Adropin decreases endothelial monolayer permeability after cell-free hemoglobin exposure and reduces MCP-1-induced macrophage transmigration

Background: Cell-free heme-containing proteins mediate endothelial injury in a variety of disease states including subarachnoid hemorrhage and sepsis by increasing endothelial permeability. Inflammatory cells are also attracted to sites of vascular injury by monocyte chemotactic protein 1 (MCP-1) and other chemokines. We have identified a novel peptide hormone, adropin, that protects against hemoglobin-induced endothelial permeability and MCP-1-induced macrophage migration.

Methods: Human microvascular endothelial cells were exposed to cell-free hemoglobin (CFH) with and without adropin treatment before measuring monolayer permeability using a FITC-dextran tracer assay. mRNA and culture media were collected for molecular studies. We also assessed the effect of adropin on macrophage movement across the endothelial monolayer using an MCP-1-induced migration assay.

Results: CFH exposure decreases adropin expression and increases paracellular permeability of human endothelial cells. Treating cells with synthetic adropin protects against the increased permeability observed during the natural injury progression. Cell viability was similar in all groups and Hmox1 expression was not affected by adropin treatment. MCP-1 potently induced macrophage migration across the endothelial monolayer and adropin treatment effectively reduced this phenomenon.

Conclusions: Endothelial injury is a hallmark of many disease states. Our results suggest that adropin treatment could be a valuable strategy in preventing heme-mediated endothelial injury and macrophage infiltration. Further investigation of adropin therapy in animal models and human tissue specimens is needed.