title: Na+/H+-exchanger-1 inhibition counteracts diabetic cataract formation and retinal oxidative-nitrative stress and apoptosis.
abstract: The Na⁺-H⁺-exchanger-1 (NHE-1) controls intracellular pH and glycolytic enzyme activities, and its expression and activity are increased by diabetes and high glucose. NHE-1-dependent upregulation of the upper part of glycolysis, under conditions of inhibition (lens) or insufficient activation (retina) of glyceraldehyde 3-phosphate dehydrogenase, underlies diversion of the excessive glycolytic flux towards several pathways contributing to oxidative stress, a causative factor in diabetic cataractogenesis and retinopathy. This study evaluated the role for NHE-1 in diabetic cataract formation and retinal oxidative stress and apoptosis. Control and streptozotocin-diabetic rats were maintained with or without treatment with the NHE-1 inhibitor cariporide (Sanofi-Aventis, 10 mgkg-1d-1) for 3.5 months. In in vitro studies, bovine retinal pericytes and endothelial cells were cultured in 5 or 30 mM glucose, with or without 10 µM cariporide, for 7 days. A several-fold increase of the by-product of glycolysis, α-glycerophosphate, indicative of activation of the upper part of glycolysis, was present in both rat lens and retina at an early (1-month) stage of streptozotocin-diabetes. Cariporide did not affect diabetic hyperglycemia and counteracted lens oxidative-nitrative stress and p38 MAPK activation, without affecting glucose or sorbitol pathway intermediate accumulation. Cataract formation (indirect ophthalmoscopy and slit-lamp examination) was delayed, but not prevented. The number of TUNEL-positive cells per flat-mounted retina was increased 4.4-fold in diabetic rats (101 ± 17 vs. 23 ± 8 in controls , P<0.01), and this increase was attenuated by cariporide (45 ± 12, P<0.01). Nitrotyrosine and poly(ADP-ribose) fluorescence and percentage of TUNEL-positive cells were increased in pericytes and endothelial cells cultured in 30 mM glucose, and these changes were at least partially prevented by cariporide. In conclusion, NHE-1 contributes to diabetic cataract formation, and retinal oxidative-nitrative stress and apoptosis. The findings identify a new therapeutic target for diabetic ocular complications.
authors.affiliation: Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA.
authors.forename: Sergey
authors.initials: S
authors.lastname: Lupachyk
authors.forename: Roman
authors.initials: R
authors.lastname: Stavniichuk
authors.forename: Julia I
authors.initials: JI
authors.lastname: Komissarenko
authors.forename: Viktor R
authors.initials: VR
authors.lastname: Drel
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Obrosov
authors.forename: Azza B
authors.initials: AB
authors.lastname: El-Remessy
authors.forename: Pal
authors.initials: P
authors.lastname: Pacher
authors.forename: Irina G
authors.initials: IG
authors.lastname: Obrosova
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001786:Blood Glucose / Q000378:metabolism; D015153:Blotting, Western; D002386:Cataract / Q000097:blood / Q000188:drug therapy / Q000473:pathology*; D002417:Cattle; D048909:Diabetes Complications / Q000097:blood / Q000188:drug therapy / Q000473:pathology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005215:Fasting / Q000097:blood; D006146:Guanidines / Q000494:pharmacology / Q000627:therapeutic use; D020287:In Situ Nick-End Labeling; D007908:Lens, Crystalline / Q000187:drug effects / Q000201:enzymology / Q000473:pathology; D008297:Male; D015538:Nitrosation / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000473:pathology*; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013450:Sulfones / Q000494:pharmacology / Q000627:therapeutic use; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000447:Aldehydes; D001786:Blood Glucose; D006146:Guanidines; D017923:Sodium-Hydrogen Exchangers; D013450:Sulfones; C002744:3-nitrotyrosine; D014443:Tyrosine; C093373:cariporide; D011065:Poly(ADP-ribose) Polymerases; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C027576:4-hydroxy-2-nonenal