Radiation-induced Endothelial Inflammation is Transferred via Secretome to Recipient Cells in a STAT-Driven Process

Irradiation is the most common treatment of cancer. However, minimizing the normal tissue injury, especially the damage to vascular endothelium, still remains a challenge. This study aimed to analyze direct and indirect radiation effects by investigating mechanisms of signal transfer from irradiated to non-irradiated endothelial cells by means of secreted proteins. It is known that human coronary artery endothelial cells (HCAECest2) undergo radiation-induced senescence 14 days post-exposure to 10 Gy X-rays. Proteomics analysis was performed using label-free technology on HCAECest2 at this time point after irradiation with X-ray doses of 0 Gy (control) or 10 Gy. Additionally, the proteomes of control and radiation-induced secretomes, and those of non-irradiated HCAECest2 exposed for 24 hours to secreted proteins of either condition were measured. Key changes identified by proteomics and bioinformatics were validated by immunoblotting, ELISA, bead-based multiplex assays, and targeted transcriptomics. The irradiated cells, their secretome and the non-irradiated recipient cells showed inflammatory response, characterized by induction of interferon type I-related proteins and activation of STAT3 pathway. These data show that radiation-induced premature senescence in endothelial cells exerts detrimental effects via senescence-associated secretory phenotype on the non-irradiated microenvironment. This study adds to our knowledge of the pathological background of radiation-induced cardiovascular disease.