The effects of antiinflammatory and antiallergic drugs on cytokine release after stimulation of human whole blood by lipopolysaccharide and zymosan A

Inhibition of p38α MAPK restores neuronal p38γ MAPK and ameliorates synaptic degeneration in a mouse model of DLB/PD

Alterations in the p38 mitogen-activated protein kinases (MAPKs) play an important role in the pathogenesis of dementia with Lewy bodies (DLB) and Parkinson's disease (PD). Activation of the p38α MAPK isoform and mislocalization of the p38γ MAPK isoform are associated with neuroinflammation and synaptic degeneration in DLB and PD. Therefore, we hypothesized that p38α might be associated with neuronal p38γ distribution and synaptic dysfunction in these diseases. To test this hypothesis, we treated in vitro cellular and in vivo mouse models of DLB/PD with SKF-86002, a compound that attenuates inflammation by inhibiting p38α/β, and then investigated the effects of this compound on p38γ and neurodegenerative pathology. We found that inhibition of p38α reduced neuroinflammation and ameliorated synaptic, neurodegenerative, and motor behavioral deficits in transgenic mice overexpressing human α-synuclein. Moreover, treatment with SKF-86002 promoted the redistribution of p38γ to synapses and reduced the accumulation of α-synuclein in mice overexpressing human α-synuclein. Supporting the potential value of targeting p38 in DLB/PD, we found that SKF-86002 promoted the redistribution of p38γ in neurons differentiated from iPS cells derived from patients with familial PD (carrying the A53T α-synuclein mutation) and healthy controls. Treatment with SKF-86002 ameliorated α-synuclein-induced neurodegeneration in these neurons only when microglia were pretreated with this compound. However, direct treatment of neurons with SKF-86002 did not affect α-synuclein-induced neurotoxicity, suggesting that SKF-86002 treatment inhibits α-synuclein-induced neurotoxicity mediated by microglia. These findings provide a mechanistic connection between p38α and p38γ as well as a rationale for targeting this pathway in DLB/PD.

Inflammation-Responsive Drug-Conjugated Dextran Nanoparticles Enhance Anti-Inflammatory Drug Efficacy

Stimuli-responsive nanoparticles (NPs) are especially interesting to enhance the drug delivery specificity for biomedical applications. With the aim to achieve a highly stable and inflammation-specific drug release, we designed a reactive oxygen species (ROS)-responsive dextran-drug conjugate (Nap-Dex). By blending Nap-Dex with the acid-sensitive acetalated dextran polymer, we achieved a dual-responsive NP with high specificity toward the inflammatory environment. The inflammatory environment not only has elevated ROS levels but also has a lower pH than healthy tissues, making pH and ROS highly suitable triggers to target inflammatory diseases. The anti-inflammatory cyclooxygenase inhibitor naproxen was modified with an ROS-responsive phenylboronic acid (PBA) and conjugated onto dextran. The dextran units were functionalized with up to 87% modified naproxen. This resulted in a complete drug release from the polymer within 20 min at 10 mM H2O2. The dual-responsive NPs reduced the levels of the proinflammatory cytokine IL-6 120 times more efficiently and TNFα 6 times more efficiently than free naproxen from lipopolysaccharide (LPS)-activated macrophages. These additional anti-inflammatory effects were found to be mainly attributed to ROS-scavenging effects. In addition, the model cargo fluorescein diacetate was released in an LPS-induced inflammatory response in vitro. We believe that drug conjugation using PBA can be applied to various drugs and dextran-based materials for enhanced drug efficacy, where this work demonstrates the significance of functionalized carbohydrates polymer-drug conjugates.

Resolvin E1, an EPA-derived mediator in whole blood, selectively counterregulates leukocytes and platelets

Resolvin E1 (RvE1) is an omega-3 eicosapentaenoic acid (EPA)-derived lipid mediator generated during resolution of inflammation and in human vasculature via leukocyte-endothelial cell interactions. RvE1 possesses anti-inflammatory and proresolving actions. Here, we report that RvE1 in human whole blood rapidly regulates leukocyte expression of adhesion molecules. RvE1 in the 10- to 100-nM range stimulated L-selectin shedding, while reducing CD18 expression in both neutrophils and monocytes. When added to whole blood, RvE1 did not stimulate reactive oxygen species by either neutrophils or monocytes, nor did it directly stimulate cytokine/chemokine production in heparinized blood. Intravital microscopy (IVM) demonstrated that RvE1 rapidly reduced leukocyte rolling (approximately 40%) in venules of mice. In human platelet-rich plasma (PRP), RvE1 selectively blocked both ADP-stimulated and thromboxane receptor agonist U46619-stimulated platelet aggregation in a concentration-dependent manner. In contrast, Delta 6,14-trans-RvE1 isomer was inactive. RvE1 did not block collagen-stimulated aggregation, and regulation of ADP-induced platelet aggregation was not further enhanced with aspirin treatment. These results indicate RvE1 is a potent modulator of leukocytes as well as selective platelet responses in blood and PRP, respectively. Moreover, the results demonstrate novel agonist-specific antiplatelet actions of RvE1 that are potent and may underlie some of the beneficial actions of EPA in humans.

Antiinflammatory properties of the muscadine grape (Vitis rotundifolia)

The muscadine grape possesses one of the highest antioxidant levels among fruits; yet, the effect of this fruit on mammalian metabolic systems has not received significant attention. To examine the antiinflammatory properties of the muscadine, grape skins were dried, pulverized, and extracted (10% w/v) with 50% ethanol. The extract was then tested in two different assays: the release of superoxide in phorbol myristate acetate-activated neutrophils and the release of cytokines [tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-beta), and interleukin-6 (IL-6)] by lipopolysaccharide-activated peripheral blood mononuclear cells. The release of superoxide and cytokines was inhibited by increasing concentrations of the extract. A 1:100 dilution of the extract inhibited superoxide release by approximately 60% while the release of TNF-alpha and IL-1beta was reduced at a dilution of 1:200 by approximately 15 and 90%, respectively (all P < 0.05). The inhibition pattern on the release of IL-6 was similar to that seen with TNF-alpha. In a related in vivo study, rats were fed a diet containing 5% (wt/wt) dried muscadine grape skins for 14 days and then were injected with carrageenan in the foot pad. After 3 h, paw edema was measured and the rats on the grape skin diet had approximately 50% less paw edema than controls (P < 0.05). These results demonstrate that the muscadine grape skin powder possesses significant in vitro and in vivo antiinflammatory properties.

PDE4 inhibitors as new anti-inflammatory drugs: effects on cell trafficking and cell adhesion molecules expression

Phosphodiesterase 4 (PDE4) is a major cyclic AMP-hydrolyzing enzyme in inflammatory and immunomodulatory cells. The wide range of inflammatory mechanisms under control by PDE4 points to this isoenzyme as an attractive target for new anti-inflammatory drugs. Selective inhibitors of PDE4 have demonstrated a broad spectrum of anti-inflammatory activities including the inhibition of cellular trafficking and microvascular leakage, cytokine and chemokine release from inflammatory cells, reactive oxygen species production, and cell adhesion molecule expression in a variety of in vitro and in vivo experimental models. The initially detected side effects, mainly nausea and emesis, appear at least partially overcome by the 'second generation' PDE4 inhibitors, some of which like roflumilast and cilomilast are in the later stages of clinical development for treatment of chronic obstructive pulmonary disease. These new drugs may also offer opportunities for treatment of other inflammatory diseases.

Inflammatory mediator production in swine following endotoxin challenge with or without co-administration of dexamethasone

The inflammatory response in swine challenged with lipopolysaccharide (LPS) has only been partially characterized. As swine are increasingly used in biomedical research, it is important to determine if they respond to endotoxin challenge in a manner similar to other model systems. Accordingly, 24 Poland China x Landrace barrows were treated with saline, LPS, dexamethasone, or LPS and dexamethasone, with six animals in each treatment group. The kinetics of TNFalpha, IL-1beta, IL-6, IL-8, IL-10, nitric oxide (nitrate/nitrite), and neopterin production in swine plasma were examined at 1, 3, 6, 9, and 24 h after acute LPS challenge. Lipopolysaccharide increased plasma TNFalpha levels, which peaked 1 h post-challenge. Dexamethasone decreased LPS-induced TNFalpha by approximately 60%. Plasma IL-6 levels peaked 3 h post-LPS challenge, returning to basal levels by 9 h. Swine given both LPS and dexamethasone had minimal IL-6 levels. Control and dexamethasone-only treated animals never exhibited systemic TNFalpha or IL-6 levels. Lipopolysaccharide increased plasma IL-10 1 h after challenge. Dexamethasone did not alter plasma IL-10 levels in LPS-challenged swine. Interleukin-1beta was constitutively present in plasma and was not altered by any combination of treatments. Plasma IL-8 was not observed in any treatment group. Plasma nitrate/nitrite levels were maximal 24 h post-challenge. Dexamethasone treatment prevented increases in plasma nitrate/nitrite levels in LPS-treated animals. Lipopolysaccharide induced levels of neopterin; dexamethasone served to further increase plasma neopterin levels in LPS-challenged animals. The discordant regulation of inflammatory mediators suggests that the immunological responses by swine to LPS are distinct from the responses seen in rodent and human studies.

An in-vitro screening assay for the detection of inhibitors of proinflammatory cytokine synthesis: a useful tool for the development of new antiarthritic and disease modifying drugs

OBJECTIVE

This work targets the development of a new tool to help develop new anticytokine drugs that prevent or reduce the progression of arthritic diseases. The specific aim of our study was to establish a fast and reliable in vitro screening assay of cytokine synthesis inhibitors (TNFalpha, IL-1beta) which shows better correlation with enzyme assays than previously reported in vitro assays. The test system should be able to detect p38-MAP kinase inhibitors.

MATERIAL AND METHODS

Human peripheral blood mononuclear cells (PBMCs) were isolated by Ficoll density gradient centrifugation from human EDTA-potassium whole blood. Cells were adjusted at 1 x 10(6) cells/ml. PBMCs were stimulated with lipopolysaccharide (LPS; E. coli serotype 026:B6: 1 microg/ml) in the presence of test compound (10(-5)-10(-8)M) for 4h at 37 degrees C in a 5% CO(2)-incubator. Induced TNFalpha and IL-1beta protein were measured by ELISA.

RESULTS

The following are representative examples of inhibitors which effect cytokine synthesis. Corticoid Dexamethasone inhibits IL-1beta and TNFalpha synthesis at IC(50) of 38 nM and 25 nM, respectively. ERK1/ERK2 inhibitor U0126 effects cytokine synthesis at IC(50) of 0.34 microM for IL-1beta production and 0.26 microM for TNFalpha synthesis.p38-MAP kinase inhibitor SB 203580 inhibits IL-1beta- and TNF-alpha-synthesis (IC(50)sof 0.052 microM and 0.46 microM) in the same degree as p38-MAP kinase activity (IC(50): 0.34 microM). Same results could be shown for SB 210313, which had same efficacy on IL-1beta and TNFalpha biosynthesis (IC(50)'s: 1.88 microM and 1.01 microM) and on p38-MAP kinase (IC(50): 6.85 microM). Also for SB 202190 this correlation in inhibition of IL-1beta and TNFalpha synthesis (IC(50)'s: 0.055 microM and 1.01 microM) and p38-MAP kinase inhibition (IC(50): 0.088 microM) could be shown.

CONCLUSION

This study shows the screening assay using PBMCs stimulated with LPS for IL-1beta and TNFalpha synthesis is a reliable test system for the quantification of the effectiveness of new drugs modulating IL-1beta and TNFalpha synthesis which is mainly mediated by p38-MAP Kinase. These assay allows fast detection of IL-1beta and TNFalpha synthesis inhibitors with different modes of action, including p38-MAP kinase inhibitors. The results obtained with our in-vitro screening assay show good correlation with results from enzyme assays.

Novel selective PDE4 inhibitors. 3. In vivo antiinflammatory activity of a new series of N-substituted cis-tetra- and cis-hexahydrophthalazinones

The synthesis and biological activities of a series of N-substituted cis-4a,5,6,7,8,8a-hexa- and cis-4a,5,8,8a-tetrahydro-2H-phthalazin-1-ones are described. It was found that compounds bearing a cycloalkyl group at the 2-position exhibit the highest PDE4 inhibitory activities (pIC(50) = 8.6-9.4). The N-cycloheptyl- and N-adamantanyltetrahydrophthalazinones (7h, 8, 10, 11) show high in vivo antiinflammatory activities after oral application. Additionally, some phthalazinones were found to exhibit potent suppression of LPS-induced TNFalpha release and show moderate potency against fMLP-stimulated production of ROS.

Comparison of inhibition of ovalbumin-induced bronchoconstriction in guinea pigs and in vitro inhibition of tumor necrosis factor-alpha formation with phosphodiesterase 4 (PDE4) selective inhibitors

Phosphodiesterase 4 (PDE4) inhibitors elevate cyclic adenosine 5'-monophosphate (cAMP), and this elevation has been shown to inhibit inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha). Using TNF-alpha as a biomarker, we have developed transcription-based assays to examine inhibition of PDE4 activity in human and guinea pig whole blood. In vitro inhibition by PDE4 inhibitors was measured using quantitative PCR (qPCR) analysis of TNF-alpha mRNA levels in whole blood stimulated with lipopolysaccharide (LPS). The kinetics of human TNF-alpha mRNA production were analyzed and shown to be highest 4 hr following LPS stimulation. The guinea pig displayed kinetics of TNF-alpha transcription similar to those of the human. Analysis of inhibition of human TNF-alpha protein production was performed by immunoassay and shown to correlate with inhibition of transcription for three of the four compounds tested. Roflumilast was found to be 9-fold more potent for TNF-alpha inhibition in the qPCR assay than in the protein assay. The potencies of L-826,141 and roflumilast were determined in human and guinea pig whole blood by qPCR, with IC(50) values of 270 and 20 nM, respectively, in humans and 100 and 10 nM, respectively, in guinea pigs. These results show that the potency of PDE4 inhibitors can be monitored in whole blood using a transcription-based assay, and that this type of assay can be adapted to various species provided the TNF-alpha nucleotide sequence is known. The in vitro whole blood IC(50) for TNF-alpha inhibition was compared to inhibition in the ovalbumin-challenged guinea pig model of bronchoconstriction. Obtaining plasma levels at the IC(50) determined in vitro for L-826,141 and roflumilast provides significant inhibition of bronchoconstriction. This suggests that TNF-alpha can be used as a whole blood biomarker in the guinea pig for PDE4 inhibition in this inflammatory model.

Effects of FK506 and other immunosuppressive anti-rheumatic agents on T cell activation mediated IL-6 and IgM production in vitro

The objective of this study was to investigate the therapeutic potential of FK506 and other immunosuppressive agents for the treatment of rheumatoid arthritis (RA), focusing on the effects on in vitro IL-6 production and IL-6-mediated immune response. We employed an in vitro model producing IL-6 via T cell activation in human PBMC, based on the hypothesis that T cells play a central role in the pathogenesis of RA. FK506 potently inhibited IL-6 production from PBMC stimulated with anti-CD3 and anti-CD28 monoclonal antibody (anti-CD3/CD28). Cyclosporin A (CsA) also inhibited the anti-CD3/CD28 induced IL-6 production but was about 100 times less potent than FK506. Dexamethasone (DEX) inhibited both anti-CD3/CD28 and LPS induced IL-6 production at almost the same concentration. Methotrexate (MTX) did not affect cytokine production. Anti-CD3/CD28 stimulated PBMC culture supernatants were found to enhance IgM production in SKW6.4 cells. The effects of anti-CD3/CD28 stimulated culture supernatants in the presence of agents on IgM production in SKW6.4 cells were investigated. FK506 and CsA led to suppression of IgM production induced by culture supernatants probably via inhibition of IgM inducible cytokine production from PBMC. DEX profoundly enhanced IgM production, although IL-6 production from PBMC was strongly inhibited by the agent. MTX decreased IgM production although it has no inhibitory effect on IL-6 production. The present study suggests that FK506 is the most effective among the four agents for the suppression of IL-6 production and IL-6-mediated autoantibody production in T cell activation related autoimmune diseases such as RA.

Inhibition of cytokine release by and cardiac effects of type IV phosphodiesterase inhibition in early, profound endotoxaemia in vivo

1. In rats, inhibition of type IV phosphodiesterase (PDE4) attenuates acute renal failure and early (hours) mortality induced by high-dose endotoxin. Because it is unlikely that protection of renal function accounts for improved early survivability, most likely PDE4 inhibition exerts multiple beneficial effects in endotoxaemia and the purpose of the present study was to test this hypothesis. 2. In study 1, we determined, in anaesthetized rats, the effects of endotoxin (30 mg/kg, i.v.) on cardiac performance parameters (heart rate (HR), ventricular peak systolic pressure (VPSP), maximum positive change in left ventricular pressure with respect to time (+dP/dt), maximum negative change in left ventricular pressure with respect to time (-dP/dtmax), ventricular end-diastolic pressure (VEDP), ventricular minimum diastolic pressure (VMDP) and HR-pressure product), plasma catecholamine levels, plasma renin activity (PRA) and plasma levels of inflammatory cytokines (tumour necrosis factor (TNF)-alpha and interleukin (IL)-lbeta). 3. In study 2, we determined, in anaesthetized rats, whether inhibition of PDE4 attenuates lipopolysaccharide (LPS)-induced changes in the aforementioned parameters of heart performance and neurohumoral status. We compared the changes in these parameters induced by endotoxaemia in animals treated with either RO 20-1724 (10 microg/kg per min; a selective PDE4 inhibitor) or its vehicle (DMSO; 1.35 microL/min). 4. At 90 min postadministration, endotoxin significantly increased HR and reduced -dP/dtmax and VEDP and caused a several-fold increase in plasma levels of TNF-alpha, IL-1beta, noradrenaline, adrenaline and PRA. RO20-1724 significantly blunted the endotoxin-induced reduction in -dP/dtmax and decreased endotoxin-induced increases in TNF-alpha and IL-1beta without significantly altering endotoxin-induced changes in HR, VEDP, catecholamine levels and PRA. 5. Results from these studies indicate that, in addition to preserving renal function, PDE4 inhibition attenuates inflammatory cytokine release caused by high-dose endotoxin and may have protective effects on diastolic function in early profound endotoxaemia.

Effect of isoproterenol and dexamethasone on the lipopolysaccharide induced expression of CD11b on bovine neutrophils

The present experiments investigate the changes in expression of CD11b on bovine neutrophils and its modulation by isopropylnoradrenaline (IPN, isoproterenol), dexamethasone (DX), phenylephrine (alpha-agonist) and clenbuterol (beta-agonist). Both IPN and DX caused a dose-dependent inhibition of LPS-induced CD11b expression. A combination of IPN and DX elicited a synergistical decrease of the CD11b expression. Clenbuterol mimicked the effect of IPN, whereas phenylephrine did not. The effect of IPN and DX could at least partly be mediated through a decreased TNF-alpha production by monocytes since tumor necrosis factor-alpha (TNF-alpha) is shown to mediate a dose-dependent CD11b up-regulation. Stimulation of stress hormone receptors partly immuno-suppresses neutrophil functions by inhibition of CD11b expression on the neutrophil surface upon LPS stimulation. This inhibition is probably related to a decrease in TNF-alpha production. A similar mechanism of immuno-suppression could contribute to the higher susceptibility of cattle to Gram-negative bacterial infections of the udder and lung during periods of stress.

FK506 potently inhibits T cell activation induced TNF-alpha and IL-1beta production in vitro by human peripheral blood mononuclear cells

The aim of this study was to elucidate the in vitro inhibitory potency of FK506 on production of the inflammatory cytokines, tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta, with a view to assessing this immunosuppressive agent as a potential anti-rheumatic drug. We employed an in vitro model which produces TNF-alpha and IL-1beta through T cell activation. Human peripheral blood mononuclear cells (PBMC) were cultured with immobilized anti-CD3/CD28 monoclonal antibody in this model. FK506 inhibited anti-CD3/CD28 induced TNF-alpha and IL-1beta production at concentrations less than 1 ng ml(-1). Flow cytometric analysis of intracellular TNF-alpha and IL-1beta positive cells showed that FK506 potently suppresses inflammatory cytokine production from CD14+ monocytes as well as from T cells. Cyclosporin A (CsA) and dexamethasone (DEX) also inhibited the anti-CD3/CD28 induced cytokine production, but were less potent than FK506. FK506 and CsA, but not DEX, specifically inhibited anti-CD3/CD28 induced inflammatory cytokine production without affecting the lipopolysaccaride (LPS) induced effect. Methotrexate (MTX) was completely inactive for suppressing cytokine production under either condition. Anti-CD3/CD28 stimulated PBMC culture supernatants were found to enhance the expression of adhesion molecules in human vascular endothelial cells. FK506, CsA and DEX led to the suppression of adhesion molecule expression probably by inhibiting cytokine production from PBMC. The inhibitory potency of agents on TNF-alpha and IL-1beta production was compared with cytotoxicity and FK506 was not cytotoxic at concentrations several orders of magnitude greater than those required for cytokine inhibition. These results strongly suggest that FK506 may be most effective to specifically prevent T cell activation mediated inflammatory cytokine production in a clinical setting.

Signals for proinflammatory cytokine secretion by human Schwann cells

Wallerian degeneration is a post-traumatic process of the peripheral nervous system whereby damaged axons and their surrounding myelin sheaths are phagocytosed by infiltrating leukocytes. Our studies indicate that Schwann cells could initiate the process of Wallerian degeneration by releasing proinflammatory cytokines involved in leukocyte recruitment and differentiation including IL-1beta, MCP-1, IL-8 and IL-6. A comparison of the secretory pattern between nerve explants and cultured Schwann cells showed that each cytokine was differentially regulated by growth factor deprivation or axonal membrane fragments. Since Wallerian-like degeneration occurs in a wide variety of peripheral neuropathies, Schwann cell-mediated cytokine production may play an important role in many disease processes.

The effects of phosphodiesterase type 4 inhibitors on tumour necrosis factor-alpha and leukotriene B4 in a novel human whole blood assay

1. The aim of this study was to assess the inhibitory activities of phosphodiesterase type 4 (PDE4) inhibitors on tumour necrosis factor-alpha (TNF-alpha) and leukotriene B4 (LTB4) production in a novel human whole blood assay. 2. Lipopolysaccharide (LPS) stimulation of human whole blood caused a time dependent increase in TNF-alpha and prostaglandin E2 (PGE2) plasma levels. Inhibition of LPS-induced TNF-alpha by the selective PDE4 inhibitor RP73401 was proportionally enhanced with endogenous PGE2 (maximal after 24 h). In contrast, blocking endogenous PGE2 production with indomethacin in blood stimulated with LPS for 24 h decreased the potency of RP73401 to that observed with a 4 h LPS incubation. 3. Non-selective and selective PDE4 inhibitors showed greater inhibition of LPS-induced TNF-alpha after 24 h compared to 4 h. Stereoselectivity was only achieved in the 24 h method. 4. LPS-stimulation of whole blood for either 30 min or 24 h followed by N-formyl-Met-Leu-Phe (fMLP) activation resulted in low plasma LTB4 levels. Combination of both treatments resulted in a greater than 7 fold increase in plasma LTB4 levels. Inhibition of the double LPS and fMLP-activated LTB4 production was observed with non-selective and PDE4-selective inhibitors. Their LTB4 inhibitory potencies were similar to that observed in the 24 h LPS-induced TNF-alpha assay. Thus, stimulation of human whole blood with two LPS stimulations followed by fMLP gives rise to both TNF-alpha and LTB4 and their inhibition by various compounds can be assessed in the same blood sample. 5. Calcium ionophore (A23187) stimulation of whole blood resulted in plasma LTB4 levels similar to the double LPS and fMLP method. Inhibition of A23187-induced LTB4 biosynthesis was also achieved by PDE4-selective inhibitors as well as the direct 5-lipoxygenase (5-LO) inhibitor L-739,010. 6. These results confirm the anti-inflammatory properties of PDE4 inhibitors. Thus, this novel human whole blood can be used to assess the biochemical efficacy of PDE4 inhibitors in human subjects.

Induction of endogenous tumor necrosis factor-alpha: suppression of centrally stimulated gastric motility

Gastric stasis is frequently seen in conjunction with critical infectious illness, chronic inflammatory disorders, radiation sickness, and carcinogenesis. These conditions are associated with elevated circulating levels of the cytokine tumor necrosis factor-alpha (TNF-alpha). The present studies examined the relationship between endogenously produced TNF-alpha and the central neural mechanisms that augment gastric motility. Systemic lipopolysaccharide (LPS) was employed to induce TNF-alpha production in thiobutabarbital-anesthetized rats. Sixty minutes after intravenous LPS injection, gastric motility could not be stimulated by a potent centrally acting gastrokinetic stimulant, thyrotropin-releasing hormone (TRH). This failure to elicit gastric motility via central mechanisms coincided with high circulating levels of TNF-alpha. However, intravenous injections of bethanecol, a peripherally acting cholinergic agonist with direct gastrokinetic effects, were still able to elicit normal increases in gastric motility in the presence of TNF-alpha and LPS. Therefore, the inability to stimulate gastric motility via central TRH could not be attributed to the direct inhibitory effects of either LPS or TNF-alpha on the stomach. If the production of endogenous TNF-alpha was suppressed via the use of urethan as the anesthetic agent, then intravenous injections of LPS were no longer effective in suppressing gastric motility. Thus these effects on gastric motility are not directly attributable to LPS nor are they due to direct effects on the gastric smooth muscle. Our previous study demonstrated that microinjection of femtomole quantities of TNF-alpha in the brain stem dorsal vagal complex (DVC) can modulate gastric motility. This central TNF-alpha effect on gastric motility was dose dependent and required an intact vagal efferent pathway. The results from these two studies suggest that systemically produced TNF-alpha may gain access to the DVC to modulate gastric function.

Beta 2-adrenergic activation enhances interleukin-8 production by human monocytes

Interleukin-8 (IL-8) is an important cytokine in inflammatory processes by functioning as a chemoattractant and as an activator of oxygen metabolism. In the present study we demonstrate that beta 2-adrenergic agonists potentiate the lipopolysaccharide (LPS) and IL-1 induced production of IL-8 by human monocytes. In addition, beta 2-adrenergic activation enhances IL-8 release and mRNA expression for IL-8 in the human monocytic cell line U937. beta 2-adrenergic activation of these cells also results in enhanced production of the anti-inflammatory cytokine IL-10. However, IL-10 is not involved in the regulation of IL-8 production. The effect of the beta 2-adrenergic agonist on IL-8 production is presumably mediated via increased cAMP formation, since it can be mimicked by the cAMP analogue dibutyryl-cAMP (db-cAMP). We conclude that enhancement of IL-8 production is one of the pathways via which beta 2-adrenergic agonists such as catecholamines can influence inflammatory responses.

Differential effects on TNF alpha production by pharmacological agents with varying molecular sites of action

This study describes the activation conditions for tumor necrosis factor-alpha (TNF alpha) production in myelomonocytic U937 cells and human primary peripheral blood monocytes in response to lipopolysaccharide (LPS) and/or phorbol 12-myristate 13-acetate (PMA). PMA itself induced only low levels of TNF alpha production with delayed kinetics (e.g. 0.758 +/- 0.128 ng/ml from U937 cells after 48 h) while LPS induced greater levels of TNF alpha production in less time (e.g. 2.083 +/- 0.96 ng/ml from monocytes in 24 h). Pharmacological agents with various molecular sites of action were used to validate the two systems, with the protein serine-threonine kinase inhibitors staurosporine and Ro-31-8220, the protein tyrosine kinase inhibitor herbimycin A (HBA) and dexamethasone exhibiting the greatest potency (IC50S 5-350 nM). In contrast to the effect on TNF alpha production, PMA induced strong phosphorylation/activation of p42/p44mapk in monocytes by 10 min determined in a mobility shift assay, while LPS was a weaker inducer. Additionally, staurosporine (to LPS and PMA) and HBA (to LPS only) inhibited the activation of these mitogen-activated protein kinase (MAPK) isoforms at doses 10-100 fold higher than those required to inhibit maximal TNF alpha production. These data indicate the involvement of the p42/p44mapk signalling pathway in LPS-induced pro-inflammatory cytokine production but suggest that other signalling pathways are also implicated in this phenomenon.

Distinct tumorigenic potential of abl and raf in B cell neoplasia: abl activates the IL-6 signaling pathway

The development of murine plasma cell tumors induced by raf/myc containing retroviruses is facilitated by T cells and completely dependent on IL-6. To determine whether kinases with differing specificities reflect alternative biochemical pathways in B cell tumorigenesis, we have employed an abl/myc containing retrovirus to assess neoplastic development. In contrast with raf/myc, abl/myc disease is T cell and IL-6 independent. An examination of the IL-6 signal transduction pathway reveals that this pathway, as defined by activation of Stat3, is inducible by IL-6 in raf/myc tumors but constitutively activated in abl/myc tumors. These findings provide a mechanism for the derivation of cytokine-independent plasma cell tumors and suggest that both IL-6-dependent and independent tumors may arise in vivo depending on the particular mutational events incurred during tumorigenesis.