Abstract 47: High-Density Lipoproteins Induce Neutrophil-miRNA Transcription and Export: Contribution to HDL-miRNA Cell to Cell Communication
Background: We have recently shown that high-density lipoproteins (HDL)-associated miR-223 is exported from HDL to endothelial cells in a key pathway mechanism by which HDL mediate the suppression of endothelial cell adhesion molecule expression. Interestingly, miR-223 was found to be the most abundant miRNA in polymorphonuclear neutrophils (PMNs) and miR-223 is critical to PMNs activation. Here, we sought to determine if PMNs export miR-223 to HDL and if PMNs are a significant contributor to HDL-miR-223 cell-to-cell communication, which we previously reported.
Results: To determine if PMNs export miR-223 to native HDL, PMNs and HDL were collected from 8 healthy donors by polymorph preps and density-gradient ultracentrifugation; respectively. HDL (1 mg/mL) were incubated with PMNs for 4 h and HDL were then isolated from culture media using apoA-I immunoprecipitation columns. Total RNA was isolated from HDL, and miR-223 levels were measured by TaqMan assays. miRNA export assays showed a significant increase in miR-223 on HDL post-PMN incubation compared to pre-incubation. To determine if other myeloid cells also export miR-223 to HDL, we isolated human monocytes by elutriation and differentiated them to macrophages (HMDM) over 7 days. Similar to PMNs, HMDM were also found to export miR-223 to HDL after 16 h. As a consequence of miR-223 export, we predicted that PMN cellular levels of mature miR-223 would decrease. Strikingly, we found no differences in cellular mature miR-223 levels in PMNs or HMDM treated with HDL. To determine if cellular miR-223 levels are supported by increased miR-223 transcription in response to HDL induction and miRNA export, we quantified primary (pri)-miR-223 levels using real-time PCR and TaqMan assays. We found that HDL induce a significant 3.75-fold increase in PMN pri-miR-223 levels after 4 h. Likewise; we found a significant 2.24-fold increase in HMDM pri-miR-223 levels after 16 h of HDL treatment
Conclusion: PMNs export miR-223 to HDL; however, miRNA export does not reduce cellular mature miR-223 levels likely due to HDL-induced pri-miR-223 transcription. This suggests that HDL induce the transcription of miRNAs selected for export and indicates that cells can satisfy demand for export and maintain cellular miRNA levels.
Author Disclosures: F. Tabet: None. L.F. Cuesta Torres: None. C.B. Wiese: None. G. Öhrling: None. R. Larsson: None. P.J. Barter: None. K.C. Vickers: None. K. Rye: None.
- © 2015 by American Heart Association, Inc.