0022-5347/00/1646-2119/0
THE JOURNAL OF UROLOGY®
Copyright © 2000 by AMERICAN UROLOGICAL ASSOCIATION, INC.®
Vol. 164, 2119 –2125, December 2000
Printed in U.S.A.
PENTOSANPOLYSULFATE INHIBITS MAST CELL HISTAMINE
SECRETION AND INTRACELLULAR CALCIUM ION LEVELS: AN
ALTERNATIVE EXPLANATION OF ITS BENEFICIAL EFFECT IN
INTERSTITIAL CYSTITIS
GEORGE CHIANG,* PHANI PATRA, RICHARD LETOURNEAU, SHEILA JEUDY,
WILLIAM BOUCHER, MARLON GREEN, GRANNUM R. SANT† AND THEOHARIS C. THEOHARIDES
From the Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine and Department of Urology,
New England Medical Center, Boston, Massachusetts
ABSTRACT
Purpose: Mast cells are ubiquitous cells derived from the bone marrow and are responsible for
allergic reactions as they release numerous vasodilatory, nociceptive and pro-inflammatory
molecules in response to immunoglobulin E (IgE) and specific antigen. Mast cell secretion is also
triggered by a number of peptides, such as bradykinin and substance P, and may also be involved
in the development of inflammatory responses. An example is interstitial cystitis, which is a
sterile painful bladder disorder that has been associated with a defective glycosaminoglycan
bladder mucosal layer and an increased number of activated mast cells. Pentosanpolysulfate is
a synthetic, sulfated polysaccharide that has been approved for the treatment of interstitial
cystitis on the premise that it may replenish the defective glycosaminoglycan layer. We hypothesize that pentosanpolysulfate may also have an additional or alternate action on bladder mast
cells. We report that pentosanpolysulfate has a powerful dose dependent inhibitory effect on
mast cell release of histamine induced by the mast cell secretagogue compound 48/80.
Materials and Methods: Inhibition of mast cell secretion was documented by light and electron
microscopy and extended to stimulation by substance P or IgE and antigen.
Results: The inhibition was more potent than that seen with the clinically available mast cell
stabilizer disodium cromoglycate (cromolyn). Maximal inhibition by pentosanpolysulfate was
apparent within 1 minute, was unaffected by the length of pre-incubation and persisted after the
drug was washed off. In contrast, the effect of cromolyn was limited by rapid tachyphylaxis. In
addition, while cromolyn has no effect on mucosal or rat basophilic leukemia cells, pentosanpolysulfate inhibited histamine secretion from both. Confocal microscopy using a calcium indicator dye showed that pentosanpolysulfate decreased intracellular calcium ion levels.
Conclusions: Pentosanpolysulfate appears to be a potent inhibitor of allergic and nonimmune
mast cell stimulation, which is an alternative explanation of its benefit in interstitial cystitis.
KEY WORDS: heparin; histamine; cystitis, interstitial; pentosan sulfuric polyester; proteoglycans
Interstitial cystitis is a sterile bladder condition that occurs primarily in women, and is characterized by urinary
frequency, urgency, burning and suprapubic pain.1 There are
2 different but not mutually exclusive theories to explain the
pathophysiology of interstitial cystitis. One theory is based
on the presence of some defect in the protective glycosaminoglycan layer of the bladder mucosa2 and the other is based
on numerous reports of increased numbers of activated bladder mast cells.3 Mast cells are necessary for the development
of allergic reactions but may also be involved in inflammatory disorders4 since they secrete vasoactive and nociceptive
molecules, as well as numerous cytokines.5 Mast cells are
located close to neurons6 – 8 and are activated by neuropeptides,9, 10 antidromic nerve stimulation11 and acute stress.12
Patients with interstitial cystitis also suffer from allergies,13
irritable and inflammatory bowel syndrome, and migraines,3
all of which are exacerbated by stress.1, 3
There are no clinically available drugs capable of effectively blocking mast cell activation, except for the mast cell
stabilizer cromolyn. However, the inhibitory action of cromolyn on histamine release is short-lived due to the induction of tachyphylaxis, and does not inhibit histamine
secretion from mucosal mast cells.14 Sulfated proteoglycans
are the major constituents of mast cell secretory granules
with heparin present in connective tissue mast cells5 and
chondroitin sulfate in mucosal mast cells.15 We hypothesize
that such polysaccharides may have an inhibitory effect on
mast cell secretion. Pentosanpolysulfate is structurally related to these natural proteoglycans and has been reported to
have a beneficial effect in interstitial cystitis.16 We show that
pentosanpolysulfate is a potent inhibitor of histamine release
from connective tissue and mucosal mast cells, which may
provide an alternative explanation for its beneficial effect in
interstitial cystitis.
METHODS
Mast cell purification and treatment. Peritoneal mast cells
were isolated from male Sprague-Dawley rats weighing 250
Accepted for publication June 19, 2000.
Supported by a grant from Alza Pharmaceuticals.
to 300 gm. using Locke’s solution, which contained 150 mM.
* Recipient of a medical student summer research fellowship from sodium chloride, 5 mM. potassium chloride, 5 mM. HEPES, 2
the American Urological Association.
† Financial interest and/or other relationship with Alza Pharma- mM. calcium chloride, 0.1% bovine serum albumin and 0.1%
dextrose, pH 7.2. Greater than 95% of the cells were purified
ceuticals.
2119
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PENTOSANPOLYSULFATE INHIBITS MAST CELL SECRETION
by centrifugation through 22.5% metrizamide,17 and the remaining cells were lymphocytes and a few macrophages. The
cell pellet was washed and resuspended (105 cells per ml.) in
Locke’s solution. Following the indicated incubation times
with pentosanpolysulfate, the cells were washed by centrifugation at 350 ⫻ g. for 5 minutes at room temperature and
resuspended in Locke’s solution. The cells were then stimulated with either 0.1 ␮g./ml. compound 48/80, 10⫺5 M. substance P in Locke’s solution without calcium plus 0.1 mM.
ethylenediaminetetraacetic acid (EDTA) for 30 minutes or
immunologically. For immunological stimulation unpurified
mast cells (106/ml.) were incubated with 1.5 ␮g./105 cells per
ml. rat immunoglobulin E (IgE) for 30 minutes to occupy the
respective receptors and protect them from destruction during purification, following which they were incubated with 3
to 15 ␮g./104 cells per ml. rabbit anti-IgE for 30 minutes at
37C. The reaction was stopped by centrifuging the cells
at 350 ⫻ g. for 5 minutes at 4C.
An equal volume of Locke’s solution was added to the
supernatant and cell pellet, which were acidified with 20%
perchloric acid for histamine secretion. After freezing and
boiling for 5 minutes, the supernatant and pellet were centrifuged at 17,000 ⫻ g. for 5 minutes at room temperature to
remove denatured protein, and histamine was assayed fluorometrically. The results are expressed as (supernatant/
supernatant ⫹ pellet) ⫻ 100. The data for each incubation
time and condition are expressed as mean plus or minus
standard error of mean (SEM) and statistical analysis was
performed using analysis of variance with p ⬍0.05 considered significant.
Bladders were removed from the same animals from which
peritoneal cells were obtained and cut in 5 ⫻ 5 mm. slices.
They were washed twice, distributed in separate wells and
then stimulated in a perfusion apparatus.18 Histamine release is expressed as described previously and was corrected
for the weight of bladder slices used in each chamber. Rat
basophilic leukemia cells were grown in monolayer cultures
as described previously.19
Intracellular calcium measurement. Mast cells (106/ml.)
were incubated with 5 ␮g./ml. crimson calcium AM cell permeant probe for 5 minutes at 37C in Locke’s solution without
calcium and with 0.1 mM. EDTA. They were then washed
and resuspended in Locke’s solution without calcium and
with 0.1 mM. EDTA. Mast cells were then stimulated with
0.1 ␮g./ml. compound 48/80 with or without pre-incubation
with pentosanpolysulfate for 10 minutes at room temperature, and examined with a confocal laser scanning imaging
system equipped with a crypton-argon laser set at 560␭. (42%
intensity) and attached to a computer.
Microscopy. For light microscopy cells were fixed with 4%
paraformaldehyde in phosphate buffered saline (PBS) for 30
minutes at room temperature. They were then washed with
PBS, aliquoted onto slides and stored at ⫺20C for further
analysis. For electron microscopy the samples were washed
in PBS after immersion fixation of the cell pellet in 2.5%
glutaraldehyde, postfixed in 2% osmium tetroxide, dehydrated in graded ethanol solutions and embedded in Epon as
described previously. Semithin 0.5 ␮m. sections were stained
with toluidine blue, while ultrathin sections (1,000 A.) were
contrasted in 7.5% uranyl acetate in 50% ethanol and 0.1%
aqueous lead citrate. Grids with the sections were examined
and photographed using a transmission electron microscope.
RESULTS
Histamine release stimulated with 0.1 ␮g./ml. of the classic
mast cell secretagogue compound 48/80 for 30 minutes at 37C
was 29.2 ⫾ 1.1% (11). A time course showed that preincubation with pentosanpolysulfate resulted in inhibition of
histamine release. Maximal inhibition of 88% (8, p ⫽ 0.0004)
was achieved by 1 minute and remained unchanged for up to
30 minutes (fig. 1, A). In contrast, the inhibitory action of
cromolyn decreased rapidly if incubation lasted for more than
1 minute. We then investigated whether this inhibitory effect
may have been due to an electrostatic interaction between
the negatively charged pentosanpolysulfate and the cationic
compound 48/80, leading to neutralization of the latter. After
incubation with 10⫺4 M. pentosanpolysulfate, mast cells
were washed up to 5 times before stimulation with 0.1 ␮g./ml.
compound 48/80. The extent of inhibition was not diminished
by the washes. We also investigated how long the inhibitory
activity of pentosanpolysulfate lasted after 2 washes. Mast
cells were incubated with 10⫺4 M. pentosanpolysulfate for 10
minutes at 37C, washed twice in Locke’s solution and then
stimulated by 0.1 ␮g./ml. compound 48/80 immediately or at
5, 30 and 60 minutes after the wash. There was no statistically significant reduction of the inhibitory effect even when
compound 48/80 was added 2 hours later (results not shown).
Pre-incubation with pentosanpolysulfate for 10 minutes at
37C inhibited histamine release triggered by 0.1 ␮g./ml. com-
FIG. 1. A, Time course relationship of inhibitory effect of pentosanpolysulfate on compound 48/80 induced histamine release. Purified
(greater than 95%) rat peritoneal mast cells (105 per ml.) were pre-incubated with 10⫺4 M. pentosanpolysulfate for times indicated followed
by stimulation with 0.1 ␮g./ml. compound 48/80 for 30 minutes at 37C. At 1 minute, inhibition was 88% (9, p ⫽ 0.0004). B, dose response
relationship of inhibitory effect of pentosanpolysulfate on compound 48/80 induced histamine release. Purified (greater than 95%) rat
peritoneal mast cells (105 per ml.) were first incubated with or without pentosanpolysulfate or cromolyn for 1 minute at 37C. After incubation
with designated concentrations of pentosanpolysulfate, mast cells were washed twice in Locke’s solution and stimulated with 0.1 ␮g./ml.
compound 48/80 for 30 minutes at 37C. Inhibition was 88% at 10⫺4 M. (9, p ⫽ 0.0004), 85% at 10⫺5 M. (10, p ⬍0.05), 41% at 10⫺6 M. (10,
p ⬍0.05) and 11% at 10⫺7 M. (8, p ⫽ 0.05).
PENTOSANPOLYSULFATE INHIBITS MAST CELL SECRETION
pound 48/80 in a dose dependent manner (fig. 1, B). Maximal
inhibition of 88% (p ⫽ 0.0004) was seen at 10⫺4 M. when
histamine release decreased from 29.2 ⫾ 1.1% (11) to 3.6 ⫾
0.6% (9). At 10⫺5 M. histamine decreased to 4.4 ⫾ 0.6% (85%
inhibition, p ⬍0.05, 10) at 10⫺6 M. to 17.1 ⫾ 1.7% (41% inhibition, p ⬍0.05, 10) and at 10⫺7 M. to 25.9 ⫾ 1.9% (11% inhibition,
8). Thus, the inhibitory effect of pentosanpolysulfate was comparable to that of cromolyn but pentosanpolysulfate was more
potent at the highest concentrations.
Staining of mast cells with toluidine blue after stimulation
with 0.1 ␮g./ml. compound 48/80 showed that most mast cells
had released their contents to various degrees (fig. 2, A and
C). Incubation with 10⫺4 M. pentosanpolysulfate for 10 minutes at 37C alone had no effect on mast cell morphology but
pre-incubation before stimulation with compound 48/80 inhibited mast cell activation (fig. 2, B and D). The inhibitory
effect of pentosanpolysulfate was also confirmed by transmission electron microscopy. Ultrastructural observations
showed that most control (fig. 3, A) and mast cells treated
with 10⫺4 M. pentosanpolysulfate alone for 10 minutes at
37C (fig. 3, B) contained intact electron dense granules compared to mast cells stimulated by 0.1 ␮g./ml. compound 48/80
which had undergone extensive degranulation (fig. 3, C).
Mast cells incubated with 10⫺4 M. pentosanpolysulfate for 10
minutes at 37C before stimulation with 0.1 ␮g./ml. compound
48/80 contained mostly intact electron dense granules
(fig. 3, D).
The inhibitory effect of pentosanpolysulfate extended to
stimulation of mast cells by the neuropeptide substance P
and by IgE and anti-IgE (table 1). Inhibition of histamine
release in response to 5 ⫻ 10⫺5 M. substance P was less (33%,
p ⬍0.05) than that seen with compound 48/80 possibly be-
2121
cause stimulation by substance P was stronger (49.3 ⫾ 1.3%,
3) than that induced by compound 48/80 (29.2 ⫾ 1.1%, 11) in
the absence of extracellular calcium (table 1). Immunological
stimulation of mast cells was also inhibited. Histamine secretion was 17.4 ⫾ 1.0% (3) and was reduced by 42% to 9.7 ⫾
1.5% (4) by 10⫺4 M. pentosanpolysulfate, which was statistically significant (p ⬍0.05, table 1).
The possibility that the mechanism of action of chondroitin
sulfate may be through an effect on the availability of intracellular calcium ions was investigated. Purified rat peritoneal mast cells were loaded with a calcium indicator dye in
the absence of extracellular calcium and observed live using
a confocal microscope. During stimulation of secretion by 0.1
␮g./ml. compound 48/80 for 10 minutes at room temperature,
intracellular calcium ion levels observed with real time sequence were greatly elevated as seen within 10-second
frames (fig. 4). Pre-incubation with 10⫺4 M. chondroitin sulfate for 10 minutes at 37C before stimulation with compound
48/80 inhibited calcium ion levels significantly (fig. 4). The
extent of reduction of the inhibitory effect on intracellular
calcium ion levels was confirmed.
Mucosal mast cells are increased and activated in interstitial cystitis, while cromolyn does not inhibit histamine secretion from mucosal mast cells.14 Therefore, we tested pentosanpolysulfate on secretion from rat basophil leukemia
cells, which are considered similar to mucosal mast cells20
but are not inhibited by cromolyn.14 Histamine secretion
from rat basophil leukemia cells stimulated with IgE and
2,4-dinitrophenol (DNP)-bovine serum albumin increased
from 0.9 ⫾ 0.5% (10 controls) to 8.2 ⫾ 4.6% (10, p ⬍0.05)
(table 2). Pre-incubation with 10⫺4 M. pentosanpolysulfate
for 10 minutes at 37C decreased histamine release to 1.2 ⫾
FIG. 2. Photomicrographs show inhibition of mast cell activation by pentosanpolysulfate. Purified (greater than 95%) peritoneal mast cells
were washed and resuspended in Locke’s solution. A, control, not treated. B, 10⫺4M. pentosanpolysulfate for 10 minutes at 37C. C, stimulated
with 0.1 ␮g./ml. compound 48/80 alone for 30 minutes at 37C. D, pre-incubated with 10⫺4 M. pentosanpolysulfate for 10 minutes at 37C,
washed and stimulated with 0.1 ␮g./ml. compound 48/80 for 30 minutes at 37C. Stained with 0.2% toluidine blue, pH less than 2.5. Bar equals
10 ␮.
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PENTOSANPOLYSULFATE INHIBITS MAST CELL SECRETION
FIG. 3. Electron photomicrographs of mast cells show inhibitory effect of pentosanpolysulfate. A, control, not treated. B, 10⫺4 M.
pentosanpolysulfate for 30 minutes at 37C. C, 0.1 ␮g./ml. compound 48/80 for 30 minutes at 37C. D, pre-incubated with 10⫺4 M.
pentosanpolysulfate for 10 minutes at 37C, washed and stimulated with 0.1 ␮g./ml. compound 48/80 for 30 minutes at 37C. Bar equals 1 ␮.
TABLE 1. Effect of pentosanpolysulfate on mast cell secretion
induced by different stimuli
% Histamine Release ⫾ SEM
(No. experiments)
Control
0.1 ␮g./ml. Compound 48/80
5 ⫻ 10⫺5 M. Substance P
IgE/anti-IgE
* p ⫽ 0.0004.
† p ⫽ 0.014.
‡ p ⫽ 0.003.
Buffer
Pentosanpolysulphate
5.1 ⫾ 0.4 (14)
29.2 ⫾ 1.1 (11)
49.3 ⫾ 1.3 (3)
17.4 ⫾ 1.0 (3)
2.5 ⫾ 0.4 (9)
3.6 ⫾ 0.5* (9)
28.1 ⫾ 1.1† (3)
9.7 ⫾ 1.5 (4)
%
Inhibition
88*
33‡
42†
0.6% (3, 86% inhibition, p ⬍0.05) while pre-incubation with
10⫺5 M. pentosanpolysulfate decreased histamine release to
2.9 ⫾ 1.8% (3, 65% inhibition, p ⬍0.05).
Finally, we investigated the ability of pentosanpolysulfate
to inhibit histamine secretion from rat bladder mast cells in
situ by using bladder slices in a perfusion apparatus (table 3).
Bladder slices contained connective tissue and mucosal mast
cells that were stimulated by 3 secretagogues used at 10⫺5
M., which were substance P, bradykinin and the stable analogue of acetylcholine carbachol. Substance P stimulated
13.5 ⫾ 0.8% (7) histamine release which was reduced by
10-minute pretreatment with 10⫺4 M. pentosanpolysulfate to
7.9 ⫾ 0.6% (7, 41% inhibition, p ⬍0.05). Bradykinin stimulated 15.4 ⫾ 0.7% (7) histamine release which was reduced to
11.3 ⫾ 0.7% (7, 26% inhibition, p ⬍0.05). Carbachol induced
13.9 ⫾ 0.7% (8) histamine release which was reduced to 9.8 ⫾
0.5% (7, 30% inhibition, p ⬍0.05).
DISCUSSION
Our results show that pentosanpolysulfate is a potent inhibitor of histamine secretion from connective tissue and
mucosal mast cells. The inhibitory action of pentosanpolysulfate on histamine release was stronger than that of the
antiallergic drug cromolyn. Although inhibition by cromolyn
disappeared with pre-incubation times of more than 1
minute, the inhibitory action of pentosanpolysulfate was
near maximal at 1 minute and did not decrease after 30
minutes. Cromolyn is known as a mast cell stabilizer21 and is
available for allergic conjunctivitis, rhinitis, asthma and food
allergies. However, its inhibitory action on histamine release
is modest and short-lived, and it does not inhibit histamine
secretion from mucosal mast cells.14
Pentosanpolysulfate is a synthetic, branched polysaccharide that resembles the natural proteoglycan chondroitin sulfate, which is present in both mast cells.15 Heparin is another
structurally related polysaccharide that is also stored in and
released from mast cells.22 It has been shown to inhibit in
vivo release of histamine,23 the immediate response to antigen in the skin and lungs of allergic subjects24 and bronchoconstriction in exercise induced asthma. Heparin prevents
allergic airway hyperresponsiveness, has a protective effect
on immunological and nonimmunological tracheal smooth
muscle contraction in vitro,25 and inhibits histamine release
from isolated human uterine mast cells.26
To our knowledge pentosanpolysulfate is the only polysaccharide tested clinically after oral administration that has
been shown to reduce successfully interstitial cystitis symptoms.27 In fact, intravesical pentosanpolysulfate has also
been reported to be effective in the treatment of interstitial
cystitis28 as has intravesical heparin16 and another related
polysaccharide, sodium hyaluronate.29 The precise mechanism through which pentosanpolysulfate inhibits mast cell
secretion is not entirely clear. Our results indicate that it
inhibits mast cell intracellular free calcium ion levels. This
action could not be through a calcium ion channel as compound 48/80 is known to induce secretion using intracellular
calcium17 and substance P is most potent in the absence of
extracellular calcium. However, pentosanpolysulfate may be
acting by preventing activation of a key calcium dependent
process. For instance, heparin has previously been reported
to inhibit inositol triphosphate induced intracellular calcium
release from permeable rat liver cells.30
The prevailing theory to explain why the synthetic, sulfo-
PENTOSANPOLYSULFATE INHIBITS MAST CELL SECRETION
2123
FIG. 4. Photomicrographs show inhibition of intracellular calcium levels by pentosanpolysulfate. Purified (greater than 95%) rat peritoneal mast cells were washed, loaded with crimson calcium solution as described previously and resuspended in Locke’s solution. A and C,
stimulated with 0.1 ␮g./ml. compound 48/80 for 10 minutes at room temperature. B and D, pre-incubated with 10⫺4 M. pentosanpolysulfate
for 10 minutes at 37C, washed and stimulated with 0.1 ␮g./ml. compound 48/80 for 10 minutes at room temperature. Frames were taken at
10 second intervals. Bar equals 10 ␮.
TABLE 2. Inhibitory effect of pentosanpolysulfate on rat basophilic
leukemia cell secretion
% Histamine
Release ⫾ SEM
(No. experiments)
Control
IgE/DNP
0.1 mM. pentosanpolysulfate ⫹ IgE/DNP
0.01 mM. pentosanpolysulfate ⫹ IgE/DNP
0.9 ⫾ 0.5 (10)
8.2 ⫾ 4.6 (10)
1.2 ⫾ 0.6 (3)
2.9 ⫾ 1.8 (3)
%
Inhibition
86
65
TABLE 3. Inhibitory effect of pentosanpolysulfate on rat bladder
mast cell secretion
% Histamine
Release ⫾ SEM
(No. experiments)
10⫺5 M. substance P
Pentosanpolysulfate ⫹ 10⫺5 M. substance P
10⫺5 M. bradykinin
Pentosanpolysulfate ⫹ 10⫺5 M. bradykinin
10⫺5 M. carbachol
Pentosanpolysulfate ⫹ 10⫺5 M. carbachol
* p ⬍0.05.
13.5 ⫾ 0.8 (7)
7.9 ⫾ 0.6* (7)
15.4 ⫾ 0.7* (7)
11.3 ⫾ 0.7 (7)
13.9 ⫾ 0.7* (8)
9.8 ⫾ 0.5 (7)
%
Inhibition
41
26
30
nated glycosaminoglycan sodium pentosanpolysulfate and
related polysaccharides or proteoglycans may be helpful in
interstitial cystitis stems from the premise that they replenish the protective glycosaminoglycan layer that may be defective in interstitial cystitis. The hypothesis of a defective
glycosaminoglycan layer was supported by a report that
showed that patients with interstitial cystitis may have a
leaky bladder epithelium, since intravesical placement of
a concentrated urea solution resulted in 25% absorption in
those patients compared to 4% in controls.31 However, other
findings have challenged this theory. For instance, transvesical absorption of 99mtechnetium was similar between patients with interstitial cystitis and normal volunteers.32 Levels of chondroitin sulfates, heparin sulfate and total sulfated
glycosaminoglycan-to-creatinine ratios were similar in inter-
stitial cystitis and control urines.33 Finally, ultrastructural
studies of interstitial cystitis bladder epithelium did not support a deficiency of the glycosaminoglycan layer.34 An alternative hypothesis could be that pentosanpolysulfate inhibits
activation of mast cells3 especially since the effect of protamine on the bladder31 could be explained by the known ability of protamine to activate mast cells.4
Interstitial cystitis bladders have increased numbers of
sympathetic neurons35 and neurons positive for neuropeptide
Y, calcitonin gene related peptide36, 37 and substance P.38, 39
Moreover, substance P positive fibers adjacent to mast cells
were increased in the bladder and colon of a patient with
interstitial cystitis and the irritable bowel syndrome,40 the
latter of which is also known to be exacerbated by stress.41
The release of neuropeptides during stress may lead to local
bladder mast cell secretion of vasoactive, pro-inflammatory
and nociceptive mediators. For instance, acute immobilization stress triggers bladder mast cell degranulation,12 which
is an effect mediated through the release of substance P and
neurotensin.42 Acute stress by immobilization also resulted
in mast cell activation and mucin release in the rat colon.43
Our findings with pentosanpolysulfate and those we reviewed with heparin and chondroitin sulfate suggest that
proteoglycans liberated from activated mast cells and/or connective tissues can act as natural inhibitors of mast cell
secretion and, thus, also reduce the extent of local inflammation. Such inhibitory action may occur through different
mechanisms. Proteoglycans may compete for substance P
binding to surface polysaccharides, as sialidase treated rat
peritoneal mast cells could not be stimulated by compound
48/80 or substance P, and lectins specific for N-acetyl galactosamine and N-acetyl glucosamine oligomers blocked stimulation by compound 48/80.44 Alternatively, proteoglycans
may interfere with the action of inositol triphosphate and
subsequent increases in intracellular calcium ions, especially
since heparin has been shown to act as a competitive inhibitor of inositol triphosphate receptors.30
Pentosanpolysulfate and naturally occurring proteogly-
2124
PENTOSANPOLYSULFATE INHIBITS MAST CELL SECRETION
cans may have additional actions leading to inhibition of
inflammatory responses. For instance, they may act as decoys to prevent or limit the action of growth factors on local
immune cells or neurons since proteoglycans have been
shown to extend the life of growth factors.45 Additional possible beneficial effects of natural or synthetic proteoglycans
in reducing inflammation could be the reported ability of
chondroitin sulfate to bind intercellular adhesion molecules,46 which are often expressed in response to tumor necrosis factor-␣ released from mast cells,47 and to neutralize
proteolytic enzymes that are released during inflammatory
responses.5 It is noteworthy that heparin sulfate has recently
been shown to bind to CD48,48 which is a molecule that is
up-regulated in various autoimmune disorders. Such findings are provocative in view of the fact that mast cells are
increasingly implicated in inflammatory processes.4 For example, mast cells have been implicated in sterile inflammatory disorders other than interstitial cystitis,1 such as the
irritable bowel syndrome,49 which has a higher prevalence in
patients with interstitial cystitis.3, 13 It is of interest that a
deficit of some glycosaminoglycan has been reported in interstitial cystitis50 and inflammatory bowel disease.51
Rat basophil leukemia cells were obtained from Dr. Henry
Metzger from the National Institutes of Health. The use of
proteoglycans in mast cell related diseases is covered by
United States Patent No. 09 0561707 to TCT.
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