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So, A., De Smedt, T., Revaz, S. & Tschopp, J. A pilot study of IL-1 inhibition by anakinra in acute gout. Arthritis Res. Ther. 9, R28

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Monosodium urate crystals stimulate monocytes and macrophages to release IL-1beta through the NALP3 component of the inflammasome. The effectiveness of IL-1 inhibition in hereditary autoinflammatory syndromes with mutations in the NALP3 protein suggested that IL-1 inhibition might also be effective in relieving the inflammatory manifestations of acute gout. The effectiveness of IL-1 inhibition was first evaluated in a mouse model of monosodium urate crystal-induced inflammation. IL-1 inhibition prevented peritoneal neutrophil accumulation but TNF blockade had no effect. Based on these findings, we performed a pilot, open-labeled study (trial registration number ISRCTN10862635) in 10 patients with gout who could not tolerate or had failed standard antiinflammatory therapies. All patients received 100 mg anakinra daily for 3 days. All 10 patients with acute gout responded rapidly to anakinra. No adverse effects were observed. IL-1 blockade appears to be an effective therapy for acute gouty arthritis. The clinical findings need to be confirmed in a controlled study.
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Vol 9 No 2
Research article
A pilot study of IL-1 inhibition by anakinra in acute gout
Alexander So1, Thibaut De Smedt2, Sylvie Revaz1 and Jürg Tschopp3
1Service of Rhumatologie, Department of Medicine, Centre Hospitalier Universtaire Vaudois and University of Lausanne, 1011 Lausanne, Switzerland
2Apoxis SA, Avenue de Sévelin 18-20, 1004 Lausanne, Switzerland
3Institute of Biochemistry, University of Lausanne, chemin de Boveresses 155, 1066 Epalinges, Switzerland
Corresponding author: Alexander So, AlexanderKai-Lik.So@chuv.ch
Received: 13 Feb 2007 Revisions requested: 1 Mar 2007 Revisions received: 5 Mar 2007 Accepted: 12 Mar 2007 Published: 12 Mar 2007
Arthritis Research & Therapy 2007, 9:R28 (doi:10.1186/ar2143)
This article is online at: http://arthritis-research.com/content/9/2/R28
© 2007 So et al., licensee BioMed Central Ltd.
This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Monosodium urate crystals stimulate monocytes and
macrophages to release IL-1β through the NALP3 component
of the inflammasome. The effectiveness of IL-1 inhibition in
hereditary autoinflammatory syndromes with mutations in the
NALP3 protein suggested that IL-1 inhibition might also be
effective in relieving the inflammatory manifestations of acute
gout. The effectiveness of IL-1 inhibition was first evaluated in a
mouse model of monosodium urate crystal-induced
inflammation. IL-1 inhibition prevented peritoneal neutrophil
accumulation but TNF blockade had no effect. Based on these
findings, we performed a pilot, open-labeled study (trial
registration number ISRCTN10862635) in 10 patients with
gout who could not tolerate or had failed standard
antiinflammatory therapies. All patients received 100 mg
anakinra daily for 3 days. All 10 patients with acute gout
responded rapidly to anakinra. No adverse effects were
observed. IL-1 blockade appears to be an effective therapy for
acute gouty arthritis. The clinical findings need to be confirmed
in a controlled study.
Introduction
Acute gout is a common cause of arthritis, affecting approxi-
mately 1% of the adult population, and epidemiological evi-
dence suggests that its prevalence is increasing [1]. Current
treatments during an acute attack include nonsteroidal antiin-
flammatory drugs (NSAIDs), colchicine and corticosteroids.
Although these agents are generally effective, they also
present significant risks in patients who have pre-existing
renal, cardiovascular and gastrointestinal diseases.
Gouty inflammation is due to monosodium urate (MSU) crys-
tal-induced release of proinflammatory cytokines from leuko-
cytes. Among the many cytokines implicated [2,3], IL-1 may
have a special role in the inflammatory network, as MSU crys-
tals stimulate IL-1 release by monocytes and synovial mononu-
clear cells [4]. The MSU crystals trigger IL-1 release through
innate immune pathways, which include TLR-2 and TLR-4,
found on the surface of monocytes and macrophages, as well
as the 'inflammasome' complex that leads to IL-1β activation
[5,6]. The inflammasome acts as an intracellular sensor of
inflammatory stimuli and regulates the activation of caspase-1.
On assembly of the inflammasome, which consists of a mem-
ber of the nucleotide-binding oligomerization domain-leucine
rich repeat protein family (such as NALP1, NALP2, NALP3, or
IPAF), the adaptor protein ASC and caspase-1 [7], caspase-1
becomes active and cleaves pro-IL-1β to release the mature
p17 form of IL-1β. Activators of the NALP3 inflammasome
include ATP, the microbial cell-wall component muramyl
dipeptide and bacterial RNAs [8-10]. MSU and calcium pyro-
phosphate dihydrate crystals directly activate the inflammas-
ome via NALP3 in monocytes or macrophages to release
active IL-1β and cause neutrophil influx into the peritoneal
space when administered by intraperitoneal injection. These
responses were abrogated in ASC-/- or caspase-1-/- mice [6].
Spontaneous activation of the NALP3 inflammasome due to
mutations in the NALP3 gene has been implicated in heredi-
tary autoinflammatory syndromes such as Muckle–Wells syn-
drome and chronic infantile neurologic cutaneous articular
[11]. Affected patients respond dramatically to IL-1 inhibition
[12,13], suggesting that IL-1β plays a crucial role in the patho-
genesis of inflammation in these conditions. Based on these
IL = interleukin; mAb = monoclonal antibody; MSU = monosodium urate; NALP = Nacht, LRR and Pyrin domain containing protein; NSAID = nons-
teroidal antiinflammatory drug; PBS = phosphate-buffered saline; TLR = Toll-like receptor; TNF = tumor necrosis factor.
Arthritis Research & Therapy Vol 9 No 2 So et al.
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findings, we questioned whether IL-1 inhibition may also have
a beneficial effect in gouty inflammation.
As treatment with drugs currently used in acute gout is not
always well tolerated or is contraindicated due to coexistent
medical problems, we investigated the validity of IL-1 blockade
as therapy in acute gout. We first analyzed the effects of IL-1
inhibition using the mouse peritoneal model of MSU-induced
inflammation and then assessed the effects of anakinra in
patients with acute gout who presented contraindications or
were refractory to standard treatment in an open study.
Methods
Reagents
MSU crystals were prepared based on the method described
previously [14]. Briefly, 1.68 g uric acid was dissolved in 500
ml of 0.01 M NaOH and heated to 70°C. NaOH was added as
required to maintain the pH between 7.1 and 7.2, and the solu-
tion was filtered and incubated at room temperature with little
stirring slowly and continuously 24 hours.
Animal studies
BALB/C mice were treated intraperitoneally with PBS or 0.5
mg MSU crystals in 0.5 ml sterile PBS. Some mice were
injected intraperitoneally with 200 μg anti-IL-1RI mAb (clone
35F5; BD Pharmingen, San Jose, CA, USA) or with 200 μg
anti-TNF mAb (clone TN3-19.12; BD Pharmingen) or with 200
μg anakinra (Kineret; Amgen, Thousand Oaks, CA, USA) at
the time of MSU injection. Mice were euthanized after 6 hours
by CO2 exposure and the peritoneal cavities were washed
with 10 ml cold PBS. The lavage fluids were analyzed for neu-
trophil recruitment by fluorescence-activated cell sorting using
the neutrophil markers Ly-6G and CD11b (BD Pharmingen).
Five mice per group were used for study.
Human studies
The diagnosis of gout arthritis was based on clinical and labo-
ratory features. All patients fulfilled the American College of
Rheumatology criteria for acute gouty arthritis [15], but all had
a long previous history of either recurrent gouty attacks or
tophaceous gout. Patients were treated with anakinra on an
open-label basis. All subjects had either failed conventional
treatment with NSAIDs, colchicine or corticosteroids for at
least 48 hours or had developed significant side-effects on
these drugs in the past. Patients with an active untreated infec-
tion, with uncontrolled diabetes, with uncontrolled heart or res-
piratory failure or with chronic renal failure with a creatinine
clearance <30 ml/min were not eligible. Joint infection was
excluded by prior bacterial culture in all cases that underwent
joint aspiration.
All patients consented to receive anakinra. Treatment was
administered daily at a dose of 100 mg subcutaneously for 3
days. On starting anakinra, the NSAID or colchicine therapy
was discontinued. Patients who were already on low-dose cor-
ticosteroids continued their treatment at the same dose. Clin-
ical efficacy was assessed by clinical examination of the
swollen and tender joint count as well as the patient's evalua-
tion of the efficacy of treatment in terms of pain reduction after
3 days of therapy in comparison with their symptoms before
treatment. All patients were followed up for >1 month. During
follow-up, patients were evaluated for side-effects related to
the treatment and for joint symptoms related to gout. All
patients were followed by physicians responsible for this study
(AS and SR). The study protocol was approved by the local
institution's ethics committee and has the ISRTCN trial regis-
tration number 10862635.
Results
MSU-induced peritoneal inflammation and its inhibition
by anakinra or anti-IL-1RI mAb
To study the inflammatory response to MSU crystals in vivo,
we used a well-described model of neutrophil infiltration in the
peritoneal cavity subsequent to MSU crystal administration. In
previous experiments we determined that intraperitoneal
administration of MSU crystals induced a dose-dependent
neutrophil accumulation at the site of crystal deposition, with a
plateau effect observed at 500 μg (data not shown), and this
dose was therefore used in subsequent experiments. We went
on to determine whether IL-1 blockade reduced the inflamma-
tory response in the same model. Coadministration of MSU
crystals with two different IL-1 inhibitors (anti-IL-1RI mAb or IL-
1R antagonist (anakinra)) had similar and marked inhibitory
effects on neutrophil recruitment (Figure 1a). This effect was
not observed when anti-TNF blocking mAb was administered
in the same fashion as the IL-1 inhibitors (Figure 1b). The dif-
ferences were statistically significant in comparison with the
positive MSU control.
The same dose of TNF inhibitor was effective in suppressing
liver inflammation induced by concavalin A administration, a
model of hepatitis dependent on TNF production (data not
shown).
Effects of anakinra in gout patients
The effectiveness of IL-1 inhibition in suppressing the symp-
toms of acute gout was assessed in 10 patients who could not
tolerate or did not respond to standard antiinflammatory treat-
ments. A summary of the medical histories is presented in
Table 1. All patients responded rapidly to the drug, with the
most rapid onset observed within 24 hours. In all patients, sub-
jective symptoms of gout were greatly relieved by 48 hours
after the first injection. No side-effects were observed during
the study period. Clinical examination of affected joints
showed complete resolution of signs of arthritis in 9/10
patients on day 3 after initiation of treatment.
Case 1
A 72-year-old woman with a 13-year history of chronic topha-
ceous gout and hyperuricemia was treated with rasburicase.
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The patient previously had a severe cutaneous reaction to
allopurinol, and uricosuric treatment with benzbromazone
caused renal stones. During previous gout flares, medical
treatment was unsatisfactory. She could only tolerate a low
dose of diclofenac (50–100 mg/day), as higher doses caused
gastrointestinal side-effects including one episode of gastroin-
testinal hemorrhage. Colchicine at 1 mg/day provoked intoler-
able diarrhea, and oral corticosteroid caused severe
abdominal pain.
Uricase treatment was commenced (14 mg intravenously daily
for 5 days) and resulted in rapid lowering of the patient's uric
acid levels. On the fourth day of treatment, arthritis developed
in her hand and foot joints. As treatment with diclofenac during
previous flares took more than 1 week to relieve her
symptoms, treatment with anakinra was started. Her arthritis
responded rapidly and she was able to continue the course of
uricase. No acute flares were observed during the following 2
months.
Case 2
A 70-year-old man with an 8-year history of chronic topha-
ceous gout was assessed for hypouricemic treatment. The
patient's past medical history included congestive cardiac fail-
ure, severe ischemic heart disease, hypertension and renal
insufficiency (serum creatinine, 202 μmol/l; normal range, 44–
80 μmol/l). Previous trials of treatment with allopurinol had to
be abandoned because acute gout developed after the first
dose, which did not respond to small doses of NSAIDs. Higher
doses of NSAIDs were contraindicated because of renal fail-
ure. Colchicine at low doses (<1 mg/day) provoked rapid
onset of diarrhea.
The patient was again started on a low dose of allopurinol
(100 mg), and after the first dose developed acute arthritis of
the right foot and ankle. Anakinra was administered for 3 days
with rapid and complete resolution of signs and symptoms of
arthritis. The patient continued on allopurinol 100 mg daily,
and at follow-up 2 months later he had no further flare-ups
while continuing on the same dose of allopurinol.
Case 3
A 72-year-old man with a past history of diabetes, hyperten-
sion, renal failure and ischemic heart disease presented with
polyarticular gout. Arthritis involved the knees, the right ankle
and the right tarsal joints. MSU crystals were detected in the
knee joint aspirate.
Owing to renal impairment and a history of rectal bleeding on
colchicine, treatment with oral prednisone at 30 mg daily was
started with a tapering dose over 7 days. Despite steroids, the
arthritis remained active and the patient could not walk. After
Figure 1
Inhibition of monosodium urate-induced peritoneal neutrophil influx by anti-IL-1 treatmentInhibition of monosodium urate-induced peritoneal neutrophil influx by anti-IL-1 treatment. (a) BALB/C mice were injected intraperitoneally with 0.5
mg monosodium urate (MSU) crystals together with PBS or anti-IL-1RI mAb (200 μg) or anakinra (200 μg). (b) BALB/C mice were injected intra-
peritoneally with 0.5 mg MSU crystals together with PBS or anti-TNF mAb (200 μg) or anakinra (200 μg). Neutrophil influx in the peritoneum was
quantified 6 hours later. Values are the mean ± standard error of the mean of five mice per group. An unpaired Student's t test was used to calculate
the P value.
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steroids were stopped, the patient received a 3-day course of
anakinra, with complete resolution of arthritis by the second
day. There had been no recurrence of arthritis at follow-up 1
month later.
Case 4
A 50-year-old man with a 20-year history of polyarticular gout
principally involving the right ankle and big toe sought medical
advice because of increasingly frequent gout attacks. He had
started allopurinol but could not continue treatment because it
induced flare-ups of arthritis. NSAIDs caused severe gastroin-
testinal pain, and colchicine at 1 mg daily was ineffective.
Higher doses of colchicine provoked diarrhea. On examina-
tion, he had arthritis of the right ankle joint and MSU crystals
were identified in the joint aspirate.
A trial of anakinra was initiated at the same time as starting
allopurinol (300 mg/day). The patient's arthritis responded
rapidly and he continued on allopurinol. He was asymptomatic
2 months later.
Case 5
A 40-year-old man with a 12-year history of gout presented
with recurrent podagra of the right big toe. The attacks
occurred approximately once every 2 months, and responded
normally to indomethacin 150 mg daily over 7 days. The
patient was taking allopurinol 300 mg daily and his uric acid
level was stable at 322 μmol/l. He could not tolerate colchi-
cine, which induced diarrhea when given at doses above 1.5
mg daily.
The patient consulted after another attack, which did not
respond to indomethacin over 2 days. Joint aspiration con-
firmed the presence of urate crystals in the joint fluid. The
patient received anakinra and his symptoms completely
resolved 36 hours after the first injection. He has had no fur-
ther attacks at the 6-week follow-up.
Case 6
A 73-year-old female presented with acute gout involving the
big toes of both feet for the first time. She had a past medical
history of hypertension and knee osteoarthritis. On examina-
tion, both metatarsophalangeal-1 joints were red and swollen
and tender to the touch. The joint aspirate did not yield any
fluid. Serum uric acid was raised at 572 μmol/l and serum cre-
atinine was normal at 72 μmol/l. A presumptive diagnosis of
acute gout was made because of the patient's clinical presen-
tation and the hyperuricemia.
The patient's symptoms had not responded to 2 days of treat-
ment with diclofenac (100 mg daily), so anakinra was started.
Her joint pains were 50% improved by 24 hours and 80% by
36 hours after the injections. No further recurrence was
reported on follow-up at 1 month. The patient was started sub-
sequently on allopurinol.
Case 7
A 76-year-old man developed polyarticular gout affecting his
right ankle, the right tarsal joint and both big toe joints during
hospitalization for acute cholecystitis and bacterial sepsis. The
patient had a past medical history of cardiovascular disease
treated with low-dose aspirin and nitrates, of hypertension, of
obstructive airway disease and of cirrhosis. On examination,
Table 1
Clinical summary of the 10 patients studied and their response to treatment
Patient Clinical
presentation
Affected joints Serum uric acid
(normal range,
160–390 μmol/l)
Serum creatinine
(normal range,
44–80 μmol/l)
Hypouricemic
treatment
Effect of
anakinra
(hours)
Patient
assessment of
improvement in
pain (%)
Case 1 (female, 72 years old) Chronic
tophaceous gout,
renal stones
Fingers, toes 637 79 Uricase 36 70
Case 2 (male, 70 years old) Chronic
tophaceous gout
Ankle, toes 564 202 Allopurinol 24 90
Case 3 (male, 72 years old) Acute gout Knee, ankle, foot 482 121 Allopurinol 24 90
Case 4 (male, 51 years old) Acute gout Ankle, toe 396 84 Allopurinol 24 100
Case 5 (male, 40 years old) Acute gout Ankle, toe 322 113 Allopurinol 36 100
Case 6 (female, 72 years old) Acute gout Feet, toe 572 72 None 36 80
Case 7 (male, 76 years old) Acute gout Ankle, foot 338 79 None 36 100
Case 8 (male, 70 years old) Acute gout Wrist, elbow, hand 779 406 None 48 50
Case 9 (male, 53 years old) Chronic
tophaceous gout
Elbow, finger, foot,
ankle
660 84 Allopurinol 48 50
Case 10 (male, 38 years old) Acute gout Wrist, finger 540 84 None 24 60
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joint inflammation was observed at the aforementioned
affected sites. Aspiration of the ankle joint revealed uric acid
crystals.
Owing to a lack of response to NSAIDs over 48 hours, anak-
inra treatment was started. The patient responded after the
first injection, and the symptoms and signs of gout were com-
pletely abolished 48 hours afterwards.
Case 8
A 70-year-old man developed arthritis of his right wrist, elbow,
hand and shoulder. The patient's past medical history included
chronic renal failure, diabetes, and cardiovascular disease
with atrial fibrillation. Gout was suspected because of hyperu-
ricemia and he was treated with colchicine, which provoked
rectal bleeding and a worsening of renal failure. The patient's
serum urate was raised at 779 μmol/l and his serum creatinine
was 258 μmol/l. The joint aspiration of the left elbow revealed
MSU crystals.
A trial of treatment with prednisone caused a decompensation
of the patient's diabetes. Anakinra was started and on review,
after completing the injections, the symptoms of arthritis of the
knee and elbow were greatly reduced, but the right wrist and
hand remained moderately painful.
Case 9
A 53-year-old male presented with severe tophaceous gout of
17 years' duration. In the past, treatment with allopurinol and
uricosurics had been attempted but discontinued because
treatment provoked acute attacks of gout that were not well
controlled by NSAIDs. Colchicine caused severe diarrhea at a
dose of 1 mg/day. There was a positive family history of gout.
On examination, tophi were detected over the elbows, fingers,
knees, ankles and feet, with signs of inflammation in the hands,
knees and right foot. The patient's serum urate was increased
at 660 μmol/l and his renal function was normal.
Owing to the patient's prior intolerance of NSAIDs and colch-
icine, a further attempt to start allopurinol was made under
cover of anakinra, given at 100 mg daily over 3 days. On start-
ing anakinra, the patient reported a 50% decrease in joint
pains after 2 days and he started allopurinol 200 mg daily and
acetametacin 90 mg daily without complications. On follow-up
1 month later, the patient had one minor attack of gout and the
allopurinol was continued.
Case 10
A 38-year-old male presented with painful arthritis of the left
wrist. In the past, the left wrist was fractured in a road traffic
accident and the patient also had a past history of gout affect-
ing the ankles and the left knee. Aspiration of the left wrist
showed MSU crystals. Colchicine (2 mg/day) over 5 days was
not effective in controlling the symptoms of gout.
Anakinra was administered and there was a rapid clinical
response. On follow-up at day 7 after the first injection, the left
wrist was still slightly swollen and tender but the ankle and
knee were asymptomatic. The patient was subsequently
started on allopurinol.
Discussion
MSU crystals induce tissue inflammation via multiple mecha-
nisms. The release of monocyte-derived cytokines, triggered
by urate crystals, can in turn modulate endothelial expression
of adhesion molecules that enhance neutrophil recruitment to
the site of inflammation [16]. Within the joint, the release of
chemokines, prostanoids as well as kinins further amplifies the
inflammatory response [17]. The recent finding that MSU crys-
tals induce IL-1 release by activation of the NALP3 inflammas-
ome led us to investigate whether IL-1 blockade could inhibit
inflammation provoked by MSU. Our results from animal stud-
ies confirmed the effectiveness of IL-1 inhibition in preventing
neutrophil trafficking to the peritoneum, whereas TNF inhibi-
tion did not have any effect. Indeed, TNF inhibition aggravated
neutrophil influx. At present we do not have any simple expla-
nation for the apparent increase in neutrophil accumulation in
mice treated with the anti-TNF mAb. This observation was
made in the two separate experiments performed with five ani-
mals per group. The anti-TNF agent employed inhibited con-
cavalin A-induced hepatitis, demonstrating that the reagent is
biologically active.
The latter results differed from those reported by Chapman
and colleagues, who found that anti-TNF inhibited MSU-
induced endothelial activation, as evidenced by scintigraphy,
in a porcine monoarthritis model [16]. These differences may
be due to the different species employed in the animal models
as well as to the differences in the cytokine inhibitors tested.
Apart from the inflammasome, IL-1 secretion by macrophages
in contact with MSU can also be induced through a TLR-
dependent mechanism [5]. In the current experiments, IL-1
inhibitors would block the effects of activation via both the TLR
and the inflammasome pathways.
As proof of concept that IL-1 inhibition may be clinically effec-
tive, we performed an open-label study of anakinra treatment
in patients with acute gout. All patients had acute excacerba-
tions of longstanding gout and three had severe tophaceous
gout. All the patients had either not responded adequately to
standard treatment with NSAIDs, colchicine or steroids (n = 7)
or had significant comorbidities that made use of these treat-
ments hazardous (n = 4). Three patients could not continue
hypouricemic treatment with allopurinol because of the acute
flares provoked at the start of treatment. Only three daily injec-
tions were administered, and in all cases the symptoms of gout
responded rapidly. All patients had responded within 48
hours, and in four patients (cases 2, 3, 4 and 10) the symp-
toms improved within 24 hours. Patients' subjective assess-
ment of pain due to gout was positive, and the mean
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diminution of pain was 79% by day 3 after the first injection.
Not all patients responded so well, particularly in two of the
patients who had tophaceous gout. They had a moderate
response, although still with >50% reduction of pain. As IL-1
blockade may increase the risk of infection, we excluded any
patient who had proven or clinically suspected active infection.
When appropriate, joint aspiration was performed to exclude
septic arthritis. No treatment-related side-effects were
observed during therapy and there were no infectious
complications. On follow-up, three patients who had topha-
ceous gout reported mild joint pains but no acute flare during
the first month.
Although these findings are positive, we have to stress that
this was an open-label study and confirmation of these results
would require a randomized controlled trial to prove that IL-1
inhibition is effective in acute gout. If the effectiveness of IL-1
is confirmed, then a short course of IL-1 inhibition may prove
to be a valid addition to the therapeutic arsenal when the phy-
sician is confronted with complicated cases of gouty arthritis.
Conclusion
In this pilot study involving 10 patients with gouty arthritis
refractory to conventional therapies, anakinra given at 100 mg
daily for 3 days rapidly relieved the inflammatory symptoms of
gout. These results reinforce the findings that implicate IL-1β
in the pathophysiology of gout and need to be confirmed by
randomized controlled trials. IL-1 inhibition may be a promising
therapeutic target in crystal-induced arthritis.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
The study was conceived by AS and JT. TDS performed the
animal studies. AS and SR performed the clinical study.
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... Commonly used drugs to treat acute gout attacks include nonsteroidal anti-inflammatory drugs (NSAIDs), colchicine, and glucocorticoids (Terkeltaub, 2003). Several biologically targeted agents have also been developed, such as IL-1/1β antagonists, anakinra, rilonacept, canakinumab (So et al., 2007;Terkeltaub et al., 2009;Neogi, 2010;So et al., 2010). In addition, patients with gout require a combination of long-term treatments to lower uric acid levels, such as allopurin, probenecid, and sulfinpyrazone (Terkeltaub, 2003). ...
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... The major role of IL-1β in gout and pseudogout has been confirmed by the efficacy of blocking agents against IL-1 signaling. Anakinra, IL-1Ra recombinant, and canakinumab, an anti-IL-1β monoclonal antibody, have been found to reduce acute arthritis [131][132][133]. ...
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... It triggers inflammation by inducing cell death and release of pro-inflammatory cytokines that recruit and activate other myeloid cells. Thus, it is of major interest to investigate whether mice lacking components of the NLRP3 inflammasome pathway may be protected in murine models of RA, especially following reports of increased NLRP3 and IL-1β levels in the synovium of patients with RA [222][223][224][225][226]. Additionally, it is known that monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) crystals, responsible for acute-gout arthritis and inflammation in joints, activate the NLRP3 inflammasome [227], where anti-IL-1β therapy significantly improves symptoms in patients [228][229][230][231]. ...
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... However, such traditional therapy is difficult to conduct in patients with certain underlying diseases or for long-term periods due to the risk of side effects. Previous animal model studies using anakinra (IL-1R antagonist) suggested the possibility of targeting IL-1β to modulate MSU-induced inflammation (Martin et al., 2009;Torres et al., 2009), and early clinical studies also demonstrated efficacy in the treatment of acute and chronic gout patients (Mcgonagle et al., 2007;So et al., 2007;McGonagle et al., 2008). With the increased understanding of the pathophysiology of gout, new methods of gout treatment in relation to the inflammatory process have been introduced. ...
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We found previously that crystals of sodium urate and silicon dioxide (silica) can stimulate the production of endogenous pyrogen (EP), now called interleukin-1 (IL-1), the polypeptide mediator of fever and other aspects of inflammation. We have confirmed and extended the work with urate crystals and have examined 2 other crystals associated with joint problems, hydroxyapatite (HA) and calcium pyrophosphate dihydrate (CPPD). The crystals were added to suspensions of human blood leukocytes (2.5 X 10(6) monocytes/dose, with 10% fresh autologous plasma); after 18 hours of incubation, the EP content of the supernatants was assayed in the rabbit pyrogen test. HA and CPPD crystals neither induced EP production nor reduced the amount of staphylococci-induced EP. Presized (10 - 40 micron) urate crystals were pyrogenic, but less so than the unsized and aggregated urate crystals investigated previously and reexamined here. On ultrasonication, the aggregated urate crystals became first more pyrogenic and then less so as the crystals were dispersed and broken down. Ultrasound did not impart pyrogenicity to HA or CPPD crystals: their failure to stimulate EP/IL-1 production from leukocytes in vitro indicates a difference in their phlogistic properties, compared with crystals of urate or silica. The results with urate crystals have pathogenetic implications in a number of areas of gouty inflammation: initiation of the acute attack, other aspects of the acute-phase response, polyarticular involvement, and the inflammatory consequences of chronic stimulation by tophaceous material.
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We reported before that monosodium urate (MSU) crystals were potent stimulators of endogenous pyrogen (EP) production from human and rabbit mononuclear phagocytes, and proposed that this property of MSU crystals may be important in the pathogenesis of gout. EP activity is now attributed to interleukin 1 (IL 1) peptides but IL 1 is not the only pyrogenic monocyte-derived cytokine, since both interferon-alpha (alpha-IFN) and tumor necrosis factor (TNF) are also pyrogenic in rabbits. Using a T cell comitogenic assay based on a murine helper T cell clone that does not respond to IFN or TNF, we now report the release of IL 1 activity from human blood monocytes and synovial fluid mononuclear cells (MNC), following stimulation with MSU crystals. MSU-induced supernatants with IL 1 activity were neutralized with rabbit antiserum to human IL 1 and also stimulated the growth ([3H]thymidine incorporation) of long-term fibroblast-like cell lines derived from human synovial rheumatoid exudate. Two other crystals associated with articular inflammation were tested: hydroxyapatite was a much less potent stimulus compared with MSU crystals, and calcium pyrophosphate dihydrate did not stimulate IL 1 release from human monocytes or synovial fluid MNC. As a model for the inflammatory consequences of acute and chronic overproduction of IL 1, gout is the only sterile inflammatory disease where the local and systemic pathology is compatible with such overproduction; raised IL 1 levels have been found at the site of inflammation, and a necessary etiologic agent, crystalline urate, has been shown unequivocally to be a direct activator of mononuclear IL 1 release.
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Proteins binding monosodium urate (MSU) crystals alter their phlogistic potential in vitro and in vivo. These proteins and other materials capable of interacting with crystals could enter the joint space from the circulation and/or could be produced locally. Using the rat subcutaneous air pouch synovium-like model, we observed different effects of collected pouch fluid supernatants from acute (6 h) and from subsiding (72 h) inflammation, and from autologous rat serum on MSU crystal induced inflammation in new air pouches. Plain crystals at 6 h produced a mean leukocyte count (WBC) of 18,156/mm3 with 12% of cells showing phagocytosis of MSU; reaction to plain crystals at 72 h had subsided to only 75 WBC/mm3 and 1% phagocytosis; new crystals preincubated in supernatant from acutely inflamed 6 h air pouches produced higher numbers of WBC in new pouches at 6 h (34,044/mm3); while crystals preincubated in 72 h supernatant gave only 9,825/mm3 and 7% phagocytosis; crystals preincubated in rat serum produced similar pouch WBC to plain crystals at 6 h, but resulted in only 2% phagocytosis. Our study provides evidence that components generated locally during subsiding inflammation as well as serum components could bind to MSU crystals and affect the generation of chemotactic factors and/or crystal phagocytosis contributing in the self-limited nature of acute gouty arthritis.
Article
There is relatively little direct evidence for the roles of interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF alpha) in activating endothelium in vivo. The aim of this study was to use in vitro and in vivo models to investigate the contribution of these cytokines to both E-selectin expression and the recruitment of polymorphonuclear cells (PMN) in monosodium urate monohydrate (MSU) crystal-induced inflammation. MSU crystals were incubated with freshly isolated mononuclear cells, after which the harvested supernatants were tested for their ability to induce E-selectin expression during coculture with human umbilical vein endothelial cells. Subsequent experiments were performed with the addition of neutralizing anticytokine antibodies/antisera. The role of TNF alpha was then studied in an MSU crystal-induced monarthritis model, in the presence or absence of anti-TNF alpha (5 mg/kg intravenously). 99mtechnetium (99mTc)-labeled PMN cells and (111)indium (111In)-labeled anti-E-selectin monoclonal antibody (MAb) 1.2B6 were intravenously administered 4 hours after intraarticular injection to quantify PMN recruitment and E-selectin expression in inflamed joints. MSU crystals were a potent stimulus for IL-1 and TNF alpha production by monocytes in vitro, and these cytokines fully accounted for MSU crystal-stimulated, monocyte-mediated endothelial activation. In the MSU crystal-induced monarthritis model, TNF alpha blockade was very effective in suppressing both E-selectin expression and PMN emigration into the inflamed joints, as judged by gamma-camera image analysis and postmortem tissue counting following the intravenous injection of 99mTc-PMN and 111In-anti-E-selectin MAb. IL-1 and TNF alpha appear to be the only factors released by monocytes following incubation with MSU crystals, which induce E-selectin expression in vitro. Anti-TNF alpha is effective in suppressing endothelial activation and PMN recruitment in vivo E-selectin imaging can be used to assess the endothelial response to therapy and may prove useful for clinical studies.