Purinergic P2X receptors, when activated under pathological conditions, participate in induction of the inflammatory response and/or cell death. Both neuroinflammation and neurodegeneration represent hallmarks of multiple sclerosis (MS), an autoimmune disease of the central nervous system. In the current study, we examined whether P2X7R is expressed in brain microvasculature of rats subjected to experimental autoimmune encephalomyelitis (EAE) and explore possible relationships with blood-brain barrier (BBB) protein-claudin-5 after administration of P2X7R antagonist-Brilliant Blue G (BBG). Capillary fraction isolated from control and EAE rat brains was subjected to immunohistochemical and Western blot analyses. We document the presence of P2X7R in brain capillaries isolated from brain tissue of EAE rats. P2X7R is found to be localized on the abluminal surface of the microvessels and is co-expressed with PDGFβR, a marker of pericytes. We also show over-expression of this receptor in isolated capillaries during the course of EAE, which is temporally correlated with a lower protein level of PDGFβR, as well as claudin-5, a tight junction-building protein. Administration of a P2X7R antagonist to the immunized rats significantly reduced clinical signs of EAE and enhances protein expression of both claudin-5 and PDGFβR. These results indicate that P2X7 receptor located on pericytes may contribute to pathological mechanisms operated during EAE in cerebral microvessels influencing the BBB integrity.
Keywords: Blood-brain barrier; Multiple sclerosis; Pericytes; Purinergic receptors; Tight junction proteins.