Neurotrophic factor GDNF promotes survival of salivary stem cells

Stem cell-based regenerative therapy is a promising treatment for head and neck cancer patients that suffer from chronic dry mouth (xerostomia) due to salivary gland injury from radiation therapy. Current xerostomia therapies only provide temporary symptom relief, while permanent restoration of salivary function is not currently feasible. Here, we identified and characterized a stem cell population from adult murine submandibular glands. Of the different cells isolated from the submandibular gland, this specific population, Lin-CD24+c-Kit+Sca1+, possessed the highest capacity for proliferation, self renewal, and differentiation during serial passage in vitro. Serial transplantations of this stem cell population into the submandibular gland of irradiated mice successfully restored saliva secretion and increased the number of functional acini. Gene-expression analysis revealed that glial cell line-derived neurotrophic factor (Gdnf) is highly expressed in Lin-CD24+c-Kit+Sca1+ stem cells. Furthermore, GDNF expression was upregulated upon radiation therapy in submandibular glands of both mice and humans. Administration of GDNF improved saliva production and enriched the number of functional acini in submandibular glands of irradiated animals and enhanced salisphere formation in cultured salivary stem cells, but did not accelerate growth of head and neck cancer cells. These data indicate that modulation of the GDNF pathway may have potential therapeutic benefit for management of radiation-induced xerostomia.

Availability of Pre- and Pro-regions of Transgenic GDNF Affects the Ability to Induce Axonal Sprout Growth

Plasmids containing four GFP-tagged isoforms of the human GDNF gene, with both pre- and pro-regions (pre-pro- GDNF), with the pre- (pre-GDNF) or the pro-region (pro-GDNF) alone, and without the pre- and pro-regions (mGDNF), were used to transfect HEK293 cells (human embryonic kidney cell line). The effect of the transgenic products on the growth of processes was studied in the spinal ganglia of 14-day rat embryos. Media conditioned by the transgenic cells were used to culture explants and dissociated cells of embryonic dorsal root ganglia attached to the bottom of the plate. Medium conditioned by gfp-transgenic HEK293 cells was used as the control. Spinal ganglia explants and dissociated cells cultured in a medium supplemented with recombinant GDNF (recGDNF) as well as in conditioned media containing the pre-GDNF and mGDNF products demonstrated active growth of processes immunopositive for neuronal marker beta-3-tubulin as early as on culture day 4. The ganglia and cells cultured in control medium and media conditioned by cells transgenic for pro-GDNF had no or very few processes even after 10 days of culture.

[Advances in the application of gene therapy for Parkinson's disease with adeno-associated virus]

Vectors used to carry foreign genes play an important role in gene therapy, among which, the adeno-associated virus (AAV) has many advantages, such as nonpathogenicity, low immunogenicity, stable and long-term expression and multiple-tissue-type infection, etc. These advantages have made AAV one of the most potential vectors in gene therapy, and widely used in many clinical researches, for example, Parkinson's disease. This paper introduces the biological characteristics of AAV and the latest research progress of AAV carrying neurotrophic factor, dopamine synthesis related enzymes and glutamic acid decarboxylase gene in the gene therapy of Parkinson's disease.

Human neural stem cells survive long term in the midbrain of dopamine-depleted monkeys after GDNF overexpression and project neurites toward an appropriate target

Transplanted multipotent human fetal neural stem cells (hfNSCs) significantly improved the function of parkinsonian monkeys in a prior study primarily by neuroprotection, with only 3%-5% of cells expressing a dopamine (DA) phenotype. In this paper, we sought to determine whether further manipulation of the neural microenvironment by overexpression of a developmentally critical molecule, glial cell-derived neurotrophic factor (GDNF), in the host striatum could enhance DA differentiation of hfNSCs injected into the substantia nigra and elicit growth of their axons to the GDNF-expressing target. hfNSCs were transplanted into the midbrain of 10 green monkeys exposed to 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridine. GDNF was delivered concomitantly to the striatum via an adeno-associated virus serotype 5 vector, and the fate of grafted cells was assessed after 11 months. Donor cells remained predominantly within the midbrain at the injection site and sprouted numerous neurofilament-immunoreactive fibers that appeared to course rostrally toward the striatum in parallel with tyrosine hydroxylase-immunoreactive fibers from the host substantia nigra but did not mature into DA neurons. This work suggests that hfNSCs can generate neurons that project long fibers in the adult primate brain. However, in the absence of region-specific signals and despite GDNF overexpression, hfNSCs did not differentiate into mature DA neurons in large numbers. It is encouraging, however, that the adult primate brain appeared to retain axonal guidance cues. We believe that transplantation of stem cells, specifically instructed ex vivo to yield DA neurons, could lead to reconstruction of some portion of the nigrostriatal pathway and prove beneficial for the parkinsonian condition.

Pharmacologically controlled, discontinuous GDNF gene therapy restores motor function in a rat model of Parkinson's disease

Neurotrophic factors have raised hopes to be able to cure symptoms and to prevent progressive neurodegeneration in devastating neurological diseases. Gene therapy by means of viral vectors can overcome the hurdle of targeted delivery, but its current configuration is irreversible and thus much less controllable than that of classical pharmacotherapies. We thus aimed at developing a strategy allowing for both curative and controllable neurotrophic factor expression. Therefore, the short-term, intermittent and reversible expression of a neutrophic factor was evaluated for therapeutic efficacy in a slowly progressive animal model of Parkinson's disease (PD). We demonstrate that short-term induced expression of glial cell line derived neurotrophic factor (GDNF) is sufficient to provide i) substantial protection of nigral dopaminergic neurons from degeneration and ii) restoration of dopamine supply and motor behaviour in the partial striatal 6-OHDA model PD. These neurorestorative effects of GDNF lasted several weeks beyond the time of its expression. Later on, therapeutic efficacy ceased, but was restored by a second short induction of GDNF expression, demonstrating that monthly application of the inducing drug mifepristone was sufficient to maintain neuroprotective and neurorestorative GDNF levels. These findings suggest that forthcoming gene therapies for PD or other neurodegenerative disorders can be designed in a way that low frequency application of an approved drug can provide controllable and therapeutically efficient levels of GDNF or other neurotrophic factors. Neurotrophic factor expression can be withdrawn in case of off-target effects or sufficient clinical benefit, a feature that may eventually increase the acceptance of gene therapy for less advanced patients, which may profit better from such approaches.

Enhanced neuroprotection and improved motor function in traumatized rat spinal cords by rAAV2-mediated glial-derived neurotrophic factor combined with early rehabilitation training

BACKGROUND

Spinal cord injury (SCI) is a serious neurological injury that often leads to permanent disabilities for the victims. The aim of this study was to determine the effects of glial-derived neurotrophic factor (GDNF) mediated by recombinant adeno-associated virus type 2 (rAAV2) alone or in combination with early rehabilitation training on SCI.

METHODS

SCI was induced on the T8-9 segments of the spinal cord by laminectomy in adult male Sprague-Dawley rats. Then besides the sham operation group, the SCI rats were randomly divided into four groups: natural healing group, gene therapy group, rehabilitation training group, and combination therapy group (gene therapy in combination with rehabilitation training). Motor dysfunction, protein expression of GDNF, edema formation, and cell injury were examined 7, 14, and 21 days after trauma.

RESULTS

The topical application of rAAV-GDNF-GFP resulted in strong expression of GDNF, especially after the 14th day, and could protect the motor neuron cells. Early rehabilitative treatment resulted in significantly improved motor function, reduced edema formation, and protected the cells from injury, especially after the 7th and 14th days, and increased the GDNF expression in the damaged area, which was most evident after Day 14. The combined application of GDNF and early rehabilitative treatment after SCI resulted in a significant reduction in spinal cord pathology and motor dysfunction after the 7th and 14th days.

CONCLUSION

These observations suggest that rAAV2 gene therapy in combination with rehabilitation therapy has potential clinical value for the treatment of SCI.

Co-transplantation of GDNF-overexpressing neural stem cells and fetal dopaminergic neurons mitigates motor symptoms in a rat model of Parkinson's disease

Striatal transplantation of dopaminergic (DA) neurons or neural stem cells (NSCs) has been reported to improve the symptoms of Parkinson's disease (PD), but the low rate of cell survival, differentiation, and integration in the host brain limits the therapeutic efficacy. We investigated the therapeutic effects of intracranial co-transplantation of mesencephalic NSCs stably overexpressing human glial-derived neurotrophic factor (GDNF-mNSCs) together with fetal DA neurons in the 6-OHDA rat model of PD. Striatal injection of mNSCs labeled by the contrast enhancer superparamagnetic iron oxide (SPIO) resulted in a hypointense signal in the striatum on T2-weighted magnetic resonance images that lasted for at least 8 weeks post-injection, confirming the long-term survival of injected stem cells in vivo. Co-transplantation of GDNF-mNSCs with fetal DA neurons significantly reduced apomorphine-induced rotation, a behavioral endophenotype of PD, compared to sham-treated controls, rats injected with mNSCs expressing empty vector (control mNSCs) plus fetal DA neurons, or rats injected separately with either control mNSCs, GDNF-mNSCs, or fetal DA neurons. In addition, survival and differentiation of mNSCs into DA neurons was significantly greater following co-transplantation of GDNF-mNSCs plus fetal DA neurons compared to the other treatment groups as indicated by the greater number of cell expressing both the mNSCs lineage tracer enhanced green fluorescent protein (eGFP) and the DA neuron marker tyrosine hydroxylase. The success of cell-based therapies for PD may be greatly improved by co-transplantation of fetal DA neurons with mNSCs genetically modified to overexpress trophic factors such as GDNF that support differentiation into DA cells and their survival in vivo.

Tricyclic antidepressant amitriptyline indirectly increases the proliferation of adult dentate gyrus-derived neural precursors: an involvement of astrocytes

Antidepressants increase the proliferation of neural precursors in adult dentate gyrus (DG), which is considered to be involved in the therapeutic action of antidepressants. However, the mechanism underlying it remains unclear. By using cultured adult rat DG-derived neural precursors (ADP), we have already shown that antidepressants have no direct effects on ADP. Therefore, antidepressants may increase the proliferation of neural precursors in adult DG via unknown indirect mechanism. We have also shown that amitriptyline (AMI), a tricyclic antidepressant, induces the expressions of GDNF, BDNF, FGF2 and VEGF, common neurogenic factors, in primary cultured astrocytes (PCA). These suggest that AMI-induced factors in astrocytes may increase the proliferation of neural precursors in adult DG. To test this hypothesis, we examined the effects of AMI-induced factors and conditioned medium (CM) from PCA treated with AMI on ADP proliferation. The effects of CM and factors on ADP proliferation were examined with BrdU immunocytochemistry. AMI had no effect on ADP proliferation, but AMI-treated CM increased it. The receptors of GDNF, BDNF and FGF2, but not VEGF, were expressed in ADP. FGF2 significantly increased ADP proliferation, but not BDNF and GDNF. In addition, both of a specific inhibitor of FGF receptors and anti-FGF2 antibody significantly counteracted the increasing effect of CM on ADP proliferation. In addition, FGF2 in brain is mainly derived from astrocytes that are key components of the neurogenic niches in adult DG. These suggest that AMI may increase ADP proliferation indirectly via PCA and that FGF2 may a potential candidate to mediate such an indirect effect of AMI on ADP proliferation via astrocytes.

Antenatal taurine supplementation improves cerebral neurogenesis in fetal rats with intrauterine growth restriction through the PKA-CREB signal pathway

OBJECTIVE

This study seeks to explore whether antenatal supplement of taurine may improve the brain development of fetal rats with intrauterine growth restriction (IUGR) via the protein kinase A-cyclic adenosine monophosphate (cAMP) response element protein (PKA-CREB) pathway.

METHODS

Fifteen pregnant rats were randomly divided into control group, IUGR model, and IUGR with antenatal taurine supplement group. Brain tissues were obtained immediately after rats were born. PKA-CREB signal pathway activity and glial cell line-derived neurotrophic factor (GDNF) mRNA and protein levels were measured by reverse transcription polymerase chain reaction and immunohistochemistry stains, whereas immunoreactive cells of neuron-specific enolase (NSE) and proliferating cell nuclear antigen (PCNA) were detected by immunohistochemistry stains.

RESULTS

The results showed that: (1) In the IUGR group, a greater number of PCNA and NSE immunoreactive cells were found in brain tissues compared with controls, and prenatal taurine supplementation led to a further increase. (2) Expression of PKA, CREB, and GDNF were increased in mRNA and protein levels due to taurine supplementation.

DISCUSSION

Antenatal taurine supplementation shows effects of promotion of cell proliferation and activation of neurotrophic factors on fetal rat brain in a model of IUGR by activating the PKA-CREB signal pathway, increasing expression of neurotrophic factors, and promoting cell proliferation to counteract neuron loss caused by IUGR.

[Construction and identification of rhesus monkey Schwann cells modified with human glial cell derived neurotrophic factor gene]

OBJECTIVE

To construct the rhesus monkey Schwann cells (SCs) modified with human glial cell derived neurotrophic factor (hGDNF) gene.

METHODS

The coding sequence ofhGDNF amplified by PCR from pUC19-hGDNF was inserted into eukaryotic expression vector pBABE-puro. The recombinant eukaryotic expression vector pBABE-puro-hGDNF was identified with restriction enzyme digestion and DNA sequencing. The SCs were isolated from rhesus monkeys, cultured and purified. The SCs were transfected with the recombinant retrovirus vector containing hGDNF gene. The mRNA and protein expressions of hGDNF were analyzed by real-time fluorescent quantitative PCR and Western blot.

RESULTS

The PCR product of hGDNF coding sequence was a 596 bp specific segment. The recombinant eukaryotic expression vector was digested into a 596 bp specific segment by specific restriction enzyme and another segment. The 596 bp segment confirmed by DNA sequencing was consistent with hGDNF sequence on GenBank. Restriction enzyme digestion and sequencing results showed that the coding sequence of hGDNF was successfully inserted into the recombinant retrovirus vector and the mRNA and protein expressions of hGDNF were significantly higher in transfected SCs than non-transfected SCs (P < 0.05).

CONCLUSION

The rhesus monkey SCs modified with hGDNF gene are successfully constructed and hGDNF can be released continuously and stably, which will provide a foundation for the further research about cell therapy of hGDNF-SCs in the repair of injured nerve.

Scutellarin and caffeic acid ester fraction, active components of Dengzhanxixin injection, upregulate neurotrophins synthesis and release in hypoxia/reoxygenation rat astrocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Scutellarin (Scu) and caffeic acid ester fraction (Caf), the extracts from the traditional Chinese herb, Erigeron breviscapus, are known to ameliorate post ischemic neuronal dysfunction.

AIM OF THE STUDY

Neurotrophic factors (NTFs) are essential for neuronal growth and survival. We explored the neuroprotective effect of Scu and Caf by synthesis and release of NGF, BDNF and GDNF in rat astrocytes exposed to hypoxia/reoxygenation and MACO rats. And the neuroprotection of Scu and Caf was also explored.

MATERIALS AND METHODS

The primary rat astrocytes were cultured in vitro. The temporal mRNA and protein expression profile during hypoxia/reoxygenation were analyzed using real-time RT-PCR and ELISA. The expression of p-CREB, p-Akt, p-MAPKs and Bax were analyzed by western blotting. Cell viability of neuro-2A was measured using CCK-8 and cell cytotoxicity was measured with LDH release.

RESULTS

During hypoxia/reoxygenation a similar decrease pattern of NTFs (NGF, BDNF and GDNF) was observed in both mRNA and protein; Scu and Caf enhanced the expressions of NGF, BDNF and GDNF mRNA and protein in astrocytes under hypoxia/reoxygenation condition. CREB and Akt, but not MAPKs ( p-JNK, p-ERK1/2 and p-38) may be involved in the expression of NTFs. Concomitantly, conditioned medium from astrocytes which was treated by Scu or Caf after hypo3h/Reox24h significantly reduced neurotoxicity compared with conditioned medium from hypo3h/Reox24h astrocytes alone, and they show the tendency of increased neurons viability accompanied with Bax changes.

CONCLUSIONS

These results indicate that the neuroprotective effect of Scu and Caf might be mediated, at least in part, via a stimulation of the production and release of NTFs through p-CREB and p-Akt signaling. Furthermore, Scu and Caf could antagonistic the hypoxia induced toxicity through astrocytes conditioned medium. Those results suggested that Scu and Caf might have therapeutic potential for stroke.

Differences in laryngeal neurotrophic factor gene expression after recurrent laryngeal nerve and vagus nerve injuries

OBJECTIVES

Recurrent laryngeal nerve (RLN) and vagus nerve (VN) injuries characteristically are followed by differing degrees of spontaneous reinnervation, yet laryngeal muscle neurotrophic factor (NF) expression profiles after RLN and VN injuries have not been well elucidated. This study's objective was to determine the relative changes in gene expression of 5 well-characterized NFs from laryngeal muscle after RLN or VN injuries in a time-dependent fashion, and demonstrate how these changes correspond with electromyography-assessed innervation status.

METHODS

Thirty-six male rats underwent left RLN transection (12 rats), left VN transection (12 rats), or a sham procedure (12 rats). The primary outcomes included electromyographic assessment and laryngeal muscle NF expression quantification with reverse transcription polymerase chain reaction at 3 days and at 1 month.

RESULTS

Electromyography at 3 days demonstrated electrical silence in the VN injury group, normal activity in the sham group, and nascent units with decreased recruitment in the RLN injury group. Reverse transcription polymerase chain reaction demonstrated that changes in NF gene expression from laryngeal muscles varied depending on the type of nerve injury (RLN or VN) and the specific laryngeal muscle (posterior cricoarytenoid or adductor) assessed.

CONCLUSIONS

Laryngeal muscle NF expression profiles after cranial nerve X injury depend both upon the level of nerve injury and upon the muscles involved.

Glial cell line-derived neurotrophic factor (GDNF) induced migration of spermatogonial cells in vitro via MEK and NF-kB pathways

Glial cell line-derived neurotrophic factor (GDNF) regulates spermatogonial stem cell (SSC) maintenance. In the present study, we examined the levels and the cellular origin of GDNF in mouse testes during age-development, and the capacity of GDNF to induce migration of enriched GFR-α1 positive cells in vitro. The involvement of MAP kinase (MEK) and NF-kB signal pathways were examined. Our results show high levels of GDNF in testicular tissue of one-week-old mice which significantly decreased with age when examined by ELISA, real time PCR (qPCR) and immunofluorescence staining (IF) analysis. GDNF receptor (GFR-α1) expression was similar to GDNF when examined by qPCR analysis. Only Sertoli cell cultures (SCs) from one-week-old mice produced GDNF compared to SCs from older mice. However, peritubular cells from all the examined ages did not produce GDNF. The addition of recombinant GDNF (rGDNF) or supernatant from SCs from one-week-old mice to GFR-α1 positive cells induced their migration in vitro. This effect was significantly reduced by the addition of inhibitors to MEK (PD98059, U0126), NF-kB (PDTC) and IkB protease inhibitor (TPCK). Our results show for the first time the capacity of rGDNF and supernatant from SCs to induce migration of enriched GFR-α1 positive cells, and the possible involvement of MEK, NF-kB and IkB in this process. This study may suggest a novel role for GDNF in the regulation SSC niches and spermatogenesis.

[Effect of GDNF on the behavior of ASC mice with high hereditary predisposition to catalepsy]

ASC mice, which were selected for high predisposition to catalepsy, are convenient genetic model for research of central mechanisms related to disorder of motor regulation. The aim of the work was to study the effect of glial cell line-derived neurotrophic factor (GDNF) on catalepsy, locomotor activity, stereotyping behavior in the marble burying test and on the dopamine level in striatum of ASC mice. It was shown that GDNF increased the locomotor activity in the open field, reduced catalepsy expression and stimulated the stereotyping obsessive-compulsive behavior. These changes in behavior were accompanied by increasing dopamine level in striatum.

The GDNF System Is Altered in Diverticular Disease - Implications for Pathogenesis

Background & Aims

Absence of glial cell line-derived neurotrophic factor (GDNF) leads to intestinal aganglionosis. We recently demonstrated that patients with diverticular disease (DD) exhibit hypoganglionosis suggesting neurotrophic factor deprivation. Thus, we screened mRNA expression pattern of the GDNF system in DD and examined the effects of GDNF on cultured enteric neurons.

Methods

Colonic specimens obtained from patients with DD (n = 21) and controls (n = 20) were assessed for mRNA expression levels of the GDNF system (GDNF, GDNF receptors GFRα1 and RET). To identify the tissue source of GDNF and its receptors, laser-microdissected (LMD) samples of human myenteric ganglia and intestinal muscle layers were analyzed separately by qPCR. Furthermore, the effects of GDNF treatment on cultured enteric neurons (receptor expression, neuronal differentiation and plasticity) were monitored.

Results

mRNA expression of GDNF and its receptors was significantly down-regulated in the muscularis propria of patients with DD. LMD samples revealed high expression of GDNF in circular and longitudinal muscle layers, whereas GDNF receptors were also expressed in myenteric ganglia. GDNF treatment of cultured enteric neurons increased mRNA expression of its receptors and promoted neuronal differentiation and plasticity revealed by synaptophysin mRNA and protein expression.

Conclusions

Our results suggest that the GDNF system is compromised in DD. In vitro studies demonstrate that GDNF enhances expression of its receptors and promotes enteric neuronal differentiation and plasticity. Since patients with DD exhibit hypoganglionosis, we propose that the observed enteric neuronal loss in DD may be due to lacking neurotrophic support mediated by the GDNF system.

TRPV1 and TRPV4 play pivotal roles in delayed onset muscle soreness

Unaccustomed strenuous exercise that includes lengthening contraction (LC) often causes tenderness and movement related pain after some delay (delayed-onset muscle soreness, DOMS). We previously demonstrated that nerve growth factor (NGF) and glial cell line-derived neurotrophic factor (GDNF) are up-regulated in exercised muscle through up-regulation of cyclooxygenase (COX)-2, and they sensitized nociceptors resulting in mechanical hyperalgesia. There is also a study showing that transient receptor potential (TRP) ion channels are involved in DOMS. Here we examined whether and how TRPV1 and/or TRPV4 are involved in DOMS. We firstly evaluated a method to measure the mechanical withdrawal threshold of the deep tissues in wild-type (WT) mice with a modified Randall-Selitto apparatus. WT, TRPV1−/− and TRPV4−/− mice were then subjected to LC. Another group of mice received injection of murine NGF-2.5S or GDNF to the lateral gastrocnemius (LGC) muscle. Before and after these treatments the mechanical withdrawal threshold of LGC was evaluated. The change in expression of NGF, GDNF and COX-2 mRNA in the muscle was examined using real-time RT-PCR. In WT mice, mechanical hyperalgesia was observed 6–24 h after LC and 1–24 h after NGF and GDNF injection. LC induced mechanical hyperalgesia neither in TRPV1−/− nor in TRPV4−/− mice. NGF injection induced mechanical hyperalgesia in WT and TRPV4−/− mice but not in TRPV1−/− mice. GDNF injection induced mechanical hyperalgesia in WT but neither in TRPV1−/− nor in TRPV4−/− mice. Expression of NGF and COX-2 mRNA was significantly increased 3 h after LC in all genotypes. However, GDNF mRNA did not increase in TRPV4−/− mice. These results suggest that TRPV1 contributes to DOMS downstream (possibly at nociceptors) of NGF and GDNF, while TRPV4 is located downstream of GDNF and possibly also in the process of GDNF up-regulation.

[Association between mood characteristics and polymorphisms of glial cell line-derived neurotrophic factor (GNDF) in patients with depression]

Glial cell line-derived neurotrophic factor (GNDF) plays an important role in the development and synaptic plasticity of dopaminergic neurons, thus it could be an important therapeutic factor in Parkinson's disease. Results from candidate gene studies of GDNF in psychiatric disorders are contradictory. Moreover, the possible association between GDNF polymorphisms and major- or bipolar depression has not been studied to date. Recently, our research group has published an association between two GDNF polymorphisms (rs3812047, rs3096140) and the individual variability of anxiety measured by the Hospital Anxiety and Depression Scale (HADS) on a non-clinical sample. In the present study we further analyzed this association on a sample with major- and bipolar depression: we used data from 183 MDD, 116 BP, and 1172 control subjects and tested effect of GDNF rs3812047 and rs3096140 polymorphisms on mood disorders. The case control design did not show significant differences in the genotype distribution of BP or MDD versus control patients. However, in the bipolar group subjects with rs3812047 A allele showed a significantly higher anxiety and depression mean score then subjects with G allele (p=0.043). This result supports our previous findings demonstrated on a non-clinical sample. Interestingly we found an opposite effect of the rs3812047 using data from MDD patients: subjects with the G allele had higher depression scores (p=0.012). An interaction effect of patient subgroups and genetic variants of the rs3812047 was observed for both HADS subscales (anxiety: p=0.029; depression: 0.004). In summary, we confirmed the previously published association between the rs3812047 A allele and mood characteristics on the bipolar sample, and an effect in the opposite direction was detected in the patient group with major depression.

Calcitriol imparts neuroprotection in vitro to midbrain dopaminergic neurons by upregulating GDNF expression

During development a tightly controlled signaling cascade dictates the differentiation, maturation and survival of developing neurons. Understanding this signaling mechanism is important for developing therapies for neurodegenerative illnesses. In previous work we have sought to understand the complex signaling pathways responsible for the development of midbrain dopamine neurons using a proteomic approach. One protein we have identified as being expressed in developing midbrain tissue is the vitamin D receptor. Therefore we investigated the effect of the biologically active vitamin D3 metabolite, calcitriol, on primary fetal ventral mesencephalic cultures of dopamine neurons. We observed a dose responsive increase in numbers of rat primary dopamine neurons when calcitriol was added to culture media. Western blot data showed that calcitriol upregulated the expression of glial derived neurotrophic factor (GDNF). Blocking GDNF signaling could prevent calcitriol's ability to increase numbers of dopamine neurons. An apoptosis assay and cell birth dating experiment revealed that calcitriol increases the number of dopamine neurons through neuroprotection and not increased differentiation. This could have implications for future neuroprotective PD therapies.

GDNF mediates glioblastoma-induced microglia attraction but not astrogliosis

High-grade gliomas are the most common primary brain tumors. Their malignancy is promoted by the complex crosstalk between different cell types in the central nervous system. Microglia/brain macrophages infiltrate high-grade gliomas and contribute to their progression. To identify factors that mediate the attraction of microglia/macrophages to malignant brain tumors, we established a glioma cell encapsulation model that was applied in vivo. Mouse GL261 glioma cell line and human high-grade glioma cells were seeded into hollow fibers (HF) that allow the passage of soluble molecules but not cells. The glioma cell containing HF were implanted into one brain hemisphere and simultaneously HF with non-transformed fibroblasts (controls) were introduced into the contralateral hemisphere. Implanted mouse and human glioma- but not fibroblast-containing HF attracted microglia and up-regulated immunoreactivity for GFAP, which is a marker of astrogliosis. In this study, we identified GDNF as an important factor for microglial attraction: (1) GL261 and human glioma cells secret GDNF, (2) reduced GDNF production by siRNA in GL261 in mouse glioma cells diminished attraction of microglia, (3) over-expression of GDNF in fibroblasts promoted microglia attraction in our HF assay. In vitro migration assays also showed that GDNF is a strong chemoattractant for microglia. While GDNF release from human or mouse glioma had a profound effect on microglial attraction, the glioma-induced astrogliosis was not affected. Finally, we could show that injection of GL261 mouse glioma cells with GDNF knockdown by shRNA into mouse brains resulted in reduced tumor expansion and improved survival as compared to injection of control cells.

Glial cell-line derived neurotrophic factor (GDNF) replacement attenuates motor impairments and nigrostriatal dopamine deficits in 12-month-old mice with a partial deletion of GDNF

Glial cell-line derived neurotrophic factor (GDNF) has been established as a growth factor for the survival and maintenance of dopamine (DA) neurons. In phase I clinical trials, GDNF treatment in Parkinson's disease patients led to improved motor function and GDNF has been found to be down regulated in Parkinson's disease patients. Studies using GDNF heterozygous (Gdnf(+/-)) mice have demonstrated that a partial reduction of GDNF leads to an age-related accelerated decline in nigrostriatal DA system- and motor-function and increased neuro-inflammation and oxidative stress in the substantia nigra (SN). Therefore, the purpose of the current studies was to determine if GDNF replacement restores motor function and functional markers within the nigrostriatal DA system in middle-aged Gdnf(+/-) mice. At 11months of age, male Gdnf(+/-) and wildtype (WT) mice underwent bilateral intra-striatal injections of GDNF (10μg) or vehicle. Locomotor activity was assessed weekly 1-4weeks after treatment. Four weeks after treatment, their brains were processed for analysis of GDNF levels and various DAergic and oxidative stress markers. An intrastriatal injection of GDNF increased motor activity in Gdnf(+/-) mice to levels comparable to WT mice (1week after injection) and this effect was maintained through the 4-week time point. This increase in locomotion was accompanied by a 40% increase in striatal GDNF protein levels and SN GDNF expression in Gdnf(+/-) mice. Additionally, GDNF treatment significantly increased the number of tyrosine hydroxylase (TH)-positive neurons in the SN of middle-aged Gdnf(+/-) mice, but not WT mice, which was coupled with reduced oxidative stress in the SN. These studies further support that long-term changes related to the dysfunction of the nigrostriatal pathway are influenced by GDNF expression and add that this dysfunction appears to be responsive to GDNF treatment. Additionally, these studies suggest that long-term GDNF depletion alters the biological and behavioral responses to GDNF treatment.

GDNF contributes to oestrogen-mediated protection of midbrain dopaminergic neurones

Parkinson's disease (PD) is characterised by the preferential loss of dopaminergic neurones from the substantia nigra (SN) that leads to the hallmark motor disturbances. Animal and human studies suggest a beneficial effect of oestrogen to the nigrostriatal system, and the regulation of neurotrophic factor expression by oestrogens has been suggested as a possible mechanism contributing to that neuroprotective effect. The present study was designed to investigate whether the neuroprotection exerted by 17β-oestradiol on nigrostriatal dopaminergic neurones is mediated through the regulation of glial cell line-derived neurotrophic factor (GDNF) expression. Using an in vivo rat model of PD, we were able to confirm the relevance of 17β-oestradiol in defending dopaminergic neurones against 6-hydroxydopamine (6-OHDA) toxicity. 17β-oestradiol, released by micro-osmotic pumps, implanted 10 days before intrastriatal 6-OHDA injection, prevented the loss of dopaminergic neurones induced by 6-OHDA. 17β-oestradiol treatment also promoted an increase in GDNF protein levels both in the SN and striatum. To explore the relevance of GDNF increases to 17β-oestradiol neuroprotection, we analysed, in SN neurone-glia cultures, the effect of GDNF antibody neutralisation and RNA interference-mediated GDNF knockdown. The results showed that both GDNF neutralisation and GDNF silencing abolished the dopaminergic protection provided by 17β-oestradiol against 6-OHDA toxicity. Taken together, these results strongly identify GDNF as an important player in 17β-oestradiol-mediated dopaminergic neuroprotection.

[Participation of GDNF, LIMK1 signal pathways and heat shock proteins in processes of Drosophila learning and memory formation]

Molecular mechanisms of the synapse and dendrite maintenance and their disturbance in psychiatric and neurodegenerative diseases (ND) are intensively studied in searching for target genes of therapeutic actions. It is suggested that glia, alongside with well-studied pre- and postsynaptic neurons, is the third, poorly studied partner in synaptic transmission (the tripartite synapse) that is involved in the positive feedback between the first two partners. This bidirectional coupling between presynaptic neurons and their postsynaptic targets involve neurotrophins (NTF), such as glial cell-derived neurotrophic factor (GDNF) that is produced LIM kinase 1 (LIMK1, the key enzyme of actin remodeling). The cytoplasmic domain of neuregulins interacts with LIMK1. Since neurons and axons that do not receive a sufficient NTF amount are at risk of degeneration and synapse elimination, GDNF seems to be the best studied factor of the ND therapy. The delivery of GDNF stem cells to the neurodegeneration locus is very efficient. There has been proposed a new approach based on use of Drosophila heat shock (hs) promoter. This promoter responds to the mammalian body temperature as to the shock factor resulting in the constant expression of the GDNF gene. The Drosophila models allow studying any given component of the bidirectional communication between pre- and postsynaptic neurons in development of the main diagnostic ND symptom, such as defective memory resulted from synaptic atrophy. In the present study we used the Drosophila stocks imitating different disturbances of the nervous system: Canton-S (wild type), GDNF (transgenic flies that carry human glial-cell-line derived nerve factor (GDNF) gene under hs promoter), l(1)ts403 with dusturbance of HSPs mRNA extranuclear transport, a defect of intracellular stress report, and agn(ts3) mutation in LIMK1 gene. We have revealed functional connections at the behavioral level (learning/memory) depending on the GDNF and LIMK1 brain expression and HSPs transduction that might provide targets for complex approaches for the ND treatment.

[Effect of electroacupuncture at different acupoints on expression of cervico-spinal GDNF and BDNF and their receptor genes in neck-incision pain rats]

OBJECTIVE

To observe the effect of electroacupuncture (EA) of "Futu" (LI 18), etc. on the expression of genes of glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF) and their receptors in the cervico-spinal cord in neck-incision pain rats, so as to study its mechanism underlying incision-pain relief.

METHODS

A total of 50 Sprague Dawley male rats were randomly divided into normal, model (incision pain), EA-Futu (LI 18), EA- Hegu (LI 4) - Neiguan (PC 6, LI 4-PC 6) and EA-Zusanli (ST 36)-Yanglingquan (GB 34, ST 36-GB 34) groups (n = 10/group). A 1.5 cm long longitudinal incision was made along the midline of the neck under anesthesia to duplicate neck-incision pain model. Thermal pain threshold (PT) was measured before and after modeling and after the treatment, respectively. EA (1-2 mA, 2 Hz/100 Hz) was applied to bilateral LI 18, PC 6-LI 4 and ST 36-GB 34 for 30 min. The expression of genes of GDNF and its receptor GFRalpha-1, and BDNF and its receptors TrkA, TrkB in the spinal cord (C1 - C4) tissue was detected by quantitative real-time-PCR.

RESULTS

In comparison with pre-modeling in the same one group, the thermal PT levels were decreased obviously in the model, LI 18, LI 4-PC 6 and ST 36-GB 34 groups after neck incision (P < 0.05). Compared with the model group, the PT levels were increased markedly in LI 18, LI 4-PC 6 and ST 36-GB 34 groups after the EA treatment (P < 0.05). Correspondingly, the expression levels of spinal GDNF mRNA and GFRalpha-1 mRNA were obviously lower, as well as BDNF mRNA was markedly higher in the model group than in the control group (P < 0.05), and those of TrkA mRNA and TrkB mRNA were increased slightly in the model group than in the control group (P > 0.05). In comparison with the model group, the expression levels of spinal GDNF mRNA and GFRalpha-1 mRNA were up-regulated considerably (P < 0.001), whereas those of BDNF mRNA, TrkA mRNA and TrkB mRNA were decreased slightly (P > 0.05) in the LI 18, LI 4-PC 6 and ST 36-GB 34 groups after EA treatment.

CONCLUSION

EA stimulation can significantly suppress pain reaction of neck incision, which is closely associated with its effects in up-regulating the expression of GDNF and its receptor GFRalpha-1 genes in the cervical spinal cord (C1 - C4).

Destabilizing domains mediate reversible transgene expression in the brain

Regulating transgene expression in vivo by delivering oral drugs has been a long-time goal for the gene therapy field. A novel gene regulating system based on targeted proteasomal degradation has been recently developed. The system is based on a destabilizing domain (DD) of the Escherichia coli dihydrofolate reductase (DHFR) that directs fused proteins to proteasomal destruction. Creating YFP proteins fused to destabilizing domains enabled TMP based induction of YFP expression in the brain, whereas omission of TMP resulted in loss of YFP expression. Moreover, induction of YFP expression was dose dependent and at higher TMP dosages, induced YFP reached levels comparable to expression of unregulated transgene., Transgene expression could be reversibly regulated using the DD system. Importantly, no adverse effects of TMP treatment or expression of DD-fusion proteins in the brain were observed. To show proof of concept that destabilizing domains derived from DHFR could be used with a biologically active molecule, DD were fused to GDNF, which is a potent neurotrophic factor of dopamine neurons. N-terminal placement of the DD resulted in TMP-regulated release of biologically active GDNF. Our findings suggest that TMP-regulated destabilizing domains can afford transgene regulation in the brain. The fact that GDNF could be regulated is very promising for developing future gene therapies (e.g. for Parkinson's disease) and should be further investigated.

[Epigenetic regulation in depression]

Recent research has raised the notion that epigenetic mechanisms (e.g., DNA methylation and histone modifications), which exert lasting control over gene expression without altering the genetic code, could mediate stable changes in brain function. However, the role of environmental factors along with genetic factors in the epigenetic regulation of the pathogenesis of depression is largely unknown. Two genetically distinct mice strains, BALB/c (BALB) and C57BL/6 (B6), exhibit different behavioral responses to chronic stress. With chronic stress, BALB mice showed depressive-like behaviors, but not B6 mice, and glial cell-derived neurotrophic factor (GDNF) expression level was decreased in the ventral striatum of BALB mice but increased in B6 mice. In BALB mice, depressive-like behaviors and decreased GDNF expression were recovered by chronic antidepressant treatment. Therefore, we used these two mice strains to investigate how the epigenetic status of the GDNF gene in the ventral striatum modulates stress vulnerability. Both mice strains showed increased DNA methylation levels and MeCP2 recruitment in the GDNF promoter region. However, histone H3 acetylation level was decreased in BALB mice, but increased in B6 mice. Furthermore, BALB mice showed increased histone deacetylase2 (HDAC2) expression level and Re-ChIP assay revealed HDAC2-MeCP2 complex in BALB mice. Our results indicate the crucial role of histone modification by HDAC2 and MeCP2 complex for the control of GDNF expression and subsequent behavioral responses to chronic stress, in other words, the susceptibility to stress. In addition, we investigated the effect of antidepressants on the epigenetic regulation of GDNF expression. We found a reduced level of HDAC4 recruitment at the GDNF promoter region with antidepressants. Thus, our data suggest that antidepressants increase transcriptional activity of the GDNF gene through the modulation of histone acetylation by HDAC4. Finally, we examined the expressions of GDNF and epigenetic-related molecules mRNAs with major depressive and bipolar disorder patients by using quantitative real-time PCR. We found the aberrant expression of GDNF and epigenetic-related genes including HDAC2 and HDAC4 in mood disorder patients. Thus, our data provide novel insights suggesting that epigenetic mechanisms of GDNF expression are involved in the pathogenesis or pathophysiology of depression.

Gene expression in skin, muscle, and dorsal root ganglion after plantar incision in the rat

BACKGROUND

Treating postoperative pain remains a significant challenge for perioperative medicine. Recent studies have shown that nerve growth factor is up-regulated and contributes to incisional pain. To date, few studies have examined expression of other neurotrophin-related mediators that may contribute to the development and/or maintenance of incisional pain.

METHODS

Male Sprague-Dawley rats underwent a plantar incision, and pain behaviors were examined (n = 6). In a separate group of rats, expression of neurotrophic factors were studied. At various times after incision (n = 4) or sham surgery (n = 4), the skin, muscle, and dorsal root ganglia were harvested and total RNA isolated. Real-time reverse transcription polymerase chain reaction was performed and the fold change in gene expression was analyzed using significance analysis of microarrays.

RESULTS

Several genes were changed (P < 0.05) as early as 1 h after incision. Expression of artemin and nerve growth factor were increased in both incised skin and muscle. Brain-derived neurotrophic factor, neurotrophin-3, and neurotrophin-5 were all down-regulated in the skin but up-regulated in the muscle 48 h after incision. Few genes changed in the dorsal root ganglion. Most changes in expression occurred in the first 48 h after incision, a timeframe when pain behavior was the greatest.

CONCLUSION

Surgical incision is associated with pain-related gene expression changes in skin, muscle, and, to a lesser extent, dorsal root ganglion. The gene expression profile provides clues as to mediators that are involved in peripheral sensitization and pain transmission after surgical incision and also suggest mechanisms for resolution of postoperative pain when more persistent pain syndromes like neuropathic pain continue.

A monoclonal antibody-GDNF fusion protein is not neuroprotective and is associated with proliferative pancreatic lesions in parkinsonian monkeys

Glial cell line derived neurotrophic factor (GDNF) is a neurotrophic factor that has neuroprotective effects in animal models of Parkinson’s disease (PD) and has been proposed as a PD therapy. GDNF does not cross the blood brain barrier (BBB), and requires direct intracerebral delivery to be effective. Trojan horse technology, in which GDNF is coupled to a monoclonal antibody (mAb) against the human insulin receptor (HIR), has been proposed to allow GDNF BBB transport (ArmaGen Technologies Inc.). In this study we tested the feasibility of HIRMAb-GDNF to induce neuroprotection in parkinsonian monkeys, as well as its tolerability and safety. Adult rhesus macaques were assessed throughout the study with a clinical rating scale, a computerized fine motor skills task and general health evaluations. Following baseline measurements, the animals received a unilateral intracarotid artery MPTP injection. Seven days later the animals were evaluated, matched according to disability and blindly assigned to receive twice a week iv. treatments (vehicle, 1 or 5 mg/kg HIRmAb-GDNF) for a period of three months. HIRmAb-GDNF did not improve parkinsonian motor symptoms and induced a dose-dependent hypersensitivity reaction. Quantification of dopaminergic striatal optical density and stereological nigral cell counts did not demonstrate differences between treatment groups. Focal pancreatic acinar to ductular metaplasia (ADM) was noted in four of seven animals treated with 1 mg/kg HIRmAb-GDNF; two of four with ADM also had focal pancreatic intraepithelial neoplasia 1B (PanIN-1B) lesions. Minimal to mild, focal to multifocal, nonsuppurative myocarditis was noted in all animals in the 5 mg/kg treatment group. Our results demonstrate that HIRmAb-GDNF dosing in a monkey model of PD is not an effective neuroprotective strategy and may present serious health risks that should be considered when planning future use of the IR antibody as a carrier, or of any systemic treatment of a GDNF-containing molecule.

Methylphenidate exposure induces dopamine neuron loss and activation of microglia in the basal ganglia of mice

Background

Methylphenidate (MPH) is a psychostimulant that exerts its pharmacological effects via preferential blockade of the dopamine transporter (DAT) and the norepinephrine transporter (NET), resulting in increased monoamine levels in the synapse. Clinically, methylphenidate is prescribed for the symptomatic treatment of ADHD and narcolepsy; although lately, there has been an increased incidence of its use in individuals not meeting the criteria for these disorders. MPH has also been misused as a “cognitive enhancer” and as an alternative to other psychostimulants. Here, we investigate whether chronic or acute administration of MPH in mice at either 1 mg/kg or 10 mg/kg, affects cell number and gene expression in the basal ganglia.

Methodology/Principal Findings

Through the use of stereological counting methods, we observed a significant reduction (∼20%) in dopamine neuron numbers in the substantia nigra pars compacta (SNpc) following chronic administration of 10 mg/kg MPH. This dosage of MPH also induced a significant increase in the number of activated microglia in the SNpc. Additionally, exposure to either 1 mg/kg or 10 mg/kg MPH increased the sensitivity of SNpc dopaminergic neurons to the parkinsonian agent 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Unbiased gene screening employing Affymetrix GeneChip® HT MG-430 PM revealed changes in 115 and 54 genes in the substantia nigra (SN) of mice exposed to 1 mg/kg and 10 mg/kg MPH doses, respectively. Decreases in the mRNA levels of gdnf, dat1, vmat2, and th in the substantia nigra (SN) were observed with both acute and chronic dosing of 10 mg/kg MPH. We also found an increase in mRNA levels of the pro-inflammatory genes il-6 and tnf-α in the striatum, although these were seen only at an acute dose of 10 mg/kg and not following chronic dosing.

Conclusion

Collectively, our results suggest that chronic MPH usage in mice at doses spanning the therapeutic range in humans, especially at prolonged higher doses, has long-term neurodegenerative consequences.

RET PLCγ phosphotyrosine binding domain regulates Ca2+ signaling and neocortical neuronal migration

The receptor tyrosine kinase RET plays an essential role during embryogenesis in regulating cell proliferation, differentiation, and migration. Upon glial cell line-derived neurotrophic factor (GDNF) stimulation, RET can trigger multiple intracellular signaling pathways that in concert activate various downstream effectors. Here we report that the RET receptor induces calcium (Ca²⁺) signaling and regulates neocortical neuronal progenitor migration through the Phospholipase-C gamma (PLCγ) binding domain Tyr1015. This signaling cascade releases Ca²⁺ from the endoplasmic reticulum through the inositol 1,4,5-trisphosphate receptor and stimulates phosphorylation of ERK1/2 and CaMKII. A point mutation at Tyr1015 on RET or small interfering RNA gene silencing of PLCγ block the GDNF-induced signaling cascade. Delivery of the RET mutation to neuronal progenitors in the embryonic ventricular zone using in utero electroporation reveal that Tyr1015 is necessary for GDNF-stimulated migration of neurons to the cortical plate. These findings demonstrate a novel RET mediated signaling pathway that elevates cytosolic Ca²⁺ and modulates neuronal migration in the developing neocortex through the PLCγ binding domain Tyr1015.

[Transgenic cell cultures that synthesize neurotrophic factors and the possibility of therapeutic use of its cells]

Under the leadership of Corresponding Member of the Russian Academy of Sciences L.I. Korochkin, the Laboratory of Neurogenetics and Developmental Genetics (Institute of Gene Biology, Russian Academy of Sciences) for many years has been conducting studies of nervous system development, neural cell differentiation, and application of gene and cell technology to cure neurodegenerative diseases. The results of the study initiated by L.I. Korochkin and continued by his scientific successors support the direction of allocation of transgenic neurotrofic factors and heat-shock proteins as neuroprotectors for cell therapy. Potential for usage of promoter of HSP70 heat-shock gene of Drosophila to create transgenic constructs for therapy has been shown. Further improvement of technology of nonvirus transfer for therapeutic genes, as well as production of multicomponent genetic constructs coding several therapeutic factors with synergy effect, would stimulate creation of efficient cell medicals to cure neurodegenerative diseases.

Evaluation of an AAV2-based rapamycin-regulated glial cell line-derived neurotrophic factor (GDNF) expression vector system

Effective regulation of transgene product in anatomically circumscribed brain tissue is dependent on the pharmacokinetics of the regulating agent, the kinetics of transcriptional activation and degradation of the transgene product. We evaluated rapamycin-regulated AAV2-GDNF expression in the rat brain (striatum). Regulated (a dual-component system: AAV2-FBZhGDNF + AAV2-TF1Nc) and constitutive (CMV-driven) expression vectors were compared. Constitutively active AAV2-GDNF directed stable GDNF expression in a dose-dependent manner and it increased for the first month, thereafter reaching a plateau that was maintained over a further 3 months. For the AAV2-regGDNF, rapamycin was administered in a 3-days on/4-days off cycle. Intraperitoneal, oral, and direct brain delivery (CED) of rapamycin were evaluated. Two cycles of rapamycin at an intraperitoneal dose of 10 mg/kg gave the highest GDNF level (2.75±0.01 ng/mg protein). Six cycles at 3 mg/kg resulted in lower GDNF values (1.36±0.3 ng/mg protein). Interestingly, CED of rapamycin into the brain at a very low dose (50 ng) induced GDNF levels comparable to a 6-week intraperitoneal rapamycin cycle. This study demonstrates the effectiveness of rapamycin regulation in the CNS. However, the kinetics of the transgene in brain tissue, the regulator dosing amount and schedule are critical parameters that influence the kinetics of accumulation and zenith of the encoded transgene product.

Antidepressants elevate GDNF expression and release from C₆ glioma cells in a β-arrestin1-dependent, CREB interactive pathway

Glial cell line-derived neurotrophic factor (GDNF), essential for neuronal survival, plasticity and development, has been implicated in the mechanism of action of antidepressant drugs (ADs). β-arrestin1, a member of the arrestin protein family, was found to play a role in AD mechanism of action. The present study aimed at evaluating whether the effect of ADs on GDNF in C6 rat glioma cells is exerted through a β-arrestin1-dependent, CREB-interactive pathway. For chronic treatment, C6 rat glioma cells were treated for 3 d with different classes of ADs: imipramine - a non-selective monoamine reuptake inhibitor, citalopram - a serotonin selective reuptake inhibitor (SSRI) or desipramine - a norepinephrine selective reuptake inhibitor (NSRI) and compared to mood stabilizers (lithium and valproic acid) or to the antipsychotic haloperidol. Only ADs significantly elevated β-arrestin1 levels in the cytosol, while reducing phospho-β-arrestin1 levels in the cell nuclear fraction. ADs significantly increased both GDNF expression and release from the cells, but were unable to induce such effects in β-arrestin1 knock-down cells. Chronic AD treatment significantly increased CREB phosphorylation without altering the level of total CREB in the nuclear fraction of the cells. Moreover, treatment with ADs significantly increased β-arrestin1/CREB interaction. These findings support the involvement of β-arrestin1 in the mechanism of action of ADs. We suggest that following AD treatment, β-arrestin1 generates a transcription complex involving CREB essential for GDNF expression and release, thus enhancing GDNF's neuroprotective action that promotes cellular survival and plasticity when the survival and function of neurons is compromised as occurs in major depression.

Optimized quantities of GDNF overexpressed by engineered astrocytes are critical for protection of neuroblastoma cells against 6-OHDA toxicity

Optimized levels of glial cell line-derived neurotrophic factor (GDNF) are critical for protection of dopaminergic neurons against parkinsonian cell death. Recombinant lentiviruses harboring GDNF coding sequence were constructed and used to infect astrocytoma cell line 1321N1. The infected astrocytes overexpressed GDNF mRNA and secreted an average of 2.2 ng/mL recombinant protein as tested in both 2 and 16 weeks post-infection. Serial dilutions of GDNF-enriched conditioned medium from infected astrocytes added to growing neuroblastoma cell line SK-N-MC resulted in commensurate resistance against 6-OHDA toxicity. SK-N-MC cell survival rate rose from 51% in control group to 84% in the cells grown with astro-CM containing 453 pg secreted GDNF, an increase that was highly significant (P < 0.0001). However, larger volumes of the GDNF-enriched conditioned medium failed to improve cell survival and addition of volumes that contained 1,600 pg or more GDNF further reduced survival rate to below 70%. Changes in cell survival paralleled to changes in the percent of apoptotic cell morphologies. These data demonstrate the feasibility of using astrocytes as minipumps to stably oversecrete neurotrophic factors and further indicate that GDNF can be applied to neuroprotection studies in PD pending the optimization of its concentrations.

S100B protein, brain-derived neurotrophic factor, and glial cell line-derived neurotrophic factor in human milk

Background

Human milk contains a wide variety of nutrients that contribute to the fulfillment of its functions, which include the regulation of newborn development. However, few studies have investigated the concentrations of S100B protein, brain-derived neurotrophic factor (BDNF), and glial cell line-derived neurotrophic factor (GDNF) in human milk. The associations of the concentrations of S100B protein, BDNF, and GDNF with maternal factors are not well explored.

Methodology/Principal Findings

To investigate the concentrations of S100B protein, BDNF, and GDNF in human milk and characterize the maternal factors associated with their levels in human milk, human milk samples were collected at days 3, 10, 30, and 90 after parturition. Levels of S100B protein, BDNF, and GDNF, and their mRNAs in the samples were detected. Then, these concentrations were compared with lactation and other maternal factors. S100B protein levels in human milk samples collected at 3, 10, 30, and 90 d after parturition were 1249.79±398.10, 1345.05±539.16, 1481.83±573.30, and 1414.39±621.31 ng/L, respectively. On the other hand, the BDNF concentrations in human milk samples were 10.99±4.55, 13.01±5.88, 13.35±6.43, and 2.83±5.47 µg/L, while those of GDNF were 10.90±1.65, 11.38±1., 11.29±3.10, and 11.40±2.21 g/L for the same time periods. Maternal post-pregnancy body mass index was positively associated with S100B levels in human milk (r = 0.335, P = 0.030<0.05). In addition, there was a significant correlation between the levels of S100B protein and BDNF (z = 2.09, P = 0.037<0.05). Delivery modes were negatively associated with the concentration of GDNF in human milk.

Conclusions

S100B protein, BDNF, and GDNF are present in all samples of human milk, and they may be responsible for the long term effects of breast feeding.

Evaluation of the physical and in vitro protective activity of three synthetic peptides derived from the pro- and mature GDNF sequence

Recently, a small 11-amino acid amidated peptide, dopamine neuron stimulating peptide-11 (DNSP-11), was shown to exert neurotrophic-like actions on primary dopaminergic neurons and in parkinsonian rat models. This suggests smaller neurotrophic-like molecules may be deliverable and modifiable for therapeutic use. Here we evaluate the molecular and cellular protection properties of DNSP-11 and two other amidated-peptides, a 5-mer (DNSP-5) and a 17-mer (DNSP-17), hypothesized to be endoproteolytically processed from the pro- and mature glial cell line-derived neurotrophic factor (GDNF) protein sequence, respectively. Far-UV circular dichroism spectra show that the three DNSPs are soluble and act independently in vitro. Reverse phase HPLC and mass spectrometry analysis show that the three peptides are stable for one month at a variety of storage and experimental conditions. To gain insight into their biodistribution properties in the brain, we used affinity chromatography to show that DNSP-17 binds heparin equally as tight as GDNF, whereas DNSP-5 and DNSP-11 do not bind heparin, which should facilitate their delivery in vivo. Finally, we present data showing that DNSP-11 provides dose-dependent protection of HEK-293 cells from staurosporine and 3-nitropropionate (3-NP) cytotoxicity, thereby supporting its broad mitochondrial-protective properties.

GDNF and protection of adult central catecholaminergic neurons

Neurotrophic factors are small proteins necessary for neuron survival and maintenance of phenotype. They are considered as promising therapeutic tools for neurodegenerative diseases. The glial cell line-derived neurotrophic factor (GDNF) protects catecholaminergic cells from toxic insults; thus, its potential therapeutic applicability in Parkinson's disease has been intensely investigated. In recent years, there have been major advances in the analysis of GDNF signaling pathways in peripheral neurons and embryonic dopamine mesencephalic cells. However, the actual physiological role of GDNF in maintaining catecholaminergic central neurons during adulthood is only starting to be unraveled, and the mechanisms whereby GDNF protects central brain neurons are poorly known. In this study, we review the current knowledge of GDNF expression, signaling, and function in adult brain, with special emphasis on the genetic animal models with deficiency in the GDNF-dependent pathways.

Transplantation of neuronal-primed human bone marrow mesenchymal stem cells in hemiparkinsonian rodents

Bone marrow-derived human mesenchymal stem cells (hMSCs) have shown promise in in vitro neuronal differentiation and in cellular therapy for neurodegenerative disorders, including Parkinson' disease. However, the effects of intracerebral transplantation are not well defined, and studies do not agreed on the optimal neuronal differentiation method. Here, we investigated three growth factor-based neuronal differentiation procedures (using FGF-2/EGF/PDGF/SHH/FGF-8/GDNF), and found all to be capable of eliciting an immature neural phenotype, in terms of cell morphology and gene/protein expression. The neuronal-priming (FGF-2/EGF) method induced neurosphere-like formation and the highest NES and NR4A2 expression by hMSCs. Transplantation of undifferentiated and neuronal-primed hMSCs into the striatum and substantia nigra of 6-OHDA-lesioned hemiparkinsonian rats revealed transient graft survival of 7 days, despite the reported immunosuppressive properties of MSCs and cyclosporine-immunosuppression of rats. Neither differentiation of hMSCs nor induction of host neurogenesis was observed at injection sites, and hMSCs continued producing mesodermal fibronectin. Strategies for improving engraftment and differentiation post-transplantation, such as prior in vitro neuronal-priming, nigral and striatal grafting, and co-transplantation of olfactory ensheathing cells that promote neural regeneration, were unable to provide advantages. Innate inflammatory responses (Iba-1-positive microglia/macrophage and GFAP-positive astrocyte activation and accumulation) were detected around grafts within 7 days. Our findings indicate that growth factor-based methods allow hMSC differentiation toward immature neuronal-like cells, and contrary to previous reports, only transient survival and engraftment of hMSCs occurs following transplantation in immunosuppressed hemiparkinsonian rats. In addition, suppression of host innate inflammatory responses may be a key factor for improving hMSC survival and engraftment.

Endogenous GDNF in ventral tegmental area and nucleus accumbens does not play a role in the incubation of heroin craving

Glial cell line-derived neurotrophic factor (GDNF) activity in ventral tegmental area (VTA) mediates the time-dependent increases in cue-induced cocaine-seeking after withdrawal (incubation of cocaine craving). Here, we studied the generality of these findings to incubation of heroin craving. Rats were trained to self-administer heroin for 10 days (6 hours/day; 0.075 mg/kg/infusion; infusions were paired with a tone-light cue) and tested for cue-induced heroin-seeking in extinction tests after 1, 11 or 30 withdrawal days. Cue-induced heroin seeking was higher after 11 or 30 days than after 1 day (incubation of heroin craving), and the time-dependent increases in extinction responding were associated with time-dependent changes in GDNF mRNA expression in VTA and nucleus accumbens. Additionally, acute accumbens (but not VTA) GDNF injections (12.5 µg/side) administered 1-3 hours after the last heroin self-administration training session enhanced the time-dependent increases in extinction responding after withdrawal. However, the time-dependent increases in extinction responding after withdrawal were not associated with changes in GDNF protein expression in VTA and accumbens. Additionally, interfering with endogenous GDNF function by chronic delivery of anti-GDNF monoclonal neutralizing antibodies (600 ng/side/day) into VTA or accumbens had no effect on the time-dependent increases in extinction responding. In summary, heroin self-administration and withdrawal regulate VTA and accumbens GDNF mRNA expression in a time-dependent manner, and exogenous GDNF administration into accumbens but not VTA potentiates cue-induced heroin seeking. However, based on the GDNF protein expression and the anti-GDNF monoclonal neutralizing antibodies manipulation data, we conclude that neither accumbens nor VTA endogenous GDNF mediates the incubation of heroin craving.

Modulation of the tyrosine kinase receptor Ret/glial cell-derived neurotrophic factor (GDNF) signaling: a new player in reproduction induced anterior pituitary plasticity?

During gestation, parturition, and lactation, the endocrine axis of the dam must continually adapt to ensure the continual and healthy development of offspring. The anterior pituitary gland, which serves as the endocrine interface between the brain and periphery, undergoes adaptations that contribute to regulation of the reproductive axis. Growth factors and their receptors are potential candidates for intrapituitary and paracrine factors to participate in the functional and anatomical plasticity of the gland. We examined the involvement of the growth factor glial cell-derived neurotrophic factor (GDNF) and its receptor tyrosine kinase rearranged during transfection (Ret) in the physiological functional and anatomical plasticity of the anterior pituitary gland. We found that variations in both expression and subcellular localization of Ret during gestation and lactation are temporally correlated with changes in pituitary gland function. We showed that Ret/GDNF signaling could endorse two different functional roles depending on the physiological status. At the end of lactation and after weaning, Ret was colocalized with markers of apoptosis. We found that Ret could therefore act as a physiological dependence receptor capable of inducing apoptosis in the absence of GDNF. In addition, we identified the follicullostellate cell as a probable source for intrapituitary GDNF and proposed GDNF as a potential physiological modulator of endocrine cell function. During all stages studied, we showed that acute application of GDNF to pituitary slices was able to modulate both positively and negatively intracellular calcium activity. Altogether our results implicate Ret/GDNF as a potent pleiotropic factor able to influence pituitary physiology during a period of high plasticity.

[Effects of electroacupuncture on the expression of GDNF and Ret in Parkinson's disease model rats]

OBJECTIVE

To explore the mechanism of electroacupuncture therapy on Parkinson's disease (PD).

METHODS

Fifty Wistar rats were randomly divided into a normal group, a sham-operation group, a model group, a Fengfu-Taichong group and a Shuanggu Yitong group. PD model was duplicated by microinjection of 6-Hydroxyl-Dopamine into right corpora striata, and by microinjection of normal saline in sham-operation group. Rats in normal group, sham-operation group and model group were not treated. In Fengfu-Taichong group, the rats were treated by electroacupuncture at "Fengfu" (GV 16) and "Taichong" (LR 3) on the basis of the PD model, and by electroacupuncture at "Fengfu" (GV 16), "Taichong" (LR 3), "Guanyuan" (CV 4) and "Zusanli" (ST 36) in Shuanggu Yitong group, once daily for 2 weeks. GDNF and Ret expression were detected by immunohistochemistry and western blotting, respectively.

RESULTS

The number of GDNF positive cells and the content of Ret receptor increased significantly in the two electroacupuncture groups compared with those in the other groups (all P < 0.01), and the expression of GDNF increased significantly in Shuanggu Yitong group compared with that in Fengfu-Taichong group (P < 0.01).

CONCLUSION

Electroacupuncture can not only increase the expression of GDNF, but also enhance its effect. "Shuanggu Yitong" method is better than simple acupuncture at "Fengfu" (GV 16) and "Taichong" (LR 3) in increasing expression of GDNF.

Regeneration of the MPTP-lesioned dopaminergic system after convection-enhanced delivery of AAV2-GDNF

Clinical studies to date have failed to establish therapeutic benefit of glial cell-derived neurotrophic factor (GDNF) in Parkinson's disease (PD). In contrast to previous nonclinical neuroprotective reports, this study shows clinically relevant and long-lasting regeneration of the dopaminergic system in rhesus macaques lesioned with 1-methy-4-phenyl-1,2,3,6-tetrahydropyridine 3-6 months before GDNF gene delivery (AAV2-GDNF). The observed progressive amelioration of functional deficits, recovery of dopamine, and regrowth of fibers to the striatal neuropil demonstrate that high GDNF expression in the putamen promotes restoration of the dopaminergic system in a primate model of advanced PD. Extensive distribution of GDNF within the putamen and transport to the severely lesioned substantia nigra, after convection-enhanced delivery of AAV2-GDNF into the putamen, indicates anterograde transport via striatonigral connections and is anticipated to occur in PD patients. Overall, these data demonstrate nonclinical neurorestoration after putaminal infusion of AAV2-GDNF and suggest that clinical investigation in PD patients is warranted.

Glial cell line-derived neurotrophic factor gene therapy ameliorates chronic hyperprolactinemia in senile rats

Progressive dysfunction of hypothalamic tuberoinfundibular dopaminergic (TIDA) neurons during normal aging is associated in the female rat with chronic hyperprolactinemia. We assessed the effectiveness of glial cell line-derived neurotrophic factor (GDNF) gene therapy to restore TIDA neuron function in senile female rats and reverse their chronic hyperprolactinemia. Young (2.5 months) and senile (29 months) rats received a bilateral intrahypothalamic injection (10(10) pfu) of either an adenoviral vector expressing the gene for beta-galactosidase; (Y-betagal and S-betagal, respectively) or a vector expressing rat GDNF (Y-GDNF and S-GDNF, respectively). Transgenic GDNF levels in supernatants of GDNF adenovector-transduced N2a neuronal cell cultures were 25+/-4 ng/ml, as determined by bioassay. In the rats, serum prolactin (PRL) was measured at regular intervals. On day 17 animals were sacrificed and neuronal nuclear antigen (NeuN) and tyrosine hydroxylase (TH) immunoreactive cells counted in the arcuate-periventricular hypothalamic region. The S-GDNF but not the S-betagal rats, showed a significant reduction in body weight. The chronic hyperprolactinemia of the senile females was significantly ameliorated in the S-GDNF rats (P<0.05) but not in the S-betagal rats. Neither age nor GDNF induced significant changes in the number of NeuN and TH neurons. We conclude that transgenic GDNF ameliorates chronic hyperprolactinemia in aging female rats, probably by restoring TIDA neuron function.

c-RET molecule in malignant melanoma from oncogenic RET-carrying transgenic mice and human cell lines

Malignant melanoma is one of the most aggressive cancers and its incidence worldwide has been increasing at a greater rate than that of any other cancer. We previously reported that constitutively activated RFP-RET-carrying transgenic mice (RET-mice) spontaneously develop malignant melanoma. In this study, we showed that expression levels of intrinsic c-Ret, glial cell line-derived neurotrophic factor (Gdnf) and Gdnf receptor alpha 1 (Gfra1) transcripts in malignant melanomas from RET-transgenic mice were significantly upregulated compared with those in benign melanocytic tumors. These results suggest that not only introduced oncogenic RET but also intrinsic c-Ret/Gdnf are involved in murine melanomagenesis in RET-mice. We then showed that c-RET and GDNF transcript expression levels in human malignant melanoma cell lines (HM3KO and MNT-1) were higher than those in primary cultured normal human epithelial melanocytes (NHEM), while GFRa1 transcript expression levels were comparable among NHEM, HM3KO and MNT-1. We next showed c-RET and GFRa1 protein expression in HM3KO cells and GDNF-mediated increased levels of their phosphorylated c-RET tyrosine kinase and signal transduction molecules (ERK and AKT) sited potentially downstream of c-RET. Taken together with the finding of augmented proliferation of HM3KO cells after GDNF stimulation, our results suggest that GDNF-mediated c-RET kinase activation is associated with the pathogenesis of malignant melanoma.

Development of gene therapy for neurological disorders

Given improvements in viral vector design, production and efficiency of transduction in the central nervous system (CNS), as well as increased knowledge of neuropathological mechanisms in neurological disorders, success in treating a CNS disorder with gene transfer seems inevitable. Several different vector systems have been studied extensively and the adeno-associated viral vector system has been utilized in most early stage clinical trials in neurological disorders. Other vector systems, such as lentivirus, adenovirus, and herpes simplex virus are also viable vector platforms that should fill significant clinical niches based on their specific characteristics. In addition to the choice of the appropriate vector, the proper choice of transgene for the appropriate strategy to treat a neurological disorder is also critical. The example of glial cell line-derived neurotrophic factor ligands to treat Parkinson's disease is used to illustrate the importance of the interface between interpretation of pre-clinical data and consideration of the natural history of the disorder. This interface dictates the proper design of clinical trials that are capable of testing whether the treatment is actually successful.

A dual-hit animal model for age-related parkinsonism

Parkinson's disease is a neurological disorder which afflicts an increasing number of individuals. If the wider complex of extrapyramidal symptoms referred to as "age-related parkinsonism" is included, the incidence is near 50% of the population above 80 years of age. This review summarizes recent studies from our laboratories as well as other research groups in the quest to explore the multi-faceted etiology of age-related neurodegeneration, in general, and degeneration of the substantia nigra dopaminergic neurons, in particular. Our work during recent years has focused on assessment of potential interactive effects of a reduction in glial cell line-derived neurotrophic factor (GDNF) and the aging process (intrinsic factors) and early neurotoxin exposure (an extrinsic factor) on dopamine (DA) systems and the behaviors they mediate. The guiding hypothesis directing the research to be described was that a combination of the two factors would exacerbate the decline in the DA transmitter system function that occurs during aging. The results obtained were consistent with the well-established aging-related decline in function and structure of neurons utilizing DA as a transmitter and motor function, and extended knowledge by establishing that the genetic reduction of Gdnf exacerbated these aging related changes. Thus, GDNF reduction appears to increase the vulnerability of the DA neurons to the many different challenges associated with the aging process. Assessment of methamphetamine effects on young Gdnf(+/-) mice indicated that reduced GDNF availability increased the vulnerability of DA systems to this well-established neurotoxin. The work discussed in this review is consistent with earlier work demonstrating the importance of GDNF for maintenance of DA neurons and also provides a novel model for progressive DA degeneration and motor dysfunction.

[The repair of acute spinal cord injury in rats by olfactory ensheathing cells graft modified by glia cell line-derived neurotrophic factor gene in combination with the injection of monoclonal antibody IN-1]

OBJECTIVE

To research the repair effect of transplantation of glial cell line-derived neurotrophic factor (GDNF) modified olfactory ensheathing cells (OECs) combination with injecting axonal growth inhibiting protein antibody (IN-1) in vivo.

METHODS

To construct lentivirus vector with GDNF gene and infect OECs in vitro, use the immunoblotting (Western Blot) to observe the expression of GDNF was detected through Western Blot. Fifty adult female SD rats which to establish thoracic spinal cord transection injury model were randomly divided into A (control group), B (IN-1 antibody group), C (OECs group), D (GDNF-OECs group), and E (GDNF-OECs+IN-1 group) 5 groups of each 10 rats. To observe regeneration of the impaired nerve axon by NF200 immunohistochemistry, Biotinylated dextran amine (BDA) anterograde tracing corticospinal tract. Basso, Beattie and Bresnahan (BBB) score was used to evaluating hindlimb motor function recovery.

RESULTS

Add up to 13 rats died post operation. OECs labeled by hoechst still survived and migrated in spinal cord 8 weeks post operation. Lots of confused and disorderly regenerated axons which crossing the injured region of spinal cord were displayed between spinal cord stumps in GDNF-OECs+IN-1 group and GDNF-OECs group; some of axons existed in OECs group, but there is no obviously continue nerve fibers crossing the injured region of spinal cord;in contrast to IN-1 and control groups, few of regenerated axons and atrophy of spinal cord stumps were observed. The results of BBB hindlimb motor rating scale were 7.70+/-0.24, 7.89+/-0.15, 10.50+/-0.25, 11.43+/-0.23 and 12.81+/-0.40 for the control group, IN-1 group, OECs group, GDNF-OECs group and the allied treatment group respectively.

CONCLUSIONS

The transplantation of GDNF-OECs combination with IN-1 antibody may benefit the survival and regeneration of the injured axons, and accelerate the repair of the injured spinal cord and functional recover of hindlimb locomotor in rats in a more efficient way than that with OECs or IN-1 alone.

[Effects of prenatal taurine on mRNA expression of PKA CREB signal pathway and glial cell line derived neurotrophic factor in fetal rat brains of intrauterine growth restriction]

OBJECTIVE

This study examined the effects of prenatal application of taurine on mRNA expression of protein kinase A cAMP response element binding protein (PKA-CREB) signal pathway and glial cell line derived neurotrophic factor (GDNF) in fetal rat brains of intrauterine growth restriction (IUGR).

METHODS

Pregnant rats were randomly divided into 4 groups: normal control, IUGR model, low dose (100 mg/kg x d) and high dose (300 mg/kg x d) taurine treatment IUGR (n = 5 each). IUGR was induced by food restriction throughout pregnancy. PKA, CREB and GDNF mRNA expression in brains of newborn rats was detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

PKA, CREB and GDNF mRNA expression in the IUGR model group was significantly higher than that in the normal control group (p<0.05). Compared with the IUGR model group, mRNA expression of PKA and CREB in both the low dose and high dose taurine treatment groups increased significantly (p<0.05); GDNF mRNA expression in the high dose taurine treatment group also increased significantly (p<0.01).

CONCLUSIONS

Taurine can increase mRNA expression of PKA, CREB and GDNF in fetal rat brains of IUGR. This suggests that prenatal application of taurine may increase neurogenesis of the central nervous system and endogenous secretion of neurotrophic factors, thus providing neuroprotective effects.