Yun Bai

Peking University Health Science Center, Peping, Beijing, China

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Publications (13)25.5 Total impact

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    ABSTRACT: Neuropathologic processes such as cerebral ischemia can enhance neurogenesis. Angiopoietin-1 (Ang1) emerges as a critical regulator of physiological and pathological angiogenesis during embryonic and postnatal life. Although Ang1 could protect peripheral vasculature from vascular leakage following ischemic injury, the role of Ang1 in long-term neurological recovery after ischemic stroke remains elusive. This study aims to examine whether Ang1 overexpression via lentivirus-mediated gene transfer enhances neurovascular remodeling and improves functional outcome in a rat model of focal cerebral ischemia. Our results demonstrated that lentivirus-mediated Ang1 gene transfer led to improved neurological behavior and reduced infarction volume, and protected against blood-brain barrier (BBB) leakage in the ischemic rats. In addition, we revealed that these effects of Ang1 are related to the ability of Ang1 to increase vascular density and accelerate endogenous neuronal differentiation. These findings suggest that Ang1 is a promising agent for the treatment of cerebral ischemia.
    Neuroscience 03/2014; · 3.12 Impact Factor
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    ABSTRACT: Since morbidity and mortality rates of anaphylaxis diseases have been increasing year by year, how to prevent and manage these diseases effectively has become an important issue. Mast cells play a central regulatory role in allergic diseases. Angiopoietin1 (Ang-1) exhibits anti-inflammatory properties by inhibiting vascular permeability, leukocyte migration and cytokine production. However, Ang-1's function in mast cell activation and anaphylaxis diseases is unknown. The results of our study suggest that Ang-1 decreased lipopolysaccharide (LPS)-induced pro-inflammatory cytokines production of mast cells by suppressing IκB phosphorylation and NF-κB nuclear translocation. Ang-1 also strongly inhibited compound 48/80 induced and FcεRI-mediated mast cells degranulation by decreasing intracellular calcium levels in vitro. In vivo lentivirus-mediated delivery of Ang-1 in mice exhibited alleviated leakage in IgE-dependent passive cutaneous anaphylaxis (PCA). Furthermore, exogenous Ang-1 intervention treatment prevented mice from compound 48/80-induced mesentery mast cell degranulation, attenuated increases in pro-inflammatory cytokines, relieved lung injury, and improved survival in anaphylaxis shock. The results of our study reveal, for the first time, the important role of Ang-1 in the activation of mast cells, and identify a therapeutic effect of Ang-1 on anaphylaxis diseases.
    PLoS ONE 01/2014; 9(2):e89148. · 3.73 Impact Factor
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    ABSTRACT: Coronary heart disease (CHD) is characterized by inflammatory process and endothelial dysfunction. To investigate angiopoietin-2 (Ang-2) profiles, we evaluated serum Ang-2 levels in different types of CHD in 166 subjects. Ang-2 was measured by enzyme-linked immunosorbent assay. Serum Ang-2 levels were significantly elevated in patients with CHD and gradually increased with advance of CHD. Ang-2 was positively correlated with Gensini scores and hs-CRP. Ang-2 might have potential implication in detecting and monitoring the progression of CHD.
    Biomarkers 12/2012; 17(8):745-9. · 1.88 Impact Factor
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    ABSTRACT: Angiopoietin-1 (Ang1) is a ligand for the endothelial-specific tyrosine kinase receptor Tie2 and has been shown to play an essential role in embryonic vasculature development. There have been many studies about the anti-inflammatory effects of Ang1, most of which focus on endothelium cells. In the present study, we explore the role of Ang1-Tie2 signaling in the activation of macrophages upon lipopolysaccharide (LPS) stimulation. We found that Tie2 receptor is expressed on macrophages and Ang1 could inhibit LPS-induced activation of macrophages, as evidenced by cell migration and TNF-alpha production, specifically through Tie2 receptor. We further investigated the mechanism and found that Ang1-Tie2 could block LPS-induced activation of NF-kappaB which has been shown to be necessary for macrophage activation with LPS treatment. Thus, we described, for the first time, the role of Ang1-Tie2 signaling in macrophage activation and the possible mechanisms in response to immune stimulation.
    Biochemical and Biophysical Research Communications 02/2010; 392(2):178-82. · 2.41 Impact Factor
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    ABSTRACT: The G-protein-coupled receptor 56 (GPR56) plays important roles in brain development and tumorigenesis. cDNA data suggest that GPR56 has potential to become a neural stem cell (NSC) or neural progenitor cell (NPC) marker. However, expression of GPR56 protein in human NSC/NPCs was not explored. Using specific antibodies and immunochemistry, we showed that GPR56 was highly expressed in nestin-positive NSC/NPCs in the ventricular/subventricular zone of human and mouse fetal brains, and in cultured neurospheres derived from both human and mouse fetal brains. Downregulation of GPR56 protein occurred earlier than that of nestin in differentiating neurosphere cultures. Loss of GPR56 protein was also evident in well-differentiated glial fibrillary acidic protein-positive astrocytes and betaIII-tubulin-positive neurons. Our data suggest that GPR56 can be used as an NSC/NPC marker within the neural cell lineage, especially in combination with nestin.
    Neuroreport 08/2009; 20(10):918-22. · 1.40 Impact Factor
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    ABSTRACT: In regions of adult neurogenesis, neural progenitor cells (NPCs) are found in close proximity to blood vessels within a so-called 'vascular niche'. Neurogenesis is linked to angiogenesis via certain growth factors. We propose that angiopoietin-1 (Ang1), which is similar to VEGF, has a unique role in neurogenesis independent of its role in angiogenesis. In this study, primary cultures of NPCs were transduced with recombinant adenoviruses expressing Ang1 and induced to differentiate with dibutyryl cyclic AMP (dbcAMP). Neuronal differentiation was evaluated by quantitative PCR, immunofluorescence microscopy and Western blot analysis. The results show that ectopic expression of Ang1 promotes neuronal differentiation and neurite outgrowth in NPCs, while this effect was blocked by the presence of anti-Tie2 receptor antibody or the PI3-K inhibitor, LY294002. Our results suggest that Ang1, identified originally as an angiogenic factor, can also stimulate in vitro neurogenesis in NPCs through the Akt pathway.
    Biochemical and Biophysical Research Communications 12/2008; 378(2):296-301. · 2.41 Impact Factor
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    ABSTRACT: Loss of cardiomyocytes by apoptosis is proposed to cause ventricular remodeling and heart failure. Reactive oxygen species-induced apoptosis of cardiomyocytes has been reported to play an important role in many types of pathological processes of the heart. We investigated whether angiopoietin-1 (Ang1) has direct cytoprotective effects on cardiomyocytes against oxidative stress. Cultured H9c2 cells (cardiomyocytes) were treated with hydrogen peroxide (H(2)O(2)). Apoptosis was evaluated by flow cytometry, TUNEL assay and DNA laddering. The H(2)O(2) treatment caused typical apoptosis of H9c2 cells in a time-dependent manner. Transfection of recombinant adenovirus expressing Ang1 resulted in a sustained phosphorylation of AKT and inhibition of H(2)O(2)-induced apoptosis in H9c2 cells. This effect could be reversed by AKT inhibition. These results suggest that Ang1 protects cardiomyocytes from oxidative stress-induced apoptosis by regulating the activity of AKT.
    Biochemical and Biophysical Research Communications 09/2007; 359(3):685-90. · 2.41 Impact Factor
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    ABSTRACT: This paper described that neural stem cells (hsNSCs) were isolated and expanded rapidly from human fetal striatum in adherent culture. The population was serum- and growth factor-dependent and expressed neural stem cell markers. They were capable of multi-differentiation into neurons, astrocytes, and oligodendrocytes. When plated in the dopaminergic neuron inducing medium, human striatum neural stem cells could differentiate into tyrosine hydroxylase positive neurons. hsNSCs were morphologically homogeneous and possessed high proliferation ability. The population doubled every 44.28h and until now it has divided for more than 82 generations in vitro. Normal human diploid karyotype was unchanged throughout the in vitro culture period. Together, this study has exploited a method for continuous and rapid expansion of human neural stem cells as pure population, which maintained the capacity to generate almost fifty percent neurons. The availability of such cells may hold great interest for basic and applied neuroscience.
    Biochemical and Biophysical Research Communications 02/2005; 326(2):425-34. · 2.41 Impact Factor
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    ABSTRACT: The hypothesis that stem cells may seed cancer has emerged from the cancer stem cells concept. However, the experimental systems necessary to provide more direct evidence to support the hypothesis have been lacking. We have used fetal neural progenitor cells (hNPC) transduced with the telomerase hTERT gene to investigate the neoplastic potential of hNPCs. The hTERT-transduced line, hNPCs-G3 lost normal diploid karyotype, showed loss of contact inhibition, anchorage independence, and formed neuroblastoma-like tumours in all of 10 mice. These data suggest that hNPCs have the potential for neoplastic transformation. These data have implications for providing a novel tool to test the feasibility of new anticancer treatment strategies and raise the possibility of a risk for the use of hNPCs in cell transplantation.
    Neuroreport 09/2004; 15(12):1907-12. · 1.40 Impact Factor
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    ABSTRACT: It is necessary to expand human neural progenitor cells in vitro to obtain large numbers for research purposes and cell transplantation. A potential obstacle to in vitro expansion, however, is that neural progenitor cells have a limited replication life-span and gradually lose their differentiation potential. We report here that ectopic expression of the catalytic subunit of human telomerase (hTERT) gene in neural progenitor cells could induce telomerase activity, stabilize telomeres and extend their replicative life-spans. The telomerase-immortalized cells (hNPC-TERT) maintained the normal diploid karyotype, expressed the markers of human neural progenitor cells and meanwhile held the differentiation potential in vitro for up to 120 population doublings. This study provides a new approach for obtaining unlimited quantities of normal phenotypic and homogeneous human neural progenitor cells in vitro.
    Neuroreport 03/2004; 15(2):245-9. · 1.40 Impact Factor
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    ABSTRACT: Human neural progenitor cells hold great promise for treating a variety of human neurological diseases such as spinal cord injury. One of the issues limiting this technology is how to expand neural progenitor cells in vitro to obtain sufficient number of cells for clinical transplantation. We have established a homogeneous population of human neural progenitor cells (hNPC-TERT) immortalized by the human telomerase reverse transcriptase (hTERT) gene. Then we studied whether these cells could differentiate into neural cells in vivo and improve the recovery of spinal cord-injured rats. The hNPC-TERT cells had been transplanted into the injured spinal cord and the functional recovery of the rats with spinal cord contusion injury was evaluated through BBB locomotor scale and Motor Evoked Potentials. Additionally, the differentiation of hNPC-TERT cells was shown by immunocytochemistry. As revealed by this animal model, hNPC-TERT cells developed into functional cells in the injured spinal cord and improved recovery from spinal cord injury in both locomotor scores and electrophysiological parameter in this animal model. This study is the first demonstration of the use of telomerase-driven human progenitor cells to treat spinal cord injury and should provide a new cell source for research of clinical application.
    Restorative neurology and neuroscience 02/2004; 22(6):469-76. · 2.93 Impact Factor
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    ABSTRACT: To investigate whether the dopamine receptor D2 can express or can be induced to express in HNG1210-E, a monoclonal, telomerase-immortalized, human neural progenitor cell line. By means of RT-PCR, immuno-fluorescent staining, and fluo3 Ca2+ imaging to the expression of D2 mRNA and protein as well as the reaction to dopamine were demonstrated. HNG1210-E cells could be induced to express D2 mRNA and its proteins. The induced cells also reacted to dopamine (5 mmol.L-1), which caused rapid rising of cytoplasm Ca2+. HNG1210-E cells can be induced to express D2 mRNA and functional proteins.
    Beijing da xue xue bao. Yi xue ban = Journal of Peking University. Health sciences 07/2003; 35(3):271-3.
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    ABSTRACT: To investigate the ability of human GFAP positive neural progenitor cell line from the subventricular zone (SVZ) to differentiate into neurons. Real-time RT-PCR, Western blot analysis and immunocytochemistry were used to examine the expression level of the neural stem cell marker and neuronal-specific marker before and after all-trans-retinoic acid (AT-RA) induction in the GFAP positive neural progenitor cell line. Immunocytochemistry was used to examine the expression of the neuronal-specific marker after transplantation the GFAP positive neural progenitor cell line into the animal model. After induction, in the GFAP positive neural progenitor cell line the expression levels of the neuronal-specific marker increased, while the neural stem cell marker decreased both in mRNA and protein levels. After transplantation into animal model, the GFAP positive neural progenitor cell line could differentiate into neurons. The GFAP positive neural progenitor cell line could be induced to differentiate into neurons both in vitro and in vivo.
    Beijing da xue xue bao. Yi xue ban = Journal of Peking University. Health sciences 07/2003; 35(3):266-70.