Chronic inflammatory effects of in vivo irradiation of the murine heart on endothelial cells mimic mechanisms involved in atherosclerosis.

PURPOSE

Radiotherapy is a major pillar in the treatment of solid tumors including breast cancer. However, epidemiological studies have revealed an increase in cardiac diseases approximately a decade after exposure of the thorax to ionizing irradiation, which might be related to vascular inflammation. Therefore, chronic inflammatory effects were examined in primary heart and lung endothelial cells (ECs) of mice after local heart irradiation.

METHODS

Long-lasting effects on primary ECs of the heart and lung were studied 20-50 weeks after local irradiation of the heart of mice (8 and 16 Gy) in vivo by multiparameter flow cytometry using antibodies directed against cell surface markers related to proliferation, stemness, lipid metabolism, and inflammation, and compared to those induced by occlusion of the left anterior descending coronary artery.

RESULTS

In vivo irradiation of the complete heart caused long-lasting persistent upregulation of inflammatory (HCAM, ICAM‑1, VCAM-1), proliferation (CD105), and lipid (CD36) markers on primary heart ECs and an upregulation of ICAM‑1 and VCAM‑1 on primary ECs of the partially irradiated lung lobe. An artificially induced heart infarction induces similar effects with respect to inflammatory markers, albeit in a shorter time period.

CONCLUSION

The long-lasting upregulation of prominent inflammatory markers on primary heart and lung ECs suggests that local heart irradiation induces chronic inflammation in the microvasculature of the heart and partially irradiated lung that leads to cardiac injury which might be related to altered lipid metabolism in the heart.