title: Lysosomal membrane permeabilization: carbon nanohorn-induced reactive oxygen species generation and toxicity by this neglected mechanism.
abstract: Understanding the molecular mechanisms responsible for the cytotoxic effects of carbon nanomaterials is important for their future biomedical applications. Carbon nanotubular materials induce the generation of reactive oxygen species (ROS), which causes cell death; however, the exact details of this process are still unclear. Here, we identify a mechanism of ROS generation that is involved in the apoptosis of RAW264.7 macrophages caused by excess uptake of carbon nanohorns (CNHs), a typical type of carbon nanotubule. CNH accumulated in the lysosomes, where they induced lysosomal membrane permeabilization (LMP) and the subsequent release of lysosomal proteases, such as cathepsins, which in turn caused mitochondrial dysfunction and triggered the generation of ROS in the mitochondria. The nicotinamide adenine dinucleotide phosphate oxidase was not directly involved in CNH-related ROS production, and the ROS generation cannot be regulated by mitochondrial electron transport chain. ROS fed back to amplify the mitochondrial dysfunction, leading to the subsequent activation of caspases and cell apoptosis. Carbon nanotubules commonly accumulate in the lysosomes after internalization in cells; however, lysosomal dysfunction has not attracted much attention in toxicity studies of these materials. These results suggest that LMP, a neglected mechanism, may be the primary reason for carbon nanotubule toxicity.
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology 5-2, 1-1-1 Higashi, Tsukuba 305-8565, Japan. Electronic address: happy_deercn@163.com.
authors.forename: Mei
authors.initials: M
authors.lastname: Yang
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology 5-2, 1-1-1 Higashi, Tsukuba 305-8565, Japan.
authors.forename: Minfang
authors.initials: M
authors.lastname: Zhang
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology 5-2, 1-1-1 Higashi, Tsukuba 305-8565, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Tahara
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology 5-2, 1-1-1 Higashi, Tsukuba 305-8565, Japan.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Chechetka
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology 5-2, 1-1-1 Higashi, Tsukuba 305-8565, Japan.
authors.forename: Eijiro
authors.initials: E
authors.lastname: Miyako
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology 5-2, 1-1-1 Higashi, Tsukuba 305-8565, Japan; Faculty of Science and Technology, Meijo University, 1-501 Shiogamaguchi, Tenpaku, Nagoya 468-8502, Japan.
authors.forename: Sumio
authors.initials: S
authors.lastname: Iijima
authors.affiliation: Nanotube Research Center, National Institute of Advanced Industrial Science and Technology 5-2, 1-1-1 Higashi, Tsukuba 305-8565, Japan. Electronic address: m-yudasaka@aist.go.jp.
authors.forename: Masako
authors.initials: M
authors.lastname: Yudasaka
mesh_terms: D000818:Animals; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D007425:Intracellular Membranes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D008247:Lysosomes / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D037742:Nanotubes, Carbon / Q000633:toxicity* / Q000648:ultrastructure; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D037742:Nanotubes, Carbon; D017382:Reactive Oxygen Species
keywords: Apoptosis; Carbon nanohorns; Cytotoxicity; Lysosomal membrane permeabilization; Mitochondrial membrane potential; Reactive oxygen species