Pregnenolone

About: Pregnenolone is a research topic. Over the lifetime, 3539 publications have been published within this topic receiving 126444 citations. The topic is also known as: (3b)-3-hydroxy-Pregn-5-en-20-one & 3-Hydroxypregn-5-en-20-one.

Pregnenolone rescues schizophrenia-like behavior in dopamine transporter knockout mice.

Abstract: Pregnenolone belongs to a class of endogenous neurosteroids in the central nervous system (CNS), which has been suggested to enhance cognitive functions through GABAA receptor signaling by its metabolites. It has been shown that the level of pregnenolone is altered in certain brain areas of schizophrenic patients, and clozapine enhances pregnenolone in the CNS in rats, suggesting that pregnenolone could be used to treat certain symptoms of schizophrenia. In addition, early phase proof-of-concept clinical trials have indicated that pregnenolone is effective in reducing the negative symptoms and cognitive deficits of schizophrenia patients. Here, we evaluate the actions of pregnenolone on a mouse model for schizophrenia, the dopamine transporter knockout mouse (DAT KO). DAT KO mice mirror certain symptoms evident in patients with schizophrenia, such as the psychomotor agitation, stereotypy, deficits of prepulse inhibition and cognitive impairments. Following acute treatment, pregnenolone was found to reduce the hyperlocomotion, stereotypic bouts and pre-pulse inhibition (PPI) deficits in DAT KO mice in a dose-dependent manner. At 60 mg/kg of pregnenolone, there were no significant differences in locomotor activities and stereotypy between wild-type and DAT KO mice. Similarly, acute treatment of 60 mg/kg of pregnenolone fully rescued PPI deficits of DAT KO mice. Following chronic treatment with pregnenolone at 60 mg/kg, the cognitive deficits of DAT KO mice were rescued in the paradigms of novel object recognition test and social transmission of food preference test. Pregnenolone thus holds promise as a therapeutic candidate in schizophrenia.

Deletion of the mouse P450c17 gene causes early embryonic lethality.

Abstract: Dehydroepiandrosterone (DHEA), a 19-carbon precursor of sex steroids, is abundantly produced in the human but not the mouse adrenal. However, mice produce DHEA and DHEA-sulfate (DHEAS) in the fetal brain. DHEA stimulates axonal growth from specific populations of mouse neocortical neurons in vitro, while DHEAS stimulates dendritic growth from those cells. The synthesis of DHEA and sex steroids, but not mouse glucocorticoids and mineralocorticoids, requires P450c17, which catalyzes both 17-hydroxylase and 17,20lyase activities. We hypothesized that P450c17-knockout mice would have disordered sex steroid synthesis and disordered brain DHEA production and thus provide phenotypic clues about the functions of DHEA in mouse brain development. We deleted the mouse P450c17 gene in 127/SvJ mice and obtained several lines of mice from two lines of targeted embryonic stem cells. Heterozygotes were phenotypically and reproductively normal, but in all mouse lines, P450c17 / zygotes died by embryonic day 7, prior to gastrulation. The cause of this early lethality is unknown, as there is no known function of fetal steroids at embryonic day 7. Immunocytochemistry identified P450c17 in embryonic endoderm in E7 wild-type and heterozygous embryos, but its function in these cells is unknown. Enzyme assays of wild-type embryos showed a rapid rise in 17-hydroxylase activity between E6 and E7 and the presence of C17,20-lyase activity at E7. Treatment of pregnant females with subcutaneous pellets releasing DHEA or 17-OH pregnenolone at a constant rate failed to rescue P450c17 / fetuses. Treatment of normal pregnant females with pellets releasing pregnenolone or progesterone did not cause fetal demise. These data suggest that steroid products of P450c17 have heretofore-unknown essential functions in early embryonic mouse development. The synthesis of steroid hormones in the adrenals, gonads, placenta, and brain requires the expression of several steroidogenic enzymes. In all tissues, steroidogenesis is initiated by conversion of cholesterol to pregnenolone by the mitochondrial cholesterol side chain cleavage enzyme, P450scc. Thereafter, the specific steroid that is synthesized by a particular tissue depends upon the differential expression of additional steroidogenic enzymes. The conversion of pregnenolone and progesterone to their 17-hydroxylated products and then to either dehydroepiandrosterone (DHEA) or androstenedione, respectively, is mediated by a single microsomal enzyme, P450c17 (33, 34, 48), encoded by a single gene (22, 39). The pattern of P450c17 expression in steroidogenic tissues is species specific: it is expressed in the human adrenal and gonad but not placenta (9, 11, 15, 44), and it is expressed in the rodent gonad and placenta but not adrenal (19, 23, 25). P450c17 is also expressed in the fetal mouse brain beginning at embryonic day 9.5 (E9.5) (12). At this time, P450c17 is found in cells migrating from the neural crest, and subsequently, P450c17 is found in many cells derived from the neural crest. P450c17 is also expressed in the neocortical subplate, a region that receives thalamic projections, produces signals for cortical projections, and may produce signals for efferent thalamic projections from the cortex (32, 41). We hypothesized that DHEA, a steroid product of P450c17, may be an endogenous signal in the subplate to target axons coming from this region to specific sites in the developing cortex and showed that DHEA increased axonal outgrowth while DHEA-sulfate (DHEAS) increased dendritic growth (13). DHEA, but not DHEAS, induced other morphological indices of synaptic contacts, increased mRNAs for Tau-1 and type 1 and 2 dopamine receptors (14), mediated increases in intracellular calcium via N-methyl-D-aspartic acid receptors (13), protected hippocampal neurons from glutamate toxicity (27), and stimulated neurogenesis in the hippocampus (26). Thus, DHEA may serve as an endogenous neurotrophic agent. However, all these studies have been performed with cultured neuronal cells derived from specific regions of the nervous system at particular times in development. Thus, we sought to determine the function of DHEA and DHEAS in vivo during the development of the nervous system by deleting the gene encoding P450c17 in genetargeted mice.

A Pregnenolone Radioimmunoassay Utilizing a New Fractionation Technique for Sheep Antiserum

Abstract: Antibodies against pregnenolone were generated in a ewe immunized with a pregnenolone 3-bovine serum albumin conjugate. Upon fractionation of the resultant antiserum using QAE-Sephadex chromatography, a 7-8S highly negatively-charged antibody fraction was isolated possessing substantially increased sensitivity towards pregnenolone relative to the crude antiserum. On the basis of this novel fractionation procedure it was possible to devise a radioimmunoassay sensitive to 20 pg of pregnenolone. Normal serum concentrations in ng/ml obtained with this assay were: men (1.05 ± 0.19 se); women, follicular phase, (0.96 ± 0.16 se); women, luteal phase, (1.23 ± .25 se). These mean values were not significantly different from each other. It is speculated that our purified antibody preparation may represent a previously unidentified subclass of IgG in the sheep, and that the chromatographic method described may be generally useful for isolating highly sensitive antibodies against steroids or other hapten-BSA...