The S1PR modulator Ozanimod reverses spine deficits, Amyloid-β plaques deposition and neuroinflammation in aged APP/PS1 mice

Innovative therapeutic approaches providing clinically effective medication for Alzheimer’s disease (AD) patients are urgently needed. In recent years, monoclonal antibodies against Amyloid-β (Aβ) oligomers were approved as the first disease modifying AD therapies. However, their effects on cognitive decline of AD patients are still limited – most likely because neuroinflammatory processes downstream of Aβ plaques remain activated, even when plaques are depleted. Accordingly, anti-inflammatory drugs are currently considered as valuable (co-)treatments to target Aβ associated neuro-inflammation. The anti-inflammatory sphingosine-1-phosphate receptor (S1PR) modulator fingolimod (FTY720) has been shown to alleviate synaptic and cognitive deficits in numerous mouse models of AD. Whether other S1PR modulators exert similar beneficial effects is largely unknown. Here we used a transgenic APP/PS1 AD mouse model to investigate whether the S1PR modulator Ozanimod (RPC1063) can rescue AD pathology and synaptic dysfunctions even when treatment is initiated at 16-17 months of age, which is 10 months after onset of cognitive deficits. We performed quantitative dendritic spine analysis in hippocampal CA1 pyramidal neurons and immunohistochemical labelling of Iba1-positive activated microglia, GFAP-positive reactive astrocytes, and Aβ plaques in hippocampus and neocortex. Our results reveal that 6 weeks of Ozanimod treatment via drinking water rescues synaptic spine deficits, counteracts Aβ pathology and reduces neuro-inflammation in the hippocampus and neocortex of APP/PS1 mice. Therefore, it might hold promise to examine a potential disease-modifying effect of S1PR modulators in clinical trials with AD patients.