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Cystamine and ethyl-eicosapentaenoic acid treatment fail to prevent malonate-induced striatal toxicity in mice
Neurobiology of Aging 32 (2011) 2326.e1–2326.e4 www.elsevier.com/locate/neuaging
Negative results
Cystamine and ethyl-eicosapentaenoic acid treatment fail to prevent malonate-induced striatal toxicity in mice Saskia N. Sivananthan, Blair R. Leavitt* Department of Medical Genetics and Centre for Molecular Medicine and Therapeutics, British Columbia, Canada Research Institute for Children’s and Women’s Health, University of British Columbia, Vancouver, British Columbia, Canada Received 1 November 2010; received in revised form 19 April 2011; accepted 25 May 2011
Abstract Cystamine has demonstrated neuroprotective activity in a variety of studies, and is currently being evaluated in a human clinical trial in Huntington’s disease (HD). Cystamine treatment of various genetic models of HD demonstrated protection against neurodegeneration and/or improvement in behavior. Given the need for a rapid screening tool for HD therapeutics, we assessed the potential therapeutic benefits of cystamine in a short-term acute toxicity murine model of striatal cell death. Cystamine did not provide neuroprotection against bilateral intrastriatal malonate injections in mice as measured by lesion size, loss of striatal volume, or decreased striatal neuronal counts. Similar results were obtained for treatment with another potential therapeutic agent that was protective in genetic mouse models of HD, the essential fatty acid ethyl-eicosapentaenoic acid. Our findings suggest that this toxic model is not reflective or predictive of findings in genetic mouse models, and may not be useful as a preclinical screen for HD therapeutics. © 2011 Elsevier Inc. All rights reserved. Keywords: Huntington disease; Mouse models; Malonate; Cystamine; Neurodegeneration; Striatum
1. Introduction Huntington’s disease (HD) is an autosomal dominant neurodegenerative disease caused by a polyglutamine expansion in the huntingtin protein encoded by the HTT gene (the Huntington’s Disease Collaborative Research Group, 1993). Though the cause of neuronal death in HD is still unknown, a leading hypothesis is that HD may arise due to impaired energy metabolism produced by mitochondrial dysfunction (Beal, 1992). Malonate, a well-known inhibitor of the mitochondrial Complex II enzyme succinate dehydrogenase, competitively binds and depletes adenosine trisphosphate production. Intrastriatal malonate injections in rats induce selective neuropathology that has been sug* Corresponding author at: Centre for Molecular Medicine and Therapeutics, BC Research Institute for Women and Children’s Health, Department of Medical Genetics, University of British Columbia, 950 West 28th Avenue, Vancouver, BC, V5Z 4H4, Canada. Tel.: ⫹1 604 875 3801; fax: ⫹1 604 875 3840. E-mail address: [email protected] (B.R. Leavitt). 0197-4580/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.neurobiolaging.2011.05.020
gested to represent a toxic model of HD. Cystamine, a potent free radical scavenger, antioxidant, and transglutaminase inhibitor, has been examined extensively for its neuroprotective ability. In mice, cystamine protected against peripheral administration of the mitochondrial Complex II toxin 3-nitropropionic acid (3-NP) which has also been used to model HD. Cystamine treatment of various genetic models of HD including the R6/1, R6/2, and YAC128 mouse models all demonstrated protection against neurodegeneration or improvement in behavior (Dedeoglu et al., 2002; Van Raamsdonk et al., 2005a). Eicosapentaenoic acid (EPA) is an essential fatty acid that has potential therapeutic properties (Das and Vaddadi, 2004). Studies have demonstrated that EPA can be anti-inflammatory (Babcock et al., 2000) and enhance mitochondrial function (Frøyland et al., 1997). Ethyl-EPA was found to have benefit in genetic models of HD (Clifford et al., 2002; Van Raamsdonk et al., 2005b) and recent studies in which ethyl-EPA was delivered orally to patients with HD were reported to result in mild motor and cognitive improvement (Puri et al.,
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Fig. 1. Cystamine treatment did not prevent any of the effects of malonate toxicity in the striatum. Cystamine was administered orally in drinking water for 2 weeks prior to bilateral intrastriatal injections. Treatment was continued for another week postinjection. Treated and untreated mice received intrastriatal malonate injections, while control mice received phosphate-buffered saline injections. Photomicrographs of representative Fluoro-Jade stained sections from wild type (WT) FVB mice. (A) Representative intermediate lesion produced at a dose of 0.6 M. Lesions appeared be diffuse with dispersed Fluoro-Jade positive cells. (B) Analysis of striatal volume showed significant shrinkage of striatal volume in the cystamine treated mice compared with control mice. Cystamine treatment did not improve striatal volume compared with untreated mice. (C) Analysis of striatal neuronal count revealed a small statistically significant decrease in neuronal count between treated and control mice, and untreated and control mice, but not between treated and untreated mice. (D) Lesion volume induced by malonate injection was statistically higher in cystamine-treated mice compared with untreated mice. However, these results were not correlated in striatal volume and striatal neuronal count. Control mice had no Fluoro-Jade positive lesions. n ⫽ 8 WT untreated, n ⫽ 7 WT cystamine-treated, n ⫽ 8 WT control. Error bars show standard error of the mean (SEM). * p ⬍ 0.05; ** p ⬍ 0.01; *** p ⬍ 0.001.
2005). In view of the existing data on EPA and relevance to ongoing human cystamine trials in HD, we examined whether the therapeutic benefits provided by Cystamine or EPA would be reproducible in this short-term acute toxicity model of HD. 2. Materials and methods Wild type FVB/N mice (Charles River, Wilmington, MA, USA), 3– 4 months old, were treated for a total of 3 weeks with cystamine delivered in drinking water and for 5 weeks with ethyl-EPA administered orally in the powdered chow. Intrastriatal injections of malonate were administered to cystamine-treated mice 2 weeks after treatment was initiated, and 4 weeks after treatment for ethyl-EPA treated mice. Blind neuropathological analysis that measured lesion site, striatal volume, and size was conducted and analyzed via repeated measures of analysis of variance (ANOVA). 3. Results Cystamine did not provide neuroprotection against bilateral intrastriatal malonate injections in mice. Lesion volume was used as the primary outcome measure, along with
striatal volume and striatal neuronal counts as secondary measures. A malonate dose of 0.6 M was used which produced intermediate lesion sizes (Fig. 1A). No benefit to cystamine treatment was demonstrated in striatal volume loss (Fig. 1B) or striatal neuronal counts (Fig. 1C). Lesion volume was slightly increased in cystamine treated mice versus untreated mice (Fig. 1D) though this was not correlated with our other outcome measures. Similarly, treatment with ethyl-EPA did not provide neuroprotection against intrastriatally injected malonate in these mice as measured by striatal lesion size (Fig. 2B), striatal volume (Fig. 2C), and striatal neuronal numbers (Fig. 2D). Please refer to the online supplement for additional information. 4. Discussion In this study, cystamine treatment provided no improvement in lesion size, striatal volume, or striatal neuronal counts following intrastriatal malonate injections in mice. This is in contrast to findings in which an identical regimen of cystamine treatment in transgenic mouse models of HD significantly decreased neuronal atrophy suggesting that a short-term acute toxicity model is not necessarily predictive of the response in genetic mouse
S.N. Sivananthan, B.R. Leavitt / Neurobiology of Aging 32 (2011) 2326.e1–2326.e4
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Fig. 2. Treatment of mice with ethyl-eicosapentaenoic acid (EPA) did not prevent neuropathology caused by malonate-induced striatal toxicity. Mice were treated with 1% ethyl-EPA orally for 5 weeks and received bilateral intrastriatal injections of malonate at week 4. (A) To ensure EPA was efficiently administered to treated animals, red blood cell membranes were isolated to measure percentage of EPA in blood. Treated mice that received ethyl-EPA in chow showed an increased level of EPA in red blood cell membranes demonstrating successful administration of EPA. (B) Analysis of lesion volume showed significant striatal neuronal death, which was not improved by ethyl-EPA treatment. (C) Malonate-induced striatal lesion caused striatal volume shrinkage, however, EPA treatment did not significantly improve volume shrinkage. (D) Similarly, EPA did not prevent neuronal loss in treated mice. n ⫽ 8 wild type untreated, n ⫽ 9 wild type EPA-treated. Error bars show standard error of the mean SEM. * p ⬍ 0.05; ** p ⬍ 0.01; *** p ⬍ 0.001.
models of HD. Our goal was to test a short-term neurotoxin model of HD and assess its use as a rapid preclinical screening tool for HD therapeutics. While intrastriatal injections of malonate reliably reproduce certain aspects of HD neuropathology, some therapeutic agents may not be neuroprotective in this form of acute toxic neuronal death. Cystamine was found to be neuroprotective in previous studies of mice given interperitonal injections of the mitochondrial II inhibitor 3-nitropropionic acid (Fox et al., 2004). The difference in results may be explained by systemic administration of toxin in the previous studies and direct central administration in this study. Cystamine appears to be neuroprotective in slowly progressive genetic models of HD, such as transgenic mouse models, but not effective against the acute neuronal death caused by direct intrastriatal injection. These data suggest that this toxic model should not be used as a preclinical screen for HD therapeutics. Disclosure statement Both authors declare that they do not have any actual or potential conflicts of interest. Dr. Blair Leavitt was previously a coprinciple investigator on 2 human trials of ethyl-EPA sponsored by Laxdale/ Amarin Neuroscience, and in the past has been a paid expert presenter at the EMEA and FDA regarding these studies and this compound for Laxdale, Ltd. No relationship still exists with this company.
Acknowledgements We thank Ge Lu for all technical assistance as well as Ms. Sheena Rowbottom and Dr. Crispin Bennett (Laxdale, Ltd) for performing RBC fatty acid analysis. This work was supported by CHDI, CIHR, and MSFHR. Ethyl-eicosapentaenoic acid was provided by Laxdale, Ltd. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.neurobiolaging. 2011.05.020.
References Babcock, T., Helton, W.S., Espat, N.J., 2000. Eicosapentaenoic acid (EPA): an antiinflammatory omega-3 fat with potential clinical applications. Nutrition 16, 1116 –1118. Beal, M.F., 1992. Does impairment of energy metabolism result in excitotoxic neuronal death in neurodegenerative illnesses. Ann. Neurol. 31, 119 –130. Clifford, J.J., Drago, J., Natoli, A.L., Wong, J.Y., Kinsella, A., Waddington, J.L., Vaddadi, K.S., 2002. Essential fatty acids given from conception prevent topographies of motor deficit in a transgenic model of Huntington’s disease. Neuroscience 109, 81– 88. Das, U.N., Vaddadi, K.S., 2004. Essential fatty acids in Huntington’s disease. Nutrition 20, 942–947. Dedeoglu, A., Kubilus, J.K., Jeitner, T.M., Matson, S.A., Bogdanov, M., Kowall, N.W., Matson, W.R., Cooper, A.J., Ratan, R.R., Beal, M.F., Hersch, S.M., Ferrante, R.J., 2002. Therapeutic effects of
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S.N. Sivananthan, B.R. Leavitt / Neurobiology of Aging 32 (2011) 2326.e1–2326.e4
cystamine in a murine model of Huntington’s disease. J. Neurosci. 22, 8942– 8950. Fox, J.H., Barber, D.S., Singh, B., Zucker, B., Swindell, M.K., Norflus, F., Buzescu, R., Chopra, R., Ferrante, R.J., Kazantsev, A., Hersch, S.M., 2004. Cystamine increases L-cysteine levels in Huntington’s disease transgenic mouse brain and in a PC12 model of polyglutamine aggregation. J. Neurochem. 91, 413– 422. Frøyland, L., Madsen, L., Vaagenes, H., Totland, G.K., Auwerx, J., Kryvi, H., Staels, B., Berge, R.K., 1997. Mitochondrion is the principal target for nutritional and pharmacological control of triglyceride metabolism. J. Lipid Res. 38, 1851–1858. Puri, B.K., Bydder, G.M., Counsell, S.J., Corridan, B.J., Richardson, A.J., Hajnal, J.V., Appel, C., Mckee, H.M., Vaddadi, K.S., Horrobin, D.F., 2002. MRI and neuropsychological improvement in Hun-
tington disease following ethyl-EPA treatment. Neuroreport 13, 123–126. The Huntington’s Disease Collaborative Research Group, 1993. A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington’s disease chromosome. Cell 72, 971–983. Van Raamsdonk, J.M., Pearson, J., Bailey, C.D.C., Rogers, D.A., Johnson, G.V.W., Hayden, M.R., Leavitt, B.R., 2005a. Cystamine treatment is neuroprotective in the YAC128 mouse model of Huntington’s disease. J. Neurochem. 95, 210 –220. Van Raamsdonk, J.M., Pearson, J., Rogers, D.A., Lu, G., Barakauskas, V.E., Barr, A.M., Honer, W.G., Hayden, M.R., Leavitt, B.R., 2005b. Ethyl-EPA treatment improves motor dysfunction, but not neurodegeneration in the YAC128 mouse model of Huntington disease. Exp. Neurol. 196, 266 –272.
Negative results
Cystamine and ethyl-eicosapentaenoic acid treatment fail to prevent malonate-induced striatal toxicity in mice Saskia N. Sivananthan, Blair R. Leavitt* Department of Medical Genetics and Centre for Molecular Medicine and Therapeutics, British Columbia, Canada Research Institute for Children’s and Women’s Health, University of British Columbia, Vancouver, British Columbia, Canada Received 1 November 2010; received in revised form 19 April 2011; accepted 25 May 2011
Abstract Cystamine has demonstrated neuroprotective activity in a variety of studies, and is currently being evaluated in a human clinical trial in Huntington’s disease (HD). Cystamine treatment of various genetic models of HD demonstrated protection against neurodegeneration and/or improvement in behavior. Given the need for a rapid screening tool for HD therapeutics, we assessed the potential therapeutic benefits of cystamine in a short-term acute toxicity murine model of striatal cell death. Cystamine did not provide neuroprotection against bilateral intrastriatal malonate injections in mice as measured by lesion size, loss of striatal volume, or decreased striatal neuronal counts. Similar results were obtained for treatment with another potential therapeutic agent that was protective in genetic mouse models of HD, the essential fatty acid ethyl-eicosapentaenoic acid. Our findings suggest that this toxic model is not reflective or predictive of findings in genetic mouse models, and may not be useful as a preclinical screen for HD therapeutics. © 2011 Elsevier Inc. All rights reserved. Keywords: Huntington disease; Mouse models; Malonate; Cystamine; Neurodegeneration; Striatum
1. Introduction Huntington’s disease (HD) is an autosomal dominant neurodegenerative disease caused by a polyglutamine expansion in the huntingtin protein encoded by the HTT gene (the Huntington’s Disease Collaborative Research Group, 1993). Though the cause of neuronal death in HD is still unknown, a leading hypothesis is that HD may arise due to impaired energy metabolism produced by mitochondrial dysfunction (Beal, 1992). Malonate, a well-known inhibitor of the mitochondrial Complex II enzyme succinate dehydrogenase, competitively binds and depletes adenosine trisphosphate production. Intrastriatal malonate injections in rats induce selective neuropathology that has been sug* Corresponding author at: Centre for Molecular Medicine and Therapeutics, BC Research Institute for Women and Children’s Health, Department of Medical Genetics, University of British Columbia, 950 West 28th Avenue, Vancouver, BC, V5Z 4H4, Canada. Tel.: ⫹1 604 875 3801; fax: ⫹1 604 875 3840. E-mail address: [email protected] (B.R. Leavitt). 0197-4580/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.neurobiolaging.2011.05.020
gested to represent a toxic model of HD. Cystamine, a potent free radical scavenger, antioxidant, and transglutaminase inhibitor, has been examined extensively for its neuroprotective ability. In mice, cystamine protected against peripheral administration of the mitochondrial Complex II toxin 3-nitropropionic acid (3-NP) which has also been used to model HD. Cystamine treatment of various genetic models of HD including the R6/1, R6/2, and YAC128 mouse models all demonstrated protection against neurodegeneration or improvement in behavior (Dedeoglu et al., 2002; Van Raamsdonk et al., 2005a). Eicosapentaenoic acid (EPA) is an essential fatty acid that has potential therapeutic properties (Das and Vaddadi, 2004). Studies have demonstrated that EPA can be anti-inflammatory (Babcock et al., 2000) and enhance mitochondrial function (Frøyland et al., 1997). Ethyl-EPA was found to have benefit in genetic models of HD (Clifford et al., 2002; Van Raamsdonk et al., 2005b) and recent studies in which ethyl-EPA was delivered orally to patients with HD were reported to result in mild motor and cognitive improvement (Puri et al.,
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Fig. 1. Cystamine treatment did not prevent any of the effects of malonate toxicity in the striatum. Cystamine was administered orally in drinking water for 2 weeks prior to bilateral intrastriatal injections. Treatment was continued for another week postinjection. Treated and untreated mice received intrastriatal malonate injections, while control mice received phosphate-buffered saline injections. Photomicrographs of representative Fluoro-Jade stained sections from wild type (WT) FVB mice. (A) Representative intermediate lesion produced at a dose of 0.6 M. Lesions appeared be diffuse with dispersed Fluoro-Jade positive cells. (B) Analysis of striatal volume showed significant shrinkage of striatal volume in the cystamine treated mice compared with control mice. Cystamine treatment did not improve striatal volume compared with untreated mice. (C) Analysis of striatal neuronal count revealed a small statistically significant decrease in neuronal count between treated and control mice, and untreated and control mice, but not between treated and untreated mice. (D) Lesion volume induced by malonate injection was statistically higher in cystamine-treated mice compared with untreated mice. However, these results were not correlated in striatal volume and striatal neuronal count. Control mice had no Fluoro-Jade positive lesions. n ⫽ 8 WT untreated, n ⫽ 7 WT cystamine-treated, n ⫽ 8 WT control. Error bars show standard error of the mean (SEM). * p ⬍ 0.05; ** p ⬍ 0.01; *** p ⬍ 0.001.
2005). In view of the existing data on EPA and relevance to ongoing human cystamine trials in HD, we examined whether the therapeutic benefits provided by Cystamine or EPA would be reproducible in this short-term acute toxicity model of HD. 2. Materials and methods Wild type FVB/N mice (Charles River, Wilmington, MA, USA), 3– 4 months old, were treated for a total of 3 weeks with cystamine delivered in drinking water and for 5 weeks with ethyl-EPA administered orally in the powdered chow. Intrastriatal injections of malonate were administered to cystamine-treated mice 2 weeks after treatment was initiated, and 4 weeks after treatment for ethyl-EPA treated mice. Blind neuropathological analysis that measured lesion site, striatal volume, and size was conducted and analyzed via repeated measures of analysis of variance (ANOVA). 3. Results Cystamine did not provide neuroprotection against bilateral intrastriatal malonate injections in mice. Lesion volume was used as the primary outcome measure, along with
striatal volume and striatal neuronal counts as secondary measures. A malonate dose of 0.6 M was used which produced intermediate lesion sizes (Fig. 1A). No benefit to cystamine treatment was demonstrated in striatal volume loss (Fig. 1B) or striatal neuronal counts (Fig. 1C). Lesion volume was slightly increased in cystamine treated mice versus untreated mice (Fig. 1D) though this was not correlated with our other outcome measures. Similarly, treatment with ethyl-EPA did not provide neuroprotection against intrastriatally injected malonate in these mice as measured by striatal lesion size (Fig. 2B), striatal volume (Fig. 2C), and striatal neuronal numbers (Fig. 2D). Please refer to the online supplement for additional information. 4. Discussion In this study, cystamine treatment provided no improvement in lesion size, striatal volume, or striatal neuronal counts following intrastriatal malonate injections in mice. This is in contrast to findings in which an identical regimen of cystamine treatment in transgenic mouse models of HD significantly decreased neuronal atrophy suggesting that a short-term acute toxicity model is not necessarily predictive of the response in genetic mouse
S.N. Sivananthan, B.R. Leavitt / Neurobiology of Aging 32 (2011) 2326.e1–2326.e4
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Fig. 2. Treatment of mice with ethyl-eicosapentaenoic acid (EPA) did not prevent neuropathology caused by malonate-induced striatal toxicity. Mice were treated with 1% ethyl-EPA orally for 5 weeks and received bilateral intrastriatal injections of malonate at week 4. (A) To ensure EPA was efficiently administered to treated animals, red blood cell membranes were isolated to measure percentage of EPA in blood. Treated mice that received ethyl-EPA in chow showed an increased level of EPA in red blood cell membranes demonstrating successful administration of EPA. (B) Analysis of lesion volume showed significant striatal neuronal death, which was not improved by ethyl-EPA treatment. (C) Malonate-induced striatal lesion caused striatal volume shrinkage, however, EPA treatment did not significantly improve volume shrinkage. (D) Similarly, EPA did not prevent neuronal loss in treated mice. n ⫽ 8 wild type untreated, n ⫽ 9 wild type EPA-treated. Error bars show standard error of the mean SEM. * p ⬍ 0.05; ** p ⬍ 0.01; *** p ⬍ 0.001.
models of HD. Our goal was to test a short-term neurotoxin model of HD and assess its use as a rapid preclinical screening tool for HD therapeutics. While intrastriatal injections of malonate reliably reproduce certain aspects of HD neuropathology, some therapeutic agents may not be neuroprotective in this form of acute toxic neuronal death. Cystamine was found to be neuroprotective in previous studies of mice given interperitonal injections of the mitochondrial II inhibitor 3-nitropropionic acid (Fox et al., 2004). The difference in results may be explained by systemic administration of toxin in the previous studies and direct central administration in this study. Cystamine appears to be neuroprotective in slowly progressive genetic models of HD, such as transgenic mouse models, but not effective against the acute neuronal death caused by direct intrastriatal injection. These data suggest that this toxic model should not be used as a preclinical screen for HD therapeutics. Disclosure statement Both authors declare that they do not have any actual or potential conflicts of interest. Dr. Blair Leavitt was previously a coprinciple investigator on 2 human trials of ethyl-EPA sponsored by Laxdale/ Amarin Neuroscience, and in the past has been a paid expert presenter at the EMEA and FDA regarding these studies and this compound for Laxdale, Ltd. No relationship still exists with this company.
Acknowledgements We thank Ge Lu for all technical assistance as well as Ms. Sheena Rowbottom and Dr. Crispin Bennett (Laxdale, Ltd) for performing RBC fatty acid analysis. This work was supported by CHDI, CIHR, and MSFHR. Ethyl-eicosapentaenoic acid was provided by Laxdale, Ltd. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.neurobiolaging. 2011.05.020.
References Babcock, T., Helton, W.S., Espat, N.J., 2000. Eicosapentaenoic acid (EPA): an antiinflammatory omega-3 fat with potential clinical applications. Nutrition 16, 1116 –1118. Beal, M.F., 1992. Does impairment of energy metabolism result in excitotoxic neuronal death in neurodegenerative illnesses. Ann. Neurol. 31, 119 –130. Clifford, J.J., Drago, J., Natoli, A.L., Wong, J.Y., Kinsella, A., Waddington, J.L., Vaddadi, K.S., 2002. Essential fatty acids given from conception prevent topographies of motor deficit in a transgenic model of Huntington’s disease. Neuroscience 109, 81– 88. Das, U.N., Vaddadi, K.S., 2004. Essential fatty acids in Huntington’s disease. Nutrition 20, 942–947. Dedeoglu, A., Kubilus, J.K., Jeitner, T.M., Matson, S.A., Bogdanov, M., Kowall, N.W., Matson, W.R., Cooper, A.J., Ratan, R.R., Beal, M.F., Hersch, S.M., Ferrante, R.J., 2002. Therapeutic effects of
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S.N. Sivananthan, B.R. Leavitt / Neurobiology of Aging 32 (2011) 2326.e1–2326.e4
cystamine in a murine model of Huntington’s disease. J. Neurosci. 22, 8942– 8950. Fox, J.H., Barber, D.S., Singh, B., Zucker, B., Swindell, M.K., Norflus, F., Buzescu, R., Chopra, R., Ferrante, R.J., Kazantsev, A., Hersch, S.M., 2004. Cystamine increases L-cysteine levels in Huntington’s disease transgenic mouse brain and in a PC12 model of polyglutamine aggregation. J. Neurochem. 91, 413– 422. Frøyland, L., Madsen, L., Vaagenes, H., Totland, G.K., Auwerx, J., Kryvi, H., Staels, B., Berge, R.K., 1997. Mitochondrion is the principal target for nutritional and pharmacological control of triglyceride metabolism. J. Lipid Res. 38, 1851–1858. Puri, B.K., Bydder, G.M., Counsell, S.J., Corridan, B.J., Richardson, A.J., Hajnal, J.V., Appel, C., Mckee, H.M., Vaddadi, K.S., Horrobin, D.F., 2002. MRI and neuropsychological improvement in Hun-
tington disease following ethyl-EPA treatment. Neuroreport 13, 123–126. The Huntington’s Disease Collaborative Research Group, 1993. A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington’s disease chromosome. Cell 72, 971–983. Van Raamsdonk, J.M., Pearson, J., Bailey, C.D.C., Rogers, D.A., Johnson, G.V.W., Hayden, M.R., Leavitt, B.R., 2005a. Cystamine treatment is neuroprotective in the YAC128 mouse model of Huntington’s disease. J. Neurochem. 95, 210 –220. Van Raamsdonk, J.M., Pearson, J., Rogers, D.A., Lu, G., Barakauskas, V.E., Barr, A.M., Honer, W.G., Hayden, M.R., Leavitt, B.R., 2005b. Ethyl-EPA treatment improves motor dysfunction, but not neurodegeneration in the YAC128 mouse model of Huntington disease. Exp. Neurol. 196, 266 –272.