High-density lipoprotein mimetic peptide 4F ameliorates APOE4-associated lipid dysfunction in primary and iPSC-derived astrocytes and cerebral organoids

APOE is the greatest genetic risk factor for late-onset Alzheimers disease (AD). In humans, APOE has three isoforms: APOE2 (E2), APOE3 (E3), and APOE4 (E4); E4 increases AD risk, while E3 is neutral and E2 decreases risk. In the brain, APOE is predominantly produced by astrocytes, where it binds lipids to form HDL-like particles, and plays a central role in lipid homeostasis, A{beta} clearance, and neuroimmune modulation. Its lipidation state is critical for function, with E4 being poorly lipidated compared to E2 and E3, contributing to the pathogenic effects of E4 while also offering a potential therapeutic target. We have previously demonstrated that the HDL-mimetic peptide 4F increases APOE secretion and lipidation in wild-type mouse astrocytes and counteracts the inhibitory effects of A{beta}42. Here, we assessed the ability of 4F to mitigate E4-associated dysfunction using primary astrocytes from humanized E3 and E4 knock-in mice and isogenic human iPSC-derived astrocytes and cerebral organoids. Results showed that 4F enhanced APOE secretion and lipidation in both cellular and organoid models in the absence or presence of aggregated A{beta}42. Compared to E3 astrocytes, E4 astrocytes were prone to A{beta}42-induced inhibition of APOE secretion and lipidation and increased accumulation of lipid droplets. 4F treatment ameliorated the inhibitory effects of A{beta}42 and reduced lipid droplet accumulation. These findings support the therapeutic potential of HDL-mimetic peptides for E4-associated dysfunction in AD.