Induction of Endothelial Nitric-oxide Synthase Phosphorylation by the Raloxifene Analog LY117018 Is Differentially Mediated by Akt and Extracellular Signal-regulated Protein Kinase in Vascular Endothelial Cells

Hisamoto, Koji; Ohmichi, Masahide; Kanda, Yuki; Adachi, K.; Nishio, Yukihiro; Hayakawa, Jun; Mabuchi, Seiji; Takahashi, Kazuhiro; Tasaka, Keiichi; Miyamoto, Yasuhide; Taniguchi, Naoyuki; Murata, Yuji

doi:10.1074/jbc.m103853200

Cited by 67 publications

(52 citation statements)

References 69 publications

(79 reference statements)

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“…It is generally assumed that transient versus delayed ERK phosphorylation determines the proliferative or differentiating outcome, respectively (Marshall, 1995;Seger and Krebs, 1995). Biphasic ERK phosphorylation has been described for diverse stimuli (Cowan et al, 2000;Hisamoto et al, 2001;Reusch et al, 2001), including apoptosis mediated by cytotoxic drugs (Ding and Templeton, 2000). In the case of taxol or vitamin E, ERK activation is essential for drug cytotoxicity (Bacus et al, 2001;Yu et al, 2001) whilst for cisplatin, induction of ERK, although not essential, serves a putative protective role against the cytotoxic effects of the drug (Persons et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

Aplidin™ induces the mitochondrial apoptotic pathway via oxidative stress-mediated JNK and p38 activation and protein kinase C δ

et al. 2002

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AplidinTM , a new antitumoural drug presently in phase II clinical trials, has shown both in vitro and in vivo activity against human cancer cells. Aplidin TM effectively inhibits cell viability by triggering a canonical apoptotic program resulting in alterations in cell morphology, caspase activation, and chromatin fragmentation. Pro-apoptotic concentrations of Aplidin TM induce early oxidative stress, which results in a rapid and persistent activation of both JNK and p38 MAPK and a biphasic activation of ERK. Inhibition of JNK and p38 MAPK blocks the apoptotic program induced by Aplidin TM , demonstrating its central role in the integration of the cellular stress induced by the drug. JNK and p38 MAPK activation results in downstream cytochrome c release and activation of caspases -9 and -3 and PARP cleavage, demonstrating the mediation of the mitochondrial apoptotic pathway in this process. We also demonstrate that protein kinase C delta (PKC-d) mediates the cytotoxic effect of Aplidin TM and that it is concomitantly processed and activated late in the apoptotic process by a caspase mediated mechanism. Remarkably, cells deficient in PKC-d show enhanced survival upon drug treatment as compared to its wild type counterpart. PKC-d thus appears as an important component necessary for full caspase cascade activation and execution of apoptosis, which most probably initiates a positive feedback loop further amplifying the apoptotic process.

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Section: Discussionmentioning

confidence: 99%

Aplidin™ induces the mitochondrial apoptotic pathway via oxidative stress-mediated JNK and p38 activation and protein kinase C δ

et al. 2002

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“…5D), suggesting that association between NFB and hTERT was involved in the raloxifene-induced telomerase activation. To confirm the specificity of the effects of LY294002, SN50, and BAY-11-7082 on the PI3K/Akt/NFB cascade, we examined the effects of LY294002, SN50, and BAY-11-7082 on the raloxifene-induced ERK phsphorylation, which we reported previously (9). For this, cells were treated with raloxifene Ϯ LY294002, SN50, or BAY-11-7082 and then subjected to Western blotting with antiphospho-ERK antibody.…”

Section: Raloxifene Induces Endothelial Cell Proliferation Via the Rementioning

confidence: 99%

“…We reported that raloxifene induces eNOS phosphorylation via the Akt cascade (9). NO was reported to activate telomerase and delay endothelial cell senescence (15).…”

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confidence: 99%

Raloxifene Increases Proliferation and Up-regulates Telomerase Activity in Human Umbilical Vein Endothelial Cells

Doshida

Ohmichi

Tsutsumi

et al. 2006

Journal of Biological Chemistry

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Vascular endothelial senescence is involved in human atherosclerosis. Telomerase activity is known to be critical in cellular senescence and its level is modulated by regulation of telomerase catalytic subunit (telomerase reverse transcriptase (TERT)) at both the transcriptional and post-transcriptional levels. Since the cardioprotective effect of estrogen itself has not been ruled out, we examined that of raloxifene, which has been classified as a selective estrogen receptor modulator, on the proliferation and telomerase activity of human umbilical vein endothelial cells (HUVECs). Raloxifene, like estrogen, clearly induced the telomerase activity and human TERT (hTERT) expression via estrogen receptor (ER) ␣ and ER␤. Treatment with raloxifene for 5 days significantly induced cell growth, and either cotreatment with a telomerase inhibitor, 3-azido-3-deoxythymidine, or transfection with hTERT-specific small interfering RNA significantly attenuated the raloxifene-induced cell growth. Raloxifene also induced the phosphorylation of Akt, and pretreatment with a phosphatidylinositol 3-kinase inhibitor, LY294002, significantly attenuated the raloxifene-induced telomerase activity. In addition, raloxifene induced both the phosphorylation of hTERT and IB. Moreover, cotreatment with an IB␣ phosphorylation inhibitor, BAY-11-7082, or a specific NFB nuclear translocation inhibitor, SN50, significantly attenuated the raloxifene-induced telomerase activity and the association of NFB with hTERT. These results show that raloxifene induced the up-regulation of telomerase activity not only by the transcriptional regulation of hTERT but also by posttranslational regulation of the phosphorylation of Akt and hTERT and the association of hTERT with NFB in HUVECs. Thus, the up-regulation of telomerase activity in vascular endothelial cells might be one mechanism contributing to the potential atheroprotective effect of raloxifene.The risk of cardiovascular disease steeply increases after menopause. Many epidemiological and basic studies have shown that estrogen has the significant function in the vasculature of preventing the primary development of cardiovascular disease in women (1-2). In the Women's Health Initiative, a large prospective randomized controlled study, although women on the conjugated equine estrogen-medroxyprogesterone acetate arm had an increase in the relative risk of cardiovascular events and breast cancer (3), the more recent reports indicated that on women on the conjugated equine estrogenonly treatment arm experienced a significant increase in the risk of stroke compared with women treated with placebo but did not show an increase in cardiovascular disease (4). Thus, the cardioprotective effect of estrogen itself has not been ruled out by the results of the Women's Health Initiative study.Recently, we reported that medroxyprogesterone acetate attenuates the induction of both endothelial nitric-oxide synthase (eNOS) 2 activity and NO production by estrogen in human umbilical vein endothelial cells (HUVECs) (5). Thu...

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“…In addition, it was reported that proatherogenic factors induce telomerase inactivation in endothelial cells through an Akt-dependent mechanism (Breitschopf et al, 2001). We previously reported that both estrogen (Hisamoto et al, 2001b) and raloxifene (Hisamoto et al, 2001a) induce eNOS activation via an Akt cascade. In addition, it was reported that an Akt cascade mediates the estrogen-induced S-phase entry and cyclin D1 promoter activity in MCF-7 cells (Castoria et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Induction of hTERT expression and phosphorylation by estrogen via Akt cascade in human ovarian cancer cell lines

et al. 2004

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We examined the mechanism by which estrogen regulates telomerase activity in Caov-3 human ovarian cancer cell lines, which express ER, to determine whether the regulation affects the expression and/or phosphorylation of the telomerase catalytic subunit (hTERT). 17b-Estradiol (E 2 ) induced telomerase activity and hTERT expression. Transient expression assays using luciferase reporter plasmids containing various fragments of hTERT promoter showed that the estrogen-responsive element appeared to be partially responsible for the E 2 -induced activation of the hTERT promoter. Either pretreatment with a phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, or transfection with a dominantnegative Akt attenuated the E 2 -induced activation of the hTERT promoter. In addition, estrogen induced the phosphorylation of IjB inhibitor protein via the Akt cascade, and cotransfection with a dominant-negative subunit of NFjB attenuated the response of the ERE-deleted hTERT promoter to E 2 . Moreover, E 2 induced the phosphorylation of hTERT, the association of 14-3-3 protein and NFjB with hTERT, and nuclear accumulation of hTERT in an Akt-dependent manner. These results indicate that E 2 induces telomerase activity not only by transcriptional regulation of hTERT via an ERE-dependent mechanism and a PI3K/Akt/NFjB cascade, but also by post-transcriptional regulation via Akt-dependent phosphorylation of hTERT. Thus, the phosphorylation of Akt is a key event in the induction of telomerase activity by E 2 in human ovarian cancer cells.

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Induction of Endothelial Nitric-oxide Synthase Phosphorylation by the Raloxifene Analog LY117018 Is Differentially Mediated by Akt and Extracellular Signal-regulated Protein Kinase in Vascular Endothelial Cells

Cited by 67 publications

References 69 publications

Aplidin™ induces the mitochondrial apoptotic pathway via oxidative stress-mediated JNK and p38 activation and protein kinase C δ

Aplidin™ induces the mitochondrial apoptotic pathway via oxidative stress-mediated JNK and p38 activation and protein kinase C δ

Raloxifene Increases Proliferation and Up-regulates Telomerase Activity in Human Umbilical Vein Endothelial Cells

Induction of hTERT expression and phosphorylation by estrogen via Akt cascade in human ovarian cancer cell lines

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