Nitric oxide production and nitric oxide synthase type 2 expression by human mononuclear phagocytes: a review

Protection of Mycobacterium tuberculosis from reactive oxygen species conferred by the mel2 locus impacts persistence and dissemination

Persistence of Mycobacterium tuberculosis in humans represents a major roadblock to elimination of tuberculosis. We describe identification of a locus in M. tuberculosis, mel2, that displays similarity to bacterial bioluminescent loci and plays an important role during persistence in mice. We constructed a deletion of the mel2 locus and found that the mutant displays increased susceptibility to reactive oxygen species (ROS). Upon infection of mice by aerosol the mutant grows normally until the persistent stage, where it does not persist as well as wild type. Histopathological analyses show that infection with the mel2 mutant results in reduced pathology and both CFU and histopathology indicate that dissemination of the mel2 mutant to the spleen is delayed. These data along with growth in activated macrophages and infection of Phox(-/-) and iNOS(-/-) mice and bone marrow-derived macrophages suggest that the primary mechanism by which mel2 affects pathogenesis is through its ability to confer resistance to ROS. These studies provide the first insight into the mechanism of action for this novel class of genes that are related to bioluminescence genes. The role of mel2 in resistance to ROS is important for persistence and dissemination of M. tuberculosis and suggests that homologues in other bacterial species are likely to play a role in pathogenesis.

Use of diaminofluoresceins to detect and measure nitric oxide in low level generating human immune cells

Nitric oxide ((*)NO) has been implicated in multiple physiological and pathological immune processes. Different methods have been developed to detect and quantify (*)NO, where one of the principal difficulties are the accurately detection in cellular system with low levels of (*)NO production. The choice of the (*)NO detection method to be used depends on the characteristics of the experimental system and the levels of (*)NO production which depend on either the organism source of samples or the experimental conditions. Recently, high sensitive methods to detect and image (*)NO have been reported using 4,5-diaminofluorescein-based fluorescent probes (DAF) and its derivate 4,5-diaminofluorescein diacetate (DAF-2 DA). This work was aimed to adapt and optimize the use of DAF probes to detect and quantify the (*)NO production in systems of high, moderate and low out-put production, especially in human PBMC and their subpopulations. Here, we report an original experimental design which is useful to detect and estimate (*)NO fluxes in human PBMC and their subpopulations with high specificity and sensitivity.

Selective CB2 up-regulation in women affected by endometrial inflammation

Endometritis is defined as an inflammation of the endometrial mucosa of the uterus. In endometritis large amounts of toxic mediators, including nitric oxide (NO) are released by inflammatory cells. As a consequence of nitric oxide-dependent injury, the cells respond by triggering protective mechanisms, by changing the endocannabinoid system (ECS) which comprises both CB(1) and CB(2) cannabinoid receptors and their endogenous ligands. The aim of our study was to seek out evidence for the presence of cannabinoid receptors in inflammatory endometrial tissue as well as for their potential role in endometrial inflammation. Our results showed a selective up-regulation of both transcription and expression of CB(2) receptors in biopsies from women affected by endometrial inflammation compared to healthy women. The experiments with the nitric oxide-donor S-Nitroso-L-Glutathione (GSNO) suggest that such a selective up-regulation may be related to the nitric oxide release occurring during endometrial inflammation. In addition, we demonstrated an increase in chymase expression, a marker of mast cells, in biopsies of women affected by endometritis. Therefore our results support the hypothesis that the up-regulation of CB(2) occurs mainly on mast cells and that it might tend to sensitize these cells to the anti-inflammatory effect exerted by endogenous cannabinoids by binding their receptor and thus preventing the mast cell degranulation and the release of pro-inflammatory mediators. In conclusion, we believe that the selective CB(2) up-regulation might play a role as a novel prognostic factor in endometrial inflammation.

Analysis of nitric oxide-dependent antimicrobial actions in macrophages and mice

Nitric oxide (NO*) is a critical component of mammalian host defense that is produced in macrophages and other cells comprising the innate immune system. Isolated mammalian macrophages have been utilized to measure the kinetics of NO production and to demonstrate NO-related antimicrobial actions. Some microorganisms possess enzymes to detoxify nitrogen oxides, and mutant strains lacking these enzymes can be used to demonstrate the importance of these mechanisms for intracellular bacterial survival. This chapter describes techniques with which to analyze the antimicrobial actions of nitric oxide in murine and human macrophages and in laboratory mice.

Lung Defenses

We breathe to live, but the air we breathe carries many potentially harmful agents. To protect us against these constant challenges, our lungs have defenses that are remarkably effective, biologically complex, and scientifically fascinating. It is not hyperbole to say that the pathogenesis of most lung disease begins with a breach of these defenses. This chapter surveys these normal lung defense systems. Just as this text assumes familiarity with general pathology, we also assume knowledge of basic immunology. This chapter emphasizes the lung’s variations on themes of innate and adaptive immunity, and discusses the special role of granulomatous inflammation in lung defenses.

Inflammation and lung cancer: roles of reactive oxygen/nitrogen species

The lung is a highly specialized organ that facilitates uptake of oxygen and release of carbon dioxide. Due to its unique structure providing enormous surface area to outside ambient air, it is vulnerable to numerous pathogens, pollutants, oxidants, gases, and toxicants that are inhaled continuously from air, which makes the lung susceptible to varying degrees of oxidative injury. To combat these unrelenting physical, chemical, and biological insults, the respiratory epithelium is covered with a thin layer of lining fluid containing several antioxidants and surfactants. Inhaled toxic agents stimulate the generation of reactive oxygen/nitrogen species (ROS/RNS), which in turn provoke inflammatory responses resulting in the release of proinflammatory cytokines and chemokines. These subsequently stimulate the influx of polymorphonuclear leukocytes (PMNs) and monocytes into the lung so as to combat the invading pathogens or toxic agents. In addition to the beneficial effects, persistent inhalation of the invading pathogens or toxic agents may result in overwhelming production of ROS/RNS, producing chronic inflammation and lung injury. During inflammation, enhanced ROS/RNS production may induce recurring DNA damage, inhibition of apoptosis, and activation of proto-oncogenes by initiating signal transduction pathways. Therefore, it is conceivable that chronic inflammation-induced production of ROS/RNS in the lung may predispose individuals to lung cancer. This review describes the complex relationship between lung inflammation and carcinogenesis, and highlights the role of ROS/RNS in cancer development.

Determinants of exhaled nitric oxide levels in healthy, nonsmoking African American adults

BACKGROUND

Asthma is a significant cause of morbidity and mortality for African Americans. Fraction of exhaled nitric oxide (FeNO) levels are increased in patients with asthma, and airway levels of nitric oxide metabolites regulate airway inflammation and airway diameter. More needs to be known about the factors that regulate FeNO. There is a need for FeNO reference values for African Americans.

OBJECTIVE

We sought to establish reference values and identify factors associated with FeNO levels in healthy African American adults.

METHODS

FeNO levels were measured in 895 healthy, nonsmoking African Americans between the ages of 18 and 40 years. FeNO measurements were repeated in 84 subjects. Factors potentially associated with FeNO were measured, including blood pressure, height, weight, and serum total IgE, eosinophil cationic protein, C-reactive protein, and nitrate levels. Data on respiratory symptoms, including upper respiratory tract infection (URI) symptoms, were collected. Univariate and multivariate analyses of the relationship between these variables and FeNO levels were performed.

RESULTS

In healthy, nonsmoking African Americans FeNO levels were stable during repeated measurements (intraclass correlation coefficient, 0.81). Sex (P < .0001), serum total IgE levels (P < .0001), and current URI symptoms (P = .0002) contributed significantly to FeNO variability but together accounted for less than 50% of the variation in FeNO levels.

CONCLUSION

The high correlation between repeated measurements of FeNO and the low correlation coefficients of known factors associated with FeNO suggest that other factors might contribute substantially to variability of FeNO levels in African Americans.

Identification of conserved domains in the promoter regions of nitric oxide synthase 2: implications for the species-specific transcription and evolutionary differences

BACKGROUND

The majority of the genes involved in the inflammatory response are highly conserved in mammals. These genes are not significantly expressed under normal conditions and are mainly regulated at the transcription and prost-transcriptional level. Transcription from the promoters of these genes is very dependent on NF-kappaB activation, which integrates the response to diverse extracellular stresses. However, in spite of the high conservation of the pattern of promoter regulation in kappaB-regulated genes, there is inter-species diversity in some genes. One example is nitric oxide synthase 2 (NOS-2), which exhibits a species-specific pattern of expression in response to infection or pro-inflammatory challenge.

RESULTS

We have conducted a comparative genomic analysis of NOS-2 with different bioinformatic approaches. This analysis shows that in the NOS-2 gene promoter the position and the evolutionary divergence of some conserved regions are different in rodents and non-rodent mammals, and in particular in primates. Two not previously described distal regions in rodents that are similar to the unique upstream region responsible of the NF-kappaB activation of NOS-2 in humans are fragmented and translocated to different locations in the rodent promoters. The rodent sequences moreover lack the functional kappaB sites and IFN-gamma response sites present in the homologous human, rhesus monkey and chimpanzee regions. The absence of kappaB binding in these regions was confirmed by electrophoretic mobility shift assays.

CONCLUSION

The data presented reveal divergence between rodents and other mammals in the location and functionality of conserved regions of the NOS-2 promoter containing NF-kappaB and IFN-gamma response elements.

Mycobacterium tuberculosis DosS is a redox sensor and DosT is a hypoxia sensor

A fundamental challenge to the study of oxidative stress responses of Mycobacterium tuberculosis (Mtb) is to understand how the protective host molecules are sensed and relayed to control bacilli gene expression. The genetic response of Mtb to hypoxia and NO is controlled by the sensor kinases DosS and DosT and the response regulator DosR through activation of the dormancy/NO (Dos) regulon. However, the regulatory ligands of DosS and DosT and the mechanism of signal sensing were unknown. Here, we show that both DosS and DosT bind heme as a prosthetic group and that DosS is rapidly autooxidized to attain the met (Fe3+) form, whereas DosT exists in the O2-bound (oxy) form. EPR and UV-visible spectroscopy analysis showed that O2, NO, and CO are ligands of DosS and DosT. Importantly, we demonstrate that the oxidation or ligation state of the heme iron modulates DosS and DosT autokinase activity and that ferrous DosS, and deoxy DosT, show significantly increased autokinase activity compared with met DosS and oxy DosT. Our data provide direct proof that DosS functions as a redox sensor, whereas DosT functions as a hypoxia sensor, and that O2, NO, and CO are modulatory ligands of DosS and DosT. Finally, we identified a third potential dormancy signal, CO, that induces the Mtb Dos regulon. We conclude that Mtb has evolved finely tuned redox and hypoxia-mediated sensing strategies for detecting O2, NO, and CO. Data presented here establish a paradigm for understanding the mechanism of bacilli persistence.

Cisplatin-treated murine peritoneal macrophages induce apoptosis in L929 cells: role of Fas-Fas ligand and tumor necrosis factor-tumor necrosis factor receptor 1

Cisplatin [cis-diamminedichloroplatinum (II)]-treated murine peritoneal macrophages interact with L929 cells in vitro in a sequential manner, resulting in the formation of contact between the two cells. This interaction leads to the death of L929 cells by the process of apoptosis. The detailed investigations have suggested the involvement of two different pathways in macrophage-mediated L929 cell apoptosis. It is observed that the induction of apoptosis in L929 cells by cisplatin-treated macrophages is contact dependent and is mediated through Fas-Fas ligand and tumor necrosis factor-tumor necrosis factor receptor 1 pathways. This conclusion was based on the Western blot and immunoprecipitation analysis of Fas-Fas ligand, tumor necrosis factor-tumor necrosis factor receptor 1, Fas-associated death domain and tumor necrosis factor receptor-associated death domain. The Fas-Fas ligand interaction between macrophages and L929 cells increased the expression of Fas-associated death domain, and tumor necrosis factor-tumor necrosis factor receptor 1 interaction between macrophages and L929 cells increased the expression of tumor necrosis factor receptor-associated death domain in L929 cells. The induction of apoptosis in L929 cells was investigated by DNA fragmentation, Annexin V staining and Western blot analysis of Bax, Bcl-2, Bid, cytochrome c, poly(ADP ribose) polymerase, CAD, caspase-8 and caspase-3.

Nitric oxide and peroxynitrite in health and disease

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

Therapeutic and preventive properties of quercetin in experimental arthritis correlate with decreased macrophage inflammatory mediators

Pentahydroxyflavone dihydrate, quercetin (QU) is one of common flavonols biosynthesized by plants and has been suggested to modulate inflammatory responses in various models. In the present study, we investigated in vivo effects of oral or intra-cutaneous QU in chronic rat adjuvant-induced arthritis (AA). Growth delay and arthritic scores were evaluated daily after AA induction in Lewis rats. Oral administration of QU (5 x 160 mg/kg) to arthritic rats resulted in a clear decrease of clinical signs compared to untreated controls. Intra-cutaneous injections of lower doses (5 x 60 mg/kg) of QU gave similar anti-arthritic effects, while 5 x 30 mg/kg concentrations were inefficient in this respect. Finally, injection of relatively low QU doses (5 x 30 mg/kg) prior to AA induction significantly reduced arthritis signs. As QU was suggested to inhibit macrophage-derived cytokines and nitric oxide (NO), we then analyzed macrophage response ex vivo. Anti-arthritic effects of QU correlated with significant decrease of inflammatory mediators produced by peritoneal macrophages, ex vivo and in vitro. These data indicate that QU is a potential anti-inflammatory therapeutic and preventive agent targeting the inflammatory response of macrophages.

Female infertility and free radicals: potential role in adhesions and endometriosis

Free radicals are highly reactive molecules produced in the cell either as part of, or as end-products of, biochemical reactions that have crucial roles in the homeostasis of the organism. Thus, excess production or impaired elimination of free radicals leads to increased oxidative stress, which has been implicated in the development of several different disease states, including hypoxia-reperfusion injury, cancer, and aging. Peritoneal adhesions and endometriosis are relatively commonly identified in women, and are known to be associated with infertility without clearly understood pathophysiology. The prevention and treatment strategies of these conditions, both of which have tremendous propensity to recur, have not been completely established. The development of both disorders has been shown to be closely related to the presence of increased oxidative stress in the tissues. In this article, we review this relationship with reference to the mechanistic steps involved and their regulation. As our knowledge of both conditions expands, we believe there will be opportunities for specific steps to intervention in free radical metabolism to reduce and/or prevent further development of endometriosis and adhesions.

Characterization of NO and cytokine production in immune-activated microglia and peritoneal macrophages derived from a mouse model expressing the human NOS2 gene on a mouse NOS2 knockout background

Significant differences exist in the production and release of nitric oxide (NO) from human macrophages versus macrophages of mouse origin. Human macrophages have been shown to respond poorly to stimuli that provoke strong inflammatory reactions from mouse macrophages. To address the differences in macrophage function in an animal model, a transgenic mouse was created that contained the entire human NOS2 gene, including the human promoter and all of its exons and introns. The huNOS2 transgenic mouse was then mated to mice lacking a functional NOS2 gene (muNOS2(/) or NOS2 knockout mice) to generate a double transgenic mouse (huNOS2(+/0)/muNOS2(/)) that expresses a functional human NOS2 gene in place of the mouse NOS2 gene. These double transgenic mice were found to express only human NOS2 mRNA and human iNOS proteins in response to immune stimulation. The production and release of nitric oxide from isolated macrophages from the doubly transgenic mouse also more closely paralleled human responses rather than mouse. Peritoneal macrophages from double transgenic mice generated nanomolar levels of nitrite in response to inflammatory stimuli, while peritoneal macrophages from wild-type mice generated micromolar levels of nitrite in response to the same inflammatory stimuli. Similarly, microglia from the huNOS2(+/0)/muNOS2(/) mice accumulated nanomolar levels of nitrite following inflammatory stimulation. Reduced nitrite release persisted in spite of normal responsiveness to inflammatory stimulation as measured by tumor necrosis factor alpha and interleukin-6 production and release. These data suggest that the human-specific release of nanomolar levels of nitrite may largely result from differences between the human and mouse NOS2 genes, which may program different degrees of nitric oxide responses to inflammatory signals in humans than in mice.

The continuing challenges of leprosy

Leprosy is best understood as two conjoined diseases. The first is a chronic mycobacterial infection that elicits an extraordinary range of cellular immune responses in humans. The second is a peripheral neuropathy that is initiated by the infection and the accompanying immunological events. The infection is curable but not preventable, and leprosy remains a major global health problem, especially in the developing world, publicity to the contrary notwithstanding. Mycobacterium leprae remains noncultivable, and for over a century leprosy has presented major challenges in the fields of microbiology, pathology, immunology, and genetics; it continues to do so today. This review focuses on recent advances in our understanding of M. leprae and the host response to it, especially concerning molecular identification of M. leprae, knowledge of its genome, transcriptome, and proteome, its mechanisms of microbial resistance, and recognition of strains by variable-number tandem repeat analysis. Advances in experimental models include studies in gene knockout mice and the development of molecular techniques to explore the armadillo model. In clinical studies, notable progress has been made concerning the immunology and immunopathology of leprosy, the genetics of human resistance, mechanisms of nerve injury, and chemotherapy. In nearly all of these areas, however, leprosy remains poorly understood compared to other major bacterial diseases.

Nitric oxide: an antiparasitic molecule of invertebrates

Since Furchgott, Ignarro and Murad won the Nobel prize in 1998 for their work on the role of nitric oxide (NO) as a signaling molecule, many reports have shown the seemingly limitless range of body functions controlled by this compound. In vertebrates, the role of NO as a defense against infection caused by viruses, bacteria, and protozoan and metazoan parasites has been known for several years. New evidence, however, shows that NO is also important in defending invertebrates against parasites. This discovery is a breakthrough in the understanding of how the invertebrate immune system works, and it has implications for the emerging field of invertebrate ecological immunology.

Production and characterization of guinea pig recombinant gamma interferon and its effect on macrophage activation

Gamma interferon (IFN-gamma) plays a critical role in the protective immune responses against mycobacteria. We previously cloned a cDNA coding for guinea pig IFN-gamma (gpIFN-gamma) and reported that BCG vaccination induced a significant increase in the IFN-gamma mRNA expression in guinea pig cells in response to living mycobacteria and that the virulent H37Rv strain of Mycobacterium tuberculosis stimulated less IFN-gamma mRNA than did the attenuated H37Ra strain. In this study, we successfully expressed and characterized recombinant gpIFN-gamma with a histidine tag at the N terminus (His-tagged rgpIFN-gamma) in Escherichia coli. rgpIFN-gamma was identified as an 18-kDa band in the insoluble fraction; therefore, the protein was purified under denaturing conditions and renatured. N-terminal amino acid sequencing of the recombinant protein yielded the sequence corresponding to the N terminus of His-tagged gpIFN-gamma. The recombinant protein upregulated major histocompatibility complex class II expression in peritoneal macrophages. The antiviral activity of rgpIFN-gamma was demonstrated with a guinea pig fibroblast cell line (104C1) infected with encephalomyocarditis virus. Interestingly, peritoneal macrophages treated with rgpIFN-gamma did not produce any nitric oxide but did produce hydrogen peroxide and suppressed the intracellular growth of mycobacteria. Furthermore, rgpIFN-gamma induced morphological alterations in cultured macrophages. Thus, biologically active rgpIFN-gamma has been successfully produced and characterized in our laboratory. The study of rgpIFN-gamma will further increase our understanding of the cellular and molecular responses induced by BCG vaccination in the guinea pig model of pulmonary tuberculosis.

Regulating immunity to malaria

The optimal outcome of a malaria infection is that parasitized cells are killed and degraded without inducing significant pathology. Since much of the pathology of malaria infection can be immune-mediated, this implies that immune responses have to be carefully regulated. The mechanisms by which anti-malarial immune responses are believed to be regulated were discussed at the recent Malaria Immunology Workshop (Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA; February 2005). Potential regulatory mechanisms include regulatory T cells, which have been shown to significantly modify cellular immune responses to various protozoan infections, including leishmania and malaria; neutralising antibodies to pro-inflammatory malarial toxins such as glycosylphosphatidylinositol and haemozoin; and self-regulating networks of effector molecules. Innate and adaptive immune responses are further moderated by the broader immunological environment, which is influenced by both the genetic background of the host and by co-infection with other pathogens. A detailed understanding of the interplay between these different immunoregulatory processes may facilitate the rationale design of vaccines and novel therapeutics.

Rheumatoid arthritis: a disease associated with accelerated atherogenesis

OBJECTIVES

Rheumatoid arthritis (RA) is a systemic inflammatory disease associated with an increased prevalence of coronary heart disease and a high cardiovascular (CV) mortality. In this article, a review of mechanisms implicated in the development of accelerated atherogenesis in RA was performed. The potential role of treatment to reduce the incidence of CV events in RA was also discussed.

METHODS

Retrospective review of the literature. The potential mechanisms implicated in the development of accelerated atherogenesis in RA, information on carotid ultrasonography, and the potential implication of treatment to prevent accelerated atherogenesis in individuals with RA were examined.

RESULTS

Endothelial dysfunction, which is an early step in the development of atherosclerosis, has been observed in patients with RA. Deleterious effects resulting from persistent chronic inflammation may lead to endothelial dysfunction, insulin resistance, and a dyslipidemic pattern in these patients. Other mechanisms different from those related to classic atherogenesis risk factors, such as hyperhomocysteinemia and increased oxidative stress, are considered to be implicated in the pathogenesis of atherosclerosis in RA. Increased carotid intima-media thickness and carotid plaques have been found in RA patients compared with matched controls. Active MTX treatment of the disease has been associated with decreased CV mortality. Additional drugs such as statins may be considered in the management of these patients.

CONCLUSIONS

The increased prevalence of CV mortality rate in RA cannot only be explained by the presence of traditional atherosclerotic risk factors. A chronic inflammatory response may promote the development of accelerated atherogenesis in these patients. Active treatment of the disease is required to reduce the risk of developing CV complications in individuals with RA.

Nitric Oxide in Salmonella and Escherichia coli Infections

This review discusses the role that nitric oxide (NO) and its congeners play on various stages in the pathophysiology of Escherichia coli and Salmonella infections, with special emphasis on the regulatory pathways that lead to high NO synthesis, the role of reactive nitrogen species (RNS) in host resistance, and the bacterial molecular targets and defense mechanisms that protect enteric bacteria against the nitrosative stress encountered in diverse host anatomical sites. In general, NO can react directly with prosthetic groups containing transition metal centers, with other radicals, or with sulfhydryl groups in the presence of an electron acceptor. Binding to iron complexes is probably the best characterized direct reaction of NO in biological systems. The targets of RNS are numerous. RNS can facilitate oxidative modifications including lipid peroxidation, hydroxylation, and DNA base and protein oxidation. In addition, RNS can inflict nitrosative stress through the nitrosation of amines and sulfhydryls. Numerous vital bacterial molecules can be targeted by NO. It is therefore not surprising that enteropathogenic bacteria are armed with a number of sensors to coordinate the protective response to nitrosative stress, along with an assortment of antinitrosative defenses that detoxify, repair, or avoid the deleterious effects of RNS encountered within the host. NO and NO-derived RNS play important roles in innate immunity to Salmonella and E. coli. Enzymatic NO production by NO synthases can be enhanced by microbial and other inflammatory stimuli and it exerts direct antimicrobial actions as well as immunomodulatory and vasoregulatory effects.

Alterations in nitric oxide and cytokine production with airway inflammation in the absence of IL-10

IL-10 is an anti-inflammatory cytokine that suppresses NO synthase (NOS) and production of NO; its lack may promote NO production and alterations in cytokines modulated by NO with allergic airway inflammation (AI), such as IL-18 and IL-4. Therefore, we induced AI in IL-10 knockout ((-/-)) and IL-10-sufficient C57BL/6 (C57) mice with inhaled OVA and measured airway NO production, as exhaled NO (E(NO)) and bronchoalveolar lavage fluid nitrite levels. E(NO) and nitrite levels were elevated significantly in naive IL-10(-/-) mice as compared with C57 mice. With AI, E(NO) and nitrite levels increased in C57 mice and decreased in IL-10(-/-) mice. IL-18 production fell with both AI and addition of S-nitroso-N-acetyl-d,l-penicillamine (a NO donor) but was not significantly increased by chemical NOS inhibition by l-N(5)-(1-iminoethyl)-ornithine. IL-4 AI was increased significantly (up to 10-fold greater) in the absence of IL-10 but was reduced significantly with chemical inhibition of NOS. Airway responsiveness was lower in IL-10(-/-) mice and was associated with alteration in production of NO and IL-4. Thus, IL-4 production was increased, and likely decreased NO production, in a way not predicted by the absence of IL-10. Inhibition of IL-4 production, with inhibition of NOS in the absence of IL-10, demonstrated the importance of a NO and IL-4 feedback mechanism regulating this interaction.

Interferon gamma promotes survival of lymphoblasts overexpressing 9-O-acetylated sialoglycoconjugates in childhood acute lymphoblastic leukaemia (ALL)

An enhanced linkage-specific 9-O-acetylated sialic acid (9-O-AcSA) on peripheral blood mononuclear cells (PBMC) of children with acute lymphoblastic leukaemia, ALL (PBMC(ALL), 9-O-AcSA+ cells) was demonstrated by using a lectin, Achatinin-H, whose lectinogenic epitope was 9-O-AcSAalpha2-6GalNAc. Our aim was to evaluate the in vitro contributory role of this glycotope (9-O-AcSAalpha2-6GalNAc) towards the survival of these 9-O-AcSA+ cells in ALL patients. For direct comparison, 9-O-AcSA- cells were generated by removing O-acetyl group of 9-O-AcSA present on PBMC(ALL) using O-acetyl esterase. An elevated level of serum interferon gamma (IFN-gamma) in affected children led us to think that PBMC(ALL) are continuously exposed specifically to this cytokine. Accordingly, 9-O-AcSA+ and 9-O-AcSA- cells were exposed in vitro to IFN-gamma. A twofold increased NO release along with inducible NO synthase (iNOS) mRNA expression by the 9-O-AcSA+ cells was observed as compared to the 9-O-AcSA- cells. The decreased viability of IFN-gamma exposed 9-O-AcSA- cells as compared to 9-O-AcSA+ cells were reflected from a 5.0-fold increased caspase-3-like activity and a 10.0-fold increased apoptosis in the 9-O-AcSA- cells when production of NO was lowered by adding competitive inhibitor of iNOS in reaction mixture. Therefore, it may be envisaged that a link exists between induction of this glycotope and their role in regulating viability of PBMC(ALL). Taken together, it is reasonable to hypothesise that O-acetylation of sialic acids on PBMC(ALL) may be an additional mechanism that promotes the survival of lymphoblasts by avoiding apoptosis via IFN-gamma-induced NO production.

TNF-alpha, TGF-beta and NO relationship in sera from tuberculosis (TB) patients of different severity

Tuberculosis (TB) is the main cause of death by infection diseases worldwide. Considering that NO, TNF-alpha and TGF-beta participate a great deal in TB immunopathogenesis, we wished to analyse whether these mediators showed some relationship with the degree of pulmonary affectation. The sample comprised 29 TB (HIV-), inpatients with mild-moderate (n = 10) or advanced (n = 19) newly-diagnosed disease, together with 12 healthy controls HCo. Serum nitrite was assessed by reducing nitrate to nitrite, and further measured by the Griess reaction. Levels of TNF-alpha and TGF-beta were determined by ELISA (R&D Systems). Serum levels of TNF-alpha were significantly higher in the advanced TB cases if compared with HCo, (p < 0.05 ) and from values of Mild-Moderate TB patients (p < 0.05). Serum levels of TGF-beta from advanced TB patients have increased values if compared with Hco (p < 0.005) and Mild-Moderate patients (p < 0.05). These values were also significantly different from Mild-Moderate cases + HCo (p = 0.01) Advanced TB patients had significantly reduced nitrite levels compared with those of Mild-Moderate patients and HCo (p < 0.002). Taken as a whole NO-derived metabolites in TB patients (M-M and Advanced cases) remained lower than values in HCo (p = 0.005) A negative correlation was found when comparing the two cytokines with nitrites(r = -0.44 ).TGF-beta and TNF-alpha were positively correlated (r = 0.44, p < 0.01), 0.44, p < 0.01. In synthesis, the inverse correlation found between both cytokines concentrations and NO levels in TB patients may be viewed as a consequence of a more predominant TGF-beta effect.

Analysis of differentially expressed genes in nitric oxide-exposed human monocytic cells

In this study we examined the gene expression pattern of *NO-dependent genes in U937 and Mono Mac 6 monocytes exposed to the synthetic NO-donor DPTA-NO using microarray technology. cDNA microarray data were validated by Northern blot analysis and quantitative real-time PCR. This approach allowed the identification of 17 *NO-sensitive genes that showed at least a twofold difference in expression, in both U937 cells and Mono Mac 6 cells exposed to 500 microM DPTA-NO for 4 h. NO-stimulated genes belong to various functional groups, including transcription factors, signaling molecules, and cytokines. Among the selected genes, 11 (ATF-4, c-maf, SGK-1, PBEF, ATPase 8, NADH dehydrogenase 4, STK6, TRAF4-associated factor 1, molybdopterin synthase, CKS1, and CIDE-B) have not been previously reported to be sensitive to *NO. Because several *NO-stimulated genes are transcription factors, we analyzed the mRNA expression profile in U937 cells exposed to DPTA-NO for 14 h. We found that long-term *NO treatment influenced transcription rates of a rather limited set of genes, including CIDE-B, BNIP3, p21/Cip1, molybdopterin synthase, and TRAF4-associated factor 1. To accelerate formation of nitrosating species, U937 cells were exposed to DPTA-NO along with suboptimal concentrations of 2-phenyl-4,4,5,5-tetramethylimidazole-1-oxyl 3-oxide (PTIO). PTIO-mediated increase in nitrosating species remarkably enhanced *NO-dependent induction of IL-8, p21/Cip1, and MKP-1 and built a specific gene expression profile.

Myeloperoxidase: friend and foe

Neutrophilic polymorphonuclear leukocytes (neutrophils) are highly specialized for their primary function, the phagocytosis and destruction of microorganisms. When coated with opsonins (generally complement and/or antibody), microorganisms bind to specific receptors on the surface of the phagocyte and invagination of the cell membrane occurs with the incorporation of the microorganism into an intracellular phagosome. There follows a burst of oxygen consumption, and much, if not all, of the extra oxygen consumed is converted to highly reactive oxygen species. In addition, the cytoplasmic granules discharge their contents into the phagosome, and death of the ingested microorganism soon follows. Among the antimicrobial systems formed in the phagosome is one consisting of myeloperoxidase (MPO), released into the phagosome during the degranulation process, hydrogen peroxide (H2O2), formed by the respiratory burst and a halide, particularly chloride. The initial product of the MPO-H2O2-chloride system is hypochlorous acid, and subsequent formation of chlorine, chloramines, hydroxyl radicals, singlet oxygen, and ozone has been proposed. These same toxic agents can be released to the outside of the cell, where they may attack normal tissue and thus contribute to the pathogenesis of disease. This review will consider the potential sources of H2O2 for the MPO-H2O2-halide system; the toxic products of the MPO system; the evidence for MPO involvement in the microbicidal activity of neutrophils; the involvement of MPO-independent antimicrobial systems; and the role of the MPO system in tissue injury. It is concluded that the MPO system plays an important role in the microbicidal activity of phagocytes.

Antimicrobial reactive oxygen and nitrogen species: concepts and controversies

Phagocyte-derived reactive oxygen and nitrogen species are of crucial importance for host resistance to microbial pathogens. Decades of research have provided a detailed understanding of the regulation, generation and actions of these molecular mediators, as well as their roles in resisting infection. However, differences of opinion remain with regard to their host specificity, cell biology, sources and interactions with one another or with myeloperoxidase and granule proteases. More than a century after Metchnikoff first described phagocytosis, and more than four decades after the discovery of the burst of oxygen consumption that is associated with microbial killing, the seemingly elementary question of how phagocytes inhibit, kill and degrade microorganisms remains controversial. This review updates the reader on these concepts and the topical questions in the field.

Elevated nitric oxide production in children with malarial anemia: hemozoin-induced nitric oxide synthase type 2 transcripts and nitric oxide in blood mononuclear cells

Experiments outlined here investigate the role of nitric oxide (NO) in the pathogenesis of Plasmodium falciparum-induced malarial anemia (MA). The results show that ex vivo and in vitro NO synthase (NOS) activity in peripheral blood mononuclear cells (PBMCs) is significantly elevated in children with MA and inversely associated with hemoglobin levels. Additional experiments using PBMCs from non-malaria-exposed donors demonstrate that physiologic amounts of P. falciparum-derived hemozoin augment NOS type 2 (NOS2) transcripts and NO production. Results of these experiments illustrate that elevated NO production in children with MA is associated with decreased hemoglobin concentrations and that hemozoin can induce NOS2-derived NO formation in cultured blood mononuclear cells.

Of mice and not men: differences between mouse and human immunology

Mice are the experimental tool of choice for the majority of immunologists and the study of their immune responses has yielded tremendous insight into the workings of the human immune system. However, as 65 million years of evolution might suggest, there are significant differences. Here we outline known discrepancies in both innate and adaptive immunity, including: balance of leukocyte subsets, defensins, Toll receptors, inducible NO synthase, the NK inhibitory receptor families Ly49 and KIR, FcR, Ig subsets, the B cell (BLNK, Btk, and lambda5) and T cell (ZAP70 and common gamma-chain) signaling pathway components, Thy-1, gammadelta T cells, cytokines and cytokine receptors, Th1/Th2 differentiation, costimulatory molecule expression and function, Ag-presenting function of endothelial cells, and chemokine and chemokine receptor expression. We also provide examples, such as multiple sclerosis and delayed-type hypersensitivity, where complex multicomponent processes differ. Such differences should be taken into account when using mice as preclinical models of human disease.

Alveolar Macrophages as Orchestrators of COPD

Alveolar macrophages play a critical role in the pathophysiology of COPD and are a major target for future anti-inflammatory therapy. Macrophage numbers are markedly increased in the lung and alveolar space of patients with COPD and are localized to sites of alveolar destruction. The increased numbers of macrophages may result from increased recruitment of blood monocytes, prolonged survival in the lung and to a lesser extent to increased proliferation in the lung. Alveolar macrophages from COPD patients have an increased baseline and stimulated secretion of inflammatory proteins, including certain cytokines, chemokines, reactive oxygen species and elastolytic enzymes, which together could account for all of the pathophysiological features of COPD. Alveolar macrophages form COPD appear to be resistant to the anti-inflammatory effects of corticosteriods and this is linked to reduced activity and expression of histone deacetylase 2, a nuclear enzyme that switches off inflammatory genes activated through the transcription factor nuclear factor-KB. Alternative anti-inflammatory therapies that inhibit macrophages are therefore needed in the future to deal with the chronic inflammation of COPD. These drugs may include resveratrol, theophylline derivatives, MAP kinase inhibitors and phosphodiesterase-4 inhibitors.

Mechanisms for impaired effector function in alveolar macrophages from marijuana and cocaine smokers

Lung macrophages provide a first line of host defense against inhaled pathogens and their function is impaired in the lungs of inhaled substance abusers. In order to investigate the mechanism for this impairment, alveolar macrophages (AM) were recovered from nonsmokers (NS), regular tobacco smokers (TS), marijuana smokers (MS), or crack cocaine smokers (CS), and evaluated for their production of nitric oxide (NO) and the role of NO as an antimicrobial effector molecule. AM from NS and TS efficiently killed Staphylococcus aureus and their antibacterial activity correlated closely with the production of nitrite and the expression of mRNA encoding for inducible nitric oxide synthase (iNOS). In contrast, AM collected from MS and CS exhibited limited antimicrobial activity that was not affected by an inhibitor of iNOS, or associated with expression of iNOS. Treatment with either granulocyte/macrophage colony-stimulating factor (GM-CSF) or interferon-gamma restored the ability of these cells to produce NO and to kill bacteria. These findings confirm a significant role for NO as an antibacterial effector molecule used by normal human AM and suggest that this host defense mechanism is suppressed by habitual exposure to inhaled marijuana or crack cocaine in vivo.

Impairment of Brucella growth in human macrophagic cells that produce nitric oxide

In mice, nitric oxide (NO) production by inducible NO synthase (iNOS), is a component of the control of Brucella infection. In humans, the involvement of iNOS in infection is still a matter of debate. Based on in vitro experiments, it was recently postulated that in humans, Brucella infection tends to become chronic because NO cannot exert its deleterious effect. In fact, conditions allowing NO production by human macrophages in culture are poorly defined, rendering the in vitro study of NO function difficult. Using DFGiNOS U937 macrophagic cells engineered to produce NO and U937 cells activated by ligation of IgE receptors, we showed that the intracellular development of Brucella was impaired in human macrophages, which produced NO. Although Brucella-infected human macrophagic phagocytes did not release NO in commonly used models of infection, the machinery required to produce NO was expressed in these cells and could be triggered by cell membrane receptors present on the infected cells. Therefore, the lack of NO production in isolated human macrophages infected by Brucella under in vitro conditions did not exclude a possible involvement of NO in the control of human brucellosis.

Differential production of cytokines, reactive oxygen and nitrogen by bovine macrophages and dendritic cells stimulated with Toll-like receptor agonists

Toll-like receptors (TLR) have been described as partially sharing signalling pathways but showing unique ligand specificity and tissue distribution. Here, the response of bovine macrophages (Mphi) and dendritic cells (DC), both derived from monocytes, was compared by exposing them to the TLR-specific ligands lipopolysaccharide, poly(I:C)-double-stranded RNA, and CpG-DNA, as well as inactivated Gram-negative and Gram-positive bacteria, shown to bind to TLR. The production of NO, superoxide anion, interleukin-10 (IL-10), IL-12 and tumour necrosis factor (TNF) was determined. Compared to monocytes, Mphi expressed more TLR2 and similar levels of TLR4 mRNA transcripts, as analysed by quantitative polymerase chain reaction, whereas DC expressed reduced amounts. Although both DC and Mphi recognized the TLR ligands, dramatic differences were seen in their reaction pattern to them. Both cell types responded with the production of TNF, but DC produced more IL-12, whereas Mphi produced more IL-10, regardless of the TLR agonist used. Co-stimulation with interferon-gamma influenced the amount of cytokine production, but did not alter the cell type-specific response pattern. Compared to Mphi, DC produced > 10 times less NO upon triggering with TLR ligands. In addition, DC produced superoxide anion to opsonized and non-opsonized zymosan, but not to phorbol 12-myristate 13-acetate, a response pattern confirmed for human Mphi and DC, respectively. Different protein kinase C isoforms and extracellular signal-regulated kinase patterns were detected in cell lysates of resting and stimulated Mphi and DC. Collectively, our results point to profound differences in pathogen-derived signal-response coupling occurring commensurate with distinct functions carried out by Mphi or DC.

Differential production of cytokines, reactive oxygen and nitrogen by bovine macrophages and dendritic cells stimulated with Toll-like receptor agonists

Toll-like receptors (TLR) have been described as partially sharing signalling pathways but showing unique ligand specificity and tissue distribution. Here, the response of bovine macrophages (Mphi) and dendritic cells (DC), both derived from monocytes, was compared by exposing them to the TLR-specific ligands lipopolysaccharide, poly(I:C)-double-stranded RNA, and CpG-DNA, as well as inactivated Gram-negative and Gram-positive bacteria, shown to bind to TLR. The production of NO, superoxide anion, interleukin-10 (IL-10), IL-12 and tumour necrosis factor (TNF) was determined. Compared to monocytes, Mphi expressed more TLR2 and similar levels of TLR4 mRNA transcripts, as analysed by quantitative polymerase chain reaction, whereas DC expressed reduced amounts. Although both DC and Mphi recognized the TLR ligands, dramatic differences were seen in their reaction pattern to them. Both cell types responded with the production of TNF, but DC produced more IL-12, whereas Mphi produced more IL-10, regardless of the TLR agonist used. Co-stimulation with interferon-gamma influenced the amount of cytokine production, but did not alter the cell type-specific response pattern. Compared to Mphi, DC produced > 10 times less NO upon triggering with TLR ligands. In addition, DC produced superoxide anion to opsonized and non-opsonized zymosan, but not to phorbol 12-myristate 13-acetate, a response pattern confirmed for human Mphi and DC, respectively. Different protein kinase C isoforms and extracellular signal-regulated kinase patterns were detected in cell lysates of resting and stimulated Mphi and DC. Collectively, our results point to profound differences in pathogen-derived signal-response coupling occurring commensurate with distinct functions carried out by Mphi or DC.

Reactive oxygen species in pulmonary inflammation by ambient particulates

Exposure to ambient air pollution particles (PM) has been associated with increased cardiopulmonary morbidity and mortality, particularly in individuals with pre-existing disease. Exacerbation of pulmonary inflammation in susceptible people (e.g., asthmatics, COPD patients) appears to be a central mechanism by which PM exert their toxicity. Health effects are seen most consistently with PM with aerodynamic diameter < 2.5 micrometers (PM(2.5)), although 10 micrometers < PM < 2.5 micrometers can also be toxic. Through its metal, semi-quinone, lipopolysaccaride, hydrocarbon, and ultrafine constituents, PM may exert oxidative stress on cells in the lung by presenting or by stimulating the cells to produce reactive oxygen (ROS). In vivo, PM increase cytokine and chemokine release, lung injury, and neutrophil influx. In vitro analysis of PM effects on the critical cellular targets, alveolar macrophages, epithelial cells, and neutrophils, demonstrates PM- and oxidant-dependent responses consistent with in vivo data. These effects have been observed with PM samples collected over years as well as concentrated PM(2.5) (CAPs) collected in real time. Oxidative stress mediated by ROS is an important mechanism of PM-induced lung inflammation.

The pathophysiology of falciparum malaria

Falciparum malaria is a complex disease with no simple explanation, affecting organs where the parasite is rare as well as those organs where it is more common. We continue to argue that it can best be understood in terms of excessive stimulation of normally useful pathways mediated by inflammatory cytokines, the prototype being tumor necrosis factor (TNF). These pathways involve downstream mediators, such as nitric oxide (NO) that the host normally uses to control parasites, but which, when uncontrolled, have bioenergetic failure of patient tissues as their predictable end point. Falciparum malaria is no different from many other infectious diseases that are clinically confused with it. The sequestration of parasitized red blood cells, prominent in some tissues but absent in others with equal functional loss, exacerbates, but does not change, these overriding principles. Recent opportunities to stain a wide range of tissues from African pediatric cases of falciparum malaria and sepsis for the inducible NO synthase (iNOS) and migration inhibitory factor (MIF) have strengthened these arguments considerably. The recent demonstration of bioenergetic failure in tissue removed from sepsis patients being able to predict a fatal outcome fulfils a prediction of these principles, and it is plausible that this will be demonstrable in severe falciparum malaria. Understanding the disease caused by falciparum malaria at a molecular level requires an appreciation of the universality of poly(ADP-ribose) polymerase-1 (PARP-1) and Na(+)/K(+)-ATPase and the protean effects of activation by inflammation of the former that include inactivation of the latter.

IL-4 and interferon gamma regulate expression of inducible nitric oxide synthase in chronic lymphocytic leukemia cells

Chronic lymphocytic leukemia (B-CLL) is characterized by the accumulation of long-lived non-dividing CD5(+) B cells. Nitric oxide (NO) is an important regulator of apoptosis, and the viability of cultured B-CLL cells may be dependent on the autocrine production of nitric oxide by inducible nitric oxide synthase (NOS2). We performed this study to determine whether cytokine factors that prevent spontaneous in vitroapoptosis of B-CLL cells induce B-CLL cell NOS2 enzyme activity. B-CLL cells expressed NOS enzyme activity and NOS2 protein and mRNA. IL-4 and IFN-gamma increased B-CLL cell NOS2 enzyme activity and protein expression during in vitro culture. IFN-gamma, but not IL-4, increased NOS2 mRNA expression in cultured B-CLL cells suggesting that IL-4-mediated changes of NOS2 protein expression occurred at the post-transcriptional level. We were unable to detect increased concentrations of nitrite or nitrate (NO(x)) as surrogate markers of NO production in B-CLL cell cultures treated with IL-4 or IFN-gamma. IL-4 and IFN-gamma diminished NOS inhibitor-induced B-CLL cell death. In summary, we found that B-CLL cells expressed NOS2 and that IL-4 and IFN-gamma increased B-CLL NOS2 expression. Cytokine-mediated expression of NOS2 by B-CLL cells may promote their survival, and therapeutic strategies that target NOS2 or quench NO may be beneficial in patients with B-CLL.

Nitrogen monoxide-mediated control of ferritin synthesis: implications for macrophage iron homeostasis

Intracellular iron homeostasis is regulated posttranscriptionally by iron regulatory proteins 1 and 2 (IRP1 and IRP2). In the absence of iron in the labile pool, IRPs bind to specific nucleotide sequences called iron responsive elements (IREs), which are located in the 5' untranslated region of ferritin mRNA and the 3' untranslated region of transferrin receptor mRNA. IRP binding to the IREs suppresses ferritin translation and stabilizes transferrin receptor mRNA, whereas the opposite scenario develops in iron-replete cells. Binding of IRPs to the IREs is also affected by nitrogen monoxide (NO), but there are conflicting reports regarding the effect of NO on ferritin synthesis. In this study, we demonstrated that a short exposure of RAW 264.7 cells (a macrophage cell line) to the NO+ donor, sodium nitroprusside (SNP), resulted in a dramatic increase in ferritin synthesis. The SNP-mediated increase of ferritin synthesis could be blocked by MG132, an inhibitor of proteasome-dependent protein degradation, which also prevented the degradation of IRP2 caused by SNP treatment. Moreover, treatment of RAW 264.7 cells with IFN-gamma and lipopolysaccharide caused IRP2 degradation and stimulated ferritin synthesis, changes that could be prevented by specific inhibitors of inducible nitric oxide synthase. Furthermore, the SNP-mediated increase in ferritin synthesis was associated with a significant enhancement of iron incorporation into ferritin. These observations indicate that NO+-mediated modulation of IRP2 plays an important role in controlling ferritin synthesis and iron metabolism in murine macrophages.

Genetic determinants of rheumatoid arthritis: the inducible nitric oxide synthase (NOS2) gene promoter polymorphism

An association study and a linkage analysis were carried out in parallel in order to investigate the association of the inducible nitric oxide synthase (NOS2) gene promoter polymorphism with rheumatoid arthritis (RA) predisposition and/or outcome including a -954G-C mutation, a di-allelic (TAAA)(n) marker and the highly polymorphic (CCTTT). The -954G-C point mutation occurred non-polymorphic and the di-allelic (TAAA)(n) marker was not associated with RA predisposition. The (CCTTT)(n)locus showed a trend for RA association in the case-control study, however, stratification data by Class II status did not yield significant effect and overall, the family study showed no significant association nor linkage for any of the markers under study using TDT and non-parametric linkage respectively. Finally, no influence was detected regarding any of the clinical parameters tested. After evaluating for the first time the influence of NOS2 promoter polymorphism in RA, it seems to have no major effect on disease susceptibility and/or outcome.

Expression of inducible nitric oxide synthase in skin lesions of patients with american cutaneous leishmaniasis

Cytokine-inducible (or type 2) nitric oxide synthase (iNOS) is indispensable for the resolution of Leishmania major or Leishmania donovani infections in mice. In contrast, little is known about the expression and function of iNOS in human leishmaniasis. Here, we show by immunohistological analysis of skin biopsies from Mexican patients with local (LCL) or diffuse (DCL) cutaneous leishmaniasis that the expression of iNOS was most prominent in LCL lesions with small numbers of parasites whereas lesions with a high parasite burden (LCL or DCL) contained considerably fewer iNOS-positive cells. This is the first study to suggest an antileishmanial function of iNOS in human Leishmania infections in vivo.

Apolipoprotein E isoform mediated regulation of nitric oxide release

Progressive dysfunction and death of neurons in Alzheimer's dementia is enhanced in patients carrying one or more APOE4 alleles who also display increased presence of oxidative stress markers. Modulation of oxidative stress is a nontraditional and physiologically relevant immunomodulatory function of apolipoprotein E (apoE). Stimulated peritoneal macrophages from APOE-transgenic replacement (APOE-TR) mice expressing only human apoE3 or human apoE4 protein isoforms were utilized as mouse models to investigate the role of apoE protein isoforms and gender in the regulation of oxidative stress. Macrophages from male APOE4/4-TR mice produced significantly higher levels of nitric oxide than from male APOE3/3-TR mice, while macrophages from female APOE3/3-TR and female APOE4/4-TR mice produced the similar levels of nitric oxide. Primary cultures of microglial cells of APOE4 transgenic mice also produced significantly more nitric oxide than microglia from APOE3 transgenic mice. These data suggest a potentially novel mechanism for gender-dependent and apoE isoform-dependent immune responses that parallel the genetic susceptibility of APOE4 carriers for the development of Alzheimer's disease.

No evidence for association of the inducible nitric oxide synthase promoter polymorphism with Trypanosoma cruzi infection

The purpose of the present study was to address the possible contribution of the (CCTTT)n microsatellite polymorphism in the NOS2 promoter region to the susceptibility to chronic Trypanosoma cruzi infection and to Chagas' disease related cardiomyopathy. We determined the (CCTTT)n genotypes in a sample of 76 serologically positive chagasic individuals and in 78 healthy controls. No statistically significant differences were observed between total chagasic patients and healthy controls with regard to frequency of the (CCTTT)n microsatellite repeat of any given length. Likewise, we found no differences in the distribution of the (CCTTT)n microsatellite repeats between seropositives without manifestations of the disease and those with chagasic cardiomyopathy. Our data suggest that the NOS2 promoter pentanucleotide microsatellite polymorphisms analyzed do not play a major role in the pathogenesis of chronic T. cruzi infection in this Peruvian sample.

Nitric oxide induces the apoptosis of human BCR-ABL-positive myeloid leukemia cells: evidence for the chelation of intracellular iron

Anti-leukemia activity of human macrophages involves the generation of nitric oxide (NO) derivatives. However, leukemic transformation may involve mechanisms that rescue cells from NO-mediated apoptosis. In the present work, we analyzed the effects of exogenous NO on the proliferation of BCR-ABL(+) chronic myelogenous leukemia (CML) cells. As normal leukocytes, the proliferation of leukemia cells was inhibited by SNAP (S-nitroso-N-acetyl-penicillamine), GEA (Oxatriazolium amino-chloride), and SIN-1 (Morpholino-sydnonimine), whereas SNP (sodium nitroprusside) had no effect on leukemia cell growth. SIN-1 induced higher anti-proliferation activity in BCR-ABL(+) cells, compared to normal hemopoietic cells. Inhibition of leukemia cell proliferation correlated with increased apoptosis and DEVDase activity. The simultaneous addition of exogenous iron reversed NO-mediated inhibition of cell growth, caspase activation and apoptosis in all BCR-ABL(+) cells tested. The quantification of intracellular iron levels in leukemia cells indicated that NO induced an early, dose-dependent decrease in ferric iron levels. Accordingly, elevation of intracellular iron protected leukemia cells from NO-mediated apoptosis. Together, the present work reveals the presence of an iron-dependant mechanism for leukemia cell rescue from NO-induced growth inhibition and apoptosis.

Reactive nitrogen and oxygen intermediates and bacterial defenses: unusual adaptations in Mycobacterium tuberculosis

The production of reactive oxygen and reactive nitrogen intermediates is an important host defense mechanism mediated in response to infection by bacterial pathogens. Not surprisingly, intracellular pathogens have evolved numerous defense strategies to protect themselves against the damaging effects of these agents. In enteric bacteria, exposure to oxidative or nitrosative stress induces expression of numerous pathways that allow the bacterium to resist the toxic effects of these compounds during growth in the host. In contrast, members of pathogenic mycobacterial species, including the frank human pathogens Mycobacterium tuberculosis and Mycobacterium leprae, are dysfunctional in aspects of the oxidative and nitrosative stress response, yet they remain able to establish and maintain productive acute and persistent infections in the host. This article reviews the current knowledge regarding reactive oxygen and nitrogen intermediates, and compares the adaptative mechanisms utilized by enteric organisms and mycobacterial species to resist the bactericidal and bacteriostatic effects resulting from exposure to these compounds.

Inducible nitric oxide synthase expression by peritoneal macrophages in endometriosis-associated infertility

OBJECTIVE

Determine whether peritoneal macrophages from women with endometriosis-associated infertility express more inducible nitric oxide synthase (NOS2) and produce more NO than fertile controls.

DESIGN

Unblinded clinical study.

PATIENT(S)

Nine infertile women with endometriosis and nine normal fertile women undergoing laparoscopy.

INTERVENTION(S)

Peritoneal fluid and macrophages were collected. Cells were also cultured with the NOS2 inducers interferon-alpha (IFN-alpha) or IFN-gamma plus lipopolysaccharide (LPS).

MAIN OUTCOME MEASURE(S)

Peritoneal fluid NO levels, peritoneal macrophage NOS activity, and peritoneal macrophage NOS2 protein expression.

RESULT(S)

NOS enzyme activity was higher in peritoneal macrophages from endometriosis patients. Immunoblots demonstrated NOS2 protein only in peritoneal macrophages from women with endometriosis. Peritoneal fluid NO concentration was similar in the two groups, but total peritoneal fluid NO content was higher in endometriosis patients. After 3 days' culture, peritoneal macrophages from women with endometriosis produced more NO in response to IFN-alpha or IFN-gamma plus LPS than controls.

CONCLUSION(S)

Peritoneal macrophages from women with endometriosis-associated infertility express higher levels of NOS2, have higher NOS enzyme activity, and produce more NO in response to immune stimulation in vitro. As high levels of NO adversely affect sperm, embryos, implantation, and oviductal function, reducing peritoneal fluid NO production or blocking NO effects may improve fertility in women with endometriosis.