Abstract 151: ZBTB46 is a Shear Stress Sensitive Transcription Factor in Endothelial Cells

Abstract

Background: ZBTB46, also known as zDC or BTBD4, is a member of the BTB-ZF protein family which comprises a diverse group of transcription factors. Recently, ZBTB46 was identified as a transcription repressor specific to classical dendritic cells (cDCs) among immune cells and responsible for keeping cDCs in a quiescent state. ZBTB46 down-regulation by TLR signaling leads to cDC activation. Interestingly, endothelial cells also express ZBTB46, and may be viewed as part of the immune system; expressing functional TLRs and interacting with other immune cells. However, the role of ZBTB46 in endothelial cells has not been studied. Endothelial cell activation in areas of disturbed flow is a critical step in initiation of atherosclerosis, leading to heart attacks and stroke. Hypothesis: ZBTB46 is expressed in quiescent endothelial cells under laminar shear conditions and is down-regulated by low and oscillatory shear stress patterns as seen in areas of disturbed flow, leading to endothelial cell activation. Methods: We used the mouse partial carotid ligation model to assess ZBTB46 shear responsiveness in vivo and a cone and plate cell culture model to assess shear responsiveness in vitro . We measured endothelial cell mRNA using qPCR and protein via western blot. We used immunofluorescence to show localization of ZBTB46 in the arterial wall. Results: We showed that ZBTB46 is expressed in both human and mouse endothelial cells by mRNA and protein measurements. We also showed that ZBTB46 is down-regulated under low and oscillatory shear conditions after 48 hours both in vivo (Figure 1-A) and in vitro (Figure 1-B). Further functional studies including monocyte adhesion and migration assays as well as mechanistic studies assessing upstream and downstream pathways are currently underway.