Apolipoprotein (apo) E is the major cholesterol carrier in the central nervous system (CNS); however, the clinical relevance of its cysteine-thiol redox status in cerebrospinal fluid (CSF) remains unc Show more
Apolipoprotein (apo) E is the major cholesterol carrier in the central nervous system (CNS); however, the clinical relevance of its cysteine-thiol redox status in cerebrospinal fluid (CSF) remains unclear. We investigated whether CSF apoE redox indices (redox-IDX-apoE) reflect cholesterol transport efficiency and disease-specific pathologies. We quantified reduced (red), reversibly oxidized (roxi), and irreversibly oxidized (oxi) apoE in CSF and serum using a maleimide-based band-shift assay. We analyzed relationships between redox-IDX-apoE, CSF cholesterol (TC) level, and the TC/apoE ratio (inverse transport efficiency) in patients with apoE3/E3 and identified transport determinants using isometric log-ratio (ILR) regression. Significant but only moderate correlations between CSF and serum indices suggested distinct redox behavior in the two compartments. ApoE3/E4 carriers exhibited higher oxi-apoE, reflecting reduced buffering capacity. In apoE3/E3 CSF, aging increased roxi/total and decreased red/roxi, suggesting a shift toward oxidized forms. CSF TC level positively correlated with roxi-related indices. Conversely, the TC/apoE ratio negatively correlated with red/roxi, indicating that red-apoE supports higher efficiency. ILR analysis confirmed that maintaining the reduced monomeric state, rather than the reversibly oxidized form, was independently associated with improved transport efficiency. Diagnostic groups exhibited distinct signatures: neurodegenerative disorders showed elevated irreversible oxidation, whereas neuroimmunological and infectious conditions exhibited profiles suggestive of reversible and acute oxidation, respectively. The CSF apoE redox status links local redox balance to cholesterol handling and reflects CNS pathophysiology. Maintaining reduced cysteine-thiol appears important for functional capacity, whereas a shift toward oxidation reflects a trade-off between buffering ability and transport efficiency. These indices may serve as potential biomarkers. Show less
ABCA1, a member of the ATP-binding cassette transporter family, regulates high-density lipoprotein (HDL) metabolism and cholesterol transport. Its expression is upregulated mainly by the activation of Show more
ABCA1, a member of the ATP-binding cassette transporter family, regulates high-density lipoprotein (HDL) metabolism and cholesterol transport. Its expression is upregulated mainly by the activation of the liver X receptor (LXR). Since ABCA1 plays a pivotal role in cholesterol and HDL metabolism, identification of a compound capable of increasing its expression may be beneficial for the prevention and therapy of atherosclerosis. Firefly luciferase reporter assays were developed for human ABCA1 promoters and LXR enhancers, and an in-house phytochemical library was screened. It was found that a citrus flavonoid, hesperetin (1), increased ABCA1 promoter and LXR enhancer activities in THP-1 macrophages. It was also found that this flavonoid promoted PPAR-enhancing activity. In accordance with these findings, 1 increased mRNA and protein expression of ABCA1 and consequently upregulated ApoA-I-mediated cholesterol efflux. These results provide evidence that 1 promotes ApoA-I-mediated cholesterol efflux from macrophages by increasing ABCA1 expression through the activation of LXRα and PPARγ. Show less