Short and long-term exposure of CNS cell lines to BPA-f a radiosensitizer for Boron Neutron Capture Therapy: safety dose evaluation by a battery of cytotoxicity tests

Despite the current clinical use of boronophenylalanine-fructose (BPA-f), as radiosensitizer, in BNCT application for brain tumors, still remains to be determined the safety dose of this agent. We evaluated the potential risk of primary BPA-f toxicity before neutronic irradiation at different concentrations (0–100 μg Beq/ml) after short- and long-term exposure (4–48 h and 7–10 days), using a battery of tests (i.e. MTT assay, calcein-AM/Propidium Iodide staining, clonogenic test) in CNS cell models (D384 and SH-SY5Y), and non-neuronal primary human fibroblasts (F26). MTT data showed: (i) no cytotoxic effects after short-term exposure (4 h) to any of BPA-f concentrations tested in all cell models; (ii) dose- and time-dependent mitochondrial activity impairment in D384 and SH-SY5Y cells only (with 60% and 40% cell death in D384 and SH-SY5Y, respectively, after 48 h exposure to BPA-f 100 μg Beq/ml). By Calcein-AM/PI staining, BPA-f treatment was specific toward SH-SY5Y cells only: a dose-dependent cell density reduction was observed, with a more pronounced effect after 48 h exposure (15–40% at doses ranging 20–100 μg Beq/ml). Clonogenic data revealed dose-dependent decrease of cell proliferative capacity in all cell lines, still the SH-SY5Y cells were the most sensitive ones: the lowest dose (20 μg Beq/ml) produced 90% cell decrease. These results indicate dose- and time-dependent cytotoxic effects of BPA-f, with CNS cells showing a lower tolerance compared to fibroblasts. Long-term exposure to BPA-f compromised the proliferative capacity regardless of cell model type (cell sensitivity being SH-SY5Y > D384 > F26). In short-time exposure, BPA-f exhibits a safe dosage up to 40 μg Beq/ml for the viability of CNS cell lines.

► The dose level or exposure time may be critical factors.
► BPA-f can be toxic before irradiation (CNS cells show a lower tolerance compared to fibroblasts).
► Long-term exposure impairs the proliferative capacity irrespective of cell model type.
► A safety dose of 40 μg Beq/ml has been observed for short-time exposure to BPA-f of CNS cells.