Expression of purinergic P2X7 receptor in rat brain during the symptomatic phase of experimental autoimmune encephalomyelitis and after recovery of neurological deficits.

Purinergic ionotropic P2X(7) receptor is widely distributed in brain. Strong evidence suggests that this receptor is related to inflammatory and neurodegenerative changes in many pathological states of central nervous system (CNS), including multiple sclerosis (MS). Experimental autoimmune encephalomyelitis (EAE) is the commonly used animal model of MS. In this study we investigate the expression of P2X(7)R protein in rat brain in the symptomatic phase of EAE (day 10 post immunization) and after reversion of neurological symptoms (day 20 p.i.). We found the increased level of P2X(7)R protein in brain homogenates of EAE rats in both examined time windows. Immunohistochemical study revealed enhanced receptor's immunoreactivity. Immunoblots done with isolated cellular brain fractions indicated that the P2X(7)R overexpression is related to synaptosomal fraction in the symptomatic phase and to the glial (GPV) fraction in the recovery phase of EAE. Concomitantly, we noticed overexpression of astroglial marker GFAP in brain homogenates and astroglial fraction (GPV), so as its enhanced immunoreactivity in brain sections (10 days p.i.) which did not decline to control values in the recovery phase, similarly to P2X(7)R expression. Results suggest the involvement of P2X(7)R-mediated signaling in the pathomechanisms of EAE with the possible relevance of astrocytic pool of cells.