# Cholesterol homeostasis in pathogenesis of DR

> **NIH NIH R01** · UNIVERSITY OF ALABAMA AT BIRMINGHAM · 2020 · $413,020

## Abstract

Disruptions in cholesterol homeostasis and metabolism can lead to high cholesterol
concentrations in diseased tissue and the formation of cholesterol crystals (CC). CC are often
overlooked in traditional histo/immunohistochemistry as the ethanol, used for tissue processing,
can dissolve them. This masks CC presence and potential involvement in pathogenic
mechanisms. Using Scanning Electron Microscopy (SEM) of tissues prepared without an
ethanol dehydration step, we identified the presence of CC: i) in “lipid pools” between retinal
pigment epithelium (RPE) and photoreceptors (PR); ii) circulating freely in diabetic murine
blood; and iii) within circulating monocytes of diabetic human subjects. Since CC are very stable
physiologically and are not easily amenable to dissolving in vivo, they become a source of
chronic inflammation. CC are recognized by the innate immune system as foreign bodies
because of their shape, firmness, and inability to be dissolved. Moreover, CC also induce
inflammation via the NLRP3 inflammasome activation. These novel preliminary and published
studies have led us to propose the following hypothesis (see schematic in Fig.1): Diabetes-
induced disruption of i) systemic cholesterol homeostasis, ii) blood retinal barrier function; and
iii) SIRT1, LXR and CYP46A1 expression alters retinal cholesterol homeostasis leading to
CC formation within key locations: RPE, PR, monocytes/macrophages, and in the circulation
affecting the endothelium. This CC formation results in intra- and extracellular complement
activation and priming of the NLRP3 inflammasome for its activation and release of highly
damaging pro-inflammatory cytokines, promoting development of DR. To test this hypothesis,
we propose the following Specific Aims: Aim1: To determine the temporal changes in retinal
cholesterol accumulation that lead to CC formation. Aim 2: To test the hypothesis that diabetes-
induced cholesterol accumulation and CC formation in the retina and in
monocytes/macrophages induces activation of intracellular and extracellular complement to
trigger the NLRP3 inflammasome and IL-1β production. Aim 3: To test the hypothesis that LXR
activation and direct sequestration of cholesterol by alpha-cyclodextrin can inhibit CC-induced
complosome and NLRP3 inflammasome formation in the diabetic retina and in
monocytes/macrophages cells, thus preventing chronic inflammation and development of DR.
Impact: The successful completion of this project will result in identifying an entirely novel
pathway in which CC-induced complosome and NLRP3 inflammasome formation that can be
pharmacologically targeted to prevent DR.

## Key facts

- **NIH application ID:** 10072467
- **Project number:** 2R01EY025383-05A1
- **Recipient organization:** UNIVERSITY OF ALABAMA AT BIRMINGHAM
- **Principal Investigator:** Julia V Busik
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $413,020
- **Award type:** 2
- **Project period:** 2015-09-01 → 2025-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10072467

## Citation

> US National Institutes of Health, RePORTER application 10072467, Cholesterol homeostasis in pathogenesis of DR (2R01EY025383-05A1). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10072467. Licensed CC0.

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