title: Erythropoietin protects from axotomy-induced degeneration of retinal ganglion cells by activating ERK-1/-2.
abstract: Apart from its hematopoietic function, erythropoietin (Epo) exerts neuroprotective activity upon reduced oxygenation or ischemia of brain, retina, and spinal cord. To examine whether Epo has an impact on the retrograde degeneration of retinal ganglion cells (RGCs) following optic nerve transection in vivo, we made use of our transgenic mouse line tg21 that constitutively expresses human Epo preferentially in neuronal cells without inducing polycythemia. We show that the tg21 retina expresses human Epo and that RGCs in this mouse line carry the Epo receptor. Upon axotomy, the RGCs of Epo transgenic tg21 mice were protected against degeneration, as compared with wild-type control animals. Western blot analysis revealed decreased phosphorylation levels of STAT-5 and reduced expression of Bcl-XL in RGCs of axotomized tg21 animals, suggesting that the corresponding pathways are not crucial for Epo's neuroprotective activity. Increased phosphorylation levels of ERK-1/-2 and Akt, as well as decreased caspase-3 activity, however, were observed in injured tg21 retinae. Injection of selective inhibitors of ERK-1/-2 (PD98059) or Akt (Wortmannin) pathways into the vitreous space revealed that transgenic Epo protected the RGCs by a pathway involving ERK-1/-2 but not Akt. In view that axotomy-induced degeneration of RGC occurs slowly, and considering the earlier data on the safety and efficacy of Epo in human stroke patients, we predict the clinical implementation of recombinant human Epo not only in patients with acute ischemic stroke, but also with more delayed degenerative neurological diseases.
authors.affiliation: Department of Neurology, University Hospital Zurich, Switzerland. uelkan.kilic@usz.ch
authors.forename: Ulkan
authors.initials: U
authors.lastname: Kilic
authors.forename: Ertugrul
authors.initials: E
authors.lastname: Kilic
authors.forename: Jorge
authors.initials: J
authors.lastname: Soliz
authors.forename: Claudio I
authors.initials: CI
authors.lastname: Bassetti
authors.forename: Max
authors.initials: M
authors.lastname: Gassmann
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Hermann
mesh_terms: D000818:Animals; D019771:Axotomy / Q000009:adverse effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004921:Erythropoietin / Q000096:biosynthesis / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D053614:Janus Kinase 2; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008894:Milk Proteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009410:Nerve Degeneration / Q000517:prevention & control*; D018696:Neuroprotective Agents / Q000494:pharmacology / Q000627:therapeutic use; D009900:Optic Nerve / Q000601:surgery; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000096:biosynthesis; D012160:Retina / Q000601:surgery; D012165:Retinal Ganglion Cells / Q000201:enzymology* / Q000378:metabolism*; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000502:physiology; D015534:Trans-Activators / Q000378:metabolism; D051020:bcl-X Protein
chemical_list: D053148:Caspase 3; D020169:Caspases; D004268:DNA-Binding Proteins; D004921:Erythropoietin; D048031:JNK Mitogen-Activated Protein Kinases; D053614:Janus Kinase 2; D008894:Milk Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D018696:Neuroprotective Agents; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D017467:Receptors, Erythropoietin; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D051020:bcl-X Protein; C494811:BCL2L1 protein, human; C494812:Bcl2l1 protein, mouse; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; C494918:AKT1 protein, human; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse