Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.
College of Life Science, Hunan Normal University, Changsha, Hunan 410081, China.
Toxicol Appl Pharmacol. 2019 Sep 1;378:114602. doi: 10.1016/j.taap.2019.114602. Epub 2019 May 29.
Arsenic, in the trivalent form (AsIII), is a human co-carcinogen reported to enhance mutagenesis effects of other carcinogens such as UV radiation by inhibiting DNA repair. The zinc finger DNA repair protein Poly (ADP-ribose) polymerase 1 (PARP-1) is a sensitive target of AsIII and both reactive oxygen and nitrogen species (ROS/RNS) generated by AsIII contribute to PARP-1 inhibition. However, the mechanisms of ROS/RNS-mediated PARP inhibition and how AsIII-generated ROS/RNS may be interconnected are still unclear. In this study, we found AsIII exposure of normal human keratinocyte (HEKn) cells generated peroxynitrite through superoxide and nitric oxide production in an AsIII concentration dependent manner. Peroxynitrite inhibited PARP-1 activity and caused zinc loss from PARP-1 protein while scavenging peroxynitrite was protective of the impacts on PARP-1. We identified peroxynitrite was responsible for S-nitrosation on cysteine residues resulting in PARP-1 zinc finger conformational changes. Taken together, the evidence indicates AsIII generates peroxynitrite through superoxide and nitric oxide production, induces S-nitrosation on PARP-1, leading to zinc loss and activity inhibition of PARP-1, thus enhancing DNA damage caused by UV radiation. These findings highlight a role for peroxynitrite as a key molecule of ROS/RNS mediated DNA repair inhibition by AsIII which should inform the development of prevention and intervention strategies against AsIII co-carcinogenesis.
砷，以三价形式（AsIII）存在，是一种人类协同致癌物质，据报道，它通过抑制 DNA 修复来增强其他致癌物质（如紫外线辐射）的致突变作用。锌指 DNA 修复蛋白多聚（ADP-核糖）聚合酶 1（PARP-1）是 AsIII 的敏感靶标，而 AsIII 产生的活性氧和活性氮物种（ROS/RNS）有助于 PARP-1 抑制。然而，ROS/RNS 介导的 PARP 抑制的机制以及 AsIII 产生的 ROS/RNS 如何相互关联仍不清楚。在这项研究中，我们发现，正常人类角质形成细胞（HEKn）细胞暴露于砷后，会产生过氧亚硝酸盐，这是一种通过超氧化物和一氧化氮生成的、依赖于砷浓度的物质。过氧亚硝酸盐抑制 PARP-1 活性，并导致 PARP-1 蛋白中的锌丢失，而清除过氧亚硝酸盐对 PARP-1 具有保护作用。我们发现，过氧亚硝酸盐导致 PARP-1 上的半胱氨酸残基发生 S-亚硝基化，从而导致 PARP-1 锌指构象发生变化。综上所述，这些证据表明，AsIII 通过超氧化物和一氧化氮的生成产生过氧亚硝酸盐，诱导 PARP-1 的 S-亚硝基化，导致锌丢失和 PARP-1 活性抑制，从而增强紫外线辐射引起的 DNA 损伤。这些发现突出了过氧亚硝酸盐作为 AsIII 介导的 ROS/RNS 抑制 DNA 修复的关键分子的作用，这应该为制定针对 AsIII 协同致癌作用的预防和干预策略提供信息。
