title: The synthetic progestin norgestrel acts to increase LIF levels in the rd10 mouse model of retinitis pigmentosa.
abstract: OBJECTIVE
  Retinal degenerative conditions affect thousands of people worldwide. Retinitis pigmentosa (RP) is among the most common, but it is currently incurable. It is characterized by the progressive death of photoreceptor cells, eventually leading to blindness. Neurotrophic factors play an important role in such retinopathies, and much research has been performed on their use as treatments. Our group previously demonstrated the ability of the synthetic progestin norgestrel to rescue photoreceptors from cell death, the mechanism of which is believed to include upregulation of the neurotrophic factor basic fibroblast growth factor (bFGF). The objective of the present study was to investigate whether the protection provided by norgestrel is likely to be mediated by other neurotrophins.
  
  
  METHODS
  The 661W photoreceptor cells and retinal explants from P30 to P40 wild-type (wt) C57BL/6 mice were treated with norgestrel over time. Homozygous rd10/rd10 mice that mimic the human form of RP were fed either a control or a norgestrel-containing diet. Changes in neurotrophic factor expression in response to norgestrel were detected with real-time PCR, western blotting, or immunofluorescence staining. Using specific siRNA, leukemia inhibitory factor (Lif) expression was knocked down in 661W photoreceptor cells that were stressed by serum starvation. Cells were treated with norgestrel followed by measurement of cell viability with (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) assay.
  
  
  RESULTS
  LIF, a potent neuroprotective cytokine, was found to be upregulated in response to norgestrel in vitro and in vivo. Upregulation of LIF in degenerating rd10 retinas coincided with preservation of the photoreceptor layer. We also found LIF was necessary for the norgestrel-mediated rescue of stressed photoreceptor cells from cell death in vitro.
  
  
  CONCLUSIONS
  LIF was upregulated in response to norgestrel in all models studied and is necessary for the protective effects of norgestrel in vitro. The increase in LIF expression in rd10 mice undergoing retinal degeneration was concurrent with rescue of the photoreceptor cell layer. These results highlight the ability of norgestrel to induce prosurvival molecules in the compromised retina, underlining norgestrel's potential as a viable drug for treatment of RP.
authors.affiliation: Cell Development and Disease Laboratory, Biochemistry Department, Biosciences Institute, University College Cork, Cork, Ireland.
authors.forename: Ashleigh M
authors.initials: AM
authors.lastname: Byrne
authors.affiliation: Cell Development and Disease Laboratory, Biochemistry Department, Biosciences Institute, University College Cork, Cork, Ireland.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Roche
authors.affiliation: Cell Development and Disease Laboratory, Biochemistry Department, Biosciences Institute, University College Cork, Cork, Ireland.
authors.forename: Ana M
authors.initials: AM
authors.lastname: Ruiz-Lopez
authors.affiliation: Cell Development and Disease Laboratory, Biochemistry Department, Biosciences Institute, University College Cork, Cork, Ireland.
authors.forename: Alice C Wyse
authors.initials: AC
authors.lastname: Jackson
authors.affiliation: Cell Development and Disease Laboratory, Biochemistry Department, Biosciences Institute, University College Cork, Cork, Ireland.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Cotter
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002470:Cell Survival; D002478:Cells, Cultured; D003280:Contraceptives, Oral, Synthetic / Q000138:chemical synthesis / Q000494:pharmacology*; D004032:Diet; D004195:Disease Models, Animal; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000502:physiology*; D053605:Leukemia Inhibitory Factor / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009644:Norgestrel / Q000138:chemical synthesis / Q000494:pharmacology*; D020419:Photoreceptor Cells, Vertebrate / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D012174:Retinitis Pigmentosa / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D003280:Contraceptives, Oral, Synthetic; D053605:Leukemia Inhibitory Factor; C507838:Lif protein, mouse; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D009644:Norgestrel