Abstract 595: Anti-inflammatory and Anti-proliferative Action of Cylindromatosis (CYLD) in Atherosclerosis as a Deubiquitinating Enzyme
Growing evidence in clinical studies suggests that ubiquitin systems are greatly related to the progression of atherosclerosis, particularly in relation to inflammation and cell proliferation. However, there were few reports referred to molecular mechanisms of vascular remodeling related to ubiquitin systems. NF-κB is an important transcriptional factor which plays central roles in pathogenesis of atherosclerosis. Thus, in this study, we focused on CYLD which is a NF-κB-related deubiquitinating enzyme and may be a therapeutic target of tumor in cancer research. From Northern blot and immunohistology, CYLD was endogenously expressed in vascular endothelial cells (EC) and smooth muscle cells (VSMC). Interestingly, the treatment of TNF-α significantly increased CYLD expression in EC and VSMC. CYLD was markedly induced in the neointima of the balloon-injured carotid arteries, and was also present in atherosclerotic lesions from human carotid arteries. Thus, the expression of CYLD could be upregulated according to the activation of ubiquitin system. Over-expressed CYLD significantly attenuated TNF-α-induced NF-κB activity in EC, accompanied with suppression of the attachment with monocyte cells through suppression of adhesion molecules expression. Also in VSMC, CYLD inhibited TNF-α-induced NF-κB activity and inflammatory cytokines expression. As a deubiq-uitinating enzyme, CYLD deubiquitinated TRAF2, which usually interacts with IKK kinase by being ubiquitinated. Therefore, CYLD inactivated the NF-κB signaling by deubiquitination of TRAF2. Of importance, we also confirmed that over-expressed CYLD suppressed PDGF-BB-induced cell viability assessed by MTS assay and E2F activity in VSMC. The main target molecule of its anti-proliferative effect was Bcl-3, but not TRAF2. As a deubiqitinating enzyme, CYLD deubiquitinated Bcl-3 and inhibited translocation into nucleus and interaction of p50 and p52, leading to inactivation of cyclin D1. Therefore, CYLD attenuated cell proliferation by deubiquitination of Bcl-3. Here is the first evidence to show the important function of CYLD in vasculature through interaction of NF-κB signaling via deubiquitination. These results suggest that CYLD would be a novel target gene to treat atherosclerosis.