Differential Regulation of Pulmonary Endothelial Cell Response to Hypoxia by NF‐kB Family

Abstract

Endothelial cells (EC) play a central and critical role in the initiation and progression of pulmonary hypertension (PH). The NF-kB family (NFkB1, NFkB2, RELA, RELB, and C-REL) regulates a wide array of genes involving inflammatory responses, cell proliferation, and survival. The role of specific NF-kB family member in the pathogenesis of PH remains to be determined. Our objective was to evaluate the specific role of each NF-kB family member in mediating endothelial cell response to hypoxia. In particular, (1) Induction of pulmonary smooth muscle cell (SMC) proliferation by Endothelin1 release and (2) Inflammatory response by expression of ICAM1 (Intercellular Adhesion Molecule 1) and activation of STAT family proteins in EC. Each NF-kB family member was knocked down using siRNA in human pulmonary microvascular endothelial cell line (HPMEC ST1.6R) Cells were exposed to hypoxia (1%) for 24 hours. Endothelin1 and ICAM1 were assayed by RT-qPCR. Gene knockdown, Stat1 and Stat3 phosphorylation were assessed by western blot. SMC was cultured for 24 hours with EC conditioned media and proliferation was assessed by cell count. Both NFkB2 and RELA knockdown in EC, led to significant decrease in Endothelin1 and ICAM1 gene expression and also showed a significant reduction of SMC proliferation, when cultured with hypoxia exposed-EC-conditioned media. Interestingly, only C-real knockdown showed a significant increase of phosphorylated STAT1 and significantly decreased phosphorylated STAT3 in EC. In conclusion, NFkB dimers play a crucial role in PH pathogenesis and each dimer has a different role in EC response to hypoxia, which could be used as a potential drug targets.