title: Retinoid X receptor activation is essential for docosahexaenoic acid protection of retina photoreceptors.
abstract: We have established that docosahexaenoic acid (DHA), the major polyunsaturated fatty acid in the retina, promotes survival of rat retina photoreceptors during early development in vitro and upon oxidative stress by activating the ERK/MAPK signaling pathway. Here we have investigated whether DHA turns on this pathway through activation of retinoid X receptors (RXRs) or by inducing tyrosine kinase (Trk) receptor activation. We also evaluated whether DHA release from phospholipids was required for its protective effect. Addition of RXR antagonists (HX531, PA452) to rat retinal neuronal cultures inhibited DHA protection during early development in vitro and upon oxidative stress induced with Paraquat or H2O2. In contrast, the Trk inhibitor K252a did not affect DHA prevention of photoreceptor apoptosis. These results imply that activation of RXRs was required for DHA protection whereas Trk receptors were not involved in this protection. Pretreatment with 4-bromoenol lactone, a phospholipase A2 inhibitor, blocked DHA prevention of oxidative stress-induced apoptosis of photoreceptors. It is noteworthy that RXR agonists (HX630, PA024) also rescued photoreceptors from H2O2-induced apoptosis. These results provide the first evidence that activation of RXRs prevents photoreceptor apoptosis and suggest that DHA is first released from phospholipids and then activates RXRs to promote the survival of photoreceptors.
authors.affiliation: Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur-CONICET, Buenos Aires, Argentina.
authors.forename: Olga L
authors.initials: OL
authors.lastname: German
authors.affiliation: Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur-CONICET, Buenos Aires, Argentina.
authors.forename: Sandra
authors.initials: S
authors.lastname: Monaco
authors.affiliation: Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur-CONICET, Buenos Aires, Argentina.
authors.forename: Daniela L
authors.initials: DL
authors.lastname: Agnolazza
authors.affiliation: Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur-CONICET, Buenos Aires, Argentina. Electronic address: inpoliti@criba.edu.ar.
authors.forename: Nora P
authors.initials: NP
authors.lastname: Rotstein
authors.affiliation: Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur-CONICET, Buenos Aires, Argentina. Electronic address: inrotste@criba.edu.ar.
authors.forename: Luis E
authors.initials: LE
authors.lastname: Politi
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001565:Benzoates / Q000494:pharmacology; D001713:Biphenyl Compounds / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D004281:Docosahexaenoic Acids / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D018384:Oxidative Stress / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D017948:Retinal Rod Photoreceptor Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D047488:Retinoid X Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D001565:Benzoates; D001713:Biphenyl Compounds; D047488:Retinoid X Receptors; C438269:diazepinylbenzoic acid; D004281:Docosahexaenoic Acids
keywords: RXR agonists; apoptosis; oxidative damage; photoreceptor survival