Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA.
J Toxicol Environ Health A. 2009;72(19):1141-9. doi: 10.1080/15287390903091764.
Titanium dioxide (TiO(2)), a commercially important material, is used in a wide variety of products. Although TiO(2) is generally regarded as nontoxic, the cytotoxicity, pathogenicity, and carcinogenicity of TiO(2) nanoparticles have been recently recognized. The present study investigated TiO(2) nanoparticle-induced cell apoptosis and molecular mechanisms involved in this process in a mouse epidermal (JB6) cell line. Using the 3-(4,5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide (MTT) assay, TiO(2) nanoparticles were found to exhibit higher cytotoxicity than fine particles. YO-PRO-1 iodide (YP) staining demonstrated that both TiO(2) nanoparticles and fine particles induced cell death through apoptosis. The signaling pathways involved in TiO(2) particle-induced apoptosis were investigated. Western-blot analysis showed an activation of caspase-8, Bid, BAX, and caspase-3 and a decrease of Bcl-2 in JB6 cells treated with TiO(2) particles. Time-dependent poly(ADP)ribose polymerase (PARP) cleavage induced by TiO(2) nanoparticles was observed. TiO(2) particles also induced cytochrome c release from mitochondria to cytosol. Further studies demonstrated that TiO(2) nanoparticles induced significant changes in mitochondrial membrane permeability, suggesting the involvement of mitochondria in the apoptotic process. In conclusion, evidence indicated that TiO(2) nanoparticles exhibit higher cytotoxicity and apoptotic induction compared to fine particles in JB6 cells. Caspase-8/Bid and mitochondrial signaling may play a major role in TiO(2) nanoparticle-induced apoptosis involving the intrinsic mitochondrial pathway. Unraveling the complex mechanisms associated with these events may provide further insights into TiO(2) nanoparticle-induced pathogenicity and potential to induce carcinogenicity.
二氧化钛（TiO(2)）是一种具有广泛用途的商业重要材料。尽管 TiO(2)通常被认为是无毒的，但最近人们已经认识到 TiO(2)纳米颗粒具有细胞毒性、致病性和致癌性。本研究在小鼠表皮（JB6）细胞系中研究了 TiO(2)纳米颗粒诱导细胞凋亡的作用及其相关的分子机制。使用 3-(4,5-二甲基噻唑基-2)-2,5-二苯基四氮唑溴盐（MTT）法，发现 TiO(2)纳米颗粒比细颗粒具有更高的细胞毒性。YO-PRO-1 碘化物（YP）染色表明，TiO(2)纳米颗粒和细颗粒均通过细胞凋亡诱导细胞死亡。研究了 TiO(2)颗粒诱导凋亡涉及的信号通路。Western-blot 分析显示，JB6 细胞用 TiO(2)颗粒处理后，半胱天冬酶-8、Bid、BAX 和半胱天冬酶-3被激活，Bcl-2 减少。观察到 TiO(2)纳米颗粒诱导的多聚（ADP-核糖）聚合酶（PARP）的时间依赖性切割。TiO(2)颗粒还诱导细胞色素 c 从线粒体释放到细胞质。进一步的研究表明，TiO(2)纳米颗粒诱导线粒体膜通透性发生显著变化，表明线粒体参与了凋亡过程。总之，证据表明 TiO(2)纳米颗粒在 JB6 细胞中表现出比细颗粒更高的细胞毒性和诱导凋亡作用。半胱天冬酶-8/Bid 和线粒体信号可能在涉及线粒体内在途径的 TiO(2)纳米颗粒诱导凋亡中起主要作用。揭示与这些事件相关的复杂机制可能为进一步了解 TiO(2)纳米颗粒诱导的致病性和致癌潜力提供了线索。
