Department of Biology, McMaster University, Hamilton, Ontario, Canada.
Radiat Res. 2018 Sep;190(3):262-270. doi: 10.1667/RR15072.1. Epub 2018 Jul 2.
The radiation-induced bystander effect is mechanistically complex, involving many different signaling components. Serotonin, present in fetal bovine serum (FBS), has been implicated in the modulation of cellular responses to radiation. However, the role of this ubiquitous signaling molecule has yet to be elucidated with regard to cell line-specific radiation responses. In this study, cell survival was measured in HCT116 p53 wild-type (HCT116) and HaCaT cell cultures treated with media containing serotonin-depleted FBS and compared to our standard FBS-supplemented media, using clonogenic assays. We utilized an enzyme-linked immunosorbent assay to quantify the difference (4.3 ± 1.3 ng/ml) in serotonin concentrations among the media. Serotonin-depleted media significantly reduced survival in both nonirradiated cell lines. Furthermore, we sought to determine the effects to cells in this media exposed to direct irradiation as well as bystander media from irradiated cells. Cell survival was significantly increased when HCT116 cells were directly irradiated in serotonin-depleted media, while HaCaT cells showed no significant difference in survival between the media. Bystander investigations demonstrated that HCT116 cells were only able to generate a bystander effect when cultured in standard media conditions containing greater serotonin levels. Conversely, HaCaT cells were unaffected by the different media in terms of producing a bystander response, generating bystander effects irrespective of the media. Previous research linking serotonin receptors to the bystander effect, together with our results, indicate that receptor heterogeneity among cell types may underlie serotonin sensitivity in direct irradiation and bystander responses through serotonin receptor-mediated cell signaling cascades.
辐射诱导的旁观者效应在机制上很复杂，涉及许多不同的信号成分。血清素存在于胎牛血清（FBS）中，被认为参与了细胞对辐射反应的调节。然而，这种普遍存在的信号分子在细胞系特异性辐射反应中的作用尚未阐明。在这项研究中，使用克隆形成测定法，测量了在含有血清素耗尽的 FBS 的培养基中处理的 HCT116 p53 野生型（HCT116）和 HaCaT 细胞培养物中的细胞存活情况，并将其与我们的标准 FBS 补充培养基进行了比较。我们利用酶联免疫吸附测定法来量化培养基中血清素浓度的差异（4.3±1.3ng/ml）。血清素耗尽的培养基显著降低了未辐照细胞系的存活。此外，我们试图确定暴露于直接照射的细胞以及来自照射细胞的旁观者培养基的细胞的影响。当 HCT116 细胞在血清素耗尽的培养基中直接照射时，细胞存活显著增加，而 HaCaT 细胞在两种培养基之间的存活没有显著差异。旁观者研究表明，只有在含有较高血清素水平的标准培养基中培养时，HCT116 细胞才能产生旁观者效应。相反，HaCaT 细胞在产生旁观者反应方面不受不同培养基的影响，无论培养基如何，都能产生旁观者效应。先前将血清素受体与旁观者效应联系起来的研究，以及我们的结果表明，细胞类型之间的受体异质性可能是通过血清素受体介导的细胞信号级联反应，导致直接照射和旁观者反应中对血清素的敏感性。
