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

Novel 1,2,4-triazoles derived from Ibuprofen: synthesis and in vitro evaluation of their mPGES-1 inhibitory and antiproliferative activity

Some novel triazole-bearing ketone and oxime derivatives were synthesized from Ibuprofen. In vitro cytotoxic activities of all synthesized molecules against five cancer lines (human breast cancer MCF-7, human lung cancer A549, human prostate cancer PC-3, human cervix cancer HeLa, and human chronic myelogenous leukemia K562 cell lines) were evaluated by MTT assay. In addition, mouse embryonic fibroblast cells (NIH/3T3) were also evaluated to determine the selectivity. Compounds 18, 36, and 45 were found to be the most cytotoxic, and their IC50 values were in the range of 17.46-68.76 µM, against the tested cancer cells. According to the results, compounds 7 and 13 demonstrated good anti-inflammatory activity against the microsomal enzyme prostaglandin E2 synthase-1 (mPGES-1) enzyme at IC50 values of 13.6 and 4.95 µM. The low cytotoxicity and non-mutagenity of these compounds were found interesting. Also, these compounds significantly prevented tube formation in angiogenesis studies. In conclusion, the anti-inflammatory and angiogenesis inhibitory activities of these compounds without toxicity suggested that they may be promising agents in anti-inflammatory treatment and they may be supportive agents for the cancer treatment.

Chemistry and biology of microsomal prostaglandin E2 synthase-1 (mPGES-1) inhibitors as novel anti-inflammatory agents: recent developments and current status

Prostaglandin (PG) E₂, a key mediator of inflammatory pain and fever, is biosynthesized from PGH₂ by mPGES-1.

Prostaglandin catabolic enzymes as tumor suppressors

15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is a key prostaglandin catabolic enzyme catalyzing the oxidation and inactivation of prostaglandin E(2) (PGE(2)) synthesized from the cyclooxygenase (COX) pathway. Accumulating evidence indicates that 15-PGDH may function as a tumor suppressor antagonizing the action of COX-2 oncogene. 15-PGDH has been found to be down-regulated contributing to elevated levels of PGE(2) in most tumors. The expression of 15-PGDH and COX-2 appears to be regulated reciprocally in cancer cells. Down-regulation of 15-PGDH in tumors is due, in part, to transcriptional repression and epigenetic silencing. Numerous agents have been found to up-regulate 15-PGDH by down-regulation of transcriptional repressors and by attenuation of the turnover of the enzyme. Up-regulation of 15-PGDH may provide a viable approach to cancer chemoprevention. Further catabolism of 15-keto-prostaglandin E(2) is catalyzed by 15-keto-prostaglandin-∆(13)-reductase (13-PGR), which also exhibits LTB(4)-12-hydroxydehydrogenase (LTB(4)-12-DH) activity. 13-PGR/LTB(4)-12-DH behaves as a tumor suppressor as well. This review summarizes current knowledge of the expression and function of 15-PGDH and 13-PGR/LTB(4)-12-DH in lung and other tissues during tumor progression. Future directions of research on these prostaglandin catabolic enzymes as tumor suppressors are also discussed.

Interleukin-4 up-regulates 15-hydroxyprostaglandin dehydrogenase (15-PGDH) in human lung cancer cells

IL-4, an anti-inflammatory cytokine, was found to stimulate 15-PGDH activity in A549 and other lung cancer cells. Increase in 15-PGDH activity was due to increased transcription and decreased protein turnover of 15-PGDH. MMP-9 was shown to result in decreased levels of 15-PGDH in A549 cells. IL-4 induced down-regulation of MMP-9 mRNA and up-regulation of TIMP-1, an inhibitor of MMP-9. These data suggest that IL-4-induced down-regulation of MMP-9 activity may contribute to up-regulation of 15-PGDH in A549 cells. The role of JAK-STAT6 in IL-4-induced 15-PGDH expression was examined by using inhibitors. Inhibitors of JAKs, kaempferol and JAK inhibitor I, attenuated IL-4-stimulated STAT6 phosphorylation and 15-PGDH activity in a comparable concentration-dependent manner. Furthermore, JAK inhibitor I blocked IL-4-induced down-regulation of MMP-9 mRNA and up-regulation of TIMP-1 but not IL-4-stimulated up-regulation of 15-PGDH mRNA. These results indicate that JAK-STAT6 participated in IL-4-induced up-regulation of 15-PGDH through inhibition of MMP-9-mediated degradation. The roles of other signaling kinases in IL-4-induced 15-PGDH expression were also examined by using various inhibitors. Inhibitors of various MAPKs, PI-3K and PKC attenuated significantly IL-4-stimulated 15-PGDH activity indicating that MAPKs, PI-3K/Akt and PKC pathways participated in IL-4-induced up-regulation of 15-PGDH. Our results indicate that IL-4 up-regulates 15-PGDH by increased gene transcription and decreased protein turnover and the up-regulation can be mediated by JAK-STAT6 as well as MAPKs, PI-3K/Akt and PKC pathways.

Understanding microscopic binding of human microsomal prostaglandin E synthase-1 (mPGES-1) trimer with substrate PGH2 and cofactor GSH: insights from computational alanine scanning and site-directed mutagenesis

Microsomal prostaglandin E synthase-1 (mPGES-1) is an essential enzyme involved in a variety of diseases and is the most promising target for the design of next-generation anti-inflammatory drugs. In order to establish a solid structural base, we recently developed a model of mPGES-1 trimer structure by using available crystal structures of both microsomal glutathione transferase-1 (MGST1) and ba3-cytochrome c oxidase as templates. The mPGES-1 trimer model has been used in the present study to examine the detailed binding of mPGES-1 trimer with substrate PGH(2) and cofactor GSH. Results obtained from the computational alanine scanning reveal the contribution of each residue at the protein-ligand interaction interface to the binding affinity, and the computational predictions are supported by the data obtained from the corresponding wet experimental tests. We have also compared our mPGES-1 trimer model with other available 3D models, including an alternative homology model and a low-resolution crystal structure, and found that our mPGES-1 trimer model based on the crystal structures of both MGST1 and ba3-cytochrome c oxidase is more reasonable than the other homology model of mPGES-1 trimer constructed by simply using a low-resolution crystal structure of MGST1 trimer alone as a template. The available low-resolution crystal structure of mPGES-1 trimer represents a closed conformation of the enzyme and thus is not suitable for studying mPGES-1 binding with ligands. Our mPGES-1 trimer model represents a reasonable open conformation of the enzyme and is therefore promising for studying mPGES-1 binding with ligands in future structure-based drug design targeting mPGES-1.

Activation of thromboxane receptor alpha induces expression of cyclooxygenase-2 through multiple signaling pathways in A549 human lung adenocarcinoma cells

Human lung adenocarcinoma A549 cells stably transfected with TPalpha (A549-TPalpha) were used to study agonist I-BOP-induced expression of cyclooxygenase-2 (COX-2) and the related mechanisms of induced expression. I-BOP, a TP agonist, induced a time- and dose-dependent expression of COX-2 in A549-TPalpha cells. The signaling pathways of I-BOP-induced COX-2 expression were elucidated by using various inhibitors of the signaling molecules. The effects of these inhibitors were assessed at protein level, enzyme activity and promoter activity of COX-2. Within MAPK family, both ERK and p38 MAPK but not JNK/SAPK pathways were involved in the induction. Other pathways such as JAK/Stat3 pathway and beta-catenin/TCF/LEF pathway also participated in the induction. The activation of key signaling molecules, ERK, p38 MAPK, CREB and NF-kappaB, involved in the COX-2 transcription was further studied at the phosphorylation step. Activation of ERK and p38 MAPK appeared to be mediated primarily by transactivation of EGFR, whereas activation of CREB and NF-kappaB was mediated by PKA, PKC and ERK. The role of CREB and NF-kappaB in I-BOP-induced COX-2 expression was further explored at the promoter level. Studies on promoter fragments and mutation of responsive motifs indicated that CRE and NF-kappaB sites are critical for the COX-2 induction. Distal NF-kappaB site is essential for the basal induction of the COX-2 transcription, whereas CRE and proximal NF-kappaB sites are important for the induced transcription. These results indicate that I-BOP-induced COX-2 expression through multiple signaling pathways.

IFN-gamma-mediated inhibition of COX-2 expression in the placenta from term and preterm labor pregnancies

PROBLEM

The inflammatory-anti-inflammatory cytokine network is thought to play a critical role in regulated progression and termination of pregnancy. The aim of this study was to evaluate the effects of interferon (IFN)-gamma on the expression of Cyclooxygenase (COX)-2 and production of prostaglandin E(2) (PGE(2)) in the human placenta from term and preterm labor deliveries.

METHOD OF STUDY

Placental explant culture system was used. COX-2 expression was determined by complementary techniques of immunohistochemistry and Western blotting. Released IFN-gamma and PGE(2) by placental explants were measured by enzyme-linked immunosorbent assay. Signal transducer and activator of transcription 1 (STAT1) phosphorylation was evaluated by Western blotting using a specific antibody.

RESULTS

IFN-gamma was poorly detected in the placenta but was significantly expressed in decidual tissues from both term and preterm pregnancies as detected by immunohistochemistry. IFN-gamma significantly inhibited COX-2 expression and PGE(2) release in cultured placental explants from term and preterm labor deliveries. This effect most likely occurred in a STAT1-dependent manner as this regulatory protein was phosphorylated in response to IFN-gamma. IFN-gamma receptor (IFN-gammaR) was expressed in normal early pregnancy placental samples. However, its expression was significantly reduced in placental samples from term and preterm deliveries. Of interest, IFN-gammaR was expressed in placentas from term and preterm labor deliveries after 24 hr in culture.

CONCLUSIONS

Our data suggest that the human placenta is an important site for IFN-gamma-mediated repression of COX-2 expression and PGE2 production, implying that functional withdrawal of IFN-gamma may be involved in the onset of term or preterm labor.

Interleukin-1alpha stimulated prostacyclin release by increasing gene transcription of prostaglandin H synthase and phospholipase A2 in human vascular endothelial cells

This study was conducted to evaluate the effects of interleukin-1alpha (IL-1alpha) on prostacyclin (PGI2) production in cultured human vascular endothelial cells in association with intracellular Ca2+, inositol 1,4,5-trisphosphate (IP3), and with prostaglandin H synthase (PGHS) and phospholipase A2 (PLA2) gene expression by using the competitive polymerase chain reaction (PCR) method. IL-1alpha did not increase PGI2 production for 15 min, but induced an increase of about three-fold relative to that in controls at 60 and 180 min. IL- 1alpha had no effect on intracellular Ca2+ levels throughout the experimental period. In this study, consistent with previous reports, PGHS-1 messenger RNA (mRNA) was constitutively expressed, whereas PLA2 mRNA was not. After stimulation with IL-1alpha, PLA2 mRNA level showed an eightfold increase within 15 min, and PGHS-2 mRNA level increased by 76-fold within 180 min. PGHS-1 mRNA level was increased 1.6-fold at 180 min. These results suggest the existence of regulatory mechanisms of IL-1alpha-induced PGI2 production, which involve PGHS and PLA2 gene transcription.

Key enzymes of prostaglandin biosynthesis and metabolism. Coordinate regulation of expression by cytokines in gestational tissues: a review

Preterm labor is frequently associated with ascending intrauterine infection, accompanied by leukocytes infiltration and enhanced local production of cytokines and other inflammatory mediators. The resulting amplification of the inflammatory response, and of prostanoid production in particular, is postulated to be a principal mechanism of infection-driven preterm labor. In this review the effects of pro- and anti-inflammatory cytokines are discussed with respect to the expression of enzymes involved in three key steps of prostanoid biosynthesis and metabolism: liberation of arachidonic acid (AA), conversion of AA to bioactive prostanoids, and prostanoid catabolism. We suggest that by exerting coordinate actions on all three key steps, through multiple molecular mechanisms, inflammatory cytokines acutely up-regulate prostanoid production in intrauterine tissues.

Interleukin-4 differentially regulates prostaglandin production in amnion-derived WISH cells stimulated with pro-inflammatory cytokines and epidermal growth factor

Cytokines and growth factors have been proposed to act as in vivo modulators of amnion prostaglandin production at parturition. To characterize the effects of the 'anti-inflammatory' cytokine interleukin (IL)-4 on amnion prostaglandin production, amnion epithelium-derived WISH cells were treated with IL-4 in the presence/absence of IL-1beta, tumour necrosis factor-alpha (TNF-alpha) or epidermal growth factor (EGF). IL-4 (0.08-10 ng/ml) potently inhibited cytokine-stimulated PGE2 production over 16 h (maximal inhibition approximately 66% at 2.0 ng/ml IL-4). Delaying addition of IL-4 (1 ng/ml) by up to 8 h after IL-1beta addition only slightly attenuated its inhibitory effects, from approximately 65% to approximately 50%. EGF-stimulated PGE2 production was either not inhibited or slightly stimulated by IL-4. Immunoblotting studies revealed that IL-4 (10 ng/ml) significantly suppressed prostaglandin-H synthase-2 (PGHS-2) levels in cells stimulated with IL-1beta and TNF-alpha over 16 h, but had no consistent effects on cytosolic phospholipase A2 (cPLA2) levels under any condition. In the presence of arachidonic acid (10 microM), IL-4 again inhibited cytokine-stimulated, but not EGF-stimulated, PGE2 production. The presence of IL-4 also failed to alter the amount of arachidonic acid released in response to EGF. These findings suggest a role and potential therapeutic application for IL-4 in inhibiting amnion PGHS-2 expression and hence prostaglandin production in infection-driven preterm labour, but not labour in the absence of inflammatory initiators.

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.

Comparative studies on the effects of interleukin-4 and interleukin-13 on cytokine and prostaglandin E2 production by amnion-derived WISH cells

PROBLEM

In hematopoietic cells, interleukin (IL)-13 shares many actions with IL-4. The effects of IL-13 in gestational tissues have yet to be reported, however. We compared the effects of IL-4 and IL-13 on the production of cytokines and prostaglandin E2 (PGE2) in epithelial amnion-derived WISH cells.

METHOD OF STUDY

WISH cells were treated with IL-4 or IL-13 (0.08-10 ng/ml) with/without cotreatment with IL-1 beta (0.2 ng/ml), tumor necrosis factor-alpha (10 ng/ml) or epidermal growth factor (5 ng/ml). The production of IL-6, IL-8, and PGE2 was measured by immunoassay after 16 hr.

RESULTS

Both IL-4 and IL-13 inhibited PGE2 production with indistinguishable concentration-response curves, under basal or stimulated conditions. The maximal inhibition of IL-1 beta-stimulated PGE2 production (to 28% +/- 10% of control) was seen at 10 ng/ml of IL-4 or IL-13. Basal IL-6 production was stimulated approximately twofold by IL-4 and IL-13, whereas IL-4 and IL-13 both inhibited cytokine-stimulated (but not basal) IL-8 production by approximately 50%. In the presence of 1 ng/ml of IL-4, IL-13 was unable to further inhibit PGE2 production.

CONCLUSIONS

The inhibition of PGE2 and IL-8 production by IL-4 in WISH cells is mimicked by IL-13. Both cytokines, probably through binding to a common receptor complex, may share a role in suppressing inflammatory reactions within intrauterine tissues.

Interleukin-1 beta and dexamethasone regulate gene expression of prostaglandin H synthase-2 via the NF-kB pathway in human amnion derived WISH cells

Interleukin-1beta (IL-1beta) stimulated PGE2 synthesis in human amnion derived WISH cells, whereas dexamethasone blocked IL-1beta-mediated stimulation of PGE2 production. Sequence analysis of the 5'-flanking region of the human prostaglandin H synthase-2 (PGHS-2) gene indicates two putative NF-kB binding sites. Mutation of a single site or both sites resulted in significantly decreased activity of the PGHS-2 promoter. IL-1beta treatment increased significantly the native promoter activity and this increase was attenuated by using the NF-kB-mutant promoter. Dexamethasone treatment also decreased the IL-1beta mediated stimulation of the PGHS-2 native promoter but not the NF-kB mutant promoter. Furthermore, the involvement of the NF-kB was supported by electrophoretic mobility shift assay which revealed an increased nuclear binding of the NF-kB probe upon IL-1beta induction and a decreased nuclear binding of the NF-kB probe upon dexamethasone pre-treatment. These results provide convincing evidence that NF-kB may mediate the IL-1beta stimulation of PGHS-2 gene expression as well as the dexamethasone inhibition of the IL-1beta induction process in WISH cells.