Inhibition of monocyte IL-1 production by the anti-inflammatory compound, SK&F 86002

p38 MAPKs - roles in skeletal muscle physiology, disease mechanisms, and as potential therapeutic targets

p38 MAPKs play a central role in orchestrating the cellular response to stress and inflammation and in the regulation of myogenesis. Potent inhibitors of p38 MAPKs have been pursued as potential therapies for several disease indications due to their antiinflammatory properties, although none have been approved to date. Here, we provide a brief overview of p38 MAPKs, including their role in regulating myogenesis and their association with disease progression. Finally, we discuss targeting p38 MAPKs as a therapeutic approach for treating facioscapulohumeral muscular dystrophy and other muscular dystrophies by addressing multiple pathological mechanisms in skeletal muscle.

Exploring the optical reporting characteristics of drugs: UV-Vis spectra and conformations of the tyrosine kinase inhibitor SKF86002

The ultimate understanding of drug–protein interactions relies on understanding drug behaviours in solution, at the molecular level.

Small-molecule therapeutics in rheumatoid arthritis: scientific rationale, efficacy and safety

Rheumatoid arthritis (RA) remains a formidable clinical challenge. This is despite remarkable recent advances in our understanding of pathogenesis and the introduction of a variety of novel agents, particularly biologic therapeutics that are potent inhibitors of extracellular immune pathways. Whereas the latter have brought substantial improvements in efficacy and thus outcomes, there remain significant numbers of non- or partial responders to current standard of care. The discovery of key intracellular pathways, particularly kinases that subserve the function of these pivotal cytokine and immune cell receptors implicated in RA pathogenesis, has facilitated the advent of a new phase of RA drug development. Thus, a range of kinase inhibitors has entered clinical trials and one agent has been licenced for use in some regions. Herein we summarise the chequered history of kinase inhibitor development in RA, describing successes and failures alike, and thereafter examine future trends in this exciting field.

Pyridinyl imidazole inhibitors of p38 MAP kinase impair viral entry and reduce cytokine induction by Zaire ebolavirus in human dendritic cells

Antigen presenting cells (APCs), including macrophages and dendritic cells, are early and sustained targets of Ebola virus (EBOV) infection in vivo. Because EBOV activates mitogen-activated protein kinase (MAPK) signaling upon infection of APCs, we evaluated the effect of pyridinyl imidazole inhibitors of p38 MAPK on EBOV infection of human APCs and EBOV mediated cytokine production from human DCs. The p38 MAPK inhibitors reduced viral replication in PMA-differentiated macrophage-like human THP-1 cells with an IC50 of 4.73μM (SB202190), 8.26μM (p38kinhIII) and 8.21μM (SB203580) and primary human monocyte-derived dendritic cells (MDDCs) with an IC50 of 2.67μM (SB202190). Furthermore, cytokine production from EBOV-treated MDDCs was inhibited in a dose-dependent manner. A control pyridinyl imidazole compound failed to inhibit either EBOV infection or cytokine induction. Using an established EBOV virus-like particle (VLP) entry assay, we demonstrate that inhibitor pretreatment blocked VLP entry suggesting that the inhibitors blocked infection and replication at least in part by blocking EBOV entry. Taken together, our results indicate that pyridinyl imidazole p38 MAPK inhibitors may serve as leads for the development of therapeutics to treat EBOV infection.

Functional roles of p38 mitogen-activated protein kinase in macrophage-mediated inflammatory responses

Inflammation is a natural host defensive process that is largely regulated by macrophages during the innate immune response. Mitogen-activated protein kinases (MAPKs) are proline-directed serine and threonine protein kinases that regulate many physiological and pathophysiological cell responses. p38 MAPKs are key MAPKs involved in the production of inflammatory mediators, including tumor necrosis factor-α (TNF-α) and cyclooxygenase-2 (COX-2). p38 MAPK signaling plays an essential role in regulating cellular processes, especially inflammation. In this paper, we summarize the characteristics of p38 signaling in macrophage-mediated inflammation. In addition, we discuss the potential of using inhibitors targeting p38 expression in macrophages to treat inflammatory diseases.

BIRB 796 has Distinctive Anti-inflammatory Effects on Different Cell Types

The pro-inflammatory cytokines tumor necrosis factor-α (TNFα) and interleukin (IL)-1β are crucial mediators involved in chronic inflammatory diseases. Inflammatory signal pathways regulate inflammatory cytokine expression-mediated by p38 mitogen activated protein kinase (p38MAPK). Therefore, considerable attention has been given to p38MAPK as a target molecule for the development of a novel anti-inflammatory therapeutics. BIRB 796, one of p38MAPK inhibitor, is a candidate of therapeutic drug for chronic inflammatory diseases. In this study, we investigated the effect of BIRB 796 on inflammatory cytokine productions by lipopolysaccharide (LPS) in different immune cell types. BIRB 796 reduced LPS-mediated IL-8 production in THP-1 cells but not in Raw 264.7 cells. Further analysis of signal molecules by western blot revealed that BIRB 796 sufficiently suppressed LPS-mediated phosphorylation of p38MAPK in both cell types whereas it failed to block inhibitor of kappa B (I-κB) degradation in Raw 264.7 cells. Taken together, these results suggest that the anti-inflammatory function of BIRB 796 depends on cell types.

Targeting kinases: a new approach to treating inflammatory rheumatic diseases

After two decades of research and development activity focussed on orally active kinase inhibitors, the first such drug (the JAK inhibitor Xeljanz, tofacitinib) was approved by the FDA in November 2012 for the treatment of rheumatoid arthritis (RA). There is an intense activity in many companies both on expanding the utility of JAK inhibitors in other auto-immune indications and in discovering inhibitors of the JAK family with different and more selective profiles. Progress is also being made with orally active Syk inhibitors. One such inhibitor (fostamatinib) is currently in large-scale phase 3 trials, and there are others in clinical development. The last two to three years have been transformative for kinase inhibitors in auto-immune diseases, as several inhibitors have finally progressed beyond phase 2 trials after so many failures on other targets. Thus, there are new treatment options for RA patients beyond existing oral DMARDs and parenteral biologics.

Potential of p38-MAPK inhibitors in the treatment of ischaemic heart disease

Chronic heart failure is debilitating, often fatal, expensive to treat and common. In most patients it is a late consequence of myocardial infarction (MI). The intracellular signals following infarction that lead to diminished contractility, apoptosis, fibrosis and ultimately heart failure are not fully understood but probably involve p38-mitogen activated protein kinases (p38), a family of serine/threonine kinases which, when activated, cause cardiomyocyte contractile dysfunction and death. Pharmacological inhibitors of p38 suppress inflammation and are undergoing clinical trials in rheumatoid arthritis, Chrohn's disease, psoriasis and surgery-induced tissue injury. In this review, we discuss the mechanisms, circumstances and consequences of p38 activation in the heart. The purpose is to evaluate p38 inhibition as a potential therapy for ischaemic heart disease.

In vivo anticancer, anti-inflammatory, and toxicity studies of mixed-ligand Cu(II) complexes of dien and its Schiff dibases with heterocyclic aldehydes and 2-amino-2-thiazoline. Crystal structure of [Cu(dien)(Br)(2a-2tzn)](Br)(H2O)

A new series of complexes of the type [Cu(dien)(2a-2tzn)Y(2)] and [Cu(dienXX)(2a-2tzn)Y(2)], where dien=diethylenetriamine and dienXX=Schiff dibase of diethylenetriamine formed with 2-furaldehyde (dienOO), 2-thiophenecarboxaldehyde (dienSS), or pyrrol-2-carboxaldehyde (dienNN); Y=Cl, Br or NO(3); and 2a-2tzn=2-amino-2-thiazoline, were synthesized and their structure established by C, H, N and Cu analysis; IR and electronic spectra; magnetic susceptibility; and molar conductivity. The isolated complexes are monomers, paramagnetic, and electrolytes of types 1:1 or 1:2. In both types of solid state complexes, [Cu(dien)(2a-2tzn)Y(2)] and [Cu(dienXX)(2a-2tzn)Y(2)], dien and its Schiff dibases are bonded to Cu(II) in a tridentate fashion through 3N atoms. The coordination sphere is completed by the endocyclic nitrogen of the thiazoline moiety and by two Cl, Br, or NO(3) groups with distorted octahedral geometry. The proposed structure of these compounds was supported by X-ray analysis of [Cu(dien)(Br)(2a-2tzn)](Br)(H(2)O). The coordination polyhedron around the copper atom can be described as a distorted square pyramid [Cu(dien)(Br)(2a-2tzn)](+). Its basal plane is occupied by the four nitrogen atoms of the dien and thiazoline ligands with Cu-N distances ranging between 1.996(6) and 2.032(3)A, and the axial position is occupied by one of the two bromine atoms (Br1) with a Cu1-Br1 bond distance of 2.782(1)A. The second bromine atom (Br2) is 4.694(2)A from the copper atom, which exists as a discrete anion and is responsible for the cationic nature of the complex. Results regarding toxicity, antitumor, and anti-inflammatory activities of the investigated compounds are promising and allow the selection of a lead compound for further biological studies.

Pharmacological inhibition of Mannheimia haemolytica lipopolysaccharide and leukotoxin-induced cytokine expression in bovine alveolar macrophages

The inflammatory cytokines tumor necrosis factor-alpha (TNFalpha), interleukin-1 beta (IL-1beta), and interleukin-8 (IL-8) are believed to contribute to the pathogenesis of lung injury in bovine pneumonic mannheimiosis (BPM) caused by Mannheimia (Pasteurella) haemolytica. Inflammatory cytokines may, therefore, represent therapeutic targets to be modulated for the purpose of treating or preventing this important disease of cattle. The purpose of this study was to evaluate the ability of six pharmacological agents to suppress the expression of TNFalpha, IL-1beta, and IL-8 genes and proteins in bovine alveolar macrophages (AM) exposed to M. haemolytica lipopolysaccharide (LPS) and leukotoxin (LktA) in vitro. The compounds tested included dexamethasone (DEX), tetrahydropapaveroline (THP), pentoxifylline (PTX), rolipram (ROL), SB203580 (SB), and thalidomide (THL). Cytokine expression was induced by the addition of purified M. haemolytica LPS and LktA to AM cell cultures following pretreatment with inhibitor compounds. Secretion of TNFalpha, IL-1beta, and IL-8 proteins into the cell culture supernatant was measured using enzyme-linked immunosorbent assays, and steady-state accumulation of cytokine-specific mRNA was measured by northern blot analysis. Dose-dependent inhibition of cytokine secretion occurred in response to pretreatment of AM with DEX (TNFalpha, IL-1beta, IL-8), THP (TNFalpha, IL-1beta, IL-8), PTX (TNFalpha, IL-1beta, IL-8), ROL (TNFalpha, IL-1beta), and SB (TNFalpha, IL-8). Significant dose-dependent inhibition of cytokine mRNA expression occurred in response to pretreatment with DEX (TNFalpha, IL-1beta, IL-8), THP (TNFalpha, IL-1beta, IL-8), and PTX (TNFalpha). DEX was the most effective inhibitor by far; pretreatment with this compound yielded greater than 95% inhibition of cytokine gene and protein expression over a broad range of concentrations. These findings demonstrate that DEX, THP, PTX, ROL, and SB are capable of suppressing inflammatory cytokine secretion by bovine AM in vitro. If pulmonary cytokine secretion may be similarly inhibited in vivo, anti-cytokine therapy may represent a novel strategy for the management of BPM.

Inhibitors of p38 mitogen-activated protein kinase: potential as anti-inflammatory agents in asthma?

Asthma is an inflammatory disease of the airways, which in patients with mild to moderate symptoms is adequately controlled by either beta(2)-adrenoceptor agonists or corticosteroids, or a combination of both. Despite this, there are classes of patients that fail to respond to these treatments. In addition, there is a general trend towards increasing morbidity and mortality due to asthma, which suggests that there is a need for new and improved treatments. The p38 mitogen-activated protein kinases (MAPKs) represent a point of convergence for multiple signalling processes that are activated in inflammation and that impact on a diverse range of events that are important in inflammation. Small molecule pyridinyl imidazole inhibitors of p38 MAPK have proved to be highly effective in reducing various parameters of inflammation, in particular cytokine expression. Like corticosteroids, inhibitors of p38 MAPK appear to be able to repress gene expression at multiple levels, for example, by transcriptional, posttranscriptional and translational repression, and this raises the possibility of a similarly broad spectrum of anti-inflammatory activities. Indeed these molecules have proved to be effective in numerous in vitro and in vivo models of inflammation and septicaemia, which suggests that such compounds may be effective as therapeutic agents against inflammatory disorders. Despite these very promising indications of the possible therapeutic use of p38 MAPK inhibitors, a number of events that are p38-dependent are in fact also beneficial to the resolution or modulation of diseases such as asthma. We conclude that the overall effect of p38 MAPK inhibition would be beneficial in inflammatory diseases such as rheumatoid arthritis and asthma. However, these drugs may result in a complex phenotype that will require careful evaluation. Currently, a number of second or third generation inhibitors of p38 MAPK are being tested in phase I and phase II clinical trials.

Benzydamine inhibits monocyte migration and MAPK activation induced by chemotactic agonists

1. The present study was aimed to investigate the effect of benzydamine, an anti-inflammatory drug devoid of activity on arachidonic acid metabolism, on monocyte chemotaxis and to define the possible biochemical correlates of activity. 2. Benzydamine inhibited monocyte chemotaxis in response to three classes of chemoattractants: the prototypic CC-chemokine CCL2 (MCP-1), the microbial product fMLP and the complement cascade component C5a. The effect was dose-dependent with IC50's of 100, 50 and 45 microm for MCP-1/CCL2, fMLP and C5a, respectively. At the dose of 100 microm, the effect resulted in a 50+/-10% inhibition of MCP-1/CCL2-induced chemotaxis and 53+/-6 and 54+/-5% inhibitions of chemotaxis in response of fMLP and C5a, respectively (n=3). 3. Receptor expression as well as calcium fluxes in response to chemoattractants were not affected by benzydamine. 4. Benzydamine strongly inhibited chemoattractant-induced activation of the mitogen-activated protein kinase (MAPK) ERK1/2, and of its upstream activator kinase MEK1/2. ERK1/12 activation in response to chemoattractants was 89-98% inhibited by a 100 microm concentration of benzydamine with an IC50 of 30 microm. 5. Under the same experimental conditions, pretreatment with 100 microm benzydamine caused a 75-89% inhibition of p38 activation (IC50 25 microm). 6. These results indicate that the anti-inflammatory activity of benzydamine is exerted at multiple levels, including monocyte migration to chemotactic factors associated to a blockage of ERK and p38 MAPK pathways.

p38 MAP kinases: key signalling molecules as therapeutic targets for inflammatory diseases

The p38 MAP kinases are a family of serine/threonine protein kinases that play important roles in cellular responses to external stress signals. Since their identification about 10 years ago, much has been learned of the activation and regulation of the p38 MAP kinase pathways. Inhibitors of two members of the p38 family have been shown to have anti-inflammatory effects in preclinical disease models, primarily through the inhibition of the expression of inflammatory mediators. Several promising compounds have also progressed to clinical trials. In this review, we provide an overview of the role of p38 MAP kinases in stress-activated pathways and the progress towards clinical development of p38 MAP kinase inhibitors in the treatment of inflammatory diseases.

Induction of HL-60 cell differentiation by the p38 mitogen-activated protein kinase inhibitor SB203580 is mediated through the extracellular signal-regulated kinase signaling pathway

The pyridinyl imidazole p38 kinase inhibitor, SB203580, was initially used to block inflammatory cytokine synthesis. Here we report that SB203580 by itself could induce human promyeloid leukemic HL-60 cells to differentiate mainly along the granulocytic lineage, as evidenced by cellular morphological changes, and the concurrent expression of cell surface markers CD11b and CD14. This differentiation induction was time and dose dependent. After 12 h exposure to 10 microM SB203580, 12.5% of the cells became CD11b as compared to only 2.6% in untreated control cells. By 96 h, CD11b cells increased to 72.3%, and among them, 26% were CD14. Morphologically, the cells were smaller in size with lower nuclear/cytoplasmic ratio. The nucleus was indented and nucleoli markedly reduced. However, 10 microM SB203580 had little effect on HL-60 cell growth and survival during the first 72 h, but by 96 h the percentage of cells in G1 phase was markedly increased. These effects of SB203580 were not attributable to its inhibition of p38 kinase activity. Instead, the essential kinases in the extracellular signal-regulated kinase (ERK) pathway such as phospho-Raf-1, phospho-MEK1/2, phospho-ERK1/2 and phospho-p90RSK were all elevated dramatically shortly after cells were exposed to SB203580 and lasted for 24 h before declining. Pre-incubation of cells with 20 microM of PD98059 1 h before addition of SB203580 could completely block the expression of differentiation markers. Our results suggest that SB203580-induced differentiation in HL-60 cells was mediated by activation of MEK/ERK signaling. In conclusion, our data have shown that SB203580 possessed biological activities other than inhibition of p38 and these activities could make it a potential candidate as an inducing agent for cell differentiation in the therapeutic treatment of leukemia.

A postmodern moral tale: the ethics of research relationships

Once upon a time, universities were ivory towers--or, at least, most people saw them as such. Academics prided themselves on not being influenced by, or answerable to, anyone except the academy, and perceived themselves as free from conflicts of interest arising from relationships with people or institutions outside the walls of the university. None of this holds true today and, as the case of Dr Nancy Olivieri illustrates, universities are facing some difficult times in adjusting to these changes.

Inhibition of p38 MAP kinase as a therapeutic strategy

Since the discovery of p38 MAP kinase in 1994, our understanding of its biology has progressed dramatically. The key advances include (1) identification of p38 MAP kinase homologs and protein kinases that act upstream and downstream from p38 MAP kinase, (2) identification of interesting and potentially important substrates, (3) elucidation of the role of p38 MAP kinase in cellular processes and (4) the establishment of the mechanism by which the pyridinylimidazole p38 MAP kinase inhibitors inhibit enzyme activity. It is now known that there are four members of the p38 MAP kinase family. They differ in their tissue distribution, regulation of kinase activation and subsequent phosphorylation of downstream substrates. They also differ in terms of their sensitivities toward the p38 MAP kinase inhibitors. The best-studied isoform is p38 alpha, whose activation has been observed in many hematopoietic and non-hematopoietic cell types upon treatment with appropriate stimuli. The pyridinylimidazole compounds, exemplified by SB 203580, were originally prepared as inflammatory cytokine synthesis inhibitors that subsequently were found to be selective inhibitors of p38 MAP kinase. SB 203580 inhibits the catalytic activity of p38 MAP kinase by competitive binding in the ATP pocket. X-ray crystallographic studies of the target enzyme complexed with inhibitor reinforce the observations made from site-directed mutagenesis studies, thereby providing a molecular basis for understanding the kinase selectivity of these inhibitors. The p38 MAP kinase inhibitors are efficacious in several disease models, including inflammation, arthritis and other joint diseases, septic shock, and myocardial injury. In all cases, p38 activation in key cell types correlated with disease initiation and progression. Treatment with p38 MAP kinase inhibitors attenuated both p38 activation and disease severity. Structurally diverse p38 MAP kinase inhibitors have been tested extensively in preclinical studies.

p38α Mitogen-Activated Protein Kinase Is Activated by CD28-Mediated Signaling and Is Required for IL-4 Production by Human CD4+CD45RO+ T Cells and Th2 Effector Cells

T cell proliferation and cytokine production usually require stimulation via both the TCR/CD3 complex and the CD28 costimulatory receptor. Using purified human CD4+ peripheral blood T cells, we show that CD28 stimulation alone activates p38α mitogen-activated protein kinase (p38α). Cell proliferation induced by CD28 stimulation alone, a response attributed to CD4+CD45RO+ memory T cells, was blocked by the highly specific p38 inhibitors SB 203580 (IC50 = 10–80 nM) and RWJ 67657 (IC50 = 0.5–4 nM). In contrast, proliferation induced by anti-CD3 plus anti-CD28 mAbs was not blocked. Inhibitors of p38 also blocked CD4+ T cell production of IL-4 (SB 203580 IC50 = 20–100 nM), but not IL-2, in response to CD3 and CD28 stimulation. IL-5, TNF-α, and IFN-γ production were also inhibited, but to a lesser degree than IL-4. IL-4 production was attributed to CD4+CD45RO+ T cells, and its induction was suppressed by p38 inhibitors at the mRNA level. In polarized Th1 and Th2 cell lines, SB 203580 strongly inhibited IL-4 production by Th2 cells (IC50 = 10–80 nM), but only partially inhibited IFN-γ and IL-2 production by Th1 cells (<50% inhibition at 1 μM). In both Th1 and Th2 cells, CD28 signaling activated p38α and was required for cytokine production. These results show that p38α plays an important role in some, but not all, CD28-dependent cellular responses. Its preferential involvement in IL-4 production by CD4+CD45RO+ T cells and Th2 effector cells suggests that p38α may be important in the generation of Th2-type responses in humans.

p38 mitogen-activated protein kinase inhibitors--mechanisms and therapeutic potentials

The pyridinylimidazole compounds, exemplified by SB 203580, originally were prepared as inflammatory cytokine synthesis inhibitors. Subsequently, the compounds were found to be selective inhibitors for p38 mitogen-activated protein kinase (MAPK), a member of the MAPK family. SB 203580 inhibits the catalytic activity of p38 MAPK by competitive binding in the ATP pocket. Four homologues of p38 MAPK have been identified to date, and interestingly, their biochemical properties and their respective sensitivities to the inhibitors are distinct. X-ray crystallographic analysis of p38-inhibitor complexes reinforces the observations made from site-directed mutagenesis studies, thereby providing a molecular basis for understanding the kinase selectivity of these inhibitors. The p38 MAPK inhibitors are efficacious in several disease models, including inflammation, arthritis and other joint diseases, septic shock, and myocardial injury.

Signal transduction triggered by lipid A-like molecules in 70Z/3 pre-B lymphocyte tumor cells

The lipid A (endotoxin) moiety of lipopolysaccharide (LPS) elicits rapid cellular responses from many cell types, including macrophages, lymphocytes, and monocytes. In CD14 transfected 70Z/3 pre-B lymphocyte tumor cells, these responses include activation of the MAP kinase homolog, p38, activation of NF-kappaB, and transcription of kappa light chains, leading to the assembly of surface IgM. In this work, we explored the specificity of the response with regard to lipid structure, and the requirement for p38 kinase activity prior to NF-kappaB activation in control and CD14 transfected 70Z/3 (CD14-70Z/3) cells. A p38-specific inhibitor, SB203580, was used to block p38 kinase activity in cells. CD14-70Z/3 cells were incubated with 1-50 microM SB203580, and then stimulated with LPS. Nuclear extracts were prepared, and NF-kappaB activation was measured using an electrophoretic mobility shift assay. SB203580 did not inhibit LPS induced NF-kappaB activation. In addition, LPS failed to activate p38 tyrosine phosphorylation in 70Z/3 cells lacking CD14, in spite of rapid NF-kappaB activation and robust surface IgM production with appropriate higher doses of LPS. LPS stimulation of p38 phosphorylation, NF-kappaB activation, and surface IgM expression were all blocked completely by lipid A-like endotoxin antagonists whether or not CD14 was present. Acidic glycerophospholipids and ceramides did not mimic lipid A-like molecules either as agonists or antagonists in this system. Our data support the hypothesis that lipid A-mediated activation of cells requires stimulation of a putative lipid A sensor that is downstream of CD14, but upstream of p38 and NF-kappaB.

T Cell Activation Signals Up-Regulate p38 Mitogen-Activated Protein Kinase Activity and Induce TNF-α Production in a Manner Distinct from LPS Activation of Monocytes

p38 mitogen-activated protein kinase (MAPK) (p38) is involved in various cellular responses, including LPS stimulation of monocytes, resulting in production of proinflammatory cytokines such as TNF-α. However, the function of p38 during antigenic stimulation of T cells is largely unknown. Stimulation of the human Th cell clone HA-1.70 with either the superantigen staphylococcal enterotoxin B (SEB) or with a specific antigenic peptide resulted in p38 activation and the release of TNF-α. MAPK-activated protein kinase-2 (MAPKAPK-2), an in vivo substrate for p38, was also activated by T cell signaling. SB 203580, a selective inhibitor of p38, blocked p38 and MAPKAPK-2 activation in the T cell clone but did not completely inhibit TNF-α release. PD 098059, a selective inhibitor of MAPK kinase 1 (MEK1), blocked activation of extracellular signal-regulated kinase (ERK) and partially blocked TNF-α production by the clone. In human peripheral T cells, p38 was not activated by SEB, but rather by CD28 cross-linking, whereas in the human leukemic T cell line Jurkat, p38 was activated by CD3 and CD28 cross-linking in an additive fashion. TNF-α production by peripheral T cells in response to SEB and anti-CD28 mAb correlated more closely with ERK activity than with p38 activity. Therefore, various forms of T cell stimulation can activate the p38 pathway depending on the cells examined. Furthermore, unlike LPS-stimulated monocytes, TNF-α production by T cells is only partially p38-dependent.

Inhibitors of the p38 Mitogen-Activated Kinase Modulate IL-4 Induction of Low Affinity IgE Receptor (CD23) in Human Monocytes

CD23, the low affinity IgE receptor, is up-regulated on the surface of IL-4-treated B cells and monocytes and is immediately proteolytically processed, releasing soluble fragments of CD23. Here, we report that inhibitors of the p38 mitogen-activated kinase (p38 MAPK), SK&F 86002 or the more selective inhibitor, SB 203580, reduce the levels of soluble CD23 formed by IL-4-stimulated human monocytes or the human monocytic cell line, U937. In contrast to compounds such as the metalloprotease inhibitor batimastat ([4-(N-hydroxyamino)-2-(R)-isobutyl-3-(S)-(2-thiophenethiomethyl)succinyl]-(S)-phenylalanine-N-methylamide, sodium salt), p38 MAPK inhibitors do not directly inhibit proteolytic processing of CD23. Further, evaluation of surface intact CD23 (iCD23) by flow cytometry demonstrated that SK&F 86002 and SB 203580 reduced the surface expression of iCD23 in a concentration-dependent fashion, while batimastat increased the surface expression of iCD23. The decrease in surface iCD23 was accompanied by a decrease in total cell-associated CD23 protein levels but not CD23 mRNA. IL-4 induced a late (>4-h) increase in p38 MAPK activity and corresponding activation of its substrate MAPKAPK-2. This activation was blocked by addition of SB 203580 before IL-4 induction, in parallel with the inhibition of CD23 expression. Modulation of CD23 by antibodies has been shown to alleviate the symptoms of murine collagen-induced arthritis, implicating CD23 as an important proinflammatory agent. These data show that in addition to the known cytokine inhibitory actions of SK&F 86002 and SB 203580, they also confer an additional potential anti-inflammatory activity through modulation of CD23 expression.

Regulation of stress-induced cytokine production by pyridinylimidazoles; inhibition of CSBP kinase

Members of three classes of pyridinylimidazoles bind with varying affinities to CSBP (p38) kinase which is a member of a stress-induced signal transduction pathway. Based upon SAR and protein homology modeling, the pharmacophore and three potential modes of binding to the enzyme are presented. For a subset of pyridinylimidazoles, binding is shown to correlate with inhibition of CSBP kinase activity, whereas no significant inhibition of PKA, PKC alpha and ERK kinase activity is observed.

Pyridinyl imidazoles inhibit the inflammatory phase of delayed type hypersensitivity reactions without affecting T-dependent immune responses

The effects of pyridinyl imidazoles, specifically SK&F 105809 and its metabolite, on normal T-cell and B-cell mediated immune responses were examined and compared to the fungal macrolide immunosuppressives, cyclosporin A, FK506 and rapamycin and to the corticosteroid, dexamethasone. The orally active prodrug SK&F 105809 [2-(4-methylsulfinylphenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo [1,2-a] imidazole[ and its metabolite, SK&F 105561 [2-(4-methylthiophenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo[1,2 -a] imidazole] are dual 5-lipoxygenase (5-LO) and cycloxygenase (CO) inhibitors with potent anti-inflammatory and cytokine (IL-1/TNF) suppressive activities. The anti-inflammatory activity of SK&F 105809 and its metabolite were evaluated in an antigen-specific murine model of delayed type hypersensitivity (DTH) response, where they were found to affect only the inflammatory and not the induction phase of this response. In contrast, these compounds and other pyridinyl imidazoles (SK&F 86002 and its analog, SK&F 104351) exhibited no immunosuppressive activity under conditions where the macrolide rapamycin and the corticosteroid dexamethasone abrogated both the cellular and humoral immune responses. Thus, the ability of pyridinyl imidazoles to attenuate independently the inflammatory components of the disease without causing generalized immunosuppression enhances their profile as candidates for therapy of chronic inflammatory diseases, specifically those mediated by cytokines (e.g. IL-1, TNF) and eicosanoids.

Cytokine suppressive anti-inflammatory compounds inhibit bone resorption in vitro

Data from several laboratories suggest a role for a variety of cytokines in the process of bone resorption. SK&F 86002 [5-(4-pyridyl)-6(4-fluorophenyl)-2,3-dihydroimidazo(2,1-b) thiazole], a potent cytokine-suppressive anti-inflammatory agent, has been shown to inhibit cyclooxygenase (CO) and 5-lipoxygenase (LO) activity and to inhibit the production of cytokines both in vitro and in vivo. In the present study, SK&F 86002 inhibited fetal rat long bone (FRLB) resorption induced by parathyroid hormone (PTH), 1,25-dihydroxy-vitamin D3, tumor necrosis factor alpha, and Escherichia coli lipopolysaccharide in a dose-dependent (IC50 of 0.5-1 microM) and reversible manner. Under identical conditions, selective CO inhibitors (indomethacin, ibuprofen, naproxen) and 5-LO inhibitors (phenidone, SK&F 107649) were inactive. Analogs of SK&F 86002, which are dual CO/LO inhibitors devoid of cytokine inhibitory activity (SK&F 81114 and SK&F 86055), also failed to significantly inhibit PTH-induced FRLB resorption. Analogs of SK&F 86002, which retain cytokine inhibitory activity (SK&F 104493 and SK&F 105561), inhibit bone resorption. These data indicate that the observed inhibition of bone resorption by compounds of this class correlates with their cytokine suppressive activity.

Pyridinyl imidazoles inhibit IL-1 and TNF production at the protein level

The mechanism by which SK&F 86002 and other pyridinyl imidazoles inhibit the production of IL-1 and TNF from LPS-stimulated human monocytes was examined. Inhibition of IL-1 and TNF production was found to depend on the time of addition of SK&F 86002, with diminishing effect when added more than 2 h after LPS stimulation. Analysis of Western blots confirmed that both intracellular IL-1 beta and extracellular TNF were significantly reduced in response to SK&F 86002, but these reductions were not paralleled by changes in IL-1 and TNF mRNA. 35S methionine pulse and pulse-chase studies on IL-1 biosynthesis suggest that significant inhibition by SK&F 86002 and related compounds occurs at the translational level.

RP 54745, a potential antirheumatic compound. II. In vivo properties in different animal models

The results obtained with RP 54745, an amino-dithiole-one compound, on stimulated macrophages, revealing inhibition of the hexose monophosphate pathway (HMP), of the exocytosis of lysosomal enzymes and of the production of interleukin-1 (IL-1), by the compound in vitro as well as in vivo, suggested that RP 5475 might influence cells and cytokines implicated in the regulation of the immune system, the disfunctioning of which can lead to inflammatory disorders or autoimmune pathologies. RP 54745 was effective at moderate oral doses (around 5 mg kg-1) in different mouse models of induced arthritis and in the MRL/lpr mice, genetically predisposed to develop an autoimmune pathology including arthritic disorders. The clinical status of the MRL mice, and several of their disturbed biochemical and immunological parameters, improved after a 3-month treatment with RP 54745. This activity of RP 54745 makes it a very attractive antirheumatic compound and a potentially effective treatment in pathologies where IL-1 production is exacerbated.

RP 54745, a potential antirheumatic compound. I. Inhibitor of macrophage stimulation and interleukin-1 production

RP 54745 is an amino-dithiole-one compound found to be active at micromolar concentration on the metabolism of stimulated macrophages, for example, the hexose monophosphate pathway (HMP) and the exocytosis of lysosomal enzymes. LPS-induced interleukin-1 (IL-1) production by murine peritoneal macrophages was also diminished by this compound in vitro as well as in vivo. This effect was confirmed at the mRNA level; at the concentration of 3 x 10(-6) M, the IL-1 alpha and beta mRNA signals were inhibited, whereas the TNF alpha mRNA signal was only slightly lessened. These observations were confirmed in vivo, with a dose of RP 54745 of 25 mg kg-1. These results led us to consider that RP 54745 might influence certain cells and cytokines implicated in the regulation of the immune system, the disfunctioning of which can lead to inflammatory disorders or autoimmune pathologies.

5-lipoxygenase inhibitors and their anti-inflammatory activities

A wide variety of agents have been reported as 5-LO inhibitors. The majority of the series appear to be lipophilic reducing agents, including phenols, partially saturated aromatics, and compounds containing heteroatom-heteroatom bonds. Many of these are not selective 5-LO inhibitors, but often affect CO and other LOs as well. In vivo systemic activity for many of these has been, in general, disappointing, probably because of poor bioavailability caused by lipophilicity and metabolic instability (oxidation, and conjugation of phenolic compounds). However, topically a number of agents have shown promise for skin inflammation, with Syntex's lonapalene the most advanced of these. Most results published to date appear more disappointing in the allergy/asthma field. More excitingly, a few structural types are selective 5-LO inhibitors which have shown systemic activity in vivo and in the clinic. Abbott's zileuton (136) appears to be one of the leading compounds in this category, along with other hydroxamates such as BW-A4C (129) from Burroughs-Wellcome. Recent selective non-reducing agents such as Wyeth-Ayerst's Wy-50,295 (143) and the similar ICI compounds such as ICI 216800 (145) also hold promise. The enantiospecific effects of (106) and (145) are especially interesting for the design of new inhibitors. If compounds like these validate the hypothesis that inhibition of 5-LO will have a significant anti-inflammatory effect, a redoubling of effort throughout the industry to find second- and third-generation selective agents may be expected. Part of the difficulty in interpreting and comparing the 5-LO literature is the plethora of test methods and activity criteria. As pointed out in the introduction, inhibition of product release from cells, often stimulated with A23187, has commonly been used to demonstrate 5-LO inhibition. However, this type of assay cannot be assumed to be diagnostic for 5-LO inhibition. Only if specificity for 5-LO product generation and (ideally) activity in cell-free enzymes is also shown should mechanistic interpretations be made. Recently, a new class of compounds was found at Merck which inhibited LT biosynthesis without inhibiting 5-LO, but apparently by a novel, specific mechanism. L-655,240 (169) and L-663,536 (MK-886) (170) were both active in human ISN, with IC50 values in the low micromolar range. Both also orally inhibited GPB (< 1 mg/kg). MK-886 was effective in Ascaris-induced asthma in squirrel monkeys, in rat carrageenan pleurisy, in rat Arthus pleurisy, and (topically) in guinea-pig ear oedema induced by A23187.(ABSTRACT TRUNCATED AT 400 WORDS)

Oligonucleotides antisense to the interleukin 1 receptor mRNA block the effects of interleukin 1 in cultured murine and human fibroblasts and in mice

Phosphodiester and phosphorothioate oligodeoxynucleotides (18 mers) were constructed antisense to sequences of the recently cloned murine and human IL-1 receptors. Murine antisense oligonucleotides inhibited IL-1-stimulated PGE2 synthesis by murine fibroblasts in culture in a time (days) and concentration-dependent (3 microM-30 microM) fashion. Murine sense oligonucleotide and an oligonucleotide antisense to human IL-1 receptor were without effect. Moreover, murine antisense oligonucleotides did not affect tumor necrosis factor- or bradykinin-stimulated PGE2 synthesis by murine fibroblasts. Similarly, antisense oligonucleotides to the human, but not the murine, IL-1 receptor inhibited IL-1-stimulated PGE2 synthesis by cultured human fibroblasts. The attenuation of the cellular response to IL-1 caused by the antisense oligonucleotides correlated with a loss in cell surface receptors for IL-1, without any change in the number of bradykinin receptors on these cells. When antisense oligonucleotides were encapsulated in liposomes, they blocked completely the appearance of newly synthesized IL-1 receptors and IL-1-stimulated PGE2 synthesis. In mice, subcutaneous injection with an oligonucleotide antisense to the murine IL-1 receptor markedly inhibited the infiltration of neutrophils in response to subsequent injection of IL-1. These data suggest that antisense oligodeoxynucleotides may share a role in the design of antiinflammatory therapeutics.

Pharmacology of the pyrroloimidazole, SK&F 105809--I. Inhibition of inflammatory cytokine production and of 5-lipoxygenase- and cyclooxygenase-mediated metabolism of arachidonic acid

SK&F 105809 [2-(4- methylsulfinylphenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo[1,2- a] imidazole] was determined to be a prodrug for the sulfide metabolite SK&F 105561 [2-(4- methylthiophenyl)-3-(4-pyridyl)-6,7-dihydro-[5H]-pyrrolo[1,2-a] imidazole] which inhibited interleukin-1 (IL-1) production in vitro and both 5-lipoxygenase (5-LO) and prostaglandin H (PGH) synthase activities in vitro and ex vivo. SK&F 105561 inhibited partially purified 5-LO with a half-maximal concentration (IC50) of 3 microM. This inhibition was reversible, independent of preincubation time, and dependent on the concentration of the substrate arachidonic acid. SK&F 105561 also inhibited purified PGH synthase with the potency dependent on the level of peroxidase activity. The IC50 was 100 microM in the absence of peroxidase activity, whereas an IC50 of 3 microM was observed in the presence of peroxidase activity. Using human monocytes, SK&F 105561 inhibited A23187-stimulated prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) production with IC50 values of 0.1 and 2 microM, respectively. In addition, IL-1 production by lipopolysaccharide-stimulated human monocytes was also inhibited (IC50 2 microM). Oral administration of SK&F 105809 to rats resulted in a dose-related generation of SK&F 105561 and in the inhibition of thromboxane B2 and LTB4 production ex vivo with a half-maximal dose (ED50) of 15 and 60 mg/kg, respectively. SK&F 105561 showed weak inhibitory activity on 12-lipoxygenase with an IC50 of greater than 200 microM. Neither SK&F 105561 nor SK&F 105809 inhibited the stimulated-turnover of arachidonic acid-containing phospholipids in human monocytes or the activity of cell-free phospholipases A2 and C. Moreover, neither SK&F 105561 nor SK&F 105809 antagonized the binding of LTB4 or leukotriene D4 to membrane receptors. From these results, SK&F 105561, the active principle of SK&F 105809, acts as an inhibitor of both inflammatory cytokine and eicosanoid production.

Absence of modulation of monokine production via endogenous cyclooxygenase or 5-lipoxygenase metabolites: MK-886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2- dimethylpropanoic acid), indomethacin, or arachidonate fail to alter immunoreactive interleukin-1 beta, or TNF-alpha production by human monocytes in vitro

Human peripheral blood monocytes exposed to MK-886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2- dimethylpropanoic acid) at doses which abolish formation of 5-lipoxygenase metabolites showed unaltered interleukin-1 beta (IL-1 beta) or tumor necrosis factor-alpha (TNF-alpha) levels in response to phorbol ester, concanavalin A, serum-treated zymosan, or lipopolysaccharide. Indomethacin (10 microM), alone or in combination with MK-886, also failed to modulate monokine production in response to any stimulus. Exogenous arachidonate (3-30 microM) which augmented the formation of PGE2 and LTB4 in the absence of stimulation, also had no effect on monokine production. LPS-induced IL-1 and TNF production occurred despite stimulation of PGE2 synthesis. The results make a role for endogenous prostaglandins and leukotrienes in the regulation of monocyte IL-1 beta and TNF-alpha production unlikely. These data also indicate that MK-886, a novel inhibitor of 5-lipoxygenase product formation, is a potentially useful leukotriene inhibitor which does not affect monokine production.

Inhibition by cyclo-oxygenase inhibitors of interleukin-6 production by human peripheral blood mononuclear cells

The effects of cyclo-oxygenase inhibitors on interleukin-6 (IL-6) production by human peripheral blood mononuclear cells were examined. Indomethacin and Y-9223, a novel cyclo-oxygenase inhibitor, inhibited the increases in the IL-6 level in the culture medium of both mitogen-stimulated adherent cells and non-adherent cells fractionated from mononuclear cells. Northern blotting showed that the mitogen-induced increase in the expression of IL-6 mRNA was inhibited by indomethacin and Y-9223, indicating that these agents inhibit IL-6 biosynthesis. Aspirin, ibuprofen, and phenylbutazone also inhibited IL-6 production by adherent cells stimulated with lipopolysaccharide (LPS). There was, however, no direct relationship between inhibition of IL-6 and prostaglandin E2 (PGE2) production by these agents. The addition of PGE2 corresponding to the amount produced by adherent cells stimulated with LPS slightly increased IL-6 production by unstimulated adherent cells, but to a lower level than that reached with LPS. An anti-PGE2 antibody partially blocked IL-6 production by adherent cells stimulated with LPS. These results suggest that, in addition to the inhibition of PGE2 production, other mediators including cyclooxygenase products or other action mechanisms are involved in the inhibition of IL-6 production by these drugs.

Leukotrienes do not regulate interleukin 1 production by activated macrophages

The objective of this work was to investigate the role of leukotrienes in the production of IL-1 by activated human peripheral blood monocytes and mouse peritoneal macrophages. Using overnight adherent macrophages, stimulation with lipopolysaccharide or zymosan caused a time-dependent increase in IL-1 production. LTC4 was detected and preceded IL-1 production only in zymosan-treated macrophages. Lipopolysaccharide did not stimulate macrophages to produce LTC4. Zymosan-stimulated LTC4 production was inhibited by the lipoxygenase inhibitors, ICI207968 (3.20 microM), nordihydroguaiaretic acid (0.22 microM), phenidone (4.60 microM), REV5901 (0.20 microM), and the Merck 5-lipoxygenase "translocation inhibitor" MK886 (0.02 microM) with IC50 values as shown in parenthesis. However, none of these inhibitors reduced IL-1 production at concentrations which completely inhibited leukotriene synthesis. Taken together, these results do not support a role for leukotrienes in the production of IL-1 by zymosan-activated macrophages.

The effect of dual inhibitor, SK&F 86002, on helper T cell functions

SK&F 86002, a mixed cyclooxygenase-lipoxygenase inhibitor, was examined for its effects on helper T cell functions. The drug was found to inhibit concanavalin A-induced mitogenesis of splenic T cells (IC50 = 13 microns), the mixed lymphocyte response (IC50 = 16 microM), and proliferation of antigen specific T cells (cloned line, IC50 = 11 microM; uncloned line, IC50 = 13 microM). In contrast, another mixed cycloxygenase-lipoxygenase inhibitor, BW775c, did not have such effects at non-cytotoxic levels. These T cell functions are believed to be dependent on the effects of elaborated IL-1. SK&F 86002 has been shown to inhibit the production of mature IL-1 (IC50 = 1 microM), possibly accounting for the anti-inflammatory effects of the drug in rheumatoid arthritis models. In an in vivo model of contact sensitivity, SK&F 86002 was able to inhibit mouse footpad swelling, demonstrating additional anti-inflammatory activity. As an inhibitor of IL-1 synthesis or release, SK&F 86002 may be useful for the treatment of T cell-dependent inflammation.

Effect of SK&F 86002 on cytokine production by human monocytes

Human monocytes respond to a variety of stimuli in vitro by producing a number of physiologically important macromolecules including the cytokines. SK&F 86002, a dual inhibitor of the arachidonate metabolism, has been shown to inhibit LPS induced IL-1 production in human monocytes. We examined its effect on the production of other cytokines which are coordinately expressed as a result of LPS stimulation such as tumor necrosis factor alpha (TNF), alpha interferon (IFN-A), interferon beta-2 (IL-6) and granulocyte colony stimulating factor (g-CSF). The IC50 of SK&F 86002 for the TNF production was 5-8 microM, and greater than 20 microM for the other three cytokines. These IC50s were significantly higher than that previously reported for IL-1 production (1-2 microM). Taken together these data indicate that the inhibitory effect of SK&F 86002 on IL-1 production is selective and the production of cytokines in drug treated monocytes can be differentially affected.

Inhibitory effect of SK&F 86002 on monocyte IL-1 production

The effects of several anti-inflammatory and anti-arthritic drugs on the in vitro production of interleukin-1 by human monocytes were examined. SK&F 86002-A2 was shown to be a potent inhibitor of IL-1 production with a 50% inhibitory concentration (IC50) of 1.3 +/- 0.5 microM. Standard compounds which inhibit the cyclooxygenase (CO) or CO and 5-lipoxygenase (5LO) pathways of arachidonic acid metabolism did not inhibit IL-1 production at nontoxic concentrations. Analysis of SK&F 86002 analogs also showed no clear correlation between 5LO and IL-1 synthesis inhibitory activity. The precise mechanism of action is not known except that it is post-transcriptional. Thus, SK&F 86002 may serve as a useful reagent in the understanding of the synthetic, processing and/or secretory pathways of interleukin-1, and may provide important insight into the treatment of disease states where aberrant IL-1 production is implicated.