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Enzyme-Releasing Peptide
Published in Jason Kelley, Cytokines of the Lung, 2022
Allen B. Cohen, Edmund J. Miller, Cassandra MacArthur
Neutrophils contain different kinds of granules or packets of enzymes that are released to the extracellular milieu when the granules are extruded (degranulated). Each type of granule contains different enzymes, and each is released by separate kinds of stimuli. Some of the granules are easy to release, and the release of others is difficult. One type of granule, the specific granule, contains receptors on the granule membrane. When the specific granule constituents are extruded, the granule’s membranes become part of the plasma membrane and the receptors become accessible to their agonists or up-regulated. Azurophilic granules are more difficult to release and contain elastase, myeloperoxidase, and other proteinases and hydrolases.
Constitutive Host Resistance
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
The granules of the neutrophil and eosinophil contain enzymes, whereas those within the basophil contain biologically active amines. The enzymes in the neutrophilic granules are important for the destruction and digestion of microorganisms and other foreign organic materials (Table 3.1). The granules are classified into two types: the primary or azurophilic granules, and the secondary, or specific, granules. The terms primary and secondary refer to the color or appearance of the granules during differentiation rather than to the importance of the granules. The azurophilic granules contain peroxidase, myeloperoxidase, acid hydrolases, neutral proteases, cationic antimicrobial proteins, and lysozyme. The neutral proteases include elastase, collagenase, and cathepsin G. Enzymes released by neutrophils will activate complement and generate kinins (see chapter 4); the enzymes therefore enhance vascular permeability and chemotaxis indirectly. The specific granules contain lactoferrin and lysozyme.
Phagocytosis By Human Neutrophils
Published in Hans H. Gadebusch, Phagocytes and Cellular Immunity, 2020
The large peak of turbidity (peak III) represents the azurophil granules of the cell.24,267,268 These are generally considered to be true lysosomes and contain a large number of acid hydrolases. In addition to the acid hydrolases typical of most lyso somes, the azurophil granules also contain the myeloperoxidase (MPO) of the cell and about 50% of the lysozyme.M267,268 The remaining lysozyme is found in the specific granules. A number of neutral proteases have been localized to the azurophil granule.272 A series of seven cationic proteins with bactericidal activity has been localized to the azurophil granules in rabbit neutrophils;26 similar proteins have been identified in human neutrophils.273
A novel 4-dimensional live-cell imaging system to study leukocyte-endothelial dynamics in ANCA-associated vasculitis
Published in Autoimmunity, 2020
Catriona A. Walls, Neil Basu, Gayle Hutcheon, Lars P. Erwig, Mark A. Little, Dana Kidder
Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) is a group of devastating autoimmune disorders characterised by relapsing necrotising vasculitis of small blood vessels, commonly involving kidneys and lungs. Considering the aggressive inflammation and multisystem nature of AAV, it is associated with significant morbidity and mortality [1]. The aetiology of AAV is unclear, but genetic and environmental factors, including infections, are proposed in the initiation of autoimmunity through dysfunctional innate and adaptive immune responses [2]. ANCA autoantibodies develop in susceptible individuals and target the antigens myeloperoxidase (MPO) and proteinase 3 (PR3). These antigens are present in the azurophilic granules of neutrophils and lysosomes of monocytes [3].
Role of Mac-1 integrin in generation of extracellular vesicles with antibacterial capacity from neutrophilic granulocytes
Published in Journal of Extracellular Vesicles, 2020
Ákos M. Lőrincz, Balázs Bartos, Dávid Szombath, Viktória Szeifert, Csaba I. Timár, Lilla Turiák, László Drahos, Ágnes Kittel, Dániel S. Veres, Ferenc Kolonics, Attila Mócsai, Erzsébet Ligeti
The presented experiments indicate the role of Mac-1/CR3 in initiating the formation of antibacterial EVs from neutrophilic granulocytes. In human neutrophils, only under conditions of costimulation of complement receptors could we observe the characteristic triad of (i) strong increase in the number and protein content of the produced EVs, (ii) reproducible enrichment of proteins issued from azurophilic and specific granules and (iii) appearance of the capability to impair bacterial growth. Similar to human neutrophils, significant increase of EV formation could be achieved upon stimulation with fully opsonized particles also in murine cells. Generation of these CabzEVs was completely blocked in the absence of either chain of the Mac-1 integrin. In contrast, stimulation of Fc receptors alone (on IC surface, Figure 2(b)) or in combination with PRR (in the soluble system, Figure 2(a)) did not result in generation of aEVs. In the murine system lack of signal transduction via Fc receptors did not affect CabzEV generation. Whereas our experiments do not formally exclude the possibility of participation of Fc receptors in triggering of aEV formation, they do not provide experimental support for it. Stimulation of unidentified PRRs did induce a slight increase in EV number, but these vesicles had no enrichment of granule proteins as compared to sEV and were devoid of antibacterial capacity; however, their costimulatory role cannot be excluded. Previous investigations showed that soluble proinflammatory mediators such as FMLF, TNFα, CXCL12 and LPS were not able to initiate aEV production either [18].
Syzygium aromaticum aqueous extract inhibits human neutrophils myeloperoxidase and protects mice from LPS-induced lung inflammation
Published in Pharmaceutical Biology, 2019
Amina Chniguir, Fatma Zioud, Viviana Marzaioli, Jamel El-Benna, Rafik Bachoual
MPO is an important indicator of polymorphonuclear leukocytes activation. It is released from azurophil granules of activated neutrophils. We evaluated the effect of SAAE on MPO degranulation. Results show that SAAE had no effect on MPO degranulation in resting neutrophils (Figure 5(A)) and also in neutrophils stimulated with PMA (Figure 5(B)).