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Steroid hormones mostly act via nuclear receptors. Dehydroepiandrosterone (DHEA), pregnenolone (PREG) and their sulphate(s), classically known only as hormonal precursors, are also neurosteroidal efficacious signals, modulating neurotransmitter receptor function at the membrane level. An additional unforeseen mechanism of steroid action is reported here: PREG binds to neural microtubule-associated protein MAP2 and increases both the rate and extent of tubulin polymerization studied in vitro with purified tubulin and MAP2, forming microtubules of normal electron microscopic appearance. Progesterone and PREGS also bind to MAP2, but counteract PREG activity. In cultured neurons, PREG specifically increased immunostaining by an antiMAP2 monoclonal antibody and its extension into neurites. This novel mechanism may play a role in regulating microtubule formation and dynamics, which are altered in brain ageing and diseases.

The effects of cyclosporin A (CsA), FK506 and rapamycin (Rapa) on the intracellular localization of a mutated rabbit progesterone receptor (PR) which lacks the main constitutive nuclear localization signal (NLS) (delta 638-642) and is cytoplasmic in the absence of progesterone (Prog), were assayed by indirect immunofluorescence in Lcl3 cells, a mouse L-cell line stably expressing this mutant. CsA alone, at 5-10 microM concentrations, induced almost complete nuclear transfer of the PR-mutant within 18 h. In contrast, FK506 and Rapa at the same concentrations had no effect. This nuclear transfer induced by CsA was concentration and time dependent and was independent of protein synthesis. It was not a potentiation of hormone action since it took place in the absence of hormone, including in serum-free culture conditions. The implications of this specific effect of CsA are discussed.

27-hydroxycholesterol is shown to be 7 alpha-hydroxylated by microsomal preparations of rat brain. The apparent Km was about 2 microM and Vmax about 15 pmol/min x mg protein. The reaction might modulate biological functions of 27-hydroxycholesterol, such as its suppressive effect on the activity of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, and supports the possibility of bile acid formation in the brain.

We have recently shown that the N-terminal ATPase fragment of hsp70 (1-375, composed of domains I and II) as well as the subsequent domain III (376-520) may share three-dimensional similarities with hsp60. In this study, we propose that domain III, common to the hsp60s and hsp70s is also found in the hsp90s and adopts a beta-alpha-beta Rossmann-folded structure which is encountered in the NAD-binding domain of dehydrogenases. Consequently, with the help of the domain IV (in hsp70s and hsp90s) or of hsp10/GroES (in hsp60s) and possibly that of auxilliary partners, the hsp molecules could act as "unfoldases" or "reset systems" by disrupting secondary structures through redox reactions on the main polypeptidic chain with which they interact. The models built on this hypothesis may open up a new way for understanding the chaperone functions within the folding/unfolding processes.

The growth of mouse L-929 fibroblasts in culture is inhibited by dexamethasone, a synthetic glucocorticosteroid, and this effect is itself suppressed by the antiglucocorticosteroid RU486 (mifepristone). Neither RU486 nor the immunosuppressant FK506 alone influence L-929 growth, and FK506 does not modify dexamethasone action. However, FK506 suppresses the antiglucocorticosteroid activity of RU486. The implication of the "anti-antagonist" activity of FK506 in its immunosuppressant properties has still to be explained. The role of the recently cloned, FK506-binding, p59 immunophilin, which binds to the heat shock protein hsp90 which itself interacts with the glucocorticosteroid receptor, is discussed.

p59/HBI, a Heat shock protein (hsp90)-Binding-Immunophilin of approximately 59 kDa, was originally detected in the heterooligomeric, non-DNA binding form of numerous mammalian steroid hormone receptors. P59/HBI belongs to the FKBP family since it binds the immunosuppressants FK506 and Rapamycin. Using immobilized FK506, we purified [3H]Org 2058-progesterone receptor (PR)-hsp90-complexes from chick oviduct cytosol in a species migrating at 9S in density gradient. This led to suppose that a protein present in these complexes is a FK506 binding protein. Following incubation of this FK506-affinity purified 9S-PR with BF4, a specific anti-chick hsp90 monoclonal antibody, a shift of the [3H]Org 2058-PR complexes from 9S to 11S has been observed, indicating the presence of hsp90, hsp70 also is included in the 9S-PR complexes as demonstrated by Western blotting and density gradient experiments. Two lines of evidence support the notion that an immunophilin of 50 kDa also associates to heterooligomeric 9S-PR complexes. Firstly, a shift at 11S of the FK506 eluted 9S-PR occurs in sucrose gradient after incubation with 419, a new polyclonal antibody raised against a peptide corresponding to the Hinge I region [Callebaut I., Renoir J. M., Lebeau M. C., Massol N., Burny A., Baulieu E. E., Mornon J. P. (1992) Proc. Natl. Acad. Sci. USA 89, 6270-6274] of the rabbit p59/HBI (amino acids Phe135 to Gly149). Secondly, in Western blotting experiments, both 419 and another anti-FKBP antibody, raised against purified Streptomyces Crysomallus FKBP12 [Pahl A. and Keller U. (1992) J. Bacteriol., 3, 325-333], allow detection of the same 50 kDa protein in the affinity purified PR.(ABSTRACT TRUNCATED AT 250 WORDS)

Pregnenolone (PREG) and corticosterone were measured in sciatic nerves and plasma of adult male rats by radioimmunoassays. Concentrations of PREG were higher in nerves than in plasma, whereas those of corticosterone were lower. In contrast to corticosterone, PREG was not reduced by castration and adrenalectomy, strongly suggesting a local synthesis of this steroid independent of glandular sources. In fact, Schwann cells in culture produced PREG from 25-hydroxy-cholesterol. They also converted PREG and dehydroepiandrosterone to the respective 7 alpha-hydroxylated metabolites and to 5-androstene-3 beta,17 beta-diol. The metabolism of steroids was increased when Schwann cells were grown in the presence of insulin and forskolin. These findings may have important implications for understanding the regeneration of peripheral nerves.

In the absence of hormonal ligand, inactive, heterooligomeric, 8-10S steroid receptor complexes include a p59 protein (apparent M(r) approximately 59 kDa) bound to th heat shock protein hsp90 (apparent M(r) approximately 90 kDa), which itself binds to the ligand binding domain LBD of the receptor molecule, p59 is thus an hsp binding immunophilin HBI, which, through its interaction with a chaperone, may intervene in several cellular functions. We report that, in cell-free experiments at 0 degrees C, FK506 and rapamycin do not release p59 nor hsp90 from the 9.5S rabbit uterus progesterone receptor, suggesting that the binding of p59 to hsp90 does not interfere with the rotamase site of HBI. There is no "transformation/activation" of the receptor, but an up to 2 fold increase in progesterone agonist and antagonist binding to the receptor is observed. It is suggested that a functional interaction between HBI and receptor activity may be mediated by hsp90.

Female mice of an inbred Swiss strain were injected subcutaneously (s.c.) with either testosterone propionate or oil-vehicle on the day of birth. Once adult (8 week-old), they were spayed, and then treated either with dehydroepiandrosterone (80 micrograms/day s.c. for 15 days) or with solvent. The decrease of biting attacks by dehydroepiandrosterone was definitely more prominent in neonatally imprinted females than in controls.

The most used medical method for early pregnancy interruption associates the antiprogestin RU486 (Mifepristone) and an intramuscularly injected prostaglandin (Sulprostone) (Silvestre et al., New Engl. J. Med., 322, 1990, pp. 645-648). Misoprostol, an orally active PGE1 synthetic derivative, showed the same efficacy as Sulprostone in a trial including 100 patients. The medical characteristics and potential of the new method are briefly discussed.

Purified "B" protein (MW approximately 110 kDa) that binds progesterone, and more than 90% of the activated receptor labelled with tritiated hormone in the oviduct cytosol of chicks pretreated with estrogen have the same chromatography behavior on DNA-cellulose. Conversely, neither the nonactivated "8S" receptor, that includes the heat-shock protein hsp90, nor the later bind to DNA. With other biochemical and immunological arguments, these results indicate that the hormone binding B unit of the progesterone receptor binds DNA as do all steroid hormone receptors.

The induction of meiosis reinitiation by steroid hormones (progesterone and testosterone) in Xenopus laevis oocytes was studied in vitro in presence of inhibitors of phosphatase activity such as beta-glycerophosphate, considered as a competitive inhibitor, and the two ions, Zn++ and MoO--4. Kinetics of the germinal vesicle breakdown indicating the reinitiation of meiosis, have shown that while these phosphatase inhibitors were not active by themselves under the present experimental conditions, they enhanced the process elicited by progesterone or testosterone.

Ten male and eleven female Chimpanzees from three to nine years of age were studied to establish possible correlations between behavioral changes and hormonal changes peculiar to adrenarche and the pre-puberty period. Most of the thirteen behaviors studied varied with age, body weight and hormones. For the males, the correlations were significant statistically for age, weight and plasma concentration of testosterone and of FSH. The correlations for the females were more often not significant statistically. In ten out of the thirteen behaviors for the female, however, the correlations with the sulfate of plasma dehydroepiandrosterone were in the same direction as those observed for the males with testosterone.

The antiprogesterone steroid RU 486 (17 beta-hydroxy-11 beta-(4-dimethylaminophenyl l)-17 alpha-(prop-1-ynyl) estra-4,9-dien-3-one), orally administered once (600 mg), is an efficient contragestive agent in approximately 80% of pregnant women who have been amenorrheic for up to 41 days. Later on, its use is not recommended since after 41 day of amenorrhea there is an increase in the number of incomplete expulsions. A vaginal suppository of 1 mg Gemeprost, a synthetic PG-E1 analogue, has been prescribed 36-48 hrs. after the administration of RU 486. Such a suppository cannot provoke the interruption of the pregnancy by itself. In 106 women seeking for the interruption of pregnancy, and who were amenorrheic for 49 days or less, RU 486 plus prostaglandin association led to the interruption of pregnancy in all cases, and no further instrumental intervention was required. This preliminary report suggests that this method is an efficient alternative to conventional techniques available presently.

Primary cultures of glial cells from newborn rat forebrain were tested after 3 to 4 weeks. Oligodendrocytes and astrocytes were characterized by immunofluorescence with monoclonal antibodies to galactocerebroside and glial fibrillary acidic protein, respectively. The cytoplasm of oligodendrocytes was specifically and intensely immunostained with monospecific polyclonal antibodies to the cytochrome P-450scc involved in the synthesis of pregnenolone from cholesterol. This observation brings additional support to the concept of "neurosteroids".

In North American women at low or high risk of developing breast cancer, as assessed by an epidemiologic questionnaire, the plasma concentration of dehydroepiandrosterone sulfate shows a statistically significant circannual variation. In adolescents, in all seasons, circulating dehydroepiandrosterone sulfate is a classifier of the risk of developing breast cancer, a relatively low concentration of this hormone being associated with an increased risk.

Corticosterone (B), pregnenolone (P) and dehydroepiandrosterone (D) undergo circadian variations in the rat plasma and brain. When the data are interpreted by the Cosinor method, the acrophases of P in brain and of D in plasma significantly precede the acrophase of B. The asynchrony of delta 5-3 beta-hydroxysteroid and glucocorticosteroid rhythms brings an additional argument in favor of separate regulatory mechanisms.

In adrenalectomized and orchidectomized rats, the removal of the steroidogenic endocrine glands is associated with a near-disappearance of corticosterone (B) from plasma and brain; circadian variations of B and of plasma dehydroepiandrosterone (D), characteristic of the intact rat, are no more detected. By contrast, analyses of brain D measurements by the cosinor method demonstrate a persisting circadian rhythm of large amplitude.