Peroxynitrite: a two-faced metabolite of nitric oxide

Steroid Phobia: Is There a Basis? A Review of Topical Steroid Safety, Addiction and Withdrawal

There is a growing concern amongst patients about topical corticosteroid (TCS) side effects, with increasing discussion of topical steroid addiction (TSA) and topical steroid withdrawal (TSW) particularly on social media platforms. However, the acceptance of TSA/TSW as a distinct condition remains controversial within the dermatological community. We conducted a literature search using PubMed, MEDLINE, Cochrane Library, Google Scholar, Embase and Web of Science to identify original articles addressing TSA/TSW. We described the definition and reported clinical features of TSA/TSW including its classification into erythemato-edematous and papulopustular subtype. To assess the validity of TSA/TSW, we summarised and objectively appraised the postulated mechanisms for this condition, including tachyphylaxis, dysregulation of glucocorticoid receptors, rebound vasodilation and impaired skin barrier leading to a cytokine cascade. Understanding the evidence including its limitations and uncertainties highlights areas for future research and helps medical practitioners better counsel and provide care to patients who may be experiencing or who have concerns about TSA/TSW.

Insights in pathogenesis of multiple sclerosis: nitric oxide may induce mitochondrial dysfunction of oligodendrocytes

Demyelinating diseases, such as multiple sclerosis (MS), are kinds of common diseases in the central nervous system (CNS), and originated from myelin loss and axonal damage. Oligodendrocyte dysfunction is the direct reason of demyelinating lesions in the CNS. Nitric oxide (NO) plays an important role in the pathological process of demyelinating diseases. Although the neurotoxicity of NO is more likely mediated by peroxynitrite rather than NO itself, NO can impair oligodendrocyte energy metabolism through mediating the damaging of mitochondrial DNA, mitochondrial membrane and mitochondrial respiratory chain complexes. In the progression of MS, NO can mainly mediate demyelination, axonal degeneration and cell death. Hence, in this review, we extensively discuss endangerments of NO in oligodendrocytes (OLs), which is suggested to be the main mediator in demyelinating diseases, e.g. MS. We hypothesize that NO takes part in MS through impairing the function of monocarboxylate transporter 1, especially causing axonal degeneration. Then, it further provides a new insight that NO for OLs may be a reliable therapeutic target to ameliorate the course of demyelinating diseases.

Effect of Nitric Oxide and Peroxynitrite on Mucociliary Transport Function of Experimental Otitis Media

OBJECTIVES: To determine the role of nitric oxide (NO) and peroxynitrite on mucociliary activity in experimental otitis media with effusion (OME).

STUDY DESIGN AND SETTING: Twenty guinea pigs were divided into 1 control and 3 experimental groups; lipopolysaccharide (LPS), NG-nitro-L-arginine methyl ester (L-NAME), and uric acid (UA) groups. Ten ears were used in each group. OME was induced by transtympanic injection of LPS in experimental groups. Twenty-four hours after the transtympanic injection, dye transfer time (DTT) was measured and the temporal bone was taken for histopathologic examination. Expression of peroxynitrite was determined by immunohistochemical stain for 3-nitrotyrosine (3-NT).

RESULTS: Dye transfer time was significantly delayed in LPS group compared to control group; by contrast it was significantly reduced in L-NAME or UA treated groups ( P < 0.01). Histopathologic examination showed reduced inflammation and mucosal thickening in the treatment groups when compared to LPS group. These findings, however, were not statistically significant. Immunoreactivity to 3-NT was intense in LPS group and decreased in the treatment groups ( P < 0.05).

CONCLUSIONS: It is suggested that LPS induced mucociliary dysfunction in the middle ear by NO and peroxynitrite-mediated pathways.

The inhibitory effect of mesenchymal stem cell on blood-brain barrier disruption following intracerebral hemorrhage in rats: contribution of TSG-6

Background

Mesenchymal stem cells (MSCs) are well known having beneficial effects on intracerebral hemorrhage (ICH) in previous studies. The therapeutic mechanisms are mainly to investigate proliferation, differentiation, and immunomodulation. However, few studies have used MSCs to treat blood–brain barrier (BBB) leakage after ICH. The influence of MSCs on the BBB and its related mechanisms were investigated when MSCs were transplanted into rat ICH model in this study.

Methods

Adult male Sprague–Dawley (SD) rats were randomly divided into sham-operated group, PBS-treated (ICH + PBS) group, and MSC-treated (ICH + MSC) group. ICH was induced by injection of IV collagenase into the rats’ brains. MSCs were transplanted intravenously into the rats 2 h after ICH induction in MSC-treated group. The following factors were compared: inflammation, apoptosis, behavioral changes, inducible nitric oxide synthase (iNOS), matrix metalloproteinase 9 (MMP-9), peroxynitrite (ONOO⁻), endothelial integrity, brain edema content, BBB leakage, TNF-α stimulated gene/protein 6 (TSG-6), and nuclear factor-κB (NF-κB) signaling pathway.

Results

In the ICH + MSC group, MSCs decreased the levels of proinflammatory cytokines and apoptosis, downregulated the density of microglia/macrophages and neutrophil infiltration at the ICH site, reduced the levels of iNOS and MMP-9, attenuated ONOO⁻ formation, and increased the levels of zonula occludens-1 (ZO-1) and claudin-5. MSCs also improved the degree of brain edema and BBB leakage. The protective effect of MSCs on the BBB in ICH rats was possibly invoked by increased expression of TSG-6, which may have suppressed activation of the NF-κB signaling pathway. The levels of iNOS and ONOO⁻, which played an important role in BBB disruption, decreased due to the inhibitory effects of TSG-6 on the NF-κB signaling pathway.

Conclusions

Our results demonstrated that intravenous transplantation of MSCs decreased the levels of ONOO⁻ and degree of BBB leakage and improved neurological recovery in a rat ICH model. This strategy may provide a new insight for future therapies that aim to prevent breakdown of the BBB in patients with ICH and eventually offer therapeutic options for ICH.

Regulation of nitric oxide production by δ-opioid receptors during glaucomatous injury

To determine the roles of nitric oxide in glaucomatous injury and its regulation by δ-opioid-receptor activation, animals were treated with: 1) a selective inducible nitric oxide synthase (iNOS) inhibitor (aminoguanidine; AG; 25 mg/kg, i.p.); 2) δ-opioid-receptor agonist (SNC-121; 1 mg/kg, i.p.); or 3) with both drugs simultaneously for 7 days, once daily. The loss in retinal ganglion cell (RGC) numbers and their function in glaucomatous eyes were significantly improved in the presence of AG or SNC-121; however, we did not see any significant additive or synergistic effects when animals were treated with both drugs simultaneously. The levels of nitrate-nitrite were significantly increased in the glaucomatous retina when compared with normal retina (normal retina 86±9 vs. glaucomatous retina 174±10 mM/mg protein), which was reduced significantly when animals were treated either with SNC-121 (121±7 mM/mg protein; P<0.05) or AG (128±10 mM/mg protein; P<0.05). Additionally, SNC-121-mediated reduction in nitrate-nitrite levels was not only blocked by naltrindole (a δ-opioid-receptor antagonist), but naltrindole treatment potentiated the nitrate-nitrite production in glaucomatous retina (235±4 mM/mg protein; P<0.001). As expected, naltrindole treatment also fully-blocked SNC-121-mediated retina neuroprotection. The nitrotyrosine level in the glaucomatous retina was also increased, which was significantly reduced in the SNC-121-treated animals. Additionally, the expression level of iNOS was clearly increased over the control levels in the glaucomatous retina and optic nerves, which was also reduced by SNC-121 treatment. In conclusion, our data support the notion that nitric oxide plays a detrimental role during glaucomatous injury and inhibition of nitric oxide production provided RGC neuroprotection. Furthermore, δ-opioid receptor activation regulates the production of nitric oxide via inhibiting the activity of iNOS in the retina and optic nerve.

Blood-brain barrier disruption induced by hemoglobin in vivo: Involvement of up-regulation of nitric oxide synthase and peroxynitrite formation

Accumulating evidence has demonstrated that up-regulation of nitric oxide synthase (NOS) and subsequent peroxynitrite (ONOO(-)) formation exert a devastating effect on the damage of BBB in multiple diseases. However, considerably less attention has been focused on the role of NOS/ONOO(-) in BBB disruption after intracerebral hemorrhage (ICH). Using an experimental stroke model by injecting hemoglobin (Hb) into the caudate nucleus of male Sprague Dawley rats, we explored the role of NOS/ONOO(-) in BBB disruption after ICH. Brain edema content, behavioral changes, alterations of TJ proteins (claudin-5 and ZO-1), expression of neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS), formation of 3-nitrotyrosine (3-NT), as well as NO production were investigated. Hb in the rat brain led to a significant brain edema production and neurological deficits. Overexpressed NOS was concomitant with large quantities of 3-NT formation. Moreover, sites of enhanced nNOS, iNOS, eNOS and 3-NT immunoreactivity were colocalized with diminished or discontinuous ZO-1 and/or claudin-5 staining as evidenced by Western blot and immunofluorescence, indicating the involvement of NOS and ONOO(-) in the BBB disruption. Meaningfully, levels of 3-NT in serum, which had a similar tendency with that of in brain tissues (r=0.934, P<0.001), had a marked correlation with brain edema content (r=0.782, P<0.001) and neurological deficits (r=0.851, P<0.001). We concluded that ONOO(-) formation by the upregulation of NOS may play a central role in promoting the BBB damage following ICH. Moreover, ONOO(-) may be a promising biomarker for the judgment or prediction of brain injury and clinical prognosis after ICH.

Effects of ischemia and reperfusion on production of nitrotyrosine, activation of eosinophils, and apoptosis in the large colonic mucosa of horses

OBJECTIVE

To assess the effects of ischemia and reperfusion on indicators of oxidative stress, activation of eosinophils, and apoptosis in the large colonic mucosa of horses.

ANIMALS

40 horses.

PROCEDURES

In 1 or two 20-cm-long segments of the pelvic flexure, ischemia was induced for 1 or 2 hours followed by no reperfusion or 30 minutes and 18 hours of reperfusion in anesthetized horses. Mucosal specimens were collected before (controls; n = 20 horses) and after each period of ischemia, and full-thickness tissue samples were collected after each period of reperfusion. Sections of colonic tissues were stained for histomorphometric analysis or assessment of eosinophil accumulation. Nitrotyrosine was identified immunohistochemically, and severity of apoptosis was determined via the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method.

RESULTS

Numbers of mucosal eosinophils were similar before induction of ischemia, after ischemia, and after ischemia-reperfusion. Eosinophil nitrotyrosine production increased significantly during ischemia and continued through 30 minutes of reperfusion; production was decreased at 18 hours of reperfusion but remained greater than that of the controls. In other leukocytes, nitrotyrosine generation peaked at 1 hour of ischemia and again at 18 hours of reperfusion. Compared with control findings, epithelial apoptosis increased gradually at 1 through 2 hours of ischemia with no further progression after reperfusion.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that resident eosinophils in the large colon of horses react to mucosal injury from ischemia and reperfusion and may undergo oxidative stress under those conditions. Epithelial apoptosis could contribute to tissue damage.

Inducible nitric oxide synthase inhibition attenuates physical stress-induced lung hyper-responsiveness and oxidative stress in animals with lung inflammation

Mechanisms involved in stress-induced asthmatic alterations have been poorly characterised. We assessed whether inducible nitric oxide synthase (iNOS) inhibition modulates the stress-amplified lung parenchyma responsiveness, oxidative stress and extracellular matrix remodelling that was previously increased by chronic lung inflammation. Guinea pigs were subjected to 7 exposures to ovalbumin (1-5 mg/ml) or saline (OVA and SAL groups) over 4 weeks. To induce behavioural stress, animals were subjected to a forced swimming protocol (5 times/week, over 2 weeks; SAL-Stress and OVA-Stress groups) 24 h after the 4th inhalation. 1400W (iNOS-specific inhibitor) was administered intraperitoneally in the last 4 days of the protocol (SAL-1400W, OVA-1400W, SAL-Stress+1400W and OVA-Stress+1400W groups). Seventy-two hours after the last inhalation, animals were anaesthetised and exsanguinated, and adrenal glands were removed. Lung tissue resistance and elastance were evaluated by oscillatory mechanics and submitted for histopathological evaluation. Stressed animals had higher adrenal weights compared to non-stressed groups, which were reduced by 1400W treatment. Behavioural stress in sensitised animals amplified the resistance and elastance responses after antigen challenge, numbers of eosinophils and iNOS+ cells, actin content and 8-iso-PGF2α density in the distal lung compared to the OVA group. 1400W treatment in ovalbumin-exposed and stressed animals reduced lung mechanics, iNOS+ cell numbers and 8-iso-PGF2α density compared to sensitised and stressed animals that received vehicle treatment. We concluded that stress amplifies the distal lung constriction, eosinophilic inflammation, iNOS expression, actin content and oxidative stress previously induced by chronic lung inflammation. iNOS-derived NO contributes to stress-augmented lung tissue functional alterations in this animal model and is at least partially due to activation of the oxidative stress pathway.

CGS 21680, an agonist of the adenosine (A2A) receptor, decreases acute lung inflammation

Adenosine A(2A) receptor agonists may be important regulators of inflammation. The aim of this study was to investigate the effects of CGS 21680 (0.1mg/kgi.p.), an agonist of the adenosine (A(2A)) receptor, in a mouse model of carrageenan-induced pleurisy. Injection of carrageenan into the pleural cavity of mice elicited an acute inflammatory response characterised by: infiltration of neutrophils in lung tissues and subsequent lipid peroxidation, increased production of nitric oxide (NO), cytokines such as tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) and increased expression of intercellular adhesion molecule (ICAM-1) and platelet-adhesion molecule (P-selectin). Furthermore, carrageenan induced the expression of nuclear factor-κB (NF-κB), inducible nitric oxide synthase (iNOS), nitrotyrosine, the activation of poly-ADP-ribosyl polymerase (PARP), as well as induced apoptosis (FAS-ligand expression, Bax and Bcl-2 expression) in the lung tissues. Administration of CGS 21680, 30 min prior to challenge with carrageenan, caused a significant reduction of all the parameters of inflammation measured. In addition, to confirm the anti-inflammatory effect of CGS 21680, we have also evaluated the effects of CGS 21680 post-treatment (30 min after the challenge with carrageenan) and we have demonstrated that also it caused a reduction of neutrophil infiltration and the degree of lung injury. Thus, based on these findings we propose that adenosine A(2A) receptor agonists such as CGS 21680 may be useful in the treatment of various inflammatory diseases.

Effect of apocynin, a NADPH oxidase inhibitor, on acute lung inflammation

NADPH-oxidase is an enzyme responsible for reactive oxygen species production (ROS) and inhibition of this enzyme represents an attractive therapeutic target for the treatment of many diseases. The aim of this study was to investigate the effects of apocynin, a NADPH-oxidase inhibitor, in a mouse model of carrageenan-induced pleurisy. Injection of carrageenan into the pleural cavity of mice elicited an acute inflammatory response characterized by: infiltration of neutrophils in lung tissues and subsequent lipid peroxidation, increased production of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) and increased expression of intercellular adhesion molecule (ICAM-1) and platelet-adhesion molecule (P-selectin). Furthermore, carrageenan induced the expression of nuclear factor-κB (NF-κB) inducible nitric oxide synthase (iNOS), nitrotyrosine, poly-ADP-ribosyl polymerase (PARP) as well as induced apoptosis (TUNEL staining, FAS-ligand expression, Bax and Bcl-2 expression) and mitogen-activated protein kinase (MAPK) activation in the lung tissues. Administration of apocynin, 30min after the challenge with carrageenan, caused a significant reduction of all the parameters of inflammation measured. Thus, based on these findings we propose that NADPH oxidase inhibitor such as apocynin may be useful in the treatment of various inflammatory diseases.

Antioxidant properties of propargylamine derivatives: assessment of their ability to scavenge peroxynitrite

A series of arylpropargylamines, variously substituted in the hydrogen in p-position and in the propargyl moiety, were studied as potential peroxynitrite scavengers. The scavenging activity of these compounds was evaluated through peroxynitrite (ONOO−)-mediated oxidation of dichlorofluorescin and linoleic acid by measuring the dichlorofluorescein formation and oxygen consumption, respectively. Among tested compounds, only 1-phenylpropargylamine (AP3) promoted concentration-dependent inhibition of ONOO−-induced dichlorofluorescin and linoleic acid oxidation with IC50 values of 637 and 63 μm, respectively. The AP3 spectral changes in UV-visible absorbance properties in the presence of peroxynitrite suggested the formation of a new compound. This was identified by gas-chromatograph-mass spectrometer analysis as phenylpropargyl alcohol. Structure—activity relationship analysis indicated that the scavenging activity of AP3 was due to the aminopropargyl moiety and availability of the nitrogen electron pair. This data suggested that AP3 could be considered a lead compound for the synthesis of new ONOO− scavenger derivatives.

Protein tyrosine nitration: selectivity, physicochemical and biological consequences, denitration, and proteomics methods for the identification of tyrosine-nitrated proteins

Protein tyrosine nitration (PTN) is a post-translational modification occurring under the action of a nitrating agent. Tyrosine is modified in the 3-position of the phenolic ring through the addition of a nitro group (NO2). In the present article, we review the main nitration reactions and elucidate why nitration is not a random chemical process. The particular physical and chemical properties of 3-nitrotyrosine (e.g., pKa, spectrophotometric properties, reduction to aminotyrosine) will be discussed, and the biological consequences of PTN (e.g., modification of enzymatic activity, sensitivity to proteolytic degradation, impact on protein phosphorylation, immunogenicity and implication in disease) will be reviewed. Recent data indicate the possibility of an in vivo denitration process, which will be discussed with respect to the different reaction mechanisms that have been proposed. The second part of this review article focuses on analytical methods to determine this post-translational modification in complex proteomes, which remains a major challenge.

Biological Time‐Dependent Difference in Effect of Peroxynitrite Demonstrated by the Mouse Hot Plate Pain Model

We previously demonstrated the rhythmic pattern of L-arginine/nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) cascade in nociceptive processes. The coupled production of excess NO and superoxide leads to the formation of an unstable intermediate peroxynitrite, which is primarily responsible for NO-mediated toxicity. In the present study, we evaluated the biological time-dependent effects of exogenously administered peroxynitrite on nociceptive processes and peroxynitrite-induced changes in the analgesic effect of morphine using the mouse hot-plate pain model. Experiments were performed at four different times of day (1, 7, 13, and 19 hours after lights on, i.e., HALO) in mice of both sexes synchronized to a 12 h:12 h light-dark cycle. Animals were injected intraperitoneally (i.p.) with saline or 10 mg/kg morphine 30 min before and 0.001 mg/kg peroxynitrite 30 sec before hot-plate testing, respectively. The analgesic effect of morphine exhibited significant biological time-dependent differences in the thermally-induced algesia; whereas, administration of peroxynitrite alone exhibited either significant algesic or analgesic effect, depending on the circadian time of its injection. Concomitant administration of peroxynitrite and morphine reduced morphine-induced analgesia at three of the four different study time points. In conclusion, peroxynitrite displayed nociceptive and antinociceptive when administered alone according to the circadian time of treatment, while it diminished analgesic activity when administered in combination with morphine at certain biological times.

Inducible nitric oxide synthase inhibition attenuates lung tissue responsiveness and remodeling in a model of chronic pulmonary inflammation in guinea pigs

We evaluated the influence of iNOS-derived NO on the mechanics, inflammatory, and remodeling process in peripheral lung parenchyma of guinea pigs with chronic pulmonary allergic inflammation. Animals treated or not with 1400 W were submitted to seven exposures of ovalbumin in increasing doses. Seventy-two hours after the 7th inhalation, lung strips were suspended in a Krebs organ bath, and tissue resistance and elastance measured at baseline and after ovalbumin challenge. The strips were submitted to histopathological measurements. The ovalbumin-exposed animals showed increased maximal responses of resistance and elastance (p<0.05), eosinophils counting (p<0.001), iNOS-positive cells (p<0.001), collagen and elastic fiber deposition (p<0.05), actin density (p<0.05) and 8-iso-PGF2alpha expression (p<0.001) in alveolar septa compared to saline-exposed ones. Ovalbumin-exposed animals treated with 1400 W had a significant reduction in lung functional and histopathological findings (p<0.05). We showed that iNOS-specific inhibition attenuates lung parenchyma constriction, inflammation, and remodeling, suggesting NO-participation in the modulation of the oxidative stress pathway.

Apocynin: molecular aptitudes

Apocynin is a naturally occurring methoxy-substituted catechol, experimentally used as an inhibitor of NADPH-oxidase. It can decrease the production of superoxide (O(2)(-)) from activated neutrophils and macrophages while the ability of phagocytosis remains unaffected. The anti-inflammatory activity of apocynin has been demonstrated in a variety of cell and animal models of inflammation. Apocynin, after metabolic conversion, inhibits the assembly of NADPH-oxidase that is responsible for reactive oxygen species (ROS) production. It is, therefore, extensively used to reveal the role of this enzyme in cell and experimental models. Although some of the ROS serve as signaling molecules in the cells, excessive production is damaging and has been implicated to play an important role in the progression of many disease processes. This is why in many studies apocynin presents a promising potential treatment for some disorders; however, its utility with inflammatory diseases remains to be determined. Since its mode of action is not well defined, we tried to get a more precise insight into the mechanisms by which apocynin exerts its activity. Considering the anti-inflammatory activities of apocynin, we may conclude that this compound definitely deserves further study.

Effects of aminoguanidine, an inhibitor of inducible nitric oxide synthase, on nitric oxide production and its metabolites in healthy control subjects, healthy smokers, and COPD patients

BACKGROUND

Nitric oxide (NO) is produced by resident and inflammatory cells in the respiratory tract by the enzyme NO synthase (NOS), which exists in three isoforms: neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS. NO production is increased in patients with COPD, and the production of NO under oxidative stress conditions generates reactive nitrogen species that may amplify the inflammatory response in COPD.

METHODS

To examine the role of increased NO in COPD, we administered a relatively selective iNOS inhibitor, aminoguanidine, by nebulization in a double-blind, placebo-controlled study in COPD patients, healthy smokers, and healthy nonsmoking subjects. We investigated whether aminoguanidine had any effect on exhaled NO produced in the central lung (flux of NO from the airways [Jno] and peripheral lungs (concentration of NO in peripheral lung [Calv], on NO metabolites (nitrite [NO(2)(-)]/nitrate [NO(3)(-)], peroxinitrite [ONOO(-)], nitrotyrosine), and on a marker of oxidative stress (8-isoprostane) in exhaled breath condensate (EBC) and in sputum.

RESULTS

Aminoguanidine administration resulted in a significant reduction in Jno compared with administration of the saline solution control in healthy subjects, smokers, and COPD patients. Calv in smokers and in COPD patients was not completely inhibited 1 h after aminoguanidine inhalation, in marked contrast to previous results in asthma. Moreover, ONOO(-) and NO(2)(-)/NO(3)(-) levels were also increased in EBC and in sputum of smokers and COPD and were not completely inhibited following aminoguanidine inhalation. 8-Isoprostane levels were also increased in smokers and in COPD patients but were not reduced after aminoguanidine inhalation.

CONCLUSIONS

These results suggest that the constitutive NOS isoform as well as iNOS might be involved in NO release and contribute to the high Calv and ONOO(-) production in patients with COPD.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT00180635.

Glycyrrhizin Attenuates MPTP Neurotoxicity in Mouse and MPP-Induced Cell Death in PC12 Cells

The present study examined the inhibitory effect of licorice compounds glycyrrhizin and a metabolite 18beta-glycyrrhetinic acid on the neurotoxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in the mouse and on the 1-methyl-4-phenylpyridinium (MPP(+))-induced cell death in differentiated PC12 cells. MPTP treatment increased the activities of total superoxide dismutase, catalase and glutathione peroxidase and the levels of malondialdehyde and carbonyls in the brain compared to control mouse brain. Co-administration of glycyrrhizin (16.8 mg/kg) attenuated the MPTP effect on the enzyme activities and formation of tissue peroxidation products. In vitro assay, licorice compounds attenuated the MPP(+)-induced cell death and caspase-3 activation in PC12 cells. Glycyrrhizin up to 100microM significantly attenuated the toxicity of MPP(+). Meanwhile, 18beta-glycyrrhetinic acid showed a maximum inhibitory effect at 10microM; beyond this concentration the inhibitory effect declined. Glycyrrhizin and 18beta-glycyrrhetinic acid attenuated the hydrogen peroxide- or nitrogen species-induced cell death. Results from this study indicate that glycyrrhizin may attenuate brain tissue damage in mice treated with MPTP through inhibitory effect on oxidative tissue damage. Glycyrrhizin and 18beta-glycyrrhetinic acid may reduce the MPP(+) toxicity in PC12 cells by suppressing caspase-3 activation. The effect seems to be ascribed to the antioxidant effect.

Effects of chronic L-NAME treatment lung tissue mechanics, eosinophilic and extracellular matrix responses induced by chronic pulmonary inflammation

The importance of lung tissue in asthma pathophysiology has been recently recognized. Although nitric oxide mediates smooth muscle tonus control in airways, its effects on lung tissue responsiveness have not been investigated previously. We hypothesized that chronic nitric oxide synthase (NOS) inhibition by N(omega)-nitro-L-arginine methyl ester (L-NAME) may modulate lung tissue mechanics and eosinophil and extracellular matrix remodeling in guinea pigs with chronic pulmonary inflammation. Animals were submitted to seven saline or ovalbumin exposures with increasing doses (1 approximately 5 mg/ml for 4 wk) and treated or not with L-NAME in drinking water. After the seventh inhalation (72 h), animals were anesthetized and exsanguinated, and oscillatory mechanics of lung tissue strips were performed in baseline condition and after ovalbumin challenge (0.1%). Using morphometry, we assessed the density of eosinophils, neuronal NOS (nNOS)- and inducible NOS (iNOS)-positive distal lung cells, smooth muscle cells, as well as collagen and elastic fibers in lung tissue. Ovalbumin-exposed animals had an increase in baseline and maximal tissue resistance and elastance, eosinophil density, nNOS- and iNOS-positive cells, the amount of collagen and elastic fibers, and isoprostane-8-PGF(2alpha) expression in the alveolar septa compared with controls (P<0.05). L-NAME treatment in ovalbumin-exposed animals attenuated lung tissue mechanical responses (P<0.01), nNOS- and iNOS-positive cells, elastic fiber content (P<0.001), and isoprostane-8-PGF(2alpha) in the alveolar septa (P<0.001). However, this treatment did not affect the total number of eosinophils and collagen deposition. These data suggest that NO contributes to distal lung parenchyma constriction and to elastic fiber deposition in this model. One possibility may be related to the effects of NO activating the oxidative stress pathway.

Role of oxygen in postischemic myocardial injury

Myocardial function is dependent on a constant supply of oxygen from the coronary circulation. A reduction of oxygen supply due to coronary obstruction results in myocardial ischemia, which leads to cardiac dysfunction. Reperfusion of the ischemic myocardium is required for tissue survival. Thrombolytic therapy, coronary artery bypass surgery and coronary angioplasty are some of the treatments available for the restoration of blood flow to the ischemic myocardium. However, the restoration of blood flow may also lead to reperfusion injury, resulting in myocyte death. Thus, any imbalance between oxygen supply and metabolic demand leads to functional, metabolic, morphologic, and electrophysiologic alterations, causing cell death. Myocardial ischemia reperfusion (IR) injury is a multifactorial process that is mediated by oxygen free radicals, neutrophil activation and infiltration, calcium overload, and apoptosis. Controlled reperfusion of the ischemic myocardium has been advocated to prevent the IR injury. Studies have shown that reperfusion injury and postischemic cardiac function are related to the quantity and delivery of oxygen during reperfusion. Substantial evidence suggests that controlled reoxygenation may ameliorate postischemic organ dysfunction. In this review, we discuss the role of oxygenation during reperfusion and subsequent biochemical and pathologic alterations in reperfused myocardium and recovery of heart function.

The role of free radicals and nitric oxide in the ischemia–reperfusion injury mediated by acute bladder outlet obstruction

Free-radical generation and nitric oxide (NO) generation were detected in the rat bladder following acute bladder outlet obstruction (BOO), and the results were compared with those for vascular ischemia and reperfusion (I-R). Forty male Sprague Dawley rats were used. In the acute BOO plus I-R group (group 1), rats were catheterized with a 3-Fr catheter and an inflated balloon was positioned at the bladder neck. The bladder was overdistended after administration of Ringer solution and furosemide (12 mg/kg, each) for 60 min, and was then drained to allow reperfusion for 30 min. In the acute BOO plus nerve stimulation group (group 2), the pelvic nerve was stimulated in the distended bladder for 60 min (5 s every 5 min, 10 V/0.1 ms, 20 Hz). Pelvic nerve stimulation was performed in nonobstructed animals in group 3. In the I-R group (group 4), the distal aorta was occluded for 60 min followed by reperfusion for 30 min. Sham-operated animals served as the control group (group 5). At the end of the protocols, the levels of hydroxyl and superoxide radicals and NO levels were measured in the bladder tissues with luminol- and lucigenin-enhanced chemiluminescence methods. The results were compared by a one-way analysis of variance test. The levels of hydroxyl radicals were not significantly different between the study groups. In contrast, superoxide radicals and NO levels were significantly increased in both group 1 and group 4 compared with those in control animals (P<0.05 for all comparisons). Superoxide radical generation in group 2 was comparable to the levels in group 1 (P>0.05), whereas NO levels were substantially lower than in group 1 (P=0.06). In summary, vascular I-R causes significant oxidative damage to the bladder. Acute BOO with overdistension of the bladder mimics the effects of true vascular I-R injury. The NO pathway has possibly a major role in I-R-induced bladder damage. Prolonged BOO may therefore significantly enhance the oxidative damage to the bladder and further accentuate the effects of generalized atherosclerotic processes in the elderly adult.

Nitric oxide, antioxidant capacity, nitric oxide synthase and xanthine oxidase plasma levels in a cohort of burn patients

BACKGROUND

Nitric oxide (NO) is an important signal molecule in many types of cells and tissues. Efficiently balanced NO production was noted to play an important role in the healing of burns. However, the exact pathophysiological role of NO in burns and its potent relation with clinical and laboratory parameters has not been elucidated.

METHODS

A cohort of 23 burn patients followed for 5 days were enrolled. NO, antioxidant capacity (AC), NO synthase (NOS) activity and xanthine oxidase (XO) activity were indirectly determined by fluorophotometer. Multiple regression against total burn surface area (TBSA), age, weight, height, proximity of septic episode, hemoglobin, white blood cells, percent of neutrophils, platelets, glucose, urea, potassium, sodium and albumin was performed.

RESULTS

Elevation of NO, XO and AC levels is observed from day 2 (p<0.00001), day 4 (p=0.005) and day 6 (p=0.036), respectively. At the end of follow-up period (day 6), NO production was found to independently correlate with TBSA, glucose levels and percent of neutrophils (p=0.0004), AC with age, hemoglobin and glucose levels (p=0.012), and NOS with proximity of septic episode and glucose levels (p=0.027).

CONCLUSIONS

NO production exerts its prophylactic effect from the first 24h after burn, and is independently correlated with severe injury, enhanced neutrophil motivation and augmented glucose levels, thus possibly representing a response to stress. This need might trigger induction of XO and salvage of antioxidants, as suggested by their rise at a later stage. These data underline that an effort to compromise stress and to administer antioxidants could be a priority in the treatment of these patients.

Glycyrrhizin protection against 3-morpholinosydnonime-induced mitochondrial dysfunction and cell death in lung epithelial cells

The present study was designed to assess the preventive effect of licorice compounds glycyrrhizin and 18beta-glycyrrhetinic acid against mitochondrial damage and cell death in lung epithelial cells exposed to 3-morpholinosydnonime, a donor of nitric oxide and superoxide. Treatment of lung epithelial cells with 3-morpholinosydnonime resulted in the nuclear damage, decrease in the mitochondrial transmembrane potential, cytosolic accumulation of cytochrome c, activation of caspase-3, increase in the formation of reactive oxygen species and depletion of GSH. Treatment of glycyrrhizin and 18beta-glycyrrhetinic acid attenuated the 3-morpholinosydnonime-induced mitochondrial damage, formation of reactive oxygen species and GSH depletion and revealed a maximal inhibitory effect at 10 and 1 muM, respectively; beyond these concentrations the inhibitory effect declined. Melatonin, carboxy-PTIO, rutin and uric acid reduced the 3-morpholinosydnonime-induced cell death. The results show that glycyrrhizin and 18beta-glycyrrhetinic acid seem to prevent the toxic effect of 3-morpholinosydnonime against lung epithelial cells by suppressing the mitochondrial permeability transition that leads to the release of cytochrome c and activation of caspase-3. The preventive effect may be ascribed to the inhibitory action on the formation of reactive oxygen species and depletion of GSH. The findings suggest that licorice compounds seem to prevent the nitrogen species-mediated lung cell damage.

Diabetes mellitus and anal sphincter pressures: an experimental model in rats

PURPOSE

Symptoms of the gastrointestinal tract, frequent in patients with diabetes mellitus, which may be related to an increase in the production of free radicals, include alterations in the function of the sphincter anal musculature. Such alterations are characterized by a decrease of muscular tone associated with different degrees of fecal incontinence. This study was performed to show the alterations in the anal sphincter pressures of diabetic rats and to evaluate the role of nitric oxide and oxidative stress in this situation.

METHODS

Male Wistar rats weighing 250 to 400 g were used. The animals were divided in two groups: control and diabetic. Diabetes was induced through intraperitoneal injection of streptozotocin and the anal pressures were gauged by anorectal manometry. Nitric oxide was evaluated through measures of nitrites and nitrates, and oxidative stress through the technique of chemoluminescence.

RESULTS

There was a significant decrease in the sphincter anal pressure of diabetic animals 60 days after induction (P < 0.05). This pressure returned to basal values after administration of a nitric oxide synthase antagonist. The levels of nitrites and nitrates as well as of lipoperoxidation were significantly increased in the diabetic compared with the control group (P < 0.05).

CONCLUSIONS

In this study, hyperglycemia of diabetes mellitus caused an increase in the oxidative stress. Apparently the elevation of nitric oxide levels was one of the responsible factors for the decrease of anal sphincter pressures.

Efficiency of lornoxicam in lung and trachea injury caused by peroxynitrite

Peroxynitrite is involved in the pathogenesis of pulmonary diseases such as asthma, occupational pulmonary diseases and acute respiratory distress syndrome (ARDS) due to excessive production of nitric oxide or superoxide or both. Lornoxicam, a new oxicam derivative, is a potent anti-inflammatory agent. In this study, we evaluated the role of lornoxicam in a peroxynitrite-induced pulmonary and tracheal injury model by measuring myeloperoxidase (MPO) activity, malondialdehyde (MDA) and 3-nitrotyrosine (3-NT) levels in lung tissue and bronco-alveolar lavage fluid. The study protocol was based on three experimental groups as treatment (T), control (C) and peroxynitrite (P). Each group was subdivided into three subgroups as 2nd, 24th and 48th hour groups. P and T groups were injected intratracheal peroxynitrite. The T group received intraperitoneal lornoxicam before and 24h after peroxynitrite installation. Tissue and serum MDA, MPO values and tissue 3-NT value of the treatment and control groups were found significantly lower than the peroxynitrite group at the 2nd, 24th and 48th hours (p<0.05). Similarly, values obtained from bronco-alveolar lavage fluid examination in the control and treatment groups were significantly less than those in the peroxynitrite group (p<0.01). Therefore, Lornoxicam has been found to be effective in attenuating peroxynitrite induced pulmonary and tracheal injury in rats.

Expression of cyclooxygenase-2, alpha 1-acid-glycoprotein and inducible nitric oxide synthase in the developing lesions of murine leprosy

Murine leprosy is a chronic disease of the mouse, the most popular animal model used in biomedical investigation, which is caused by Mycobacterium lepraemurium (MLM) whose characteristic lesion is the macrophage-made granuloma. From onset to the end of the disease, the granuloma undergoes changes that gradually transform the environment into a more appropriate milieu for the growth of M. lepraemurium. The mechanisms that participate in the formation and maturation of the murine leprosy granulomas are not completely understood; however, microbial and host-factors are believed to participate in their formation. In this study, we analysed the role of various pro-inflammatory and anti-inflammatory proteins in granulomas of murine leprosy after 21 weeks of infection. We assessed the expression of cyclooxygenase-2 (COX-2), alpha acid-glycoprotein (AGP), and inducible nitric oxide synthase (iNOS) at sequential stages of infection. We also looked for the nitric-oxide nitrosylation product, nitrotyrosine (NT) in the granulomatous lesions of murine leprosy. We found that a pro-inflammatory environment predominates in the early granulomas while an anti-inflammatory environment predominates in late granulomas. No obvious signs of bacillary destruction were observed during the entire period of infection, but nitrosylation products and cell alterations were observed in granulomas in the advanced stages of disease. The change from a pro-inflammatory to an anti-inflammatory environment, which is probably driven by the bacillus itself, results in a more conducive environment for both bacillus replication and the disease progression.

Asymmetric dimethylarginine induces oxidative and nitrosative stress in murine lung epithelial cells

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) produced by epithelial and inflammatory cells are key mediators of the chronic airway inflammation of asthma. Low L-arginine levels can result in the uncoupling of nitric oxide synthase (NOS) leading to production of both ROS and RNS. Asymmetric dimethylarginine (ADMA) is a competitive endogenous inhibitor of all NOS isoforms and has been demonstrated to inhibit NO formation and increase oxidative stress in vascular endothelial and smooth muscle cells. The effect of ADMA on inducible NOS (iNOS) activity in epithelial cells has not been explored. In this study, we investigated whether addition of exogenous ADMA alters the generation of NO and superoxide anion (O2-), leading to peroxynitrite (ONOO-) formation in a mouse epithelial cell line. In stimulated LA-4 cells, ADMA dose-dependently inhibited nitrite accumulation after 24 h of treatment. In addition, ADMA concentrations as low as 10 microM induced rapid increases in O2- production as measured by dihydroethidium oxidation. Furthermore, using dihydrorhodamine to monitor ONOO- formation, ADMA caused a dose-dependent increase in ONOO- after treatment for 24 h. Similar effects of ADMA were seen using purified iNOS protein in a cell-free system. Together, these data indicate that elevated ADMA may contribute to the production of ROS and RNS in airway inflammation.

Nitrotyrosine formation and heme oxygenase-1 expression in endotoxemic cirrhotic rats

BACKGROUND

Endotoxemia increases hepatic toxicity and mortality in cirrhosis. Because the mechanism of augmented hepatotoxicity in endotoxemic cirrhotic rats is still unclear, we wanted to investigate whether oxidative and nitrosative stress play a causative role in lipopolysaccharide (LPS)-treated cirrhotic rats.

METHODS

Liver cirrhosis was produced by the administration of thioacetamide (0.3 g/L of tap water) for a period of 3 months in rats. At the end of this period, cirrhotic rats were sacrificed 6 h after LPS injection (5 mg/kg, intraperitoneally). Serum transaminase activities, plasma total nitrite and nitrotyrosine (NT) levels as well as hepatic lipid peroxides, NT formation and heme oxygenase 1 (HO-1) expression were determined.

RESULTS

LPS administration to cirrhotic rats caused further increases in serum transaminase activities, and plasma total nitrite and NT levels as well as hepatic lipid peroxide levels as compared to cirrhotic rats. Hepatic NT formation and HO-1 expression were also found to be increased in LPS-injected cirrhotic rats.

CONCLUSIONS

Our results indicate that increased oxidative and nitrosative stress may have a synergistic effect in LPS-augmented hepatotoxicity in cirrhotic rats.

Effects of aminoguanidine against renal ischaemia-reperfusion injury in rats

Aminoguanidine is an inhibitor of nitric oxide synthase (NOS), with high selectivity for the inducible isoform (iNOS). In addition to being an inhibitor of NOS, aminoguanidine also exhibits antioxidant activity. Recent studies suggest that aminoguanidine reduces ischaemia-reperfusion (I/R)-induced damage. However, the role of aminoguanidine, in renal injury associated with I/R remains unknown. This study was designed to investigate the effects of aminoguanidine on renal I/R injury. There were three groups of eight rats each. I/R was induced by occlusion of the left renal vessels for 60 min, followed by 24 h reperfusion in rats. Malondialdehyde (MDA) levels, a stable metabolite of the free radical-mediated lipid peroxidation cascade, were found to be significantly higher in the I/R group (30.3 +/- 0.1 nmol g(-1) tissue) than in the control group (10 +/- 0.05 nmol g(-1)). Aminoguanidine (100 mg kg(-1)) administration to rats significantly reduced the MDA values. We also demonstrated that I/R leads to structural change but aminoguanidine did not reverse this change. Aminoguanidine, according to the biochemical finding is protective but histopathological findings did not reveal protection against I/R injury in kidney. The effects of aminoguanidine on I/R-induced damage remain a subject for future investigations.

Immobilization stress causes extra-cellular oxidant-antioxidant imbalance in rats: restoration by L-NAME and vitamin E

Stress has been shown to be associated with altered homeostasis that may lead to oxidant-antioxidant imbalance. Non-enzymatic antioxidants are important regulators of reactive oxygen species produced in extra-cellular milieu and represent the first line of defense against them. Extra-cellular non-enzymatic antioxidants may be disturbed by the production of superoxide and nitric oxide and this has not been studied in stressful situation previously. In the present study, effects of immobilization stress (IS), both acute (IS x 1) and repeated (IS x 7) were assessed on extra-cellular total antioxidant capacity measured as plasma ferric reducing antioxidant power (FRAP) and protein sulfhydryls, and oxidative stress measured as leukocyte superoxide generation, plasma nitric oxide production (total nitrates and nitrites, NOx) and lipid peroxides in rats. Effects of pretreatment with nitric oxide synthase (NOS) inhibitors and vitamin E were also studied on these biochemical parameters. The results showed that both IS x 1 and IS x 7 resulted in extra-cellular oxidant-antioxidant imbalance as oxidant generation was increased and non-enzymatic antioxidants were depleted. Pretreatment either with NOS inhibitors or vitamin E restored stress-induced extracellular oxidant-antioxidant imbalance implying their potential role as antioxidants. Our data suggest that there is extra-cellular oxidant-antioxidant imbalance in the stressed rats, with greater magnitude of severity in repeated stress paradigm. Augmentation of antioxidant defenses might be beneficial in long-term stress.

Generation of nitric oxide in the opossum lower esophageal sphincter during physiological experimentation

Lipopolysaccharide (LPS), given in vivo, modulates opossum esophageal motor functions by inducing the inducible nitric oxide synthase (iNOS), which increases nitric oxide (NO) production. Superoxide, a NO scavenger, is generated during this endotoxemia. Superoxide is cleared by superoxide dismutase (SOD) and catalase (CAT) to protect the physiological function of NO. This study examined whether lower esophageal sphincter (LES) motility, NO release, and iNOS and nitrotyrosine accumulation in the LES are affected by LPS in vitro. Muscle strips from the opossum LES were placed in tissue baths containing oxygenated Krebs buffer. NO release was measured with a chemiluminescence NOx analyzer, and Western blots were performed to analyze iNOS and nitrotyrosine production. The percent change in resting LES tone after a 6-hour exposure to LPS was significantly increased compared to pretreatment values. The percent LES relaxation upon electrical stimulation was significantly decreased in the control group at 6 hours, indicating that the LPS treatment had an effect. The NO concentration in the tissue bath of LPS- treated muscle without nerve stimulation was significantly less than that of LPS treatment combined with SOD/CAT or SOD/CAT alone. iNOS and nitrotyrosine were detectable and increased over time in the LES muscle of both the control and LPS-treated groups. Antioxidant enzymes may play a role in regulating NO-mediated neuromuscular functions in the LES.

Reactive nitrogen species in the respiratory tract

Endogenous Nitric Oxide (NO) plays a key role in the physiological regulation of airway functions. In response to various stimuli activated inflammatory cells (e.g., eosinophils and neutrophils) generate oxidants ("oxidative stress") which in conjunction with exaggerated enzymatic release of NO and augmented NO metabolites produce the formation of strong oxidizing reactive nitrogen species, such as peroxynitrite, in various airway diseases including asthma, chronic obstructive pulmonary diseases (COPD), cystic fibrosis and acute respiratory distress syndrome (ARDS). Reactive nitrogen species provoke amplification of inflammatory processes in the airways and lung parenchyma causing DNA damage, inhibition of mitochondrial respiration, protein dysfunction and cell damage ("nitrosative stress"). These effects alter respiratory homeostasis (such as bronchomotor tone and pulmonary surfactant activity) and the long-term persistence of "nitrosative stress" may contribute to the progressive deterioration of pulmonary functions leading to respiratory failure. Recent studies showing that protein nitration can be dynamic and reversible ("denitration mechanisms") open new horizons in the treatment of chronic respiratory diseases affected by the deleterious actions of "nitrosative stress".

Nitric oxide down-regulates caveolin-1 expression in rat brains during focal cerebral ischemia and reperfusion injury

As a signalling molecule of the integral membrane protein family, caveolin participates in cellular signal transduction via interaction with other signalling molecules. The nature of interaction between nitric oxide (NO) and caveolin in the brain, however, remains largely unknown. In this study we investigated the role(s) of NO in regulating caveolin-1 expression in rat ischemic brains with middle cerebral artery occlusion (MCAO). Exposure to 1 h ischemia induced the increases in neuronal nitric oxide synthase (nNOS) and NO concentration with concurrent down-regulation of caveolin-1 expression in the ischemic core of rat brains. Subsequent 24 h or more reperfusion time led to an increase in inducible NOS (iNOS) expression and NO production, as well as a decline of caveolin-1 protein at the core and penumbra of the ischemic brain. Afterwards, NOS inhibitors and an NO donor were utilized to clarify the link between NO production and caveolin-1 expression in the rats with 1 h ischemia plus 24 h reperfusion. N(G)-nitro-l-arginine methyl ester (L-NAME, a non-selective NOS inhibitor), N(6)-(1-iminoethyl)-lysine (NIL, an iNOS inhibitor), and 7-nitroindazole (7-NI, a nNOS inhibitor) prevented the loss of caveolin-1 in the core and penumbra of the ischemic brain, whereas l-N(5)-(1-iminoethyl)-ornithine (L-NIO, an endothelial NOS inhibitor) showed less effect than the other NOS inhibitors. S-Nitroso-N-acetylpenicillamine (SNAP, a NO donor) down-regulated the expression of caveolin-1 protein in normal and ischemic brains. These results, when taken together, suggest that NO modulates the expression of caveolin-1 in the brain and that the loss of caveolin-1 is associated with NO production in the ischemic brain.

Antioxidant activity and antiproliferative action of methanolic extract of Geum quellyon Sweet roots in human tumor cell lines

Geum quellyon Sweet, a perennial herb of the Rosaceae family, has been used in the traditional medicine of the Mapuche Amerindians of Chile to treat tooth neuralgia, gastric inflammation, prostatitis and to regulate menstruation, and for its diuretic and aphrodisiac properties. Although many benefits have been claimed for this plant, few scientific studies are available in the literature. In this study, we investigated the antioxidant activity of a methanolic extract of Geum quellyon roots. We also examined the anticancer action of this plant on Caco-2 (colon adenocarcinoma cells), DU-145 (androgen-insensitive prostate cancer cells) and KB (oral squamous carcinoma cells) human tumor cell lines. Our data showed that Geum quellyon extract, containing tannins, exhibits interesting antioxidant properties, expressed by its capacity to scavenge 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH) and superoxide anion (O(2)*-), to inhibit xanthine oxidase activity, to chelate metals, and to protect plasmid DNA from cleavage induced by hydroxyl radicals (*OH) and nitric oxide (NO). These results may explain, at least in part, its use in Mapuche traditional medicine for gastric inflammation and prostatitis. The assays on human tumor cell lines demonstrated that this natural product exhibits a inhibitory effect on all human cancer cells examined, and seem to indicate that necrosis cell death is triggered in KB cells and Caco-2, while apoptotic cell demise appears to be induced in DU-145. The effect evidenced in Caco-2 cells can be in part correlated to a modulation of redox-sensitive mechanisms.

Effect of preventive and regressive isosorbide 5-mononitrate treatment on catecholamine levels in plasma, platelets, adrenals, left ventricle and aorta in cyclosporin A-induced hypertensive rats

Increased vascular reactivity associated with cyclosporin A (CsA)-induced arterial hypertension might result from increased vasoconstriction and/or decreased vasodilatation. The administration of organic NO donors could have beneficial effects by the NO-cGMP reposition, but there is the risk of sympathetic nervous system worsening by neuro-hormonal counter-regulation. We evaluate the effect of preventive and regressive (curative) isosorbide 5-mononitrate (Is-5-Mn) treatment on blood pressures and on plasma, platelets, adrenals, left ventricle and aorta norepinephrine (NE) and epinephrine (E) contents, assessed by HPLC, in CsA-induced hypertensive rats. Five rat groups were tested: control (orange juice), CsA (5 mg/kg/day) and Is-5-Mn (150 mg/kg/day, bid) groups were treated for 7 weeks; preventive group (Is-5-Mn+CsA): Is-5-Mn during 2 weeks plus 7 weeks of Is-5-Mn+CsA; regressive group (CsA+Is-5-Mn): CsA during 7 weeks plus 5 weeks of CsA+Is-5-Mn. The increased BP in the CsA group was prevented, but was not reverted, by concomitant Is-5-Mn treatment. In the CsA-treated rats, there was a noticeable decrease in left ventricle NE and E contents and aorta NE levels and a moderate increase in circulating catecholamines, without significant effect in the adrenals values. When Is-5-Mn was preventively used, the CsA-induced effect on left ventricle and aorta was prevented. Concomitantly, however, the plasma-platelet catecholamine balance was disrupted, accumulating NE in plasma, whereas E increased in aorta, mimic the single Is-5-Mn-treated group. In opposition, in the group used as regressive Is-5-Mn therapy, the adrenals contents were higher compared with the CsA-group and, simultaneously, the CsA-evoked effects on circulating, left ventricle and aorta catecholamines were not reverted. In conclusion, regressive Is-5-Mn therapy was unable to attenuate CsA-induced catecholamine changes and BP values even worsened. On the contrary, preventive Is-5-Mn treatment prevented the catecholamine changes on left ventricle and aorta, but increased plasma NE and aorta E accumulation. Even though with those effects, hypertension development was totally prevented, suggesting that peripheral SNS per se cannot fully explain CsA-induced hypertension. Furthermore, Is-5-Mn might produce beneficial effects only if preventively employed but, considering the changes on peripheral catecholamine contents, a judicious evaluation of the nitrate therapy impact is recommended in order to avoid further deleterious effects.

Na+-K+ pump activation inhibits endothelium-dependent relaxation by activating the forward mode of Na+/Ca2+ exchanger in mouse aorta

The effect of Na+-K+ pump activation on endothelium-dependent relaxation (EDR) and on intracellular Ca2+ concentration ([Ca2+]i) was examined in mouse aorta and mouse aortic endothelial cells (MAECs). The Na+-K+ pump was activated by increasing extracellular K+ concentration ([K+]o) from 6 to 12 mM. In aortic rings, the Na+ ionophore monensin evoked EDR, and this EDR was inhibited by the Na+/Ca2+ exchanger (NCX; reverse mode) inhibitor KB-R7943. Monensin-induced Na+ loading or extracellular Na+ depletion (Na+ replaced by Li+) increased [Ca2+]i in MAECs, and this increase was inhibited by KB-R7943. Na+-K+ pump activation inhibited EDR and [Ca2+]i increase (K+-induced inhibition of EDR and [Ca2+]i increase). The Na+-K+ pump inhibitor ouabain inhibited K+-induced inhibition of EDR. Monensin (>0.1 microM) and the NCX (forward and reverse mode) inhibitors 2'4'-dichlorobenzamil (>10 microM) or Ni2+ (>100 microM) inhibited K+-induced inhibition of EDR and [Ca2+]i increase. KB-R7943 did not inhibit K+-induced inhibition at up to 10 microM but did at 30 microM. In current-clamped MAECs, an increase in [K+]o from 6 to 12 mM depolarized the membrane potential, which was inhibited by ouabain, Ni2+, or KB-R7943. In aortic rings, the concentration of cGMP was significantly increased by acetylcholine and decreased on increasing [K+]o from 6 to 12 mM. This decrease in cGMP was significantly inhibited by pretreating with ouabain (100 microM), Ni2+ (300 microM), or KB-R7943 (30 microM). These results suggest that activation of the forward mode of NCX after Na+-K+ pump activation inhibits Ca2+ mobilization in endothelial cells, thereby modulating vasomotor tone.

Antiphospholipid antibodies are associated with enhanced oxidative stress, decreased plasma nitric oxide and paraoxonase activity in an experimental mouse model

OBJECTIVE

Oxidative stress contributes to atherosclerosis, and evidence of enhanced oxidative stress exists in antiphospholipid syndrome (APS). In a non-lupus murine model, we evaluated whether anticardiolipin (aCL) antibodies could affect the oxidant/antioxidant balance as an early biochemical step of APS.

METHODS

Hybridomas producing human and murine aCL and anti-beta(2)-glycoprotein I (abeta2-GPI) monoclonal antibodies were injected into three groups of five female BALB/c severe combined immunodeficiency (SCID) mice. Corresponding hybridomas secreting non-antiphospholipid antibodies of the same isotype were employed as controls. Sera and organs were collected after 30 days. Paraoxonase (PON) activity, peroxynitrite, superoxide, nitric oxide (NO) and nitrotyrosine were measured in plasma. Expression of endothelial nitric oxide synthase and inducible nitric oxide synthase (iNOS) was assessed by western blot and immunohistochemistry.

RESULTS

PON activity and NO (sum of nitrate and nitrite) levels were reduced in the human aCL IgG group (P<0.002 and P<0.04, respectively), whilst peroxynitrite and superoxide and expression of total antioxidant capacity of plasma were increased (P<0.01). PON and NO were decreased in the murine abeta2-GPI IgG and IgM aCL groups (P<0.03 and P<0.05, respectively). Nitrotyrosine was elevated in the human aCL IgG group (P<0.03). Western blotting showed reduced iNOS expression in the hearts of the IgG aCL group, confirmed by immunostaining. PON inversely correlated with IgG aCL titres (P<0.001), superoxide (P<0.008) and peroxynitrite levels (P<0.0009). Peroxynitrite and total IgG aCL were independent predictors of PON (P<0.0009 and P<0.02, respectively). Superoxide was the only independent predictor of NO (P<0.008) and of nitrotyrosine (P<0.002).

CONCLUSION

aCL antibodies are associated with the decreased PON activity and reduced NO that may occur in the preclinical phase of APS.

Tumour necrosis factor alpha, lipid peroxidation and NO* are increased and associated with decreased free-radical scavenging enzymes in patients with Weill-Marchesani syndrome

AIM: Weill-Marchesani syndrome (WMS) is a rare systemic disorder with both autosomal recessive and dominant inheritances. Accumulation of reactive oxygen species such as O2*-, H2O2 and OH* causes lipid peroxidation (LPO), whereas antioxidant enzymes (superoxide dismutase (SOD), glutathione peroxidase (GSHPx)) mediate defence against oxidative stress. Excess tumour necrosis factor (TNF)-alpha and NO* react with O2*- and cause further antioxidant depletion with an increase in mutation frequency by H2O2. This study investigated the levels of SOD, GSHPx, catalase (CAT), TNF-alpha, NO and LPO in patients with WMS. METHODS: A group of 10 WMS patients (four males, six females; age, 26.5+/-19.0 years) and 10 age-matched and sex-matched controls (five males, five females; age, 27.3+/-18.2 years) were included. Serum TNF-alpha levels were determined by a spectrophotometer technique using immulite chemiluminescent immunometric assay. Malondialdehyde (MDA) was determined in plasma; CAT in red blood cells (RBCs), and SOD and GSHPx in both plasma and RBCs. Total serum NO* levels were evaluated by Griess reaction. RESULTS: Mean levels of TNF-alpha (8.3+/-0.6 pg/ml) in WMS patients were significantly (p<0.001) higher than controls (4.3+/-0.2 pg/ml). Plasma MDA levels in patients and controls were 5.4+/-0.8 and 1.8+/-0.6 micromol/l, respectively, and the difference was significant (p=0.0002). SOD and GSHPx activities were significantly lower in both RBCs and plasma of WMS than in controls (RBC-SOD, 3981.9+/-626.6 versus 5261.6+/-523.0 U/g haemoglobin (Hb), p=0.0005; plasma-SOD, 529.4+/-49.3 versus 713.4+/-55.7 U/g protein, p=0.0002; RBC-GSHPx, 682.7+/-42.0 versus 756.5+/-47.6 U/g Hb, p=0.0011; plasma-GSHPx, 107.3+/-15.0 versus 131.4+/-19.7 U/g protein, p=0.0113). In addition, serum NO (NO*-2 + NO*-3) levels were also significantly (p = 0.0002) increased in WMS patients (54.4+/-5.7 versus 26.9+/-6.7 micromol/l). RBC-CAT levels were similar between groups (125.6+/-21.3 versus 131.0+/-21.5 k/g Hb, p = 0.8798). CONCLUSIONS: The elevated LPO, TNF-alpha and NO* with decreased antioxidant enzyme activities indicated impaired antioxidative defence mechanisms with an oxidative injury and cell toxicity in WMS patients. The use of multiple antioxidants and free radical scavengers might be helpful in this genetic disorder.

Expression of HSP 70 and its mRNAS during ischemia-reperfusion in the rat bladder

HSP 70 is an important protein that repairs damaged tissue after injury. In the present study, we investigated the expression of HSP 70 and its mRNAs during ischemia-reperfusion in the rat bladder. Rat abdominal aorta was clamped with a small clip to induce ischemia-reperfusion injury in the bladder dome. Male Wistar rats, 8 weeks old, were divided into six groups: controls, 30-min ischemia, 30-min ischemia and 30-, 60-minute, 1- and 7-day reperfusion, groups A, B, C, D, E, and F, respectively. In functional studies, contractile responses to carbachol were measured in these groups. The expression of HSP 70-1/2 mRNAs was quantified using a real-time PCR method, and that of HSP 70 proteins was measured using ELISA in the bladders. In the functional study, Emax values of carbachol to bladders in the A, B, C, D, E and F groups were 9.3 +/- 1.3, 7.9 +/- 1.7, 4.3 +/- 0.8, 4.2 +/- 0.7, 4.5 +/- 0.6, and 8.1 +/- 1.2 g/mm2, respectively. In the control group, the expression of HSP 70-1/2 mRNA was detected, and the expression of HSP 70-1 mRNAs was significantly higher than that of HSP 70-2 mRNAs in each group. The expression of HSP 70-1 mRNA increased in groups B and C, but decreased in groups D, E, and F. The expression of HSP 70-2 mRNA in group C was significantly higher than that of groups A, D, E, and F. The expression of HSP 70-1/2 mRNAs after 1 day or 1 week of reperfusion was similar to control levels. The expression of HSP 70 proteins was increased shortly after the expression of their mRNAs. The expression of HSP 70 after 1 day or 1 week of reperfusion was almost identical to control levels. Our data indicate that contractile responses of the bladder were decreased by ischemia reperfusion, and that expression of HSP 70 and its mRNAs appeared to increase after a short period of the insult.

Macrophage production of inflammatory mediators is potently inhibited by a butyric acid derivative demonstrated to inactivate antigen-stimulated T cells

The butyric acid derivative, 2-(4-morpholynl) ethyl butyrate hydrochloride (MEB), has been reported to induce antigen-specific T cell unresponsiveness and to block T cell-mediated graft-versus-host disease. As a potential therapeutic agent, it was important to determine the effects of MEB on other cells that contribute to immunopathology. Accordingly, we tested the effects of MEB on macrophage functions. MEB did not affect macrophage viability, phagocytic activity, or the activation-induced up-regulation of molecules associated with antigen presentation: MHC-II, CD86, CD40, or ICAM-1. However, MEB potently inhibited activation-induced production of inflammatory mediators, including tumor necrosis factor-alpha (TNF-alpha), IL-6, chemokine CCL2 and nitric oxide (NO). MEB inhibited the induction of NO synthase (NOS2), which is necessary for inducible NO, and inhibited nuclear translocation of NFkappaB, suggesting that MEB interferes with the signaling pathway involved in NOS2 induction. Thus, while inducing specific T cell unresponsiveness, MEB also exerts anti-inflammatory activity by acting on macrophages to suppress production of cytokines and NO.

Anti-inflammatory effects of nitric oxide-releasing hydrocortisone NCX 1022, in a murine model of contact dermatitis

1 The concept that nitric oxide (NO) release can be beneficial in inflammatory conditions has raised more attention in the recent years, particularly with the development of nitric oxide-releasing anti-inflammatory drugs. There is considerable evidence that NO is capable of enhancing the anti-inflammatory benefits of conventional anti-inflammatory drugs. 2 Since hydrocortisone is the most widely used anti-inflammatory drug for the treatment of skin inflammation, we compared the anti-inflammatory effects of hydrocortisone to an NO-releasing derivative of hydrocortisone, NCX 1022, in a murine model of irritant contact dermatitis, induced by epidermal application of benzalkonium chloride. 3 Topical pre- and post-treatment with NCX 1022 (3 nmol) in C57BL6 mice not only reduced ear oedema formation in a dose-dependent manner, but also was significantly more effective than the parent compound during the initial stages of inflammation (from 1 to 5 h). NCX 1022, but not hydrocortisone, significantly inhibited granulocyte recruitment (tissue myeloperoxidase activity). Histological samples of mouse ears treated with NCX 1022 showed significant reduction in both the number of infiltrated cells and disruption of the tissue architecture compared to hydrocortisone-treated tissues. 4 With intravital microscopy, we observed that both pre- and post-treatments with NCX 1022 were more effective than hydrocortisone in terms of inhibiting benzalkonium chloride-induced leukocyte adhesion to the endothelium, without affecting the flux of rolling leukocytes or venule diameter. 5 These results suggest that by releasing NO, NCX 1022 modulates one of the early events of skin inflammation: the recruitment of leukocytes to the site of inflammation. Overall, we have shown that NO-hydrocortisone provided faster and greater protective effects, reducing major inflammatory parameters (leukocyte adhesion and recruitment, oedema formation, tissue disruption) compared to its parental compound.

Nitric oxide in health and disease of the respiratory system

During the past decade a plethora of studies have unravelled the multiple roles of nitric oxide (NO) in airway physiology and pathophysiology. In the respiratory tract, NO is produced by a wide variety of cell types and is generated via oxidation of l-arginine that is catalyzed by the enzyme NO synthase (NOS). NOS exists in three distinct isoforms: neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS). NO derived from the constitutive isoforms of NOS (nNOS and eNOS) and other NO-adduct molecules (nitrosothiols) have been shown to be modulators of bronchomotor tone. On the other hand, NO derived from iNOS seems to be a proinflammatory mediator with immunomodulatory effects. The concentration of this molecule in exhaled air is abnormal in activated states of different inflammatory airway diseases, and its monitoring is potentially a major advance in the management of, e.g., asthma. Finally, the production of NO under oxidative stress conditions secondarily generates strong oxidizing agents (reactive nitrogen species) that may modulate the development of chronic inflammatory airway diseases and/or amplify the inflammatory response. The fundamental mechanisms driving the altered NO bioactivity under pathological conditions still need to be fully clarified, because their regulation provides a novel target in the prevention and treatment of chronic inflammatory diseases of the airways.

Haplotypic relationship between SNP and microsatellite markers at the NOS2A locus in two populations

The density of genetic markers required for successful association mapping of complex diseases depends on linkage disequilibrium (LD) between non-functional markers and functional variants. The haplotypic relationship between stable markers and potentially unstable but highly informative markers (e.g. microsatellites) indicates that LD might be maintained over considerable genetic distance in non-African populations, supporting the use of such 'mixed marker haplotypes' in LD-based mapping, and allowing inferences to be drawn about human origins. We investigated sequence variation in the proximal 2.6 kb of the inducible nitric oxide synthase (NOS2A) promoter and the relationship between SNP haplotypes and a pentanucleotide microsatellite (the 'NOS2A(-2.6) microsatellite') in Gambians and UK Caucasians. UK Caucasians exhibited a subset of sequence diversity observed in Gambians, sharing four of 11 SNPs and a similar haplotypic structure. Five SNPs were found in the sequence of interspersed repetitive DNA elements. In both populations, there was dramatic loss of LD between SNP haplotypes and microsatellite alleles across a very short physical distance, suggesting a high intrinsic mutation rate of the NOS2A(-2.6) microsatellite, the SNP haplotypes are relatively ancient, or that this was a region of frequent recombination. Understanding locus- and population-specific LD is essential when designing and interpreting genetic association studies.

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.