Mane Shirish D, Kamatham Akhilender Naidu
Department of Biochemistry, CSIR-Central Food Technological Research Institute, Mysore, 570020, India.
Department of Biochemistry, CSIR-Central Food Technological Research Institute, Mysore, 570020, India.
Chem Biol Interact. 2018 Feb 1;281:37-50. doi: 10.1016/j.cbi.2017.12.028. Epub 2017 Dec 19.
Ascorbyl stearate (Asc-s) is a derivative of ascorbic acid with better anti-tumour efficacy compared to its parent compound ascorbic acid. In this study, we have examined radio-sensitizing effect of Asc-s in murine T cell lymphoma (EL4) cells at 4 Gy. Asc-s and radiation treatment reduced cell proliferation, induced apoptosis in a dose dependent manner by arresting the cells at S/G2-M phase of cell cycle. It also decreased the frequency of cancer stem cells per se, with significantly higher decrease in combination with radiation treatment./Further, Asc-s and radiation treatment increased the level of reactive oxygen species (ROS), drop in mitochondrial membrane potential (MMP) and increased caspase-3 activity resulting in apoptosis of EL4 cells. Further it also significantly decreased GSH/GSSG ratio due to binding of Asc-s with thiols. The increase in oxidative stress induced by Asc-s and radiation treatment was abrogated by thiol antioxidants in EL4 cells. Interestingly, this redox modulation triggered significant increase in protein glutathionylation in a time dependent manner. Asc-s treatment resulted in glutathionylation of IKK, p50-NF-kB and mutated p53, thereby inhibiting cancer progression during oxidative stress. Asc-s quenches GSH ensuing Asc-s + GSH adduct thereby further modulating GSH/GSSG ratio as evident from HPLC and docking studies. The anti-tumour effect of Asc-s along with radiation was studied by injecting EL4 cells in synegenicC57/BL6 male mice. Intraperitoneal injection of Asc-s followed by radiation exposure at 4 Gy to the tumour bearing mice resulted in radio-sensitization which is evident from significant regression of tumour as evident from tumour burden index. The survival study supports the data that Asc-s pre-treatment enhances radio-sensitization in murine lymphoma. Our data, suggest that Asc-s and ionizing radiation induced cell cycle arrest and apoptosis by perturbing redox balance through irreversible complexes of thiols with Asc-s, disturbed mitochondrial membrane permeability and activation of caspase-3 in EL4 cells.
硬脂酸抗坏血酸酯（Asc-s）是抗坏血酸的衍生物，与其母体化合物抗坏血酸相比具有更好的抗肿瘤功效。在本研究中，我们检测了Asc-s在4 Gy剂量下对小鼠T细胞淋巴瘤（EL4）细胞的放射增敏作用。Asc-s和放射治疗降低了细胞增殖，通过使细胞停滞在细胞周期的S/G2-M期以剂量依赖的方式诱导细胞凋亡。它还降低了癌症干细胞本身的频率，与放射治疗联合使用时降低幅度显著更高。此外，Asc-s和放射治疗增加了活性氧（ROS）水平，降低了线粒体膜电位（MMP）并增加了半胱天冬酶-3活性，导致EL4细胞凋亡。此外，由于Asc-s与硫醇结合，它还显著降低了谷胱甘肽/氧化型谷胱甘肽（GSH/GSSG）比值。硫醇抗氧化剂消除了EL4细胞中Asc-s和放射治疗诱导的氧化应激增加。有趣的是，这种氧化还原调节以时间依赖的方式引发了蛋白质谷胱甘肽化的显著增加。Asc-s处理导致IKK、p50-NF-κB和突变型p53的谷胱甘肽化，从而在氧化应激期间抑制癌症进展。Asc-s淬灭谷胱甘肽，形成Asc-s + GSH加合物，从而进一步调节GSH/GSSG比值，这从高效液相色谱（HPLC）和对接研究中可以明显看出。通过将EL4细胞注射到同基因C57/BL6雄性小鼠中，研究了Asc-s与放射联合的抗肿瘤作用。对荷瘤小鼠腹腔注射Asc-s，随后进行4 Gy的放射暴露，导致放射增敏，从肿瘤负荷指数明显看出肿瘤显著消退。生存研究支持了Asc-s预处理增强小鼠淋巴瘤放射增敏作用的数据。我们的数据表明，Asc-s和电离辐射通过硫醇与Asc-s的不可逆复合物扰乱氧化还原平衡、干扰线粒体膜通透性并激活EL4细胞中的半胱天冬酶-3，从而诱导细胞周期停滞和细胞凋亡。
