Retinoic acid induction of calcium channel expression in human NT2N neurons

Antiepileptogenic Effect of Retinoic Acid

Retinoic acid, a metabolite of vitamin A, acts through either genomic or nongenomic actions. The genomic action of retinoids exerts effects on gene transcription through interaction with retinoid receptors such as retinoic acid receptors (RARα, β, and γ) and retinoid X receptors (RXRα, β, and γ) that are primarily concentrated in the amygdala, pre-frontal cortex, and hippocampal areas in the brain. In response to retinoid binding, RAR/RXR heterodimers undergo major conformational changes and orchestrate the transcription of specific gene networks. Previous experimental studies have reported that retinoic acid exerts an antiepileptogenic effect through diverse mechanisms, including the modulation of gap junctions, neurotransmitters, long-term potentiation, calcium channels and some genes. To our knowledge, there are no previous or current clinical trials evaluating the use of retinoic acid for seizure control.

Treating TB human neuroectodermal cell line with retinoic acid induces the appearance of neuron-like voltage-gated ionic currents

TB is a cell line derived from the cerebrospinal fluid sample of a patient with primary leptomeningeal melanomatosis. Our previous immunological and ultrastructural analysis revealed that TB cells differentiate towards a neuronal phenotype when grown in vitro up to 7 days in presence of 10 µM all-trans retinoic acid (RA). Recently, we reported that TB cells are sensitive to the cytotoxic effects of β-amyloid peptides, activating the cytosolic phospholipase A2. To date, it is not known if RA, in addition to inducing morphological changes, also causes functional modification in TB cells, by regulating voltage-gated ionic currents. To this purpose, we performed electrophysiological characterization of undifferentiated (TB) and differentiated (RA-TB) cells by means of whole-cell patch clamp recordings. Upon depolarizing stimuli, both groups displayed voltage-gated K⁺ outward currents of similar amplitude. By contrast, the low amplitude voltage-gated Na⁺ currents recorded in undifferentiated TB cells were largely up-regulated by RA exposure. This current was strongly reduced by TTX and lidocaine and completely abolished by removal of extracellular sodium. Furthermore, treatment with RA caused the appearance of a late-onset inward current carried by Ca²⁺ ions in a subpopulation of TB cells. This current was not affected by removal of extracellular Na⁺ and was completely blocked by Cd²⁺, a broad-spectrum blocker of Ca²⁺ currents. Altogether, our results indicate that RA-differentiation of TB cells induces functional changes by augmenting the amplitude of voltage-gated sodium current and by inducing, in a subpopulation of treated cells, the appearance of a voltage-gated calcium current.

All-Trans Retinoic Acid Enhances Matrix Metalloproteinase 2 Expression and Secretion in Human Myeloid Leukemia THP-1 Cells

All-trans retinoic acid (ATRA) is an effective drug for the induction therapy of acute promyelocytic leukemia. However, the treatment is associated with adverse events such as retinoic acid syndrome (RAS) in some patients, whose histologic characteristics included organ infiltration by leukemic cells. Matrix metalloproteinase 2 (MMP-2) is often upregulated in tumor cells and plays a role in tumor cell migration and invasion by degrading the extracellular matrix. In this study, we examined the possible modulatory effects of ATRA on MMP-2 expression and secretion in human myeloid leukemia cell line THP-1. The cells were treated with various concentrations of ATRA, and MMP-2 expression and secretion were examined. MMP-2 expression and secretion started to increase with ATRA concentration as low as 0.1 nM and gradually increased thereafter. Agonists of retinoic acid receptor (RAR) or retinoid X receptor (RXR) alone could enhance MMP-2 secretion, and RAR or RXR antagonists alone could reverse ATRA-induced MMP-2 secretion. ATRA increased intracellular calcium ion levels, and a calcium-channel blocker inhibited ATRA-induced MMP-2 secretion. Dexamethasone suppressed ATRA-induced MMP-2 secretion. Our results suggest that ATRA enhances MMP-2 expression and secretion in human myeloid leukemia THP-1 cells in a calcium ion dependent manner through RAR/RXR signaling pathways, and this enhanced expression and secretion may be associated with the possible mechanisms of RAS.

Active DNA demethylation of the vertebrate genomes by DNA methyltransferases: deaminase, dehydroxymethylase or demethylase?

Vertebrate DNA methyltransferases (DNMTs) have been thought to primarily function to covalently add a methyl group to the 5-position of cytosine. However, recent discovery of the DNA demethylation and dehydroxymethylation activities of DNMTs in vitro suggest new routes to complete the dynamic cycle of DNA methylation-demethylation of the vertebrate genomes. The in vitro reaction conditions suggest that vertebrate DNMTs can switch from DNA methylases to DNA dehydroxymethylases under oxidative stress and to DNA demethylases in the presence of calcium ion under nonreducing conditions. These environmental parameters provide clues regarding the choices in vivo of DNMT activities utilized in different physiological systems. In particular, the nature of these parameters suggest that the DNA demethylation and dehydroxymethylation activities of the vertebrate DNMTs play essential roles in multiple biological processes including early embryo development, regulation of neuronal plasticity, tumorigenesis and hormone-regulated transcription.

Reprogramming of HUVECs into induced pluripotent stem cells (HiPSCs), generation and characterization of HiPSC-derived neurons and astrocytes

Neurodegenerative diseases are characterized by chronic and progressive structural or functional loss of neurons. Limitations related to the animal models of these human diseases have impeded the development of effective drugs. This emphasizes the need to establish disease models using human-derived cells. The discovery of induced pluripotent stem cell (iPSC) technology has provided novel opportunities in disease modeling, drug development, screening, and the potential for “patient-matched” cellular therapies in neurodegenerative diseases. In this study, with the objective of establishing reliable tools to study neurodegenerative diseases, we reprogrammed human umbilical vein endothelial cells (HUVECs) into iPSCs (HiPSCs). Using a novel and direct approach, HiPSCs were differentiated into cells of central nervous system (CNS) lineage, including neuronal, astrocyte and glial cells, with high efficiency. HiPSCs expressed embryonic genes such as nanog, sox2 and Oct-3/4, and formed embryoid bodies that expressed markers of the 3 germ layers. Expression of endothelial-specific genes was not detected in HiPSCs at RNA or protein levels. HiPSC-derived neurons possess similar morphology but significantly longer neurites compared to primary human fetal neurons. These stem cell-derived neurons are susceptible to inflammatory cell-mediated neuronal injury. HiPSC-derived neurons express various amino acids that are important for normal function in the CNS. They have functional receptors for a variety of neurotransmitters such as glutamate and acetylcholine. HiPSC-derived astrocytes respond to ATP and acetylcholine by elevating cytosolic Ca²⁺ concentrations. In summary, this study presents a novel technique to generate differentiated and functional HiPSC-derived neurons and astrocytes. These cells are appropriate tools for studying the development of the nervous system, the pathophysiology of various neurodegenerative diseases and the development of potential drugs for their treatments.

TRPP2-dependent Ca2+ signaling in dorso-lateral mesoderm is required for kidney field establishment in Xenopus

In Xenopus laevis embryos, kidney field specification is dependent on retinoic acid (RA) and coincides with a dramatic increase of Ca(2+) transients, but the role of Ca(2+) signaling in the kidney field is unknown. Here, we identify TRPP2, a member of the transient receptor potential (TRP) superfamily of channel proteins encoded by the pkd2 gene, as a central component of Ca(2+) signaling in the kidney field. TRPP2 is strongly expressed at the plasma membrane where it might regulate extracellular Ca(2+) entry. Knockdown of pkd2 in the kidney field results in the downregulation of pax8, but not of other kidney field genes (lhx1, osr1 and osr2). We further show that inhibition of Ca(2+) signaling with an inducible Ca(2+) chelator also causes downregulation of pax8, and that pkd2 knockdown results in a severe inhibition of Ca(2+) transients in kidney field explants. Finally, we show that disruption of RA results both in an inhibition of intracellular Ca(2+) signaling and of TRPP2 incorporation into the plasma membrane of kidney field cells. We propose that TRPP2-dependent Ca(2+) signaling is a key component of pax8 regulation in the kidney field downstream of RA-mediated non-transcriptional control of TRPP2.

Retinoic acid affects calcium signaling in adult molluscan neurons

Retinoic acid, the active metabolite of vitamin A, is important for nervous system development, regeneration, as well as cognitive functions of the adult central nervous system. These central nervous system functions are all highly dependent on neuronal activity. Retinoic acid has previously been shown to induce changes in the firing properties and action potential waveforms of adult molluscan neurons in a dose- and isomer-dependent manner. In this study, we aimed to determine the cellular pathways by which retinoic acid might exert such effects, by testing the involvement of pathways previously shown to be affected by retinoic acid. We demonstrated that the ability of all-trans retinoic acid (atRA) to induce electrophysiological changes in cultured molluscan neurons was not prevented by inhibitors of protein synthesis, protein kinase A or phospholipase C. However, we showed that atRA was capable of rapidly reducing intracellular calcium levels in the same dose- and isomer-dependent manner as shown previously for changes in neuronal firing. Moreover, we also demonstrated that the transmembrane ion flux through voltage-gated calcium channels was rapidly modulated by retinoic acid. In particular, the peak current density was reduced and the inactivation rate was increased in the presence of atRA, over a similar time course as the changes in cell firing and reductions in intracellular calcium. These studies provide further evidence for the ability of atRA to induce rapid effects in mature neurons.

Retinoic acid induces changes in electrical properties of adult neurons in a dose- and isomer-dependent manner

The electrical activity of neurons is known to play a role in neuronal development, as well as repair of adult nervous tissue. For example, the extension of neurites and motility of growth cones can be modulated by changes in the electrical firing of neurons. The vitamin A metabolite retinoic acid also plays a critical role during nervous system development and is also known to elicit regenerative responses, namely the induction, enhancement, and directionality of neurite outgrowth. However, no studies have previously reported the ability of retinoic acid to modify the electrical activity of neurons. In this study, we determined whether retinoic acid might exert effects on the nervous system by altering the electrical properties of neurons. Using cultured adult neurons from Lymnaea stagnalis, we showed that acute application of retinoic acid can rapidly elicit changes in neuronal firing properties. Retinoic acid caused the presence of atypical firing behavior such as rhythmic bursting and altered the shape of action potentials, causing increases in half-amplitude duration and decay time. Retinoic acid also caused cell silencing, whereby neuronal activity was halted within an hour. These effects of retinoic acid were shown to be both dose and isomer dependent. We then showed that the effects of retinoic acid on cell firing (but not silencing) were significantly reduced in the presence of an retinoid X receptor pan-antagonist HX531. This study suggests that some of the effects of retinoic acid during neuronal development or regeneration might possibly occur as a result of changes in electrical activity of neurons.

Non ionising radiation as a non chemical strategy in regenerative medicine: Ca(2+)-ICR "In Vitro" effect on neuronal differentiation and tumorigenicity modulation in NT2 cells

In regenerative medicine finding a new method for cell differentiation without pharmacological treatment or gene modification and minimal cell manipulation is a challenging goal. In this work we reported a neuronal induced differentiation and consequent reduction of tumorigenicity in NT2 human pluripotent embryonal carcinoma cells exposed to an extremely low frequency electromagnetic field (ELF-EMF), matching the cyclotron frequency corresponding to the charge/mass ratio of calcium ion (Ca(2+)-ICR). These cells, capable of differentiating into post-mitotic neurons following treatment with Retinoic Acid (RA), were placed in a solenoid and exposed for 5 weeks to Ca(2+)-ICR. The solenoid was installed in a μ-metal shielded room to avoid the effect of the geomagnetic field and obtained totally controlled and reproducible conditions. Contrast microscopy analysis reveled, in the NT2 exposed cells, an important change in shape and morphology with the outgrowth of neuritic-like structures together with a lower proliferation rate and metabolic activity alike those found in the RA treated cells. A significant up-regulation of early and late neuronal differentiation markers and a significant down-regulation of the transforming growth factor-α (TGF-α) and the fibroblast growth factor-4 (FGF-4) were also observed in the exposed cells. The decreased protein expression of the transforming gene Cripto-1 and the reduced capability of the exposed NT2 cells to form colonies in soft agar supported these last results. In conclusion, our findings demonstrate that the Ca(2+)-ICR frequency is able to induce differentiation and reduction of tumorigenicity in NT2 exposed cells suggesting a new potential therapeutic use in regenerative medicine.

Acute effects of all-trans-retinoic acid in ischemic injury

All-trans-retinoic acid (ATRA) is a vitamin A derivative that is important in neuronal patterning, survival, and neurite outgrowth. Neuroprotective effects of ATRA in ischemia have been demonstrated but its effects on glial swelling are not known. We investigated the relatively acute effects of ATRA on cell swelling in ischemic injury and on key features hypothesized to contribute to cell swelling including increased reactive oxygen species/reactive nitrogen species (ROS/RNS), depolarization of the inner mitochondrial membrane potential (ΔΨm), and increased intracellular calcium ([Ca2+]i). C6 glial cultures were subjected to 5 hr oxygen-glucose deprivation (OGD). ATRA was added to separate groups after the end of OGD. OGD increased cell volume by 43%, determined at 90 min after the end of OGD, but this increase was significantly attenuated by ATRA. OGD induced an increase in ROS/RNS production in the whole cell and mitochondria, as assessed by the fluorescent dyes CM-H2DCFDA and MitoTracker CM-H2-XROS at the end of OGD. The increase in mitochondrial ROS, but not cellular ROS, was significantly attenuated by ATRA. OGD also induced a 67% decline in mitochondrial ΔΨm but this decline was significantly attenuated by ATRA. OGD-induced increase in [Ca2+]i was also significantly attenuated by ATRA. Taken together with our previous results where calcium channel blockers reduced cell swelling, the effects of ATRA in attenuating swelling are possibly mediated through its effects in regulating [Ca2+]i. Considering the paucity of agents in attenuating brain edema in ischemia, ATRA has the potential to reduce brain edema and associated neural damage in ischemic injury.

Nitric oxide and cyclic nucleotide signal transduction modulates synaptic vesicle turnover in human model neurons

The human Ntera2 (NT2) teratocarcinoma cell line can be induced to differentiate into post-mitotic neurons. Here, we report that the human NT2 neurons generated by a spherical aggregate cell culture method express increasing levels of typical pre-synaptic proteins (synapsin and synaptotagmin I) along the neurite depending on the length of in vitro culture. By employing an antibody directed against the luminal domain of synaptotagmin I and the fluorescent dye N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl)pyridinium dibromide, we show that depolarized NT2 neurons display calcium-dependent exo-endocytotic synaptic vesicle recycling. NT2 neurons express the neuronal isoform of neuronal nitric oxide synthase and soluble guanylyl cyclase (sGC), the major receptor for nitric oxide (NO). We tested whether NO signal transduction modulates synaptic vesicle turnover in human NT2 neurons. NO donors and cylic guanosine-monophosphate analogs enhanced synaptic vesicle recycling while a sGC inhibitor blocked the effect of NO donors. Two NO donors, sodium nitroprusside, and and N-Ethyl-2-(1-ethyl-2-hydroxy-2-nitrosohydrazino) ethanamine evoked vesicle exocytosis which was partially blocked by the sGC inhibitor. The activator of adenylyl cyclase, forskolin, and a cAMP analog induced synaptic vesicle recycling and exocytosis via a parallel acting protein kinase A pathway. Our data from NT2 neurons suggest that NO/cyclic nucleotide signaling pathways may facilitate neurotransmitter release in human brain cells.

TRPV1 expression and activity during retinoic acid-induced neuronal differentiation

The transient receptor potential vanilloid subtype 1 (TRPV1) is a Ca(2+)-permeable channel primarily expressed in dorsal root ganglion neurons. Besides its function in thermogenic nociception and neurogenic inflammation, TRPV1 is involved in cell migration, cytoskeleton re-organisation and in neuronal guidance. To explore the TRPV1 level and activity during conditions for neuronal maturation, TRPV1-expressing SHSY5Y neuroblastoma cells were differentiated into a neuronal phenotype using all-trans-retinoic acid (RA). We show that RA highly up-regulated the total and cell surface TRPV1 protein expression but the TRPV1 mRNA level was unaffected. The up-regulated receptors were localised to the cell bodies and the developed neurites. Furthermore, RA increased both the basal intracellular free Ca(2+) concentration by 30% as well as the relative capsaicin-induced Ca(2+) influx. The results show that TRPV1 protein expression increases during RA-induced differentiation in vitro, which generates an altered intracellular Ca(2+) homeostasis.

An increase in intracellular Ca2+ is involved in pronephric tubule differentiation in the amphibian Xenopus laevis

The pronephros is the first kidney to develop and is the functional embryonic kidney in lower vertebrates. It has previously been shown that pronephric tubules can be induced to form ex vivo in ectodermal tissue by treatment with activin A and retinoic acid. In this study, we investigated the role of Ca(2+) signaling in the formation of the pronephric tubules both in intact Xenopus embryos and ex vivo. In the ex vivo system, retinoic acid but not activin A stimulated the generation of Ca(2+) transients during tubule formation. Furthermore, tubule differentiation could be induced by agents that increase the concentration of intracellular Ca(2+) in activin A-treated ectoderm. In addition, tubule formation was inhibited by loading the ectodermal tissue with the Ca(2+) chelator, BAPTA-AM prior to activin A/retinoic acid treatment. In intact embryos, Ca(2+) transients were also recorded during tubule formation, and photo-activation of the caged Ca(2+) chelator, diazo-2, localized to the pronephric domain, produced embryos with a shortened and widened tubule phenotype. In addition, the location of the Ca(2+) transients observed, correlated with the expression pattern of the specific pronephric tubule gene, XSMP-30. These data indicate that Ca(2+) might be a necessary signal in the process of tubulogenesis both ex vivo and in intact embryos.

Characterisation of large-conductance calcium-activated potassium channels (BK(Ca)) in human NT2-N cells

Large-conductance calcium-activated potassium (BK(Ca)) channels were studied in inside-out patches of human NTERA2 neuronal cells (NT2-N). In symmetrical (140 mM) K(+) the channel mean conductance was 265 pS, the current reversing at approximately 0 mV. It was selective (P(K)/P(Na)=20:1) and blocked by internal paxilline and TEA. The open probability-voltage relationship for BK(Ca) was fitted with a Boltzmann function, the V((1/2)) being 76.3 mV, 33.6 mV and -14.1 mV at 0.1 muM, 3.3 muM and 10 muM [Ca(2+)](i), respectively. The relationship between open probability and [Ca(2+)](i) was fitted by the Hill equation (Hill coefficient 2.7, half maximal activation at 2.0 muM [Ca(2+)](i)). Open and closed dwell time histograms were fitted by the sum of two and three voltage-dependent exponentials, respectively. Increasing [Ca(2+)](i) produced both an increase in the longer open time constant and a decrease in the longest closed time constant, so increasing mean open time. "Intracellular" ATP evoked a concentration-dependent increase in NT2-N BK(Ca) activity. At +40 mV half-maximum activation occurred at an [ATP](i) of 3 mM (30 nM [Ca(2+)](i)). ADP and GTP were less potent, and AMP-PNP was inactive. This is the first characterisation of a potassium channel in NT2-N cells showing that it is similar to the BK(Ca) channel of other preparations.

Retinoic acid induces neurite outgrowth and growth cone turning in invertebrate neurons

Identification of molecules involved in neurite outgrowth during development and/or regeneration is a major goal in the field of neuroscience. Retinoic acid (RA) is a biologically important metabolite of vitamin A that acts as a trophic factor and has been implicated in neurite outgrowth and regeneration in many vertebrate species. Although abundant in the CNS of many vertebrates, the precise role of RA in neural regeneration has yet to be determined. Moreover, very little information is available regarding the role of RA in invertebrate nervous systems. Here, we demonstrate for the first time that RA induces neurite outgrowth from invertebrate neurons. Using individually identified neurons isolated from the CNS of Lymnaea stagnalis, we demonstrated that a significantly greater proportion of cells produced neurite outgrowth in RA. RA also extended the duration of time that cells remained electrically excitable in vitro, and we showed that exogenously applied RA acted as a chemoattractive factor and induced growth cone turning toward the source of RA. This is the first demonstration that RA can induce turning of an individual growth cone. These data strongly suggest that the actions of RA on neurite outgrowth and cell survival are highly conserved across species.

A rapid, nongenomic pathway facilitates the synaptic transmission induced by retinoic acid at the developing synapse

We have previously shown that retinoic acid (RA), a factor highly expressed in spinal cord, rapidly and specifically enhances the spontaneous acetylcholine release at developing neuromuscular synapses in Xenopus cell culture, using whole-cell patch-clamp recording. We have now further investigated the underlying mechanisms that are involved in RA-induced facilitation on the frequency of spontaneous synaptic currents (SSCs). Buffering the rise of intracellular Ca2+ with BAPTA-AM hampered the facilitation of SSC frequency induced by RA. The prompt RA-enhanced SSC frequency was not abolished when Ca2+ was eliminated from the culture medium or there was bath application of the pharmacological Ca2+ channel inhibitor Cd2+, indicating that Ca2+ influx through voltage-activated Ca2+ channels are not required. Application of membrane-permeable inhibitors of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] or ryanodine receptors effectively blocked the increase of SSC frequency elicited by RA. Treating cells with either wortmannin or LY294002, two structurally different inhibitors of phosphatidylinositol 3-kinase (PI 3-kinase) and with the phospholipase Cgamma (PLCgamma) inhibitor U73122, abolished RA-induced facilitation of synaptic transmission. Preincubation of the cultures with pharmacological inhibitors, either genistein, a broad-spectrum tyrosine kinase inhibitor, or PP2, which predominantly inhibits the Src family of nonreceptor tyrosine kinase, completely abolished RA-induced synaptic facilitation. Taken collectively, these results suggest that RA elicits Ca2+ release from Ins1,4,5P3 and/or ryanodine-sensitive intracellular Ca2+ stores of the presynaptic nerve terminal. This is done via PLCgamma/PI 3-kinase signaling cascades and Src tyrosine kinase activation, leading to an enhancement of spontaneous transmitter release.

Role of retinoid signalling in the adult brain

Vitamin A (all-trans-retinol) is the parent compound of a family of natural and synthetic compounds, the retinoids. Retinoids regulate gene transcription in numerous cells and tissues by binding to nuclear retinoid receptor proteins, which act as transcription factors. Much of the research conducted on retinoid signalling in the nervous system has focussed on developmental effects in the embryonic or early postnatal brain. Here, we review the increasing body of evidence indicating that retinoid signalling plays an important role in the function of the mature brain. Components of the metabolic pathway for retinoids have been identified in adult brain tissues, suggesting that all-trans-retinoic acid (ATRA) can be synthesized in discrete regions of the brain. The distribution of retinoid receptor proteins in the adult nervous system is different from that seen during development; and suggests that retinoid signalling is likely to have a physiological role in adult cortex, amygdala, hypothalamus, hippocampus, striatum and associated brain regions. A number of neuronal specific genes contain recognition sequences for the retinoid receptor proteins and can be directly regulated by retinoids. Disruption of retinoid signalling pathways in rodent models indicates their involvement in regulating synaptic plasticity and associated learning and memory behaviours. Retinoid signalling pathways have also been implicated in the pathophysiology of Alzheimer's disease, schizophrenia and depression. Overall, the data underscore the likely importance of adequate nutritional Vitamin A status for adult brain function and highlight retinoid signalling pathways as potential novel therapeutic targets for neurological diseases.

Region-specific cell grafting into cervical and lumbar spinal cord in rat: a qualitative and quantitative stereological study

In the present study, we have characterized an atraumatic grafting technique which permits multiple, segmental, and lamina-specific injections into cervical or lumbar spinal cord. Cell injections were performed in spinally mounted rats of different ages and spinal cord size, using a micromanipulator and glass microcapillary connected to a digital microinjector. For grafting, we used human neuroteratoma (hNT) cells, BrdU-labeled rat spinal precursors or primary embryonic spinal cord neurons isolated from E14 spinal cord of the eGFP+ rat. Systematic quantification of grafted cells was performed using stereological principles of systematic random sampling and semi-automated optical Disector software. Volume reconstruction was performed using serial sections from grafted areas and custom-developed software (Ellipse) which permits "two reference points" semi-automated alignment of images, as well as volume reconstruction and calculation. By coupling these techniques, it is possible to achieve a relatively precise and atraumatic cell delivery into multiple spinal cord segments and specific spinal laminae. Consistency of the multiple grafts position in the targeted laminar areas was verified by a systematic volume reconstruction. Good survival of implanted cells for the three different cell lines used indicate that this grafting technique coupled with a systematic analysis of the individual grafting sites can represent a valuable implantation-analytical system.

Spinal implantation of hNT neurons and neuronal precursors: graft survival and functional effects in rats with ischemic spastic paraplegia

Transient spinal ischemia, a complication associated with aortic cross-clamp may lead to spastic paraplegia. Once fully developed this deficit is permanent. Quantitative histopathological assessments and pharmacological studies show that the ischemic spasticity is secondary to the loss of lumbar GABA and glycinergic inhibitory interneurons. In the present study, we investigated whether human hNT neurons or committed Sprague-Dawley rat spinal neuronal precursors (SNPs) when grafted into previously ischemic spinal segments depleted of inhibitory neurons would restore local inhibitory tone and ameliorate spasticity. Rats with functionally and electrophysiologically defined spasticity that received spinal graft of hNT neurons or neuronal precursors and immunosuppressive treatment displayed a progressive recovery of motor function that correlated with the improvement of otherwise exacerbated peripheral motor response evoked by stimulation of motor cortex. In contrast, in control, medium-injected or oligodendrocyte-grafted animals no significant therapeutic effect was seen. Stereological quantification of grafted neurons revealed 1-2% survival at three months after transplantation. These surviving neurons displayed a robust axo-dendritic sprouting and expression of markers typical of mature neurons including NSE, NeuN and synaptophysin. In both treatment groups a subpopulation of grafted neurons developed GABA immunoreactivity. These data provide evidence that a region specific grafting of hNT neurons or other neuronally committed cells, which have a potential to develop inhibitory neurotransmitter phenotype, represent an effective treatment modality to modulate ischemia-induced spastic paraplegia.

Translocation and phosphorylation of calcyclin binding protein during retinoic acid-induced neuronal differentiation of neuroblastoma SH-SY5Y cells

For better understanding of functions of the Calcyclin Binding Protein (CacyBP) and exploring its possible roles in neuronal differentiation, the subcellular localization of human CacyBP was examined in retinoic acid(RA)-induced and uninduced neuroblastoma SH-SY5Y cells. Immunostaining indicated that CacyBP was present in the cytoplasm of uninduced SH-SY5Y cells, in which the resting Ca(2+) concentration was relatively lower than that of RA-induced cells. After the RA induction, immunostaining was seen in both the nucleus and cytoplasm. In the RA-induced differentiated SH-SY5Y cells, CacyBP was phosphorylated on serine residue(s), while it existed in a dephosphorylated form in normal (uninduced) cells. Thus, the phosphorylation of CacyBP occurs when it is translocated to the nuclear region. The translocation of CacyBP during the RA-induced differentiation of SH-SY5Y cells suggested that this protein might play a role in neuronal differentiation.

Genetically modified NT2N human neuronal cells mediate long-term gene expression as CNS grafts in vivo and improve functional cognitive outcome following experimental traumatic brain injury

Human Ntera-2 (NT2) cells can be differentiated in vitro into well-characterized populations of NT2N neurons that engraft and mature when transplanted into the adult CNS of rodents and humans. They have shown promise as treatments for neurologic disease, trauma, and ischemic stroke. Although these features suggest that NT2N neurons would be an excellent platform for ex vivo gene therapy in the CNS, stable gene expression has been surprisingly difficult to achieve in these cells. In this report we demonstrate stable, efficient, and nontoxic gene transfer into undifferentiated NT2 cells using a pseudotyped lentiviral vector encoding the human elongation factor 1-alpha promoter and the reporter gene eGFP. Expression of eGFP was maintained when the NT2 cells were differentiated into NT2N neurons after treatment with retinoic acid. When transplanted into the striatum of adult nude mice, transduced NT2N neurons survived, engrafted, and continued to express the reporter gene for long-term time points in vivo. Furthermore, transplantation of NT2N neurons genetically modified to express nerve growth factor significantly attenuated cognitive dysfunction following traumatic brain injury in mice. These results demonstrate that defined populations of genetically modified human NT2N neurons are a practical and effective platform for stable ex vivo gene delivery into the CNS.

Differential toxicity of nitric oxide, aluminum, and amyloid beta-peptide in SN56 cholinergic cells from mouse septum

A characteristic feature of several encephalopathies is preferential impairment of cholinergic neurons. Their particular susceptibility to cytotoxic insults may result from the fact that they utilise acetyl-CoA both for energy production and acetylcholine synthesis. In addition, phenotypic modifications of cholinergic neurons are likely to influence their susceptibility to specific harmful conditions. SN56 cholinergic cells were differentiated by the combination of dibutyryl cAMP and retinoic acid. Al and sodium nitroprusside (SNP, NO donor) exerted direct additive inhibitory effects on mitochondrial aconitase activity. However, NO, Al, or amyloid beta (Abeta)(25-35) caused none or only slight changes of choline O-acetyl transferase (ChAT) and pyruvate dehydrogenase (PDH) activity and relatively small loss of non-differentiated cells (NCs). On the other hand, in differentiated cells (DCs) these neurotoxins brought about marked decreases of these enzyme activities along with greater than in non-differentiated ones increase of cell-death rate. Abeta(35-25) had no effect on these cell parameters. NO and other compounds aggravated detrimental effect of each other particularly in differentiated cells. Thus, differential vulnerability of brain cholinergic neurons to various degenerative signals may result from their phenotype-dependent ratios of acetylcholine to acetyl-CoA synthesising capacities.

Expression of calcium channels along the differentiation of cultured trophoblast cells from human term placenta

Placental transfer of maternal calcium (Ca2+) is carried out in vivo by the syncytiotrophoblast layer. Although this process is crucial for fetal development, it remains poorly understood. Cytotrophoblasts isolated from human term placenta undergo spontaneous syncytiotrophoblast-like morphological and biochemical differentiation in vitro and are thought to reflect in vivo syncytiotrophoblast. In the present study, we characterized the Ca2+ uptake potential and the expression of several Ca2+ channels by human trophoblasts during differentiation in vitro for up to 6 days. Secretion of hCG (specific differentiation marker) and uptake of Ca2+ by trophoblasts increased gradually as a function of days in culture. Both hCG secretion and Ca2+ uptake were maximal on Day 4 and declined on Days 5-6. Expression of the Ca2+ transporter proteins CaT1 and CaT2 was revealed by reverse transcription-polymerase chain reaction in cytotrophoblasts freshly isolated from human term placenta. In addition, messengers for two L-type Ca2+ channel isoforms (alpha(1C) and alpha(1D)) were also detected. Levels of CaT1, CaT2, and L-type Ca2+ channel mRNA increased gradually during culture, reaching a maximum between Days 2 and 3. In contrast to CaT1 and CaT2 expression that declined thereafter to levels observed on Day 1, L-type channel expression decreased by 50% but remained above the expression level of Day 1. Our results indicate that the pattern of CaT1 and CaT2 expression correlates with the Ca2+ uptake potential along the differentiation of cultured human trophoblasts isolated from term placenta. This correlation provides circumstantial evidence for a role of this family of channels in basal Ca2+ uptake by the syncytiotrophoblast.

Role and distribution of retinoic acid during CNS development

Retinoic acid (RA), the biologically active derivative of vitamin A, induces a variety of embryonal carcinoma and neuroblastoma cell lines to differentiate into neurons. The molecular events underlying this process are reviewed with a view to determining whether these data can lead to a better understanding of the normal process of neuronal differentiation during development. Several transcription factors, intracellular signaling molecules, cytoplasmic proteins, and extracellular molecules are shown to be necessary and sufficient for RA-induced differentiation. The evidence that RA is an endogenous component of the developing central nervous system (CNS) is then reviewed, data which include high-pressure liquid chromotography (HPLC) measurements, reporter systems and the distribution of the enzymes that synthesize RA. The latter is particularly relevant to whether RA signals in a paracrine fashion on adjacent tissues or whether it acts in an autocrine manner on cells that synthesize it. It seems that a paracrine system may operate to begin early patterning events within the developing CNS from adjacent somites and later within the CNS itself to induce subsets of neurons. The distribution of retinoid-binding proteins, retinoid receptors, and RA-synthesizing enzymes is described as well as the effects of knockouts of these genes. Finally, the effects of a deficiency and an excess of RA on the developing CNS are described from the point of view of patterning the CNS, where it seems that the hindbrain is the most susceptible part of the CNS to altered levels of RA or RA receptors and also from the point of view of neuronal differentiation where, as in the case of embryonal carcinoma (EC) cells, RA promotes neuronal differentiation. The crucial roles played by certain genes, particularly the Hox genes in RA-induced patterning processes, are also emphasized.

Single-Cell Antisense RNA Amplification and Microarray Analysis as a Tool for Studying Neurological Degeneration and Restoration

Neurodegenerative diseases typically affect subpopulations of neurons. Characterizing these vulnerable cells and identifying the factors that make them susceptible to damage while neighboring cells remain resistant are essential to the understanding of molecular pathogenesis that underlies neurodegenerative diseases. Classically, molecular analysis of the central nervous system involves the identification and isolation of an anatomic region of interest; next, the relevant tissue is pulverized, and the resulting homogenate is analyzed. Although this method provides useful data, its effectiveness diminishes when used in areas of high cellular diversity or in instances in which one cell type is lost as a consequence of selective cell death or quiescence. A technique that affords the ability to assess molecular events in a very precise anatomical site would provide a powerful tool for this research discipline. In this review, we discuss the amplification of messenger RNA from single neural cells and the subsequent use of the RNA to probe DNA microarrays in an effort to create cell-specific molecular profiles. Specifically, recent work in single-cell expression profiling in Alzheimer's and Huntington's diseases is discussed. We also review some new work with neural stem cells and their application to restorative neurobiology. Finally, we discuss the use of cell-specific molecular profiles to better understand the basics of neuronal cell biology.

Functional expression of L-, N-, P/Q-, and R-type calcium channels in the human NT2-N cell line

The biophysical and pharmacological properties of voltage-gated calcium channel currents in the human teratocarcinoma cell line NT2-N were studied using the whole cell patch-clamp technique. When held at -80 mV, barium currents (I(Ba)s) were evoked by voltage commands to above -35 mV that peaked at +5 mV. When holding potentials were reduced to -20 mV or 5 mM barium was substituted for 5 mM calcium, there was a reduction in peak currents and a right shift in the current-voltage curve. A steady-state inactivation curve for I(Ba) was fit with a Boltzmann curve (V(1/2) = -43.3 mV; slope = -17.7 mV). Maximal current amplitude increased from 1-wk (232 pA) to 9-wk (1025 pA) postdifferentiation. Whole cell I(Ba)s were partially blocked by specific channel blockers to a similar extent in 1- to 3-wk and 7- to 9-wk postdifferentiation NT2-N cells: 10 microM nifedipine (19 vs. 25%), 10 microM conotoxin GVIA (27 vs. 25%), 10 microM conotoxin MVIIC (15 vs. 16%), and 1.75 microM SNX-482 (31 vs. 33%). Currents were completely blocked by 300 microM cadmium. In the presence of nifedipine, GVIA, and MVIIC, approximately 35% of current remained, which was reduced further by SNX-482 (7-14% of current remained), consistent with functional expression of L-, N-, and P/Q-calcium channel types and one or more R-type channel. The presence of multiple calcium currents in this human neuronal-type cell line provides a potentially useful model for study of the regulation, expression and cellular function of human derived calcium channel currents; in particular the R-type current(s).