17β-Estradiol reduces nitrotyrosine immunoreactivity and increases SOD1 and SOD2 immunoreactivity in nigral neurons in male mice following MPTP insult

Iron-induced cytotoxicity mediated by endolysosomal TRPML1 channels is reverted by TFEB

Increased brain iron content has been consistently reported in sporadic Parkinson's disease (PD) patients, and an increase in cytosolic free iron is known to cause oxidative stress and cell death. However, whether iron also accumulates in susceptible brain areas in humans or in mouse models of familial PD remains unknown. In addition, whilst the lysosome functions as a critical intracellular iron storage organelle, little is known about the mechanisms underlying lysosomal iron release and how this process is influenced by lysosome biogenesis and/or lysosomal exocytosis. Here, we report an increase in brain iron content also in PD patients due to the common G2019S-LRRK2 mutation as compared to healthy age-matched controls, whilst differences in iron content are not observed in G2019S-LRRK2 knockin as compared to control mice. Chemically triggering iron overload in cultured cells causes cytotoxicity via the endolysosomal release of iron which is mediated by TRPML1. TFEB expression reverts the iron overload-associated cytotoxicity by causing lysosomal exocytosis, which is dependent on a TRPML1-mediated increase in cytosolic calcium levels. Therefore, approaches aimed at increasing TFEB levels, or pharmacological TRPML1 activation in conjunction with iron chelation may prove beneficial against cell death associated with iron overload conditions such as those associated with PD.

Brain Selective Estrogen Treatment Protects Dopaminergic Neurons and Preserves Behavioral Function in MPTP-induced Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is characterized by progressive degeneration of dopaminergic neurons in the substantia nigra and loss of both motor and non-motor features. Several clinical and preclinical studies have provided evidence that estrogen therapy reduces the risk of PD but have limitations in terms of adverse peripheral effects. Therefore, we examined the potential beneficial effects of the brain-selective estrogen prodrug, 10β, 17β-dihydroxyestra-1,4-dien-3-one (DHED) on nigrostriatal dopaminergic neurodegeneration and behavioral abnormalities in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. Wild-type mice were treated with daily subcutaneous injections of DHED (50 and 100 µg/kg) or vehicle for four weeks. To produce PD-like symptoms, mice were injected with MPTP (18 mg/kg in saline; intraperitoneally) four times at 2-hr intervals for one day. After behavioral examination, mice were sacrificed, and the brains were isolated for neurochemical and morphological examinations. MPTP injected mice exhibited loss of dopaminergic neurons and fibers in substantia nigra and striatum respectively, along with impaired motor function at day 7 post MPTP injection. These phenotypes were associated with significantly increased oxidative stress and inflammatory responses in the striatum regions. DHED treatments significantly mitigated behavioral impairments and dopaminergic neurodegeneration induced by MPTP. We further observed that DHED treatment suppressed oxidative stress and inflammation in the striatum of MPTP treated mice when compared to vehicle treated mice. In conclusions, our findings suggest that DHED protects dopaminergic neurons from MPTP toxicity in mouse model of PD and support a beneficial effect of brain-selective estrogen in attenuating neurodegeneration and motor symptoms in PD-related neurological disorders. Graphical Abstract.

Molecular mechanisms and cellular events involved in the neuroprotective actions of estradiol. Analysis of sex differences

Estradiol, either from peripheral or central origin, activates multiple molecular neuroprotective and neuroreparative responses that, being mediated by estrogen receptors or by estrogen receptor independent mechanisms, are initiated at the membrane, the cytoplasm or the cell nucleus of neural cells. Estrogen-dependent signaling regulates a variety of cellular events, such as intracellular Ca²⁺ levels, mitochondrial respiratory capacity, ATP production, mitochondrial membrane potential, autophagy and apoptosis. In turn, these molecular and cellular actions of estradiol are integrated by neurons and non-neuronal cells to generate different tissue protective responses, decreasing blood-brain barrier permeability, oxidative stress, neuroinflammation and excitotoxicity and promoting synaptic plasticity, axonal growth, neurogenesis, remyelination and neuroregeneration. Recent findings indicate that the neuroprotective and neuroreparative actions of estradiol are different in males and females and further research is necessary to fully elucidate the causes for this sex difference.

Effects of lipoic acid and n-3 long-chain polyunsaturated fatty acid on the liver ovariectomized rat model of menopause

BACKGROUND

Bilateral ovariectomy is an experimental model used to analyse the effects of menopause and develop strategies to mitigate the deleterious effects of this condition. Supplementation of the diet with antioxidants has been used to reduce potential oxidative stress caused by menopause. The purpose of the study was to analyse the effects of α-lipoic acid (LA), docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), dietary supplementation on oxidative stress in the livers of ovariectomized rats.

METHODS

In this study, we evaluated the effect of dietary supplementation with LA, DHA and EPA for a period of 16 weeks on oestrogen levels and oxidative stress biomarkers in the livers of ovariectomized 25 three-month-old rats.

RESULTS

Serum oestrogen levels were lower after ovariectomy but were not altered by dietary treatments. LA was capable of acting in the liver, recovering the activity of the antioxidant enzymes superoxide dismutase and glutathione peroxidase, and reducing protein oxidative damage. Moreover, LA supplementation reduced nitrite and nitrate levels. DHA and EPA recovered the antioxidant activity of cytosolic and mitochondrial superoxide dismutase, decreasing protein oxidation. Protection against lipid oxidation differed between treatments. The DHA-treated group showed increased levels of the lipid peroxidation biomarker malondialdehyde compared to the ovariectomized group. However, malondialdehyde levels were not altered by EPA treatment.

CONCLUSIONS

The results suggest that the antioxidant response varies among evaluated supplementations and all supplements were able to alter enzymatic and non-enzymatic antioxidants in the livers of ovariectomized rats. DHA presented the most evident antioxidant effect, decreasing protein and lipid damage.

Potentiation of 17β-estradiol synthesis in the brain and elongation of seizure latency through dietary supplementation with docosahexaenoic acid

Several studies have shown that docosahexaenoic acid (DHA) attenuates epileptic seizures; however, the molecular mechanism by which it achieves this effect is still largely unknown. DHA stimulates the retinoid X receptor, which reportedly regulates the expression of cytochrome P450 aromatase (P450arom). This study aimed to clarify how DHA suppresses seizures, focusing on the regulation of 17β-estradiol synthesis in the brain. Dietary supplementation with DHA increased not only the expression of P450arom, but also 17β-estradiol in the cerebral cortex. While DHA did not affect the duration or scores of the seizures induced by pentylenetetrazole, DHA significantly prolonged the seizure latency. A P450arom inhibitor, letrozole, reduced 17β-estradiol levels and completely suppressed the elongation of seizure latency elicited by DHA. These results suggest that DHA delays the onset of seizures by promoting the synthesis of 17β-estradiol in the brain. DHA upregulated the expression of anti-oxidative enzymes in the cerebral cortex. The oxidation in the cerebral cortex induced by pentylenetetrazole was significantly attenuated by DHA, and letrozole completely inhibited this suppressive action. Thus, the anti-oxidative effects of 17β-estradiol may be involved in the prevention of seizures mediated by DHA. This study revealed that 17β-estradiol in the brain mediated the physiological actions of DHA.

miR-17-3p Exacerbates Oxidative Damage in Human Retinal Pigment Epithelial Cells

Oxidative stress has been shown to contribute to the development of age-related macular degeneration (AMD). MicroRNAs (miRNA) are small non-coding RNA molecules that function in RNA silencing and post-transcriptional regulation of gene expression. We showed miR-17-3p to be elevated in macular RPE cells from AMD patients and in ARPE-19 cells under oxidative stress. Transfection of miR-17-3p mimic in ARPE-19 induced cell death and exacerbated oxidative lethality that was alleviated by miR-17-3p inhibitor. The expression of antioxidant enzymes manganese superoxide dismutase (MnSOD) and thioredoxin reductase-2 (TrxR2) were suppressed by miR-17-3p mimic and reversed by miR-17-3p inhibitor. These results suggest miR-17-3p aggravates oxidative damage-induced cell death in human RPE cells, while miR-17-3p inhibitor acts as a potential protector against oxidative stress by regulating the expression of antioxidant enzymes.

Dietary Vitamin D3 Restriction Exacerbates Disease Pathophysiology in the Spinal Cord of the G93A Mouse Model of Amyotrophic Lateral Sclerosis

Background

Dietary vitamin D₃ (D₃) restriction reduces paw grip endurance and motor performance in G93A mice, and increases inflammation and apoptosis in the quadríceps of females. ALS, a neuromuscular disease, causes progressive degeneration of motor neurons in the brain and spinal cord.

Objective

We analyzed the spinal cords of G93A mice following dietary D₃ restriction at 2.5% the adequate intake (AI) for oxidative damage (4-HNE, 3-NY), antioxidant enzymes (SOD2, catalase, GPx1), inflammation (TNF-α, IL-6, IL-10), apoptosis (bax/bcl-2 ratio, cleaved/pro-caspase 3 ratio), neurotrophic factor (GDNF) and neuron count (ChAT, SMI-36/SMI-32 ratio).

Methods

Beginning at age 25 d, 42 G93A mice were provided food ad libitum with either adequate (AI;1 IU D₃/g feed; 12 M, 11 F) or deficient (DEF; 0.025 IU D₃/g feed; 10 M, 9 F) D₃. At age 113 d, the spinal cords were analyzed for protein content. Differences were considered significant at P ≤ 0.10, since this was a pilot study.

Results

DEF mice had 16% higher 4-HNE (P = 0.056), 12% higher GPx1 (P = 0.057) and 23% higher Bax/Bcl2 ratio (P = 0.076) vs. AI. DEF females had 29% higher GPx1 (P = 0.001) and 22% higher IL-6 (P = 0.077) vs. AI females. DEF males had 23% higher 4-HNE (P = 0.066) and 18% lower SOD2 (P = 0.034) vs. AI males. DEF males had 27% lower SOD2 (P = 0.004), 17% lower GPx1 (P = 0.070), 29% lower IL-6 (P = 0.023) and 22% lower ChAT (P = 0.082) vs. DEF females.

Conclusion

D₃ deficiency exacerbates disease pathophysiology in the spinal cord of G93A mice, the exact mechanisms are sex-specific. This is in accord with our previous results in the quadriceps, as well as functional and disease outcomes.

Protective actions of 17β-estradiol and progesterone on oxidative neuronal injury induced by organometallic compounds

Steroid hormones synthesized in and secreted from peripheral endocrine glands pass through the blood-brain barrier and play a role in the central nervous system. In addition, the brain possesses an inherent endocrine system and synthesizes steroid hormones known as neurosteroids. Increasing evidence shows that neuroactive steroids protect the central nervous system from various harmful stimuli. Reports show that the neuroprotective actions of steroid hormones attenuate oxidative stress. In this review, we summarize the antioxidative effects of neuroactive steroids, especially 17β-estradiol and progesterone, on neuronal injury in the central nervous system under various pathological conditions, and then describe our recent findings concerning the neuroprotective actions of 17β-estradiol and progesterone on oxidative neuronal injury induced by organometallic compounds, tributyltin, and methylmercury.

17β-estradiol ameliorates light-induced retinal damage in Sprague-Dawley rats by reducing oxidative stress

Oxidative stress is considered as a major cause of light-induced retinal neurodegeneration. The protective role of 17β-estradiol (βE2) in neurodegenerative disorders is well known, but its underlying mechanism remains unclear. Here, we utilized a light-induced retinal damage model to explore the mechanism by which βE2 exerts its neuroprotective effect. Adult male and female ovariectomized (OVX) rats were exposed to 8,000 lx white light for 12 h to induce retinal light damage. Electroretinogram (ERG) assays and hematoxylin and eosin (H&E) staining revealed that exposure to light for 12 h resulted in functional damage to the rat retina, histological changes, and retinal neuron loss. However, intravitreal injection (IVI) of βE2 significantly rescued this impaired retinal function in both female and male rats. Based on the level of malondialdehyde (MDA) production (a biomarker of oxidative stress), an increase in retinal oxidative stress followed light exposure, and βE2 administration reduced this light-induced oxidative stress. Quantitative reverse-transcriptase (qRT)-PCR indicated that the messenger RNA (mRNA) levels of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (Gpx) were downregulated in female OVX rats but were upregulated in male rats after light exposure, suggesting a gender difference in the regulation of these antioxidant enzyme genes in response to light. However, βE2 administration restored or enhanced the SOD and Gpx expression levels following light exposure. Although the catalase (CAT) expression level was insensitive to light stimulation, βE2 also increased the CAT gene expression level in both female OVX and male rats. Further examination indicated that the antioxidant proteins thioredoxin (Trx) and nuclear factor erythroid 2-related factor 2 (Nrf2) are also involved in βE2-mediated antioxidation and that the cytoprotective protein heme oxygenase-1 (HO-1) plays a key role in the endogenous defense mechanism against light exposure in a βE2-independent manner. Taken together, we provide evidence that βE2 protects against light-induced retinal damage via its antioxidative effect, and its underlying mechanism involves the regulation of the gene expression levels of antioxidant enzymes (SOD, CAT, and Gpx) and proteins (Trx and Nrf2). Our study provides conceptual evidence in support of estrogen replacement therapy for postmenopausal women to reduce the risk of age-related macular degeneration.

Behavioral and neurotransmitter abnormalities in mice deficient for Parkin, DJ-1 and superoxide dismutase

Parkinson’s disease (PD) is a progressive neurodegenerative disease characterized by loss of neurons in the substantia nigra that project to the striatum and release dopamine. The cause of PD remains uncertain, however, evidence implicates mitochondrial dysfunction and oxidative stress. Although most cases of PD are sporadic, 5-10% of cases are caused by inherited mutations. Loss-of-function mutations in Parkin and DJ-1 were the first to be linked to recessively inherited Parkinsonism. Surprisingly, mice bearing similar loss-of-function mutations in Parkin and DJ-1 do not show age-dependent loss of nigral dopaminergic neurons or depletion of dopamine in the striatum. Although the normal cellular functions of Parkin and DJ-1 are not fully understood, we hypothesized that loss-of-function mutations in Parkin and DJ-1 render cells more sensitive to mitochondrial dysfunction and oxidative stress. To test this hypothesis, we crossed mice deficient for Parkin and DJ-1 with mice deficient for the mitochondrial antioxidant protein Mn-superoxide dismutase (SOD2) or the cytosolic antioxidant protein Cu-Zn-superoxide dismutase (SOD1). Aged Parkin^-/-DJ-1^-/- and Mn-superoxide dismutase triple deficient mice have enhanced performance on the rotorod behavior test. Cu/Zn-superoxide dismutase triple deficient mice have elevated levels of dopamine in the striatum in the absence of nigral cell loss. Our studies demonstrate that on a Parkin/DJ-1 null background, mice that are also deficient for major antioxidant proteins do not have progressive loss of dopaminergic neurons but have behavioral and striatal dopamine abnormalities.

The protective effect of 17 beta-estradiol on oxygen-induced retinopathy and its relation with the changes of malondialdehyde

Objective

Retinopathy of prematurity is becoming obvious with the improvement of neonatal ambulance. However there is still not a good treatment. The present study is to observe the effect of 17 beta-estradiol (E2) on oxygen-induced retinopathy (OIR), and explore the relationship between the changes of avascular area and malondialdehyde (MDA) in retina.

Methods

Newborn oxygen-exposed mice underwent subcutaneous injections of different dose of E2 (0.1 µg, 1.0 µg, 10.0 µg ), tamoxifen or phosphate buffered saline (PBS; controls)everyday from post-natal day (p)7 to p17. At p17, retinal flat mounts were scored for the percentage of avascular/total retinal area, and pathological changes during revascularization. The MDA concentration in the retina was determined also. In the most efficacious E2 group (10.0 µg), 100.0 µg tamoxifen was also administered, and the percentage of capillary-free/total retinal area determined, and the retinal malondialdehyde concentration assayed.

Results

The mean percentage of capillary-free area over total retinal area was 0(PBS, in room air), 34.197±1.301(PBS, in hyperoxia), 23.685±0.407 (0.1 µg E2), 14.648±0.355 (1.0 µg E2), 4.693±0.450 (10.0 µg E2) and 32.240±0.654 (10.0 µg E2 +100.0 µg tamoxifen). The difference was significant (F = 2778.759, P < 0.01), and the difference between any two groups were also significant (all P value were less than 0.01). The predilection of tufts and clusters during revascularization was mainly aggregated in zones 2 and 3, but the difference of retinal neovascular clusters and tufts in fourth zone among different groups were significant [clusters (F = 44.719, P < 0.01) vs tufts (F = 39.997, P < 0.01)]. The mean MDA concentration were 0.711±0.037(PBS, in room air), 2.084±0.066 (PBS, in hyperoxia), 1.829±0.091(0.1 µg E2), 1.152±0.067(1.0 µg E2), 0.796±0.027(10.0 µg E2), 1.988±0.049(10.0 µg E2 +100.0 µg tamoxifen) (F = 628.103, P < 0.01). The difference between any two groups were also significant (all P value were less than 0.05). The close relation between the percentage of avascular/total retinal area and MDA concentration was also verified (r = 0.981, P < 0.01).

Conclusion

Oxidative stress responses play a pivotal role in OIR, by means of receptor pathway. E2 can alleviate oxidative stress reaction, and thus ameliorate the severity of oxygen induced retinopathy.

Novel mitochondrial targets for neuroprotection

Mitochondrial dysfunction contributes to the pathophysiology of acute neurologic disorders and neurodegenerative diseases. Bioenergetic failure is the primary cause of acute neuronal necrosis, and involves excitotoxicity-associated mitochondrial Ca(2+) overload, resulting in opening of the inner membrane permeability transition pore and inhibition of oxidative phosphorylation. Mitochondrial energy metabolism is also very sensitive to inhibition by reactive O(2) and nitrogen species, which modify many mitochondrial proteins, lipids, and DNA/RNA, thus impairing energy transduction and exacerbating free radical production. Oxidative stress and Ca(2+)-activated calpain protease activities also promote apoptosis and other forms of programmed cell death, primarily through modification of proteins and lipids present at the outer membrane, causing release of proapoptotic mitochondrial proteins, which initiate caspase-dependent and caspase-independent forms of cell death. This review focuses on three classifications of mitochondrial targets for neuroprotection. The first is mitochondrial quality control, maintained by the dynamic processes of mitochondrial fission and fusion and autophagy of abnormal mitochondria. The second includes targets amenable to ischemic preconditioning, e.g., electron transport chain components, ion channels, uncoupling proteins, and mitochondrial biogenesis. The third includes mitochondrial proteins and other molecules that defend against oxidative stress. Each class of targets exhibits excellent potential for translation to clinical neuroprotection.

Manganese-induced NF-kappaB activation and nitrosative stress is decreased by estrogen in juvenile mice

Manganese toxicity can cause a neurodegenerative disorder affecting cortical and basal ganglia structures with a neurological presentation resembling features of Parkinson's disease. Children are more sensitive to Mn-induced neurological dysfunction than adults, and recent studies from our laboratory revealed a marked sensitivity of male juvenile mice to neuroinflammatory injury from Mn, relative to females. To determine the role of estrogen (E2) in mediating sex-dependent vulnerability to Mn-induced neurotoxicity, we exposed transgenic mice expressing an NF-κB-driven enhanced green fluorescent protein (EGFP) reporter construct (NF-κB-EGFP mice) to Mn, postulating that supplementing male mice with E2 during juvenile development would attenuate neuroinflammatory changes associated with glial activation, including expression of inducible nitric oxide synthase (NOS2) and neuronal protein nitration. Juvenile NF-κB-EGFP mice were separated in groups composed of females, males, and males surgically implanted with Silastic capsules containing 25 μg of 17-β-estradiol (E2) or vehicle control. Mice were then treated with 0 or 100 mg/Kg MnCl(2) by intragastric gavage from postnatal days 21-34. Manganese treatment caused alterations in levels of striatal dopamine, as well as increases in NF-κB reporter activity and NOS2 expression in both microglia and astrocytes that were prevented by supplementation with E2. E2 also decreased neuronal protein nitration in Mn-treated mice and inhibited apoptosis in striatal neurons cocultured with Mn-treated astrocytes in vitro. These data indicate that E2 protects against Mn-induced neuroinflammation in developing mice and that NF-κB is an important regulator of neuroinflammatory gene expression in glia associated with nitrosative stress in the basal ganglia during Mn exposure.

The possible role of estrogen and selective estrogen receptor modulators in a rat model of Parkinson's disease

AIM

The aim of the present study was to assess and compare the effect of 17β-estradiol and two different selective estrogen receptor modulators (SERMs), tamoxifen and raloxifene, as well as a selective estrogen receptor alpha agonist, propyl-pyrazole-triol (PPT) and a selective estrogen receptor beta agonist, diarylpropionitrile (DPN), on behavioral and biochemical alterations in 6-hydroxydopamine (6-OHDA)-induced nigral dopaminergic cell death in rats.

MAIN METHODS

80 female Wister rats were used. Animals were divided into eight equal groups: Group I; Sham operated, Group II; subjected to ovariectomy (OVX), Group III; OVX rats received striatal injection of 6-OHDA, Groups IV-VIII; OVX rats received striatal injection of 6-OHDA and were injected daily with 17β-estradiol, tamoxifen, raloxifene, PPT and DPN respectively for 5days before 6-OHDA and continued for further 2weeks.

KEY FINDINGS

Results showed that striatal injection of 6-OHDA produced significant behavioral alteration suggestive of PD, together with significant decrease in striatal dopamine, homovanillic acid (HVA) and 3,4-dihydroxyphenyl acetic acid (DOPAC) concentrations. 6-OHDA-induced nigral dopaminergic cell death was characterized by oxidative stress, evidenced by significant decrease in striatal glutathione peroxidase activity, as well as apoptosis, evidenced by significant increase in nigral caspase-3 activity. Treatment with 17β-estradiol, raloxifene, PPT, but neither tamoxifen nor DPN, resulted in significant amelioration of the behavioral and biochemical alterations induced by 6-OHDA.

SIGNIFICANCE

These findings suggest that estrogen and some SERMs having estrogenic agonist activity in the brain, like raloxifene, might exert beneficial effect in PD.

Mechanisms of estrogens' dose-dependent neuroprotective and neurodamaging effects in experimental models of cerebral ischemia

Ever since the hypothesis was put forward that estrogens could protect against cerebral ischemia, numerous studies have investigated the mechanisms of their effects. Despite initial studies showing ameliorating effects, later trials in both humans and animals have yielded contrasting results regarding the fundamental issue of whether estrogens are neuroprotective or neurodamaging. Therefore, investigations of the possible mechanisms of estrogen actions in brain ischemia have been difficult to assess. A recently published systematic review from our laboratory indicates that the dichotomy in experimental rat studies may be caused by the use of insufficiently validated estrogen administration methods resulting in serum hormone concentrations far from those intended, and that physiological estrogen concentrations are neuroprotective while supraphysiological concentrations augment the damage from cerebral ischemia. This evidence offers a new perspective on the mechanisms of estrogens’ actions in cerebral ischemia, and also has a direct bearing on the hormone replacement therapy debate. Estrogens affect their target organs by several different pathways and receptors, and the mechanisms proposed for their effects on stroke probably prevail in different concentration ranges. In the current article, previously suggested neuroprotective and neurodamaging mechanisms are reviewed in a hormone concentration perspective in an effort to provide a mechanistic framework for the dose-dependent paradoxical effects of estrogens in stroke. It is concluded that five protective mechanisms, namely decreased apoptosis, growth factor regulation, vascular modulation, indirect antioxidant properties and decreased inflammation, and the proposed damaging mechanism of increased inflammation, are currently supported by experiments performed in optimal biological settings.

Age-dependent susceptibility to manganese-induced neurological dysfunction

Chronic exposure to manganese (Mn) produces a spectrum of cognitive and behavioral deficits associated with a neurodegenerative disorder resembling Parkinson's disease. The effects of high-dose exposure to Mn in occupational cohorts and in adult rodent models of the disease are well described but much less is known about the behavioral and neurochemical effects of Mn in the developing brain. We therefore exposed C57Bl/6 mice to Mn by intragastric gavage as juveniles, adults, or both, postulating that mice exposed as juveniles and then again as adults would exhibit greater neurological and neurochemical dysfunction than mice not preexposed as juveniles. Age- and sex-dependent vulnerability to changes in locomotor function was detected, with juvenile male mice displaying the greatest sensitivity, characterized by a selective increase in novelty-seeking and hyperactive behaviors. Adult male mice preexposed as juveniles had a decrease in total movement and novelty-seeking behavior, and no behavioral changes were detected in female mice. Striatal dopamine levels were increased in juvenile mice but were decreased in adult preexposed as juveniles. Levels of Mn, Fe, and Cu were determined by inductively coupled plasma-mass spectrometry, with the greatest accumulation of Mn detected in juvenile mice in the striatum, substantia nigra (SN), and cortex. Only modest changes in Fe and Cu were detected in Mn-treated mice, primarily in the SN. These results reveal that developing mice are more sensitive to Mn than adult animals and that Mn exposure during development enhances behavioral and neurochemical dysfunction relative to adult animals without juvenile exposure.

Age- and sex-differences in the nitric oxide synthase expression and dopamine concentration in the murine model of Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

Parkinson's disease (PD) is an age- and sex-related neurodegenerative disorder of unknown aetiology. The involvement of nitric oxide synthase (NOS) in the etiopathogenesis of PD is quite well documented. We decided to examine changes in dopamine (DA) levels as well as iNOS, nNOS, eNOS mRNA and protein expression in the striatum of C57BL male and female (2- and 12-month old) mice in the course of PD-related neurodegeneration induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The significantly decreased level of DA was previously observed in male than in female, irrespective of age. In young mice the recovery of DA was significantly greater in female compared to male mice. On the contrary, both in male and female old animals the low concentration of DA was extended up to 21 days post MPTP injection. The increases in iNOS protein expression post MPTP intoxication occurred more rapidly in male (young and old) than in female mice. The pattern of changes in iNOS protein expression was also different in young versus aged mice. nNOS protein expression increased earlier in young male than young female mice. No changes were observed in eNOS expression. In conclusion, our results support the hypothesis of the involvement of iNOS and nNOS, but not eNOS in neurodegenerative processes. Our findings suggest that age- and sex-differences in DA concentration and iNOS expression as well as sex-differences of nNOS expression after intoxication may depend on the increased susceptibility of males as well as older animals to toxic effect of MPTP and aggravated process of recovery in old brains.