Abstract 3: HDL-MicroRNA-92a and Interleukin-33 Axis Underlies Endothelial Dysfunction Associated With Atherosclerosis and Chronic Kidney Disease

Chronic kidney disease (CKD) is associated with endothelial dysfunction and atherosclerosis. High-density lipoproteins (HDL) serve as a general cargo carrier for a wide-variety of proteins, nucleic acids, and small molecules which likely confer many of HDL’s alternative functions. Human coronary artery endothelial cells (HCAEC) treated with native HDL were found to have increased intracellular levels of miR-92a, a miRNA recently found to protect against endothelial dysfunction and atherosclerosis. Moreover, HDL delivery of miR-92a was inhibited using SR-BI blocking antibodies in endothelial cells. Likewise, aortic endothelial miR-92a levels were found to be significantly decreased (50%) in Apoe-/- mice compared to wild-type controls, which may be a function of the absence of HDL in these mice. Using photoactivatable-ribonucleoside-crosslinked-immunoprecipitation-high-throughput-sequencing, we found that HDL transfer multiple miR-92a isomiR variants from macrophages to HCAECs, which were found in association with Argonaute2 RNA-induced silencing complexes. Using whole-genome arrays, we found that HDL alters the expression of many genes in HCAECs, including the significant down-regulation of 18 putative miR-92a targets. Strikingly, miR-92a was found to be significantly increased 8.5-fold on HDL from CKD subjects. Interleukin-33 (IL-33) is a cytokine and nuclear transcription factor largely expressed in endothelial cells. HDL from both normal and CKD subjects significantly decreased IL-33 expression in HCAECs, as determined by real-time PCR and microarrays. In a mouse model of CKD (Apoe-/-; 5/6 nephrectomy), IL-33 expression was increased in aortic endothelial cells; however, a single HDL injection (4mg) reduced IL-33 mRNA back to sham levels at 7d post-injection. Most interestingly, HDL loaded with locked-nucleic acid miR-92a inhibitors blocked HDL’s ability to suppress CKD induced IL-33 expression in the aortic endothelium. IL-33 may represent a novel marker of endothelial dysfunction, as IL-33 mRNA levels were also found to be increased in HCAECs under disturbed flow conditions. Results from this study suggest that HDL suppression of IL-33 in CKD requires miR-92a, which is also transferred to endothelial cells by HDL.