The metabolic syndrome (MetS) is a cluster of interrelated risk factors for cardiovascular disease and atherosclerosis including hyperglycemia, dyslipidemia, hypertension and obesity. We have previously shown that circulating levels of microparticles (MPs), small vesicles released from plasma membrane, from MetS patients induce endothelial dysfunction.

Here, we analyze whether MPs from MetS patients may participate to the alteration of smooth muscle cells (SMC) function described during the atherosclerosis development.

Circulating MPs of non-MetS subjects and MetS patients have been isolated from plasma and characterized by proteomic analysis. Then, the involvement of Rap1 in the effects of MPs on human aortic SMC (HASMC) proliferation and migration was analyzed.

Differential proteomic analysis of MPs from both types of individuals identifies Rap1, a small GTPase, as two-fold overexpressed in MPs from MetS compared with non-MetS subjects. In addition, Rap1 is in active state, that is, GTP-associated, in both type of MPs. When HASMC are incubated with MPs for 24h, both types of MPs significantly promote proliferation and migration. Even more, MetS MPs are able to increase the expression of the pro-inflammatory molecules MCP-1 and IL-6. Neutralization of Rap-1 by specific antibody or pharmacological inhibition of Rap-1 with GGTI-298 either partially or completely prevents the effects of MPs from MetS patients but not those from non-MetS MPs. These effects includes HASMC proliferation, migration, inflammation and increase of p38 and ERK5 phosphorylation.

These data suggest that overexpression of Rap1 in MetS MPs might participate in the enhanced SMC proliferation, migration and activation of MAPK/ERK pathway leading to atherosclerosis.