Biomedical subjects

Yan Zhao

Publications and source records attributed to Yan Zhao.

At least 91 records · Page 5Linked to original sources

PubMed2005

[Up-regulation of thymidine phosphorylase and anti-angiogenesis by interferon alpha in human hepatocellular carcinoma cell line and xenograft].

OBJECTIVE: To further study the impact of interferon-alpha (IFN-alpha) on thymidine phosphorylase (TP) expression and angiogenesis. METHODS: Human hepatocellular carcinoma cells of the line SMMC-7721 were cultured and added with IFN-alpha of different doses: 0 (as control group), 1000, 5000 and 10,000 U/ml. Twenty-four hours later RT-PCR was used to detect the TP mRNA expression. Boyden chamber method was used to examine the endothelial cells migration. Suspension of SMMC-7721 cells was inoculated subcutaneously into 30 male BALB/c-nu/nu mice, the mice were randomly divided into 5 equal groups to be subcutaneously injected with IFN-alpha of different doses: 0 (as control group), 1.0 x 10(6), 3.0 x 10(6), 9.0 x 10(6), and 1.5 x 10(7) U.kg(-1).d(-1) for 3 weeks. The eating behavior, activity, body weight, and tumor size were observed. The rats were killed 2 days after the drug injection was stopped. The subcutaneous tumors were taken out to undergo histological examination and TP protein expression by ELISA. The microvessel density (MVD) was detected using anti-CD34 monoclonal antibody. RESULTS: The TP mRNA expression of the SMMC-7721 cells induced by IFN-alpha of the doses of 5000 U/ml and 10,000 U/ml significantly increased in comparison with the un-treated SMMC-7721 cells (0 U/ml, P < 0.05). The endothelial cell migration significantly increased in the IFN-alpha 1000 U/ml group compared with the control group (P < 0.001), and then decreased along with the increase of IFN-alpha dose; there were no significant differences in the epithelial migration among the groups of 0, 5000, and 10,000 U/ml IFN-alpha doses (all P > 0.05). The TP protein expression levels of the tumor in the rats treated with IFN-alpha of the doses of 9.0 x 10(6), and 1.5 x 10(7) U.kg(-1).d(-1) were 48 ng/mg +/- 24 ng/mg and 60 ng/mg +/- 6 ng/mg respectively, 1.9 and 2.4 times that of the control group (both P < 0.01). The MVD of the tumors was 6.0 +/- 1.8 in the 9.0 x 10(6) U.kg(-1).d(-1) IFN-alpha group, significantly higher than that of the control group (P < 0.01); and was 4.0 +/- 1.5 in the 1.5 x 10(7) U.kg(-1).d(-1) group, significantly lower than that of the 9.0 x 10(6) U.kg(-1).d(-1) group (P < 0.05) and not significantly different from that of the control group. The tumor inhibiting rate of the 1.5 x 10(7) U.kg(-1).d(-1) IFN-alpha group was 68%, significantly higher than that of the untreated group (P < 0.05). CONCLUSION: IFN-alpha of certain doses up-regulate the TP expression, and inhibit the angiogenesis induced by TP as well.

Animals↗

PubMed2005

Ionotropic glutamatergic neurotransmission in the ventral tegmental area modulates DeltaFosB expression in the nucleus accumbens and abstinence syndrome in morphine withdrawal rats.

The present study sought to assess whether the blockade of ionotropic glutamate receptors in the ventral tegmental area could modulate morphine withdrawal in morphine-dependent rats and the expression of stable DeltaFosB isoforms in the nucleus accumbens during morphine withdrawal. Rats were injected (i.p.) with increasing doses of morphine for 1 week to develop physical dependence, and withdrawal was then precipitated by one injection of naloxone (2 mg/kg, i.p.). Abstinence signs such as jumping, wet-dog shake, writhing posture, weight loss, and Gellert-Holtzman scale score were recorded to evaluate naloxone-induced morphine withdrawal. Two ionotropic glutamate receptor antagonists, dizocilpine (MK-801) and 6, 7-dinitroquinnoxaline-2, 3-dione (DNQX), were microinjected unilaterally into the ventral tegmental area 30 min before naloxone precipitation. A second injection of naloxone (2 mg/kg i.p.) was given 1 h after the first naloxone injection to sustain a maximal level of withdrawal so that the expression of stable DeltaFosB isoforms in the nucleus accumbens could be measured. This would enable determination of the correlation between the MK-801 or DNQX-induced decrease in somatic withdrawal signs and the change in neuronal activity in the nucleus accumbens. The results showed that both MK-801 and DNQX significantly alleviated all symptoms of morphine withdrawal except for weight loss and reduced the expression of stable DeltaFosB isoforms within the nucleus accumbens. These data suggest that ionotropic glutamatergic neurotransmission in the ventral tegmental area regulates the levels of stable DeltaFosB isoforms in the nucleus accumbens, which play a very important role in modulating opiate withdrawal.

Animals↗

PubMed2005

Exchange-correlation functional with broad accuracy for metallic and nonmetallic compounds, kinetics, and noncovalent interactions.

By incorporating kinetic-energy density in a balanced way in the exchange and correlational functionals and removing self-correlation effects, we have designed a density functional that is broadly applicable to organometallic, inorganometallic, and nonmetallic bonding, thermochemistry, thermochemical kinetics, and noncovalent interactions as well as satisfying the uniform electron gas limit. The average error is reduced by a factor of 1.3 compared with the best previously available functionals, but even more significantly, we find a functional that has a high accuracy for all four categories of interaction.

Journal Article↗

PubMed2005

Inhibitors of histone deacetylases target the Rb-E2F1 pathway for apoptosis induction through activation of proapoptotic protein Bim.

Inhibitors of histone deacetylases (HDACIs) are a new generation of anticancer agents that selectively kill tumor cells. However, the molecular basis for their tumor selectivity is not well understood. We investigated the effects of HDACIs on the oncogenic Rb-E2F1 pathway, which is frequently deregulated in human cancers. Here, we report that cancer cells with elevated E2F1 activity, caused either by enforced E2F1 expression, or by E1A oncogene expression, are highly susceptible to HDACI-induced cell death. This E2F1-mediated apoptosis is neither p53- nor p73-dependent but proceeds through selective induction of proapoptotic BH3-only protein Bim. We show that Bim is a direct target of E2F1 and that HDAC inhibition promotes the recruitment of E2F1 to the Bim promoter. Moreover, silencing of Bim by specific small interfering RNA (siRNA) effectively abolishes the E2F1-mediated cell death sensitization to HDACIs. These findings suggest that the oncogenic E2F1 pathway participates in HDACIs-induced apoptosis in cancer cells and underscore the importance of Bim as a key mediator of oncogene-induced apoptosis. Our study provides an important insight into the molecular mechanism of tumor selectivity of HDACIs and predicts that, clinically, HDACIs will be more effective in tumors with high E2F1 activity.

Antineoplastic Agents↗

PubMed2005

How well can density functional methods describe hydrogen bonds to pi acceptors?

We employed four newly developed density functional theory (DFT) methods for the calculation of five pi hydrogen bonding systems, namely, H2O-C6H6, NH3-C6H6, HCl-C6H6, H2O-indole, and H2O-methylindole. We report new coupled cluster calculations for HCl-C6H6 that support the experimental results of Gotch and Zwier. Using the best available theoretical and experimental results for all five systems, our calculations show that the recently proposed MPW1B95, MPWB1K, PW6B95, and PWB6K methods give accurate energetic and geometrical predictions for pi hydrogen bonding interactions, for which B3LYP fails and PW91 is less accurate. We recommend the most recent DFT method, PWB6K, for investigating larger pi hydrogen bonded systems, such as those that occur in molecular recognition, protein folding, and crystal packing.

Letter↗

PubMed2005

Local application of morphine suppresses glutamate-evoked activities of C and Adelta afferent fibers in rat hairy skin.

Behavior studies have demonstrated that local application of morphine in peripheral tissues resulted in a significant antinociceptive effect, but there has been no electrophysiological evidence to support the peripheral mechanism of opioid antinociception. The purpose of the present study was to investigate whether local application of morphine suppressed the glutamate-evoked activities of C and Adelta primary afferent fibers in dorsal hairy skin of rat in vivo. The single unit activities of the C and Adelta afferent fibers were recorded by means of isolation of the fiber filaments from the dorsal cutaneous nerve branches, and the effects of glutamate and glutamate plus morphine injected into the receptive field on these activities were determined. The results revealed that most of the C and Adelta fibers were excited significantly by local injection of glutamate (0.3 mM), with the percentage being 81% (22/27, for C fibers) and 73% (36/49, for Adelta fibers), respectively. The glutamate-induced excitatory response was significantly suppressed by co-injection of morphine (1.0 mM). The mean discharge rates of C fibers and Adelta fibers decreased from 28.96 +/- 6.85, 28.99 +/- 3.79 impulses/min to 4.40 +/- 1.76, 2.72 +/- 0.71 impulses/min, respectively. The suppressing effect of morphine was reversed by pretreatment with opioid receptor antagonist naloxone (1.0 mM). These findings suggest that local application of morphine can suppress the glutamate-evoked activities of the fine fibers in rat hairy skin and thus provide an electrophysiological evidence for peripheral antinociception of opioids.

Action Potentials↗

PubMed2005

Solvent-tunable binding of hydrophilic and hydrophobic guests by amphiphilic molecular baskets.

[reaction: see text] Responsive amphiphilic molecular baskets were obtained by attaching four facially amphiphilic cholate groups to a tetraaminocalixarene scaffold. Their binding properties can be switched by solvent changes. In nonpolar solvents, the molecules utilize the hydrophilic faces of the cholates to bind hydrophilic molecules such as glucose derivatives. In polar solvents, the molecules employ the hydrophobic faces of the cholates to bind hydrophobic guests. A water-soluble basket can bind polycyclic aromatic hydrocarbons including anthracene, pyrene, and perylene. The binding free energy (-deltaG) ranges from 5 to 8 kcal/mol and is directly proportional to the surface area of the aromatic hosts. Binding of both hydrophilic and hydrophobic guests is driven by solvophobic interactions.

Journal Article↗

PubMed2005

Estrogen provides neuroprotection against activated microglia-induced dopaminergic neuronal injury through both estrogen receptor-alpha and estrogen receptor-beta in microglia.

Estrogen provides neuroprotection against neurodegenerative diseases, including Parkinson's disease. Its effects may stem from interactions with neurons, astrocytes, and microglia. We demonstrate here in primary cultures of rat mesencephalic neurons that estrogen protects them from injury induced by conditioned medium obtained from lipopolysaccharide (LPS)-activated microglia. LPS-induced nitrite production and tumor necrosis factor-alpha up-regulation in microglia were blocked by estrogen pretreatment. Estrogen neuroprotection was related to microglial activation of estrogen receptors (ERs), insofar as the protective effect of the microglia-conditioned medium was overridden by pretreatment of microglia with the ER antagonist ICI 182,780. On the other hand, the specific ERalpha antagonist, MPP dihydrochloride, only partially blocked the effects of estrogen, suggesting that estrogen protection was mediated via both ERalpha and ERbeta. LPS treatment did not change ERalpha mRNA levels in microglia, astrocytes, and neurons, but it up-regulated ERbeta mRNA levels in microglia and astrocytes. Similarly, increased ERbeta protein levels were detected in LPS-activated microglia. More interesting was that immunocytochemical analysis revealed that ERbeta was localized in the cytoplasm of microglia and in the cell nucleus of astrocytes and neurons. In summary, our results support the notion that estrogen inhibits microglial activation and thus exhibits neuroprotective effects through both ERalpha and ERbeta activation. The cytoplasm location of microglial ERbeta suggests the possible involvement of nonclassical effects of estrogen on microglia. Changes in microglial ERbeta expression levels may modulate such effects of estrogen.

Animals↗

PubMed2005

Infinite-basis calculations of binding energies for the hydrogen bonded and stacked tetramers of formic acid and formamide and their use for validation of hybrid DFT and ab initio methods.

Benchmark stabilization energies for planar H-bonded and stacked structures of formic acid tetramers and formamide tetramers were determined as the sum of the infinite basis set limit of MP2 energies and a CCSD(T) correction term evaluated with the 6-31G*(0.25) basis set. The infinite basis (IB) set limit of MP2 energies was determined by two-point extrapolation using the aug-cc-pVXZ basis sets for X = D and T and separate extrapolation of the Hartree-Fock and correlation energies with new IB parameters for augmented basis sets determined here. Final stabilization energies (kcal/mol) for the tetramer studied are in the range of 4.6 to approximately 6.7 kcal/mol and they were used as reference data to test 14 density functionals. Among the tested DFT methods, PWB6K gives the best performance with an average error equal to only 30% of the average binding energy. In contrast, the popular B3LYP functional has an average error of 85%. We recommend the PWB6K method for exploring the potential energy surfaces of organic complexes and clusters and supramolecular assemblies.

Algorithms↗

PubMed2005

Cholic acid-derived facial amphiphiles with different ionic characteristics.

A cholate derivative with three epoxide groups was synthesized from cholic acid by allylation followed by epoxidation. Ring opening of the epoxides by various nucleophiles yielded facial amphiphiles with anionic, cationic, or nonionic functional groups. The critical micelle concentrations of these amphiphiles largely depend on the number of charged groups on the molecule. A facial amphiphile with pH-tunable micellization was prepared. Its aggregation behavior changes abruptly at pH = 7.6-6.6 as a result of protonation of its amino groups.

Journal Article↗

PubMed2005

Design of density functionals that are broadly accurate for thermochemistry, thermochemical kinetics, and nonbonded interactions.

This paper develops two new hybrid meta exchange-correlation functionals for thermochemistry, thermochemical kinetics, and nonbonded interactions. The new functionals are called PW6B95 (6-parameter functional based on Perdew-Wang-91 exchange and Becke-95 correlation) and PWB6K (6-parameter functional for kinetics based on Perdew-Wang-91 exchange and Becke-95 correlation). The resulting methods were comparatively assessed against the MGAE109/3 main group atomization energy database, against the IP13/3 ionization potential database, against the EA13/3 electron affinity database, against the HTBH38/4 and NHTBH38/04 hydrogen-transfer and non-hydrogen-transfer barrier height databases, against the HB6/04 hydrogen bonding database, against the CT7/04 charge-transfer complex database, against the DI6/04 dipole interaction database, against the WI7/05 weak interaction database, and against the new PPS5/05 pi-pi stacking interaction database. From the assessment and comparison of methods, we draw the following conclusions, based on an analysis of mean unsigned errors: (i) The PW6B95, MPW1B95, B98, B97-1, and TPSS1KCIS methods give the best results for a combination of thermochemistry and nonbonded interactions. (ii) PWB6K, MPWB1K, BB1K, MPW1K, and MPW1B95 give the best results for a combination of thermochemical kinetics and nonbonded interactions. (iii) PWB6K outperforms the MP2 method for nonbonded interactions. (iv) PW6B95 gives errors for main group covalent bond energies that are only 0.41 kcal (as measured by mean unsigned error per bond (MUEPB) for the MGAE109 database), as compared to 0.56 kcal/mol for the second best method and 0.92 kcal/mol for B3LYP.

Journal Article↗

PubMed2005

Expression of mediators of renal injury in the remnant kidney of ROP mice is attenuated by cyclooxygenase-2 inhibition.

To investigate the effects of cyclooxygenase-2 (COX-2) inhibition on renal injury of mice, ROP mice were subjected to subtotal ablation ('remnant'). A subset of the remnant group was treated with a selective COX-2 inhibitor, SC58236, in the drinking water. At 12 weeks the remnant group developed significant albuminuria (181.3 +/- 15.8 microg/24 h), which was blunted by SC58236 treatment (138.9 +/- 17.1; p < 0.05 compared to remnant). SC58236 did not alter systemic blood pressure or GFR significantly. Immunoreactive COX-2 was upregulated in remnant (1.88 +/- 0.35 fold sham, n = 8, p < 0.05), which was blunted by SC58236 (to 1.26 +/- 0.31 fold sham). Collagen IV mRNA increased significantly in remnant kidneys (2.69 +/- 0.34 fold sham, n = 8, p < 0.05), and this increase was inhibited by SC58236 treatment (to 1.84 +/- 0.32 fold control). Immunoreactive TGF-beta1, connective tissue growth factor, HGF receptor, c-Met, and fibronectin all increased in remnant (2.85 +/- 0.51, 3.83 +/- 0.55, 2.56 +/- 0.31, and 2.80 +/- 0.39 fold sham respectively, n = 4-8, p < 0.05), and SC58236 blunted the increases (to 1.45 +/- 0.34, 1.85 +/- 0.13, 1.75 +/- 0.30, and 1.60 +/- 0.32 fold sham). Immunohistochemistry indicated that the major localization for these progression factors was in the tubulointerstitium, especially in the scar area, which is in agreement with the expression of a macrophage marker, F4/80. Therefore, these results indicate that in a mouse model of subtotal renal ablation, COX-2 inhibition blocks expression of mediators of renal tubulointerstitial injury.

Animals↗

PubMed2005

Grifolin, a potential antitumor natural product from the mushroom Albatrellus confluens, inhibits tumor cell growth by inducing apoptosis in vitro.

Grifolin is a natural biologically active substance isolated from the fresh fruiting bodies of the mushroom Albatrellus confluens. Here, for the first time, we describe a novel activity of grifolin, namely its ability to inhibit the growth of tumor cells by the induction of apoptosis. Grifolin strongly inhibited the growth of tumor cell lines: CNE1, HeLa, MCF7, SW480, K562, Raji and B95-8. Analysis of acridine orange (AO)/ethidium bromide (EB) staining and flow cytometry showed that grifolin possessed apoptosis induction activity to CNE1, HeLa, MCF7 and SW480. Furthermore, the cytochrome c release from mitochondria was detected by confocal microscopy in CNE1 cells after a 12h treatment with grifolin. The increase of caspase-8, 9, 3 activities revealed that caspase was a key mediator of the apoptotic pathway induced by grifolin, and the underexpression of Bcl-2 and up-regulation of Bax resulted in the increase of Bax: Bcl-2 ratio, suggesting that Bcl-2 family involved in the control of apoptosis. Owing to the combination of the significant antitumor activity by inducing apoptosis and natural abundance of the compound, grifolin holds the promise of being an interesting antitumor agent that deserves further laboratory and in vivo exploration.

Animals↗

PubMed2005

How well can new-generation density functional methods describe stacking interactions in biological systems?

We compare the performance of four recently developed DFT methods (MPW1B95, MPWB1K, PW6B95, and PWB6K) and two previous, generally successful DFT methods (B3LYP and B97-1) for the calculation of stacking interactions in six nucleic acid bases complexes and five amino acid pairs and for the calculation of hydrogen bonding interactions in two Watson-Crick type base pairs. We found that the four newly developed DFT methods give reasonable results for the stacking interactions in the DNA base pairs and amino acid pairs, whereas the previous DFT methods fail to describe interactions in these stacked complexes. We conclude that the new generation of DFT methods have greatly improved performance for stacking interaction as compared to previously available methods. We recommend the PWB6K method for investigating large DNA or protein systems where stacking plays an important role.

Algorithms↗

PubMed2005

Dithiocarbamate assembly on gold.

Au surfaces are functionalized by stable dithiocarbamate ligands when exposed to carbon disulfide and secondary amines. The adsorbed dithiocarbamates are robust under a wide pH range and can resist displacement by other chemisorptive surfactants, providing an attractive method for conjugating sensitive molecules onto metal surfaces.

Amines↗

PubMed2005

Databases for transition element bonding: metal-metal bond energies and bond lengths and their use to test hybrid, hybrid meta, and meta density functionals and generalized gradient approximations.

We propose a data set of bond lengths for 8 selected transition metal dimers (Ag(2), Cr(2), Cu(2), CuAg, Mo(2), Ni(2), V(2), and Zr(2)) and another data set containing their atomization energies and the atomization energy of ZrV, and we use these for testing density functional theory. The molecules chosen for the test sets were selected on the basis of the expected reliability of the data and their ability to constitute a diverse and representative set of transition element bond types while the data sets are kept small enough to allow for efficient testing of a large number of computational methods against a very reliable subset of experimental data. In this paper we test 42 different functionals: 2 local spin density approximation (LSDA) functionals, 12 generalized gradient approximation (GGA) methods, 13 hybrid GGAs, 7 meta GGA methods, and 8 hybrid meta GGAs. We find that GGA density functionals are more accurate for the atomization energies of pure transition metal systems than are their meta, hybrid, or hybrid meta analogues. We find that the errors for atomization energies and bond lengths are not as large if we limit ourselves to dimers with small amounts of multireference character. We also demonstrate the effects of increasing the fraction of Hartree-Fock exchange in multireference systems by computing the potential energy curve for Cr(2) and Mo(2) with several functionals. We also find that BLYP is the most accurate functional for bond energies and is reasonably accurate for bond lengths. The methods that work well for transition metal bonds are found to be quite different from those that work well for organic and other main group chemistry.

Journal Article↗

PubMed2005

Multicoefficient extrapolated density functional theory studies of pi...pi interactions: the benzene dimer.

We report tests of new (2005) and established (1999-2003) multilevel methods against essentially converged benchmark results for nonbonded interactions in benzene dimers. We found that the newly developed multicoefficient extrapolated density functional theory (DFT) methods (which combine DFT with correlated wave function methods) give better performance than multilevel methods such as G3SX, G3SX(MP3), and CBS-QB3 that are based purely on wave function theory (WFT); furthermore, they have a lower computational cost. We conclude that our empirical approach for combining WFT methods with DFT methods is a very efficient and effective way for describing not only covalent interactions (as shown previously) but also nonbonded interactions.

Benzene↗

PubMed2005

Transfection of thymidine phosphorylase cDNA to human hepatocellular carcinoma cells enhances sensitivity to fluoropyrimidine but augments endothelial cell migration.

PURPOSE: To investigate the effects on sensitivity to fluoropyrimidine and endothelial cell (EC) migration by transfection with thymidine phosphorylase (TP) cDNA to a hepatocellular carcinoma (HCC) cell line SMMC-7721. METHODS: SMMC-7721 was transfected with pcDNA3.1/zeo (+) with human TP cDNA. TP mRNA expression was determined by RT-PCR. Sensitivity to fluoropyrimidine was determined by 3-[4,5-dimethylthiazol-2-yl]-2, 5-diphenyl-tetrazolium bromide (MTT) assay. Induction of EC migration was detected by Boyden chamber assay. RESULTS: The construction of pcDNA3.1/zeo(+)-TP was verified by digestion with restriction endonuclease Apa1. When comparison was made between SMMC-7721 cell clone transfected with pcDNA3.1/zeo(+)-TP (S-TP) and control clone transfected with pcDNA3.1/zeo(+) (S-vector), we found that TP mRNA expression level was much higher in S-TP, being 2.09+/-0.16 vs 0.48+/-0.06 in S-vector (P < 0.01), sensitivity to 5'-deoxy-5-fluorouridine (5'-dFUrd, a prodrug of 5-fluorouracil) in S-TP was significantly enhanced compared with that in S-vector (IC(50); 56.81+/-9.85 micromol/l vs 162.25+/-11.03 micromol/l, P < 0.01), and the culture medium of S-TP possessed more potential to induce EC migration than that of S-vector (the number of ECs appearing on the outer surfaces of the membrane was 275+/-29 vs 122+/-35 per field, P < 0.01). CONCLUSION: Sensitivity to 5'-dFUrd could be enhanced by transfection with TP cDNA for SMMC-7721 cells. However, EC migration was also promoted at the same time. Therefore, transfection with TP alone might have no potential to enhance anti-tumoral effects of fluoropyrimidine in HCC.

Antigens, Neoplasm↗