Effective GDNF brain delivery using microspheres--a promising strategy for Parkinson's disease.

Glial cell line-derived neurotrophic factor (GDNF) has shown promise in the treatment of neurodegenerative disorders of basal ganglia origin such us Parkinson's disease (PD). In this study, we investigated the neurorestorative effect of controlled GDNF delivery using biodegradable microspheres in an animal model with partial dopaminergic lesion. Microspheres were loaded with N-glycosylated recombinant GDNF and prepared using the Total Recirculation One-Machine System (TROMS). GDNF-loaded microparticles were unilaterally injected into the rat striatum by stereotaxic surgery two weeks after a unilateral partial 6-OHDA nigrostriatal lesion. Animals were tested for amphetamine-induced rotational asymmetry at different times and were sacrificed two months after microsphere implantation for immunohistochemical analysis. The putative presence of serum IgG antibodies against rat glycosylated GDNF was analyzed for addressing safety issues. The results demonstrated that GDNF-loaded microspheres, improved the rotational behavior induced by amphetamine of the GDNF-treated animals together with an increase in the density of TH positive fibers at the striatal level. The developed GDNF-loaded microparticles proved to be suitable to release biologically active GDNF over up to 5 weeks in vivo. Furthermore, none of the animals developed antibodies against GDNF demonstrating the safety of glycosylated GDNF use.

Sustained release of bioactive glycosylated glial cell-line derived neurotrophic factor from biodegradable polymeric microspheres.

Glial cell-line derived neurotrophic factor (GDNF), a potent neurotrophic factor for dopaminergic neurons, appeared as a promising candidate for treating Parkinson's disease. GDNF microencapsulation could ensure protection against degradation due to the fragile nature of the protein. Poly(lactide-co-glycolide) (PLGA) microparticles loaded with recombinant glycosylated GDNF obtained in a mammalian cell line were prepared by TROMS, a semi-industrial technique capable of encapsulating fragile molecules maintaining their native properties. The effects of several parameters as PLGA copolymer type, PEG 400 quantity co-encapsulated with GDNF or drug loading, on the properties of the particles were investigated. Microparticles showed a mean diameter between 8 and 30 microm, compatible with their stereotaxic implantation. The drug entrapment efficiency ranged from 50.6% to 100% depending on the microsphere composition. GDNF was better encapsulated using hydrophilic polymers with high molecular weight such as RG 503H. In vitro drug release was influenced by the polymer type as well as by the amount of PEG 400 co-encapsulated with GDNF. Microparticles prepared using PLGA RG 503H released 67% of the total protein content within 40 days. Moreover, very low concentrations of poly(vinyl alcohol) were detected after microparticles washing and freeze-drying. Finally, a PC-12 bioassay demonstrated that the in vitro GDNF released was bioactive.

Purification of bioactive glycosylated recombinant glial cell line-derived neurotrophic factor.

Glial cell line-derived neurotrophic factor (GDNF) neuroprotective effect on dopaminergic neurons has been described in vitro and in vivo, turning up as a promising drug for the treatment of Parkinson's disease. Unglycosylated bacteria-obtained GDNF has already been successfully delivered for a long period of time through an infusion pump directly to the putamen of Parkinsonian patients. Nevertheless, improved distribution and safety issues need to be solved and alternative strategies to long-term delivery seem necessary. The use of glycosylated GDNF could eliminate some safety concerns regarding the presence of antibodies against exogenous unglycosylated GDNF used for the treatment. Therefore, we have chosen a mammalian expression system as a source of glycosylated GDNF. In the present work, we describe the purification of recombinant rat GDNF from the culture media of baby hamster kidney (BHK) cells through several purification steps. Highly pure N-glycosylated recombinant GDNF has been obtained similar to the endogenous protein. Furthermore, the purified protein is biologically active when tested its ability to induce PC12 neurite outgrowth.

Terapias neuroprotectoras y neurorestauradoras en el tratamiento de la enfermedad de Parkinson / Neuroprotective and neurorestorative therapies for the treatment of Parkinson’s disease

La enfermedad de Parkinson es la segunda enfermedad neurodegenerativa más común después del Alzheimer. Actualmente se dispone únicamente de terapias sintomáticas que, aunque son muy eficaces en las primeras etapas de la enfermedad poseen a largo plazo considerables efectos secundarios. La terapia ideal sería aquella que permitiese frenar o detener la progresión de la enfermedad. Este es el caso de las terapias neuroprotectoras y neurorestauradoras. De entre todas ellas, la terapia celular y la terapia con factores tróficos tipo GDNF son las que mayores expectativas han generado en la comunidad científica. Aunque ya se ha planteado el uso de GDNF para el tratamiento de la enfermedad de Parkinson, es necesario buscar nuevas estrategias que permitan administrar dicho factor neurotrófico en las zonas concretas del cerebro donde vaya a ejercer su acción. Aquí se discute el uso de micropartículas como el sistema más apropiado para la administración de dicho factor neurotrófico

Parkinson´s disease is the second most common neurodegenerative disorder after Alzheimer´s disease. Current therapies are symptomatic and, although these therapies are efficacious during the early stages of the disease, they present important side effects when they are used for a long time. The ideal therapy would be the one that would slow down or stop the progression of the disease. This can be achieved, for instance, with neuroprotective and neurorestorative therapies. Among them, cell therapy and therapy with trophic factors such as glial cell line derived neurotrophic factor (GDNF) are the most challenging and promising ones for the scientific community. Although the use of GDNF as a treatment for Parkinson ´s disease was proposed several years ago, it is necessary to develop alternative strategies to deliver GDNF appropriately to concrete areas of the brain. Here, the use of microspheres as the most suitable tool for the administration of this neurotrophic factor is discussed

Consequences of unilateral nigrostriatal denervation on the thalamostriatal pathway in rats.

The position of the caudal intralaminar nuclei within basal ganglia circuitry has largely been neglected in most studies dealing with basal ganglia function. During the past few years, there has been a growing body of evidence suggesting that the thalamic parafascicular nucleus in rodents (PF) exerts a multifaceted modulation of basal ganglia nuclei, at different levels. Our aim was to study the activity of the thalamostriatal pathway in rats with unilateral dopaminergic depletion. The experimental approach comprised first unilateral delivery of 6-OHDA in the medial forebrain bundle. Thirty days post-lesioning, animals showing a clear asymmetry were then subjected to bilateral injection of Fluoro-Gold (FG) within the striatum. Subsequently, expression of the mRNA encoding the vesicular glutamate transporter 2 (vGLUT2) was detected within thalamostriatal-projecting neurons (FG-labeled) by in situ hybridization and the results were confirmed by laser-guided capture microdissection microscopy followed by real-time PCR. The data showed that there was a marked neuronal loss restricted to PF neurons projecting to the dopamine-depleted striatum. Moreover, PF neurons innervating the dopamine-depleted striatum were intensely hyperactive. These neurons showed a marked increase on the expression of vGLUT2 mRNA as well as for the mRNA encoding the subunit I of cytochrome oxidase as compared with those neurons projecting to the striatum with normal dopamine content. Thus, the selective neurodegeneration of PF neurons innervating the striatum together with the increased activity of the thalamostriatal pathway coexist after nigrostriatal denervation.

Expresión y purificación de GDNF para su microencapsulación y aplicación en la enfermedad de Parkinson / Expression and Purification of GDNF for its microencapsulation in drug delivery systems and application in Parkinson’s disease

La enfermedad de Parkinosn (EP) es un proceso neurodegenerativodel sistema nervioso central que afecta a las neuronasde dopamina de la sustancia negra, núcleo mesoencefálico delcontrol motor. La perdida en el cerebro de este neurotransmisorvital causa los síntomas de la enfermedad. La EP afectaactualmente a 200 de cada 100.000 personas y a 2 de cada100 entre los mayores de 60 años. En España hay unos110.000 enfermos. Además, hoy por hoy no se conoce nadaque pueda prevenir o curar la enfermedad, ni existe ningunaprueba de laboratorio que permita diagnosticarla. Recentiementese ha demostrado que el GDNF, factor neurotrófico derivadode las células gliales, es capaz de proteger las neuronasdopaminérgicas e incluso inducir la regeneración del tejidodopaminérgico dañado in vivo.El objetivo del trabajo fue diseñar y desarrolar un método deexpresión y purificación de GDNF bioactivo para su posteriormicroencapsulación y aplicación en la enfermedad de Parkison.El sistema escogido para expresar el GDNF fue el sistema decélulas eucariotas de mamífero. El vector utilizado para la produccióndel GDNF en células eucariotas fue el pDEST26 (TecnologíaGateway de Invitrogen). Como sistema de expresión deGDNF se utilizaron las líneas celulares eucariota BHK, 293 yCOS 7. Estas células fueron cultivadas en medio D-MEM (Invitrogen)complementado con un 10% de suero fetal bovino(FBS) y Penicilina/Streptomicina (100u/ml) (Invitrogen). Latransfección se realizó con Lipofectamine Plus (Invitrogen). Seanalizó la expresión de GDNF a nivel de mRNA mediante PCR ya nivel de proteína mediante Western Blot del medio condicionado. Los clones positivos se crecieron en botellas de cultivode 850 cm2 (Corning) y se realizaron ciclos de recolección delmedio. Cada ciclo fue analizado por SDS-PAGE y Western Blot.Para evaluar la actividad de la proteína se ha desarrollado unensayo de actividad en el que se demuestra la diferenciaciónmorfológica de células PC-12 inducida por GDNF. La presenciade los receptores GFRa1 y RET, necesarios para que el GDNFejerza su acción, fue determinada por PCR.Las conclusiones obtenidas de este estudio son la obtenciónde GDNF recombinante a partir de un sistema de expresión encélulas eucariotas, el desarrollo de un protocolo para su posteriorpurificación y la obtención de GDNF recombinante biológicamenteactivo

Parkinson’s disease (PD) is a slowly progressive neurodegenerativedisorder caused by decreased levels of dopamine in thesubstantia nigra, brain region responsible for movement. Thelack of dopamine is believe to be responsible of the symptomsof PD. Parkinson’s affects 200 in 100000 people and 2 inevery 100 persons over 60 years old. In Spain, there areabout 110000 people with PD. There is no cure at this time,and there are no prevention techniques or therapies. Recently,it has been demonstrated that GDNF, a glial-derived neurotrophicfactor is able to protect the dopaminergic neurons of thesubstancia nigra and it can also induce regeneration of injuredneurons in the central nervous system in vivo.The aim of this work was to develop a procedure for theexpression and purification of bioactive GDNF in view of itsmicroencapsulation for the treatment of PD.The cDNA of the GDNF gene was cloned in the expressionvector pDEST26 (Invitrogen) using the Gateway® Technology.Several eukaryotic mammalian cell lines (BHK, COS-7, and293) were stably transfected with the construction with LipofectaminePlus (Invitrogen). In those clones in which the presenceof the mRNA of the GDNF was confirmed by PCR studies,the expression of the recombinant protein in the serumfree medium was analyzed by Western Blot studies. The highestGDNF-producing clone, obtained from the BHK cell line,was cultured in 850 cm2 roller bottles (Corning) alternatingthe presence or the absence of FBS in the medium every 24hours, being collected only the serum free medium for theproduction of the recombinant GDNF. Each cycle protein expression was analyzed by SDS-PAGE and by Western Blot.The secreted protein was purified by several chromatographysteps. After each step of the purification procedure the fractionsobtained were analyzed by SDS-PAGE, Western Blotand silver staining analysis. A neuronal differentiation PC-12cell-based bioassay was also developed to confirm the biologicalactivity of the purified recombinant protein. Previously,the presence of GFRa1 and RET, receptors required forGDNF activity were confirmed by PCR.In conclusion, recombinant GDNF was produced in an eukaryoticmammalian cell line-based system. The protein purificationprocedure developed, allowed to obtain a highly purifiedrecombinant GDNF. Furthermore, the recombinant protein isbioactive

[Neuroprotective and neurorestorative therapies for the treatment of Parkinson's disease]. / Terapias neuroprotectoras y neurorestauradoras en el tratamiento de la enfermedad de Parkinson.

Parkinson's disease is the second most common neurodegenerative disorder after Alzheimer's disease. Current therapies are symptomatic and, although these therapies are efficacious during the early stages of the disease, they present important side effects when they are used for a long time. The ideal therapy would be the one that would slow down or stop the progression of the disease. This can be achieved, for instance, with neuroprotective and neurorestorative therapies. Among them, cell therapy and therapy with trophic factors such as glial cell line derived neurotrophic factor (GDNF) are the most challenging and promising ones for the scientific community. Although the use of GDNF as a treatment for Parkinson s disease was proposed several years ago, it is necessary to develop alternative strategies to deliver GDNF appropriately to concrete areas of the brain. Here, the use of microspheres as the most suitable tool for the administration of this neurotrophic factor is discussed.

Evidence for pigment epithelium-derived factor receptors in the neural retina.

PURPOSE: The neurotrophic activity of pigment epithelium-derived factor (PEDF), an extracellular factor present in the retina, is mediated by binding to cell-surface receptors in responsive cell cultures. In the present study, the expression of PEDF receptors in native neural retinas from adult steers was examined. METHODS: Binding reactions were performed with (125)I-PEDF and fluoresceinated PEDF using plasma membranes, detergent-soluble membrane proteins, or cryosections of retina from adult bovine eyes. Radioligand-binding and competition analyses were performed with a computer-assisted program. Ligand blot analysis of detergent-soluble membrane proteins was performed with (125)I-PEDF followed by autoradiography. Ligand-affinity column chromatography of detergent-soluble membrane proteins was performed with PEDF-coupled resin followed by SDS-PAGE. Binding of fluoresceinated PEDF to retina cryosections was detected by confocal microscopy. RESULTS: Radioligand-binding assays showed that (125)I-PEDF bound in a specific and saturable fashion to one class of sites on retina membranes (K(d) = 2.5-6.5 nM; maximum binding [B(max)] = 1-48 x 10(10) sites/retina). A peptide of 44 amino acids (44-mer), identified as the receptor-binding region of PEDF, competed efficiently for (125)I-PEDF binding to retina membranes with kinetics similar to the full-length PEDF. Ligand blot analysis and ligand-affinity chromatography revealed a specific and high-affinity PEDF-binding protein of approximately 85 kDa in retina plasma membranes. Confocal microscopy showed that fluorescein-conjugated PEDF stained exclusively the inner segments of photoreceptors and cells of the ganglion cell layer in retinal cryosections. CONCLUSIONS: Altogether, these data conclusively demonstrate the existence of PEDF receptors discretely distributed on the surface of cells from the adult neural retina of bovine eyes. Furthermore, they provide evidence for the direct action of PEDF on photoreceptor and ganglion cell neurons and an anatomic basis for studies to assess PEDF neurotrophic effects on the adult retina.

Binding of pigment epithelium-derived factor (PEDF) to retinoblastoma cells and cerebellar granule neurons. Evidence for a PEDF receptor.

Pigment epithelium-derived factor (PEDF) has neuronal differentiation and survival activity on retinoblastoma and cerebellar granule (CG) cells. Here, we investigated the presence of PEDF receptors on retinoblastoma Y-79 and CG cells. PEDF radiolabeled with (l25)I remained biologically active and was used for radioligand binding analysis. The binding was saturable and specific to a single class of receptors on both cells and with similar affinities (K(d) = 1.7-3.6 nM, B(max) = 0.5-2.7 x 10(5) sites/Y-79 cell; and K(d) = 3.2 nM, B(max) = 1.1 x 10(3) sites/CG cell). A polyclonal antiserum to PEDF, previously shown to block the PEDF neurotrophic activity, prevented the (125)I-PEDF binding. We designed two peptides from a region previously shown to confer the neurotrophic property to human PEDF, synthetic peptides 34-mer (positions 44-77) and 44-mer (positions 78-121). Only peptide 44-mer competed for the binding to Y-79 cell receptors (EC(50) = 5 nM) and exhibited neuronal differentiating activity. PEDF affinity column chromatography of membrane proteins from both cell types revealed a PEDF-binding protein of approximately 80 kDa. These results are the first demonstration of a PEDF-binding protein with characteristics of a PEDF receptor and suggest that the region comprising amino acid positions 78-121 of PEDF might be involved in ligand-receptor interactions.

Inducible nitric oxide synthase (iNOS) expression in human monocytes triggered by beta-endorphin through an increase in cAMP.

Evidence suggesting a relationship between neuroendocrine and immune systems is steadily growing. We demonstrate now that inducible nitric oxide synthase (iNOS) is expressed in human peripheral blood monocytes after incubation of lymphomononuclear cells in the presence of beta-endorphin, a neuropeptide released by the pituitary in response to mental or physical stress or by activated lymphocytes. beta-endorphin raised cAMP level in monocytes. The possible relationship between cAMP and iNOS expression on monocytes was investigated. Immunostaining for iNOS decreased, when besides beta-endorphin an inhibitor of protein kinase A (H-89) was added to the medium at the beginning of the incubation. The cAMP level raised by beta-endorphin was lowered by naloxone, which also reduced slightly iNOS expression. These results clearly point to the monocyte as a link between neuroendocrine and immune systems, an observation of potential relevance in our understanding of how stress and autoimmunity could be interconnected.

Monocyte inducible nitric oxide synthase in multiple sclerosis: regulatory role of nitric oxide.

Immunophenotypic analysis of peripheral blood leukocytes from patients with multiple sclerosis (MS) showed a profile reflecting a state of activation and differentiation of monocytes. A subset of CD16+ monocytes with high HLA-DR expression was more prominent in patients with MS than in healthy subjects. The presence of the inducible form of nitric oxide synthase (iNOS) in these differentiated and activated monocytes freshly obtained from patients with MS was demonstrated by immunocytochemistry and flow cytometry analysis with two different antibodies. Incubation of lymphomononuclear cells from healthy volunteers in the presence of an immunomodulating peptide (NVLGAPKKLNESQAV) led to stimulation and maturation of monocytes manifested by changes in phenotype and an increase in both iNOS mRNA and protein, as well as HLA-DR expression. In this case also iNOS was expressed mainly on subsets of CD16+ monocytes with high HLA-DR expression. NO produced by human monocytes seems to have a function in the upregulation of membrane HLA-DR. These results are suggestive of a role for monocytic iNOS in the autoimmune response underlying the pathogenesis of multiple sclerosis.

Inducible nitric oxide synthase in monocytes from patients with Graves' disease.

The presence of inducible nitric oxide synthase (iNOS) in fresh monocytes from patients with Graves' disease was demonstrated for the first time. Immunophenotypic analysis showed a profile reflecting a state of activation and differentiation of monocytes. Incubation of lymphomononuclear cells from healthy volunteers in the presence of synthetic peptides with sequences related to thyroid autoantigens (TSH receptor, thyroid peroxidase, or thyroglobulin) led to a stimulation of monocytes manifested by a change in phenotype and expression of iNOS. This expression did not take place on isolated monocytes, unless products associated with Th1 activity were present in the medium. Active peptides contained a characteristic "2-6-11" motif already described [López-Moratalla et al. (1995) Biochim. Biophys. Acta 1265, 181-188]. These results are suggestive of a new role for autoantigens in the pathogenesis of Graves' disease: that of inducing the expression of iNOS and activating the monocyte possibly underlying the autoimmune response.