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Event: 1387

Key Event Title

A descriptive phrase which defines a discrete biological change that can be measured. More help

7α-hydroxypregnenolone synthesis in the brain, decreased

Short name
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7α-hydroxypregnenolone synthesis in the brain, decreased
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Biological Context

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Level of Biological Organization
Cellular

Cell term

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Organ term

The location/biological environment in which the event takes place.The biological context describes the location/biological environment in which the event takes place.  For molecular/cellular events this would include the cellular context (if known), organ context, and species/life stage/sex for which the event is relevant. For tissue/organ events cellular context is not applicable.  For individual/population events, the organ context is not applicable.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Key Event Components

The KE, as defined by a set structured ontology terms consisting of a biological process, object, and action with each term originating from one of 14 biological ontologies (Ives, et al., 2017; https://aopwiki.org/info_pages/2/info_linked_pages/7#List). Biological process describes dynamics of the underlying biological system (e.g., receptor signalling).Biological process describes dynamics of the underlying biological system (e.g., receptor signaling).  The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signaling by that receptor).  Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description.  To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons.  If a desired term does not exist, a new term request may be made via Term Requests.  Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add.  Further information on Event Components and Biological Context may be viewed on the attached pdf. More help

Key Event Overview

AOPs Including This Key Event

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AOP Name Role of event in AOP Point of Contact Author Status OECD Status
Inhibition of CYP7B leads to decreased locomotor activity KeyEvent Florence Pagé-Larivière (send email) Not under active development
Inhibition of CYP7B activity leads to decreased sexual behavior KeyEvent Florence Pagé-Larivière (send email) Not under active development

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KE.In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
Japanese quail Coturnix japonica High NCBI
Cynops pyrrhogaster Cynops pyrrhogaster High NCBI
mouse Mus musculus High NCBI
human Homo sapiens High NCBI
salmonid fish salmonid fish High NCBI

Life Stages

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Life stage Evidence
During development and at adulthood

Sex Applicability

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Term Evidence
Unspecific

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. More help

7α-hydroxypregnenolone is an active neurosteroid synthesized in the brain from pregnenolone via a reaction catalyzed by CYP7B (R08943). Pregnenolone can also be synthesized in most vertebrate brain by CYP11A from cholesterol (Tsutsui and Yamazaki, 1995; do Rego et al., 2016).

Compared to other brain regions of the male quail and newt, 7α-hydroxypregnenolone concentration is higher in the diencephalon. In the brain of both salmon and newt, the peak concentrations are measured in the hypothalamus and optic tectum (Matsunaga et al., 2004; Tsutsui et al., 2008; Haraguchi et al., 2015). 

7α-hydroxypregnenolone synthesis in the brain is cyclic and driven by a different mechanism according to the specie.

  • In male quail, a diurnal animal, it is inhibited by a melatonin-receptor mechanism after melatonin secretion from the pineal gland (Tsutsui et al., 2008). 
  • In male newt, a nocturnal animal, melatonin secretion stimulates its synthesis in the brain.
  • Another regulating mechanism is observed in male newt where 7α-hydroxypregnenolone concentration peaks during the breeding period in response to prolactin signal (Matsunaga et al., 2004). 
  • In salmon, 7α-hydroxypregnenolone stays high during homing migration (Haraguchi et al., 2015). The endogenous factor regulating its synthesis has yet to be determined.

Thus, 7α-hydroxypregnenolone synthesis is regulated by the circadian cycle and/or by seasonal factors such as breeding and migration.

How It Is Measured or Detected

A description of the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements.These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA). Do not provide detailed protocols. More help

Detection and quantification of 7α-hydroxypregnenolone can be performed using GC-MS and/or HPLC analysis.

In vitro

  • Cell not expressing CYP7B can be transfected with CYP7B cDNA and incubated in presence of pregnenolone and NADPH. Concentration of 7α-hydroxypregnenolone can be measured by HPLC analysis (Haraguchi et al., 2015). 
  • To distinguish 7α- and 7β-hydroxypregnenolone, HPLC analysis was performed (Tsutsui et al., 2008). Brain homogenates can be incubated in presence of pregnenolone and NADPH. Concentration of 7α-hydroxypregnenolone can be measured by HPLC analysis Haraguchi et al., 2015).  

In vivo

The extracted steroids derived from brain homogenates and plasma can be measured using GC-MS analysis (Tsutsui et a;., 2008). 

Domain of Applicability

A description of the scientific basis for the indicated domains of applicability and the WoE calls (if provided).  More help

The enzyme synthesizing 7α-hydroxypregnenolone is known to be conserved in chimpanzee, Rhesus monkey, dog, cow, mouse, rat, chicken, zebrafish, and frog. https://www.ncbi.nlm.nih.gov/homologene/3544

References

List of the literature that was cited for this KE description. More help

Haraguchi, S., Koyama, T., Hasunuma, I., Vaudry, H., and Tsutsui, K. (2010). Prolactin increases the synthesis of 7alpha-hydroxypregnenolone, a key factor for induction of locomotor activity, in breeding male Newts. Endocrinology 151, 2211-2222.

Haraguchi, S., Yamamoto, Y., Suzuki, Y., Hyung Chang, J., Koyama, T., Sato, M., Mita, M., Ueda, H., and Tsutsui, K. (2015). 7alpha-Hydroxypregnenolone, a key neuronal modulator of locomotion, stimulates upstream migration by means of the dopaminergic system in salmon. Sci Rep 5, 12546.

Matsunaga, M., Ukena, K., Baulieu, E.E., and Tsutsui, K. (2004). 7alpha-Hydroxypregnenolone acts as a neuronal activator to stimulate locomotor activity of breeding newts by means of the dopaminergic system. Proc Natl Acad Sci U S A 101, 17282-17287.

Petkam, R., Renaud, R.L., Freitas, A.M., Canario, A.V., Raeside, J.I., Kime, D.E., and Leatherland, J.F. (2003). In vitro metabolism of pregnenolone to 7alpha-hydroxypregnenolone by rainbow trout embryos. Gen Comp Endocrinol 131, 241-249.

Tsutsui, K., Inoue, K., Miyabara, H., Suzuki, S., Ogura, Y., and Haraguchi, S. (2008). 7Alpha-hydroxypregnenolone mediates melatonin action underlying diurnal locomotor rhythms. J Neurosci 28, 2158-2167.

Tsutsui, K., and Yamazaki, T. (1995). Avian neurosteroids. I. Pregnenolone biosynthesis in the quail brain. Brain Res 678, 1-9.

Yau, J.L., Noble, J., Graham, M., and Seckl, J.R. (2006). Central administration of a cytochrome P450-7B product 7 alpha-hydroxypregnenolone improves spatial memory retention in cognitively impaired aged rats. J Neurosci 26, 11034-11040.