Endothelial Shp2 deficiency controls alternative activation of macrophage preventing radiation-induced lung injury through Notch signaling

Radiation-induced lung injury is a common late side-effect of thoracic radiotherapy. The inflammatory microenvironment plays a key role in this process. Endothelial cells are the goalkeeper of inflammation. Endothelial dysfunction following leukocytes infiltrated is a prominent feature in the pathogenesis of radiation-induced lung injury. Tyrosine phosphatase Shp2 is a key regulator of endothelial functions and inflammation. Here, we established a clinical-mimicking mouse model of radiation-induced lung injury and found that Shp2 activity was elevated in endothelium after injury. Mice with endothelium-specific Shp2 deletion showed relieved collagen deposition along with disrupted radiation-induced Jag1 expression in the endothelium. Furthermore, endothelium-derived Jag1 activated the alternative activation of macrophages in vitro and in vivo by paracrine Notch signaling. Consistently, Notch pathway was significant activated by chest irradiation in the peripheral blood leukocytes of cancer patients. Collectively, this is the first demonstration of radiation-induced lung injury regulation by endothelial Shp2. Shp2 participates in the radiation-induced endothelial dysfunction and subsequently inflammatory microenvironment producing. Relative mRNA level in irradiated shScr and shShp2 HUVECs.