Platelet Microparticles Enriched in miR-223 Reduce ICAM-1-Dependent Vascular Inflammation in Septic Conditions

Abstract

In the process of sepsis, activated platelets shed microvesicles containing microRNAs (miRNAs), which can be internalized by distinct recipient cells in circulation, consequently eliciting a potent capability to regulate their cellular functions in different diseases. In the present study, activated human platelets transferring miR-223 into endothelial cells via platelet-derived microparticles (PMPs) was investigated in vitro during septic conditions with a proposed mechanism involving in downregulation of the enhanced expression of intercellular adhesion molecule-1 (ICAM-1). The uptake of PMPs encasing miR-223 and the adhesion of peripheral blood mononuclear cells (PBMCs) on human coronary artery endothelial cells (HCAECs) were observed by immunofluorescence microscopy upon co-culture with PMPs isolated from sepsis or control plasma. The expression of miR-223-3p and its gene target ICAM1 in HCAECs were quantified by RT-qPCR and ELISA after the cells were incubated with septic or control PMPs, whose levels were induced with thrombin-receptor activating peptide (TRAP). Leukocyte-depleted platelets (LDPs) from septic patients showed a decreased miR-223 level, while septic plasma and PMPs revealed an elevated miRNA level compared to control samples. Similarly, TRAP-activated LDPs demonstrated a reduced intracellular miR-223 expression, while increased levels in the supernatant and PMP isolates were observed vs. untreated samples. Furthermore, TNF-α alone resulted in decreased miR-223 and elevated ICAM1 levels in HCAECs, while PMPs raised the miRNA level that was associated with downregulated ICAM1 expression at both mRNA and protein levels under TNF-α treatment. Importantly, miR-223 was turned out not to be newly synthesized as shown in unchanged pre-miR-223 level, and mature miR-223 expression was also elevated in the presence of PMPs in HCAECs after transfection with Dicer1 siRNA. In addition, septic PMPs containing miR-223 decreased ICAM1 with a reduction of PBMC binding to HCAECs. In conclusion, septic platelets released PMPs carrying functional miR-223 lower ICAM1 expression in endothelial cells, which may be a protective role against excessive sepsis-induced vascular inflammation.