Endotoxin-mediated pulmonary endothelial cell injury

Area of Science:

• Pulmonary Medicine
• Immunology
• Cell Biology

Background:

• Endotoxemia causes pulmonary endothelial damage.
• The roles of complement activation and granulocyte sequestration in this damage are unclear.

Purpose of the Study:

• To investigate whether complement/granulocyte activation contributes to endotoxin-induced pulmonary endothelial damage.
• To determine if granulocyte migration across the endothelium causes damage.
• To assess direct endotoxin effects on pulmonary endothelium.

Main Methods:

• Infusion of complement-activated plasma into sheep.
• In vitro studies using bovine pulmonary endothelial monolayers exposed to endotoxin.
• Assessment of endothelial structural integrity, vascular permeability, prostacyclin production, and lactic dehydrogenase release.

Main Results:

• Complement-activated plasma caused transient endothelial damage in sheep, despite granulocyte sequestration.
• Granulocyte migration across endothelial explants did not cause significant damage or increased permeability.
• In vitro, endotoxin directly damaged pulmonary endothelium in a dose-dependent manner, exacerbated by serum.
• Endotoxin increased endothelial permeability, prostacyclin production, and LDH release.

Conclusions:

• Endotoxin directly injures pulmonary endothelium.
• Complement and granulocyte activation may enhance endotoxin-induced endothelial damage but are not solely responsible.
• Granulocyte migration across the endothelium does not appear to be a primary cause of severe endothelial damage in this model.