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Biomedical subjects

S K Chiou

Publications and source records attributed to S K Chiou.

9 recordsLinked to original sources
PubMed2004

Rebamipide activates genes encoding angiogenic growth factors and Cox2 and stimulates angiogenesis: a key to its ulcer healing action?

Clinical and experimental data indicate that rebamipide accelerates ulcer healing, improves scar quality, and prevents ulcer recurrence. However, the mechanisms responsible for these rebamipides' actions are not fully elucidated. We studied, using gene expression microarray analysis, which of the ulcer healing genes are activated by rebamipide treatment. Normal rat gastric epithelial cells (RGM1) were treated with either vehicle or rebamipide. Gene expression was determined using Affymetrix rat genome U34A gene chip arrays and data were analyzed using the GeneSpring program. Activation of some of the genes and protein translation were also examined by RT/PCR and Western blotting. Rebamipide significantly upregulated the proangiogenic genes encoding vascular endothelial growth factor (VEGF), by 7.5-fold, heparin binding epidermal growth-like factor (HB-EGF), by approximately 5-fold, fibroblast growth factor receptor-2 (FGFR2), by 4.4-fold, and cyclooxygenase-2 (Cox2), by 9.3-fold, as well as growth promoting genes, e.g., insulin growth factor-1 (IGF-1), by 5-fold. RT/PCR and Western blotting demonstrated that Cox2 mRNA and protein were upregulated; the latter, approximately 6-fold. Treatment of rat gastric mucosal endothelial cells with rebamipide stimulated in vitro angiogenesis by approximately 240% (vs. controls, P < 0.001). Conclusions are as follows. (1) Rebamipide activates in gastric epithelial RGM-1 cells a genetic program that promotes angiogenesis and signals cell growth and tissue regeneration. (2) In addition, rebamipide treatment directly stimulates angiogenesis in gastric microvascular endothelial cells. Thus rebamipide has two separate and distinct mechanisms of proangiogenic action: one through activation in gastric epithelial cells of proangiogenic growth factor genes and the second a direct angiogenic action on microvascular endothelial cells.

Alanine↗
PubMed2000

Estrogen receptor variants are present in many normal human tissues.

Estrogen receptors (ER) are present in various reproductive tissues as well as in other tissues not considered classical targets for estrogen. A variety of alternatively spliced ER variants which co-exist with the wild-type receptor has also been described in many tissues. We analyzed the presence of both wild-type and variant receptors from normal human tissues of various origin using semi-nested PCR and direct automated sequence of the amplified products. We demonstrate that many normal human tissues of various origin contain a number of spliced variants of the estrogen receptor that co-exist with the wild-type receptor. Variants lacking exons 2, 4, 5, and 7 are detected in a variety of normal human tissues.

Adolescent↗
PubMed1998

Inhibition of ICE-like proteases inhibits apoptosis and increases virus production during adenovirus infection.

Interleukin-1b converting enzyme (ICE)-related cysteine proteases are required for E1A-induced, p53-dependent apoptosis in baby rat kidney (BRK) cells. Adenovirus E1B 19K protein, which is a potent inhibitor of apoptosis, inhibits activation of these proteases in BRK cells. E1A expression induces apoptosis during infection of human cells by mutant adenoviruses which contain nonfunctional E1B 19K. The question arises as to whether ICE-related proteases are involved in E1A-induced apoptosis during mutant adenovirus infection of human cells. To test the involvement of the cysteine proteases in E1A-induced apoptosis during productive adenovirus infection of HeLa cells, we examined whether Z-VAD-FMK, an inhibitor of ICE-related proteases, can inhibit apoptosis induced by mutant adenovirus which lacks functional E1B 19K. Z-VAD-FMK inhibited E1A-induced apoptosis in adenovirus-infected Hela cells, suggesting that the ICE family proteases are involved in this apoptosis pathway. Z-VAD-FMK also inhibited cleavage of substrates such as cysteine protease CPP32 and nuclear lamins, whereas cleavage of poly(ADP-ribose) polymerase was partially inhibited during infection with an E1B 19K mutant. Inhibition of apoptosis by Z-VAD-FMK significantly enhanced production of infectious adenovirus and attenuated virus release. Thus apoptosis may be a method for the host cell to limit virus production and release at the end of the infection cycle.

Adenovirus E1A Proteins↗
PubMed1997

p300 binding by E1A cosegregates with p53 induction but is dispensable for apoptosis.

E1A expression during adenovirus infection induces apoptosis. E1A expression causes accumulation of the p53 tumor suppressor protein, and E1A-induced apoptosis is p53 mediated in primary rodent cells, implying that p53 induction may be linked to apoptosis induction by E1A. Adenoviruses containing mutations in the E1A gene were tested for the ability to trigger both p53 accumulation and the appearance of enhanced cytopathy (cyt phenotype) and degradation of DNA (deg phenotype), indicative of apoptosis in infected HeLa cells. The adenoviruses had mutations which disrupted the pRb- and/or p300-binding activities of E1A so that the relationship between p53 induction and apoptosis and binding to these cellular proteins by E1A could be determined. An E1A mutation that specifically disrupted the p300-binding activity failed to induce p53 accumulation, whereas mutations in E1A which affected pRb binding induced p53 accumulation. Thus, p300 binding was required and pRb binding was dispensable for E1A-mediated accumulation of p53 in HeLa cells. All the E1A mutant viruses, regardless of the ability to induce p53 accumulation, induced the cyt and deg phenotypes, suggesting that p53 induction in infected HeLa cells was not essential for apoptosis, nor was binding of E1A to the pRb and/or p300 protein. The possibility that E1A induced a p53-independent apoptosis pathway was tested by analyzing the appearance of the cyt and deg phenotypes in Saos-2 cells, which were null for both alleles of p53, upon adenovirus infection. An adenovirus expressing wild-type 12S E1A induced both the cyt and deg phenotypes in Saos-2 cells, as did all the E1A mutant viruses. Thus, E1A expression during infection of human cells may trigger redundant p53-independent and -dependent apoptotic pathways.

Adenovirus E1A Proteins↗
PubMed1997

Interleukin 1 beta converting enzyme-like proteases are essential for p53-mediated transcriptionally dependent apoptosis.

p53-mediated apoptosis in baby rat kidney (BRK) cell lines transformed by E1A and p53(val135) requires a transcriptionally functional p53. Coexpression of the E1B 19K protein in BRK cell lines transformed by E1A and p53(val135) rescues cells from p53-mediated apoptosis, and this is paralleled by the absence of both lamin and poly(ADP-ribose) polymerase cleavage. Therefore, the role of interleukin 1 beta converting enzyme (ICE)-like porteases in p53-mediated, transcriptionally dependent apoptosis was investigated. The ICE-like protease CPP32 was proteolytically activated during p53-mediated apoptosis in BRK cells, and this required a transcriptionally competent p53. Substitution of the p53 transactivation domain with the transactivation domain of herpes simplex virus VP16 (VP16/p53) resulted in accelerated kinetics of both apoptosis and Bax induction. Moreover, apoptosis induced by p53, VP16/p53, and Bax was abrogated by Z-VAD.FMK, an inhibitor of ICE-like proteases. These results indicate that all apoptotic pathways downstream of p53-mediated transcription converge upon the activation of ICE-like proteases.

Adenovirus E1A Proteins↗
PubMed1995

Modulation of p53-mediated transcriptional repression and apoptosis by the adenovirus E1B 19K protein.

BRK cell lines that stably express adenovirus E1A and a murine temperature-sensitive p53 undergo apoptosis when p53 assumes the wild-type conformation. Expression of the E1B 19,000-molecular-weight (19K) protein rescues cells from this p53-mediated apoptosis and diverts cells to a growth-arrested state. As p53 likely functions as a tumor suppressor by regulating transcription, the ability of the E1B 19K protein to regulate p53-mediated transactivation and transcriptional repression was investigated. In promoter-reporter assays the E1B 19K did not block p53-mediated transactivation but did alleviate p53-mediated transcriptional repression. E1B 19K expression permitted efficient transcriptional activation of the p21/WAF-1/cip-1 mRNA by p53, consistent with maintenance of the growth arrest function of p53. The E1B 19K protein is thereby unique among DNA virus-transforming proteins that target p53 for inactivation in that it selectively modulates the transcriptional properties of p53. The E1B 19K protein also rescued cells from apoptosis induced by inhibitors of transcription and protein synthesis. This suggests that cell death may result from the inhibition of expression of survival factors which function to maintain cell viability. p53 may induce apoptosis through generalized transcriptional repression. In turn, the E1B 19K protein may prevent p53-mediated apoptosis by alleviating p53-mediated transcriptional repression.

Adenovirus E1B Proteins↗
PubMed1994

Functional complementation of the adenovirus E1B 19-kilodalton protein with Bcl-2 in the inhibition of apoptosis in infected cells.

Expression of the adenovirus E1A oncogene induces apoptosis which impedes both the transformation of primary rodent cells and productive adenovirus infection of human cells. Coexpression of E1A with the E1B 19,000-molecular-weight protein (19K protein) or the Bcl-2 protein, both of which have antiapoptotic activity, is necessary for efficient transformation. Induction of apoptosis by E1A in rodent cells is mediated by the p53 tumor suppressor gene, and both the E1B 19K protein and the Bcl-2 protein can overcome this p53-dependent apoptosis. The functional similarity between Bcl-2 and the E1B 19K protein suggested that they may act by similar mechanisms and that Bcl-2 may complement the requirement for E1B 19K expression during productive infection. Infection of human HeLa cells with E1B 19K loss-of-function mutant adenovirus produces apoptosis characterized by enhanced cytopathic effects (cyt phenotype) and degradation of host cell chromosomal DNA and viral DNA (deg phenotype). Failure to inhibit apoptosis results in premature host cell death, which impairs virus yield. HeLa cells express extremely low levels of p53 because of expression of human papillomavirus E6 protein. Levels of p53 were substantially increased by E1A expression during adenovirus infection. Therefore, E1A may induce apoptosis by overriding the E6-induced degradation of p53 and promoting p53 accumulation. Stable Bcl-2 overexpression in HeLa cells infected with the E1B 19K- mutant adenovirus blocked the induction of the cyt and deg phenotypes. Expression of Bcl-2 in HeLa cells also conferred resistance to apoptosis mediated by tumor necrosis factor alpha and Fas antigen, which is also an established function of the E1B 19K protein. A comparison of the amino acid sequences of Bcl-2 family members and that of the E1B 19K protein indicated that there was limited amino acid sequence homology between the central conserved domains of E1B 19K and Bcl-2. This domain of the E1B 19K protein is important in transformation and regulation of apoptosis, as determined by mutational analysis. The limited sequence homology and functional equivalency provided further evidence that the Bcl-2 and E1B 19K proteins may possess related mechanisms of action and that the E1B 19K protein may be the adenovirus equivalent of the cellular Bcl-2 protein.

Adenovirus E1A Proteins↗
PubMed1994

Bcl-2 blocks p53-dependent apoptosis.

Adenovirus E1A expression recruits primary rodent cells into proliferation but fails to transform them because of the induction of programmed cell death (apoptosis). The adenovirus E1B 19,000-molecular-weight protein (19K protein), the E1B 55K protein, and the human Bcl-2 protein each cause high-frequency transformation when coexpressed with E1A by inhibiting apoptosis. Thus, transformation of primary rodent cells by E1A requires deregulation of cell growth to be coupled to suppression of apoptosis. The product of the p53 tumor suppressor gene induces apoptosis in transformed cells and is required for induction of apoptosis by E1A. The ability of Bcl-2 to suppress apoptosis induced by E1A suggested that Bcl-2 may function by inhibition of p53. Rodent cells transformed with E1A plus the p53(Val-135) temperature-sensitive mutant are transformed at the restrictive temperature and undergo rapid and complete apoptosis at the permissive temperature when p53 adopts the wild-type conformation. Human Bcl-2 expression completely prevented p53-mediated apoptosis at the permissive temperature and caused cells to remain in a predominantly growth-arrested state. Growth arrest was leaky, occurred at multiple points in the cell cycle, and was reversible. Bcl-2 did not affect the ability of p53 to localize to the nucleus, nor were the levels of the p53 protein altered. Thus, Bcl-2 diverts the activity of p53 from induction of apoptosis to induction of growth arrest, and it is thereby identified as a modifier of p53 function. The ability of Bcl-2 to bypass induction of apoptosis by p53 may contribute to its oncogenic and antiapoptotic activity.

Animals↗