Adenosine Stimulates Beating of Neonatal Brain-Derived Cilia through Adenosine A2B Receptor on the Cilia and Activation of Protein Kinase A Pathway

Motile cilia in the ependymal cells that line the brain ventricles play pivotal roles in cerebrospinal fluid (CSF) flow in well-defined directions. However, the substances and pathways which regulate their beating have not been well studied. Here, we used primary cultured cells derived from neonatal mouse brain that possess motile cilia and found that adenosine (ADO) stimulates ciliary beating by increasing the ciliary beat frequency (CBF) in a concentration-dependent manner, with the ED₅₀ value being 5 µM. Ciliary beating stimulated by ADO was inhibited by A_2B receptor (A_2BR) antagonist MRS1754 without any inhibition by antagonists of other ADO receptor subtypes. The expression of A_2BR on the cilia was also confirmed by immunofluorescence. The values of CBF were also increased by forskolin, which is an activator of Adenylate Cyclase, whereas they were not further increased by the addition of ADO. Furthermore, ciliary beating was not stimulated by ADO in the presence of a protein kinase A (PKA) inhibitors. These results altogether suggest that ADO stimulates ciliary beating through A_2BR on the cilia, and activation of PKA.

adenosine; cilium; ependyma; primary culture; protein kinase A.