Activation of sirtuin 1 as therapy for the peroxisomal disease adrenoleukodystrophy.

Oxidative stress and mitochondrial failure are prominent factors in the axonal degeneration process. In this study, we demonstrate that sirtuin 1 (SIRT1), a key regulator of the mitochondrial function, is impaired in the axonopathy and peroxisomal disease X-linked adrenoleukodystrophy (X-ALD). We have restored SIRT1 activity using a dual strategy of resveratrol treatment or by the moderate transgenic overexpression of SIRT1 in a X-ALD mouse model. Both strategies normalized redox homeostasis, mitochondrial respiration, bioenergetic failure, axonal degeneration and associated locomotor disabilities in the X-ALD mice. These results indicate that the reactivation of SIRT1 may be a valuable strategy to treat X-ALD and other axonopathies in which the control of redox and energetic homeostasis is impaired.

Impaired brain creatine kinase activity in Huntington's disease.

BACKGROUND: Huntington's disease (HD) is associated with impaired energy metabolism in the brain. Creatine kinase (CK) catalyzes ATP-dependent phosphorylation of creatine (Cr) into phosphocreatine (PCr), thereby serving as readily available high-capacity spatial and temporal ATP buffering. OBJECTIVE: Substantial evidence supports a specific role of the Cr/PCr system in neurodegenerative diseases. In the brain, the Cr/PCr ATP-buffering system is established by a concerted operation of the brain-specific cytosolic enzyme BB-CK and ubiquitous mitochondrial uMt-CK. It is not yet established whether the activity of these CK isoenzymes is impaired in HD. METHODS: We measured PCr, Cr, ATP and ADP in brain extracts of 3 mouse models of HD - R6/2 mice, N171-82Q and HdhQ(111) mice - and the activity of CK in cytosolic and mitochondrial brain fractions from the same mice. RESULTS: The PCr was significantly increased in mouse HD brain extracts as compared to nontransgenic littermates. We also found an approximately 27% decrease in CK activity in both cytosolic and mitochondrial fractions of R6/2 and N171-82Q mice, and an approximately 25% decrease in the mitochondria from HdhQ(111) mice. Moreover, uMt-CK and BB-CK activities were approximately 63% lower in HD human brain samples as compared to nondiseased controls. CONCLUSION: Our findings lend strong support to the role of impaired energy metabolism in HD, and point out the potential importance of impairment of the CK-catalyzed ATP-buffering system in the etiology of HD.

Influence of mitochondrial enzyme deficiency on adult neurogenesis in mouse models of neurodegenerative diseases.

Mitochondrial defects including reduction of a key mitochondrial tricarboxylic acid cycle enzyme alpha-ketoglutarate-dehydrogenase complex (KGDHC) are characteristic of many neurodegenerative diseases. KGDHC consists of alpha-ketoglutarate dehydrogenase, dihydrolipoyl succinyltransferase (E2k), and dihydrolipoamide dehydrogenase (Dld) subunits. We investigated whether Dld or E2k deficiency influences adult brain neurogenesis using immunohistochemistry for the immature neuron markers, doublecortin (Dcx) and polysialic acid-neural cell adhesion molecule, as well as a marker for proliferation, proliferating cell nuclear antigen (PCNA). Both Dld- and E2k-deficient mice showed reduced Dcx-positive neuroblasts in the subgranular zone (SGZ) of the hippocampal dentate gyrus compared with wild-type mice. In the E2k knockout mice, increased immunoreactivity for the lipid peroxidation marker, malondialdehyde occurred in the SGZ. These alterations did not occur in the subventricular zone (SVZ). PCNA staining revealed decreased proliferation in the SGZ of E2k-deficient mice. In a transgenic mouse model of Alzheimer's disease, Dcx-positive cells in the SGZ were also reduced compared with wild type, but Dld deficiency did not exacerbate the reduction. In the malonate lesion model of Huntington's disease, Dld deficiency did not alter the lesion-induced increase and migration of Dcx-positive cells from the SVZ into the ipsilateral striatum. Thus, the KGDHC subunit deficiencies associated with elevated lipid peroxidation selectively reduced the number of neuroblasts and proliferating cells in the hippocampal neurogenic zone. However, these mitochondrial defects neither exacerbated certain pathological conditions, such as amyloid precursor protein (APP) mutation-induced reduction of SGZ neuroblasts, nor inhibited malonate-induced migration of SVZ neuroblasts. Our findings support the view that mitochondrial dysfunction can influence the number of neural progenitor cells in the hippocampus of adult mice.

Creatine in Huntington disease is safe, tolerable, bioavailable in brain and reduces serum 8OH2'dG.

In a randomized, double-blind, placebo-controlled study in 64 subjects with Huntington disease (HD), 8 g/day of creatine administered for 16 weeks was well tolerated and safe. Serum and brain creatine concentrations increased in the creatine-treated group and returned to baseline after washout. Serum 8-hydroxy-2'-deoxyguanosine (8OH2'dG) levels, an indicator of oxidative injury to DNA, were markedly elevated in HD and reduced by creatine treatment.

Tolerance of high-dose (3,000 mg/day) coenzyme Q10 in ALS.

An open-label dose-escalation trial was performed to assess the safety and tolerability of high doses of coenzyme Q10 (CoQ10) in ALS. CoQ10, a cofactor in mitochondrial electron transfer, may improve the mitochondrial dysfunction in ALS. In this study, CoQ10 was safe and well tolerated in 31 subjects treated with doses as high as 3,000 mg/day for 8 months.

Oral dyskinesias and histopathological alterations in substantia nigra after long-term haloperidol treatment of old rats.

The pathophysiologic basis of tardive dyskinesia remains unclear, but several lines of evidence suggest that persistent neuronal changes in the basal ganglia produced by oxidative stress or glutamate toxicity may play a role, especially in the elderly. In the present study we examined whether histopathological alterations in substantia nigra are related to oral dyskinesia in a rodent model of tardive dyskinesia. Haloperidol decanoate (38 mg/kg/4 weeks) was administered to young (8 weeks) and old (38 weeks) rats for a total period of 28 weeks, and the development of vacuous chewing movements (VCM) was observed. Rats with high and low levels of VCM and saline-treated controls were analyzed for histopathological alterations. Reduced nerve cell number and atrophic neurons were prominent features in the substantia nigra of old rats with high levels of VCM. Some alterations were also present in the substantia nigra of the old rats with low levels of VCM and young rats with high VCM levels, but these were significantly less affected than the high VCM rats. These results show that the development of haloperidol-induced oral dyskinesias in old rats is associated with histopathological alterations in the substantia nigra. This suggests that nigral degeneration induced by neuroleptics may contribute to the development of persistent VCM in rats and possibly irreversible tardive dyskinesia in humans.

Tissue inhibitors of matrix metalloproteinases are elevated in cerebrospinal fluid of neurodegenerative diseases.

Matrix metalloproteinases (MMPs) are implicated in the pathogenesis of diseases such as Alzheimer's Disease (AD) and amyotrophic lateral sclerosis (ALS). Increased expression of MMP-9 and TIMPs has been reported in postmortem AD and ALS brain tissue, as well as in ALS cerebrospinal fluid (CSF) and plasma. Although individual studies of MMP and TIMP expression in CSF have included AD and ALS samples, there are no studies comparing the expression of these proteins between neurodegenerative diseases. We measured the levels of matrix metalloproteinases (MMPs)-2 and -9 and the tissue inhibitor of MMPs (e.g. TIMP-1 and TIMP-2) in CSF samples from patients with Parkinson's Disease (PD), Huntington's Disease (HD), AD and ALS as compared to age-matched control patients. There was constitutive expression of the proform of gelatinase A (proMMP-2) on zymography gels in all CSF samples. Unexpectedly, there was an additional gelatinolytic band at 130 kDa of unknown etiology in the CSF samples of patients with PD (61% of patients studied), AD (61%), HD (25%) and ALS (39%). Levels of TIMP-1 were significantly elevated in CSF samples from all disease groups. TIMP-2 was significantly increased in CSF of AD and HD patients. MMP-2 levels did not differ significantly between groups. These findings show that TIMPs are elevated in the CSF of patients with neurodegenerative diseases suggesting a potential role of these endogenous inhibitors of matrix metalloproteinases in neurodegenerative diseases.

Caspase-9 activation results in downstream caspase-8 activation and bid cleavage in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease.

Parkinson's disease (PD) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity are both associated with dopaminergic neuron death in the substantia nigra (SN). Apoptosis has been implicated in this cell loss; however, whether or not it is a major component of disease pathology remains controversial. Caspases are a major class of proteases involved in the apoptotic process. To evaluate the role of caspases in PD, we analyzed caspase activation in MPTP-treated mice, in cultured dopaminergic cells, and in postmortem PD brain tissue. MPTP was found to elicit not only the activation of the effector caspase-3 but also the initiators caspase-8 and caspase-9, mitochondrial cytochrome c release, and Bid cleavage in the SN of wild-type mice. These changes were attenuated in transgenic mice neuronally expressing the general caspase inhibitor protein baculoviral p35. These mice also displayed increased resistance to the cytotoxic effects of the drug. MPTP-associated toxicity in culture was found temporally to involve cytochrome c release, activation of caspase-9, caspase-3, and caspase-8, and Bid cleavage. Caspase-9 inhibition prevented the activation of both caspase-3 and caspase-8 and also inhibited Bid cleavage, but not cytochrome c release. Activated caspase-8 and caspase-9 were immunologically detectable within MPP(+)-treated mesencephalic dopaminergic neurons, dopaminergic nigral neurons from MPTP-treated mice, and autopsied Parkinsonian tissue from late-onset sporadic cases of the disease. These data demonstrate that MPTP-mediated activation of caspase-9 via cytochrome c release results in the activation of caspase-8 and Bid cleavage, which we speculate may be involved in the amplification of caspase-mediated dopaminergic cell death. These data suggest that caspase inhibitors constitute a plausible therapeutic for PD.

N(epsilon)-(gamma-L-glutamyl)-L-lysine (GGEL) is increased in cerebrospinal fluid of patients with Huntington's disease.

Pathological-length polyglutamine (Q(n)) expansions, such as those that occur in the huntingtin protein (htt) in Huntington's disease (HD), are excellent substrates for tissue transglutaminase in vitro, and transglutaminase activity is increased in post-mortem HD brain. However, direct evidence for the participation of tissue transglutaminase (or other transglutaminases) in HD patients in vivo is scarce. We now report that levels of N(epsilon)-(gamma-L-glutamyl)-L-lysine (GGEL)--a 'marker' isodipeptide produced by the transglutaminase reaction--are elevated in the CSF of HD patients (708 +/- 41 pmol/mL, SEM, n = 36) vs. control CSF (228 +/- 36, n = 27); p < 0.0001. These data support the hypothesis that transglutaminase activity is increased in HD brain in vivo.

Increased oxidative damage to DNA in a transgenic mouse model of Huntington's disease.

Mitochondrial dysfunction and oxidative damage may play a role in the pathogenesis of Huntington's disease (HD). We examined concentrations of 8-hydroxy-2-deoxyguanosine (OH(8)dG), a well-established marker of oxidative damage to DNA, in a transgenic mouse model of HD (R6/2). Increased concentrations of OH(8)dG were found in the urine, plasma and striatal microdialysates of the HD mice. Increased concentrations were also observed in isolated brain DNA at 12 and 14 weeks of age. Immunocytochemistry showed increased OH(8)dG staining in late stages of the illness. These results suggest that oxidative damage may play a role in the pathogenesis of neuronal degeneration in the R6/2 transgenic mouse model of HD.

Mitochondrial impairment in the cerebellum of the patients with progressive supranuclear palsy.

Abnormalities in energy metabolism and oxidative stress accompany many neurodegenerative diseases, including progressive supranuclear palsy (PSP). Previously, we showed decreased activities of a mitochondrial enzyme complex, alpha-ketoglutarate dehydrogenase complex (KGDHC), and marked increases in tissue malondialdehyde levels in post-mortem superior frontal cortex from the patients with PSP. The current study demonstrates that KGDHC is also significantly diminished (-58%) in the cerebellum from patients with PSP (n = 14), compared to age-matched control brains (n = 13). In contrast to cortex, markers of oxidative stress, such as malondialdehyde, tyrosine nitration or general protein carbonyl modification, did not increase in cerebellum. Furthermore, the protein levels of the individual components of KGDHC did not decline. The activities of two other mitochondrial enzymes were measured to determine whether the changes in KGDHC were selective. The activity of aconitase, a mitochondrial enzyme with an iron/sulfur cluster, is also significantly diminished (-50%), whereas glutamate dehydrogenase activity is unchanged. The present results suggest that the interaction of metabolic impairment and oxidative stress is region-specific in PSP brain. In cerebellum, reductions in KGDHC occur in the absence of increases in common measures of oxidative stress, and may underlie the metabolic deficits and contribute to pathological and clinical manifestation related to the cerebellum in patients with PSP.

Lipoic acid improves survival in transgenic mouse models of Huntington's disease.

There is substantial evidence implicating excitotoxicity and oxidative damage in the pathogenesis of Huntington's disease (HD). We therefore examined whether the antioxidants 2-sulpho-tert-phenyibutyinitrone (S-PBN) and alpha-lipoic acid could exert neuroprotective effects in transgenic mouse models of HD. S-PBN showed no effects on either weight loss or survival in the R6/2 transgenic HD mice. alpha-Lipoic acid produced significant increases in survival in both R6/2 and N171-82Q transgenic mouse models of HD. These findings suggest that alpha-lipoic acid might have beneficial effects in HD patients.

Therapeutic efficacy of EGb761 (Gingko biloba extract) in a transgenic mouse model of amyotrophic lateral sclerosis.

EGb761 is a standardized extract of green Gingko biloba, which exerts protective effects against mitochondrial damage and oxidative stress. We examined whether oral administration of 0.022% or 0.045% EGb761 in the diet could impart neuroprotective effects in a transgenic mouse model (G93A) of amyotrophic lateral sclerosis (ALS). EGb761 significantly improved motor performance and survival, and protected against a loss of spinal-cord anterior motor horn neurons in male G93A mutant transgenic ALS mice, but not in littermate female mutant transgene mice. While EGb761 extended survival in littermate female G93A mice, significance was not reached. EGb761, however, significantly improved weight loss in both male and female transgenic ALS mice. These findings provide evidence for a gender-specific neuroprotective effect of EGb761 in a transgenic model of ALS and suggest that EGb761 may be a potential effective treatment in patients with ALS.

In vivo regulation of oxidative phosphorylation in cells harboring a stop-codon mutation in mitochondrial DNA-encoded cytochrome c oxidase subunit I.

The mechanisms that regulate oxidative phosphorylation in mammalian cells are largely unknown. To address this issue, cybrids were generated by fusing osteosarcoma cells devoid of mitochondrial DNA (mtDNA) with platelets from a patient with a stop-codon mutation in cytochrome c oxidase subunit I (COX I). The molecular and biochemical characteristics of cybrids harboring varying levels of mutated mitochondrial DNA were studied. We found a direct correlation between the levels of mutated COX I DNA and mutated COX I mRNA, whereas the levels of COX I total mRNA were unchanged. COX I polypeptide synthesis and steady-state levels were inversely proportional to mutation levels. Cytochrome c oxidase subunit II was reduced proportionally to COX I, indicating impairment in complex assembly. COX enzymatic activity was inversely proportional to the levels of mutated mtDNA. However, both cell respiration and ATP synthesis were preserved in cells with lower proportions of mutated genomes, with a threshold at approximately 40%, and decreased linearly with increasing mutated mtDNA. These results indicate that COX levels in mutated cells were not regulated at the transcriptional, translational, and post-translational levels. Because of a small excess of COX capacity, the levels of expression of COX subunits exerted a relatively tight control on oxidative phosphorylation.

Striatal volume loss in HD as measured by MRI and the influence of CAG repeat.

BACKGROUND: Huntington's disease (HD) is an autosomal dominant neurodegenerative disease that results from the expansion of a trinucleotide (CAG) repeat on chromosome 4. Progressive degeneration of the striatum is the pathologic hallmark of the disease. Little is known about the regional selectivity of the neurodegeneration and its relationship to the genetic expansion. METHODS: The authors used high-resolution MRI to determine the relationship between the genetic expansion and the degree of striatal degeneration. Morphometric analyses of the striatum from high-resolution MR images from 27 subjects with HD were compared with those of 24 healthy control subjects. RESULTS AND CONCLUSIONS: Striatal volumes were reduced in subjects with HD as compared with control subjects, in agreement with previously published reports. Left-sided volumes were smaller than right-sided volumes in subjects with HD; in healthy subjects, right-sided volumes were smaller. Finally, volume loss was significantly correlated with CAG repeat number. These results have potential implications for the design and assessment of therapeutic agents in the future.

Creatine increase survival and delays motor symptoms in a transgenic animal model of Huntington's disease.

There is substantial evidence for bioenergetic defects in Huntington's disease (HD). Creatine administration increases brain phosphocreatine levels and it stabilizes the mitochondrial permeability transition. We examined the effects of creatine administration in a transgenic mouse model of HD produced by 82 polyglutamine repeats in a 171 amino acid N-terminal fragment of huntingtin (N171-82Q). Dietary supplementation of 2% creatine significantly improved survival, slowed the development of motor symptoms, and delayed the onset of weight loss. Creatine lessened brain atrophy and the formation of intranuclear inclusions, attenuated reductions in striatal N-acetylaspartate as assessed by NMR spectroscopy, and delayed the development of hyperglycemia. These results are similar to those observed using dietary creatine supplementation in the R6/2 transgenic mouse model of HD and provide further evidence that creatine may exert therapeutic effects in HD.

Dichloroacetate exerts therapeutic effects in transgenic mouse models of Huntington's disease.

Dichloroacetate (DCA) stimulates pyruvate dehydrogenase complex (PDHC) activity and lowers cerebral lactate concentrations. In the R6/2 and N171-82Q transgenic mouse models of Huntington's disease (HD), DCA significantly increased survival, improved motor function, delayed loss of body weight, attenuated the development of striatal neuron atrophy, and prevented diabetes. The percentage of PDHC in the active form was significantly reduced in R6/2 mice at 12 weeks of age, and DCA ameliorated the deficit. These results provide further evidence for a role of energy dysfunction in HD pathogenesis and suggest that DCA may exert therapeutic benefits in HD.

Metal chelator decreases Alzheimer beta-amyloid plaques.

Transgenic mice developing beta-amyloid (Abeta) plaques are advancing experimental treatment strategies for Alzheimer's disease. The metal chelator, clioquinol, is reported by Cherny et al. (2001) to reduce Abeta plaques, presumably by chelation of Abeta-associated zinc and copper. This and other recent Abeta-modulating treatment approaches are discussed.

Low mutational burden of individual acquired mitochondrial DNA mutations in brain.

Neurons may be particularly susceptible to oxidative damage, which has been proposed to induce somatic mutations, particularly in mitochondrial DNA (mtDNA). Therefore, acquired mtDNA mutations might preferentially accumulate in the brain and could play a role in aging and neurodegenerative disorders. Recently, a somatic T to G mtDNA mutation at noncoding nucleotide position 414 was reported in fibroblasts specifically from elderly subjects, with mutational burdens of up to 50%. We screened for this mutation in brain-derived mtDNA from 8 Alzheimer's disease patients, 27 Parkinson's disease patients, 4 multiple system atrophy patients, and 44 controls using up to three RFLP analyses. A total of 73 of these subjects were over the age of 65. The 414 mutation was absent in all cases. Next, individual mtDNA fragments from 6 elderly subjects were cloned, and a total of 70 clones were sequenced. The 414 mutation was absent in all clones, though occasional sequence variations were identified at other sites in single clones. The 414 mutation also was absent in blood (n = 6) and fibroblasts (n = 11) from elderly subjects. Our data suggest that it is rare for any one particular acquired mtDNA mutation to reach levels in the brain that are functionally significant. This does not exclude the possibility that the cumulative burden of multiple, individually rare, acquired mutations impairs mitochondrial function.

Potential for creatine and other therapies targeting cellular energy dysfunction in neurological disorders.

Substantial evidence indicates that bioenergetic dysfunction plays either a primary or secondary role in the pathophysiology of cell death in neurodegenerative and neuromuscular disorders, and even in normal aging. Agents that ameliorate bioenergetic defects may therefore be useful in therapy. Creatine, which increases muscle and brain phosphocreatine concentrations, and may inhibit the activation of the mitochondrial permeability transition, protects against neuronal degeneration in transgenic murine models of amyotrophic lateral sclerosis and Huntington's disease and in chemically mediated neurotoxicity. Initial studies of creatine use in humans appear promising; however, further long-term, well-designed trials are needed. Coenzyme Q10, Gingko biloba, nicotinamide, riboflavin, carnitine, lipoic acid, and dichloroacetate are other agents which may have beneficial effects on energy metabolism, but the preclinical and clinical evidence for efficacy in neurological diseases remains limited. These compounds are widely used as dietary supplements; however, they must be subjected to rigorous evaluation through randomized, double-blinded trials to establish efficacy, cost-effectiveness and safety in neurological disorders.