HIF‐1α forms regulatory loop with YAP to coordinate hypoxia‐induced adriamycin resistance in acute myeloid leukemia cells

Despite the improvement in acute myeloid leukemia (AML) treatments, most patients had a poor prognosis and suffered from chemoresistance and disease relapse. Therefore, there is an urgent need for elucidation of mechanism(s) underlying drug resistance in AML. In the present study, we found that AML cells showed less susceptibility to adriamycin (ADR) in the presence of hypoxia, while inhibition of hypoxia‐inducible factor 1α (HIF‐1α) by CdCl₂ can make AML cells re‐susceptibile to ADR even under hypoxia. Moreover, HIF‐1α is overexpressed and plays an important role in ADR‐resistance maintenance in resistant AML cells. We further found hypoxia or induction of HIF‐1α can significantly upregulate yes‐associated protein (YAP) expression in AML cells, and resistant cells express a high level of YAP. Finally, we found that YAP may not only enhance HIF‐1α stability but also promote HIF‐1α's activity on the target gene pyruvate kinase M2. In conclusion, our data indicate that HIF‐1α or YAP may represent a therapeutic target for overcoming resistance toward adriamycin‐based chemotherapy in AML.     

17β—雌二醇下调血管平滑肌内皮素A型受体的表达

为进一步探讨雌激素对心血管的保护作用,实验在双侧卵巢去势大鼠模型和培养的血管平滑肌细胞（VSMCs)上,观察17β－雌二醇（E2）对血管反应性及VSMCs增殖的影响,以RT－PCR和Western blot检测内皮素受体（ETAR）的表达,结果显示：去势雌性大鼠血管对内皮素（ET－1）的反应性明显增高,ETAR特异性受体阻断剂BQ123能完全阻断ET－1对VSMCs增殖的影响,E2能明显抑制ET－1对VSMCs增殖的作用,RT－PCR结果显示E2能抑制ETAR mRNA的表达,Western blot进一步证实E2能抑制ETAR蛋白表达,E2受体阻断剂Tamoxifen能部分抑制ET－1对VSMCs的增殖及ETAR的mRNA和蛋白 的表达。以上结果提示;ET－1促VSMCs增殖的效应主要是由ETAR介导的,雌激素能通过下调ETAR来抑制ET－1对VSMCs 促增殖的作用和血管对ET－1的反应,且此作用与雌激素受体有关。     

Acquisition of chemoresistance in intrahepatic cholangiocarcinoma cells by activation of AKT and extracellular signal-regulated kinase (ERK)1/2

Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignant tumor and is refractory to conventional chemotherapy. The aim of this study is therefore to elucidate the mechanism of chemoresistance in ICC which is not fully understood. We generated cisplatin resistant ICC cells via long term exposure to cisplatin and found that these cells are also resistant to 5-fluorouracil (5-FU) and gemcitabine. The chemoresistant cells showed enhanced Bcl-2 expression and reduced Bax expression compared to parental ICC cells. In addition, the resistant cells showed enhanced activation of AKT and extracellular signal-regulated kinase (ERK) 1/2. Inhibition of AKT activation by phosphoinocitide 3-kinase (PI3K) inhibitor LY294002 resulted in reduced Bcl-2 expression and enhanced Bax expression and thus induced apoptosis in the resistant cells, whereas inhibition of ERK1/2 activation by mitogen-activated protein kinase (MEK) inhibitor U0126 did not induce apoptosis without affecting the expression of Bcl-2 and Bax but decreased cell growth. Moreover, the inhibition of AKT or ERK1/2 sensitized the resistant cells to cisplatin and therefore resulted in greatly enhanced cisplatin-induced apoptosis and growth inhibition in the cells. The results indicate that AKT and ERK1/2 signaling mediate chemoresistance in the cells and could be important therapeutic targets for overcoming chemoresistance in ICC.     

Activation of PERK in ET-1- and thrombin-induced pulmonary fibroblast differentiation: Inhibitory effects of curcumin

In the present study, we investigated the role of PKR-like endoplasmic reticular kinase (PERK), an endoplasmic reticulum (ER) stress kinase, in endothelin 1 (ET-1)- and thrombin-induced pulmonary fibrosis (PF), and the preventive effects of curcumin (CUR). Using the human embryonic WI-38 lung fibroblast cell line, ET-1 and thrombin induced the expression of ER stress-related proteins (CCAAT-enhancer-binding protein homologous protein, PERK, and binding immunoglobulin protein), a profibrogenic factor (cellular communication network factor 2 [CCN2]), and differentiation markers including α-smooth muscle actin (α-SMA), collagen I (Col I), and Col IV. Knockdown of PERK expression via small interfering RNA (siRNA) significantly reduced the increases in CCN2, α-SMA, Col I, and Col IV proteins in WI-38 cells according to western blot analysis and immunohistochemistry (IHC). Activation of c-Jun N-terminal kinase (JNK) was observed in ET-1- and thrombin-treated WI-38 cells, and the addition of a JNK inhibitor (SP) suppressed the induction of the indicated proteins by ET-1 and thrombin. Thapsigargin (TG), an ER stress inducer, elevated expressions of PERK and ER stress-related proteins with increased differentiation of WI-38 cells. Knockdown of PERK by siRNA or the PERK inhibitor glycogen synthesis kinase reduced expressions of the differentiation markers, α-SMA and Col IV, in WI-38 cells. CUR concentration-dependently inhibited ET-1- or thrombin-induced CCN2, α-SMA, and vimentin proteins with decreased levels of phosphorylated mitogen-activated protein kinase and PERK in WI-38 cells. An in vivo bleomycin-induced PF study showed that an intraperitoneal injection of CUR (30 mg/kg) reduced expressions of α-SMA, CCN2, Col IV, and vimentin in lung tissues via IHC staining using specific antibodies. This study is the first to demonstrate that PERK activation contributes to pulmonary fibroblast differentiation elicited by ET-1 or thrombin, and the inhibitory activity of CUR against PF is demonstrated herein.     

Angiotensin II enhances endothelin-1-induced vasoconstriction through upregulating endothelin type A receptor

Endothelin-1 (ET-1) is the most potent vasoconstrictor by binding to endothelin receptors (ET_AR) in vascular smooth muscle cells (VSMCs). The complex of angiotensin II (Ang II) and Ang II type one receptor (AT₁R) acts as a transient constrictor of VSMCs. The synergistic effect of ET-1 and Ang II on blood pressure has been observed in rats; however, the underlying mechanism remains unclear. We hypothesize that Ang II leads to enhancing ET-1-mediated vasoconstriction through the activation of endothelin receptor in VSMCs. The ET-1-induced vasoconstriction, ET-1 binding, and endothelin receptor expression were explored in the isolated endothelium-denuded aortae and A-10 VSMCs. Ang II pretreatment enhanced ET-1-induced vasoconstriction and ET-1 binding to the aorta. Ang II enhanced ET_AR expression, but not ET_BR, in aorta and increased ET-1 binding, mainly to ET_AR in A-10 VSMCs. Moreover, Ang II-enhanced ET_AR expression was blunted and ET-1 binding was reduced by AT₁R antagonism or by inhibitors of PKC or ERK individually. In conclusion, Ang II enhances ET-1-induced vasoconstriction by upregulating ET_AR expression and ET-1/ET_AR binding, which may be because of the AngII/Ang II receptor pathways and the activation of PKC or ERK. These findings suggest the synergistic effect of Ang II and ET-1 on the pathogenic development of hypertension.     

Endothelin-1 stimulates cyclin D1 expression in rat cultured astrocytes via activation of Sp1

Endothelins (ETs), a family of vasoconstrictor peptides, are up-regulated in several pathological conditions in the brain, and induce astrocytic proliferation. We previously observed that ET-1 increased the expression of cyclin D1 protein. Thus, we confirmed the intracellular up-regulation of cyclin D1 by ET-1 in rat cultured astrocytes. Real-time PCR analysis indicated that ET-1 (100 nM) and Ala^1,3,11,15-ET-1 (100 nM), a selective agonist of the ET_B receptor, induced a time-dependent and transient increase in cyclin D1 mRNA. The effect of ET-1 was diminished by an ET_B antagonist (1 μM BQ788) or inhibitors of Sp1 (500 nM mithramycin), ERK (50 μM PD98059), p38 (20 μM SB203580) and JNK (1 μM SP600125), but not inhibitors of NF-κB (10 μM SN50 and 100 μM pyrrolidine dithiocarbamate). The binding assay for Sp1 indicated that ET-1 increased the binding activity of Sp1 to consensus sequences, and two oligonucleotides of the cyclin D1 promoter including the Sp1-binding sites diminished the effect of ET-1. Western blot analysis showed that ET-1 induced time-dependent and transient phosphorylation of Sp1 on Thr453 and Thr739 via the ET_B receptor. ET-1-induced phosphorylation of Sp1 was attenuated by PD98059 and SP600125. Additionally, ET-1 increased the incorporation of bromodeoxyuridine (BrdU) in cultured astrocytes and the number of BrdU-positive cells decreased in the presence of PD98059, SP600125 and mithramycin. These results suggest that ET-1 increases the expression of cyclin D1 via activation of Sp1 and induces astrocytic proliferation.     

A transformed murine Leydig cell line expresses the ETA receptor subtype

We recently demonstrated that transformed murine Leydig cells (MA-10) responded to endothelin-1 (ET-1) via increased steroidogenesis. This study addresses the endothelin receptor subtype present on this cell line and whether or not the cells produce ET-1. The expression of the preproendothelin-1 (PPET-1) gene was investigated by Northern blot analysis, and PPET-1 mRNA was found to be <0.2% of that present in pulmonary endothelial cells. The medium from MA-10 cells, maintained under serum-free conditions, was analyzed by radio-immunoassay to determine immunoreactive-ET-1 production and ET-1 levels were found to be below the sensitivity of the assay (<10 pg/ml). The data from competitive binding experiments with [¹²⁵I]ET-1 and unlabeled ET-1, ET-3 and receptor subtype selective ligands yielded a single class of high affinity binding sites with ET_A receptor subtype characteristics. The results of this study demonstrate that MA-10 cells possess the ET_A receptor subtype but do not produce significant quantities of ET-1 under basal conditions.     

Exosomes derived from acute myeloid leukemia cells promote chemoresistance by enhancing glycolysis-mediated vascular remodeling

Acute myeloid leukemia (AML) is the most common type of leukemia in adults. AML cells secrete angiogenic factors to remodel vasculature and acquire chemoresistance; however, antiangiogenic drugs are often ineffective in AML treatment. Cancer cell-derived exosomes can induce angiogenesis, but their role in vascular remodeling during AML is unclear. Here, we found that exosomes secreted by AML cells promoted proliferation and migration and tube-forming activity of human umbilical vein endothelial cells (HUVECs), whereas HUVECs conferred chemoresistance to AML cells. AML cell-derived exosomes contained vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) messenger RNA and induced VEGFR expression in HUVECs. Furthermore, they enhanced glycolysis, which correlated with HUVEC proliferation, tube formation, and resistance to apoptosis. Thus, AML cells secrete VEGF/VEGFR-containing exosomes that induce glycolysis in HUVECs leading to vascular remodeling and acquisition of chemoresistance. These findings may contribute to the development of novel therapeutic strategies targeting exosomes in AML.     

Alterations in subcellular localization of p38 MAPK potentiates endothelin-stimulated COX-2 expression in glomerular mesangial cells

Endothelin-1 (ET-1) is a potent vasoconstrictor peptide with mitogenic actions linked to activation of tyrosine kinase signaling pathways. ET-1 induces cyclooxygenase-2 (COX-2), an enzyme that converts arachidonic acid to pro-inflammatory eicosanoids. Activation of each of the three major mitogen-activated protein kinase (MAPK) pathways, ERK1/2, JNK/SAPK, and p38 MAPK (p38), have been shown to enhance the expression of COX-2. Negative regulation of MAPK may occur via a family of dual specificity phosphatases referred to as mitogen-activated protein kinase phosphatases (MKP). The goal of this work was to test the hypothesis that wild type MKP-1 regulates the expression of ET-1-induced COX-2 expression by inhibiting the activation of p38 in cultured glomerular mesangial cells (GMC). An adenovirus expressing both wild type and a catalytically inactive mutant of MKP-1 (MKP-1/CS) were constructed to study ET-1-regulated MAPK signaling and COX-2 expression in cultured GMC. ET-1 stimulated the phosphorylation of ERK and p38 alpha MAPK and induced the expression of COX-2. Expression of COX-2 was partially blocked by U0126, a MEK inhibitor, and SB 203580, a p38 MAPK inhibitor. Adenoviral expression of MKP-1/CS augmented basal and ET-1-induced phosphorylation of p38 alpha MAPK with less pronounced effects on ERK1/2 phosphorylation. Ectopic expression of wild type MKP-1 blocked the phosphorylation of p38 alpha MAPK by ET-1 but increased the phosphorylation of p38 gamma MAPK. Co-precipitation studies demonstrated association of MKP-1 with p38 alpha MAPK and ERK1/2. Immunofluorescent image analysis demonstrated trapping of phospho-p38 MAPK in the cytoplasm by MKP-1/CS/green fluorescent protein. ET-1-stimulated expression of COX-2 was increased in MKP-1/CS versus LacZ or green fluorescent protein-infected control cells. These results indicate that MKP-1 demonstrates a relative selectivity for p38 alpha MAPK versus p38 gamma MAPK in GMC and is likely to indirectly regulate the expression of COX-2.     

Inhibition of platelet-derived growth factor-induced mesangial cell proliferation by cyclooxygenase-2 overexpression is abolished through reactive oxygen species

Proliferation of mesangial cells (MC) is an early event in many forms of glomerulonephritis. We have previously shown that platelet-derived growth factor (PDGF)-induced proliferation of MC was inhibited by the overexpression of cyclooxygenase-2 (COX-2). Since reactive oxygen species (ROS) are important mediators of mitogenic signaling, we evaluated the role of ROS in the COX-2 induced growth arrest in MC. We demonstrate that ROS are reduced in COX-2 overexpressing MC. Intracellular elevation of ROS restored PDGF-induced proliferation, while the expression of the cyclin-dependent kinase inhibitors p21(cip1) and p27(kip1) were decreased in these cells. The data suggest that COX-2 decreases ROS formation which consequently leads to the PDGF-induced inhibition of MC proliferation.     

Endothelin-converting enzyme-1 expression in acute and chronic liver injury in fibrogenesis

Endothelin-1 (ET-1) induces contraction, proliferation, and collagen synthesis of activated hepatic stellate cells and is a potent mediator of portal hypertension. Endothelin-converting enzyme-1 (ECE-1) generates ET-1 from the inactive precursor big-endothelin-1. The cellular distribution and activity of ECE-1 in the liver is unknown. Hepatic fibrogenesis was induced in rats by CCl₄ administration and secondary biliary cirrhosis after 6 weeks of complete bile duct occlusion (BDO). The tissue ET-1 and ET receptor protein levels were quantified, the ECE-1 isoform mRNAs were measured by RNase protection assay and ECE-1 activity was analyzed. ECE-1a and -b mRNA were upregulated in biliary cirrhosis and in CCl₄-injured livers, whereas ECE-1c mRNA remained unchanged. ECE-1 activity was increased after BDO and peaked at 12?h after acute CCl₄-intoxication. Tissue levels of ET-1, ET_A- and ET_B receptors were elevated 7-, 5-, and 4.6-fold in cirrhotic rats, respectively. ECE-1 activity increased following BDO and acute CCl₄-intoxication. In conclusion, ECE-1a and -b RNAs are upregulated in fibrogenesis, indicating that these isoforms play a central role in ET-1 generation during fibrogenesis and portal hypertension.     

Insulin-like growth factor-1 increases endothelin receptor A levels and action in cultured rat aortic smooth muscle cells

Insulin is known to cause an increase in endothelin-1 (ET-1) receptors in vascular smooth muscle cells (SMCs), but the effect of insulin-like growth factor 1 (IGF-1) on ET-1 receptor expression is not known. We therefore carried out the present study to determine the effect of IGF-1 on the binding of ET-1 to, and ET type A receptor (ETAR) expression and ET-1-induced 3H-thymidine incorporation in, vascular SMCs. In serum-free medium, IGF-1 treatment increased the binding of 125I-ET-1 to SMC cell surface ET receptors from a specific binding of 20.1%+/-3.1% per mg of protein in control cells to 45.1%+/-8.6% per mg of protein in cells treated with IGF-1 (10 nM). The effect of IGF-1 was dose-related, with a significant effect (1.4-fold) being seen at 1 nM. The minimal time for IGF-1 treatment to be effective was 30 min and the maximal effect was reached at 6 h. Immunoblotting analysis showed that ETAR expression in IGF-1-treated cells was increased by 1.7-fold compared to controls. Levels of ETAR mRNA measured by the RT-PCR method and Northern blotting were also increased by 2-fold in IGF-1-treated SMCs. These effects of IGF-1 were abolished by cycloheximide or genistein. Finally, ET-1-stimulated thymidine uptake and cell proliferation were enhanced by IGF-1 treatment, with a maximal increase of 3.2-fold compared to controls. In conclusion, in vascular SMCs, IGF-1 increases the expression of the ET-1 receptor in a dose- and time-related manner. This effect is associated with increased thymidine uptake and involves tyrosine kinase activation and new protein synthesis. These findings support the role of IGF-1 in the development of atherosclerotic, hypertensive, and diabetic vascular complications.     

Endothelin-1 enhances cell migration through COX-2 up-regulation in human chondrosarcoma

Background

Chondrosarcoma is a type of highly malignant tumor with a potent capacity of local invasion and distant metastasis. The effect of endothelin-1 (ET-1) on migration activity in human chondrosarcoma cells is not clearly understood. Here, we found that ET-1 increased the migration and expression of cyclooxygenase (COX)-2 in human chondrosarcoma cells.

Methods

ET-1-mediated COX-2 expression was assessed by qPCR and Western blot analysis. The mechanisms of action of ET-1 in different signaling pathways were studied using Western blotting. Knockdown of proteins was achieved by transfection with siRNA. Chromatin immunoprecipitation assays were used to study in vivo binding of c-Jun to the COX-2 promoter.

Results

Human chondrosarcoma tissues had significant expression levels of ET-1 and COX-2, which were higher than that in normal cartilage. Exogenous ET-1 increased cell migration and the expression of COX-2. In addition, COX-2 protein levels and cell migration ability were abolished by ET receptor antagonists. Activation of the mitogen-activated protein kinase (MAPK) and activator protein-1 (AP-1) pathways after ET-1 treatment was demonstrated, and ET-1-induced COX-2 expression and cell migration activity were inhibited by the specific inhibitor and mutant of MAPK and AP-1 cascades. ET-1 increased the binding of c-Jun to the AP-1 element on the COX-2 promoter. Furthermore, knockdown of ET-1 decreased cell metastasis in vitro and in vivo.

Conclusions

Our results indicated that ET-1 enhances the cell migration of chondrosarcoma by increasing COX-2 expression through the ET receptors, MAPK, and AP-1 signal transduction pathway.

General significance

We link high ET-1 and COX-2 expression to chondrosarcoma.     

HOTAIR/miR-125 axis-mediated Hexokinase 2 expression promotes chemoresistance in human glioblastoma

Drug resistance is one of the major obstacles in glioblastoma (GBM) treatments using temozolomide (TMZ) based conventional chemotherapy. Recent studies revealed that Hexokinase 2 (HK2)-mediated glycolysis is one of the sources, as the association of chemoresistance and the expression of HK2 was confirmed in multiple cancers. However, there has been little knowledge of the functional contribution of HK2 to TMZ resistance in GBM. In our study, we found that HK2 expression is crucial for GBM proliferation and chemoresistance. In contrast to the healthy brain, HK2 expression is much higher in human GBM, especially in those patients with GBM recurrence. High HK2 expression is negatively related to the overall survival in GBM patients. HK2 depletion in GBM cells suppressed the GBM cell proliferation and increased sensitivity to TMZ-induced apoptosis. Both HK2-mediated glycolysis and mitochondria permeability transition pore opening (MPTP) were associated with its function in chemoresistance. Furthermore, we also revealed that the abnormal expression of HK2 was modulated by the expression of HOTAIR, a long non-coding RNA (lncRNA). The absence of HOTAIR in GBM cells suppressed the HK2 expression in protein and mRNA level and, therefore, inhibited the cell proliferation and enhanced the cytotoxicity of TMZ both in vivo and in vitro. HOTAIR promoted the expression of HK2 by targeting mir-125, which suppressed the GBM cell proliferation and increased the TMZ-induced apoptosis. These findings shed light on a new therapeutic strategy in modulating HOTAIR/miR-125, which may interfere with the expression of HK2, and enhance the therapeutic sensitivity of GBM to TMZ.     

Interaction of atrial natriuretic factor and endothelin-1 signals through receptor guanylate cyclase in pulmonary artery endothelial cells

The endothelial cell has a unique intrinsic feature: it produces a most potent vasopressor peptide hormone, endothelin (ET-1), yet it also contains a signaling system of an equally potent hypotensive hormone, atrial natriuretic factor (ANF). This raises two related curious questions: does the endothelial cell also contain an ET-1 signaling system? If yes, how do the two systems interact with each other? The present investigation was undertaken to determine such a possibility. Bovine pulmonary artery endothelial (BPAE) cells were chosen as a model system. Identity of the ANF receptor guanylate cyclase was probed with a specific polyclonal antibody to the 180 kDa membrane guanylate cyclase (mGC) ANF receptor. A Western-blot analysis of GTP-affinity-purified endothelial cell membrane proteins recognized a 180 kDa band; the same antibody inhibited the ANF-stimulated guanylate cyclase activity; the ANF-dependent rise of cyclic GMP in the intact cells was dose-dependent. By affinity cross-linking technique, a predominant 55 kDa membrane protein band was specifically labeled with [¹²⁵I]ET-1. ET-1 treatment of the cells showed a migration of the protein kinase C (PKC) activity from cytosol to the plasma membrane; ET-1 inhibited the ANF-dependent production of cyclic GMP in a dose-dependent fashion with an EC₅₀ of 100 nM. This inhibitory effect was duplicated by phorbol 12-myristate 13-acetate (PMA), a known PKC-activator. The EC₅₀ of PMA was 5 nM. A PKC inhibitor, 1-(5-isoquinolinyl-sulfonyl)-2-methyl piperazine (H-7), blocked the PMA-dependent attenuation of ANF-dependent cyclic GMP formation. These results demonstrate that the 180 kDa mGC-coupled ANF and ET-1 signaling systems coexist in endothelial cells and that the ET-1 signal negates the ANF-dependent guanylate cyclase activity and cyclic GMP formation. Furthermore, these results support the paracrine and/or autocrine role of ET-1.     

Endothelin stimulates tyrosine phosphorylation of p125 and p130 in rat cerebral cortex

Stimulation of rat cerebral cortex with endothelin-1 (ET-1) caused an increase in the tyrosine phosphorylation of several proteins. Two of these phosphoproteins were identified by the immunoprecipitation assays as being the focal adhesion kinase p125^FAK and crk-associated substrate p130^Cas. This effect was time- and dose-dependent, with an EC₅₀ value of 3.9×10⁻⁸ M. In addition, the cerebral cortex ET receptor subtype involved in this action was determined by using BQ-123 and BQ-788, which are ET_A and ET_B receptor antagonists respectively. Our results indicate that the ET-1 effect on protein tyrosine phosphorylation occurred through ET_B receptors. The requirement for extracellular Ca²⁺ on ET-1 action was also studied. ET-1-stimulated tyrosine phosphorylation of both p125^FAK and p130^Cas was abolished in the absence of external Ca²⁺ or in the presence of nimodipine, a Ca²⁺ channel-blocker. These results suggest that the ET-1-stimulated protein tyrosine phosphorylation was secondary to Ca²⁺ influx through the dihydropyridine Ca²⁺-channel. In slices where protein kinase C was inhibited, ET-1-stimulated tyrosine phosphorylation of both proteins was reduced. These results indicate that ET-1 modulates the tyrosine phosphorylation of specific proteins, which may be involved in adhesion processes in the brain.     

一氧化氮抑制内皮素促血管平滑肌细胞增殖作用的信号转导途径

培养的家兔胸主动脉血管平滑肌细胞（ＶＳＭＣ）分别以内皮素（ＥＴ－１）、一氧化氮（ＮＯ）前体Ｌ－Ａｒｇ和ＮＯ供体ＳＩＮ－１刺激,或用ＥＴ－１＋Ｌ－Ａｒｇ、ＥＴ－１＋ＳＩＮ－１联合刺激,测ＶＳＭＣ＾３Ｈ－ＴｄＲ掺入、丝裂素活化蛋白激酶（ＭＡＰＫ）活性及蛋白激酶Ｃ（ＰＫＣ）活性的改变,以研究ＮＯ抑制ＥＴ－１促ＶＳＭＣ增殖作用的信号转导途径。结果表明：（１）ＥＴ－１ １０＾－８ｍｏｌ／Ｌ单独刺激,＾３Ｈ－     

Endothelin-1-induced prostaglandin E2-EP2, EP4 signaling regulates vascular endothelial growth factor production and ovarian carcinoma cell invasion

Cyclooxygenase (COX)-1- and COX-2-derived prostaglandins are implicated in the development and progression of several malignancies. We have recently demonstrated that treatment of ovarian carcinoma cells with endothelin-1 (ET-1) induces expression of both COX-1 and COX-2, which contributes to vascular endothelial growth factor (VEGF) production. In this study, we show that in HEY and OVCA 433 ovarian carcinoma cells, ET-1, through the binding with ETA receptor (ETAR), induces prostaglandin E2 (PGE2) production, as the more represented PG types, and increases the expression of PGE2 receptor type 2 (EP2) and type 4 (EP4). The use of pharmacological EP agonists and antagonists indicates that ET-1 and PGE2 stimulate VEGF production principally through EP2 and EP4 receptors. At the mechanistic level, we prove that the induction of PGE2 and VEGF by ET-1 involves Src-mediated epidermal growth factor receptor transactivation. Finally, we demonstrate that ETAR-mediated activation of PGE2-dependent signaling participates in the regulation of the invasive behavior of ovarian carcinoma cells by activating tumor-associated matrix metalloproteinase. These results implicate EP2 and EP4 receptors in the induction of VEGF expression and cell invasiveness by ET-1 and provide a mechanism by which ETAR/ET-1 can promote and interact with PGE2-dependent machinery to amplify its proangiogenic and invasive phenotype in ovarian carcinoma cells. Pharmacological blockade of ETAR can therefore represent an additional strategy to control PGE2 signaling, which has been associated with ovarian carcinoma progression.