Intestinal dysbiosis and impaired gut barrier function lead to increased blood lipopolysaccharide (LPS) load, a condition known as endotoxemia. We investigated whether intracellular LPS induces activation of the noncanonical caspase-4 and -5 inflammasome in human coronary artery endothelial cells (HCAECs) and whether this contributes to arterial wall inflammation. Cytosolic LPS induced activation of the noncanonical inflammasome in endothelial cells, leading to marked increase in extracellular vesicle (EV) secretion. These EVs were enriched with biologically active proteins, particularly kinases, involved in bacterial invasion, cell survival, and pyroptosis. EV secretion was dependent on the pore forming proteins Gasdermin D and Mixed lineage kinase domain-like pseudokinase (MLKL). Intracellular LPS also upregulated the expression of adhesion molecules, which increased monocyte attachment to HCAECs. EVs from activated endothelial cells stimulated expression of proinflammatory cytokines and interferon-stimulated genes in macrophages. Ultimately, noncanonical inflammasome activation increased endothelial cell pyroptosis. These findings suggest that activation of the noncanonical inflammasome in endothelial cells could represent a novel link between intestinal dysbiosis and the ensuing endotoxemia and arterial wall inflammation.
Keywords: Arterial endothelium; Bacterial outer membrane vesicle; Caspase-4/-5; Coronary artery disease; Dysbiosis; Lipopolysaccharide; MLKL.