1,661 research outputs found
Inhibitory Effect of Yc-1 on the Hypoxic Induction of Erythropoietin and Vascular Endothelial Growth Factor in Hep3b Cells
No full textYC-1 is a newly developed agent that inhibits platelet aggregation and vascular contraction. Although its effects are independent of nitric oxide (NO), it mimics some of the biological actions of NO. For example, it stimulates soluble guanylate cyclase (sGC) and increases intracellular cGMP concentration. Here, we tested the possibility that YC-1 inhibits hypoxia-inducible factor (HIF)-1-mediated hypoxic responses, as does NO. Hep3B cells were used during the course of this work to observe hypoxic induction of erythropoietin (EPO) and vascular endothelial growth factor ( VEGF), and the effects of YC-1 were compared with those of a NO donor, sodium nitropurruside (SNP). In hypoxic cells, YC-1 blocked the induction of EPO and VEGF mRNAs, and inhibited the DNA-binding activity of HIF-1. It suppressed the hypoxic accumulation of HIF-1, but not its mRNA level. It also reduced HIF-1 accumulation induced by cobalt and desferrioxamine. Treatment with antioxidants did not recover the HIF-1 suppressed by YC-1. We examined whether these effects of YC-1 are related to the sGC/cGMP signal transduction system. Two sGC inhibitors examined failed to block the effects of YC-1, and 8-bromo-cGMP did not mimic actions of YC-1. The effects of YC-1 on the hypoxic responses were comparable with those of SNP . These results suggest that YC-1 and SNP suppressed the hypoxic responses by post-translationally inhibiting HIF-1 accumulation. The YC-1 effect may be linked with the metal-related oxygen sensing pathway, and is not due to the stimulation of sGC. This observation implies that the inhibitory effects of YC-1 on hypoxic responses can be developed to suppress EPO- overproduction by tumor cells and tumor angiogenesis
Yc-1 Increases Cyclo-Oxygenase-2 Expression through Protein Kinase G- and P44/42 Mitogen-Activated Protein Kinase-Dependent Pathways in A549 Cells
No full text1 YC-1, an activator of soluble guanylate cyclase (sGC), has been shown to increase the intracellular cGMP concentration . This study was designed to investigate the signaling pathway involved in the YC-1-induced COX-2 expression in A 549 cells. 2 YC-1 caused a concentration- and time- dependent increase in COX activity and COX-2 expression in A549 cells . Pretreatment of the cells with the sGC inhibitor (ODQ), the protein kinase G (PKG) inhibitor (KT-5823), and the PKC inhibitors (Go 6976 and GF10923X ), attenuated the YC-1- induced increase in COX activity and COX-2 expression. 3 Exposure of A549 cells to YC-1 caused an increase in PKC activity; this effect was inhibited by ODQ, KT-5823 or Go 6976. Western blot analyses showed that PKC-alpha, -iota, - lambda, -zeta and -mu isoforms were detected in A549 cells. Treatment of A549 cells with YC-1 or PMA caused a translocation of PKC-alpha, but not other isoforms, from the cytosol to the membrane fraction. Long-term (24 h) treatment of A549 cells with PMA down-regulated the PKC- alpha. 4 The MEK inhibitor, PD 98059 (10-50 muM), concentration-dependently attenuated the YC-1-induced increases in COX activity and COX-2 expression. Treatment of A549 cells with YC-1 caused an activation of p44/42 MAPK; this effect was inhibited by KT-5823, Go 6976, long-term (24 h) PMA treatment or PD98059, but not the p38 MAPK inhibitor , SB 03580. 5 These results indicate that in human pulmonary epithelial cells, YC-1 might activate PKG through an upstream sGC/cGMP pathway to elicit PKC-alpha activation, which in turn, initiates p44/42 MAPK activation, and finally induces COX-2 expression
Yc-1 Potentiates the Antiplatelet Effect of Hydrogen Peroxide Via Sensitization of Soluble Guanylate Cyclase
No full textthe present study, we showed that 3-(5'-hydroxymethyl-2'- furyl)-1-benzyl indazole (YC-1), a nitric oxide (NO)- independent activator of soluble guanylate cyclase, could potentiate H2O2-induced inhibition of platelet aggregation and increase of platelet cGMP levels. The synergistic effect of YC-1 and H2O2 on platelet aggregation and increases of cGMP were almost completely prevented by catalase and a selective soluble guanylate cyclase inhibitor (1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), or partially attenuated by the hydroxyl radical scavenger mannitol. In contrast, superoxide dismutase failed to influence H2O2/YC-1 -induced inhibition of aggregation. Furthermore, YC-1 could enhance the activation of soluble guanylate cyclase caused by FeSO4/H2O2 and, this effect was prevented markedly by mannitol. These results suggest that YC-1 may enhance the antiaggregatory effect of H2O2 via the sensitization of platelet soluble guanylate cyclase. In addition, this phenomenon is, at least in part, dependent on H2O2-derived hydroxyl radical. (C) 1999 Elsevier Science B.V. All rights reserved
Yc-1 Inhibits Proliferation of Human Vascular Endothelial Cells through a Cyclic Gmp-Independent Pathway
No full textThis study was designed to investigate the effect of YC-1, 3 -(5'- hydroxymethyl-2'-furyl)-1-benzylindazole, in human umbilical vein endothelial cells (HUVECs) proliferation and its underlying mechanism. YC- 1 at a range of concentrations( 5-50 muM) inhibited DNA synthesis and decreased cell number in cultured HUVEC in a dose- and time-dependent manner. YC- 1 was not cytotoxic at these concentrations. [H-3]thymidine incorporation and flow cytometry analyses revealed that YC-1 treatment decreased DNA synthesis and arrested the cells at the G0/G1 phase of the cell cycle. Western blot analysis demonstrated that YC-1 (5-50 muM) increased the levels of cyclin-dependent kinase (CDK)-inhibitory proteins (CKIs), p 21 and p27, but did not induce any significant changes of cyclins and CDKs. In the YC-1-treated HUVEC, the formation of CDK2-p21 complex, but not CDK2-p27 complex, was increased and the assayable CDK2 kinase activity was decreased. These changes were in a dose-dependent manner. In contrast, the formations of CDK4-p21 and CDK4-p27 complex were slightly increased and the assayable CDK4 kinase activity was slightly decreased (if there were any changes). Pretreatment with guanylyl cyclase inhibitors, 1H-(1,2,4)oxadiazolo[4,3- a]quinozalin-1-one (ODQ) and methylene blue, inhibited the YC-1-induced increase of cyclic GMP level, but did not change significantly the magnitude of the YC-1-induced inhibition of thymidine incorporation and cell number in HUVEC. These results indicate that YC-1-induced cell cycle arrest in HUVEC occurred when the cyclin-CDK system was inhibited just as p21 and p27 protein levels were augmented. This YC-1-induced antiproliferation effect in HUVEC is via acyclic GMP-independent pathway
The Mechanism of Actions of 3-(5 '-(Hydroxymethyl-2 '-Furyl)-1-Benzyl Indazole (Yc-1) on Ca2+-Activated K+ Currents in Gh(3) Lactotrophs
No full textThe effects of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), an activator of soluble guanylyl cyclase, on ionic currents have been assessed in rat pituitary GH(3) lactotrophs. In GH(3) cells bathed in normal Tyrode's solution, YC-1 (1 mu M) reversibly suppressed the amplitude of the Ca2+-activated K+ current (I-K(Ca)). YC-1 at a concentration above 10 mu M produced a biphasic response in the amplitude of I-K(Ca), i.e., an initial decrease followed by a sustained increase. When the pipette solutions were filled with high EGTA (10 mM), the YC-1- induced stimulatory effect on I-K(Ca) was abolished. Over a similar concentration range, YC-1 also effectively inhibited the voltage-dependent K+ current (I-K(V)) in GH(3) cells. The IC 50 value required for the inhibition of I-K(V) by YC-1 was 1 mu M. Unlike YC-1, 8-bromo cGMP did not inhibit I-K(Ca). However, YC-1 (10 mu M) did not affect the amplitude of L- type Ca2+ current. In the cell-attached configuration, application of YC-1 (10 mu M) to the bath did not change the single-channel conductance of the large-conductance Ca2+- activated K+ (BKCa) channels; however, it did increase the opening probability of BKCa channels. In contrast, in the outside-out configuration, YC-1 (10 mu M) significantly suppressed the opening probability of BKCa channels. The present study shows dual effects of YC-1 on I-K(Ca) in GH, cells. The YC-1-mediated stimulation of I-K(Ca) may result from elevated cytosolic Ca2+, whereas the inhibition of I-K( Ca) and I-K(V) by YC-1 appears to be direct and independent of the activation of soluble guanylyl cyclase. Caution thus needs to be used in attributing the YC-1-mediated response to the activation of soluble guanylyl cyclase. (C) 2000 Elsevier Science Ltd. All rights reserved
Yc-1 Prevents Sodium Nitroprusside-Mediated Apoptosis in Vascular Smooth Muscle Cells
No full textObjective: Nitric oxide signaling pathways are of central importance in both the maintenance of vascular homeostasis and the progression of vascular disease. Since smooth muscle cell apoptosis is associated with numerous vascular disorders, the authors investigated whether YC-1, a soluble guanylyl cyclase (sGC) activator, regulates apoptosis in vascular smooth muscle cells (VSMC). Methods and results: Sodium nitroprusside (SNP ) (1 mM) induced cGMP (guanosine 3' :5'-cyclic monophosphate)-independent apoptosis in rat vascular smooth muscle cells using MTT assay and TUNEL- reaction techniques. Furthermore, sodium nitroprusside induced apoptosis via Bcl-2 down-regulation, cytochrome c release reaction, and caspase-3 activation by Western blotting analysis and enzymatic assay methods. YC-1 abolished these apoptotic signaling cascades and prevented apoptosis through a cGMP-involved pathway, and phosphatidylinositol (PI) 3-kinase behaved a downstream event in this pathway. Conclusions: These results suggest that YC-1 inhibits sodium nitroprusside-induced vascular smooth muscle cells apoptosis via a cGMP- and phosphatidylinositol 3-kinase- involved inhibition on Bcl-2 down-regulation/cytochrome c release/ caspase -3 activation cascades. The ability of YC-1 to prevent smooth muscle cell apoptosis may play an important role in blocking lesion formation at sites of vascular injury. (C) 2003 European Society of Cardiology. Published by Elsevier B.V. All rights reserved
Yc-1 Inhibits Hif-1 Expression in Prostate Cancer Cells: Contribution of Akt/Nf-Kappa B Signaling to Hif-1 Alpha Accumulation during Hypoxia
No full textHypoxia-inducible factor 1 ( HIF-1), a transcription factor that is critical for tumor adaptation to microenvironmental stimuli, represents an attractive chemotherapeutic target. YC-1 is a novel antitumor agent that inhibits HIF-1 through previously unexplained mechanisms. In the present study, YC- 1 was found to prevent HIF-1 alpha and HIF-1 beta accumulation in response to hypoxia or mitogen treatment in PC-3 prostate cancer cells. Neither HIF-1 alpha protein half -life nor mRNA level was affected by YC- 1. However, YC-1 was found to suppress the PI3K/Akt/mTOR/4E-BP pathway, which serves to regulate HIF-1 alpha expression at the translational step. We demonstrated that YC-1 also inhibited hypoxia-induced activation of nuclear factor ( NF)-kappa B, a downstream target of Akt. Two modulators of the Akt/NF- kappa B pathway, caffeic acid phenethyl ester and evodiamine , were observed to decrease HIF-1 alpha expression. Additionally, overexpression of NF-kappa B partly reversed the ability of wortmannin to inhibit HIF-1 alpha-dependent transcriptional activity, suggesting that NF-kappa B contributes to Akt-mediated HIF-1 alpha accumulation during hypoxia. Overall, we identify a potential molecular mechanism whereby YC-1 serves to reduce HIF-1 expression
Inhibitory Mechanisms of Yc-1 and Pmc in the Induction of Inos Expression by Lipoteichoic Acid in Raw 264.7 Macrophages
No full textIn the present study, the signal pathways involved in NO formation and iNOS expression in RAW 264.7 macrophages stimulated by LTA were investigated. We also compared the relative inhibitory activities and mechanisms of PMC, a novel potent antioxidant of alpha-tocopherol derivatives, with those of YC-1, an sGC activator, on the induction of iNOS expression by LTA in cultured macrophages ill vitro and LTA-induced hypotension ill vivo. LTA induced concentration (0.1-50 mug/mL)- and time (4-24 hr)-dependent increases in nitrite (an indicator of NO biosynthesis) in macrophages. Both PMC (50 muM) and YC-1 (10 muM) inhibited NO production, iNOS protein, mRNA expression, and IkappaBalpha degradation upon stimulation by LTA (20 mug/mL) in macrophages. On the other hand, PMC (50 muM) almost completely suppressed JNK/ SAPK activation, whereas YC-1 (10 muM) only partially inhibited its activation in LTA-stimulated macrophages. Moreover, PMC (10 mg/kg, i.v.) and YC-1 (5 mg/kg, i.v.) significantly inhibited the fall in MA-P stimulated by LTA ( 10 mg/kg, i.v .) in rats. In conclusion, we demonstrate that YC-1 shows more-potent activity than PMC at abrogating the expression of iNOS in macrophages in vitro and reversing delayed hypotension in rats with endotoxic shock stimulated by LTA. The inhibitory mechanisms of PMC may be due to its antioxidative properties, with a resulting influence on JNK/ SAPK and NF- kappaB activations. YC-1 may be mediated by increasing cyclic GMP, followed by, at least partly, inhibition of JNK/SAPK and NF-kappaB activations, thereby leading to inhibition of iNOS expression. (C) 2004 Elsevier Inc. All rights reserved
Investigation of anticancer mechanism of clavulone II, a coral cyclopentenone prostaglandin analog, in human acute promyelocytic leukemia.
No full textSoluble Guanylyl Cyclase Activator Yc-1 Inhibits Human Neutrophil Functions through a Cgmp-Independent but Camp-Dependent Pathway
No full text3-(5-Hydroxymethyl-2'- furyl)-1-benzyl indazole (YC-1), a novel type of soluble guanylyl cyclase (sGC) activator, is useful in investigating the signaling of cGMP and may provide a new approach for treating cardiovascular diseases. Herein, YC-1 was demonstrated to inhibit the generation of superoxide anion (O-2(radical anion)) and the release of beta-glucuronidase release, to diminish the membrane- associated p47(phox) and to accelerate resequestration of cytosolic calcium in formyl-L- methionyl-L-leucyl-L- phenylalanine-activated human neutrophils. YC-1 not only directly promoted sGC activity and cGMP formation but also dramatically potentiated sodium nitroprusside-induced sGC activity and cGMP formation in human neutrophils. However, the synergistic increase in the amount of cGMP was inconsistent with its cellular response. Moreover, neither an sGC inhibitor nor protein kinase G inhibitors reversed the inhibitory effect of YC-1. Interestingly, YC-1 also increased the cAMP concentration and protein kinase (PK) A activity. The inhibitory effect of YC-1 was significantly enhanced by prostaglandin (PG)E-1` and isoproterenol, and almost abolished by PKA inhibitors. These results show that cAMP, but not cGMP, mediates the YC-1-induced inhibition of human neutrophils. YC-1 increased the PGE(1)- and forskolin- induced but not 3- isobutyl-1-methylxanthine-produced cAMP formation, suggesting inhibition of phosphodiesterase. These findings thus reveal novel mechanism-mediated anti- inflammatory properties of YC-1 in human neutrophils, which can influence the progression of cardiovascular disease. cAMP, but not cGMP, plays an important role in the regulation of respiratory burst and degranulation in human neutrophils
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