The neurosteroid 3α-hydroxy-5α-pregnan-20-one affects dopamine-mediated behavior in rodents

RATIONALE: The neurosteroid 3alpha-hydroxy-5alpha-pregnan-20-one (3alpha,5alpha-THP) has been previously shown to induce catalepsy in mice that is modified by GABAergic, dopaminergic, adenosinergic and serotonergic agents. In light of the interaction of this endogenous neurosteroid with GABAergic and dopaminergic transmission, there is potential interest in the possible role of 3alpha,5alpha-THP in psychotic disorders. OBJECTIVE: This study assessed the effect of 3alpha,5alpha-THP in certain dopamine-mediated behavioral paradigms that are widely used to predict antipsychotic-like activity. METHODS: 3alpha,5alpha-THP (1-8 microg per animal, i.c.v.), the classic neuroleptic (dopamine receptor antagonist) haloperidol (0.25 mg/kg, i.p.), and the benzodiazepine diazepam (7 mg/kg, i.p.) were injected into different groups of animals, and their behavior was screened using the following animal tests: conditioned avoidance response, apomorphine-induced climbing, and amphetamine-induced motor hyperactivity. Separate groups of mice that received 3alpha,5alpha-THP (1-8 microg per animal, i.c.v.) were screened for catalepsy. Furthermore, the effect of a sub-cataleptic dose (0.1 microg per mouse, i.c.v.) of 3alpha,5alpha-THP, either alone or in combination with the GABA(A) receptor antagonist picrotoxin (0.8 mg/kg, i.p.) was measured on haloperidol-induced catalepsy. RESULTS: 3alpha,5alpha-THP like haloperidol reduced conditioned avoidance, apomorphine-induced cage climbing and amphetamine-induced motor hyperactivity. Diazepam only affected conditioned avoidance. 3alpha,5alpha-THP also induced dose-dependent catalepsy. Furthermore, sub-cataleptic doses of 3alpha,5alpha-THP potentiated haloperidol-induced catalepsy. This potentiation was blocked by prior treatment with the GABA(A) receptor antagonist picrotoxin. CONCLUSION: These findings suggest that 3alpha,5alpha-THP, by its action at the GABA(A) receptors, increases GABAergic tone leading to a behavioral profile similar to that of dopamine receptor antagonists.     

Adenosinergic modulation of 3α-hydroxy-5α-pregnan-20-one induced catalepsy in mice

  Rationale: Neurosteroid 3α, 5α THP, a positive allosteric modulator of the GABA_A receptor Cl^– ionophore complex, induces catalepsy-like dopamine antagonists, adenosine agonists or GABA agonists. Adenosine and dopamine receptors are co-localized on GABAergic neurons in the striatum and regulate GABA-mediated neurotransmission. Moreover, the antagonistic interactions between specific subtypes of adenosine and dopamine receptors are involved in motor depressant or motor stimulant effects of adenosine receptor agonists or antagonists, respectively. Such interaction may modulate neurosteroid-induced catalepsy. Objective: This study examined the modulation of 3α, 5α THP-induced catalepsy by adenosinergic agents. Methods: Catalepsy induced by 3α, 5α THP (2–8 μg, ICV) was assessed by bar test periodically up to 3 h in mice. Adenosine A₁, A_2A or A₃ receptor agonists or antagonists were given IP or ICV prior to 3α, 5α THP. Some animals received IP dopamine D₂ receptor agonist or antagonist 30 min prior to above combination treatment. Results: Adenosine A₁, A_2A, and A₃ receptor agonists potentiated, whereas adenosine A_2A receptor antagonists, but not A₁ antagonists, reversed 3α, 5α THP-induced catalepsy. These effects of adenosine agonists and antagonists were abolished by prior administration of bromocriptine, the dopamine D₂ receptor agonist and spiperone, the dopamine D₂ receptor antagonist, respectively. Conclusions: These findings suggest specific adenosine-dopamine receptor interaction in the striatum to modulate 3α, 5α THP-induced catalepsy. Received: 1 November 1998 / Final version: 5 January 1999     

Behavioral characterization of Co 134444 (3α-hydroxy-21-(1'-imidazolyl)-3β-methoxymethyl-5α-pregnan-20-one), a novel sedative-hypnotic neuroactive steroid

RATIONALE: Neuroactive steroids have been shown to exhibit a wide range of behavioral activities that are similar but not identical to those of benzodiazepines. These activities include anticonvulsant, anxiolytic and sedative-hypnotic effects. OBJECTIVE: The purpose of the present study was to characterize Co 134444 (3alpha-hydroxy-21-(1'-imidazolyl)-3 -methoxymethyl-5alpha-pregnan-20-one), a novel sedative-hypnotic neuroactive steroid, in a variety of behavioral procedures. METHODS: Anticonvulsant effects were determined by the ability to protect against pentylenetetrazol- and maximal electroshock-induced seizures in mice and rats. Anxiolytic-like effects were determined using a punished drinking procedure in rats. Ataxic effects were determined using a horizontal wire procedure in mice and a rotorod procedure in mice and rats. The discriminative stimulus effects were evaluated in rats trained to discriminate pregnanolone from vehicle. RESULTS: Co 134444 exhibited oral anticonvulsant activity against pentylenetetrazol and maximal electroshock with ED50s of 9.8 and 20.6 mg/kg, respectively, in mice and 23.6 and 25.3 mg/kg, respectively, in rats. Anxiolytic-like efficacy was observed at a dose as low as 3.0 mg/kg, PO, in rats. Ataxic effects were observed with rapid onset and short duration. TD50s were 17.4 and 21.2 mg/kg orally in mice in the horizontal wire and rotorod procedures, respectively, and 39.0 mg/kg in rats using the rotorod. Co 134444 completely substituted for pregnanolone as a discriminative stimulus with little effect on response rate. CONCLUSIONS: Co 134444 exhibits a wide variety of behavioral effects; however, its rapid onset and short duration are consistent with its potential use as a sedative-hypnotic drug.     

Ethanol-like discriminative stimulus effects of the neurosteroid 3α-hydroxy-5α-pregnan-20-one in femaleMacaca fascicularis monkeys

The present study was designed to characterize the discriminative stimulus effects of ethanol and the neurosteroid 3-hydroxy-5-pregnan-20-one (allopregnanolone) in non-human primates. Female cynomolgus monkeys (Macaca fascicularis) were trained in a two-le-ver procedure to discriminate 1.0 g/kg ethanol (IG, 30 min pretreatment) from water using food reinforcement. Consistent with previous results in a variety of species, pentobarbital (0.56–17 mg/kg, IG) resulted in a dose-dependent substitution for the discriminative stimulus effects of ethanol, with an average ED₅₀ value of 1.9 mg/kg. Administration of allopregnanolone (0.3–5.6 mg/kg, IV) also produced complete substitution for the discriminative stimulus effects of ethanol, with an ED₅₀ value of 1.0 mg/kg. Plasma allopregnanolone levels 35 min following the administration of 3.0 mg/kg allopregnanolone ranged from 33 to 69 ng/ml. The ethanollike discriminative stimulus effects of 1.0 mg/kg allopregnanolone (IV) were present for 60 min, with a return to complete water-appropriate responding at 90 min post-treatment. The results indicate that the endogenous neuroactive steroid allopregnanolone produces subjective effects in cynomolgus monkeys that are similar to ethanol. These findings suggest that changes in the endogenous levels of allopregnanolone could alter sensitivity to the subjective effects of ethanol.     

Cortical 3α-hydroxy-5α-pregnan-20-one levels after acute administration of Δ9-tetrahydrocannabinol,cocaine and morphine

Rationale The neuroactive steroid, 3-hydroxy-5-pregane-20-one (allopregnanolone) is a potent modulator of GABA_A receptor function. Moreover, pharmacologically relevant concentrations of allopregnanolone are found in brain during physiological conditions (stress, pregnancy and menstrual cycle) and pharmacological challenge (ethanol, fluoxetine, olanzapine). Enhanced levels of neurosteroids are thought to contribute to the therapeutic effects of fluoxetine and various effects of ethanol via GABA_A receptors. Moreover, neurosteroids influence rewarding effects of ethanol in some models and modulate activation of the hypothalamic pituitary adrenal (HPA) axis. Thus, it is possible that enhanced allopregnanolone levels are involved in the effects of abused drugs.Objectives To determine if other abused drugs elicit alterations in brain neurosteroid levels, 9-tetrahydrocannabinol (9-THC), cocaine and morphine were administered to male rats.Methods Cortical brain tissue and plasma were collected and analyzed for steroid concentrations using radioimmunoassays.Results 9-THC (5 mg/kg, IP) elevated cortical allopregnanolone levels to pharmacologically active levels, while morphine (15 mg/kg, SC) produced a small but significant increase. Cocaine (30 mg/kg, IP) did not alter allopregnanolone levels, nor did lower doses of 9-THC or morphine. Plasma progesterone levels were elevated in both 9-THC and cocaine-treated animals.Conclusions Some, but not all, drugs of abuse produce increases in cortical allopregnanolone levels. In addition, increases in plasma steroid precursor levels do not always translate into increases in brain allopregnanolone levels.     

Evaluation of GABAergic neuroactive steroid 3α-hydroxy-5α-pregnane-20-one as a neurobiological substrate for the anti-anxiety effect of ethanol in rats

Rationale Acute systemic ethanol administration is known to elevate plasma and cerebral levels of neuroactive steroid 3-hydroxy-5-pregnane-20-one (3, 5-THP; allopregnanolone) to a concentration sufficient to potentiate GABA_A receptors. We have earlier demonstrated that 3, 5-THP mediates the antidepressant-like effect of ethanol in Porsolt forced swim test.Objective The aim of the present study is to explain the relationship between endogenous GABAergic neurosteroids and anxiolytic effect of ethanol in Sprague–Dawley rats.Method The mediation of 3, 5-THP in the anti-anxiety effect of ethanol was assessed by pharmacological interactions of ethanol with various endogenous neurosteroidal modulators and using simulated physiological conditions of altered neurosteroid content in elevated plus maze (EPM) test.Results Pretreatment of 3, 5-THP (0.5–2.5 g/rat, i.c.v.) or neurosteroidogenic agents such as 3, 5-THP precursor progesterone (5 or 10 mg/kg, i.p.), 11- hydroxylase inhibitor metyrapone (50 or 100 mg/kg, i.p.) or the GABA_A receptor agonist muscimol (25 ng/rat, i.c.v.) significantly potentiated the anti-anxiety effect of ethanol (1 g/kg, i.p.). On the other hand, the GABAergic antagonistic neurosteroid dehydroepiandrosterone sulphate (DHEAS) (1 mg/kg, i.p.), the GABA_A receptor blocker bicuculline (1 mg/kg, i.p.), the 5-reductase inhibitor finasteride (50×2 mg/kg, s.c.) or the mitochondrial diazepam binding inhibitory receptor antagonist PK11195 (1 mg/kg, i.p.) reduced ethanol-induced preference of time spent and number of entries into open arms. Anti-anxiety effect of ethanol was abolished in adrenalectomized (ADX) rats as compared to sham-operated control. This ADX-induced blockade was restored by prior systemic injection of progesterone, signifying the contribution of peripheral steroidogenesis in ethanol anxiolysis. Socially isolated animals known to exhibit decreased brain 3, 5-THP and GABA_A receptor functions displayed reduced sensitivity to the effects of ethanol and 3, 5-THP in EPM test.Conclusions Our results demonstrated the contributory role of neuroactive steroid 3, 5-THP in the anti-anxiety effect of ethanol. It is speculated that ethanol-induced modulation of endogenous GABAergic neurosteroids, especially 3, 5-THP, might be crucial pertinent to the etiology of trait anxiety (tension reduction) and ethanol abuse.     

Transformations of 3-hydroxy steroids with lewis and anhydrous protic acids: the case of pregn-4-en-3β,17α,20β-triol

The acid-catalyzed dehydration is one of the most important processes, which transforms 3-hydroxy steroids into their corresponding unsaturated derivatives. This reaction is of great importance because it can produce molecules that play a key role in the understanding of the natural metabolism of steroids. Sterol dehydration is generally performed with aqueous acidic systems, and the treatment often affords low yields of the desired compounds and/or complex mixtures of by-products. In this paper, we report the results obtained from the study of the structural and stereochemical effects of the acid-induced reaction of pregn-4-en-3β,17α,20β-triol in anhydrous systems. In particular, the treatment of this trihydroxy steroid model with Lewis acids leads to the corresponding Δ(3,5) -steradiene as the only product and in very high yields. With Lewis acids, no modifications of the 1,2-diol function on the D-ring are observed, even when the reactions are performed at high temperatures. Protic acid catalysis in non-aqueous organic solvents causes the formation of an epimeric mixture of the corresponding Δ(3,5) -steradiene derivatives by a partial stereochemical inversion of the asymmetric C-17. The reactivity of the 17α,20β-diolic residue is also evaluated by exposing pregn-4-en-3β,17α,20β-triol and the corresponding Δ(3,5) -steradiene to the prolonged action of anhydrous protic acid systems under thermal conditions.     

An autoradiographic study comparing the interactions of 3α-OH-5α-pregnan-20-one,pregnenolone sulfate and pentobarbital with [35S]-TBPS binding sites and their modulation by GABA in different structures of the rat brain

Using quantitative autoradiography, we have studied the distribution of the [³⁵S]-TBPS binding sites of the GABA-A receptor complex in various structures of the rat brain. High densities of binding sites were observed in layer IV of the cerebral cortex, in the globus pallidus, and in the thalamus. Intermediate densities of binding sites were observed in superficial and deep layers of the cerebral cortex, in the dentate gyrus and in the hippocampus . For all of these structures, the interactions of 3-OH-5-pregnan-20-one (35P), pregnenolone sulfate (PS), and pentobarbital with [³⁵S]-TBPS binding, in the presence or the absence of GABA were studied. In the absence of GABA, IC₅₀ values for the inhibition of [³⁵S]-TBPS binding were 10^–6 M for 35P and 10^–4 M for PS and pentobarbital in all of the brain regions studied. In the presence of GABA (5 × 10^–6 M), IC₅₀ values were decreased by one order of magnitude for 35P, PS, and pentobarbital in all structures studied except layer IV of the cortex, where the IC₅₀ value for PS was more markedly decreased (up to two orders of magnitude). By contrast, IC₅₀ values for picrotoxin and TBPS to inhibit [³⁵S]-TBPS binding were 10^–7 M and 10^–8 M, respectively, in the presence or absence of GABA.     

Ethanol Alters Local Cellular Levels of (3α,5α)-3-Hydroxypregnan-20-one (3α,5α-THP) Independent of the Adrenals in Subcortical Brain Regions

The neuroactive steroid (3α,5α)-3-hydroxypregnan-20-one (3α,5α-THP or allopregnanolone) is a positive modulator of GABA_A receptors synthesized in the brain, adrenal glands, and gonads. In rats, ethanol activates the hypothalamic–pituitary–adrenal axis and elevates 3α,5α-THP in plasma, cerebral cortex, and hippocampus. In vivo, these effects are dependent on both the pituitary and adrenal glands. In vitro, however, ethanol locally increases 3α,5α-THP in hippocampal slices, in the absence of adrenal influence. Therefore, it is not known whether ethanol can change local brain levels of 3α,5α-THP in vivo, independent of the adrenals. To directly address this controversy, we administered ethanol (2 g/kg) or saline to rats that underwent adrenalectomy (ADX) or received sham surgery and performed immunohistochemistry for 3α,5α-THP. In the medial prefrontal cortex (mPFC), ethanol increased 3α,5α-THP after sham surgery, compared with saline controls, with no ethanol-induced change in 3α,5α-THP following ADX. In subcortical regions, 3α,5α-THP was increased independent of adrenals in the CA1 pyramidal cell layer, dentate gyrus polymorphic layer, bed nucleus of the stria terminalis, and paraventricular nucleus of the hypothalamus. Furthermore, ethanol decreased 3α,5α-THP labeling in the nucleus accumbens shore and central nucleus of the amygdala, independent of the adrenal glands. These data indicate that ethanol dynamically regulates local 3α,5α-THP levels in several subcortical regions; however, the adrenal glands contribute to 3α,5α-THP elevations in the mPFC. Using double immunofluorescent labeling we determined that adrenal dependence of 3α,5α-THP induction by ethanol is not due to a lack of colocalization of 3α,5α-THP with the cholesterol transporters steroidogenic acute regulatory protein (StAR) or translocator protein (TSPO).     

The neurosteroid 5β-pregnan-3α-ol-20-one enhances actions of etomidate as a positive allosteric modulator of α1β2γ2L GABAA receptors

Background and Purpose

Neurosteroids potentiate responses of the GABA_A receptor to the endogenous agonist GABA. Here, we examined the ability of neurosteroids to potentiate responses to the allosteric activators etomidate, pentobarbital and propofol.

Experimental Approach

Electrophysiological assays were conducted on rat α1β2γ2L GABA_A receptors expressed in HEK 293 cells. The sedative activity of etomidate was studied in Xenopus tadpoles and mice. Effects of neurosteroids on etomidate-elicited inhibition of cortisol synthesis were determined in human adrenocortical cells.

Key Results

The neurosteroid 5β-pregnan-3α-ol-20-one (3α5βP) potentiated activation of GABA_A receptors by GABA and allosteric activators. Co-application of 1 μM 3α5βP induced a leftward shift (almost 100-fold) of the whole-cell macroscopic concentration–response relationship for gating by etomidate. Co-application of 100 nM 3α5βP reduced the EC₅₀ for potentiation by etomidate of currents elicited by 0.5 μM GABA by about three-fold. In vivo, 3α5βP (1mg kg^-1) reduced the dose of etomidate required to produce loss of righting in mice (ED₅₀) by almost 10-fold. In tadpoles, the presence of 50 or 100 nM 3α5βP shifted the EC₅₀ for loss of righting about three- or ten-fold respectively. Exposure to 3α5βP did not influence inhibition of cortisol synthesis by etomidate.

Conclusions and Implications

Potentiating neurosteroids act similarly on orthosterically and allosterically activated GABA_A receptors. Co-application of neurosteroids with etomidate can significantly reduce dosage requirements for the anaesthetic, and is a potentially beneficial combination to reduce undesired side effects.Tables of Links

Moderate doses of ethanol fail to increase plasma levels of neurosteroid 3α-hydroxy-5α-pregnan-20-one-like immunoreactivity in healthy men and women

Rationale: The endogenous GABAergic neuroactive steroid 3α-hydroxy-5α-pregnan-20-one (3α,5α-THP, allopregnanolone) has been proposed to contribute to ethanol actions. Humans synthesize 3α,5α-THP, but its role in response to systemic administration of ethanol is unclear. Objective: The present study aims to determine the effect of a moderate dose of ethanol on progesterone and 3α,5α-THP concentrations in plasma samples of healthy male and female subjects and to determine if these levels are related to the subjective effects of ethanol. Females were tested in both the follicular and luteal phases of the menstrual cycle. Methods: Healthy men (N=9) and women (N=12) aged 21–35 participated in the study. Men participated in two sessions on which they received ethanol (0.8 g/kg) or placebo. Women participated in four sessions on which they received ethanol (0.7 g/kg) or placebo during the follicular and luteal phases of their cycle. Subjective states and mood were measured by standardized self-report questionnaires and a measure of psychomotor performance. Steroid levels (progesterone, 3α,5α-THP, estradiol, and cortisol) were measured in plasma samples by radioimmunoassay. Results: Ethanol significantly increased plasma levels of progesterone, but not 3α,5α-THP-like immunoreactivity, in women in the luteal phase. Ethanol had no effect on progesterone or 3α,5α-THP-like immunoreactivity levels in women in the follicular phase or in men, and it did not increase cortisol in men or women. Ethanol also did not affect estradiol in men or women. Conclusions: 3α,5α-THP-like immunoreactivity levels in human plasma are not increased following moderate ethanol consumption, suggesting that circulating levels of progesterone or its tetrahydro-reduced metabolites do not play a major role in ethanol action. However, the possibility remains that ethanol increases endogenous brain production of GABAergic neurosteroids without affecting plasma levels. Moreover, humans synthesize 5β-reduced GABAergic steroids, and levels of these steroids may be altered in plasma or brain.     

Identification of the designer steroid 17β-hydroxy 5α-androst-1-en-3-one cypionate in an injectable liquid

In the screening of an injectable liquid marketed for body building, a steroid resembling 1-testosterone was found. The compound of interest was isolated using HPLC-UV detection coupled to an analytical scale fraction collector and subsequently characterized using HRAM-MS, NMR spectrometry, and GC-MS. The designer steroid was identified as 17β-hydroxy 5α-androst-1-en-3-one cypionate, an analog of 1-testosterone that had not been reported.     

Reduction of circulating and selective limbic brain levels of (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP) following forced swim stress in C57BL/6J mice

Rationale

Stress activates the hypothalamic-pituitary-adrenal (HPA) axis, and GABAergic neuroactive steroids contribute to homeostatic regulation of this circuitry. Acute forced swim stress (FSS) increases plasma, cortical, and hypothalamic (3α,5α)-3-hydroxy-pregnan-20-one (3α,5α-THP) levels in rats. However, there have not been systemic investigations of acute stress on changes in plasma and brain levels of 3α,5α-THP in mouse models.

Objectives

The present experiments aimed to assess circulating and local brain levels of 3α,5α-THP following acute FSS in C57BL/6J mice.

Methods

Mice were exposed to FSS (10 min), and 50 min later, blood and brains were collected. Circulating pregnenolone and 3α,5α-THP levels were assessed in serum. Free-floating brain sections (40 μm, four to five sections/region) were immunostained and analyzed in cortical and limbic brain structures.

Results

FSS decreased circulating 3α,5α-THP (?41.6?±?10.4 %) and reduced 3α,5α-THP immunolabeling in the paraventricular nucleus of the hypothalamus (?15.2?±?5.7 %), lateral amygdala (LA, ?31.1?±?13.4 %), and nucleus accumbens (NAcc) shell (?31.9?±?14.6). Within the LA, vesicular glutamate transporter 1 (VGLUT1) and vesicular GABA transporter were localized in 3α,5α-THP-positively stained cells, while in the NAcc shell, only VGLUT1 was localized in 3α,5α-THP-positively stained cells, suggesting that both glutamatergic and GABAergic cells within the LA are 3α,5α-THP-positive, while in the NAcc shell, 3α,5α-THP only localizes to glutamatergic cells.

Conclusions

The decrease in circulating and brain levels of 3α,5α-THP may be due to alterations in the biosynthesis/metabolism or changes in the regulation of the HPA axis following FSS. Changes in GABAergic neuroactive steroids in response to stress likely mediate functional adaptations in neuronal activity. This may provide a potential targeted therapeutic avenue to address maladaptive stress responsivity.     

Estradiol and testosterone modulate the anesthetic action of the GABA-A agonist THIP,but not of the neurosteroid 3α,5β-pregnanolone in the rat

Rationale As sex steroids modify the number and distribution of brain -aminobutyric acid (GABA)_A receptor subunits, we investigated the potential modulation of anesthesia, induced by agents acting on the GABA_A receptor, by estrogen and androgen.Objectives To assess possible effects of sex and hormonal condition (i.e., intact vs castrate; estradiol vs testosterone treatment) on the anesthetic effect of a GABA_A agonist, THIP (4,5,6,7-tetrahydroisoxazolo[5,4,-c]pyridin-3-ol hydrochloride), and an allosteric modulator of the GABA_A receptor: 3-hydroxy-5-pregnan-20-one (epipregnanolone).Methods The potencies of THIP and epipregnanolone for inducing loss of the righting response were compared between: (a) female and male rats; (b) intact and castrated animals of each sex; (c) untreated castrates and castrates given estradiol or testosterone.Results Sex and endocrine condition influenced sensitivity to i.v. THIP for the induction of anesthesia. ED₅₀ values were: gonadectomized females, 80 mg/kg > intact males, 50 mg/kg > proestrous females, 35 mg/kg > gonadectomized males, 28 mg/kg. Estradiol benzoate (EB; 3 g/day for 5 days) significantly increased THIP sensitivity in gonadectomized females: THIP + EB: ED₅₀=26 mg/kg vs THIP + sesame oil: ED₅₀=94 mg/kg, while testosterone propionate (TP; 10 mg injected 24 h before THIP) decreased THIP sensitivity in orchidectomized males when compared with vehicle-injected animals (ED₅₀=72 mg/kg vs 22 mg/kg, respectively).Conclusions Results suggest that estrogen increases the density or availability of GABA_A receptor subtypes on which THIP acts, while testosterone exerts the opposite effect. Neither sex nor gonadal condition influenced the anesthetic action of epipregnanolone as a similar potency was found in intact and in gonadectomized males and females.     

Selectively induced apoptosis in human neutrophils in the presence of oxidative phenoxazines, 2-amino-4,4α-dihydryo-4α-7H-phenoxazine-3-one and 2-aminophenoxazine-3-one, preceded by decrease of intracellular pH, depolarization of the mitochondria, and inhibition of superoxide generation

The present research investigated the effect of the oxidative phenoxazines, 2-amino-4,4α-dihydryo-4α-7H-phenoxazine-3-one (Phx-1) and 2-amino-phenoxazine-3-one (Phx-3) on apoptosis induction and apoptosis-related early events in human neutrophils. When Phx-1 or Phx-3 was administered to freshly drawn human blood for 18 h, these phenoxazines caused apoptotic cell death morphologically characterized by condensation of the nucleus in neutrophils, without causing it in lymphocytes and monocytes. Apoptosis, which was detectable by microscopic analysis and by using flow-cytometry, occurred significantly in human neutrophils isolated from freshly drawn blood, 6 h after the administration of 50 μM Phx-1 and Phx-3. After 24 h, every isolated neutrophil treated with Phx-1 or Phx-3 fell into apoptosis or lost its morphology, while many of the neutrophils without these phenoxazines remained alive, with normal morphology. Apoptosis-related early events including a decrease in intracellular pH (pHi) and depolarization of the mitochondria occurred in the isolated neutrophils, 30 min and 6 h after the administration of Phx-1 or Phx-3, respectively. Superoxide generation from the isolated neutrophils mimicked by phorbol myristate acetate (PMA) was very markedly inhibited by 100 μM Phx-1 or Phx-3. This result could be explained, in part, by the fact that the insufficient supply of NADPH (nicotinamide adenine dinucleotide phosphate, reduced form) was caused by pHi decrease in neutrophils treated with Phx-1 or Phx, because NADPH is necessary for NADPH oxidase responsible for generating superoxide in the cells. The present results suggest that Phx-1 and Phx-3 have the capacity of selectively inducing apoptosis in human neutrophils and that these phenoxazines may be useful as specific drugs to induce apoptotic cell death of human neutrophils and thereby prevent inflammation caused by these phagocytic cells.     

Microwave-accelerated preparation and analytical characterization of 5-ethoxy-N,N-dialkyl-[α,α,β,β-H(4) ]- and [α,α,β,β-D(4) ]-tryptamines

The increased interest in N,N-dialkyl tryptamines is a reflection of their diverse range of biologically active properties. Deuterated derivatives are of interest for use as internal standards in bioanalytical or pharmacological assays. The present study reports on the synthesis of twelve novel 5-ethoxy-N,N-dialkyl-[α,α,β,β-H(4) ]-tryptamines and their [α,α,β,β-D(4) ]-counterparts following the Speeter and Anthony procedure. The normally time-consuming reduction step was carried out in 5 min under microwave-accelerated conditions. Good yields were obtained using tetrahydrofuran as the solvent at 150 °C. The resulting 24 tryptamines have been characterized by 1D/2D nuclear magnetic resonance spectroscopy and gas chromatography ion trap mass spectrometry. Differential fragmentation of side-chain-related iminium ions has been observed as a key principle. Because many N,N-dialkyltryptamines are available outside of traditional pharmaceutical supply chains as so-called 'research chemicals', the availability, as standards, of these new N,N-dialkyltryptamines will aid in identifiying novel tryptamines arising from these other souces. They should therefore be of immediate value within forensic, research, and public health contexts.     

Variation in AKR1C3, which encodes the neuroactive steroid synthetic enzyme 3α-HSD type 2 (17β-HSD type 5), moderates the subjective effects of alcohol

Rationale

Animal models suggest that neuroactive steroids contribute to alcohol’s acute effects. We previously reported that a common nonsynonymous polymorphism, AKR1C3*2 in the gene encoding the enzyme 3α-HSD2/17β-HSD5, and a synonymous single nucleotide polymorphism (SNP), rs248793, in SRD5A1, which encodes 5α-reductase, were associated with alcohol dependence (AD).

Objectives

The aim of the study was to investigate whether these polymorphisms moderate subjective effects of alcohol in humans and whether AKR1C3*2 affects neuroactive steroid synthesis.

Methods

Sixty-five Caucasian men (34 lighter and 31 heavier drinkers; mean age 26.2 years) participated in a double-blind laboratory study where they consumed drinks containing no ethanol or 0.8 g/kg of ethanol. Breath alcohol, heart rate (HR), and self-reported alcohol effects were measured at 40-min intervals, and genotype was examined as a moderator of alcohol’s effects. Levels of the neuroactive steroid 5α-androstane-3α,17β-diol and its precursors, 3α,5α-androsterone and dihydrotestosterone, were measured at study entry using GC/MS.

Results

Initially, carriers of the AD-protective AKR1C3*2?G allele had higher levels of 5α-androstane-3α,17β-diol relative to the precursor 3α,5α-androsterone than C allele homozygotes. AKR1C3*2?G allele carriers exhibited greater increases in heart rate and stimulant and sedative effects of alcohol than C allele homozygotes. The genotype effects on sedation were observed only in heavier drinkers. The only effect of the SRD5A1 SNP was to moderate HR. There were no interactive effects of the two SNPs.

Conclusions

The observed effects of variation in a gene encoding a neuroactive steroid biosynthetic enzyme on the rate of 17β-reduction of androsterone relative to androstanediol and on alcohol’s sedative effects may help to explain the association of AKR1C3*2 with AD.     

Inhibitory influences of the adrenal steroid, 3α, 5α-tetrahydroxycorticosterone on aggression and defeat-induced analgesia in mice

The effects of intraperitoneal administrations of the deoxycorticosterone metabolite, 5-pregnane-, 21 diol-20-one (3, 5-tetrahydrodeoxycorticosterone; -THDOC) on the responses to aggression and defeat-induced analgesia were examined in subordinate intruder male mice in resident-intruder pairings. -THDOC reduced in a dose-dependent mannter (1–20 mg/kg) the number of bites and time to obtain defeat in subordinate mice during the agonistic encounters, as well as attenuating defeat-induced analgesia. These inhibitory effects of -THDOC were separate from its sedative actions at 20–30 mg/kg. In addition, the stereo-isomer, 3-pregnane-3, 21 diol-20-one (20 mg/kg) had no significant effects on the agonistic encounters and defeat, indicating that the inhibitory effects of -THDOC on agonistic interactions are stereospecific. Pretreatment with the benzodiazepine antagonist Ro 15-1788 (5 and 10 mg/kg) attenuated the inhibitory effects of -THDOC on defeat-induced analgesia. Ro 15-1788 (5, 10 mg/kg) by itself, however, had minimal effects on these agonistic interactions and subsequent defeat-induced analgesia. These results indicate that the naturally occurring steroid, -THDOC, has significant effects on responses to aggression and defeat-induced analagesia.     

Anti-nociceptive and anti-inflammatory activities of (−)-α-bisabolol in rodents

(−)-α-Bisabolol is an unsaturated, optically active sesquiterpene alcohol obtained by the direct distillation of essential oil from plants such as Vanillosmopsis erythropappa and Matricaria chamomilla. (−)-α-Bisabolol has generated considerable economic interest, as it possesses a delicate floral odour and has been shown to have antiseptic and gastroprotective activities. In this study, (−)-α-bisabolol was tested in standardised rodent models by gavage administration at doses of 100 and 200 mg/kg in the models of inflammation and 25 and 50 mg/kg in the models of nociception. In the inflammatory models of paw oedema induced by carrageenan and dextran, the mice treated with (−)-α-bisabolol showed smaller oedemas compared to animals treated only with the vehicle. (−)-α-Bisabolol was capable of reducing paw oedemas induced by 5-HT but not oedemas induced by histamine. (−)-α-Bisabolol demonstrated anti-nociceptive activity in the models of visceral nociception induced by acetic acid and in the second phase of the nociception test induced by the intraplantar administration of formalin. (−)-α-Bisabolol did not have any effect in a thermal nociception model using a hot plate but was able to diminish mechanical inflammatory hypernociception evoked by carrageenan. These findings suggest that the anti-nociceptive action of (−)-α-bisabolol is not linked to a central mechanism but instead is related to the inflammatory process. (−)-α-Bisabolol was able to decrease leukocyte migration, protein extravasations and the amount of TNF-α to the peritoneal cavity in response to carrageenan. Additionally, (−)-α-bisabolol reduced neutrophil degranulation in response to phorbol-myristate-acetate. We demonstrate, for the first time, the peripheral anti-inflammatory and anti-nociceptive activities of (−)-α-bisabolol.     

The antidepressant-like effects of the 3β-hydroxysteroid dehydrogenase inhibitor trilostane in mice is related to changes in neuroactive steroid and monoamine levels

In the present study, we analyzed the effects of a systemic treatment with the competitive 3β-hydroxysteroid dehydrogenase (3β-HSD) inhibitor trilostane on: (i) neurosteroid and monoamine levels in the brain, and (ii) the antidepressant activity of steroids and antidepressants in the forced swimming test (FST). 3β-HSD converts pregnenolone (PREG) into progesterone (PROG) or dehydroepiandrosterone (DHEA) into androstenedione. These neuroactive steroids are known to regulate neurotransmitters effects in the brain, particularly glutamate, γ-aminobutyric acid (GABA) and serotonin (5-HT), with consequences on mood and depression. We previously reported that trilostane showed antidepressant-like properties in the FST and concomitantly regulated plasma adrenocorticotropin (ACTH) and corticosterone levels, markers of the stress-induced hypothalamus-pituitary-adrenal (HPA) axis activation. We here observed that adrenalectomy/castration blocked the trilostane effect, outlining the importance of peripheral steroid levels. Trilostane (25 mg/kg) decreased hippocampus PROG contents and paradoxically increased circulating PROG levels. It also increased PREG levels in the hippocampus and frontal cortex. In the FST, a co-treatment with trilostane facilitated DHEAS (5-20 mg/kg) antidepressant activity, but showed only an additive, not facilitative, effect with PREGS (10-40 mg/kg), PROG (10-40 mg/kg) or allopregnanolone (ALLO, 1-8 mg/kg). Trilostane (25 mg/kg) treatment significantly increased 5-HT and (-)-norepinephrine (NE) turnovers in the hippocampus, an effect likely related to its antidepressant action. In co-administration studies, trilostane further decreased immobility following fluoxetine (30-60 mg/kg), sertraline (20-40 mg/kg) and imipramine (20-40 mg/kg), but not desipramine (20-40 mg/kg), treatments. A significant additive effect was observed for the selective 5-HT reuptake inhibitors (SSRI) at their highest dose. This study confirmed that a systemic administration of trilostane directly affected peripheral and brain levels in neuroactive steroids and monoamine turnover, resulting in antidepressant activity. The drug could be proposed as a co-treatment with SSRI. This article is part of a Special Issue entitled 'Anxiety and Depression'.