title: Methylglyoxal, a reactive glucose metabolite, enhances autophagy flux and suppresses proliferation of human retinal pigment epithelial ARPE-19 cells.
abstract: Methylglyoxal (MGO), a glycolytic metabolite, induces oxidative injury and apoptotic cell death that play a pathogenetic role in age-related macular degeneration (AMD). This study examined the impact of MGO on cell proliferation and autophagy flux in retinal pigment epithelium (RPE) ARPE-19 cells and elucidated the underlying mechanism. Short-term MGO exposure suppressed cell proliferation without induction of apoptotic cell death, increased production of reactive oxygen species, and potentiated H2O2-exhibited cytotoxicity in ARPE-19 cells. Conversely, pretreatment with N-acetylcysteine, a ROS scavenger, and aminoguanidine, an MGO blocker, prevented MGO-induced growth retardation. MGO significantly enhanced autophagy flux and increased intracellular accumulation of autophagosomes, which was functionally confirmed by addition of autophagy enhancer or inhibitors. Signaling kinetic observation indicated that MGO remarkably triggered phosphorylation of Akt, ERK1/2, p38 MAPK, and JNK1/2. Blockade of kinase activity demonstrated that the hyperphosphorylation of Akt, ERK1/2, JNK, and p38 MAPK were all involved in the MGO-enhanced autophagy and growth-arresting effect in ARPE-19 cells. Moreover, pretreatment with autophagic flux inhibitors including 3-methyladenine, bafilomycin A, and chloroquine effectively ameliorated MGO- but not H2O2-mediated ARPE-19 cytotoxicity. In conclusion, modulation of autophagy flux activity by using autophagic or kinase inhibitors may be an applicable modality to treat AMD.
authors.affiliation: Department of Ophthalmology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Ophthalmology, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Yo-Chen
authors.initials: YC
authors.lastname: Chang
authors.affiliation: Department of Ophthalmology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Ming-Chu
authors.initials: MC
authors.lastname: Hsieh
authors.affiliation: Department of Ophthalmology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Ophthalmology, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Horng-Jiun
authors.initials: HJ
authors.lastname: Wu
authors.affiliation: Department of Ophthalmology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan. Electronic address: wuoph@kmu.edu.tw.
authors.forename: Wen-Chuan
authors.initials: WC
authors.lastname: Wu
authors.affiliation: Department of Medical Research, E-Da Hospital, Kaohsiung 82445, Taiwan; Department of Medical Laboratory Sciences and Biotechnology, Fooyin University, Kaohsiung, Taiwan. Electronic address: danyhkao@gmail.com.
authors.forename: Ying-Hsien
authors.initials: YH
authors.lastname: Kao
mesh_terms: D001343:Autophagy / Q000187:drug effects; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D008268:Macular Degeneration; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011765:Pyruvaldehyde / Q000633:toxicity*; D055213:Retinal Pigment Epithelium / Q000166:cytology
chemical_list: D047428:Protein Kinase Inhibitors; D011765:Pyruvaldehyde; D006861:Hydrogen Peroxide; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D005947:Glucose
keywords: Age-related macular degeneration; Autophagosomes; Autophagy flux; Methylglyoxal; Reactive oxygen species; Signal transduction