Defining the inflammasome and its activators in Human Aortic Endothelial Cells

Abstract

The endothelium is the internal first line of defence against blood borne stressors. It recognises these stressors through the pattern recognition receptors (PRRs) that it harbours. Nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs) are a diverse family of PRRs that mount immune responses against danger signals including pathogens. Prolonged exposure to such stressors leads to a dysfunctional endothelium. Despite the central role of the human endothelium in host defence, it is unclear which NLRs are actively engaged in danger recognition. Using knock out studies and functional assays, we report that in primary human aortic endothelial cells (HAECs), only NLRP1 and CARD8 are expressed and functional, mediating pyroptotic cell death and IL-18 secretion in response to a synthetic ligand Talabostat. In contrast, NLRP3 is not functional even after LPS priming. Using this, we performed functional assays in order to identify novel ligand(s) of the endothelial inflammasome. Our studies give us a deeper insight into the inner workings of the innate immune machinery in endothelial cells, revealing candidate therapeutic targets against chronic inflammatory conditions in general.