title: Impaired activation of mitogen-activated protein kinases after hemorrhagic shock.
abstract: BACKGROUND
  Patients sustaining major trauma are at risk of developing organ dysfunction. We have previously shown that resuscitated hemorrhagic shock primes for increased lung injury in response to lippolysaccharide (LPS), in part by preventing upregulation of the counterinflammatory cytokine IL-10. Because the mitogen-activated protein kinase (MAPK) family is known to participate in LPS signaling, we hypothesized that altered upstream signaling through these kinases might contribute to impaired LPS-simulated IL-10 release after shock and resuscitation.
  
  
  METHODS
  Rats were bled to a mean arterial pressure of 40 mm Hg and maintained for 1 hour, then resuscitated. Alveolar macrophages were retrieved at the end of resuscitation and exposed to LPS (0.5 microg/mL). Western blotting for p38, extracellular-regulated protein kinase, and c-Jun NH2-terminal kinase was performed on whole cell lysates. In some studies, the alveolar macrophages were preincubated with the p38 inhibitor or the extracellular-regulated protein kinase inhibitor before LPS stimulation. IL-10 levels were measured by enzyme-linked immunosorbent assay.
  
  
  RESULTS
  LPS caused an early activation in all members of the MAPK family, whereas antecedent shock both delayed and attenuated the LPS induction. To discern whether this reduction in LPS-stimulated MAPK activation after shock might contribute to reduced IL-10, specific inhibitors were used. Inhibition of p38 MAPK completely inhibited LPS-induced IL-10 production, whereas blockade of extracellular-regulated protein kinase pathway had no effect.
  
  
  CONCLUSIONS
  Shock resuscitation impairs LPS-induced activation of the members of the MAPK family. For the critical counterinflammatory cytokine IL-10, inhibition of p38 activation appears to contribute to the reduced levels of this cytokine in response to LPS. This study provides in vitro evidence for altered signaling through p38 MAPK, as a mechanism leading to failed upregulation of a counterinflammatory cytokine, and thus the propagation of an unrestrained proinflammatory state. Restoration of normal signaling may represent an effective strategy to reverse this effect.
authors.affiliation: Department of Surgery, University Health Network, and University of Toronto, Ontario, Canada.
authors.forename: Rachel G
authors.initials: RG
authors.lastname: Khadaroo
authors.forename: Ziyue
authors.initials: Z
authors.lastname: Lu
authors.forename: Kinga A
authors.initials: KA
authors.lastname: Powers
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Papia
authors.forename: Andras
authors.initials: A
authors.lastname: Kapus
authors.forename: Ori D
authors.initials: OD
authors.lastname: Rotstein
mesh_terms: D000818:Animals; D004789:Enzyme Activation / Q000187:drug effects; D016753:Interleukin-10 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000201:enzymology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism; D012771:Shock, Hemorrhagic / Q000378:metabolism*; D015854:Up-Regulation / Q000502:physiology
chemical_list: D008070:Lipopolysaccharides; D016753:Interleukin-10; D020928:Mitogen-Activated Protein Kinases