Endothelial-specific c-Myc depletion enhances diet-induced liver inflammation and fibrosis

Endothelial cells play an essential role in inflammation through synthesis and secretion of chemoattractant cytokines and expression of adhesion molecules required for inflammatory cell attachment and infiltration. The mechanisms by which endothelial cells control its pro-inflammatory response depends on the type of inflammatory stimuli, endothelial cell origin and tissue involved. In the present study, we investigate the role of the transcription factor c-Myc in inflammation using a conditional knockout mouse model in which Myc is specifically deleted in the endothelium (EC-Myc KO). Using an experimental model of nonalcoholic steatohepatitis, we investigated the involvement of endothelial c-Myc in diet-induced inflammation. EC-Myc KO animals displayed enhanced pro-inflammatory response relative to control, which was characterized by increased expression of pro-inflammatory cytokines and leukocyte infiltration as well as worsened liver fibrosis. Transcriptome analysis suggested that different pro-inflammatory pathways are activated in control and endothelial Myc knockout after exposure to high-fat diet. Analysis of published single cell RNA-sequencing data available on human cirrhotic livers indicated that MYC was downregulated in endothelial cells relative to healthy individuals. Our results suggest a protective role for endothelial c-Myc in diet-induced liver inflammation and fibrosis. Targeting c-Myc and its downstream pathways in the endothelium may be a promising strategy for treatment of diet-induced inflammatory disease. Overall design: Floxed control (CT) and endothelial c-Myc knockout (EC-Myc KO) mice received tamoxifen injection at 5 weeks of age to induce Cre activity. 2 weeks after injection, animals were fed with low fat control diet (CTD) or high-fat/cholesterol diet (HFC) for 5 weeks. Livers were haversted for transcriptome analysis.