Natural killer cells and nitric oxide

Mycobacterium tuberculosis suppresses APLP2 expression to enhance its survival in macrophage

Mycobacterium tuberculosis (M.tb), the most successful pathogen responsible for approximately 1.6 million deaths in 2021, employs various strategies to evade host antibacterial defenses, including mechanisms to counteract nitric oxide (NO) and certain cytokines. While Amyloid β (A4) precursor-like protein 2 (Aplp2) has been implicated in various physiological and pathological processes, its role in tuberculosis (TB) pathogenesis remains largely uncharted. This study unveils a significant reduction in Aplp2 levels in TB patients, M.tb-infected macrophages, and mice. Intriguingly, Aplp2 mutation or knockdown results in diminished macrophage-mediated killing of M.tb, accompanied by decreased inducible nitric oxide synthase (iNOS) expression and reduced cytokine production, notably interleukin-1β (Il-1β). Notably, Aplp2 mutant mice exhibit heightened susceptibility to mycobacterial infection, evident through aggravated histopathological damage and increased lung bacterial loads, in contrast to Mycobacterium bovis BCG-infected wild-type (WT) mice. Mechanistically, the cleaved product of APLP2, AICD2, generated by γ-secretase, translocates to the nucleus, where it interacts with p65, culminating in enhanced the nuclear factor κB (NF-κB) transcriptional activity. This interaction triggers the upregulation of Il-1β and iNOS expression. Collectively, our findings illuminate Aplp2's pivotal role in safeguarding against mycobacterial infections by promoting M.tb clearance through NO- or IL-1β-mediated bactericidal effects. Therefore, we unveil a novel immune evasion strategy employed by M.tb, which could potentially serve as a target for innovative TB interventions.

Opportunities for Nitric Oxide in Potentiating Cancer Immunotherapy

Despite nearly 30 years of development and recent highlights of nitric oxide (NO) donors and NO delivery systems in anticancer therapy, the limited understanding of exogenous NO's effects on the immune system has prevented their advancement into clinical use. In particular, the effects of exogenously delivered NO differing from that of endogenous NO has obscured how the potential and functions of NO in anticancer therapy may be estimated and exploited despite the accumulating evidence of NO's cancer therapy-potentiating effects on the immune system. After introducing their fundamentals and characteristics, this review discusses the current mechanistic understanding of NO donors and delivery systems in modulating the immunogenicity of cancer cells as well as the differentiation and functions of innate and adaptive immune cells. Lastly, the potential for the complex modulatory effects of NO with the immune system to be leveraged for therapeutic applications is discussed in the context of recent advancements in the implementation of NO delivery systems for anticancer immunotherapy applications. SIGNIFICANCE STATEMENT: Despite a 30-year history and recent highlights of nitric oxide (NO) donors and delivery systems as anticancer therapeutics, their clinical translation has been limited. Increasing evidence of the complex interactions between NO and the immune system has revealed both the potential and hurdles in their clinical translation. This review summarizes the effects of exogenous NO on cancer and immune cells in vitro and elaborates these effects in the context of recent reports exploiting NO delivery systems in vivo in cancer therapy applications.

Modulating the Antioxidant Response for Better Oxidative Stress-Inducing Therapies: How to Take Advantage of Two Sides of the Same Medal?

Oxidative stress-inducing therapies are characterized as a specific treatment that involves the production of reactive oxygen and nitrogen species (RONS) by external or internal sources. To protect cells against oxidative stress, cells have evolved a strong antioxidant defense system to either prevent RONS formation or scavenge them. The maintenance of the redox balance ensures signal transduction, development, cell proliferation, regulation of the mechanisms of cell death, among others. Oxidative stress can beneficially be used to treat several diseases such as neurodegenerative disorders, heart disease, cancer, and other diseases by regulating the antioxidant system. Understanding the mechanisms of various endogenous antioxidant systems can increase the therapeutic efficacy of oxidative stress-based therapies, leading to clinical success in medical treatment. This review deals with the recent novel findings of various cellular endogenous antioxidant responses behind oxidative stress, highlighting their implication in various human diseases, such as ulcers, skin pathologies, oncology, and viral infections such as SARS-CoV-2.

Sildenafil Citrate Downregulates PDE5A mRNA Expression in Women with Recurrent Pregnancy Loss without Altering Angiogenic Factors-A Preliminary Study

In our previous study, we showed that sildenafil citrate (SC), a selective PDE5A blocker, modulated NK cell activity in patients with recurrent pregnancy loss, which correlated with positive pregnancy outcomes. It was found that NK cells had a pivotal role in decidualization, angiogenesis, spiral artery remodeling, and the regulation of trophoblast invasion. Thus, in the current study, we determined the effects of SC on angiogenic factor expression and production, as well as idNK cell activity in the presence of nitric synthase blocker L-NMMA. Methods: NK cells (CD56⁺) were isolated from the peripheral blood of 15 patients and 15 fertile women on MACS columns and cultured in transformation media containing IL-15, TGF-β, and AZA—a methylation agent—for 7 days in hypoxia (94% N₂, 1% O₂, 5% CO₂). Cultures were set up in four variants: (1) with SC, (2) without SC, (3) with NO, a synthase blocker, and (4) with SC and NO synthase blocker. NK cell activity was determined after 7 days of culturing as CD107a expression after an additional 4h of stimulation with K562 erythroleukemia cells. The expression of the PDE5A, VEGF-A, PIGF, IL-8, and RENBP genes was determined with quantitative real-time PCR (qRT-PCR) using TaqMan probes and ELISA was used to measure the concentrations of VEGF-A, PLGF, IL-8, Ang-I, Ang-II, IFN–γ proteins in culture supernatants after SC supplementation. Results: SC downregulated PDE5A expression and had no effect on other studied angiogenic factors. VEGF-A expression was increased in RPL patients compared with fertile women. Similarly, VEGF production was enhanced in RPL patients’ supernatants and SC increased the concentration of PIGF in culture supernatants. SC did not affect the expression or concentration of other studied factors, nor idNK cell activity, regardless of NO synthase blockade.

The implications of nitric oxide metabolism in the treatment of glial tumors

Glial tumors are the most common intracranial malignancies. Unfortunately, despite such a high prevalence, patients' prognosis is usually poor. It is related to the high invasiveness, tendency to relapse and the resistance of tumors to traditional methods of treatment. An important link in the aspect of these issues may be nitric oxide (NO) metabolism. It is a very complex mechanism with multidirectional effects on the neoplastic process. Depending on the concentration axis, it can both exert pro-tumor action as well as contribute to the inhibition of tumorigenesis. The latest observations show that the control of its metabolism can be very helpful in the development of new methods of treating gliomas, as well as in increasing the effectiveness of the agents currently used. The influence of nitric oxide and nitric oxide synthase (NOS) activity on glioma stem cells seem to be of particular importance. The use of specific inhibitors may allow the reduction of tumor growth and its tendency to relapse. Another important feature of GSCs is their conditioning of glioma resistance to traditional forms of treatment. Recent studies have shown that modulation of NO metabolism can suppress this effect, preventing the induction of radio and chemoresistance. Moreover, nitric oxide is involved in the regulation of a number of immune mechanisms. Adequate modulation of its metabolism may contribute to the induction of an anti-tumor response in the patients' immune system.

Nitric Oxide and Immune Responses in Cancer: Searching for New Therapeutic Strategies

In recent years, there has been an increasing interest in understanding the mysterious functions of nitric oxide (NO) and how this pleiotropic signaling molecule contributes to tumorigenesis. This review attempts to expose and discuss the information available on the immunomodulatory role of NO in cancer and recent approaches to the role of NO donors in the area of immunotherapy. To address the goal, the following databases were searched to identify relevant literature concerning empirical evidence: The Cochrane Library, Pubmed, Medline, EMBASE from 1980 through March 2020. Valuable attempts have been made to develop distinctive NO-based cancer therapy. Although the data do not allow generalization, the evidence seems to indicate that low / moderate levels may favor tumorigenesis while higher levels would exert anti-tumor effects. In this sense, the use of NO donors could have an important therapeutic potential within immunotherapy, although there are still no clinical trials. The emerging understanding of NO-regulated immune responses in cancer may help unravel the recent features of this "double-edged sword" in cancer physiological and pathologic processes and its potential use as a therapeutic agent for cancer treatment. In short, in this review, we discuss the complex cellular mechanism in which NO, as a pleiotropic signaling molecule, participates in cancer pathophysiology. We also debate the dual role of NO in cancer and tumor progression, and clinical approaches for inducible nitric oxide synthase (iNOS) based therapy against cancer.

S-Nitrosylation in Tumor Microenvironment

S-nitrosylation is a selective and reversible post-translational modification of protein thiols by nitric oxide (NO), which is a bioactive signaling molecule, to exert a variety of effects. These effects include the modulation of protein conformation, activity, stability, and protein-protein interactions. S-nitrosylation plays a central role in propagating NO signals within a cell, tissue, and tissue microenvironment, as the nitrosyl moiety can rapidly be transferred from one protein to another upon contact. This modification has also been reported to confer either tumor-suppressing or tumor-promoting effects and is portrayed as a process involved in every stage of cancer progression. In particular, S-nitrosylation has recently been found as an essential regulator of the tumor microenvironment (TME), the environment around a tumor governing the disease pathogenesis. This review aims to outline the effects of S-nitrosylation on different resident cells in the TME and the diverse outcomes in a context-dependent manner. Furthermore, we will discuss the therapeutic potentials of modulating S-nitrosylation levels in tumors.

Implications of SARS-Cov-2 infection on eNOS and iNOS activity: Consequences for the respiratory and vascular systems

Symptoms of COVID-19 range from asymptomatic/mild symptoms to severe illness and death, consequence of an excessive inflammatory process triggered by SARS-CoV-2 infection. The diffuse inflammation leads to endothelium dysfunction in pulmonary blood vessels, uncoupling eNOS activity, lowering NO production, causing pulmonary physiological alterations and coagulopathy. On the other hand, iNOS activity is increased, which may be advantageous for host defense, once NO plays antiviral effects. However, overproduction of NO may be deleterious, generating a pro-inflammatory effect. In this review, we discussed the role of endogenous NO as a protective or deleterious agent of the respiratory and vascular systems, the most affected in COVID-19 patients, focusing on eNOS and iNOS roles. We also reviewed the currently available NO therapies and pointed out possible alternative treatments targeting NO metabolism, which could help mitigate health crises in the present and future CoV's spillovers.

Understanding the tumour micro-environment communication network from an NOS2/COX2 perspective

Recent findings suggest that co-expression of NOS2 and COX2 is a strong prognostic indicator in triple-negative breast cancer patients. These two key inflammation-associated enzymes are responsible for the biosynthesis of NO and PGE2 , respectively, and can exert their effect in both an autocrine and paracrine manner. Impairment of their physiological regulation leads to critical changes in both intra-tumoural and intercellular communication with the immune system and their adaptation to the hypoxic tumour micro-environment. Recent studies have also established a key role of NOS2-COX2 in causing metabolic shift. This review provides an extensive overview of the role of NO and PGE2 in shaping communication between the tumour micro-environment composed of tumour and immune cells that in turn favours tumour progression and metastasis. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

The value of Nigella sativa in the treatment of experimentally induced rhinosinusitis

The aim of this study was to investigate the effect of Nigella sativa and cephalexin in the therapy of experimental bacterial rhinosinusitis. Bacterial rhinosinusitis was induced with Staphylococcus aureus. Rabbits were divided into five groups; control (n = 6), N. sativa 50 mg/ kg/d (n = 6), N. sativa 100 mg/kg/d (n = 6), N. sativa 200 mg/kg/d (n = 6), and cephalexin 20 mg/kg/d (n = 6) groups. N. sativa was given orally for 7 days. The same volume of normal saline (0.9% NaCl) was given as a vehicle to the control group for the same period. After treatment period, sinus mucosa samples were evaluated using stereological and histopathological methods. Half of the maxillary sinus mucosa samples were frozen at -800C for further analysis of NO levels. Pathology revealed a severe acute inflammatory process in rabbits treated with saline. Only mild inflammation was determined in cephalexin group, N. sativa 100 mg/kg/d and N. sativa 200 mg/kg/d groups. The level of NO increased in the saline group was significantly reduced in all treatment groups. N. sativa may prevent histopathological changes of rhinosinusitis via decreased NO levels in a dose dependent manner and can be used in the treatment of rhinosinusitis diseases.

Therapeutic-Gas-Responsive Hydrogel

Nitric oxide (NO) is a crucial signaling molecule with various functions in physiological systems. Due to its potent biological effect, the preparation of responsive biomaterials upon NO having temporally transient properties is a challenging task. This study represents the first therapeutic-gas (i.e., NO)-responsive hydrogel by incorporating a NO-cleavable crosslinker. The hydrogel is rapidly swollen in response to NO, and not to other gases. Furthermore, the NO-responsive gel is converted to enzyme-responsive gels by cascade reactions from an enzyme to NO production for which the NO precursor is a substrate of the enzyme. The application of the hydrogel as a NO-responsive drug-delivery system is proved here by revealing effective protein drug release by NO infusion, and the hydrogel is also shown to be swollen by the NO secreted from the cultured cells. The NO-responsive hydrogel may prove useful in many applications, for example drug-delivery vehicles, inflammation modulators, and as a tissue scaffold.

Immunological consequences of ageing microvascular hemodynamic changes in view of cancer development and treatment

Risk factors of cardiovascular diseases have long been implicated as risk factors for carcinogenesis, but clear explanations for their association have not been presented. In this article, fundamental concepts from carcinogenesis, microvascular hemodynamics, and immunity are collectively reviewed and analyzed in context of the known features of vascular ageing effects, in formulating a theory that suggests reduced microvascular immunity as an important driving factor for carcinogenesis. Furthermore, scientific, preclinical, and clinical evidence that support this new theory are presented in an interdisciplinary manner, offering new explanations to previously unanswered factors that impact cancer risks and its treatment outcome such as chronic drug use, temperature, stress and exercise effects among others. Forward-looking topics discussing the implications of this new idea to cancer immunotherapeutics are also discussed.

NO-dependent attenuation of TPA-induced immunoinflammatory skin changes in Balb/c mice by pindolol, heptaminol or ATRA, but not by verapamil

Recently a mouse skin carcinogenesis study reported that a β-blocker carvedilol displayed antitumor-properties via antihyperplastic effects. However, the antihyperplastic mechanism is unclear as the β-blocker is characterized with multiple pleiotropic effects including stimulation of endothelial NO release and verapamil-like calcium channel blocking activity. To investigate the nature and the origin of the antihyperplastic effects, we tested topical pretreatment with pindolol, heptaminol, ATRA or verapamil against Balb/c mouse ear skin hyperplasia that was induced by TPA. We found that pindolol, heptaminol or ATRA, but not verapamil, inhibited the TPA-induced immunoinflammatory skin changes in an NO-dependent manner, which included epidermal hyperplasia, skin edema and fibrosis. Furthermore, we also observed NO-dependent alleviation of the TPA-induced NK cell depletion in the ear tissues by heptaminol pretreatment. Together our results suggest that stimulation of NO generation from constitutive synthases may be primarily responsible for the reported antihyperplastic and NK cell-preserving effects of the β-blockers, and that similar effects may be observed in other immunity normalizing compounds that also promote endothelial NO synthesis.

Mitochondrial reactive oxygen species and inflammation: Molecular mechanisms, diseases and promising therapies

Over the last few decades, many different groups have been engaged in studies of new roles for mitochondria, particularly the coupling of alterations in the redox pathway with the inflammatory responses involved in different diseases, including Alzheimer's disease, Parkinson's disease, atherosclerosis, cerebral cavernous malformations, cystic fibrosis and cancer. Mitochondrial dysfunction is important in these pathological conditions, suggesting a pivotal role for mitochondria in the coordination of pro-inflammatory signaling from the cytosol and signaling from other subcellular organelles. In this regard, mitochondrial reactive oxygen species are emerging as perfect liaisons that can trigger the assembly and successive activation of large caspase-1- activating complexes known as inflammasomes. This review offers a glimpse into the mechanisms by which inflammasomes are activated by mitochondrial mechanisms, including reactive oxygen species production and mitochondrial Ca²⁺ uptake, and the roles they can play in several inflammatory pathologies.

A Bivalent, Chimeric Rabies Virus Expressing Simian Immunodeficiency Virus Envelope Induces Multifunctional Antibody Responses

We previously showed that a matrix (M) gene-deleted rabies virus (RABV)-based vaccine (RABV-ΔM) is highly immunogenic and induces potent B cell responses in the context of RABV infection. We speculated that RABV-ΔM expressing HIV proteins would also induce potent B cell responses against HIV antigens. As a prerequisite to future studies in nonhuman primates, we completed immunogenicity studies in mice to confirm the ability of RABV-ΔM to induce polyfunctional B cell responses in the context of HIV. To that end, the envelope protein from the mac239 strain of SIV (SIVmac239Env) was cloned into RABV-ΔM, resulting in RABV-ΔM-Env. Infectious virus was recovered following standard methods and propagated on baby hamster kidney cells stably expressing RABV M [>10(7) focus forming units (ffu)/ml]. Western blot analysis of cell lysates or of purified virions confirmed Env expression on the surface of infected cells and within virus particles, respectively. Positive neutralization activity against a neutralization-sensitive SIV strain and to a lesser extent against a neutralization-resistant SIV strain was detected in mice after a single intramuscular inoculation with RABV-ΔM-Env. The quality, but not quantity, of the antibody response was enhanced via boosting with recombinant gp130 or RABV-ΔM-Env as measured by an increase in antibody avidity and a skewing toward a Th1-type antibody response. We also show that an intradermal inoculation induces higher antibodies than an intramuscular or intranasal inoculation. An intradermal inoculation of RABV-ΔM-Env followed by a boost inoculation with recombinant gp130 produced anti-SIV antibodies with neutralizing and nonneutralizing antibody (nNAb) effector functions. Together, RABV-ΔM-Env induces B cells to secrete antibodies against SIV with the potential to clear both "free" and cell-associated virus. Strategies capable of eliciting both NAbs as well as nNAbs might help to improve the efficacy of HIV-1 vaccines.

Spotlights on immunological effects of reactive nitrogen species: When inflammation says nitric oxide

Over the last decades, nitric oxide (NO) has been definitively recognised as one of the key players involved in immunity and inflammation. NO generation was originally described in activated macrophages, which still represent the prototype of NO-producing cells. Notwithstanding, additional cell subsets belonging to both innate and adaptive immunity have been documented to sustain NO propagation by means of the enzymatic activity of different nitric oxide synthase isoforms. Furthermore, due to its chemical characteristics, NO could rapidly react with other free radicals to generate different reactive nitrogen species (RNS), which have been intriguingly associated with many pathological conditions. Nonetheless, the plethora of NO/RNS-mediated effects still remains extremely puzzling. The aim of this manuscript is to dig into the broad literature on the topic to provide intriguing insights on NO-mediated circuits within immune system. We analysed NO and RNS immunological clues arising from their biochemical properties, immunomodulatory activities and finally dealing with their impact on different pathological scenarios with far prompting intriguing perspectives for their pharmacological targeting.

Nitric oxide donors increase PVR/CD155 DNAM-1 ligand expression in multiple myeloma cells: role of DNA damage response activation

Background

DNAX accessory molecule-1 (DNAM-1) is an activating receptor constitutively expressed by macrophages/dendritic cells and by T lymphocytes and Natural Killer (NK) cells, having an important role in anticancer responses; in this regard, combination therapies able to enhance the expression of DNAM-1 ligands on tumor cells are of therapeutic interest. In this study, we investigated the effect of different nitric oxide (NO) donors on the expression of the DNAM-1 ligand Poliovirus Receptor/CD155 (PVR/CD155) in multiple myeloma (MM) cells.

Methods

Six MM cell lines, SKO-007(J3), U266, OPM-2, RPMI-8226, ARK and LP1 were used to investigate the activity of different nitric oxide donors [DETA-NO and the NO-releasing prodrugs NCX4040 (NO-aspirin) and JS-K] on the expression of PVR/CD155, using Flow Cytometry and Real-Time PCR. Western-blot and specific inhibitors were employed to investigate the role of soluble guanylyl cyclase/cGMP and activation of the DNA damage response (DDR).

Results

Our results indicate that increased levels of nitric oxide can upregulate PVR/CD155 cell surface and mRNA expression in MM cells; in addition, exposure to nitric oxide donors renders myeloma cells more efficient to activate NK cell degranulation and enhances their ability to trigger NK cell-mediated cytotoxicity. We found that activation of the soluble guanylyl cyclase and increased cGMP concentrations by nitric oxide is not involved in the up-regulation of ligand expression. On the contrary, treatment of MM cells with nitric oxide donors correlated with the activation of a DNA damage response pathway and inhibition of the ATM /ATR/Chk1/2 kinase activities by specific inhibitors significantly abrogates up-regulation.

Conclusions

The present study provides evidence that regulation of the PVR/CD155 DNAM-1 ligand expression by nitric oxide may represent an additional immune-mediated mechanism and supports the anti-myeloma activity of nitric oxide donors.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1023-5) contains supplementary material, which is available to authorized users.

Immunomodulatory effects of Bacillus subtilis (natto) B4 spores on murine macrophages

To investigate the immunomodulatory effects of Bacillus subtilis (B. subtilis) (natto) B4 spores on murine macrophage, RAW 264.7 cells were cultured alone or with B subtilis (natto) B4 spores at 37°C for 12 hrs, then both cells and culture supernatants were collected for analyses. Exposure of RAW 264.7 cells to B. subtilis (natto) B4 spores had no significant effects on macrophage viability and amounts of extracellular lactate dehydrogenase (LDH). However, it remarkably increased the activities of acid phosphatase (ACP), lactate dehydrogenase (LDH) and inducible nitric oxide synthase (iNOS) in cells and the amounts of nitric oxide (NO) and cytokines (tumor necrosis factor-alpha, interferon-gamma, interleukin [IL]-1 beta, IL-6, IL-12, IL-10 and macrophage inflammatory protein-2) in culture supernatants. These results demonstrate that B. subtilis (natto) B4 spores are harmless to murine macrophages and can stimulate their activation through up-regulation of ACP and LDH activities and enhance their immune function by increasing iNOS activity and stimulating NO and cytokine production. The above findings suggest that B. subtilis (natto) B4 spores have immunomodulatory effects on macrophages.

Expression of innate immune genes, proteins and microRNAs in lung tissue of pigs infected experimentally with influenza virus (H1N2)

This study aimed at providing a better understanding of the involvement of innate immune factors, including miRNA, in the local host response to influenza virus infection. Twenty pigs were challenged by influenza A virus subtype H1N2. Expression of microRNA (miRNA), mRNA and proteins were quantified in lung tissue at different time points after challenge (24 h, 72 h and 14 d post-infection (p.i.). Several groups of genes were significantly regulated according to time point and infection status including pattern recognition receptors (TLR2, TLR3, TLR7, retinoic acid-inducible gene I, melanoma differentiation associated protein-5), IFN and IFN-induced genes (IFN-β, IFN-γ, IRF7, STAT1, ISG15 and OASL), cytokines (IL-1 β, IL-1RN, IL-6, IL-7, IL-10, IL-12A, TNF-α, CCL2, CCL3 and CXCL10) and several acute phase proteins. Likewise, the following miRNAs were differentially expressed in one or more time groups compared with the control pigs: miR-15a, miR-21, miR-146, miR-206, miR-223 and miR-451. At d 1 p.i. lung tissue protein levels of IL-6, IL-12 and IFN-α were significantly increased compared with the control group, and haptoglobin and C-reactive protein were significantly increased at d 3 p.i. Our results suggest that, in addition to a wide range of innate immune factors, miRNAs may also be involved in controlling acute influenza infection in pigs.

Interleukin-32 enhances cytotoxic effect of natural killer cells to cancer cells via activation of death receptor 3

Studies have demonstrated that the anti-tumour effect of natural killer (NK) cells is successful for patients with several cancers. Although interleukin-32 (IL-32) is endogenously expressed in NK cells, cytolytic function of NK cells against cancer cells has not been fully demonstrated. In the present study, we found that the growth of cancer cells was suppressed when colon cancer cells or prostate cancer cells were co-cultured with NK-92 cells, an NK cell line. We also found that the expression of tumour necrosis factor receptor 2 and death receptor 3 (DR3) was increased in PC3 cells, and the expression of FAS and DR3 was increased in SW620 cells by co-culture with NK-92 cells. However, cancer cell growth inhibition and IL-32 expression were abolished when cancer cells were co-cultured with NK cells transfected with small interfering (si) RNA of IL-32. DR3 expression was also diminished by co-culture with IL-32-specific siRNA-transfected NK-92 cells. Expression of APO3L, a ligand of DR3, was elevated in NK cells that were co-cultured with cancer cells. It was also found that expression of apoptosis-related proteins such as cleaved caspase-3 and bax was increased in cancer cells co-cultured with NK-92 cells, but their expression was abolished by co-culture with IL-32 siRNA-transfected NK-92 cells. Moreover, knockdown of DR3 in co-culture of NK-92 cells with cancer cells by siRNA or antibodies of DR3 and APO3L reversed the growth inhibitory effect of NK-92 cells. In conclusion, our study showed that IL-32 enhanced the cytotoxic effect of NK-92 cells on the cancer cells through activation of DR3 and caspase-3.

Acupuncture May Stimulate Anticancer Immunity via Activation of Natural Killer Cells

This article presents the hypothesis that acupuncture enhances anticancer immune functions by stimulating natural killer (NK) cells. It provides background information on acupuncture, summarizes the current scientific understanding of the mechanisms through which NK cells act to eliminate cancer cells, and reviews evidence that acupuncture is associated with increases in NK cell quantity and function in both animals and humans. The key contribution of this article involves the use of cellular immunology and molecular biological theory to interpret and synthesize evidence from disparate animal and human studies in formulating the 'acupuncture immuno-enhancement hypothesis': clinicians may use acupuncture to promote the induction and secretion of NK-cell activating cytokines that engage specific NK cell receptors that endogenously enhance anticancer immune function.

Regulation of lymphocytes by nitric oxide

Shortly after the identification of nitric oxide (NO) as a product of macrophages, it was discovered that NO generated by inducible NO synthase (iNOS) inhibits the proliferation of T lymphocytes. Since then, it has become clear that iNOS activity also regulates the development, differentiation, and/or function of various types of T cells and B cells and also affects NK cells. The three key mechanisms underlying the iNOS-dependent immunoregulation are (a) the modulation of signaling processes by NO, (b) the depletion of arginine, and (c) the alteration of accessory cell functions. This chapter highlights important principles of iNOS-dependent immunoregulation of lymphocytes and also reviews more recent evidence for an effect of endothelial or neuronal NO synthase in lymphocytes.

Ipomoea obscura (L.) enhances the functions of immunological effector cells, inhibits proinflammatory cytokines and nitric oxide production by LPS induced macrophages

Most of the synthetic chemotherapeutic agents available today are immunosuppressant, cytotoxic and exerts variety of side effects. Botanical based immunomodulators are often employed as supportive or adjuvant therapy to overcome the undesired effects of cytotoxic chemotherapeutic agents and to restore normal health. The methanolic extract of traditionally important medicinal plant Ipomoea obscura exhibited immunomodulatory activity in BALB/c mice. Intraperitoneal administration of five doses of the extract (10 mg/kg body wt) was found to enhance the total WBC count (13912 cells/mm(3)) on the 12(th) day, bone marrow cellularity (28.9 x 10(6)cells/femur) and number of alpha-esterase positive cells (1246 cells/4000 cells). Treatment with the extract along with the antigen, sheep red blood cells (SRBC), produced an enhancement in the circulating antibody titer and the number of plaque forming cells (PFC) in the spleen. Maximum number of PFC (267.6 PFC/10(6) spleen cells) was obtained on the 6(th) day. At the same time administration of Ipomoea obscura extract significantly reduced the elevated levels of proinflammatory cytokines and nitric oxide production by lipopolysaccharide stimulated macrophages. These results indicate the immunomodulatory activity of the alcoholic extract of Ipomoea obscura.

Infections

This chapter reviews the epidemiological evidence implicating infectious pathogens as triggers and will discuss the mechanisms of interaction between the host–pathogen response and preexisting airway pathology that result in an exacerbation. Asthma is a multifaceted syndrome involving atopy, bronchial hyperreactivity, and IgE and non-IgE-mediated acute and chronic immune responses. The asthmatic airway is characterized by an infiltrate of eosinophils and of T-lymphocytes expressing the type 2 cytokines IL-4, IL-5, and IL-13. Trigger factors associated with acute exacerbations of asthma include exposure to environmental allergens, especially animals, molds, pollens and mites, cold, exercise, and drugs. The frequency of exacerbations is a major factor in the quality of life of patients with COPD. The typical clinical features of an exacerbation include increased dyspnea, wheezing, cough, sputum production, and worsened gas exchange. Although noninfectious causes of exacerbations such as allergy, air pollution, or inhaled irritants including cigarette smoke may be important, acute airway infections are the major precipitants. The infection and consequent host inflammatory response result in increased airway obstruction. The success of vaccination to prevent respiratory virus infections has been limited by significant variation within the major virus types causing disease. Currently much of the treatment of infective exacerbations of asthma and COPD is symptomatic, consisting of increased bronchodilators, either short-acting β 2—agonists in inhaled or intravenous form or anticholinergics or theophyllines, or supportive in the form of oxygen and in severe cases noninvasive or invasive ventilatory measures.

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.

Metabolic mechanisms of tumor resistance to T cell effector function

Established tumors develop ways to elude destruction by the host immune system. Recent work has revealed that tumors can take advantage of the generation of metabolic dysregulation to inhibit immune responses. Effector T-cell functions are particularly sensitive to nutrient availability in the tumor microenvironment. In this review, we highlight experimental data supporting the importance of glucose, oxygen, tryptophan, and arginine for optimal T-cell function, and the mechanisms by which these nutrients may become depleted in the tumor microenvironment. These observations provide a conceptual framework for modulating metabolic features of the T cell-tumor interaction, toward the end of promoting more effective immune-mediated tumor destruction in vivo.

Humoral immunity to HIV-1: neutralization and beyond

Humoral immunity is considered a key component of effective vaccines against HIV-1. Hence, an enormous effort has been put into investigating the neutralizing antibody response to HIV-1 over the past 20 years which generated key information on epitope specificity, potency, breadth and in vivo activity of the neutralizing antibodies. Less clear is still the role of antibody-mediated effector functions (antibody-dependent cellular cytotoxicity, phagocytosis, complement system) and uncertainty prevails whether Fc-mediated mechanisms are largely beneficial or detrimental for the host. The current knowledge on the manifold functions of the humoral immune response in HIV infection, their underlying mechanisms and potential in vaccine-induced immunity will be discussed in this review.

Vitamin C supplementation influences the antioxidant response and nitric oxide handling of erythrocytes and lymphocytes to diving apnea

OBJECTIVE

We have investigated the influence of vitamin C diet supplementation on the antioxidant response and nitrite levels in lymphocytes and erythrocytes during diving apnea.

SUBJECTS

Seven male professional apnea divers participated in a double blind crossover study. Divers were randomly assigned to either vitamin C supplemented or placebo groups. The subjects did not take any other supplements than the ones provided for this study.

INTERVENTION

One group was supplemented with vitamin C capsules (1 g per day) for 7 days while the other group took a placebo composed of lactose. The usual dietary habits of participants were assessed using a self-reported 7-days 24-h recall before the day of the study. Blood samples were taken under basal conditions, immediately after diving apnea for 4 h and after 1 h of recovery.

RESULTS

Catalase activity increased in erythrocytes (23%) and superoxide dismutase increased in lymphocytes (35%) during the recovery only in the placebo group. Lymphocyte ascorbate levels increased in the supplemented group after diving (85%) and maintained high at recovery. Plasma nitrite levels increased about twofold in both groups during the recovery. Erythrocyte nitrite levels increased after diving (50%) and about twofold during the recovery in the supplemented group. Nitrite levels and iNOS levels in lymphocytes were higher in the placebo group than in the supplemented during the recovery. Erythrocyte carbonyl derivates were unchanged in all situations.

CONCLUSIONS

Vitamin C supplementation influenced the antioxidant response and NO handling in erythrocytes and lymphocytes to the oxidative stress induced by hypoxia-reoxygenation.

Nitric oxide released by accessory cells mediates the gastrin-releasing peptide effect on murine lymphocyte chemotaxis

Several neuropeptides, including gastrin-releasing peptide (GRP), modulate the immune response, specifically lymphocyte chemotaxis. In the present work the effect of GRP on the chemotaxis of murine lymphocytes from different immune locations in both, total leukocyte populations and populations depleted of adherent cells have been studied. Specificity of the GRP effect on chemotaxis using an antagonist of the GRP receptor, as well as the implication of nitric oxide (NO), using inhibitors of NO synthase and donors of NO, were investigated. The effects of GRP stimulating the chemotaxis of lymphocytes from peritoneum, axillary nodes and spleen and decreasing the chemotaxis from thymus were receptor-specific and disappeared in lymphocytes from populations depleted of adherent cells. NO synthase inhibitors blocked the GRP effect on lymphocyte chemotaxis, and this action was reversed in the presence of l-arginine. Thus, the effect of GRP on murine lymphocyte chemotaxis appears to be mediated by NO secreted by adherent cells.

Distinct roles of reactive nitrogen and oxygen species to control infection with the facultative intracellular bacterium Francisella tularensis

Reactive nitrogen species (RNS) and reactive oxygen species (ROS) are important mediators of the bactericidal host response. We investigated the contribution of these two mediators to the control of infection with the facultative intracellular bacterium Francisella tularensis. When intradermally infected with the live vaccine strain F. tularensis LVS, mice deficient in production of RNS (iNOS(-/-) mice) or in production of ROS by the phagocyte oxidase (p47(phox-/-) mice) showed compromised resistance to infection. The 50% lethal dose (LD(50)) for iNOS(-/-) mice was <20 CFU, and the LD(50) for p47(phox-/-) mice was 4,400 CFU, compared to an LD(50) of >500,000 CFU for wild-type mice. The iNOS(-/-) mice survived for 26.4 +/- 1.8 days, and the p47(phox-/-) mice survived for 10.1 +/- 1.3 days. During the course of infection, the serum levels of gamma interferon (IFN-gamma) and interleukin-6 were higher in iNOS(-/-) and p47(phox-/-) mice than in wild-type mice. Histological examination of livers of iNOS(-/-) mice revealed severe liver pathology. Splenocytes obtained 5 weeks after primary infection from antibiotic-treated iNOS(-/-) mice showed an in vitro recall response that was similar in magnitude and greater secretion of IFN-gamma compared to cells obtained from wild-type mice. In summary, mice lacking expression of RNS or ROS showed extreme susceptibility to infection with F. tularensis LVS. The roles of RNS and ROS seemed to be distinct since mice deficient in production of ROS showed dissemination of infection and died during the early phase of infection, whereas RNS deficiency led to severe liver pathology and a contracted course of infection.

Immune responses to HTLV-I(ACH) during acute infection of pig-tailed macaques

Human T cell lymphotropic virus type 1 (HTLV-I) is causally linked to adult T cell leukemia/lymphoma (ATL) and a chronic progressive neurological disease, HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). A nonhuman primate model that reproduces disease symptoms seen in HTLV-I-infected humans might facilitate identification of initial immune responses to the virus and an understanding of pathogenic mechanisms in HTLV-I-related disease. Previously, we showed that infection of pig-tailed macaques with HTLV-I(ACH) is associated with multiple signs of disease characteristic of both HAM/TSP and ATL. We report here that within the first few weeks after HTLV-I(ACH) infection of pig-tailed macaques, serum concentrations of interferon (IFN)-alpha increased and interleukin-12 decreased transiently, levels of nitric oxide were elevated, and activation of CD4(+) and CD8(+) lymphocytes and CD16(+) natural killer cells in peripheral blood were observed. HTLV-I(ACH) infection elicited virus-specific antibodies in all four animals within 4 to 6 weeks; however, Tax-specific lymphoproliferative responses were not detected until 25-29 weeks after infection in all four macaques. IFN-gamma production by peripheral blood cells stimulated with a Tax or Gag peptide was detected to varying degrees in all four animals by ELISPOT assay. Peripheral blood lymphocytes from one animal that developed only a marginal antigen-specific cellular response were unresponsive to mitogen stimulation during the last few weeks preceding its death from a rapidly progressive disease syndrome associated with HTLV-I(ACH) infection of pig-tailed macaques. The results show that during the first few months after HTLV-I(ACH) infection, activation of both innate and adaptive immunity, limited virus-specific cellular responses, sustained immune system activation, and, in some cases, immunodeficiency were evident. Thus, this animal model might be valuable for understanding early stages of infection and causes of immune system dysregulation in HTLV-I-infected humans.

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.

Host defense function of the airway epithelium in health and disease: clinical background

Respiratory infection is extremely common and a major cause of morbidity and mortality worldwide. The airway epithelium has an important role in host defense against infection and this is illustrated in this review by considering infection by respiratory viruses. In patients with asthma or chronic obstructive pulmonary disease, respiratory viruses are a common trigger of exacerbations. Rhinoviruses (RV) are the most common virus type detected. Knowledge of the immunopathogenesis of such RV-induced exacerbations remains limited, but information is available from in vitro and from in vivo studies, especially of experimental infection in human volunteers. RV infects and replicates within epithelial cells (EC) of the lower respiratory tract. EC are an important component of the innate-immune response to RV infection. The interaction between virus and the intracellular signaling pathways of the host cell results in activation of potentially antiviral mechanisms, including type 1 interferons and nitric oxide, and in the production of cytokines and chemokines [interleukin (IL)-1 beta, IL-6, IL-8, IL-11, IL-16, tumor necrosis factor alpha, granulocyte macrophage-colony stimulating factor, growth-regulated oncogene-alpha, epithelial neutrophil-activating protein-78, regulated on activation, normal T expressed and secreted, eotaxin 1/2, macrophage-inflammatory protein-1 alpha], which influence the subsequent induced innate- and specific-immune response. Although this is beneficial in facilitating clearance of virus from the respiratory tract, the generation of proinflammatory mediators and the recruitment of inflammatory cells result in a degree of immunopathology and may amplify pre-existing airway inflammation. Further research will be necessary to determine whether modification of EC responses to respiratory virus infection will be of therapeutic benefit.

Arrest of B16 melanoma cells in the mouse pulmonary microcirculation induces endothelial nitric oxide synthase-dependent nitric oxide release that is cytotoxic to the tumor cells

Metastatic cancer cells seed the lung via blood vessels. Because endothelial cells generate nitric oxide (NO) in response to shear stress, we postulated that the arrest of cancer cells in the pulmonary microcirculation causes the release of NO in the lung. After intravenous injection of B16F1 melanoma cells, pulmonary NO increased sevenfold throughout 20 minutes and approached basal levels by 4 hours. NO induction was blocked by N(G)-nitro-L-arginine methyl ester (L-NAME) and was not observed in endothelial nitric oxide synthase (eNOS)-deficient mice. NO production, visualized ex vivo with the fluorescent NO probe diaminofluorescein diacetate, increased rapidly at the site of tumor cell arrest, and continued to increase throughout 20 minutes. Arrested tumor cells underwent apoptosis with apoptotic counts more than threefold over baseline at 8 and 48 hours. Neither the NO signals nor increased apoptosis were seen in eNOS knockout mice or mice pretreated with L-NAME. At 48 hours, 83% of the arrested cells had cleared from the lungs of wild-type mice but only approximately 55% of the cells cleared from eNOS-deficient or L-NAME pretreated mice. eNOS knockout and L-NAME-treated mice had twofold to fivefold more metastases than wild-type mice, measured by the number of surface nodules or by histomorphometry. We conclude that tumor cell arrest in the pulmonary microcirculation induces eNOS-dependent NO release by the endothelium adjacent to the arrested tumor cells and that NO is one factor that causes tumor cell apoptosis, clearance from the lung, and inhibition of metastasis.

Nitric oxide: a regulator of mast cell activation and mast cell-mediated inflammation

Nitric oxide (NO) plays diverse roles in physiological and pathological processes. During immune and inflammatory responses, for example in asthma, NO is generated at relatively high and sustained levels by the inducible form of nitric oxide synthase (NOS-2). NOS-2 derived NO regulates the function, growth, death and survival of many immune and inflammatory cell types. In the case of mast cells, NO suppresses antigen-induced degranulation, mediator release, and cytokine expression. The action of NO on mast cells is time dependent, requiring several hours, and noncGMP mediated, most probably involving chemical modification of proteins. NO inhibits a number of mast cell-dependent inflammatory processes in vivo, including histamine mediated vasodilatation, vasopermeation and leucocyte-endothelial cell attachment. In human asthma and animal models of lung inflammation the role of NO is harder to define. However, although there are conflicting data, the balance of evidence favours a predominantly protective role for NO. Mimicking or targeting NO dependent pathways may prove to be a valuable therapeutic approach to mast cell mediated diseases.

Nitric oxide in immunity and inflammation

Nitric oxide (NO) is synthesised by many cell types involved in immunity and inflammation. The principal enzyme involved is the inducible type-2 isoform of nitric oxide synthase (NOS-2), which produces high-level sustained NO synthesis. 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. NO does not act through a receptor-its target cell specificity depends on its concentration, its chemical reactivity, the vicinity of target cells and the way that target cells are programmed to respond. At high concentrations as generated by NOS-2, NO is rapidly oxidised to reactive nitrogen oxide species (RNOS) that mediate most of the immunological effects of NOS-2-derived NO. RNOS can S-nitrosate thiols to modify key signalling molecules such as kinases and transcription factors. Several key enzymes in mitochondrial respiration are also inhibited by RNOS and this leads to a depletion of ATP and cellular energy. A combination of these interactions may explain the multiple actions of NO in the regulation of immune and inflammatory cells.