title: Mutant erythropoietin without erythropoietic activity is neuroprotective against ischemic brain injury.
abstract: OBJECTIVE
  Erythropoietin (EPO) confers potent neuroprotection against ischemic injury. However, treatment for stroke requires high doses and multiple administrations of EPO, which may cause deleterious side effects due to its erythropoietic activity. This study identifies a novel nonerythropoietic mutant EPO and investigates its potential neuroprotective effects and underlying mechanism in an animal model of cerebral ischemia.
  
  
  METHODS
  We constructed a series of mutant EPOs, each containing a single amino acid mutation within the erythropoietic motif, and tested their erythropoietic activity. Using cortical neuronal cultures exposed to N-methyl-d-aspartate neurotoxicity and a murine model of transient middle cerebral artery occlusion, neuroprotection and neurofunctional outcomes were assessed as well as activation of intracellular signaling pathways.
  
  
  RESULTS
  The serine to isoleucine mutation at position 104 (S104I-EPO) completely abolished the erythropoietic and platelet-stimulating activity of EPO. Administration of S104I-EPO significantly inhibited N-methyl-d-aspartate-induced neuronal death in primary cultures and protected against cerebral infarction and neurological deficits with an efficacy similar to that of wild-type EPO. Both S104-I-EPO and wild-type EPO activated similar prosurvival signaling pathways such as phosphatidylinositol 3-kinase/AKT, mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2, and STAT5. Inhibition of phosphatidylinositol 3-kinase/AKT or mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2 signaling pathways significantly attenuated the neuroprotective effects of S104-I-EPO, indicating that activation of these pathways underlies the neuroprotective mechanism of mutant EPO against cerebral ischemia.
  
  
  CONCLUSIONS
  S104-I-EPO confers neuroprotective effects comparable to those of wild-type EPO against ischemic brain injury with the added benefit of lacking erythropoietic and platelet-stimulating side effects. Our novel findings suggest that the nonerythropoietic mutant EPO is a legitimate candidate for ischemic stroke intervention.
authors.affiliation: Geriatric Research, Education and Clinical Center, Veterans Affairs Pittsburgh Healthcare System, Pittsburgh, PA 15260, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Gan
authors.forename: Juan
authors.initials: J
authors.lastname: Xing
authors.forename: Zheng
authors.initials: Z
authors.lastname: Jing
authors.forename: R Anne
authors.initials: RA
authors.lastname: Stetler
authors.forename: Feng
authors.initials: F
authors.lastname: Zhang
authors.forename: Yumin
authors.initials: Y
authors.lastname: Luo
authors.forename: Xunming
authors.initials: X
authors.lastname: Ji
authors.forename: Yanqin
authors.initials: Y
authors.lastname: Gao
authors.forename: Guodong
authors.initials: G
authors.lastname: Cao
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000188:drug therapy* / Q000503:physiopathology; D004195:Disease Models, Animal; D004921:Erythropoietin / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D018696:Neuroprotective Agents / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology
chemical_list: D018696:Neuroprotective Agents; D004921:Erythropoietin