Neurosteroidogenesis inhibitor

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A neurosteroidogenesis inhibitor is a drug that inhibits the production of endogenous neurosteroids. Neurosteroids include the excitatory neurosteroids pregnenolone sulfate, dehydroepiandrosterone (DHEA), and dehydroepiandrosterone sulfate (DHEA-S), and the inhibitory neurosteroids allopregnanolone, tetrahydrodeoxycorticosterone (THDOC), and 3α-androstanediol, among others. [1] By inhibiting the synthesis of endogenous neurosteroids, neurosteroidogenesis inhibitors have effects in the central nervous system.

Inhibitory neurosteroids are biosynthesized from steroid hormones by the action of two enzymes, 5α-reductase and 3α-hydroxysteroid dehydrogenase (3α-HSD). [1] These enzymes can be inhibited by 5α-reductase inhibitors such as finasteride and dutasteride and by inhibitors of 3α-HSD such as medroxyprogesterone acetate. [2] [3] [4] Contrarily, 3α-HSD is induced to varying extents by certain selective serotonin reuptake inhibitors (SSRIs), including fluoxetine, fluvoxamine, sertraline, and paroxetine, as well as by certain other antidepressants like venlafaxine and mirtazapine, and these antidepressants have been found to increase inhibitory neurosteroid levels. [1] [5] [6] [7] Inhibition of inhibitory neurosteroid biosynthesis by 5α-reductase inhibitors and 3α-HSD inhibitors has been associated with depression, anxiety, irritability, and sexual dysfunction, [2] [4] [8] whereas enhancement of their biosynthesis has been implicated in the antidepressant and anxiolytic effects of some of the SSRIs. [1]

Inhibitors of cholesterol side-chain cleavage enzyme (P450scc), such as aminoglutethimide and ketoconazole, may block production of both excitatory and inhibitory neurosteroids, while CYP17A1 (17α-hydroxylase/17,20 lyase) inhibitors, such as abiraterone acetate, may mainly block production of excitatory neurosteroids. [9] Antigonadotropins may also have the effect of lowering circulating neurosteroid levels.

The translocator protein (TSPO), also initially described as the peripheral benzodiazepine receptor (PBR), is a mitochondrial protein that is involved in neurosteroid biosynthesis. [10] [11] It is activated by certain benzodiazepines such as diazepam and midazolam, and via this action, inhibitory neurosteroid levels are increased. [1] [10] [11] Selective TSPO activators, such as emapunil, are under investigation for clinical use as possible anxiolytics. [1]

Progesterone, which is the endogenous precursor to the inhibitory neurosteroids 5α-dihydroprogesterone and allopregnanolone, as well as, more distantly, THDOC, [1] [12] when administered exogenously, has been found to behave as a prodrug to these neurosteroids, [13] [14] with clinical signs of their action, such as sedation, readily evident in humans. [15] [16] [17] Exogenous pregnenolone has similarly been found to act as a prodrug of allopregnanolone. [18]

Metyrapone, a reversible inhibitor of the enzyme steroid 11β-hydroxylase, may increase inhibitory neurosteroid levels. [19] Conversely, it may inhibit the production of cortisol-derived excitatory neurosteroids. [9]

Paracetamol (acetaminophen; Tylenol) has been shown to act at SULT2A1 (and potentially at SULT2B1) as an inhibitor of neurosteroidogenesis. [20] Specifically, the production of sulfate-containing neurosteroids, such as DHEA-S and pregnenolone sulfate, were decreased in patients taking paracetamol. [20]

See also

Related Research Articles

<span class="mw-page-title-main">Progestogen</span> Steroid hormone that activates the progesterone receptor

Progestogens, also sometimes written progestagens or gestagens, are a class of natural or synthetic steroid hormones that bind to and activate the progesterone receptors (PR). Progesterone is the major and most important progestogen in the body. The progestogens are named for their function in maintaining pregnancy, although they are also present at other phases of the estrous and menstrual cycles.

<span class="mw-page-title-main">Androsterone</span> Endogenous steroid hormone

Androsterone, or 3α-hydroxy-5α-androstan-17-one, is an endogenous steroid hormone, neurosteroid, and putative pheromone. It is a weak androgen with a potency that is approximately 1/7 that of testosterone. Androsterone is a metabolite of testosterone and dihydrotestosterone (DHT). In addition, it can be converted back into DHT via 3α-hydroxysteroid dehydrogenase and 17β-hydroxysteroid dehydrogenase, bypassing conventional intermediates such as androstanedione and testosterone, and as such, can be considered to be a metabolic intermediate in its own right.

5α-Reductase Enzyme family

5α-Reductases, also known as 3-oxo-5α-steroid 4-dehydrogenases, are enzymes involved in steroid metabolism. They participate in three metabolic pathways: bile acid biosynthesis, androgen and estrogen metabolism. There are three isozymes of 5α-reductase encoded by the genes SRD5A1, SRD5A2, and SRD5A3.

<span class="mw-page-title-main">Pregnenolone</span> Chemical compound

Pregnenolone (P5), or pregn-5-en-3β-ol-20-one, is an endogenous steroid and precursor/metabolic intermediate in the biosynthesis of most of the steroid hormones, including the progestogens, androgens, estrogens, glucocorticoids, and mineralocorticoids. In addition, pregnenolone is biologically active in its own right, acting as a neurosteroid.

<span class="mw-page-title-main">Neurosteroid</span> Compounds that affect neuronal excitability through modulation of specific ionotropic receptors

Neurosteroids, also known as neuroactive steroids, are endogenous or exogenous steroids that rapidly alter neuronal excitability through interaction with ligand-gated ion channels and other cell surface receptors. The term neurosteroid was coined by the French physiologist Étienne-Émile Baulieu and refers to steroids synthesized in the brain. The term, neuroactive steroid refers to steroids that can be synthesized in the brain, or are synthesized by an endocrine gland, that then reach the brain through the bloodstream and have effects on brain function. The term neuroactive steroids was first coined in 1992 by Steven Paul and Robert Purdy. In addition to their actions on neuronal membrane receptors, some of these steroids may also exert effects on gene expression via nuclear steroid hormone receptors. Neurosteroids have a wide range of potential clinical applications from sedation to treatment of epilepsy and traumatic brain injury. Ganaxolone, a synthetic analog of the endogenous neurosteroid allopregnanolone, is under investigation for the treatment of epilepsy.

3β-Hydroxysteroid dehydrogenase/Δ5-4 isomerase (3β-HSD) is an enzyme that catalyzes the biosynthesis of the steroid progesterone from pregnenolone, 17α-hydroxyprogesterone from 17α-hydroxypregnenolone, and androstenedione from dehydroepiandrosterone (DHEA) in the adrenal gland. It is the only enzyme in the adrenal pathway of corticosteroid synthesis that is not a member of the cytochrome P450 family. It is also present in other steroid-producing tissues, including the ovary, testis and placenta. In humans, there are two 3β-HSD isozymes encoded by the HSD3B1 and HSD3B2 genes.

<span class="mw-page-title-main">Allopregnanolone</span> Endogenous inhibitory neurosteroid

Allopregnanolone is a naturally occurring neurosteroid which is made in the body from the hormone progesterone. As a medication, allopregnanolone is referred to as brexanolone, sold under the brand name Zulresso, and used to treat postpartum depression. It is given by injection into a vein.

17β-Hydroxysteroid dehydrogenases, also 17-ketosteroid reductases (17-KSR), are a group of alcohol oxidoreductases which catalyze the reduction of 17-ketosteroids and the dehydrogenation of 17β-hydroxysteroids in steroidogenesis and steroid metabolism. This includes interconversion of DHEA and androstenediol, androstenedione and testosterone, and estrone and estradiol.

<span class="mw-page-title-main">3α-Hydroxysteroid dehydrogenase</span> Protein-coding gene in the species Homo sapiens

3α-Hydroxysteroid dehydrogenase is an enzyme that in humans is encoded by the AKR1C4 gene. It is known to be necessary for the synthesis of the endogenous neurosteroids allopregnanolone, THDOC, and 3α-androstanediol. It is also known to catalyze the reversible conversion of 3α-androstanediol (5α-androstane-3α,17β-diol) to dihydrotestosterone and vice versa.

<span class="mw-page-title-main">Pregnanolone</span> Chemical compound

Pregnanolone, also known as eltanolone, is an endogenous inhibitory neurosteroid which is produced in the body from progesterone. It is closely related to allopregnanolone, which has similar properties.

<span class="mw-page-title-main">5α-Dihydroprogesterone</span> Chemical compound

5α-Dihydroprogesterone is an endogenous progestogen and neurosteroid that is synthesized from progesterone. It is also an intermediate in the synthesis of allopregnanolone and isopregnanolone from progesterone.

<span class="mw-page-title-main">Pregnenolone sulfate</span> Chemical compound

Pregnenolone sulfate is an endogenous excitatory neurosteroid that is synthesized from pregnenolone. It is known to have cognitive and memory-enhancing, antidepressant, anxiogenic, and proconvulsant effects.

GABA<sub>A</sub> receptor positive allosteric modulator GABAA receptor positive modulators

In pharmacology, GABAA receptor positive allosteric modulators, also known as GABAkines or GABAA receptor potentiators, are positive allosteric modulator (PAM) molecules that increase the activity of the GABAA receptor protein in the vertebrate central nervous system.

<span class="mw-page-title-main">Isopregnanolone</span> Chemical compound

Isopregnanolone, also known as isoallopregnanolone and epiallopregnanolone, as well as sepranolone, and as 3β-hydroxy-5α-pregnan-20-one or 3β,5α-tetrahydroprogesterone (3β,5α-THP), is an endogenous neurosteroid and a natural 3β-epimer of allopregnanolone. It has been reported to act as a subunit-selective negative allosteric modulator of the GABAA receptor, and antagonizes in animals and humans some but not all of the GABAA receptor-mediated effects of allopregnanolone, such as anesthesia, sedation, and reduced saccadic eye movements, but not learning impairment. Isopregnanolone has no hormonal effects and appears to have no effect on the GABAA receptor by itself; it selectively antagonizes allopregnanolone and does not affect the effects of other types of GABAA receptor positive allosteric modulators such as benzodiazepines or barbiturates.

<span class="mw-page-title-main">3α-Dihydroprogesterone</span> Chemical compound

3α-Dihydroprogesterone (3α-DHP), also known as 3α-hydroxyprogesterone, as well as pregn-4-en-3α-ol-20-one, is an endogenous neurosteroid. It is biosynthesized by 3α-hydroxysteroid dehydrogenase from progesterone. 3α-DHP has been found to act as a positive allosteric modulator of the GABAA receptor and is described as being as active as allopregnanolone in regard to this action. In accordance, it has anxiolytic effects in animals. 3α-DHP has also been found to inhibit the secretion of follicle-stimulating hormone (FSH) from the rat pituitary gland, demonstrating possible antigonadotropic properties. Unlike the case of most other inhibitory neurosteroids, 3α-DHP production is not blocked by 5α-reductase inhibitors like finasteride. No data were available on the progestogenic activity of 3α-DHP as of 1977. Levels of 5α-DHP have been quantified.

<span class="mw-page-title-main">3β-Dihydroprogesterone</span> Chemical compound

3β-Dihydroprogesterone (3β-DHP), also known as 3β-hydroxyprogesterone, or pregn-4-en-3β-ol-20-one, is an endogenous steroid. It is biosynthesized by 3β-hydroxysteroid dehydrogenase from progesterone. Unlike 3α-dihydroprogesterone (3α-DHP), 3β-DHP does not act as a positive allosteric modulator of the GABAA receptor, which is in accordance with the fact that other 3β-hydroxylated progesterone metabolites such as isopregnanolone and epipregnanolone similarly do not act as potentiators of this receptor and instead inhibit it as well as reverse the effects of potentiators like allopregnanolone. 3β-DHP has been reported to possess about the same potency as progesterone in a bioassay of progestogenic activity, whereas 3α-DHP was not assessed.

A steroidogenesis inhibitor, also known as a steroid biosynthesis inhibitor, is a type of drug which inhibits one or more of the enzymes that are involved in the process of steroidogenesis, the biosynthesis of endogenous steroids and steroid hormones. They may inhibit the production of cholesterol and other sterols, sex steroids such as androgens, estrogens, and progestogens, corticosteroids such as glucocorticoids and mineralocorticoids, and neurosteroids. They are used in the treatment of a variety of medical conditions that depend on endogenous steroids.

An androgen synthesis inhibitor is a type of drug which inhibits the enzymatic synthesis of androgens, such as testosterone and dihydrotestosterone (DHT). They include:

<span class="mw-page-title-main">Pregnenolone (medication)</span> Medication and supplement

Pregnenolone, sold under the brand name Enelone among others, is a medication and supplement as well as a naturally occurring and endogenous steroid. It is described as a neurosteroid and anti-inflammatory drug and was used in the treatment of rheumatoid arthritis and soft-tissue rheumatism in the 1950s but is no longer used today. Pregnenolone can be taken by mouth, as a topical medication, or by injection into muscle.

References

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