Trauma/Hemorrhagic Shock Mesenteric Lymph Upregulates Adhesion Molecule Expression and IL-6 Production in Human Umbilical Vein Endothelial Cells

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Abstract
Trauma/hemorrhagic shock (T/HS) is associated with significant lung injury, which is mainly due to an inflammatory process, resulting from the local activation and subsequent interaction of endothelial cells and leukocytes. Adhesion molecules expressed by both cell types play a crucial role in the process of neutrophil-mediated endothelial cell injury. We have previously shown that mesenteric lymph duct ligation prevents T/HS-induced lung leukocyte infiltration and endothelial injury, suggesting that inflammatory factors originating from the gut and carried in the lymph are responsible for the lung injury observed following T/HS. Based on these observations, we hypothesized that inflammatory substances in T/HS lymph trigger lung injury by a mechanism involving the upregulation of adhesion molecules. To test this hypothesis, we examined whether T/HS mesenteric lymph induces the expression of E-selectin, P-selectin, and intracellular adhesion molecule-1 (ICAM-1) in human umbilical vein endothelial cells (HUVECs). Furthermore, because the cytokine IL-6 is an important component of the endothelial inflammatory process, we investigated how T/HS lymph affects the production of IL-6 by HUVECs. Mesenteric lymph from T/HS rats increased both E- and P-selectin, as well as ICAM-1 expression on HUVECS, as compared to trauma/sham shock (T/SS) lymph or medium only groups. However, T/HS lymph failed to induce the shedding of E-selectin. In HUVECs treated with T/HS lymph, IL-6 concentrations were higher than HUVECs treated with T/SS lymph. These findings suggest that mesenteric lymph produced after hemorrhagic shock potentiates lung injury by the upregulation of endothelial cell adhesion molecule expression and IL-6 production.