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Barbara M Schreiber

Publications and source records attributed to Barbara M Schreiber.

10 recordsLinked to original sources
PubMed2006

Collagen and major histocompatibility class II expression in mesenchymal cells from CIITA hypomorphic mice.

Major histocompatibility class II (MHC II) transactivator (CIITA) is critical for interferon-gamma (IFN-gamma)-induced repression of collagen [Xu, Y., Wang, L., Buttice, G., Sengupta, P.K., Smith, B.D., 2004. Major histocompatibility class II transactivator (CIITA) mediates repression of collagen (COL1A2) transcription by interferon gamma (IFN-gamma). J. Biol. Chem. 279, 41319-41332] and activation of MHC II transcription. To better understand the role of CIITA and IFN-gamma induced repression of collagen, mesenchymal cells (lung fibroblasts, adventitial fibroblasts, and smooth muscle cells) were isolated from a CIITA deficient mouse (C2ta(tm1Ccum)). IFN-gamma induced MHC II expression and repressed collagen type I expression in all three cell types isolated from the wild type background. As expected, IFN-gamma treatment of cells isolated from CIITA deficient mice did not induce MHC II production or activate the MHC II promoter. Interestingly, collagen gene expression and promoter activity was similar to that of wild type. Moreover, IFN-gamma induced CIITA mRNA and a truncated form of CIITA protein in all cells isolated from CIITA deficient mice. Most importantly, truncated CIITA occupied the collagen alpha 2(I) gene (col1a2) transcription start site during IFN-gamma treatment, but it did not occupy the MHC II promoter as judged by chromatin immunoprecipitation assays. Exogenous expression of a similar truncated form of CIITA maintained its ability to repress col1a2 transcription, but lost its ability to activate MHC II gene transcription suggesting a role for the CIITA C-terminal domain in activation, but not repression. IFN-gamma induced primarily types I and IV CIITA isoforms in the mouse cells. All three isoforms of CIITA were capable of repressing col1a2 and activating MHC II gene transcription. These data suggest that the previously described CIITA knockout mouse carries a hypomorphic mutation, rather than a null mutation. The removal of the leucine rich region in CIITA blocks activation of MHC II without altering repression of collagen transcription.

Animals↗
PubMed2006

The A2B adenosine receptor protects against inflammation and excessive vascular adhesion.

Adenosine has been described as playing a role in the control of inflammation, but it has not been certain which of its receptors mediate this effect. Here, we generated an A2B adenosine receptor-knockout/reporter gene-knock-in (A2BAR-knockout/reporter gene-knock-in) mouse model and showed receptor gene expression in the vasculature and macrophages, the ablation of which causes low-grade inflammation compared with age-, sex-, and strain-matched control mice. Augmentation of proinflammatory cytokines, such as TNF-alpha, and a consequent downregulation of IkappaB-alpha are the underlying mechanisms for an observed upregulation of adhesion molecules in the vasculature of these A2BAR-null mice. Intriguingly, leukocyte adhesion to the vasculature is significantly increased in the A2BAR-knockout mice. Exposure to an endotoxin results in augmented proinflammatory cytokine levels in A2BAR-null mice compared with control mice. Bone marrow transplantations indicated that bone marrow (and to a lesser extent vascular) A2BARs regulate these processes. Hence, we identify the A2BAR as a new critical regulator of inflammation and vascular adhesion primarily via signals from hematopoietic cells to the vasculature, focusing attention on the receptor as a therapeutic target.

Animals↗
PubMed2005

Vascular smooth muscle cell polyploidization involves changes in chromosome passenger proteins and an endomitotic cell cycle.

Vascular smooth muscle cell polyploidization occurs during normal development and is enhanced under physiologic stress, but the mechanism of this cell cycle has not been explored. We show via time-lapse video imaging and immunofluorescence analyses that primary vascular smooth muscle cells (VSMC) undergo an endomitotic-type cell cycle, including a normal progression through part of mitosis. Mononuclear polyploid cells are generated by defects in sister chromatid separation and/or segregation, and cellular binucleation occurs by reversal of cytokinesis. To obtain further leads to regulators involved, we examined the chromosomal passenger proteins, Aurora B, inner centromere protein and Survivin, and concluded that Aurora B and inner centromere protein are normally colocalized in centromeres, the midzone, and the midbody during mitosis. Survivin, however, is dim and diffused; it does not colocalize with either Aurora B or inner centromere protein in VSMC, which could account for defects in sister chromatid separation and/or segregation and reversal of cytokinesis. In accordance with the reported dependency of Aurora B activity on Survivin, the Aurora B substrate, vimentin, is not phosphorylated during cytokinesis. Finally, the data show that ectopically expressed Survivin inhibits polyploidization in vascular smooth muscle cells. Hence, aberrant chromosome passenger protein activity and endomitosis are associated with VSMC polyploidization.

Animals↗
PubMed2005

PPARgamma2 regulates lipogenesis and lipid accumulation in steatotic hepatocytes.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is considered to be one of the master regulators of adipocyte differentiation. PPARgamma2 is abundantly expressed in mature adipocytes and is elevated in the livers of animals that develop fatty livers. The aim of this study was to determine the ability of PPARgamma2 to induce lipid accumulation in hepatocytes and to delineate molecular mechanisms driving this process. The hepatic cell line AML-12 was used to generate a cell line stably expressing PPARgamma2. Oil Red O staining revealed that PPARgamma2 induces lipid accumulation in hepatocytes. This phenotype is accompanied by a selective upregulation of several adipogenic and lipogenic genes including adipose differentiation-related protein (ADRP), adipocyte fatty acid-binding protein 4, sterol regulatory element-binding protein-1 (SREBP-1), fatty acid synthase (FAS), and acetyl-CoA carboxylase, genes whose expression levels are known to increase in steatotic livers of ob/ob mice. Furthermore, the PPARgamma2-regulated induction of both SREBP-1 and FAS parallels an increase in de novo triacylglycerol synthesis in hepatocytes. Triacylglycerol synthesis and lipid accumulation are further enhanced by culturing hepatocytes with troglitazone in the absence of exogenous lipids. These results correspond with an increase in the lipid droplet protein, ADRP, and the data demonstrate that ADRP functions to coat lipid droplets in hepatocytes as observed by confocal microscopy. Taken together, these observations propose a role for PPARgamma2 as an inducer of steatosis in hepatocytes and suggest that this phenomenon occurs through an induction of pathways regulating de novo lipid synthesis.

Acetyl-CoA Carboxylase↗
PubMed2005

Effects of elastase on the mechanical and failure properties of engineered elastin-rich matrices.

Pulmonary emphysema and vessel wall aneurysms are diseases characterized by elastolytic damage to elastin fibers that leads to mechanical failure. To model this, neonatal rat aortic smooth muscle cells were cultured, accumulating an extracellular matrix rich in elastin, and mechanical measurements were made before and during enzymatic digestion of elastin. Specifically, the cells in the cultures were killed with sodium azide, the cultures were lifted from the flask, cut into small strips, and fixed to a computer-controlled lever arm and a force transducer. The strips were subjected to a broadband displacement signal to study the dynamic mechanical properties of the samples. Also, quasi-static stress-strain curves were measured. The dynamic data were fit to a linear viscoelastic model to estimate the tissues' loss (G) and storage (H) modulus coefficients, which were evaluated before and during 30 min of elastase treatment, at which point a failure test was performed. G and H decreased significantly to 30% of their baseline values after 30 min. The failure stress of control samples was approximately 15 times higher than that of the digested samples. Understanding the structure-function relationship of elastin networks and the effects of elastolytic injury on their mechanical properties can lead to the elucidation of the mechanism of elastin fiber failure and evaluation of possible treatments to enhance repair in diseases involving elastolytic injury.

Animals↗
PubMed2005

Analysis of gene ontology features in microarray data using the Proteome BioKnowledge Library.

Microarray technology has resulted in an explosion of complex, valuable data. Integrating data analysis tools with a comprehensive underlying database would allow efficient identification of common properties among differentially regulated genes. In this study we sought to compare the utility of various databases in microarray analysis. The Proteome BioKnowledge Library (BKL), a manually curated, proteome-wide compilation of the scientific literature, was used to generate a list of Gene Ontology (GO) Biological Process (BP) terms enriched among proteins involved in cardiovascular disease. Analysis of DNA microarray data generated in a study of rat vascular smooth muscle cell responses revealed significant enrichment in a number of GO BPs that were also enriched among cardiovascular disease-related proteins. Using annotation from LocusLink and chip annotation from the Gene Expression Omnibus yielded fewer enriched cardiovascular disease-associated GO BP terms. Data sets of orthologous genes from mouse and human were generated using the BKL Retriever. Analysis of these sets focusing on BKL Disease annotation, revealed a significant association of these genes with cardiovascular disease. These results and the extensive presence of experimental evidence for BKL GO and Disease features, underscore the benefits of using this database for microarray analysis.

Animals↗
PubMed2004

B-Myb represses elastin gene expression in aortic smooth muscle cells.

B-Myb represses collagen gene transcription in vascular smooth muscle cells (SMCs) in vitro and in vivo. Here we sought to determine whether elastin is similarly repressed by B-Myb. Levels of tropoelastin mRNA and protein were lower in aortas and isolated SMCs of adult transgenic mice expressing the human B-myb gene, driven by the basal cytomegalovirus promoter, compared with age-matched wild type (WT) animals. However, the vessel wall architecture and levels of insoluble elastin revealed no differences. Since elastin deposition occurs early in development, microarray analysis was performed using nontransgenic mice. Aortic levels of tropoelastin mRNA were low during embryonal growth and increased substantially in neonates, whereas B-myb levels varied inversely. Tropoelastin mRNA expression in aortas of 6-day-old neonatal transgenic and WT animals was comparable. Recently, we demonstrated that cyclin A-Cdk2 prevents B-Myb-mediated repression of collagen promoter activity. Cyclin A2 levels were higher in neonatal versus adult WT or transgenic mouse aortas. Ectopic cyclin A expression reversed the ability of B-Myb to repress elastin gene promoter activity in adult SMCs. These results demonstrate for the first time that B-Myb represses SMC elastin gene expression and that cyclin A plays a role in the developmental regulation of elastin gene expression in the aorta. Furthermore, the findings provide additional insight into the mechanism of B-myb-mediated resistance to femoral artery injury.

Animals↗
PubMed2004

A(3) adenosine receptor deficiency does not influence atherogenesis.

Atherosclerosis is a multifactorial disease, the progression of which is modulated by several factors, including inflammation and hypercholesterolemia. The A(3) adenosine receptor (A(3)AR) has been reported to affect mast cell degranulation leading to inflammation, as well as to influence cardiovascular homeostasis. Here, we show that its deletion can also impact vascular smooth muscle cell (VSMC) proliferation in vitro. Based on these observations, we hypothesized that A(3)AR deficiency would affect atheromatous lesion development in vivo. Our results indicate that the expression of the matrix enzyme lysyl oxidase (LO) is increased while the proliferation potential of VSMC is decreased in A(3)AR-null aortas. This is in accordance with the previously reported inverse correlation between LO level and proliferation. Nevertheless, we found that A(3)-deficiency does not protect vessels against atherogenesis. This was demonstrated in mouse models of high fat diet-induced atherosclerosis and guidewire-induced femoral artery injury. We conclude that the contributions of the A(3)AR to inflammation and to modulating LO levels are not significant enough to control vascular response to injury.

Animals↗
PubMed2004

B-Myb represses vascular smooth muscle cell collagen gene expression and inhibits neointima formation after arterial injury.

OBJECTIVE: The function of B-Myb, a negative regulator of vascular smooth muscle cell (SMC) matrix gene transcription, was analyzed in the vasculature. METHODS AND RESULTS: Mice were generated in which the human B-myb gene was driven by the basal cytomegalovirus promoter, and 3 founders were identified. Mice appeared to develop normally, and human B-myb was expressed in the aortas. Total B-Myb levels were elevated in aortas of adult transgenic versus wild-type (WT) animals and varied inversely with alpha1(I) collagen mRNA expression. However, neonatal WT and transgenic aortas displayed comparable levels of alpha1(I) collagen mRNA, likely resulting from elevated levels of cyclin A, which ablated repression by B-Myb. Aortic SMCs from adult transgenic animals displayed decreased alpha1(I) collagen mRNA levels. To examine the role of B-Myb after vascular injury, animals were subjected to femoral artery denudation, which induces SMC-rich lesion formation. A dramatic reduction in neointima formation and lumenal narrowing was observed in arteries of B-myb transgenic versus WT mice 4 weeks after injury. CONCLUSIONS: Data indicate that B-Myb, which inhibits matrix gene expression in the adult vessel wall, reduces neointima formation after vascular injury. To analyze B-Myb function in the vasculature, mice overexpressing B-myb were generated. Neonates displayed normal alpha1(I) collagen mRNA levels, whereas adults expressed decreased collagen mRNA in aortas and isolated vascular SMCs. On femoral artery denudation, neointima formation was dramatically reduced in B-myb transgenic mice.

Age Factors↗