title: Impaired Purinergic Regulation of the Glial (Müller) Cell Volume in the Retina of Transgenic Rats Expressing Defective Polycystin-2.
abstract: Retinal glial (Müller) cells possess an endogenous purinergic signal transduction cascade which normally prevents cellular swelling in osmotic stress. The cascade can be activated by osmotic or glutamate receptor-dependent ATP release. We determined whether activation of this cascade is altered in Müller cells of transgenic rats that suffer from a slow photoreceptor degeneration due to the expression of a truncated human cilia gene polycystin-2 (CMV-PKD21/703 HA). Age-matched Sprague-Dawley rats served as control. Retinal slices were superfused with a hypoosmotic solution (60 % osmolarity). Müller cells in retinas of PKD21/703 rats swelled immediately in hypoosmotic stress; this was not observed in control retinas. Pharmacological blockade of P2Y1 or adenosine A1 receptors induced osmotic swelling of Müller cells from control rats. The swelling induced by the P2Y1 receptor antagonist was mediated by induction of oxidative-nitrosative stress, mitochondrial dysfunction, production of inflammatory lipid mediators, and a sodium influx from the extracellular space. Exogenous VEGF or glutamate prevented the hypoosmotic swelling of Müller cells from PKD21/703 rats; this effect was mediated by activation of the purinergic signaling cascade. In neuroretinas of PKD21/703 rats, the gene expression levels of P2Y1 and A1 receptors, pannexin-1, connexin 45, NTPDases 1 and 2, and various subtypes of nucleoside transporters are elevated compared to control. The data may suggest that the osmotic swelling of Müller cells from PKD21/703 rats is caused by an abrogation of the osmotic ATP release while the glutamate-induced ATP release is functional. In the normal retina, ATP release and autocrine P2Y1 receptor activation serve to inhibit the induction of oxidative-nitrosative stress, mitochondrial dysfunction, and production of inflammatory lipid mediators, which otherwise will induce a sodium influx and cytotoxic Müller cell swelling under anisoosmotic conditions. Purinergic receptors may represent a target for the protection of retinal glial cells from mitochondrial oxidative stress.
authors.affiliation: Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Vogler
authors.affiliation: Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Pannicke
authors.affiliation: Department of Ophthalmology and Eye Hospital, University of Leipzig, Liebigstrasse 10-14, 04103, Leipzig, Germany.
authors.forename: Margrit
authors.initials: M
authors.lastname: Hollborn
authors.affiliation: 5th Medical Department, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Kolibabka
authors.affiliation: Department of Ophthalmology and Eye Hospital, University of Leipzig, Liebigstrasse 10-14, 04103, Leipzig, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Wiedemann
authors.affiliation: Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Reichenbach
authors.affiliation: 5th Medical Department, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Hammes
authors.affiliation: Department of Ophthalmology and Eye Hospital, University of Leipzig, Liebigstrasse 10-14, 04103, Leipzig, Germany. bria@medizin.uni-leipzig.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bringmann
mesh_terms: D000818:Animals; D048429:Cell Size; D063928:Ependymoglial Cells / Q000378:metabolism* / Q000473:pathology; D005786:Gene Expression Regulation; D006801:Humans; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D043682:Receptor, Adenosine A1 / Q000502:physiology*; D058472:Receptors, Purinergic P2Y1 / Q000502:physiology*; D012160:Retina / Q000378:metabolism* / Q000473:pathology; D050396:TRPP Cation Channels / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D043682:Receptor, Adenosine A1; D058472:Receptors, Purinergic P2Y1; D050396:TRPP Cation Channels
keywords: ATP; Adenosine; Cell swelling; Glia; Osmotic stress; Retina