Jpn. J. Pharmacol. 90, 7 – 11 (2002)
REVIEW
—Current Perspective—
Mast Cells as a Target of Rheumatoid Arthritis Treatment
Yuta Kobayashi* and Hideki Okunishi
Department of Pharmacology, Shimane Medical University, Izumo 693-8501, Japan
Received April 18, 2002
ABSTRACT—Rheumatoid arthritis (RA) is a chronic inflammatory disease and its exact cause and pathophysiological process remain unclear. Fibroblast-like synoviocytes, macrophages and T lymphocytes are
considered to be the major contributors in the pathophysiological process of RA; however, an increasing
number of papers have drawn attention to the potential role of mast cells (MCs) in the process. In an animal
model of RA, we reported an increase in MC numbers in the arthritic region, which agreed with the observation in human RA. In addition, a good correlation between the number of MCs and the development of
disease was observed. However, there has been little experimental or clinical evidence of the beneficial
effects of the modification of MC activity on the pathogenesis of RA and this is the weak point of the
hypothesis. We therefore studied the effects of a MC-stabilizing compound, cromoglicate lisetil (CL), which
is an orally deliverable prodrug of cromolyn sodium, on the RA disease model. The MC-stabilizer had
efficacy in a mouse model. The beneficial effects of CL in this animal model further suggested the contribution of MCs in the pathophysiological process of RA. Concerning the contributive mechanism of MC on
the pathogenesis of RA, our results using a disease model suggested that activation of MC chymase and
matrix metalloproteinases might be involved. MC is now considered to be one of the targets of RA treatment.
Keywords: Mast cell, Rheumatoid arthritis, Collagen arthritis, Cromolyn, Matrix metalloproteinases
Introduction
Rheumatoid arthritis (RA) is an autoimmune disease in
which persistent inflammatory synovitis, then cartilage
destruction, bone erosions, and finally changes in joint
integrity are observed (1). Genetic risk factors for RA
such as HLA-DR4 alleles are known; however, they do not
fully account for the incidence of RA, and environmental
factors also play a role in the etiology of the disease (1).
The exact cause and pathophysiological process of RA
remain unclear.
Various drugs such as steroids, non-steroidal antiinflammatory drugs, and disease-modifying anti-rheumatic
drugs are prescribed for RA patients. However, all these
drugs have the limitation of insufficient clinical remission,
especially for joint damage, and considerable risk of
adverse effects has been known (2, 3). Although combination therapies of agents have been developed (3), some RA
patients are still not satisfactorily palliated. The development of novel drugs for RA from new aspects is desired.
Pathologically, fibroblast-like synoviocytes, macrophages
and T lymphocytes have been considered to be the three
major contributors among a number of cells thought to be
involved in the initiation and development of RA (4)
(Fig. 1). T lymphocyte is the predominant infiltrating cell
in the rheumatoid synovium. Activated synoviocytes are
particularly prominent in the lining layer and at the interface with bone and cartilage. Activated synoviocyte is
considered as a kind of fibroblast and it is called the
fibroblast-like synoviocyte (4). The rheumatoid synovium
is characterized by the presence of a number of secreted
products of activated T cells, macrophages and fibroblastlike synoviocytes.
Mast cells (MCs) are multifunctional cells of the immune
system and the role of MCs in the acute inflammation
process has been well established. In addition, an increasing body of evidence has drawn attention to the possible
contribution of MCs in the pathophysiological process of
RA (for review see refs. 5 and 6) (Fig. 1). In this review,
we will discuss the role of MC on the pathogenesis of
RA based on our recent results.
*Corresponding author. FAX: +81-853-20-2130
E-mail: [email protected]
Mast cells in rheumatoid arthritis and its models
MCs are usually distributed throughout the normal
7
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Y. Kobayashi & H. Okunishi
We reported an increase in MC numbers in the arthritic
region of the CII-immunized mice (19). Then, we compared CIA of 3 strains of rats among which the severity
of arthritic response was different (20). The numbers of
MCs in the arthritic region of the CII-immunized rats
increased; however, those in the non-arthritic region of the
same animals did not change. MC numbers in the arthritic
region and arthritic scores showed a good correlation in
the 3 strains of CII-immunized rats. Thus, similar changes
in MC numbers in the arthritic region of the disease model
and RA patients were observed.
Fig. 1. Scheme showing major contributors in the pathophysiological process of rheumatoid arthritis. Fibroblast-like synoviocytes,
macrophage and T lymphocytes are considered to be the major
contributors (see text). Activated synoviocytes are particularly
prominent in activated synovium and they are considered as a kind
of fibroblasts; thus, they are called the fibroblast-like synoviocytes
(4). Mast cells are also considered to have an important role. Mast
cell products stimulated fibroblast-like synoviocytes or macrophages
to produce the matrix metalloproteinases (MMPs). Mast cell chymase
have been suggested to destroy the matrix by activating MMPs.
connective tissues including the synovium (5). Numerous
potent proinflammatory and fibrogenic mediators and
various cytokines are expressed in MCs and their release
may affect the pathogenesis of RA (for review see refs. 6
and 7). Various studies have suggested the contribution of
MCs on the process of chronic inflammation and matrix
degradation involved in the pathogenesis of RA (8 – 15,
for review see refs. 5 – 7). In a significant proportion of
rheumatoid specimens, MC activation or degranulation has
been demonstrated at sites of cartilage erosion (8, 9). Most
quantitative studies have reported an increase in the number
of MCs in the synovium and fluids from RA patient joints
compared with that from normal joints (8, 10, 11), especially
at sites of cartilage erosion (12). A positive correlation was
noted between clinical parameters of disease activity and
the number of MCs in the synovial tissue (10, 11). Clinical
improvement with some drug therapy can be accompanied
by a decrease in MC numbers (11). An increase in the levels
of MC-derived mediators, including histamine, heparin,
chymase, and tryptase, has been observed in the inflamed
synovial fluid (9, 12, 13). Thus, an increase in MC numbers
is considered to be a symptom of the disease, although
degeneration of some MCs occurred in parallel during the
pathological process and MC-derived mediators should be
important for the process.
Collagen-induced arthritis (CIA) in experimental animals
is a disease model of human RA (16, 17). Chronic joint
inflammation was observed in bovine type II collagen (CII)immunized mice and this model has also been demonstrated
to share many characteristics with human RA (2, 17, 18).
Mast cells as a target of rheumatoid arthritis treatment
A possible role of MC in the pathophysiological processes of RA has been suggested as above. However, there
has been little experimental or clinical evidence of the
beneficial effects of the modification of MC activity on the
pathogenesis of RA or its animal models and this is the
weak point of the hypothesis. We therefore studied the
effects of MC-stabilizing compounds on the RA disease
model to clarify the role of MC in the pathogenesis of RA.
Cromolyn sodium is widely used for prophylactic treatment of allergic diseases as a prototype of MC-stabilizing
compounds (21). However, it is hardly absorbed from
the digestive tract. Then, an orally deliverable prodrug,
cromoglicate lisetil (CL), was designed (22). So we studied
the effects of orally applied CL on arthritis in CII-immunized mice (23).
CL was applied to CIA mice for 6 weeks, starting after
the apparent occurrence of arthritis. The arthritis scores
increased significantly in the non drug-treated CIA mice,
whereas elevation of the scores was suppressed by CLtreatment, indicating the beneficial effects of the prodrug
of cromolyn sodium, CL. The drug also improved the
radiographic scores of phalangeal destruction. The decrease
in the radiographic scores and pathohistological observations indicated the efficacy of CL on the improvement of
joint destruction in CIA mice. Thus, CL evidently inhibited
the arthritis development including phalangeal destruction.
The increase of the number of MCs in the arthritic region
of the non-treated CII-immunized mice was suppressed by
CL-treatment (Fig. 2). Furthermore, we found a correlation
between the reduction in MC numbers in the arthritic region and the improvement of arthritis by the drug.
Efficacious treatment with CL on CIA may support the
hypothesis that MCs are important in the pathogenesis of
the RA model. However, pemirolast, another MC-stabilizing drug, was not effective in this disease model, indicating
that not all MC-stabilizing drugs may have the same antiRA effect.
There is a possibility that cromolyn sodium affects other
systems as well as MCs directly (for review, see ref. 24).
For example, IgE synthesis in human B cells was blocked
Mast Cells in Rheumatoid Arthritis
9
Fig. 2. Mast cell numbers in the arthritis region or corresponding
region of mice. The mast cell number increased significantly in
collagen-induced arthritis mice (Collagen). The increase in mast
cell number was significantly inhibited by a mast cell-stabilizer,
cromoglicate lisetil (CL). CL (100 mg /kg per day) was given to
CII-immunized mice once daily for 6 weeks, starting when arthritic
symptoms became evident. Mean ± .S.E.M. Numbers in each of the
columns indicate the number of animals. ###P<0.001 vs. control
group. **P<0.01 vs. collagen-induced arthritis group. (Reproduced
from ref. 23 with modification)
by cromolyn in vitro (25). Further study is necessary to
clarify whether the direct target of CL in the present disease
model is MCs and /or other cells, although the increase in
MC numbers at the arthritic site was suppressed by CL.
Cromolyn has been used clinically with relative safety.
Further studies on the mechanism of action of CL may
contribute to the development of novel drugs for controlling RA in the future.
In the case of cyclosporin A (CsA) treatment in the disease model mice, the number of MCs in the CsA-treated
CIA mice was lower than that in the normal control mice.
However, suppressed but apparent arthritis was observed
in the CsA-treated CIA mice. These results indicate that
MC is not the sole factor in the pathogenesis of the present
disease model (Y. Kobayashi et al., unpublished observation).
Possible mechanism of the contribution of mast cells on
the pathogenesis of rheumatoid arthritis
The pathophysiological role of MCs in RA is probably
very complex and is just starting to be outlined. Because
large amounts of various proinflammatory mediator substances and cytokines, such as tumor necrosis factor (TNF)= , were produced and stored by MCs, they can release such
compounds in response to cell activation (5, 9). Their activation affects the matrix turnover as well as the neighboring cells.
Fig. 3. Immunostaining for MMP3 in the normal (Top) and the
collagen-immunized arthritic (Bottom) joints of mice. Deformity
of the cartilage and pannus formation are evident in the arthritic joint
of collagen-immunized mice and there are many MMP3-positive
cells in the arthritic region. The positive cells in the arthritic joint
are mainly fibroblast-like synoviocytes. The bar indicates 50 m m.
Human MCs can synthesize a variety of immunoregulatory cytokines and chemokines. Some MC-derived
cytokines and chemokines are lymphocyte chemotactic
factors and they may contribute to lymphocytes, especially
T lymphocytes infiltration at sites of tissue damage in RA
(6). The activation of MCs also induced macrophages to
increase interleukin (IL)-1 production (26). Increased IL-1
may affect fibroblasts. The induction of migration and
proliferation of fibroblasts by MCs has been demonstrated
and results in the acceleration of fibrosis (27). Such a
complex interaction among synovial cells including MCs
may be important in the pathogenesis of RA (Fig. 1).
Synovial MCs may also be important in cartilage destruction and bone remodeling (5). MC products stimulated
fibroblast-like synoviocytes or chondrocytes to produce
increased amounts of the matrix metalloproteinases (MMPs)
(Fig. 1) (14, 28). MC tryptase and /or chymase have been
10
Y. Kobayashi & H. Okunishi
shown to destroy the matrix by activating MMPs directly or
indirectly (15, 29). We have already reported the increase
of chymase activity with arthritis in the animal model
(19). Furthermore, we have recently observed immunohistochemically that MMPs such as MMP-2, -3 and -9
also showed parallel changes with the severity of arthritis
in the animal model (Fig. 3). The measurement of the
expression of mRNAs for MMP-2, -3 and -9 in the disease
model by competitive RT-PCR is now in progress. The
importance of MMPs activation on RA pathogenesis has
also been reported in humans (14, 15). The activation of
MMPs may be one of the possible mechanisms of the
contribution of MCs to the arthritic process of RA.
In contrast, MCs may mediate matrix regeneration and
pathological fibrosis as they contain a variety of profibrotic cytokines and growth factors (5, 9, 30). Histamine
is synthesized and released in large quantities by MCs and
its effects are mostly suppressive for acute inflammation
(5). Thus, MCs may exert bi-directional effects on the
matrix turnover.
Closing remarks
There is an increasing body of evidence that MCs represent one of the central components in the inflammatory and
immune responses in RA. The beneficial effects of a
MC-stabilizer, CL, in the CIA model further suggested the
potential contribution of MCs to the pathophysiological
process of RA. Thus, MCs are now considered to be one
of the targets of RA treatment.
Acknowledgments
This work was supported in part by Grants-in-Aid from the
Ministry of Education, Culture, Sports, Science, and Technology,
Japan and a grant from the Smoking Research Foundation, Japan. CL
was kindly donated from Kyoto Pharmaceutical Industries, Ltd.,
Kyoto, Japan.
REFERENCES
1 Lipsky PE: Rheumatoid arthritis. In Harrison’s Principles of
Internal Medicine, 15th edn, Edited by Braunwald E et al,
pp 1928 – 1937, MaGrow-Hill, New York (2001)
2 Weinblatt ME: Treatment of rheumatoid arthritis. In Arthritis
and Allied Conditions, 13th edn, Edited by Koopman WJ,
pp 1131 – 1141, Williams & Wilkins, Baltimore (1997)
3 Pincus T, Breedveld FC and Emery P: Does partial control of
inflammation prevent long-term joint damage? Clinical rationale
for combination therapy with multiple disease-modifying antirheumatic drugs. Clin Exp Rheumatol 17, Suppl 18, S2 – S7
(1999)
4 Muller-Ladner U, Gay RE and Gay S: Structure and function
of synoviocytes. In Arthritis and Allied Conditions, 13th edn,
Edited by Koopman WJ, pp 243 – 254, Williams & Wilkins,
Baltimore (1997)
5 Arnason JA and Malone DG: Role of mast cells in arthritis.
Chem Immunol 62, 204 – 238 (1995)
6 Marone G: Mast cells in rheumatic disorders: mastermind or
workhorse? Clin Exp Rheumatol 16, 245 – 249 (1998)
7 Gordon JR, Burd PR and Galli SJ: Mast cells as a source of
multifunctional cytokines. Immunol Today 11, 458 – 464 (1990)
8 Bridges AJ, Malone DG, Jicinsky J, Chen M, Ory P, Engber W
and Graziano FM: Human synovial mast cell involvement in
rheumatoid arthritis and osteoarthritis. Relationship to disease
type, clinical activity, and antirheumatic therapy. Arthritis
Rheum 34, 1116 – 1124 (1991)
9 Schwartz LB: Mast cells: function and contents. Curr Opin
Immunol 6, 91 – 97 (1994)
10 Gotis-Graham I and McNeil HP: Mast cell responses in rheumatoid synovium. Association of the MCTC subset with matrix
turnover and clinical progression. Arthritis Rheum 40, 479 – 489
(1997)
11 Malone DG, Wilder RL, Saavedra-Delgado AM and Metcalfe
DD: Mast cell numbers in rheumatoid synovial tissues-Correlations with quantitative measures of lymphocytic infiltration and
modulation by antiinflammatory therapy. Arthritis Rheum 30,
130 – 137 (1987)
12 Bromley M and Woolley DE: Histopathology of the rheumatoid
lesion. Identification of cell types at sites of cartilage erosion.
Arthritis Rheum 27, 857 – 863 (1984)
13 Malone DG, Irani A-M, Schwartz LB, Barrett KE and Metcalfe
DD: Mast cell numbers and histamine levers in synovial fluids
from patients with diverse arthritides. Arthritis Rheum 29, 956 –
963 (1986)
14 Tetlow LC, Harper N, Dunningham T, Morris MA, Bertfield H
and Woolley DE: Effects of induced mast cell activation
prostaglandin E and metalloproteinase production by rheumatoid
synovial tissue in vitro. Ann Rheum Dis 57, 25 – 32 (1998)
15 Tetlow LC and Wooley DE: Mast cells, cytokines, and metalloproteinases at the rheumatoid lesion: dual immunolocalisation
studies. Ann Rheum Dis 54, 896 – 903 (1995)
16 Courtenay JS, Dallman MJ, Dayan AD, Martin A and Mosedale
B: Immunisation against heterologous type II collagen induces
arthritis in mice. Nature 283, 666 – 668 (1980)
17 Myers LK, Rosloniec EF, Cremer MA and Kang AH: Collageninduced arthritis, an animal model of autoimmunity. Life Sci
61, 1861 – 1878 (1997)
18 Andriopoulos NA, Mestecky J, Miller EJ and Bradley EL:
Antibodies to native and denatured collagens in sera of patients
with rheumatoid arthritis. Arthritis Rheum 19, 613 – 617 (1976)
19 Kakizoe E, Li S-H, Kobayashi Y, Nishikori N, Dekio S and
Okunishi H: Increases in mast cells and chymase in fibroproliferative paws of collagen-induced arthritic mice. Inflamm
Res 48, 318 – 324 (1999)
20 Zhao H-F, Kobayashi Y, Kakizoe E, Shimoura K and Okunishi
H: Potential pathogenic role of mast cells in type II collageninduced arthritis of rats. Jpn J Pharmacol 79, Suppl I, 289P
(1999)
21 Cox JS, Beach JE, Blair AM, Clarke AJ, King J, Lee TB,
Loveday DE, Moss GF, Orr TS, Ritchie JT and Sheard P:
Disodium cromoglycate (Intal). Adv Drug Res 5, 115 – 196
(1970)
22 Mori T, Nishimura K, Tamaki S, Nakamura S, Tsuda H and
Kakeya N: Pro-drugs for the oral delivery of disodium
cromoglycate. Chem Pharm Bull (Tokyo) 36, 338 – 344 (1988)
23 Kobayashi Y, Shirahase H, Zhao H-F, Kakizoe E and Okunishi
H: Effects of orally available prodrug of cromoglycic acid on
collagen-induced arthritis mice. Folia Pharmacol Jpn (Nippon
Mast Cells in Rheumatoid Arthritis
24
25
26
27
Yakurigaku Zasshi) 114, Suppl 1, 154P – 158P (1999) (text in
Japanese witgh English abstract)
Norris AA: Pharmacology of sodium cromoglycate. Clin Exp
Allergy 26, Suppl 4, 5 – 7 (1996)
Loh RKS, Jabara HH and Geha RS: Disodium cromoglycate
inhibits Sm to Se deletional switch recombination and IgE
synthesis in human B cells. J Exp Med 180, 663 – 671 (1994)
Yoffe JR, Taylor DJ and Wooley DE: Mast cell products
stimulate collagenase and prostaglandin E production by cultures of adherent rheumatoid synovial cells. Biochem Biophys
Res Commun 122, 270 – 276 (1984)
Lees M, Taylor DJ and Woolley DE: Mast cell proteinases
activate precursor forms of collagenase and stromelysin, but
11
not of gelatinases A and B. Eur J Biochem 223, 171 – 177 (1994)
28 Yoffe JR, Taylor DJ and Woolley DE: Mast-cell products and
heparin stimulate the production of mononuclear-cell factor by
cultured human monocyte /macrophages. Biochem J 230, 83 –
88 (1985)
29 Levi-Schaffer F and Kupietzky A: Mast cells enhance migration
and proliferation of fibroblasts into an in vitro wound. Exp Cell
Res 188, 42 – 49 (1990)
30 Qu Z, Liebler JM, Powers MR, Galey T, Ahmadi P, Huang X-N,
Ansel JC, Butterfield JH, Planck SR and Rosenbaum JT: Mast
cells are a major source of basic fibroblast growth factor in
chronic inflammation and cutaneous hemangioma. Am J Pathol
147, 564 – 573 (1995)