Temporal sequence of pulmonary and systemic inflammatory responses to graded polymicrobial peritonitis in mice

The lungs are the remote organ most commonly affected in human peritonitis. The major goals of this study were to define the dose- and time-dependent relationship between graded septic peritonitis and systemic and pulmonary inflammatory responses in mice. BALB/c mice were treated with intraperitoneal polymicrobial inoculi and sacrificed at 3, 12, and 24 h. The treatment protocol resulted in distinct groups of animals with respect to mortality rate, kinetics, and concentrations of a broad spectrum of pro- and anti-inflammatory endogenous mediators, intrapulmonary bacterial accumulation, and static lung compliance. In sublethally infected mice, pulmonary bacterial proliferation was controlled. Levels of monocyte chemoattractant protein-1 (MCP-1), interleukin-10, interleukin-6, granulocyte colony-stimulating factor (G-CSF), and tumor necrosis factor (TNF) in plasma were elevated 3 h after infection exclusively. At 3 h, MCP-1, gamma interferon, and TNF were detected in extracts of pulmonary tissue or in bronchoalveolar lavage (BAL) fluid. Static lung compliance (C(st)) was transiently decreased at 12 h. In contrast, in lethally infected mice pulmonary bacterial proliferation was not contained. Concentrations of MCP-1, G-CSF, and TNF in plasma were maximal at 24 h, as were pulmonary MCP-1 levels. Lung myeloperoxidase activity was increased at 3, 12, and 24 h. C(st) was reduced after 3 h and did not reach control values at 24 h. Pulmonary cyclooxygenase-2 mRNA and eicosanoids in BAL fluid and plasma were elevated at 3 and 24 h. This study shows that polymicrobial peritonitis in mice leads to dose-dependent systemic and pulmonary inflammation accompanied by a decrease in lung compliance.

Concanavalin A hepatotoxicity in mice: tumor necrosis factor-mediated organ failure independent of caspase-3-like protease activation

Several models of tumor necrosis factor (TNF)/TNF-receptor 1 (TNF-R1)-dependent liver injury in mice were investigated with respect to caspase-3-like protease activation representing a pivotal mechanism of apoptotic cell death. Injection of TNF or T-cell-activating agents (i.e., agonistic anti-CD3 antibody or staphylococcal enterotoxin B [SEB]) into galactosamine (GalN)-sensitized mice caused TNF/TNF-R1-dependent liver injury. Intravenous concanavalin A (Con A) alone induced TNF-mediated hepatotoxicity dependent on both TNF-R1 and TNF-R2. Hepatic caspase-3-like proteases were activated in GalN/TNF, GalN/anti-CD3, or GalN/SEB-treated mice, but not in Con A-treated mice. Consistently, the broad-spectrum caspase inhibitor, benzoyloxycarbonyl-val-ala-asp-fluoromethylketone (zVADfmk), prevented TNF-mediated hepatotoxicity in all GalN-dependent models, but failed to protect against Con A. Under transcriptional arrest, however, Con A induced TNF-R1-dependent, but not TNF-R2-dependent, activation of caspase-3-like proteases, and zVADfmk prevented animals from Con A-mediated liver injury under this condition. Histological analysis revealed distinct differences between Con A- and GalN/Con A-induced liver injury regarding apoptotic morphology of hepatocytes. We conclude that impaired transcription induces a switch of Con A hepatotoxicity toward a caspase-3-like protease-dependent pathway. The observation that the functional state of the transcriptional machinery decides whether TNF-driven hepatocyte apoptosis involves activation of caspase-3-like proteases or alternative signaling pathways in vivo might be of relevance for the immunopathology of the liver.

Quinolines attenuate PAF-induced pulmonary pressor responses and edema formation

In the present study we have investigated the mechanisms of pulmonary edema caused by platelet-activating factor (PAF) in isolated rat lungs as well as in mice in vivo. In blood-free perfused and ventilated rat lungs, PAF increased lung weight by 0.59 +/- 0.18 g. The cyclooxygenase inhibitor aspirin (500 microM) blocked this response by one-third, and the quinolines quinine (330 microM), quinidine (100 microM), and chloroquine (100 microM) by two-thirds. Lipoxygenase inhibition (10 microM AA861) alone or in combination with thromboxane receptor antagonism (10 microM SQ29548) had no effect on PAF-induced weight gain. In combination with aspirin, quinine or quinidine completely prevented PAF-induced weight gain and the concomitant increase of the capillary filtration coefficient (K(f,c)). Pretreatment with quinine in vivo prevented not only PAF-, but also endotoxin-induced edema formation as assessed by Evans Blue extravasation. In addition, in vivo quinine prevented the endotoxin-induced release of tumor neurosis factor (TNF). Furthermore, in perfused lungs quinine reduced the PAF-induced increases in airway and vascular resistance, as well as thromboxane release. These findings demonstrate the following anti-inflammatory properties of quinolines: reduction of thromboxane and TNF formation; reduction of PAF-induced vasoconstriction and bronchoconstriction; and attenuation of PAF- and lipopolysaccharide (LPS)-induced edema formation. We conclude that the PAF- induced edema consists of two separate mechanisms, one dependent on an unknown cyclooxygenase metabolite, the other one sensitive to quinolines.

Effect of filgrastim treatment on inflammatory cytokines and lymphocyte functions

Twenty-four healthy male volunteers received either placebo or 75, 150, or 300 microg filgrastim (recombinant methionyl human granulocyte colony-stimulating factor) for 12 days to study effects on monocytes and lymphocytes. In all filgrastim-treated groups, tumor necrosis factor alpha (TNF-alpha), interleukin-12 (IL-12), and interferon gamma (IFN-gamma) release by whole blood in response to endotoxin (lipopolysaccharide) was reduced. IL-12 added in vitro to lipopolysaccharide-stimulated blood of filgrastim-treated donors restored IFN-gamma and TNF-alpha release, suggesting that the anti-inflammatory effect of granulocyte colony-stimulating factor is exercised through IL-12 suppression. Phytohemagglutinin- or anti-CD3 antibody-induced lymphocyte proliferation ex vivo was reduced by 60% from day 5 to day 15, after a 50% increase at day 2 with concomitant doubled IL-2 release. In vivo, filgrastim induced doubling of all T-cell populations by day 8. Filgrastim decreased proinflammatory cytokine production and lymphocyte proliferation ex vivo throughout prolonged treatment at all doses. This indicates that endogenous granulocyte colony-stimulating factor may counterregulate the inflammatory cytokine cascade and implies a potential indication for filgrastim in chronic inflammatory conditions.

Prevention of endotoxin-induced lethality, but not of liver apoptosis in poly(ADP-ribose) polymerase-deficient mice

Activation of poly-(ADP-ribose) polymerase (PARP) is often associated with cytotoxicity, but its precise role in shock-induced lethality and in different modes of tissue injury is still unknown. We took advantage of the existence of mice with a targeted deletion of the PARP gene (PARP-/-) to examine the differential sensitivity of wild-type (wt) and PARP-/- mice toward endotoxin (LPS)-induced lethality and different forms of liver damage. All PARP-/- animals survived high-dose (20 mg/kg) LPS-mediated shock, which killed 60% of wt animals. Moreover, LPS-induced necrotic liver damage was significantly reduced. In contrast, when apoptotic liver damage was induced via injection of low concentrations of LPS (30 microgram/kg) into D-galactosamine-sensitized mice, or via activation of hepatic cell death receptors, PARP-/- animals were not protected. We conclude that PARP is involved in systemic LPS toxicity, while it plays a minor role in apoptotic liver damage mediated by TNF or CD95.

CD95-Mediated murine hepatic apoptosis requires an intact glutathione status

Agonistic engagement of the cytokine receptor CD95 in mice leads to activation of hepatic caspases, followed by massive hepatocyte apoptosis, acute liver failure, and death. This mechanism of cell death is thought to be associated with several human liver disorders. Because hepatic glutathione represents the major defense against toxic liver injury, we investigated its role in CD95-mediated liver failure, which represents a model for hyperinflammatory organ destruction. As a tool for modulating the liver glutathione status of mice in vivo, we used the GSH transferase substrate, phorone, which rapidly depleted hepatic glutathione in a dose-dependent manner. When GSH was depleted, CD95-initiated hepatic caspase-3-like activity and DNA fragmentation were completely blocked, and animals were protected from liver injury dose-dependently as assessed by histological examination and determination of liver enzymes in plasma. Conversely, repletion of hepatic glutathione by treatment with the permeable glutathione monoethylester restored susceptibility of GSH-depleted mice toward CD95-mediated liver injury. In contrast, the antioxidants, GSH, N-acetyl cysteine, alpha-tocopherol, butyl-hydroxytoluene, and catalase failed to do so. Animals treated once with phorone survived for more than 3 months after an otherwise lethal injection of the activating anti-CD95 antibody. We investigated the thiol sensitivity of recombinant caspase-3 in vitro and observed that its activity was dependent on the presence of a reducing agent such as GSH, while GSSG attenuated proteolytic activity. Based on our finding that CD95-mediated hepatocyte apoptosis requires an intact intracellular glutathione status, we propose that the activation of apoptosis-executing caspases is controlled by reduced glutathione.

Cystic renal cell carcinoma is cured by resection: a study of 24 cases with long-term followup

PURPOSE

The true incidence and biological behavior of cystic renal cell carcinoma are not known. To our knowledge we present the largest series of patients with cystic renal cell carcinoma with long-term followup.

MATERIALS AND METHODS

We reviewed the Mayo Clinic surgical pathology files of renal cell cancer cases with a cystic component resected from 1969 to 1997, and arbitrarily chose 75% tumor involvement by cysts as a cutoff for inclusion in the study.

RESULTS

We identified 24 cases of clear cell renal cell carcinoma with 75% or greater involvement by cysts comprising 0.79% of 3,047 renal cell cancer cases resected at our institution between 1969 and 1997. Mean patient age was 62.7 years (range 40 to 83). A total of 11 patients (46%) underwent radical nephrectomy, 4 (17%) simple nephrectomy, 3 (12%) partial nephrectomy and 6 (25%) tumor enucleation. Mean tumor involvement by cysts was 84% (range 75 to 95) and in 11 cases (46%) involvement was 90% or greater. Cancer stage was T1 in 20 patients (83%), T2 in 1 (4.4%) and T3a in 4 (12.5%). Cancers were diploid in all but 1 case. Mean followup was 77.6 months (range 8 to 428, median 51). A total of 22 patients (92%) had no evidence of cancer and 2 died of intercurrent disease.

CONCLUSIONS

Our results indicate that cystic renal cell carcinoma is uncommon and usually cured by resection, regardless of size, stage or number of cysts. These patients may benefit from nephron sparing surgery, such as partial nephrectomy.

Ebselen protects mice against T cell-dependent, TNF-mediated apoptotic liver injury

The seleno-organic drug ebselen (2-phenyl-1, 2-benzoisoselenazol-3(2H)-one) has glutathione peroxidase-like activity, and inhibits lipoxygenases, oxidative burst of leukocytes, nitric oxide synthases, protein kinases and leukocyte migration. This study elaborates in vivo in mice hitherto unknown immunopharmacological properties of ebselen. The compound was comparatively investigated in two different T cell-dependent hepatic hyperinflammation models and in two alternative models of receptor-activated liver apoptosis. Mice orally pretreated with ebselen were dose-dependently protected from concanavalin A (ConA)-induced liver injury. In livers from ebselen-pretreated mice exposed to ConA, the nuclear antiapoptotic transcription factor NFkappaB was upregulated. The release of the proinflammatory cytokine tumor necrosis factor-alpha (TNF) was downregulated, while the ciculating amount of the anti-inflammatory cytokine interleukin-10 (IL-10) was increased. Ebselen protected also from liver injury induced by the superantigen staphylococcal enterotoxin B in galactosamine (GalN)-sensitized mice. Furthermore, ebselen protected the liver and enhanced circulating IL-10 in GalN-sensitized mice treated with recombinant TNF, i.e., the common distal mediator of ConA and SEB-induced hepatotoxicity. The activation of apoptosis-executing proteases, i.e., caspases, was blocked in livers of ebselen-treated mice following TNF receptor, but not following CD95 receptor activation. We propose a novel mechanism for the immunomodulatory properties of the drug and suggest that it might be useful in the therapy of T cell-mediated inflammatory disorders.

Filgrastim restores interleukin-2 production in blood from patients with advanced human immunodeficiency virus infection

Filgrastim induces lymphocytosis, including all T cell subsets, and increased ex vivo interleukin (IL)-2 release as well as lymphocyte proliferation. Since Filgrastim is increasingly used in patients with human immunodeficiency virus (HIV) infection, the effect of Filgrastim on ex vivo cytokine production was determined. Whole blood from 8 healthy volunteers, 5 high-risk volunteers, and 31 HIV-infected outpatients was assayed for cytokine production in response to endotoxin (LPS) or staphylococcal enterotoxin B (SEB) in the presence or absence of 100 ng/mL Filgrastim. LPS-inducible blood cytokine release of HIV-infected patients was not different from that of normal or high-risk volunteers. The suppressive effect of Filgrastim on LPS-inducible blood tumor necrosis factor-alpha and interferon-gamma formation in normal volunteers was not found in HIV-infected patients. Patients with advanced HIV infection showed reduced IL-2 and IL-4 release in the presence of SEB. In the presence of Filgrastim, IL-2 production was partially restored.

Early alterations in intracellular and alveolar surfactant of the rat lung in response to endotoxin

The aim of this study was to characterize early ultrastructural, biochemical, and functional alterations of the pulmonary surfactant system induced by Salmonella minnesota lipopolysaccharide (LPS) in rat lungs. Experimental groups were: (1) control in vitro, 150 min perfusion; (2) LPS in vitro, 150 min perfusion, infusion of 50 microg/ml LPS after 40 min; (3) control ex vivo, 10 min perfusion; (4) LPS ex vivo, lungs perfused for 10 min from rats treated for 110 min with 20 mg/kg LPS intraperitoneally. Morphometry of type II pneumocytes showed that LPS increased stored surfactant. Lamellar bodies were increased in size, but decreased in numerical density, suggesting that giant lamellar bodies observed in LPS-treated lungs may result from fusion of normal bodies. Structural analysis of alveolar surfactant composition showed that LPS elicited an increase in lamellar body-like and multilamellar forms. Bronchoalveolar lavage (BAL) material from LPS-treated lungs was decreased in phospholipids. BAL bubble surfactometer analysis showed a reduction in hysteresis area caused by LPS. We conclude that LPS leads to alterations of intracellular and alveolar surfactant within 2 h: fusion of lamellar bodies, reduction in surfactant secretion, and changes in alveolar surfactant transformation, composition, and function, which may contribute to the development of respiratory distress.

Phosphodiesterase profile of human B lymphocytes from normal and atopic donors and the effects of PDE inhibition on B cell proliferation

1. CD19+ B lymphocytes were purified from the peripheral blood of normal and atopic subjects to analyse and compare the phosphodiesterase (PDE) activity profile, PDE mRNA expression and the importance of PDE activity for the regulation of B cell function. 2. The majority of cyclic AMP hydrolyzing activity of human B cells was cytosolic PDE4, followed by cytosolic PDE7-like activity; marginal PDE3 activity was found only in the particulate B cell fraction. PDE1, PDE2 and PDE5 activities were not detected. 3. By cDNA-PCR analysis mRNA of the PDE4 subtypes A, B (splice variant PDE4B2) and D were detected. In addition, a weak signal for PDE3A was found. 4. No differences in PDE activities or mRNA expression of PDE subtypes were found in B cells from either normal or atopic subjects. 5. Stimulation of B lymphocytes with the polyclonal stimulus lipopolysaccharide (LPS) induced a proliferative response in a time- and concentration-dependent manner, which was increased in the presence of interleukin-4 (IL-4). PDE4 inhibitors (rolipram, piclamilast) led to an increase in the cellular cyclic AMP concentration and to an augmentation of proliferation, whereas a PDE3 inhibitor (motapizone) was ineffective, which is in accordance with the PDE profile found. The proliferation enhancing effect of the PDE4 inhibitors was partly mimicked by the cyclic AMP analogues dibutyryl (db) cyclic AMP and 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-3',5'-cyclic monophosphorothioate, Sp-isomer (dcl-cBIMPS), respectively. However, at concentrations exceeding 100 microM db-cyclic AMP suppressed B lymphocyte proliferation, probably as a result of cytotoxicity. Prostaglandin E2 (PGE2, 1 microM) and forskolin (10 microM) did not affect B cell proliferation, even when given in combination with rolipram. 6. Inhibition of protein kinase A (PKA) by differentially acting selective inhibitors (KT 5720, Rp-8-Br-cyclic AMPS) decreased the proliferative response of control cells and reversed the proliferation enhancing effects of rolipram. 7. Importantly, PDE4 activity in LPS/IL-4-activated B lymphocytes decreased by about 50% compared to unstimulated control values. 8. We conclude that an increase in cyclic AMP, mediated by down-regulation of PDE4 activity, is involved in the stimulation of B cell proliferation in response to LPS/IL-4. B cell proliferation in response to a mitogenic stimulus can be further enhanced by pharmacological elevation of cyclic AMP.

Hyperventilation induces release of cytokines from perfused mouse lung

Artificial mechanical ventilation represents a major cause of iatrogenic lung damage in intensive care. It is largely unknown which mediators, if any, contribute to the onset of such complications. We investigated whether stress caused by artificial mechanical ventilation leads to induction, synthesis, and release of cytokines or eicosanoids from lung tissue. We used the isolated perfused and ventilated mouse lung where frequent perfusate sampling allows determination of mediator release into the perfusate. Hyperventilation was executed with either negative (NPV) or positive pressure ventilation (PPV) at a transpulmonary pressure that was increased 2.5-fold above normal. Both modes of hyperventilation resulted in an approximately 1.75-fold increased expression of tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6) mRNA, but not of cyclooxygenase-2 mRNA. After switching to hyperventilation, prostacyclin release into the perfusate increased almost instantaneously from 19 +/- 17 pg/min to 230 +/- 160 pg/min (PPV) or 115 +/- 87 pg/min (NPV). The enhancement in TNFalpha and IL-6 production developed more slowly. In control lungs after 150 min of perfusion and ventilation, TNFalpha and IL-6 production was 23 +/- 20 pg/min and 330 +/- 210 pg/min, respectively. In lungs hyperventilated for 150 min, TNFalpha and IL-6 production were increased to 287 +/- 180 pg/min and more than 1,000 pg/min, respectively. We conclude that artificial ventilation might cause pulmonary and systemic adverse reactions by inducing the release of mediators into the circulation.

Quantification of apoptotic and lytic cell death by video microscopy in combination with artificial neural networks

Apoptosis is characterized by chromatin condensation and DNA fragmentation in the absence of release of cytosolic enzymes such as lactate dehydrogenase (LDH). In contrast, necrosis is characterized by cell swelling, membrane disintegration with cytosolic enzyme release, and absence of chromatin condensation. Staining of cells with Hoechst H33342 dye is a routine method for identifying apoptotic nuclei. However, this process is tedious and prone to individual bias. Therefore, we investigated the suitability of an artificial neural network (ANN) to recognize and distinguish between apoptosis and necrosis. Using a human endothelial cell line (ECV304), we trained an ANN with DNA-stained apoptotic and necrotic nuclei obtained from cells exposed for 8 h to cycloheximide (Chx; 100 microM)/tumour necrosis factor-alpha (TNF; 50 ng/ml) or tert-butylhydroperoxide (t-BH; 2 mM), respectively. After this training step, the ANN correctly assigned necrosis induced by t-BH and apoptosis induced via Chx/TNF, Chx/CD95 activation, Pseudomonas exotoxin A/TNF, or X-rays. In all cases, apoptosis and necrosis as assigned by the ANN correlated with DNA fragmentation and LDH release.

Attenuation by phosphodiesterase inhibitors of lipopolysaccharide-induced thromboxane release and bronchoconstriction in rat lungs

Exposure of perfused rat lungs to lipopolysaccharides (LPS) causes induction of cyclooxygenase-2 followed by thromboxane (TX)-mediated bronchoconstriction (BC). Recently, phosphodiesterase (PDE) inhibitors have received much interest because they not only are bronchodilators but also can suppress release of proinflammatory mediators. In the present study, we investigated the effect of three different PDE inhibitors on TX release and BC in LPS-exposed perfused rat lungs. The PDE inhibitors used were motapizone (PDE III specific), rolipram (PDE IV specific), and zardaverine (mixed PDE III and IV specific). At 5 microM, a concentration at which all three compounds selectively block their respective PDE isoenzyme, rolipram (IC50 = 0.04 microM) and zardaverine (IC50 = 1.8 microM) largely attenuated the LPS-induced BC, whereas motapizone was almost ineffective (IC50 = 40 microM). In contrast to LPS, BC induced by the TX-mimetic U46619 was prevented with comparable strength by motapizone and rolipram. In LPS-treated lungs, the TX release was reduced to 50% of controls by rolipram and zardaverine but was unaltered in the presence of 5 microM motapizone. Increasing intracellular cAMP through perfusion of db-cAMP or forskolin (activates adenylate cyclase) also reduced TX release and BC. We conclude that PDE inhibitors act via elevation of intracellular cAMP. Although both PDE III and PDE IV inhibitors can relax airway smooth muscle, in the model of LPS-induced BC, PDE IV inhibitors are more effective because (in contrast to PDE III inhibitors) they also attenuate TX release.

In vivo evidence for a functional role of both tumor necrosis factor (TNF) receptors and transmembrane TNF in experimental hepatitis

The significance of tumor necrosis factor receptor 1 (TNFR1) for TNF function in vivo is well documented, whereas the role of TNFR2 so far remains obscure. In a model of concanavalin A (Con A)-induced, CD4+ T cell-dependent experimental hepatitis in mice, in which TNF is a central mediator of apoptotic and necrotic liver damage, we now provide evidence for an essential in vivo function of TNFR2 in this pathophysiological process. We demonstrate that a cooperation of TNFR1 and TNFR2 is required for hepatotoxicity as mice deficient of either receptor were resistant against Con A. A significant role of TNFR2 for Con A-induced hepatitis is also shown by the enhanced sensitivity of transgenic mice overexpressing the human TNFR2. The ligand for cytotoxic signaling via both TNF receptors is the precursor of soluble TNF, i.e. transmembrane TNF. Indeed, transmembrane TNF is sufficient to mediate hepatic damage, as transgenic mice deficient in wild-type soluble TNF but expressing a mutated nonsecretable form of TNF developed inflammatory liver disease.

Phosphodiesterase profiles of highly purified human peripheral blood leukocyte populations from normal and atopic individuals: a comparative study

BACKGROUND

Several previous reports have suggested an increased activity of cAMP phosphodiesterases (PDEs) and a higher sensitivity of these enzymes toward PDE inhibitors in leukocytes of patients suffering from atopic dermatitis.

OBJECTIVE

The purpose of the present study was to comprehensively analyze and compare the PDE expression and activity profile of highly purified populations of leukocytes from normal and atopic blood donors. In addition, the influence of PDE inhibitors on function of leukocytes from normal and atopic individuals was investigated.

METHODS

Density gradient centrifugation, elutriation, and magnetic cell sorting techniques were used to purify eosinophils, monocytes, and B and T lymphocytes from peripheral human blood. Complementary DNA-polymerase chain reaction was used to analyze PDE4 subtype messenger RNA (mRNA) expression levels in addition to PDE isoenzyme activities. PDE4 inhibitor sensitivity was determined in monocyte homogenates from both groups. Functionally, suppression of lipopolysaccharide-induced synthesis of tumor necrosis factor-alpha in monocytes as well as phytohemagglutinin-induced T cell proliferation in peripheral blood mononuclear cell fractions by PDE4 and PDE3/4 inhibitors was compared.

RESULTS

Identical PDE activities and mRNA expression profiles were found in all cells from normal and atopic donors except that there was an increase in the mRNA levels of PDE4A and PDE4B2 in atopic T cells, which was, however, not reflected in overall PDE4A activity. In addition, no differences in sensitivity of the functional responses to PDE inhibitors were noted. The mixed PDE3/4 inhibitor zardaverine was a more potent inhibitor of T cell proliferation than rolipram, a selective PDE4 inhibitor.

CONCLUSION

No evidence for alterations of PDE activities in atopy is provided by our findings.

Ebselen--an in vivo immune response modifier

Numerous biochemical activities are known for the selenoorganic drug ebselen [(2-phenyl-1,2-benzoisoselenazol-3-(2H)-one]. The initial interest focussed on its GSH peroxidase-like activity and its inhibitory activity on 5-lipoxygenase, however, further activities of the drug on oxidative burst of leukocytes, nitric oxide synthases, protein kinases and on leukocyte migration were recognized. Here we report that Ebselen differentially interacts in vivo with the production and action of systemically released cytokines in various hyperinflammation models in mice. Ebselen given orally to mice protected dose-dependently from Concanavalin A-induced, T-cell dependent inflammatory liver injury. The release of the proinflammatory cytokines Tumor Necosis Factor alpha and Interferon gamma was downregulated, while the production of the anti-inflammatory cytokine Interleukin 10 was increased. Similar results were found in galactosamine-sensitized mice in an inflammatory liver model using the superantigen staphylococcal enterotoxin B as a T-cell activator. Moreover, Ebselen inhibited the release of TNF alpha initiated by endotoxin in vivo in mice. In galactosamine-pretreated mice. Ebselen also attenuated liver injury induced by recombinant Tumor Necosis Factor alpha and initiated enhanced release of Interleukin 10. These findings expand the pharmacological knowledge on ebselen to hitherto unknown immunomodulatory properties which encourage to develop the drug for treatment of T-cell related autoimmune diseases.

In vitro differentiation of human monocytes to macrophages: change of PDE profile and its relationship to suppression of tumour necrosis factor-alpha release by PDE inhibitors

1. During in vitro culture in 10% human AB serum, human peripheral blood monocytes acquire a macrophage-like phenotype. The underlying differentiation was characterized by increased activities of the macrophage marker enzymes unspecific esterase (NaF-insensitive form) and acid phosphatase, as well as by a down-regulation in surface CD14 expression. 2. In parallel, a dramatic change in the phosphodiesterase (PDE) profile became evident within a few days that strongly resembled that previously described for human alveolar macrophages. Whereas PDE1 and PDE3 activities were augmented, PDE4 activity, which represented the major cyclic AMP-hydrolysing activity of peripheral blood monocytes, rapidly declined. 3. Monocytes and monocyte-derived macrophages responded to lipopolysaccharide (LPS) with the release of tumour necrosis factor-alpha (TNF). In line with the change in CD14 expression, the EC50 value of LPS for induction of TNF release increased from approximately 0.1 ng ml-1 in peripheral blood monocytes to about 2 ng ml-1 in macrophages. 4. Both populations of cells were equally susceptible towards inhibition of TNF release by cyclic AMP elevating agents such as dibutyryl cyclic AMP, prostaglandin E2 (PGE2) or forskolin, which all led to a complete abrogation of TNF production in a concentration-dependent manner and which were more efficient than the glucocorticoid dexamethasone. 5. In monocytes, PDE4 selective inhibitors (rolipram, RP73401) suppressed TNF formation by 80%, whereas motapizone, a PDE3 selective compound, exerted a comparatively weak effect (10-15% inhibition). Combined use of PDE3 plus PDE4 inhibitors resulted in an additive effect and fully abrogated LPS-induced TNF release as did the mixed PDE3/4 inhibitor tolafentrine. 6. In monocyte-derived macrophages, neither PDE3- nor PDE4-selective drugs markedly affected TNF generation when used alone (< 15% inhibition), whereas in combination, they led to a maximal inhibition of TNF formation by about 40-50%. However, in the presence of PGE2 (10 nM), motapizone and rolipram or RP73401 were equally effective and blocked TNF release by 40%. Tolafentrine or motapizone in the presence of either PDE4 inhibitor, completely abrogated TNF formation in the presence of PGE2. Thus, an additional cyclic AMP trigger is necessary for PDE inhibitors to become effective in macrophages. 7. Finally, the putative regulatory role for PDE1 in the regulation of TNF production in macrophages was investigated. Zaprinast, at a concentration showing 80% inhibition of PDE1 activity (100 micromol l-1), did not influence TNF release. At higher concentrations (1 mmol l-1), zaprinast became effective, but this inhibition of TNF release can be attributed to a significant inhibitory action of this drug on PDE3 and PDE4 isoenzymes. 8. In summary, the in vitro differentiation of human peripheral blood monocytes to macrophages is characterized by a profound change in the PDE isoenzyme pattern. The change in the PDE4 to PDE3 ratio is functionally reflected by an altered susceptibility towards selective PDE inhibitors under appropriate stimulating conditions.

In vitro prevention and reversal of lipopolysaccharide desensitization by IFN-gamma, IL-12, and granulocyte-macrophage colony-stimulating factor

LPS tolerance is characterized by a diminished monocytic synthesis of TNF-alpha and, interestingly, IL-10 after LPS restimulation. We wondered whether granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-12, and IFN-gamma can prevent or reverse this down-regulation of TNF-alpha and IL-10 production. The LPS-induced TNF-alpha amounts in desensitized PBMC treated with GM-CSF, IFN-gamma, or IL-12 and in naive, non-cytokine-primed cultures were similar, while much more TNF-alpha was induced in cytokine-primed naive cells. The effect of IL-12 was dependent on the presence of nonmonocytic cells and could be completely blocked with an IFN-gamma antiserum. Treatment of LPS-desensitized pure monocytes with IFN-gamma or GM-CSF resulted in a very high TNF-alpha expression and no difference to cytokine-primed naive monocytes was evident any longer. While IFN-gamma and IL-12 decreased IL-10 expression in naive PBMC, it was increased by both and by GM-CSF in LPS-tolerant cultures. Again, only IL-12 was dependent on the presence of nonmonocytic cells. For prevention of LPS tolerance, similar results were obtained. Recently, we have shown that IL-10 and TGF-beta mediate LPS desensitization in vitro and can be used to establish LPS hyporesponsiveness in the absence of LPS. IFN-gamma and GM-CSF prevented and reversed down-regulation of TNF-alpha and IL-10 synthesis also in the model of IL-10/TGF-beta1-induced LPS hyporesponsiveness, while IL-12 was ineffective because of its obvious inability to induce IFN-gamma. In summary, after LPS desensitization/hyporesponsiveness, IFN-gamma and GM-CSF tended to normalize pro- and anti-inflammatory monocytic behavior. Our results suggest that during LPS desensitization/hyporesponsiveness, monocytes acquire a hitherto unknown functional state with an altered reaction to biologic response modifiers.

In vitro prevention and reversal of lipopolysaccharide desensitization by IFN-gamma, IL-12, and granulocyte-macrophage colony-stimulating factor

LPS tolerance is characterized by a diminished monocytic synthesis of TNF-alpha and, interestingly, IL-10 after LPS restimulation. We wondered whether granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-12, and IFN-gamma can prevent or reverse this down-regulation of TNF-alpha and IL-10 production. The LPS-induced TNF-alpha amounts in desensitized PBMC treated with GM-CSF, IFN-gamma, or IL-12 and in naive, non-cytokine-primed cultures were similar, while much more TNF-alpha was induced in cytokine-primed naive cells. The effect of IL-12 was dependent on the presence of nonmonocytic cells and could be completely blocked with an IFN-gamma antiserum. Treatment of LPS-desensitized pure monocytes with IFN-gamma or GM-CSF resulted in a very high TNF-alpha expression and no difference to cytokine-primed naive monocytes was evident any longer. While IFN-gamma and IL-12 decreased IL-10 expression in naive PBMC, it was increased by both and by GM-CSF in LPS-tolerant cultures. Again, only IL-12 was dependent on the presence of nonmonocytic cells. For prevention of LPS tolerance, similar results were obtained. Recently, we have shown that IL-10 and TGF-beta mediate LPS desensitization in vitro and can be used to establish LPS hyporesponsiveness in the absence of LPS. IFN-gamma and GM-CSF prevented and reversed down-regulation of TNF-alpha and IL-10 synthesis also in the model of IL-10/TGF-beta1-induced LPS hyporesponsiveness, while IL-12 was ineffective because of its obvious inability to induce IFN-gamma. In summary, after LPS desensitization/hyporesponsiveness, IFN-gamma and GM-CSF tended to normalize pro- and anti-inflammatory monocytic behavior. Our results suggest that during LPS desensitization/hyporesponsiveness, monocytes acquire a hitherto unknown functional state with an altered reaction to biologic response modifiers.

Granulocyte-macrophage colony-stimulating factor and IFN-gamma restore the systemic TNF-alpha response to endotoxin in lipopolysaccharide-desensitized mice

The influence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and IFN-gamma on the restoration of impaired TNF-alpha release in LPS-desensitized mice or their refractory macrophages was investigated. Mice pretreated with GM-CSF or IFN-gamma (50 microg/kg i.v.) and injected with 3 mg/kg LPS i.p. displayed increased plasma TNF-alpha levels compared with LPS controls. IL-10 was marginally up-regulated by GM-CSF but abrogated by IFN-gamma pretreatment. LPS-tolerant mice (30 microg/kg LPS i.p., -24 h) showed an attenuated plasma TNF-alpha and IL-10 response to LPS and survived LPS shock. Pretreatment of such mice with GM-CSF or IFN-gamma restored the previously impaired TNF-alpha response. In cultures of murine monocyte/macrophage-containing cell populations, i.e., alveolar, peritoneal, spleen, bone marrow cells, or blood, the presence of GM-CSF or IFN-gamma (10 ng/ml) resulted in an enhanced release of TNF-alpha initiated by 1 microg/ml LPS. Cells from LPS-tolerant mice showed a diminished responsiveness to LPS. However, when exposed to GM-CSF or IFN-gamma ex vivo, their TNF-alpha response to LPS was partially restored. These findings characterize GM-CSF and IFN-gamma as potent enhancers of LPS-induced TNF-alpha production in normal as well as in experimentally immunocompromised mice and provide the rationale for further experiments to explore the pharmacologic use of these cytokines for restoration of immunocompetence in sepsis-associated immunosuppression.

Granulocyte-macrophage colony-stimulating factor and IFN-gamma restore the systemic TNF-alpha response to endotoxin in lipopolysaccharide-desensitized mice

The influence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and IFN-gamma on the restoration of impaired TNF-alpha release in LPS-desensitized mice or their refractory macrophages was investigated. Mice pretreated with GM-CSF or IFN-gamma (50 microg/kg i.v.) and injected with 3 mg/kg LPS i.p. displayed increased plasma TNF-alpha levels compared with LPS controls. IL-10 was marginally up-regulated by GM-CSF but abrogated by IFN-gamma pretreatment. LPS-tolerant mice (30 microg/kg LPS i.p., -24 h) showed an attenuated plasma TNF-alpha and IL-10 response to LPS and survived LPS shock. Pretreatment of such mice with GM-CSF or IFN-gamma restored the previously impaired TNF-alpha response. In cultures of murine monocyte/macrophage-containing cell populations, i.e., alveolar, peritoneal, spleen, bone marrow cells, or blood, the presence of GM-CSF or IFN-gamma (10 ng/ml) resulted in an enhanced release of TNF-alpha initiated by 1 microg/ml LPS. Cells from LPS-tolerant mice showed a diminished responsiveness to LPS. However, when exposed to GM-CSF or IFN-gamma ex vivo, their TNF-alpha response to LPS was partially restored. These findings characterize GM-CSF and IFN-gamma as potent enhancers of LPS-induced TNF-alpha production in normal as well as in experimentally immunocompromised mice and provide the rationale for further experiments to explore the pharmacologic use of these cytokines for restoration of immunocompetence in sepsis-associated immunosuppression.