title: A positive feedback loop between nitric oxide and amyloid β (1-42) accelerates mitochondrial damage in human lens epithelial cells.
abstract: We have reported that excessive nitric oxide (NO), like other reactive oxygen species (ROS), causes a decrease in cytochrome c oxidase (CCO) activity and ATP levels (mitochondrial damage) resulting in lens opacity. In addition, previous reports have shown that oxidative stress caused by ROS enhances amyloid β (Aβ) production in mammalian lenses, and that Aβ1-42stimulates inducible nitric oxide synthase (iNOS) promoter activity. Based on these reports, we investigated the relationship between NO and Aβ1-42production in human lens epithelial (HLE) cells. iNOS was induced by the co-incubation of HLE cells with 1000 IU interferon-γ (IFN-γ) and 100ng/ml lipopolysaccharide (LPS) for 48h. This led to enhanced NO release, an increase in the gene expression levels of proteins related to Aβ production, and the cellular accumulation of Aβ1-42. Moreover, both aminoguanidine (AG, a selective inhibitor of iNOS) and diethyldithiocarbamate (DDC, a nuclear factor-kappa B (NFκB) inhibitor) attenuated these changes in IFN-γ and LPS stimulated HLE cells. Based on our finding that Aβ1-42accumulation is induced by co-incubation of HLE cells with both IFN-γ and LPS, we prepared a HLE cell model with Aβ1-42accumulation (Aβ-accumulated-HLE cell model) by pre-stimulating cells with IFN-γ and LPS for 48h. Aβ1-42accumulation caused NO production via iNOS, resulting in an enhancement in the mRNA levels for enzymes necessary for the proteolysis of amyloid precursor protein (APP) to Aβ in HLE cells. In addition, excessive NO produced in response to Aβ1-42accumulation led to a decrease in CCO activity and ATP levels. Taken together, we hypothesize that excessive NO production in the lens epithelium enhances Aβ1-42production, and that this enhancement accelerates NO release. The enhancement in NO production in the lens epithelium based on positive feedback (NO-Aβ positive feedback loop, a vicious cycle) may promote the onset of cataracts (lens opacification) via the decrease in CCO activity and ATP levels. These findings provide significant information that can be used to design further studies aimed at developing anti-cataract drugs.
authors.affiliation: Faculty of Pharmacy, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka, 577-8502, Japan. Electronic address: nagai_n@phar.kindai.ac.jp.
authors.forename: Noriaki
authors.initials: N
authors.lastname: Nagai
authors.affiliation: Faculty of Pharmacy, Kindai University, 3-4-1 Kowakae, Higashi-Osaka, Osaka, 577-8502, Japan.
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Ophthalmology, Kanazawa Medical University, 1-1 Daigaku Uchinada-machi, Kahoku-gun, Ishikawa, 920-0293, Japan.
authors.forename: Teppei
authors.initials: T
authors.lastname: Shibata
authors.affiliation: Department of Ophthalmology, Kanazawa Medical University, 1-1 Daigaku Uchinada-machi, Kahoku-gun, Ishikawa, 920-0293, Japan.
authors.forename: Eri
authors.initials: E
authors.lastname: Kubo
authors.affiliation: Department of Ophthalmology, Kanazawa Medical University, 1-1 Daigaku Uchinada-machi, Kahoku-gun, Ishikawa, 920-0293, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sasaki
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000235:genetics / Q000378:metabolism*; D002386:Cataract / Q000139:chemically induced / Q000473:pathology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004050:Ditiocarb / Q000494:pharmacology; D003576:Electron Transport Complex IV / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D006146:Guanidines / Q000494:pharmacology; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D007908:Lens, Crystalline / Q000166:cytology / Q000187:drug effects*; D008070:Lipopolysaccharides / Q000633:toxicity; D008928:Mitochondria / Q000187:drug effects* / Q000473:pathology; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000633:toxicity*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D006146:Guanidines; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010446:Peptide Fragments; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; C075222:amyloid beta-protein (1-42); D009569:Nitric Oxide; D007371:Interferon-gamma; D000255:Adenosine Triphosphate; D004050:Ditiocarb; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II; D003576:Electron Transport Complex IV; C004479:pimagedine
keywords: Amyloid β; Cataract; Cytochrome c oxidase; Lens epithelial cells; Nitric oxide