Secondary Granule Proteins Research Articles

Eosinophil peroxidase promotes bronchial epithelial cells to secrete asthma-related factors and induces the early stage of airway remodeling

Asthma is a heterogeneous disease characterized by chronic airway inflammation, reversible airflow limitation, and airway remodeling. Eosinophil peroxidase (EPX) is the most abundant secondary granule protein unique to activated eosinophils. In this study, we aimed to illustrate the effect of EPX on the epithelial-mesenchymal transition (EMT) in BEAS-2B cells. Our research found that both EPX and ADAM33 were negatively correlated with FEV1/FVC and FEV1%pred, and positively correlated with IL-5 levels. Asthma patients had relatively higher levels of ADAM33 and EPX compared to the healthy control group. The expression of TSLP, TGF-β1 and ADAM33 in the EPX intervention group was significantly higher. Moreover, EPX could promote the proliferation, migration and EMT of BEAS-2B cells, and the effect of EPX on various factors was significantly improved by the PI3K inhibitor LY294002. The findings from this study could potentially offer a novel therapeutic target for addressing airway remodeling in bronchial asthma, particularly focusing on EMT.

A cross-sectional cohort study of the activity and turnover of neutrophil granulocytes in juvenile idiopathic arthritis

BackgroundThe inflammatory process in juvenile idiopathic arthritis (JIA) involves both the innate and the adaptive immune system. The turnover and activity of neutrophil granulocytes may be reflected by proteins secreted from primary or secondary granules and from the cytoplasm of sequestered cells. Our primary aim was to compare the levels of the secondary neutrophil granule protein human neutrophil lipocalin (HNL), in JIA patients and controls, and to explore a possible priming of neutrophils through parallel analyses in plasma and serum. A secondary aim was to relate the levels of HNL to two other well-studied leukocyte proteins, S100A8/A9 and myeloperoxidase (MPO), as well as to clinical aspects of JIA.MethodsThe concentrations of the three biomarkers in serum, two of them also in plasma, were measured using enzyme-linked immunosorbent assay in 37 children with JIA without medical treatment, in high disease activity based on juvenile arthritis disease activity score 27 (JADAS27), 32 children on medical treatment, mainly in lower disease activity, and 16 healthy children. We assessed for differences between two groups using the Mann-Whitney U test, and used the Kruskal-Wallis test for multiple group comparisons. Spearman rank correlation, linear and multiple regression analyses were used for evaluation of associations between biomarker concentrations and clinical scores.ResultsThe concentrations of HNL and MPO in serum were significantly increased in children with JIA (p < 0.001, p = 0.002) compared with healthy children, but we found no difference in the plasma levels of HNL and MPO between children with JIA and controls. The serum concentrations of MPO and HNL were unaffected by medical treatment, but S100A8/A9 was reduced by medical treatment and correlated with JADAS27 in both univariate (r = 0.58, p < 0.001) and multivariate (r = 0.59, p < 0.001) analyses.ConclusionsNeutrophil granulocytes in children with JIA are primed to release primary and secondary granule proteins, without relation to medical treatment, whereas signs of increased turnover and sequestration of neutrophil granulocytes are reduced by treatment. Levels of neutrophil-originating proteins in serum most likely reflect underlying disease activities of JIA.

Identification of a Novel CEBPE Enhancer Essential for Granulocytic Differentiation

CEBPE is a member of the CCAAT/enhancer binding protein (C/EBP) family of transcription factors essential for granulocytic differentiation. CEBPE is expressed in a stage-specific manner during myeloid differentiation and regulates transition from the promyelocyte to the myelocyte stage. It is essential for secondary and tertiary granule formation in granulocytes. We and others found germline mutations of the CEBPE gene in patients with neutrophil-specific granule deficiency. Their neutrophils display atypical bilobed nuclei, lack expression of granule proteins and these patients often have frequent bacterial infections. Cebpe knock-out mice resemble this clinical phenotype displaying a block in terminal differentiation and absence of secondary granule proteins.Given the tissue specific expression of CEBPE, we were interested in identifying genomic regions and factors that could regulate its lineage specific expression. Our CEBPE ChIP-seq in murine bone marrow cells showed binding of CEBPE to a region 6kb upstream of Cebpe gene. Chromosome conformation capture-on-chip (4C-seq) demonstrated an interaction between this putative regulatory element (6kb upstream region) and the core promoter of Cebpe. Analysis of available DNase-seq data sets revealed that the region bound by CEBPE displayed an open chromatin only in myeloid lineage cells. Further examination revealed binding of a myriad of hematopoietic transcription factors to the +6kb enhancer in HPC-7 (hematopoietic progenitor cells) and in 416B (myeloid progenitor cells), indicating that this region/enhancer might regulate the expression of CEBPE.Targeting of this region using dCas9-KRAB in murine 32D cells caused significant downregulation of RNA and protein levels of CEBPE compared to control cells. These targeted cells also exhibited impaired granulocytic differentiation with lower transcript levels of secondary granule proteins (Ltf and Ngp).To investigate further the role of the +6kb enhancer region in myelopoiesis, mice were generated with deletion of this region using CRISPR/Cas9 technology. Germ line deletion of the +6kb enhancer resulted in reduced levels of CEBPE and its target genes, accompanied by a severe block in granulocytic differentiation and a complete absence of CD11b+/Gr1hi population. This phenotype is nearly identical to our Cebpe KO mice.In summary, we have identified a novel enhancer crucial for regulating Cebpe, and required for normal granulocytic differentiation. DisclosuresNo relevant conflicts of interest to declare.

Lung Pathologies in a Chronic Inflammation Mouse Model Are Independent of Eosinophil Degranulation.

The release of eosinophil granule proteins in the lungs of patients with asthma has been dogmatically linked with lung remodeling and airway hyperresponsiveness. However, the demonstrated inability of established mouse models to display the eosinophil degranulation occurring in human subjects has prevented a definitive in vivo test of this hypothesis. To demonstrate in vivo causative links between induced pulmonary histopathologies/lung dysfunction and eosinophil degranulation. A transgenic mouse model of chronic T-helper cell type 2-driven inflammation overexpressing IL-5 from T cells and human eotaxin 2 in the lung (I5/hE2) was used to test the hypothesis that chronic histopathologies and the development of airway hyperresponsiveness occur as a consequence of extensive eosinophil degranulation in the lung parenchyma. Studies targeting specific inflammatory pathways in I5/hE2 mice surprisingly showed that eosinophil-dependent immunoregulative events and not the release of individual secondary granule proteins are the central contributors to T-helper cell type 2-induced pulmonary remodeling and lung dysfunction. Specifically, our studies highlighted a significant role for eosinophil-dependent IL-13 expression. In contrast, extensive degranulation leading to the release of major basic protein-1 or eosinophil peroxidase was not causatively linked to many of the induced pulmonary histopathologies. However, these studies did define a previously unappreciated link between the release of eosinophil peroxidase (but not major basic protein-1) and observed levels of induced airway mucin. These data suggest that improvements observed in patients with asthma responding to therapeutic strategies ablating eosinophils may occur as a consequence of targeting immunoregulatory mechanisms and not by simply eliminating the destructive activities of these purportedly end-stage effector cells.

Leucine Rich α-2 Glycoprotein: A Novel Neutrophil Granule Protein and Modulator of Myelopoiesis.

Leucine-rich α2 glycoprotein (LRG1), a serum protein produced by hepatocytes, has been implicated in angiogenesis and tumor promotion. Our laboratory previously reported the expression of LRG1 in murine myeloid cell lines undergoing neutrophilic granulocyte differentiation. However, the presence of LRG1 in primary human neutrophils and a role for LRG1 in regulation of hematopoiesis have not been previously described. Here we show that LRG1 is packaged into the granule compartment of human neutrophils and secreted upon neutrophil activation to modulate the microenvironment. Using immunofluorescence microscopy and direct biochemical measurements, we demonstrate that LRG1 is present in the peroxidase-negative granules of human neutrophils. Exocytosis assays indicate that LRG1 is differentially glycosylated in neutrophils, and co-released with the secondary granule protein lactoferrin. Like LRG1 purified from human serum, LRG1 secreted from activated neutrophils also binds cytochrome c. We also show that LRG1 antagonizes the inhibitory effects of TGFβ1 on colony growth of human CD34+ cells and myeloid progenitors. Collectively, these data invoke an additional role for neutrophils in innate immunity that has not previously been reported, and suggest a novel mechanism whereby neutrophils may modulate the microenvironment via extracellular release of LRG1.

Human α-Defensin Expression Is Not Dependent on CCAAT/Enhancer Binding Protein-ε in a Murine Model

Specific granule deficiency (SGD) is a rare congenital disorder characterized by recurrent infections. The disease is caused by inactivating mutations of the CCAAT/enhancer binding protein-ε (C/EBP-ε) gene. As a consequence, specific and gelatinase granules lack most matrix proteins. Furthermore, azurophil granules contain diminished amounts of their most abundant proteins, α-defensins, also known as human neutrophil peptides (HNPs). In accordance with this, in vitro models have demonstrated induction of HNPs by C/EBP-ε. Since mice do not express myeloid defensins, they cannot per se be used to characterize the role of C/EBP-ε in controlling HNP expression in vivo. We therefore crossed a transgenic HNP-1-expressing mouse with the Cebpe-/- mouse to study the in vivo significance of C/EBP-ε for HNP-1 transcription and expression. Surprisingly, neither expression nor processing of HNP-1 was affected by lack of C/EBP-ε in these mice. Transduction of C/EBP-ε into primary bone marrow cells from HNP-1 mice induced some HNP-1 expression, but not to levels comparable to expression human cells. Taken together, our data infer that the HNP-1 of the transgenic mouse does not show an expression pattern equivalent to endogenous secondary granule proteins. This limits the use of these transgenic mice as a model for human conditions.

MiRNA-130a regulates C/EBP-ε expression during granulopoiesis

CCAAT/enhancer binding protein-ε (C/EBP-ε) is considered a master transcription factor regulating terminal neutrophil maturation. It is essential for expression of secondary granule proteins, but it also regulates proliferation, cell cycle, and maturation during granulopoiesis. Cebpe(-/-) mice have incomplete granulocytic differentiation and increased sensitivity toward bacterial infections. The amount of C/EBP-ε messenger RNA (mRNA) increases with maturation from myeloblasts with peak level in myelocytes (MC)/metamyelocytes (MM), when the cells stop proliferating followed by a decline in more mature cells. In contrast, C/EBP-ε protein is virtually detectable only in the MC/MM population, indicating that expression in more immature cells could be inhibited by microRNAs (miRNAs). We found that miRNA-130a (miR-130a) regulates C/EBP-ε protein expression in both murine and human granulocytic precursors. Overexpression of miR-130a in a murine cell line downregulated C/EBP-ε protein and lactoferrin (Ltf), cathelicidin antimicrobial protein (Camp), and lipocalin-2 (Lcn2) mRNA expression giving rise to cells with a more immature phenotype, as seen in the Cebpe(-/-) mouse. Introduction of a C/EBP-ε mRNA without target site for miR-130a restored both C/EBP-ε production, expression of Camp and Lcn2, and resulted in the cells having a more mature phenotype. We conclude that miR-130a is important for the regulation of the timed expression of C/EBP-ε during granulopoiesis.

The Circulating Proteinase Inhibitor α-1 Antitrypsin Regulates Neutrophil Degranulation and Autoimmunity

Pathological inflammation and autoimmune disease frequently involve elevated neutrophil activity in the absence of infectious agents. Tumor necrosis factor-α (TNF-α) contributes to many of the problems associated with autoimmune diseases. We investigated the ability of serum α-1 antitrypsin (AAT) to control TNF-α biosynthesis and signaling in neutrophils and assessed whether AAT deficiency (AATD) is a TNF-α-related disease. In vitro studies demonstrate that serum AAT coordinates TNF-α intracellular signaling and neutrophil degranulation of tertiary and secondary granules via modulation of ligand-receptor interactions. AATD patients homozygous for the Z allele were characterized by increased activation of the TNF-α system, as demonstrated by increased membrane TNF-α levels and increased plasma concentrations of TNF receptor 1 and neutrophil-released secondary and tertiary granule proteins. The incidence of autoantibodies directed against degranulated lactoferrin and surface protein accessible to these antibodies was increased in ZZ-AATD, leading to an enhanced rate of neutrophil reactive oxygen species production. Treatment of ZZ-AATD individuals with AAT augmentation therapy resulted in decreased membrane TNF-α expression and plasma levels of granule antigenic proteins and immunoglobulin G class autoantibodies. These results provide a mechanism by which AAT augmentation therapy affects TNF-α signaling in the circulating neutrophil, indicating promising potential of this therapy for other TNF-α-related diseases.

Thiocyanate Blocks Peroxidase-Dependent Extracellular Trap (ET) Formation By PMN and Eosinophils: Heme Is a Potent New Agonist For The ET Pathway

PMN and eosinophils (EO) activated by physiologic agonist such as LPS, C5a, GM-CSF and IL-5 form extracellular traps (ET) comprised of extracellular DNA, histones, and active secondary granule constituents that retain microbicidal capacity and thus contribute to host defense but also participate in the pathogenesis of sepsis, microangiopathy, vasculitis, asthma and thrombosis. Previous studies have implicated superoxide, H2O2 and myeloperoxidase (MPO) in PMN ET formation, which reflects a novel death pathway dubbed “ETosis.” Thiocyanate (SCN-) is the principle physiologic substrate for eosinophil peroxidase (EPO) and a major substrate for MPO. Because previous studies of ET were all performed in the absence of SCN- and HOSCN, the product of SCN- peroxidation, is a weak, sulfhydryl-specific oxidant markedly less toxic than HOCl or HOBr, we hypothesized SCN- blocks PMN and EO ET formation. We also hypothesized that heme, elevated levels of which occur in intravascular hemolytic states such as sickle cell disease, induces PMN ETosis because both LPS and heme signal by engaging TLR4. We assessed ET formation by human PMN stimulated with either GM-CSF + C5a or 10 µM heme in RPMI one hour using glass slide-attached leukocytes with both cell impermeant (Sytox Orange) and permeant (Syto13) DNA stains and IF localization of secondary granule proteins using confocal microscopy. ET formation in response to to both stimuli was 5-20% of PMN in stimulated cells (vs. 0% in control). The NADPH oxidase inhibitor DPI, MPO inhibitor 4-ABAH and 1 mM SCN- all diminished ET formation by >80% in response to both stimuli. Heme-dependent ET formation was inhibited 80% by the TLR4 antagonist TAK242 (see figure below in which intracellular DNA stains green and extracellular and membrane-compromised PMN DNA stains orange). PMA-induced PMN ET formation requires singlet O2 resulting from the secondary reaction of HOCl with excess H2O2. In PMN stimulated with GM-CSF + C5a, the singlet O2 scavenger edaravone (10 µM) inhibited ETs by 80%. ETs also formed in 4-8% of EOs stimulated by IL-5 + C5a, vs. 0% in control EO and 22.5% in unstimulated EO supplemented with the alternative EPO substrate 1 mM Br-. The EPO inhibitor resorcinol decreased by >90% EO ET formation stimulated with by IL-5 + C5a or by adding Br-, as did addition of SCN- or edaravone. These studies show that both PMN and EO ETosis depend upon MPO- and EPO- generated oxidants, respectively, and the presence of an alternative physiologic substrate, SCN-, markedly antagonizes ETosis. We propose that SCN- inhibits ET formation by generating HOSCN that reacts with H2O2 to yield cyanate, not singlet O2. In addition, we also demonstrate that heme is a potent inducer of PMN ETosis through a mechanism dependent upon TLR4, NADPH oxidase and MPO, raising the possibility that this pathway may directly promote the inflammation and thrombosis that contribute of the pathogenesis of sickle cell disease. Based on these findings, we speculate that dietary augmentation of SCN- to normal or supranormal levels might have clinically beneficial therapeutic effects in a variety of inflammatory states, including sickle cell disease. [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Expression of the secondary granule proteins major basic protein 1 (MBP-1) and eosinophil peroxidase (EPX) is required for eosinophilopoiesis in mice

AbstractEosinophil activities are often linked with allergic diseases such as asthma and the pathologies accompanying helminth infection. These activities have been hypothesized to be mediated, in part, by the release of cationic proteins stored in the secondary granules of these granulocytes. The majority of the proteins stored in these secondary granules (by mass) are major basic protein 1 (MBP-1) and eosinophil peroxidase (EPX). Unpredictably, a knockout approach targeting the genes encoding these proteins demonstrated that, unlike in mice containing a single deficiency of only MBP-1 or EPX, the absence of both granule proteins resulted in the near complete loss of peripheral blood eosinophils with no apparent impact on any other hematopoietic lineage. Moreover, the absence of MBP-1 and EPX promoted a concomitant loss of eosinophil lineage-committed progenitors in the marrow, identifying a specific blockade in eosinophilopoiesis as the causative event. Significantly, this blockade of eosinophilopoiesis is also observed in ex vivo cultures of marrow progenitors and is not rescued in vivo by adoptive bone marrow engraftment, suggesting a cell-autonomous defect in marrow progenitors. These observations implicate a role for granule protein gene expression as a regulator of eosinophilopoiesis and provide another strain of mice congenitally deficient of eosinophils.

Impaired Neutrophil Function in 24p3 Null Mice Contributes to Enhanced Susceptibility to Bacterial Infections

Lipocalin 24p3 (24p3) is a neutrophil secondary granule protein. 24p3 is also a siderocalin, which binds several bacterial siderophores. It was therefore proposed that synthesis and secretion of 24p3 by stimulated macrophages or release of 24p3 upon neutrophil degranulation sequesters iron-laden siderophores to attenuate bacterial growth. Accordingly, 24p3-deficient mice are susceptible to bacterial pathogens for which siderophores would normally be chelated by 24p3. Specific granule deficiency (SGD) is a rare congenital disorder characterized by complete absence of proteins in secondary granules. Neutrophils from SGD patients, who are prone to bacterial infections, lack normal functions, but the potential role of 24p3 in neutrophil dysfunction in SGD is not known. In this study, we show that neutrophils from mice genetically deficient for lipocalin 24p3 (24p3(-/-)) are defective in many neutrophil functions. Specifically, neutrophils in 24p3(-/-) mice do not extravasate to sites of infection and are defective for chemotaxis. A transcriptome analysis revealed that genes that control cytoskeletal reorganization are selectively suppressed in 24p3(-/-) neutrophils. Additionally, small regulatory RNAs (microRNAs) that control upstream regulators of cytoskeletal proteins are also increased in 24p3(-/-) neutrophils. Further, 24p3(-/-) neutrophils failed to phagocytose bacteria, which may account for the enhanced sensitivity of 24p3(-/-) mice to both intracellular (Listeria monocytogenes) and extracellular (Candida albicans and Staphylococcus aureus) pathogens. Listeria does not secrete siderophores, and additionally, the siderophore secreted by Candida is not sequestered by 24p3. Therefore, the heightened sensitivity of 24p3(-/-) mice to these pathogens is not due to sequestration of siderophores limiting iron availability, but is a consequence of impaired neutrophil function.

Impaired Neutrophil Function in 24p3 Null Mice Contributes to Enhanced Susceptibility to Bacterial Infections

Abstract 833Lipocalin 24p3 (24p3) is a neutrophil secondary granule protein. 24p3 is also a siderocalin, which binds several bacterial siderophores. It was therefore proposed that synthesis and secretion of 24p3 by stimulated macrophages or release of 24p3 upon neutrophil degranulation sequesters iron-laden siderophores to attenuate bacterial growth. Accordingly, 24p3-deficient mice are susceptible to bacterial pathogens whose siderophores are chelated by 24p3. Specific granule deficiency (SGD) is a rare congenital disorder characterized by complete absence of proteins of secondary granules. Neutrophils from SGD patients lack normal functions and are prone to bacterial infections, but the importance of 24p3 for neutrophil dysfunction in SGD is not known. Here we show that neutrophils of 24p3−/− mice are defective for many neutrophil functions. Specifically, neutrophils in 24p3−/− mice do not extravasate to sites of infection and are defective for chemotaxis. A transcriptome analysis revealed that genes that control cytoskeletal reorganization are selectively suppressed in 24p3−/− neutrophils. Additionally, small regulatory RNAs (miRNAs) that control upstream regulators of cytoskeletal proteins are also increased in 24p3−/− neutrophils. Further, 24p3−/− neutrophils failed to phagocytose bacteria, which may account for the enhanced sensitivity of 24p3−/− mice to both intracellular (Listeria monocytogenes) and extracellular (Candida albicans, Staphylococcus aureus) pathogens. Interestingly, Listeria does not secrete siderophores and additionally, the siderophore secreted by Candida is not sequestered by 24p3. Therefore, the heightened sensitivity of 24p3−/− mice to these pathogens is not due to sequestration of siderophores to limit the iron availability but as a consequence of impaired neutrophil functions. Disclosures:No relevant conflicts of interest to declare.

The oesophageal string test: a novel, minimally invasive method measures mucosal inflammation in eosinophilic oesophagitis

ObjectiveEosinophil predominant inflammation characterises histological features of eosinophilic oesophagitis (EoE). Endoscopy with biopsy is currently the only method to assess oesophageal mucosal inflammation in EoE. We hypothesised that measurements of...

Neutrophils in Atherosclerosis

Inflammation and activation of immune cells are key mechanisms in the development of atherosclerosis.1 Elegant experimental studies, typically performed in compound mutant mice susceptible to diet-induced atherosclerosis, indicate important roles for monocytes, T lymphocytes, and mast cells in lesion formation (Figure). Moreover, inflammatory pathways promote thrombosis, a late complication of atherosclerosis responsible for myocardial infarction and ischemic stroke. However, a direct contribution of neutrophils as the first line of immune offense (ie, acute inflammation) in atherosclerosis is controversial and uncertain. In this issue of Circulation Research , Doring and colleagues2 report that the neutrophil secondary granule protein cathelicidin (CRAMP in mice, LL37 in humans) directly promotes atherosclerosis by enhancement of the recruitment of inflammatory monocytes. Figure. The inflammatory basis of atherosclerosis. The progression of atherosclerosis is associated with multiple inter-related immune mechanisms. Proximate signals include a combination of endothelial injury, platelet adhesion, and stimulation of macrophage and T cell responses by modified LDL particles in the intima. The response of the innate immune system may also involve the transient recruitment of neutrophils expressing of alarmins, such as MRP-8/14 and CRAMP. The adaptive immune system includes proatherosclerotic responses such as IFN-γ production by CD4+ Th1 lymphocytes as well as protective mechanisms, such as the secretion of neutralizing antibodies by B lymphocytes and the anti-inflammatory activity of regulatory T cells. IL indicates interleukin; TNF, tumor necrosis factor; IFN, interferon. Article, see p 1052 Early histological studies of human atherosclerotic plaque identified a rich infiltrate of immune cells including monocyte/macrophages and T lymphocytes, but failed to identify significant neurophilic accumulation.3 The paradigm of atherosclerosis as a chronic inflammatory condition gained further traction as chemokines responsible for monocyte and lymphocyte trafficking were found to regulate atherosclerosis.1 Yet, tantalizing indirect evidence implicating neutrophils in the initiation, progression, and complications of atherosclerosis has …

The expression of the abundant secondary granule proteins MBP-1 and EPO is required for the maturation of eosinophil-lineage committed progenitor cells in the hematopoietic compartments of mice (153.27)

Abstract Eosinophil effector functions have been hypothesized to be mediated in part by the release of proteins stored in the secondary granules of mature cells of this leukocyte lineage. Major basic protein-1 (MBP-1) and eosinophil peroxidase (EPO) comprise the majority of protein in these granules. No role has been speculated for these proteins in eosinophilopoiesis and/or the accumulation of mature cells in circulation. Methods: Eosinophilopoiesis and eosinophil accumulation in the periphery were assessed in single and double knockout (MBP-1-/- and/or EPO-/-) mice. Bone marrow and peripheral blood leukocytes were assessed by IHC, FACS and in vitro cell culture assays. Mice were subjected to an acute OVA protocol assessing induced pulmonary pathologies in each of the strains of granule protein knockout mice. Results: We demonstrate that, unlike the single deficiency of MBP-1 or EPO, the absence of both granule proteins resulted in the loss of peripheral blood eosinophils. IHC assessments of bone marrow and spleen demonstrate that eosinophil lineage commitment occurs in these mice. However, these assessments and FACS studies demonstrated a blockade in the maturation of eosinophil-lineage committed cells. This blockade is not rescued by ex vivo culture or by bone marrow engraftment into wild type recipient mice. Similar to other eosinophil-less mouse models, MBP-1-/-/EPO-/- mice also fail to develop pulmonary inflammation in an OVA protocol.

Mouse Eosinophils Possess Potent Antibacterial Properties In Vivo

Eosinophils are best known as the predominant cellular infiltrate associated with asthma and parasitic infections. Recently, numerous studies have documented the presence of Toll-like receptors (TLRs) on the surfaces of eosinophils, suggesting that these leukocytes may participate in the recognition and killing of viruses and bacteria. However, the significance of this role in the innate immune response to bacterial infection is largely unknown. Here we report a novel role for eosinophils as antibacterial defenders in the host response. Isolated mouse eosinophils possessed antipseudomonal properties in vitro. In vivo, interleukin-5 transgenic mice, which have profound eosinophilia, demonstrated improved clearance of Pseudomonas aeruginosa introduced into the peritoneal cavity. The findings of improved bacterial clearance following adoptive transfer of eosinophils, and impaired bacterial clearance in mice with a congenital eosinophil deficiency, established that this effect was eosinophil specific. The data presented also demonstrate that eosinophils mediate this antibacterial effect in part through the release of cationic secondary granule proteins. Specifically, isolated eosinophil granules had antibacterial properties in vitro, and administration of eosinophil granule extracts significantly improved bacterial clearance in vivo. These data suggest a potent yet underappreciated antibacterial role for eosinophils in vivo, specifically for eosinophil granules. Moreover, the data suggest that the administration of eosinophil-derived products may represent a viable adjuvant therapy for septic or bacteremic patients in the intensive care unit.

A Novel Histologic Scoring System to Evaluate Mucosal Biopsies From Patients With Eosinophilic Esophagitis

Eosinophilic esophagitis (EoE) is characterized by medically/surgically-resistant gastroesophageal reflux symptoms and dense squamous eosinophilia. Studies suggest that histologic assessment of esophageal eosinophilia alone cannot reliably separate patients with EoE from those with gastroesophageal reflux disease (GERD). Our goal was to develop an assay to identify EoE patients and perhaps differentiate EoE from other causes of esophageal eosinophilia. A monoclonal antibody specific for an eosinophil secondary granule protein (eosinophil peroxidase [EPX]) was developed and shown to specifically identify intact eosinophils and detect eosinophil degranulation in formalin-fixed specimens. A histopathologic scoring algorithm was developed to analyze data from patient evaluations; the utility of this algorithm was assessed by using archived esophageal tissues from patients with known diagnoses of EoE and GERD as well as controls from 2 tertiary care centers. Intraobserver/interobserver blinded evaluations demonstrated a significant difference (P < .001) between scores of samples taken from control subjects, from patients with esophageal eosinophilia who had a diagnosis of EoE, and from patients with GERD (P < .001). This algorithm also was able to identify patients whose clinical course was suggestive of a diagnosis of EoE, but that nonetheless failed to reach the critical threshold number of > or =15 eosinophils in a high-power (40x) microscopy field. A novel immunohistochemical scoring system was developed to address an unmet medical need to differentiate histologic specimens from patients with EoE relative to those with GERD. The availability of a unique anti-EPX-specific monoclonal antibody, combined with the ease/rapidity of this staining method and scoring system, will provide a valuable strategy for the assessment of esophageal eosinophilia.

Generation of a Factor Dependent Myeloid Cell Line from Nucleophosmin-1 Heterozygous (NPM-1+/−) Mouse Bone Marrow as a Model for 5q- MDS

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal disorders characterized by ineffective and disordered hematopoiesis with an increased risk of transformation to acute myeloid leukemia (AML). Interstitial deletion of 5q (del 5q) is the most frequent chromosomal abnormality seen in MDS. Two subgroups of MDS with del 5q have been described. The first, the so called “5q-syndrome” is defined by isolated del 5q and no excess blasts in the bone marrow, female predominance, typical dysmegakaryopoiesis, thrombocytosis and a favorable outcome. The second subgroup involves MDS with del 5q associated with an excess of marrow blasts and/or chromosomal abnormalities in addition to del 5q, that usually do not have the typical features of the 5q-syndrome and carry poorer prognosis. Haploinsufficiency for the ribosomal protein RPS14 gene has recently been identified as a compelling candidate gene for causing the 5q- syndrome, but the genes responsible for poor prognosis del 5q MDS remain to be determined. NPM-1, a highly conserved, ubiquitously expressed nucleolar phosphoprotein that belongs to the nucloeplasmin family of nuclear chaperones, maps to a region on chromosome 5q that is the target of deletions in both denovo and therapy-associated MDS in humans.. NPM-1 has been implicated in ribosome biogenesis and the transport of pre-ribosomal particles, maintenance of genomic stability by the control of cellular ploidy, in DNA repair and in the regulation of DNA transcription by controlling chromatin condensation/decondensation. NPM1−/− mice die at mid-gestion (E11.5) due to severe anemia. NPM-1 has been shown to be deleted or involved with chromosomal translocations in hematologic malignancies, and is one of the most frequently mutated genes in AML. NPM-1+/− mice develop a hematological syndrome very similar to that observed in MDS patients. The haploinsufficient NPM-1 model therefore provides an excellent platform to examine not only MDS but also to study AML progression. Studies on the molecular mechanisms underlying 5q- syndrome have been hampered by the lack of in vitro model cell lines. We have generated a factor dependent myeloid cell line from the bone marrow of NPM-1+/+ and NPM-1+/− mice using retroviral transduction of a truncated retinoic acid receptor alpha gene. The resulting cell lines are IL-3-dependent and can be induced to undergo neutrophil maturation by the addition of GM-CSF and/or all- trans retinoic acid (ATRA). We have shown that, like neutrophils derived from the bone marrow of NPM1+/− mice, the NPM-1+/− cell line-derived neutrophils display both defective neutrophil-specific gene expression and abnormal neutrophil function. We found in particular, that the expression of the myeloid master regulator C/EBPα but not that of the related myeloid-specific C/EBPε gene, was significantly decreased in NPM-1+/− cells as compared to their wild type counterparts (NPM-1+/+). While neutrophils derived from NPM1+/− cells appear morphologically normal, the expression of both neutrophil primary granule protein genes (defensins) and secondary granule protein genes (lactoferrin, MMP8 and MMP9) was significantly decreased. The relationship between NPM-1 and C/EBPα is currently being investigated. Additionally, the function of NPM-1+/− derived neutrophils was compromised as assessed by ROS production as well as by chemotaxis assays. The defective oxidative burst may be the result of decreased expression of a key component of the neutrophil NADPH oxidase complex i.e. gp91phox, which is critical for ROS production. We confirmed that these neutrophil-associated defects were also seen in primary neutrophils from the NPM-1+/− mice. We are currently examining the effect of knocking down RPS14 in our factor-dependent NPM-1+/− cells to determine if the two genes cooperate to render the cells factor independent. This cell line will help to delineate the functions of NPM-1 and provide a platform for examining the potential role of haploinsufficiency of NPM-1 in the propensity for 5q- MDS to progress to AML.

The secretory leukocyte protease inhibitor (SLPI) and the secondary granule protein lactoferrin are synthesized in myelocytes, colocalize in subcellular fractions of neutrophils, and are coreleased by activated neutrophils

The secretory leukocyte protease inhibitor (SLPI) re-establishes homeostasis at sites of infection by virtue of its ability to exert antimicrobial activity, to suppress LPS-induced cellular immune responses, and to reduce tissue damage through inhibition of serine proteases released by polymorphonuclear neutrophil granulocytes (PMNs). Microarray analysis of bone marrow (BM) populations highly enriched in promyelocytes, myelocytes/metamyelocytes (MYs), and BM neutrophils demonstrates a transient, high mRNA expression of SLPI and genuine secondary granule proteins (GPs) in MYs. Consistent with this finding, immunostaining of BM cells showed SLPI and the secondary GP lactoferrin (LF) to be present in cells from the myelocyte stage and throughout neutrophil differentiation. Subcellular fractionation studies demonstrated the colocalization of SLPI and LF in subcellular fractions highly enriched in secondary granules. Finally, exocytosis studies demonstrated a corelease of SLPI and LF within minutes of activation. Collectively, these findings strongly indicate that SLPI is localized in secondary granules of PMNs. However, the amount of SLPI detected in PMNs is low compared with primary keratinocytes stimulated by growth factors involved in wound healing. This implicates that neutrophil-derived SLPI might not contribute essentially to re-establishment of homeostasis at sites of infection but rather, exert physiologically relevant intracellular activities. These might include the protection of secondary GPs against proteolytic activation and/or degradation by proteases, which might be dislocated to secondary granules at minute amounts as a consequence of spillover.

Leukemic Promyelocytes Possess Self-Renewal Capacity and Leukemia Stem Cell Properties in a Mouse Model of Acute Promyelocytic Leukemia.

It has been determined that within the heterogeneous leukemic population, there is a rare subset of leukemia stem cells that are responsible for continued maintenance and propagation of the tumor. Recent evidence suggests that during disease pathogenesis, more mature progenitor cells are capable of acquiring stem cell-like characteristics including properties of self-renewal and the capacity to differentiate into progeny that lack self-renewing potential. Acute promyelocytic leukemia (APL) is associated with the t(15;17)(q22;q12) chromosomal translocation that produces the PML-RARa fusion protein, and is unusual among the various subtypes of AML in that it is characterized by hyperproliferation of differentiated promyelocyte progenitors. In a mouse model in which PML-RARa is expressed under the control of the endogenous murine cathepsin G promoter, we observed that whole bone marrow expressing PML-RARa derived from pre-leukemic mice has certain properties of self-renewal, such as serial replating potential in methylcellulose cultures, and serial transplantation of disease into recipient animals. Using multiparameter flow cytometry, we demonstrated that preleukemic PML-RARa animals have an expansion of mature Gr-1+c-kit-CD34− granulocytes that are not capable of self-renewal. However, in the leukemic state, the expanded population shifted to a more immature population with an immunophenotype of Gr-1+c-kit+CD34+. This population was capable of transplanting disease to secondary recipients that recapitulated the disease of the primary donor, and thus contained leukemia-initiating activity. Morphologically, these cells resembled promyelocytes, and their promyelocytic identity was confirmed by quantitative PCR detection of the expression of azurophilic primary granule components associated with the promyelocyte stage of development, including myeloperoxidase, neutrophil elastase, and cathepsin G. However, these cells lacked expression of the secondary granule protein gelatinase B associated with the more mature myelocyte stage of granulocytic differentiation. Additionally, these leukemia-initiating promyelocytes responded to differentiation and cell death signals mediated by administration of all-trans retinoic acid (ATRA). These data indicate that in APL, a highly differentiated promyelocyte compartment does in fact possess properties of leukemia stem cells. This suggests that an important step in disease pathogenesis mediated by PML-RARa is the acquisition of properties of self-renewal in a terminally differentiating progenitor that normally lacks this potential.