Theses and Dissertations

Jia Zhao

Issuing Body

Mississippi State University

Advisor

Dawe, Angus

Committee Member

Gordon, Donna M.

Committee Member

Thornton, Justin

Committee Member

Simpson, C. LaShan

Committee Member

Stewart, James A., Jr.

Date of Degree

12-8-2017

Document Type

Dissertation - Open Access

Major

Biological Sciences

Degree Name

Doctor of Philosophy

College

College of Arts and Sciences

Department

Department of Biological Sciences

Abstract

Type II diabetes mellitus (TIIDM) causes multiple complications under chronic hyperglycemia. Long term persistent exposure to elevated glucose conditions is considered one of the major factors for diabetic complications. Pathologically, mechanical and biochemical stimuli will induce a signaling cascade in cardiac fibroblasts, which causes myocardial fibrosis and leading to ventricular stiffness. Non-enzymatically, high levels of glucose can react with long-lived proteins, such as collagen to form advanced glycation end-products (AGEs). AGEs have been shown to be associated with many of the diabetic cardiovascular complications due to their interaction with the receptor for AGE (RAGE). AGE/RAGE activation stimulates the secretion of growth factors, promotes increased collagen production that leads to tissue fibrosis, and increased RAGE expression. The purpose of this study is to identify the role for Rap1a in regulating fibrosis under TIIDM conditions, as well as to offer insight into the AGE-RAGE signaling cascade definition for cardiovascular extracellular matrix remodeling under TIIDM condition. To test our hypothesis, both loss-ofunction and gain-ofunction based experiments were performed to manipulate Rap1a protein expression in AGE-RAGE mediated fibrosis. Also, we down-regulated the activity of downstream molecules in the AGE-RAGE signaling cascade, such as protein kinase C-ζ (PKC-ζ) and ERK1/2 by specific inhibitor treatments, to test their positions in AGE-RAGE mediated fibrosis pathway. To perform our experiment in vivo, we used high fat diet to feed Rap1a heterozygous mice in order to build a Rap1a heterozygous diabetic animal model. Our results showed that Rap1a protein plays a key role in AGE-RAGE signaling pathway under TIIDM, and changes in Rap1a activity altered the signaling pathway. Also, we found that PKC-ζ is the upstream player relatively to ERK1/2, and Rap1a is the upstream player for both PKC-ζ and ERK1/2. By understanding the role Rap1a played in AGE-RAGE signaling cascade, a new molecular mechanism is found possibly to reduce the cardiac fibrosis in TIIDM patients.

URI

https://hdl.handle.net/11668/19584

Comments

rap1a||type II diabetes||signaling pathway

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