# Macrophage small RNA export to HDL protects against inflammation and atherosclerosis

> **NIH NIH P01** · VANDERBILT UNIVERSITY MEDICAL CENTER · 2021 · $389,250

## Abstract

Summary: Atherosclerosis is the underlying cause for ischemic cardiovascular disease (CVD), a pathology best
characterized as uncontrolled inflammation in response to continual lipid deposition in the arterial wall. Despite
the importance of inflammation in the progression of atherosclerosis, very few therapies are designed to target
this process due to a general lack of knowledge of atherogenic stimuli outside of bioactive lipids. Previously, we
have reported that lipoproteins, namely HDL and LDL, transport small non-coding RNAs (sRNA), and recently,
we discovered that lipoproteins are highly-enriched with sRNAs derived from bacterial and fungal species in the
microbiome and environment. Interestingly, these foreign, microbial sRNAs (msRNAs) are also highly-abundant
in macrophages within the atherosclerotic lesions and activate sRNA-sensing toll-like receptors (TLR)7/8 in
lesion macrophages. We posit that HDL accepts msRNAs from lesion macrophages, and thus, suppresses
TLR7/8 activation and down-stream pro-inflammatory gene expression. Supporting this model, macrophages
were found to readily export msRNAs to HDL and HDL treatments were found to block msRNA-induced
activation. In CVD, HDL acquire reactive dicarbonyl modifications which are associated with HDL dysfunction.
In preliminary studies, we found that reactive dicarbonyl modifications on HDL, e.g. isolevuglandins (IsoLG),
impair HDL-msRNA export. Moreover, we found that IsoLG-modified HDL had increased macrophage uptake
and retention and induced pro-inflammatory gene expression. Preliminary studies also found that treating mouse
models with reactive scavengers to block IsoLG modifications decreased atherosclerosis. Therefore, we aimed
to block msRNA activation of TLR7/8 using non-targeting locked-nucleic acids (ntLNA). Strikingly, we found that
ntLNA treatments significantly reduced atherosclerotic lesion area by 30% over 4 weeks in Apoe-/- mice on
western diet. In addition, single-cell RNA sequencing approaches demonstrated that ntLNA therapy repressed
pro-inflammatory gene expression in lesion macrophages and reduced the number of pro-inflammatory
macrophages in atherosclerotic lesions. Based on preliminary studies, we hypothesize HDL removes msRNA
from lesion macrophages through retro-endocytosis, a process that is inhibited by IsoLG modifications on HDL.
Furthermore, we posit that msRNA activation of endo-lysosome TLR7/8 in lesion macrophages can be readily
targeted with ntLNAs to reduce atherosclerosis. To test this hypothesis, we aim to I.) Determine the
mechanism(s) and consequences of macrophage msRNA export to HDL, the impact of HDL-msRNA export on
macrophage activation, and define the HDL-mediated reverse sRNA transport (RsRT) pathway in vivo, II.) Define
the impact of dicarbonyl modifications and msRNA cargo on HDL dysfunction in CVD, and III.) Target
macrophage msRNA receptors to inhibit atherosclerosis progression and promote regression. This project will
open entirely new fi...

## Key facts

- **NIH application ID:** 10089342
- **Project number:** 2P01HL116263-06A1
- **Recipient organization:** VANDERBILT UNIVERSITY MEDICAL CENTER
- **Principal Investigator:** Kasey C Vickers
- **Activity code:** P01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $389,250
- **Award type:** 2
- **Project period:** 2014-06-01 → 2025-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10089342

## Citation

> US National Institutes of Health, RePORTER application 10089342, Macrophage small RNA export to HDL protects against inflammation and atherosclerosis (2P01HL116263-06A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10089342. Licensed CC0.

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