Upregulation Of Cyclooxygenase-2 Expression Research Articles

Fluorinated 2′-hydroxychalcones as garcinol analogs with enhanced antioxidant and anticancer activities

Chalcones are involved in the synthesis of flavonoids and are themselves known to exhibit multiple pharmacological properties. However, compared to other structurally similar phytochemicals like garcinol and curcumin, the therapeutic use of chalcones is limited because of their lower bioavailability and rapid metabolic clearance from biological system. In the present work, we have attempted to overcome these limitations in case of 2′-hydroxychalcones through bioisosteric substitution of fluoro groups in place of phenolic hydroxyls. The fluorinated chalcones were found to be more potent antioxidant and anti-proliferative compounds than their hydroxyl counterparts indicating the influence of metabolically stable C–F bonds towards bioavailability. The difluoro derivatives were found to be most effective against human pancreatic BxPC-3 cancer cells which possess up-regulated COX-2 expression and also showed activity against human breast cancer BT-20 cells with triple negative phenotype, suggesting that these compounds will have broader application in the future.

Pivotal Advance: Tumor-mediated induction of myeloid-derived suppressor cells and M2-polarized macrophages by altering intracellular PGE2 catabolism in myeloid cells

Recent studies suggest that tumor-infiltrated myeloid cells frequently up-regulate COX-2 expression and have enhanced PGE₂ metabolism. This may affect the maturation and immune function of tumor-infiltrated antigen-presenting cells. In vitro studies demonstrate that tumor-derived factors can skew GM-CSF-driven differentiation of T(h)1-oriented myeloid APCs into M2-oriented Ly6C(+)F4/80(+) MDSCs or Ly6C(-)F4/80(+) arginase-expressing macrophages. These changes enable myeloid cells to produce substantial amounts of IL-10, VEGF, and MIP-2. The tumor-mediated inhibition of APC differentiation was associated with the up-regulated expression of PGE₂-forming enzymes COX-2, mPGES1 in myeloid cells, and the simultaneous repression of PGE(2)-catabolizing enzyme 15-PGDH. The presence of tumor-derived factors also led to a reduced expression of PGT but promoted the up-regulation of MRP4, which works as a PGE₂ efflux receptor. Addition of COX-2 inhibitor to the BM cell cultures could prevent the tumor-induced skewing of myeloid cell differentiation, partially restoring cell phenotype and down-regulating the arginase expression in the myeloid APCs. Our study suggests that tumors impair the intracellular PGE(2) catabolism in myeloid cells through simultaneous stimulation of PGE(2)-forming enzymes and inhibition of PGE₂-degrading systems. This tumor-induced dichotomy drives the development of M2-oriented, arginase-expressing macrophages or the MDSC, which can be seen frequently among tumor-infiltrated myeloid cells.

Abstract LB-426: Delphinidin suppresses ultraviolet B-induced cyclooxygenases-2 expression through inhibition of MAPKK4 and PI-3 kinase

Abstract Cyclooxygenase-2 (COX-2), a key mediator of inflammation, and its product, prostaglandin E2 (PGE2), enhance carcinogenesis, particularly in skin. Ultraviolet (UV) B is the most carcinogenic component of solar irradiation, and a crucial role of COX-2 in UVB-mediated skin carcinogenesis has been reported. Here, we investigated the effects of delphinidin, an abundant dietary anthocyanin, on UVB-induced COX-2 upregulation and the underlying molecular mechanism. We found that delphinidin suppressed UVB-induced COX-2 expression in JB6 P+ mouse epidermal cells. COX-2 promoter activity and PGE2 production were also suppressed by delphinidin treatment within non-cytotoxic concentrations. Activator protein-1 and nuclear factor- B, crucial transcription factors involved in COX-2 expression, were activated by UVB and delphinidin abolished this activation. UVB-induced phosphorylation of c-Jun N-terminal kinase, p38 kinase and Akt was inhibited by delphinidin. The activities of mitogenactivated protein kinase kinase (MAPKK) 4 and phosphatidylinositol-3 kinase (PI-3K) were inhibited markedly by delphinidin. A pull-down assay using delphinidin-Sepharose beads revealed that delphinidin binds directly with MAPKK4 or PI-3K in a manner that was competitive with adenosine triphosphate. Moreover, in vivo investigations using mouse skin revealed that the upregulation of COX-2 expression, MAPKK4 activity and PI-3K activity induced by UVB was abolished with delphinidin treatment. Collectively, our results demonstrated that delphinidin targets MAPKK4 and PI-3K directly to suppress COX-2 overexpression, suggesting a potential protective role for delphinidin against UVB-mediated skin carcinogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-426.

Abstract 5592: Lovastatin and low dose celecoxib decrease proliferation and inflammation in a cellular model of lung pre-malignancy

Abstract Statin drugs, such as lovastatin and pravastatin, block the cellular synthesis of cholesterol by inhibiting the function of HMG-CoA reductase. In a prospective study, patients undergoing statin treatment for prevention of atherosclerosis were at a lower risk of developing certain cancers, including lung and breast, suggesting a possible use for lovastatin in the chemoprevention of lung cancer. Here, we show that lovastatin dose-dependently decreases proliferation in both histologically normal and Kras-mutated human bronchial epithelial cells (HBECs) through the inhibition of cholesterol production. However, increased expression of PGE2, which we and others have shown to contribute to lung cancer progression, was noted with lovastatin treatment alone. Lovastatin up-regulates the production of PGE2 by up-regulating COX-2 expression and simultaneously down-regulating metabolism of PGE2 via down-regulation of 15-PGDH expression. Treatment with the cholesterol precursor, mevalonic acid, inhibited up-regulation of PGE2 and blocked dose-dependent anti-proliferative activity of lovastatin, indicating sterol-dependence. Treatment with both lovastatin and low dose (0.1uM) celecoxib, a COX-2 inhibitor, decreased PGE2 protein production in vector control and Kras-mutated HBECs. These findings suggest that the combination of lovastatin and low dose celecoxib overcomes up-regulation of PGE2 by lovastatin alone and that the combination represents a potentially effective lung cancer chemopreventative regimen worthy of further investigation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5592.

Activation of cardiac muscarinic M3 receptors induces delayed cardioprotection by preserving phosphorylated connexin43 and up‐regulating cyclooxygenase‐2 expression

Activation of muscarinic M(3) mucarinic acetylcholine receptors (M(3)-mAChRs) has been previously shown to confer short-term cardioprotection against ischaemic injuries. However, it is not known whether activation of these receptors can provide delayed cardioprotection. Consequently, the present study was undertaken to investigate whether stimulation of M(3)-mAChRs can induce delayed preconditioning in rats, and to characterize the potential mechanism. Rats were pretreated (24 h), respectively, with M(3)-mAChRs agonist choline, M(3)-mAChRs antagonist 4-DAMP or M(2)-mAChRs antagonist methoctramine followed by the administration of choline. This was followed by 30 min of ischaemia and then 3 h of reperfusion. Ischaemia-induced arrhythmias and ischaemia-reperfusion (I/R)-induced infarction were determined. The phosphorylation status of connexin43 (Cx43) after 30 min ischaemia, and the expression level of Hsp70, cyclooxygenase-2 (COX-2) and iNOS effected by administration of choline were also measured. Compared to the control group, pretreatment with choline significantly decreased ischaemia-induced arrhythmias, reduced the total number of ventricular premature beats, the duration of ventricular tachycardia episodes and markedly reduced I/R-induced infarct size. Furthermore, choline attenuated ischaemia-induced dephosphorylation of Cx43, and up-regulated the expression of Hsp70 and COX-2. Administration of 4-DAMP abolished these changes, while methoctramine had no effect. Our results suggest that stimulation of M(3)-mAChRs with choline elicits delayed preconditioning, which we propose is the result of up-regulation of the expression of COX-2 and inhibition of the ischaemia-induced dephosphorylation of Cx43. Therefore, M(3)-mAChRs represent a promising target for rendering cardiomyocytes tolerant to ischaemic injury.

Highlights of This Issue

EGFR and EGFRvIII can be detected in tumor nuclei, in which nuclear EGFR regulates gene expression. It remains unknown if the nuclear EGFR pathway is valid in glioblastoma (GBM) and whether nuclear EGFRvIII plays a significant role in any cancer type. Lo and colleagues showed both receptors to undergo nuclear translocalization in GBM. Via gene expressing profiling of GBM cells with wild-type EGFR and genetically modified EGFR, COX-2 was identified as one of the novel nuclear EGFR-targeted genes. Nuclear EGFR/EGFRvIII cooperates with STAT3 to upregulate COX-2 expression, thus linking nuclear EGFR-STAT3 and nuclear EGFRvIII-STAT3 signaling axes to COX-2-mediated pro-inflammatory pathway.Abnormal expression of myeloid zinc finger 1 (MZF1) and Axl leads to cancer progression. However, the potential role of MZF1 in regulating Axl expression and metastasis is not clear. To explore MZF1's role in Axl regulation and metastasis, Mudduluru and coworkers performed in vitro and in vivo chicken– embryo–metastasis (CAM) assays either with MZF1-overexpression/sh-Axl knockdown or in combination of both. In vitro results showed that MZF1-significantly induces Axl expression and MZF1-induced migration and invasion is at least in part mediated through Axl. CAM assay showed that MZF1 significantly induces tumor formation and liver metastasis, furthermore, MZF1 expression positively correlated with Axl expression in resected colorectal cancer tissues.Elevated expression of antiapoptotic Bcl-2 not only enhances carcinoma cell survival but also increases malignant behavior leading to increased invasion and dissemination. Ectopic Bcl-2 expression in head and neck squamous cell carcinoma (HNSCC) cells promoted tumor growth and pulmonary metastasis, initiated an EMT phenotype with induction of N-cadherin expression, stimulated cell locomotion and invasion, and induced MMP-9 production through the MAPK/FGFR signaling–dependent pathway. These findings provide a basis for further characterization of the molecular mechanisms of EMT-mediated invasion that cooperate with Bcl-2 family member regulation of anti-apoptotic functions in the development of highly metastatic cell variants in HNSCC.c-Jun NH2-terminus kinase (JNK) is known to mediate the cytotoxic effect of anticancer therapies. Paradoxically, elevated JNK activity is associated with poor prognosis in human cancers. We found that hyperactive JNK did not cause apoptosis in breast cancer cells, but induced a phenotype associated with epithelial-mesenchymal transition (EMT) and enhanced ERK activation by increasing IRS-2, which upregulated the AP-1 transcription factor. Modulation of ERK by hyperactive JNK also attenuated paclitaxel-induced apoptosis. Our findings identify a novel mechanism of cross-talk between JNK and ERK signaling and might provide insight into the recently reported link between chemoresistance and EMT.

Proinflammatory Mediators Upregulate Snail in Head and Neck Squamous Cell Carcinoma

Inflammatory cytokines have been implicated in the progression of head and neck squamous cell carcinoma (HNSCC). Herein we investigate the mechanisms by which interleukin-1beta (IL-1beta) might contribute to Epithelial-Mesenchymal Transition (EMT) in HNSCC. We evaluated the effect of IL-1beta on the molecular events of EMT in surgical specimens and HNSCC cell lines. We examined the correlation with tumor histologic features, and a SCID xenograft model was used to assess the effects of Snail overexpression. Cyclooxygenase-2 (COX-2)-dependent pathways contribute to the modulation of E-cadherin expression in HNSCC. An inverse relationship between COX-2 and E-cadherin was shown in situ by double immunohistochemical staining of human HNSCC tissue sections. Treatment of HNSCC cells with IL-1beta caused the downregulation of E-cadherin expression and upregulation of COX-2 expression. This effect was blocked in the presence of COX-2 small hairpin RNA. IL-1beta-treated HNSCC cell lines showed a significant decrease in E-cadherin mRNA and an increase in the mRNA expression of the transcriptional repressor Snail. IL-1beta exposure led to enhanced Snail binding at the chromatin level. Small hairpin RNA-mediated knockdown of Snail interrupted the capacity of IL-1beta to downregulate E-cadherin. In a SCID xenograft model, HNSCC Snail-overexpressing cells showed significantly increased primary and metastatic tumor burdens. IL-1beta modulates Snail and thereby regulates COX-2-dependent E-cadherin expression in HNSCC. This is the first report indicating the role of Snail in the inflammation-induced promotion of EMT in HNSCC. This newly defined pathway for transcriptional regulation of E-cadherin in HNSCC has important implications for targeted chemoprevention and therapy.

Delphinidin suppresses ultraviolet B-induced cyclooxygenases-2 expression through inhibition of MAPKK4 and PI-3 kinase

Cyclooxygenase-2 (COX-2), a key mediator of inflammation, and its product, prostaglandin E(2) (PGE(2)), enhance carcinogenesis, particularly in skin. Ultraviolet (UV) B is the most carcinogenic component of solar irradiation, and a crucial role of COX-2 in UVB-mediated skin carcinogenesis has been reported. Here, we investigated the effects of delphinidin, an abundant dietary anthocyanin, on UVB-induced COX-2 upregulation and the underlying molecular mechanism. We found that delphinidin suppressed UVB-induced COX-2 expression in JB6 P+ mouse epidermal cells. COX-2 promoter activity and PGE(2) production were also suppressed by delphinidin treatment within non-cytotoxic concentrations. Activator protein-1 and nuclear factor-kappaB, crucial transcription factors involved in COX-2 expression, were activated by UVB and delphinidin abolished this activation. UVB-induced phosphorylation of c-Jun N-terminal kinase, p38 kinase and Akt was inhibited by delphinidin. The activities of mitogen-activated protein kinase kinase (MAPKK) 4 and phosphatidylinositol-3 kinase (PI-3K) were inhibited markedly by delphinidin. A pull-down assay using delphinidin-Sepharose beads revealed that delphinidin binds directly with MAPKK4 or PI-3K in a manner that was competitive with adenosine triphosphate. Moreover, in vivo investigations using mouse skin revealed that the upregulation of COX-2 expression, MAPKK4 activity and PI-3K activity induced by UVB was abolished with delphinidin treatment. Collectively, our results demonstrated that delphinidin targets MAPKK4 and PI-3K directly to suppress COX-2 overexpression, suggesting a potential protective role for delphinidin against UVB-mediated skin carcinogenesis.

Resistin Up-Regulates COX-2 Expression via TAK1-IKK-NF-κB Signaling Pathway

The hormone resistin, which was originally shown to induce insulin resistance, has been implicated in the regulation of inflammatory processes, but the molecular mechanism underlying such regulation has not been clearly defined. The goal of our study was to determine whether the expression of COX-2 can be induced by resistin and what the potential signaling pathway involved in this process is. Compared with controls, resistin significantly upregulated COX-2 expression in RAW264.7 macrophage cells. Administration of anti-resistin antibody could significantly reduce this effect. Induction of COX-2 by resistin was also markedly reduced in the presence of either dominant negative mutant IkappaBalpha or PDTC, a pharmacological inhibitor of NF-kappaB. On the other hand, NF-kappaB subunit p65 was upregulated by resistin. Moreover, we found that transforming growth factor-beta-activated kinase 1 (TAK1), a mitogen-activated protein kinase kinase kinase (MAPKKK), could be activated in response to resistin. These results suggest that resistin enhances COX-2 expression in mouse macrophage cells in a TAK1-IKK-NF-kappaB-dependent manner and therefore plays a critical role in inflammatory processes.

Hypoxia-induced hyperreactivity of pulmonary arteries: role of cyclooxygenase-2, isoprostanes, and thromboxane receptors

This study investigates the role of the cyclooxygenase (COX)/prostanoid pathway in chronic hypoxia-induced hyperreactivity of pulmonary arteries. Pulmonary arteries were removed from normoxic or hypoxic (0.5 atm for 21 days) mice and studied for protein expression/localization of COX-1, COX-2, and thromboxane A2 (TXA2)-synthase, release of TXA2, prostacyclin (PGI2) and the isoprostane 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha), and vasomotor responses. COX-2 expression was increased in all layers of pulmonary arteries from hypoxic mice. In contrast, COX-1 expression was not significantly modified following chronic hypoxia, whereas TXA2-synthase was decreased. Chronic hypoxia differentially affected prostanoid release from pulmonary arteries: TXA2 secretion was not significantly modified; PGI2 secretion was decreased, whereas 8-iso-PGF2alpha secretion was increased. A selective COX-2 inhibitor decreased 8-iso-PGF2alpha release. Arachidonic acid elicited an endothelium- and COX-1-dependent relaxation in pulmonary arteries from normoxic mice. In contrast, arachidonic acid induced an endothelium-independent contraction in pulmonary arteries from hypoxic mice that was partially reduced by catalase, COX-1, COX-2, or TXA2-synthase inhibitors and was totally abolished by blockade of the thromboxane (TP) receptor. Hyperresponsiveness to phenylephrine (PE) of pulmonary arteries from hypoxic mice was also decreased by COX-2 inhibitors, TP receptor antagonists or catalase, but not by TXA2-synthase inhibitors. Finally, 8-iso-PGF2alpha induced a TP receptor-dependent contraction in pulmonary arteries and markedly potentiated the contractile response to PE. Chronic hypoxia up-regulates COX-2 expression, increases 8-iso-PGF2alpha release, and shifts arachidonic acid-induced, endothelium-dependent relaxation to an endothelium-independent and TP receptor-dependent contraction in pulmonary arteries. COX-2-dependent production of 8-iso-PGF2alpha, by activating TP receptors, participates in hypoxia-induced hyperreactivity of pulmonary arteries.

Toll-like receptor 9 agonists up-regulates the expression of cyclooxygenase-2 via activation of NF-κB in prostate cancer cells

CpG-oligonucleotides (CpG-ODNs), mimicking bacterial DNA, have recently been shown to stimulate prostate cancer invasion in vitro via Toll-like receptor 9 (TLR9). Since cyclooxygenase 2 (COX-2), frequently overexpressed in multiple tumor types including prostate cancer, is a causal factor for tumor development, invasion and metastasis, an interesting question is raised whether TLR9 regulates COX-2 expression in prostate cancer cells. To address this question, herein we examined COX-2 expression in PC-3 cells stimulated with different doses and time courses of CpG-ODNs. The regulatory role of NF-kappaB in TLR9-mediated COX-2 expression was also investigated. CpG-ODN was found to up-regulate the expression of COX-2 in PC-3 cells in a dose- and time-dependent manner, but have little impact on COX-1 expression. Moreover, CpG-ODN also promoted nuclear translocation and activation of NF-kappaB, which appeared to be required for COX-2 induction by CpG-ODN. Overall, TLR9 up-regulates COX-2 expression in prostate cancer cells, at least partially through the activation of NF-kappaB, which may be implicated in tumor invasion and metastasis.

JNK inhibitor protects dopaminergic neurons by reducing COX-2 expression in the MPTP mouse model of subacute Parkinson's disease

Increasing evidence suggests that inflammation may be involved in the loss of dopaminergic neurons in Parkinson's disease (PD). Among inflammatory molecules, COX-2, a key kinase for the inflammatory response, has been suggested to play an important role in dopaminergic neuron loss in PD. However, the upstream molecular pathways of COX-2 expression remain uncertain. In the present study, we investigated the role of c-Jun [1] N-terminal kinase (JNK) in the process of COX-2 expression in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of subacute PD. Our data showed that MPTP induced a transient JNK activation of dopaminergic neurons, upregulated COX-2 expression in dopaminergic neurons, and caused the loss of dopaminergic neurons. We found that inhibiting JNK with SP600125, a special inhibitor of JNK, reduced the levels of c-Jun phosphorylation, blocked p-c-Jun translocation from the cytoplasm to the nucleus in dopaminergic neurons of substantia nigra, mitigated the loss of dopaminergic neurons, and improved motor function in MPTP-induced PD in C57BL/6N mice. These results indicate that JNK signaling pathway may be the major upstream mediator of regulation of COX-2 expression induced by MPTP in vivo and inhibiting JNK activity may represent a new and effective strategy to PD.

W1718 Up-Regulation of COX-2 Expression in the Spinal Cord and Dorsal Root Ganglia of Rats Exposed to Chronic Psychological Stress

W1718 Up-Regulation of COX-2 Expression in the Spinal Cord and Dorsal Root Ganglia of Rats Exposed to Chronic Psychological Stress

Involvement of NF- B and AP-1 in COX-2 upregulation by human papillomavirus 16 E5 oncoprotein

The human papillomavirus (HPV) E6 and E7 oncoproteins play important roles in cervical carcinogenesis through multiple mechanisms, including upregulation of cyclooxygenase-2 (COX-2), which has been shown to be involved in both carcinogenesis and cancer progression. To explore the role of E5 in cervical carcinogenesis, we herein investigated the effect of HPV 16 E5 on COX-2 expression. Our results revealed that E5 induced COX-2 expression through the epidermal growth factor receptor-signaling pathway, with nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) acting as critical factors in E5-induced COX-2 expression. NF-kappaB inhibition blocked COX-2 expression more potently than inhibition of AP-1. Our findings collectively suggest that the HPV 16 E5 oncoprotein mediates cervical carcinogenesis at least in part via upregulation of COX-2 expression through NF-kappaB and AP-1, with NF-kappaB playing a larger role.

Sulforaphane down-regulates COX-2 expression by activating p38 and inhibiting NF-κB-DNA-binding activity in human bladder T24 cells

Cyclooxygenase-2 (COX-2) overexpression has been associated with the grade, prognosis and recurrence of transitional cell carcinoma (TCC) of the bladder. In this study, sulforaphane, a dietary isothiocyanate, down-regulated COX-2 expression in human bladder transitional cancer T24 cells at both transcriptional- and translational levels. Sulforaphane (5-20 microM) induced nuclear translocation of NF-kappaB and reduced its binding to the COX-2 promoter, a key mechanism for suppressing COX-2 expression by sulforaphane. Moreover, sulforaphane increased expression of p38 and phosphorylated-p38 protein. A specific inhibitor of p38 MAPK, SB202190, was used to further investigate its pivotal role in sulforaphane-mediated down-regulation of COX-2. Exposure of T24 cells to SB202190 1 hour prior to sulforaphane treatment abolished the effect of sulforaphane on COX-2 mRNA down-regulation, but enhanced COX-2 transcription. Furthermore, SB202190 alone induced NF-kappaB translocation to the nucleus, promoted NF-kappaB binding to the COX-2 promoter and resulted in up-regulation of COX-2 expression. Taken together, these data suggest that p38 is essential in sulforaphane-mediated COX-2 suppression and provide new insights into the molecular mechanisms of sulforaphane in the chemoprevention of bladder cancer.

Up-Regulation of Cyclooxygenase-2 Expression and Prostaglandin E2 Production in Human Endometriotic Cells by Macrophage Migration Inhibitory Factor: Involvement of Novel Kinase Signaling Pathways

Cyclooxygenase (COX) is the rate-limiting enzyme in the metabolic conversion of arachidonic acid to prostaglandins (PGs), including prostaglandin E(2) (PGE(2)), a major mediator of inflammation and angiogenesis. Herein, we report that macrophage migration inhibitory factor (MIF), a potent proinflammatory and growth-promoting factor found at elevated concentrations in the peritoneal fluid of women with endometriosis and active endometriosis lesions, acts directly on ectopic endometrial cells to stimulate the synthesis of COX-2, the inducible form of COX, and the release of PGE(2). MIF treatment strongly activated p38 and ERK MAPK, and specific inhibitors of both pathways completely blocked basal and MIF-induced PGE(2) synthesis. Whereas p38 inhibitors negatively affected the stimulated synthesis of COX-2 and that of PGE(2), ERK inhibitors only decreased the production of PGE(2). These findings show for the first time a direct role for MIF in the up-regulation of COX-2 synthesis and PGE(2) secretion in ectopic endometrial cells. They further indicate that whereas p38 and ERK MAPK signaling pathways both play a significant role in the regulation of basal and MIF-induced synthesis of PGE(2) by ectopic endometrial cells, only p38 kinase is involved in the regulation of COX-2 expression in these cells. This suggests that MIF acts at more than one level to stimulate the synthesis of PGE(2) and triggers the coordinate activation of multiple enzymes in the biosynthesis pathway. Our data provide evidence for a novel mechanism by which MIF can induce a proinflammatory phenotype in ectopic endometrial cells, and favor the establishment of endometriosis and its related clinical symptoms.

Functional expression of the olfactory signaling system in the kidney

Olfactory-like chemosensory signaling occurs outside of the olfactory epithelium. We find that major components of olfaction, including olfactory receptors (ORs), olfactory-related adenylate cyclase (AC3) and the olfactory G protein (G(olf)), are expressed in the kidney. AC3 and G(olf) colocalize in renal tubules and in macula densa (MD) cells which modulate glomerular filtration rate (GFR). GFR is significantly reduced in AC3(-/-) mice, suggesting that AC3 participates in GFR regulation. Although tubuloglomerular feedback is normal in these animals, they exhibit significantly reduced plasma renin levels despite up-regulation of COX-2 expression and nNOS activity in the MD. Furthermore, at least one member of the renal repertoire of ORs is expressed in a MD cell line. Thus, key components of olfaction are expressed in the renal distal nephron and may play a sensory role in the MD to modulate both renin secretion and GFR.

Novel signaling pathways promote a paracrine wave of prostacyclin-induced vascular smooth muscle differentiation

The important athero-protective role of prostacyclin is becoming increasingly evident as recent studies have revealed adverse cardiovascular effects in mice lacking the prostacyclin receptor, in patients taking selective COX-2 inhibitors, and in patients in the presence of a dysfunctional prostacyclin receptor genetic variant. We have recently reported that this protective mechanism includes the promotion of a quiescent differentiated phenotype in human vascular smooth muscle cells (VSMC). Herein, we address the intriguing question of how localized endothelial release of the very unstable eicosanoid, prostacyclin, exerts a profound effect on the vascular media, often 30 cell layers thick. We report a novel PKA-, Akt-1- and ERK1/2-dependent prostacyclin-induced prostacyclin release that appears to play an important role in propagation of the quiescent, differentiated phenotype through adjacent arterial smooth muscle cells in the vascular media. Treating VSMC with the prostacyclin analog iloprost induced differentiation (contractile protein expression and contractile morphology), and also up-regulated COX-2 expression, leading to prostacyclin release by VSMC. This paracrine prostacyclin release, in turn, promoted differentiation and COX-2 induction in neighboring VSMC that were not exposed to iloprost. Using siRNA and pharmacologic inhibitors, we report that this positive feedback mechanism, prostacyclin-induced prostacyclin release, is mediated by cAMP/PKA signaling, ERK1/2 activation, and a novel prostacyclin receptor signaling pathway, inhibition of Akt-1. Furthermore, these pathways appear to be regulated by the prostacyclin receptor independently of one another. We conclude that prevention of de-differentiation and proliferation through a paracrine positive feedback mechanism is a major cardioprotective function of prostacyclin.

The mRNA Binding Proteins HuR and Tristetraprolin Regulate Cyclooxygenase 2 Expression During Colon Carcinogenesis

During tumorigenesis, loss of rapid messenger RNA (mRNA) decay allows for overexpression of cancer-associated genes. The RNA-binding proteins Hu antigen R (HuR) and tristetraprolin (TTP) bind AU-rich elements in the 3' untranslated region of many cancer-associated mRNAs and target them for stabilization or rapid decay, respectively. We examined the functions of HuR and TTP during colon tumorigenesis and their ability to regulate cyclooxygenase (COX-2), a mediator of prostaglandin synthesis that increases in the colon tumor microenvironment. We evaluated expression of HuR and TTP during colorectal tumorigenesis and in colon cancer cells and associated them with COX-2 expression. HuR and TTP-inducible cells were created to investigate HuR- and TTP-mediated regulation of COX-2. In normal colon tissues, low levels of nuclear HuR and higher levels of TTP were observed. By contrast, increased HuR expression and cytoplasmic localization were observed in 76% of adenomas and 94% of adenocarcinomas, and TTP expression was lost in >75% of adenomas and adenocarcinomas. Similar results were obtained for HuR and TTP mRNA levels in normal and staged tumor samples. In both adenomas and adenocarcinomas, COX-2 overexpression was associated with increased HuR and decreased TTP (P < .0001); similar associations were observed in colon cancer cells. HuR overexpression in cells up-regulated COX-2 expression, whereas overexpression of TTP inhibited it; limited TTP expression antagonized HuR-mediated COX-2 overexpression. Increased expression of the mRNA stability factor HuR and loss of the decay factor TTP occurs during early stages of colorectal tumorigenesis. These changes promote COX-2 overexpression and could contribute to colon tumorigenesis.

41: Cigarette smoke up-regulates cyclooxygenase-2 expression in endothelial cells via NADPH oxidase activation

41: Cigarette smoke up-regulates cyclooxygenase-2 expression in endothelial cells via NADPH oxidase activation