Date of Award
1-1-2025
Document Type
Dissertation
Degree Name
Ph.D. in Pharmaceutical Sciences
First Advisor
James A. Stewart
Second Advisor
Gregg Roman
Third Advisor
Jason Hoeksema
School
University of Mississippi
Relational Format
dissertation/thesis
Abstract
Cardiovascular complications are a leading cause of mortality in individuals with diabetes, driven in part by fibrotic remodeling of the heart. Advanced glycation end-products (AGEs), which accumulate under hyperglycemic conditions, activate the receptor for AGEs (RAGE), promoting inflammation, fibrosis, and hypertrophy. RAGE signaling is also known to intersect with angiotensin II (AngII) signaling via the AT1 receptor (AT1R), though the shared molecular mechanisms remain unclear. Rap1a, a Ras-like GTPase, has emerged as a potential integrator of these pathways, but its role in diabetic cardiac remodeling is not well defined.
This dissertation explores the hypothesis that Rap1a mediates pathological signaling downstream of AGE-RAGE and AT1R in cardiac fibroblasts, particularly through Extracellular Signal-Regulated Kinases 1 and 2 (ERK1/2) and Nuclear Factor Kappa B (NF-κ[kappa]B) activation. The first project assessed the in vivo effects of AngII infusion in wild-type, RAGE knockout, and Rap1a knockout mice. Both knockouts were partially protected against AngII-induced ventricular thickening, suggesting a role for Rap1a and RAGE in hypertrophic remodeling. The second project focused on in vitro signaling in cardiac fibroblasts from diabetic and non-diabetic, RAGE knockout, and Rap1a knockout mice. Results showed that ERK1/2 activation by AGE or Exchange Protein Activated by cAMP (EPAC ) stimulation was significantly reduced in the absence of Rap1a or RAGE, indicating a convergence on Rap1a-dependent ERK1/2 signaling. The third project evaluated U0126, a MEK inhibitor, as a pharmacological strategy to block Rap1a-dependent signaling. While U0126 suppressed ERK and NF-κ[kappa]B phosphorylation, it did not consistently reduce α[alpha]-Smooth Muscle Actin (α[alpha]SMA) expression, pointing to parallel, ERK-independent mechanisms in fibroblast activation.
These findings support a model in which Rap1a integrates profibrotic signaling from AGERAGE and AT1R pathways. Although ERK1/2 inhibition blunts some aspects of this response, additional signaling nodes likely contribute to the persistence of inflammation and fibrosis. Rap1a thus represents a promising therapeutic target, but its inhibition may require combination strategies to fully reverse diabetic cardiac remodeling.
Recommended Citation
Porter, Cody Shayne, "The Role of RAP1A and Age-Rage Signaling in Cardiac Hypertrophy and Inflammation" (2025). Electronic Theses and Dissertations. 3361.
https://egrove.olemiss.edu/etd/3361