Martine Torres

Redox signaling in macrophages

Macrophages are phagocytic cells that produce and release reactive oxygen species (ROS) in response to phagocytosis or stimulation with various agents. The enzyme responsible for the production of superoxide and hydrogen peroxide is a multi-component NADPH oxidase that requires assembly at the plasma membrane to function as an oxidase. In addition to participating in bacterial killing, ROS, which have recently been shown to be produced enzymatically by non-phagocytic cells, have been implicated in inflammation and tissue injury. These toxic effects have been largely explored over the years and these studies have overshadowed initial observations supporting a role for ROS in modulating cellular function. In recent years, it has become increasingly evident that ROS can function as second messengers and, at low levels, can activate signaling pathways resulting in a broad array of physiological responses from cell proliferation to gene expression and apoptosis. Macrophages can also produce large amounts of nitric oxide (nitrogen monoxide, *NO). *NO was first identified as the endothelial-derived relaxing factor, EDRF and its role in the signaling pathway leading to its physiological effect was rapidly established. The ability of *NO to react with O(2)(*-) to produce peroxynitrite (ONOO(-)) was later recognized. As it is diffusion-limited, this reaction is more likely to occur in cells like macrophages that produce both ROS and RNS. In this review, we will summarize the current knowledge in redox signaling, and describe more specifically studies that are particular to macrophages.

Impact of early transcranial Doppler screening and intensive therapy on cerebral vasculopathy outcome in a newborn sickle cell anemia cohort

Transcranial Doppler (TCD) is used to detect children with sickle cell anemia (SCA) who are at risk for stroke, and transfusion programs significantly reduce stroke risk in patients with abnormal TCD. We describe the predictive factors and outcomes of cerebral vasculopathy in the Créteil newborn SCA cohort (n = 217 SS/Sβ(0)), who were early and yearly screened with TCD since 1992. Magnetic resonance imaging/magnetic resonance angiography was performed every 2 years after age 5 (or earlier in case of abnormal TCD). A transfusion program was recommended to patients with abnormal TCD and/or stenoses, hydroxyurea to symptomatic patients in absence of macrovasculopathy, and stem cell transplantation to those with human leukocyte antigen-genoidentical donor. Mean follow-up was 7.7 years (1609 patient-years). The cumulative risks by age 18 years were 1.9% (95% confidence interval [95% CI] 0.6%-5.9%) for overt stroke, 29.6% (95% CI 22.8%-38%) for abnormal TCD, which reached a plateau at age 9, whereas they were 22.6% (95% CI 15.0%-33.2%) for stenosis and 37.1% (95% CI 26.3%-50.7%) for silent stroke by age 14. Cumulating all events (stroke, abnormal TCD, stenoses, silent strokes), the cerebral risk by age 14 was 49.9% (95% CI 40.5%-59.3%); the independent predictive factors for cerebral risk were baseline reticulocytes count (hazard ratio 1.003/L × 10(9)/L increase, 95% CI 1.000-1.006; P = .04) and lactate dehydrogenase level (hazard ratio 2.78/1 IU/mL increase, 95% CI1.33-5.81; P = .007). Thus, early TCD screening and intensification therapy allowed the reduction of stroke-risk by age 18 from the previously reported 11% to 1.9%. In contrast, the 50% cumulative cerebral risk suggests the need for more preventive intervention.

G6PD deficiency, absence of α-thalassemia, and hemolytic rate at baseline are significant independent risk factors for abnormally high cerebral velocities in patients with sickle cell anemia

Stroke is predicted by abnormally high cerebral velocities by transcranial doppler (TCD). This study aimed at defining predictive factors for abnormally high velocities (>/= 2 m/sec) based on the Créteil pediatric sickle cell anemia (SCA) cohort composed of 373 stroke-free SCA children. alpha genes and beta-globin haplotypes were determined. Biologic parameters were obtained at baseline. alpha-thalassemia was present in 155 of 325 and G6PD deficiency in 36 of 325 evaluated patients. TCD was abnormal in 62 of 373 patients. Multivariate logistic regression analysis showed that G6PD deficiency (odds ratio [OR] = 3.36, 95% confidence interval [CI] 1.10-10.33; P = .034), absence of alpha-thalassemia (OR = 6.45, 95% CI 2.21-18.87; P = .001), hemoglobin (OR per g/dL = 0.63, 95% CI 0.41-0.97; P = .038), and lactate dehydrogenase (LDH) levels (OR per IU/L = 1.001, 95% CI 1.000-1.002; P = .047) were independent risk factors for abnormally high velocities. This study confirms the protective effect of alpha-thalassemia and shows for the first time that G6PD deficiency and hemolysis independently increase the risk of cerebral vasculopathy.

Signaling by the respiratory burst in macrophages.

During phagocytosis or stimulation with a wide variety of agents, macrophages and other phagocytic cells produce reactive oxygen species (ROS) through activation of a multicomponent NADPH oxidase. ROS production through related NADPH oxidases has recently been demonstrated in several other cell types. Furthermore, the physiological generation of ROS production has now been clearly implicated in activating signaling pathways resulting in a broad array of physiological responses from cell proliferation to gene expression and apoptosis. This brief review suggests that: 1) hydrogen peroxide and superoxide, but not the hydroxyl radical, function as second messengers; 2) antioxidant enzymes function in the “turn‐off” phase of signal transduction; 3) the chemistry of thiols is critical in redox signaling; and 4) the primary physiological role of the respiratory burst in macrophages may be in redox signaling rather than microbicidal activity.

The Adp-stimulated Nadph Oxidase Activates The Ask-1/mkk4/jnk Pathway In Alveolar Macrophages

The role of H2O2 as a second messenger in signal transduction pathways is well established. We show here that the NADPH oxidase-dependent production of and H2O2 or respiratory burst in alveolar macrophages (AM) (NR8383 cells) is required for ADP-stimulated c-Jun phosphorylation and the activation of JNK1/2, MKK4 (but not MKK7) and apoptosis signal-regulating kinase-1 (ASK1). ASK1 binds only to the reduced form of thioredoxin (Trx). ADP induced the dissociation of ASK1/Trx complex and thus resulted in ASK1 activation, as assessed by phosphorylation at Thr845, which was enhanced after treatment with aurothioglucose (ATG), an inhibitor of Trx reductase. While dissociation of the complex implies Trx oxidation, protein electrophoretic mobility shift assay detected oxidation of Trx only after bolus H2O2 but not after ADP stimulation. These results demonstrate that the ADP-stimulated respiratory burst activated the ASK1–MKK4–JNK1/c-Jun signaling pathway in AM and suggest that transient and localized oxidation of Trx by the NADPH oxidase-mediated generation of H2O2 may play a critical role in ASK1 activation and the inflammatory response.

Signal transduction by reactive oxygen and nitrogen species : pathways and chemical principles

Redox State and Redox Environment in Biology.- Sulfur and Selenium Catalysis as Paradigms for Redox Regulations.- Thiols of Thioredoxin and Glutaredoxin in Redox Signaling.- Reactivity and Diffusivity of Nitrogen Oxides in Mammalian Biology.- Bacterial Peroxiredoxins.- The Nox Enzymes and the Regulated Generation of Reactive Oxygen Species.- NO Synthesis and NOS Regulation.- S-nitrosothiols in Cell Signaling.- Hydrogen Peroxide as Intracellular Messenger: Identification of Protein Tyrosine Phosphatases and Pten as H2O2 Target.- 4-Hydroxynonenal Signaling.- Ceramide Signaling under Oxidative Stress.- Map Kinases in Redox Signaling.- Activation of Prostaglandin Biosynthesis: Peroxynitrite vs Hydroperoxides.- Phylogenetic Conservation of the Nrf2-Keap1 Signaling System.- The NO-cytochrome C Oxidase Signaling Pathway Mechanisms and Biological Implications.- The Concept of Compartmentalization in Signaling by Reactive Oxygen Species.- Role of Mitochondrial Oxygen and Nitrogen Reactive Species in Signaling.- Redox Regulation of Gene Expression: Transcriptional Induction of Heme Oxygenase-1.- Apoptosis Mechanisms Initiated by Oxidative Stress.- Reactive Oxygen and Nitrogen Species in the Production of Congenital Malformations by Known Teratogenic Agents and Maternal Conditions.

Asthma is associated with acute chest syndrome, but not with an increased rate of hospitalization for pain among children in France with sickle cell anemia: a retrospective cohort study

Asthma and sickle cell disease are two common chronic diseases that may exist as co-morbid conditions. Our group has recently demonstrated that asthma, the most common chronic disease among children, is a distinct co-morbid condition among children with sickle cell anemia (SCA)[1][1] and has a

Function of the cytoskeleton in human neutrophils and methods for evaluation.

The cytoskeleton plays a critical role in the determination of cell shape and serves as a scaffold for critical cellular enzymes and adhesion molecules. It provides structural integrity for the cell and regulates the function of many biochemical events that are critical to cellular function. The microfilamentous cytoskeleton participates in force generation necessary for shape change and motion. In neutrophils and other motile cells, polymerization of actin likely drives extension of the lamellae and participates in force generation through interaction with myosin, by polymerization alone and by osmotic mechanisms. Here, we will focus on the microfilamentous cytoskeleton in the neutrophil and briefly review its function as well as some direct and indirect methods that have been used to asses its role in neutrophil function. The discussion will address general approaches and leaves the details of the methods to the references.

Bio-effectiveness of Tat-catalase conjugate: a potential tool for the identification of H2O2-dependent cellular signal transduction pathways ☆

Reactive oxygen species such as hydrogen peroxide (H(2)O(2)) have taken center stage as bona fide second messengers in various signaling pathways. Here, we report the synthesis, metabolic fate, and effectiveness in modulating such pathways of a Tat-catalase conjugate. Incubation of L2 cells with Tat-catalase greatly increased cell-associated enzymatic activity, reaching close to a plateau by 30 min. The cell-associated catalase activity and antibody-detectable Tat-derivatives declined over time after changing medium, although still remaining at significantly higher levels than baseline even at 4h. While most cell-associated Tat-catalase was apparently tightly attached to the cell surface, a small fraction entered the cells as the proteasome inhibitor MG-132 slightly prevented the disappearance of the enzyme. Tat-catalase, either membrane-bound or intracellular, but not native catalase, inhibited serum-induced Elk phosphorylation and anisomycin- and/or MG-132-induced ERK phosphorylation, suggesting the involvement of H(2)O(2). Thus, Tat-catalase should be a useful tool to dissect H(2)O(2)-dependent events in signaling pathways.

ADP stimulates the respiratory burst without activation of ERK and AKT in rat alveolar macrophages

Alveolar macrophages (AM) are the first line of defense against infection in the lungs. We previously showed that the production of superoxide and hydrogen peroxide, i.e., the respiratory burst, is stimulated by adenine nucleotides (ADP >> ATP) in rat AM through signaling pathways involving calcium and protein kinase C. Here, we further show that ADP induces a rapid increase in the tyrosine phosphorylation of several proteins that was reduced by the tyrosine kinase inhibitor genistein, which also inhibited the respiratory burst. Interestingly, ADP did not trigger the activation of the mitogen-activated protein kinases ERK1 and ERK2, or that of protein kinase B/AKT, a downstream target of the phosphatidylinositol 3-kinase (PI3K) pathway. This is in contrast to another stimulus of the respiratory burst, zymosan-activated serum (ZAS), which activates both the ERK and PI3K pathways. Thus, this study demonstrates that the receptor for ADP in rat AM is not coupled to the ERK and AKT pathways and, that neither the ERK pathway nor AKT is essential to induce the activation of the NAPDH oxidase by ADP in rat AM while tyrosine kinases appeared to be required. The rate and amount of hydrogen peroxide released by the ADP-stimulated respiratory burst was similar to that produced by ZAS stimulation. The absence of ERK activation after ADP stimulation therefore suggests that hydrogen peroxide is not sufficient to activate the ERK pathway in rat AM. Nonetheless, as hydrogen peroxide was necessary for ERK activation by ZAS, this indicates that, in contrast to ADP, ZAS stimulates a pathway that is targeted by hydrogen peroxide and leads to ERK activation.