title: Intracellular oxidation of allopregnanolone by human brain type 10 17beta-hydroxysteroid dehydrogenase.
abstract: Allopregnanolone is a positive allosteric modulator of GABAA receptors, generated by the reduction of 5alpha-dihydroprogesterone (5alpha-DHP) in astrocytes. This neuroactive steroid can be inactivated by its 3alpha-oxidation to yield 5alpha-DHP. It was found that 5alpha-DHP levels in HEK293 cells expressing type 10 17beta-hydroxysteroid dehydrogenase (17beta-HSD10), but not its catalytic inactive mutant, increased significantly as allopregnanolone was added to culture media. The results demonstrate that mitochondrial 17beta-HSD10 effectively catalyzes the intracellular oxidation of allopregnanolone. Moreover, brain astrocytes contain a moderate level of 17beta-HSD10, which is elevated in activated astrocytes of brains with Alzheimer type pathology, including sporadic Alzheimer's disease (AD) and Down's syndrome with AD. The distribution of 17beta-HSD10 was found not to parallel that of 3alpha-HSD3. Cerebral cortex has the lowest level of 17beta-HSD10; whereas the hippocampus, hypothalamus, and amygdala possess relatively higher levels of this enzyme. The catalysis of 17beta-HSD10 appears to be essential for maintaining normal functions of GABAergic neurons. The elevated level of 17beta-HSD10 in activated astrocytes is a new feature found in brains of people with AD, and it may have important impact on AD pathogenesis.
authors.affiliation: Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY 10314, USA.
authors.forename: Xue-Ying
authors.initials: XY
authors.lastname: He
authors.forename: Jerzy
authors.initials: J
authors.lastname: Wegiel
authors.forename: Song-Yu
authors.initials: SY
authors.lastname: Yang
mesh_terms: D015094:3-Hydroxyacyl CoA Dehydrogenases / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000201:enzymology / Q000473:pathology; D001921:Brain / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D002460:Cell Line; D005260:Female; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010084:Oxidation-Reduction; D011280:Pregnanolone / Q000378:metabolism*
chemical_list: D011280:Pregnanolone; D015094:3-Hydroxyacyl CoA Dehydrogenases; C108634:HSD17B10 protein, human