Endothelial Cell Migration was Impaired by Irradiation-Induced Inhibition of SHP-2 in Radiotherapy: an In vitro Study

The response of endothelial cells to radiation in the context of wound healing is not yet completely understood. In this study we investigated the mechanism involved in the wound healing process after low linear energy transfer (LET) radiation exposure. A scratch wound model on primary vascular endothelial cell monolayer was exposed to acute dose of 0.1, 2 or 10 Gy. The number of cells crossing the wound border and the wound closure percentage was measured. The expression of α(v)β₃ integrins, focal adhesion kinase (FAK) and phosphorylated FAK (tyr397) as well as SHP-2 phosphatase were assayed through immunoblotting, immunoprecipitation and optical imaging. Compared to the low dose irradiation, 2 and 10 Gy had remarkably inhibitory effects on cell motility and consequently the wound closure. Integrins α(v) and β₃ showed no irradiation-dose dependent variation. Contrast to the relatively constant level of FAK in all groups, the amount of phosphor-FAK tyr397 was higher with dose increasing. The protein and PCR analysis of SHP-2 revealed an opposite expression pattern to FAK tyr397. In conclusion, radiation-induced inhibition of cell migration could be attributed to the irradiative inhibition to SHP-2 phosphatase, and the subsequent accumulated phosphorylated FAK abrogated the contraction-extension cycle of cytoskeletons.