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Articles by L Du
Total Records ( 5 ) for L Du
  J. H Hu , L Du , T Chu , G Otsuka , N Dronadula , M Jaffe , S. E Gill , W. C Parks and D. A. Dichek

Background— The mechanisms of atherosclerotic plaque rupture are poorly understood. Urokinase-type plasminogen activator (uPA) is expressed at elevated levels by macrophages in advanced human plaques. Patients with evidence of increased plasminogen activation have an elevated risk of major cardiovascular events. We used atherosclerotic mice to test the hypothesis that increased macrophage uPA expression in advanced plaques would cause histological features similar to those in ruptured human plaques.

Methods and Results— Bone marrow from transgenic mice with increased macrophage uPA expression or nontransgenic controls (all apolipoprotein E–null [Apoe–/–]) was transplanted into 35-week-old Apoe–/– recipients, and innominate lesions and aortas were examined 8 to 13 weeks later. Donor macrophages accumulated in innominate lesions adjacent to plaque caps and in aortas, increasing uPA expression at both sites. Recipients of uPA-overexpressing macrophages had an increased prevalence of intraplaque hemorrhage (61% versus 13%; P=0.002) as well as increased lesion fibrin staining and fibrous cap disruption (P=0.06 for both). Transplantation of uPA-overexpressing macrophages increased aortic matrix metalloproteinase activity (40%; P=0.02). This increase was independent of matrix metalloproteinase-9.

Conclusions— In advanced plaques of Apoe–/– mice, macrophage uPA overexpression causes intraplaque hemorrhage and fibrous cap disruption, features associated with human plaque rupture. uPA overexpression also increases vascular matrix metalloproteinase activity. These data provide a mechanism that connects macrophage uPA expression, matrix metalloproteinase activity, and plaque rupture features in mice. The data also suggest that elevated plaque plasminogen activator expression and plasminogen activation in humans may be causally linked to plaque rupture and cardiovascular events.

  D. L Gibbons , W Lin , C. J Creighton , Z. H Rizvi , P. A Gregory , G. J Goodall , N Thilaganathan , L Du , Y Zhang , A Pertsemlidis and J. M. Kurie

Metastatic disease is a primary cause of cancer-related death, and factors governing tumor cell metastasis have not been fully elucidated. Here, we address this question by using tumor cell lines derived from mice that develop metastatic lung adenocarcinoma owing to expression of mutant K-ras and p53. Despite having widespread somatic genetic alterations, the metastasis-prone tumor cells retained a marked plasticity. They transited reversibly between epithelial and mesenchymal states, forming highly polarized epithelial spheres in three-dimensional culture that underwent epithelial-to-mesenchymal transition (EMT) following treatment with transforming growth factor-β or injection into syngeneic mice. This transition was entirely dependent on the microRNA (miR)-200 family, which decreased during EMT. Forced expression of miR-200 abrogated the capacity of these tumor cells to undergo EMT, invade, and metastasize, and conferred transcriptional features of metastasis-incompetent tumor cells. We conclude that tumor cell metastasis is regulated by miR-200 expression, which changes in response to contextual extracellular cues.

  C Wang , G Xie , B Cheng , L Du , L Shi , L Tan , Q Shu and X. Fang

Pediatric Risk of Mortality (PRISM), Pediatric Index of Mortality (PIM) and PIM2 could be applicable to the subset of term neonates has not been well investigated. The purpose of this study is to access and compare the performance of these scoring systems in predicting mortality probability in term Chinese neonates with critical illness. PRISM, PIM and PIM2 scores were calculated prospectively during a 1-year period on 243 neonates admitted to the neonatal intensive care unit (NICU) in the Children’s Hospital of Zhejiang University in China. Of these, 36 neonates (14.81%) died in the NICU, while the mortality rates estimated by PRISM, PIM and PIM2 were 16.19, 14.58 and 11.12%, respectively. The area under the receiver-operating characteristic (ROC) curve [95% confidence intervals (CIs)] were 0.834 (0.767–0.902), 0.851 (0.786–0.916) and 0.854 (0.790–0.918) for PRISM, PIM and PIM2, respectively. The Hosmer–Lemeshow test gave a chi-square of 1.35 (p = 0.930) for PRISM, 1.03 (p = 0.960) for PIM and 4.58 (p = 0.469) for PIM2. The standardized mortality rates (SMRs) (95% CI) using PRISM, PIM and PIM2 were 0.92 (0.79–1.08), 1.02 (0.88–1.20) and 1.33 (1.13–1.62), respectively. Although PRISM, PIM and PIM2 have displayed good discrimination and calibration in the present setting, PIM is considered as the most accurate and appropriate tool for predicting mortality in the studied NICU.

  W Zhang , L Du and S. J. Gunst

The small GTPase RhoA increases the Ca2+ sensitivity of smooth muscle contraction and myosin light chain (MLC) phosphorylation by inhibiting the activity of MLC phosphatase. RhoA is also a known regulator of cytoskeletal dynamics and actin polymerization in many cell types. In airway smooth muscle (ASM), contractile stimulation induces MLC phosphorylation and actin polymerization, which are both required for active tension generation. The objective of this study was to evaluate the primary mechanism by which RhoA regulates active tension generation in intact ASM during stimulation with acetylcholine (ACh). RhoA activity was inhibited in canine tracheal smooth muscle tissues by expressing the inactive RhoA mutant, RhoA T19N, in the intact tissues or by treating them with the cell-permeant RhoA inhibitor, exoenzyme C3 transferase. RhoA inactivation reduced ACh-induced contractile force by ~60% and completely inhibited ACh-induced actin polymerization but inhibited ACh-induced MLC phosphorylation by only ~20%. Inactivation of MLC phosphatase with calyculin A reversed the reduction in MLC phosphorylation caused by RhoA inactivation, but calyculin A did not reverse the depression of active tension and actin polymerization caused by RhoA inactivation. The MLC kinase inhibitor, ML-7, inhibited ACh-induced MLC phosphorylation by ~80% and depressed active force by ~70% but did not affect ACh-induced actin polymerization, demonstrating that ACh-stimulated actin polymerization occurs independently of MLC phosphorylation. We conclude that the RhoA-mediated regulation of ACh-induced contractile tension in ASM results from its role in mediating actin polymerization rather than from effects on MLC phosphatase or MLC phosphorylation.

  L Du , R Damoiseaux , S Nahas , K Gao , H Hu , J. M Pollard , J Goldstine , M. E Jung , S. M Henning , C Bertoni and R. A. Gatti

Large numbers of genetic disorders are caused by nonsense mutations for which compound-induced readthrough of premature termination codons (PTCs) might be exploited as a potential treatment strategy. We have successfully developed a sensitive and quantitative high-throughput screening (HTS) assay, protein transcription/translation (PTT)–enzyme-linked immunosorbent assay (ELISA), for identifying novel PTC-readthrough compounds using ataxia-telangiectasia (A-T) as a genetic disease model. This HTS PTT-ELISA assay is based on a coupled PTT that uses plasmid templates containing prototypic A-T mutated (ATM) mutations for HTS. The assay is luciferase independent. We screened ~34,000 compounds and identified 12 low-molecular-mass nonaminoglycosides with potential PTC-readthrough activity. From these, two leading compounds consistently induced functional ATM protein in ATM-deficient cells containing disease-causing nonsense mutations, as demonstrated by direct measurement of ATM protein, restored ATM kinase activity, and colony survival assays for cellular radiosensitivity. The two compounds also demonstrated readthrough activity in mdx mouse myotube cells carrying a nonsense mutation and induced significant amounts of dystrophin protein.

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