Dopamine Transporter Immunoreactivity Research Articles

Applications of the Dopaminergic System Expressed by Peripheral Blood Lymphocytes in Neuropsychiatric Disorders

Introduction: Dopamine (DA) is essential for the central nervous system (CNS) regulation of neurological, psychological, behavioral, and hormonal processes. Objective: In order to establish the viability of peripheral blood lymphocytes (PBL) as a molecular tool for examining DA dysregulation in neurological diseases, this research sets out to establish current characterization of the DA system in PBL. Methods: This study was carried out at Khyber teaching hospital from Jan 2022 to April 2022. Twenty-three (23) patients suffering with Parkinson's disease (PD) participated in that research (average age 56 years, mean disorder length 28 months). Nine of these participants received treatment with direct dopamine agonist medications, whereas the other 14 patients were drug-naive (levodopa-naive group). Results: Norpramin, a noradrenaline uptake blocker, established its efficacy at dosages numerous times elevated than blockers of dopamine uptake, but the serotonin uptake inhibitor Prozac was inactive. Dopamine transporter immunoreactivity levels varied significantly across groups, according to the ANOVA analysis (KW=27, P=0.001). Conclusion: PBL may function as a biological probe to identify DA transmission disruption in neuropsychiatric illnesses and to track the efficacy of pharmaceutical therapies Keywords: dopamine, dopaminergic system, peripheral blood lymphocytes, neuropsychiatric disorders

Small intestine neuromuscular dysfunction in a mouse model of dextran sulfate sodium-induced ileitis: Involvement of dopaminergic neurotransmission

AimsAnomalies in dopaminergic machinery have been shown in inflammatory bowel disease (IBD) patients and preclinical models of IBD. Thus, we aimed to evaluate the impact of dextran sodium sulfate (DSS)-induced ileitis on enteric dopaminergic pathways. Materials and methodsMale C57/Bl6 mice (10 ± 2 weeks old) received 2% DSS in drinking water for 5 days and were then switched to regular drinking water for 3 days. To measure ileitis severity inflammatory cytokines (IL-1β, TNFα, IL-6) levels were assessed. Changes in ileal muscle tension were isometrically recorded following: 1) cumulative addition of dopamine on basal tone (0.1–1000 μM); ii) 4-Hz electric field stimulation (EFS) in the presence of 30 μM dopamine with/without 10 μM SCH-23390 (dopamine D1 receptor (D1R) antagonist) or 10 μM sulpiride (D2R antagonist). Immunofluorescence distribution of the neuronal HuC/D protein, glial S100β marker, D1R, and dopamine transporter (DAT) were determined in longitudinal-muscle-myenteric plexus whole-mounts (LMMPs) by confocal microscopy. D1R and D2R mRNA transcripts were evaluated by qRT-PCR. Key findingsDSS caused an inflammatory process in the small intestine associated to dysmotility and altered barrier permeability, as suggested by decreased fecal output and enhanced stool water content. DSS treatment caused a significant increase of DAT and D1R myenteric immunoreactivity as well as of D1R and D2R mRNA levels, accompanied by a significant reduction of dopamine-mediated relaxation, involving primarily D1-like receptors. SignificanceMouse ileitis affects enteric dopaminergic neurotransmission mainly involving D1R-mediated responses. These findings provide novel information on the participation of dopaminergic pathways in IBD-mediated neuromuscular dysfunction.

Physical exercise modifies behavioral and molecular parameters related to opioid addiction regardless of training time

Addiction is a devastating worldwide disorder that requires effective and innovative therapies. Physical exercise could be useful in addiction treatment because it shares a common neural circuit with addictive drugs. Based on this, molecular adaptations consequent to time of exercise in opioid exposed animals were evaluated. Rats were designed as sedentary (SED) or exercised (EXE). This last group was separated to perform three different periods of swimming: short-term (S-EXE), medium-term (M-EXE) and long-term (L-EXE) for 14, 28 and 42 days, respectively. On the last exercising week, one-half of the animals from SED and all animals from S-, M- and l-EXE were concomitantly exposed to morphine-conditioned place preference (CPP) paradigm and y-maze task for behavioral assessments followed by molecular assays in both Nucleus accumbens (NAc) and hippocampus. Between SED groups, morphine conditioning showed drug-CPP and increased dopamine transporter (DAT), dopamine receptor type-1 (D1R), type-2 (D2R) and glucocorticoid receptor (GR) in both brain areas in relation to saline group. Besides the small morphine-CPP in relation to SED group, all periods decreased DAT, D1R, and GR immunoreactivity in NAc, DAT and D1R in hippocampus, while D2R in both brain areas and GR in hippocampus were primarily decreased by L-EXE. Our findings show that even a short-term exercise modifies behaviors related to drug withdrawal, changing DA targets and GR, which are closely linked to addiction. Therefore, our outcomes involving physical exercise are interesting to perform a possible clinical trial, thus expanding the knowledge about drug addiction.

Antibiotic-induced microbiome depletion protects against MPTP-induced dopaminergic neurotoxicity in the brain.

Although the brain–gut axis appears to play a role in the pathogenesis of Parkinson’s disease, the precise mechanisms underlying the actions of gut microbiota in this disease are unknown. This study was undertaken to investigate whether antibiotic-induced microbiome depletion affects dopaminergic neurotoxicity in the mouse brain after administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP significantly decreased dopamine transporter (DAT) immunoreactivity in the striatum and tyrosine hydroxylase (TH) immunoreactivity in the substantia nigra of water-treated mice. However, MPTP did not decrease DAT or TH immunoreactivity in the brains of mice treated with an antibiotic cocktail. Furthermore, antibiotic treatment significantly decreased the diversity and altered the composition of the host gut microbiota at the genus and species levels. Interestingly, MPTP also altered microbiome composition in antibiotic-treated mice. These findings suggest that antibiotic-induced microbiome depletion might protect against MPTP-induced dopaminergic neurotoxicity in the brain via the brain–gut axis.

Early Postnatal Exposure to Paraquat and Maneb in Mice Increases Nigrostriatal Dopaminergic Susceptibility to a Re-challenge with the Same Pesticides at Adulthood: Implications for Parkinson’s Disease

Exposure to environmental contaminants represents an important etiological factor in sporadic Parkinson's disease (PD). It has been reported that PD could arise from events that occur early in development and that lead to delayed adverse consequences in the nigrostriatal dopaminergic system at adult life. We investigated the occurrence of late nigrostriatal dopaminergic neurotoxicity induced by exposures to the pesticides paraquat (PQ) and maneb (MB) during the early postnatal period in mice, as well as whether the exposure to pesticides during development could enhance mice vulnerability to subsequent challenges. Male Swiss mice were exposed to a combination of 0.3mg/kg PQ and 1.0mg/kgMB (PQ + MB) from postnatal (PN) day 5 to 19. PN exposure to pesticides neither induced mortally nor modified motor-related parameters. However, PN pesticides exposure decreased the number of tyrosine hydroxylase (TH)- and dopamine transporter (DAT)-positive neurons in the substantia nigra pars compacta (SNpc), as well as reduced TH and DAT immunoreactivity in the striatum. A parallel group of animals developmentally exposed to the pesticides was re-challenged at 3months of age with 10mg/kg PQ plus 30mg/kgMB (twice a week, 6weeks). Mice exposed to pesticides at both periods (PN + adulthood) presented motor deficits and reductions in the number of TH- and DAT-positive neurons in the SNpc. These findings indicate that the exposure to PQ + MB during the early PN period can cause neurotoxicity in the mouse nigrostriatal dopaminergic system, rendering it more susceptible to a subsequent adult re-challenge with the same pesticides.

Neurotoxicity to dopamine neurons after the serial exposure to alcohol and methamphetamine: Protection by COX-2 antagonism

A significant co-morbidity exists between alcohol and methamphetamine (Meth) in humans but the consequences and mechanisms underlying their co-morbid effects remain to be identified. A consequence associated with the abuse of either alcohol or Meth involves inflammation but little is known about the role of inflammation in a possible neurotoxicity arising from their co-exposure. Sprague Dawley rats were allowed 28 days of intermittent, voluntary access to 10% ethanol (EtOH) followed by a neurotoxic binge administration of Meth. EtOH drinking followed by Meth increased microglial cell counts and produced morphological changes in microglia of the substantia nigra pars compacta 2 h after Meth administration that were distinct from those produced by either EtOH or Meth alone. These effects preceded the activation of cleaved caspase-3 in dopamine cell bodies, as well as decreases in tyrosine hydroxylase (TH) immunoreactivity in the substantia nigra and dopamine transporter (DAT) immunoreactivity in the striatum measured at 7 days after Meth. Intervention with a selective COX-2 inhibitor during EtOH drinking prevented the changes in microglia, and attenuated the increase in cleaved caspase-3, and decreases in TH and DAT after Meth administration. Furthermore, motor dysfunction measured by a rotarod test was evident but only in rats that were exposed to both EtOH and Meth. The motor dysfunction was ameliorated by prior inhibition of COX-2 during EtOH drinking. The exaggerated neurochemical and behavioral deficits indicate that the comorbidity of EtOH and Meth induces a degeneration of the nigrostriatal pathway and support the role of inflammation produced by EtOH drinking that primes and mediates the neurotoxic consequences associated with the common co-morbidity of these drugs.

Neuroprotective effects of acetyl-l-carnitine (ALC) in a chronic MPTP-induced Parkinson’s disease mouse model: Endothelial and microglial effects

Parkinson’s disease (PD) is a progressive motor disease with clinical features emerging due to degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc), which project to the caudate putamen (CPu) where they release dopamine (DA). The current study investigated whether acetyl-l-carnitine (ALC) could ameliorate the pathology seen in an in vivoin vivo chronic 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of PD. Four treatment groups were included: 1) CONTROL receiving probenecid (PROB; 250 mg/kg) only, 2) MPTP (25 mg/kg) + PROB, 3) MPTP + ALC (100 mg/kg), and 4) ALC alone. MPTP-induced losses in tyrosine hydroxylase and DA transporter immunoreactivity in the SNc and CPu were significantly reduced by ALC. HPLC data further suggests that decreases in CPu DA levels produced by MPTP were also attenuated by ALC. Additionally, microglial activation and astrocytic reactivity induced by MPTP were greatly reduced by ALC, indicating protection against neuroinflammation. Glucose transporter-1 and the tight junction proteins occludin and zonula occludins-1 were also protected from MPTP-induced down-regulation by ALC. Together, data suggest that in this model, ALC protects against MPTP-induced damage to endothelial cells and loss of DA neurons in the SNc and CPu, suggesting that ALC therapy may have the potential to slow or ameliorate the progression of PD pathology in a clinical setting.

Mesolimbic dopamine system and its modulation by vitamin D in a chronic mild stress model of depression in the rat

Depression, a common mood disorder, involves anhedonia and defects in reward circuits and mesolimbic dopamine transmission in the striatum and nucleus accumbens (NAc). Active vitamin-D, (1,25-(OH)2 vitamin-D3), exerts protective and regulatory effects on the brain dopamine system. In this study, key depression-like symptoms were induced in rats by chronic mild-stress (CMS) and the comparative effect of treatment with 1,25-(OH)2 vitamin-D3 (5, 10 μg/kg, or vehicle; i.p., twice weekly) or fluoxetine (5 mg/kg or vehicle, i.p., daily) on anhedonic behavior, locomotor activity and anxiety-like behavior was examined using sucrose preference test (SPT), open field test (OFT) and novel object exploration test (NOT), respectively. We also measured serum corticosterone levels and dopamine transporter-immunoreactivity (DAT-ir) levels in NAc shell and core. CMS exposure for 3 weeks was followed by a SPT and thereafter CMS was continued for 5 weeks, along with vitamin-D or fluoxetine treatment and further testing, which was concluded with another SPT. Vitamin-D treatment enhanced sucrose preference (P < 0.01; an hedonic effect) and increased object exploration (P < 0.01) in CMS rats. CMS significantly reduced the level of DAT-ir in NAc (P < 0.0001). Vitamin-D treatment restored/increased DAT-ir levels (P < 0.0001) in CMS rat NAc (core/ shell), compared to levels in fluoxetine treated and non-treated CMS rats. Vitamin-D did not alter locomotor activity or produce an anxiolytic effect in the OFT. These data suggest that similar to the antidepressant, fluoxetine, regular vitamin-D treatment can improve ‘anhedonia-like symptoms’ in rats subjected to CMS, probably by regulating the effect of dopamine-related actions in the NAc.

Ultrasound-Triggered Effects of the Microbubbles Coupled to GDNF Plasmid-Loaded PEGylated Liposomes in a Rat Model of Parkinson's Disease.

Background: The purpose of this study was to investigate ultrasound-triggered effects of PEGylated liposomes-coupled microbubbles mediated gene transfer of glial cell line-derived neurotrophic factor (GDNF) plasmid (PLs-GDNF-MBs) on behavioral deficits and neuron loss in a rat model of Parkinson's disease (PD).Methods: The unloaded PLs-MBs were characterized for particle size, concentration and zeta potential. PD rat model was established by a unilateral 6-hydroxydopamine (6-OHDA) lesion. Rotational, climbing pole, and suspension tests were used to evaluate behavioral deficits. The immunohistochemical staining of tyrosine hydroxylase (TH) and dopamine transporter (DAT) was used to assess the neuron loss. The expression levels of GDNF and nuclear receptor-related factor 1 (Nurr1) were determined by western blot and qRT-PCR analysis.Results: The particle size of PLs-MBs was gradually increased, while the concentration and absolute zeta potential were gradually decreased in a time-dependent manner after injection. 6-OHDA elevated amphetamine-induced rotations and decreased the TH and DAT immunoreactivity compared to sham group. However, these effects were blocked by the PLs-GDNF-MBs. In addition, the mRNA and protein expression levels of GDNF and Nurr1 were increased after PLs-GDNF-MBs treatment.Conclusions: The delivery of PLs-GDNF-MBs into the brains using MRI-guided focused ultrasound alleviates the behavioral deficits and neuron loss in the rat model of PD.

Ultrasound-triggered effects of the microbubbles coupled to GDNF- and Nurr1-loaded PEGylated liposomes in a rat model of Parkinson's disease.

The purpose of this study was to investigate ultrasound-triggered effects of the glial cell line-derived neurotrophic factor (GDNF) + nuclear receptor-related factor 1 (Nurr1)-polyethylene glycol (PEG)ylated liposomes-coupled microbubbles (PLs-GDNF + Nurr1-MBs) on behavioral impairment and neuron loss in a rat model of Parkinson's disease (PD). The unloaded PEGylated liposomes-coupled microbubbles (PLs-MBs) were characterized for zeta potential, particle size, and concentration. 6-hydroxydopamine (6-OHDA) was used to establish the PD rat model. Rotational, climbing pole, and suspension tests were used to detect behavioral impairment. The immunohistochemical staining of tyrosine hydroxylase (TH) and dopamine transporter (DAT) was used to assess the neuron loss. Western blot and quantitative real-time PCR (qRT-PCR) analysis were used to measure the expression levels of GDNF and Nurr1. The particle size of PLs-MBs was gradually increased, while the concentration and absolute zeta potential were gradually decreased as the time prolongs. 6-OHDA increased amphetamine-induced rotations and loss of dopaminergic neurons as compared to sham group. Interestingly, PLs-GDNF-MBs or PLs-Nurr1-MBs decreased rotations and increased the TH and DAT immunoreactivity. Combined of both genes resulted in a robust reduction in the rotations and a greater increase of the dopaminergic neurons. The delivery of PLs-GDNF + Nurr1-MBs into the brains using magnetic resonance imaging (MRI)-guided focused ultrasound may be more efficacious for the treatment of PD than the single treatment.

Methamphetamine-Induced Brain Injury and Alcohol Drinking.

A majority of methamphetamine (Meth) abusers also abuse alcohol but the neurochemical consequences of this co-abuse are unknown. Individually, alcohol and Meth cause inflammation and long-term alterations in dopamine and serotonin signaling within the brain. Experiments were conducted to identify if serial exposure to alcohol and Meth has neurochemical consequences that are greater than after either drug alone. Male Sprague Dawley rats voluntarily drank 10% ethanol (EtOH) every other day for 4weeks and were then exposed to a binge injection regimen of Meth (10mg/kg injected every 2h, for a total of 4 injections). EtOH drinking and preference increased over the 4weeks and caused inflammation evidenced by increases in serum and brain lipopolysaccharide (LPS) and brain cyclooxygenase-2 (COX-2) 24h after the last day of drinking. Meth alone depleted dopamine and serotonin in the striatum, as well as serotonin in the prefrontal cortex when measured 1week later. In contrast, EtOH drinking alone did not affect dopamine and serotonin content in the striatum and prefrontal cortex, but prior EtOH drinking followed by injections of Meth enhanced Meth-induced depletions of dopamine, serotonin, as well as dopamine and serotonin transporter immunoreactivities in a manner that was correlated with the degree of EtOH consumption. Cyclooxygenase inhibition by ketoprofen during EtOH drinking blocked the increases in LPS and COX-2 and the enhanced decreases in dopamine and serotonin produced by Meth. Therefore, prior EtOH drinking causes an increase in inflammatory mediators that mediate a synergistic interaction with Meth to cause an enhanced neurotoxicity.

Prolyl Oligopeptidase Regulates Dopamine Transporter Phosphorylation in the Nigrostriatal Pathway of Mouse.

Alpha-synuclein is the main component of Lewy bodies, a histopathological finding of Parkinson's disease. Prolyl oligopeptidase (PREP) is a serine protease that binds to α-synuclein and accelerates its aggregation in vitro. PREP enzyme inhibitors have been shown to block the α-synuclein aggregation process in vitro and in cellular models, and also to enhance the clearance of α-synuclein aggregates in transgenic mouse models. Moreover, PREP inhibitors have induced alterations in dopamine and metabolite levels, and dopamine transporter immunoreactivity in the nigrostriatal tissue. In this study, we characterized the role of PREP in the nigrostriatal dopaminergic and GABAergic systems of wild-type C57Bl/6 and PREP knockout mice, and the effects of PREP overexpression on these systems. Extracellular concentrations of dopamine and protein levels of phosphorylated dopamine transporter were increased and dopamine reuptake was decreased in the striatum of PREP knockout mice, suggesting increased internalization of dopamine transporter from the presynaptic membrane. Furthermore, PREP overexpression increased the level of dopamine transporters in the nigrostriatal tissue but decreased phosphorylated dopamine transporters in the striatum in wild-type mice. Our results suggest that PREP regulates the function of dopamine transporter, possibly by controlling the phosphorylation and transport of dopamine transporter into the striatum or synaptic membrane.

Pharmacologic antagonism of dopamine receptor D3 attenuates neurodegeneration and motor impairment in a mouse model of Parkinson's disease

Neuroinflammation involves the activation of glial cells, which is associated to the progression of neurodegeneration in Parkinson's disease. Recently, we and other researchers demonstrated that dopamine receptor D3 (D3R)-deficient mice are completely refractory to neuroinflammation and consequent neurodegeneration associated to the acute intoxication with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). In this study we examined the therapeutic potential and underlying mechanism of a D3R-selective antagonist, PG01037, in mice intoxicated with a chronic regime of administration of MPTP and probenecid (MPTPp). Biodistribution analysis indicated that intraperitoneally administered PG01037 crosses the blood-brain barrier and reaches the highest concentration in the brain 40 min after the injection. Furthermore, the drug was preferentially distributed to the brain in comparison to the plasma. Treatment of MPTPp-intoxicated mice with PG01037 (30 mg/kg, administrated twice a week for five weeks) attenuated the loss of dopaminergic neurons in the substantia nigra pars compacta, as evaluated by stereological analysis, and the loss of striatal dopaminergic terminals, as determined by densitometric analyses of tyrosine hydroxylase and dopamine transporter immunoreactivities. Accordingly, the treatment resulted in significant improvement of motor performance of injured animals. Interestingly, the therapeutic dose of PG01037 exacerbated astrogliosis and resulted in increased ramification density of microglial cells in the striatum of MPTPp-intoxicated mice. Further analyses suggested that D3R expressed in astrocytes favours a beneficial astrogliosis with anti-inflammatory consequences on microglia. Our findings indicate that D3R-antagonism exerts a therapeutic effect in parkinsonian animals by reducing the loss of dopaminergic neurons in the nigrostriatal pathway, alleviating motor impairments and modifying the pro-inflammatory phenotype of glial cells.

Differences in Number of Midbrain Dopamine Neurons Associated with Summer and Winter Photoperiods in Humans.

Recent evidence indicates the number of dopaminergic neurons in the adult rodent hypothalamus and midbrain is regulated by environmental cues, including photoperiod, and that this occurs via up- or down-regulation of expression of genes and proteins that are important for dopamine (DA) synthesis in extant neurons (‘DA neurotransmitter switching’). If the same occurs in humans, it may have implications for neurological symptoms associated with DA imbalances. Here we tested whether there are differences in the number of tyrosine hydroxylase (TH, the rate-limiting enzyme in DA synthesis) and DA transporter (DAT) immunoreactive neurons in the midbrain of people who died in summer (long-day photoperiod, n = 5) versus winter (short-day photoperiod, n = 5). TH and DAT immunoreactivity in neurons and their processes was qualitatively higher in summer compared with winter. The density of TH immunopositive (TH+) neurons was significantly (~6-fold) higher whereas the density of TH immunonegative (TH-) neurons was significantly (~2.5-fold) lower in summer compared with winter. The density of total neurons (TH+ and TH- combined) was not different. The density of DAT+ neurons was ~2-fold higher whereas the density of DAT- neurons was ~2-fold lower in summer compared with winter, although these differences were not statistically significant. In contrast, midbrain nuclear volume, the density of supposed glia (small TH- cells), and the amount of TUNEL staining were the same in summer compared with winter. This study provides the first evidence of an association between environmental stimuli (photoperiod) and the number of midbrain DA neurons in humans, and suggests DA neurotransmitter switching underlies this association.

376. Overexpression of Pitx3 in the SNpc and Protection from MPTP Toxicity

In the brain, expression of the transcription factor Pituitary Homeobox 3 or Paired-Like Homeodomain Transcription Factor 3 (PITX3) is crucial to the development and maintenance of dopaminergic neurons. During brain development, PITX3 functions in concert with the transcription factors NURR1 and LMX1b to facilitate dopaminergic neuron maturation. In the mature brain, PITX3 promotes the dopaminergic phenotype by positively regulating tyrosine hydroxylase (TH), dopamine transporter (DAT), and vesicular monoamine transporter 2 (VMAT2), either singly or in concert with NURR1. PITX3 also positively regulates expression of the pro-survival factors brain-derived neurotrophic factor (BDNF) and glial-derived neurotropic factor (GDNF). PITX3 is endogenously expressed in the dopaminergic neurons of the substantia nigra pars compacta (SNpc) and ventral tegmental area (VTA). However, in Pitx3 null mouse models, perturbations of cell number are observed only in the SNpc, a situation that resembles the relative sparing of the VTA in early-stage Parkinson's disease (PD). Systemic administration of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) results in the degeneration of SN dopaminergic neurons via a mechanism thought to involve the inhibition of mitochondrial respiration and the generation of reactive oxygen species, both of which are implicated in the pathogenesis of PD. Recent work in muscle demonstrates that PITX3 regulates expression of antioxidant enzymes and genes involved in mitochondrial biogenesis via the transcription factor NRF1. We have overexpressed murine Pitx3 (or mCherry control) from the CMV promoter in the SN of C57BL/6J mice using an AAV2/10 viral vector, and tested for neuroprotection in a sub-chronic MPTP model of PD (5 × 20 mg/kg MPTP over 9 days) by assaying for striatal dopamine, stratial TH and DAT immunoreactivity, and SN neuronal number. We will present results from these assays and changes in expression of Pitx3 target genes (TH, DAT, VMAT2, BDNF and GDNF) after Pitx3 overexpression in the SN.

Progressive Axonal Degeneration of Nigrostriatal Dopaminergic Neurons in Calcium-Independent Phospholipase A2β Knockout Mice.

Calcium-independent phospholipase A2β (iPLA2β, PLA2G6) is essential for the remodeling of membrane glycerophospholipids. Mutations in this gene are responsible for autosomal recessive, young onset, L-dopa-responsive parkinsonism (PARK14), suggesting a neurodegenerative condition in the nigrostriatal dopaminergic system in patients with PLA2G6 mutations. We previously observed slowly progressive motor deficits in iPLA2β-knockout (KO) mice. To clarify whether a deficiency of iPLA2β leads to the degeneration of nigrostriatal dopaminergic neurons, we analyzed the striatum of iPLA2β-KO mice. At all clinical stages, nerve terminals in the striatum were immunopositive for tyrosine hydroxylase (TH) and dopamine transporter (DAT) in wild-type (WT) control mice. In iPLA2β-KO mice, focal loss of nerve terminals positive for TH and DAT was found from 56 weeks (early clinical stage), although iPLA2β-KO mice at 56 weeks showed no significant decrease in the number of dopaminergic neurons in the substantia nigra compared with age-matched WT mice, as reported previously. At 100 weeks (late clinical stage), greater decreases in DAT immunoreactivity were observed in the striatum of iPLA2β-KO mice. Moreover, strongly TH-positive structures, presumed to be deformed axons, were observed in the neuropils of the striatum of iPLA2β-KO mice starting at 15 weeks (preclinical stage) and increased with age. These results suggest that the degeneration of dopaminergic neurons occurs mainly in the distal region of axons in iPLA2β-KO mice.

Succinobucol, a Non-Statin Hypocholesterolemic Drug, Prevents Premotor Symptoms and Nigrostriatal Neurodegeneration in an Experimental Model of Parkinson's Disease.

Parkinson's disease (PD) is a neurodegenerative disorder characterized by non-motor and motor disabilities. This study investigated whether succinobucol (SUC) could mitigate nigrostriatal injury caused by intranasal 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) administration in mice. Moreover, the effects of SUC against MPTP-induced behavioral impairments and neurochemical changes were also evaluated. The quantification of tyrosine hydroxylase-positive (TH+) cells was also performed in primary mesencephalic cultures to evaluate the effects of SUC against 1-methyl-4-phenylpyridinium (MPP+) toxicity in vitro. C57BL/6 mice were treated with SUC (10mg/kg/day, intragastric (i.g.)) for 30days, and thereafter, animals received MPTP infusion (1mg/nostril) and SUC treatment continued for additional 15days. MPTP-infused animals displayed significant non-motor symptoms including olfactory and short-term memory deficits evaluated in the olfactory discrimination, social recognition, and water maze tasks. These behavioral impairments were accompanied by inhibition of mitochondrial NADH dehydrogenase activity (complex I), as well as significant decrease of TH and dopamine transporter (DAT) immunoreactivity in the substantia nigra pars compacta and striatum. Although SUC treatment did not rescue NADH dehydrogenase activity inhibition, it was able to blunt MPTP-induced behavioral impairments and prevented the decrease in TH and DAT immunoreactivities in substantia nigra (SN) and striatum. SUC also suppressed striatal astroglial activation and increased interleukin-6 levels in MPTP-intoxicated mice. Furthermore, SUC significantly prevented the loss of TH+ neurons induced by MPP+ in primary mesencephalic cultures. These results provide new evidence that SUC treatment counteracts early non-motor symptoms and neurodegeneration/neuroinflammation in the nigrostriatal pathway induced by intranasal MPTP administration in mice by modulating events downstream to the mitochondrial NADH dehydrogenase inhibition.

The Persistent Neurotoxic Effects of Methamphetamine on Dopaminergic and Serotonergic Markers in Male and Female Rats.

Methamphetamine (METH) is a highly addictive substance abused world-wide in both males and females. Preclinical studies in male rodents suggest that large-dose exposure to METH can lead to persistent neurotoxic consequences to various brain regions. However, little research has focused on the potential role of sex in the neurotoxic consequences of METH exposure. The current study exposed male and female rats to large-doses of METH (4 injections of 7.5 mg/kg) or saline. Hyperthermia was promoted in the females exposed to METH such that similar hyperthermia occurred in males and females. Rats were sacrificed 8 d later and neurochemical changes were assessed in the striatum, hippocampus, frontal cortex and olfactory bulbs. Results revealed that male and female rats exposed to METH had similar decreases in dopamine (DA) transporter (DAT) immunoreactivity in the striatum, serotonin (5-HT) content and 5-HT transporter (SERT) function in the hippocampus, and 5-HT content in the frontal cortex. However, female rats exposed to METH had greater decreases in 5-HT content in the olfactory bulbs compared to sex-matched controls while male rats exposed to METH did not significantly differ from sex-matched controls. These findings suggest that when similar hyperthermia is maintained between male and female rats exposed to METH, the neurotoxic effects of METH were similar in some, but not all brain regions.

Behavioral and neurochemical effects induced by reserpine in mice.

Reserpine, a monoamine-depleting agent, which irreversibly and non-selectively blocks the vesicular monoamine transporter, has been used as an animal model to study several neurological disorders, including tardive dyskinesia and Parkinson's disease. The purpose of this study was to examine if motor deficits induced by reserpine in mice could be related to alterations in the expression of dopaminergic system proteins such as tyrosine hydroxylase (TH) and dopamine transporter (DAT) and in the activity of monoamine oxidase (MAO). Mice received either vehicle or reserpine (0.1, 0.5, or 1 mg/kg, s.c.) for four consecutive days. Two, 20, or 60 days after reserpine withdrawal, behavioral, and neurochemical changes were evaluated. Reserpine at a dose of 0.5 and 1 mg/kg increased vacuous chewing movements (VCMs) and reduced locomotion. Behavioral changes were accompanied by reduction in TH immunoreactivity in the striatum evaluated on days 2 and 20 after the last injection of 1 mg/kg reserpine. Furthermore, negative correlations were found between VCM and MAO-A or MAO-B on day 2 and TH striatal immunoreactivity on day 20 after the last injection of 1 mg/kg reserpine. A positive correlation was observed between VCMs and DAT immunoreactivity in the substantia nigra on day 2 after the last injection of 0.5 mg/kg reserpine. These findings suggest that the pharmacological blockage of vesicular monoamine transporter (VMAT) by reserpine caused neurochemical and behavioral alterations in mice.

Fenpropathrin, a Widely Used Pesticide, Causes Dopaminergic Degeneration.

Fenpropathrin is one of the widely used pyrethroids in agriculture and household and also reported to have neurotoxic effects in rodent models. In our Parkinson's disease (PD) clinic, there was a unique patient with a history of daily exposure to fenpropathrin for 6 months prior to developing Parkinsonian symptoms progressively. Since whether fenpropathrin is related to any dopaminergic degeneration was unknown, we aimed in this study to evaluate the neurotoxic effects of fenpropathrin on the dopaminergic system and associated mechanisms in vitro and in vivo. In cultured SH-SY5Y cells, fenpropathrin caused cell death, reactive oxygen species generation, Lewy body-associated proteins aggregation, and Lewy body-like intracytoplasmic inclusions formation. In rodent animals, two different injections of fenpropathrin were used for administrations, intraperitoneal (i.p), or stereotaxical (ST). The rats exhibited lower number of pokes 60 days after first i.p injection, while the rats in ST group showed a significant upregulation of apomorphine-evoked rotations 60 days after first injection. Decreased tyrosine hydroxylase (TH) and vesicular monoamine transporter 2 (VMAT2) immunoreactivity, while increased dopamine transporter (DAT) immunoreactivity were observed in rats of either i.p or ST group 60 days after the last exposure to fenpropathrin. However, the number of TH-positive cells in the substantia nigra was more reduced 120 days after the first i.p injection than those of 60 days. Our data demonstrated that exposure to fenpropathrin could mimic the pathologic and pathogenetic features of PD especially in late onset cases. These results imply fenpropathrin as a DA neurotoxin and a possible environmental risk factor for PD.