Irradiation induces gene expression changes in cultured murine brain endothelial cells

Brain arteriovenous malformations (AVMs) are abnormal connections between arteries and veins and are the leading cause of hemorrhagic stroke in children and young adults. Treatment of large and deep AVMs remains challenging, therefore new and safe treatment methods are required. Our hypothesis is that stereotactic radiosurgery can be used to selectively alter AVM endothelial cell phenotype, allowing targeted molecular therapies that spare normal vessels. This study examined the post-radiation time course of gene expression changes of potential molecular targets. A murine brain endothelial cell culture (bEnd.3) was treated with 25 Gy using a linear accelerator; non-irradiated cells were used as controls. Quantitative real-time PCR was used to measure the relative gene expression at 1, 6, 12, 24, 48, 72, 96, 120, 144, and 168 h after radiation. Genes encoding for intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were found to be significantly up-regulated post irradiation (p<0.0001), with the maximum level of gene expression for ICAM-1 being evident at 144 h (9-fold) and for VCAM-1 at 120 h (23-fold). Additionally, leukocyte-endothelial cell adhesion molecule 2 (E-selectin) and leukocyte-endothelial cell adhesion molecule 3 (P-selectin) showed significantly increased gene expression at 24 h with 1.5-fold (p<0.001) and 2-fold (p<0.0001) increases respectively. These data support the hypothesis that stereotactic radiosurgery can significantly alter endothelial cell phenotype in AVMs, potentially enabling the use of ligand-based molecular targeting therapies such as the stimulation of thrombosis for AVM treatment.