PKCβ Promotes Vascular Inflammation and Acceleration of Atherosclerosis in Diabetic ApoE Null Mice

Abstract

Subjects with diabetes mellitus are at high risk for developing atherosclerosis through a variety of mechanisms. Because the metabolism of glucose results in production of activators of protein kinase C (PKC)β, it was logical to investigate the role of PKCβ in modulation of atherosclerosis in diabetes mellitus. ApoE(-/-) and PKCβ(-/-)/ApoE(-/-) mice were rendered diabetic with streptozotocin. Quantification of atherosclerosis, gene expression profiling, or analysis of signaling molecules was performed on aortic sinus or aortas from diabetic mice. Diabetes mellitus-accelerated atherosclerosis increased the level of phosphorylated extracellular signal-regulated kinase 1/2 and Jun-N-terminus kinase mitogen-activated protein kinases and augmented vascular expression of inflammatory mediators, as well as increased monocyte/macrophage infiltration and CD11c(+) cells accumulation in diabetic ApoE(-/-) mice, processes that were diminished in diabetic PKCβ(-/-)/ApoE(-/-) mice. In addition, pharmacological inhibition of PKCβ reduced atherosclerotic lesion size in diabetic ApoE(-/-) mice. In vitro, the inhibitors of PKCβ and extracellular signal-regulated kinase 1/2, as well as small interfering RNA to Egr-1, significantly decreased high-glucose-induced expression of CD11c (integrin, alpha X 9 complement component 3 receptor 4 subunit]), chemokine (C-C motif) ligand 2, and interleukin-1β in U937 macrophages. These data link enhanced activation of PKCβ to accelerated diabetic atherosclerosis via a mechanism that includes modulation of gene transcription and signal transduction in the vascular wall, processes that contribute to acceleration of vascular inflammation and atherosclerosis in diabetes mellitus. Our results uncover a novel role for PKCβ in modulating CD11c expression and inflammatory response of macrophages in the development of diabetic atherosclerosis. These findings support PKCβ activation as a potential therapeutic target for prevention and treatment of diabetic atherosclerosis.