|
|
||||||||
Cutting Edge |



*
R&D Center, BML, Saitama, Japan;
Graduate School of Science and Engineering and
Department of Environmental Sciences, Faculty of Science, Ibaraki University, Ibaraki, Japan; and
Human Gene Sciences Center, Tokyo Medical and Dental University, Tokyo, Japan
| Abstract |
|---|
|
|
|---|
i-dependent manner as PGD2 did.
Other nonsteroidal anti-inflammatory drugs (aspirin, sulindac,
diclofenac, and acemetacin) had no such effect even at micromolar
concentrations. In chemotaxis assay, three CRTH2-expressing cell types,
Th2 cells, eosinophils, and basophils, were all
significantly attracted by indomethacin (EC50, 50500 nM)
as well as by PGD2 (EC50, 220 nM), and the
effects of indomethacin were blocked by anti-CRTH2 mAb. These
results suggest the involvement of CRTH2 in mediating some of
therapeutic and/or unwanted side effects of indomethacin, independently
of cyclooxygenases and peroxisome proliferator-activated
receptors. | Introduction |
|---|
|
|
|---|
s-type G protein, induces cAMP generation, and is generally
thought to be involved in relaxant/inhibitory activities of
PGD2 such as inhibition of platelet
aggregation, relaxation of various smooth muscles, and inhibition of
cell migration (3, 7, 8, 9). Moreover, DP was also shown to
contribute to the formation of allergic inflammations by unknown
mechanisms in studies with DP-deficient mice (10).
In contrast to DP, CRTH2 is coupled with
G
i-type G protein and is thought to be involved
in stimulatory activities of PGD2 such as
induction of cell migration and up-modulation of adherent molecules
(8, 11). CRTH2 is intriguing in that it is selectively
expressed in allergy-related cell types, including Th2 cells, T
cytotoxic 2 cells, eosinophils, and basophils, and in yet
unidentified monocyte/dendritic cell-like leukocytes
(12, 13, 14, 15). However, exact roles of CRTH2 in vivo still
remain to be examined due to the lack of selective agonists and
antagonists. Prostanoids including PGD2 are synthesized in various tissues by the constitutive enzyme cyclooxygenase (COX)-1 and its inducible isoform COX-2 (16, 17). Indomethacin and other nonsteroidal anti-inflammatory drugs (NSAIDs) have the ability to inhibit the activity of COX, a property that accounts for their shared therapeutic effects (18). In the course of identification of PGD2 as a sole CRTH2 agonist produced by mast cells (8), indomethacin was used to suppress PGD2 production. We unexpectedly found that indomethacin by itself has an agonistic effect on CRTH2. In this paper, we present evidence that indomethacin appears to be unique among various NSAIDs in that it can effectively activate CRTH2 to induce cell migration in Th2 cells, eosinophils, and basophils, independently of its anti-COX activity.
It has been well appreciated that indomethacin and eicosatetraynoic acid, an inhibitor of lipoxygenases, can inhibit the binding of some chemotactic peptides to leukocytes at high concentrations (19, 20). Our finding is interesting in view of the clinical significance because it shows that a widely used inhibitor of COXs can stimulate rather than inhibit a chemoattractant receptor and actually lead to cell migration in particular cell types of leukocytes at usual therapeutic concentrations.
| Materials and Methods |
|---|
|
|
|---|
Aspirin, diclofenac, sulindac, and acemetacin (1-(p-chlorobenzoyl)-5-methoxy-2-methylindole-3-acetic acid carboxy-methyl ester) were purchased from Sigma-Aldrich (St. Louis, MO). Indomethacin was purchased from Wako Pure Chemical (Osaka, Japan) and Sigma-Aldrich. PGD2 was obtained from Cayman Chemicals (Ann Arbor, MI). Thrombin and monocyte chemotactic protein-1 (MCP-1) were obtained from Sigma-Aldrich and PeproTech (Rocky Hill, NJ), respectively. CRTH2-specific rat mAbs BM7 and BM16 were described previously (12, 13). PerCP-conjugated anti-CD4 mAb (clone Leu-3a) and FITC-conjugated anti-CD3 mAb (Lue-4) were purchased from BD Biosciences (San Jose, CA). PE-labeled streptavidin was obtained from Life Technologies (Long Island, NY).
Cells
K562 and Jurkat lines were transfected with a CRTH2 expression vector pRc/B19 (12), a DP expression vector pRc/DP (8), or a control vector pRc/CMV (Invitrogen, San Diego, CA) and cloned as described (12). Human Th1 and Th2 lines were generated as described in our previous report (12). PBMCs and granulocytes were isolated from heparinized peripheral blood of consenting healthy subjects by density gradient centrifugation on Mono-Poly Resolving Medium (Dainippon Pharmaceutical, Osaka, Japan). CD16- leukocytes were purified with anti-CD16 microbeads on MACS system (Miltenyi Biotec, Bergisch Gladbach, Germany) as described (8).
Ligand binding, Ca2+ mobilization, and chemotaxis assays
Ligand binding, Ca2+ mobilization, and chemotaxis assays were performed as described (8, 13). For inactivation of G proteins, cells (2.5 x 106/ml) were incubated in RPMI 1640 medium containing 10% FBS (growth medium) with 1 µg/ml of either pertussis toxin (PTX; Sigma-Aldrich) or cholera toxin (CTX; Sigma-Aldrich) at 37°C for 2 h. In some cases, cells were pretreated with 600 µg/ml of either BM7 or normal rat IgG for 20 min at room temperature before being subjected to the assays.
Receptor down-modulation assay
Th2 cells were incubated in growth medium with various concentrations of test compounds for 60 min at 37°C. The cells were washed twice with PBS and then stained with biotinylated BM16 and PE-labeled streptavidin, along with PerCP-conjugated mAb to CD4 and FITC-labeled mAb to CD3, as described (13). The stained cells were analyzed by three-color flow cytometry on aFACSCalibur flow cytometer using CellQuest software (BD Biosciences).
| Results |
|---|
|
|
|---|
As reported previously (8),
PGD2 induced Ca2+
mobilization in both CRTH2-transfected (K562/CRTH2) and DP-transfected
(K562/DP) K562 cells at nanomolar concentrations
(EC50, 15 nM) but not in mock-transfected K562
(K562/neo) cells even at 2.5 µM (Fig. 1
A). Indomethacin induced
Ca2+ mobilization in K562/CRTH2 cells at
submicromolar concentrations (approximate EC50,
50 nM) with around one order of magnitude lower potency than that of
PGD2; however, it induced no significant
Ca2+ mobilization in K562/DP and K562/neo cells
even at 2.5 µM (Fig. 1
A). Similar results were obtained in
transient transfection experiments with the parental K562 line (data
not shown). Four different lots of indomethacin samples (the purity of
each was >99%) showed identical potencies, and following their
reversed-phase chromatography purification on µRPC C2/C18 SC 2.1/10
column (Amersham Pharmacia Biotech, Uppsala, Sweden), the agonist
activity was exclusively confined in the major peak fraction of each
indomethacin sample, indicating that indomethacin by itself was the
active substance. Interestingly, no Ca2+
mobilization was induced in K562/CRTH2 cells by up to 10 µM of other
NSAIDs tested (aspirin, dichlofenac, acemetacin, and sulindac) or of an
indomethacin analog indoleacetic acid (Fig. 1
A and data not
shown). Furthermore, prior inactivation of COXs by aspirin (500
µg/ml) or diclofenac (500 µg/ml) did not inhibit the
indomethacin-induced Ca2+ mobilization in
K562/CRTH2 cells (Fig. 1
A and data not shown). These results
indicated that COX products were not involved in this system.
|
i inhibitor PTX but not by a
G
s inhibitor CTX, as that of PGD2 (Fig. 1Induction of Ca2+ mobilization and CRTH2 down-modulation by indomethacin in Th2 cells
Cultured Th2 but not Th1 cells constitutively expressed CRTH2
(12) and showed Ca2+ mobilization in
response to indomethacin as well as to PGD2 (Fig. 2
A). The effect of
indomethacin was selectively inhibited by BM7 (Fig. 2
B) and
was again sensitive to PTX but not to CTX (data not shown). We further
confirmed the selective interaction between CRTH2 and indomethacin by a
ligand-induced receptor down-modulation assay. As shown in Fig. 2
C, surface CRTH2 expression was selectively down-modulated
by PGD2 and indomethacin at nanomolar to
micromolar concentrations without any significant change in the levels
of other irrelevant cell surface molecules, CD4 and CD3 (data not
shown).
|
Previous studies showed that CRTH2 mediates
PGD2-dependent cell migration (8).
Therefore, we next examined effects of indomethacin on cell migration
using four different CRTH2-expressing cell types. CRTH2-transfected
Jurkat cells (Jurkat/CRTH2) were indeed attracted by indomethacin and
PGD2 (approximate EC50, 50
nM and 1 nM, respectively) but mock-transfected Jurkat cells
(Jurkat/neo) were not (Fig. 3
A). DP-transfected Jurkat
cells (Jurkat/DP) were suppressed in their spontaneous migration by
PGD2, as shown previously (8), but
not by indomethacin (Fig. 3
A). Indomethacin and
PGD2 also induced chemotactic migration of Th2
but not Th1 cells at submicromolar concentrations
(EC50, 50100 nM and 23 nM, respectively; Fig. 3
B). When total peripheral blood leukocytes were examined,
only basophils and eosinophils were significantly attracted
by indomethacin at 1.25 µM or lower concentrations as well as by
PGD2 (EC50, 300500 nM for
indomethacin and 1020 nM for PGD2; Fig. 3
, C and D). A neutralizing anti-CRTH2 mAb BM7
but not control rat IgG significantly blocked the migratory responses
to indomethacin of Th2 cells, basophils, and eosinophils
(Fig. 3
E). Similar results were obtained in three
independent pairs of Th1 and Th2 lines and leukocytes from two
different donors. Taken together, these results demonstrate that, like
PGD2, indomethacin induces cell migration
via CRTH2.
|
| Discussion |
|---|
|
|
|---|
and, possibly, PPAR
and
induces adipocyte differentiation at micromolar concentrations
(24).
In this study we present several lines of evidence to demonstrate that
indomethacin can directly activate CRTH2 independently of COXs and
PPARs. First, induction of Ca2+ mobilization
and/or chemotaxis by submicromolar concentrations of indomethacin was
consistently observed in CRTH2-expressing cells regardless of cell
types, while it was not observed in cells lacking CRTH2. Second, such
effects of indomethacin were always blocked by an anti-CRTH2 mAb
BM7, or the effects were completely canceled by prior desensitization
with natural CRTH2 ligand PGD2. Conversely,
binding of [3H]PGD2 to
CRTH2 was specifically inhibited by indomethacin. These findings
demonstrate the direct interaction between indomethacin and CRTH2.
Third, other potent COX inhibitors such as aspirin and diclofenac
(22) showed little, if any, effect even at 10 µM, and
prior inactivation of COXs could not affect indomethacin actions. These
findings demonstrate lack of contribution of COXs to this system and
uniqueness of indomethacin among tested NSAIDs, which may imply that
the CRTH2 mechanisms could not contribute significantly to a wide range
of adverse effects of indomethacin that are common to other NSAIDs.
Finally, the reported concentrations of indomethacin required to induce
adipocyte differentiation via PPARs (10100 µM) (24)
are two to three orders of magnitude higher than that required to
induce Ca2+ mobilization or chemotaxis in
CRTH2-expressing cells. Moreover, in the immune system, activation of
PPAR
is generally associated with an inhibitory nature as shown in
monocytes (25) and Th cells (26).
At present, clinical significance of the indomethacin-triggered CRTH2 activation is unclear. It was reported that IC50 values for indomethacin on COX-1 and COX-2 in intact cells were 0.01 µM and 0.6 µM, respectively (16), and that the peak plasma level of indomethacin after the usual therapeutic dose of 25 mg in humans was 0.8 µg/ml (2.2 µM) (21). In this study, we demonstrated that indomethacin can fully activate CRTH2 at submicromolar concentrations in Th2 cells, basophils, and eosinophils. Therefore, it is conceivable that therapeutic concentrations of indomethacin in tissues may be on levels sufficient to activate CRTH2. The direct effects of indomethacin in vivo on Th2 cells, eosinophils, or basophils have not been reported. It is interesting to learn the observation that infiltration of mucosal epithelium by eosinophils was one of the earliest histological features of indomethacin-induced intestinal injury in rats (27). Furthermore, in vitro studies showed that, like PGD2, indomethacin can enhance Ag-induced histamine release from human basophils at submicromolar concentrations (28). The findings may be simply explained by the action of indomethacin on CRTH2. In contrast, PGD2 has recently been shown to have an anti-inflammatory property in rats (5, 6). The action of PGD2 was suggested to be mediated by DP because a DP-specific agonist, BW245C, could mimic the PGD2 effect (6). Indomethacin, an agonist for CRTH2 but not for DP, had no such anti-inflammatory effect in the same report (6). These findings suggest that CRTH2 is not responsible for PGD2-dependent anti-inflammatory action. We thus further speculate a concept that PGD2 exhibits its inhibitory functions via DP and its stimulatory functions through CRTH2 (8, 11), even though the clinical consequences of CRTH2 activation remains largely to be elucidated.
Our present study, which indicates that indomethacin is a potent agonist for CRTH2, provides new insights into the pharmacological actions of indomethacin and, furthermore, the physiological and pathophysiological functions of CRTH2. Studies, especially with specific CRTH2 antagonists or CRTH2-deficient mice, are required to clarify the clinical significance of the CRTH2-mediated activities.
| Acknowledgments |
|---|
| Footnotes |
|---|
2 Abbreviations used in this paper: DP, PG D receptor; CRTH2, chemoattractant receptor-homologous molecule expressed on Th2 cells; NSAID, nonsteroidal anti-inflammatory drug; COX, cyclooxygenase; PPAR, peroxisome proliferator-activated receptor; PTX, pertussis toxin; CTX, cholera toxin; MCP-1, monocyte chemotactic protein-1. ![]()
Received for publication October 16, 2001. Accepted for publication November 28, 2001.
| References |
|---|
|
|
|---|
and
are activated by indomethacin and other non-steroidal anti-inflammatory drugs. J. Biol. Chem. 272:3406.
agonists inhibit production of monocyte inflammatory cytokines. Nature 391:82.[Medline]
and immunoregulation: PPAR
mediates inhibition of helper T cell responses. J. Immunol. 164:1364.This article has been cited by other articles:
![]() |
P. Schratl, J. F. Royer, E. Kostenis, T. Ulven, E. M. Sturm, M. Waldhoer, G. Hoefler, R. Schuligoi, I. Th. Lippe, B. A. Peskar, et al. The Role of the Prostaglandin D2 Receptor, DP, in Eosinophil Trafficking J. Immunol., October 1, 2007; 179(7): 4792 - 4799. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Cossette, S. E. Walsh, S. Kim, G.-J. Lee, J. A. Lawson, S. Bellone, J. Rokach, and W. S. Powell Agonist and Antagonist Effects of 15R-Prostaglandin (PG) D2 and 11-Methylene-PGD2 on Human Eosinophils and Basophils J. Pharmacol. Exp. Ther., January 1, 2007; 320(1): 173 - 179. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Hori, J. Ishijima, T. Yokomizo, H. Ago, T. Shimizu, and M. Miyano Crystal Structure of Anti-Configuration of Indomethacin and Leukotriene B4 12-Hydroxydehydrogenase/15-Oxo-Prostaglandin 13-Reductase Complex Reveals the Structural Basis of Broad Spectrum Indomethacin Efficacy J. Biochem., September 1, 2006; 140(3): 457 - 466. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. Xue, S. L. Gyles, F. R. Wettey, L. Gazi, E. Townsend, M. G. Hunter, and R. Pettipher Prostaglandin D2 Causes Preferential Induction of Proinflammatory Th2 Cytokine Production through an Action on Chemoattractant Receptor-Like Molecule Expressed on Th2 Cells J. Immunol., November 15, 2005; 175(10): 6531 - 6536. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. N. Hata, T. P. Lybrand, and R. M. Breyer Identification of Determinants of Ligand Binding Affinity and Selectivity in the Prostaglandin D2 Receptor CRTH2 J. Biol. Chem., September 16, 2005; 280(37): 32442 - 32451. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. M. Mathiesen, T. Ulven, L. Martini, L. O. Gerlach, A. Heinemann, and E. Kostenis Identification of Indole Derivatives Exclusively Interfering with a G Protein-Independent Signaling Pathway of the Prostaglandin D2 Receptor CRTH2 Mol. Pharmacol., August 1, 2005; 68(2): 393 - 402. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Mimura, T. Ikemura, O. Kotera, M. Sawada, S. Tashiro, E. Fuse, K. Ueno, H. Manabe, E. Ohshima, A. Karasawa, et al. Inhibitory Effect of the 4-Aminotetrahydroquinoline Derivatives, Selective Chemoattractant Receptor-Homologous Molecule Expressed on T Helper 2 Cell Antagonists, on Eosinophil Migration Induced by Prostaglandin D2 J. Pharmacol. Exp. Ther., July 1, 2005; 314(1): 244 - 251. [Abstract] [Full Text] [PDF] |
||||
![]() |
F. G. Gervais, J.-P. Morello, C. Beaulieu, N. Sawyer, D. Denis, G. Greig, A. D. Malebranche, and G. P. O'Neill Identification of a Potent and Selective Synthetic Agonist at the CRTH2 Receptor Mol. Pharmacol., June 1, 2005; 67(6): 1834 - 1839. [Abstract] [Full Text] [PDF] |
||||
![]() |
I. Spik, C. Brenuchon, V. Angeli, D. Staumont, S. Fleury, M. Capron, F. Trottein, and D. Dombrowicz Activation of the Prostaglandin D2 Receptor DP2/CRTH2 Increases Allergic Inflammation in Mouse J. Immunol., March 15, 2005; 174(6): 3703 - 3708. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. Shiraishi, K. Asano, T. Nakajima, T. Oguma, Y. Suzuki, T. Shiomi, K. Sayama, K. Niimi, M. Wakaki, J. Kagyo, et al. Prostaglandin D2-Induced Eosinophilic Airway Inflammation Is Mediated by CRTH2 Receptor J. Pharmacol. Exp. Ther., March 1, 2005; 312(3): 954 - 960. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. N. Hata, T. P. Lybrand, L. J. Marnett, and R. M. Breyer Structural Determinants of Arylacetic Acid Nonsteroidal Anti-Inflammatory Drugs Necessary for Binding and Activation of the Prostaglandin D2 Receptor CRTH2 Mol. Pharmacol., March 1, 2005; 67(3): 640 - 647. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. Monneret, R. Boumiza, S. Gravel, C. Cossette, J. Bienvenu, J. Rokach, and W. S. Powell Effects of Prostaglandin D2 and 5-Lipoxygenase Products on the Expression of CD203c and CD11b by Basophils J. Pharmacol. Exp. Ther., February 1, 2005; 312(2): 627 - 634. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. L. Clarke, M. G. Belvisi, S. J. Smith, E. Hardaker, M. H. Yacoub, K. K. Meja, R. Newton, D. M. Slater, and M. A. Giembycz Prostanoid receptor expression by human airway smooth muscle cells and regulation of the secretion of granulocyte colony-stimulating factor Am J Physiol Lung Cell Mol Physiol, February 1, 2005; 288(2): L238 - L250. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. Bohm, G. J. Sturm, I. Weiglhofer, H. Sandig, M. Shichijo, A. McNamee, J. E. Pease, M. Kollroser, B. A. Peskar, and A. Heinemann 11-Dehydro-thromboxane B2, a Stable Thromboxane Metabolite, Is a Full Agonist of Chemoattractant Receptor-homologous Molecule Expressed on TH2 Cells (CRTH2) in Human Eosinophils and Basophils J. Biol. Chem., February 27, 2004; 279(9): 7663 - 7670. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. J. Holtzman Drug Development for Asthma Am. J. Respir. Cell Mol. Biol., August 1, 2003; 29(2): 163 - 171. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. N. Hata, R. Zent, M. D. Breyer, and R. M. Breyer Expression and Molecular Pharmacology of the Mouse CRTH2 Receptor J. Pharmacol. Exp. Ther., August 1, 2003; 306(2): 463 - 470. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Sugimoto, M. Shichijo, T. Iino, Y. Manabe, A. Watanabe, M. Shimazaki, F. Gantner, and K. B. Bacon An Orally Bioavailable Small Molecule Antagonist of CRTH2, Ramatroban (BAY u3405), Inhibits Prostaglandin D2-Induced Eosinophil Migration in Vitro J. Pharmacol. Exp. Ther., April 1, 2003; 305(1): 347 - 352. [Abstract] [Full Text] |
||||
![]() |
G. Monneret, C. Cossette, S. Gravel, J. Rokach, and W. S. Powell 15R-Methyl-Prostaglandin D2 Is a Potent and Selective CRTH2/DP2 Receptor Agonist in Human Eosinophils J. Pharmacol. Exp. Ther., January 1, 2003; 304(1): 349 - 355. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. E. L. Stubbs, P. Schratl, A. Hartnell, T. J. Williams, B. A. Peskar, A. Heinemann, and I. Sabroe Indomethacin Causes Prostaglandin D2-like and Eotaxin-like Selective Responses in Eosinophils and Basophils J. Biol. Chem., July 12, 2002; 277(29): 26012 - 26020. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |