Abstract P165: Vascular Endothelial Exosomes Propogate Inflammation in Vascular Smooth Muscle Cells Through Up-Regulation of HMGB1

Abstract

Vascular homeostasis is predicated on the integral interaction between a myriad of cell types. Principle to homeostasis is the interaction between the endothelial cells (ECs) of the intima and the vascular smooth muscle cells (VSMCs) of the media. Disruption of the tightly controlled communication between these cell types can lead to development of pathophysiology. In the past decade, much study has been given to a novel means of intercellular communication in exosomes. Exosomes are nanovesicles derived from endosomal compartments capable of carrying functional proteins, small RNAs and lipids into extracellular space. Initially characterized in the field of immunology, little is known on exosomes within vascular biology. Therefore, we present a model through which EC exosomes initiate inflammatory signaling and remodeling within VSMC. Primary rat aortic EC and VSMC exosomes isolated in serum-free conditions displayed characteristic size, shape and protein content of exosomes as analyzed through nanoparticle tracking analysis, electron microscopy, and western blot. Proteomics identified differential expression between EC and VSMC exosomes suggesting altered cargo between the two populations. Incubation of EC exosomes with VSMC identified a dose- and time-dependent increase in the expression of vascular cell adhesion molecule 1 (VCAM1) in VSMC (2.6 fold, p<0.01) and functional increase in leukocyte adhesion (p<0.05), that was a one-way mechanism of EC-VSMC. EC exosomes increased the prevalence of senescence cells (1.62 fold, p<0.05) in VSMC with increases in cellular volume, suggesting a pro-inflammatory remodeling. Unbiased mass spectroscopy on VSMC incubated with EC exosomes derived with/without TNF stimulation identified pro-inflammatory mediator HMGB1 as significantly up-regulated in both conditions. Interestingly, use of HMGB1 inhibitor Glycyrrhizin was able to abolish increase in VCAM1 (p<0.05) and increases in THP-1 adhesion (p<0.05). Identification of HMGB1 was also present in unbiased proteomics performed on EC exosomes themselves. Taken together, this suggests that EC exosomes derived from nutrient-stressed conditions induce inflammatory remodeling and signaling in VSMC through an HMGB1-dependent mechanism.