Effect of beta-escin sodium on endothelial cells proliferation, migration and apoptosis

beta-Escin, the major active compound in extracts of the horse chestnut Aesculus hippocastanum seed, has shown clinically significant activity in chronic venous insufficiency (CVI). Our previous studies had shown that beta-escin sodium inhibited angiogenesis in chick chorioallantoic membrane (CAM) and in aortic disk assay. In this study, we explored the direct effect of beta-escin sodium on proliferation, migration and apoptosis in human umbilical vein endothelial cells (HUVECs) and ECV304 cells. Sulforhodamine B (SRB) assay showed that beta-escin sodium (10, 20, 40 microg/ml) inhibited endothelial cells (ECs) proliferation dose-dependently. beta-escin sodium also induced ECs apoptosis at 40 microg/ml. Cell migration was evaluated by an improved wound assay: barren spot assay. And the direct effect on cell motility excluding influence of cell proliferation was examined by High Content Screening (HCS, Cellomics) assay. The data indicated that beta-escin sodium suppressed ECs migration and cell motility. Western blot results suggested that beta-escin sodium acts on ECs possibly by increasing expression of thrombospondin-1 (TSP-1), and decreasing expression of PKC-alpha and activation of p44/42 mitogen-activated protein kinase (ERK) and p38 mitogen-activated protein kinase (p38 MAPK). Our findings give the evidence that beta-escin sodium might have potential anti-angiogenic activity via its direct effects on ECs.     

Inhibition of vascular endothelial growth factor-induced angiogenesis by resveratrol through interruption of Src-dependent vascular endothelial cadherin tyrosine phosphorylation

Resveratrol, a polyphenolic compound found in grapes and other fruits, has been reported to inhibit angiogenesis with an as yet elusive mechanism. Here, we investigate the detailed mechanism by which resveratrol inhibits vascular endothelial growth factor (VEGF)-induced angiogenic effects in human umbilical endothelial cells (HUVECs). Exposure of HUVECs to 1 to 2.5 muM resveratrol significantly blocked VEGF-mediated migration and tube formation but not cell proliferation. Under the same concentrations, resveratrol failed to affect VEGF-stimulated activation of VEGF receptor, extracellular signal-regulated protein kinase 1/2, p38 mitogen-activated protein kinase, and Akt. Of interest, resveratrol, at the dose of 1 or 2.5 muM, effectively abrogated VEGF-mediated tyrosine phosphorylation of vascular endothelial (VE)-cadherin and its complex partner, beta-catenin. This inhibitory effect of resveratrol reflected on the retention of VE-cadherin at cell-cell contacts as demonstrated by immunofluorescence. Src kinase assay showed that VEGF-induced endogenous Src kinase activation was strongly inhibited by 1 and 2.5 muM resveratrol. Supportively, inhibition of Src activity by overexpression of Csk resulted in attenuation of the tyrosine phosphorylation of VE-cadherin and endothelial cell (EC) tube formation. Again, transfection with v-Src, an active form of Src, could reverse resveratrol inhibition of VE-cadherin tyrosine phosphorylation and EC tube formation. Reactive oxygen species (ROS) has been shown to be involved in VE-cadherin phosphorylation and its related functions. Flow cytometric analysis showed that VEGF stimulated an evident increase of peroxide, which was strongly attenuated by resveratrol. In addition, antioxidant N-acetyl-cysteine was demonstrated to strongly inhibit VEGF-mediated Src activation, VE-cadherin tyrosine phosphorylation, and HUVEC tube formation. Together, our data suggest that resveratrol inhibition of VEGF-induced angiogenesis was mediated by disruption of ROS-dependent Src kinase activation and the subsequent VE-cadherin tyrosine phosphorylation.     

A novel Src kinase inhibitor, M475271, inhibits VEGF-induced human umbilical vein endothelial cell proliferation and migration

Vascular endothelial growth factor (VEGF) was reported to be a potent proangiogenic factor that plays a pivotal role in both physiological and pathological angiogenesis. M475271, 4-quinazolinamine, N-(2-chloro-5-methoxyphenyl)-6-methoxy-7-[(1-methyl-4-piperidinyl) methoxy]-(9Cl), is a new anilinoquinazoline derivative that showed selective inhibition of Src kinase activity and tumor growth in vivo. Here, we examined the effect of M475271 on VEGF-induced human umbilical vein endothelial cell (HUVEC) proliferation and migration and their intracellular mechanisms. Our findings showed that M475271 pretreatment resulted in a significant inhibition of VEGF-induced HUVEC proliferation, [(3)H]thymidine incorporation, and migration. M475271 inhibited VEGF-induced Flk-1 and Src phosphorylation and their association. Confocal laser microscopic examination confirmed the inhibitory effect of M475271 on VEGF-induced Flk-1/Src association. M475271 inhibited VEGF-induced extracellular signal-regulated kinase1/2 (ERK1/2) and p38 but not Akt activation in a concentration-dependent manner. M475271, PI3-K inhibitor, and p38 inhibitor inhibited VEGF-induced HUVEC proliferation and migration. However, a MEK1/2 inhibitor inhibited VEGF-induced proliferation but not migration. These findings suggest that M475271 attenuates VEGF-induced HUVEC proliferation and migration through the inhibition of signaling pathways involving Src, ERK1/2, and/or p38. Taken together, these data indicate that M475271 may be a useful candidate for inhibition of endothelial cell proliferation and migration relevant to angiogenesis.     

Effect of β-escin sodium on endothelial cells proliferation, migration and apoptosis

β-Escin, the major active compound in extracts of the horse chestnut Aesculus hippocastanum seed, has shown clinically significant activity in chronic venous insufficiency (CVI). Our previous studies had shown that β-escin sodium inhibited angiogenesis in chick chorioallantoic membrane (CAM) and in aortic disk assay. In this study, we explored the direct effect of β-escin sodium on proliferation, migration and apoptosis in human umbilical vein endothelial cells (HUVECs) and ECV304 cells. Sulforhodamine B (SRB) assay showed that β-escin sodium (10, 20, 40 μg/ml) inhibited endothelial cells (ECs) proliferation dose-dependently. β-escin sodium also induced ECs apoptosis at 40 μg/ml. Cell migration was evaluated by an improved wound assay: barren spot assay. And the direct effect on cell motility excluding influence of cell proliferation was examined by High Content Screening (HCS, Cellomics) assay. The data indicated that β-escin sodium suppressed ECs migration and cell motility. Western blot results suggested that β-escin sodium acts on ECs possibly by increasing expression of thrombospondin-1 (TSP-1), and decreasing expression of PKC-α and activation of p44/42 mitogen-activated protein kinase (ERK) and p38 mitogen-activated protein kinase (p38 MAPK). Our findings give the evidence that β-escin sodium might have potential anti-angiogenic activity via its direct effects on ECs.     

Inhibitory effects of sepiapterin on vascular endothelial growth factor-A-induced proliferation and adhesion in human umbilical vein endothelial cells

Tetrahydrobiopterin (BH₄) has been known to be an essential cofactor for the activities of nitric oxide (NO) synthase and aromatic amino acid hydroxylases, which are involved in physiological and pathological processes. In the present study, we report that sepiapterin, the more stable form of BH4 precursor, modulates vascular endothelial growth factor-A (VEGF-A)-induced cell proliferation and adhesion in human umbilical vein endothelial cells (HUVECs). The antiproliferative activity of sepiapterin in VEGF-A-treated HUVECs is associated with inhibition of the expression of cyclin-dependent kinases (Cdks) such as Cdk4 and Cdk2. Pretreatment with NO synthase inhibitor does not abrogate the ability of sepiapterin to inhibit VEGF-A-induced cell proliferation and adhesion, indicating that the suppressive effects of sepiapterin on VEGF-Ainduced responses are mediated by NO-independent mechanism. Finally, we show that sepiapterin modulates VEGF-A-induced cell proliferation and adhesion through down-regulation of VEGF receptor-2 downstream signaling pathways. Taken together, these findings represent a novel function of sepiapterin in the regulation of angiogenesis, supporting further development and evaluation of sepiapterin as an antiangiogenic agent.     

Cryptotanshinone inhibits chemotactic migration in macrophages through negative regulation of the PI3K signaling pathway

BACKGROUND AND PURPOSE: Cryptotanshinone, the major tanshinone isolated from Salvia miltiorrhiza Bunge, exhibits anti-inflammatory activity. However, there is no report on the effect of cryptotanshinone on recruitment of leukocytes to inflammatory sites. We therefore assessed the effects of cryptotanshinone on macrophage chemotaxis. EXPERIMENTAL APPROACH: Macrophage migration induced by complement 5a (C5a) or macrophage inflammatory protein-1alpha (MIP-1alpha) was measured in vitro. Intracellular kinase translocation and phosphorylation was assessed by Western blotting. KEY RESULTS: RAW264.7 cell migration towards C5a (1 microg ml(-1)) was significantly inhibited by cryptotanshinone (1, 3, 10 and 30 microM) in a concentration-dependent manner. Primary human macrophages stimulated by C5a were similarly inhibited. C5a-evoked migration in RAW264.7 cells was significantly suppressed by wortmannin (phosphatidylinositol 3-kinase (PI3K) inhibitor), PD98059 (MEK1/2 inhibitor) and SB203580 (p38 mitogen-activated protein kinase (MAPK) inhibitor), but not by SP600125 (c-Jun N-terminal kinase (JNK) inhibitor), suggesting that activation of PI3K, ERK1/2 and p38 MAPK signal pathways was involved in responses to C5a. Western blotting revealed that cryptotanshinone significantly inhibited PI3K-p110gamma membrane translocation and phosphorylation of Akt (PI3K downstream effector protein) and ERK1/2 induced by C5a. However, neither p38 MAPK nor JNK phosphorylation was affected by cryptotanshinone. Wortmannin significantly attenuated C5a-induced PI3K-p110gamma translocation, Akt and ERK1/2 phosphorylation. PD98059 suppressed ERK1/2 phosphorylation but failed to modify PI3K-p110gamma translocation by C5a stimulation. Furthermore, MIP-1alpha-induced cell migration and PI3K-p110gamma translocation were also inhibited by cryptotanshinone in a concentration-dependent manner. CONCLUSIONS AND IMPLICATIONS: Inhibition of macrophage migration by cryptotanshinone involved inhibition of PI3K activation with consequent reduction of phosphorylation of Akt and ERK1/2.     

Zerumbone,Sesquiterpene Photochemical from Ginger,Inhibits Angiogenesis

Here, we investigated the role of zerumbone, a natural cyclic sesquiterpene of Zingiber zerumbet Smith, on angiogenesis using human umbilical vein endothelial cells (HUVECs). Zerumbone inhibited HUVECs proliferation, migration and tubule formation, as well as angiogenic activity by rat aorta explants. In particular, zerumbone inhibited phosphorylation of vascular endothelial growth factor receptor-2 and fibroblast growth factor receptor-1, which are key regulators of endothelial cell function and angiogenesis. In vivo matrigel plug assay in mice demonstrated significant decrease in vascularization and hemoglobin content in the plugs from zerumbone-treated mice, compared with control mice. Overall, these results suggest that zerumbone inhibits various attributes of angiogenesis, which might contribute to its reported antitumor effects.     

ICAM-1 and p38 MAPK mediate fibrinogen-induced migration of human vascular smooth muscle cells

Fibrinogen deposition in the vessel wall represents an independent atherogenic risk factor. In Boyden-chamber assays, fibrinogen concentration-dependently (1-100 microM) induced migration of human vascular smooth muscle cells (SMC). This was inhibited by antibodies to intercellular adhesion molecule-1 (ICAM-1, 10 microg/ml), and by inhibitors of PI3-kinase (LY294002, 10 microM) and MAPK (mitogen-activated protein kinase) p38 (SB203580, 10 microM). The MEK (MAP kinase kinase) inhibitor PD98059 (10 muM) and the GPIIb/IIIa antagonist abciximab (10 mug/ml) had no effect. ICAM-1 antibodies inhibited fibrinogen-induced Akt and p38 phosphorylation. Thus fibrinogen stimulates human SMC migration through binding to ICAM-1 and activation of Akt and p38.     

Galbanic Acid Isolated from Ferula assafoetida Exerts In Vivo Anti-tumor Activity in Association with Anti-angiogenesis and Anti-proliferation

Purpose

To investigate whether galbanic acid (GBA) exerts anti-angiogenic and anti-cancer activities.

Methods

Using human umbilical vein endothelial cell (HUVEC) model, we analyzed effects of GBA on cellular and molecular events related to angiogenesis. We tested its direct anti-proliferative action on mouse Lewis lung cancer (LLC) cells and established its in vivo anti-angiogenic and anti-tumor efficacy using LLC model.

Results

GBA significantly decreased vascular endothelial growth factor (VEGF)-induced proliferation and inhibited VEGF-induced migration and tube formation of HUVECs. These effects were accompanied by decreased phosphorylation of p38-mitogen-activated protein kinase (MAPK), c-jun N-terminal kinase (JNK), and AKT, and decreased expression of VEGFR targets endothelial nitric oxide synthase (eNOS) and cyclin D1 in VEGF-treated HUVECs. GBA also decreased LLC proliferation with an apparent G2/M arrest, but did not induce apoptosis. In vivo, inclusion of GBA in Matrigel plugs reduced VEGF-induced angiogenesis in mice. Galbanic acid given by daily i.p. injection (1 mg/kg) inhibited LLC-induced angiogenesis in an intradermal inoculation model and inhibited the growth of s.c. inoculated LLC allograft in syngenic mice. Immunohistochemistry revealed decreased CD34 microvessel density index and Ki-67 proliferative index in GBA-treated tumors.

Conclusions

GBA exerts anti-cancer activity in association with anti-angiogenic and anti-proliferative actions.     

Pravastatin induces rat aortic endothelial cell proliferation and migration via activation of PI3K/Akt/mTOR/p70 S6 kinase signaling

The HMG-CoA reductase inhibitors (statins) have been shown to exert several vascular protective effects that are not related to changes in cholesterol profile, and these effects of statins are partly caused by the activation of angiogenesis. Endothelial cell (EC) proliferation and migration are crucial events for angiogenesis and statins are known to enhance these events. However, the molecular mechanism by which statins promote EC proliferation and migration is not fully understood. In this study, we show Akt and its downstream target mammalian target of rapamycin (mTOR) play an important role in pravastatin-induced EC proliferation and migration. We found that pravastatin significantly enhanced the proliferation and migration of rat aortic endothelial cells (rAECs). The addition of pravastatin to rAECs resulted in rapid phosphorylation of Akt and p70 S6 kinase (p70S6K). LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), blocked both Akt and p70S6K phosphorylation, whereas rapamycin, a specific inhibitor of mTOR, suppressed only p70S6K phosphorylation induced by pravastatin. Furthermore, both LY294002 and rapamycin inhibited pravastatin-induced rAEC proliferation and migration. Taken together, our findings indicate that pravastatin activates PI3K/Akt/mTOR /p70S6K signaling in this sequential manner and this pathway contributes to pravastatin-induced rAEC proliferation and migration.     

Andrographolide acts through inhibition of ERK1/2 and Akt phosphorylation to suppress chemotactic migration

We now evaluated the anti-inflammatory mechanisms of andrographolide on complement 5a (C5a)-induced macrophage recruitment in vitro. Andrographolide concentration dependently inhibited cell migration toward C5a with an IC50 of 5.6+/-0.7 microM. With relatively specific kinase inhibitors (PD98059, SB203580, SP600125, wortmannin and LY294002, respectively) the results showed that extracellular signal-regulated kinase1/2 (ERK1/2), p38 mitogen-activated protein kinase (p38 MAPK) and phosphatidylinositol-3-kinase (PI3K) were necessary for C5a-induced migration, whereas c-Jun N-terminal kinase (JNK) was nonessential. Andrographolide significantly attenuated C5a-stimulated phosphorylation of ERK1/2, and of its upstream activator, MAP kinase-ERK kinase (MEK1/2). C5a-activated ERK1/2 phosphorylation was 86+/-9% inhibited by 30 microM andrographolide. Under the same conditions, however, andrographolide failed to affect C5a-stimulated p38 MAPK and JNK phosphorylation. Andrographolide also strongly abolished C5a-stimulated Akt phosphorylation, a downstream target protein for PI3K. These results indicate that inhibition of cell migration by interfering with ERK1/2 and PI3K/Akt signal pathways may contribute to the anti-inflammatory activity of andrographolide.     

Estrogen down-regulates nicotine-induced adhesion molecule expression via nongenomic signal pathway in endothelial cells

Although gonadal hormone mostly causes genotropic actions through the members of nuclear receptor family, it also can regulate these actions via membrane receptor. To explore the possibility of plasma membrane estrogen receptors (mER) mediating genotropic events, we have investigated estrogen's effect on nicotine-stimulated adhesion molecule expression and evaluated whether this effect depends on calcium, MAPK signal pathway. Fluorescence Spectroscopy analysis of Ca2+ from human umbilical vein endothelial cells (HUVECs) showed through mER, estrogen induced a rapid rise of intracellular free Ca2+ concentration and this rise could not be inhibited by tamoxifen (classic ER inhibitor). In the context of nicotine stimulating, however, estrogen attenuated phosphorylation of mitogen-activated protein kinase (MAPK) family members, extracellular signal regulated kinase 1/2 (ERK1/2), p38 but not c-Jun-N-terminal kinase (JNK) in HUVECs and this effect could not still be prevented by tamoxifen. In the meantime, estrogen also down-regulated surface/soluble vascular cell adhesion molecule (VCAM-1, sVCAM-1) and endothelial selectin (E-selectin, sE-selectin) levels, which was not abolished by tamoxifen either. Moreover, calcium chelator BAPTA, ERK1/2 inhibitor PD98059, p38 inhibitor SB203580 significantly reduced the production of nicotine-activated surface/soluble VCAM-1 and E-selectin and both of the remained levels were no longer regulated by estrogen. Our study here provides the information of decrease effect of mER-mediated estrogen through Ca2+ and ERK1/2, p38 MAPK signaling pathway on nicotine-stimulated expression of surface/soluble VCAM-1 and E-selectin in HUVECs.     

Actions of the Kunitz-type serine protease inhibitor Amblyomin-X on VEGF-A-induced angiogenesis

Amblyomin-X is a Kunitz-type serine protease inhibitor (Kunitz-type SPI) designed from the cDNA library of the Amblyomma cajennense tick, which displays in vivo anti-tumor activities. Here, the mechanisms of actions of Amblyomin-X in vascular endothelial growth factor A (VEGF-A)-induced angiogenesis were characterized. Topical application of Amblyomin-X (10 or 100 ng/10 μl; each 48 h) inhibited VEGF-A-induced (10 ng/10 μl; each 48 h) angiogenesis in the dorsal subcutaneous tissue in male Swiss mice. Moreover, similar effect was observed in the VEGF-A-induced angiogenesis in the chicken chorioallantoic membrane (CAM). Additional in vitro assays in t-End cells showed that Amblyomin-X treatment delayed the cell cycle, by maintaining them in G0/G1 phase, and inhibited cell proliferation and adhesion, tube formation and membrane expression of the adhesion molecule platelet-endothelial cell adhesion molecule-1 (PECAM-1), regardless of mRNA synthesis. Together, results herein reveal the role of Kunitz-type SPI on in vivo VEGF-A-induced angiogenesis, by exerting modulatory actions on endothelial cell proliferation and adhesion, especially on membrane expression of PECAM-1. These data provide further mechanisms of actions of Kunitz-type SPI, corroborating their relevance as scientific tools in the design of therapeutic molecules.     

Protective effects of aspirin against oxidized LDL-induced inflammatory protein expression in human endothelial cells

Atherosclerosis is a complex vascular inflammatory disease. Oxidized low-density lipoprotein (ox-LDL) is directly associated with chronic vascular inflammation. In this study, we hypothesized that nonselective cyclooxygenase inhibitor aspirin might affect the ox-LDL-induced inflammatory responses on human endothelial cells. To test this assumption, cyclooxygenase-2 (COX-2) and intercellular adhesion molecule-1 (ICAM-1) expression, IkappaB and p38 mitogen-activated protein kinase (MAPK) phosphorylation were determined in endothelial cells exposed to ox-LDL in the presence of aspirin. The results showed that aspirin significantly suppressed COX-2 and ICAM-1 expression induced by ox-LDL and also inhibited IkappaB phosphorylation in human umbilical vein endothelial cells (HUVECs). Moreover, aspirin reduced the level of p38 MAPK phosphorylation. Our findings suggest that aspirin can decrease inflammatory responses induced by ox-LDL, and the mechanism might be associated with NF-kappaB activation pathway and inhibition of p38 MAPK phosphorylation.     

OSU-A9 inhibits angiogenesis in human umbilical vein endothelial cells via disrupting Akt–NF-κB and MAPK signaling pathways

Since the introduction of angiogenesis as a useful target for cancer therapy, few agents have been approved for clinical use due to the rapid development of resistance. This problem can be minimized by simultaneous targeting of multiple angiogenesis signaling pathways, a potential strategy in cancer management known as polypharmacology. The current study aimed at exploring the anti-angiogenic activity of OSU-A9, an indole-3-carbinol-derived pleotropic agent that targets mainly Akt–nuclear factor-kappa B (NF-κB) signaling which regulates many key players of angiogenesis such as vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs). Human umbilical vein endothelial cells (HUVECs) were used to study the in vitro anti-angiogenic effect of OSU-A9 on several key steps of angiogenesis. Results showed that OSU-A9 effectively inhibited cell proliferation and induced apoptosis and cell cycle arrest in HUVECs. Besides, OSU-A9 inhibited angiogenesis as evidenced by abrogation of migration/invasion and Matrigel tube formation in HUVECs and attenuation of the in vivo neovascularization in the chicken chorioallantoic membrane assay. Mechanistically, Western blot, RT-PCR and ELISA analyses showed the ability of OSU-A9 to inhibit MMP-2 production and VEGF expression induced by hypoxia or phorbol-12-myristyl-13-acetate. Furthermore, dual inhibition of Akt–NF-κB and mitogen-activated protein kinase (MAPK) signaling, the key regulators of angiogenesis, was observed. Together, the current study highlights evidences for the promising anti-angiogenic activity of OSU-A9, at least in part through the inhibition of Akt–NF-κB and MAPK signaling and their consequent inhibition of VEGF and MMP-2. These findings support OSU-A9's clinical promise as a component of anticancer therapy.     

MAPKs signaling in 5-LOX pathway-associated inflammatory responses

5-Lipoxygenase(5-LOX) is a crucial enzyme catalyzing arachidonic acid to form cysteinyl leukotrienes(Cys LTs, including LTC4, LTD4, LTE4). Cys LTs are potent inflammatory mediators that mediate many pathophysiological responses by activating two distinct G-protein-coupled receptors(CysLT1R and CysLT2R). 5-LOX pathway is implicated in inflammatory pathological processes. Mitogenactivated protein kinases(MAPKs) are important signal transduction pathways of complex cellular processes.Classical MAPK families in mammalian cells include the P38 MAPK, extracellular signal-regulated kinases(ERK)and c-Jun amino N-terminal kinase(JNK). Increasing evidence has suggested that MAPKs signaling acts as key modulator in 5-LOX pathway-related pathological processes. It was reported that P38 MAPK and 5-LOX were dramatically activated to mediate neuronal injury in oxygen-glucose deprivation(OGD)-treated PC12 cells,which could be inhibited by P38 MAPK inhibitor SB203580 and nonselective 5-LOX inhibitor caffeic acid. In primary cultured rat astrocytes, OGD induced increased expression of CysLT2R and aquaporin 4, and ischemic astrocyte injury. Also, OGD increased phosphorylation of ERK and P38 MAPK. These astrocyte responses were attenuated by P38 MAPK inhibitor SB203580, ERK inhibitor U0126, CysLT2R antagonist Bay Cys LT2 and non-selective Cys LTR antagonist Bay u9773, but not by JNK inhibitor SP600125 and CysLT1R antagonist montelukast. These data demonstrate the roles of ERK and P38 MAPK signaling pathways in 5-LOX and CysLT2R-mediated ischemic-like injury in neuron-like PC12 cel s and rat astrocytes. Furthermore, CysLT1R and ERK signaling were found to be involved in regulation of LTD4-stimulated expression of glial fibrillary acidic protein and cell proliferation in astrocytes. ERK inhibitor PD98059 and CysLT1R antagonist montelukast, MK-571 abolished Cys LTs-induced astrocyte proliferation. Vascular endothelial cells play a pivotal role in maintaining brain homeostasis. Endothelial cells undergo a number of pathological changes that can be characterized as uncontrolled cell proliferation, migration and dysfunction in respond to brain insults. In human endothelial cell line EA.hy926, LTD4-induced migration of endothelial cells could be modulated by CysLT1R via phosphorylation of ERK. LTD4 was also reported to enhanced cell proliferation mediated by activating CysLT1R in human umbilical vein endothelial cells(HUVECs), and this is regulated by ERK pathway. ERK inhibitor(U0126, PD98059), CysLT1R antagonist(montelukast, MK571) and dual antagonist(Bay u9773)suppressed LTD4-induced endothelial responses in EA.hy926 cells and HUVECs. Consistent with these results,a study showed that the involvement of ERK/early growth response-1(Egr-1) pathway in CysLT2R-mediated cytokine IL-8 production. ERK inhibitor U0126 and CysLT2R antagonist HAMI3379 inhibited Egr-1 and IL-8 expression as well as IL-8 release in LTC4 and LTD4-stimulated hCys LT2-HEK293 cells. In addition, LTD4 and LTC4 induced monocyte chemoattractant protein-1(MCP-1) by enhanced CysLT1R via phosphorylations of ERK and JNK in human monocytes/macrophages. Pretreatment with the ERK inhibitor PD98059 and JNK inhibitor SP600125 reduced MCP-1 production. CysLT1R antagonist pranlukast inhibited Cys LTs-induced phosphorylation of ERK and JNK as well as production of MCP-1. A better understanding of the roles of MAPKs signaling in 5-LOX pathway-associated pathological processes may open up new avenues for the development of therapeutic strategies targeting inflammatory diseases.