Endothelial nitric oxide synthase regulates T cell receptor signaling at the immunological synapse

B7-H4 reduces the infiltration of CD8+T cells and induces their anti-tumor dysfunction in gliomas

B7-H4 is a promising immune checkpoint molecule in tumor immunotherapy. Our previous study showed that high B7-H4 expression was strongly correlated with deficiency in tumor infiltrated lymphocytes (TILs) in glioma patients. On this basis, we investigated the impact of B7-H4 on CD8+TILs in gliomas and the associated molecular mechanism here. B7-H4-positive tumor samples (n=129) from our glioma cohort were used to assess B7-H4 expression and CD8+TIL quantification by immunohistochemistry. CD8+TILs from five glioma patients cultured with B7-H4 protein were used to evaluate anti-tumor dysfunction by flow cytometry and ELISpot. An orthotopic murine glioma model was used to investigate the role of B7-H4 in glioma CD8+TILs by immunohisto- chemistry and flow cytometry. CD8+TILs from glioma patients cultured with B7-H4 protein were used to explore the potential molecular mechanism by RNA sequencing and western blot. Our results showed that glioma CD8+TIL density was negatively correlated with B7-H4 expression both in glioma patient cohort (P < 0.05) and orthotopic glioma murine model (P < 0.01). B7-H4 also lowered the expression of CD137 and CD103 (P < 0.05 for both) in glioma CD8+TILs and reduced their secretion of the anti-tumor cytokines IFN-γ and TNF-α (P < 0.01 for both) in a dose-dependent manner. Furthermore, B7-H4 was found to induce early dysfunction of glioma CD8+TILs by downregulating the phosphorylation of AKT and eNOS (P < 0.05 for both). In conclusion, B7-H4 reduced the infiltration of glioma CD8+TILs and induced an anti-tumor dysfunction phenotype. B7-H4 may also impair the anti-tumor function of glioma CD8+TILs via the AKT-eNOS pathway. These results indicated that B7-H4 may serve as a potential target in future glioma immunotherapy.

GSNOR overexpression enhances CAR-T cell stemness and anti-tumor function by enforcing mitochondrial fitness

Chimeric antigen receptor-T (CAR-T) cell has been developed as a promising agent for patients with refractory or relapsed lymphoma and leukemia, but not all the recipients could achieve a long-lasting remission. The limited capacity of in vivo expansion and memory differentiation post activation is one of the major reasons for suboptimal CAR-T therapeutic efficiency. Nitric oxide (NO) plays multifaceted roles in mitochondrial dynamics and T cell activation, but its function on CAR-T cell persistence and anti-tumor efficacy remains unknown. Herein, we found the continuous signaling from CAR not only promotes excessive NO production, but also suppressed S-nitrosoglutathione reductase (GSNOR) expression in T cells, which collectively led to increased protein S-nitrosylation, resulting in impaired mitochondrial fitness and deficiency of T cell stemness. Intriguingly, enforced expression of GSNOR promoted memory differentiation of CAR-T cell after immune activation, rendered CAR-T better resistance to mitochondrial dysfunction, further enhanced CAR-T cell expansion and anti-tumor capacity in vitro and in a mouse tumor model. Thus, we revealed a critical role of NO in restricting CAR-T cell persistence and functionality, and defined that GSNOR overexpression may provide a solution to combat NO stress and render patients with more durable protection from CAR-T therapy.

Biopterin metabolism and nitric oxide recoupling in cancer

Tetrahydrobiopterin is a cofactor necessary for the activity of several enzymes, the most studied of which is nitric oxide synthase. The role of this cofactor-enzyme relationship in vascular biology is well established. Recently, tetrahydrobiopterin metabolism has received increasing attention in the field of cancer immunology and immunotherapy due to its involvement in the cytotoxic T cell response. Past research has demonstrated that when the availability of BH4 is low, as it is in chronic inflammatory conditions and tumors, electron transfer in the active site of nitric oxide synthase becomes uncoupled from the oxidation of arginine. This results in the production of radical species that are capable of a direct attack on tetrahydrobiopterin, further depleting its local availability. This feedforward loop may act like a molecular switch, reinforcing low tetrahydrobiopterin levels leading to altered NO signaling, restrained immune effector activity, and perpetual vascular inflammation within the tumor microenvironment. In this review, we discuss the evidence for this underappreciated mechanism in different aspects of tumor progression and therapeutic responses. Furthermore, we discuss the preclinical evidence supporting a clinical role for tetrahydrobiopterin supplementation to enhance immunotherapy and radiotherapy for solid tumors and the potential safety concerns.

Nitric Oxide Synthases in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by severe joint damage and disability. However, the specific mechanism of RA has not been thoroughly clarified over the past decade. Nitric oxide (NO), a kind of gas messenger molecule with many molecular targets, is demonstrated to have significant roles in histopathology and homeostasis. Three nitric oxide synthases (NOS) are related to producing NO and regulating the generation of NO. Based on the latest studies, NOS/NO signaling pathways play a key role in the pathogenesis of RA. Overproduction of NO can induce the generation and release of inflammatory cytokines and act as free radical gas to accumulate and trigger oxidative stress, which can involve in the pathogenesis of RA. Therefore, targeting NOS and its upstream and downstream signaling pathways may be an effective approach to managing RA. This review clearly summarizes the NOS/NO signaling pathway, the pathological changes of RA, the involvement of NOS/NO in RA pathogenesis and the conventional and novel drugs based on NOS/NO signaling pathways that are still in clinical trials and have good therapeutic potential in recent years, with an aim to provide a theoretical basis for further exploration of the role of NOS/NO in the pathogenesis, prevention and treatment of RA.

Tingli Dazao Xiefei Decoction ameliorates asthma in vivo and in vitro from lung to intestine by modifying NO-CO metabolic disorder mediated inflammation, immune imbalance, cellular barrier damage, oxidative stress and intestinal bacterial disorders

ETHNOPHARMACOLOGICAL RELEVANCE

Asthma is a chronic airway inflammatory disease. Current treatment of mainstream medications has significant side effects. There is growing evidence that the refractoriness of asthma is closely related to common changes in the lung and intestine. The lungs and intestines, as sites of frequent gas exchange in the body, are widely populated with gas signaling molecules NO and CO, which constitute NO-CO metabolism and may be relevant to the pathogenesis of asthma in the lung and intestine. The Chinese herbal formula Tingli Dazao Xiefei Decoction (TD) is commonly used in clinical practice to treat asthma with good efficacy, but there are few systematic evaluations of the efficacy of asthma on NO-CO metabolism, and the mode of action of its improving effect on the lung and intestine is unclear.

AIM OF THE STUDY

To investigate the effect of TD on the lung and intestine of asthmatic rats based on NO-CO metabolism.

MATERIALS AND METHODS

In vivo, we established a rat asthma model by intraperitoneal injection of sensitizing solution with OVA atomization, followed by intervention by gavage administration of TD. We simultaneously examined alterations in basal function, pathology, NO-CO metabolism, inflammation and immune cell homeostasis in the lungs and intestines of asthmatic rats, and detected changes in intestinal flora by macrogenome sequencing technology, with a view to multi-angle evaluation of the treatment effects of TD on asthmatic rats. In vitro, lung cells BEAS-2B and intestinal cells NCM-460 were used to establish a model of lung injury causing intestinal injury using LPS and co-culture chambers, and lung cells or intestinal cells TD-containing serum was administered to intervene. Changes in inflammatory, NO-CO metabolism-related, cell barrier-related and oxidative stress indicators were measured in lung cells and intestinal cells to evaluate TD on intestinal injury by way of amelioration and in-depth mechanism.

RESULTS

In vivo, our results showed significant basal functional impairment in the lung and intestine of asthmatic rats, and an inflammatory response, immune cell imbalance and intestinal flora disturbance elicited by NO-CO metabolic disorders were observed (P < 0.05 or 0.01). The administration of TD was shown to deliver a multidimensional amelioration of the impairment induced by NO-CO metabolic disorders (P < 0.05 or 0.01). In vitro, the results showed that LPS-induced lung cells BEAS-2B injury could cause NO-CO metabolic disorder-induced inflammatory response, cell permeability damage and oxidative stress damage in intestinal cells NCM-460 (P < 0.01). The ameliorative effect on intestinal cells NCM-460 could only be exerted when TD-containing serum interfered with lung cells BEAS-2B (P < 0.01), suggesting that the intestinal ameliorative effect of TD may be exerted indirectly through the lung.

CONCLUSION

TD can ameliorate NO-CO metabolism in the lung and thus achieve the indirectly amelioration of NO-CO metabolism in the intestine, ultimately achieving co-regulation of lung and intestinal inflammation, immune imbalance, cellular barrier damage, oxidative stress and intestinal bacterial disorders in asthma in vivo and in vitro. Targeting lung and intestinal NO-CO metabolic disorders in asthma may be a new therapeutic idea and strategy for asthma.

Lymphostatin, a virulence factor of attaching and effacing Escherichia coli, inhibits proliferation and cytokine responses of human T cells in a manner associated with cell cycle arrest but not apoptosis or necrosis

Lymphostatin is a virulence factor of enteropathogenic E. coli (EPEC) and non-O157 serogroup enterohaemorrhagic E. coli. Previous studies using whole-cell lysates of EPEC showed that lymphostatin inhibits the mitogen-activated proliferation of bulk human peripheral blood mononuclear cells (PBMCs) and the production of cytokines IL-2, IL-4, IL-5, and IFN-γ. Here, we used highly purified lymphostatin and PBMC-derived T cells to show that lymphostatin inhibits anti-CD3/anti-CD28-activated proliferation of human CD4⁺ and CD8⁺ T cells and blocks the synthesis of IL-2, IL-4, IL-10 and IFN-γ without affecting cell viability and in a manner dependent on an N-terminal DTD glycosyltransferase motif. Such inhibition was not observed with T cells activated by phorbol 12-myristate 13-acetate and ionomycin, implying that lymphostatin targets T cell receptor signaling. Analysis of the expression of CD69 indicated that lymphostatin suppresses T cell activation at an early stage and no impacts on apoptosis or necrosis were observed. Flow cytometric analysis of the DNA content of lymphostatin-treated CD4⁺ and CD8⁺ T cells showed a concentration- and DTD-dependent accumulation of the cells in the G0/G1 phase of the cell cycle, and corresponding reduction of the percentage of cells in S phase. Consistent with this, we found a marked reduction in the abundance of cyclins D3, E and A and loss of phosphorylated Rb over time in activated T cells from 8 donors treated with lymphostatin. Moreover, the cyclin-dependent kinase (cdk) inhibitor p27^kip1, which inhibits progression of the cell cycle at G1 by acting on cyclin E-cdk2 or cyclin D-cdk4 complexes, was found to be accumulated in lymphostatin-treated T cells. Analysis of the abundance of phosphorylated kinases involved in signal transduction found that 30 of 39 were reduced in abundance following lymphostatin treatment of T cells from 5 donors, albeit not significantly so. Our data provide novel insights into the mode of action of lymphostatin on human T lymphocytes.

Inflammation of the Human Dental Pulp Induces Phosphorylation of eNOS at Thr495 in Blood Vessels

The activity of endothelial nitric oxide synthase (eNOS) in endothelial cells increased with the phosphorylation of the enzyme at Ser1177 and decreased at Thr495. The regulation of the phosphorylation sites of eNOS at Ser1177 and Thr495 in blood vessels of the healthy and inflamed human dental pulp is unknown. To investigate this, healthy and carious human third molars were immersion-fixed and decalcified. The localization of eNOS, Ser1177, and Thr495 in healthy and inflamed blood vessels was examined in consecutive cryo-sections using quantitative immunohistochemical methods. We found that the staining intensity of Ser1177 in healthy blood vessels decreased in inflamed blood vessels, whereas the weak staining intensity of Thr495 in healthy blood vessels strongly increased in inflamed blood vessels. In blood vessels of the healthy pulp, eNOS is active with phosphorylation of the enzyme at Ser1177. The phosphorylation of eNOS at Thr495 in inflamed blood vessels leads to a decrease in eNOS activity, contributing to eNOS uncoupling and giving evidence for a decrease in NO and an increase in O2− production. Since the formation of the tertiary dentin matrix depends on intact pulp circulation, eNOS uncoupling and phosphorylation of eNOS at Thr495 in the inflamed pulp blood vessels should be considered during caries therapy.

Reactive oxygen species: The Yin and Yang in (auto-)immunity

Reactive oxygen species (ROS) are produced by immune cells in response to antigens. They are produced mostly in the mitochondria and their levels are tightly controlled by a series of metabolic processes. ROS are necessary for the development of the immune response but the role of ROS in the development of autoimmune disease needs further clarification. Early clinical information points to the beneficial role of supplementation of antioxidant agents or the reduction of ROS production. We review recent information in the field in an effort to identify areas more studies are needed.

Nitric Oxide and Electrophilic Cyclopentenone Prostaglandins in Redox signaling, Regulation of Cytoskeleton Dynamics and Intercellular Communication

Nitric oxide (NO) and electrophilic cyclopentenone prostaglandins (CyPG) are local mediators that modulate cellular response to oxidative stress in different pathophysiological processes. In particular, there is increasing evidence about their functional role during inflammation and immune responses. Although the mechanistic details about their relationship and functional interactions are still far from resolved, NO and CyPG share the ability to promote redox-based post-translational modification (PTM) of proteins that play key roles in cellular homeostasis, signal transduction and transcription. NO-induced S-nitrosylation and S-glutathionylation as well as cyclopentenone-mediated adduct formation, are a few of the main PTMs by which intra- and inter-cellular signaling are regulated. There is a growing body of evidence indicating that actin and actin-binding proteins are susceptible to covalent PTM by these agents. It is well known that the actin cytoskeleton is key for the establishment of interactions among leukocytes, endothelial and muscle cells, enabling cellular activation and migration. In this review we analyze the current knowledge about the actions exerted by NO and CyPG electrophilic lipids on the regulation of actin dynamics and cytoskeleton organization, and discuss some open questions regarding their functional relevance in the regulation of intercellular communication.

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.

The Redox-Metabolic Couple of T Lymphocytes: Potential Consequences for Hypertension

Significance: T lymphocytes, as part of the adaptive immune system, possess the ability to activate and function in extreme cellular microenvironments, which requires these cells to remain highly malleable. One mechanism in which T lymphocytes achieve this adaptability is by responding to cues from both reactive oxygen and nitrogen species, as well as metabolic flux, which together fine-tune the functional fate of these adaptive immune cells. Recent Advances: To date, examinations of the redox and metabolic effects on T lymphocytes have primarily investigated these biological processes as separate entities. Given that the redox and metabolic environments possess significant overlaps of pathways and molecular species, it is inevitable that perturbations in one environment affect the other. Recent consideration of this redox-metabolic couple has demonstrated the strong link and regulatory consequences of these two systems in T lymphocytes. Critical Issues: The redox and metabolic control of T lymphocytes is essential to prevent dysregulated inflammation, which has been observed in cardiovascular diseases such as hypertension. The role of the adaptive immune system in hypertension has been extensively investigated, but the understanding of how the redox and metabolic environments control T lymphocytes in this disease remains unclear. Future Directions: Herein, we provide a discussion of the redox and metabolic control of T lymphocytes as separate entities, as well as coupled to one another, to regulate adaptive immunity. While investigations examining this pair together in T lymphocytes are sparse, we speculate that T lymphocyte destiny is shaped by the redox-metabolic couple. In contrast, disrupting this duo may have inflammatory consequences such as hypertension.

Control of T-Cell Activation and Signaling by Amino-Acid Catabolizing Enzymes

Amino acids are essential for protein synthesis, epigenetic modification through the methylation of histones, and the maintenance of a controlled balance of oxidoreduction via the production of glutathione and are precursors of certain neurotransmitters. T lymphocytes are particularly sensitive to fluctuations in amino acid levels. During evolution, the production of amino-acid catabolizing enzymes by mainly antigen-presenting cells has become a physiological mechanism to control T-cell activation and polarization. The action of these enzymes interferes with TCR and co-stimulation signaling, allowing tuning of the T-cell response. These capacities can be altered in certain pathological conditions, with relevant consequences for the development of disease.

Systematic Analysis of the Pharmacological Effects of Alcoholic Components in Maotai

Maotai liquor is one of the most famous traditional Chinese distilled liquor enjoyed by many people all over the world for its unique production method, impressive liquor quality, and soy sauce-like and roasted aroma style. It is known that aroma characteristics of liquor mainly depend on the aroma compounds. Alcohols as one of the most important categories of aroma components have been determined in Maotai liquor. However, the systemic analysis of alcoholic compounds in liquor is limited, especially the active alcoholic components and their pharmacological effects. Therefore, in this study, a systemic analysis method was proposed by combining in silico absorption, distribution, metabolism, and excretion (ADME) evaluation, target fishing, network pharmacology technology, pathway analysis, and experimental verification to interpret the pharmacological mechanism of alcoholic compounds in Maotai liquor. Finally, 15 compounds with favorable pharmacokinetic profiles were screened through in silico ADME models. Thirty-eight related targets of these active compounds were identified by target prediction method. The network pharmacology and pathway analysis were developed to clarify the pharmacological effect of alcoholic compounds in Maotai liquor at the system and pathway level. Moreover, the key active compounds were validated by in vitro experiments that verified the effectiveness of our methods. Our study provides a novel approach to systematically analyze the pharmacological effect of alcoholic compounds in Maotai liquor, which would be beneficial for promoting the in-depth study of various liquors. PRACTICAL APPLICATION: Maotai liquor is popularly enjoyed in the world for a very long time. However, the systemic analysis of compounds in liquor is limited. Our systematic analysis approach was developed to explore the bioactive ingredients and their related target proteins as well as the pharmacological effects of Maotai liquor. This will provide a new method to understand the pharmacological mechanisms of compounds in various liquors at the systems level, so as to promote the development of liquors and to increase the public awareness of science about alcohol consumption.

Adhesive Interactions Delineate the Topography of the Immune Synapse

T cells form adhesive contacts with antigen-presenting cells (APCs) as part of the normal surveillance process that occurs in lymph nodes and other tissues. Most of these adhesive interactions are formed by integrins that interact with ligands expressed on the surface of the APC. The interactive strength of integrins depends on their degree of membrane proximity as well as intracellular signals that dictate the conformation of the integrin. Integrins appear in different conformations that endow them with different affinities for their ligand(s). Integrin conformation and thus adhesive strength between the T cell and the APC is tuned by intracellular signals that are turned on by ligation of the T cell receptor (TCR) and chemokine receptors. During the different stages of the process, integrins, the TCR and chemokine receptors may be interconnected by the actin cytoskeleton underneath the plasma membrane, forming a chemical and physical network that facilitates the spatiotemporal dynamics, positioning, and function of these receptors and supports cell-cell adhesion during T cell activation, allowing it to perform its effector function.

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.

Circulating miRNAs in Pediatric Pulmonary Hypertension Show Promise as Biomarkers of Vascular Function

BACKGROUND/OBJECTIVES

The objective of this study was to evaluate the utility of circulating miRNAs as biomarkers of vascular function in pediatric pulmonary hypertension.

METHOD

Fourteen pediatric pulmonary arterial hypertension patients underwent simultaneous right heart catheterization (RHC) and blood biochemical analysis. Univariate and stepwise multivariate linear regression was used to identify and correlate measures of reactive and resistive afterload with circulating miRNA levels. Furthermore, circulating miRNA candidates that classified patients according to a 20% decrease in resistive afterload in response to oxygen (O₂) or inhaled nitric oxide (iNO) were identified using receiver-operating curves.

RESULTS

Thirty-two circulating miRNAs correlated with the pulmonary vascular resistance index (PVRi), pulmonary arterial distensibility, and PVRi decrease in response to O₂ and/or iNO. Multivariate models, combining the predictive capability of multiple promising miRNA candidates, revealed a good correlation with resistive (r = 0.97, P_2-tailed < 0.0001) and reactive (r = 0.86, P_2-tailed < 0.005) afterloads. Bland-Altman plots showed that 95% of the differences between multivariate models and RHC would fall within 0.13 (mmHg-min/L)m² and 0.0085/mmHg for resistive and reactive afterloads, respectively. Circulating miR-663 proved to be a good classifier for vascular responsiveness to acute O₂ and iNO challenges.

CONCLUSION

This study suggests that circulating miRNAs may be biomarkers to phenotype vascular function in pediatric PAH.

Myristoylation: An Important Protein Modification in the Immune Response

Protein N-myristoylation is a cotranslational lipidic modification specific to the alpha-amino group of an N-terminal glycine residue of many eukaryotic and viral proteins. The ubiquitous eukaryotic enzyme, N-myristoyltransferase, catalyzes the myristoylation process. Precisely, attachment of a myristoyl group increases specific protein–protein interactions leading to subcellular localization of myristoylated proteins with its signaling partners. The birth of the field of myristoylation, a little over three decades ago, has led to the understanding of the significance of protein myristoylation in regulating cellular signaling pathways in several biological processes especially in carcinogenesis and more recently immune function. This review discusses myristoylation as a prerequisite step in initiating many immune cell signaling cascades. In particular, we discuss the hitherto unappreciated implication of myristoylation during myelopoiesis, innate immune response, lymphopoiesis for T cells, and the formation of the immunological synapse. Furthermore, we discuss the role of myristoylation in inducing the virological synapse during human immunodeficiency virus infection as well as its clinical implication. This review aims to summarize existing knowledge in the field and to highlight gaps in our understanding of the role of myristoylation in immune function so as to further investigate into the dynamics of myristoylation-dependent immune regulation.

eNOS S-nitrosylates β-actin on Cys374 and regulates PKC-θ at the immune synapse by impairing actin binding to profilin-1

The actin cytoskeleton coordinates the organization of signaling microclusters at the immune synapse (IS); however, the mechanisms involved remain poorly understood. We show here that nitric oxide (NO) generated by endothelial nitric oxide synthase (eNOS) controls the coalescence of protein kinase C-θ (PKC-θ) at the central supramolecular activation cluster (c-SMAC) of the IS. eNOS translocated with the Golgi to the IS and partially colocalized with F-actin around the c-SMAC. This resulted in reduced actin polymerization and centripetal retrograde flow of β-actin and PKC-θ from the lamellipodium-like distal (d)-SMAC, promoting PKC-θ activation. Furthermore, eNOS-derived NO S-nitrosylated β-actin on Cys374 and impaired actin binding to profilin-1 (PFN1), as confirmed with the transnitrosylating agent S-nitroso-L-cysteine (Cys-NO). The importance of NO and the formation of PFN1-actin complexes on the regulation of PKC-θ was corroborated by overexpression of PFN1- and actin-binding defective mutants of β-actin (C374S) and PFN1 (H119E), respectively, which reduced the coalescence of PKC-θ at the c-SMAC. These findings unveil a novel NO-dependent mechanism by which the actin cytoskeleton controls the organization and activation of signaling microclusters at the IS.

T cells are an essential arm of the immunity against the invasion of pathogenic agents in organisms. These specialized cells recognize foreign antigens displayed on the surface of antigen-presenting cells (APC) by means of the T cell receptor (TCR). Early signaling takes place in these cells through the specific clustering of TCRs, which trigger the recruitment of signaling molecules to the immune synapse (IS), a plasma membrane–associated intercellular domain important for T cell activation. In this location, several signaling molecules that include the protein kinase C-θ (PKC-θ) form microclusters that are translocated centripetally towards the center of the IS, following the retrograde movement of actin. In this study, we show that nitric oxide (NO) formed by endothelial nitric oxide synthase (eNOS) regulates the translocation of PKC-θ to the IS, increasing its activation. eNOS can effectively modify β-actin by S-nitrosylation on Cys374, reducing its ability to bind profilin-1 (PFN1)—a protein required for actin polymerization—polymerize and flow from the periphery to the central region of the IS. We propose that eNOS-derived NO controls actin polymerization via S-nitrosylation of actin as one of the major driving forces for the transport of PKC-θ towards the central area of the IS, which is essential for T cell activation.

Orchestrating Lymphocyte Polarity in Cognate Immune Cell-Cell Interactions

The immune synapse (IS) is a specialized structure established between different immune cells that fulfills several functions, including a role as a communication bridge. This intimate contact between a T cell and an antigen-presenting cell promotes the proliferation and differentiation of lymphocytes involved in the contact. T-cell activation requires the specific triggering of the T-cell receptor (TCR), which promotes the activation of different signaling pathways inducing the polarization of the T cell. During this process, different adhesion and signaling receptors reorganize at specialized membrane domains, concomitantly to the polarization of the tubulin and actin cytoskeletons, forming stable polarization platforms. The centrosome also moves toward the IS, driving the movement of different organelles, such as the biosynthetic, secretory, degrading machinery, and mitochondria, to sustain T-cell activation. A proper orchestration of all these events is essential for T-cell effector functions and the accomplishment of a complete immune response.

Glial-cell-derived neuroregulators control type 3 innate lymphoid cells and gut defence

Group 3 innate lymphoid cells (ILC3) are major regulators of inflammation and infection at mucosal barriers. ILC3 development is thought to be programmed, but how ILC3 perceive, integrate and respond to local environmental signals remains unclear. Here we show that ILC3 in mice sense their environment and control gut defence as part of a glial–ILC3–epithelial cell unit orchestrated by neurotrophic factors. We found that enteric ILC3 express the neuroregulatory receptor RET. ILC3-autonomous Ret ablation led to decreased innate interleukin-22 (IL-22), impaired epithelial reactivity, dysbiosis and increased susceptibility to bowel inflammation and infection. Neurotrophic factors directly controlled innate Il22 downstream of the p38 MAPK/ERK-AKT cascade and STAT3 activation. Notably, ILC3 were adjacent to neurotrophic-factor-expressing glial cells that exhibited stellate-shaped projections into ILC3 aggregates. Glial cells sensed microenvironmental cues in a MYD88-dependent manner to control neurotrophic factors and innate IL-22. Accordingly, glial-intrinsic Myd88 deletion led to impaired production of ILC3-derived IL-22 and a pronounced propensity towards gut inflammation and infection. Our work sheds light on a novel multi-tissue defence unit, revealing that glial cells are central hubs of neuron and innate immune regulation by neurotrophic factor signals.

Dual targeting of the thioredoxin and glutathione systems in cancer and HIV

Although the use of antioxidants for the treatment of cancer and HIV/AIDS has been proposed for decades, new insights gained from redox research have suggested a very different scenario. These new data show that the major cellular antioxidant systems, the thioredoxin (Trx) and glutathione (GSH) systems, actually promote cancer growth and HIV infection, while suppressing an effective immune response. Mechanistically, these systems control both the redox- and NO-based pathways (nitroso-redox homeostasis), which subserve innate and cellular immune defenses. Dual inhibition of the Trx and GSH systems synergistically kills neoplastic cells in vitro and in mice and decreases resistance to anticancer therapy. Similarly, the population of HIV reservoir cells that constitutes the major barrier to a cure for AIDS is exquisitely redox sensitive and could be selectively targeted by Trx and GSH inhibitors. Trx and GSH inhibition may lead to a reprogramming of the immune response, tilting the balance between the immune system and cancer or HIV in favor of the former, allowing elimination of diseased cells. Thus, therapies based on silencing of the Trx and GSH pathways represent a promising approach for the cure of both cancer and AIDS and warrant further investigation.

Promoting thiol expression increases the durability of antitumor T-cell functions

Ex vivo-expanded CD8(+) T cells used for adoptive immunotherapy generally acquire an effector memory-like phenotype (TEM cells). With regard to therapeutic applications, two undesired features of this phenotype in vivo are limited persistence and reduced antitumor efficacy, relative to CD8(+) T cells with a central memory-like phenotype (TCM cells). Furthermore, there is incomplete knowledge about all the differences between TEM and TCM cells that may influence tumor treatment outcomes. Given that TCM cells survive relatively longer in oxidative tumor microenvironments, we investigated the hypothesis that TCM cells possess relatively greater antioxidative capacity than TEM cells. Here, we report that TCM cells exhibit a relative increase compared with TEM cells in the expression of cell surface thiols, a key target of cellular redox controls, along with other antioxidant molecules. Increased expression of redox regulators in TCM cells inversely correlated with the generation of reactive oxygen and nitrogen species, proliferative capacity, and glycolytic enzyme levels. Notably, T-cell receptor-transduced T cells pretreated with thiol donors, such as N-acetyl cysteine or rapamycin, upregulated thiol levels and antioxidant genes. A comparison of antitumor CD8(+) T-cell populations on the basis of surface thiol expression showed that thiol-high cells persisted longer in vivo and exerted superior tumor control. Our results suggest that higher levels of reduced cell surface thiols are a key characteristic of T cells that can control tumor growth and that profiling this biomarker may have benefits to adoptive T-cell immunotherapy protocols.

Nuclear envelope lamin-A couples actin dynamics with immunological synapse architecture and T cell activation

In many cell types, nuclear A-type lamins regulate multiple cellular functions, including higher-order genome organization, DNA replication and repair, gene transcription, and signal transduction; however, their role in specialized immune cells remains largely unexplored. We showed that the abundance of A-type lamins was almost negligible in resting naïve T lymphocytes, but was increased upon activation of the T cell receptor (TCR). The increase in lamin-A was an early event that accelerated formation of the immunological synapse between T cells and antigen-presenting cells. Polymerization of F-actin in T cells is a critical step for immunological synapse formation, and lamin-A interacted with the linker of nucleoskeleton and cytoskeleton (LINC) complex to promote F-actin polymerization. We also showed that lamin-A expression accelerated TCR clustering and led to enhanced downstream signaling, including extracellular signal-regulated kinase 1/2 (ERK1/2) signaling, as well as increased target gene expression. Pharmacological inhibition of the ERK pathway reduced lamin-A-dependent T cell activation. Moreover, mice lacking lamin-A in immune cells exhibited impaired T cell responses in vivo. These findings underscore the importance of A-type lamins for TCR activation and identify lamin-A as a previously unappreciated regulator of the immune response.

Dynamin related protein 1-dependent mitochondrial fission regulates oxidative signalling in T cells

In T cells mitochondria-derived reactive oxygen species (ROS) are indispensible for activation of the transcription factor NF-κB, expression of cytokines and the CD95 ligand (CD95L/FasL). Here we show that activation-induced ROS generation is dependent on mitochondrial fission. Inhibition of dynamin related protein 1 (Drp1) results in reduced ROS levels and transcriptional activity of NF-κB leading to diminished proliferation and CD95L-dependent activation-induced cell death (AICD). Upon stimulation Drp1 is S-nitrosylated, which is required for oxidative signalling, AICD and cytokine production. In conclusion, we describe a novel signalling pathway that links TCR-induced nitric oxide release to mitochondrial fission and oxidative signalling.

T cell–derived inducible nitric oxide synthase switches off Th17 cell differentiation

Nitric oxide derived from iNOS in activated T cells negatively regulates Th17 cell differentiation.

RORγt is necessary for the generation of T_H17 cells but the molecular mechanisms for the regulation of T_H17 cells are still not fully understood. We show that activation of CD4⁺ T cells results in the expression of inducible nitric oxide synthase (iNOS). iNOS-deficient mice displayed enhanced T_H17 cell differentiation but without major effects on either T_H1 or T_H2 cell lineages, whereas endothelial NOS (eNOS) or neuronal NOS (nNOS) mutant mice showed comparable T_H17 cell differentiation compared with wild-type control mice. The addition of N6-(1-iminoethyl)-l-lysine dihydrochloride (L-NIL), the iNOS inhibitor, significantly enhanced T_H17 cell differentiation, and S-nitroso-N-acetylpenicillamine (SNAP), the NO donor, dose-dependently reduced the percentage of IL-17–producing CD4⁺ T cells. NO mediates nitration of tyrosine residues in RORγt, leading to the suppression of RORγt-induced IL-17 promoter activation, indicating that NO regulates IL-17 expression at the transcriptional level. Finally, studies of an experimental model of colitis showed that iNOS deficiency results in more severe inflammation with an enhanced T_H17 phenotype. These results suggest that NO derived from iNOS in activated T cells plays a negative role in the regulation of T_H17 cell differentiation and highlight the importance of intrinsic programs for the control of T_H17 immune responses.

Mitochondria as oxidative signaling organelles in T-cell activation: physiological role and pathological implications

Early scientific reports limited the cell biological role of reactive oxygen species (ROS) to the cause of pathological damage. However, extensive research performed over the last decade led to a wide recognition of intracellular oxidative/redox signaling as a crucial mechanism of homeostatic regulation. Amongst different cellular processes known to be influenced by redox signaling, T-cell activation is one of the most established. Numerous studies reported an indispensible role for ROS as modulators of T-cell receptor-induced transcription. Nevertheless, mechanistic details regarding signaling pathways triggered by ROS are far from being delineated. The nature and interplay between enzymatic sources involved in the generation of "oxidative signals" are also a matter of ongoing research. In particular, active participation of the mitochondrial respiratory chain as ROS producer constitutes an intriguing issue with various implications for bioenergetics of activated T cells as well as for T-cell-mediated pathologies. The aim of the current review is to address these interesting concepts.

Nitrosothiols in the immune system: signaling and protection

SIGNIFICANCE

In the immune system, nitric oxide (NO) has been mainly associated with antibacterial defenses exerted through oxidative, nitrosative, and nitrative stress and signal transduction through cyclic GMP-dependent mechanisms. However, S-nitrosylation is emerging as a post-translational modification (PTM) involved in NO-mediated cell signaling.

RECENT ADVANCES

Precise roles for S-nitrosylation in signaling pathways have been described both for innate and adaptive immunity. Denitrosylation may protect macrophages from their own S-nitrosylation, while maintaining nitrosative stress compartmentalized in the phagosomes. Nitrosothiols have also been shown to be beneficial in experimental models of autoimmune diseases, mainly through their role in modulating T-cell differentiation and function.

CRITICAL ISSUES

Relationship between S-nitrosylation, other thiol redox PTMs, and other NO-signaling pathways has not been always taken into account, particularly in the context of immune responses. Methods for assaying S-nitrosylation in individual proteins and proteomic approaches to study the S-nitrosoproteome are constantly being improved, which helps to move this field forward.

FUTURE DIRECTIONS

Integrated studies of signaling pathways in the immune system should consider whether S-nitrosylation/denitrosylation processes are among the PTMs influencing the activity of key signaling and adaptor proteins. Studies in pathophysiological scenarios will also be of interest to put these mechanisms into broader contexts. Interventions modulating nitrosothiol levels in autoimmune disease could be investigated with a view to developing new therapies.

End-binding protein 1 controls signal propagation from the T cell receptor

The role of microtubules (MTs) in the control and dynamics of the immune synapse (IS) remains unresolved. Here, we show that T cell activation requires the growth of MTs mediated by the plus-end specific protein end-binding 1 (EB1). A direct interaction of the T cell receptor (TCR) complex with EB1 provides the molecular basis for EB1 activity promoting TCR encounter with signalling vesicles at the IS. EB1 knockdown alters TCR dynamics at the IS and prevents propagation of the TCR activation signal to LAT, thus inhibiting activation of PLCγ1 and its localization to the IS. These results identify a role for EB1 interaction with the TCR in controlling TCR sorting and its connection with the LAT/PLCγ1 signalosome.

Evidence for a relationship between mitochondrial Complex I activity and mitochondrial aldehyde dehydrogenase during nitroglycerin tolerance: effects of mitochondrial antioxidants

The medical use of nitroglycerin (GTN) is limited by patient tolerance. The present study evaluated the role of mitochondrial Complex I in GTN biotransformation and the therapeutic effect of mitochondrial antioxidants. The development of GTN tolerance (in rat and human vessels) produced a decrease in mitochondrial O(2) consumption. Co-incubation with the mitochondria-targeted antioxidant mitoquinone (MQ, 10(-6)mol/L) or with glutathione ester (GEE, 10(-4)mol/L) blocked GTN tolerance and the effects of GTN on mitochondrial respiration and aldehyde dehydrogenase 2 (ALDH-2) activity. Biotransformation of GTN depended on the mitochondria being functionally active, particularly mitochondrial Complex I. Tolerance induced mitochondrial ROS production and oxidative stress, though these effects were not detected in HUVECρ(0) cells or Complex I mutant cells. Experiments performed to evaluate Complex I-dependent respiration demonstrated that its inhibition by GTN was prevented by the antioxidants in control samples. These results point to a key role for mitochondrial Complex I in the adequate functioning of ALDH-2. In addition, we have identified mitochondrial Complex I as one of the targets at which the initial oxidative stress responsible for GTN tolerance takes place. Our data also suggest a role for mitochondrial-antioxidants as therapeutic tools in the control of the tolerance that accompanies chronic nitrate use.

Assessment of mitochondrial dysfunction in lymphocytes of patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by abnormal activation and cell death signaling within the immune system. Activation, proliferation, or death of cells of the immune system is dependent on controlled reactive oxygen intermediates (ROI) production and ATP synthesis in mitochondria. The mitochondrial transmembrane potential (∆ψ (m)) reflects the energy stored in the electrochemical gradient across the inner mitochondrial membrane which, in turn, is used by F(0)F(1)-ATPase to convert ADP to ATP during oxidative phosphorylation. Mitochondrial hyperpolarization (MHP) and transient ATP depletion represent early and reversible steps in T cell activation and apoptosis. By contrast, T lymphocytes of patients with SLE exhibit elevated ∆ψ (m), i.e., persistent mitochondrial hyperpolarization (MHP), cytoplasmic alkalinization, increased ROI production, as well as diminished levels of intracellular glutathione and ATP. Increased production of nitric oxide has been identified as a cause of MHP and increased mitochondrial biogenesis. Oxidative stress affects signaling through the T cell receptor as well as activity of redox--sensitive caspases. ATP depletion causes diminished activation-induced apoptosis and sensitizes lupus T cells to necrosis. Activation of the mammalian target of rapamycin (mTOR) has recently emerged as a key sensor of MHP and mediator of enhanced Ca(2+) flux in lupus T cells.

The role of endocytic recycling in autoimmunity

Abnormalities in T cell signal transduction underlie pathology in systemic lupus erythematosus. Lupus T cells are more sensitive to stimulation, yet have reduced expression of T cell antigen receptor (TCR) at the surface. The amount of TCR expressed at the surface of a T cell directly determines the ability of a T cell to become activated. The endocytic recycling machinery regulates transport of T cell receptors to the plasma membrane, internalization of surface receptors, and recycling to the cell surface, which determines the ability of a T cell to become activated. Increased recycling of CD3 and CD4 receptors occurs in lupus T cells, and could represent a mechanism by which T cells are sensitized to stimulation. This chapter explains methods used to investigate endocytic recycling of the TCR, CD4, and CD8 co-receptors in peripheral blood lymphocytes, T cells, and in splenocytes from lupus-prone murine models. The assays described will allow the study of surface receptor turnover in live untouched lymphocytes by flow cytometry.

Increased sensitivity to apoptosis induced by methotrexate is mediated by JNK

OBJECTIVE

Low-dose methotrexate (MTX) is an effective therapy for rheumatoid arthritis (RA), yet its mechanism of action is incompletely understood. The aim of this study was to explore the induction of apoptosis by MTX.

METHODS

Flow cytometry was performed to assess changes in the levels of intracellular proteins, reactive oxygen species (ROS), and apoptosis. Quantitative polymerase chain reaction was performed to assess changes in the transcript levels of select target genes in response to MTX.

RESULTS

MTX did not directly induce apoptosis but rather "primed" cells for markedly increased sensitivity to apoptosis via either mitochondrial or death receptor pathways, by a JNK-dependent mechanism. Increased sensitivity to apoptosis was mediated, at least in part, by MTX-dependent production of ROS, JNK activation, and JNK-dependent induction of genes whose protein products promote apoptosis. Supplementation with tetrahydrobiopterin blocked these MTX-induced effects. Patients with RA who were receiving low-dose MTX therapy expressed elevated levels of the JNK target gene, jun.

CONCLUSION

Our results support a model whereby MTX inhibits reduction of dihydrobiopterin to tetrahydrobiopterin, resulting in increased production of ROS, increased JNK activity, and increased sensitivity to apoptosis. The finding of increased jun levels in patients with RA receiving low-dose MTX supports the notion that this pathway is activated by MTX in vivo and may contribute to the efficacy of MTX in inflammatory disease.

Nitric oxide modulates TGF-beta-directive signals to suppress Foxp3+ regulatory T cell differentiation and potentiate Th1 development

TGF-β can induce Foxp3(+) inducible regulatory T cells (Treg) and also synergize with IL-6 and IL-4 to induce Th17 and Th9 cells. We now report that NO modulates TGF-β activity away from Treg but toward the Th1 lineage. NO potentiated Th1 differentiation in the presence of TGF-β in both IL-12-independent and -dependent fashions by augmenting IFN-γ-activated STAT-1 and T-bet. Differentiation into Treg, Th1, and Th17 lineages could be modulated by NO competing with other cofactors, such as IL-6 and retinoic acid. NO antagonized IL-6 to block TGF-β-directed Th17 differentiation, and together with IL-6, NO suppressed Treg development induced by TGF-β and retinoic acid. Furthermore, we show that physiologically produced NO from TNF and inducible NO synthase-producing dendritic cells can contribute to Th1 development predominating over Treg development through a synergistic activity induced when these cells cocluster with conventional dendritic cells presenting Ag to naive Th cells. This illustrates that NO is another cofactor allowing TGF-β to participate in development of multiple Th lineages and suggests a new mechanism by which NO, which is associated with protection against intracellular pathogens, might maintain effective Th1 immunity.

Role of increased guanosine triphosphate cyclohydrolase-1 expression and tetrahydrobiopterin levels upon T cell activation

Tetrahydrobiopterin (BH(4)) is an essential co-factor for the nitric-oxide (NO) synthases, and in its absence these enzymes produce superoxide (O(2)(·-)) rather than NO. The rate-limiting enzyme for BH(4) production is guanosine triphosphate cyclohydrolase-1 (GTPCH-1). Because endogenously produced NO affects T cell function, we sought to determine whether antigen stimulation affected T cell GTPCH-1 expression and ultimately BH(4) levels. Resting T cells had minimal expression of inducible NOS (NOS2), endothelial NOS (NOS3), and GTPCH-1 protein and nearly undetectable levels of BH(4). Anti-CD3 stimulation of T cells robustly stimulated the coordinated expression of NOS2, NOS3, and GTPCH-1 and markedly increased both GTPCH-1 activity and T cell BH(4) levels. The newly expressed GTPCH-1 was phosphorylated on serine 72 and pharmacological inhibition of casein kinase II reduced GTPCH-1 phosphorylation and blunted the increase in T cell BH(4). Inhibition of GTPCH-1 with diaminohydroxypyrimidine (1 mmol/liter) prevented T cell BH(4) accumulation, reduced NO production, and increased T cell O(2)(·-) production, due to both NOS2 and NOS3 uncoupling. GTPCH-1 inhibition also promoted TH(2) polarization in memory CD4 cells. Ovalbumin immunization of mice transgenic for an ovalbumin receptor (OT-II mice) confirmed a marked increase in T cell BH(4) in vivo. These studies identify a previously unidentified consequence of T cell activation, promoting BH(4) levels, NO production, and modulating T cell cytokine production.

The mitochondrial fission factor dynamin-related protein 1 modulates T-cell receptor signalling at the immune synapse

During antigen-specific T-cell activation, mitochondria mobilize towards the vicinity of the immune synapse. We show here that the mitochondrial fission factor dynamin-related protein 1 (Drp1) docks at mitochondria, regulating their positioning and activity near the actin-rich ring of the peripheral supramolecular activation cluster (pSMAC) of the immune synapse. Mitochondrial redistribution in response to T-cell receptor engagement was abolished by Drp1 silencing, expression of the phosphomimetic mutant Drp1S637D and the Drp1-specific inhibitor mdivi-1. Moreover, Drp1 knockdown enhanced mitochondrial depolarization and T-cell receptor signal strength, but decreased myosin phosphorylation, ATP production and T-cell receptor assembly at the central supramolecular activation cluster (cSMAC). Our results indicate that Drp1-dependent mitochondrial positioning and activity controls T-cell activation by fuelling central supramolecular activation cluster assembly at the immune synapse.

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.

Central role of nitric oxide in the pathogenesis of rheumatoid arthritis and systemic lupus erythematosus

Nitric oxide (NO) has been shown to regulate T cell functions under physiological conditions, but overproduction of NO may contribute to T lymphocyte dysfunction. NO-dependent tissue injury has been implicated in a variety of rheumatic diseases, including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Several studies reported increased endogenous NO synthesis in both SLE and RA, and recent evidence suggests that NO contributes to T cell dysfunction in both autoimmune diseases. The depletion of intracellular glutathione may be a key factor predisposing patients with SLE to mitochondrial dysfunction, characterized by mitochondrial hyperpolarization, ATP depletion and predisposition to death by necrosis. Thus, changes in glutathione metabolism may influence the effect of increased NO production in the pathogenesis of autoimmunity.

Astaxanthin prevents in vitro auto-oxidative injury in human lymphocytes

Upon mitogen sensitization, lymphocytes undergo proliferation by oxyradical-based mechanisms. Through continuous resting-restimulation cycles, lymphocytes accumulate auto-induced oxidative lesions which lead to cell dysfunction and limit their viability. Astaxanthin (ASTA) is a nutritional carotenoid that shows notable antioxidant properties. This study aims to evaluate whether the in vitro ASTA treatment can limit oxyradical production and auto-oxidative injury in human lymphocytes. Activated lymphocytes treated with 5 microM ASTA showed immediate lower rates of O(2)(*-) /H(2)O(2) production whilst NO* and intracellular Ca(2+) levels were concomitantly enhanced (<or=4 h). In long-term treatments (>24 h), the cytotoxicity test for ASTA showed a sigmoidal dose-response curve (LC50 = 11.67 +/- 0.42 microM), whereas higher activities of superoxide dismutase and catalase in 5 microM ASTA-treated lymphocytes were associated to significant lower indexes of oxidative injury. On the other hand, lower proliferative scores of ASTA lymphocytes might be a result of diminished intracellular levels of pivotal redox signaling molecules, such as H(2)O(2). Further studies are necessary to establish the ASTA-dose compensation point between minimizing oxidative damages and allowing efficient redox-mediated immune functions, such as proliferation, adhesion, and oxidative burst.

Systems biology of lupus: mapping the impact of genomic and environmental factors on gene expression signatures, cellular signaling, metabolic pathways, hormonal and cytokine imbalance, and selecting targets for treatment

Systemic lupus erythematosus (SLE) is characterized by the dysfunction of T cells, B cells, and dendritic cells, the release of pro-inflammatory nuclear materials from necrotic cells, and the formation of antinuclear antibodies (ANA) and immune complexes of ANA with DNA, RNA, and nuclear proteins. Activation of the mammalian target of rapamycin (mTOR) has recently emerged as a key factor in abnormal activation of T and B cells in SLE. In T cells, increased production of nitric oxide and mitochondrial hyperpolarization (MHP) were identified as metabolic checkpoints upstream of mTOR activation. mTOR controls the expression T-cell receptor-associated signaling proteins CD4 and CD3zeta through increased expression of the endosome recycling regulator Rab5 and HRES-1/Rab4 genes, enhances Ca2+ fluxing and skews the expression of tyrosine kinases both in T and B cells, and blocks the expression of Foxp3 and the generation of regulatory T cells. MHP, increased activity of mTOR, Rab GTPases, and Syk kinases, and enhanced Ca2+ flux have emerged as common T and B cell biomarkers and targets for treatment in SLE.

The Rho/Rac exchange factor Vav2 controls nitric oxide-dependent responses in mouse vascular smooth muscle cells

The regulation of arterial contractility is essential for blood pressure control. The GTPase RhoA promotes vasoconstriction by modulating the cytoskeleton of vascular smooth muscle cells. Whether other Rho/Rac pathways contribute to blood pressure regulation remains unknown. By studying a hypertensive knockout mouse lacking the Rho/Rac activator Vav2, we have discovered a new signaling pathway involving Vav2, the GTPase Rac1, and the serine/threonine kinase Pak that contributes to nitric oxide-triggered blood vessel relaxation and normotensia. This pathway mediated the Pak-dependent inhibition of phosphodiesterase type 5, a process that favored RhoA inactivation and the subsequent depolymerization of the F-actin cytoskeleton in vascular smooth muscle cells. The inhibition of phosphodiesterase type 5 required its physical interaction with autophosphorylated Pak1 but, unexpectedly, occurred without detectable transphosphorylation events between those 2 proteins. The administration of phosphodiesterase type 5 inhibitors prevented the development of hypertension and cardiovascular disease in Vav2-deficient animals, demonstrating the involvement of this new pathway in blood pressure regulation. Taken together, these results unveil one cause of the cardiovascular phenotype of Vav2-knockout mice, identify a new Rac1/Pak1 signaling pathway, and provide a mechanistic framework for better understanding blood pressure control in physiological and pathological states.

Estradiol targets T cell signaling pathways in human systemic lupus

The major risk factor for developing systemic lupus erythematosus (SLE) is being female. The present study utilized gene profiles of activated T cells from females with SLE and healthy controls to identify signaling pathways uniquely regulated by estradiol that could contribute to SLE pathogenesis. Selected downstream pathway genes (+/- estradiol) were measured by real time polymerase chain amplification. Estradiol uniquely upregulated six pathways in SLE T cells that control T cell function including interferon-alpha signaling. Measurement of interferon-alpha pathway target gene expression revealed significant differences (p= 0.043) in DRIP150 (+/- estradiol) in SLE T cell samples while IFIT1 expression was bimodal and correlated moderately (r= 0.55) with disease activity. The results indicate that estradiol alters signaling pathways in activated SLE T cells that control T cell function. Differential expression of transcriptional coactivators could influence estrogen-dependent gene regulation in T cell signaling and contribute to SLE onset and disease pathogenesis.

T-cell and B-cell signaling biomarkers and treatment targets in lupus

PURPOSE OF REVIEW

Systemic lupus erythematosus is characterized by the production of antinuclear autoantibodies and dysfunction of T-cells, B-cells, and dendritic cells. Here, we review newly recognized genetic factors and mechanisms that underlie abnormal intracellular signal processing and intercellular communication within the immune system in systemic lupus erythematosus.

RECENT FINDINGS

Activation of the mammalian target of rapamycin plays a pivotal role in abnormal activation of T and B-cells in systemic lupus erythematosus. In T-cells, increased production of nitric oxide and mitochondrial hyperpolarization were identified as metabolic checkpoints upstream of mammalian target of rapamycin activation. Mammalian target of rapamycin controls the expression T-cell receptor-associated signaling proteins CD4 and CD3zeta through increased expression of the endosome recycling regulator HRES-1/Rab4 gene, mediates enhanced Ca2+ fluxing and skews the expression of tyrosine kinases both in T and B-cells, and blocks the expression of Foxp3 and the expansion of regulatory T-cells. Mitochondrial hyperpolarization and the resultant ATP depletion predispose T-cells to necrosis, thus promoting the dendritic cell activation, antinuclear autoantibody production, and inflammation.

SUMMARY

Mitochondrial hyperpolarization, increased activity of mammalian target of rapamycin and Syk kinases, enhanced receptor recycling and Ca2+ flux have emerged as common T and B-cell biomarkers and targets for treatment in systemic lupus erythematosus.

Protein S-nitrosylation in health and disease: a current perspective

Protein S-nitrosylation constitutes a large part of the ubiquitous influence of nitric oxide on cellular signal transduction and accumulating evidence indicates important roles for S-nitrosylation both in normal physiology and in a broad spectrum of human diseases. Here we review recent findings that implicate S-nitrosylation in cardiovascular, pulmonary, musculoskeletal and neurological (dys)function, as well as in cancer. The emerging picture shows that, in many cases, pathophysiology correlates with hypo- or hyper-S-nitrosylation of specific protein targets rather than a general cellular insult due to loss of or enhanced nitric oxide synthase activity. In addition, it is increasingly evident that dysregulated S-nitrosylation can not only result from alterations in the expression, compartmentalization and/or activity of nitric oxide synthases, but can also reflect a contribution from denitrosylases, including prominently the S-nitrosoglutathione (GSNO)-metabolizing enzyme GSNO reductase. Finally, because exogenous mediators of protein S-nitrosylation or denitrosylation can substantially affect the development or progression of disease, potential therapeutic agents that modulate S-nitrosylation could well have broad clinical utility.

Susceptible and protective endothelial nitric oxide synthase gene polymorphism in alopecia areata in the Kuwaiti population

Alopecia areata (AA) is a chronic inflammatory disease with evidence of T-cell involvement that causes hair follicle "immune privilege collapse". Nitric monoxide was shown to contribute in the pathogenesis of AA. We are investigating evidence for the association of eNOS gene polymorphism with AA. Genomic DNA was extracted from 176 subjects, 87 Kuwaiti AA patients and 89 matched (for ethnicity, gender and age) healthy controls. A variable number tandem repeat (VNTR) located in intron-4 of the eNOS gene consisting of either four or five (27-base pair) repeats was analyzed by polymerase chain reaction and electrophoresis fragment analysis using ABI 3100 genetic analyzer. Haploview and GenePOP software were used for data analysis. A significant association was found between the intron-4 27 bp-VNTR and AA, where 4b was identified as the risk allele had (chi(2) = 4.42, p = 0.035, OR = 2.03). Genotype (4b/4b) showed a significant association with susceptibility to AA and have a frequency of 22% higher in AA patients than in healthy controls (71 vs 49%) and a chi(2) = 6.39, (p = 0.011, OR = 2.63). We report a significant association of a polymorphism within the eNOS gene and susceptibility to AA.