Is brain dehydroepiandrosterone synthesis modulated by free radicals in mice?

Dehydroepiandrosterone (DHEA) is a neurosteroid synthesized de novo in the brain, in addition to the periphery, modulating some membrane, ion-gated channel neurotransmitter receptors. P450-17alpha-hydroxylase activity converting pregnenolone to DHEA, has not yet been identified in the brain of rodents. Studies in brain-derived primary cultures and cell lines, suggest a possible alternative pathway for DHEA synthesis involving oxygenated hydroxyperoxides. We investigated DHEA synthesis in the brains of castrated male mice before and after treatment with N-acetylcysteine amide (AD4) (a newly developed brain penetrating antioxidant). We found a significant increase in brain DHEA level 24 h after castration, which was totally blocked by AD4. This blockade of castration-induced increased brain DHEA synthesis, supports the assumption that this synthesis may also be affected by free radicals. This is the first in vivo study indicating the possible existence of an in-brain oxidative stress-related pathway leading to brain DHEA production.

Influence of 17beta-estradiol on the synthesis of reduced neurosteroids in the brain (in vivo) and in glioma cells (in vitro): possible relevance to mental disorders in women.

Brain neurosteroids modulate gamma-aminobutyric acid type A (GABAA) receptor activity, thereby playing a role in mood disorders. Alterations in 17beta-estradiol (E2) and progesterone (P) are also known to play a significant role in psychopathology in women. The aim of the present study was to evaluate the synthesis of dihydroprogesterone (DHP), tetrahydroprogesterone (THP), and the activity of 5alpha-reductase (5alphaR) which regulates the reduction of P to DHP on exposure to supraphysiological levels of E2 in vitro (C6 glioma cells) and in vivo (mouse brain). The results showed that supraphysiological levels of E2 induced a decrease in the accumulation of both neurosteroids, probably by decreasing the activity of 5alphaR. We hypothesize that the high levels of E2 in pregnancy attenuate the increase in the conversion of P to THP in the brain and that the ratio of E2/P modulates the sedative effect of THP. This process may be relevant to psychopathological disorders that are ascribed to drastic alterations in estrogen levels, such as premenstrual syndrome, pregnancy-related mental disorders, and postpartum "blues".