Systemic not just mesenteric lymph causes acute lung injury following hemorrhagic shock

Recent studies have demonstrated a significant role for factor(s) present in mesenteric lymph following hemorrhagic shock in the etiology of post-hemorrhagic shock acute lung injury (ALI). Earlier studies have shown that ischemia-reperfusion insults to systemic tissue beds can also result in ALI. We therefore hypothesized that factors in systemic lymph may cause lung injury after hemorrhagic shock; this was studied in vitro.

Confluent human pulmonary microvascular endothelial cells (HMVEC) maintained in a 2-chamber cell culture system were exposed to systemic lymph obtained from dogs exposed to sham operation or hemorrhagic shock and resuscitation. HMVEC injury was indexed by apoptosis (% Apo, Hoechst staining) and permeability to albumin (microL/min). HMVEC activation was indexed by surface expression of intracellular adhesion molecule-1 (ICAM-1) expressed as mean fluorescence intensity using flow cytometry.

There was a 2-fold increase in HMVEC permeability and apoptotic rate after incubation with postshock systemic lymph. A similar effect was noted with ICAM expression, which was 2.5 fold higher after incubation with postshock lymph. These biologic effects were first noted with the 120-minute postresuscitation lymph. Lymph obtained during shock or from sham animals had no effect.

Pulmonary microvascular endothelial dysfunction is evident after exposure to lymph obtained from systemic sites after hemorrhagic shock. The "unique" properties ascribed to post-hemorrhagic shock mesenteric lymph in causing ALI seem to be shared by lymph from systemic sites as well.