Nitric oxide-mediated bystander effect induced by heavy-ions in human salivary gland tumour cells.
OBJECTIVE
To investigate the signal factor and its function in the medium-mediated bystander effect during heavy-ion irradiation of human salivary gland (HSG) neoplastic cells.


METHODS
Unirradiated recipient HSG cells were co-cultivated with HSG donor cells irradiated with 290 MeV/u carbon beams having different LET values. Cell proliferation and micronucleus (MN) induction in recipient cells with and without treatment of a NO scavenger (PTIO) were measured and the concentration of nitrite in the co-culture medium was detected. As a direct control, the effects of a nitric oxide (NO) generator (sper/NO) on cell proliferation and MN induction were also examined.


RESULTS
Increases in cell proliferation and MN induction were found in the recipient HSG cells as a result of co-culturing and cell proliferation was obviously enhanced during a further subculture. In comparison with 13keV/microm, 100keV/microm carbon-ion irradiation was found to be a more efficient inducer of the medium-mediated bystander effect. The treatment of cells by PTIO resulted in elimination of such effects, which supports a role for NO in the medium-mediated bystander effect. As an oxidization product of NO, nitrite was detected in the co-culture medium, and the dose-response for its concentration was similar to that of cell proliferation and MN induction in the recipient cells. When the HSG cells were treated by sper/NO with a concentration of less than 20 microM cell proliferation was enhanced, whereas MN increased along with sper/NO concentration.


CONCLUSIONS
NO participated in the medium-mediated bystander effects on cell proliferation and MN induction, depending on the LET of irradiation.
Shao
C
C
Heavy-Ion Radiobiology Research Group, National Institute of Radiological Sciences, Inage, Chiba, Japan. clshao@nirs.go.jp
Furusawa
Y
Y
Aoki
M
M
Matsumoto
H
H
Ando
K
K
D002455:Cell Division / Q000528:radiation effects; D018920:Coculture Techniques; D006801:Humans; D018499:Linear Energy Transfer; D048629:Micronuclei, Chromosome-Defective / Q000528:radiation effects; D009569:Nitric Oxide / Q000378:metabolism*; D011836:Radiation Tolerance; D012468:Salivary Gland Neoplasms / Q000378:metabolism* / Q000532:radiotherapy*; D014407:Tumor Cells, Cultured
D009569:Nitric Oxide