Changes in lymph proteome induced by hemorrhagic shock: the appearance of damage-associated molecular patterns.

BACKGROUND: Damage-associated molecular patterns (DAMPs) released from host tissue after trauma and hemorrhagic shock (HS) have been shown to activate polymorphonuclear cells (PMNs) and lead to acute lung injury and systemic inflammatory response syndrome. The avenue by which DAMPs reach the circulation is unclear; however post-HS lymph has been shown to contain biologically active mediators. We therefore studied the time course of DAMP detection in systemic lymph and the effect of isotonic versus hypertonic resuscitation on DAMPs production and PMN activation in vitro.
METHODS: A canine HS/hind-limb lymph cannulation model was used. Animals were bled to a mean arterial pressure of 40 mm Hg and were resuscitated with shed blood plus equivalent amounts of Na+as either lactated Ringer's solution or 7.5% hypertonic saline solution (HSS). Lymph samples were collected at baseline, end-shock, and at various times after resuscitation. DAMPs were isolated from lymph samples and detected by Western blot for high-mobility group box 1 and mitochondrial DNA. Priming of naive PMNs was indexed by mitogen-associated protein kinase phosphorylation. Human pulmonary microvascular endothelial cell monolayers were established and exposed to the various lymph samples. Endothelial intracellular adhesion molecule expression, apoptosis, and monolayer permeability were determined.
RESULTS: DAMPs were detected in lymph samples starting at the end of the shock period and peaking at 120 minutes after resuscitation. HSS resuscitation resulted in the highest levels of DAMPs detected in systemic lymph and plasma. PMN mitogen-associated protein kinase activation was noted during the resuscitation phase and peaked 120 minutes after resuscitation. Similar temporal changes in human pulmonary microvascular endothelial cell intracellular adhesion molecule expression and cellular injury were noted after shock with the greatest effect noted with the hypertonic saline resuscitation regimen.
CONCLUSION: Lymph represents an important avenue for the delivery of DAMPs into the systemic circulation after HS. HSS lead to a significant increase in DAMPs production in the model. This finding may account for the conflicting data regarding the salutary effects of HSS resuscitation noted in clinical versus experimental shock studies. ).