Biomedical subjects

Mengsu Yang

Publications and source records attributed to Mengsu Yang.

At least 19 recordsLinked to original sources

PubMed2006

Hypoxia induces the activation of human hepatic stellate cells LX-2 through TGF-beta signaling pathway.

Hypoxia is a common environmental stress factor and is also associated with various physiological and pathological conditions such as fibrogenesis. The activation of hepatic stellate cells (HSCs) is the key event in the liver fibrogenesis. In this study, the behavior of human HSCs LX-2 in low oxygen tension (1% O2) was analyzed. Upon hypoxia, the expression of HIF-1alpha and VEGF gene was induced. The result of Western blotting showed that the expression of alpha-SMA was increased by hypoxic stimulation. Furthermore, the expression of MMP-2 and TIMP-1 genes was increased. Hypoxia also elevated the protein expression of the collagen type I in LX-2 cells. The analysis of TGF-beta/Smad signaling pathway showed that hypoxia potentiated the expression of TGF-beta1 and the phosphorylation status of Smad2. Gene expression profiles of LX-2 cells induced by hypoxia were obtained by using cDNA microarray technique.

Anaerobiosis↗

PubMed2006

Effects of rhDecorin on TGF-beta1 induced human hepatic stellate cells LX-2 activation.

Decorin is a small leucine-rich extracellular matrix proteoglycan composed of a core protein with a single glycosaminoglycan (GAG) chain near the N-terminus and N-glycosylated at three potential sites. Decorin is involved in the regulation of formation and organization of collagen fibrils, modulation of the activity of growth factors such as transforming growth factor beta (TGF-beta), and exerts other effects on cell proliferation and behavior. Increasing evidences show that decorin plays an important role in fibrogenesis by regulating TGF-beta, a key stimulator of fibrosis, and by directly modulating the degradation of extracellular matrix (ECM) from activated hepatic stellate cells (HSCs). In this study, the core protein of human decorin was cloned and expressed in Escherichia coli. The purified recombinant human decorin (rhDecorin) significantly inhibited the proliferation of LX-2 cells, a human HSC cell line, stimulated by TGF-beta1. RT-PCR result showed that the expression of metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were reduced by rhDecorin in LX-2 cells stimulated by TGF-beta1. Furthermore, the protein expression of smooth muscle-alpha-actin (alpha-SMA), collagen type III and phosphorylated Smad2 (p-Smad2) was significantly decreased in the presence of rhDecorin. rhDecorin also reduced fibrillogenesis of collagen type I in a dose-dependent manner. Gene expression profiles of LX-2 cells stimulated by TGF-beta1 in the presence and the absence of rhDecorin were obtained by using cDNA microarray technique and differentially expressed genes were identified to provide further insight into the molecular action mechanism of decorin on LX-2 cells.

Cell Proliferation↗

PubMed2006

Dose-dependent cell-based assays in V-shaped microfluidic channels.

The capability of lab-on-a-chip technologies in controlling cell transportation, generating concentration gradients, and monitoring cellular responses offers an opportunity to integrate dose-dependent cell-based bioassays on a chip. In this study, we have developed microfluidic modules featured with channel components and sandbag structures for positioning biological cells within the microchip. We have demonstrated that by geometric modulation of the microchannel architectures, it is possible to immobilize individual cells at desired locations with controllable numbers, to generate defined concentration gradients at various channel lengths, and to improve the efficiency and reproducibility in data acquisition. The microfluidic module was used to exercise a series of cell-based assays, including the measurement of kinetics and dynamics of intracellular enzymatic activities, the analysis of cellular response under the stimulation of two chemicals with defined concentration profiles, and the study of laser irradiation effect on cellular uptake of photosensitizers. The results demonstrated the capabilities of the microfluidic module for simultaneously conducting multiple sets of dose-dependent, cell-based bioassays, and for quantitatively comparing responses of individual cells under various stimulations.

Biological Assay↗

PubMed2006

Effect of WeiJia on carbon tetrachloride induced chronic liver injury.

AIM: To study the effect of WeiJia on chronic liver injury using carbon tetrachloride (CCl(4)) induced liver injury animal model. METHODS: Wistar rats weighing 180-220g were randomly divided into three groups: normal control group (Group A), CCl(4) induced liver injury control group (Group B) and CCl(4) induction with WeiJia treatment group (Group C). Each group consisted of 14 rats. Liver damage and fibrosis was induced by subcutaneous injection with 40% CCl(4) in olive oil at 3 mL/kg body weight twice a week for eight weeks for Groups B and C rats whereas olive oil was used for Group A rats. Starting from the third week, Group C rats also received daily intraperitoneal injection of WeiJia at a dose of 1.25 microg/kg body weight. Animals were sacrificed at the fifth week (4 male, 3 female), and eighth week (4 male, 3 female) respectively. Degree of fibrosis were measured and serological markers for liver fibrosis and function including hyaluronic acid (HA), type IV collagen (CIV), gamma-glutamyl transferase (gamma-GT), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined. Alpha smooth muscle actin (alpha-SMA) and proliferating cell nuclear antigen (PCNA) immunohistochemistry were also performed. RESULTS: CCl(4) induction led to the damage of liver and development of fibrosis in Group B and Group C rats when compared to Group A rats. The treatment of WeiJia in Group C rats could reduce the fibrosis condition significantly compared to Group B rats. The effect could be observed after three weeks of treatment and was more obvious after eight weeks of treatment. Serum HA, CIV, ALT, AST and gamma-GT levels after eight weeks of treatment for Group C rats were 58+/-22 microg/L (P<0.01), 57+/-21 microg/L (P<0.01), 47+/-10 U/L (P<0.01), 139+/-13 U/L (P<0.05) and 52+/-21 U/L (P>0.05) respectively, similar to normal control group (Group A), but significantly different from CCl(4) induced liver injury control group (Group B). An increase in PCNA and decrease in alpha-SMA expression level was also observed. CONCLUSION: WeiJia could improve liver function and reduce liver fibrosis which might be through the inhibition of stellate cell activity.

Actins↗

PubMed2006

Methyl protodioscin induces G2/M cell cycle arrest and apoptosis in HepG2 liver cancer cells.

Methyl protodioscin (NSC-698790) is one of the main bioactive components in the traditional Chinese medicine Dioscorea collettii var. hypoglauca (Dioscoreaceae). In this study, we investigated the anti-proliferative effect of methyl protodioscin on the HepG2 cells and the mechanism of the induced cytotoxicity. Treatment of methyl protodioscin resulted in G2/M arrest and apoptosis in HepG2 cells. These effects were attributed to down-regulation of Cyclin B1 and the signaling pathways leading to up-regulation of Bax and down-regulation of BCL2, suggesting that methyl protodioscin may be a novel anti-mitotic agent.

Apoptosis↗

PubMed2006

Optical and electrochemical detection techniques for cell-based microfluidic systems.

The ability to fabricate microfluidic systems with complex structures and with compatible dimensions between the microfluidics and biological cells have attracted significant attention in the development of microchips for analyzing the biophysical and biochemical functions of cells. Just as cell-based microfluidics have become a versatile tool for biosensing, diagnostics, drug screening and biological research, detector modules for cell-based microfluidics have also undergone major development over the past decade. This review focuses on detection methods commonly used in cell-based microfluidic systems, and provides a general survey and an in-depth look at recent developments in optical and electrochemical detection methods for microfluidic applications for biological systems, particularly cell analysis. Selected examples are used to illustrate applications of these detection systems and their advantages and weaknesses.

Biosensing Techniques↗

PubMed2006

A low temperature bonding of quartz microfluidic chip for serum lipoproteins analysis.

A low-temperature bonding method for microfabrication of quartz microfluidic chips has been developed. The bonding process involved two steps: pre-bonding and post-annealing at low temperature. The bonding quality was evaluated by measuring the shear force at bonding interface and the electrical properties of the chips. Shear force of 5.66 MPa (566 N/cm(2)) was obtained in a bonded chip after a post-annealing at 200 degrees C for 6 h. We owe the strong bonding strength to the formation of Si-O-Si bonds at the bonding interface during the post-annealing stage. The bonding procedures were not sensitive to surrounding and could be performed in a routine laboratory without clean room conditions. The performance of the fabricated microfluidic chips was tested by capillary zone electrophoresis (CZE) of serum lipoproteins with laser-induced fluorescence (LIF). The low-density (LDL) and high-density (HDL) lipoproteins in the serum was separated completely by using tricine buffer with methylglucamine.

Cold Temperature↗

PubMed2006

Cytotoxic cycloartane triterpene saponins from Actaea asiatica.

Three new 9,19-cycloartane triterpene glycosides, asiaticoside A (1), asiaticoside B (2), and 25-O-ethylcimigenol-3-O-beta-D-xylopyranoside (3), together with cimiacemoside I (4), 25-O-acetylcimigenol-3-beta-O-D-xyloside (5), and 25-anhydrocimigenol-beta-O-D-xyloside (6) were isolated from the roots/rhizomes extract of Actaea asiatica, and their structures were established by spectroscopic methods (IR, HRESIMS, and NMR). Compounds 1-3, 5, and 6 had notable cytotoxicity against HepG2 and MCF-7 cancer cell lines.

Actaea↗

PubMed2006

Anti-cancer activity and mechanisms of 25-anhydrocimigenol-3-O-beta-D-xylopyranoside isolated from Souliea vaginata on hepatomas.

Our previous study first revealed the cytotoxicity and relative selectivity of 25-anhydrocimigenol-3-O-beta-D-xylopyranoside (ACX) on HepG2 and R-HepG2 cells. In the present study, the anti-cancer activity and mechanisms of ACX isolated from S. vaginata were investigated both in vitro and in vivo. ACX showed significant, consistent anti-proliferative activity on hepatoma bel-7402 cells by MTT and clone formation assays with an IC50 value of 18 mumol/l. Morphological observation and flow cytometry results showed that apoptosis and G0/G1 cell cycle arrest contributed to the cytotoxic and cytostatic effects. Further studies showed that Bax and p21 protein expression were upregulated, Bcl-2 protein expression was downregulated, and poly(ADP-ribose) polymerase protein was cleaved. Moreover, ACX also exhibited a dose-dependent inhibition of tumor growth on mice implanted with H22 in vivo. These findings implicate ACX as a promising anti-cancer agent for chemotherapy of certain cancers.

Animals↗

PubMed2005

Triptolide induces Bcl-2 cleavage and mitochondria dependent apoptosis in p53-deficient HL-60 cells.

Triptolide, a bioactive component of the Chinese medicinal herb Tripterygium wilfordii Hook F., induces p53-mediated apoptosis in cancer cells. This study demonstrated that triptolide activated an alternative p53-independent apoptotic pathway in HL-60 cells. In the absence of an intact p53 and without changing Bax level, at nM range triptolide induced apoptosis with concomitant DNA fragmentation, S phase cell cycle arrest, mitochondrial cytochrome c release and the activation of caspases. Besides, both caspases 8 and 9 were activated and the simultaneous inhibition of both was required to completely block triptolide's apoptotic effect. Importantly, triptolide induced the appearance of a truncated 23kD Bcl-2 which was inhibited by the general caspase inhibitor Z-VAD-FMK. In the MCF-7 cells that possessed the wild type p53 but lacked caspases 3, triptolide induced cell death with an increase in p53 but Bcl-2 remained unaltered. On the other hand, transfected cells overexpressing the 28kD Bcl-2 became more resistant to triptolide and upon triptolide treatment accumulated in the G(1) instead of S phase. After 36h treatment, triptolide activated JNK pathways, at the same time inactivated the ERK and p38 pathways. However, SP600125, a specific JNK inhibitor, could not inhibit the triptolide-mediated cleavage of caspase 3, indicated that activation of JNK might not be related to the apoptotic effects of triptolide. Our data suggest that in the absence of an intact p53 and without altering Bax level triptolide induces apoptosis activates a positive amplification loop involving caspase-mediated Bcl-2 cleavage/activation, mitochondrial cytochrome c release and further activation of caspases.

Caspases↗

PubMed2005

Honokiol inhibits TNF-alpha-stimulated NF-kappaB activation and NF-kappaB-regulated gene expression through suppression of IKK activation.

Honokiol, a small molecular weight lignan originally isolated from Magnolia officinalis, shows anti-angiogenic, anti-invasive and anti-proliferative activities in a variety of cancers. In this study, we investigated whether honokiol affects the transcription factor nuclear factor-kappa B (NF-kappaB) which controls a large number of genes involved in angiogenesis, metastasis and cell survival. We observed that the tumor necrosis factor-alpha (TNF-alpha)-induced NF-kappaB activation was blocked by honokiol in four different cancer cell lines as evidenced by EMSA. Honokiol did not directly affect the NF-kappaB-DNA binding. Immunoblot experiments demonstrated that honokiol inhibited the TNF-alpha-stimulated phosphorylation and degradation of the cytosolic NF-kappaB inhibitor IkappaBalpha. Furthermore, honokiol suppressed the intrinsic and TNF-alpha-stimulated upstream IkappaB kinases (IKKs) activities measured by a non-radioactive kinase assay using immunoprecipitated IKKs, suggesting a critical role of honokiol in abrogating the phosphorylation and degradation of IkappaBalpha. In a HeLa cell NF-kappaB-dependent luciferase reporter system, honokiol suppressed luciferase expression stimulated by TNF-alpha and by the transient transfection and expression of NIK (NF-kappaB-inducing kinase), wild type IKKbeta, constitutively active IKKalpha and IKKbeta, or the p65 subunit. Honokiol was also found to inhibit the nuclear translocation and phosphorylation of p65 subunit of NF-kappaB. RT-PCR results showed that honokiol suppressed NF-kappaB-regulated inflammatory and carcinogenic gene products including MMP-9, TNF-alpha, IL-8, ICAM-1 and MCP-1. In line with the observation that NF-kappaB activation may up-regulate anti-apoptotic genes, it was shown that honokiol enhanced TNF-alpha-induced apoptotic cell death. In summary, our results demonstrate that honokiol suppresses NF-kappaB activation and NF-kappaB-regulated gene expression through the inhibition of IKKs, which provides a possible mechanism for its anti-tumor actions.

Antineoplastic Agents↗

PubMed2005

Water soluble luminescent platinum terpyridine complexes with glycosylated acetylide and arylacetylide ligands: photoluminescent properties and cytotoxicities.

Platinum(II) terpyridine complexes with glycosylated acetylide and arylacetylide ligands bind to DNA with binding constants approximately 10(5) mol(-1) dm(3); the glycosylated arylacetylide complexes exhibit emission at lambda(max) approximately 620 nm in water and are up to approximately 100-times higher in potency than the clinical cisplatin drug in killing cancer cells.

Antineoplastic Agents↗

PubMed2005

The cytotoxicity of naturally occurring styryl lactones.

We extracted and isolated three natural styryl lactones from Goniothalamus griffithii Hook f. Thoms and investigated their cytotoxicity on a panel of three hepatocyte cell lines, HepG2, drug resistant HepG2 (HepG2-R) and primary cultured normal mice hepatocyte in order to find candidates of potential anti-cancer drugs which have low toxicity on normal cells and high effect on tumors or drug resistant tumors. All the three styryl lactones showed evident cytotoxic activities on both HepG2 and HepG2-R cell lines; however, gonithalamin and goniodiol shows less toxicity on normal mice hepatocyte as the IC(50) values of them on normal mice hepatocyte were about three times of that on HepG2. Morphological observation and cell cycle analysis were employed to elucidate the mechanisms of cytotoxicity of the tested compounds. Many apoptotic cells were observed in gonithalamin- and altholactone-treated cells, whereas, cells with chromosomes gathered at the equator were easily found in goniodiol-treated cultures. The analysis of cell cycle showed that G(2)/M arrest contributed to goniothalimin- and gonidiol-caused cell death and apoptosis was the cause of gonithalamin- and altholactone-induced cell death. Our results suggest that the three styryl lactones may be prospectively developed into anti-tumor drugs, especially on treating drug-resistance tumor after structure modification.

Animals↗

PubMed2005

Impedance analysis of an electrode-separated piezoelectric sensor as a surface-monitoring technique for gelatin adsorption on quartz surface.

The early events pertaining to gelatin adsorption and desorption onto quartz surfaces were studied, employing an electrode-separated piezoelectric sensor (ESPS). The adsorption of gelatin on a quartz crystal surface corresponds to a mass increase, which can be monitored in real time by the changes in the impedance parameters of the ESPS. It was shown that the adsorption of gelatin on a quartz surface is partly irreversible with respect to the dilution of the bulk phase. The observed adsorption kinetics is compatible with a mechanism that involves adsorption, desorption, and transformation from a reversible adsorption state to irreversible one. A progressive approach method was established to simulate the adsorption process. The adsorption densities and kinetic parameters in the early adsorption process were obtained from the responses of the ESPS in the adsorption process. The influence of pH and ionic strength was tested. A comparison with the Langmuir adsorption model was made.

Adsorption↗

PubMed2004

Cytotoxicity of three cycloartane triterpenoids from Cimicifuga dahurica.

We first investigated the cytotoxicity of three cycloartane triterpenoids isolated from the aerial part of C. dahurica. Their cytotoxic activity was investigated on several cancer cell lines including solid tumor (HepG2), blood tumor (HL-60), drug resistant tumor (R-HepG2) and primary cultured normal mouse and rat hepatocytes in order to find efficient anti-tumor agents against both parental and drug-resistant tumor with reduced toxicity. Evident cytotoxicity of these compounds on all tested neoplastic cell lines revealed that they are efficient on both drug-resistant tumor and parental tumor. Furthermore, they all showed relatively selective cytotoxicity on cancerous cells based on the higher IC(50) values of them on normal cells than that on tumor cells. Morphological observation and cell cycle analysis were employed to elucidate the cytotoxicity of the tested compounds. They brought out similar apoptotic morphological changes and G(2)/M cell cycle arrest in HepG2, R-HepG2 and HL-60 cells. Moreover, they suppressed the expression of cdc2 and COX-2 protein. These results imply that the three compounds possess potential anti-tumor activities and they exert their cytotoxicity via apoptosis and G(2)/M arrest. In addition, inhibition of cdc2 protein expression correlates with mechanism of G(2)/M arrest.

Animals↗

PubMed2004

Trichosanthin's interfacial interactions with phospholipids: a monolayer study.

Lipid monolayer at the air/water interface, as half a membrane, was used here to investigate the interaction between trichosanthin (TCS), a ribosome inactivating protein, and phospholipid membrane. First, the protein adsorption experiments showed that the negatively charged DPPG caused obvious enrichment of TCS beneath the monolayer, indicating electrostatic attraction between TCS and the negatively charged phospholipid. Second, when TCS was incorporated into the phospholipid monolayer, it could not be completely squeezed out until the monolayer collapsed. The results were demonstrated to be irrelative with the phospholipid headgroup, suggesting a strong hydrophobic force between TCS and phospholipid hydrocarbon chain was involved in the interaction. Third, the protein/membrane interaction was further studied with fluorescence microscope. The results showed that TCS could penetrate into both the condensed and the fluid phase of the DPPG monolayer under low pH condition and eventually resulted in a homogeneous phospholipid phase. The breakage of ordered packing of phospholipid by TCS may be responsible for this homogenizing effect.

Adsorption↗

PubMed2004

Surface plasmon resonance study of the molecular recognition between polymerase and DNA containing various mismatches and conformational changes of DNA-protein complexes.

Although surface plasmon resonance (SPR) biosensor technique has been used to study protein-protein interactions and to detect conformational changes of proteins, it has not been shown whether the SPR biosensor can be used to study a complex kinetic system such as the protein-DNA binding, which sometimes involves several binding steps as well as dynamic conformational changes of the complexes. In this study, we have used SPR biosensor and T7 polymerase as the model system to study the interactions of the polymerase with a series of DNA template-primer duplexes containing different number of mismatches and GC contents at various positions near the primer 3'-end. In general, the binding constants measured by the SPR are several magnitudes smaller than those determined in solution, indicating the limitation of the surface-based technique for measuring solution-based interactions. However, the distinct polymerase binding profiles obtained for DNA duplexes differed by as low as a single mismatch suggest that the SPR data can be used for relative comparison purpose among a set of experiments carried out under identical conditions. The successful fitting of the binding profiles using the established translocation model also demonstrated that SPR can be used to monitor conformational changes, as well as to derive relative kinetic values, within a complicated DNA-protein interaction system. The results also demonstrated that SPR biosensor may be used as a sensitive technique for studying molecular recognition events, such as single-base discrimination involved in protein-DNA interactions.

Base Sequence↗

PubMed2004

Association of Vimentin overexpression and hepatocellular carcinoma metastasis.

The poor prognosis of hepatocellular carcinoma (HCC) has been associated with recurrence and metastasis. Recently, we established a pair of HCC cell lines from a primary (H2-P) and its matched metastatic (H2-M) HCC tumors. A high density of cDNA microarray with 9184 human cDNA was used to identify the differentially expressed genes between H2-P and H2-M. Comparing with H2-P, eight upregulated and six downregulated genes were detected in H2-M. One interesting finding is the overexpression of Vimentin (VIM), a well-defined intermediate filament, which has been linked to a more aggressive status in various tumors. The correlation of overexpression of VIM and HCC metastasis was studied by immunohistochemistry using a tissue microarray with 200 primary HCCs and 60 pairs of primary and matched metastatic HCC samples. Tissue microarray demonstrated that the overexpression of VIM was significantly associated with HCC metastasis (P<0.01). This finding strongly suggests that the overexpression of VIM may play an important role in the metastasis of HCC.

Adult↗