Figure Legends
Figure 1. Biosynthesis of simple oxysterols. Enzymes are marked in blue. Non-enzymatic oxidation marked in red.
Figure 2. Biosynthesis of 24S,25-EC and other oxysterols from cholesterol precursors. Enzymes are marked in blue. Non-enzymatic oxidation marked in red.
Figure 3. Biosynthesis of cholestenoic acids. Enzymes are marked in blue.
Figure 4. Biosynthesis of SMO ligands from 7-DHC. Enzymes are marked in blue. Non-enzymatic oxidation marked in red. CYP27A1 is the likely catalyst for reactions with broken arrows.
Figure 5. LC-MS(MS3) analysis of neuro-sterols and neuro-oxysterols after EADSA treatment. (A) Reconstructed ion chromatograms (RICs) showing the most abundant neuro-sterols and neuro-oxysterols extracted from a 400 x 400 µm spot of striatum from a 10 µm thick sagittal section of mouse brain (Yutuc et al., 2020). MS3 spectra of (B) 24S-HC; and (C) 24S,25-EC from the same brain extract as the chromatograms shown in (A). Note in the EADSA method 24S,25-EC isomerises to 24-OC. (D) RICs showing how the pattern of neuro-oxysterols differ in pooled human plasma (upper panel) and CSF (lower panel) samples. MS3 spectra of different oxysterols found in plasma (E) 24S-HC; (F) 25-HC; (G) (25R)26-HC; and (H) 7α-HC. Note the CSF sample was hydrolysed to release oxysterols esterified to fatty acids but the plasma sample was not.