Abstract 537: Lipoproteins Transport Functional Non-human Small RNAs that Regulate Gene Networks Spanning Inflammation and Lipid Metabolism

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Cardiovascular disease (CVD) is a significant health and financial burden to our society that demands new and more effective therapies. Although dyslipidemias are primary risk factors for CVD, alternative lipoprotein functions also contribute to CVD and warrant greater understanding. We have found that high-density lipoproteins (HDL) transport microRNAs (miRNA) in circulation and HDL-miRNA signatures are significantly altered in hypercholesterolemia and atherosclerosis. Moreover, we found that HDL transfers extracellular miRNAs to recipient cells where they regulate gene expression through post-transcriptional repression of mRNA targets. We used high-throughput small RNA (sRNA) sequencing to identify and quantify miRNAs and novel sRNAs on HDL and other lipoproteins. Most interestingly, we found that the majority of sRNAs on lipoproteins are likely derived from non-human organisms of multiple kingdoms. Based on these observations, we hypothesized that human and non-human sRNAs on lipoproteins are unique regulators of gene networks that contribute to the complex pathophysiology of CVD. To assess this hypothesis, highly pure lipoproteins (HDL, low-density lipoproteins (LDL), and very low-density lipoproteins (VLDL)) were isolated from plasma of hypercholesterolemic (heterozygous familial hypercholesterolemia, n=9) and healthy (n=7) subjects. We found that HDL, LDL, and VLDL each transport unique sRNA signatures, which are differentially altered in hypercholesterolemic subjects. Using a human tissue library, we identified tissues that likely take up non-human sRNAs. We also found that each class of lipoprotein is capable of transferring non-human sRNAs to multiple cell types, and that transfer efficiency is altered in hypercholesterolemia. Lastly, using a combination of in vitro over-expression and locked-nucleic-acid inhibition for candidate, lipoprotein-enriched, non-human sRNAs, we have discovered novel regulatory networks for critical genes in inflammation and lipid metabolism. This work demonstrates that lipoprotein transport of endogenous and exogenous sRNAs likely have complex roles in the progression and resolution of CVD and are a source of untapped potential for nucleic-acid based therapeutics.