Evaluation of human cytokine production and effects of pharmacological agents in a heterologous system in vivo

Synthesis, characterization and pharmacological evaluation of pyrazolyl urea derivatives as potential anti-inflammatory agents

p38α mitogen activated protein kinase (MAPK) inhibitors provide a novel approach for the treatment of inflammatory disorders. A series of fifteen pyrazolyl urea derivatives (3a—o) were synthesized and evaluated for their p38α MAPK inhibition and antioxidant potential. Compounds 3a—e, 3g and 3h showed low micromolar range potency (IC₅₀ values ranging from 0.037 ± 1.56 to 0.069 ± 0.07 µmol/L) compared to the standard inhibitor SB 203580 (IC₅₀ = 0.043 ± 3.62 µmol/L) when evaluated for p38α MAPK inhibition by an immunosorbent-based assay. Antioxidant activity was measured by a 2,2′-diphenyl-1-picryl hydrazyl radical (DPPH) free radical scavenging method and one of the compounds, 3c, showed better percentage antioxidant activity (75.06%) compared to butylated hydroxy anisole (71.53%) at 1 mmol/L concentration. Compounds 3a—e, 3g and 3h showed promising in vivo anti-inflammatory activity (ranging from 62.25% to 80.93%) in comparison to diclofenac sodium (81.62%). The ulcerogenic liability and lipid peroxidation activity of these compounds were observed to be less in comparison to diclofenac sodium. These compounds also potently inhibited the lipopolysaccharide (LPS)-induced TNF-α release in mice (ID₅₀ of 3a—c = 19.98, 11.32 and 9.67 mg/kg, respectively). Among the screened compounds, derivative 3c was found to be the most potent and its binding mode within the p38α MAPK is also reported.

No evidence for an involvement of the p38 and JNK mitogen-activated protein in inflammatory bowel diseases

Involvement of mitogen-activated protein (MAPK) in inflammatory bowel disease (IBD) remains enigmatic. We sought to evaluate the expression and activity of p38 and JNK MAPK in IBD and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis; and the effects of a p38 inhibitor, SB203580, in TNBS colitis. P38 and JNK were quantified in colonic mucosa of 28 IBD patients and 19 controls and in 77 TNBS or control mice treated or not with SB203580. Colitis severity was assessed by survival, macroscopic and microscopic scoring, and molecular markers. Expression and activity of p38 and JNK were similar in IBD patients and controls and not modified by inflammation. In mice, p38 and JNK expression or activity did not increase following the induction of colitis. SB203580 decreased the p38 activity but displayed no clinical nor biological therapeutic effect. In conclusion, these results minimize the role of p38 and JNK in inflammatory colitis and the interest of p38 as a therapeutic target in IBD.

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.

Induced stabilization of IkappaBalpha can facilitate its re-synthesis and prevent sequential degradation

The transcription factor NF-kappaB is responsible for regulating genes that can profoundly impact cell proliferation, apoptosis, inflammation, and immune responses. The NF-kappaB inhibitor IkappaBalpha is rapidly degraded and then re-synthesized after an NF-kappaB stimulus. We have found that the re-synthesis of IkappaBalpha in a human colon-derived cell line (HT-29) includes the post-translational stabilization of newly synthesized IkappaBalpha. The TNF-alpha-induced stabilization of newly synthesized IkappaBalpha involves the C-terminal PEST region of the protein: N-terminal deletion mutants (lacking the IkappaB kinase phosphorylation sites) were readily stabilized by TNF-alpha, whereas deletion of the C-terminus resulted in a constitutively stable protein. The role of the C-terminus in stabilization was further supported by the finding that fusion of the IkappaBalpha C-terminus to GFP generated a protein that could also be stabilized by TNF-alpha. The p38 mitogen-activated protein (MAP) kinase inhibitor SB203580 prevented stabilization of IkappaBalpha and delayed the re-emergence of IkappaBalpha following TNF-alpha-induced degradation. The IkappaBalpha stabilization pathway could prevent sequential rounds of IkappaBalpha degradation without preventing IkappaBalpha phosphorylation. Analysis of two other cell lines (SW480 and THP-1) revealed similarities and cell-specific differences in the regulation of IkappaBalpha stabilization. We propose that cytokine stabilization of newly synthesized IkappaBalpha in some cell types is a critical homeostatic mechanism that limits inflammatory gene expression.

Role of MAP kinase signalling pathways in the mode of action of peroxisome proliferators

Peroxisome proliferators (PPs) are a class of non-genotoxic chemicals that cause rodent liver enlargement and hepatocarcinogenesis. In primary rat hepatocytes, PPs cause cell proliferation, suppression of apoptosis and peroxisome proliferation. We have investigated the role of different families of mitogen-activated protein (MAP) kinases in the mode of action of PPs. Addition of 50 microM nafenopin to primary rat hepatocyte cultures caused weak activation of extracellular signal regulated kinases and p38 MAP kinase. However, incubation of primary hepatocytes with the p38 MAP kinase inhibitor SB203580 or the MAP kinase kinase (MEK) inhibitor PD098059 prevented the induction of DNA synthesis and the suppression of transforming growth factor beta(1)-induced apoptosis by the PP nafenopin. In contrast, in the presence of these MAP kinase inhibitors, nafenopin still induced palmitoyl CoA oxidation, a measure of peroxisome proliferation. We have shown previously that PPs such as nafenopin require tumour necrosis factor alpha (TNF-alpha) to exert their effects on cellular proliferation and apoptosis. Here we show that treatment of primary rat hepatocyte cultures with nafenopin causes an increase in bioactive TNF-alpha and that this process requires p38 MAP kinase activity.

The role of protein kinase B and mitogen-activated protein kinase in epidermal growth factor and tumor necrosis factor alpha-mediated rat hepatocyte survival and apoptosis

Perturbation of hepatocyte growth regulation is associated with a number of liver diseases such as fibrosis and cancer. These diseases are mediated by a network of growth factors and cytokines that regulate the induction of hepatocyte proliferation and apoptosis. In this study, we have investigated the role of signaling pathways activated by tumor necrosis factor alpha (TNF-alpha) and epidermal growth factor (EGF) in the regulation of apoptosis induced by transforming growth factor beta(1) (TGF-beta(1)), because this physiological factor is believed to regulate spontaneous apoptosis in the liver. We show that pretreatment with (10 ng/mL) EGF or (25 ng/mL) TNF-alpha can suppress TGF-beta(1)-induced apoptosis by 73% and 50%, respectively, in isolated rat hepatocytes. However, suppression of TGF-beta(1)-induced apoptosis by EGF and TNF-alpha occurs via different protein kinase signaling pathways. Using specific inhibitors, we show that suppression of apoptosis by EGF is dependent on activation of phosphoinositide 3-kinase (PI 3-kinase) and the extracellular signal regulated kinase (ERK) mitogen-activated protein (MAP) kinase pathways, but not p38 MAP kinase. In contrast, suppression of TGF-beta(1)-induced apoptosis by TNF-alpha does not require PI 3-kinase and protein kinase B (PKB or Akt)-mediated pathways, but is dependent on ERK and p38 MAP kinase activity. These data contribute to our understanding of the intracellular survival signals that play a role in normal liver homeostasis and in diverse pathological conditions.

Phosphodiesterase 4 (PDE4) inhibitors in asthma and chronic obstructive pulmonary disease (COPD)

Phosphodiesterases (PDE) are a family of enzymes responsible for the metabolism of the intracellular second messengers cyclic AMP and cyclic GMP. PDE4 is a cyclic AMP specific PDE that is the major if not sole cyclic AMP metabolizing enzymes found in inflammatory and immune cells, and contributes significantly to cyclic AMP metabolism in smooth muscles. Based on its cellular and tissue distribution and the demonstration that selective inhibitors of this isozyme reduce bronchoconstriction in animals and suppress the activation of inflammatory cells, PDE4 has become an important molecular target for the development of novel therapies for asthma and COPD. This chapter will review the evidence demonstrating the ability of PDE4 inhibitors to modify airway obstruction, airway inflammation and airway remodelling and hyperreactivity, will present some preliminary findings obtained with theses compounds in clinical trials and and will discuss experimental approaches designed to identify novel compounds that maintain the beneficial activity of the initial selective PDE4 inhibitors but with a reduced tendency of elicit the gastrointestinal side effects observed with this class of compounds.

1,4-Cyclohexanecarboxylates: potent and selective inhibitors of phosophodiesterase 4 for the treatment of asthma

Evaluation of a variety of PDE4 inhibitors in a series of cellular and in vivo assays suggested a strategy to improve the therapeutic index of PDE4 inhibitors by increasing their selectivity for the ability to inhibit PDE4 catalytic activity versus the ability to compete for high affinity [3H]rolipram-binding sites in the central nervous system. Use of this strategy led ultimately to the identification of cis-4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexane-1-carboxyl ic acid (1, SB 207499, Ariflo), a potent second-generation inhibitor of PDE4 with a decreased potential for side effects versus the archetypic first generation inhibitor, (R)-rolipram.