Effect of sphingosine kinase modulators on interleukin-1β release, sphingosine 1-phosphate receptor 1 expression and experimental autoimmune encephalomyelitis: FTY720 analogues and inflammation

Background and Purpose: The sphingosine analogue, FTY720 (Gilenya®) alleviates clinical disease progression in multiple sclerosis. Here we variously assessed the effects of an azide analogue of (S)-FTY720 vinylphosphonate (compound 5; a sphingosine kinase 1 activator), (R)-FTY720 methyl ether (ROMe, a sphingosine kinase 2 inhibitor) and RB-020 (a sphingosine kinase 1 inhibitor and sphingosine kinase 2 substrate) on IL-1beta formation, sphingosine 1-phosphate levels and S1P₁ expression. We also assessed the effect of compound 5 and ROMe in an experimental autoimmune encephalomyelitis (EAE) model.
Experimental Approach: We measured IL-1beta formation by macrophages, sphingosine 1-phosphate levels and S1P₁ expression levels in vitro and clinical score and inflammatory cell infiltration into the spinal cord in vivo.
Key Results: Treatment of differentiated U937 macrophages with compound 5, RB-020 or sphingosine (but not ROMe) enhanced IL-1beta release. This data suggests these compounds might be pro-inflammatory in vitro. However, compound 5 or ROMe reduced disease progression and infiltration of inflammatory cells into the spinal cord in EAE and ROMe induced a reduction in CD4⁺ and CD8⁺ T-cell levels in the blood (lymphopenia). Indeed, ROMe induced a marked decrease in cell surface S1P₁ expression in vitro.
Conclusion and Implications: This is the first demonstration that an activator of SK1 (compound 5) and an inhibitor of SK2 (ROMe, which also reduces cell surface S1P₁ expression) have an anti-inflammatory action in EAE.