Human neutrophil azurocidin synergizes with leukocyte elastase and cathepsin G in the killing of Capnocytophaga sputigena

Identification of diagnostic upper gastrointestinal cancer tissue type-specific urinary biomarkers

Several potential urinary biomarkers exhibiting an association with upper gastrointestinal tumour growth have been previously identified, of which S100A6, S100A9, rabenosyn-5 and programmed cell death 6-interacting protein (PDCD6IP) were further validated and found to be upregulated in malignant tumours. The cancer cohort from our previous study was subclassified to assess whether distinct molecular markers can be identified for each individual cancer type using a similar approach. Urine samples from patients with cancers of the stomach, oesophagus, oesophagogastric junction or pancreas were analysed by surface-enhanced laser desorption/ionization-time-of-flight mass spectrometry using both CM10 and IMAC30 (Cu²⁺-complexed) chip types and LC-MS/MS-based mass spectrometry after chromatographic enrichment. This was followed by protein identification, pattern matching and validation by western blotting. We found 8 m/z peaks with statistical significance for the four cancer types investigated, of which m/z 2447 and 2577 were identified by pattern matching as fragments of cathepsin-B (CTSB) and cystatin-B (CSTB); both molecules are indicative of pancreatic cancer. Additionally, we observed a potential association of upregulated α-1-antichymotrypsin with pancreatic and gastric cancers, of PDCD6IP, vitelline membrane outer layer protein 1 homolog (VMO1) and triosephosphate isomerase (TPI1) with oesophagogastric junctional cancers, and of complement C4-A, prostatic acid phosphatase, azurocidin and histone-H1 with oesophageal cancer. Furthermore, the potential pancreatic cancer biomarkers CSTB and CTSB were validated independently by western blotting. Therefore, the present study identified two new potential urinary biomarkers that appear to be associated with pancreatic cancer. This may provide a simple, non-invasive screening test for use in the clinical setting.

Super-silent FRET Sensor Enables Live Cell Imaging and Flow Cytometric Stratification of Intracellular Serine Protease Activity in Neutrophils

Serine proteases are released by neutrophils to act primarily as antimicrobial proteins but excessive and unbalanced serine protease activity results in serious host tissue damage. Here the synthesis of a novel chemical sensor based on a multi-branched fluorescence quencher is reported. It is super-silent, exhibiting no fluorescence until de-quenched by the exemplar serine protease human neutrophil elastase, rapidly enters human neutrophils, and is inhibited by serine protease inhibitors. This sensor allows live imaging of intracellular serine protease activity within human neutrophils and demonstrates that the unique combination of a multivalent scaffold combined with a FRET peptide represents a novel and efficient strategy to generate super-silent sensors that permit the visualisation of intracellular proteases and may enable point of care whole blood profiling of neutrophils.

Isolation of Rat Lung Mast Cells for Purposes of One-Week Cultivation Using Novel Percoll Variant Percoll PLUS

Prolonged cultivation of separated rat lung mast cells (LMC) in vitro is necessary to better investigate a possible role of LMC in different stages of tissue remodeling induced by hypoxia. Rat lung mast cells (LMC) were separated using a protocol including an improved proteolytic extraction and two subsequent density gradient separations on Ficoll-Paque PLUS and a new generation of Percoll, i.e. Percoll PLUS. Instead of usual isotonic stock Percoll solution, an alternative “asymptotically isotonic” stock solution was more successful in our density separation of LMC on Percoll PLUS. Separated cells were cultivated for six days in media including stem cell factor, interleukins IL-3 and IL-6, and one of two alternative mixtures of antibiotics. These cultivations were performed without any contamination and with only rare changes in cell size and morphology. Model co-cultivation of two allogenic fractions of LMC often caused considerable rapid changes in cell morphology and size. In contrast to these observations no or rare morphological changes were found after cultivation under hypoxic conditions. In conclusions, we modified separation on Percoll PLUS to be widely used, altered LMC separation with respect to purposes of long-lasting cultivation and observed some model morphological changes of LMC.

Antimicrobial proteins with homology to serine proteases

The azurophil granule, a specialized lysosome of human neutrophils, contains a family of antimicrobial proteins with structural homology to serine proteases, the serprocidins. Three members of this family are serine proteases (cathepsin G, elastase and proteinase-3) and one is a proteolytically inactive homologue (azurocidin). They are synthesized as preproproteins with a characteristic leader peptide and a propiece, both of which are removed by processing enzymes to yield the mature protein. The functional genes for three serprocidins (elastase, proteinase-3 and azurocidin) are grouped in a single genetic locus on chromosome 19 and are coordinately expressed and regulated during haemopoietic differentiation. Multiple and sometimes overlapping biological functions are a feature of this family, yet they all seem to pertain to host immunity. The structural requirements for the function of one member of this group (azurocidin), particularly its antibiotic function, are under investigation.

Antimicrobial proteins and peptides: anti-infective molecules of mammalian leukocytes

Phagocytic leukocytes are a central cellular element of innate-immune defense in mammals. Over the past few decades, substantial progress has been made in defining the means by which phagocytes kill and dispose of microbes. In addition to the generation of toxic oxygen radicals and nitric oxide, leukocytes deploy a broad array of antimicrobial proteins and peptides (APP). The majority of APP includes cationic, granule-associated (poly)peptides with affinity for components of the negatively charged microbial cell wall. Over the past few years, the range of cells expressing APP and the potential roles of these agents have further expanded. Recent advances include the discovery of two novel families of mammalian APP (peptidoglycan recognition proteins and neutrophil gelatinase-associated lipocalin), that the oxygen-dependent and oxygen-independent systems are inextricably linked, that APP can be deployed in the context of novel subcellular organelles, and APP and the Toll-like receptor system interact. From a clinical perspective, congeners of several of the APP have been developed as potential therapeutic agents and have entered clinical trials with some evidence of benefit.

Antimicrobial proteins and peptides of blood: templates for novel antimicrobial agents

The innate immune system provides rapid and effective host defense against microbial invasion in a manner that is independent of prior exposure to a given pathogen.1 It has long been appreciated that the blood contains important elements that mediate rapid responses to infection. Thus, anatomic compartments with ample blood supply are less frequently infected and recover more readily once infected, whereas regions with poor perfusion are prone to severe infection and may require surgical débridement. Blood-borne innate immune mediators are either carried in circulating blood cells (ie, leukocytes and platelets) or in plasma after release from blood cells or on secretion by the liver.

Antimicrobial proteins and peptides of blood: templates for novel antimicrobial agents

The innate immune system provides rapid and effective host defense against microbial invasion in a manner that is independent of prior exposure to a given pathogen.1 It has long been appreciated that the blood contains important elements that mediate rapid responses to infection. Thus, anatomic compartments with ample blood supply are less frequently infected and recover more readily once infected, whereas regions with poor perfusion are prone to severe infection and may require surgical débridement. Blood-borne innate immune mediators are either carried in circulating blood cells (ie, leukocytes and platelets) or in plasma after release from blood cells or on secretion by the liver.

Identification of constituents of human neutrophil azurophil granules that mediate fungistasis against Histoplasma capsulatum

Previously we demonstrated that human neutrophils mediate potent and long-lasting fungistasis against Histoplasma capsulatum yeasts and that all of the fungistatic activity resides in the azurophil granules. In the present study, specific azurophil granule constituents with fungistatic activity were identified by incubation with H. capsulatum yeasts for 24 h and by quantifying the subsequent growth of yeasts via the incorporation of [(3)H]leucine. Human neutrophil defensins HNP-1, HNP-2, and HNP-3 inhibited the growth of H. capsulatum yeasts in a concentration-dependent manner with maximum inhibition at 8 microg/ml. At a concentration of 4 microg/ml, all possible paired combinations of defensins exhibited additive fungistatic activity against H. capsulatum yeasts. Cathepsin G and bactericidal-permeability-increasing protein (BPI) also mediated fungistasis against H. capsulatum in a concentration-dependent manner. The fungistatic activities of combinations of cathepsin G and BPI were additive, as were those of combinations of cathepsin G or BPI with HNP-1, HNP-2, and HNP-3. Lysozyme and elastase exhibited modest antifungal activity, and azurocidin and proteinase 3 exhibited no significant fungistasis against H. capsulatum yeasts. Thus, defensins, cathepsin G, and BPI are the major anti-H. capsulatum effector molecules in the azurophil granules of human neutrophils.

Elastase is the only human neutrophil granule protein that alone is responsible for in vitro killing of Borrelia burgdorferi

Phagocytosis of Borrelia burgdorferi by human polymorphonuclear leukocytes triggers oxygen-dependent and -independent mechanisms of potentially cidal outcome. Nevertheless, no factor or process has yet been singled out as being borreliacidal. We have studied the B. burgdorferi-killing ability of the myeloperoxidase-H2O2-chloride system and that of primary and secondary granule components in an in vitro assay. We found that neither secondary granule acid extracts nor the chlorinating system could kill these microorganisms, while primary granule extracts were effective. The Borrelia-killing factor was purified to homogeneity and demonstrated to be elastase. Its cidal activity was found to be independent of its proteolytic activity.

pH-dependent hysteretic behaviour of human myeloblastin (leucocyte proteinase 3)

Human myeloblastin (leucocyte proteinase 3) showed a very slow approach to the steady-state velocity when the pH was rapidly increased from 3.2 to 7.0. The kinetic mechanism of this hysteretic process was interpreted as a slow conformational change of myeloblastin from an inactive form at acidic pH to the active form at neutral pH. The transition between the two enzyme forms could occur spontaneously in the absence of substrates with a first-order rate constant of 0.0033 s-1. In the presence of peptide substrates activation occurred more rapidly: the observed rate constant was linearly dependent upon the substrate concentration and contained a contribution of the spontaneous as well as of the substrate-dependent process, whose second-order rate constant was characteristic of the particular substrate. This pH-dependent phenomenon of hysteresis on the part of myeloblastin, that is not manifested by the closely related leucocyte elastase, may have a physiological control function during phagocytosis by damping the rate of interconversion between enzymically inactive and active enzyme conformations.

Antibiotic proteins of polymorphonuclear leukocytes

The polymorphonuclear leukocyte (PMN) plays an essential role in the innate defense of the mammalian host against bacterial invaders. Responding chemotactically, the PMN delivers a complex antibiotic arsenal to sites of infection. Among these cytotoxic systems is an array of antimicrobial proteins and peptides that the PMN directs at microorganisms both before (i.e. extracellularly) and after sequestration into a phagocytic vacuole. In addition to their microbicidal capacity, several of these proteins bind to and neutralize the endotoxic activity of Gram-negative bacterial lipopolysaccharides (LPS). In this review the principle features of these antibiotic proteins are briefly summarized with emphasis on their possible actions in biological settings. In many instances, additional functions independent of cytotoxicity have been described raising the possibility that some of these proteins subserve multiple roles in inflammation.

Azurocidin is a novel antigen for anti-neutrophil cytoplasmic autoantibodies (ANCA) in systemic vasculitis

We isolated a 27-kD protein using cation exchange chromatography from an acid extract of neutrophil granules. N-terminal amino acid sequence analysis of the first 10 residues showed that this protein is azurocidin, a member of the family of neutral serine proteinase found in the neutrophil, which shares amino acid sequence homology with the three other neutral serine proteinases, elastase, proteinase 3 (PR3) and cathepsin G, but unlike them is without proteolytic activity. To test whether, in addition to these proteases, azurocidin might be a target for the humoral autoimmune responses associated with human vasculitis, 185 indirect immunofluorescence (IIF)-positive ANCA sera, made up of four groups of sera with specificities for PR3 (n=37), myeloperoxidase (MPO; n=50), bactericidal/permeability-increasing protein (BPI; n=41) and sera that recognized none of them (triple negative, n=57), and 46 normal sera were screened for IgG anti-azurocidin antibodies using an ELISA incorporating purified azurocidin. Twenty of the 185 IIF-positive sera and 2/46 normal sera displayed reactivity with azurocidin. Positive sera could blot the 27-kD band by Western blot analysis. Further study of the 20 positive sera revealed that: (i) 10 also had autoreactivity for MPO, of which six additionally recognized lactoferrin; (ii) two had reactivity with BPI; (iii) the remaining eight sera were positive only for azurocidin. All 20 sera were from patients with systemic vasculitis, and four of the six sera with triple reactivity (for azurocidin, MPO and lactoferrin) were from patients with hydralazine-induced vasculitis. We concluded that: (i) azurocidin is a novel ANCA antigen; (ii) anti-azurocidin antibodies from a subgroup of patients might represent the consequence of a drug-induced multi-clone activation.

Individual and synergistic effects of rabbit granulocyte proteins on Escherichia coli

Affinity purification of crude acid extracts of rabbit polymorphonuclear leukocytes using Escherichia coli (J5) as adsorbent yields the bactericidal/permeability-increasing protein (BPI), two 15-kD species (p15s), and the two most potent (cationic) defensin species (neutrophil peptides [NP] -1 and -2). Tested in buffered isotonic medium, the relative antibacterial potency of these proteins against E. coli J5 is BPI (IC50 0.2 nM) > p15A (10 nM) > NP -1 (400 nM). Sublethal doses of p15A or NP-1 can synergize with BPI to decrease the dose required to inhibit the growth of E. coli by up to 50-fold. BPI and p15A display similar features of antibacterial action distinct from defensin NP-1, but NP-1 acts synergistically only with BPI and not with p15A. All aspects of the combined action of BPI and NP-1 resemble those observed with higher concentrations of BPI alone, implying that NP-1 enhances BPI potency. Neither NP-1 nor p15A alter the amount of BPI binding to E. coli but BPI enhances binding of p15A to E. coli, raising the possibility that synergy between these two proteins may occur at least partially at the level of binding. The potent synergistic actions of these proteins can also be demonstrated against serum-resistant clinical isolates of encapsulated E. coli tested in whole blood and plasma ex vivo, suggesting that such combined action may contribute to host defense in vivo.

The in vitro effect of human polymorphonuclear leukocyte azurophil granule components on natural killer cell cytotoxicity

We previously demonstrated that human polymorphonuclear leukocyte (PMN) secretions are capable of activating and inhibiting natural killer cell (NK) cytotoxicity depending on the eliciting PMN stimulus. Serum-opsonized zymosan induced PMN to secrete substances that enhanced NK activity in vitro. Serum-opsonized zymosan stimulates the release of PMN azurophil granules, which contain both human neutrophil peptides (HNPs) and neutral serine proteases (NSPs). When HNPs and NSPs were tested for their ability to activate NK cells in peripheral blood lymphocytes, all but cathepsin G consistently enhanced cytotoxicity above control values. HNP-induced cytotoxicity was significantly enhanced within 12 h, peaking at approximately 24 h. Of the HNPs, HNP-1 was the most potent activator, enhancing NK activity at 1.25 micrograms/ml. Interleukin-2 and interferon-gamma were not involved in this activational process, as antibodies to interleukin-2 and interferon-gamma did not block activation by HNPs and NSPs, and interleukin-2 receptor expression was unaltered after 24 h of incubation. Enzymatically inactivated elastase and cathepsin G produced equivalent activational effects to their active counterparts. Antisera to elastase and cathepsin G decreased but did not eliminate NK activation over untreated peripheral blood lymphocytes. These data suggest that certain PMN azurophil granule components, including HNPs and NSPs directly increase the cytotoxic activity of NK cells.

Antibiotic peptides and serine protease homologs in human polymorphonuclear leukocytes: defensins and azurocidin

The azurophil granule, a specialized lysosome of neutrophils, contains two families of antimicrobial proteins, each with four members. They are the defensins, comprising human neutrophil protein 1, -2, -3 and -4, on the one hand and the serprocidins, comprising cathepsin G, elastase, proteinase 3 and azurocidin, on the other. Defensins appear to contribute to mammalian as well as invertebrate immunity. Recent studies show that defensins and structurally related peptides are found not only in phagocytes but also in intestinal and respiratory cells. Aside from their antibiotic function, members of the defensin family may also act as hormonal agents. Within the serprocidin family the genes encoding the novel antibiotics and serine protease homologs azurocidin and proteinase 3 have been identified recently.