Cytokine-stimulated Smooth Muscle Cells Research Articles

Protective Role of RNA Helicase DEAD-Box Protein 5 in Smooth Muscle Cell Proliferation and Vascular Remodeling.

RNA helicases, highly conserved enzymes, are currently believed to be not only involved in RNA modulation, but also in other biological processes. We recently reported that RNA helicase DDX (DEAD-box protein)-5 is required for maintaining the homeostasis of vascular smooth muscle cells (SMCs). However, the expression and function of RNA helicase in vascular physiology and disease is unknown. To investigate the role of RNA helicase in vascular diseases. We showed here that DDX-5 was the most abundant DEAD-box protein expressed in human and rodent artery, which mainly located in SMCs. It was demonstrated that DDX-5 levels were reduced in cytokine-stimulated SMCs and vascular lesions. DDX-5 knocking down or deficiency increased SMC proliferation and migration, whereas overexpression of DDX-5 prevented aberrant proliferation and migration of SMCs. Mechanistic studies revealed transcription factor GATA (GATA-binding protein)-6 as a novel downstream target of DDX-5, which directly interacted with GATA-6 and protected it from MDM (mouse double minute)-2-mediated degradation. Our ChIP assay identified a previously unreported binding of p27Kip1 promoter to GATA-6. DDX-5 increased the recruitment of GATA-6 to p27Kip1 promoter, which enhanced p27Kip1 expression and maintained SMC quiescence. Finally, we showed exacerbated neointima formation in DDX-5 SMC-deficient mice after femoral artery injury, whereas overexpression of DDX-5 potently inhibited vascular remodeling in balloon-injured rat carotid artery. These findings provide the first evidence for a role of RNA helicase DDX-5 in the protection against SMC proliferation, migration, and neointimal hyperplasia. Our data extend the fundamental role of RNA helicase beyond RNA modulation, which provides the basic information for new therapeutic strategies for vascular diseases.

Silencing of the F11R gene reveals a role for F11R/JAM-A in the migration of inflamed vascular smooth muscle cells and in atherosclerosis

Rationale and objectiveOur previous studies have determined that the F11 receptor (F11R; aka JAM-A) exerts a critical force in the adhesion of human platelets to inflamed endothelial cells (ECs), and thus can play a significant role in the initiation of atherosclerotic plaque formation. In the present study, we focus on a subsequent event in plaque development – the migration of smooth muscle cells (SMCs) from the media to the intima of inflamed vessels. Here we report our investigation of the expression of F11R in atherosclerotic arteries of coronary artery disease (CAD) patients, and of the role of F11R in the migration of SMCs involved in atherogenesis. Methods and resultsHistological staining and specific-antibody immunofluorescence of excised, human atherosclerotic coronary arteries revealed the expression of F11R in the SMCs of the intima. RT-PCR and SDS-PAGE followed by immunoblotting procedures demonstrated that F11R mRNA and the F11R protein levels were enhanced by the stimulation of cultured human aortic SMCs with a combined treatment of proinflammatory cytokines (TNFα+INFγ+IL-β1). Neither the F11R message nor protein was expressed in non-stimulated SMCs. The functional role of F11R in SMCs’ migration was studied in cytokine-stimulated SMCs by interference of F11R expression with siRNA. Silencing of the F11R gene of cytokines-treated SMCs inhibited the expression of both F11R mRNA and F11R protein. Functionally, silencing of the F11R gene blocked the proliferation and migration of these inflamed SMCs, both critical events in atherogenesis. ConclusionsThe new findings of this study are that F11R mRNA and F11R protein are expressed in SMCs of the intima (but not in the media) of atherosclerotic arteries of CAD patients, and that F11R is required for the proliferation and migration of inflamed SMCs. Based on these findings, we conclude that in addition to the previously reported role of F11R in the initiation of plaque formation, F11R plays also an important role in the subsequent growth of atherosclerotic plaques. Identification of drugs that interfere with these pathophysiologic actions of F11R thus represents an effective new approach for the prevention and treatment of atherosclerosis, heart attacks and stroke.