title: Autophagy induced by cathepsin S inhibition induces early ROS production, oxidative DNA damage, and cell death via xanthine oxidase.
abstract: Cathepsin S plays multiple roles in MHC class II antigen presentation, extracellular matrix degradation, angiogenesis, and tumorogenesis. Our previous study revealed that targeting cathepsin S could induce cellular cytotoxicity and reduce cell viability. For the current study, we further investigated the molecular mechanism responsible for targeting cathepsin S-induced cell death and its association with autophagy. Distinct from regulation of the classic autophagy pathway by reactive oxygen species (ROS), we demonstrated that autophagy is the genuine regulator of early ROS production. The molecular silencing of autophagy-dependent ATG genes (ATG5, ATG7, and LC3) and the pharmacologic inhibition of autophagy with 3-MA and wortmannin reduced ROS production significantly. In addition, xanthine oxidase (XO), which is upregulated by autophagy, is required for early ROS production, oxidative DNA damage, and consequent cell death. Autophagy inhibition suppresses the upregulation of XO, which is induced by cathepsin S inhibition, resulting in reduced ROS generation, DNA damage, and cell death. Collectively, our study reveals a noncanonical molecular pathway in which, after the inhibition of cathepsin S, autophagy induces early ROS production for oxidative DNA damage and cell death through XO.
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan, Republic of China.
authors.forename: Chien-Chang
authors.initials: CC
authors.lastname: Huang
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan, Republic of China.
authors.forename: Kuo-Li
authors.initials: KL
authors.lastname: Chen
authors.affiliation: Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China; The Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China.
authors.forename: Chun Hei Antonio
authors.initials: CHA
authors.lastname: Cheung
authors.affiliation: National Institute of Cancer Research, National Health Research Institutes, Tainan, Taiwan, Republic of China; Division of Hematology and Oncology, Department of Internal Medicine, National Cheng Kung University Hospital, Tainan, Taiwan, Republic of China; Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan, Republic of China. Electronic address: jychang@nhri.org.tw.
authors.forename: Jang-Yang
authors.initials: JY
authors.lastname: Chang
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000730:Androstadienes / Q000494:pharmacology; D017951:Antigen Presentation / Q000276:immunology; D017209:Apoptosis / Q000276:immunology; D001343:Autophagy / Q000276:immunology*; D000071187:Autophagy-Related Protein 5; D000071193:Autophagy-Related Protein 7; D002403:Cathepsins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology*; D045744:Cell Line, Tumor; D002470:Cell Survival; D004249:DNA Damage; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000235:genetics; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species / Q000276:immunology*; D044764:Ubiquitin-Activating Enzymes / Q000235:genetics; D000077191:Wortmannin; D014969:Xanthine Oxidase / Q000096:biosynthesis / Q000276:immunology*
chemical_list: C502778:ATG5 protein, human; D000730:Androstadienes; D000071187:Autophagy-Related Protein 5; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C025946:3-methyladenine; D014969:Xanthine Oxidase; D002403:Cathepsins; C028217:cathepsin S; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes; D000225:Adenine; D000077191:Wortmannin
keywords: 2′,7′-dichlorofluorescein diacetate; 3-MA; 3-methyladenine; AVOs; Acidic vesicular organelles; Autophagy; BAF; Bafilomycin A1; CQ; Cathepsin S; Chloroquine; DCFH-DA; DHR; DNA damage; Dihydroethidium; Dihydrorhodamine; Early ROS; HE; LTR; LysoTracker Red; N-acetyl-l-cysteine; NAC; ROS; Reactive oxygen species; V-ATPase; Vacuolar-type H(+)-ATPase; XO; Xanthine oxidase