Parkinson's disease and α-synuclein expression

Genetic studies of Parkinson's disease over the last decade or more have revolutionized our understanding of this condition. α-Synuclein was the first gene to be linked to Parkinson's disease, and is arguably the most important: the protein is the principal constituent of Lewy bodies, and variation at its locus is the major genetic risk factor for sporadic disease. Intriguingly, duplications and triplications of the locus, as well as point mutations, cause familial disease. Therefore, subtle alterations of α-synuclein expression can manifest with a dramatic phenotype. We outline the clinical impact of α-synuclein locus multiplications, and the implications that this has for Parkinson's disease pathogenesis. Finally, we discuss potential strategies for disease-modifying therapies for this currently incurable disorder.     

Pericentrin expression in Down’s syndrome

Down’s syndrome (DS) is the most frequent genetic cause of intellectual disability and is a chromosomal abnormality of chromosome 21 trisomy. The pericentrin gene (PCNT) has sequenced in 21q22.3 inside of the minimal critical region for Down’s syndrome. Alterations of PCNT gene are associated with dwarfism, cardiomyopathy and other pathologies. In this study, we have evaluated the possible differential expression of PCNT mRNA, by qRT-PCR, in peripheral blood leukocytes of DS subjects compared with the normal population. In the present case–control study, PCNT gene expression was increased by 72.72 % in 16 out 22 DS samples compared with normal subjects. Our data suggest that changes in the expression levels of PCNT in DS subjects may be involved into the molecular mechanism of Down’s syndrome.     

Apopotic gene Bax expression in carotid plaque

The expression of BAX in carotid atherosclcrosis and its regulation is far from defined. Objectives To investigate BAX expression in stable/fibrous and instable/vulnerable carotid plaque and its clinical significance. Methods 25 cases of carotid plaque specimens obtained from endarterectomy were divided into two groups, stable/fibrous 14 cases, vulnerable/instable 11 cases; aortic artery and its branches from hepatic transplantation donors 6 case as control. The expression of proapoptotic BAX was detected by immunohistochemistry (IHC), in situ hybridization(ISH) and in situ TdT dUTP nick end labeling (TUNEL). Results 5 eases of BAX ( ) were detected by ICH and ISH, 4 case of TUNEL ( ) were detected by TUNEL in stable/fibrous carotid plaque, while 10 cases were BAX ( )by IHC(P<0.05) , 11 case by ISH and 9 case by TUNEL were detected in instable/vulnerable carotid plaque (P<0.01), respectively. The intensity of BAX ( ) cells by IHC and ISH was 8.63±2.62 and 10.32±3.12 in fibrous plaques, whereas 122±21.64 and 152±23.35 in vulnerable plaques, respectively. No expression of BAX was found in controlled group. Conclusion The higher expression of Bax in vulnerable carotid plaque may be one mechanisms in molecular pathogenesis of carotid atherosclerosis which affect plaque stability and be the cause of higher incidence of stroke than fibrous carotid plaques, the regulation of BAX expression in different stage of atherosclerosis may provide targets in gene therapy for carotid atherosclerosis.     

Increased caveolin-1 expression precedes decreased expression of occludin and claudin-5 during blood–brain barrier breakdown

The significance of caveolin-1, a major constituent of caveolae, and the tight junction proteins occludin and claudin-5 in early blood–brain barrier (BBB) breakdown was assessed by sequential demonstration of the expression of these proteins over a period of 12 h to 6 days post-lesion in the rat cortical cold injury model. Pial and intracerebral vessels of control rats showed punctuate endothelial immunoreactivity for caveolin-1 and caveolin-2, while claudin-5 and occludin were localized as longitudinal strands in endothelium. During the early phase of BBB breakdown following injury at 12 h and on day 2, western blot analyses detected a significant increase in caveolin-1 expression at the lesion site while immunohistochemistry showed that the caveolin-1 increase was localized to the endothelium of lesion vessels. Decreased expression of occludin occurred at the lesion site only on days 2 and 4 post-lesion while claudin-5 expression was decreased only on day 2. Dual labeling for fibronectin, a marker of BBB breakdown, and caveolin-1 or the tight junction proteins demonstrated that only lesion vessels with BBB breakdown showed a marked increase of caveolin-1, loss of occludin and reduced localization of claudin-5. The issue whether these alterations precede or follow BBB breakdown is uncertain; however, increased expression of caveolin-1 preceded the decreased expression of occludin and claudin-5. Thus caveolae and caveolin-1 have an important role in early BBB breakdown and could be potential therapeutic targets in the control of early brain edema.     

GFAP expression withdraws--a trend of glial evolution?

This study is a summary of investigations in the last decade with several collaborators on representatives of different vertebrate stocks. The results suggest that in the main vertebrate stocks (Agnathi, Chondrichthyes, Actinopterygii, Sarcopterygii-Amniotes), which had their parallel brain evolutions from the laminar brains to the elaborated ones, the astroglia also developed in parallel, and had a common trend of evolution. With growing brain complexity, free astrocytes arose and tended to predominate, and the spontaneous glial fibrillary acidic protein (GFAP)-expression regressed, in several areas. In the mammalian, avian, teleost, and batoid brains, therefore, large areas display a paucity, almost a lack of GFAP-immunoreactivity. The GFAP-expression in the GFAP-free areas seems to be inducible only in the presence of free astrocytes.     

Regulation of α-synuclein expression in Down syndrome

The triplication of genes located on chromosome 21 is known to cause a wide spectrum of pathology seen in Down syndrome (DS), including leukemia, seizures, stroke, and mental retardation. Studies on RNA and protein expression of genes in DS brain have demonstrated the role of triplicated genes in several DS phenotypes. Significant changes in the expression of nontriplicated genes have also been observed. However, little information is available regarding the role of nonchromosome 21 genes in DS pathology. We have found that α-synuclein (SNCA), a presynaptic protein whose gene is located on chromosome 6 in the Ts65Dn mouse model for DS, is significantly reduced in the cortex and other brain regions. We hypothesize that this alteration may play a critical role in the reduced synaptic function observed in DS. We have found an increase in the level of neurosin, a key negative regulator of SNCA in Ts65Dn cortex. We have also found increased levels of protein phosphatase 2A, a negative regulator of the activation of tyrosine hydroxylase and a key enzyme in the biosynthetic pathway for dopamine in Ts65Dn cortex. These findings reveal potential target sites for intervention in the treatment of DS pathology.     

Dopamine-1 receptor agonist, but not cocaine, modulates σ1 gene expression in SVG cellsgene expression in SVG cells

It has been hypothesized that σ₁ receptors (σ₁Rs) are involved in the effects of cocaine abuse. Many in vitro and in vivo studies have already indicated an influence of σ₁R ligands on dopaminergic transmission; however, the direct effect on the brain is poorly understood. Herein we describe the effects of cocaine and the selective dopamine-1 receptor (D₁R) agonist, (+)-SKF38393, on gene expression of the σ ₁R in a human fetal a strocyte cell line (SVG cells). This study provides the first evidence for the expression of σ₁ mRNA in these cells. Our results show that treatment of SVG cells with various cocaine concentrations for several time durations showed no significant alternations in σ ₁R gene expression, as detected by real-time quantitative RT-PCR, whereas treating cells for 24 h with (+)-SKF38393 caused a significant down-regulation in σ₁ transcrits. This (+)-SKF38393-induced effect was blocked by the D₁R selective antagonist (+)-SCH23390. These results suggest that the effect of cocaine on σ₂ gene expression in the brain might be indirect and mediated through D₁R.     

Does urbanicity shift the population expression of psychosis?

Growing up in an urban area has been shown to be associated with an increased risk of psychotic disorder in later life. While it is commonly held that a only a tiny fraction of exposed individuals will develop schizophrenia, recent evidence suggests that expression of psychosis in exposed individuals may be much more common, albeit at attenuated levels. Findings are based on a population sample of 2548 adolescents and young adults aged originally 14–24 years, and followed up over almost 5 years up to ages 17–28 years. Trained psychologists assessed all these subjects with the core psychosis sections on delusions and hallucinations of the Munich-Composite International Diagnostic Interview. Growing up in an urban area was associated with an increased risk of expression of psychosis in the adolescents and young adults (adjusted OR 1.31, 95% CI 1.03–1.66). The proxy environmental risk factor that urbanicity represents may shift a relatively large section of the adolescent population along a continuum of expression of psychosis. Other causal influences may be required to make the transition to schizophrenia in adult life.     

Voluntary exercise training in mice increases the expression of antioxidant enzymes and decreases the expression of TNF-α in intestinal lymphocytes

Acute exercise in mice induces intestinal lymphocyte (IL) apoptosis. Freewheel running reduces apoptosis and forced exercise training increases splenocyte antioxidant levels. The purpose of this study was to examine the effect of freewheel running and acute exercise on mouse IL numbers and concentrations of apoptosis and antioxidant proteins and pro-inflammatory cytokines in IL. Female C57BL/6 mice had access to in-cage running wheels (RW) or cages without wheels (NRW) for 16 weeks and were randomized at the end of training to no exercise control (TC) or to treadmill exercise with sacrifice after 90 min of running (TREAD; 30 min, 22 m min^?1; 30 min, 25 m min^?1; 30 min, 28 m min^?1; 2° slope). IL were analyzed for pro-(caspase 3 and 7) and anti-(Bcl-2) apoptotic proteins, endogenous antioxidants (glutathione peroxidase: GPx; catalase: CAT) and the pro-inflammatory cytokine, TNF-α. RW mice had higher cytochrome oxidase (p < 0.001) and citrate synthase (p < 0.01) activities in plantaris and soleus muscles and higher GPx and CAT expression in IL (p < 0.05) (indicative of training) compared with NRW mice. TNF-α expression was lower (p < 0.05) and IL numbers higher (p < 0.05) in RW vs. NRW mice. No training effect was observed for apoptotic protein expression, although TREAD resulted in higher caspase and lower Bcl-2. These results suggest that freewheel running in mice for 16 weeks enhances antioxidant and reduces TNF-α expression in IL but does not reduce pro-apoptotic protein expression after acute exercise. Results are discussed in terms of implications for inflammatory bowel diseases where apoptotic proteins and TNF-α levels are elevated.     

Vascular endothelial growth factor induces brain erythropoietin expression?

To investigate whether the formation of vascular endothelial growth factor (VEGF) influences erythropoietin (EPO) expression in physiological conditions, we injected into the left lateral cerebral ventricle of the Mongolian gerbil an adeno-associated virus (AAV) vector capable of expressing the 165-amino-acid isoform of VEGF (VEGF165). Twelve and 18 days after AAV vector injection, the experimental animals were sacrificed and expression of EPO was evaluated through immunohistochemical analysis of both the hippocampus and the frontal cortex. We observed that VEGF165 induces EPO expression in the hippocampal pyramidal layers and in the frontal cortex of the gerbil, particularly after the 18th day following treatment with the vector, which suggests that VEGF165 could act as a hypoxic-like signal for EPO production. This finding could help to clarify the functional role of EPO and the molecular mechanisms by which VEGF might mediate its effects in the brain.     

Neuronal expression of αB crystallin in cerebral infarction

alphaB crystallin (alphaBC) is one of the heat shock proteins that are induced under stressful conditions. In normal brains, alphaBC is present in oligodendrocytes and astrocytes, but not in neurons. Neuronal alphaBC expression in the central nervous system under pathological conditions has been investigated in several previous studies, most of which dealt with various neurodegenerative diseases with and without ballooned neurons. Neuronal expression of alphaBC has seldom been studied in cerebral infarction (CI), and the frequency of alphaBC-positive neurons in the various stages of CI is unknown. To investigate this issue, we examined 48 autopsy brains of patients with CI, and found neuronal expression of alphaBC in 68.8% of the cases. We found three types of alphaBC-positive neurons: normal morphological, convex, and ballooned neurons. Although alphaBC-positive neurons were present in the every stage of CI, they were more frequent later than 10 days after the onset of CI, and the frequency of alphaBC-positive ballooned neurons was particularly increased in the later stages of CI. This may indicate that morphologically normal neurons gradually swelled up through convex neurons, finally forming ballooned neurons. Previous studies indicated that alphaBC might have a cytoprotective function as a molecular chaperone, and we speculate that alphaBC is expressed in neurons subjected to ischemic stress, and exerts a cytoprotective effect on the neurons.     

α7 nicotinic acetylcholine receptor expression in Alzheimer's disease

The brains of people with Alzheimer's disease (AD) display several characteristic pathological features, including deposits (plaques) of beta-amyloid 1-42 (Abeta1-42), intraneuronal accumulations (tangles) of hyperphosphorylated tau, degeneration of the basal forebrain cholinergic pathway, and gliosis. Abeta1-42 plaques develop in specific brain regions, including hippocampus and cortex, as well as in the vasculature. Abeta1-42 might promote neurodegeneration through the induction of free radicals and disruption of Ca2+ homeostasis, giving rise to the symptoms of AD. Abeta1-42 interacts with the alpha7 subtype of the nicotinic acetylcholine receptor (alpha7 nAChR), which is widely expressed throughout the central and peripheral nervous systems, as well as in several nonneuronal loci, such as epithelial cells, lymphoid tissues, and peripheral blood lymphocytes. Western blot and autoradiographic analyses indicate that the alpha7 nAChR subunit protein is up-regulated in human brain samples from Alzheimer patients, as well as in animal models of AD (Dineley et al., 2001; Bednar et al., 2002), and might be involved in nicotine-mediated reduction of Abeta1-42 deposition (Hellstrom et al., 2004), although the nature of this relationship remains ill-defined. We have undertaken a semiquantitative histological evaluation of alpha7 nAChR expression in a mouse model of AD pathology, as well as a comparison of alpha7 nAChR levels in lymphocytes from AD patients and control subjects.     

Biperiden (M₁ antagonist) impairs the expression of cocaine conditioned place preference but potentiates the expression of cocaine-induced behavioral sensitization

Cocaine addiction is a public health issue in many countries, stressing the need for more effective treatments. As all drugs of abuse, cocaine acts on the brain reward system, increasing dopamine (DA) levels. Other neurotransmitters such as acetylcholine (ACh) are involved in the mechanisms underlying the development and the maintenance of cocaine addiction. ACh plays an important role in learning and memory processes and also regulates DA in some specific regions of the central nervous system. The present study investigated the effects of biperiden, a muscarinic cholinergic (mACh) antagonist in two animal models: conditioned place preference (CPP) and behavioral sensitization. Male C57BL/6J mice were used in both studies. The CPP protocol was unbiased and carried out in three phases: habituation, conditioning and testing. For conditioning, cocaine was injected at a dose of 10mg/kg in eight 15 min-sessions. The treatment with biperiden (doses of 0.1, 1 and 10 mg/kg) was made 30 min prior to the testing session. For behavioral sensitization development, cocaine was administered at the dose of 10 mg/kg for 10 days. After sensitization, two challenges were performed: saline and cocaine (5 mg/kg). Biperiden (10 mg/kg) was administered 30 min before the cocaine challenge. At the dose of 10 mg/kg, biperiden blocked the cocaine-CPP expression, suggesting an effect on conditioned memory retrieval. However, the same dose potentiated the expression of behavioral sensitization, suggesting an increase in DA release, probably in the NAc. Biperiden, as other mACh antagonists, may be a promising drug for the pharmacologic treatment of cocaine addiction.     

IFN-beta-regulated genes show abnormal expression in therapy-naïve relapsing-remitting MS mononuclear cells: gene expression analysis employing all reported protein-protein interactions

The molecular mechanism by which interferon beta (IFN-β) is effective in treating multiple sclerosis is not well understood. Mononuclear cells from therapy-naïve MS patients, IFN-β-1b-treated MS patients, and healthy controls were analyzed to examine mRNA changes that characterize both the disease and its treatment. The scientific literature was comprehensively searched for all protein–protein interactions. In MS patients who had never been treated with IFN-β, statistical analysis revealed coordinate changes in mRNA expression for proteins reported in the literature as “regulated by IFN-β.” As a positive control for this approach, samples from a separate MS patient cohort showed significant change of these same genes during in vivo treatment with IFN-β-1b.The strength of effect observed for regulation by IFN-β was greater than for IFN-, IFN-γ (Th1), or IL-4 (Th2). Of the sets we investigated, the most strongly affected by disease was the subset defined by regulation by both IFN-β and IFN-. Changes in cells from therapy-naïve MS patients thus anticipated the importance of IFN-β in therapy. These findings are a significant step towards marrying MS disease etiology and IFN-β mechanism of action at a molecular level.     

Decreased α-synuclein expression in the aging mouse substantia nigra

Because of its normal function in synaptic plasticity and pathologic involvement in age-related neurodegenerative diseases, the protein α-synuclein could play an important role in aging processes. Here we compared α-synuclein expression in the substantia nigra and other brain regions of young (2-month-old), middle-aged (10-month-old), and old (20-month-old) mice. Levels of nigral α-synuclein mRNA, as assessed by both in situ hybridization and qPCR, were high in young mice and progressively declined in middle-aged and old animals. This age-dependent mRNA loss was paralleled by a marked reduction of α-synuclein protein; immunoreactivity of midbrain sections stained with an anti-α-synuclein antibody was most robust in 2-month-old mice and weakest in 20-month-old animals. Lowering of nigral α-synuclein could not be explained by a loss of dopaminergic neurons and was relatively specific since no change in β-synuclein mRNA and protein occurred with advancing age. Finally, age-related decreases in α-synuclein were widespread throughout the mouse brain, affecting other regions (e.g., hippocampus) besides the substantia nigra. The data suggest that loss of α-synuclein could contribute to or be a marker of synaptic dysfunction in the aging brain. They also emphasize important differences in α-synuclein expression between rodents and primates since earlier reports have shown a marked elevation of α-synuclein protein in the substantia nigra of older humans and non-human primates.     

Glutamate stimulates neurotrophin expression in cultured Müller cells

The uptake of excess extracellular glutamate and the secretion of neurotrophins by glial cells have been suggested to protect CNS neurons from glutamate-induced toxicity. In the retina, perturbation of glutamate transport and decreased retrograde transport of neurotrophic factors such as brain-derived neurotrophic factor (BDNF) may contribute to ganglion cell death in experimental glaucoma. Although many studies show a clear relationship between glutamate and neurotrophic factors, such relationship has not been thoroughly investigated in the retinal environment. In the following study, we determined the effects of glutamate on early passaged rat Müller cells, specifically their expression of neurotrophic factors including BDNF, nerve growth factor (NGF), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), and glial-cell line derived neurotrophic factor (GDNF); and of glutamate receptors and transporters using immunoblots or enzyme-linked immunosorbent assays. Binding of BDNF to its cognate receptor TrkB was also determined using co-immunoprecipitation studies. Cultured Müller cells grown in the presence of glutamate were also assayed for survival using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS). Our study showed that while glutamate treatment did not promote cell death, it upregulated secretion of BDNF, NGF, NT-3, NT-4, and GDNF by Müller cells. While solitary bands at approximately 13-14 kDa were observed for NGF, NT-3, and NT-4; two BDNF-reactive bands were observed in immunoblots: a faster migrating band at the reported size of the BDNF monomer (approximately 13 kDa); and a more intense band at approximately 36 kDa. GDNF-reactive bands were observed at approximately 22, approximately 28, and approximately 55 kDa. Glutamate also induced significant changes in glutamate receptor and transporter proteins, as well maintained the association of BDNF to TrkB in Müller cells. The decreased N-methyl-D-aspartate receptor (NMDAR) levels and sustained activation of TrkB by BDNF could serve as protective mechanisms for Müller cell survival. Moreover, the increased secretion of neurotrophic factors and upregulation of L-glutamate/L-aspartate transporter (GLAST) expression in Müller cells may protect retinal neurons from glutamate toxicity.     

Cerebrovascular P-glycoprotein expression is decreased in Creutzfeldt–Jakob disease

The abnormal conformation and assembly of proteins in the central nervous system is increasingly thought to be a critical pathogenic mechanism in neurodegenerative disorders such as Creutzfeldt–Jakob disease (CJD) and Alzheimer’s disease (AD). CJD is marked primarily by the buildup of misfolded prion protein (PrP^Sc) in brain, whereas the accrual of β-amyloid protein (Aβ) and tau protein are characteristic for AD. Prior studies have shown that the ATP-binding cassette transporter P-glycoprotein (P-gp) is a cellular efflux pump for Aβ, and that age-associated deficits in P-gp may be involved in the pathogenesis of Alzheimer’s disease. In the present study, we investigated the relationship between P-gp and idiopathic CJD, and found that CJD, like AD, is associated with a decrease in the expression of cerebrovascular P-gp. In some instances, Aβ and PrP deposits coexist in cases of CJD, suggesting the possibility of pathogenic interactions. Since there is, to date, no evidence that PrP itself is a substrate for P-gp, we hypothesize that the age-related deficits in P-gp could promote the accumulation of PrP^Sc either by promoting the buildup of Aβ (which could act as a seed for the aggregation of PrP^Sc), or by overloading the ubiquitin-proteasomal catabolic system, and thereby facilitating the accumulation of PrP. Alternatively, the loss of P-gp could be a non-specific response to neurodegenerative changes in the central nervous system. In either case, dysfunction of this critical toxin-elimination pathway in CJD and AD suggests that selectively increasing cerebrovascular P-gp function could open new therapeutic pathways for the prevention and/or treatment of a number of proteopathic disorders of the central nervous system.     

Regional differences in expression of β-tubulin isoforms in schizophrenia

A growing body of evidence suggests that abnormal elements of the cytoskeleton may be associated with the pathophysiology of schizophrenia. Isoforms of a major cytoskeleton protein, β-tubulin, were recently demonstrated to have distinct roles in neuronal differentiation and cell viability. For these reasons, we tested the hypothesis that there are differences in the expression of β-tubulin isoforms (βI-βIV) in the brain in schizophrenia, using western blot analysis in an elderly group of subjects with this illness and a control group. We found that βI-tubulin protein expression was decreased in the anterior cingulate cortex and increased in the dorsolateral prefrontal cortex, but not changed in superior temporal gyrus or hippocampus in schizophrenia. Our data supports the growing body of evidence suggesting abnormalities of the cytoskeleton in schizophrenia.     

α-Synuclein expression is modulated at the translational level by iron

Several studies have suggested an interaction between α-synuclein protein and iron in Parkinson's disease. The presence of iron together with α-synuclein in Lewy bodies, the increase of iron in the substantia nigra and the correlation between polymorphism of the several genes implicated in iron metabolism and Parkinson's disease, support a role for iron in the neurodegeneration. Analysis of post mortem brains revealed increased amount of insoluble α-synuclein protein despite unchanged/reduced levels of α-synuclein mRNA in Parkinson's disease. Interestingly, on the basis of the presence of a putative iron responsive element in the 5'-UTR, it has been suggested that there is a possible iron-dependent translational control of human α-synuclein mRNA. Considering the similarity between the sequences present in human α-synuclein mRNA and the ferritin iron responsive element, we postulated that iron deficiency would decrease the translation of α-synuclein mRNA. Here we used HEK293 cells treated with iron chelator deferoxamine or ferric ammonium citrate to verify the possible iron-dependent translational control of human α-synuclein biosynthesis. We show that the amount of polysome-associated endogenous human α-synuclein mRNA decreases in presence of deferoxamine. Our data demonstrate that human α-synuclein expression is regulated by iron mainly at the translational level. This result not only supports a role for iron in the translational control of α-synuclein expression, but also suggests that iron chelation may be a valid approach to control α-synuclein levels in the brain.