Estrogen enhances the number of nigral dopaminergic neurons of adult male mice without affecting nigral neuroglial number and morphology

Age-related effects and gender differences in Japanese healthy controls for [123I] FP-CIT SPECT

OBJECTIVE

Dopamine transporter (DAT) imaging with [¹²³I]FP-CIT (DaTSCAN) is a widely used diagnostic tool for Parkinsonism and dementia. Since it was approved by the Japanese Ministry of Health, Labor, and Welfare in 2013, there have been no articles focusing on a Japanese normal population. The aim of this study was to examine the effect of aging and gender on DAT availability in Japanese people.

METHODS

SPECT imaging of 30 healthy Japanese controls (17 males, 13 females; range 50-86 years, mean 70 years) was performed. SPECT images were reconstructed using a three-dimensional order subset expectation maximization (OSEM) algorithm with correction of the point spread function and scatter correction, without attenuation correction. The specific binding ratio (SBR) was calculated by DATview software. Statistical analyses were performed using linear regression analysis, analysis of variance, and multiple comparison analysis.

RESULTS

A strong correlation between the SBR and age was observed. The correlation coefficient in males and females were -0.566 and -0.502, respectively. The analysis of variance revealed that aging led to a decline of the SBR, and a significant difference (p = 0.005) was observed among generations. Gender also affected the SBR, and there was a significant difference between males and females (p = 0.036). The SBR in females was higher than in males. Consequently, the multiple comparison revealed a significant difference between 50s and 70s (p = 0.015) and 50s and 80s (p = 0.006).

CONCLUSIONS

This is the first [¹²³I]FP-CIT SPECT study on subjects with normal dopamine function in Asian countries. This study provides a database of [¹²³I]FP-CIT SPECT in Japanese healthy controls. Higher DAT availability was found in women than in men. An average age-related decline in DAT availability of 8.9% was found in both genders. The data collected in this study would be helpful for Japanese physicians to make a differential diagnosis in Parkinsonian syndrome. The registration identification number for this study is UMIN000018045.

Estrogen modulation of calretinin and BDNF expression in midbrain dopaminergic neurons of ovariectomised mice

Estrogen attenuates the loss of dopamine neurons from the substantia nigra in animal models of Parkinson's disease (PD) and excitatory amino-acid induced neurotoxicity by interactions with brain-derived neurotrophic factor (BDNF), and calretinin (CR) containing dopaminergic (DA) neurons. To examine this interaction more closely, we treated the ovariectomised (OVX) mice with estrodial for 10days, and compared these mice to those OVX mice injected with the vehicle or control mice. Estrogen treatment in OVX mice had significantly more tyrosine hydroxylase (TH) positive neurons in the substantia nigra pars compacta (SNpc). Dopamine transporter (DAT) mRNA and BDNF mRNA levels in the midbrain were also significantly increased by estrogen treatment (P<0.05). OVX markedly decreased the number of TH/CR double stained cells in the SNpc (P<0.05), a trend which could be reversed by estrogen treatment. However, the number of GFAP positive cells in the substantia nigra did not show significant changes (P >0.05) after vehicle or estrodial treatment. Furthermore, we found that estrogen treatment abrogated the OVX-induced decrease in the phosphorylated AKT (p-AKT), but not p-ERK. We hypothesize that short-term treatment with estrogen confers neuroprotection to DA neurons by increasing CR in the DA neurons and BDNF in the midbrain, which possibly related to activation of the PI3K/Akt signaling pathway.

Reproductive life characteristics in females affected with Parkinson's disease and in healthy control subjects - a comparative study on Polish population

BACKGROUND

Sex and blood level of sex hormones play a key role not only in the susceptibility to develop Parkinson's disease (PD) but also influence the natural course of the disease. The aim of this study was to compare reproductive lifespan events in females affected with PD and in "non-parkinsonian" age matched subjects and to evaluate whether the whole life endogenous oestrogen level is associated with variables describing the course of the disease.

MATERIALS AND METHODS

Reproductive lifespan, age at menarche, age at menopause, gynaecological interventions and parity were compared in 76 women with idiopathic PD and in the age-adjusted control group of 74 subjects. Affected women underwent neurological and psychological assessment. Data were analysed using Mann-Whitney U Test and Spearman Rank Correlation Test.

RESULTS

Women affected with PD had a shorter reproductive lifespan and experienced final menstruation earlier than the control group. Early menopause was reported by 24% of the patients and only by 16% of the control subjects. Parkinsonian women reported more commonly the history of surgical menopause. Duration of reproductive lifespan, age at menopause and the type of menopause influenced both motor and cognitive functioning of patients.

CONCLUSIONS

There may be a relationship between the lifetime average endogenous oestrogen level and the susceptibility to develop PD. Longer reproductive lifespan resulting in higher "whole life" female sex steroids concentrations may exert a protective effect on central nervous system, resulting in milder course of the disease.

Dangguijakyak-san protects dopamine neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity under postmenopausal conditions

Dangguijakyak-san protects dopamine neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity under postmenopausal conditions.

ETHNOPHARMACOLOGICAL RELEVANCE

Dangguijakyak-san (DJS), a famous traditional herbal formula, has long been used to treat gynecological disorders, including postmenopausal symptoms. This study evaluated the effects and mechanism of DJS on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity in a postmenopausal mouse model induced by ovariectomy.

MATERIALS AND METHODS

Three weeks after ovariectomy, C57bl/6 female mice were divided randomly into (1) control, (2) MPTP (30 mg/kg/day, i.p., 5 days), (3) MPTP+estrogen (50 μg/kg/day, i.p., 5 days), and (4) MPTP+DJS (50 mg/kg/day, p.o., 5 days) groups. We investigated the behavioral recovery and dopamine neuron protection of DJS using the pole test and tyrosine hydroxylase (TH) immunohistochemistry. We also explored the mechanism by assessing the protein expression of Bax, Bcl-2, cytochrome c, and cleaved caspase-3.

RESULTS

DJS treatment restored the movement behavior impaired by MPTP, showing a similar or better effect than estrogen. DJS protected TH-immunoreactive cells and fibers in the nigrostriatal region from MPTP toxicity. In addition, DJS inhibited the Bcl-2 decrease and Bax increase in mitochondria, cytochrome c release to the cytosol, and caspase-3 activation induced by MPTP.

CONCLUSIONS

DJS showed behavior recovery and dopamine neuron protection against MPTP-induced toxicity via anti-apoptotic activities in ovariectomized female mice. These results suggest that DJS treatment is effective for postmenopausal neurodegenerative diseases.

Oestrogen receptors and signalling pathways: implications for neuroprotective effects of sex steroids in Parkinson's disease

Parkinson's disease (PD) is an age-related neurodegenerative disorder with a higher incidence in the male population. In the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD, 17β-oestradiol but not androgens were shown to protect dopamine (DA) neurones. We report that oestrogen receptors (ER)α and β distinctly contribute to neuroprotection against MPTP toxicity, as revealed by examining the membrane DA transporter (DAT), the vesicular monoamine transporter 2 (VMAT2) and tyrosine hyroxylase in ER wild-type (WT) and knockout (ERKO) C57Bl/6 male mice. Intact ERKOβ mice had lower levels of striatal DAT and VMAT2, whereas ERKOα mice were the most sensitive to MPTP toxicity compared to WT and ERKOβ mice and had the highest levels of plasma androgens. In both ERKO mice groups, treatment with 17β-oestradiol did not provide neuroprotection against MPTP, despite elevated plasma 17β-oestradiol levels. Next, the recently described membrane G protein-coupled oestrogen receptor (GPER1) was examined in female Macaca fascicularis monkeys and mice. GPER1 levels were increased in the caudate nucleus and the putamen of MPTP-monkeys and in the male mouse striatum lesioned with methamphetamine or MPTP. Moreover, neuroprotective mechanisms in response to oestrogens transmit via Akt/glycogen synthase kinase-3 (GSK3) signalling. The intact and lesioned striata of 17β-oestradiol treated monkeys, similar to that of mice, had increased levels of pAkt (Ser 473)/βIII-tubulin, pGSK3 (Ser 9)/βIII-tubulin and Akt/βIII-tubulin. Hence, ERα, ERβ and GPER1 activation by oestrogens is imperative in the modulation of ER signalling and serves as a basis for evaluating nigrostriatal neuroprotection.

WITHDRAWN: Effect of phytoestrogen isoflavone on MPP(+)-induced apoptosis in PC12 cells

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.bionut.2010.09.004. The duplicate article has therefore been withdrawn.

Androgen decreases dopamine neurone survival in rat midbrain

Clinical studies show that men are more likely to develop disorders affecting midbrain dopaminergic pathways, such as drug addiction and Parkinson's disease (PD). Although a great deal of focus has been given to the role of oestrogen in the maintenance of midbrain dopaminergic pathways, little is known about how testosterone influences these pathways. In the present study, we used stereological analysis of tyrosine hydroxylase-immunoreactive (TH-IR) cell bodies to determine how testosterone influences the dopaminergic cell bodies of the substantia nigra pars compacta (SNpc) and ventral tegmental area (VTA). Rats and mice were castrated at postnatal day (PN) 60, and these midbrain cell populations were counted on PN 90. One month after castration, TH-IR cell number had increased in the SNpc and VTA of rats and mice. Replacement with testosterone or the non-aromatisable analogue dihydrotestosterone (DHT) in castrated animals reduced TH-IR cell number in the SNpc and VTA in rats. In mice, the decrease of TH-IR cell number with testosterone or DHT replacement was observed only in the SNpc. The apparent increase in TH-IR neurone number after castration is not explained by an increase in TH expression because the number of nondopaminergic cells (TH-immunonegative, TH-IN) did not decrease proportionally after castration. TH-IN cell number did not change after castration or hormone replacement in rat or mouse SNpc or VTA. These findings suggest that testosterone may play a suppressive role in midbrain dopaminergic pathways.

Does estrogen receptor gene polymorphism play a role in Parkinson's disease?

This study was designed to investigate the frequency of estrogen receptor (ER) gene polymorphism in Chinese patients with Parkinson's disease (PD). Polymerase chain reaction (PCR) method and restriction fragment length polymorphism (RFLP) were used to detect the ER gene polymorphisms in 158 PD patients and 146 healthy controls. In the PD and control groups, "x" accounted for 83.5% and 80.8%, respectively (P>0.05). "xx" was found in 77.2% of the PD group and in 69.9% of the control group (P>0.05). The frequency of "p" in the PD and control group was 67.7% and 64.0%, respectively (P>0.05). "pp" was 51.9% in the PD group and 43.8% in the control group (P>0.05). "ppxx" was found in 49.4% of the PD and 43.0% of the control subjects (P>0.05). There was no significant difference in the "x", "xx", "p", "pp" or "ppxx" between males and females within the PD or control groups. In conclusion, we found no significant differences in the genotype or allele frequencies between patients with Parkinson's disease and healthy subjects. These findings suggest that the estrogen receptor gene polymorphism may not play a key role in the pathogenesis PD in Chinese patients.

Circuit-based framework for understanding neurotransmitter and risk gene interactions in schizophrenia

Many risk genes interact synergistically to produce schizophrenia and many neurotransmitter interactions have been implicated. We have developed a circuit-based framework for understanding gene and neurotransmitter interactions. NMDAR hypofunction has been implicated in schizophrenia because NMDAR antagonists reproduce symptoms of the disease. One action of antagonists is to reduce the excitation of fast-spiking interneurons, resulting in disinhibition of pyramidal cells. Overactive pyramidal cells, notably those in the hippocampus, can drive a hyperdopaminergic state that produces psychosis. Additional aspects of interneuron function can be understood in this framework, as follows. (i) In animal models, NMDAR antagonists reduce parvalbumin and GAD67, as found in schizophrenia. These changes produce further disinhibition and can be viewed as the aberrant response of a homeostatic system having a faulty activity sensor (the NMDAR). (ii) Disinhibition decreases the power of gamma oscillation and might thereby produce negative and cognitive symptoms. (iii) Nicotine enhances the output of interneurons, and might thereby contribute to its therapeutic effect in schizophrenia.