Dual Mechanisms of Cognitive Function and Pathological Improvements by the Selective S1PR1/5 Modulator Siponimod in...

Alzheimer's disease (AD) is characterized by progressive cognitive decline, with neuroinflammation and myelin dysfunction as crucial pathological mechanisms. Siponimod, a selective S1PR1/5 modulator, shows promising therapeutic potential through enhanced brain penetration and improved pharmacokinetic properties compared to first-generation modulators. Network pharmacology and molecular docking analyses were utilized to comprehensively elucidate the underlying mechanisms of Siponimod in the context of AD. Specifically, network pharmacology identified key targets and pathways associated with Siponimod, while molecular docking facilitated predictions of binding affinities to these targets. For in vitro assessments, BV2 microglia cells were used to investigate the effects of Siponimod after stimulation with LPS, focusing on inflammatory responses and cellular signaling pathways. Concurrently, in vivo studies employed the 3xTg-AD mouse model to investigate behavioral outcomes related to cognitive function, alongside evaluations of neuroinflammation and the integrity of myelin sheaths. Siponimod treatment resulted in a significant reduction in pro-inflammatory cytokines and ROS production in BV2 microglia cells, thereby indicating its robust anti-inflammatory and antioxidant properties. In the 3xTg-AD mouse model, administration of Siponimod led to marked improvements in cognitive performance as assessed through various behavioral tests. Additionally, there was a noteworthy decrease in Aβ plaque deposition, coupled with evidence of myelin repair, which was reflected in the increased expression of myelination-related proteins, namely OLIG2 and MBP. Furthermore, Siponimod was found to activate the PI3K-AKT signaling pathway, which plays a crucial role in promoting neuroprotection and enhancing cellular resilience against neurodegenerative processes. This study demonstrates that Siponimod effectively treats AD through dual mechanisms: reducing neuroinflammation and promoting myelin repair via the S1PR1/5 and PI3K-AKT signaling pathway. These findings suggest Siponimod's potential as a promising therapeutic agent for AD treatment.