In the CNS an intensive communication between neurons and glial cells occurs. Activation of astrocytes is observed under different pathological conditions, including multiple sclerosis, which results in overexpression of number of proteins, like GFAP and S-100β, which is involved in development of infl ammatory reaction. There is a growing number of evidence that different brain pathologies are characterized by very early active contribution of astrocytes to neurodegenerative axonal damage. Our study presents time-dependent analysis of astroglia-specifi c protein expression in different phases of EAE (from 4 to 25 days after immunization). The biphasic response of astroglia was observed ñ upregulation of both proteins, GFAP and S-100β, in the early stages of the disease and in the peak of the neurological defi cits in animals (10 dpi). Astrocytes build a network within the CNS and are connected by gap junctions, formed by connexins, mostly Cx43 which was shown to induce ATP release via hemichannels. In the cross-talk between astrocytes and neurons may be involved purinergic receptor P2X7, ATP-gated ion channel activated in pathological conditions and participating in regulation of infl ammatory response. In the EAE rats, in the early stages of the disease, we observed the enhanced level of Cx43 protein and P2X7R protein which was accompanied by changes in mRNA profi le. We conclude that early activation of astroglia in the inductive phase of EAE occurs which is connected with the overexpression of purinergic receptor P2X7. The results suggest that in MS/EAE pathology activation of astroglia in the preclinical stage, may contribute to the axonal damage and subsequent infl ammation, and that the purinergic signaling may play a role in both these phenomena.
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