Molecular Biology and Genomics Laboratory, Department of Botany, Berhampur University, Berhampur 760 007, India.
Mutagenesis. 2010 Mar;25(2):201-9. doi: 10.1093/mutage/gep063. Epub 2009 Dec 2.
Experiments employing growing root cells of Allium cepa were conducted with a view to elucidate the role of reactive oxygen intermediates (ROI) in aluminium (Al)-induced DNA damage, cell death and adaptive response to genotoxic challenge imposed by ethyl methanesulphonate (EMS) or methyl mercuric chloride (MMCl). In a first set of experiments, root cells in planta were treated with Al at high concentrations (200-800 microM) for 3 h without or with pre-treatments of dihydroxybenzene disulphonic acid (Tiron) and dimethylthiourea (DMTU) for 2 h that trap O(2)(.-)and hydrogen peroxide (H(2)O(2)), respectively. At the end of treatments, generation of O(2)(.-) and H(2)O(2), cell death and DNA damage were determined. In a second set of experiments, root cells in planta were conditioned by Al at low concentrations (5 or 10 microM) for 2 h and after a 2 h intertreatment interval challenged by MMCl or EMS for 3 h without or with a pre-treatment of Tiron or DMTU. Conditioning treatments, in addition, included two oxidative agents viz rose bengal and H(2)O(2) for comparison. Following treatments, root cells in planta were allowed to recover in tap water. Genotoxicity and DNA damage were evaluated by micronucleus (MN), chromosome aberration (CA) or spindle aberration (SA) and comet assays at different hours (0-30 h) of recovery. The results demonstrated that whereas Al at high concentrations induced DNA damage and cell death, in low concentrations induced adaptive response conferring genomic protection from genotoxic challenge imposed by MMCl, EMS and Al. Pre-treatments of Tiron and DMTU prevented Al-induced DNA damage, cell death, as well as genotoxic adaptation to MMCl and EMS, significantly. The findings underscored the biphasic (hormetic) mode of action of Al that at high doses induced DNA damage and at low non-toxic doses conferred genomic protection, both of which were mediated through ROI but perhaps involving different networks.
采用洋葱根尖细胞进行实验，旨在阐明活性氧中间体（ROI）在铝（Al）诱导的 DNA 损伤、细胞死亡以及对乙基甲磺酸（EMS）或甲基汞（MMCl）引起的遗传毒性挑战的适应性反应中的作用。在一组实验中，将植物中的根细胞用高浓度的 Al（200-800 μM）处理 3 小时，并用二羟基苯二磺酸（Tiron）和二甲基硫脲（DMTU）预处理 2 小时，分别捕获 O2(-)和过氧化氢（H2O2）。处理结束时，测定 O2(-)和 H2O2 的产生、细胞死亡和 DNA 损伤。在第二组实验中，将植物中的根细胞用低浓度的 Al（5 或 10 μM）预处理 2 小时，然后在 2 小时的中间处理间隔后，用 MMCl 或 EMS 处理 3 小时，并用 Tiron 或 DMTU 预处理。预处理处理还包括两种氧化剂，即玫瑰红和 H2O2，用于比较。处理后，让植物中的根细胞在自来水中恢复。通过微核（MN）、染色体畸变（CA）或纺锤体畸变（SA）和彗星试验，在不同的恢复时间（0-30 小时）评估遗传毒性和 DNA 损伤。结果表明，高浓度的 Al 诱导 DNA 损伤和细胞死亡，而低浓度的 Al 诱导适应性反应，赋予基因组对 MMCl、EMS 和 Al 引起的遗传毒性挑战的保护。Tiron 和 DMTU 的预处理可显著预防 Al 诱导的 DNA 损伤、细胞死亡以及对 MMCl 和 EMS 的遗传毒性适应。研究结果强调了 Al 的双相（适应原）作用模式，即在高剂量下诱导 DNA 损伤，在低非毒性剂量下赋予基因组保护，这两种作用都是通过 ROI 介导的，但可能涉及不同的网络。
