specifically, in the vitamin E group (17%, 24%, and 28%) (P<.05). The mixture of vitamins and minerals was comparatively more efficient than vitamin C or E alone, presumably because MAOx contains various antioxidant compounds with different redox potentials, leading to the possible development of chain reactions.

Application of pharmacogenomics in the prevention of diabetic cardiovascular disease: Mechanistic basis and clinical evidence for utilization of the haptoglobin genotype in determining benefit from antioxidant therapy

Atherosclerotic cardiovascular disease (CVD) and diabetic vascular disease have been associated with an increase in oxidative stress. Mechanistic studies in vitro and in animals have demonstrated a direct role for oxidatively modified protein and lipid molecules in the pathophysiology of these diseases. As a result of this oxidation hypothesis numerous studies have been carried out over the past 5-10 years testing the ability of antioxidant vitamins to decrease the incidence of these diseases. The general consensus from these studies, involving over 200,000 individuals, has been that antioxidant vitamins do not provide any vascular protection. Moreover, several of these studies have demonstrated that antioxidant supplementation may be associated with an increased incidence of disease and mortality. One reason why these antioxidant vitamins may have failed to demonstrate benefit may have been due to inappropriate patient selection. In this review we provide supporting clinical evidence and a mechanistic basis for utilizing a genetic marker, the haptoglobin (Hp) genotype, in determining whether antioxidant vitamin therapy may or may not be beneficial for a given patient with diabetes.

NADPH oxidase mediates vascular endothelial cadherin phosphorylation and endothelial dysfunction

Vascular endothelial activation is an early step during leukocyte/endothelial adhesion and transendothelial leukocyte migration in inflammatory states. Leukocyte transmigration occurs through intercellular gaps between endothelial cells. Vascular endothelial cadherin (VE-cadherin) is a predominant component of endothelial adherens junctions that regulates intercellular gap formation. We found that tumor necrosis factor (TNF) caused tyrosine phosphorylation of VE-cadherin, separation of lateral cell-cell junctions, and intercellular gap formation in human umbilical vein endothelial cell (HUVEC) monolayers. These events appear to be regulated by intracellular oxidant production through endothelial NAD(P)H (nicotinamide adenine dinucleotide phosphate) oxidase because antioxidants and expression of a transdominant inhibitor of the NADPH oxidase, p67(V204A), effectively blocked the effects of TNF on all 3 parameters of junctional integrity. Antioxidants and p67(V204A) also decreased TNF-induced JNK activation. Dominant-negative JNK abrogated VE-cadherin phosphorylation and junctional separation, suggesting a downstream role for JNK. Finally, adenoviral delivery of the kinase dead PAK1(K298A) decreased TNF-induced JNK activation, VE-cadherin phosphorylation, and lateral junctional separation, consistent with the proposed involvement of PAK1 upstream of the NADPH oxidase. Thus, PAK-1 acts in concert with oxidase during TNF-induced oxidant production and loss of endothelial cell junctional integrity.

Selenium-dependent enzymes in endothelial cell function

Glutathione peroxidases and thioredoxin reductases are the main selenoproteins expressed by endothelial cells. These enzymes reduce hydroperoxides, their role in endothelial cell physiology, however, by far exceeds prevention of oxidative damage. Reactive oxygen and nitrogen species, especially superoxide, hydroperoxides, and nitric oxide, are crucial signaling molecules in endothelial cells. Their production is regulated by vascular NAD(P)H oxidases and the endothelial nitric oxide synthase. Their metabolism and physiological functions are coordinated by glutathione peroxidases and the thioredoxin/thioredoxin reductase system. Endothelial selenoproteins are involved in the regulation of the vascular tone by maintaining the superoxide anion/nitric oxide balance, of cell adhesion by controlling cell adhesion molecule expression, of apoptosis via inhibition/activation of apoptosis signal-regulating kinase-1, and of eicosanoid production by controlling the activity of cyclooxygenases and lipoxygenases. Accordingly, they regulate inflammatory processes and atherogenesis. The underlying mechanisms are various and differ between individual selenoproteins. Scavenging of hydroperoxides not only prevents oxidative damage, but also interferes with signaling cascades and enzymes involved. Modulation of proteins by hydroperoxide-driven thiol/disulfide exchange is a novel mechanism that needs to be further investigated. A better understanding of the complex interplay of selenoproteins in regulating endothelial cell functions will help to develop a rationale for an improvement of health by an optimum selenium supply.

The antioxidant role of selenium and seleno-compounds

Selenium (Se) is an essential trace element for animals and humans that is obtained from dietary sources including cereals, grains and vegetables. The Se content of plants varies considerably according to its concentration in soil. Plants convert Se mainly into Se-methionine (Se-Met) and incorporate it into protein in place of methionine (Met). Selenocystine (Se-Cys), methyl-Se-Cys and gamma-glutamyl-Se-methyl-Cys are not significantly incorporated into plant protein and are at relatively low levels irrespective of soil Se content. Higher animals are unable to synthesize Se-Met and only Se-Cys was detected in rats supplemented with Se as selenite. Renal regulation is the mode by which whole body Se is controlled. Se is concentrated in hair and nail and it occurs almost exclusively in organic compounds. The potentiating effect of Se deficiency on lipid peroxidation is enhanced in some tissues by concurrent deficiency of copper or manganese. In the in vitro system, the chemical form of Se is an important factor in eliciting cellular responses. Although the cytotoxic mechanisms of selenite and other redoxing Se compounds are still unclear, it has been suggested that they derive from their ability to catalyze the oxidation of thiols and to produce superoxide simultaneously. Selenite-induced cytotoxicity and apoptosis in human carcinoma cells can be inhibited with copper (CuSO(4)) as an antioxidant. High doses of selenite result in induction of 8-hydroxydeoxyguanosine (8-OHdG) in mouse skin cell DNA and in primary human keratinocytes. It may cause DNA fragmentation and decreased DNA synthesis, cell growth inhibition, DNA synthesis, blockade of the cell cycle at the S/G(2)-M phase and cell death by necrosis. In contrast, in cells treated with methylselenocyanate or Se methylselenocysteine, the cell cycle progression was blocked at the G(1) phase and cell death was predominantly induced by apoptosis.

Differential effects of ebselen on neutrophil recruitment, chemokine, and inflammatory mediator expression in a rat model of lipopolysaccharide-induced pulmonary inflammation

We postulated that the seleno-organic compound ebselen would attenuate neutrophil recruitment and activation after aerosolized challenge with endotoxin (LPS) through its effect as an antioxidant and inhibitor of gene activation. Rats were given ebselen (1-100 mg/kg i.p.) followed by aerosolized LPS exposure (0.3 mg/ml for 30 min). Airway inflammatory indices were measured 4 h postchallenge. Bronchoalveolar lavage (BAL) fluid cellularity and myeloperoxidase activity were used as a measure of neutrophil recruitment and activation. RT-PCR analysis was performed in lung tissue to assess gene expression of TNF-alpha, cytokine-induced neutrophil chemoattractant-1 (CINC-1), macrophage-inflammatory protein-2 (MIP-2), ICAM-1, IL-10, and inducible NO synthase. Protein levels in lung and BAL were also determined by ELISA. Ebselen pretreatment inhibited neutrophil influx and activation as assessed by BAL fluid cellularity and myeloperoxidase activity in cell-free BAL and BAL cell homogenates. This protective effect was accompanied by a significant reduction in lung and BAL fluid TNF-alpha and IL-1 beta protein and/or mRNA levels. Ebselen pretreatment also prevented lung ICAM-1 mRNA up-regulation in response to airway challenge with LPS. This was not a global effect of ebselen on LPS-induced gene expression, because the rise in lung and BAL CINC-1 and MIP-2 protein levels were unaffected as were lung mRNA expressions for CINC-1, MIP-2, IL-10, and inducible NO synthase. These data suggest that the anti-inflammatory properties of ebselen are achieved through an inhibition of lung ICAM-1 expression possibly through an inhibition of TNF-alpha and IL-1 beta, which are potent neutrophil recruiting mediators and effective inducers of ICAM-1 expression.

Inhibition of TNF-alpha induced ICAM-1, VCAM-1 and E-selectin expression by selenium

The initiation of an atherosclerotic lesion involves an endothelial cell pro-inflammatory state that recruits leukocytes and promotes their movement across the endothelium. These processes require endothelial expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and endothelial-leukocyte adhesion molecule-1 (E-selectin). Tumor necrosis factor-alpha (TNF-alpha) is a powerful inducer of these adhesion molecules. Selenium status is known to affect the rate of atherosclerosis. These experiments tested whether selenium alters cytokine-induced expression of these adhesion molecules. Human umbilical vein endothelial cells (HUVECs) were pretreated for 24 h with sodium selenite (0-2 microM) and then treated with 0 or 50 U/ml TNF-alpha in the presence of 0-2 microM selenite. ICAM-1, VCAM-1 and E-selectin were detected by ELISA and their mRNAs were evaluated by Northern blots. Selenite significantly inhibited TNF-alpha-induced expression of each adhesion molecule in a dose-dependent manner and reduced the level of the respective mRNAs. Nuclear factor-kappa B (NF-kappa B) is required for transcription of these adhesion molecule genes. Western blot analysis revealed that selenite did not inhibit the translocation of the p65 subunit of NF-kappa B to the nucleus. In conclusion, these data indicate selenium can modulate cytokine-induced expression of ICAM-1, VCAM-1 and E-selectin in HUVECs without interfering with translocation of NF-kappa B.

Reactive oxygen species as mediators in asthma

This review describes production and effects of reactive oxygen species (ROS) on airway function. ROS are important in many physiological processes but can also have detrimental effects on airway cells and tissues when produced in high quantities or during the absence of sufficient amounts of anti-oxidants. Therefore, these mediators play a prominent role in the pathogenesis of various inflammatory airway disorders, including asthma. Effects of ROS on airway function in asthma have been studied with isolated airway cells and tissues and with animal models and patients. With the use of inhibitors, transgenic animals and measurements of the release of ROS within the airways, it became clear that oxidative stress contributes to the initiation and worsening of inflammatory respiratory disorders.