Hepatocyte-derived exosomal microRNAs orchestrate vascular inflammation and endothelial function: insights into molecular mechanisms of trimethylamine-N-Oxide in atherosclerosis

Abstract Background: Trimethylamine-N-oxide (TMAO) has been proved to be a new proatherogenic compound for promoting vascular inflammation and endothelial dysfunction. Hepatocyte-derived exosomes played an important role in the regulation of vascular inflammation and endothelial function. Since TMAO is produced in the liver, hepatocytes may be the first potential target of TMAO. However, it is not clear whether TMAO can directly stimulate normal hepatocytes to produce exosomes so as to mediate the motivating effects of TMAO on inflammation and endothelial dysfunction.Methods: The hepatocytes were cultured and treated with TMAO at a physiological concentration for 24 hours (TMAO-Exos). The untreated group served as the control (Control-Exos). The exosomes were isolated from the culture supernatant and then added to the human aortic endothelial cells (HAECs) for 48 hours. The mRNA expressions of inflammatory cytokines and caspase-3 were determined by qPCR and cell apoptosis was evaluated by using the Hoechst 33342 staining solution. The miRNA profile in the exosomes were detected using an RNA-sequencing strategy. The miRNA-mRNA network was predicted, and the biological functions of the target genes were annotated by using bioinformatics methods.Results: TMAO-Exos were able to promote the expressions of inflammatory cytokines and HAECs apoptosis. Moreover, miRNAs carried by the TMAO-Exos were quite different from that in the Control-Exos, including miR-92a-3p, miR-103-3p and miR-122-5p, etc. Further analysis showed that these differentially expressed miRNAs were predicted to target genes such as Mapk8, Casp9, Mapk10, Bcl2l11, Ikbkg and Akt1, which were supposed to be involved in the signal pathways related to vascular inflammation and endothelial function.Conclusions: These novel results provided evidence that TMAO could indirectly talk to vascular endothelial via promoting hepatocytes to secreting exosomes that carried important genetic information, which may give a new insight into the interactions between liver and vasculature in the atherogenesis caused by TMAO. New intervention targeting this cellular crosstalk may be feasible and effective in the prevention and treatment of TMAO-induced atherogenesis.