Cell Line-derived Neurotrophic Factor Receptor Research Articles

The high expression of glial cell line-derived neurotrophic factor receptor alpha Ⅱ (GFRA2) as a predictor of poor prognosis in gastric cancer patients: A survival and regression analysis approach

Gastric cancer has high mortality rates worldwide. Therefore, there is a need to identify prognostic biomarkers. This study evaluated the association between GFRA2 expression levels with clinicopathological features and prognosis in gastric cancer using data extracted from The Cancer Genome Atlas (TCGA) database and a series of algorithms. Survival analysis was performed using the Kaplan-Meier method. Univariate and multivariate Cox regression analyses were used to analyze the association between different clinical features and survival. Single-sample gene set enrichment analysis (GSEA) was used to examine the correlation between GFRA2 expression and immune infiltration. The results showed that the expression of GFRA2 in tumor samples was significantly lower than that in normal samples. High expression of GFRA2 was significantly associated with histological type, histologic grade, and worse overall survival, disease-specific survival, and progression-free survival. The univariate Cox analysis showed that the expression of GFRA2 was significantly correlated with T stage, N stage, M stage, and age. The multivariate analysis identified GFRA2 expression as an independent prognostic factor for gastric cancer. GSEA showed that GFRA2 might regulate the calcium signaling pathway, focus adhesion, olfactory conduction, the extracellular matrix glycoproteins, and response to the Leishmania parasitic infection. GFRA2 showed a significant moderate positive correlation with the infiltration of mast cells. In summary, a high expression of GFRA2 may contribute to poor survival in gastric cancer patients and could be used as a potential prognostic biomarker.

Biallelic loss-of-function variants of GFRA1 cause lethal bilateral renal agenesis

Bilateral renal agenesis belongs to a group of perinatal lethal renal diseases. To date, pathogenic variants in three genes (ITGA8, GREB1L, and FGF20) have been shown to cause renal agenesis in humans. Recently GFRA1 has been linked to a phenotype consistent with a nonsyndromic form of bilateral renal agenesis. GFRA1 encodes a member of the glial cell line-derived neurotrophic factor receptor family of proteins. The receptor on the Wolffian duct regulates ureteric bud outgrowth in developing a functional renal system. We report on four additional affected neonates from a consanguineous family who presented with a similar lethal phenotype whereby whole exome sequencing identified a homozygous deleterious sequence variant in GFRA1 (NM_005264.8:c.628G > T:p.[Gly210Ter]). The current study represents a second confirmation report on the causal association of GFRA1 pathogenic variants with lethal nonsyndromic bilateral renal agenesis in humans.

Elevated expression of endogenous glial cell line-derived neurotrophic factor impairs spatial memory performance and raises inhibitory tone in the hippocampus.

Parvalbumin-positive interneurons (PV+) are a key component of inhibitory networks in the brain and are known to modulate memory and learning by shaping network activity. The mechanisms of PV+ neuron generation and maintenance are not fully understood, yet current evidence suggests that signalling via the glial cell line-derived neurotrophic factor (GDNF) receptor GFRα1 positively modulates the migration and differentiation of PV+ interneurons in the cortex. Whether GDNF also regulates PV+ cells in the hippocampus is currently unknown. In this study, we utilized a Gdnf "hypermorph" mouse model where GDNF is overexpressed from the native gene locus, providing greatly increased spatial and temporal specificity of protein expression over established models of ectopic expression. Gdnfwt/hyper mice demonstrated impairments in long-term memory performance in the Morris water maze test and an increase in inhibitory tone in the hippocampus measured electrophysiologically in acute brain slice preparations. Increased PV+ cell number was confirmed immunohistochemically in the hippocampus and in discrete cortical areas and an increase in epileptic seizure threshold was observed in vivo. The data consolidate prior evidence for the actions of GDNF as a regulator of PV+ cell development in the cortex and demonstrate functional effects upon network excitability via modulation of functional GABAergic signalling and under epileptic challenge.

Neurturin regulates the lung-resident macrophage inflammatory response to viral infection.

Lung-resident macrophages are crucial to the maintenance of health and in the defence against lower respiratory tract infections. Macrophages adapt to local environmental cues that drive their appropriate function; however, this is often dysregulated in many inflammatory lung pathologies. In mucosal tissues, neuro-immune interactions enable quick and efficient inflammatory responses to pathogenic threats. Although a number of factors that influence the antimicrobial response of lung macrophages are known, the role of neuronal factors is less well understood. Here, we show an intricate circuit involving the neurotrophic factor, neurturin (NRTN) on human lung macrophages that dampens pro-inflammatory cytokine release and modulates the type of matrix metalloproteinases produced in response to viral stimuli. This circuit involves type 1 interferon-induced up-regulation of RET that when combined with the glial cell line-derived neurotrophic factor (GDNF) receptor α2 (GFRα2) allows binding to epithelial-derived NRTN. Our research highlights a non-neuronal immunomodulatory role for NRTN and a novel process leading to a specific antimicrobial immune response by human lung-resident macrophages.

Small Molecules and Peptides Targeting Glial Cell Line-Derived Neurotrophic Factor Receptors for the Treatment of Neurodegeneration.

Glial cell line-derived neurotrophic factor (GDNF) family ligands (GFLs) are able to promote the survival of multiple neuronal populations in the body and, therefore, hold considerable promise for disease-modifying treatments of diseases and conditions caused by neurodegeneration. Available data reveal the potential of GFLs for the therapy of Parkinson’s disease, neuropathic pain and diseases caused by retinal degeneration but, also, amyotrophic lateral sclerosis and, possibly, Alzheimer’s disease. Despite promising data collected in preclinical models, clinical translation of GFLs is yet to be conducted. The main reasons for the limited success of GFLs clinical development are the poor pharmacological characteristics of GFL proteins, such as the inability of GFLs to cross tissue barriers, poor diffusion in tissues, biphasic dose-response and activation of several receptors in the organism in different cell types, along with ethical limitations on patients’ selection in clinical trials. The development of small molecules selectively targeting particular GFL receptors with improved pharmacokinetic properties can overcome many of the difficulties and limitations associated with the clinical use of GFL proteins. The current review lists several strategies to target the GFL receptor complex with drug-like molecules, discusses their advantages, provides an overview of available chemical scaffolds and peptides able to activate GFL receptors and describes the effects of these molecules in cultured cells and animal models.

Nociceptive afferent phenotyping reveals that transient receptor potential ankyrin 1 promotes cold pain through neurogenic inflammation upstream of the neurotrophic factor receptor GFRα3 and the menthol receptor transient receptor potential melastatin 8.

The proper detection and behavioral response to painfully cold temperatures is critical for avoiding potentially harmful tissue damage. Cold allodynia and hyperalgesia, pain associated with innocuous cooling and exaggerated pain with noxious cold, respectively, are common in patients with chronic pain. In peripheral somatosensory afferents, the ion channels transient receptor potential melastatin 8 (TRPM8) and transient receptor potential ankyrin 1 (TRPA1) are candidate receptors for innocuous and noxious cold temperatures, respectively. However, the role of TRPA1 as a cold sensor has remained controversial, and recent evidence suggests that TRPM8 channels and afferents mediate the detection of both pleasant and painful cold. To determine the role of TRPA1 afferents in cold-induced mouse behaviors in vivo, we used functional phenotyping by targeted nerve conduction block with the cell-impermeant lidocaine derivative QX-314. Surprisingly, we find that injection of QX-314 with TRPA1 agonists reduces cold-induced behaviors in mice, but does so in a TRPM8-dependent manner. Moreover, this effect is sexually dimorphic and requires the glial cell line-derived neurotrophic factor receptor GFRα3, as does cold hypersensitivity produced by the activation of TRPA1 channels. Taken together, these results suggest that under conditions of neurogenic inflammation, TRPA1 works upstream of GFRα3 and TRPM8 to produce cold hypersensitivity, providing novel insights into the role of TRPA1 channels in cold pain.

Role of GFRα3 in expression and membrane trafficking of TRPM8 in dorsal root ganglion during cold hyperalgesia in rats with neuropathic pain

Objective To evaluate the role of glial cell line-derived neurotrophic factor family receptor alpha3(GFRα3)in the expression and membrane trafficking of transient receptor potential melastatin 8(TRPM8)in the dorsal root ganglion(DRG)during cold hyperalgesia in rats with neuropathic pain(NP). Methods Thirty-two healthy adult male Sprague-Dawley rats, aged 10-12 weeks, weighing 250-280 g, in which intrathecal catheters were successfully implanted, were divided into 4 groups(n=8 each)using a random number table: sham operation plus GFRα3 dsRNA group(Sham+ dsRNA group), sham operation plus GFRα3 siRNA group(group Sham+ siRNA), NP plus GFRα3 dsRNA group(group NP+ dsRNA)and NP plus GFRα3 siRNA group(group NP+ siRNA). NP was produced by chronic constriction injury to the sciatic nerve.At 10-30 days after operation, GFRα3 dsRNA 10 μg/20 μl was intrathecally injected once a day for 4 consecutive days in Sham+ dsRNA and NP+ dsRNA groups, and 10 μg/20 μl GFRα3 siRNA, of which the sense strand was modified with 2′-O-methyl and 5′-cholesterol, was intrathecally injected once a day for 4 consecutive days in Sham+ siRNA and NP+ siRNA groups.The number of paw lifts on the cold plate, mechanical paw withdrawal threshold(MWT)and thermal paw withdrawal latency(TWL)were measured on 1 day before operation and 10, 11, 12, 13(before intrathecal injection)and 14 days after operation.The rats were sacrificed after the last behavioral testing, and ipsilateral DRGs of the lumbar segment(L4-6)were dissected for detection of the expression of GFRα3 and TRPM8 in total and membrane proteins by Western blot, and the ratio of TRPM8 expression in the membrane protein to that in the total protein(m/t ratio)was calculated. Results Compared with group Sham+ dsRNA, the number of paw lifts on the cold plate was significantly increased, the MWT was decreased, and TWL was shortened after operation in NP+ dsRNA and NP+ siRNA groups, the expression of GFRα3 and TRPM8 in total and membrane proteins was significantly up-regulated, and m/t ratio was increased in group NP+ dsRNA, and the expression of GFRα3 in DRGs was significantly down-regulated(P 0.05). Compared with group NP+ dsRNA, the number of paw lifts on the cold plate was significantly decreased, the expression of GFRα3 and TRPM8 in total and membrane proteins was down-regulated, m/t ratio was decreased(P 0.05). Conclusion GFRα3 in DRGs can up-regulate the expression of TRPM8 and enhance the membrane trafficking of TRPM8, which may be involved in the maintenance mechanism of cold hyperalgesia in rats with NP. Key words: Glial cell line-derived neurotrophic factor receptors; TRPM cation channels; Neuralgia; Hyperalgesia, cold; Ganglia, spinal

Neuropilin-1 is a glial cell line-derived neurotrophic factor receptor in glioblastoma.

The aim of this study was to identify the receptor for glial cell line-derived neurotrophic factor (GDNF) in glioblastoma multiforme (GBM). After GST pull-down assays, membrane proteins purified from C6 rat glioma cells were subjected to liquid chromatography-tandem mass spectrometry (LC-MS/MS). The differentially expressed proteins were annotated using Gene Ontology, and neuropilin-1 (NRP1) was identified as the putative GDNF receptor in glioma. NRP1 was more highly expressed in human GBM brains and C6 rat glioma cells than in normal human brains or primary rat astrocytes. Immunofluorescence staining showed that NRP1 was recruited to the membrane by GDNF, and NRP1 co-immunoprecipitated with GDNF. Using the NRP1 and GDNF protein structures to assess molecular docking in the ZDOCK server and visualization with the PyMOL Molecular Graphics System revealed 8 H-bonds and stable positive and negative electrostatic interactions between NRP1 and GDNF. RNAi knockdown of NRP1 reduced proliferation of C6 glioma cells when stimulated with GDNF. NRP1 was an independent risk factor for both survival and recurrence in GBM patients. High NRP1 mRNA expression correlated with shorter OS and DFS (OS: χ2=4.6720, P=0.0307; DFS: χ2=11.013, P=0.0009). NRP1 is thus a GDNF receptor in glioma cells and a potential therapeutic target.

Expressions of glial cell line-derived neurotrophic factor and its tyrosine kinase receptor RET in the terminal rectum of fetal rats with congenital anorectal malformations at different gestational ages

Objective To explore the expressions and distributions of glial cell line-derived neurotrophic factor (GDNF) and itstyrosine kinase receptor RET in the terminal rectums of fetal rats with congenital anorectal malformations (ARM) at different gestationalage, and to explore their effects on the enteric nervous system in the terminal rectum of ARM fetal rats. Methods Thirty-five SD pregnancy rats were divided into a saline group (n=10) and an ethylenethiourea experiment group (n=25) by simple randomized study.The fetal rats were removed from the pregnant rats at the gestational 16 d, 18 d and 20 d. The fetal rats were divided into the saline control group, the ethylenethiourea control group (fetal rats without ARM) and the ethylenethiourea malformation group (ARM fetal rats) by the naked eye and dissecting microscope.HE staining was used to observe the morphology and the intestinal ganglion cells in the terminal rectum were counted.The immunohistochemical staining and Western blot methods were used to observe the distributions of GDNF and RET in the rectum at the gestational 16 d, 18 d and 20 d. The quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of GDNF mRNA in the fetal rats in the terminal rectum at the gestational 16 d, 18 d and 20 d. Results HE staining: the development of anorectal terminal in 3 groups of fetal rats was unclear at the gestational 16 d. A small amount of scattered nerve plexuses were observed in the muscular layer.The nuclei were small and sparse.The axons and cytoplasms were less.The serosal layer, muscular layer, submucosa, mucosal layer and glands in the terminal rectum were gradually clear in the saline control group and the ethylenethiourea control group at the gestational 18 d and 20 d. The intermuscular submucosal nerve plexuses increased gra-dually (11.400±3.134 and 11.200±3.425 at the gestational 18 d; 66.100±4.954 and 67.600±5.481 at the gestational 20 d). While, the layer was unclear in the ethylenethiourea malformation group and the nerve plexus was less (7.800±1.989 at the gestational 18 d, and 25.200±3.048 at the gestational 20 d), and the difference was statistically significant compared with 2 control groups (F=7.591, 271.833, all P 0.05); the expressions of GDNF and RET protein were 103.624±27.533 and 105.184±19.634 at the gestational 18 d; 151.496±33.622 and 150.738±21.423 at the gestational 20 d in 2 control groups.Compared with the ethylenethiourea malformation group (79.169±11.697 at the gestational 18 d; 94.873±11.309 at the gestational 20 d), and the difference were statistically significant (all P<0.05). Conclusions The expressions of GDNF and its tyrosine kinase receptor RET had a certain temporal correlation in the terminal rectum of normal fetal rats at different gestational ages and ARM.Moreover, the abnormal expressions of GDNF and its tyrosine kinase receptor RET in the distal rectum of ARM fetal rats can affect the development of enteric nervous system. Key words: Glial cell line-derived neurotrophic factor; RET; Signal pathway; Enteric nervous system; Congenital anorectal malformation

GFRA2 Identifies Cardiac Progenitors and Mediates Cardiomyocyte Differentiation in a RET-Independent Signaling Pathway

SummaryA surface marker that distinctly identifies cardiac progenitors (CPs) is essential for the robust isolation of these cells, circumventing the necessity of genetic modification. Here, we demonstrate that a Glycosylphosphatidylinositol-anchor containing neurotrophic factor receptor, Glial cell line-derived neurotrophic factor receptor alpha 2 (Gfra2), specifically marks CPs. GFRA2 expression facilitates the isolation of CPs by fluorescence activated cell sorting from differentiating mouse and human pluripotent stem cells. Gfra2 mutants reveal an important role for GFRA2 in cardiomyocyte differentiation and development both in vitro and in vivo. Mechanistically, the cardiac GFRA2 signaling pathway is distinct from the canonical pathway dependent on the RET tyrosine kinase and its established ligands. Collectively, our findings establish a platform for investigating the biology of CPs as a foundation for future development of CP transplantation for treating heart failure.

Protein regulation of induced pluripotent stem cells by transplanting in a Huntington's animal model.

The purpose of this study was to determine the functional recovery and protein regulation by transplanted induced pluripotent stem cells in a rat model of Huntington's disease (HD). In a quinolinic acid-induced rat model of striatal degeneration, induced pluripotent stem cells were transplanted into the ipsilateral lateral ventricle 10 days after the quinolinic acid injection. At 8 weeks after transplantation, fluorodeoxyglucose-PET/CT scan and balance-beam test were performed to evaluate the functional recovery of experimental rats. In addition, immunofluorescence and protein array analysis were used to investigate the regulation of stimulated protein expression in the striatum. At 8 weeks after induced pluripotent stem cell transplantation, motor function was improved in comparison with the quinolinic acid-treated rats. High fluorodeoxyglucose accumulation in the injured striatum was also observed by PET/CT scans. In addition, immunofluorescence analysis demonstrated that implanted cells migrated from the lateral ventricle into the lesioned striatum and differentiated into striatal projection neurons. Array analysis showed a significant upregulation of GFR (Glial cell line-derived neurotrophic factor receptor) alpha-1, Adiponectin/Acrp30, basic-fibroblast growth factors, MIP-1 (Macrophage-inflammatory protein) alpha and leptin, as well as downregulation of cytokine-induced neutrophil chemoattractant-3 in striatum after transplantatation of induced pluripotent stem cells in comparison with the quinolinic acid -treated rats. The findings in this work indicate that transplantation of induced pluripotent stem cells is a promising therapeutic candidate for HD.

Growth arrest specific 1 (Gas1) and glial cell line-derived neurotrophic factor receptor α1 (Gfrα1), two mouse oocyte glycosylphosphatidylinositol-anchored proteins, are involved in fertilisation.

Recently, Juno, the oocyte receptor for Izumo1, a male immunoglobulin, was discovered. Juno is an essential glycosylphosphatidylinositol (GIP)-anchored protein. This result did not exclude the participation of other GIP-anchored proteins in this process. After bibliographic and database searches we selected five GIP-anchored proteins (Cpm, Ephrin-A4, Gas1, Gfra1 and Rgmb) as potential oocyte candidates participating in fertilisation. Western blot and immunofluorescence analyses showed that only three were present on the mouse ovulated oocyte membrane and, of these, only two were clearly involved in the fertilisation process, namely growth arrest specific 1 (Gas1) and glial cell line-derived neurotrophic factor receptor α1 (Gfrα1). This was demonstrated by evaluating oocyte fertilisability after treatment of oocytes with antibodies against the selected proteins, with their respective short interference RNA or both. Gfrα1 and Gas1 seem to be neither redundant nor synergistic. In conclusion, oocyte Gas1 and Gfrα1 are both clearly involved in fertilisation.

Exercise-Mediated Increase in Nigral Tyrosine Hydroxylase Is Accompanied by Increased Nigral GFR-α1 and EAAC1 Expression in Aging Rats.

Exercise may alleviate locomotor impairment in Parkinson's disease (PD) or aging. Identifying molecular responses immediately engaged by exercise in the nigrostriatal pathway and allied tissue may reveal critical targets associated with its long-term benefits. In aging, there is loss of tyrosine hydroxylase (TH) and the glial cell line-derived neurotrophic factor (GDNF) receptor, GFR-α1, in the substantia nigra (SN). Exercise can increase GDNF expression, but its effect on GFR-α1 expression is unknown. Infusion of GDNF into striatum or GFR-α1 in SN, respectively, can increase locomotor activity and TH function in SN but not striatum in aged rats. GDNF may also increase glutamate transporter expression, which attenuates TH loss in PD models. We utilized a footshock-free treadmill exercise regimen to determine the immediate impact of short-term exercise on GFR-α1 expression, dopamine regulation, glutamate transporter expression, and glutamate uptake in 18 month old male Brown-Norway/Fischer 344 F1 hybrid rats. GFR-α1 and TH expression significantly increased in SN but not striatum. This exercise regimen did not affect glutamate uptake or glutamate transporter expression in striatum. However, EAAC1 expression increased in SN. These results indicate that nigral GFR-α1 and EAAC1 expression increased in conjunction with increased nigral TH expression following short-term exercise.

Hierarchical differentiation competence in response to retinoic acid ensures stem cell maintenance during mouse spermatogenesis.

Stem cells ensure tissue homeostasis through the production of differentiating and self-renewing progeny. In some tissues, this is achieved by the function of a definitive stem cell niche. However, the mechanisms that operate in mouse spermatogenesis are unknown because undifferentiated spermatogonia (Aundiff) are motile and intermingle with differentiating cells in an ‘open’ niche environment of seminiferous tubules. Aundiff include glial cell line-derived neurotrophic factor receptor α1 (GFRα1)+ and neurogenin 3 (NGN3)+ subpopulations, both of which retain the ability to self-renew. However, whereas GFRα1+ cells comprise the homeostatic stem cell pool, NGN3+ cells show a higher probability to differentiate into KIT+ spermatogonia by as yet unknown mechanisms. In the present study, by combining fate analysis of pulse-labeled cells and a model of vitamin A deficiency, we demonstrate that retinoic acid (RA), which may periodically increase in concentration in the tubules during the seminiferous epithelial cycle, induced only NGN3+ cells to differentiate. Comparison of gene expression revealed that retinoic acid receptor γ (Rarg) was predominantly expressed in NGN3+ cells, but not in GFRα1+ cells, whereas the expression levels of many other RA response-related genes were similar in the two populations. Ectopic expression of RARγ was sufficient to induce GFRα1+ cells to directly differentiate to KIT+ cells without transiting the NGN3+ state. Therefore, RARγ plays key roles in the differentiation competence of NGN3+ cells. We propose a novel mechanism of stem cell fate selection in an open niche environment whereby undifferentiated cells show heterogeneous competence to differentiate in response to ubiquitously distributed differentiation-inducing signals.

Treating congenital megacolon by transplanting GDNF and GFRα-1 double genetically modified rat bone marrow mesenchymal stem cells.

We studied the survival and gene expression of glial cell line-derived neurotrophic factor (GDNF) and GDNF receptor α-1 (GFRα-1) double-genetically modified rat bone marrow mesenchymal stem cells (BMSCs) transplanted into the intestinal walls of the rat models with congenital megacolon and determine the feasibility of treatment by transplantation of double-genetically modified rat BMSCs. The rat colorectal intestinal wall nerve plexus was treated with the cationic surface active agent benzalkonium chloride to establish an experimental megacolon model. The rat target genes GDNF and GFRα-1 were extracted and ligated into pEGFP-N1. Eukaryotic fluorescent expression vectors carrying the GDNF and GFRα-1 genes were transfected into BMSCs by in vitro culture. We treated congenital megacolon by transplanting double-genetically modified rat bone marrow mesenchymal stem cells. The pEGFP-EGFP-GDNF-GFRα-1 double-gene co-expressing the eukaryotic expression plasmid vector was successfully established. Protein gene protein 9.5 and vasoactive intestinal peptide-positive ganglion cells showed no positive expression in the phosphate-buffered saline transplantation group based on an immunofluorescence test at 1, 2, and 4 weeks after transplantation of BMSCs. Additionally, compared with the phosphate-buffered saline transplantation group, the expression of rearranged during transfection, GDNF, and GFRα-1 mRNA in the stem cell transplantation group increased gradually. The double-genetically modified BMSCs colonized and survived in the intestinal wall of the experimental megacolon rat model and expressed related genes, partially recovering the colonic neuromuscular regulatory functions and thus providing an experimental basis for treating congenital megacolon by cellular transplantation.

Coexpression of recombinant adenovirus carrying GDNF and EDNRB genes in neural stem cells in vitro

Gene therapy and nerve stem cells isolated from the developing human enteric nervous system (ENS) are significant. They may open the route for the cell therapy of Hirschsprung's disease (HD). We have constructed the recombinant adenovirus-carrying glial cell line-derived neurotrophic factor (GDNF) and endothelin receptor B (EDNRB) gene, and investigated the exosomatic coexpression in neural stem cells. The recombinant adenovirus Ad-GE coexpressing GDNF and EDNRB gene was constructed by the AdEasy system and confirmed by the reverse transcription polymerase chain reaction (RT-PCR) method. Expression of exogenous genes in neural stem cells after transfection was confirmed by the flow cytometry and real-time fluorescence quantitative PCR. Fragments of pAd Track-CMV-GE were consistent with GDNF and EDNRB. The green fluorescence of the positive cells was followed by fluorescence microscopy at 24 h after NSCs had been transfected, reaching a peak at 72 h after transfection. Flow cytometry showed that the efficiency of transfection was 15.0, 23.6, and 25.4% at 24, 48 and 72 h respectively. Real-time fluorescence quantitative PCR showed the expression levels of mRNA of GDNF and EDNRB in 48 and 72 h groups were obviously higher than that in 24 and 96 h groups. Recombinant adenovirus carrying GDNF and EDNRB genes are coexpressed in neural stem cells, which may offer the possibility of a novel approach to local combination gene therapy for Hirschsprung's disease.

The Neuregulin‐Rac‐MKK7 pathway regulates antagonistic c‐jun/Krox20 expression in Schwann cell dedifferentiation

Schwann cells respond to nerve injury by dedifferentiating into immature states and producing neurotrophic factors, two actions that facilitate successful regeneration of axons. Previous reports have implicated the Raf-ERK cascade and the expression of c-jun in these Schwann cell responses. Here we used cultured primary Schwann cells to demonstrate that active Rac1 GTPase (Rac) functions as a negative regulator of Schwann cell differentiation by upregulating c-jun and downregulating Krox20 through the MKK7-JNK pathway, but not through the Raf-ERK pathway. The activation of MKK7 and induction of c-jun in sciatic nerves after axotomy was blocked by Rac inhibition. Microarray experiments revealed that the expression of regeneration-associated genes, such as glial cell line-derived neurotrophic factor and p75 neurotrophin receptor, after nerve injury was dependent on Rac but not on ERK. Finally, the inhibition of ErbB2 signaling prevented MKK7 activation, c-jun induction, and Rac-dependent gene expression in sciatic nerve explant cultures. Taken together, our results indicate that the neuregulin-Rac-MKK7-JNK/c-jun pathway regulates Schwann cell dedifferentiation following nerve injury.

Establishment and expression of recombinant human glial cell linederived neurotrophic factor and TNF α receptor in human neural stem cells

ObjectiveTo investigate the interference and expression of human glial cell line-derived neurotrophic factor (hGDNF) and soluble TNF alpha (sTNFR |) receptor genes in neural stem cells and to evaluate the roles of these proteins in the genetic treatment of spinal cord injury. MethodsFull-length of GDNF cDNA (558 bp) and sTNFR|cDNA (504 bp) were inserted into the early 1 region of adenovirus genomic DNA respectively and were immediated by the human cytomegalovirus (gene promoter/enhancer). These adenoviruses were propagated in HEK293 cells via homologous recombination for 7-10 days in vivo, then they were used to infect human neural stem cells. The infection and expression of gene were tested under immunofluorescence, ELISA and Western-blot after 48 hours. ResultsAlmost all the cultured cells showed the nestin immunofluorescence positive staining, which was the characteristics of neural stem cell. A great quantity of EGFP and RFP were observed in neural stem cells, which indicated the expression of GDNF and sTNFR |. After transfection of GDNF and sTNFR | genes, many neural stem cells show GFAP and tubulin immunofluorescence positive staining, which meant that most neural stem cells differentiated into neuron at that condition. ConclusionsThe infective efficiency of adenovirus is greatly acceptable to neural stem cell, thus adenovirus provide a useful vector for exogenous GDNF and sTNFR | genes expressing in neural stem cells, which is useful for differentiation of neural stem cell.

Sildenafil promotes neuroprotection of the pelvic ganglia neurones after bilateral cavernosal nerve resection in the rat

To determine the gene expression profile of pelvic ganglia neurones after bilateral cavernosal nerve resection (BCNR) and subsequent treatment with sildenafil in relation to neurotrophic-related pathways. Fisher rats aged 5 months were subjected to BCNR or sham operation and treated with or without sildenafil (20 mg/kg body-weight in drinking water) for 7 days. Total RNA isolated from pelvic ganglia was subjected to reverse transcription and then to quantitative reverse transcriptase-polymerase chain reaction (PCR) with the RAT-neurotrophic array. Results were corroborated by real-time PCR and western blotting. Another set of animals were injected with a fluorescent tracer at the base of the penis, 7 days before BCNR or sham operation, and were sacrificed 7 days after surgery. Sections of pelvic ganglia were used for immunohistochemistry with antibodies against neurturin, neuronal nitric oxide synthase, tyrosine hydroxylase and glial cell line-derived neurotrophic factor receptor α2. A down-regulation of the expression of neuronal nitric oxide synthase accompanied by changes in the level of cholinergic neurotrophic factors, such as neurturin and its receptor glial cell line-derived neurotrophic factor receptor α2, artemin, neurotrophin-4 and cilliary neurotrophic factor, was observed 7 days after BCNR in pelvic ganglia neurones. Treatment with sildenafil, starting immediately after surgery, reversed all these changes at a level similar to that in sham-operated animals. Sildenafil treatment promotes changes in the neurotrophic phenotype, leading to a regenerative state of pelvic ganglia neurones. The present study provides a justification for the use of phosphodiesterase 5 inhibitors as a neuroprotective agent after BCNR.

Preclinical anti-angiogenesis and anti-tumor activity of SIM010603, an oral, multi-targets receptor tyrosine kinases inhibitor

SIM010603 is a structurally novel, oral, multi-targeted receptor tyrosine kinase inhibitor. This study investigated the anti-angiogenic and anti-tumor effects of SIM010603. A radiometric protein kinase assay was used for measuring the kinase activity of the 32 protein kinases. Receptor phosphorylation was determined by enzyme-linked immunosorbent assay (ELISA). Cell proliferation was measured by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Cell chemotaxis was evaluated by modified Boyden chamber assay. Effect of SIM010603 on angiogenesis was examined by mouse cornea angiogenesis assay. Effect of SIM010603 on xenografts was assessed by tumor growth delay. Effects of SIM010603 on tumor microvascular density (MVD), recruitment of pericytes, and pericyte encapsulation of tumor vessels were analyzed by immunofluorescent staining technique. SIM010603 inhibited stem cell factor receptor (Kit), vascular endothelial growth factor receptor-2 (VEGFR-2), platelet-derived growth factor receptor-β (PDGFR-β), glial cell line-derived neurotrophic factor receptor (Rearranged during Transfection; RET), and Fms-like tyrosine kinase-3 (FLT3) with IC(50) values between 5.0 and 68.1nmol/l. SIM010603 inhibited the phosphorylation of PDGFR-β and VEGFR-2. Moreover, SIM010603 inhibited endothelial cell proliferation, endothelial cells chemotaxis, and corneal angiogenesis. Although SIM010603 exhibited lower activity in regard to proliferation of NCI-H460, MDA-MB-435, and T241-VEGF-A cells (IC(50)>1μmol/l), SIM010603 inhibited tumor growth in these xenograft tumor growth models. SIM010603 reduced tumor MVD in T241-VEGF-A tumor xenograft models and decreased positive signals of CD31, NG2 in MDA-MB-435, and LLC-SW-44 xenograft tumor models. These results support the clinical assessment of SIM010603 as a therapeutic agent for cancer.