Biomedical subjects

Seung U Kim

Publications and source records attributed to Seung U Kim.

At least 19 recordsLinked to original sources

PubMed2007

Human neural stem cells over-expressing VEGF provide neuroprotection, angiogenesis and functional recovery in mouse stroke model.

BACKGROUND: Intracerebral hemorrhage (ICH) is a lethal stroke type. As mortality approaches 50%, and current medical therapy against ICH shows only limited effectiveness, an alternative approach is required, such as stem cell-based cell therapy. Previously we have shown that intravenously transplanted human neural stem cells (NSCs) selectively migrate to the brain and induce behavioral recovery in rat ICH model, and that combined administration of NSCs and vascular endothelial growth factor (VEGF) results in improved structural and functional outcome from cerebral ischemia. METHODS AND FINDINGS: We postulated that human NSCs overexpressing VEGF transplanted into cerebral cortex overlying ICH lesion could provide improved survival of grafted NSCs, increased angiogenesis and behavioral recovery in mouse ICH model. ICH was induced in adult mice by unilateral injection of bacterial collagenase into striatum. HB1.F3.VEGF human NSC line produced an amount of VEGF four times higher than parental F3 cell line in vitro, and induced behavioral improvement and 2-3 fold increase in cell survival at two weeks and eight weeks post-transplantation. CONCLUSIONS: Brain transplantation of F3 human NSCs over-expressing VEGF near ICH lesion sites provided differentiation and survival of grafted human NSCs and renewed angiogenesis of host brain and functional recovery of ICH animals. These results suggest a possible application of the human neural stem cell line, which is genetically modified to over-express VEGF, as a therapeutic agent for ICH-stroke.

Animals↗

PubMed2007

Brain transplantation of immortalized human neural stem cells promotes functional recovery in mouse intracerebral hemorrhage stroke model.

We have generated stable, immortalized cell lines of human NSCs from primary human fetal telencephalon cultures via a retroviral vector encoding v-myc. HB1.F3, one of the human NSC lines, expresses a normal human karyotype of 46, XX, and nestin, a cell type-specific marker for NSCs. F3 has the ability to proliferate continuously and differentiate into cells of neuronal and glial lineage. The HB1.F3 human NSC line was used for cell therapy in a mouse model of intracerebral hemorrhage (ICH) stroke. Experimental ICH was induced in adult mice by intrastriatal administration of bacterial collagenase; 1 week after surgery, the rats were randomly divided into two groups so as to receive intracerebrally either human NSCs labeled with beta-galactosidase (n = 31) or phosphate-buffered saline (PBS) (n = 30). Transplanted NSCs were detected by 5-bromo-4-chloro-3-indolyl-beta-d-galactoside histochemistry or double labeling with beta-galactosidase (beta-gal) and mitogen-activated protein (MAP)2, neurofilaments (both for neurons), or glial fibrillary acidic protein (GFAP) (for astrocytes). Behavior of the animals was evaluated for period up to 8 weeks using modified Rotarod tests and a limb placing test. Transplanted human NSCs were identified in the perihematomal areas and differentiated into neurons (beta-gal/MAP2(+) and beta-gal/NF(+)) or astrocytes (beta-gal/GFAP(+)). The NSC-transplanted group showed markedly improved functional performance on the Rotarod test and limb placing after 2-8 weeks compared with the control PBS group (p < .001). These results indicate that the stable immortalized human NSCs are a valuable source of cells for cell replacement and gene transfer for the treatment of ICH and other human neurological disorders. Disclosure of potential conflicts of interest is found at the end of this article.

Animals↗

PubMed2007

Tumor-targeted enzyme/prodrug therapy mediates long-term disease-free survival of mice bearing disseminated neuroblastoma.

Neural stem cells and progenitor cells migrate selectively to tumor loci in vivo. We exploited the tumor-tropic properties of HB1.F3.C1 cells, an immortalized cell line derived from human fetal telencephalon, to deliver the cDNA encoding a secreted form of rabbit carboxylesterase (rCE) to disseminated neuroblastoma tumors in mice. This enzyme activates the prodrug CPT-11 more efficiently than do human enzymes. Mice bearing multiple tumors were treated with rCE-expressing HB1.F3.C1 cells and schedules of administration of CPT-11 that produced levels of active drug (SN-38) tolerated by patients. Both HB1.F3.C1 cells and CPT-11 were given i.v. None of the untreated mice and 30% of mice that received only CPT-11 survived long term. In contrast, 90% of mice treated with rCE-expressing HB1.F3.C1 cells and 15 mg/kg CPT-11 survived for 1 year without detectable tumors. Plasma carboxylesterase activity and SN-38 levels in mice receiving both rCE-expressing HB1.F3.C1 cells (HB1.F3.C1/AdCMVrCE) and CPT-11 were comparable with those in mice receiving CPT-11 only. These data support the hypothesis that the antitumor effect of the described neural stem/progenitor cell-directed enzyme prodrug therapy (NDEPT) is mediated by production of high concentrations of active drug selectively at tumor sites, thereby maximizing the antitumor effect of CPT-11. NDEPT approaches merit further investigation as effective, targeted therapy for metastatic tumors. We propose that the described approach may have greatest use for eradicating minimum residual disease.

Adenoviridae↗

PubMed2007

Intravascular administration of tumor tropic neural progenitor cells permits targeted delivery of interferon-beta and restricts tumor growth in a murine model of disseminated neuroblastoma.

BACKGROUND: Interferon-beta (IFN-beta) has potent antitumor activity; however, systemic toxicity has limited its clinical use. We investigated the potential of targeted delivery using tumor-tropic neural progenitor cells (NPCs) transduced to express human IFN-beta (hIFN-beta). METHODS: Disseminated neuroblastoma was established in SCID mice by tail vein injection of tumor cells. Fourteen days after tumor cell inoculation, systemic disease was confirmed with bioluminescence imaging (BLI). Mice were then treated by intravenous injection of human F3.C1 NPCs that had been transduced with a replication deficient adenovirus to overexpress hIFN-beta (F3-IFN-beta). Two injections were given: the first at 14 days and the second at 28 days following tumor cell injection. Control mice received NPCs transduced with empty vector adenovirus at the same time points. Progression of disease was monitored using BLI. At sacrifice, organ weights and histology further evaluated tumor burden. RESULTS: After initiation of therapy, BLI demonstrated a significant decrease in the rate of disease progression in mice receiving F3-IFN-beta. At necropsy, control mice had bulky tumor replacing the liver and kidneys, as well as extensive retroperitoneal and mediastinal adenopathy. Impressively, these sites within mice receiving F3-IFN-beta therapy appeared grossly normal with the exception of small nodules within the kidneys of some of the F3-IFN-beta-treated mice. The accumulation of F3.C1 cells within sites of tumor growth was confirmed by fluorescence imaging. Importantly, systemic levels of hIFN-beta in the treated mice remained below detectable levels. CONCLUSIONS: These data indicate that in this model of disseminated neuroblastoma, the tumor-tropic property of F3.C1 NPCs was exploited to target delivery of IFN-beta to disseminated tissue foci, resulting in significant tumor growth delay. The described novel approach for effective IFN-beta therapy may circumvent limitations associated with the systemic toxicity of IFN-beta.

Adenoviridae↗

PubMed2006

Development of a tumor-selective approach to treat metastatic cancer.

BACKGROUND: Patients diagnosed with metastatic cancer have almost uniformly poor prognoses. The treatments available for patients with disseminated disease are usually not curative and have side effects that limit the therapy that can be given. A treatment that is selectively toxic to tumors would maximize the beneficial effects of therapy and minimize side effects, potentially enabling effective treatment to be administered. METHODS AND FINDINGS: We postulated that the tumor-tropic property of stem cells or progenitor cells could be exploited to selectively deliver a therapeutic gene to metastatic solid tumors, and that expression of an appropriate transgene at tumor loci might mediate cures of metastatic disease. To test this hypothesis, we injected HB1.F3.C1 cells transduced to express an enzyme that efficiently activates the anti-cancer prodrug CPT-11 intravenously into mice bearing disseminated neuroblastoma tumors. The HB1.F3.C1 cells migrated selectively to tumor sites regardless of the size or anatomical location of the tumors. Mice were then treated systemically with CPT-11, and the efficacy of treatment was monitored. Mice treated with the combination of HB1.F3.C1 cells expressing the CPT-11-activating enzyme and this prodrug produced tumor-free survival of 100% of the mice for >6 months (P<0.001 compared to control groups). CONCLUSIONS: The novel and significant finding of this study is that it may be possible to exploit the tumor-tropic property of stem or progenitor cells to mediate effective, tumor-selective therapy for metastatic tumors, for which no tolerated curative treatments are currently available.

Animals↗

PubMed2006

Transplantation of human neural stem cells exerts neuroprotection in a rat model of Parkinson's disease.

Neural stem cells (NSCs) possess high potencies of self-renewal and neuronal differentiation. We explored here whether transplantation of human NSCs cloned by v-myc gene transfer, HB1.F3 cells, is a feasible therapeutic option for Parkinson's disease. In vivo, green fluorescent protein-labeled HB1.F3 cells (200,000 viable cells in 3 microl of PBS) when stereotaxically transplanted (same-day lesion-transplant paradigm) into the 6-hydroxydopamine-lesioned striatum of rats significantly ameliorated parkinsonian behavioral symptoms compared with controls (vehicle, single bolus, or continuous minipump infusion of trophic factor, or killed cell grafts). Such graft-derived functional effects were accompanied by preservation of tyrosine hydroxylase (TH) immunoreactivity along the nigrostriatal pathway. Grafted HB1.F3 cells survived in the lesioned brain with some labeled with neuronal marker mitogen-activated protein 2 and decorated with synaptophysin-positive terminals. Furthermore, endogenous neurogenesis was activated in the subventricular zone of transplanted rats. To further explore the neuroprotective mechanisms underlying HB1.F3 cell transplantation, we performed cell culture studies and found that a modest number of HB1.F3 cells were TH and dopamine and cAMP-regulated phosphoprotein 32 positive, although most cells were nestin positive, suggesting a mixed population of mature and immature cells. Administration of the HB1.F3 supernatant to human derived dopaminergic SH-SY5Y cells and fetal rat ventral mesencephalic dopaminergic neurons protected against 6-hydroxydopamine neurotoxicity by suppressing apoptosis through Bcl-2 upregulation, which was blocked by anti-stem cell factor antibody alone, the phosphatidylinositol 3-kinase/Akt inhibitor LY294002 [2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one] alone, or a combination of both. These results suggest that HB1.F3 cell transplantation exerts neuroprotective effects against dopaminergic depletion in vitro and in vivo because of trophic factor secretion and neuronal differentiation.

Animals↗

PubMed2006

Broad-spectrum effects of 4-aminopyridine to modulate amyloid beta1-42-induced cell signaling and functional responses in human microglia.

We investigated the modulating actions of the nonselective K(+) channel blocker 4-aminopyridine (4-AP) on amyloid beta (Abeta(1-42))-induced human microglial signaling pathways and functional processes. Whole-cell patch-clamp studies showed acute application of Abeta(1-42) (5 mum) to human microglia led to rapid expression of a 4-AP-sensitive, non-inactivating outwardly rectifying K(+) current (I(K)). Intracellular application of the nonhydrolyzable analog of GTP, GTPgammaS, induced an outward K(+) current with similar properties to the Abeta(1-42)-induced I(K) including sensitivity to 4-AP (IC(50) = 5 mm). Reverse transcriptase-PCR showed a rapid expression of a delayed rectifier Kv3.1 channel in Abeta(1-42)-treated microglia. Abeta(1-42) peptide also caused a slow, progressive increase in levels of [Ca(2+)](i) (intracellular calcium) that was partially blocked by 4-AP. Chronic exposure of human microglia to Abeta(1-42) led to enhanced p38 mitogen-activated protein kinase and nuclear factor kappaB expression with factors inhibited by 4-AP. Abeta(1-42) also induced the expression and production of the pro-inflammatory cytokines interleukin (IL)-1beta, IL-6, and tumor necrosis factor-alpha, the chemokine IL-8, and the enzyme cyclooxygenase-2; 4-AP was effective in reducing all of these pro-inflammatory mediators. Additionally, toxicity of supernatant from Abeta(1-42)-treated microglia on cultured rat hippocampal neurons was reduced if 4-AP was included with peptide. In vivo, injection of Abeta(1-42) into rat hippocampus induced neuronal damage and increased microglial activation. Daily administration of 1 mg/kg 4-AP was found to suppress microglial activation and exhibited neuroprotection. The overall results suggest that 4-AP modulation of an Abeta(1-42)-induced I(K) (candidate channel Kv3.1) and intracellular signaling pathways in human microglia could serve as a therapeutic strategy for neuroprotection in Alzheimer's disease pathology.

4-Aminopyridine↗

PubMed2006

Transient receptor potential vanilloid subtype 1 mediates microglial cell death in vivo and in vitro via Ca2+-mediated mitochondrial damage and cytochrome c release.

The present study examined the expression of transient receptor potential vanilloid subtype 1 (TRPV1) in microglia, and its association with microglial cell death. In vitro cell cultures, RT-PCR, Western blot analysis, and immunocytochemical staining experiments revealed that rat microglia and a human microglia cell line (HMO6) showed TRPV1 expression. Furthermore, exposure of these cells to TRPV1 agonists, capsaicin (CAP) and resiniferatoxin (RTX), triggered cell death. This effect was ameliorated by the TRPV1 antagonists, capsazepine and iodo-resiniferatoxin (I-RTX), suggesting that TRPV1 is directly involved. Further examinations revealed that TRPV1-induced toxicity was accompanied by increases in intracellular Ca(2+), and mitochondrial damage; these effects were inhibited by capsazepine, I-RTX, and the intracellular Ca(2+) chelator BAPTA-AM. Treatment of cells with CAP or RTX led to increased mitochondrial cytochrome c release and enhanced immunoreactivity to cleaved caspase-3. In contrast, the caspase-3 inhibitor z-DEVD-fmk protected microglia from CAP- or RTX-induced toxicity. In vivo, we also found that intranigral injection of CAP or 12-hydroperoxyeicosatetraenoic acid, an endogenous agonist of TRPV1, into the rat brain produced microglial damage via TRPV1 in the substantia nigra, as visualized by immunocytochemistry. To our knowledge, this study is the first to demonstrate that microglia express TRPV1, and that activation of this receptor may contribute to microglial damage via Ca(2+) signaling and mitochondrial disruption.

Animals↗

PubMed2006

Human neural stem cells target experimental intracranial medulloblastoma and deliver a therapeutic gene leading to tumor regression.

PURPOSE: Medulloblastoma, a malignant pediatric brain tumor, is incurable in about one third of patients despite multimodal treatments. In addition, current therapies can lead to long-term disabilities. Based on studies of the extensive tropism of neural stem cells (NSC) toward malignant gliomas and the secretion of growth factors common to glioma and medulloblastoma, we hypothesized that NSCs could target medulloblastoma and be used as a cellular therapeutic delivery system. EXPERIMENTAL DESIGN: The migratory ability of HB1.F3 cells (an immortalized, clonal human NSC line) to medulloblastoma was studied both in vitro and in vivo. As proof-of-concept, we used HB1.F3 cells engineered to secrete the prodrug activating enzyme cytosine deaminase. We investigated the potential of human NSCs to deliver a therapeutic gene and reduce tumor growth. RESULTS: The migratory capacity of HB1.F3 cells was confirmed by an in vitro migration assay, and corroborated in vivo by injecting chloromethylbenzamido-Dil-labeled HB1.F3 cells into the hemisphere contralateral to established medulloblastoma in nude mice. In vitro studies showed the therapeutic efficacy of HB1.F3-CD on Daoy cells in coculture experiments. In vitro therapeutic studies were conducted in which animals bearing intracranial medulloblastoma were injected ipsilaterally with HB1.F3-CD cells followed by systemic 5-flourocytosine treatment. Histologic analyses showed that human NSCs migrate to the tumor bed and its boundary, resulting in a 76% reduction of tumor volume in the treatment group (P<0.01). CONCLUSION: These studies show for the first time the potential of human NSCs as an effective delivery system to target and disseminate therapeutic agents to medulloblastoma.

Animals↗

PubMed2006

Interleukin-13 enhances cyclooxygenase-2 expression in activated rat brain microglia: implications for death of activated microglia.

Brain inflammation has recently attracted widespread interest because it is a risk factor for the onset and progression of brain diseases. In this study, we report that cyclooxygenase-2 (COX-2) plays a key role in the resolution of brain inflammation by inducing the death of microglia. We previously reported that IL-13, an anti-inflammatory cytokine, induced the death of activated microglia. These results revealed that IL-13 significantly enhanced COX-2 expression and production of PGE(2) and 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) in LPS-treated microglia. Two other anti-inflammatory cytokines, IL-10 and TGF-beta, neither induced microglial death nor enhanced COX-2 expression or PGE(2) or 15d-PGJ(2) production. Therefore, we hypothesized that the effect of IL-13 on COX-2 expression may be linked to death of activated microglia. We found that COX-2 inhibitors (celecoxib and NS398) suppressed the death of microglia induced by a combination of LPS and IL-13 and that exogenous addition of PGE(2) and 15d-PGJ(2) induced microglial death. Agonists of EP2 (butaprost) and peroxisome proliferator-activated receptor gamma (ciglitazone) mimicked the effect of PGE(2) and 15d-PGJ(2), and an EP2 antagonist (AH6809) and a peroxisome proliferator-activated receptor gamma antagonist (GW9662) suppressed microglial death induced by LPS in combination with IL-13. In addition, IL-13 potentiated LPS-induced activation of JNK, and the JNK inhibitor SP600125 suppressed the enhancement of COX-2 expression and attenuated microglial death. Taken together, these results suggest that IL-13 enhanced COX-2 expression in LPS-treated microglia through the enhancement of JNK activation. Furthermore, COX-2 products, PGE(2) and 15d-PGJ(2), caused microglial death, which terminates brain inflammation.

Animals↗

PubMed2006

Cyclooxygenase-2 inhibitor, celecoxib, inhibits the altered hippocampal neurogenesis with attenuation of spontaneous recurrent seizures following pilocarpine-induced status epilepticus.

Recent evidences suggest key roles of abnormal neurogenesis and astrogliosis in the pathogenesis of epilepsy. Alterations in the microenvironment of the stem cell, such as microglial activation and cyclooxygenase-2 induction may cause ectopic neurogenesis or astrogliosis. Here, we examined if inflammatory blockade with celecoxib, a selective cyclooxygenase-2 inhibitor, could modulate the altered microenvironment in the epileptic rat brain. Celecoxib attenuated the likelihood of developing spontaneous recurrent seizures after pilocarpine-induced prolonged seizure. During the latent period, celecoxib prevented neuronal death and microglia activation in the hilus and CA1 and inhibited the generation of ectopic granule cells in the hilus and new glia in CA1. The direct inhibition of precursor cells by celecoxib was further demonstrated in human neural stem cells culture. These findings raise the evidence of COX-2 induction to act importantly on epileptogenesis and suggest a potential therapeutic role for COX-2 inhibitors in chronic epilepsy.

Animals↗

PubMed2006

Regulation of human tyrosine hydroxylase gene by neuron-restrictive silencer factor.

Tyrosine hydroxylase (TH), the biosynthetic enzyme of catecholamine, is synthesized specifically in catecholaminergic neurons. Thus, it is possible that neuronal cell type-specific expression of this gene is coordinately regulated. One of the neuron-specific transcription regulators, neuron-restrictive silencer factor (NRSF)/repressor element 1 (RE1) silencing transcription factor (REST), represses the expression of neuronal genes in non-neuronal cells. To elucidate the molecular mechanisms that control catecholaminergic neuronal expression of human TH, we initially characterized the 5' regulatory region. Previous studies have shown that a 3174 bp fragment of the human TH promoter confers specific expression to the reporter gene in dopaminergic neuron-like cell lines. Within this 5' regulatory region, three putative neuron-restrictive silencer elements (NRSE)/RE1 were identified, which bound NRSF/REST in a sequence-specific manner, as confirmed using EMSA and ChIP assays. In transient transfection assays, deletion or mutation of NRSE/RE1 elements led to a 7-fold increase in activity of the 3.2 kb TH promoter in human neural stem cells (NSCs), but had no major effects on differentiated neuron-like cells. Suppression of NRSF/REST functions with either the histone deacetylase inhibitor, trichostatin, or DN-NRSF induced TH promoter activity. Our data strongly suggest that NRSF/REST functions as a repressor of TH transcription in NSCs via a mechanism dependent on the TH NRSE/RE1 sites.

Base Sequence↗

PubMed2006

Quantification of human neural stem cell engraftments in rat brains using ERV-3 real-time PCR.

Few sensitive and reliable methods have been available for quantifying the number of transplanted human neural stem cells (hNSC) in the animal brain. To develop an accurate method for quantifying the number of hNSC incorporated in rat brain, we performed real-time PCR on hNSC-transplanted rat brains using a target sequence for ERV-3, which is an endogenous retrovirus present with a known copy number in all human cells, but not present in rodent cells. A standard curve was developed for known amount of different mixes of hNSC and rat fibroblasts, and test samples were prepared by manually incorporating variable, predefined numbers of hNSCs into rat brains. A cerebral rat hemisphere injected with 10(7) hNSC revealed 1.125% chimerism. Moreover, a linear correlation was found between hNSC numbers injected and their concentrations in the rat brain. In conclusion, the developed quantitative ERV-3 assay enables a simple, fast, and reproducible detection and quantitation of hNSC numbers in the rat brain.

Animals↗

PubMed2006

Mitochondrial ligand inhibits store-operated calcium influx and COX-2 production in human microglia.

We used calcium sensitive fluorescence microscopy to investigate the actions of PK11195, a ligand for the mitochondrial peripheral benzodiazepine receptor (PBR), to modulate Ca2+ influx through store-operated channels (SOC) in human microglia. PK11195 effectively blocked SOC-mediated Ca2+ influx induced by platelet-activating factor (PAF) in a dose-dependent manner (IC50 of 9 microM). A prolonged SOC-mediated Ca2+ entry was also induced using the sarcoplasmic endoreticulum Ca2+-ATPase (SERCA) inhibitor cyclopiazonic acid (CPA) to deplete intracellular endoplasmic reticulum (ER) stores; a single concentration of PK11195 (at 20 microM) reduced SOC-mediated Ca2+ influx by 78%. RT-PCR and immunocytochemical analysis results showed PK11195 also inhibited the expression and production of cyclooxygenase-2 (COX-2) triggered by PAF stimulation. These results suggest that activation of the PBR in mitochondria is linked to reduced entry of Ca2+ through plasmalemmal SOC and subsequent modulation of cellular functions in human microglia.

Antineoplastic Agents↗

PubMed2006

Differential regulation of tyrosine hydroxylase expression by sonic hedgehog.

Sonic hedgehog functions to induce floor plate in early stages, and spinal motor neurons and midbrain dopaminergic neurons in later stages of development. Here, we investigated the effects of sonic hedgehog on tyrosine hydroxylase expression in three cell lines that correspond to different stages of neural development. Sonic hedgehog increased the tyrosine hydroxylase gene expression in pluripotent P19 cells but repressed it in tyrosine hydroxylase-producing PC12 cells. Promoter analysis in mouse neural stem cells indicated that the N-terminal of sonic hedgehog repressed both the basal and cAMP-dependent protein kinase A-mediated tyrosine hydroxylase activity. These results suggest that the N-terminal of sonic hedgehog increases tyrosine hydroxylase gene expression in cells to acquire dopaminergic phenotypes, but decreases expression in late born neurons by antagonizing the protein kinase A cAMP-responsive element binding protein pathway.

Animals↗

PubMed2006

Granulocyte colony-stimulating factor stimulates neurogenesis via vascular endothelial growth factor with STAT activation.

The adult brain harbors multipotent stem cells, which reside in specialized niches that support self-renewal. Granulocyte colony-stimulating factor (G-CSF) induces bone marrow stem cells proliferation and mobilization from their niche, and activates endothelial cell proliferation, which might help to establish a vascular niche for neural stem cells (NSCs). Here, we show that G-CSF induced receptor-mediated proliferation and differentiation of neural precursors in human NSCs cultures and in adult rat brain in vivo. In human NSCs cultures, G-CSF activated STAT3 and 5, and increased VEGF and its receptor, VEGFR2 (Flk-1) expression, and VEGFR2 tyrosine kinase inhibitor blocked the neurogenesis stimulated by G-CSF. G-CSF also activated endothelial cell proliferation in adult rat brain in vivo. Our results indicate that G-CSF stimulates neurogenesis through reciprocal interaction with VEGF and STAT activation.

Brain↗

PubMed2006

Upregulation of protease-activated receptor-1 in astrocytes in Parkinson disease: astrocyte-mediated neuroprotection through increased levels of glutathione peroxidase.

In the present study, we investigated the expression of protease-activated receptors (PARs), receptors for thrombin, in substantia nigra pars compacta (SNpc) of Parkinson disease (PD) brains and cultures of human neurons, astrocytes, oligodendrocytes, and microglia as determined by immunocytochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR). Expression of PAR-1 was demonstrated only in glial fibrillary acidic protein-positive astrocytes in SNpc, and the number of astrocytes expressing PAR-1 increased in SNpc of PD as compared with nonneurologic control brain. Immunoreactivity for thrombin and prothrombin was stronger in astrocytes and the vessel walls in SNpc of PD brains. PAR-1 was expressed in human astrocytes and neurons, but not in oligodendrocytes or microglia as determined by RT-PCR. We investigated thrombin-mediated activation of human astrocytes. Thrombin treatment activates human astrocytes and induces morphologic change and a marked increase in proliferation of astrocytes. Increased expression of glial cell line-derived growth factor and glutathione peroxidase (GPx) but no change in the expression of nerve growth factor and inflammatory cytokines/chemokine (IL-1beta, IL-6, IL-8, MCP-1) was found in thrombin/PAR-activated astrocytes. Next, we studied the neuroprotective effect exerted by thrombin-activated astrocytes in human cerebral neuron x human neuroblastoma hybrid neurons. Although thrombin showed neurotoxicity against human hybrid neurons in a dose-dependent manner, the conditioned media derived from thrombin-pretreated astrocyte cultures promoted the survival of human hybrid neurons. The protective effect was completely inhibited with a GPx inhibitor, mercaptosuccinic acid, indicating that GPx released from thrombin/PAR-activated astrocytes is responsible for neuroprotection of hybrid neurons against thrombin cytotoxicity. The present study suggests that the increased expression of PAR-1 in astrocytes in SNpc of PD brain is the restorative move taken by the brain to provide neuroprotection against neuronal degeneration and cell death of dopaminergic neurons caused by noxious insults during the progression of PD pathology.

Aged↗

PubMed2006

Bilateral perisylvian ulegyria: clinicopathological study of patients presenting with pseudobulbar palsy and epilepsy.

Structural abnormalities related with pseudobulbar palsy have been gaining attention because of their characteristic symptoms and unique pathogenesis. We present five cases of bilateral perisylvian ulegyria (BPU) presenting epilepsy and pseudobulbar palsy with pathogenesis different from previously reported syndromes. All patients showed medically intractable seizures, complex partial seizures with secondary generalization and clinical symptoms of pseudobulbar palsy, including dysarthria, limitation of tongue movement and drooling. MRI revealed BPU in all patients, and BPU associated with hippocampal sclerosis in four patients. Intracranial EEG recording with subdural grip and stripe was helpful for localizing the area of ictal generation. Resective surgeries, including the temporal lobe, central area and parietal lobe, were performed depending on the localizing information. The surgical outcome was favorable after 9.8 years of follow-up. Characteristic features of ulegyria were confirmed on pathological examination. Ulegyria is considered to be another important perinatal or postnatal structural abnormality which can explain the etiological heterogeneity for pseudobulbar palsy, which results from bilateral perisylvian lesions. Awareness of this disorder can provide a useful strategy for evaluation and treatment which differs from that in perisylvian polymicrogyria.

Adult↗