Biomedical subjects

Hui Dai

Publications and source records attributed to Hui Dai.

12 recordsLinked to original sources

PubMed2006

BRIT1 regulates early DNA damage response, chromosomal integrity, and cancer.

BRIT1, initially identified as an hTERT repressor, has additional functions at DNA damage checkpoints. Here, we demonstrate that BRIT1 formed nuclear foci minutes after irradiation. The foci of BRIT1 colocalized with 53BP1, MDC1, NBS1, ATM, RPA, and ATR. BRIT1 was required for activation of these elements, indicating that BRIT1 is a proximal factor in the DNA damage response pathway. Depletion of BRIT1 increased the accumulation of chromosomal aberrations. In addition, decreased levels of BRIT1 were detected in several types of human cancer, with BRIT1 expression being inversely correlated with genomic instability and metastasis. These results identify BRIT1 as a crucial DNA damage regulator in the ATM/ATR pathways and suggest that it functions as a tumor suppressor gene.

Base Sequence↗

PubMed2006

Inducing hepatic differentiation of human mesenchymal stem cells in pellet culture.

Extensive cell-cell or cell-matrix interaction in three-dimensional (3D) culture is important for the maintenance of adult hepatocyte function and the maturation of hepatic progenitors. However, although there is significant interest in inducing the transdifferentiation of adult stem cells into the hepatic lineage, very few studies have been conducted in a 3D culture configuration. The aim of this study is to investigate the differentiation of mesenchymal stem cells (MSC) into hepatocytes in a pellet configuration, with or without the presence of small intestinal submucosa (SIS). After 4 weeks of differentiation with growth factors bFGF, HGF, and OsM, we obtained hepatocyte-like cells that expressed a subset of hepatic genes, secreted albumin and urea, stored glycogen, and showed inducible CYP3A4 mRNA levels. When these cells were implanted into livers of hepatectomized rats, they secreted human albumin into the bloodstream. The hepatic differentiation of MSC was faster in cell pellets without SIS. The plausible explanations for this finding may be related to the mass transport issues of the two different pellets and the role of cell-cell contact over cell-matrix interactions. The findings of this study should help in the design of optimal culture configurations for efficient hepatic differentiation of adult stem cells.

Biocompatible Materials↗

PubMed2006

Chitosan-g-PEG/DNA complexes deliver gene to the rat liver via intrabiliary and intraportal infusions.

BACKGROUND: Chitosan has been shown to be a non-toxic and efficient vector for in vitro gene transfection and in vivo gene delivery through pulmonary and oral administrations. Recently, we have shown that chitosan/DNA nanoparticles could mediate high levels of gene expression following intrabiliary infusion 1. In this study, we have examined the possibility of using polyethylene glycol (PEG)-grafted chitosan/DNA complexes to deliver genes to the liver through bile duct and portal vein infusions. METHODS: PEG (Mw: 5 kDa) was grafted onto chitosan (Mw: 47 kDa, deacetylation degree: 94%) with grafting degrees of 3.6% and 9.6% (molar percentage of chitosan monosaccharide units grafted with PEG). The stability of chitosan-g-PEG/DNA complexes was studied by measuring the change in particle size and by agarose gel electrophoresis against bile or serum challenge. The influence of PEG grafting on gene transfection efficiency was evaluated in HepG2 cells using luciferase reporter gene. Chitosan and chitosan-g-PEG/DNA complexes were delivered to the liver through bile duct and portal vein infusions with a syringe pump. Gene expression in the liver and the distribution of gene expression in other organs were evaluated. The acute liver toxicity of chitosan and chitosan-g-PEG/DNA complexes was examined by measuring serum alanine aminotranferase (ALT) and aspartate aminotransferase (AST) activities as a function of time. RESULTS: Both chitosan and chitosan-g-PEG displayed comparable gene transfection efficiency in HepG2 cells. After challenge with serum and bile, chitosan-g-PEG/DNA complexes, especially those prepared with chitosan-g-PEG (GD = 9.6%), did not form large aggregates like chitosan/DNA complexes but remained stable for up to 30 min. In addition, chitosan-g-PEG prevented the degradation of DNA in the presence of serum and bile. On day 3 after bile duct infusion, chitosan-g-PEG (GD = 9.6%)/DNA complexes mediated three times higher gene expression in the liver than chitosan/DNA complexes and yielded background levels of gene expression in other organs. On day 1 following portal vein infusion, gene expression level induced by chitosan/DNA complexes was hardly detectable but chitosan-g-PEG (GD = 9.6%) mediated significant transgene expression. Interestingly, transgene expression by chitosan-g-PEG/DNA complexes in other organs after portal vein infusion increased with increasing grafting degree of PEG. The ALT and AST assays indicated that grafting of PEG to chitosan reduced the acute liver toxicity towards the complexes. CONCLUSION: This study demonstrated the potential of chitosan-g-PEG as a safe and more stable gene carrier to the liver.

Animals↗

PubMed2006

A fructan, from Radix ophiopogonis, stimulates the proliferation of cultured lymphocytes: structural and functional analyses.

A fructan, Opaw-2, with molecular mass of about 14 kDa, was isolated from the tuberous roots of Ophiopogon japonicus. Opaw-2 comprises fructose and glucose with a molar ratio of 30:1. Linkage and NMR analyses indicated that Opaw-2 has a backbone structure of beta-(1-->2)-Fruf and beta-(2-->6)-Fruf residues that branches at O-6 of beta-(1-->2)-Fruf residues with alpha-1-linkage to the Glcp residues and terminates with Fruf residues. In cultured lymphocytes, the application of Opaw-2 significantly stimulated the proliferation of lymphocytes in a dose-dependent manner. By using atomic force microscopy, Opaw-2 showed a morphological change from globular to helical fibrous shape at increasing concentrations.

Animals↗

PubMed2004

Immune receptors for polysaccharides from Ganoderma lucidum.

This study was designed to identify and characterize the immune receptors for polysaccharides from Ganoderma lucidum, a Chinese medicinal fungus that exhibits anti-tumor activities via enhancing host immunity. We herein demonstrate that G. lucidum polysaccharides (GLPS) activated BALB/c mouse B cells and macrophages, but not T cells, in vitro. However, GLPS was unable to activate splenic B cells from C3H/HeJ mice that have a mutated TLR4 molecule (incapable of signal transduction) in proliferation assays. Rat anti-mouse TLR4 monoclonal antibody (Ab) inhibited the proliferation of BALB/c mouse B cells under GLPS stimulation. Combination of Abs against mouse TLR4 and immunoglobulin (Ig) achieved almost complete inhibition of GLPS-induced B cell proliferation, implying that both membrane Ig and TLR4 are required for GLPS-mediated B cell activation. In addition, GLPS significantly inhibited the binding of mouse peritoneal macrophages with polysaccharides from Astragalus membranaceus, which is known to bind directly with TLR4 on macrophage surface. Moreover, GLPS induced IL-1beta production by peritoneal macrophages from BALB/c, but not C3H/HeJ, mice, suggesting that TLR4 is also involved in GLPS-mediated macrophage activation. We Further identified a unique 31 kDa serum protein and two intracellular proteins (ribosomal protein S7 and a transcriptional coactivator) capable of binding with GLPS in co-precipitation experiments. Our results may have important implications for our understanding on the molecular mechanisms of immunopotentiating polysaccharides from traditional Chinese medicine.

Animals↗

PubMed2004

A study on the immune receptors for polysaccharides from the roots of Astragalus membranaceus, a Chinese medicinal herb.

The immunopotentiating effect of the roots of Astragalus membranaceus, a medicinal herb, has been associated with its polysaccharide fractions (Astragalus polysaccharides, APS). We herein demonstrate that APS activates mouse B cells and macrophages, but not T cells, in terms of proliferation or cytokine production. Fluorescence-labeled APS (fl-APS) was able to selectively stain murine B cells, macrophages and a also human tumor cell line, THP-1, as determined in flow cytometric analysis and confocal laser scanning microscopy. The specific binding of APS to B cells and macrophages was competitively inhibited by bacterial lipopolysaccharides. Rabbit-anti-mouse immunoglobulin (Ig) antibody was able to inhibit APS-induced proliferation of, and APS binding to, mouse B cells. Additionally, APS effectively stimulated the proliferation of splenic B cells from C3H/HeJ mice that have a mutated TLR4 molecule incapable of signal transduction. These results indicate that APS activates B cells via membrane Ig in a TLR4-independent manner. Interestingly, macrophages from C3H/HeJ mice were unable to respond to APS stimulation, suggesting a positive involvement of the TLR4 molecule in APS-mediated macrophage activation. Monoclonal Ab against mouse TLR4 partially inhibited APS binding with macrophages, implying direct interaction between APS and TLR4 on cell surface. These results may have important implications for our understanding on the molecular mechanisms of immunopotentiating polysaccharides from medicinal herbs.

Animals↗

PubMed2004

[Heat shock induced transcription of hsp90alpha gene on chromatin template].

OBJECTIVE: A CAT reporter plasmid (pBLCAT3alpha1) driven by the promoter of hsp90alpha was in vitro assembled into chromatin to investigate the transcription activity of the reporter gene upon heat shock. METHODS: A competitive RT-PCR-based technique was used to quantify the promoter activity of hsp90alpha gene on chromatin or naked DNA templates in vitro. RESULTS: The in vitro transcription efficiency was first optimized by using different amounts of whole cell extracts from heat shock-treated HeLa cells. In vitro chromatin assembly was carried out with purified components of chromatin assembly associated factors, core histones and CAT reporter gene driven by the promoter of hsp90alpha gene. Results showed that chromatin formation repressed the in vitro transcription of the gene. CONCLUSION: The heat shock induced transcription of hsp90alpha gene on chromatin template is more efficient than that on naked DNA in vitro.

Chromatin Assembly and Disassembly↗

PubMed2003

[Adenovirus mediate FGF receptor gene transfer inhibits accelerated graft arteriosclerosis in rat aortic transplants].

OBJECTIVE: To evaluate the efficacy of adenovirus mediated fibroblast growth factor (FGF) receptor gene transfer in inhibition of accelerated graft arteriosclerosis (AGA) in rat aorta transplantation model. METHODS: The PCR product of rat sFGFR-1 cDNA was cloned into pCMV1-flag vector, then flag-sFGFR was cloned into pAdvs6a to construct recombinant vector pAv3flag-sFGFR1. The abdominal aorta was injected with buffer containing 5 x 10(9) pfu Adv3-sFGFR-1 and then resected in 30 DA rats. A section of abdominal aorta was resected in 30 PVG rats and the abdominal aorta of DA rats was transplanted. Av3-Nall and normal saline of the same volume were injected into the abdominal aortae of and rats as experimental controls and blank controls. Six rats were killed 5, 30, 60, and 90 days after the operation respectively. The transplanted aorta was harvested. RT-PCR was performed to detect the expression of sFGFR-1 gene with pCMV-Flag-sFGFR1 cDNA as positive control and the abdominal aorta RNA of non-transfected rats as negative control. Immunohistochemistry and HE staning were used to detect the localization and expression of sFGFR-1, and the morphology and cytology of the transplanted vessels. RESULTS: A construct encoding the FGFR1 ectodomain produced secreted sFGFR1 protein, which bound [(125)I]FGF-2 with high affinity and specificity, and inhibited FGF-2 stimulated 3T3 fibroblast proliferation in vitro. Gene transfer of sFGFR1 into rat aortic grafts, using an adenoviral vector, resulted in expression of sFGFR1 protein in endothelium and adventitia. Neointimal formation 60 and 90 days after transplantation was inhibited (P = 0.013) in aortic allograft transduced with sFGFR1, compared to allograft transduced with Null virus and saline. CONCLUSION: FGFs play a causal role in the development of AGA in the rat aortic transplant model and postulate that targeted interruption of FGF function could similarly reduce neointimal formation in transplant setting.

Adenoviridae↗

PubMed2003

Development and validation of a high-performance liquid chromatography-electrospray ionization-mass spectrometry assay for the determination of zaleplon in human plasma.

In this paper, a sensitive and rapid chromatographic procedure using a selective analytical detection method (electrospray ionization-mass spectrometry in selected-ion monitoring mode) in combination with a simple and efficient sample preparation step is first presented for the determination of zaleplon in human plasma. The separation of the analyte, internal standard, and possible endogenous compounds are accomplished on a phenomenex Luna 5-microm C8(2) column (250- x 4.6-mm i.d.) with methanol-water (75:25, v/v) as the mobile phase. In order to optimize the mass detection of zaleplon, several parameters such as ionization mode, fragmentor voltage, m/z ratios of ions monitored, type of organic modifier, and eluent additive in the mobile phase are discussed. An internal standard is selected to guarantee the quantitative accuracy. Each analysis takes less than 6 min. The calibration curve of zaleplon in the range of 0.1-60.0 ng/mL in plasma is linear with a correlation coefficient of > 0.9992, and the detection limit (s/n = 3) is 0.1 ng/mL. The within- and between-day variations (relative standard deviation) in the zaleplon plasma analysis are less than 2.4% (n = 15) and 4.7% (n = 15), respectively. The application of this method is demonstrated for the analysis of zeleplon plasma samples in a Phase-I human pharmacokinetic study.

Acetamides↗

PubMed2002

[Reversal of multidrug-resistance in human leukemia cell line K562/A02 by a cyclosporin D analogue PSC 833].

OBJECTIVE: To explore the efficacy of PSC 833 on multidrug resistance (MDR) reversal and its mechanism. METHODS: Human erythroleukemic cell line K562 and its doxorubicin-resistant counterpart K562/A02 were used in the study. Cytotoxicity was assessed by MTT assay, P-gp expression by direct immunofluorescence and mdr1 mRNA expression by reverse transcriptase polymerase chain reaction (RT-PCR) with beta-actin as internal control. Intracellular DNR retention was measured with flow cytometry. RESULTS: K562/A02 cells displayed high levels of mdr1 mRNA and P-glycoprotein and reduced DNR retention compared to their parental K562 cells. 1 micromol/L of PSC 833 had no effect on the levels of mdr1 mRNA and P-gp expression in K562/A02 cells (P > 0.05). PSC 833 conferred a dose-dependent increase on chemosensitivity of K562/A02 to DNR, and its effect was at least 3-fold more potent than that of CsA or Ver. PSC 833 could increase DNR retention in K562/A02 cells. A 100.9% restoration of intracellular DNR retention of the level of K562 cells was gained by PSC 833 at 1.0 micromol/L in K562/A02 cells, whereas only a 86.9% restoration of DNR retention was obtained by CsA at 10 micromol/L in the K562/A02 cells. No effect on DNR sensitivity and retention was found in K562 cells (P > 0.05). CONCLUSION: PSC 833 is at least 3 approximately 10 fold more potent than CsA or Ver with respect to MDR reversing activity, and it may function by inhibiting the function of P-gp and not reducing the levels of mdr1 mRNA and P-gp directly.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMedDate not supplied

PEI-g-chitosan, a novel gene delivery system with transfection efficiency comparable to polyethylenimine in vitro and after liver administration in vivo.

Polyethylenimine-graft-chitosan (PEI-g-chitosan) was synthesized by performing cationic polymerization of aziridine in the presence of water-soluble oligo-chitosan (M(n) = 3400). The absolute molecular weight and chemistry of the PEI-g-chitosan obtained were characterized using GPC, 13C and 1H NMR, respectively. The results indicated that all the amines of chitosan were grafted with oligo-PEI, and the average length of the oligo-PEI side chains was determined by the feed molar ratio of aziridne/amine in chitosan. PEI-g-chitosan of M(n) = 7400 with a polydispersity index (PDI) of 1.50, and PEI side chains of M(n) = 206 was prepared for gene delivery. Gel electrophoresis showed that DNA migration was retarded completely at a N/P ratio of 2.5/1, indicating good DNA condensation capability of PEI-g-chitosan. The sizes and the zeta-potentials of the complexes of PEI-g-chitosan/DNA were characterized. The cytotoxicity of PEI-g-chiotsan was evaluated, and the results reflected that PEI-g-chitosan had a lower cytotoxicity than PEI (25 K). Gene transfection efficiency of PEI-g-chitosan in HepG2, HeLa, and primary hepatocytes cells and after administration in the common bile duct of rat liver was determined. Remarkably, PEI-g-chitosan showed a higher transfection efficiency than that of PEI (25 K) both in vitro and in vivo. The systematic distribution and the distribution in liver of the gene expression of the complexes of PEI-chitosan/DNA were determined as well.

Animals↗

PubMedDate not supplied

Simple and robust two-layer matrix/sample preparation method for MALDI MS/MS analysis of peptides.

Recent advances in MALDI MS/MS instrumentation allow a high degree of automation in the efficient detection of peptide fragment ions that can be used for protein identification. However, the performance of the technique is dependent on the MALDI sample preparation. We present a simple and robust two-layer sample preparation method tailored for sensitive and reproducible generation of MALDI MS/MS data. This method produces a strong and uniform crystal layer which allows acquisition of high quality MS/MS spectra over the entire sample surface area. Furthermore, due to its crystal strength, the matrix/sample layer can be washed extensively on target, enabling direct analysis of samples containing impurities, such as salts and surfactants. This method is demonstrated to be very useful in routine analysis of in-gel tryptic digests of silver-stained protein gel spots, without the need of desalting steps or hunting for "hot" spots. As an example, seven threonine-phosphorylated proteins involved in signal transduction in response to growth factor stimulation within the lipid raft fractions of the IMR5 neuroblastoma cells have been identified using differential gel display, in-gel digestion and MALDI MS/MS with the new two-layer sample preparation method. Some of these proteins have the functions of maintaining raft structure or cell signaling.

Cell Line, Tumor↗