title: Toxicity and detoxification of lipid-derived aldehydes in cultured retinal pigmented epithelial cells.
abstract: Age-related macular degeneration (ARMD) is the leading cause of blindness in the developed world and yet its pathogenesis remains poorly understood. Retina has high levels of polyunsaturated fatty acids (PUFAs) and functions under conditions of oxidative stress. To investigate whether peroxidative products of PUFAs induce apoptosis in retinal pigmented epithelial (RPE) cells and possibly contribute to ARMD, human retinal pigmented epithelial cells (ARPE-19) were exposed to micromolar concentrations of H2O2, 4-hydroxynonenal (HNE) and 4-hydroxyhexenal (HHE). A concentration- and time-dependent increase in H2O2-, HNE-, and HHE-induced apoptosis was observed when monitored by quantifying DNA fragmentation as determined by ELISA, flow cytometry, and Hoechst staining. The broad-spectrum inhibitor of apoptosis Z-VAD inhibited apoptosis. Treatment of RPE cells with a thionein peptide prior to exposure to H2O2 or HNE reduced the formation of protein-HNE adducts as well as alteration in mitochondrial membrane potential and apoptosis. Using 3H-HNE, various metabolic pathways to detoxify HNE by ARPE-19 cells were studied. The metabolites were separated by HPLC and characterized by ElectroSpray Ionization-Mass Spectrometry (ESI-MS) and gas chromatography-MS. Three main metabolic routes of HNE detoxification were detected: (1) conjugation with glutathione (GSH) to form GS-HNE, catalyzed by glutathione-S-transferase (GST), (2) reduction of GS-HNE catalyzed by aldose reductase, and (3) oxidation of HNE catalyzed by aldehyde dehydrogenase (ALDH). Preventing HNE formation by a combined strategy of antioxidants, scavenging HNE by thionein peptide, and inhibiting apoptosis by caspase inhibitors may offer a potential therapy to limit retinal degeneration in ARMD.
authors.affiliation: Department of Human Biological Chemistry and Genetics, The University of Texas Medical Branch, Galveston, TX 77555-0647, USA.
authors.forename: S
authors.initials: S
authors.lastname: Choudhary
authors.forename: T
authors.initials: T
authors.lastname: Xiao
authors.forename: S
authors.initials: S
authors.lastname: Srivastava
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: L L
authors.initials: LL
authors.lastname: Chan
authors.forename: L A
authors.initials: LA
authors.lastname: Vergara
authors.forename: F J G M
authors.initials: FJ
authors.lastname: Van Kuijk
authors.forename: N H
authors.initials: NH
authors.lastname: Ansari
mesh_terms: D000447:Aldehydes / Q000009:adverse effects* / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004880:Ergothioneine / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000009:adverse effects / Q000037:antagonists & inhibitors; D050356:Lipid Metabolism; D008055:Lipids / Q000009:adverse effects* / Q000037:antagonists & inhibitors*; D008668:Metallothionein / Q000494:pharmacology; D018384:Oxidative Stress; D010857:Pigment Epithelium of Eye / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding / Q000187:drug effects; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors; D014343:Trypan Blue
chemical_list: D000447:Aldehydes; D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D008055:Lipids; D013778:Tetrazolium Salts; D013844:Thiazoles; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C063409:4-hydroxyhexenal; D008668:Metallothionein; D006861:Hydrogen Peroxide; D004880:Ergothioneine; D020169:Caspases; D014343:Trypan Blue; C027576:4-hydroxy-2-nonenal