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Oral N-acetyl-cysteine attenuates loss of dopaminergic terminals in alpha-synuclein overexpressing mice.

Clark J, Clore EL, Zheng K, Adame A, Masliah E, Simon DK - PLoS ONE (2010)

Bottom Line: Despite the transient nature of the impact of NAC on brain glutathione, the loss of dopaminergic terminals at 1 year associated with SNCA overexpression was significantly attenuated by NAC supplementation, as measured by immunoreactivity for tyrosine hydroxylase in the striatum (p = 0.007; unpaired, two-tailed t-test), with a similar but nonsignificant trend for dopamine transporter (DAT) immunoreactivity.This was associated with a decrease in nuclear NFkappaB localization and an increase in cytoplasmic localization of NFkappaB in the NAC-treated transgenics.Overall, these results indicate that oral NAC supplementation decreases SNCA levels in brain and partially protects against loss of dopaminergic terminals associated with overexpression of alpha-synuclein in this model.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America.

ABSTRACT
Levels of glutathione are lower in the substantia nigra (SN) early in Parkinson's disease (PD) and this may contribute to mitochondrial dysfunction and oxidative stress. Oxidative stress may increase the accumulation of toxic forms of alpha-synuclein (SNCA). We hypothesized that supplementation with n-acetylcysteine (NAC), a source of cysteine--the limiting amino acid in glutathione synthesis, would protect against alpha-synuclein toxicity. Transgenic mice overexpressing wild-type human alpha-synuclein drank water supplemented with NAC or control water supplemented with alanine from ages 6 weeks to 1 year. NAC increased SN levels of glutathione within 5-7 weeks of treatment; however, this increase was not sustained at 1 year. Despite the transient nature of the impact of NAC on brain glutathione, the loss of dopaminergic terminals at 1 year associated with SNCA overexpression was significantly attenuated by NAC supplementation, as measured by immunoreactivity for tyrosine hydroxylase in the striatum (p = 0.007; unpaired, two-tailed t-test), with a similar but nonsignificant trend for dopamine transporter (DAT) immunoreactivity. NAC significantly decreased the levels of human SNCA in the brains of PDGFb-SNCA transgenic mice compared to alanine treated transgenics. This was associated with a decrease in nuclear NFkappaB localization and an increase in cytoplasmic localization of NFkappaB in the NAC-treated transgenics. Overall, these results indicate that oral NAC supplementation decreases SNCA levels in brain and partially protects against loss of dopaminergic terminals associated with overexpression of alpha-synuclein in this model.

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NAC increases striatal area occupied by TH-positive terminals in SNCA-overexpressing mice at 12 months of age.A–D. Representative images of TH-immunostained 30 µm sections of alanine or NAC-treated wild-type or transgenic mouse striatum. A. Wild-type, alanine treated; B. Wild-type, NAC treated; C. Transgenic, alanine treated; D. Transgenic, NAC treated. E. Density of TH-positive terminals in the striatum of alanine or NAC-treated wild-type or transgenic mouse striatum. F. Density of DAT-positive terminals in the striatum of alanine or NAC-treated wild-type or transgenic mouse striatum. Data in E and F were analyzed using a 2-tailed Student's t-test. All relevant statistically significant comparisons are indicated on the graph. WT ALA N = 4, WT NAC  = 6, TG ALA  = 4, TG NAC  = 3.
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pone-0012333-g001: NAC increases striatal area occupied by TH-positive terminals in SNCA-overexpressing mice at 12 months of age.A–D. Representative images of TH-immunostained 30 µm sections of alanine or NAC-treated wild-type or transgenic mouse striatum. A. Wild-type, alanine treated; B. Wild-type, NAC treated; C. Transgenic, alanine treated; D. Transgenic, NAC treated. E. Density of TH-positive terminals in the striatum of alanine or NAC-treated wild-type or transgenic mouse striatum. F. Density of DAT-positive terminals in the striatum of alanine or NAC-treated wild-type or transgenic mouse striatum. Data in E and F were analyzed using a 2-tailed Student's t-test. All relevant statistically significant comparisons are indicated on the graph. WT ALA N = 4, WT NAC  = 6, TG ALA  = 4, TG NAC  = 3.

Mentions: Transgenic mice overexpressing SNCA showed a mean decrease of 45.2% (95% CI 31.5–59.0%; p<0.001) in the percentage of striatal area covered by tyrosine hydroxylase positive (TH+) terminals compared to wild-type littermate controls at 1 year of age (Fig. 1A, 1C,1E). This loss of TH+ terminals was significantly attenuated by chronic oral NAC supplementation beginning at 3 weeks of age (p = 0.007; Fig. 1D, 1E). NAC supplementation did not significantly alter the percentage of striatal area covered by TH+ terminals in wild-type mice. As an additional measure of dopaminergic terminals in the striatum, the percentage of striatal area covered by dopamine transporter positive (DAT+) terminals also was assessed (Fig. 1F). Similar to the findings for TH+ terminals, the percentage of striatal area covered DAT+ terminals was reduced by 43.2% (95% CI 12.0–74.3%; p = 0.015) in SNCA overexpressing mice compared to littermate controls (Fig. 1F). There was a non-significant trend towards protection against this loss of striatal DAT+ terminals by chronic oral NAC supplementation (p = 0.19).


Oral N-acetyl-cysteine attenuates loss of dopaminergic terminals in alpha-synuclein overexpressing mice.

Clark J, Clore EL, Zheng K, Adame A, Masliah E, Simon DK - PLoS ONE (2010)

NAC increases striatal area occupied by TH-positive terminals in SNCA-overexpressing mice at 12 months of age.A–D. Representative images of TH-immunostained 30 µm sections of alanine or NAC-treated wild-type or transgenic mouse striatum. A. Wild-type, alanine treated; B. Wild-type, NAC treated; C. Transgenic, alanine treated; D. Transgenic, NAC treated. E. Density of TH-positive terminals in the striatum of alanine or NAC-treated wild-type or transgenic mouse striatum. F. Density of DAT-positive terminals in the striatum of alanine or NAC-treated wild-type or transgenic mouse striatum. Data in E and F were analyzed using a 2-tailed Student's t-test. All relevant statistically significant comparisons are indicated on the graph. WT ALA N = 4, WT NAC  = 6, TG ALA  = 4, TG NAC  = 3.
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getmorefigures.php?uid=PMC2925900&req=5

pone-0012333-g001: NAC increases striatal area occupied by TH-positive terminals in SNCA-overexpressing mice at 12 months of age.A–D. Representative images of TH-immunostained 30 µm sections of alanine or NAC-treated wild-type or transgenic mouse striatum. A. Wild-type, alanine treated; B. Wild-type, NAC treated; C. Transgenic, alanine treated; D. Transgenic, NAC treated. E. Density of TH-positive terminals in the striatum of alanine or NAC-treated wild-type or transgenic mouse striatum. F. Density of DAT-positive terminals in the striatum of alanine or NAC-treated wild-type or transgenic mouse striatum. Data in E and F were analyzed using a 2-tailed Student's t-test. All relevant statistically significant comparisons are indicated on the graph. WT ALA N = 4, WT NAC  = 6, TG ALA  = 4, TG NAC  = 3.
Mentions: Transgenic mice overexpressing SNCA showed a mean decrease of 45.2% (95% CI 31.5–59.0%; p<0.001) in the percentage of striatal area covered by tyrosine hydroxylase positive (TH+) terminals compared to wild-type littermate controls at 1 year of age (Fig. 1A, 1C,1E). This loss of TH+ terminals was significantly attenuated by chronic oral NAC supplementation beginning at 3 weeks of age (p = 0.007; Fig. 1D, 1E). NAC supplementation did not significantly alter the percentage of striatal area covered by TH+ terminals in wild-type mice. As an additional measure of dopaminergic terminals in the striatum, the percentage of striatal area covered by dopamine transporter positive (DAT+) terminals also was assessed (Fig. 1F). Similar to the findings for TH+ terminals, the percentage of striatal area covered DAT+ terminals was reduced by 43.2% (95% CI 12.0–74.3%; p = 0.015) in SNCA overexpressing mice compared to littermate controls (Fig. 1F). There was a non-significant trend towards protection against this loss of striatal DAT+ terminals by chronic oral NAC supplementation (p = 0.19).

Bottom Line: Despite the transient nature of the impact of NAC on brain glutathione, the loss of dopaminergic terminals at 1 year associated with SNCA overexpression was significantly attenuated by NAC supplementation, as measured by immunoreactivity for tyrosine hydroxylase in the striatum (p = 0.007; unpaired, two-tailed t-test), with a similar but nonsignificant trend for dopamine transporter (DAT) immunoreactivity.This was associated with a decrease in nuclear NFkappaB localization and an increase in cytoplasmic localization of NFkappaB in the NAC-treated transgenics.Overall, these results indicate that oral NAC supplementation decreases SNCA levels in brain and partially protects against loss of dopaminergic terminals associated with overexpression of alpha-synuclein in this model.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Beth Israel Deaconess Medical Center, Boston, Massachusetts, United States of America.

ABSTRACT
Levels of glutathione are lower in the substantia nigra (SN) early in Parkinson's disease (PD) and this may contribute to mitochondrial dysfunction and oxidative stress. Oxidative stress may increase the accumulation of toxic forms of alpha-synuclein (SNCA). We hypothesized that supplementation with n-acetylcysteine (NAC), a source of cysteine--the limiting amino acid in glutathione synthesis, would protect against alpha-synuclein toxicity. Transgenic mice overexpressing wild-type human alpha-synuclein drank water supplemented with NAC or control water supplemented with alanine from ages 6 weeks to 1 year. NAC increased SN levels of glutathione within 5-7 weeks of treatment; however, this increase was not sustained at 1 year. Despite the transient nature of the impact of NAC on brain glutathione, the loss of dopaminergic terminals at 1 year associated with SNCA overexpression was significantly attenuated by NAC supplementation, as measured by immunoreactivity for tyrosine hydroxylase in the striatum (p = 0.007; unpaired, two-tailed t-test), with a similar but nonsignificant trend for dopamine transporter (DAT) immunoreactivity. NAC significantly decreased the levels of human SNCA in the brains of PDGFb-SNCA transgenic mice compared to alanine treated transgenics. This was associated with a decrease in nuclear NFkappaB localization and an increase in cytoplasmic localization of NFkappaB in the NAC-treated transgenics. Overall, these results indicate that oral NAC supplementation decreases SNCA levels in brain and partially protects against loss of dopaminergic terminals associated with overexpression of alpha-synuclein in this model.

Show MeSH
Related in: MedlinePlus