Endothelial Heterogeneity Across Vascular Beds Impacts Inflammatory Signaling and Neutrophil Adhesion

Endothelial cells (ECs) are key players in maintaining homeostasis and coordinating immune responses, activating during acute inflammation to recruit immune cells. Endothelial heterogeneity has been found to impact transcription level differences across EC sources, but how these differences drive downstream effects in inflammatory signaling and immune interactions remains unclear. Here, we employed multiplexed ELISA to quantify secretion for 19 inflammatory factors following tumor necrosis factor (TNF) or Pseudomonas aeruginosa activation of four primary human EC sources: umbilical artery (HUAEC), umbilical vein (HUVEC), dermal microvascular (HDMEC), and pulmonary microvascular (HPMEC) endothelial cells. We also quantified changes in neutrophil adhesion to each EC source and used partial least squares regression (PLSR) to identify key inflammatory proteins associated with changes in neutrophil adhesion. We found distinct inflammatory secretion profiles across all cell types, with veinous ECs showing the highest basal secretion of most inflammatory proteins and pulmonary ECs exhibiting the lowest. Arterial ECs exhibited the lowest sensitivity to inflammatory stimulus, while pulmonary ECs exhibited dynamic responses following activation. Furthermore, inflammatory stimulus caused large differences in expression across cell sources for six factors: GM-CSF, IL-1{beta}, IL-6, IP-10, E-selectin, and ICAM-1. We found endothelial heterogeneity also contributed to differences in neutrophil adhesion to unstimulated ECs. Our PLSR analysis revealed five secreted factors most indicative of changes in neutrophil adhesion: E-selectin, ICAM-1, PECAM1, IL-6, and IL-8. Collectively, our findings strengthen the emerging view that vascular-bed specific differences in EC phenotype can impact downstream immune responses.