Correction to "Chiral Cyclohexane 1,3-Diones as Inhibitors of Mutant SOD1-Dependent Protein Aggregation for the Treatment of ALS".

[This corrects the article DOI: 10.1021/ml3000963.].

The Wnt receptor Ryk reduces neuronal and cell survival capacity by repressing FOXO activity during the early phases of mutant huntingtin pathogenicity.

The Wnt receptor Ryk is an evolutionary-conserved protein important during neuronal differentiation through several mechanisms, including γ-secretase cleavage and nuclear translocation of its intracellular domain (Ryk-ICD). Although the Wnt pathway may be neuroprotective, the role of Ryk in neurodegenerative disease remains unknown. We found that Ryk is up-regulated in neurons expressing mutant huntingtin (HTT) in several models of Huntington's disease (HD). Further investigation in Caenorhabditis elegans and mouse striatal cell models of HD provided a model in which the early-stage increase of Ryk promotes neuronal dysfunction by repressing the neuroprotective activity of the longevity-promoting factor FOXO through a noncanonical mechanism that implicates the Ryk-ICD fragment and its binding to the FOXO co-factor ß-catenin. The Ryk-ICD fragment suppressed neuroprotection by lin-18/Ryk loss-of-function in expanded-polyQ nematodes, repressed FOXO transcriptional activity, and abolished ß-catenin protection of mutant htt striatal cells against cell death vulnerability. Additionally, Ryk-ICD was increased in the nucleus of mutant htt cells, and reducing γ-secretase PS1 levels compensated for the cytotoxicity of full-length Ryk in these cells. These findings reveal that the Ryk-ICD pathway may impair FOXO protective activity in mutant polyglutamine neurons, suggesting that neurons are unable to efficiently maintain function and resist disease from the earliest phases of the pathogenic process in HD.

The sirtuin 2 inhibitor AK-7 is neuroprotective in Huntington's disease mouse models.

Inhibition of sirtuin 2 (SIRT2) deacetylase mediates protective effects in cell and invertebrate models of Parkinson's disease and Huntington's disease (HD). Here we report the in vivo efficacy of a brain-permeable SIRT2 inhibitor in two genetic mouse models of HD. Compound treatment resulted in improved motor function, extended survival, and reduced brain atrophy and is associated with marked reduction of aggregated mutant huntingtin, a hallmark of HD pathology. Our results provide preclinical validation of SIRT2 inhibition as a potential therapeutic target for HD and support the further development of SIRT2 inhibitors for testing in humans.

Chiral cyclohexane 1,3-diones as inhibitors of mutant SOD1-dependent protein aggregation for the treatment of ALS.

Cyclohexane 1,3-diones were identified as a class of molecules exhibiting a protective effect against mutant SOD1 induced toxicity in PC-12 cells, but an optimized analogue had little or no effect on life extension in the G93A SOD1 mouse model for amyotrophic lateral sclerosis (ALS). Additional testing showed that these compounds were inactive in neurons and further analogue synthesis was carried out to identify compounds with neuronal activity. Starting from two racemic derivatives that were active in cortical neurons, two potent analogues (1b and 2b) were resolved, which were protective against mutant SOD1 induced toxicity in PC-12 cells. Both compounds were found to be active in cortical neurons and presented good ADME profiles in vitro. On the basis of these results, an ALS mouse trial with 1b was carried out, which showed slightly greater life extension than the FDA-approved ALS drug riluzole, thereby validating cyclohexane 1,3-diones as a novel therapeutic class for the treatment of ALS.

Mitochondrial loss, dysfunction and altered dynamics in Huntington's disease.

Although a direct causative pathway from the gene mutation to the selective neostriatal neurodegeneration remains unclear in Huntington's disease (HD), one putative pathological mechanism reported to play a prominent role in the pathogenesis of this neurological disorder is mitochondrial dysfunction. We examined mitochondria in preferentially vulnerable striatal calbindin-positive neurons in moderate-to-severe grade HD patients, using antisera against mitochondrial markers of COX2, SOD2 and cytochrome c. Combined calbindin and mitochondrial marker immunofluorescence showed a significant and progressive grade-dependent reduction in the number of mitochondria in spiny striatal neurons, with marked alteration in size. Consistent with mitochondrial loss, there was a reduction in COX2 protein levels using western analysis that corresponded with disease severity. In addition, both mitochondrial transcription factor A, a regulator of mtDNA, and peroxisome proliferator-activated receptor-co-activator gamma-1 alpha, a key transcriptional regulator of energy metabolism and mitochondrial biogenesis, were also significantly reduced with increasing disease severity. Abnormalities in mitochondrial dynamics were observed, showing a significant increase in the fission protein Drp1 and a reduction in the expression of the fusion protein mitofusin 1. Lastly, mitochondrial PCR array profiling in HD caudate nucleus specimens showed increased mRNA expression of proteins involved in mitochondrial localization, membrane translocation and polarization and transport that paralleled mitochondrial derangement. These findings reveal that there are both mitochondrial loss and altered mitochondrial morphogenesis with increased mitochondrial fission and reduced fusion in HD. These findings provide further evidence that mitochondrial dysfunction plays a critical role in the pathogenesis of HD.

Uridine ameliorates the pathological phenotype in transgenic G93A-ALS mice.

There is strong evidence from studies in humans and animal models to suggest the involvement of energy metabolism defects in neurodegenerative diseases. Uridine, a pyrimidine nucleoside, has been suggested to be neuroprotective in neurological disorders by improving bioenergetic effects, increasing ATP levels and enhancing glycolytic energy production. We assessed whether uridine treatment extended survival and improved the behavioral and neuropathological phenotype observed in G93A-ALS mice. In vitro and in vivo pharmacokinetic analyses in mutant SOD models provided optimal dose and assurance that uridine entered the brain. A dose-ranging efficacy trial in G93A mice was performed using survival, body weight, open-field analysis, and neuropathology as outcome measures. Urinary levels of 8-hydroxy-2'-deoxyguanosine, identifying DNA oxidative damage, were measured and used as a pharmacodynamic biomarker. Uridine administration significantly extended survival in a dose-dependent manner in G93A mice, while improving the behavioral and neuropathological phenotype. Uridine increased survival by 17.4%, ameliorated body weight loss, enhanced motor performance, reduced gross lumbar and ventral horn atrophy, attenuated lumbar ventral horn neuronal cell death, and decreased reactive astrogliosis. Consistent with a therapeutic effect, uridine significantly reduced urinary 8-hydroxy-2'-deoxyguanosine in G93A mice. These data suggest that uridine may be a therapeutic candidate in ALS patients.

Reduced creatine kinase as a central and peripheral biomarker in Huntington's disease.

A major goal of current clinical research in Huntington's disease (HD) has been to identify preclinical and manifest disease biomarkers, as these may improve both diagnosis and the power for therapeutic trials. Although the underlying biochemical alterations and the mechanisms of neuronal degeneration remain unknown, energy metabolism defects in HD have been chronicled for many years. We report that the brain isoenzyme of creatine kinase (CK-BB), an enzyme important in buffering energy stores, was significantly reduced in presymptomatic and manifest disease in brain and blood buffy coat specimens in HD mice and HD patients. Brain CK-BB levels were significantly reduced in R6/2 mice by approximately 18% to approximately 68% from 21 to 91 days of age, while blood CK-BB levels were decreased by approximately 14% to approximately 44% during the same disease duration. Similar findings in CK-BB levels were observed in the 140 CAG mice from 4 to 12 months of age, but not at the earliest time point, 2 months of age. Consistent with the HD mice, there was a grade-dependent loss of brain CK-BB that worsened with disease severity in HD patients from approximately 28% to approximately 63%, as compared to non-diseased control patients. In addition, CK-BB blood buffy coat levels were significantly reduced in both premanifest and symptomatic HD patients by approximately 23% and approximately 39%, respectively. The correlation of CK-BB as a disease biomarker in both CNS and peripheral tissues from HD mice and HD patients may provide a powerful means to assess disease progression and to predict the potential magnitude of therapeutic benefit in this disorder.

Defining the role of syndecan-4 in mechanotransduction using surface-modification approaches.

The ability of cells to respond to external mechanical stimulation is a complex and robust process involving a diversity of molecular interactions. Although mechanotransduction has been heavily studied, many questions remain regarding the link between physical stimulation and biochemical response. Of significant interest has been the contribution of the transmembrane proteins involved, and integrins in particular, because of their connectivity to both the extracellular matrix and the cytoskeleton. Here, we demonstrate the existence of a mechanically based initiation molecule, syndecan-4. We first demonstrate the ability of syndecan-4 molecules to support cell attachment and spreading without the direct extracellular binding of integrins. We also examine the distribution of focal adhesion-associated proteins through controlling surface interactions of beads with molecular specificity in binding to living cells. Furthermore, after adhering cells to elastomeric membranes via syndecan-4-specific attachments we mechanically strained the cells via our mechanical stimulation and polymer surface chemical modification approach. We found ERK phosphorylation similar to that shown for mechanotransductive response for integrin-based cell attachments through our elastomeric membrane-based approach and optical magnetic twisting cytometry for syndecan-4. Finally, through the use of cytoskeletal disruption agents, this mechanical signaling was shown to be actin cytoskeleton dependent. We believe that these results will be of interest to a wide range of fields, including mechanotransduction, syndecan biology, and cell-material interactions.