Effect of the 5α-reductase enzyme inhibitor dutasteride in the brain of intact and parkinsonian mice

Sex and Age Differences in a Progressive Synucleinopathy Mouse Model

The mutation and overexpression of the alpha-synuclein protein (αSyn), described as synucleinopathy, is associated with Parkinson's disease (PD)-like pathologies. A higher prevalence of PD is documented for men versus women, suggesting female hormones' implication in slowing PD progression. The nigrostriatal dopamine (DA) neurons in rodent males are more vulnerable to toxins than those in females. The effect of biological sex on synucleinopathy remains poorly described and was investigated using mice knocked out for murine αSyn (SNCA-/-) and also overexpressing human αSyn (SNCA-OVX) compared to wildtype (WT) mice. All the mice showed decreased locomotor activity with age, and more abruptly in the male than in the female SNCA-OVX mice; anxiety-like behavior increased with age. The SNCA-OVX mice had an age-dependent accumulation of αSyn. Older age was associated with the loss of nigral DA neurons and decreased striatal DA contents. The astrogliosis, microgliosis, and cytokine concentrations increased with aging. More abrupt nigrostriatal DA decreases and increased microgliosis were observed in the male SNCA-OVX mice. Human αSyn overexpression and murine αSyn knockout resulted in behavioral dysfunctions, while only human αSyn overexpression was toxic to DA neurons. At 18 months, neuroprotection was lost in the female SNCA-OVX mice, with a likely loss of estrus cycles. In conclusion, sex-dependent αSyn toxicity was observed, affecting the male mice more significantly.

Three-Dimensional Analysis of Sex- and Gonadal Status- Dependent Microglial Activation in a Mouse Model of Parkinson’s Disease

Parkinson’s disease (PD) is characterized by neurodegeneration and neuroinflammation. PD prevalence and incidence are higher in men than in women and modulation of gonadal hormones could have an impact on the disease course. This was investigated in male and female gonadectomized (GDX) and SHAM operated (SHAM) mice. Dutasteride (DUT), a 5α-reductase inhibitor, was administered to these mice for 10 days to modulate their gonadal sex hormones. On the fifth day of DUT treatment, mice received 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to model PD. We have previously shown in these mice the toxic effect of MPTP in SHAM and GDX males and in GDX females on dopamine markers and astrogliosis whereas SHAM females were protected by their female sex hormones. In SHAM males, DUT protected against MPTP toxicity. In the present study, microglial density and the number of doublets, representative of a microglial proliferation, were increased by the MPTP lesion only in male mice and prevented by DUT in SHAM males. A three-dimensional morphological microglial analysis showed that MPTP changed microglial morphology from quiescent to activated only in male mice and was not prevented by DUT. In conclusion, microgliosis can be modulated by sex hormone-dependent and independent factors in a mice model of PD.

[Androgens and Parkinson's disease: the role in humans and in experiment]

Parkinson's disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease. There is evidence that PD has a wider prevalence among men, which indicates the existing role of sex hormones in the pathogenesis of the disease. The article presents an overview of studies devoted to the study of sex differences in the incidence and symptoms of PD. Drug therapy with androgens, androgen precursors, antiandrogens and drugs that modify androgen metabolism is available for the treatment of various endocrine conditions, having translational significance for PD, but none of these drugs has yet shown sufficient effectiveness. Although PD has now been proven to be more common in men than in women, androgens do not always have any effect on the symptoms or progression of the disease. 5α-reductase inhibitors have shown neuroprotective and anti-dyskinetic activity and need further investigation. Despite the fact that the neuroprotective effect of dutasteride was observed only before damage to DA neurons, the absence of a negative effect makes it an attractive drug for use in patients with PD due to its anti-dyskinetic properties.

Is Dutasteride a Therapeutic Alternative for Amyotrophic Lateral Sclerosis?

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that is characterized by the loss of upper and lower motor neurons (MNs) in the cerebral cortex, brainstem and spinal cord, with consequent weakness, atrophy and the progressive paralysis of all muscles. There is currently no medical cure, and riluzole and edaravone are the only two known approved drugs for treating this condition. However, they have limited efficacy, and hence there is a need to find new molecules. Dutasteride, a dual inhibitor of type 1 and type 2 5α-reductase (5AR) enzymes, the therapeutic purposes of which, to date, are the treatment of benign prostatic hyperplasia and androgenic alopecia, shows great anti-ALS properties by the molecular-topology methodology. Based on this evidence, this review aims to assess the effects of dutasteride on testosterone (T), progesterone (PROG) and 17β-estradiol (17BE) as a therapeutic alternative for the clinical improvement of ALS, based on the hormonal, metabolic and molecular pathways related to the pathogenesis of the disease. According to the evidence found, dutasteride shows great neuroprotective, antioxidant and anti-inflammatory effects. It also appears effective against glutamate toxicity, and it is capable of restoring altered dopamine activity (DA). These effects are achieved both directly and through steroid hormones. Therefore, dutasteride seems to be a promising molecule for the treatment of ALS, although clinical studies are required for confirmation.

Peripheral Neuroprotective and Immunomodulatory Effects of 5α-Reductase Inhibitors in Parkinson’s Disease Models

Gastrointestinal disorders in Parkinson’s disease (PD) have been associated with neuronal alteration in the plexus of the gut. We previously demonstrated the immunomodulatory effect of female hormones to treat enteric neurodegeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. This study made the hypothesis of obtaining similar neuroprotection as with hormone treatments by affecting steroidogenesis with two 5α-reductase inhibitors, finasteride and dutasteride. These drugs are approved to treat benign prostatic hyperplasia and alopecia and display mitochondrial effects. In MPTP-treated mice, the dopaminergic and vasoactive intestinal peptide (VIP) neurons alteration was prevented by finasteride and dutasteride, while the increase in proinflammatory macrophages density was inhibited by dutasteride treatment but not finasteride. NF-κB response, oxidative stress, and nitric oxide and proinflammatory cytokines production in vitro were only prevented by dutasteride. In addition, mitochondrial production of free radicals, membrane depolarization, decreased basal respiration, and ATP production were inhibited by dutasteride, while finasteride had no effect. In conclusion, the present results indicate that dutasteride treatment prevents enteric neuronal damages in the MPTP mouse model, at least in part through anti-inflammatory and mitochondrial effects. This suggests that drug repurposing of dutasteride might be a promising avenue to treat enteric neuroinflammation in early PD.

Allopregnanolone: An overview on its synthesis and effects

Allopregnanolone, a 3α,5α-progesterone metabolite, acts as a potent allosteric modulator of the γ-aminobutyric acid type A receptor. In the present review, the synthesis of this neuroactive steroid occurring in the nervous system is discussed with respect to physiological and pathological conditions. In addition, its physiological and neuroprotective effects are also reported. Interestingly, the levels of this neuroactive steroid, as well as its effects, are sex-dimorphic, suggesting a possible gender medicine based on this neuroactive steroid for neurological disorders. However, allopregnanolone presents low bioavailability and extensive hepatic metabolism, limiting its use as a drug. Therefore, synthetic analogues or a different therapeutic strategy able to increase allopregnanolone levels have been proposed to overcome any pharmacokinetic issues.

Androgens and Parkinson's Disease: A Review of Human Studies and Animal Models

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease. A greater prevalence and incidence of PD are reported in men than in women, suggesting a potential contribution of sex, genetic difference and/or sex hormones. This review presents an overview of epidemiological and clinical studies investigating sex differences in the incidence and symptoms of PD. This sex difference is replicated in animal models of PD showing an important neuroprotective role of sex steroids. Therefore, although gender and genetic factors likely contribute to the sex difference in PD, focus here will be on sex hormones because of their neuroprotective role. Androgens receive less attention than estrogen. It is well known that endogenous androgens are more abundant in healthy men than in women and decrease with aging; lower levels are reported in PD men than in healthy male subjects. Drug treatments with androgens, androgen precursors, antiandrogens, and drugs modifying androgen metabolism are available to treat various endocrine conditions, thus having translational value for PD but none have yet given sufficient positive effects for PD. Variability in the androgen receptor is reported in humans and is an additional factor in the response to androgens. In animal models of PD used to study neuroprotective activity, the androgens testosterone and dihydrotestosterone have given inconsistent results. 5α-Reductase inhibitors have shown neuroprotective activity in animal models of PD and antidyskinetic activity. Hence, androgens have not consistently shown beneficial or deleterious effects in PD but numerous androgen-related drugs are available that could be repurposed for PD.

Effect of sex and gonadectomy on brain MPTP toxicity and response to dutasteride treatment in mice

The main neuropathological feature of Parkinson's disease (PD) is degeneration of dopamine (DA) neurons in the substantia nigra (SN); PD prevalence is higher in men, suggesting a role of sex hormones in neuroprotection. This study sought the effects of sex hormones in the brain in a mouse model of PD and modulation of steroid metabolism/synthesis with the 5α-reductase inhibitor dutasteride shown to protect 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) male mice. Male and female mice were gonadectomized (GDX) or SHAM operated. They were treated with vehicle or dutasteride (5 mg/kg) for 10 days and administered a low dose of MPTP (5.5 mg/kg) or saline on the 5th day to model early PD; brains were collected thereafter. Striatal measures of the active metabolite 1-methyl-4-phenylpyridinium (MPP+) contents showed no difference supporting an effect of the experimental conditions investigated. In SHAM MPTP male mice loss of striatal DA and metabolites, DA transporter (DAT) and vesicular monoamine transporter 2 (VMAT2) specific binding in the striatum and SN was prevented by dutasteride treatment; these changes were inversely correlated with glial fibrillary acidic protein (GFAP, an astrogliosis marker) levels. In SHAM female mice MPTP treatment had little or no effect on striatal and SN DA markers and GFAP levels whereas GDX male and female mice showed a similar loss of striatal DA markers and increase of GFAP. No effect of dutasteride treatment was observed in GDX male and female mice. In conclusion, sex differences in mice MPTP toxicity and response to dutasteride were observed that were lost upon gonadectomy implicating neuroinflammation.

LINCS Dataset-Based Repositioning of Dutasteride as an Anti-Neuroinflammation Agent

Neuroinflammation is often accompanied by central nervous system (CNS) injury seen in various CNS diseases, with no specific treatment. Drug repurposing is a strategy of finding new uses for approved or investigational drugs, and can be enabled by the Library of Integrated Network-based Cellular Signatures (LINCS), a large drug perturbation database. In this study, the signatures of Lipopolysaccharide (LPS) were compared with the signatures of compounds contained in the LINCS dataset. To the top 100 compounds obtained, the Quantitative Structure-Activity Relationship (QSAR)-based tool admetSAR was used to identify the top 10 candidate compounds with relatively high blood–brain barrier (BBB) penetration. Furthermore, the seventh-ranked compound, dutasteride, a 5-α-reductase inhibitor, was selected for in vitro and in vivo validation of its anti-neuroinflammation activity. The results showed that dutasteride significantly reduced the levels of IL-6 and TNF-α in the supernatants of LPS-stimulated BV2 cells, and decreased the levels of IL-6 in the hippocampus and plasma, and the number of activated microglia in the brain of LPS administration mice. Furthermore, dutasteride also attenuated the cognitive impairment caused by LPS stimulation in mice. Taken together, this study demonstrates that the LINCS dataset-based drug repurposing strategy is an effective approach, and the predicted candidate, dutasteride, has the potential to ameliorate LPS-induced neuroinflammation and cognitive impairment.

Impact of short-term Dutasteride treatment on prostate-specific membrane antigen expression in a mouse xenograft model

Background

Dutasteride has been shown to increase expression of the prostate‐specific membrane antigen (PSMA) in prostate cancer cells in previous in vitro studies. This 5‐alpha‐reductase inhibitor is commonly used for the treatment of symptomatic benign prostatic enlargement. The modulation of PSMA expression might affect PSMA‐based prostate cancer imaging and therapy.

Aim

The purpose of this work was to further analyze concentration‐dependent effects of Dutasteride on PSMA expression in a mouse xenograft model.

Methods and results

Four groups of mice bearing LNCaP xenografts were treated for 14 days with daily intraperitoneal injections of either vehicle control or different concentrations of Dutasteride (0.1, 1, 10 mg/kg). Total expression of PSMA, androgen receptor (AR), and caspase‐3 protein was analyzed using immunoblotting (WES). In addition, PSMA, cleaved caspase‐3 and Ki‐67 expression was assessed and quantified by immunohistochemistry. Tumor size was measured by caliper on day 7 and 14, tumor weight was assessed following tissue harvesting.

The mean PSMA protein expression in mice increased significantly after treatment with 1 mg/kg (10‐fold) or 10 mg/kg (sixfold) of Dutasteride compared to vehicle control. The mean fluorescence intensity significantly increased by daily injections of 0.1 mg/kg Dutasteride (1.6‐fold) as well as 1 and 10 mg/kg Dutasteride (twofold). While the reduction in tumor volume following treatment with high concentrations of 10 mg/kg Dutasteride was nonsignificant, no changes in AR, caspase‐3, cleaved caspase‐3, and Ki‐67 expression were observed.

Conclusion

Short‐term Dutasteride treatments with concentrations of 1 and 10 mg/kg significantly increase the total PSMA protein expression in a mouse LNCaP xenograft model. PSMA fluorescence intensity increases significantly even using lower daily concentrations of 0.1 mg/kg Dutasteride. Further investigations are needed to elucidate the impact of Dutasteride treatment on PSMA expression in patients.

Physiopathological role of the enzymatic complex 5α-reductase and 3α/β-hydroxysteroid oxidoreductase in the generation of progesterone and testosterone neuroactive metabolites

The enzymatic complex 5α-reductase (5α-R) and 3α/3β-hydroxysteroid oxidoreductase (HSOR) is expressed in the nervous system, where it transforms progesterone (PROG) and testosterone (T) into neuroactive metabolites. These metabolites regulate myelination, brain maturation, neurotransmission, reproductive behavior and the stress response. The expression of 5α-R and 3α-HSOR and the levels of PROG and T reduced metabolites show regional and sex differences in the nervous system and are affected by changing physiological conditions as well as by neurodegenerative and psychiatric disorders. A decrease in their nervous tissue levels may negatively impact the course and outcome of some pathological events. However, in other pathological conditions their increased levels may have a negative impact. Thus, the use of synthetic analogues of these steroids or 5α-R modulation have been proposed as therapeutic approaches for several nervous system pathologies. However, further research is needed to fully understand the consequences of these manipulations, in particular with 5α-R inhibitors.

Sex differences in steroid levels and steroidogenesis in the nervous system: Physiopathological role

The nervous system, in addition to be a target for steroid hormones, is the source of a variety of neuroactive steroids, which are synthesized and metabolized by neurons and glial cells. Recent evidence indicates that the expression of neurosteroidogenic proteins and enzymes and the levels of neuroactive steroids are different in the nervous system of males and females. We here summarized the state of the art of neuroactive steroids, particularly taking in consideration sex differences occurring in the synthesis and levels of these molecules. In addition, we discuss the consequences of sex differences in neurosteroidogenesis for the function of the nervous system under healthy and pathological conditions and the implications of neuroactive steroids and neurosteroidogenesis for the development of sex-specific therapeutic interventions.

Repurposing sex steroids and related drugs as potential treatment for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder for which a greater prevalence and incidence is described in men. This suggests a protective effect of sex hormones in the brain. Therefore, steroids and drugs to treat endocrine conditions could have additional application for PD. Here, we review the protective effect of sex hormones, particularly estrogens, progesterone, androgens and dehydroepiandrosterone, in animal models of PD and also in human studies. Data also support that drugs affecting estrogen neurotransmission such as selective estrogen receptor modulators or affecting steroid metabolism with 5α-reductase inhibitors could be repositioned for treatment of PD. Sex steroids are also modulator of neurotransmission, thus they could repurposed to treat PD motor symptoms and to modulate the response to PD medication. No drug is yet available to limit PD progression. PD is a complex disease implicating multiple pathological processes and a therapeutic strategy using drugs with several mechanisms of action, such as sex steroids and endocrine drugs are interesting repositioning options for symptomatic treatment and disease-modifying activity for PD. This article is part of the Special Issue entitled 'Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders'.