LDL Cholesterol Modulates Astrocyte Metabolism, Lipid Handling, and Morphology: Evidence From In Vitro and In Vivo Models

TL;DR

This study shows that LDL cholesterol affects astrocyte function and structure in both lab and animal models, suggesting a link between high cholesterol and brain health.

Contribution

The study reveals novel insights into how LDL cholesterol alters astrocyte metabolism, gene expression, and morphology in both in vitro and in vivo settings.

Findings

LDL cholesterol increases lipid accumulation and alters gene expression in astrocytes.

LDL exposure reduces LDL receptor and cholesterol metabolism gene expression while increasing GFAP and NRF2.

In vivo, LDL receptor knockout mice show age-related astrocyte morphological changes in the hippocampus.

Abstract

Astrocytes are the primary antioxidant defense cells of the brain, protecting the central nervous system (CNS) through a controlled inflammatory response and acting as metabolic suppliers to neurons. These cells exhibit morphological, functional, and molecular changes in pathological conditions, such as neurodegenerative diseases. Previous studies have demonstrated a link between hypercholesterolemia, especially elevated levels of low‐density lipoprotein (LDL) cholesterol, and brain disorders, including hippocampal astrogliosis. In this context, this study aimed to investigate how LDL cholesterol modulates astrocyte biology. In vitro, high‐passage rat C6 astroglial cells were exposed to human LDL cholesterol (50 or 300 μg/mL) for 24 or 48 h. We evaluated lipid accumulation, cholesterol metabolism‐related gene expression, astrocyte‐related gene expression, reactive species production, antioxidant activity, redox‐related gene expression, fatty acid and glucose uptake, cell proliferation, and metabolic activity ‐ 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) reduction. LDL exposure increased intracellular lipid content and downregulated LDL receptor (LDLR), 3‐hydroxy‐3‐methylglutaryl‐coenzyme A reductase (HMGCR), and sterol regulatory element‐binding transcription factor 1 (SREBF1) gene expression. LDL exposure altered astrocytic marker expression, as evidenced by increased glial fibrillary acid protein (GFAP) messenger RNA (mRNA) levels at 24 h with 300 μg/mL LDL and at 48 h with 50 μg/mL LDL. LDL cholesterol decreased long‐chain fatty acids (LCFA) uptake and superoxide dismutase (SOD) activity at 24 h and increased cluster of differentiation 36 (CD36), also known as fatty acid translocase levels, at 48 h. Nuclear factor erythroid 2‐related factor 2 (NRF2) expression was significantly increased after 48 h of incubation with 300 μg/mL LDL. The MTT reduction assay did not indicate decreased cell viability; instead, it revealed increased metabolic activity after 24 h of incubation with 300 μg/mL LDL, with no changes observed in glucose uptake. In vivo, hippocampal astrocytes from young (3‐month‐old) and middle‐aged (14‐month‐old) LDL receptor knockout (LDLr−/−) and wild‐type C57BL/6 mice were analyzed by immunofluorescence and quantitative reverse transcription polymerase chain reaction (RT‐qPCR). In the hippocampal Cornu Ammonis 3 (CA3) region, 14‐month‐old LDLr−/− mice showed an increase in the number of processes compared to 3‐month‐old wild‐type C57BL/6 mice. Aging and genotype influenced astrocyte morphology and expression of genes such as S100 calcium‐binding protein B (S100B) and aquaporin‐4 (AQP4). Our findings demonstrate that LDL cholesterol induces morphological, metabolic, and molecular changes in astrocytes, both in vitro and in vivo, suggesting that astroglial cells are sensitive to lipid imbalance and may play a role in the brain consequences of hypercholesterolemia.

In vitro, low‐density lipoprotein cholesterol (LDL cholesterol) promotes the accumulation of lipid derivatives in astrocytes. Additionally, LDL cholesterol exposure causes a decrease in the expression of low‐density lipoprotein receptor (LDLr), 3‐hydroxy‐3‐methylglutaryl‐CoA reductase (HMGCR), and sterol regulatory element‐binding transcription factor 1 (SREBF1) genes. It also reduces superoxide dismutase (SOD) activity and long‐chain fatty acids (LCFA) uptake while increasing cluster of differentiation 36 (CD36) levels. Also, incubation with LDL cholesterol resulted in increased glial fibrillary acidic protein (GFAP) and nuclear factor erythroid 2‐related factor 2 (NRF2) expression. In vivo, an experimental model of familial hypercholesterolemia (FH) showed an increase in the number of astrocytic processes in middle age, especially in Cornu Ammonis area 3 (CA3) region and decreased messenger RNA (mRNA) levels of aquaporin‐4 (AQP4). Created in BioRender. De bem, L. (2025) https://BioRender.com/undefined.

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