Biomedical subjects

Yan Shi

Publications and source records attributed to Yan Shi.

At least 19 recordsLinked to original sources

PubMed2026

[Empirical Classification of Tri-Allelic Genotype Cases and Parentage Index Calculation].

OBJECTIVES: To standardize the calculation method of the parentage index (PI) for short tandem repeat (STR) tri-allelic genotypes, thereby ensuring the accuracy and reliability of parentage tes‑ ting conclusions. METHODS: A systematic analysis of 160 real cases was conducted. A classification system was constructed based on the occurrence mechanisms and inheritance patterns of STR tri-alleles, and the PI calculation method was optimized by integrating previous research findings with empirical data. RESULTS: A mechanism-based classification system for STR tri-allelic genotypes was established, comprising Type I (2 subtypes), Type II (6 subtypes), and the trisomic type (2 subtypes). On this basis, a standardized PI calculation method covering all categories of STR tri-allelic genotypes was developed. CONCLUSIONS: This study provides methodological guidance for the scientific and standardized calculation of PI for STR tri-allelic genotypes and offers an important reference for the formulation and refinement of relevant industry standards.

Humans↗

PubMed2007

Compressed oxygen in drug stability experiments.

A drug stability experiment accelerated by compressed oxygen was established. The stability of 10% ascorbic acid solution as a model was studied and the kinetic parameters were obtained with the newly established experimental method. Because ascorbic acid degrades under both anaerobic and aerobic conditions, the total rate constant k(total) can be expressed as: k(total)=k(anaerobic) + k(aerobic), where k(anaerobic) and k(aerobic) are the rate constants of anaerobic and aerobic degradations, respectively. The k(anaerobic) can be expressed as k(anaerobic) = A(anaerobic) x exp(-E(a,anaerobic)/RT) according to Arrhenius equation, and the k(aerobic) was found to be k(aerobic) = A(aerobic) x exp(-E(a,aerobic)/RT) x p(O2) in our study.

Ascorbic Acid↗

PubMed2006

Inhibitory effects of phloridzin dihydrate on the activity of mushroom (Agaricus bisporus) tyrosinase.

The inhibitory effects of phloridzin dihydrate on the activity of mushroom tyrosinase have been studied. The results show that phloridzin can inhibit the diphenolase activity of the enzyme and the inhibition displays to be reversible. The IC(50) value was estimated as 110microM. The kinetic analysis showed that the inhibition of phloridzin on the diphenolase activity of the enzyme is of competitive type, and the inhibition constant (K(I)) was determined to be 64.3microM. The inhibitory effects of the different concentrations of phloridzin on the monophenolase activity were also studied. There were almost no changes in the lag period and the steady-state rate, while the plateaus in the inhibitory curve lowered with increasing the concentration of phloridzin when using tyrosine as a substrate.

Agaricales↗

PubMed2006

Molecular cloning and characterization of human Aph2 gene, involved in AP-1 regulation by interaction with JAB1.

A human Aph2 gene (hAph2) was identified and cloned from a human placenta cDNA library. Bioinformatics analysis revealed hAPH2 protein shares 96% identity with mouse APH2 and contains a zf-DHHC domain (148-210aa), which is always involved in protein-protein or protein-DNA interaction. Differential expression patterns of hAph2 mRNA were observed in normal human tissues. Yeast two-hybrid screening found another hAPH2-interacting protein JAB1. The zf-DHHC domain of hAPH2 and the C-terminal of JAB1 were confirmed to be critical for the interaction. Fused with GFP and expressed in COS-7, NIH/3T3 and SMMC-7721 cell lines, hAPH2 showed predominant distribution in the cytoplasm and co-localized with JAB1 around the nucleus. Furthermore, overexpression of hAPH2 could increase apoptosis of COS-7 cells and negatively regulate JAB1-induced activation of AP-1 in a concentration dependent manner. The expression level of c-jun was also down-regulated by overexpression of hAPH2 in COS-7 cells. These data showed some basic characterization and function of hAph2 (hAPH2), dependent or independent with JAB1.

Amino Acid Sequence↗

PubMed2006

Quantitative analysis of anti-apoptotic function of Akt in Akt1 and Akt2 double knock-out mouse embryonic fibroblast cells under normal and stressed conditions.

The serine/threonine kinases Akt1/PKBalpha, Akt2/PKBbeta, and Akt3/PKBgamma have been implicated in preventing cells from undergoing apoptosis. Although several small molecule inhibitors of Akt have been reported to induce apoptosis in cancer cells, these inhibitors may have additional targets. In the current study, we used an Akt3 small interfering RNA (Akt3 siRNA) to analyze apoptosis induction in Akt1 and Akt2 double knock-out mouse embryonic fibroblast cells (MEF-Akt1,2-DKO). Our data indicated that Akt3 siRNA inhibited Akt3 protein expression in a dose-dependent manner. As a result, phosphorylation of Akt and its downstream targets, including FKHRL1 and GSK3alpha/beta, were reduced accordingly. The treatment also induced apoptosis in MEF-Akt1,2-DKO cells. However, apoptosis induction is significant only when more than 80% of Akt3 protein was depleted. Reintroducing Akt3 totally rescued Akt3-siRNA-induced apoptosis in MEF-Akt1,2-DKO cells. In addition, reintroducing Akt1 also inhibited apoptosis induced by Akt3 siRNA. Moreover, Akt3 siRNA potentiated different stress-induced apoptosis in MEF-Akt1,2-DKO cells at a lower dose when compared with what is required for apoptosis induction by itself. Our study suggests that only a small portion of Akt is active in wild-type MEF cells and a threshold of Akt inhibition is required to induce apoptosis by pure Akt inhibitors. In addition, our data indicate that cells under stress require more Akt for its survival.

Animals↗

PubMed2006

The innate immune response to grass carp hemorrhagic virus (GCHV) in cultured Carassius auratus blastulae (CAB) cells.

Virus infection of mammalian cells activates an innate antiviral immune response characterized by production of interferon (IFN) and the subsequent transcriptional upregulation of IFN-stimulated genes (ISGs) by the JAK-STAT signaling pathway. Here, we report that a fish cell line, crucian carp (Carassius auratus L.) blastulae embryonic (CAB) cells, can produce IFN activity and then form an antiviral state after infection with UV-inactivated grass carp hemorrhagic virus (GCHV), a double-stranded (ds) RNA virus. From UV-inactivated GCHV-infected CAB cells, 15 pivotal genes were cloned and sequenced, and all of them were shown to be involved in IFN antiviral innate immune response. These IFN system genes include the dsRNA signal sensing factor TLR3, IFN, IFN signal transduction factor STAT1, IFN regulatory factor IRF7, putative IFN antiviral effectors Mx1, Mx2, PKR-like, Viperin, IFI56, and other IFN stimulated genes (ISGs) IFI58, ISG15-1, ISG15-2, USP18, Gig1 and Gig2. The identified fish IFN system genes were highly induced by active GCHV, UV-inactivated GCHV, CAB IFN or poly(I).poly(C), and showed similar expression patterns to mammals. The data indicate that an IFN antiviral innate immune response similar to that in mammals exists in the UV-inactivated GCHV-infected CAB cells, and the IFN response contributes to the formation of an antiviral state probably through JAK-STAT signaling pathway. This study provides strong evidence for existence of IFN antiviral innate immune response in fish, and will assist in elucidating the origin and evolution of vertebrate IFN system.

Animals↗

PubMed2006

Synthesis and SAR of indazole-pyridine based protein kinase B/Akt inhibitors.

A series of heteroaryl-pyridine containing inhibitors of Akt are reported. The synthesis and structure-activity relationships are discussed, leading to the discovery of a indazole-pyridine analogue (K(i)=0.16 nM). These compounds bind in the ATP binding site, are potent, ATP competitive, and reversible inhibitors of Akt activity. No selectivity amongst the Akt isoforms is observed for this analogue, but there is good selectivity against an panel of other kinases. It is least selective for other members of the AGC family of kinases but is nonetheless 40-fold selective for Akt over PKA. The compound shows cellular activity and significantly slows tumor growth in vivo.

Indazoles↗

PubMed2006

Identification of a novel 3,5-disubstituted pyridine as a potent, selective, and orally active inhibitor of Akt1 kinase.

Based on lead compounds 2 and 3 a series of 3,5-disubstituted pyridines have been designed and evaluated for inhibition of AKT/PKB. Modifications at the 3 position of the pyridine ring led to a number of potent compounds with improved physical properties, resulting in the identification of 11g as a promising, orally active Akt inhibitor. The synthesis, structure-activity relationship studies, and pharmacokinetic data are presented in this paper.

3-Phosphoinositide-Dependent Protein Kinases↗

PubMed2006

Discovery and SAR of oxindole-pyridine-based protein kinase B/Akt inhibitors for treating cancers.

We describe a series of potent and selective oxindole-pyridine-based protein kinase B/Akt inhibitors. The most potent compound 11n in this series demonstrated an IC(50) of 0.17nM against Akt1 and more than 100-fold selectivity over other Akt isozymes. The selectivity against other protein kinases was highly dependent on the C-3 substitutions at the oxindole scaffold, with unsubstituted 9e or 3-furan-2-ylmethylene (11n) more selective and 3-(1H-pyrrol-2-yl)methylene (11f) or 3-(1H-imidazol-2-yl)methylene (11k) less selective. In a mouse xenograft model, 9d, 11f, and 11n inhibited tumor growth but with accompanying toxicity.

Animals↗

PubMed2006

Isoquinoline-pyridine-based protein kinase B/Akt antagonists: SAR and in vivo antitumor activity.

The structure-activity relationships of a series of isoquinoline-pyridine-based protein kinase B/Akt antagonists have been investigated in an effort to improve the major short-comings of the lead compound 3, including poor pharmacokinetic profiles in several species (e.g., mouse i.v. t(1/2) = 0.3 h, p.o. F = 0%). Chlorination at C-1 position of the isoquinoline improved its pharmacokinetic property in mice (i.v. t(1/2) = 5.0 h, p.o. F = 51%) but resulted in >500-fold drop in potency. In a mouse MiaPaCa-2 xenograft model, an amino analog 10y significantly slowed the tumor growth, however was accompanied by toxicity.

Animals↗

PubMed2006

Cutting edge: elimination of an endogenous adjuvant reduces the activation of CD8 T lymphocytes to transplanted cells and in an autoimmune diabetes model.

The generation of adaptive immune responses is thought to require the presence of adjuvants. Although microbial adjuvants are well characterized, little is known about what provides the adjuvant effect in responses to transplanted cells or in autoimmune diseases. It had been postulated that, in these situations, injured cells instead released "endogenous adjuvants." We previously identified uric acid as an endogenous adjuvant for coinjected Ags. We now report that elimination of uric acid reduced the generation of CTL to an Ag in transplanted syngeneic cells and the proliferation of autoreactive T cells in a transgenic diabetes model. In contrast, uric acid depletion did not reduce the stimulation of T cells to mature APCs or when endogenous APCs were activated with anti-CD40 Ab. These findings support the concept that danger signals contribute to the T cell responses to cell-associated Ags by activating APCs and identify uric acid as one of these signals.

Adjuvants, Immunologic↗

PubMed2006

Inhibitory effects of cis- and trans-isomers of 3,5-dihydroxystilbene on the activity of mushroom tyrosinase.

The effects of cis- and trans-isomers of 3,5-dihydroxystilbene on the activity of mushroom tyrosinase have been studied. The results show that both cis- and trans-isomers of 3,5-dihydroxystilbene can inhibit the diphenolase activity of the enzyme and the inhibition type was reversible. The IC(50) values were estimated as 0.405+/-0.013 and 0.705+/-0.017 mM, respectively. Kinetic analysis showed that the inhibition of cis-3,5-dihydroxystilbene and trans-3,5-dihydroxystilbene on the diphenolase activity of the enzyme belonged to competitive type, and the inhibition constants (K(I)) were determined to be 0.232+/-0.015 and 0.395+/-0.020 mM, respectively. In this investigation, the inhibitory effects of cis-3,5-dihydroxystilbene and trans-3,5-dihydroxystilbene on the diphenolase activity of mushroom tyrosinase were compared. The inhibitory capacity of cis-isomer was stronger than that of corresponding trans-isomer. Nevertheless, the trans-3,5-dihydroxystilbene was used more frequently than its corresponding cis-form compound. This research may offer some references for designing and synthesizing some novel and effective tyrosinase inhibitors. Furthermore, it may improve the use of stilbenes on the field of food preservation and depigmentation.

Agaricales↗

PubMed2006

Resonance Raman investigation of the short-time photodissociation dynamics of the charge-transfer absorption of the I2-benzene complex in benzene solution.

Resonance Raman spectra were obtained for the I2-benzene complex in benzene solvent with excitation wavelengths in resonance with the CT-band absorption. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion mainly along the nominal I-I stretch mode nu(18), the nominal symmetric benzene ring stretch mode nu5, and the nominal symmetric CCH bending nu7. There is also a small contribution from the nominal out-of-plane CH oop wag nu15. A preliminary resonance Raman intensity analysis was done, and the results for the I2-benzene complex were compared to results previously reported for the 1-hexene-I2 complex. We briefly discuss the differences and similarities in the CT-band absorption excitation of an I2-benzene complex relative to those of an I2-alkene complex.

Journal Article↗

PubMed2006

Synthesis and structure-activity relationship of 3,4'-bispyridinylethylenes: discovery of a potent 3-isoquinolinylpyridine inhibitor of protein kinase B (PKB/Akt) for the treatment of cancer.

Structure-based design and synthesis of the 3,4'-bispyridinylethylene series led to the discovery of 3-isoquinolinylpyridine 13a as a potent PKB/Akt inhibitor with an IC(50) of 1.3nM against Akt1. Compound 13a shows excellent selectivity against distinct families of kinases such as tyrosine kinases and CAMK, and displays poor to marginal selectivity against closely related kinases in the AGC and CMGC families. Moreover, 13a demonstrates potent cellular activity comparable to staurosporine, with IC(50) values of 0.42 and 0.59microM against MiaPaCa-2 and the Akt1 overexpressing FL5.12-Akt1, respectively. Inhibition of phosphorylation of the Akt downstream target GSK3 was also observed in FL5.12-Akt1 cells with an EC(50) of 1.5microM. The X-ray structures of 12 and 13a in complex with PKA in the ATP-binding site were determined.

Antineoplastic Agents↗

PubMed2006

Discovery of trans-3,4'-bispyridinylethylenes as potent and novel inhibitors of protein kinase B (PKB/Akt) for the treatment of cancer: Synthesis and biological evaluation.

A novel series of Akt/PKB inhibitors derived from a screening lead (1) has been prepared. The novel trans-3,4'-bispyridinylethylenes described herein are potent inhibitors of Akt/PKB with IC(50) values in the low double-digit nanomolar range against Akt1. Compound 2q shows excellent selectivity against distinct families of kinases such as tyrosine kinases and CAMK, and displays poor to modest selectivity against closely related kinases in the AGC and CMGC families. The cellular activities including inhibition of cell growth and phosphorylation of downstream target GSK3 are also described. The X-ray structure of compound 2q complexed with PKA in the ATP binding site was determined.

Adenosine Triphosphate↗

PubMed2006

Inhibition of the alpha-mannosidase Man2c1 gene expression enhances adhesion of Jurkat cells.

Protein N-glycosylation plays very important roles in immunity and alpha-mannosidase is one of the key enzymes in N-glycosylation. This paper reports that inhibition of alpha-mannosidase Man2c1 gene expression enhances adhesion of Jurkat T cells. In comparison to the controls with normal expression of the enzyme, Jurkat cells with the inhibition of Man2c1 gene expression (AS cell) formed larger aggregates in culture, indicating an enhancement of adhesion between the cells. mRNA differential display analysis discovered up-regulation of several adhesion molecule genes in the AS cell. Because of the pivotal role played by CD54-LFA-1 interaction in immune cell interaction, this study focused on the contribution of enhanced expression of CD54 and LFA-1 to the enhanced adhesion of AS Jurkat cells. These facts, including increased binding of AS cells to ICAM-1-Fc, Mg(2+) activation of the binding of AS cells to ICAM-1-Fc and enhanced aggregation of AS cells, together with the inhibiting effect of a blocking CD11a mAb on the binding to ICAM-1-Fc and aggregation of the cells demonstrate an important contribution of enhanced CD54-LFA-1 interaction to increased adhesion between AS cells. The enhanced CD54-LFA-1 interaction also resulted in increased adhesion between AS Jurkat T cells and Raji B cells. In addition, AS cells showed cytoskeletal rearrangement. The data imply a biological significance of MAN2C1 in T-cell functioning.

Cell Adhesion↗

PubMed2006

Role of coordinated molecular alterations in the development of androgen-independent prostate cancer: an in vitro model that corroborates clinical observations.

OBJECTIVE: To investigate the role of potential downstream targets of HER-2/neu, including the cell-cycle regulator p27, proliferation-associated protein Ki-67, apoptosis inhibitor Bcl-2, and signal-transduction molecule Akt (which is associated with cell survival), as the development of androgen-independent prostate cancer (AIPC) in patients who are initially responsive to androgen-ablation therapy (AAT) is a significant clinical problem. PATIENTS AND METHODS: Earlier studies showed that high levels of HER-2/neu tyrosine kinase receptor expression as assessed by immunohistochemistry were significantly associated with the development of AIPC, and we hypothesised that HER-2/neu overexpression provides an alternative proliferative stimulus upon androgen depletion. We established a unique clinical model system, comprising patients who received no AAT, or who had preoperative AAT, or those with advanced tumours resistant to AAT. To test our hypothesis in vitro, we stably transfected full-length HER-2/neu cDNA in androgen-responsive LNCaP cells and examined the effects of HER-2/neu overexpression on cell proliferation, apoptosis, androgen-receptor activation, and Akt phosphorylation upon androgen deprivation by using immunohistochemistry and Western blot technique. RESULTS: p27 expression was initially induced on exposure to AAT, and significantly decreased in AIPC (P < 0.001). There was also a significant increase in the Ki-67 index in AIPC (P = 0.001). Elevated Bcl-2 expression was closely associated with AAT (P = 0.002), suggesting that Bcl-2 expression is induced on initial exposure to AAT. Further, Bcl-2 expression was highest in hormone-resistant cancers (P < 0.001). Using the HER-2/neu transfected cell-line model, we confirmed the mechanistic basis of the clinical observations which elucidate the pathway leading to HER-2/neu-mediated androgen independence. On androgen deprivation, the HER-2/neu transfected cells had higher proliferation rates, lower G1 arrest, inhibited p27 up-regulation, a lower apoptotic index, and higher Bcl-2, prostate-specific antigen and phosphorylated Akt expression than the mock-transfected LNCaP cells. CONCLUSION: This study suggests that prostate cancer cells undergo a series of coordinated changes after exposure to AAT, which eventually result in the development of androgen independence. Further, in support of previous results, it appears that a major factor in this process is the induction of HER-2/neu overexpression, which occurs after initial exposure to AAT. HER-2/neu may contribute to the development of androgen independence through: (i) maintaining cell proliferation; (ii) inhibiting apoptosis; and/or (iii) inducing AR activation in a ligand-independent fashion. These effects may be mediated, at least in part, through activation of the PI3K/Akt pathway.

Aged↗

PubMed2006

Inhibition of the phosphatidylinositol 3-kinase/Akt pathway sensitizes MDA-MB468 human breast cancer cells to cerulenin-induced apoptosis.

Fatty acid synthase is overexpressed in cancer especially in tumors with a poor prognosis. The specific fatty acid synthase inhibitor cerulenin can induce apoptosis in cancer cells. Likewise, phosphatidylinositol 3-kinase (PI3K)/Akt kinase activities are elevated in primary tumors and cancer cell lines. Here, we tested whether inhibition of PI3K/Akt pathway would sensitize cancer cells to cerulenin-induced apoptosis. We show that LY294002, an inhibitor of PI3K, sensitized MDA-MB468 breast cancer cells to cerulenin-induced apoptosis. In MDA-MB468 cells, cerulenin- and LY294002-mediated apoptosis was associated with caspase-3 activation and the release of cytochrome c from mitochondria to cytosol. In addition, we observed additional species of Bak in mitochondria, suggesting a possible Bak activation. Treatment of cells with cerulenin and LY294002 down-regulated the protein levels of X chromosome-linked inhibitor of apoptosis (XIAP), cellular inhibitor of apoptosis 1 (cIAP-1), and Akt, whereas the levels of mitogen-activated protein/extracellular signal-regulated kinase kinase and other antiapoptotic Bcl-2 family proteins (Bcl-2 and Bcl-xl) did not change. Interestingly, the nonspecific caspase inhibitor, z-VAD-FMK, inhibited the down-regulation of Akt, XIAP, and cIAP-1 in cerulenin- and LY294002-treated cells. In conclusion, these studies show that inhibition of PI3K can sensitize cerulenin-induced apoptosis in MBA-MB468 breast cancer cells via activation of caspases, down-regulation of antiapoptotic proteins, such as XIAP, cIAP-1 and Akt, and possibly, activation of Bak in mitochondria.

Amino Acid Chloromethyl Ketones↗