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Degree Name

PhD (Doctor of Philosophy)

Program

Biomedical Sciences

Date of Award

12-2007

Committee Chair or Co-Chairs

Krishna Singh

Committee Members

William Joyner, Mahipal Singh, Fred E. Hossler, Brian P. Rowe, Antonio E. Rusinol

Abstract

Angiogenesis, the formation of new vessels from a preexisting vasculature, is critical for supplying a healing myocardium with oxygen and nutrients to sustain metabolism post myocardial infarction (MI). Interleukin-1β (IL-1β), a proinflammatory cytokine increased in the heart post-MI, is considered essential for angiogenesis in tumor growth and metastasis, arthritis, endometriosis, and wound healing. Matrix metalloproteinases (MMPs) are implicated in angiogenesis because of their ability to selectively degrade components of the extracellular matrix. Vascular endothelial growth factors (VEGFs) play a vital role in angiogenesis because of their involvement in the recruitment and proliferation of endothelial cells. The current study explores IL-1β-stimulated regulation of angiogenic genes in cardiac microvascular endothelial cells (CMECs), the signaling mechanisms involved, and the implications in the processes of angiogenesis. DNA microarray analysis indicated IL-1β modulates the expression of numerous angiogenesis-related genes, notably upregulating MMP-2 and downregulating VEGF-D expression. RT-PCR and Western blot analyses confirmed the differential expression in response to IL-1β. In-gel zymographic analysis demonstrated IL-1β-stimulated increase in MMP-2 activity. IL-1β activated ERK1/2 and JNKs, not p38 kinase, and activated PKCα/β1 independent of MAPKs. IL-1β inactivated GSK3β via ERK1/2. Pharmacological inhibition of these signaling cascades indicated IL-1β-stimulated regulation of MMP-2 and VEGF-D occurs via ERK1/2, JNKs, and PKCα/β1-dependent mechanisms. In addition, inactivation of GSK3β inhibited basal VEGF-D expression. H2O2 significantly increased MMP-2 protein levels while IL-1β-induced VEGF-D downregulation was further potentiated by ROS scavenging compounds and inhibition of NF-κB. Phalloidin-FITC stain indicated a sharp reduction in fibrillar actin in the cytoskeleton of IL-1β-stimulated cells. Wounding assays revealed that IL-1β induced CMEC migration but prevented cell-to-cell contact and restoration of the monolayer. Flow cytometric analysis revealed a G0/G1 phase cell cycle arrest in IL-1β-stimulated cells, indicative of decreased proliferation. IL-1β inhibited three-dimensional in vitro tube formation by CMECs. Lastly, IL-1β inhibited microvessel sprouting from aortic rings, an assay examining the collective response of multiple cell types. Collectively, the data presented in this study provide evidence that IL-1β differentially regulates important angiogenesis-related genes in CMECs. This differential regulation may lead to interruptions in the processes of angiogenesis, ultimately creating a dysfunctional phenotype for myocardial vessel formation.

Document Type

Dissertation - Campus Only

Copyright

Copyright by the authors.

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