Data from several studies suggest that the ubiquitin-proteasome system may play 
a role in the progression of atherosclerosis. Here, we examined the potential 
role of the deubiquitinating enzyme CYLD (cylindromatosis), mutation of which 
has been reported to cause familial cylindromatosis. Northern blot analysis 
revealed expression of CYLD mRNA in the aorta, as well as in cultured human 
aortic endothelial cells (ECs) and vascular smooth muscle cells. Treatment with 
recombinant tumor necrosis factor (TNF)-alpha significantly increased CYLD 
expression in ECs and vascular smooth muscle cells. Immunostaining showed CYLD 
expression in atherosclerotic lesions from human carotid arteries and 
up-regulation of CYLD expression in the neointima of rat carotid arteries after 
balloon injury. Overexpression of CYLD in ECs resulted in inhibition of 
TNF-alpha-induced nuclear factor-kappaB activity through deubiquitination of 
TNFR-associated factor 2 (TRAF2), whereas overexpression of catalytically 
inactive CYLD had no effect. CYLD overexpression also inhibited expression of 
cyclin D1 and activation of the E2F pathway through deubiquitination of the 
upstream molecule Bcl-3 and inhibition of its translocation into the nucleus. 
Overexpressed CYLD also significantly inhibited cell viability. Furthermore, 
overexpression of CYLD in rat balloon-injured carotid artery attenuated 
neointimal formation through inactivation of nuclear factor-kappaB and E2F. In 
conclusion, these data demonstrate that the deubiquitinating enzyme CYLD may 
inhibit inflammation and proliferation in vascular cells and may represent a 
novel target for the treatment or prevention of atherosclerosis.