Abstract

Erythropoietin (EPO) is typically known for its role in erythropoiesis but is also a potent neurotrophic/neuroprotective factor for spinal motor neurons. Another trophic factor regulated by hypoxia-inducible factor-1, vascular endothelial growth factor (VEGF), signals via ERK and Akt activation to elicit long-lasting phrenic motor facilitation (pMF). Because EPO also signals via ERK and Akt activation, we tested the hypothesis that EPO elicits similar pMF. Using retrograde labeling and immunohistochemical techniques, we demonstrate in adult, male, Sprague Dawley rats that EPO and its receptor, EPO-R, are expressed in identified phrenic motor neurons. Intrathecal EPO at C4 elicits long-lasting pMF; integrated phrenic nerve burst amplitude increased >90 min after injection (63 ± 12% baseline 90 min after injection; p < 0.001). EPO increased phosphorylation (and presumed activation) of ERK (1.6-fold vs controls; p < 0.05) in phrenic motor neurons; EPO also increased pAkt (1.6-fold vs controls; p < 0.05). EPO-induced pMF was abolished by the MEK/ERK inhibitor U0126 [1,4-diamino-2,3-dicyano-1,4-bis(o-aminophenylmercapto)butadiene] and the phosphatidylinositol 3-kinase/Akt inhibitor LY294002 [2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one], demonstrating that ERK MAP kinases and Akt are both required for EPO-induced pMF. Pretreatment with U0126 and LY294002 decreased both pERK and pAkt in phrenic motor neurons (p < 0.05), indicating a complex interaction between these kinases. We conclude that EPO elicits spinal plasticity in respiratory motor control. Because EPO expression is hypoxia sensitive, it may play a role in respiratory plasticity in conditions of prolonged or recurrent low oxygen.

Links

Publisher Full Text

Authors

Dale EA, Satriotomo I, Mitchell GS

Institution

Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin 53706, USA.

Source

The Journal of neuroscience : the official journal of the Society for Neuroscience 32:17 2012 Apr 25 pg 5973-83

MeSH

Action Potentials
Animals
Blood Gas Analysis
Body Temperature
Cholera Toxin
Dose-Response Relationship, Drug
Enzyme Inhibitors
Erythropoietin
Extracellular Signal-Regulated MAP Kinases
Gene Expression Regulation
Male
Motor Neurons
Phrenic Nerve
Proto-Oncogene Proteins c-akt
Rats
Rats, Sprague-Dawley
Receptors, Erythropoietin
Signal Transduction
Vagotomy

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

22539857