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Jia-Yi Li

Publications and source records attributed to Jia-Yi Li.

At least 19 recordsLinked to original sources
PubMed2006

Cholinergic neuronal defect without cell loss in Huntington's disease.

Huntington's disease (HD) is a neurodegenerative disorder caused by a CAG-repeat expansion in the huntingtin (IT15) gene. The striatum is one of the regions most affected by neurodegeneration, resulting in the loss of the medium-sized spiny neurons. Traditionally, the large cholinergic striatal interneurons are believed to be spared. Recent studies demonstrate that neuronal dysfunction without cell death also plays an important role in early and mid-stages of the disease. Here, we report that cholinergic transmission is affected in a HD transgenic mouse model (R6/1) and in tissues from HD patients. Stereological analysis shows no loss of cholinergic neurons in the striatum or septum in R6/1 mice. In contrast, the levels of mRNA and protein for vesicular acetylcholine transporter (VAChT) and choline acetyltransferase (ChAT) are decreased in the striatum and cortex, and acetylcholine esterase activity is lowered in the striatum of R6/1 mice already at young ages. Accordingly, VAChT is also reduced in striatal tissue from patients with HD. The decrease of VAChT in the patient samples studied is restricted to the striatum and does not occur in the hippocampus or the spinal cord. The expression and localization of REST/NRSF, a transcriptional regulator for the VAChT and ChAT genes, are not altered in cholinergic neurons. We show that the R6/1 mice exhibit severe deficits in learning and reference memory. Taken together, our data show that the cholinergic system is dysfunctional in R6/1 and HD patients. Consequently, they provide a rationale for testing of pro-cholinergic drugs in this disease.

Animals↗
PubMed2006

Laminin alpha1 chain improves laminin alpha2 chain deficient peripheral neuropathy.

Absence of laminin alpha2 chain leads to a severe form of congenital muscular dystrophy (MDC1A) associated with peripheral neuropathy. Hence, future therapies should be aimed at alleviating both muscle and neurological dysfunctions. Pre-clinical studies in animal models have mainly focused on ameliorating the muscle phenotype. Here we show that transgenic expression of laminin alpha1 chain in muscles and the peripheral nervous system of laminin alpha2 chain deficient mice reduced muscular dystrophy and largely corrected the peripheral nerve defects. The presence of laminin alpha1 chain in the peripheral nervous system resulted in near-normal myelination, restored Schwann cell basement membranes and improved rotarod performance. In summary, we postulate that laminin alpha1 chain is an excellent substitute for laminin alpha2 chain in multiple tissues and suggest that treatment with laminin alpha1 chain may be beneficial for MDC1A in humans.

Animals↗
PubMed2006

Neuropeptide Y2 receptors are involved in enhanced neurogenic vasoconstriction in spontaneously hypertensive rats.

1. The present study addressed the role of neuropeptide (NPY) Y2 receptors in neurogenic contraction of mesenteric resistance arteries from female spontaneously hypertensive rats (SHR). Arteries were suspended in microvascular myographs, electrical field stimulation (EFS) was performed, and protein evaluated by Western blotting and immunohistochemistry. 2. In vasopressin-activated endothelium-intact arteries, NPY and fragments with selectivity for Y1 receptors, [Leu31,Pro34]NPY, Y2 receptors, NPY(13-36), and rat pancreatic polypeptide evoked more pronounced contractions in segments from SHR than in Wistar Kyoto (WKY) arteries, even in the presence of the Y1 receptor antagonist, BIBP3226 (0.3 microM, (R)-N(2)-(diphenacetyl)-N-[(4-hydroxyphenyl)methyl]D-arginineamide). 3. In the presence of prazosin and during vasopressin activation, EFS-evoked contractions were larger in arteries from SHR compared to WKY. EFS contractions were enhanced by the Y2 receptor selective antagonist BIIE0246TF (0.5 microM, (S)-N2-[[1-[2-[4-[(R,S)-5,11-dihydro-6(6h)-oxodibenz[b,e]azepin-11-y1]-1-piperazinyl]-2-oxoethyl]cyclo-pentyl-N-[2-[1,2-dihydro-3,5 (4H)-dioxo-1,2-diphenyl-3H-1,2,4-triazol-4-yl]ethyl]-argininamide), reduced by BIBP3226, and abolished by the combination of BIBP3226 and BIIE0246TF. 4. Immunoblotting showed NPY Y1 and Y2 receptor expression to be similar in arteries from WKY and SHR, although a specific Y2 receptor band at 80 kDa was detected only in arteries from WKY. 5. Immunoreaction for NPY was enhanced in arteries from SHR. In contrast to arteries from WKY, BIIE0246TF increased NPY immunoreactivity in EFS-stimulated arteries from SHR. 6. The present results suggest that postjunctional neuropeptide Y1 and Y2 receptors contribute to neurogenic contraction of mesenteric small arteries. Moreover, both enhanced NPY content and altered neuropeptide Y1 and Y2 receptor activation apparently contribute to the enhanced neurogenic contraction of arteries from SHR.

Animals↗
PubMed2006

Transplantation of human embryonic stem cell-derived cells to a rat model of Parkinson's disease: effect of in vitro differentiation on graft survival and teratoma formation.

Human embryonic stem cells (hESCs) have been proposed as a source of dopamine (DA) neurons for transplantation in Parkinson's disease (PD). We have investigated the effect of in vitro predifferentiation on in vivo survival and differentiation of hESCs implanted into the 6-OHDA (6-hydroxydopamine)-lesion rat model of PD. The hESCs were cocultured with PA6 cells for 16, 20, or 23 days, leading to the in vitro differentiation into DA neurons. Grafted hESC-derived cells survived well and expressed neuronal markers. However, very few exhibited a DA neuron phenotype. Reversal of lesion-induced motor deficits was not observed. Rats grafted with hESCs predifferentiated in vitro for 16 days developed severe teratomas, whereas most rats grafted with hESCs predifferentiated for 20 and 23 days remained healthy until the end of the experiment. This indicates that prolonged in vitro differentiation of hESCs is essential for preventing formation of teratomas.

Animals↗
PubMed2006

Failure of transdifferentiation of adult hematopoietic stem cells into neurons.

Previous studies of bone marrow-derived stem cell transdifferentiation into neurons have not involved purified cell populations and determined their exact phenotype prior to differentiation. The present study investigates whether highly purified mouse adult hematopoietic stem cells (HSCs), characterized by lineage marker depletion and expression of the cell surface markers Sca1 and c-Kit (Lin(-) Sca1(+) c-Kit(+) [LSK]), can be stimulated to adopt a neuronal fate. When the HSC(LSK) cells were cultured in vitro in neuronal differentiation medium supplemented with retinoic acid, 50% of the cells expressed the neural progenitor marker nestin and no cells had become postmitotic. Electrophysiological recordings on neuron-like cells showed that these cells were incapable of generating action potentials. When the HSC(LSK) cells either were grown in vitro together with neural precursor cells or were transplanted into the striatum or cerebellum of wild-type mouse, they either differentiated into Iba1-immunopositive macrophage/microglia or died. In conclusion, we demonstrate that adult HSC(LSK) cells do not have the capacity to leave the hematopoietic lineage and differentiate into neurons.

Animals↗
PubMed2005

Stromal cell-derived inducing activity does not promote dopaminergic differentiation, but enhances differentiation and proliferation of neural stem cell-derived astrocytes.

Previous evidence has shown that stromal cell-derived inducing activity (SDIA), produced by the mouse PA6 stromal cell line, promotes dopaminergic differentiation of mouse, monkey and human embryonic stem cells in vitro. To examine whether PA6 stromal cells can enhance the yield of dopaminergic differentiation from neural progenitors, we generated neurospheres from embryonic day 11.5 (E11.5) (midbrain and forebrain) and E14.5 (ventral mesencephalon and cortex) rat embryos and allowed them to differentiate in co-culture with PA6 cells or poly-l-lysine/laminin-coated dishes. We observed that SDIA did not promote dopaminergic differentiation of E11.5 and E14.5 neurospheres but more prominently, enhanced astrocyte differentiation, cell survival and astrocyte proliferation. Our results suggest that PA6 cells do not have a general capacity to promote differentiation into dopaminergic neurons from all types of stem cells, but that they may specifically induce dopaminergic differentiation of highly uncommitted stem cells such as embryonic stem cells.

Analysis of Variance↗
PubMed2005

Depletion of rabphilin 3A in a transgenic mouse model (R6/1) of Huntington's disease, a possible culprit in synaptic dysfunction.

Huntington's disease (HD) is a hereditary neurodegenerative disorder characterized by progressive psychiatric, cognitive, and motor disturbances. We studied the expression of synaptic vesicle proteins in the R6/1 transgenic mouse model of HD. We observed that the levels of rabphilin 3A, a protein involved in exocytosis, is substantially decreased in synapses of most brain regions in R6/1 mice. The appearance of the reduction coincides with the onset of motor deficits and behavioral disturbances. Double immunohistochemistry did not show colocalization between rabphilin 3A and huntingtin aggregates in the HD mice. Using in situ hybridization, we demonstrated that rabphilin 3A mRNA expression was substantially reduced in the R6/1 mouse cortex compared to wild-type mice. Our results indicate that a decrease in mRNA levels underlie the depletion of protein levels of rabphilin 3A, and we suggest that this reduction may be involved in causing impaired synaptic transmission in R6/1 mice.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Reduced hippocampal neurogenesis in R6/2 transgenic Huntington's disease mice.

We investigated whether cell proliferation and neurogenesis are altered in R6/2 transgenic Huntington's disease mice. Using bromodeoxyuridine (BrdU), we found a progressive decrease in the number of proliferating cells in the dentate gyrus of R6/2 mice. This reduction was detected in pre-symptomatic mice, and by 11.5 weeks, R6/2 mice had 66% fewer newly born cells in the hippocampus. The results were confirmed by immunohistochemistry for the cell cycle markers Ki-67 and proliferating cell nuclear antigen (PCNA). We did not observe changes in cell proliferation in the R6/2 subventricular zone, indicating that the decrease in cell proliferation is specific for the hippocampus. This decrease corresponded to a reduction in actual hippocampal neurogenesis as assessed by double immunostaining for BrdU and the neuronal marker neuronal nuclei (NeuN) and by immunohistochemistry for the neuroblast marker doublecortin. Reduced hippocampal neurogenesis may be a novel neuropathological feature in R6/2 mice that could be assessed when evaluating potential therapies.

Animals↗
PubMed2005

Abundant expression of zinc transporters in Bergman glia of mouse cerebellum.

Zinc transporters (ZnTs) are membrane proteins involved in zinc ion transportation in mammalian cells. Seven members of ZnT family, ZnT1-7, have been cloned and characterized. These transporter proteins have different cellular and sub-cellular locations, suggesting that they may play different roles in zinc homeostasis in normal and pathological conditions in different tissues. Cerebellum is one of the most zinc-enriched regions in the central nervous system, but little is known about zinc metabolism in the cerebellum. In the present study, we investigated the detailed distributions of four members (ZnT1, ZnT3, ZnT4 and ZnT6) of the ZnT family, in the mouse cerebellum. Immunostaining and confocal microscopic observations revealed a similar staining pattern of ZnTs in the molecular layer and the Purkinje cell layer. Double labeling with anti-S-100beta or anti-MAP2 and anti-ZnTs clearly showed that the Bergman glial cell bodies in the Purkinje cell layer and their radial processes in the molecular layer exhibited strong immunofluorescence of all the tested ZnTs. However, the somata of the Purkinje cells contained a moderate immunostaining for ZnT1, but virtually lack of other three ZnTs. In the granular layer, ZnTs appeared with different immunostaining patterns. ZnT1 was expressed in a small number of neuronal cell bodies and their primary dendrites, whereas ZnT3 and ZnT4 were present in nerve terminals but not in the neuronal somata. ZnT6 was undetectable in either the cell bodies or processes in the granular layer. The present results indicate that the Bergman glial cells may play an important role in zinc metabolism in the mouse cerebellar cortex.

Animals↗
PubMed2005

The R6/2 transgenic mouse model of Huntington's disease develops diabetes due to deficient beta-cell mass and exocytosis.

Diabetes frequently develops in Huntington's disease (HD) patients and in transgenic mouse models of HD such as the R6/2 mouse. The underlying mechanisms have not been clarified. Elucidating the pathogenesis of diabetes in HD would improve our understanding of the molecular mechanisms involved in HD neuropathology. With this aim, we examined our colony of R6/2 mice with respect to glucose homeostasis and islet function. At week 12, corresponding to end-stage HD, R6/2 mice were hyperglycemic and hypoinsulinemic and failed to release insulin in an intravenous glucose tolerance test. In vitro, basal and glucose-stimulated insulin secretion was markedly reduced. Islet nuclear huntingtin inclusions increased dramatically over time, predominantly in beta-cells. beta-cell mass failed to increase normally with age in R6/2 mice. Hence, at week 12, beta-cell mass and pancreatic insulin content in R6/2 mice were 35+/-5 and 16+/-3% of that in wild-type mice, respectively. The normally occurring replicating cells were largely absent in R6/2 islets, while no abnormal cell death could be detected. Single cell patch-clamp experiments revealed unaltered electrical activity in R6/2 beta-cells. However, exocytosis was virtually abolished in beta- but not in alpha-cells. The blunting of exocytosis could be attributed to a 96% reduction in the number of insulin-containing secretory vesicles. Thus, diabetes in R6/2 mice is caused by a combination of deficient beta-cell mass and disrupted exocytosis.

Age Factors↗
PubMed2005

Stem cell-based therapy for Parkinson's disease.

Motor dysfunctions in Parkinson's disease are considered to be primarily due to the degeneration of dopaminergic neurons in the substantia nigra pars compacta. Pharmacological therapies based on the principle of dopamine replacement are extremely valuable, but suffer from two main drawbacks: troubling side effects (e.g. dyskinesia) and loss of efficacy with disease progression. Transplantation of embryonic dopaminergic neurons has emerged as a therapeutic alternative. Enthusiasm following the success of the initial open-label trials has been dampened by the negative outcome of double-blind placebo controlled trials. Additionally, the emergence of graft-related dyskinesia indicates that the experimental grafting procedure requires further refinement before it can be developed into a therapy. Shortage of embryonic donor tissue limits large-scale clinical transplantation trials. We review three of the most attractive tissue sources of dopaminergic neurons for cell replacement therapy: human embryonic ventral mesencephalic tissue, embryonic and adult multipotent region-specific stem cells and embryonic stem cells. Recent developments in embryonic stem cell research and on their implications for a future transplantation therapy in Parkinson's disease are described. Finally, we discuss how human embryonic stem cells can be differentiated into dopaminergic neurons, and issues such as the numbers of dopaminergic neurons required for success and the risk for teratoma formation after implantation.

Animals↗
PubMed2004

Orexin loss in Huntington's disease.

Huntington's disease (HD) is a devastating neurodegenerative disorder caused by an expanded CAG repeat in the gene encoding huntingtin, a protein of unknown function. Mutant huntingtin forms intracellular aggregates and is associated with neuronal death in select brain regions. The most studied mouse model (R6/2) of HD replicates many features of the disease, but has been reported to exhibit only very little neuronal death. We describe for the first time a dramatic atrophy and loss of orexin neurons in the lateral hypothalamus of R6/2 mice. Importantly, we also found a significant atrophy and loss of orexin neurons in Huntington patients. Like animal models and patients with impaired orexin function, the R6/2 mice were narcoleptic. Both the number of orexin neurons in the lateral hypothalamus and the levels of orexin in the cerebrospinal fluid were reduced by 72% in end-stage R6/2 mice compared with wild-type littermates, suggesting that orexin could be used as a biomarker reflecting neurodegeneration. Our results show that the loss of orexin is a novel and potentially very important pathology in HD.

Animals↗
PubMed2004

Stem cell therapy for Parkinson's disease: where do we stand?

A major neuropathological feature of Parkinson's disease (PD) is the loss of nigrostriatal dopaminergic neuron. Patients exhibit motor symptoms, including bradykinesia, rigidity, and tremor. Neural grafting has been reported to restore striatial dopaminergic neurotransmission and induce symptomatic relief. The major limitation of cell replacement therapy for PD is the shortage of suitable donor tissue. The present review describes the possible sources of cells, including embryonic stem cells and somatic adult stem cells, both of which potentially could be used in cell therapy for PD, and discusses the advantages and disadvantages of each cell type.

Animals↗
PubMed2004

Detection of multidrug resistant gene 1 in pancreatic cancer.

BACKGROUND: The results are conflicting in detecting P-glycoprotein (P-gp) in pancreatic cancer. The aim of this study was to detect the expression of multidrug resistant gene 1 (MDR1) in pancreatic cancer cell lines. METHODS: MDR1 mRNA and P-gp were detected by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemical assay (IHC) in three pancreatic cancer cell lines SW1990, CAPAN-1 and P3. P-gp functions were evaluated through the rhodamine extrusion test. RESULTS: Two of the three cell lines expressed MDR1 positively at different levels. The rhodamine extrusion test showed that the percentage of positive cells in MDR(+) cells was significantly lower than that in MDR1(-) cells. The results of IHC, RT-PCR and the rhodamine extrusion test were consistent with each other. CONCLUSION: All of these methods are reliable in the detection of MDR1 in pancreatic cancer tissue, thus providing a guide for clinical chemotherapy of pancreatic cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Huntington's disease: a synaptopathy?

Huntington's disease (HD) is caused by a polyglutamine expansion in the protein huntingtin. In its terminal stage, HD is characterized by widespread neuronal death in the neocortex and the striatum. Classically, this neuronal death has been thought to underlie most of the symptoms of the disease. Accumulating evidence suggests, however, that cellular dysfunction is important in the pathogenesis of HD. We propose that specific impairment of the exocytosis and endocytosis machinery contributes to the development of HD. We also suggest that abnormal synaptic transmission underlies the early symptoms of HD and can contribute to the triggering of cell death in later stages of the disease.

Humans↗
PubMed2003

Adrenergic differentiation and SSR2a receptor expression in CAD-cells cultured in serum-free medium.

The CAD cell line originates from catecholaminergic neurons in the central nervous system (CNS) of a simian virus large T antigen transgenic mouse. In the present study, we have immunohistochemically characterized the cell line after differentiation in serum-free medium, using immunofluorescence in combination with confocal laser scanning microscopy (CLSM), immunoblot, and ribonuclease protection assay (RPA). Tyrosine hydroxylase (TH)-, phenylethanolamine-N-methyltransferase (PNMT)-, neuropeptide Y (NPY)-, vesicular monoamine transporter subtype 2-, vasoactive intestinal peptide (VIP)-, somatostatin (SS)-, synaptophysin-, synaptic vesicle protein 2 (SV2)-, and growth-associated protein of 43 (GAP-43)-immunoreactivities (IRs) were present in the cells but not choline acetyltransferase and vesicular acetylcholine transporter. The immunoreactive substances were present in cell bodies in serum-containing medium (SCM), but after serum withdrawal (protein-free medium, PFM) these proteins and peptides were partially shifted into the long process and their varicosities. A few cells cultured in PFM were occasionally found with extremely high TH-immunoreactivity (IR) in cell bodies and processes. Growth-associated protein of 43-immunoreactivity was weak in SCM but was up-regulated (verified with immunoblot) in PFM and concentrated in varicosities along the processes and the distal tips of neurites. The somatostatin receptor subtype 2a (SSR(2(a))) was found in the cytoplasm and the plasma membrane of the CAD-cells. After serum deprivation, all three methods showed that SSR(2(a)) was up-regulated in the cells. Thus, the CAD cell line after differentiation may be suitable for studying dynamics of SSR(2(a)).

Animals↗
PubMed2003

SSR2(a) receptor expression and adrenergic/cholinergic characteristics in differentiated SH-SY5Y cells.

Somatostatin (SS) is an inhibitory regulator of secretory and proliferative responses that activates a group of receptors in the plasma membrane termed SSR1-5. SSR2 is one of the most abundant SSR, which also is expressed in high numbers in many neuroendocrine tumor types. Here, we describe a study of the presence and intracellular localization of the spliced variant SSR2(a) and its endogenous ligand SS in the cultured human neuroblastoma (NB) cell line, SH-SY5Y, by immunohistochemistry and confocal laser scanning. The integral neuronal synaptic vesicle membrane proteins synaptophysin (p38) and SV2 were studied, as well as the IR of catecholaminergic and cholinergic markers. RA treatment was used as an inducer of neuronal-like differentiation in our SH-SY5Y cell line. After the treatment, the presence of catecholaminergic markers (including NPY) decreased while the cholinergic markers (including VIP) increased. p38 and SV2 as well as VIP were shifted into the rather long neuritic processes, indicating efficient intracellular transport. The SSR2(a) protein was significantly increased by RA treatment, but only minor increases in mRNA for this receptor protein could be seen. No subcellular co-localization between p38/SV2 and the cytoplasmic granular receptor material was demonstrated. The SSR2(a) receptor ligand SS was found to be present not only in the cytoplasm but also in the nucleus, and more strongly so after RA treatment. The possible reason for this may be that this peptide, like other small peptides, may serve as transcription factor, or cofactor.

Biomarkers↗