Research

Activation of adenosine A_2B receptors enhances ciliary beat frequency in mouse lateral ventricle ependymal cells

Jonathan R Genzen^1,4 , Dan Yang³ , Katya Ravid³ and Angelique Bordey²

¹  Department of Laboratory Medicine, Yale University School of Medicine, New Haven, CT 06520-8082, USA

²  Departments of Neurosurgery & Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520-8082, USA

³  Departments of Biochemistry, Medicine, and Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, MA 02118, USA

⁴  Department of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York-Presbyterian Hospital, New York, NY 10065, USA

author email corresponding author email

Cerebrospinal Fluid Research 2009, 6:15doi:10.1186/1743-8454-6-15

Published:	18 November 2009

Abstract

Background

Ependymal cells form a protective monolayer between the brain parenchyma and cerebrospinal fluid (CSF). They possess motile cilia important for directing the flow of CSF through the ventricular system. While ciliary beat frequency in airway epithelia has been extensively studied, fewer reports have looked at the mechanisms involved in regulating ciliary beat frequency in ependyma. Prior studies have demonstrated that ependymal cells express at least one purinergic receptor (P2X₇). An understanding of the full range of purinergic receptors expressed by ependymal cells, however, is not yet complete. The objective of this study was to identify purinergic receptors which may be involved in regulating ciliary beat frequency in lateral ventricle ependymal cells.

Methods

High-speed video analysis of ciliary movement in the presence and absence of purinergic agents was performed using differential interference contrast microscopy in slices of mouse brain (total number of animals = 67). Receptor identification by this pharmacological approach was corroborated by immunocytochemistry, calcium imaging experiments, and the use of two separate lines of knockout mice.

Results

Ciliary beat frequency was enhanced by application of a commonly used P2X₇ agonist. Subsequent experiments, however, demonstrated that this enhancement was observed in both P2X₇^+/+ and P2X₇^-/- mice and was reduced by pre-incubation with an ecto-5'-nucleotidase inhibitor. This suggested that enhancement was primarily due to a metabolic breakdown product acting on another purinergic receptor subtype. Further studies revealed that ciliary beat frequency enhancement was also induced by adenosine receptor agonists, and pharmacological studies revealed that ciliary beat frequency enhancement was primarily due to A_2B receptor activation. A_2B expression by ependymal cells was subsequently confirmed using A_2B^-/-/β-galactosidase reporter gene knock-in mice.

Conclusion

This study demonstrates that A_2B receptor activation enhances ciliary beat frequency in lateral ventricle ependymal cells. Ependymal cell ciliary beat frequency regulation may play an important role in cerebral fluid balance and cerebrospinal fluid dynamics.