Effect of inhibitors of eicosanoid metabolism in murine collagen-induced arthritis

Bacterial lipopolysaccharide potentiates type II collagen-induced arthritis in mice

Collagen-induced arthritis (CIA) is an immunologically relevant animal model of human rheumatoid arthritis. Studies comparing the disease incidence in genetically susceptible male and female DBA/1LacJ mice demonstrated that under low density/low stress housing conditions, female mice had earlier onset (day 35) and higher disease incidence (25%) than the male mice (17% at day 49) when immunized with bovine type II collagen. A single subcutaneous or intraperitoneal injection of bacterial lipopolysaccharide (LPS) 17–24 days after collagen immunization greatly potentiated this standard CIA model in a dose related manner. 20–40 μg of LPS accelerated the onset of disease from day 35 to day 21 and exacerbated the clinical severity score from 0.27 to 2.00 at day 42. A similar administration of 6 μg of recombinant interleukin-β produced a comparable potentiated CIA model. The acute phase protein, serum amyloid P (SAP), was elevated in the serum at day 26 to 440 μg ml⁻¹ for the LPS potentiated CIA mice compared to 65 μg ml⁻¹ in the non-potentiated immunized CIA mice. There was a significant correlation (r = 0.78) between SAP levels and disease expression in the LPS treated CIA mice. The rapidity and uniformity of disease expression in this LPS potentiated CIA model will allow more and different drugs to be evaluated with a smaller number of animals.

Individual isomers of conjugated linoleic acid reduce inflammation associated with established collagen-induced arthritis in DBA/1 mice

Previously, dietary conjugated linoleic acid [(CLA), an equal mixture of cis-9, trans-11 (c9t11) and trans-10, cis-12 (t10c12) CLA isomers], was found to reduce inflammation in the murine collagen antibody-induced arthritis model, but less so in the murine collagen-induced arthritis (CIA) model, an arthritic model dependent upon acquired immunity. Because CLA is known to alter the acquired immune response, it was hypothesized that feeding CLA after the establishment of arthritis would reduce paw swelling in the CIA model. In this study, upon the establishment of arthritic symptoms, mice were randomized to the following dietary treatments: corn oil (CO) control (n = 6), 0.5% c9t11-CLA (n = 8), 0.5% t10c12-CLA (n = 6), or 1% combined CLA (1:1 c9t11:t10c12-CLA, n = 6). Paws were scored for severity of arthritis and measured for changes in thickness during an 84-d study period. Dietary c9t11- and combined-CLA similarly decreased the arthritic score (29%, P = 0.036, P = 0.049, respectively, when normalized to initial score) and paw thickness (0.11 mm, P = 0.027, P = 0.035, respectively) compared with CO. Dietary t10c12-CLA reduced the arthritic score (41%, P = 0.007 when normalized) and paw thickness (0.12 mm, P = 0.013) relative to CO. Reduced interleukin-1beta on d 7 and 21 for all CLA treatments (n = 3) relative to CO suggested that antiinflammatory effects of CLA isomers might work by common mechanisms of known pathways involved in chronic inflammation. In conclusion, dietary CLA reduced inflammation associated with CIA, and both c9t11-CLA and t10c12-CLA exhibited antiinflammatory effects.

Reduction of cPLA2alpha overexpression: an efficient anti-inflammatory therapy for collagen-induced arthritis

Cytosolic phospholipase A2alpha (cPLA2) plays an important role in the development of several inflammatory diseases. The aim of the present study is to determine whether inhibition of cPLA2 expression, using specific antisense oligonucleotides against cPLA2 (antisense), is efficient in reducing inflammation after its development. Two mouse models of inflammation were included in the study: thioglicolate peritonitis and collagen-induced arthritis (CIA). The antisense was found to be specific and efficient in inhibiting cPLA2 expression and NADPH oxidase activity ex vivo in peritoneal phagocytes. Immunoblotting and immunohistochemistry analysis showed a significant elevation in cPLA2 expression in the inflamed joints of collagen-induced arthritis mice localized in cell infiltrate, chondrocytes and the surrounding skin and skeletal muscle. Similarly, the cPLA2 metabolite, leukotriene B4, accumulated in the peritoneal cavity of mice with peritonitis. Inhibition of elevated cPLA2 expression after development of inflammation by intravenous administration of antisense resulted in a dramatic reduction in inflammation and a significant reduction in neutrophils recruitment to the site of inflammation in both mouse models of inflammation. Our results demonstrate the critical role of cPLA2 for the duration of inflammation and suggest that inhibition of cPLA2 expression by antisense oligonucleotides may serve as an efficient treatment of inflammatory diseases.

Chromatin-mediated regulation of nucleolar structure and RNA Pol I localization by TOR

The target of rapamycin (TOR) protein is a conserved regulator of ribosome biogenesis, an important process for cell growth and proliferation. However, how TOR is involved remains poorly understood. In this study, we find that rapamycin and nutrient starvation, conditions inhibiting TOR, lead to significant nucleolar size reduction in both yeast and mammalian cells. In yeast, this morphological change is accompanied by release of RNA polymerase I (Pol I) from the nucleolus and inhibition of ribosomal DNA (rDNA) transcription. We also present evidence that TOR regulates association of Rpd3-Sin3 histone deacetylase (HDAC) with rDNA chromatin, leading to site-specific deacetylation of histone H4. Moreover, histone H4 hypoacetylation mutations cause nucleolar size reduction and Pol I delocalization, while rpd3Delta and histone H4 hyperacetylation mutations block the nucleolar changes as a result of TOR inhibition. Taken together, our results suggest a chromatin-mediated mechanism by which TOR modulates nucleolar structure, RNA Pol I localization and rRNA gene expression in response to nutrient availability.

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.

Cytosolic phospholipase A2alpha-deficient mice are resistant to collagen-induced arthritis

Pathogenic mechanisms relevant to rheumatoid arthritis occur in the mouse model of collagen-induced arthritis (CIA). Cytosolic phospholipase A2alpha (cPLA2alpha) releases arachidonic acid from cell membranes to initiate the production of prostaglandins and leukotrienes. These inflammatory mediators have been implicated in the development of CIA. To test the hypothesis that cPLA2alpha plays a key role in the development of CIA, we backcrossed cPLA2alpha-deficient mice on the DBA/1LacJ background that is susceptible to CIA. The disease severity scores and the incidence of disease were markedly reduced in cPLA2alpha-deficient mice compared with wild-type littermates. At completion of the study, >90% of the wild-type mice had developed disease whereas none of the cPLA2alpha-deficient mice had more than one digit inflamed. Furthermore, visual disease scores correlated with severity of disease determined histologically. Pannus formation, articular fibrillation, and ankylosis were all dramatically reduced in the cPLA2alpha-deficient mice. Although the disease scores differed significantly between cPLA2alpha mutant and wild-type mice, anti-collagen antibody levels were similar in the wild-type mice and mutant littermates. These data demonstrate the critical role of cPLA2alpha in the pathogenesis of CIA.

Inhibition of the p38 pathway upregulates macrophage JNK and ERK activities, and the ERK, JNK, and p38 MAP kinase pathways are reprogrammed during differentiation of the murine myeloid M1 cell line

Mitogen-activated protein (MAP) kinases have been implicated as important mediators of the inflammatory response. Here we report that c-Jun NH(2)-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and p38 MAP kinase activities are reprogrammed during the IL-6 induced macrophage-like differentiation of the murine myeloid M1 cell line. Moreover, p38 inhibition upregulates JNK and ERK activity in M1 cells and in thioglycollate-elicited peritoneal exudate macrophages. IL-6-induced M1 differentiation also induces expression of the anti-inflammatory cytokine IL-10, and p38 inhibition potentiates this increase in IL-10 expression in an ERK-dependent manner. Thus, we speculate that during inflammatory conditions in vivo macrophage p38 may regulate JNK and ERK activity and inhibit IL-10 expression. These data highlight the importance of p38 in the molecular mechanisms of macrophage function.

Selective suppression of neutrophil accumulation in ongoing pulmonary inflammation by systemic inhibition of p38 mitogen-activated protein kinase

The p38 mitogen-activated protein kinase (MAPK) signaling pathway regulates a wide range of inflammatory responses in many different cells. Inhibition of p38 MAPK before exposing a cell to stress stimuli has profound anti-inflammatory effects, but little is known about the effects of p38 MAPK inhibition on ongoing inflammatory responses. LPS-induced activation of p38 MAPK in human neutrophils was inhibited by poststimulation exposure to a p38 MAPK inhibitor (M39). Release of TNF-alpha, macrophage-inflammatory protein (MIP)-2 (MIP-1beta), and IL-8 by LPS-stimulated neutrophils was also reduced by poststimulation p38 MAPK inhibition. In contrast, release of monocyte chemoattractant protein-1 was found to be p38 MAPK independent. Ongoing chemotaxis toward IL-8 was eliminated by p38 MAPK inhibition, although the rate of nondirectional movement was not reduced. A murine model of acute LPS-induced lung inflammation was used to study the effect of p38 MAPK inhibition in ongoing pulmonary inflammation. Initial pulmonary cell responses occur within 4 h of stimulation in this model, so M39 was administered 4 h or 12 h after exposure of the animals to aerosolized LPS to avoid inhibition of cytokine release. Quantities of TNF-alpha, MIP-2, KC, or monocyte chemoattractant protein-1 recovered from bronchial alveolar lavage or serum were not changed. Recruitment of neutrophils, but not other leukocytes, to the airspaces was significantly reduced. Together, these data demonstrate the selective reduction of LPS-induced neutrophil recruitment to the airspaces, independent of suppression of other inflammatory responses. These findings support the feasibility of p38 MAPK inhibition as a selective intervention to reduce neutrophilic inflammation.

Synthesis of a magnosalin derivative, 4-(3,4,5-trimethoxyphenyl)-6-(2,4,5-trimethoxyphenyl)-2-diethylaminopyrimidine, and the anti-angiogenic and anti-rheumatic effect on mice by oral administration

We describe here the synthesis and the anti-angiogenic and anti-rheumatic activities of 4-(3,4,5-trimethoxyphenyl)-6-(2,4,5-trimethoxyphenyl)-2-diethylaminopyrimidine (TAS-202), a derivative of magnosalin, which is a natural product isolated from Flos magnoliae. TAS-202 inhibited the proliferation of vascular endothelial cells more potently than magnosalin, and when given orally it inhibited basic fibroblast growth factor (bFGF)-induced angiogenesis and collagen-induced arthritis in mice. This magnosalin derivative with anti-angiogenic effects is a candidate for the treatment of rheumatoid arthritis.

Blockade of the p38 mitogen-activated protein kinase pathway inhibits inducible nitric oxide synthase and interleukin-6 expression in MC3T3E-1 osteoblasts

Treatment of MC3T3E-1 osteoblast cultures with combined interferon- gamma(IFN- gamma), lipopolysaccharide (LPS) and tumor necrosis factor- alpha(TNF- alpha) induces expressions of inducible nitric oxide synthase (iNOS) and interleukin-6 (IL-6), resulting in sustained releases of large amounts of nitric oxide and IL-6. However IFN- gamma, LPS and TNF- alpha individually induces non-detectable or small amounts of NO and IL-6 in MC3T3E-1 osteoblasts. The role of mitogen-activated protein kinase (MAPK) activation in the early intracellular signal transduction involved in iNOS and IL-6 transcription in the combined agents-stimulated osteoblasts has been investigated. The p38 MAPK pathway is specifically involved in the combined agents-induced NO and IL-6 release, since NO and IL-6 release in the presence of a specific inhibitor of p38 MAPK, 4-(4-fluorophenyl)-2-(4-metylsulfinylphenyl)-5-(4-pyridyl)imidazole (SB203580), are significantly diminished. In contrast, PD98059, a specific inhibitor of MEK1, had no effect on NO and IL-6 release. Northern blot analysis showed that the p38 MAPK pathway controlled iNOS and IL-6 transcription levels. These data suggest that p38 MAPK plays an important role in the secretion of NO and IL-6 in LPS/IFN- gamma or TNF- alpha /IFN- gamma -treated MC3T3E-1 osteoblasts.

The JNK and P38 MAP kinase signaling pathways in T cell-mediated immune responses

The mitogen-activated protein (MAP) kinase family members, which include the extracellular response kinases (ERK), p38, and c-Jun amino terminal kinases (JNK), play a role in mediating signals triggered by cytokines, growth factors, and environmental stress. JNK and p38 MAP kinases have been involved in inflammatory processes induced by a variety of stimuli, such as oxidative stress. Here, we describe the role of the JNK and p38 MAP kinase signaling pathways in the development of T cells in the thymus, and activation and differentiation of T cells in the peripheral immune system.

Role of p38 mitogen-activated protein kinase in a murine model of pulmonary inflammation

Early inflammatory events include cytokine release, activation, and rapid accumulation of neutrophils, with subsequent recruitment of mononuclear cells. The p38 mitogen-activated protein kinase (MAPK) intracellular signaling pathway plays a central role in regulating a wide range of inflammatory responses in many different cells. A murine model of mild LPS-induced lung inflammation was developed to investigate the role of the p38 MAPK pathway in the initiation of pulmonary inflammation. A novel p38 MAPK inhibitor, M39, was used to determine the functional consequences of p38 MAPK activation. In vitro exposure to M39 inhibited p38 MAPK activity in LPS-stimulated murine and human neutrophils and macrophages, blocked TNF-alpha and macrophage inflammatory protein-2 (MIP-2) release, and eliminated migration of murine neutrophils toward the chemokines MIP-2 and KC. In contrast, alveolar macrophages required a 1000-fold greater concentration of M39 to block release of TNF-alpha and MIP-2. Systemic inhibition of p38 MAPK resulted in significant decreases in the release of TNF-alpha and neutrophil accumulation in the airspaces following intratracheal administration of LPS. Recovery of MIP-2 and KC from the airspaces was not affected by inhibition of p38 MAPK, and accumulation of mononuclear cells was not significantly reduced. When KC was instilled as a proinflammatory stimulus, neutrophil accumulation was significantly decreased by p38 MAPK inhibition independent of TNF-alpha or LPS. Together, these results demonstrate a much greater dependence on the p38 MAPK cascade in the neutrophil when compared with other leukocytes, and suggest a means of selectively studying and potentially modulating early inflammation in the lung.

Disease-modifying activity of SB 242235, a selective inhibitor of p38 mitogen-activated protein kinase, in rat adjuvant-induced arthritis

OBJECTIVE

To evaluate the effects of SB 242235, a potent and selective inhibitor of p38 mitogen-activated protein (MAP) kinase, on joint integrity in rats with adjuvant-induced arthritis (AIA).

METHODS

Male Lewis rats with AIA were orally treated either prophylactically (days 0-20) or therapeutically (days 10-20) with SB 242235. Efficacy was determined by measurements of paw inflammation, dual-energy x-ray absorptiometry for bone-mineral density (BMD), magnetic resonance imaging (MRI), microcomputed tomography (CT), and histologic evaluation. Serum tumor necrosis factor alpha (TNFalpha) in normal (non-AIA) rats and serum interleukin-6 (IL-6) levels in rats with AIA were measured as markers of the antiinflammatory effects of the compound.

RESULTS

SB 242235 inhibited lipopolysaccharide-stimulated serum levels of TNFalpha in normal rats, with a median effective dose of 3.99 mg/kg. When SB 242235 was administered to AIA rats prophylactically on days 0-20, it inhibited paw edema at 30 mg/kg and 10 mg/kg per day by 56% and 33%, respectively. Therapeutic administration on days 10-20 was also effective, and inhibition of paw edema was observed at 60, 30, and 10 mg/kg (73%, 51%, and 19%, respectively). Significant improvement in joint integrity was demonstrated by showing normalization of BMD and also by MRI and micro-CT analysis. Protection of bone, cartilage, and soft tissues was also shown histologically. Serum IL-6 levels were decreased in AIA rats treated with the 60 mg/kg dose of compound.

CONCLUSION

Symptoms of AIA in rats were significantly reduced by both prophylactic and therapeutic treatment with the p38 MAP kinase inhibitor, SB 242235. Results from measurements of paw inflammation, assessment of BMD, MRI, and micro-CT indicate that this compound exerts a protective effect on joint integrity, and thus appears to have disease-modifying properties.

SB 203580 Inhibits p38 Mitogen-Activated Protein Kinase, Nitric Oxide Production, and Inducible Nitric Oxide Synthase in Bovine Cartilage-Derived Chondrocytes

Nitric oxide (NO) is implicated in a number of inflammatory processes and is an important mediator in animal models of rheumatoid arthritis and in in vitro models of cartilage degradation. The pyridinyl imidazole SB 203580 inhibits p38 mitogen-activated protein (MAP) kinase in vitro, blocks proinflammatory cytokine production in vitro and in vivo, and is effective in animal models of arthritis. The purpose of this study was to determine whether SB 203580 could inhibit p38 MAP kinase activity, NO production, and inducible NO synthase (iNOS) in IL-1 stimulated bovine articular cartilage/chondrocyte cultures. The results indicated that SB 203580 inhibited both IL-1 stimulated p38 MAP kinase activity in isolated chondrocytes and NO production in bovine chondrocytes and cartilage explants with an IC50 value of approximately 1 μM. To inhibit NO production, SB 203580 had to be present in cartilage explant cultures during the first 8 h of IL-1 stimulation, and activity was lost when it was added 24 h following IL-1. SB 203580 did not inhibit iNOS activity, as measured by the conversion of arginine to citrulline, when added directly to cultures where the enzyme had already been induced, but had to be present during the induction period. Using a 372-bp probe for bovine iNOS we demonstrated inhibition of IL-1-induced mRNA by SB 203580 at both 4 and 24 h following IL-1 treatment. The iNOS mRNA levels were consistent with NO levels in 24-h cell culture supernatants of the IL-1-stimulated bovine chondrocytes used to obtain the RNA.

Interferon-gamma expression by Th1 effector T cells mediated by the p38 MAP kinase signaling pathway

Signal transduction via MAP kinase pathways plays a key role in a variety of cellular responses, including growth factor-induced proliferation, differentiation and cell death. In mammalian cells, p38 MAP kinase can be activated by multiple stimuli, such as pro-inflammatory cytokines and environmental stress. Although p38 MAP kinase is implicated in the control of inflammatory responses, the molecular mechanisms remain unclear. Upon activation, CD4+ T cells differentiate into Th2 cells, which potentiate the humoral immune response or pro-inflammatory Th1 cells. Here, we show that pyridinyl imidazole compounds (specific inhibitors of p38 MAP kinase) block the production of interferon-gamma (IFNgamma) by Th1 cells without affecting IL-4 production by Th2 cells. These drugs also inhibit transcription driven by the IFNgamma promoter. In transgenic mice, inhibition of the p38 MAP kinase pathway by the expression of dominant-negative p38 MAP kinase results in selective impairment of Th1 responses. In contrast, activation of the p38 MAP kinase pathway by the expression of constitutivelyactivated MAP kinase kinase 6 in transgenic mice caused increased production of IFNgamma during the differentiation and activation of Th1 cells. Together, these data demonstrate that the p38 MAP kinase is relevant for Th1 cells, not Th2 cells, and that inhibition of p38 MAP kinase represents a possible site of therapeutic intervention in diseases where a predominant Th1 immune response leads to a pathological outcome. Moreover, our study provides an additional mechanism by which the p38 MAP kinase pathway controls inflammatory responses.

Monosodium Urate Microcrystals Induce Cyclooxygenase-2 in Human Monocytes

The formation and deposition of monosodium urate (MSU) microcrystals in articular and periarticular tissues is the causative agent of acute or chronic inflammatory responses known as gouty arthritis. Mononuclear phagocyte activation is involved in early triggering events of gout attacks. Because stimulated mononuclear phagocytes can constitute an important source of the inducible isoform of cyclooxygenase (COX-2), we evaluated the effects that proinflammatory microcrystals might have on COX-2 protein expression in crystal-stimulated monocytes. We found that MSU crystals, but not calcium pyrophosphate dihydrate (CPPD) crystals, induced COX-2, which correlated with the synthesis of prostaglandin E2 (PGE2) and thromboxane A2(TXA2). Crystal-induced de novo synthesis of COX-2 was dependent on transcriptional and translational events. Inhibition of tyrosine phosphorylation, by herbimycin A, blocked crystal-induced COX-2. Similarly, an inhibitor of the p38 mitogen-activated protein kinase, SB 203580, inhibited the stimulation of COX-2. Colchicine inhibited crystal-induced COX-2. In all cases, prostanoid synthesis was concomitantly inhibited. Taken together, these results implicate COX-2 in the development of MSU-induced inflammation.

Monosodium Urate Microcrystals Induce Cyclooxygenase-2 in Human Monocytes

The formation and deposition of monosodium urate (MSU) microcrystals in articular and periarticular tissues is the causative agent of acute or chronic inflammatory responses known as gouty arthritis. Mononuclear phagocyte activation is involved in early triggering events of gout attacks. Because stimulated mononuclear phagocytes can constitute an important source of the inducible isoform of cyclooxygenase (COX-2), we evaluated the effects that proinflammatory microcrystals might have on COX-2 protein expression in crystal-stimulated monocytes. We found that MSU crystals, but not calcium pyrophosphate dihydrate (CPPD) crystals, induced COX-2, which correlated with the synthesis of prostaglandin E2 (PGE2) and thromboxane A2(TXA2). Crystal-induced de novo synthesis of COX-2 was dependent on transcriptional and translational events. Inhibition of tyrosine phosphorylation, by herbimycin A, blocked crystal-induced COX-2. Similarly, an inhibitor of the p38 mitogen-activated protein kinase, SB 203580, inhibited the stimulation of COX-2. Colchicine inhibited crystal-induced COX-2. In all cases, prostanoid synthesis was concomitantly inhibited. Taken together, these results implicate COX-2 in the development of MSU-induced inflammation.

The effect of leukotriene synthesis inhibitors in models of acute and chronic inflammation

OBJECTIVE

To assess the efficacy of leukotriene synthesis inhibitors, alone and in combination with a nonsteroidal antiinflammatory drug, as potential treatments for rheumatoid arthritis (RA), using the mouse air pouch model and the collagen-induced arthritis (CIA) model.

METHODS

Two selective leukotriene synthesis inhibitors, Bay x 1005 and Bay y 1015, were compared with zileuton in terms of their ability to decrease exudate volume, cell infiltration, and leukotriene B4 (LTB4) production in response to zymosan injection in the mouse air pouch model. The mouse CIA model was used to assess the effect of leukotriene synthesis inhibitors in a model of chronic inflammation. Bay y 1015 and Bay x 1005, and the cyclooxygenase inhibitor naproxen, were evaluated individually and in combination, for their antiarthritic potency in the mouse CIA model.

RESULTS

The results indicate that neither zileuton, Bay x 1005, nor Bay y 1015 inhibited exudate production. All 3 compounds decreased LTB4 levels in be air pouch, with Bay y 1015 being the most effective. Cell infiltration was significantly decreased with Bay x 1005, but the degree of this decrease did not appear to correlate with LTB4 levels. No inhibition of arthritis was observed with any compound administered alone. In contrast, a significant inhibition of CIA was observed in animals that received both naproxen and either Bay y 1015 or Bay x 1005.

CONCLUSION

Inhibitors of both cyclooxygenase and leukotriene synthesis in combination may be a more effective treatment of RA than either class of inhibitors alone.

Appearance of calpain correlates with arthritis and cartilage destruction in collagen induced arthritic knee joints of mice

OBJECTIVES

To determine the relevance of calpain in murine collagen induced arthritis (CIA) and to correlate the presence of m-calpain with the appearance of arthritis and cartilage destruction.

METHODS

The immunohistochemical appearance and localisation of m-calpain at different stages of arthritis were analysed and compared with the histological changes occurring during type II CIA. The arthritic knee joint lavage was also examined for m-calpain by immunoelectrophoretic blotting.

RESULTS

Immunohistochemical staining demonstrated a clear positive correlation between the appearance of m-calpain and both a histological grade of arthritis and an acute phase of cartilage destruction. Further development of the disease showed continual presence of m-calpain but with reduced intensity. Intra-articular inflammatory cells (mainly polymorphonuclear leucocytes, synovial lining cells, and sublining fibroblasts) were found to be the most positively stained, but extracellular localisation of m-calpain on the surface of cartilage and synovium, and in the articular cartilage matrix and chondrocyte lacunae, was also observed. In the knee joint lavage obtained at the most intensive stage of acute arthritis, m-calpain was detectable by immunoelectrophoretic blotting.

CONCLUSIONS

The findings suggest that m-calpain may act at an early phase of CIA as a matrix proteinase and take part in the destruction of articular cartilage or activate other destructive enzymes.

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.

Protective effects of D-penicillamine and a thiazole derivative, SM-8849, on pristane-induced arthritis in mice

To evaluate the antiarthritic properties of a novel thiazole derivative, the drugs SM-8849, D-penicillamine and indomethacin were administered to pristane-injected DBA/1 mice. The mice were treated daily with the agents for 32 weeks, starting from the day of the pristane injection. Treatment with SM-8849 (50 mg/kg) resulted in an amelioration of arthritic disease, as assessed by clinical, radiographic, and histologic examinations. Similar results were obtained in mice treated with 50 mg/kg D-penicillamine, although this disease modifying antirheumatic drug was slightly less effective than the same dose of SM-8849. In contrast, indomethacin at the maximum tolerated dose of 2 mg/kg did not alter the course of the disease. SM-8849 and D-penicillamine were also shown to reduce serum levels of rheumatoid factors and the acute-phase reactant, serum amyloid P component. Indomethacin failed to affect either parameter. Flow cytometric analysis revealed an elevation in the T-cell population that expressed CD44, a marker of murine memory T-cells, in spleens from pristane-injected mice. SM-8849, but not D-penicillamine, prevented the increase in this cell population. These results led us to conclude that pristine-induced arthritis was a useful model for the evaluation of antirheumatic agents, in that using this model, we were able to distinguish disease modifying antirheumatic drugs from nonsteroidal anti-inflammatory drugs. Our findings also indicate that SM-8849 shows antiarthritic activity, with a unique mechanism of action, differing from that of D-penicillamine.

Effects of a highly selective plasma kallikrein inhibitor on collagen-induced arthritis in mice

A study was conducted to evaluate the effects of a new, highly selective plasma kallikrein inhibitor, PKSI-527, on collagen-induced arthritis (CIA) in mice. PKSI-527 or indomethacin was administered daily intraperitoneally from day 20 postimmunization. Clinical evaluation was performed, and two of the components of the kallikrein-kinin system, high-molecular-weight (HMW) kininogen and plasma prekallikrein, were assayed. PKSI-527, as well as indomethacin, reduced the severity of arthritis significantly. PKSI-527, but not indomethacin, restored consumed components of the kallikrein-kinin system. These results suggest that PKSI-527 suppresses CIA by modifying the kallikrein-kinin system and PKSI-527 as a synthetic plasma kallikrein inhibitor would be a valuable tool to study the mechanism of inflammation of arthritic diseases.

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)