Y Yuan(1), J Milic(1), L Klose(1), M Avdic(1), S Ebert(1), R Pardi(2), Y Asare(1), J Bernhagen(1,3,4)

1: Institute for Stroke and Dementia Research (ISD), Klinikum der Universität München, Ludwig Maximilian University (LMU), Munich, Germany; 2: Division of Immunology, Transplantation, and Infectious Disease, IRCCS San Raffaele Scientific Institute, Milan, Italy; 3: Munich Cluster for Systems Neurology (SyNergy), Munich, Germany; 4: Munich Heart Alliance (DZHK), Munich, Germany

The constitutive photomorphogenesis 9 (COP9) signalosome (CSN) exhibits a deNEDDylase function through which it controls the ubiquitination activity of cullin-RING-E3 ligases (CRLs) and thus the levels of various cellular proteins. The CSN and its catalytic subunit CSN5 have been extensively studied in cancer, but its role in atherosclerosis remainsunclear. Previous work from our lab had shown a protective role for myeloid Csn5, but the contribution of endothelial CSN remains unclear. Here we studied artery-endothelial-specific deletion of Csn5 in HFD-fed Apoe–/–mice and performed siPool-induced Csn5 knock down in mouse aortic endothelial cells (MAECs). Additionally, MLN4924 as CSN5 mimic was applied. Conditional deletion of Csn5 in arterial endothelial cells in hyperlipidemic Apoe–/–mice (Csn5Δarterial/Apoe–/–) led to increased atherosclerosis and plaque vulnerability. Of note, tissue inhibitor of metalloproteinases (Timp-1) decreased in plasma of Csn5Δarterial/Apoe–/–mice, while MLN4924 treatment reversed these alterations. In vitro, Csn5 knock down in MAECs downregulated Timp-1, but upregulated MMP2 and MMP9. Notably, bulk RNAseq analysis of Csn5 knock down versuscontrol siRNA-treated MAECs indicated that Csn5 silencing activates the IFN-β pathway and enhances Cxcl10 as well as other IFN-related genes. Follow-up in vitro experiments in human aortic endothelial cells (HAoECs) with MLN4924 treatment showed a downregulation of IFN related genes, suggesting a similar atheroprotective function of CSN5 in HAoECs. In conclusion, arterial Csn5 depletion promotes the size and vulnerability of atherosclerotic plaques by (i) affecting the balance between TIMP-1 and MMPs and by (ii) upregulating a type I IFN-driven inflammatory chemokine response.