The radiobiological effectiveness of carbon-ion beams on growing neurons.
OBJECTIVE
Recently carbon-ion beams have been reported to be remarkably effective for controlling various cancers with less toxicity and are thought to be a promising modality for cancer treatment. However, the biological effect of carbon-ion beams arising on normal neuron remains unknown. Therefore, this study was undertaken to investigate the effect of carbon-ion beams on neurons by using both morphological and functional assays.


METHODS
Dorsal root ganglia (DRG) and sympathetic ganglion chains (SYMP) were isolated from day-8 and day-16 chick embryos and cultured for 20 h. Cultured neurons were exposed to carbon-ion beams and X-rays. Morphological changes, apoptosis and cell viability were evaluated with the Growth Cone Collapse (GCC), Terminal deoxynucleotidyl Transferase (TdT)-mediated deoxyUridine TriPhosphate (dUTP) nick End Labeling [TUNEL] assay and 4-[3-(4-iodophenyl)- 2-(4-nitrophenyl)- 2H-5-tetrazolio]- 1,3-benzenedisulfonate [WST-1] assays, respectively.


RESULTS
Irradiation caused GCC and neurite destruction on a time- and irradiation dose-dependent manner. Changes in morphological characteristics were similar following either irradiation. Morphological and functional assays showed that day-8 neurons were more radiosensitive than day-16 neurons, whereas, radiosensitivity of DRG was comparable to that of SYMP. The dose-response fitting curve utilising both GCC and TUNEL labeling index showed higher relative biological effectiveness (RBE) values were associated with lower lethal dose (LD) values, while lower RBE was associated with higher LD values.


CONCLUSIONS
Exposure to high-linear energy transfer (LET) irradiation is up to 3.2 more efficient to induce GCC and apoptosis, in early developed neuronal cells, than low-LET irradiation. GCC is a reliable method to assess the radiobiological response of neurons.
Al-Jahdari
Wael S
WS
Department of Radiation Oncology, Gunma University Graduate School of Medicine, Gunma, Japan.
Suzuki
Yoshiyuki
Y
Yoshida
Yukari
Y
Hamada
Nobuyuki
N
Shirai
Katsuyuki
K
Noda
Shin-Ei
SE
Funayama
Tomoo
T
Sakashita
Tetsuya
T
Kobayashi
Yasuhiko
Y
Saito
Shigeru
S
Goto
Fumio
F
Nakano
Takashi
T
D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D002244:Carbon; D002470:Cell Survival / Q000528:radiation effects; D002642:Chick Embryo; D004307:Dose-Response Relationship, Radiation; D020450:Heavy Ions; D018499:Linear Energy Transfer; D009474:Neurons / Q000528:radiation effects*; D011853:Radiobiology; D012062:Relative Biological Effectiveness
D002244:Carbon