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Biomedical subjects

Xing Chen

Publications and source records attributed to Xing Chen.

At least 37 records · Page 2Linked to original sources
PubMed2005

The ability of AIF-1 to activate human vascular smooth muscle cells is lost by mutations in the EF-hand calcium-binding region.

Allograft Inflammatory Factor-1 (AIF-1) is a cytoplasmic calcium-binding protein expressed in vascular smooth muscle cells (VSMC) in response to injury or cytokine stimulation. AIF-1 contains a partially conserved EF-hand calcium-binding domain, and participates in VSMC activation by activation of Rac1 and induction of Granulocyte-Colony Stimulating Factor (G-CSF) expression; however, the mechanism whereby AIF-1 mediates these effects is presently uncharacterized. To determine if calcium binding plays a functional role in AIF-1 activity, a single site-specific mutation was made in the EF-hand calcium-binding domain to abrogate binding of calcium (AIF-1DeltaA), which was confirmed by calcium overlay. Functionally, similar to wild-type AIF-1, AIF-1DeltaA was able to polymerize F-actin in vitro. However, in contrast to wild-type AIF-1, over-expression of AIF-1DeltaA was unable to increase migration or proliferation of primary human VSMC. Further, it was unable to activate Rac1, or induce G-CSF expression to the degree as wild-type AIF-1. Taken together, modification of the wild-type EF-hand domain and native calcium-binding activity results in a loss of AIF-1 function. We conclude that appropriate calcium-binding potential is critical in AIF-1-mediated effects on VSMC pathophysiology, and that AIF-1 activity is mediated by Rac1 activation and G-CSF expression.

Amino Acid Substitution↗
PubMed2005

Tryptamine and homotryptamine-based sulfonamides as potent and selective inhibitors of 15-lipoxygenase.

A series of inhibitors of mammalian 15-lipoxygenase based on tryptamine and homotryptamine scaffolds is described. Compounds with aryl substituents at C-2 of the indole core of tryptamine and homotryptamine sulfonamides (e.g., 37a-p) proved to be potent inhibitors of the isolated enzyme. Selected compounds also demonstrated desirable inhibition selectivities over isozymes 5- and P-12-LO.

Animals↗
PubMed2005

Cloning and biochemical properties of CDPK gene OsCDPK14 from rice.

A rice CDPK gene, OsCDPK14 (AY144497), was cloned from developing caryopses of rice (Oryza sativa cv. Zhonghua 15). Its cDNA sequence (1922 bp) contains an ORF encoding a 514 amino acids protein (56.7kD, pl 5.18). OsCDPK14 shows the typical structural features of the CDPK family, including a conserved catalytic Ser/Thr kinase domain, an autoinhibitory domain and a CaM-like domain with four putative Ca2+-binding EF hands. Subcellular targeting indicated that OsCDPK14 was located in the cytoplasm, probably due to the absence of myristoylation and palmitoylation motifs. OsCDPK14 was expressed in Escherichia coli and purified from bacterial extracts. The recombinant protein was shown to be a functional protein kinase using Syntide-2, a synthetic peptide. Kinase activity was shown to be Ca2+-dependent, and this activation was strongly enhanced by Mn2+ and inhibited by W7 in vitro. These results provide significant insights into the regulation and biochemical properties of OsCDPK14, suggesting OsCDPK14 may be a signal factor of cytoplasm in rice plant.

Amino Acid Sequence↗
PubMed2005

[Bayesian representation of prior information and MCMC method in microwave imaging].

Microwave imaging for dielectric objects was considered in this paper. Applying Bayesian approach to represent prior information about permittivity distribution of observed object by prior probability density and combine measurements information of scattering field, we obtained posterior probability density that included synthetic information about the observed object. And then, Gibbs sampler, one of Markov Chain Monte Carlo method, was used to sample the posterior probability density. The sample mean was regarded as an evaluation of the permittivity distribution. The results of simulation imaging with "blocky" objects showed that this set of methods made good use of information and had the advantages of feasibility and very strong anti-noise ability. In addition,it is capable of describing (definite or indefinite) prior information in a convenient and controllable way, as well as capable of giving the "complete" solution, i.e., the occurrence probability of every permittivity distribution.

Bayes Theorem↗
PubMed2004

Expression of granulocyte colony-stimulating factor is induced in injured rat carotid arteries and mediates vascular smooth muscle cell migration.

Granulocyte colony-stimulating factor (G-CSF) is a lineage-restricted hematopoietic growth factor that stimulates proliferation and maturation of hematopoietic progenitors and is a known powerful mobilizer of bone marrow-derived stem cells. Very little has been reported on G-CSF expression and modulation of vascular smooth muscle cell (VSMC) activation. The purpose of this study was to characterize the expression and effects of G-CSF on primary human VSMC and balloon angioplasty-injured rat carotid arteries. In cultured human VSMC, G-CSF mRNA and protein expression are induced by several cytokines, with the most potent being fetal calf serum and T-lymphocyte-conditioned media. G-CSF is not expressed in naive rat carotid arteries but is induced in neointimal SMC in carotid arteries subject to balloon angioplasty. G-CSF is chemotactic for human VSMC. There is a significant difference between unstimulated cells and those treated with G-CSF at 100 and 1,000 pg/ml (P < 0.01 and 0.05 for 3 experiments). G-CSF also activates the GTPase Rac1, a regulator of cellular migration in VSMC. Inhibition of Rac1 inhibits G-CSF-driven VSMC migration. Important signal transduction protein kinases, including p44/42 MAPK, Akt, and S6 kinase, are also activated in response to G-CSF. This is the first report describing the expression of G-CSF in injured arteries and the multiple effects of G-CSF on VSMC activation. Together, our data suggest that G-CSF is an important mediator of inflammatory cell-VSMC communication and VSMC autocrine activation and may be an important mediator of the VSMC response to injury.

Angioplasty, Balloon↗
PubMed2004

AIF-1 expression modulates proliferation of human vascular smooth muscle cells by autocrine expression of G-CSF.

OBJECTIVE: Allograft inflammatory factor-1 (AIF-1) is associated with vascular smooth muscle cell (VSMC) activation and vascular injury. The purpose of this study was to characterize the molecular mechanism of AIF-1 growth-enhancing effects in human VSMC. METHODS AND RESULTS: Primary human VSMCs were stably transduced with AIF-1 retrovirus (RV). Impact on cell growth was evaluated by the increase in cell number, and the effects on gene expression were determined by cDNA microarray analysis. AIF-RV overexpressing cells grew significantly more rapidly than empty-RV control cells in growth medium and serum-reduced medium (P<0.01 and 0.02, respectively). cDNA microarray analysis and Western blotting on serum-starved AIF-1-transduced VSMCs identified increased mRNA expression of several cell cycle proteins and, surprisingly, the cytokine G-CSF. Addition of G-CSF caused a 75% increase in proliferation of VSMCs in the absence of serum growth factors. The proliferative effects of AIF-1 were abrogated by neutralizing antibodies to G-CSF (P<0.05), and AIF-1-transduced VSMCs are chemotactic for human monocytes. Increased expression of G-CSF and colocalization with AIF-1 positive cells were seen in diseased, not normal human coronary arteries. CONCLUSIONS: This study indicates that AIF-1 enhances VSMC growth by autocrine production of G-CSF, and AIF-1 expression may influence VSMC-inflammatory cell communication.

Autocrine Communication↗
PubMed2004

Development of cancer vaccines using autologous and recombinant high molecular weight stress proteins.

High molecular weight heat shock proteins (HSPs), hsp110 and grp170, derived from cancer cells have been previously shown to elicit tumor-specific immunity. This phenomenon is attributed to the antigenic peptides associated with the HSPs. Based on the unique chaperoning properties of these HSPs, a new vaccination strategy has been recently developed to elicit antigen-specific antitumor immunity. This approach utilizes tumor-associated antigens naturally complexed to these highly efficient molecular chaperones under heat shock conditions. This chapter focuses on the methodologies of these two vaccine strategies: I. purification of hsp110 and grp170 from tumor tissue or cell lines; II. generation and characterization of in vitro HSP-antigen complexes by heat shock using recombinant HSPs derived from a baculovirus protein expression system.

Animals↗
PubMed2004

[Preparation of rabbit anti-STAT5 antibody and its application in breast cancer diagnosis].

AIM: To prepare and purify rabbit antibody against STAT5 and evaluate its application in breast cancer diagnosis. METHODS: The rabbits were immunized with recombinant mouse STAT5 protein for preparing antibody against STAT5. The purity and specificity of the antibody were analyzed by Western blot. The proteins expressed in human breast cancer cell lines and normal breast tissue and breast cancer tissues were analyzed by Western blot and immunohistochemical staining with the anti-STAT5 antibody. RESULTS: The titer of anti-STAT5 antibody in the serum was 1:204 800 (A(450)=1.07) at 6 weeks after being immunized with STAT5. The SDS-PAGE and Western blot analysis showed that there was a obvious protein band with M(r) 90 000-95 000, confirming the specificity of obtained anti-STAT5 antibody. The expression of STAT5 could be detected with Western blot in both human breast cancer cell lines MCF-7 and MDA-MB-231. Immunohistochemical staining indicated that STAT5 was expressed in cytoplasm of normal breast tissues while in cytoplasm and nucleolus of breast cancer tissues. CONCLUSION: The rabbit anti-STAT5 antibody with high titer and specificity has been prepared. The STAT5 is expressed in cytoplasm of normal breast tissue, and in nucleolus of breast cancer tissue. The preparation of anti-STAT5 antibody provides an important reagent for clinical diagnosis of breast cancer.

Animals↗
PubMed2004

[Carotenoid biosynthesis in plants and application of its relative genes in gene engineering].

In recent years, the cloning and characterization of carotenogenic genes has provided new gene resources and molecular tools, which can be utilized to genetically alter carotenoid composition and enrich the carotenoid content in vivo by gene engineering technique for plants. Increasing evidences in the studies of biochemistry of carotenogenesis and its regulation in vivo make the genetically manipulating carotenoid biosynthesis pathway to be possible in plants. In this review, the carotenoid biosynthesis pathways and the some genes involved in this pathway in plants are summarized, and some progresses including author's work in the successful manipulation of carotenoid composition and content in plants using gene-transfer technology are also covered.

Carotenoids↗
PubMed2003

The chaperoning properties of mouse grp170, a member of the third family of hsp70 related proteins.

The 170 kDa glucose-regulated protein (grp170) is an endoplasmic reticulum resident protein that shares some sequence homology with both the hsp70 and hsp110 heat shock protein (hsp) families, yet is representative of a third and unique family of stress proteins. Despite observations indicating important roles in normal cellular functions, the in vitro chaperone properties of grp170 have not been rigorously examined. We have cloned mouse grp170 and expressed the recombinant protein in a baculovirus expression system. The function of recombinant grp170 was then assessed by determining its ability to bind to and prevent aggregation of heat-denatured luciferase. Grp170 maintains heat-denatured luciferase in a soluble state in the absence of ATP. In the presence of rabbit reticulocyte lysate, grp170 can refold and partially restore function to denatured luciferase. The chaperoning function of grp170 was also studied using domain deletion mutants, designed using the crystal structure of DnaK and the theoretical secondary structure of hsp110 as guides. Unlike hsp70 and hsp110, grp170 appears to have two domains capable of binding denatured luciferase and inhibiting its heat-induced aggregation. The two domains were identified as being similar to the classical beta-sandwich peptide binding domain and the C-terminal alpha-helical domain in hsp70 and hsp110. The ability of the C-terminal region to bind peptides is a unique feature of grp170.

Animals↗
PubMed2003

HSP110-HER2/neu chaperone complex vaccine induces protective immunity against spontaneous mammary tumors in HER-2/neu transgenic mice.

Heat shock proteins (HSPs) are shown to be strong immunoadjuvants, eliciting both innate and adaptive immune responses against cancers. HSP110 is related in sequence to HSP70 and is approximately 4-fold more efficient in binding to and stabilizing denatured protein substrates compared with HSP70. In the present study we evaluated the ability of a heat shock complex of HSP110 with the intracellular domain (ICD) of human HER-2/neu to elicit effective antitumor immune responses and to inhibit spontaneous mammary tumors in FVB-neu (FVBN202) transgenic mice. The HSP110-ICD complex was capable of breaking tolerance against the rat neu protein and inhibiting spontaneous mammary tumor development. This vaccine induced ICD-specific IFN-gamma and IL-4 production. Depletion studies revealed that CD8(+) T cells were involved in protection against challenge with mouse mammary tumors, whereas CD4(+) T cells revealed partial protection. Increased IgG2a Ab titer in the sera of tumor-free animals after vaccination and elevated CD4(+) CD25(+) regulatory T cells in the PBL of tumor-bearing animals suggested that IFN-gamma-producing Th1 cells may be responsible for partial protection of CD4(+) T cells against the mammary tumor challenge, whereas CD4(+)CD25(+) regulatory T cells (Th2 cells) may suppress the antitumor immune responses. Together, these results suggest that HSP110-ICD complex can elicit effective IFN-gamma-producing T cells against spontaneous mammary tumors and that up-regulation of CD4(+) CD25(+) regulatory T cells may prevent complete eradication of the tumor following immunotherapy.

Animals↗
PubMed2003

Targeted immunotherapy using reconstituted chaperone complexes of heat shock protein 110 and melanoma-associated antigen gp100.

This report defines a novel approach to heat shock protein vaccine formulation that takes advantage of the chaperoning property of heat shock protein hsp110 to efficiently bind a large protein substrate (specifically, human melanoma-associated antigen gp100) during heat shock. We demonstrate that hsp110 can form chaperone complexes with gp100 and prevent heat-induced aggregation of gp100. The resultant natural hsp110-gp100 complexes are strongly immunogenic as determined by their ability to elicit an antigen-specific IFN-gamma production and a cytotoxic T-cell response. Immunization with the hsp110-gp100 complex protected mice against subsequent challenge with human gp100-transduced B16 melanoma, which involves both CD4(+) and CD8(+) T-cell populations. Administration of the hsp110-gp100 vaccine also significantly suppressed the growth of established tumors in a therapeutic model. Furthermore, the hsp110-gp100 chaperone complex exhibited inhibitory effects on the progression of wild-type B16 tumor, suggesting that the induced immune response by human gp100 cross-reacts with mouse gp100. More importantly, the antitumor response obtained with the hsp110-gp100 complex is more potent than that obtained using Complete Freund's Adjuvant with gp100, whereas no response was observed against mouse hsp110 itself. Thus, the use of hsp110 to form natural chaperone complexes with tumor protein antigens such as gp100 represents a powerful approach to therapeutic vaccine formulation with significant potential for clinical application.

Animals↗
PubMed2003

[Influence of modeling sodium on the dialysis disequilibrium syndrome in hemodialysis].

OBJECTIVE: To observe the influence of modeling sodium on the dialysis disequilibrium syndrome in hemodialysis. METHODS: Sixteen patients received hemodialysis for the first time. Eight of them received the hemodialysis in the order of common sodium, modeling sodium, common sodium, and modeling sodium, whereas the other 8 patients were treated in the order of modeling sodium, common sodium, modeling sodium, and common sodium. The symptoms of the dialysis disequilibrium syndrome were observed and blood sodium concentration was examined before and after the dialysis. RESULTS: The main symptoms of the dialysis disequilibrium syndrome were headache, nausea, vomiting, hypertension, and dyspnea. Modeling sodium hemodialysis could significantly decrease the occurrence of these symptoms (P < 0.05). The blood sodium concentration after the hemodialysis was not significantly changed compared with that before the hemodialysis (P > 0.05). CONCLUSION: Modeling sodium hemodialysis can effectively prevent the occurrence of the dialysis disequilibrium syndrome without increasing the natrium load of the patients.

Acid-Base Equilibrium↗
PubMed2003

Hirulog-like peptide reduces restenosis and expression of tissue factor and transforming growth factor-beta in carotid artery of atherosclerotic rabbits.

Restenosis is responsible to approximately 30% of long-term failure following therapeutic vascular procedures. Thrombosis plays a key role in the development of restenosis. Thrombin-specific inhibitors have been considered as one type of candidates for the prevention of restenosis. Previous studies by our group demonstrated that a novel thrombin-specific inhibitor, hirulog-like peptide (HLP), reduced balloon catheter-induced neointima formation in rat carotid arteries. The present study examined the effect of HLP on angioplasty-induced restenosis in carotid arteries of atherosclerotic rabbits. New Zealand white rabbits were subject to air desiccation of the lumen of the right carotid arteries, then received high cholesterol/fat diet for 3 weeks. The rabbits were intravenously infused with HLP (1.6 mg/(kg/h)) or saline (n=7 per group) for 4 h started before angioplasty which dilated atherosclerotic lesions in right common carotid artery. Four weeks after the angioplasty, neointimal area, stenosis and neointima/media ratio in injured carotid arteries were reduced in atherosclerotic rabbits treated with HLP compared to saline controls by 62, 39 and 59% (P<0.05). The expression of tissue factor (TF) and transforming growth factor (TGF)-beta in the neointima of carotid arteries of rabbits treated with HLP was significantly weaker than saline controls (P<0.05 or <0.01). Activated partial thromboplastin time and bleeding time in HLP-treated rabbits were not significantly prolonged compared to controls. The results of the present study suggest that HLP may substantially reduce angioplasty-induced restenosis in atherosclerotic rabbits without increasing bleeding tendency. The inhibition on the expression of TF and TGF-beta in the neointima of the arterial wall may contribute to the preventive effect of HLP on restenosis in atherosclerotic rabbits.

Animals↗
PubMed2003

[Teratogenicity of bisphenol A on post-implanted rat and mouse embryos: an in vitro study].

In order to evaluate the developmental toxicity of BPA and to investigate the possible mechanism of it in vitro, whole embryo culture was used for the study. The embryos that removed from mother mice on gestational 8.5d (GD8.5) and mother rats on gestational 9.5d (GD9.5) were cultured immediately in centrifugal serum (ICS) with a series of concentrations of 0, 40, 60, 80, 100 mg/L of BPA for 48 h to evaluate the embryo development and morphological differentiation. The results showed that the BPA inhibited the development of embryos in vitro and there was a dose-response relationship between concentrations of BPA. At high level (> or = 60 mg/L), BPA could delayed the growth and cardiac tube differentiation of visceral yolk sac (VYS), and induced various embryo defects, including abnormal neural system, arch, optic, flexion and small limb bud, etc. It is concluded that at high level, BPA had toxicity to mice and rat embryos in vitro. The damage on structure and function of VYS might be part of teratogenic mechanisms of BPA.

Animals↗