A potent and selective Sirtuin 1 inhibitor alleviates pathology in multiple animal and cell models of Huntington's disease.

Protein acetylation, which is central to transcriptional control as well as other cellular processes, is disrupted in Huntington's disease (HD). Treatments that restore global acetylation levels, such as inhibiting histone deacetylases (HDACs), are effective in suppressing HD pathology in model organisms. However, agents that selectively target the disease-relevant HDACs have not been available. SirT1 (Sir2 in Drosophila melanogaster) deacetylates histones and other proteins including transcription factors. Genetically reducing, but not eliminating, Sir2 has been shown to suppress HD pathology in model organisms. To date, small molecule inhibitors of sirtuins have exhibited low potency and unattractive pharmacological and biopharmaceutical properties. Here, we show that highly selective pharmacological inhibition of Drosophila Sir2 and mammalian SirT1 using the novel inhibitor selisistat (selisistat; 6-chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide) can suppress HD pathology caused by mutant huntingtin exon 1 fragments in Drosophila, mammalian cells and mice. We have validated Sir2 as the in vivo target of selisistat by showing that genetic elimination of Sir2 eradicates the effect of this inhibitor in Drosophila. The specificity of selisistat is shown by its effect on recombinant sirtuins in mammalian cells. Reduction of HD pathology by selisistat in Drosophila, mammalian cells and mouse models of HD suggests that this inhibitor has potential as an effective therapeutic treatment for human disease and may also serve as a tool to better understand the downstream pathways of SirT1/Sir2 that may be critical for HD.

Promising in Vitro anti-Alzheimer Properties for a Ruthenium(III) Complex.

Metal complexes represent today an attractive class of experimental anti-Alzheimer agents with the potential of blocking ß-amyloid 1-42 aggregation and scavenging its toxicity. Three representative ruthenium(III) complexes, namely NAMI A, KP1019, and PMRU20, were specifically evaluated to this end in an established in vitro model of AD relying on primary cortical neurons. Notably, PMRU20 turned out to be highly effective in protecting cortical neurons against Aß 1-42 toxicity, while the other tested ruthenium compounds were poorly active or even inactive; we also found that PMRU20 is virtually devoid of any significant toxicity in vitro at the applied concentrations. Interestingly, PMRU20 was neuroprotective even against the toxicity induced by Aß 25-35. The direct reaction of PMRU20 with Aß 1-42 was explored through ESI MS analysis and some adduct formation evidenced. In addition, thioflavin T assays revealed that PMRU20 greatly reduces Aß 1-42 aggregation. The implications of these findings are discussed in relation to emerging treatment strategies for the Alzheimer's disease.