Regulation of calcium homeostasis in activated human neutrophils - potential targets for anti-inflammatory therapeutic strategies

Objectives. The objectives of the current study were to: (i) present an integrated model for the restoration of calcium homeostasis in activated human neutrophils based on current knowledge and recent research; and (ii) identify potential targets for the modulation of calcium fluxes in activated neutrophils based on this model and to investigate the effects of intracellular probes which target key processes involved in calcium homeostasis and pro-inflammatory activity in these cells. Design and setting. Laboratory-based experimental research using purified human neutrophils from healthy, adult human volunteers. Outcome measures. Calcium metabolism and pro-inflammatory activity of neutrophils. Results. Modulation of calcium fluxes in activated human neutrophils can be achieved by cAMP-dependent upregulation of the activity of the endomembrane Ca2+-ATPase which resequesters cytosolic Ca2+. Formoterol, a long-acting b2-agonist, elevates intracellular cAMP levels, accelerates Ca2+ restoration in activated neutrophils and downregulates the pro-inflammatory responses of these cells. Alterations in the membrane potential of activated neutrophils may play a role in regulating calcium reuptake into the cells as attenuation of the membrane depolarisation response is associated with accelerated calcium influx. Conclusions. Modulation of the activity of the endomembrane Ca2+-ATPase in human neutrophils represents an important target for anti-inflammatory therapeutic strategies, while new insights into the role played by membrane depolarisation in regulating calcium fluxes in these cells may also facilitate development of novel anti-inflammatory agents directed against neutrophils. (South African Medical Journal: 2002 92(12): 990-996

Pharmacological control of neutrophil-mediated inflammation: Strategies targeting calcium handling by activated polymorphonuclear leukocytes

Unlike most other effector cells of the innate, as well as the adaptive immune systems, the neutrophil is a relatively undiscerning aggressor with scant regard for damage limitation. Although this highly combative, professional phagocyte has become increasingly implicated in the immunopathogenesis of many acute and chronic inflammatory disorders, of both infective and noninfective origin, effective pharmacological strategies to counter neutrophilaggression have remained elusive. Activation of neutrophils results in rapid mobilization of both stored and extracellular Ca2+, resulting in abrupt, usually transient increases in cytosolic Ca2+, which precede, and are a prerequisite for activation of the Ca2+-dependent pro-inflammatory activities of these cells. Mobilization of Ca2+ by, and restoration of Ca2+ homeostasis to activated neutrophils are multistep processes which present a number of potential targets, some well recognized and others noveland unconventional, for the pharmacological control of neutrophil-mediated inflammation. Uncovering these targets represents the primary focus of this review

An unusual cause of dyspnoea – can you spot the diagnosis?

A 66-year-old man presented with a complaint of shortness of breath. He had a significant smoking history but no known medical conditions. Two years prior, he had been involved in a motor vehicle accident and sustained blunt trauma to his chest.http://www.ajtccm.org.za/index.php/SARJam2023Internal Medicin

Protein kinase C promotes restoration of calcium homeostasis to platelet activating factor-stimulated human neutrophils by inhibition of phospholipase C

<p>Abstract</p> <p>Background</p> <p>The role of protein kinase C (PKC) in regulating the activity of phospholipase C (PLC) in neutrophils activated with the chemoattractant, platelet-activating factor (PAF, 20 and 200 nM), was probed in the current study using the selective PKC inhibitors, GF10903X (0.5 - 1 μM) and staurosporine (400 nM).</p> <p>Methods</p> <p>Alterations in cytosolic Ca²⁺, Ca²⁺influx, inositol triphosphate (IP₃), and leukotriene B₄production were measured using spectrofluorimetric, radiometric and competitive binding radioreceptor and immunoassay procedures, respectively.</p> <p>Results</p> <p>Activation of the cells with PAF was accompanied by an abrupt increase in cytosolic Ca²⁺followed by a gradual decline towards basal levels. Pretreatment of neutrophils with the PKC inhibitors significantly increased IP₃production with associated enhanced Ca²⁺release from storage vesicles, prolongation of the peak cytosolic Ca²⁺transients, delayed clearance and exaggerated reuptake of the cation, and markedly increased synthesis of LTB₄. The alterations in Ca²⁺fluxes observed with the PKC inhibitors were significantly attenuated by U73122, a PLC inhibitor, as well as by cyclic AMP-mediated upregulation of the Ca²⁺-resequestering endomembrane ATPase.</p> <p>Taken together, these observations are compatible with a mechanism whereby PKC negatively modulates the activity of PLC, with consequent suppression of IP₃production and down-regulation of Ca²⁺mediated pro-inflammatory responses of PAF-activated neutrophils.</p> <p>Conclusion</p> <p>Although generally considered to initiate and/or amplify intracellular signalling cascades which activate and sustain the pro-inflammatory activities of neutrophils and other cell types, the findings of the current study have identified a potentially important physiological, anti-inflammatory function for PKC, at least in neutrophils.</p

La femme est-elle l’avenir de l’humanitaire ?

Pour qui s’est déjà aventuré dans les couloirs d’une ONG, le constat est évident : les femmes y sont largement représentées. Sur les terrains de crises, notamment les conflits, elles figurent bien souvent au premier rang des victimes. C’est en partant de ce simple constat que nous avons invité des étudiantes du IIIe cycle Affaires humanitaires et coopération internationale de l’Université Aix-Marseille II – dont la revue est partenaire – à décliner sur le mode humanitaire une question éternelle

Harmful interactions of non-essential heavy metals with cells of the innate immune system

In trace amounts, some heavy metals are essential for optimum health, while exposure to others, which are non-essential, presents the potential hazard of acute or chronic organ toxicity. Cadmium, mercury, lead, vanadium, platinum and palladium are commonly encountered, non-essential heavy metals which mediate their toxic activities by various mechanisms. All have the potential to interact with extracellular and intracellular protein sulfhydryls, rendering them not only potentially allergenic, but also predisposing to oxidative stress, while displacement of essential elements from their protein carriers may result in deficiency disorders. In addition, several of these metals, especially cadmium, palladium, platinum, and vanadium interact pro-oxidatively with the phagocytic cells of the innate immune system, potentiating the reactivity and toxicity of phagocyte-derived reactive oxygen species. This review is focused on the pro-oxidative/pro-inflammatory interactions of non-essential heavy metals with the cells of the innate immune system, a somewhat under-appreciated mechanism of metal induced toxicity.This article was originally published in a special issue, Heavy Metal Toxicity handled by Editor(s). Dr. Noreen Khan-Mayberry, National Aeronautics & Space Administration at Lyndon B. Johnson Space Center in Houston, USAhttp://http://www.omicsonline.org/jcthome.phpam201

Montelukast: More than a Cysteinyl Leukotriene Receptor Antagonist?

The prototype cysteinyl leukotriene receptor antagonist, montelukast, is generally considered to have a niche application in the therapy of exercise- and aspirin-induced asthma. It is also used as add-on therapy in patients whose asthma is poorly controlled with inhaled corticosteroid monotherapy, or with the combination of a long-acting β(2)-agonist and an inhaled corticosteroid. Recently, however, montelukast has been reported to possess secondary anti-inflammatory properties, apparently unrelated to conventional antagonism of cysteinyl leukotriene receptors. These novel activities enable montelukast to target eosinophils, monocytes, and, in particular, the corticosteroid-insensitive neutrophil, suggesting that this agent may have a broader spectrum of anti-inflammatory activities than originally thought. If so, montelukast is potentially useful in the chemotherapy of intermittent asthma, chronic obstructive pulmonary disease, cystic fibrosis, and viral bronchiolitis, which, to a large extent, involve airway epithelial cell/neutrophil interactions. The primary objective of this mini-review is to present evidence for the cysteinyl leukotrien–independent mechanisms of action of montelukast and their potential clinical relevance

Adverse effects of biologic anti-inflammatory agents on the respiratory system : a review

The therapy of autoimmune rheumatological conditions has undergone significant changes with the introduction of biologic antiinflammatory agents including cytokine antagonists and agents that interfere with the function of T and B cells or those that inhibit intracellular enzymes such as Janus kinase (JAK). Although useful to control inflammation, these agents may be associated with drug-induced lung disease, which may be difficult to differentiate from pulmonary disorders caused by the underlying autoimmune diseases. This review aims to provide a description of lung disease, both infectious and non-infectious, that may be induced by the administration of biologic anti-inflammatory agents with emphasis on inhibitors of tumour necrosis factor, interleukin-1, interleukin-6 and JAK.https://journals.co.za/journal/m.ajtccmam2022Internal Medicin

Cigarette smoke condensate attenuates phorbol ester-mediated neutrophil extracellular trap formation.

Background: Neutrophil extracellular traps (NETs) constitute a network of chromatin fibres containing histone and antimicrobial peptides that are released by activated neutrophils. NETs protect the host against infection by trapping and facilitating phagocytosis of potentially harmful pathogens. Objectives: The aim of the current study was to investigate the effects of cigarette smoke condensate (CSC) on phorbol-ester (PMA)-mediated NETosis in vitro. Methods: Isolated human blood neutrophils were exposed to PMA (6.25 ng/ml) in the presence or absence of CSC (40-80 \ub5g/ ml) for 90 min at 37oC. NET formation was measured using a spectrofluorimetric procedure to detect extracellular DNA and fluorescence microscopy was used to visualize nets. Oxygen consumption by PMA-activated neutrophils was measured using an oxygen sensitive electrode. Results: Activation of neutrophils with PMA was associated with induction of NETosis that was significantly attenuated in the presence of CSC (40 and 80 \ub5g/ml), with mean fluorescence intensities of 65% and 66% of that observed with untreated cells, respectively, and confirmed by fluorescence microscopy. The rate and magnitude of oxygen consumption by activated neutrophils pre-treated with CSC (80 \ub5g/ml) was significantly less than that observed with untreated cells (73% of the control system), indicative of decreased production of reactive oxidants in the presence of CSC. Conclusion: The inhibition of NETosis observed in the presence of CSC correlated with attenuation of oxygen consumption by PMA-activated neutrophils suggesting a mechanistic relationship between these events. If operative in vivo, smoking-related attenuation of NETosis may impair host immune responses and increase the risk of respiratory infections