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PGC-1α activity in nigral dopamine neurons determines vulnerability to α-synuclein.

Ciron C, Zheng L, Bobela W, Knott GW, Leone TC, Kelly DP, Schneider BL - Acta Neuropathol Commun (2015)

Bottom Line: Mitochondrial dysfunction and oxidative stress are critical factors in the pathogenesis of age-dependent neurodegenerative diseases.PGC-1α, a master regulator of mitochondrial biogenesis and cellular antioxidant defense, has emerged as a possible therapeutic target for Parkinson's disease, with important roles in the function and survival of dopaminergic neurons in the substantia nigra.The objective of this study is to determine if the loss of PGC-1α activity contributes to α-synuclein-induced degeneration.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: Mitochondrial dysfunction and oxidative stress are critical factors in the pathogenesis of age-dependent neurodegenerative diseases. PGC-1α, a master regulator of mitochondrial biogenesis and cellular antioxidant defense, has emerged as a possible therapeutic target for Parkinson's disease, with important roles in the function and survival of dopaminergic neurons in the substantia nigra. The objective of this study is to determine if the loss of PGC-1α activity contributes to α-synuclein-induced degeneration.

Results: We explore the vulnerability of PGC-1α mice to the accumulation of human α-synuclein in nigral neurons, and assess the neuroprotective effect of AAV-mediated PGC-1α expression in this experimental model. Using neuronal cultures derived from these mice, mitochondrial respiration and production of reactive oxygen species are assessed in conditions of human α-synuclein overexpression. We find ultrastructural evidence for abnormal mitochondria and fragmented endoplasmic reticulum in the nigral dopaminergic neurons of PGC-1α mice. Furthermore, PGC-1α nigral neurons are more prone to degenerate following overexpression of human α-synuclein, an effect more apparent in male mice. PGC-1α overexpression restores mitochondrial morphology, oxidative stress detoxification and basal respiration, which is consistent with the observed neuroprotection against α-synuclein toxicity in male PGC-1α mice.

Conclusions: Altogether, our results highlight an important role for PGC-1α in controlling the mitochondrial function of nigral neurons accumulating α-synuclein, which may be critical for gender-dependent vulnerability to Parkinson's disease.

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Alpha-synuclein impairs basal mitochondrial respiration in PGC1α-KO neurons. Primary neuronal cultures were derived from the cerebral cortex of PGC1α-KO mice and co-transduced with either a non-coding AAV vector (NCV), an AAV vector encoding human aSyn, or with an AAV vector encoding PGC-1α (PGC1α). (a,b) Basal oxygen consumption was measured from individual cultures in the conditions NCV alone (n = 15), NCV + aSyn (n = 20), NCV + PGC1α (n = 19) and aSyn + PGC1α (n = 15). (a,d) Some of the individual cultures were treated with CCCP, in order to determine the percentage of spare respiratory capacity (d): NCV alone (n = 6), NCV + aSyn (n = 10), NCV + PGC1α (n = 4) and aSyn + PGC1α (n = 5). Other individual cultures were treated with oligomycin to determine (c) the oligomycin-resistant residual respiration and (e) the percentage of oxygen consumption used for ATP production: NCV alone (n = 9), NCV + aSyn (n = 10), NCV + PGC1α (n = 10) and aSyn + PGC1α (n = 10). Statistical analysis: two-way ANOVA with Newman-Keuls post-hoc test. (b-d): significant interaction between the aSyn and PGC1α effects, *p < 0.05; **p < 0.01; ***p < 0.001; (e): significant group effect of PGC1α, ***p < 0.001.
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Fig6: Alpha-synuclein impairs basal mitochondrial respiration in PGC1α-KO neurons. Primary neuronal cultures were derived from the cerebral cortex of PGC1α-KO mice and co-transduced with either a non-coding AAV vector (NCV), an AAV vector encoding human aSyn, or with an AAV vector encoding PGC-1α (PGC1α). (a,b) Basal oxygen consumption was measured from individual cultures in the conditions NCV alone (n = 15), NCV + aSyn (n = 20), NCV + PGC1α (n = 19) and aSyn + PGC1α (n = 15). (a,d) Some of the individual cultures were treated with CCCP, in order to determine the percentage of spare respiratory capacity (d): NCV alone (n = 6), NCV + aSyn (n = 10), NCV + PGC1α (n = 4) and aSyn + PGC1α (n = 5). Other individual cultures were treated with oligomycin to determine (c) the oligomycin-resistant residual respiration and (e) the percentage of oxygen consumption used for ATP production: NCV alone (n = 9), NCV + aSyn (n = 10), NCV + PGC1α (n = 10) and aSyn + PGC1α (n = 10). Statistical analysis: two-way ANOVA with Newman-Keuls post-hoc test. (b-d): significant interaction between the aSyn and PGC1α effects, *p < 0.05; **p < 0.01; ***p < 0.001; (e): significant group effect of PGC1α, ***p < 0.001.

Mentions: Next, we used primary cortical neurons derived from PGC1α-KO mice to explore the effect of aSyn on mitochondrial function. Neurons were transduced with AAV expressing either aSyn or PGC-1α. Seven days later, we measured extracellular oxygen flux to evaluate mitochondrial activity. Oxygen consumption rate (OCR) was assessed in basal conditions, in presence of carbonyl cyanide m-chlorophenyl hydrazone (CCCP), a compound dissipating the proton gradient across the mitochondrial membrane, and in presence of oligomycin, an inhibitor of the mitochondrial ATP synthase (Figure 6a). We observed that overexpression of aSyn induces a significant decrease in basal OCR in PGC1α-KO neurons (Figure 6b). This effect of aSyn was completely suppressed by the expression of PGC-1α. The changes in OCR appeared very similar in presence of oligomycin, indicating that the reduced respiration found in PGC1α-KO neurons expressing aSyn is not caused by any defect in ATP synthase activity. Therefore, aSyn is likely to lower the overall ETC activity, which can be corrected by restoring PGC-1α expression (Figure 6c).Figure 6


PGC-1α activity in nigral dopamine neurons determines vulnerability to α-synuclein.

Ciron C, Zheng L, Bobela W, Knott GW, Leone TC, Kelly DP, Schneider BL - Acta Neuropathol Commun (2015)

Alpha-synuclein impairs basal mitochondrial respiration in PGC1α-KO neurons. Primary neuronal cultures were derived from the cerebral cortex of PGC1α-KO mice and co-transduced with either a non-coding AAV vector (NCV), an AAV vector encoding human aSyn, or with an AAV vector encoding PGC-1α (PGC1α). (a,b) Basal oxygen consumption was measured from individual cultures in the conditions NCV alone (n = 15), NCV + aSyn (n = 20), NCV + PGC1α (n = 19) and aSyn + PGC1α (n = 15). (a,d) Some of the individual cultures were treated with CCCP, in order to determine the percentage of spare respiratory capacity (d): NCV alone (n = 6), NCV + aSyn (n = 10), NCV + PGC1α (n = 4) and aSyn + PGC1α (n = 5). Other individual cultures were treated with oligomycin to determine (c) the oligomycin-resistant residual respiration and (e) the percentage of oxygen consumption used for ATP production: NCV alone (n = 9), NCV + aSyn (n = 10), NCV + PGC1α (n = 10) and aSyn + PGC1α (n = 10). Statistical analysis: two-way ANOVA with Newman-Keuls post-hoc test. (b-d): significant interaction between the aSyn and PGC1α effects, *p < 0.05; **p < 0.01; ***p < 0.001; (e): significant group effect of PGC1α, ***p < 0.001.
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Fig6: Alpha-synuclein impairs basal mitochondrial respiration in PGC1α-KO neurons. Primary neuronal cultures were derived from the cerebral cortex of PGC1α-KO mice and co-transduced with either a non-coding AAV vector (NCV), an AAV vector encoding human aSyn, or with an AAV vector encoding PGC-1α (PGC1α). (a,b) Basal oxygen consumption was measured from individual cultures in the conditions NCV alone (n = 15), NCV + aSyn (n = 20), NCV + PGC1α (n = 19) and aSyn + PGC1α (n = 15). (a,d) Some of the individual cultures were treated with CCCP, in order to determine the percentage of spare respiratory capacity (d): NCV alone (n = 6), NCV + aSyn (n = 10), NCV + PGC1α (n = 4) and aSyn + PGC1α (n = 5). Other individual cultures were treated with oligomycin to determine (c) the oligomycin-resistant residual respiration and (e) the percentage of oxygen consumption used for ATP production: NCV alone (n = 9), NCV + aSyn (n = 10), NCV + PGC1α (n = 10) and aSyn + PGC1α (n = 10). Statistical analysis: two-way ANOVA with Newman-Keuls post-hoc test. (b-d): significant interaction between the aSyn and PGC1α effects, *p < 0.05; **p < 0.01; ***p < 0.001; (e): significant group effect of PGC1α, ***p < 0.001.
Mentions: Next, we used primary cortical neurons derived from PGC1α-KO mice to explore the effect of aSyn on mitochondrial function. Neurons were transduced with AAV expressing either aSyn or PGC-1α. Seven days later, we measured extracellular oxygen flux to evaluate mitochondrial activity. Oxygen consumption rate (OCR) was assessed in basal conditions, in presence of carbonyl cyanide m-chlorophenyl hydrazone (CCCP), a compound dissipating the proton gradient across the mitochondrial membrane, and in presence of oligomycin, an inhibitor of the mitochondrial ATP synthase (Figure 6a). We observed that overexpression of aSyn induces a significant decrease in basal OCR in PGC1α-KO neurons (Figure 6b). This effect of aSyn was completely suppressed by the expression of PGC-1α. The changes in OCR appeared very similar in presence of oligomycin, indicating that the reduced respiration found in PGC1α-KO neurons expressing aSyn is not caused by any defect in ATP synthase activity. Therefore, aSyn is likely to lower the overall ETC activity, which can be corrected by restoring PGC-1α expression (Figure 6c).Figure 6

Bottom Line: Mitochondrial dysfunction and oxidative stress are critical factors in the pathogenesis of age-dependent neurodegenerative diseases.PGC-1α, a master regulator of mitochondrial biogenesis and cellular antioxidant defense, has emerged as a possible therapeutic target for Parkinson's disease, with important roles in the function and survival of dopaminergic neurons in the substantia nigra.The objective of this study is to determine if the loss of PGC-1α activity contributes to α-synuclein-induced degeneration.

View Article: PubMed Central - PubMed

ABSTRACT

Introduction: Mitochondrial dysfunction and oxidative stress are critical factors in the pathogenesis of age-dependent neurodegenerative diseases. PGC-1α, a master regulator of mitochondrial biogenesis and cellular antioxidant defense, has emerged as a possible therapeutic target for Parkinson's disease, with important roles in the function and survival of dopaminergic neurons in the substantia nigra. The objective of this study is to determine if the loss of PGC-1α activity contributes to α-synuclein-induced degeneration.

Results: We explore the vulnerability of PGC-1α mice to the accumulation of human α-synuclein in nigral neurons, and assess the neuroprotective effect of AAV-mediated PGC-1α expression in this experimental model. Using neuronal cultures derived from these mice, mitochondrial respiration and production of reactive oxygen species are assessed in conditions of human α-synuclein overexpression. We find ultrastructural evidence for abnormal mitochondria and fragmented endoplasmic reticulum in the nigral dopaminergic neurons of PGC-1α mice. Furthermore, PGC-1α nigral neurons are more prone to degenerate following overexpression of human α-synuclein, an effect more apparent in male mice. PGC-1α overexpression restores mitochondrial morphology, oxidative stress detoxification and basal respiration, which is consistent with the observed neuroprotection against α-synuclein toxicity in male PGC-1α mice.

Conclusions: Altogether, our results highlight an important role for PGC-1α in controlling the mitochondrial function of nigral neurons accumulating α-synuclein, which may be critical for gender-dependent vulnerability to Parkinson's disease.

Show MeSH
Related in: MedlinePlus