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Degree Name
PhD (Doctor of Philosophy)
Program
Biomedical Sciences
Date of Award
5-2024
Committee Chair or Co-Chairs
Krishna Singh
Committee Members
Antonio Rusinol, Douglas Thewke, Chuanfu Li, Cerrone Foster, Suman Dalal
Abstract
Ischemic heart disease is a leading cause of death worldwide. Ubiquitin (UB), an evolutionary conserved protein, is found in all eukaryotic cells. Previous work has shown that treatment of mice with exogenous UB (eUB) reduces inflammatory response and preserves heart function 3 days following ischemia/reperfusion injury (I/R). This study investigated the long-term (28 days post-I/R) cardioprotective potential of eUB using a mouse model of myocardial I/R; and tested the hypothesis that eUB modulates phenotype and function of macrophages (key cells involved in inflammation post-I/R) using thioglycolate-elicited mouse peritoneal macrophages. Heart function measured at 3, 7, 14 and 28 days post-I/R using echocardiography showed that eUB improves heart function throughout the observation period, and decreases I/R-mediated increase in left ventricular dilation at 3, 14 and 28 days timepoints. Myocardial fibrosis, hypertrophy and apoptosis were lower in eUB-treated hearts 28 days post-I/R. These changes in the heart associated with decreased expression of fibrosis-related proteins (collagen-1α1 and MMP-2) and hypertrophy-related protein (MYH-7B) in UB-treated hearts. Activation of GSK3β (pro-apoptotic kinase) was lower (vs. Sham), while activation of anti-apoptotic kinases, ERK1/2 (vs. I/R) and Akt (vs. Sham), was higher in eUB-treated hearts 28 days post-I/R. Serum levels of IL-6, IL-2 and G-CSF were lower in I/R+UB vs. I/R group 28 days post-I/R. In peritoneal macrophages, eUB induced cytoskeleton reorganization in M1-polarized (IFNγ treatment for 72 hours; 100U/mL) and M2-polarized (IL-4 treatment for 72 hours; 20ng/mL) cells. eUB decreased secretion of IL-1β and TNFα in M1-polarized macrophages, while it decreased secretion of TNFα, IL-10 and GM-CSF in M2-polarized macrophages. Efferocytosis was lower in eUB-treated M2-polarized macrophages, which was reversed by CXCR4 receptor antagonist (AMD3100). eUB enhanced migration of M1-polarized macrophages, while it decreased the migration of M2-polarized macrophages. AMD3100 negated the effects of eUB on M1-polarized macrophage migration. eUB decreased activation of STAT1 and FAK, while increasing activation of ERK1/2 in M1-polarized macrophages. In M2-polarized macrophages, eUB decreased Akt activation. Thus, UB treatment preserves heart function and decreases adverse cardiac remodeling 28 days post-I/R. In polarized macrophages, eUB reduces secretion of inflammatory cytokines, and alters phenotype and function of M1- and M2-polarized macrophages.
Document Type
Dissertation - restricted
Recommended Citation
Shook, Paige, "Exogenous Ubiquitin: Role in Myocardial Ischemia/Reperfusion Injury, and Macrophage Phenotype and Function" (2024). Electronic Theses and Dissertations. Paper 4394. https://dc.etsu.edu/etd/4394
Copyright
Copyright by the authors.