Researchers have identified a new treatment candidate that appears to not only halt neurodegenerative symptoms in mouse models of dementia and Alzheimer’s disease, but also reverse the effects of the disorders.
The team, based at Tohoku University, published their results on June 8 in the International Journal of Molecular Sciences. The treatment candidate has been declared safe by Japan’s governing board, and the researchers plan to begin clinical trials in humans in the next year.
“There are currently no disease-modifying therapeutics for neurodegenerative disorders such as Alzheimer’s disease, Lewy body dementia, Huntington disease and frontotemporal dementia in the world,” said paper author Kohji Fukunaga, professor emeritus in Tohoku University’s Graduate School of Pharmaceutical Sciences. “We discovered the novel, disease-modifying therapeutic candidate SAK3, which, in our studies, rescued neurons in most protein-misfolding, neurodegenerative diseases.”
In comparison, Aduhelm, the Alzheimer’s drug recently approved by the U.S. Food and Drug Administration, reduces the number of amyloid plaques in the brain, but it is not yet known if the amyloid reduction actually prevents further cognitive or motor decline in patients. According to Fukunaga, SAK3 helps destroy amyloid plaque – at least in mice.
SAK3 also helps manage the destruction of misfolded alpha-synuclein. Normal alpha-synuclein helps regulate neurotransmitter transmission in the brain. The protein can misfold and aggregate, contributing to what researchers suspect may be an underlying cause of neurodegenerative symptoms. This aggregation can also lead to the loss of dopamine neurons, which help with learning and memory.
“We found that chronic administration of SAK3 significantly inhibited the accumulation of alpha-synuclein in the mice,” Fukunaga said, noting that the mice received a daily oral dose of SAK3.
According to Fukunaga, SAK3 enhances the activity of the system that identifies and destroys misfolded proteins. In neurodegenerative diseases, this system is often dysfunctional, leaving misfolded proteins to muck up the cell’s machinery.
“SAK3 is the first compound targeting this regulatory activity in neurodegenerative disorders,” Fukunaga said. “SAK3 administration promotes the destruction of misfolded proteins, meaning the therapeutic has the potential to solve the problems of diverse protein misfolding diseases such as Parkinson’s disease, Lewy body dementia and Huntington disease, in addition to Alzheimer’s disease.”
Lewy bodies are pathological characteristics of Lewy body dementia (LBD) and are composed of α-synuclein (α-Syn), which is mostly degraded via the ubiquitin–proteasome system. More importantly, 26S proteasomal activity decreases in the brain of LBD patients. We recently introduced a T-type calcium channel enhancer SAK3 (ethyl-8-methyl-2,4-dioxo-2-(piperidin-1-yl)- 2H-spiro[cyclopentane-1,3-imidazo [1,2-a]pyridin]-2-ene-3-carboxylate) for Alzheimer’s disease therapeutics. SAK3 enhanced the proteasome activity via CaMKII activation in amyloid precursor protein knock-in mice, promoting the degradation of amyloid-β plaques to improve cognition. At this point, we addressed whether SAK3 promotes the degradation of misfolded α-Syn and the aggregates in α-Syn preformed fibril (PFF)-injected mice. The mice were injected with α-Syn PFF in the dorsal striatum, and SAK3 (0.5 or 1.0 mg/kg) was administered orally for three months, either immediately or during the last month after injection. SAK3 significantly inhibited the accumulation of fibrilized phosphorylated-α-Syn in the substantia nigra. Accordingly, SAK3 significantly recovered mesencephalic dopamine neurons from cell death. Decreased α-Syn accumulation was closely associated with increased proteasome activity. Elevated CaMKII/Rpt-6 signaling possibly mediates the enhanced proteasome activity after SAK3 administration in the cortex and hippocampus. CaMKII/Rpt-6 activation also accounted for improved memory and cognition in α-Syn PFF-injected mice. These findings indicate that CaMKII/Rpt-6-dependent proteasomal activation by SAK3 recovers from α-Syn pathology in LBD.
SOURCES – Xu, J.; Kawahata, I.; Izumi, H.; Fukunaga, K. T-Type Ca2+ Enhancer SAK3 Activates CaMKII and Proteasome Activities in Lewy Body Dementia Mice Model. Int. J. Mol. Sci. 2021, 22, 6185. https://doi.org/10.3390/ijms22126185, Tohoku University
Written By Brian Wang, Nextbigfuture.com
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