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Modulation of mitochondrial complex I activity averts cognitive decline in multiple animal models of familial Alzheimer's Disease.

Zhang L, Zhang S, Maezawa I, Trushin S, Minhas P, Pinto M, Jin LW, Prasain K, Nguyen TD, Yamazaki Y, Kanekiyo T, Bu G, Gateno B, Chang KO, Nath KA, Nemutlu E, Dzeja P, Pang YP, Hua DH, Trushina E - EBioMedicine (2015)

Bottom Line: Furthermore, modulation of complex I activity augmented mitochondrial bioenergetics increasing coupling efficiency of respiratory chain and neuronal resistance to stress.Concomitant reduction of glycogen synthase kinase 3β activity and restoration of axonal trafficking resulted in elevated levels of neurotrophic factors and synaptic proteins in adult AD mice.Our results suggest metabolic reprogramming induced by modulation of mitochondrial complex I activity represents promising therapeutic strategy for AD.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Mayo Clinic Rochester, MN 55905, USA.

ABSTRACT

Development of therapeutic strategies to prevent Alzheimer's Disease (AD) is of great importance. We show that mild inhibition of mitochondrial complex I with small molecule CP2 reduces levels of amyloid beta and phospho-Tau and averts cognitive decline in three animal models of familial AD. Low-mass molecular dynamics simulations and biochemical studies confirmed that CP2 competes with flavin mononucleotide for binding to the redox center of complex I leading to elevated AMP/ATP ratio and activation of AMP-activated protein kinase in neurons and mouse brain without inducing oxidative damage or inflammation. Furthermore, modulation of complex I activity augmented mitochondrial bioenergetics increasing coupling efficiency of respiratory chain and neuronal resistance to stress. Concomitant reduction of glycogen synthase kinase 3β activity and restoration of axonal trafficking resulted in elevated levels of neurotrophic factors and synaptic proteins in adult AD mice. Our results suggest metabolic reprogramming induced by modulation of mitochondrial complex I activity represents promising therapeutic strategy for AD.

No MeSH data available.


Related in: MedlinePlus

CP2 binds to the flavin mononucleotide subunit of complex I and inhibits its activity without inducing oxidative stress.(A) Activity of respiratory complexes I–V in isolated mitochondria treated with different concentrations of CP2. *P < 0.001, two-tailed t-test; n = 3–5 replicates per data point. (B, C) CP2 treatment in APP (25 mg/kg/day, 14 months, n = 4) and APP/PS1 (25 mg/kg/day, 4 months, n = 5) mice did not change the expression of HO-1 (B) and iNOS (C) genes compared to untreated NTG (n = 4) or WT mice (n = 5). (D) Electron micrographs of mitochondria in the hippocampus of APP mouse treated with CP2 for 14 months (bottom) compared to untreated APP mouse (top) of the same age. Scale bar, 500 nm (top) and 200 nm (bottom). (E) Overview of the CP2-bound flavin mononucleotide subunit of human complex I. (F) Residues of the complex I subunit that interact with CP2 (the subunit is in stick model; CP2 is in ball-and-stick model; dashed lines denote hydrogen bonds). (G) Levels of NADH and NAD+ in WT neurons treated with different concentration of CP2, vehicle or inactive CP2 analog, TP17; n = 8–11 replicates per data point. ***P < 0.00001. See also Fig. S6.
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f0025: CP2 binds to the flavin mononucleotide subunit of complex I and inhibits its activity without inducing oxidative stress.(A) Activity of respiratory complexes I–V in isolated mitochondria treated with different concentrations of CP2. *P < 0.001, two-tailed t-test; n = 3–5 replicates per data point. (B, C) CP2 treatment in APP (25 mg/kg/day, 14 months, n = 4) and APP/PS1 (25 mg/kg/day, 4 months, n = 5) mice did not change the expression of HO-1 (B) and iNOS (C) genes compared to untreated NTG (n = 4) or WT mice (n = 5). (D) Electron micrographs of mitochondria in the hippocampus of APP mouse treated with CP2 for 14 months (bottom) compared to untreated APP mouse (top) of the same age. Scale bar, 500 nm (top) and 200 nm (bottom). (E) Overview of the CP2-bound flavin mononucleotide subunit of human complex I. (F) Residues of the complex I subunit that interact with CP2 (the subunit is in stick model; CP2 is in ball-and-stick model; dashed lines denote hydrogen bonds). (G) Levels of NADH and NAD+ in WT neurons treated with different concentration of CP2, vehicle or inactive CP2 analog, TP17; n = 8–11 replicates per data point. ***P < 0.00001. See also Fig. S6.

Mentions: To further investigate the mechanism of CP2-induced reduction in basal OCR, we substituted specific inhibitors of ETC and FCCP with CP2, one at a time, and evaluated whether CP2 prompts changes in OCR similar to any of the mitochondrial toxicants (Fig. 4H). Addition of CP2 to intact WT neurons induced changes similar to rotenone/antimycin A but not oligomycin or FCCP suggesting that CP2 inhibits complexes I and/or III (Fig. 4H). To confirm these findings, we examined the effect of CP2 on the activity of each of the respiratory complexes using enzymatic assays and mitochondria isolated from the brain of WT mice (Fig. 5A). The addition of CP2 did not alter the activity of complexes II, III, IV and V, while complex I activity was inhibited in a dose-dependent manner. However, the effect was mild compared to 80% of inhibition induced under the same experimental conditions by 10 μM of rotenone (data not shown). It is well known that inhibition of complex I could increase production of reactive oxygen species (ROS) contributing to neurodegenerative processes (Dumont and Beal, 2011). Nevertheless, the expression of oxidant-inducible gene, heme oxygenase-1 (HO-1) (Nath et al., 2001), or genes related to inflammation (iNOS, RANTES and interferon-gamma, IFNγ) was not affected in the brain tissue of FAD mice after 4 or 14 months of CP2 treatment (Figs. 5B, C and S6). Moreover, there appears a trend toward a reduction in expression of HO-I, iNOS, IFNγ in hippocampus of CP2-treated FAD animals. We previously reported that CP2 modestly inhibited the activity of Acyl-CoA:cholesterol acyltransferase, which could increase the expression of cholesterol transporter genes (Pokhrel et al., 2012). However, gene expression analysis failed to detect activation of cholesterol transporter genes ABCA1 or ABCG1 suggesting that therapeutic effect of CP2 was not related to enhanced cholesterol efflux (Fig. S6). We next assayed the activity of citrate synthase, an enzyme of the mitochondrial matrix that is a marker of organelle integrity and oxidative capacity. Citrate synthase activity in mitochondria isolated from brain tissue of CP2-treated APP/PS1 mice was similar to the observed in WT animals (Fig. S5C) suggesting that CP2 does not damage inner mitochondrial membrane causing leakage of the matrix and does not affect oxidative capacity or TCA cycle. These results are also supported by electron microscopy examination demonstrating robust mitochondrial morphology and cristae organization in the hippocampus of APP, PS1 and APP/PS1 mice treated with CP2 through life (Fig. 5D).


Modulation of mitochondrial complex I activity averts cognitive decline in multiple animal models of familial Alzheimer's Disease.

Zhang L, Zhang S, Maezawa I, Trushin S, Minhas P, Pinto M, Jin LW, Prasain K, Nguyen TD, Yamazaki Y, Kanekiyo T, Bu G, Gateno B, Chang KO, Nath KA, Nemutlu E, Dzeja P, Pang YP, Hua DH, Trushina E - EBioMedicine (2015)

CP2 binds to the flavin mononucleotide subunit of complex I and inhibits its activity without inducing oxidative stress.(A) Activity of respiratory complexes I–V in isolated mitochondria treated with different concentrations of CP2. *P < 0.001, two-tailed t-test; n = 3–5 replicates per data point. (B, C) CP2 treatment in APP (25 mg/kg/day, 14 months, n = 4) and APP/PS1 (25 mg/kg/day, 4 months, n = 5) mice did not change the expression of HO-1 (B) and iNOS (C) genes compared to untreated NTG (n = 4) or WT mice (n = 5). (D) Electron micrographs of mitochondria in the hippocampus of APP mouse treated with CP2 for 14 months (bottom) compared to untreated APP mouse (top) of the same age. Scale bar, 500 nm (top) and 200 nm (bottom). (E) Overview of the CP2-bound flavin mononucleotide subunit of human complex I. (F) Residues of the complex I subunit that interact with CP2 (the subunit is in stick model; CP2 is in ball-and-stick model; dashed lines denote hydrogen bonds). (G) Levels of NADH and NAD+ in WT neurons treated with different concentration of CP2, vehicle or inactive CP2 analog, TP17; n = 8–11 replicates per data point. ***P < 0.00001. See also Fig. S6.
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f0025: CP2 binds to the flavin mononucleotide subunit of complex I and inhibits its activity without inducing oxidative stress.(A) Activity of respiratory complexes I–V in isolated mitochondria treated with different concentrations of CP2. *P < 0.001, two-tailed t-test; n = 3–5 replicates per data point. (B, C) CP2 treatment in APP (25 mg/kg/day, 14 months, n = 4) and APP/PS1 (25 mg/kg/day, 4 months, n = 5) mice did not change the expression of HO-1 (B) and iNOS (C) genes compared to untreated NTG (n = 4) or WT mice (n = 5). (D) Electron micrographs of mitochondria in the hippocampus of APP mouse treated with CP2 for 14 months (bottom) compared to untreated APP mouse (top) of the same age. Scale bar, 500 nm (top) and 200 nm (bottom). (E) Overview of the CP2-bound flavin mononucleotide subunit of human complex I. (F) Residues of the complex I subunit that interact with CP2 (the subunit is in stick model; CP2 is in ball-and-stick model; dashed lines denote hydrogen bonds). (G) Levels of NADH and NAD+ in WT neurons treated with different concentration of CP2, vehicle or inactive CP2 analog, TP17; n = 8–11 replicates per data point. ***P < 0.00001. See also Fig. S6.
Mentions: To further investigate the mechanism of CP2-induced reduction in basal OCR, we substituted specific inhibitors of ETC and FCCP with CP2, one at a time, and evaluated whether CP2 prompts changes in OCR similar to any of the mitochondrial toxicants (Fig. 4H). Addition of CP2 to intact WT neurons induced changes similar to rotenone/antimycin A but not oligomycin or FCCP suggesting that CP2 inhibits complexes I and/or III (Fig. 4H). To confirm these findings, we examined the effect of CP2 on the activity of each of the respiratory complexes using enzymatic assays and mitochondria isolated from the brain of WT mice (Fig. 5A). The addition of CP2 did not alter the activity of complexes II, III, IV and V, while complex I activity was inhibited in a dose-dependent manner. However, the effect was mild compared to 80% of inhibition induced under the same experimental conditions by 10 μM of rotenone (data not shown). It is well known that inhibition of complex I could increase production of reactive oxygen species (ROS) contributing to neurodegenerative processes (Dumont and Beal, 2011). Nevertheless, the expression of oxidant-inducible gene, heme oxygenase-1 (HO-1) (Nath et al., 2001), or genes related to inflammation (iNOS, RANTES and interferon-gamma, IFNγ) was not affected in the brain tissue of FAD mice after 4 or 14 months of CP2 treatment (Figs. 5B, C and S6). Moreover, there appears a trend toward a reduction in expression of HO-I, iNOS, IFNγ in hippocampus of CP2-treated FAD animals. We previously reported that CP2 modestly inhibited the activity of Acyl-CoA:cholesterol acyltransferase, which could increase the expression of cholesterol transporter genes (Pokhrel et al., 2012). However, gene expression analysis failed to detect activation of cholesterol transporter genes ABCA1 or ABCG1 suggesting that therapeutic effect of CP2 was not related to enhanced cholesterol efflux (Fig. S6). We next assayed the activity of citrate synthase, an enzyme of the mitochondrial matrix that is a marker of organelle integrity and oxidative capacity. Citrate synthase activity in mitochondria isolated from brain tissue of CP2-treated APP/PS1 mice was similar to the observed in WT animals (Fig. S5C) suggesting that CP2 does not damage inner mitochondrial membrane causing leakage of the matrix and does not affect oxidative capacity or TCA cycle. These results are also supported by electron microscopy examination demonstrating robust mitochondrial morphology and cristae organization in the hippocampus of APP, PS1 and APP/PS1 mice treated with CP2 through life (Fig. 5D).

Bottom Line: Furthermore, modulation of complex I activity augmented mitochondrial bioenergetics increasing coupling efficiency of respiratory chain and neuronal resistance to stress.Concomitant reduction of glycogen synthase kinase 3β activity and restoration of axonal trafficking resulted in elevated levels of neurotrophic factors and synaptic proteins in adult AD mice.Our results suggest metabolic reprogramming induced by modulation of mitochondrial complex I activity represents promising therapeutic strategy for AD.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Mayo Clinic Rochester, MN 55905, USA.

ABSTRACT

Development of therapeutic strategies to prevent Alzheimer's Disease (AD) is of great importance. We show that mild inhibition of mitochondrial complex I with small molecule CP2 reduces levels of amyloid beta and phospho-Tau and averts cognitive decline in three animal models of familial AD. Low-mass molecular dynamics simulations and biochemical studies confirmed that CP2 competes with flavin mononucleotide for binding to the redox center of complex I leading to elevated AMP/ATP ratio and activation of AMP-activated protein kinase in neurons and mouse brain without inducing oxidative damage or inflammation. Furthermore, modulation of complex I activity augmented mitochondrial bioenergetics increasing coupling efficiency of respiratory chain and neuronal resistance to stress. Concomitant reduction of glycogen synthase kinase 3β activity and restoration of axonal trafficking resulted in elevated levels of neurotrophic factors and synaptic proteins in adult AD mice. Our results suggest metabolic reprogramming induced by modulation of mitochondrial complex I activity represents promising therapeutic strategy for AD.

No MeSH data available.


Related in: MedlinePlus