title: Paraquat Induces Cell Death Through Impairing Mitochondrial Membrane Permeability.
abstract: Paraquat (PQ) as a Parkinsonian mimetic has been demonstrated to impair dopaminergic (DAergic) neurons and is highly correlated with the etiology of Parkinson's disease (PD) where the death of DAergic neurons has been mainly attributed to impaired mitochondrial functioning. In this study, PQ-induced cytotoxicity focusing on mitochondrial membrane permeability (MMP), which has been implicated to play a part in neurodegeneration, was investigated. Primarily, PQ-induced cytotoxicity and reactive oxygen species (ROS) were inhibited by an inhibitor of NADPH oxidase (NOX), indicating the toxic effect of PQ redox cycling. Further, dibucaine and cyclosporin A which respectively inhibit mitochondrial apoptosis-induced channels (MAC) and mitochondrial permeability transition pores (mPTP) were used and found to prevent PQ-induced mitochondrial dysfunction, such as decreased mitochondrial membrane potential and increased MMP, mitochondrial ROS, and pro-apoptotic factor release. Knockdown of bax and/or bak blocked PQ-induced mitochondrial clusterization of Bax and/or Bak and cytotoxicity, demonstrating the significance of MAC which is composed of Bax and/or Bak. This clusterization coincided with the release of mitochondrial apoptotic factors before there was an increase in inner MMP, indicating that MAC may precede mPTP formation. Besides, NOX inhibitor but not dibucaine attenuated the earlier PQ-induced cytosolic ROS formation or Bax and/or Bak clusterization indicating PQ redox cycling may account for MAC formation. In this model, we have resolved for the first that PQ cytotoxicity through redox cycling may sequentially result in increased outer (MAC) and inner (mPTP) MMP and suggested MMP could be implicated as a therapeutic target in treating neurodegenerative diseases like PD.
authors.affiliation: Medical Research Center, Cardinal Tien Hospital, Hsintien, New Taipei City, Taiwan, Republic of China.|Graduate Institute of Physiology & Department of Physiology and Biophysics, National Defense Medical Center, Taipei, Taiwan, Republic of China.
authors.forename: Chuen-Lin
authors.initials: CL
authors.lastname: Huang
authors.affiliation: Institute of Neuroscience, National Chengchi University, Taipei, Taiwan, Republic of China.
authors.forename: Chih-Chang
authors.initials: CC
authors.lastname: Chao
authors.affiliation: Program for Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, 11031, Taiwan, Republic of China.
authors.forename: Yi-Chao
authors.initials: YC
authors.lastname: Lee
authors.affiliation: National Research Institute of Chinese Medicine, Ministry of Health and Welfare, 155-1 Li-Nung St., Sec. 2, Shipai, Peitou, Taipei, 112, Taiwan, Republic of China.
authors.forename: Mei-Kuang
authors.initials: MK
authors.lastname: Lu
authors.affiliation: National Research Institute of Chinese Medicine, Ministry of Health and Welfare, 155-1 Li-Nung St., Sec. 2, Shipai, Peitou, Taipei, 112, Taiwan, Republic of China.|Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan, Republic of China.
authors.forename: Jing-Jy
authors.initials: JJ
authors.lastname: Cheng
authors.affiliation: Department of Biotechnology and Animal Science, National Ilan University, Ilan, Taiwan, Republic of China.
authors.forename: Ying-Chen
authors.initials: YC
authors.lastname: Yang
authors.affiliation: School of Medicine, Fu-Jen Catholic University, New Taipei City, Taiwan, Republic of China.|Neurological Center, Cardinal Tien Hospital, New Taipei City, Taiwan, Republic of China.
authors.forename: Vin-Chi
authors.initials: VC
authors.lastname: Wang
authors.affiliation: Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, 11031, Taiwan, Republic of China.
authors.forename: Wen-Chang
authors.initials: WC
authors.lastname: Chang
authors.affiliation: Program for Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, 11031, Taiwan, Republic of China. andrew@nricm.edu.tw.|National Research Institute of Chinese Medicine, Ministry of Health and Welfare, 155-1 Li-Nung St., Sec. 2, Shipai, Peitou, Taipei, 112, Taiwan, Republic of China. andrew@nricm.edu.tw.|Institute of Biophotonics, National Yang-Ming University, Taipei, Taiwan, Republic of China. andrew@nricm.edu.tw.
authors.forename: Nai-Kuei
authors.identifier: http://orcid.org/0000-0001-9262-4774
authors.initials: NK
authors.lastname: Huang
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001522:Behavior, Animal; D016923:Cell Death / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology; D003992:Dibucaine / Q000494:pharmacology; D020868:Gene Silencing / Q000187:drug effects; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D009861:Onium Compounds / Q000494:pharmacology; D016716:PC12 Cells; D010269:Paraquat / Q000633:toxicity*; D010539:Permeability / Q000187:drug effects; D055503:Protein Multimerization; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D009861:Onium Compounds; D017382:Reactive Oxygen Species; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; C007517:diphenyleneiodonium; D016572:Cyclosporine; D003992:Dibucaine; D010269:Paraquat
keywords: Mitochondrial apoptosis-induced channels; Mitochondrial membrane permeability; Mitochondrial permeability transition pores; Paraquat; Parkinson’s disease