Proinflammatory cytokines interact synergistically with epidermal growth factor to stimulate PGE2 production in amnion-derived cells

The Bradykinin System Contributes to the Regulation of Prostaglandin-Endoperoxide Synthase 2 Expression in Human Amnion Fibroblasts: Implications for Term and Preterm Birth

BACKGROUND

Bradykinin (BK) and its biologically active metabolite des-Arg9 bradykinin (DABK) play a pivotal role in inflammation. Since chorioamnionitis is the leading cause of preterm birth and prostaglandin E2 (PGE2) derived from the amnion is key to labor initiation, we investigated if bradykinin peptides are part of the regulatory network of PGE2 synthesis in human amnion at parturition.

METHODS

Human amnion tissue was obtained from term and preterm birth for the study of the changes of the bradykinin system at parturition. Cultured primary human amnion fibroblasts, the major source of PGE2, were used to study the effects of bradykinin peptides on PTGS2 expression and PGE2 production as well as the effects of infection mediators on bradykinin receptors.

RESULTS

Bradykinin peptides and their receptors BDKRB1 and BDKRB2 were present in human amnion, and their abundance increased in term and preterm labor. However, transcripts of the genes encoding the bradykinin precursor and its proteolytic cleavage enzymes were hardly detectable in human amnion despite the increased abundance of bradykinin peptides in term and preterm labor, suggesting that there is an alternative source of bradykinin peptides for human amnion and their actions are enhanced in human amnion at parturition. In-vitro studies in cultured human amnion fibroblasts showed that both BK and DABK increased the expression of prostaglandin-endoperoxide synthase 2 (PTGS2), the rate-limiting enzyme in prostaglandin synthesis, and subsequent PGE2 production. These effects of BK and DABK were mediated through BDKRB2 and BDKRB1 receptors, respectively, with subsequent activation of the p38 and ERK1/2 pathways. Moreover, lipopolysaccharide (LPS) and serum amyloid A1 (SAA1), the important mediators of infectious inflammation, induced the expression of both BDKRB1 and BDKRB2 through toll-like receptor 4 (TLR4). Induction of BDKRB1 and BDKRB2 expression by LPS and SAA1 enhanced BK- or DABK-induced PTGS2 expression and PGE2 production in human amnion fibroblasts.

CONCLUSIONS

This study demonstrated for the first time that the human amnion is a target tissue of bradykinin peptides and the bradykinin system may be part of the regulatory network of PTGS2 expression and PGE2 production in human amnion fibroblasts at both term and preterm birth, which may be enhanced by infection.

Antigen-presenting cells in pregnant and non-pregnant human myometrium

PROBLEM

Inflammatory cells play a crucial role in human parturition. Different populations of leucocytes invade the reproductive tract. Numerous studies have described the decidual immune cell population in pregnant and non-pregnant endometrium. However, little is known about the presence of immune cells in human myometrium.

METHOD OF STUDY

we herein analysed a spectrum of immune cells in human myometrium comparing tissue samples from non-pregnant (n = 8) and pregnant (n = 10) uteri. Applying immunohistochemistry with a panel of antibodies specific for T cells, monocytes, natural killer cells, B cells and antigen-presenting cells (CD4, CD8, CD14, CD15, CD16, CD19, CD56, CD68, CD83, HLA-DR, DC-Sign, mast cell tryptase), we characterized the immune cell population of human myometrium.

RESULTS

a significantly higher number of CD14, CD15, CD16, DC-SIGN as well as CD4-positive cells were found in myometrium of pregnant compared to non-pregnant uteri, while mast cells were significantly reduced in pregnant myometrium.

CONCLUSION

all markers found increased in pregnant myometrium indicate monocyte/macrophage lineage cells and thus suggest a possible involvement of these cells in healthy pregnancy maintenance. Monocytes/macrophages might produce a microenvironment that permits a controlled invasion of trophoblast cells into the myometrium while preventing a rejection of the semiallogenic conceptus and providing an important barrier against invading pathogenes.

Epidermal growth factor synergistically enhances interleukin-8 production in human gingival fibroblasts stimulated with interleukin-1beta

The chemokine interleukin-8 (IL-8) has been implicated in inflammatory diseases including periodontitis. In this study the effect of epidermal growth factor (EGF) on the production and regulation of interleukin-8 (IL-8) in human gingival fibroblasts challenged with interleukin-1beta (IL-1beta) was investigated. EGF, in comparison to the effect of IL-1beta, weakly increased the mRNA and protein expression of IL-8 in gingival fibroblasts. When the cells were treated simultaneously with EGF and IL-1beta, however, EGF synergistically enhanced the mRNA expression and production of IL-8. The stimulatory effect of EGF on IL-1beta-induced IL-8 production was completely abolished by the broad range tyrosine kinase inhibitor Herbimycin A, and considerably reduced by the receptor tyrosine kinase specific inhibitor PD 153035. Herbimycin A abolished IL-8 production induced by IL-1beta, whereas PD 153035 had no effect on the cytokine-induced IL-8 production. Furthermore, the p38 mitogen-activated protein (MAP) kinase inhibitor SB 203580 reduced IL-8 production induced by IL-1beta as well as by the combination of EGF and IL-1beta but had no effect on EGF-induced IL-8 production. In conclusion, the study demonstrates that EGF synergistically stimulates IL-8 production in the presence of IL-1beta and that tyrosine kinase(s) seem to be involved in the signalling pathway of IL-1beta and EGF. The synergistic interactions between EGF and IL-1beta on IL-8 production may play an essential role in the pathogenesis of the inflammatory disease periodontitis.

Modulation of cytokine-induced cyclooxygenase 2 expression by PPARG ligands through NFkappaB signal disruption in human WISH and amnion cells

Cyclooxygenase (COX) activity increases in the human amnion in the settings of term and idiopathic preterm labor, contributing to the generation of uterotonic prostaglandins (PGs) known to participate in mammalian parturition. Augmented COX activity is highly correlated with increased COX2 (also known as prostaglandin-endoperoxide synthase 2, PTGS2) gene expression. We and others have demonstrated an essential role for nuclear factor kappaB (NFkappaB) in cytokine-driven COX2 expression. Peroxisome proliferator-activated receptor gamma (PPARG), a member of the nuclear hormone receptor superfamily, has been shown to antagonize NFkappaB activation and inflammatory gene expression, including COX2. We hypothesized that PPARG activation might suppress COX2 expression during pregnancy. Using primary amnion and WISH cells, we evaluated the effects of pharmacological (thiazolidinediones) and putative endogenous (15-deoxy-Delta(12,14)-prostaglandin J2, 15d-PGJ2) PPARG ligands on cytokine-induced NFkappaB activation, COX2 expression, and PGE2 production. We observed that COX2 expression and PGE2 production induced by tumor necrosis factor alpha (TNF) were significantly abrogated by 15d-PGJ2. The thiazolidinediones rosiglitazone (ROSI) and troglitazone (TRO) had relatively little effect on cytokine-induced COX2 expression except at high concentrations, at which these agents tended to increase COX2 abundance relative to cells treated with TNF alone. Interestingly, treatment with ROSI, but not TRO, led to augmentation of TNF-stimulated PGE2 production. Mechanistically, we observed that 15d-PGJ2 markedly diminished cytokine-induced activity of the NFkappaB transcription factor, whereas thiazolidinediones had no discernable effect on this system. Our data suggest that pharmacological and endogenous PPARG ligands use both receptor-dependent and -independent mechanisms to influence COX2 expression.

Epidermal growth factor and interleukin-1beta utilize divergent signaling pathways to synergistically upregulate cyclooxygenase-2 gene expression in human amnion-derived WISH cells

In human parturition, uterotonic prostaglandins (PGs) arise predominantly via increased expression of cyclooxygenase-2 (COX-2 [also known as prostaglandin synthase 2]) within intrauterine tissues. Interleukin-1 (IL-1) and epidermal growth factor (EGF), both inducers of COX-2 transcription, are among numerous factors that accumulate within amniotic fluid with advancing gestation. It was previously demonstrated that EGF could potentiate IL-1beta-driven PGE(2) production in amnion and amnion-derived (WISH) cells. To define the mechanism for this observation, we hypothesized that EGF and IL-1beta might exhibit synergism in regulating COX-2 gene expression. In WISH cells, combined treatment with EGF and IL-1beta resulted in a greater-than-additive increase in COX-2 mRNA relative to challenge with either agent independently. Augmentation of IL-1beta-induced transactivation by EGF was not observed in cells harboring reporter plasmids bearing nuclear factor-kappa B (NFkappaB) regulatory elements alone, but was evident when a fragment (-891/ +9) of the COX-2 gene 5'-promoter was present. Both agents transiently activated intermediates of multiple signaling pathways potentially involved in the regulation of COX-2 gene expression. The 26 S proteasome inhibitor, MG-132, selectively abrogated IL-1beta-driven NFkappaB activation and COX-2 mRNA expression. Only pharmacologic blockade of the p38 mitogen-activated protein kinase eliminated COX-2 expression following EGF stimulation. We conclude that EGF and IL-1beta appear to signal through different signaling cascades leading to COX-2 gene expression. IL-1beta employs the NFkappaB pathway predominantly, while the spectrum of EGF signaling is broader and includes p38 kinase. The synergism observed between IL-1beta and EGF does not rely on augmented NFkappaB function, but rather, occurs through differential use of independent response elements within the COX-2 promoter.

Effects of inflammatory cytokines on prostaglandin E(2) production from human amnion cells cultured in serum-free condition

The effects of five inflammatory cytokines, i.e. interleukin(IL)-1alpha, IL-1beta, IL-6, IL-8 and tumor necrosis factor-alpha (TNF-alpha) on prostaglandin E(2) (PGE(2)) production from amnion cells cultured in a serum-free condition was evaluated. After human amnion cells obtained from term placenta were incubated with the inflammatory cytokines at various concentrations, PGE(2) production in the culture supernatant was determined using an enzyme immunoassay method. Under a serum-free culture condition, an increase in PGE(2) production by IL-1alpha and IL-1beta was observed at concentrations of 10 and 100 ng/ml compared to control cultures. However, the increases in PGE(2) production by IL-6 and IL-8 were found at relatively high concentrations, i.e. at 100 and 200 ng/ml. TNF-alpha induced a significant increase in PGE(2) production at 50 and 100 ng/ml, but not at 200 ng/ml. These data suggest that these inflammatory cytokines directly stimulate PGE(2) production from amnion cells and may initiate premature labor if amniotic inflammatory cytokines are elevated, e.g. following intrauterine infection.

Cyclic AMP response element mediates dexamethasone induced suppression of prostaglandin H synthase-2 gene expression in human amnion derived WISH cells

A human PGHS-2 promoter fragment (300 BP) linked to the luciferase reporter was used to study the regulation of PGHS-2 gene expression in human amnion-derived WISH cells. A cyclic AMP (cAMP) response element (CRE) was found to be important in the induction of PGHS-2 gene expression. This was demonstrated by showing that coexpression of CREB stimulated native but not CRE mutant promoter and that IL-1beta and PMA induced less activity with the mutant promoter as compared to the native promoter. The effect of dexamethasone on IL-1beta and PMA induced promoter activities was further examined. IL-1beta or PMA induced activity was blocked by dexamethasone, whereas IL-1beta or PMA induced mutant activity was not responsive to dexamethasone. Direct activation of CRE by a cAMP elevating agent, isoproterenol, was found to be inhibited significantly dexamethasone. These results suggest that CRE may mediate the induction of PGHS-2 by IL-1beta and PMA as well as the suppression of expression by dexamethasone in amnion-derived cells.

The effect of interleukin-1 beta and interleukin-4 on the expression of prostaglandin receptors EP1 and EP3 in amnion WISH cells

PROBLEM

Although prostaglandin E2 (PGE2) is believed to modulate biochemical and immunological events leading to parturition, the role of prostaglandin E receptors during labor has not been investigated.

METHOD OF STUDY

Amnion WISH cells were incubated in media containing increasing concentrations of either interleukin-1 beta (IL-1 beta) or IL-4. Increased EP1 and EP3 protein expression was determined by Western blot analysis with peptide-specific antibodies. Concomitant measurements of culture media PGE2 were made by an enzyme immunoassay.

RESULTS

Incubation of WISH cells with IL-1 beta or IL-4 caused a two- to three-fold increase in EP1 protein levels. IL-1 beta and IL-4 also caused six- and two-fold increases, respectively, in culture fluid PGE2 concentrations. IL-1 beta or IL-4 had no effect on EP3 protein levels.

CONCLUSIONS

Based on these results, it is proposed that IL-1 beta and IL-4 may be involved in the initiation and promotion of labor by inducing EP1 levels and PGE2 production in amnion.

Stimulation of prostaglandin E2 synthesis by interleukin-1beta is amplified by interferons but inhibited by interleukin-4 in human amnion-derived WISH cells

Human amnion-derived WISH cells synthesize little prostaglandin E2 at the basal state. However, the cells were stimulated greatly to synthesize prostaglandin E2 by interleukin-1beta in a dose-dependent manner. Stimulation by interleukin-1beta was synergistically increased by pretreatment of the cells with interferon alpha or gamma, which alone were inactive. Synergism by interferons was dose-dependent. Stimulation by interleukin-1beta, on the contrary, was inhibited by preincubation of the cells with interleukin-4. Inhibition by interleukin-4 was also dose-dependent. Regulation of prostaglandin E2 synthesis by cytokines was further examined at the m-RNA level of cyclooxygenase-2. Quantitative reverse transcription-polymerase chain reaction indicated that the m-RNA level was not increased by interferon-gamma but was synergistically increased by interferon-gamma plus interleukin-1beta. Furthermore, the m-RNA level increased by interleukin-1beta was attenuated by interleukin-4. These results indicate that regulation of interleukin-1beta-stimulated prostaglandin E2 synthesis by interferons and interleukin-4 is controlled at the m-RNA level of cyclooxygenase-2.

Interleukin-1 beta regulates the inducible cyclooxygenase in amnion-derived WISH cells

The purpose of this study was to determine the mechanism of enhanced prostaglandin synthesis in amnion-derived WISH cell cultures when stimulated by interleukin-1 beta (IL-1 beta). Confluent monolayer cultures of WISH cells were incubated with human recombinant IL-1 beta (0.001-10 ng/ml) for 0-24 hours, while control cells received medium alone. PGE2 production was measured by specific radioimmunoassay. IL-1 beta enhanced the production of PGE2 in a dose- and time-dependent manner with enhanced production detectable by 2 h following exposure. Immunoblot analysis using isoform-specific antibodies showed that the inducible cyclooxygenase enzyme, i.e., COX-2, was expressed by 2 h in IL-1 treated cells, while the constitutive COX-1 remained unaltered in its expression. Northern blot analysis demonstrated that COX-2 mRNA expression was not detected in untreated cells, but became evident after a 30-min exposure to IL-1 beta (10 ng/ml). COX-1 mRNA was detected under basal conditions and did not increase significantly following IL-1 beta treatment. The close parallel between the kinetics of COX-2 mRNA and protein expression and PGE2 accumulation in the medium, as well as the constitutive, unregulated nature of the COX-1 isoform, indicates that cytokine-driven PGE2 formation in WISH cells may be mediated by de novo expression of the novel COX-2 enzyme.

Epidermal growth factor and transforming growth factor-alpha enhance the interleukin-1- and tumor necrosis factor-stimulated prostaglandin E2 production and the interleukin-1 specific binding on amnion cells

Interleukin-1 (IL-1), tumor necrosis factor (TNF), epidermal growth factor (EGF), and transforming growth factor-alpha (TGF-alpha) stimulate prostaglandin E2 (PGE2) production by amnion cells whereas TGF-beta inhibits the PGE2 production. During labor occurring in the setting of infection, several of these cytokines may be simultaneously present in amniotic fluid. The aim of the present study was to examine whether these cytokines modify each others' effects on amnion cell PGE2 production. Amnion cells in monolayer culture were treated with IL-1, TNF, EGF, TGF-alpha, TGF-beta 1, their combination, or vehicle. The PGE2 production and the specific binding of radiolabeled IL-1 beta on the cells were measured. IL-1 or TNF in combination with EGF or TGF-alpha stimulated synergistically the production of PGE2 by amnion cells. TGF-beta 1 did not modify the PGE2-stimulatory effect of EGF/TGF-alpha. Untreated amnion cells expressed 1030 +/- 100 IL-1 beta receptors per cell with a binding affinity of 1.40 +/- 0.26 nM. Treatment with TGF-alpha increased the number of receptors to 3940 +/- 260 per cell with no change in binding affinity. The potentiation of the PGE2-stimulatory effect of IL-1 by TGF-alpha may be related to its ability to induce IL-1 receptors on amnion cells. The synergistic effects of cytokines on amnion cell PGE2 production may promote labor.

Transforming growth factor-beta potentiates epidermal growth factor-induced prostaglandin E2 production in amnion cells

Primary cultures of human amnion cells and the amnion-derived cell line WISH were used to evaluate the hypothesis that transforming growth factor-beta (TGF-beta) can modulate epidermal growth factor (EGF)- induced prostaglandin E2 (PGE2) production. Cells were preincubated for 1 hr with TGF-beta (0.0001-10 ng/ml) and then incubated in the presence or absence of EGF (10 ng/ml) for 4 hrs. TGF-beta alone did not stimulate PGE2 synthesis at any dose examined. However, when primary cultures of amnion cells or WISH cells were preincubated with TGF-beta and then challenged with EGF, there was a potentiation of PGE2 production that was much greater than the additive values of TGF-beta or EGF alone. These data suggest that EGF-induced PGE2 production by amnion cells can be modulated by low concentrations of TGF-beta.