Immunomodulatory-antiinflammatory functions of E-type prostaglandins. Minireview with emphasis on macrophage-mediated effects

Morphological Findings in Trophozoites during Amoebic Abscess Development in Misoprostol-Treated BALB/c Mice

During amoebic liver abscess (ALA) formation in susceptible animals, immune response is regulated by prostaglandin E₂ (PGE₂) dependent mechanisms. The aim of this study was to analyze the effect of misoprostol (MPL), a PGE₁ analogue, on ALA formation in BALB/c mice. Male mice from BALB/c strain were intrahepatically infected with 7.5 × 10⁵ trophozoites of E. histolytica strain HM1:IMSS and treated with 10⁻⁴ M of MPL daily until sacrifice at 2, 4, and 7 days postinfection (p.i.). ALA formation was evaluated at 2, 4, and 7 days postinfection; trophozoite morphology was analyzed using immunohistochemistry and image analysis. Results showed an increase in frequency of ALA formation in infected and MPL-treated mice only at 2 days p.i. (P = 0.03). A significant diminution in the size of trophozoites was detected in abscesses from mice independently of MPL treatment (from 5.8 ± 1.1 µm at 2 days p.i. to 2.7 ± 1.9 µm at 7 days p.i.) compared with trophozoites dimensions observed in susceptible hamsters (9.6 ± 2.7 µm) (P < 0.01). These results suggest that MPL treatment may modify the adequate control of inflammatory process to allow the persistence of trophozoites in the liver; however, natural resistance mechanisms cannot be discarded.

Phosphodiesterase 4 inhibitor GPD-1116 markedly attenuates the development of cigarette smoke-induced emphysema in senescence-accelerated mice P1 strain

Phosphodiesterase 4 (PDE4) is an intracellular enzyme specifically degrading cAMP, a second messenger exerting inhibitory effects on many inflammatory cells. To investigate whether GPD-1116 (a PDE4 inhibitor) prevents murine lungs from developing cigarette smoke-induced emphysema, the senescence-accelerated mouse (SAM) P1 strain was exposed to either fresh air or cigarette smoke for 8 wk with or without oral administration of GPD-1116. We confirmed the development of smoke-induced emphysema in SAMP1 [air vs. smoke (means +/- SE); the mean linear intercepts (MLI), 52.9 +/- 0.8 vs. 68.4 +/- 4.2 microm, P < 0.05, and destructive index (DI), 4.5% +/- 1.3% vs. 16.0% +/- 0.4%, P < 0.01]. Emphysema was markedly attenuated by GPD-1116 (MLI = 57.0 +/- 1.4 microm, P < 0.05; DI = 8.2% +/- 0.6%, P < 0.01) compared with smoke-exposed SAMP1 without GPD-1116. Smoke-induced apoptosis of lung cells were also reduced by administration of GPD-1116. Matrix metalloproteinase (MMP)-12 activity in bronchoalveolar lavage fluid (BALF) was increased by smoke exposure (air vs. smoke, 4.1 +/- 1.1 vs. 40.5 +/- 16.2 area/microg protein; P < 0.05), but GPD-1116 significantly decreased MMP-12 activity in smoke-exposed mice (5.3 +/- 2.1 area/microg protein). However, VEGF content in lung tissues and BALF decreased after smoke exposure, and the decrease was not markedly restored by oral administration of GPD-1116. Our study suggests that GPD-1116 attenuates smoke-induced emphysema by inhibiting the increase of smoke-induced MMP-12 activity and protecting lung cells from apoptosis, but is not likely to alleviate cigarette smoke-induced decrease of VEGF in SAMP1 lungs.

Postoperative serum attenuates LPS-induced release of TNF-alpha in orthopaedic surgery

Studies with ex vivo stimulation of whole blood samples from injured patients have revealed a diminished production capacity for a broad range of secretory products, including inflammatory cytokines. Recent interest has focused on the release of mediators in serum that depress the cell-mediated immune response following trauma. The involvement of the lipid mediator prostaglandin E2 (PGE2) has been assumed because it is a potent endogenous immunosuppressor. In the present study, we tested the hypothesis that inhibitory substances circulating in the patient's serum after a major musculoskeletal trauma might impair leukocyte function by evaluating the effect of such serum on cytokine release in a whole blood model. Six females and three males undergoing elective total hip replacement were included in the study. Ex vivo LPS-induced TNF-alpha and IL-10 were measured in whole blood sampled preoperatively and added serum taken before, at the end of operation, and at postoperative days 1 and 6 with saline as negative control. LPS induced significant releases of TNF-alpha and IL-10 in whole blood. Addition of preoperative, postoperative, and day-1 postoperative serum did not alter the LPS-induced release of TNF-alpha as compared to saline. In the presence of serum from postoperative day 6, however, the expression of TNF-alpha was significantly reduced as compared to saline and preoperative serum (p = 0.021 and 0.008, respectively). Neither of the serum samples altered the release of IL-10. PGE2 was significantly (p = 0.008) increased in serum at postoperative day 6 as compared to preoperative levels. In conclusion, these data show that at day 6 after major orthopaedic surgery, the patient serum contained activity that inhibited ex vivo LPS-induced TNF-alpha release. The potent TNF-alpha inhibitory activity found at day 6 after injury correlated with increased levels of PGE2 and indicates cell-mediated hyporesponsiveness to a second stimulus.

Molecular Analysis of Inflammatory Markers in Trauma Patients at Risk of Postinjury Complications

BACKGROUND

Genetic differences associated with individual's immune responses appear to be a major contributing factor to the development of trauma- induced sepsis. Thus, effective treatment of sepsis requires the identification of the patients who are at increased risk for sepsis.

METHODS

Sixty-eight patients, of which the majority had an injury severity score >15, and 118 controls from the same geographic region were genotyped. Cytokine and Toll-like receptor (TLR) genotypes and expressions were tested using polymerase chain reaction (PCR).

RESULTS

Fifty percent of African American and 42% of Caucasian patients developed posttrauma sepsis. Frequency distribution of the polymorphism for some cytokine genes such as Interleukin (IL)-10 low/high and interferon (IFN)-gamma low producer were statistically different between the septic and aseptic patients, for others, such as tumor necrosis factor (TNF)-alpha, IL-6, and IL-18, there was no statistical difference. The TLR-2 genotypes (A/G) were considered a sepsis risk marker as compared with A/A (62.5% versus 37.5%, p < 0.03; relative risk = 2.5) in African American patients. Cytokine mRNA levels correlated with genotype definition, particularly, for IL-10, IL-6, IL-18, and TNF-alpha. A time course study demonstrated a significant difference in cytokines expression profile in septic and aseptic patients before the development of sepsis.

CONCLUSION

Monitoring cytokine expression levels before the disease might predict the outcome of sepsis. A large cohort study is needed to assess the diagnostic potential of the genotypes.

Eicosanoids: mediators and therapeutic targets in fibrotic lung disease

Fibrosis is a common end-stage sequella of a number of acute and chronic lung diseases. Current concepts of pathogenesis implicate dysregulated interactions between epithelial cells and mesenchymal cells. Although investigative efforts have documented important roles for cytokines and growth factors in the pathogenesis of fibrotic lung diseases, these observations have not as yet been translated into efficacious therapies, and there is a pressing need for new pathogenetic insights and therapeutic approaches for these devastating disorders. Eicosanoids are lipid mediators derived from arachidonic acid, the most studied of which are the prostaglandins and leukotrienes. Although they are primarily known for their roles in asthma, pain, fever and vascular responses, present evidence indicates that eicosanoids exert relevant effects on immune/inflammatory, as well as structural, cells pertinent to fibrogenesis. In general, leukotrienes promote, whereas prostaglandin E(2) opposes, fibrogenic responses. An imbalance of eicosanoids also exists in pulmonary fibrosis, which favours the production of leukotrienes over prostaglandin E(2). This review highlights the role of this imbalance in the evolution of fibrotic lung disease, discusses the mechanisms by which it may arise and considers approaches for therapeutic targeting of eicosanoids in these conditions.

Clinical review: immunodepression in the surgical patient and increased susceptibility to infection

Several studies indicate that organ failure is the leading cause of death in surgical patients. An excessive inflammatory response followed by a dramatic paralysis of cell-mediated immunity following major surgery appears to be responsible for the increased susceptibility to subsequent sepsis. In view of this, most of the scientific and medical research has been directed towards measuring the progression and inter-relationship of mediators following major surgery. Furthermore, the effect of those mediators on cell-mediated immune responses has been studied. This article will focus on the effect of blood loss and surgical injury on cell-mediated immune responses in experimental studies utilizing models of trauma and hemorrhagic shock, which have defined effects on the immunoinflammatory response. Subsequently these findings will be correlated with data generated from surgical patients. The results of these studies may generate new approaches for the treatment of immunodepression following major surgery, thus reducing the susceptibility to infection and increasing the survival rate of the critical ill surgical patient.

Altered expression and localization of 5-lipoxygenase accompany macrophage differentiation in the lung

The alveolar macrophage (AM) exhibits a greater capacity to synthesize bioactive leukotrienes from arachidonic acid than does its circulating precursor the peripheral blood monocyte. Macrophage differentiation in the lung entails cellular residence within both the pulmonary interstitial and alveolar compartments. In the present study, we sought to determine 1) whether this enhanced metabolic activity was acquired during maturation within the alveolar space and 2) the underlying mechanisms responsible for this upregulation. Rat AMs were separated by Percoll gradient centrifugation into four density-defined subpopulations thought to reflect their degree of maturation. On stimulation with a calcium ionophore, synthesis of leukotriene B4 increased with the degree of maturation, although it was diminished in the oldest subpopulation. This maturation-dependent upregulation was not explained by increases in arachidonic acid release but was associated with increased expression of 5-lipoxygenase (5-LO) protein as determined by immunoblot analysis. Whereas 5-LO is primarily cytosolic in monocytes, it is known to be primarily intranuclear in unfractionated AMs. Here, the localization of 5-LO was investigated by immunofluorescence microscopy and was found to be predominantly nuclear in all AM subpopulations; by contrast, the protein was cytosolic in interstitial macrophages isolated by mechanical and enzymatic lung digestion. These divergent localization patterns in AMs and interstitial macrophages were verified in situ by immunohistochemical staining of sections of normal rat lung. When unfractionated AMs were isolated and maintained in culture for 3 days, a shift in 5-LO distribution from nucleus to cytosol was observed. We conclude that 1) nuclear import of 5-LO occurs within the alveolar space and is reversible on removal from the alveolar milieu and 2) leukotriene synthetic capacity increases further during AM residence within the alveolar space as a result of a progressive increase in the amount of 5-LO protein.

IL-17 Stimulates the Production and Expression of Proinflammatory Cytokines, IL-β and TNF-α, by Human Macrophages

IL-17 is a newly described, T cell-derived cytokine with ill-defined physiologic properties. As such, we examined the release of proinflammatory mediators by human macrophages in response to recombinant human (rh) IL-17. IL-1β and TNF-α expression and synthesis were up-regulated by rhIL-17 in a dose (ED50 was 50 ± 9 ng/ml)- and time-dependent fashion, with cytokine accumulation reaching a zenith after 9 h. Release of IL-6, PGE2, IL-10, IL-12, IL-1R antagonist, and stromelysin was also stimulated by rhIL-17. IL-1β and TNF-α mRNA expression levels were controlled by rhIL-17 in a complex manner with an initial 30-min inhibitory phase, and then up-regulation beginning at 1 h and reaching a plateau at about 3 h. The latter expression pattern closely mirrored the nuclear accumulation of the transcription factor nuclear factor-κB. cAMP mimetics isobutyl-1-methylxanthine (IBMX), forskolin, PGE2, and cholera toxin reversed rhIL-17-induced release of TNF-α, but had no consistent effect on induced IL-1β synthesis. Induced release of TNF-α was also inhibited by serine/threonine protein kinase inhibitors KT-5720 (protein kinase A) and Calphostin C (protein kinase C), mitogen-activated protein kinase kinase inhibitor PD098059, and a nonspecific tyrosine kinase inhibitor, genistein. Calphostin C alone abrogated the rhIL-17-induced release of IL-1β. The antiinflammatory cytokines IL-4 (p &lt; 0.01) and IL-10 (p &lt; 0.02) completely reversed rhIL-17-stimulated IL-1β release, while IL-13 and TGF-β2 were partially effective (59 and 43% diminution, respectively). IL-10 exerted a significant suppressive effect on IL-17-induced TNF-α release (99%, p &lt; 0.02), while the inhibitory effects of IL-4, IL-13, and TGF-β2 on TNF-α secretion were partial (48, 10, and 23%, respectively). The data suggest a pivotal role for IL-17 in initiating and/or sustaining an inflammatory response.

Role of prostaglandin E2 on amoebic liver abscess formation in hamsters

Entamoeba histolytica can modulate macrophage functions and cytokine production by a prostaglandin E2 (PGE2) mechanism. To study the participation of PGE2 on amoebic liver abscess formation, we tested the effect of the PG synthesis inhibitor indomethacin (INDO) on abscess development in hamsters infected intrahepatically with E. histolytica trophozoites. Male infected animals had higher levels of plasma PGE2 (5.7 +/- 0.7 pg/ml pre-infection; 26.0 +/- 2.0 pg/ml 7 days postinfection; p < 0.001). INDO prevented this increase, so that infected-treated and control non-infected animals had similar levels of plasma PGE2. INDO reduced liver and abscess weight by 18% and 30% respectively (p < 0.05). Cyclooxygenase (COX) activity determination by thin layer chromatography using (1-14C) arachidonic acid (AA) showed that liver microsomes from infected animals produced more PGE2 than controls. COX activity was considerably inhibited in infected INDO-treated animals. Our data suggest that E. histolytica can stimulate the hepatic production of PGE2 which contributes to pathogenesis of amoebic abscesses through generation and support of the inflammation. The partial effect of INDO treatment suggests that additional factors are involved.

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.

Reduction of circulating prostaglandin E2 level by antiserum against core lipopolysaccharide in a rabbit model of multiple organ failure

OBJECTIVE

To determine the potential role of prostaglandin E2 (PGE2) in the development of multiple organ dysfunction or failure (MOF), the possible effects of antiserum directed against Re chemotype lipopolysaccharide (LPS, from Re mutant of Escherichia coli F515) on circulating PGE2 level and survival rate, and whether there is an elevation in the plasma LPS concentration that could account for the induction of arachidonic acid metabolite in a rabbit model of MOF caused by acute hypovolemic insult.

DESIGN, MATERIALS, AND METHODS

An animal model of MOF in rabbits, engendered by feeding live Escherichia coli O111:B4 before hemorrhagic shock (35-40 mm Hg for 60 min), was used in the present study. Re-LPS antiserum was given intravenously in the treatment group at the onset of hemorrhage and 4 hours after resuscitation. The animals that received equal volumes of normal rabbit serum and antiserum served as the control group.

MEASUREMENTS AND MAIN RESULTS

The circulating PGE2 level was not increased at the end of shock (p > 0.05), but it was found to be significantly elevated 24 hours after hemorrhage and resuscitation in both groups. However, Re-LPS antiserum administration markedly decreased peak PGE2 level (p < 0.05) and attenuated multiple organ damage caused by acute insult. Concomitantly, there were also lower LPS concentrations in the treatment group as compared with the control group (p < 0.05-0.01). The survival rate was significantly increased in antiserum-treated rabbits 96 hours postinjury (treatment vs. control: 58.0% vs. 11.1%, p < 0.01).

CONCLUSIONS

The results suggest that an excessive generation and release of PGE2 may be involved in the pathogenesis of immunosuppression and MOF following hemorrhage and resuscitation. Re-LPS antiserum has an inhibitory effect on overproduction of circulating PGE2 and the ability to improve survival with MOF. Gut-derived endotoxemia, bacterial translocation, or both, could account, at least in part, for the PGE2 formation and release in animals response to acute hypovolemic insult.

Patterns of prostaglandin E2 and leukotriene B4 production in inflammation induced by peptidoglycan-polysaccharide polymers of bacterial cell walls

The changing levels of prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) were compared over a period of 1 h to 15 days in two kinds of inflammatory responses induced in the rat air pouch by chemically similar polymers of peptidoglycan-polysaccharide (PG-PS) isolated from cell walls of group A streptococci. The smaller polymers (100 s, average mol. wt 5.3 x 10(6)) induced a more severe acute response over the first 24 h, whereas, from 3 to 15 days the larger polymers (10 p, average mol. wt 5 x 10(8)) induced greater chronic inflammation, as measured by pouch fluid volume, number of infiltrating cells and weight of granulation tissue. The most prominent difference between the two kinds of responses in the pattern of PGE2 and LTB4 were: (a) A shift between 1 to 6 h to much higher production of PGE2 in the exudate induced by large polymers. During this time the level of LTB4 also increased, but continued to be higher in the exudate induced by small polymers. (b) The sustained production of relatively high levels of LTB4 and PGE2 in the large polymer exudate at 15 days. Changes such as these indicate that this model is useful for analyzing mediators which regulate the evolution of acute into chronic inflammation.

Eicosanoids mediate insect nodulation responses to bacterial infections

We propose that nodule formation is mediated by eicosanoids in insects. Nodulation is the temporally and quantitatively predominant cellular defense response to bacterial infection in insects and other invertebrates. Inhibition of eicosanoid biosynthesis in larvae of the tobacco hornworm Manduca sexta immediately prior to intrahemocoelic infections with the bacterium Serratia marcescens strongly reduced the nodulation response. Inhibition of eicosanoid biosynthesis also reduced formation of cellular aggregates at 1 hr postinfection, which indicates that eicosanoids mediate early stages of nodulation. Separate treatments with specific inhibitors of phospholipase A2, cyclooxygenase, and lipoxygenase reduced nodulation, which supports the view that nodule formation is a complex process involving prostaglandins and lipoxygenase products. The inhibitory effects of the phospholipase A2 inhibitor dexamethasone on nodulation were apparent by 1 hr after infection, and the effects increased, relative to controls, over 24 hr. The dexamethasone effects were expressed in a dose-dependent manner, and they were reversed by treating infected insects with eicosanoid-precursor polyunsaturated fatty acids. Treatments with the saturated fatty acid 16:0, which is not an eicosanoid precursor, did not reverse the dexamethasone effects on nodulation. These findings strongly support the identification of nodulation as a specific insect cellular defense mechanism that is mediated by eicosanoids.

In vitro effects of live and killed Brucella abortus on bovine cytokine and prostaglandin E2 production

Live and gamma-irradiated-killed Brucella abortus strain 2308 increased interleukin 1 (IL-1), but not interleukin 2 (IL-2), interferon-gamma (IFN-gamma), or prostaglandin E2 (PGE2) production when incubated with normal bovine peripheral blood mononuclear cells (PBMC). Live B. abortus was more effective than killed B. abortus in stimulating IL-1 production by normal PBMC. Both live and killed B. abortus were equally effective in suppressing IL-2 and IFN-gamma production by Concanavalin A-stimulated PBMC. Incubation of PBMC with the cyclo-oxygenase inhibitor, indomethacin, blocked PGE2 synthesis, but did not further enhance IL-1 production or prevent suppressed IL-2 and IFN-gamma production that was induced by live and killed B. abortus. These results suggest that B. abortus-induced suppression of IL-2 and IFN-gamma production did not appear to be mediated by the suppressive prostaglandin, PGE2, or other cyclo-oxygenase metabolites.

Stimulation of cyclic AMP production in human alveolar macrophages induced by inflammatory mediators and beta-sympathicomimetics

We have investigated the effects of inflammatory mediators and beta-adrenoceptor agonists on the adenylyl cyclase responsiveness in alveolar macrophages from control subjects, patients suffering from chronic obstructive pulmonary disease (COPD) and asthmatics. Basal cyclic AMP (cAMP) levels in alveolar macrophages from COPD patients were significantly elevated (plus 42%) as compared to controls. In addition, the adenylyl cyclase responsiveness to prostaglandin E2, histamine and the beta-adrenoceptor agonist salbutamol was significantly impaired in alveolar macrophages from COPD patients and asthmatics. The lipid mediator platelet activating factor showed no effect on cAMP production in all three alveolar macrophage populations. Furthermore, the cAMP-enhancing effects of isoprenaline, salbutamol and histamine appeared to be mediated via beta 2-adrenoceptors and histamine H2-receptor subtypes respectively. Taken together, these data suggest an intrinsic desensitization phenomenon in alveolar macrophages from COPD patients and asthmatics.

Effects of gamma interferon and indomethacin in preventing Brucella abortus infections in mice

Increased resistance to infection with Brucella abortus 2308 resulted when recombinant murine gamma interferon (rMuIFN-gamma) was given to mice both before and during infection but not when given only before infection. Mice given rMuIFN-gamma had enhanced peritoneal and splenic macrophage bactericidal activity against B. abortus. Treatment of mice with rMuIFN-gamma plus indomethacin did not further enhance resistance to infection or macrophage bactericidal activity compared with that after treatment of mice with rMuIFN-gamma alone.

Phorbol ester-like action of staurosporine on the cAMP response to prostaglandin E2 in two macrophage-like cell lines at distinct differentiation stages

The purpose of this study is to investigate the involvement of protein kinase C (PKC) in prostaglandin E2 (PGE2)-stimulated cAMP production of two macrophage-like cell lines (G3 and XC). XC cells are thought to be placed at a more differentiated stage than G3 cells [Orikasa et al. (1991) Cell Immunol. 132, 350-365]. In RPMI 1640 containing 10% (v/v) heat-inactivated foetal calf serum (FCS), in which the cAMP response of both cells to PGE2 increased with duration of culture, XC cells showed greater response than G3 cells at 2 days of culture. In alpha-minimum essential medium (alpha-MEM) containing 20% (v/v) heat-inactivated horse serum (HS), the cAMP response of both cells was apparently greater than that in RPMI 1640 containing 10% (v/v) FCS. These cells increased cAMP production also in response to PGE1 and PGF2 alpha, and the order of potency in increase was PGE1 > PGE2 >> PGF2 alpha. Interestingly, a short-term (20 min) treatment with phorbol 12-myristate 13-acetate (PMA), a direct activator of PKC or staurosporine, a relatively specific inhibitor of PKC, augmented the PGE2-stimulated cAMP production in these cells cultured in alpha-MEM containing 20% (v/v) HS. However, a long-term (24 h) treatment with these compounds did not alter the cAMP response. In G3 cells, PMA appeared more potent than staurosporine in terms of augmentation, whereas in XC cells, the former appeared less potent than the latter.(ABSTRACT TRUNCATED AT 250 WORDS)

Peritoneal macrophages from patients on continuous ambulatory peritoneal dialysis show a differential secretion of prostanoids and interleukin-1 beta

In vitro secretion of the prostanoids PGE2 and PGI2 and of the cytokine IL-1 beta by peritoneal macrophages obtained from CAPD patients during episodes of peritonitis and infection free periods, was determined, after culturing with or without 5 micrograms/ml of LPS. The release of PGE2 and PGI2 as measured by its stable metabolite 6-keto-PGF alpha was determined in 10 episodes of peritonitis and 10 infection free periods. IL-1 beta release was determined in 14 episodes of peritonitis and 20 infection free periods. PGI2 release from macrophages declined sharply during peritonitis both in the absence and presence of LPS in the culture medium (p less than 0.005). A tendency to decreased PGE2 release was found during peritonitis, when macrophages were cultured in the absence of LPS. In the presence of LPS, the same amounts of PGE2 were released during peritonitis and during an infection free period. On the other hand, peritoneal macrophages released significantly more IL-1 beta during peritonitis as compared to an infection free period, provided that the cells were in vitro stimulated with LPS. In view of the interregulatory effects between prostanoids and macrophage cytokines in their production, these findings may indicate that the impaired release of PGI2 during peritonitis has allowed the macrophages to secrete more IL-1 beta after in vitro stimulation with LPS. This implies that PGI2 and PGE2 may play a distinct role in the regulation of cytokine secretion by these cells.

Prostaglandin E2 inhibits the release of tumor necrosis factor-alpha, rather than interleukin 1 beta, from human macrophages

We have reported previously that macrophages obtained from renal patients on continuous ambulatory peritoneal dialysis (CAPD) during an episode of infectious peritonitis display a decrease in intracellular cAMP levels and in spontaneous in vitro release of PGE2 and PGI2. Such macrophages also release large quantities of IL-1 beta and TNF alpha when stimulated in vitro by LPS. In view of the interregulatory effects between PGE2 and macrophage cytokines (IL-1 beta and TNF alpha) in their production, we examined in the present work to what extent the LPS-induced release of either IL-1 beta or TNF alpha in vitro from CAPD-originated peritoneal macrophages is affected by graded doses of exogenous PGE2 (range 0-1000 ng/ml) and by the cyclooxygenase inhibitor indomethacin (INDO) (10(-6) M). IL-1 beta and TNF alpha were determined using an enzyme-linked immunoabsorbent assay and an immunoradiometric assay, respectively. We found that PGE2 invariably induced a dose-dependent decrease in TNF alpha release. In peritoneal macrophages collected during an infection-free period, TNF alpha release decreased from 3225 pg/ml (controls) to 353 pg/ml at 1000 ng/ml of PGE2, and in peritoneal macrophages collected during an episode of infectious peritonitis, it decreased from 4100 pg/ml (controls) to 545 pg/ml at 100 ng/ml of PGE2. However, PGE2 failed to influence the secretion of IL-1 beta. INDO induced an approx. two-fold increase in TNF alpha release, but had no effect on IL-1 beta release. These findings indicate that exogenous and endogenous PGE2 controls the release of TNF alpha rather than IL-1 beta from LPS-stimulated peritoneal macrophages.

Sensitization enhances the adenylyl cyclase responsiveness in alveolar macrophages. Changes induced at post-receptor level

Using membrane fractions (MF) from guinea pig alveolar macrophages (AM), we investigated the effects of sensitization and antigen challenge on the stepwise activation of adenylyl cyclase considering receptor binding, G-protein coupling and direct stimulation of the enzyme. Receptor binding studies, using [125I]ICYP as the beta-adrenoceptor specific ligand, show that neither receptor number (Bmax) nor receptor affinity constants (Kd values) were affected by sensitization or antigen challenge. Using forskolin as a direct stimulant of AC, alterations in the enzymatic activity of AC could be excluded. Pretreatment of the different MF with cholera toxin (CT, a toxin which eliminates GTPase activity) and subsequent stimulation of AC with GTP, shows an increased responsiveness in MF from sensitized and antigen challenged AM. In addition, pretreatment of MF from naive AM with increasing doses of CT results in a maximal AC response at the higher concentrations used (50-100 micrograms/mL), an effect not observed in MF from sensitized and antigen challenged AM. In these MF, the AC response still increases after pretreatment with such doses of CT. These data suggest that the enhanced AC responsiveness in AM, induced by sensitization and antigen challenge, results from alterations in alpha s-subunits.

Insect immune response to bacterial infection is mediated by eicosanoids

Inhibition of eicosanoid formation in larvae of the tobacco hornworm Manduca sexta, using specific inhibitors of phospholipase A2, cyclooxygenase, and lipoxygenase, severely weakened the ability of larvae to clear the bacterium Serratia marscescens from their hemolymph. The reduced capability to remove bacteria is associated with increased mortality due to these bacteria. There is a dose-dependent relationship between the phospholipase A2 inhibitor dexamethasone and both the reduced bacterial clearance and increased larval mortality. The dexamethasone effects on larval survival were reversed by treatment with arachidonic acid. Maleic acid, a nonspecific antioxidant, did not interfere with the insects' ability to remove bacterial cells from hemolymph. The larvae were shown to contain all of the C20 polyunsaturated fatty acids necessary for eicosanoid biosynthesis and to be capable of converting radioactive arachidonic acid into several primary prostaglandins. These results strongly suggest that eicosanoids mediate transduction of bacterial infection signals into the complex of cellular and humoral responses that comprise invertebrate immunity.

Interactions between inflammatory mediators in expression of antitumor cytostatic activity of macrophages

Antitumor properties and participation in inflammatory events are important characteristics of activated macrophages. We show here that both antitumor cytostatic function of macrophages and participation of these cells at inflammatory sites are controlled by two main groups of mediators: cytokines (IL-1, TNF alpha) and eicosanoids (prostanoids and leukotrienes). These two groups of mediators represent a complex system of mutual interactions in regulation of their production and activities. Multiple sets of experiments with murine macrophages are discussed in favor of the views that PGE2 and lipoxygenase products oppose each other's actions, and that the regulating role of PGE2 in the secretions of cytokines are of pivotal importance in antitumor cytostasis of macrophages in vitro. Such observations can be extended to a situation ex vivo, showing that human macrophages harvested from inflammatory sites have markedly augmented cytostatic expression. It thus appears that the antitumor cytostatic function of macrophages is related to the production of inflammatory mediators by these cells. Accordingly, it might be that occurrence of inflammation in tumor-bearing individuals plays a role in the promotion of antitumor activity of macrophages.

Identification of beta 2-adrenoceptors on guinea pig alveolar macrophages using (-)-3-[125I]iodocyanopindolol

The beta-adrenoceptor antagonist (-)-3-[125I]iodocyanopindolol ([125I]ICYP) binds with high affinity and in saturable way to membranes of guinea pig alveolar macrophages. The equilibrium dissociation constant for [125I]ICYP is 24.3 +/- 1.2 pM, and the number of binding sites is 166.3 +/- 13.7 fmol/mg protein (N = 4, +/- SEM). Displacement studies with selective antagonists showed that [125I]ICYP labels beta 2-adrenoceptors on guinea pig alveolar macrophages.

Endotoxin-stimulated peritoneal macrophages obtained from continuous ambulatory peritoneal dialysis patients show an increased capacity to release interleukin-1 beta in vitro during infectious peritonitis

Interleukin-1 (IL-1) release by peritoneal macrophages obtained from patients on continuous ambulatory peritoneal dialysis (CAPD) was studied in nine patients during an infection-free period and eight patients during an infectious peritonitis, using an ELISA for IL-1 beta. Without exogenous stimulation with LPS, peritoneal macrophages from infected and uninfected patients released the same amounts of IL-1 beta, 183 +/- 40 pg ml-1 24 h-1) per 10(6) cells (means +/- SEM) and 251 +/- 96 pg ml-1, respectively. However, in response to a dose of 5 micrograms ml-1 of LPS, peritoneal macrophages released significantly more (P less than 0.005) IL-1 beta during peritonitis (6579 +/- 2793 pg ml-1 24 h-1 per 10(6) cells) compared with the infection-free period (1040 +/- 182 pg ml-1). These findings show that after microbial invasion of the peritoneal cavity, peritoneal macrophages are primed in vivo to release an increased amount of IL-1 beta in vitro after subsequent exogenous stimulation with LPS, indicating that peritoneal macrophage activation for IL-1 beta secretion occurs in steps.

Eicosanoid synthesis in human peritoneal macrophages stimulated with S. epidermidis

Peritoneal macrophages isolated from CAPD patients phagocytosed S. epidermidis in a time dependent manner. Coincident with a maximum phagocytic uptake of 56% by 12 hours, there was secretion of a significant amount of neutral protease (1.37 +/- 0.2 mg [3H]-casein degraded/10(6) cells, P = 0.05). In contrast to these delayed effects, coincubation of PMO with S. epidermidis resulted in a significant increase in both LTB4 and LTC4 synthesis above that of controls, with 6.33 +/- 1.20 ng LTB4/10(6) cells (P less than 0.01) and 2.06 +/- 0.68 ng LTC4/10(6) cells (P = 0.014) being generated by three hours. The generation of these lipoxygenase products was both time and dose dependent, and the rapid production and release of the potently chemotactic LTB4 is consistent with the observed clinical response, where a rapid influx of PMN into the peritoneal cavity occurs during episodes of peritonitis, while the generation of LTC4 may contribute to the hyperemia and interstitial edema. In contrast, although there was a time dependent rise in cyclooxygenase product generation by unstimulated cells, a dose dependent inhibition of synthesis was clearly demonstrated when cells were incubated with bacteria, with a mean 40% reduction in generation of PGE2 and a mean 34% reduction in TXB2 generation (P = 0.01 and P less than 0.025, respectively). It was demonstrated that the inhibition was not due to lack of available substrate and that the generation of eicosanoids was unrelated to phagocytosis, bacterial/PMO contact or bacterial surface characteristics. Instead, the observed effect of S. epidermidis on the PMO was attributable to a secreted bacterial product.

Antigen challenge modifies the cyclic AMP response of inflammatory mediators and beta-adrenergic drugs in alveolar macrophages

Adenylate cyclase activity was determined in alveolar macrophages (AMs) obtained from bronchoalveolar lavage (BAL) fluids of naive and antigen-challenged guinea pigs. After the anaphylactic reaction in ovalbumin-sensitized guinea pigs, the basal levels of cyclic AMP in AMs were significantly increased compared to the levels in naive AMS (1.87 +/- 0.22 versus 5.26 +/- 0.45 pmol cyclic AMP/5.10(6) cells). Prostaglandin E2 (PGE2), prostacyclin (DC-PGI2), histamine, isoprenaline and salbutamol stimulated adenylate cyclase activity more effectively in AMs obtained from sensitized guinea pigs after the booster injection compared to AMs obtained from non-treated animals. Moreover, DC-PGI2 and histamine, which were hardly able to induce a rise in cyclic AMP levels in naive AMs, become effective activators in AMs obtained after antigen challenge (100 and 60% increase in the response, respectively). Using selective receptor ligands, we have shown that beta 2-adrenoceptors and H2-subtype histamine receptors are functionally coupled to macrophage adenylate cyclase activity. The present data indicate that sensitization does not affect the configuration of the receptor on the outer membrane (no change in affinity constants), but affects other parts of the transmembrane signal system leading to the intracellular production of cyclic AMP (e.g. regulatory binding proteins or increases in the number of receptors).

Enhancement of leukotriene C4 release from primate airway macrophages by cellular interactions

1. Cells were obtained from the lungs of Macaque monkeys by bronchoalveolar lavage in order to study the role of cellular interactions in the release of leukotriene C4 (LTC4). 2. In normal monkeys, macrophages were the most abundant cell type recovered, whereas in monkeys sensitized with Ascaris suum there was an increase in the numbers of eosinophils and mast cells recovered. 3. Challenge of cells from both groups of animals with an optimal concentration of opsonized zymosan (OPZ) resulted in the time-dependent release of LTC4 from macrophages. However, release was significantly greater in cells obtained from sensitized donors compared to normal donors. 4. Density-gradient centrifugation of cells lavaged from sensitized donors was used to prepare fractions containing both eosinophils and mast cells. Addition of these cells to macrophage populations obtained from non-sensitized donors caused a significant enhancement of OPZ-induced LTC4 release. In the absence of macrophages no significant release of LTC4 was detected from eosinophil/mast cell-containing fractions stimulated with OPZ, despite the fact that the zymosan had been phagocytosed by the eosinophils. 5. There was a significant correlation between the percentage enhancement of LTC4 release and the number of eosinophils added. However, there was not a significant correlation with the number of mast cells added. 6. These results suggest that a cellular interaction between macrophages and eosinophils may be important in the regulation of mediator synthesis and release. The precise mechanism of this effect remains to be elucidated.

Stimulation of anaphylaxis in the mouse footpad by dietary fish oil fatty acids

The effect of fish oil-derived omega-3 (omega-3) fatty acids on anaphylaxis, Arthus and delayed type hypersensitivity reactions in mice has been investigated. Mice on a normal chow diet were fed eicosapentaenoic acid and docosahexaenoic acid at a dose of 500 and 333 mg/kg/day, respectively, by a gastric tube over a period of 61 days. Control groups were given water, safflower oil or oleic acid. Anaphylactic and Arthus type reactions were induced in the mouse footpad using bovine serum albumin as an antigen. Carrageenin was utilized to produce a delayed type hypersensitivity reaction. The animals fed omega-3 fatty acids induced a more anaphylactic foodpad reaction. There was no significant effect of the diet on Arthus and delayed type hypersensitivity responses. There was no effect of the fish oil-supplemented diet on production of antibodies to bovine serum albumin. Synthesis of prostaglandin E2 by peritoneal macrophages was significantly inhibited in the animals fed omega-3 fatty acid-enriched fish oil, while leukotriene B4 production was not affected. These results suggest that a diet enriched in omega-3 fatty acids modulates production of arachidonic acid metabolites and this may influence anaphylaxis, but not Arthus and cellular mediated hypersensitivity responses.

Prostaglandin E2 inhibits and indomethacin and aspirin enhance, A23187-stimulated leukotriene B4 synthesis by rat peritoneal macrophages

1. The calcium ionophore, A23187, stimulated leukotriene B4 (LTB4), thromboxane B2 (TxB2) and prostaglandin E2 (PGE2) synthesis by 4 day carrageenin-elicited rat peritoneal macrophages. 2. At concentrations of 2 x 10(-7)-2 x 10(-5) M indomethacin and aspirin enhanced A23187-stimulated LTB4 synthesis and inhibited PGE2 and TXB2 formation. 3. PGE2 inhibited A23187-stimulated LTB4 and TXB2 formation as well as the augmentation of LTB4 release caused by aspirin and indomethacin. However, PGE2 was ineffective when the cells were challenged with arachidonic acid (AA). 4. Dibutyryl adenosine 3':5'-cyclic monophosphate (db-cyclic AMP) partially inhibited A23187-stimulated LTB4 production. 5. Our results suggest that PGE2 inhibits macrophage LTB4 synthesis by limiting the availability of AA. Indomethacin and aspirin, possibly by removing the regulatory effect of PGE2, promote the synthesis of the pro-inflammatory LTB4.

Beta-adrenoceptor antagonist-induced psoriasiform eruption. Clinical and pathogenetic aspects

A number of beta-adrenoceptor blocking drugs have been reported to induce a papulosquamous eruption which resembles psoriasis. We report distinctive clinical, histopathologic, immunocytochemical, and electron microscopic features in beta-blocker-induced psoriasiform eruptions that differentiate this syndrome from psoriasis. Preliminary data suggest that biopsy specimens from eruptions caused by beta 1-selective adrenoceptor blocking agents (metoprolol and atenolol) were characterized by excessive degranulation of the neutrophils in the dermis, while the nonselective beta blockers (propranolol, nadolol, and sotalol) were marked by excessive release of proteolytic enzymes from macrophages, which are thought to possess beta 2-adrenergic receptors. Surprisingly, excessive release of enzymes by lymphocytes were noted in both the beta 1-selective and in the nonselective induced syndromes. It is believed that excessive lysosomal enzyme release by neutrophils, lymphocytes, and macrophages is responsible for the presence of basal keratinocyte herniations, which have previously been shown to correlate with hyperproliferation and psoriasiform changes, as well as with the presence of excessive proteolytic enzymes in the skin. It is postulated that the beta-blocker-induced syndrome may result from enhanced proliferation, motility, and activity of lymphocytes, neutrophils, and cells of the macrophage-Langerhans cell series, stemming from depressed intracellular cyclic adenosine monophosphate levels caused by the beta blockade.

The adenylate cyclase of rheumatoid synovial fluid macrophages is more sensitive for dl-5E, 19,14-di dehydro-carbo-prostacyclin, a stable prostacyclin analogue, than for prostaglandin E2

dl-5E, 19,14-di dehydro-carbo-prostacyclin (DDH-carbo PGI2), a stable prostacyclin (PGI2) derivative, but not prostaglandin (PG) E2, stimulated the adenylate cyclase of synovial fluid macrophages, isolated from rheumatoid patients with an active synovitis, in a dose dependent manner (10-1000 ng/ml). DDH-carbo PGI2 also stimulated synovial macrophage cAMP synthesis when injected into the knee joint. Exogenous arachidonic acid (AA) had little effect on cyclic-AMP (cAMP) formation or PGI2 release (assayed as 6ketoPGF1 alpha). It stimulated, however, the release of PGE2 and, to a lesser extent, thromboxane (Tx) A2 (measured as TxB2).

Quantitative, functional and biochemical alterations in the peritoneal cells of mice exposed to whole-body gamma-irradiation. I. Changes in cellular protein, adherence properties and enzymatic activities associated with platelet-activating factor formation and inactivation, and arachidonate metabolism

Changes in total number, differentials, cell protein, adherence properties, acetyltransferase and acetylhydrolase activities, prostaglandin E2 and leukotriene C4 production, as well as Ca2+ ionophore A23187 stimulation were examined in resident peritoneal cells isolated from mice 2 h to 10 days postexposure to a single dose (7, 10 or 12 Gy) of gamma-radiation. Radiation dose-related reductions in macrophage and lymphocyte numbers and increases in cellular protein and capacity to adhere to plastic surfaces were evident. In vivo irradiation also elevated the activities of acetyltransferase and acetylhydrolase (catalysing platelet-activating factor biosynthesis and inactivation, respectively) in adherent and nonadherent peritoneal cells, particularly 3-4 days postexposure. Blood plasma from irradiated animals did not reflect the increased cellular acetylhydrolase activity. Prostaglandin E2 and leukotriene C4 synthesis were elevated postexposure, suggesting increased substrate (arachidonate) availability and increased cyclooxygenase and lipoxygenase activities. Ionophore stimulation of enzyme activities and eicosanoid release also differed in irradiated peritoneal cells. While the properties of adherence, platelet-activating factor synthesis/inactivation-associated enzyme activities, and eicosanoid production are generally characterized as those of macrophages, lymphocytes or their products may influence or contribute to the observed radiation-induced changes.

Dibutyryl Cytidine and Adenosine 3':5'-Cyclic Monophosphates Inhibit A23187-Stimulated Rat Peritoneal Macrophage Leukotriene B4 Synthesis

Dibutyryl cytidine and adenosine 3':5'-cyclic monophosphates (db-cCMP and db-cAMP respectively) inhibited the synthesis of thromboxane (TX) B2, the stable product of TXA2, and leukotriene (LT) B4 by 4-day carrageenin-elicited rat peritoneal macrophages stimulated by the calcium ionophore A23187. Incubation of macrophages with dbcAMP, at concentrations inhibiting eicosanoid release, was associated with an increase in intracellular cAMP concentrations. No such increase was seen when db-cCMP was used.

Interaction between PAF-acether and drugs that stimulate cyclic AMP in guinea-pig alveolar macrophages

The PAF-acether (1-alkyl-2-acetyl-sn-glycero-3-phosphocholine)-induced arachidonate release from alveolar macrophages was significantly reduced by prostaglandin E2 (PGE2) and by the beta-adrenoceptor agonist salbutamol. In addition, PAF-acether markedly reduced the increase in intracellular cyclic AMP (cAMP) concentrations induced by PGE2 and salbutamol. Our data indicate an inverse relationship between intracellular cAMP levels and free arachidonate availability in alveolar macrophages treated with PAF-acether. A rise in intracellular cAMP therefore represents an important alternative route for controlling the effects of PAF-acether and the resulting inflammatory alterations in the respiratory system.

Copper modulation of macrophage cyclooxygenase metabolite synthesis

The effect of copper on the release of cyclooxygenase metabolites from starch elicited, rat, peritoneal macrophages was investigated. Copper sulphate, in the range 10(-6)-10(-5) M, inhibited the formation of prostaglandin (PG) E2 and thromboxane (Tx) B2, the stable metabolite of TxA2, in a dose dependent manner but had no effect on the production of 6-keto-PGF1 alpha, the stable product of prostacyclin. At higher concentrations (5 x 10(-5) and 10(-4) M) the synthesis of all three metabolites of arachidonic acid (AA) was stimulated as was the release of radioactivity from macrophages prelabelled with 14C AA. Copper had no effect on the metabolism of exogenous AA however. At 10(-4) M copper also stimulated secretion of the lysosomal enzyme, beta-glucuronidase (GUR). Copper nitrate (10(-4) M), but not zinc sulphate, also stimulated eicosanoid formation and lysosomal enzyme release. Our results are consistent with the idea that copper stimulates eicosanoid formation via an effect on PL activity.

Head injury induces increased prostaglandin synthesis in rat brain

Head injury was induced in the left hemisphere of rats. The rats were killed at various time intervals after trauma (immediately, 15 min, 1 and 18 h, and 4 and 10 days), and the rates of synthesis and release of prostaglandin PGE2, 6-keto-PGF1 alpha, and thromboxane TXB2 from cortical slices of both hemispheres were studied. The rate of synthesis of PGE2 after 18 h was six and four times higher than control in the contused and contralateral hemispheres, respectively. By 10 days post-trauma, both hemispheres had normal rate of PGE2 release. TXB2 and 6-keto-PGF1 alpha synthetases were affected already 15 min after the injury, and a similarly elevated rate of synthesis was found in both hemispheres. The maximal effect was detected after 1 or 18 h with return to normal after 4 or 10 days for TXB2 and 6-keto-PGF1 alpha, respectively. Tissue specific gravity was determined for both hemispheres using linear gradient columns. The results of these determinations indicate that development of edema occurs in the contused hemisphere as early as 15 min post trauma; it reaches its maximal level at 18 h and returns to normal at 10 days. Arterial pressure was monitored, and a transient increase was found at 10 min post trauma. We suggest that the production of edema after brain injury may be related to the increased rate of PGE2 and PGI2 synthesis, which occurs at similar time intervals after injury.

The production of prostaglandin and the regulation of cell division in neonate rat primary mixed glial cultures

The production of prostaglandins has been studied in neonate rat primary mixed glial cultures. A correlation was found between inhibition of [3H]thymidine incorporation in the cultures and production of prostaglandin, which was stimulated by the addition of supernatant from Con A-activated rat splenocytes. Inhibition of prostaglandin synthesis in the cultures by indomethacin results in a striking increase in incorporation of [3H]thymidine into the cultures, an effect which was reversed by the addition of exogenous PGE2, but not PGF2 alpha. PGE was the principal prostaglandin detected, with both macrophages/microglia and astrocytes contributing to the output. A possible role for prostaglandins in the modulation of inflammatory responses in the central nervous system is discussed.

Prostaglandin-mediated suppression of delayed-type hypersensitivity to infected erythrocytes during Babesia microti infection in mice

The mechanism of suppression of delayed-type hypersensitivity (DTH) to intraerythrocytic Babesia microti which occurs during infection in mice was examined. The suppression was not specific for anti-parasite DTH; infected mice immunized and challenged with sheep red blood cells had a similar depression of anti-sheep red blood cell DTH. Sublethal or lethal irradiation did not significantly alter the suppression of the DTH response, and cyclophosphamide pretreatment of infected mice also had no effect on suppression. Multiple passive transfer experiments using serum or regional lymph node cells from immunized or infected and immunized (suppressed) donor animals failed to demonstrate any ability to transfer suppression of DTH. Adherent cells from the spleens or peritoneal exudates of suppressed mice, however, did significantly depress the ability of immunized mice to express a DTH response. The cells responsible for this suppression were Thy 1- and nonspecific esterase+. Treatment of suppressive cell populations with 10 micrograms/ml indomethacin for 24 hr in vitro abrogated their suppressive ability, and in vivo administration of indomethacin to suppressed mice also restored DTH to normal levels. By examining levels of prostaglandin E2 (PGE2) in supernates of cultured peritoneal exudate cells from immune or suppressed mice, it was shown that infected mice had peritoneal exudate cells which produced significantly more PGE2 than similar cells from immune mice. These data suggest that B. microti infection elicits synthesis of PGE2 by macrophage-like cells which results in suppression of DTH to parasite as well as heterologous antigens.

Activation of suppressor cells by low molecular weight factors secreted by spleen cells of tumor-bearing mice: modulatory role of prostaglandins

We have shown previously that the spleens of mice bearing large M-1 fibrosarcomas contain inducer cells which secrete dialysable factors which activate suppressor T cells from unprimed, normal precursor spleen cells. Once activated, the suppressor cells inhibit the in vitro antibody synthesis of cocultured syngeneic splenocytes stimulated by T cell dependent antigens. In this paper we have examined the possibility that prostaglandins are involved in the activation process. Inducer and precursor cells were cultured in Marbrook vessels in chambers separated by dialysis membranes. Using this procedure, suppressor cells were activated following 12 h of culture but were not detectable after 6 h. The cyclooxygenase inhibitors, indomethacin, acetyl salicylic acid (ASA), and ibuprofen all prevented the activation of suppressor cells in a dose dependent manner. Prostaglandin (PG) E1, but not PGF2a or PGD2, restored the activation of suppressor cells in cultures containing the cyclooxygenase inhibitors. Restoration of suppressor cell activation was seen with 1 X 10(-7) M PGE1 but no activation of suppressor cells was seen in control cultures containing up to 1 X 10(-5) M PGE1. In addition, cultured spleen cells from tumor-bearing mice did not secrete higher quantities of PGE than did cells from age and sex matched normal mice. These data suggest that PGE has a modulatory rather than a direct role in the activation of suppressor cells by inducer factors from tumor-activated inducer cells.

The effect of carbaryl on the arachidonic acid metabolism and superoxide production by mouse resident peritoneal macrophages challenged by zymosan

Carbaryl, a broad spectrum insecticide with anticholinesterase activity, was tested for its ability to disturb resident peritoneal macrophages stimulated by opsonized zymosan. The effect of carbaryl on superoxide production and on the release of [1-14C] arachidonic acid and 14C-labelled prostaglandins was dose-dependent. For 2.5 X 10(-6) M of carbaryl, superoxide production and prostaglandin release were not significantly inhibited. At 12.5 X 10(-6) M, the inhibitory effect was apparent for superoxide production (33%) and for the release of 6 KPGF1 alpha (60%), PGE2 (42%), PGF2 alpha (38%), PGD2 (33%). Carbaryl had no effect on the level of free arachidonic acid. Insecticide at 12.5 X 10(-6) M significantly decreased the deacylation of the phosphatidylcholine (20%). Incubation of resident peritoneal macrophages with indomethacin studied conjointly decreased only the prostaglandin release. These results suggest that carbaryl decreases the sequence of events following the binding of a particulate agent to its receptor and leading to the induction of phospholipase activity and the subsequent release of 20:4 and the oxidative burst in the cells. The effect of this pesticide on phospholipid metabolism and its consequences on macrophage stimulation are discussed. Ecto-serine esterase inhibition in the effect mechanism of the pesticide was suggested.