Adenosine A2B receptors inhibit K+ currents and cell differentiation in cultured oligodendrocyte precursor cells and modulate sphingosine-1-phosphate signaling pathway

Abstract

Oligodendrocytes are the only myelinating cells in the brain and differentiate from their progenitors (OPCs) throughout adult life. However, this process fails in demyelinating pathologies. Adenosine is emerging as an important player in OPC differentiation and we recently demonstrated that adenosine A_2A receptors inhibit cell maturation by reducing voltage-dependent K⁺ currents. No data are available to date about the A_2B receptor (A_2BR) subtype. The bioactive lipid mediator sphingosine-1-phosphate (S1P) and its receptors (S1P_1-5) are also crucial modulators of OPC development. An interaction between this pathway and the A_2BR is reported in peripheral cells. We studied the role of A_2BRs in modulating K⁺ currents and cell differentiation in OPC cultures and we investigated a possible interplay with S1P signaling. Our data indicate that the A_2BR agonist BAY60-6583 and its new analogue P453 inhibit K⁺ currents in cultured OPC and the effect was prevented by the A_2BR antagonist MRS1706, by K⁺ channel blockers and was differently modulated by the S1P analogue FTY720-P. An acute (10 min) exposure of OPCs to BAY60-6583 also increased the phosphorylated form of sphingosine kinase 1 (SphK1). A chronic (7 days) treatment with the same agonist decreased OPC differentiation whereas SphK1/2 inhibition exerted the opposite effect. Furthermore, A_2BR was overexpressed during OPC differentiation, an effect prevented by the pan SphK1/2 inhibitor VPC69047. Finally, A_2BR silenced cells showed increased cell maturation, decreased SphK1 expression and enhanced S1P lyase levels. We conclude that A_2BRs inhibit K⁺ currents and cell differentiation and positively modulate S1P synthesis in cultured OPCs.

Keywords: A(2B) adenosine receptors; K(+) currents; OPC differentiation; Remyelination; Sphingosine-1-phosphate.