title: Hypertonic saline induces prostacyclin production via extracellular signal-regulated kinase (ERK) activation.
abstract: BACKGROUND
  Hypertonic saline (HTS) resuscitation exerts protective effects in reperfusion injury including a decrease in pulmonary vascular resistance and an increase in microvascular perfusion and cerebral blood flow; however, the mediators of these effects are unknown. Prostacyclin (PGI2) is a paracrine mediator with two main effects, vasodilation and inhibition of platelet aggregation. We hypothesized that HTS may induce PGI2 production by endothelial cells.
  
  
  METHODS
  Human umbilical vein endothelial cells (HUVECs) were treated with varying concentrations of NaCl. After 12 h of incubation, the supernatant was assayed for 6-keto-prostaglandin F1, a stable metabolite of PGI2, by ELISA. Phospho-specific ERK-1 and ERK-2 mitogen-activated protein kinase (MAPK) antibody, which recognizes only activated ERK, was used to determine ERK activation status by Western blotting.
  
  
  RESULTS
  Addition of 20-100 mM NaCl or endotoxin [lipopolysaccharide (LPS)] induced PGI2 production by HUVECs. HTS and LPS induced ERK-1 and ERK-2 activation. PGI2 production was inhibited when the HUVECs were pretreated with PD 98059, a specific inhibitor of ERK phosphorylation.
  
  
  CONCLUSIONS
  These data suggest that HTS induces PGI2 production in HUVECs. In addition, HTS and LPS induce activation of ERK which is required for PGI2 production. HTS resuscitation may improve microvascular circulation and decrease reperfusion injury via induction of PGI2 production by endothelial cells.
mesh_terms: D015121:6-Ketoprostaglandin F1 alpha / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011464:Epoprostenol / Q000096:biosynthesis*; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D014471:Umbilical Veins