|
|
||||||||
Depts of 1 Clinical and Laboratory Medicine and 2 Oto-Rhino-Laryngology, Akita University School of Medicine, Akita, Japan
CORRESPONDENCE: J. Chihara, Dept of Clinical and Laboratory Medicine, Akita University School of Medicine, Hondo, Akita 010-8543, Japan. Fax: 81 188362624. E-mail: chihara@hos.akita-u.ac.jp
Keywords: CC chemokine receptor 3, eosinophils, eotaxin, interleukin-5, reactive oxygen species, regulated on activation, normal T-cell expressed and secreted
Received: April 4, 2002
Accepted January 14, 2003
This study was supported by grants-in-aid for Scientific Research from the Ministry of Education and Science, and the Ministry of Health and Welfare (both Tokyo, Japan).
| Abstract |
|---|
|
|
|---|
After pretreatment with chemokines, eosinophils were stimulated with calcium ionophore A23187 [GenBank] . ROS production by eosinophils was measured using luminol-dependent chemiluminescence.
Both RANTES and eotaxin exhibited a priming effect on calcium ionophore-induced ROS production from eosinophils. Despite there being no difference in expression of CC chemokine receptor 3, the priming effect of RANTES and eotaxin was significantly enhanced in eosinophils from the patients. Interleukin-5 further enhanced the priming effect of chemokines in eosinophils from normal subjects, but not those from allergic subjects.
The present results suggest an upregulated response to chemokines in eosinophils from allergic patients, and that interleukin-5 can induce a similar phenotype to that found in vivo in allergic patients.
One characteristic feature of allergic disease is tissue inflammation, involving the activation of T-lymphocytesand eosinophils 1. The severity of allergic disease is influenced bythe degree of eosinophil activation. During the process ofallergic inflammation, eosinophils migrate into tissues andrelease toxic granule proteins and reactive oxygen species (ROS), leading to tissue damage 2.
ROS production is elicited by several stimuli, such as immunoglobulins (Igs) and cytokines 3. It has been previously reported that the signal from adhesion molecules plays a critical role in ROS production by eosinophils 4. TheCC chemokines, especially eotaxin and regulated on activation, normal T-cell expressed and secreted (RANTES), possess a selective chemotactic activity for eosinophils. Besides chemotaxis, these chemokines are involved in eosinophil activation. Indeed, it has been shown recently that chemokines prime ROS production by eosinophils 5, 6.
It has been shown that eosinophils from allergic patients are not equivalent in effector function to those from normalsubjects 79. However, the different response of eosinophils to chemokines has not been fully elucidated. Therefore, in thepresent paper, comparative studies were performed inallergic patients and normal subjects regarding the primingeffects of chemokines on ROS production from eosinophils.
| Materials and methods |
|---|
|
|
|---|
24 h or steroids for
2 weeks before blood collection. Normal subjects were defined on thebasis of a lack of a clinical history of allergy or other similar diseases. All patients had allergic asthma and/or allergic rhinitis, IgE concentrations of >400 International Units (IU)·mL1 and an IgE radioallergosorbent test result of higher than class 3 against at least one of the common airborne allergens, such as house dust mite, pollens or fungi. The numbers of patients with asthma and allergic rhinitis were seven and 11, respectively (three had both asthma and allergic rhinitis). Asthmatic patients participating in the present study met the American Thoracic Society's definition of asthma. Allpatients with allergic rhinitis showed symptoms at the time of blood collection (nasal congestion, sneezing, rhinorrhoea, itchy eyes, etc.). The eosinophil counts in the peripheral blood of patients were significantly higher than those of normal subjects (683.3±374.0 versus 126.0±80.4 cells·mm3; p<0.01).
Eosinophil isolation
Eosinophils were isolated from heparinised venous blood using a modified CD16 negative selection method, as previously described 10. In brief, cells obtained from the buffy coat were incubated with anti-CD16, anti-CD3, anti-CD20 and anti-CD14 monoclonal antibodies (mouse IgG; Nichirei, Tokyo, Japan), and subsequently reacted with antimouse IgG magnetic beads (Dynal, Oslo, Norway). CD16-, CD3-, CD20- and CD14-negative eosinophils were obtained using a magnetic cell-sorting system (Miltenyi Biotec, Bergisch Gladbach, Germany). The purity of the eosinophils was >97%.
Luminol-dependent chemiluminescence
ROS production from eosinophils was examined by means of luminol-dependent chemiluminescence 5. Previously, an apparent effect of eotaxin and RANTES on eosinophil oxidative metabolism was found after 15-min incubation 5, 6. Thus purified eosinophils (1x106 cells·mL1) were suspended in Roswell Park Memorial Institute (RPMI) 1640 medium and incubated with 1100 nM eotaxin (R & D Systems, Minneapolis, MN, USA) or RANTES (Sigma, St Louis, MO, USA) in 96-well flat-bottomed plates in the presence or absence of 1 ng·mL1 interleukin (IL)-5 or granulocyte macrophage-colony stimulating factor (GM-CSF) (R & D Systems) for 15 min at 37°C. In some experiments, eosinophils were pretreated with an anti-IL-5 receptor alpha (IL-5R
) antibody (mouse IgG1
; Pharmingen, San Diego, CA, USA) or an isotype-matched control (Pharmingen), both at 0.2 µg·mL1, for 60 min at 4°C, or a CC chemokine receptor (CCR) 3 antagonist (Compound X; a gift from Banyu Pharmaceutical Co., Ltd., Tsukuba, Japan) for 30 min at 37°C. ROS production was evoked by adding 50 µL calcium ionophore A23187
[GenBank]
(Sigma; final concentration 1x105 M) to 100 µL eosinophil suspension (5x104 cells) containing 0.25 mM luminol (Futaba Medical, Tokyo, Japan). Maximal and integral intensity chemiluminescence were determined for 60 min using an ARGUS-50/2D luminometer (Hamamatsu Photonics, Hamamatsu, Japan).
Flow cytometric analysis of eosinophil surface CC chemokine receptor 3
Purified eosinophils (<1x106 cells) were incubated with a fluorescein isothiocyanate (FITC)-conjugated antihuman CCR3 monoclonal antibody (mouse IgG2; DAKO, Glostrup, Denmark; 0.5 µg·mL1) for 30 min at 37°C. An FITC-conjugated IgG2 isotype-matched control monoclonal antibody (Beckton-Dickinson, San Jose, CA, USA; 0.5 µg·mL1) was applied to assess the degree of nonspecificity. After washing the cells, thestained cells were analysed using a FACScan flow cytometer (Beckton-Dickinson).
Measurement of intracellular calcium concentration
Purified eosinophils from normal subjects were suspended in Hank's balanced salt solution (HBSS) containing Ca2+ (0.14 g·mL1 CaCl2), Mg2+ (0.1 g·mL1 MgCl2·6H2O; 0.1 g·mL1 MgSO4·7H2O) and 2% foetal calf serum (Sigma) at a cell density of2x106 cells·mL1. Fura-2-acetoxymethyl ester (DOJINDO, Kumamoto, Japan) was added at a final concentration of 2 µM. After incubation for 40 min, excess dye was removed by centrifugation for 5 min at 270xg at 4°C, and the cells were resuspended in HBSS containing 20 mM hydroxyethyl piperazine ethane sulphonic acid (HEPES) (pH 7.4) at a concentration of2x106 cells·mL1. Calcium influx was measured using excitation at 340 and 380 nm in a fluorescence spectrometer (ARGUS; Hamamatsu Photonics).
Statistical analysis
Data were analysed using paired and unpaired t-tests, analysis of variance (ANOVA) or the Mann-Whitney U-test. A p-value of
0.05 was considered to indicate significance.
| Results |
|---|
|
|
|---|
|
|
|
|
|
|
|
on allergic eosinophils is able to reverse this augmentative effect on chemokine priming, allergic eosinophils were preincubated with the anti-IL-5R
antibody prior to eotaxin stimulation. Blockade of the IL-5 receptor did not affect the priming effect of eotaxin in allergic eosinophils (156.6±10.2 versus 159.6±18.8% control integral chemiluminescent intensity, eotaxin alone versus eotaxin plus anti-IL-5R
; n=4).
Effect of interleukin-5 on chemokine-induced calcium influx in eosinophils
In order to study whether IL-5 modulates the downstream signalling of CCR3 to enhance the response to eotaxin, the effect of IL-5 on chemokine-induced calcium influx was investigated. However, IL-5 did not affect the calcium influx induced by eotaxin (fig. 8
).
|
| Discussion |
|---|
|
|
|---|
Moreover, in the present study, functional upregulation of the response to chemokines in ROS production by eosinophils obtained from allergic patients was observed. The priming effect of both RANTES and eotaxin on ROS production was significantly greater than that on eosinophils from normal subjects. Even at the suboptimal dose for eosinophils from normal subjects, eosinophils from allergic patients showed enhanced ROS production after treatment with chemokines. These results suggest that eosinophils from allergic patients are more sensitive and responsive to chemokines.
It has been reported that eotaxin and IL-5 cooperate to regulate eosinophil trafficking during allergic inflammation 20, 21. Schweizer et al. 22 reported that chemokine-induced responses are very sensitive to priming by cytokines such as IL-5. Therefore, in order to extend understanding of these upregulated sensitivities and their responsiveness to chemokines, the possible involvement of cytokines, such as IL-5 and GM-CSF, in the priming effect of chemokines was examined. It was demonstrated that a low concentration (1 ng·mL1) of IL-5 enhanced chemokine-primed ROS production by eosinophils, suggesting that IL-5 may enhance the responsiveness to chemokines. Although a similar tendency has been observed in other eosinophil functions, such as degranulation and migration 14, 22, 23, this is the first report of a priming effect of IL-5 on chemokine-primed ROS production from eosinophils. Interestingly, no augmentative effect of GM-CSF was demonstrated despite the ß subunit (ßc) being common to both IL-5 and GM-CSF receptors. Although ßc plays a major role in IL-5 signalling 24, recent evidence indicates that the specific IL-5 receptor IL-5R
is also involved in signal transduction. Geijsen et al. 25 have cloned an IL-5R
-associated molecule, syntenin, which is required for activation of the transcription factor Sox4. IL-5R
also associates with a novel signalling molecule, IL-5 receptor-interacting protein, which activates Lyn and Hck in eosinophils 26. Therefore, these IL-5R
-specific molecules may be responsible for the distinct response to IL-5.
It has been reported that IL-5 is produced by eosinophils themselves, especially in allergic conditions 27. One possibility is that allergic eosinophils can be primed by IL-5 produced by themselves. However, it was demonstrated thatblockade of the IL-5 receptor on allergic eosinophils could not reverse the priming effect of chemokines. This resultindicates that the upregulated response to chemokines observed in allergic eosinophils was not elicited by IL-5 produced after eosinophil isolation. Moreover, the augmentative effect of IL-5 was observed only in eosinophils from normal subjects and not in those from allergic patients. This distinct phenotype is in line with data demonstrating in vivo priming of adhesion-associated responses of peripheral blood eosinophils of patients with allergic diseases 13, 14. Therefore, eosinophils from allergic patients may undergo IL-5 exposure in the blood stream, resulting in great enhancement of responsiveness to chemokines, as demonstrated in the present study.
The possibility of differences in expression of CCR3 as a means of explaining the different responses to chemokines was examined, but no significant difference was found in CCR3 expression between patients and normal subjects. Furthermore, CCR3 expression of eosinophils did not change after treatment with IL-5. These observations suggest that functional upregulation of response through CCR3 in allergic patients does not depend on an increase in CCR3 expression. As regards signalling of eosinophils, it was examined whether IL-5 modulates the calcium mobilisation induced by chemokines. However, IL-5 did not affect the intracellular calcium influx induced by eotaxin. It has recently been reported that the baseline activity of phosphatidylinositol 3-kinase is elevated in allergic patients compared to normal subjects, together with involvement of IL-5 in phosphatidylinositol 3-kinase activation 28, 29. Thus, it may be assumed that IL-5 modulates the downstream signalling of CCR3 to enhance the response to eotaxin. Beside the involvement of cytokines, such as IL-5, in the upregulated response of eosinophils from allergic patients to chemokines, it can be presumed that other mechanisms, such as CCR3 polymorphism 30 and change in affinity/avidity, are involved. Recently, CCR3 has become a target in the treatment of allergic diseases such as asthma, atopic dermatitis and allergic rhinitis. Indeed, an inhibitory effect of CCR3 antagonist on chemokine-mediated eosinophil function has been found (manuscript in preparation).
In conclusion, the present study has demonstrated an enhanced response to chemokines in the reactive oxygen species production of eosinophils from allergic patients, with the possible involvement of interleukin-5 in that enhancement, and without changes in CC chemokine receptor 3 expression. Further studies are required to elucidate the mechanisms of the different responses of CC chemokine receptor 3.
| Acknowledgements |
|---|
|
|
|---|
| References |
|---|
|
|
|---|
interacting protein. Science 2001;293:11361138.
-associated signaling molecule-IRIP that activates Lyn and Hck tyrosine kinases in eosinophils. J Allergy Clin Immunol 2001;107:S147.
R functioning on eosinophils of allergic asthmatics. J Leukoc Biol 2000;68:655661.This article has been cited by other articles:
![]() |
T. V. Grissell, H. Powell, D. R. Shafren, M. J. Boyle, M. J. Hensley, P. D. Jones, B. F. Whitehead, and P. G. Gibson Interleukin-10 Gene Expression in Acute Virus-induced Asthma Am. J. Respir. Crit. Care Med., August 15, 2005; 172(4): 433 - 439. [Abstract] [Full Text] [PDF] |
||||
![]() |
N. Skorohod and D. B. Yeates Superoxide dismutase failed to attenuate allergen-induced nasal congestion in ragweed-sensitized dogs J Appl Physiol, April 1, 2005; 98(4): 1478 - 1486. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |