Biomedical subjects

Xueying Jiang

Publications and source records attributed to Xueying Jiang.

12 recordsLinked to original sources

PubMed2005

The excitoprotective effect of N-methyl-D-aspartate receptors is mediated by a brain-derived neurotrophic factor autocrine loop in cultured hippocampal neurons.

The neuroprotective effect and molecular mechanisms underlying preconditioning with N-methyl-D-aspartate (NMDA) in cultured hippocampal neurons have not been described. Pre-incubation with subtoxic concentrations of the endogenous neurotransmitter glutamate protects vulnerable neurons against NMDA receptor-mediated excitotoxicity. As a result of physiological preconditioning, NMDA significantly antagonizes the neurotoxicity resulting from subsequent exposure to an excitotoxic concentration of glutamate. The protective effect of glutamate or NMDA is time- and concentration-dependent, suggesting that sufficient agonist and time are required to establish an intracellular neuroprotective state. In these cells, the TrkB ligand, brain-derived neurotrophic factor (BDNF) attenuates glutamate toxicity. Therefore, we tested the hypothesis that NMDA protects neurons via a BDNF-dependent mechanism. Exposure of hippocampal cultures to a neuroprotective concentration of NMDA (50 microM) evoked the release of BDNF within 2 min without attendant changes in BDNF protein or gene expression. The accumulated increase of BDNF in the medium is followed by an increase in the phosphorylation (activation) of TrkB receptors and a later increase in exon 4-specific BDNF mRNA. The neuroprotective effect of NMDA was attenuated by pre-incubation with a BDNF-blocking antibody and TrkB-IgG, a fusion protein known to inhibit the activity of extracellular BDNF, suggesting that BDNF plays a major role in NMDA-mediated survival. These results demonstrate that low level stimulation of NMDA receptors protect neurons against glutamate excitotoxicity via a BDNF autocrine loop in hippocampal neurons and suggest that activation of neurotrophin signaling pathways plays a key role in the neuroprotection of NMDA.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed2005

BDNF variation and mood disorders: a novel functional promoter polymorphism and Val66Met are associated with anxiety but have opposing effects.

The brain-derived neurotrophic factor (BDNF) gene is critical for neuronal function and survival, and is likely to be important in psychiatric disorders. In this study, we used single-nucleotide polymorphism (SNP) discovery, functional analyses, and genetic association studies to better understand the potential role of BDNF sequence variation in behavior. Screening 480 unrelated individuals for SNPs and genotyping was performed in US Caucasian, American Indian, and African American populations. Lifetime DSM-III-R psychiatric diagnoses were assigned and the Tridimensional Personality Questionnaire (TPQ) was administered to measure anxious temperament (harm avoidance (HA)) and novelty seeking (NS). A novel SNP (-281 C>A) in promoter 1 was discovered that had decreased DNA binding in vitro and decreased basal reporter gene activity in transfected rat hippocampal neurons. The frequency of the -281 A allele was 0.03 in a Caucasian sample, but was virtually absent in other populations. Association analyses in a community-based sample showed that individuals with the -281 A allele (13 heterozygotes) had lower TPQ HA (F=4.8, p<0.05). In contrast, the Met 66 allele was associated with increased HA (F=4.1, p=0.02) and was most abundant in individuals with both anxiety disorders and major depression (p<0.05). Among the Val66Val homozygotes, individuals who were -281 CA heterozygotes had significantly lower HA than the -281 CC homozygotes (p<0.01). Our results suggest that in this population, the low activity -281 A allele may be protective against anxiety and psychiatric morbidity, whereas Met 66 may be a risk allele.

Adult↗

PubMed2005

Delineating and understanding cerebellar neuroprotective pathways: potential implication for protecting the cortex.

The cerebellum is a brain region that is resistant to many of the neurodegenerative disorders such as stroke and Alzheimer's disease. In contrast, the neocortex (cerebrum, cerebral cortex) is vulnerable to these disorders. While there may be many reasons for the differences in vulnerability to acute and chronic neurodegenerative disorders, the cerebellum appears to be equipped with the tools necessary to protect itself against these types of insults. Over the last century, evidence has accumulated to suggest that the cerebellum is also involved in memory and higher cognitive function. We have discovered that intrinsic survival pathways exist in cerebellar granule cells that are regulated by low level stimulation of N-methyl-d-aspartate (NMDA) receptors. Activation of NMDA receptors protects vulnerable neurons against glutamate-mediated excitotoxicity acting on NMDA receptors. This report focuses on how modulation of neuronal survival by NMDA receptors through a brain-derived neurotrophic factor (BDNF)-mediated pathway may be incorporated into a network of cerebellar function, particularly in light of recent findings suggesting that the cerebellum plays a vital role in learning, memory, fear conditioning, and cognitive processing.

Animals↗

PubMed2004

Identification of human chronic myelogenous leukemia progenitor cells with hemangioblastic characteristics.

Overwhelming evidence from leukemia research has shown that the clonal population of neoplastic cells exhibits marked heterogeneity with respect to proliferation and differentiation. There are rare stem cells within the leukemic population that possess extensive proliferation and self-renewal capacity not found in the majority of the leukemic cells. These leukemic stem cells are necessary and sufficient to maintain the leukemia. Interestingly, the BCR/ABL fusion gene, which is present in chronic myelogenous leukemia (CML), was also detected in the endothelial cells of patients with CML, suggesting that CML might originate from hemangioblastic progenitor cells that can give rise to both blood cells and endothelial cells. Here we isolated fetal liver kinase-1-positive (Flk1+) cells carrying the BCR/ABL fusion gene from the bone marrow of 17 Philadelphia chromosome-positive (Ph+) patients with CML and found that these cells could differentiate into malignant blood cells and phenotypically defined endothelial cells at the single-cell level. These findings provide direct evidence for the first time that rearrangement of the BCR/ABL gene might happen at or even before the level of hemangioblastic progenitor cells, thus resulting in detection of the BCR/ABL fusion gene in both blood and endothelial cells.

Adolescent↗

PubMed2004

Inhibition of protein kinase C promotes neuronal survival in low potassium through an Akt-dependent pathway.

Cerebellar granule cell neurons undergo apoptotic cell death when subjected to serum-free conditions at physiological concentrations of potassium (5 mM). Protein kinase C (PKC) is known to play a role in preventing neuronal apoptosis under trophic factor deprivation, but its role in protecting cerebellar neurons from cell death under conditions of low potassium is unknown. This study sought to determine the involvement of PKC in neuronal survival and to determine if PKC regulated the phosphatidylinositol 3-kinase (PI 3-K)/Akt pathway in low physiologic concentrations of potassium. Incubation with a pan-PKC inhibitor, Ro-31-8220 (2 microm), or a specific PKCAlpha inhibitor, Gö6976, protected cerebellar granule cell neurons from low potassium-mediated cell death. In contrast, phorbol ester (TPA, 100 nm), a PKC activator, increased cell death. Incubation with, Ro-31-8220 rescued neurons from cell death induced by the PI 3-K inhibitor, LY294002, suggesting that Ro-31-8220 may affect Akt phosphorylation. Western blot analysis showed that serum-free, low potassium conditions decreased Akt phosphorylation, which was exacerbated by treatment with LY294002. In contrast, PKC inhibitors, Gö6976 or Ro-31-8220, increased Akt phosphorylation approximately two and four-fold, respectively in low potassium conditions. Because Akt activation appears to be critical in promoting neuronal survival under these culture conditions, increased Akt phosphorylation brought about by inhibiting PKC promotes neuronal survival.

Animals↗

PubMed2004

AMPA protects cultured neurons against glutamate excitotoxicity through a phosphatidylinositol 3-kinase-dependent activation in extracellular signal-regulated kinase to upregulate BDNF gene expression.

The signal transduction and molecular mechanisms underlying alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)-mediated neuroprotection are unknown. In the present study, we determined a major AMPA receptor-mediated neuroprotective pathway. Exposure of cerebellar granule cells to AMPA (500 microM) + aniracetam (1 microM), a known blocker of AMPA receptor desensitization, evoked an accumulation of brain-derived neurotropic factor (BDNF) in the culture medium and enhanced TrkB-tyrosine phosphorylation following the release of BDNF. AMPA also activated the src-family tyrosine kinase, Lyn, and the downstream target of the phosphatidylinositol 3-kinase (PI3-K) pathway, Akt. Extracellular signal regulated kinase (ERK), a component of the mitogen-activated protein kinase (MAPK) pathway, was also activated. K252a, a selective inhibitor of neurotrophin signaling, blocked the AMPA-mediated neuroprotection. The involvement of BDNF release in protecting neurons by AMPA was confirmed using a BDNF-blocking antibody. AMPA-mediated neuroprotection is blocked by PP1, an inhibitor of src family kinases, LY294002, a PI3-K inhibitor, or U0126, a MAPK kinase (MEK) inhibitor. Neuroprotective concentrations of AMPA increased BDNF mRNA levels that was blocked by the AMPA receptor antagonist, 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX). The increase in BDNF gene expression appeared to be the downstream target of the PI3-K-dependent activation of the MAPK cascade since MEK or the PI3-K inhibitor blocked the AMPA receptor-mediated increase in BDNF mRNA. Thus, AMPA receptors protect neurons through a mechanism involving BDNF release, TrkB receptor activation, and a signaling pathway involving a PI3-K dependent activation of MAPK that increases BDNF expression.

Animals↗

PubMed2004

Role of brain-derived neurotrophic factor and NF-kappaB in neuronal plasticity and survival: From genes to phenotype.

PURPOSE: Brain-derived neurotrophic factor (BDNF) is a member of the family of neurotrophins and promotes diverse effects in neurons including development, maintenance of function, synaptic plasticity, and survival in different animal models. We present advances in our understanding of the genomics of the BDNF gene (bdnf) and its regulation by calcium-activated transcription factors, including cAMP response element binding protein (CREB) and more recently, nuclear factor kappaB (NF-kappaB) and discuss these findings in the context of neuronal plasticity and survival. METHODS: We used amplified bdnf complementary DNAs (cDNAs) and genomic DNA templates for direct sequencing and sequence variant discovery, information mining of public databases, and conventional molecular and cellular biology approaches to screen bdnf for novel regulatory elements, alternatively spliced exons, and functional sequence variants. RESULTS: We discovered a candidate NF-kappaB site in promoter 3 of bdnf and showned that activation of N-methyl-D-aspartate (NMDA) inotropic glutamate receptors increased bdnf expression through an NF-kappaB-dependent pathway and extended the finding to show that NF-kappaB was required for NMDA neuroprotection in vitro. In addition, sequence analysis of bdnf cDNAs from different brain regions predicted at least three pre-pro-BDNF protein isoforms, two of which were previously unknown. Each isoform differs at the amino terminus and may have functional importance. CONCLUSIONS: Given the central role that BDNF plays in the developing and adult nervous system, understanding how BDNF is regulated and how it functions will enhance our knowledge of its diverse effects, which may lead to more effective treatments for neurodegenerative disorders and reveal the role of BDNF in complex phenotypes related to behavior.

Animals↗

PubMed2004

A single chain antibody obtained by cell panning of antibody phage inhibits homoaggregation of human leukemia cells.

The aim of this study was to establish a method to obtain antibodies against cell-surface molecules of hematopoietic stem and progenitor cells in situ. A phage-displayed scFv antibody library with a size of 2 x 10(6) clones was constructed from spleens of mice immunized with living KG1a human leukemia cells. Living cell panning was used to screen anti-KG1a cell antibody fragments. After four rounds of panning, 27 out of 126 scFv fragments showed detectable binding to KG1a cells without cross-reaction to non-hematopoietic cell lines. Individual clones were analyzed by cell-based ELISA and flow cytometry for their binding specificity. Their sequence analysis showed highest homology to mouse gamma heavy chain subgroup II and mouse Kappa subgroup III genes, with four amino acids difference in VH and identical VL. Further, a fusion protein of scFv 5C1 to core-streptavidin was cloned and produced. It was used to search for cell-surface antigen on immunoblots and to test its effect on KG1a cell growth in cell culture. The scFv5C1::core-streptavidin fusion protein recognized a molecule with MW 85/125 KDa in immunoblots of KG1a cell membrane proteins and inhibited KG1a cell homoaggregation in cell cultures. The results validate an efficient approach of making antibodies against living cells and searching for functional inhibitors of cell-surface molecules.

Amino Acid Sequence↗

PubMed2003

Isolation and identification of mesenchymal stem cells from human fetal pancreas.

Mesenchymal stem cells (MSCs) have been cultured from many sources, including bone marrow and liver. To further support our hypothesis that MSCs exist in most postnatal tissues, we isolated a clonogenic, multipotent, rapidly proliferating population of cells from a fetal pancreas and termed them "pancreas-derived mesenchymal stem cells" (PMSCs). They withstood being passaged as many as 30 times without sustaining significant structural changes. In this study, we showed that PMSCs are positive for CD44, CD29, and CDI3 but negative for CD34 and HLA-DR and that they stained with collagen I and III but not with von Willebrand factor antibody. During the log phase of growth, PMSCs proliferated, doubling in population in about 30 hours. Cell-cycle analysis showed that more than 90% of cells were in the G0 and G1 phases, whereas a small subpopulation of cells were actively engaged in proliferation (S + G2 + M = 3.55%). Under differentiation culture conditions, PMSCs differentiated into cells of osteogenic, chondrogenic, and adipogenic lineages. These results demonstrate that PMSCs can be isolated from human fetal pancreas by means of their adherent ability and that they are capable of self-renewal, propagation, and multipotent differentiation.

Base Sequence↗

PubMed2003

N-methyl-D-aspartate and TrkB receptor activation in cerebellar granule cells: an in vitro model of preconditioning to stimulate intrinsic survival pathways in neurons.

Delineating the mechanisms of survival pathways that exist in neurons will provide important insight into how neurons utilize intracellular proteins as neuroprotectants against the causes of acute neurodegeneration. We have employed cultured rat cerebellar granule cells as a model for determining the mechanisms of these intraneuronal survival pathways. Glutamate has long been known to kill neurons by an N-methyl-d-aspartate (NMDA) receptor-mediated mechanism. Paradoxically, subtoxic concentrations of NMDA protect neurons against glutamate-mediated excitotoxicity. Because NMDA protects neurons in physiologic concentrations of glucose and oxygen, we refer to this phenomenon as physiologic preconditioning. One of the major mechanisms of NMDA neuroprotection involves the activation of NMDA receptors leading to the rapid release of brain-derived neurotrophic factor (BDNF). BDNF then binds to and activates its cognate receptor, receptor tyrosine kinase B (TrkB). The efficient utilization of these two receptors confers remarkable resistance against millimolar concentrations of glutamate that kill more than eighty percent of the neurons in the absence of preconditioning the neurons with a subtoxic concentration of NMDA. Exactly how the neurons mediate neuroprotection by activation of both receptors is just beginning to be understood. Both NMDA and TrkB receptors activate nuclear factor kappaB (NF-kappaB), a transcription factor known to be involved in protecting neurons against many different kinds of toxic insults. By converging on survival transcription factors, such as NF-kappaB, NMDA and TrkB receptors protect neurons. Thus, crosstalk between these very different receptors provides a rapid means of neuronal communication to upregulate survival proteins through release and transcriptional activation of messenger RNA.

Animals↗

PubMed2002

A clinical and experimental study on the protective effects of jiangzhi tongmai fang on endothelial injury.

31 cases of atherosclerosis (AS) were treated with Jiang Zhi Tong Mai Fang ([symbol: see text], formula of JZTMF), and its effect was compared with 30 cases treated with lovastatin in the control group. Clinically, the JZTMF formula showed an effect of regulating blood lipids, and therefore it was antiatherosclerotic. The mechanism is, probably, restoration of the function of endothelial cells (EC) by increasing the synthesis of 6-keto-PGF1 alpha and decreasing the release of endothelin (ET) as evidenced in the experimental study.

6-Ketoprostaglandin F1 alpha↗

PubMed2002

[Comparative study of human fetal and adult bone marrow derived mesenchymal stem cells].

OBJECTIVE: To explore the differences of phenotype and biological characteristics between fetal and adult bone marrow derived mesenchymal stem cells. METHODS: Mononuclear cells from 4-5 months old human aborted fetus and normal adult bone marrow were cultured in SF medium to obtain mesenchymal stem cells. The growth curve, cell cycle, immunophenotype, in vitro expansion potential, differentiation capacities were investigated. RESULTS: The adherent fetal and adult bone marrow-derived cells cultured in the absence of differentiation stimuli gave rise to a population of cells with phenotypical features of mesenchymal stem cells (MSC). These MSCs were similar in cell morphology and antigenic phenotype. The proliferative and multilineage differentiation potential of the bone marrow derived MSC from the fetus is higher than that from the adult, but the adherent ability of the MSCs from the adult is higher than that from the fetus. CONCLUSION: Fetal bone marrow derived MSCs should be enough to sustain a steady supply of low differentiated cells for proliferation, hence an abundant and accessible cellular reservoir for stem cell bioengineering, whereas adult bone marrow derived MSCs are more useful in hematopoietic reconstitution in bone marrow transplantation.

Adult↗