Selenoorganic compound, ebselen, inhibits nitric oxide and tumor necrosis factor-? production by the modulation of Jun-N-terminal kinase and the NF-?b signaling pathway in rat Kupffer cells

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Mechanisms of ebselen as a therapeutic and its pharmacology applications

Ebselen is a synthetic organoselenium radical scavenger compound that possesses glutathione peroxidase-like activity and its own unique bioactivity by reacting with thiols, hydroperoxides and peroxynitrites. Owing to its high affinity toward several essential reactions, ebselen protects cellular components from oxidative and free radical damage, and it has been employed as a useful tool for studying redox-related mechanisms. Based on numerous in vitro and in vivo research, mechanisms are proposed to understand the biomedical and molecular actions of ebselen in health and disease, and it is currently under clinical trials for the prevention and treatment of various human disorders. Based on these outstanding discoveries, this review summarizes the current understanding of the biochemical and molecular characteristics, pharmacological applications and future directions of ebselen.

NADPH oxidase 2 inhibitors CPP11G and CPP11H attenuate endothelial cell inflammation & vessel dysfunction and restore mouse hind-limb flow

First described as essential to the phagocytic activity of leukocytes, Nox2-derived ROS have emerged as mediators of a range of cellular and tissue responses across species from salubrious to deleterious consequences. Knowledge of their role in inflammation is limited, however. We postulated that TNFα-induced endothelial reactive oxygen species (ROS) generation and pro-inflammatory signaling would be ameliorated by targeting Nox2. Herein, we in silico-modelled two first-in-class Nox2 inhibitors developed in our laboratory, explored their cellular mechanism of action and tested their efficacy in in vitro and mouse in vivo models of inflammation. Our data show that these inhibitors (CPP11G and CPP11H) disrupted canonical Nox2 organizing factor, p47^phox, translocation to Nox2 in the plasma membrane; and abolished ROS production, markedly attenuated stress-responsive MAPK signaling and downstream AP-1 and NFκB nuclear translocation in human cells. Consequently, cell adhesion molecule expression and monocyte adherence were significantly inhibited by both inhibitors. In vivo, TNFα-induced ROS and inflammation were ameliorated by targeted Nox2 inhibition, which, in turn, improved hind-limb blood flow. These studies identify a proximal role for Nox2 in propagated inflammatory signaling and support therapeutic value of Nox2 inhibitors in inflammatory disease.

Selenium ameliorates Staphylococcus aureus-induced inflammation in bovine mammary epithelial cells by inhibiting activation of TLR2, NF-κB and MAPK signaling pathways

BACKGROUND

Staphylococcus aureus (S. aureus) internalization into bovine mammary epithelial cells (bMECs) is considered an important pathogenic mechanism for the establishment of mastitis. Given the interesting link between selenium (Se) status and mastitis, our objective was to prove that Se was essential to suppress pro-inflammatory mediators, in part, by modulation of Toll-like receptor2 (TLR2), nuclear factor kappaB (NF-κB) and mitogen activated protein kinase (MAPK) signal transduction pathway in bMECs.

RESULTS

Results showed that Se (0~ 16 μM) did not affect the growth of bMECs. The mRNA expression of TLR2, Myeloid differentiation factor 88 (Myd88), Interleukin-1 receptor-associated kinase4 (Irak4), Interleukin-1 receptor-associated kinase1 (Irak1) and TNF receptor-associated factor6 (Traf6) in TLR2 signal pathway were increased or significantly increased by S. aureus. Se played an important role in regulating the genes expression of TLR2, Myd88, Traf6 but not in controlling the expression of Irak4 and Irak1. In addition, Se exerted strong inhibitory effects on the genes expression of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) induced by S. aureus. To further investigate the possible signaling mechanisms involved in the processes, we analyzed the role of MAPK and NF-κB signaling pathway in inflammation response in S. aureus-stimulated bMECs in vitro. Results showed that the phosphorylation of inhibitory kappaB alpha (IκBα), p65, p38 and extracellular regulated protein kinase (Erk) were significantly increased in S. aureus-stimulated bMECs. It indicated that S. aureus activated NF-κB and MAPK signaling pathway. We also examined the effects of Se on the phosphorylation of IκBα, p65, p38 and Erk in NF-κB and MAPK signaling pathway, which have well been proved to control the synthesis and release of pro-inflammatory mediators during inflammation. The findings are exciting, that pretreatment with Se (4, 8 μM) significantly suppressed the phosphorylation of IκBα, p65, p38 and Erk.

CONCLUSIONS

These results suggest that Se down-regulates inflammatory mediators TNF-α, IL-1β and IL-6 gene expressions via TLR2, NF-κB and MAPK signaling pathway in S. aureus-stimulated bMECs, which may be responsible for the anti-inflammatory effect of Se.

Oxidative stress in sepsis: Pathophysiological implications justifying antioxidant co-therapy

Sepsis is one of the main causes of death among critically ill patients. Sepsis pathogenesis includes infection by gram-negative and gram-positive bacteria, fungi, or both; exacerbated inflammatory response; hypotension, with potential to cause vasodilatory shock; and lesser delivery of oxygen to tissues due to impairment of oxygen utilization by cells. The participation of reactive species and/or free radicals such as nitric oxide (NO), peroxynitrite (ONOO^-), superoxide (O₂^-), hydrogen peroxide (H₂O₂), and hydroxyl radical (OH) has been reported to underlie these effects. Mitochondrial dysfunction is related to loss of inner membrane potential and inhibition of the mitochondrial electron transfer chain and FoF1-adenosine triphosphate-synthase, resulting in cellular energetic failure. In addition, overproduction of NO due to inducible nitric oxide synthase (iNOS) activity has been associated with harmful effects such as general vasodilatation and hypo-responsiveness to therapeutic vasoconstrictor agents. Considering that iNOS expression is regulated by nuclear factor-κB, which may be activated by ROS, antioxidants could inhibit the overexpression of iNOS in sepsis. In line with this, several antioxidants such as vitamins C and E, polyphenols, melatonin, β-glucan, N-acetylcysteine, mitochondrion-targeted antioxidants (MitoQ, MitoE, and peptides associated with dimethyltyrosine), selenium salts, and organoselenium compounds were effective in ameliorating oxidative stress in animal models of sepsis and in a number of clinical trials with septic patients.

Selenium Deficiency Facilitates Inflammation Through the Regulation of TLR4 and TLR4-Related Signaling Pathways in the Mice Uterus

Selenium (Se) is an essential nutritional trace element that affects the development and function of the reproductive system. Endometritis is a reproductive obstacle disease that can seriously reduce the reproductive capacity of animal. To study the effects of dietary Se deficiency on lipopolysaccharide (LPS)-induced mice endometritis, we generated a model of LPS-induced mice endometritis. The Se content in uterine tissues was detected by fluorescence spectrophotometry. The levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR). The extent of phosphorylation of IκBα, NF-κB p65, ERK, JNK, and p38 and the expression of Toll-like receptor 4 (TLR4) were detected with Western blots. The TLR4 messenger RNA (mRNA) was analyzed with qRT-PCR. The results indicated that dietary Se intake significantly influenced Se levels in uterine tissues. The Se-deficient mice model was successfully replicated, and Se deficiency exacerbated uterine tissue histopathology; increased the expression of TNF-α, IL-1β, and IL-6; facilitated the activation of TLR4; and enhanced the phosphorylation of IκBα, p65, ERK, JNK, and p38 in LPS-induced mice endometritis. Also, the effects were inhibited by a supplement of Se. In conclusion, our studies demonstrated that Se deficiency makes mice uterus more prone to inflammation. An appropriate Se supplement could enhance the immune condition of the uterus.

Biological activity of selenorganic compounds at heavy metal salts intoxication

Possible mechanisms of the antitoxic action of organoselenium compounds in heavy metal poisoning have been considered. Heavy metal toxicity associated with intensification of free radical oxidation, suppression of the antioxidant system, damage to macromolecules, mitochondria and the genetic material can cause apoptotic cell death or the development of carcinogenesis. Organic selenium compounds are effective antioxidants during heavy metal poisoning; they exhibit higher bioavailability in mammals than inorganic ones and they are able to activate antioxidant defense, bind heavy metal ions and reactive oxygen species formed during metal-induced oxidative stress. One of promising organoselenium compounds is diacetophenonyl selenide (DAPS-25), which is characterized by antioxidant and antitoxic activity, under conditions including heavy metal intoxication

Ebselen and congeners inhibit NADPH oxidase 2-dependent superoxide generation by interrupting the binding of regulatory subunits

NADPH oxidases (Nox) are a primary source of reactive oxygen species (ROS), which function in normal physiology and, when overproduced, in pathophysiology. Recent studies using mice deficient in Nox2 identify this isoform as a novel target against Nox2-implicated inflammatory diseases. Nox2 activation depends on the binding of the proline-rich domain of its heterodimeric partner p22phox to p47phox. A high-throughput screen that monitored this interaction via fluorescence polarization identified ebselen and several of its analogs as inhibitors. Medicinal chemistry was performed to explore structure-activity relationships and to optimize potency. Ebselen and analogs potently inhibited Nox1 and Nox2 activity but were less effective against other isoforms. Ebselen also blocked translocation of p47phox to neutrophil membranes. Thus, ebselen and its analogs represent a class of compounds that inhibit ROS generation by interrupting the assembly of Nox2-activating regulatory subunits.

The role of selenium in inflammation and immunity: from molecular mechanisms to therapeutic opportunities

Dietary selenium (]Se), mainly through its incorporation into selenoproteins, plays an important role in inflammation and immunity. Adequate levels of Se are important for initiating immunity, but they are also involved in regulating excessive immune responses and chronic inflammation. Evidence has emerged regarding roles for individual selenoproteins in regulating inflammation and immunity, and this has provided important insight into mechanisms by which Se influences these processes. Se deficiency has long been recognized to negatively impact immune cells during activation, differentiation, and proliferation. This is related to increased oxidative stress, but additional functions such as protein folding and calcium flux may also be impaired in immune cells under Se deficient conditions. Supplementing diets with above-adequate levels of Se can also impinge on immune cell function, with some types of inflammation and immunity particularly affected and sexually dimorphic effects of Se levels in some cases. In this comprehensive article, the roles of Se and individual selenoproteins in regulating immune cell signaling and function are discussed. Particular emphasis is given to how Se and selenoproteins are linked to redox signaling, oxidative burst, calcium flux, and the subsequent effector functions of immune cells. Data obtained from cell culture and animal models are reviewed and compared with those involving human physiology and pathophysiology, including the effects of Se levels on inflammatory or immune-related diseases including anti-viral immunity, autoimmunity, sepsis, allergic asthma, and chronic inflammatory disorders. Finally, the benefits and potential adverse effects of intervention with Se supplementation for various inflammatory or immune disorders are discussed.

Ebselen abrogates TNFalpha induced pro-inflammatory response in glioblastoma

We investigated the pro-inflammatory response mediated by TNFalpha in glioblastoma and whether treatment with organoselenium Ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]one) can affect TNFalpha induced inflammatory response. Exposure to TNFalpha increased the expression of pro-inflammatory mediator interleukin IL-6, IL-8, monocyte chemoattractant protein-1 (MCP-1) and cyclooxygenase (COX-2). Treatment with Ebselen abrogated TNFalpha induced increase in pro-inflammatory mediators. Ebselen not only abrogated TNFalpha induced enhanced invasiveness of glioma cells by down-regulating matrix metallo proteinase (MMP-9) and urokinase plasminogen (uPa) activity, but also inhibited glioma cell migration. Treatment with Ebselen also down-regulated the enhanced ROS production of TNFalpha treated glioma cells. In addition, Ebselen induced DNA damage repair signaling response in glioma cells both in the presence and absence of TNFalpha. These studies indicate that together with its known ability to sensitize glioma cell to TNFalpha induced apoptosis, Ebselen can overcome TNFalpha induced pro-inflammatory mediators to prevent a build up of a deleterious pro-inflammatory tumor microenvironment.

Selenium suppresses the activation of transcription factor NF-kappa B and IRF3 induced by TLR3 or TLR4 agonists

Toll-like receptors (TLRs) play an important role in recognition of microbial components and induce innate immune responses by recognizing invading microbial pathogens leading to the activation of the adaptive immune responses. The microbial components trigger the activation of two downstream signaling pathways of TLRs; MyD88- and TRIF-dependent pathways leading to the expression of pro-inflammatory cytokines and type I interferons (IFNs). The MyD88- and TRIF-dependent pathways lead to the activation of NF-kappa B and IRF3 through the activation of IKK-beta and TBK1, respectively. Selenium is an essential trace element nutrient possessing anticarcinogenic properties. Here, we attempted to identify the molecular targets of selenium in TLR signaling pathways. Selenium inhibited NF-kappaB activation induced by poly[I:C] (TLR3 agonist), LPS (TLR4 agonist) or overexpression of MyD88 or IKK-beta which is the key kinase of MyD88-dependent signaling pathway. Selenium inhibited IRF3 activation induced by poly[I:C], LPS or the overexpression of TRIF or TBK1. Selenium also suppressed the expression of COX-2 and iNOS and the endogenous IFN beta mRNA induced by poly[I:C] or LPS. Therefore, our results suggest that selenium can modulate both MyD88- and TRIF-dependent signaling pathways of TLRs leading to decreased inflammatory gene expression.

NF-κB signaling pathway, not IFN-β/STAT1, is responsible for the selenium suppression of LPS-induced nitric oxide production

Upon stimulation of macrophages with lipopolysaccharide (LPS), Toll-like receptor 4 recognizes LPS, leading to expression of inducible nitric oxide synthase (iNOS), via MyD88/NF-kappaB and TRIF/IFN-beta/STAT pathways. Although selenium (Se) was reported to inhibit nitric oxide (NO) production, it is unclear which signaling pathway is inhibited by Se. Here, we investigated how Se inhibits NO production in LPS-stimulated RAW 264.7 cells. When the cells were pretreated with Se for 1 h followed by LPS treatment, iNOS mRNA expression and subsequent NO production declined significantly in a dose-dependent manner. Se inhibited IkappaBalpha degradation in the cytosol and NF-kappaB binding to its recognition site in the nucleus of the LPS-stimulated cells. Meanwhile, Se did not inhibit IFN-beta mRNA induction or STAT1 phosphorylation in the LPS-stimulated cells. These results suggest that Se down-regulates iNOS gene expression and NO production in the LPS-stimulated macrophages through inhibition of the NF-kappaB activation pathway but not the IFN-beta/STAT1 signaling pathway.

A cell-based assay for IkappaBalpha stabilization using a two-color dual luciferase-based sensor

A cell-sensor assay for stabilization of IkappaBalpha was developed in the activated B cell-like diffuse large B-cell lymphoma cell line OCI-Ly3. This cell line expresses known nuclear factor kappaB (NFkappaB) target genes due to high constitutive activity of IkappaB kinase (IKK), which phosphorylates the protein IkappaBalpha leading to proteasomal degradation of IkappaBalpha and activation of NFkappaB. The cell-sensor assay uses green and red light-emitting beetle luciferases, with the green luciferase fused to IkappaBalpha (IkappaBalpha-CBG68) and the red luciferase (CBR) present in its native state. The IkappaBalpha-CBG68 reporter functions as a sensor of IKK and proteasome activity, while CBR serves to normalize for cell number and nonspecific effects. Both reporter constructs were stably integrated and placed under the control of an inducible promoter system, which increased fold responsiveness to inhibitors when assay incubations were performed simultaneous to reporter induction by doxycycline. The assay was miniaturized to a 1,536-well plate format and showed a Z' of 0.6; it was then used to panel 2,677 bioactive compounds by a concentration-response-based screening strategy. The concentration-effect curves for the IkappaBalpha-CBG68 and CBR signals were then used to identify specific stabilizers of IkappaBalpha, such as IKK inhibitors or proteasome inhibitors, which increased the doxycycline-induced rise in IkappaBalpha-CBG68 without affecting the rise in CBR. Known and unexpected inhibitors of NFkappaB signaling were identified from the bioactive collection. We describe here the development and performance of this assay, and discuss the merits of its specific features.

Selenium in Intensive Care (SIC): Results of a prospective randomized, placebo-controlled, multiple-center study in patients with severe systemic inflammatory response syndrome, sepsis, and septic shock*

OBJECTIVE

Sepsis is associated with an increase in reactive oxygen species and low endogenous antioxidative capacity. We postulated that high-dose supplementation of sodium-selenite would improve the outcome of patients with severe sepsis and septic shock.

DESIGN

Prospective randomized, placebo-controlled, multiple-center trial.

SETTING

Eleven intensive care units in Germany.

PATIENTS

Patients were 249 patients with severe systemic inflammatory response syndrome, sepsis, and septic shock and an Acute Physiology and Chronic Health Evaluation (APACHE) III score >70.

INTERVENTIONS

Patients received 1000 microg of sodium-selenite as a 30-min bolus injection, followed by 14 daily continuous infusions of 1000 microg intravenously, or placebo.

MEASUREMENTS AND MAIN RESULTS

The primary end point was 28-day mortality; secondary end points were survival time and clinical course of APACHE III and logistic organ dysfunction system scores. In addition, selenium levels in serum, whole blood, and urine as well as serum glutathione-peroxidase-3 activity were measured. From 249 patients included, 11 patients had to be excluded. The intention-to-treat analysis of the remaining 238 patients revealed a mortality rate of 50.0% in the placebo group and 39.7% in the selenium-treated group (p = .109; odds ratio, 0.66; confidence interval, 0.39-1.1). A further 49 patients had to be excluded before the final analysis because of severe violations of the study protocol. In the remaining 92 patients of the study group, the 28-day mortality rate was significantly reduced to 42.4% compared with 56.7% in 97 patients of the placebo group (p = .049, odds ratio, 0.56; confidence interval, 0.32-1.00). In predefined subgroup analyses, the mortality rate was significantly reduced in patients with septic shock with disseminated intravascular coagulation (n = 82, p = .018) as well as in the most critically ill patients with an APACHE III score > or =102 (>75% quartile, n = 54, p = .040) or in patients with more than three organ dysfunctions (n = 83, p = .039). Whole blood selenium concentrations and glutathione peroxidase-3 activity were within the upper normal range during selenium treatment, whereas they remained significantly low in the placebo group. There were no side effects observed due to high-dose sodium-selenite treatment.

CONCLUSIONS

The adjuvant treatment of patients with high-dose sodium-selenite reduces mortality rate in patients with severe sepsis or septic shock.

REDOX REGULATION BY INTRINSIC SPECIES AND EXTRINSIC NUTRIENTS IN NORMAL AND CANCER CELLS

Cells in multicellular organisms are exposed to both endogenous oxidative stresses generated metabolically and to oxidative stresses that originate from neighboring cells and from other tissues. To protect themselves from oxidative stress, cells are equipped with reducing buffer systems (glutathione/GSH and thioredoxin/thioredoxin reductase) and have developed several enzymatic mechanisms against oxidants that include catalase, superoxide dismutase, and glutathione peroxidase. Other major extrinsic defenses (from the diet) include ascorbic acid, beta-carotene and other carotenoids, and selenium. Recent evidence indicates that in addition to their antioxidant function, several of these redox species and systems are involved in regulation of biological processes, including cellular signaling, transcription factor activity, and apoptosis in normal and cancer cells. The survival and overall well-being of the cell is dependent upon the balance between the activity and the intracellular levels of these antioxidants as well as their interaction with various regulatory factors, including Ref-1, nuclear factor-kappaB, and activating protein-1.

Selenium Compounds Prevent the Effects of Methylmercury on the in Vitro Phosphorylation of Cytoskeletal Proteins in Cerebral Cortex of Young Rats

In this study we investigated the protective ability of the selenium compounds ebselen and diphenyldiselenide against the effect of methylmercury on the in vitro incorporation of 32P into intermediate filament (IF) proteins from the cerebral cortex of 17-day-old rats. We observed that methylmercury in the concentrations of 1 and 5 microM was able to inhibit the phosphorylating system associated with IF proteins without altering the immunocontent of these proteins. Concerning the selenium compounds, diselenide (1, 15, and 50 microM) did not induce alteration of the in vitro phosphorylation of IF proteins. Conversely, 15 microM diselenide was effective in preventing the toxic effects induced by methylmercury. Otherwise, ebselen induced an altered in vitro phosphorylation of the cytoskeletal proteins in a dose-dependent manner. Ebselen at intermediate concentrations (15 and 30 microM) increased the in vitro phosphorylation. However, at low (5 microM) or high (50 and 100 microM) concentrations it was ineffective in altering the cytoskeletal-associated phosphorylating system. Furthermore, 5 microM ebselen presented a protective effect against the action of methylmercury on the phosphorylating system. In conclusion, our results indicate that the selenium compounds ebselen and diselenide present protective actions toward the alterations of the phosphorylating system associated with the IF proteins induced by methylmercury in slices of the cerebral cortex of rats.

Lipopolysaccharides induced increases in Fas ligand expression by Kupffer cells via mechanisms dependent on reactive oxygen species

Fas-Fas ligand (FasL)-dependent pathways exert a suppressive effect on inflammatory responses in immune-privileged organs. FasL expression in hepatic Kupffer cells (KC) has been implicated in hepatic immunoregulation. In this study, modulation of FasL expression of KC by endogenous gut-derived bacterial LPS and the role of reactive oxygen species (ROS) as potential mediators of FasL expression in KC were investigated. LPS stimulation of KC resulted in upstream ROS generation and, subsequently, increased FasL expression and consequent Jurkat cell (Fas-positive) apoptosis. The NADPH oxidase and xanthine oxidase enzymatic pathways appear to be major sources of this upstream ROS generation. Increased FasL expression was blocked by antioxidants and by enzymatic blocking of ROS generation. Exogenous administration of H2O2 stimulated KC FasL expression and subsequent Jurkat cell apoptosis. Intracellular endogenous ROS generation may therefore represent an important signal transduction pathway for FasL expression in KC.

Selenium attenuates lipopolysaccharide-induced oxidative stress responses through modulation of p38 MAPK and NF-kappaB signaling pathways

Lipopolysaccharide (LPS) produces reactive oxygen species (ROS) and nitric oxide (NO) in macrophages. These molecules are involved in inflammation associated with endotoxic shock. Selenium (Se), a biologically essential trace element, modulates the functions of many regulatory proteins involved in signal transduction and affects a variety of cellular activities, including cell growth and survival. We demonstrate that Se attenuated LPS-induced ROS and NO production in murine macrophage cultures in vitro. This Se-decreased production of NO was demonstrated by decreases in both mRNA and protein expression for inducible NO synthase (iNOS). The preventive effects of Se on iNOS were p38 mitogen-activated protein kinase- and nuclear factor-kappaB-dependent. Se specifically blocked the LPS-induced activation of p38 but not that of c-jun-N-terminal kinase and extracellular signal-regulated kinase; the p38-specific pathway was confirmed using p38 inhibitor SB 203580. These results suggest that the mechanism by which Se may act as an anti-inflammatory agent and that Se may be considered as a possible preventive intervention for endotoxemia, particularly in Se-deficient locations. However, the efficacy and safety of Se need to be further investigated, because long-term intake > 0.4 mg Se/day in adults can produce adverse effects.

Ebselen inhibits tumor necrosis factor-alpha-induced c-Jun N-terminal kinase activation and adhesion molecule expression in endothelial cells

Tumor necrosis factor-alpha (TNF-alpha) stimulates expression of endothelial cell (EC) genes that may promote atherosclerosis in part by an activation of mitogen-activated protein (MAP) kinases. Ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one), a selenoorganic compound, is effective for acute ischemic stroke; however, its effect on EC has not yet been elucidated. We examined the effect of ebselen on TNF-alpha-induced MAP kinase activation and adhesion molecule expression in cultured human umbilical vein endothelial cells (HUVEC). Extracellular signal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK) and p38 were rapidly and significantly activated by TNF-alpha in HUVEC. TNF-alpha-induced JNK activation was inhibited by ebselen, whereas ERK1/2 and p38 were not affected. Apoptosis signal-regulated kinase 1 (ASK1) was suggested to be involved in TNF-alpha-induced JNK activation because transfection of kinase-inactive ASK1 inhibited TNF-alpha-induced JNK activation. Ebselen inhibited TNF-alpha-induced TNF receptor-associated factor 2 (TRAF2)-ASK1 complex formation and phosphorylation of stress-activated protein kinase ERK kinase 1 (SEK1), which is an upstream signaling molecule of JNK. Finally, TNF-alpha-induced activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) activation and resultant intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expressions were inhibited by ebselen. Specific inhibitors for JNK and NF-kappaB also inhibited TNF-alpha-induced ICAM-1 and VCAM-1 expressions in HUVEC. These findings suggest that ebselen prevents TNF-alpha-induced EC activation through the inhibition of TRAF2-ASK1-SEK1 signaling pathway, which leads to JNK activation. Inhibition of JNK by ebselen may imply its usefulness for the prevention of atherosclerosis relevant to EC activation.

Diphenyl diselenide protects rat hippocampal slices submitted to oxygen-glucose deprivation and diminishes inducible nitric oxide synthase immunocontent

Diphenyl diselenide (PhSe)2 is an organic selenium compound that has been little studied. In this study we investigated the effects of (PhSe)2 (0.1-3 microM) in a classical model of in vitro brain ischemia, which consists of exposing rat hippocampal slices to oxygen-glucose deprivation (OGD). Hippocampal slices were exposed for 60 min to OGD and the cellular viability (performed by MTT assay) as well as the immunocontent of nitric oxide synthase inducible (iNOS) were evaluated after 180 min of a recovery period. OGD decreased cellular viability by 50% and increased more than twice the immunocontent of iNOS of hippocampal slices. (PhSe)2 (1 and 3 microM) added during OGD and the recovery period abolished both effects. These results demonstrate for the first time the neuroprotective effects of (PhSe)2. Although the selenium analog--ebselen--has been widely used in ischemia models, our results suggest that other selenoorganic compounds could be investigated as pharmacological tools against brain disorders.

Metalloendopeptidase Inhibition Regulates Phosphorylation of p38???Mitogen-Activated Protein Kinase and Nitric Oxide Synthase in Heart After Endotoxemia

We tested the hypothesis that metalloendopeptidase inhibition using phosphoramidon during induction of endotoxemia 24 h later would down-regulate the protein expression of myocardial inducible nitric oxide synthase (iNOS) and phosphorylation of p38-mitogen-activated protein kinase (p38-MAPK). Male Sprague-Dawley rats (350-400 g) were randomly divided into sham-treated and LPS-treated groups (Escherichia. coli lipopolysaccharide [LPS] 2 mg/kg bolus + 2 mg/kg infusion for 30 min). The animals in each group were further subdivided into vehicle- and phosphoramidon (1 mg/kg bolus)-treated subgroups. Blood and heart samples were collected at 2- and 24-h postendotoxemia/phosphoramidon treatment. LPS at 2 h after its administration produced a significant decrease in mean arterial pressure that was blocked by phosphoramidon treatment. LPS at 2 and 24 h produced a significant elevation in the concentration of left ventricular endothelin-1 (ET-1) both in heart and plasma as compared with control group. This LPS-induced left ventricular ET-1 elevation at 24 h was significantly reduced by phosphoramidon. No significant alterations were observed in the myocardial protein expression of preproET-1, iNOS, and eNOS at 2 h post LPS. In 24-h post treatment groups phosphoramidon upregulated the expression of myocardial preproET-1 protein both in control and endotoxemic rat groups. Also, LPS-induced upregulated protein expression of myocardial-inducible nitric oxide synthase and increased levels of nitric oxide byproducts at 24 h were blocked by phosphoramidon. Phosphoramidon inhibited LPS-induced down-regulated expression of myocardial endothelial nitric oxide synthase and upregulated p38-MAPK phosphorylation. These results indicated that inhibition of metalloendopeptidase during induction of endotoxemia could regulate the phosphorylation of myocardial p38-MAPK and iNOS protein expression at 24-h post endotoxemia. We concluded that inhibition of metalloendopeptidases during early endotoxemia not only decreased the biosynthesis of ET-1 in heart locally but also simultaneously down-regulated myocardial protein expression of iNOS and p38-MAPK phosphorylation in the later stage of endotoxemia.

Generation and function of reactive oxygen species in dendritic cells during antigen presentation

Although reactive oxygen species (ROS) have long been considered to play pathogenic roles in various disorders, this classic view is now being challenged by the recent discovery of their physiological roles in cellular signaling. To determine the immunological consequence of pharmacological disruption of endogenous redox regulation, we used a selenium-containing antioxidant compound ebselen known to modulate both thioredoxin and glutaredoxin pathways. Ebselen at 5-20 micro M inhibited Con A-induced proliferation and cytokine production by the HDK-1 T cell line as well as the LPS-triggered cytokine production by XS52 dendritic cell (DC) line. Working with the in vitro-reconstituted Ag presentation system composed of bone marrow-derived DC, CD4(+) T cells purified from DO11.10 TCR-transgenic mice and OVA peptide (serving as Ag), we observed that 1) both T cells and DC elevate intracellular oxidation states upon Ag-specific interaction; 2) ebselen significantly inhibits ROS production in both populations; and 3) ebselen at 5-20 micro M inhibits DC-induced proliferation and cytokine production by T cells as well as T cell-induced cytokine production by DC. Thus, Ag-specific, bidirectional DC-T cell communication can be blocked by interfering with the redox regulation pathways. Allergic contact hypersensitivity responses in BALB/c mice to oxazolone, but not irritant contact hypersensitivity responses to croton oil, were suppressed significantly by postchallenge treatment with oral administrations of ebselen (100 mg/kg per day). These results provide both conceptual and technical frameworks for studying ROS-dependent regulation of DC-T cell communication during Ag presentation and for testing the potential utility of antioxidants for the treatment of immunological disease.

An inducible nitric oxide synthase-luciferase reporter system for in vivo testing of anti-inflammatory compounds in transgenic mice

The inducible NO synthase gene (iNOS) plays a role in a number of chronic and acute conditions, including septic shock and contact hypersensitivity autoimmune diseases, such as rheumatoid arthritis, gastrointestinal disorders, and myocardial ischemia. The iNOS gene is primarily under transcriptional control and is induced in a variety of conditions. The ability to monitor and quantify iNOS expression in vivo may facilitate a better understanding of the role of iNOS in different diseases. In this study, we describe a transgenic mouse (iNos-luc) in which the luciferase reporter is under control of the murine iNOS promoter. In an acute sepsis model produced by injection of IFN-gamma and LPS, we observed an induction of iNOS-driven luciferase activity in the mouse liver. This transgene induction is dose and time dependent and correlated with an increase of liver iNOS protein and iNOS mRNA levels. With this model, we tested 11 compounds previously shown to inhibit iNOS induction in vitro or in vivo. Administration of dexamethasone, epigallocatechin gallate, alpha-phenyl-N-tert-butyl nitrone, and ebselen significantly suppressed iNOS transgene induction by IFN-gamma and LPS. We further evaluated the use of the iNos-luc transgenic mice in a zymosan-induced arthritis model. Intra-articular injection of zymosan induced iNos-luc expression in the knee joint. The establishment of the iNos-luc transgenic model provides a valuable tool for studying processes in which the iNOS gene is induced and for screening anti-inflammatory compounds in vivo.

Adrenomedullin and adrenomedullin binding protein-1 downregulate TNF-alpha in macrophage cell line and rat Kupffer cells

Recent studies have demonstrated that administration of adrenomedullin (AM) and AM binding protein-1 (AMBP-1) maintains cardiovascular stability and reduces mortality in sepsis. However, the mechanism responsible for the beneficial effect of AM/AMBP-1 remains unknown. The aim of this study therefore was to determine whether AM/AMBP-1 directly reduces lipopolysaccharide (LPS)-induced secretion of TNF-alpha from murine macrophage-like cell line RAW 264.7 cells and Kupffer cells isolated from normal rats. TNF-alpha release and gene expression were determined by ELISA and RT-PCR, respectively. The results indicated that LPS increased TNF-alpha production from RAW cells by 38-63-fold in a dose- and time-dependent manner. Although incubation with AM or AMBP-1 alone inhibited LPS-induced TNF-alpha release by 14-22% and 13-22%, respectively, AM and AMBP-1 in combination significantly suppressed TNF-alpha production (by 24-35%). Moreover, the upregulated TNF-alpha mRNA by LPS stimulation was significantly reduced by AM/AMBP-1, but not by AM or AMBP-1 alone. In the Kupffer cells primary culture, AM or AMBP-1 alone inhibited LPS-induced TNF-alpha production by 52% and 44%, respectively. Co-culture with AM/AMBP-1 markedly reduced TNF-alpha production (by 90%). Moreover, AM or AMBP-1 alone decreased TNF-alpha mRNA expression by 41% and 36%, respectively, whereas the combination of AM/AMBP-1 decreased its expression by 63%. These results indicate that AM and AMBP-1 in combination effectively suppress LPS-induced TNF-alpha expression and release especially from primary cultured Kupffer cells, suggesting that the downregulatory effect of AM/AMBP-1 on proinflammatory cytokine TNF-alpha may represent a mechanism responsible for their beneficial effects in preventing inflammatory responses and tissue damage in sepsis.

Kinetics of mitogen-activated protein kinase family in lipopolysaccharide-stimulated mouse Kupffer cells and their role in cytokine production

This study was designed to systemically investigate the kinetics of extracellular signal-regulated kinase (ERK) 1/2, p54 c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinases (MAPKs) in lipopolysaccharide (LPS)-stimulated Kupffer cells (KC) simultaneously at the levels of protein expression, phosphorylation, and kinase activity, respectively, and their role in mediating pro- and anti-inflammatory cytokines. The protein expression, phosphorylation, and activities of these MAPKs in LPS-stimulated primary mouse KCs were determined with SDS-PAGE and western blotting using nonphosphorylated or phosphospecific antibodies or their corresponding substrates. The levels of TNF-alpha and IL-10 in culture supernatants were measured with ELISA kits. The results revealed that LPS stimulation, although not up- or downregulating the protein expression of ERK1/2, p54JNK, and p38 MAPKs in KCs, could induce rapid and significant activation of these kinases, with parallel profiles of changes in both phosphorylation and kinase activities. Although ERK1/2, p54JNK, and p38 kinases in LPS-stimulated KCs have similar kinetics of activation, the activation of ERK1/2 and p38 kinases was the most prominent. Inhibition of p38 MAPK with SB203580 inhibited the production of TNF-alpha and IL-10 by LPS-stimulated KCs, whereas blockade of ERK1/2 with PD98059 could reduce TNF-alpha production, but did not affect IL-10 production. Furthermore, PD98059 and SB203580 had an additive effect on TNF-alpha production, but PD98059 did not augment the SB203580-induced inhibition of IL-10 production. These data indicate that LPS stimulation, although not inducing any change in protein expression, results in rapid activation of ERK1/2, p54JNK, and p38 kinases in KCs, and that they may have different importance in the regulation of pro- and anti-inflammatory responses by LPS-stimulated KCs.

c-Jun N-terminal kinase activation during warm hepatic ischemia/reperfusion injuries in a rat model

Ischemia/reperfusion injuries are a major problem in liver resections and transplantations. Tumor necrosis factor-alpha has been widely investigated as a key mediator in the mechanism of ischemia/reperfusion injury. Upstream signal transduction mechanisms for tumor necrosis factor-alpha have not been well documented. Therefore, we assessed c-Jun N-terminal kinase activation during warm hepatic ischemia/reperfusion injuries in a rat model. Male Wistar rats were subjected to 30 minutes of ischemia followed by reperfusion. Hepatic enzymes, histological examinations, microfluorographs, and tumor necrosis factor-alpha protein production (in the serum and liver tissue) were analyzed during the course of reperfusion. c-Jun N-terminal kinase activity was measured by a radioisotope kinase assay. Ischemia/reperfusion injuries were characterized by an elevation in hepatic enzyme, the histological degeneration of hepatocytes, and an increase in the number of nonviable cells. Moreover, increased endothelial-adherent leukocytes and tumor necrosis factor-alpha protein production were also observed. c-Jun N-terminal kinase activity at 60 minutes after reperfusion was 12.4 times higher than the pre-ischemia level. These results suggest that c-Jun N-terminal kinase may play some role in the mechanism of ischemia/reperfusion injuries.

Ebselen attenuates oxidative stress-induced apoptosis via the inhibition of the c-Jun N-terminal kinase and activator protein-1 signalling pathway in PC12 cells

1: Ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one) is a selenoorganic compound exhibiting both glutathione peroxidase activity and antioxidant activity. Although it has been reported that ebselen is effective for oxidative stress-induced neuronal damage both in vivo and clinically, the precise mechanisms of the efficacy have not yet been elucidated. Thus, we hypothesized that ebselen may affect reactive oxygen species-induced mitogen-activated protein (MAP) kinase activation in cultured PC12 cells. 2: Our findings showed that hydrogen peroxide (H(2)O(2)) stimulated rapid and significant activation of extracellular signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK) and p38 in PC12 cells, which is a model of catecholamine-containing neurons. 3: H(2)O(2)-induced JNK activation was inhibited by ebselen, whereas ERK1/2 and p38 activation by H(2)O(2) were not affected by ebselen. 4: Inhibition by ebselen of H(2)O(2)-induced hydroxyl radical generation in PC12 cells was observed using electron paramagnetic resonance measurements. Ebselen also inhibited H(2)O(2)-induced increases in DNA binding activity of activator protein-1 (AP-1), a downstream transcription factor of JNK, composed of the c-Jun homo/heterodimer. 5: Finally, pretreatment of cells with ebselen resulted in a significant recovery from cell death including apoptosis by H(2)O(2) in PC12 cells. 6 These findings suggest that ebselen attenuates oxidative stress-induced neuronal cell death through the inhibition of the JNK and AP-1 signalling pathway. Thus, inhibition of JNK by ebselen may imply its usefulness for treatment of ischaemic cerebral diseases relevant to neuronal cell death.

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.

Ebselen suppresses late airway responses and airway inflammation in guinea pigs

Although ebselen, a seleno-organic compound, inhibits inflammation in various animal models, its efficacy as an anti-asthma drug remains to be clarified. In this study, we investigated the inhibitory effect of ebselen on a guinea pig asthma model. Ebselen was orally administered at dosages of 1-20 mg/kg 2 h before an ovalbumin (OA) challenge, and then airway responses, airway inflammation, the generation of superoxide, H(2)O(2), and nitrotyrosine, and the induction of inducible nitric oxide synthase (iNOS) were evaluated. Sensitized animals challenged with OA aerosol showed dual airflow limitations, i.e., immediate and late airway responses (IAR and LAR). Ebselen significantly inhibited LAR at dosages greater than 10 mg/kg, but did not inhibit IAR at any dosage. Bronchoalveolar lavage (BAL) examination showed that airway inflammation was significantly suppressed by ebselen at 10 mg/kg. The generation of superoxide and H(2)O(2) occurred on endothelial cells of LAR bronchi, and was inhibited by 10 mg/kg of ebselen. Superoxide generation was inhibited by diphenyleneiodonium chloride (DPI), a NAD(P)H oxidase inhibitor, but not by allopurinol, a xanthine oxidase inhibitor. Immunoreactivities for iNOS and nitrotyrosine were also observed on endothelial cells of LAR bronchi and were abolished in ebselen-treated animals. The present findings suggest that ebselen can be applied as a new therapeutic agent for asthma. The possible mechanisms by which ebselen inhibits LAR likely involve suppression of oxidant formation and iNOS induction in endothelial cells.

Ebselen protects both gray and white matter in a rodent model of focal cerebral ischemia

BACKGROUND AND PURPOSE

The neuroprotective efficacy of an intravenous formulation of the antioxidant ebselen has been comprehensively assessed with specific regard to conventional quantitative histopathology, subcortical axonal damage, neurological deficit, and principal mechanism of action.

METHODS

Transient focal ischemia (2 hours of intraluminal thread-induced ischemia with 22 hours of reperfusion) was induced in the rat. Ebselen (1 mg/kg bolus plus 1 mg/kg per hour IV) or vehicle was administered at the start of reperfusion and continued to 24 hours. Neurological deficit was assessed 24 hours after ischemia. Gray matter damage was evaluated by quantitative histopathology. Axonal damage was determined with amyloid precursor protein immunohistochemistry used as a marker of disrupted axonal flow and Tau-1 immunohistochemistry to identify oligodendrocyte pathology. Oxidative damage was determined by 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 4-hydroxynonenal (4-HNE) immunohistochemistry.

RESULTS

Ebselen significantly reduced the volume of gray matter damage in the cerebral hemisphere (by 53.6% compared with vehicle, P<0.02). Axonal damage was reduced by 46.8% (P<0.002) and the volume of oligodendrocyte pathology was reduced by 60.9% (P<0.005). The neurological deficit score was reduced by 40.7% (P<0.05) and the volume of tissue immunopositive for 8-OHdG and 4-HNE was reduced by 65% (P<0.002) and 66% (P<0.001), respectively, in ebselen-treated animals.

CONCLUSIONS

Delayed (2-hour) treatment with intravenous ebselen significantly reduced gray and white matter damage and neurological deficit associated with transient ischemia. The reduction in tissue displaying evidence of oxidative stress suggests that the major mechanism of action is attenuation of free radical damage.

A selective ROCK inhibitor, Y27632, prevents dimethylnitrosamine-induced hepatic fibrosis in rats

BACKGROUND

p160ROCK is a direct Rho target which mediates Rho-induced assembly of focal adhesions and stress fibers. We previously reported that Rho signaling pathways are involved in the activation of hepatic stellate cells (HSC) in vitro. The aim of the present study was to test the hypothesis that an inhibitor specific for p160ROCK (Y27632) could prevent experimental hepatic fibrosis induced by dimethylnitrosamine (DMN) in rats.

METHODS

Y27632 was given orally at 30 mg/kg daily for 4 weeks after the first injection of DMN. The degree of fibrosis was evaluated by image analysis and also by measurements of collagen and hydroxyproline content in the liver. The expression of alpha-smooth muscle actin (alpha-SMA) in the liver and in the primary cultured HSC was also evaluated. Semi-quantitative RT-PCR was performed to evaluate the expression of type I collagen mRNA in the liver.

RESULTS

Y27632 treatment significantly decreased the occurrence of DMN-induced hepatic fibrosis and reduced the collagen and hydroxyproline content and alpha-SMA expression in the liver. The expression of alpha-SMA in HSC was also suppressed in vitro.

CONCLUSIONS

These findings indicate that inhibitors of the Rho-ROCK pathway might be useful therapeutically in hepatic fibrosis.