Enhanced expression of netrin-1 protein in the sciatic nerves of Lewis rats with experimental autoimmune neuritis: Possible role of the netrin-1/DCC binding pathway in an autoimmune PNS disorder

Netrin-1 is a chemotropic factor that plays an important role as a survival factor in the adult nervous system. To investigate whether netrin-1 is involved in autoimmune injury of the peripheral nervous system (PNS), the temporal expression of netrin-1 protein was analyzed in the sciatic nerves of Lewis rats with experimental autoimmune neuritis (EAN). Western blot analysis revealed a significant increase in the level of netrin-1 protein in the sciatic nerves of rats on days 11 to 24 post-immunization (p.i.) compared to controls; netrin-1 expression declined by day 30 p.i. Immunohistochemistry revealed that netrin-1 protein was expressed weakly in Schwann cells and vessels in the sciatic nerves of normal and CFA-immunized control rats. In the sciatic nerves of EAN-affected rats, netrin-1 immunoreactivity was increased mainly in the cell membrane and extracellular matrix of OX42-positive macrophages and S100-positive Schwann cells at the peak and recovery phases of EAN. Moreover, the putative netrin-1 receptor, deleted in colorectal cancer (DCC), was expressed mainly in axons, some macrophages, and Schwann cells in EAN-affected sciatic nerves, although the level of protein expression did not change significantly over the course of EAN. We suggest that a significant increase in netrin-1 expression contributes to host cell survival and axon regeneration to counter autoimmune injury and inflammation, which may play a role in recovery from EAN-induced paralysis.