Cyclooxygenase-2-issued prostaglandin e(2) enhances the production of endogenous IL-10, which down-regulates dendritic cell functions

Multifaceted roles of cyclooxygenase-2 in lung cancer

Lung cancer is the leading cause of cancer death in the United States. Although the low 5-year survival rate (under 15%) has changed minimally in the last 25 years, new agents and combinations of agents that target tumor proliferation, invasion, and survival may lead to improvement in patient outcomes. There is evidence that cyclooxygenase-2 (COX-2) is overexpressed in lung cancer and promotes tumor proliferation, invasion, angiogenesis, and resistance to apoptosis. COX-2 inhibitors have been found to inhibit tumor growth in animal models and have demonstrated responses when combined with conventional therapy in phase II clinical trials. Further understanding of the mechanisms involved in COX-2-mediated tumorigenesis and its interaction with other molecules in lung cancer may lead to improved therapeutic strategies for this disease. In addition, delineation of how COX-2-dependent genes modulate the malignant phenotype will provide novel insights in lung cancer pathogenesis.

Prostaglandin E2-dependent enhancement of tissue inhibitors of metalloproteinases-1 production limits dendritic cell migration through extracellular matrix

Dendritic cell (DC) migration is crucial for the initiation of immune responses. The balance between metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) has been shown to modulate DC migration. PGE2, which is overproduced in a wide variety of human malignancies, has been implicated in MMP and TIMP regulation in various cells, including monocytes. In the present study, we hypothesized that tumor-derived PGE2 would affect DC migratory capacity through the extracellular matrix (ECM) by altering MMP and TIMP balance. Treatment of monocyte-derived immature DC with exogenous PGE2 induced TIMP-1 secretion but not MMP-9 production and was correlated with reduced DC migration through ECM. Because recombinant TIMP-1 replicated PGE2 inhibition of DC migration while anti-TIMP-1 neutralizing Ab reversed it, we conclude that PGE2-mediated induction of TIMP-1 was responsible for the reduced migration of PGE2-treated DC. Similarly, DC cultured for 48 h in supernatants from cyclooxygenase-2 overexpressing lung cancer cells that secrete high levels of PGE2, exhibited decreased migration through ECM. Finally, analysis of E prostanoid receptor expression and their selective inhibition revealed that the enhanced TIMP-1 secretion in PGE2-treated DC was mediated predominantly by the E prostanoid receptor 2. These findings indicate that PGE2-dependent enhancement of TIMP-1 production causes reduced migration of DC through ECM.

Characterization of breast milk received by infants with gross blood in stools

OBJECTIVE

The aim of this study was to ascertain factors that might be protective of the appearance of gross blood in the stools of breast-fed infants.

METHODS

Logistic regression models were formed to search for variables possibly explaining the condition. In addition to the analyzed breast milk factors, mother's allergic disease was introduced into the models to control for its possible confounding effect. The breast milk samples, collected from mothers of infants with gross blood in stools (n = 23) and from mothers of healthy age-matched infants (n = 71), were analyzed for concentrations of transforming growth factor-beta2, tumor necrosis factor-alpha, interleukin (IL)-4, IL-10, prostaglandin (PG)E2, cysteinyl leukotrienes (Cys-LTs) and fatty acid composition.

RESULTS AND CONCLUSIONS

Increase in the concentrations of PGE2 and Cys-LTs in the breast milk together with mother's allergic disease reduced the likelihood of gross blood in stools in the breast-fed infant. The results suggest that no single factor, but a combination of immunomodulatory factors may protect the child from gross blood in the stools of breast-fed infants. Allergic disease was not a risk factor as mother's allergic disease appeared to counterbalance the gross blood in stools. Due to the preliminary nature of the study, the results need to be verified in a larger setting. The challenge for the future lies in identifying of such active compounds for dietary modification to enforce particularly the properties of the breast milk which are immunoprotective for the infant and to reduce the likelihood of intestinal disorders in at risk infants.

A Novel Role of Cysteinyl Leukotrienes to Promote Dendritic Cell Activation in the Antigen-Induced Immune Responses in the Lung

Although the critical role of cysteinyl leukotrienes (cysLTs) in the inflammation, especially eosinophilic lung inflammation, in asthma has been well documented, their role in the early stage of Ag-specific immune response has not been completely clarified. In the present study, with a mouse model of asthma and in vitro studies we demonstrated that cysLTs potentiated dendritic cell (DC) functions such as Ag-presenting capacity and cytokine production. The cysLT-1 receptor antagonist (LTRA) strongly suppressed the activation of these DC functions and led to inhibition of subsequent not only Th2, but also Th1, responses in the early stage of immune response. Moreover, treatment with LTRA during the early stage of the immune response potently suppressed the development of Ag inhalation-induced eosinophilic airway inflammation, mucus production, and airway hyper-reactivity in vivo. Treatment with LTRA significantly increased PGE(2) production in the lung, and treatment with the cyclooxygenase inhibitor indomethacin abolished LTRA's suppressive effect on DCs and deteriorated the Th2 and Th1 responses and airway inflammation. With in vitro studies, we also confirmed that cysLTs production by DCs increased with LPS stimulation, and that LTRA directly suppressed the alloantigen-presenting capacity of DCs. These results suggested that cysLTs potentiate DC functions both in vivo and in vitro, and that LTRA could be beneficial to suppress the initial immune response in many immune-mediated disorders beyond asthma.

Activated human dendritic cells express inducible cyclo-oxygenase and synthesize prostaglandin E2 but not prostaglandin D2

Prostaglandins (PG) are well known lipid mediators with important immunoregulatory properties. While exogenous PGE2 has the ability to modulate the function and maturation of antigen presenting cells, such as dendritic cells (DC), it is not clear whether human DC have the capacity to synthesize PGE2 and other prostaglandins themselves. We therefore examined the expression of inducible cyclo-oxygenase (COX-2) by monocyte derived DC and the production of PGE2 and PGD2. Both monocyte derived DC and freshly isolated blood myeloid DC expressed little COX-2 constitutively, though COX-2 expression was rapidly but transiently upregulated in response to lipopolysaccharide stimulation. COX-2 mRNA was detectable within 1 h of LPS exposure, peaked at 4-6 h, and rapidly declined thereafter. COX-2 expression was accompanied by DC synthesis of PGE2, with peak levels present at 6-18 h post-stimulation. In contrast, PGD2 synthesis was not detected at any time point. When DC were activated with LPS in the presence of nimesulide, a COX-2 selective inhibitor, IL-10 synthesis was inhibited, indicating that endogenous prostaglandins regulate DC cytokine production. PGE2 production by DC may therefore modulate DC and T-cell function, thereby shaping the character of the immune response.

A novel signaling pathway mediates the inhibition of CCL3/4 expression by prostaglandin E2

In response to pathogen-associated molecular patterns, dendritic cells initiate an innate immune response characterized by expression and release of proinflammatory cytokines and chemokines. The extent of the inflammatory response is limited by various endogenous factors, including lipid mediators such as prostaglandin E(2) (PGE(2)). We described previously the inhibitory effect of PGE(2) on the expression and release of the inflammatory chemokines CCL3 and CCL4 from activated dendritic cells. In this study we describe a novel PGE(2) signaling pathway that proceeds through EP-2 --> cAMP --> EPAC --> phosphatidylinositol 3-kinase --> protein kinase B --> GSK-3 and results in increased DNA binding of the CCAAT displacement protein (CDP), a potent mammalian transcriptional repressor. The direct link between CDP and CCL3/4 transcription was established in knock-down experiments using CDP small interference RNA.

Induction of a CD4+ T Regulatory Type 1 Response by Cyclooxygenase-2-Overexpressing Glioma

PGE(2), synthesized by cyclooxygenase-2 (COX-2)-overexpressing tumor, is known to contribute to cellular immune suppression in cancer patients, but the mechanism remains unclear. We report the mechanism of a CD4(+) T regulatory type 1 (Tr1) induction by CD11c(+) mature dendritic cells (DCs) that phagocytose allogeneic and autologous COX-2-overexpressing glioma. A human glioma cell line, U-87MG, and primary cultured glioblastoma cells (MG-377) overexpressed COX-2. We did not detect IL-10Ralpha expression in these gliomas, and rIL-10 did not suppress their COX-2 expression. Exposure to COX-2-overexpressing glioma induced mature DCs to overexpress IL-10 and decreased IL-12p70 production. These DCs induced a Tr1 response, which is characterized by robust secretion of IL-10 and TGF-beta with negligible IL-4 secretion by CD4(+) T cells, and an inhibitory effect on admixed lymphocytes. Peripheral CD4(+) T cell populations isolated from an MG-377 patient also predominantly demonstrated a Tr1 response against MG-377 cells. Selective COX-2 inhibition in COX-2-overexpressing gliomas at the time of phagocytic uptake by DCs abrogated this regulatory response and instead elicited Th1 activity. COX-2 stable transfectants in LN-18 (LN-18-COX2) also induced a Tr1 response. The effect of a COX-2 inhibition in LN-18-COX2 is reversible after administration of PGE(2). Taken together, robust levels of PGE(2) from COX-2-overexpressing glioma, which is unresponsive to IL-10 within the local microenvironment, may cause DCs to secrete high levels of IL-10. These results indicate that COX-2-overexpressing tumors induce a Tr1 response, which is mediated by tumor-exposed, IL-10-enhanced DCs.

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.

Prostanoids and their receptors that modulate dendritic cell‐mediated immunity

Dendritic cells (DC) are essential for the initiation of immune responses by capturing, processing and presenting antigens to T cells. In addition to their important role as professional APC, they are able to produce immunosuppressive and pro-inflammatory prostanoids from arachidonic acid (AA) by the action of cyclooxygenase (COX) enzymes. In an autocrine and paracrine fashion, the secreted lipid mediators subsequently modulate the maturation, cytokine production, Th-cell polarizing ability, chemokine receptor expression, migration, and apoptosis of these extremely versatile APC. The biological actions of prostanoids, including their effects on APC-mediated immunity and acute inflammatory responses, are exerted by G protein-coupled receptors on plasma membrane. Some COX metabolites act as anti-inflammatory lipid mediators by binding to nuclear receptors and modulating DC functions. Although the role of cytokines in DC function has been studied extensively, the effects of prostanoids on DC biology have only recently become the focus of investigation. This review summarizes the current knowledge about the role of prostanoids and their receptors in modulating DC function and the subsequent immune responses.

The spectrum of gastrointestinal toxicity and effect on disease activity of selective cyclooxygenase-2 inhibitors in patients with inflammatory bowel disease

The safety and toxicity associated with the use of selective cyclooxygenase-2 (COX-2) inhibitors in patients with inflammatory bowel disease (IBD) has not been extensively studied. Thirty-three patients with IBD who were prescribed celecoxib or rofecoxib were identified from questionnaire during their clinic visit at the Cedars-Sinai IBD Center between 1999 and 2002. Twenty-six had Crohn's disease (CD), 6 had ulcerative colitis (UC), and 1 had indeterminate colitis (IC). Twenty-one received rofecoxib, 10 celecoxib, and 2 received both medications at different time points. Overall, 13 (39%) patients experienced disease exacerbation, 7 of which had received celecoxib and six rofecoxib. IBD exacerbation associated with COX-2 treatment did not correlate with age, disease activity, or use of immunosuppressive medications. All patients experienced flare-up of their underlying IBD within 6 weeks of initiating COX-2 therapy. Five of 13 (38%) patients had resolution of their symptoms after discontinuing the COX-2 inhibitor, but the remaining patients required additional medical therapy to control their disease. Six other patients (18%) experienced GI side effects not associated with their underlying IBD. Five developed abdominal pain, and one developed a duodenal ulcer and a circumferential ileo-colonic ulceration with GI bleeding. Treatment with COX-2 inhibitors is associated with a high incidence of exacerbation of the underlying IBD and GI-related complications.

Prostaglandin E2Inhibits Alveolar Macrophage Phagocytosis through an E-Prostanoid 2 Receptor-Mediated Increase in Intracellular Cyclic AMP

Prostaglandin E(2) is a potent lipid mediator of inflammation that effects changes in cell functions through ligation of four distinct G protein-coupled receptors (E-prostanoid (EP)1, EP2, EP3, and EP4). During pneumonia, PGE(2) production is enhanced. In the present study, we sought to assess the effect of endogenously produced and exogenously added PGE(2) on FcRgamma-mediated phagocytosis of bacterial pathogens by alveolar macrophages (AMs), which are critical participants in lung innate immunity. We also sought to characterize the EP receptor signaling pathways responsible for these effects. PGE(2) (1-1000 nM) dose-dependently suppressed the phagocytosis by rat AMs of IgG-opsonized erythrocytes, immune serum-opsonized Klebsiella pneumoniae, and IgG-opsonized Escherichia coli. Conversely, phagocytosis was stimulated by pretreatment with the cyclooxygenase inhibitor indomethacin. PGE(2) suppression of phagocytosis was associated with enhanced intracellular cAMP production. Experiments using both forskolin (adenylate cyclase activator) and rolipram (phosphodiesterase IV inhibitor) confirmed the inhibitory effect of cAMP stimulation. Immunoblot analysis of rat AMs identified expression of only EP2 and EP3 receptors. The selective EP2 agonist butaprost, but neither the EP1/EP3 agonist sulprostone nor the EP4-selective agonist ONO-AE1-329, mimicked the effects of PGE(2) on phagocytosis and cAMP stimulation. Additionally, the EP2 antagonist AH-6809 abrogated the inhibitory effects of both PGE(2) and butaprost. We confirmed the specificity of our results by showing that AMs from EP2-deficient mice were resistant to the inhibitory effects of PGE(2). Our data support a negative regulatory role for PGE(2) on the antimicrobial activity of AMs, which has important implications for future efforts to prevent and treat bacterial pneumonia.

Cyclooxygenase-2-mediated prostaglandin E2 production in mesenteric lymph nodes and in cultured macrophages and dendritic cells after infection with Salmonella

Although numerous studies have demonstrated the ability of intestinal epithelial cells to produce PGs after infection with wild-type strains of Salmonella, few studies have focused on Salmonella-induced prostanoids in mucosal lymphoid tissues. This is surprising in view of the profound effects PGs can have on the host response. To begin to address PG production at mucosal sites, mice were orally inoculated with Salmonella, and at varying times postinfection cyclooxygenase-2 (COX-2) mRNA expression and PGE(2) synthesis were investigated. COX-2 mRNA expression was highly inducible in the mesenteric lymph nodes, whereas COX-1 mRNA levels were constitutive. PGE(2) production also increased significantly in the mesenteric lymph nodes following exposure to viable Salmonella, but not after exposure to killed bacteria. This increased PGE(2) response could be blocked by treatment of mice with the selective COX-2 inhibitor, celecoxib. Treatment of mice with celecoxib during salmonellosis resulted in increased viable bacteria in the mesenteric lymph nodes by day 3 postinfection. However, celecoxib treatment prolonged the survival of lethally infected animals. In vitro studies demonstrated Salmonella-induced up-regulation of COX-2 mRNA expression and PGE(2) secretion by both macrophages and dendritic cells, which could also be blocked in the presence of celecoxib. Interestingly, exposure of these cultured APCs to viable Salmonella was a much greater stimulus for induction of PGE(2) synthesis than exposure to Salmonella-derived LPS. The present study demonstrates induction of PGE(2) synthesis in mesenteric lymph nodes, macrophages, and dendritic cells after infection with wild-type salmonella.

Prostaglandin E2 induces IL-23 production in bone marrow-derived dendritic cells

Interleukin-23, a recently described cytokine produced by activated antigen-presenting cells, including dendritic cells, is a p19/p40 heterodimer. The p40 subunit is shared with IL-12, the major Th1-driving cytokine, while p19 is distantly related to IL-12 p35. IL-23 has pro-inflammatory actions, inducing IL-17 secretion from activated CD4+ T cells, and stimulating the proliferation of memory CD4+ T cells. Here, we examined the effects of PGE2, a well-known immunomodulator, on the production of IL-23 by bone marrow- derived dendritic cells (BM-DCs). Our results indicate that PGE2 increases the production of functional IL-23 from immature BM-DCs in a time- and dose-dependent manner. PGE2 induces both the expression of p19 and p40, without affecting p35 expression. The effect of PGE2 is mediated through the specific receptors EP2/4 and is mimicked by cAMP-inducing agents, such as forskolin and dbcAMP. Although PGE2 also induces IL-1beta and IL-6 expression in non-stimulated DCs, the stimulatory effect of PGE2 on IL-23 production is not mediated through IL-1beta or IL-6. GM-CSF, the pro-inflammatory cytokine required for the generation of BM-DCs, amplifies the IL-23 inducing activity of PGE2 in a synergistic manner. Recent studies described both pro- and anti-inflammatory effects of PGE2, and our results suggest an additional mechanism for its pro-inflammatory role, particularly significant for autoimmune diseases, such as rheumatoid arthritis.

E-prostanoid (EP)2/EP4 receptor-dependent maturation of human monocyte-derived dendritic cells and induction of helper T2 polarization

Prostaglandin (PG) E(2) induces dendritic cell maturation in cooperation with proinflammatory cytokines [such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta]. To clarify the involvement of E-prostanoid (EP) receptors in the effect of prostaglandin E(2) on human monocyte-derived dendritic cell (MoDC) maturation, we examined the effect of four types of EP receptor-selective agonists on MoDC maturation. PGE(2) as well as 11,15-O-dimethyl prostaglandin (E(2)ONO-AE1-259-01) (EP2 receptor agonist) and ONO-AE1-329 (EP4 receptor agonist) concentration dependently enhanced the expression of CD80, CD86, CD83, and HLA-DR on MoDCs during maturation, especially in the presence of TNF-alpha, whereas 17S-2,5-ethano-6-oxo-17,20-dimethyl prostaglandin E(1) (EP1 receptor agonist) and 16S-9-deoxy-9beta-chloro-15-deoxy-16-hyfroxy-17,17-trimethylene-19,20-didehydro prostaglandin F(2) (EP3 receptor agonist) showed no effect. The maximal effect of ONO-AE1-259-01 was higher than that of ONO-AE1-329; however, the stimulation with ONO-AE1-259-01 was less effective than that with PGE(2). Simultaneous stimulation with both EP receptor agonists produced additive effects and 11-deoxy-PGE(1) (EP2/EP4 receptor mixed agonist) mimicked the effects of PGE(2). Dibutyryl cAMP mimicked the effects of PGE(2), indicating the mediation of PGE(2) action by cAMP. Matured MoDCs induced by PGE(2) or EP2 and/or EP4 receptor agonists showed a decrease in lipopolysaccharide (LPS)-stimulated IL-12p70, IL-6, and IL-10 production. The coculture of naive T cells with matured MoDCs induced under different conditions showed that EP2/EP4-stimulated MoDCs preferentially induced alloresponsive helper T (Th)2 cells. Together, it was concluded that the cooperative stimulation of EP2 and EP4 receptor subtypes by PGE(2) promoted MoDC maturation and inhibited LPS-induced cytokine production in MoDCs. The matured MoDCs under such conditions preferably induced Th2 polarization, indicating the importance of EP2 and EP4 receptors in the determination of Th1/Th2 development of naive T cells.

Reduced T-cell and dendritic cell function is related to cyclooxygenase-2 overexpression and prostaglandin E2 secretion in patients with breast cancer

BACKGROUND

In several neoplastic diseases, including breast cancer, immunosuppression correlates with disease stage, progression, and outcome. Thus, thorough analysis of immune parameters in breast cancer patients may be beneficial in designing effective anticancer immune-based therapies.

METHODS

We investigated dendritic cell and T-cell function in breast cancer patients at various stages of the disease and in age-matched controls. We also evaluated cyclooxygenase-2 (COX-2) expression and prostaglandin E2 (PGE2) levels within the tumor milieu and in the circulation.

RESULTS

T cells from cancer patients showed decreased proliferation in response to CD3 antibody stimulation. Analysis of T-cell helper type 1 and 2 cytokines revealed reduced levels of interferon-gamma, tumor necrosis factor-alpha, interleukin (IL)-12, and IL-2 and increased levels of IL-10 and IL-4. Dendritic cells from these patients showed significantly reduced expression of co-stimulatory molecules (B7 and CD40) and demonstrated reduced phagocytic ability, reduced antigen presentation to T cells, and reduced ability to mature in response to lipopolysaccharide. Data revealed increased synthesis of PGE2, an immune suppressor, along with increased expression of COX-2, a key regulator of PGE2 synthesis.

CONCLUSIONS

COX-2-induced PGE2 may contribute to immunosuppression and may directly block antitumor immunity while promoting tumor growth, providing us with the rationale for using COX-2 inhibition combined with immunotherapy.

Higher prostaglandin e2 production by dendritic cells from subjects with asthma compared with normal subjects

Dendritic cells (DCs) are thought to play an important role in the pathogenesis of allergic disorders through their ability to interact with T cells to initiate and amplify helper T cell Type 2 immune responses. The mechanisms by which this occurs are not completely understood, nor is it clear whether DC function differs between normal individuals and individuals with asthma. We compared the function of DCs from 10 subjects with allergic asthma and 10 normal individuals, focusing on the production of prostaglandin E (PGE) 2, interleukin (IL)-10, and IL-12 p70, mediators that play an important role in helper T cell Type 1/Type 2 polarization. Monocyte-derived DCs were established by culturing monocytes with granulocyte-macrophage colony-stimulating factor and IL-4 for 7 days, and then stimulated with LPS plus IFN-gamma. PGE2, IL-10, and IL-12 production was evaluated by ELISA, whereas cyclooxygenase-1, and -2 messenger RNA expression was analyzed using reverse transcription-polymerase chain reaction. LPS-stimulated monocyte-derived DCs from individuals with asthma exhibited increased PGE2 and IL-10 production, but equivalent IL-12 p70 synthesis, when compared with DCs from normal subjects. Increased PGE2 synthesis by DCs from subjects with asthma was associated with an increase in cyclooxygenase-2 messenger RNA expression. These findings support the notion that DC function is significantly altered in allergic asthma.

Cysteinyl leukotrienes regulate dendritic cell functions in a murine model of asthma

Dendritic cells (DCs) act as APCs in the airway and play a critical role in allergy. Cysteinyl leukotrienes (cysLTs) synthesized from arachidonic acid are primary mediators of immediate asthmatic reaction. The aim of this study was to investigate the effects of cysLTs on Dermatophagoides farinae (Der f)-pulsed mouse myeloid DCs in inducing allergic airway inflammation in vitro and in vivo. Control DC (medium-pulsed), Der f-pulsed DC, cysLT-pulsed DC, Der f- and cysLT-pulsed DC, and Der f-pulsed and cysLT receptor antagonist (LTRA)-treated DC were prepared from murine bone marrow, and the production of cytokines ws compared. Subsequently, these DCs were intranasally instilled into another group of naive mice, followed by intranasal Der f challenge to induce allergic airway inflammation in vivo. Der f-pulsed DC produced significantly higher amounts of IL-10 and IL-12 compared with control DC. Der f- and cysLT-pulsed DC further increased IL-10 production compared with Der f-pulsed DC. In contrast, treatment of Der f-pulsed DC with LTRA increased IL-12 and decreased IL-10. Intranasal instillation of Der f-pulsed DC resulted in airway eosinophilia associated with a significant rise in IL-5 levels in the airway compared with control DC. Pulmonary eosinophilia and excess IL-5 were further enhanced in Der f- and cysLT-pulsed DC-harboring mice. In contrast, Der f-pulsed and LTRA-treated DC significantly inhibited airway eosinophilia, reduced IL-5, and increased IFN-gamma in the airway. Our results suggest that cysLTs play an important role in the development of allergic airway inflammation by regulating the immunomodulatory functions of DCs.

Regulation of interleukin-12 gene expression and its anti-tumor activities by prostaglandin E2 derived from mammary carcinomas

Interleukin-12 (IL-12)-mediated immune responses are critical for the control of malignant development. Tumors can actively resist detrimental immunity of the host via many routes. Prostaglandin E2 (PGE2) is one of the major immune-suppressive factors derived from many types of tumors. Here, we show that systemic administration of recombinant IL-12 could therapeutically control the growth of aggressive TS/A and 4T1 mouse mammary carcinomas. However, PGE2 produced by tumors potently inhibits the production of endogenous IL-12 at the level of protein secretion, mRNA synthesis, and transcription of the constituent p40 and p35 genes. The inhibition can be reversed by NS-398, a selective inhibitor of the enzymatic activity of cyclooxygenase 2 in PGE2 synthesis. Moreover, PGE2-mediated inhibition of IL-12 production requires the functional cooperation of AP-1 and AP-1 strongly suppresses IL-12 p40 transcription. Blocking PGE2 production in vivo results in a marked reduction in lung metastasis of 4T1 tumors, accompanied by enhanced ability of peritoneal macrophages to produce IL-12 and spleen lymphocytes to produce interferon-gamma. This study contributes to the elucidation of the molecular mechanisms underlying the interaction between a progressive malignancy and the immune defense apparatus.

Aging and innate immune cells

The innate immune system serves an important role in preventing microbial invasion. However, it experiences significant changes with advancing age. Among the age-associated changes are: Aged macrophages and neutrophils have impaired respiratory burst and reactive nitrogen intermediates as a result of altered intracellular signaling, rendering them less able to destroy bacteria. Aged neutrophils are also less able to respond to rescue from apoptosis. Aged dendritic cells (DC) are less able to stimulate T and B cells. The altered T cell stimulation is a result of changes in human leukocyte antigen expression and cytokine production, and lower B cell stimulation is a result of changes in DC immune complex binding. Natural killer (NK) cells from the elderly are less capable of destroying tumor cells. NK T cells increase in number and have greater interleukin-4 production with age. Levels of various complement components are also altered with advancing age.

Environmental oxygen tension affects phenotype in cultured bone marrow-derived macrophages

This study tested the hypothesis that the unique phenotype of alveolar macrophages (AM) is maintained through adaptation to the relatively high oxygen partial pressure (Po2) of the lung, through modification of redox-sensitive transcription factors. BALB/c mouse bone marrowderived macrophages (BMC) were differentiated under different Po2and compared functionally to AM and peritoneal macrophages (PM). BMC differentiated in normoxia (Po2140 Torr, BMChigh) were similar to AM in having low phagocytic and antigen presenting cell (APC) activities. However, BMC grown in low oxygen tension as found in other tissues (<40 Torr, BMClow) were better phagocytes and APCs, similar to PM. BMChighwere more oxidative intracellularly than BMClow, based on oxidation of dichlorofluorescein and higher glutathione disulfide/glutathione (GSH) ratios, despite having more GSH. Finally, lipopolysaccharide-induced nuclear factor-κB translocation, measured by laser scanning cytometry, was reduced in BMChighand AM, compared with BMClowand PM, respectively. These data suggest that regulation of the AM phenotype may occur, at least in part, via inhibition of NF-κB by the unique redox environment.

The Immunological Paradox of Pregnancy: A Reappraisal

The survival of the allogeneic conceptus has long been an immunological paradox. Medawar was the first to propose an evasive mechanism based on the concept of self/non-self recognition described in classical transplantation immunology. Since then, several newer models of self/non-self recognition have been proposed, such as the PAMP/PRR system, the Missing Self and the Danger Hypothesis. The present paper considers the fetal-maternal relationship in the context of all these models. The conclusion reached is that none of them is really appropriate because the interface between trophoblast cells of the fetal placenta and the leukocytes of the maternal decidua is unique. Pregnancy is not simply a case of acceptance or rejection like a transplant. The immunological mechanism must provide a balanced environment whereby the conceptus is nurtured by the mother and yet prevented from excessive invasion. Future identification of trophoblast ligands and their respective receptors on uterine Natural Killer cells and other leukocytes is likely to offer the best insight as to how this symbiotic state is achieved.

Pioglitazone and rofecoxib combined with angiostatically scheduled trofosfamide in the treatment of far-advanced melanoma and soft tissue sarcoma

BACKGROUND

Combined treatment approaches targeting tumor cells as well as stromal cells may control chemorefractory malignancies. In the current study, the authors sought to test one such combined approach in the treatment of chemorefractory melanoma and soft tissue sarcoma.

METHODS

A Phase II trial was initiated to analyze the activity of a continuously administered molecularly targeted treatment regimen (daily pioglitazone [45 mg administered orally] and rofecoxib [25 mg administered orally]) combined with sequentially added angiostatic chemotherapy for patients with previously treated metastatic melanoma (n = 19) or soft tissue sarcoma (n = 21). Angiostatic chemotherapy consisted of trofosfamide (50 mg) administered orally 3 times daily beginning on the 15th day after the start of molecularly targeted therapy.

RESULTS

Forty patients were evaluable for response and toxicity. Major side effects (World Health Organization Grade 3 or 4) were not observed. Objective responses and disease stabilization lasting longer than 6 months were noted in 11% and 11%, respectively, of all patients with melanoma and in 19% and 14%, respectively, of all patients with soft tissue sarcoma. Complete remission was noted in one patient with melanoma and in three patients with sarcoma. Both normal C-reactive protein (CRP) levels and CRP levels that decreased by > 30% during the 14-day biomodulator pretreatment period were found to be predictive of prolonged progression-free survival.

CONCLUSIONS

To our knowledge, the current study is the first to demonstrate that a novel, completely orally administered combined biomodulator/metronomic chemotherapy regimen may be active and well tolerated in patients with chemorefractory malignancies.

Effect of Aspirin and Indomethacin on Prostaglandin E2 Synthesis in C6 Glioma Cells

Prostaglandin E2 (PGE2) plays an important role in immunosuppression and tumor growth. PGE2 inhibitors such as aspirin and indomethacin suppress experimental tumor growth. Little is known of the relationship between PGE2 synthesis in brain tumors and the dose of aspirin or indomethacin. The present study was undertaken to evaluate the effect of different doses of aspirin and indomethacin on PGE2 synthesis in C6 glioma cells. C6 glioma cells were incubated with different concentrations (2, 4, and 8 microM) of aspirin and indomethacin for 1, 2, 4, 6, 8, 12, and 24 hours. Intracellular PGE2 concentration was measured by enzyme immunoassay. Each concentration of aspirin and indomethacin effectively inhibited PGE2 synthesis. Concentrations of 2, 4, and 8 microM of aspirin significantly inhibited PGE2 production at 6, 4, and 1 hour, respectively, and the inhibition persisted for more than 24 hours (p < 0.05). Concentrations of 2 and 4 microM of indomethacin were effective at 4 and 2 hours (p < 0.05), respectively. However, inhibition was not observed beyond 12 hours (p > 0.05). Indomethacin 8 microM was effective at 1 hour and the inhibition persisted beyond 24 hours (p < 0.05). Our study demonstrates that aspirin and indomethacin inhibit PGE2 synthesis in C6 glioma cells and that low-dose aspirin is as effective as high-dose aspirin. This study may encourage future clinical use of low-dose aspirin in the prevention or treatment of brain tumors.

Prostaglandin E2 inhibits TNF production in murine bone marrow-derived dendritic cells

Exposure to pathogens induces dendritic cells to release inflammatory cytokines and chemokines. The inflammatory response is controlled by endogenous agents such as anti-inflammatory cytokines, glucocorticoids, anti-inflammatory neuropeptides, and lipid mediators. This study is the first report on the inhibition by prostaglandin E2 (PGE2) of TNF release from bone marrow-derived dendritic cells stimulated with lipopolysaccharide (LPS), a TLR4 ligand, or peptidoglycan, a TLR2 ligand. The inhibition of TNF occurs at both mRNA and protein level. The inhibitory effect of PGE2 is mediated by the EP2 and EP4 receptors, and involves both PKA signaling and mediation by DC-derived IL-10. Intraperitoneal administration of PGE2 together with LPS results in a reduction in serum TNF and intracellular TNF in peritoneal exudate cells, compared to LPS alone. In addition, administration of PGE2 in vivo reduces the numbers of CD11c+ DCc that accumulate in the peritoneal cavity in response to LPS. The various implications of the PGE2-induced reduction in TNF are discussed.

Altered maturation of peripheral blood dendritic cells in patients with breast cancer

Tumours have at least two mechanisms that can alter dendritic cell (DC) maturation and function. The first affects the ability of haematopoietic progenitors to differentiate into functional DCs; the second affects their differentiation from CD14+ monocytes, promoting an early but dysfunctional maturation. The aim of this study was to evaluate the in vivo relevance of these pathways in breast cancer patients. For this purpose, 53 patients with invasive breast cancer were compared to 68 healthy controls. To avoid isolation or culture procedures for enrichment of DCs, analyses were directly performed by flow cytometry on whole-blood samples. The expression of surface antigens and intracellular accumulation of regulatory cytokines upon LPS stimulation were evaluated. The number of DCs, and in particular of the myeloid subpopulation, was markedly reduced in cancer patients (P<0.001). Patient DCs were characterized by a more mature phenotype compared with controls (P=0.016), and had impaired production of IL-12 (P<0.001). These alterations were reverted by surgical resection of the tumour. To investigate the possible role of some tumour-related immunoactive soluble factors, we measured the plasmatic levels of vascular endothelial growth factor, IL-10 and spermine. A significant inverse correlation between spermine concentration and the percentage of DCs expressing IL-12 was found. Evidence was also obtained that in vitro exposure of monocyte-derived DCs to spermine promoted their activation and maturation, and impaired their function. Taken together, our results suggest that both the above-described mechanisms could concomitantly act in breast cancer to affect DC differentiation, and that spermine could be a mediator of dysfunctional maturation of DCs.

Thrombospondin 1 is an autocrine negative regulator of human dendritic cell activation

Thrombospondin 1 (TSP) elicits potent antiinflammatory activities in vivo, as evidenced by persistent, multiorgan inflammation in TSP null mice. Herein, we report that DCs represent an abundant source of TSP at steady state and during activation. Human monocyte-derived immature dendritic cells (iDCs) spontaneously produce TSP, which is strongly enhanced by PGE₂ and to a lesser extent by transforming growth factor (TGF) β, two soluble mediators secreted by macrophages after engulfment of damaged tissues. Shortly after activation via danger signals, DCs transiently produce interleukin (IL) 12 and tumor necrosis factor (TNF) α, thereby eliciting protective and inflammatory immune responses. Microbial stimuli increase TSP production, which is further enhanced by IL-10 or TGF-β. The endogenous TSP produced during early DC activation negatively regulates IL-12, TNF-α, and IL-10 release through its interactions with CD47 and CD36. After prolonged activation, DCs extinguish their cytokine synthesis and become refractory to subsequent stimulation, thereby favoring the return to steady state. Such “exhausted” DCs continue to release TSP but not IL-10. Disrupting TSP–CD47 interactions during their restimulation restores their cytokine production. We conclude that DC-derived TSP serves as a previously unappreciated negative regulator contributing to arrest of cytokine production, further supporting its fundamental role in vivo in the active resolution of inflammation and maintenance of steady state.

Prostaglandin E2 inhibits production of the inflammatory chemokines CCL3 and CCL4 in dendritic cells

Dendritic cells bridge innate and adaptive immunity and participate in both responses. Upon capture of pathogens, dendritic cells release inflammatory cytokines and chemokines, attracting other immune cells to the infection site. Anti-inflammatory cytokines, glucocorticoids, anti-inflammatory neuropeptides, and lipid mediators such as prostaglandin E2 (PGE2) limit and control the inflammatory response. In this study we report that exogenous PGE2 inhibits CCL3 (MIP-1alpha) and CCL4 (MIP-1beta) expression and release from dendritic cells stimulated with either lipopolysaccharide (LPS), a TLR4 ligand, or peptidoglycan, a TLR2 ligand. The inhibition is dose-dependent and occurs at both the mRNA and protein levels. The inhibitory effect is mediated through EP2 and EP4 receptors and requires the presence of PGE2 at the time of LPS stimulation. Intraperitoneal administration of PGE2 together with LPS results in a reduction in the levels of CCL3 and CCL4 released in the peritoneal fluid, a reduction in the number of dendritic cells accumulating in the peritoneal cavity, and a reduction in CCL3 amount per cell in the peritoneal cell population. These results suggest that one of the mechanisms by which endogenous PGE2 acts as an anti-inflammatory agent, is the inhibition of inflammatory chemokine release from activated dendritic cells, preventing the excess accumulation of activated immune cells.

Chapter 4: Genital tract infections, cervical inflammation, and antioxidant nutrients--assessing their roles as human papillomavirus cofactors

Cervical infections by approximately 15 human papillomavirus (HPV) types are the necessary cause of cervical cancer and its immediate precursor lesions. However, oncogenic HPV infections are usually benign and usually resolve within 1-2 years. A few of these infections persist and progress to cervical precancer and cancer. A number of cervical factors, such as infection by sexually transmitted pathogens other than HPV, cervical inflammation, and antioxidant nutrients, may influence the natural history of HPV infection along the pathways of persistence and progression or resolution. We examine the possible roles of these HPV cofactors in cervical carcinogenesis and discuss new methodologies that may enable researchers to measure relevant markers of the cervical microenvironment in which these cofactors may be active.

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.

Dendritic cells in the human decidua

Dendritic cells (DCs) in the pregnant human uterine mucosa have been poorly characterized, although they are likely to regulate immune responses to both placental trophoblast cells and uterine infections. In this study an HLA-DR+, CD11c+ lin- (CD3-, CD19-, CD56-, CD14-) population has been identified by three-color flow cytometry. The cell isolates were prepared either by collagenase digestion or mechanically from first-trimester decidual tissue. The decidual DCs comprised approximately 1.7% of CD45+ cells in the isolates and had the phenotype of immature myeloid DCs. No CD1a+ Langerhans cells or CD123+ plasmacytoid DCs were detected. The decidual DCs were DC-SIGN-, DEC-205+, CD40+. Two subsets could be distinguished on the basis of relative expression of HLA-DR, which also differed in expression of DC-activation markers. The DCs were identified in situ by immunohistology by DEC-205 staining. Cells with dendritic processes were found scattered through both the decidua basalis (in which trophoblast cells are infiltrating) and the decidua parietalis. They were also visible in endothelial-lined spaces. This is the first study to identify and describe the phenotype and distribution of human decidual DCs.

Cyclooxygenase-2 expression and angiogenesis in colorectal cancer

AIM: Cyclooxygenase-2 is involved in a variety of important cellular functions, including cell growth and differentiation, cancer cell motility and invasion, angiogenesis and immune function. However, the role of cyclooxygenase-2 as an angiogenic factor in colorectal cancer tissue is still unclear. We investigated the relationship between cyclooxygenase-2 and angiogenesis by analyzing the expression of cyclooxygenase-2 in colorectal cancer tissue, as well as its association with vascular endothelial growth factor (VEGF) and microvascular density (MVD).

METHODS: The expression of cyclooxygenase-2, VEGF, as well as MVD was detected in 128 cases of colorectal cancer by immunohistochemical staining. The relationship between the cyclooxygenase-2 and VEGF expression and MVD was evaluated. Our objective was to determine the effect of cyclooxygenase-2 on the angiogenesis of colorectal cancer tissue.

RESULTS: Among 128 cases of colorectal cancer, 87 were positive for cyclooxygenase-2 (67.9%), and 49 for VEGF (38.3%), respectively. The microvessel counts ranged from 23 to 142, with a mean of 51.7 (standard deviation, 19.8). The expression of cyclooxygenase-2 was correlated significantly with the depth of invasion, stage of disease, metastasis (lymph node and liver), VEGF expression and MVD. Patients in T3-T4, stage III-IV and with metastasis had much higher expression of cyclooxygenase-2 than patients in T1-T2, stage I-II and without metastasis (P < 0.05). The positive expression rate of VEGF (81.6%) in the cyclooxygenase-2 positive group was higher than that in the cyclooxygenase-2 negative group (18.4%, P < 0.05). Also, the microvessel count (56 ± 16) in cyclooxygenase-2 positive group was significantly higher than that in cyclooxygenase-2 negative group (43 ± 12, P < 0.05). The microvessel count in tumors with positive cyclooxygenase-2 and VEGF was the highest (60 ± 18, 41-142, P < 0.05), whereas that in tumors with negative cyclooxygenase-2 and VEGF was the lowest (39 ± 16, 23-68, P < 0.05).

CONCLUSION: Cyclooxygenase-2 may be associated with tumor progression by madulating the angiogenesis in colorectal cancer tissue and used as a possible biomarker.

Exogenous but not endogenous prostanoids regulate cytokine secretion from murine bone marrow dendritic cells: EP2, DP, and IP but not EP1, EP3, and FP prostanoid receptors are involved

Murine bone marrow-derived dendritic cells (DC), stimulated with lipopolysaccharide (LPS) and/or LPS+interferon-gamma (IFN-gamma), secrete a variety of inflammatory mediators which may modulate their functions. We have examined the potential for exogenous prostanoids, acting in a paracrine fashion, and endogenous prostanoids, acting in an autocrine fashion, to regulate secretion of tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), IL-10, and IL-12 in DC. In order to identify receptors mediating these effects, DC were treated in vitro with receptor-selective prostanoids. Agonists of cyclic AMP-elevating receptors, namely, prostaglandin E(2) (PGE(2)), butaprost (EP(2) receptor), iloprost (IP receptor), and BW245C (DP receptor), dose-dependently inhibited the release of IL-6, TNF-alpha, and IL-12 and enhanced the release of IL-10 from LPS-stimulated DC, with TNF-alpha secretion being the most strongly affected. In contrast, 15-deoxy-Delta(12,14)-PGJ(2)-an activator of nuclear peroxisome proliferator-activated receptor-gamma (PPAR-gamma) receptors-inhibited release of all tested cytokines. Exogenous prostanoids, cyclic AMP-elevating analogs, lost their ability to modulate cytokine release in cells pre-incubated for 4 h with LPS, indicating that prostanoids may affect DC functions during initial phases of LPS stimulation only. Sulprostone and (+)-fluprostenol failed to modulate any of responses tested, suggesting lack of involvement/expression of EP(1), EP(3), and FP receptors in DC activation. In order to examine the role of endogenous prostanoids, DC were treated with inhibitors of cyclooxygenases (COX). At concentrations that completely blocked PGE(2) release, neither indomethacin (nonselective inhibitor) nor rofecoxib (COX-2-selective inhibitor) influenced cytokine release from LPS-stimulated DC. Thus, cytokine release from LPS-stimulated DC does not seem to be autoregulated by endogenous prostanoids, whereas in vivo regulatory function may be fulfilled in a paracrine manner by PGD(2), PGE(2), and PGI(2) released from neighboring cells.

Prostaglandin E2 modulates dendritic cell function via EP2 and EP4 receptor subtypes

We have reported previously that PGE(2) inhibits dendritic cells (DC) functions. Because E prostanoid receptor (EPR) subtypes involved in this action are unknown, expression and functions of these receptors were examined in DC. Western blot and flow cytometry analyses showed that all EPRs were coexpressed in DC. In a dose-dependent manner, lipopolysaccharide (LPS) enhanced EP(2)R/EP(4)R but not EP(1)R/EP(3)R expressions. NS-398, a cyclooxygenase (COX)-2-selective inhibitor, suppressed LPS-enhanced EP(2)R/EP(4)R expression, suggesting that COX-2-issued prostaglandin E(2) (PGE(2)) modulates DC function through stimulation of specific EPR subtypes. Using selective agonists, we found that butaprost, an EP(2)R agonist, and PGE(1) alcohol, an EP(2)R and EP(2)R/EP(4)R agonist, inhibited major histocompatibility complex class II expression and enhanced interleukin-10 production from DC. However, no effect was observed with sulprostone and 17-phenyl-omega-trinor-PGE(2), selective agonists for EP(1)R and EP(1)R/EP(3)R, respectively. Treatment of DC with dibutyryl cyclic adenosine monophosphate (cAMP), an analog of cAMP, mimics PGE(2)-induced, inhibitory effects. Taken together, our data demonstrate that EP(2)R/EP(4)R are efficient for mediating PGE(2)-induced modulation of DC functions.

Antigen presentation and processing in the intestinal mucosa and lymphocyte homing

OBJECTIVE

The mucosal surface of the gastro-intestinal tract is our major interface to the environment. Much of the control of the immune response to the myriads of antigen present at this interface is mediated by professional antigen-presenting dendritic cells (DCs). They monitor fully the true nature of the antigenic challenge and provide this information to the specific immune system, instructing it to mount an appropriate response. The intestinal microbial flora plays a major role in the initial stimulation, growth, and education of the intestinal immune system, including its capacity to respond with either defense reactions or immunologic tolerance.

DATA SOURCES

To review the recent literature on the process of antigen sampling, processing, presentation, and initiation of immune recognition that take place on mucosal surfaces and their draining lymph nodes, especially the intestinal mucosa. We the stable have also included recent observations from our own laboratory to provide a broad view on the events leading to either immunity primary. or tolerance to environmental antigens.

RESULTS

Antigen presentation takes place both via DCs that, like adjoining stars, line the intestinal mucosa and DCs in the Peyer patches, which are the organized lymphoid follicles dispersed throughout the small intestinal mucosa. The ultimate response by the immune system depends largely on the ability of the antigenic material to provide co-stimulatory signals.

CONCLUSIONS

Antigen sampling is prominent at mucosal sites to ensure a fast protective response to pathogenic intruders; however, during steady-state immunologic tolerance initiated via mucosal membranes especially in the gut is a major component in human's capacity to avoid aggressive immune reactivity against harmless materials like foods.

Interleukin-12 p40 secretion by cutaneous CD11c+ and F4/80+ cells is a major feature of the innate immune response in mice that develop Th1-mediated protective immunity to Schistosoma mansoni

Radiation-attenuated (RA) schistosome larvae are potent stimulators of innate immune responses at the skin site of exposure (pinna) that are likely to be important factors in the development of Th1-mediated protective immunity. In addition to causing an influx of neutrophils, macrophages, and dendritic cells (DCs) into the dermis, RA larvae induced a cascade of chemokine and cytokine secretion following in vitro culture of pinna biopsy samples. While macrophage inflammatory protein 1alpha and interleukin-1beta (IL-1beta) were produced transiently within the first few days, the Th1-promoting cytokines IL-12 and IL-18 were secreted at high levels until at least day 14. Assay of C3H/HeJ mice confirmed that IL-12 secretion was not due to lipopolysaccharide contaminants binding Toll-like receptor 4. Significantly, IL-12 p40 secretion was sustained in pinnae from vaccinated mice but not in those from nonprotected infected mice. In contrast, IL-10 was produced from both vaccinated and infected mice. This cytokine regulates IL-12-associated dermal inflammation, since in vaccinated IL-10(-/-) mice, pinna thickness was greatly increased concurrent with elevated levels of IL-12 p40. A significant number of IL-12 p40(+) cells were detected as emigrants from in vitro-cultured pinnae, and most were within a population of rare large granular cells that were Ia(+), consistent with their being antigen-presenting cells. Labeling of IL-12(+) cells for CD11c, CD205, CD8alpha, CD11b, and F4/80 indicated that the majority were myeloid DCs, although a proportion were CD11c(-) F4/80(+), suggesting that macrophages were an additional source of IL-12 in the skin.

Fatty acids, the immune response, and autoimmunity: a question of n-6 essentiality and the balance between n-6 and n-3

The essentiality of n-6 polyunsaturated fatty acids (PUFA) is described in relation to a thymus/thymocyte accretion of arachidonic acid (20:4n-6, AA) in early development, and the high requirement of lymphoid and other cells of the immune system for AA and linoleic acid (1 8:2n-6, LA) for membrane phospholipids. Low n-6 PUFA intakes enhance whereas high intakes decrease certain immune functions. Evidence from in vitro and in vivo studies for a role of AA metabolites in immune cell development and functions shows that they can limit or regulate cellular immune reactions and can induce deviation toward a T helper (Th)2-like immune response. In contrast to the effects of the oxidative metabolites of AA, the longer-chain n-6 PUFA produced by gamma-linolenic acid (18:3n-6, GLA) feeding decreases the Th2 cytokine and immunoglobulin (Ig)G1 antibody response. The n-6 PUFA, GLA, dihomo-gamma-linolenic acid (20:3n-6, DHLA) and AA, and certain oxidative metabolites of AA can also induce T-regulatory cell activity, e.g., transforming growth factor (TGF)-beta-producing T cells; GLA feeding studies also demonstrate reduced proinflammatory interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha production. Low intakes of long-chain n-3 fatty acids (fish oils) enhance certain immune functions, whereas high intakes are inhibitory on a wide range of functions, e.g., antigen presentation, adhesion molecule expression, Th1 and Th2 responses, proinflammatory cytokine and eicosanoid production, and they induce lymphocyte apoptosis. Vitamin E has a demonstrable critical role in long-chain n-3 PUFA interactions with immune functions, often reversing the effects of fish oil. The effect of dietary fatty acids on animal autoimmune disease models depends on both the autoimmune model and the amount and type of fatty acids fed. Diets low in fat, essential fatty acid deficient (EFAD), or high in long-chain n-3 PUFA from fish oils increase survival and reduce disease severity in spontaneous autoantibody-mediated disease, whereas high-fat LA-rich diets increase disease severity. In experimentally induced T cell-mediated autoimmune disease, EFAD diets or diets supplemented with long-chain n-3 PUFA augment disease, whereas n-6 PUFA prevent or reduce the severity. In contrast, in both T cell- and antibody-mediated autoimmune disease, the desaturated/elongated metabolites of LA are protective. PUFA of both the n-6 and n-3 families are clinically useful in human autoimmune-inflammatory disorders, but the precise mechanisms by which these fatty acids exert their clinical effects are not well understood. Finally, the view that all n-6 PUFA are proinflammatory requires revision, in part, and their essential regulatory and developmental role in the immune system warrants appreciation.

Anatomical basis of tolerance and immunity to intestinal antigens

The intestinal immune system has to discriminate between harmful and beneficial antigens. Although strong protective immunity is essential to prevent invasion by pathogens, equivalent responses against dietary proteins or commensal bacteria can lead to chronic disease. These responses are normally prevented by a complex interplay of regulatory mechanisms. This article reviews the unique aspects of the local microenvironment of the intestinal immune system and discuss how these promote the development of regulatory responses that ensure the maintenance of homeostasis in the gut.

Cancer-associated immunodeficiency and dendritic cell abnormalities mediated by the prostaglandin EP2 receptor

Prostaglandin E(2) (PGE(2)), a major COX metabolite, plays important roles in several facets of tumor biology. We characterized the contribution of the PGE(2) EP2 receptor to cancer-associated immune deficiency using EP2(-/-) mice. EP2(-/-) mice exhibited significantly attenuated tumor growth and longer survival times when challenged with MC26 or Lewis lung carcinoma cell lines as compared with their wild-type littermates. While no differences in T cell function were observed, PGE(2) suppressed differentiation of DCs from wild-type bone marrow progenitors, whereas EP2-null cells were refractory to this effect. Stimulation of cells in mixed lymphocyte reactions by wild-type DCs was suppressed by treatment with PGE(2), while EP2(-/-)-derived DCs were resistant to this effect. In vivo, DCs, CD4(+), and CD8(+) T cells were significantly more abundant in draining lymph nodes of tumor-bearing EP2(-/-) mice than in tumor-bearing wild-type mice, and a significant antitumor cytotoxic T lymphocyte response could be observed only in the EP2(-/-) animals. Our data demonstrate an important role for the EP2 receptor in PGE(2)-induced inhibition of DC differentiation and function and the diminished antitumor cellular immune responses in vivo.

Comparative research of dendritic cells cultured from mice bone marrow with different ways

AIM: To compare the biological characteristics of cultured mice bone marrow dendritic cell (BM-DC) in cultural media with peritoneum or with growth stimulating factor.

METHODS: DC progenitors of were isolated from bone marrow of Balb/C mice, and transformed into DC cell by culturing with secretary fluid of peritoneum, mGM-CSF, and mIL-4, respectively. The biological features and immunity of the DC cells were studied with mixed lymphocyte reaction, immunohistochemistry staining, light microscope and scanning electronic microscope.

RESULTS: After culturing for 6-8 days, the number of BM-DC (6x106) released from proliferating colony in media containing mGM-CSF and mIL-4 was higher than that in media containing peritoneum without significant difference. High level of expressed CD86 on BM-DC was demonstrated on day 7 in culture, MLR results indicated that the stimulating ability for proliferation of T cell was higher in media with mGM-CSF, mIL-4 than that with peritoneum, while the control media without stimulating factors showed no ability to stimulate the growth of T cells

CONCLUSION: These observations demonstrated that auto-peritoneum can substitute for cytokines in media and stimulate the growth of bone marrow-derived DCs, which possess the corresponding cellular biological features and cellular immunity.

Mechanisms of enhanced macrophage-mediated prostaglandin E2 production and its suppressive role in Th1 activation in Th2-dominant BALB/c mice

PGE(2) has been known to suppress Th1 responses. We studied the difference in strains of mice in PGE(2) production by macrophages and its relation to Th1 activation. Macrophages from BALB/c mice produced greater amounts of PGE(2) than those from any other strains of mice, including C57BL/6, after LPS stimulation. In accordance with the amount of PGE(2) produced, macrophage-derived IL-12 and T cell-derived IFN-gamma production were more strongly suppressed in BALB/c macrophages than in C57BL/6 macrophages. When macrophages were treated with indomethacin or EP4 antagonist, Th1 cytokines were more markedly increased in cells from BALB/c mice than in those from C57BL/6 mice. Although cyclooxygenase-2 was expressed similarly after LPS stimulation in these mouse strains, the release of arachidonic acid and the expression of type V secretory phospholipase A(2) mRNA were greater in BALB/c macrophages. However, exogenous addition of arachidonic acid did not reverse the lower production of PGE(2) by C57BL/6 macrophages. The expression of microsomal PGE synthase, a final enzyme of PGE(2) synthesis, was also greater in BALB/c macrophages. These results indicate that the greater production of PGE(2) by macrophages, which is regulated by secretory phospholipase A(2) and microsomal PGE synthase but not by cyclooxygenase-2, is related to the suppression of Th1 cytokine production in BALB/c mice.

Differential expression of platelet-activating factor acetylhydrolase in macrophages and monocyte-derived dendritic cells

Although macrophages (Mphi) and monocyte-derived dendritic cells (MDDC) come from a common precursor, they are distinct cell types. This report compares the two cell types with respect to the metabolism of platelet-activating factor (PAF), a biologically active lipid mediator. These experiments were prompted by our studies of localized juvenile periodontitis, a disease associated with high IgG2 production and a propensity of monocytes to differentiate into MDDC. As the IgG2 Ab response is dependent on PAF, and MDDC selectively induce IgG2 production, we predicted that PAF levels would be higher in MDDC than in Mphi. To test this hypothesis, human MDDC were prepared by treating adherent monocytes with IL-4 and GM-CSF, and Mphi were produced by culture in M-CSF. Both Mphi and MDDC synthesized PAF; however, MDDC accumulated significantly more of this lipid. We considered the possibility that PAF accumulation in MDDC might result from reduced turnover due to lower levels of PAF acetylhydrolase (PAFAH), the enzyme that catabolizes PAF. Although PAFAH increased when monocytes differentiated into either cell type, MDDC contained significantly less PAFAH than did Mphi and secreted almost no PAFAH activity. The reduced levels of PAFAH in MDDC could be attributed to lower levels of expression of the enzyme in MDDC and allowed these cells to produce PGE(2) in response to exogenous PAF. In contrast, Mphi did not respond in this manner. Together, these data indicate that PAF metabolism may impinge on regulation of the immune response by regulating the accessory activity of MDDC.

Prostaglandins inhibit 5-lipoxygenase-activating protein expression and leukotriene B4 production from dendritic cells via an IL-10-dependent mechanism

PGs produced from arachidonic acid by the action of cyclooxygenase enzymes play a pivotal role in the regulation of both inflammatory and immune responses. Because leukotriene B4 (LTB4), a product of 5-lipoxygenase (5-LO) pathway, can exert numerous immunoregulatory and proinflammatory activities, we examined the effects of PGs on LTB4 release from dendritic cells (DC) and from peritoneal macrophages. In concentration-dependent manner, PGE1 and PGE2 inhibited the production of LTB4 from DC, but not from peritoneal macrophage, with an IC50 of 0.04 microM. The same effect was observed with MK-886, a 5-LO-activating protein (FLAP)-specific inhibitor. The decreased release of LTB4 was associated with an enhanced level of IL-10. Furthermore, the inhibition of LTB4 synthesis by PGs was significantly reversed by anti-IL-10, suggesting the involvement of an IL-10-dependent mechanism. Hence, we examined the effects of exogenous IL-10 on the 5-LO pathway. We demonstrate that IL-10 suppresses the production of LTB4 from DC by inhibiting FLAP protein expression without any effect on 5-LO and cytosolic phospholipase A2. Taken together, our results suggest links between DC cyclooxygenase and 5-LO pathways during the inflammatory response, and FLAP is a key target for the PG-induced IL-10-suppressive effects.

A clinical grade cocktail of cytokines and PGE2 results in uniform maturation of human monocyte-derived dendritic cells: implications for immunotherapy

Dendritic cells (DCs) can induce tumor- or pathogen-specific T cell responses in humans. We comprehensively compared the clinically available DC maturation stimuli for their ability to promote uniformly mature DCs that elicit higher levels of T cell responses. We compared the standard maturation stimulus, autologous monocyte-conditioned medium (MCM), with a synthetic double stranded RNA (poly I:C), soluble CD40 ligand trimer, and a defined cocktail of cytokines (TNF-alpha, IL-1 beta, IL-6) and PGE(2) to promote mature phenotype and function in human monocyte-derived DCs. The cocktail was the most efficient despite the lack of induction of IL-12p70. While these results support the use of the MCM-mimic cocktail in clinical DC immunotherapy trials, the roles of it's individual constituents remain to be completely defined.

Comparative study of the endotoxemia and endotoxin tolerance on the production of Th cytokines and macrophage interleukin-6: differential regulation of indomethacin

Endotoxin tolerance reduces the capacity of monocytes to produce proinflammatory cytokines, results in cellular immune paralysis, and down-regulates the production of helper T (Th)1 type cytokines with a shift toward a Th2 cytokine response. Prostaglandin (PG)E2 in the immune system also results in macrophage inactivation and the suppression of Th1 activation and the enhancement of Th2 activation. However, the inhibitory effects of PGE2 on the altered polarization of the Th cell and macrophage interleukin (IL)-6 production characterized in part by cellular immune paralysis in a state of endotoxin tolerance is unclear. This study was undertaken, using indomethacin, to investigate the role of endogenous PGE2 on the Th cytokines and macrophage IL-6 production in a state of endotoxin tolerance compared to those with endotoxemia mice, wherein, in this latter case, the increased production of proinflammatory cytokines and PGE2 is exhibited. Endotoxemia was induced by injection of lipopolysaccharide (LPS; 10 mg/kg in saline) ip. once in BALB/c mice, and endotoxin tolerance was induced by pretreatment with LPS (1 mg/kg in saline) injected i.p. daily for two consecutive days and then with LPS 10 mg/kg on day 4. Splenocytes or macrophages were obtained from endotoxemia and endotoxin tolerance models pretreated with indomethacin, and then cytokine production was induced by Con A-stimulated splenocytes for the Th cytokine assays and LPS-stimulated macrophages for the IL-6 assay. Our results showed that endotoxemia led to significantly reduced IL-2 and IL-4 production, to significantly increased IL-6 production, whereas interferon (IFN)-gamma production was not affected. Indomethacin in the case of endotoxemia markedly attenuated IFN-gamma and IL-6 production and didnt reverse IL-2 and IL-4 production. Endotoxin tolerance resulted in the significantly reduced production of IL-2 and IFN-gamma and the significantly increased production of IL-4 and IL-6. Indomethacin in endotoxin tolerance greatly augmented IL-2 production, significantly decreased IL-4 production, and slightly attenuated IL-6 production. These findings indicate that endogenous PGE2 may mediate the suppressed Th1 type immune response, with a shift toward a Th2 cytokine response in a state of endotoxin tolerance, whereas endotoxemia may be regulated differentially. Also, endogenous PGE2 may mediate macrophage IL-6 production in the case of endotoxemia to a greater extent than in the case of endotoxin tolerance.

Mast cells, neuropeptides, histamine, and prostaglandins in UV-induced systemic immunosuppression

There is a direct correlation between dermal mast cell prevalence in dorsal skin of different mouse strains and susceptibility to UVB-induced systemic immunosuppression; highly UV-susceptible C57BL/6 mice have a high dermal mast cell prevalence while BALB/c mice, which require considerable UV radiation for 50% immunosuppression, have a low mast cell prevalence. There is also a functional link between the prevalence of dermal mast cells and susceptibility to UVB- and cis-urocanic acid (UCA)-induced systemic immunosuppression. Mast cell-depleted mice are unresponsive to UVB or cis-UCA for systemic immunosuppression unless they are previously reconstituted at the irradiated or cis-UCA-administered site with bone marrow-derived mast cell precursors. cis-UCA does not stimulate mast cell degranulation directly. Instead, in support of studies showing that neither UVB nor cis-UCA was immunosuppressive in capsaicin-treated, neuropeptide-depleted mice, cis-UCA-stimulated neuropeptide release from sensory c-fibers which, in turn, could efficiently degranulate mast cells. Studies in mice suggested that histamine, and not tumor necrosis factor alpha (TNF-alpha), was the product from mast cells that stimulated downstream immunosuppression. Histamine receptor antagonists reduced by approximately 60% UVB and cis-UCA-induced systemic immunosuppression. Indomethacin administration to mice had a similar effect which was not cumulative with the histamine receptor antagonists. Histamine can stimulate keratinocyte prostanoid production. We propose that both histamine and prostaglandin E(2) are important in downstream immunosuppression; both are regulatory molecules supporting the development of T helper 2 cells and reduced expression of type 1 immune responses such as a contact hypersensitivity reaction.

PPAR and immune system--what do we know?

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear steroid receptor superfamily. Originally, the receptors were identified as critical controllers for several key enzymes that catalyze the oxidation of fatty acids. PPARs consist of three members: PPAR-alpha, PPAR-beta/delta, and PPAR-gamma. Among them, PPAR-gamma is essential for controlling thermogenesis and adipocyte differentiation. The ligands for PPAR-gamma include 15-deoxy-delta(12,14)-prostaglandin J2 (15d-PGJ2)--a metabolite from the prostaglandin synthesis pathway, and "glitazones"--drugs utilized in the treatment of patients with diabetes. The precursors for prostaglandins are fatty acids consumed from diet and these precursors have long been postulated to have a regulatory role in immune functions. Emerging evidence indicates that PPAR-gamma and its ligands are indeed important for the modulation of immune and inflammatory reactions. In this review, we will spotlight the molecular mechanisms of receptor/ligand function and how they may regulate immune and inflammatory reactions. We also propose that PPAR-gamma and its endogenous ligands are participating factors for Type 1/Type 2 T and NK cell differentiation and development. Deciphering the mechanism of action of PPAR-gamma and its ligands may lead to a new therapeutic regiment for treatment of diseases involving dysfunction of the immune system.