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Abstract |
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Abstract
Introduction
Materials & Methods
Results
Discussion
References
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Increased bone marrow granulocyte-macrophage colony forming units (GM-CFU) in dogs developing allergen-induced airway hyperresponsiveness can be accounted for by a factor(s) present in serum following the allergen challenge. The present study evaluated whether in vitro treatment of bone marrow with budesonide or prostaglandin (PG)E2, prevents allergen-induced bone marrow stimulation. Eight dogs were studied after allergen and diluent inhalation challenges. Budesonide (10
7 M) or PGE2 (106 M) was added to
bone marrow aspirated 24 h after challenge. Budesonide or PGE2 was also added to bone marrow aspirated
before challenge, to which serum taken 24 h after challenge was subsequently added. Non-adherent mononuclear bone marrow cells were incubated in the presence of the serum and granulocyte/macrophage colony stimulating factor (GM-CSF), granulocyte stimulating factor (G-CSF), or stem cell factor (SCF), and
the number of GM-CFU counted. Allergen-induced increases in the number of GM-CFU in bone marrow
aspirated 24 h after allergen (P < 0.001) were not attenuated by budesonide or PGE2 treatment (P > 0.05).
However, GM-CFU increases in bone marrow aspirated before challenge and incubated with post-allergen challenge serum (P < 0.001) were blocked by either budesonide or PGE2 (P < 0.01). These findings demonstrate that budesonide and PGE2 can act directly on the bone marrow, preventing allergen-induced increases in inflammatory cell progenitor production. This suggests that the bone marrow must be considered as a possible site of action for drugs which attenuate allergen-induced asthmatic responses.
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Introduction |
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Abstract
Introduction
Materials & Methods
Results
Discussion
References
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Airway inflammation is an important feature of asthma (1, 2), involving several cell types including eosinophils, neutrophils, metachromatic cells, and lymphocytes (3). Furthermore, airway inflammation is associated with airway hyperresponsiveness, another important characteristic of asthma (7, 8). Increased understanding of the underlying inflammatory basis of asthma has led to asthma treatment guidelines which have focused on the increased use of anti-inflammatory agents, primarily inhaled corticosteroids (9).
It is believed that the primary mechanism of action of inhaled corticosteroids in the treatment of asthma is through the reduction of airway inflammation, possibly by preventing the production or release of inflammatory mediators in the airway (12, 13). The marked efficacy of inhaled corticosteroids in asthma suggests that their effect is mainly topical, rather than systemic. However, systemic corticosteroids are the treatment of choice for severe asthma exacerbations, which raises the possibility that some systemic effects of corticosteroids may also be important, at least in managing some components of asthma.
Recently, the role of inflammatory cell progenitors in the pathogenesis of airway inflammation has been investigated. In earlier studies, atopic subjects were shown to have higher numbers of circulating eosinophil-basophil colony forming units (Eo-CFU) than matched non-atopic controls (14). Later, allergen-induced asthma was also found to be associated with increased circulating Eo-CFU (15), and increases in circulating Eo-CFU were found to be associated with asthma exacerbations following decreased treatment with inhaled steroids (16). In dogs, we have shown that allergen-induced airway hyperresponsiveness and airway neutrophilia is associated with an increase in bone marrow granulocyte-macrophage colony forming units (GM-CFU) (progenitors for either neutrophils or monocyte/macrophages), an effect that could be prevented by prior treatment with inhaled steroids (17). These findings raise the possibility that prevention of inflammatory cell production by glucocorticoids may be an important therapeutic mechanism in the treatment of allergen-induced asthma.
We have recently demonstrated that, using dogs who develop allergen-induced airway hyperresponsiveness, the development of allergen-induced increases in bone marrow progenitors is dependent on the presence of a hemopoietic factor in serum, present 24 h after allergen inhalation (18). In that same series of experiments we evaluated whether known anti-asthma treatment has a direct effect in preventing allergen-induced bone marrow stimulation. In the current paper we therefore present the results of the investigation of the effects of in vitro treatment of bone marrow aspirates with two drugs, a corticosteroid budesonide, and prostaglandin (PG)E2, known to be effective in preventing allergen-induced airway responses in humans (19, 20), on allergen-induced increases in bone marrow progenitors, as well as on the progenitors stimulated by post-allergen challenge serum. As these experiments were carried out in parallel with those in our earlier publication, the portion of the results demonstrating the hemopoietic effect of post-allergen challenge serum have been previously published (18).
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Materials and Methods |
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Abstract
Introduction
Materials & Methods
Results
Discussion
References
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Study Design
Eight dogs, known to develop greater than 2-fold increases in airway acetylcholine (ACh) responsiveness 24 h after allergen inhalation, were studied. All dogs were studied on two occasions, before and after allergen and diluent challenges, separated by at least 4 wk, and performed in random order.
Protocol
Each study period was performed over two consecutive days (Figure 1A). On the first day, dogs were anesthetized after an overnight fast. Serum was obtained immediately prior to anesthesia induction, and a bone marrow aspirate was performed in the 5-min period following anesthesia induction. An airway ACh challenge was performed 30 min following anesthesia induction. Forty-five minutes after the completion of the ACh challenge, dogs were given an airway challenge with allergen or diluent. Following this the dog was allowed to fully recover.
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The following day, 24 h after challenge, a serum sample was obtained immediately prior to anesthesia induction and a second bone marrow aspirate was performed in the 5-min period following anesthesia induction. Thirty minutes after anesthesia induction a second ACh challenge was performed. All procedures were performed as in previous studies (17), with slight modifications.
Anesthesia
Dogs were sedated with intramuscular meperedine hydrochloride (3 mg/kg; Demerol; Abbott Laboratories, Toronto, ON, Canada) and acepromazine maleate (0.05 mg/ kg; Atravet; Ayerst Laboratories, Montreal, PQ, Canada). Intravenous thiopental sodium (11 mg/kg; Pentothal, Abbott Laboratories, Montreal, PQ, Canada) was given as a bolus 20 min following sedation. An endotracheal tube (9- 10 mm id) was inserted into the dog's airway following anesthesia induction and removed during recovery after establishing the presence of a gag reflex. Additional anesthesia with intravenous pentobarbitol sodium (Somnatol; MTC Pharmaceuticals, Mississauga, ON, Canada) was given as required during the course of the experiment, but not prior to bone marrow aspiration, to avoid potential effects of anesthetic agents on progenitor activity. We have observed decreased growth of GM-CFU during anesthesia with pentobarbitol sodium but not thiopental sodium (unpublished observations).
Serum Sampling
Non-heparinized venous samples were obtained before and 24 h after challenge. Serum required for bone marrow cultures was removed after centrifugation at 500 × g for 10 min.
Measurement of Total Pulmonary Resistance
An esophageal balloon catheter was inflated as previously described (21) and inserted into the dog's esophagus to the point of lowest (most negative) end expiratory pressure while the dog was breathing spontaneously. Transpulmonary pressure was estimated as the subtraction of esophageal balloon pressure from mouth pressure using a differential pressure transducer (Hewlett-Packard 267BC; Waltham, MA). Flow was measured using a pneumotach (Fleisch No. 1; Instrumentation Associates, New York, NY) and a differential pressure transducer (Hewlett-Packard 270). Signals from both transducers were amplified (Hewlett-Packard 267BC) and directed to an analogue computer (Respiratory Analyser, Hewlett-Packard 8816A). The endotracheal tube was connected to a constant volume ventilator (Model 551; Harvard Apparatus, South Natick, MA) with a breathing frequency set at 30 breaths/min and tidal volume set at 10 ml/kg. Total pulmonary resistance was calculated by the analogue computer with the method of Mead and Wittenburger (22) using two points from each inspiration and expiration. Output from the computer was recorded on a paper chart recorder (Hewlett-Packard 7758A).
Measurement of Airway Responsiveness
The concentration of inhaled ACh required to increase total pulmonary resistance by 5 cm H2O · l1 · s1 was determined as an index of airway responsiveness. Following baseline measurements of pulmonary resistance, dogs inhaled normal saline, followed by 2-fold increasing concentrations of acetylcholine (initial concentration 0.078125 mg/ml; Sigma Chemical Co., St. Louis, MO). Solutions
were aerosolized using a twinjet nebulizer (Bennet Respiration Products, Los Angeles, CA) and delivered via the
endotracheal tube over 5 breaths of 3 s duration each. The nebulizer output was 0.196 ml/min with droplets of 2.5 um
(SD 2.3) mass median aerodynamic diameter. Increasing
ACh concentration was administered every 4 min until
pulmonary resistance (the peak value measured during the
30 s period after administration) increased by at least 5 cm
H2O · l1 · s1 above that measured following saline inhalation. The dose of ACh required to increase resistance by
exactly 5 cm H2O · l1 · s1 was calculated by logarithmic
extrapolation between points encompassing this value. A
decrease in this value, termed the ACh provocative concentration, reflects increased airway responsiveness.
Allergen/Diluent Challenges
Allergen challenges involved inhalation of Ascaris suum
(A. suum) (stock extract 101 wt/vol; Greer Laboratories,
Lenoir, NC). During the initial screening challenge, increasing concentrations of A. suum (105, 104, 103, 102,
101 wt/vol) were inhaled until pulmonary resistance increased by 10 cm H2O · l1 · s1 above pre-allergen levels.
The concentration of A. suum producing this resistance
change was used for the allergen challenge during the
study (for some dogs, resistance did not increase by 10 cm H2O · l1 · s1, in which case 101 wt/vol was used). A. suum
was delivered over 50 inhalations of 3 s duration each, using the same nebulizer as used for ACh challenges. Ten
minutes was allowed between doses during screening and
the post-challenge resistance was taken as the peak value
in the 10 min following the inhalation. The diluent used in
A. suum preparation (0.4% phenol) was inhaled in the
same concentration and manner as allergen during the
control challenges.
Bone Marrow Aspiration and Progenitor Cultures
Bone marrow was aspirated prior to and 24 h following allergen/diluent challenges. Immediately following anesthesia induction, bone marrow (3 ml) was aspirated using a 16-gauge Rosenthal needle under aseptic conditions from the posterior iliac crest into 1,000 U of heparin. Constant volumes were aspirated on all occasions to minimize variability in the degree of peripheral blood contamination (23). Methylcellulose cultures of low density non-adherent mononuclear cells were performed as described previously (17), with some modifications. Bone marrow cultures were performed under 7 different conditions: (1) bone marrow and serum obtained before challenge, to determine baseline GM-CFU growth (Figure 1B[i] - culture 1); (2) bone marrow and serum obtained 24 h after challenge, to determine the effect of challenge on GM-CFU growth (Figure 1B[ii] - culture 2); (3) bone marrow aspirated before challenge with serum obtained 24 h postchallenge, to determine the effect of postchallenge serum on GM-CFU growth (Figure 1B[ii] - culture 3); (4) bone marrow and serum obtained 24 h after challenge, treated with budesonide (Figure 1B[iii] - culture 4); (5) bone marrow and serum obtained 24 h after challenge, treated with PGE2 (Figure 1B[iii] - culture 5); (6) bone marrow aspirated before challenge with serum obtained 24 h postchallenge, treated with budesonide (Figure 1B[iii] - culture 6); (7) bone marrow aspirated before challenge with serum obtained 24 h postchallenge, treated with PGE2 (Figure 1B[iii] - culture 7).
In each of the previously mentioned culture conditions,
heparinized bone marrow volume was brought to 50 ml using McCoy's 5A medium and then separated on a density
gradient by centrifugation through Percoll (Pharmacia,
Uppsala, Sweden). Low density mononuclear cells were
collected from the interface and washed in McCoy's 5A
medium and then incubated in this medium with 15% fetal
calf serum (same lot used throughout study), 1% penicillin-streptomycin (GIBCO, Grand Island, NY) and 5 × 105 M 2-mercaptoethanol for 2 h in plastic flasks at 37°C
and 5% CO2. For the conditions where post-challenge serum was applied to pre-challenge bone marrow, this incubation period was extended to 24 h, as post-challenge serum was not available until this time. Following incubation,
cell viability was determined using Trypan blue (Life
Technologies Inc., Grand Island, NY) and non-adherent cells were then cultured in aliquots of 1 × 105 cells per 35 × 10-mm culture dish (Falcon Plastics, Oxnard, CA). For
each condition, duplicate cultures were set up in supplemented Iscove's modified Dulbecco's medium (with 1%
penicillin-streptomycin and 5 × 105 M 2-mercaptoethanol), 0.9% methylcellulose, 20% fetal calf serum, 10% autologous canine serum, and one of the following growth
factors: recombinant canine (rc) granulocyte/macrophage
colony stimulating factor (GM-CSF) (1 ug/ml; AMGEN,
Thousand Oaks, CA), rc granulocyte stimulating factor
(G-CSF) (1 ug/ml; AMGEN) and rc stem cell factor (SCF)
(5 ng/ml; AMGEN). Colonies (groups of 40 cells) were
counted after 8 days of incubation, identified as GM-CFU
by inverted microscopy (24), and confirmed by Diff-Quick
staining of 5 colonies picked at random from each culture
dish. All counts were performed by one investigator, blinded
to the experimental condition.
In Vitro Treatment
Aspirated bone marrow cells were treated in vitro at the
time of incubation in the plastic flask. Thus, post-challenge
bone marrow was treated for 2 h, while pre-challenge bone
marrow was treated for 24 h prior to addition of post-challenge serum. Budesonide was prepared dissolved in 70%
ethanol and then diluted with phosphate buffered saline
(PBS). The final concentration of budesonide during the
incubation period was 107 M, while the concentration of
ethanol was 0.007%. PGE2 was dissolved in PBS and applied during the incubation period at a final concentration of 106 M. Ethanol (0.007%) was added to both the untreated and PGE2-treated incubations for control purposes.
Analysis
Measurements of airway responsiveness are logarithmically distributed. For this reason, analysis of ACh provocative concentration was performed on log10 transformed data. The summary results presented are geometric means. All other data were analyzed parametrically with summary results expressed as arithmetic means and standard error of the mean (SEM).
Repeated measures Student's t-tests (25) were used to compare ACh provocative concentrations between conditions and to compare the change in resistance in response to allergen with that in response to diluent challenge.
The effect of allergen versus diluent challenge, as well as in vitro treatment effects, on bone marrow progenitor cultures was analyzed by calculating growth indices for each post-challenge condition. For each condition, the growth index was calculated by subtracting the pre-challenge GM-CFU colony growth (i.e., culture condition "1" in Figure 1B) from the post-challenge growth. Paired t-tests were used to compare growth indices between allergen and diluent conditions, both for postallergen bone marrow, and for the effect of added serum. Treatment effects on postallergen bone marrow and the added serum effect were analyzed separately using 2-way (2 × 2) repeated measures analysis of variance (factors: allergen versus diluent and budesonide versus PGE2).
All post-hoc comparisons were carried out using Neuman-Keuls test for significant effects (25). All comparisons were two-tailed, with a probability of < 0.05 considered significant.
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Results |
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Abstract
Introduction
Materials & Methods
Results
Discussion
References
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Allergen inhalation caused an immediate increase in total pulmonary resistance (Figure 2) (P < 0.005) and resulted in a greater than 2-fold reduction in the ACh provocative concentration in all dogs, 24 h after the challenge (Figure 3) (P < 0.0005). Diluent challenge caused no change in total pulmonary resistance from baseline (Figure 2), and less than 2-fold reductions in the ACh provocative concentration (Figure 3). For all dogs, pulmonary resistance returned to baseline within 60 min of allergen inhalation.
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The viability of the non-adherent mononuclear cells assessed following the incubation period was greater than 95% for all dogs in all conditions. Allergen inhalation caused a significant increase in GM-CFU numbers from post-challenge bone marrow aspirates under all three culture conditions when compared to diluent (P < 0.001) (Figure 4). The number of GM-CFU when GM-CSF was used as the growth stimulus were 20.9 (SEM 4.6) and 35.8 (SEM 5.1) before and 24 h after allergen challenge (P < 0.001), compared with 14.5 (SEM 2.6) and 17.8 (SEM 3.3) before and 24 h after diluent challenge, respectively (P > 0.05) (Figure 4). Similar significant changes were seen when G-CSF and SCF were used as growth conditions (Figure 4).
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= GM-CFU grown with serum collected 24 h post-allergen added to pre-allergen bone marrow
greater than pre-allergen serum added to same marrow (P < 0.05) (matched measurements under diluent conditions were subtracted as control).
The addition of serum taken 24 h after allergen challenge to bone marrow aspirated before allergen challenge also produced a significant increase in GM-CFU under all three culture conditions, when compared with diluent challenge (P < 0.001) (Figure 4). The number of GM-CFU with the addition of post-allergen serum, when GM-CSF was used as the growth stimulus, was 36.4 (SEM 5.9), compared with 11.4 (SEM 2.6) with the addition of post-diluent serum (P < 0.0005). Similar significant changes were seen when G-CSF and SCF were used as growth conditions (Figure 4).
The addition of budesonide or PGE2 had no effect on GM-CFU growth when added to post-allergen or post-diluent bone marrow aspirate (P > 0.05) (Figure 5). The number of GM-CFU, when GM-CSF was used as the growth stimulus on post-allergen bone marrow, was 35.6 (SEM 5.1), 36.4 (SEM 6.3), and 32.5 (SEM 5.6) under untreated, budesonide, and PGE2 conditions, respectively (P > 0.05 after subtracting growth under the treatment matched diluent condition). Similar effects were seen when G-CSF and SCF were used as growth conditions (Figure 5).
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The addition of budesonide or PGE2 to the pre-allergen bone marrow, prior to the addition of post-allergen serum prevented the serum-induced increase in GM-CFU in all three culture conditions (Figure 6) (P < 0.01). The number of GM-CFU from the untreated bone marrow was 36.4 (SEM 5.9) after the addition of post-allergen when GM-CSF was used as the growth stimulus. The number of GM-CFU was significantly reduced to 18.8 (SEM 3.9) (P < 0.005 after subtracting growth under the treatment matched diluent condition) and 19.5 (SEM 4.5) (P < 0.005 after subtracting growth under the treatment matched diluent condition) following budesonide and PGE2 treatment, respectively (Figure 6). GM-CFU growth from the pre-diluent bone marrow treated with budesonide or PGE2 prior to the addition of postdiluent serum was not different than that from untreated marrow in all three culture media (P > 0.05) (Figure 6). Similar effects were seen when G-CSF and SCF were used as growth conditions (Figure 6).
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Discussion |
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Materials & Methods
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In this study, we have demonstrated that the hemopoietic effect of post-allergen challenge serum from dogs developing airway hyperresponsiveness after allergen inhalation challenge is prevented by prior treatment in vitro of the bone marrow with either budesonide or PGE2. However, treatment in vitro of bone marrow aspirated after allergen challenge, with either budesonide or PGE2, had no effect on the increase in bone marrow progenitors.
The portion of the results demonstrating allergen- induced increases in GM-CFU formation and the hemopoietic effect of post-allergen serum (Figure 4) has been previously published (18). The important novel findings in the current publication are the in vitro treatment effects from budesonide and PGE2.
These findings suggest that to be effective, treatment of bone marrow with either budesonide or PGE2 must occur prior to its exposure to the allergen-induced hemopoietic factor(s). Presumably the post-allergen bone marrow had already been exposed to these factor(s) in vivo and that, by the time of marrow aspiration, 24 h after allergen challenge, it was too late for either treatment to reverse the process of induction of granulocyte progenitor growth and differentiation. This observation is perhaps not surprising, given that both inhaled corticosteroids or PGE2 need to be given prior to or, in the case of corticosteroids, shortly following allergen exposure in order to prevent allergen- induced late asthmatic responses (19, 20, 26).
It is possible that the duration of in vitro treatment with
budesonide and PGE2 may have influenced our results. The
post-challenge bone marrow was treated for 2 h prior to
adding post-challenge serum and setting up of colony cultures, whereas the pre-challenge bone marrow was treated
for 24 h prior to the addition of post-challenge serum and
setting up of colony cultures. This time difference existed
because of the necessity of incubating the pre-challenge bone marrow for 24 h until the post-challenge serum was
available. Because of the concern of treatment duration
effects, we incubated post-allergen challenge bone marrow
from two dogs for 24 h either with added diluent, PGE2
(106 M), or budesonide (107 M). Neither treatment was
effective in attenuating the allergen-induced increase in
colony numbers (unpublished observation).
The concentration of budesonide used in these studies
was 107 M. This was chosen because this was the highest
plasma concentration measured in dogs following budesonide inhalation in vivo which was previously found to be
effective in attenuating allergen-induced airway hyperresponsiveness and increased bone marrow hemopoietic activity (17). The concentration of PGE2 in vitro treatment was 106 M. This concentration was chosen because it has
been shown to be effective in vitro in modulating release
or production of several pro-inflammatory mediators (27-
30). However, the pharmacokinetics of inhaled PGE2 have
not been studied in dogs, and it is not known whether
these concentrations are achieved in plasma. Obviously, the
pharmacodynamics of both budesonide and PGE2 are dose-dependent. However, in this study, we have chosen single
doses of each compound rather than to measure dose-
response characteristics. This decision was based on the number of colony assays we are capable of running at a single
time. It is likely that further important information would be
gained through repeating these studies at different dosages. For example, it is possible that at higher doses of budesonide or PGE2, the treatment of post-allergen challenge
bone marrow may be effective. Furthermore, comparing
the maximal degrees of colony suppression by budesonide
and PGE2 may provide valuable insight as to whether they
share mechanisms of action in this effect. Clearly, having
established that both compounds are effective, the next
step in determining mechanisms of action is to determine and compare their dose-response characteristics.
Inhaled corticosteroids, including budesonide, have been shown to be effective in preventing allergen-induced late asthmatic responses and airway hyperresponsiveness and allergen-induced airway inflammation in stable asthmatics (12, 13, 19). Inhaled PGE2 has also been shown to be effective in preventing allergen-induced early and late asthmatic responses and airway hyperresponsiveness (20). The proposed mechanisms by which both corticosteroids and PGE2 protect against airway responses have to date focused on the prevention of formation and release of mediators that activate and recruit inflammatory cells into the airway (12, 13, 20). In an earlier study, using Ascaris-sensitized dogs, we observed that inhaled budesonide attenuates both allergen-induced airway hyperresponsiveness and increases in bone marrow GM-CFU (17). In that study, we hypothesized that the inhaled corticosteroid was preventing the production and/or release of pro-inflammatory/hemopoietic factors from the airway, thus removing a stimulus to increased bone marrow progenitor formation. While this hypothesis may still hold, the current findings indicate that both corticosteroids and PGE2 can also prevent progenitor growth and differentiation by directly "protecting" the marrow from the effects of the serum hemopoietic factor(s), presumably generated from the challenged airway. Thus, the bone marrow can be considered as a possible site of action for corticosteroids or other medications effective in allergen-induced airway responses.
In previous studies, we hypothesized that the serum factor that stimulates bone marrow progenitor formation was one of the hemopoietic cytokines, known to be produced/released at the airway during allergic airway responses (17), such as GM-CSF (31). However, results from the current study suggest that this may not be the case. If the serum factor were GM-CSF, G-CSF, or SCF, then the treatment with budesonide or PGE2 should at least partially attenuate each of these cytokine's hemopoietic effects on the bone marrow after diluent challenge. However, in contrast to the effects of budesonide and PGE2 in preventing the hemopoietic effect of the post-allergen serum, the GM-CFU growth stimulated by GM-CSF, G-CSF, or SCF was not different for the budesonide or PGE2 treated bone marrow, compared with the untreated bone marrow after diluent challenge (Figure 5). Thus, overall, it appears unlikely that the hemopoietic serum factor is GM-CSF, G-CSF, or SCF acting alone.
In vitro studies on the mechanisms of action of corticosteroids have demonstrated that they prevent the formation and release of pro-inflammatory mediators (12, 13). Furthermore, in vitro studies on the mechanism of action of PGE2 point to the modulation of pro-inflammatory mediator release (27, 32, 33), in addition to smooth muscle relaxation (34, 35). Our finding that both corticosteroids and PGE2 prevent the hemopoietic effects of the serum factor should provide some insight into the factor's identity; however, a common mechanism by which both agents antagonize the hemopoietic activity of a known mediator has not been identified. One possible explanation is that the serum signal is not itself a hemopoietic cytokine, but rather a factor which, at the level of the bone marrow, acts by stimulating the production/release of hemopoietic cytokines and/or acts in concert with these. If this were the case, then the known actions of both corticosteroids and PGE2 in attenuating production/release of pro-inflammatory (including hemopoietic) cytokines might explain the observations made in this study. This hypothesis will require either the measurement of cytokines generated in the bone marrow as a result of added serum, or blocking specific cytokines and preventing the hemopoietic effect of the added serum. Either of these approaches will require the development of specific canine anti-antibodies, or development of another animal model, where these blocking antibodies are available.
In summary, we have observed that the increased hemopoietic activity in naive bone marrow, stimulated by serum obtained 24 h after allergen inhalation from sensitized dogs, can be prevented by prior incubation of the marrow with either budesonide or PGE2, while neither drug itself can attenuate the hemopoietic activity in bone marrow aspirated 24 h after allergen inhalation. These results raise the possibility that part of the activity of drugs which are inhaled and believed to act topically to attenuate allergen-induced airway responses may also have a systemic activity at the level of the bone marrow to prevent allergen-induced bone marrow stimulation from occurring and contributing to the inflammatory process.
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Footnotes |
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Abbreviations: Ascaris suum, A. suum; eosinophil-basophil colony forming units, Eo-CFU; granulocyte stimulating factor, G-CSF; granulocyte-macrophage colony forming units, GM-CFU; granulocyte/macrophage colony stimulating factor, GM-CFS; prostaglandin E2, PGE2; stem cell factor, SCF.
(Received in original form August 20, 1996 and in revised form March 12, 1997).
Acknowledgments: The authors gratefully acknowledge the technical support provided by Jennifer Wattie and Cathy Lane. Mark D. Inman is a Canadian Lung Association/Medical Research Council of Canada Fellow. Paul M. O'Byrne is a Medical Research Council of Canada Senior Scientist. This work was supported by Astra Draco AB and the Medical Research Council of Canada.
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References |
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References
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