Functional changes in brain microvascular endothelial cells upon low-energy accelerated proton-irradiation

Nowadays, it has become a common practice to use ionizing radiation during justified diagnostic and therapeutic medical procedures. The ionizing radiation exposure can induce endothelial activation, dysfunction, reactive oxygen species formation, blood brain barrier permeability elevation and tight junction morphology changes [1,2]. The neuro-oncology specialists intend to develop a controlled method to disrupt the BBB in strategic places in the brain or tumor bed before the administration of chemotherapeutics in order to increase their distribution and efficacy. Thus, a complex characterization of the brain microvasculature after irradiation is imposed. The main objective of our study is to understand how accelerated proton beams affect the brain microvascular endothelial cells functionality. We obtained preliminary results after low energy accelerated proton irradiation (<10 MeV) regarding the cytotoxic, genotoxic and functional effects upon an in vitro model of murine cerebral microvasculature (bEnd.3 cell line, ATCC). One beam line of a TR19 cyclotron was adapted to irradiate cell cultures in controlled conditions. We exposed the cell cultures to various doses in the range 0-10 Gy, the dose rate being of 1 Gy/min. After irradiation, the cellular capacity of proliferation and surviving in stress-induced conditions were tested using clonogenic assay method. Also, to assess the ionizing radiation-induced DNA damage, we measured the expression of micronuclei and g- H2AX foci. It is questionable the cellular functionality after irradiation and thus calcium ions dynamics was observed at different time intervals post-irradiation. As results, we observed a significant modification of the measured parameters with increasing the dose and the LET (linear energy transfer) values. Our study presents preliminary results for genotoxicity and cytotoxicity after proton irradiation which will contribute to our on-going study regarding the post-irradiation functional changes in endothelial cells. Considering that bEnd.3 is a popular cell line used for BBB model, our data are valuable in understanding the barrier behavior in oxidative stress conditions. (author)