Dexamethasone and pentoxifylline inhibit endotoxin-induced cachectin/tumor necrosis factor synthesis at separate points in the signaling pathway

Increased pulmonary secretion of tumor necrosis factor-alpha in calves experimentally infected with bovine respiratory syncytial virus

Bovine respiratory syncytial virus (BRSV) is an important cause of respiratory disease among calves in the Danish cattle industry. An experimental BRSV infection model was used to study the pathogenesis of the disease in calves. Broncho alveolar lung lavage (BAL) was performed on 28 Jersey calves, of which 23 were experimentally infected with BRSV and five were given a mock inoculum. The presence of the cytokine tumor necrosis factor alpha (TNF-alpha) in the BAL fluids was detected and quantified by a capture ELISA. TNF-alpha was detected in 21 of the infected animals. The amount of TNF-alpha in the BAL fluid of calves killed post inoculation day (PID) 2 and 4 was at the same very low level as in the uninfected control animals. Large amounts of TNF-alpha were detected on PID 6, maximum levels of TNF-alpha were reached on PID 7, and smaller amounts of TNF-alpha were seen on PID 8. The high levels of TNF-alpha appeared on the days where severe lung lesions and clinical signs were obvious and the amounts of BRSV-antigen were at their greatest. Although Pasteurellaceae were isolated from some of the BRSV-infected calves, calves treated with antibiotics before and through the whole period of the infection, as well as BRSV-infected calves free of bacteria reached the same level of TNF-alpha as animals from which bacteria were isolated from the lungs. It is concluded that significant quantities of TNF-alpha are produced in the lungs of the calves on PID 6-7 of BRSV infection. The involvement of TNF-alpha in the pathogenesis of, as well as the anti-viral immune response against, BRSV infection is discussed.

Differential effects of pentoxifylline, a non-specific phosphodiesterase inhibitor, on the production of IL-10, IL-12 p40 and p35 subunits by murine peritoneal macrophages

Pentoxifylline (PTX), a methylxanthine derivative, has been reported to be an effective drug in inhibiting TNF-alpha responses during septic shock. The inhibition of TNF-alpha production seems to be correlated with increased intracellular cAMP levels. PTX also affects the production of other cytokines such as IL-1, IL-6, IL-10, IL-12, and IFN-gamma. However, inhibition, as well as enhancement of cytokine production, has been observed in vitro, depending on the PTX concentration and cell type used.IL-12 is a heterodimeric cytokine that plays an important role in the development of Th1-mediated inflammatory responses. IL-12 along with TNF-alpha and other proinflammatory cytokines has shown to be responsible for the pathological reaction, which may lead to septic shock. For biological activity, the expression of both subunits of IL-12, p35 and p40, is required. Moreover, the p40 chain of IL-12 specifically inhibits the effects of the IL-12 heterodimer. In this study, we investigated the effects of PTX on the production of both proinflammatory (TNF-alpha, IL-6, IL-12) and anti-inflammatory (IL-10) cytokines by murine macrophages (Mφ). We have found that PTX, at concentrations below 100 microg/ml, selectively inhibited the production of TNF-alpha. Forskolin, a cAMP-elevating agent, similarly affected the production of the cytokines tested. However, at higher concentrations, PTX inhibited the production of TNF-alpha, IL-10, and IL-12 p35, but surprisingly, PTX enhanced the production of IL-12 p40. Concentrations of IL-10 were negatively correlated with the concentrations of IL-12 p40 subunit. These results further confirm the relevance of the use of PTX in clinical trials of immunological disorders characterised by inappropriate Th1 type immune responses.

Glucocorticoids suppress tumor necrosis factor-alpha expression by human monocytic THP-1 cells by suppressing transactivation through adjacent NF-kappa B and c-Jun-activating transcription factor-2 binding sites in the promoter

Glucocorticoid drugs suppress tumor necrosis factor-alpha (TNF-alpha) synthesis by activated monocyte/macrophages, contributing to an anti-inflammatory action in vivo. In lipopolysaccharide (LPS)-activated human monocytic THP-1 cells, glucocorticoids acted primarily on the TNF-alpha promoter to suppress a burst of transcriptional activity that occurred between 90 min and 3 h after LPS exposure. LPS increased nuclear c-Jun/ATF-2, NF-kappaB(1)/Rel-A, and Rel-A/C-Rel transcription factor complexes, which bound specifically to oligonucleotide sequences from the -106 to -88 base pair (bp) region of the promoter. The glucocorticoid, dexamethasone, suppressed nuclear binding activity of these complexes prior to and during the critical phase of TNF-alpha transcription. Site-directed mutagenesis in TNF-alpha promoter-luciferase reporter constructs showed that the adjacent c-Jun/ATF-2 (-106 to -99 bp) and NF-kappaB (-97 to -88 bp) binding sites each contributed to the LPS-stimulated expression. Mutating both sites largely prevented dexamethasone from suppressing TNF-alpha promoter-luciferase reporters. LPS exposure also increased nuclear Egr-1 and PU.1 abundance. The Egr-1/Sp1 (-172 to -161 bp) binding sites and the PU.1-binding Ets site (-116 to -110 bp) each contributed to the LPS-stimulated expression but not to glucocorticoid response. Dexamethasone suppressed the abundance of the c-Fos/c-Jun complex in THP-1 cell nuclei, but there was no direct evidence for c-Fos/c-Jun transactivation through sites in the -172 to -52 bp region. Small contributions to glucocorticoid response were attributable to promoter sequences outside the -172 to -88 bp region and to sequences in the TNF-alpha 3'-untranslated region. We conclude that glucocorticoids suppress LPS-stimulated secretion of TNF-alpha from human monocytic cells largely through antagonizing transactivation by c-Jun/ATF-2 and NF-kappaB complexes at binding sites in the -106 to -88 bp region of the TNF-alpha promoter.

Administration of endotoxin associated with lipopolysaccharide tolerance protects mice against fungal infection

Lipopolysaccharide (LPS) pretreatment of mice resulted in a significantly enhanced survival after disseminated Cryptococcus neoformans infection. The survival was associated with reduced fungal burden in tissues. LPS-pretreated mice had lower levels of cytokines in blood, spleen, and lungs and higher levels in brain. Pentoxifylline abolished the beneficial effect of LPS pretreatment.

Lisofylline ameliorates intestinal and hepatic injury induced by hemorrhage and resuscitation in rats

OBJECTIVE

We sought to determine whether treatment with lisofylline (LSF) preserves intestinal barrier function in rats subjected to hemorrhagic shock and resuscitation (HS/R).

SETTING

Research laboratory at a major university teaching hospital.

DESIGN

Rats were bled to a mean arterial pressure of 30 mm Hg and maintained at that pressure for 90 mins. One group (n = 8) was treated with LSF (bolus doses of 15 mg/kg at 45 and 89 min plus infusion at 10 mg x kg(-1) x hr(-1)), whereas another group (n = 8) received only the lactated Ringer's solution (LRS) vehicle. At 90 mins, the animals were resuscitated with shed blood and LRS (55 mL x kg(-1) x hr(-1)). Intestinal mucosal permeability was determined by measuring the mucosal-to-serosal clearance of fluorescein isothiocyanate dextran (molecular weight = 4 kDa) into everted gut sacs.

MEASUREMENTS AND MAIN RESULTS

Intestinal and hepatic blood flow (assessed by laser Doppler flowmetry) was greater in LSF-treated rats. Treatment with LSF ameliorated the development of histologic evidence of mucosal damage and hyperpermeability. Rats treated with LSF had lower plasma concentrations of the intracellular hepatic enzyme, aspartate aminotransferase. After 90 mins of resuscitation, concentrations of adenosine triphosphate in intestinal and hepatic tissue were greater in LSF-treated as compared with LRS-treated rats, but concentrations of the endogenous antioxidant, glutathione, in intestinal and hepatic tissue, although lower than in rats not subjected to HS/R, were similar in the two treatment groups.

CONCLUSION

Treatment with LSF ameliorated HS/R-induced derangements in intestinal structure and function and hepatic injury, possibly by preserving microvascular perfusion and tissue adenosine triphosphate concentrations.

Review article: the clinical role of anti-TNFalpha antibody treatment in Crohn's disease

The recent licensing of anti-TNFalpha antibody treatment offers the potential to radically alter the course of severe Crohn's disease using genetically-engineered drugs directed against a specific inflammatory mediator. Controlled randomized trials have demonstrated clinical benefit associated with tissue healing in patients with active intestinal disease and fistulae, often when conventional therapies were unsuccessful. This therapy is expensive, however, and long-term efficacy and safety data are still awaited. This review considers the nature of this therapy and the current evidence for its clinical benefit and adverse effects. The treatment is also considered in the context of available immunosuppressive agents, with suggestions about its practical application.

Aged mice exhibit greater mortality concomitant to increased brain and plasma TNF-alpha levels following intracerebroventricular injection of lipopolysaccharide

BACKGROUND

Age-related defects in the development of peripheral inflammatory responses have been observed in rodents and humans.

OBJECTIVE

We examined the effects of age on a centrally injected endotoxin-induced cytokine production and cellular activation in mice.

METHODS

Male C57BL/6J (B6) mice, C3H/HeN mice, and C3H/HeJ mice received an intracerebroventricular injection of lipopolysaccharide (LPS) and were sacrificed at various times (2, 4, 8 h) thereafter. ELISA for IL-1beta, IL-6, IL-12, and TNF-alpha were conducted on forebrain tissue homogenates as well as plasma samples, and lectin staining to detect activated microglia was prepared for selected brain slices.

RESULTS

Intracerebroventricular injection of LPS in B6 mice produced an age-associated increase in mortality which was paralleled with a significant increase in brain and plasma levels of TNF-alpha. AntiTNF-alpha- and IL-6-immunoreactive cells possessed macrophagelike morphologies and were observed along the LPS injection tract and scattered throughout the hilus of the dorsal hippocampus and cerebral cortices. This LPS-mediated response was found to be specific in that the LPS-hyporesponsive mouse strain (C3H/HeJ) failed to demonstrate significant brain or plasma levels of TNF-alpha after LPS administration compared to C3H/HeN mice.

CONCLUSION

These results suggest that the age-related increases in TNF-alpha production and mortality following the intracerebroventricular administration of LPS may be due to an increased endotoxin hypersensitivity of brain microglia/macrophages within aged animals.

Immunomodulatory effect of pentoxifylline during human allograft rejection: involvement of tumor necrosis factor-alpha and adhesion molecules

BACKGROUND

Pentoxifylline (PTX), a methylxanthine phosphodiesterase inhibitor, is poorly active as an immunosuppressant but prevents the synthesis of proinflammatory cytokines. In a randomized double-blind study comparing PTX versus placebo in 140 patients receiving cadaveric kidney grafts under cyclosporine and prednisone, we have shown that PTX weakened the consequences of rejection on graft survival. To assess the mechanism underlying the beneficial effect recorded during this trial, we analyzed the impact of PTX on tumor necrosis factor (TNF-alpha) production and expression of cell adhesion molecules.

METHODS

Plasma levels of TNF-alpha and its soluble receptors (sTNF-RI, sTNF-RII) and of soluble vascular cell adhesion molecule 1 (sVCAM-1) were monitored over the 6 months postgraft period when PTX or placebo were administered. Expression of VCAM-1 and intercellular cell adhesion molecule 1 was scored by immunohistochemical staining of biopsy specimens from patients who underwent rejection crisis. Lymphocyte subset composition was analyzed longitudinally during cytomegalovirus (CMV) infections.

RESULTS

Plasma TNF-alpha levels were significantly reduced in the PTX-treated group over the 6 months of administration, and specifically during isolated rejection episodes and during CMV infections. Plasma levels of sTNFR-I, sTNFR-II, and sVCAM-1 did not differ between the two groups of patients, but a decrease in renal tubular VCAM-1 expression was observed in the PTX group. During CMV infections, CD8 lymphocytosis and expansion of CD57+ (CD28-) CD8+ T cells were similar in the two groups.

CONCLUSION

The data collected during this double-blind study point to an immunomodulatory role of PTX, the beneficial effect on graft survival resulting from a restraining effect of the drug on the inflammatory conditions involved in acute graft rejection.

Patients with myelodysplastic syndromes benefit from palliative therapy with amifostine, pentoxifylline, and ciprofloxacin with or without dexamethasone

Thirty-five patients with myelodysplastic syndrome (MDS) were registered on protocol MDS 96-02 and were receiving continuous therapy with pentoxifylline 800 mg 3 times a day and ciprofloxacin 500 mg twice a day by mouth; dexamethasone was added to the regimen for the partial responders and the nonresponders after 12 weeks at a dose of 4 mg by mouth every morning for 4 weeks. Amifostine was administered intravenously 3 times a week at 3 dose levels (200 mg/M2, 300 mg/M2, and 400 mg/M2) to cohorts of 10 patients each. Therapy has been continued for 1 year in responders. Twenty-nine have completed at least 12 weeks of therapy and are available for response evaluation. Of the 21 men and 8 women (median age, 67 years), 20 had refractory anemia (RA), 3 had RA with ringed sideroblasts (RARS), 5 had RA with excess blasts (RAEB), and 1 had chronic myelomonocytic leukemia (CMMoL). Five had secondary MDS. No differences were noted in response rates among the 3 dose levels. Seven patients did not respond at all, and 22 showed an improvement in cytopenias (76%). Three had a triple lineage response, 10 had a double lineage response, and 9 had a single lineage response (8 of 9 in absolute neutrophil count [ANC] and 1 had more than a 50% reduction in packed red blood cell transfusions). Fifteen patients responded only after the addition of dexamethasone, whereas 7 responded before. When examined by lineage, 19 of 22 showed improved ANC, 11 of 22 demonstrated more than 50% reduction in blood transfusions, improved Hb levels, or both, and 7 of 22 showed improvement in platelet counts. Interestingly, the responses were frequently slow to appear, and continued improvement in counts was seen up to 12 months of therapy and beyond. This study supports the feasibility of treating patients with MDS with the unique approach of cytoprotection and anticytokine therapies as well as the principle that prolonged commitment to treatment is desirable when noncytotoxic agents are administered.

Pentoxifylline inhibits ICAM-1 expression and chemokine production induced by proinflammatory cytokines in human pulmonary epithelial cells

Airway epithelium participates in inflammatory reactions by producing chemokines and expressing cell-surface adhesion molecules which aid in the selective recruitment of effector cells. Previous studies showed that proinflammatory cytokines, interleukin 1 (IL-1) and tumor necrosis factor alpha (TNF alpha), induce surface expression of intercellular adhesion molecule 1 (ICAM-1) and the production of the chemokines interleukin 8 (IL-8) and monocyte chemoattractant protein (MCP-1) on pulmonary epithelial cell lines in vitro. In this study, the dose response of four cytokines, IL-1alpha, IL-1beta, TNF alpha and TNF beta, in inducing ICAM-1 expression and production of IL-8 and MCP-1 on pulmonary A549 epithelial cells was examined. Both IL-1alpha and IL-1beta induced ICAM-1 expression and IL-8 and MCP-1 production at lower doses than TNF alpha or TNF beta. Pentoxifylline, an anti-inflammatory agent used to treat vascular diseases, was tested for its ability to inhibit the activation of airway epithelial cells by these cytokines. Pentoxifylline completely inhibited the surface expression of ICAM-1 and the production of IL-8 and MCP-1 by cytokine-activated epithelial cells. As elevated levels of chemokines are often present in bronchial lavage fluids of patients suffering from various acute respiratory diseases, pentoxifylline may be useful for preventing the rapid development of immune reactions leading to lung injury.

The effect of pentoxifiline on post-injury hyperalgesia in rats and postoperative pain in patients

Recent studies demonstrate that activation of proinflammatory cytokines following injury intensifies the process of nociception. The present investigation assessed the influence of pre-injury pentoxifiline (PTFL, a non-specific cytokine inhibitor) on the development of post-injury nociception in animals and patients. It was established that intrathecal or intraperitoneal PTFL, elevated the nociceptive threshold for mechanical stimuli in the formalin test in rats. Pre-injury PTFL also inhibited pain-related behaviour. These findings correlate with a lower TNFalpha level in the serum of animals receiving pre-injury PTFL. In clinical investigations PTFL was administered intravenously before elective cholecystectomy. Patients who received preoperative PTFL had lower opioid requirements in the early postoperative period than control. At the same time, serum levels of TNFalpha and IL6 were lower in the PTFL group. Our results confirm the hypothesis as to the possibility of modulating of nociception through preemptive administration of a cytokine inhibitor.

Synthetic melanin suppresses production of proinflammatory cytokines

An overproduction of proinflammatory cytokines mediates the damaging sequelae of inflammation in pathologic conditions such as rheumatoid arthritis, graft-vs-host reaction, cachexia, and sepsis syndrome. We examined the cytokine regulatory activity of synthetic melanin, exemplified by biosynthetic l-glycine-l-tyrosine-based polymer (ME-1) and chemosynthetic dihydroxyphenylalanine-based polymer (MC-1). At nontoxic concentrations, both compounds effectively (>/=60%) and reversibly suppressed the production of tumor necrosis factor (TNF), even when applied after stimulation of human peripheral blood monocytes with lipopolysaccharide (LPS). The inhibitory activity of melanin was selective with regard to cytokine response but not inducer- or cell-type-specific. In addition to TNF, melanin inhibited production of interleukin (IL)-1beta, IL-6, and IL-10 but not granulocyte-macrophage colony-stimulating factor by the LPS-stimulated monocytes. Melanin was equally effective in inhibiting production of TNF by monocytes stimulated with the purified protein derivative of Mycobacterium tuberculosis and production of IL-6 by IL-1alpha-stimulated human fibroblasts and endothelial cells. Northern blot analysis, mRNA stability determination, immunoprecipitation studies on metabolically labeled intracellular TNF, and pulse chase experiments revealed that melanin reduced efficiency of mRNA translation. The finding that melanin arrests ongoing cytokine synthesis suggests that this compound may be useful as an adjunct therapy for conditions showing involvement of proinflammatory cytokines.

Detection of TNFalpha expression in the bone marrow and determination of TNFalpha production of peripheral blood mononuclear cells in myelodysplastic syndrome

TNFalpha is a highly active cytokine which plays an important role in the regulation of apoptotic cell death, a mechanism involved in the pathophysiology of myelodysplastic syndrome (MDS). In this study we investigated the expression of TNFalpha of the bone marrow trephine biopsies by immunohistochemical method and the TNFalpha production of peripheral blood mononuclear cells by ELISA method in 15 patients affected by MDS. Five of seven patients without excess of blasts showed high or intermediate TNFalpha expression in the bone marrow biopsies, whereas two patients with excess of blasts were negative and one had low expression. The five CMML patients revealed low or intermediate expression. The production of TNFalpha by the PBMC was analysed in 10 patients, four patients with RA and two with CMML produced higher level of TNFalpha which increased after stimulation with phorbol myristic acetate, but none of the RAEB patients revealed increase in TNFalpha production. In conclusion we suppose that increased TNFalpha expression and production by PBMC may be an indirect evidence of the role of increased apoptosis in low risk MDS patients.

The role of local induction of tumor necrosis factor by LPS within a subcutaneous air pouch in the development of a febrile response in guinea pigs

In rats, fever can be induced by injection of bacterial lipopolysaccharide (LPS) into a subcutaneous air pouch. This febrile response is in part dependent on the local action of interleukin-1beta within the pouch. In the present study, we tried to find out if this model of fever induction can be applied in guinea pigs and if the local LPS-induced formation of tumor necrosis factor-alpha (TNF-alpha) participates in the development of the febrile response. A dose of 100 microg/kg LPS was injected into a subcutaneous air pouch along with solvent (0.9% saline), or 100 mg/kg pentoxifylline, or 1 mg/animal soluble 55-kD TNF receptor (referred to as TNF-binding protein, TNF bp). The mean LPS-induced concentration of TNF in the lavage of the air pouch (measured 60 min after injection) was 17,765 pg/ml in animals injected with LPS and solvent. This value was reduced to 7,631 pg/ml if pentoxifylline was injected along with LPS into the pouch. If LPS was injected along with TNF bp, no bioactive TNF was detected in the lavage of the air pouch. Simultaneously, TNF was measured in blood plasma. Circulating concentrations of TNF were about 5-8% of the values detected in the lavage of the air pouch (mean values: 1,366 pg/ml in response to LPS plus solvent; 377 pg/ml in response to LPS plus pentoxifylline; no circulating TNF at all in response to LPS plus TNF bp). These data indicated a small spill-over of TNF from the air pouch into the circulation. Neither the reduction of local TNF formation in the air pouch by pentoxifylline nor the complete neutralization of TNF within the pouch by TNF bp resulted in a significant attenuation of the febrile response induced by injection of LPS into the subcutaneous air pouch. If there were an activation of cutaneous nerves to induce fever by a local formation of cytokines within the air pouch, TNF would not represent a likely candidate to be responsible for such a neural stimulation.

Post-transcriptional regulation of pro-inflammatory gene expression

The cytokine tumour necrosis factor (TNF)alpha is a vital mediator of the innate immune response, and a pleiotropic regulator of cellular function. Its involvement in rheumatoid arthritis is illustrated by the clinical benefits of TNF alpha blockade. Post-transcriptional regulation (the control of mRNA stability and translation) appears to play a critical role in the regulation of TNF alpha expression by mitogen activated protein kinase signal transduction pathways and by anti-inflammatory agents. The aim of this article is to review some recent advances in our understanding of these processes, and to speculate on mechanisms of regulation of TNF alpha and other pro-inflammatory genes.

Mycoplasma fermentans-induced inflammatory response of astrocytes: selective modulation by aminoguanidine, thalidomide, pentoxifylline and IL-10

Exposure of primary rat glial cells, mostly astrocytes, to heat-inactivated Mycoplasma fermentans triggers the production of tumor necrosis factor alpha (TNFalpha) nitric oxide (NO) and prostaglandin E2 (PGE2). To attenuate the production of these proinflammatory mediators, four agents: aminoguanidine, pentoxifylline, thalidomide and IL-10 were added to astrocyte cultures. Aminoguanidine (1 and 3 mM), an inhibitor of inducible nitric oxide synthase (iNOS), suppressed the production of the three mediators. TNFalpha was the most sensitive to thalidomide, showing dose-response inhibition at concentrations of 20 microg/ml, 50 microg/ml and 250 microg/ml. PGE2 was affected only by concentrations of 50 microg/ml and 250 microg/ml, whereas NO responded solely to the highest amount of this inhibitor. The cytokine IL-10, at 10 U and 50 U, inhibited only TNFalpha production. Our results imply that selective suppression of proinflammatory mediators by various agents may prove feasible for amelioration of central nervous system inflammatory diseases.

Interleukin-11 attenuates pulmonary inflammation and vasomotor dysfunction in endotoxin-induced lung injury

Interleukin (IL)-11, like other members of the gp130 receptor class, possesses anti-inflammatory properties. We hypothesized that IL-11 pretreatment would attenuate endotoxin [lipopolysaccharide (LPS)]-induced lung inflammation and diminish injury to endothelium-dependent and -independent mechanisms of pulmonary vasorelaxation that require cGMP in Sprague-Dawley rats. LPS (20 mg/kg ip) increased lung tumor necrosis factor (TNF)-alpha compared with the saline control (0.7 +/- 0.15 ng/g lung wet wt for control vs. 3.5 +/- 0.09 ng/g lung wet wt for LPS; P < 0.05). IL-11 (200 mg/kg ip) injected 10 min before LPS administration attenuated the LPS-induced lung TNF-alpha levels (1.6 +/- 0.91 ng/g lung wet wt; P < 0.05 vs. LPS). IL-11 also diminished LPS-induced lung neutrophil sequestration as assessed by myeloperoxidase units (2.1 +/- 0.25 U/g lung wet wt for saline and 15.6 +/- 2.02 U/g lung wet wt for LPS vs. 7.07 +/- 1.65 U/g lung wet wt for LPS plus IL-11; P < 0.05). Similarly, TNF-alpha binding protein (175 mg/kg) attenuated LPS-induced myeloperoxidase activity (6.04 +/- 0.14 U/g lung wet wt; P < 0.05). Both IL-11 and TNF-alpha binding protein similarly attenuated LPS-induced endothelium-dependent vasomotor dysfunction with improved relaxation responses to 10(-7) and 10(-6) M acetylcholine and A-23187 in phenylephrine-preconstricted isolated pulmonary artery rings (P < 0.05 vs. LPS). Endothelium-independent relaxation responses to sodium nitroprusside were also improved after LPS at 10(-6) M (P < 0.05 vs. LPS). Moreover, IL-11 decreased endotoxin-induced mortality in CF1 mice from 90 to 50% (P </= 0.05 vs. LPS). Therefore, IL-11 prevents LPS-induced lung TNF-alpha production, neutrophil sequestration, and pulmonary vasomotor dysfunction. We conclude that IL-11 possesses anti-inflammatory activity that protects against LPS-induced lung injury and lethality.

Glucocorticoids Induce Apoptosis in Human Monocytes: Potential Role of IL-1β

Glucocorticoids (GC) are potent anti-inflammatory and immunosuppressive agents that act on a variety of immune cells, including monocytes and macrophages. However, the exact cellular mechanisms underlying this anti-inflammatory capacity are still unknown. In our study, we determined the induction of apoptosis by GC in human monocytes. Peripheral blood monocytes were isolated by density centrifugation methods with a purity of &gt;90% and were cultured in RPMI 1640 medium. Monocyte apoptosis was determined by four independent methods, including annexin-V staining, TUNEL, DNA-laddering, and typical morphology by means of transmission electron microscopy. TNF-α and IL-1β were measured by ELISA. GC receptor was blocked with mifepristone. Caspase 3 was inhibited with caspase-3 inhibitor (DEVD-CHO). Stimulation with different GC at therapeutic concentrations resulted in monocyte apoptosis in a time- and dose-dependent manner. Necrosis was excluded by propidium iodide staining. Proinflammatory cytokines such as IL-1β and TNF-α were down-regulated by GC treatment. Continuous treatment of monocytes with IL-1β, but not with TNF-α, could almost completely prevent GC-induced cell death. The addition of mifepristone or caspase-3 inhibitor could partially abrogate GC-induced apoptosis as well as GC-induced inhibition of IL-1β. This is the first study to demonstrate induction of apoptosis by GC in human monocytes. GC-induced monocyte apoptosis may be partially mediated through effects on IL-1β production. It is conceivable that GC exert their anti-inflammatory capacity in various diseases, at least in part, by the induction of apoptosis in monocytes.

Prevention and treatment of chemotherapy- and radiotherapy-induced oral mucositis: a review

Oral mucositis is a distressing toxic effect of systemic chemotherapy with many commonly utilized drugs and of head and neck irradiation in patients with cancer. The agents and methods that have been used and studied in chemotherapy- and radiotherapy-induced oral mucositis, their mechanisms of action, and the current knowledge of their efficiency to reduce the incidence, severity or shorten the duration of oral mucositis are reviewed in this article. Oral cooling is a cheap and available method to lower the severity of bolus 5-fluorouracil-induced oral mucositis. However, more effective methods are needed. Results of studies with granulocyte-macrophage colony-stimulating factor or granulocyte colony-stimulating factor are promising. Lasers are partly beneficial, but equipment-demanding. Modification of the chemotherapy regimen resulting in shortening of the exposition time to chemotherapy agents or chronomodulation of chemotherapy has been shown to lower mucosal toxicity of some regimens. Results of animal studies with locally applied transforming growth factor beta 3 and interleukin-11 are also promising. Based on the findings of the role of the inflammatory cascade in the response of normal tissues to chemotherapy and radiotherapy, anti-inflammatory drugs might be beneficial. At the present time, no agent has been shown to be uniformly efficacious and can be accepted as standard therapy of chemotherapy- and radiotherapy-induced oral mucositis. Further intensive research is needed.

Dexamethasone differentially regulates cytokine transcription and translation in macrophages responding to bacteria or okadaic acid

Many microorganisms and microbial products induce expression of pro-inflammatory cytokines such as interleukin-1 (IL-1alpha/beta) and tumour necrosis factor-alpha (TNF-alpha) in macrophages, primarily by transcriptional activation. We show here, by using mouse macrophages in primary culture, that pre-treatment with dexamethasone inhibits bacteria-induced IL-1beta expression as mRNA and cellular pro-IL-1beta in parallel, consistent with an effect primarily on transcriptional activation. In contrast, the expression of TNF-alpha mRNA was only partly inhibited despite virtually complete inhibition of TNF-alpha protein formation. Furthermore, the selective induction of primarily cell-associated 26,000 M, pro-TNF-alpha by the protein phosphatase inhibitor okadaic acid also was partly inhibited at the mRNA level by dexamethasone, whereas additional translational inhibition appeared to be lacking. This latter finding is reminiscent of earlier findings regarding signalling to activation of cytosolic phospholipase A2, which is sensitive to dexamethasone when elicited by bacteria, but not when elicited by okadaic acid. The present results raise the possibility that the inhibitory effect of dexamethasone on TNF-alpha translation, but not on transcriptional activation, is mediated by one or more okadaic acid-sensitive protein phosphatases.

S-adenosylmethionine attenuates the lipopolysaccharide-induced expression of the gene for tumour necrosis factor alpha

Intracellular deficiency of S-adenosylmethionine (AdoMet) and elevated serum concentrations of tumour necrosis factor alpha (TNF) are hallmarks of toxin-induced liver injury. In these models, the administration of either exogenous AdoMet or antibody/soluble receptor for TNF attenuates the injury. We have demonstrated previously that the administration of exogenous AdoMet to AdoMet-deficient rats attenuated lipopolysaccharide (LPS)-induced liver injury and serum TNF concentrations. Here we report that AdoMet lowered the amount of TNF secreted by LPS-stimulated murine macrophage cells (RAW 264.7) in a dose-dependent manner. The inhibition of TNF release was correlated with changes in the steady-state TNF mRNA concentrations. Changes in TNF mRNA were not due to its altered stability and might have been due to an attenuation of the transcription rate of the TNF gene. The inhibition of TNF release in RAW cells was not mediated by GSH because treatment with AdoMet did not increase intracellular GSH. In addition, N-acetylcysteine, whereas it did increase GSH concentration, had no effect on LPS-stimulated TNF release in these cells. Exogenous AdoMet also attenuated LPS-induced serum TNF levels in normal rats sensitized with lead. Thus AdoMet administration might exert its hepatoprotective effects at least in part by its inhibitory effect on expression of the gene for TNF.

Pentoxifylline inhibits superantigen-induced toxic shock and cytokine release

Tumor necrosis factor alpha (TNF-alpha) is a critical cytokine that mediates the toxic effects of bacterial superantigens like staphylococcal enterotoxin B (SEB) and toxic shock syndrome toxin 1 (TSST-1). Pentoxifylline, an anti-inflammatory agent that inhibits endotoxemia and lipopolysaccharide (LPS)-induced release of TNF-alpha, was tested for its ability to inhibit SEB- and TSST-1-induced activation of human peripheral blood mononuclear cells (PBMCs) in vitro and toxin-mediated shock in mice. Stimulation of PBMCs by SEB or TSST-1 was effectively blocked by pentoxifylline (10 mM), as evidenced by the inhibition of TNF-alpha, interleukin 1beta (IL-1beta), gamma interferon (IFN-gamma), and T-cell proliferation. The levels of TNF-alpha, IL-1alpha, and IFN-gamma in serum after an SEB or TSST-1 injection were significantly lower in mice given pentoxifylline (5.5 mg/animal) versus control mice. Additionally, pentoxifylline diminished the lethal effects and temperature fluctuations elicited by SEB and TSST-1. Thus, in addition to treating endotoxemias, the cumulative in vitro and in vivo data suggest that pentoxifylline may also be useful in abrogating the ill effects of staphylococcal enterotoxins and TSST-1.

MAP kinase pathways

MAP kinases help to mediate diverse processes ranging from transcription of protooncogenes to programmed cell death. More than a dozen mammalian MAP kinase family members have been discovered and include, among others, the well studied ERKs and several stress-sensitive enzymes. MAP kinases lie within protein kinase cascades. Each cascade consists of no fewer than three enzymes that are activated in series. Cascades convey information to effectors, coordinates incoming information from other signaling pathways, amplify signals, and allow for a variety of response patterns. Subcellular localization of enzymes in the cascades is an important aspect of their mechanisms of action and contributes to cell-type and ligand-specific responses. Recent findings on these properties of MAP kinase cascades are the major focus of this review.

Inhibition of Ca2+ influx by pentoxifylline in NR8383 alveolar macrophages

Pentoxifylline (PTF), a phosphodiesterase (PDE) inhibitor, can prevent inflammation and tissue damage in animal and in vitro human studies. However, the underlying mechanism remains unclear. Since Ca2+ is a critical signal regulating the release of inflammatory mediators in macrophages, the effects of PTF on Ca2+ influx were examined in NR8383 alveolar macrophages (AMs). PTF induced a dose-dependent inhibition on Ca2+ influx activated by zymosan and by protein kinase C (PKC) activators 1,2-dioctanoyl-sn-glycerol (DOG) or phorbol-12-myristate 13-acetate (PMA). The inhibition appeared to be specifically on the receptor-operated Ca2+ entry. The capacitative Ca2+ entry was not affected by PTF. The inhibition was not due to altered cAMP levels since the zymosan-activated Ca2+ influx was not affected by the adenylate cyclase activator forskolin, nor by dibutyryl cAMP. Pretreatment with protein tyrosine kinase (PTK) inhibitor genistein abolished zymosan-induced, but not DOG-induced Ca2+ influx, suggesting that PTK is an upstream element of the signaling cascade and not the target of PTF. The Ca2+ entry activated by zymosan and by PKC activators was inhibited by the mitogen-activated protein kinase (MAPK) inhibitor PD98059. Moreover, activation of MAPK by C6-ceramide (C6C) triggered a similar Ca2+ influx as elicited by zymosan and PKC activators, suggesting that MAPK is an element of the pathway. The C6C-induced Ca2+ influx was also inhibited by PTF. These results indicate that PTF blocks the receptor-operated Ca2+ influx in NR8383 AMs by inhibiting PDE which may acts as a downstream element of the signaling pathway or by direct interaction with Ca2+ channels.

On the role of tumor necrosis factor and receptors in models of multiorgan failure, rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease

The specific role of the tumor necrosis factor (TNF)/TNF receptor (TNFR) system in disease pathogenesis still remains an unresolved puzzle. Recent studies in transgenic and knockout animals, where the pathogenic influence of genetically perturbed TNF expression has been evaluated, indicate that several pathways of TNF/TNFR action may contribute independently or in concert to initiate, promote or downregulate disease pathogenesis. Evidently, organ-specific inflammatory or autoimmune pathology may ensue due to sustained activation by TNF of innate immune cells and inflammatory responses, which may consequently lead to tissue damage and to organ-specific chronic pathology. However, more cryptic functions of this molecule may be considered to play a significant part in the development of TNF-mediated pathologies. Direct interference of TNF with the differentiation, proliferation or death of specific pathogenic cell targets may be an alternative mechanism for disease initiation or progression. In addition to these activities, there is now considerable evidence to suggest that TNF may also directly promote or downregulate the adaptive immune response. It is therefore evident that no general scenario may adequately describe the role of TNF in disease pathogenesis. In this article, we aim to place these diverse functions of TNF/TNFRs into context with the development of specific pathology in murine models of multiorgan failure, rheumatoid arthritis, multiple sclerosis and inflammatory bowel disease.

Early-onset inflammatory responses in vivo to adenoviral vectors in the presence or absence of lipopolysaccharide-induced inflammation

Adenoviral vectors (Ad) have potential for use in pulmonary gene transfer for treating cystic fibrosis (CF). However, Ad may induce inflammation even in the absence of gene expression. Endotoxin from gram-negative bacteria in the airways of CF patients may also induce inflammation, and may further inhibit vector delivery and gene transfer. We used a mouse model to study the time course of Ad-induced lung inflammation and to assess additivity with lipopolysaccharide (LPS)-induced inflammatory responses. C3H/HeJ endotoxin-resistant (RES) mice hyporesponsive to inflammatory stimuli and normoresponsive C3HeB/FeJ endotoxin-sensitive (SEN) mice were studied to characterize inflammatory responses that follow intratracheal instillation of inactivated Ad, with or without simultaneous inhalation exposure to LPS. Instillation of 10(10) Ad particles dramatically increased bronchoalveolar lavage fluid (BALF) concentrations of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 at 3 to 6 h and induced profound neutrophilia, maximal at 12 to 24 h. SEN mice had tenfold greater responses than did RES mice at 6, 12, and 24 h. Mice exposed to Ad alone, LPS alone, or Ad + LPS had significant inflammation at the 3-h time point as demonstrated by BALF neutrophils, TNF-alpha, and IL-6. With all three treatments, SEN mice had a five- to 300-fold greater response than did RES mice. Importantly, Ad + LPS yielded no greater inflammatory response than LPS without Ad. These data demonstrate that replication-deficient Ad induce early inflammation and LPS-induced inflammation is not augmented by concurrent treatment with Ad.

Soluble tumor necrosis factor receptor prevents post-pump syndrome

Post-pump syndrome is an acute lung injury following cardiopulmonary bypass (CPB) which is indistinguishable from the adult respiratory distress syndrome (ARDS). Tumor necrosis factor (TNF) is central to the inflammatory process and is capable of triggering the entire pathophysiologic response leading to ARDS. We hypothesized that treatment with a soluble TNF receptor-binding protein (TNFbp) would reduce the increase in serum TNF and prevent acute lung injury in our sequential insult model of ARDS following CPB. Anesthetized pigs were randomized to one of three groups: Control (n = 3), surgical preparation only; CPB + LPS (n = 6), femoral-femoral hypothermic bypass for 1 h followed by infusion of low dose Escherichia coli lipopolysaccharide (LPS; 1 microg/kg); and TNFbp + CPB + LPS (n = 4), pretreatment with intravenous TNFbp (2 mg/kg) followed immediately by both insults. CPB + LPS caused severe lung injury demonstrated by a significant fall in PaO2 and an increase in both intrapulmonary shunt and peak airway pressure as compared to all groups (P < 0.05). These changes were associated with a significant increase in plasma TNF level and pulmonary neutrophil sequestration. TNFbp significantly reduced plasma levels of TNF and prevented the lung injury typically observed with this ARDS model, but did not reduce pulmonary neutrophil sequestration. Thus, elevated serum TNF is not responsible for neutrophil sequestration but does play a role in neutrophil activation which causes lung injury. Prophylactic use of TNFbp in CPB patients may prevent neutrophil activation and reduce the incidence of post-pump ARDS.

Pentoxifylline decreases neutrophil respiratory bursts in patients with stable angina

We estimated the effect of pentoxifylline (PTX) on the respiratory burst (examined by chemiluminescence method) of unprimed and primed neutrophils with tumor necrosis factor-alpha (TNF-alpha) in patients with stable angina pectoris. Chemiluminescence of non-stimulated as well as formyl-methionyl-leucyl-phenylalanine (fMLP) and phorbol myristate acetate (PMA) stimulated neutrophils was measured. We studied 45 patients with stable angina subjected to percutaneous transluminal coronary angioplasty (PTCA) procedure, who were randomly divided into two groups. The study group consisted of 24 patients who were administered pentoxifylline orally, and the control group consisted of 21 patients without pentoxifylline administration. Blood samples for examination were collected from the coronary sinus and peripheral vein just before the PTCA procedure. Pentoxifylline decreased the respiratory burst of non-stimulated and fMLP-stimulated neutrophils without affecting the chemiluminescence of PMA stimulated neutrophils. Moreover, pentoxifylline diminished the chemiluminescence non-stimulated and stimulated by fMLP but not by PMA of TNF-alpha primed neutrophils. We presume that administration of PTX in stable angina patients may have a beneficial effect.

[TNF-alpha secretion by human macrophage-like cells in response to wear particles and its modification by drugs]

Tumour necrosis factor (TNF) is considered to be the initiator protein of particle disease leading to aseptic loosening of endoprostheses. The aim of the present study was to investigate the TNF response of the macrophage-like cells (MLC) to the periprosthetic particles typically found during revision surgery. For this purpose, particles of polyethylene (PE), pure titanium (Ti), chromium (Cr), cobalt (Co), alumina ceramic (Al2O3) and zirconium dioxide (ZrO2) were used. Additionally, the therapeutic effect of non-steroidal and steroidal drugs, biphosphonates and pentoxyfylline on PE particles was investigated with the aim of differentiating drugs with, from those without, a positive effect on aseptic loosening.

METHOD

In an established macrophage model (Rader et al. 1999), THP1 cells (human monocytic cell line) were differentiated over a period of five days in the presence of vitamin D3 and GM-CSF in macrophage-like cells (MLC). To obtain a TNF profile of the different materials, 10(6) MLC were incubated with each of a range of different particle concentrations. For drug testing purposes 80 x 10(8) PE particles, which evoked a maximum TNF response, were applied together with increasing drug concentrations in the same manner. The supernatant was then investigated for TNF secretion using ELISA.

RESULTS

It was found that the greatest TNF response was provoked by Co and PE particles, and was 25 and 23 times as high, respectively, in comparison with control. The smallest TNF secretion was seen with Al2O3 (4 x control) and ZrO2 (5 x control). At the recommended dose, non-steroidal anti-inflammatory drugs (NSAIDs) produced no decrease in TNF secretion. The biphosphonates, etidronate and ibendronate significantly reduced the TNF response of the PE-stimulated macrophages (by 1/7 and 1/5, respectively). Therapeutic doses of pentoxyfylline also led to a decrease of 1/5 in maximum TNF release.

CONCLUSION

Ceramic articulating surfaces are superior to metal/metal or PE/PE matings in terms of the biological effects of their wear particles. At therapeutic doses, NSAIDs have no beneficial effect on the process of aseptic loosening. Certain biphosphonates and pentoxyfylline have a positive effect on aseptic loosening.

Thalidomide increases both intra-tumoural tumour necrosis factor-alpha production and anti-tumour activity in response to 5,6-dimethylxanthenone-4-acetic acid

5,6-Dimethylxanthenone-4-acetic acid (DMXAA), synthesized in this laboratory and currently in phase I clinical trial, is a low molecular weight inducer of tumour necrosis factor-alpha (TNF-alpha). Administration of DMXAA to mice with established transplantable tumours elicits rapid vascular collapse selectively in the tumour, followed by extensive haemorrhagic necrosis mediated primarily through the production of TNF-alpha. In this report we have investigated the synthesis of TNF-alpha mRNA in hepatic, splenic and tumour tissue. Co-administration of thalidomide with DMXAA increased anti-tumour activity and increased intra-tumoural TNF-alpha production approximately tenfold over that obtained with DMXAA alone. Thalidomide increased splenic TNF-alpha production slightly but significantly decreased serum and hepatic levels of TNF-alpha induced with DMXAA. Lipopolysaccharide (LPS) induced 300-fold higher serum TNF-alpha than did DMXAA at the maximum tolerated dose, but induced similar amounts of TNF-alpha in spleen, liver and tumour. Splenic TNF-alpha activity induced with LPS was slightly increased with thalidomide, but serum and liver TNF-alpha levels were suppressed. Thalidomide did not increase intra-tumoural TNF-alpha production induced with LPS, in sharp contrast to that obtained with DMXAA. While thalidomide improved the anti-tumour response to DMXAA, it had no effect on the anti-tumour action of LPS that did not induce a significant growth delay or cures against the Colon 38 tumour. The increase in the anti-tumour action by thalidomide in combination with DMXAA corresponded to an increase in intra-tumoural TNF-alpha production. Co-administration of thalidomide may represent a novel approach to improving selective intra-tumoural TNF-alpha production and anti-tumour efficacy of DMXAA.

Lipopolysaccharide-induced tumor necrosis factor-alpha promoter activity is inhibitor of nuclear factor-kappaB kinase-dependent

The adverse effects of lipopolysaccharide (LPS) are primarily mediated by tumor necrosis factor-alpha (TNF-alpha). TNF-alpha production by LPS-stimulated macrophages is regulated both transcriptionally and post-transcriptionally. Transcriptional regulation of the TNF-alpha gene is dependent on nuclear factor-kappaB (NF-kappaB). We examined the signaling pathways involved in the regulation of NF-kappaB that lead to TNF-alpha promoter activity. We determined a role for one or both of the recently identified inhibitor of NF-kappaB kinases, IkappaB kinase-1 and IkappaB kinase-2, in LPS induction of an NF-kappaB reporter and of TNF-alpha promoter activity. IkappaB kinase activation is one of the earliest signaling events known to be induced by LPS. Furthermore, our results suggest roles for the IkappaB kinases NF-kappaB-inducing kinase and mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 1 in the regulation of IkappaB kinase-2, as well as in LPS-induced TNF-alpha transcription.

Prednisone and plasma exchange improve suppressor cell function in chronic inflammatory demyelinating polyneuropathy

We have recently demonstrated that ConA-induced suppressor cell function is defective in chronic inflammatory demyelinating polyneuropathy (CIDP). To assess whether this defect plays a role in disease activity and its reversal is important in recovery, we studied modifications of ConA-induced suppressor cell function induced by prednisone and plasma exchange in 20 patients with CIDP. We found a significant increase towards normal of ConA-induced suppressor cell function after treatment in concurrence with clinical improvement. Induction of suppression, presumably through favorable modifications of the cytokine network or other humoral mediators, might be one, among others, of the mechanisms through which prednisone and plasma exchange are effective in CIDP.

Urinary protein excretion and serum tumor necrosis factor in diabetic patients with advanced renal failure: effects of pentoxifylline administration

In 24 diabetic patients with advanced renal failure (creatinine clearance [C(Cr)] < 35 mL/min), we prospectively studied serum tumor necrosis factor-alpha (TNF-alpha) levels, the possible relationship with urinary protein excretion, and the effects of pentoxifylline (PTF) administration. PTF (400 mg daily) was administered for 6 months to 14 patients, and the results were compared with data from a control group (n = 10). Baseline parameters were similar in both groups. At the end of the study, urinary protein excretion and serum TNF-alpha decreased in the active group from 2.7 (1.2 to 5.8) g/d and 569 +/- 285 pg/mL to 1.1 (0.3 to 4.0) g/d and 329 +/- 232 pg/mL, respectively (P < 0.001). By contrast, proteinuria and TNF-alpha did not change in the control group. Regression analysis showed a significant correlation between proteinuria and serum TNF-alpha both at basal (r = 0.55) and at the sixth month (r = 0.57). Furthermore, the reduction of urinary protein excretion was strongly correlated with the decrease of TNF-alpha (r = 0.72, P < 0.01). Serum Cr and C(Cr) remained stable in both groups during the study. Our findings suggest that cytokines might play a role in renal damage in diabetic nephropathy. PTF is effective in reducing proteinuria in diabetic patients with advanced renal failure. The anticytokine activity of PTF may be a further explanation for this antiproteinuric effect.

Pentoxifylline inhibits TNF-alpha production from human alveolar macrophages

Tumor necrosis factor-alpha (TNF-alpha) is an important proinflammatory cytokine. Recently, pentoxifylline (POF) has been shown to suppress the synthesis of TNF-alpha from lipopolysaccharide (LPS)-stimulated human monocytes in cell cultures and in vivo. The aim of this study was to investigate whether POF-induced suppression of TNF-alpha secretion affects peripheral blood monocytes (PBM) and alveolar macrophages (AM) equally, and whether POF is able to suppress the spontaneous TNF-alpha production from AM in pulmonary sarcoidosis in vitro. In seven patients without interstitial lung disease we studied the effect of POF on LPS-stimulated PBM and AM cultured for 24 h. In six patients with sarcoidosis we investigated the effect of POF on the enhanced spontaneous TNF-alpha production by AM in vitro. POF induced a dose-dependent suppression of the LPS-stimulated TNF-alpha production which was not different for PBM and AM, respectively. In sarcoidosis, POF inhibited the spontaneous TNF-alpha production of AM at 0.1 mM by 91% and at 1 mM by 98%. In conclusion, POF inhibits LPS-induced TNF-alpha production from PBM and AM to a similar extent and can also inhibit the exaggerated spontaneous TNF-alpha production from AM in sarcoidosis in vitro. This may be the basis for further clinical trials to evaluate POF as an immunotherapeutic agent in sarcoidosis.

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.

The differential effect of pentoxifylline on cytokine production by alveolar macrophages and its clinical implications

The aim of this study was to investigate the effects of pentoxifylline (PTX) on the production of TNF-alpha, IL-1 beta, IL-6 and GM-CSF by lipopolysaccharide (LPS)-stimulated alveolar macrophages (AM). AM and peripheral blood monocytes (PBM) from 10 patients were cultured for 24 h in the presence of LPS (10 micrograms ml-1) and PTX at concentrations of 2.0 mM, 1.0 mM, 0.5 mM, 0.1 mM and 0.01 mM. TNF-alpha and GM-CSF were measured from the culture supernatants of both the AM and PBM from all 10 patients and IL-1 beta and IL-6 from the culture supernatants of the AM from five patients. The TNF-alpha production by AM was significantly suppressed in the presence of PTX at concentrations of 2.0 and 1.0 mM, while production of IL-1 beta, IL-6 and GM-CSF remained unaffected. In PBM cultures, PTX significantly suppressed the production of TNF-alpha and GM-CSF, at all tested concentrations. The present study provides evidence that PTX selectively suppresses the production of TNF-alpha by LPS-stimulated AM and may have a role in the treatment of lung diseases where TNF-alpha is involved. The mode of administration of PTX should take into account the suppressive effect of this drug on GM-CSF production by PBM.

Tumor necrosis factor-alpha production by human hepatoma cell lines is resistant to drugs that are inhibitory to macrophages

Little is known about the potential of immunomodulatory agents to lower tumor necrosis factor-alpha (TNF-alpha) synthesis in tissues of nonmonocytic origin. We studied effects of diverse drugs on the formation of immunoreactive TNF-alpha in the human hepatoma cell lines HepG2 and Hep3B, in which TNF-alpha production was induced by treatment (3 h incubation periods) with interleukin-1beta (IL-1beta, 300 pg/ml) or phorbol myristate acetate (PMA, 100 nmol/l). TNF-alpha production in IL-1beta-stimulated or PMA-stimulated hepatocyte cultures was not altered following the addition of dihydrocortisone (< or = 1 microg/ml), dibutyryl-cAMP (db-cAMP, < or = 100 micromol/l), adenosine (< or = 1 mmol/l), thalidomide (< or = 25 microg/ml), or cyclosporine (< or = 300 ng/ml). TNF-alpha production was inhibited by taurolidine (> or = 300 microg/ml), but this inhibition was associated with reduced cell viability. Pentoxifylline (1 mg/ml) did not influence PMA-induced TNF-alpha production, but it augmented IL-1beta-induced TNF-alpha production. Measurements of TNF-alpha mRNA by RT-PCR indicated that pentoxifylline exerted its effect posttranscriptionally. Additional studies with PMA-treated human whole blood cultures confirmed that pentoxifylline, db-cAMP, and adenosine reduced TNF-alpha production by leukocytes. These results provide first evidence to assume cell type-specific effects of immunomodulatory drugs on TFN-alpha synthesis, which may be relevant with respect to their clinical application.

Examining a paradox in the pathogenesis of human pulmonary tuberculosis: immune activation and suppression/anergy

Protective immunity against Mycobacterium tuberculosis (MTB) in animal models is based on cell-mediated immunity (CMI), involving bi-directional interactions between T cells and cells of the monocyte/macrophage (MO/MA) lineage. Key factors include MO-derived interleukin (IL)-12 and tumor necrosis factor (TNF)-alpha as well as T cell derived IL-2 and interferon (IFN)-gamma. These cytokines appear particularly crucial in the induction of MA-mediated elimination of mycobacteria. Several lines of evidence indicate that similar mechanisms are operating in humans. During active pulmonary tuberculosis (PTB), signs of both immune depression and immune activation are concomitantly present. Decreased tuberculin skin test reactivity in vivo and deficient IFN-gamma production by MTB-stimulated mononuclear cells in vitro are observed. On the other hand, the serum levels of several cytokines, including TNF, and other inflammatory mediators are increased and circulating MO and T cell show phenotypic and functional evidence of in vivo activation. In this review, we will discuss the evidence for three models, which could explain this apparent paradox: 1. Stimulation of the T cell-suppressive function from MO/MA; 2. Intrinsic T cell refractoriness, possibly associated with tendency to apoptosis (programmed cell death), and 3. Compartmentalization and redistribution of immune responses to the site of disease. The opportunistic behavior of MTB during human immunodeficiency virus (HIV) infection can be explained by suppression of type-1 responses at the level of antigen-presenting cells, CD4 T cells and effector macrophages. The ominous prognostic significance of intercurrent PTB during HIV infection seems primarily due to prolonged activation of HIV replication in macrophages. Supportive immune therapy during PTB could aim at correcting the type-1 deficiency either by IFN-gamma inducers (e.g. IL-12, IL-18) or by neutralizing the suppressive cytokines transforming growth factor beta (TGF-beta) and IL-10. Alternatively, inflammatory over-activity could be reduced by neutralizing TNF. Finally, anti-apoptotic therapies (e.g. IL-15) might be considered.

A carbocyclic nucleoside analogue is a TNF-alpha inhibitor with immunosuppressive action: role of prostaglandin E2 and protein kinase C and comparison with pentoxifylline

Tumor necrosis factor-alpha (TNF-alpha) is associated with several acute and chronic inflammatory conditions. New therapies directed at inhibiting TNF-alpha will be important in treating pathological processes mediated by TNF-alpha. In this study, we studied and compared the effect of the carbocyclic nucleoside analogue (9-[(1R, 3R)-trans-cyclopentan-3-ol] adenine) with pentoxifylline on modulating TNF-alpha production. The carbocyclic nucleoside analogue inhibited TNF-alpha production in a dose-dependent manner (1 microM-1 mM) by stimulated peripheral blood mononuclear cells and cell lines of both monocyte (THP-1) and T-lymphocyte phenotypes (CEM x 174). The drug potently inhibited TNF production in cells stimulated by endotoxin, the superantigen (staphylococci enterotoxin A), the mitogen (phytohemagglutinin), and the protein kinase C activator (phorbol myristate acetate) with ED50 ranging from 5 to 30 microM. At moderate concentrations, the carbocyclic nucleoside analogue inhibited superantigen (ED50 = 300 microM) and alloantigen (mixed lymphocyte reaction) T cell proliferative responses (ED50 = 150 microM). The involvement of protein kinase C and prostaglandin E2 (PGE2), mediators that regulate TNF-alpha production, was also investigated. Unlike PTX, the nucleoside analogue did not upregulate PGE2 production. The inhibition of TNF-alpha production appeared to be mediated at least partly by PKC, since the nucleoside analogue caused suppression of PKC activity in stimulated cells. The results show that the carbocyclic nucleoside analogue is a TNF-alpha inhibitor that may be appropriate in the therapy of TNF-alpha-associated complications. The suppressive properties of the carbocyclic nucleoside analogue on antigen and alloantigen (mixed lymphocyte reaction) responses may be appropriate in disease conditions in which inhibiting both TNF-alpha and T-cell reactivity is desirable.

Interaction of thalidomide, phthalimide analogues of thalidomide and pentoxifylline with the anti-tumour agent 5,6-dimethylxanthenone-4-acetic acid: concomitant reduction of serum tumour necrosis factor-alpha and enhancement of anti-tumour activity

DMXAA (5,6-dimethylxanthenone-4-acetic acid), a novel anti-tumour agent currently undergoing clinical evaluation, appears to mediate its anti-tumour effects through immune modulation and the production of the cytokine tumour necrosis factor-alpha (TNF). Our previous studies have shown that thalidomide, a potent inhibitor of TNF biosynthesis that has numerous biological effects, including inhibition of tumour angiogenesis, unexpectedly augments the anti-tumour response in mice to DMXAA. We show here that thalidomide (100 mg kg(-1)) has no effect when administered with inactive doses of DMXAA, and that it must be given simultaneously with an active dose of DMXAA to have its maximum potentiating effect on the growth of the murine Colon 38 adenocarcinoma. To address the issue of whether inhibition of serum TNF production is important for potentiation of anti-tumour activity, we have tested three potent analogues of thalidomide. All three analogues, when co-administered with DMXAA to mice at doses lower than those used with thalidomide, inhibited TNF production and were effective in potentiating the anti-tumour activity of DMXAA against transplanted Colon 38 tumours. One of the analogues, N-phenethyltetrafluorophthalimide, was 1000-fold more potent than thalidomide and at a dose of 0.1 mg kg(-1) in combination with DMXAA (30 mg kg(-1)) cured 100% of mice, compared with 67% for the group treated with DMXAA alone. We also tested pentoxifylline and found it to suppress TNF production in response to DMXAA and to potentiate the anti-tumour effect of DMXAA. The results are compatible with the hypothesis that pharmacological reduction of serum TNF levels might benefit the anti-tumour effects of DMXAA and suggest new strategies for therapy using this agent.

Production of adrenomedullin in macrophage cell line and peritoneal macrophage

We demonstrate that adrenomedullin (AM) is produced and secreted from cultured murine monocyte/macrophage cell line (RAW 264.7) as well as mouse peritoneal macrophage. Immunoreactive (IR) AM secreted from RAW 264.7 cells was chromatographically identified to be native AM. To elucidate the regulation mechanism of AM production in macrophage, we examined the effects of various substances inducing differentiation or activation of monocyte/macrophage. Phorbol ester (TPA), retinoic acid (RA), lipopolysaccharide (LPS), and interferon-gamma (IFN-gamma) increased AM production 1.5-7-fold in RAW 264.7 cells in a dose- as well as time-dependent manner. By LPS stimulation, the AM mRNA level in RAW 264.7 cells was augmented up to 7-fold after 14 h incubation. RA exerted a synergistic effect when administered with TPA, LPS, or IFN-gamma, whereas IFN-gamma completely suppressed AM production in RAW 264.7 cells stimulated with LPS. Dexamethasone, hydrocortisone, estradiol, and transforming growth factor-beta dose-dependently suppressed AM production in RAW 264.7 cells. AM production was also investigated in mouse peritoneal macrophage. Primary mouse macrophage secreted IR-AM at a rate similar to that of RAW 264.7 cells, and its production was enhanced 9-fold by LPS stimulation. AM was found to increase basal secretion of tumor necrosis factor alpha (TNF-alpha) from RAW 264.7 cells, whereas AM suppressed the secretion of TNF-alpha and interleukin-6 from that stimulated with LPS. Thus, macrophage should be recognized as one of the major sources of AM circulating in the blood. Especially in cases of sepsis and inflammation, AM production in macrophage is augmented, and the secreted AM is deduced to function as a modulator of cytokine production.

Pentoxifylline prevents concanavalin A-induced hepatitis by reducing tumor necrosis factor alpha levels and inhibiting adhesion of T lymphocytes to extracellular matrix

BACKGROUND/AIMS

Concanavalin A activates T lymphocytes and causes T cell-mediated hepatic injury in mice. Tumor necrosis factor alpha is a critical mediator in this experimental model. T-cell-mediated liver injury involves the migration of immune cells, notably CD4+ T lymphocytes, into liver tissue. Pentoxifylline is a strong suppressor of tumor necrosis factor alpha release and prevents leukocyte adherence to vascular endothelium and down-regulates the expression of intercellular adhesion molecule-1 in monocytes. In this study, we examined the efficacy of pentoxifylline as a potential therapeutic compound for the treatment of concanavalin A hepatitis.

METHODS

Balb/c mice were injected with 12 mg/kg concanavalin A with or without a single injection of pentoxifylline (5-300 mg/kg), 2 h prior to concanavalin A administration. Liver damage was evaluated by determining serum levels of liver enzymes and tumor necrosis factor alpha, and hepatic histopathology compared to mice treated with concanavalin A only. We also assessed the effects of pentoxifylline on the adhesive properties of T lymphocytes to fibronectin, as a paradigm for immune cell-extracellular matrix interactions required for migration. Pretreatment with pentoxifylline significantly reduced serum levels of liver enzymes (3800+/-650 vs 150+/-28 IU/l) and tumor necrosis factor alpha (710+/-105 vs 113+/-15 pg/ml) with no evidence of inflammation in histopathologic examination compared to control mice treated with concanavalin A. Pentoxifylline also inhibited the binding of murine T cells to fibronectin. All the effects of pentoxifylline were dose-dependent.

CONCLUSIONS

These results indicate that high doses of pentoxifylline can prevent concanavalin A hepatitis by suppression of tumor necrosis factor alpha release and inhibition of T cells adhesion to extracellular matrix.

Pentoxifylline and skin inflammation

Cyclic nucleotide phosphodiesterase inhibitors, such as pentoxifylline, have been shown to beneficially influence a large number of inflammatory skin diseases. The biological effects of pentoxifylline on the production of proinflammatory cytokines, leukocyte-endothelial cell adhesion, chemokines and leukocyte-keratinocyte adhesion in skin inflammation are discussed.

Inhibition of tumour necrosis factor and reversal of endotoxin-induced shock by U-83836E, a 'second generation' lazaroid in rats

1. Antioxidants can exert protective effects in endotoxic shock by either a reduction of the oxidant damage or attenuation of Tumour Necrosis Factor (TNF-alpha) production. 2. Lazaroids are a family of compounds that inhibit lipid peroxidation. Besides, they can also reduce TNF-alpha. U-83836E is a new lazaroid lacking the glucocorticoid ring. 3. Aim of our study was to investigate the effect of U-83836E on TNF-alpha production either in vivo or in vitro. Endotoxic shock was produced in male rats by a single intravenous (i.v.) injection of 20 mg kg(-1) of S. enteritidis lipopolysaccharide (LPS). LPS administration reduced survival rate (0% survival, 72 h after endotoxin administration), decreased mean arterial blood pressure, increased serum and macrophage TNF-alpha and enhanced plasma malonylaldehyde (MAL) levels. Furthermore aortic rings from shocked rats showed a marked hyporeactivity to phenylephrine (PE 1 nM-10 microM). 4. Treatment with U-83836E (7.5, 15 and 30 mg kg(-1), i.v.) 5 min after endotoxin challenge significantly protected against LPS induced lethality (90% survival rate and 80% survival rate 24 h and 72 h after LPS injection respectively, following the highest dose of the drug), reduced hypotension, blunted plasma MAL, decreased serum and macrophage TNF-alpha and restored the hyporeactivity of aortic rings to control values. In vitro LPS stimulation (50 microg ml(-1) for 4 h) significantly increased cytokine production in macrophages (Mphi) harvested from untreated normal rats. Pretreatment with pertussis toxin (PT; 0.1, 1 and 10 ng ml(-1) 4 h before LPS) significantly increased TNF-alpha production. PT effects on these LPS responses were correlated with a PT mediated ADP ribosylation of a 41 kDa protein. U-83836E (50 microM) reduced, in a dose dependent manner, LPS induced TNF-alpha production and inhibited the PT effects on cytokine production and on ADP ribosylation of the protein. 5. Our data suggest that lazaroids may affect the early events associated with LPS receptor mediated activation of a G protein in LPS induced TNF-alpha production. These molecular events may explain, at least in part, the in vivo inhibition of cytokine production and reversal of endotoxic shock.