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Dan Luo

Publications and source records attributed to Dan Luo.

36 records · Page 2Linked to original sources
PubMed2004

Charge-reversal amphiphiles for gene delivery.

Delivering a missing gene or a functional substitute of a defective gene has the potential to revolutionize current medical care. Of the two gene delivery approaches, viral and synthetic vectors, synthetic cationic vectors possess several practical advantages but suffer from poor transfection efficiency. A new approach to gene delivery using charge-reversal amphiphiles is described. This synthetic vector transforms from a cationic to an anionic amphiphile intracellularly. This amphiphile performs two roles: first, it binds and then releases DNA, and second, as an anionic multicharged amphiphile, it destabilizes lipid bilayers. A charge-reversal amphiphile was synthesized and fully characterized, including the supramolecular complex it forms with DNA. Enhanced gene transfection was observed using these vectors compared to current cationic amphiphiles.

Animals↗
PubMed2004

A self-assembled, modular DNA delivery system mediated by silica nanoparticles.

Due to the growing concerns over the toxicity and immunogenicity of viral DNA delivery systems, DNA delivery via non-viral routes has become more desirable and advantageous. The ideal non-viral DNA delivery system should be a synthetic system that mimics viral vectors. It should also be biocompatible, efficient, and modular so that it is tunable to various applications in both research and clinical settings. The first successful step towards this modular synthetic DNA delivery system is demonstrated: a three-component transfection system mediated by silica nanoparticles. Dense silica nanoparticles serve as an uptake-enhancing component by physical concentration at the cell surface; enhanced transfection due to the particles is seen with almost every transfection reagent tested with little toxicity. In addition, a mathematical model has been built that successfully predicts several important parameters of transfection enhancement. This three-component transfection system lays the groundwork for a future multi-component modular synthetic DNA delivery system that may be useful in non-viral gene therapy and DNA vaccination.

Animals↗
PubMed2004

Differential expression of genes during aflatoxin B(1)-induced hepatocarcinogenesis in tree shrews.

AIM: Through exploring the regulation of gene expression during hepatocarcinogenesis induced by aflatoxin B(1) (AFB(1)), to find out the responsible genes for hepatocellular carcinoma (HCC) and to further understand the underlying molecular mechanism. METHODS: Tree shrews (Tupaia belangeri chinensis) were treated with or without AFB(1) for about 90 weeks. Liver biopsies were performed regularly during the animal experiment. Eight shares of total RNA were respectively isolated from 2 HCC tissues, 2 HCC-surrounding non-cancerous liver tissues, 2 biopsied tissues at the early stage (30th week) of the experiment from the same animals as above, 1 mixed sample of three liver tissues biopsied at the beginning (0th week) of the experiment, and another 1 mixed sample of two liver tissues from the untreated control animals biopsied at the 90th week of the experiment. The samples were then tested with the method of Atlas(TM) cDNA microarray assay. The levels of gene expression in these tissues taken at different time points during hepatocarcinogenesis were compared. RESULTS: The profiles of differently expressed genes were quite different in different ways of comparison. At the same period of hepatocarcinogenesis, the genes in the same function group usually had the same tendency for up- or down-regulation. Among the checked 588 genes that were known to be related to human cancer, 89 genes (15.1%) were recognized as "important genes" because they showed frequent changes in different ways of comparison. The differentially expressed genes during hepatocarcinogenesis could be classified into four categories: genes up-regulated in HCC tissue, genes with similar expressing levels in both HCC and HCC-surrounding liver tissues which were higher than that in the tissues prior to the development of HCC, genes down-regulated in HCC tissue, and genes up-regulated prior to the development of HCC but down-regulated after the development of HCC. CONCLUSION: A considerable number of genes could change their expressing levels both in HCC and in HCC-surrounding non-cancerous liver tissues. A few modular genes were up-regulated only in HCC but not in surrounding liver tissues, while some apoptosis-related genes were down-regulated in HCC and up-regulated in surrounding liver tissues. To compare gene-expressing levels among the liver tissues taken at different time points during hepatocarcinogenesis may be helpful to locate the responsible gene (s) and understand the mechanism for AFB(1) induced liver cancer.

Aflatoxin B1↗
PubMed2004

A new solution for improving gene delivery.

Intense research has focused on methods for overcoming the various barriers to DNA delivery while simultaneously reducing toxicity. Recently, Yuan and colleagues discovered a 'leakage route', whereby viral vectors escaped the injection site and entered the systemic circulation and contributed to the systemic toxicity in cancer gene therapy. They also demonstrated that alginate solution sealed this leak. Although their work focused on intratumoral injection of viral vectors, the findings can be extended to drug delivery in general, particularly DNA delivery.

Adenoviridae↗
PubMed2004

3,4,5,6-Tetrahydroxyxanthone protects against myocardial ischemia-reperfusion injury in rats.

In the present study, we tested the protective effect of 3,4,5,6-tetrahydroxyxanthone, a synthetic xanthone derivative, on myocardial ischemia-reperfusion injury in rats. Ischemia-reperfusion injury was induced by 30 min of global ischemia and 30 min of reperfusion in isolated rat hearts or 30 min coronary artery occlusion and 120 min reperfusion in vivo, respectively. Heart rate, coronary flow (CF), left ventricular pressure (LVP), and its first derivative (+/- dp/dt (max)) were recorded, and the activity of creatine kinase in coronary effluent and tumor necrosis factor-alpha (TNF-alpha) content in myocardial tissues were measured in vitro. The activity of serum creatine kinase, the level of TNF-alpha and interleukin-6 (IL-6), and myocardial infarct size were measured in vivo. 3,4,5,6-tetrahydroxyxanthone (30, 100 or 300 microM) caused a significant improvement of cardiac function (LVP and +/- dp/dt (max)) and a decrease in the release of creatine kinase in coronary effluent as well as the level of TNF-alpha in myocardial tissues in vitro. 3,4,5,6-tetrahydroxyxanthone (0.5 or 1.0 mg/kg, i.v.) also markedly decreased infarct size and the release of creatine kinase and TNF-alpha, and increased serum IL-6 level in vivo. These results suggest that 3,4,5,6-tetrahydroxyxanthone possesses a protective effect on myocardial ischemia-reperfusion injury, and that the protective effects of 3,4,5,6-tetrahydroxyxanthone may be related to inhibition of TNF-alpha production and stimulation of IL-6 generation by inhibition of ROS production.

Animals↗
PubMed2004

Solar-simulated irradiation evokes a persistent and biphasic IL-1alpha response.

Exposure of skin to solar-simulated irradiation generates a multitude of adaptive responses including cytokine transcription, synthesis and secretion. Interleukin-1 (IL-1) is one of the cytokines induced in epidermal cells in response to UV irradiation. It displays a broad range of mitogenic and inflammatory activities including fibroblast proliferation and T-cell activation. There are two forms, IL-1alpha and IL-1beta; and IL-1alpha is the predominant form secreted by epidermal keratinocytes. UV-induced modulations of IL-1alpha message levels have been extensively studied within the first 48 h after irradiation, but longer term changes and impact on IL-1alpha cellular protein levels are virtually unexplored. We now report that cells of keratinocyte origin (SCC 12F) respond to a single physiologic dose of solar-simulated irradiation with both early (8 h) and late (72 h) peaks of IL-1alpha mRNA induction. UV-stimulated IL-1alpha secretion is increased above sham-irradiated control secretion for at least 96 h after irradiation. Our study provides evidence that UV-induced adaptive cutaneous responses persist for at least several days, and suggests that different mechanisms may mediate the early vs. late inductions.

Carcinoma, Squamous Cell↗
PubMed2003

Controlled assembly of dendrimer-like DNA.

DNA possesses many desirable chemical/physical properties as a polymeric material. With the myriad of tools available to manipulate DNA, there is great potential for using DNA as a generic instead of a genetic material. Although much progress has been made in DNA computing and DNA nanotechnology, the full achievement of DNA-based materials has not yet been realized. As almost all DNA molecules are either linear or circular, to rationally construct DNA materials one must first create additional shapes of DNA as basic building blocks. In addition, these DNA building blocks must be readily incorporated into larger structures in a controlled manner. Here, we show the controlled assembly of dendrimer-like DNA (DL-DNA) from Y-shaped DNA (Y-DNA). The synthesis of Y-DNA and controlled assembly of DL-DNA were robust and efficient; the resulting DL-DNA was stable and almost monodisperse. The multivalent DNA dendrimers can be either isotropic or anisotropic, providing great potential to link other entities.

Base Sequence↗
PubMed2003

The regulation of catalase gene expression in mouse muscle cells is dependent on the CCAAT-binding factor NF-Y.

Catalase is an antioxidant enzyme whose expression is transcriptionally regulated and tissue-specific. The level of expression determines, in part, the susceptibility of a cell to oxidative stress. Skeletal muscle is a tissue that experiences high levels of oxidative stress during normal metabolic activity, so the expression of antioxidant enzymes is critical to preventing cellular damage. To study the transcriptional regulation of the catalase gene in mouse muscle cells, the 5'-flanking region of the mouse catalase gene was isolated from genomic DNA. The transcriptional activity of the 5'-flanking region was investigated in transiently transfected murine myoblasts using a promoter-less luciferase reporter vector and site-directed mutagenesis. Strikingly, we found that nearly all of the transcriptional activity was restricted to the final 191 bp of the greater than 2.5 kb of the 5'-flanking region examined. Of the potential consensus binding sites for transcriptional regulators within this 191-bp region, we identified two CCAAT boxes and no other consensus sites that were important for the transcriptional activity of this promoter. Gel shift and super shift assays indicated that the transcription factor NF-Y bound to both CCAAT boxes. Furthermore, co-transfection of reporter constructs with NF-Y expression vectors into Drosophila SL2 cells demonstrated NF-Y-mediated transcriptional activation of the catalase gene. Interestingly, there were no nearby sites that appeared to interact with either NF-Y binding sites, and thus it appears that NF-Y acts as a bona fide transcription factor for catalase gene expression in mouse muscle cells. These data provide the first examination of the regulation of the mouse catalase gene and indicate unique aspects of its regulation that may pertain to the tissue-specific patterns of expression.

5' Untranslated Regions↗
PubMed2000

Growth-inhibiting effects of taxol on human liver cancer in vitro and in nude mice.

AIM:To investigate the effects of taxol on SMMC-7721 human hepatoma and its mechanisms.METHODS:In vitro cell growth was assessed by trypan blue exclusion method. Experimental hepatoma model was established by seeding SMMC-7721 cells subcutaneously into Balb/c (nu/nu) nude mice. In vivo tumor growth was determined by measurement of tumor diameter with Vernier calipers. The syntheses of DNA, RNA and protein were analyzed by incorporation of (3)H-thymidine, (3)H-uridine and (3)H-leucine respec-tively. Using light and electron microscopes to observe the morphological changes of cells including mitosis and apoptosis.RESULTS:Taxol was effective against SMMC-7721 human hepatoma cell growth in the ranges of 2.5nmol/L-10nmol/L with mitotic arrest and apoptosis in vitro. DNA, RNA and protein syntheses in cells were also obviously suppressed by in vitro treatment of taxol for 72h. Taxol at 2.5nmol/L reduced (3)H-thymidine uptake to about 34% of the control value (P<0.05). Increasing the dose of taxol to 20nmol/L resulted in a greater decrease in (3)H-thymidine incorporation to 60% of the control value (P < 0.01). At a concentration of 20nmol/L, the (3)H-uridine and (3)H-leucine uptakes were reduced to 52% (P<0.05) and 63% (P<0.01), respectively. In vivo,taxol significantly inhibited SMMC-7721 tumor growth at 10mg/kg, i.p., once daily for 10d. A more than 90% decrease in tumor volume was observed by day 11 (P < 0.01) similarly with mitotic arrest and cell apoptosis.CONCLUSION:Taxol has a marked anticancer activity in SMMC-7721 human hepatoma both in vitro and in nude mice. Its mechanisms might be associated with mitotic arrest, subsequently, apoptosis of the hepatoma cells. No obvious toxicity was observed with in vivo administration of taxol.

Journal Article↗
PubMed1998

Analysis of N-ras gene mutation and p53 gene expression in human hepatocellular carcinomas.

AIM:To study the relationship between N-ras gene mutation and p53 gene expression in the carcinogenesis and the development of human hepatocellular carcinomas (HCC).METHODS:The N-ras gene mutation and the p53 gene expression were analyzed in 29 cases of HCC by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) and immunohistochemistry.RESULTS:Thirteen cases of HCCs were p53 positive (44.8%), which showed a rather high Cpercen-tage of p53 gene mutation in Guangxi. The aberrations at N-ras codon 2-37 were found in 79.31% of HCCs and 80.77% of adjacent non-tumorous liver tissues. More than 2 point mutations of N-ras gene were observed in 22 cases (75.86%). Twelve cases (41.37%) of HCCs showed both N-ras gene mutation and p53 gene expression.CONCLUSION:N-ras gene and p53 gene may be involved in the carcinogenesis and the development of HCC.That 38% of HCCs with N-ras gene mutation did not express p53 protein indicates that some other genes or factors may participate in the carcinogenesis and the development of HCC.

Journal Article↗
PubMedDate not supplied

The regulation of Notch signaling in muscle stem cell activation and postnatal myogenesis.

The Notch signaling pathway is an evolutionarily conserved pathway that is critical for tissue morphogenesis during development, but is also involved in tissue maintenance and repair in the adult. In skeletal muscle, regulation of Notch signaling is involved in somitogenesis, muscle development, and the proliferation and cell fate determination of muscle stems cells during regeneration. During each of these processes, the spatial and temporal control of Notch signaling is essential for proper tissue formation. That control is mediated by a series of regulatory proteins and protein complexes that enhance or inhibit Notch signaling by regulating protein processing, localization, activity, and stability. In this review, we focus on the regulation of Notch signaling during postnatal muscle regeneration when muscle stem cells ("satellite cells") must activate, proliferate, progress along a myogenic lineage pathway, and ultimately differentiate to form new muscle. We review the regulators of Notch signaling, such as Numb and Deltex, that have documented roles in myogenesis as well as other regulators that may play a role in modulating Notch signaling during satellite cell activation and postnatal myogenesis.

Animals↗
PubMedDate not supplied

Cellular fate of a modular DNA delivery system mediated by silica nanoparticles.

Development of efficient molecular medicines, including gene therapeutics, RNA therapeutics, and DNA vaccines, depends on efficient means of transfer of DNA or RNA into the cell. Potential problems, including toxicity and immunogenicity, surrounding viral methods of DNA delivery have necessitated the use of nonviral, synthetic carriers. To better design synthetic carriers, or transfection reagents, the modular design of viruses has inspired a modular approach to DNA and RNA delivery. Each modular component can be designed to circumvent each of the many barriers. The modular approach will allow modification of individual components for a specific application. By utilizing a dense silica nanoparticle to form a ternary complex, transfection efficiency of a DNA-transfection reagent complex was increased by a factor of approximately 10 by concentrating the DNA at the surface of cells. Surface modification of the silica nanoparticles allowed determination of the cellular uptake mechanism with only minor alteration of transfection efficiency. Nanoparticles are internalized by an endosome-lysosomal route followed by perinuclear accumulation. The modification mechanism confirms that surface modification of the modular system can allow specific moieties to be incorporated into the modular system without significant alteration of the transfection efficiency. By showing that the modular system based upon concentration of DNA at the level of the cell can be used to increase transfection efficiency, we have shown that further modification of the system may better target DNA delivery and overcome other barriers of DNA expression.

Animals↗