Abstract
Steroid sulfonation in the human brain has not been well characterized. The major sulfotransferase (SULT) isoforms that conjugate steroids in humans are SULT1E1, SULT2A1, and SULT2B1b. SULT2B1b catalyzes the sulfonation of 3β-hydroxysteroids, including neurosteroids dehydroepiandrosterone and pregnenolone, as well as cholesterol and several hydroxycholesterols. SULT2B1b mRNA and protein expression were detected in adult and fetal human brain sections, whereas neither mRNA, nor protein expression were identified for SULT1E1 or SULT2A1. Using immunohistochemical analysis, SULT2B1b expression was detected in neurons and oligodendrocytes in adult brain and in epithelial tissues in 28-week-old fetal brain. Sulfonation of cholesterol, oxysterols, and neurosteroids in the brain is apparently catalyzed by SULT2B1b since expression of neither SULT2A1 nor SULT1E1 was detected in human brain sections. SULT2B1b mRNA and protein were also detected in human U373-MG glioblastoma cells. Both mRNA and protein expression of liver X receptor (LXR)-β, but not LXR-α, were detected in U373-MG cells, and LXR-β activation resulted in a decrease in SULT2B1b protein expression. Since hydroxycholesterols are important physiological LXR activators, this suggests a role for regulation of sterol metabolism by LXR and SULT2B1b. Therefore, elucidating key enzymes in the metabolism of cholesterol and neurosteroids could help define the properties of steroid conjugation in the human brain.