HDAC inhibitors chemotherapy improves the homeostatic response to excitotoxicity in Huntington’s disease models

• Type: National Conference Proceedings Book
• Date: 2005

Authors

Jorge M.A. Oliveira (Author) FFUP; Chen S (Author) Other; Almeida S (Author) Other; Riley R (Author) Other; Gonçalves J (Author) Other; Oliveira CR (Author) Other; Hayden MR (Author) Other; Nicholls DG (Author) Other; Ellerby LM (Author) Other; Rego AC (Author) Other

Publisher

Sinapse

Conference National

9ª reunião da Sociedade Portuguesa de Neurociências,

Grande Hotel do Luso, Portugal, 19 a 20 de Maio de 2005

Scientific classification

FOS: Medical and Health sciences > Health sciences

CORDIS: Health sciences > Neuroscience > Neurochemistry ; Health sciences > Neuroscience > Neurophysiology ; Health sciences > Pharmacological sciences

Other information

Resumo (PT): Huntington’s disease (HD) is a progressive and fatal neurological disorder caused by a mutant form of huntingtin (htt). Excitotoxicity and transcriptional deregulation are believed to play an important role in the selective degeneration of striatal neurons in HD. Histone deacetylase (HDAC) inhibitors promote transcriptional activation and were shown to be neuroprotective, improving survival of HD transgenic mice. However, the precise cellular changes that are ultimately responsible for neuroprotection remain unknown. In the present study we tested the hypothesis that HDAC inhibitors improve the cellular mechanisms involved in the maintenance of Ca2+ homeostasis, thus protecting neurons from excitotoxicity. We used two HD models expressing full-length mutant htt: immortalized striatal progenitor cells (STHdh) from knock-in mice and primary striatal neurons from YAC128 mice. Dynamic changes in intracellular Ca2+, mitochondrial membrane potential (Δψm) and somatic swelling were continuously monitored in single cells by fluorescence microscopy. Expression of normal and mutant htt, and levels of histone acetylation following treatment with HDAC inhibitors were assessed by Western blotting. Challenge with the Ca2+ ionophore 4-BrA23187 or brief NMDA-receptor activation were used as excitotoxic stimuli in STHdh cells or striatal neurons, respectively. Recovery from excitotoxic stimuli was influenced by pharmacological manipulation of Δψm, highly suggesting mitochondrial involvement which was further emphasized by experiments performed in glucose-free, pyruvate-based media. In both HD models, cells expressing mutant htt presented a significantly delayed recovery from excitotoxic stimuli when compared to wild-type controls. This delayed recovery is associated with a slower restoration of intracellular Ca2+, mitochondrial depolarization and somatic swelling. In both HD models, recovery was improved by protracted treatment with HDAC inhibitors, sodium butyrate (SB) or trichostatin A (TSA). Improved recovery was more pronounced for SB than for TSA treatment, in agreement with changes in histone acetylation. These results, in two distinct HD models, suggest an overall ability of HDAC inhibitors to improve the homeostatic response to excitotoxicity through more efficient Ca2+-handling. Furthermore, population analysis of striatal neurons revealed the existence of subpopulations refractory to treatment. Taken together, these results provide an in vitro explanation for neuroprotective effects of HDAC inhibitors observed in animal models of HD. Acknowledgements: This work was supported by a grant from the HighQ Foundation, the Calouste Gulbenkian Foundation and Fundação para a Ciência e Tecnologia

Abstract (EN): Huntington’s disease (HD) is a progressive and fatal neurological disorder caused by a mutant form of huntingtin (htt). Excitotoxicity and transcriptional deregulation are believed to play an important role in the selective degeneration of striatal neurons in HD. Histone deacetylase (HDAC) inhibitors promote transcriptional activation and were shown to be neuroprotective, improving survival of HD transgenic mice. However, the precise cellular changes that are ultimately responsible for neuroprotection remain unknown. In the present study we tested the hypothesis that HDAC inhibitors improve the cellular mechanisms involved in the maintenance of Ca2+ homeostasis, thus protecting neurons from excitotoxicity. We used two HD models expressing full-length mutant htt: immortalized striatal progenitor cells (STHdh) from knock-in mice and primary striatal neurons from YAC128 mice. Dynamic changes in intracellular Ca2+, mitochondrial membrane potential (Δψm) and somatic swelling were continuously monitored in single cells by fluorescence microscopy. Expression of normal and mutant htt, and levels of histone acetylation following treatment with HDAC inhibitors were assessed by Western blotting. Challenge with the Ca2+ ionophore 4-BrA23187 or brief NMDA-receptor activation were used as excitotoxic stimuli in STHdh cells or striatal neurons, respectively. Recovery from excitotoxic stimuli was influenced by pharmacological manipulation of Δψm, highly suggesting mitochondrial involvement which was further emphasized by experiments performed in glucose-free, pyruvate-based media. In both HD models, cells expressing mutant htt presented a significantly delayed recovery from excitotoxic stimuli when compared to wild-type controls. This delayed recovery is associated with a slower restoration of intracellular Ca2+, mitochondrial depolarization and somatic swelling. In both HD models, recovery was improved by protracted treatment with HDAC inhibitors, sodium butyrate (SB) or trichostatin A (TSA). Improved recovery was more pronounced for SB than for TSA treatment, in agreement with changes in histone acetylation. These results, in two distinct HD models, suggest an overall ability of HDAC inhibitors to improve the homeostatic response to excitotoxicity through more efficient Ca2+-handling. Furthermore, population analysis of striatal neurons revealed the existence of subpopulations refractory to treatment. Taken together, these results provide an in vitro explanation for neuroprotective effects of HDAC inhibitors observed in animal models of HD. Acknowledgements: This work was supported by a grant from the HighQ Foundation, the Calouste Gulbenkian Foundation and Fundação para a Ciência e Tecnologia

Language: Portuguese

Type (Professor's evaluation): Scientific