A pro-inflammatory role of deubiquitinating enzyme cylindromatosis (CYLD) in vascular smooth muscle cells

Abstract

CYLD, a deubiquitinating enzyme (DUB), is a critical regulator of diverse cellular processes, ranging from proliferation and differentiation to inflammatory responses, via regulating multiple key signaling cascades such as nuclear factor kappa B (NF-κB) pathway. CYLD has been shown to inhibit vascular lesion formation presumably through suppressing NF-κB activity in vascular cells. However, herein we report a novel role of CYLD in mediating pro-inflammatory responses in vascular smooth muscle cells (VSMCs) via a mechanism independent of NF-κB activity. Adenoviral knockdown of Cyld inhibited basal and the tumor necrosis factor alpha (TNFα)-induced mRNA expression of pro-inflammatory cytokines including monocyte chemotactic protein-1 (Mcp-1), intercellular adhesion molecule (Icam-1) and interleukin-6 (Il-6) in rat adult aortic VSMCs (RASMCs). The CYLD deficiency led to increases in the basal NF-κB transcriptional activity in RASMCs; however, did not affect the TNFα-induced NF-κB activity. Intriguingly, the TNFα-induced IκB phosphorylation was enhanced in the CYLD deficient RASMCs. While knocking down of Cyld decreased slightly the basal expression levels of IκBα and IκBβ proteins, it did not alter the kinetics of TNFα-induced IκB protein degradation in RASMCs. These results indicate that CYLD suppresses the basal NF-κB activity and TNFα-induced IκB kinase activation without affecting TNFα-induced NF-κB activity in VSMCs. In addition, knocking down of Cyld suppressed TNFα-induced activation of mitogen activated protein kinases (MAPKs) including extracellular signal-activated kinases (ERK), c-Jun N-terminal kinase (JNK), and p38 in RASMCs. TNFα-induced RASMC migration and monocyte adhesion to RASMCs were inhibited by the Cyld knockdown. Finally, immunochemical staining revealed a dramatic augment of CYLD expression in the injured coronary artery with neointimal hyperplasia. Taken together, our results uncover an unexpected role of CYLD in promoting inflammatory responses in VSMCs via a mechanism involving MAPK activation but independent of NF-κB activity, contributing to the pathogenesis of vascular disease.

CYLD-Mediated Signaling and Diseases

“…Apparently, knockout of CYLD did not affect albumin or peroxide-related cell death in human epithelial HK-2 cells, but it did increase ICAM-1 and JNK levels upon TNFα stimulation. Another report dealt with the vascular smooth muscle cells (VSMCs) in the aortic arch, thought to be involved in lesion formation [13]. An adenoviral knockdown of CYLD showed a notable decrease in TNFα-induced inflammatory cytokines Mcp-1, IL-6 and ICAM-1.…”

“…Exploration then continued with the thought of CYLD as being a tumor suppressor and inflammatory control factor, especially in the skin [9, 10]. As more pathogen responses and developmental aspects of cellular biology began to be linked to inflammation, CYLD’s role as a master regulator of NF-kB-induced inflammation came into the forefront as a factor that could switch off NF-kB and prevent tissue damage that leads to necrosis, cancer and loss of cell proliferation [11–13]. From 2009, many reports detailing specific instances in diverse tissue types (such as lungs, immune cells, breast tissue and bone) where CYLD loss of function is deleterious have been published [14–22].…”

DNA Enzyme ED5 Depletes Egr-1 and Inhibits Neointimal Hyperplasia in Rats

“…Leukocyte infiltration is guided by chemotactic factors, and the release of cytokines recruits additional inflammatory cells. Adhesion molecules such as ICAM-1 and chemokines such as MCP-1 are fundamental to inflammatory processes [32]. Inoue et al [33] demonstrated that serum levels of ICAM-1 significantly increased in human coronary sinus blood samples immediately after angioplasty.…”

Deubiquitinating Enzymes as Promising Drug Targets for Infectious Diseases

“…CYLD is a DUB controlling inflammatory responses via regulating such signalling cascades as nuclear factor kappa B (NF-κB) pathway [12–14]. Specifically, it has been shown to down-regulate NF-κB activation through deubiquitination of TRAF2, 6, and 7, therefore preventing the formation of an antiviral response [14–17].…”

“…Specifically, it has been shown to down-regulate NF-κB activation through deubiquitination of TRAF2, 6, and 7, therefore preventing the formation of an antiviral response [14–17]. E3 ligase Itch and deubiquitinase CYLD form a complex that cleaves lysine (Lys) 63-linked ubiquitin chains and catalyze Lys48-linked ubiquitination on the kinase Tak1, which is a common substrate for these two proteins, thereby contributing to decreased inflammatory signalling [18].…”