COP9 signalosome deneddylation activity is required for proliferation but not dedifferentiation of vascular smooth muscle cells in neointimal hyperplasia

Neointimal hyperplasia (NH) is a prominent pathological consequence following vascular injury and is driven in part by aberrant vascular smooth muscle cell (VSMC) proliferation. COP9 signalosome (CSN) subunit 5 (CSN5/JAB1/COPS5) is the deneddylase component of the CSN holocomplex responsible for deneddylation of cullin-RING ligases. Although CSN5/CSN is well studied in cancer biology, the role of CSN5/CSN in NH and vascular biology remain largely unexplored. Here, we investigated whether selective inhibition of CSN5 deneddylase activity using CSN5i-3 could mitigate neointimal remodeling following arterial injury. Adult mice were subjected to daily intraperitoneal injections of CSN5i-3 (20 mg/kg/day) or vehicle and left common carotid artery ligation. The left and the right common carotid arteries were then assessed for VSMC phenotypic modulation and neointima formation after 7 days of treatment. CSN5i-3 treatment markedly attenuated the ligation-induced changes in the mRNA level of COL1A1, FN1, CCND1, and CCND2, genes associated with extracellular matrix deposition and cell-cycle progression but did not alter expression changes of canonical smooth muscle differentiation markers ( MYOCD, MYH11, ACTA2) and KLF4 in the ligated vessel. Importantly, CSN5i-3 significantly blunted the increases of PCNA expression and Ki67-positive VSMCs and reduced neointimal areas. These findings demonstrate that CSN deneddylase activity is dispensable for the dedifferentiation of contractile VSMCs into the synthetic state but promotes VSMC proliferation, supporting the concept that the dedifferentiation and proliferation of VSMCs in neointimal formation are separately regulated processes and differentially regulated by different CSN actions. This study also indicates that CSN5i-3 is highly promising in preventing neointimal hyperplasia.