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Articles by K Zhang
Total Records ( 9 ) for K Zhang
  K Zhang , D Wang and J. Song
 

Cortactin is an F-actin binding protein, regulating cell movement and adhesive junction assembly. However, the function of cortactin in epithelial-mesenchymal transition (EMT) remains elusive. Here we found that during transforming growth factor-β1 (TGF-β1)-induced EMT in AML-12 murine hepatocytes, cortactin underwent tyrosine dephosphorylation. Inhibition of the dephosphorylation of cortactin by sodium vanadate blocked TGF-β1-induced EMT. Knockdown of cortactin by RNAi led to decrease of intercellular junction proteins E-cadherin and Zonula occludens-1 and induced expression of mesenchymal protein fibronectin. Additionally, knockdown of cortactin further promoted TGF-β1-induced EMT in AML-12 cells, as determined by EMT markers and cell morphological changes. Moreover, migration assay showed that cortactin knockdown promoted the migration of AML-12 cells, and also enhanced TGF-β1-induced migration. Our study showed the involvement of cortactin in the TGF-β1-induced EMT.

  J Lu , K Zhang , S Nam , R. A Anderson , R Jove and W. Wen
 

As a critical factor in the induction of angiogenesis, vascular endothelial growth factor (VEGF) has become an attractive target for anti-angiogenesis treatment. However, the side effects associated with most anti-VEGF agents limit their chronic use. Identification of naturally occurring VEGF inhibitors derived from diet is a potential alternative approach, with the advantage of known safety. To isolate natural inhibitors of VEGF, we established an in vitro tyrosine kinase assay to screen for diet-based agents that suppress VEGFR2 kinase activity. We found that a water-based extract from cinnamon (cinnamon extract, CE), one of the oldest and most popular spices, was a potent inhibitor of VEGFR2 kinase activity, directly inhibiting kinase activity of purified VEGFR2 as well as mitogen-activated protein kinase- and Stat3-mediated signaling pathway in endothelial cells. As a result, CE inhibited VEGF-induced endothelial cell proliferation, migration and tube formation in vitro, sprout formation from aortic ring ex vivo and tumor-induced blood vessel formation in vivo. Depletion of polyphenol from CE with polyvinylpyrrolidone abolished its anti-angiogenesis activity. While cinnamaldehyde, a component responsible for CE aroma, had little effect on VEGFR2 kinase activity, high-performance liquid chromatography-purified components of CE, procyanidin type A trimer (molecular weight, 864) and a tetramer (molecular weight, 1152) were found to inhibit kinase activity of purified VEGFR2 and VEGFR2 signaling, implicating procyanidin oligomers as active components in CE that inhibit angiogenesis. Our data revealed a novel activity in cinnamon and identified a natural VEGF inhibitor that could potentially be useful in cancer prevention and/or treatment.

  K Zhang , L Zhang , F Rao , B Brar , J. L Rodriguez Flores , L Taupenot and D. T. O'Connor
 

Background— Tyrosine hydroxylase (TH) is the rate-limiting enzyme in catecholamine biosynthesis. Common genetic variation at the human TH promoter predicts alterations in autonomic activity and blood pressure, but how such variation influences human traits and, specifically, whether such variation affects transcription are not yet known.

Methods and Results— Pairwise linkage disequilibrium across the TH locus indicated that common promoter variants (C-824T, G-801C, A-581G, and G-494A) were located in a single 5' linkage disequilibrium block in white, black, Hispanic, and Asian populations. Polymorphisms C-824T and A-581G were located in highly conserved regions and were predicted to disrupt known transcriptional control motifs myocyte enhancer factor-2 (MEF2), sex-determining region Y (SRY), and forkhead box D1 (FOXD1) at C-824T and G/C-rich binding factors specificity protein 1 (SP1), activating enhancer-binding protein 2 (AP2)], early growth response protein 1 (EGR1) at A-581G. At C-824T and A-581G, promoter and luciferase reporter plasmids indicated differential allele strength (T>C at C-824T; G>A at A-581G) under both basal circumstances and secretory stimulation. C-824T and A-581G displayed the most pronounced effects on both transcription in cella and catecholamine secretion in vivo. We further probed the functional significance of C-824T and A-581G by cotransfection of trans-activating factors in cella; MEF2, SRY, and FOXD1 differentially activated C-824T, whereas the G/C-rich binding factors SP1, AP2, and EGR1 differentially activated A-581G. At C-824T, factor MEF2 acted in a directionally coordinate fashion (at T>C) to explain the in vivo trait associations, whereas at A-581G, factors SP1, AP2, and EGR1 displayed similar differential actions (at G>A). Finally, chromatin immunoprecipitation demonstrated that the endogenous factors bound to the motifs in cella.

Conclusion— We conclude that common genetic variants in the proximal TH promoter, especially at C-824T and A-581G, are functional in cella and alter transcription so as to explain promoter marker-on-trait associations in vivo. MEF2, FOXD1, and SRY contribute to functional differences in C-824T expression, whereas SP1, AP2, and EGR1 mediate those of A-581G. The SRY effect on TH transcription suggests a mechanism whereby male and female sex may differ in sympathetic activity and hence blood pressure. These results point to new strategies for diagnostic and therapeutic intervention into disorders of human autonomic function and their cardiovascular consequences.

  J. R Gayen , K Zhang , S. P RamachandraRao , M Mahata , Y Chen , H. S Kim , R. K Naviaux , K Sharma , S. K Mahata and D. T. O'Connor
  Background—

Oxidative stress, an excessive production of reactive oxygen species (ROS) outstripping antioxidant defense mechanisms, occurs in cardiovascular pathologies, including hypertension. In the present study, we used biochemical, physiological, and pharmacological approaches to explore the role of derangements of catecholamines, ROS, and the endothelium-derived relaxing factor nitric oxide (NO) in the development of a hyperadrenergic model of hereditary hypertension: targeted ablation (knockout [KO]) of chromogranin A (Chga) in the mouse.

Methods and Results—

Homozygous (–/–) Chga gene knockout (KO) mice were compared with wild-type (WT, +/+) control mice. In the KO mouse, elevations of systolic and diastolic blood pressure were accompanied by not only elevated catecholamine (norepinephrine and epinephrine) concentrations but also increased ROS (H2O2) and isoprostane (an index of lipid peroxidation), as well as depletion of NO. Renal transcript analyses implicated changes in Nox1/2, Xo/Xdh, and Sod1,2 mRNAs in ROS elevation by the KO state. KO alterations in blood pressure, catecholamines, H2O2, isoprostane, and NO could be abrogated or even normalized (rescued) by either sympathetic outflow inhibition (with clonidine) or NADPH oxidase inhibition (with apocynin). In cultured renal podocytes, H2O2 production was substantially augmented by epinephrine (probably through β2-adrenergic receptors) and modestly diminished by norepinephrine (probably through 1-adrenergic receptors).

Conclusions—

ROS appear to play a necessary role in the development of hyperadrenergic hypertension in this model, in a process mechanistically linking elevated blood pressure with catecholamine excess, renal transcriptional responses, ROS elevation, lipid peroxidation, and NO depletion. Some of the changes appear to be dependent on transcription, whereas others are immediate. The cycle could be disrupted by inhibition of either sympathetic outflow or NADPH oxidase. Because common genetic variation at the human CHGA locus alters BP, the results have implications for antihypertensive treatment as well as prevention of target-organ consequences of the disease. The results document novel pathophysiological links between the adrenergic system and oxidative stress and suggest new strategies to probe the role and actions of ROS within this setting.

  J. B Li , Y Gao , J Aach , K Zhang , G. V Kryukov , B Xie , A Ahlford , J. K Yoon , A. M Rosenbaum , A. W Zaranek , E LeProust , S. R Sunyaev and G. M. Church
 

Utilizing the full power of next-generation sequencing often requires the ability to perform large-scale multiplex enrichment of many specific genomic loci in multiple samples. Several technologies have been recently developed but await substantial improvements. We report the 10,000-fold improvement of a previously developed padlock-based approach, and apply the assay to identifying genetic variations in hypermutable CpG regions across human chromosome 21. From ~3 million reads derived from a single Illumina Genome Analyzer lane, ~94% (~50,500) target sites can be observed with at least one read. The uniformity of coverage was also greatly improved; up to 93% and 57% of all targets fell within a 100- and 10-fold coverage range, respectively. Alleles at >400,000 target base positions were determined across six subjects and examined for single nucleotide polymorphisms (SNPs), and the concordance with independently obtained genotypes was 98.4%–100%. We detected >500 SNPs not currently in dbSNP, 362 of which were in targeted CpG locations. Transitions in CpG sites were at least 13.7 times more abundant than non-CpG transitions. Fractions of polymorphic CpG sites are lower in CpG-rich regions and show higher correlation with human–chimpanzee divergence within CpG versus non-CpG sites. This is consistent with the hypothesis that methylation rate heterogeneity along chromosomes contributes to mutation rate variation in humans. Our success suggests that targeted CpG resequencing is an efficient way to identify common and rare genetic variations. In addition, the significantly improved padlock capture technology can be readily applied to other projects that require multiplex sample preparation.

  H Wang , A Chattopadhyay , Z Li , B Daines , Y Li , C Gao , R Gibbs , K Zhang and R. Chen
 

One of the key advantages of using Drosophila melanogaster as a genetic model organism is the ability to conduct saturation mutagenesis screens to identify genes and pathways underlying a given phenotype. Despite the large number of genetic tools developed to facilitate downstream cloning of mutations obtained from such screens, the current procedure remains labor intensive, time consuming, and costly. To address this issue, we designed an efficient strategy for rapid identification of heterozygous mutations in the fly genome by combining rough genetic mapping, targeted DNA capture, and second generation sequencing technology. We first tested this method on heterozygous flies carrying either a previously characterized dac5 or sensE2 mutation. Targeted amplification of genomic regions near these two loci was used to enrich DNA for sequencing, and both point mutations were successfully identified. When this method was applied to uncharacterized twr mutant flies, the underlying mutation was identified as a single-base mutation in the gene Spase18-21. This targeted-genome-sequencing method reduces time and effort required for mutation cloning by up to 80% compared with the current approach and lowers the cost to <$1000 for each mutant. Introduction of this and other sequencing-based methods for mutation cloning will enable broader usage of forward genetics screens and have significant impacts in the field of model organisms such as Drosophila.

  X. j Cai , L Chen , L Li , M Feng , X Li , K Zhang , Y. y Rong , X. b Hu , M. x Zhang , Y Zhang and M. Zhang
 

Adiponectin is an important antiatherogenic adipocytokine that inhibits inflammation, insulin resistance, and oxide stress. Inflammation in the vascular adventitia is a crucial factor in the pathogenesis of atherosclerosis. Adventitial fibroblasts (AFs) can proliferate, divide into myofibroblasts, and migrate to the intima to become a new component of atherosclerotic plaque under inflammation and atherosclerosis. We investigated whether adiponectin might prevent AFs from proliferating, migrating, and transforming into myofibroblasts. Cultured AFs were stimulated with lipopolysaccharide (LPS) in the presence or absence of adiponectin. Methyl thiazolyl tetrazolium assay and migration and scratch-wound assays demonstrated that adiponectin reduced the AF proliferation and migration induced by LPS, respectively, whereas treatment with AdipoR1 small interfering (si) RNA (siAdipoR1), AMP-activated protein kinase (AMPK) siRNA (siAMPK), and an AMPK inhibitor reversed the effect. Immunocytochemistry and Western blot revealed that adiponectin reduced the transition of AFs to myofibroblasts, and treatment with siAdipoR1, siAMPK, and the AMPK inhibitor increased the transition. RT-PCR, Western blotting, and nitric oxide (NO) assay showed that adiponectin reduces induced NO synthase (iNOS) and nitrotyrosine expression and NO and ONOO production induced by LPS. Treatment with siAdipoR1, siAMPK, and the AMPK inhibitor significantly attenuated adiponectin-induced phosphorylation of AMPK and its downstream target acetyl-coenzyme A carboxylase and up-regulated iNOS mRNA and protein expression, which resulted in a marked increase of NO and ONOO production. In apolipoprotein E-deficient mice, immunohistochemistry of treated vascular adventitia showed that both iNOS expression and ONOO production could be reversed with an adenovirus-adiponectin vector. Taken together, these results suggest that adiponectin reduces LPS-induced NO production and nitrosative stress and prevents AFs from proliferating, transforming to myoflbroblasts, and migrating to the intima, thus worsening atherosclerosis, by inhibiting the AdipoR1-AMPK-iNOS pathway in AFs.

  B Oqvist , B. M Brenner , J. P Oliveira , A Ortiz , R Schaefer , E Svarstad , C Wanner , K Zhang and D. G. Warnock
  No Description
  K Zhang , J Sha and M. L. Harter
 

Cdc6, which alters chromatin ultrastructure to allow DNA replication in muscle stem cells transitioning out of quiescence, is identified as a target of the MyoD transcription factor.

 
 
 
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