Characterization of superoxide overproduction by the D-Loop(Nox4)-Nox2 cytochrome b(558) in phagocytes-Differential sensitivity to calcium and phosphorylation events

Neutrophils: Many Ways to Die

Neutrophils or polymorphonuclear leukocytes (PMN) are key participants in the innate immune response for their ability to execute different effector functions. These cells express a vast array of membrane receptors that allow them to recognize and eliminate infectious agents effectively and respond appropriately to microenvironmental stimuli that regulate neutrophil functions, such as activation, migration, generation of reactive oxygen species, formation of neutrophil extracellular traps, and mediator secretion, among others. Currently, it has been realized that activated neutrophils can accomplish their effector functions and simultaneously activate mechanisms of cell death in response to different intracellular or extracellular factors. Although several studies have revealed similarities between the mechanisms of cell death of neutrophils and other cell types, neutrophils have distinctive properties, such as a high production of reactive oxygen species (ROS) and nitrogen species (RNS), that are important for their effector function in infections and pathologies such as cancer, autoimmune diseases, and immunodeficiencies, influencing their cell death mechanisms. The present work offers a synthesis of the conditions and molecules implicated in the regulation and activation of the processes of neutrophil death: apoptosis, autophagy, pyroptosis, necroptosis, NETosis, and necrosis. This information allows to understand the duality encountered by PMNs upon activation. The effector functions are carried out to eliminate invading pathogens, but in several instances, these functions involve activation of signaling cascades that culminate in the death of the neutrophil. This process guarantees the correct elimination of pathogenic agents, damaged or senescent cells, and the timely resolution of the inflammation that is essential for the maintenance of homeostasis in the organism. In addition, they alert the organism when the immunological system is being deregulated, promoting the activation of other cells of the immune system, such as B and T lymphocytes, which produce cytokines that potentiate the microbicide functions.

Obesity as an Inflammatory Agent Can Cause Cellular Changes in Human Milk due to the Actions of the Adipokines Leptin and Adiponectin

Adiponectin and leptin play roles in the hunger response, and they can induce the inflammatory process as the initial mechanism of the innate immune response. It is possible for alterations in the levels of these adipokines to compromise the functional activity of human colostrum phagocytes. Therefore, the objective of this study is to analyze the effects of adiponectin and leptin on colostrum mononuclear (MN) cells. Colostrum was collected from 80 healthy donors, who were divided into two groups: the control group and the high body mass index (BMI) group. MN cells were used to analyze phagocytosis by flow cytometry, and reactive oxygen species (ROS), intracellular calcium, and apoptosis were assessed by fluorimetry using a microplate reader. Adipokines restored the levels of phagocytosis to the high BMI group (p < 0.05), with a mechanism that is action-dependent on the release of ROS and intracellular calcium. However, adiponectin and leptin simultaneously contributed to better microbicidal activity, thus reflecting an increase in the apoptosis level (p < 0.05) in the high BMI group. Probably, the maintenance of the balance between adiponectin and leptin levels enhances the protection and decreases the indices of neonatal infection in the breastfeeding infants of women with high BMI values. Therefore, policies that support pre-gestational weight control should be encouraged.

The X-CGD PLB-985 Cell Model for NOX2 Structure-Function Analysis

Structure-function analysis of specific regions of NOX2 can be carried out after stable expression of site-directed mutagenesis-modified NOX2 in the X⁰-CGD PLB-985 cell model. Indeed, the generation of this human cellular model by Prof. MC Dinauer's team gave researchers the opportunity to gain a deeper understanding of functional regions of NOX2. With this model cell line, the functional impact of X⁺-CGD or of new mutations in NOX2 can be highlighted, as the biological material is not limited. PLB-985 cells transfected with various NOX2 mutations can be easily cultured and differentiated into neutrophils or monocytes/macrophages. Several measurements in intact mutated NOX2 PLB-985 cells can be carried out such as NOX2 expression, cytochrome b ₅₅₈ spectrum, enzymatic activity, and assembly of the NADPH oxidase complex. Purified membranes or purified cytochrome b ₅₅₈ from mutated NOX2 PLB-985 cells can be used for the study of the impact of specific mutations on NADPH oxidase or diaphorase activity, FAD incorporation, and NADPH or NADH binding in a cell-free assay system. Here, we describe a method to generate mutated NOX2 PLB-985 cells in order to analyze NOX2 structure-function relationships.

Down-regulation of NOX2 activity in phagocytes mediated by ATM-kinase dependent phosphorylation

NADPH oxidases (NOX) have many biological roles, but their regulation to control production of potentially toxic ROS molecules remains unclear. A previously identified insertion sequence of 21 residues (called NIS) influences NOX activity, and its predicted flexibility makes it a good candidate for providing a dynamic switch controlling the NOX active site. We constructed NOX2 chimeras in which NIS had been deleted or exchanged with those from other NOXs (NIS1, 3 and 4). All contained functional heme and were expressed normally at the plasma membrane of differentiated PLB-985 cells. However, NOX2-ΔNIS and NOX2-NIS1 had neither NADPH-oxidase nor reductase activity and exhibited abnormal translocation of p47^phox and p67^phox to the phagosomal membrane. This suggested a functional role of NIS. Interestingly after activation, NOX2-NIS3 cells exhibited superoxide overproduction compared with wild-type cells. Paradoxically, the V_max of purified unstimulated NOX2-NIS3 was only one-third of that of WT-NOX2. We therefore hypothesized that post-translational events regulate NOX2 activity and differ between NOX2-NIS3 and WT-NOX2. We demonstrated that Ser486, a phosphorylation target of ataxia telangiectasia mutated kinase (ATM kinase) located in the NIS of NOX2 (NOX2-NIS), was phosphorylated in purified cytochrome b₅₅₈ after stimulation with phorbol 12-myristate-13-acetate (PMA). Moreover, ATM kinase inhibition and a NOX2 Ser486Ala mutation enhanced NOX activity whereas a Ser486Glu mutation inhibited it. Thus, the absence of Ser486 in NIS3 could explain the superoxide overproduction in the NOX2-NIS3 mutant. These results suggest that PMA-stimulated NOX2-NIS phosphorylation by ATM kinase causes a dynamic switch that deactivates NOX2 activity. We hypothesize that this downregulation is defective in NOX2-NIS3 mutant because of the absence of Ser486.

Crystal structures and atomic model of NADPH oxidase

NADPH oxidases (NOXs) are the only enzymes exclusively dedicated to reactive oxygen species (ROS) generation. Dysregulation of these polytopic membrane proteins impacts the redox signaling cascades that control cell proliferation and death. We describe the atomic crystal structures of the catalytic flavin adenine dinucleotide (FAD)- and heme-binding domains of Cylindrospermum stagnale NOX5. The two domains form the core subunit that is common to all seven members of the NOX family. The domain structures were then docked in silico to provide a generic model for the NOX family. A linear arrangement of cofactors (NADPH, FAD, and two membrane-embedded heme moieties) injects electrons from the intracellular side across the membrane to a specific oxygen-binding cavity on the extracytoplasmic side. The overall spatial organization of critical interactions is revealed between the intracellular loops on the transmembrane domain and the NADPH-oxidizing dehydrogenase domain. In particular, the C terminus functions as a toggle switch, which affects access of the NADPH substrate to the enzyme. The essence of this mechanistic model is that the regulatory cues conformationally gate NADPH-binding, implicitly providing a handle for activating/deactivating the very first step in the redox chain. Such insight provides a framework to the discovery of much needed drugs that selectively target the distinct members of the NOX family and interfere with ROS signaling.

Therapeutic effects of proteoliposomes on X-linked chronic granulomatous disease: proof of concept using macrophages differentiated from patient-specific induced pluripotent stem cells

Chronic granulomatous disease (CGD) is a rare inherited immunodeficiency due to dysfunction of the phagocytic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex leading to severe and recurrent infections in early childhood. The main genetic form is the X-linked CGD leading to the absence of cytochrome b₅₅₈ composed of NOX2 and p22^phox, the membrane partners of the NADPH oxidase complex. The first cause of death of CGD patients is pulmonary infections. Recombinant proteoliposome-based therapy is an emerging and innovative approach for membrane protein delivery, which could be an alternative local, targeted treatment to fight lung infections in CGD patients. We developed an enzyme therapy using recombinant NOX2/p22^phox liposomes to supply the NADPH oxidase activity in X⁰-linked CGD (X⁰-CGD) macrophages. Using an optimized prokaryotic cell-free protein synthesis system, a recombinant cytochrome b₅₅₈ containing functional hemes was produced and directly inserted into the lipid bilayer of specific liposomes. The size of the NOX2/p22^phox liposomes was estimated to be around 700 nm. These proteoliposomes were able to generate reactive oxygen species (ROS) in an activated reconstituted cell-free NADPH oxidase activation assay in the presence of recombinant p47^phox, p67^phox and Rac, the cytosolic components of the NADPH oxidase complex. Furthermore, using flow cytometry and fluorescence microscopy, we demonstrated that cytochrome b₅₅₈ was successfully delivered to the plasma membrane of X⁰-CGD-induced pluripotent stem cell (iPSC)-derived macrophages. In addition, NADPH oxidase activity was restored in X⁰-CGD iPSC-derived macrophages treated with NOX2/p22^phox liposomes for 8 h without any toxicity. In conclusion, we confirmed that proteoliposomes provide a new promising technology for the delivery of functional proteins to the membrane of targeted cells. This efficient liposomal enzyme replacement therapy will be useful for future treatment of pulmonary infections in CGD patients refractory to conventional anti-infectious treatments.

TNF and ROS Crosstalk in Inflammation

Tumor necrosis factor (TNF) is tremendously important for mammalian immunity and cellular homeostasis. The role of TNF as a master regulator in balancing cell survival, apoptosis and necroptosis has been extensively studied in various cell types and tissues. Although these findings have revealed much about the direct impact of TNF on the regulation of NF-κB and JNK, there is now rising interest in understanding the emerging function of TNF as a regulator of the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). In this review we summarize work aimed at defining the role of TNF in the control of ROS/RNS signaling that influences innate immune cells under both physiological and inflammatory conditions.

Genetic disorders coupled to ROS deficiency

Maintaining the redox balance between generation and elimination of reactive oxygen species (ROS) is critical for health. Disturbances such as continuously elevated ROS levels will result in oxidative stress and development of disease, but likewise, insufficient ROS production will be detrimental to health. Reduced or even complete loss of ROS generation originates mainly from inactivating variants in genes encoding for NADPH oxidase complexes. In particular, deficiency in phagocyte Nox2 oxidase function due to genetic variants (CYBB, CYBA, NCF1, NCF2, NCF4) has been recognized as a direct cause of chronic granulomatous disease (CGD), an inherited immune disorder. More recently, additional diseases have been linked to functionally altered variants in genes encoding for other NADPH oxidases, such as for DUOX2/DUOXA2 in congenital hypothyroidism, or for the Nox2 complex, NOX1 and DUOX2 as risk factors for inflammatory bowel disease. A comprehensive overview of novel developments in terms of Nox/Duox-deficiency disorders is presented, combined with insights gained from structure-function studies that will aid in predicting functional defects of clinical variants.

Fast, Ultrasensitive Detection of Reactive Oxygen Species Using a Carbon Nanotube Based-Electrocatalytic Intracellular Sensor

Herein, we report a highly sensitive electrocatalytic sensor-cell construct that can electrochemically communicate with the internal environment of immune cells (e.g., macrophages) via the selective monitoring of a particular reactive oxygen species (ROS), hydrogen peroxide. The sensor, which is based on vertically aligned single-walled carbon nanotubes functionalized with an osmium electrocatalyst, enabled the unprecedented detection of a local intracellular "pulse" of ROS on a short second time scale in response to bacterial endotoxin (lipopolysaccharide-LPS) stimulation. Our studies have shown that this initial pulse of ROS is dependent on NADPH oxidase (NOX) and toll like receptor 4 (TLR4). The results suggest that bacteria can induce a rapid intracellular pulse of ROS in macrophages that initiates the classical innate immune response of these cells to infection.

Nanoparticles of barium induce apoptosis in human phagocytes

Purpose

Nutrients and immunological factors of breast milk are essential for newborn growth and the development of their immune system, but this secretion can contain organic and inorganic toxins such as barium. Colostrum contamination with barium is an important issue to investigate because this naturally occurring element is also associated with human activity and industrial pollution. The study evaluated the administration of barium nanoparticles to colostrum, assessing the viability and functional activity of colostral mononuclear phagocytes.

Methods

Colostrum was collected from 24 clinically healthy women (aged 18–35 years). Cell viability, superoxide release, intracellular Ca²⁺ release, and phagocyte apoptosis were analyzed in the samples.

Results

Treatment with barium lowered mononuclear phagocyte viability, increased superoxide release, and reduced intracellular calcium release. In addition, barium increased cell death by apoptosis.

Conclusion

These data suggest that nanoparticles of barium in colostrum are toxic to cells, showing the importance of avoiding exposure to this element.

The effect of IFN-γ and TGF-β in the functional activity of mononuclear cells in the presence of Entamoeba histolytica

Background

Entamoeba histolytica (E. histolytica) causes amoebiasis, which is a disease with significant morbidity and mortality. Phagocytic cells and cytokines appear to be important in amoebiasis, but very little is known about the influence of these cells and cytokines in protozoan infections. The aim of this study was to analyse the supernatant of cultures of mononuclear (MN) cells with E. histolytica to determine: 1) the levels of the cytokines IFN-γ and TGF-β, and 2) the amoebicidal activity of MN cells after incubation with cytokines.

Methods

Blood samples were collected from 30 volunteer donors. The cytokine concentrations in MN cells culture supernatants, superoxide release, leukophagocytosis, amoebicide activity, intracellular calcium release and apoptosis were analysed.

Results

The IFN-γ concentrations were 6.22 ± 0.36 and TGF-β concentrations were 17.01 ± 2.21 in cells–trophozoite culture supernatants. MN cells, independently of cytokines, in the presence of amoeba increase the superoxide release. In the absence of cytokines, the ingestion of MN cells by amoebae was higher. In the presence of IFN- γ or TGF- β, a lower ingestion of MN cells was observed by amoebae. MN cells treated with cytokines exhibited higher amoebicide and apoptosis indexes. The incubation of cytokines increased the intracellular calcium release by MN cells.

Conclusions

These results suggest that cytokines play a beneficial role for the host by activating MN cells against E. histolytica. The increased death of amoebae during the leukophagocytosis suggests that both cytokines (IFN-γ and TGF-β) can modulate the functional activity of MN cells and that these cytokines probably are important in the control of amoebic infections.

Defects in NADPH Oxidase Genes NOX1 and DUOX2 in Very Early Onset Inflammatory Bowel Disease

BACKGROUND & AIMS

Defects in intestinal innate defense systems predispose patients to inflammatory bowel disease (IBD). Reactive oxygen species (ROS) generated by nicotinamide-adenine dinucleotide phosphate (NADPH) oxidases in the mucosal barrier maintain gut homeostasis and defend against pathogenic attack. We hypothesized that molecular genetic defects in intestinal NADPH oxidases might be present in children with IBD.

METHODS

After targeted exome sequencing of epithelial NADPH oxidases NOX1 and DUOX2 on 209 children with very early onset inflammatory bowel disease (VEOIBD), the identified mutations were validated using Sanger Sequencing. A structural analysis of NOX1 and DUOX2 variants was performed by homology in silico modeling. The functional characterization included ROS generation in model cell lines and in in vivo transduced murine crypts, protein expression, intracellular localization, and cell-based infection studies with the enteric pathogens Campylobacter jejuni and enteropathogenic Escherichia coli.

RESULTS

We identified missense mutations in NOX1 (c.988G>A, p.Pro330Ser; c.967G>A, p.Asp360Asn) and DUOX2 (c.4474G>A, p.Arg1211Cys; c.3631C>T, p.Arg1492Cys) in 5 of 209 VEOIBD patients. The NOX1 p.Asp360Asn variant was replicated in a male Ashkenazi Jewish ulcerative colitis cohort. All NOX1 and DUOX2 variants showed reduced ROS production compared with wild-type enzymes. Despite appropriate cellular localization and comparable pathogen-stimulated translocation of altered oxidases, cells harboring NOX1 or DUOX2 variants had defective host resistance to infection with C. jejuni.

CONCLUSIONS

This study identifies the first inactivating missense variants in NOX1 and DUOX2 associated with VEOIBD. Defective ROS production from intestinal epithelial cells constitutes a risk factor for developing VEOIBD.

The human Nox4: gene, structure, physiological function and pathological significance

Increased generation of reactive oxygen species (ROS) has been implicated in the pathogenesis of a variety of diseases such as cardiovascular diseases and cancer. NADPH oxidase (Nox), a multicomponent enzyme, has been identified as one of the key sources of ROS. Nox4, one of the seven members of Nox family (Nox1, Nox2, Nox3, Nox4, Nox5, Duox1 and Duox2), has been extensively investigated in recent years. Its unique structures result in the constitutive generation of hydrogen peroxide (H2O2) as the main product. As a key oxygen sensor, Nox4-derived H2O2 plays diverse roles in cell proliferation, migration and death. Increased expression of Nox4 in cancer has been observed, which participates in metastasis, angiogenesis and apoptosis. Expression of Nox4 in endothelial cells actively mediated endothelial activation, dysfunction and injury, which contributes to the development of atherosclerosis, hypertension, cardiac hypertrophy and among others. This article explores the experimental studies related to the gene, structure, physiological function and pathological significance of Nox4. As Nox4 might serve as a potential target for the therapy of cardiovascular diseases and cancer, the Nox4 inhibitor is also discussed in this article.

Identification of NOX2 regions for normal biosynthesis of cytochrome b558 in phagocytes highlighting essential residues for p22phox binding

Cytochrome b558, the redox core of the NADPH oxidase (NOX) complex in phagocytes, is composed of NOX2 and p22phox, the synthesis of which is intimately connected but not fully understood. We reproduced 10 rare X-minus chronic granulomatous disease (CGD) mutations of highly conserved residues in NOX1-NOX4, in X0-CGD PLB-985 cells in order to analyse their impact on the synthesis of cytochrome b558. According to the impact of these mutations on the level of expression of NADPH oxidase 2 (NOX2) and its activity, mutants were categorized into group A (W18C, E309K, K315del and I325F), characterized by a linear relationship between NOX2 expression and NOX activity, and group B (H338Y, P339H, G389A and F656-F570del), showing an absence of NOX activity associated with variable levels of NOX2 expression. These last residues belong to the FAD-binding pocket of NOX2, suggesting that this functional domain also plays a role in the structural integrity of NOX2. Finally, we observed an abnormal accumulation of p65 (65-kDa monomer), the NOX2 precursor and p65-p22phox dissociation in the W18C, E309K, I325F and G389A mutants, pointing out a possible role of the first transmembrane domain (Trp18), and the region between the membrane and the dehydrogenase domain of NOX2 (Glu309, Ile325 and Gly389), in the binding with p22phox.

Optimized Generation of Functional Neutrophils and Macrophages from Patient-Specific Induced Pluripotent Stem Cells: Ex Vivo Models of X(0)-Linked, AR22(0)- and AR47(0)- Chronic Granulomatous Diseases

Chronic granulomatous disease (CGD) is an inherited orphan disorder caused by mutations in one of the five genes encoding reduced nicotinamide-adenine-dinucleotide-phosphate oxidase subunits, which subsequently lead to impairment in the production of microbicidal reactive oxygen species (ROS). In order to offer several cell line models of CGD and therefore support research on pathophysiology and new therapeutic approaches, we optimized protocols to differentiate induced pluripotent stem cells (iPSCs) from wild-type, X⁰-, AR22⁰- and AR47⁰-CGD patient's fibroblasts into neutrophils and into macrophages. Aberrant genetic clones were discarded after chromosome karyotyping and array-comparative genomic hybridization analysis. All remaining iPSC lines showed human embryonic stem cell–like morphology, expressed all tested pluripotency markers and formed embryoid bodies that contained cells originating from all three primary germ layers. Furthermore, each CGD patient-specific iPSC line retained the gp91^phox, p47^phox, and p22^phox mutations found in the corresponding patient's neutrophils. The average production of CD34⁺ progenitors was of 1.5×10⁶ cells after 10 days of differentiation of 10×10⁶ iPSCs. They were terminally differentiated into about 3×10⁵ neutrophils or into 3×10⁷ macrophages. Based on morphological, phenotypical, and functional criteria both phagocyte types were mature and indistinguishable from the native human neutrophils and macrophages. However, neutrophils and macrophages derived from X⁰-, AR22⁰-, and AR47⁰-CGD patient-specific iPSC lines lacked ROS production and the corresponding mutated proteins. To simplify the phagocytes' production upon request, progenitors can be cryopreserved. In conclusion, we describe a reproducible, simple, and efficient way to generate neutrophils and macrophages from iPSCs and provide a new cellular model for the AR22⁰-CGD genetic form that has not been described before.

Scavenging of reactive oxygen species by tryptophan metabolites helps Pseudomonas aeruginosa escape neutrophil killing

Pseudomonas aeruginosa is responsible for persistent infections in cystic fibrosis patients, suggesting an ability to circumvent innate immune defenses. This bacterium uses the kynurenine pathway to catabolize tryptophan. Interestingly, many host cells also produce kynurenine, which is known to control immune system homeostasis. We showed that most strains of P. aeruginosa isolated from cystic fibrosis patients produce a high level of kynurenine. Moreover, a strong transcriptional activation of kynA (the first gene involved in the kynurenine pathway) was observed upon contact with immune cells and particularly with neutrophils. In addition, using coculture of human neutrophils with various strains of P. aeruginosa producing no (ΔkynA) or a high level of kynurenine (ΔkynU or ΔkynA pkynA), we demonstrated that kynurenine promotes bacterial survival. In addition, increasing the amount kynurenine inhibits reactive oxygen species production by activated neutrophils, as evaluated by chemiluminescence with luminol or isoluminol or SOD-sensitive cytochrome c reduction assay. This inhibition is due neither to a phagocytosis defect nor to direct NADPH oxidase inhibition. Indeed, kynurenine has no effect on oxygen consumption by neutrophils activated by PMA or opsonized zymosan. Using in vitro reactive oxygen species-producing systems, we showed that kynurenine scavenges hydrogen peroxide and, to a lesser extent, superoxide. Kynurenine׳s scavenging effect occurs mainly intracellularly after bacterial stimulation, probably in the phagosome. In conclusion, the kynurenine pathway allows P. aeruginosa to circumvent the innate immune response by scavenging neutrophil reactive oxygen species production.

Cellular and molecular mechanisms activating the cell death processes by chalcones: Critical structural effects

Chalcones are naturally occurring compounds with diverse pharmacological activities. Chalcones derive from the common structure: 1,3-diphenylpropenone. The present study aims to better understand the mechanistic pathways triggering chalcones anticancer effects and providing evidences that minor structural difference could lead to important difference in mechanistic effect. We selected two recently investigated chalcones (A and B) and investigated them on glioblastoma cell lines. It was found that chalcone A induced an apoptotic process (type I PCD), via the activation of caspase-3, -8 and -9. Chalcone A also increased CDK1/cyclin B ratios and decreased the mitochondrial transmembrane potential (ΔΨm). Chalcone B induced an autophagic cell death process (type II PCD), ROS-related but independent of both caspases and protein synthesis. Both chalcones increased Bax/Bcl2 ratios and decreased Ki67 and CD71 antigen expressions. The present investigation reveals that despite the close structure of chalcones A and B, significant differences in mechanism of effect were found.

New insights into the regulation of neutrophil NADPH oxidase activity in the phagosome: a focus on the role of lipid and Ca(2+) signaling

SIGNIFICANCE

Reactive oxygen species, produced by the phagosomal NADPH oxidase of neutrophils, play a significant physiological role during normal defense. Their role is not only to kill invading pathogens, but also to act as modulators of global physiological functions of phagosomes. Given the importance of NADPH oxidase in the immune system, its activity has to be decisively controlled by distinctive mechanisms to ensure appropriate regulation at the phagosome.

RECENT ADVANCES

Here, we describe the signal transduction pathways that regulate phagosomal NADPH oxidase in neutrophils, with an emphasis on the role of lipid metabolism and intracellular Ca(2+) mobilization.

CRITICAL ISSUES

The potential involvement of Ca(2+)-binding S100A8 and S100A9 proteins, known to interact with the plasma membrane NADPH oxidase, is also considered.

FUTURE DIRECTIONS

Recent technical progress in advanced live imaging microscopy will permit to focus more accurately on phagosomal rather than plasma membrane NADPH oxidase regulation during neutrophil phagocytosis.

Antioxidant effect of melatonin on the functional activity of colostral phagocytes in diabetic women

Melatonin is involved in a number of physiological and oxidative processes, including functional regulation in human milk. The present study investigated the mechanisms of action of melatonin and its effects on the functional activity of colostral phagocytes in diabetic women. Colostrum samples were collected from normoglycemic (N = 38) and diabetic (N = 38) women. We determined melatonin concentration, superoxide release, bactericidal activity and intracellular Ca(2+) release by colostral phagocytes treated or not with 8-(Diethylamino) octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8) and incubated with melatonin and its precursor (N-acetyl-serotonin-NAS), antagonist (luzindole) and agonist (chloromelatonin-CMLT). Melatonin concentration was higher in colostrum samples from hyperglycemic than normoglycemic mothers. Melatonin stimulated superoxide release by colostral phagocytes from normoglycemic but not hyperglycemic women. NAS increased superoxide, irrespective of glycemic status, whereas CMTL increased superoxide only in cells from the normoglycemic group. Phagocytic activity in colostrum increased significantly in the presence of melatonin, NAS and CMLT, irrespective of glycemic status. The bactericidal activity of colostral phagocytes against enterophatogenic Escherichia coli (EPEC) increased in the presence of melatonin or NAS in the normoglycemic group, but not in the hyperglycemic group. Luzindole blocked melatonin action on colostrum phagocytes. Phagocytes from the normoglycemic group treated with melatonin exhibited an increase in intracellular Ca(2+) release. Phagocytes treated with TMB-8 (intracellular Ca(2+) inhibitor) decreased superoxide, bactericidal activity and intracellular Ca(2+) release in both groups. The results obtained suggest an interactive effect of glucose metabolism and melatonin on colostral phagocytes. In colostral phagocytes from normoglycemic mothers, melatonin likely increases the ability of colostrum to protect against EPEC and other infections. In diabetic mothers, because maternal hyperglycemia modifies the functional activity of colostrum phagocytes, melatonin effects are likely limited to anti-inflammatory processes, with low superoxide release and bactericidal activity.

Modulation of Human Colostrum Phagocyte Activity by the Glycine-Adsorbed Polyethylene Glycol Microspheres

Colostrum is a secretion that contains immunologically active components, including immunocompetent cells and glycine, which has anti-inflammatory, immunomodulatory, and cytoprotective effects. The aim of this study was to evaluate the adsorption of glycine onto polyethylene glycol (PEG) microspheres and to verify the immunomodulatory effect of this nanomaterial on human colostrum phagocytes. The PEG microspheres were evaluated by fluorescence microscopy. The effects of PEG microspheres with adsorbed glycine on viability, superoxide release, phagocytosis, microbicidal activity, and intracellular calcium release of mononuclear (MN) and polymorphonuclear (PMN) colostrum phagocytes were determined. Fluorescence microscopy analyses revealed that glycine was able to be adsorbed to the PEG microspheres. The PMN phagocytes exposed to glycine-PEG microspheres showed the highest superoxide levels. The phagocytes (both MN and PMN) displayed increased microbicidal activity and intracellular calcium release in the presence of PEG microspheres with adsorbed glycine. These data suggest that the adsorption of PEG microspheres with adsorbed glycine was able to stimulate the colostrum phagocytes. This material may represent a possible alternative therapy for future clinical applications on patients with gastrointestinal infections.

Store-operated Ca2+ entry is remodelled and controls in vitro angiogenesis in endothelial progenitor cells isolated from tumoral patients

BACKGROUND

Endothelial progenitor cells (EPCs) may be recruited from bone marrow to sustain tumor vascularisation and promote the metastatic switch. Understanding the molecular mechanisms driving EPC proliferation and tubulogenesis could outline novel targets for alternative anti-angiogenic treatments. Store-operated Ca(2+) entry (SOCE), which is activated by a depletion of the intracellular Ca(2+) pool, regulates the growth of human EPCs, where is mediated by the interaction between the endoplasmic reticulum Ca(2+)-sensor, Stim1, and the plasmalemmal Ca(2+) channel, Orai1. As oncogenesis may be associated to the capability of tumor cells to grow independently on Ca(2+) influx, it is important to assess whether SOCE regulates EPC-dependent angiogenesis also in tumor patients.

METHODOLOGY/PRINCIPAL FINDINGS

The present study employed Ca(2+) imaging, recombinant sub-membranal and mitochondrial aequorin, real-time polymerase chain reaction, gene silencing techniques and western blot analysis to investigate the expression and the role of SOCE in EPCs isolated from peripheral blood of patients affected by renal cellular carcinoma (RCC; RCC-EPCs) as compared to control EPCs (N-EPCs). SOCE, activated by either pharmacological (i.e. cyclopiazonic acid) or physiological (i.e. ATP) stimulation, was significantly higher in RCC-EPCs and was selectively sensitive to BTP-2, and to the trivalent cations, La(3+) and Gd(3+). Furthermore, 2-APB enhanced thapsigargin-evoked SOCE at low concentrations, whereas higher doses caused SOCE inhibition. Conversely, the anti-angiogenic drug, carboxyamidotriazole (CAI), blocked both SOCE and the intracellular Ca(2+) release. SOCE was associated to the over-expression of Orai1, Stim1, and transient receptor potential channel 1 (TRPC1) at both mRNA and protein level The intracellular Ca(2+) buffer, BAPTA, BTP-2, and CAI inhibited RCC-EPC proliferation and tubulogenesis. The genetic suppression of Stim1, Orai1, and TRPC1 blocked CPA-evoked SOCE in RCC-EPCs.

CONCLUSIONS

SOCE is remodelled in EPCs from RCC patients and stands out as a novel molecular target to interfere with RCC vascularisation due to its ability to control proliferation and tubulogenesis.

Oxidases and peroxidases in cardiovascular and lung disease: new concepts in reactive oxygen species signaling

Reactive oxygen species (ROS) are involved in numerous physiological and pathophysiological responses. Increasing evidence implicates ROS as signaling molecules involved in the propagation of cellular pathways. The NADPH oxidase (Nox) family of enzymes is a major source of ROS in the cell and has been related to the progression of many diseases and even environmental toxicity. The complexity of this family's effects on cellular processes stems from the fact that there are seven members, each with unique tissue distribution, cellular localization, and expression. Nox proteins also differ in activation mechanisms and the major ROS detected as their product. To add to this complexity, mounting evidence suggests that other cellular oxidases or their products may be involved in Nox regulation. The overall redox and metabolic status of the cell, specifically the mitochondria, also has implications on ROS signaling. Signaling of such molecules as electrophilic fatty acids has an impact on many redox-sensitive pathologies and thus, as anti-inflammatory molecules, contributes to the complexity of ROS regulation. This review is based on the proceedings of a recent international Oxidase Signaling Symposium at the University of Pittsburgh's Vascular Medicine Institute and Department of Pharmacology and Chemical Biology and encompasses further interaction and discussion among the presenters.