Integrative Proteomics and Targeted Transcriptomics Analyses in Cardiac Endothelial Cells Unravel Mechanisms of Long-Term Radiation-Induced Vascular Dysfunction

Epidemiological data
from radiotherapy patients show the damaging
effect of ionizing radiation on heart and vasculature. The endothelium
is the main target of radiation damage and contributes essentially
to the development of cardiac injury. However, the molecular mechanisms
behind the radiation-induced endothelial dysfunction are not fully
understood. In the present study, 10-week-old C57Bl/6 mice received
local X-ray heart doses of 8 or 16 Gy and were sacrificed after 16
weeks; the controls were sham-irradiated. The cardiac microvascular
endothelial cells were isolated from the heart tissue using streptavidin-CD31-coated
microbeads. The cells were lysed and proteins were labeled with duplex
isotope-coded protein label methodology for quantification. All samples
were analyzed by LC–ESI–MS/MS and Proteome Discoverer
software. The proteomics data were further studied by bioinformatics
tools and validated by targeted transcriptomics, immunoblotting, immunohistochemistry,
and serum profiling. Radiation-induced endothelial dysfunction was
characterized by impaired energy metabolism and perturbation of the
insulin/IGF-PI3K-Akt signaling pathway. The data also strongly suggested
premature endothelial senescence, increased oxidative stress, decreased
NO availability, and enhanced inflammation as main causes of radiation-induced
long-term vascular dysfunction. Detailed data on molecular mechanisms
of radiation-induced vascular injury as compiled here are essential
in developing radiotherapy strategies that minimize cardiovascular
complications.