Enhanced Generation of Reactive Species by Cold Plasma in Gelatin Solutions for Selective Cancer Cell Death

Atmospheric pressure plasma jets generate reactive oxygen and nitrogen species (RONS) in liquids and biological media, which find application in the new area of plasma medicine. These plasma-treated liquids were demonstrated recently to possess selective properties on killing cancer cells and attracted attention toward new plasma-based cancer therapies. These allow for local delivery by injection in the tumor but can be quickly washed away by body fluids. By confining these RONS in a suitable biocompatible delivery system, great perspectives can be opened in the design of novel biomaterials aimed for cancer therapies. Gelatin solutions are evaluated here to store RONS generated by atmospheric pressure plasma jets, and their release properties are evaluated. The concentration of RONS was studied in 2% gelatin as a function of different plasma parameters (treatment time, nozzle distance, and gas flow) with two different plasma jets. Much higher production of reactive species (H₂O₂ and NO₂^-) was revealed in the polymer solution than in water after plasma treatment. The amount of RONS generated in gelatin is greatly improved with respect to water, with concentrations of H₂O₂ and NO₂^- between 2 and 12 times higher for the longest plasma treatments. Plasma-treated gelatin exhibited the release of these RONS to a liquid media, which induced an effective killing of bone cancer cells. Indeed, in vitro studies on the sarcoma osteogenic (SaOS-2) cell line exposed to plasma-treated gelatin led to time-dependent increasing cytotoxicity with the longer plasma treatment time of gelatin. While the SaOS-2 cell viability decreased to 12%-23% after 72 h for cells exposed to 3 min of treated gelatin, the viability of healthy cells (hMSC) was preserved (∼90%), establishing the selectivity of the plasma-treated gelatin on cancer cells. This sets the basis for designing improved hydrogels with high capacity to deliver RONS locally to tumors.

Protective effect of L-ascorbic acid on nickel induced pulmonary nitrosative stress in male albino rats

Nickel sulfate stimulates inducible nitric oxide synthase (i-NOS) and increases serum nitric oxide concentration by overproduction of reactive nitrogen species due to nitrosative stress. The present study was undertaken to assess possible protective role of L-ascorbic acid as an antioxidant against nickel induced pulmonary nitrosative stress in male albino rats. We studied the effect of the simultaneous treatment with L-ascorbic acid (50 mg/100 g b. wt.; orally) and nickel sulfate (2.0 mg/100 g b. wt.; i.p.) on nitric oxide synthesis by quantitative evaluation of serum i-NOS activities, serum and lung nitric oxide, L-ascorbic acid and protein concentrations of Wistar strain male albino rats. We have further studied histopathological changes in lung tissue after nickel sulfate treatment along with simultaneous exposure of L-ascorbic acid. Nickel sulfate treatment significantly increased the serum i-NOS activity, serum and pulmonary nitric oxide concentration and decreased body weight, pulmonary somatic index, serum and lung L-ascorbic acid and protein concentration as compared to their respective controls. Histopathological changes induced by nickel sulfate showed loss of normal alveolar architecture, inflammation of bronchioles, infiltration of inflammatory cells and patchy congestion of alveolar blood vessels. The simultaneous administration of L-ascorbic acid and nickel sulfate significantly improved all the above biochemical parameters along with histopathology of lung tissues of rats receiving nickel sulfate alone. The study clearly showed a protective role of L-ascorbic acid against nickel induced nitrosative stress in lung tissues.

[Beta-glucan as a natural anticancer agent]

Beta-glucans participate in the processes of repair, metabolism and detoxification, and affect the overall health of the body counteract the pathological conditions of reactive oxygen and nitrogen and the processes in which they participate. Reactive oxygen species (ROS) and nitrogen (RNS) play an important role in the pathogenesis of many diseases. Production of ROS is an integral part of aerobic metabolism of cells. Physiological concentrations of ROS play an important role in proper functioning of many cellular processes, and their overproduction occurs during induced oxidative stress. Very closely associated with oxidative stress is nitrosative stress. Nitric oxide (NO) reacts with molecular oxygen, superoxide anion radical and metal cations to give more reactive oxygen species. Reactive oxygen and nitrogen react with proteins to cause impairment of their function by oxidation or nitrosylation of amino acid residues, which can direct the path of apoptotic cells. In addition, nitric oxide enhances the effect induced by cyclooxygenase and becomes a mediator of inflammation.

Peroxynitrite formation and function in plants

Peroxynitrite (ONOO(-)) is a reactive nitrogen species formed when nitric oxide (NO) reacts with the superoxide anion (O(2)(-)). It was first identified as a mediator of cell death in animals but was later shown to act as a positive regulator of cell signaling, mainly through the posttranslational modification of proteins by tyrosine nitration. In plants, peroxynitrite is not involved in NO-mediated cell death and its physiological function is poorly understood. However, it is emerging as a potential signaling molecule during the induction of defense responses against pathogens and this could be mediated by the selective nitration of tyrosine residues in a small number of proteins. In this review we discuss the general role of tyrosine nitration in plants and evaluate recent evidence suggesting that peroxynitrite is an effector of NO-mediated signaling following pathogen infection.

Role of reactive nitrogen species in blood platelet functions

Blood platelets, in analogy to other circulating blood cells, can generate reactive oxygen/nitrogen species (ROS/RNS) that may behave as second messengers and may regulate platelet functions. Accumulating evidence suggest a role of ROS/RNS in platelet activation. On the other hand, an increased production of ROS/RNS causes oxidative stress, and thus, may contribute to the development of different diseases, including vascular complications, inflammatory and psychiatric illnesses. Oxidative stress in platelets leads to chemical changes in a wide range of their components, and platelet proteins may be initial targets of ROS/RNS action. It has been demonstrated that reaction of proteins with ROS/RNS results in the oxidation and nitration of some amino acid residues, formation of aggregates or fragmentation of proteins. In oxidized proteins new carbonyl groups and protein hydroperoxides are also formed. In platelets, low molecular weight thiols such as glutathione (GSH), cysteine and cysteinylglycine and protein thiols may be also target for ROS/RNS action. This review describes the chemical structure and biological activities of reactive nitrogen species, mainly nitric oxide ((*)NO) and peroxynitrite (ONOO(-)) and their effects on blood platelet functions, and the mechanisms involved in their action on platelets.

Anti-oxidant strategies

Oxidative stress plays an important role in causing organ injury in the compromised fetus and neonate. Recent experimental research and clinical studies have clarified important pathways in the production of reactive oxygen and nitrogen species. Free radicals are involved in causing cerebral damage after perinatal hypoxia-ischemia affecting membrane lipids, proteins, and DNA. Anti-oxidant strategies can be used as add-on neuroprotective therapy after perinatal oxidative stress. Selective inhibitors of neuronal and inducible nitric oxide synthase, allopurinol, melatonin, and erythropoietin are among the first compounds that are ready for clinical trials.

Pharmacological evaluation of anti-leishmanial activity by in vivo nitric oxide modulation in Balb/c mice infected with Leishmania major MRHO/IR/75/ER: An Iranian strain of cutaneous leishmaniasis

Cutaneous leishmaniasis with a variation in its clinical signs is still one of the health problems in the world, region and Iran. Immune responses against leishmania consist of cytokines, immune cells and mediators. Macrophages participate actively in the inflammatory response by releasing chemokines and mediators including nitric oxide (NO) and reactive oxygen and nitrogen intermediates. This study investigates whether NO had anti-leishmanial effects and/or mediated pathology in mice infected with Leishmania major MRHO/IR/75/ER (IR/75). NO inducer lipopolysaccharide (LPS) and NO donor S-nitrosoglutathione (SNOG) were used for their ability to increase RNI and to modify leishmania infection in susceptible Balb/c mice, in order to evaluate the effects of NO production on size and lesion macroscopy, delay of lesion formation and proliferation of amastigotes inside macrophages. Liver, spleen and lymph nodes were also studied as target organs to detect amastigotes. In addition to plasma, liver and spleen suspensions were investigated for NO induction by using Griess microassay. Statistical analysis of data revealed an association between increases in NO level with the pathology of disease in Balb/c mice infected with L. major IR/75. The survival of leishmania parasite inside the macrophages and its proliferation was affected by LPS and SNOG-treatments. An inconsistent relationship was evident between the NO modulation and pathological changes in treated Balb/c mice infected with L. major IR/75.

Inhibition of reactive nitrogen species production in COPD airways: comparison of inhaled corticosteroid and oral theophylline

BACKGROUND

Reactive nitrogen species (RNS) are thought to be one of the important factors in the pathogenesis of chronic obstructive pulmonary disease (COPD). A study was undertaken to examine the effects of theophylline and fluticasone propionate (FP) on RNS production in subjects with COPD.

METHODS

Sixteen COPD subjects participated in the study. Theophylline (400 mg/day orally) or FP (400 mug/day inhalation) were administered for 4 weeks in a randomised crossover manner with a washout period of 4 weeks. Induced sputum was collected at the beginning and end of each treatment period. 3-nitrotyrosine (3-NT), which is a footprint of RNS, was quantified by high performance liquid chromatography with an electrochemical detection method as well as by immunohistochemical staining.

RESULTS

Theophylline significantly reduced the level of 3-NT in the sputum supernatant as well as the number of 3-NT positive cells (both p<0.01). FP also reduced 3-NT formation, but the effect was smaller than that of theophylline. Theophylline also significantly reduced the neutrophil cell counts in the sputum (p<0.01), while FP treatment had no effect on the number of inflammatory cells in the sputum, except eosinophils.

CONCLUSIONS

Theophylline reduces nitrative stress and neutrophil infiltration in COPD airways to a larger extent than inhaled corticosteroid.

Effect of immune serum and role of individual Fcgamma receptors on the intracellular distribution and survival of Salmonella enterica serovar Typhimurium in murine macrophages

Immune serum has a protective role against Salmonella infections in mice, domestic animals and humans. In this study, the effect of antibody on the interaction between murine macrophages and S. enterica serovar Typhimurium was examined. Detailed analysis at the single-cell level demonstrated that opsonization of the bacteria with immune serum enhanced bacterial uptake and altered bacterial distribution within individual phagocytic cells. Using gene-targeted mice deficient in individual Fc gamma receptors it was shown that immune serum enhanced bacterial internalization by macrophages via the high-affinity immunoglobulin G (IgG) receptor, Fc gamma receptor I. Exposure of murine macrophages to S. enterica serovar Typhimurium opsonized with immune serum resulted in increased production of superoxide, leading to enhanced antibacterial functions of the infected cells. However, opsonization of bacteria with immune serum did not increase either nitric oxide production in response to S. enterica serovar Typhimurium or fusion of phagosomes with lysosomes.

Pharmacological strategies for the regulation of inducible nitric oxide synthase: neurodegenerative versus neuroprotective mechanisms

Inducible nitric oxide synthase (iNOS) is one of three NOS isoforms generating nitric oxide (NO) by the conversion of l-arginine to l-citrulline. iNOS has been found to be a major contributor to initiation/exacerbation of the central nervous system (CNS) inflammatory/degenerative conditions through the production of excessive NO which generates reactive nitrogen species (RNSs). Activation of iNOS and NO generation has come to be accepted as a marker and therapeutic target in neuroinflammatory conditions such as those observed in ischemia, multiple sclerosis (MS), spinal cord injury (SCI), Alzheimer's disease (AD), and inherited peroxisomal (e.g. X-linked adrenoleukodystrophy; X-ALD) and lysosomal disorders (e.g. Krabbe's disease). However, with the emergence of reports on the neuroprotective facets of NO, the prior dogma about NO being solely detrimental has had to be modified. While RNSs such as peroxynitrite (ONOO(-)) have been linked to lipid peroxidation, neuronal/oligodendrocyte loss, and demyelination in neurodegenerative diseases, limited NO generation by GSNO has been found to promote vasodilation and attenuate vascular injury under the same ischemic conditions. NO generated from GSNO acts as second messenger molecular which through S-nitrosylation has been shown to control important cellular processes by regulation of expression/activity of certain proteins such as NF-kappaB. It is now believed that the environment and the context in which NO is produced largely determines the actions (good or bad) of this molecule. These multi-faceted aspects of NO make therapeutic interference with iNOS activity even more complicated since complete ablation of iNOS activity has been found to be rather more detrimental than protective in most neurodegenerative conditions. Investigators in search of iNOS modulating pharmacological agents have realized the need of a delicate balance so as to allow the production of physiologically relevant amounts of NO (such as those required for host defence/neutotransmission/vasodilation, etc.) but at the same time block the generation of RNSs through repressing excessive NO levels (such as those causing neuronal/tissue damage and demyelination, etc.). The past years have seen a noteworthy increase in novel agents that might prove useful in achieving the aim of harnessing the good and blocking the undesirable actions of NO. It is the aim of this review to provide basic insights into the NOS family of enzymes with special emphasis of the role of iNOS in the CNS, in the first part. In the second part of the review, we will strive to provide an exhaustive compilation of the prevalent strategies being tested for the therapeutic modulation of iNOS and NO production.

Drugs modulating the biological effects of peroxynitrite and related nitrogen species

The term "reactive nitrogen species" includes nitrogen monoxide, commonly called nitric oxide, and some other remarkable chemical entities (peroxynitrite, nitrosoperoxycarbonate, etc.) formed mostly from nitrogen monoxide itself in biological environments. Regardless of the specific mechanisms implicated in their effects, however, it is clear that an integrated pharmacological approach to peroxynitrite and related species is only just beginning to take shape. The array of affected chemical and pathological processes is extremely broad. One of the most conspicuous mechanisms observed thus far has been the scavenging of the peroxynitrite anion by molecules endowed with antioxidant activity. This discovery has in turn lent great significance to several naturally occurring and synthetic antioxidants, which usually protect not only against oxidative reactions, but also from nitrating ones, both in vitro and in vivo. This has proven to be beneficial in different tissues, especially within the central nervous system. Taking these results and those of other biochemical investigations into account, many research lines are currently in progress to establish the true potential of reactive nitrogen species deactivators in the therapy of neurological diseases, ischemia-reperfusion damage, renal failure, and lung injury, among others.

Mitochondria produce reactive nitrogen species via an arginine-independent pathway

We measured the contribution of mitochondrial nitric oxide synthase (mtNOS) and respiratory chain enzymes to reactive nitrogen species (RNS) production. Diaminofluorescein (DAF) was applied for the assessment of RNS production in isolated mouse brain, heart and liver mitochondria and also in a cultured neuroblastoma cell line by confocal microscopy and flow cytometry. Mitochondria produced RNS, which was inhibited by catalysts of peroxynitrite decomposition but not by nitric oxide (NO) synthase inhibitors. Disrupting the organelles or withdrawing respiratory substrates markedly reduced RNS production. Inhibition of complex I abolished the DAF signal, which was restored by complex II substrates. Inhibition of the respiratory complexes downstream from the ubiquinone/ubiquinol cycle or dissipating the proton gradient had no effect on DAF fluorescence. We conclude that mitochondria from brain, heart and liver are capable of significant RNS production via the respiratory chain rather than through an arginine-dependent mtNOS.

Thyroid hormone-induced oxidative stress

Hypermetabolic state in hyperthyroidism is associated with tissue oxidative injury. Available data indicate that hyperthyroid tissues exhibit an increased ROS and RNS production. The increased mitochondrial ROS generation is a side effect of the enhanced level of electron carriers, by which hyperthyroid tissues increase their metabolic capacity. Investigations of antioxidant defence system have returned controversial results. Moreover, other thyroid hormone-linked biochemical changes increase tissue susceptibility to oxidative challenge, which exacerbates the injury and dysfunction they suffer under stressful conditions. Mitochondria, as a primary target for oxidative stress, might account for hyperthyroidism linked tissue dysfunction. This is consistent with the inverse relationship found between functional recovery of ischemic hyperthyroid hearts and mitochondrial oxidative damage and respiration impairment. However, thyroid hormone-activated mitochondrial mechanisms provide protection against excessive tissue dysfunction, including increased expression of uncoupling proteins, proteolytic enzymes and transcriptional coactivator PGC-1, and stimulate opening of permeability transition pores.

Modification of tryptophan and tryptophan residues in proteins by reactive nitrogen species

Formation of 3-nitrotyrosine by the reaction between reactive nitrogen species (RNS) and tyrosine residues in proteins has been analyzed extensively and it is used widely as a biomarker of pathophysiological and physiological conditions mediated by RNS. In contrast, few studies on the nitration of tryptophan have been reported. This review provides an overview of the studies on tryptophan modifications by RNS and points out the possible importance of its modification in pathophysiological and physiological conditions. Free tryptophan can be modified to several nitrated products (1-, 4-, 5-, 6-, and 7-), 1-N-nitroso product, and several oxidized products by reaction with various RNS, depending on the conditions used. Among them, 1-N-nitrosotryptophan and 6-nitrotryptophan (6-NO(2)Trp) have been found as the abundant products in the reaction with peroxynitrite, and 6-NO(2)Trp has been the most abundant product in the reaction with the peroxidase/hydrogen peroxide/nitrite systems. 6-NO(2)Trp has also been observed as the most abundant nitrated product of the reactions between peroxynitrite or myeloperoxidase/hydrogen peroxide/nitrite and tryptophan residues both in human Cu,Zn-superoxide dismutase and in bovine serum albumin, as well as the reaction of peroxynitrite with myoglobin and hemoglobin. Several oxidized products have also been identified in the modified Cu,Zn-SOD. However, no 1-N-nitrosotryptophan and 1-N-nitrotryptophan has been observed in the proteins reacted with peroxynitrite or the myeloperoxidase/H(2)O(2)/nitrite system. The modification of tryptophan residues in proteins may occur at a more limited number of sites in vivo than that of tyrosine residues, since tryptophan residues are more buried inside proteins and exist less frequently in proteins, generally. However, surface-exposed tryptophan residues tend to participate in the interaction with the other molecules, therefore the modification of those tryptophans may result in modulation of the specific interaction of proteins and enzymes with other molecules.

Mitochondrial NO and reactive nitrogen species production: Does mtNOS exist?

It is more than 10 years now that mitochondria are suspected to be sources of nitric oxide (NO). This hypothesis is intriguing since NO has multiple targets within the organelle and it is even suggested that mitochondria are the primary targets of NO in the cell. Most remarkably, nanomolar concentrations of NO can inhibit mitochondrial respiration, so even a small amount of NO in the mitochondrial matrix may regulate ATP synthesis. Therefore, the idea that mitochondria themselves are capable of NO production is an important concept in several physiological and pathological mechanisms. However, this field of research generates surprisingly few original papers and the published studies contain conflicting results. The reliability of the results is frequently questioned since they are seldom reproduced by independent investigators. Until 2003, all papers published in this field showed affirmative results but since then several studies directly challenged the existence of a mitochondrial nitric oxide synthase. The present review aims to summarize the most recent developments in mitochondrial NO production, highlights a few unsolved questions, and proposes new directions for future work in this research area.

Suppressive effects of mioga ginger and ginger constituents on reactive oxygen and nitrogen species generation, and the expression of inducible pro-inflammatory genes in macrophages

We previously conducted screening tests of the chloroform extracts from a total of 89 species of Japanese plant food items for their suppressive effects on superoxide (O(2) ()) generation through both NADPH oxidase and xanthine oxidase, and reported that mioga ginger (Zingiber mioga Roscoe) indicated the strongest suppressive activities. In this study, the suppressive effects of mioga ginger constituents, aframodial, and galanal B, together with [6]-gingerol and galanolactone occurring in ginger, on free radical generation and inducible proinflammatory gene expressions were investigated. Of these constituents, aframodial (20 microM) exhibited marked suppressive effects on 12-O-tetradecanoylphorbol-13-acetate-induced O(2) () generation in HL-60 cells and lipopolysaccharide (LPS)/interferon-gamma-induced nitric oxide (NO) generation in RAW264.7 cells (inhibition rates [IRs]=84.6% and 95.9%, respectively). Aframodial also strongly suppressed the stimulated HL-60 cell-induced mutagenicity in AS52 cells (IR=95.9%). The LPS-induced expression of inducible proinflammatory genes such as inducible NO synthase, interleukin (IL)-1beta, IL-6, and granulocyte-macrophage colony-stimulating factor was significantly abolished (IRs=99.1%, 74.6%, 74.0%, and 64.4%, respectively) by aframodial. In addition, degradation of the inhibitor of nuclear factor kappaB was suppressed by this compound (IR=100%), suggesting that the suppression of nuclear factor kappaB activation, at least in part, is involved. Taken together, these results suggest that aframodial has potent antioxidative and anti-inflammatory potentials, and may be a promising candidate in prevention and/or therapy for chronic inflammationassociated carcinogenesis.

Inorganic arsenic compounds cause oxidative damage to DNA and protein by inducing ROS and RNS generation in human keratinocytes

Arsenic is a naturally occurring element that is present in food, soil, and water. Inorganic arsenic can accumulate in human skin and is associated with increased risk of skin cancer. Oxidative stress due to arsenic exposure is proposed as one potential mode of carcinogenic action. The purpose of this study is to investigate the specific reactive oxygen and nitrogen species that are responsible for the arsenic-induced oxidative damage to DNA and protein. Our results demonstrated that exposure of human keratinocytes to trivalent arsenite caused the generation of 8-hydroxyl-2'-deoxyguanine (8-OHdG) and 3-nitrotyrosine (3-NT) in a concentration- and time-dependent manner. Pentavalent arsenate had similar effects, but to a significantly less extent. The observed oxidative damage can be suppressed by pre-treating cells with specific antioxidants. Furthermore, we found that pre-treating cells with Nomega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), or with 5,10,15,20-tetrakis (N-methyl-4'-pyridyl) porphinato iron (III) chloride (FeTMPyP), a decomposition catalyst of peroxynitrite, suppressed the generation of both 8-OHdG and 3-NT, which indicated that peroxynitrite, a product of the reaction of nitric oxide and superoxide, played an important role in arsenic-induced oxidative damage to both DNA and protein. These findings highlight the involvement of peroxynitrite in the molecular mechanism underlying arsenic-induced human skin carcinogenesis.

Mechanisms underlying resistance of pancreatic islets from ALR/Lt mice to cytokine-induced destruction

Nuclear and mitochondrial genomes combine in ALR/Lt mice to produce systemically elevated defenses against free radical damage, rendering these mice resistant to immune-mediated pancreatic islet destruction. We analyzed the mechanism whereby isolated islets from ALR mice resisted proinflammatory stress mediated by combined cytokines (IL-1beta, TNF-alpha, and IFN-gamma) in vitro. Such damage entails both superoxide and NO radical generation, as well as peroxynitrite, resulting from their combination. In contrast to islets from other mouse strains, ALR islets expressed constitutively higher glutathione reductase, glutathione peroxidase, and higher ratios of reduced to oxidized glutathione. Following incubation with combined cytokines, islets from control strains produced significantly higher levels of hydrogen peroxide and NO than islets from ALR mice. Nitrotyrosine was generated in NOD and C3H/HeJ islets but not by ALR islets. Western blot analysis showed that combined cytokines up-regulated the NF-kappaB inducible NO synthase in NOD-Rag and C3H/HeJ islets but not in ALR islets. This inability of cytokine-treated ALR islets to up-regulate inducible NO synthase and produce NO correlated both with reduced kinetics of IkappaB degradation and with markedly suppressed NF-kappaB p65 nuclear translocation. Hence, ALR/Lt islets resist cytokine-induced diabetogenic stress through enhanced dissipation and/or suppressed formation of reactive oxygen and nitrogen species, impaired IkappaB degradation, and blunted NF-kappaB activation. Nitrotyrosylation of beta cell proteins may generate neoantigens; therefore, resistance of ALR islets to nitrotyrosine formation may, in part, explain why ALR mice are resistant to type 1 diabetes when reconstituted with a NOD immune system.

Irradiation of the rabbit cornea with UVB rays stimulates the expression of nitric oxide synthases-generated nitric oxide and the formation of cytotoxic nitrogen-related oxidants

Until now, the role of nitric oxide (NO) in cornea irradiated with UVB rays remains unknown. Therefore, we investigated nitric oxide synthase isomers (NOS), enzymes that generate NO, nitrotyrosine (NT), a cytotoxic byproduct of NO, and malondialdehyde (MDA), a byproduct of lipid peroxidation, in rabbit corneas repeatedly irradiated with UVB rays (312 nm, 1x daily for 6 days, the dose per day 1.01 J/cm2) using immunohistochemical methods. The biochemical measurement of nitrite and nitrate has been used for the indirect investigation of NO concentration in the aqueous humor. Results show that in contrast to normal corneas, where of the NOS isomers only endothelial nitric oxide synthase (NOS3) was expressed in a significant amount (in the epithelium and endothelium), in irradiated corneas all NOS isomers (also brain nitric oxide synthase, NOS1, and inducible nitric oxide synthase, NOS2) as well as an indirect measure of ONOO-formation and MDA were gradually expressed, first in the epithelium, the endothelium and the keratocytes beneath the epithelium and finally in the cells of all corneal layers and the inflammatory cells that invaded the corneal stroma. This was accompanied by an elevated concentration of NO in the aqueous humor. In conclusion, repeated irradiation with UVB rays evoked the stimulation of NO production, peroxynitrite formation (demonstrated by NT residues) and lipid peroxidation (evaluated by MDA staining).

Kinetoplastid Membrane Protein-11 DNA Vaccination Induces Complete Protection against Both Pentavalent Antimonial-Sensitive and -Resistant Strains ofLeishmania donovaniThat Correlates with Inducible Nitric Oxide Synthase Activity and IL-4 Generation: Evidence for Mixed Th1- and Th2-Like Responses in Visceral Leishmaniasis

The emergence of an increasing number of Leishmania donovani strains resistant to pentavalent antimonials (SbV), the first line of treatment for visceral leishmaniasis worldwide, accounts for decreasing efficacy of chemotherapeutic interventions. A kinetoplastid membrane protein-11 (KMP-11)-encoding construct protected extremely susceptible golden hamsters from both pentavalent antimony responsive (AG83) and antimony resistant (GE1F8R) virulent L. donovani challenge. All the KMP-11 DNA vaccinated hamsters continued to survive beyond 8 mo postinfection, with the majority showing sterile protection. Vaccinated hamsters showed reversal of T cell anergy with functional IL-2 generation along with vigorous specific anti-KMP-11 CTL-like response. Cytokines known to influence Th1- and Th2-like immune responses hinted toward a complex immune modulation in the presence of a mixed Th1/Th2 response in conferring protection against visceral leishmaniasis. KMP-11 DNA vaccinated hamsters were protected by a surge in IFN-gamma, TNF-alpha, and IL-12 levels along with extreme down-regulation of IL-10. Surprisingly the prototype candidature of IL-4, known as a disease exacerbating cytokine, was found to have a positive correlation to protection. Contrary to some previous reports, inducible NO synthase was actively synthesized by macrophages of the protected hamsters with concomitant high levels of NO production. This is the first report of a vaccine conferring protection to both antimony responsive and resistant Leishmania strains reflecting several aspects of clinical visceral leishmaniasis.

Inhibition of poly(ADP-ribose) polymerase attenuates lung tissue damage after hind limb ischemia-reperfusion in rats

The objective of this study was to investigate the effects of 3-aminobenzamide (3-AB) on tissue damage in lung after hind limb ischemia-reperfusion (I/R), by assessing blood biochemical assay and histopathological analysis. Thirty-five adult Wistar rats were divided into five groups. After application of anaesthesia both hind limbs were occluded with tourniquets. Following ischemia period for 60 min, the tourniquets were removed allowing reperfusion for 120 min. The IR group received 0.5 ml of saline while the IR+AB group received 3-AB (10 mgkg(-1) intraperitoneally). The IR+DMSO group was given 0.5 ml 10% DMSO 30 min before the removal of the tourniquets. The control group received 0.5 ml saline and the AB group received 0.5 ml 3-AB (10 mgkg(-1)) intraperitoneally. At the end of the reperfusion period, mid-line sternotomy was performed. Blood samples were taken with cardiac puncture. Bronchoalveolar lavage (BAL) of the left lung was performed with saline. Right lung was preserved for histopathological evaluation and biochemical examination. Lung tissue malondialdehyde (MDA) and 3-nitrotyrosine levels, myeloperoxidase and Na+/K+ ATP-ase activities, wet to dry weight ratios, and plasma and BAL fluid MDA levels were determined. Histopathological evaluation was performed, too. Hind limb IR caused significant increase in the lung tissue 3-NT to total tyrosine ratio (p = 0.014), wet to dry weight ratio (p = 0.000), MPO activity (p = 0.000), and MDA levels (p = 0.000). The animals treated with 3-AB showed a statistically significant decrease in these values (p < 0.05). Na+/K+ ATP-ase activity which was found to be decreased significantly with IR, returned to near normal levels with 3-AB treatment. Additionally, lung tissue injury in IR group characterized with moderate interstitial congestion and neutrophil infiltration, showed remarkable amelioration following 3-AB treatment. Our results strongly support the view that poly(ADP-ribose) polymerase (PARP) plays an important role in the inflammatory process in hind limb I/R-induced lung injury and as a PARP inhibitor, 3-AB seems to have a potential to treat this inflammatory injury.

Activity of taraxasteryl acetate on inflammation and heat shock protein synthesis

Pluchea sagittalis whole plant dichloromethane extract showed inhibitory activity in several inflammatory models: rat hind paw-edema, mice ear edema, and air-pouch rat granuloma. The extract inhibited the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in stimulated human neutrophils. It also showed inhibitory effect on heat shock protein 72 (hsp72) synthesis in stimulated neutrophils, while it had opposite effects on unstimulated cells. The triterpene taraxasteryl acetate was obtained from the dichloromethane extract by bioassay directed isolation, being active against induced ROS and RNS production in human neutrophils. In mice ear edema (induced by phorbol-12-mirystate-13-acetate, croton oil and arachidonic acid), taraxasteryl acetate showed a topical anti-inflammatory activity similar to the extract, but at 1/20 of the dose. The same ratio was observed for the inhibition of hsp72 production in stimulated human neutrophils. In unstimulated monocytes and neutrophils, taraxasteryl acetate showed a higher stimulating activity of hsp72 production than the extract, involving different mechanisms in each cell type. To our knowledge, taraxasteryl acetate is the first natural product for which a dual effect on the hsp response is reported.

6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase form a supramolecular complex in human neutrophils that undergoes retrograde trafficking during pregnancy

Neutrophils from pregnant women display reduced neutrophil-mediated effector functions, such as reactive oxygen metabolite (ROM) release. Because the NADPH oxidase and NO synthase produce ROMs and NO, the availability of their substrate NADPH is a potential regulatory factor. NADPH is produced by glucose-6-phosphate dehydrogenase (G-6-PDase) and 6-phosphogluconate dehydrogenase (6-PGDase), which are the first two steps of the hexose monophosphate shunt (HMS). Using immunofluorescence microscopy, we show that 6-PGDase, like G-6-PDase, undergoes retrograde transport to the microtubule-organizing centers in neutrophils from pregnant women. In contrast, 6-PGDase is found in an anterograde distribution in cells from nonpregnant women. However, lactate dehydrogenase distribution is unaffected by pregnancy. Cytochemical studies demonstrated that the distribution of 6-PGDase enzymatic activity is coincident with 6-PGDase Ag. The accumulation of 6-PGDase at the microtubule-organizing centers could be blocked by colchicine, suggesting that microtubules are important in this enzyme's intracellular distribution. In situ kinetic studies reveal that the rates of 6-gluconate turnover are indistinguishable in samples from nonpregnant and pregnant women, suggesting that the enzyme is functionally intact. Resonance energy transfer experiments showed that 6-PGDase and G-6-PDase are in close physical proximity within cells, suggesting the presence of supramolecular enzyme complexes. We suggest that the retrograde trafficking of HMS enzyme complexes during pregnancy influences the dynamics of NADPH production by separating HMS enzymes from glucose-6-phosphate generation at the plasma membrane and, in parallel, reducing ROM and NO production in comparison with fully activated neutrophils from nonpregnant women.

Impaired Production of Proinflammatory Cytokines and Host Resistance to Acute Infection withTrypanosoma cruziin Mice Lacking Functional Myeloid Differentiation Factor 88

Studies performed in vitro suggest that activation of Toll-like receptors (TLRs) by parasite-derived molecules may initiate inflammatory responses and host innate defense mechanisms against Trypanosoma cruzi. Here, we evaluated the impact of TLR2 and myeloid differentiation factor 88 (MyD88) deficiencies in host resistance to infection with T. cruzi. Our results show that macrophages derived from TLR2 (-/-) and MyD88(-/-) mice are less responsive to GPI-mucin derived from T. cruzi trypomastigotes and parasites. In contrast, the same cells from TLR2(-/-) still produce TNF-alpha, IL-12, and reactive nitrogen intermediates (RNI) upon exposure to live T. cruzi trypomastigotes. Consistently, we show that TLR2(-/-) mice mount a robust proinflammatory cytokine response as well as RNI production during the acute phase of infection with T. cruzi parasites. Further, deletion of the functional TLR2 gene had no major impact on parasitemia nor on mortality. In contrast, the MyD88(-/-) mice had a diminished cytokine response and RNI production upon acute infection with T. cruzi. More importantly, we show that MyD88(-/-) mice are more susceptible to infection with T. cruzi as indicated by the higher parasitemia and accelerated mortality, as compared with the wild-type mice. Together, our results indicate that T. cruzi parasites elicit an alternative inflammatory pathway independent of TLR2. This pathway is partially dependent on MyD88 and necessary for mounting optimal inflammatory and RNI responses that control T. cruzi replication during the early stages of infection.

[Mycobacterium tuberculosis virulence factors and its immune evasion mechanisms]

One-third of the world population is infected with Mycobacterium tuberculosis. When tuberculosis develops, the disease localization, severity, and outcome are highly variable between different individuals. The various manifestations of infection with M. tuberculosis reflect the balance between the bacilli and host defense mechanisms, in which the quality of host defense determines the outcome. Recent studies have identified several mycobacterial cell wall components that may be involved in the key steps of pathogenicity. M. tuberculosis is successful as a pathogen because of its ability to persist in an immunocompetent host. This bacterium lives within the macrophages. Hosts infected with M. tuberculosis mount a strong immune response. This response is usually sufficient to prevent progression to active disease. The strong immune response can control, but not eliminate the bacilli, indicating that M. tuberculosis has evolved mechanisms to modulate or avoid detection by the host immune response. Recent advances have improved our understanding of how M. tuberculosis evades two major antimicrobial mechanisms of macrophages; phagolysosome fusion and the production of toxic reactive nitrogen intermediates (RNI). In this review, the recent evidence of M. tuberculosis evasion from phagolysosome fusion and RNI toxicity, as well as prevention of the recognition of infected macrophages by CD4+ T lymphocytes by inhibiting MHC class II presentation, were discussed.

Xanthine oxidase inhibition reduces reactive nitrogen species production in COPD airways

Reactive nitrogen species (RNS) have been reported to be involved in the inflammatory process in chronic obstructive pulmonary disease (COPD). However, there are no studies on the modulation of RNS in COPD. It was hypothesised that inhibition of xanthine oxidase (XO) might decrease RNS production in COPD airways through the suppression of superoxide anion production. Ten COPD and six healthy subjects participated in the study. The XO inhibitor allopurinol (300 mg x day(-1) p.o. for 4 weeks) was administered to COPD patients. RNS production in the airway was assessed by 3-nitrotyrosine immunoreactivity and enzymic activity of XO in induced sputum as well as by exhaled nitric oxide (eNO) concentration. XO activity in the airway was significantly elevated in COPD compared with healthy subjects. Allopurinol administration to COPD subjects significantly decreased XO activity and nitrotyrosine formation. In contrast, eNO concentration was significantly increased by allopurinol administration. These results suggest that oral administration of the xanthine oxidase inhibitor allopurinol reduces airway reactive nitrogen species production in chronic obstructive pulmonary disease subjects. This intervention may be useful in the future management of chronic obstructive pulmonary disease.

Comparative profiles of intramacrophage behavior of Mycobacterium tuberculosis and Mycobacterium avium complex with different levels of virulence

Mycobacterium tuberculosis (MTB) and M. avium complex (MAC) strains with different levels of virulence in mice were examined for profiles of interaction with murine peritoneal macrophages (Mphis). Their growth rates in Mphis were in these orders: H37Ra strain (attenuated) > H37Rv strain (virulent) for MTB, and N-260 strain (moderate virulence) > MAC N-444 strain (low virulence) for MAC. MTB but not MAC caused the necrotic death of host Mphis in terms of increased release of lactate dehydrogenase from infected Mphis. The MTB H37Ra strain induced a greater production of reactive nitrogen intermediates (RNI) by Mphis than the MTB H37Rv strain did. However, this phenomenon was not observed with MAC, implying less important roles of RNI in the expression of Mphi antimicrobial activity against MAC organisms.

Oxidative stress in airways: is there a role for extracellular superoxide dismutase?

Airways are exposed to high levels of environmental oxidants, yet they also have enriched extracellular antioxidants. Airways disease such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease have evidence of increased oxidative stress, suggesting that reactive oxygen and nitrogen species may overwhelm antioxidant defenses in airway diseases. Extracellular superoxide dismutase is abundant in pulmonary tissues and protects the lung from increased oxidative stress; however, its role in asthma and other airway diseases has not been fully elucidated. Proteolytic processing of extracellular superoxide dismutase decreases its affinity for the extracellular matrix and may be a mechanism to regulate its distribution during conditions of inflammation or oxidative stress.

[3-nitrotyrosine--an indicator of changes in the formation of reactive oxygen and nitrogen species]

3-nitrotyrosine (3NTYR) produced by the reaction of nitrogen and oxygen species is used as a suitable marker of radical mediated tissue damage. Free or protein-bound tyrosin residues are in vivo nitrated most likely by peroxynitrite or myeloperoxidase. Processes involved in formation and degradation of 3NTYR are not completely clear. It seems that degradation depends on the way in which 3NTYR is formed, characteristics of the tissue or organ where 3NTYR was formed and even general condition of the organism. Nitration of tyrosine does not only modify the biochemical structure of the protein but usually affects its function. Nitrated proteins are probably specific for each organ and may influence the pathogenesis of the disease. The review also describes the methods of 3NTYR detection and summarizes published data on 3NTYR concentration in various human diseases.

Cutting edge: fever-associated temperatures enhance neutrophil responses to lipopolysaccharide: a potential mechanism involving cell metabolism

Although much progress has been made in elucidating the mechanisms underlying the physiological regulation of fever, there is little understanding of the biological utility of fever's thermal component. Considering the evolutionary co-conservation of fever and innate immunity, we hypothesize that fever's thermal component might in general augment innate immune function and, in particular, neutrophil activation. Accordingly, we have evaluated the effect of febrile temperatures on neutrophil function at the single-cell level. We find that reactive oxygen intermediates and NO release are greatly enhanced at febrile temperatures for unstimulated as well as LPS-stimulated adherent human neutrophils. Furthermore, our studies suggest that these changes in oxidant release are linked to upstream changes in NADPH dynamics. Inasmuch as reactive oxygen intermediates and NO production are important elements in innate immune responses to bacterial pathogens, we suggest that the febrile rise in core temperature is a broad-based systemic signaling mechanism to enhance innate immunity.

TNF regulates chemokine induction essential for cell recruitment, granuloma formation, and clearance of mycobacterial infection

Host immunity to mycobacterial infection is dependent on the activation of T lymphocytes and their recruitment with monocytes to form granulomas. These discrete foci of activated macrophages and lymphocytes provide a microenvironment for containing the infection. The cytokine, TNF, is essential for the formation and maintenance of granulomas, but the mechanisms by which TNF regulates these processes are unclear. We have compared the responses of TNF-deficient (TNF(-/-)) and wild-type C57BL/6 mice to infection with Mycobacterium smegmatis, a potent inducer of TNF, and virulent Mycobacterium tuberculosis to delineate the TNF-dependent and -independent components of the process. The initial clearance of M. smegmatis was TNF independent, but TNF was required for the early expression of mRNA encoding C-C and C-X-C chemokines and the initial recruitment of CD11b(+) macrophages and CD4(+) T cells to the liver during the second week of infection. Late chemokine expression and cell recruitment developed in TNF(-/-) mice associated with enhanced Th1-like T cell responses and mycobacterial clearance, but recruited leukocytes did not form tight granulomas. Infection of TNF(-/-) mice with M. tuberculosis also resulted in an initial delay in chemokine induction and cellular recruitment to the liver. Subsequently, increased mRNA expression was evident in TNF(-/-) mice, but the loosely associated lymphocytes and macrophages failed to form granulomas and prevent progressive infection. Therefore, TNF orchestrates early induction of chemokines and initial leukocyte recruitment, but has an additional role in the aggregation of leukocytes into functional granulomas capable of controlling virulent mycobacterial infection.

Nitric oxide metabolites in naturally occurring canine babesiosis

Babesiosis, caused by the virulent haemoprotozoan parasite Babesia canis rossi, is an important disease of dogs in South Africa. The nitric oxide metabolites, nitrate and nitrite (collectively termed reactive nitrogen intermediates or RNIs) were measured in admission sera from dogs in a babesiosis-endemic area. Five groups were prospectively studied: mild uncomplicated (n=9), severe uncomplicated (severe anaemia) (n=10) and complicated babesiosis (n=11); and two groups of healthy aparasitaemic dogs: endemic controls from the study area (n=10) and experimental dogs kept in tick-free conditions (n=10). Four measures of RNI production were studied: (i) serum RNI; (ii) serum RNI/creatinine ratio; (iii) fractional clearance of RNI (FC(RNI)); (iv) fractional excretion of RNI (FE(RNI)). Marked elevations of serum RNI occurred in only two dogs, both in the severe uncomplicated group. The highest concentration (log value 5.29 micromol/l) was in a dog that died, but concentrations in the other four dogs that died were unremarkable (0, 0.34, 1.66 and 2.64 micromol/l). Age, appetite and free serum haemoglobin were significant covariates for measures of RNI production. There were no significant differences among the babesiosis groups for serum RNI. Adjustment for creatinine had minor effects on the results. All babesiosis groups had significantly higher serum RNI and RNI/creatinine than the tick-free control group, but did not differ from the endemic controls except for the severe uncomplicated group, which had higher RNI/creatinine. The complicated group had significantly lower FC(RNI) and FE(RNI) than all other groups, except for the tick-free control group, which had similar FE(RNI). The results indicate that, in an endemic area, measures of RNI production are unlikely to be useful indicators of severity or outcome in canine babesiosis.

Increased susceptibility of C1q-deficient mice to Salmonella enterica serovar Typhimurium infection

The role of the complement system in host defense against Salmonella infection is poorly defined. Bacterial cell wall O-antigen polysaccharide can activate the alternative pathway in vitro. No studies, however, have elucidated the role of the classical pathway in immunity to Salmonella spp. in vivo. C1q-deficient mice (C1qa(-/-)) on a 129/Sv genetic background and strain-matched controls were infected intraperitoneally and intravenously with Salmonella enterica serovar Typhimurium and monitored over a 14-day period. After inoculation by either route, the C1qa(-/-) mice were found to be significantly more susceptible to Salmonella infection. Hepatic and splenic bacterial counts, performed at various time points, showed increased numbers of colonies in complement-deficient mice compared to controls. Analysis of blood clearance showed no difference between the two experimental groups during the first 15 min. However, after 20 min and until 6 h postinfection, numbers of circulating bacteria were significantly higher in complement-deficient mice. In vitro experiments using either resident or thioglycolate-elicited peritoneal macrophages showed a significant increase in the number of bacteria inside C1q-deficient macrophages compared to controls irrespective of the serum used for opsonizing the bacteria. These findings could not be explained either by an increased bacterial uptake, analyzed in vitro and in vivo using green fluorescent protein-tagged salmonellae, or by a defect in the respiratory burst or in NO production. The data presented here suggest the possibility of novel pathways by which C1q may modulate the pathogenesis of infectious diseases caused by intracellular pathogens.

Mitochondrial tyrosine nitration precedes chronic allograft nephropathy

Endogenous tyrosine nitration and inactivation of manganese superoxide dismutase (MnSOD) has previously been reported to occur during end-stage human renal allograft rejection. In order to determine whether nitration and inactivation of this critical mitochondrial protein might play a contributory role in the onset of transplant rejection, we employed a rodent model of Chronic Allograft Nephropathy (or CAN). Using this model we followed kidney function from 2-52 weeks post-transplant and correlated graft function with levels of nitration in the renal allograft. Tyrosine nitration of both glomerular and tubular structures occurred at 2 weeks post-transplant. At later times (16 weeks) post-transplant, tyrosine nitration appeared to be confined to tubular structures; however glomerular nitration returned at 52 weeks post-transplant. Interestingly, nitration and inactivation of MnSOD occurs prior to the onset of renal dysfunction in this rat model of chronic allograft nephropathy (2 weeks versus 16 weeks post-transplant). Furthermore, we have identified an additional mitochondrial protein, cytochrome c, as being endogenously nitrated during chronic rejection. The kinetics of cytochrome c nitration lagged behind MnSOD nitration and inactivation (4 weeks compared to 2 weeks); suggesting that loss of MnSOD activity likely contributes to elevation of the nitrating species and further nitration of other targets.

Functional transitions in macrophages during in vivo infection with Mycobacterium bovis bacillus Calmette-Guérin

Macrophage activation during the immune response to intracellular bacteria is critical for resolution of the infection. We have investigated the pathway of macrophage activation during murine Mycobacterium bovis bacillus Calmette-Guérin (BCG) infection. Three distinct phenotypes of macrophages were identified and compared: resident peritoneal macrophages, day 2 postinfection macrophages, and 12-day postinfection macrophages. Compared with resident peritoneal macrophages, day 2 BCG macrophages expressed intermediate levels of the cell surface receptors Mac1 and F4/80 and low levels of MHC class II molecules. These cells were highly phagocytic and produced large amounts of mRNA encoding the chemokine IP-10. In addition, day 2 BCG macrophages did not generate reactive nitrogen intermediates, though they were primed to do so, and did not have increased levels of TNF-alpha mRNA. Blockade of monocyte influx into the peritoneal cavity using Abs to platelet endothelial cell adhesion molecule 1 had no effect on the appearance of day 2 BCG macrophages, suggesting this cell can differentiate from resident peritoneal macrophages. In contrast to day 2 BCG macrophages, day 12 BCG macrophages were poorly phagocytic, but produced high levels of reactive nitrogen intermediates, IP-10 and TNF-alpha mRNA, and class II MHC molecules. We propose that day 2 BCG macrophages are specialized for phagocytic uptake of pathogens from the extracellular space, whereas day 12 BCG macrophages are specialized for killing of the internalized pathogens. This functional transition during activation is reminiscent of that seen during maturation/activation of the related dendritic cell lineage induced by bacterial or inflammatory stimuli.