Antiangiogenic Effect of Rosiglitazone Is Mediated via Peroxisome Proliferator-activated Receptor γ-activated Maxi-K Channel Opening in Human Umbilical Vein Endothelial Cells

Abstract

Recent evidence shows that peroxisome proliferator-activated receptor γ (PPARγ) ligands induce the antiangiogenic effect in endothelial cells and tumors. In the present study, we elucidated the involvement of maxi-K channel activation in the antiangiogenic effect of rosiglitazone, a well known PPARγ ligand in human umbilical vein endothelial cells. We found that the antiangiogenic effects of rosiglitazone were reversed by either bisphenol A diaglycidyl ether, a PPARγ antagonist, or iberiotoxin, a maxi-K channel blocker. Knockdown of maxi-K channel expression also reversed the antiangiogenic effects. Iberiotoxin reversed the rosiglitazone-induced hyperpolarization while having no effect on the endogenous PPARγ activation, suggesting that rosiglitazone activates maxi-K channel via PPARγ. In the rosiglitazone-induced antiangiogenic process, endothelial nitric-oxide synthase-Ser1179 phosphorylation and NO production were significantly elevated, and treatment with the NOS inhibitor NG-monomethyl-l-arginine acetate abolished the antiangiogenic and apoptotic effects of rosiglitazone, indicating NO as a key mediator of the rosiglitazone actions. In conclusion, rosiglitazone significantly inhibited VEGF165-induced angiogenesis by a proapoptotic mechanism via PPARγ-mediated NO production, followed by maxi-K channel opening. Recent evidence shows that peroxisome proliferator-activated receptor γ (PPARγ) ligands induce the antiangiogenic effect in endothelial cells and tumors. In the present study, we elucidated the involvement of maxi-K channel activation in the antiangiogenic effect of rosiglitazone, a well known PPARγ ligand in human umbilical vein endothelial cells. We found that the antiangiogenic effects of rosiglitazone were reversed by either bisphenol A diaglycidyl ether, a PPARγ antagonist, or iberiotoxin, a maxi-K channel blocker. Knockdown of maxi-K channel expression also reversed the antiangiogenic effects. Iberiotoxin reversed the rosiglitazone-induced hyperpolarization while having no effect on the endogenous PPARγ activation, suggesting that rosiglitazone activates maxi-K channel via PPARγ. In the rosiglitazone-induced antiangiogenic process, endothelial nitric-oxide synthase-Ser1179 phosphorylation and NO production were significantly elevated, and treatment with the NOS inhibitor NG-monomethyl-l-arginine acetate abolished the antiangiogenic and apoptotic effects of rosiglitazone, indicating NO as a key mediator of the rosiglitazone actions. In conclusion, rosiglitazone significantly inhibited VEGF165-induced angiogenesis by a proapoptotic mechanism via PPARγ-mediated NO production, followed by maxi-K channel opening. Angiogenesis, the growth of new capillaries from preexisting microvessels (1Cao Y. Ji R.W. Davidson D. Schaller J. Marti D. Sohndel S. McCance S.G. O-Reilly M.S. Llinas M. Folkman J. J. Biol. Chem. 1996; 271: 29461-29467Abstract Full Text Full Text PDF PubMed Scopus (373) Google Scholar), plays an important role in a variety of physiological processes, including embryonic development, wound healing, and tissue or organ regeneration (2Folkman J. Nat. Med. 1995; 1: 27-31Crossref PubMed Scopus (7209) Google Scholar) and in the pathological development and progression of various cancers, rheumatoid arthritis, diabetic retinopathy, and psoriasis (3Margeli A. Kouraklis G. Theocharis S. Angiogenesis. 2003; 6: 165-169Crossref PubMed Scopus (78) Google Scholar). Among many factors stimulating angiogenesis, vascular endothelial growth factor (VEGF) 2The abbreviations used are: VEGF, vascular endothelial growth factor; PPAR, peroxisome proliferator-activated receptor; HUVEC, human umbilical vein endothelial cell; BADGE, bisphenol A diglycidyl ether; IBTX, iberiotoxin; l-NMMA, NG-monomethyl-l-arginine acetate; NOS, nitric-oxide synthase; DiBAC, bis-1,3-dibutylbarbituric acid-trimethine oxonol; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; eNOS, endothelial NOS; RNAi, RNA interference. 2The abbreviations used are: VEGF, vascular endothelial growth factor; PPAR, peroxisome proliferator-activated receptor; HUVEC, human umbilical vein endothelial cell; BADGE, bisphenol A diglycidyl ether; IBTX, iberiotoxin; l-NMMA, NG-monomethyl-l-arginine acetate; NOS, nitric-oxide synthase; DiBAC, bis-1,3-dibutylbarbituric acid-trimethine oxonol; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; eNOS, endothelial NOS; RNAi, RNA interference. is a key regulatory factor of the angiogenic process in either physiological or pathological conditions (4Risau W. 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Recent investigations suggested that PPARγ ligands have inhibitory effects on tumor cell lines, but the effects appear not to be entirely elicited by the direct action on tumor cells. Similarly, Panigrahy et al. (12Panigrahy D. Singer S. Shen L.Q. Butterfield C.E. Freedman D.A. Chen E.J. Moses M.A. Kilroy S. Duensing S. Fletcher C. Fletcher J.A. Hlatky L. Hahnfeldt P. Folkman J. Kaipainen A. J. Clin. Invest. 2002; 110: 923-932Crossref PubMed Scopus (348) Google Scholar) reported that PPARγ is expressed in tumor endothelium and in cultured endothelial cells and that rosiglitazone inhibits angiogenesis in vitro and in vivo via its effects on endothelium. In addition, 15-deoxy-Δ-12,14-prostaglandin J2, an endogenous PPARγ ligand, inhibited VEGF-induced angiogenesis in the rat cornea (13Xin X. Yang S. Kowalski J. Gervitsen M.E. J. Biol. Chem. 1999; 13: 9116-9119Abstract Full Text Full Text PDF Scopus (477) Google Scholar) and induced caspase-mediated endothelial cell apoptosis via a PPAR-dependent pathway (9Bishop-Bailey D. Hla T. J. Biol. Chem. 1999; 274: 17042-17048Abstract Full Text Full Text PDF PubMed Scopus (406) Google Scholar). Possible mechanisms of antiangiogenic actions by PPARγ activation include the inhibition of mitogen-activated protein kinase-dependent activation (14Goetze S. Bungenstock A. Czupalla C. Eilers F. Stawowy P. Kintscher U. Spencer-Hansch C. Graf K. Nurnberg B. Law R.E. Fleck E. Grafe M. Hypertension. 2002; 40: 748-754Crossref PubMed Scopus (174) Google Scholar); up-regulation of angiogenesis inhibitor maspin and CD36 (15Huang H. Campbell S.C. Bedford D.F. Nelius T. Veliceasa D. Shroff E.H. Henkin J. Schneider A. Bouck N. Volpert O.V. Mol. Cancer Res. 2004; 2: 541-550PubMed Google Scholar), the receptor for antiangiogenic thrombospondin; inhibition of matrix metalloproteinase, VEGF, and VEGF receptor expression; and increase of plasminogen activator inhibitor and matrix metalloproteinase inhibitor expression (12Panigrahy D. Singer S. Shen L.Q. Butterfield C.E. Freedman D.A. Chen E.J. Moses M.A. Kilroy S. Duensing S. Fletcher C. Fletcher J.A. Hlatky L. Hahnfeldt P. Folkman J. Kaipainen A. J. Clin. Invest. 2002; 110: 923-932Crossref PubMed Scopus (348) Google Scholar, 13Xin X. Yang S. Kowalski J. Gervitsen M.E. J. Biol. Chem. 1999; 13: 9116-9119Abstract Full Text Full Text PDF Scopus (477) Google Scholar, 16Sierra-Honigmann M.R. Nath A.K. Murakami C. Garcia-Cardena G. Papapetropoulos A. Sessa W.C. Madge L.A. Schechner J.S. Schwabb M.B. Polverini P.J. Flores-Riveros J.R. Science. 1998; 281: 1683-1686Crossref PubMed Scopus (1271) Google Scholar). However, the direct mechanism for the antiangiogenic effects of PPARγ activation in the endothelial cells remains currently unclear. The endothelium plays a pivotal role in a variety of vascular functions such as blood pressure control, vascular remodeling, and angiogenesis, where ion channels, particularly large conductance Ca2+-activated K+ channels (also known as the BK channel or maxi-K channel), are the key mediators (17Ling S. Woronuk G. Sy L. Lev S. Braun A.P. J. Biol. Chem. 2000; 275: 30683-30689Abstract Full Text Full Text PDF PubMed Scopus (82) Google Scholar). Maxi-K channels are distributed in various tissues, such as human brain tumors, vascular smooth muscle cells, and endothelial cells, and their activations were shown to inhibit migration of human glioma cells (18Kraft R. Krause P. Jung S. Basrai D. Liebmann L. Bolz J. Patt S. Pflugers Arch. 2003; 446: 248-255Crossref PubMed Scopus (67) Google Scholar). The maxi-K channels are synergistically regulated by various intracellular second messengers, such as cytoplasmic Ca2+ concentration, cGMP, hydrogen peroxide, and nitric oxide (NO) (19Bolotina V.M. Najibi S. Palacino J.J. Pagano P.J. Cohen R.A. Nature. 1994; 368: 850-853Crossref PubMed Scopus (1510) Google Scholar, 20Fukao M. Mason H.S. Britton F.C. Kenyon J.L. Horowitz B. Keef K.D. J. Biol. Chem. 1999; 274: 10927-10935Abstract Full Text Full Text PDF PubMed Scopus (177) Google Scholar, 21Brakemeier S. Eichler I. Knorr A. Fassheber T. Kohler R. Hoyer J. Kidney Int. 2003; 64: 199-207Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar). NO is produced by a group of enzymes called nitric-oxide synthases (NOS), and endothelial NOS (eNOS or NOS3) is responsible for the production of NO in vascular endothelial cells. Although the expression and activity of eNOS seems to be constitutive, the activity was shown to be regulated by serine phosphorylation (22Cho D.H. Choi Y.J. Jo S.A. Jo I. J. Biol. Chem. 2004; 279: 2499-2506Abstract Full Text Full Text PDF PubMed Scopus (151) Google Scholar). In this study, we investigated the possible involvement of maxi-K channels in the antiangiogenic effects of rosiglitazone in human umbilical vein endothelial cells (HUVECs). The inhibitory action of rosiglitazone on VEGF-stimulated angiogenesis was blocked either by iberiotoxin or by knockdown of maxi-K channel expression, and the effect was associated with apoptotic action as shown by DNA fragmentation and Bcl-2 and Bax regulation. The mediator involved in the maxi-K channel opening by rosiglitazone appears to be NO, produced by PPARγ-activated eNOS. These findings provide important understanding that maxi-K channel plays a critical role in the rosiglitazone-induced antiangiogenesis in HUVECs. Cell Cultures—HUVEC (ATCC CRL-1730; endothelial cell line derived from vein of human umbilical cord) were cultured in Kaighn's F12K medium supplemented with 10% heat-inactivated fetal bovine serum, 0.1 mg/ml heparin sodium, mg/ml endothelial cell growth and and were to in on and used for no was on with of and for with either bisphenol A diaglycidyl or iberiotoxin for were a of a of and followed by the of either rosiglitazone or were for and in vivo was by of and heparin were and was with 10% and with the of new blood the of was the The of was from a known of in Cell a of in were for in Kaighn's F12K medium fetal bovine and to rosiglitazone or for followed by stimulation for an was T. J. PubMed Scopus Google Scholar), and the was a were with either rosiglitazone or for in the or of either iberiotoxin or cells were with for DNA fragmentation was by of DNA on followed by and were by was by as reported A. A. A. 2003; PubMed Scopus Google Scholar). as were by and for and cells were as were with for or and or of cell of protein was an and to were and with and Bcl-2 were from were with in for and to iberiotoxin or NG-monomethyl-l-arginine acetate for and by rosiglitazone or for followed by for The of were a resulted in the of the from cells, a in Maxi-K Knockdown was by with the to human maxi-K the G. The was used as a was a and to be The were and The of was to RNA expression, and the was to the medium to the treatment of The of the to maxi-K channel expression was by and on cell of Ca2+ and NO with either or Maxi-K channel were in tissue and with Kaighn's F12K medium fetal bovine or iberiotoxin for and to rosiglitazone or for was and for Ca2+ was by the of a NO production by was as of in cell human was from was in the of iberiotoxin, BADGE, endothelial cell growth and were from The was from and were from was from BADGE, iberiotoxin, and were in as a and with are expressed as was used for and was to be of Maxi-K and on VEGF-induced and in the of VEGF, a as by rosiglitazone and a maxi-K channel the of The of by rosiglitazone was reversed by either a PPARγ antagonist, or iberiotoxin a maxi-K channel blocker. The of and iberiotoxin were as and effect of in and of of were The and were significantly in the and significantly the of and rosiglitazone was by either or iberiotoxin These that rosiglitazone elicited a in vivo antiangiogenic activity via maxi-K channel opening. of Maxi-K and on the VEGF-induced Cell were in the medium for cell was to the cell in a with inhibition The effect of rosiglitazone was reversed by and iberiotoxin suggesting that the effects of rosiglitazone in by PPARγ activation and by maxi-K channel opening The of the inhibitory effects of rosiglitazone was to that in (13Xin X. Yang S. Kowalski J. Gervitsen M.E. J. Biol. Chem. 1999; 13: 9116-9119Abstract Full Text Full Text PDF Scopus (477) Google Scholar, T. Y. T. S. Law R.E. Arch. PubMed Scopus Google Scholar). In significantly the cell induced by in a was reversed by iberiotoxin but was not reversed by of on antiangiogenic and of rosiglitazone are with we the effects of rosiglitazone on DNA induced DNA indicating the apoptotic action of rosiglitazone cell induced by rosiglitazone was by and shown in and cells a in but cells of in the The rosiglitazone-induced apoptosis was inhibited by either or iberiotoxin suggesting that the apoptosis seems to be by maxi-K channel opening. significantly induced the DNA fragmentation and in the was reversed by iberiotoxin but not by or iberiotoxin no effect on DNA the an of Ca2+-activated K+ channel and an K+ channel were not of rosiglitazone-induced DNA suggesting the specific involvement of maxi-K channel in the rosiglitazone-induced apoptotic action The DNA fragmentation by rosiglitazone was by of Bcl-2 expression and Bax expression suggesting that the of endothelial cell is associated with apoptotic effects. These effects were also reversed by and iberiotoxin of Knockdown of Maxi-K on the and of in resulted in the of maxi-K channel expression to 10% of In to the antiangiogenic and effects of rosiglitazone in rosiglitazone was on VEGF165-induced and cell in maxi-K cells and These provide evidence that maxi-K channel activation is for the antiangiogenic and effects of rosiglitazone on endothelial cells. Maxi-K via PPARγ that rosiglitazone maxi-K channel we the effect of rosiglitazone on the of endothelial was reversed by either or iberiotoxin These provide the direct evidence that rosiglitazone activates maxi-K channel opening in HUVECs. also resulted in the endothelial hyperpolarization reversed by iberiotoxin but not reversed by either or that maxi-K channel activation is the effect of rosiglitazone-induced PPARγ activation, the effect of iberiotoxin on the rosiglitazone-induced endogenous PPARγ activation was endogenous PPARγ expression as but this effect was not by iberiotoxin indicating that activation of maxi-K channel is the of PPARγ activation by In addition, iberiotoxin no effect on the endogenous PPARγ transcriptional activity by rosiglitazone with a genes not of on eNOS and NO rosiglitazone the maxi-K channel via NO production, we the eNOS phosphorylation by The phosphorylation was significantly and by rosiglitazone and expression was by but not by iberiotoxin the phosphorylation was by rosiglitazone with rosiglitazone NO production, as shown in NO production to the to maxi-K channels (19Bolotina V.M. Najibi S. Palacino J.J. Pagano P.J. Cohen R.A. Nature. 1994; 368: 850-853Crossref PubMed Scopus (1510) Google Scholar). NO production by rosiglitazone was by either or not but not by iberiotoxin or by knockdown of maxi-K channel expression In addition, rosiglitazone-induced hyperpolarization suggesting that NO is an important for PPARγ-mediated maxi-K channel The DNA fragmentation and of in vitro and by rosiglitazone were by l-NMMA, indicating that NO is involved as a key mediator of rosiglitazone-induced apoptotic and antiangiogenic effects. no effect on VEGF165-induced in vitro and DNA The of of was effect of on Ca2+ the effects of rosiglitazone and on the Ca2+ on the that maxi-K channel activation resulted in the increase of intracellular Ca2+ J.R. Y. D. A.K. U. T. S. H. A. 2004; PubMed Scopus Google Scholar). Ca2+ was either by iberiotoxin or by In treatment also intracellular Ca2+ not Ca2+ is the or effect of maxi-K channel activation by rosiglitazone, we the effects of rosiglitazone on the Ca2+ in the maxi-K channel cells. The Ca2+ by rosiglitazone was abolished in maxi-K channel cells, suggesting that Ca2+ be the of the maxi-K channel activation by PPARγ as a for the treatment of (13Xin X. Yang S. Kowalski J. Gervitsen M.E. J. Biol. Chem. 1999; 13: 9116-9119Abstract Full Text Full Text PDF Scopus (477) Google Scholar, T. Y. T. S. Law R.E. Arch. PubMed Scopus Google Scholar), various PPARγ ligands inhibited growth migration of vascular endothelial cells, smooth muscle cells, and tumor cells Law R.E. Biol. PubMed Scopus Google Scholar, T.M. Kliewer S.A. PubMed Scopus Google Scholar). The present the that the antiangiogenic effect of rosiglitazone is by maxi-K channel opening and apoptosis in HUVECs. Among many cell involved in the PPARγ-mediated antiangiogenic investigations the of endothelial cells in the inhibitory activity of PPARγ ligands with the of PPARγ expression in the tumor endothelium and in the endothelial cells (9Bishop-Bailey D. Hla T. J. Biol. Chem. 1999; 274: 17042-17048Abstract Full Text Full Text PDF PubMed Scopus (406) Google Scholar, D. Singer S. Shen L.Q. Butterfield C.E. Freedman D.A. Chen E.J. Moses M.A. Kilroy S. Duensing S. Fletcher C. Fletcher J.A. Hlatky L. Hahnfeldt P. Folkman J. Kaipainen A. J. Clin. Invest. 2002; 110: 923-932Crossref PubMed Scopus (348) Google Scholar, 13Xin X. Yang S. Kowalski J. Gervitsen M.E. J. Biol. Chem. 1999; 13: 9116-9119Abstract Full Text Full Text PDF Scopus (477) Google Scholar). endogenous ligand, 15-deoxy-Δ-12,14-prostaglandin and inhibited endothelial and and VEGF-induced angiogenesis (13Xin X. Yang S. Kowalski J. Gervitsen M.E. J. Biol. Chem. 1999; 13: 9116-9119Abstract Full Text Full Text PDF Scopus (477) Google Scholar, P. J. Biol. 1999; PubMed Scopus Google Scholar). Similarly, and rosiglitazone inhibited VEGF-induced and of bovine endothelial cells (13Xin X. Yang S. Kowalski J. Gervitsen M.E. J. Biol. Chem. 1999; 13: 9116-9119Abstract Full Text Full Text PDF Scopus (477) Google Scholar), and rosiglitazone growth of a variety of and by antiangiogenic effect (12Panigrahy D. Singer S. Shen L.Q. Butterfield C.E. Freedman D.A. Chen E.J. Moses M.A. Kilroy S. Duensing S. Fletcher C. Fletcher J.A. Hlatky L. Hahnfeldt P. Folkman J. Kaipainen A. J. Clin. Invest. 2002; 110: 923-932Crossref PubMed Scopus (348) Google Scholar). the (13Xin X. Yang S. Kowalski J. Gervitsen M.E. J. Biol. Chem. 1999; 13: 9116-9119Abstract Full Text Full Text PDF Scopus (477) Google Scholar) that rosiglitazone, a PPARγ induced a inhibition of in to in vitro and in with the PPARγ-mediated apoptosis in endothelial cells (9Bishop-Bailey D. Hla T. J. Biol. Chem. 1999; 274: 17042-17048Abstract Full Text Full Text PDF PubMed Scopus (406) Google Scholar), we also that the effects of rosiglitazone were by DNA fragmentation with Bcl-2 and Bax In addition, the apoptotic cell by rosiglitazone was by and and cells a in but cells of in the The effects of rosiglitazone were abolished by with BADGE, a PPARγ antagonist, suggesting that rosiglitazone-induced via apoptosis is PPARγ activation in HUVECs. Maxi-K channels, widely expressed channels in various cell action and cell in D. J. 1999; PubMed Google Scholar, J.H. J.H. M.A. J. 2004; PubMed Scopus Google Scholar), and induce cell and apoptosis to of K+ in endothelial cells. we that maxi-K channels be involved in the inhibitory action of rosiglitazone in VEGF165-induced angiogenesis of HUVECs. from (12Panigrahy D. Singer S. Shen L.Q. Butterfield C.E. Freedman D.A. Chen E.J. Moses M.A. Kilroy S. Duensing S. Fletcher C. Fletcher J.A. Hlatky L. Hahnfeldt P. Folkman J. Kaipainen A. J. Clin. Invest. 2002; 110: 923-932Crossref PubMed Scopus (348) Google Scholar, M. R. M. N. J. 2002; PubMed Scopus Google Scholar), maxi-K channels as well as PPARγ were expressed in by in not of the involvement of maxi-K channels in rosiglitazone-induced in endothelial cells in a the antiangiogenic effect by rosiglitazone was reversed by either iberiotoxin, a maxi-K channel or BADGE, a PPARγ a specific maxi-K channel antiangiogenic was reversed by iberiotoxin but not by and knockdown of maxi-K channel expression by abolished the antiangiogenic effects of the either an of Ca2+-activated K+ channel or an K+ channel was on the action of rosiglitazone, indicating that PPARγ activation induced the maxi-K channel in in the proapoptotic and antiangiogenic effects in endothelial cells. The of rosiglitazone action by maxi-K channel inhibition iberiotoxin and be to either the of the rosiglitazone-induced activation of PPARγ or the effects of PPARγ activation by In the present study, we that the effects of rosiglitazone on PPARγ activation were not with by we that rosiglitazone maxi-K as by hyperpolarization reversed in the of either iberiotoxin or of that rosiglitazone induced maxi-K channel opening via PPARγ activation, antiangiogenic effects in endothelial cells. Maxi-K channels are regulated by various intracellular second messengers, including NO (19Bolotina V.M. Najibi S. Palacino J.J. Pagano P.J. Cohen R.A. Nature. 1994; 368: 850-853Crossref PubMed Scopus (1510) Google Scholar, 20Fukao M. Mason H.S. Britton F.C. Kenyon J.L. Horowitz B. Keef K.D. J. Biol. Chem. 1999; 274: 10927-10935Abstract Full Text Full Text PDF PubMed Scopus (177) Google Scholar, 21Brakemeier S. Eichler I. Knorr A. Fassheber T. Kohler R. Hoyer J. Kidney Int. 2003; 64: 199-207Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar). NO appears to maxi-K channel activity either via or via direct (19Bolotina V.M. Najibi S. Palacino J.J. Pagano P.J. Cohen R.A. Nature. 1994; 368: 850-853Crossref PubMed Scopus (1510) Google Scholar, 20Fukao M. Mason H.S. Britton F.C. Kenyon J.L. Horowitz B. Keef K.D. J. Biol. Chem. 1999; 274: 10927-10935Abstract Full Text Full Text PDF PubMed Scopus (177) Google Scholar), the regulatory role of NO in the endothelial maxi-K channel is S. Eichler I. Knorr A. Fassheber T. Kohler R. Hoyer J. Kidney Int. 2003; 64: 199-207Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar, M. L. F. J. G. B. Cell 1997; PubMed Scopus Google Scholar). reported that PPARγ activation endothelial NO production (22Cho D.H. Choi Y.J. Jo S.A. Jo I. J. Biol. Chem. 2004; 279: 2499-2506Abstract Full Text Full Text PDF PubMed Scopus (151) Google Scholar, L. S. J. Biol. 2003; PubMed Scopus Google Scholar), via of eNOS phosphorylation serine and In suggested that eNOS phosphorylation is not involved in the maxi-K NO production J.R. Y. D. A.K. U. T. S. H. A. 2004; PubMed Scopus Google Scholar). we elucidated the pathway of rosiglitazone-induced maxi-K channel opening by of eNOS phosphorylation and NO The phosphorylation was significantly and by rosiglitazone, in the NO production, phosphorylation was not NO production by rosiglitazone was by but not by either iberiotoxin or knockdown of maxi-K channel In addition, blocked rosiglitazone-induced that NO as a mediator of rosiglitazone for maxi-K channel opening. the the of on the hyperpolarization is with the J.R. Y. D. A.K. U. T. S. H. A. 2004; PubMed Scopus Google Scholar), and the found NO production of the maxi-K channel opening that NO also a role as a A increase in cytoplasmic Ca2+ was maxi-K channel opening and induced apoptosis in vascular smooth muscle cells S. M. H. J. PubMed Google Scholar, M. 2003; PubMed Scopus Google Scholar). with J.R. Y. D. A.K. U. T. S. H. A. 2004; PubMed Scopus Google Scholar, M. 2003; PubMed Scopus Google Scholar), the present that and rosiglitazone but this increase was not in maxi-K channel cells, indicating that the increase of intracellular Ca2+ be the effect of rosiglitazone-induced maxi-K channel the present shows that rosiglitazone significantly inhibited VEGF165-induced angiogenesis in endothelial cells by a proapoptotic mechanism via PPARγ-mediated NO production, followed by maxi-K channel opening. to the that PPARγ NO production is to the vascular effects (22Cho D.H. Choi Y.J. Jo S.A. Jo I. J. Biol. Chem. 2004; 279: 2499-2506Abstract Full Text Full Text PDF PubMed Scopus (151) Google Scholar), the present that NO produced by rosiglitazone as an important mediator of apoptotic cell the pathway maxi-K channel We that the evidence of maxi-K channel activity in the rosiglitazone-induced in endothelial cells. Although in vivo antiangiogenic activity of rosiglitazone seems to be a from the effects on many cell the of the present provide an important on the antiangiogenic mechanism of rosiglitazone in the endothelial cells. the as maxi-K channel in endothelial cells provide a for antiangiogenic therapy.