A genome-wide association study in human lymphoblastoid cells supports safety of mitochondrial complex I inhibitor

Novel therapeutic strategies for Alzheimer's disease (AD) are of the greatest priority given the consistent failure of recent clinical trials focused on Aβ or pTau. Earlier, we demonstrated that mild mitochondrial complex I inhibitor CP2 blocks neurodegeneration and cognitive decline in multiple mouse models of AD. To evaluate the safety of CP2 in humans, we performed a genome-wide association study (GWAS) using 196 lymphoblastoid cell lines and identified 11 SNP loci and 64 mRNA expression probe sets that potentially associate with CP2 susceptibility. Using primary mouse neurons and pharmacokinetic study, we show that CP2 is generally safe at a therapeutic dose.

Partial Inhibition of Mitochondrial Complex I Reduces Tau Pathology and Improves Energy Homeostasis and Synaptic Function in 3xTg-AD Mice

Background:

Accumulation of hyperphosphorylated tau (pTau) protein is associated with synaptic dysfunction in Alzheimer’s disease (AD). We previously demonstrated that neuroprotection in familial mouse models of AD could be achieved by targeting mitochondria complex I (MCI) and activating the adaptive stress response. Efficacy of this strategy on pTau-related pathology remained unknown.

Objective:

To investigate the effect of specific MCI inhibitor tricyclic pyrone compound CP2 on levels of human pTau, memory function, long term potentiation (LTP), and energy homeostasis in 18-month-old 3xTg-AD mice and explore the potential mechanisms.

Methods:

CP2 was administered to male and female 3xTg-AD mice from 3.5–18 months of age. Cognitive function was assessed using the Morris water maze. Glucose metabolism was measured in periphery using a glucose tolerance test and in the brain using fluorodeoxyglucose F18 positron-emission tomography (FDG-PET). LTP was evaluated using electrophysiology in the hippocampus. The expression of key proteins associated with neuroprotective mechanisms were assessed by western blotting.

Results:

Chronic CP2 treatment restored synaptic activity in female 3xTg-AD mice; cognitive function, levels of synaptic proteins, glucose metabolism, and energy homeostasis were improved in male and female 3xTg-AD mice. Significant reduction of human pTau in the brain was associated with increased activity of protein phosphatase of type 2A (PP2A), and reduced activity of cyclin-dependent kinase 5 (CDK5) and glycogen synthase kinase 3β (GSK3β).

Conclusion:

CP2 treatment protected against synaptic dysfunction and memory impairment in symptomatic 3xTg-AD mice, and reduced levels of human pTau, indicating that targeting mitochondria with small molecule specific MCI inhibitors represents a promising strategy for treating AD.