title: Erythropoietin improves skeletal muscle microcirculation through the activation of eNOS in a mouse sepsis model.
abstract: BACKGROUND
  Sepsis and septic shock remain the major causes of morbidity and mortality in intensive care units. One mechanism that leads to organ failure is microcirculatory dysfunction. Erythropoietin (EPO) is a glycoprotein produced by the kidney that primarily regulates erythropoiesis, but it also can exert hemodynamic, anti-inflammatory, and tissue protective effects. We previously reported that administration of EPO to septic mice improves mouse skeletal muscle capillary perfusion and tissue bioenergetics. The objective of this study was to explore the potential mechanism(s) involved.
  
  
  METHODS
  Sepsis was induced by intraperitoneal (i.p.) injection of a fecal suspension (12.5 g in 0.5 saline/mouse) in mice. At 18 hours after sepsis induction, a single dose of rHuEPO (400 U/kg) was given to the mice. Mouse capillary perfusion density and nicotinamide adenine dinucleotide (NADH) fluorescence in skeletal muscle were observed using intravital microscopy. Endothelial cells derived from the skeletal muscle were treated with rHuEPO (5 U/mL) and endothelial nitric oxide synthase (eNOS) activation and activity were assessed.
  
  
  RESULTS
  Septic mice had decreased capillary perfusion density and increased tissue NADH fluorescence indicating impaired tissue bioenergetics, whereas animals treated with rHuEPO demonstrated an improvement in capillary perfusion density and decreased skeletal muscle NADH fluorescence. The beneficial effect of rHuEPO did not occur in septic mice treated with l-NAME (an NOS inhibitor, 20 mg/kg) or mice genetically deficient in eNOS. Treatment of endothelial cells with rHuEPO resulted in activation of eNOS as indicated by increased eNOS phosphorylation and NO production.
  
  
  CONCLUSIONS
  Our results suggest that eNOS plays an important role in mediating the beneficial effect of rHuEPO on microcirculation in this septic mouse model.
authors.affiliation: Department of National Defense, Canadian Forces Health Services, Ottawa, Ontario, Canada. rkao3@uwo.ca
authors.forename: Raymond L C
authors.initials: RL
authors.lastname: Kao
authors.forename: Claudio M
authors.initials: CM
authors.lastname: Martin
authors.forename: Anargyros
authors.initials: A
authors.lastname: Xenocostas
authors.forename: Weixiong
authors.initials: W
authors.lastname: Huang
authors.forename: Tao
authors.initials: T
authors.lastname: Rui
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004789:Enzyme Activation / Q000187:drug effects*; D004921:Erythropoietin / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008833:Microcirculation / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000201:enzymology; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D018805:Sepsis / Q000188:drug therapy / Q000201:enzymology / Q000503:physiopathology*; D016896:Treatment Outcome
chemical_list: D004921:Erythropoietin; D052250:Nitric Oxide Synthase Type III