title: Deregulation of ocular nucleotide homeostasis in patients with diabetic retinopathy.
abstract: Clear signaling roles for ATP and adenosine have been established in all tissues, including the eye. The magnitude of signaling responses is governed by networks of enzymes; however, little is known about the regulatory mechanisms of purinergic signaling in the eye. By employing thin-layer chromatographic assays with3H-labeled substrates, this study aimed to evaluate the role of nucleotide homeostasis in the pathogenesis of vitreoretinal diseases in humans. We have identified soluble enzymes ecto-5'-nucleotidase/CD73, adenylate kinase-1, and nucleoside diphosphate kinase in the vitreous fluid that control active cycling between pro-inflammatory ATP and anti-inflammatory adenosine. Strikingly, patients with proliferative form of diabetic retinopathy (DR) had higher adenylate kinase activity and ATP concentration, when compared to non-proliferative DR eyes and non-diabetic controls operated for rhegmatogenous retinal detachment, macular hole, and pucker. The non-parametric correlation analysis revealed positive correlations between intravitreal adenylate kinase and concentrations of ATP, ADP, and other angiogenic (angiopoietins-1 and -2), profibrotic (transforming growth factor-β1), and proteolytic (matrix metalloproteinase-9) factors but not erythropoietin and VEGF. Immunohistochemical staining of postmortem human retina additionally revealed selective expression of ecto-5'-nucleotidase/CD73 on the rod-and-cone-containing photoreceptor cells. Collectively, these findings provide novel insights into the regulatory mechanisms that influence purinergic signaling in diseased eye and open up new possibilities in the development of enzyme-targeted therapeutic approaches for prevention and treatment of DR.
  
  
  
  Ecto-5'-nucleotidase/CD73 and adenylate kinase-1 circulate in human vitreous fluid. Adenylate kinase activity is high in diabetic eyes with proliferative retinopathy. Diabetic eyes display higher intravitreal ATP/ADP ratio than non-diabetic controls. Soluble adenylate kinase maintains resynthesis of inflammatory ATP in diabetic eyes.
authors.affiliation: Unit of Vitreoretinal Surgery, Department of Ophthalmology, Helsinki University Central Hospital and University of Helsinki, Helsinki, Finland.
authors.forename: Sirpa
authors.initials: S
authors.lastname: Loukovaara
authors.affiliation: Cell Imaging Core, Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, Turku, Finland.
authors.forename: Jouko
authors.initials: J
authors.lastname: Sandholm
authors.affiliation: MediCity Research Laboratory and Department of Medical Microbiology and Immunology, University of Turku, Tykistökatu 6A, 20520, Turku, Finland.
authors.forename: Kristiina
authors.initials: K
authors.lastname: Aalto
authors.affiliation: Department of Ophthalmology, Turku University Hospital, Turku, Finland.
authors.forename: Janne
authors.initials: J
authors.lastname: Liukkonen
authors.affiliation: MediCity Research Laboratory and Department of Medical Microbiology and Immunology, University of Turku, Tykistökatu 6A, 20520, Turku, Finland.
authors.forename: Sirpa
authors.initials: S
authors.lastname: Jalkanen
authors.affiliation: MediCity Research Laboratory and Department of Medical Microbiology and Immunology, University of Turku, Tykistökatu 6A, 20520, Turku, Finland. gennady.yegutkin@utu.fi.
authors.forename: Gennady G
authors.initials: GG
authors.lastname: Yegutkin
mesh_terms: D015720:5'-Nucleotidase / Q000378:metabolism; D000241:Adenosine / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000263:Adenylate Kinase / Q000378:metabolism; D000328:Adult; D000368:Aged; D002855:Chromatography, Thin Layer; D003930:Diabetic Retinopathy / Q000378:metabolism*; D004921:Erythropoietin / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009701:Nucleoside-Diphosphate Kinase / Q000378:metabolism; D012160:Retina / Q000378:metabolism*; D018709:Statistics, Nonparametric; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D014822:Vitreous Body / Q000201:enzymology
chemical_list: C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D004921:Erythropoietin; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D000263:Adenylate Kinase; C110939:adenylate kinase 1; D009701:Nucleoside-Diphosphate Kinase; D015720:5'-Nucleotidase; D000241:Adenosine
keywords: ADP; ATP; Adenylate kinase-1; Diabetic retinopathy; Ecto-5′-nucleotidase/CD73; Vitreous fluid