Haemopoietic mechanisms in allergic rhinitis.
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Allergens↗
Biomedical subjects
R Sehmi
Publications and source records attributed to R Sehmi.
Hemopoietic progenitor cells and hemopoietic factors: potential targets for treatment of allergic inflammatory diseases.
Eosinophilic infiltration is a cardinal feature of allergic inflammation; based upon its biological actions, the eosinophil has assumed the role as the principal inflammatory cell in asthma. In assessing the mechanisms by which eosinophils are recruited to sites of inflammation, a sizeable body of evidence exists supporting the proposal that expansion of hemopoietic compartments in the bone marrow stimulates an increased turnover and traffic of mature eosinophils to the site of allergic inflammation. In addition, recent findings point to the possible egress and traffic of primitive progenitor cells to the site of inflammation where in-situ differentiation may provide a continued supply of pro-inflammatory cells. In the present article, we will review the evidence for these findings, and discuss the rationale for targeting hemopoiesis and migrational pathways of hemopoietic cells in the treatment of allergic disease. In this context, we will discuss the effect of corticosteroid treatment on hemopoietic mechanisms; the effects of therapies that inhibit the actions of cysteinyl leukotrienes (CysLTs); the effects of in vivo blockade of the eosinophil-active cytokine, interleukin (IL)-5; and, the effects of antihistamines on hemopoiesis. In addition, we will address the potential role that small molecular weight chemokine receptor antagonists may play in modulating progenitor cell trafficking to tissue sites of inflammation.
Animals↗
Distinct phenotypic adhesion molecule expression on human cord blood progenitors during early Eosinophilic commitment: upregulation of beta(7) integrins.
Increasing levels of proinflammatory cells, including eosinophils and basophils, are seen at the site of allergen challenge in allergic disease of the airways. Mechanisms for the recruitment of these cell types could involve either specific upregulation of adhesion molecule and chemoattraction, or the initiation of proliferation and differentiation of inflammatory cell progenitors derived from the bone marrow. In this study, we demonstrate, in two systems of eosinophilic-basophilic lineage-committed granulocytes of relative immaturity, that eosinophilic differentiation in vivo implies the induction of a distinct adhesion phenotype, characterized by the upregulation of beta(7) integrin and downregulation of beta(1) and alpha(5) integrins. Moreover, the eosinophilic differentiation induced an upregulation of complement receptor type 1 and type 3, and the expression was further enhanced upon a short-course in vitro activation with ionomycin. These data indicate a sequential alteration of disparate members of the integrin family during eosinophilic-basophilic differentiation, which may attribute to specific adhesion requirements at distinct stages of cell maturation.
Antigens, CD↗
Selective upregulation of a functional beta7 integrin on differentiating eosinophils.
BACKGROUND: The sequence of adhesion-molecule expression during eosinophil differentiation remains unclear. METHODS: We analyzed the surface expression of alpha4, beta1, and beta7 integrins and compared it to established myeloid developmental markers, using the eosinophilic cell line HL-60 clone 15, as well as cord and peripheral blood differentiation assays. RESULTS: Cells induced to eosinophil differentiation by treatment with butyric acid, IL-5, and GM-CSF showed a significant upregulation of beta7 integrin expression coincident with a marked upregulation of CD35 and attenuation of CD33 and beta1 integrin expression. In addition, adhesion of induced HL-60 clone 15 cells to fibronectin was attenuated by a beta7 integrin antibody. CONCLUSIONS: Our data show that protein synthesis-dependent upregulation of the functional beta7 integrin occurs under conditions when beta4 and beta1 integrins are fully expressed, indicating a sequential appearance of specific adhesion molecules on differentiating eosinophil progenitors.
Antigens, CD↗
Systemic aspects of allergic disease: bone marrow responses.
In patients with allergic diseases, allergen provocation can activate a systemic response that provokes inflammatory cell production by the bone marrow. After release and differentiation of progenitor cells, eosinophils, basophils, and mast cells are typically recruited to tissues in atopic individuals. An understanding at the molecular level of the signaling process that leads to these systemic responses between the target organ, especially the airways, and the bone marrow may open up new avenues of therapy for allergic inflammatory disease. Studies that support the critical involvement of the bone marrow in the development of eosinophilic inflammation of the airways point out the systemic nature of these conditions and their potential for biologic intervention. Hemopoietic events that originate in the bone marrow are potential targets of long-term therapy for rhinitis and asthma. For example, the "beneficial" systemic activity of cortico-steroids through modulation of hemopoietic mechanisms and inflammatory cell recruitment to the airways is essential for the optimal treatment of both upper and lower airway inflammation.
Animals↗
The effects of inhaled budesonide on circulating eosinophil progenitors and their expression of cytokines after allergen challenge in subjects with atopic asthma.
Allergen inhalation by dual responder subjects with atopic asthma is associated with an increase in circulating eosinophil/basophil colony-forming units (Eo/B CFU) and granulocyte-macrophage colony- stimulating factor (GM-CSF) immunolocalization in Eo/B colony cells grown in vitro. The current study examined the effect of the inhaled corticosteroid, budesonide, on the number of allergen- induced circulating eosinophils and Eo/B CFU, and immunolocalization of GM-CSF and interleukin-5 (IL-5) in Eo/B colony cells grown in vitro. Sixteen subjects with mild atopic asthma were treated for either 7 or 8 d with 200 microg inhaled budesonide or placebo twice a day. Peripheral blood was collected before and 24 h after allergen inhalation challenge and nonadherent mononuclear cells (NAMC) were grown in methylcellulose culture. Eo/B CFU were enumerated after 14 d in culture, and prepared on slides for immunocytochemistry. Budesonide attenuated the allergen-induced increase in circulating eosinophils (4.0 +/- 0.4 x 10(5)/ml versus 6.5 +/- 0.7 x 10(5)/ml, p = 0.0001), circulating Eo/B CFU (12.4 +/- 2.3/10(6) NAMC versus 18.8 +/- 4.6/10(6) NAMC, p = 0.05), and immunolocalization of GM-CSF in Eo/B colony cells (11.8 +/- 1.9% positive versus 18.0 +/- 2.2%, p = 0.01) but not immunolocalization of IL-5 (7.9 +/- 1.4% versus 4.5 +/- 0.6%, p > 0.05). Inhaled budesonide attenuated the number of allergen-induced circulating eosinophils and their progenitors grown in the presence of GM-CSF, which may partially be a result of regulating eosinophil progenitor expression of the autocrine growth factor GM-CSF.
Administration, Inhalation↗
Differentiation of human eosinophils. Role in allergic inflammation.
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Bone Marrow Cells↗
Reduced expression of hemopoietic cytokine receptors on cord blood progenitor cells in neonates at risk for atopy.
BACKGROUND: Recent findings point to an association between allergic asthma in adults and increased responsiveness of myeloid progenitor cells to certain hemopoietic growth factors. However, it is not clear at what age these changes in progenitor cells first become manifest, although increasing evidence suggests that the allergic phenotype may begin to emerge in very early life. OBJECTIVE: We sought to compare expression of hemopoietic cytokine receptors on CD34(+) progenitor cells in cord blood from normal infants ("low risk" for subsequent atopy) and infants with at least one atopic first degree relative ("at risk" for subsequent atopy). METHODS: Cord blood was obtained from 21 neonates. Nonadherent mononuclear cells were stained with mAbs directed against CD45, CD34, and the alpha-chains of the GM-CSF, IL-3, and IL-5 receptors and analyzed by flow cytometry. RESULTS: No differences in absolute CD34(+) numbers were observed between the 2 groups. However, expression of GM-CSF receptor on CD34(+) cells was reduced in the "at-risk" compared with the "low- risk" group (P =.021), although no significant differences were noted between the 2 groups with respect to IL-3 and IL-5 receptor expression. CONCLUSION: The functional sequelae of reduced GM-CSF receptor expression on CD34(+) cells remain to be determined. Nonetheless, these findings show an association between genetic risk for atopy and changes in the expression of hemopoietic cytokine receptors on cord blood progenitor cells and support the notion that the allergic phenotype may begin to evolve in the perinatal period.
Adult↗
An inhaled corticosteroid, budesonide, reduces baseline but not allergen-induced increases in bone marrow inflammatory cell progenitors in asthmatic subjects.
We have previously shown that allergen inhalation by asthmatics is associated with increases in bone marrow eosinophil/basophil colony-forming cells (Eo/B-CFU), and increases in CD34(+) hemopoietic progenitors expressing the alpha-subunit of the IL-5 receptor (IL-5Ralpha). This study investigated the effect of inhaled corticosteroid on baseline numbers and allergen-induced increases in these parameters. Nine subjects with mild, stable asthma inhaled budesonide (400 microgram/d) for 8 d in a placebo-controlled, double-blind, randomized crossover study. On Day 7, subjects inhaled allergen, with bone marrow sampling before and 24 h after challenge. Budesonide inhalation significantly attenuated the allergen-induced early and late asthmatic responses, degree of increase in sputum and blood eosinophils, as well as the baseline numbers of total bone marrow CD34(+) cells (p < 0.05), CD34(+)IL-3Ralpha+ cells (p < 0.01) and IL-5-responsive Eo/B-CFU (p < 0.05). Allergen inhalation significantly increased Eo/B-CFU grown in the presence of IL-3, GM-CSF, or IL-5 alone (p < 0.05) and in combination (p < 0.01), as well as the number of CD34(+)IL-5Ralpha+ cells (p < 0.01). However, these increases in Eo/B-CFU and CD34(+)IL-5Ralpha+ cells were not affected by budesonide treatment. These data demonstrate that short-term inhaled budesonide treatment has a systemic effect in inhibiting the turnover of a subpopulation of bone-marrow-derived progenitors, but that inhalation of allergen overcomes this inhibitory effect.
Administration, Inhalation↗
Hemopoietic mechanisms in allergic airway inflammation.
The bone marrow actively participates in the production of IgER-positive inflammatory cells (eosinophils, basophils and mast cells), which are typically recruited to tissues in atopic individuals. Understanding the signalling between the tissue and the bone marrow at the molecular level may well open up new avenues of therapy for allergic inflammation.
Asthma↗
Allergen-induced increases in IL-5 receptor alpha-subunit expression on bone marrow-derived CD34+ cells from asthmatic subjects. A novel marker of progenitor cell commitment towards eosinophilic differentiation.
We have proposed previously that hemopoietic myeloid progenitors contribute to the ongoing recruitment of proinflammatory cells, namely eosinophils, to sites of allergen challenge in allergic diseases such as asthma. In this study, we investigated the involvement of bone marrow-derived progenitors in the development of allergen-induced pulmonary inflammation in mild asthmatic subjects. By flow cytometry, we enumerated the level of expression of CD34, a hemopoietic progenitor cell marker, on bone marrow aspirates taken before and 24 h after allergen challenge. In addition, the coexpression of the alpha-subunits of IL-3 receptor (IL-3R) and IL-5 receptor (IL-5R) on CD34+ cells was investigated. After allergen-challenge, although no significant change in total BM CD34+ cell numbers was observed, a significant increase in the proportion of CD34+ cells expressing IL-5R alpha, but not IL-3R alpha, was detected in the 24-h post-allergen, compared with the pre-allergen bone marrow. This was associated with a significant blood and sputum eosinophilia and increased methacholine airway responsiveness, 24 h post-allergen. Using simultaneous in situ hybridization and immunocytochemistry, we colocalized the expression of messenger RNA for membrane-bound IL-5R alpha to CD34+ cells. In summary, our data suggest that increased expression of IL-5R alpha on CD34+ cells favors eosinophilopoiesis and may thus contribute to the subsequent development of blood and tissue eosinophilia, a hallmark of allergic inflammation.
Adult↗
Bone marrow contribution to eosinophilic inflammation.
Allergen-induced bone marrow responses are observable in human allergic asthmatics, involving specific increases in eosinophil-basophil progenitors (Eo/B-CFU), measured either by hemopoietic assays or by flow cytometric analyses of CD34-positive, IL-3R alpha-positive, and/or IL-5-responsive cell populations. The results are consistent with the upregulation of an IL-5-sensitive population of progenitors in allergen-induced late phase asthmatic responses. Studies in vitro on the phenotype of developing eosinophils and basophils suggest that the early acquisition of IL-5R alpha, as well as the capacity to produce cytokines such as GM-CSF and IL-5, are features of the differentiation process. These observations are consistent with findings in animal models, indicating that allergen-induced increases in bone marrow progenitor formation depend on hemopoietic factor(s) released post-allergen. The possibility that there is constitutive marrow upregulation of eosinophilopoiesis in allergic airways disease is also an area for future investigation.
Allergens↗
The role of the bone marrow in allergy and asthma.
The above studies have begun to address the fundamental question of the mechanisms of bone marrow involvement and response to allergen challenge in allergic asthmatics. Further studies in this area should complement our investigations in human asthma--which suggest that a particular bias toward differentiation of Eo-Baso progenitors characterizes the atopic state--as well as our findings in the dog model of allergen-induced airway hyperresponsiveness, which indicate that the bone marrow responds to inhalation of allergen or corticosteroids. Taken in the context of previous indications that IgE and bronchial responsiveness may both be transferrable through bone marrow transplantation (109), these findings indicate a physiologic role for the bone marrow in allergic inflammation. Likewise, these concepts provide a basis for making certain predictions regarding management and novel therapeutic interventions in atopy and asthma.
Animals↗
Increased levels of CD34+ hemopoietic progenitor cells in atopic subjects.
We investigated the contribution of hemopoietic progenitors to the accumulation of inflammatory cells in allergic airways disease. Using a multiparameter flow-cytometric method, the detection of peripheral blood (PB) and bone marrow (BM) cells expressing CD34, a progenitor cell marker, was explored. True CD34+ blast cells were detected as a discrete cluster exhibiting low intensity CD45 expression, low granularity, and low to intermediate cell size. A significantly greater number of CD34+ cells was detected in the PB of atopic individuals (1,438 +/- 347/10(6) nonadherent mononuclear cells [NAMNC], n = 19) compared with nonatopics (236 +/- 77/10(6) NAMNC, n = 13; P = 0.006). Similarly, in BM samples, a significantly greater number of CD34+ cells was detected in atopic (17,537 +/- 4,986/10(6) NAMNC, n = 7) compared with nonatopic subjects (6,422 +/- 1,853/10(6) NAMNC, n = 13, P = 0.02). Greater numbers of total colony-forming units (CFU) (granulocyte/macrophage [GM] and Eo/Baso) were present in cultures of PB NAMNC from atopics (24 +/- 5 CFU/10(6) NAMNC) cultured with recombinant human interleukin 5 (rhIL-5) (1 ng/ml) compared with nonatopics (5 +/- 2 CFU/10(6) NAMNC; P = 0.003). Analyses of colony subtypes showed significantly greater numbers of IL-5-responsive Eo/Baso-CFU in cultures from atopics (15 +/- 2 CFU/10(6) NAMNC) compared with nonatopics (5 +/- 2 CFU/10(6) NAMNC; P = 0.011). In contrast, no significant differences in colony counts were found between the two subject groups in cultures with rhIL-3 (1 ng/ml) or rhGM-CSF (10 ng/ml). A positive correlation was observed between PB CD34+ cell numbers and total CFU in cultures with rhIL-5 (r = 0.43, n = 32, P = 0.01) and rhGM-CSF (r = 0.45, n = 32, P = 0.009). Purging BM NAMNC with an anti-CD34 monoclonal antibody completely abrogated in vitro colony growth, supporting the view that a subset of CD34+ cells represents the relevant population of progenitors growing in culture. These data indicate that flow cytometric estimation of CD34+ cells is predictive of the colony-forming capacity of the sample and may be a useful alternative tool to clonogenic assays for enumerating progenitors. In addition, raised levels of CD34+ cells and IL-5-responsive Eo/Baso-CFU in atopics, including patients with atopic asthma, indicate a role for progenitors in allergic airways disease.
Antibodies, Monoclonal↗
Interleukin-8 is a chemo-attractant for eosinophils purified from subjects with a blood eosinophilia but not from normal healthy subjects.
Interleukin-8 (IL-8), a pro-inflammatory cytokine with potent neutrophil chemotactic activity, was studied for its effect on eosinophil migration responses, in vitro. Normal density eosinophils were isolated from healthy, non-atopic subjects (<0.35 x 10(9) eosinophils/l) and individuals with various diseases associated with a blood eosinophilia (range 0.56 x 10(9)-12.2 x 10(9) eosinophils/l). IL-8 produced a dose-dependent migrational response for eosinophils from subjects with an eosinophilia, optimal at 10(-8) M (P < 0.01) and the major component of the migrational response was chemokinesis. On a molar basis, IL-8 (EC50 approximately 10(10) M) was 100-fold more potent than platelet activating factor (PAF), although a comparison of the migrational responses showed that at optimal concentrations IL-8 (10(-8) M) produced only 30% maximal responses stimulated by PAF (10(-6) M). In contrast, IL-8 tested over a wide concentration range had a negligible effect on eosinophils from normal subjects. A direct correlation between the total blood eosinophil counts for all subjects and the absolute magnitude of the migrational response to IL-8 (r = 0.727, P < 0.01 at 10(-8) M), PAF (r = 0.551, P < 0.03 at 10(-6) M) and N-formyl-methionyl-leucyl-phenylalanine (fMLP) (r = 0.689, P < 0.02 at 10(-8) M), suggested that heightened eosinophil migrational responses to inflammatory mediators may arise as a consequence of in vivo priming mechanism(s) associated with the development of an eosinophilia. In this regard, eosinophils derived from human cord blood mononuclear cells cultured in the presence of eosinophilopoietic cytokines IL-3 and IL-5, produced migrational responses to IL-8 and PAF, that were comparable with that of eosinophils from eosinophilic subjects. Furthermore, incubation of eosinophils from normal donors with IL-5 (optimal concentration 10(-9) M), significantly enhanced the subsequent migrational responses to both IL-8 (10(-8) M, P < 0.01) and PAF (10(-8) M, P < 0.05). Therefore, the increased responsiveness of eosinophils from eosinophilic subjects may reflect in vivo priming by IL-5 and this phenomenon may contribute partly to the mechanism(s) by which eosinophils preferentially accumulate at sites of allergic inflammation.
Cells, Cultured↗
Modulation of human eosinophil chemotaxis and adhesion by anti-allergic drugs in vitro.
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Cell Adhesion↗
Interleukin-5 selectively enhances the chemotactic response of eosinophils obtained from normal but not eosinophilic subjects.
We have attempted to determine whether interleukin-5 (IL-5), a cytokine that selectively affects eosinophil (as opposed to neutrophil) differentiation and activation, also modulates eosinophil migrational responses. Using a modified Boyden chemotaxis assay, IL-5, IL-3, and granulocyte-macrophage colony-stimulating factor (GM-CSF) gave a weak locomotory response for eosinophils from normal nonatopic subjects (optimal at 10(-11), 10(-8), and 10(-9) mol/L, respectively), but not for eosinophils from subjects with an eosinophilia associated with asthma and/or allergic rhinitis. In contrast, IL-5 and IL-3 had no effect on neutrophils, while GM-CSF was chemotactic for neutrophils over a limited concentration range, optimal at 10(-8) mol/L. When eosinophils from normal subjects were incubated with IL-5 (10(-9) mol/L), the locomotory response to platelet-activating factor (PAF; 10(-8) mol/L, P less than .05), leukotriene B4 (LTB4; 10(-6) mol/L, P less than .01), and N-formyl-methionyl-leucyl-phenylalanine (FMLP; 10(-8) mol/L, P less than .01) was significantly enhanced. The percentage enhancement of eosinophil locomotion by IL-5 was greater for eosinophils from normal as compared with subjects with an eosinophilia associated with asthma (P less than .05 for PAF and LTB4; P less than .01 for FMLP). Preincubation of eosinophils from normal subjects with IL-5 (10(-9) mol/L) attenuated the subsequent locomotory response to IL-5 (10(-12) and 10(-11) mol/L, P less than .05). Therefore, the observed refractoriness of eosinophils from eosinophilic subjects to both directional migratory and priming effects of IL-5 in vitro, may reflect a deactivation process resulting from prior exposure in vivo. The selective priming of eosinophil but not neutrophil locomotion by IL-5 suggests that this cytokine may play a significant role in the preferential accumulation of eosinophils at sites of allergic inflammation.
Asthma↗
Identification on receptors for leukotriene B4 expressed on guinea-pig peritoneal eosinophils.
We have recently reported that guinea-pig eosinophil chemotactic factor of anaphylaxis (ECF-A), an activity present in diffusates from antigen-challenged sensitized lung, is largely accounted for by leukotriene B4 (LTB4) and to a lesser extent 8(S)15(S)-dihydroxy 5,9,11,13 (Z,E,Z,E) eicosatetraenoic acid. We characterized cell surface receptors for LTB4 on guinea-pig eosinophils in order to demonstrate an association between receptor occupancy and eosinophiliotactic activity of guinea-pig ECF-A. Equilibrium binding studies showed that peritoneal eosinophils bound [3H]LTB4 in a cell concentration and time-dependent fashion. The binding was saturable and specific for LTB4 as other eosinophil chemoattractants, i.e. platelet-activating factor (PAF) and 8(S)15(S)-diHETE, were unable to displace significant amounts of [3H]LTB4. In addition the binding was readily reversed by the LTB4 receptor antagonist LY 255283 (Ki 4.30 nM). Scatchard plot analysis revealed two discrete populations of binding sites, high affinity (Kd1 = 0.30 nM; Bmax = 900 sites/cell) and low-affinity sites (Kd2 = 140 nM; Bmax = 60,000 sites/cell). The major migratory component of LTB4-stimulated eosinophil locomotion was chemotaxis, optimal at 1 x 10(-7) M (P < 0.01) with EC50 value of 3 x 10(-9) M. A comparison of the profile of arachidonic acid metabolism by RP-HPLC analysis showed that following stimulation with calcium ionophore (A23187) guinea-pig eosinophils preferentially synthesized LTB4 (10 ng/10(6) cells) while in contrast human eosinophils synthesized LTC4 (10 ng/10(6) cells). Therefore our data show that guinea-pig eosinophils express both high- and low-affinity receptors for LTB4 and that the chemotactic response to this mediator may be mediated by ligation of the high-affinity binding site. Furthermore guinea-pig peritoneal eosinophils can synthesize LTB4, a mediator which constitutes > 60% of guinea-pig ECF-A.
Animals↗