# APOE3 astrocytes can rescue lipid abnormalities and dystrophic neurites of APOE4 human neurons

## TL;DR

APOE3 astrocytes can reverse lipid-related damage in neurons linked to Alzheimer's disease, unlike APOE4 astrocytes.

## Contribution

This study demonstrates that APOE3 astrocytes rescue lipid abnormalities and dystrophic neurites in APOE4 neurons.

## Key findings

- APOE3 astrocytes prevent cholesterol- and lipid-induced neurite damage in APOE4 neurons.
- APOE3 astrocytes produce larger, more lipidated high-density lipoprotein-like particles compared to APOE4 astrocytes.
- APOE3 astrocytes enhance lipid homeostasis and rescue neurite structural abnormalities relevant to Alzheimer's disease.

## Abstract

Lipid abnormalities are emerging as key pathogenic mechanisms in neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Lewy body dementia. Astrocytes in the brain provide apolipoprotein E (APOE) proteins and influence neuronal metabolism and health. Using live-cell imaging and objective neurite imaging techniques, we induced cellular lipid load (cholesterol and triglycerides) by inhibiting the lysosomal cholesterol transport protein NPC1 in human neuron−astrocyte cocultures and examined the effects of CRISPR-edited APOE3 and APOE4 human astrocytes on the rescue of dystrophic neurites, where axons and dendrites of nerve cells become disfigured. APOE3, but not APOE4 or APOE knockout, astrocytes prevented cholesterol- and lipid-induced neurite damage in APOE4 neurons. In the media of APOE3 neuron−astrocyte cocultures, high-density lipoprotein−like particles were larger and presumably more lipidated than those in equivalent APOE4 cocultures. This discovery highlights that living APOE3 astrocytes control key biological mechanisms by physiologically enhancing lipid cellular homeostasis and rescuing lipid-induced neurite structural abnormalities relevant to Alzheimer's disease and neurodegenerative diseases.