Biomedical subjects

Young Hyun Yoo

Publications and source records attributed to Young Hyun Yoo.

At least 19 recordsLinked to original sources

PubMed2006

zVAD-fmk, unlike BocD-fmk, does not inhibit caspase-6 acting on 14-3-3/Bad pathway in apoptosis of p815 mastocytoma cells.

In a preliminary study, we found that benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone (zVAD- fmk), unlike Boc-aspartyl(OMe)-fluoromethylketone (BocD-fmk), at usual dosage could not prevent genistein-induced apoptosis of p815 mastocytoma cells. This study was undertaken to reveal the mechanism underlying the incapability of zVAD-fmk in preventing this type of apoptosis. We observed that 14-3-3 protein level was reduced in genistein-treated cells and that BocD-fmk but not zVAD-fmk prevented the reduction of 14-3-3 protein level and the release of Bad from 14-3-3. We also demonstrated that truncated Bad to Bcl-xL interaction in genistein- treated cells was prevented by BocD-fmk but not by zVAD-fmk treatment. Our data indicate that BocD- fmk, compared to zVAD-fmk, has a certain preference for inhibiting 14-3-3/Bad signalling pathway. We also elucidated that this differential efficacy of BocD-fmk and zVAD-fmk resulted from the different effect in inhibiting caspase-6 and that co-treatment of zVAD-fmk and caspase-6 specific inhibitor substantially prevented genistein-induced apoptosis. Our data shows that caspase-6 plays a role on Bad/14-3-3 pathway in genistein-induced apoptosis of p815 cells, and that the usual dose of zVAD-fmk, in contrast to BocD-fmk, did not prevent caspase-6 acting on 14-3-3/Bad-mediated event.

14-3-3 Proteins↗

PubMed2006

Diphenyleneiodonium induces ROS-independent p53 expression and apoptosis in human RPE cells.

The diphenyleneiodonium (DPI) is widely used as an inhibitor of flavoenzymes, particularly NADPH oxidase. In this study, we investigated the effect of DPI on the apoptosis of human RPE cells. DPI treatment in ARPE-19 cells evoked a dose- and time-dependent growth inhibition, and also induced DNA fragmentation and protein content of the proapoptotic factor Bax. In addition, DPI significantly induced the expression and phosphorylation of p53, which induces proapoptotic genes in response to DNA damage or irreparable cell cycle arrest. ROS have been implicated as a key factor in the activation of p53 by many chemotherapeutic drugs. Recent data on the regulation of intracellular ROS by DPI are controversial. Therefore, we analyzed whether DPI could contribute to the generation of intracellular ROS. Although there was increase in ROS level from cells treated for 24h with DPI, it was not detectable at early time points, required to induce p53 expression. And DPI-induced p53 expression was not affected by the ROS scavenger NAC. We conclude that DPI induces the expression of p53 by ROS-independent mechanism in ARPE-19 cells, and renders cells sensitive to drug-induced apoptosis by induction of p53 expression.

Acetophenones↗

PubMed2006

A purified extract from Clematis mandshurica prevents staurosporin-induced downregulation of 14-3-3 and subsequent apoptosis on rat chondrocytes.

OBJECTIVE: To dissect the mechanism of the protection of staurosporin-induced apoptosis on rat chondrocytes by a purified extract from Clematis mandshurica. DESIGN: Primary cultured rat articular chondrocytes as well as RCJ3.1C.18 cells were incubated with 1 microM staurosporin and 300 microg/ml purified extract from Clematis mandshurica. Western blot assay, silencing 14-3-3 gene and immunoprecipitation were conducted. RESULTS: Clematis mandshurica prevented staurosporin-induced downregulation of several antiapoptotic bcl-2 family proteins Bcl-xL and Bcl-2, and staurosporin-induced upregulation of an apoptotic bcl-2 family protein Bax. Clematis mandshurica also prevented staurosporin-induced downregulation of a premitochondrial antiapoptotic protein 14-3-3. It is noticeable that siRNA to 14-3-3 abolished the prevention of caspase-3 activation by Clematis mandshurica. Furthermore viability assay corroborated that silencing of 14-3-3 gene abolished this apoptosis protection efficacy by Clematis mandshurica. Immunoprecipitation assay elucidated that Clematis mandshurica prevented the staurosporin-induced reduction of the interactions between 14-3-3 with phospho-ser112-Bad and Bcl-xL to phospho-ser155-Bad. CONCLUSIONS: Clematis mandshurica prevents staurosporin-induced apoptosis of rat chondrocytes via 14-3-3.

14-3-3 Proteins↗

PubMed2006

Nuclear interaction of Smac/DIABLO with Survivin at G2/M arrest prompts docetaxel-induced apoptosis in DU145 prostate cancer cells.

Smac/DIABLO is released by mitochondria in response to apoptotic stimuli and is thought to antagonize the function of inhibitors of apoptosis proteins. Recently, it has been shown that, like XIAP, Survivin can potentially interact with Smac/DIABLO. However, the precise mechanisms and cellular location of their action have not been determined. We report for the first time that Smac/DIABLO translocates to the nucleus and is colocalized with Survivin at mitotic spindles during apoptosis resulting from G2/M arrest due to docetaxel treatment of DU145 prostate cancer cells. Our data demonstrate that the nuclear interaction of Smac/DIABLO with Survivin is an important step for suppressing the anti-apoptotic function of Survivin in Doc-induced apoptosis. This suggests that the balance between cellular Smac/DIABLO and Survivin levels could be critical for cellular destiny in taxane-treated cancer cells.

Antineoplastic Agents↗

PubMed2006

Caspase-dependent and caspase-independent apoptosis induced by evodiamine in human leukemic U937 cells.

Evodiamine is one of the major bioactive compounds that have been isolated and purified from the fruit of Evodiae fructus. Evodiamine exhibits antitumor activities against the human tumor cells, including multidrug-resistant tumor cells. However, the molecular mechanism involved in cell death induced by evodiamine treatment remains poorly understood. In the present study, we showed that evodiamine activated the caspase-dependent apoptotic pathway. This apoptosis was only partially inhibited by a pancaspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone, which suggested that evodiamine-induced apoptosis in leukemic U937 cells is partially caspase independent. We observed the nuclear translocation of apoptosis-inducing factor in evodiamine-induced apoptosis of U937 cells, which may be responsible for the caspase-independent apoptotic execution. We next showed that evodiamine induced the substantial amount of apoptosis both in Bcl-2- and Akt-overexpressing U937 cells but not in human peripheral blood mononuclear cells. Although benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone inhibited caspase activity in Bcl-2-overexpressing U937 cells, it completely prevented neither the induction of apoptosis or the nuclear translocation of apoptosis-inducing factor, which suggests that evodiamine is, at least in part, able to bypass the resistance of leukemia cells via caspase-independent apoptotic pathways. Thus, therapeutic strategy using evodiamine may warrant further evaluation.

Apoptosis↗

PubMed2006

Amniotic membrane corrects surgically induced astigmatism.

Human amniotic membrane (AM) has been widely used for the reconstruction of ocular surface. We conducted this study to investigate whether AM shows efficacy in maintaining the correction of astigmatism or not. We performed photoastigmatic refractive keratectomy (PARK) on rabbits and grafted AM on the cornea. The effect of AM on the degree of astigmatism was evaluated by topography and cycloplegic refraction. As will be shown, AM did not show any efficacy in maintaining the correction of astigmatism. On the contrary, AM not only eliminated PARK-induced astigmatism but prevented surgically induced astigmatism. We suggest that AM could be a useful tool for controlling the astigmatism induced by laser refractive surgery. Further clinical study is still left to be elucidated.

Amnion↗

PubMed2006

Modulation of the cell cycle and induction of apoptosis in human cancer cells by synthetic bile acids.

In this paper, we will outline the current understanding of cell cycle modulation and induction of apoptosis in cancer cells by natural and synthetic bile acid. Bile acid homeostasis is tightly regulated in health, and their cellular and tissue concentrations are restricted. However, when pathophysiological processes impair their biliary secretion, hepatocytes are exposed to elevated concentrations of bile acids which trigger cell death. In this context, we developed several newly synthesized bile acid derivatives. These synthetic bile acids modulated the cell cycle and induced apoptosis in several human cancer cells similar to natural bile acids. In human breast and prostate cancer cells with different tumor suppressor p53 status, synthetic bile acid-induced growth inhibition and apoptosis were associated with up-regulation of Bax and p21(WAF1/CIP1) via a p53-independent pathway. In Jurkat human T cell leukemia cells, the synthetic bile acids induced apoptosis through caspase activation. In addition to this, the synthetic bile acids induced apoptosis in a JNK dependent manner in SiHa human cervical cancer cells, via induction of Bax and activation of caspases in PC3 prostate cancer cells and induction of G1 phase arrest in the cell cycle in HT29 colon cancer cells. Moreover, they induced apoptosis in four human glioblastoma multiform cell lines (i.e., U-118MG, U-87MG, T98G, and U-373MG) and one human TE671 medulloblastoma cells. In addition to this, a chenodeoxycholic acid derivative, called HS-1200, significantly decreased the growth of TE671 medulloblastoma tumor size and increased life span in non-obese diabetic and severe combined immunodeficient (NOD/SCID) mice. Therefore, these new synthetic bile acids, which are novel apoptosis mediators, might be applicable to the treatment of various human cancer cells.

Apoptosis↗

PubMed2005

Application of newly developed amniotic membrane ointment for photorefractive keratectomy in rabbits.

We developed amniotic membrane ointment (AMO), and the effect of instilling the AMO after photorefractive keratectomy (PRK) was investigated with respect to inflammatory cell infiltration into the corneal stroma, apoptosis of keratocytes, and suppression of lipid peroxidation of cellular walls. The PRK procedure was performed on both eyes of 10 white rabbits. One eye of each rabbit (the experimental eye) was instilled with the AMO and the other eye of the rabbit (the control eye) with a base ointment 0, 8 and 16 h after the PRK procedure. Corneal specimens were collected 24 h after the PRK procedure. Hematoxylin-eosin stain and TUNEL assay were conducted to demonstrate polymorphonuclear and apoptotic cells, respectively. To assess lipid peroxidation, immunohistochemical staining with an antibody to malondialdehyde was undertaken. Compared to the control, the cornea instilled with the AMO had significantly less polymorphonuclear cells infiltrating into the corneal stroma as well as keratocytes subjected to apoptosis. These corneas also showed a significantly less extent of lipid peroxidation than the control. These data support that instillation of the AMO effectively reduced the recruitment of polymorphonuclear cells, the induction of apoptosis in keratocytes, and lipid peroxidation induced by PRK. Thus, this study could provide basic data on the clinical application of the AMO in the days ahead.

Amnion↗

PubMed2005

Lysophosphatidic acid stimulates cell proliferation in rat chondrocytes.

Rat primary chondrocytes express the lysophosphatidic acid (LPA) receptor, LPA1, LPA3, but not LPA2. When chondrocytes were stimulated with LPA, phospholipase C-mediated cytosolic calcium increase was dramatically induced. LPA also stimulated two kinds of mitogen-activated protein kinase, extracellular signal-regulated kinase (ERK) and p38 kinase in chondrocytes. In terms of the LPA-mediated functional modulation of chondrocytes, LPA stimulated cellular proliferation. We examined the signaling pathways involved in LPA-mediated cellular proliferation. LPA-induced chondrocyte proliferation was almost completely blocked by 2'-amino-3'-methoxyflavone (PD98059) but not by 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580), suggesting that ERK activity is essentially required for the process. Pertussis toxin almost completely inhibited the LPA-induced cellular proliferation and ERK activation, indicating the role of G(i/o) protein(s) in the processes. This study demonstrates the physiological role of LPA on the modulation of rat primary chondrocyte proliferation, and the crucial role played by ERK in the process.

Animals↗

PubMed2005

Sulindac activates nuclear translocation of AIF, DFF40 and endonuclease G but not induces oligonucleosomal DNA fragmentation in HT-29 cells.

Sulindac is one of the most widely studied nonsteroidal anti-inflammatory drugs in the prevention of colon cancer. Thus, from the viewpoint of colon cancer chemotherapy it is important to reveal the mechanism of sulindac-induced cell death. This study was undertaken to dissect the molecular mechanism underlying sulindac-induced apoptosis in human colon cancer cell line HT-29 (mutant p53), focusing on nuclear translocation of AIF, DFF and endonuclease G. On induction of apoptosis by sulindac, it was associated with decreased mitochondrial membrane potential, nuclear expression of active caspase-3, cleavage of poly(ADP-ribose) polymerase, translocation of mitochondrial proteins to the nucleus, and morphological evidence of nuclear condensation. However, sulindac led to only disintegration of nuclear DNA into high molecular weight DNA fragments of about 100-300 kbp as determined by a pulse-field gel electrophoresis, suggesting a predominantly AIF-mediated cell death process. In summary, our findings indicate that sulindac induces large-scale DNA fragmentation without oligonucleosomal DNA fragmentation. This result suggests that nuclear translocation of DFF and endonuclease G are not sufficient for the induction of oligonucleosomal DNA fragmentation in HT-29 cells.

Active Transport, Cell Nucleus↗

PubMed2005

Synthetic bile acid derivatives induce apoptosis through a c-Jun N-terminal kinase and NF-kappaB-dependent process in human cervical carcinoma cells.

Recently, we have reported that a synthetic derivative of ursodeoxycholic acid (UDCA), HS-1183, and those of chenodeoxycholic acid (CDCA), HS-1199 and HS-1200, induced apoptosis in human breast carcinoma cells through a p53-independent pathway. Here, we present that the synthetic bile acid derivatives induce apoptosis in SiHa human cervical carcinoma cells as well. The parental compounds, UDCA and CDCA, exhibited no significant effect on the cell viability at the concentration ranges tested. However, their synthetic bile acid derivatives significantly decreased cell viability in a concentration dependent manner. Characteristic manifestations of apoptosis including DNA fragmentation, an increased level of proapoptotic protein Bax, and cleavage of poly(ADP-ribose) polymerase were shown when the cells were treated with these synthetic compounds. Nuclear translocation of nuclear transcription factor NF-kappaB was increased and this suggests that the synthetic compounds induce apoptosis in a NF-kappaB dependent pathway. Phosphorylations of p38 and extracellular signal-regulated kinase were not affected, whereas c-Jun N-terminal kinase (JNK) was activated along with an increased level of transcription factor c-Jun. Our studies demonstrate that the newly synthesized bile acids are capable of inhibiting cell proliferation and inducing apoptosis in SiHa cells through activation of JNK and NF-kappaB.

Apoptosis↗

PubMed2005

Doxorubicin induces apoptosis with profile of large-scale DNA fragmentation and without DNA ladder in anaplastic thyroid carcinoma cells via histone hyperacetylation.

Doxorubicin is known to be the most effective single cytotoxic drug against anaplastic thyroid carcinoma (ATC). Although doxorubicin has been shown to cause cell death, at least partly, by inducing apoptosis in ATC cells, the mechanism underlying its pharmacological efficacy has not been fully delineated. We, in this study, revealed that doxorubicin induced apoptosis in ATC cells by altering the acetylation state of histone. Doxorubicin reduced histone deacetylase activity and induced hyperacetylation of histone 3. Noticeably, ladder-like DNA fragments from their genomic DNA on agarose gel were not detected irrespective of several lines of evidence supporting the induction of apoptosis. Pulse field electrophoresis showed disintegration of nuclear DNA into giant fragments of 1-2 Mbp and high molecular-weight fragments of 100-1000 kbp. We next examined whether a histone deacetylase inhibitor trichostatin A (TsA) augmented doxorubicin-induced apoptosis in ATC cells. TSA potentiated doxorubicin-induced stage I apoptosis in ATC cells. Our study sheds light on the development of a new combination therapy strategy for more effective responses for ATC treatment.

Acetylation↗

PubMed2005

Synthetic chenodeoxycholic acid derivatives inhibit glioblastoma multiform tumor growth in vitro and in vivo.

We previously reported that the synthetic chenodeoxycholic acid (CDCA) derivatives showed apoptosis-inducing activity on various cancer cells in vitro. This study was undertaken to explore whether synthetic CDCA derivatives, HS-1199 and HS-1200, had an anticancer effect on malignant glioblastoma cells. We administered them in culture to U-118MG, U-87MG, T98G, and U-373MG cells. The tested glioblastoma cells showed several lines of apoptotic manifestations, such as activation of caspase-3, degradation of DFF, production of poly(ADP-ribose) polymerase cleavage, nuclear condensation, inhibition of proteasome activity, reduction of mitochondrial membrane potential and the release of cytochrome c to cytosol and translocation of AIF to nuclei. Between the two synthetic derivatives, HS-1200 showed a stronger apoptosis-inducing effect than HS-1199. In vivo efficacy of HS-1200 was tested in U87MG cells inoculated into non-obese diabetic and severe combined immunodeficient (NOD/SCID) mice. The HS-1200 treatment significantly inhibited the increase of tumor size in NOD/SCID mice and prolonged the life spans. This study supports the possibility of synthetic CDCA derivatives as a potential chemotherapeutic agent.

Animals↗

PubMed2004

Acetylcholinesterase plays a pivotal role in apoptosome formation.

Although a recent study (Zhang et al. Cell Death Differ 2002; 9; 790-800) presented that acetylcholinesterase (AChE) might be an important common component in leading to various types of apoptosis, the molecular mechanism, by which AChE functions, had remained elusive before that study. We explored the role of AChE in apoptosis by silencing the AChE gene. Silencing of the AChE gene abolished the expression of AChE and prevented caspase-9 activation, decrease of cell viability, nuclear condensation and poly(adenosine diphosphate-ribose) polymerase cleavage but not mitochondrial events. Importantly, silencing of the AChE gene blocked the interaction between apoptotic protease-activating factor-1 and cytochrome c. Here we propose that AChE plays a pivotal role in the formation of apoptosome.

Acetylcholinesterase↗

PubMed2004

Overexpression of redox factor-1 negatively regulates NO synthesis and apoptosis in LPS-stimulated RAW 264.7 macrophages.

Redox factor-1 (Ref-1) is a ubiquitously expressed protein with proven roles as a modulator of redox-sensitive transcription, and as an endonuclease in the base excision repair pathway of oxidatively damaged DNA. Although Ref-1 is induced by a variety of oxidative stress and protects cells against oxidative stress, the function of Ref-1 in regulating nitric oxide (NO) synthesis has not been elucidated to date. We investigated the role of Ref-1 in regulating NO synthesis and NO-mediated apoptosis employing adenoviral-mediated overexpression of Ref-1 in lipopolysaccharide (LPS)-stimulated macrophage RAW 264.7 cells. LPS treatment produced NO synthesis and NO-mediated apoptosis. Forced overexpression of Ref-1 suppressed LPS-stimulated NO synthesis. In parallel with this, Ref-1 also mitigated alteration of inducible NO synthase expression and NO-mediated apoptosis. Our findings suggest that Ref-1 is implicated in protection against cell death resulting from oxidative stimuli containing NO.

Adenoviridae↗

PubMed2004

TRAIL induces apoptosis of chondrocytes and influences the pathogenesis of experimentally induced rat osteoarthritis.

OBJECTIVE: To investigate whether TRAIL influences the pathogenesis of osteoarthritis (OA). METHODS: A recombinant adenoviral vector system (Ad-TRAIL) was used. Expression of TRAIL in a rat chondrocyte cell line (RCJ3.1C.18) and alterations in the expression of death and decoy receptors after Ad-TRAIL infection were measured by Western blot assay. To explore the underlying mechanism, Western blot assays (to detect caspase 8, poly[ADP-ribose] polymerase [PARP], and caspase 3 activation), mitochondrial membrane potential (DeltaPsim) measurement, Hoechst staining, and DNA electrophoresis were conducted. Next, expression of TRAIL and death and decoy receptors was examined by immunochemistry in primary cultured chondrocytes and on cartilage obtained from rats with experimentally induced OA. RESULTS: Ad-TRAIL infection induced expression of TRAIL in RCJ3.1C.18 cells, increased expression of death receptor 4 (DR4), and decreased expression of DR5 and decoy receptor 1 (DcR1). Ad-TRAIL, at doses of 10 and 100 multiplicities of infection, decreased the viability of chondrocytes 4 days after infection. Reduction of DeltaPsim, cytochrome c release, nuclear condensation, activation of caspase 3 and PARP, and DNA fragmentation proved the induction of apoptosis. Activation of caspase 8 was also observed. Ad-TRAIL also induced apoptosis in primary cultured chondrocytes, in which alterations in expression of TRAIL and death receptors were similar to those observed in RCJ3.1C.18 cells. Cartilage obtained from rats with experimentally induced OA showed increased expression of TRAIL and DR4 and decreased expression of DR5 and DcR1 compared with control cartilage. CONCLUSION: TRAIL induces chondrocyte apoptosis, and TRAIL-induced chondrocyte apoptosis may play a role in the pathogenesis of OA.

Animals↗

PubMed2004

Synthetic bile acid derivatives inhibit cell proliferation and induce apoptosis in HT-29 human colon cancer cells.

As previously demonstrated, the synthetic bile acid derivatives mediate anti-proliferative properties in a variety of human cancer cells. In the present study, the effects of the synthetic derivatives of ursodeoxycholic acid (UDCA), HS-1030 and HS-1183, and chenodeoxycholic acid (CDCA), HS-1199 and HS-1200, on the proliferation of HT-29 human colon cancer cells were investigated. Whereas UDCA and CDCA had no effect on the growth of cells in the concentration ranges we have tested, HS-1199 and HS-1200 completely inhibited cell proliferation, while HS-1030 and HS-1183 showed weak inhibitory activities. Simultaneous estimation of cell cycle parameters and apoptosis by flow cytometry showed that the synthetic bile acid derivatives produced the arrest of cell cycle progression at the G1 phase and ensuing increase of sub-G1 fraction, which resulted in the induction of apoptosis. The induction of apoptosis was confirmed by observation of cleavages of poly(ADP-ribose) polymerase and DNA fragmentation. Furthermore, Western blot analysis showed decreased expression levels of cyclin D1, cyclin E, cyclin A, Cdk2, Cdk4, and Cdk6 proteins. In addition, the synthetic bile acid derivatives markedly induced the level of Cdk inhibitor, p21WAF1/CIP1, in a p53-independent manner. Furthermore, the exposure of cells to the synthetic bile acid derivatives resulted in a decrease in the level of pRb and enhanced binding between pRb and E2F-1. Based on these data, these synthetic bile acid derivatives may serve as potential lead compounds in the treatment of colon cancer.

Apoptosis↗

PubMed2004

Trichostatin A induces apoptosis of p815 mastocytoma cells in histone acetylation- and mitochondria-dependent fashion.

Although inhibition of histone deacetylase has been demonstrated to induce apoptosis of various cancer cells, there is no report on its effect on mast cell demise to date. Here we studied whether a histone deacetylase inhibitor Trichostatin A (TSA) produces apoptosis in p815 mastocytoma cells. TSA prominently increased the amount of acetylated histones, H3, H4, H2A and H2B, in p815 mastocytoma cells. TSA reduced the viability of p815 mastocytoma cells, and many apoptotic manifestations such as generation of DNA fragmentation, activation of caspase-3, cleavage of poly (ADP-ribose) polymerase (PARP), and increase of DNA hypoploidy proved that the reduction of viability resulted from apoptosis. Whereas TSA treatment increased the expression level of Bad, it decreased the level of Bcl-2, Bcl-xL, and X-linked inhibitor of apoptosis protein. The reduction of mitochondrial membrane potential, the release of cytochrome c and Smac/DIABLO to cytosol, and mitochondrial localization of Bad were also shown. Taken together, TSA induces apoptosis on p815 mastocytoma cells in histone acetylation- and mitochondria-dependent fashion. Our data therefore provide the possibility that TSA could be considered as a novel therapeutic strategy for mastocytoma from its apoptosis-inducing activity.

Acetylation↗