Partial volume rat lung irradiation: An evaluation of early DNA damage
Partial volume rat lung irradiation: An evaluation of early DNA damage
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DOI：
10.1016/s0360-3016(97)00736-0
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发表时间：
1998-01-15
影响因子：
7
通讯作者：
Van Dyk, J
中科院分区：
文献类型：
--
作者：
Khan, MA;Hill, RP;Van Dyk, J
目的:1。目的探讨单剂量部分体积照射（肺底和肺尖）对大鼠肺细胞早期DNA损伤的影响。2. 测定不同肺区DNA损伤的差异。3. 探讨肺辐照后早期DNA损伤的可能机制。方法与材料：将Sprague-Dawley大鼠全肺或全肺上半部分或下半部分暴露于10 Gy (60)Co γ射线下。动物在辐照后42小时的不同时间被处死。制备胰蛋白酶消化的肺细胞悬浮液，然后在最初24小时内附着在载玻片上的细胞在含有细胞松弛素b的培养基中再生长72小时。使用具有良好特征的微核试验，对来自辐照和未辐照肺区域的细胞（主要是成纤维细胞）中辐射诱导的DNA损伤进行量化。结果：全肺辐照后16-18 h取肺时，辐照动物肺细胞中每双核细胞（BNC）微核数约为0.85，对照组为0.02 MN/BNC。仅肺基部辐照时，微核频率为0.85 MN/BNC，而辐照后肺尖细胞微核频率为0.43 MN/BNC。特别令人感兴趣的是，发现未照射的肺尖在肺底照射后也显示出较大的微核频率（0.43 MN/BNC），而未照射的肺底相对于肺尖照射后的自发频率仅显示出边际（类似于2倍）的增加。微核频率的变化随早期大鼠肺切除时间的变化而变化，但在照射后18 h趋于稳定。正常（未辐照）细胞在经过过滤或未经过滤的条件培养基中生长，相对于自发频率，微核数量的边际增加不显著。从健康对照者的肺基部或肺尖处获得的肺细胞，分别在体外照射时，微核诱导没有区域差异。注射过超氧化物歧化酶的大鼠肺细胞，在肺底照射前1 h内，以及照射后16-18 h处理后，肺尖屏蔽区MN数量减少，提示可能与氧自由基有关。结论：这些数据表明，在任何一个区域受到辐射时，肺基部的细胞比肺顶端的细胞受到更大的DNA损伤；然而，当整个肺被照射时，观察到的肺损伤在两个区域相似。此外，在肺尖处观察到场外效应，而在肺底处没有。可能的机制包括辐照后血浆中产生的致裂因子和/或活化淋巴细胞/单核细胞产生的氧自由基。超氧化物歧化酶在肺基部辐照后未辐照肺尖观察到DNA损伤的部分阻断，表明氧自由基参与了这种场外效应。这些自由基可能是由于照射诱导炎症细胞因子，如肿瘤坏死因子（TNF）和白介素-1 （IL-1）而产生的。肺尖照射时肺底没有场外效应的原因尚不清楚，但可能是由于肺下场照射的肺体积更大，因为这可能影响产生的细胞因子水平。或者，它可能反映了部分肝脏照射下肺野所产生的细胞因子。(C) 1998爱思唯尔科学有限公司
Purpose: 1. To investigate early DNA damage induced in rat lung cells following single-dose, partial-volume irradiation (lung base and lung apex). 2. To determine the variation in DNA damage in different lung regions. 3. To investigate the possible mechanisms associated with early DNA damage after lung irradiation.Methods and Materials: The whole lung or the upper or lower half of the entire lung of Sprague-Dawley rats was exposed to 10 Gy (60)Co gamma rays. The animals were sacrificed at various times up to 42 h after irradiation. A trypsin-digested lung cell suspension was prepared and cells that attached to slides in the initial 24-h period were then grown in the presence of culture medium with cytochalasin-B for a further 72 h. Radiation-induced DNA damage was quantified in the cells (primarily fibroblasts) from both irradiated and unirradiated lung regions by using a well-characterized micronucleus assay.Results: When the lungs were removed at 16-18 h after whole-lung irradiation, about 0.85 micronuclei (MN) per binucleate cell (BNC) were observed in the lung cells of the irradiated animals, compared to 0.02 MN/BNC in the lung cells of the controls. When only the lung base was irradiated, the frequency of micronuclei was 0.85 MN/BNC compared to 0.43 MN/BNC observed in cells from the irradiated lung apex. Of particular interest was the finding that the unirradiated lung apex also showed a large frequency of micronuclei (0.43 MN/BNC) after the irradiation of the lung base, whereas the unirradiated lung base showed only a marginal (similar to 2-fold) increase relative to the spontaneous frequency following irradiation of the lung apex. The changes in the frequency of micronuclei varied with the time at which the lungs were removed from the rats for early times, but had stabilized by 18 h after irradiation. Normal (unirradiated) cells grown in filtered or unfiltered conditioned media obtained from irradiated cell cultures showed an insignificant marginal increase in the number of micronuclei relative to the spontaneous frequency. Lung cells obtained from the lung base or the lung apex of healthy controls and irradiated separately in vitro showed no regional differences in the induction of micronuclei. Cells from the lungs of rats injected with superoxide dismutase, within 1 h prior to irradiation of the lung base, and processed 16-18 h after irradiation showed a reduction in the number of MN in the shielded lung apex, indicating the possible involvement of oxygen radicals.Conclusions: These data indicate that cells in the lung base sustain more DNA damage than those in the lung apex when either region is irradiated; however, when the whole lung, is irradiated, the lung damage observed is similar in the two regions. Also, out-of-field effects are observed for the lung apex but not the lung base. Possible mechanisms include a clastogenic (chromosome damaging) factor produced in the plasma following irradiation and/or the production of oxygen radicals by activated lymphocytes/monocytes. The partial blocking of the DNA damage, observed in the unirradiated lung apex following irradiation of the lung base, by superoxide dismutase, suggests that oxygen radicals are involved in this out-of-field effect. These radicals are likely produced as a result of the induction of inflammatory cytokines, such as tumor necrosis factor (TNF) and interteukin-1 (IL-1) by the irradiation. The reason for the lack of an out-of-field effect in the lung base when the lung apex is irradiated is unknown, but may be due to the greater volume of lung irradiated in the lower lung field, because this is likely to affect the level of cytokines produced. Alternatively, it may reflect cytokines produced as a result of the partial liver irradiation that occurs with the lower lung field. (C) 1998 Elsevier Science Inc.