Group of Environmental Adaptation Science, Faculty of Environmental Earth Sciences, Hokkaido University, Kita 10, Nishi 5, Kita-ku, Sapporo, 060-0810, Japan.
Nanoscience and Technology Research Laboratory, Chemistry Division, Atomic Energy Centre, Bangladesh Atomic Energy Commission, Dhaka, 1000, Bangladesh.
Biol Trace Elem Res. 2021 Sep;199(9):3272-3286. doi: 10.1007/s12011-020-02463-7. Epub 2020 Nov 24.
Green synthesized silver nanoparticles (Ag-NPs) have demonstrated promising effects, including cytotoxicity and anticancer potential, in different cell lines. Therefore, in our previous study, Ag-NPs were synthesized from the reduction of AgNO using Brassica rapa var. japonica (Bj) leaf extract as a reducing and stabilizing agent. The synthesized Ag-NPs were spherical in shape, with a size range of 15-30 nm. They had phase-centered cubic structure with strong growth inhibition potential against some bacteria. In continuation with our previous study, in the present study, we aimed to investigate the autophagy-regulated cytotoxic effect of Ag-NPs against human epithelial colorectal adenocarcinoma cells (Caco-2 cells). We found that the Bj leaf aqueous extract facilitated Brassica silver nanoparticles (Brassica Ag-NPs)-induced NF-κB mediated autophagy in Caco-2 cells. Results showed that Ag-NPs reduced cell viability of Caco-2 cells by inducing oxidative stress and DNA damage. Therefore, to understand the mechanism underlying the death-promoting activity of Ag-NPs in Caco-2 cells, western blotting was performed. Western blot analysis showed decreased expression of NFκB and increased expression of IκB, which is a sign of autophagy initiation. In addition, autophagosome formation was accelerated by the activity of p53 and light chain 3 (LC3) II. In addition, inhibition of Akt and mTOR also played a pivotal role in autophagy formation. Finally, excessive expansion of autophagy promoted apoptosis, which subsequently resulted in necrosis. These findings support a novel cell death-promoting function of autophagy by Ag-NPs in Caco-2 cells.
绿色合成的银纳米粒子（Ag-NPs）在不同的细胞系中显示出有希望的效果，包括细胞毒性和抗癌潜力。因此，在我们之前的研究中，Ag-NPs 是从 AgNO 的还原中合成的，使用 Brassica rapa var. japonica（Bj）叶提取物作为还原剂和稳定剂。合成的 Ag-NPs 呈球形，尺寸范围为 15-30nm。它们具有相中心立方结构，对一些细菌具有强烈的生长抑制潜力。在我们之前的研究的基础上，在本研究中，我们旨在研究 Ag-NPs 对人上皮结肠直肠腺癌细胞（Caco-2 细胞）的自噬调控细胞毒性作用。我们发现，Bj 叶水提物促进了 Brassica 银纳米粒子（Brassica Ag-NPs）诱导的 Caco-2 细胞中 NF-κB 介导的自噬。结果表明，Ag-NPs 通过诱导氧化应激和 DNA 损伤降低 Caco-2 细胞的活力。因此，为了了解 Ag-NPs 在 Caco-2 细胞中促进死亡的活性的机制，进行了 Western blot 分析。Western blot 分析显示 NFκB 的表达降低，IκB 的表达增加，这是自噬起始的标志。此外，p53 和轻链 3（LC3）II 的活性加速了自噬体的形成。此外，Akt 和 mTOR 的抑制也在自噬形成中发挥了关键作用。最后，自噬的过度扩张促进了细胞凋亡，随后导致了坏死。这些发现支持了 Ag-NPs 在 Caco-2 细胞中通过自噬促进细胞死亡的新功能。
