Mitchell J B, DeGraff W, Kim S, Cook J A, Gamson J, Christodoulou D, Feelisch M, Wink D A
Radiation Biology Branch, National Cancer Institute, Bethesda, MD 20892, USA.
Int J Radiat Oncol Biol Phys. 1998 Nov 1;42(4):795-8. doi: 10.1016/s0360-3016(98)00327-7.
Previous studies have shown that nitric oxide (NO) delivered from NO donor agents sensitizes hypoxic cells to ionizing radiation. In the present study, nitroxyl (NO-), a potential precursor to endogenous NO production, was evaluated for hypoxic cell radiosensitization, either alone or in combination with electron acceptor agents.
Radiation survival curves of Chinese hamster V79 lung fibroblasts under aerobic and hypoxic conditions were assessed by clonogenic assay. Hypoxia induction was achieved by metabolism-mediated oxygen depletion in dense cell suspensions. Cells were treated with NO- produced from the nitroxyl donor Angeli's salt (AS, Na2N2O3, sodium trioxodinitrate), in the absence or presence of electron acceptor agents, ferricyanide, or tempol. NO concentrations resulting from the combination of AS and ferricyanide or tempol were measured under hypoxic conditions using an NO-sensitive electrode.
Treatment of V79 cells under hypoxic conditions with AS alone did not result in radiosensitization; however, the combination of AS with ferricyanide or tempol resulted in significant hypoxic radiosensitization with SERs of 2.5 and 2.1, respectively. Neither AS alone nor AS in combination with ferricyanide or tempol influenced aerobic radiosensitivity. The presence of NO generated under hypoxic conditions from the combination of AS with ferricyanide or tempol was confirmed using an NO-sensitive electrode.
Combining NO- generated from AS with electron acceptors results in NO generation and substantial hypoxic cell radiosensitization. NO- derived from donor agents or endogenously produced in tumors, combined with electron acceptors, may provide an important strategy for radiosensitizing hypoxic cells and warrants in vivo evaluation.
先前的研究表明，一氧化氮供体产生的一氧化氮（NO）可使缺氧细胞对电离辐射敏感。在本研究中，对作为内源性NO产生潜在前体的硝酰阴离子（NO-）单独或与电子受体剂联合用于缺氧细胞放射增敏作用进行了评估。
通过克隆形成试验评估中国仓鼠V79肺成纤维细胞在有氧和缺氧条件下的辐射存活曲线。通过在密集细胞悬液中代谢介导的氧消耗来实现缺氧诱导。在不存在或存在电子受体剂铁氰化物或Tempol 的情况下，用硝酰阴离子供体安吉利盐（AS，Na2N2O3，三氧二硝酸钠）产生的NO-处理细胞。在缺氧条件下使用NO敏感电极测量AS与铁氰化物或Tempol组合产生NO的浓度。
在缺氧条件下单独用AS处理V79细胞不会导致放射增敏；然而，AS与铁氰化物或Tempol的组合导致显著的缺氧放射增敏，其增强比分别为2.5和2.1。单独使用AS或AS与铁氰化物或Tempol的组合均不影响有氧放射敏感性。使用NO敏感电极证实了在缺氧条件下AS与铁氰化物或Tempol组合产生的NO的存在。
将AS产生的NO-与电子受体结合可产生NO并导致显著缺氧细胞放射增敏。来自供体剂或肿瘤内源性产生的NO-与电子受体结合，可能为缺氧细胞放射增敏提供重要策略，值得进行体内评估。
