The endothelium is the barrier separating blood and tissue. Radiation-induced enhanced inflammation leading to permeability of this barrier may increase the risk of cardiovascular disease. The aim of this study was to investigate the onset of endothelial inflammatory pathways after radiation exposure. Human coronary artery endothelial cells (HCECest2) were exposed to radiation doses of 0, 0.25, 0.5, 2.0 and 10 Gy (60Co-γ). The cells were harvested 4 h, 24 h, 48 h and 1 wk post-irradiation. The proteomics analysis was performed in a label-free data-independent acquisition mode. The data were validated using bioinformatics and immunoblotting. The low- and moderate-dose-treated samples showed only small proteome changes. In contrast, an activation of DNA-damage repair, inflammation, and oxidative stress pathways was seen after high-dose treatments (2 and 10 Gy). The level of the DNA damage response protein DDB2 was enhanced early at the 10 Gy dose. The expression of proteins belonging to the inflammatory response or cGAS-STING pathway (STING, STAT1, ICAM1, ISG15) increased in a dose-dependent manner showing the strongest effects at 10 Gy after one week. This study suggests a connection between radiation-induced DNA damage and induction of inflammation and supports inhibition of cGAS-STING pathway in the prevention of radiation-induced cardiovascular disease.