Neuroactive steroids and Parkinson's disease: Review of human and animal studies.

The greater prevalence and incidence of Parkinson's disease (PD) in men suggest a beneficial effect of sex hormones. Neuroactive steroids have neuroprotective activities thus offering interesting option for disease-modifying therapy for PD. Neuroactive steroids are also neuromodulators of neurotransmitter systems and may thus help to control PD symptoms and side effect of dopamine medication. Here, we review the effect on sex hormones (estrogen, androgen, progesterone and its metabolites) as well as androstenediol, pregnenolone and dehydroepiandrosterone) in human studies and in animal models of PD. The effect of neuroactive steroids is reviewed by considering sex and hormonal status to help identify specifically for women and men with PD what might be a preventive approach or a symptomatic treatment. PD is a complex disease and the pathogenesis likely involves multiple cellular processes. Thus it might be useful to target different cellular mechanisms that contribute to neuronal loss and neuroactive steroids provide therapeutics options as they have multiple mechanisms of action.

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.

Impact of sex on neuroimmune contributions to Parkinson's disease.

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease. Inflammation has been observed in both the idiopathic and familial forms of PD. Importantly, PD is reported more often in men than in women, men having at least 1.5- fold higher risk to develop PD than women. This review summarizes the impact of biological sex and sex hormones on the neuroimmune contributions to PD and its investigation in animal models of PD. Innate and peripheral immune systems participate in the brain neuroinflammation of PD patients and is reproduced in neurotoxin, genetic and α-synuclein based models of PD. Microglia and astrocytes are the main cells of the innate immune system in the central nervous system and are the first to react to restore homeostasis in the brain. Analysis of serum immunoprofiles in female and male control and PD patients show that a great proportion of these markers differ between males and females. The relationship between cerebrospinal fluid inflammatory markers and PD clinical characteristics or PD biomarkers shows sex differences. Conversely, in animal models of PD, sex differences in inflammation are well documented and the beneficial effects of endogenous and exogenous estrogenic modulation in inflammation have been reported. Targeting neuroinflammation in PD is an emerging therapeutic option but gonadal drugs have not yet been investigated in this respect, thus offering new opportunities for sex specific treatments.

Foliglurax, a positive allosteric modulator of the metabotrophic glutamate receptor 4, protects dopaminergic neurons in MPTP-lesioned male mice.

Overactivity of the corticostriatal glutamatergic pathway is documented in Parkinson's disease (PD) and stimulation of presynaptic metabotropic glutamate (mGlu) receptors 4 on these striatal afferents inhibits glutamate release normalizing neuronal activity in the basal ganglia. Moreover, mGlu4 receptors are also expressed in glial cells and are able to modulate glial function making this receptor a potential target for neuroprotection. Hence, we investigated whether foliglurax, a positive allosteric modulator of mGlu4 receptors with high brain exposure after oral administration, has neuroprotective effects in MPTP mice to model early PD. Male mice were treated daily from day 1 to 10 with 1, 3 or 10 mg/kg of foliglurax and administered MPTP on the 5th day then euthanized on the 11th day. Dopamine neuron integrity was assessed with measures of striatal dopamine and its metabolites levels, striatal and nigral dopamine transporter (DAT) binding and inflammation with markers of striatal astrocytes (GFAP) and microglia (Iba1). MPTP lesion produced a decrease in dopamine, its metabolites and striatal DAT specific binding that was prevented by treatment with 3 mg/kg of foliglurax, whereas 1 and 10 mg/kg had no beneficial effect. MPTP mice had increased levels of GFAP; foliglurax treatment (3 mg/kg) prevented this increase. Iba1 levels were unchanged in MPTP mice compared to control mice. There was a negative correlation between dopamine content and GFAP levels. Our results show that positive allosteric modulation of mGlu4 receptors with foliglurax provided neuroprotective effects in the MPTP mouse model of PD.

AV-101, a Pro-Drug Antagonist at the NMDA Receptor Glycine Site, Reduces L-Dopa Induced Dyskinesias in MPTP Monkeys.

N-methyl-D-aspartate (NMDA) receptors have been implicated in L-Dopa-induced dyskinesias (LID) in Parkinson's disease patients, but the use of antagonists that directly inhibit this receptor is associated with severe side effects. L-4-chlorokynurenine (4-Cl-KYN or AV-101) is a pro-drug of 7-chlorokynurenic acid (7-Cl-KYNA), a potent and specific antagonist of the glycine (GlyB) co-agonist site of NMDA receptors. The 7-Cl-KYNA has limited ability to cross the blood-brain barrier, whereas AV-101 readily accesses the brain. We investigated if AV-101 reduces LID in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned monkeys while maintaining the antiparkinsonian activity of L-Dopa. A first pilot study using three dyskinetic MPTP monkeys showed that acute AV-101 treatment (250 and 450 mg/kg) reduced LID and maintained the antiparkinsonian activity of L-Dopa. The main study using six additional dyskinetic MPTP monkeys showed that repeated AV-101 treatment (250 mg/kg, b.i.d. for 4 consecutive days) maintained their L-Dopa antiparkinsonian response. We measured significantly less LID when AV-101 was combined with L-Dopa treatment. AV-101 alone or with L-Dopa had no non-motor adverse effects in MPTP monkeys. Our study showed antidyskinetic activity of AV-101 in MPTP monkeys was comparable to amantadine tested previously in our laboratory in this model. We observed no adverse effects with AV-101, which is an improvement over amantadine, with its known side effects.

Differential contribution of estrogen receptors to the intestinal therapeutic effects of 17ß-estradiol in a murine model of Parkinson's disease.

Beneficial effects of estrogens have been reported in Parkinson's disease (PD) for many years. We previously reported their neuroprotective and anti-inflammatory potentials in the enteric nervous system of the intestine, a region possibly affected during the early stages of the disease according to Braak's hypothesis. Three different estrogen receptors have been characterized to date: the estrogen receptor alpha (ERα), the estrogen receptor beta (ERß) and the G protein coupled estrogen receptor 1 (GPER1). The aim of the present study was to decipher the individual contribution of each estrogen receptor to the therapeutic properties of 17ß-estradiol (E2) in the myenteric plexus of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Different agonists, 4,4',4''-(4-propyl-[1H]-pyrazole-1,3,5-triyl)trisphenol (PPT; ERα), 2,3-bis(4-hydroxyphenyl)-propionitrile (DPN; ERß), G1 (GPER1), and antagonists, ICI 182,780 (ERα and ERß), G15 (GPER1), were used to analyze the involvement of each receptor. We confirmed that G1 protects dopamine (DA) neurons to a similar extent as E2. An anti-inflammatory effect on proinflammatory macrophages and cultured human monocytes was also demonstrated with E2 and G1. The effects of PPT and DPN were less potent than G1 with only a partial neuroprotection of DA neurons by PPT and a partial reduction of interleukin (IL)- 1ß production in monocytes by PPT and DPN. Overall, the present results indicate that the positive outcomes of estrogens are mainly through activation of GPER1. Therefore, this suggests that targeting GPER1 could be a promising approach for future estrogen-based hormone therapies during early PD.

Prevention of L-Dopa-Induced Dyskinesias by MPEP Blockade of Metabotropic Glutamate Receptor 5 Is Associated with Reduced Inflammation in the Brain of Parkinsonian Monkeys.

Proinflammatory markers were found in brains of Parkinson's disease (PD) patients. After years of L-Dopa symptomatic treatment, most PD patients develop dyskinesias. The relationship between inflammation and L-Dopa-induced dyskinesias (LID) is still unclear. We previously reported that MPEP (a metabotropic glutamate receptor 5 antagonist) reduced the development of LID in de novo MPTP-lesioned monkeys. We thus investigated if MPEP reduced the brain inflammatory response in these MPTP-lesioned monkeys and the relationship to LID. The panmacrophage/microglia marker Iba1, the phagocytosis-related receptor CD68, and the astroglial protein GFAP were measured by Western blots. The L-Dopa-treated dyskinetic MPTP monkeys had increased Iba1 content in the putamen, substantia nigra, and globus pallidus, which was prevented by MPEP cotreatment; similar findings were observed for CD68 contents in the putamen and globus pallidus. There was a strong positive correlation between dyskinesia scores and microglial markers in these regions. GFAP contents were elevated in MPTP + L-Dopa-treated monkeys among these brain regions and prevented by MPEP in the putamen and subthalamic nucleus. In conclusion, these results showed increased inflammatory markers in the basal ganglia associated with LID and revealed that MPEP inhibition of glutamate activity reduced LID and levels of inflammatory markers.

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.

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.

Levodopa partially rescues microglial numerical, morphological, and phagolysosomal alterations in a monkey model of Parkinson's disease.

Parkinson's disease (PD) is the most common neurodegenerative motor disorder. The mechanisms underlying the onset and progression of Levodopa (L-Dopa)-induced dyskinesia (LID) during PD treatment remain elusive. Emerging evidence implicates functional modification of microglia in the development of LID. Thus, understanding the link between microglia and the development of LID may provide the knowledge required to preserve or promote beneficial microglial functions, even during a prolonged L-Dopa treatment. To provide novel insights into microglial functional alterations in PD pathophysiology, we characterized their density, morphology, ultrastructure, and degradation activity in the sensorimotor functional territory of the putamen, using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) cynomolgus monkeys. A subset of MPTP monkeys was treated orally with L-Dopa and developed LID similar to PD patients. Using a combination of light, confocal and transmission electron microscopy, our quantitative analyses revealed alterations of microglial density, morphology and phagolysosomal activity following MPTP intoxication that were partially normalized with L-Dopa treatment. In particular, microglial density, cell body and arborization areas were increased in the MPTP monkeys, whereas L-Dopa-treated MPTP animals presented a microglial phenotype similar to the control animals. At the ultrastructural level, microglia did not differ between groups in their markers of cellular stress or aging. Nevertheless, microglia from the MPTP monkeys displayed reduced numbers of endosomes, compared with control animals, that remained lower after L-Dopa treatment. Microglia from MPTP monkeys treated with L-Dopa also had increased numbers of primary lysosomes compared with non-treated MPTP animals, while secondary and tertiary lysosomes remained unchanged. Moreover, a decrease microglial immunoreactivity for CD68, considered a marker of phagocytosis and lysosomal activity, was measured in the MPTP monkeys treated with L-Dopa, compared with non-treated MPTP animals. Taken together, these findings revealed significant changes in microglia during PD pathophysiology that were partially rescued by L-Dopa treatment. Albeit, this L-Dopa treatment conferred phagolysosomal insufficiency on microglia in the dyskinetic Parkinsonian monkeys.

Neuroprotection and immunomodulation of progesterone in the gut of a mouse model of Parkinson's disease.

Gastrointestinal symptoms appear in Parkinson's disease patients many years before motor symptoms, suggesting the implication of dopaminergic neurones of the gut myenteric plexus. Inflammation is also known to be increased in PD. We previously reported neuroprotection with progesterone in the brain of mice lesioned with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and hypothesised that it also has neuroprotective and immunomodulatory activities in the gut. To test this hypothesis, we investigated progesterone administered to adult male C57BL/6 mice for 10 days and treated with MPTP on day 5. In an additional experiment, progesterone was administered for 5 days following MPTP treatment. Ilea were collected on day 10 of treatment and microdissected to isolate the myenteric plexus. Dopaminergic neurones were reduced by approximately 60% and pro-inflammatory macrophages were increased by approximately 50% in MPTP mice compared to intact controls. These changes were completely prevented by progesterone administered before and after MPTP treatment and were normalised by 8 mg kg-1 progesterone administered after MPTP. In the brain of MPTP mice, brain-derived neurotrophic peptide (BDNF) and glial fibrillary acidic protein (GFAP) were associated with progesterone neuroprotection. In the myenteric plexus, increased BDNF levels compared to controls were measured in MPTP mice treated with 8 mg kg-1 progesterone started post MPTP, whereas GFAP levels remained unchanged. In conclusion, the results obtained in the present study show neuroprotective and anti-inflammatory effects of progesterone in the myenteric plexus of MPTP mice that are similar to our previous findings in the brain. Progesterone is non-feminising and could be used for both men and women in the pre-symptomatic stages of the disease.

Neuroprotection and immunomodulation in the gut of parkinsonian mice with a plasmalogen precursor.

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide. It is typically associated with motor symptoms originating from the degeneration of nigrostriatal dopamine (DA) neurons. Early stages of PD have been associated with an alteration in DA production in intestinal DAergic neurons along with inflammation. Interestingly, decreased serum concentrations of ethanolamine plasmalogens (PlsEtn) have been reported in PD patients. Ethanolamine plasmalogens play a role in vesicular fusion and release during neurotransmission, and store neuroprotective polyunsaturated fatty acids, such as docosahexaenoic acid (DHA) and are strong anti-oxidants, highlighting areas of potential therapeutic interest. Docosahexaenoic acid is known to play important roles in both the central nervous and peripheral systems, in addition to acting as a precursor of several molecules that regulate the resolution of inflammation. The present study investigated the neuroprotective and anti-inflammatory properties of the DHA-containing PlsEtn precursor, PPI-1011, in the intestine of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mice. Treatment with PPI-1011 prevented the MPTP-induced decrease in PlsEtn levels. In addition it prevented the loss of tyrosine hydroxylase (TH) expression and reduced the infiltration of macrophages in the myenteric plexus of MPTP-treated mice. The protective effects of PPI-1011 were observed regardless of whether it was administered pre- or post- MPTP treatment. These results suggest that PPI-1011 has neuroprotective and anti-inflammatory properties in the gut and indicate its potential utility as a treatment for both early and more advanced stages of PD.

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'.

The plasmalogen precursor analog PPI-1011 reduces the development of L-DOPA-induced dyskinesias in de novo MPTP monkeys.

The gold standard therapy for Parkinson's disease (PD), L-3,4-dihydroxyphenylalanine (L-DOPA), induces dyskinesias in the majority of patients after years of treatment. Ethanolamine plasmalogens (PlsEtn) play critical roles in membrane structure mediated functions and as a storage depot of polyunsaturated fatty acids such as docosahexaenoic acid. We previously showed that a PlsEtn precursor PPI-1011 reduced already established L-DOPA-induced dyskinesias (LID) in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) lesioned monkeys as a PD model. We hypothesize that development of LID can be prevented with a PPI-1011 treatment in de novo MPTP-lesioned monkeys. MPTP-lesioned monkeys were treated once daily for 28days with either L-DOPA or L-DOPA+PPI-1011 (25mg/kg). The antiparkinsonian effect of L-DOPA was maintained throughout the treatment period in MPTP-lesioned monkeys treated with L-DOPA alone and L-DOPA+PPI-1011. Over the 28days of treatment, the mean dyskinesia score increased in L-DOPA-treated monkeys whereas this increase was significantly less in the L-DOPA+PPI-1011 group. This was followed by a washout period of 2 weeks of both experimental groups without treatment. Then both groups were administered once during week 7 and twice during week 8 with L-DOPA with behavioral measures recorded on treatment days. MPTP monkeys of both experimental groups administered L-DOPA in experimental week 7 showed reduced LID. During week 8, the L-DOPA group showed increased LID whereas LID remained low in the group previously treated with L-DOPA+PPI-1011. The present results suggest that PPI-1011 can prevent/delay the development of LID while maintaining the antiparkinsonian activity of L-DOPA.

Plasmalogen precursor mitigates striatal dopamine loss in MPTP mice.

Ethanolamine plasmalogens (PlsEtn) are a class of glycerophospholipids characterized by a vinyl-ether bond at the sn-1 position that play an important role in the structure and function of membranes. Previous reports have suggested a link between reduced blood and brain PlsEtn levels and Parkinson's disease (PD). We recently reported that the DHA containing plasmalogen precursor PPI-1011 protected striatal dopamine (DA) against MPTP toxicity in mice. In this paper, we further investigate the specificity requirements of the lipid side chains by testing the oleic acid-containing plasmalogen precursor PPI-1025. Male mice were treated for 10days with daily oral administration of PPI-1025 (10, 50 or 200mg/kg). On day 5 mice received MPTP and were sacrificed on Day 11. Treatment with PPI-1025 prevented MPTP-induced decrease of DA and serotonin, as well as their metabolites. In addition, PPI-1025 treatment prevented the MPTP-induced decrease of the striatal dopamine transporter (DAT) and vesicular monoamine transporter 2 (VMAT2) specific binding. Significant positive correlations were measured between striatal DA concentrations and DAT or VMAT2 specific binding, as well as with serum plasmalogen concentrations. The neuroprotective effect of PPI-1025 displayed a bell-curve dose-dependency losing effect at the highest dose tested. The similar protective response of oleic and docosahexaenoic acid (DHA)-containing plasmalogen precursors suggests that the neuroprotection observed is not only due to DHA but to the oleic substituent and the plasmalogen backbone.

Neuroprotective and immunomodulatory effects of raloxifene in the myenteric plexus of a mouse model of Parkinson's disease.

Motor symptoms in Parkinson's disease (PD) are often preceded by nonmotor symptoms related to dysfunctions of the autonomic nervous system such as constipation, defecatory problems, and delayed gastric emptying. These gastrointestinal impairments are associated with the alteration of dopaminergic (DAergic) neurons in the myenteric plexus of the gut. Recently, we demonstrated the anti-inflammatory properties of estrogens to treat intestinal neurodegeneration in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. The present study aimed to investigate the neuroprotective and anti-inflammatory roles of raloxifene, a selective estrogen receptor modulator (SERM) already commercialized for osteoporosis treatment. In MPTP-treated mice, we found that raloxifene decreased the loss of DAergic neurons and prevented the increase in proinflammatory macrophage density in the myenteric plexus. Interestingly, raloxifene activity was prevented by the G protein-coupled estrogen receptor 1 (GPER1) antagonist G15, suggesting that raloxifene effects were mainly mediated by GPER1. Moreover, monocytic cell proinflammatory polarization, nuclear factor-kappa B (NF-κB) response, nitric oxide (NO), and proinflammatory cytokines production following 1-methyl-4-phenylpyridinium (MPP+) treatment were also prevented by raloxifene in vitro. Overall, the present results suggest that raloxifene may help preventing the loss of DAergic neurons in the myenteric plexus in an MPTP mouse model of PD, at least in part through its anti-inflammatory effects. This suggests that drug repurposing of raloxifene might represent a promising therapeutic avenue to prevent systemic inflammation and peripheral neuronal dysfunction at early PD stages.

Plasmalogen Augmentation Reverses Striatal Dopamine Loss in MPTP Mice.

Plasmalogens are a class of glycerophospholipids shown to play critical roles in membrane structure and function. Decreased plasmalogens are reported in the brain and blood of Parkinson's disease (PD) patients. The present study investigated the hypothesis that augmenting plasmalogens could protect striatal dopamine neurons that degenerate in response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment in mice, a PD model. First, in a pre-treatment experiment male mice were treated for 10 days with the docosahexaenoic acid (DHA)-plasmalogen precursor PPI-1011 (10, 50 and 200 mg/kg). On day 5 mice received MPTP and were killed on day 11. Next, in a post-treatment study, male mice were treated with MPTP and then received daily for 5 days PPI-1011 (5, 10 and 50 mg/kg). MPTP treatment reduced serum plasmalogen levels, striatal contents of dopamine (DA) and its metabolites, serotonin, DA transporter (DAT) and vesicular monoamine transporter 2 (VMAT2). Pre-treatment with PPI-1011 (10 and 50 mg/kg) prevented all MPTP-induced effects. Positive correlations were measured between striatal DA contents and serum plasmalogen levels as well as striatal DAT and VMAT2 specific binding. Post-treatment with PPI-1011 prevented all MPTP-induced effects at 50 mg/kg but not at lower doses. Positive correlations were measured between striatal DA contents and serum plasmalogen levels as well as striatal DAT and VMAT2 specific binding in the post-treatment experiment. PPI-1011 treatment (10 days at 5, 10 and 50 mg/kg) of intact mice left unchanged striatal biogenic amine contents. These data demonstrate that treatment with a plasmalogen precursor is capable of protecting striatal dopamine markers in an animal model of PD.

Neuroprotective Effect of Progesterone in MPTP-Treated Male Mice.

BACKGROUND: Numerous studies have reported on the neuroprotective activity of estradiol, whereas the effect of the other ovarian steroid, progesterone, is much less documented. METHODS: This study sought to investigate neuroprotection with a low dose of progesterone (1 µg) in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated male mice to model Parkinson's disease and compare it to the effect of this steroid in intact mice (experiment 1). We also investigated if high doses of progesterone could protect dopaminergic neurons already exposed to MPTP (experiment 2). We measured progesterone effects on various dopaminergic markers [dopamine and its metabolites, dopamine transporter (DAT) and vesicular monoamine transporter 2 (VMAT2)] and on neuroactive steroids in both plasma and the brain. RESULTS: For experiment 1, our results showed that progesterone completely prevented the effect of MPTP toxicity on dopamine concentrations, on the increase in the 3-methoxytyramine/dopamine ratio, as well as on VMAT2-specific binding in the striatum and the substantia nigra. Progesterone decreased MPTP effects on 3,4-dihydroxyphenylacetic acid concentrations and DAT-specific binding in the lateral part of the anterior striatum and in the middle striatum (medial and lateral parts). Progesterone treatment of intact mice had no effect on the markers investigated. For experiment 2, measures of dopaminergic markers in the striatum showed that 8 mg/kg of progesterone was the most effective dose to reduce MPTP effects, and more limited effects were observed with 16 mg/kg. We found that progesterone treatment increases the levels of brain progesterone itself as well as of its metabolites. CONCLUSION: Our result showed that progesterone has neuroprotective effects on dopaminergic neurons in MPTP-treated male mice.

GPER1-mediated immunomodulation and neuroprotection in the myenteric plexus of a mouse model of Parkinson's disease.

Lewy pathology affects the gastrointestinal tract in Parkinson's disease (PD) and recent reports suggest a link between the disorder and gut inflammation. In this study, we investigated enteric neuroprotection and macrophage immunomodulation by 17ß-estradiol (E2) and the G protein-coupled estrogen receptor 1 (GPER1) in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse PD model. We found that both E2 and the GPER1 agonist G1 are protective against the loss of dopamine myenteric neurons and inhibited enteric macrophage infiltration in MPTP-treated mice. Coadministration of GPER1 antagonist G15, while completely blocking the neuroprotective and anti-inflammatory effects of G1 also partially prevented those of E2. Interestingly, we found that E2 and G1 treatments could directly alter MPTP-mediated immune responses independently from neurodegenerative processes. Analyses of monocyte/macrophage NF-κB and iNOS activation and FACs immunophenotype indicated that 1-methyl-4-phenylpyridinium (MPP(+)) treatment induces a strong immune response in monocytes, comparable to that of canonical challenge by lipopolysaccharide. In these cells, G1 and E2 treatment are equally potent in promoting a shift toward an anti-inflammatory "M2" immunophenotype reducing MPP(+)-induced NF-κB and iNOS activation. Moreover, G15 also antagonized the immunomodulatory effects of G1 in MPP(+)-treated macrophages. Together these data provide the first evidence for the role of GPER1 in enteric immunomodulation and neuroprotection. Considering increasing recognition for myenteric pathology as an early biomarker for PD, these findings provide a valuable contribution for better understanding and targeting of future therapeutic strategies.

The 5α-reductase inhibitor Dutasteride but not Finasteride protects dopamine neurons in the MPTP mouse model of Parkinson's disease.

Finasteride and Dutasteride are 5α-reductase inhibitors used in the clinic to treat endocrine conditions and were recently found to modulate brain dopamine (DA) neurotransmission and motor behavior. We investigated if Finasteride and Dutasteride have a neuroprotective effect in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) male mice as a model of Parkinson's disease (PD). Experimental groups included saline treated controls and mice treated with saline, Finasteride (5 and 12.5 mg/kg) or Dutasteride (5 and 12.5 mg/kg) for 5 days before and 5 days after MPTP administration (4 MPTP injections, 6.5 mg/kg on day 5 inducing a moderate DA depletion) and then they were euthanized. MPTP administration decreased striatal DA contents measured by HPLC while serotonin contents remained unchanged. MPTP mice treated with Dutasteride 5 and 12.5 mg/kg had higher striatal DA and metabolites (DOPAC and HVA) contents with a decrease of metabolites/DA ratios compared to saline-treated MPTP mice. Finasteride had no protective effect on striatal DA contents. Tyrosine hydroxylase (TH) mRNA levels measured by in situ hybridization in the substantia nigra pars compacta were unchanged. Dutasteride at 12.5 mg/kg reduced the effect of MPTP on specific binding to striatal DA transporter (DAT) and vesicular monoamine transporter 2 (VMAT2) measured by autoradiography. MPTP reduced compared to controls plasma testosterone (T) and dihydrotestosterone (DHT) concentrations measured by liquid chromatography-tandem mass spectrometry; Dutasteride and Finasteride increased plasma T levels while DHT levels remained low. In summary, our results showed that a 5α-reductase inhibitor, Dutasteride has neuroprotective activity preventing in male mice the MPTP-induced loss of several dopaminergic markers.