A potent and selective p38 inhibitor protects against bone damage in murine collagen-induced arthritis: a comparison with neutralization of mouse TNFalpha

Therapeutic Opportunities Presented by Modulation of Cellular Senescence

Cellular senescence is a permanent state of growth arrest coupled with profound changes in phenotype that can be triggered by multiple extrinsic or intrinsic stimuli. Senescence is a process-level example of the evolution of ageing mechanisms through antagonistic pleiotropy and plays a primary role in tumour suppression, although evidence is mounting for its involvement in other fundamental physiological processes. Evidence from human premature ageing diseases and from transgenic mice in which it is possible to specifically delete senescent cells is consistent with a model in which the accumulation of senescent cells through the life course is responsible for later life chronic disease and impairment. The removal of senescent cells or their reversion to a phenotypically benign state is thus an important emerging goal of translational medicine.Modern bioinformatic approaches based on text mining have compiled co-mentions of cell senescence and age-related diseases allowing an impartial ranking of the impairments most closely associated with this process. Following this schema, the evidence for the involvement of senescence in several highly ranked pathologies is reviewed, alongside potential methods for the ablation of senescent cells or their reversion to their primary phenotype with polyphenolics or inhibitors of p38 MAP kinase. Lastly, the potential for senescence to act as a barrier to the development of bioartificial organs designed to treat some of these conditions is discussed.

Stress signaler p38 mitogen-activated kinase activation: a cause for concern?

Oxidative stress (OS) induced activation of p38 mitogen-activated kinase (MAPK) and cell fate from p38 signaling was tested using the human fetal membrane's amnion epithelial cells (AEC). We created p38 KO AEC using the CRISPR/Cas9 approach and tested cell fate in response to OS on an AEC-free fetal membrane extracellular matrix (ECM). Screening using image CyTOF indicated OS causing epithelial-mesenchymal transition (EMT). Further testing revealed p38 deficiency prevented AEC senescence, EMT, cell migration, and inflammation. To functionally validate in vitro findings, fetal membrane-specific conditional KO (cKO) mice were developed by injecting Cre-recombinase encoded exosomes intra-amniotically into p38αloxP/loxP mice. Amnion membranes from p38 cKO mice had reduced senescence, EMT, and increased anti-inflammatory IL-10 compared with WT animals. Our study suggested that overwhelming activation of p38 in response to OS inducing risk exposures can have an adverse impact on cells, cause cell invasion, inflammation, and ECM degradation detrimental to tissue homeostasis.

Synthesis and in vitro antiproliferative activity of certain novel pyrazolo[3,4-b]pyridines with potential p38α MAPK-inhibitory activity

Novel series of pyrazolo[3,4-b]pyridines 9a-j and 14a-f were prepared via a one-pot three-component reaction. Compounds 9a-j were synthesized by the reaction of 3-(4-chlorophenyl)-1-phenyl-1H-pyrazol-5-amine (4) with benzoyl acetonitriles 3a,b and aldehydes 5a-e, whereas the spiro derivatives 14a-f were synthesized by the reaction of pyrazole derivative 4 with 3a-c and indoline-2,3-diones 10a,b. Screening of the antiproliferative activity of 9a-j and 14a-f revealed that 14a and 14d were the most potent analogues against HepG2 and HeLa cells, with IC₅₀  = 4.2 and 5.9 μM, respectively. Moreover, compounds 9c and 14a could promote cell cycle disturbance and apoptosis in HepG2 cells, as evidenced by DNA flow cytometry and Annexin V-FITC/PI assays. Cell cycle analysis of 9c and 14a indicated a reduction in HepG2 cells in the G1 phase, with arrest in the S phase and the G2/M phase, respectively. Also, 9c and 14a are good apoptotic inducers in the HepG2 cell line. Furthermore, compounds 9h and 14d stood out as the most efficient antiproliferative agents in the NCI 60-cell line panel screening, with mean GI % equal to 60.3% and 55.4%, respectively. Additionally, 9c, 9h, 14a, and 14d showed good inhibitory action against the cellular pathway regulator p38α kinase, with IC₅₀  = 0.42, 0.41, 0.13, and 0.64 μM, respectively. A docking study was carried out on the p38α kinase active site, showing a binding mode comparable to that of reported p38 mitogen-activated protein kinase inhibitors. These newly discovered pyrazolo[3,4-b]pyridines could be considered as potential candidates for the development of newly targeted anticancer agents.

Targeting Toll-like Receptor (TLR) Pathways in Inflammatory Arthritis: Two Better Than One?

Inflammatory arthritis is a cluster of diseases caused by unregulated activity of the immune system. The lost homeostasis is followed by the immune attack of one’s self, what damages healthy cells and tissues and leads to chronic inflammation of various tissues and organs (e.g., joints, lungs, heart, eyes). Different medications to control the excessive immune response are in use, however, drug resistances, flare-reactions and adverse effects to the current therapies are common in the affected patients. Thus, it is essential to broaden the spectrum of alternative treatments and to develop disease-modifying drugs. In the last 20 years, the involvement of the innate immune receptors TLRs in inflammatory arthritis has been widely investigated and targeting either the receptor itself or the proteins in the downstream signalling cascades has emerged as a promising therapeutic strategy. Yet, concerns about the use of pharmacological agents that inhibit TLR activity and may leave the host unprotected against invading pathogens and toxicity issues amid inhibition of downstream kinases crucial in various cellular functions have arisen. This review summarizes the existing knowledge on the role of TLRs in inflammatory arthritis; in addition, the likely druggable related targets and the developed inhibitors, and discusses the pros and cons of their potential clinical use.

JTP-117968, a novel selective glucocorticoid receptor modulator, exhibits significant anti-inflammatory effect while maintaining bone mineral density in mice

Classic glucocorticoids have been prescribed for various inflammatory diseases, such as rheumatoid arthritis, due to their outstanding anti-inflammatory effects. However, glucocorticoids cause numerous unwanted side effects, including osteoporosis and diabetes. Hence, selective glucocorticoid receptor modulators (SGRMs), which retain anti-inflammatory effects with minimized side effects, are among the most anticipated drugs in the clinical field. The assumption is that there are two major mechanisms of action via glucocorticoid receptors, transrepression (TR) and transactivation (TA). In general, anti-inflammatory effects of glucocorticoids are largely due to TR, while the side effects associated with glucocorticoids are mostly mediated through TA. We previously reported that JTP-117968, a novel SGRM, maintained partial TR activity while remarkably reducing the TA activity. In this study, we investigated the anti-inflammatory effect of JTP-117968 on a lipopolysaccharide (LPS) challenge model and collagen-induced arthritis (CIA) model in mice. Meanwhile, we tested the effect of JTP-117968 on the bone mineral density (BMD) in mouse femur to evaluate the side effect. Based on the evaluation, JTP-117968 reduced the plasma levels of tumor necrosis factor α induced by LPS challenge in mice significantly. Remarkably, CIA development was suppressed by JTP-117968 comparably with prednisolone and PF-802, an active form of fosdagrocorat that has been developed clinically as an orally available SGRM. Strikingly, the side effect of JTP-117968 on mouse femoral BMD was much lower than those of PF-802 and prednisolone. Therefore, JTP-117968 has attractive potential as a new therapeutic option against inflammatory diseases with minimized side effects compared to classic glucocorticoids.

Design, synthesis and anti-inflammatory activity of imidazol-5-yl pyridine derivatives as p38α/MAPK14 inhibitor

P38α/MAPK14 is intracellular signalling regulator involved in biosynthesis of inflammatory mediator cytokines (TNF-α, IL-1, IL-6, and IL-1b), which induce the production of inflammatory proteins (iNOS, NF-kB, and COX-2). In this study, drug repurposing strategies were followed to repositioning of a series of B-RAF ^V600E imidazol-5-yl pyridine inhibitors to inhibit P38α kinase. A group 25 reported P38α kinase inhibitors were used to build a pharmacophore model for mapping the target compounds and proving their affinity for binding in P38α active site. Target compounds were evaluated for their potency against P38α kinase, compounds 11a and 11d were the most potent inhibitors (IC₅₀ = 47 nM and 45 nM, respectively). In addition, compound 11d effectively inhibited the production of proinflammatory cytokinesTNF-α, 1L-6, and 1L-1β in LPS-induced RAW 264.7 macrophages with IC₅₀ values of 78.03 nM, 17.6 µM and 82.15 nM, respectively. The target compounds were tested for their anti-inflammatory activity by detecting the reduction of Nitric oxide (NO) and prostaglandin (PGE2) production in LPS-stimulated RAW 264.7 macrophages. Compound 11d exhibited satisfied inhibitory activity of the production of PGE2 and NO with IC₅₀ values of 0.29 µM and 0.61 µM, respectively. Molecular dynamics simulations of the most potent inhibitor 11d were carried out to illustrate its conformational stability in the binding site of P38α kinase.

Hydrogen Sulfide: a Novel Immunoinflammatory Regulator in Rheumatoid Arthritis

Hydrogen sulfide (H₂S), an endogenous, gaseous, signaling transmitter, has been shown to have vasodilative, anti-oxidative, anti-inflammatory, and cytoprotective activities. Increasing evidence also indicates that H₂S can suppress the production of inflammatory mediators by immune cells, for example, T cells and macrophages. Inflammation is closely related to an immune response in several diseases such as rheumatoid arthritis (RA), multiple sclerosis (MS), systemic lupus erythematosus (SLE), and cancer. Considering these biological effects of H₂S, a potential role in the treatment of immune-related RA is being exploited. In the present review, we will provide an overview of the therapeutic potential of H₂S in RA treatment.

Proof of pharmacology of Org 48775-0, a p38 MAP kinase inhibitor, in healthy volunteers

AIM

To investigate the safety, tolerability, pharmacokinetics and pharmacodynamics of the highly selective oral p38alpha/beta mitogen-activated protein (MAP) kinase inhibitor Org 48,775-0 in a first-in-human study.

METHODS

In the single ascending dosing (SAD) study, an oral dose of Org 48,775-0 (0.3-600 mg) was evaluated in healthy males. In the multiple ascending dosing (MAD) study, levels of 30, 70 and 150 mg were dosed for six consecutive days, twice daily. Both studies were performed in a double-blind, randomized, placebo-controlled, cross-over fashion and evaluated pharmacokinetics, pharmacodynamics (ex vivo inhibition of lipopolysaccharide [LPS]-induced tumor necrosis factor (TNFα) release) and routine clinical and laboratory data. Pharmacokinetic and pharmacodynamic parameters of Org 48,775-0 were compared between healthy males and postmenopausal females, and the effect of a standardized fat meal was evaluated.

RESULTS

All adverse events observed in the SAD (16; dizziness and headache, diarrhoea and catheter-related phlebitis) and MAD (43; mainly somnolence, dizziness, headache and nasopharyngitis) cohorts were mild, transient and completely reversible. Pharmacokinetics were linear up to single doses of 400 mg. Median T_max ranged from 0.5 to 1.8 hours, geometric mean for T_1/2 from 7.0 to 14.4 hours. Org 48,775-0 doses equal to and greater than 30 mg significantly inhibited LPS-induced TNFα release (42.3%; 95% CI = -65.2, -4.3) compared to placebo. In the MAD study, Org 48,775-0 treatment inhibited LPS-induced TNFα release during the entire steady-state period. Levels of inhibition amounted 30-75% for 30 mg, 53-80% for 70 mg and 77-92% for 150 mg Org 48,775-0.

CONCLUSION

Org 48,775-0 has the capacity to significantly inhibit MAP kinase activity in humans without safety concerns.

Inhibition of Osteoclastogenesis by Thioredoxin-Interacting Protein-Derived Peptide (TN13)

Overactivated osteoclasts lead to many bone diseases, including osteoporosis and rheumatoid arthritis. The p38 MAPK (p38) is an essential regulator of the receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclastogenesis and bone loss. We previously reported TAT conjugated thioredoxin-interacting protein-derived peptide (TAT-TN13) as an inhibitor of p38 in hematopoietic stem cells (HSCs). Here, we examined the role of TAT-TN13 in the differentiation and function of osteoclasts. TAT-TN13 significantly suppressed RANKL-mediated differentiation of RAW 264.7 cells and bone marrow macrophages (BMMs) into osteoclasts. TAT-TN13 also inhibited the RANKL-induced activation of NF-κB and nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), leading to the decreased expression of osteoclast-specific genes, including tartrate-resistant acid phosphatase (TRAP) and Cathepsin K. Additionally, TAT-TN13 treatment protected bone loss in ovariectomized (OVX) mice. Taken together, these results suggest that TAT-TN13 inhibits osteoclast differentiation by regulating the p38 and NF-κB signaling pathway; thus, it may be a useful agent for preventing or treating osteoporosis.

TNF-α-induced protein 3 (TNFAIP3)/A20 acts as a master switch in TNF-α blockade-driven IL-17A expression

BACKGROUND

Anti-TNF inhibitors successfully improve the quality of life of patients with inflammatory disease. Unfortunately, not all patients respond to anti-TNF therapy, and some patients show paradoxical immune side effects, which are poorly understood. Surprisingly, anti-TNF agents were shown to promote IL-17A production with as yet unknown clinical implications.

OBJECTIVE

We sought to investigate the molecular mechanism underlying anti-TNF-driven IL-17A expression and the clinical implications of this phenomenon.

METHODS

Fluorescence-activated cell sorting, RNA sequencing, quantitative real-time PCR, Western blotting, small interfering RNA interference, and kinase inhibitors were used to study the molecular mechanisms in isolated human CD4⁺ T cells from healthy donors. The clinical implication was studied in blood samples of patients with inflammatory bowel disease (IBD) receiving anti-TNF therapy.

RESULTS

Here we show that anti-TNF treatment results in inhibition of the anti-inflammatory molecule TNF-α-induced protein 3 (TNFAIP3)/A20 in memory CD4⁺ T cells. We found an inverse relationship between TNFAIP3/A20 expression levels and IL-17A production. Inhibition of TNFAIP3/A20 promotes kinase activity of p38 mitogen-activated protein kinase and protein kinase C, which drives IL-17A expression. Regulation of TNFAIP3/A20 expression and cognate IL-17A production in T cells are specifically mediated through TNF receptor 2 signaling. Ex vivo, in patients with IBD treated with anti-TNF, we found further evidence for an inverse relationship between TNFAIP3/A20 expression levels and IL-17A-producing T cells.

CONCLUSION

Anti-TNF treatment interferes in the TNFAIP3/A20-mediated anti-inflammatory feedback loop in CD4⁺ T cells and promotes kinase activity. This puts TNFAIP3/A20, combined with IL-17A expression, on the map as a potential tool for predicting therapy responsiveness or side effects of anti-TNF therapy. Moreover, it provides novel targets related to TNFAIP3/A20 activity for superior therapeutic regimens in patients with IBD.

Differential expression of STAT-3 in subtypes of oral lichen planus: a preliminary study

OBJECTIVE

This study aimed to examine the expression of signaling transduction proteins and their possible correlation with different clinical subtypes of oral lichen planus (OLP).

STUDY DESIGN

We examined the immunoexpression and phosphorylation status of 21 signaling transduction proteins of OLP (n = 10) and normal groups (n = 8) using PathScan analysis. Using immunohistochemistry, we detected expression of STAT-3 and p38 MAPK in tissues of OLP (n = 40) and normal controls (n = 10).

RESULTS

PathScan analysis showed that STAT-3 (Ser727) expression in normal control (N), reticular OLP (R-OLP) and erosive OLP (E-OLP) group was gradually elevated (R-OLP vs N, P = .001; E-OLP vs N, P < .001; E-OLP vs R-OLP, P = .002). Immunohistochemistry showed that STAT-3 expression in the epithelium of normal control, reticular OLP and erosive OLP was consistent with PathScan analysis (R-OLP vs N, P < .001; E-OLP vs N, P < .001; E-OLP vs R-OLP, P = .036). Both PathScan (P = .012) and immunohistochemistry (P < .001) showed that, p38 MAPK expression was significantly higher in OLP compared with normal controls. However, a significant difference was not seen between the reticular OLP and erosive OLP groups.

CONCLUSIONS

Our results indicate that STAT-3 may be involved in OLP development and progression and account for different clinical manifestations.

Assessment of collagen antibody-induced arthritis in BALB/c mice using bioimaging analysis and histopathological examination

The aim of this study was to examine the therapeutic potential of sulfasalazine and prednisolone in a mouse collagen antibody-induced arthritis (CAIA) model. Twenty-five male BALB/c mice were randomly divided into five groups: group 1 (G1): control, group 2 (G2): probe control, group 3 (G3): CAIA, group 4 (G4): CAIA+sulfasalazine (10 mg/kg, oral), and group 5 (G5): CAIA+prednisolone (100 mg/kg, oral). Fluorescence bioimaging was performed in vivo 24 and 48 h after treatment with a fluorescence probe (OsteoSense® 680 EX), and all mice were sacrificed. The hind knee joints were fixed in 10% neutral phosphate-buffered formalin, and micro-computed tomography (micro-CT) and histopathological analyses were performed. The paw thickness increased in a time-dependent manner in G3 mice, but trended toward a decrease in both G4 and G5 mice. Fluorescence intensity increased in G3 mice at 24 and 48 h after fluorescence probe treatment, but the fluorescence intensity in G4 and G5 mice was lower than that in G3. Micro-CT analyses showed that the joint surfaces of G3 mice had a rough and irregular articular appearance, but the occurrence of these irregularities was lower in G4 and G5. Hematoxylin and eosin and Safranin O-fast green staining confirmed that destruction of the cartilage and bony structures, synovial hyperplasia, and inflammatory cell infiltration all occurred in G3, and that the occurrence of these phenomena was lower in G4 and G5 than in G3. Taken together, these results suggest that sulfasalazine and prednisolone can reduce acute rheumatoid arthritis in mice.

The Role of Presenilin-1 in the Excitotoxicity of Ethanol Withdrawal

Presenilin-1 (PS1) is a core component of γ-secretase that is involved in neurodegeneration. We have previously shown that PS1 interacts with a mitogen-activated protein kinase [(MAPK) jun-NH2-terminal-kinase], and another MAPK (p38) is activated by ethanol withdrawal (EW), abrupt termination from chronic ethanol exposure. EW is excitotoxic in nature, induces glutamate upregulation, and provokes neuronal damage. Here, we explored a potential mechanistic pathway involving glutamate, p38 (p38α isozyme), and PS1 that may mediate EW-induced excitotoxic stress. We used the prefrontal cortex of male rats withdrawn from a chronic ethanol diet. Additionally, we used ethanol-withdrawn HT22 cells (mouse hippocampal) treated with the inhibitor of glutamate receptors [dizocilpine (MK-801)], p38α (SB203580; 4-[4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-1H-imidazol-5-yl]pyridine), or γ-secretase [N-[N- (3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT)] during EW. Separately, ethanol-free HT22 cells were exposed to glutamate with or without SB203580 or DAPT. Protein levels, mRNA levels, and cell viability were assessed using immunoblotting, qualitative polymerase chain reaction, and calcein assay, respectively. The prefrontal cortex of ethanol-withdrawn rats or HT22 cells showed an increase in PS1 and p38α, which was attenuated by MK-801 and SB203580, but mimicked by glutamate treatment to ethanol-free HT22 cells. DAPT attenuated the toxic effect of EW or glutamate on HT22 cells. These results suggest that PS1 expression is triggered by glutamate through p38α, contributing to the excitotoxic stimulus of EW.

Evaluating the Role of p38 MAPK in the Accelerated Cell Senescence of Werner Syndrome Fibroblasts

Progeroid syndromes show features of accelerated ageing and are used as models for human ageing, of which Werner syndrome (WS) is one of the most widely studied. WS fibroblasts show accelerated senescence that may result from p38 MAP kinase activation since it is prevented by the p38 inhibitor SB203580. Thus, small molecule inhibition of p38-signalling may be a therapeutic strategy for WS. To develop this approach issues such as the in vivo toxicity and kinase selectivity of existing p38 inhibitors need to be addressed, so as to strengthen the evidence that p38 itself plays a critical role in mediating the effect of SB203580, and to find an inhibitor suitable for in vivo use. In this work we used a panel of different p38 inhibitors selected for: (1) having been used successfully in vivo in either animal models or human clinical trials; (2) different modes of binding to p38; and (3) different off-target kinase specificity profiles, in order to critically address the role of p38 in the premature senescence seen in WS cells. Our findings confirmed the involvement of p38 in accelerated cell senescence and identified p38 inhibitors suitable for in vivo use in WS, with BIRB 796 the most effective.

Suppression of the senescence-associated secretory phenotype (SASP) in human fibroblasts using small molecule inhibitors of p38 MAP kinase and MK2

Senescent cells show an altered secretome profile termed the senescence-associated secretory phenotype (SASP). There is an increasing body of evidence that suggests that the accumulation of SASP-positive senescent cells in humans is partially causal in the observed shift to a low-level pro-inflammatory state in aged individuals. This in turn suggests the SASP as a possible therapeutic target to ameliorate inflammatory conditions in the elderly, and thus a better understanding of the signalling pathways underlying the SASP are required. Prior studies using the early generation p38 MAPK inhibitor SB203580 indicated that p38 signalling was required for the SASP. In this study, we extend these observations using two next-generation p38 inhibitors (UR-13756 and BIRB 796) that have markedly improved selectivity and specificity compared to SB203580, to strengthen the evidence that the SASP is p38-dependent in human fibroblasts. BIRB 796 has an efficacy and toxicity profile that has allowed it to reach Phase III clinical trials, suggesting its possible use to suppress the SASP in vivo. We also demonstrate for the first time a requirement for signalling through the p38 downstream MK2 kinase in the regulation of the SASP using two MK2 inhibitors. Finally, we demonstrate that a commercially-available multiplex cytokine assay technology can be used to detect SASP components in the conditioned medium of cultured fibroblasts from both young and elderly donors. This assay is a high-throughput, multiplex microtitre-based assay system that is highly sensitive, with very low sample requirements, allowing it to be used for low-volume human biological fluids. Our initial studies using existing multiplex plates form the basis for a “SASP signature” assay that could be used as a high-throughput system in a clinical study setting. Our findings therefore provide important steps towards the study of, and intervention in, the SASP in human ageing and age-related disease.

Roles of p38α mitogen-activated protein kinase in mouse models of inflammatory diseases and cancer

The p38α mitogen‐activated protein kinase pathway not only regulates the production of inflammatory mediators, but also controls processes related to tissue homeostasis, such as cell proliferation, differentiation and survival, which are often disrupted during malignant transformation. The versatility of this signaling pathway allows for the regulation of many specific functions depending on the cell type and context. Here, we discuss mouse models that have been used to identify in vivo functions of p38α signaling in the pathogenesis of inflammatory diseases and cancer. Experiments using genetically modified mice and pharmacological inhibitors support that targeting the p38α pathway could be therapeutically useful for some inflammatory diseases and tumor types.

The inhibition of RANKL-induced osteoclastogenesis through the suppression of p38 signaling pathway by naringenin and attenuation of titanium-particle-induced osteolysis

The aim of this study was to assess the effect of naringenin on osteoclastogenesis and titanium particle-induced osteolysis. Osteolysis from wear-induced particles and aseptic loosening are the most frequent late complications of total joint arthroplasty leading to revision of the prosthesis. Osteolysis during aseptic loosening is most likely due to increased bone resorption by osteoclasts. Through in vitro studies, we demonstrated that naringenin, a naturally occurring flavanone in grapefruit and tomatoes, exerts potent inhibitory effects on the ligand of the receptor activator of nuclear factor-κB (RANKL)-induced osteoclastogenesis and revealed that the mechanism of action of naringenin, which inhibited osteoclastogenesis by suppression of the p38 signaling pathway. Through in vivo studies, we proved that naringenin attenuated titanium particle-induced osteolysis in a mouse calvarial model. In general, we demonstrated that naringenin inhibited osteoclastogenesis via suppression of p38 signaling in vitro and attenuated titanium particle-induced osteolysis in vivo. This study also suggested that naringenin has significant potential for the treatment of osteolysis-related diseases caused by excessive osteoclast formation and activity.

Oral administration of the p38α MAPK inhibitor, UR13870, inhibits affective pain behavior after spinal cord injury

The p38α mitogenous activated protein kinase (MAPK) cell signaling pathway is a key mechanism of microglia activation and has been studied as a target for neuropathic pain. The effect of UR13870, a p38α MAPK inhibitor, on microglia expression in the anterior cingulate cortex (ACC) and spinal dorsal horn was addressed after T9 contusion spinal cord injury (SCI) in the rat, in addition to behavioral testing of pain-related aversion and anxiety. Administration of intravenous UR13870 (1mg/kg i.v.) and pregabalin (30 mg/kg i.v.) reduced place escape avoidance paradigm (PEAP) but did not affect open-field anxiety behavior 42 days after SCI. PEAP behavior was also reduced in animals administered daily with oral UR13870 (10mg/kg p.o.) and preserved spinal tissue 28 days after SCI. Although UR13870 (10mg/kg p.o.) failed to reduce OX-42 and glial fibrillar acid protein immunoreactivity within the spinal dorsal horn, a reduction toward the control level was observed close to the SCI site. In the anterior cingulate cortex (ACC), a significant increase in OX-42 immunoreactivity was identified after SCI. UR13870 (10mg/kg p.o.) treatment significantly reduced OX-42, metabotropic glutamate type 5 receptor (mGluR5), and NMDA (N-methyl-d-aspartate) 2B subunit receptor (NR2B) expression in the ACC after SCI. To conclude, oral treatment with a p38α MAPK inhibitor reduces the affective behavioral component of pain after SCI in association with a reduction of microglia and specific glutamate receptors within the ACC. Nevertheless the role of neuroinflammatory processes within the vicinity of the SCI site in the development of affective neuropathic pain cannot be excluded.

Proof of concept: enthesitis and new bone formation in spondyloarthritis are driven by mechanical strain and stromal cells

OBJECTIVES

Spondyloarthritides (SpA) are characterised by both peripheral and axial arthritis. The hallmarks of peripheral SpA are the development of enthesitis, most typically of the Achilles tendon and plantar fascia, and new bone formation. This study was undertaken to unravel the mechanisms leading towards enthesitis and new bone formation in preclinical models of SpA.

RESULTS

First, we demonstrated that TNF(ΔARE) mice show typical inflammatory features highly reminiscent of SpA. The first signs of inflammation were found at the entheses. Importantly, enthesitis occurred equally in the presence or absence of mature T and B cells, underscoring the importance of stromal cells. Hind limb unloading in TNF(ΔARE) mice significantly suppressed inflammation of the Achilles tendon compared with weight bearing controls. Erk1/2 signalling plays a crucial role in mechanotransduction-associated inflammation. Furthermore, new bone formation is strongly promoted at entheseal sites by biomechanical stress and correlates with the degree of inflammation.

CONCLUSIONS

These findings provide a formal proof of the concept that mechanical strain drives both entheseal inflammation and new bone formation in SpA.

A guide to picking the most selective kinase inhibitor tool compounds for pharmacological validation of drug targets

To establish the druggability of a target, genetic validation needs to be supplemented with pharmacological validation. Pharmacological studies, especially in the kinase field, are hampered by the fact that many reference inhibitors are not fully selective for one target. Fortunately, the initial trickle of selective inhibitors released in the public domain has steadily swelled into a stream. However, rationally picking the most selective tool compound out of the increasing amounts of available inhibitors has become progressively difficult due to the lack of accurate quantitative descriptors of drug selectivity. A recently published approach, termed 'selectivity entropy', is an improved way of expressing selectivity as a single-value parameter and enables rank ordering of inhibitors. We provide a guide to select the best tool compounds for pharmacological validation experiments of candidate drug targets using selectivity entropy. In addition, we recommend which inhibitors to use for studying the biology of the 20 most investigated kinases that are clinically relevant: Abl (ABL1), AKT1, ALK, Aurora A/B, CDKs, MET, CSF1R (FMS), EGFR, FLT3, ERBB2 (HER2), IKBKB (IKK2), JAK2/3, JNK1/2/3 (MAPK8/9/10), MEK1/2, PLK1, PI3Ks, p38α (MAPK14), BRAF, SRC and VEGFR2 (KDR).

Cannabinoids: novel therapies for arthritis?

A key feature of osteoarthritis and rheumatoid arthritis is the loss of articular cartilage. Cartilage breakdown is mediated by complex interactions of proinflammatory cytokines, such as IL-1, inflammatory mediators, including nitric oxide and prostaglandin E2, and proteases, including matrix metalloproteinases and aggrecanases, such as ADAMTS-4 and -5. Cannabinoids have been shown to reduce joint damage in animal models of arthritis. They have also been shown to prevent IL-1-induced matrix breakdown of collagen and proteoglycan, indicating that cannabinoids may mediate chondroprotective effects. Cannabinoids produce their effects via several cannabinoid receptors and it is important to identify the key cannabinoids and their receptors that are involved in chondroprotection. This review aims to outline the current and future prospects of cannabinoids as anti-arthritic therapeutics, in terms of their ability to prevent cartilage breakdown.

Molecular pathway profiling of T lymphocyte signal transduction pathways; Th1 and Th2 genomic fingerprints are defined by TCR and CD28-mediated signaling

Background

T lymphocytes are orchestrators of adaptive immunity. Naïve T cells may differentiate into Th1, Th2, Th17 or iTreg phenotypes, depending on environmental co-stimulatory signals. To identify genes and pathways involved in differentiation of Jurkat T cells towards Th1 and Th2 subtypes we performed comprehensive transcriptome analyses of Jurkat T cells stimulated with various stimuli and pathway inhibitors. Results from these experiments were validated in a human experimental setting using whole blood and purified CD4+ Tcells.

Results

Calcium-dependent activation of T cells using CD3/CD28 and PMA/CD3 stimulation induced a Th1 expression profile reflected by increased expression of T-bet, RUNX3, IL-2, and IFNγ, whereas calcium-independent activation via PMA/CD28 induced a Th2 expression profile which included GATA3, RXRA, CCL1 and Itk. Knock down with siRNA and gene expression profiling in the presence of selective kinase inhibitors showed that proximal kinases Lck and PKCθ are crucial signaling hubs during T helper cell activation, revealing a clear role for Lck in Th1 development and for PKCθ in both Th1 and Th2 development. Medial signaling via MAPkinases appeared to be less important in these pathways, since specific inhibitors of these kinases displayed a minor effect on gene expression. Translation towards a primary, whole blood setting and purified human CD4+ T cells revealed that PMA/CD3 stimulation induced a more pronounced Th1 specific, Lck and PKCθ dependent IFNγ production, whereas PMA/CD28 induced Th2 specific IL-5 and IL-13 production, independent of Lck activation. PMA/CD3-mediated skewing towards a Th1 phenotype was also reflected in mRNA expression of the master transcription factor Tbet, whereas PMA/CD28-mediated stimulation enhanced GATA3 mRNA expression in primary human CD4+ Tcells.

Conclusions

This study identifies stimulatory pathways and gene expression profiles for in vitro skewing of T helper cell activation. PMA/CD3 stimulation enhances a Th1-like response in an Lck and PKCθ dependent fashion, whereas PMA/CD28 stimulation results in a Th2-like phenotype independent of the proximal TCR-tyrosine kinase Lck. This approach offers a robust and fast translational in vitro system for skewed T helper cell responses in Jurkat T cells, primary human CD4+ Tcells and in a more complex matrix such as human whole blood.

Anti-inflammatory effects of LASSBio-998, a new drug candidate designed to be a p38 MAPK inhibitor, in an experimental model of acute lung inflammation

We investigated the effects of LASSBio-998 (L-998), a compound designed to be a p38 MAPK (mitogen-activated protein kinase) inhibitor, on lipopolysaccharide (LPS)-induced acute lung inflammation in vivo. BALB/c mice were challenged with aerosolized LPS inhalation (0.5 mg/ml) 4 h after oral administration of L-998. Three hours after LPS inhalation, bronchoalveolar lavage fluid was obtained to measure the levels of the proinflammatory cytokines TNF-α (tumor necrosis factor-α) and IL-1 (interleukin-1) and the chemokines MCP-1 (monocyte chemoattractant protein-1) and KC (keratinocyte chemoattractant). In addition, neutrophil infiltration and p38 MAPK phosphorylation was measured. L-998 inhibited LPS-induced production of TNF-α and IL-1β and did not alter KC and MCP-1 levels. Furthermore, L-998 also significantly decreased neutrophil accumulation in lung tissues. As expected, L-998 diminished p38 MAPK phosphorylation and reduced acute lung inflammation. Inhibition of p38 MAPK phosphorylation by L-998 was also demonstrated in LPS-challenged murine C57BL/6 peritoneal macrophages in vitro, with concentration-dependent effects. L-998 suppressed LPS-induced lung inflammation, most likely by inhibition of the cytokine-p38 MAPK pathway, and we postulate that L-998 could be a clinically relevant anti-inflammatory drug candidate.

Small-molecule protein and lipid kinase inhibitors in inflammation and specific models for their evaluation

The inflammatory response requires complex and coordinated cooperation of different signaling pathways and cell types. Therefore, more than 40 different protein or lipid kinases can be regarded as potential small-molecule inhibitor targets to approach a therapy of acute inflammation, such as septic syndrome, and especially chronic inflammation, such as rheumatoid arthritis or inflammatory bowel disease. Besides the general considerations about selectivity and potency of small-molecule kinase inhibitors, in this chapter special emphasis is put on the inflammation-specific methods and assays available for testing potential small-molecule inhibitors for their anti-inflammatory activity. Examples for human cell-based assays for characterization of the effect of inhibitors on contribution of various cell types, such as monocytes, neutrophils, mast cells, T-cells, and synovial fibroblasts, to the inflammatory scenario are given. It is further demonstrated how these assays are complemented by rodent models for septic syndrome, rheumatoid arthritis, ulcerative colitis, Crohn's disease, and systemic lupus erythematosus. Finally, it is discussed how the results obtained by these methods can be further validated and which future strategies for the treatment of chronic inflammation will exist.

Synthesis of the highly selective p38 MAPK inhibitor UR-13756 for possible therapeutic use in Werner syndrome

BACKGROUND

UR-13756 is a potent and selective p38 mitogen-activated protein kinase (MAPK) inhibitor, reported to have good bioavailability and pharmacokinetic properties and, thus, is of potential use in the treatment of accelerated aging in Werner syndrome.

RESULTS AND DISCUSSION

Irradiation of 2-chloroacrylonitrile and methylhydrazine in ethanol at 100 °C gives 1-methyl-3-aminopyrazole, which reacts with 4-fluorobenzaldehyde and a ketone, obtained by Claisen condensation of 4-picoline, in a Hantzsch-type 3-component hereocyclocondensation, to give the pyrazolopyridine UR-13756. UR-13756 shows p38 MAPK inhibitory activity in human telomerase reverse transcriptase-immortalized HCA2 dermal fibroblasts, with an IC(50) of 80 nm, as shown by ELISA, is 100% efficacious for up to 24 h at 1.0 μm and displays excellent kinase selectivity over the related stress-activated c-Jun kinases. In addition, UR-13756 is an effective p38 inhibitor at 1.0 μm in Werner syndrome cells, as shown by immunoblot.

CONCLUSION

The convergent synthesis of UR-13756 is realized using microwave dielectric heating and provides a highly selective inhibitor that shows excellent selectivity for p38 MAPK over c-Jun N-terminal kinase.

Differential pharmacological behaviour of p38 inhibitors in regulating the LPS-induced TNF-α production in human and rat whole blood in vitro

p38 inhibitors are potent TNF-α suppressors in LPS-stimulated human whole blood and promote efficacy in the rat adjuvant arthritis model. However, the anti-TNF-α activity of p38 inhibitors in rat whole blood has not been explored, preventing the establishment of a potential relation between in vitro and in vivo activity data in the same species. We have pharmacologically characterized a rat whole blood assay based on LPS stimulation. While p38 inhibitors showed good activity in the human assay, they failed to inhibit TNF-α in the rat whole blood assay. At high LPS concentration some compounds even potentiated TNF-α production in the rat assay, which could be reverted in the presence of the ERK pathway inhibitor U0126. Our results suggest that p38 contributes directly to TNF-α production in human whole blood while playing a negative regulatory role in rat blood which can be overridden by p38 inhibition in the presence of high stimulus concentration.

An essential role for mast cells as modulators of neutrophils influx in collagen-induced arthritis in the mouse

Mast cells are involved in immune disorders so that many of the proinflammatory and tissue destructive mediators produced by these cells have been implicated in the pathogenesis of rheumatoid arthritis. This scenario prompted us to investigate the correlation between mast cell degranulation and neutrophil influx within the digits and knees joints of arthritic mice assessing what could be the functional role(s) of joint mast cells in the response to collagen immunization. DBA/1J mice were submitted to collagen-induced arthritis and disease was assessed on day 21, 32 and 42 post-immunization. Pharmacological treatment with the glucocorticoid prednisolone, commonly used in the clinic, and nedocromil, a mast cell stabilizer, was performed from day 21 to 30. Arthritis develop after immunization, gradually increased up to day 42. Neutrophil infiltration peaked on day 32 and 21, in the digits and knees, respectively, showing an unequal pattern of recruitment between these tissues. This difference emerged for mast cells: they peaked in the digits on day 21, but a higher degree of degranulation could be measured in the knee joints. Uneven modulation of arthritis occurred after treatment of mice with prednisolone or nedocromil. Neutrophils migration to the tissue was reduced after both therapies, but only prednisolone augmented mast cell migration to the joints. Nedocromil exerted inhibitory properties both on mast cell proliferation and migration, more effectively on the digit joints. Thus, collagen induced an inflammatory process characterized by tissue mast cells activation and degranulation, suggesting a potential driving force in propagating inflammatory circuits yielding recruitment of neutrophils. However, the different degree of affected joint involvement suggests a time-related implication of digits and knees during collagen-induced arthritis development. These results provide evidence for local alterations whereby mast cells contribute to the initiation of inflammatory arthritis and may be targeted in intervention strategies.

Inhibitors of p38 suppress cytokine production in rheumatoid arthritis synovial membranes: does variable inhibition of interleukin-6 production limit effectiveness in vivo?

OBJECTIVE

The activity of p38 MAPK regulates lipopolysaccharide (LPS)-stimulated production of key proinflammatory cytokines such as tumor necrosis factor α (TNFα). Consequently, p38 MAPK inhibitors have attracted considerable interest as potential treatments of rheumatoid arthritis (RA), and studies in murine models of arthritis have yielded promising results. However, the performance of several compounds in human clinical trials has been disappointing. At present, the reason for this poor performance is unclear. The aim of this study was to examine the effects of p38 inhibitors on both diseased and normal human tissue and cells, in order to test whether this kinase still plays a critical role in cytokine production under conditions of chronic inflammation.

METHODS

Proinflammatory and antiinflammatory cytokine production was monitored after treatment of primary human monocytes, macrophages, and RA synovial membrane cultures with p38 MAPK inhibitor compounds. The following 3 inhibitors were used in these studies: SB-203580 (inhibits the α and β isoforms), BIRB-796 (inhibits the α, β, γ, and δ isoforms), and a novel, structurally distinct p38 MAPK inhibitor, SB-731445 (inhibits the α and β isoforms).

RESULTS

SB-731445 and SB-203580 produced profound inhibition of spontaneous production of proinflammatory cytokines (TNFα and interleukin-1 [IL-1]) in both RA membrane cultures and LPS-stimulated primary human monocytes. However, this and other p38 MAPK inhibitors produced a significant increase in IL-6 production by LPS-stimulated primary human macrophages and a decrease in IL-10 production by all cell types examined.

CONCLUSION

The potentially proinflammatory consequences of these activities (decreased IL-10 production and increased IL-6 production) may offer some explanation for the inability of p38 MAPK inhibitors to provide the therapeutic benefit that had been hoped for in RA.

Interleukin-20 antibody is a potential therapeutic agent for experimental arthritis

OBJECTIVE

Interleukin-20 (IL-20) is a proinflammatory cytokine involved in the pathogenesis of rheumatoid arthritis (RA). We investigated whether anti-IL-20 antibody treatment would modulate the severity of the disease in a collagen-induced arthritis (CIA) rat model.

METHODS

We generated a CIA model by immunizing rats with bovine type II collagen. Rats with CIA were treated subcutaneously with anti-IL-20 antibody 7E, with the tumor necrosis factor (TNF) blocker etanercept, or with 7E in combination with etanercept. Arthritis severity was determined according to the hind paw thickness, arthritis severity score, degree of cartilage damage, bone mineral density, and cytokine production, which were evaluated using radiologic scans, microfocal computed tomography, and enzyme-linked immunosorbent assay. To analyze gene regulation by IL-20, rat synovial fibroblasts (SFs) were isolated and analyzed for the expression of RANKL, IL-17, and TNFα. We also used real-time quantitative polymerase chain reaction analysis and flow cytometry to determine IL-20-regulated RANKL in mouse osteoblastic MC3T3-E1 cells and Th17 cells.

RESULTS

In vivo, treatment with 7E alone or in combination with etanercept significantly reduced the severity of arthritis by decreasing the hind paw thickness and swelling, preventing cartilage damage and bone loss, and reducing the expression of IL-20, IL-1β, IL-6, RANKL, and matrix metalloproteinases (MMPs) in synovial tissue. In vitro, IL-20 induced TNFα expression in SFs from rats with CIA. IL-20 markedly induced RANKL production in SFs, osteoblasts, and Th17 cells.

CONCLUSION

Selectively blocking IL-20 inhibited inflammation and bone loss in rats with CIA. Treatment with 7E combined with etanercept protected rats from CIA better than treatment with etanercept alone. Our findings provide evidence that IL-20 is a novel target and that 7E may be a potential therapeutic agent for RA.

In vivo RNAi-mediated silencing of TAK1 decreases inflammatory Th1 and Th17 cells through targeting of myeloid cells

Cells from the mononuclear phagocyte system (MPS) act as systemic and local amplifiers that contribute to the progression of chronic inflammatory disorders. Transforming growth factor-β–activated kinase 1 (TAK1) is a pivotal upstream mitogen-activated protein kinase-kinase-kinase acting as a mediator of cytokine expression. It remains critical to determine in vivo the implication of TAK1 in controlling the innate immune system. Here, we describe a vehicle tailored to selectively deliver siRNAs into MPS cells after intravenous administration, and validate in vivo the potential of the RNAi-mediated TAK1 knock down for immunomodulation. In a mouse model of immune-mediated inflammatory disorder, we show that anti-TAK1 siRNA lipoplexes efficiently alleviate inflammation, severely impair the downstream c-Jun N-terminal kinase and nuclear factor-κB signaling pathways, and decrease the expression of proinflammatory mediators. Importantly, the systemic TAK1 gene silencing decreases the frequency of Th1 and Th17 cells, both mediating autoimmunity in experimental arthritis, demonstrating the immunomodulatory potential of TAK1. Finally, in vitro inhibition of TAK1 in myeloid cells decreases interferon-γ–producing T cells, suggesting that a delivery sys-tem able to target MPS cells and to silence TAK1 impacts on pathogenic T effector cells in autoimmunity.

Use of p38 MAPK Inhibitors for the Treatment of Werner Syndrome

Werner syndrome provides a convincing model for aspects of the normal ageing phenotype and may provide a suitable model for therapeutic interventions designed to combat the ageing process. Cultured primary fibroblast cells from Werner syndrome patients provide a powerful model system to study the link between replicative senescence in vitro and in vivo pathophysiology. Genome instability, together with an increased pro-oxidant state, and frequent replication fork stalling, all provide plausible triggers for intracellular stress in Werner syndrome cells, and implicates p38 MAPK signaling in their shortened replicative lifespan. A number of different p38 MAPK inhibitor chemotypes have been prepared rapidly and efficiently using microwave heating techniques for biological study in Werner syndrome cells, including SB203580, VX-745, RO3201195, UR-13756 and BIRB 796, and their selectivity and potency evaluated in this cellular context. Werner syndrome fibroblasts treated with a p38 MAPK inhibitor reveal an unexpected reversal of the accelerated ageing phenotype. Thus the study of p38 inhibition and its effect upon Werner pathophysiology is likely to provide new revelations into the biological mechanisms operating in cellular senescence and human ageing in the future.

Optical tomographic imaging discriminates between disease-modifying anti-rheumatic drug (DMARD) and non-DMARD efficacy in collagen antibody-induced arthritis

Introduction

Standard measurements used to assess murine models of rheumatoid arthritis, notably paw thickness and clinical score, do not align well with certain aspects of disease severity as assessed by histopathology. We tested the hypothesis that non-invasive optical tomographic imaging of molecular biomarkers of inflammation and bone turnover would provide a superior quantitative readout and would discriminate between a disease-modifying anti-rheumatic drug (DMARD) and a non-DMARD treatment.

Methods

Using two protease-activated near-infrared fluorescence imaging agents to detect inflammation-associated cathepsin and matrix metalloprotease activity, and a third agent to detect bone turnover, we quantified fluorescence in paws of mice with collagen antibody-induced arthritis. Fluorescence molecular tomographic (FMT) imaging results, which provided deep tissue detection and quantitative readouts in absolute picomoles of agent fluorescence per paw, were compared with paw swelling, clinical scores, a panel of plasma biomarkers, and histopathology to discriminate between steroid (prednisolone), DMARD (p38 mitogen-activated protein kinase (MAPK) inhibitor) and non-DMARD (celecoxib, cyclooxygenase-2 (COX-2) inhibitor) treatments.

Results

Paw thickness, clinical score, and plasma biomarkers failed to discriminate well between a p38 MAPK inhibitor and a COX-2 inhibitor. In contrast, FMT quantification using near-infrared agents to detect protease activity or bone resorption yielded a clear discrimination between the different classes of therapeutics. FMT results agreed well with inflammation scores, and both imaging and histopathology provided clearer discrimination between treatments as compared with paw swelling, clinical score, and serum biomarker readouts.

Conclusions

Non-invasive optical tomographic imaging offers a unique approach to monitoring disease pathogenesis and correlates with histopathology assessment of joint inflammation and bone resorption. The specific use of optical tomography allowed accurate three-dimensional imaging, quantitation in picomoles rather than intensity or relative fluorescence, and, for the first time, showed that non-invasive imaging assessment can predict the pathologist's histology inflammation scoring and discriminate DMARD from non-DMARD activity.

Two additive mechanisms impair the differentiation of 'substrate-selective' p38 inhibitors from classical p38 inhibitors in vitro

Background

The success of anti-TNF biologics for the treatment of rheumatoid arthritis has highlighted the importance of understanding the intracellular pathways that regulate TNF production in the quest for an orally-available small molecule inhibitor. p38 is known to strongly regulate TNF production via MK2. The failure of several p38 inhibitors in the clinic suggests the importance of other downstream pathways in normal cell function. Recent work has described a 'substrate-selective' p38 inhibitor that is able to preferentially block the activity of p38 against one substrate (MK2) versus another (ATF2). Using a combined experimental and computational approach, we have examined this mechanism in greater detail for two p38 substrates, MK2 and ATF2.

Results

We found that in a dual (MK2 and ATF2) substrate assay, MK2-p38 interaction reduced the activity of p38 against ATF2. We further constructed a detailed kinetic mechanistic model of p38 phosphorylation in the presence of multiple substrates and successfully predicted the performance of classical and so-called 'substrate-selective' p38 inhibitors in the dual substrate assay. Importantly, it was found that excess MK2 results in a stoichiometric effect in which the formation of p38-MK2-inhibitor complex prevents the phosphorylation of ATF2, despite the preference of the compound for the p38-MK2 complex over the p38-ATF2 complex. MK2 and p38 protein expression levels were quantified in U937, Thp-1 and PBMCs and found that [MK2] > [p38].

Conclusion

Our integrated mechanistic modeling and experimental validation provides an example of how systems biology approaches can be applied to drug discovery and provide a basis for decision-making with limited chemical matter. We find that, given our current understanding, it is unlikely that 'substrate-selective' inhibitors of p38 will work as originally intended when placed in the context of more complex cellular environments, largely due to a stoichiometric excess of MK2 relative to p38.

The tumour necrosis factor as a mediator of vessel inflammation: importance of exposed receptor residues for its neutralization

BACKGROUND

The analysis of the macromolecular tumour necrosis factor (TNF)-receptor interface helps to understand the antigenicity of this inflammatory protein.

METHOD

The calculations are based on structural data from the protein database. The residues of the macromolecular interface are identified in the interface contact matrix, a plot of pair-wise interactions between adjacent residues in the TNF-receptor complex. Starting from the matrix elements, the most exposed residues of the receptor, together with their relative contribution to the interface, are determined. This is done by Voronoi tessellation, a unique and well defined partition of the protein into polyhedral cells defining the proprietary space of the associated amino acid and its contact faces with neighboured residue cells.

RESULTS

Several interfacial receptor residues, contributing with a total amount of 63% to the macromolecular interface, could be identified.

CONCLUSION

Based on the assumption that residues with higher interfacial exposure values are playing the most important role in TNF-receptor complex, they will be the original material for further developments in engineering more efficient TNF blockers.

Proteinases involved in matrix turnover during cartilage and bone breakdown

The joint is a discrete unit that consists of cartilage, bone, tendon and ligaments. These tissues are all composed of an extracellular matrix made of collagens, proteoglycans and specialised glycoproteins that are actively synthesised, precisely assembled and subsequently degraded by the resident connective tissue cells. A balance is maintained between matrix synthesis and degradation in healthy adult tissues. Different classes of proteinases play a part in connective tissue turnover in which active proteinases can cleave matrix protein during resorption, although the proteinase that predominates varies between different tissues and diseases. The metalloproteinases are potent enzymes that, once activated, degrade connective tissue and are inhibited by tissue inhibitors of metalloproteinases (TIMPs); the balance between active matrix metalloproteinases and TIMPs determines, in many tissues, the extent of extracellular matrix degradation. The serine proteinases are involved in the initiation of activation cascades and some, such as elastase, can directly degrade the matrix. Cysteine proteinases are responsible for the breakdown of collagen in bone following the removal of the osteoid layer and the attachment of osteoclasts to the exposed bone surface. Various growth factors increase the synthesis of matrix and proteinase inhibitors, whereas cytokines (alone or in combination) can inhibit matrix synthesis and stimulate proteinase production and matrix destruction.

The alpha-isoform of p38 MAPK specifically regulates arthritic bone loss

Pharmacological inhibitors have provided evidence for the key role of p38 MAPK in osteoclast differentiation and in inflammation-induced bone loss. However, these inhibitors block more than one of the four p38 isoforms, usually p38alpha and p38beta, and sometimes also other kinases such as JNK3. We show in this study that p38alpha is the main p38 isoenzyme expressed in the osteoclast precursors and in the mature osteoclasts. p38alpha as well as its downstream substrates were phosphorylated in osteoclast progenitors stimulated by TNF-alpha. Using Mx-cre-mediated conditional gene inactivation we demonstrated that mice lacking p38alpha were protected against TNF-alpha-induced bone destruction at the site of inflammation as well as against TNF-alpha-mediated systemic bone loss. The bone protection was associated to decreased osteoclast numbers in vivo as well as a decreased IL-1beta expression in the inflamed tissue and in the isolated monocytes. The phenotype was cell autonomous because, similarly to p38alpha-deficient cells, knockdown of p38alpha in monocytes resulted in a decreased osteoclast differentiation in vitro. It was not caused by major changes in RANKL-mediated ERK or JNK activation but rather associated to an increased NF-kappaB activation caused by a decrease in IkappaBalpha recovery. Thus, our data show that developing specific inhibitors of the alpha-isoenzyme of p38 would be beneficial for the treatment of inflammation-induced bone destruction as observed in rheumatoid arthritis.

Therapeutic antibody targeting of CD97 in experimental arthritis: the role of antigen expression, shedding, and internalization on the pharmacokinetics of anti-CD97 monoclonal antibody 1B2

CD97 is a member of the EGF-TM7 family of adhesion class receptors, with a proposed role in inflammatory cell recruitment. Neutralization of murine CD97 with the anti-mCD97 mAb 1B2 was efficacious in prevention of murine collagen-induced arthritis, a model with features resembling rheumatoid arthritis. Here, the therapeutic potential of neutralizing CD97 in arthritis was studied with emphasis on the 1B2 pharmacokinetics. Mice with established arthritis were treated with anti-mCD97 or anti-TNF-alpha serum. Ab pharmacokinetics and biodistribution were studied in diseased and nondiseased mice using labeled 1B2. The impact of CD97 expression on Ab pharmacokinetics was studied using CD97 knockout mice. Treatment with 1B2 showed an efficacy comparable to anti-TNF-alpha treatment. Pharmacokinetic analysis of 1B2 in wild-type and CD97 knockout mice indicated a dose-dependent Ab clearance, due to specific interaction with CD97. Biodistribution studies showed accumulation of 1B2 in spleen and lung. In vitro studies using murine splenocytes revealed that CD97 when bound to Ab was internalized. Moreover, soluble CD97 was detected in the supernatant, suggesting Ag shedding. Finally, in arthritic mice, higher levels of soluble CD97 were found and 1B2 treatment led to specific targeting of inflamed paws, resulting in a higher clearance rate of 1B2 in arthritic mice than in wild-type mice. In conclusion, our data support a therapeutic value of CD97 neutralization in experimental arthritis. The pharmacokinetic profile of the 1B2 Ab illustrates the complexity of Ab elimination from an organism and stresses the importance of understanding Ag-Ab interactions when developing therapeutic mAbs.

Reduced incidence and severity of experimental autoimmune arthritis in mice expressing catalytically inactive A disintegrin and metalloproteinase 8 (ADAM8)

A disintegrin and metalloproteinase 8 (ADAM8), a catalytically active member of the ADAMs family of enzymes, is expressed primarily on immune cells and thus probably involved in inflammatory responses. ADAM8 is also produced by chondrocytes, and recombinant ADAM8 can induce cartilage catabolism. We therefore decided to test the role of ADAM8 in autoimmune inflammatory arthritis using transgenic mice expressing catalytically inactive ADAM8. Transgenic DBA/1J mice expressing an inactivating point mutation in the ADAM8 gene to change Glu330 to Gln330 (ADAM8(EQ)) were generated to evaluate the proteolytic function of ADAM8 in an lipopolysaccharide-synchronized collagen-induced arthritis (LPS-CIA) model of autoimmune arthritis. The systemic inflammatory reaction to LPS was also evaluated in these mice. Expression profiling of paw joints from wild-type mice revealed that ADAM8 mRNA levels increased at the onset of clinical arthritis and correlated well with cellular macrophage markers. When subjected to LPS-CIA, ADAM8(EQ) mice demonstrated decreased incidence and severity of clinical arthritis compared to wild-type mice. Histological examination of paw joints from ADAM8(EQ) mice confirmed marked attenuation of synovial inflammation, cartilage degradation and bone resorption when compared to wild-type mice. However, transgenic mice and wild-type mice responded similarly to LPS-induced systemic inflammation with regard to mortality, organ weights, neutrophil sequestration and serum cytokine/chemokine production. We conclude that ADAM8 proteolytic activity plays a key role in the development of experimental arthritis and may thus be an attractive target for the treatment of arthritic disorders while minimizing risk of immunocompromise.

Species Comparison of the Role of p38 MAP Kinase in the Female Reproductive System

The p38 mitogen-activated protein kinases (MAPKs) are members of discrete signal transduction pathways that have significant regulatory roles in a variety of biological processes, depending on the cell, tissue and organ type. p38 MAPKs are involved in inflammation, cell growth and differentiation and cell cycle. In the female reproductive system, p38 MAPKs are known to regulate various aspects of the reproductive process such as mammalian estrous and menstrual cycles as well as early pregnancy and parturition. p38 MAPKs have also been implicated in alterations and pathologies observed in the female reproductive system. Therefore, pharmacologic modulation of p38 MAPKs, and inter-connected signaling pathways (e.g., estrogen receptor signaling, c-fos, c-jun), may influence reproductive physiology and function. This article provides a critical, comparative review of available data on the roles of p38 MAPKs in the mammalian female reproductive system and in reproductive pathophysiology in humans and preclinical species. We first introduce fundamental differences and similarities of the mammalian female reproductive system that should be considered by toxicologists and toxicologic pathologists when assessing the effects of new pharmacologic agents on the female reproductive system. We then explore in detail the known roles for p38 MAPKs and related molecules in female reproduction. This foundation is then extended to pathological conditions in which p38 MAPKs are thought to play an integral role.

Modulation of p38 MAPK activity in regulatory T cells after tolerance with anti-DNA Ig peptide in (NZB x NZW)F1 lupus mice

Treatment of (NZB x NZW)F(1) (NZB/W) lupus-prone mice with the anti-DNA Ig-based peptide pConsensus prolongs the survival of treated animals and effectively delays the appearance of autoantibodies and glomerulonephritis. We have previously shown that part of these protective effects associated with the induction of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) that suppressed autoantibody responses. Because the effects of pConsensus appeared secondary to qualitative rather than quantitative changes in Tregs, we investigated the molecular events induced by tolerance in Tregs and found that signaling pathways including ZAP70, p27, STAT1, STAT3, STAT6, SAPK, ERK, and JNK were not significantly affected. However, peptide tolerization affected in Tregs the activity of the MAPK p38, whose phosphorylation was reduced by tolerance. The pharmacologic inhibition of p38 with the pyridinyl imidazole inhibitor SB203580 in naive NZB/W mice reproduced in vivo the effects of peptide-induced tolerance and protected mice from lupus-like disease. Transfer experiments confirmed the role of p38 in Tregs on disease activity in the NZB/W mice. These data indicate that the modulation of p38 activity in lupus Tregs can significantly influence the disease activity.

Targeting innate immunity protein kinase signalling in inflammation

Inflammation is an evolutionarily conserved host reaction that is initiated in response to trauma, tissue damage and infection. It leads to changes in tissue homeostasis and blood flow, immune-cell activation and migration, and secretion of cytokines and mediators in a spatio-temporally coordinated manner. Progress in understanding of the mechanisms of the inflammatory response has identified various protein kinases that act as essential signalling components and therefore represent potential therapeutic targets. This article summarizes advances in the identification and validation of such targets, and discusses key issues for the development of small-molecule kinase inhibitors as a new generation of oral anti-inflammatory drugs, including feedback loops, inhibitor specificity and combination therapy.

MAPK phosphatases as novel targets for rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) represents a challenge for therapeutic interventions due to complex inflammatory signalling pathways underlying its pathogenesis. The MAPK signalling network, a major effector limb of the inflammatory lesion, is an attractive therapeutic target. MAPK phosphatases (MKPs), endogenous negative regulators of MAPK signalling, have received increasing recognition as modulators of inflammatory and immune responses, and hence as a potential therapeutic avenue for RA.

OBJECTIVE

To present the rationale for therapeutically targeting MAPK signalling and explore the case for addressing MKP1 as a novel therapeutic strategy for RA.

METHODS

We summarise literature describing the importance of MAPK signalling in RA and review reports describing the roles of MKPs in modulating innate and adaptive immune responses. Finally we expand on the role of MKP1 in RA pathogenesis and explore data defining MKP1 as a mediator of glucocorticoid action.

CONCLUSION

MKP1 constitutes an exciting, novel potential therapeutic target for RA.