title: 2-Aminophenoxazine-3-one induces cellular apoptosis by causing rapid intracellular acidification and generating reactive oxygen species in human lung adenocarcinoma cells.
abstract: 2-Aminophenoxazine-3-one (Phx-3)-induced apoptosis was investigated. Phx-3 suppressed the viability of human lung adenocarcinoma cell line A549 and induced cellular apoptosis 6 h after treatment. Prior to these events, intracellular pH (pHi) was rapidly decreased from pH 7.65 to 7.10 within 30 min when A549 cells were treated with 7 microM Phx-3. This intracellular acidification continued for 3 h in the cells. Augmented production of reactive oxygen species (ROS) was obseved 1 h after treatment of A549 cells with 7 microM Phx-3, and cell cycle arrest at G1 was indicated 3 h after treatment. The translocation of NF-kappaB from the cytosol to the nucleus was clearly indicated 1 h after the administration of Phx-3 to A549 cells, while it was significantly suppressed when Nac, a scavenger of ROS, was added to the cells with Phx-3. The Phx-3-induced apoptosis in A549 cells was significantly suppressed when Nac was administered to the cells. These results suggest that a decrease of pHi, caused by depolarization of the mitochondria, may trigger the dysfunction of mitochondria causing ROS production; therefore, both the translocation of NF-kappaB from the cytoplasm to the nucleus and apoptosis induction were promoted in A549 cells. Microscopic examination of the cellular localization of Phx-3 in A549 cells revealed that Phx-3 was mainly localized in the cytoplasm and the mitochondria, but not in the nucleus. The present results indicate that Phx-3 might be a strong anticancer drug against lung cancer, which is intractable to chemotherapy, by causing various early events, including the decrease of pHi and ROS production, and finally inducing cellular apoptosis.
authors.affiliation: Department of Medical Oncology, Cancer Hospital, Fudan University, 200032, Shanghai, China.
authors.forename: Chun-Lei
authors.initials: CL
authors.lastname: Zheng
authors.forename: Xiao-Fang
authors.initials: XF
authors.lastname: Che
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Akiyama
authors.forename: Keisuke
authors.initials: K
authors.lastname: Miyazawa
authors.forename: Akio
authors.initials: A
authors.lastname: Tomoda
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism*; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival; D003593:Cytoplasm / Q000378:metabolism; D005434:Flow Cytometry / Q000379:methods; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008175:Lung Neoplasms / Q000473:pathology*; D009336:Necrosis; D010078:Oxazines / Q000494:pharmacology*; D017382:Reactive Oxygen Species; D013997:Time Factors
chemical_list: D000970:Antineoplastic Agents; D010078:Oxazines; D017382:Reactive Oxygen Species; C005512:3-aminophenoxazone