Neutrophil Hyperactivation Research Articles

Inositol trisphosphate 3-kinase B (InsP3KB) as a physiological modulator of myelopoiesis.

Inositol trisphosphate 3-kinase B (InsP3KB) belongs to a family of kinases that convert inositol 1,4,5-trisphosphate (Ins(1,4,5)P3 or IP3) to inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4). Previous studies have shown that disruption of InsP3KB leads to impaired T cell and B cell development as well as hyperactivation of neutrophils. Here, we demonstrate that InsP3KB is also a physiological modulator of myelopoiesis. The InsP3KB gene is expressed in all hematopoietic stem/progenitor cell populations. In InsP3KB null mice, the bone marrow granulocyte monocyte progenitor (GMP) population was expanded, and GMP cells proliferated significantly faster. Consequently, neutrophil production in the bone marrow was enhanced, and the peripheral blood neutrophil count was also substantially elevated in these mice. These effects might be due to enhancement of PtdIns(3,4,5)P3/Akt signaling in the InsP3KB null cells. Phosphorylation of cell cycle-inhibitory protein p21(cip1), one of the downstream targets of Akt, was augmented, which can lead to the suppression of the cell cycle-inhibitory effect of p21.

Immunopathogenesis of Behçet’s disease with special emphasize on the possible role of antigen presenting cells

Behçet's disease (BD) is a systemic vasculitis with unclear etiology and pathogenesis. Although several viral and bacterial causes have been investigated in detail for several years, of late it is widely accepted that microorganisms may play a role as a trigger, or as a cross-reactive antigens that interfere with self-antigens, such as heat-shock proteins. Genes such as HLA-B51, MICA and TNF, considered to play a crucial role in the pathogenesis of BD, are located in the major histocompatibility complex (MHC). However, it has been accepted that, only HLA-B51 is directly related with pathogenesis of the disease, and others have strong linkage disequilibrium with HLA-B51. Some other genes such as IL1, Factor V and ICAM-1, KIR and eNOS assumed to take a part in the pathogenesis are settled out of the MHC region. In patients with BD, several abnormalities in innate and acquired immunity were detected. Mainly, the hypersensitivity of T lymphocytes to different types of antigens plays a critical role in the pathogenesis. However, it is not clear that whether defective signal transduction or antigen presenting cell (APC) dysfunction is responsible for T cell hypersensitivity. Cytokines and chemokines secreted from APCs and T cells are suggested to cause the neutrophil hyperactivation. Activated neutrophils secrete some cytokines, which prime themselves and also stimulate Th1 cells. These relationships among APCs, Th1 lymphocytes and neutrophils constitute the basis of immune responses in BD. In this review, we focus on the possible role of APC in the pathogenesis of BD with an attempt to take attention of researchers in this field to these cells at the crossroads of innate and adaptive immunity, and discuss other potential contributors including cells of the immune system and mediators.

Neutrophils and the blood–brain barrier dysfunction after trauma

Despite the fact that neutrophils are essential for the protection from invading pathogens, hyperactive neutrophils may elicit detrimental cerebral damage after severe trauma. The neutrophil interactions with the neurovascular unit entail endothelial dysfunction involving endothelial leakage, formation of edema, coagulation abnormalities, disturbed hemodynamics, tissue infiltration etc. These elements of the "whole body inflammation," designated systemic inflammatory response syndrome (SIRS) in conjunction with intracerebral proinflammatory activities, are important triggers of post-traumatic cerebral damage and mortality according to the "second hit" concept. From the immunologic point of view, the brain is an immune privileged site, known to resist autodestructive inflammatory activity much more efficiently than other organs because of the highly efficient diverse functions of the blood-brain barrier (BBB). However, both the underlying strategy of the BBB to maintain cerebral protecting functions against the post-traumatic neutrophil-mediated "second hit" and how activated neutrophils may overcome the BBB are currently unknown. Therefore, this review summarizes the current understanding of the "second hit," the BBB physiology, and its role in the maintenance of cerebral immune privilege, and discusses recent findings that may explain the pathophysiologic neutrophil-BBB interactions occurring after severe trauma, thus offering novel therapeutic options to protect from post-traumatic brain damage.

SIMVASTATIN ATTENUATES POSTBURN INTESTINAL TISSUE DAMAGE IN RATS.

Objective: To test the effects of early postburn treatment with statins on major postburn sepsis pathogenesis in the form of gut inflammation and transepithelial leakiness. Rationale: We and others have demonstrated intestinal structural and permeability changes within three days after major thermal injury (Critical Care Medicine 32:1730-9, 2004). These changes are associated with gut tissue inflammation and immediate postburn systemic neutrophil hyperactivation and extravasation. Here, we hypothesize that such changes can be suppressed by treatment with simvastatin which had been shown to have antiinflammatory effects that include inhibition of neutrophil extravasation (Circulation 106:2104-2110, 2002). Methods: Utilizing a rat burn model with third degree burn over 30% total body surface area, we assessed gut inflammation and transepithelial permeability three days postburn with or without daily intraperitoneal injection of simvastatin. Gut inflammation was assessed by measuring tissue myeloperoxidase (MPO) activity and nitrotyrosine immunohistochemistry. Transepithelial leakiness across ex vivo gut specimens was measured utilizing FITC-dextran-40S with an Ussing diffusion chamber. Results: Our results show a substantial increase in tissue MPO activity and nitrotyrosine immunoreactivity in rat ileum and mesenteric lymph nodes 1 to 3 days postburn. However, both MPO activity and nitrotyrosine immunolabeling were largely diminished in sham and simvastatin-treated rats. Furthermore, transepithelial large molecule leakage was increased three days postburn with evidence of paracellular transport. This leakage was also significantly attenuated in sham rats and in simvastatintreated postburn rats. Conclusion: Simvastatin treatment appears to be beneficial in preventing inflammation-mediated postburn gut tissue damage that is presumed to precipitate postburn sepsis pathogenesis. Acknowledgements: This work was supported by National NIH grant# 3 S06 GM008043-34S1 (project# 6) and by NSF BIOMRI Award# DBI-0520869.

First Efficacy and Safety Results with the Antibody Containing Leukocyte Inhibition Module in Cardiac Surgery Patients with Neutrophil Hyperactivity

Systemic administration of immune modulating antibodies may play an important role in reducing neutrophil hyperactivity, for example, in patients undergoing cardiac surgery with extracorporeal circulation or in trauma patients. However, this strategy has extremely high costs and is often associated with severe adverse effects. We developed the Leukocyte-Inhibition-Module (LIM), an extracorporeal circulation (ECC) device housing a polyurethane matrix with covalently bound Fas (CD95; APO-1) stimulating antibodies to rapidly prevent neutrophil hyperactivation. A feasibility study with 14 patients undergoing cardiac surgery with the use of immunogenic ECC without (n = 5) and with (n = 9) LIM (venous line) was performed. Our data show that the usually observed ECC associated perioperative increase in neutrophils (control) was prevented by LIM (p = 0.023). Moreover, the increase of the proinflammatory markers tumor necrosis factor (TNF)-alpha and polymorphonuclear elastase was limited by LIM (p = 0.038 and p = 0.002). In both groups, no significant changes in liver enzymes or in clotting were detected after surgery, and up to 12 months follow up, no unusual complications were reported. This study shows for the first time to our knowledge the feasibility, efficacy, and safety of a new cost effective, immune management strategy in patients with aberrant immune activation by exposing the blood stream to immobilized agonistic anti-Fas antibodies.

Anaphylatoxin Signaling in Human Neutrophils: A KEY ROLE FOR SPHINGOSINE KINASE

Anaphylatoxins activate immune cells to trigger the release of proinflammatory mediators that can lead to the pathology of several immune-inflammatory diseases. However, the intracellular signaling pathways triggered by anaphylatoxins are not well understood. Here we report for the first time that sphingosine kinase (SPHK) plays a key role in C5a-triggered signaling, leading to physiological responses of human neutrophils. We demonstrate that C5a rapidly stimulates SPHK activity in neutrophils and differentiated HL-60 cells. Using the SPHK inhibitor N,N-dimethylsphingosine (DMS), we show that inhibition of SPHK abolishes the Ca2+ release from internal stores without inhibiting phospholipase C or protein kinase C activation triggered by C5a but has no effect on calcium signals triggered by other stimuli (FcgammaRII). We also show that DMS inhibits degranulation, activation of the NADPH oxidase, and chemotaxis triggered by C5a. Moreover, an antisense oligonucleotide against SPHK1, in neutrophil-differentiated HL-60 cells, had similar inhibitory properties as DMS, suggesting that the SPHK utilized by C5a is SPHK1. Our data indicate that C5a stimulation decreases cellular sphingosine levels and increases the formation of sphingosine-1-phosphate. Exogenously added sphingosine has a dual effect on C5a-stimulated oxidative burst: it has a priming effect at lower concentrations but a dose-dependent inhibitory effect at higher concentrations; however, C5a-triggered protein kinase C activity was only reduced at high concentration of sphingosine. In contrast, C5a-triggered Ca2+ signals, chemotaxis, and degranulation were not affected by sphingosine at all. Exogenous sphingosine-1-phosphate, by itself, did not induce degranulation or chemotaxis, but it did marginally induce Ca2+ signals and oxidative burst and had a priming effect, enhancing all the C5a-triggered responses. Taken together, these results suggest that SPHK plays an important role in the immune-inflammatory pathologies triggered by anaphylatoxins in human neutrophils and point out SPHK as a potential therapeutic target for the treatment of diseases associated with neutrophil hyperactivation.

Accelerated calcium influx and hyperactivation of neutrophils in chronic granulomatous disease.

The relationship between activation of NADPH-oxidase, alterations in membrane potential and triggering of Ca2+ fluxes in human phagocytes has been investigated using neutrophils from four subjects with chronic granulomatous disease (CGD). Cytosolic Ca2+ and membrane potential were measured by spectrofluorimetry, and net efflux and influx of Ca2+ by radiometric procedures. Exposure of normal neutrophils to the chemotactic tripeptide, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP; 1 microM) was accompanied by an abrupt increase in cytosolic Ca2+ coincident with membrane depolarization and efflux of the cation. These events terminated at around 30 s after the addition of FMLP and were followed by membrane repolarization and store-operated influx of Ca2+, both of which were superimposable and complete after about 5 min. Activation of CGD neutrophils was also accompanied by an increase in cytosolic Ca2+, which, in spite of an efficient efflux response, was prolonged in relation to that observed in normal cells. This prolonged increase in cytosolic Ca2+ in activated CGD neutrophils occurred in the setting of trivial membrane depolarization and accelerated influx of Ca2+, and was associated with hyperactivity of the cells according to excessive release of elastase and increased activity of phospholipase A2. Treatment of CGD neutrophils with the type 4 phosphodiesterase inhibitor, rolipram (1 microM) restored Ca2+ homeostasis and attenuated the increase in elastase release. These findings support the involvement of NADPH-oxidase in regulating membrane potential and Ca2+ influx in activated neutrophils, and may explain the disordered inflammatory responses and granuloma formation which are characteristic of CGD.

Exuberant Ca2+Signaling in Neutrophils: A Cause for Concern

Under inflammatory conditions after burn/trauma injuries, circulating neutrophils are frequently hyperactive, contributing to excessive superoxide production and related tissue damage. Although normal neutrophil activation is cooperatively controlled by Ca(2+)-independent and Ca(2+)-linked signaling pathways, exuberant Ca(2+)-linked signaling appears to cause neutrophil hyperactivation in the injury conditions.

Increased amounts of laminin in GCF from untreated patients with periodontitis

Our aim was to compare the levels of laminin and interleukin-8 (IL-8) in GCF from inflamed shallow (GP) and deep pockets (PP) in patients with periodontitis to these levels in GCF from inflamed shallow pockets (GG) in subjects with gingivitis alone. Lactoferrin was used as a marker for the number of neutrophils in the sites sampled. The periodontitis group consisted of 13 subjects, having at least 6 sites with a pocket depth > or = 5 mm. The healthy control group consisted of 12 subjects with no clinical signs of periodontal destruction. GCF was collected with paper strips and the volume was measured immediately after sampling. Laminin, lactoferrin and IL-8 were measured using specific antibodies with an ELISA. The total amount of laminin was significantly higher in PP than in GG, but no significant difference was seen between GP and PP. The concentration and the total amounts of lactoferrin were similar in the three groups. The ratio between laminin and lactoferrin was higher in the samples from the patient, suggesting that neutrophils in patients are more activated and degrades more of the membrane per cell. The total amounts of IL-8 were very similar in the 3 groups, while the concentration also tended to be higher in the GP. Our study showed higher amounts of laminin in GCF from patients with periodontitis suggesting the presence of hyperactive neutrophils during the transmigration process through the endothelium/epithelium.

Role of tumor necrosis factor-α in Sneddon-Wilkinson subcorneal pustular dermatosis: A model of neutrophil priming in vivo

A patient with IgG-kappa-associated subcorneal pustular dermatosis (Sneddon-Wilkinson disease) refractory to dapsone, etretinate, and plasma exchange was successfully treated with corticosteroids. A study of neutrophils from both blood and pustules was carried out before and during treatment. Levels of tumor necrosis factor-alpha were measured in serum, pustules, content, and supernatant of monocytes. The results suggest that a hyperactivation of neutrophils in the skin is due at least partly to excessive production of tumor necrosis factor-alpha.