H istone deacetylases (HDACs) play a central role in the epigenetic regulation of gene expression. To date, 18 human HDACs have been identified, and they were classified into 4 classes: class I HDACs (HDAC1, 2, 3, and 8), class II HDACs (HDAC4, 5, 6, 7, 9, and 10), class III HDAC (Sir2), and class IV HDAC (HDAC11). Class II HDACs are further classified into class IIa (HDAC4, 5, 7, 9, and the HDAC9 splice variant myocyte enhancer factor [MEF]-2 interacting transcription repressor) and class IIb (HDAC6 and 10).1 Class IIa HDACs (4, 5, 7, and 9) seem to have critical roles in many diseases processes, including cardiac diseases, 2 cancer, 3 and viral infection. 4 Among them, recent study demonstrated that HDAC4 plays important roles in mediating cardiovascular diseases. For example, (1) Ca 2+ /calmodulin-dependent protein kinase (CaMK) II promoted hypertrophic growth via phosphorylation of HDAC4 in cultured cardiomyocytes, 5 (2) activation of HDAC4 promoted angiotensin II-induced vascular smooth muscle hypertrophy, 6 and (3) CaMKIIδA mediated cardiac hypertrophy by interfering with the HDAC4-MEF-2 signaling pathway. 7 In addition, we have recently demonstrated that expression of HDAC4 protein increased in mesenteric artery of spontaneously hypertensive rats. 8 Moreover, we demonstrated that HDAC4 promoted reactive oxygen species (ROS)-dependent vascular inflammation and mediated the development of hypertension in spontaneously hypertensive rats. 9 Proliferation and migration of vascular smooth muscle cells (SMCs) lead to the medial thickening (structural remodeling), which has a significant role on the processes of hypertension development. 10,11 In addition, ROS contribute to the pathogenesis of cardiovascular diseases, including hypertension 12 via promoting proliferation and migration of vascular SMCs. 13,14 Nevertheless, it remains to be clarified how HDAC4 controls SMCs proliferation and migration through ROS regulation. Therefore, we examined whether HDAC4 affects vascular neointimal hyperplasia via SMC proliferation and migration by especially focusing on cellular signaling related to ROS. Here, for the first time, we demonstrate that HDAC4 mediates ROS-dependent SMC proliferation and migration via activation of p38 mitogen-activated protein kinase (MAPK)/ heat shock protein (HSP) 27 pathway in a CaMKII-dependent manner, which may lead to the in vivo neointimal hyperplasia.
Abstract
Materials and MethodsThe detailed methods are available as an online-only Data Supplement.
Results
Effects of HDAC4 Knockdown on Platelet-Derived Growth Factor-BB-Induced SMC ProliferationFirst, we examined whether HDAC4 mediates SMC proliferation. SMC proliferation was evaluated by a cell counting. Platelet-derived growth factor (PDGF)-BB (20 ng/mL, 24 hours)-induced SMC proliferation was significantly inhibited by HDAC4 small interfering RNA (siRNA; Figure 1A and 1B). SMC proliferation was also evaluated by a bromodeoxyuridine incorporation assay. PDGF-BB (10 ng/mL, 24 hours)-induced bromodeoxyuridine incorporation was si...
