Abstract P3025: CXCL10 Impairs Endothelial Barrier Integrity In Endothelial Pparδ-deficient Mice Identified By Single-cell RNA Sequencing

Abstract

Rationale and Background: CXCL10 is a pro-inflammatory chemokine produced by monocytes and endothelial cells (ECs) in response to IFNγ, acting as a chemoattractant for monocytes and T cells etc., through the CXCR3 receptor. The previous study from our group showed that selective deletion of PPARδ in the endothelium worsens ischemic vascular injury in mouse model of hindlimb ischemia. Single-cell RNA sequencing of muscle endothelial cells showed that PPARδ regulates genes involved in endothelial barrier function and vascular inflammatory responses. Methods and Results: To further understand the role of PPARδ in endothelial cells from different vascular beds, we induced acute lung inflammation by lipopolysaccharide (LPS) in EC-selective PPARδ knockout mice (Ppard EC-KO ) and their wild-type littermates (Ppard EC-WT ) and analyzed the lung ECs by scRNAseq. After LPS injection, lung ECs were collected as CD45 - CD31 + CD144 + cells by FACSorting, and scRNAseq was performed using 10X genomics method. General capillary ECs and aerocyte capillary ECs were identified by distinctive marker genes as the two most abundant lung ECs. The capillary ECs from LPS-challenged Ppard EC-KO mice showed high enrichment of inflammatory signaling including IFN-IRF, IL6-STAT3, and TNFα-NFκB. Further sub-clustering analysis revealed a capillary EC subset with upregulation of IFN signaling and identified CXCL10 as the top marker-gene in LPS-challenged mice. CXCL10 expression was indeed upregulated in the lung tissue of LPS-treated Ppard EC-KO mice and in TNFα-treated human lung microvascular endothelial cells (HLMVECs). CXCL10 decreased the expression of EC tight junctional proteins ZO-1 and Claudin-5 through the ubiquitin-proteosome system-mediated degradation in HLMVECs. Blocking the CXCR3 by AMG487 suppressed vascular leakage and EC activation in response to LPS. Conclusion: These results suggested the possibility of targeting CXCL10 signaling for restoring vascular homeostasis in acute lung inflammation. (Supported by Hong Kong Research Grant Council GRF 14107822 and 14105321)