An inhaled corticosteroid, budesonide, reduces baseline but not allergen-induced increases in bone marrow inflammatory cell progenitors in asthmatic subjects

May a different kinetic mode explain the high efficacy/safety profile of inhaled budesonide?

The claimed functional basis for ICSs in asthma and COPD is airway selectivity, attained by inhaling a potent, lipophilic compound with long local dissolution/absorption time. The development has been empirically based, resulting in five widely used ICSs. Among them, budesonide (BUD) deviates by being less lipophilic, leading to a more rapid systemic uptake with plasma peaks with some systemic anti-inflammatory activity. By this, BUD fits less well into the current pharmacological dogma of optimal ICS profile. In this review we compared the physicochemical, pharmacological and clinical properties of BUD, fluticasone propionate (FP) and fluticasone furoate (FF), representing different levels of lipophilicity, airway and systemic kinetics, focusing on their long-acting β2-agonist (LABA) combinations, in line with current GINA and GOLD recommendations. We are aware of the differences between formoterol (FORM) and the not rapid acting LABAs such as e.g. salmeterol and vilanterol but our comparisons are based on currently available combination products. A beclomethasone dipropionate (BDP)/FORM combination is also commented upon. Based on clinical comparisons in asthma and COPD, we conclude that the BUD/formoterol (BUD/FORM) combination is as effective and safe as the FP and FF combinations, and is in some cases even better as it can be used as "maintenance plus reliever therapy" (MART) in asthma and as maintenance in COPD. This is difficult to explain by current views of required ICS's/LABAs pharmacokinetic profiles. We propose that BUD achieves its efficacy by a combination of airway and systemic activity. The airway activity is dominating. The systemic activity contributes by plasma peaks, which are high enough for supportive anti-inflammatory actions at the blood and bone marrow levels but not sufficiently long to trigger a similar level of systemic adverse effects. This may be due to BUD's capacity to exploit a systemic differentiation mechanism as programmed for cortisol's various actions. This differentiation prospect can be reached only for an ICS with short plasma half-life. Here we present an alternative mode for an ICS to reach combined efficacy and safety, based on a poorly investigated and exploited physiological mechanism. A preference of this mode is broader versatility, due to that its straighter dose-response should allow a better adaptation to disease fluctuations, and that its rapid activity enables use as "anti-inflammatory reliever".

Corticosteroid resistance in asthma: Cellular and molecular mechanisms

Inhaled glucocorticoids (GCs) are drugs widely used as treatment for asthma patients. They prevent the recruitment and activation of lung immune and inflammatory cells and, moreover, have profound effects on airway structural cells to reverse the effects of disease on airway inflammation. GCs bind to a specific receptor, the glucocorticoid receptor (GR), which is a member of the nuclear receptor superfamily and modulates pro- and anti-inflammatory gene transcription through a number of distinct and complementary mechanisms. Targets genes include many pro-inflammatory mediators such as chemokines, cytokines, growth factors and their receptors. Inhaled GCs are very effective for most asthma patients with little, if any, systemic side effects depending upon the dose. However, some patients show poor asthma control even after the administration of high doses of topical or even systemic GCs. Several mechanisms relating to inflammation have been considered to be responsible for the onset of the relative GC resistance observed in these patients. In these patients, the side-effect profile of GCs prevent continued use of high doses and new drugs are needed. Targeting the defective pathways associated with GC function in these patients may also reactivate GC responsiveness.

Modulating the Human Basophil Phenotype During Its Development and Maturation: Basophils Derived from In Vitro Cultures of CD34+ Progenitor Cells

Historically, the human basophil that is studied experimentally comes from peripheral blood. But there is evidence that only a short portion of the basophil life cycle related to IgE-mediated function occurs in the blood. The same evidence suggests that IgE-mediated functionality is present for 5-7 days in the bone marrow (or other tissues) during which the cell modulates its phenotype according to local conditions. It is suggested that to properly understand the nature of basophil behavior, a better understanding of its biology during maturation would be helpful. For example, one highly suggestive line of evidence for the relevance of understanding the maturation period is related to the change in basophil phenotype that occurs during treatment of patients with omalizumab. During this treatment, the intrinsic reactivity or sensitivity of the basophils is significantly increased despite, or perhaps because of, the dramatic reduction in FcεRI expression that accompanies this treatment. One of the critical signaling enzymes to increase expression selectively in basophils during treatment is SYK, which is one of the earliest signaling tyrosine kinases involved in translating the aggregation of FcεRI into secretion from the cell. Treatment with omalizumab increases SYK expression, and this observation focuses some attention of how SYK expression is regulated. It is possible that the key regulation occurs during maturation of the basophil. Regardless of the mechanisms operative in this particular treatment, understanding the process of maturation and the extrinsic factors that influence it may lead to better understanding of disease processes. Therefore, this chapter will discuss and present techniques to work with maturing human basophils.

Route of Administration Affects Corticosteroid Sensitivity of a Combined Ovalbumin and Lipopolysaccharide Model of Asthma Exacerbation in Guinea Pigs

Lipopolysaccharide (LPS) contributes to asthma exacerbations and development of inhaled corticosteroid insensitivity. Complete resistance to systemic corticosteroids is rare, and most patients lie on a continuum of steroid responsiveness. This study aimed to examine the sensitivity of combined ovalbumin- (Ova) and LPS-induced functional and inflammatory responses to inhaled and systemic corticosteroid in conscious guinea pigs to test the hypothesis that the route of administration affects sensitivity. Guinea pigs were sensitized to Ova and challenged with inhaled Ova alone or combined with LPS. Airway function was determined by measuring specific airway conductance via whole-body plethysmography. Airway hyper-responsiveness to histamine was determined before and 24 hours post-Ova challenge. Airway inflammation and underlying mechanisms were determined from bronchoalveolar lavage cell counts and lung tissue cytokines. Vehicle or dexamethasone was administered by once-daily i.p. injection (5, 10, or 20 mg/kg) or twice-daily inhalation (4 or 20 mg/ml) for 6 days before Ova challenge or Ova with LPS. LPS exacerbated Ova-induced responses, elongating early asthmatic responses (EAR), prolonging histamine bronchoconstriction, and further elevating airway inflammation. Intraperitoneal dexamethasone (20 mg/kg) significantly reduced the elongated EAR and airway inflammation but not the increased bronchoconstriction to histamine. In contrast, inhaled dexamethasone (20 mg/ml), which inhibited responses to Ova alone, did not significantly reduce functional and inflammatory responses to combined Ova and LPS. Combined Ova and LPS–induced functional and inflammatory responses are insensitive to inhaled, but they are only partially sensitive to systemic, dexamethasone. This finding suggests that the route of corticosteroid administration may be important in determining corticosteroid sensitivity of asthmatic responses.

Toll-like receptor-induced expression of epithelial cytokine receptors on haemopoietic progenitors is altered in allergic asthma

BACKGROUND

Haemopoietic progenitor cells (HPC) migrate to sites of allergic inflammation where, upon stimulation with epithelial cytokines, they produce Th2 cytokines and differentiate into mature eosinophils and basophils. They also express Toll-like receptors (TLR) involved in antimicrobial responses.

OBJECTIVE

The objective of this study was to compare TLR expression on peripheral blood HPC and TLR-induced responses, in particular changes in epithelial cytokine receptors, in healthy and asthmatic subjects at baseline and following allergen challenge.

METHODS

Ten healthy and 11 allergic asthmatic subjects were studied. HPC-enriched cell populations were stimulated with TLR-2, TLR-4 or TLR-9 ligands. TLR expression by circulating HPC and interleukin (IL)-25 (IL-17RB), IL-33 (ST2) and thymic stromal lymphopoietin receptor (TSLPR) expression after TLR ligation were examined by flow cytometry at baseline and, in asthmatics, following allergen challenge. The effects of dexamethasone (Dex) on TLR-induced responses were also assessed.

RESULTS

Asthmatics had significantly lower circulating HPC expressing TLR-2 and TLR-9 with a similar trend for TLR-4. TLR-4 stimulation of HPC yielded higher numbers of TSLPR+ cells in asthmatics compared with healthy subjects. A similar trend was seen for TLR-9 ligation, an effect further augmented by allergen inhalation. Allergen challenge also enhanced TLR-induced ST2 expression on HPC. Treatment with Dex in vitro increased TLR-4-induced TSLPR expression but had no effect on other epithelial cytokine receptors.

CONCLUSIONS AND CLINICAL RELEVANCE

These data demonstrate an interaction between allergen and TLR ligand exposure in asthmatics. Allergen inhalation augments the TLR-induced inflammatory response by HPC, possibly leading to increased "in situ haemopoiesis" through up-regulation of TSLPR. These findings show that HPC may be a part of the pro-inflammatory cascade in pathogen-induced asthma exacerbation through their increased responsiveness to TLR stimulation.

Functional interleukin-33 receptors are expressed in early progenitor stages of allergy-related granulocytes

Interleukin-33 (IL-33) induces T helper type 2 (Th2) cytokine production and eosinophilia independently of acquired immunity, leading to innate immunity-mediated allergic inflammation. Allergy-related innate myeloid cells such as eosinophils, basophils and mast cells express the IL-33 receptor (IL-33R), but it is still unknown how IL-33 regulates allergic inflammation involving these cells and their progenitors. Here, we revealed that the functional IL-33R was expressed on eosinophil progenitors (EoPs), basophil progenitors (BaPs) and mast cell progenitors (MCPs). In the presence of IL-33, these progenitors did not expand, but produced a high amount of Th2 and pro-inflammatory cytokines such as IL-9, IL-13, IL-1β and IL-6. The amount of cytokines produced by these progenitors was greater than that by mature cells. In vivo, IL-33 stimulated the expansion of EoPs, but it was dependent upon the elevated serum IL-5 that is presumably derived from type 2 innate lymphoid cells that express functional IL-33R. These data collectively suggest that EoPs, BaPs and MCPs are not only the sources of allergy-related granulocytes, but can also be sources of allergy-related cytokines in IL-33-induced inflammation. Because such progenitors can differentiate into mature granulocytes at the site of inflammation, they are potential therapeutic targets in IL-33-related allergic diseases.

CSL311, a novel, potent, therapeutic monoclonal antibody for the treatment of diseases mediated by the common β chain of the IL-3, GM-CSF and IL-5 receptors

The β common-signaling cytokines interleukin (IL)-3, granulocyte-macrophage colony stimulating factor (GM-CSF) and IL-5 stimulate pro-inflammatory activities of haematopoietic cells via a receptor complex incorporating cytokine-specific α and shared β common (βc, CD131) receptor. Evidence from animal models and recent clinical trials demonstrate that these cytokines are critical mediators of the pathogenesis of inflammatory airway disease such as asthma. However, no therapeutic agents, other than steroids, that specifically and effectively target inflammation mediated by all 3 of these cytokines exist. We employed phage display technology to identify and optimize a novel, human monoclonal antibody (CSL311) that binds to a unique epitope that is specific to the cytokine-binding site of the human βc receptor. The binding epitope of CSL311 on the βc receptor was defined by X-ray crystallography and site-directed mutagenesis. CSL311 has picomolar binding affinity for the human βc receptor, and at therapeutic concentrations is a highly potent antagonist of the combined activities of IL-3, GM-CSF and IL-5 on primary eosinophil survival in vitro. Importantly, CSL311 inhibited the survival of inflammatory cells present in induced sputum from human allergic asthmatic subjects undergoing allergen bronchoprovocation. Due to its high potency and ability to simultaneously suppress the activity of all 3 β common cytokines, CSL311 may provide a new strategy for the treatment of chronic inflammatory diseases where the human βc receptor is central to pathogenesis. The coordinates for the βc/CSL311 Fab complex structure have been deposited with the RCSB Protein Data Bank (PDB 5DWU).

Allergen-induced airway responses

Environmental allergens are an important cause of asthma and can contribute to loss of asthma control and exacerbations. Allergen inhalation challenge has been a useful clinical model to examine the mechanisms of allergen-induced airway responses and inflammation. Allergen bronchoconstrictor responses are the early response, which reaches a maximum within 30 min and resolves by 1-3 h, and late responses, when bronchoconstriction recurs after 3-4 h and reaches a maximum over 6-12 h. Late responses are followed by an increase in airway hyperresponsiveness. These responses occur when IgE on mast cells is cross-linked by an allergen, causing degranulation and the release of histamine, neutral proteases and chemotactic factors, and the production of newly formed mediators, such as cysteinyl leukotrienes and prostaglandin D2. Allergen-induced airway inflammation consists of an increase in airway eosinophils, basophils and, less consistently, neutrophils. These responses are mediated by the trafficking and activation of myeloid dendritic cells into the airways, probably as a result of the release of epithelial cell-derived thymic stromal lymphopoietin, and the release of pro-inflammatory cytokines from type 2 helper T-cells. Allergen inhalation challenge has also been a widely used model to study potential new therapies for asthma and has an excellent negative predictive value for this purpose.

In situ hematopoiesis: a regulator of TH2 cytokine-mediated immunity and inflammation at mucosal surfaces

Hematopoiesis refers to the development of blood cells in the body through the differentiation of pluripotent stem cells. Although hematopoiesis is a multifocal process during embryonic development, under homeostatic conditions it occurs exclusively within the bone marrow. There, a limited number of hematopoietic stem cells differentiate into a rapidly proliferating population of lineage-restricted progenitors that serve to replenish circulating blood cells. However, emerging reports now suggest that under inflammatory conditions, alterations in hematopoiesis that occur outside of the bone marrow appear to constitute a conserved mechanism of innate immunity. Moreover, recent reports have identified previously unappreciated pathways that regulate the egress of hematopoietic progenitor cells from the bone marrow, alter their activation status, and skew their developmental potential. These studies suggest that progenitor cells contribute to inflammatory response by undergoing in situ hematopoiesis (ISH). In this review, we highlight the differences between homeostatic hematopoiesis, which occurs in the bone marrow, and ISH, which occurs at mucosal surfaces. Further, we highlight factors produced at local sites of inflammation that regulate hematopoietic progenitor cell responses and the development of TH2 cytokine-mediated inflammation. Finally, we discuss the therapeutic potential of targeting ISH in preventing the development of inflammation at mucosal sites.

Human mast cell and basophil/eosinophil progenitors

Mast cell, basophil, and eosinophil lineages all derive from CD34(+) hemopoietic stem cells; however, mast cells are derived from a distinct, nonmyeloid progenitor, while eosinophils and basophils share a common myeloid progenitor. These progenitors likely evolved from an ancestral leukocyte population involved in innate immunity and currently play a central role in the pathology of allergic disease. Advances in isolation and analysis of mast cell and basophil/eosinophil progenitor populations have been critical to understanding lineage commitment, differentiation, function, and transcriptional regulation of these cells and have provided a way of monitoring the effect of novel investigational therapies on these cell populations in samples of blood, bone marrow, and airway secretions.

Acinar effect of inhaled steroids evidenced by exhaled nitric oxide

BACKGROUND

The effects of inhaled corticosteroids (ICSs) on distal lung inflammation, as assessed by alveolar nitric oxide concentration (C(A)NO), are a matter of debate. Recently, a theoretic study suggested that acinar airway obstruction that is relieved by ICS treatment and associated with a decrease in fraction of exhaled nitric oxide (FeNO) concentration might, paradoxically, increase C(A)NO. This increase could be a hallmark effect of ICSs at the acinar level.

OBJECTIVE

In the light of this new hypothesis, we studied changes in C(A)NO and FeNO after administration of ICSs.

METHODS

C(A)NO and FeNO were measured before and after ICS treatment of 38 steroid-naive patients with uncontrolled asthma who showed clinical improvement after ICS therapy.

RESULTS

The average FeNO decreased from 78.3 to 28.9 ppb (P < .001); C(A)NO decreased from 7.7 to 4.3 ppb (P = .009). In 14 subjects (low-slope group), slope (= ΔC(A)NO/ΔFeNO) values (Δ = post-ICS - pre-ICS value) were less than the 95% normal CI (average ΔFeNO = -32.7 ppb and average ΔC(A)NO= +2.9 ppb). In this group, baseline C(A)NO was abnormally low when FeNO was taken into account. In 11 subjects (the high-slope group), the slope was above the normal interval (average ΔFeNO = -42.5 ppb and average ΔC(A)NO = -14.7 ppb).

CONCLUSION

Opposite patterns (one that was predicted) can indicate peripheral actions of ICSs; this difference might account for conflicting data reported from studies using C(A)NO to determine the peripheral action of ICSs. We show that a low C(A)NO does not preclude distal inflammation.

Hemopoietic progenitors: the role of eosinophil/basophil progenitors in allergic airway inflammation

Progenitor cells play important roles in the physiology and homeostasis of the overall hemopoietic system. The majority of hemopoietic activity takes place in the bone marrow, under the influence of resident marrow stromal cells, accessory cells, and/or their products. This constitutes the complex network of the hemopoietic inductive microenvironment, which is crucial for providing signals necessary for the maintenance of populations of progenitors at varying stages of lineage commitment. Accumulation of eosinophils and basophils in tissues is characteristic of allergic inflammation. A large body of evidence now exists which confirms that these tissue inflammatory events are coincident with relevant changes in progenitors; it has thus been hypothesized that the observed changes in mature cell numbers occur directly or indirectly as a result of differentiation of lineage-committed eosinophil/basophil, and perhaps other, progenitor cells. Differentiation and maturation of hemopoietic cells have traditionally been thought to be restricted to the bone marrow microenvironment. More recently, evidence has accumulated to suggest that some hemopoietic cells present in allergic tissue may be recruited from the bone marrow, traffic through the peripheral circulation and into tissues to participate in the ongoing inflammatory process at these distal sites. The clinical administration of monotherapy with topical corticosteroids, oral cysteinyl leukotriene antagonists and cytokine antagonists such as antibodies to interleukin-5, suggest that suppression of hemopoietic contributions to allergic inflammation may be necessary for full control of allergic inflammation and disease manifestations. In addition to progenitors being targets of therapy, they may well determine how and whether allergic inflammation is generated in early life, thus serving as biomarkers of disease.

Haemopoietic processes in allergic disease: eosinophil/basophil development

Haemopoietic myeloid progenitors contribute to the ongoing recruitment of pro-inflammatory cells, such as eosinophils and basophils (Eo/B), to target tissue sites in allergic diseases. It is apparent that the development of allergic inflammation is critically dependent on the ability of the bone marrow to support the proliferation, differentiation and mobilization of haemopoietic progenitors. The haemopoietic inductive microenvironment in the bone marrow is crucial for providing signals necessary for maintenance of progenitor populations at varying stages of lineage commitment and permitting these cells to circulate in the bloodstream. Progenitors demonstrate responsiveness to specific cytokines, which varies with stage of differentiation. Pro-inflammatory signals, Th2 cytokines in particular, generated following allergen challenge, can impact on haemopoietic progenitor differentiation and mobilization, leading to accelerated Eo/B production. Allergen inhalation by allergic asthmatics induces a time-dependent change in cytokine levels within the bone marrow compartment, influencing differentiation of Eo/B progenitors, as evidenced by the relationship between increased bone marrow IL-5 levels and Eo/B production. It is proposed that inhaled allergen induces trafficking of IL-5-producing T lymphocytes to the bone marrow, further promoting eosinophilopoiesis through IL-5R signalling. In this manner, Th2 lymphocyte trafficking from the airway may regulate events occurring in the bone marrow. Negative regulators of Eo/B differentiation, including Th1 cytokines, may prove to be important for restoring homeostasis. Eo/B progenitors are also altered in cord blood of infants at risk of atopy and asthma, offering a potential biomarker for, and raising the possibility that Eo/B progenitors are directly involved in the development of allergic disease. For example, changes in the expression of haemopoietic cytokine receptors on cord blood progenitor cells are associated with maternal allergic sensitization, atopic risk and its development, suggesting that haemopoietic processes underlying the allergic phenotype may begin to evolve in the perinatal period.

Early timing of low-dose dexamethasone decreases inflammation in a murine model of eosinophilic airway disease

CONCLUSION

A very low dose of dexamethasone (DEX) was as equally as sufficient as a pharmacological dose to decrease eosinophil inflammation in airways and bone marrow. The timing of DEX treatment in relation to allergen challenge was strongly decisive for the outcome of the inflammatory response.

OBJECTIVES

We aimed to study compartmental allergic airway inflammatory responses to classic pharmacological and also extremely low physiological DEX dosage, given at different time points close to allergen challenge in a murine model.

MATERIALS AND METHODS

Ovalbumin-sensitized BALB/c-mice were exposed to intra-nasal ovalbumin. DEX was given i.p. as 1 microg/kg low-dose or 500 microg/kg pharmacological single-dose 2 h before, immediately before or 7 h after each of three challenges. Inflammatory cells were evaluated in bronchoalveolar lavage (BAL), lungs, nasal mucosa, and bone marrow.

RESULTS

Groups treated with low-dose DEX decreased eosinophilia in BAL to the same extent as the pharmacological dose, but only when administered before challenge. The most prominent decrease of eosinophils in BAL was seen in mice treated with the low dose 2 h before challenge. A similar response pattern as in BAL eosinophilia was detected in lung histopathology. DEX treatments had no obvious effects on inflammation in nasal mucosa.

Asthma progression to airway remodeling and bone marrow eosinophil responses in genetically distinct strains of mice

BACKGROUND

Patient factors that cause long-term airway remodeling are largely unidentified. This suggests that genetic differences may determine which asthmatic patients develop airway remodeling. A murine model with repeated allergen exposure leading to peribronchial fibrosis in complement factor 5 (C5)-deficient A/J mice has been used to study asthma progression. No studies have addressed the systemic effects of allergen sensitization or chronic allergen exposure on bone marrow eosinophilopoiesis in this mouse strain.

OBJECTIVE

To investigate bone marrow eosinophil responses during acute sensitization and chronic allergen exposure using genetically distinct mouse strains differing in persistent airway reactivity and remodeling.

METHODS

The C5-sufficient BALB/c and C5-deficient A/J mice were repetitively exposed to intranasal ovalbumin for 12 weeks. Subsequently, the mice were evaluated for airway eosinophilia, mucus-containing goblet cells, and peribronchial fibrosis. Both strains of mice were also acutely sensitized to ovalbumin. Bone marrow eosinophil progenitor cells and mature eosinophils were enumerated.

RESULTS

BALB/c and A/J mice have similar bone marrow responses after acute allergen exposure, with elevations in bone marrow eosinophil progenitor cell and eosinophil numbers. After chronic allergen exposure, only C5-deficient A/J mice that developed peribronchial fibrosis exhibited bone marrow eosinophilia. BALB/c mice lacked peribronchial fibrosis and extinguished accelerated eosinophil production after long-term allergen challenge.

CONCLUSIONS

Chronic airway remodeling after repeated allergen exposure in genetically different mice correlated with differences in long-term bone marrow eosinophilopoiesis. Preventing asthma from progressing to chronic airway remodeling with fibrosis may involve identifying genetically determined influences on bone marrow responses to chronic allergen exposure.

Eosinophil progenitors in allergy and asthma - do they matter?

Allergic inflammation is associated with marked infiltration of eosinophils in affected tissues. The eosinophil is believed to be a key effector cells in allergen induced asthma pathogenesis. However, the role of eosinophils in the clinical manifestation of asthma has recently been questioned, since therapies directed against eosinophil infiltration (i.e. anti-interleukin-5) failed to improve clinical symptoms such as airways hyper-responsiveness (AHR) in patients with asthma. Although eosinophils in peripheral blood and the airways were largely depleted after anti-IL-5 treatment, residual eosinophilia in lung tissue persisted, which permits speculation that the remaining eosinophils may be sufficient to drive the asthma symptomatology. Furthermore, recent findings suggest that primitive eosinophil progenitor cells traffic from the bone marrow to sites of inflammation in response to allergen exposure. These progenitors may then differentiate in situ and thus provide an ongoing supply of mature pro-inflammatory cells and secretory mediators that augment the inflammatory response. In the present article, we will review the evidence for these findings, and discuss the rationale for targeting hematopoiesis and their migration pathways in the treatment of allergic diseases. Furthermore, this review will highlight the hypothesis that both IL-5- and CCR3-mediated signaling pathways may need to be targeted in order to control the inflammation and AHR associated with asthma.

Recruitment of CD34+ progenitor cells into peripheral blood and asthma severity

BACKGROUND

Previous studies have suggested that the number of progenitor cells is elevated in the peripheral blood of asthmatic patients and that the number of progenitors correlate with the severity of the disease.

OBJECTIVE

To evaluate the number of leukocyte progenitor and eosinophil progenitor cells in the peripheral blood of patients with bronchial asthma in relation to disease severity.

METHODS

The study involved 51 patients with asthma (25 patients with a mild form and 26 with a severe form of the disease) and a group of 12 healthy controls. Using the flow cytometric method, leukocyte (CD34+ leukocytes) and eosinophil progenitors (CD34+CD125+) were detected in the peripheral blood of both asthmatic patients and healthy controls.

RESULTS

Patients with asthma had significantly more leukocyte progenitor cells (median, 0.06% vs 0.016%) and eosinophil progenitor cells (median, 0.046% vs 0.004%) compared with the controls. Patients with severe asthma had more leukocyte progenitor cells (0.12% vs 0.035%) and more eosinophil progenitor cells (0.102% vs 0.019%) than patients with mild asthma. The number of circulating leukocyte and eosinophil progenitor cells inversely correlated with the forced expiratory volume in 1 second percentage of predicted value (r = -0.4 and r = -0.35, respectively) and positively correlated (r = 0.63 and r = 0.65, respectively) with the dose of inhaled steroids used to control asthma.

CONCLUSION

These data suggest that the presence of leukocyte precursors and eosinophil progenitor cells in the peripheral blood of asthmatic patients may reflect ongoing airway inflammation.

In vitro effects of budesonide on eosinophil-basophil lineage commitment

IL-5 is the primary cytokine that stimulates the production and survival of eosinophils and basophils from progenitor cells. The inhaled glucocorticoid, budesonide, has been shown to exert a therapeutic effect via suppression of eosinophil/basophil progenitors in vivo. Since various steroids have exhibited the ability to enhance eosinophil/basophil progenitor differentiation, we examined the effects of budesonide in vitro. Bone marrow and cord blood samples were obtained and cultured in the presence of IL-5 alone or IL-5 plus budesonide. Eosinophil/basophil colony-forming units were enumerated from cultured nonadherent mononuclear cells and from purified CD34⁺ cells. CD34⁺ cells with and without budesonide were also examined for up-regulation of ERK1/2, MAPK and GATA-1 using real time-PCR.

RESULTS

i) up-regulation of eosinophil/basophil colony-forming units is due to the direct effects of budesonide on IL-5-stimulated progenitors; ii) GATA-1 is likely involved in the early amplification of eosinophil/basophil progenitor commitment leading to increased differentiation. A potential transcriptional pathway has been identified which may mediate the effects of budesonide on eosinophil/basophil lineage commitment.

Mycophenolate mofetil and triptolide alleviating airway inflammation in asthmatic model mice partly by inhibiting bone marrow eosinophilopoiesis

The bone marrow eosinophilopoiesis makes a major contribution to the chronic airway inflammation in asthmatic animals and patients. Some anti-asthmatic medicines alleviated the asthmatic airway inflammation by inhibiting the bone marrow eosinophilopoiesis. Immunosuppressive agents have been commonly used in patients with glucocorticoid refractory asthma and have been proved to be effective. However, the research on the effect of the immunosuppressive agents on the bone marrow eosinophilopoiesis has seldom been reported. The purpose of the study was to explore the effect of mycophenolate mofetil (MMF) and triptolide (TP) on the bone marrow eosinophilopoiesis and to further investigate the mechanisms of the immunosuppressive agents involved in the anti-asthmatic effect. Balb/c mice were sensitized and challenged by OVA to establish the asthmatic model, and respectively administered orally with sterile saline, MMF, and TP once daily for 2 weeks. Airway inflammation, and inflammatory mediators IL-5 and eotaxin in the peripheral blood and bone marrow were measured by histology and ELISA. Immunocytochemistry combined with in situ hybridization technique and Western blot analysis was performed to estimate the amount of CD34+ IL-5R mRNA+ cells and IL-5R expression in the bone marrow. The count of new produced eosinophils in the bone marrow was detected by anti-BrdU immunocytochemistry. We found that MMF and TP attenuated OVA-induced eosinophil (EOS) recruitment in bronchoalveolar lavage fluid (BALF), inflammatory mediator expression of IL-5 and eotaxin in the peripheral blood, inflammatory cells expressing eotaxin in the lung tissues and the number of new produced EOS in the bone marrow. Also, MMF abated the migration of CD34+ cells from the bone marrow to the peripheral blood, which was associated with a decreased eotaxin expression in the bone marrow and a decreased CCR3 expression on bone marrow cells. While, MMF or TP failed to decrease the amount of CD34+ IL-5R mRNA+ cells (EOS progenitors), and IL-5R expression in the bone marrow of asthmatic model mice. These results demonstrated that MMF and TP reduce the eosinophilopoiesis of the bone marrow; this is associated with a decrease of IL-5 produced by T cells, which contribute to alleviate the allergic airway inflammation in asthma. In addition, MMF decreased the CD34+ cells migration from the bone marrow to the peripheral blood by the reduction of the level of eotaxin in the bone marrow and the expression of CCR3 on the bone marrow cells.

Time for a paradigm shift in asthma treatment: from relieving bronchospasm to controlling systemic inflammation

Inflammation is a key pathology in asthma. In the central airways local inflammation leads to irreversible remodeling and airway dysfunction. Complex inflammatory changes also occur in the nose, sinuses, and small airways. In particular, rhinitis and asthma are linked by a common pathogenic process with common inflammatory cells, mediators, and cytokines. Cross-communication between the airways and bone marrow through inflammatory mediators in the circulation leads to systemic propagation of airway inflammation. Treatment of asthma has traditionally focused on relieving bronchospasm with beta(2)-agonists, which do not affect inflammation. Treatment of eosinophilic inflammation in the central airways with inhaled corticosteroids reduces local inflammation and improves pulmonary function but does not improve the systemic manifestations of asthma. If asthma is a systemic disease, the underlying systemic pathology should be targeted by identifying common disease mediators, mechanisms, or both that are triggered only during active disease. Of currently available therapies, leukotriene receptor antagonists block the action of cysteinyl leukotrienes and thus improve both asthma and rhinitis and other conditions systemically linked with asthma. Other potential treatments include receptor-blocking molecules and synthesis inhibitors related to eicosanoid inflammation. Treatment of asthma as a systemic disease requires clinical trials that evaluate the effects of new treatments on both lung function and the wider systemic pathology.

The impact of comorbid atopic disease on asthma: clinical expression and treatment

Clinically, asthma and allergic rhinitis involve separate regions of the respiratory tract while representing a common underlying inflammatory syndrome. Much evidence supports an epidemiologic association between the diseases, paranasal sinus involvement in both conditions, and parallel relationship in severity and treatment outcomes. Pathophysiologic mechanisms, including immunoglobulin E (IgE)- mediated inflammation, are also shared. Blocking IgE with the recombinant humanized monoclonal antibody omalizumab demonstrated clinical efficacy in patients with upper and lower airway diseases. IgE blockade, leukotriene modulation, and B-cell depletion therapy have all exhibited success in chronic inflammation, reinforcing and expanding the beneficial role of immunomodulation of global mediators.

The effect of CD14-c159T genotypes on the cytokine response to endotoxin by peripheral blood mononuclear cells from asthmatic children

BACKGROUND

A C-T polymorphism at position 159 in the promoter of CD14 (C-159T) modulates the cellular response to endotoxin and significantly influences total IgE levels. The effect of this genetic variant on the cytokine response of the inflammatory cells is incompletely understood.

OBJECTIVE

To investigate the effects of CD14-C159T genotypes on the response to endotoxin by peripheral blood mononuclear cells (PBMCs) in children with asthma.

METHODS

The PBMCs from asthmatic children with the TT (n = 11) and CC (n = 11) genotypes at the CD14 promoter were cultured in the presence of endotoxin, 100 ng/mL; concanavalin A, 10 microg/mL; or medium alone. Concentrations of soluble CD14 (sCD14), interleukin (IL) 1beta, IL-4, IL-10, IL-12, IL-13, interferon-gamma, and transforming growth factor beta were determined in culture supernatants by enzyme-linked immunosorbent assay, and the transcriptional differences were evaluated using reverse-transcriptase polymerase chain reaction.

RESULTS

Under unstimulated conditions, children with the TT genotype produced higher levels of sCD14 into the culture supernatant compared with children with the CC genotype (P = .03, Mann Whitney U test). Both IL-10 and IL-1beta concentrations were significantly higher in culture supernatants of children with the TT genotype after endotoxin stimulation (P = .02 and P = .009, respectively, by analysis of covariance [ANCOVA]). Messenger RNA expression was consistent with the results of protein concentration for IL-10 and sCD14. Concanavalin A stimulation resulted in lower levels of IL-4 in children with the TT genotype (P = .02, ANCOVA).

CONCLUSION

The genotype at the CD14 promoter C159T locus may significantly influence the cytokine response of PBMCs obtained from asthmatic children. Differences in IL-10 and IL-4 production by alternative genotypes may contribute to the observed genotype effect on total IgE.

The effect of polymorphisms at the CD14 promoter and the TLR4 gene on asthma phenotypes in Turkish children with asthma

BACKGROUND

Endotoxin, with its potential to enhance type 1 immunity, is a significant player in the hygiene hypothesis. The combined effects of the genetic variants of various molecules in the endotoxin response pathway on asthma related phenotypes are largely unknown.

OBJECTIVE

To investigate the effects of the genetic variants of CD14 and TLR4 genes on asthma phenotypes in a large number of asthmatic children.

METHODS

613 asthmatic children were genotyped at the CD14-C159T, TLR4-A896G and TLR4-C1196T loci. IgE, eosinophil numbers and FEV1 were compared in 327 children who were not on any controller medications and were symptom free. Multivariate logistic regression was used to determine the factors associated with total IgE.

RESULTS

Among children with atopic asthma, total IgE levels were significantly different among the three genotypes in the co-dominant model [CC: 435 kU/l (interquartile range: 146-820); CT: 361 (140-710); TT 204 (98-435), P = 0.035]. TT genotype was significantly and independently associated with lower IgE levels (OR: 0.5 95%; CI = 0.28-0.90, P = 0.021). Both TLR4-A896G and TLR4-C1196T polymorphisms were more frequent in the mild asthma group with atopy (P = 0.032, 0.018, respectively). The combined effects of the genetic variants in CD14 and TLR4 genes did not improve the observed associations.

CONCLUSION

Our study demonstrates that the CD14-C159T promoter variant influences total IgE levels and also indicates that the T allele has a more profound effect on total IgE in children with atopic asthma. Polymorphisms in the TLR4 gene may be associated with milder forms of disease in atopic asthmatics in the population studied.

The effect of desloratadine on eosinophil/basophil progenitors and other inflammatory markers in seasonal allergic rhinitis: a placebo-controlled randomized study

BACKGROUND

Eosinophil/basophil (Eo/B) progenitors fluctuate in the peripheral circulation during seasonal allergen exposure in atopic subjects. Several drugs have been shown to modulate Eo/B progenitor levels in the peripheral blood but, to date, the possible effect of antihistamines on Eo/B progenitors has not been explored. Our objective was to evaluate whether the antihistamine desloratadine (DL) can modulate peripheral blood Eo/B progenitors or other markers of allergic inflammation.

METHODS

We performed a randomized double-blind placebo-controlled study on the effects of DL on peripheral blood Eo/B progenitors in subjects with symptomatic, seasonal allergic rhinitis during a ragweed pollen season. Forty-five subjects were randomized to treatment for 4 weeks with DL 20 mg daily or placebo.

RESULTS

The expected fall in the number of Eo/B progenitors from baseline to 2 weeks of treatment was seen in the placebo group [median drop of 1.0 colony-forming unit (CFU)/10(6) cells], and was greater than in the DL group (median drop of 0.0 CFU/10(6) cells) (p = 0.013). The change in histamine concentration per colony from baseline to 2 weeks of treatment was lower in the DL group (median decrease of 6.1 pg/colony) compared to placebo (median increase of 1.8 pg/colony) (p = 0.01). An increase in the nasal lavage eotaxin concentration from baseline to 4 weeks of treatment was statistically significant in the placebo group but not in the DL group. Eo/B CFU were not affected by varying in vitro concentrations of DL.

CONCLUSION

These results suggest that DL can modulate aspects of allergic inflammation in vivo through mechanisms other than simple blockade of H1 histamine receptors.

Protection by budesonide and fluticasone on allergen-induced airway responses after discontinuation of therapy

BACKGROUND

Treatment with inhaled steroids is an effective method of reducing bronchoconstriction and airway inflammation after allergen challenge. However, the duration of the protective effects of inhaled steroids after discontinuation of therapy has not been established.

OBJECTIVE

We sought to evaluate the protective effect of 1 week of inhaled steroid therapy against inhaled allergen challenge 12 hours after discontinuation of therapy.

METHODS

In this randomized, double-blind, placebo-controlled crossover trial, 26 asthmatic subjects (>18 years old) not using inhaled steroids were administered 200 microg of budesonide twice daily, 200 microg of fluticasone twice daily, or placebo twice daily for 1 week. Twelve hours after discontinuation of therapy, subjects were administered an inhaled allergen challenge. Each treatment period was separated by a 3-week washout period.

RESULTS

When compared with placebo (26% +/- 14%), there was a slight but significant protection against the allergen-induced early response after fluticasone treatment (19% +/- 10%, P = .001) but not after budesonide treatment (23% +/- 13%, P = .08). However, when the area under the curve for the early airway response was examined, there was no difference between the 2 drugs in the amount of protection ( P = .62). Partial protection was demonstrated against the late-response allergen-induced sputum eosinophilia with both treatments ( P = .001). By contrast, no protection was observed against allergen-induced airway hyperresponsiveness for either treatment.

CONCLUSIONS

The protective effects of inhaled steroids against allergen-induced early responses, airway eosinophilia, and allergen-induced airway hyperresponsiveness are partially or completely lost as early as 12 hours after discontinuation of therapy.

Increased number of CD34+ cells in nasal mucosa of allergic rhinitis patients: inhibition by a local corticosteroid

BACKGROUND

Eosinophils develop from CD34+ haematopoietic progenitor cells. Allergen exposure in susceptible individuals is known to induce a local eosinophilic inflammation, but the effect on progenitor cells is much less understood.

OBJECTIVE

We aimed to evaluate how allergen exposure affects the number of tissue CD34+ cells and CD34+ eosinophils in allergic rhinitis (AR) patients and whether any such effect is influenced by local corticosteroid treatment. Also, we evaluated changes in the number of CXC receptor 4-positive cells (CXCR4+), since the CXCR4 ligand (stromal cell-derived factor-1 (SDF-1)) is a potent chemoattractant for haematopoietic progenitors.

METHODS

In a double-blind, randomized study, pollen-sensitized AR patients were treated with a nasal corticosteroid fluticasone propionate (FP, 200 microg/day) or placebo throughout the pollen season. Nasal biopsies were taken before and during the season. CD34 and CXCR4 were stained using immunohistochemistry.

RESULTS

The pollen season significantly increased the number of CD34+ cells, CD34+/CXCR4+ cells and CD34+ eosinophils in placebo-treated patients, but not in FP-treated patients. The mean pollen season-induced increase in CD34+ cells, CD34+/CXCR4+ cells and CD34+ eosinophils in FP-treated patients was lower compared with placebo-treated patients.

CONCLUSION

A pollen season increases the number of CD34+ cells in nasal tissue accompanied by an increase in the number of CD34+/CXCR4+ haematopoietic progenitors and also the number of CD34+ eosinophils in subjects with AR. Treatment with a local corticosteroid provides protection against this pollen-induced increase in tissue CD34+ cells and CD34+ eosinophils possibly via inhibition of allergen-induced CXCR4-mediated recruitment of CD34+ haematopoietic progenitors into airways and their further differentiation into eosinophils within the tissue.

The effect of pranlukast on allergen-induced bone marrow eosinophilopoiesis in subjects with asthma

We investigated the mechanisms by which leukotriene receptor antagonists decrease airway eosinophil number. In a randomized, double-blind crossover study, we examined the effects of 2 weeks of treatment with pranlukast 300 mg twice a day or placebo on allergen-induced changes in airway eosinophil number and bone marrow eosinophil progenitors in 15 subjects with mild asthma. Pranlukast treatment for 2 weeks decreased mean sputum eosinophil count from 0.15 x 10(6)/g (5.3% of cells) before treatment to 0.02 x 10(6)/g (0.7% of cells) after treatment (p < 0.05), whereas placebo did not. Pranlukast also decreased the eosinophil count (5.6% at 7 hours and 7.5% at 24 hours) (p < 0.05) after allergen inhalation compared with placebo (13.8% at 7 hours and 15.3% at 24 hours). There was a similar trend for sputum cells immunostaining for EG2, eotaxin, interleukin-5, and regulated upon activation, normal T cell expressed and secreted. Pranlukast also significantly attenuated the allergen-induced increase in the number of bone marrow eosinophil/basophil cfu (mean 0.3) at 24 hours compared with placebo (mean 6.2). The proportion of CD34(+) cells expressing the eotaxin receptor CC chemokine receptor 3, 24 hours after allergen inhalation, was also reduced by pranlukast. We conclude that, the cysteinyl leukotriene receptor antagonist, pranlukast, attenuates allergen-induced increase in airway eosinophils by decreasing bone marrow eosinophilopoiesis and airway chemotactic and eosinophilopoietic cytokines.

Pharmacology of airway inflammation in asthma and COPD

The current asthma therapies are not cures and symptoms return soon after treatment is stopped even after long term treatment. Although inhaled glucocorticoids are highly effective in controlling airway inflammation in asthma, they are ineffective in the small group of patients with glucocorticoid-dependent and -resistant asthma. With very few exceptions, COPD is caused by tobacco smoking, and smoking cessation is the only truly effective treatment of COPD available. Current pharmacological treatment of COPD is unsatisfactory, as it does not significantly influence the severity of the disease or its natural course. Glucocorticoids are scarcely effective in COPD patients without concomitant asthma. Bronchodilators improves symptoms and quality of life, in COPD patients, but, with the exception of tiotropium, they do not significantly influence the natural course of the disease. Theophylline is the only drug which has been demonstrated to have a significant effect on airway inflammation in patients with COPD. Here we review the pharmacology of currently used antiinflammatory therapies for asthma and COPD and their proposed mechanisms of action. Recent understanding of disease mechanisms in severe steroid-dependent and -resistant asthma and in COPD, has lead to the development of novel compounds, which are in various stages of clinical development. We review the current status of some of these new potential drugs.

The effects of an anti-CD11a mAb, efalizumab, on allergen-induced airway responses and airway inflammation in subjects with atopic asthma

BACKGROUND

Efalizumab is a humanized IgG(1) mAb against the lymphocyte function antigen-1 (LFA-1) alpha chain, CD11a. Blocking of LFA-1/intercellular adhesion molecule interactions could inhibit asthmatic inflammation by blocking adhesion and activation of LFA-1-positive leukocytes.

OBJECTIVE

A randomized, double-blinded, placebo-controlled, parallel group, multicenter study investigated the effects of efalizumab on allergen-induced airway responsiveness and airway inflammation.

METHODS

Thirty-five nonsmoking subjects with mild allergic asthma were randomized to receive efalizumab (n = 24) or placebo (n = 11) in 8 weekly subcutaneous doses (0.7 mg/kg conditioning dose followed by 7 weekly doses of 2.0 mg/kg). Allergen challenges were performed at screening and after 4 and 8 weeks of treatment. Samples of sputum (n = 18 subjects) and blood (n = 35 subjects) were collected the day before challenges, and sputum was collected again at 7 and 24 hours after each challenge. Nonparametric tests were used to compare allergen-induced differences between efalizumab and placebo groups.

RESULTS

Subjects receiving efalizumab developed headache (48%) and flu syndrome (28%) compared to subjects receiving placebo (0%). After 8 weeks of efalizumab, the maximum late percent fall in FEV(1) (late asthmatic response) was inhibited by 50%, but neither the late response nor the late area under the curve was statistically different than placebo (P =.098 and.062, respectively). Efalizumab had no effect on the maximum early percent fall in FEV(1) (early asthmatic response) or early area under the curve compared to placebo (P >.59). Efalizu-mab significantly reduced the postallergen increase in sputum EG2-positive cells and metachromatic cells (P <.05). No other comparisons were statistically different.

CONCLUSIONS

Blocking of LFA-1/intercellular adhesion module interactions by efalizumab inhibits the development of allergen-induced cellular inflammatory responses measured in induced sputum and might attenuate the late asthmatic response. Larger studies are needed to confirm this.

Effect of SCH55700, a humanized anti-human interleukin-5 antibody, in severe persistent asthma: a pilot study

Antagonizing the effect of interleukin (IL)-5 is a potential new treatment strategy in allergic disorders. We evaluated the safety, biological activity, and pharmacokinetics of SCH55700, a humanized anti-human IL-5 antibody, in subjects with severe persistent asthma treated with oral or high doses of inhaled steroids. In a double-blind, randomized, multicenter trial, a rising single dose of SCH55700 (0.03 mg/kg [n = 2], 0.1 mg/kg [n = 4], 0.3 mg/kg [n = 6], or 1.0 mg/kg [n = 12]) or placebo (n = 8) was administered intravenously. SCH55700 dose dependently reduced circulating eosinophil counts. At a dose of 1.0 mg/kg, the decrease remained significant up to Day 30 [(0.07 +/- 0.01) x 10(9)/L versus (0.23 +/- 0.04) x 10(9)/L at baseline] (mean +/- SEM) (p = 0.05). After administration of SCH55700 at 0.3 and 1.0 mg/kg, a trend toward improvement in baseline FEV1 was observed, which reached significance 24 hours after the 0.3-mg/kg dose (p = 0.019 versus placebo). No significant changes occurred in other clinical indices of disease activity. Adverse events were not different between active treatment and placebo. We conclude that SCH55700 is a biologically active anti-human IL-5 antibody that can be safely used in severe steroid-treated asthma. Its therapeutic potential needs to be addressed in specifically designed efficacy trials.

Intranasal fluticasone propionate inhibits allergen induced bone marrow eosinophilia in mice

Local corticosteroids are currently the most efficient safe anti-allergic treatment, which attenuate eosinophilic tissue inflammation through several mechanisms. We evaluated the effect of local airways corticosteroid on repeated allergen exposure-induced bone marrow activation and airway eosinophilia using the number of eosinophils in bone marrow, bronchoalveolar lavage fluid (BALf) and airways tissue as study end-points. Male BALB/c mice were sensitized by intraperitoneal injections of aluminum-precipitated ovalbumin (OVA) on two different days (5 days apart). Eight days after the second sensitization, the animals were challenged intranasally with OVA or phosphate-buffered saline (PBS) on 5 consecutive days. Concomitantly with challenges mice were treated with fluticasone propionate or respective vehicle. OVA exposures induced a significant increase in eosinophil numbers in bone marrow, BALf and airways tissue (P<0.005). Treatment with fluticasone propionate significantly reduced the increase of absolute number of mature bone marrow eosinophils (P=0.014) and showed a tendency towards decrease in the immature bone marrow eosinophil number (P=0.057) compared to controls. However, fluticasone propionate had no significant effect on BALf and airways tissue eosinophils (P=0.28 and 0.07, respectively). In this murine allergy model intranasal corticosteroid reduced number of bone marrow mature eosinophils, but did not significantly affect airways cell populations.

The effects of intranasal budesonide on allergen-induced production of interleukin-5 and eotaxin, airways, blood, and bone marrow eosinophilia, and eosinophil progenitor expansion in sensitized mice

We have previously demonstrated that allergen inhalation induces expansion of bone marrow eosinophil progenitors in sensitized mice and subjects with asthma and that the inhaled corticosteroid, budesonide, reduced baseline but not allergen-induced increase in bone marrow eosinophil/basophil progenitors (EoB-CFU) in subjects with asthma. Here, we evaluated the effects of intranasal budesonide on allergen-induced increases in interleukin (IL)-5 and eotaxin in the airway and peripheral blood, expansion of bone marrow Eo-CFU and eosinophilia in bone marrow, peripheral blood and airway, as well as airway hyperresponsiveness, in ovalbumin (OVA)-sensitized mice. Budesonide treatment attenuated allergen-induced eosinophilia in bone marrow, peripheral blood, and airways as well as allergen-induced increases in bone marrow eosinophil progenitors but not allergen-induced increases in IL-5 or eotaxin 12 h following the second of two daily exposures to allergen; at later time points treatment was associated with attenuation of IL-5, eosinophilia, Eo-CFU, and airway hyperresponsiveness. These results suggest that a component of the mechanism by which corticosteroid treatment attenuates allergen-induced airway inflammation is through suppression of bone marrow eosinophilopoiesis, and that this is likely not mediated simply through the blocking of IL-5 production at the airway.

Anti-allergic therapies: effects on eosinophil progenitors

Marked eosinophilic infiltration is the typical inflammatory response associated with allergic inflammation. Previous research involving animal and human models has established a role for the eosinophil/basophil hematopoietic progenitor in a systemic process of allergic inflammation. In this article, we will review the evidence implicating eosinophil/basophil progenitors in this systemic response and will discuss the rationale for targeting this cell in the treatment of allergic disease. In this context, we discuss corticosteroid treatment of allergic diseases, such as asthma and its effects on hematopoietic mechanisms, the effects of therapies that inhibit the actions of cysteinyl leukotrienes, the effects of in vivo blockade of the eosinophil-active cytokine interleukin-5, and the effects of antihistamines on hematopoiesis. It is suggested that several anti-allergic therapies exert their beneficial effects on allergic inflammation by influencing eosinophil production systemically. Therefore, targeting the systemic hematopoietic response may provide additional, more beneficial, therapeutic effects.

Inhaled corticosteroid effects on bone metabolism in asthma and mild chronic obstructive pulmonary disease

BACKGROUND

Inhaled corticosteroids form the main therapy for asthma, but there is increasing concern about the potential systematic effects of long-term inhaled corticosteroids including their effect on bone metabolism and bone loss.

OBJECTIVES

To determine the effect of inhaled corticosteroids use on biochemical markers of bone turnover, bone mineral density and the development of fractures.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register, electronic reference databases, UK National Research Register, bibliographies of included studies, and contacted pharmaceutical companies.

SELECTION CRITERIA

Randomised trials of the effect of inhaled steroid versus placebo on markers of bone function and metabolism, in adults with asthma or mild COPD.

DATA COLLECTION AND ANALYSIS

Trial quality was assessed and data extracted from the papers included (2 reviewers per paper) and from additional data supplied by the authors.

MAIN RESULTS

Of 438 references found, seven met the inclusion criteria. Three studies were in healthy subjects asthma or COPD. The patients were generally less than 60 years old and the male:female ratio was 2:1. There was no evidence of increased risk of loss of bone mineral density (BMD) or fractures. There was no significant change in osteocalcin at conventional doses of inhaled corticosteroids (Standardised Mean Difference [SMD] -0.34 (95% Confidence Interval [CI] -0.72, 0.04), although a statistically significant change was seen in those studies using experimental doses of inhaled steroid in excess of the doses recommended by the British Thoracic Society SMD 0.97 (95% CI -1.61, -0.34). A statistically significant change in parathyroid hormone seen in one small short trial (n=10, 6 weeks) may have been due to the trial design and outcome measurements used.

REVIEWER'S CONCLUSIONS

In patients with asthma or mild COPD, there is no evidence of an effect of inhaled corticosteroid at conventional doses given for two or three years on BMD or vertebral fracture. Higher doses were associated with biochemical markers of increased bone turnover, but data on BMD and fractures at these doses are not available. There is a need for further, even longer term prospective studies of conventional and high doses of inhaled corticosteroids.

Systemic aspects of allergic disease: the role of the bone marrow

In recent years, there has been an increasing appreciation of the important contribution of bone-marrow-related, hemopoietic mechanisms to allergic diseases. Eosinophil/basophil-progenitor levels fluctuate in the peripheral blood during allergen exposure and the cells home to peripheral tissue, where they differentiate. It is becoming apparent that several cytokines, particularly IL-5, have multiple effects on progenitors and allergic inflammation. Within the past few years, studies of the therapeutic implications of this bone marrow contribution to atopy have been initiated; the effects of corticosteroids, leukotriene-receptor blockers, antagonism of IL-5 and modulation of differentiation by retinoic acid on progenitors will be reviewed.

Interleukin-5 in growth and differentiation of blood eosinophil progenitors in asthma: effect of glucocorticoids

1. There are increased numbers of circulating CD34(+) progenitor cells for eosinophils in patients with atopic asthma, with a further increase following allergen exposure or spontaneous worsening of asthma. We investigated the expression of IL-5 and IL-5Ralpha receptor in circulating CD34(+) progenitor cells in allergic asthmatics and the effects of corticosteroids. 2. Using double-staining techniques, up to 50% of CD34(+) cells expressed intracellular IL-5, and by RT - PCR, there was significant expression of IL-5 mRNA. When cultured in a semi-liquid methylcellulose medium, there were more eosinophil colony-forming units grown from asthmatic non-adherent mononuclear cell depleted of T cells in the presence of the growth factors GM-CSF, SCF and IL-3, but not of IL-5. 3. An anti-IL-5Ralpha receptor antibody and an anti-sense IL-5 oligonucleotide reduced the number of eosinophil colony forming units. No IL-5 mRNA or protein expression on T cells was observed in asthmatics or normal subjects. In the presence of growth factors including IL-5, there were significantly greater colony numbers with eosinophilic lineage grown from either asthmatics or normal subjects. 4. Dexamethasone (10(-6) M) suppressed IL-5 mRNA and protein expression in CD34(+) cells, and reduced eosinophil colony-forming units in asthmatics, but not in normal subjects. Dexamethasone did not change the expression of IL-5Ralpha on CD34(+) cells. 5. We conclude that there is increased expression of IL-5 on blood CD34(+) cells of patients with asthma and that this expression may auto-regulate eosinophilic colony formation from these progenitor cells. Corticosteroids inhibit the expression of IL-5 in circulating CD34(+) progenitor cells.

The use of sputum cell counts to evaluate asthma medications

Total and differential cell counts from hypertonic-induced, dithiothreitol-dispersed sputum provide reproducible measurements of airway inflammatory cell counts, which are responsive to treatment with anti-inflammatory drugs. They have helped to understand the kinetics of inflammatory cell changes in asthma after the reduction of corticosteroids and the subsequent re-introduction of treatment. They have identified that the presence of sputum eosinophilia in asthma, chronic cough and chronic airflow limitation is a predictor of steroid-responsiveness and of lack of 'asthma control'. They can be used to study the dose-response effect of inhaled corticosteroids and may be useful to establish the relative potency of different corticosteroid formulations and delivery devices. Sputum cell counts are also useful to study the potential anti-inflammatory effects of drugs like theophylline, long-acting beta-adrenoceptor agonists, leukotriene antagonists and newer drugs in development. They may be helpful to select add-on therapy to corticosteroids in 'difficult-to-control' asthma.

An increase in circulating mast cell colony-forming cells in asthma

We compared a potential to generate mast cells among various sources of CD34(+) peripheral blood (PB) cells in the presence of stem cell factor (SCF) with or without thrombopoietin (TPO), using a serum-deprived liquid culture system. From the time course of relative numbers of tryptase-positive and chymase-positive cells in the cultured cells grown by CD34(+) PB cells of nonasthmatic healthy individuals treated with G-CSF, TPO appears to potentiate the SCF-dependent growth of mast cells without influencing the differentiation into mast cell lineage. CD34(+) PB cells from asthmatic patients in a stable condition generated significantly more mast cells under stimulation with SCF alone or SCF+TPO at 6 wk of culture than did steady-state CD34(+) PB cells of normal controls. Single-cell culture studies showed a substantial difference in the number of SCF-responsive or SCF+TPO-responsive mast cell progenitors in CD34(+) PB cells between the two groups. In the presence of TPO, CD34(+) PB cells from asthmatic children could respond to a suboptimal concentration of SCF to a greater extent, compared with the values obtained by those of normal controls. Six-week cultured mast cells of asthmatic subjects had maturation properties (intracellular histamine content and tryptase/chymase enzymatic activities) similar to those derived from mobilized CD34(+) PB cells of nonasthmatic subjects. An increase in a potential of circulating hemopoietic progenitors to differentiate into mast cell lineage may contribute to the recruitment of mast cells toward sites of asthmatic mucosal inflammation.

Regulation of allergic airways inflammation by cytokines and glucocorticoids

Cytokines mediate the allergic inflammatory response of the airways, and glucocorticosteroids ameliorate allergy symptoms by regulating cytokine expression. Recent studies provide insight into the manner by which cytokines work together to mediate allergic airway disease. Real progress has also been gained in our understanding of subcellular mechanisms of allergic inflammation, particularly the role of transcription factors in regulating the expression of specific cytokine profiles and the differentiation of the TH2 subset. This article provides an update of recently reported findings in this field and highlights emerging concepts of allergic inflammation.

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.

Budesonide inhalation suspension: a review of its use in infants, children and adults with inflammatory respiratory disorders

Budesonide, a topically active corticosteroid, has a broad spectrum of clinically significant local anti-inflammatory effects in patients with inflammatory lung diseases including persistent asthma. In infants and young children with persistent asthma, day- and night-time symptom scores, and the number of days in which beta2-agonist bronchodilators were required, were significantly lower during randomised, double-blind treatment with budesonide inhalation suspension 0.5 to 2 mg/day than placebo in 3 multicentre trials. Significantly fewer children discontinued therapy with budesonide inhalation suspension than with placebo because of worsening asthma symptoms in a study that included children who were receiving inhaled corticosteroids at baseline. Recent evidence indicates that budesonide inhalation suspension is significantly more effective than nebulised sodium cromoglycate in improving control of asthma in young children with persistent asthma. At a dosage of 2 mg/day, budesonide inhalation suspension significantly reduced the number of asthma exacerbations and requirements for systemic corticosteroids in preschool children with severe persistent asthma. In children with acute asthma or wheezing, the preparation was as effective as, or more effective than oral prednisolone in improving symptoms. In children with croup, single 2 or 4mg dosages of budesonide inhalation suspension were significantly more effective than placebo and as effective as oral dexamethasone 0.6 mg/kg or nebulised L-epinephrine (adrenaline) 4mg in alleviating croup symptoms and preventing or reducing the duration of hospitalisation. Early initiation of therapy with budesonide inhalation suspension 1 mg/day appears to reduce the need for mechanical ventilation and decrease overall corticosteroid usage in preterm very low birthweight infants at risk for chronic lung disease. In adults with persistent asthma, budesonide inhalation suspension < or =8 mg/day has been compared with inhaled budesonide 1.6 mg/day and fluticasone propionate 2 mg/day administered by metered dose inhaler. Greater improvements in asthma control occurred in patients during treatment with budesonide inhalation suspension than with budesonide via metered dose inhaler, whereas fluticasone propionate produced greater increases in morning peak expiratory flow rates than nebulised budesonide. Several small studies suggest that the preparation has an oral corticosteroid-sparing effect in adults with persistent asthma and that it may be as effective as oral corticosteroids during acute exacerbations of asthma or chronic obstructive pulmonary disease. The frequency of adverse events was similar in children receiving budesonide inhalation suspension 0.25 to 2 mg/day or placebo in 12-week studies. During treatment with budesonide inhalation suspension 0.5 to 1 mg/day in 3 nonblind 52-week studies, growth velocity in children was generally unaffected; however, a small but statistically significant decrease in growth velocity was detected in children who were not using inhaled corticosteroids prior to the introduction of budesonide inhalation suspension. Hypothalamic-pituitary-adrenal axis function was not affected by short (12 weeks) or long (52 weeks) term treatment with nebulised budesonide. In conclusion, budesonide inhalation suspension is the most widely available nebulised corticosteroid, and in the US is the only inhaled corticosteroid indicated in children aged > or =1 year with persistent asthma. The preparation is suitable for use in infants, children and adults with persistent asthma and in infants and children with croup.

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.