Biomedical subjects

Margaret A Schwarz

Publications and source records attributed to Margaret A Schwarz.

7 recordsLinked to original sources

PubMed2006

Identification of protease-sensitive sites in Human Endothelial-Monocyte Activating Polypeptide II protein.

The cleaved approximately 22-kDa form of Endothelial-Monocyte Activating Polypeptide [mature (m)EMAP II] functions as a potent inhibitor of tumor growth. Although the anti-tumor effect of mEMAP II has been described, little is known regarding the cleavage of mEMAP II from its precursor form (pEMAP II). We determined that pEMAP II is expressed at the cell membrane surface and proteinases MMP-9, elastase, and cathepsin L release protein fragments consistent with mEMAP II molecular mass. MMP-9 and elastase generate a approximately 25-26 kDa spanning fragments, while cathepsin L generates a approximately 22 kDa fragment. Although several fragments are processed from pEMAP II within a 44 AA residue stretch, cathepsin L cleaves pEMAP II within 4 amino acids of the determined N-terminal sequence, suggesting that this region is sensitive to proteinases.

Amino Acid Sequence↗

PubMed2005

Endothelial-monocyte activating polypeptide II alters fibronectin based endothelial cell adhesion and matrix assembly via alpha5 beta1 integrin.

Mature Endothelial-Monocyte Activating Polypeptide (mEMAP) II functions as a potent antiangiogenic peptide. Although the anti-tumor effect of mEMAP II has been described, little is known regarding its mechanism of action. Observations that mEMAP II induced apoptosis only in a subset of migrating and proliferating endothelial cells (EC) suggests a targeted effect on cells engaged in angiogenic activities which are known to rely upon cell adhesion and migration. Indeed, we demonstrate that mEMAP II inhibited fibronectin (FN) dependent microvascular EC (MEC) adhesion and spreading and we show that this depends upon the alpha5 beta1 integrin. Immunofluorescence analysis demonstrated that mEMAP II-dependent blockade of FN-alpha5 beta1 interactions was associated with disassembly of both actin stress fiber networks and FN matrix. These findings suggest that mEMAP II blocks MEC adhesion and spreading on fibronectin, via a direct interaction with the integrin alpha5 beta1, thus implicating that alpha5 integrin may be a mediator of mEMAP II's antiangiogenic function.

Angiogenesis Inhibitors↗

PubMed2005

Developmental regulation of p66Shc is altered by bronchopulmonary dysplasia in baboons and humans.

RATIONALE: The p66(Shc) adapter protein antagonizes mitogen-activated protein, or MAP, kinase, mediates oxidative stress, and is developmentally regulated in fetal mouse lungs. OBJECTIVES: To determine if p66(Shc) is similarly regulated in primates and in bronchopulmonary dysplasia (BPD), which results from oxidative injury to immature lungs. METHODS: Normal and injured lungs from humans and baboons were evaluated by Western analysis and immunohistochemistry. MEASUREMENTS AND MAIN RESULTS: In baboons, p66(Shc) decreased 80% between 125 and 175 days' gestation (p = 0.025), then doubled after term delivery at 185 days (p = 0.0013). In the hyperoxic 140-day fetal baboon BPD model, p66(Shc) expression persisted, and its localization shifted from the epithelium of gestational controls to the mesenchyme of diseased lungs, coincident with expression of proliferating cell nuclear antigen and cleaved poly(adenyl ribose) polymerase, a marker of apoptosis. Treatment with the antibombesin antibody 2A11 attenuated BPD, reduced cell proliferation, increased p66(Shc) expression 10.5-fold, and preserved epithelial p66(Shc) localization. p66(Shc) also decreased during normal human lung development, falling 87% between 18 and 24 weeks' gestation (p = 0.02). p66(Shc) was expressed throughout 18-week human lungs, became restricted to scattered epithelial cells by 24 weeks, and localized to isolated mesenchymal cells after term delivery. In contrast, p66(Shc) remained prominent in the epithelium of lungs with acute injury or mild BPD, and in the mesenchyme of lungs with severe disease. p66(Shc) localized to tissues expressing proliferating cell nuclear antigen and cleaved poly(adenyl ribose) polymerase. CONCLUSIONS: p66(Shc) expression, cell proliferation, and apoptosis are concomitantly altered during lung development and in BPD.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Potential role for antiangiogenic proteins in the myocardial infarction repair process.

OBJECTIVE: Although angiogenic proteins have been identified as positive modulators of myocardial revascularization following acute myocardial infarction, little if anything is known regarding the role that antiangiogenic proteins have in myocardial revascularization. We explored the temporospatial distribution of endothelial-monocyte activating polypeptide (EMAP) II to determine whether antiangiogenic proteins have a role in the repair of myocardial tissue following infarction. METHODS: A rat model of myocardial infarction was utilized to examine EMAP II distribution (in situ hybridization) and protein expression (Western analysis) over a 6-week period. RESULTS: At baseline, EMAP II protein and mRNA are minimally expressed with transcription products localizing predominately to the perivascular stroma region in the normal rat myocardium. Six hours following myocardial infarction, EMAP II changes its distribution from the perivascular stroma to an invading inflammatory cell population. This is associated with a 2-fold (P < 0.0009) increase in EMAP II protein and its transcription primarily localized to the infarct region. EMAP II protein expression remains elevated throughout the weeks following the infarction with transcription limited to the infarct region and a notable decrease in EMAP II transcription products noted in the viable vasculature surrounding the infarct zone. Six weeks following myocardial infarction, EMAP II protein is elevated above control, changes its location of transcription from the inflammatory cell population to that of the fibroblasts located in the relative avascular scar tissue, and has resumed its perivascular stromal distribution in the viable periinfarct tissue. CONCLUSIONS: Thus, the temporospatial distribution of this antiangiogenic protein suggests that negative vascular modulators may have a function in the revascularization process following acute myocardial infarction.

Angiogenesis Inhibitors↗

PubMed2004

In vivo therapy of local tumor progression by targeting vascular endothelium with EMAP-II.

BACKGROUND: Continued growth of solid tumors beyond a critical diameter is thought to require active angiogenic mechanisms, the inhibition of which carries therapeutic potential. We tested this strategy in an in vivo model of local tumor progression utilizing an agent with previously identified direct antiendothelial properties. MATERIALS AND METHODS: Nonmetastatic C(6) glioma cells (10(6) per animal) were injected subcutaneously into the flank of nude mice with 6 to 8 animals per treatment group. Nodules at the injection site were measured at day 3 and every fourth day thereafter until day 15. Endothelial-monocyte-activating polypeptide II (EMAP-II), a substance known to induce endothelial cell apoptosis, was injected intraperitoneally daily from day 3 to day 15 at doses of 8 microg/kg (low dose) and 80 microg/kg (high dose). Tumor growth kinetics, histologic parameters, and tissue expression of VEGF were studied. RESULTS: Tumor growth was significantly decreased in the EMAP-II-treated animals. Median tumor volume (in mm(3)) at day 15 was 2311 (Control), 727 (low dose), and 454 (high dose, P = 0.003). Median tumor weight (g) measured 1.8 (Control, 0.95 low dose), and 0.9 (high dose, P = 0.06). Median 12-day specific tumor growth rate (in mm(3)/day) per group was 191, 60, and 36 (P = 0.003). Decreased tumor growth after EMAP-II treatment correlated with significantly reduced microvessel counts, higher vascular thrombosis rate, and reduced tumor cell proliferation indices within the neoplastic tissue. Tumor levels, but not serum levels, of VEGF were significantly reduced after EMAP-II treatment. At the doses administered, there was no obvious systemic toxicity. EMAP-II had no direct cytotoxic or antiproliferative effects on tumor cells in vitro. CONCLUSIONS: Daily administration of the antiendothelial agent EMAP-II led to a significant retardation of tumor growth, but no complete cancer abrogation. The findings support the hypothesis of an in vivo therapeutic benefit to antiangiogenic therapy with an agent that displays specific toxicity in vitro against endothelial cells. The mechanism of action remains unclear, but likely involves vascular thrombosis and leads to decreased VEGF expression.

Angiogenesis Inhibitors↗

PubMed2004

Potential role for antiangiogenic proteins in the evolution of bronchopulmonary dysplasia.

Impaired neovascularization is associated with the pathologic presentation of bronchopulmonary dysplasia (BPD). To determine if neovascularization and factors that negatively influence blood vessel formation play a role in the evolution of BPD, we examined the temporospatial distribution of a protein known to inhibit fetal lung neovascularization with associated dysplastic lung formation, endothelial-monocyte activating polypeptide (EMAP) II. Immunohistochemical analysis of EMAP II in lung tissues of human infants with BPD indicated an elevation in EMAP II abundance as compared with control. Utilizing a baboon model, western analysis indicated that EMAP II was increased twofold in those baboons with pathologic signs of BPD as compared with gestational controls. Consistent with our findings in human tissues, immunohistochemistry and in situ hybridization demonstrate that EMAP II is highly expressed in the perivascular stroma and dysplastic lung periphery in neonatal baboons with BPD as compared with controls. Lastly, there is a premature acceleration in EMAP II's perivascular distribution in term newborn baboon as compared with gestational control. The marked increase in EMAP II's temporal expression, its distribution in the perivascular and dysplastic alveolar regions of the lungs, and the interruption in vasculogenesis in BPD suggest that neovascularization and factors that negatively influence blood vessel formation may play a role in BPD evolution.

Angiogenesis Inhibitors↗

PubMed2003

Epithelial-mesenchymal interactions are linked to neovascularization.

Lung morphogenesis is dependent on interactions between mesenchymal and epithelial cells. We have previously demonstrated that inhibition of neovascularization by endothelial monocyte-activating polypeptide (EMAP) II also attenuates fetal lung morphogenesis in vivo, and hypothesized that epithelial-mesenchymal interactions are regulated by vascular signals. To address this postulate, we evaluated the formation of epithelial cysts in vitro and assessed this complex interaction through: (i) identification of vascular formation in vitro; (ii) assessment of the effect of selective vascular inhibition on cell viability, proliferation, and cellular interactions as measured by epithelial cyst formation; and (iii) examination of whether there is an interdependent relationship between epithelial and mesenchymal cells and a vascular mediator's protein expression. Vascular networks in vitro formed in direct relationship to the presence of epithelial cysts. Disruption of the vasculature by delivery of a selective antiangiogenic protein EMAP II was associated with disruption of epithelial cyst formation. Lastly, control of the vascular formation regulatory protein EMAP II is a direct result of epithelial-mesenchymal cell interactions. These findings suggest that vascular formation modulates and is modulated by the normal cellular communication and interactions that direct lung morphology.

Angiogenesis Inhibitors↗