Interleukin-10 overexpression mediates phenyl-N-tert-butyl nitrone protection from endotoxemia

Insights into the Antioxidant Mechanism of Newly Synthesized Benzoxazinic Nitrones: In Vitro and In Silico Studies with DPPH Model Radical

Synthetic nitrone spin-traps are being explored as therapeutic agents for the treatment of a wide range of oxidative stress-related pathologies, including but not limited to stroke, cancer, cardiovascular, and neurodegenerative diseases. In this context, increasing efforts are currently being made to the design and synthesis of new nitrone-based compounds with enhanced efficacy. The most researched nitrones are surely the ones related to α-phenyl-tert-butylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) derivatives, which have shown to possess potent biological activity in many experimental animal models. However, more recently, nitrones with a benzoxazinic structure (3-aryl-2H-benzo[1,4]oxazin-N-oxides) have been demonstrated to have superior antioxidant activity compared to PBN. In this study, two new benzoxazinic nitrones bearing an electron-withdrawing methoxycarbonyl group on the benzo moiety (in para and meta positions respect to the nitronyl function) were synthesized. Their in vitro antioxidant activity was evaluated by two cellular-based assays (inhibition of AAPH-induced human erythrocyte hemolysis and cell death in human retinal pigmented epithelium (ARPE-19) cells) and a chemical approach by means of the α,α-diphenyl-β-picrylhydrazyl (DPPH) scavenging assay, using both electron paramagnetic resonance (EPR) spectroscopy and UV spectrophotometry. A computational approach was also used to investigate their potential primary mechanism of antioxidant action, as well as to rationalize the effect of functionalization on the nitrones reactivity toward DPPH, chosen as model radical in this study. Further insights were also gathered by exploring the nitrone electrochemical properties via cyclic voltammetry and by studying their kinetic behavior by means of EPR spectroscopy. Results showed that the introduction of an electron-withdrawing group in the phenyl moiety in the para position significantly increased the antioxidant capacity of benzoxazinic nitrones both in cell and cell-free systems. From the mechanistic point of view, the calculated results closely matched the experimental findings, strongly suggesting that the H-atom transfer (HAT) is likely to be the primary mechanism in the DPPH quenching.

The effect of human umbilical cord blood cells on survival and cytokine production by post-ischemic astrocytes in vitro

Cerebral ischemia induces death of all neural cell types within the region affected by the loss of blood flow. We have shown that administering human umbilical cord blood cells after a middle cerebral artery occlusion in rats significantly reduces infarct size, presumably by rescuing cells within the penumbra. In this study we examined whether the cord blood cells enhanced astrocyte survival in an in vitro model of hypoxia with reduced glucose availability. Primary astrocyte cultures were incubated for 2 h in no oxygen (95% N, 5% CO(2)) and low glucose (1% compared to 4.5%) media. Cord blood mononuclear cells were added to half the cultures at the beginning of hypoxia. Astrocyte viability was determined using fluorescein diacetate/propidium iodide (FDA/PI) labeling and cytokine production by the astrocytes measured using ELISA. In some studies, T cells, B cells or monocytes/macrophages isolated from the cord blood mononuclear fraction with magnetic antibody cell sorting (MACS) were used instead to determine which cellular component of the cord blood mononuclear fraction was responsible for the observed effects. Co-culturing mononuclear cord blood cells with astrocytes during hypoxia stimulated production of IL-6 and IL-10 during hypoxia. The cord blood T cells decreased survival of the astrocytes after hypoxia but had no effect on the examined cytokines. Our data demonstrate that the tested cord blood fractions do not enhance astrocyte survival when delivered individually, suggesting there is either another cellular component that is neuroprotective or an interaction of all the cells is essential for protection.

Intestinal glucose uptake protects liver from lipopolysaccharide and D-galactosamine, acetaminophen, and alpha-amanitin in mice

We have recently observed that oral administration of D-glucose saves animals from lipopolysaccharide (LPS)-induced death. This effect is the likely consequence of glucose-induced activation of the sodium-dependent glucose transporter-1. In this study, we investigated possible hepatoprotective effects of glucose-induced, sodium-dependent, glucose transporter-1 activation. We show that oral administration of D-glucose, but not of either D-fructose or sucrose, prevents LPS-induced liver injury, as well as liver injury and death induced by an overdose of acetaminophen. In both of these models, physiological liver morphology is maintained and organ protection is confirmed by unchanged levels of the circulating markers of hepatotoxicity, such as alanine transaminase or lactate dehydrogenase. In addition, D-glucose was found to protect the liver from alpha-amanitin-induced liver injury. In this case, in contrast to the previously described models, a second signal had to be present in addition to glucose to achieve protective efficacy. Toll-like receptor 4 stimulation that was induced by low doses of LPS was identified as such a second signal. Eventually, the protective effect of orally administered glucose on liver injury induced by LPS, overdose of acetaminophen, or alpha-amanitin was shown to be mediated by the anti-inflammatory cytokine interleukin-10. These findings, showing glucose-induced protective effects in several animal models of liver injury, might be relevant in view of possible therapeutic interventions against different forms of acute hepatic injury.

Magnolol attenuates sepsis-induced gastrointestinal dysmotility in rats by modulating inflammatory mediators

AIM: To investigate the protective effects of magnolol on sepsis-induced inflammation and intestinal dysmotility.

METHODS: Sepsis was induced by a single intraperitoneal injection of lipopolysaccharide (LPS). Male Wistar rats were randomly assigned to one of three treatment groups: magnolol prior to LPS injection (LPS/Mag group); vehicle prior to LPS injection (LPS/Veh group); vehicle prior to injection of saline (Control/Veh). Intestinal transit and circular muscle mechanical activity were assessed 12 h after LPS injection. Tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10), monocyte chemoattractant protein-1 (MCP-1) and inducible nitric oxide synthase (iNOS) mRNA in rat ileum were studied by RT-PCR 2 h after LPS injection. Nuclear factor-κB (NF-κB) activity in the intestine was also investigated at this time using electrophoretic mobility shift assay. In addition, antioxidant activity was determined by measuring malondialdehyde (MDA) concentration and superoxide dismutase (SOD) activity in the intestine 2 h after LPS injection.

RESULTS: Magnolol significantly increased intestinal transit and circular muscle mechanical activity in LPS-treated animals. TNF-α, MCP-1 and iNOS mRNA expression in the small intestine were significantly reduced after magnolol treatment in LPS-induced septic animals, compared with untreated septic animals. Additionally, magnolol significantly increased IL-10 mRNA expression in septic rat ileum. Magnolol also significantly suppressed NF-κB activity in septic rat intestine. In addition, magnolol significantly decreased MDA concentration and increased SOD activity in rat ileum.

CONCLUSION: Magnolol prevents sepsis-induced suppression of intestinal motility in rats. The potential mechanism of this benefit of magnolol appears to be modulation of self-amplified inflammatory events and block of oxidative stress in the intestine.

A New Amphiphilic Derivative,N-{[4-(Lactobionamido)methyl]benzylidene}- 1,1-dimethyl-2-(octylsulfanyl)ethylamineN-Oxide, Has a Protective Effect Against Copper-Induced Fulminant Hepatitis inLong–Evans Cinnamon Rats at an Extremely Low Concentration Compared with Its Original Formα-Phenyl-N-(tert-butyl) Nitrone

An amphiphilic alpha-phenyl-N-(tert-butyl) nitrone (PBN) derivative, N-{[4-(lactobionamido)methyl]benzylidene}-1,1-dimethyl-2-(octylsulfanyl)ethylamine N-oxide (LPBNSH), newly synthesized from its original form PBN in hopes of clinical use, was intraperitoneally administered to Long-Evans Cinnamon (LEC) rats every 2 days at the concentrations of 0.1, 0.5, 1.0, and 2.0 mg/kg. We found that LPBNSH protected against copper-induced hepatitis with jaundice in LEC rats at concentrations of 0.1 and 0.5 mg/kg, which were extremely low compared with that of PBN. It also effectively prevented the loss of body weight, reduced the death rate, and suppressed the increase in serum aspartate aminotransferase and alanine aminotransferase values arising from fulminant hepatitis with jaundice at the same concentrations. Similar results were observed when PBN was administered at the concentration of 150 mg/kg. Immunohistochemical analysis of 8-hydroxy-2'-deoxyguanosine and measurement of thiobarbituric acid-reactive substances in the liver showed that LPBNSH largely suppressed the formation of these oxidative products at same concentrations. No difference in the abnormal accumulation of copper in the liver between the LPBNSH administered and control groups was observed. From these results, it was concluded that LPBNSH exhibited liver-protective effects against fulminant hepatitis with jaundice at ca. 1/1000, 500 the molar concentration of PBN and, therefore, was clinically promising.

STRESS-INDUCED IMMUNE CONDITIONING AFFECTS THE COURSE OF EXPERIMENTAL PERITONITIS

Septic patients show individually different courses of disease that are hard to predict. Little is known about preconditioning influences that may render one person liable to have overwhelming hyperinflammatory response syndrome (systemic inflammatory response syndrome) and another from compensatory anti-inflammatory response syndrome. Here, we show in a murine model that chronic psychological stress before the onset of polymicrobial peritonitis influences the balance between both types of immune response. Chronically stressed mice which had increased lymphocyte apoptosis, severe functional lymphocyte defects, and an anti-inflammatory cytokine bias had a reduced mortality rate during the continuous outflow of gut content in the hyperinflammatory sepsis model of colon ascendens stent peritonitis. In contrast, they had enhanced long-lasting bacterial dissemination in a sepsis model of mild cecal ligation and puncture. Chronic stress therefore is an important preconditioning factor in the individuals' ability to cope with systemic infections after abdominal surgery. It ameliorates lethal shock responses but reduces the capacity to eradicate bacterial infection during mild peritonitis.

Differential nephron HO-1 expression following glomerular epithelial cell injury

BACKGROUND

In proteinuria of glomerular origin there is upregulation of heme-oxygenase (HO), the rate-limiting enzyme of heme degradation, in the nephron in a segment-specific manner. To better characterize this phenomenon, we employed a model of proteinuria resulting from disruption of the glomerular capillary permeability barrier to protein by administration of the glomerular epithelial cell toxin puromycin aminonucleoside (PAN) to rats. In this model, we assessed nephron distribution of the expression of the inducible HO isoform, HO-1, and the role of free radicals in modulating HO-1 expression.

METHODS

Rats were injected with either vehicle (dimethyl sulfoxide) or PAN or the spin trap free radical stabilizer alpha-phenyl-N-tert butyl nitrone (PBN), or with both PAN and PBN. Ten days following the PAN injection, urine protein, creatinine, nitric oxide (NO) and malonyldialdehyde (MDA) were measured. Kidney sections and protein lysates were assessed for changes in HO-1 expression by immunohistochemistry and Western blot analysis.

RESULTS

In control animals (DMSO or PBN alone) there was no proteinuria and very weak or absent HO-1 staining in nephron segments. PAN treatment induced proteinuria and increased urine MDA excretion. In these animals, there was a robust HO-1 expression mainly in tubules and in glomerular parietal but not visceral epithelial cells. Unilateral ureteral obstruction to interrupt glomerular filtration in animals treated with PAN abrogated tubular HO-1 expression in the kidney ipsilateral to the obstruction. Administration of PBN to PAN-treated animals reduced proteinuria and MDA excretion while it markedly augmented tubular HO-1 expression. This augmentation was prominent in tubular cells of the inner cortex/outer medulla.

CONCLUSIONS

These observations indicate that upregulation of nephron HO-1 following disruption of the glomerular permeability barrier occurs at sites downstream of this barrier and is mediated by a filtered HO-1 inducer(s). Scavenging of free radicals potentiates the effect of this inducer and unmasks nephron segments most and least capable of upregulating HO-1.

Analysis of gene expression in apoptosis of human lymphoma U937 cells induced by heat shock and the effects of α-phenyl N-tert-butylnitrone (PBN) and its derivatives

Hyperthermia, a modality of cancer therapy, has been known as a stress to induce apoptosis. However, the molecular mechanism of heat shock-induced apoptosis, especially on roles of intracellular oxidative stress, is not fully understood. First, when human lymphoma U937 cells were treated with heat shock (44 degrees C, 30 min), the fraction of apoptosis, revealed by phosphatidylserine externalization, increased gradually and peaked at 6 hr after the treatment. In contrast, intracellular superoxide formation increased early during the heat shock treatment and peaked at 30 min after the treatment. When the cells were treated with heat shock in the presence of alpha -phenyl-N-tert-butylnitrone (PBN) and its derivatives, which are potent antioxidants, the DNA fragmentation was inhibited in an order according to the agents' hydrophobicity. PBN showing the highest inhibitory effects suppressed not only intracellular superoxide formation but also various apoptosis indicators. cDNA microarray was employed to analyze gene expression associated with heat shock-induced apoptosis, and the time-course microarray analysis revealed 5 groups showing changes in their pattern of gene expression. Among these genes, c-jun mRNA expression showed more than 40 fold increase 2 hr after heat treatment. The expression level of c-jun mRNA verified by quantitative real-time PCR was about 20 fold increase, and c-jun expression was similarly suppressed by PBN and its derivatives. These results suggest that the change of c-jun expression is an excellent molecular marker for apoptosis mediated by intracellular oxidative stress induced by heat shock.

Preconditioning: evolution of basic mechanisms to potential therapeutic strategies

Preconditioning describes the phenomenon by which a traumatic or stressful stimulus confers protection against subsequent injury. Originally recognized in dog heart subjected to ischemic challenges, preconditioning has been demonstrated in multiple species, can be induced by various stimuli, and is applicable in different organ systems. Tremendous progress has been made elucidating the signal transduction cascade of preconditioning. Preconditioning represents a potent tissue-protective condition, and mechanistic understanding may allow safe clinical application. This review recalls the history of preconditioning and how it relates to the history of the investigation of endogenous adaptation; summarizes the current mechanistic understanding of acute preconditioning; outlines the signal transduction cascade leading to the development of delayed preconditioning; discusses preconditioning in noncardiac tissue; and explores the potential of using preconditioning clinically.

MAGNOLOL ALTERS THE COURSE OF ENDOTOXIN TOLERANCE AND PROVIDES EARLY PROTECTION AGAINST ENDOTOXIN CHALLENGE FOLLOWING SUBLETHAL HEMORRHAGE IN RATS

The endotoxin tolerance induced by sublethal hemorrhage (SLH) is associated with an initial surge of proinflammatory cytokines such as TNF-alpha. Magnolol, a potent antioxidative herb, is hypothesized to suppress TNF-alpha production after SLH and to alter or attenuate subsequent endotoxin tolerance. A prospective, randomized experimental study was performed. Male Sprague-Dawley rats were randomly segregated into one of four groups. Rats in the Sham/Veh and Sham/Mag groups received a sham operation for SLH and treatment with vehicle or magnolol, respectively. Rats in the SLH/Veh and SLH/Mag groups received SLH and treatment with vehicle or magnolol, respectively. Animals were subjected to endotoxin challenge (EC) at 12, 24, or 36 h after these procedures. Cytokines (TNF-alpha and IL-10), lipid peroxidation, and superoxide dismutase (SOD) activity were measured in lung tissue following SLH. Plasma cytokines were assessed after SLH or EC at different time points, and survival analyses were performed after EC. Plasma and tissue TNF-alpha increased after SLH; this increase was significantly suppressed by magnolol. Additionally, a significant increase in plasma and tissue IL-10 after SLH was observed in the SLH/Mag group. Lipid peroxidation and SOD activity increased after SLH; magnolol suppressed the lipid peroxidation but not the SOD activity. If EC was performed 12 or 24 h after SLH, greater survival with decreased TNF-alpha and increased IL-10 in plasma was observed in the SLH/Mag group. If EC was performed 24 or 36 h after SLH, greater survival with decreased plasma TNF-alpha was observed in the SLH/Veh group. In conclusion, magnolol induces an antiinflammatory response and provides early protection against EC following SLH; however, magnolol attenuates the protraction of endotoxin tolerance and inhibits late protection against EC following SLH.

PCT-233, a novel modulator of pro- and anti-inflammatory cytokine production

Plant extracts have been implicated in various immunoregulatory effects that are poorly understood. Thus, we investigated the modulatory activity of PureCell Complex (PCT)-233, an active molecular complex from mesophyll tissue of Spinacia oleacea on the inflammatory process. Alveolar macrophages (AM) were treated with PCT-233 and/or budesonide, a well-known anti-inflammatory agent, before or after being stimulated with lipopolysaccharides (LPS). Pro- and anti-inflammatory cytokine production, tumour necrosis factor (TNF) and interleukin (IL)-10, respectively, were measured in cell-free supernatants at different times after the treatment. PCT-233 increased unstimulated AM release of both TNF and IL-10, whereas heat- and light-inactivated PCT-233 stimulated only the release of TNF without affecting IL-10 production, suggesting that different mechanisms are involved in the modulation of TNF and IL-10 release by PCT-233. The presence of LPS did not modify PCT-233-stimulated TNF production, but the ratio TNF/IL-10 production by LPS-stimulated AM was reduced significantly in the presence of PCT-233. Pretreatment of AM with PCT-233 and budesonide before LPS stimulation reduced TNF production at both protein and mRNA levels, whereas IL-10 production was increased. Moreover, TNF/IL-10 ratio was reduced further with the combination PCT-233/budesonide. Interestingly, AM treatment with PCT-233 and budesonide 18 h after LPS stimulation did not modulate TNF release significantly but it did increase IL-10 production, and a synergistic effect was observed with the combination PCT-233/budesonide. These exciting data suggest that PCT-233 possesses some anti-inflammatory properties, even when added during the inflammatory process, and could potentiate the effect of other anti-inflammatory agents.

The Genetic Background of Hypertensive, Septic Rats Determines Outcome Improvement With Antibiotic and G-CSF Prophylaxis

Hypertension is proposed as a risk factor among others (high age, diabetes mellitus, and pre- and intraoperative bleeding) for adverse outcomes, such as severe infections, leading to sepsis and to multiple organ failure as the most deleterious complication. Hypertension was modeled with spontaneous hypertensive rats (SHR) and Dahl salt-sensitive (DS) rats and the infective complication by polymicrobial, peritoneal contamination, and infection (PCI). The concept of clinic modeling randomized trials was used to simulate clinical complexity, including a relevant antibiotic prophylaxis in combination with granulocyte-colony stimulating factor (G-CSF) and clinical trial conditions. Outcome parameters were: survival, systemic cytokines (protein), and organ-specific cytokine levels (mRNA). With low complexity (no prophylaxis), 28% of the animals in the Wistar and 50% in the SHR group survived (P=0.17). Tumor necrosis factor-alpha levels were lower in the liver of SHR vs. Wistar rats with PCI (P<0.01). The anti-inflammatory cytokine interleukin (IL)-10 was expressed on a higher level in SHR with PCI compared with Wistar rats (P<0.01). With increased complexity (antibiotic and G-CSF prophylaxis) the survival rate was increased from 50% in Wistar rats to 89% in SHR (P<0.01) and the mRNA expression of IL-6 was decreased in the kidney of SHR (P<0.05). Survival rate was 44% in the DS rats vs. 67% of the Wistar rats (P=0.18). The mRNA expression of tumor necrosis factor-alpha and IL-10 was reduced (P<0.01) by pretreatment in the liver of DS rats with PCI. The hypertensive, genetically distinct SHR and DS rats express different patterns of pro- and anti-inflammatory cytokine levels after PCI. G-CSF and antibiotic prophylaxis increases only in SHR survival and decreases IL-6 mRNA expression in the kidney significantly.

Magnolol alters cytokine response after hemorrhagic shock and increases survival in subsequent intraabdominal sepsis in rats

Magnolol is a Chinese herb that has potent antioxidant effects. This study evaluated the effect of magnolol in the treatment of severe injury using a two-hit model in Sprague-Dawley rats. Hemorrhagic shock followed by resuscitation was performed. Intra-abdominal sepsis was induced by cecal ligation puncture. The rats were randomly segregated into the following three groups: group 1 (sham group) rats were sham-operated; group 2 (untreated group) rats received hemorrhagic shock and resuscitation and cecal ligation puncture 24 h later; and group 3 (treated group) rats were treated with magnolol and subjected to the same procedures as group 2. Plasma cytokine levels and tissue cytokine contents of lung, including tumor necrosis factor alpha (TNFalpha) and interleukin (IL)-10 were assayed after hemorrhagic shock and sepsis. Pulmonary injury study was performed using Evans blue dye and survival analysis was performed after development of sepsis. Plasma and tissue TNFalpha levels increased after hemorrhagic shock. Magnolol treatment blunted the TNFalpha levels in plasma and tissue. The plasma IL-10 level increased after hemorrhagic shock, whereas the tissue level of IL-10 did not change. Magnolol treatment did not alter the plasma level of IL-10 but did increase tissue level. After sepsis, TNFalpha levels in both plasma and tissue of magnolol-treated animals were significantly lower than those in untreated animals, whereas plasma and tissue IL-10 levels were not significantly different between treated and untreated groups. Pulmonary injury study showed that magnolol-treated rats had decreased pulmonary permeability after the onset of sepsis. Survival analysis showed that survival rate was significantly higher in the treated group. In conclusion, magnolol modifies the cytokine response after hemorrhagic shock and resuscitation; the proinflammatory cytokine response is suppressed. The modified cytokines response induced by magnolol may result in decreased tissue injury and increased survival in subsequent intra-abdominal sepsis.

Antioxidant amplifies antibiotic protection in the cecal ligation and puncture model of microbial sepsis through interleukin-10 production

Preadministration of antioxidants such as pyrrolidine dithiocarbamate (PDTC) and phenyl N-tert-butyl nitrone (PBN) protects animals from lethality in sepsis models. However, the requirement of preadministration greatly diminishes the clinical significance of these studies. Although the synthetic antioxidant PBN has been shown to effectively protect rodents from lethality in endotoxemia (lipopolysaccharide [LPS] model), preliminary screening indicates that pre- or postadministration of PBN does not protect in the rat cecal ligation and puncture (CLP) model. We show in this report that in a rat CLP model, the administration of PBN (150 mg/kg, 30 min after CLP) followed by the antibiotic imipenem (IMP; 10 mg/kg, 1 h after CLP) significantly increased survival compared with other single treatment groups. Previously, we have shown that PBN's protection in a rat LPS model is mediated by the overproduction of the anti-inflammatory cytokine interleukin (IL)-10. We show in this study that the increase in survival found in the PBN + IMP-treated group was abrogated by immunoneutralization with anti-IL-10 antibody, indicating that endogenous IL-10 is an effective protective factor. Plasma LPS levels were shown to be elevated after imipenem treatment, and the increased LPS level could have assisted to overproduce endogenous IL-10, as in the case of the PBN-treated LPS model. Statistical analysis indicated that the increase of IL-10 in PBN + IMP-treated group at early time period has significant association to the improvement of survival.