Beneficial effects of tempol, a membrane-permeable radical scavenger, on the multiple organ failure induced by zymosan in the rat

Hippo pathway activated by circulating reactive oxygen species mediates cardiac diastolic dysfunction after acute kidney injury

Acute kidney injury (AKI) can cause distal cardiac dysfunction; however, the underlying mechanism is unknown. Oxidative stress is proved prominent in AKI-induced cardiac dysfunction, and a possible bridge role of oxidative-stress products in cardio-renal interaction has been reported. Therefore, this study aimed to investigate the critical role of circulating reactive oxygen species (ROS) in mediating cardiac dysfunction after bilateral renal ischemia-reperfusion injury (IRI). We observed the diastolic dysfunction in the mice following renal IRI, accompanied by reduced ATP levels, oxidative stress, and branched-chain amino acids (BCAA) accumulation in the heart. Notably, ROS levels showed a sequential increase in the kidneys, circulation, and heart. Treatment with tempol, an ROS scavenger, significantly restored cardiac diastolic function in the renal IRI mice, corroborating the bridge role of circulating ROS. Accumulating evidence has identified oxidative stress as upstream of Mst1/Hippo in cardiac injury, which could regulate the expression of downstream genes related to mitochondrial quality control, leading to lower ATP, higher ROS and metabolic disorder. To verify this, we examined the activation of the Mst1/Hippo pathway in the heart of renal IRI mice, which was alleviated by tempol treatment as well. In vitro, analysis revealed that Mst1-knockdown cardiomyocytes could be activated by hydrogen peroxide (H2O2). Analysis of Mst1-overexpression cardiomyocytes confirmed the critical role of the Mst1/Hippo pathway in oxidative stress and BCAA dysmetabolism. Therefore, our results indicated that circulating ROS following renal IRI activates the Mst1/Hippo pathway of myocardium, leading to cardiac oxidative stress and diastolic dysfunction. This finding provides new insights for the clinical exploration of improved treatment options for cardiorenal syndrome.

Rebalancing NOX2/Nrf2 to limit inflammation and oxidative stress across gut-brain axis in migraine

Migraine is one of the most common neurological illnesses, and it is characterized by complicated neurobiology. It was confirmed the influence of inflammation and oxidative stress in migraines and also in distal organs such as the intestine. Indeed, the constant bidirectional communication between the Central Nervous System (CNS) and the gastrointestinal (GI) tract, known as the gut-brain axis, has become an attractive target involved in different human disorders. Herein, we explored the role of NADPH oxidase 2 (NOX2) in nitroglycerin (NTG)-induced migraine in mice models to discover the mechanism by which, during migraine attack, oxidative stress is sustained within trigeminal neurons and GI. Considering the inverse relationship between NOX2 and Nrf2, Nrf2 upregulation seems to be a promising approach to decrease NOX2 expression and consequently limit oxidative stress and inflammation spread in neurological and non-neurological diseases. With this aim, we exploited tempol's Nrf2-inducer ability to better understand the involvement of Nrf2/NOX2 axis in migraine and associated GI comorbidities. Behavioral tests confirmed that tempol, in a dose-dependent manner, moderated clinical signs of migraine and abdominal pain. Moreover, we demonstrated that the decrease in migraine-related symptomatology was strongly linked to the modulation of Nrf2/NOX2 signaling pathway in the brain and colon. In the brain, the rebalancing of Nrf2/NOX2 prevented neuronal loss, decreased glia reactivity while inhibiting NF-κB and NLRP3 inflammasome activation. In the colon, Nrf2 upregulation and consequent NOX2 decrease reduced the histological damage, mast cells infiltration as well as tumor necrosis factor (TNF)-α and interleukin (IL)-1β release. Furthermore, the attenuation of inflammation and oxidative stress led to the restoration of the intestinal barrier through TJs replacement. Taken as a whole, data suggested that the regulation of Nrf2/NOX2 balance is a successful way to reduce neurological and related intestinal impairments during migraine and could be of relevance for migraine-like attacks in humans.

The Cellular and Organismal Effects of Nitroxides and Nitroxide-Containing Nanoparticles

Nitroxides are stable free radicals that have antioxidant properties. They react with many types of radicals, including alkyl and peroxyl radicals. They act as mimics of superoxide dismutase and stimulate the catalase activity of hemoproteins. In some situations, they may exhibit pro-oxidant activity, mainly due to the formation of oxoammonium cations as products of their oxidation. In this review, the cellular effects of nitroxides and their effects in animal experiments and clinical trials are discussed, including the beneficial effects in various pathological situations involving oxidative stress, protective effects against UV and ionizing radiation, and prolongation of the life span of cancer-prone mice. Nitroxides were used as active components of various types of nanoparticles. The application of these nanoparticles in cellular and animal experiments is also discussed.

Subcellular delivery of lipid nanoparticles to endoplasmic reticulum and mitochondria

Primarily responsible for the biogenesis and metabolism of biomolecules, endoplasmic reticulum (ER) and mitochondria are gradually becoming the targets of therapeutic modulation, whose physiological activities and pathological manifestations determine the functional capacity and even the survival of cells. Drug delivery systems with specific physicochemical properties (passive targeting), or modified by small molecular compounds, polypeptides, and biomembranes demonstrating tropism for ER and mitochondria (active targeting) are able to reduce the nonselective accumulation of drugs, enhancing efficacy while reducing side effects. Lipid nanoparticles feature high biocompatibility, diverse cargo loading, and flexible structure modification, which are frequently used for subcellular organelle-targeted delivery of therapeutics. However, there is still a lack of systematic understanding of lipid nanoparticle-based ER and mitochondria targeting. Herein, we review the pathological significance of drug selectively delivered to the ER and mitochondria. We also summarize the molecular basis and application prospects of lipid nanoparticle-based ER and mitochondria targeting strategies, which may provide guidance for the prevention and treatment of associated diseases and disorders. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Biology-Inspired Nanomaterials > Lipid-Based Structures Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Effect of Tempol, a Membrane-Permeable Free Radical Scavenger, on In Vitro Model of Eye Inflammation on Rabbit Corneal Cells

Purpose: Inflammatory corneal diseases such as bacterial keratitis provoke severe injury to the visual functions and physical structure, leading to opaqueness, wounding, damage to the cornea, and even long-lasting vision loss. Usually antioxidant substances have been of great attention as candidate therapies in the management of keratitis in both humans and animals. Based on the findings, the aim of our research was to examine the effects of Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a membrane-permeable free radical scavenger with exclusive antioxidant properties, on in vitro model of eye inflammation of rabbit corneal cells stimulated with lipopolysaccharide (LPS) (Seruminstitute Rabbit Cornea). Methods: The cells were pretreated with Tempol and incubated with LPS for 24 h. LPS stimulation triggered increased cellular mortality, oxidative stress, cytokine levels expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, and also enhanced prostaglandin E₂ (PGE₂) levels and cyclooxygenase-2 (COX-2) expression. Results: Pretreatment with Tempol (3 mM) significantly increased cell viability and antioxidant activity as well as decreased reactive oxygen species production, cytokines, PGE₂ levels, and COX-2 expression. Conclusions: Taken together, Tempol could be a new therapeutic strategy for management of ocular inflammatory disorders for clinical and veterinary use.

Metabolic Resuscitation Strategies to Prevent Organ Dysfunction in Sepsis

Significance: Sepsis is the main cause of death among patients admitted to the intensive care unit. As current treatment is limited to antimicrobial therapy and supportive care, mortality remains high, which warrants efforts to find novel therapies. Recent Advances: Mitochondrial dysfunction is emerging as a key process in the induction of organ dysfunction during sepsis, and metabolic resuscitation might reveal to be a novel cornerstone in the treatment of sepsis. Critical Issues: Here, we review novel strategies to maintain organ function in sepsis by precluding mitochondrial dysfunction by lowering energetic demand to allow preservation of adenosine triphosphate-levels, while reducing free radical generation. As the most common strategy to suppress metabolism, that is, cooling, does not reveal unequivocal beneficial effects and may even increase mortality, caloric restriction or modulation of energy-sensing pathways (i.e., sirtuins and AMP-activated protein kinase) may offer safe alternatives. Similar effects may be offered when mimicking hibernation by hydrogen sulfide (H₂S). In addition H₂S may also confer beneficial effects through upregulation of antioxidant mechanisms, similar to the other gasotransmitters nitric oxide and carbon monoxide, which display antioxidant and anti-inflammatory effects in sepsis. In addition, oxidative stress may be averted by systemic or mitochondria-targeted antioxidants, of which a wide range are able to lower inflammation, as well as reduce organ dysfunction and mortality from sepsis. Future Directions: Mitochondrial dysfunction plays a key role in the pathophysiology of sepsis. As a consequence, metabolic resuscitation might reveal to be a novel cornerstone in the treatment of sepsis.

Nitroxides as Antioxidants and Anticancer Drugs

Nitroxides are stable free radicals that contain a nitroxyl group with an unpaired electron. In this paper, we present the properties and application of nitroxides as antioxidants and anticancer drugs. The mostly used nitroxides in biology and medicine are a group of heterocyclic nitroxide derivatives of piperidine, pyrroline and pyrrolidine. The antioxidant action of nitroxides is associated with their redox cycle. Nitroxides, unlike other antioxidants, are characterized by a catalytic mechanism of action associated with a single electron oxidation and reduction reaction. In biological conditions, they mimic superoxide dismutase (SOD), modulate hemoprotein’s catalase-like activity, scavenge reactive free radicals, inhibit the Fenton and Haber-Weiss reactions and suppress the oxidation of biological materials (peptides, proteins, lipids, etc.). The use of nitroxides as antioxidants against oxidative stress induced by anticancer drugs has also been investigated. The application of nitroxides and their derivatives as anticancer drugs is discussed in the contexts of breast, hepatic, lung, ovarian, lymphatic and thyroid cancers under in vivo and in vitro experiments. In this article, we focus on new natural spin-labelled derivatives such as camptothecin, rotenone, combretastatin, podophyllotoxin and others. The applications of nitroxides in the aging process, cardiovascular disease and pathological conditions were also discussed.

Modulating inflammation and neuroprotection in multiple sclerosis

Multiple sclerosis (MS) is a neurological disorder of the central nervous system with a presentation and disease course that is largely unpredictable. MS can cause loss of balance, impaired vision or speech, weakness and paralysis, fatigue, depression, and cognitive impairment. Immunomodulation is a major target given the appearance of focal demyelinating lesions in myelin-rich white matter, yet progression and an increasing appreciation for gray matter involvement, even during the earliest phases of the disease, highlights the need to afford neuroprotection and limit neurodegenerative processes that correlate with disability. This review summarizes key aspects of MS pathophysiology and histopathology with a focus on neuroimmune interactions in MS, which may facilitate neurodegeneration through both direct and indirect mechanisms. There is a focus on processes thought to influence disease progression and the role of oxidative stress and mitochondrial dysfunction in MS. The goals and efficacy of current disease-modifying therapies and those in the pipeline are discussed, highlighting recent advances in our understanding of pathways mediating disease progression to identify and translate both immunomodulatory and neuroprotective therapeutics from the bench to the clinic.

Protective Effect of Tempol on Acute Kidney Injury Through PI3K/Akt/Nrf2 Signaling Pathway

BACKGROUND/AIMS

Tempol is a protective antioxidant against ischemic injury in many animal models. The molecular mechanisms are not well understood. Nuclear factor erythroid 2-related factor (Nrf2) is a master transcription factor during oxidative stress, which is enhanced by activation of protein kinase C (PKC) pathway. Another factor, tubular epithelial apoptosis, is mediated by activation of phosphoinositide 3-kinase (PI3K)/protein kinase B (PKB, Akt) signaling pathway during renal ischemic injury. We tested the hypothesis that tempol activates PKC or PI3K/Akt/Nrf2 pathways to transcribe many genes that coordinate endogenous antioxidant defense.

METHODS

The right renal pedicle was clamped for 45 minutes and the left kidney was removed to study renal ischemia/reperfusion (I/R) injury in C57BL/6 mice. The response was assessed from serum parameters, renal morphology and renal expression of PKC, phosphorylated-PKC (p-PKC), Nrf2, heme oxygenase-1 (HO-1), Akt, phosphorylated-Akt (p-Akt), pro-caspase-3 and cleaved caspase-3 in groups of sham and I/R mice given vehicle, or tempol (50 or 100 mg/kg, intraperitoneal injection).

RESULTS

The serum malondialdehyde (MDA, marker of reactive oxygen species) doubled and the BUN and creatinine increased 5- to 10-fold after I/R injury. Tempol (50 or 100 mg/kg) prevented the increases in MDA but only tempol (50 mg/kg) lessened the increases in BUN and creatinine and moderated the acute tubular necrosis. I/R did not change expression of PKC or p-PKC but reduced renal expression of Nrf2, p-Akt, HO-1 and pro-caspase-3 and increased cleaved caspase-3. Tempol (50 mg/kg) prevented these changes produced by I/R whereas tempol (100 mg/kg) had lesser or inconsistent effects.

CONCLUSION

Tempol (50 mg/kg) prevents lipid peroxidation and attenuates renal damage after I/R injury. The beneficial pathway apparently is not dependent on upregulation or phosphorylation of PKC, at lower tempol doses, does implicate upregulation of Akt with expression of Nrf2 that could account for the increase in the antioxidant gene HO-1 and a reduction in the cleavage of the cellular damage marker pro-caspase-3.

Transcriptional regulation of renal dopamine D1 receptor function during oxidative stress

There exists a strong link between oxidative stress, renal dopaminergic system, and hypertension. It is reported that reactive oxygen species attenuate renal proximal tubular dopamine receptor (D1R) function, which disrupts sodium regulation and leads to hypertension. However, the mechanisms for renal D1R dysfunction are not clear. We investigated the role of redox-sensitive transcription factors AP1 and SP3 in transcriptional suppression of D1R gene and subsequent D1R signaling. Human kidney proximal tubular cells were treated with a pro-oxidant l-buthionine sulfoximine (BSO) with and without an antioxidant tempol. In human kidney cells, BSO caused oxidative stress and reduced D1R mRNA and membrane receptor expression. Incubation of human kidney cells with SKF38393, a D1R agonist, caused a concentration-dependent inhibition of Na/K-ATPase. However, SKF38393 failed to inhibit Na/K-ATPase in BSO-treated cells. BSO increased AP1 and SP3 nuclear expression. Transfection with AP1- or SP3-specific siRNA abolished BSO-induced D1R downregulation. Treatment of rats with BSO for 4 weeks increased oxidative stress and SP3-AP1 expression and reduced D1R numbers in renal proximal tubules. These rats exhibited high blood pressure, and SKF38393 failed to inhibit proximal tubular Na/K-ATPase activity. Control rats were kept on tap water. Tempol per se had no effect on D1R expression or other signaling molecules but prevented BSO-induced oxidative stress, SP3-AP1 upregulation, and D1R dysfunction in both human kidney cells and rats. These data show that oxidative stress via AP1-SP3 activation suppresses D1R transcription and function. Tempol mitigates oxidative stress, blocks AP1-SP3 activation, and prevents D1R dysfunction and hypertension.

Does the use of chitosan contribute to oxalate kidney stone formation?

Chitosan is widely used in the biomedical field due its chemical and pharmacological properties. However, intake of chitosan results in renal tissue accumulation of chitosan and promotes an increase in calcium excretion. On the other hand, the effect of chitosan on the formation of calcium oxalate crystals (CaOx) has not been described. In this work, we evaluated the antioxidant capacity of chitosan and its interference in the formation of CaOx crystals in vitro. Here, the chitosan obtained commercially had its identity confirmed by nuclear magnetic resonance and infrared spectroscopy. In several tests, this chitosan showed low or no antioxidant activity. However, it also showed excellent copper-chelating activity. In vitro, chitosan acted as an inducer mainly of monohydrate CaOx crystal formation, which is more prevalent in patients with urolithiasis. We also observed that chitosan modifies the morphology and size of these crystals, as well as changes the surface charge of the crystals, making them even more positive, which can facilitate the interaction of these crystals with renal cells. Chitosan greatly influences the formation of crystals in vitro, and in vivo analyses should be conducted to assess the risk of using chitosan.

Cytokine and radical inhibition in septic intestinal barrier failure

BACKGROUND

Breakdown of the intestinal barrier is a driving force of sepsis and multiple organ failure. Radical scavengers or cytokine inhibitors may have a therapeutic impact on intestinal failure. Therapeutic effects on different sites of small intestine and colon have not been compared. Therefore, we investigated time-dependent intestinal permeability changes and their therapeutic inhibition in colon and small intestine with an ex vivo model.

METHODS

Male Sprague-Dawley rats were either pretreated for 24 h with lipopolysaccharide (LPS) intraperitoneally alone or in combination with a radical scavenger (pyruvate or Tempol) or a cytokine inhibitor (parecoxib or vasoactive intestinal peptide). The gastrointestinal permeability was measured by time-dependent fluorescein isothiocyanate inulin diffusion using washed and everted tube-like gut segments. Blood and tissue samples were taken to investigate the development of inflammatory cytokine level (interleukin 6) in the context of cytokine inhibition and reactive oxygen species level via nicotinamide adenine dinucleotide phosphate oxidase activity in radical scavenger groups.

RESULTS

After LPS treatment, mucosal permeability was enhanced up to 170% in small intestine and colon. In the small intestine the most significant reduction in permeability was found for pyruvate and parecoxib. Treatment with vasoactive intestinal peptide and parecoxib resulted in the most pronounced reduction of permeability in the colon.

CONCLUSIONS

Our data suggest that cytokine inhibitors and radical scavengers have pronounced effects in LPS-induced disrupted intestinal barrier of the colon and small intestine. Our novel model comparing different anatomic sites and different points in time after the onset of sepsis may contribute to gain new insight into mechanisms and treatment options of sepsis-related gut mucosal breakdown.

Reactive oxygen species are involved in regulating hypocontractility of mesenteric artery to norepinephrine in cirrhotic rats with portal hypertension

Background: Oxidative stress is involved in the hypocontractility of visceral artery to vasoconstrictors and formation of hyperdynamic circulation in cirrhosis with portal hypertension. In the present study, we investigated the effect of reactive oxygen species (ROS) on the mesenteric artery contractility in CCl₄-induced cirrhotic rats, and the roles of G protein-coupled receptors (GPCRs) desensitization and RhoA /Rho associated coiled-coil forming protein kinase (ROCK) pathways.

Methods: The mesenteric artery contraction to norepinephrine (NE) was determined by vessel perfusion system following treatments with apocynin, tempol or PEG-catalase. The protein expression of α1 adrenergic receptor, β-arrestin-2, ROCK-1, moesin and p-moesin was measured by western blot. The interaction between α1 adrenergic receptor and β-arrestin-2 was assessed by co-immunoprecipitation.

Results: Pretreatment with apocynin or PEG-catalase in cirrhotic rats, the hydrogen peroxide level in the mesenteric arteriole was significantly decreased, and the dose-response curve of mesenteric arteriole to NE moved to the left with EC₅₀ decreased. There was no significant change for the expression of α1 adrenergic receptor. However, the protein expression of β-arrestin-2 and its affinity with α1 adrenergic receptor were significantly decreased. The ROCK-1 activity and anti- Y-27632 inhibition in cirrhotic rats increased significantly with the protein expression unchanged. Such effects were not observed in tempol-treated group.

Conclusion: The H₂O₂ decrease in mesenteric artery from rats with cirrhosis resulted in down regulation of the β-arrestin-2 expression and its binding ability with α1 adrenergic receptor, thereby affecting the agonist-induced ROCK activation and improving the contractile response in blood vessels.

SERCA Cys674 sulphonylation and inhibition of L-type Ca2+ influx contribute to cardiac dysfunction in endotoxemic mice, independent of cGMP synthesis

The goal of this study was to identify the cellular mechanisms responsible for cardiac dysfunction in endotoxemic mice. We aimed to differentiate the roles of cGMP [produced by soluble guanylyl cyclase (sGC)] versus oxidative posttranslational modifications of Ca(2+) transporters. C57BL/6 mice [wild-type (WT) mice] were administered lipopolysaccharide (LPS; 25 μg/g ip) and euthanized 12 h later. Cardiomyocyte sarcomere shortening and Ca(2+) transients (ΔCai) were depressed in LPS-challenged mice versus baseline. The time constant of Ca(2+) decay (τCa) was prolonged, and sarcoplasmic reticulum Ca(2+) load (CaSR) was depressed in LPS-challenged mice (vs. baseline), indicating decreased activity of sarco(endo)plasmic Ca(2+)-ATPase (SERCA). L-type Ca(2+) channel current (ICa,L) was also decreased after LPS challenge, whereas Na(+)/Ca(2+) exchange activity, ryanodine receptors leak flux, or myofilament sensitivity for Ca(2+) were unchanged. All Ca(2+)-handling abnormalities induced by LPS (the decrease in sarcomere shortening, ΔCai, CaSR, ICa,L, and τCa prolongation) were more pronounced in mice deficient in the sGC main isoform (sGCα1(-/-) mice) versus WT mice. LPS did not alter the protein expression of SERCA and phospholamban in either genotype. After LPS, phospholamban phosphorylation at Ser(16) and Thr(17) was unchanged in WT mice and was increased in sGCα1(-/-) mice. LPS caused sulphonylation of SERCA Cys(674) (as measured immunohistochemically and supported by iodoacetamide labeling), which was greater in sGCα1(-/-) versus WT mice. Taken together, these results suggest that cardiac Ca(2+) dysregulation in endotoxemic mice is mediated by a decrease in L-type Ca(2+) channel function and oxidative posttranslational modifications of SERCA Cys(674), with the latter (at least) being opposed by sGC-released cGMP.

Altered MARCH1 ubiquination-regulated dendritic cell immune functions during the early stage of zymosan-induced multiple organ dysfunction syndrome (MODS) in mice

Using a zymosan-induced mouse model of multiple organ dysfunction syndrome (MODS), we previously found profound increases in spleen immune cells' expressions of ubiquitin and MHC-II molecules and increased CD11c+ dendritic cells (DCs) within 24h of zymosan injection. We postulated that the early stage of MODS altered DCs function via an ubiquitination-associated mechanism. We intraperitoneally injected zymosan into 100 male C57BL/6 mice (0.8mg/g) and randomly divided them into 5 groups based on the days after injection (20mice/group): 1d, 3d, 5d, 7d, and 10d. Mice were examined for spleen CD11c+ DC functions at the indicated days. Untreated mice were used for normal spleen tissue and T cell samples. By qPCR, IL-12 and TNF-α mRNA expressions in spleen CD11c+ DCs were significantly increased in MODS 1d mice; on subsequent days post-injection, these mRNA levels gradually returned to control levels. The same patterns were found for MODS mice DCs induction of untreated mouse T cells proliferation and IL-2 and IFN-γ mRNA expressions. When T cell functions were examined using MODS 1d DCs with and without MG132 treatment, an inhibitor of ubiquitinated protein degradation, T cell functional activities were enhanced by DCs treated with MG132. MODS 1d DCs also had significantly reduced MARCH1 mRNA expression, a key ubiquitin ligase that regulates DCs MHC-II expression. Silencing DCs MARCH1 expression with siRNA resulted in enhancing their induction of T cell functional activities. Using co-immunoprecipitation, Western blot, and flow cytometry assays, we deduced that MARCH1 ubiquitinated DC surface MHC-II molecules to regulate DC's immune functions in MODS mice. Our results suggest that aberrant degradation of spleen DCs MARCH1-mediated ubiquitinated proteins is involved during the earliest stage of MODS development.

Melanocortins protect against multiple organ dysfunction syndrome in mice

BACKGROUND AND PURPOSE

Melanocortins reverse circulatory shock and improve survival by counteracting the systemic inflammatory response, and through the activation of the vagus nerve-mediated cholinergic anti-inflammatory pathway. To gain insight into the potential therapeutic value of melanocortins against multiple organ damage following systemic inflammatory response, here we investigated the effects of the melanocortin analogue [Nle⁴ D-Phe⁷]α-MSH (NDP-α-MSH) in a widely used murine model of multiple organ dysfunction syndrome (MODS).

EXPERIMENTAL APPROACH

MODS was induced in mice by a single intraperitoneal injection of lipopolysaccharide followed, 6 days later (= day 0), by zymosan. After MODS or sham MODS induction, animals were randomized to receive intraperitoneally NDP-α-MSH (340 µg·kg⁻¹ day) or saline for up to 16 days. Additional groups of MODS mice were concomitantly treated with the melanocortin MC₄ receptor antagonist HS024, or the nicotinic acetylcholine receptor antagonist chlorisondamine, and NDP-α-MSH.

KEY RESULTS

At day 7, in the liver and lung NDP-α-MSH, significantly reduced mRNA expression of tumour necrosis factor-α (TNF-α), increased mRNA expression of interleukin-10 and improved the histological picture, as well as reduced TNF-α plasma levels; furthermore, NDP-α-MSH dose-dependently increased survival rate, as assessed throughout the 16 day observation period. HS024 and chlorisondamine prevented all the beneficial effects of NDP-α-MSH in MODS mice.

CONCLUSIONS AND IMPLICATIONS

These data indicate that NDP-α-MSH protects against experimental MODS by counteracting the systemic inflammatory response, probably through brain MC₄ receptor-triggered activation of the cholinergic anti-inflammatory pathway. These findings reveal previously undescribed effects of melanocortins and could have clinical relevance in the MODS setting.

Effects of reactive oxygen species scavenger on the protective action of 100% oxygen treatment against sterile inflammation in mice

Sepsis/multiple organ dysfunction syndrome (MODS) is a major cause of high mortality in the intensive care unit. We have recently reported that 100% oxygen treatment is beneficial to mice with zymosan-induced sterile inflammation by increasing antioxidant enzymatic activities. Yet, the use of hyperoxia is hindered by concerns that it could exacerbate organ injury by increasing free radical formation. It is believed that systemic inflammation and overproduction of reactive oxygen species (ROS) contribute to the mechanism underlying sepsis/MODS. A ROS scavenger has been proven to protect against sepsis/MODS in some animal models. Therefore, we hypothesized that ROS scavenger pretreatment might enhance the protective action of 100% oxygen treatment against zymosan-induced sterile inflammation in mice. In the present study, we showed that 100% oxygen treatment prevented the abnormal changes in serum biochemical parameters, tissue oxygenation, and organ histopathology, and improved the 14-day survival rate in zymosan-stimulated mice, indicating that 100% oxygen treatment had a protective action on sterile inflammation. We found that pretreatment with a ROS scavenger (N-acetylcysteine, vitamin C, or dimethylthiourea) abolished this protective action of 100% oxygen treatment. We also showed that 100% oxygen treatment decreased the levels of serum proinflammatory cytokines (TNF-alpha, IL-6, and high-mobility group box 1), increased the level of serum anti-inflammatory cytokine (IL-10), and upregulated the activities of serum and tissue antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) in zymosan-stimulated mice, which were reversed by the pretreatment with a ROS scavenger (N-acetylcysteine, vitamin C, or dimethylthiourea). We thus conclude that ROS scavenger pretreatment partly abolishes the protective effects of 100% oxygen treatment on sterile inflammation in mice by regulating inflammatory cytokines as well as antioxidant enzymes.

A systematic review of experimental treatments for mitochondrial dysfunction in sepsis and multiple organ dysfunction syndrome

Sepsis and multiple organ dysfunction syndrome (MODS) are major causes of morbidity and mortality in the intensive care unit. Recently mitochondrial dysfunction has been proposed as a key early cellular event in critical illness. A growing body of experimental evidence suggests that mitochondrial therapies are effective in sepsis and MODS. The aim of this article is to undertake a systematic review of the current experimental evidence for the use of therapies for mitochondrial dysfunction during sepsis and MODS and to classify these mitochondrial therapies. A search of the MEDLINE and PubMed databases (1950 to July 2009) and a manual review of reference lists were conducted to find experimental studies containing data on the efficacy of mitochondrial therapies in sepsis and sepsis-related MODS. Fifty-one studies were included in this review. Five categories of mitochondrial therapies were defined-substrate provision, cofactor provision, mitochondrial antioxidants, mitochondrial reactive oxygen species scavengers, and membrane stabilizers. Administration of mitochondrial therapies during sepsis was associated with improvements in mitochondrial electron transport system function, oxidative phosphorylation, and ATP production and a reduction in cellular markers of oxidative stress. Amelioration of proinflammatory cytokines, caspase activation, and prevention of the membrane permeability transition were reported. Restoration of mitochondrial bioenergetics was associated with improvements in hemodynamic parameters, organ function, and overall survival. A substantial body of evidence from experimental studies at both the cellular and the organ level suggests a beneficial role for the administration of mitochondrial therapies in sepsis and MODS. We expect that mitochondrial therapies will have an increasingly important role in the management of sepsis and MODS. Clinical trials are now required.

Chemistry and antihypertensive effects of tempol and other nitroxides

Nitroxides can undergo one- or two-electron reduction reactions to hydroxylamines or oxammonium cations, respectively, which themselves are interconvertible, thereby providing redox metabolic actions. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (tempol) is the most extensively studied nitroxide. It is a cell membrane-permeable amphilite that dismutates superoxide catalytically, facilitates hydrogen peroxide metabolism by catalase-like actions, and limits formation of toxic hydroxyl radicals produced by Fenton reactions. It is broadly effective in detoxifying these reactive oxygen species in cell and animal studies. When administered intravenously to hypertensive rodent models, tempol caused rapid and reversible dose-dependent reductions in blood pressure in 22 of 26 studies. This was accompanied by vasodilation, increased nitric oxide activity, reduced sympathetic nervous system activity at central and peripheral sites, and enhanced potassium channel conductance in blood vessels and neurons. When administered orally or by infusion over days or weeks to hypertensive rodent models, it reduced blood pressure in 59 of 68 studies. This was accompanied by correction of salt sensitivity and endothelial dysfunction and reduced agonist-evoked oxidative stress and contractility of blood vessels, reduced renal vascular resistance, and increased renal tissue oxygen tension. Thus, tempol is broadly effective in reducing blood pressure, whether given by acute intravenous injection or by prolonged administration, in a wide range of rodent models of hypertension.

Hemigramicidin-TEMPO conjugates: novel mitochondria-targeted antioxidants

Reactive oxygen species (ROS) are reactive, partially reduced derivatives of molecular oxygen. ROS are important in the pathogenesis of a wide range of acute pathologic processes, including ischemia/reperfusion injury, sepsis, and shock. Accordingly, effective ROS scavengers might be useful therapeutic agents for these conditions. Since mitochondria are the primary sites for ROS production within cells, it seems reasonable that targeting ROS scavengers to these organelles could be a particularly effective strategy. Indeed, a number of compounds or classes of compounds have been described that are based on this concept. One approach consists of coupling a payload--the portion of the molecule with ROS-scavenging activities--to a targeting moiety--the portion of the molecule that promotes selective accumulation within mitochondria. For example, the payload portion of XJB-5-131 consists of a stable nitroxide radical, which has been extensively investigated as a cytoprotective agent in a number of experimental models of oxidative stress. The targeting portion of XJB-5-131 consists of a portion of the membrane-active cyclopeptide antibiotic, gramicidin S. The gramicidin segment was used to target the nitroxide payload to mitochondria because antibiotics of this type have a high affinity for bacterial membranes and because of the close relationship between bacteria and mitochondria. In a rat model of hemorrhagic shock, delayed treatment with XJB-5-131 has been shown to prolong survival time in the absence of resuscitation with blood or a large volume of crystalloid fluid. Compounds like XJB-5-131 warrant further evaluation for the treatment of hemorrhagic shock as well as other acute conditions associated with increased mitochondrial production of ROS.

The pharmokinetic limitations of antioxidant treatment for COPD

COPD is one of the leading causes of death worldwide and the age-adjusted mortality for this disease has risen significantly over the past 30 years. Current pharmacological treatments do not effectively address the inflammatory and apoptotic mechanisms that are critical in the development of this disease. Thus, despite therapy, patients typically experience a continued deterioration of their clinical status. Markers of oxidative stress are increased in the lungs of COPD patients and epidemiologic and animal studies indicate that antioxidants can protect the lungs from the damaging effects of cigarette smoke. To date, however, clinical trials of antioxidants for COPD have yielded disappointing results. This review discusses the pharmokinetic factors that limit the use of exogenous antioxidants as a treatment for this disease. In addition, it addresses strategies to overcome these limitations so that the beneficial properties of antioxidants can be translated into effective therapies for COPD patients.

Hemigramicidin–TEMPO conjugates: Novel mitochondria-targeted anti-oxidants

Oxidative damage to various cellular constituents (such as, proteins and lipids) mediated by reactive oxygen species (ROS) is thought to be an important mechanism underlying the pathogenesis of a variety of acute and chronic diseases. Mitochondria are the main source of ROS within most cells. Accordingly, there is increasing interest in the development of pharmacological ROS scavengers, which are specifically targeted to and concentrated within mitochondria. Numerous compounds with these general characteristics have been synthesized and evaluated in a variety of in vitro and in vivo models of redox stress. Among the more promising of these mitochondria-targeted anti-oxidants are those that employ various peptides (or peptide-like moieties) derived from the antibiotic, gramicidin S, as the targeting construct and employ the stable free radical, 4-amino-2,2,6,6-tetramethylpiperidine-N-oxyl (4-NH(2)-TEMPO), as the ROS scavenging "payload." One of these hemigramicidin-TEMPO conjugates, XJB-5-131, has been shown to ameliorate intestinal mucosal injury and prolong survival in rats subjected to lethal hemorrhage.

Nitric oxide and peroxynitrite in health and disease

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

Role of oxidative stress in experimental sepsis and multisystem organ dysfunction

Massive increase in radical species can lead to oxidative stress, promoting cell injury and death. This review focuses on experimental evidence of oxidative stress in critical illnesses, sepsis and multisystem organ dysfunction. Oxidative stress could negatively affect organ injury and thus overall survival of experimental models. Based on this experimental evidence, we could improve the rationale of supplementation of antioxidants alone or in combination with standard therapies aimed to reduce oxidative stress as novel adjunct treatment in critical care.

Erythropoietin reduces the development of nonseptic shock induced by zymosan in mice*

OBJECTIVE

Erythropoietin is a potent stimulator of erythroid progenitor cells, and its expression is enhanced by hypoxia. In the present study, we investigated the effects of erythropoietin (1000 IU/kg subcutaneously) on the development of nonseptic shock caused by zymosan.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Male CD mice.

INTERVENTIONS

Mice received either intraperitoneally zymosan (500 mg/kg, administered intraperitoneally as a suspension in saline) or vehicle (0.25 mL/mouse saline). Erythropoietin was administered at the dose of 1000 IU/kg subcutaneously, 1 and 6 hrs after zymosan administration. Organ failure and systemic inflammation in mice was assessed 18 hrs after administration of zymosan and/or erythropoietin.

MEASUREMENTS AND MAIN RESULTS

Treatment of mice with erythropoietin (1000 IU/kg subcutaneously, 1 and 6 hrs after zymosan administration) attenuated the peritoneal exudation and the migration of polymorphonuclear cells caused by zymosan. Erythropoietin also attenuated the lung, liver, and pancreatic injury and renal dysfunction caused by zymosan as well as the increase in myeloperoxidase activity caused by zymosan in the lung and intestine. Immunohistochemical analysis for nitrotyrosine and poly(ADP-ribose) revealed positive staining in lung and intestine tissues obtained from zymosan-treated mice. The degree of staining for nitrotyrosine and poly(ADP-ribose) was markedly reduced in tissue sections obtained from zymosan-treated mice, which received erythropoietin. In addition, administration of zymosan caused severe illness in the mice characterized by a systemic toxicity, significant loss of body weight, and a 70% mortality rate at the end of observation period (7 days). Treatment with erythropoietin significantly reduced the development of systemic toxicity, the loss in body weight, and the mortality caused by zymosan.

CONCLUSIONS

This study provides evidence, for the first time, that erythropoietin attenuates the degree of zymosan-induced nonseptic shock in mice.

Structure−Activity Relationship of Cyclic Nitroxides as SOD Mimics and Scavengers of Nitrogen Dioxide and Carbonate Radicals

Synthetic nitroxide antioxidants attenuate oxidative damage in various experimental models. Their protective effect reportedly depends on ring size and ring substituents and is greater for nitroxides having lower oxidation potential. The present study focuses on the kinetics and mechanisms of the reactions of piperidine, pyrrolidine and oxazolidine nitroxides with HO2*/O2*-, *NO2 and CO3*- radicals, which are key intermediates in many inflammatory and degenerative diseases. It is demonstrated that nitroxides are the most efficient scavengers of *NO2 at physiological pH (k = (3-9) x 10(8) M(-1) s(-1)) and among the most effective metal-independent scavengers of CO3*- radicals (k = (2 - 6) x 10(8) M(-1) s(-1)). Their reactivity toward HO2*, though not toward *NO2 and CO3*-, depends on the nature of the ring side-chain and particularly on the ring-size. All nitroxide derivatives react slowly with O2*- and are relatively inefficient SOD mimics at physiological pH. Even piperidine nitroxides, having the highest SOD-like activity, demonstrate a catalytic activity of about 1000-fold lower than that of native SOD at pH 7.4. The present results do not indicate any correlation between the kinetics of HO2*/O2*-, *NO2 and CO3*- removal by nitroxides and their protective activity against biological oxidative stress and emphasize the importance of target-oriented nitroxides, i.e., interaction between the biological target and specific nitroxides.

Oxidative Stress Promotes Endothelial Cell Apoptosis and Loss of Microvessels in the Spontaneously Hypertensive Rats

OBJECTIVE

Endothelial cell apoptosis caused by oxidative stress may lead to the loss of microvessels (rarefaction) in hypertension. We examine here the effects of antioxidants on cell apoptosis and rarefaction.

METHODS AND RESULTS

The juvenile spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were treated with superoxide scavengers, Tempol or Tiron, during growth. After the treatment, oxidative stress status, endothelial cell apoptosis rate, and microvessel length density in skeletal muscle and mesentery were evaluated in comparison with age-matched controls. Untreated 16-week-old SHR had higher oxidative stress (P<0.01) and cell apoptosis rate (P<0.05) and lower microvessel length density (371+/-17 mm/mm3 [P<0.01]) compared with age-matched WKY rats (435+/-15 mm/mm3). In the SHR, but not in WKY rats, systemically applied antioxidants attenuated oxidative stress and cell apoptosis rate (P<0.05 versus untreated controls) and prevented the loss of microvessels (411+/-15 mm/mm3 for Tempol [P<0.01 versus untreated control] and 399+/-17 mm/mm3 for Tiron [P<0.05]).

CONCLUSIONS

Antioxidant treatment with cell-permeable superoxide scavengers inhibits endothelial cell apoptosis and prevents microvessel rarefaction in the SHR during growth.

N/A

N/A

Zymosan-induced generalized inflammation: experimental studies into mechanisms leading to multiple organ dysfunction syndrome

Patients suffering from multiple organ dysfunction syndrome (MODS) comprise a heterogeneous population, which complicates research in its pathogenesis. Elucidation of the mechanisms involved in the development of MODS will ultimately necessitate the collection of tissue samples and the performance of invasive procedures. These requirements greatly reduce the possibilities for research in human subjects. Therefore, an animal model for MODS is a necessary and valuable tool. In the mid 1980s, the zymosan-induced generalized inflammation (ZIGI) model was introduced. Intraperitoneal injection of zymosan in mice or rats leads, in the course of 1 to 2 weeks, to increasing organ damage and dysfunction. The ZIGI model has been recognized as the one that best resembles human MODS and it has been used widely to study systemic inflammation in relation to organ failure. This review describes the ZIGI model and gives an overview of the results obtained.

Modulation of prostaglandin biosynthesis by nitric oxide and nitric oxide donors

The biosynthesis and release of nitric oxide (NO) and prostaglandins (PGs) share a number of similarities. Two major forms of nitric-oxide synthase (NOS) and cyclooxygenase (COX) enzymes have been identified to date. Under normal circumstances, the constitutive isoforms of these enzymes (constitutive NOS and COX-1) are found in virtually all organs. Their presence accounts for the regulation of several important physiological effects (e.g. antiplatelet activity, vasodilation, and cytoprotection). On the other hand, in inflammatory setting, the inducible isoforms of these enzymes (inducible NOS and COX-2) are detected in a variety of cells, resulting in the production of large amounts of proinflammatory and cytotoxic NO and PGs. The release of NO and PGs by the inducible isoforms of NOS and COX has been associated with the pathological roles of these mediators in disease states as evidenced by the use of selective inhibitors. An important link between the NOS and COX pathways was made in 1993 by Salvemini and coworkers when they demonstrated that the enhanced release of PGs, which follows inflammatory mechanisms, was nearly entirely driven by NO. Such studies raised the possibility that COX enzymes represent important endogenous "receptor" targets for modulating the multifaceted roles of NO. Since then, numerous papers have been published extending the observation across various cellular systems and animal models of disease. Furthermore, other studies have highlighted the importance of such interaction in physiology as well as in the mechanism of action of drugs such as organic nitrates. More importantly, mechanistic studies of how NO switches on/off the PG/COX pathway have been undertaken and additional pathways through which NO modulates prostaglandin production unraveled. On the other hand, NO donors conjugated with COX inhibitors have recently found new interest in the understanding of NO/COX reciprocal interaction and potential clinical use. The purpose of this article is to cover the advances which have occurred over the years, and in particular, to summarize experimental data that outline how the discovery that NO modulates prostaglandin production has impacted and extended our understanding of these two systems in physiopathological events.

Effects of tempol, a free radical scavenger, on long-term hyperdynamic porcine bacteremia*

OBJECTIVES

Pretreatment with tempol, a membrane-permeable radical scavenger, has been shown to be protective in rodent models of endotoxic and Gram-positive shock. However, neither the pretreatment design nor hypodynamic endotoxic shock in rodents mimics the clinical scenario. Therefore, we investigated the effects of tempol in a posttreatment model of long-term, volume-resuscitated, hyperdynamic porcine bacteremia.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

University animal laboratory.

SUBJECTS

Sixteen anesthetized, mechanically ventilated, and instrumented pigs.

INTERVENTIONS

Sepsis was induced and maintained for 24 hrs with continuous infusion of live Pseudomonas aeruginosa. After 12 hrs of hyperdynamic sepsis, animals were randomized to receive either vehicle (control, n = 8) or continuous infusion of tempol (n = 8, 30 mg/kg/hr).

MEASUREMENTS AND MAIN RESULTS

Systemic and hepatosplanchnic hemodynamics, oxygen exchange, metabolism, ileal mucosal microcirculation, and tonometry as well as oxidative stress and coagulation variables were assessed before and after 12, 18, and 24 hrs of P. aeruginosa infusion. Tempol significantly attenuated reduction in mean arterial pressure. Despite comparable mesenteric macrocirculation, tempol attenuated the otherwise progressive deterioration in ileal mucosal microcirculation and prevented mucosal acidosis. By contrast, treatment with tempol failed to influence the P. aeruginosa-induced derangements of hepatosplanchnic redox state, liver lactate clearance, and regional acidosis but prevented the development of renal dysfunction. In addition, tempol reduced nitrosative stress without significant effect on the gradual increase in plasma 8-isoprostanes. Finally, tempol attenuated sepsis-induced endothelial (von Willebrand factor) and hemostatic dysfunction (thrombin-antithrombin complexes, plasminogen activator inhibitor-type 1).

CONCLUSIONS

The radical scavenger tempol partially prevented live bacteria from causing key features of hemodynamic and metabolic derangements in porcine hyperdynamic sepsis and beneficially affected surrogate markers of sepsis-induced endothelial and coagulation dysfunction. Incomplete reduction of oxidative stress because of dilutional effects and/or missed optimal therapeutic window for antioxidant treatment when used in posttreatment approach may account for the only partial protection by tempol in this model.

The effects of selective nitric oxide synthase blocker on survival, mesenteric blood flow and multiple organ failure induced by zymosan1

BACKGROUND

Circulatory failure in multiple organ dysfunction syndromes (MODS) is characterized with systemic vasodilation, diminished blood flow to various vascular beds. The aim of this study was to investigate the effects of selective inhibition of nitric oxide on the mesenteric arterial blood flow (MABF), survival and organ injury of the liver, kidney, lung and spleen in zymosan-induced MODS.

MATERIALS AND METHODS

Forty Swiss albino mice (20-40 g), 7 to 9 weeks old, were obtained. Animals were randomly divided into four groups. The first group were treated intraperitoneally (i.p) with vehicle (saline) and served as a sham group for aminoguanidine (AG) (n=10). The second group was treated with zymosan (500 mg/kg, suspended in saline solution, i.p). The mice in the third and fourth group received AG (15 mg/kg) 1 h and 6 h after zymosan or saline administration, respectively. Eighteen hours after the administration of zymosan, animals were assessed for MODS described subsequently. The signals from the flowmeter were also recorded on mesenteric arterial blood flow values.

RESULTS

In zymosan-treated animals, the MABF was significantly lower than that of solvent (saline)-treated controls (ml min(-1), controls: 4.6 +/- 0.6; zymosan: 1.6 +/- 0.9, P <0.05). When animals were treated with AG, there were no significant differences in MABF values between AG group and solvent (saline)-treated control group. However AG prevented zymosan-induced mesenteric MABF decrease. Treatment with aminoguanidine also decreased mortality.

CONCLUSION

AG is capable of inhibiting both the induction and the activity of the already iNOS; it remains a potential therapeutic agent in patients with MODS.

Pentoxifylline does not improve outcome in a murine model for the multiple-organ dysfunction syndrome

OBJECTIVE

To investigate the effects of pentoxifylline (PTX) administration in a murine model for the multiple-organ dysfunction syndrome (MODS).

DESIGN AND SETTING

Prospective double-blind randomized animal study in a university research laboratory.

INTERVENTIONS AND MEASUREMENTS

Sixty C57BL/6 mice were given an aseptic intraperitoneal injection of lipopolysaccharide followed after 6 days by zymosan (day 0) at a dose of either 0.9 or 1.0 mg/g body weight. Starting on day 0 mice were administered PTX at a dose of 80 mg/kg body weight or saline per os every 8 h. On day 17 surviving animals were killed, and their liver, lungs, spleen, and kidneys were collected.

RESULTS

Mortality, course of body temperature, body weight, and macroscopic lung damage were similar between zymosan-treated groups. Administration of PTX did not significantly alter survival, body temperature, body weight, or macroscopic lung damage. In addition, there were no significant differences in organ weights between mice that received PTX and mice that received PBS. Although PTX inhibited the lipopolysaccharide-induced increase in tumor necrosis factor alpha and interleukin 6 expression (but not interleukin 1beta expression) at both mRNA and protein level in a murine macrophage cell line, tumor necrosis factor alpha mRNA expression in the livers of PTX-treated mice was not significantly inhibited.

CONCLUSIONS

The results reported here do not support the hypothesis that PTX improves outcome in zymosan-induced multiple-organ dysfunction in mice.

Chronic post-ischemia pain (CPIP): a novel animal model of complex regional pain syndrome-type I (CRPS-I; reflex sympathetic dystrophy) produced by prolonged hindpaw ischemia and reperfusion in the rat

A neuropathic-like pain syndrome was produced in rats following prolonged hindpaw ischemia and reperfusion, creating an animal model of complex regional pain syndrome-Type I (CRPS-I; reflex sympathetic dystrophy) that we call chronic post-ischemia pain (CPIP). The method involves placing a tourniquet (a tight fitting O-ring) on one hindlimb of an anesthetized rat just proximal to the ankle joint for 3 h, and removing it to allow reperfusion prior to termination of the anesthesia. Rats exhibit hyperemia and edema/plasma extravasation of the ischemic hindpaw for a period of 2-4 h after reperfusion. Hyperalgesia to noxious mechanical stimulation (pin prick) and cold (acetone exposure), as well as mechanical allodynia to innocuous mechanical stimulation (von Frey hairs), are evident in the affected hindpaw as early as 8 h after reperfusion, and extend for at least 4 weeks in approximately 70% of the rats. The rats also exhibit spontaneous pain behaviors (hindpaw shaking, licking and favoring), and spread of hyperalgesia/allodynia to the uninjured contralateral hindpaw. Light-microscopic examination of the tibial nerve taken from the region just proximal to the tourniquet reveals no signs of nerve damage. Consistent with the hypothesis that the generation of free radicals may be partly responsible for CRPS-I and CPIP, two free radical scavengers, N-acetyl-L-cysteine (NAC) and 4-hydroxy-2,2,6,6-tetramethylpiperydine-1-oxyl (Tempol), were able to reduce signs of mechanical allodynia in this model.

Increased expression of matrix metalloproteinases in the murine zymosan-induced multiple organ dysfunction syndrome

Matrix metalloproteinases (MMPs) have been implicated as mediators of tissue damage in several inflammatory diseases. Since the multiple organ dysfunction syndrome (MODS) is thought to result from systemic inflammation, overactivation of MMPs could contribute to the organ damage observed. The expression and activity of several MMPs were studied in a murine model for MODS. Sixty mice were given an aseptic intraperitoneal injection of lipopolysaccharide, followed, after 6 days, by zymosan. At days 2, 5, 8, 12, and 16 after the injection of zymosan, the liver, lungs, spleen, and kidneys were collected from groups of mice for either RNA extraction, gelatinase zymography and collagenase (MMP-1 and -13) assays (six mice per time point), or immunohistochemistry (three mice per time point). A group of nine mice did not receive zymosan and acted as controls. The expression of MMP-2 mRNA in zymosan-treated mice was strongly up-regulated in liver tissue only. For MMP-9, this was the case in all organs examined. Quantitative gelatin zymography demonstrated the near complete absence of any gelatinase activity in tissues from control mice. However, in the liver, lungs, and especially the spleen of zymosan-treated animals, significantly increased activity of proform and active MMP-2 and -9 was observed with time. Overall, MMP-1 and -13 activities were very low in all samples from the liver and lungs. In the spleen, however, high levels of MMP-1 and -13 were observed in zymosan-treated animals. Immunohistochemical staining for MMP-2 was detected in the liver and spleen, but not in lung and kidney tissue of zymosan-treated animals. Staining for MMP-9 could be detected in liver, lung, and spleen tissues of zymosan-treated mice. For both MMPs, staining appeared to be limited to phagocytes. In conclusion, the data suggest a role for MMPs, especially MMP-9, in the pathogenesis of MODS.

Treatment with a novel poly(ADP-ribose) glycohydrolase inhibitor reduces development of septic shock-like syndrome induced by zymosan in mice

OBJECTIVE

Poly(ADP-ribose) is synthesized from nicotinamide adenine dinucleotide by poly(ADP-ribose) polymerase (PARP) and degraded by poly(ADP-ribose) glycohydrolase (PARG). The activation of the PARP/PARG pathway has been found in a variety of animal models of diseases, including septic shock-like syndrome. We have previously demonstrated that PARP inhibition by 3-ami-nobenzamide or GPI 6150 ameliorates multiple organ dysfunctions induced by zymosan. In the present study, we investigated whether similar effect could be achieved through PARG inhibition to break the cycle of poly(ADP-ribose) turnaround.

DESIGN

Experimental study.

SETTING

University laboratory.

SUBJECTS

Male CD mice (20-22 g).

INTERVENTIONS

We tested the effects of GPI 18214 (40 mg/kg intraperitoneally bolus), a novel and potent PARG inhibitor, at 1 and 6 hr after zymosan (500 mg/kg, administered intraperitoneally as a suspension in saline) on the development of septic shock-like syndrome in mice. Organ failure and systemic inflammation in mice were assessed 18 hrs after administration of zymosan and/or GPI 18214 and monitored for 12 days (for loss of body weight and mortality).

MEASUREMENTS AND MAIN RESULTS

At 18 hrs after zymosan administration, we found a significant increase of peritoneal exudates, leukocyte infiltration in peritoneal cavity as well as an infiltration of neutrophils in lung and ileum tissues and subsequent lipid peroxidation, and increased production of plasma tumor necrosis factor-alpha and interleukin-1 beta. Furthermore, zymosan administration induced significant liver, lung, pancreas, intestine, and kidney dysfunction as well as a systemic toxicity and significant loss of body weight. At the end of observation period (12 days), 90% of zymosan-treated mice were dead. GPI 18214 (40 mg/kg intraperitoneally, 1 and 6 hrs after zymosan) treatment significantly reduced peritoneal exudates, inflammatory cell infiltration, and organ injury and mortality rate in zymosan-treated mice.

CONCLUSIONS

This study supports early studies that show efficacy from blocking the poly(ADP-ribose) pathway in septic shock-like syndrome model. It provides evidence that GPI 18214, a PARG inhibitor, attenuates the degree of zymosan-induced nonseptic shock in mice, suggesting that PARG may be an alternative therapeutic target for shock treatment.

Tissue- and time-dependent upregulation of cytokine mRNA in a murine model for the multiple organ dysfunction syndrome

OBJECTIVE

We sought to quantitate the course of specific cytokine mRNA expression in tissues that exhibit increasing histopathological changes in time in an animal model for the multiple organ dysfunction syndrome (MODS).

SUMMARY BACKGROUND DATA

The development of treatment protocols for MODS requires elucidation of the mechanisms and mediators involved. To devise logical interventions, it is necessary to collect data on cytokine expression at tissue level during the development of MODS.

METHODS

Ninety-four C57BL/6 mice were given an intraperitoneal injection of 40 microg of lipopolysaccharide (LPS), followed by zymosan at a dose of 0.8 mg/g body weight 6 days later (day 0). Six additional animals did not receive zymosan and acted as controls. At several time points after zymosan injection, 6 randomly assigned, zymosan-treated animals were killed, and their livers, lungs, spleens, and kidneys were collected. mRNA expression of tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, macrophage migration inhibiting factor, IL-12, interferon-gamma, and IL-10 was measured using a real-time reverse transcription-polymerase chain reaction assay.

RESULTS

The injection of zymosan induced an acute peritonitis, followed by an apparent recovery. From approximately day 6 onwards, animals started to display MODS-like symptoms. During the peritonitis phase, up-regulation of cytokine mRNA was limited. During the period of apparent recovery, cytokine mRNA expression strongly increased, mostly reaching its maximum at day 9 when deterioration of the clinical condition had already set in. The up-regulation of tumor necrosis factor-alpha mRNA was most pronounced, especially in the lungs and liver.

CONCLUSIONS

Interventions should preferentially be targeted against multiple cytokines and, at least in this model, there may be a treatment window well after the initial challenge.

Comparison of acute and chronic antioxidant interventions in experimental renovascular disease

Reactive oxygen species (ROS) can modulate renal hemodynamics and function both directly, by leading to vasoconstriction, and indirectly, by inducing renal inflammation and tissue growth. The involvement of oxidative stress in the pathogenesis of renovascular disease (RVD) is increasingly recognized, but the relative contribution of long-term tissue injury to renal dysfunction remains unclear. We hypothesized that functional and structural alterations elicited by oxidative stress in RVD would be more effectively modulated by chronic than by acute antioxidant intervention. Renal hemodynamics and function were quantified in vivo in pigs using electron-beam computed tomography at baseline and after vasoactive challenge (ACh and sodium nitroprusside); after 12 wk of RVD (simulated by concurrent hypercholesterolemia and renal artery stenosis, n = 7); RVD acutely infused with the SOD-mimetic tempol (RVD+tempol, n = 7); RVD chronically supplemented with antioxidant vitamins C (1 g) and E (100 IU/kg; RVD+vitamins, n = 7); or control (normal, n = 7). Renal tissue was studied ex vivo using immunoblotting and immunohistochemistry. Basal renal blood flow (RBF) and glomerular filtration rate were similarly decreased in all RVD groups. ACh-stimulated RBF remained unchanged in RVD, increased in RVD+tempol, but further increased (similarly to normal) in RVD+vitamins ( P < 0.05 vs. RVD). Furthermore, RVD+vitamins also showed a decreased presence of superoxide anion, decreased NAD(P)H-oxidase and nitrotyrosine expression, increased endothelial nitric oxide synthase expression, and attenuated renal fibrosis. Chronic antioxidant intervention in early RVD improved renal hemodynamic responses more effectively than acute intervention, likely due to increased nitric oxide bioavailability and decreased structural injury. These suggest that chronic tissue changes play an important role in renal compromise mediated by oxidative stress in RVD.

Immune cells: free radicals and antioxidants in sepsis

The excessive production of reactive oxygen species (ROS), associated with inflammation, leads to a condition of oxidative stress. Oxidative stress is a major contributing factor to the high mortality rates associated with several diseases such as endotoxic shock. This condition can be controlled to a certain degree by antioxidant therapies. Immune cells use ROS in order to support their functions and therefore need adequate levels of antioxidant defenses in order to avoid the harmful effect of an excessive production of ROS. This review discusses the toxic effects of endotoxin, paying particular attention to immune function. It continues by analyzing the mechanism to which specific cells of the immune system recognize endotoxin, and the resulting pathways leading to nuclear factor-kappaB activation and proinflammatory gene transcription. We also focus on the involvement of reactive oxygen and nitric oxide (NO) and the protective role of antioxidants. The potential clinical use of antioxidants in the treatment of sepsis and the effects on the redox state of the immune cells are discussed.

The anti-oxidant Tempol reverses and partially prevents adrenocorticotrophic hormone-induced hypertension in the rat

OBJECTIVE

To investigate the effects of the antioxidant Tempol on prevention and reversal of adrenocorticotrophic hormone (ACTH)-induced hypertension in the rat, a model of hypertension characterized by nitric oxide deficiency.

METHODS

Male Sprague-Dawley rats (n = 10 in each group) were treated with either saline or ACTH (0.2 mg/kg per day, s.c.) for 12 days. Tempol (1 mmol/l in drinking water) treatment was started on either day 8 (T8) of ACTH or saline treatment (reversal study), or 4 days prior to ACTH or saline treatment (prevention study). Systolic blood pressure (SBP) was measured using tail-cuff sphygmomanometry. Plasma F2-isoprostanes, a marker of oxidative stress, were measured by gas chromatography-mass spectrometry.

RESULTS

ACTH increased SBP (mean +/- SEM: 119 +/- 5 to 147 +/- 7 mmHg, P < 0.0005) and plasma F2-isoprostane concentration (8.4 +/- 1.2 saline versus 12.9 +/- 1.6 nmol/l ACTH, P < 0.05). Tempol alone did not alter SBP, but administration of Tempol on T8 reversed ACTH-induced hypertension (from 134 +/- 4 T8 to 118 +/- 3 mmHg, P < 0.005). Tempol pre-treatment partially prevented ACTH-induced hypertension (123 +/- 2 mmHg, P' < 0.05). However, Tempol had no effect on F2-isoprostane concentrations at the dose used in this study.

CONCLUSIONS

ACTH-induced hypertension in the rat is associated with increased oxidative stress. Tempol treatment reversed, and pretreatment partially prevented ACTH-induced hypertension, independent of improvement in systemic oxidative stress.

Stable nitroxide Tempol ameliorates brain injury by inhibiting lipid peroxidation in a rat model of transient focal cerebral ischemia

Oxygen free radicals have been implicated in the pathogenesis of cerebral ischemia and reperfusion injury. 4-Hydroxy-2,2,6,6-tetramethylpiperidene-1-oxyl (Tempol) has been reported as a stable nitroxide and a membrane-permeable free radical scavenger. This study was performed to investigate the mechanism of Tempol in attenuating ischemia-reperfusion injury in a rat model of transient focal cerebral ischemia. We measured the cerebral 2,3-dihydroxybenzoic acid (DHBA) level as the amount of hydroxyl radical production using a microdialysis technique with salicylic acids trapping during ischemia and reperfusion. The concentration of cerebral thiobarbituric acid reactive substances (TBARS), representing the extent of lipid peroxidation by free radicals, and the area of cerebral infarction were also measured. The level of cerebral 2,3-DHBA was increased during ischemia and reperfusion, especially during the early reperfusion stage at the periphery of the infarct area (nearly 500-fold). Intravenous administration of Tempol at the time of reperfusion reduced 2,3-DHBA production (Vehicle group: 472.2+/-196.2, Tempol group: 238.3+/-77.2) and the cerebral TBARS level (Vehicle group: 541.7+/-84.7, Tempol group: 339.0+/-147.2 nmol/g), and decreased the size of the cerebral infarction (Vehicle group: 202.2+/-98.4, Tempol group: 98.5+/-13.7 mm(3)). In contrast, Tempol administered 15 min prior to reperfusion reduced neither the TBARS level nor the size of the infarction. These results indicate that Tempol administration at the time of reperfusion reduced lipid peroxidation by scavenging free radicals, resulting in a reduction of the infarct size.

Oxidative stress and gene expression in sepsis

Dysregulation of the immuno-inflammatory response, as seen in sepsis, may culminate in host cell and organ damage. Lipopolysaccharide from Gram-negative bacterial cell walls induces gene activation and subsequent inflammatory mediator expression. Gene activation is regulated by a number of transcription factors at the nuclear level, of which nuclear factor kappaB appears to have a central role. The redox (reduction-oxidation) cellular balance is important for normal cellular function, including transcription factor regulation. In sepsis, a state of severe oxidative stress is encountered, with host endogenous antioxidant defences overcome. This has implications for cellular function and the regulation of gene expression. This review gives an overview of the mechanisms by which transcription factor activation and inflammatory mediator overexpression occur in sepsis, together with the events surrounding the state of oxidative stress encountered and the effects on the host's antioxidant defences. The effect of oxidative stress on transcription factor regulation is considered, together with the role of antioxidant repletion in transcription factor activation and in sepsis in general. Other interventions that may modulate transcription factor activation are also highlighted.