OC 16.1 - The Role of Endothelial Glycogen Synthase Kinase (GSK)-3α in Hyperglycemia-Induced Endothelial Activation and Atherosclerosis

Background: Cardiovascular risk factors have been implicated in endothelial activation and the development of atherothrombosis. Activated endothelial cells (ECs) express adhesion proteins that recruit monocytes to the sub-endothelium initiating atherosclerosis. Glycogen synthase kinase (GSK)-3α/β are constitutively active kinases that are involved in many cellular processes regulating cell viability and metabolism. While roles for myeloid GSK3α/β in the development of atherosclerosis have been established, there is limited knowledge of the potential role of endothelial GSK3α/β.

Aims: This study examines the role of endothelial GSK3α/β in hyperglycemia-induced EC activation and the initiation and progression of atherosclerosis.

Methods: Human aortic endothelial cells (HAECs) were exposed to control (5mM) or elevated (30mM) concentrations of glucose for 24 hours. Subsets of cells were treated with the chemical chaperone 4-phenylbutyric acid (4PBA, 3mM) or the GSK3α/β inhibitor tideglusib (25µM). Thp-1 monocyte adherence was assessed and the expression of adhesive proteins P-selectin, E- selectin, VCAM-1 and ICAM-1 were quantified by RT-PCR. In vivo, atherosclerosis-prone, low-density lipoprotein receptor deficient (LDLR-/-) mouse strains were created in which endothelial GSK3α or GSK3β were genetically ablated (Tie2CreGSK3α/βfl/flLDLR-/-). Mice were fed a high fat diet until 15 weeks of age, and atherosclerosis and adhesion protein expression were quantified by immunostaining cross sections of the aortic sinus.

Results: In vitro studies revealed that exposure of HAECs to 30mM glucose significantly increased the expression of P-selectin, E-selectin and VCAM-1, but not ICAM-1. Attenuation of ER stress with 4PBA, or inhibition of GSK3α/β with tideglusib, reduced adhesion protein expression and monocyte adherence to ECs. In vivo studies showed that adhesion protein expression, macrophage recruitment and plaque volume were significantly reduced in GSK3α, but not GSK3β, knockout mice.

Conclusion(s): Together these findings are the first to suggest a pro-atherogenic role of endothelial GSK3α and support existing evidence for targeting GSK3α in the treatment of atherosclerotic CVD.