title: Lipotoxicity augments glucotoxicity-induced mitochondrial damage in the development of diabetic retinopathy.
abstract: OBJECTIVE
  Although hyperglycemia is the main instigator in the development of diabetic retinopathy, dyslipidemia is also considered to play an important role. In the pathogenesis of diabetic retinopathy, cytosolic NADPH oxidase 2 (Nox2) is activated before retinal mitochondria are damaged. Our aim was to investigate the effect of lipids in the development of diabetic retinopathy.
  
  
  METHODS
  Reactive oxygen species (ROS, by 2',7'-dichlorofluorescein diacetate) and activities of Nox2 (by a lucigenin-based method) and Rac1 (by G-LISA) were quantified in retinal endothelial cells incubated with 50 μM palmitate in 5 mM glucose (lipotoxicity) or 20 mM glucose (glucolipotoxicity) for 6 to 96 hours. Mitochondrial DNA (mtDNA) damage was evaluated by extended-length PCR and its transcription by quantifying cytochrome b transcripts.
  
  
  RESULTS
  Within 6 hours of exposure of endothelial cells to lipotoxicity, or glucotoxicity (20 mM glucose, without palmitate), significant increase in ROS, Nox2, and Rac1 was observed, which was exacerbated by glucolipotoxic insult. At 48 hours, neither lipotoxicity nor glucotoxicity had any effect on mtDNA and its transcription, but glucolipotoxicity significantly damaged mtDNA and decreased cytochrome b transcripts, and at 96 hours, glucotoxicity and glucolipotoxicity produced similar detrimental effects on mitochondrial damage.
  
  
  CONCLUSIONS
  Although during initial exposure, lipotoxic or glucotoxic insult produces similar increase in ROS, addition of lipotoxicity in a glucotoxic environment further exacerbates ROS production, and also accelerates their damaging effects on mitochondrial homeostasis. Thus, modulation of Nox2 by pharmacological agents in prediabetic patients with dyslipidemia could retard the development of retinopathy before their hyperglycemia is observable.
authors.affiliation: Kresge Eye Institute Wayne State University, Detroit, Michigan, United States.
authors.forename: Binit
authors.initials: B
authors.lastname: Kumar
authors.affiliation: Pharmaceutical Sciences, Wayne State University, Detroit, Michigan, United States 3ß-Cell Biochemistry Laboratory, John D. Dingell VA Medical Center, Detroit, Michigan, United States.
authors.forename: Anjan
authors.initials: A
authors.lastname: Kowluru
authors.affiliation: Kresge Eye Institute Wayne State University, Detroit, Michigan, United States.
authors.forename: Renu A
authors.initials: RA
authors.lastname: Kowluru
mesh_terms: D000818:Animals; D045303:Cytochromes b; D004249:DNA Damage; D004272:DNA, Mitochondrial / Q000235:genetics; D003930:Diabetic Retinopathy / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000633:toxicity*; D006801:Humans; D006943:Hyperglycemia / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects* / Q000235:genetics; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000378:metabolism; D019308:Palmitic Acid / Q000633:toxicity*; D016133:Polymerase Chain Reaction; D017382:Reactive Oxygen Species / Q000378:metabolism; D012160:Retina / Q000187:drug effects* / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D019308:Palmitic Acid; D045303:Cytochromes b; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D020830:rac1 GTP-Binding Protein; D005947:Glucose