Cloning of the murine eosinophil peroxidase gene (mEPO): characterization of a conserved subgroup of mammalian hematopoietic peroxidases

Protective role of IL33 signaling in negative pregnancy outcomes associated with lipopolysaccharide exposure

Interleukin 33 (IL33) signaling has been implicated in the establishment and maintenance of pregnancy and in pregnancy disorders. The goal of this project was to evaluate the role of IL33 signaling in rat pregnancy. The rat possesses hemochorial placentation with deep intrauterine trophoblast invasion; features also characteristic of human placentation. We generated and characterized a germline mutant rat model for IL33 using CRISPR/Cas9 genome editing. IL33 deficient rats exhibited deficits in lung responses to an inflammatory stimulus (Sephadex G-200) and to estrogen-induced uterine eosinophilia. Female rats deficient in IL33 were fertile and exhibited pregnancy outcomes (gestation length and litter size) similar to wild-type rats. Placental weight was adversely affected by the disruption of IL33 signaling. A difference in pregnancy-dependent adaptations to lipopolysaccharide (LPS) exposure was observed between wild-type and IL33 deficient pregnancies. Pregnancy in wild-type rats treated with LPS did not differ significantly from pregnancy in vehicle-treated wild-type rats. In contrast, LPS treatment decreased fetal survival rate, fetal and placental weights, and increased fetal growth restriction in IL33 deficient rats. In summary, a new rat model for investigating IL33 signaling has been established. IL33 signaling participates in the regulation of placental development and protection against LPS-induced fetal and placental growth restriction.

5-lipoxygenase- and Glucocorticoid-dependent eosinophilia in a novel surgical model in mice

BACKGROUND

Subcutaneous implants of heat-coagulated egg white (egg white implants, EWI) induce intense local eosinophilia and prime for hyperreactivity following airway ovalbumin challenge. The roles of allergen sensitization, surgical trauma-induced glucocorticoids, and the 5-lipoxygenase (5-LO) pathway were hitherto unexplored in this model, in which quantitative recovery and large-scale purification of the eosinophils from the inflammatory site for functional and immunopharmacological studies are difficult to achieve.

METHODS

We overcame this limitation by shifting the implantation site to the peritoneal cavity (EWIp), thereby enabling quantitative leukocyte retrieval.

RESULTS

By day 7 post-surgery, eosinophil counts reached ~ 30% of all leukocytes recovered. Eosinophilia was prevented by: a) induction of allergen-specific oral tolerance to ovalbumin, the main allergen in egg white; b) inactivation of the 5-lipoxygenase pathway; c) blockade of endogenous glucocorticoid signaling by pretreatment with metirapone plus mifepristone before surgery. Highly purified eosinophils (~99% pure) could be obtained from the peritoneal exudate of EWIp-carrier mice in 2 simple, antibody-free steps. Preparative-scale yields, suitable for most biochemical, pharmacological, and molecular applications, were routinely obtained, and could be further enhanced through addition of pre-or post-surgery immunization steps (active or adoptive). The recovered eosinophils were fully functional in vivo, as demonstrated by the transfer of purified eosinophils into eosinophil-deficient Δdbl-GATA-1-KO mice, which upon subsequent challenge with eotaxin-1 present secondary accumulation of neutrophils, but not of mononuclear phagocytes.

CONCLUSION

These findings document glucocorticoid-, allergen- and 5-lipoxygenase-dependent eosinophilia, which makes EWIp carriers an abundant source of pure, nontransgenic eosinophils for immunopharmacological studies.

Impact of eosinophil-peroxidase (EPX) deficiency on eosinophil structure and function in mouse airways

Eosinophil peroxidase (EPX) is a major constituent of the large cytoplasmic granules of both human and mouse eosinophilic leukocytes. Human EPX deficiency is a rare, autosomal-recessive disorder limited to the eosinophil lineage. Our intent was to explore the impact of EPX gene deletion on eosinophil content, structure, and function. In response to repetitive intranasal challenge with a filtrate of the allergen, Alternaria alternata, we found significantly fewer eosinophils peripherally and in the respiratory tracts of EPX^-/- mice compared to wild-type controls; furthermore, both the major population (Gr1^-/lo ) and the smaller population of Gr1^hi eosinophils from EPX^-/- mice displayed lower median fluorescence intensities (MFIs) for Siglec F. Quantitative evaluation of transmission electron micrographs of lung eosinophils confirmed the relative reduction in granule outer matrix volume in cells from the EPX^-/- mice, a finding analogous to that observed in human EPX deficiency. Despite the reduced size of the granule matrix, the cytokine content of eosinophils isolated from allergen-challenged EPX^{-/ -} and wild-type mice were largely comparable to one another, although the EPX^-/- eosinophils contained reduced concentrations of IL-3. Other distinguishing features of lung eosinophils from allergen-challenged EPX^-/- mice included a reduced fraction of surface TLR4⁺ cells and reduced MFI for NOD1. Interestingly, the EPX gene deletion had no impact on eosinophil-mediated clearance of gram-negative Haemophilus influenzae from the airways. As such, although no clinical findings have been associated with human EPX deficiency, our findings suggest that further evaluation for alterations in eosinophil structure and function may be warranted.

Haemopedia: An Expression Atlas of Murine Hematopoietic Cells

Hematopoiesis is a multistage process involving the differentiation of stem and progenitor cells into distinct mature cell lineages. Here we present Haemopedia, an atlas of murine gene-expression data containing 54 hematopoietic cell types, covering all the mature lineages in hematopoiesis. We include rare cell populations such as eosinophils, mast cells, basophils, and megakaryocytes, and a broad collection of progenitor and stem cells. We show that lineage branching and maturation during hematopoiesis can be reconstructed using the expression patterns of small sets of genes. We also have identified genes with enriched expression in each of the mature blood cell lineages, many of which show conserved lineage-enriched expression in human hematopoiesis. We have created an online web portal called Haemosphere to make analyses of Haemopedia and other blood cell transcriptional datasets easier. This resource provides simple tools to interrogate gene-expression-based relationships between hematopoietic cell types and genes of interest.

Blockage of Eosinopoiesis by IL-17A Is Prevented by Cytokine and Lipid Mediators of Allergic Inflammation

Interleukin- (IL-) 17A, a pleiotropic mediator of inflammation and autoimmunity, potently stimulates bone-marrow neutrophil production. To explore IL-17A effects on eosinopoiesis, we cultured bone-marrow from wild-type mice, or mutants lacking inducible nitric oxide synthase (iNOS−/−), CD95 (lpr), IL-17RA, or IL-4, with IL-5, alone or associated with IL-17A. Synergisms between IL-17A-activated, NO-dependent, and NO-independent mechanisms and antagonisms between IL-17A and proallergic factors were further examined. While IL-17A (0.1–10 ng/mL) had no IL-5-independent effect on eosinopoiesis, it dose-dependently suppressed IL-5-induced eosinophil differentiation, by acting during the initial 24 hours. Its effectiveness was abolished by caspase inhibitor, zVAD-fmk. The effect of IL-17A (0.1–1 ng/mL) was sensitive to the iNOS-selective inhibitor aminoguanidine and undetectable in iNOS−/− bone-marrow. By contrast, a higher IL-17A concentration (10 ng/mL) retained significant suppressive effect in both conditions, unmasking a high-end iNOS-independent mechanism. Lower IL-17A concentrations synergized with NO donor nitroprusside. Eosinopoiesis suppression by IL-17A was (a) undetectable in bone-marrow lacking IL-17RA or CD95 and (b) actively prevented by LTD4, LTC4, IL-13, and eotaxin. Sensitivity to IL-17A was increased in bone-marrow lacking IL-4; adding IL-4 to the cultures restored IL-5 responses to control levels. Therefore, effects of both IL-17A and proallergic factors are transduced by the iNOS-CD95 pathway in isolated bone-marrow.

The In Vivo Granulopoietic Response to Dexamethasone Injection Is Abolished in Perforin-Deficient Mutant Mice and Corrected by Lymphocyte Transfer from Nonsensitized Wild-Type Donors

Exogenously administered glucocorticoids enhance eosinophil and neutrophil granulocyte production from murine bone-marrow. A hematological response dependent on endogenous glucocorticoids underlies bone-marrow eosinophilia induced by trauma or allergic sensitization/challenge. We detected a defect in granulopoiesis in nonsensitized, perforin-deficient mice. In steady-state conditions, perforin- (Pfp-) deficient mice showed significantly decreased bone-marrow and blood eosinophil and neutrophil counts, and colony formation in response to GM-CSF, relative to wild-type controls of comparable age and/or weight. By contrast, peripheral blood or spleen total cell and lymphocyte numbers were not affected by perforin deficiency. Dexamethasone enhanced colony formation by GM-CSF-stimulated progenitors from wild-type controls, but not Pfp mice. Dexamethasone injection increased bone-marrow eosinophil and neutrophil counts in wild-type controls, but not Pfp mice. Because perforin is expressed in effector lymphocytes, we examined whether this defect would be corrected by transferring wild-type lymphocytes into perforin-deficient recipients. Short-term reconstitution of the response to dexamethasone was separately achieved for eosinophils and neutrophils by transfer of distinct populations of splenic lymphocytes from nonsensitized wild-type donors. Transfer of the same amount of splenic lymphocytes from perforin-deficient donors was ineffective. This demonstrates that the perforin-dependent, granulopoietic response to dexamethasone can be restored by transfer of innate lymphocyte subpopulations.

Roles of 5-lipoxygenase and cysteinyl-leukotriene type 1 receptors in the hematological response to allergen challenge and its prevention by diethylcarbamazine in a murine model of asthma

Diethylcarbamazine (DEC), which blocks leukotriene production, abolishes the challenge-induced increase in eosinopoiesis in bone-marrow from ovalbumin- (OVA-) sensitized mice, suggesting that 5-lipoxygenase (5-LO) products contribute to the hematological responses in experimental asthma models. We explored the relationship between 5-LO, central and peripheral eosinophilia, and effectiveness of DEC, using PAS or BALB/c mice and 5-LO-deficient mutants. We quantified eosinophil numbers in freshly harvested or cultured bone-marrow, peritoneal lavage fluid, and spleen, with or without administration of leukotriene generation inhibitors (DEC and MK886) and cisteinyl-leukotriene type I receptor antagonist (montelukast). The increase in eosinophil numbers in bone-marrow, observed in sensitized/challenged wild-type mice, was abolished by MK886 and DEC pretreatment. In ALOX mutants, by contrast, there was no increase in bone-marrow eosinophil counts, nor in eosinophil production in culture, in response to sensitization/challenge. In sensitized/challenged ALOX mice, challenge-induced migration of eosinophils to the peritoneal cavity was significantly reduced relative to the wild-type PAS controls. DEC was ineffective in ALOX mice, as expected from a mechanism of action dependent on 5-LO. In BALB/c mice, challenge significantly increased spleen eosinophil numbers and DEC treatment prevented this increase. Overall, 5-LO appears as indispensable to the systemic hematological response to allergen challenge, as well as to the effectiveness of DEC.

Essential roles of PKA, iNOS, CD95/CD95L, and terminal caspases in suppression of eosinopoiesis by PGE2 and other cAMP-elevating agents

Up- and downregulation of eosinopoiesis control pulmonary eosinophilia in human asthma. In mice, eosinopoiesis is suppressed in vitro by prostaglandin E2 (PGE2) and in vivo by diethylcarbamazine, through a proapoptotic mechanism sequentially requiring inducible NO synthase (iNOS) and the ligand for death receptor CD95 (CD95L). We examined the roles of iNOS, cAMP-mediated signaling, caspases, and CD95L/CD95 in suppression of eosinopoiesis by PGE2 and other agents signaling through cAMP. Bone-marrow collected from BALB/c mice, or from iNOS-, CD95-, or CD95L-deficient mutants (and wild-type controls), was cultured with interleukin-5 (IL-5), alone or associated with PGE2, cAMP-inducing/mimetic agents, caspase inhibitor zVAD-fmk, iNOS inhibitor aminoguanidine, or combinations thereof, and eosinopoiesis was evaluated at various times. PGE2, added up to 24 hours of culture, dose-dependently suppressed eosinopoiesis, by inducing apoptosis. This effect was (a) paralleled by induction of iNOS in eosinophils; (b) duplicated by sodium nitroprusside, isoproterenol, and cAMP-inducing/mimetic agents; (c) prevented by protein kinase A inhibition. NO was produced through iNOS by dibutyryl-cAMP-stimulated bone-marrow. Overall, PGE2 and isoproterenol shared a requirement for four effector elements (iNOS, CD95L, CD95, and terminal caspases), which together define a pathway targeted by several soluble up- and downmodulators of eosinopoiesis, including drugs, mediators of inflammation, and cytokines.

Essential roles of endogenous glucocorticoids and TNF/TNFR1 in promoting bone-marrow eosinopoiesis in ovalbumin-sensitized, airway-challenged mice

AIMS

Stress mechanisms paradoxically contribute to allergic episodes in humans and mice. Glucocorticoids (GC) and interleukin (IL)-5 synergically upregulate murine bone-marrow eosinophil production. Here we explored the role of endogenous GC in allergen-stimulated bone-marrow eosinophil production in ovalbumin-sensitized/challenged mice.

MAIN METHODS

In BALB/c or C57BL/6 mice, sensitized and intranasally challenged with ovalbumin, we monitored eosinophil numbers in freshly harvested or cultured bone-marrow, and plasma corticosterone levels. Metyrapone (MET) was used to inhibit GC synthesis, and RU486 to block GC actions. In sensitized mice challenged intraperitoneally, we examined the relationship between eosinophilia of bone-marrow and peritoneal cavity, in the absence or presence of RU486. In experiments involving in vivo neutralization of tumor necrosis factor-α (TNF) by specific antibodies, or using mice which lack functional type I TNF receptors (TNFRI), we evaluated the relationship between TNF blockade, corticosterone levels, RU486 or MET treatment and challenge-induced bone-marrow eosinophilia.

KEY FINDINGS

RU486 or MET pretreatments abolished challenge-induced increases in eosinophil numbers in bone-marrow (in vivo and ex vivo), and in the peritoneal cavity. MET, but not RU486, prevented the challenge-induced increase in corticosterone levels. Challenge-induced bone-marrow eosinophilia and corticosterone surge were abolished in TNFRI-deficient mice. Anti-TNF-treatment very effectively prevented challenge-induced bone-marrow eosinophilia, in the absence of RU486 or MET, but had no independent effect in the presence of either drug.

SIGNIFICANCE

Endogenous GC was essential for allergen challenge-induced increases in eosinophil numbers inside bone-marrow. This effect required TNF and TNFRI, which suggests an immunoendocrine mechanism.

Modulation of the effects of lung immune response on bone marrow by oral antigen exposure

Allergic airway inflammation is attenuated by oral tolerization (oral exposure to allergen, followed by conventional sensitization and challenge with homologous antigen), which decreases airway allergen challenge-induced eosinophilic infiltration of the lungs and bone marrow eosinophilia. We examined its effects on bone marrow eosinophil and neutrophil production. Mice of wild type (BP-2, BALB/c, and C57BL/6) and mutant strains (lacking iNOS or CD95L) were given ovalbumin (OVA) or water (vehicle) orally and subsequently sensitized and challenged with OVA (OVA/OVA/OVA and H₂O/OVA/OVA groups, resp.). Anti-OVA IgG and IgE, bone marrow eosinophil and neutrophil numbers, and eosinophil and neutrophil production ex vivo were evaluated. T lymphocytes from OVA/OVA/OVA or control H₂O/OVA/OVA donors were transferred into naïve syngeneic recipients, which were subsequently sensitized/challenged with OVA. Alternatively, T lymphocytes were cocultured with bone marrow eosinophil precursors from histocompatible sensitized/challenged mice. OVA/OVA/OVA mice of the BP-2 and BALB/c strains showed, relative to H₂O/OVA/OVA controls, significantly decreased bone marrow eosinophil counts and ex vivo eosinopoiesis/neutropoiesis. Full effectiveness in vivo required sequential oral/subcutaneous/intranasal exposures to the same allergen. Transfer of splenic T lymphocytes from OVA/OVA/OVA donors to naive recipients prevented bone marrow eosinophilia and eosinopoiesis in response to recipient sensitization/challenge and supressed eosinopoiesis upon coculture with syngeneic bone marrow precursors from sensitized/challenged donors.

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

Eosinophil 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.

Homologous recombination into the eosinophil peroxidase locus generates a strain of mice expressing Cre recombinase exclusively in eosinophils

Eosinophils are generally linked to innate host defense against helminths, as well as the pathologies associated with allergic diseases, such as asthma. Nonetheless, the activities of eosinophils remain poorly understood, which in turn, has prevented detailed definitions of their role(s) in health and disease. Homologous recombination in embryonic stem cells was used to insert a mammalianized Cre recombinase in the ORF encoding Epx. This knock-in strategy overcame previous inefficiencies associated with eosinophil-specific transgenic approaches and led to the development of a knock-in strain of mice (eoCRE), capable of mediating recombination of "floxed" reporter cassettes in >95% of peripheral blood eosinophils. We also showed that this Cre expression was limited exclusively to eosinophil-lineage committed cells with no evidence of Cre-mediated toxicity. The efficiency and specificity of Cre expression in eoCRE mice were demonstrated further in a cross with a knock-in mouse containing a "(flox-stop-flox)" DTA cassette at the ROSA26 locus, generating yet another novel, eosinophil-less strain of mice. The development of eoCRE mice represents a milestone in studies of eosinophil biology, permitting eosinophil-specific gene targeting and overexpression in the mouse as part of next-generation studies attempting to define eosinophil effector functions.

Human versus mouse eosinophils: "that which we call an eosinophil, by any other name would stain as red"

The respective life histories of human subjects and mice are well defined and describe a unique story of evolutionary conservation extending from sequence identity within the genome to the underpinnings of biochemical, cellular, and physiologic pathways. As a consequence, the hematopoietic lineages of both species are invariantly maintained, each with identifiable eosinophils. This canonical presence nonetheless does not preclude disparities between human and mouse eosinophils, their effector functions, or both. Indeed, many books and reviews dogmatically highlight differences, providing a rationale to discount the use of mouse models of human eosinophilic diseases. We suggest that this perspective is parochial and ignores the wealth of available studies and the consensus of the literature that overwhelming similarities (and not differences) exist between human and mouse eosinophils. The goal of this review is to summarize this literature and in some cases provide experimental details comparing and contrasting eosinophils and eosinophil effector functions in human subjects versus mice. In particular, our review will provide a summation and an easy-to-use reference guide to important studies demonstrating that although differences exist, more often than not, their consequences are unknown and do not necessarily reflect inherent disparities in eosinophil function but instead species-specific variations. The conclusion from this overview is that despite nominal differences, the vast similarities between human and mouse eosinophils provide important insights as to their roles in health and disease and, in turn, demonstrate the unique utility of mouse-based studies with an expectation of valid extrapolation to the understanding and treatment of patients.

The development of a sensitive and specific ELISA for mouse eosinophil peroxidase: assessment of eosinophil degranulation ex vivo and in models of human disease

Mouse models of eosinophilic disorders are often part of preclinical studies investigating the underlying biological mechanisms of disease pathology. The presence of extracellular eosinophil granule proteins in affected tissues is a well established and specific marker of eosinophil activation in both patients and mouse models of human disease. Unfortunately, assessments of granule proteins in the mouse have been limited by the availability of specific antibodies and a reliance on assays of released enzymatic activities that are often neither sensitive nor eosinophil specific. The ability to detect immunologically and quantify the presence of a mouse eosinophil granule protein in biological fluids and/or tissue extracts was achieved by the generation of monoclonal antibodies specific for eosinophil peroxidase (EPX). This strategy identified unique pairs of antibodies with high avidity to the target protein and led to the development of a unique sandwich ELISA for the detection of EPX. Full factorial design was used to develop this ELISA, generating an assay that is eosinophil-specific and nearly 10 times more sensitive than traditional OPD-based detection methods of peroxidase activity. The added sensitivity afforded by this novel assay was used to detect and quantify eosinophil degranulation in several settings, including bronchoalveolar fluid from OVA sensitized/challenged mice (an animal model of asthma), serum samples derived from peripheral blood recovered from the tail vasculature, and from purified mouse eosinophils stimulated ex vivo with platelet activating factor (PAF) and PAF + ionomycin. This ability to assess mouse eosinophil degranulation represents a specific, sensitive, and reproducible assay that fulfills a critical need in studies of eosinophil-associated pathologies in mice.

Eosinophils in innate immunity: an evolving story

Eosinophils are innate immune leukocytes found in relatively low numbers within the blood. Terminal effector functions of eosinophils, deriving from their capacity to release their content of tissue-destructive cationic proteins, have historically been considered primary effector mechanisms against specific parasites, and are likewise implicated in tissue damage accompanying allergic responses such as asthma. However, the past decade has seen dramatic advancements in the field of eosinophil immunobiology, revealing eosinophils to also be key participants in many other facets of innate immunity, from bridging innate and adaptive immune responses to orchestrating tissue remodeling events. Here, we review the multifaceted functions of eosinophils in innate immunity that are currently known, and discuss new avenues in this evolving story.

Redox control of asthma: molecular mechanisms and therapeutic opportunities

An imbalance in reducing and oxidizing (redox) systems favoring a more oxidative environment is present in asthma and linked to the pathophysiology of the defining symptoms and signs including airflow limitation, hyper-reactivity, and airway remodeling. High levels of hydrogen peroxide, nitric oxide ((*)NO), and 15-F(2t)-isoprostane in exhaled breath, and excessive oxidative protein products in lung epithelial lining fluid, peripheral blood, and urine provide abundant evidence for pathologic oxidizing processes in asthma. Parallel studies document loss of reducing potential by nonenzymatic and enzymatic antioxidants. The essential first line antioxidant enzymes superoxide dismutases (SOD) and catalase are reduced in asthma as compared to healthy individuals, with lowest levels in those patients with the most severe asthma. Loss of SOD and catalase activity is related to oxidative modifications of the enzymes, while other antioxidant gene polymorphisms are linked to susceptibility to develop asthma. Monitoring of exhaled (*)NO has entered clinical practice because it is useful to optimize asthma care, and a wide array of other biochemical oxidative and nitrative biomarkers are currently being evaluated for asthma monitoring and phenotyping. Novel therapeutic strategies that target correction of redox abnormalities show promise for the treatment of asthma.

Inducible nitric oxide synthase/CD95L-dependent suppression of pulmonary and bone marrow eosinophilia by diethylcarbamazine

RATIONALE

The mechanism of action of diethylcarbamazine (DEC), an antifilarial drug effective against tropical pulmonary eosinophilia, remains controversial. DEC effects on microfilariae depend on inducible NO synthase (iNOS). In eosinophilic pulmonary inflammation, its therapeutic mechanism has not been established. We previously described the rapid up-regulation of bone marrow eosinophilopoiesis in ovalbumin (OVA)-sensitized mice by airway allergen challenge, and further evidenced the down-regulation of eosinophilopoiesis by iNOS- and CD95L-dependent mechanisms.

OBJECTIVES

We investigated whether: (1) DEC can prevent the effects of airway challenge of sensitized mice on lungs and bone marrow, and (2) its effectiveness depends on iNOS/CD95L.

METHODS

OVA-sensitized BALB/c mice were intranasally challenged for 3 consecutive days, with DEC administered over a 12-, 3-, or 2-day period, ending at the day of the last challenge. We evaluated: (1) airway resistance, cytokine (IFN-gamma, IL-4, IL-5, and eotaxin) production, and pulmonary eosinophil accumulation; and (2) bone marrow eosinophil numbers in vivo and eosinophil differentiation ex vivo.

MEASUREMENTS AND MAIN RESULTS

DEC effectively prevented the effects of subsequent challenges on: (1) airway resistance, Th1/Th2 cytokine production, and pulmonary eosinophil accumulation; and (2) eosinophilopoiesis in vivo and ex vivo. Recovery from unprotected challenges included full responses to DEC during renewed challenges. DEC directly suppressed IL-5-dependent eosinophilopoiesis in naive bone marrow. DEC was ineffective in CD95L-deficient gld mice and in mice lacking iNOS activity because of gene targeting or pharmacological blockade.

CONCLUSIONS

DEC has a strong impact on pulmonary eosinophilic inflammation in allergic mice, as well as on the underlying hemopoietic response, suppressing the eosinophil lineage by an iNOS/CD95L-dependent mechanism.

A novel histologic scoring system to evaluate mucosal biopsies from patients with eosinophilic esophagitis

BACKGROUND & AIMS

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Evidence for a regulatory role of alpha 4-integrins in the maturation of eosinophils generated from the bone marrow in the presence of dexamethasone

BACKGROUND

Although eosinophils co-express multiple integrin receptors, the contributions of integrins to eosinophil development have not been explored. We previously described extensive aggregation and cytological immaturity in eosinophils developing in bone-marrow (BM) cultures exposed to dexamethasone. Here we examined the relationship of alpha 4 integrins with these effects of dexamethasone.

OBJECTIVES

We evaluated: (a) the effects of exposure to dexamethasone in BM culture on eosinophil expression of alpha 4 integrin receptors and ligands; (b) the contribution of alpha 4 integrins to eosinophil aggregation and maturation.

METHODS

Cultures were established with IL-5 (alone or with dexamethasone) for up to 7 days, and eosinophil production, alpha 4 integrin receptor/ligand expression, aggregation and morphology were evaluated before and after targeting alpha 4 integrin-dependent adhesions. Because prostaglandin E2 (PGE2) modifies the effects of dexamethasone on eosinophilopoiesis, PGE2 effects on alpha 4 integrin expression and function were also evaluated.

RESULTS

Dexamethasone increased the yield of eosinophils up to day 7. The frequency of eosinophils expressing alpha 4, beta1 and beta 7 integrin receptors at day 7 was also increased by dexamethasone. Eosinophils also expressed the alpha 4 beta 1 ligand, VCAM-1. Dexamethasone increased the expression of alpha 4 integrin and VCAM-1 in aggregates containing eosinophils as early as day 3. PGE2, added up to day 3, modified the effects of dexamethasone to suppress the expression of alpha 4 integrin, decrease aggregation and promote cytological maturation of eosinophils recovered at day 7. Dissociation of immature eosinophils from clusters present at day 3 by reagents targeting alpha 4 or beta1 integrins or VCAM-1 also induced cytological maturation. The concordant effects of targeting alpha 4 integrins with drugs and antibodies support a relationship between alpha 4-mediated aggregation and maturational arrest.

CONCLUSIONS

These observations support a novel role for alpha 4 integrin receptors and ligands in eosinophilopoiesis. In addition, increased alpha 4 expression following glucocorticoid exposure may contribute to the retention and accumulation of eosinophils in haemopoietic tissue.

Intrauterine fate of invasive trophoblast cells

Invasion of trophoblast cells into the uterine spiral arteries and the uterine wall is characteristic of hemochorial placentation. In the rat, trophoblast cells penetrate through the uterine decidua and well into the metrial gland. In this report, we examined the fate of these invasive trophoblast cells following parturition. Invasive trophoblast endocrine cells were retained in the postpartum mesometrial uterus in the rat. The demise of invasive trophoblast cells was followed by the appearance of differentiated smooth muscle cells surrounding blood vessels previously lined by invasive trophoblast cells and an infiltration of macrophages. Regulation of intrauterine trophoblast cell fate was investigated following premature removal of the fetus or removal of the fetus and chorioallantoic placenta. The presence of the fetus affected the distribution of invasive trophoblast cells within the uterus but did not negatively impact their survival. Premature removal of all chorioallantoic placentas and associated fetuses from a uterus resulted in extensive removal of intrauterine trophoblast cells. In summary, the postpartum demise of intrauterine invasive trophoblast cells is a dynamic developmental event regulated in part by the removal of trophic signals emanating from the chorioallantoic placenta.

Post-translational tyrosine nitration of eosinophil granule toxins mediated by eosinophil peroxidase

Nitration of tyrosine residues has been observed during various acute and chronic inflammatory diseases. However, the mechanism of tyrosine nitration and the nature of the proteins that become tyrosine nitrated during inflammation remain unclear. Here we show that eosinophils but not other cell types including neutrophils contain nitrotyrosine-positive proteins in specific granules. Furthermore, we demonstrate that the human eosinophil toxins, eosinophil peroxidase (EPO), major basic protein, eosinophil-derived neurotoxin (EDN) and eosinophil cationic protein (ECP), and the respective murine toxins, are post-translationally modified by nitration at tyrosine residues during cell maturation. High resolution affinity-mass spectrometry identified specific single nitration sites at Tyr349 in EPO and Tyr33 in both ECP and EDN. ECP and EDN crystal structures revealed and EPO structure modeling suggested that the nitrated tyrosine residues in the toxins are surface exposed. Studies in EPO(-/-), gp91phox(-/-), and NOS(-/-) mice revealed that tyrosine nitration of these toxins is mediated by EPO in the presence of hydrogen peroxide and minute amounts of NOx. Tyrosine nitration of eosinophil granule toxins occurs during maturation of eosinophils, independent of inflammation. These results provide evidence that post-translational tyrosine nitration is unique to eosinophils.

Eosinophilic granulocytes and damage-associated molecular pattern molecules (DAMPs): role in the inflammatory response within tumors

The development of a tumor over many years typically leads to reciprocal alternations in the host and the tumor, enabling tumor growth paradoxically in the setting of substantial necrosis and inflammation. When evaluating a tumor, it is important to assess 3 elements: (1) the quantity and quality of tumor-associated leukocytes, (2) their state of activation, and (3) tumor microenvironment. Peripheral blood eosinophilia and tumor-associated tissue eosinophilia are frequently associated with some tumor types and also found after immunotherapy with IL-2, IL-4, granulocyte-macrophage colony-stimulating factor, and antibody to CTLA-4. Within several tumor types including gastrointestinal tumors, tumor-associated tissue eosinophilia is associated with a significantly better prognosis. The converse is true in other tumor types such as differentiated oral squamous cell carcinoma. On the basis of the emergent data, tumor-associated eosinophils have at least 2 dominant nonoverlapping activities: (1) destructive effector functions potentially limiting tumor growth as well as causing recruitment and activation of other leukocytes, (2) immunoregulative and remodeling activities which suppress immune response and promote tumor proliferation. The mechanism by which eosinophils in particular are recruited into tumor tissue is largely unknown. Candidates for causing eosinophil chemotaxis into tumor tissue are the released damage-associated molecular pattern molecules (DAMPs) including the nuclear protein high mobility group box 1. High mobility group box 1 is released upon necrotic cell death and secreted by many cells, particularly during periods of nutrient, hypoxic, or oxidant stress. This overview on eosinophil biology in the context of cancer and necrosis, introduces intriguing and novel strategies targeting eosinophils to enable more effective biologic therapy for cancer patients.

Schistosoma mansoni infection in eosinophil lineage-ablated mice

We explore the controversial issue of the role of eosinophils in host defense against helminthic parasites using the established Schistosoma mansoni infection model in 2 novel mouse models of eosinophil lineage ablation (DeltadblGATA and TgPHIL). No eosinophils were detected in bone marrow of infected DeltadblGATA or TgPHIL mice, despite the fact that serum IL-5 levels in these infected mice exceeded those in infected wild type by approximately 4-fold. Liver granulomata from infected DeltadblGATA and TgPHIL mice were likewise depleted of eosinophils compared with those from their respective wild types. No eosinophil-dependent differences in granuloma number, size, or fibrosis were detected at weeks 8 or 12 of infection, and differential accumulation of mast cells was observed among the DeltadblGATA mice only at week 12. Likewise, serum levels of liver transaminases, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) increased in all mice in response to S mansoni infection, with no eosinophil-dependent differences in hepatocellular damage observed. Finally, eosinophil ablation had no effect on worm burden or on egg deposition. Overall, our data indicate that eosinophil ablation has no impact on traditional measures of disease in the S mansoni infection model in mice. However, eosinophils may have unexplored immunomodulatory contributions to this disease process.

Mucosal B cell deficiency in IgA-/- mice abrogates the development of allergic lung inflammation

We have investigated the consequence of lack of IgA on host immunity using a murine model of allergic lung inflammation. Mice with a targeted disruption of the alpha-switch region and 5' H chain gene (IgA(-/-) mice), which lack total IgA, developed significantly reduced pulmonary inflammation with fewer inflammatory cells in lung tissue and bronchoalveolar lavage fluids, as well as reduced levels of total and IgG1 OVA-specific Abs and decreased IL-4 and IL-5 in bronchoalveolar lavage fluids compared with IgA(+/+) controls, following allergen sensitization and challenge. This defect was attributable to fewer B cells in the lungs of IgA(-/-) mice. Polymeric IgR-deficient (pIgR(-/-)) mice, which lack the receptor that transports polymeric IgA across the mucosal epithelium where it is cleaved to form secretory IgA, were used to assess the contribution of secretory IgA vs total IgA in the induction of allergic lung inflammation. pIgR(-/-) and pIgR(+/+) mice had comparable levels of inflammation, demonstrating that IgA bound to secretory component is not necessary for the development of allergic lung inflammation, although this does not necessarily rule out a role for transudated IgA in lung secretions because of "mucosal leakiness" in these mice. The results indicate that Ag-specific B cells are required at mucosal surfaces for induction of inflammation and likely function as major APCs in the lung for soluble protein Ags.

Cells isolated from bone-marrow and lungs of allergic BALB/C mice and cultured in the presence of IL-5 are respectively resistant and susceptible to apoptosis induced by dexamethasone

We have previously reported that, in IL-5-stimulated bone-marrow cultures, dexamethasone upregulates eosinophil differentiation and protects developing eosinophils from apoptosis induced by a variety of agents. Recently developed procedures for the isolation of hemopoietic cells from allergic murine lungs have enabled us to evaluate how these cells respond to dexamethasone in IL-5-stimulated cultures, when compared with bone-marrow-derived cells isolated from the same donors, and whether differences in response patterns were linked to apoptosis. Ovalbumin challenge of sensitized mice increased significantly the numbers of mature leukocytes as well as hemopoietic cells recovered from digested lung fragments, relative to saline-challenged, sensitized controls. Both mature eosinophils and cells capable of differentiating into eosinophils in the presence of IL-5 were present in lungs from sensitized mice 24 h after airway challenge. Dexamethasone strongly inhibited eosinophil differentiation in IL-5-stimulated cultures of lung hemopoietic cells. By contrast, dexamethasone enhanced eosinophil differentiation in cultures of allergic bone-marrow cells, in identical conditions. Hemopoietic cells from lungs and bone-marrow were respectively susceptible and resistant to induction of apoptosis by dexamethasone. The dexamethasone-sensitive step was the response to IL-5 in culture, while accumulation of IL-5 responsive cells in allergen-challenged lungs was dexamethasone-resistant. Cells from lungs and bone-marrow, cultured for 3 days with IL-5 in the absence of dexamethasone, did not respond to a subsequent exposure to dexamethasone in the presence of IL-5. These findings confirm that IL-5-responsive hemopoietic cells found in challenged, sensitized murine lungs differ from those in bone-marrow, with respect to the cellular responses induced by dexamethasone, including apoptosis.

Induction of bone-marrow eosinophilia in mice submitted to surgery is dependent on stress-induced secretion of glucocorticoids

1 We examined bone-marrow in mice receiving subcutaneous implants of heat-coagulated egg white, which are known to present chronic eosinophilic inflammation at the implant site. Egg white implants (EWIs) induced marked bone-marrow eosinophilia, and increased bone-marrow cell responses to granulocyte-macrophage colony-stimulating factor and interleukin-5 in culture. These effects were observed as early as 24 h and lasted for, at least, 30 days in implant recipients. 2 We found, however, that increased eosinophil production was also observed in control mice which underwent surgery but received no EWI (sham-implanted mice), up to 15 days post-surgery. As this suggests an important contribution of nonspecific stress mechanisms to eosinopoiesis, we further evaluated the role of stress hormones produced by the adrenal glands in the bone-marrow eosinophilia of sham-implanted mice. 3 Bone-marrow eosinophilia in mice undergoing surgery was dissociated from increases in other haemopoietic lineages. Surgery by itself increased circulating corticosterone levels by 24 h, and the increase was prevented by inhibition of adrenal glucocorticoid production by metyrapone. The effect of surgery on bone-marrow eosinophilia was prevented by pretreatment with both the glucocorticoid receptor antagonist, mifepristone, and metyrapone, and by surgical adrenalectomy. 4 By contrast, cathecolamine receptor antagonists (propranolol, prazosin and yohimbine) were ineffective, indicating that cathecolamine release from the adrenal glands was not responsible for the effects on bone-marrow. 5 These results highlight a critical role for stress-induced glucocorticoid hormones in selectively upregulating bone-marrow eosinopoiesis in mice submitted to surgery.

Defining a link with asthma in mice congenitally deficient in eosinophils

Eosinophils are often dominant inflammatory cells present in the lungs of asthma patients. Nonetheless, the role of these leukocytes remains poorly understood. We have created a transgenic line of mice (PHIL) that are specifically devoid of eosinophils, but otherwise have a full complement of hematopoietically derived cells. Allergen challenge of PHIL mice demonstrated that eosinophils were required for pulmonary mucus accumulation and the airway hyperresponsiveness associated with asthma. The development of an eosinophil-less mouse now permits an unambiguous assessment of a number of human diseases that have been linked to this granulocyte, including allergic diseases, parasite infections, and tumorigenesis.

Characterization of biological activities of feline eosinophil granule proteins

OBJECTIVE

To characterize eosinophil granule-derived proteins in cats.

SAMPLE POPULATION

Eosinophils collected via peritoneal lavage from 2 cats.

PROCEDURE

The cats were infested orally with Toxocara canis eggs and subsequently challenge-exposed with T. canis antigen injected IP to induce peritoneal eosinophilia; eosinophils were collected via peritoneal lavage. Eosinophil granule proteins were acid-extracted, separated by gel-filtration chromatography, and examined for their peroxidase, ribonuclease, and bactericidal activities; the N-terminal sequence of some of these proteins was determined and compared with homologue proteins from other species.

RESULTS

3 protein peaks were separated in the chromatogram. The first peak had both peroxidase and bactericidal activities. The second peak had ribonuclease and bactericidal activities, and the N-terminal sequence of the major protein was homologous with that of proteins of the ribonuclease A superfamily, including eosinophil ribonucleases from humans and other animal species. The third protein peak had bactericidal activity, and the N-terminal sequence of the major protein was homologous with that of human and murine major basic proteins.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that feline eosinophil granules contain major basic protein and eosinophil-associated ribonuclease and the granule proteins have peroxidase, ribonuclease, and bactericidal activities. In cats, characterization of eosinophil granule proteins may be useful in elucidation of the mechanism of tissue damage in eosinophil-associated diseases and development of new treatment options for those diseases. In addition, the identification of conserved structure and function of eosinophil granule proteins in cats is relevant from an evolutionary viewpoint.

Isolation and characterization of hemopoietic cells from lungs of allergic mice

We developed a procedure for the isolation of hemopoietic cells from murine lung. Ovalbumin sensitization and challenge increased the numbers of functionally intact hemopoietic progenitors recovered from digested lung fragments by 80-fold to 120-fold, relative to naive controls. Eosinophil precursors, which are absent in the naive mouse lung, accumulated in the lungs of sensitized/challenged mice. Progenitors in allergic BALB/c mice were recoverable from lung parenchyma, not blood or airways, and were exclusively CD34+. Precursors isolated from allergic lung, unlike those from bone marrow, were inhibited by dexamethasone and were stimulated by prostaglandin D(2). This directly demonstrates that sensitized/challenged lungs accumulate hemopoietic progenitors and precursors, distinct from those in bone marrow.

Allergenic sensitization prevents upregulation of haemopoiesis by cyclo-oxygenase inhibitors in mice

1. We evaluated whether immunization affects bone-marrow responses to indomethacin, because allergenic sensitization and challenge upregulate responses to haemopoietic cytokines (including IL-5-driven eosinopoiesis) in murine bone-marrow, while indomethacin upregulates haemopoiesis and protects bone-marrow from radiation damage. 2. Progenitor (semi-solid) and/or precursor (liquid) cultures were established from bone-marrow of: (a) normal mice; (b) ovalbumin-sensitized mice, with or without intranasal challenge. Cultures were established with GM-CSF (2 ng ml(-1)) or IL-5 (1 ng ml(-1)), respectively, alone or associated with indomethacin (10(-7) - 10(-11) M) or aspirin (10(-7) - 10(-8) M). Total myeloid colony numbers and numbers of eosinophil-peroxidase-positive cells were determined at day 7. 3. In naïve BALB/c mice, indomethacin (10(-7) - 10(-9) M) increased GM-CSF-stimulated myeloid colony formation (P=0.003 and P=0.009, respectively). In contrast, it had no effect on bone-marrow of ovalbumin-sensitized and challenged mice. Indomethacin (10(-7) - 10(-9) M) also increased eosinophil precursor responses to IL-5 in bone-marrow of naïve (P<0.001 and P=0.002 respectively), but not sensitized-challenged mice. Aspirin (10(-7) M) had similar effects, equally abolished by sensitization. Enhancement of haemopoiesis by indomethacin required adherent cells from naïve bone-marrow. Nonadherent cells responded to IL-5 but not to indomethacin. Indomethacin was effective on bone-marrow from sham-sensitized, ovalbumin-challenged, but not from sensitized, saline-challenged mice. Plasma transfer from immune mice abolished eosinophil precursor responses to indomethacin in bone-marrow of naïve recipients. This was not prevented by previous removal of antibody from immune plasma. 4. COX inhibitors enhance haemopoiesis in naïve but not allergic mice. Responsiveness to indomethacin can be abolished either by active sensitization or by immune plasma transfer. Specific antibody is not involved.

A simple method for the in situ detection of eosinophils

A simple and rapid method for identifying eosinophils in tissue sections is described. The assay is based on the incubation of frozen tissue sections with phenol red and the detection of cellular fluorescence. A one-to-one relationship was observed between cells exhibiting fluorescence following exposure to phenol red and eosinophils as identified by histochemical detection of eosinophil peroxidase (EPO) activity. Using the phenol red assay, eosinophils were detected in various eosinophil-infiltrated tissues, including uteri of rats from day 1 of pregnancy and uteri of prepubertal estrogen-treated rats. Intensity of the fluorescing eosinophils was dependent upon phenol red concentration and duration of incubation. The phenol red method of eosinophil identification was disrupted by co-incubation with resorcinol, an EPO inhibitor, or catalase, a hydrogen peroxide scavenger. The merits of this assay are its simplicity and compatibility with other procedures, such as histochemistry, immunocytochemistry, and in situ ligand-receptor binding.

The neutrophil NADPH oxidase

The NADPH oxidase of phagocytes catalyzes the conversion of oxygen to O2(-). This multicomponent enzyme complex contains five essential protein components, two in the membrane and three in the cytosol. Unassembled and inactive in resting phagocytes, the oxidase becomes active after translocation of cytosolic components to the membrane to assemble a functional oxidase. Multiple factors regulate its assembly and activity, thus serving to maintain this highly reactive system under spatial and temporal control until recruited for antimicrobial or proinflammatory events. The recent identification of homologs of one of the membrane components in nonphagocytic cells will expand understanding of the biological contexts in which this system may function.

Eosinophil peroxidase mediates protein nitration in allergic airway inflammation in mice

The eosinophilic inflammatory response in asthma is associated with protein nitration, detected as immunostaining for 3-nitrotyrosine (3NT). As the presence of 3NT is strongly correlated with upregulation of the inducible form of nitric oxide synthase (NOS II), it has been hypothesized that 3NT formation results from the action of peroxynitrite (ONOO-), a highly reactive NO derivative produced from the reaction of molecular NO and O2-. However, recent observations have suggested that the action of peroxidases, including eosinophil peroxidase (EPO), may be responsible for protein nitration. In this study, we used murine models of allergic asthma to address the relative contribution of EPO and NOS II to protein nitration. We studied EPO-deficient New Zealand White (NZW) mice, which were sensitized and challenged intranasally with ovalbumin (OVA). Despite comparable levels of eosinophilia, NO, and superoxide production, NZW mice exhibited markedly decreased 3NT staining around the airways after OVA challenge when compared with two other strains (A/J and C57BL/6J). Immunocytochemical analysis of bronchoalveolar lavage (BAL) cells and lung sections suggested that 3NT staining was largely confined to eosinophils. This was confirmed by Western Blot analysis of proteins from different subsets of BAL cells that demonstrated a marked decrease in 3NT formation in eosinophils from NZW mice. These results contrast with those obtained in OVA-sensitized and -challenged NOS II deficient mice, which despite decreased NO production, exhibited similar 3NT staining in the airways after OVA challenge as in wild-type control mice. In this model, protein nitration was thus not a function of NO production by NOS II. We conclude that in the mouse, 3NT formation after specific allergen challenge is dependent on EPO activity, particularly in eosinophils themselves. In contrast, 3NT formation is not driven by upregulation of NOS II expression in this model and does not appear to depend on increases in the level of NO production.

Extensive eosinophil degranulation and peroxidase-mediated oxidation of airway proteins do not occur in a mouse ovalbumin-challenge model of pulmonary inflammation

Paradigms of eosinophil effector function in the lungs of asthma patients invariably depend on activities mediated by cationic proteins released from secondary granules during a process collectively referred to as degranulation. In this study, we generated knockout mice deficient for eosinophil peroxidase (EPO) to assess the role(s) of this abundant secondary granule protein in an OVA-challenge model. The loss of EPO had no effect on the development of OVA-induced pathologies in the mouse. The absence of phenotypic consequences in these knockout animals extended beyond pulmonary histopathologies and airway changes, as EPO-deficient animals also displayed OVA-induced airway hyperresponsiveness after provocation with methacholine. In addition, EPO-mediated oxidative damage of proteins (e.g., bromination of tyrosine residues) recovered in bronchoalveolar lavage from OVA-treated wild-type mice was <10% of the levels observed in bronchoalveolar lavage recovered from asthma patients. These data demonstrate that EPO activities are inconsequential to the development of allergic pulmonary pathologies in the mouse and suggest that degranulation of eosinophils recruited to the lung in this model does not occur at levels comparable to those observed in humans with asthma.

Murine myeloid progenitor responses to GM-CSF and eosinophil precursor responses to IL-5 represent distinct targets for downmodulation by prostaglandin E(2)

1. Because Prostaglandin E(2) (PGE(2)) and dibutiryl cyclic AMP (dbcAMP) modulate the production and effects of haemopoietic cytokines in allergy, we examined their ability to modulate responses of myeloid progenitors to GM-CSF, and of eosinophil precursors to IL-5. 2. The ability of PGE(2), dbcAMP, rolipram, forskolin, dbcGMP and PGD(2), to modulate the responses to GM-CSF and IL-5 in colony formation (progenitor) and eosinophil differentiation (precursor) assays using bone-marrow from nonsensitized or from intranasally-challenged, ovalbumin-sensitized mice of five strains was studied. 3. PGE(2) (10(-7) M) inhibited GM-CSF-stimulated colony formation in bone-marrow from BP-2 mice. This effect was duplicated by dbcAMP (0.3 - 1x10(-6) M), Rolipram (10(-5) M) and forskolin (3x10(-5) M), but not Prostaglandin D(2) (10(-6) M). Inhibition affected similarly all myeloid colony types. Progenitors from sensitized and challenged BP-2 mice were also inhibited by PGE(2) and cyclic AMP. PGE(2) inhibited progenitors from C57BL/10, CBA/J and A/J, but not BALB/c mice. However, BALB/c progenitors were sensitive to dbcAMP and Forskolin (10(-4) M). In contrast, in precursor assays, PGE(2) (10(-7) - 10(-9) M) blocked responses to IL-5 in bone-marrow from BP-2 and BALB/c mice, either naïve or sensitized and challenged, to a similar extent. PGD(2) (10(-6) M) was ineffective, as was PGE(2) (10(-7) M), if added after 48 h of culture. 4. In conclusion, PGE(2) inhibits the responses of bone-marrow myeloid progenitors to GM-CSF and of eosinophil precursors to IL-5, in naïve or ovalbumin sensitized and challenged mice. These effects are duplicated by cyclic AMP-elevating agents. In the BALB/c strain, the resistance of progenitors, but not precursors, to PGE(2) inhibition, indicates these developmental stages are separate targets for PGE(2) modulation.

Upregulation by glucocorticoids of responses to eosinopoietic cytokines in bone-marrow from normal and allergic mice

Since the production of eosinopoietic cytokines (GM-CSF, IL-3, IL-5) is inhibited by glucocorticoids, while responsiveness to these cytokines is enhanced in bone-marrow of allergic mice, we studied the ability of glucocorticoids to modulate murine bone-marrow eosinopoiesis. Progenitor (semi-solid) and/or precursor (liquid) cultures were established from bone-marrow of: (a) normal mice; (b) ovalbumin-sensitized and challenged mice or (c) dexamethasone (1-5 mg kg(-1)) injected mice. Cultures were established with GM-CSF (2 ng ml(-1)) or IL-5 (1 ng ml(-1)), respectively, alone or associated with dexamethasone, hydrocortisone or corticosterone. Total myeloid colony numbers, frequency and size of eosinophil colonies, and numbers of eosinophil-peroxidase-positive cells were determined at day 7. In BALB/c mice, dexamethasone (10(-7) M) increased GM-CSF-stimulated myeloid colony formation (P = 0.01), as well as the frequency (P=0.01) and size (P<0.01) of eosinophil colonies. Dexamethasone (10(-7) M) alone had no effect. Dexamethasone (10(-7)-10(-10) M) increased (P<0.002) eosinophil precursor responses to IL-5. Potentiation by dexamethasone was still detectable: (a) on low density, immature, nonadherent BALB/c bone-marrow cells, (b) on bone-marrow from other strains, and (c) on cells from allergic mice. Hydrocortisone and corticosterone had similar effects. Dexamethasone administered in vivo, 24 h before bone-marrow harvest, increased subsequent progenitor responses to GM-CSF (P = 0.001) and precursor responses to IL-5 (P<0.001). These effects were blocked by RU 486 (20 mg kg(-1), orally, 2 h before dexamethasone, or added in vitro at 10 microM, P<0.001). Glucocorticoids, acting in vivo or in vitro, through glucocorticoid receptors, enhance bone-marrow eosinopoiesis in naïve and allergic mice.

Recombinant herpes simplex virus type 1 engineered for targeted binding to erythropoietin receptor-bearing cells

The utility of recombinant herpes simplex virus type 1 (HSV-1) vectors may be expanded by manipulation of the virus envelope to achieve cell-specific gene delivery. To this end, an HSV-1 mutant virus deleted for glycoprotein C (gC) and the heparan sulfate binding domain of gB (KgBpK-gC-) was engineered to encode different chimeric proteins composed of N-terminally truncated forms of gC and the full-length erythropoietin hormone (EPO). Biochemical analyses demonstrated that one gC-EPO chimeric molecule (gCEPO2) was posttranslationally processed, incorporated into recombinant HSV-1 virus (KgBpK-gCEPO2), and neutralized with antibodies directed against gC or EPO in a complement-dependent manner. Moreover, KgBpK-gCEPO2 recombinant virus was specifically retained on a soluble EPO receptor column, was neutralized by soluble EPO receptor, and stimulated proliferation of FD-EPO cells, an EPO growth-dependent cell line. FD-EPO cells were nevertheless refractory to productive infection by both wild-type HSV-1 and recombinant KgBpK-gCEPO2 virus. Transmission electron microscopy of FD-EPO cells infected with KgBpK-gCEPO2 showed virus endocytosis leading to aborted infection. Despite the lack of productive infection, these data provide the first evidence of targeted HSV-1 binding to a non-HSV-1 cell surface receptor.

Representational difference analysis of a committed myeloid progenitor cell line reveals evidence for bilineage potential

In this study we have sought to characterize a committed myeloid progenitor cell line in an attempt to isolate general factors that may promote differentiation. We used cDNA representational difference analysis (RDA), which allows analysis of differential gene expression, to compare EML and EPRO cells. We have isolated nine differentially expressed cDNA fragments as confirmed by slot blot, Northern, and PCR analysis. Three of nine sequences appear to be novel whereas the identity of the remaining fragments suggested that the EPRO cell line is multipotent. Among the isolated sequences were eosinophilic, monocytic, and neutrophilic specific genes. Therefore, we tested the ability of EPRO cells to differentiate along multiple myeloid lineages and found that EPRO cells exhibited morphologic maturation into either monocyte/macrophages or neutrophils, but not eosinophils. Furthermore, when EPRO cells were exposed to ATRA, neutrophil specific genes were induced, whereas monocytic markers were induced by phorbol ester treatment. This study highlights the use of cDNA RDA in conjunction with the EML/EPRO cell line to isolate markers associated with macrophage and neutrophil differentiation and establishes the usefulness of this system in the search for factors involved in myeloid commitment.

Rapid increase in bone-marrow eosinophil production and responses to eosinopoietic interleukins triggered by intranasal allergen challenge

To define the effects of immunization and exposure to allergen on the eosinophil lineage, we studied blood and bone-marrow eosinophil numbers, serum interleukin (IL)-5 levels, and eosinophil progenitor and precursor responses to IL-3 and IL-5 in ovalbumin-immunized BALB/c mice after intranasal challenge. Increased blood eosinophilia was found in immune relative to nonimmune mice, but the differences between challenged and unchallenged immune animals were not significant. In contrast, significantly increased circulating levels of IL-5 and numbers of bone-marrow eosinophils were found in sensitized animals exposed to allergen, relative to unchallenged, sensitized controls. An allergen-induced increase in IL-3-sensitive progenitors yielding eosinophil-bearing colonies was also found at 2 h after challenge. Furthermore, an eosinophil differentiation assay showed a marked increase in the magnitude of the responses to IL-5 and IL-3 over a 7-day period in bone-marrow cells of sensitized animals, which was detectable at 24 h after allergen challenge, but not at 2 h and not in unchallenged controls. Modulation of the responses of bone-marrow cells to IL-5 is induced by a circulating factor present in challenged immune animals, as shown by in vivo plasma transfer, but is at best only partly blocked by in vivo treatment with the anti-IL-5 antibody TRFK-5. These data indicate that allergen challenge in the airways leads to rapid long-term modifications in bone-marrow eosinophil progenitors and precursors, and that increased responses to eosinopoietins in bone marrow depend on the release, between 2 h and 24 h after challenge, of a circulating factor distinct from IL-5.

Interleukin-5 expression in the lung epithelium of transgenic mice leads to pulmonary changes pathognomonic of asthma

We have generated transgenic mice that constitutively express murine interleukin (IL)-5 in the lung epithelium. Airway expression of this cytokine resulted in a dramatic accumulation of peribronchial eosinophils and striking pathologic changes including the expansion of bronchus-associated lymphoid tissue (BALT), goblet cell hyperplasia, epithelial hypertrophy, and focal collagen deposition. These changes were also accompanied by eosinophil infiltration of the airway lumen. In addition, transgenic animals displayed airway hyperresponsiveness to methacholine in the absence of aerosolized antigen challenge. These findings demonstrate that lung-specific IL-5 expression can induce pathologic changes characteristic of asthma and may provide useful models to evaluate the efficacy of potential respiratory disease therapies or pharmaceuticals.

The single MyoD family gene of Ciona intestinalis encodes two differentially expressed proteins: implications for the evolution of chordate muscle gene regulation

A MyoD family gene was identified in the ascidian Ciona intestinalis and designated CiMDF (Ciona intestinalis Muscle Determination Factor). Expression of CiMDF was restricted to the muscle cells of the developing embryo and the body-wall muscle of adults. Northern blots showed that two differentially regulated CiMDF transcripts were expressed during development. A 1.8 kb transcript (CiMDFa) appeared first and was gradually replaced by a 2.7 kb transcript (CiMDFb). These transcripts encoded essentially identical MyoD family proteins with the exception of a 68 amino acid C-terminal sequence present in CiMDFb that was absent from CiMDFa. Although both CiMDFa and CiMDFb contained the cysteine-rich/basic-helix loop helix domain (Cys-rich/bHLH) present in all MyoD family proteins, only CiMDFb contained the region near the C terminus (Domain III) characteristic of this gene family. Genomic Southern blots showed that C. intestinalis has only one MyoD family gene, suggesting that CiMDFa and CiMDFb result from differential processing of primary transcripts. The existence of two MyoD family proteins that are differentially expressed during ascidian embryogenesis has novel parallels to vertebrate muscle development and may reflect conserved myogenic regulatory mechanisms among chordates.

Two highly homologous ribonuclease genes expressed in mouse eosinophils identify a larger subgroup of the mammalian ribonuclease superfamily

Two putative ribonucleases have been isolated from the secondary granules of mouse eosinophils. Degenerate oligonucleotide primers inferred from peptide sequence data were used in reverse transcriptase-PCR reactions of bone marrow-derived cDNA. The resulting PCR product was used to screen a C57BL/6J bone marrow cDNA library, and comparisons of representative clones showed that these genes and encoded proteins are highly homologous (96% identity at the nucleotide level; 92/94% identical/similar at the amino acid level). The mouse proteins are only weakly homologous (approximately 50% amino acid identity) with the human eosinophil-associated ribonucleases (i.e., eosinophil-derived neurotoxin and eosinophil cationic protein) and show no sequence bias toward either human protein. Phylogenetic analyses established that the human and mouse loci shared an ancestral gene, but that independent duplication events have occurred since the divergence of primates and rodents. The duplication event generating the mouse genes was estimated to have occurred < 5 x 10(6) years ago (versus 30 to 40 x 10(6) years ago in primates). The identification of independent duplication events in two extant mammalian orders suggests a selective advantage to having multiple eosinophil granule ribonucleases. Southern blot analyses in the mouse demonstrated the existence of three additional highly homologous genes (i.e., five genes total) as well as several more divergent family members. The potential significance of this observation is the implication of a larger gene subfamily in primates (i.e., humans).