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

Defining the metabolic signatures associated with human macrophage polarisation

Macrophages are essential components of the innate immune system that play both homeostatic roles in healthy organs, and host defence functions against pathogens after tissue injury. To accomplish their physiological role, macrophages display different profiles of gene expression, immune function, and metabolic phenotypes that allow these cells to participate in different steps of the inflammatory reaction, from the initiation to the resolution phase. In addition, significant differences exist in the phenotype of macrophages depending on the tissue in which they are present and on the mammalian species. From a metabolic point of view, macrophages are essentially glycolytic cells; however, their metabolic fluxes are dependent on the functional polarisation of these cells. This metabolic and cellular plasticity offers the possibility to interfere with the activity of macrophages to avoid harmful effects due to persistent activation or the release of molecules that delay tissue recovery after injury.

Targeting Nitric Oxide: Say NO to Metastasis

Utilizing targeted therapies capable of reducing cancer metastasis, targeting chemoresistant and self-renewing cancer stem cells, and augmenting the efficacy of systemic chemo/radiotherapies is vital to minimize cancer-associated mortality. Targeting nitric oxide synthase (NOS), a protein within the tumor microenvironment, has gained interest as a promising therapeutic strategy to reduce metastatic capacity and augment the efficacy of chemo/radiotherapies in various solid malignancies. Our review highlights the influence of nitric oxide (NO) in tumor progression and cancer metastasis, as well as promising preclinical studies that evaluated NOS inhibitors as anticancer therapies. Lastly, we highlight the prospects and outstanding challenges of using NOS inhibitors in the clinical setting.

Graphene Particles Interfere with Pro-Inflammatory Polarization of Human Macrophages: Functional and Electrophysiological Evidence

The interaction of two types of fragmented graphene particles (30-160 nm) with human macrophages is studied. Since macrophages have significant phagocytic activity, the incorporation of graphene particles into cells has an effect on the response to functional polarization stimuli, favoring an anti-inflammatory profile. Incubation of macrophages with graphene foam particles, prepared by chemical vapor deposition, and commercially available graphene nanoplatelet particles does not affect cell viability when added at concentrations up to 100 µg mL^-1 ; macrophages exhibit differential quantitative responses to each type of graphene particles. Although both materials elicit similar increases in the release of reactive oxygen species, the impact on the transcriptional regulation associated with the polarization profile is different; graphene nanoplatelets significantly modify this transcriptomic profile. Moreover, these graphene particles differentially affect the motility and phagocytosis of macrophages. After the incorporation of both graphene types into the macrophages, they exhibit specific responses in terms of the mitochondrial oxygen consumption and electrophysiological potassium currents at the cell plasma membrane. These data support the view that the physical structure of the graphene particles has an impact on human macrophage responses, paving the way for the development of new mechanisms to modulate the activity of the immune system.

Nitric Oxide Synthase Inhibitors into the Clinic at Last

The 1998 Nobel Prize in Medicine and Physiology for the discovery of nitric oxide, a nitrogen containing reactive oxygen species (also termed reactive nitrogen or reactive nitrogen/oxygen species) stirred great hopes. Clinical applications, however, have so far pertained exclusively to the downstream signaling of cGMP enhancing drugs such as phosphodiesterase inhibitors and soluble guanylate cyclase stimulators. All clinical attempts, so far, to inhibit NOS have failed even though preclinical models were strikingly positive and clinical biomarkers correlated perfectly. This rather casts doubt on our current way of target identification in drug discovery in general and our way of patient stratification based on correlating but not causal biomarkers or symptoms. The opposite, NO donors, nitrite and enhancing NO synthesis by eNOS/NOS3 recoupling in situations of NO deficiency, are rapidly declining in clinical relevance or hold promise but need yet to enter formal therapeutic guidelines, respectively. Nevertheless, NOS inhibition in situations of NO overproduction often jointly with enhanced superoxide (or hydrogen peroxide production) still holds promise, but most likely only in acute conditions such as neurotrauma (Stover et al., J Neurotrauma 31(19):1599-1606, 2014) and stroke (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019). Conversely, in chronic conditions, long-term inhibition of NOS might be too risky because of off-target effects on eNOS/NOS3 in particular for patients with cardiovascular risks or metabolic and renal diseases. Nitric oxide synthases (NOS) and their role in health (green) and disease (red). Only neuronal/type 1 NOS (NOS1) has a high degree of clinical validation and is in late stage development for traumatic brain injury, followed by a phase II safety/efficacy trial in ischemic stroke. The pathophysiology of NOS1 (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016) is likely to be related to parallel superoxide or hydrogen peroxide formation (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 114(46):12315-12320, 2017; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019) leading to peroxynitrite and protein nitration, etc. Endothelial/type 3 NOS (NOS3) is considered protective only and its inhibition should be avoided. The preclinical evidence for a role of high-output inducible/type 2 NOS (NOS2) isoform in sepsis, asthma, rheumatic arthritis, etc. was high, but all clinical development trials in these indications were neutral despite target engagement being validated. This casts doubt on the role of NOS2 in humans in health and disease (hence the neutral, black coloring).

Induction of Innate Immune Memory by Engineered Nanoparticles in Monocytes/Macrophages: From Hypothesis to Reality

The capacity of engineered nanoparticles to activate cells of the innate immune system, in particular monocytes and macrophages, is considered at the basis of their toxic/inflammatory effects. It is, however, evident that even nanoparticles that do not directly induce inflammatory activation, and are therefore considered as safe, can nevertheless induce epigenetic modifications and affect metabolic pathways in monocytes and macrophages. Since epigenetic and metabolic changes are the main mechanisms of innate memory, we had previously proposed that nanoparticles can induce/modulate innate memory, that is, have the ability of shaping the secondary response to inflammatory challenges. In light of new data, it is now possible to support the original hypothesis and show that different types of nanoparticles can both directly induce innate memory, priming macrophages for a more potent response to subsequent stimuli, and modulate bacteria-induced memory by attenuating the priming-induced enhancement. This evidence raises two important issues. First, in addition to overt toxic/inflammatory effects, we should consider evaluating the capacity to induce innate memory and the related epigenetic and metabolic changes in the immunosafety assessment of nanomaterials, since modulation of innate memory may be at the basis of long-term unwanted immunological effects. The other important consideration is that this capacity of nanomaterials could open a new avenue in immunomodulation and the possibility of using engineered nanomaterials for improving immune responses to vaccines and resistance to infections, and modulate anomalous immune/inflammatory reactions in chronic inflammatory diseases, autoimmunity, and a range of other immune-related pathologies.

Rojo A, Manda G, Boscá L, Cuadrado A. Inflammation in Parkinson's Disease: Mechanisms and Therapeutic Implications

Parkinson's disease (PD) is a common neurodegenerative disorder primarily characterized by the death of dopaminergic neurons that project from the substantia nigra pars compacta. Although the molecular bases for PD development are still little defined, extensive evidence from human samples and animal models support the involvement of inflammation in onset or progression. However, the exact trigger for this response remains unclear. Here, we provide a systematic review of the cellular mediators, i.e., microglia, astroglia and endothelial cells. We also discuss the genetic and transcriptional control of inflammation in PD and the immunomodulatory role of dopamine and reactive oxygen species. Finally, we summarize the preclinical and clinical approaches targeting neuroinflammation in PD.

Self-defense of macrophages against oxidative injury: Fighting for their own survival

Activated macrophages play a central role in both the development and resolution of inflammation. These immune cells need to be functional in harmful conditions with high levels of reactive oxygen and nitrogen species that can damage their basic cell components, which may alter their metabolism. An excessive accumulation of these cell alterations drives macrophages inexorably to cell death, which has been associated to the development of several inflammatory diseases and even with aging in a process termed as "immunosenescence". Macrophages, however, exhibit a prolonged survival in this hostile environment because they equip themselves with a complex network of protective mechanisms. Here we provide an overview of these self-defense mechanisms with special attention being paid to bioactive lipid mediators, NRF2 signaling and metabolic reprogramming.

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

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

Influence of corticosteroid therapy on IL-18 and nitric oxide production during Behçet's disease

BACKGROUND AND AIMS

Behçet's disease (BD) is a chronic multisystemic inflammatory disease with complex etiopathogenesis. Th1-proinflammatory cytokines seem to be involved in its pathogenesis. Our current study aims to evaluate interleukin-18 (IL-18) and nitric oxide (NO) involvement in the development of different clinical manifestations of BD as well as to investigate the corticosteroid therapy effect on this production in Algerian patients.

METHODS

For this purpose, we evaluated in vivo and ex vivo IL-18, interferon-γ (IFN-γ) levels using ELISA and NO production by the Griess' method in naïve-active and corticosteroid-treated BD patients with different clinical manifestations. Additionally, we assessed CD40/CD40L expression by flow cytometrics assay in these groups of patients.

RESULTS AND DISCUSSION

Our results indicate that IL-18 and nitrite levels were higher in naïve-active BD patients. Interestingly, this high production differed according to the clinical manifestations and was associated with an increased risk of mucocutaneous and vascular involvement. Concerning corticosteroid treated-active BD patients, no difference was observed in this production between each clinical subgroup. However, IFN-γ levels increased in all categories of active patients. Interestingly, corticosteroid therapy reduced significantly these inflammatory mediators regardless of the clinical manifestations studied. In addition, the CD40/CD40L expression differed according to the clinical presentations.

CONCLUSION

Collectively, our results suggest that concomitant high production of IL-18 and NO in naïve-active BD patients is related to an increased risk of mucocutaneous lesions and vascular involvement. Moreover, the relationship between these two inflammatory markers could constitute a predictable tool of BD clinical presentations and an early factor of therapy efficiency.

Nitric Oxide Signaling in T Cell-Mediated Immunity

Nitric oxide (NO) is a key messenger in the pathogenesis of inflammation, linking innate and adaptive immunity. By targeting signaling molecules, NO from inducible NO synthase (iNOS) and endothelial (e)NOS affects T helper cell differentiation and the effector functions of T lymphocytes, and is a potential target for therapeutic manipulation. In this review we discuss the regulatory actions exerted by NO on T cell functions, focusing on S-nitrosylation as an important post-translational modification by which NO acts as a signaling molecule during T cell-mediated immunity. We also present recent findings showing novel mechanisms through which NO regulates the activation of human T cells, and consider their potential in strategies to treat tumoral, allergic, and autoimmune diseases.

Metabolic signatures linked to macrophage polarization: from glucose metabolism to oxidative phosphorylation

Macrophages are present in a large variety of locations, playing distinct functions that are determined by its developmental origin and by the nature of the activators of the microenvironment. Macrophage activation can be classified as pro-inflammatory (M1 polarization) or anti-inflammatory-pro-resolution-deactivation (M2), these profiles coexisting in the course of the immune response and playing a relevant functional role in the onset of inflammation (Figure 1). Several groups have analysed the metabolic aspects associated with macrophage activation to answer the question about what changes in the regulation of energy metabolism and biosynthesis of anabolic precursors accompany the different types of polarization and to what extent they are necessary for the expression of the activation phenotypes. The interest of these studies is to regulate macrophage function by altering their metabolic activity in a 'therapeutic way'.

Loss of methylation in CpG sites in the NF-κB enhancer elements of inducible nitric oxide synthase is responsible for gene induction in human articular chondrocytes

OBJECTIVE

To investigate whether the abnormal expression of inducible nitric oxide synthase (iNOS) by osteoarthritic (OA) human chondrocytes is associated with changes in the DNA methylation status in the promoter and/or enhancer elements of iNOS.

METHODS

Expression of iNOS was quantified by quantitative reverse transcriptase-polymerase chain reaction. The DNA methylation status of the iNOS promoter and enhancer regions was determined by bisulfite sequencing or pyrosequencing. The effect of CpG methylation on iNOS promoter and enhancer activities was determined using a CpG-free luciferase vector and a CpG methyltransferase. Cotransfections with expression vectors encoding NF-κB subunits were carried out to analyze iNOS promoter and enhancer activities in response to changes in methylation status.

RESULTS

The 1,000-bp iNOS promoter has only 7 CpG sites, 6 of which were highly methylated in both control and OA samples. The CpG site at -289 and the sites in the starting coding region were largely unmethylated in both groups. The NF-κB enhancer region at -5.8 kb was significantly demethylated in OA samples compared with control samples. This enhancer element was transactivated by cotransfection with the NF-κB subunit p65, alone or together with p50. Critically, methylation treatment of the iNOS enhancer element significantly decreased its activity in a reporter assay.

CONCLUSION

These findings demonstrate the association between demethylation of specific NF-κB-responsive enhancer elements and the activation of iNOS transactivation in human OA chondrocytes, consistent with the differences in methylation status observed in vivo in normal and human OA cartilage and, importantly, show association with the OA process.

Four mood stabilizers commonly induce FEZ1 expression in human astrocytes

OBJECTIVES

  Mood stabilizers influence the morphology, chemotaxis, and survival of neurons, which are considered to be related to the mood-stabilizing effects of these drugs. Although previous studies suggest glial abnormalities in patients with bipolar disorder and an effect of mood stabilizers on certain genes in astrocytes, less is known about the effects of mood stabilizers in astrocytes than in neurons. The present study identifies a common underlying response to mood stabilizers in astrocytes.

METHODS

  Human astrocyte-derived cells (U-87 MG) were treated with the four most commonly used mood stabilizers (lithium, valproic acid, carbamazepine, and lamotrigine) and subjected to microarray gene expression analyses. The most prominently regulated genes were validated by qRT-PCR and western blot analysis. The intercellular localization of one of these regulated genes, fasciculation and elongation protein zeta 1 (FEZ1), was evaluated by immunofluorescence staining.

RESULTS

  The microarray data indicated that FEZ1 was the only gene commonly induced by the four mood stabilizers in human astrocyte-derived cells. An independent experiment confirmed astrocytic FEZ1 induction at both the transcript and protein levels following mood stabilizer treatments. FEZ1 localized to the cytoplasm of transformed and primary astrocytes from the human adult brain.

CONCLUSIONS

  Our data suggest that FEZ1 may play important roles in human astrocytes, and that mood stabilizers might exert their cytoprotective and mood-stabilizing effects by inducing FEZ1 expression in astrocytes.

Interferon-γ and nitric oxide production during Behçet uveitis: immunomodulatory effect of interleukin-10

Uveitis is one of the major manifestations of Behçet Disease, a systemic inflammatory vasculitis. Our aim is to investigate in vivo and in vitro production of interferon (IFN)-γ and nitric oxide (NO) during Behçet uveitis (BU). Moreover, we evaluated the implication of IFN-γ and interleukin (IL)-10 in the regulation of NO production in vitro. Cytokines' concentrations were measured by ELISA, and NO levels were assessed by modified Griess's method. Our results showed that patients with active disease had significant elevation of IFN-γ and NO concentrations in both plasma and peripheral blood mononuclear cell culture supernatants compared with controls (P<0.01) or to patients with inactive disease (P<0.05). Further, IFN-γ induced significantly higher production of NO in cell culture supernatants, whereas IL-10 significantly reduced it (P<0.05). In conclusion, the elevated levels of IFN-γ in vivo and in vitro in patients with BU reflect the implication of this cytokine in the disease physiopathology. These results suggest that IFN-γ, through the induction of NO synthase 2 and the production of NO, is implicated in the genesis of the inflammatory process during active BU; whereas IL-10 seems to have protective properties.

Mechanical stretch enhances NF-kappaB-dependent gene expression and poly(ADP-ribose) synthesis in synovial cells

Temporomandibular joint disorders (TMD) show complex symptoms associated with inflammation, pain and degeneration of the peripheral tissues including synovium. Although it is believed that excessive mechanical stress on synovium causes development of TMD, the molecular mechanism by which mechanical stress triggers TMD has still remained unclear. In order to examine the effect of mechanical stress on synoviocytes, rabbit synovial cells were cyclically stretched in vitro. The stretch efficiently increased the gene expressions of cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and NF-kappaB responsive reporter gene constructs. The interruption of NF-kappaB activating pathway by inhibitors resulted in the abrogation of those expressions, indicating the pivotal role of NF-kappaB in the mechanical stretch-mediated COX-2 and iNOS expressions. In parallel, the stretch remarkably increased NO production and poly(ADP-ribose) (PAR) synthesis, suggesting that excessive amounts of NO causes DNA injury and in turn activates PAR synthesis by poly(ADP-ribose) polymerase (PARP). The inhibition of PAR synthesis by a PARP inhibitor or a radical scavenger enhanced the mechanical stretch-induced gene expressions in a NF-kappaB-independent manner, implying an involvement of PARP in the gene expression. Taken together, these results demonstrate that mechanical stress on synovial cells not only induces gene expressions of COX-2 and iNOS but also affects PAR synthesis.