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Patrick Aebischer

Publications and source records attributed to Patrick Aebischer.

At least 19 recordsLinked to original sources
PubMed2006

CA150 expression delays striatal cell death in overexpression and knock-in conditions for mutant huntingtin neurotoxicity.

Transcriptional dysregulation caused by expanded polyglutamines (polyGlns) in huntingtin (htt) may be central to cell-autonomous mechanisms for neuronal cell death in Huntington's disease (HD) pathogenesis. We hypothesized that these mechanisms may involve the dysfunction of the transcriptional regulator CA150, a putative modifier of onset age in HD, because it binds to htt and accumulates in an HD grade-dependent manner in striatal and cortical neurons. Consistently, we report herein that CA150 expression rescues striatal cell death in lentiviral overexpression (rats) and knock-in (mouse cells) conditions for mutant htt neurotoxicity. In both systems, rescue was dependent on the (Gln-Ala)38 repeat normally found in CA150. We excluded the possibility that rescue may be caused by the (Gln-Ala)38 repeat interacting with polyGlns and, by doing so, blocking mutant htt toxicity. In contrast, we found the (Gln-Ala)38 repeat is required for the nuclear restriction of exogenous CA150, suggesting that rescue requires nuclear CA150. Additionally, we found the (Gln-Ala)38 repeat was dispensable for CA150 transcriptional repression ability, suggesting further that CA150 localization is critical to rescue. Finally, rescue was associated with increased neuritic aggregation, with no reduction of nuclear inclusions, suggesting the solubilization and nuclear export of mutant htt. Together, our data indicate that mutant htt may induce CA150 dysfunction in striatal neurons and suggest that the restoration of nuclear protein cooperativity may be neuroprotective.

Animals↗
PubMed2006

Inhibition of calcineurin by FK506 protects against polyglutamine-huntingtin toxicity through an increase of huntingtin phosphorylation at S421.

Huntington's disease (HD) is caused by an abnormal expanded polyglutamine (polyQ) repeat in the huntingtin protein. Insulin-like growth factor-1 acting through the prosurvival kinase Akt mediates the phosphorylation of huntingtin at S421 and inhibits the toxicity of polyQ-expanded huntingtin in cell culture, suggesting that compounds enhancing phosphorylation are of therapeutic interest. However, it is not clear whether phosphorylation of S421 is crucial in vivo. Using a rat model of HD based on lentiviral-mediated expression of a polyQ-huntingtin fragment in the striatum, we demonstrate here that phosphorylation of S421 is neuroprotective in vivo. We next demonstrate that calcineurin (CaN), a calcium/calmodulin-regulated Ser/Thr protein phosphatase, dephosphorylates S421 in vitro and in cells. Inhibition of calcineurin activity, either by overexpression of the dominant-interfering form of CaN or by treatment with the specific inhibitor FK506, favors the phosphorylation of S421, restores the alteration in huntingtin S421 phosphorylation in HD neuronal cells, and prevents polyQ-mediated cell death of striatal neurons. Finally, we show that administration of FK506 to mice increases huntingtin S421 phosphorylation in brain. Collectively, these data highlight the importance of CaN in the modulation of S421 phosphorylation and suggest the potential use of CaN inhibition as a therapeutic approach to treat HD.

Animals↗
PubMed2006

A versatile tool for conditional gene expression and knockdown.

Drug-inducible systems allowing the control of gene expression in mammalian cells are invaluable tools for genetic research, and could also fulfill essential roles in gene- and cell-based therapy. Currently available systems, however, often have limited in vivo functionality because of leakiness, insufficient levels of induction, lack of tissue specificity or prohibitively complicated designs. Here we describe a lentiviral vector-based, conditional gene expression system for drug-controllable expression of polymerase (Pol) II promoter-driven transgenes or Pol III promoter-controlled sequences encoding small inhibitory hairpin RNAs (shRNAs). This system has great robustness and versatility, governing tightly controlled gene expression in cell lines, in embryonic or hematopoietic stem cells, in human tumors xenotransplanted into nude mice, in the brain of rats injected intraparenchymally with the vector, and in transgenic mice generated by infection of fertilized oocytes. These results open up promising perspectives for basic or translational research and for the development of gene-based therapeutics.

Animals↗
PubMed2005

Transient striatal delivery of GDNF via encapsulated cells leads to sustained behavioral improvement in a bilateral model of Parkinson disease.

Numerous studies have shown the neuroprotective and regenerative benefits of glial cell line-derived neurotrophic factor (GDNF) in animal models of PD. Brain delivery of GDNF can, however, be associated with limiting side-effects in both primates and PD patients, rendering the duration of delivery a critical factor. In the present study, the effects of transient vs. sustained GDNF delivery by encapsulated cells were evaluated in a bilateral animal model, closely mimicking advanced PD. One week following bilateral striatal 6-hydroxydopamine injections in rats, capsules loaded with human fibroblasts genetically engineered to release GDNF were bilaterally implanted in the striatum. GDNF delivery resulted in a significant improvement of movement initiation and swimming performance in the lesioned animals, associated with striatal reinnervation of dopaminergic fibers. To test the sustainability of the behavioral improvement, GDNF-secreting capsules were withdrawn in a subgroup of animals, 7 weeks post-implantation. Strikingly, both the behavioral and morphological improvements were maintained until the sacrifice of the animals 6 weeks post-GDNF withdrawal. The sustained cellular and behavioral benefits after GDNF washout suggest the need for temporary delivery of the trophic factor in PD. Retrievable encapsulated cells represent an attractive delivery tool to achieve this purpose.

Animals↗
PubMed2005

Inducing tolerance to a soluble foreign antigen by encapsulated cell transplants.

The immune response to soluble antigens constitutes a current clinical problem impeding the development of protein therapeutics. We have developed an encapsulated-cell delivery system, which, transiently combined with an anti-CD154 antibody treatment, allows for the suppression of this immune response and the establishment of long-term secretion of a foreign antigen, human erythropoietin (huEPO). The chronic presence of antigen appears to be required to maintain this tolerance, as a 21-day gap in the exposure to huEPO is sufficient to restore the ability of mice to mount an antibody response. In contrast, chronic huEPO expression maintains tolerance even in the absence of further anti-CD154 treatment. These results suggest that a soluble antigenic protein can be continuously released, without inducing an antibody response, using encapsulated allogeneic cells. The temporary anti-CD154 treatment induces immune unresponsiveness to the delivered antigen, while the immunoprotected cell implant allows for chronic antigen release, favoring the establishment of tolerance.

Animals↗
PubMed2005

Increased fiber outgrowth from xeno-transplanted human embryonic dopaminergic neurons with co-implants of polymer-encapsulated genetically modified cells releasing glial cell line-derived neurotrophic factor.

We investigated whether a continuous supply of glial cell line-derived neurotrophic factor (GDNF) via encapsulated genetically modified cells can promote survival and fiber outgrowth from xenotransplanted human dopaminergic neurons. Cells genetically engineered to continuously secrete GDNF were confined in hollow fiber-based macrocapsules. Each hemiparkinsonian rat received either a single C2C12-hGDNF capsule (n=8) or a C2C12-control capsule (n=8) concomitantly with human embryonic ventral mesencephalic cell suspension transplants. Our results show that fiber outgrowth in the area between the capsule and the graft is more extensive in rats with GDNF-releasing capsules than in rats with control capsules. We suggest that continuous and safe delivery of GDNF to the brain could be a potential way to optimize neural transplantation as a therapy for Parkinson's disease.

Analysis of Variance↗
PubMed2005

Lentivirus-mediated expression of glutathione peroxidase: neuroprotection in murine models of Parkinson's disease.

Reactive oxygen species are considered to contribute to the pathogenesis of Parkinson's disease (PD). In order to study viral vector-mediated overexpression of the antioxidant enzyme glutathione peroxidase (GPX) as a potential neuroprotective approach in both an in vitro and in vivo model of PD, we have developed a lentiviral vector carrying the human GPX1 gene. Neuroblastoma cells infected with this vector showed a 2-fold increase in GPX activity compared to cells infected with a control vector. In addition, overexpression of GPX protected 83.0 +/- 14.2% of these cells against 6-hydroxydopamine (6-OHDA)-induced toxicity, while only 22.9 +/- 4.6% of the cells infected with a control vector survived. Furthermore, lentivirus-mediated expression of GPX1 in nigral dopaminergic neurons in vivo prior to intrastriatal injection of 6-OHDA led to a small, but significant protection of these cells against drug-induced toxicity. These results indicate that antioxidative gene therapy strategies may be relevant for PD.

Animals↗
PubMed2005

Progressive and selective striatal degeneration in primary neuronal cultures using lentiviral vector coding for a mutant huntingtin fragment.

A lentiviral vector expressing a mutant huntingtin protein (htt171-82Q) was used to generate a chronic model of Huntington's disease (HD) in rat primary striatal cultures. In this model, the majority of neurons expressed the transgene so that Western blot analysis and flow cytometry measurement could complement immunohistological evaluation. Mutant huntingtin produced a slowly progressing pathology characterized after 1 month by the appearance of neuritic aggregates followed by intranuclear inclusions, morphological anomalies of neurites, loss of neurofilament 160, increased expression in stress response protein Hsp70, and later loss of neuronal markers such as NeuN and MAP-2. At 2 months post-infection, a significant increase in TUNEL-positive cells confirmed actual striatal cell loss. Interestingly, cortical cultures infected with the same vector showed no sign of neuronal dysfunction despite accumulation of numerous inclusions. We finally examined whether the trophic factors CNTF and BDNF that were found neuroprotective in acute HD models could prevent striatal degeneration in a chronic model. Results demonstrated that both agents were neuroprotective without modifying inclusion formation. The present study demonstrates that viral vectors coding for mutant htt provides an advantageous system for histological and biochemical analysis of HD pathogenesis in primary striatal cultures.

Animals↗
PubMed2005

Lentiviral-mediated silencing of SOD1 through RNA interference retards disease onset and progression in a mouse model of ALS.

Mutations in Cu/Zn superoxide dismutase (encoded by SOD1), one of the causes of familial amyotrophic lateral sclerosis (ALS), lead to progressive death of motoneurons through a gain-of-function mechanism. RNA interference (RNAi) mediated by viral vectors allows for long-term reduction in gene expression and represents an attractive therapeutic approach for genetic diseases characterized by acquired toxic properties. We report that in SOD1(G93A) transgenic mice, a model for familial ALS, intraspinal injection of a lentiviral vector that produces RNAi-mediated silencing of SOD1 substantially retards both the onset and the progression rate of the disease.

Amyotrophic Lateral Sclerosis↗
PubMed2005

GDNF delivery using human neural progenitor cells in a rat model of ALS.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of spinal cord, brainstem, and cortical motor neurons. In a minority of patients, the disease is caused by mutations in the copper (2+)/zinc (2+) superoxide dismutase 1 (SOD1) gene. Recent evidence suggests that astrocytes are dysfunctional in ALS and may be a critical link in the support of motor neuron health. Furthermore, growth factors, such as glial cell line-derived neurotrophic factor (GDNF), have a high affinity for motor neurons and can prevent their death following various insults, but due to the protein's large size are difficult to directly administer to brain. In this study, human neural progenitor cells (hNPC) isolated from the cortex were expanded in culture and modified using lentivirus to secrete GDNF (hNPC(GDNF)). These cells survived up to 11 weeks following transplantation into the lumbar spinal cord of rats overexpressing the G93A SOD1 mutation (SOD1 (G93A)). Cellular integration into both gray and white matter was observed without adverse behavioral effects. All transplants secreted GDNF within the region of cell survival, but not outside this area. Fibers were seen to upregulate cholinergic markers in response to GDNF, indicating it was physiologically active. We conclude that genetically modified hNPC can survive, integrate, and release GDNF in the spinal cord of SOD1 (G93A) rats. As such, they provide an interesting source of cells for both glial replacement and trophic factor delivery in future human clinical studies.

Amyotrophic Lateral Sclerosis↗
PubMed2005

Akt is altered in an animal model of Huntington's disease and in patients.

The insulin-like growth factor I (IGF-1)/Akt pathway plays a crucial role in Huntington's disease by phosphorylating the causative protein, polyQ-huntingtin, and abolishing its toxic properties [Humbert et al. (2002)Dev. Cell, 2, 831-837; Rangone et al. (2004)Eur. J. Neurosci., 19, 273-279]. Therefore, dysregulation of this pathway may be essential for disease progression. In the present report, we thus aimed to analyse the status of Akt in brain or in peripheral tissues in Huntington's disease. Using a genetic model of Huntington's disease in rat that reproduces neuronal dysfunction and death, we show a progressive alteration of Akt during neuronal dysfunction and prior neurodegeneration. By analysing a limited number of lymphoblasts and lymphocytes, we detected modifications of Akt in Huntington's disease patients confirming a dysregulation of Akt in the disease process. Finally, we demonstrate that during late stages of the disease, Akt is cleaved into an inactive form by caspase-3. These observations demonstrate a progressive but marked alteration of this pro-survival pathway in Huntington's disease, and further implicate it as a key transduction pathway regulating the toxicity of huntingtin.

Animals↗
PubMed2005

Long-term glial cell line-derived neurotrophic factor overexpression in the intact nigrostriatal system in rats leads to a decrease of dopamine and increase of tetrahydrobiopterin production.

Parkinson's disease (PD) is characterized by the progressive degeneration of the nigrostriatal dopaminergic system. Brain delivery of glial cell line-derived neurotrophic factor (GDNF) has been shown to protect and restore the dopaminergic pathway in various animal models of PD. However, GDNF overexpression in the dopaminergic pathway leads to a time-dependent down-regulation of tyrosine hydroxylase (TH), a key enzyme in dopamine synthesis. In order to elucidate GDNF-mediated biochemical effects on dopaminergic neurons, we overexpressed GDNF in the intact rat striatum using a lentiviral vector-mediated gene transfer technique. Long-term GDNF overexpression led to increased GTP cyclohydrolase I (GTPCH I) activity and tetrahydrobiopterin (BH4) levels. Further, we observed a down-regulation of TH enzyme activity in morphologically intact striatal dopaminergic nerve terminals, as well as a significant decrease of dopamine levels in striatal tissue samples. These results indicate that long-term GDNF delivery is a major factor affecting dopamine biosynthesis via a direct or indirect modulation of TH and GTPCH I and further underscore the importance of assessing both GDNF dose and delivery duration prior to clinical application in order to circumvent potentially adverse pharmacological effects on the biosynthesis of dopamine.

Animals↗
PubMed2004

Lentiviral vector delivery of parkin prevents dopaminergic degeneration in an alpha-synuclein rat model of Parkinson's disease.

Parkinson's disease (PD) is characterized by a progressive loss of midbrain dopamine neurons and the presence of cytoplasmic inclusions called Lewy bodies. Mutations in several genes including alpha-synuclein and parkin have been linked to familial PD. The loss of parkin's E3-ligase activity leads to dopaminergic neuronal degeneration in early-onset autosomal recessive juvenile parkinsonism, suggesting a key role of parkin for dopamine neuron survival. To evaluate the potential neuroprotective role of parkin in the pathogenesis of PD, we tested whether overexpression of wild-type rat parkin could protect against the toxicity of mutated human A30P alpha-synuclein in a rat lentiviral model of PD. Animals overexpressing parkin showed significant reductions in alpha-synuclein-induced neuropathology, including preservation of tyrosine hydroxylase-positive cell bodies in the substantia nigra and sparing of tyrosine hydroxylase-positive nerve terminals in the striatum. The parkin-mediated neuroprotection was associated with an increase in hyperphosphorylated alpha-synuclein inclusions, suggesting a key role for parkin in the genesis of Lewy bodies. These results indicate that parkin gene therapy may represent a promising candidate treatment for PD.

Alanine↗
PubMed2004

Wlds-mediated protection of dopaminergic fibers in an animal model of Parkinson disease.

Parkinson disease (PD) is characterized by the progressive degeneration of substantia nigra dopaminergic neurons projecting to the striatum. Since the deficit in striatal dopamine is the main cause of PD symptoms, it appears critical to preserve axon terminals. Significant axon protection from peripheral nerve Wallerian degeneration is observed in Wlds mice, a phenotype conferred by a spontaneous dominant mutation. To assess any Wlds-mediated rescue of dopamine fibers in a PD model, the nigrostriatal pathway of Wlds mice was lesioned with 6-hydroxydopamine (6-OHDA), a catecholaminergic neurotoxin. Following 6-OHDA injection in the medial forebrain bundle, Wlds mice showed remarkable dopamine fiber protection in the striatum. Drug-induced rotational behavior confirmed the nigrostriatal fiber ability to release dopamine, although revealing an abnormal neurotransmitter control presumably due to disrupted axonal transport. Following 6-OHDA injection in the midstriatum, only a protection trend was observed. Strikingly, no protection of Wlds nigral dopaminergic cell bodies was obtained following either nigrostriatal lesion. Besides showing subtle differences in the degeneration process between subcellular compartments, the reported Wlds-mediated protection of the dopamine axon terminals in an animal model of PD may lead to the understanding of mechanisms underlying axon loss and to the development of new therapeutic approaches.

Amphetamine↗
PubMed2004

Long-term lentiviral-mediated expression of ciliary neurotrophic factor in the striatum of Huntington's disease transgenic mice.

Ciliary neurotrophic factor (CNTF) has been shown to prevent behavioral deficits and striatal degeneration in neurotoxic models of Huntington's disease (HD), but its effect in a genetic model has not been evaluated. Lentiviral vectors expressing the human CNTF or LacZ reporter gene were therefore injected in the striatum of wild-type (WT) and transgenic mice expressing full-length huntingtin with 72 CAG repeats (YAC72). Behavioral analysis showed increased locomotor activity in 5- to 6-month-old YAC72-LacZ mice compared to WT-LacZ animals. Interestingly, CNTF expression reduced the activity levels of YAC72 mice compared to control animals. In both WT and YAC72 mice, CNTF expression was demonstrated in striatal punches, up to a year after lentiviral injection. Stereological analysis revealed that the number of LacZ and DARPP-32-positive neurons were decreased in YAC72-LacZ mice compared to WT-LacZ animals. Assessment of the benefit of CNTF expression in the YAC72 mice was, however, complicated by a down-regulation of DARPP-32 and to a lesser extent of NeuN in all mice treated with CNTF. The expression of the neuronal marker NADPH-d was unaffected by CNTF, but expression of the astrocytic marker glial fibrillary acidic protein (GFAP) was increased. Finally, a reduction of the number of striatal dark cells was observed in YAC mice treated with CNTF compared to LacZ. These data indicate that sustained striatal expression of CNTF can be achieved with lentiviruses. Further studies are, however, needed to investigate the intracellular signaling pathways mediating the long-term effects of CNTF expression on dopamine signaling, glial cell activation and how these changes may affect HD pathology.

Animals↗
PubMed2004

Local GDNF expression mediated by lentiviral vector protects facial nerve motoneurons but not spinal motoneurons in SOD1(G93A) transgenic mice.

Approximately 2% of amyotrophic lateral sclerosis (ALS) cases are associated with mutations in the cytosolic Cu/Zn superoxide dismutase 1 (SOD1) gene. Transgenic SOD1 mice constitute useful models of ALS to screen therapeutical approaches. Glial cell line-derived neurotrophic factor (GDNF) holds promises for the treatment of motoneuron disease. In the present study, GDNF expression in motoneurons of SOD1(G93A) transgenic mice was assessed by facial nucleus or intraspinal injection of lentiviral vectors (LV) encoding GDNF. We show that lentiviral vectors allow the expression for at least 12 weeks of GDNF that was clearly detected in motoneurons. This robust intraspinal expression did, however, not prevent the loss of motoneurons and muscle denervation of transgenic mice. In contrast, LV-GDNF induced a significant rescue of motoneurons in the facial nucleus and prevented motoneuron atrophy. The differential effect of GDNF on facial nucleus versus spinal motoneurons suggests different vulnerability of motoneurons in ALS.

Animals↗
PubMed2004

Encapsulated GDNF-producing C2C12 cells for Parkinson's disease: a pre-clinical study in chronic MPTP-treated baboons.

Glial cell line-derived neurotrophic factor (GDNF), a potent neurotrophic factor with restorative effects in a variety of rodent and primate models of Parkinson's disease (PD), could be of therapeutic value to PD. In this study, we show that intraventricular chronic infusion of low doses of GDNF using encapsulated genetically engineered C2C12 cells can exert: (1) transient recovery of motor deficits (hypokinesia); (2) significant protection of intrinsic striatal dopaminergic function in the immediate vicinity of the site of implantation of the capsule in the caudate nucleus, and (3) significant-long-lasting-neurotrophic properties at the nigral level with an increase volume of the cell bodies. These observations confirm the potent neurorestorative potential of GDNF in PD and the safety/efficacy of the encapsulation technology as a means to deliver in situ this neurotrophic cytokine even using an intraventricular approach.

Animals↗