Diabetes-Mediated Vascular Calcification is RAGE-dependent
Amber M. Kennon1 & James A. Stewart, Jr.1
1Departmenet of BioMolecular Sciences, University of Mississippi School of Pharmacy, Oxford, MS
Type II diabetes mellitus (DM) is characterized by chronic hyperglycemia, and medial vascular calcification is a common cardiovascular complication of DM. This leads to aortic stiffening, which can leave patients at an increased risk for heart attack or stroke. Advanced Glycation End-Products (AGEs)/Receptor for AGEs (RAGE) signaling cascade has been implicated as a potentiator of diabetes-mediated vascular calcification, but it is not well understood. AGE/RAGE signaling influences both cellular and systemic responses to increase bone matrix proteins in hyperglycemic and calcification conditions and has also been shown to increase oxidative stress by promoting diabetes-mediated vascular calcification. This causes a phenotypic switch of vascular smooth muscle cells (VSMCs) to osteoblast-like cells and the hypothesized activation of adventitial fibroblasts (AFBs) to a myofibroblast phenotype. The purpose of this research is to understand AGE/RAGE mediated vascular calcification as a complication of diabetes. Calcification was induced for 7 days in primary mouse VSMCs and AFBs of non-diabetic, diabetic, non-diabetic RAGE knockout (RKO), and diabetic RKO, and then treated with AGEs to activate RAGE. Alizarin Red S staining was utilized to visualize calcification. Intracellular calcium levels were quantified and normalized to cell number (DAPI). Pronounced calcification was observed in non-diabetic VSMCs with the addition of AGEs and the loss of RAGE resulted in decreased calcification in the non-diabetic RKO VSMCs. AFBs were exposed to the same experimental conditions as the VSMCs and calcification was increased in the diabetic AFBs while calcification was significantly decreased in the diabetic RKO AFBs. These data demonstrated that diabetes-mediated vascular calcification was RAGE-dependent in both cell types. Literature has cited the VSMC as the primary mediator for vascular calcification, but we have shown that the AFBs in the outer layer of the aorta have the ability to calcify and this is mediated by RAGE signaling, which elucidates a role for RAGE in diabetes-mediated vascular calcification. Understanding the role of AGE/RAGE signaling in diabetes-mediated vascular calcification will allow for possible targets for pharmacological intervention.