In vitro cytokine release by activated murine peritoneal macrophages: role of prostaglandins in the differential regulation of tumor necrosis factor alpha, interleukin 1, and interleukin 6

Intracellular role of IL-6 in mesenchymal stromal cell immunosuppression and proliferation

Interleukin (IL)-6 is a pleiotropic cytokine involved in the regulation of hematological and immune responses. IL-6 is secreted chiefly by stromal cells, but little is known about its precise role in the homeostasis of human mesenchymal stromal cells (hMSCs) and the role it may play in hMSC-mediated immunoregulation. We studied the role of IL-6 in the biology of bone marrow derived hMSC in vitro by silencing its expression using short hairpin RNA targeting. Our results show that IL-6 is involved in immunosuppression triggered by hMSCs. Cells silenced for IL-6 showed a reduced capacity to suppress activated T-cell proliferation. Moreover, silencing of IL-6 significantly blocked the capacity of hMSCs to proliferate. Notably, increasing the intracellular level of IL-6 but not recovering the extracellular level could restore the proliferative impairment observed in IL-6-silenced hMSC. Our data indicate that IL-6 signals in hMSCs by a previously undescribed intracellular mechanism.

A randomised trial on the effect of anti-platelet therapy on the systemic inflammatory response in human endotoxaemia

The use of acetylsalicylic acid (ASA) is associated with improved outcome in patients with sepsis, and P2Y₁₂ inhibitors have been suggested to also have immunomodulatory effects. Therefore, we evaluated the effects of clinically relevant combinations of antiplatelet therapy on the immune response in experimental endotoxaemia in humans in vivo. Forty healthy subjects were randomised to seven days of placebo, placebo with ASA, ticagrelor and ASA, or clopidogrel and ASA treatment. Systemic inflammation was elicited at day seven by intravenous administration of Escherichia coli endotoxin. ASA treatment profoundly augmented the plasma concentration of pro-inflammatory cytokines, but did not affect anti-inflammatory cytokines. Addition of either P2Y₁₂ antagonist to ASA did not affect any of the circulating cytokines, except for an attenuation of the ASA-induced increase in TNFα by ticagrelor. Systemic inflammation increased plasma adenosine, without differences between groups, and although P2Y₁₂ inhibition impaired platelet reactivity, there was no correlation with cytokine responses.

Carnitine and septic shock: a review

Most studies have reported reduced carnitine levels in the tissues of patients with sepsis, probably due to increased urinary excretion. Because of the increased utilization of fatty acids and ketone bodies as sources of energy in sepsis, the carnitine deficiency can further impair the fuel metabolism and contribute to the unregulated lipid metabolism in these patients.

Recently, experimental and clinical studies have shown that carnitine and its congeners are able to: (a) downmodulate the spontaneous and endotoxin (LPS)-triggered overproduction of tumor necrosis factor (TNF)-alpha; (b) ameliorate the lipid metabolism; and (c) reduce the severity of illness, accelerate recovery, and, in some cases, improve survival in experimental septic shock.

Many questions concerning the ultimate molecular mechanism of action of these compounds in endotoxaemia are still unanswered. Yet, these compounds may be helpful in patients with sepsis, when associated with conventional therapy, in that they can effectively reduce TNF-alpha levels and ameliorate the host's metabolic processes.

LPS-induced serum TNF production and lethality in mice: effect of L-carnitine and some acyl-derivatives

The effect of L-carnitine and some of its acyl derivatives on serum TNF production and lethality in a murine experimental endotoxin shock model was investigated. In some instances, serum IL-6 production was also evaluated. In this experimental model, C57BL/6 mice received 30 mg/kg LPS (E. cell 055:B5) injected intraperitoneally, while L-carnitine and its derivatives were administered according to different schedules. Serum levels of TNF and IL-6 were evaluated 1 h following LPS injection. The treated animals were also monitored daily for differences in body temperature, feeding, and survival for 10 days after LPS injection. Although some derivatives were able to significantly affect TNF production, the marked decrease in serum TNF levels of LPS-treated mice was not paralleled by a substantial increase in survival.

Unique proteomic signatures distinguish macrophages and dendritic cells

Monocytes differentiate into heterogeneous populations of tissue macrophages and dendritic cells (DCs) that regulate inflammation and immunity. Identifying specific populations of myeloid cells in vivo is problematic, however, because only a limited number of proteins have been used to assign cellular phenotype. Using mass spectrometry and bone marrow-derived cells, we provided a global view of the proteomes of M-CSF-derived macrophages, classically and alternatively activated macrophages, and GM-CSF-derived DCs. Remarkably, the expression levels of half the plasma membrane proteins differed significantly in the various populations of cells derived in vitro. Moreover, the membrane proteomes of macrophages and DCs were more distinct than those of classically and alternatively activated macrophages. Hierarchical cluster and dual statistical analyses demonstrated that each cell type exhibited a robust proteomic signature that was unique. To interrogate the phenotype of myeloid cells in vivo, we subjected elicited peritoneal macrophages harvested from wild-type and GM-CSF-deficient mice to mass spectrometric and functional analysis. Unexpectedly, we found that peritoneal macrophages exhibited many features of the DCs generated in vitro. These findings demonstrate that global analysis of the membrane proteome can help define immune cell phenotypes in vivo.

Dehydroxymethylepoxyquinomicin (DHMEQ) can suppress tumour necrosis factor-α production in lipopolysaccharide-injected mice, resulting in rescuing mice from death in vivo

Dehydroxymethylepoxyquinomicin (DHMEQ), a new nuclear factor (NF)-κB inhibitor, has several beneficial effects, including the suppression of tumour growth and anti-inflammatory effects. DHMEQ can also suppress the production of tumour necrosis factor (TNF)-α induced by lipopolysaccharide (LPS) in vitro. In the present study, we examine the effects of DHMEQ on TNF-α production in vivo and on the survival of mice injected with LPS. When DHMEQ was injected into mice 2 h before LPS injection, the survival of the LPS-injected mice was prolonged. When DHMEQ was injected twice (2 h before LPS injection and the day after LPS injection), all the mice were rescued. The injection of DHMEQ 1 h after LPS injection and the day after LPS injection also resulted in the rescue of all mice. The serum levels of TNF-α in the mice that received both LPS and DHMEQ were suppressed compared to the mice that received only LPS. These results suggest that DHMEQ can be utilized for the prevention and treatment of endotoxin shock.

Macrophages induce COX-2 expression in breast cancer cells: role of IL-1β autoamplification

Tumor-associated macrophages and high levels of cyclooxygenase-2 (COX-2) are associated with poor prognosis in breast cancer patients, but their potential interdependence has not been evaluated. The objective of this study was to determine whether macrophages regulate COX-2 expression in breast cancer cells. For this purpose, THP-1 cells were cocultured with HCC1954 breast cancer cells. Coculture led to increased COX-2 expression in the HCC1954 cells and elevated prostaglandin E(2) levels in conditioned media. Similar results were observed when THP-1 cells were incubated with HCC1937 breast cancer cells or when human monocyte-derived macrophages were cocultured with HCC1954 cells. Coculture triggered production of reactive oxygen species (ROS) in HCC1954 cells. COX-2 induction was blocked in cells preincubated with an reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor or by silencing p67PHOX, a subunit of NADPH oxidase. ROS production triggered activation of Src and mitogen-activated protein kinases (MAPKs). Blocking Src or MAPK activities or antagonizing the activator protein-1 (AP-1) transcription factor attenuated COX-2 induction in HCC1954 cells. Coculture caused rapid induction of interleukin-1β (IL-1β) in both breast cancer cells and macrophages. Increased IL-1β expression was blocked by an interleukin-1 receptor antagonist (IL-1Ra), suggesting autocrine and paracrine effects. Importantly, macrophage-induced COX-2 expression was blocked in HCC1954 cells preincubated with IL-1Ra or anti-IL-1β IgG. Together, these results indicate that macrophage-mediated induction of COX-2 in breast cancer cells is a consequence of IL-1β-mediated stimulation of ROS→Src→MAPK→AP-1 signaling. IL-1β-dependent induction of COX-2 in breast cancer cells provides a mechanism whereby macrophages contribute to tumor progression and potential therapeutic targets in breast cancer.

Activation of cytosolic phospholipase A2alpha in resident peritoneal macrophages by Listeria monocytogenes involves listeriolysin O and TLR2

Eicosanoid production by macrophages is an early response to microbial infection that promotes acute inflammation. The intracellular pathogen Listeria monocytogenes stimulates arachidonic acid release and eicosanoid production from resident mouse peritoneal macrophages through activation of group IVA cytosolic phospholipase A2 (cPLA2alpha). The ability of wild type L. monocytogenes (WTLM) to stimulate arachidonic acid release is partially dependent on the virulence factor listeriolysin O; however, WTLM and L. monocytogenes lacking listeriolysin O (DeltahlyLM) induce similar levels of cyclooxygenase 2. Arachidonic acid release requires activation of MAPKs by WTLM and DeltahlyLM. The attenuated release of arachidonic acid that is observed in TLR2-/- and MyD88-/- macrophages infected with WTLM and DeltahlyLM correlates with diminished MAPK activation. WTLM but not DeltahlyLM increases intracellular calcium, which is implicated in regulation of cPLA2alpha. Prostaglandin E2, prostaglandin I2, and leukotriene C4 are produced by cPLA2alpha+/+ but not cPLA2alpha-/- macrophages in response to WTLM and DeltahlyLM. Tumor necrosis factor (TNF)-alpha production is significantly lower in cPLA2alpha+/+ than in cPLA2alpha-/- macrophages infected with WTLM and DeltahlyLM. Treatment of infected cPLA2alpha+/+ macrophages with the cyclooxygenase inhibitor indomethacin increases TNFalpha production to the level produced by cPLA2alpha-/- macrophages implicating prostaglandins in TNFalpha down-regulation. Therefore activation of cPLA2alpha in macrophages may impact immune responses to L. monocytogenes.

Regulation of NF-kappaB-dependent gene expression by the POU domain transcription factor Oct-1

Maintenance of the cells of the vessel wall in a quiescent state is an important aspect of normal vascular physiology. Transcriptional repressors are widely believed to regulate this process, yet the exact factors involved and the mechanism of repression are not known. Here, we report that the POU domain transcription factor Oct-1 represses the expression of E-selectin and vascular cell adhesion molecule (VCAM-1), two cytokine-inducible, NF-kappaB-dependent endothelial-leukocyte adhesion molecules that participate in the leukocyte recruitment phase of the inflammatory response. Co-transfection and microinjection studies demonstrate that Oct-1 blocks tumor necrosis factor alpha-stimulated E-selectin and VCAM-1 expression. Gene expression arrays indicate that control of tumor necrosis factor alpha-induced, NF-kappaB-dependent gene expression by Oct-1 is promoter-specific. A DNA-binding mutant of Oct-1 represses NF-kappaB-dependent reporter gene expression. Biochemically, Oct-1 interacts with p65, suggesting that Oct-1 is involved in the regulation of NF-kappaB transactivation function. NF-kappaB-dependent gene expression is more pronounced in Oct-1-deficient than in wild-type murine embryonic fibroblasts, and reintroduction of human Oct-1 abolishes these differences. Finally, the cytokine interleukin-6 induces Oct-1 gene expression, providing a biologically relevant means by which NF-kappaB-dependent gene expression can be selectively reverted by Oct-1 to quiescent levels.

INFLUENCE OF CYCLOOXYGENASE INHIBITORS ON GUT IMMUNE CELL DISTRIBUTION AND APOPTOSIS RATE IN EXPERIMENTAL SEPSIS

The aim of this study was to determine if cyclooxygenase (COX) inhibitors influence immune cell distribution in the small intestinal mucosa and mesenteric lymph nodes (MLNs), the grade of mucosal damage, and the rate of apoptosis in septic rats. The effects induced by a selective COX-2 inhibitor (SC-236) were compared with those of a nonselective COX-1 and -2 inhibitor (indomethacin). Cecal ligation and puncture (CLP), CLP + SC-236 p.o, and CLP + indomethacin p.o, were evaluated. Animals were harvested 6 and 24 h after CLP, respectively. The concentration of proinflammatory cytokines was higher in ascitic fluid than in blood. CLP + SC-236 attenuated IL-6 in plasma and in ascitic fluid and CLP + indomethacin augmented TNF-alpha in ascitic fluid compared with CLP at 6 h. CLP + SC-236 gave a lesser degree of mucosal damage compared with CLP alone or with indomethacin at 6 and 24 h (P < 0.05). Untreated CLP had significant reductions in the number of T lymphocytes in the villi and increases of macrophages in the mucosa and MLNs compared with controls (P < 0.05). CLP + indomethacin decreased T lymphocytes in the villi and MLNs. CLP caused an enhanced apoptosis in the mucosa compared with controls (P < 0.05), pretreatment with COX inhibitors did not significantly change this. Both COX inhibitors enhanced apoptosis in MLNs and attenuated the increase of macrophages in mucosa and MLNs (P < 0.05). It is proposed that the increased apoptosis and the decrease in T cells in the mucosa may be causally related. Apoptosis of lymphocytes may impair the immunologic defense in sepsis. Furthermore, loss of intestinal epithelial cells may compromise bowel wall integrity and facilitate translocation.

Therapeutic effects of rectal administration of basic fibroblast growth factor on experimental murine colitis

BACKGROUND & AIMS

Basic fibroblast growth factor (bFGF) is a promising therapeutic agent for various diseases. It remains unclear, however, whether bFGF is effective for the treatment of inflammatory bowel disease. The aim of this study was to examine the efficacy of bFGF on 2 experimental murine colitis models and to investigate its molecular mechanisms.

METHODS

We evaluated the effects of human recombinant bFGF (hrbFGF) on mice with dextran sulfate sodium (DSS)-induced colitis and mice with trinitrobenzene sulfonic acid (TNBS)-induced colitis as well as normal mice. Body weight, survival rate, and histologic findings of the colonic tissues were examined. Gene expression of tumor necrosis factor (TNF)-alpha, cyclooxygenase (COX)-2, transforming growth factor (TGF)-beta, mucin 2 (MUC2), intestinal trefoil factor (ITF), and vascular endothelial growth factor (VEGF) in the colonic tissues was determined. The proliferation activity of hrbFGF on the colonic epithelium was evaluated by immunohistochemistry.

RESULTS

Rectal administration of hrbFGF ameliorated DSS-induced colitis in a dose-dependent manner. Gene expression of TNF-alpha was significantly reduced in the colonic tissues of mice with DSS-induced colitis treated with hrbFGF, whereas MUC2 and ITF messenger RNA expression was up-regulated. Rectal administration of hrbFGF significantly improved the survival rate of mice with TNBS-induced colitis and partially ameliorated colitis. hrbFGF significantly increased the number of Ki-67-positive cells in the colonic epithelium of normal mice, and up-regulated the gene expression of COX-2, TGF-beta, MUC2, ITF, and VEGF in the colonic tissues.

CONCLUSIONS

Rectal administration of bFGF might be a promising option for the treatment of inflammatory bowel disease.

Inhibition of IL-6, TNF-alpha, and cyclooxygenase-2 protein expression by prostaglandin E2-induced IL-10 in bone marrow-derived dendritic cells

Several endogenously produced mediators, including cytokines such as IL-6, IL-10, and TNF-alpha and prostanoids such as prostaglandin E(2) (PGE(2)), regulate dendritic cell (DC) function and contribute to immune homeostasis. In this study, we report that exogenous PGE(2) enhances the production of IL-10 from bone marrow-derived DC (BM-DC). IL-6, but not TNF-alpha, release is enhanced by PGE(2) in the presence of anti-IL-10, suggesting that endogenous IL-10 masks PGE(2)-induced IL-6. Furthermore, both exogenous IL-10 and PGE(2) inhibit LPS-induced IL-6 and TNF-alpha, whereas selective inhibition of cyclooxygenase-2 (COX-2) or addition of anti-IL-10 causes the reverse effects. Exogenous IL-10, but not IL-6, dose-dependently suppresses COX-2 protein expression and PGE(2) production, and TNF-alpha does not reverse this effect. In contrast, anti-IL-10 up-regulates prostanoid production by LPS-stimulated BM-DC. Taken together, our results show that in response to PGE(2), BM-DC produce IL-10, which in turn down-regulates their own production of IL-6-, TNF-alpha-, and COX-2-derived prostanoids, and plays crucial roles in determining the BM-DC pro-inflammatory phenotype.

Insulin receptor substrate-2-dependent interleukin-4 signaling in macrophages is impaired in two models of type 2 diabetes mellitus

We have shown previously that hyperinsulinemia inhibits interferon-alpha-dependent activation of phosphatidylinositol 3-kinase (PI3-kinase) through mammalian target of rapamycin (mTOR)-induced serine phosphorylation of insulin receptor substrate (IRS)-1. Here we report that chronic insulin and high glucose synergistically inhibit interleukin (IL)-4-dependent activation of PI3-kinase in macrophages via the mTOR pathway. Resident peritoneal macrophages (PerMPhis) from diabetic (db/db) mice showed a 44% reduction in IRS-2-associated PI3-kinase activity stimulated by IL-4 compared with PerMPhis from heterozygote (db/+) control mice. IRS-2 from db/db mouse PerMPhis also showed a 78% increase in Ser/Thr-Pro motif phosphorylation without a difference in IRS-2 mass. To investigate the mechanism of this PI3-kinase inhibition, 12-O-tetradecanoylphorbol-13-acetate-matured U937 cells were treated chronically with insulin (1 nm, 18 h) and high glucose (4.5 g/liter, 48 h). In these cells, IL-4-stimulated IRS-2-associated PI3-kinase activity was reduced by 37.5%. Importantly, chronic insulin or high glucose alone did not impact IL-4-activated IRS-2-associated PI3-kinase. Chronic insulin + high glucose did reduce IL-4-dependent IRS-2 tyrosine phosphorylation and p85 association by 54 and 37%, respectively, but did not effect IL-4-activated JAK/STAT signaling. When IRS-2 Ser/Thr-Pro motif phosphorylation was examined, chronic insulin + high glucose resulted in a 92% increase in IRS-2 Ser/Thr-Pro motif phosphorylation without a change in IRS-2 mass. Pretreatment of matured U937 cells with rapamycin blocked chronic insulin + high glucose-dependent IRS-2 Ser/Thr-Pro motif phosphorylation and restored IL-4-dependent IRS-2-associated PI3-kinase activity. Taken together these results indicate that IRS-2-dependent IL-4 signaling in macrophages is impaired in models of type 2 diabetes mellitus through a mechanism that relies on insulin/glucose-dependent Ser/Thr-Pro motif serine phosphorylation mediated by the mTOR pathway.

Prostanoids and MPO–halide system products as a link between innate and adaptive immunity

and The crosstalk between innate adaptive immunity is regulated by cytokines and complex interactions between cells of the immune system. A variety of endogenous agents are involved in the regulation of the cytokine network. Especially, eicosanoids and ROIs have a great impact on the regulation of cytokine production. Eicosanoids (prostanoids, leukotrienes and lipoxins) are produced mainly by inflammatory cells while their receptors are distributed on the cells of both arms of the immune system. Depending on the predominant prostanoid produced and the profile of prostanoid receptors expression on immune cells, eicosanoids can selectively regulate the production of Th1 and Th2 driven cytokines. Inflammatory cells (neutrophils, macrophages), are also a rich source of large amounts of ROIs. In this paper we have focused on the role of taurine chloramine (TauCl), the physiological product of neutrophil MPO-halide system, in the regulation of immune system. It is well documented that TauCl has pleiotropic effects on the inductive phase of the immune response. TauCl's immunoregulatory properties result from its ability to modulate the production of cytokines and eicosanoids. Finally, we conclude that eicosanoids and ROIs provide an important link between the afferent branches and the innate and adaptive immune response.

A novel human fibroblast growth factor treats experimental intestinal inflammation

BACKGROUND & AIMS

We recently identified a novel member of the human fibroblast growth factor (FGF) family of signaling molecules, designated FGF-20. In the present study, we examined the activity of this protein in 2 animal models of acute intestinal inflammation and in mechanistic studies in vitro.

METHODS

In vivo experiments consisted of a murine dextran sulfate sodium (DSS) model of colitis and a rat indomethacin model of small intestinal ulceration/inflammation. Cell growth, restitution, gene expression (cyclooxygenase-2 [COX-2] and intestinal trefoil factor [ITF]), and prostaglandin E2 (PGE2) levels were examined in vitro.

RESULTS

In the DSS-colitis model, prophylactic administration of FGF-20 significantly reduced the severity and extent of mucosal damage as indicated by a 55%-93% reduction in luminal blood loss, distal colonic edema, histologic inflammation, and epithelial cell loss relative to animals administered vehicle control. No toxicity was noted during administration of FGF-20 to normal controls. In addition, therapeutic administration of FGF-20 enhanced survival in this model. In the indomethacin-small bowel ulceration/inflammation model, administration of FGF-20 reduced small intestinal weight gain, necrosis, inflammation, and weight loss (36%-53% relative to vehicle control). In vitro studies demonstrated that FGF-20 stimulates growth, restitution, mRNA expression of COX-2 and ITF, and PGE2 levels in human intestinal epithelial cells and enhances the growth of human intestinal fibroblasts.

CONCLUSIONS

FGF-20, having demonstrated therapeutic activity in 2 experimental models of intestinal inflammation, represents a promising new candidate for the treatment of human inflammatory bowel disease.

Cyclooxygenase 2 pathway mediates IL-1beta regulation of IL-1alpha, -1beta, and IL-6 mRNA levels in Leydig cell progenitors

Prostanoids are arachidonic acid (AA) metabolites derived from the cyclooxygenase (COX1 and COX2 isozymes) pathway and are involved in signal transduction pathways activated by distinct ILs. Although COX1 is the constitutive isoform of COX, IL-1beta is a potent inducer of COX2 expression in distinct cell types. This study was designed to determine whether cyclooxygenases could mediate endogenous cytokine regulation in rat progenitor Leydig cells. COX and IL (IL-1alpha, IL-1beta, and IL-6) mRNAs were measured by PCR and real-time PCR analyses, respectively. COX function was assessed using COX activity inhibitors: indomethacin (INDO; COX1 and COX2 inhibitor) and NS-398 (COX2 selective inhibitor). Our data indicate that endogenous progenitor COX1 mRNA levels are low and are not regulated by IL-1beta. In contrast, COX2 mRNA is induced by IL-1beta at 6, 9, and 24 h. IL-1beta induction of IL mRNAs was in part significantly impaired in the presence of INDO or NS-398. Among the prostanoids tested, prostaglandin E(2) (PGE(2)), PGF(2alpha), and carbaprostacyclin reversed the INDO inhibition of IL production. PGs alone have no (IL-1alpha and IL-1beta) or a modest (IL-6) effect on IL mRNA levels. PGE(2), PGF(2alpha), and PGI(2) measurements show that IL-1beta treatment significantly increases progenitor Leydig cell production of these PGs. Taken together, our data demonstrate that this COX2 cascade is a regulator of cytokines in Leydig progenitors.

Celecoxib, a selective cyclo-oxygenase-2 inhibitor reduces the severity of experimental colitis induced by dinitrobenzene sulfonic acid in rats

Inflammatory bowel disease is characterised by oxidative and nitrosative stress, leukocyte infiltration, upregulation of the expression of intercellular adhesion molecule 1 (ICAM-1) and upregulation of P-selectin in the colon. Here, we investigate the effects of the selective cyclo-oxygenase-2 inhibitor, celecoxib, in rats subjected to experimental colitis. Colitis was induced in rats by intracolonic instillation of dinitrobenzene sulfonic acid (DNBS). Rats experienced hemorrhagic diarrhoea and weight loss. At 4 days after administration of DNBS, the mucosa of the colon exhibited large areas of necrosis. Neutrophil infiltration (determined by histology, as well as an increase in myeloperoxidase activity in the mucosa) was associated with upregulation of ICAM-1 and P-selectin, as well as high tissue levels of malondialdehyde. Immunohistochemistry for nitrotyrosine and poly(ADP-ribose) polymerase showed intense staining in the inflamed colon. Celecoxib (5 mg/kg twice a day orally) significantly reduced the degree of hemorrhagic diarrhoea and the weight loss caused by administration of DNBS. Celecoxib also caused a substantial reduction of (i) the degree of colonic injury, (ii) the rise in myeloperoxidase activity (mucosa), (iii) the increase in the tissue levels of malondialdehyde, (iv) the increase in staining (immunohistochemistry) for nitrotyrosine, as well as (v) the upregulation of ICAM-1 and P-selectin caused by DNBS in the colon. Thus, we provide the first evidence that a selective cyclo-oxygenase-2 inhibitor celecoxib reduces the degree of colitis caused by DNBS.

In vitro cytokine production by mononuclear cells exposed to bone cement extracts

The authors evaluated the ability of bone cement to modify the profile of pro-inflammatory cytokines secreted by the immune cells. Peripheral blood mononuclear cells (PBMC) collected from healthy individuals were cultured with cement extracts and tested to assess the release of IL-1beta, TNFalpha, GM-CSF and IL-6 in both unstimulated and PHA-stimulated PBMC. The cytokine release of unstimulated PBMC was very poor, and in particular the IL-1beta was undetectable: the addition of cement extract increased both TNFalpha and GM-CSF release and decreased IL-6, sometimes significantly. The most recurrent observation in PHA-stimulated PBMCs exposed to bone cement extract was the increase in both IL-1beta and IL-6 release, while both the mean concentration and the index of release of TNFalpha and GM-CSF were changeable. In conclusion our results showed that leachable components of some bone cements can induce in vitro the release of pro-inflammatory cytokines which are known to be involved in the bone resorption associated with aseptic loosening of hip prostheses. These findings allowed us to identify materials endowed with the highest inflammatory power.

Stimulatory effects of dibutyryl cyclic adenosine monophosphate on cytokine production by keratinocytes and fibroblasts

BACKGROUND

Clinical studies have shown that ointment containing dibutyryl cyclic adenosine monophosphate (DBcAMP) promotes wound healing.

OBJECTIVES

We aimed to elucidate the mechanisms of the beneficial effect of DBcAMP in wound healing.

METHODS

An investigation was made of the effects of DBcAMP on in vitro cytokine release from cultured keratinocytes and fibroblasts derived from normal human skin.

RESULTS

DBcAMP stimulated keratinocyte proliferation through increased interleukin (IL)-6 production by fibroblasts, and transiently enhanced production of transforming growth factor (TGF)-beta1 by fibroblasts at an early stage of incubation. DBcAMP also stimulated fibroblast proliferation, resulting in further increases in IL-6 and TGF-beta1.

CONCLUSIONS

We conclude that this series of stimulative actions on cytokine secretion, together with the facilitation of cell proliferation, contribute to the effects of DBcAMP on the healing of skin ulcers.

IFN-gamma inhibits the suppressive effects of PGE2 on the production of tumor necrosis factor-alpha by mouse macrophages

Tumor necrosis factor-alpha (TNF-alpha) has become known as a central mediator of responses to endotoxin, rheumatoid diseases, and other forms of inflammation. Current investigations indicate that the production of TNF-alpha is controlled by other mediators, including interferon-gamma (IFN-gamma) and prostaglandin E2 (PGE2). In the present study, we investigated the regulatory effects of IFN-gamma and/or PGE2 on LPS-induced TNF-alpha production and mRNA expression in mouse peritoneal macrophages using the enzyme immunoassay and Northern blot analysis, respectively. In response to 10 ng/ml of LPS, TNF-alpha production reached a maximum at approximately 4 hrs, followed by rapid decline. At the molecular level, TNF-alpha mRNA accumulated rapidly after LPS exposure, reaching a peak by 3 hr, and declined more rapidly than did the production of TNF-alpha. Exposure of macrophages to 100 U/ml of IFN-gamma caused an increase in both the TNF-alpha production and mRNA expression induced by LPS. Exogenous PGE2 caused a dose dependent reduction in LPS-induced TNF-alpha mRNA accumulation as well as TNF-alpha production. Macrophages primed with IFN-gamma showed the reduced responsiveness to the suppressive effect of PGE2 on the production of TNF-alpha and the accumulation of TNF-alpha mRNA. These findings indicate that the suppressive effects induced by PGE2 on the accumulation of TNF-alpha mRNA as well as the production of TNF-alpha can be reduced by the pretreatment of macrophages with IFN-gamma. These studies demonstrate the role of IFN-gamma as an immunomodulating compound that may effectively regulate TNF-alpha production by modulation of macrophage responsiveness to PGE2.

Regulation of macrophage interleukin-6 (IL-6) and IL-10 expression by prostaglandin E2: the role of p38 mitogen-activated protein kinase

Prostaglandin E2 (PGE2) regulates production of a wide array of cytokines. We have found that PGE2 can upregulate the levels of both interleukin-10 (IL-10) and IL-6 produced by activated murine macrophages, but the molecular pathways leading to their augmentation differ. Synthesis of IL-10 in response to PGE2 is dependent on p38 MAP kinase activity, whereas synthesis of IL-6 is not. Evidence to support this derives from two experimental approaches. First, we established that PGE2 is effective in elevating IL-10 levels only when it is added to cells in which p38 kinase has been activated. In contrast, PGE2 can augment IL-6 levels regardless of whether or not p38 kinase is active. Second, we showed that inhibitors that are selective for p38 kinase prevent the IL-10 response to PGE2 but not the IL-6 response. We found that p38 kinase inhibitors are able to inhibit IL-6 production in activated macrophages, but this occurs primarily as a result of their concurrent inhibition of cyclooxygenase-2 and endogenous PGE2 synthesis. These results indicate that macrophage IL-10 and IL-6 expression is differentially regulated by PGE2 and p38 MAP kinase in murine inflammatory macrophages.

Impaired mucosal defense to acute colonic injury in mice lacking cyclooxygenase-1 or cyclooxygenase-2

To investigate roles in intestinal inflammation for the 2 cyclooxygenase (COX) isoforms, we determined susceptibility to spontaneous and induced acute colitis in mice lacking either the COX-1 or COX-2 isoform. We treated wild-type, COX-1(-/-), COX-2(-/-), and heterozygous mice with dextran sodium sulfate (DSS) to provoke acute colonic inflammation, and we quantified tissue damage, prostaglandin (PG) E(2), and interleukin-1beta. No spontaneous gastrointestinal inflammation was detected in mice homozygous for either mutation, despite almost undetectable basal intestinal PGE(2) production in COX-1(-/-) mice. Both COX-1(-/-) and COX-2(-/-) mice showed increased susceptibility to a low-dose of DSS that caused mild colonic epithelial injury in wild-type mice. COX-2(-/-) mice were more susceptible than COX-1(-/-) mice, and selective pharmacologic blockade of COX-2 potentiated injury in COX-1(-/-) mice. At a high dose, DSS treatment was fatal to 50% of the animals in each mutant group, but all wild-type mice survived. DSS treatment increased PGE(2) intestinal secretion in all groups except COX-2(-/-) mice. These results demonstrate that COX-1 and COX-2 share a crucial role in the defense of the intestinal mucosa (with inducible COX-2 being perhaps more active during inflammation) and that neither isoform is essential in maintaining mucosal homeostasis in the absence of injurious stimuli.

Therapeutic effects of benzoxazinorifamycin KRM-1648 administered alone or in combination with a half-sized secretory leukocyte protease inhibitor or the nonsteroidal anti-inflammatory drug diclofenac sodium against Mycobacterium avium complex infection in mice

The effects of half-sized secretory leukocyte protease inhibitor or diclofenac sodium administered alone or in combination with the benzoxazinorifamycin KRM-1648 on the therapeutic efficacy of KRM-1648 against Mycobacterium avium complex (MAC) in mice were studied. Neither of the two anti-inflammatory drugs affected the efficacy of KRM-1648, while they exerted significant modulating effects on tumor necrosis factor alpha production by MAC-infected macrophages.

Inhibition of the synthesis of eicosanoid-like substances in a human oral cancer cell line by interferon-gamma and eicosapentaenoic acid

The objectives were to examine the production of eicosanoids in a Chinese human oral cancer cell line (OEC-M1) and to test the effects of interferon-gamma (IFN-gamma), eicosapentaenoic acid (EPA) and enzyme inhibitors on this biosynthesis. The eicosanoids were identified by reverse phase-high performance liquid chromatography. Two predominant peaks appeared in the chromatograms. One compound (P-1) was identified by ultraviolet absorption at a lambda(max) of 278nm with shoulders at 272 and 284nm. The other compound (P-2) was identified by ultraviolet absorption at a lambda(max) of 284 nm with shoulders at 278 and 290 nm. The production of P- was significantly inhibited by the addition of IFN-gamma (200 and 400 U/ml), and EPA (10 to 40 microM). It was only partially inhibited (p < 0.05) by indomethacin (INDO) (0.5 and 1 microM), nordihydroguaiaretic acid (NDGA) (30 and 60 microM/ml), and eicosa-5,8,11,14-tetraynoic acid (ETYA) (20-60 microM). It was almost completely inhibited by indomethacin (2 and 3 microM), and dexamethasone (0.6 and 6 microM). The production of P-2 was almost completely inhibited by IFN-gamma (200 and 400 U/ml), and partially inhibited (p < 0.05) by EPA (10 and 20 microM), NDGA (30 and 60 microM), ETYA (20 and 40 microM), dexamethasone (0.6 and 6 microM). The production of both peaks was significantly reduced by excluding arachidonic acid (AA), and almost completely inhibited by heating at 100 degrees C for 10 min during incubation. These results demonstrate that two eicosanoid-like compounds are synthesized by the OEC-M cell line and that their production can be modulated by IFN-gamma, EPA, indomethacin, NDGA, ETYA, and dexamethasone.

Specific NF-kappaB blockade selectively inhibits tumour necrosis factor-alpha-induced COX-2 but not constitutive COX-1 gene expression in HT-29 cells

Cyclo-oxygenase (COX) is the key regulatory enzyme of the prostaglandin/eicosanoid pathway. While COX-1 is mostly constitutively expressed, the COX-2 isoform is inducible by proinflammatory cytokines. We used an adenoviral vector containing an NF-kappaB super-repressor (Ad5IkappaB) to investigate the role of NF-kappaB in tumour necrosis factor-alpha (TNF-alpha)-mediated COX-2 gene expression in a colonic epithelial cell line. COX-1 mRNA and protein were constitutively expressed in uninfected, control Ad5LacZ- or Ad5IkappaB-infected HT-29 cells with no apparent change following TNF-alpha exposure. COX-2 mRNA and protein expression was undetectable in unstimulated cells but was strongly up-regulated after TNF-alpha stimulation in uninfected and Ad5LacZ-infected HT-29 cells. This induction was prevented in Ad5IkappaB cells. TNF-alpha increased prostaglandin E2 production by 20-fold in Ad5LacZ-infected HT-29 cells compared with uninfected cells and was significantly inhibited in Ad5IkappaB-infected cells in agreement with the COX-2 mRNA findings. We conclude that NF-kappaB activation is critical in mediating COX-2, but not COX-1 gene expression in HT-29 cells. Selective inhibition of COX-2 expression with the NF-kappaB super-repressor may be useful in distinguishing the role of inducible versus constitutive prostaglandins in intestinal function and provides greater specificity than pharmacological inhibitors.

Macrophage function in alloxan diabetic mice: expression of adhesion molecules, generation of monokines and oxygen and NO radicals

The increased incidence of bacterial and mycotic infections in poorly controlled diabetic patients or animals is frequently attributed to impaired activities of professional phagocytes (granulocytes, macrophages) in hypoinsulinaemic milieu. We measured production of monokines (IL-6 and tumour necrosis factor-alpha (TNF-alpha)), active NO and reactive oxygen intermediates (ROIs), as well as expression of several cell surface adhesion molecules (Mac-1, -2 and -3, intercellular adhesion molecule-1 (ICAM-1) and Fc gammaRII), by thioglycollate medium-induced peritoneal macrophages of normoglycaemic and alloxan diabetic CBA/J mice (blood glucose level in the range 300 or 500 mg/dl). Macrophages of animals with moderate diabetes (300 mg/dl) produced significantly more IL-6 and TNF-alpha and ROIs than cells of control mice and showed an increased expression of all cell surface molecules, except Mac-3. NO/NO2 production was not affected. Administration of insulin restored enhanced values to normal levels, except for the production of ROIs which remained unusually high. We conclude that two separate mechanisms influence macrophage physiology in diabetes--lack of saturation of insulin receptors on macrophages and an indirect effect due to formation of advanced glycosylation endproducts (AGE) on their surfaces. The latter is possibly responsible for increased generation of ROIs, since it cannot be down-regulated by prolonged insulin treatment. How the increased activity of macrophages of moderately diabetic mice (enhanced production of proinflammatory monokines and oxygen radicals as well as expression of molecules) is related to their ability to kill bacteria is now under investigation.

Role of nitric oxide in depressed lymphoproliferative responses and altered cytokine production following thermal injury in rats

Immunodeficiency follows extensive burns. We investigated some underlying mechanisms in rats, 10 days after a full-thickness skin burn affecting 20% of total body surface area. In both normal and burned rats the splenocyte proliferative response to Con A was linearly and negatively correlated with nitric oxide (NO) production. In all burned rats, the proliferative response was depressed by more than 80% and NO production corresponded to a nitrite concentration above 20 microM. Proliferative responses in burned rats were fully restored in the presence of 250 microM NG-monomethyl-L-arginine (NMMA). A time course study of NO production in response to Con A, LPS, anti-CD3, and IFN-gamma showed that splenic macrophages from burned rats responded to direct and indirect stimuli more rapidly and more intensively than normal macrophages. In the second part of this work, the effect of the overproduction of NO on the synthesis of immunoregulatory and proinflammatory cytokines was investigated. Although it was inhibited, IFN-gamma production by splenocytes from burned rats remained sufficient for NO synthase induction and was restored by NMMA. Concomitantly, IL-2 concentration was enhanced but returned to normal in the presence of NMMA. TNF production was halved after burn injury and NMMA partially restored it. In contrast, IL-6 production was enhanced and increased further in the presence of NMMA. Therefore, cytokines were differently affected by burn injury and variously regulated by NO.

Enhancement of CD4+ T-cell-dependent interleukin-2 production in vitro by murine alveolar macrophages: the role of leukotriene B4

Local tissue macrophages are known to play a key role in regulation of adaptive immune responses, often by inhibition of T-cell activation and proliferation. In this study, we compare the influence of alveolar and peritoneal macrophages on T-cell-dependent interleukin-2 (IL-2) release. Alveolar macrophages, in contrast to peritoneal macrophages, enhance IL-2 release. Assay of a panel of potential macrophage-derived mediators indicated that activated alveolar macrophages stimulated greater release of IL-1 beta, tumour necrosis factor-alpha and, especially, leukotriene B4 (> 100 times) than activated peritoneal macrophages. Inhibition of prostaglandin synthesis by alveolar macrophages further enhanced the production of IL-2, while inhibition of leukotriene synthesis abolished the enhancement. The addition of exogenous prostaglandin E2 inhibited IL-2 release, while exogenous leukotriene B4 enhanced IL-2 release. When added simultaneously, the two compounds antagonized each other's activity. In conclusion, this study confirms that alveolar macrophages enhance IL-2 secretion, and suggests that this enhancement may be due at least in part to the very high rates of production of leukotriene B4. The overall influence of macrophage populations on T cells in vivo will reflect the complex balance between the multiple mediators produced within the local tissue microenvironment.

Differential effects of cyclo-oxygenase pathway metabolites on cytokine production by T lymphocytes

Cyclo-oxygenase pathway metabolites released in the microenvironment by activated platelets and endothelial cells are potential local modulators of the immune response. In the present study, we have investigated the modulatory role of PGE2, iloprost (prostacyclin analogue), U-46619 (thromboxane analogue) on the release of IL-2, IFN-gamma, TNF-alpha and IL-6 by T lymphocytes. Our results show that PGE2 and prostacyclin differ in the regulation of cytokine production. PGE2 inhibited the release of IL-2 and IFN-gamma, while iloprost did not affect their production. The addition of PGE2 or iloprost greatly decreased the amount of TNF-alpha measured in the supernatants, although the rates of inhibition differed according to the kind of stimulation. Unlike that of PGE2, inhibition by iloprost was stronger in alloactivated cultures than in PHA-stimulated ones. In vitro IL-6 production was stimulated by PGE2 in alloactivated cultures and by iloprost, whatever the stimulus. These results are probably due to other cellular subsets contaminating the T-lymphocyte preparations. After complete removal of monocytes from cell cultures, there were inhibitory effects of lloprost and PGE2 on IL-6 released in the supernatants. We did not observe any significant effect of thromboxane analogue on the production of either cytokine.

Repression of inducible nitric oxide synthase and cyclooxygenase-2 by prostaglandin E2 and other cyclic AMP stimulants in J774 macrophages

The enhanced nitric oxide (NO) and prostaglandin (PG) generation of activated macrophages is controlled by glucocorticoid-sensitive inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), respectively. Negative feedback regulation of iNOS expression by the products of both pathways has been suggested, but their effects on COX-2 expression have not been examined. We hae investigated the effect of E- and l-series prostaglandins that activate adenylate cyclase (AC), forskolin (a direct activator of AC), and other agents that influence the cyclicAMP/cyclicGMP systems on the ability of E. coli endotoxin (lipopolysaccharide, LPS) to induce iNOS and COX-2 in the murine macrophage cell line J774. After a 2-hr pretreatment before adding endotoxin, PGE2, PGI2, forskolin, IBMX (isobutylmethylxanthine, a cyclicAMP/cyclicGMP phosphodiesterase inhibitor), 8-bromo cyclicAMP, and arachidonic acid itself all inhibited the expression of both iNOS and COX-2 (as shown by Western blotting) and reduced NO release and COX activity, whereas PGF2 alpha and 8-bromo cyclic GMP were only weakly effective. The effects of PGE2, PGI2, and forskolin were enhanced by cotreatment with IBMX. The suppression of LPS-induced iNOS induction by PGE2 was functionally significant, in that it protected against the mild cytotoxicity of the NO generated in response to endotoxin. These results provide the first direct evidence for the feedback regulatory suppression of COX-2 induction by a PG-driven cAMP-mediated process, and show that the modulation of iNOS and COX-2 induction shares common features. They also suggest that such modulation is normally held in check by high phosphodiesterase activity within these cells.

Staphylococcal exoproducts down-regulate cyclooxygenase 1 and 2 in peritoneal macrophages

Peritoneal macrophages (PMOs) are important components of the host defense against microbial infection in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Incubation of human PMOs with cell-free supernatant (BFS), prepared from Staphylococcus aureus, inhibited prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) production. Slot-blot analysis of cyclooxygenase-1 (Cox-1) and Cox-2 demonstrated a decrease in both Cox-1 (29%) and, to a greater extent, Cox-2 (65%) protein expression after BFS stimulation. When competitive polymerase chain reaction (PCR) was used, the peak levels of Cox-1 and Cox-2 messenger ribonucleic acid (mRNA) in unstimulated PMOs were 0.304+/-0.13 pmol/L and 9.61+/-2.84 pmol/L (mean+/-SEM, n = 3), respectively. After exposure of samples to BFS for 30 minutes, the level of Cox-2 mRNA was reduced to 0.59+/-0.449 pmol/L (16-fold reduction, p < 0.05), and the level of Cox-1 mRNA was reduced to 0.02+/-0.002 pmol/L (15-fold reduction, p < 0.05). In contrast, these same PMOs showed an increased expression of IL-6 mRNA and increased secretion of IL-6 protein. These results indicate that prostaglandin production in PMOs is regulated by alterations in both immunoreactive Cox-1 and Cox-2. The down-regulation of Cox metabolism in these cells is primarily related to the delayed and depressed increase in the Cox-2 gene product.

The in vivo and in vitro effects of an alkylating agent, mechlorethamine, on IL-6 production in mice and the role of macrophages

Alkylating agents, cyclophosphamide (CY) and the related compound mechlorethamine (NM), significantly increase in vivo the blood level of IL-6 but not of IL-1. Since in vitro CY is inactive we have used in our experiments NM, a compound structurally and functionally related to phosphoramide mustard, the natural biologically active metabolite of CY. Thioglycollate or oil-induced peritonal macrophages (Mf) of four different mouse strains treated with NM produce significantly more IL-6 than the non-treated cells. In contrast, under these conditions, the production of IL-1, TNF alpha and NO/NO2 radicals is not affected. The NM-induced elevated production of IL-6 by Mf could not be further increased by the treatment of cells with LPS, which may suggest that both agonists stimulate the same signalling pathway. The antineoplastic activity of the alkylating agents like CY or NM is usually attributed to the interstrand cross-linking of the DNA of the dividing cells. Our experiments can be tentatively interpreted as the induced overplus of IL-6 can also contribute to the stimulation of the cytotoxic NK-cells.

Prostaglandin I1 analogues, SM-10902 and SM-10906, affect human keratinocytes and fibroblasts in vitro in a manner similar to PGE1: therapeutic potential for wound healing

The newly synthesized prostaglandin (PG) I1 analogues, SM-10902 and SM-10906, were compared with PGE1 in terms of their biological effects on cultured normal human keratinocytes (NHKs) and human dermal fibroblasts (HDFs) in order to evaluate their therapeutic potential for cutaneous wound healing. The PGI1 analogues had a direct effect on cell proliferation of HDFs as did PGE1, but inhibited cell growth of NHKs in contrast to the stimulatory effect observed with PGE1. In contrast to NHKs stimulated with PGI1 analogues, which exhibited low levels of adenosine 3,5-cyclic monophosphate (cAMP). HDFs stimulated with these analogues responded in a dose-dependent manner with extremely high levels of cAMP. Conditioned media (CM) derived from media in which HDFs had been incubated with both the PGI1 analogues promoted NHK proliferation. HDF production of interleukin (IL)-6 increased in response to the PGI1 analogues. Since IL-6 was shown to promote cell growth of NHKs, enhancement of NHK proliferation by CM was thought to be due to IL-6 derived from HDFs stimulated with the PGI1 analogues.

Nitric oxide up-regulates the release of inflammatory mediators by mouse macrophages

Nitric oxide (NO) plays a key role in mediating macrophage cytotoxicity towards different targets, including tumoral cells and intracellular pathogens. However, its role in macrophage immunoregulation is less well defined. In this study, we have investigated the effect of altering NO levels on the production by mouse macrophages of cytokines, and reactive oxygen intermediates as measured by luminol-dependent chemiluminescence. Our results demonstrate that NO can enhance the release of both tumor necrosis factor-alpha and interleukin-1 alpha, and chemiluminescence. Thus, in addition to acting as a powerful effector molecule in mediating cytotoxic activities of mouse macrophages, NO can play a role in enhancing the production of a variety of other inflammatory mediators, and thus can contribute both directly and indirectly to the immunopathology of macrophage-dependent inflammation.

Modulation by nitric oxide of prostaglandin biosynthesis in the rat

1. Modulation of prostaglandin biosynthesis in vivo by either exogenous or endogenous nitric oxide (NO) has been studied in the rat using arachidonic acid (AA)-induced paw oedema and measuring both the foot volume and the amount of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), the stable metabolite of prostacyclin (PGI2), in the oedematous fluid recovered from inflamed paws. 2. Paw injections of 150 or 300 nmol of AA were virtually inactive whereas 600 nmol produced a moderate oedema which was greatly reduced by the NO synthase inhibitor L-NG-nitro arginine methyl ester (L-NAME, 100 nmol/paw) and the NO scavenger haemoglobin (Hb, 30 mumol/paw), but unaffected by the inhibitor of the soluble guanylate cyclase, methylene blue (Mb, 3 mumol/paw) and L-arginine (15 mumol/paw). 3. The NO-donors (10 mumol/paw) 3-morpholino-sydnonimine-hydrochloride (SIN-1), S-nitroso-N-acetyl-D, L-penicillamine (SNAP) and sodium nitroprusside (SNP) significantly potentiated the paw oedema induced by AA (300 nmol/paw). 4. SIN-1 (2.5, 5 and 10 mumol/paw) produced a significant dose-dependent increase of the oedema induced by AA which was correlated with increased amounts of 6-keto-PGF1 alpha in the fluid recovered from inflamed paws. 5. Both oedema and prostaglandin biosynthesis induced by the combination AA+SIN-1 were greatly suppressed by either Hb (30 mumol/paw) or indomethacin (3 mumol/paw or 5 mg kg-1 s.c.) but unaffected by Mb (3 mumol/paw). 6. In LPS-treated rats (6 mg kg-1, i.p.) doses of AA inactive in normal animals produced a remarkable oedema which was reduced by L-NAME or Hb, unaffected by Mb and increased by L-arginine.7. These results demonstrate that NO increases prostaglandin biosynthesis in vivo through a guanosine 3': 5'-cyclic monophosphate (cyclic GMP)-independent mechanism and suggest that the interaction between NO synthase and cyclo-oxygenase (COX) pathways may represent an important mechanism for the modulation of the inflammatory response.

Role of 5'-lipoxygenase metabolites in the activation of peritoneal macrophages for tumoricidal function

Metabolites of arachidonic acid have been shown to be potent biological modulators of macrophage function. While the role of cyclooxygenase metabolites of arachidonic acid have been well studied, metabolites of lipoxygenase have not. In this report, we evaluate the role that select 5'-lipoxygenase (5'-LO) products may play in macrophage activation for select tumoricidal functions. When thioglycollate-elicited macrophages were treated with inhibitors of 5'-LO during activation, cytolytic capacity, nitric oxide production, and tumor necrosis factor-alpha production were significantly inhibited. Moreover, both an inhibitor of the 5'-LO-activating protein and an inhibitor of glutathione-s-transferase (GST) significantly decreased macrophage tumoricidal function. The activating agents used were able to stimulate 5'-LO activity which was measured by quantitating secreted LTC4. Increased production of PGE2 by shunting could have been the cause for decreased macrophage tumoricidal function. However, treatment of macrophages with inhibitors of 5'-LO during lipopolysaccharide stimulation did not increase formation of PGE2. When select 5'-LO metabolites were added to cultures during activation and 5'-LO inhibition, tumoricidal activity could not be restored, even when the metabolites were encapsulated in liposomes. These results suggest that the activity of 5'-LO and GST are important for macrophage activation. However, the specific role of 5'-LO metabolites has not been completely established.

Cyclophosphamide uncovers two separate macrophage subpopulations with opposite immunogenic potential and different patterns of monokine production

As shown previously, thioglycollate-induced peritoneal macrophages consist of two subpopulations which differ morphologically and functionally. When tagged with trinitrophenyl hapten (TNP), one macrophage subpopulation induced in vivo effector cells (Th1) of contact sensitivity (CS) reaction, while the other induced suppressor T cells (Ts) which inhibit CS and are highly sensitive to the in vivo action of cyclophosphamide (CY). Our present experiments show that CY-resistant (Th inducers) and CY-sensitive macrophages (Ts inducers) differ also in the spectrum of biologically relevant molecules which they secrete when stimulated by LPS. Thus macrophages which preferentially induce Th1 cells have a cytokine pattern IL-1LOW, IL-6HIGH, TNF-alpha LOW, while macrophages which recruit Ts cells are IL-1HIGH, IL-6LOW, TNF-alpha HIGH. TH1 inducers produced also somewhat better PGE2 then Ts inducers. Production of reactive nitrogen intermediates (NO/NO2-) was similar in both groups of macrophages. The reasons for the differential effect of CY on these two populations is not clear at present, although it is known that CY metabolites can bind to sulfhydryl groups on antigen presenting cells (APC) and thereby up- or downregulate the antigen presenting capacities of separate subpopulations of APC.

Effects of prostaglandin E1 on human keratinocytes and dermal fibroblasts: a possible mechanism for the healing of skin ulcers

The effects of prostaglandin E1 (PGE1) on cell growth, cytokine production and interaction of cultured normal human keratinocytes (NHKs) and human dermal fibroblasts (HDFs) were investigated. When NHKs were treated with PGE1 directly, only a slight increase in cell growth and a transient decrease in interleukin 1 alpha (IL-1 alpha) secretion were observed. No IL-6 was detected either before or after PGE1 treatment. In addition, IL-8 and transforming growth factor alpha (TGF alpha) production were uninfluenced by PGE1. The response of HDFs to PGE1 differed from that of NHKs. Following PGE1 treatment, IL-1 alpha and TGF alpha from HDFs remained undetectable while IL-6 production was enhanced markedly. IL-8 production was also slightly enhanced. Exposure of HDFs to PGE1 for 96 hours significantly promoted cell proliferation. Two kinds of conditioned media (CM) were prepared by a brief feeding of HDFs with keratinocyte basic medium or Dulbecco's modified Eagle's medium supplemented with 5% FCS with or without PGE1. NHKs proliferated more rapidly in CM than in corresponding basic medium. Moreover, CM prepared with PGE1 treatment showed a stronger effect in promoting NHK proliferation than CM without PGE1 treatment. This promoting effect was inhibited by anti-human IL-6 monoclonal antibody dose-dependently. These results indicate that fibroblasts are more sensitive than keratinocytes in response to PGE1 and that, upon PGE1 stimulation, HDF-derived IL-6 may play an essential role in NHK cell proliferation which may at least partly account for the beneficial effects of PGE1 in the treatment of cutaneous ulcerations.

Up-regulation of cytokine production in alveolar macrophages by histogranin, a novel endogenous pentadecapeptide

Recently, histogranin (HN), a newly found pentadecapeptide, was shown to enhance tumor necrosis factor (TNF) production by alveolar macrophages (AM). In this study, we have investigated whether HN was present in tissues rich with immune cells and further explored the effect of HN and [Ser1]HN on the production of TNF and other key cytokines. Relatively high levels of immunoreactive (ir)-HN were found in rat lung (14.9 pmol/g) and spleen (12.3 pmol/g), indicating its localization in close proximity to macrophages/monocytes and lymphocytes. Furthermore, HN and [Ser1]HN (10(-8)-10(-7) M) stimulated basal and lipopolysaccharide (LPS)-induced interleukin 1 (IL-1) mRNA expression and IL-1 release from rat AM. [Ser1]HN also stimulated basal and LPS-induced interleukin-6 (IL-6) release. Although HN did not affect the kinetics of cytokine production, the maximal enhancing effect of HN was seen at 3 h for TNF, 6 h for IL-1 and 18 h for IL-6. These data indicate that HN can up-regulate a cytokine cascade involving TNF, IL-1 and IL-6 and suggest a role for this endogenous peptide in immune regulation.

Prostaglandin E2 stimulates the production of interleukin-6 by neonatal mouse parietal bones

The pleiotropic cytokine interleukin-6 (IL-6) is thought to be involved in bone homeostasis. A number of bone resorbing agents have been shown to induce the release of IL-6 from bone. We wished to determine whether prostaglandin E2 (PGE2), which is a mediator of bone resorption, can elicit the production of IL-6. IL-6 was measured by the proliferative response of B9 hybridoma cells and could be completely neutralised by an anti-IL-6 antibody. Parietal bones from neonatal mice were maintained in culture in the presence of indomethacin (10(-6) M) with or without PGE2. The time course and dose-response to PGE2 of IL-6 production were determined. After 6 h in culture, 10(-8) M PGE2 produced significantly more IL-6 than the controls (P < 0.005). PGE2 (10(-6) M) stimulated the production of a mean of 12.8 ng/ml IL-6 over 6 h. Preincubating bones with indomethacin for 20 h prior to a 6 h culture with indomethacin led to a lowering of the production of IL-6 (mean 1.8 ng/ml) compared to bones cultured without the preincubation period (5.8 ng/ml). When the indomethacin preincubation period was used, a significant increase in IL-6 production was found with 10(-9) M PGE2 (P < 0.005), and 10(-6) M PGE2 caused the production of 39.9 ng/ml IL-6 over 6 h. Stripping endocranial and ectocranial membranes from bones demonstrated the membranes to be the major site of IL-6 production. However, intact bones were required for maximal stimulated IL-6 production.

Production of cytokines and PGE2 and cytotoxicity of stimulated bone marrow macrophages after thermal injury and cytotoxicity of stimulated U-937 macrophages

Bone marrow-derived macrophages from normal and burned rats were cultured for one and four days in the presence of LPS, PHA, or opsonized zymosan as activators, and the supernatants were assayed for the inflammatory mediators TNF, IL-6, and PGE2 and the cells assayed for cytotoxicity. The macrophages responded differently to the various stimuli regarding cytotoxicity and the production of mediators, perhaps implicating the complement receptor CR1 in TNF production and the LPS receptor CD14 or the PHA lectin receptor in IL-6 and PGE2 production and for cytotoxicity. The response of the cells also depended on culture time and postburn time; in addition, macrophages from burned and unburned animals responded differently, depending on postburn day and the type of stimulus. TNF production was generally higher for one-day compared to four-day cultures (i.e., TNF was disappearing in the cultures), but IL-6 and PGE2 production was greater in four-day cultures. The results of this study suggest that thermal injury can contribute to the development of inflammatory and cytotoxic macrophages from bone marrow progenitor cells.

In vitro interleukin-1 and tumor necrosis factor-alpha production by macrophages from chickens infected with either Eimeria maxima or Eimeria tenella

We measured the in vitro production of interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF- ) by macrophages from chickens during and immediately following an infection with one of two different species of Eimeria, E. maxima and E. tenella. Quantitatively, the amounts of IL-1 produced during each infection were nearly identical regardless of the oocyst dose of each parasite. TNF production followed a biphasic pattern of increased production with the first peak associated with the pathogenesis of disease and the second peak associated with the development of protective immunity. These experiments together with others we have reported imply cells taken from chickens infected with coccidia have a greater capacity to produce cytokines upon stimulation in vitro than cells from non-infected birds. The production of significantly greater amounts of TNF during the days 3-6 after inoculation correlates with the appearance of the most characteristic local and systemic pathophysiological changes in the host induced by the coccidia. The excessive release of TNF in response to a heavy coccidial infection may account for many of the pathological features observed with avian coccidiosis probably through the release of other mediators.

Aging and eliciting agents: effect on murine peritoneal macrophage monokine bioactivity

Decreased responsiveness of the aged to infection may be associated with a decline in monokine production. Prior studies in macrophages have used different eliciting agents, and results have varied. We assessed the effect of age on interleukin-1 (IL-1), tumor necrosis factor (TNF), and interleukin-6 (IL-6) in unelicited, thioglycollate (TG)-elicited, and complete Freund's adjuvant (CFA)-elicited peritoneal macrophages. Resident macrophages or CFA-elicited macrophages from middle aged or aged mice produced significantly less monokine bioactivity than resident or CFA-elicited macrophages from young mice. Monokine bioactivity from TG-elicited macrophages from aged and middle aged mice was significantly increased when compared with macrophages of young mice. Eliciting agents may alter macrophage populations and interactions with other cells leading to changes in monokine bioactivity with aging.

RP 54745, a potential antirheumatic compound. II. In vivo properties in different animal models

The results obtained with RP 54745, an amino-dithiole-one compound, on stimulated macrophages, revealing inhibition of the hexose monophosphate pathway (HMP), of the exocytosis of lysosomal enzymes and of the production of interleukin-1 (IL-1), by the compound in vitro as well as in vivo, suggested that RP 5475 might influence cells and cytokines implicated in the regulation of the immune system, the disfunctioning of which can lead to inflammatory disorders or autoimmune pathologies. RP 54745 was effective at moderate oral doses (around 5 mg kg-1) in different mouse models of induced arthritis and in the MRL/lpr mice, genetically predisposed to develop an autoimmune pathology including arthritic disorders. The clinical status of the MRL mice, and several of their disturbed biochemical and immunological parameters, improved after a 3-month treatment with RP 54745. This activity of RP 54745 makes it a very attractive antirheumatic compound and a potentially effective treatment in pathologies where IL-1 production is exacerbated.