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Biomedical subjects

Weidong Le

Publications and source records attributed to Weidong Le.

At least 19 recordsLinked to original sources
PubMed2006

Neuroprotective effects of (-)-epigallocatechin-3-gallate in a transgenic mouse model of amyotrophic lateral sclerosis.

The purpose of this study is to evaluate neuroprotective effects of (-)-Epigallocatechin-3-gallate (EGCG) in a transgenic mouse model of Amyotrophic lateral sclerosis (ALS). SOD1-G93A transgenic mice and wild-type mice were randomly divided into EGCG-treated groups (10 mg/kg, p.o) and vehicle-treated control groups. Rotarod measurement was performed to assess the motor function of mice starting at the age of 70 days. Nissl staining to examine the number of motor neurons and CD11b immunohistochemical staining to evaluate activation of microglia in the lumbar spinal cords were conducted at the age of 120 days. In addition, for further observation of regulation of cell signaling pathways by EGCG, we used immunohistochemical analysis for nuclear factor kappa B (NF-kappaB) and cleaved caspase-3 as well as western blot analysis to determine the expression of nitric oxide synthase (iNOS) and NF-kappaB in the spinal cord. This study demonstrated that oral administration of EGCG beginning from a pre-symptomatic stage significantly delayed the onset of disease, and extended life span. Furthermore, EGCG-treated transgenic mice showed increased number of motor neurons, diminished microglial activation, reduced immunohistochemical reaction of NF-kappaB and cleaved caspase-3 as well as reduced protein level of iNOS and NF-kappaB in the spinal cords. In conclusion, this study provides further evidences that EGCG has multifunctional therapeutic effects in the mouse model of ALS.

Amyotrophic Lateral Sclerosis↗
PubMed2006

Nurr1 in Parkinson's disease and related disorders.

In mammals, the transcription factor Nurr1 is expressed early in development and continues to be detectable throughout the organism's lifetime. Nurr1 is involved in the establishment and maintenance of the dopaminergic phenotype within specific central nervous system neuronal subpopulations including the nigrostriatal dopamine system. This protein is reduced over the course of normal aging, which is a major risk factor for Parkinson's disease (PD). However, whether Nurr1 expression is affected by PD has not been documented. The present study examined the role of Nurr1 in the maintenance of the dopaminergic phenotype within neurons in substantia nigra in PD compared with patients with diagnoses of progressive supranuclear palsy (PSP) or Alzheimer's disease (AD) or age-matched-matched controls. In PD, the optical density (OD) of Nurr1 immunofluorescence was significantly decreased in nigral neurons containing alpha-synuclein-immunoreactive inclusions. Similarly, the OD of Nurr1 immunofluorescence intensity in the nigra of AD cases was decreased in neurons with neurofibrillary tangles (NFTs). In contrast to PD and AD, the OD of Nurr1 immunofluorescence intensity was severely decreased in the neurons with or without NFTs in PSP cases. Decline of Nurr1-ir neuronal number and OD was observed within substantia nigra (SN) neurons in PD but not within hippocampal neurons. The decline in Nurr1-ir expression was correlated with loss of tyrosine hydroxylase immunofluorescence across the four groups. These data demonstrate that Nurr1 deficiency in dopaminergic neurons is associated with the intracellular pathology in both synucleinopathies and tauopathies.

Aged↗
PubMed2005

Valproic acid-mediated Hsp70 induction and anti-apoptotic neuroprotection in SH-SY5Y cells.

Valproic acid (VPA), an anticonvulsant and mood-stabilizing drug, has been reported to exert neuroprotection against a variety of insults. We now show that VPA attenuates rotenone (a potent complex I inhibitor)-induced apoptosis through the induction of heat shock protein 70, which may interact with apoptotic-protease-activating factor 1. Activation of p-Akt, p-Bcl-2, as well as p-Erk1/2 by VPA may be co-contributors to the protection.

Apoptosis↗
PubMed2005

Small interfering RNA targeting the PINK1 induces apoptosis in dopaminergic cells SH-SY5Y.

PTEN-induced kinase 1 (PINK1) is a recently identified gene, mutations of which cause levodopa-responsive parkinsonism. An over-expression of wild-type PINK1 protects neurons from stress-induced mitochondrial dysfunction and apoptosis. We studied the effects of PINK1 suppression using small interfering RNA (siRNA), which can inhibit PINK1 mRNA expression up to 87%, and decrease PINK1 protein up to 80% in human dopaminergic cell line SH-SY5Y. Incubation with PINK1 siRNA decreased SH-SY5Y cell viability and significantly increased MPP(+) or rotenone-induced cytotoxicity. Our results indicate that reduction in PINK1 expression can trigger apoptotic process that can be exacerbated by the presence of MPP(+) or rotenone. These findings support the hypothesis that PINK1 participates in the protection of dopaminergic neurons.

Amino Acid Sequence↗
PubMed2005

Neuroprotection by iron chelator against proteasome inhibitor-induced nigral degeneration.

The cause of the neurodegenerative process in Parkinson's disease (PD) remains unclear, but evidence suggests that failure of the ubiquitin-proteasome system may play a major role in the pathogenesis of the disease. Iron is believed to be a key contributor to PD pathology by inducing aggregation of alpha-synuclein and by generating oxidative stress. Our present studies have shown that micro-injection of the proteasome inhibitor lactacystin into the substantia nigra (SN) of C57BL/6 mice causes significant loss of dopaminergic cells and induces intracellular inclusion body formation. We have also found that co-injection of the iron chelator desferrioxamine not only attenuates the lactacystin-induced dopamine neuron loss, but also reduces the presence of ubiquitin-positive intracellular inclusions in the SN, whereas use of iron-deficient diet has no such protective effects. These results may support that iron plays a key role in proteasome inhibitor-induced nigral pathology and that reducing iron reactivity may prevent dopaminergic neuron degeneration and reduce abnormal protein aggregation.

Acetylcysteine↗
PubMed2005

Interferon-alpha-induced modulation of glucocorticoid and serotonin receptors as a mechanism of depression.

BACKGROUND/AIMS: The mechanism of interferon (IFN)-alpha-induced depression remains poorly understood. Recently, modulation of glucocorticoid receptor (GR) and serotonin receptor 1A (5-HTR1A) were implicated in mechanism(s) leading to depression. To gain insight into this mechanism, we assessed the effect of IFN-alpha on the modulation of GR and 5-HTR1A expression. METHODS: Hepatoblastoma, myelocyte-derived and T cell leukemia-derived cell lines were treated with titrated doses of IFN-alpha for different incubation times and analyzed by Western blot, RT-PCR, and microarrays. Dose- and time-dependent decreases of proteins and mRNA levels of GR and 5-HTR1A were observed. RESULTS: The expression of GR and 5-HTR1A in cells treated for 6 days decreased by 74 and 72%, respectively. Recovery was observed following IFN-alpha withdrawal. Co-incubation with tricyclic antidepressants (desipramine) or serotonin reuptake inhibitors (fluoxetine) attenuated the effect of IFN-alpha on GR or 5-HTR1A. GR and 5-HTR1A were unaffected by treatment with either IFN-gamma or tauroursodeoxycholic acid (TUDCA). However, the effect of IFN-alpha on GR was abolished when used in combination with TUDCA. CONCLUSIONS: In conclusion, IFN-alpha downregulated GR and 5-HTR1A levels in cell lines. These levels of GR and 5-HTR1A, following IFN-alpha-induced downregulation, recovered after withdrawal of IFN-alpha or addition of desipramine or fluoxetine. These data provide insights regarding pathogenesis of IFN-alpha-induced depression.

Antidepressive Agents, Second-Generation↗
PubMed2005

Biological effects of pramipexole on dopaminergic neuron-associated genes: relevance to neuroprotection.

Pramipexole (PRX) is a non-ergot dopamine (DA) D2/D3 receptor agonist. Experimental studies have provided evidence that PRX may exert neuroprotective effects on the nigro-striatal system. Recent studies have demonstrated a slower decline of DAT density in Parkinson's disease patients treated with PRX as measured by SPECT. The aim of this study is to determine whether PRX has direct biological effects on DAergic neuron-associated genes expression, including DAT, VMAT2, and Nurr1. The human neuroblastoma SH-SY5Y cells were treated with PRX for various time periods and harvested to measure the mRNA and protein products of these genes. Treatment with PRX at 10 microM significantly increased DAT mRNA levels by 54-130% in 4-8 h, VMAT2 mRNA levels by 34% in 4 h, and Nurr1 mRNA levels by 31-39% in 2-4 h, which was the earliest induction among these three genes. The protein levels of DAT, VMAT2, and Nurr1 were markedly increased after PRX treatment, among which the increase of Nurr1 protein level was the highest at first 2 h treatment of PRX. Nafadotride, a D3 DA receptor antagonist, blocked the increase of Nurr1 gene expression induced by PRX, while eticlopride, a D2 DA receptor antagonist, didn't show this effect. Our findings that PRX has biological regulatory effects on DAergic neuron-associated genes may explain both the slower decline of imaged DAT and the neuroprotective effect of PRX. Furthermore, our results suggest that the induction of Nurr1 gene expression by PRX may be mediated by D3 DA receptor.

Benzothiazoles↗
PubMed2005

Age-dependent dopaminergic dysfunction in Nurr1 knockout mice.

The Nurr1 gene, which codes for a transcriptional factor in the nuclear receptor superfamily, plays an important role in the development of the mesencephalic dopaminergic (DAergic) system. To study the age-dependent effects of Nurr1 expression in maintaining mature nigrostriatal DAergic neuronal function, we examined motor behaviors, determined nigrostriatal dopamine (DA) levels and the number of nigral DAergic neurons, and measured the expression of several DAergic neuron-associated genes in heterozygous Nurr1-deficient (Nurr1+/-) and wild-type mice of different ages. In contrast to the same-aged, wild-type mice, old Nurr1+/- mice (>15 months) had a significant decrease in both rotarod performance and locomotor activities, suggesting a motor impairment that is analogous to parkinsonian deficit. Furthermore, the abnormal motor behaviors in old Nurr1+/- mice were associated with decreased DA levels in the striatum, decreased number of DAergic neurons in the nigra, and reduced expression of Nurr1 and DA transporter in the nigra. Our data indicate that Nurr1 plays an important role in the functional maintenance and survival of nigral DAergic neurons and suggest that the Nurr1+/- mouse is a useful animal model to study the pathogenesis of Parkinson disease (PD) and to explore disease-modifying strategies.

Aging↗
PubMed2005

Dopamine D3 receptor-preferring agonists induce neurotrophic effects on mesencephalic dopamine neurons.

Anti-parkinsonian agents, pramipexole (PPX) and ropinirole (ROP), have been reported to possess neuroprotective properties, both in vitro and in vivo. The mechanisms underlying neuroprotection afforded by the D3-preferring receptor agonists remain poorly understood. The present study demonstrates that incubation of primary mesencephalic cultures with PPX and ROP or the conditioned medium from PPX- or ROP-treated primary cultures induced a marked increase in the number of dopamine (DA) neurons in the cultures. Similar effects can be observed after incubating with the conditioned medium derived from PPX- and ROP-treated substantia nigra astroglia. Meanwhile, PPX and ROP can protect the primary cells from insult of 1-methyl-4-phenylpyridinium (MPP+), the active metabolite of the neurotoxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP). Furthermore, the neurotrophic effects of PPX and ROP on mesencephalic dopamine neurons could be significantly blocked by D3 receptor antagonist, but not by D2 receptor antagonist. Moreover, we found that the levels of glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) in the conditioned medium of mesencephalic cultures treated with PPX and ROP were significantly increased. Blocking GDNF and BDNF with the neutralizing antibodies, the neurotrophic effects of PPX and ROP were greatly diminished. These results suggest that D3 dopamine receptor-preferring agonists, PPX and ROP, exert neurotrophic effects on cultured DA neurons by modulating the production of endogenous GDNF and BDNF, which may participate in their neuroprotection.

Animals↗
PubMed2005

[Effects of 2,5-hexanedione on NGF expression in motor and sensory neuronal cells of rats].

OBJECTIVE: To investigate the effects of 2,5-Hexanedione (2,5-HD), a metabolite of n-hexane,on nerve growth factor (NGF) expression in motor and sensory neuronal cells of peripheral nervous system of rats. METHODS: Primary cultured dorsal root ganglion (DRG) neurons were obtained from new born rats on day 4. The cell line VSC4.1 were cultured. The growth condition of cells were observed with a phase contrast microscope. Immunohistochemistry technology was used to analyze the NGF expression in both VSC4.1 cells and primary cultured DRG cells treated with 4 different dosages of 2, 5-HD (2.5, 5.0, 10.0, 20.0 mmol/L) respectively for 24 hours. RESULTS: The NGF expression decreased significantly in both DRG neurons and VSC4.1 cells dosed respectively with 5.0,10.0,20.0 mmol/L 2,5-HD in comparison with the control group (P < 0.05), with a tendency of dose-effect correlation. CONCLUSION: The results suggested that 2,5-HD can decrease the endogenous NGF levels in both cultured DRG sensory neurons and VSC4.1 motor neuron cells of rats.

Animals↗
PubMed2004

Mutant genes responsible for Parkinson's disease.

Recent progress has documented the presence of at least 10 disease-related genes or loci linked to Parkinson's disease. Analysis of the genotypes and phenotypes of these mutant genes has revealed a broad spectrum of clinical and pathological presentations, many of which share a common feature of alteration in the ubiquitin proteasome system. Further understanding of the pathogenesis of these inherited cases of Parkinson's disease and development of transgenic animal models bearing these mutations should provide novel insight into the causes of nigral cell death and meaningful strategies for future therapy.

Animals↗
PubMed2004

Activated microglia initiate motor neuron injury by a nitric oxide and glutamate-mediated mechanism.

Recent studies suggest that motor neuron (MN) death may be non-cell autonomous, with cell injury mediated by interactions involving non-neuronal cells, such as microglia and astrocytes. To help define these interactions, we used primary MN cultures to investigate the effects of microglia activated by lipopolysaccharide or IgG immune complexes from patients with amyotrophic lateral sclerosis. Following activation, microglia induced MN injury, which was prevented by a microglial iNOS inhibitor as well as by catalase or glutathione. Glutamate was also required since inhibition of the MN AMPA/kainate receptor by CNQX prevented the toxic effects of activated microglia. Peroxynitrite and glutamate were synergistic in producing MN injury. Their toxic effects were also blocked by CNQX and prevented by calcium removal from the media. The addition of astrocytes to cocultures of MN and activated microglia prevented MN injury by removing glutamate from the media. The protective effects could be reversed by inhibiting astrocytic glutamate transport with dihydrokainic acid or pretreating astrocytes with H2O2. Astrocytic glutamate uptake was also decreased by activated microglia or by added peroxynitrite. These data suggest that free radicals released from activated microglia may initiate MN injury by increasing the susceptibility of the MN AMPA/kainate receptor to the toxic effects of glutamate.

Amino Acid Transport System X-AG↗
PubMed2003

Effects of green tea polyphenols on dopamine uptake and on MPP+ -induced dopamine neuron injury.

As antioxidants, polyphenols are considered to be potentially useful in preventing chronic diseases in man, including Parkinson's disease (PD), a disease involving dopamine (DA) neurons. Our studies have demonstrated that polyphenols extracted from green tea (GT) can inhibit the uptake of 3H-dopamine (3H-DA) and 1-methyl-4-phenylpyridinium (MPP(+)) by DA transporters (DAT) and partially protect embryonic rat mesencephalic dopaminergic (DAergic) neurons from MPP(+)-induced injury. The inhibitory effects of GT polyphenols on 3H-DA uptake were determined in DAT-pCDNA3-transfected Chinese Hamster Ovary (DAT-CHO) cells and in striatal synaptosomes of C57BL/6 mice in vitro and in vivo. The inhibitory effects on 3H-MPP(+) uptake were determined in primary cultures of embryonic rat mesencephalic DAergic cells. Inhibition of uptake for both 3H-DA and 3H-MPP(+) was dose-dependent in the presence of polyphenols. Incubation with 50 microM MPP(+) resulted in a significant loss of tyrosine-hydroxylase (TH)-positive cells in the primary embryonic mesencephalic cultures, while pretreatment with polyphenols (10 to 30 microg/ml) or mazindol (10 microM), a classical DAT inhibitor, significantly attenuated MPP(+)-induced loss of TH-positive cells. These results suggest that GT polyphenols have inhibitory effects on DAT, through which they block MPP(+) uptake and protect DAergic neurons against MPP(+)-induced injury.

1-Methyl-4-phenylpyridinium↗
PubMed2003

Role of nitric oxide in rotenone-induced nigro-striatal injury.

Rotenone, a widely used pesticide, causes a syndrome in rats that mimics, both behaviorally and pathologically, the symptoms of Parkinson's disease. The present study evaluated the role of nitric oxide in rotenone-induced nigro-striatal injury. After administration of rotenone in rats for 40 days, there was a moderate but significant injury of the nigro-striatal pathway indicated by a 47% decrease in striatal dopamine levels and a 28% loss of substantia nigra tyrosine hydroxylase-immunopositive neurons. Furthermore, a significant (37%) increase in the number of cells positive for nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) in the striatum was observed, accompanied by a 83% increase in nitric oxide synthase (NOS) activity and a significant increase in the production of 3-nitrotyrosine (3-NT). There was a significant increase (45%) in the optical density of NADPH-d staining and an increase (72%) in NOS activity in the substantia nigra. Moreover, administration of the neuronal NOS inhibitor 7-nitroindazole significantly attenuated the increased NOS activity and 3-NT production, and provided significant protection against rotenone-induced nigro-striatal injury. Our data suggest that chronic rotenone administration can lead to significant injury to the nigro-striatal system, mediated by increased generation of nitric oxide.

Animals↗