Differential Effects of Carotenoids on Immune Cellular Cholesterol Efflux and Autophagy

Objectives: The study aimed to investigate the impact of lutein, zeaxanthin, and astaxanthin in combination on immune cellular processes. Methods: J774A.1 mouse macrophage and human microglial clone 3 (HMC3) were cultured and treated separately with lutein, zeaxanthin, astaxanthin, or the combination of the three overnight. Following treatment, cellular cholesterol efflux and autophagy were assessed. Cellular cholesterol efflux was measured using apolipoprotein-B (ApoB)-depleted plasma obtained with polyethylene glycol precipitation as a cholesterol acceptor. Autophagic vesicles resulting from carotenoids treatment were quantified using a CYTO-ID autophagy detection kit. Treatments were compared to a vehicle control consisting of 0.5% dimethyl sulfoxide in water. Results: Zeaxanthin and the combination of lutein, zeaxanthin, and astaxanthin significantly increased both J774A.1 and HMC3 cholesterol efflux to ApoB-depleted plasma (22.9% – 33.1%, P < 0.05 for all). Lutein and astaxanthin significantly increased HMC3 autophagy by 21.8% and 4.8%, respectively, compared to control (P < 0.05 for both). Conversely, lutein (-28.8%), zeaxanthin (-27.8%), astaxanthin (-31.5%), and the combination of the three (-37.8%) significantly decreased J774A.1 autophagy (P < 0.001 for all). Conclusions: The effects of carotenoids on immune cellular cholesterol efflux and autophagy highlight zeaxanthin's potential in promoting cholesterol homeostasis and modulating cellular autophagy. These findings underscore the importance of further mechanistic studies in carotenoid research, particularly regarding the complexities observed in cellular autophagy pathways. Funding Sources: The project described was supported by the National Institute on Aging of the National Institute of Health (R01AG062240).