Choroid plexus-selective inactivation of adenosine A2A receptors protects against T cell infiltration and experimental autoimmune encephalomyelitis

Background: Multiple sclerosis (MS) is one of the most common autoimmune disorders characterized by the infiltration of immune cells into the brain and demyelination. The unwanted immunosuppressive side effect of therapeutically successful natalizumab led us to focus on the choroid plexus (CP), a key site for the first wave of immune cell infiltration in experimental autoimmune encephalomyelitis (EAE), for the control of immune cells trafficking. Adenosine A_2A receptor (A_2AR) is emerging as a potential pharmacological target to control EAE pathogenesis. However, the cellular basis for the A_2AR-mediated protection remains undetermined.

Methods: In the EAE model, we assessed A_2AR expression and leukocyte trafficking determinants in the CP by immunohistochemistry and qPCR analyses. We determined the effect of the A_2AR antagonist KW6002 treatment at days 8-12 or 8-14 post-immunization on T cell infiltration across the CP and EAE pathology. We determined the critical role of the CP-A_2AR on T cell infiltration and EAE pathology by focal knock-down of CP-A_2AR via intracerebroventricular injection of CRE-TAT recombinase into the A_2AR^flox/flox mice. In the cultured CP epithelium, we also evaluated the effect of overexpression of A_2ARs or the A_2AR agonist CGS21680 treatment on the CP permeability and lymphocytes migration.

Results: We found the specific upregulation of A_2AR in the CP associated with enhanced CP gateway activity peaked at day 12 post-immunization in EAE mice. Furthermore, the KW6002 treatment at days 8-12 or 8-14 post-immunization reduced T cell trafficking across the CP and attenuated EAE pathology. Importantly, focal CP-A_2AR knock-down attenuated the pathogenic infiltration of Th17⁺ cells across the CP via inhibiting the CCR6-CCL20 axis through NFκB/STAT3 pathway and protected against EAE pathology. Lastly, activation of A_2AR in the cultured epithelium by A_2AR overexpression or CGS21680 treatment increased the permeability of the CP epithelium and facilitated lymphocytes migration.

Conclusion: These findings define the CP niche as one of the primary sites of A_2AR action, whereby A_2AR antagonists confer protection against EAE pathology. Thus, pharmacological targeting of the CP-A_2AR represents a novel therapeutic strategy for MS by controlling immune cell trafficking across CP.