Anti-Diabetic Atherosclerosis by Inhibiting High Glucose-Induced Vascular Smooth Muscle Cell Proliferation via Pin1/BRD4 Pathway

Background and purpose. Vascular smooth muscle cells (VSMC) proliferation and migration is the important pathological process of diabetic atherosclerosis. Bromine domain protein 4 (BRD4) is involved in cell proliferation and inflammatory disease. Pin1 enhances BRD4 stability and its transcriptional activity. This study aimed to explore the possible mechanism of Pin1/BRD4 in diabetic atherosclerosis. Methods. Diabetic Apoe-/- mice induced by streptozotocin were treated with vehicle, the Pin1 inhibitor juglone, or the BRD4 inhibitor JQ1 for 3 weeks. VSMCs were pretreated with juglone, JQ1, or vehicle for 45 min, and then exposed to high glucose for 48 h. Hematoxylin–eosin staining was performed to assess atherosclerotic plaques of the thoracic aorta. Western blotting was used to detect expression levels of Pin1, BRD4, cyclin D1, and matrix metalloproteinase-9 (MMP-9) in the thoracic aorta and VSMCs. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and transwell assay were used to measure proliferation and migration of VSMCs. Results. Juglone and JQ1 significantly improved atherosclerosis of diabetic Apoe-/- mice and reduced high glucose-induced VSMC proliferation and migration. Cyclin D1 and MMP-9 levels in the thoracic aorta were lower in diabetic Apoe-/- mice treated with juglone and JQ1 compared with vehicle-treated diabetic Apoe-/- mice. Additionally, BRD4 protein expression in high glucose-induced VSMCs was inhibited by juglone and JQ1. Upregulation of Pin1 expression by transduction of the Pin1 plasmid vector promoted BRD4 expression induced by high glucose, and stimulated proliferation and migration of VSMCs. Conclusions. Inhibition of Pin1/BRD4 pathway may improve diabetic atherosclerosis by inhibiting proliferation and migration of VSMCs.