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Articles by M Chen
Total Records ( 13 ) for M Chen
  S Chen , B Feng , B George , R Chakrabarti , M Chen and S. Chakrabarti

Sustained hyperglycemia in diabetes causes alteration of a large number of transcription factors and mRNA transcripts, leading to tissue damage. We investigated whether p300, a transcriptional coactivator with histone acetyl transferase activity, regulates glucose-induced activation of transcription factors and subsequent upregulation of vasoactive factors and extracellular matrix (ECM) proteins in human umbilical vein endothelial cells (HUVECs). HUVECs were incubated in varied glucose concentrations and were studied after p300 small interfering RNA (siRNA) transfection, p300 overexpression, or incubation with the p300 inhibitor curcumin. Histone H2AX phosphorylation and lysine acetylation were examined for oxidative DNA damage and p300 activation. Screening for transcription factors was performed with the Luminex system. Alterations of selected transcription factors were validated. mRNA expression of p300, endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), and fibronectin (FN) and its splice variant EDB+FN and FN protein production were analyzed. HUVECs in 25 mmol/l glucose showed increased p300 production accompanied by increased binding of p300 to ET-1 and FN promoters, augmented histone acetylation, H2AX phosphorylation, activation of multiple transcription factors, and increased mRNA expression of vasoactive factors and ECM proteins. p300 overexpression showed a glucose-like effect on the mRNA expression of ET-1, VEGF, and FN. Furthermore, siRNA-mediated p300 blockade or chemical inhibitor of p300 prevented such glucose-induced changes. Similar mRNA upregulation was also seen in the organ culture of vascular tissues, which was prevented by p300 siRNA transfection. Data from these studies suggest that glucose-induced p300 upregulation is an important upstream epigenetic mechanism regulating gene expression of vasoactive factors and ECM proteins in endothelial cells and is a potential therapeutic target for diabetic complications.

  M Chen , M. A. T Hildebrandt , J Clague , A. M Kamat , A Picornell , J Chang , X Zhang , J Izzo , H Yang , J Lin , J Gu , S Chanock , M Kogevinas , N Rothman , D. T Silverman , M Garcia Closas , H. B Grossman , C. P Dinney , N Malats and X. Wu

Sonic hedgehog (Shh) pathway genetic variations may affect bladder cancer risk and clinical outcomes. Therefore, we genotyped 177 single-nucleotide polymorphisms (SNP) in 11 Shh pathway genes in a study including 803 bladder cancer cases and 803 controls. We assessed SNP associations with cancer risk and clinical outcomes in 419 cases of non–muscle-invasive bladder cancer (NMIBC) and 318 cases of muscle-invasive and metastatic bladder cancer (MiMBC). Only three SNPs (GLI3 rs3823720, rs3735361, and rs10951671) reached nominal significance in association with risk (P ≤ 0.05), which became nonsignificant after adjusting for multiple comparisons. Nine SNPs reached a nominally significant individual association with recurrence of NMIBC in patients who received transurethral resection (TUR) only (P ≤ 0.05), of which two (SHH rs1233560 and GLI2 rs11685068) were replicated independently in 356 TUR-only NMIBC patients, with P values of 1.0 x 10–3 (SHH rs1233560) and 1.3 x 10–3 (GLI2 rs11685068). Nine SNPs also reached a nominally significant individual association with clinical outcome of NMIBC patients who received Bacillus Calmette-Guérin (BCG; P ≤ 0.05), of which two, the independent GLI3 variants rs6463089 and rs3801192, remained significant after adjusting for multiple comparisons (P = 2 x 10–4 and 9 x 10–4, respectively). The wild-type genotype of either of these SNPs was associated with a lower recurrence rate and longer recurrence-free survival (versus the variants). Although three SNPs (GLI2 rs735557, GLI2 rs4848632, and SHH rs208684) showed nominal significance in association with overall survival in MiMBC patients (P ≤ 0.05), none remained significant after multiple-comparison adjustments. Germ-line genetic variations in the Shh pathway predicted clinical outcomes of TUR and BCG for NMIBC patients. Cancer Prev Res; 3(10); 1235–45. ©2010 AACR.

  M Chen , A Cassidy , J Gu , G. L Delclos , F Zhen , H Yang , M. A.T Hildebrandt , J Lin , Y Ye , R. M Chamberlain , C. P Dinney and X. Wu

Genetic variations in phosphoinositide-3 kinase (PI3K)-AKT-mammalian target of rapamycin (mTOR) pathway may affect critical cellular functions and increase an individual's cancer risk. We systematically evaluate 231 single-nucleotide polymorphisms (SNPs) in 19 genes in the PI3K-AKT-mTOR signaling pathway as predictors of bladder cancer risk. In individual SNP analysis, four SNPs in regulatory associated protein of mTOR (RAPTOR) remained significant after correcting for multiple testing: rs11653499 [odds ratio (OR): 1.79, 95% confidence interval (CI): 1.24–2.60, P = 0.002], rs7211818 (OR: 2.13, 95% CI: 1.35–3.36, P = 0.001), rs7212142 (OR: 1.57, 95% CI: 1.19–2.07, P = 0.002) and rs9674559 (OR: 2.05, 95% CI: 1.31–3.21, P = 0.002), among which rs7211818 and rs9674559 are within the same haplotype block. In haplotype analysis, compared with the most common haplotypes, haplotype containing the rs7212142 wild-type allele showed a protective effect of bladder cancer (OR: 0.83, 95% CI: 0.70–0.97). In contrast, the haplotype containing the rs7211818 variant allele showed a 1.32-fold elevated bladder cancer risk (95% CI: 1.09–1.60). In combined analysis of three independent significant RAPTOR SNPs (rs11653499, rs7211818 and rs7212142), a significant trend was observed for increased risk with an increase in the number of unfavorable genotypes (P for trend <0.001). Compared with the subjects without any of the unfavorable genotypes, those carrying all three unfavorable genotypes showed a 2.22-fold (95% CI: 1.33–3.71) increased bladder cancer risk. This is the first study to evaluate the role of germ line genetic variations in PI3K-AKT-mTOR pathway as cancer susceptibility factors that will help us identify high-risk individuals for bladder cancer.

  M Chen , J Gu , G. L Delclos , A. M Killary , Z Fan , M. A. T Hildebrandt , R. M Chamberlain , H. B Grossman , C. P Dinney and X. Wu

The phosphoinositide-3 kinase (PI3K)–AKT– mammalian target of rapamycin (mTOR) pathway is an important cellular pathway controlling cell growth, tumorigenesis, cell invasion and drug response. We hypothesized that genetic variations in the PI3K–AKT–mTOR pathway may affect the survival in muscle invasive and metastatic bladder cancer (MiM-BC) patients. We conducted a follow-up study of 319 MiM-BC patients to systematically evaluate 289 single-nucleotide polymorphisms (SNPs) of 20 genes in the PI3K–AKT–mTOR pathway as predicators of survival. In multivariate Cox regression, AKT2 rs3730050, PIK3R1 rs10515074 and RAPTOR rs9906827 were significantly associated with survival. In combined analysis, we found a cumulative effect of these three SNPs on survival. With the increasing number of unfavorable genotypes, there was a significant trend of higher risk of death in multivariate Cox regression (P for trend <0.001) and shorter median survival time in Kaplan–Meier estimates (P log rank <0.001). This is the first study to evaluate the role of germ line genetic variations in the PI3K–AKT–mTOR pathway genes as predictors of MiM-BC clinical outcomes. These findings warrant further replication in independent populations and may provide information on disease management and development of target therapies.

  C Franco , K Britto , E Wong , G Hou , S. N Zhu , M Chen , M. I Cybulsky and M. P. Bendeck

Rationale: We described a critical role for the discoidin domain receptor (DDR)1 collagen receptor tyrosine kinase during atherosclerotic plaque development. Systemic deletion of Ddr1 in Ldlr–/– mice accelerated matrix accumulation and reduced plaque size and macrophage content. However, whether these effects reflected an independent role for macrophage DDR1 during atherogenesis remained unresolved.

Methods: In the present study, we performed sex-mismatched bone marrow transplantation using Ddr1+/+;Ldlr–/– and Ddr1–/–;Ldlr–/– mice to investigate the role of macrophage DDR1 during atherogenesis. Chimeric mice with deficiency of DDR1 in bone marrow–derived cells (Ddr1–/–->+/+) or control chimeric mice that received Ddr1+/+;Ldlr–/– marrow (Ddr1+/+->+/+) were fed an atherogenic diet for 12 weeks.

Results: We observed a 66% reduction in atherosclerosis in the descending aorta and a 44% reduction in plaque area in the aortic sinus in Ddr1–/–->+/+ mice compared to Ddr1+/+->+/+ mice. Furthermore, we observed a specific reduction in the number of donor-derived macrophages in Ddr1–/–->+/+ plaques, suggesting that bone marrow deficiency of DDR1 attenuated atherogenesis by limiting macrophage accumulation in the plaque. We have also demonstrated that the effects of DDR1 on macrophage infiltration and accumulation can occur at the earliest stage of atherogenesis, the formation of the fatty streak. Deficiency of DDR1 limited the appearance of 5-bromodeoxyuridine–labeled monocytes/macrophages in the fatty streak and resulted in reduced lesion size in Ldlr–/– mice fed a high fat diet for 2 weeks. In vitro studies to investigate the mechanisms involved revealed that macrophages from Ddr1–/– mice had decreased adhesion to type IV collagen and decreased chemotactic invasion of type IV collagen in response to monocyte chemoattractant protein-1.

Conclusions: Taken together, our data support an independent and critical role for DDR1 in macrophage accumulation at early and late stages of atherogenesis.

  M Chen , X Qiu , W Xu , L Wang , J Zhao and X. Li

Test case generation based on design specifications is an important part of testing processes. In this paper, Unified Modeling Language activity diagrams are used as design specifications. By setting up several test adequacy criteria with respect to activity diagrams, an automatic approach is presented to generate test cases for Java programs. Instead of directly deriving test cases from activity diagrams, this approach selects test cases from a set of randomly generated ones according to a given test adequacy criterion. In the approach, we first instrument a Java program under testing according to its activity diagram model, and randomly generate abundant test cases for the program. Then, by running the instrumented program we obtain the corresponding program execution traces. Finally, by matching these traces with the behavior of the activity diagram, a reduced set of test cases are selected according to the given test adequacy criterion. This approach can also be used to check the consistency between the program execution traces and the behavior of activity diagrams.

  S. w Peng , L. y Zhu , M Chen , M Zhang , D. z Li , Y. c Fu , S. r Chen and C. j. Wei

Understanding the mechanisms of β-cell dynamics in postnatal animals is central to cure diabetes. A major obstacle in evaluating the status of pancreatic cells is the lack of surface markers. Here we performed quantitative measurements of two internal markers to follow the developmental history of islets. One marker, cell-cycle activity, was established by measuring expression of Ki67 and the incorporation of 5-bromodeoxyuridine. The other marker, the aging process, was delineated by the determination of telomere length. Moreover, islet neogenesis, possibly from ductal precursors, was monitored by pancreatic duct labeling with an enhanced green fluorescence protein (EGFP) transgene. We found that islets from younger animals, on average, expressed higher Ki67 transcripts, displayed elevated 5-bromodeoxyuridine incorporation, and had longer telomeres. However, significant heterogeneity of these parameters was observed among islets from the same mouse. In contrast, the levels of proinsulin-1 transcripts in islets of different ages did not change significantly. Moreover, mitotic activities correlated significantly with telomere lengths of individual islets. Lastly, after 5.5 d pancreatic duct labeling, a few EGFP-positive islets could be identified in neonatal but not from adult pancreases. Compared with unlabeled control islets, EGFP-positive islets had higher mitotic activities and longer telomeres. The results suggest that islets are born at different time points during the embryonic and neonatal stages and imply that young islets might play an important role in the maintenance of islet mass in the adult pancreas.

  J Hong , H Li , M Chen , Y. C. Q Zang , S. M Skinner , J. M Killian and J. Z. Zhang

MBP-specific autoreactive T cells are considered pro-inflammatory T cells and thought to play an important role in the pathogenesis of multiple sclerosis (MS). Here, we report that MBP83–99-specific T cells generated from MS patients (n = 7) were comprised of pro-inflammatory and regulatory subsets of distinct phenotypes. The pro-inflammatory phenotype was characterized by high production of IFN-, IL-6, IL-21 and IL-17 and low expression of FOXP3, whereas the regulatory subset expressed high levels of FOXP3 and exhibited potent regulatory functions. The regulatory subset of MBP-specific T cells appeared to expand from the CD4+CD25 T-cell pool. Their FOXP3 expression was stable, independent of the activation state and it correlated with suppressive function and inversely with the production of IFN-, IL-6, IL-21 and IL-17. In contrast, the phenotype and function of FOXP3low MBP-specific T cells were adaptive and dependent on IL-6. The higher frequency of FOXP3high MBP-specific T cells was observed when IL-6 was neutralized in the culture of PBMC with MBP. The study provides new evidence that MBP-specific T cells are susceptible to pro-inflammatory cytokine milieu and act as either pro-inflammatory or regulatory T cells.

  Z Huang , M Chen , K Li , X Dong , J Han and Q. Zhang

Cryo-electron tomography was employed to reconstruct the structure of Chlamydia trachomatis. Results revealed that the features of the structures, especially those of the membranes, were preserved much better than those by conventional ultrathin section methods. This method also enabled us to determine that the thickness of the outer membrane of the elementary bodies is nearly twice of that of the reticulate bodies. Our observations give a clue to the mechanism of outer membrane changes.

  A. K Singh , B Riederer , M Chen , F Xiao , A Krabbenhoft , R Engelhardt , O Nylander , M Soleimani and U. Seidler

CFTR has been recognized to function as both an anion channel and a key regulator of Slc26 anion transporters in heterologous expression systems. Whether this regulatory relationship between CFTR and Slc26 transporters is seen in native intestine, and whether this effect is coupled to CFTR transport function or other features of this protein, has not been studied. The duodena of anesthetized CFTR-, NHE3-, Slc26a6-, and Scl26a3-deficient mice and wild-type (WT) littermates were perfused, and duodenal bicarbonate (HCO3) secretion (DBS) and fluid absorptive or secretory rates were measured. The selective NHE3 inhibitor S1611 or genetic ablation of NHE3 significantly reduced fluid absorptive rates and increased DBS. Slc26a6 (PAT1) or Slc26a3 (DRA) ablation reduced the S1611-induced DBS increase and reduced fluid absorptive rates, suggesting that the effect of S1611 or NHE3 ablation on HCO3 secretion may be an unmasking of Slc26a6- and Slc26a3-mediated Cl/HCO3 exchange activity. In the absence of CFTR expression or after application of the CFTR(inh)-172, fluid absorptive rates were similar to those of WT, but S1611 induced virtually no increase in DBS, demonstrating that CFTR transport activity, and not just its presence, is required for Slc26-mediated duodenal HCO3 secretion. A functionally active CFTR is an absolute requirement for Slc26-mediated duodenal HCO3 secretion, but not for Slc26-mediated fluid absorption, in which these transporters operate in conjunction with the Na+/H+ exchanger NHE3. This suggests that Slc26a6 and Slc26a3 need proton recycling via NHE3 to operate in the Cl absorptive mode and Cl exit via CFTR to operate in the HCO3 secretory mode.

  J. M Rodenberg , A. M Hoggatt , M Chen , K Touw , R Jones and B. P. Herring

Serum response factor (SRF) is a widely expressed protein that plays a key role in the regulation of smooth muscle differentiation, proliferation, migration, and apoptosis. It is generally accepted that one mechanism by which SRF regulates these diverse functions is through pathway-specific cofactor interactions. A novel SRF cofactor, chromodomain helicase DNA binding protein 8 (CHD8), was isolated from a yeast two-hybrid screen using SRF as bait. CHD8 is highly expressed in adult smooth muscle tissues. Coimmunoprecipitation assays from A10 smooth muscle cells demonstrated binding of endogenous SRF and CHD8. Data from GST-pulldown assays indicate that the NH2-terminus of CHD8 can interact directly with the MADS domain of SRF. Adenoviral-mediated knockdown of CHD8 in smooth muscle cells resulted in attenuated expression of SRF-dependent, smooth muscle-specific genes. Knockdown of CHD8, SRF, or CTCF, a previously described binding partner of CHD8, in A10 VSMCs also resulted in a marked induction of apoptosis. Mechanistically, apoptosis induced by CHD8 knockdown was accompanied by attenuated expression of the anti-apoptotic proteins, Birc5, and CARD10, whereas SRF knockdown attenuated expression of CARD10 and Mcl-1, but not Birc5, and CTCF knockdown attenuated expression of Birc5. These data suggest that CHD8 plays a dual role in smooth muscle cells modulating SRF activity toward differentiation genes and promoting cell survival through interactions with both SRF and CTCF to regulate expression of Birc5 and CARD10.

  S. N Zhu , M Chen , J Jongstra Bilen and M. I. Cybulsky

The contribution of intimal cell proliferation to the formation of early atherosclerotic lesions is poorly understood. We combined 5-bromo-2'-deoxyuridine pulse labeling with sensitive en face immunoconfocal microscopy analysis, and quantified intimal cell proliferation and Ly-6Chigh monocyte recruitment in low density lipoprotein receptor–null mice. Cell proliferation begins in nascent lesions preferentially at their periphery, and proliferating cells accumulate in lesions over time. Although intimal cell proliferation increases in parallel to monocyte recruitment as lesions grow, proliferation continues when monocyte recruitment is inhibited. The majority of proliferating intimal cells are dendritic cells expressing CD11c and major histocompatibility complex class II and 33D1, but not CD11b. Systemic injection of granulocyte/macrophage colony-stimulating factor (GM-CSF) markedly increased cell proliferation in early lesions, whereas function-blocking anti–GM-CSF antibody inhibited proliferation. These findings establish GM-CSF as a key regulator of intimal cell proliferation in lesions, and demonstrate that both proliferation and monocyte recruitment contribute to the inception of atherosclerosis.

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