The role of tribbles homolog 2 in vascular smooth muscle cell proliferation

Tribbles homolog 2 (TRIB2) functions as an adapter protein that regulates signal transductions involved in a variety of cellular functions, including tumorigenesis. However, the role of TRIB2 in the proliferation of vascular smooth muscle cells (VSMCs) and the underlying expression mechanisms remain unclear. The present study investigated the role of TRIB2 in VSMC proliferation and revealed that TRIB2 expression increases following vascular injury and platelet-derived growth factor (PDGF)-BB-stimulated VSMCs. We found that pretreatment with diphenyleneiodonium (a nicotinamide adenine dinucleotide phosphate oxidase inhibitor), U0126 (an inhibitor of mitogen-activated protein kinase kinase 1 [MEK1]), or siRNA targeting the gene encoding early growth response 1 (EGR-1) significantly inhibits PDGF-BB-induced TRIB2 expression in VSMCs. Furthermore, TRIB2 knockdown significantly inhibits PDGF-BB-induced proliferation of VSMCs but does not affect the phosphorylation of AKT. However, phosphorylation of ERK1 and expression of proliferating cell nuclear antibody are significantly suppressed in VSMCs by PDGF-BB stimulation. Thus, PDGF-BB-induced TRIB2 expression is mediated by ROS/ERK/EGR-1 pathways and plays a critical role in VSMC proliferation via modulation of ERK activity. We propose TRIB2 as a promising therapeutic target for the prevention of neointima formation and vascular disease.