The importance of superoxide in nitric oxide-dependent toxicity: evidence for peroxynitrite-mediated injury

Accelerated Bone Healing via Electrical Stimulation

Piezoelectric effect produces an electrical signal when stress is applied to the bone. When the integrity of the bone is destroyed, the biopotential within the defect site is reduced and several physiological responses are initiated to facilitate healing. During the healing of the bone defect, the bioelectric potential returns to normal levels. Treatment of fractures that exceed innate regenerative capacity or exhibit delayed healing requires surgical intervention for bone reconstruction. For bone defects that cannot heal on their own, exogenous electric fields are used to assist in treatment. This paper reviews the effects of exogenous electrical stimulation on bone healing, including osteogenesis, angiogenesis, reduction in inflammation and effects on the peripheral nervous system. This paper also reviews novel electrical stimulation methods, such as small power supplies and nanogenerators, that have emerged in recent years. Finally, the challenges and future trends of using electrical stimulation therapy for accelerating bone healing are discussed.

Pomegranate and Its Components, Punicalagin and Ellagic Acid, Promote Antidepressant, Antioxidant, and Free Radical-Scavenging Activity in Ovariectomized Rats

Previous reports described the antidepressant-like action of the aqueous extract of pomegranate (Punica granatum: AEPG). Thus we evaluated the effect of AEPG and the main compounds found in the extract, punicalagin (PNCG) and ellagic acid (EA), on forced swimming test and the redox environment (reactive oxygen species [ROS] production, lipoperoxidation [LPX], and cellular function) in the brain of rats treated with 3 weeks post ovariectomy exposed ex vivo to pro-oxidants. Also, we selected PNCG and EA to study their antidepressant-like effects (0.001, 0.01, 0.1, 1.0, and 10 mg/kg) in the forced swimming test and their scavenging capacities in chemical combinatorial assays (expressed as IC50 values). We observed a 2-fold increase in the formation of ROS and LPX in the brain after exposure to FeSO4. However, these effects were significantly attenuated when rats were treated with AEPG, PNCG, and EA (1 mg/kg and 0.010 mg/kg for 14 days). AEPG and EA significantly increased the cellular function values of brains that had been affected by the effect of FeSO4 and with ONOO-. PNCG and EA significantly reduced immobility behavior at the lower doses used in this study. The capacity of scavenging compounds to eliminate radicals was for hydroxyl radical (⋅OH), superoxide anion (O2⋅⁣-), and peroxynitrite (ONOO-) as follows: AEPG > punicalagin > ellagic acid. In conclusion, the AEPG and their active compounds PNCG and EA promote antidepressant-like actions and antioxidant activity as they attenuate oxidative damage and prevent cellular dysfunction in ovariectomized rat brains.

On the Antioxidant Properties of L-Kynurenine: An Efficient ROS Scavenger and Enhancer of Rat Brain Antioxidant Defense

L-kynurenine (L-KYN) is an endogenous metabolite, that has been used as a neuroprotective strategy in experimental models. The protective effects of L-KYN have been attributed mainly to kynurenic acid (KYNA). However, considering that L-KYN is prone to oxidation, this redox property may play a substantial role in its protective effects. The aim of this work was to characterize the potential impact of the redox properties of L-KYN, in both synthetic and biological systems. First, we determined whether L-KYN scavenges reactive oxygen species (ROS) and prevents DNA and protein oxidative degradation in synthetic systems. The effect of L-KYN and KYNA (0.1–100 µM) on redox markers (ROS production, lipoperoxidation and cellular function) was compared in rat brain homogenates when exposed to FeSO₄ (10 µM). Then, the effect of L-KYN administration (75 mg/kg/day for 5 days) on the GSH content and the enzymatic activity of glutathione reductase (GR) and glutathione peroxidase (GPx) was determined in rat brain tissue. Finally, brain homogenates from rats pretreated with L-KYN were exposed to pro-oxidants and oxidative markers were evaluated. The results show that L-KYN is an efficient scavenger of ^●OH and ONOO⁻, but not O₂^●– or H₂O₂ and that it prevents DNA and protein oxidative degradation in synthetic systems. L-KYN diminishes the oxidative effect induced by FeSO₄ on brain homogenates at lower concentrations (1 µM) when compared to KYNA (100 µM). Furthermore, the sub-chronic administration of L-KYN increased the GSH content and the activity of both GR and GPx, and also prevented the oxidative damage induced by the ex vivo exposure to pro-oxidants. Altogether, these findings strongly suggest that L-KYN can be considered as a potential endogenous antioxidant.

Human Nitric Oxide Synthase-Its Functions, Polymorphisms, and Inhibitors in the Context of Inflammation, Diabetes and Cardiovascular Diseases

In various diseases, there is an increased production of the free radicals needed to carry out certain physiological processes but their excessive amounts can cause oxidative stress and cell damage. Enzymes play a major role in the transformations associated with free radicals. One of them is nitric oxide synthase (NOS), which catalyzes the formation of nitric oxide (NO). This enzyme exists in three forms (NOS1, NOS2, NOS3), each encoded by a different gene. The following work presents the most important information on the NOS isoforms and their role in the human body, including NO synthesis in various tissues and cells, intercellular signaling and activities supporting the immune system and regulating blood vessel functions. The role of NOS in pathological conditions such as obesity, diabetes and heart disease is considered. Attention is also paid to the influence of the polymorphisms of these genes, encoding particular isoforms, on the development of these pathologies and the role of NOS inhibitors in the treatment of patients.

Influence of Syrgical Trauma on Nitric Oxide and Nitrotyrosine Serum Levels in Patients Undergoing Laparoscopic Or Conventional Cholecystectomy

Background

Oxidative stress represents tissue damage caused by reactive forms of oxygen and nitrogen due to the inability of antioxidant mechanisms to reduce reactive forms into more stable ones. The aim of the study was to evaluate the influence of surgical trauma on nitric oxide (NO) and nitrotyrosine (NT) values in patients undergoing conventional and laparoscopic cholecystectomy.

Methods

A prospective study included sixty patients from the Department of Emergency Surgery, Clinical Centre of Serbia who were operated for gallstone related chronic cholecystitis. All the patients enrolled in the study underwent cholecystectomy; the first group was operated conventionally (30 patients – control group), while the second group was operated laparoscopically (30 patients – treatment group).

Results

There were no statistically significant differences in the values of NO and its postoperative changes in both groups, the conventionally operated group (p=0.943) and the laparoscopically operated group (p=0.393). We found an increase in NT values 24 hours postoperatively (p=0.000) in the conventionally operated patients, while in the group operated laparoscopically we didn’t find statistically significant changes in the values of NT (conventionally operated group (p=0.943) and laparoscopically operated group (p=0.393)).

Conclusions

In our study, we found a significant increase in NT values 24 hours postoperatively in conventionally operated patients i.e. the control group, vs. the treatment group. Further randomized studies are needed for a better understanding of the impact of surgical trauma on oxidative stress response.

Antioxidant properties of xanthones from Calophyllum brasiliense: prevention of oxidative damage induced by FeSO₄

Background

Reactive oxygen species (ROS) are important mediators in a number of degenerative diseases. Oxidative stress refers to the imbalance between the production of ROS and the ability to scavenge these species through endogenous antioxidant systems. Since antioxidants can inhibit oxidative processes, it becomes relevant to describe natural compounds with antioxidant properties which may be designed as therapies to decrease oxidative damage and stimulate endogenous cytoprotective systems. The present study tested the protective effect of two xanthones isolated from the heartwood of Calophyllum brasilienses against FeSO₄-induced toxicity.

Methods

Through combinatory chemistry assays, we evaluated the superoxide (O₂^●—), hydroxyl radical (OH^●), hydrogen peroxide (H₂O₂) and peroxynitrite (ONOO^—) scavenging capacity of jacareubin (xanthone III) and 2-(3,3-dimethylallyl)-1,3,5,6-tetrahydroxyxanthone (xanthone V). The effect of these xanthones on murine DNA and bovine serum albumin degradation induced by an OH• generator system was also evaluated. Additionally, we investigated the effect of these xanthones on ROS production, lipid peroxidation and glutathione reductase (GR) activity in FeSO₄-exposed brain, liver and lung rat homogenates.

Results

Xanthone V exhibited a better scavenging capacity for O₂^●—, ONOO^- and OH^● than xanthone III, although both xanthones were unable to trap H₂O₂. Additionally, xanthones III and V prevented the albumin and DNA degradation induced by the OH^● generator system. Lipid peroxidation and ROS production evoked by FeSO₄ were decreased by both xanthones in all tissues tested. Xanthones III and V also prevented the GR activity depletion induced by pro-oxidant activity only in the brain.

Conclusions

Altogether, the collected evidence suggests that xanthones can play a role as potential agents to attenuate the oxidative damage produced by different pro-oxidants.

Immunopathologic processes in sympathetic ophthalmia as signified by microRNA profiling

PURPOSE

Recent discovery of microRNAs and their negative gene regulation have provided new understanding in the pathogenesis of inflammatory diseases. This study demonstrated microRNA expression profiling and their likely role in sympathetic ophthalmia, using formalin-fixed, paraffin embedded samples.

METHODS

Two groups of four enucleated globes (total eight globes) from patients with clinical and histopathological diagnosis of SO (experimental samples) and one group of four age-matched, noninflamed enucleated globes (control samples) were used. Human genome-wide microRNA PCR array was performed and results were subjected to bioinformatics calculation and P values stringency tests. The targets were searched using the recently published and periodically updated miRWalk software. Quantitative real-time PCR and immunohistochemical staining were performed to confirm the validated targets in the mRNA and in the protein levels, respectively.

RESULTS

No microRNA was significantly upregulated in SO, but 27 microRNAs were significantly downregulated. Among these, four microRNAs (hsa-miR-1, hsa-let-7e, hsa-miR-9, and hsa-miR-182) were known to be associated with the inflammatory signaling pathway. Only hsa-miR-9 has the validated targets, tumor necrosis factor-α, and nuclear factor kappa B1, which have been previously shown to be associated with mitochondrial oxidative stress-mediated photoreceptor apoptosis in eyes with SO.

CONCLUSIONS

Identification of altered levels of microRNAs by microRNA expression profiling may yield new insights into the pathogenesis of SO by disclosing specific microRNA signatures. In the future these may be targeted by synthetic microRNA mimic-based therapeutic strategies.

On the antioxidant properties of kynurenic acid: free radical scavenging activity and inhibition of oxidative stress

Kynurenic acid (KYNA) is an endogenous metabolite of the kynurenine pathway for tryptophan degradation and an antagonist of both N-methyl-D-aspartate (NMDA) and alpha-7 nicotinic acetylcholine (α7nACh) receptors. KYNA has also been shown to scavenge hydroxyl radicals (OH) under controlled conditions of free radical production. In this work we evaluated the ability of KYNA to scavenge superoxide anion (O(2)(-)) and peroxynitrite (ONOO(-)). The scavenging ability of KYNA (expressed as IC(50) values) was as follows: OH=O(2)(-)>ONOO(-). In parallel, the antiperoxidative and scavenging capacities of KYNA (0-150 μM) were tested in cerebellum and forebrain homogenates exposed to 5 μM FeSO(4) and 2.5 mM 3-nitropropionic acid (3-NPA). Both FeSO(4) and 3-NPA increased lipid peroxidation (LP) and ROS formation in a significant manner in these preparations, whereas KYNA significantly reduced these markers. Reactive oxygen species (ROS) formation were determined in the presence of FeSO(4) and/or KYNA (0-100 μM), both at intra and extracellular levels. An increase in ROS formation was induced by FeSO(4) in forebrain and cerebellum in a time-dependent manner, and KYNA reduced this effect in a concentration-dependent manner. To further know whether the effect of KYNA on oxidative stress is independent of NMDA and nicotinic receptors, we also tested KYNA (0-100 μM) in a biological preparation free of these receptors - defolliculated Xenopus laevis oocytes - incubated with FeSO(4) for 1 h. A 3-fold increase in LP and a 2-fold increase in ROS formation were seen after exposure to FeSO(4), whereas KYNA attenuated these effects in a concentration-dependent manner. In addition, the in vivo formation of OH evoked by an acute infusion of FeSO(4) (100 μM) in the rat striatum was estimated by microdialysis and challenged by a topic infusion of KYNA (1 μM). FeSO(4) increased the striatal OH production, while KYNA mitigated this effect. Altogether, these data strongly suggest that KYNA, in addition to be a well-known antagonist acting on nicotinic and NMDA receptors, can be considered as a potential endogenous antioxidant.

Potential utility of melatonin as an antioxidant during pregnancy and in the perinatal period

Reactive oxygen species (ROS) play a critical role in the pathogenesis of various diseases during pregnancy and the perinatal period. Newborns are more prone to oxidative stress than individuals later in life. During pregnancy, increased oxygen demand augments the rate of production of ROS and women, even during normal pregnancies, experience elevated oxidative stress compared with non-pregnant women. ROS generation is also increased in the placenta during preeclampsia. Melatonin is a highly effective direct free-radical scavenger, indirect antioxidant, and cytoprotective agent in human pregnancy and it appears to be essential for successful pregnancy. This suggests a role for melatonin in human reproduction and in neonatal pathologies (asphyxia, respiratory distress syndrome, sepsis, etc.). This review summarizes current knowledge concerning the role for melatonin in human pregnancy and in the newborn. Numerous studies agree that short-term melatonin therapy is highly effective in reducing complications during pregnancy and in the neonatal period. No significant toxicity or treatment-related side effects with long-term melatonin therapy in children and adults have been reported. Treatment with melatonin might result in a wide range of health benefits, including improved quality of life and reduced healthcare costs.

Decreased hepatic ischemia-reperfusion injury by manganese–porphyrin complexes

Reactive oxygen and nitrogen species have been implicated in ischemia-reperfusion (I/R) injury. Metalloporphyrins (MP) are stable catalytic antioxidants that can scavenge superoxide, hydrogen peroxide, peroxynitrite and lipid peroxyl radicals. Studies were conducted with three manganese-porphyrin (MnP) complexes with varying superoxide dimutase (SOD) and catalase catalytic activity to determine if the MnP attenuates I/R injury in isolated perfused mouse livers. The release of the hepatocellular enzymes alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) was maximal at 1 min reperfusion, decreased rapidly and increased gradually by 90 min. Manganese tetrakis-(N-ethyl-2 pyridyl) porphyrin (MnTE-2-PyP) decreased ALT, AST, LDH at 1-90 min reperfusion, while manganese tetrakis-(N-methyl-2 pyridyl) porphyrin (MnTM-2-PyP) and manganese tetrakis-(ethoxycarbonyl) porphyrin (MnTECP) decreased ALT and LDH from 5 to 90 min reperfusion. The release of thiobarbituric acid-reacting substances (TBARS) was diminished by MnTE-2-PyP and MnTM-2-PyP at 90 min. The extent of protein nitration (nitrotyrosine, NT) was decreased in all three MnPs treated livers. These results demonstrate that MnP complexes can attenuate hepatic I/R injury and may have therapeutic implications in disease states involving oxidants.

Oxidative stress of the newborn in the pre- and postnatal period and the clinical utility of melatonin

Newborns, and especially those delivered preterm, are probably more prone to oxidative stress than individuals later in life. Also during pregnancy, increased oxygen demand augments the rate of production of reactive oxygen species (ROS) and women, even with normal pregnancies, experience elevated oxidative stress and lipid peroxidation compared with nonpregnant women. Also, there appears to be an increase in ROS generation in the placenta of pre-eclamptic women. In comparison with healthy adults, newborn infants have lower levels of plasma antioxidants such as vitamin E, beta-carotene, and sulphydryl groups, lower levels of plasma metal binding proteins including ceruloplasmin and transferrin, and reduced activity of erythrocyte superoxide dismutase. This review summarizes conditions of newborns where there is elevated oxidative stress. Included in this group of conditions is asphyxia, respiratory distress syndrome and sepsis and the review also summarizes the literature related to clinical trials of antioxidant therapies and of melatonin, a highly effective antioxidant and free radical scavenger. The authors document there is general agreement that short-term melatonin therapy may be highly effective and that it has a remarkably benign safety profile, even when neonates are treated with pharmacological doses. Significant complications with long-term melatonin therapy in children and adults also have not been reported. None of the animal studies of maternal melatonin treatment or in postnatal life have shown any treatment-related side effects. The authors conclude that treatment with melatonin might result in a wide range of health benefits, improved quality of life and reduced healthcare costs and may help reduce complications in the neonatal period.

Pharmacological evidence for a role of peroxynitrite in the pathophysiology of spinal cord injury

Evidence suggests that the reactive oxygen species peroxynitrite (PN) is an important player in the pathophysiology of acute spinal cord injury (SCI). In the present study, we examined the ability of tempol, a catalytic scavenger of PN-derived free radicals, to alleviate oxidative damage, mitochondrial dysfunction and cytoskeletal degradation following a severe contusion (200 kdyn force) SCI in female Sprague-Dawley rats. PN-mediated oxidative damage in spinal cord tissue, including protein nitration, protein oxidation and lipid peroxidation was significantly reduced by acute tempol treatment (300 mg/kg, i.p. within 5 min post-injury). Injury-induced mitochondrial respiratory dysfunction, measured after 24 h in isolated mitochondria, was partially reversed by tempol along with an attenuation of oxidative damage to mitochondrial proteins. Mitochondrial dysfunction disrupts intracellular Ca(2+) homeostasis contributing to calpain-mediated axonal cytoskeletal protein (alpha-spectrin, 280 kD) degradation. Increased levels of alpha-spectrin breakdown proteins (SBDP 145 kD and 150 kD) were significantly decreased at 24 h in tempol-treated rats indicative of spinal axonal protection. However, a therapeutic window analysis showed that the axonal cytoskeletal protective effects require tempol dosing within the first hour after injury. Nevertheless, these findings are the first to support the concept that PN is an important neuroprotective target in early secondary SCI, and that there is a mechanistic link between PN-mediated oxidative compromise of spinal cord mitochondrial function, loss of intracellular Ca(2+) homeostasis and calpain-mediated proteolytic axonal damage.

Photoreceptor oxidative damage in sympathetic ophthalmia

PURPOSE

To determine photoreceptor oxidative stress and damage in sympathetic ophthalmia (SO).

DESIGN

Immunohistologic study.

METHODS

Eight formalin-fixed and paraffin-embedded human globes with typical histologic features of SO and five age-matched globes without intraocular inflammation (controls) were retrieved from the Doheny Eye Institute ophthalmic pathology files. Deparaffinized sections of the globes were processed to localize tumor necrosis factor-alpha (TNF-alpha), tumor necrosis factor receptor-1 (TNF-R1), acrolein, inducible nitric oxide synthase (iNOS), and nitrotyrosine by immunolocalization method. The latter two were localized to photoreceptor mitochondria using anti-cytochrome C antibody. Apoptotic cells were detected by Terminal deoxynucleotidyl transferase biotin-dUTP Nick End Labeling (TUNEL) assay and were localized to the site of oxidative stress using antinitrotyrosine antibody.

RESULTS

Increased expression of TNF-alpha can be seen in the photoreceptor nuclear layer in all SO globes, whereas no such expression was observed in control globes. TNF-R1, iNOS, acrolein, and nitrotyrosine were immunolocalized to the inner segments of the photoreceptors in all SO globes, but only mild focal staining was observed in the control retinas. Both nitrotyrosine and iNOS immunolocalization revealed positive staining restricted primarily to mitochondria at the inner segments of the photoreceptors. Most of the TUNEL-positive cells were detected in the photoreceptors at the site of nitrotyrosine staining. In contrast, the age-matched control globes showed negative results.

CONCLUSIONS

In SO, photoreceptor mitochondrial oxidative stress occurs in the absence of leukocytic infiltration of the retina and may lead to photoreceptor apoptosis and subsequent vision loss. The oxidative stress seems to be mediated by iNOS and TNF-alpha. The current anti-inflammatory therapy combined with agents that could prevent oxidative stress may prevent photoreceptor damage in SO and may preserve vision.

Kidney damage after renal ablation is worsened in endothelial nitric oxide synthase -/- mice and improved by combined administration of L-arginine and antioxidants

AIM

Reduction in nitric oxide (NO) levels during kidney failure has been related to the reaction of NO with superoxide anions to yield peroxynitrite which possesses the biological activity responsible for renal damage. However, stimulation of the NO pathway ameliorates the progression of kidney failure. Thus, it is unclear whether NO prevents or acts as the compound responsible for the cytotoxicity observed during kidney failure.

METHODS

We evaluated the development of kidney failure in animals that were wild type and deficient in endothelial NO synthase (eNOS -/-) and tested the effects of an antioxidant treatment and NO precursors on the generation of superoxide anion and kidney failure parameters.

RESULTS

In wild-type mice, five-sixths nephrectomy increased proteinuria from 3.0 +/- 0.35 to 14.5 +/- 0.76 mg protein/24 h (P < 0.05), blood pressure from 83.1 +/- 1.8 to 126.6 +/- 1.7 mmHg (P < 0.05), and superoxide production from 1.4 +/- 0.6% to 74.3 +/- 0.8% (P < 0.05). The effects of five-sixths nephrectomy on the eNOS -/- mice were greater compared with wild-type mice. Proteinuria increased from 6.7 +/- 0.5 to 22.7 +/- 2.0 mg protein/24 h (P < 0.05), blood pressure increased from 93.3 +/- 0.9 to 151.2 +/- 3.4 mmHg (P < 0.05), and superoxide production increased from 12.9 +/- 0.5% to 99.8 +/- 1.3% (P < 0.05). The nitrotyrosine levels were lower in eNOS -/- mice as compared to wild-type mice. A combination of L-arginine and antioxidant treatment ameliorated renal damage. The effect was improved in wild-type animals.

CONCLUSION

Our data support the relevance of NO as an antagonist to superoxide in renal tissues and suggest that the loss of this mechanism promotes the progression of kidney failure.

Role of oxidative stress on pathogenesis of hypertensive cerebrovascular lesions

The hypertensive rat brain exhibited softening, severe edema and intracerebral hemorrhage. The NO(2) (-) + NO(3) (-) (NOx) level in the hypertensive rat brain was higher than in the normotensive rat brain. Light microscopy demonstrated severe arterial and arteriolar lesions with fibrinoid deposits and medial lesion. After injecting hypertensive rats with nitroblue tetrazolium (NBT), formazan deposits, which are the reaction product of reduction of NBT by superoxide, were observed in the microvessels and nervous tissue around the microvessels of injured brain. Immunohistochemistry showed that copper zinc superoxide dismutase and manganese superoxide dismutase expression of the endothelial cells of hypertensive rats were also upregulated in comparison with normotensive rat endothelial cells. Inducible nitric oxide synthase and endothelial nitric oxide synthase expression in endothelial cells of normotensive rats were strongly positive, whereas the expression in hypertensive rat endothelial cells was weaker. Nitrotyrosine, a biomarker of peroxynitrite, which is a powerful oxidant formed by the reaction of nitric oxide (NO) with superoxide, was found in the microvessels, injured arteries and arterioles and infarcted brain tissue. Deposition of a major aldehydic product of lipid peroxidation, that is, 4-hydroxy-2-nonenal (4-HNE) was found in microvessels, perivascular tissue, and edematous and infarcted brain. Hypertensive cerebrovascular disease is the result of hypertension-induced oxidative stress.

Effects of prenatal lipopolysaccharide exposure on epithelial development and function in newborn rat intestine

BACKGROUND

Maternal infection during pregnancy is associated with several neonatal morbidities, including periventricular leukomalacia and lung maldevelopment and injury.

OBJECTIVE

To test the hypothesis that responses to prenatal maternal exposure to lipopolysaccharide (LPS) alter intestinal epithelial development and function in newborn rats.

DESIGN/METHODS

Timed-pregnancy female Sprague-Dawley rats were administered either 2 mg LPS or an equal volume of isotonic saline by intraperitoneal injection at E16 and allowed to deliver naturally. Pups were weighed and then killed at days of life (DOL) 0, 3, 7 and 14. Morphometric parameters were measured on standard hematoxylin and eosin-stained sections using ImagePro software. Immunohistochemistry was performed with antibody specific for inducible nitric oxide synthase (iNOS) and 3-nitrotyrosine on distal ileal intestinal samples analyzed at each time point. Optical density was determined and quantified for site-specific regions of intestinal sections. On DOL 14, in vivo mucosal permeability was measured by feeding rats fluorescein isothiocyanate (FITC) via orogastric tube; and then serum FITC was measured.

RESULTS

There were no significant differences in pup weights. Mucosal thicknesses were significantly less in the distal ileum from pups born to LPS-exposed dams on DOL 0, 3 and 7 (P < 0.001). On DOL 0, iNOS protein concentrations in the prenatal LPS treatment group were significantly greater than iNOS protein concentrations in the distal villus (P < 0.001), proximal villus/crypts (P < 0.01), submucosa (P < 0.001) and muscularis (P < 0.01) in the distal small intestine of the control group. On DOL 3, 7 and 14, significant differences were observed in iNOS protein concentrations in the distal villus and submucosal regions between groups (P < 0.001). On DOL 0, 3, 7 and 14, 3-nitrotyrosine immunostaining was significantly elevated in the prenatal LPS-exposed pups in the distal villus on (P < 0.001) as well as in the submucosa on DOL 3 (P < 0.001). Serum FITC measurement was significantly greater in prenatal LPS exposure group at DOL 14 (P < 0.001).

CONCLUSIONS

Maternal exposure to LPS during pregnancy alters intestinal growth and regulation of iNOS in the newborn rat intestine.

Role of nitric oxide on pathogenesis of 5-fluorouracil induced experimental oral mucositis in hamster

INTRODUCTION

Mucositis induced by antineoplastic drugs is an important, dose-limiting, and costly side effect of cancer therapy.

AIM

To investigate the role of nitric oxide (NO) on the pathogenesis of 5-fluorouracil (5-FU)-induced oral mucositis.

MATERIALS AND METHODS

Oral mucositis was induced by two intraperitoneal (i.p) administrations of 5-FU on the first and second days of the experiment (60 and 40 mg/kg, respectively) in male hamsters. Animals were treated subcutaneously with saline (0.4 ml), 1,400 W (1 mg/kg), aminoguanidine (5 or 10 mg/kg) or Nphi-Nitro-L-Arginine Methyl Ester (L-NAME) (5, 10, or 20 mg/kg) 1 h before the injections of 5-FU and daily until sacrifice, on the tenth day. Macroscopic and histopathological analyses were evaluated and graded. Tissues from the cheek pouches were harvested for measurement of myeloperoxidase (MPO) activity, nitrite level, and immunohistochemistry for induced nitric oxide synthase (iNOS).

RESULTS

Treatment with 1,400 W or aminoguanidine reduced macroscopic and histological parameters of oral mucositis, and reduced the inflammatory cell infiltration as detected by histopathology and by MPO activity. In contrast, the administration of L-NAME did not significantly reverse the inflammatory alterations induced by experimental mucositis. Increased NOS activity, nitrite level and immunostaining for iNOS were detected on the check pouch tissue of animals submitted to 5-FU-induced oral mucositis on the tenth day.

CONCLUSION

These results suggest an important role of NO produced by iNOS in the pathogenesis of oral mucositis induced by 5-FU.

Effect of estrogen on differentiation and senescence in endothelial progenitor cells derived from bone marrow in spontaneously hypertensive rats

The functional impairment associated with atherogenic factors, including hypertension, constitutes a limitation to the ability of endothelial progenitor cells (EPCs) to repair. In addition, estrogens have been shown to play a role in reendothelialization after vascular injury. We investigated the effects of estrogens on differentiation and senescence of EPCs derived from bone marrow (BM-EPCs) in spontaneously hypertensive rats (SHR/Izm). Bone marrow (BM) cells were obtained from the tibias and femurs of age-matched, male SHR/Izm and Wistar-Kyoto rats (WKY/Izm). The number of differentiated, adherent BM-EPCs derived from SHR/Izm was significantly smaller than the number derived from WKY/Izm. 17beta-Estradiol (E2) significantly increased the number of adherent BM-EPCs from SHR/Izm, and this effect was significantly attenuated by pharmacological phosphatidylinositol 3-kinase (PI3-K) blockers. Immunoblotting analysis revealed that E2 treatment led to phosphorylation of Akt. Senescence, as assessed by acidic beta-galactosidase staining, occurred at a significantly greater rate in the BM-EPCs from SHR/Izm than in those from WKY/Izm, but E2 treatment dramatically delayed the senescence of BM-EPCs from SHR/Izm. A polymerase chain reaction (PCR)-ELISA based assay revealed that telomerase activity in BM-EPCs from SHR/Izm was significantly lower than in those from WKY/Izm, but that E2 treatment significantly augmented it. Both MTS and colony forming unit assay revealed that E2 treatment significantly augmented the functional activity in BM-endothelial cell (EC)-like cells from SHR/Izm compared to that in control BM-EC-like cells (no treatment). In conclusion, the differentiation of BM-EPCs derived from SHR/Izm was significantly decreased compared with that of BM-EPCs from WKY/Izm. In addition, the rate of senescence was significantly greater in the BM-EPCs from SHR/Izm than in those from WKY/Izm. Estrogen was shown to augment differentiation and delay the onset of senescence in BM-EPCs from SHR/Izm.

Aminoguanidine inhibits caspase-3 and calpain activation without affecting microglial activation following neonatal transient cerebral ischemia

Microglial cells, the resident macrophages of the CNS, can be both beneficial and detrimental to the brain. These cells play a central role as mediators of neuroinflammation associated with many neurodegenerative states, including cerebral ischemia. Because microglial cells are both a major source of inducible nitric oxide synthase (iNOS)/nitric oxide (NO) production locally in the injured brain and are activated by NO-mediated injury, we tested whether iNOS inhibition reduces microglial activation and ischemic injury in a neonatal focal ischemia-reperfusion model. Post-natal day 7 rats were subjected to a 2 h transient middle cerebral artery (MCA) occlusion. Pups with confirmed injury on diffusion-weighted magnetic resonance imaging (MRI) during occlusion were administered 300 mg/kg/dose aminoguanidine (AG) or vehicle at 0, 4 and 18 h after reperfusion, and animals were killed at 24 or 72 h post-reperfusion. The effect of AG on microglial activation as judged by the acquisition of ED1 immunoreactivity and proliferation of ED1-positive cells, on activation of cell death pathways and on injury volume, was determined. The study shows that while AG attenuates caspase 3 and calpain activation in the injured tissue, treatment does not affect the rapidly occurring activation and proliferation of microglia following transient MCA occlusion in the immature rat, or reduce injury size.

Sirolimus accelerates senescence of endothelial progenitor cells through telomerase inactivation

BACKGROUND

Sirolimus-eluting stent (SES) is commonly used to prevent in-stent restenosis but is not infrequently complicated by late angiographic stent thrombosis (LAST). On the other hand, circulating endothelial progenitor cells (EPCs) play a significant role in the maintenance of endothelial integrity.

AIM

We examined whether sirolimus affects differentiation, proliferative activity, senescence, colony formation, and network formation in EPCs originated from mononuclear cells (MNCs).

METHODS AND RESULTS

MNCs were isolated from peripheral blood of healthy volunteers. EPCs outgrew from the culture of MNCs in the presence of vascular endothelial growth factor. When MNCs were incubated with sirolimus at 0.01, 0.1, and 1 ng/ml for 4 days, sirolimus dose-dependently reduced the number of differentiated, adherent EPCs, as assessed by an in vitro culture assay. After ex-vivo cultivation, EPCs became senescent as determined by acidic beta-galactosidase staining. When MNCs were treated with sirolimus, sirolimus dose-dependently accelerated the onset of EPCs senescence. RT-PCR analysis demonstrated that FK506-binding protein 12 (FKBP12), a receptor of sirolimus, was expressed in MNCs. To obtain an insight into the underlying downstream effects of sirolimus, we measured telomerase activity and the expression of p27(kip1). Sirolimus decreased telomerase activity dose-dependently, which was accompanied with down-regulation of the catalytic subunit, telomerase reverse transcriptase (TERT). Furthermore, sirolimus up-regulated the cell cycle inhibitor p27(kip1). Having demonstrated that sirolimus accelerated the onset of senescence, we examined whether that translated into a decrease in proliferative activity and clonal expansion. Both MTS assay and BrdU incorporation assay have shown that sirolimus treatment significantly diminished the proliferative activity in EPCs. In addition, colony forming unit assay revealed that sirolimus dramatically decreased colony formation as compared to control (no treatment). Finally, in a Matrigel assay, EPCs treated with sirolimus were shown to be less integrated into the network formation than control (no treatment).

CONCLUSION

The inhibitory effects of sirolimus on circulating EPCs potently may affect re-endotheliazation after SES implantation.

Opposite effects of pre- and postischemic treatments with nitric oxide donor on ischemia/reperfusion-induced renal injury

We have demonstrated previously that preischemic treatment with FK409 [(+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide], a spontaneous nitric oxide (NO) donor, markedly improves ischemia/reperfusion-induced renal injury. However, there is conflicting information (renoprotective or cytotoxic) as to the contribution of NO to ischemic acute renal failure (ARF). In the present study, we investigated the effect of postischemic treatment with FK409 (1, 3, and 10 mg/kg i.v.) at 6 h after reperfusion on ischemic ARF, in comparison with the preischemic treatment effect. Ischemic ARF was induced by clamping of the left renal artery and vein for 45 min, followed by reperfusion, 2 weeks after contralateral nephrectomy. Renal function in ARF rats markedly decreased at 24 h after reperfusion. Histopathological examination of the kidney of ARF rats revealed severe renal damage. In contrast to the renoprotective effect by preischemic treatment, postischemic treatment with FK409 aggravated the ischemia/reperfusion-induced renal dysfunction and histological damage. Immunohistochemical analysis of renal sections obtained from ARF rats revealed positive staining for nitrotyrosine, a biomarker of peroxynitrite formation, in injured tubular cells, and more intense staining was observed in renal tissues from the animals that received postischemic treatment with FK409. On the other hand, the formation of nitrotyrosine, neutrophil infiltration into renal tissues, and renal superoxide production, all of which were enhanced in ARF rats, were efficiently attenuated by the preischemic treatment with FK409. These results demonstrate that, although preischemic treatment with an NO donor is renoprotective, postischemic treatment with the same agent aggravates the ischemia/reperfusion-induced renal injury, probably through peroxynitrite overproduction.

Estrogen reduces endothelial progenitor cell senescence through augmentation of telomerase activity

BACKGROUND

Recent studies have demonstrated that aging or senescence constitutes a potential limitation to the ability of endothelial progenitor cells (EPCs) to sustain ischemic tissue and repair. Conversely, estrogens have been shown to accelerate recovery of the endothelium after vascular injury.

OBJECTIVE

To investigate whether estrogens are able to prevent senescence of EPCs.

METHODS AND RESULTS

Human EPCs were isolated from peripheral blood and characterized. After ex-vivo cultivation, the cells became senescent as determined by acidic beta-galactosidase staining. 17beta-estradiol dose-dependently inhibited the onset of EPC senescence in culture. Because cellular senescence is critically influenced by telomerase, which elongates telomeres, we measured telomerase activity using a polymerase chain reaction (PCR)-enzyme-linked immunosorbent assay (ELISA) technique. 17beta-estradiol significantly increased telomerase activity. Interestingly, reverse transcriptase-PCR analysis demonstrated that 17beta-estradiol dose-dependently increased the catalytic subunit, telomerase reverse transcriptase (TERT) - an effect that was significantly inhibited by pharmacological phosphatidylinositol 3-kinase (PI3-K) blockers (either wortmannin or LY294002). Because the expression of TERT is regulated by the PI3-K/Akt pathway, we examined the effect of 17beta-estradiol on Akt activity in EPCs. Immunoblotting analysis revealed that 17beta-estradiol dose-dependently led to phosphorylation and, thus, to activation of Akt in EPCs. We also examined whether the protective effect of 17beta-estradiol on EPC senescence translates into the augmentation of mitogenic activity in EPCs. A [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenol)-2-(4-sulfophenyl)-2H-tetrazolium] (MTS) assay demonstrated that the mitogenic potential in EPCs treated with 17beta-estradiol exceeded that in untreated (control) EPCs (P < 0.01). In addition, EPCs released vascular endothelial growth factor (VEGF) protein--an effect that was significantly augmented by 17beta-estradiol. Finally, in a Matrigel assay, EPCs treated with both 17beta-estradiol and VEGF were shown to be more likely to integrate into the network formation than those treated with VEGF alone.

CONCLUSION

The inhibition of EPC senescence by estrogen in vitro may improve the functional activity of EPCs in a way that is important for potential cell therapy.

Angiotensin II accelerates endothelial progenitor cell senescence through induction of oxidative stress

OBJECTIVES

Recent studies have revealed an association between coronary risk factors and both the number and function of bone marrow-derived endothelial progenitor cell (EPC). We investigated the effect of angiotensin II (Ang II) on EPC senescence, leading to the impairment of proliferative activity.

METHODS AND RESULTS

EPCs were isolated from peripheral blood and characterized. Both reverse transcription (RT)-polymerase chain reaction (PCR) and Western blotting were used to assess gp91phox expression. Immunofluorescence of nitrotyrosine provided evidence of peroxynitrite formation. Our data indicate that Ang II increased the expression of gp91phox mRNA in a dose-dependent manner, which was attenuated by Ang II type 1 (AT1) receptor antagonist valsartan. Similarly, Western blotting revealed that Ang II stimulated an increase in gp91phox, whereas pre-treatment with Valsartan reduced the Ang II-induced expression of gp91phox protein. Valsartan as well as superoxide dismutase (SOD) also inhibited Ang II-induced peroxynitrite formation. The exposure of cultured EPC to Ang II (100 nmol/l) significantly accelerated the rate of senescence compared to a control during 14 days in culture as determined by acidic beta-galactosidase staining. Ang II-induced EPC senescence was significantly inhibited by pre-treatment of either valsartan or SOD (P < 0.01). Because cellular senescence is critically influenced by telomerase, which elongates telomeres, we measured telomerase activity by using PCR-enzyme-linked immunosorbent-based assay. Ang II significantly diminished telomerase activity, although the effect was significantly reduced by pre-treatment with either valsartan or SOD (P < 0.01). We examined whether Ang II-induced EPC senescence translates into an impairment of EPC proliferation. MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenol)-2-(4-sulfophenyl)-2H-tetrazolium] assay disclosed an inhibitory effect of Ang II on EPC proliferation.

CONCLUSIONS

Ang II increases gp91phox expression in EPC, which may contribute to oxidative stress, as evidenced by peroxynitrite formation. Ang II accelerates the onset of EPC senescence via increased oxidative stress, which may be related to telomerase inactivation. In addition, Ang II-induced EPC senescence leads to the impairment of proliferative activity.

Lipid peroxidation induced by DHA enrichment modifies paracellular permeability in Caco-2 cells

Dietary enrichment with docosahexaenoic acid (DHA) has numerous beneficial effects on health. However, the intake of high doses of polyunsaturated fatty acids can promote lipid peroxidation and the subsequent propagation of oxygen radicals. The purpose of this study was to evaluate the effect of DHA on lipid peroxidation and tight junction structure and permeability in Caco-2 cell cultures. Moreover, the effects of taurine, a functional ingredient with antioxidant properties, were also tested. Differentiated Caco-2 cell monolayers were maintained in DHA-supplemented conditions with or without added taurine. Incubation with 100 microM DHA increased lipid peroxidation and paracellular permeability, in parallel with a redistribution of the tight junction proteins occludin and ZO-1. Taurine partially prevented all of these effects. The participation of reactive oxygen and nitrogen species in increased paracellular permeability was also examined using various agents that modify the formation of superoxide radical, hydrogen peroxide, nitric oxide, and peroxynitrite. We conclude that hydrogen peroxide and peroxynitrite may be involved in the DHA-induced increase in paracellular permeability and that the protective role of taurine may be in part related to its capacity to counteract the effects of hydrogen peroxide.

Contribution of antioxidants to preventive effect of mesna in cyclophosphamide-induced hemorrhagic cystitis in rats

PURPOSE

The aim of this study was to evaluate whether combination of antioxidants and mesna may prevent cystitis induced by cyclophosphamide better than mesna alone.

MATERIALS AND METHODS

A total of 46 male Sprague-Dawley rats were divided into six groups. Five groups received single dose of cyclophosphamide (CP, 100 mg/kg) intraperitoneally with the same time intervals: group 2 received CP only, group 3 received mesna (21.5 mg/kg for three times), group 4 beta-carotene (20 mg/kg for two times) and mesna, group 5 received alpha-tocopherol (20 mg/kg for two times) and mesna, and group 6 received melatonin (5 mg/kg for two times) and mesna on the day of CP injection. Group 1 served as control.

RESULTS

CP injection resulted in severe cystitis. Mesna has showed meaningful but not full protection against CP toxicity. Although beta-carotene did not show any additional beneficial effect when combined with mesna, alpha-tocopherol and especially melatonin with mesna resulted full protection that the pathologist, blinded to the slides, could not differ from sham control.

CONCLUSION

Oxidants may be important in the pathogenesis of CP-induced cystitis. Melatonin and alpha-tocopherol may help to ameliorate bladder damage along with other drugs such as mesna and diuretics.

Extracellular superoxide dismutase in biology and medicine

Accumulated evidence has shown that reactive oxygen species (ROS) are important mediators of cell signaling events such as inflammatory reactions (superoxide) and the maintenance of vascular tone (nitric oxide). However, overproduction of ROS such as superoxide has been associated with the pathogenesis of a variety of diseases including cardiovascular diseases, neurological disorders, and pulmonary diseases. Antioxidant enzymes are, in part, responsible for maintaining low levels of these oxygen metabolites in tissues and may play key roles in controlling or preventing these conditions. One key antioxidant enzyme implicated in the regulation of ROS-mediated tissue damage is extracellular superoxide dismutase (EC-SOD). EC-SOD is found in the extracellular matrix of tissues and is ideally situated to prevent cell and tissue damage initiated by extracellularly produced ROS. In addition, EC-SOD is likely to play an important role in mediating nitric oxide-induced signaling events, since the reaction of superoxide and nitric oxide can interfere with nitric oxide signaling. This review will discuss the regulation of EC-SOD and its role in a variety of oxidant-mediated diseases.

Mitochondrial complex I, aconitase, and succinate dehydrogenase during hypoxia-reoxygenation: modulation of enzyme activities by MnSOD

Both NADH dehydrogenase (complex I) and aconitase are inactivated partially in vitro by superoxide (O2-.) and other oxidants that cause loss of iron from enzyme cubane (4Fe-4S) centers. We tested whether hypoxia-reoxygenation (H-R) by itself would decrease lung epithelial cell NADH dehydrogenase, aconitase, and succinate dehydrogenase (SDH) activities and whether transfection with adenoviral vectors expressing MnSOD (Ad.MnSOD) would inhibit oxidative enzyme inactivation and thus confirm a mechanism involving O2-. Human lung carcinoma cells with alveolar epithelial cell characteristics (A549 cells) were exposed to <1% O2-5% CO2 (hypoxia) for 24 h followed by air-5% CO2 for 24 h (reoxygenation). NADH dehydrogenase activity was assayed in submitochondrial particles; aconitase and SDH activities were measured in cell lysates. H-R significantly decreased NADH dehydrogenase, aconitase, and SDH activities. Ad.MnSOD increased mitochondrial MnSOD substantially and prevented the inhibitory effects of H-R on enzyme activities. Addition of alpha-ketoglutarate plus aspartate, but not succinate, to medium prevented cytotoxicity due to 2,3-dimethoxy-1,4-naphthoquinone. After hypoxia, cells displayed significantly increased dihydrorhodamine fluorescence, indicating increased mitochondrial oxidant production. Inhibition of NADH dehydrogenase, aconitase, and SDH activities during reoxygenation are due to excess O2-. produced in mitochondria, because enzyme inactivation can be prevented by overexpression of MnSOD.

Superoxide anions induce the maturation of human dendritic cells

Dendritic cells play a key role in immune responses. There is growing evidence that reactive oxygen species participate in signaling pathways involving nuclear factor (NF)-kappaB, leading to expression of important immune system genes. We found that, unlike H2O2, reactive oxygen species generated by the reaction of oxidase on xanthine induced early phenotypic maturation of dendritic cells by upregulating specific markers CD80, CD83, and CD86 and downregulating mannose receptor-mediated endocytosis. Maturation induced by xanthine oxidase was prevented by allopurinol, an inhibitor of xanthine oxidase activity, and by N-acetylcysteine. The proteasome inhibitor MG-132, which blocks NF-kappaB activation, also inhibited CD86 upregulation, but not endocytosis downregulation by reactive oxygen species. Finally, xanthine-xanthine oxidase enhanced or blocked antigen presentation by dendritic cells depending on whether they had been prepulsed or not with the antigen. Taken together, these results demonstrate that oxidative stress induces phenotypic and functional maturation of dendritic cells, partly through an NF-kappaB-dependent mechanism.

The role of nitric oxide in multiple sclerosis

Nitric oxide (NO) is a free radical found at higher than normal concentrations within inflammatory multiple sclerosis (MS) lesions. These high concentrations are due to the appearance of the inducible form of nitric oxide synthase (iNOS) in cells such as macrophages and astrocytes. Indeed, the concentrations of markers of NO production (eg, nitrate and nitrite) are raised in the CSF, blood, and urine of patients with MS. Circumstantial evidence suggests that NO has a role in several features of the disease, including disruption of the blood-brain barrier, oligodendrocyte injury and demyelination, axonal degeneration, and that it contributes to the loss of function by impairment of axonal conduction. However, despite these considerations, the net effect of NO production in MS is not necessarily deleterious because it also has several beneficial immunomodulatory effects. These dual effects may help to explain why iNOS inhibition has not provided reliable and encouraging results in animal models of MS, but alternative approaches based on the inhibition of superoxide production, partial sodium-channel blockade, or the replacement of lost immunomodulatory function, may prove beneficial.

Nitric oxide mediates apoptosis induction selectively in transformed fibroblasts compared to nontransformed fibroblasts

Nitric oxide (NO) mediates apoptosis induction in fibroblasts with constitutive src or induced ras oncogene expression, whereas nontransformed parental cells and revertants are not affected. This direct link between the transformed phenotype and sensitivity to NO-mediated apoptosis induction seems to be based on the recently described extracellular superoxide anion generation by transformed cells, as NO-mediated apoptosis induction in transformed cells is inhibited by extracellular superoxide dismutase (SOD), by SOD mimetics and by apocynin, an inhibitor of NADPH oxidase. Furthermore, nonresponsive nontransformed cells can be rendered sensitive for NO-mediated apoptosis induction when they are supplemented with xanthine oxidase/xanthine as an extracellular source for superoxide anions. As superoxide anions and NO readily interact in a diffusion-controlled reaction to generate peroxynitrite, peroxynitrite seems to be the responsible apoptosis inducer in NO-mediated apoptosis induction. In line with this conclusion, NO-mediated apoptosis induction in superoxide anion-generating transformed cells is inhibited by the peroxynitrite scavengers ebselen and FeTPPS. Moreover, direct application of peroxynitrite induces apoptosis both in transformed and nontransformed cells, indicating that peroxynitrite is no selective apoptosis inducer per se, but that selective apoptosis induction in transformed cells by NO is achieved through selective peroxynitrite generation. The interaction of NO with target cell derived superoxide anions represents a novel concept for selective apoptosis induction in transformed cells. This mechanism may be the basis for selective apoptosis induction by natural antitumor systems (like macrophages, natural killer cells, granulocytes) that utilize NO for antitumor action. Apoptosis induction mediated by NO involves mitochondrial depolarization and is blocked by Bcl-2 overexpression.

Life imaging of peroxynitrite in rat microglial and astroglial cells: Role of superoxide and antioxidants

Free radicals, such as superoxide and nitric oxide, are known to play a role in a number of inflammatory and degenerative brain diseases, in which resident microglia upregulate the inducible nitric oxide synthase (iNOS) and thus produce large amounts of nitric oxide. Simultaneously, microglia generate superoxide mainly via NADPH-oxidase, which reacts at a diffusion-limited rate with nitric oxide to form the powerful oxidant peroxynitrite. We used mixed astroglial/microglial cultures to study the effects of iNOS induction by lipopolysaccharide and interferon-gamma on free radical formation. Using the fluorogenic compound 2,7-dihydrodichlorofluorescein diacetate, we monitored cellular peroxynitrite formation by confocal laser microscopy. Peroxynitrite formation in continuously nitric oxide-producing microglial cells was rather limited. However, activation of the superoxide-generating enzyme NADPH-oxidase dramatically increased DCF fluorescence within a few minutes. We conclude that superoxide is the limiting factor for peroxynitrite formation. Since the formation and oxidant activity of peroxynitrite depends strongly on the availability of cellular antioxidants, we investigated the capacity of several compounds to influence peroxynitrite formation. Among the substances under investigation in this study, glutathione and the synthetic compound ebselen had a major effect on preventing peroxynitrite formation, whereas ascorbate failed to decrease peroxynitrite levels.

Role of superoxide anion in regulating pressor and vascular hypertrophic response to angiotensin II

Our purpose was to address the role of NAPDH oxidase-derived superoxide anion in the vascular response to ANG II. Blood pressure, aortic superoxide anion, 3-nitrotyrosine, and medial cross-sectional area were compared in wild-type mice and in mice that overexpress human superoxide dismutase (hSOD). The pressor response to ANG II was significantly less in hSOD mice. Superoxide anion levels were increased twofold in ANG II-treated wild-type mice but not in hSOD mice. 3-Nitrotyrosine increased in aortic endothelium and adventitia in wild-type but not hSOD mice. In contrast, aortic medial cross-sectional area increased 50% with ANG II in hSOD mice, comparable to wild-type mice. The lower pressor response to ANG II in the mice expressing hSOD is consistent with a pressor role of superoxide anion in wild-type mice, most likely because it reacts with nitric oxide. Despite preventing the increase in superoxide anion and 3-nitrotyrosine, the aortic hypertrophic response to ANG II in vivo was unaffected by hSOD.

Nitration of manganese superoxide dismutase during ocular inflammation

Reactive nitrogen species, in particular, peroxynitrite (ONOO(-)) have been proposed to play an important role in the pathogenesis of endotoxin-induced uveitis (EIU). Tyrosine nitration by ONOO(-) has been shown in other model systems to inhibit the activity of the superoxide anion quenching enyzme, manganese superoxide dismutase (MnSOD), perhaps contributing to progression of disease. In this study, it is confirmed through immunoanalysis that nitrated proteins are produced during EIU, and furthermore, that MnSOD is a target of nitration during the inflammatory response. In addition, through microsequencing analyses, nitrated albumin--apparent in both control and EIU eyes--was identified. Positive immunostaining of nitrated proteins was seen in the ciliary epithelium, inflammatory cells, and protein exudate of eyes from rats injected with endotoxin. Incubation of nitrotyrosine immunoprecipitates from the iris and ciliary body (ICB) with a polyclonal antibody against MnSOD revealed that nitrated MnSOD was present only in the ICB of EIU rats. When the total activity of the enzyme was examined, it was observed that despite the presence of nitrated MnSOD, activity was increased relative to control. Analysis of MnSOD mRNA and protein from the ICB of both groups demonstrated an increase in mRNA expression and consequently a three- to five-fold increase in MnSOD protein in EIU rats as compared to control rats. Further examination of MnSOD protein expression through immunohistochemistry noted enhanced immunostaining in the ciliary epithelium of eyes of EIU rats. Additional investigation of a 70 kDa band apparent in nitrotyrosine immunoprecipitates from the ICB of control and EIU rats revealed that the plasma protein albumin is nitrated as well. This protein is present as a result of the breakdown of the blood-aqueous barrier during inflammation. In summary, two endogenous nitration targets, albumin and MnSOD, were identified. Nitrated MnSOD appears to be specifically targeted to the ICB during inflammation, underscoring the importance of the interface in EIU. Furthermore, the expression and activity of the enzyme is increased in the ICB during EIU, perhaps regulating reactive nitrogen species produced within the cells. This study implicates ONOO(-) in the pathogenesis of EIU and imparts the putative role MnSOD plays in disease resolution.

An alternative signaling pathway based on nitryl chloride during intercellular induction of apoptosis

Transforming growth factor (TGF)-beta pretreated nontransformed fibroblasts induce apoptosis selectively in transformed fibroblasts. This potential control step during oncogenesis has been termed intercellular induction of apoptosis. Selectivity and efficiency of intercellular induction of apoptosis depend on transformed target cell-derived superoxide anions that drive two intercellular signaling pathways--the HOCl/hydroxyl radical and the nitric oxide (NO)/peroxynitrite pathway. Other natural antitumor systems like macrophages or cells of the granulocyte lineage seem to utilize the same signaling chemistry. Our data demonstrate the existence of an alternative signaling pathway in these systems. This pathway depends on the presence of nitrite and is still effective when the two conventional signaling pathways are blocked by superoxide dismutase (SOD). Nitrite-dependent apoptosis induction is neither blocked by SOD nor by the hydroxyl radical scavenger terephthalate, but it is inhibited by the peroxidase inhibitor aminobenzoyl hydrazide and by the hypochlorous acid (HOCl) scavenger taurine. Therefore, nitrite, that is nontoxic for our cells, seems to interact with HOCl to form the apoptosis inducer nitryl chloride. Nitryl chloride-mediated apoptosis induction might be relevant for apoptosis induction in tumor cells that release SOD and thus escape the two classical signaling pathways.

Signaling and proapoptotic functions of transformed cell-derived reactive oxygen species

Transformed fibroblasts generate extracellular superoxide anions through the recently identified membrane-associated NADPH oxidase. These cell-derived superoxide anions exhibit signaling functions such as regulation of proliferation and maintenance of the transformed state. Their dismutation product hydrogen peroxide regulates the intracellular level of catalase, whose activity has been observed to be upregulated in certain transformed cells. After glutathione depletion, transformed cell-derived reactive oxygen species (ROS) exhibit apoptosis-inducing potential through the metal-catalyzed Haber-Weiss reaction. Moreover, transformed cell-derived ROS represent key elements for selective and efficient apoptosis induction by natural antitumor systems (such as fibroblasts, granulocytes and macrophages). These effector cells release peroxidase, which utilizes target cell-derived hydrogen peroxide for HOCl synthesis. In a second step, HOCl interacts with target cell-derived superoxide anions and forms apoptosis-inducing hydroxyl radicals. In a parallel signaling pathway, effector cell-derived NO interacts with target cell-derived superoxide anions and generates the apoptosis inducer peroxynitrite. Therefore, transformed cell-derived ROS determine transformed cells as selective targets for induction of apoptosis by these effector systems. It is therefore proposed that transformed cell derived ROS interact with associated cells to exhibit directed and specific signaling functions, some of which are beneficial and some of which can become detrimental to transformed cells.

Extracellular superoxide dismutase overexpression improves behavioral outcome from closed head injury in the mouse

Oxidative stress is known to play an important role in the response of brain to traumatic insults. We tested the hypothesis that increased extracellular superoxide dismutase (EC-SOD) expression can reduce injury in a mouse model of closed head injury. Neurologic, cognitive, and histologic outcomes were compared between transgenic mice exhibiting a fivefold increase in EC-SOD activity and wild-type littermate controls. Severe or moderate transcranial impact was induced in anesthetized and physiologically controlled animals. After severe impact, transgenic mice had better neurological outcome at 24 hr postinjury (p = 0.038). Brain water content was increased, but there was no difference between groups. Moderate impact resulted in predominantly mild neurologic deficits in both groups at both 24 hr and 14 days postinjury. Morris water maze performance, testing cognitive function at 14-17 days after trauma, was better in EC-SOD overexpressors (p = 0.018). No differences were observed between groups for histologic damage in hippocampal CA1 and CA3. We conclude that EC-SOD has a beneficial effect on behavioral outcome after both severe and moderate closed head injury in mice. Because EC-SOD is believed to be predominantly located in the extracellular space, these data implicate an adverse effect of extracellular superoxide anion on outcome from closed head injury.

Role of NADPH Oxidase in the Vascular Hypertrophic and Oxidative Stress Response to Angiotensin II in Mice

Abstract —Oxygen-derived free radicals are involved in the vascular response to angiotensin II (Ang II), but the role of NADPH oxidase, its subunit proteins, and their vascular localization remain controversial. Our purpose was to address the role of NADPH oxidase in the blood pressure (BP), aortic hypertrophic, and oxidant responses to Ang II by taking advantage of knockout (KO) mice that are genetically deficient in gp91 phox , an NADPH oxidase subunit protein. The baseline BP was significantly lower in KO mice than in wild-type (WT) (92±2 [KO] versus 101±1 [WT] mm Hg, P <0.01), but infusion of Ang II for 6 days caused similar increases in BP in the 2 strains (33±4 [KO] versus 38±2 [WT] mm Hg, P >0.4). Ang II increased aortic superoxide anion production 2-fold in the aorta of WT mice but did not do so in KO mice. Aortic medial area increased in WT (0.12±0.02 to 0.17±0.02 mm 2 , P <0.05), but did not do so in KO mice (0.10±0.01 to 0.11±0.01 mm 2 , P >0.05). Histochemistry and polymerase chain reaction demonstrated gp91 phox localized in endothelium and adventitia of WT mice. Levels of reactive oxidant species as indicated by 3-nitrotyrosine immunoreactivity increased in these regions in WT but not in KO mouse aorta in response to Ang II. These results indicate an essential role in vivo of gp91 phox and NADPH oxidase–derived superoxide anion in the regulation of basal BP and a pressure-independent vascular hypertrophic and oxidant stress response to Ang II.

Target cell-derived superoxide anions cause efficiency and selectivity of intercellular induction of apoptosis

Transformed fibroblasts are specifically eliminated by their nontransformed neighbors through intercellular induction of apoptosis. This process depends on the number of nontransformed effector cells and on the local density of transformed target cells. Intercellular signalling is inhibited by SOD (a scavenger of superoxide anions), taurine (a scavenger of HOCl), 4-aminobenzoyl hydrazide (a mechanism-based inhibitor of peroxidase), DMSO (a hydroxyl radical scavenger), and two inhibitors of NO synthase. Therefore, selective apoptosis induction seems to be based on superoxide anion production by transformed cells, their spontaneous dismutation to hydrogen peroxide, and HOCl generation by a novel effector cell-derived peroxidase. HOCl then interacts with target cell-derived superoxide anions to yield hydroxyl radicals. Due to the short diffusion pathway of superoxide anions, hydroxyl radical generation is confined to the intimate vicinity of transformed cells. In parallel, NO derived from effector cells interacts with superoxide anions of target cells to yield the apoptosis inducer peroxynitrite. Reconstitution experiments using transformed or nontransformed cells in conjunction with myeloperoxidase, HOCl, or an NO donor demonstrated that superoxide anions generated extracellularly by transformed cells participate in intercellular signalling and at the same time determine transformed cells as selective targets for intercellular induction of apoptosis.

Modification of inflammatory response to implanted biomedical materials in vivo by surface bound superoxide dismutase mimics

The healing response to implanted biomedical materials involves varying degrees and stages of inflammation and healing which in some cases leads to device failure. In this article, we describe synthetic methods and in vivo results of a novel surface treatment for biomedical materials involving covalent conjugation of a low molecular weight superoxide dismutase mimic (SODm), which imparts anti-inflammatory character to the material. SODm investigated in this study are a new class of anti-inflammatory drugs consisting of a Mn(II) complex of a macrocyclic polyamine ring that catalyze the dismutation of superoxide at rates equivalent to that of native enzyme. The SODms were covalently linked to small disks of ultra-high molecular weight polyethylene, poly(etherurethane urea), and tantalum metal at two concentrations and implanted in a subcutaneous rat implant model for 3, 7, 14, and 28 days. Histological examination of the implant tissue performed at 3 and 28 days revealed striking anti-inflammatory effects on both acute and chronic inflammatory responses. At 3 days, the formation of a neutrophil-rich acute inflammatory infiltrate seen in control implants was inhibited for all three materials treated with SODm. At 28 days, foreign body giant cell formation (number of FBGCs per field) and fibrous capsule formation (mean thickness of implant capsule) were also significantly inhibited over untreated control implants. A mechanism based on our current understanding of superoxide as an inflammatory mediator at implanted biomedical materials is proposed.

Mice overexpressing extracellular superoxide dismutase have increased resistance to global cerebral ischemia

Transgenic mice, which exhibit a fivefold increase in brain parenchymal extracellular superoxide dismutase (EC-SOD) activity, were used to investigate the role of EC-SOD in global ischemic brain injury. Halothane-anesthetized normothermic wild-type (n = 22) and transgenic (n = 20) mice underwent 10 min of near-complete forebrain ischemia induced by bilateral carotid artery occlusion and systemic hypotension (mean arterial pressure = 30 mm Hg). After 3 days of recovery, the brains were histologically examined. Other mice underwent autoradiographic determination of regional CBF 10 min prior to, during, and 30 min after forebrain ischemia. Histologic injury in the cortex and caudoputamen was minimal in both groups. The percentage of dead hippocampal CA1 neurons was reduced in the EC-SOD transgenic group (wild type = 44 +/- 28%; EC-SOD transgenic = 23 +/- 21%, mean +/- SD, P = 0.015). CBF was similar between groups prior to ischemia. The intraischemic blood flow was severely reduced in forebrain structures and was similar between groups. Blood flow at 30 min postischemia had recovered to 50-60% of baseline values in both groups. These results indicate that EC-SOD can play an important role in defining the magnitude of selective neuronal necrosis resulting from near-complete forebrain ischemia. This implicates involvement of extracellular superoxide anions in the pathologic response to global cerebral ischemia.

The Ginkgo biloba extract (EGb 761) protects and rescues hippocampal cells against nitric oxide-induced toxicity: involvement of its flavonoid constituents and protein kinase C

An excess of the free radical nitric oxide (NO) is viewed as a deleterious factor involved in various CNS disorders. Numerous studies have shown that the Ginkgo biloba extract EGb 761 is a NO scavenger with neuroprotective properties. However, the mechanisms underlying its neuroprotective ability remain to be fully established. Thus, we investigated the effect of different constituents of EGb 761, i.e., flavonoids and terpenoids, against toxicity induced by NO generators on cells of the hippocampus, a brain area particularly susceptible to neurodegenerative damage. Exposure of rat primary mixed hippocampal cell cultures to either sodium nitroprusside (SNP; 100 microM) or 3-morpholinosydnonimine resulted in both a decrease in cell survival and an increase in free radical accumulation. These SNP-induced events were blocked by either EGb 761 (10-100 microg/ml) or its flavonoid fraction CP 205 (25 microg/ml), as well as by inhibitors of protein kinase C (PKC; chelerythrine) and L-type calcium channels (nitrendipine). In contrast, the terpenoid constituents of EGb 761, known as bilobalide and ginkgolide B, as well as inhibitors of phospholipases A [3-[(4-octadecyl)benzoyl]acrylic acid (OBAA)] and C (U-73122), failed to display any significant effects. Moreover, EGb 761 (50 microm) CP 205 (25 microg/ml), and chelerythrine were also able to rescue hippocampal cells preexposed to SNP (up to 1 mM). Finally, EGb 761 (100 microg/ml) was shown to block the activation of PKC induced by SNP (100 microM). These data suggest that the protective and rescuing abilities of EGb 761 are not only attributable to the antioxidant properties of its flavonoid constituents but also via their ability to inhibit NO-stimulated PKC activity.

Measurement of 3-nitrotyrosine and 5-nitro-gamma-tocopherol by high-performance liquid chromatography with electrochemical detection

Nitric oxide (NO) is a lipophilic gaseous molecule synthesized by the enzymatic oxidation of L-arginine. During periods of inflammation, phagocytic cells generate copious quantities of NO and other reactive oxygen species. The combination of NO with other reactive oxygen species promotes nitration of ambient biomolecules, including protein tyrosine residues and membrane-localized gamma-tocopherol. The oxidative chemistry of NO and derived redox congeners is reviewed. Techniques are described for the determination of 3-nitro-tyrosine and 5-nitro-gamma-tocopherol in biological samples using high-performance liquid chromatography with electrochemical detection.

Activity-dependent neurotrophic factor peptide (ADNF9) protects neurons against oxidative stress-induced death

Activity-dependent neurotrophic factor (ADNF) and a 14-amino acid fragment of this peptide (sequence VLGGGSALLRSIPA) protect neurons from death associated with an array of toxic conditions, including amyloid beta-peptide, N-methyl-D-aspartate, tetrodotoxin, and the neurotoxic HIV envelope coat protein gp120. We report that an even smaller, nine-amino acid fragment (ADNF9) with the sequence SALLRSIPA potently protects cultured embryonic day 18 rat hippocampal neurons from oxidative injury and neuronal apoptosis induced by FeSO4 and trophic factor withdrawal. Among the characteristics of this protection are maintenance of mitochondrial function and a reduction in accumulation of intracellular reactive oxygen species.

Nitric oxide and peroxynitrite. The ugly, the uglier and the not so good: a personal view of recent controversies

Nitric oxide, a gaseous free radical, is poorly reactive with most biomolecules but highly reactive with other free radicals. Its ability to scavenge peroxyl and other damaging radicals may make it an important antioxidant in vivo, particularly in the cardiovascular system, although this ability has been somewhat eclipsed in the literature by a focus on the toxicity of peroxynitrite, generated by reaction of O2*- with NO* (or of NO- with O2). On balance, experimental and theoretical data support the view that ONOO- can lead to hydroxyl radical (OH*) generation at pH 7.4, but it seems unlikely that OH* contributes much to the cytotoxicity of ONOO-. The cytotoxicity of ONOO- may have been over-emphasized: its formation and rapid reaction with antioxidants may provide a mechanism of using NO* to dispose of excess O2*-, or even of using O2*- to dispose of excess NO*, in order to maintain the correct balance between these radicals in vivo. Injection or instillation of "bolus" ONOO- into animals has produced tissue injury, however, although more experiments generating ONOO- at steady rates in vivo are required. The presence of 3-nitrotyrosine in tissues is still frequently taken as evidence of ONOO- generation in vivo, but abundant evidence now exists to support the view that it is a biomarker of several "reactive nitrogen species". Another under-addressed problem is the reliability of assays used to detect and measure 3-nitrotyrosine in tissues and body fluids: immunostaining results vary between laboratories and simple HPLC methods are susceptible to artefacts. Exposure of biological material to low pH (e.g. during acidic hydrolysis to liberate nitrotyrosine from proteins) or to H2O2 might cause artefactual generation of nitrotyrosine from NO2- in the samples. This may be the origin of some of the very large values for tissue nitrotyrosine levels quoted in the literature. Nitrous acid causes not only tyrosine nitration but also DNA base deamination at low pH: these events are relevant to the human stomach since saliva and many foods are rich in nitrite. Several plant phenolics inhibit nitration and deamination in vitro, an effect that could conceivably contribute to their protective effects against gastric cancer development.

Oxidative stress in brain ischemia

Brain ischemia initiates a complex cascade of metabolic events, several of which involve the generation of nitrogen and oxygen free radicals. These free radicals and related reactive chemical species mediate much of damage that occurs after transient brain ischemia, and in the penumbral region of infarcts caused by permanent ischemia. Nitric oxide, a water- and lipid-soluble free radical, is generated by the action of nitric oxide synthases. Ischemia causes a surge in nitric oxide synthase 1 (NOS 1) activity in neurons and, possibly, glia, increased NOS 3 activity in vascular endothelium, and later an increase in NOS 2 activity in a range of cells including infiltrating neutrophils and macrophages, activated microglia and astrocytes. The effects of ischemia on the activity of NOS 1, a Ca2+-dependent enzyme, are thought to be secondary to reversal of glutamate reuptake at synapses, activation of NMDA receptors, and resulting elevation of intracellular Ca2+. The up-regulation of NOS 2 activity is mediated by transcriptional inducers. In the context of brain ischemia, the activity of NOS 1 and NOS 2 is broadly deleterious, and their inhibition or inactivation is neuroprotective. However, the production of nitric oxide in blood vessels by NOS 3, which, like NOS 1, is Ca2+-dependent, causes vasodilatation and improves blood flow in the penumbral region of brain infarcts. In addition to causing the synthesis of nitric oxide, brain ischemia leads to the generation of superoxide, through the action of nitric oxide synthases, xanthine oxidase, leakage from the mitochondrial electron transport chain, and other mechanisms. Nitric oxide and superoxide are themselves highly reactive but can also combine to form a highly toxic anion, peroxynitrite. The toxicity of the free radicals and peroxynitrite results from their modification of macromolecules, especially DNA, and from the resulting induction of apoptotic and necrotic pathways. The mode of cell death that prevails probably depends on the severity and precise nature of the ischemic injury. Recent studies have emphasized the role of peroxynitrite in causing single-strand breaks in DNA, which activate the DNA repair protein poly(ADP-ribose) polymerase (PARP). This catalyzes the cleavage and thereby the consumption of NAD+, the source of energy for many vital cellular processes. Over-activation of PARP, with resulting depletion of NAD+, has been shown to make a major contribution to brain damage after transient focal ischemia in experimental animals. Neuronal accumulation of poly(ADP-ribose), the end-product of PARP activity has been demonstrated after brain ischemia in man. Several therapeutic strategies have been used to try to prevent oxidative damage and its consequences after brain ischemia in man. Although some of the drugs used in early studies were ineffective or had unacceptable side effects, other trials with antioxidant drugs have proven highly encouraging. The findings in recent animal studies are likely to lead to a range of further pharmacological strategies to limit brain injury in stroke patients.

Biological aspects of reactive nitrogen species

Nitric oxide (NO) plays an important role as a cell-signalling molecule, anti-infective agent and, as most recently recognised, an antioxidant. The metabolic fate of NO gives rise to a further series of compounds, collectively known as the reactive nitrogen species (RNS), which possess their own unique characteristics. In this review we discuss this emerging aspect of the NO field in the context of the formation of the RNS and what is known about their effects on biological systems. While much of the insight into the RNS has been gained from the extensive chemical characterisation of these species, to reveal biological consequences this approach must be complemented by direct measures of physiological function. Although we do not know the consequences of many of the dominant chemical reactions of RNS an intriguing aspect is now emerging. This review will illustrate how, when specificity and amplification through cell signalling mechanisms are taken into account, the less significant reactions, in terms of yield or rates, can explain many of the biological responses of exposure of cells or physiological systems to RNS.