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University of Groningen
Experimental studies on signal transduction pathways in rheumatoid arthritis
Bijl-Westra, Johanna
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2
Signal transduction pathways in rheumatoid arthritis with
emphasis on the p38 mitogen-activated protein kinase
(MAPK) pathway
Johanna Westra1
Pieter C Limburg1,2
From the Departments of 1 Rheumatology and 2 Pathology and Laboratory
Medicine, University Medical Center Groningen, The Netherlands
Chapter 2
CONTENTS
1. Rheumatoid arthritis
1.1 Pathogenesis
1.2 Therapy
2. Signal transduction pathways in RA
2.1 MAPK pathways
2.1.1 ERK 1/2
2.1.2 JNK 1,2,3
2.1.3 p38 MAPKα, β, γ, and δ
2.1.4 ERK5 / BMK1
2.2 NF-κB pathway
2.3 JAK-STAT pathway
3. p38 MAPK pathway
3.1 Identification
3.2 Downstream effects of p38
3.2.1 Gene expression
3.2.2 Post transcriptional regulation of mRNA stability
3.3 Inactivation by phosphatases
4 p38 MAPK inhibitors
4.1 development
4.2 p38 MAPK inhibitors in animal models for arthritis
4.3 p38 MAPK inhibitors in human studies
5 Conclusions
14
Signal transduction pathways in RA
1. RHEUMATOID ARTHRITIS
Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease, primarily
located in the synovial joints, leading to destruction of the cartilage and bone as a
result of the chronic disease activity 1. RA affects 0.5 - 1% of the population in the
industrialized world is two to three times more frequent in women than men and can
lead to disability and reduced quality of life.
1.1. Pathogenesis
The cause of RA is still unknown, but both genetic and environmental factors appear
to play a role. The association with certain human leukocyte antigen (HLA) DR4
subtypes and RA has been recognized for a long time 2, and now it is found that rather
specific amino acid sequences, the so-called shared epitope (SE) confer the highest
risk for developing RA 3. RA is characterized by the presence of autoantibodies,
especially rheumatoid factors and antibodies to citrullinated proteins (anti-CCP) in the
majority of the patients. Recently in a study in blood bank donors it was demonstrated
that approximately half of patients with RA had specific serologic abnormalities
(rheumatoid factor and anti-CCP antibodies) several years before the onset of
symptoms 4. The earliest events in RA might involve activation of the innate immune
system, which triggers a T-cell response possibly directed towards citrullinated
proteins 5.
Infiltrating T-cells in the synovial membrane may, by cell-cell contact, and activation
by different cytokines, such as TNF-α, IFN-γ and IL-17, activate monocytes,
macrophages and synovial fibroblasts. These cells than produce pro-inflammatory
cytokines, mainly TNF-α, IL-1 and IL-6 6. As the disease progresses multiple cytokine
networks enter a state of persistent activation, triggering the production of matrix
metalloproteinases, ultimately resulting in irreversible damage of cartilage and bone 7.
1.2. Therapy
DMARDS (disease modifying anti-rheumatic drugs) are drugs that are intended to
inhibit both the inflammatory and destructive processes in RA. Of these DMARDS
methotrexate (MTX) is the most commonly used and is regarded as the gold standard
of DMARD therapy 8. At doses used in the treatment of RA, MTX is likely to act via a
number of intracellular pathways. Upon transport into cells, MTX is converted to
polyglutamated forms, which promote intracellular retention. This results eventually in
induced release of adenosine, which has an anti-inflammatory effect on neutrophils
and mononuclear cells 8;9. MTX modulates cytokine responses at a number of levels
and may promote apoptosis of activated lymphocytes 10. Since five years a new
DMARD has become available, Leflunomide, which is an active metabolite that
inhibits dihydro-orotate-dehydrogenase, an enzyme involved in de novo pyrimidine
synthesis 11. Inhibition of this enzyme affects various signal-transduction mechanisms,
the generation of cytokines, and cell proliferation and migration.
However, these DMARDS still have limited efficacy and may lead to toxicity
problems. The pro-inflammatory role of cytokines and the involvement of different
cell types led to the development of therapeutics to selectively target cytokines. The
key role of TNF-α in the pathogenesis of RA was discovered both in experimental
animal models and in RA patients by Feldmann, Maini and others 12. There are now
15
Chapter 2
three drugs clinically available for treatment that block the activity of TNF-α:
Infliximab (chimaeric monoclonal antibody to human TNF), Adalumimab (human
monoclonal antibody to TNF) and Etanercept (soluble TNF receptor construct) and
one to block IL-1 activity: Anakinra (IL-1 receptor antagonist). The efficacy and
possible toxic effects of these new drugs have been reviewed by Olsen and Stein 13.
Although TNF blockade has been a major breakthrough in the therapy of RA in the
last ten years, there are some drawbacks. About half of the patients in clinical trials do
not achieve adequate clinical responses expressed as ACR50 responses, remission is
rare and these drugs also have side effects, for instance increased risk of tuberculosis13.
New drugs to inhibit the production and activity of inflammatory cytokines may be
found in inhibitors of intracellular signal transduction pathways 14. These pathways are
involved in the primary production of these cytokines, as well as in the responses
generated by these cytokines. TNF-α and IL-1 induce a variety of signal transduction
cascades that lead to the activation of transcription factors and next to the transcription
and translation of genes, coding for inflammatory mediators. The cascades that are
important in RA and the potential inhibitors will be discussed below.
2. SIGNAL TRANSDUCTION PATHWAYS IN RA
Intracellular signal transduction pathways are intracellular mechanisms by which cells
can react to extracellular stimuli such as stress and inflammatory cytokines. In short,
intracellular signal transduction is the process by which a cell converts an extracellular
signal into a response. A key role thereby is for proteins called kinases, which act as
key regulators of cell function by catalyzing (facilitating) the addition of a negatively
charged phosphate group to proteins. These signalling cascades ultimately lead to
induction of gene transcription and translation into specific proteins. These
inflammatory proteins, including cytokines, matrix metalloproteinases, and cyclooxygenase (COX-2) are involved in the pathogenesis of RA.
The main intracellular signal transduction pathways implicated in RA include the
mitogen-activated protein kinase (MAPK) pathways, nuclear factor-kappa B (NF-κB)
and the Janus kinase (JAK-STAT) pathway.
2.1. Mitogen-activated protein kinase (MAPK) pathways (figure 1)
There are four well-characterized families of MAPKs, acting by phosphorylation of
specific serine (Ser), threonine (Thr) and tyrosine (Tyr) residues of target substrates
thereby controlling important cellular functions, such as gene expression, mitosis,
movement, metabolism and apoptosis. The MAPK isoforms themselves are
phosphorylated by dual- specificity serine-threonine MAPK-kinases (MAPKK or
MEK) which in turn are phosphorylated by upstream MAPK-kinase-kinases
(MAPKKKs or MEKKs).
The MAPK family include the extracellular signal-regulated kinases ERK1 and ERK2
(also known as the p42/p44 MAPK pathway), the c-jun NH2-terminal kinases JNK 1,
JNK 2 and JNK 3, the four p38 enzymes, p38α, p38β, p38γ and p38δ, and the ERK5
or big MAP kinase 1 (BMK1) 15. All MAPKs share the amino-acid sequence Thr-XxxTyr in which X differs: X is glutamic acid (Glu), proline (Pro) and glycine (Gly) for
the ERK, JNK and p38 MAPK respectively 16.
16
Signal transduction pathways in RA
Figure 1. Mitogen-activated protein kinase (MAPK) pathways.
2.1.1. The ERK 1/2 signaling pathway is a major determinant in the control of cell
growth, cell differentiation and cell survival. Growth factors, cytokines, viral infection,
and carcinogens are the main activators of the proto-oncogene Ras, a small GTPbinding protein, which is the common upstream molecule of the MEKKs Raf (Raf1,
A-Raf or B-Raf) 17. Activated Rafs phosphorylate MEK1/2, which in turn activate
ERK1 and ERK2. ERKs can directly phosphorylate a set of transcription factors
including Ets-1, c-Jun and c-myc, or activate RSK (ribosomal S6 kinase), which leads
to the activation of the transcription factor CREB (cyclic AMP-responsive elementbinding protein). MEK1 and MEK2 activity has been detected in a significant number
of primary human tumor cells. Inhibitors of the ERK pathway (Ras-, Raf- and Srcinhibitors) are entering clinical trials as potential anti-cancer agents. PD98059 and
U0126 are non-ATP competive MEK 1/2 inhibitors, which block phosphorylation and
activation of ERK1 and 2 by MEK 18.
2.1.2. JNKs were discovered to bind and phosphorylate the DNA-binding protein c-Jun
(a component of the AP-1 (activator protein) transcription complex) and to increase its
transcriptional activity. Regulation of the JNK pathway is extremely complex and is
influenced by many kinases. In general, stress or cytokines can initiate a series of
events in which GTP-binding proteins such as Cdc42, Rac or Ras can activate protein
kinases such as GCK (germinal centre kinase), which in turn can activate ASK
(apoptosis stimulating kinase), TAK (TGFβ-activated kinase) and the MEKKs 1,2 and
3 19. Then MKK4 and MKK7 are activated, which are the direct activators of the JNK
MAPKs. Targets of this pathway include c-Jun, ATF2 (activating transcription factor
17
Chapter 2
2) and ELK-1. JNK is one of the primary MAPKs required for expression of matrix
metalloproteinases and joint destruction in models of inflammatory arthritis 20. The
best known JNK2 inhibitor is SP600125, while another JNK pathway inhibitor
CEP1347, has been reported to inhibit members of the MLK (mixed lineage kinase)
family, which are upstream activators of the JNK pathway 18.
2.1.3. p38 MAPKs are, like the JNKs, stress-activated protein kinases, that mediate
responses to cellular stress factors, such as UV light, osmotic shock and cytokines. The
main activation route for p38 MAPK is through phosphorylation by MMK3 / MKK6
and possibly by MKK4, which in turn are activated by the MAPKKKs (figure 2).
Members of the MAPKKK superfamily include MEKK 1-4, MLK, Tpl2 (tumor
progression locus-2), TAK-1 and ASK-1 21. The MAPKKKs themselves are activated
by small GTP-binding proteins, including Rac and Cdc42, partly involving p21activated kinases (PAKs). In inflammation the most important route for activation is
via TNF-α and IL-1 by ligation of their respective membrane receptors and
recruitment of intracellular adaptor molecules. Activated p38 MAPKs can
phosphorylate downstream kinases (MAPKAPK-2, MSK-1, PRAK and MNK) and
transcription factors such as ATF-2, CHOP (C/EBP homologous protein) and ELK-1.
Lipopolysaccharide (LPS) signal transduction is also one of the activation routes for
Figure 2. p38 mitogen-activated protein kinase (MAPK) pathway.
18
Signal transduction pathways in RA
p38 MAPK. LPS is a common constituent of Gram-negative bacterial outer
membranes and is the principal initiator of septic shock. Signalling of LPS involves a
receptor complex with Toll-like receptor 4 (TLR-4), CD14 and the adaptor molecules
MyDD88 and IRAK (interleukin-receptor associated kinase). The route then resembles
the IL-1 route: via TRAF6 and TAK1 p38 MAPK can be activated as well as the JNK
and the NF-κB pathways 22.
The p38 MAPK signal transduction pathway will be discussed in detail below.
2.1.4. The fourth and least studied MAP kinase pathway, BMK1 or ERK5, is activated
in response to growth factors and stress. This pathway has not only been implicated in
cell survival, proliferation and differentiation, but also in pathologic processes such as
carcinogenesis, cardiac hypertrophy and atherosclerosis 23. MEK5 is the upstream
kinase of BMK1, and can be inhibited by inhibitors of MEK 1/2 such as PD98059 and
U0126. The MEK5 kinases identified thus far are MEKK2 and MEKK3, which are
also known to regulate p38 MAPK and JNK activity through the activation of
MKK3/6 and MKK4/7 respectively 23.
2.2. NF-κB pathway (figure 3)
The transcription factor Nuclear Factor κ-B (NF-κB) is a key factor in the
transcription of many inflammatory genes. NF-κB is a complex group of
heterodimeric and homodimeric transcription factors, consisting of five members: cRel, RelA (p65 or NF-κB3), RelB, NF-κB1 (p50/p105) and NF-κB2 (p52/p100) 24.
Normally these dimers bind to the specific inhibitors of NF-κB, known as IκB
proteins. Upstream kinases, including members of the MAPKKK family and NF-κBactivating-kinase (NAK) can induce phosphorylation and degradation of IκB, thereby
liberating the NF-κB dimers, which translocate to the nucleus and regulate gene
transcription 24;25. The modification of the IκB proteins depends on the IKK (IκB
kinase) complex, which is composed of three subunits: the catalytic subunits IKK-α(1)
and IKK-β(2), and the regulatory subunit IKK-γ (also known as NEMO). These
subunits have specific roles in the regulation of NF-κB activity. The activation of NFκB has been implicated in the pathogenesis of RA. Translocation of nuclear p50 and
p65 was demonstrated in RA synovial lining cells and in mononuclear cells of the
sublining 26. It has been demonstrated that NF-κB suppression is beneficial in many
models of inflammatory disease 27. Moreover, for many therapeutic agents it has been
shown that at least some of their effects are due to NF-κB blockade. Efforts to block
this pathway have led to the development of small-molecule inhibitors of various
kinases and regulatory proteins and also to research in gene therapy. In arthritis IKK-β
seems an attractive target for therapy, because it regulates cytokine production in
many cell types including synovial fibroblasts 28;29. Although it is obvious that NF-κB
plays a key role in inflammatory diseases, there are major safety concerns about
inhibition of this transcription factor, because of the major role that NF-κB plays in
host defence, homeostasis, cell survival and response to stress.
19
Chapter 2
Figure 3. NF-κB pathway.
2.3. JAK/STAT pathway (figure 4)
The Janus kinase (JAK) family and the signal transducer and activator of transcription
(STAT) transcription factors play an important role in cytokine signal transduction.
Type I cytokine receptors (for colony stimulating factors, and several interleukins) and
type II cytokine receptors (for interferons) lack intrinsic kinase activity and rely on Jak
proteins to initiate signalling 30. In the case of IL-6 an association with the IL-6
receptor and gp130 subunits takes place that activates JAKs. This is followed by the
phosphorylation of the tyrosine-based docking sites on the receptor and recruitment of
STATs. They form homo-hetero-dimers and translocate to the nucleus, where they
bind target sequences 31. Dimerization of the IL-6-type cytokine receptors does not
only lead to activation of the JAK/STAT signalling pathway, but also of the MAPK
cascade.
Negative regulation of IL-6 signalling via the JAK/STAT pathway may occur in
different ways 30. Suppressor of cytokine signalling (SOCS) proteins are induced in
response to IL-6 binding and can bind directly to the JAKs. SH2-domain-containing
tyrosine phosphatase-1 (SHP-1) either can dephosphorylate JAKs or activated receptor
subunits. Protein inhibitors of activated STATs (PIAS) family members inactivate
STAT dimers.
20
Signal transduction pathways in RA
Figure 4. JAK/STAT pathway.
THE p38 MAPK SIGNAL TRANSDUCTION PATHWAY
3.1. Identification
The human p38α MAPK were first identified as the molecular target of
pyridinylimidazole class of compounds, that were known to block TNF-α and IL-1
release from lipopolysaccharide (LPS)- stimulated human monocytes 32. Originally
these proteins were designated cytokine-suppressive anti-inflammatory drug-binding
proteins (CSBP) 33. Until now, five isoforms of p38 MAPK have been identified:
p38β1 and p38β2 have more than 70% identity to p38α, whereas p38γ and p38δ have
approximately 60% identity to p38α. Functional differences between the isoforms are
related to their differential expression, activation, and substrate specificity 34. p38α,
p38β and p38δ are widely produced in various tissues, while p38γ is expressed
primarily in skeletal muscle. Inflammatory cells synthesize predominantly p38α and
p38δ protein, but endothelial cells also produce p38β 35;36.
ERK, JNK and p38 MAPK activation were almost exclusively found in synovial tissue
from RA, but not osteoarthritis patients. p38 MAPK activation was observed in the
synovial lining layer and in synovial endothelial cells 37.
3.2. Downstream effects of p38 MAPK activation
3.2.1. Gene expression
One of the main downstream effects of the p38 MAPK pathway is regulation of gene
expression, which can be at the transcriptional level, but also at the translational level,
21
Chapter 2
leading to protein synthesis. p38 MAPK has been implicated in the activation of
various transcription factors including: ATF-2, MEF-2C, CHOP, and NF-κB 38-40.
Other transcription factors are phosphorylated by downstream protein kinases that are
themselves activated by phosphorylated p38 MAPK, such as MAPKAPK-2 (MAPK
activated protein kinase). Furthermore MAPKAPK-2 deficient mice show diminished
production of IL-6 and TNF-α 41. These effects are thought to be mediated by a
mechanism involving mRNA turnover and protein translation. The p38
MAPK/MAPKAPK-2 pathway is crucial to inflammatory cytokine production.
3.2.2. Post transcriptional regulation of mRNA stability
As will be discussed later, several p38 MAPK inhibitors have been developed which
were shown to block the production of inflammatory cytokines. This inhibition seems
to be a combined effect at the level of transcription and translation. Inducible
cytokines usually have short lived mRNAs and contain an AU-rich element (ARE) in
their 3’untranslated region responsible for their high turn-over rate 42. These AREs
contain repeats of the motif AUUUA, and were discovered as instability elements. In
the case of inflammatory response mRNAs, the instability is countered by signalling in
the p38 MAPK pathway 43.
Under normal conditions, these AU-rich elements are occupied by AU-binding
proteins, thereby blocking translation or transcription. It has been demonstrated that
upon stimulation these AU-binding proteins are phosphorylated in a p38 MAPKdependent manner, resulting in their release, and allowing translation of these mRNAs
43;44
. Inhibitors of p38 MAPK can target these events directly or via MAPKAPK-2. It
has been demonstrated that both translation and stability of TNF-α mRNA are
regulated by the p38MAPK pathway 45, whereas IL-6 and IL-8 mRNA stability is
regulated by p38 MAPK, but the extent of inhibition of protein production varies with
cell type 46;47. Activation of p38 MAPK has also been shown to enhance the mRNA
stability of collagenase-1 (MMP-1) and stromelysin-1 (MMP-3 ) 48. Finally, Lasa et al
demonstrated that the gluco-corticoid dexamethasone destabilizes COX-2 mRNA by
inhibiting p38 MAPK. This effect was induced by expression of MAPK-phosphatase-1
(MKP-1) 49.
3.3. Inactivation by phosphatases
For control of the MAPK signal transduction pathways dephosphorylation is
necessary. Over the last decade a family of endogenous negative regulators of MAPK,
the MAPK phosphatases (MKPs), also known as DUSPs (dual-specificity
phosphatases) have been described 50. The MKPs dephosphorylate the tyrosine and
threonine motifs of MAPK to deactivate MAPK-dependent signalling. At least 10
mammalian MKPs have been cloned and characterized, which have different
subcellular distribution, substrate specificity, and expression patterns. MKP-1 was the
first isolated MKP, and is a 39.5 kD protein that is preferentially localized in the cell
nucleus. It is capable of dephosphorylating all MAPK families, although a preference
for dephosphorylating p38 MAPK and JNK has been described 51. MKP-1 is an early
response gene that is induced by the same stimuli that activate the MAPKs, such as
cytokines, osmotic shock and UV radiation 52;53. Recently the expression of MKP-1 in
22
Signal transduction pathways in RA
rheumatoid synovial fibroblasts was demonstrated as well as a role for glucocorticoid
dependent upregulation of MKP-152.
4. p38 MAPK INHIBITORS (figure 5)
4.1. Development
Already in 1988 the inhibition of IL-1 production by the anti-inflammatory compound
SK&F 86002 was reported 54, but it took until 1994 to discover that the molecular
target of the pyridinyl imidazole class of compounds indeed proved to be p38 MAPK,
originally known as CSBP 32. Since the original report of the efficacy of these
compounds, they have become the most widely studied inhibitors of this kinase. The
compounds have been used as framework for further synthetic work and have been
utilized to elucidate the role of p38 MAPK in the immune system. Crystallographic
and kinetic experiments have shown that the pyridinyl imidazole family of p38 MAPK
inhibitors bind at the ATP binding site of p38 MAPK and compete with ATP for
binding to active, phosphorylated p38 MAPK 55. When p38 MAPK is in the
unactivated form, ATP is non-competitive with many p38 MAPK inhibitors.
After the structure-activity relationship was established SB 203580 and other 2, 4, 5triaryl imidazoles were prepared as pharmacological tools to regulate cytokine
synthesis. A large number of preclinical studies have reported that specific and
selective p38 MAPK inhibitors block the production of inflammatory cytokines in
vitro and in vivo.
Furthermore, the p38 MAPK pathway is involved in the induction of several other
inflammatory molecules such as cyclo-oxygenase-2 (COX-2) and inducible nitric
oxide synthase (iNOS).
Figure 5. p38 MAPK inhibitors.
The p38 MAPK inhibitor used in our studies, RWJ 67657, was developed by Johnson
and Johnson Pharmaceutical Research and Development and was first described in
1999 56. RWJ 67657 (4-[4-(4-fluorophenyl)-1-(3-phenylpropyl)-5-(4-pyridinyl)-1Himidazol-2-yl]-3-butyn-1-ol) has been shown to be effective in inhibiting the release of
TNF-α from LPS-treated human peripheral blood mononuclear cells with an IC50 of 3
nM. In comparison to the literature standard SB 203580 this new compound proved to
be approximately 10-fold more potent in all p38 MAPK dependent systems tested.
23
Chapter 2
Moreover the compound inhibited the enzymatic activity of p38α and β, but not of γ
and δ, in vitro and had no significant activity against a variety of other enzymes.
4.2. p38 MAPK inhibitors in animal models for arthritis
Several p38 MAPK inhibitors have been evaluated in animal arthritis models. Already
in 1996 the pharmacological profile of SB 203580 (GlaxoSmithKline) was
investigated in adjuvant-induced arthritis in Lewis rats 57, whereas in 1998 the
pharmacologically effects of SB 220025 (GlaxoSmithKline) were investigated in an
angiogenesis and chronic disease model 58. RPR-200765A (Aventis) reduced incidence
and progression in the rat streptococcal cell wall (SCW) arthritis model at doses given
orally 59, while prevention of the onset and progression of collagen-induced arthritis
were reported for FR167653 (Fujisawa Pharmaceuticals) 60. Recently SB 242235
(GlaxoSmithKline) was evaluated in a new model of arthritis, pristane-induced
arthritis, and demonstrated to significantly reduce all arthritis scores 61.
4.3. p38 MAPK inhibitors in human studies
RWJ 67657 is one of the p38 MAPK inhibitors who until now have been used in
human studies. The effects on clinical and cytokine response to endotoxaemia were
studied in healthy human volunteers and reported by Fijen et al 62. Single oral doses of
RWJ 67657 dose-dependently decreased symptoms and elevated cytokine levels,
induced after administration of endotoxin. Furthermore single-dose pharmacokinetics
and pharmacodynamics of RWJ 67657 were investigated in healthy male subjects 63.
RWJ 67657 was rapidly absorbed (mean tmax = 0.6-2.5 h) and there were no significant
adverse effects associated with single doses of this drug. This study demonstrates that
RWJ 67657 has acceptable safety and pharmacokinetics to warrant further
investigation in a repeat-dose setting. Other compounds that have been investigated in
rheumatoid arthritis patients are VX-74564 and SCIO-469, which is now in phase II
clinical trial 65.
5. CONCLUSIONS
The discovery of p38 MAPK inhibitors have dramatically increased the understanding
of signal transduction pathways involved in inflammation. It is widely expected that
p38 MAPK inhibitors will have efficacy in arthritis and other inflammatory diseases.
However, clinical trials have been stopped due to safety issues. One of the reasons for
these undesirable effects might be the cross-reactivity against other kinases. Solutions
for these problems might lie in the development of non-ATP competitive inhibitors or
inhibitors, which target other molecules in the p38 MAPK pathway.
REFERENCES
1 Choy EH, Panayi GS. Cytokine pathways and joint inflammation in rheumatoid arthritis.
N.Engl.J.Med. 2001; 344: 907-16.
2 Stastny P. Association of the B-cell alloantigen DRw4 with rheumatoid arthritis. N.Engl.J.Med.
1978; 298: 869-71.
3 McDonagh JE, Dunn A, Ollier WE, Walker DJ. Compound heterozygosity for the shared
epitope and the risk and severity of rheumatoid arthritis in extended pedigrees. Br.J.Rheumatol.
1997; 36: 322-7.
4 Nielen MM. Specific autoantibodies precede the symptoms of rheumatoid arthritis: a study of
serial measurements in blood donors. Arthritis and rheumatism 2004; 50: 380-6.
24
Signal transduction pathways in RA
5 Firestein GS, Zvaifler NJ. How important are T cells in chronic rheumatoid synovitis?: II. T
cell-independent mechanisms from beginning to end. Arthritis Rheum. 2002; 46: 298-308.
6 Bombara MP, Webb DL, Conrad P et al. Cell contact between T cells and synovial fibroblasts
causes induction of adhesion molecules and cytokines. J.Leukoc.Biol. 1993; 54: 399-406.
7 Dayer JM, Graham R, Russell G, Krane SM. Collagenase production by rheumatoid synovial
cells: stimulation by a human lymphocyte factor. Science 1977; 195: 181-3.
8 Bathon JM, Martin RW, Fleischmann RM et al. A comparison of etanercept and methotrexate in
patients with early rheumatoid arthritis. N.Engl.J.Med. 2000; 343: 1586-93.
9 Whittle SL, Hughes RA. Folate supplementation and methotrexate treatment in rheumatoid
arthritis: a review. Rheumatology.(Oxford) 2004; 43: 267-71.
10 Genestier L, Paillot R, Quemeneur L, Izeradjene K, Revillard JP. Mechanisms of action of
methotrexate. Immunopharmacology 2000; 47: 247-57.
11 Li EK, Tam LS, Tomlinson B. Leflunomide in the treatment of rheumatoid arthritis. Clin.Ther.
2004; 26: 447-59.
12 Feldmann M, Maini RN. Anti-TNF alpha therapy of rheumatoid arthritis: what have we learned?
Annu.Rev.Immunol. 2001; 19: 163-96.
13 Olsen NJ, Stein CM. New drugs for rheumatoid arthritis. N.Engl.J.Med. 2004; 350: 2167-79.
14 Smolen JS, Steiner G. Therapeutic strategies for rheumatoid arthritis. Nat.Rev.Drug Discov.
2003; 2: 473-88.
15 Johnson GL, Lapadat R. Mitogen-activated protein kinase pathways mediated by ERK, JNK,
and p38 protein kinases. Science 2002; 298: 1911-2.
16 Herlaar E, Brown Z. p38 MAPK signalling cascades in inflammatory disease. Mol.Med.Today
1999; 5: 439-47.
17 Chang F, Steelman LS, Lee JT et al. Signal transduction mediated by the Ras/Raf/MEK/ERK
pathway from cytokine receptors to transcription factors: potential targeting for therapeutic
intervention. Leukemia 2003; 17: 1263-93.
18 English JM, Cobb MH. Pharmacological inhibitors of MAPK pathways. Trends Pharmacol.Sci.
2002; 23: 40-5.
19 Barr RK, Bogoyevitch MA. The c-Jun N-terminal protein kinase family of mitogen-activated
protein kinases (JNK MAPKs). Int.J.Biochem.Cell Biol. 2001; 33: 1047-63.
20 Han Z, Boyle DL, Chang L et al. c-Jun N-terminal kinase is required for metalloproteinase
expression and joint destruction in inflammatory arthritis. J.Clin.Invest 2001; 108: 73-81.
21 Lee JC, Kumar S, Griswold DE, Underwood DC, Votta BJ, Adams JL. Inhibition of p38 MAP
kinase as a therapeutic strategy. Immunopharmacology 2000; 47: 185-201.
22 Diks SH, Richel DJ, Peppelenbosch MP. LPS signal transduction: the picture is becoming more
complex. Curr.Top.Med.Chem. 2004; 4: 1115-26.
23 Hayashi M, Lee JD. Role of the BMK1/ERK5 signaling pathway: lessons from knockout mice.
J.Mol.Med. 2004; 82: 800-8.
24 Karin M, Yamamoto Y, Wang QM. The IKK NF-kappa B system: a treasure trove for drug
development. Nat.Rev.Drug Discov. 2004; 3: 17-26.
25 Sweeney SE, Firestein GS. Signal transduction in rheumatoid arthritis. Curr.Opin.Rheumatol.
2004; 16: 231-7.
26 Handel ML, McMorrow LB, Gravallese EM. Nuclear factor-kappa B in rheumatoid synovium.
Localization of p50 and p65. Arthritis Rheum. 1995; 38: 1762-70.
27 McIntyre KW, Shuster DJ, Gillooly KM et al. A highly selective inhibitor of I kappa B kinase,
BMS-345541, blocks both joint inflammation and destruction in collagen-induced arthritis in
mice. Arthritis Rheum. 2003; 48: 2652-9.
28 Andreakos E, Smith C, Kiriakidis S et al. Heterogeneous requirement of IkappaB kinase 2 for
inflammatory cytokine and matrix metalloproteinase production in rheumatoid arthritis:
implications for therapy. Arthritis Rheum. 2003; 48: 1901-12.
29 Tak PP, Gerlag DM, Aupperle KR et al. Inhibitor of nuclear factor kappaB kinase beta is a key
regulator of synovial inflammation. Arthritis Rheum. 2001; 44: 1897-907.
30 Ortmann RA, Cheng T, Visconti R, Frucht DM, O'Shea JJ. Janus kinases and signal transducers
and activators of transcription: their roles in cytokine signaling, development and
immunoregulation. Arthritis Res. 2000; 2: 16-32.
25
Chapter 2
31 Heinrich PC, Behrmann I, Haan S, Hermanns HM, Muller-Newen G, Schaper F. Principles of
interleukin (IL)-6-type cytokine signalling and its regulation. Biochem.J. 2003; 374: 1-20.
32 Lee JC, Laydon JT, McDonnell PC et al. A protein kinase involved in the regulation of
inflammatory cytokine biosynthesis. Nature 1994; 372: 739-46.
33 Obata T, Brown GE, Yaffe MB. MAP kinase pathways activated by stress: the p38 MAPK
pathway. Crit Care Med. 2000; 28: N67-N77.
34 Kumar S, McDonnell PC, Gum RJ, Hand AT, Lee JC, Young PR. Novel homologues of
CSBP/p38 MAP kinase: activation, substrate specificity and sensitivity to inhibition by
pyridinyl imidazoles. Biochem.Biophys.Res.Commun. 1997; 235: 533-8.
35 Hale KK, Trollinger D, Rihanek M, Manthey CL. Differential expression and activation of p38
mitogen-activated protein kinase alpha, beta, gamma, and delta in inflammatory cell lineages.
J.Immunol. 1999; 162: 4246-52.
36 Herlaar E, Brown Z. p38 MAPK signalling cascades in inflammatory disease. Mol.Med.Today
1999; 5: 439-47.
37 Schett G, Tohidast-Akrad M, Smolen JS et al. Activation, differential localization, and
regulation of the stress- activated protein kinases, extracellular signal-regulated kinase, c-JUN
N-terminal kinase, and p38 mitogen-activated protein kinase, in synovial tissue and cells in
rheumatoid arthritis. Arthritis Rheum. 2000; 43: 2501-12.
38 Han J, Jiang Y, Li Z, Kravchenko VV, Ulevitch RJ. Activation of the transcription factor
MEF2C by the MAP kinase p38 in inflammation. Nature 1997; 386: 296-9.
39 Zhu T, Lobie PE. Janus kinase 2-dependent activation of p38 mitogen-activated protein kinase
by growth hormone. Resultant transcriptional activation of ATF-2 and CHOP, cytoskeletal reorganization and mitogenesis. J.Biol.Chem. 2000; 275: 2103-14.
40 Wesselborg S, Bauer MK, Vogt M, Schmitz ML, Schulze-Osthoff K. Activation of transcription
factor NF-kappaB and p38 mitogen-activated protein kinase is mediated by distinct and separate
stress effector pathways. J.Biol.Chem. 1997; 272: 12422-9.
41 Kotlyarov A, Neininger A, Schubert C et al. MAPKAP kinase 2 is essential for LPS-induced
TNF-alpha biosynthesis. Nat.Cell Biol. 1999; 1: 94-7.
42 Caput D, Beutler B, Hartog K, Thayer R, Brown-Shimer S, Cerami A. Identification of a
common nucleotide sequence in the 3'-untranslated region of mRNA molecules specifying
inflammatory mediators. Proc.Natl.Acad.Sci.U.S.A 1986; 83: 1670-4.
43 Frevel MA, Bakheet T, Silva AM, Hissong JG, Khabar KS, Williams BR. p38 Mitogenactivated protein kinase-dependent and -independent signaling of mRNA stability of AU-rich
element-containing transcripts. Mol.Cell Biol. 2003; 23: 425-36.
44 Dean JL, Sully G, Clark AR, Saklatvala J. The involvement of AU-rich element-binding
proteins in p38 mitogen-activated protein kinase pathway-mediated mRNA stabilisation. Cell
Signal. 2004; 16: 1113-21.
45 Brook M, Sully G, Clark AR, Saklatvala J. Regulation of tumour necrosis factor alpha mRNA
stability by the mitogen-activated protein kinase p38 signalling cascade. FEBS Lett. 2000; 483:
57-61.
46 Miyazawa K, Mori A, Miyata H, Akahane M, Ajisawa Y, Okudaira H. Regulation of
interleukin-1beta-induced interleukin-6 gene expression in human fibroblast-like synoviocytes
by p38 mitogen-activated protein kinase. J.Biol.Chem. 1998; 273: 24832-8.
47 Ridley SH, Sarsfield SJ, Lee JC et al. Actions of IL-1 are selectively controlled by p38 mitogenactivated protein kinase: regulation of prostaglandin H synthase-2, metalloproteinases, and IL-6
at different levels. J.Immunol. 1997; 158: 3165-73.
48 Reunanen N, Li SP, Ahonen M, Foschi M, Han J, Kahari VM. Activation of p38 alpha MAPK
enhances collagenase-1 (matrix metalloproteinase (MMP)-1) and stromelysin-1 (MMP-3)
expression by mRNA stabilization. J.Biol.Chem. 2002; 277: 32360-8.
49 Lasa M, Abraham SM, Boucheron C, Saklatvala J, Clark AR. Dexamethasone causes sustained
expression of mitogen-activated protein kinase (MAPK) phosphatase 1 and phosphatasemediated inhibition of MAPK p38. Mol.Cell Biol. 2002; 22: 7802-11.
50 Theodosiou A, Ashworth A. MAP kinase phosphatases. Genome Biol. 2002; 3: REVIEWS3009.
26
Signal transduction pathways in RA
51 Franklin CC, Kraft AS. Conditional expression of the mitogen-activated protein kinase (MAPK)
phosphatase MKP-1 preferentially inhibits p38 MAPK and stress-activated protein kinase in
U937 cells. J.Biol.Chem. 1997; 272: 16917-23.
52 Toh ML, Yang Y, Leech M, Santos L, Morand EF. Expression of mitogen-activated protein
kinase phosphatase 1, a negative regulator of the mitogen-activated protein kinases, in
rheumatoid arthritis: up-regulation by interleukin-1beta and glucocorticoids. Arthritis Rheum.
2004; 50: 3118-28.
53 Xu Q, Konta T, Nakayama K et al. Cellular defense against H2O2-induced apoptosis via MAP
kinase-MKP-1 pathway. Free Radic.Biol.Med. 2004; 36: 985-93.
54 Lee JC, Griswold DE, Votta B, Hanna N. Inhibition of monocyte IL-1 production by the antiinflammatory compound, SK&F 86002. Int.J.Immunopharmacol. 1988; 10: 835-43.
55 Young PR, McLaughlin MM, Kumar S et al. Pyridinyl imidazole inhibitors of p38 mitogenactivated protein kinase bind in the ATP site. J.Biol.Chem. 1997; 272: 12116-21.
56 Wadsworth SA, Cavender DE, Beers SA et al. RWJ 67657, a potent, orally active inhibitor of
p38 mitogen-activated protein kinase. J.Pharmacol.Exp.Ther. 1999; 291: 680-7.
57 Badger AM, Bradbeer JN, Votta B, Lee JC, Adams JL, Griswold DE. Pharmacological profile
of SB 203580, a selective inhibitor of cytokine suppressive binding protein/p38 kinase, in
animal models of arthritis, bone resorption, endotoxin shock and immune function.
J.Pharmacol.Exp.Ther. 1996; 279: 1453-61.
58 Jackson JR, Bolognese B, Hillegass L et al. Pharmacological effects of SB 220025, a selective
inhibitor of P38 mitogen-activated protein kinase, in angiogenesis and chronic inflammatory
disease models. J.Pharmacol.Exp.Ther. 1998; 284: 687-92.
59 Mclay LM, Halley F, Souness JE et al. The discovery of RPR 200765A, a p38 MAP kinase
inhibitor displaying a good oral anti-arthritic efficacy. Bioorg.Med.Chem. 2001; 9: 537-54.
60 Nishikawa M, Myoui A, Tomita T, Takahi K, Nampei A, Yoshikawa H. Prevention of the onset
and progression of collagen-induced arthritis in rats by the potent p38 mitogen-activated protein
kinase inhibitor FR167653. Arthritis Rheum. 2003; 48: 2670-81.
61 Patten C, Bush K, Rioja I et al. Characterization of pristane-induced arthritis, a murine model of
chronic disease: response to antirheumatic agents, expression of joint cytokines, and
immunopathology. Arthritis Rheum. 2004; 50: 3334-45.
62 Fijen JW, Zijlstra JG, de Boer P et al. Suppression of the clinical and cytokine response to
endotoxin by RWJ-67657, a p38 mitogen-activated protein-kinase inhibitor, in healthy human
volunteers. Clin.Exp.Immunol. 2001; 124: 16-20.
63 Parasrampuria DA, de Boer P, Desai-Krieger D, Chow AT, Jones CR. Single-dose
pharmacokinetics and pharmacodynamics of RWJ 67657, a specific p38 mitogen-activated
protein kinase inhibitor: a first-in-human study. J.Clin.Pharmacol. 2003; 43: 406-13.
64 Haddad JJ. VX-745. Vertex Pharmaceuticals. Curr.Opin.Investig.Drugs 2001; 2: 1070-6.
65 Nikas SN, Drosos AA. SCIO-469 Scios Inc. Curr.Opin.Investig.Drugs 2004; 5: 1205-12.
27