			Home About us Contact

Human Neurons (human + neuron)

Distribution by Scientific Domains

Life Sciences	58%
Medical Sciences	41%

Selected Abstracts

The Anticonvulsant SGB-017 (ADCI) Blocks Voltage-Gated Sodium Channels in Rat and Human Neurons: Comparison with Carbamazepine

EPILEPSIA, Issue 3 2000
Lucy Sun
Summary: Purpose: SGB-017 (ADCI) is a novel anticonvul-sant that blocks both voltage-activated sodium channels and N -methyl- d -aspartate (NMDA)-receptor-gated channels. Results by Rogawski et al. suggested that SGB-017 produces its anticonvulsant action primarily by inhibition of NMDA-receptor channels. However, SGB-017 is effective in several animal models of epilepsy that are unresponsive to NMDA antagonists. These results indicate that block of NMDA-receptor channels is not the only mechanism contributing to its anticonvulsant activity. Thus the effects of SGB-017 on neu-ronal sodium channels were investigated. Methods: Whole cell voltage-clamp techniques were used to record sodium currents in freshly dissociated rat superior cervical ganglion (SCG) and hippocampal neurons and cultured human NT2 neurons. The effects of SGB-017 on the amplitude of sodium currents, elicited by a depolarizing pulse to 0 mV from different holding potentials, were measured and compared with those of carbamazepine (CBZ). Results: SGB-017 inhibited sodium currents in rat SCG and hippocampal neurons with a similar potency to CBZ. Like CBZ, the inhibition of sodium channels by SGB-017 was voltage dependent. Its median inhibitory concentration (IC50) for inhibition of sodium channels at depolarized holding potentials is similar to that for its inhibition of NMDA receptor channels. In human hNT2 neurons, SGB-017 was more potent than CBZ at inhibiting sodium currents. Conclusions: SGB-017 produces its anticonvulsant activity by blocking both sodium- and NMDA-receptor channels in a voltage- and use-dependent manner. The combination of these two mechanisms of action makes SGB-017 an effective AED in several different animal models of epilepsy. [source]

Fractalkine and fractalkine receptors in human neurons and glial cells

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2002
Kozo Hatori
Abstract Fractalkine has been identified as a novel chemokine that exhibits cell adhesion and chemoattractive properties in the central nervous system (CNS), and the fractalkine receptors, CX3CR1, are also expressed in the CNS. In the present study, the expression of fractalkine and fractalkine receptors was investigated in enriched populations of human CNS neurons, astrocytes, and microglia. In addition, the regulatory role played by protein kinase C (PKC) in fractalkine secretion in neurons was determined in A1 human hybrid neuronal cell line produced between a human cerebral neuron and a human neuroblastoma cell. Human neurons and astrocytes expressed fractalkine mRNA as determined by the revserse transcriptase-polymerase chain reaction (RT-PCR) analysis, while human microglia preparation did not express the fractalkine message. Human neurons and microglia expressed CX3CR1 mRNA, but astrocytes did not. These results suggest that fractalkine secreted by CNS neurons and astrocytes produce biological effects in neurons and microglia. Although phorbol ester did not change the expression of fractalkine mRNA level in A1 hybrid neurons, it did upregulate fractalkine secretion over unstimulated controls. This upregulation of fractalkine production was suppressed by the treatment with Ro32-0432, a PKC inhibitor. These results indicate that intracellular signals transduced by PKC play an important role in the regulation of soluble fractalkine at the post-transcriptional level in human neurons. As for the biological function of fractalkine, extracellularly applied fractalkine increased the number of bromodeoxyuridine-labeled microglia 3-fold over the untreated controls, indicating fractalkine induces proliferation of human microglia. These observations suggest that fractalkine released by injured neurons could induce proliferation, activation and/or migration of microglia at the injured brain sites. © 2002 Wiley-Liss, Inc. [source]

Fractalkine reduces N -methyl- d -aspartate-induced calcium flux and apoptosis in human neurons through extracellular signal-regulated kinase activation

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2004
Kumaran Deiva
Abstract Our purpose was to investigate in human neurons the neuroprotective pathways induced by Fractalkine (FKN) against glutamate receptor-induced excitotoxicity. CX3CR1 and FKN are expressed constitutively in the tested human embryonic primary neurons and SK-N-SH, a human neuroblastoma cell line. Microfluorometry assay demonstrated that CX3CR1 was functional in 44% of primary neurons and in 70% of SK-N-SH. Fractalkine induced ERK1/2 phosphorylation within 1 min and Akt phosphorylation after 10 min, and both phosphorylation decreased after 20 min. No p38 and SAPK/JNK activation was observed after FKN treatment. Application of FKN triggered a 53% reduction of the NMDA-induced neuronal calcium influx, which was insensitive to pertussis toxin and LY294002 an inhibitor of Akt pathway, but abolished by PD98059, an ERK1/2 pathway inhibitor. Moreover, FKN significantly reduced neuronal NMDA-induced apoptosis, which was pertussis toxin insensitive and abolished in presence of PD98059 and LY294002. In conclusion, FKN protected human neurons from NMDA-mediated excitotoxicity in at least two ways with different kinetics: (i) an early ERK1/2 activation which reduced NMDA-mediated calcium flux; and (ii), a late Akt activation associated with the previously induced ERK1/2 activation. [source]

22R -Hydroxycholesterol protects neuronal cells from ,-amyloid-induced cytotoxicity by binding to ,-amyloid peptide

JOURNAL OF NEUROCHEMISTRY, Issue 5 2002
Zhi-Xing Yao
Abstract 22R -hydroxycholesterol, a steroid intermediate in the pathway of pregnenolone formation from cholesterol, was found at lower levels in Alzheimer's disease (AD) hippocampus and frontal cortex tissue specimens compared to age-matched controls. ,-Amyloid (A,) peptide has been shown to be neurotoxic and its presence in brain has been linked to AD pathology. 22R -hydroxycholesterol was found to protect, in a dose-dependent manner, against A,-induced rat sympathetic nerve pheochromocytoma (PC12) and differentiated human Ntera2/D1 teratocarcinoma (NT2N) neuron cell death. Other steroids tested were either inactive or acted on rodent neurons only. The effect of 22R -hydroxycholesterol was found to be stereospecific because its enantiomer 22S -hydroxycholesterol failed to protect the neurons from A,-induced cell death. Moreover, the effect of 22R -hydroxycholesterol was specific for A,-induced cell death because it did not protect against glutamate-induced neurotoxicity. The neuroprotective effect of 22R -hydroxycholesterol was seen when using A,1,42 but not the A,25,35 peptide. To investigate the mechanism of action of 22R -hydroxycholesterol we examined the direct binding of this steroid to A, using a novel cholesterol-protein binding blot assay. Using this method the direct specific binding, under native conditions, of 22R -hydroxycholesterol to A,1,42 and A,17,40, but not A,25,35, was observed. These data suggest that 22R -hydroxycholesterol binds to A, and the formed 22R -hydroxycholesterol/A, complex is not toxic to rodent and human neurons. We propose that 22R -hydroxycholesterol offers a new means of neuroprotection against A, toxicity by inactivating the peptide. [source]

RNA interference-mediated knockdown of ,-synuclein protects human dopaminergic neuroblastoma cells from MPP+ toxicity and reduces dopamine transport

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2007
Timothy M. Fountaine
Abstract The critical observation in the pathology of Parkinson's disease (PD) is that neurodegeneration is largely restricted to dopaminergic neurons that develop cytoplasmic inclusions called Lewy bodies. These aggregations contain the protein ,-synuclein. Furthermore, it is becoming apparent that ,-synuclein expression levels are a major factor in PD pathogenesis. Patients with additional copies of the ,-synuclein gene develop PD with a severity proportional to levels of ,-synuclein overexpression. Similarly, overexpression of ,-synuclein in in vitro and in vivo models has been shown to be toxic. However, little is known about the effects of reducing ,-synuclein expression in human neurons. To investigate this, we have developed a system in which levels of ,-synuclein can be acutely suppressed by using RNA interference (RNAi) in a physiologically relevant human dopaminergic cellular model. By using small interfering RNA (siRNA) molecules targeted to endogenous ,-synuclein, we achieved 80% protein knockdown. We show that ,-synuclein knockdown has no effect on cellular survival either under normal growth conditions over 5 days or in the presence of the mitochondrial inhibitor rotenone. Knockdown does, however, confer resistance to the dopamine transporter (DAT)-dependent neurotoxin N-methyl-4-phenylpyridinium (MPP+). We then demonstrate for the first time that ,-synuclein suppression decreases dopamine transport in human cells, reducing the maximal uptake velocity (Vmax) of dopamine and the surface density of its transporter by up to 50%. These results show that RNAi-mediated ,-synuclein knockdown alters cellular dopamine homeostasis in human cells and may suggest a mechanism for the increased survival in the presence of MPP+, a toxin used extensively to model Parkinson's disease. © 2006 Wiley-Liss, Inc. [source]

Fractalkine and fractalkine receptors in human neurons and glial cells

The constitutive and inducible expression of Nurr1, a key regulator of dopaminergic neuronal differentiation, in human neural and non-neural cell lines

NEUROPATHOLOGY, Issue 4 2002
Jun-ichi Satoh
Nur-related factor 1 (Nurr1), nerve growth factor-induced gene B (NGFI-B) and neuron-derived orphan receptor-1 (NOR-1) constitute the orphan nuclear receptor subfamily of transcription factors. Previous studies showed that midbrain dopaminergic neuronal precursor cells failed to differentiate in Nurr1-deficient mice. To investigate a role of Nurr1 in human neuronal function, Nurr1 mRNA expression was studied in human neural cell lines by RT-PCR and northern blot analysis. Nurr1, NGFI-B and NOR-1 mRNA were coexpressed in all human neural and non-neural cell lines under the serum-containing culture condition, except for SK-N-SH neuroblastoma, in which Nurr1 mRNA was undetectable. The levels of Nurr1, NGFI-B and NOR-1 mRNA were elevated markedly in NTera2 teratocarcinoma-derived neurons (NTera2-N), a model of differentiated human neurons, following a 1.5 or 3 h-exposure to 1 mm dibutyryl cyclic AMP or 100 nm phorbol 12-myristate 13-acetate. NGFI-B mRNA levels were also elevated in NTera2-N cells by exposure to 100 ng/mL brain-derived neurotrophic factor (BDNF). To identify Nurr1-target genes, the mRNA expression of 27 genes potentially involved in dopaminergic neuronal differentiation and survival, including BDNF, glia-derived neurotrophic factor, their receptors, tyrosine hydroxylase and ,-synuclein, were studied in HEK293 cells following overexpression of Nurr1. None of these genes examined, however, showed significant changes. These results indicate that Nurr1, NGFI-B and NOR-1 mRNA are expressed constitutively in various human neural and non-neural cell lines under the serum-containing culture condition, and their levels are up-regulated in human neurons by activation of protein kinase A or protein kinase C pathway, although putative coactivators expressed in dopaminergic neuronal precursor cells might be required for efficient transcriptional activation of Nurr1-target genes. [source]

Clade-specific differences in neurotoxicity of human immunodeficiency virus-1 B and C Tat of human neurons: significance of dicysteine C30C31 motif

ANNALS OF NEUROLOGY, Issue 3 2008
Mamata Mishra MPhil
Objective Human immunodeficiency virus-1 (HIV-1) causes mild to severe cognitive impairment and dementia. The transactivator viral protein, Tat, is implicated in neuronal death responsible for neurological deficits. Several clades of HIV-1 are unequally distributed globally, of which HIV-1 B and C together account for the majority of the viral infections. HIV-1,related neurological deficits appear to be most common in clade B, but not clade C prevalent areas. Whether clade-specific differences translate to varied neuropathogenesis is not known, and this uncertainty warrants an immediate investigation into neurotoxicity on human neurons of Tat derived from different viral clades Methods We used human fetal central nervous system progenitor cell,derived astrocytes and neurons to investigate effects of B- and C-Tat on neuronal cell death, chemokine secretion, oxidative stress, and mitochondrial membrane depolarization by direct and indirect damage to human neurons. We used isogenic variants of Tat to gain insights into the role of the dicysteine motif (C30C31) for neurotoxic potential of Tat Results Our results suggest clade-specific functional differences in Tat-induced apoptosis in primary human neurons. This study demonstrates that C-Tat is relatively less neurotoxic compared with B-Tat, probably as a result of alteration in the dicysteine motif within the neurotoxic region of B-Tat Interpretation This study provides important insights into differential neurotoxic properties of B- and C-Tat, and offers a basis for distinct differences in degree of HIV-1,associated neurological deficits observed in patients in India. Additional studies with patient samples are necessary to validate these findings. Ann Neurol 2007 [source]