Modulation of polymorphonuclear leukocytes function by nitric oxide

Modulations in human neutrophil metabolome and S-glutathionylation of glycolytic pathway enzymes during the course of extracellular trap formation

Neutrophil extracellular trap formation (NETosis) has been irrefutably referred to as a distinct and unique form of active cell death with the purpose to counteract invading pathogens or augmenting the inflammatory cascade. Since the discovery, consistent efforts have been made to understand the various aspects of the initiation and sustenance of NETosis. In this study, using a global metabolomics approach during the phorbol 12-myristate 13-acetate (PMA) induced NETosis in human neutrophils, various metabolic pathways were found to be altered which includes intermediates related to, carbohydrate metabolism, and redox related metabolites, nucleic acid metabolism, and amino acids metabolism. Enrichment analysis of the metabolite sets highlighted the importance of the pentose phosphate pathway (PPP) and glutathione metabolism PMA-induced NETotic neutrophils. Further, analysis of the glutathyniolation status of neutrophil proteins by Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) indicated six different glutathionylated proteins: among them, two metabolically important proteins were α-enolase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) with MALDI score 166 and 70 respectively. Other proteins were lactoferrin, β-actin, c-myc promoter-binding protein, and uracil DNA glycosylase with MALDI scores of 96, 167, 104, and 68 respectively. Besides, activation of signalling proteins involved in metabolic regulation is also correlated with NETosis. Altogether, a balance between reactive oxygen species-glutathione metabolism seems to regulate the activity of glycolytic enzymes such as GAPDH and α-enolase during PMA-induced NETosis in a time-dependent manner.

Nitrate Metabolism and Ischemic Cerebrovascular Disease: A Narrative Review

Inorganic and organic nitrates are present in vivo and in vitro. Inorganic nitrate is considered a pool of nitric oxide (NO), but it can be converted into nitrite and NO through various mechanisms. It plays an important role in the regulation of complex physiological and biochemical reactions, such as anti-inflammatory processes and the inhibition of platelet aggregation, which are closely related to the pathology and treatment of cerebrovascular disease. Ischemic cerebrovascular disease is characterized by high incidence, recurrence, and disability rates. Nitrate, nitrite, and NO were recently found to be involved in cerebrovascular disease. In this review, we describe the relationship between cerebrovascular disease and nitrate metabolism to provide a basis for further advances in laboratory and clinical medicine.

Synthesis, Molecular Docking, biological potentials, and Structure-Activity Relationship of new quinazoline & quinazoline-4-one derivatives

CONTEXT

Quinazolines are a common class of nitrogen-containing heterocyclic scaffolds exhibiting a broad spectrum of pharmacological activities.

OBJECTIVE

In the present study, quinazoline and quinazolin-4-one derivatives were prepared, characterized to evaluate their biological which may pave the way for possible therapeutic applications.

MATERIALS & METHODS

A new derivative of quinazoline and quinazolin-4-one derivatives was prepared and tested for antiulcerogenic, anti-inflammatory and hepatoprotective activity.

RESULTS

The synthesized compounds were characterized by elemental analysis and spectral data. Also, the median lethal doses (LD_50s) of compounds 1-3 in rats were 1125, 835 and 1785 mg/kg b.w., respectively. IC₅₀ values of compounds (1-3) as measured by ABTS⁺ radical method was 0.8, 0.92 and 0.08 mg/mL, respectively. Antiulcerogenic activities at dose 1/20 LD₅₀ in albino rats were 47.94, 24.60 and 56.45%, respectively. Anti-inflammatory effect at dose 1/20 LD₅₀ of compounds (1-3) induced edema model after 120 min. The prepared compounds possess hepato gastric mucosa protective activity against ibuprofen-induced ulceration and LPS-induced liver toxicity, respectively in rats via normalization of oxidative stress biomarkers and inflammatory mediators were inhibited in peritoneal macrophage cells at concentration of 100 µg/L. Molecular docking suggested that the most active compounds 1 and 2 can be positioned within the active sites of COX-2 at Arg121 & Tyr356 similar to ibuprofen (Arg-120, Glu-524, and Tyr-355). The compound 3-COX-2 complex generated by docking revealed intricate interactions with a COX-2 channel.

CONCLUSION

These findings suggest that compounds 1-3 exhibited good antioxidant, antiulcer, anti-inflammatory activity and safe on liver enzymes in rats.

Hypoxia and Inflammation: Insights From High-Altitude Physiology

The key regulators of the transcriptional response to hypoxia and inflammation (hypoxia inducible factor, HIF, and nuclear factor-kappa B, NF-κB, respectively) are evolutionarily conserved and share significant crosstalk. Tissues often experience hypoxia and inflammation concurrently at the site of infection or injury due to fluid retention and immune cell recruitment that ultimately reduces the rate of oxygen delivery to tissues. Inflammation can induce activity of HIF-pathway genes, and hypoxia may modulate inflammatory signaling. While it is clear that these molecular pathways function in concert, the physiological consequences of hypoxia-induced inflammation and how hypoxia modulates inflammatory signaling and immune function are not well established. In this review, we summarize known mechanisms of HIF and NF-κB crosstalk and highlight the physiological consequences that can arise from maladaptive hypoxia-induced inflammation. Finally, we discuss what can be learned about adaptive regulation of inflammation under chronic hypoxia by examining adaptive and maladaptive inflammatory phenotypes observed in human populations at high altitude. We aim to provide insight into the time domains of hypoxia-induced inflammation and highlight the importance of hypoxia-induced inflammatory sensitization in immune function, pathologies, and environmental adaptation.

nNOS induction and NOSIP interaction impact granulopoiesis and neutrophil differentiation by modulating nitric oxide generation

Nitric oxide (NO), a versatile free radical and a signalling molecule, plays an important role in the haematopoiesis, inflammation and infection. Impaired proliferation and differentiation of myeloid cells lead to malignancies and Hematopoietic deficiencies. This study was aimed to define the role of nNOS derived NO in neutrophil differentiation (in-vitro) and granulopoiesis (in-vivo) using multipronged approaches. The results obtained from nNOS over-expressing K562 cells revealed induction in C/EBPα derived neutrophil differentiation as evident by an increase in the expression of neutrophil specific cell surface markers, genes, transcription factors and functionality. nNOS mediated response also involved G-CSFR-STAT-3 axis during differentiation. Consistent increase in NO generation was observed during neutrophil differentiation of mice and human CD34⁺ HSPCs. Furthermore, granulopoiesis was abrogated in the nNOS inhibitor treated mice, depicting a decrease in the numbers of BM mature and progenitor neutrophils. Likewise, in vitro inhibition of nNOS in human CD34⁺ HSPCs indicated an indispensable role of nNOS in neutrophil differentiation. Expression of nNOS inhibitory protein, NOSIP was significantly and consistently decreased during the final stage of differentiation and was linked with the augmentation in NO release. Moreover, neutrophils from CML patients had more NOSIP and less NO generation as compared to the PMNs from healthy individuals. The present study thus indicates a critical role of nNOS, and its interaction with NOSIP during neutrophil differentiation. The study also highlights the importance of nNOS in the neutrophil progenitor proliferation and differentiation warranting investigations to assess its role in the haematopoiesis-related disorders.

Neuronal Nitric Oxide Synthase (nNOS) in Neutrophils: An Insight

NO (nitric oxide) is an important regulator of neutrophil functions and has a key role in diverse pathophysiological conditions. NO production by nitric oxide synthases (NOS) is under tight control at transcriptional, translational, and post-translational levels including interactions with heterologous proteins owing to its potent chemical reactivity and high diffusibility; this limits toxicity to other cellular components and promotes signaling specificity. The protein-protein interactions govern the activity and spatial distribution of NOS isoform to regulatory proteins and to their intended targets. In comparison with the vast literature available for endothelial, macrophages, and neuronal cells, demonstrating neuronal NOS (nNOS) interaction with other proteins through the PDZ domain, neutrophil nNOS, however, remains unexplored. Neutrophil's key role in both physiological and pathological conditions necessitates the need for further studies in delineating the NOS mediated NO modulations in signaling pathways operational in them. nNOS has been linked to depression, schizophrenia, and Parkinson's disease, suggesting the importance of exploring nNOS/NO-mediated neutrophil physiology in relation to such neuronal disorders. The review thus presents the scenario of neutrophil nNOS from the genetics to the functional level, including protein-protein interactions governing its intracellular sequestration in diverse cell types, besides speculating possible regulation in neutrophils and also addressing their clinical implications.

Zingerone [4-(3-Methoxy-4-hydroxyphenyl)-butan-2] Attenuates Lipopolysaccharide-Induced Inflammation and Protects Rats from Sepsis Associated Multi Organ Damage

The present investigation aimed to evaluate the protective effect of Zingerone (ZIN) against lipopolysaccharide-induced oxidative stress, DNA damage, and cytokine storm in rats. For survival study the rats were divided into four groups (n = 10). The control group was treated with normal saline; Group II received an intraperitoneal (i.p) injection (10 mg/kg) of LPS as disease control. Rats in Group III were treated with ZIN 150 mg/kg (p.o) 2 h before LPS challenge and rats in Group IV were given ZIN only. Survival of the rats was monitored up to 96 h post LPS treatment. In another set, the animals were divided into four groups of six rats. Animals in Group I served as normal control and were treated with normal saline. Animals in Group II were treated with lipopolysaccharide (LPS) and served as disease control. Group III animals were treated with ZIN 2 h before LPS challenge. Group IV served as positive control and were treated with ZIN (150 mg/kg orally). The blood samples were collected and used for the analysis of biochemical parameters like alanine transaminase (ALT), alkaline phosphatase (ALP), aspartate transaminase (AST), blood urea nitrogen (BUN), Cr, Urea, lactate dehydrogenase (LDH), albumin, bilirubin (BIL), and total protein. Oxidative stress markers malondialdehyde (MDA), glutathione peroxidase (GSH), myeloperoxidase (MPO), and (DNA damage marker) 8-OHdG levels were measured in different organs. Level of nitric oxide (NO) and inflammatory markers like TNF-α, IL-1ß, IL-1α, IL-2, IL-6, and IL-10 were also quantified in plasma. Procalcitonin (PCT), a sepsis biomarker, was also measured. ZIN treatment had shown significant (p < 0.5) restoration of plasma enzymes, antioxidant markers and attenuated plasma proinflammatory cytokines and sepsis biomarker (PCT), thereby preventing the multi-organ and tissue damage in LPS-induced rats also confirmed by histopathological studies of different organs. The protective effect of ZIN may be due to its potent antioxidant potential. Thus ZIN can prevent LPS-induced oxidative stress as well as inflammatory and multi-organ damage in rats when administered to the LPS treated animals.

Nitric oxide and peroxynitrite trigger and enhance release of neutrophil extracellular traps

Despite great interest, the mechanism of neutrophil extracellular traps (NETs) release is not fully understood and some aspects of this process, e.g. the role of reactive nitrogen species (RNS), still remain unclear. Therefore, our aim was to investigate the mechanisms underlying RNS-induced formation of NETs and contribution of RNS to NETs release triggered by various physiological and synthetic stimuli. The involvement of RNS in NETs formation was studied in primary human neutrophils and differentiated human promyelocytic leukemia cells (HL-60 cells). RNS (peroxynitrite and nitric oxide) efficiently induced NETs release and potentiated NETs-inducing properties of platelet activating factor and lipopolysaccharide. RNS-induced NETs formation was independent of autophagy and histone citrullination, but dependent on the activity of phosphoinositide 3-kinases (PI3K) and myeloperoxidase, as well as selective degradation of histones H2A and H2B by neutrophil elastase. Additionally, NADPH oxidase activity was required to release NETs upon stimulation with NO, as shown in NADPH-deficient neutrophils isolated from patients with chronic granulomatous disease. The role of RNS was further supported by increased RNS synthesis upon stimulation of NETs release with phorbol 12-myristate 13-acetate and calcium ionophore A23187. Scavenging or inhibition of RNS formation diminished NETs release triggered by these stimuli while scavenging of peroxynitrite inhibited NO-induced NETs formation. Our data suggest that RNS may act as mediators and inducers of NETs release. These processes are PI3K-dependent and ROS-dependent. Since inflammatory reactions are often accompanied by nitrosative stress and NETs formation, our studies shed a new light on possible mechanisms engaged in various immune-mediated conditions.

Biological activities, isolated compounds and HPLC profile of Verbascum nubicum

Context: Genus Verbascum (Scrophulariaceae) comprises about 360 species of flowering plants. Verbascum has been used in traditional medicine as an astringent, antitussive, analgesic and anti-inflammatory. Objective: Nothing was found in the available literature concerning Verbascum nubicum Murb; therefore, the study evaluates the biological activities, isolated compounds and HPLC profile. Materials and methods: Methanol extract (VME) and butanol fraction (VBF) of air-dried powdered V. nubicum were obtained. Four compounds were isolated from VBE and identified by 1H- and 13C-NMR. High-performance liquid chromatography (HPLC) profile was determined for (VME). LD50, in vitro antioxidant, in vivo antiulcerogenic and anti-inflammatory activities as well as hepatoprotective activity were assessed. Anti-ulcerogenic and hepatoprotective activities were supported by histopathological examinations. Results: HPLC analysis of VME revealed the presence of luteolin 7-glucoside (2215.43 mg/100 g), hesperidin (954.51 mg/100 g) and apigenin (233.15 mg/100 g) as major compounds. Four compounds were isolated and confirmed by NMR data, were identified as gentiopicroside, luteolin, aucubin and gallic acid. The LD50 of VME and VBF extracts were calculated to be 8200 and 4225 mg/kg b.w., respectively. IC50 values of VBE and VMF as measured by DPPH·method were 43.6 and 50 µg/mL, respectively. Also, anti-inflammatory effect of VME (400 mg/kg b.w.) and VBF (200 mg/kg b.w.) induced edema model after 120 min were 61.93 and 56.13%, respectively. Antiulcerogenic activity of VME (400 mg/kg b.w.) and VBF (200 mg/kg b.w.) in albino rats were 65.14 and 84.57%, respectively. Conclusions: The V. nubicum extracts displayed safe and promising antioxidant, anti-inflammatory and hepatoprotective properties. It can be also applied in the pharmacy industry, food industry and healthcare.

Bioinorganics and Wound Healing

Wound dressings and the healing enhancement (increasing healing speed and quality) are two components of wound care that lead to a proper healing. Wound care today consists mostly of providing an optimal environment by removing waste and necrotic tissues from a wound, preventing infections, and keeping the wounds adequately moist. This is however often not enough to re-establish the healing process in chronic wounds; with the local disruption of vascularization, the local environment is lacking oxygen, nutrients, and has a modified ionic and molecular concentration which limits the healing process. This disruption may affect cellular ionic pumps, energy production, chemotaxis, etc., and will affect the healing process. Biomaterials for wound healing range from simple absorbents to sophisticated bioactive delivery vehicles. Often placing a material in or on a wound can change multiple parameters such as pH, ionic concentration, and osmolarity, and it can be challenging to pinpoint key mechanism of action. This article reviews the literature of several inorganic ions and molecules and their potential effects on the different wound healing phases and their use in new wound dressings.

BAY 41-2272 inhibits human neutrophil functions

BAY 41-2272 is a guanylyl cyclase (GC) stimulator derived from YC-1 (3-[(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole]). Previous studies by our group showed that BAY 41-2272 activates human monocytes via soluble guanylyl cyclase (sGC) and cGMP. In this study, we investigated the effect of BAY 41-2272 on human neutrophil function and found that 30 μM BAY 41-2272 inhibits neutrophil migration (1.82-fold lower than FMLP, P < 0.05 by one-way ANOVA followed by Tukey's test), oxidative burst (1.70-fold lower than PMA, P < 0.05 by one-way ANOVA followed by Tukey's test), and IL-8 cytokine production (1.80-fold lower than PMA, P < 0.05 by one-way ANOVA followed by Tukey's test). Our results suggest that these effects are independent of the sGC pathway but dependent instead on cGMP production, as the response induced by 30 μM BAY 41-2272 was 6.40-fold greater than that observed in our negative control (P < 0.05 by parametric t-test). 1H-[1, 2, 4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ), which is an irreversible inhibitor of sGC, was unable to reverse the effects of BAY 41-2272 on human neutrophils, indicating that this drug acts independently of sGC. Our results confirm the immunomodulatory effect of BAY 41-2272 on human neutrophils.

L-Arginine and tetrahydrobiopterin supported nitric oxide production is crucial for the microbicidal activity of neutrophils

Recent report from this lab has shown role of Rac2 in the translocation of inducible nitric oxide synthase (iNOS) to the phagosomal compartment of polymorphonuclear leukocytes (PMNs) following phagocytosis of beads. This study was undertaken to further assess the status and role of tetrahydrobiopterin (BH4), a redox-sensitive cofactor, L-arginine, and the substrate of nitric oxide synthase (NOS) in sustained nitric oxide (˙NO) production in killing of phagocytosed microbes (Escherichia coli) by human PMNs. Time-dependent study revealed consistent NO and reactive oxygen species (ROS) production in the PMNs following phagocytosis of beads. In addition, levels of L-arginine and BH4 were maintained or increased simultaneously to support the enzymatic activity of NOS in the bead activated PMNs. Moreover, translocation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) subunits along with iNOS was reconfirmed in the isolated phagosomes. We demonstrate that increase in the level of NO was supported by L-arginine and BH4 to kill E. coli, by using PMNs from NOS2-/- mice, human PMNs treated with biopterin inhibitor, N-acetyl serotonin (NAS), or by suspending human PMNs in L-arginine deficient medium. Altogether, this study demonstrates that following phagocytosis, sustained. NO production in the PMNs was well-maintained by redox sensitive cofactor, BH4 and substrate, and L-arginine to enable microbial killing. Further results suggest NO production in the human PMNs, along with ROS and myeloperoxidase (MPO) is important to execute antimicrobial activity.

Local anaesthetics upregulate nitric oxide generation in cord blood and adult human neutrophils

Nitric oxide (NO) generation by systemic neonatal neutrophils is not clarified. It is also not known whether local anaesthetics (LAs) transferred to the fetal systemic circulation following maternal epidural blockade may affect this process. In the present study, NO generation was evaluated in neutrophils from cord blood (CB, n = 11) and adult blood (n = 10) following exposure to bupivacaine (0.0005, 0.005, 1 mM), lidocaine (0.002, 0.02, 4 mM) and ropivacaine (0.0007, 0.007, 1.4 mM) using flow cytometry, as well as indirectly by determining nitrite concentrations in cell incubation media. To determine the role of NO synthase (NOS) isoforms in NO generation following exposure to LAs, experiments were repeated in the presence of the NOS inhibitors, N^G-nitro-L-arginine methyl ester and aminoguanidine; in addition, the expression of NOS isoforms was analysed. CB neutrophils produced less NO than adult neutrophils. LAs, especially ropivacaine and lidocaine, stimulated neutrophil NO generation, but in CB neutrophils this effect was negligible at clinically relevant drug concentrations. A mechanism involving NOS activity was responsible for the observed phenomena. In conclusion, LAs are able to upregulate neutrophil NO production, but in neonates this effect is likely to be clinically insignificant.

Dendritic cell-derived nitric oxide inhibits the differentiation of effector dendritic cells

Dendritic cells (DCs) play a pivotal role in the development of effective immune defense while avoiding detrimental inflammation and autoimmunity by regulating the balance of adaptive immunity and immune tolerance. However, the mechanisms that govern the effector and regulatory functions of DCs are incompletely understood. Here, we show that DC-derived nitric oxide (NO) controls the balance of effector and regulatory DC differentiation. Mice deficient in the NO-producing enzyme inducible nitric oxide synthase (iNOS) harbored increased effector DCs that produced interleukin-12, tumor necrosis factor (TNF) and IL-6 but normal numbers of regulatory DCs that expressed IL-10 and programmed cell death-1 (PD-1). Furthermore, an iNOS-specific inhibitor selectively enhanced effector DC differentiation, mimicking the effect of iNOS deficiency in mice. Conversely, an NO donor significantly suppressed effector DC development. Furthermore, iNOS-/- DCs supported enhanced T cell activation and proliferation. Finally iNOS-/- mice infected with the enteric pathogen Citrobacter rodentium suffered more severe intestinal inflammation with concomitant expansion of effector DCs in colon and spleen. Collectively, our results demonstrate that DC-derived iNOS restrains effector DC development, and offer the basis of therapeutic targeting of iNOS in DCs to treat autoimmune and inflammatory diseases.

High oxidative stress adversely affects NFκB mediated induction of inducible nitric oxide synthase in human neutrophils: Implications in chronic myeloid leukemia

Increasing evidence support bimodal action of nitric oxide (NO) both as a promoter and as an impeder of oxygen free radicals in neutrophils (PMNs), however impact of high oxidative stress on NO generation is less explored. In the present study, we comprehensively investigated the effect of high oxidative stress on inducible nitric oxide synthase (iNOS) expression and NO generation in human PMNs. Our findings suggest that PMA or diamide induced oxidative stress in PMNs from healthy volunteers, and high endogenous ROS in PMNs of chronic myeloid leukemia (CML) patients attenuate basal as well as LPS/cytokines induced NO generation and iNOS expression in human PMNs. Mechanistically, we found that under high oxidative stress condition, S-glutathionylation of NFκB (p50 and p65 subunits) severely limits iNOS expression due to its reduced binding to iNOS promoter, which was reversed in presence of DTT. Furthermore, by using pharmacological inhibitors, scavengers and molecular approaches, we identified that enhanced ROS generation via NOX2 and mitochondria, reduced Grx1/2 expression and GSH level associated with NFκB S-glutathionylation in PMNs from CML patients. Altogether data obtained suggest that oxidative status act as an important regulator of NO generation/iNOS expression, and under enhanced oxidative stress condition, NOX2-mtROS-NFκB S-glutathionylation is a feed forward loop, which attenuate NO generation and iNOS expression in human PMNs.

Effects of docosahexaenoic supplementation and in vitro vitamin C on the oxidative and inflammatory neutrophil response to activation

We studied the effects of diet supplementation with docosahexaenoic (DHA) and in vitro vitamin C (VitC) at physiological concentrations on oxidative and inflammatory neutrophil response to phorbol myristate acetate (PMA). Fifteen male footballers ingested a beverage enriched with DHA or a placebo for 8 weeks in a randomized double-blind study. Neutrophils were isolated from blood samples collected in basal conditions at the end of nutritional intervention. Neutrophils were cultured for 2 hours at 37°C in (a) control media, (b) media with PMA, and (c) media with PMA + VitC. PMA induces neutrophil degranulation with increased extracellular myeloperoxidase and catalase activities, nitric oxide production, expression of the inflammatory genes cyclooxygenase-2, nuclear factor κβ, interleukin 8 and tumor necrosis factor α, and interleukin 6 production. DHA diet supplementation boosts the exit of CAT from neutrophils but moderates the degranulation of myeloperoxidase granules induced by PMA. VitC facilitates azurophilic degranulation of neutrophils and increases gene expression of myeloperoxidase induced by PMA. VitC and DHA diet supplementation prevent PMA effects on inflammatory gene expression, although together they do not produce additional effects. DHA diet supplementation enhances antioxidant defences and anti-inflammatory neutrophil response to in vitro PMA activation. VitC facilitates neutrophil degranulation but prevents an inflammatory response to PMA.

Interaction of inducible nitric oxide synthase with rac2 regulates reactive oxygen and nitrogen species generation in the human neutrophil phagosomes: implication in microbial killing

AIMS

Present study explores importance of inducible nitric oxide synthase (iNOS) and its interaction with Rac2 in reactive oxygen species (ROS)/reactive nitrogen species (RNS) generation, protein-nitration and in microbial killing by neutrophils.

RESULTS

The iNOS transcript and protein were constitutively present in human as well as in mice neutrophils. iNOS protein was found in cytosol, granules containing elastase and gelatinase, and in other subcellular organelles in resting human neutrophils. After phagocytosis of bovine serum albumin (BSA) coated beads, both human and mice neutrophils showed significant elevation in superoxide radicals, nitric oxide (NO), ROS/RNS and consequent BSA nitration. These responses were significantly reduced in presence of iNOS, NADPH oxidase (NOX), myeloperoxidase or Rac inhibitors, as well as in iNOS, Nox2 and Rac2 silenced human or iNOS-knockout mice neutrophils. Complex formed on interaction of iNOS with Rac2 coprecipitated with anti-Rac2, predominantly in cytosol in resting human neutrophils, while iNOS-Rac2 complex translocated to phagosomes after phagocytosis. This was accompanied by generation of superoxide radicals, NO, ROS/RNS and consequent BSA-nitration. Importance of Rac2 in iNOS mediated NO formation and microbial killing was confirmed by pretreatment of mice with Rac inhibitor, NSC23766 that significantly abrogated NO release and microbial killing in vivo.

INNOVATION

Present study highlights previously undefined role of Rac2-iNOS interaction, in translocation of iNOS to phagosomal compartment and consequent NO, superoxide radicals, ROS/RNS generation, BSA nitration and microbial killing.

CONCLUSIONS

Altogether results obtained demonstrate the role of iNOS in NO and ROS/RNS generation, after phagocytosis of coated latex beads by human polymorphonuclear neutrophils. These studies imply functional importance of iNOS and its interaction with Rac2 in pathogen killing by the neutrophils.

Routes for formation of S-nitrosothiols in blood

S-nitrosothiols (RSNO) are involved in post-translational modifications of many proteins analogous to protein phosphorylation. In addition, RSNO have many physiological roles similar to nitric oxide ((•)NO), which are presumably involving the release of (•)NO from the RSNO. However, the much longer life span in biological systems for RSNO than (•)NO suggests a dominant role for RSNO in mediating (•)NO bioactivity. RSNO are detected in plasma in low nanomolar levels in healthy human subjects. These RSNO are believed to be redirecting the (•)NO to the vasculature. However, the mechanism for the formation of RSNO in vivo has not been established. We have reviewed the reactions of (•)NO with oxygen, metalloproteins, and free radicals that can lead to the formation of RSNO and have evaluated the potential for each mechanism to provide a source for RSNO in vivo.

Myeloperoxidase: a front-line defender against phagocytosed microorganisms

Successful immune defense requires integration of multiple effector systems to match the diverse virulence properties that members of the microbial world might express as they initiate and promote infection. Human neutrophils--the first cellular responders to invading microbes--exert most of their antimicrobial activity in phagosomes, specialized membrane-bound intracellular compartments formed by ingestion of microorganisms. The toxins generated de novo by the phagocyte NADPH oxidase and delivered by fusion of neutrophil granules with nascent phagosomes create conditions that kill and degrade ingested microbes. Antimicrobial activity reflects multiple and complex synergies among the phagosomal contents, and optimal action relies on oxidants generated in the presence of MPO. The absence of life-threatening infectious complications in individuals with MPO deficiency is frequently offered as evidence that the MPO oxidant system is ancillary rather than essential for neutrophil-mediated antimicrobial activity. However, that argument fails to consider observations from humans and KO mice that demonstrate that microbial killing by MPO-deficient cells is less efficient than that of normal neutrophils. We present evidence in support of MPO as a major arm of oxidative killing by neutrophils and propose that the essential contribution of MPO to normal innate host defense is manifest only when exposure to pathogens overwhelms the capacity of other host defense mechanisms.

Angiotensin type 1a receptor signaling is not necessary for the production of reactive oxygen species in polymorphonuclear leukocytes

Background. Although angiotensin II (Ang II) has inflammatory effects, little is known about its role in polymorphonuclear leucocytes (PMLs). To elucidate the role of Ang II in PMLs ROS production, we examined hydrogen peroxide (H2O2), one of the ROS, and NO production in AT1a receptor knockout (AT1KO) mice. Methods and Results. PMLs were analyzed from Ang II type 1a receptor knockout mice (AT1KO) and C57BL/6 wild type mice. Using flow cytometry, we studied hydrogen peroxide (H2O2) production from PMLs after Staphylococcus aureus phagocytosis or phorbol myristate acetate (PMA) stimulation. Nitric oxide (NO) production in the AT1KO was low at basal and after phagocytosis. In the AT1KO, basal H2O2 production was low. After PMA or phagocytosis stimulation, however, H2O2 production was comparable to wild type mice. Next we studied the H2O2 production in C57BL/6 mice exposed to Ang II or saline. H2O2 production stimulated by PMA or phagocytosis did not differ between the two groups. Conclusions. AT1a pathway is not necessary for PMLs H2O2 production but for NO production. There was a compensatory pathway for H2O2 production other than the AT1a receptor.

Glycolaldehyde impairs neutrophil biochemical parameters by an oxidative and calcium-dependent mechanism--protective role of antioxidants astaxanthin and vitamin C

AIM

The present study examined the effects of glycolaldehyde (GC) on biochemical parameters of human neutrophils and whether the antioxidant astaxanthin associated with vitamin C can modulate these parameters.

METHODS

Neutrophils from healthy subjects were treated with GC (1mM) followed or not by the antioxidants astaxanthin (2 μM) and vitamin C (100 μM). We examined the phagocytic capacity, hypochlorous acid, myeloperoxidase (MPO) and glucose-6-phosphate dehydrogenase (G6PDH) activities, cytokines and [Ca(2+)](i). Also, superoxide anion, hydrogen peroxide, nitric oxide production, antioxidant enzyme activities and glutathione-recycling system were evaluated.

RESULTS

GC promoted a marked reduction on the phagocytic capacity, maximal G6PDH and MPO activities, hypochlorous acid production and release of IL-1β, IL-6 and TNF-α cytokines. Some impairment in the neutrophils biochemical parameters appears to be mediated by oxidative stress through ROS/RNS production and calcium reduction. Oxidative stress was evidenced by reduction in the activities of the main antioxidant enzymes, GSH/GSSG ratio and in the increment of O(2)(-) and H(2)O(2) and NO.

CONCLUSIONS

Treatment of cells with the combination of the antioxidants astaxanthin and vitamin C was able to restore some neutrophils function mainly by decreasing ROS/RNS production and improving the redox state. Overall, our findings demonstrate that GC modulates several neutrophils biochemical parameters in vitro.

Intracellular mechanisms of hydroquinone toxicity on endotoxin-activated neutrophils

Circulating neutrophils promptly react to different substances in the blood and orchestrate the beginning of the innate inflammatory response. We have shown that in vivo exposure to hydroquinone (HQ), the most oxidative compound of cigarette smoke and a toxic benzene metabolite, affects circulating neutrophils, making them unresponsive to a subsequent bacterial infection. In order to understand the action of toxic molecular mechanisms on neutrophil functions, in vitro HQ actions on pro-inflammatory mediator secretions evoked by Escherichia coli lipopolysaccharide (LPS) were investigated. Neutrophils from male Wistar rats were cultured with vehicle or HQ (5 or 10 μM; 2 h) and subsequently incubated with LPS (5 μg/ml; 18 h). Hydroquinone treatment impaired LPS-induced nitric oxide (NO), tumour necrosis factor α (TNF-α), interleukin (IL)-1β and IL-6 secretions by neutrophils. The toxic effect was not dependent on cell death, reduced expression of the LPS receptor or toll-like receptor-4 (TLR-4) or cell priming, as HQ did not induce reactive oxygen species generation or β(2)integrin membrane expression. The action of toxic mechanisms on cytokine secretion was dependent on reduced gene synthesis, which may be due to decreased nuclear factor κB (NF-κB) nuclear translocation. Conversely, this intracellular pathway was not involved in impaired NO production because HQ treatments only affected inducible nitric oxide synthase protein expression and activity, suggesting posttranscriptional and/or posttranslational mechanisms of action. Altogether, our data show that HQ alters the action of different LPS-activated pathways on neutrophils, which may contribute to the impaired triggering of the host innate immune reaction detected during in vivo HQ exposure.

Nitric oxide-mediated augmentation of neutrophil reactive oxygen and nitrogen species formation: Critical use of probes

Previous reports from this laboratory and others demonstrated NO-mediated biphasic modulation of NADPH oxidase and attenuation of neutrophil reactive oxygen species generation, whereas recently we reported augmentation in DCF fluorescence following NO treatment. These discrepancies seem to be due to utilization of different probes/methods to assess effect of NO on reactive oxygen and nitrogen species (ROS/RNS, reactive species) generation. This study aims to look into this and evaluate NO-mediated enzymatic reactive species formation by using multiple probes, human neutrophils/HL60 cells and various interventions. Addition of NO donor, SNP or SNAP (100 nM-1 mM) to PMNs suspension, exhibited a concentration- and time-dependent augmentation in DCF fluorescence, but reduced DHE fluorescence. Collective generation of reactive species was confirmed by enhanced DMPO-nitrone adduct, dityrosine and rhodamine-123 and quenching of scopoletin. NO also enhanced bacterial killing, without altering phagocytosis. Addition of NO to HL-60 cells lacking functional NADPH oxidase enhanced reactive species formation, indicating importance of other enzyme(s) too. NO-dependent ROS/RNS generation was substantially reduced by NADPH oxidase inhibitor (DPI), MPO inhibitor (ABAH), or NOS inhibitor (7-NI). However, 7-NI reduced MPO activity, warranting reappraisal of those reports, which implied NOS in reactive species formation. The results obtained demonstrated NO-mediated reactive species augmentation in human PMNs. Furthermore, superoxide scavenging by NO seems to be the key process in the decrease of DHE fluorescence and suggest usefulness of DCF as the most appropriate probe to measure the NO-mediated modulation of reactive oxygen species in particular in various pathological situations.

Primary murine microglia are resistant to nitric oxide inhibition of indoleamine 2,3-dioxygenase

Indoleamine 2,3-dioxygenase (IDO) is an intracellular heme-containing enzyme that is activated by proinflammatory cytokines, including interferon-γ (IFNγ), and metabolizes tryptophan along the kynurenine pathway. Activation of murine macrophages induces not only IDO but also nitric oxide synthase (iNOS), and the ensuing production of nitric oxide (NO) inhibits IDO. To determine the sensitivity of primary cultures of murine microglia to NO, microglia were stimulated with recombinant murine IFNγ (1 ng/ml) and lipopolysaccharide (LPS) (10 ng/ml). This combination of IFNγ+LPS synergized to produce maximal amounts of nitrite as early as 16h. Steady-state mRNAs for both iNOS and IDO were significantly increased by IFNγ+LPS at 4h post-treatment, followed by an increase in IDO enzymatic activity at 24h. Murine microglia (>95% CD11b(+)) were pretreated with the iNOS inhibitor, L-NIL hydrochloride, at a dose (30 μM) that completely abrogated production of nitrite. L-NIL had no effect on IDO mRNA at 4h or IDO enzymatic activity at 24h following stimulation with IFNγ+LPS. These data establish that IDO regulation in murine microglia is not restrained by NO, thereby permitting the accumulation of kynurenine and its downstream metabolites in the central nervous system.

Functional and molecular characterization of NOS isoforms in rat neutrophil precursor cells

Previous studies from this laboratory have demonstrated importance of neutrophil-derived nitric oxide (NO) in free radical generation, characterized nitric oxide synthase (NOS) isoforms, and have reported subcellular distribution of NOS in rat peripheral neutrophils. Maximum number of neutrophils are added per day to the circulation from bone marrow, thus neutrophils might add substantial amount of NO in the bone marrow. NO generating ability and NOS isoforms characteristics in bone marrow neutrophil precursor cells is, however, still unexplored. This study was, therefore, undertaken to investigate NO generation ability and the molecular/biochemical characteristics of NOS isoforms in neutrophil precursor cells. The neutrophil precursors were separated on Percoll density gradient and characterized by Giemsa staining, CD markers, and by their size and granularity at various stages of maturation as Bands 1, 2, and 3. Mature neutrophils were efficient in free radical generation and phagocytosis, whereas immature cells had more mitochondria and myeloperoxidase. Amount of NO augmented from immature to mature neutrophils as assessed by fluorescent probe DAF-2DA and Griess reagent. Measurement of NOS enzyme activity further confirmed the functional status of NOS in these cells. NOS isoforms were differentially expressed during neutrophil maturation as confirmed by enzyme activity, Western blotting, flowcytometry, and RT-PCR. Expression of nNOS was predominantly stable in all the stages of neutrophil maturation. iNOS expression was, however, consistently augmented during maturation, whereas eNOS expression was downregulated with neutrophil maturation. Furthermore, all NOS isoforms proteins were distributed in cytosol as well as nucleus as assessed by confocal microscopy. This study for the first time report biochemical and molecular characteristics of NOS isoforms in rat neutrophil precursor cells.

Effects of L-citrulline oral supplementation on polymorphonuclear neutrophils oxidative burst and nitric oxide production after exercise

Seventeen volunteer male professional cyclists were randomly assigned to control or supplemented (6 g L-citrulline-malate) groups and participated in a cycling stage. Blood samples were taken in basal conditions, after the race and 3 h post-race. Citrulline supplementation significantly increased plasma concentration of both arginine and citrulline after the stage only in the supplemented group. Polymorphonuclear neutrophils (PMNs) from controls responded to exercise with a progressive decrease in ROS production. Supplemented PMNs significantly increased ROS production after exercise compared to basal values and diminished to values lower than basal at recovery. PMN nitrite concentration was significantly higher after exercise and recovery only in the supplemented group. Markers of oxidative damage-CK, LDH, malondialdehyde-and DNA damage remained unchanged in both groups. In conclusion, oral L-citrulline administration previous to a cycling stage increases plasma arginine availability for NO synthesis and PMNs priming for oxidative burst without oxidative damage.

Role of hemoglobin oxygenation in the modulation of red blood cell mechanical properties by nitric oxide

It has been previously demonstrated that both externally generated and internally synthesized nitric oxide (NO) can affect red blood cell (RBC) deformability. Further studies have shown that the RBC has active NO synthesizing mechanisms and that these mechanisms may play role in maintaining normal RBC mechanical properties. However, hemoglobin within the RBC is known to be a potent scavenger of NO; oxy-hemoglobin scavenges NO faster than deoxy-hemoglobin via the dioxygenation reaction to nitrate. The present study aimed at investigating the role of hemoglobin oxygenation in the modulation of RBC rheologic behavior by NO. Human blood was obtained from healthy volunteers, anticoagulated with sodium heparin (15 IU/mL), and the hematocrit was adjusted to 0.4 L/L by adding or removing autologous plasma. Several two mL aliquots of blood were equilibrated at room temperature (22+/-2 degrees C) with moisturized air or 100% nitrogen by a membrane gas exchanger, The NO donor sodium nitroprusside (SNP), at a concentration range of 10(-7)-10(-4)M, was added to the equilibrated aliquots which were maintained under the same conditions for an additional 60 min. The effect of the non-specific NOS inhibitor l-NAME was also tested at a concentration of 10(-3)M. RBC deformability was measured using an ektacytometer with an environment corresponding to that used for the prior incubation (i.e., oxygenated or deoxygenated). Our results indicate an improvement of RBC deformability with the NO donor SNP that was much more pronounced in the deoxygenated aliquots. SNP also had a more pronounced effect on RBC aggregation for deoxygenated RBC. Conversely, l-NAME had no effect on deoxygenated blood but resulted in impaired deformability, with no change in aggregation for oxygenated blood. These findings can be explained by a differential behavior of hemoglobin under oxygenated and deoxygenated conditions; the influence of oxygen partial pressure on NOS activity may also play a role. It is therefore critical to consider the oxygenation state of intracellular hemoglobin while studying the role of NO as a regulator of RBC mechanical properties.

The effects of disodium pamidronate on human polymorphonuclear leukocytes and platelets: an in vitro study

Recent reports have indicated that, as well as having antiresorptive effects, bisphosphonates could have an application as anti-inflammatory drugs. Our aim was to investigate whether this anti-inflammatory action could be mediated by the nitric oxide (NO) released by the leukocytes migrating to the site of inflammation. In particular, we investigated in vitro the intracellular calcium concentration ([Ca2+](i)), the level of NO released by PMN and platelets, and the PMN myeloperoxidase activity after incubation with disodium pamidronate, since there was a postulated modulatory effect of this aminosubstituted bisphosphonate on leukocytes both in vitro and in vivo. Our data shows that the pamidronate treatment provoked a significant increase in the [Ca2+](i) parallel to the enhancement in NO release, suggesting a possible activation of constitutive nitric oxide synthase, while the myeloperoxidase activity was significantly reduced. In conclusion, we hypothesized that treatment with pamidronate could stimulate NO-production by cells present near the bone compartment, thus constituting a protective mechanism against bone resorption occurring during inflammation. In addition, PMN- and platelet-derived NO could act as a negative feed-back signal to restrict the inflammatory processes.

Ascorbate sustains neutrophil NOS expression, catalysis, and oxidative burst

Previous studies from this lab have demonstrated that in vitro ascorbate augments neutrophil nitric oxide (NO) generation and oxidative burst. The present study was therefore undertaken in guinea pigs to further assess the implication of ascorbate deficiency in vivo on neutrophil ascorbate and tetrahydrobiopterin content, NOS expression/activity, phagocytosis, and respiratory burst. Ascorbate deficiency significantly reduced ascorbate and tetrahydrobiopterin amounts, NOS expression/activity, and NO as well as free radical generation in neutrophils from scorbutics. Ascorbate and tetrahydrobiopterin supplementation in vitro, though, significantly enhanced NOS catalysis in neutrophil lysates and NO generation in live cells, but could not restore them to control levels. Although phagocytic activity remained unaffected, scorbutic neutrophils were compromised in free radical generation. Ascorbate-induced free radical generation was NO dependent and prevented by NOS and NADPH oxidase inhibitors. Augmentation of oxidative burst with dehydroascorbate (DHA) was counteracted in the presence of glucose (DHA uptake inhibitor) and iodoacetamide (glutaredoxin inhibitor), suggesting the importance of ascorbate recycling in neutrophils. Ascorbate uptake was, however, unaffected among scorbutic neutrophils. These observations thus convincingly demonstrate a novel role for ascorbate in augmenting both NOS expression and activity in vivo, thereby reinforcing oxidative microbicidal actions of neutrophils.

Effects of hyperoxia and nitric oxide on endogenous nitric oxide production in polymorphonuclear leukocytes

BACKGROUND

Exposure to hyperoxia and nitric oxide (NO) occur frequently during the treatment of neonatal hypoxic pulmonary failure.

OBJECTIVE

The aim of the study was to quantify the endogenous synthesis of NO in neonatal polymorphonuclear neutrophils following exposure to hyperoxia and NO in vitro.

METHODS

Neonatal cord blood was exposed to room air, 25, 30 and 100% oxygen and 10 or 20 ppm NO added to the different oxygen concentrations for up to 30 min. 4,5-Diaminofluorescein diacetate (DAF-2 DA) is an intracellular dye used to measure real-time changes in NO levels in vivo. The molecular structure of DAF-2 DA changes upon contact with NO to its oxidized and fluorescent form diaminofluorescein-triazol (DAF-2T) and after being hydrolyzed by intracellular esterases cannot leave the cell. DAF-2 DA signals following equilibration with room air were used as controls.

RESULTS

Exposure to 100% oxygen increased NO production significantly when compared to 20 ppm NO plus 100% oxygen (p = 0.031) and to 20 ppm NO alone (p = 0.006). 10 ppm NO produced a similar effect. Significant increases in NO production were also noticed following exposure to 25% oxygen. This increase was already present after 10 min of oxygen exposure.

CONCLUSION

These findings support the propagated avoidance of hyperoxia not only in preterm infants, but also in term neonates.

iNOS-mediated generation of reactive oxygen and nitrogen species by biomaterial-adherent neutrophils

Infection due to implanted cardiovascular biomaterials is a serious complication initiated by bacterial adhesion to the surface of the implant. The release of reactive oxygen species by neutrophils, particularly superoxide anion, is a well-known bactericidal mechanism. Additionally, nitric oxide (NO) has also been identified as an important cytotoxic mediator in acute and chronic inflammatory responses with enhanced NO production by upregulation of inducible nitric oxide synthase (iNOS). The interaction of NO and superoxide anion will result in the formation of peroxynitrite (OONO-), a potent cytotoxic oxidant. In this study, we have shown that biomaterial-induced neutrophil activation does not cause upregulation of iNOS and activation of iNOS-mediated pathways. However, NO and O2- production does occur over time upon adhesion to a biomaterial and is modulated by biomaterial surface chemistry. With no stimulus, the polyethylene oxide-modified polyurethane induced greater neutrophil activation than did the control as indicated by the increased production of NO and O2- over time. Adherent-stimulated neutrophils generally produced lower amounts of NO over time in comparison with unstimulated cells. Furthermore, there is no evidence of peroxynitrite activity in unstimulated neutrophils adherent to the Elasthane 80A. However, upon stimulation with adherent Staphylococcus epidermidis, peroxynitrite formation did occur. Our results suggest that bactericidal mechanisms in neutrophils involving NO generation (NOS pathway) are further compromised than O2- producing pathways (NADPH oxidase) upon exposure to biomaterials, resulting in a diminished microbial killing capacity, which can increase the probability of device-centered infections.

In vitro Effect of Carvedilol on Professional Phagocytes

AIM

Superfluous reactive nitrogen and oxygen species generation is implicated in the damage of tissues at sites of inflammation where activated neutrophils and macrophages are involved. This study was conducted to investigate whether the beneficial effects of carvedilol involve modulation of respiratory burst, degranulation-myeloperoxidase release and inducible nitric oxide synthase (iNOS) expression.

METHODS

Spectrophotometry and chemiluminescence were used to evaluate the effect of carvedilol on opsonized zymosan (0.5 mg/ml)- or N-formyl-methionyl-leucyl-phenyl-alanine (fMLP, 0.1 micromol/l)-stimulated superoxide generation and myeloperoxidase release in human neutrophils. Western blot analysis was used for iNOS expression and Griess reagent for nitric oxide production in RAW 264.7 macrophages (lipopolysaccharide (0.1 microg/ml) stimulated).

RESULTS

Carvedilol (10 and 100 micromol/l) significantly decreased opsonized zymosan- and fMPL-stimulated superoxide generation and myeloperoxidase release. Carvedilol (100 micromol/l) enhanced the effect of wortmannin (50 nmol/l), a specific inhibitor of 1-phosphatidylinositol 3-kinase and decreased iNOS expression and nitric oxide production.

CONCLUSION

Carvedilol appears to have a non-specific effect on membranes and to interfere with the phospholipase D signaling pathway, with subsequent inhibition of reactive oxygen species generation and myeloperoxidase release, without affecting iNOS expression.

Protective effect of taurine on respiratory burst activity of polymorphonuclear leukocytes in endotoxemia

The aim of this study was to evaluate the effect of endotoxin on PMN leukocyte respiratory burst activity by measuring G6PD, NADPH oxidase and XO activities in guinea pig. In addition, the possible protective role of taurine against endotoxin-mediated PMN leukocyte function was examined. All experiments were performed with four groups (control, taurine, endotoxemia, taurine plus endotoxin) of ten guinea pigs. After the endotoxin was administrated (4 mg/kg) both G6PD and NADPH oxidase activities were significantly reduced compared with the control group. NADPH oxidase activity returned to the control value and G6PD activity also increased but it did not reach the control value. However when taurine was administrated (300 mg/kg) the activity of NADPH oxidase reached the control value; furthermore, G6PD activity also increased but it could not reach to the control value. When taurine was administrated alone, no effect on these enzymes was observed. Following the endotoxin administration, the activity of XO considerably increased. When taurine was administrated together with endotoxine and alone, this activity decreased compared to control value in both conditions. These results indicate that the O2*- formation in PMN leukocytes after the endotoxin administration is ensured by the catalysis of XO due to the inhibited NADPH oxidase activity. It was observed that taurine has considerable anti-inflammatory and antioxidant effects. However, conflicting results were obtained when taurine was administrated alone or together with an oxidant agent.

5'-AMP-activated protein kinase activation prevents postischemic leukocyte-endothelial cell adhesive interactions

Preconditioning (PC) with nitric oxide (NO) donors or agents that increase endothelial NO synthase (eNOS) activity 24 h before ischemia-reperfusion (I/R) prevents postischemic leukocyte rolling (LR) and stationary leukocyte adhesion (LA). Since 5'-AMP-activated protein kinase (AMPK) phosphorylates eNOS at Ser1177, resulting in activation, we postulated that AMPK activation may trigger the development of a preconditioned anti-inflammatory phenotype similar to that induced by NO donors. Wild-type (WT) C57BL/6J and eNOS(-/-) mice were treated with the AMPK agonist 5-aminoimidazole-4-carboxamide 1-beta-d-furanoside (AICAR) 30 min (early AICAR PC) or 24 h (late AICAR PC) before I/R; LR and LA were quantified in single postcapillary venules in the jejunum using intravital microscopy. I/R induced comparable marked increases in LR and LA in WT and eNOS(-/-) mice relative to sham-operated (no ischemia) animals. Late AICAR PC prevented postischemic LR and LA, whereas early AICAR PC prevented LA in WT mice. Late AICAR PC was ineffective in preventing I/R-induced LR but not LA in the eNOS(-/-) mice, and the same pattern was seen in WT animals treated with the NOS inhibitor N(omega)-nitro-l-arginine. Early AICAR PC remained effective in preventing LA in eNOS(-/-) mice. Our results indicate that both early and late PC with an AMPK agonist produces an anti-inflammatory phenotype in postcapillary venules. Since the protection afforded by late AICAR PC on postischemic LR was prevented by NOS inhibition in WT mice and absent in eNOS-deficient mice, it appears that eNOS triggers this protective effect. In stark contrast, antecedent AMPK activation prevented I/R-induced LA by an eNOS-independent mechanism.

Nitric oxide and polyamine pathway-dependent modulation of neutrophil free amino- and α-keto acid profiles or host defense capability

We have examined the effects of N(omega)-nitro-L-arginine-methylester-hydrochloride [L-NAME; inhibitor of nitric oxide synthase], S-nitroso-N-acetyl-penicillamine [SNAP; nitric oxide donor], alpha-difluoro-methyl-ornithine [DFMO; inhibitor of ornithine decarboxylase] arginine or ornithine as well as the combination of arginine or ornithine with L-NAME, SNAP or DFMO on intracellular free amino- and alpha-keto acid profiles and the immune function markers superoxide anion and hydrogen peroxide generation as well as released myeloperoxidase activity in neutrophils (PMN). Although the underlying mechanisms still remain unclear, we believe from our results that nitric oxide as well as polyamine-dependent pathways are involved in the signal transmission of free radical molecule, beneficial nutritional therapy or maleficient pharmacological stress-induced alterations in PMN nutrient composition. Relevant changes in intragranulocyte free amino- and alpha-keto acid homeostasis and metabolism, especially, may be one of the determinants in PMN nutrition that positively or negatively influences and modulate neutrophil host defence capability and immunocompetence.

Modulation of citric acid-induced cough following lipopolysaccharide-mediated neutrophilia in the guinea pig

This investigation examined a possible correlation between lipopolysaccharide (LPS)-induced pulmonary neutrophilia and cough. Conscious male guinea pigs were acutely exposed to aerosolized LPS and thereafter at various times challenged with citric acid aerosol (CA; 250mM) to induce cough followed by bronchoalveolar lavage (BAL) to quantitate inflammatory cell accumulation. LPS caused a hyporesponsive cough at 24h post-LPS with neutrophilia apparent from 2h post-LPS. By 96h post-LPS both cough and neutrophilia had returned towards normal. Dexamethasone (DEX, 2mgkg(-1)/day for 3 days prior) did not affect the cough hyporesponsiveness at 24h; however it attenuated LPS-induced BAL fluid neutrophilia. Since LPS can stimulate inducible nitric oxide synthase (iNOS) we hypothesized that the cough hyporesponsiveness may involve nitric oxide. To investigate this we treated animals with an aerosolized iNOS inhibitor 1400W (1mM) immediately prior to LPS. 1400W had no significant effect on either cough hyporesponsiveness or BAL fluid neutrophilia at 24h post-LPS. Despite differing effects on neutrophilia, these findings clearly indicate that neither DEX nor iNOS inhibition had any direct effect on LPS-induced cough hyporesponsiveness. The mechanism underlying the LPS-induced cough hyporesponsiveness does not appear to be directly linked to LPS-induced neutrophilic inflammation.

Nitric oxide synthase localization in the rat neutrophils: immunocytochemical, molecular, and biochemical studies

Nitric oxide (NO) modulates diverse functions of polymorphonuclear neutrophils (PMNs), but localization of NO synthase (NOS) and identification of its interacting proteins remain the least defined. The present study discerns subcellular distribution of NOS and caveolin-1, a prominent NOS-interacting protein in rat PMNs. Localization of NOS was explored by confocal and immunogold electron microscopy, and its activity was assessed by L-[3H] arginine and 4,5-diaminofluorescein diacetate (DAF-2DA). Reverse transcriptase-polymerase chain reaction using NOS primers and Western blotting demonstrated the presence of neuronal NOS (nNOS) and inducible NOS (iNOS) in PMNs. Immunocytochemical studies exhibited distribution of nNOS and iNOS in cytoplasm and nucleus, and L-[3H] citrulline formation and DAF fluorescence confirmed NOS activity in both fractions. NOS activity correlated positively with calmodulin concentration in both of the fractions. nNOS and iNOS colocalized with caveolin-1, as evidenced by immunocytochemical and immunoprecipitation studies. The results thus provide first evidence of nNOS and iNOS in the nuclear compartment and suggest NOS interaction with caveolin-1 in rat PMNs.

Inducible nitric oxide synthase (iNOS) in tumor biology: the two sides of the same coin

Inducible nitric oxide synthase (iNOS) is one of three key enzymes generating nitric oxide (NO) from the amino acid l-arginine. iNOS-derived NO plays an important role in numerous physiological (e.g. blood pressure regulation, wound repair and host defence mechanisms) and pathophysiological (inflammation, infection, neoplastic diseases, liver cirrhosis, diabetes) conditions. iNOS is the synthase isoform most commonly associated with malignant disease. Nevertheless, the role of iNOS during tumor development is highly complex, and incompletely understood. Both promoting and deterring actions have been described, presumably depending upon the local concentration of iNOS within the tumor microenvironment. In particular, pivotal effects such as malingnant transformation, angiogenesis, and metastasis are modulated by iNOS. On the other hand, NO derived from macrophages has a potentially cytotoxic/cytostatic effect upon tumor cells. Hence, therapeutical interference with iNOS activity is of considerable interest, especially in tumors where metastatic activity, host defence mechanisms and the level of differentiation seem to be correlated to iNOS expression. This review will aim to summarize the dual actions of iNOS as simultaneous tumor promoter and suppressor.

l-Arginine prevents air embolism-induced acute lung injury in rats

OBJECTIVE

Pulmonary air embolism, causing vessel obstruction and primary or secondary reactions of blood, can lead to acute lung injury. In addition, nitric oxide has been known to play a key role in various causes of lung injury. In this study we employed the isolated rat lung model to investigate the effects of l-arginine on air embolism-induced lung injury.

DESIGN

Randomized, controlled study.

SETTING

Animal-care facility procedure room.

SUBJECTS

Forty-two adult male Sprague-Dawley rats each weighing 250-350 g.

INTERVENTIONS

Infusion of air at the rate of 0.25 mL/min for 1 min into the pulmonary artery in isolated and perfused rat lung resulted in pulmonary hypertension and lung edema. Air embolism elicited a significant increase in microvascular permeability as measured by the capillary filtration coefficient, lung weight gain, lung weight-to-body weight ratio, pulmonary arterial pressure, and protein concentration of bronchoalveolar lavage fluid.

MEASUREMENTS AND MAIN RESULTS

Pretreatment with L-arginine (4 mmol/L) significantly attenuated the acute lung injury induced by air embolism as shown by a significant decrease in all of the assessed variables but did not alter the pulmonary arterial pressure (p < .05). The protective effect of l-arginine was blocked when N(G)-nitro-L-arginine methyl ester (5 mmol/L) was added. Pretreatment with N(G)-nitro-L-arginine methyl ester exacerbated air embolism-induced lung injury.

CONCLUSIONS

Our findings suggest that L-arginine can prevent air embolism-induced lung injury.

Protective effect of green tea polyphenols on the SH-SY5Y cells against 6-OHDA induced apoptosis through ROS-NO pathway

Green tea polyphenols (GTP) are thought to help prevent oxidative stress-related diseases, such as cancer, cardiovascular disease, neurodegenerative disease, and aging. We here investigate the protective mechanisms of GTP on SH-SY5Y cells against apoptosis induced by the pro-parkinsonian neurotoxin 6-hydroxydopamine (6-OHDA). GTP rescued the changes in condensed nuclear and apoptotic bodies, attenuated 6-OHDA-induced early apoptosis, prevented the decrease in mitochondrial membrane potential, and suppressed accumulation of reactive oxygen species (ROS) and of intracellular free Ca(2+). GTP also counteracted the 6-OHDA-induced nitric oxide increase and overexpression of nNOS and iNOS, and decreased the level of protein-bound 3-nitrotyrosine (3-NT). In addition, GTP inhibited the autooxidation of 6-OHDA and scavenged oxygen free radicals in a dose- and time-dependent manner. Our results show that the protective effects of GTP on SH-SY5Y cells are mediated, at least in part, by controlling the ROS-NO pathway.

Neutrophil Dysfunction in Guanosine 3′,5′-Cyclic Monophosphate-Dependent Protein Kinase I-Deficient Mice

The regulation of neutrophil functions by Type I cGMP-dependent protein kinase (cGKI) was investigated in wild-type (WT) and cGKI-deficient (cGKI-/-) mice. We demonstrate that murine neutrophils expressed cGKIalpha. Similar to the regulation of Ca2+ by cGKI in other cells, there was a cGMP-dependent decrease in Ca2+ transients in response to C5a in WT, but not cGKI-/- bone marrow neutrophils. In vitro chemotaxis of bone marrow neutrophils to C5a or IL-8 was significantly greater in cGKI-/- than in WT. Enhanced chemotaxis was also observed with cGKI-/- peritoneal exudate neutrophils (PE-N). In vivo chemotaxis with an arachidonic acid-induced inflammatory ear model revealed an increase in both ear weight and myeloperoxidase (MPO) activity in ear punches of cGKI-/- vs WT mice. These changes were attributable to enhanced vascular permeability and increased neutrophil infiltration. The total extractable content of MPO, but not lysozyme, was significantly greater in cGKI-/- than in WT PE-N. Furthermore, the percentage of MPO released in response to fMLP from cGKI-/- (69%) was greater than that from WT PE-N (36%). PMA failed to induce MPO release from PE-N of either genotype. In contrast, fMLP and PMA released equivalent amounts of lysozyme from PE-N. However, the percentage released was less in cGKI-/- (approximately 60%) than in WT (approximately 90%) PE-N. Superoxide release (maximum velocity) revealed no genotype differences in responses to PMA or fMLP stimulation. In summary, these results show that cGKIalpha down-regulates Ca2+ transients and chemotaxis in murine neutrophils. The regulatory influences of cGKIalpha on the secretagogue responses are complex, depending on the granule subtype.

Nitric oxide and blood: a review

Nitric oxide (NO) was identified as a physiological mediator of vascular tone in 1987. NO produced by endothelial cells causes vasodilatation and also inhibits platelet aggregation and leucocyte adhesion. Red cells metabolize NO to nitrate but may possibly carry and release, or even produce, NO in hypoxic conditions. NO physiology may have important implications for transfusion medicine, ranging from adverse effects of haemoglobin substitutes to preservation of stored platelets and to detrimental effects of stored red cells.

Food restriction attenuates age-related increase in the sensitivity of endothelial cells to oxidized lipids

Age-related endothelial dysfunction has been suggested to play a role in atherogenesis. Food restriction (FR) has been shown to retard the development of atherosclerosis. The goal of this report is to assess the effect of aging and FR on endothelial functions, including the release of endothelial nitric oxide (NO) and the adhesion of mononuclear cells (MNCs) to endothelial cells (ECs). ECs were obtained from the aorta of young mice fed ad libitum (Y-AL), old mice fed ad libitum (O-AL), or a food-restricted diet (O-FR). When compared with those obtained from Y-AL and O-FR mice, ECs obtained from O-AL mice decreased the basal level of NO release and increased the basal level of peroxynitrite, superoxide, and hydrogen peroxide. In addition, ECs obtained from O-AL elevated the response to CuSO4-oxidized low-density lipoprotein (oxLDL). For example, incubation with oxLDL reduced NO release approximately 52% in ECs obtained from O-AL mice. In contrast, the same dose of oxLDL reduced NO release only approximately 40% in ECs obtained from Y-AL and O-FR mice. Moreover, the level of oxLDL-induced adhesion of MNCs and oxLDL-induced expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 was markedly higher in ECs obtained from O-AL mice as compared with those obtained from Y-AL and O-FR mice. These results suggest that aging increases the sensitivity of ECs in response to oxLDL-reduced endothelial NO release and oxLDL-increased adhesion of MNCs to ECs. FR attenuates age-related increase in the sensitivity of ECs to oxLDL, which might be responsible, at least in part, for the antiatherogenic action of FR.