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The non-benzodiazepine anxiolytic drug etifoxine causes a rapid, receptor-independent stimulation of neurosteroid biosynthesis.

do Rego JL, Vaudry D, Vaudry H - PLoS ONE (2015)

Bottom Line: In the present study, we have thus investigated the effect and the mechanism of action of etifoxine on neurosteroid biosynthesis using the frog hypothalamus as an experimental model.In addition, the stimulatory effects of etifoxine and the triakontatetraneuropeptide TTN, a TSPO agonist, were additive, indicating that these two compounds act through distinct mechanisms.In conclusion, the present study demonstrates that etifoxine stimulates neurosteroid production through a membrane receptor-independent mechanism.

View Article: PubMed Central - PubMed

Affiliation: Institute for Research and Innovation in Biomedicine (IRIB), University of Rouen, Mont-Saint-Aignan, France; Regional Platform for Cell Imaging (PRIMACEN), International Associated Laboratory Samuel de Champlain, University of Rouen, Mont-Saint-Aignan, France.

ABSTRACT
Neurosteroids can modulate the activity of the GABAA receptors, and thus affect anxiety-like behaviors. The non-benzodiazepine anxiolytic compound etifoxine has been shown to increase neurosteroid concentrations in brain tissue but the mode of action of etifoxine on neurosteroid formation has not yet been elucidated. In the present study, we have thus investigated the effect and the mechanism of action of etifoxine on neurosteroid biosynthesis using the frog hypothalamus as an experimental model. Exposure of frog hypothalamic explants to graded concentrations of etifoxine produced a dose-dependent increase in the biosynthesis of 17-hydroxypregnenolone, dehydroepiandrosterone, progesterone and tetrahydroprogesterone, associated with a decrease in the production of dihydroprogesterone. Time-course experiments revealed that a 15-min incubation of hypothalamic explants with etifoxine was sufficient to induce a robust increase in neurosteroid synthesis, suggesting that etifoxine activates steroidogenic enzymes at a post-translational level. Etifoxine-evoked neurosteroid biosynthesis was not affected by the central-type benzodiazepine (CBR) receptor antagonist flumazenil, the translocator protein (TSPO) antagonist PK11195 or the GABAA receptor antagonist bicuculline. In addition, the stimulatory effects of etifoxine and the triakontatetraneuropeptide TTN, a TSPO agonist, were additive, indicating that these two compounds act through distinct mechanisms. Etifoxine also induced a rapid stimulation of neurosteroid biosynthesis from frog hypothalamus homogenates, a preparation in which membrane receptor signalling is disrupted. In conclusion, the present study demonstrates that etifoxine stimulates neurosteroid production through a membrane receptor-independent mechanism.

No MeSH data available.


Related in: MedlinePlus

Time-course of the conversion of tritiated pregnenolone ([3H]Δ5P) into radioactive 17-hydroxypregnenolone (17OH-Δ5P), dehydroepiandrosterone (DHEA), progesterone (P), dihydroprogesterone (DHP) and tetrahydroprogesterone (THP) by frog hypothalamic homogenates in the absence (○) or presence of 10-6 M etifoxine (●).The values were calculated from the areas under the peaks in chromatograms similar to those presented in Fig. 6. Results are expressed as percentages of the amount of each steroid formed compared to the total amount of radiolabeled compounds resolved by HPLC analysis including [3H]Δ5P. Values are the mean (± SEM) of four independent experiments. *p<0.05; **p<0.01; ***p<0.001 compared to respective control values; NS, not statistically different (one-way ANOVA followed by a post hoc Dunnett’s test).
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pone.0120473.g009: Time-course of the conversion of tritiated pregnenolone ([3H]Δ5P) into radioactive 17-hydroxypregnenolone (17OH-Δ5P), dehydroepiandrosterone (DHEA), progesterone (P), dihydroprogesterone (DHP) and tetrahydroprogesterone (THP) by frog hypothalamic homogenates in the absence (○) or presence of 10-6 M etifoxine (●).The values were calculated from the areas under the peaks in chromatograms similar to those presented in Fig. 6. Results are expressed as percentages of the amount of each steroid formed compared to the total amount of radiolabeled compounds resolved by HPLC analysis including [3H]Δ5P. Values are the mean (± SEM) of four independent experiments. *p<0.05; **p<0.01; ***p<0.001 compared to respective control values; NS, not statistically different (one-way ANOVA followed by a post hoc Dunnett’s test).

Mentions: Kinetic experiments showed that etifoxine (10-6 M) induced within 15 min a significant increase of the biosynthesis of 17OH-Δ5P, DHEA, P and THP by hypothalamic homogenates (Fig. 9). While etifoxine provoked a sustained stimulation of 17OH-Δ5P, DHEA, P and THP, the effect on DHP was transient and gradually declined (Fig. 9). After 3h exposure to etifoxine, [3H]DHP was no longer present in the incubation medium (Fig. 9).


The non-benzodiazepine anxiolytic drug etifoxine causes a rapid, receptor-independent stimulation of neurosteroid biosynthesis.

do Rego JL, Vaudry D, Vaudry H - PLoS ONE (2015)

Time-course of the conversion of tritiated pregnenolone ([3H]Δ5P) into radioactive 17-hydroxypregnenolone (17OH-Δ5P), dehydroepiandrosterone (DHEA), progesterone (P), dihydroprogesterone (DHP) and tetrahydroprogesterone (THP) by frog hypothalamic homogenates in the absence (○) or presence of 10-6 M etifoxine (●).The values were calculated from the areas under the peaks in chromatograms similar to those presented in Fig. 6. Results are expressed as percentages of the amount of each steroid formed compared to the total amount of radiolabeled compounds resolved by HPLC analysis including [3H]Δ5P. Values are the mean (± SEM) of four independent experiments. *p<0.05; **p<0.01; ***p<0.001 compared to respective control values; NS, not statistically different (one-way ANOVA followed by a post hoc Dunnett’s test).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4364751&req=5

pone.0120473.g009: Time-course of the conversion of tritiated pregnenolone ([3H]Δ5P) into radioactive 17-hydroxypregnenolone (17OH-Δ5P), dehydroepiandrosterone (DHEA), progesterone (P), dihydroprogesterone (DHP) and tetrahydroprogesterone (THP) by frog hypothalamic homogenates in the absence (○) or presence of 10-6 M etifoxine (●).The values were calculated from the areas under the peaks in chromatograms similar to those presented in Fig. 6. Results are expressed as percentages of the amount of each steroid formed compared to the total amount of radiolabeled compounds resolved by HPLC analysis including [3H]Δ5P. Values are the mean (± SEM) of four independent experiments. *p<0.05; **p<0.01; ***p<0.001 compared to respective control values; NS, not statistically different (one-way ANOVA followed by a post hoc Dunnett’s test).
Mentions: Kinetic experiments showed that etifoxine (10-6 M) induced within 15 min a significant increase of the biosynthesis of 17OH-Δ5P, DHEA, P and THP by hypothalamic homogenates (Fig. 9). While etifoxine provoked a sustained stimulation of 17OH-Δ5P, DHEA, P and THP, the effect on DHP was transient and gradually declined (Fig. 9). After 3h exposure to etifoxine, [3H]DHP was no longer present in the incubation medium (Fig. 9).

Bottom Line: In the present study, we have thus investigated the effect and the mechanism of action of etifoxine on neurosteroid biosynthesis using the frog hypothalamus as an experimental model.In addition, the stimulatory effects of etifoxine and the triakontatetraneuropeptide TTN, a TSPO agonist, were additive, indicating that these two compounds act through distinct mechanisms.In conclusion, the present study demonstrates that etifoxine stimulates neurosteroid production through a membrane receptor-independent mechanism.

View Article: PubMed Central - PubMed

Affiliation: Institute for Research and Innovation in Biomedicine (IRIB), University of Rouen, Mont-Saint-Aignan, France; Regional Platform for Cell Imaging (PRIMACEN), International Associated Laboratory Samuel de Champlain, University of Rouen, Mont-Saint-Aignan, France.

ABSTRACT
Neurosteroids can modulate the activity of the GABAA receptors, and thus affect anxiety-like behaviors. The non-benzodiazepine anxiolytic compound etifoxine has been shown to increase neurosteroid concentrations in brain tissue but the mode of action of etifoxine on neurosteroid formation has not yet been elucidated. In the present study, we have thus investigated the effect and the mechanism of action of etifoxine on neurosteroid biosynthesis using the frog hypothalamus as an experimental model. Exposure of frog hypothalamic explants to graded concentrations of etifoxine produced a dose-dependent increase in the biosynthesis of 17-hydroxypregnenolone, dehydroepiandrosterone, progesterone and tetrahydroprogesterone, associated with a decrease in the production of dihydroprogesterone. Time-course experiments revealed that a 15-min incubation of hypothalamic explants with etifoxine was sufficient to induce a robust increase in neurosteroid synthesis, suggesting that etifoxine activates steroidogenic enzymes at a post-translational level. Etifoxine-evoked neurosteroid biosynthesis was not affected by the central-type benzodiazepine (CBR) receptor antagonist flumazenil, the translocator protein (TSPO) antagonist PK11195 or the GABAA receptor antagonist bicuculline. In addition, the stimulatory effects of etifoxine and the triakontatetraneuropeptide TTN, a TSPO agonist, were additive, indicating that these two compounds act through distinct mechanisms. Etifoxine also induced a rapid stimulation of neurosteroid biosynthesis from frog hypothalamus homogenates, a preparation in which membrane receptor signalling is disrupted. In conclusion, the present study demonstrates that etifoxine stimulates neurosteroid production through a membrane receptor-independent mechanism.

No MeSH data available.


Related in: MedlinePlus