INTRODUCTION: The Epstein-Barr virus-induced gene 2 (EBI2/GPR183) is a G protein-coupled receptor primarily expressed in the immune system, but also functional in astrocytes, microglia, and oligodendrocytes. Its most potent endogenous agonist, the oxysterol CF3-7α,25-dihydroxycholesterol, directs immune cell migration and has been implicated in the pathophysiology of multiple sclerosis (MS). Previous studies demonstrated that EBI2 deficiency leads to impaired remyelination and increased demyelination. However, the short half-life of natural oxysterols limits their therapeutic application. Therefore, we investigated a biostable synthetic analogue,CF3-7α,25-OHC, to evaluate its neuroimmunomodulatory and regenerative potential in MS models.

AIM(S): The study aims to evaluate the neuroimmunomodulatory and regenerative potential of a metabolically stable EBI2 receptor agonist, CF3-7α,25OHC. The research focuses on determining whether this compound can accelerate remyelination and modulate the autoimmune response in two distinct mice models of multiple sclerosis (MS).

METHOD(S): - Cuprizone Model: Male C57BL/6 mice were fed a 0.2% cuprizone diet for 9 weeks to induce toxic demyelination, followed by 2 weeks of CF3-7α,25OHC treatment. - EAE Model: Experimental Autoimmune Encephalomyelitis (EAE) is induced to mimic the autoimmune component of MS. Following pilot studies in SJL/J mice, the current project involves EBI2 knock-out (KO) mice. - Clinical Assessment: Disease progression in EAE is monitored daily using a clinical scoring scale (0 to 4.5), ranging from a limp tail to complete paralysis. - Analytical Techniques: Evaluation includes Luxol Fast Blue (LFB) staining for myelin density, qPCR for gene expression and blood count analysis.

RESULTS: - Accelerated Remyelination: In the cuprizone model, CF3-7α,25OHC significantly accelerated remyelination in the corpus callosum compared to vehicle-treated controls. - Immune Modulation: Treatment led to a pronounced reduction in peripheral white blood cell counts, with lymphocytes decreasing by 51% and monocytes by 66%. - Molecular Changes: The analogue upregulated Ebi2 expression in the brain and increased the synthesis of 15 lipid classes in the corpus callosum. - EAE Expectations: Preliminary data from EBI2/KO models (to be conducted in April) are expected to clarify the receptor's role in clinical onset and peak disability during autoimmune neuroinflammation.

CONCLUSIONS: The findings demonstrate that CF3-7α,25OHC acts as a dual-action agent by promoting myelin repair and exerting potent systemic immunomodulatory effects. Bridging the results from toxic and autoimmune models validates the EBI2/oxysterol axis as a promising therapeutic target for the treatment of both neurodegenerative and inflammatory phases of multiple sclerosis.

FINANCIAL SUPPORT: This project received funding from the National Science Centre, Poland, grant registration number: 2022/47/D/NZ3/02613