An enzyme known to be critical for the repair of damaged cells and the maintenance of cellular energy may be a useful target for new strategies to treat Huntington's disease (HD) and other disorders characterized by low cellular energy levels. In the August issue of Chemistry & Biology, a research team from the MassGeneral Institute for Neurodegenerative Disease (MIND) describes their discovery of a novel inhibitor of Poly (ADP-ribose) polymerase (PARP1) and their findings that PARP1 inhibitors can protect HD-affected cells from damage in laboratory assays.
"While PARP1 is essential for the repair of damaged DNA, we also know that, if overactivated, it can cause cell death by excessive energy depletion," says Aleksey Kazantsev, PhD, director of the MIND High Throughput Drug Screening Laboratory, who led the current study. "It has recently been shown that neurons from patients with Huntington's appear to be energy-deficient, so we hypothesized that modest stresses that would be tolerated by healthy cells could send HD cells below a viable energy threshold and that blocking PARP1 activation could be protective."
To test this hypothesis the MIND researchers first ran a computer search of their small-molecule library for potential novel inhibitors of PARP1, searching for those with structural similarities to known inhibitors. "Safety and efficacy of human drugs depends on many factors, so it's hard to predict which inhibitor would be most effective against a specific disorder. The more diverse novel inhibitors can be identified, the more chances there are of developing safe and effective drugs," Kazantsev explains.
Two candidate molecules were identified as potential PARP1 inhibitors based on their structure, and both of them were confirmed to inhibit the enzyme's activity in an in vitro assay. However, when tested using cultured human and rat cells, only one of the candidate molecules, K245-14, successfully prevented the death o
Contact: Sue McGreevey
Massachusetts General Hospital