Inducible nitric oxide synthase-derived nitric oxide in gene regulation, cell death and cell survival

Induced nitric oxide synthase as a major player in the oncogenic transformation of inflamed tissue

Nitric oxide (NO) is a free radical that is involved in the inflammatory process and carcinogenesis. There are four nitric oxide synthase enzymes involved in NO production: induced nitric oxide synthase (iNOS), endothelial NO synthase (eNOS), neural NO synthase (nNOS), and mitochondrial NOS. iNOS is an inducible and key enzyme in the inflamed tissue. Recent literatures indicate that NO as well as iNOS and eNOS can modulate cancer-related events including nitro-oxidative stress, apoptosis, cell cycle, angio-genesis, invasion, and metastasis. This chapter focuses on linking NO/iNOS/eNOS to inflammation and carcinogenesis from experimental evidence to potential targets on cancer prevention and treatment.

Anti-inflammatory effects of Z23 on LPS-induced inflammatory responses in RAW264.7 macrophages

AIM OF THE STUDY

Fissistigma oldhamii (Hemsl.) Merr, a traditional Chinese herb medicine, is used for treating rheumatoid arthritis in China. In our previous study, an effective compound, 7'-(3',4'-dihydroxyphenyl)-N-[(4-methoxyphenyl) ethyl] propenamide (Z23), from this herb has showed potent immunosuppressive effects both in vitro and in vivo. However, its anti-inflammatory effect and mechanism is still need to explore.

MATERIALS AND METHODS

We examined the in vitro effects of Z23 on the production of nitric oxide (NO), prostaglandin E2 (PGE2) and cytokines by lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages.

RESULTS

Z23 significantly decreased the production of PGE2, NO, tumour necrosis factor alpha (TNFalpha) and IL6 production. Inducible nitric oxide synthase (iNOS) and cyclooxygenase2 (COX2) gene expression were also significantly reduced.

CONCLUSIONS

These results demonstrated that Z23 exerted an anti-inflammatory effect through modulating the synthesis of several mediators and cytokines involved in the inflammatory process. This study provided evidence to understand the therapeutic effects of Fissistigma oldhamii (Hemsl.) Merr and indicated that Z23 has the potential for treatment of various inflammatory diseases where the overproduction of NO, PGE2 and inflammatory cytokines has been shown to play a role, e.g. rheumatoid arthritis.

The effects of NOS2 gene deletion on mice expressing mutated human AbetaPP

Nitric oxide synthase 2 (NOS2) and its gene product, inducible NOS (iNOS) play an important role in neuroinflammation by generating nitric oxide (NO), a critical signaling and redox factor in the brain. Although NO is associated with tissue damage, it can also promote cell survival. We hypothesize that during long-term exposure to amyloid-beta (Abeta) in Alzheimer's disease (AD), NO levels fall in the brain to a threshold at which the protective effects of NO cannot be sustained, promoting Abeta mediated damage. Two new mouse models of AD have been developed that utilize this concept of NO's action. These mice express human amyloid-beta protein precursor (AbetaPP) mutations that generate Abeta peptides on a mouse NOS2 knockout background. The APP/NOS2(-/-) bigenic mice progress from Abeta production and amyloid deposition to hyperphosphorylated normal mouse tau at AD-associated epitopes, aggregation and redistribution of tau to somatodendritic regions of neurons and significant neuronal loss including loss of interneurons. This AD-like pathology is accompanied by robust behavioral changes. As APP/NOS2(-/-) bigenic mice more fully model the human AD disease pathology, they may serve as a tool to better understand disease progression in AD and the role of NO in altering chronic neurological disease processes.

Nitric oxide inhibits human rhinovirus-induced transcriptional activation of CXCL10 in airway epithelial cells

BACKGROUND

Human rhinovirus (HRV) infections trigger exacerbations of asthma and chronic obstructive pulmonary disease. Nitric oxide (NO) inhibits HRV replication in human airway epithelial cells and suppresses HRV-induced epithelial production of several cytokines and chemokines.

OBJECTIVE

We sought to delineate the mechanisms by which NO inhibits HRV-induced epithelial production of CXCL10, a chemoattractant for type 1 T cells and natural killer cells.

METHODS

Primary human bronchial epithelial cells or cells of the BEAS-2B human bronchial epithelial cell line were exposed to HRV-16 in the presence or absence of the NO donor 3-(2-hydroxy-2-nitroso-1-propylhydrazino)-1-propanamine (PAPA NONOate). A cGMP analogue and an inhibitor of soluble guanylyl cyclase were used to examine the role of the cyclic guanosine monophosphate (cGMP) pathway in the actions of NO. BEAS-2B cells were transfected with CXCL10 promoter-luciferase constructs and the effects of PAPA NONOate were examined to study mechanisms of transcriptional regulation. Electrophoretic mobility shift assays were also used.

RESULTS

PAPA NONOate inhibited HRV-16-induced increases in CXCL10 mRNA and protein. Inhibition of CXCL10 production occurred through a cGMP-independent pathway. PAPA NONOate inhibited HRV-16-induced CXCL10 transcription by blocking nuclear translocation, binding, or both of both nuclear factor kappaB and IFN response factors (IRFs) to their respective recognition elements in the CXCL10 promoter.

CONCLUSIONS

NO inhibits HRV-16-induced production of CXCL10 by inhibiting viral activation of nuclear factor kappaB and of IRFs, including IRF-1, through a cGMP-independent pathway. The broad-ranging inhibition of HRV-induced epithelial cytokine and chemokine production by NO suggests a potential therapeutic utility of NO donors in viral exacerbations of asthma and chronic obstructive pulmonary disease.

Novel nitric oxide-donating compound (S,R)-3-phenyl-4,5-dihydro-5-isoxazole acetic acid-nitric oxide (GIT-27NO) induces p53 mediated apoptosis in human A375 melanoma cells

In this study we evaluated the effects of the new NO donating compound (S,R)-3-phenyl-4,5-dihydro-5-isoxazole acetic acid-nitric oxide (GIT-27NO) on the A375 human melanoma cell line. Treatment with the drug led to concentration-dependent reduction of mitochondrial respiration and number of viable cells in cultures. Decreased cell viability correlated with release and internalization of NO and was neutralized by the extracellular scavenger hemoglobin. GIT-27NO neither influenced cell division nor induced accidental or autophagic cell death. Early signs of apoptosis were observed upon coculture with the drug, and resulting in marked accumulation of hypodiploid cells, suggesting that the induction of apoptosis is one primary mode of action of the compound in A375 cells. GIT-27NO significantly inhibited the expression of the transcription repressor and apoptotic resistant factor YY1 and, in parallel, augmented the presence of total p53. The capacity of GIT-27NO to induce p53-mediated apoptosis along with inhibition of YY1 repressor in A375 melanoma cells indicates that GIT-27NO possesses an important anti-cancer pharmacological profile. The findings suggest the potential therapeutic use of GIT-27NO in the clinical setting.

Involvement of nitric oxide in the promotion of cell survival by ceramide 1-phosphate

Macrophages play vital roles in inflammatory responses, and their number at sites of inflammation is strictly regulated by cell death and division. Here, we demonstrate that production of nitric oxide (NO) is a major mechanism whereby ceramide-1-phosphate (C1P) blocks apoptosis in macrophages. However, NO failed to stimulate macrophage proliferation. The prosurvival effect of C1P was blocked by inhibitors of inducible NO synthase. The antiapoptotic effect of C1P was also blocked by phosphatidylinositol 3-kinase or nuclear factor-kappa B inhibitors. Moreover, NO reversed the inhibitory effect of C1P on acid sphingomyelinase, but the prosurvival effect of C1P was independent of this action.

Progression of amyloid pathology to Alzheimer's disease pathology in an amyloid precursor protein transgenic mouse model by removal of nitric oxide synthase 2

Alzheimer's disease (AD) is characterized by three primary pathologies in the brain: amyloid plaques, neurofibrillary tangles, and neuron loss. Mouse models have been useful for studying components of AD but are limited in their ability to fully recapitulate all pathologies. We crossed the APPSwDI transgenic mouse, which develops amyloid beta (Abeta)-protein deposits only, with a nitric oxide synthase 2 (NOS2) knock-out mouse, which develops no AD-like pathology. APPSwDI/NOS2(-/-) mice displayed impaired spatial memory compared with the APPSwDI mice, yet they have unaltered levels of Abeta. APPSwDI mice do not show tau pathology, whereas APPSwDI/NOS2(-/-) mice displayed extensive tau pathology associated with regions of dense microvascular amyloid deposition. Also, APPSwDI mice do not have any neuron loss, whereas the APPSwDI/NOS2(-/-) mice have significant neuron loss in the hippocampus and subiculum. Neuropeptide Y neurons have been shown to be particularly vulnerable in AD. These neurons appear to be particularly vulnerable in the APPSwDI/NOS2(-/-) mice as we observe a dramatic reduction in the number of NPY neurons in the hippocampus and subiculum. These data show that removal of NOS2 from an APP transgenic mouse results in development of a much greater spectrum of AD-like pathology and behavioral impairments.

A Polypodium leucotomos extract inhibits solar-simulated radiation-induced TNF-alpha and iNOS expression, transcriptional activation and apoptosis

In this report, we have examined the molecular basis of the photoprotective effect of a hydrophilic extract of the fern Polypodium leucotomos (PL) in vitro, using a solar simulator as the source of UV radiation (SSR). We found that pretreatment of human keratinocytes with PL inhibited SSR-mediated increase of tumor necrosis factor (TNF)-alpha and also abrogated nitric oxide (NO) production. Consistent with this, PL blocked the induction of inducible nitric oxide synthase (iNOS) elicited by SSR. In addition, PL inhibited the SSR-mediated transcriptional activation of NF-kappaB and AP1. Finally, we demonstrated that pretreatment with PL exerted a cytoprotective effect against SSR-induced damage, resulting in increased cell survival. Together, these data postulate a multifactor mechanism of protection not exclusively reliant on the antioxidant capability of PL, and strengthen the basic knowledge on the photoprotective effect of this botanical agent.

The role of nitric oxide in inflammatory reactions

Nitric oxide (NO) was initially described as a physiological mediator of endothelial cell relaxation, an important role in hypotension. NO is an intercellular messenger that has been recognized as one of the most versatile players in the immune system. Cells of the innate immune system--macrophages, neutrophils and natural killer cells--use pattern recognition receptors to recognize the molecular patterns associated with pathogens. Activated macrophages then inhibit pathogen replication by releasing a variety of effector molecules, including NO. In addition to macrophages, a large number of other immune-system cells produce and respond to NO. Thus, NO is important as a toxic defense molecule against infectious organisms. It also regulates the functional activity, growth and death of many immune and inflammatory cell types including macrophages, T lymphocytes, antigen-presenting cells, mast cells, neutrophils and natural killer cells. However, the role of NO in nonspecific and specific immunity in vivo and in immunologically mediated diseases and inflammation is poorly understood. This Minireview will discuss the role of NO in immune response and inflammation, and its mechanisms of action in these processes.

Efficacy of gaseous nitric oxide in the treatment of skin and soft tissue infections

Bacterial burden significantly interferes with the healing process in chronic ulcers. Nitric oxide (NO) plays a key role in regulating skin's response to infection and wound healing. In previous studies, we demonstrated that exogenous NO gas (gNO) at 200 parts per million (ppm) exhibits potent antimicrobial effects against a representative range of pathogens. The aim of the present study is to explore the antimicrobial properties of gNO in vivo and to determine skin cells' sensitivity to the cytotoxic effects of gNO. To test gNO's antimicrobial effects, full-thickness wounds were infected with Staphylococcus aureus on the dorsal skin surface of New Zealand White rabbit and treated with 200 ppm gNO for 8 hours/day for 3 consecutive days. Significant reduction in wound bacterial content was observed in the presence of gNO. In a separate experiment, primary cultures of human fibroblasts, keratinocytes, and endothelial cells were established to test gNO's cytotoxicity in the skin. Methyl thiazolyl tetrazolium proliferation assays demonstrated that human skin cells, unlike bacterial cells, exhibited significant resistance toward gNO cytotoxicity. In vitro migration studies on keratinocytes and endothelial cells revealed that gNO treatment does not seem to interfere with reepithelialization and angiogenesis during the process of wound healing. Following 24 hours of gNO treatment, fibroblasts expressed significantly higher levels of procollagen and, to a lesser degree, a decrease in matrix metalloproteinase -1 mRNA. In conclusion, the present study provides evidence for the potential application of high doses of gNO as an antimicrobial agent for the treatment of infection in chronic nonhealing ulcers or burn patients, without compromising the viability, and function of skin cells.

Inflammation, genes and zinc in ageing and age-related diseases

Lifelong antigenic burden determines a condition of chronic inflammation, with increased lymphocyte activation and pro-inflammatory cytokine production. A large number of studies have documented changes in Zn metabolism in experimental animal models of acute and chronic inflammation and in human chronic inflammatory diseases. In particular, modification of zinc plasma concentration as well as intracellular disturbance of antioxidant intracellular pathways have been found associated to age-related inflammatory diseases, like atherosclerosis. Zinc deficiency is extremely diffused in aged people that are educated to avoid meat and other high Zn-content foods due to fear of cholesterol. Rather, they increase consumption of refined wheat products that lack of Zn, magnesium and other critical nutrients in consequence of refining process. On the other hand, plasma concentration of metallic ions like Zn is influenced by pro-inflammatory cytokines production. A major target of Zn may be NF-kB, a transcription factor critical for the expression of many pro-inflammatory cytokines whose production is finely regulated by extra- and intracellular activating and inhibiting factors interacting with regulatory elements on cytokine genes. Moreover, this factor is regulated by the expression of specific cellular genes involved in inflammation. So it is not surprising that Zn deficiency is constantly observed in aged patients affected by infectious diseases. On the other hand, cytokine genes are highly polymorphic and some of these polymorphisms have been found associated to age-related diseases as atherosclerosis. Therefore, Zn deficiency in individuals genetically predisposed to a dis-regulation of inflammation response, may play a crucial role, in causing adverse events and in reducing the probability of a successful aging.

Neuronal apoptosis in neurodegeneration

Apoptosis mediates the precise and programmed natural death of neurons and is a physiologically important process in neurogenesis during maturation of the central nervous system. However, premature apoptosis and/or an aberration in apoptosis regulation is implicated in the pathogenesis of neurodegeneration, a multifaceted process that leads to various chronic disease states, such as Alzheimer's (AD), Parkinson's (PD), Huntington's (HD) diseases, amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), and diabetic encephalopathy. The current review focuses on two major areas (a) the fundamentals of apoptosis, which includes elements of the apoptotic machinery, apoptosis inducers, and emerging concepts in apoptosis research, and (b) apoptotic involvement in neurodegenerative disorders, neuroprotective treatment strategies/modalities, and the mechanisms of, and signaling in, neuronal apoptosis. Current and new experimental models for apoptosis research in neurodegenerative diseases are also discussed.

Multidrug resistance related protein (ABCC1) and its role on nitrite production by the murine macrophage cell line RAW 264.7

Multidrug resistance related protein 1 (MRP1/ABCC1) is an ABC transporter protein related to the extrusion of reduced glutathione (GSH), oxidized glutathione (GSSG) and GSH-conjugates, as well as leukotriene C(4) and cyclopentane prostaglandins. Inhibition of ABCC1 activity impairs lymphocyte activation. The present work studied ABCC1 expression and activity on a murine macrophage cell line, RAW 267.4 and the effects of ABCC1 classical inhibitors, as well as GSH metabolism modulators, on LPS induced activation. Approximately, 75% of resting cells were positive for ABCC1 and the classical ABCC1 reversors (indomethacin, 0.1-2mM; probenecid, 0.1-10mM and MK571, 0.01-1mM) were able to enhance intracellular CFDA accumulation in a concentration-dependent manner, suggesting ABCC1 inhibition. After LPS (100ng/ml) activation 50% of the population was positive for ABCC1, and this protein was still active. In LPS-activated cells, ABCC1 activity was also impaired by BSO (1mM), an inhibitor of GSH synthesis. Conversely, GSH (5mM) reversed the BSO effect. ABCC1 inhibition by indomethacin, probenecid or MK571 decreased LPS induced nitrite production in a concentration-dependent manner, the same result was observed with BSO and again GSH reversed its effect. The ABCC1 reversors were also able to inhibit iNOS expression. In conclusion, LPS modulated the expression and activity of ABCC1 transporters in RAW macrophages and inhibitors of these transporters were capable of inhibiting nitrite production suggesting a role for ABCC1 transporters in the inflammatory process.

NOS2 (iNOS) deficiency in kidney donor accelerates allograft loss in a murine model

Renal NOS2 is expressed and produces abundant nitric oxide (NO) in various renal cells in response to proinflammatory cytokines. However, the role of this enzyme in renal allograft survival remains unknown. Kidney allotransplantation was performed in the murine model of C57BL/6J (H-2(d)) to nephrectomized Balb/c (H-2(b)) mice. Here we show that deficiency in NOS2 expression in kidney donors significantly advanced allograft failure, indicated by decreasing mean survival of recipients receiving NOS2 null grafts (15.4 +/- 6.4 days) as compared to those with wild type grafts (65.4 +/- 28.1 days) (p = 0.0005). Consistent with survival results, NOS2 null grafts had more severe renal tubule injury and decreased renal function compared to wild type grafts. In vitro NOS2 expressing TEC had greater resistance to allogeneic lymphocyte-mediated apoptosis. The addition of exogenous NO inhibited Fas-mediated TEC apoptosis and reduced proliferation of allogeneic lymphocytes. These data suggest that endogenous production of NO through renal NOS2 activity can play a protective role in kidney grafts through attenuating Fas-mediated donor cell apoptosis as well as by inhibiting proliferation of inflammatory infiltrating lymphocytes. Enhanced donor NOS2 expression may be a useful strategy to improve kidney transplant survival.

Effects of low-level laser therapy (LLLT) on the nuclear factor (NF)-kappaB signaling pathway in traumatized muscle

BACKGROUND AND OBJECTIVE

To investigate the effects of low-level laser therapy (LLLT) on nuclear factor kappa B (NF-kappaB) activation and inducible nitric oxide synthase (iNOS) expression in an experimental model of muscle trauma.

STUDY DESIGN/MATERIALS AND METHODS

Injury to the gastrocnemius muscle in the rat was produced by a single impact blunt trauma. A low-level galium arsenide (Ga-As) laser (904 nm, 45 mW, and 5 J/cm2) was applied for 35 seconds duration, continuously.

RESULTS

Histological abnormalities with increase in collagen concentration, and oxidative stress were observed after trauma. This was accompanied by activation of NF-kappaB and upregulation of iNOS expression, whereas protein concentration of I kappa B alpha decreased. These effects were blocked by LLLT.

CONCLUSION

LLLT reduced the inflammatory response induced by trauma and was able to block the effects of reactive oxygen species (ROS) release and the activation of NF-kappaB. The associated reduction of iNOS overexpression and collagen production suggest that the NF-kappaB pathway may be a signaling route involved in the pathogenesis of muscle trauma.

In vivo study of the inflammatory modulating effects of low-level laser therapy on iNOS expression using bioluminescence imaging

This study was designed to demonstrate that bioluminescence imaging (BLI) can be used as a new tool to evaluate the effects of low-level laser therapy (LLLT) during in vivo inflammatory process. Here, the efficacy of LLLT in modulating inducible nitric oxide synthase (iNOS) expression using different therapeutic wavelengths was determined using transgenic animals with the luciferase gene under control of the iNOS gene expression. Thirty transgenic mice, FVB/N-Tg(iNOS-luc)Xen, were allocated randomly to one of four experimental groups treated with different wavelengths (lambda = 635, 785, 808 and 905 nm) or a control group (nontreated). Inflammation was induced by intra-articular injection of zymosan A in both knee joints. Laser treatment (25 mW cm(-2), 200 s, 5 J cm(-2)) was applied to the knees 15 min after inflammation induction. Measurements of iNOS expression were performed at various times (0, 3, 5, 7, 9 and 24 h) by measuring the bioluminescence signal using a highly sensitive charge-coupled device (CCD) camera. The results showed a significant increase in BLI signal after irradiation with 635 nm laser when compared to the nonirradiated animals and the other LLLT-treated groups, indicating wavelength dependence of LLLT effects on iNOS expression during the inflammatory process, and thus demonstrating an action spectrum of iNOS gene expression following LLLT in vivo that can be detected by BLI. Histological analysis was also performed and demonstrated the presence of fewer inflammatory cells in the synovial joints of mice irradiated with 635 nm compared with nonirradiated knee joints.

Evidence for a role of inducible nitric oxide synthase in gastric relaxation of mdx mice

Alterations of gastric mechanical activity have been reported in mdx mouse, animal model for Duchenne muscular dystrophy. This study examined if alterations in the vasoactive intestinal polypeptide (VIP) system are present in mdx stomach. Gastric mechanical activity was recorded in vitro as changes of endoluminal pressure and neurally or pharmacologically evoked relaxations were analysed in mdxvs normal stomach. Reverse-transcription polymerase chain reaction was used to detect inducible nitric oxide synthase (iNOS) expression. Relaxations to sodium nitroprusside in mdx stomach showed no difference in comparison with normal preparations. In normal stomach, VIP produced relaxation, which was reduced by VIP6-28, antagonist of VIP receptors, but was not modified by Nomega-nitro-L-arginine methyl ester (L-NAME), 1-H-oxodiazol-[1,2,4]-[4,3-a]quinoxaline-1-one (ODQ) or by N-(3-(aminomethyl)-benzyl)acetamidine (1400W) and aminoguanidine, inhibitors of iNOS. In contrast, in mdx stomach VIP responses were antagonized not only by VIP6-28, but also by L-NAME, ODQ, 1400W or aminoguanidine. In normal stomach, the slow relaxation evoked by stimulation at high frequency was reduced by VIP6-28, but it was unaffected by 1400W or aminoguanidine. In mdx stomach, it was reduced by VIP6-28 or 1400W, which did not show additive effects. iNOS mRNA was expressed only in mdx stomach. The results suggest that in mdx gastric preparations, iNOS is functionally expressed, being involved in the slow relaxation induced by VIP.

Airway inflammation and cellular stress in noneosinophilic atopic asthma

STUDY OBJECTIVES

It has been suggested that patients with noneosinophilic asthma (NEA) show increased numbers of sputum neutrophils and a lack of response to therapy with corticosteroids, which are features that are commonly related to COPD. The aim of our study was to test the hypothesis that airway inflammation in NEA patients is different from that seen in patients with eosinophilic asthma (EA) and is similar to COPD.

DESIGN

Sputum cellular stress markers and neutrophilic and eosinophilic fluid-phase mediators were analyzed in asthma and COPD patients. NEA patients were identified based on a sputum eosinophil count of < or = 2.2% of the total nonsquamous cell count, and were compared to EA and COPD patients.

SETTING

University Hospital of Heraklion, Department of Thoracic Medicine.

PATIENTS

A total of 37 atopic asthmatic patients and 25 patients with COPD.

MEASUREMENTS

Sputum cell counts, cellular expression of heme oxygenase-1, inducible nitric oxide synthase, and nitrotyrosine, and sputum levels of eosinophilic cationic protein (ECP), myeloperoxidase (MPO), interleukin-8, and granulocyte macrophage colony-stimulating factor.

RESULTS

A total of 17 asthmatic patients (46%) belonged to the NEA group and 20 patients (54%) to the EA group. Patients with NEA showed no difference in neutrophil counts, fluid-phase mediators, or cellular stress markers compared to patients with EA. Compared to COPD patients, NEA patients showed the following significant differences: lower total cell counts (p < 0.03); lower neutrophil counts (p < 0.01); lower nitrotyrosine positive cell counts (p < 0.003); lower ECP levels (p < 0.005); lower MPO levels (p < 0.000); higher lymphocyte counts (p < 0.01); and higher macrophage counts (p < 0.03).

CONCLUSIONS

Despite low eosinophil counts, airway inflammation in NEA patients may share common features with that in EA patients but is distinct from COPD. Larger studies are needed to investigate further the clinical and inflammatory characteristics of NEA before we are able to categorize asthma patients into those with or without eosinophilic inflammation.

Nitric oxide mediates neurodegeneration and breakdown of the blood-brain barrier in tPA-dependent excitotoxic injury in mice

Stroke and many neurodegenerative diseases culminate in neuronal death through a mechanism known as excitotoxicity. Excitotoxicity proceeds through a complex signaling pathway that includes the participation of the serine protease tissue plasminogen activator (tPA). tPA mediates neurotoxic effects on resident central nervous system cells as well alters blood-brain barrier (BBB) permeability, which further promotes neurodegeneration. Another signaling molecule that promotes neurodegeneration and BBB dysfunction is nitric oxide (NO), although its precise role in pathological progression remains unclear. We examine here the potentially interrelated roles of tPA, NO and peroxynitrite (ONOO-), which is the toxic metabolite of NO, in BBB breakdown and neurodegeneration following intrahippocampal injection of the glutamate analog kainite (KA). We find that NO and ONOO- production are linked to tPA-mediated excitotoxic injury, and demonstrate that NO provision suffices to restore the toxic effects of KA in tPA-deficient mice that are normally resistant to excitotoxicity. NO also promotes BBB breakdown and excitotoxicity. Interestingly, BBB breakdown in itself does not suffice to elicit neurodegeneration; a subsequent ONOO(-)-mediated event is required. In conclusion, NO and ONOO- function as downstream effectors of tPA-mediated excitotoxicity.

Estrogen regulation of nitric oxide and inducible nitric oxide synthase (iNOS) in immune cells: implications for immunity, autoimmune diseases, and apoptosis

Nitric oxide plays a central role in the physiology and pathology of diverse tissues including the immune system. It is clear that the levels of nitric oxide must be carefully regulated to maintain homeostasis. Appropriate levels of nitric oxide derived from iNOS assist in mounting an effective defense against invading microbes. Conversely, inability to generate nitric oxide results in serious, even fatal, susceptibility to infections. Further, dysregulation or overproduction of nitric oxide has been implicated in the pathogenesis of many disorders, including atherosclerosis, neurodegenerative diseases, inflammatory autoimmune diseases, and cancer. Therefore, depending upon the levels of nitric oxide generated, the potential exists for nitric oxide to behave like a "double-edged" biological sword. Taking these issues into consideration, it is thus pivotal to understand the regulation of nitric oxide. Nitric oxide is regulated by many endogenous factors including hormones such as estrogens. While the effects of estrogen on the generation of nitric oxide in non-immune tissues are relatively well documented, the effect of estrogen on iNOS/nitric oxide in immune cells is only now becoming apparent. Our laboratory has recently shown that estrogen treatment of mice markedly upregulates the levels of iNOS mRNA, iNOS protein, and nitric oxide in activated splenocytes. This upregulation of nitric oxide is in part mediated through interferon-gamma (IFN-gamma), a pro-inflammatory cytokine that is enhanced by estrogen. These findings are important considering that estrogens are not only involved in regulation of normal immune responses, but also are implicated in many autoimmune and inflammatory diseases. To date, there are no reviews on the effects of estrogen on immune tissue-derived nitric oxide and therefore this review will address this critical gap in the literature. Given the increasing importance of immune-tissue-derived iNOS in health and disease, studies on estrogen-induced regulation of iNOS may offer a better understanding of diseases and aid in devising new therapeutic interventions.

Estrogen up-regulates inducible nitric oxide synthase, nitric oxide, and cyclooxygenase-2 in splenocytes activated with T cell stimulants: role of interferon-gamma

Estrogen is implicated in many autoimmune diseases and is a robust immunomodulator. For example, it regulates interferon (IFN)-gamma, a cytokine believed to up-regulate inducible nitric oxide synthase (iNOS). A notable gap in the literature is a lack of information on the regulation of nitric oxide in immune tissues by estrogen. We now show that activation of splenocytes with T cell stimulants [concanavalin-A (Con-A) or anti-CD3 antibodies] results in copious release of nitric oxide in splenocyte cultures from estrogen-treated but not placebo-treated mice. Moreover, even a low dose of T cell stimulants induced nitric oxide in splenocytes from estrogen-treated, but not placebo-treated, mice. Con-A-activated splenocytes from estrogen-treated mice also have up-regulated iNOS mRNA, iNOS protein, and cyclooxygenase-2 (a nitric oxide-regulated downstream proinflammatory protein) when compared with controls. Our studies suggest that the induction of nitric oxide by activated splenocytes from estrogen-treated mice is mediated in part by IFNgamma. First, blocking costimulatory signals mediated through interactions of CD28 and B7 molecules by CTLA-4Ig markedly decreased not only IFNgamma but also nitric oxide. Second, estrogen treatment of IFNgamma-knockout (IFNgamma(-)/(-)) mice did not induce iNOS protein or nitric oxide. Finally, in vitro addition of recombinant IFNgamma to Con-A-activated splenocytes from IFNgamma((-)/(-)) mice induced iNOS protein primarily in estrogen-treated mice. Overall, this is the first report to show that estrogen treatment up-regulates IFNgamma-inducible-iNOS gene expression, iNOS protein, nitric oxide, and cyclooxygenase-2 as an indirect consequence of activation of T cells. These findings may have wide implications to immunity and inflammatory disorders including female-predominant autoimmune diseases.

Acidosis affects tumor cell survival through modulation of nitric oxide release

The influence of environmental pH on the production of tumoricidal free radical nitric oxide (NO) was investigated in mouse fibrosarcoma L929 and rat glioma C6 cell lines. A combination of IFN-gamma and IL-1 induced a significant NO release and subsequent reduction of cell viability in tumor cell lines. Acidification of cell culture medium reduced tumor cell NO production in a pH-dependent manner. While the inhibitory effect of acidosis on NO production in C6 cells was associated with a further decrease in cell viability, it completely rescued L929 cells from NO-dependent apoptotic and necrotic death. Acidic pH diminished IFN-gamma+ IL-1-induced expression of inducible NO synthase (iNOS) mRNA and protein, and abolished the activation of iNOS transcription factor IRF-1 in L929 cells. Moreover, extracellular acidosis significantly impaired cytokine-induced phosphorylation of MAP kinase p44/42 (ERK1/2) and subsequent expression of transcription factor c-Fos in L929 cells. Finally, mild acidosis (pH 6.8) augmented, while severe acidosis (pH 6.0) reduced, IFN-gamma-induced iNOS activation/NO release and NO-dependent anticancer activity of rat and mouse macrophages. Taken together, our findings indicate that modulation of macrophage and tumor cell iNOS by an acidic microenvironment might influence the progression of NO-sensitive solid tumors.

Impact of Mycoplasma hyorhinis infection on L-arginine metabolism: differential regulation of the human and murine iNOS gene

Infection with mycoplasma is a common problem in cell cultures, with Mycoplasma hyorhinis being the predominant species. Here we investigate the effect of M. hyorhinis infection on L-arginine metabolism, with focus on iNOS-mediated NO synthesis in murine keratinocytes and the human colon cancer cell line DLD-1. iNOS and arginase are L-arginine-metabolizing enzymes involved in the regulation of inflammatory processes, with NO contributing to innate immunity. In murine cells, M. hyorhinis infection enhances cytokine-induced iNOS expression and augments iNOS activity, whereas in the absence of cytokines it causes de novo induction of iNOS mRNA without subsequent translation into iNOS protein. In turn, arginase-1 mRNA expression is diminished in M. hyorhinis-infected murine keratinocytes, resulting in decreased arginase activity. One of the underlying upstream mechanisms is NF-kappaB activation. In contrast, in human cells neither iNOS mRNA nor protein expression is affected by M. hyorhinis infection, but NO synthesis is enhanced, which may be caused by increased L-arginine import. This demonstrates that infection with M. hyorhinis leads to different effects on gene regulation of the murine and human iNOS gene. Our study underlines the importance of routine checking of cell cultures for mycoplasma contamination, particularly in studies on NO-mediated effects or inflammatory processes.

What sense lies in antisense inhibition of inducible nitric oxide synthase expression?

The impact of nitric oxide (NO) synthesized after activation by proinflammatory cytokines and/or bacterial products by an inducible NO synthase (iNOS) is still contradictory. Expression of iNOS in inflammatory reactions is often found predominantly in cells of epithelial origin, and in these cases NO may serve as a protective agent limiting pathogen spreading, downregulating local inflammatory reactions by inducing production of Th2-like responses in a classical feedback circle, or limiting tissue damage during stress conditions. However, an abundant amount of data on chronic human disorders with predominant proinflammatory Th1-like reactions points to a destructive role of iNOS activity calling for a specific inhibition. Various methods to inhibit iNOS have been established to elucidate a protective versus a destructive role of NO during various stresses. In this review, we focus on antisense (AS)-mediated gene knock-down as a relatively new method to inhibit NO production and summarize the techniques applied and their successes. At least in theory, it provides a specific, rapid, and potentially high-throughput method for inhibiting gene expression and function. We here discuss the opportunities of iNOS-directed AS-ODN, and extensively deal with limitations and experimental problems.

Inhibition of inducible nitric oxide synthase promotes recovery of motor function in rats after sciatic nerve ischemia and reperfusion

PURPOSE

To investigate the effects of inhibition of inducible nitric oxide synthase (iNOS) on the recovery of motor function in the rat sciatic nerve after ischemia and reperfusion injury.

METHODS

A 10-mm segment of the sciatic nerve from 169 rats had 2 hours of ischemia followed by up to 42 days of reperfusion. The animals were divided into 2 groups that received either iNOS inhibitor 1400W or the same volume of sterile water subcutaneously. A walking track test was used to evaluate the motor functional recovery during reperfusion. Statistical analysis was performed for the measurements of the sciatic functional index (SFI) by using 2-way analysis of variance; 1-way analysis of variance was used for the post hoc analysis of specific values at each time point of the SFI measurement.

RESULTS

1400W-treated rats had earlier motor functional recovery than controls, with a significantly improved SFI between days 11 and 28. Histology showed less axonal degeneration and earlier regeneration of nerve fibers in the 1400W group than in the controls. Inducible NOS messenger RNA and protein were up-regulated during the first 3 days of reperfusion but there was a down-regulation of neuronal NOS and up-regulation of endothelial NOS in control animals. 1400W treatment attenuated the increase of iNOS but had no effect on neuronal NOS and endothelial NOS.

CONCLUSIONS

Our results indicate that early inhibition of iNOS appears to be critical for reducing or preventing ischemia and reperfusion injury.

Nitric oxide and the common cold

PURPOSE OF REVIEW

The common cold is a clinical syndrome triggered by a variety of viral pathogens, but rhinoviruses are the most frequent cause. Complications of such infections include sinusitis, otitis media, and exacerbations of asthma and chronic obstructive lung disease. There is growing interest in host innate defence responses that may regulate the severity of viral responses. We will review recent evidence that nitric oxide is an important contributor to the host response during colds.

RECENT FINDINGS

Infection of human airway epithelial cells with human rhinovirus has been shown to lead to the increased expression of inducible nitric oxide synthase both in vitro and in vivo. This increase in epithelial inducible nitric oxide synthase correlates with increased levels of nitric oxide in exhaled air. Importantly, nitric oxide can inhibit human rhinovirus-induced epithelial expression of several pro-inflammatory cytokines and can inhibit viral replication in epithelial cells in vitro. Moreover, nitric oxide can modulate several signal transduction pathways that are associated with cytokine generation. Nitric oxide can also nitrosylate viral proteases and can interact with the immune system. Consistent with these observations, pilot studies have indicated that the increased generation of nitric oxide during rhinovirus infections is associated with fewer symptoms and more rapid viral clearance.

SUMMARY

Further studies are warranted to evaluate the role of nitric oxide in colds and to determine whether the administration of nitric oxide donor compounds could be a viable therapeutic approach for viral exacerbations of airway diseases.

Nitrosative Stress, Heme Oxygenase-1 Expression and Airway Inflammation During Severe Exacerbations of COPD

STUDY OBJECTIVES

The aim of this study was to examine the relationship between airway inflammation, nitrosative stress, heme-oxygenase expression, and acute severe exacerbations of COPD.

DESIGN

We measured heme oxygenase (HO)-1, inducible nitric oxide (NO) synthase expression and nitrotyrosine formation, as well as eosinophilic cationic protein, myeloperoxidase (MPO), interleukin (IL-8), and granulocyte macrophage-colony stimulating factor levels in induced sputum samples from 12 COPD patients (mean +/- SD; FEV1 40 +/- 14% predicted) at the onset of an acute severe exacerbation of COPD requiring hospital admission and 16 weeks after remission.

RESULTS

We demonstrated increased percentages (p = 0.001) and absolute numbers (p = 0.028) of total nitrotyrosine positive (+ve) inflammatory cells (ie, polymorphonuclear cells and macrophages), increased percentages (p = 0.04) and absolute numbers (p = 0.05) of total HO-1 +ve inflammatory cells, and increased MPO (p = 0.005) and IL-8 levels (p = 0.028) during severe exacerbation compared with the stable state.

CONCLUSIONS

Our results support the hypothesis of an involvement of inflammatory and nitrosative stress in severe COPD exacerbations. Future therapeutic strategies may aim at regulating inflammation and NO synthesis during COPD exacerbations.

Activation of caspase-3 is associated with oxidative stress in the hydropic guinea pig cochlea

The aim of this study was to investigate the involvement of oxidative stress and apoptosis in an animal model of Meniere's disease. Endolymphatic hydrops (ELH) is generally accepted as the decisive histological characteristic of Meniere's disease. Closure of the endolymphatic duct (Kimura's method) was used to induce endolymphatic hydrops in guinea pigs. Sham-operated animals served as controls. After 4 weeks the animals operated showed a significant elevation of the hearing thresholds as measured by audiometric brainstem responses (ABR) pre- and postoperatively. Immediately after the second ABR measurement, the animals were sacrificed for further immunohistological examinations of the inner ear with specific antibodies to active caspase-3 (cas-3) as a marker for apoptosis and antibodies to 8-isoprostane (8-iso) and nitrotyrosine (NT) as indicators of oxidative stress. Compared with the sham-operated controls, hydropic cochleae showed strong immunostaining for both oxidative stress markers in spiral ganglion cells, in the blood-vessels and fibrocytes of the lateral wall, as well as in supporting cells of the organ of Corti. Activation of cas-3 in spiral ganglion cells and the lateral wall was found exclusively in hydropic cochleae. Our findings suggest that oxidative stress is involved in the development of endolymphatic hydrops and may lead to cellular damage which induces apoptosis by activation of cas-3. Apoptotic cell death might contribute to the sensorineural hearing loss found in later stages of Meniere's disease.

Relationship between iNOS expression and aortic cell proliferation and apoptosis in an elastase-induced model of aorta aneurysm and the effect of 1400 W administration

BACKGROUND

In the present study, we employed an elastase infusion-dependent abdominal aortic aneurysm (AAA) model to examine inducible nitric oxide synthase (iNOS) expression in relation to cellular proliferation and apoptosis in this pathologic condition. Furthermore, we employed N-(3-(aminomethyl)benzyl)acetamidine (1400 W), a previously shown selective iNOS inhibitor, to further explore this relationship.

METHODS

Adult male Wistar rats were randomized into separate groups. Group A served as a control and received an intra-aortic saline infusion, while groups B, C, and D received an intra-aortic elastase infusion according to standard protocols. The animals in group C were administered postoperatively the highly selective iNOS inhibitor, 1400 W, while rats in group D received regularly the same compound preoperatively and postoperatively. The animals were killed at postoperative days 7 and 14. Aorta diameter and nitric oxide (NO), nitrite/nitrate, and MDA levels were measured. iNOS expression was assessed by immunohistochemistry and Western blot analysis, while Ki-67 immunohistochemistry and TUNEL assay were used to evaluate cellular proliferation and apoptosis, respectively.

RESULTS

Increased iNOS and NO levels accompanied aneurysm development in groups B, C, and D, but these levels were significantly lower in groups C and D, compared with group B. Interestingly, very low but detectable levels of iNOS were found in the control group, indicating a basal constitutive level. Cell growth parameters were augmented in group B compared with group A. In contrast, groups C and D exhibited a significant decrease of the cellular growth parameters but did not attain normal values.

CONCLUSIONS

iNOS-derived NO is associated with the cellular growth parameters of the vessel cells, predominantly smooth muscle cells. Selective iNOS blockage ameliorates the cellular remodeling in AAAs.

Gastric helicobacter infection induces a Th2 phenotype but does not elevate serum cholesterol in mice lacking inducible nitric oxide synthase

Persistent Helicobacter felis infection in (C57BL/6 x 129SvEv)F1 mice induces chronic gastritis. Expression of inducible nitric oxide synthase (iNOS) is upregulated in response to Helicobacter infection. In this study, 20 10-week-old iNOS-/- mice and 20 wild-type [(C57BL/6 x 129SvEv)F1] mice were infected with H. felis by oral gavage and were assessed histologically and serologically at 32 weeks postinfection. Equal numbers of uninfected controls were sham inoculated. The mice were scored for severity of gastric inflammation, hyperplasia, glandular atrophy, and mucous metaplasia in the corpus and for the level of helicobacter colonization. The immunoglobulin G1 (IgG1), IgG2a, and IgG2c antibody responses to H. felis were determined. As a secondary measure, serum cholesterol levels were assessed. iNOS-/- mice have a propensity for increased serum cholesterol, and although controversial, several human epidemiologic studies have demonstrated an association between Helicobacter infection and several risk factors for cardiovascular disease, including elevated serum cholesterol. Nevertheless, no differences in serum cholesterol levels were observed between the H. felis-infected and -uninfected iNOS-/- mice in this study. The uninfected animals had minimal to no gastric pathology. The gastric pathology scores for the infected animals were reduced significantly in the iNOS-deficient mice relative to those for the wild-type mice (all P <0.01). Helicobacter-infected iNOS-/- mice had chronic lymphoid infiltration and negligible to mild glandular atrophy and mucous metaplasia in the fundic mucosa, while H. felis-infected wild-type mice had severe atrophic and metaplastic mucosal changes. The atrophic gastritis in the infected wild-type mice, particularly the female mice, was also accompanied by greater granulocytic infiltration, antral hyperplasia, and diminished antral colonization, unlike that in the infected iNOS-/- mice. iNOS-/- mice developed significantly lower Th1-associated IgG2c antibody responses to H. felis (P <0.0003); the Th2-associated IgG1 responses were similar (P=0.09), suggesting a greater effect of the iNOS defect on Th1 responses. H. felis colonization was significantly greater in the iNOS-deficient mice. These findings are indicative of an impaired Th1 component of the H. felis-induced inflammatory response when the influence of iNOS is removed.

Photocontrol of nitric oxide production in cell culture using a caged isoform selective inhibitor

Over the past decade, multiphoton microscopy has progressed from a photonic novelty to a technique whose application is currently experiencing exponential growth in the biological sciences. A novel application of this technology with significant therapeutic potential is the control of drug activity by multiphoton photolysis of caged therapeutics. As an initial case study, the potent isoform selective inhibitor N-(3-(aminomethyl)benzyl) acetamidine (1400W) of inducible nitric oxide synthase (iNOS) has been conjugated to a caging molecule 6-bromo-7-hydroxy-4-hydroxyquinoline-2-ylmethyl acetyl ester (Bhc). Here we present the first report of a bulk therapeutic effect, inhibition of nitric oxide production, in mammalian cell culture by multiphoton photolysis of a caged drug, Bhc-1400W. Mouse macrophage RAW 264.7 cells induced with bacterial lipopolysaccharides to express iNOS were used to assess the therapeutic value of the conjugated inhibitor. Both 1400W and Bhc-1400W are stable in metabolically active cells and an optimal time interval for the photorelease of the inhibitor was determined. The ratios of the IC(50) values of Bhc-1400W over 1400W calculated in the presence of iNOS enzyme and in RAW 264.7 cell culture are 19 and 100, respectively, indicating that a broad therapeutic range exists in cell culture. Multiphoton uncaging protocols and therapeutic doses of inhibitors were not cytotoxic. Photocontrol of LPS induced nitric oxide production was achieved in mammalian cell culture using a single laser focal volume. This technology has the potential to control active drug concentrations in vivo, a lack of which is one of the main problems currently associated with systemic drug administration.

Inhibition of iNOS with 1400W improves contractile function and alters nos gene and protein expression in reperfused skeletal muscle

This study examined the effects of 1400W, an inhibitor of inducible nitric oxide (iNOS), on contractile function and iNOS expression in reperfused skeletal muscle. The right extensor digitorum longus (EDL) muscle of 104 rats underwent a sham operation or 3-h ischemia followed by 3-h or 24-h reperfusion (I/R). Rats received 3 mg/kg 1400W, 10 mg/kg 1400W, or water subcutaneously. Results showed that EDL contractile function in both 1400W-treated groups significantly outperformed the controls at 24-h but not at 3-h reperfusion. Although iNOS expression increased in all three I/R groups during reperfusion, a significantly smaller increase was found in 1400W-treated muscles after 3-h reperfusion, and more dramatically so after 24-h reperfusion. Our results indicate that inhibition of iNOS preserved the contractile function in reperfused skeletal muscle, perhaps via downregulating iNOS expression. Protection by 1400W at 24-h reperfusion suggests that the role of iNOS in exaggerating reperfusion injury is more prominent in the later stages of injury.

NF-kappaB p65 involves in reperfusion injury and iNOS gene regulation in skeletal muscle

This study investigated the effects of inhibition of NF-kappaB activation on microcirculation and inducible NOS expression in reperfused rat cremaster muscle. The muscle from 16 rats underwent 5-h ischemia and 90-min reperfusion. Each rat received NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC, 150 mg/kg) or phosphate-buffered saline 15 min before reperfusion. Results showed that PDTC treatment had a significant overall increase in muscle blood flow during reperfusion. Blood flow more rapidly recovered to and over baseline in the PDTC-treated group than in controls, with a significant difference at 10-30 min and 70-90 min. Expression of iNOS mRNA had a 167-fold increase from normal in controls, but was significantly (P < 0.05) reduced to a 63-fold increase in PDTC-treated muscles. In addition, PDTC treatment significantly (P < 0.05) decreased a reperfusion-induced increase in activated NF-kappaB p65 and nuclear p65 protein. Our results suggest that NF-kappaB is involved in I/R injury and that inhibition of NF-kappaB p65 activation affords protection against I/R injury, perhaps via downregulating expression of iNOS transcription.

Involvement of iNOS-dependent NO production in the stimulation of osteoclast survival by TNF-alpha

Osteoclasts, cells primarily responsible for bone resorption, differentiate from hematopoietic progenitor cells under the influence of various hormones, cytokines, and differentiation factors. Once fully differentiated, osteoclasts rapidly die in the absence of any survival factor. We have previously shown that tumor necrosis factor alpha (TNF-alpha) promotes the survival of differentiated osteoclasts. The expression of inducible nitric oxide synthase (iNOS) and consequent NO production is often stimulated under inflammatory conditions. In this study, we found that TNF-alpha, but not receptor activator of nuclear factor kappa B ligand and interleukin 1, increased the expression of iNOS both at the mRNA and protein levels. Subsequently, an enhanced NO level was detected both inside the cells and the culture medium of TNF-alpha-stimulated osteoclasts. Blocking NOS activity with L-NAME prevented TNF-alpha-induced NO generation by osteoclasts and the osteoclast survival stimulated by TNF-alpha. The iNOS selective inhibitor L-NIL also suppressed TNF-alpha-induced osteoclast survival, whereas low concentrations of NO releaser NOC-18 were sufficient to promote osteoclast survival. Furthermore, antiapoptotic and caspase suppressive effects of TNF-alpha on osteoclasts were abolished by L-NAME. Our findings indicate that iNOS-dependent NO generation contributes to the survival-promoting function of TNF-alpha in osteoclasts.

Reperfusion injury in skeletal muscle is reduced in inducible nitric oxide synthase knockout mice

Inducible nitric oxide synthase (iNOS) participates in many pathological events, and selective inhibition of iNOS has been shown to reduce ischemia-reperfusion (I/R) injury in different tissues. To further confirm its role in this injury process, I/R injury was observed in denervated cremaster muscles of iNOS-deficient (iNOS−/−) and wild-type mice. After 3-h ischemia and 90-min reperfusion, blood flow in reperfused muscle was 80 ± 8.5% (mean ± SE) of baseline at 10-min reperfusion and completely returned to the preischemia baseline after 20 min in iNOS−/− mice. In contrast, blood flow was 32 ± 7.4% at 10 min and increased to 60 ± 20% of the baseline level at 90 min in wild-type mice ( P < 0.001 vs. iNOS−/− mice at all time points). The increased muscle blood flow in iNOS−/− mice was associated with significantly less vasospasm in all three sizes of arterial vessel size categories. The weight ratio to the contralateral muscle not subjected to I/R was greater in wild-type mice (173 ± 11%) than in iNOS−/− mice (117 ± 3%; P < 0.01). Inflammation and neutrophil extravasation were also more severe in wild-type mice. Western blot analysis demonstrated an absence of iNOS protein band in iNOS−/− mice and upregulation of iNOS protein expression in wild-type mice. Our results confirm the importance of iNOS in I/R injury. Upregulated iNOS exacerbates I/R injury and appears to be a therapeutic target in protection of tissues against this type of injury.

Inducible nitric oxide synthase is not essential for control of Trypanosoma cruzi infection in mice

Immune control of many intracellular pathogens, including Trypanosoma cruzi, is reported to be dependent on the production of nitric oxide. In this study, we show that mice deficient in inducible nitric oxide synthase (iNOS or NOS2) exhibit resistance to T. cruzi infection that is comparable to that of wild-type mice. This is the case for two iNOS-deficient mouse strains, Nos2(tm1Lau) and Nos2 N5, infected with the Brazil or Tulahuen strain of T. cruzi. In all cases, blood parasitemia, tissue parasite load, and survival rates are similar between wild-type and iNOS-deficient mice. In contrast, both wild-type and Nos2(tm1Lau) mice died within 32 days postinfection when treated with the nitric oxide synthase inhibitor aminoguanidine. Increased transcription of NOS1 or NOS3 is not found in iNOS-knockout (KO) mice, indicating that the absence of nitric oxide production through iNOS is not compensated for by increased production of other NOS isoforms. However, Nos2(tm1Lau) mice exhibit enhanced expression of tumor necrosis factor alpha, interleukin-1, and macrophage inflammatory protein 1alpha compared to that of wild-type mice, and these alterations may in part compensate for the lack of iNOS. These results clearly show that iNOS is not required for control of T. cruzi infection in mice.

Nitric oxide involvement in reperfusion injury of denervated muscle

PURPOSE

To investigate whether inhibition of inducible nitric oxide synthase (iNOS) improves microcirculation in denervated and reperfused skeletal muscle.

METHODS

The cremaster muscles of 52 rats received iNOS inhibitor 1400W (3 mg/kg) or phosphate buffered saline (PBS) and underwent either 3 hours of ischemia and 1.5 hours of reperfusion or a sham operation. During reperfusion the vessel diameters were measured by using intravital videomicroscopy and overall muscle blood flow was measured with laser Doppler flowmetry. The expression of NOS messenger RNA (mRNA) and protein was determined by using real-time reverse-transcription polymerase chain reaction and Western blot, respectively.

RESULTS

1400W treatment significantly increased the mean blood flow of the reperfused muscle compared with controls, and this was associated with significantly less vasospasm in 10 to 20 microm, 21 to 40 microm, and 41 to 70 microm arterioles. The expression of iNOS mRNA and protein in controls increased 23-fold and 6-fold from normal, respectively, but was reduced to only a 2-fold increase in the 1400W-treated muscles. The ischemia/reperfusion (I/R)-induced decrease of endothelial NOS (eNOS) and neuronal NOS (nNOS) expression in controls was not significantly changed after 1400W treatment.

CONCLUSIONS

Our data support a nitric oxide-mediated mechanism in reperfusion injury and show the importance of inhibition of iNOS in reducing reperfusion injury in denervated skeletal muscle. Our results suggest potential benefits via inhibition of iNOS to improve clinical outcomes not only for hand surgeons who work in the microsurgery field, but also for other physicians whose work involves ischemia/reperfusion injury.

Roles of heme oxygenase-1 in the antiproliferative and antiapoptotic effects of nitric oxide on Jurkat T cells

Nitric oxide (NO) has been shown to exert antiproliferative and antiapoptotic effects on human T cells. Heme oxygenase-1 (HO-1), which degrades heme into biliverdin, free iron (Fe(2+)), and carbon monoxide (CO), has also been known to have antiproliferative and antiapoptotic effects. Recent evidence suggests that HO-1 is an important cellular target of NO; whether HO-1 expression contributes to the antiproliferative and/or antiapoptotic effects mediated by NO remains to be investigated. In the present study, we examined the effects of NO on HO-1 expression and possible roles of HO-1 in T cell proliferation and apoptosis. Using human Jurkat T cells, we found that the NO donor sodium nitroprusside (SNP) induced HO-1 expression and that preincubation with SNP suppressed T cell proliferation induced by concanavalin A and apoptosis triggered by anti-Fas antibody. Suppressions of T cell proliferation and apoptosis comparable with SNP were also observed when the T cells were preincubated with the HO-1 inducer cobalt protoporphyrin. A phosphorothioate-linked HO-1 antisense oligonucleotide blocked HO-1 expression, and subsequently abrogated the antiproliferative and antiapoptotic effects of SNP. Overexpression of the HO-1 gene after transfection into Jurkat T cells resulted in significant decreases in T cell proliferation and apoptosis. The CO donor tricarbonyldichlororuthenium (II) dimer mimicked the antiproliferative effect of SNP, and the Fe(2+) donor FeSO(4) blocked anti-Fas-induced apoptosis. Taken together, our results suggest that NO induces HO-1 expression in T cells and that suppressions of T cell proliferation and apoptosis afforded by NO are associated with an increased expression of HO-1 by NO.

Microarray analysis of nitric oxide responsive transcripts in Arabidopsis

Nitric oxide (NO) is emerging as an important signalling molecule with diverse physiological functions in plants. In the current study, changes in gene expression in response to 0.1 mm and 1.0 mm sodium nitroprusside (SNP), a donor of NO, were studied in Arabidopsis using the whole genome ATH1 microarray, representing over 24,000 genes. We observed 342 up-regulated and 80 down-regulated genes in response to NO treatments. These included 126 novel genes with unknown functions. Most of these changes were specific to NO treatment, as we observed a reverse trend when the plants were treated with NO scavenger, 2-[4-carboxyphenyl]-4,4,5,5-tetramethylimidazoline-1-oxy-3-oxide (c-PTIO). Hierarchical clustering revealed 162 genes showing a dose-dependent increase in signal from 0.1 mm SNP to 1.0 mm SNP treatment. We observed the up-regulation of several genes encoding disease-resistance proteins, WRKY proteins, transcription factors, zinc finger proteins, glutathione S-transferases, ABC transporters, kinases and biosynthetic genes of ethylene, jasmonic acid, lignin and alkaloids. This report provides an insight into the molecular basis for the seemingly diverse biological functions of NO in plants. Interestingly, about 2.0% of the genes in Arabidopsis responded to NO treatment, about 10% of which were transcription factors. NO may also influence the plant's signal transduction network as indicated by the transcriptional activation of several protein kinases, including a mitogen-activated protein (MAP) kinase. We identified many genes previously not shown to be associated with NO responses in plants, and this is the first report of NO responsive genes based on a whole genome microarray.

Analysis of immunomodulating nitric oxide, iNOS and cytokines mRNA in mouse macrophages induced by microcystin-LR

Microcystins (MCs) are the toxic molecules produced by common cyanobacterium in freshwater blooms. Their toxicities have brought severe health issues to livestock and human being. Microcystin-LR (MC-LR) is one of the most toxic MCs. This paper presents the profile of the immunomodulation of MC-LR to BALB/c mice peritoneal macrophages. Macrophages were stimulated with 100microg/l lipopolysaccharide (LPS) and MC-LR at dose of 1, 10, 100, 1000nmol/l, respectively, for 24h. Nitric oxide (NO) production in cell culture supernatants was quantified by using Griess reagent method. Total RNA was extracted from incubated macrophages then the mRNA abundance of induced nitric oxide synthase (iNOS), IL-1beta, TNF-alpha, GM-CSF, IFN-gamma was monitored by using reverse-transcriptional polymerase chain reaction (RT-PCR). The results demonstrated that NO production, mRNA levels of iNOS, IL-1beta, TNF-alpha were down regulated by MC-LR dose-dependently and mRNA levels of GM-CSF and IFN-gamma were also decreased but in dose-independent manner. Our results illustrated the involvement of NO production, iNOS and some cytokines in mice immune system in microcystin shock.

Enhancement of in vitro hair shaft elongation in follicles stored in buffers that prevent follicle cell apoptosis

BACKGROUND

Viability and survival of stored micrografts during hair follicle transplantation are important limitations of micrograft transplantation procedures. In this study, we investigated the effect of different storage solutions and inhibitors of apoptotic cell death (ACD) on hair follicle cell viability by measuring in vitro hair shaft elongation (HSE) for 5 days.

METHODS

Micrografts from informed patients undergoing routine micrograft transplantation were stored for 5 hours at room temperature in phosphate-buffered salt solution (PBS) or HEPES-buffered Dulbecco's modified Eagle's medium (DMEM), containing different concentrations of the ACD-inhibitors aminoguanidine (AMG), hormones (insulin, hydrocortisone), 14,15-epoxy-eicosatrienoic acid (14,15-EET), or combinations of these.

RESULTS

In vitro, HSE was significantly increased in micrografts stored in DMEM compared with PBS (2.3%+/-0.6% vs. 28.4%+/-3.9%, P<0.0001). DMEM supplemented with AMG (10 microg/mL) or 14,15-EET (1 ng/mL) further increased in vitro HSE (33.9%+/-7.1%, p=0.01, and 32.8%+/-6.1%, P=0.02, respectively). Evaluation of ACD in stored micrografts, performed by determination of cytoplasmic histone-associated DNA fragments, confirmed the results found by HSE. ACD was detectable after a 36-hour culture in serum-containing medium and was higher in micrografts stored in PBS compared with micrografts stored in DMEM (A405nm/A492nm: 1.63+/-0.21 vs. 1.42+/-0.07, respectively; P<0.01). The addition of AMG further decreased serum-induced ACD in the micrografts (DMEM 1.42+/-0.07 vs. DMEM/AMG 0.90+/-0.11, P<0.0001).

CONCLUSION

Our study demonstrated an important role of ACD in micrograft transplantation surgery. Preconditioning of micrografts with storage buffers containing inhibitors of ACD could prevent serum-induced ACD after transplantation and might increase the viability of micrografts and the clinical outcome in micrograft transplantation.

Therapeutic interventions targeting the nitric oxide system: current and potential uses in obstetrics, bone disease and erectile dysfunction

Nitric oxide is involved in a countless number of physiological processes and is known to have cytoprotective as well as cytotoxic effects. Increased knowledge about the multifaceted role of nitric oxide in a variety of disease states has led to the design of multiple treatment strategies involving the nitric oxide system. The current review focuses on recent research advances in the fields of obstetrics, bone disease and erectile dysfunction that have led to current or potential future therapies involving nitric oxide.

Bystander effect in lymphoma cells vicinal to irradiated neoplastic epithelial cells: nitric oxide is involved

Evidence has been accumulated for attached cells demonstrating that nonirradiated cells can have a response to the ionization events delivered to their neighbors. In the present study, we first investigated the bystander responses between suspension and neoplastic cells by coculturing L5178Y (LY) cells with human salivary gland (HSG) cells that had been irradiated with either 290 MeV/u carbon ions or X-rays. After this coculture, the survival of nonirradiated recipient LY cells showed dichotomous responses to the irradiation dose delivered to HSG cells. Apoptosis and necrosis were also produced in a 48 h subculture of the recipient LY cells, and their yield increased, but then had a tendency to decrease when the irradiation dose increased. Treatment of cells with PTIO, a nitric oxide specific scavenger, diminished apoptosis and necrosis of the recipient LY cells to the control level. As an oxidization product of NO, nitrite was detected in the coculture medium and its time course corresponded well to the decrease of the viability of irradiated HSG cells. Moreover, the relationship of the survival and the apoptotic and necrotic production of the recipient LY cells to the nitrite concentration followed a linear-quadratic model. The present findings of NO being involved in the radiation-induced bystander effect may have significance in terms of radiotherapy.

Macrophage overgrowth affects neighboring nonovergrown encapsulated islets

BACKGROUND

Encapsulation significantly prolongs islet graft survival in the absence of immunosuppression. However, encapsulated islet graft survival is limited to periods of several months. Part of the encapsulated islet graft is affected by a nonprogressive pericapsular overgrowth. To investigate whether macrophages on overgrown capsules affect neighboring nonovergrown encapsulated islets, encapsulated islets were studied during coculture.

MATERIALS AND METHODS

Encapsulated islet function, islet vitality, and islet cell replication were assessed, as well as the mRNA expression of Bcl-2, Bax, inducible nitric oxide synthase, and monocyte chemoattractant protein-1 in encapsulated islets after 48 h of culture together with microcapsules with macrophage overgrowth. Overgrown capsules were retrieved from the rat peritoneum, three weeks after implantation of an encapsulated islet graft.

RESULTS

Coculture was associated with inhibition of the stimulated insulin secretion, with decreased cell replication, and with increased cell necrosis, but not with apoptosis of encapsulated islet cells. mRNA expression levels in encapsulated islets after coculture were not different from controls, except for a decrease in Bax mRNA. We found a high level of nitrite, as an indicator of nitric oxide production, but not an increase in inducible nitric oxide synthase mRNA in islets. This, in combination with the absence of increase in monocyte chemoattractant protein-1 mRNA and the lack of apoptosis, indicates that neither interleukin-1beta nor tumor necrosis factor-alpha was responsible for the deleterious effects of coculture on encapsulated islets.

CONCLUSIONS

Nonovergrown encapsulated islets are affected by the overgrowth on encapsulated islets in their close proximity. This overgrowth contains macrophages that produce nitric oxide which, rather than cytokines, may be held responsible for the deleterious effect on the neighboring encapsulated islets.

Nitric oxide regulation of human peripheral blood mononuclear cells: critical time dependence and selectivity for cytokine versus chemokine expression

NO is antiproliferative for T cells and other immune cells, but there is debate over whether it influences cytokine expression and if so whether it shows cytokine selectivity. Furthermore, the NO effect may depend on exposure time. To address these issues, we precultured human PBMC with the NO donors S-nitrosoglutathione (a natural storage form of NO) or S-nitroso-N-acetyl-D-penicillamine for up to 48 h before cell activation and then monitored proliferation and cytokine and chemokine expression. S-nitrosoglutathione or S-nitroso-N-acetyl-D-penicillamine, but not their non-NO-releasing analogues, inhibited proliferation induced by PHA or IL-2, the effect declining progressively from 48 to 0 h pre-exposure to the mitogen. This was accompanied by reduced PHA-induced IL-2 release and reduced IL-2, IFN-gamma, and IL-13 mRNA expression. In contrast, NO did not influence PHA-induced expression of mRNA for the chemokines lymphotactin, RANTES, IFN-gamma-inducible protein, macrophage-inhibitory protein-1alpha, macrophage-inhibitory protein-1beta, macrophage chemoattractant protein-1, and IL-8 or release of RANTES or IL-8. The NO effects were not toxic and were not accompanied by changes in PHA-induced CD25 expression. We conclude that exposure time to NO is critical to altered PBMC responsiveness and that NO inhibits expression of both Th1 and Th2 cytokines but not chemokines.

S-Nitrosation regulates the activation of endogenous procaspase-9 in HT-29 human colon carcinoma cells

Nitric oxide-mediated signals have been suggested to regulate the activity of caspases negatively, yet literature has provided little direct evidence. We show in this paper that cytokines and nitric-oxide synthase (NOS) inhibitors regulate S-nitrosation of an initiator caspase, procaspase-9, in a human colon adenocarcinoma cell line, HT-29. A NOS inhibitor, N(G)-methyl-l-arginine, enhanced the tumor necrosis factor-alpha (TNF-alpha)-induced cleavage of procaspase-9, procaspase-3, and poly-(ADP-ribose) polymerase, as well as the level of apoptosis. N(G)-Methyl-l-arginine, however, did not affect the cleavage of procaspase-8. These results suggest that nitric oxide regulates the cleavage of procaspase-9 and its downstream proteins and, subsequently, apoptosis in HT-29 cells. Labeling S-nitrosated cysteines with a biotin tag enabled us to reveal S-nitrosation of endogenous procaspase-9 that was immunoprecipitated from the HT-29 cell extracts. Furthermore, the treatment with TNF-alpha, as well as NOS inhibitors, decreased interferon-gamma-induced S-nitrosation in procaspase-9. Our results show that S-nitrosation of endogenous procaspase-9 occurs in the HT-29 cells under normal conditions and that denitrosation of procaspase-9 enhances its cleavage and consequent apoptosis. We, therefore, suggest that S-nitrosation regulates activation of endogenous procaspase-9 in HT-29 cells.

New method for analyzing the nitrite level in PC12 cells using capillary electrophoresis

Nitric oxide (NO) is a gaseous molecule shown to have signal transmitter properties in organisms. Direct measurement of NO in physiological conditions has been difficult due to its short lifetime and low concentration. Nitrite has been used as a marker for NO formation in biological systems. Capillary electrophoresis (CE) has been recently used to measure nitrite in biological fluids. The purpose of this study is to analyze nitrite in PC12 cells (pheochromocytoma cell line) using CE. Optimal CE performance was employed with 150 mM Tris-phosphate, 6 microM hexadecyltrimethyammonium chloride buffer at pH 7.0 and a fused-silica column of 57 cm x 75 microm I.D. The signal was measured with a UV detector at 214-nm wavelength and negative potential of 10 kV was applied for nitrite analysis. Under the optimum conditions, we monitored the changes in the concentration of the nitrite levels through synergistic stimulation of tumor necrosis factor alpha plus gamma-interferon in PC12 cells.

Hyperoxia causes inducible nitric oxide synthase-mediated cellular damage to the immature rat brain

Relative hyperoxia is a condition frequently encountered in premature infants, either spontaneously or during treatment in the Neonatal Intensive Care Unit. The effects of high inspiratory oxygen concentrations on immature brain cells and their signaling cascades are largely unknown. The aim of the study was to investigate the effect of hyperoxia on the amount and topographic distribution of iNOS-expression (inducible nitric oxide synthase) in the immature rat brain, and to localize hyperoxia-induced formation of peroxynitrite as a potential marker of cellular damage to immature cerebral structures. Seven-day-old Wistar rat pups were exposed to >80% oxygen for 24 h and were then transcardially perfused. Following paraformaldehyde fixation, brains were paraffin-embedded and immunohistochemically stained for iNOS and nitrotyrosine. iNOS protein was quantified by Western blot; iNOS mRNA expression was studied by RT-PCR. Total brain iNOS mRNA was up-regulated, demonstrating a peak at 6 h following the onset of hyperoxia. Immunohistochemical staining was predominantly observed in microglial cells of hippocampus and frontal cortex with some iNOS reactivity in endothelial and perivascular cells. Nitrotyrosine staining was positive in apical dendrites of neurons in the frontal cortex. There was no positive staining for iNOS or nitrotyrosine in control animals. Hyperoxia causes iNOS mRNA and protein up-regulation in microglial cells of the immature rat brain. Positive neuronal nitrotyrosine staining indicates formation of peroxynitrite with potential deleterious effects for immature cellular structures in the neonatal brain.

Nitric oxide induces polarization of actin in encephalitogenic T cells and inhibits their in vitro trans-endothelial migration in a p70S6 kinase-independent manner

Nitric oxide (NO) inhibits both actively induced and transferred autoimmune encephalomyelitis. To explore potential mechanisms, we examined the ability of NO to inhibit migration of T lymphoblasts through both collagen matrices and monolayers of rat brain endothelial cells. The NO donor 1-hydroxy-2-oxo-3, 3-bis (2-aminoethyl)-1-triazene (HOBAT) inhibited migration in a concentration-dependent manner. NO pretreatment of T cells inhibited migration through untreated endothelial cells, but NO pretreatment of endothelial cells had no inhibitory effect on untreated T cells. Therefore NO's migration inhibitory action was mediated through its effect on T cells and not endothelial cells. HOBAT did not inhibit migration by inducing T-cell death but rather by polarizing the T cells, resulting in a morphology suggestive of migrating cells. P70S6 kinase, shown to have a role in NO-induced migration inhibition in fibroblasts, had no role in the inhibitory effect of NO on T-cell migration. Thus, HOBAT did not alter p70S6K activity nor did rapamycin, a specific inhibitor of p70S6K, inhibit HOBAT-induced T-cell morphological changes or T-cell migration. We suggest that NO-induced morphological changes result in T cells with predefined migratory directionality, thus limiting the ability of these cells to respond to other migratory signals.