ISX9 activates the Wnt/β-catenin signaling pathway and exerts neuroprotective effects in Alzheimer's disease.

Abstract

BACKGROUND: Defective Wnt/β-catenin signaling is closely associated with the pathogenesis of Alzheimer's disease (AD), thus validating this pathway as a therapeutic target for AD. ISX9 is a potent agonist of the Wnt/β-catenin pathway. However, it remains unknown whether ISX9 exerts anti-AD effects by enhancing the Wnt/β-catenin signaling pathway. We therefore explored the neuroprotective potential of ISX9 using both hippocampal neuron-derived HT22 cells and 5×FAD transgenic mouse model of AD. METHODS: In HT22 cells, we employed the SuperTOPFlash reporter gene, Co-IP and Western blot assays to investigate the mechanism by which ISX9 activates the Wnt signaling pathway. The effects of ISX9 on the biological behavior of HT22 cells were further evaluated through MTT, BrdU and IF staining. To study the therapeutic effect of ISX9 on AD, six-month-old 5×FAD transgenic mice were randomly divided into four groups: WT, WT/ISX9, AD and AD/ISX9. The mice were intraperitoneally injected with ISX9 or vehicle at an interval of one day for 2 months. Behavioral tests were conducted to evaluate the cognitive and learning abilities of mice, while the expression levels of Aβ peptides, Tau-related proteins, neuroinflammatory factors, blood-brain barrier (BBB)-related proteins and the components of Wnt/β-catenin signaling were investigated. RESULTS: Our results demonstrated that ISX9 potently activated Wnt/β-catenin signaling by promoting the association of LRP6 with AXIN1, and increased the viability and proliferation of hippocampal cells. At the behavioral level, ISX9 improved learning and memory abilities in 5×FAD mice, and ameliorated hippocampal neuronal damage. Furthermore, ISX9 treatment effectively reduced the expression of Aβ peptides, total Tau, and phosphorylated Tau (S404) proteins in the AD mice. Mechanistically, ISX9 exhibited its neuroprotective effects, activating the Wnt/β-catenin signaling pathway via potentiating the interaction of LRP6 with AXIN1, upregulating the expression of BBB-related proteins and downregulating neuroinflammatory factors in AD mice. CONCLUSION: Our findings indicate that ISX9 potently activates the Wnt/β-catenin signaling pathway and confers cognitive protection in hippocampal cells and AD mice. This compound may serve as a promising therapeutic agent for the treatment of AD.